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1

Large Circular Basin Flooded and then Cratered  

NASA Technical Reports Server (NTRS)

As Mariner 10 passed by Mercury on its second encounter with the planet on September 21, 1974, this picture (FDS 166850) of a large circular (350 kilometer, 220 mile diameter) basin was obtained near the morning terminator. The basin appears to have been flooded with the plain material and then subsequently cratered by numerous large events. Filling of the basin, presumably by lava flows analogous to those of the lunar maria, partially inundated small craters which had formed along the basin rim (lower left) and in some places overflowed the basin rim and spilled onto the surrounding terrain (top).

The Mariner 10 mission, managed by the Jet Propulsion Laboratory for NASA's Office of Space Science, explored Venus in February 1974 on the way to three encounters with Mercury-in March and September 1974 and in March 1975. The spacecraft took more than 7,000 photos of Mercury, Venus, the Earth and the Moon.

Image Credit: NASA/JPL/Northwestern University

1974-01-01

2

Impedance of a large circular loop antenna in a magnetoplasma  

SciTech Connect

The input impedance of a large circular loop antenna with arbitrary orientation in a cold magnetoplasma is calculated by using a transmission line theory. New impedance resonances for antennas of finite size in a magnetoplasma in the frequency region below and near the electron cyclotron frequency are indicated theoretically. The resonance peak of the impedance at the lower hybrid resonance frequency is also predicted to exist for arbitrarily oriented antennas of finite size. The experiments on the impedance of a large circular loop antenna are carried out for the cases of normal and parallel orientation of the magnetic field with respect to the plane of the loop immersed in a radio frequency-generated laboratory plasma. The newly predicted impedance resonances for the antenna of finite size are observed. It is also shown that the measured impedances agree fairly well with the calculated ones.

Ohnuki, S.; Sawaya, K.; Adachi, S.

1986-08-01

3

Circular structures of large scale and great age on the earth's surface  

Microsoft Academic Search

It is pointed out that the earth's surface exhibits faint circular patterns which have not been described before. These circles are characterized by near perfection of outline, by the presence of topographic highs (rims) along parts of their circumferences, and by their generally large scale (diameters from 7 to 700 km). Circles of this nature have been observed clearly in

J. M. Saul

1978-01-01

4

Large-amplitude circularly polarized electromagnetic waves in magnetized plasma  

NASA Astrophysics Data System (ADS)

We consider large-amplitude circularly polarized (LACP) waves propagating in a magnetized plasma. It is well-known that the dispersion relation for such waves coincides with the dispersion relation given by the linear theory. We develop the model of LACP wave containing a finite population of Cerenkov resonant particles. We find that the current of resonant particles modifies the linear dispersion relation. Dispersion curves of low-frequency (i.e., whistler and magnetosonic) waves are shifted toward larger values of the wave vector, i.e., waves with arbitrarily large wavelengths do not exist in this case. Dispersion curves of high-frequency waves are modified so that the wave phase velocity becomes smaller than the speed of light.

Vasko, I. Y.; Artemyev, A. V.; Zelenyi, L. M.

2014-05-01

5

Strong K-edge Magnetic Circular Dichroism Observed in Photon-in-Photon-out Spectroscopy  

NASA Astrophysics Data System (ADS)

A large enhancement of the x-ray magnetic circular dichroism is observed at the iron K absorption preedge of magnetite. This is achieved by performing resonant inelastic x-ray scattering (RIXS) experiments with a 2p hole in the final state of the second-order optical process. We measured and calculated the full 1s2p RIXS planes for opposite helicities of the incoming circularly polarized x rays. The crystal field multiplet calculations show that the enhancement arises from 2p-3d Coulomb repulsions and 2p and 3d spin-orbit coupling. The observed magnitude of the RIXS magnetic circular dichroism effect is ˜16%. This opens up new opportunities for a broad range of research fields allowing for truly bulk-sensitive, element-, and site-selective measurements of 3d transition metal magnetic moments and their ordering using hard x-ray photons.

Sikora, Marcin; Juhin, Amélie; Weng, Tsu-Chien; Sainctavit, Philippe; Detlefs, Carsten; de Groot, Frank; Glatzel, Pieter

2010-07-01

6

Large-eddy simulation of flow past a circular cylinder  

NASA Technical Reports Server (NTRS)

Some of the most challenging applications of large-eddy simulation are those in complex geometries where spectral methods are of limited use. For such applications more conventional methods such as finite difference or finite element have to be used. However, it has become clear in recent years that dissipative numerical schemes which are routinely used in viscous flow simulations are not good candidates for use in LES of turbulent flows. Except in cases where the flow is extremely well resolved, it has been found that upwind schemes tend to damp out a significant portion of the small scales that can be resolved on the grid. Furthermore, it has been found that even specially designed higher-order upwind schemes that have been used successfully in the direct numerical simulation of turbulent flows produce too much dissipation when used in conjunction with large-eddy simulation. The objective of the current study is to perform a LES of incompressible flow past a circular cylinder at a Reynolds number of 3900 using a solver which employs an energy-conservative second-order central difference scheme for spatial discretization and compare the results obtained with those of Beaudan & Moin (1994) and with the experiments in order to assess the performance of the central scheme for this relatively complex geometry.

Mittal, R.

1995-01-01

7

Large deflections of composite circular springs with extended flat contact surfaces  

Microsoft Academic Search

Large deflections of a range of mid-surface-symmetric, woven composite circular springs with extended flat contact surfaces subject to unidirectional line and surface-loading configurations were studied experimentally and modelled numerically. Finite element analysis was employed to study the load–deflection and strain distribution characteristics. Eighteen woven fibre\\/epoxy composite circular springs covering a range of different radii and thicknesses were fabricated and tested.

P. C. Tse; S. R. Reid; K. J. Lau; W. H. Wong

2004-01-01

8

Conformation of Cyclolinopeptide A Observed by Circular Dichroism  

PubMed Central

A stereochemical investigation, by circular dichroism, of a synthetic nonapeptide (cyclolinopeptide A) in several organic and organic-sulfuric acid solvents is presented. From this examination, and results found for a conformationally rigid model compound, 1,7,7-trimethyl-3-azabicyclo [2.2.1] heptan-2-one(camphorolactam), it is concluded that cyclolinopeptide A may exist in several conformations in solution. None of these conformations is believed to be stabilized by intramolecular hydrogen bonds. Some details on an x-ray analysis of the cyclic nonapeptide are also presented.

Naider, Fred; Benedetti, Ettore; Goodman, Murray

1971-01-01

9

Some Solutions for the Large Deflections of Uniformly Loaded Circular Membranes  

NASA Technical Reports Server (NTRS)

Inconsistent citations in the literature and questions about convergence prompt reexamination of Hencky's classic solution for the large deflections of a clamped, circular isotropic membrane under uniform pressure. This classic solution is observed actually to be for uniform lateral loading because the radial component of the pressure acting on the deformed membrane is neglected. An algebraic error in Hencky's solution is corrected, additional terms are retained in the power series to assess convergence, and results are obtained for two additional values of Poisson's ratio. To evaluate the importance of the neglected radial component of the applied pressure, the problem is reformulated with this component included and is solved, with escalating algebraic complexity, by a similar power-series approach. The two solutions agree quite closely for lightly loaded membranes and diverge slowly as the load intensifies. Differences in maximum stresses and deflections are substantial only when stresses are very high. The more nearly spherical deflection shape of the membrane under true pressure loading suggests that a near-parabolic membrane reflector designed on the basis of the more convenient Hencky theory would not perform as well as expected. In addition, both theories are found to yield closed-form, nonuniform membrane-thickness distributions that produce parabolic middle-surface deflections under loading. Both distributions require that the circular boundary expand radially in amounts that depend on material and loading parameters.

Fichter, W. B.

1997-01-01

10

Reading Materials in Large Type. Reference Circular No. 87-4.  

ERIC Educational Resources Information Center

This circular provides information about reading materials in large type, i.e., materials set in type that is a minimum size of 14-point and, most commonly, 16- to 18-point size. Most of the materials listed are typeset, but a few are photographically enlarged conventionally printed books or typewritten materials prepared using a large-print…

Library of Congress, Washington, DC. National Library Service for the Blind and Physically Handicapped.

11

Large eddy simulation of the subcritical flow past a circular cylinder: numerical and modeling aspects  

Microsoft Academic Search

The turbulent flow past a circular cylinder (Re=3900) was computed by large eddy simulation (LES). The objective was not to investigate the physical phenomena of this flow in detail but to study numerical and modeling aspects which influence the quality of LES solutions. Concerning the numerical method, the most important component is the discretization of the non-linear convective fluxes. Five

M. Breuer

1998-01-01

12

Plastic Collapse Analysis of Slender Circular Tubes Subjected to Large Deformation Pure Bending  

Microsoft Academic Search

This paper presents a plastic mechanism analysis for thin-walled circular hollow section (CHS) tubes deforming in a multi-lobe or diamond collapse mode under large deformation pure bending. The fold formation process was such that the shell curvature flattened on the compression side transforming into a definite number of flat triangles attached to each other. The collapse proceeded progressively by folding

Mohamed Elchalakani; Raphael Grzebieta; Xiao-Ling Zhao

2002-01-01

13

Circularity measuring system: A shape gauge designed especially for use on large objects  

NASA Technical Reports Server (NTRS)

The Circularity Measuring System (CMS) was developed to make an in-situ determination of shape similarity for selected fit large cylinders (RSRM segments). It does this to a repeatable accuracy of 0.10 mm (0.004 inch). This is less that the goal of 0.07 mm (0.003 inch), but was determined adequate because of the addition of an assembly aid that increased the entry chamfer of the clevis side of the joint. The usefulness of the CMS is demonstrated by the application to measurements other than its specified design purpose, such as submarine hull circularity, SRM mid-case circularity, as well as circularity of interfacing SRM tooling, specifically the rounding devices and horizontal disassembly devices. Commercialization of the tool is being pursued, since it is an enhancement of metrology technology for circularity determination. The most accurate in-situ technology it replaces is determined from a template. The CMS is an improvement in accuracy and operation.

Rohrkaste, G. R.

1990-01-01

14

A circular cylinder undergoing large-amplitude transverse oscillations in a slow uniform cross flow  

NASA Astrophysics Data System (ADS)

This study explores the vortex patterns formed by a circular cylinder undergoing lateral cylinder oscillations with large amplitudes and in the presence of a slow uniform cross flow. It is an extension of our previous study (Lam et al., 2010b) in which formation of the 2S, 2P and P+S vortex modes were discussed from the viewpoint of interaction of a uniform cross-flow with the vortex street patterns of a cylinder oscillating in an otherwise quiescent fluid at Keulegan-Carpenter numbers up to KC=8.9. The present paper reports three additional experimental sets in which the amplitudes of cylinder oscillations have even larger values, at A/D>2.5, and lie beyond the vortex mode map usually quoted from Williamson and Roshko (1988). It is found that the slow uniform cross-flow at ?/D?3 and Reynolds number based on cross-flow velocity at 232 acts to convect the corresponding vortex patterns in the absence of cross-flow downstream across the line of cylinder oscillation. Vortex-vortex interaction and vortex-cylinder interaction are observed to affect the subsequent development of vortices. The P+S vortex mode is found to occur up to KC=16. At KC between 16 and 24, a new vortex mode is observed in which only one vortex pair can be convected downstream every cylinder oscillation cycle. Another new vortex mode with two vortex pairs and two stationary vortices are found at KC>24.

Lam, K. M.; Liu, P.

2013-05-01

15

Circular polarization observations and magnetic fields of O stars  

NASA Astrophysics Data System (ADS)

The results of a search for line profile variability (LPV) and polarimetric line profile variability (pLPV) in spectra of O stars are reported. The observations were made with the 1.8-m telescope of the Korean Bohyunsan Optical Astronomical Observatory (BOAO) and the 1-m and 6-m telescopes of the Special Astrophysical Observatory (SAO), Russia. Regular LPV in the spectra of all program stars are found. We analyze the connection between the presence of magnetic field and nitrogen abundance anomalies, and the influence of weak magnetic fields on pLPV. The statistical properties of mean magnetic fields and magnetic fluxes of OB stars are studied.

Sudnik, Natallia P.; Kholtygin, Alexander F.

2012-05-01

16

A challenging test case for large eddy simulation: high Reynolds number circular cylinder flow  

Microsoft Academic Search

A thorough numerical investigation of high Reynolds number (Re=140,000) circular cylinder flow was performed based on large eddy simulation (LES). The objective was to evaluate the applicability of LES for practically relevant high-Re flows and to investigate the influence of subgrid scale modeling and grid resolution on the quality of the predicted results. Because the turbulent von Kármán vortex street

Michael Breuer

2000-01-01

17

Large eddy simulations of the flow past two side-by-side circular cylinders  

Microsoft Academic Search

A LES Large Eddy Simulation is performed to study the flow past two side-by-side circular cylinders at a Reynolds number of 5800, based on the free-stream velocity and the cylinders diameter. The centre-to-centre transverse pitch ratio T\\/D is varied from 1.5 to 3. Both cylinders are slightly heated and the small amount of heat can be treated as a passive

J. Shao; C. Zhang

2008-01-01

18

Large-Scale periodic solar velocities: An observational study  

NASA Technical Reports Server (NTRS)

Observations of large-scale solar velocities were made using the mean field telescope and Babcock magnetograph of the Stanford Solar Observatory. Observations were made in the magnetically insensitive ion line at 5124 A, with light from the center (limb) of the disk right (left) circularly polarized, so that the magnetograph measures the difference in wavelength between center and limb. Computer calculations are made of the wavelength difference produced by global pulsations for spherical harmonics up to second order and of the signal produced by displacing the solar image relative to polarizing optics or diffraction grating.

Dittmer, P. H.

1977-01-01

19

Observation under the gradually increasing cyclic loading of yielding region of the circular hole vicinity  

NASA Astrophysics Data System (ADS)

Under the cyclic loading, stress concentration takes place in the member with circular hole, and it affected to fatigue fracture. Therefore, it is important to obtain the information on the stress concentration of circular hole in the study of fatigue fracture. In the carbon steel strip, it is well known under static loading that Luders' lines which arose by yield stress in the member surface and observed easily by naked eyes exists. The same phenomenon takes place by application of cyclic loading at load ratio: R=0. The direct observation using Luders' lines becomes visible smart sensor that discerns the yielding region. This method is using the property of material itself, and it is a simple method. And, the continuous change of the member surface can discern real-time. The purpose of this study is to obtain basic data on the stress concentation of the vicinity of circular hole by observing the continuous change of the specimen surface in R=0, -1, using the carbon steel strip with a circular hole. And, the stress concentration factor required by FEM analysis and experiment was compared, when yield criterion was changed.

Ichinose, Kensuke; Funamoto, Yuji; Gomi, Kenji; Taniuchi, Kiyoshi; Fukuda, Katsumi

2002-12-01

20

Semi-circular microgrooves to observe active movements of individual Navicula pavillardii cells.  

PubMed

We performed a trajectory analysis of movements of Navicula pavillardii diatom cells that were confined to semi-circular microgrooves with several different curvature radii. Using the semi-circular micropattern, we succeeded in observing change of velocity of the same cell before and after the stimulation by N,N-dimethyl-p-toluidine (DMT). Because the looped grooves had longer contour length than straight grooves, it was effective to achieve the long term observation of the stimulated active cells. Although average velocity of 150 cells was significantly increased with DMT, the maximum velocity (19 ?m/s) of the cells was not increased after the DMT injection. This may suggest that existence of the mechanical limit of the velocity of the diatom cells. Secondly, trajectories of individual cell movements along the walls of the semi-circular microgrooves were analyzed in detail. As a result, the velocity of the cells was not affected by the curvature radii of the grooves although the trajectories indicated an obvious restriction of area of the cell motion. This suggests that the surface of the diatom is effective in minimizing the frictional force between the cell body and the wall of a groove. Finally, a simple model of cell motion in the semi-circular groove was proposed to clarify the relationships among the forces that determine cell movement. PMID:23337812

Umemura, Kazuo; Haneda, Takahiro; Tanabe, Masashi; Suzuki, Akira; Kumashiro, Yoshikazu; Itoga, Kazuyoshi; Okano, Teruo; Mayama, Shigeki

2013-03-01

21

Large-amplitude circularly-polarized electromagnetic waves in magnetized plasma  

NASA Astrophysics Data System (ADS)

We consider large-amplitude circularly-polarized electromagnetic waves propagating along the uniform background magnetic field. In the absence of particles trapped by the wave there are four well-known branches of plasma oscillations. The presence of trapped particles modifies wave dispersion curves. For low-frequency waves (which frequency is smaller than the electron gyrofrequency) the presence of trapped particles results in the shift of dispersion curves to shorter wavelengths. Thus, the wave cannot have an arbitrary large wavelength. For high-frequency waves the presence of trapped particles results in the decrease of the wave phase velocity. For sufficiently large amount of trapped particles the phase velocity becomes smaller than the speed of light.

Vasko, Ivan; Artemyev, Anton; Zelenyi, Lev

2014-05-01

22

Post Main Sequence Orbital Circularization of Binary Stars in the Large and Small Magellanic Clouds.  

SciTech Connect

We present results from a study of the orbits of eclipsing binary stars (EBs) in the Magellanic Clouds. The samples comprise 4510 EBs found in the Large Magellanic Cloud (LMC) by the MACHO project, 2474 LMC EBs found by the OGLE-II project (of which 1182 are also in the MACHO sample), 1380 in the Small Magellanic Cloud (SMC) found by the MACHO project, and 1317 SMC EBs found by the OGLE-II project (of which 677 are also in the MACHO sample); we also consider the EROS sample of 79 EBs in the bar of the LMC. Statistics of the phase differences between primary and secondary minima allow us to infer the statistics of orbital eccentricities within these samples. We confirm the well-known absence of eccentric orbit in close binary stars. We also find evidence for rapid circularization in longer period systems when one member evolves beyond the main sequence, as also found by previous studies.

Faccioli, L; Alcock, C; Cook, K

2007-11-20

23

Observation of the surface circular photogalvanic effect in InN films  

NASA Astrophysics Data System (ADS)

A sizable spin-dependent photocurrent related to the interband transition in InN films is observed. The surface charge accumulation layer is suggested to be the origin of the circular photogalvanic current, which is consistent with the result of uniaxial strain experiments and the comparison of front and back incidence. The homogeneous photocurrent demonstrates the existence of spin splitting in the InN surface layer, and the structure inversion asymmetry (SIA)-dominant mechanism indicates a great possibility for the manipulation of spin splitting, which would undoubtedly benefit further research and applications of spintronics.

Zhang, Z.; Zhang, R.; Xie, Z. L.; Liu, B.; Li, M.; Fu, D. Y.; Fang, H. N.; Xiu, X. Q.; Lu, H.; Zheng, Y. D.; Chen, Y. H.; Tang, C. G.; Wang, Z. G.

2009-07-01

24

Observation and calculation of vibrational circular birefringence: a new form of vibrational optical activity.  

PubMed

We report the first mid-infrared observation of vibrational circular birefringence (VCB) arising from individual chiral molecules. VCB can also be called vibrational optical rotatory dispersion (VORD) and is the Kramers-Kronig transform of vibrational circular dichroism (VCD). The method of measurement involves a simple change in the optical set-up and electronic processing of a VCD spectrometer such that the VCB spectrum appears at twice the polarization modulation frequency as a pseudo vibrational linear dichroism (VLD) spectrum. VCB spectra are also calculated with density function theory (DFT) for the first time using a commercially available program for rotational strengths where the calculated intensities are convolved with the real, dispersive part of a normalized complex Lorentzian lineshape rather than the imaginary, absorptive part, normally used for IR and VCD intensity calculations. Comparison of the measured and calculated VCB, VCD, and IR spectra of (+)-R-limonene and (-)-S-alpha-pinene show close agreement and confirm the validity of the new VCB measurements. PMID:20034018

Lombardi, Rosina A; Nafie, Laurence A

2009-01-01

25

Nudiviruses and other large, double-stranded circular DNA viruses of invertebrates: New insights on an old topic  

Microsoft Academic Search

Nudiviruses (NVs) are a highly diverse group of large, circular dsDNA viruses pathogenic for invertebrates. They have rod-shaped and enveloped nucleocapsids, replicate in the nucleus of infected host cells, and possess interesting biological and molecular properties. The unassigned viral genus Nudivirus has been proposed for classification of nudiviruses. Currently, the nudiviruses comprise five different viruses: the palm rhinoceros beetle virus

Yongjie Wang; Johannes A. Jehle

2009-01-01

26

Psi-type circular dichroism of large molecular aggregates. III. Calculations  

SciTech Connect

Computations have been carried out to determine how the magnitude and shape of the polymer and salt induced (psi)-type CD spectra depend on the structural properties of a collection of randomly oriented large chiral aggregates. Uniaxial polarizable groups located at the cubic lattice points have been used to model the aggregates. The structure of the model is similar to that of a cholesteric liquid crystal. All computations have been carried out for the case of polarizable groups possessing only one electronic transition between 200 and 320 nm. It is found that the radiation and intermediate couplings between the chromophores in the aggregate which are neglected in previous theories play an important role in determining the shape and magnitude of the psi-type CD spectrum. It is shown that when these couplings are included, only three-dimensional large chiral aggregates show huge and nonconservative psi-type CD spectra. It is shown that the magnitude of the psi-type CD spectrum is controlled by the volume, the chromophore density, and the pitch of the aggregate, while the shape of the psi-type CD spectrum is determined mostly by the pitch and the handedness of an aggregate. When the pitch is close to the center of the absorption band of the chromophore in the aggregate the most distorted (least conservative) psi-type CD spectrum is obtained. The CD spectra of aggregates with opposite handedness are mirror images of each other. It is shown that a rotationally disordered collection of chiral aggregates cannot give rise to a selective reflection of one circular polarization over the other as shown by liquid crystals. The results obtained confirm the theoretical predictions of the two previous papers in this series.

Kim, M.; Ulibarri, L.; Keller, D.; Maestre, M.F.; Bustamante, C.

1986-03-15

27

An observational view of large scale structure  

NASA Technical Reports Server (NTRS)

A summary of recent observations of galaxy clustering is presented, including a brief review of redshift maps and galaxy clustering statistics. Simple arguments are presented that argue the underlying mass fluctuations are most likely associated with a clustering scale no larger than that of individual galaxies. The acceleration of the local group from the comoving frame of the universe and its connection to the microwave dipole anisotropy are also discussed. A final topic for consideration is the existence of large voids and clusters, and whether they are consistent with Gaussian initial conditions. The extreme size and depth of the Bootes void, if real, do present a puzzle. Finally, future directions for observational study of large scale structure are discussed.

Davis, Marc

1986-01-01

28

GEOMECHANICAL OBSERVATIONS DURING THE LARGE BLOCK TEST  

SciTech Connect

This paper presents an overview of the geomechanical studies conducted at the Large Block Test at Fran Ridge, near Yucca Mountain, Nevada. The 3-dimensional geomechanical response of the rock to heating is being monitored using instrumentation mounted in boreholes and on the surface of the block. Results show that thermal expansion of the block began a few hours after the start of heating, and is closely correlated with the thermal history. Horizontal expansion increases as a linear function of height. Comparison of observed deformations with continuum simulations shows that below the heater plane deformation is smaller than predicted, while above the heater plane, observed deformation is larger than predicted, and is consistent with opening of vertical fractures. Fracture monitors indicate that movement on a large horizontal fracture is associated with hydrothermal behavior.

STEPHEN C. BLAIR AND STEPHANIE A. WOOD

1998-04-10

29

Modeling Large Radar Observations of Meteors  

NASA Astrophysics Data System (ADS)

Despite decades of research, many questions on the global flux of meteoroids at Earth remain unanswered. We see large radar observations of meteors taken at the Arecibo, Jicamarca, ALTAIR, EISCAT and other facilities as a valuable tool for answering these questions. To improve our understanding of meteor radar observations, we model both the origin of head echo reflections and non-specular trails. To study the non-specular trails, we conducted plasma simulations demonstrating that meteor trails are unstable to growth of Farley-Buneman gradient-drift (FBGD) waves. These waves rapidly become turbulent and generate large B-field aligned irregularities (FAI) which result in radar reflections called non-specular meteor trails. To understand the head echoes (reflections from the leading edge of the meteor plasma), we model the ablation and ionization processes that create meteors. Combining these models allows us to follow meteor evolution from ablation and ionization to diffusion into the ionosphere. We will present results from this model showing that we can reproduce many aspects of these large radar observations, allowing us to better interpret meteoroid properties such as number, mass, velocity, and provide some composition information.

Dyrud, L.; Oppenheim, M.; Close, S.; Ray, L.; Denney, K.

2004-05-01

30

Observations of large transient magnetospheric electric fields  

NASA Technical Reports Server (NTRS)

Transient electric field events were observed with the long, double probe instrumentation carried by the IMP-6 satellite. Nine, clearly defined, exceptionally large amplitude events are presented here. The events are observed in the midnight sector at geocentric distances 3.5 to .5.5 R sub e at middle latitudes within a magnetic L-shell range of 4.8 to 7.5. They usually have a total duration of one to several minutes, with peak power spectra amplitudes occurring at a frequency of about 0.3 Hz. The events occur under magnetically disturbed conditions, and in most cases they can be associated with negative dH/dt excursions at magnetic observatories located near the foot of the magnetic field line intersecting IMP-6. The magnetospheric motions calculated for these electric fields indicated a quasi-stochastical diffusive process rather than the general inward magnetospheric collapsing motion expected during the expansive phases of auroral substorm activity.

Aggson, T. L.; Heppner, J. P.

1977-01-01

31

Beam Synthesis Techniques for Large Circular Arrays with Many Directive Elements.  

National Technical Information Service (NTIS)

A method is developed which permits the synthesis of a pencil beam for a circular array with an arbitrary number of directive elements. A desired pattern specified in both the azimuth and the elevation direction is approximated in the least-mean-square-er...

D. K. Cheng

1969-01-01

32

Nonlinear torsional vibration of a circular cylindrical piezoelectric rod with relatively large shear deformation.  

PubMed

We show that, in a circular cylindrical rod, torsional modes are coupling to extension when the shear deformation associated with the torsional modes is no longer infinitesimal. A set of a couple equations is derived with which the effect of extension on the torsional frequency is examined. The results are useful to the understanding and design of devices operating with torsional modes. PMID:17718339

Yang, Jiashi

2007-07-01

33

Large deflections of circular isotropic membranes subjected to arbitrary axisymmetric loading  

NASA Technical Reports Server (NTRS)

Circular membranes with fixed peripheral edges, subjected to arbitrary axisymmetric loading are analyzed. A single governing differential equation in terms of radial stress is used. This nonlinear governing equation is solved using the finite difference method in conjunction with Newton-Raphson method. Three loading cases, namely (1) uniformly loaded membrane, (2) a membrane with uniform load over an inner portion, and (3) a membrane with ring load, are analyzed. Calculated central displacement and the central and edge radial stresses for uniformly loaded membrane, agree extremely well with the classical solution.

Kelkar, A.; Elber, W.; Raju, I. S.

1984-01-01

34

Wind tunnel testing of yawed and inclined circular cylinders in the context of field observations of stay-cable vibrations  

Microsoft Academic Search

To assist the understanding of wind- and rain–wind-induced stay-cable vibrations observed in a field, sectional cable models were tested in the wind tunnel. Circular cylinders with different spatial orientations were tested to investigate the effects of cable inclination and wind direction on the excitation mechanism. The dynamic responses of the cylinders over different reduced velocity ranges were compared. In conjunction

Delong Zuo; Nicholas P. Jones

2009-01-01

35

VLBI observations of 3C 345 and NRAO 512 in right and left circular polarization. [quasars  

NASA Technical Reports Server (NTRS)

In October 1975, the radio telescopes of the Haystack, National Radio Astronomy, and Owens Valley Radio Observatories were used as an interferometer to monitor, at 8 GHz, the right and left circularly polarized radiation emitted by the quasars 3C 345 and NRAO 512. The data for each polarization are used separately to estimate several parameters describing a model of the fine structure of the radio brightness of 3C 345 and, subsequently, the angular separation between 3C 345 and NRAO 512. The results for the two polarizations are in approximate agreement, indicating that to the limit of resolution about 0.5 milliarcsec), the fourth Stokes parameter, V, is not significantly different from zero within the compact components of these radio sources. The corresponding quantitative limits on the degree of circular polarization are 0.08 + or - 0.07 for 3C 345 and 0.01 + or - 0.08 for NRAO 512.

Menyuk, C. R.; Shapiro, I. I.; Wittels, J. J.; Hinteregger, H. F.; Knight, C. A.; Rogers, A. E. E.; Whitney, A. R.; Clark, T. A.; Hutton, L. K.

1978-01-01

36

Large-area broad band saturable Bragg reflectors using oxidized AlAs in the circular and inverted mesa geometries  

NASA Astrophysics Data System (ADS)

A semiconductor Saturable Bragg Reflector (SBR) is a mirror structure comprising alternating layers of high and low refractive index materials with an incorporated saturable absorber. SBRs can be used to initiate and sustain ultra-short pulses in various laser systems. In order to form ultra-short pulses, SBRs with high reflectivity over a broad wavelength range are required. Furthermore, large-area SBRs facilitate easy integration in a laser cavity. One of the key elements for the realization of broad band SBRs is the development of the thermal oxidation process that creates buried low-index AlxOy layers over large areas. The design, fabrication, characterization, and implementation of broad band, high index contrast III-V/AlxOy SBRs in the form of circular mesas, as well as inverted mesa structures, is presented.

Nabanja, Sheila P.; Kolodziejski, Leslie A.; Petrich, Gale S.; Sander, Michelle Y.; Morse, Jonathan L.; Shtyrkova, Katia; Ippen, Erich P.; Kärtner, Franz X.

2013-04-01

37

Launch window analysis of satellites in high eccentricity or large circular orbits  

NASA Technical Reports Server (NTRS)

Numerical methods and computer programs for studying the stability and evolution of orbits of large eccentricity are presented. Methods for determining launch windows and target dates are developed. Mathematical models are prepared to analyze the characteristics of specific missions.

Renard, M. L.; Bhate, S. K.; Sridharan, R.

1973-01-01

38

Circular Coinduction  

NASA Technical Reports Server (NTRS)

Circular coinduction is a technique for behavioral reasoning that extends cobasis coinduction to specifications with circularities. Because behavioral satisfaction is not recursively enumerable, no algorithm can work for every behavioral statement. However. algorithms using circular coinduction can prove every practical behavioral result that we know. This paper proves the correctness of circular coinduction and some consequences.

Rosu, Grigore; Goguen, Joseph; Norvig, Peter (Technical Monitor)

2001-01-01

39

Solving POMDPs with Continuous or Large Discrete Observation Spaces  

Microsoft Academic Search

We describe methods to solve partially observable Markov decision processes (POMDPs) with con- tinuous or large discrete observation spaces. Real- istic problems often have rich observation spaces, posing significant problems for standard POMDP algorithms that require explicit enumeration of the observations. This problem is usually approached by imposing an a priori discretisation on the obser- vation space, which can be

Jesse Hoey; Pascal Poupart

2005-01-01

40

Large eddy simulations of a circular orifice jet with and without a cross-sectional exit plate  

NASA Astrophysics Data System (ADS)

The effect of a cross-sectional exit plane on the downstream mixing characteristics of a circular turbulent jet is investigated using large eddy simulation (LES). The turbulent jet is issued from an orifice-type nozzle at an exit Reynolds number of 5×104. Both instantaneous and statistical velocity fields of the jet are provided. Results show that the rates of the mean velocity decay and jet spread are both higher in the case with the exit plate than without it. The existence of the plate is found to increase the downstream entrainment rate by about 10% on average over the axial range of 8–30de (exit diameter). Also, the presence of the plate enables the formation of vortex rings to occur further downstream by 0.5–1.0de. A physical insight into the near-field jet is provided to explain the importance of the boundary conditions in the evolution of a turbulent jet. In addition, a method of using the decay of the centreline velocity and the half-width of the jet to calculate the entrainment rate is proposed.

Zhang, Jian-Peng; Xu, Min-Yi; Mi, Jian-Chun

2014-04-01

41

Analysis of failure mechanisms observed in axial collapse of thin-walled circular fibreglass composite tubes  

Microsoft Academic Search

Theoretical analysis of the failure mechanism of the stable mode of collapse of thin-walled fibreglass composite tubes under static axial compression, based on experimental observations and taking into account all possible energy absorbing mechanisms developed during the process, is reported. Crushing loads and the energy absorbed are theoretically predicted. The proposed theoretical model was experimentally verified for various composite materials

A. G. Mamalis; D. E. Manolakos; G. A. Demosthenous; M. B. Ioannidis

1996-01-01

42

Genome Analysis of a Glossina pallidipes Salivary Gland Hypertrophy Virus Reveals a Novel, Large, Double-Stranded Circular DNA Virus?  

PubMed Central

Several species of tsetse flies can be infected by the Glossina pallidipes salivary gland hypertrophy virus (GpSGHV). Infection causes salivary gland hypertrophy and also significantly reduces the fecundity of the infected flies. To better understand the molecular basis underlying the pathogenesis of this unusual virus, we sequenced and analyzed its genome. The GpSGHV genome is a double-stranded circular DNA molecule of 190,032 bp containing 160 nonoverlapping open reading frames (ORFs), which are distributed equally on both strands with a gene density of one per 1.2 kb. It has a high A+T content of 72%. About 3% of the GpSGHV genome is composed of 15 sequence repeats, distributed throughout the genome. Although sharing the same morphological features (enveloped rod-shaped nucleocapsid) as baculoviruses, nudiviruses, and nimaviruses, analysis of its genome revealed that GpSGHV differs significantly from these viruses at the level of its genes. Sequence comparisons indicated that only 23% of GpSGHV genes displayed moderate homologies to genes from other invertebrate viruses, principally baculoviruses and entomopoxviruses. Most strikingly, the GpSGHV genome encodes homologues to the four baculoviral per os infectivity factors (p74 [pif-0], pif-1, pif-2, and pif-3). The DNA polymerase encoded by GpSGHV is of type B and appears to be phylogenetically distant from all DNA polymerases encoded by large double-stranded DNA viruses. The majority of the remaining ORFs could not be assigned by sequence comparison. Furthermore, no homologues to DNA-dependent RNA polymerase subunits were detected. Taken together, these data indicate that GpSGHV is the prototype member of a novel group of insect viruses.

Abd-Alla, Adly M. M.; Cousserans, Francois; Parker, Andrew G.; Jehle, Johannes A.; Parker, Nicolas J.; Vlak, Just M.; Robinson, Alan S.; Bergoin, Max

2008-01-01

43

Sign reversal of a large circularly polarized luminescence signal by the twisting motion of a bidentate ligand.  

PubMed

This work demonstrates sign reversal of large circularly polarized luminescence (CPL) signal based on the hinge-like twisting motion of a bidentate ligand, 3,3-bis(diphenylphosphoryl)-2,2-bipyridine (BIPYPO), in a cis-trans isomerization of chiral europium(III) complexes. X-ray diffraction analysis revealed that twisting motion of BIPYPO provides s-cis and s-trans geometries of a chiral Eu(III) complex containing either tris[3-(trifluoromethylhydroxymethylene)-(+)-camphorate] (D-1) or tris[3-(heptafluoropropylhydroxymethylene)-(+)-camphorate] (D-2). The s-cis Eu(III) complexes show eight-coordinate geometry around the Eu(III) ion, in which the chelate between the phosphoryl oxygen and the Eu(III) ion forces the s-cis geometry of BIPYPO. In contrast, the phosphorus-nitrogen interaction provides a conformational lock for the s-trans geometry of the BIPYPO ligand, inducing a quasi-seven-coordinate Eu(III) complex. The difference in coordination geometry causes the sign change of the CPL signals between the s-cis and s-trans isomers, whereby the s-cis and s-trans isomers of Eu(III) complexes exhibit the positive and negative CPL signals, respectively, for the (5) D0 ?(7) F1 transition. The proportion of the s-trans-D-1 against s-cis-D-1 increases upon changing the solvent from [D3 ]acetonitrile to [D6 ]acetone, inducing a sign change of the CPL signals. The complexes D-1 and D-2 show a biexponential decay with two different lifetimes, suggesting two emitting species, that is, the s-cis and s-trans isomers of Eu(III) complexes. In both cases, the proportions of the longer lifetime components (?1 ) decrease and instead the shorter lifetime components (?2 ) increase upon changing the solvent from [D3 ]acetonitrile to [D6 ]acetone. PMID:24958164

Yuasa, Junpei; Ueno, Hiroshi; Kawai, Tsuyoshi

2014-07-01

44

Observability Analysis Of Large Bus - System Using Matlab Simulation  

NASA Astrophysics Data System (ADS)

This methodology provides a numerical approach to observability analysis. The approach enables observability analysis and restoration (pseudo-measurement selection) in a simple way with iteration, via triangular factorization of the jacobian matrix of the weight least square state estimator. An algorithm for precious measurement of topological observability in large bus - system state estimation has been proposed. The algorithm is based on observation that the search for a spanning tree of full rank. We use observability algorithm and state estimation algorithm. We use the Mat lab to obtain the various graphs of bus systems. By using simulation method of bus system we analyze the observability.

Gyanendrasingh, Er.; Pratibhatiwari, Prashant Kumar; Srivastava, Tushar

2013-03-01

45

Expanded Very Large Array Observations of the 6035 MHz OH Masers in ON 1  

NASA Astrophysics Data System (ADS)

This Letter reports on initial Expanded Very Large Array (EVLA) observations of the 6035 MHz masers in ON 1. The EVLA data are of good quality, lending confidence in the new receiver system. Nineteen maser features, including six Zeeman pairs, are detected. The overall distribution of 6035 MHz OH masers is similar to that of the 1665 MHz OH masers. The spatial resolution is sufficient to unambiguously determine that the magnetic field is strong (about -10 mG) at the location of the blueshifted masers in the north, consistent with Zeeman splitting detected in 13441 MHz OH masers in the same velocity range. Left- and right-circularly polarized ground-state features dominate in different regions in the north of the source, which may be due to a combination of magnetic field and velocity gradients. The combined distribution of all OH masers toward the south is suggestive of a shock structure of the sort previously seen in W3(OH).

Fish, Vincent L.

2007-11-01

46

Performance Prediction of Large-Diameter Circular Saws Based on Surface Hardness Tests for Mugla (Turkey) Marbles  

Microsoft Academic Search

Surface hardness tests such as Shore hardness (SH) and Schmidt hammer rebound hardness (SR) may provide a quick and inexpensive\\u000a measure of rock hardness, which may be widely used for estimating the mechanical properties of rock material such as strength,\\u000a sawability, drillability and cuttability. In the marble industry, circular sawing with diamond sawblades constitutes a major\\u000a cost in the processing.

Avni Güney

2011-01-01

47

Observation of a warped helical spin texture in Bi2Se3 from circular dichroism angle-resolved photoemission spectroscopy.  

PubMed

A differential coupling of topological surface states to left- versus right-circularly polarized light is the basis of many optospintronics applications of topological insulators. Here we report direct evidence of circular dichroism from the surface states of Bi(2)Se(3) using laser-based time-of-flight angle-resolved photoemission spectroscopy. By employing a novel sample rotational analysis, we resolve unusual modulations in the circular dichroism photoemission pattern as a function of both energy and momentum, which perfectly mimic the predicted but hitherto unobserved three-dimensional warped spin texture of the surface states. By developing a microscopic theory of photoemission from topological surface states, we show that this correlation is a natural consequence of spin-orbit coupling. These results suggest that our technique may be a powerful probe of the spin texture of spin-orbit coupled materials in general. PMID:22181776

Wang, Y H; Hsieh, D; Pilon, D; Fu, L; Gardner, D R; Lee, Y S; Gedik, N

2011-11-11

48

CARMA Observations of Large Organic Molecules in Orion-KL  

NASA Astrophysics Data System (ADS)

We have conducted high resolution, Combined Array for Research in Millimeter-Wave Astronomy (CARMA), 1mm observations of organic molecules in the high mass star forming region Orion-KL. This region is known to have oxygen/nitrogen chemical differentiation and can tell us much about the processes that create these molecules in the interstellar medium. We have observed a wide variety of molecular species (both O-bearing and N-bearing), including ethyl cyanide [C2H5CN], vinyl cyanide [C2H3CN], ethanol [C2H5OH], methanol [CH3OH], methyl formate [HCOOCH3] dimethyl ether [(CH3)2O], and acetone [(CH3)2CO] in order to study the chemistry of the regions. Our observations have shown that in Orion-KL the large N-bearing species are concentrated in small hot, dense clumps while most of the large O-bearing species are more widespread. An exception is (CH3)2CO, which is compact and only present in regions where both large N-bearing and O-bearing species are present. We present the results of these CARMA observations and their implications for astrochemistry.

Friedel, Douglas N.; Snyder, L. E.

2007-12-01

49

Laser mass spectrometry with circularly polarized light: circular dichroism of molecular ions.  

PubMed

In recent experiments of resonance-enhanced laser ionization, large differences between circular dichroism measured for molecular and fragment ions were found by several research groups for different molecular systems. In the case of 3-methylcyclopentanone (3-MCP) we attributed this effect to a large circular dichroism of the molecular ion. In the work presented here, this effect in 3-MCP is studied by ion spectroscopy, by varying the neutral intermediate excited state involved in resonance-enhanced multiphoton ionization (REMPI) and by performing REMPI-induced measurements of circular dichroism at different laser pulse energies. It turns out that the dynamics of structural changes in the ionic ground state strongly influences the observed ionic circular dichroism. PMID:23090920

Logé, Christoph; Boesl, Ulrich

2012-12-21

50

On tidal tilt corrections to large ring laser gyroscope observations  

NASA Astrophysics Data System (ADS)

With the fast development of the large ring laser gyroscope (RLG) technology in the last decades, promising applications in geophysics and geodesy (e.g. observations of high-frequency variations of Earth's rotation, Earth's tide tilt and seismic waves) have been realized by various groups with currently running large RLGs. In this letter, we point out that in a large number of previous tilt correction models a significant term is missing. This term is related with the Shida number l2 (called l2-term in the following) and has a contribution, which is comparable with that from high-frequency Earth rotation variations due to ocean tides, to the Sagnac frequency record of RLGs. This term has to be removed (as part of the tilt correction) from the raw data so that RLGs can efficiently be employed as Earth's rotation detectors.

Tian, Wei

2014-01-01

51

Large angular scale anisotropy of the CBR : LOBE DMR observations  

Microsoft Academic Search

Observations of the Cosmic Microwave Background Radiation (CM BR) have put the standard model of cosmology, the Big Bang, on firm footing and provide tests of various ideas of large scale structure formation and the origin of the universe. Ground-based measurements of the cosmic background radiation are hampered by emission from atmospheric O2 and H2O molecules. This has forced precision

George F. Smoot

1995-01-01

52

Large Dayside Geosynchronous Magnetic Field Compressions: Model Expectations vs. Observations  

Microsoft Academic Search

The geosynchronous magnetic field has been measured routinely for nearly 40 years. It responds to the magnetosphere's major current systems including the magnetopause current, the ring current, field-aligned currents, and the tail current. As a consequence, these measurements are valuable for probing many aspects of solar wind-magnetosphere coupling. In this presentation we will show puzzling observations of large-amplitude dayside magnetic

H. J. Singer; M. J. Wiltberger; T. G. Onsager; P. T. Loto'Ainu

2008-01-01

53

Observation of inclusive. omega. production at large transverse momentum  

SciTech Connect

We have observed the production of ..omega.. mesons at large transverse momentum produced in 200-GeV/c pBe interactions. The ratio of inclusive production of ..omega.. to ..pi../sup 0/ at transverse momenta above 2.2 GeV/c is 0.44 +- 0.08 near x=0. The upper limit for eta' to eta production is <1.4 in the same kinematic region.

Donaldson, G.J.; Gordon, H.A.; Lai, K.; Barnes, A.V.; Mellema, D.J.; Tollestrup, A.V.; Walker, R.L.; Dahl, O.I.; Johnson, R.A.; Ogawa, A.; Pripstein, M.; Shannon, S.R.

1980-02-01

54

GPS TEC Observations of Storm Time Large Amplitude ULF Pulsations  

NASA Astrophysics Data System (ADS)

Decades ago Davies and Hartmann [1976] demonstrated the ability to detect ULF waves by monitoring the carrier phase of trans-ionospheric radio waves (from geosynchronous satellites). This study was followed by several theoretical and modeling studies that addressed the physical mechanisms behind the observations. However, since then there have been relatively few studies that have utilized this observational technique to advance our understanding of ULF waves or to fully understand the mechanisms that lead to the observed variations in electron content. Here, we investigate large amplitude (> 500 nT) ULF pulsations observed during the October 31, 2003 storm using GPS TEC. This event has been recently examined by Pilipenko et al. using the EISCAT radar facility and we find that the observed variations in GPS TEC closely match the variations in electron density observed by the radar. Furthermore, we show that the GPS TEC observations provide the ability to monitor the two dimensional structure of these waves on a global scale; a capability that compliments similar capabilities of networks of ground-based magnetometers. The combination of these two data sets may significantly contribute to our understanding of the associated field-aligned current systems.

Murr, D.; Nikoukar, R.; Pilipenko, V.; Bust, G. S.

2012-12-01

55

Observations of large biologically important interstellar and cometary molecules  

NASA Astrophysics Data System (ADS)

There has been much interest in recent years in astronomical searches for large biologically-important molecules which possess known millimeter wavelength transitions. Biologically-important species include amino acids, possible precursors to amino acids, and other biologically interesting molecules. This thesis continued the search for large biomolecules towards hot molecular cores (HMCs) associated with ultracompact (HC) HII regions and comets. First, we followed up the detection of acetic acid (CH3COOH) towards Sgr B2(N-LMH) by performing a survey of transitions with large line strengths toward several hot core regions. There has been great interest in searching a variety of star forming regions for interstellar acetic acid because it shares common structural elements with glycine (NH2CH2 COOH), the simplest amino acid, and because it is an isomer to both methyl formate (HCOOCH3) and glycolaldehyde (CH2OHCHO). In our survey we detected two new sources of acetic acid and placed constraints on the detectability of acetic acid elsewhere with current generation radio telescopes. Second, in order to study the physical conditions that lead to the formation of large biomolecules toward HMCs, we observed the hot core regions W51 e1 and e2 using the symmetric top species methyl cyanide (CH3CN). Symmetric tops have properties that make them ideal probes of hot molecular cores. Thus, we obtained better measurements of the physical conditions present in these regions and a better understanding of the chemistry that forms large molecular species. Third, using multiply degenerate transitions in both the 3 mm and 1 mm wavelength regions, we conducted the most extensive survey for the elusive biomolecule urea [(NH2)2CO] toward the high mass hot molecular core sources, Sgr B2(N-LMH) and W51 e2. As a result, our spectral line data support the first detection of interstellar urea toward Sgr B2(N-LMH). Finally, we discuss the observational results of an extensive survey for biologically interesting molecules toward Comet Hale-Bopp (1995 O1). To date, no large biomolecule has ever been reported toward a comet with an array. The importance of detecting large biomolecules in comets is that in doing so will tie together the chemistry in HMCs with cometary chemistry.

Remijan, Anthony John

56

Observation of Large Amplitude Electromagnetic Wave at the Dipolarization Front  

NASA Astrophysics Data System (ADS)

Various plasma waves have been observed around the dipolarization fronts (DFs) and the rarefaction regions behind the fronts. It is widely accepted that these waves not only play crucial roles in modulating microphysics at the DF but also may potentially affect the large-scale dynamics of the magnetotail. In this paper we present a THEMIS observation of large amplitude electromagnetic waves right at the DF during a substorm expansion phase. The DF was embedded in a tailward and duskward flow at around X= -9 RE. The Doppler shifted frequency of the wave is between the local ion cyclotron frequency and lower hybrid frequency. The wave propagated highly oblique to the ambient magnetic field (~100o), with phase speed about 380 km/s, larger than the ion drift speed, and the corresponding wavelength is about 540 km ~0.8?i. The major magnetic field fluctuation is along the background magnetic field. Electric potential associated with the wave reaches up to half of the electron temperature, indicating the nonlinear feature of the wave. We suggest that the wave was excited through the coupling between the long wavelength electromagnetic lower hybrid drift wave, and the ion Bernstein mode driven by proton ring distribution. The wave is able to provide significant anomalous resistivity at the front, with major contribution from electric field fluctuations. Due to the large and steepened magnetic field fluctuations, the waves may breakup into several isolated waves resembling multiple DFs frequently observed in the near-Earth region. Its effects on the electron pitch angle scattering and energy diffusion are discussed.

Zhou, M.; Huang, S.; Pang, Y.; Deng, X.; Yuan, Z.; Li, H.

2013-12-01

57

Infrasonic observations of large-scale HE events  

NASA Technical Reports Server (NTRS)

The Los Alamos Infrasound Program has been operating since about mid-1982, making routine measurements of low frequency atmospheric acoustic propagation. Generally, the authors work between 0.1 Hz to 10 Hz; however, much of the work is concerned with the narrower range of 0.5 to 5.0 Hz. Two permanent stations, St. George, UT, and Los Alamos, NM, have been operational since 1983, collecting data 24 hours a day. For the purposes of this discussion, the authors concentrate on their measurements of large, high explosive (HE) events at ranges of 250 km to 5330 km. Because their equipment is well suited for mobile deployments, they can easily establish temporary observing sites for special events. The measurements are from the permanent sites, as well as from various temporary sites. A few observations that are typical of the full data set are given.

Whitaker, Rodney W.; Mutschlecner, J. Paul; Davidson, Masha B.; Noel, Susan D.

1990-01-01

58

Observations of large infragravity wave runup at Banneg Island, France  

NASA Astrophysics Data System (ADS)

On Banneg Island, France, very high water-level events (6.5 m above the astronomical tide) have been observed on the western cliff, exposed to large swells from the North Atlantic. The analysis of hydrodynamic measurements collected during the storm of 10 February 2009 shows unusually high (over 2 m) infragravity wave runup events. By comparing runup observations to measurements in approximately 7 m of water and numerical simulations with a simplified nonlinear model, two distinct infragravity bands may be identified: an 80 s infragravity wave, produced by nonlinear shoaling of the storm swell; and a 300 s wave, trapped on the intertidal platform of the island and generating intermittent, low-frequency inundation. Our analysis shows that the 300 s waves are a key component of the extreme water levels recorded on the island.

Sheremet, Alex; Staples, Tracy; Ardhuin, Fabrice; Suanez, Serge; Fichaut, Bernard

2014-02-01

59

Very Large Array (VLA) observations of coronal loops  

NASA Technical Reports Server (NTRS)

Advances in ground based Very Large Array (VLA) observations of the Sun, and how they complement and extend EUV and X-ray observations from space are reviewed. The VLA provides high resolution, full disk images that include hot, dense coronal loops within individual active regions (at 20 cm), and cooler, higher, more extended structures (at 90 cm) that can connect widely separated active regions, describe high lying noise storms, or act as a transition sheath between cool dark filaments and the hot enveloping corona. VLA images of both cool and hot corona loops can be compared with data from most of the SOHO (Solar and Heliospheric Observatory) instruments, thereby enhancing the scientific return of the SOHO mission beyond that expected from using its instruments alone.

Lang, Kenneth R.

1992-01-01

60

Large Amplitude Whistlers Observed by Wind-Waves  

NASA Astrophysics Data System (ADS)

Stimulated by the discovery of large amplitude whistlers by STEREO S/Waves, (Cattell et al, Geophys. Res. Lett 2008 ) we have searched for similar events in the data from Wind-Waves. Although Wind was primarily intended to monitor the solar wind, the spacecraft spent 47 hours inside 5 RE and 431 hours inside 10 RE during the 8 years that it orbited the earth. Five episodes where found when whistlers had amplitudes comparable to those of Cattell et al. Unlike STEREO, the Waves experiment also had a search coil, so magnetic measurements are available, either only one component, or in rare cases, all three components. Generally, the results confirm the interpretations of Cattell et al, As they found, such whistlers occur near the edge of the plasmasphere, but the Wind-Waves observations show that they occur at a wide range of local times. Large amplitude whistlers are frequently preceded or followed by episodes of large amplitude very narrow solitary waves (100 mV/m), presumed to be electron holes.

Kellogg, P. J.; Cattell, C. A.; Monson, S. J.; Goetz, K.

2008-12-01

61

Experimental observation of very large magnetoconductance in microbial nanowires  

NASA Astrophysics Data System (ADS)

Microbial nanowires are 2-5 nm-wide conductive proteinous pili filaments secreted by some bacteria, which can grow tens of micrometers long and may serve as a conduit for long-distance electron transport. Our previous studies demonstrated that pili of Geobacter sulfurreducens exhibit properties akin to disordered metals, and indicated a temperature-driven crossover from the regime of weak localization (WL) to strong localization (SL). Here we report a very large positive magnetoconductance (MC), up to 10,000 %, at 300K. MC increased exponentially with magnetic field. A crossover from positive MC (WL regime) to negative MC (SL) was observed at ˜ 280K when the localization and the phase-breaking lengths are expected to become comparable. We attribute positive MC to destruction of the quantum interference of delocalized electron wavefunctions and negative MC to shrinkage of the localized electron wavefunctions due to applied magnetic field, which is consistent with the temperature dependence of conductivity.

Malvankar, Nikhil; Vargas, Madeline; Lovley, Derek; Tuominen, Mark

2011-03-01

62

Evaluation of forest fire models on a large observation database  

NASA Astrophysics Data System (ADS)

This paper presents the evaluation of several fire propagation models using a large set of observed fires. The observation base is composed of 80 Mediterranean fire cases of different sizes, which come with the limited information available in an operational context (burned surface and approximative ignition point). Simulations for all cases are carried out with 4 different front velocity models. The results are compared with several error scoring methods applied to each of the 320 simulations. All tasks are performed in a fully automated manner, with simulations ran as first guesses with no tuning for any of the models or cases. This approach leads a wide range of simulation performance, including some of the bad simulation results to be expected in an operational context. Regardless the quality of the input data, it is found that the models can be ranked based on their performance and that the most complex models outperform the more empirical ones. Data and source code used for this paper are freely available to the community.

Filippi, J.-B.; Mallet, V.; Nader, B.

2014-05-01

63

Experimental study and large eddy simulation of turbulent flow around tube bundles composed of wavy and circular cylinders  

Microsoft Academic Search

This paper presents the results of an investigation on the effects of wavy cylindrical tubes in a staggered heat exchanger tube bundle. Experimental measurements and large eddy simulation (LES) technique were used to study the turbulent flow characteristics in a staggered tube bundle arrangement at a sub-critical Reynolds number of Re=7500. The aim of this investigation is to compare the

K. Lam; Y. F. Lin; L. Zou; Y. Liu

2010-01-01

64

Observational evidence for large-scale current sheets  

NASA Astrophysics Data System (ADS)

One of the most significant predictions of the catastrophe model of solar eruptions developed by Lin Forbes (2000) that a current sheet forms following the onset of the eruption. Various modes of plasma turbulence as a result of plasma instabilities are invoked inside the current sheet, yielding fast dissipation of the magnetic field, namely magnetic reconnection, through the sheet. Because the timescale of reconnection is long compared to the timescale of the onset stage, dissipation of the sheet is slow, so the current sheet is able to become fairly long. The evolution in the global feature of the current sheet is significant constrained by the local Alfven speed, and the internal properties and features of the sheet, on the other hand, are dependent in an apparent way on the development of the turbulence caused by the instabilities. The tearing mode instability among those that may occur in the sheet is the most important one that accounts for the large thickness and high electric resistivity of the current sheet. In the present work, we show a set of events that were observed to develop thick current sheets with several apparent features indicating the progress of the turbulence in the sheet, and the results for the sheet thickness determined by UVCS and LASCO experiments on SOHO, and deduce from these results the effective resistivity that is responsible for the rapid reconnection. We suggest that the high effective resistivity is related to the so-called hyper-resistivity that is produced by the tearing mode.

Lin, Jun

65

FERMI LARGE AREA TELESCOPE OBSERVATIONS OF THE VELA PULSAR  

SciTech Connect

The Vela pulsar is the brightest persistent source in the GeV sky and thus is the traditional first target for new {gamma}-ray observatories. We report here on initial Fermi Large Area Telescope observations during verification phase pointed exposure and early sky survey scanning. We have used the Vela signal to verify Fermi timing and angular resolution. The high-quality pulse profile, with some 32,400 pulsed photons at E {>=} 0.03 GeV, shows new features, including pulse structure as fine as 0.3 ms and a distinct third peak, which shifts in phase with energy. We examine the high-energy behavior of the pulsed emission; initial spectra suggest a phase-averaged power-law index of {gamma} = 1.51{sup +0.05} {sub -0.04} with an exponential cutoff at E{sub c} = 2.9 {+-} 0.1 GeV. Spectral fits with generalized cutoffs of the form e{sup -(E/E{sub c}){sup b}} require b {<=} 1, which is inconsistent with magnetic pair attenuation, and thus favor outer-magnetosphere emission models. Finally, we report on upper limits to any unpulsed component, as might be associated with a surrounding pulsar wind nebula.

Abdo, A. A. [Space Science Division, Naval Research Laboratory, Washington, DC 20375 (United States); Ackermann, M.; Bartelt, J.; Bechtol, K.; Berenji, B.; Blandford, R. D.; Bloom, E. D.; Bogart, J. R. [W. W. Hansen Experimental Physics Laboratory, Kavli Institute for Particle Astrophysics and Cosmology, Department of Physics and Stanford Linear Accelerator Center, Stanford University, Stanford, CA 94305 (United States); Atwood, W. B. [Santa Cruz Institute for Particle Physics, Department of Physics and Department of Astronomy and Astrophysics, University of California at Santa Cruz, Santa Cruz, CA 95064 (United States); Bagagli, R.; Baldini, L.; Bellardi, F.; Bellazzini, R. [Istituto Nazionale di Fisica Nucleare, Sezione di Pisa, I-56127 Pisa (Italy); Ballet, J. [Laboratoire AIM, CEA-IRFU/CNRS/Universite Paris Diderot, Service d'Astrophysique, CEA Saclay, 91191 Gif sur Yvette (France); Band, D. L. [Center for Research and Exploration in Space Science and Technology (CRESST), NASA Goddard Space Flight Center, Greenbelt, MD 20771 (United States); Barbiellini, G. [Istituto Nazionale di Fisica Nucleare, Sezione di Trieste, I-34127 Trieste (Italy); Baring, M. G. [Rice University, Department of Physics and Astronomy, MS-108, P.O. Box 1892, Houston, TX 77251 (United States); Bastieri, D.; Bisello, D. [Istituto Nazionale di Fisica Nucleare, Sezione di Padova, I-35131 Padova (Italy); Baughman, B. M. [Department of Physics, Center for Cosmology and Astro-Particle Physics, The Ohio State University, Columbus, OH 43210 (United States)], E-mail: rwr@astro.stanford.edu, E-mail: massimiliano.razzano@pi.infn.it (and others)

2009-05-10

66

Circular beams.  

PubMed

A very general beam solution of the paraxial wave equation in circular cylindrical coordinates is presented. We call such a field a circular beam (CiB). The complex amplitude of the CiB is described by either the Whittaker functions or the confluent hypergeometric functions and is characterized by three parameters that are complex in the most general situation. The propagation through complex ABCD optical systems and the conditions for square integrability are studied in detail. Special cases of the CiB are the standard, elegant, and generalized Laguerre-Gauss beams; Bessel-Gauss beams; hypergeometric beams; hypergeometric-Gaussian beams; fractional-order elegant Laguerre-Gauss beams; quadratic Bessel-Gauss beams; and optical vortex beams. PMID:18197231

Bandres, Miguel A; Gutiérrez-Vega, Julio C

2008-01-15

67

An Observation Study of a Large Public Accounting Firm  

Microsoft Academic Search

The concern of this inquiry is with management strategy in a large, international public accounting firm. The large accounting firm must deal with a variety of difficult problems in its efforts to grow and remain successful. Borrowing from the terminology of Emery and Trist, the interrelatedness of many of these problems tends to suggest a \\

C. Richard Baker

1977-01-01

68

Importance of c*-h based modes and large amplitude motion effects in vibrational circular dichroism spectra: the case of the chiral adduct of dimethyl fumarate and anthracene.  

PubMed

The role played by the C*-H based modes (C* being the chiral carbon atom) and the large amplitude motions in the vibrational absorption (VA) and vibrational circular dichroism (VCD) spectra is investigated. The example of an adduct of dimethyl fumarate and anthracene, i.e., dimethyl-(+)-(11R,12R)-9,10-dihydro-9,10-ethanoanthracene-11,12-dicarboxylate, and two deuterated isotopomers thereof specially synthesized for this goal, are considered. By comparing the experimental and DFT calculated spectra of the undeuterated and deuterated species, we demonstrate that the C*-H bending, rocking, and stretching modes in the VA and VCD spectra are clearly identified in well defined spectroscopic features. Further, significant information about the conformer distribution is gathered by analyzing the VA and VCD data of both the fingerprint and the C-H stretching regions, with particular attention paid to the band shape data. Effects related to the large amplitude motions of the two methoxy moieties have been simulated by performing linear transit (LT) calculations, which consists of varying systematically the relative positions of the two methoxy moieties and calculating VCD spectra for the partially optimized structures obtained in this way. The LT method allows one to improve the quality of calculated spectra, as compared to experimental results, especially in regard to relative intensities and bandwidths. PMID:24840313

Passarello, Marco; Abbate, Sergio; Longhi, Giovanna; Lepri, Susan; Ruzziconi, Renzo; Nicu, Valentin Paul

2014-06-19

69

A circular twin paradox  

Microsoft Academic Search

In the special relativistic twin paradox presented here, each twin lives on one ring of a counterrotating pair of infinitesimally separated rings, so that the twins travel on the same circular path but in opposite directions. The observers on the ring of one twin should see the clock of the other twin slowed by time dilation, but at each meeting

Maria B. Cranor; Elizabeth M. Heider; Richard H. Price

2000-01-01

70

Observation of coherent diffraction radiation from bunched electrons passing through a circular aperture in the millimeter- and submillimeter-wavelength regions  

NASA Astrophysics Data System (ADS)

Using a short-bunched beam of electrons of 150 MeV, we have generated diffraction radiation from a circular aperture in an aluminum plate in the region of millimeter and submillimeter wavelengths. We have observed superposition of the diffraction radiation and transition radiation from an aluminum mirror. The angular distribution of the observed radiation shows interference of the two radiations. The intensity of the radiation has been observed to be proportional to the square of the beam current. Compared with the theoretical intensity of incoherent radiation, the observed intensity of the radiation from an aperture of 10 mm at the wavelength of 1 mm has been enhanced by a factor of 1.5×108, which is roughly equal to the number of electrons in a bunch. From the observed spectrum, the longitudinal distribution of electrons in a bunch has been derived with a spatial resolution of 0.1 mm, i.e., a temporal resolution of 0.3 ps. (c) 1995 The American Physical Society

Shibata, Yukio; Hasebe, Shigeru; Ishi, Kimihiro; Takahashi, Toshiharu; Ohsaka, Toshiaki; Ikezawa, Mikihiko; Nakazato, Toshiharu; Oyamada, Masayuki; Urasawa, Shigekazu; Yamakawa, Tatsuya; Kondo, Yasuhiro

1995-12-01

71

SEARCH Workshop on Large-Scale Atmosphere/Cryosphere Observations  

NASA Technical Reports Server (NTRS)

The purpose of the workshop held in Seattle during 27-29 November 2001 was to review existing land, sea ice, and atmospheric observations and the prospect for an Arctic System Reanalysis, through white papers, invited speakers, and panels. A major task for SEARCH was to determine how existing observation systems can be best used and enhanced to understand and anticipate the course of the ongoing changes in the Arctic. The primary workshop conclusion is that there is no cohesion among various Arctic disciplines and data types to form a complete observation set of Arctic change; a second workshop conclusion is that present data sets are vastly underutilized in understanding Arctic change; a third conclusion is that a distributed observing system must accommodate a wide range of spatial patterns of variability.

2002-01-01

72

MESSENGER Observations of Large Flux Transfer Events at Mercury  

NASA Technical Reports Server (NTRS)

Six flux transfer events (FTEs) were encountered during MESSENGER's first two flybys of Mercury (MI and M2). For MI the interplanetary magnetic field (IMF) was predominantly northward and four FTEs with durations of 1 to 6 s were observed in the magnetosheath following southward 1M F turnings. The IMF was steadily southward during M2, and an FTE 4 s in duration was observed just inside the dawn magnetopause followed approx.32 s later by a 7-s FTE in the magnetosheath. Flux rope models were fit to the magnetic field data to detem11ne PTE dimensions and flux content The largest FTE observed by MESSENGER had a diameter of approx. 1 R(sub M) (where R(sub M) is Mercury's radius), and its open magnetic field increased the fraction of the surface exposed to the solar wind by 10 - 20 percent and contributed up to approx.30 kV to the cross-magnetospheric electric potential.

Slavin, James A.; Lepping, Ronald P.; Wu, Chin-Chun; Anderson, Brian J.; Baker, Daniel N.; Benna, Mehdi; Boardsen, Scott A.; Killen, Rosemary M.; Korth, Haje; Krimigis, Stamatios M.; McClintock, William E.; McNutt, Ralph L., Jr.; Sarantos, Menelaos; Schriver, David; Solomon, Sean C.; Travnicek, Pavel; Zurbuchen, Thomas H.

2010-01-01

73

Circular RNA is expressed across the eukaryotic tree of life.  

PubMed

An unexpectedly large fraction of genes in metazoans (human, mouse, zebrafish, worm, fruit fly) express high levels of circularized RNAs containing canonical exons. Here we report that circular RNA isoforms are found in diverse species whose most recent common ancestor existed more than one billion years ago: fungi (Schizosaccharomyces pombe and Saccharomyces cerevisiae), a plant (Arabidopsis thaliana), and protists (Plasmodium falciparum and Dictyostelium discoideum). For all species studied to date, including those in this report, only a small fraction of the theoretically possible circular RNA isoforms from a given gene are actually observed. Unlike metazoans, Arabidopsis, D. discoideum, P. falciparum, S. cerevisiae, and S. pombe have very short introns (? 100 nucleotides or shorter), yet they still produce circular RNAs. A minority of genes in S. pombe and P. falciparum have documented examples of canonical alternative splicing, making it unlikely that all circular RNAs are by-products of alternative splicing or 'piggyback' on signals used in alternative RNA processing. In S. pombe, the relative abundance of circular to linear transcript isoforms changed in a gene-specific pattern during nitrogen starvation. Circular RNA may be an ancient, conserved feature of eukaryotic gene expression programs. PMID:24609083

Wang, Peter L; Bao, Yun; Yee, Muh-Ching; Barrett, Steven P; Hogan, Gregory J; Olsen, Mari N; Dinneny, José R; Brown, Patrick O; Salzman, Julia

2014-01-01

74

Observation of EAS using a large water tank  

NASA Astrophysics Data System (ADS)

Using a large water tank (30 m in diameter, 4.5 m in depth) transition of extensive air showers (EAS) was investigated at Taro (200 m above sea level). There are set 150,0.4 sq m proportional counters on the bottom of the water tank. A conventional EAS array of 25 plastic scintillation detectors was arranged within several tens meter from the water tank. A proportional counter (10x10x200 cc x2) is made of a square shaped pipe of iron. Tungsten wire (100 mu m phi) is stretched tight in the center of the counter. A gas mixture of 90% argon and 10% methane is used at 760 mmHg. About 3000 EAS were obtained through 1 m of water since 1984.

Inoue, K.; Sakuyama, H.; Suzuki, N.; Suzuki, T.

1985-08-01

75

Large-scale convection patterns observed by DMSP  

SciTech Connect

The authors present a comprehensive compilation of the average distribution of the electrostatic potential across the high-latitude ionosphere. The averages are compiled from potentials along the satellite path calculated from thermal ion drift data from instrumentation on the Defense Meterological Satellite Program (DMSP) flights 8 and 9 satellites. Data were collected from the DMSP F8 satellite during the period September 1987 to December 1990 and from the DMSP F9 satellite during the period March 1988 to December 1990. The potential distributions are separated by geomagnetic position, season, and orientation of the interplanetary magnetic field (IMF), and then averages of the distributions are calculated. The average potential distributions clearly show the displacement of polar cap convection contours to the dusk or dawk flanks under the influence of the IMF B{sub y} component. The cross-cap potential decreases as IMF B{sub z} changes from southward to northward. The average distributions indicate that the development of more than two convection cells for northward IMF is either uncommon or nonexistent. For IMF B{sub z} > 0 and B{sub z} >{vert_bar}B{sub y}{vert_bar}, a distorted pattern is observed in the average potential distribution, not a four-cell pattern as some previous studies suggest it should be. For all orientations of the IMF, the convection reversal boundary at the poleward edge of the auroral zone is observed in the average distributions to be a rotational boundary. It is not a shear boundary as suggested by some previous investigations. On average, the Harang discontinuity (convection reversal in the auroral zone near midnight) is observed to exist weakly or not at all. When examining individual passes, a strong eastward flow is present sometimes in the region of the Harang discontinuity, especially on the poleward boundary, but not at all times as implied by the Heppner-Maynard model. 39 refs., 9 figs., 2 tabs.

Rich, F.J. [Hanscom Air Force Base, Bedford, MA (United States)] [Hanscom Air Force Base, Bedford, MA (United States); Hairston, M. [Univ. of Texas, Dallas, TX (United States)] [Univ. of Texas, Dallas, TX (United States)

1994-03-01

76

Modelling of Astrophysical Observables for the Very Large Telescope Interferometer  

NASA Astrophysics Data System (ADS)

For a 2, 3 and even 4 telescopes interferometer, the sparse UV coverage will generally not allow to reconstruct the image of the object. The only way to interpret the physical observables (visibility, closure phase and differential phase) is via a model of the object. The Mariotti Center is studying the development of a MODEL software package which will allow the user to implement its own analytic model of the object spatial spectrum, and to compute automatically the maximum likelihood estimates of the model parameters. We describe this module.

Tatulli, Eric; Chelli, Alain; Malbet, Fabien; Duvert, Gilles

2001-05-01

77

FERMI LARGE AREA TELESCOPE OBSERVATION OF SUPERNOVA REMNANT S147  

SciTech Connect

We present an analysis of gamma-ray data obtained with the Large Area Telescope on board the Fermi Gamma-ray Space Telescope in the region around supernova remnant (SNR) S147 (G180.0-1.7). A spatially extended gamma-ray source detected in an energy range of 0.2-10 GeV is found to coincide with SNR S147. We confirm its spatial extension at >5{sigma} confidence level. The gamma-ray flux is (3.8 {+-} 0.6) Multiplication-Sign 10{sup -8} photons cm{sup -2} s{sup -1}, corresponding to a luminosity of 1.3 Multiplication-Sign 10{sup 34} (d/1.3 kpc){sup 2} erg s{sup -1} in this energy range. The gamma-ray emission exhibits a possible spatial correlation with the prominent H{alpha} filaments of SNR S147. There is no indication that the gamma-ray emission comes from the associated pulsar PSR J0538+2817. The gamma-ray spectrum integrated over the remnant is likely dominated by the decay of neutral {pi} mesons produced through the proton-proton collisions in the filaments. The reacceleration of the pre-existing cosmic rays and subsequent adiabatic compression in the filaments is sufficient to provide the energy density required of high-energy protons.

Katsuta, J.; Uchiyama, Y.; Tanaka, T.; Tajima, H.; Bechtol, K.; Funk, S.; Lande, J. [W. W. Hansen Experimental Physics Laboratory, Kavli Institute for Particle Astrophysics and Cosmology, Department of Physics and SLAC National Accelerator Laboratory, Stanford University, Stanford, CA 94305 (United States); Ballet, J. [Laboratoire AIM, CEA-IRFU/CNRS/Universite Paris Diderot, Service d'Astrophysique, CEA Saclay, 91191 Gif sur Yvette (France); Hanabata, Y. [Department of Physical Sciences, Hiroshima University, Higashi-Hiroshima, Hiroshima 739-8526 (Japan); Lemoine-Goumard, M. [Universite Bordeaux 1, CNRS/IN2p3, Centre d'Etudes Nucleaires de Bordeaux Gradignan, 33175 Gradignan (France); Takahashi, T., E-mail: katsuta@slac.stanford.edu, E-mail: uchiyama@slac.stanford.edu [Institute of Space and Astronautical Science, Japanese Aerospace Exploration Agency, 3-1-1 Yoshinodai, Chuo-ku, Sagamihara, Kanagawa 252-5210 (Japan)

2012-06-20

78

The thermal phase of a large solar flare. [Skylab observations  

NASA Technical Reports Server (NTRS)

EUV and X-ray observations are used to derive the differential emission measures, temperatures, densities, radiative and conductive cooling rates, and thermal energy content of a class 2B flare that occurred on September 7, 1973. The results of the analysis indicate that (1) most of the flare plasma was at temperatures between 3 and 10 million degrees; (2) the peak temperature decreased with time from about 8 million K to 5 million K over a period of 3.5 hours; (3) the differential emission measure steadily decreased with time at nearly all temperatures; (4) both radiation and conduction were important cooling mechanisms for the plasma at temperatures above 100,000 K; and (5) a substantial amount of energy, of the order of 3 x 10 to the 31st power ergs, was deposited in the flare loops after flare maximum. The empirically determined flare parameters are compared with similar parameters derived from a simple theoretical loop model.

Withbroe, G. L.

1978-01-01

79

Scattering of circularly polarized radiation  

SciTech Connect

The differential refraction and absorption of circularly polarized light was applied by Henry Eyring and co-workers to study the configuration and conformation of small molecules. The differential scattering as a function of angle of circularly polarized light can provide structural information about large scattering systems. We present the general equations relating circular differential scattering to the eigenfunctions of a scatter which is of arbitrary size relative to the wavelength of light. An equiv experiment is to measure the ellipticity of the scattered light when linearly polarized light is incident.

Tinoco, I. Jr.; Keller, D.

1983-07-21

80

FERMI LARGE AREA TELESCOPE OBSERVATIONS OF MISALIGNED ACTIVE GALACTIC NUCLEI  

SciTech Connect

Analysis is presented for 15 months of data taken with the Large Area Telescope (LAT) on the Fermi Gamma-ray Space Telescope for 11 non-blazar active galactic nuclei (AGNs), including seven FRI radio galaxies and four FRII radio sources consisting of two FRII radio galaxies and two steep spectrum radio quasars. The broad line FRI radio galaxy 3C 120 is reported here as a {gamma}-ray source for the first time. The analysis is based on directional associations of LAT sources with radio sources in the 3CR, 3CRR, and MS4 (collectively referred to as 3C-MS) catalogs. Seven of the eleven LAT sources associated with 3C-MS radio sources have spectral indices larger than 2.3 and, except for the FRI radio galaxy NGC 1275 that shows possible spectral curvature, are well described by a power law. No evidence for time variability is found for any sources other than NGC 1275. The {gamma}-ray luminosities of FRI radio galaxies are significantly smaller than those of the BL Lac objects detected by the LAT, whereas the {gamma}-ray luminosities of the FRII sources are quite similar to those of FSRQs, which could reflect different beaming factors for the {gamma}-ray emission. A core dominance (CD) study of the 3CRR sample indicates that sources closer to the jet axis are preferentially detected with the Fermi LAT, insofar as the {gamma}-ray-detected misaligned AGNs have larger CD at a given average radio flux. The results are discussed in view of the AGN unification scenario.

Abdo, A. A. [Space Science Division, Naval Research Laboratory, Washington, DC 20375 (United States); Ackermann, M.; Ajello, M.; Bechtol, K.; Berenji, B.; Blandford, R. D.; Bloom, E. D.; Borgland, A. W.; Bouvier, A. [W. W. Hansen Experimental Physics Laboratory, Kavli Institute for Particle Astrophysics and Cosmology, Department of Physics and SLAC National Accelerator Laboratory, Stanford University, Stanford, CA 94305 (United States); Baldini, L.; Bellazzini, R.; Bregeon, J.; Brez, A. [Istituto Nazionale di Fisica Nucleare, Sezione di Pisa, I-56127 Pisa (Italy); Ballet, J. [Laboratoire AIM, CEA-IRFU/CNRS/Universite Paris Diderot, Service d'Astrophysique, CEA Saclay, 91191 Gif sur Yvette (France); Barbiellini, G. [Istituto Nazionale di Fisica Nucleare, Sezione di Trieste, I-34127 Trieste (Italy); Bastieri, D. [Istituto Nazionale di Fisica Nucleare, Sezione di Padova, I-35131 Padova (Italy); Bonamente, E. [Istituto Nazionale di Fisica Nucleare, Sezione di Perugia, I-06123 Perugia (Italy); Brandt, T. J. [Centre d'Etude Spatiale des Rayonnements, CNRS/UPS, BP 44346, F-30128 Toulouse Cedex 4 (France); Brigida, M. [Dipartimento di Fisica 'M. Merlin' dell'Universita e del Politecnico di Bari, I-70126 Bari (Italy); Bruel, P., E-mail: grandi@iasfbo.inaf.i [Laboratoire Leprince-Ringuet, Ecole polytechnique, CNRS/IN2P3, Palaiseau (France)

2010-09-01

81

Large-scale Observations of the Magnetopause by Cluster  

NASA Astrophysics Data System (ADS)

The magnetopause and its adjacent boundary layers are a key science target for many satellite missions. They have been sampled, at the same time, either locally by a maximum of 4 to 5 closely spaced spacecraft (from the Cluster constellation and the Double Star TC-1 satellite) or on larger scales by missions such as Geotail, Cluster and THEMIS. Unfortunately, none of the spacecraft configurations has so far permitted the 'evolution' of perturbations along their main direction of propagation to be tracked. The study of the evolution of magnetic field and plasma perturbations, such as Kelvin-Helmholtz (KH) waves or Flux Transfer Events (FTEs), together with the (associated or not) generation of Kinetic Alfvén Waves (KAWs) and the turbulence developing at the flank magnetopause boundary layer, is important for our understanding of the mechanisms that mediate solar wind plasma entry into the magnetosphere, i.e. magnetic reconnection and diffusive processes. The Cluster Guest Investigator (GI) proposal implemented in November 2012 targeted inter-spacecraft separations of ~1 RE necessary to relate disturbances and deduce their evolution. It resulted in separations of up to 36,000 km across the constellation at the magnetopause and was the largest separation ever for the Cluster mission. In this invited talk, I will present the first results from the Cluster GI observations of magnetopause boundary layer.

Foullon, Claire

2014-05-01

82

Circular differential scattering and circular differential absorption of DNA-protein condensates and of dyes bound to DNA-protein condensates  

SciTech Connect

DNA-protein condensates that give positive and negative psi-type circular dichroism (CD) spectra (psi condensates) bind intercalative and nonintercalative dyes. CD depends both on circular differential scattering and on circular differential absorption; scattering-corrected CD measurements are approximations to circular differential absorption. The circular differential scattering and scattering-corrected CD patterns observed in the DNA absorption band of psi condensates are mimicked in the induced CD band of intercalators bound to psi condensates. The induced scattering-corrected CD and circular differential scattering patterns of the groove-binding dye Hoechst 33342 bound to psi condensates are the inverse of the patterns seen with intercalative dyes, whereas the groove-binding dye manganese(III) meso-tetrakis(4-N-methylpyridyl)porphine (MnIIITMpyP-4) shows no significant induced CD patterns. The large circular differential scattering and scattering-corrected CD bands are interpreted as resulting from long-range chiral packing, rather than near-neighbor short-range interactions. Dyes intercalated into the DNA of the psi condensates have the same type of long-range chiral packing as the DNA bases. Therefore, the psi-type CD spectra seen in the UV spectra originating from the long-range packing of the DNA bases are also observed in the visible spectra when dyes are intercalated in the DNA of the psi condensates. Our interpretation comes from the observation that the induced circular differential scattering and circular differential absorption of the dye bound to the psi condensates depend only upon the sign of the circular differential absorption and the pattern of the circular differential scattering of the psi condensates without bound dye.

Phillips, C.L.; Mickols, W.E.; Maestre, M.F.; Tinoco, I. Jr.

1986-12-02

83

Circular polarization in pulsars (You+, 2006)  

NASA Astrophysics Data System (ADS)

We update the systematic studies of circular polarization in integrated pulse profiles by Han et al. (1998MNRAS.300..373H). Data of circular polarization profiles are compiled. Sense reversals can occur in core or cone components, or near the intersection between components. The correlation between the sense of circular polarization and the sense of position angle variation for conal-double pulsars is confirmed with a much large database. Circular polarization of some pulsars has clear changes with frequency. Circular polarization of millisecond pulsars is marginally different from that of normal pulsars. (2 data files).

You, X.-P.; Han, J.-L.

2006-11-01

84

Circular Polarization in Pulsar Integrated Profiles: Updates  

NASA Astrophysics Data System (ADS)

We update the systematic studies of circular polarization in integrated pulse profiles by Han et al. Data of circular polarization profiles are compiled. Sense reversals can occur in core or cone components, or near the intersection between components. The correlation between the sense of circular polarization and the sense of position angle variation for conal-double pulsars is confirmed with a much large database. Circular polarization of some pulsars has clear changes with frequency. Circular polarization of millisecond pulsars is marginally different from that of normal pulsars.

You, Xiao-Peng; Han, Jin-lin

2006-04-01

85

Normal-Mode Analysis of Circular DNA at the Base-Pair Level. 2. Large-Scale Configurational Transformation of a Naturally Curved Molecule  

Microsoft Academic Search

Fine structural and energetic details embedded in the DNA base sequence, such as intrinsic curvature, are important to the packaging and processing of the genetic material. Here we investigate the internal dynamics of a 200 bp closed circular molecule with natural curvature using a newly developed normal-mode treatment of DNA in terms of neighboring base-pair \\

Atsushi Matsumoto; Irwin Tobias; Wilma K. Olson

2005-01-01

86

Multiple circular-circular correlation coefficients for the quantification of phase synchronization processes in the brain.  

PubMed

Phase synchronization is discussed as a potential mechanism for large-scale integration in the brain. Therefore, the quantification of such synchrony is a crucial topic in brain science research. Furthermore, these cerebral integration processes are likely to involve entire brain areas; therefore, the analysis of multiple couplings is of particular interest. Because phase values are circular variables, it is possible to use circular statistical methods for their examination. In particular, circular-circular correlation coefficients form a suitable measurement to estimate the extent of phase synchronization between different signals. As a multiple circular-circular correlation concept is still pending, two new multiple circular-circular correlation coefficients are presented in this article that can be used to quantify phase couplings between one dependent and an arbitrary number of predictor signals. PMID:23435150

Pauen, Katrin; Ivanova, Galina

2013-04-01

87

Large 0/12 GMT Differences of US Vaisala RS80 Observations.  

National Technical Information Service (NTIS)

Large differences between observations taken at 0 and 12 GMT have been released during routine monitoring of observations at the Data Assimilation Office (DAO) at NASA's Goddard Space Flight Center (GSFC). As a result, an investigation has been conducted ...

C. R. Redder

2003-01-01

88

A circular twin paradox  

NASA Astrophysics Data System (ADS)

In the special relativistic twin paradox presented here, each twin lives on one ring of a counterrotating pair of infinitesimally separated rings, so that the twins travel on the same circular path but in opposite directions. The observers on the ring of one twin should see the clock of the other twin slowed by time dilation, but at each meeting of the twins symmetry demands that they agree on the amount of time that has passed since their previous meeting. The resolution of the paradox focuses attention on the relation of time dilation to clock synchronization.

Cranor, Maria B.; Heider, Elizabeth M.; Price, Richard H.

2000-11-01

89

An observer for a deployable antenna. [for large space structure flight experiment  

NASA Technical Reports Server (NTRS)

An observer is derived for use on an Orbiter-Deployable Antenna configuration. The unique feature of this observer design for this flight experiment is that all the plant inputs are not required to be directly accessible for the observer to ferret out the system states. The observer uses state and rate of the state information to reconstruct the plant states. Results are presented which show how effectively this observer design works for this large space structure flight experiment.

Waites, H. B.

1981-01-01

90

Synthetic-Aperture Coherent Imaging From A Circular Path  

NASA Technical Reports Server (NTRS)

Imaging algorithms based on exact point-target responses. Developed for use in reconstructing image of target from data gathered by radar, sonar, or other transmitting/receiving coherent-signal sensory apparatus following circular observation path around target. Potential applications include: Wide-beam synthetic-aperture radar (SAR) from aboard spacecraft in circular orbit around target planet; SAR from aboard airplane flying circular course at constant elevation around central ground point, toward which spotlight radar beam pointed; Ultrasonic reflection tomography in medical setting, using one transducer moving in circle around patient or else multiple transducers at fixed positions on circle around patient; and Sonar imaging of sea floor to high resolution, without need for large sensory apparatus.

Jin, Michael Y.

1995-01-01

91

The Cluster Galaxy Circular Velocity Function  

Microsoft Academic Search

We construct circular velocity functions for galaxies in nearby (z < 0.1) clusters using the Tully Fisher and Fundamental Plane Relations and surface photometry from the Sloan Digital Sky Survey Early Data Release. These are compared to halo circular velocity functions for a large number of clusters drawn from a high-resolution ( 106 particles within the virial radius of each

V. Desai; D. Reed; J. J. Dalcanton; L. Mayer; T. Quinn; F. Governato

2002-01-01

92

Simultaneous Solar Maximum Mission and Very Large Array (VLA) Observations of Solar Active Regions.  

National Technical Information Service (NTIS)

Simultaneous observations of solar active regions with the Solar Maximum Mission (SMM) Satellite and the Very Large Array (VLA) have been obtained and analyzed. Combined results enhance the scientific return for beyond that expected from using either SMM ...

K. R. Lang

1985-01-01

93

Satellite observations of banded VLF emissions in conjunction with energy-banded ions during very large geomagnetic storms  

NASA Astrophysics Data System (ADS)

Electromagnetic VLF emissions banded in frequency, coincident with warm energy-banded ions in the low latitude auroral zone, and associated with very strong geomagnetic storms, are observed separately on two low-earth polar orbiting satellites, FAST and DEMETER. Both satellites carry a full complement of field and particle detectors. The FAST satellite, launched August 21, 1996 into an elliptical polar orbit with perigee 350 km and apogee 4175 km, traversed the auroral zone four times per orbit across a wide range of altitudes and local times. The DEMETER satellite was launched on June 29, 2004 into a circular sun-synchronous polar orbit at altitude 710 km, with data recorded at all invariant latitudes less than ~65 degrees. The ion bands were first reported in association with the Halloween storms [Cattell et al., 2004; Kozyra et al., 2004, Yao et al., 2008]. Banded ions are observed on FAST during every large magnetic storm in discrete energy bands at energies ~10 eV - 10 keV and lasting up to 12 hrs. The energy flux peaks in the trapped population but is also evident in the precipitating ions, and in certain cases a significant upgoing ion component appears at low invariant latitudes. These bands were observed over several orbits at similar latitudes in both dawn and evening sectors, with the signature typically more pronounced in the dawn sector. In this study we focus on the coincidence of the energy-banded ions with observations of frequency-banded VLF electromagnetic emissions. During all of these very large storms, banded VLF emissions are evident in both the electric and magnetic field, appearing as discrete frequency bands between ~100 and ~1500 Hz separated by 75-150 Hz. These banded emissions persist for several FAST or DEMETER orbits, lasting up to 10 hrs, in both the northern and southern hemispheres. There appears to be a correlation between the banded wave observations and ion and electron density enhancements. Possible generation mechanisms for the banded emissions include EMIC waves generated in the equatorial ring current region which bounce to higher L-shells and propagate down auroral field lines to the spacecraft location.

Colpitts, C. A.; Cattell, C. A.; Kozyra, J. U.; Parrot, M.

2010-12-01

94

On-Line Monitoring of Large Petri Net Models Under Partial Observation  

Microsoft Academic Search

This paper deals with the on-line monitoring of large systems modeled as Petri Nets under partial observation. The plant observation is given by a subset of transitions whose occurrence is (always) acknowledged by emitting a label received by the monitoring agent at the time of the occurrence. Other transitions not in this subset are silent (unobservable). Usually on-line applications require

George Jiroveanu; René K. Boel; Behzad Bordbar

2008-01-01

95

Observations of X-ray sources in the Large Magellanic Cloud by the OSO-7 satellite  

NASA Technical Reports Server (NTRS)

Observations of the Large Magellanic Cloud with the 1-40 keV X-ray detectors on the OSO-7 satellite are reported. Results include the discovery of a previously unreported source LMC X-5, measurements of the spectral characteristics of four sources, and observations of their variability on time scales of months.

Markert, T. H.; Clark, G. W.

1975-01-01

96

Large 0/12 GMT Differences of US Vaisala RS80 Observations  

NASA Technical Reports Server (NTRS)

Large differences been observations taken at 0 and 12 GMT have been revealed during routine monitoring of observations at the Data Assimilation Office (DAO) at NASA's Goddard Space Flight Center (GSFC). As a result, an investigation has been conducted to confirm the large differences and isolate its source. The data clearly shows that 0/12 GMT differences are largely artificial especially over the central US and that the differences largely originate in the post processing software at the observing stations. In particular, the release time of the rawinsonde balloon may be misspecified to be the synoptic time which would lead to the miscalculation of the bias correction that accounts for solar radiation effects on the thermistor.

Atlas, Robert (Technical Monitor)

2002-01-01

97

Time-resolved demagnetization of Co2MnSi observed using x-ray magnetic circular dichroism and an ultrafast streak camera.  

PubMed

The demagnetization dynamics of the Heusler alloy Co(2)MnSi was studied using picosecond time-resolved x-ray magnetic circular dichroism. The sample was excited using femtosecond laser pulses. In contrast to the sub-picosecond demagnetization of the metal ferromagnet Ni, substantially slower demagnetization with a time constant of 3.5 ± 0.5 ps was measured. This could be explained by a spin-dependent band gap inhibiting the spin-flip scattering of hot electrons in Co(2)MnSi, which is predicted to be half-metallic. A universal demagnetization time constant was measured across a range of pump power levels. PMID:21389561

Opachich, Y P; Comin, A; Bartelt, A F; Young, A T; Scholl, A; Feng, J; Schmalhorst, J; Shin, H J; Engelhorn, K; Risbud, S H; Reiss, G; Padmore, H A

2010-04-21

98

Circular Dichroism Spectra of Granal and Agranal Chloroplasts of Maize  

PubMed Central

Granum-containing chloroplasts from mesophyll cells of maize (Zea mays L. var. MV 861) leaves exhibited circular dichroism spectra with a large double signal; peaks at 696 nm (+) and 680 nm (?). In the circular dichroism spectra obtained with agranal chloroplasts of bundle sheath cells, this large double signal is absent. Separation of grana lamellae, in a medium of low salt concentration and in KSCN solution, resulted only in a slight decrease of the amplitude, while upon treatment with digitonin the large double signal disappeared. A negative signal of the chlorophyll b peak at 654 nm was observed in the case of both granal and agranal chloroplasts, and it was not affected either by low salt or by digitonin treatment. A positive peak at about 515 nm was higher in granal than in agranal chloroplasts.

Faludi-Daniel, Agnes; Demeter, S.; Garay, A. S.

1973-01-01

99

Circular dichroism tensor of a triarylmethyl propeller in sodium chlorate crystals.  

PubMed

In 1919, Perucca reported anomalous optical rotatory dispersion from chiral NaClO(3) crystals that were colored by having been grown from a solution containing an equilibrium racemic mixture of a triarylmethane dye (Perucca, E. Nuovo Cimento 1919, 18, 112-154). Perucca's chiroptical observations are apparently consistent with a resolution of the propeller-shaped dye molecules by NaClO(3) crystals. This implies that Perucca achieved the first enantioselective adsorption of a racemic mixture on an inorganic crystal, providing evidence of the resolution of a triarylmethyl propeller compound lacking bulky ortho substituents. Following the earlier report, NaClO(3) crystals dyed with aniline blue are described herein. The rich linear optical properties of (001), (110), and (111) sections of these mixed crystals are described via their absorbance spectra in polarized light as well as images related to linear dichroism, linear birefringence, circular dichroism, and anomalous circular extinction. The linear dichroism fixes the transition electric dipole moments in the aromatic plane with respect to the growth faces of the NaClO(3) cubes. Likewise, circular dichroism measurements of four orientations of aniline blue in NaClO(3) fix a bisignate tensor with respect to the crystal growth faces. Electronic transition moments and circular dichroism tensors were computed ab initio for aniline blue. These calculations, in conjunction with the crystal-optical properties, establish a consistent mixed-crystal model. The nature of the circular extinction depends upon the crystallographic direction along which the crystals are examined. Along 100, the crystals evidence circular dichroism. Along 110, the crystals evidence mainly anomalous circular extinction. These two properties, while measured by the differential transmission of left and right circularly polarized light, are easily distinguished in their transformation properties with respect to reorientations of the sample plates. Circular dichroism is symmetric with respect to the wave vector, whereas anomalous circular extinction is antisymmetric. Analysis of Perucca's raw data reveals that he was observing a convolution of linear and circular optical properties. The relatively large circular dichroism should in principle establish the absolute configuration of the propeller-shaped molecules associated with d- or l-NaClO(3) crystals. However, this determination was not as straightforward as it appeared at the outset. In the solid state, unlike in solution, a strong chiroptical response is not in and of itself evidence of enantiomeric resolution. It is shown how it is possible to have a poor resolution-even an equal population of P and M propellers-within a given chiral NaClO(3) crystal and still have a large circular dichroism. PMID:20446684

Bing, Yonghong; Selassie, David; Paradise, Ruthanne H; Isborn, Christine; Kramer, Nicholas; Sadilek, Martin; Kaminsky, Werner; Kahr, Bart

2010-06-01

100

Is the ACDM Model Consistent with Observations of Large-Scale Structure?  

NASA Astrophysics Data System (ADS)

The claim that large-scale structure data independently prefers the Lambda Cold Dark Matter model is a myth. However, an updated compilation of large-scale structure observations cannot rule out Lambda CDM at 95% confidence. We explore the possibility of improving the model by adding Hot Dark Matter but the fit becomes worse; this allows us to set limits on the neutrino mass.

Gawiser, E.

101

Vision with equiluminant colour contrast: 2. A large-scale technique and observations.  

PubMed

A simple technique is described for producing large-scale, tritanopic displays. The technique reproduces the various phenomena of vision with equiluminous-colour contrast that have previously been reported with red/green stimuli. It is, however, much less demanding technically, robust against artifacts, and can be used on large-scale scenes. One advantage of the technique is that a piece of blue filter can be used individually by each observer to compare quickly tritanopic and luminance conditions. PMID:1513671

Cavanagh, P; Adelson, E H; Heard, P

1992-01-01

102

Extreme Ultraviolet Explorer deep survey observations of a large flare on AU Microscopii  

NASA Technical Reports Server (NTRS)

We have made the first extended observation of a stellar flare in the EUV with 100 s time resolution. The flare was detected on AU Mic by the Extreme Ultraviolet Explorer satellite at 12:38 UT on 1992 July 15 during a 4 d observation from 1992 July 14 to 18. This was a large flare detected in the Lexan/boron (65-190 A) band with an observed peak count rate of 7.0 +/- 0.5 counts/s, corresponding to a peak luminosity of 10 exp 30 erg/s in the Lexan/boron bandpass. This is significantly above the measured quiescent level of 0.4 +/- 0.2 counts/s. The flare consisted of a sharp peak lasting about 2 hr, followed by a decaying tail that lasted more than a day. The total EUV energy of the event is estimated to be 3 x 10 exp 34 ergs. A second, smaller flare was also observed and is described. We conclude that the large emission measures on order of 6 x 10 exp 53/cu cm are due to large volumes with characteristic length scales of order the stellar radius. We compare these EUV observations with stellar flare observations in other bandpasses and estimate the likelihood of seeing similar flares in future observations.

Cully, Scott L.; Siegmund, Oswald H. W.; Vedder, Peter W.; Vallerga, John V.

1993-01-01

103

Anomalously Large Thermal Expansion at the (0001) Surface of Beryllium without Observable Interlayer Anharmonicity  

SciTech Connect

We have measured a large thermal surface expansion, 6 times larger than the bulk, on Be(0001) using low-energy electron diffraction. This observation seems to be inconsistent with previous measurements reporting negligible anharmonicity in the surface phonon modes normal to the surface. Density-functional theory calculations for the thermal expansion from the minimum in the free energy within the quasiharmonic approximation agree with the experimental observations and demonstrate that the enhanced thermal expansion is caused largely by a softening of the in-plane vibrations. {copyright} {ital 1998} {ital The American Physical Society}

Pohl, K.; Pohl, K.; Plummer, E.W.; Plummer, E.W. [Department of Physics and Astronomy, The University of Tennessee, Knoxville, Tennessee 37996-1200 (United States)] [Department of Physics and Astronomy, The University of Tennessee, Knoxville, Tennessee 37996-1200 (United States); Cho, J.; Terakura, K. [JRCAT, National Institute of Advanced Interdisciplinary Research, 1-1-4 Higashi, Tsukuba, Ibaraki 305 (Japan)] [JRCAT, National Institute of Advanced Interdisciplinary Research, 1-1-4 Higashi, Tsukuba, Ibaraki 305 (Japan); Scheffler, M. [Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 4-6, D-14195 Berlin-Dahlem, Germany] [University of California at Los Angeles, Los Angeles, California 90024 (United States)] [Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 4-6, D-14195 Berlin-Dahlem, Germany; University of California at Los Angeles, Los Angeles, California 90024 (United States)

1998-03-01

104

Anomalously Large Thermal Expansion at the (0001) Surface of Beryllium without Observable Interlayer Anharmonicity  

NASA Astrophysics Data System (ADS)

We have measured a large thermal surface expansion, 6 times larger than the bulk, on Be(0001) using low-energy electron diffraction. This observation seems to be inconsistent with previous measurements reporting negligible anharmonicity in the surface phonon modes normal to the surface. Density-functional theory calculations for the thermal expansion from the minimum in the free energy within the quasiharmonic approximation agree with the experimental observations and demonstrate that the enhanced thermal expansion is caused largely by a softening of the in-plane vibrations.

Pohl, K.; Cho, J.-H.; Terakura, K.; Scheffler, M.; Plummer, E. W.

1998-03-01

105

Chiral correlation between low-birefringent phases with twist grain boundary-like helix and highly birefringent phases with layer chirality as elucidated from circular dichroism observations.  

PubMed

The bent-shaped molecule with a central naphthalene core, 2,7-naphthalene-bis[4-(4-dodecylphenyliminomethyl)]benzoate, forms the low-birefringent B2 (LB-B2) phase with the twist grain boundary (TGB)-like helical structure and the low-birefringent B4 (LB-B4) phase in order of decreasing temperature. By applying the electric field, the LB-B2 phase is altered to the highly birefringent B2 (HB-B2) phase because of unwinding of the TGB-like helix. The HB-B2 phase is transformed to the HB-B4 phase without a loss of birefringence on cooling. These four phases show characteristic circular dichroism spectra, showing the consistent correlation through the transformation between these phases. The source of the chirality in the achiral system and the correlation in the chirality between these phases are discussed. PMID:18471008

Lee, Seng Kue; Shi, Lu; Tokita, Masatoshi; Watanabe, Junji

2008-06-01

106

Multipoint Observations of the Large Substorm Associated with the Galaxy 15 Anomaly  

Microsoft Academic Search

On April 5, 2010 around 09 UT, the NOAA Geosynchronous Operational Environmental Satellites (GOES) observed a large reconfiguration of the magnetospheric magnetic field in the midnight to dawn local time sector. Specifically, near midnight, the GOES-11 Hp (north-south) magnetic field increased by approximately 100 nT in 15 minutes. This is one of the largest dipolarizations of Earth's field ever observed

H. J. Singer; P. T. Loto'Aniu; J. C. Green; J. V. Rodriguez; B. J. Anderson; J. J. Love; V. Angelopoulos; D. N. Baker; M. G. Connors; W. F. Denig; E. F. Donovan; O. Lecontel; T. G. Onsager; T. Nagatsuma; A. Runov; E. L. Spanswick

2010-01-01

107

The Karl G. Jansky Very Large Array radio observations of SN 2013I  

NASA Astrophysics Data System (ADS)

We observed SN 2013I (Tanaka et al., CBET 3386) with The Karl G. Jansky Very Large Array telescope in the 22 GHz frequency band on 2013 Jan 20.96 UT. We did not detect any radio emission at the supernova position R.A. = 2h49m42s.17, Decl. = +0d45'35".7 (CBET 3386). The flux at the SN position is -38.2+/-46.6 uJy. Further observations are planned.

Chandra, Poonam; Soderberg, Alicia

2013-01-01

108

Observation of events with a large rapidity gap in deep inelastic scattering at HERA  

Microsoft Academic Search

In deep inelastic, neutral current scattering of electrons and protons at sqrt(s)=296 GeV, we observe in the ZEUS detector events with a large rapidity gap in the hadronic final state. They occur in the region of small Bjorken x and are observed up to Q2 of 100 GeV2. They account for about 5% of the events with Q2>=10 GeV2. Their

M. Derrick; D. Krakauer; S. Magill; B. Musgrave; J. Repond; S. Repond; R. Stanek; R. L. Talaga; J. Thron; F. Arzarello; R. Ayad; G. Bari; M. Basile; L. Bellagamba; D. Boscherini; A. Bruni; G. Bruni; P. Bruni; G. Cara Romeo; G. Castellini; M. Chiarini; L. Cifarelli; F. Cindolo; F. Ciralli; A. Contin; S. D'Auria; C. del Papa; F. Frasconi; P. Giusti; G. Iacobucci; G. Laurenti; G. Levi; Q. Lin; B. Lisowski; G. Maccarrone; A. Margotti; T. Massam; R. Nania; C. Nemoz; F. Palmonari; G. Sartorelli; R. Timellini; Y. Zamora Garcia; A. Zichichi; A. Bargende; J. Crittenden; K. Desch; B. Diekmann; T. Doeker; A. Frey; M. Geerts; G. Geitz; H. Hartmann; D. Haun; K. Heinloth; E. Hilger; H.-P. Jakob; S. Kramarczyk; M. Kückes; A. Mass; S. Mengel; J. Mollen; D. Monaldi; H. Müsch; E. Paul; R. Schattevoy; J.-L. Schneider; D. Schramm; R. Wedemeyer; A. Cassidy; D. G. Cussans; N. Dyce; B. Foster; R. Gilmore; G. P. Heath; H. F. Heath; M. Lancaster; T. J. Llewellyn; J. Malos; C. J. S. Morgado; R. J. Tapper; S. S. Wilson; R. Yoshida; R. R. Rau; M. Arneodo; M. Schioppa; G. Susinno; A. Bernstein; A. Caldwell; I. Gialas; J. A. Parsons; S. Ritz; F. Sciulli; P. B. Straub; L. Wai; S. Yang; P. Borzemski; J. Chwastowski; A. Dwurazny; A. Eskreys; Z. Jakubowski; B. Niziol; K. Piotrzkowski; M. Zachara; L. Zawiejski; L. Adamczyk; B. Bednarek; K. Eskreys; K. Jelen; D. Kisielewska; T. Kowalski; E. Rulikowska-Zarebska; L. Suszycki; J. Zajc; T. Kedzieski; A. Kotanski; M. Przybycien; L. A. T. Bauerdick; U. Behrens; J. K. Bienlein; S. Böttcher; C. Coldewey; A. Dannemann; G. Drews; P. Erhard; M. Flasinski; I. Fleck; R. Gläser; P. Göttlicher; B. Gutjahr; T. Haas; L. Hagge; W. Hain; D. Hasell; H. Hultschig; G. Jahnen; P. Joos; M. Kasemann; R. Klanner; W. Koch; L. Köpke; U. Kötz; H. Kowalski; W. Kröger; J. Krüger; J. Labs; A. Ladage; B. Löhr; M. Löwe; D. Lüke; J. Mainusch; O. Manczak; M. Momayezi; J. S. T. Ng; S. Nickel; D. Notz; K.-U. Pösnecker; M. Rohde; J. Roldán; E. Ros; U. Schneekloth; J. Schroeder; W. Schulz; F. Selonke; E. Stiliaris; E. Tscheslog; T. Tsurugai; W. Vogel; G. Wolf; C. Youngman; H. J. Grabosch; A. Leich; A. Meyer; C. Rethfeldt; S. Schlenstedt; G. Barbagli; A. Francescato; M. Nuti; P. Pelfer; G. Anzivino; R. Casaccia; S. de Pasquale; S. Qian; L. Votano; A. Bamberger; A. Freidhof; T. Poser; S. Söldner-Rembold; G. Theisen; T. Trefzger; N. H. Brook; P. J. Bussey; A. T. Doyle; J. R. Forbes; V. A. Jamieson; C. Raine; D. H. Saxon; H. Brückmann; G. Gloth; U. Holm; H. Kammerlocher; B. Krebs; T. Neumann; K. Wick; A. Fürtjes; E. Lohrmann; J. Milewski; M. Nakahata; N. Pavel; G. Poelz; W. Schott; J. Terron; F. Zetsche; T. C. Bacon; R. Beuselinck; I. Butterworth; E. Gallo; V. L. Harris; D. B. Miller; A. Prinias; J. K. Sedgbeer; A. Vorvolakos; A. Whitfield; T. Bienz; H. Kreutzmann; U. Mallik; E. McCliment; M. Roco; M. Z. Wang; P. Cloth; D. Filges; S. H. An; S. M. Hong; C. O. Kim; T. Y. Kim; S. W. Nam; S. K. Park; M. H. Suh; S. H. Yon; R. Imlay; S. Kartik; H.-J. Kim; R. R. McNeil; W. Metcalf; V. K. Nadendla; F. Barreiro; G. Cases; L. Hervás; L. Labarga; J. del Peso; J. F. de Trocóniz; F. Ikraiam; J. K. Mayer; G. R. Smith; F. Corriveau; D. J. Gilkinson; D. S. Hanna; J. Hartmann; L. W. Hung; J. N. Lim; R. Meijer Drees; J. W. Mitchell; P. M. Patel; L. E. Sinclair; D. G. Stairs; M. St. Laurent; R. Ullmann; G. L. Bashindzhagyan; P. F. Ermolov; L. K. Gladilin; Y. A. Golubkov; V. A. Kuzmin; E. N. Kuznetsov; A. A. Savin; A. G. Voronin; N. P. Zotov; S. Bentvelsen; M. Botje; A. Dake; J. Engelen; P. de Jong; M. de Kamps; P. Kooijman; A. Kruse; H. van der Lugt; V. O'dell; A. Tenner; H. Tiecke; H. Uijterwaal; M. Vreeswijk; L. Wiggers; E. de Wolf; R. van Woudenberg; B. Bylsma; L. S. Durkin; K. Honscheid; C. Li; T. Y. Ling; K. W. McLean; W. N. Murray; I. H. Park; T. A. Romanowski; R. Seidlein; G. A. Blair; A. Byrne; R. J. Cashmore; A. M. Cooper-Sarkar; R. C. E. Devenish; D. M. Gingrich; P. M. Hallam-Baker; N. Harnew; T. Khatri; K. R. Long; P. Luffman; I. McArthur; P. Morawitz; J. Nash; S. J. P. Smith; N. C. Roocroft; F. F. Wilson; G. Abbiendi; R. Brugnera; R. Carlin; F. dal Corso; M. de Giorgi; U. Dosselli; F. Gasparini; S. Limentani; M. Morandin; M. Posocco; L. Stanco; R. Stroili; C. Voci; J. M. Butterworth; J. Bulmahn; G. Feild; B. Y. Oh; J. Whitmore; U. Contino; G. D'Agostini; M. Guida; M. Iori; S. M. Mari; G. Marini; M. Mattioli; A. Nigro; J. C. Hart; N. A. McCubbin; K. Prytz; T. P. Shah; T. L. Short; E. Barberis; N. Cartiglia; C. Heusch; B. Hubbard; J. Leslie; W. Lockman; K. O'Shaughnessy; H. F. Sadrozinski; A. Seiden; D. Zer-Zion; E. Badura; J. Biltzinger; R. J. Seifert; A. H. Walenta; G. Zech; S. Dagan; A. Levy; T. Hasegawa; M. Hazumi; T. Ishii; S. Kasai; M. Kuze; S. Mine; Y. Nagasawa; T. Nagira; M. Nakao; H. Okuno; I. Suzuki; K. Tokushuku; S. Yamada; Y. Yamazaki; M. Chiba; R. Hamatsu; T. Hirose; S. Kitamura

1993-01-01

109

Large-scale effects of aerosol on precipitation: observations and model simulations  

NASA Astrophysics Data System (ADS)

A global evaluation of large-scale aerosol effect on precipitation is attempted using long-term satellite data and simulations by a global climate model with black carbon radiative forcing. Results indicate both consistencies and discrepancies between the observations and model simulations. Both satellite observation and model simulation demonstrated precipitation suppression associated with high aerosol concentrations in the West African monsoon region. Such large-scale link between aerosol and precipitation has distinctive spatial and seasonal variability which are significantly different from the model simulated wet deposition patterns. Comparison between observation and simulation confirmed that both radiative forcing and microphysical effects of aerosols are equally important in evaluating aerosol impacts on precipitation variability in this region. In other aerosol prevailing regions like tropical Atlantic, East Asia, Indian Ocean and Eastern Pacific, large-scale aerosol effects on precipitation can be either positive or negative exhibiting large uncertainties. Results indicate that the large-scale effects of aerosol on precipitation are sensitive to aerosol types, rain rates, and ambient meteorological environments in different geographical regions.

Adams, A.; Huang, J.; Zhang, C.; Wang, C.

2008-12-01

110

Particle Filtering for Large Dimensional State Spaces with Multimodal Observation Likelihoods  

Microsoft Academic Search

Abstract—We study efficient importance sampling techniques for particle filtering (PF) when either (a) the observation likelihood (OL) is frequently multimodal or heavy-tailed, or (b) the state space dimension is large or both. When the OL is multimodal, but the state transition pdf (STP) is narrow enough, the optimal importance density is usually unimodal. Under this assumption, many techniques have been

Namrata Vaswani

2008-01-01

111

Diversidad Biotica 1. Bogotá: ICN. Observations of Large Mammals in Serranía de los Churumbelos  

Microsoft Academic Search

Summary Large mammal species observed in the field in Serranía de los Churumbelos include; an anteater (Tamandua tetradactyla), a primate of the genus Saguinus; a marsupial of the genus Marmosa or Marmosops and at least two genera of squirrel. Armadillos (Dasypus novemcinctus) and Borugas (Agouti paca) were also captured. Spectacled Bear Tremarctos ornatus, Mountain Tapir Tapirus pinchaque, and Jaguar Panthera

Thomas Donegan; Paul Salaman

2007-01-01

112

The direct observations of large aerosol radiative forcing in the Himalayan region  

Microsoft Academic Search

We show here that absorbing aerosols have led to a large reduction of surface solar radiation during winter over the Himalayan region. Our results are based on radiometric, aerosol and Lidar observations made at three sites in Nepal during winter 2003. The monthly mean aerosol optical depth (AOD) ranged from 0.2 to 0.34 and the TERRA satellite MODIS data reveal

M. V. Ramana; V. Ramanathan; I. A. Podgorny; Bidya B. Pradhan; Basanta Shrestha

2004-01-01

113

Observation of Supernova Remnant IC 443 with the Fermi Large Area Telescope.  

National Technical Information Service (NTIS)

We report observation of the supernova remnant IC 443 (G189.1+3.0) with the Fermi Gamma-ray Space Telescope Large Area Telescope (LAT) in the energy band between 200 MeV and 50 GeV. IC 443 is a shell-type supernova remnant with mixed morphology located of...

A. A. Abdo B. M. Baughman D. Bastieri G. Barbiellini J. Ballet K. Bechtol L. Baldini M. Ackermann M. Ajello

2012-01-01

114

Large-Scale, Standards-Based Earth Observation Imagery and Web Mapping Services  

Microsoft Academic Search

Earth observation (EO) and simulation data share some core characteristics: they resemble raster data of some spatio-temporal dimensionality; the complete objects are extremely large, well into Tera- and Petabyte volumes; data generation and retrieval follow very different access patterns. EO time series additionally share that acquisi- tion\\/generation happens in time slices. The central standardization body for geo service interfaces is

Peter Baumann

2003-01-01

115

Interpretation of large-scale structures observed in a turbulent plane Couette flow  

Microsoft Academic Search

Large-flow structures, not observed in turbulent Poiseuille flow, are found in direct numerical simulations of turbulent Couette flow. Because these structures are persistent in space and time, an interpretation is presented which approximates them by a secondary flow. The asymmetry of the velocity profile is favorable to the formation of flow modules that fill the whole channel. These modules can

Dimitrios V. Papavassiliou; Thomas J. Hanratty

1997-01-01

116

ARRIVAL TIME CALCULATION FOR INTERPLANETARY CORONAL MASS EJECTIONS WITH CIRCULAR FRONTS AND APPLICATION TO STEREO OBSERVATIONS OF THE 2009 FEBRUARY 13 ERUPTION  

SciTech Connect

One of the goals of the NASA Solar TErestrial RElations Observatory (STEREO) mission is to study the feasibility of forecasting the direction, arrival time, and internal structure of solar coronal mass ejections (CMEs) from a vantage point outside the Sun-Earth line. Through a case study, we discuss the arrival time calculation of interplanetary CMEs (ICMEs) in the ecliptic plane using data from STEREO/SECCHI at large elongations from the Sun in combination with different geometric assumptions about the ICME front shape [fixed-{Phi} (FP): a point and harmonic mean (HM): a circle]. These forecasting techniques use single-spacecraft imaging data and are based on the assumption of constant velocity and direction. We show that for the slow (350 km s{sup -1}) ICME on 2009 February 13-18, observed at quadrature by the two STEREO spacecraft, the results for the arrival time given by the HM approximation are more accurate by 12 hr than those for FP in comparison to in situ observations of solar wind plasma and magnetic field parameters by STEREO/IMPACT/PLASTIC, and by 6 hr for the arrival time at Venus Express (MAG). We propose that the improvement is directly related to the ICME front shape being more accurately described by HM for an ICME with a low inclination of its symmetry axis to the ecliptic. In this case, the ICME has to be tracked to >30{sup 0} elongation to obtain arrival time errors < {+-} 5 hr. A newly derived formula for calculating arrival times with the HM method is also useful for a triangulation technique assuming the same geometry.

Moestl, C.; Rollett, T.; Temmer, M.; Veronig, A. M.; Biernat, H. K. [Institute of Physics, University of Graz, Graz A-8010 (Austria); Lugaz, N. [Institute for Astronomy, University of Hawaii, Honolulu, HI 96822 (United States); Farrugia, C. J.; Galvin, A. B. [Space Science Center and Department of Physics, University of New Hampshire, Durham, NH 03824 (United States); Davies, J. A.; Harrison, R. A.; Crothers, S. [RAL Space, Harwell Oxford, Didcot OX11 0QX (United Kingdom); Luhmann, J. G. [Space Sciences Laboratory, University of California, Berkeley, CA 94720 (United States); Zhang, T. L.; Baumjohann, W., E-mail: christian.moestl@uni-graz.at [Space Research Institute, Austrian Academy of Sciences, Graz A-8042 (Austria)

2011-11-01

117

Physclips: Circular Motion  

NSDL National Science Digital Library

This web page provides a multimedia introduction to circular motion. It includes topics such as acceleration, velocity, vectors, the Earth's rotation, and nonuniform circular motion. Short video clips and diagrams are integrated with text to promote understanding of important concepts. This tutorial is part of the PhysClip collection of web-based resources on introductory mechanics, electricity, and magnetism.

Wolfe, Joe

2009-10-14

118

The Importance of Large-Amplitude Motions for the Interpretation of Mid-Infrared Vibrational Absorption and Circular Dichroism Spectra: 6,6'-Dibromo-[1,1'-binaphthalene]-2,2'-diol in Dimethyl Sulfoxide.  

PubMed

Using the 6,6'-dibromo-[1,1'-binaphthalene]-2,2'-diol molecule and its vibrational absorption (VA) and vibrational circular dichroism (VCD) spectra measured in deuterated dimethyl sulfoxide as example, we present a first detailed study of the effects induced in VCD spectra by the large-amplitude motions of solvent molecules loosely bound to a solute molecule. We show that this type of perturbation can induce significant effects in the VA and VCD spectra. We also outline a computational procedure that can effectively model the effects induced in the spectra and at the same time provide detailed structural information regarding the relative orientations of moieties involved in a solute-solvent molecular complex. PMID:24906021

Heshmat, Mojgan; Baerends, Evert Jan; Polavarapu, Prasad L; Nicu, Valentin Paul

2014-07-01

119

Large-Amplitude Electrostatic Waves Observed at a Supercritical Interplanetary Shock  

NASA Technical Reports Server (NTRS)

We present the first observations at an interplanetary shock of large-amplitude (> 100 mV/m pk-pk) solitary waves and large-amplitude (approx.30 mV/m pk-pk) waves exhibiting characteristics consistent with electron Bernstein waves. The Bernstein-like waves show enhanced power at integer and half-integer harmonics of the cyclotron frequency with a broadened power spectrum at higher frequencies, consistent with the electron cyclotron drift instability. The Bernstein-like waves are obliquely polarized with respect to the magnetic field but parallel to the shock normal direction. Strong particle heating is observed in both the electrons and ions. The observed heating and waveforms are likely due to instabilities driven by the free energy provided by reflected ions at this supercritical interplanetary shock. These results offer new insights into collisionless shock dissipation and wave-particle interactions in the solar wind.

Wilson, L. B., III; Cattell, C. A.; Kellogg, P. J.; Goetz, K.; Kersten, K.; Kasper, J. C.; Szabo, A.; Wilber, M.

2010-01-01

120

Large-scale atmospheric carbon and surface water dynamics inferred from satellite-based observations  

NASA Astrophysics Data System (ADS)

The sensitivity of Earth's wetlands to observed shifts in global precipitation and temperature patterns and their ability to produce large quantities of climate-active gases are key global change questions. Surface inundation is a crucial state variable that affects the rate of land-atmosphere carbon exchange and the partitioning of carbon between CO2 and CH4. Ground observation networks of large-scale inundation patterns are sparse because they require large fiscal, technological and human resources. Thus, satellite remote sensing products for global inundation dynamics, as well as total water storage and atmospheric carbon, can provide a complete synoptic view of past and current carbon - surface water dynamics over large areas that otherwise could not be assessed. We present results from a correlative analysis between spaceborne measurements of CO2 and CH4 as observed by SCIAMACHY and AIRS, water storage (derived from gravity anomalies provided by NASA's GRACE mission), and inundated water fraction derived from a combination of active and passive microwave remote sensing datasets. A general assessment is conducted globally, and further time-series analysis is focused on four regions of interest: North Amazon, Congo, Ob, and Ganges-Brahmaputra river basins. This analysis was supported by a grant from the NASA Terrestrial Ecology Program and the development of the inundation datasets was supported by the NASA MEaSUREs program.

Jensen, K.; McDonald, K. C.; Krakauer, N.; Schroeder, R.

2013-12-01

121

Observations of large scale steady magnetic fields in the dayside Venus ionosphere  

NASA Astrophysics Data System (ADS)

Although the dayside ionosphere of Venus is often field-free except for fine-scale features, large-scale steady ionospheric magnetic fields with magnitudes sometimes exceeding 100 gammas are occasionally observed by the Pioneer Venus Orbiter magnetometer. These fields are mainly horizontal and can assume any angle in the horizontal plane. The orientation of the field may change along the spacecraft trajectory. The field magnitude in the upper ionosphere usually shows a distinct minimum near approximately 200 km altitude, but the altitude profile is otherwise arbitrary. With few exceptions, the observations of these large scale fields occur when periapsis is at solar zenith angles less than 50 deg. The occurrence of large-scale fields is often coincident with the observation of high solar wind dynamic pressures by the Pioneer Venus Orbiter plasma analyzer closely following the ionosphere encounter. However, the detection of this phenomenon even during some orbits for which the dynamic pressure is not extraordinarily high suggests that other factors, such as hysteresis effects, must also play a role in determining the occurrence frequency of large-scale magnetic fields in the dayside Venus ionosphere.

Luhmann, J. G.; Elphic, R. C.; Russell, C. T.; Mihalov, J. D.; Wolfe, J. H.

1980-11-01

122

Large-Scale Covariability Between Aerosol and Precipitation Over the 7-SEAS Region: Observations and Simulations  

NASA Technical Reports Server (NTRS)

One of the seven scientific areas of interests of the 7-SEAS field campaign is to evaluate the impact of aerosol on cloud and precipitation (http://7-seas.gsfc.nasa.gov). However, large-scale covariability between aerosol, cloud and precipitation is complicated not only by ambient environment and a variety of aerosol effects, but also by effects from rain washout and climate factors. This study characterizes large-scale aerosol-cloud-precipitation covariability through synergy of long-term multi ]sensor satellite observations with model simulations over the 7-SEAS region [10S-30N, 95E-130E]. Results show that climate factors such as ENSO significantly modulate aerosol and precipitation over the region simultaneously. After removal of climate factor effects, aerosol and precipitation are significantly anti-correlated over the southern part of the region, where high aerosols loading is associated with overall reduced total precipitation with intensified rain rates and decreased rain frequency, decreased tropospheric latent heating, suppressed cloud top height and increased outgoing longwave radiation, enhanced clear-sky shortwave TOA flux but reduced all-sky shortwave TOA flux in deep convective regimes; but such covariability becomes less notable over the northern counterpart of the region where low ]level stratus are found. Using CO as a proxy of biomass burning aerosols to minimize the washout effect, large-scale covariability between CO and precipitation was also investigated and similar large-scale covariability observed. Model simulations with NCAR CAM5 were found to show similar effects to observations in the spatio-temporal patterns. Results from both observations and simulations are valuable for improving our understanding of this region's meteorological system and the roles of aerosol within it. Key words: aerosol; precipitation; large-scale covariability; aerosol effects; washout; climate factors; 7- SEAS; CO; CAM5

Huang, Jingfeng; Hsu, N. Christina; Tsay, Si-Chee; Zhang, Chidong; Jeong, Myeong Jae; Gautam, Ritesh; Bettenhausen, Corey; Sayer, Andrew M.; Hansell, Richard A.; Liu, Xiaohong; Jiang, Jonathan H.

2012-01-01

123

Circular Extinction Contrast Imaging Microscope.  

National Technical Information Service (NTIS)

Systems and methods for producing circular extinction (CE) contrast images of anisotropic samples. Microscope systems for determining circular extinction (CE), the differential transmission of left and right circularly polarized light resulting from circu...

B. Kahr W. Kaminsky

2004-01-01

124

Characteristics of Electron Distributions Observed During Large Amplitude Whistler Wave Events in the Magnetosphere  

NASA Technical Reports Server (NTRS)

We present a statistical study of the characteristics of electron distributions associated with large amplitude whistler waves inside the terrestrial magnetosphere using waveform capture data as an addition of the study by Kellogg et al., [2010b]. We identified three types of electron distributions observed simultaneously with the whistler waves including beam-like, beam/flattop, and anisotropic distributions. The whistlers exhibited different characteristics dependent upon the observed electron distributions. The majority of the waveforms observed in our study have f/fce < or = 0.5 and are observed primarily in the radiation belts outside the plasmapause simultaneously with anisotropic electron distributions. We also present an example waveform capture of the largest magnetic field amplitude (> or = 8 nT pk-pk) whistler wave measured in the radiation belts. The majority of the largest amplitude whistlers occur during magnetically active periods (AE > 200 nT).

Wilson, Lynn B., III

2010-01-01

125

Circular-polarization-dependent study of the microwave photoconductivity in a two-dimensional electron system.  

PubMed

The polarization dependence of the low field microwave photoconductivity and absorption of a two-dimensional electron system has been investigated in a quasioptical setup in which linear and any circular polarization can be produced in situ. The microwave induced resistance oscillations and the zero resistance regions are notably immune to the sense of circular polarization. This observation is discrepant with a number of proposed theories. Deviations between different polarizations occur only near the cyclotron resonance where an unprecedented large resistance response is observed. PMID:16197030

Smet, J H; Gorshunov, B; Jiang, C; Pfeiffer, L; West, K; Umansky, V; Umanksy, V; Dressel, M; Meisels, R; Kuchar, F; von Klitzing, K

2005-09-01

126

ISIS observations of auroral particles and large-scale Birkeland currents  

NASA Technical Reports Server (NTRS)

Simultaneous electron and positive ion observations made with single-component magnetic perturbations on the ISIS-2 satellite are used to compare and contrast the relationships between primary and secondary auroral particle distributions at 5 eV-15 keV, and the large-scale Birkeland currents, in the pre- and post-midnight local time sectors. No unique relation is found between the regions of the Birkeland current system and regions of auroral particle distribution, though repeatable systematics in the region of upward-directed current are observed, and little evidence exists in either local time sector for the direct detection of the downward current-associated current carriers.

Klumpar, D. M.

1981-01-01

127

Large-scale horizontal flows from SOUP observations of solar granulation  

NASA Technical Reports Server (NTRS)

Using high resolution time sequence photographs of solar granulation from the SOUP experiment on Spacelab 2, large scale horizontal flows were observed in the solar surface. The measurement method is based upon a local spatial cross correlation analysis. The horizontal motions have amplitudes in the range 300 to 1000 m/s. Radial outflow of granulation from a sunspot penumbra into surrounding photosphere is a striking new discovery. Both the supergranulation pattern and cellular structures having the scale of mesogranulation are seen. The vertical flows that are inferred by continuity of mass from these observed horizontal flows have larger upflow amplitudes in cell centers than downflow amplitudes at cell boundaries.

November, L. J.; Simon, G. W.; Tarbell, T. D.; Title, A. M.; Ferguson, S. H.

1987-01-01

128

Observations of the earth's polar cleft at large radial distances with the Hawkeye 1 magnetometer  

NASA Technical Reports Server (NTRS)

Based on 364 spacecraft passes through the dayside region, the position of the polar cleft at large radial distances was determined with the magnetometer flown on Hawkeye 1. This data set is ideal for the study of the cusp and cleft region. Identification of the cleft depended on noting strong negative deviations of the magnetic field strength in the region from that of the dipole field. In solar magnetic coordinates, cleft observations were found between 40 deg and 70 deg latitude and + or - 75 deg latitude and + or - 75 deg longitude, while in geocentricmagnetospheric coordinates, these observations were found between 20 deg and 75 deg latitude and + or - 75 deg longitude. The extreme longitudinal extent of 150 deg is larger than those reported in some previous studies. Large magnetic depressions associated with the cleft extend out to 12 earth radii.

Farrell, W. M.; Van Allen, J. A.

1990-01-01

129

Nearly circular pump guides  

NASA Astrophysics Data System (ADS)

How nearly circular can a double-clad fiber's pump guide be and still have good absorption in the core? D's and octagons have good absorption but can be hard to cleave and lose pump power or brightness through splices with circular fibers. Ray tracing cannot be trusted since the perturbations to the circle can be smaller than a transverse wavelength. Using an algorithm well suited to near-circular boundaries, we have computed statistics of core-overlap of the lowest 10,000 modes of many pump-guide shapes. Some with 3% radial modulation have nearly as good core-overlap as an octagon.

Morehead, James J.; Muendel, Martin H.

2011-02-01

130

Observing abnormally large group velocity at the plasmonic band edge via a universal eigenvalue analysis.  

PubMed

We developed a novel universal eigenvalue analysis for 2D arbitrary nanostructures comprising dispersive and lossy materials. The complex dispersion relation (or complex Bloch band structure) of a metallic grating is rigorously calculated by the proposed algorithm with the finite-difference implementation. The abnormally large group velocity is observed at a plasmonic band edge with a large attenuation constant. Interestingly, we found the abnormal group velocity is caused by the leaky (radiation) loss, not by metallic absorption (ohmic) loss. The periodically modulated surface of the grating significantly modifies the original dispersion relation of the semi-infinite dielectric-metal structure and induces the extraordinarily large group velocity, which is different from the near-zero group velocity at photonic band edge. The work is fundamentally important to the design of plasmonic nanostructures. PMID:24365847

Sha, Wei E I; Meng, Ling Ling; Choy, Wallace C H; Chew, Weng Cho

2014-01-01

131

BATSE Observations of the Large-Scale Isotropy of Gamma-Ray Bursts  

Microsoft Academic Search

We use dipole and quadrupole statistics to test the large-scale isotropy of\\u000athe first 1005 gamma-ray bursts observed by the Burst and Transient Source\\u000aExperiment (BATSE). In addition to the entire sample of 1005 gamma-ray bursts,\\u000amany subsets are examined. We use a variety of dipole and quadrupole statistics\\u000ato search for Galactic and other predicted anisotropies and for anisotropies

Michael S. Briggs; William S. Paciesas; Geoffrey N. Pendleton; Charles A. Meegan; Gerald J. Fishman; John M. Horack; Martin N. Brock; Chryssa Kouveliotou; Dieter H. Hartmann; Jon Hakkila

1995-01-01

132

Observation of large-scale hydrodynamic structures in a vortex tube and the Ranque effect  

Microsoft Academic Search

The existence of large-scale structures in the form of a vortical double helix in a swirling Ranque flow is observed for the\\u000a first time. The structure of the vortical double helix is visualized in real time by the method of Hilbert bichromatic filtering.\\u000a The experimental result is interpreted on the basis that the most probable physical mechanism for the spatial

V. A. Arbuzov; Yu. N. Dubnishchev; A. V. Lebedev; M. Kh. Pravdina; N. I. Yavorski

1997-01-01

133

Observations of large-scale (C I) emission from S140  

Microsoft Academic Search

We have mapped the large-scale distribution of the 492 GHz (C I) (3P1 to 3P0) and 220 GHz (13)CO J = 2 to 1 lines across the S140 molecular cloud. The observations employed the University of Texas Gaussian Focal Reducer on the Caltech Submillimeter Observatory telescope to produce a high surface accuracy off-axis telescope with a 3 min beam. The

Rene Plume; D. T. Jaffe; Jocelyn Keene

1994-01-01

134

Observation of hard scattering in photoproduction events with a large rapidity gap at HERA  

Microsoft Academic Search

Events with a large rapidity gap and total transverse energy greater than 5 GeV have been observed in quasi-real photoproduction at HERA with the ZEUS detector. The distribution of these events as a function of the ?p centre of mass energy is consistent with diffractive scattering. For total transverse energies above 12 GeV, the hadronic final states show predominantly a

S. Bhadra; W. R. Frisken; K. M. Furutani; B. Musgrave; J. Repond; J. Schlereth; R. Stanek; R. L. Talaga; J. Thron; F. Arzarello; R. Ayad; G. Bari; M. Basile; L. Bellagamba; D. Boscherini; A. Bruni; G. Bruni; P. Bruni; G. Cara Romeo; G. Castellini; M. Chiarini; L. Cifarelli; F. Cindolo; F. Ciralli; A. Contin; S. D'Auria; F. Frasconi; I. Gialas; P. Giusti; G. Iacobucci; G. Laurenti; G. Levi; A. Margotti; T. Massam; R. Nania; C. Nemoz; F. Palmonari; A. Polini; G. Sartorelli; R. Timellini; Y. Zamora Garcia; A. Zichichi; A. Bargende; J. Crittenden; K. Desch; B. Diekmann; T. Doeker; M. Eckert; L. Feld; A. Frey; M. Geerts; G. Geitz; M. Grothe; H. Hartmann; D. Haun; K. Heinloth; E. Hilger; H.-P. Jakob; U. F. Katz; S. M. Mari; A. Mass; S. Mengel; J. Mollen; E. Paul; Ch. Rembser; R. Schattevoy; D. Schramm; J. Stamm; R. Wedemeyer; S. Campbell-Robson; A. Cassidy; N. Dyce; B. Foster; S. George; R. Gilmore; G. P. Heath; H. F. Heath; T. J. Llewellyn; C. J. S. Morgado; D. J. P. Norman; J. A. O'Mara; R. J. Tapper; S. S. Wilson; R. Yoshida; R. R. Rau; M. Arneodo; L. Iannotti; M. Schioppa; G. Susinno; A. Bernstein; A. Caldwell; J. A. Parsons; S. Ritz; F. Sciulli; P. B. Straub; L. Wai; S. Yang; Q. Zhu; P. Borzemski; J. Chwastowski; A. Eskreys; K. Piotrzkowski; M. Zachara; L. Zawiejski; L. Adamczyk; B. Bednarek; K. Eskreys; K. Jelen; D. Kisielewska; T. Kowalski; E. Rulikowska-Zarebska; L. Suszycki; J. Zajac; A. Kotanski; M. Przybycien; L. A. T. Bauerdick; U. Behrens; J. K. Bienlein; S. Böttcher; C. Coldewey; G. Drews; M. Flasinski; D. J. Gilkinson; P. Göttlicher; B. Gutjahr; T. Haas; W. Hain; D. Hasell; H. Heßling; H. Hultschig; Y. Iga; P. Joos; M. Kasemann; R. Klanner; W. Koch; L. Köpke; U. Kötz; H. Kowalski; W. Kröger; J. Krüger; J. Labs; A. Ladage; B. Löhr; M. Löwe; D. Lüke; O. Manczak; J. S. T. Ng; S. Nickel; D. Notz; K. Ohrenberg; M. Roco; M. Rohde; J. Roldán; U. Schneekloth; W. Schulz; F. Selonke; E. Stiliaris; T. Voß; D. Westphal; G. Wolf; C. Youngman; H. J. Grabosch; A. Leich; A. Meyer; C. Rethfeldt; S. Schlenstedt; G. Barbagli; P. Pelfer; G. Anzivino; G. Maccarrone; S. de Pasquale; S. Qian; L. Votano; A. Bamberger; A. Freidhof; T. Poser; S. Söldner-Rembold; J. Schroeder; G. Theisen; T. Trefzger; N. H. Brook; P. J. Bussey; A. T. Doyle; I. Fleck; V. A. Jamieson; D. H. Saxon; M. L. Utley; A. S. Wilson; A. Dannemann; U. Holm; D. Horstmann; H. Kammerlocher; B. Krebs; T. Neumann; R. Sinkus; K. Wick; E. Badura; B. D. Burow; A. Fürtjes; L. Hagge; E. Lohrmann; J. Mainusch; J. Milewski; M. Nakahata; N. Pavel; G. Poelz; W. Schott; J. Terron; F. Zetsche; T. C. Bacon; R. Beuselinck; I. Butterworth; E. Gallo; V. L. Harris; B. H. Hung; K. R. Long; D. B. Miller; P. P. O. Morawitz; A. Prinias; J. K. Sedgbeer; A. F. Whitfield; U. Mallik; E. McCliment; M. Z. Wang; S. M. Wang; J. T. Wu; Y. Zhang; P. Cloth; D. Filges; S. H. An; S. M. Hong; S. W. Nam; S. K. Park; M. H. Suh; S. H. Yon; R. Imlay; S. Kartik; H.-J. Kim; R. R. McNeil; W. Metcalf; V. K. Nadendla; F. Barreiro; G. Cases; R. Graciani; J. M. Hernández; L. Hervás; L. Labarga; J. del Peso; J. Puga; J. F. de Trocóniz; G. R. Smith; F. Corriveau; D. S. Hanna; J. Hartmann; L. W. Hung; J. N. Lim; C. G. Matthews; P. M. Patel; L. E. Sinclair; D. G. Stairs; M. St. Laurent; R. Ullmann; G. Zacek; V. Bashkirov; B. A. Dolgoshein; A. Stifutkin; G. L. Bashindzhagyan; P. F. Ermolov; L. K. Gladilin; Y. A. Golubkov; V. D. Kobrin; V. A. Kuzmin; A. S. Proskuryakov; A. A. Savin; L. M. Shcheglova; A. N. Solomin; N. P. Zotov; S. Bentvelsen; M. Botje; F. Chlebana; A. Dake; J. Engelen; P. de Jong; M. de Kamps; P. Kooijman; A. Kruse; V. O'dell; A. Tenner; H. Tiecke; W. Verkerke; M. Vreeswijk; L. Wiggers; E. de Wolf; R. van Woudenberg; D. Acosta; B. Bylsma; L. S. Durkin; K. Honscheid; C. Li; T. Y. Ling; K. W. McLean; W. N. Murray; I. H. Park; T. A. Romanowski; R. Seidlein; D. S. Bailey; G. A. Blair; A. Byrne; R. J. Cashmore; A. M. Cooper-Sarkar; D. Daniels; R. C. E. Devenish; N. Harnew; M. Lancaster; P. E. Luffman; L. Lindemann; J. McFall; C. Nath; A. Quadt; H. Uijterwaal; R. Walczak; F. F. Wilson; T. Yip; G. Abbiendi; A. Bertolin; R. Brugnera; R. Carlin; F. dal Corso; M. de Giorgi; U. Dosselli; S. Limentani; M. Morandin; M. Posocco; L. Stanco; R. Stroili; C. Voci; J. Bulmahn; J. M. Butterworth; R. G. Feild; B. Y. Oh; J. J. Whitmore; G. D'Agostini; M. Iori; G. Marini; M. Mattioli; A. Nigro; E. Tassi; J. C. Hart; N. A. McCubbin; K. Prytz; T. P. Shah; T. L. Short; E. Barberis; N. Cartiglia; T. Dubbs; C. Heusch; M. van Hook; B. Hubbard; W. Lockman; J. T. Rahn; H. F.-W. Sadrozinski; A. Seiden; J. Biltzinger; R. J. Seifert; A. H. Walenta; G. Zech; H. Abramowicz; G. Briskin; S. Dagan; A. Levy; T. Hasegawa; M. Hazumi; T. Ishii; M. Kuze; S. Mine; Y. Nagasawa; T. Nagira; M. Nakao; I. Suzuki; K. Tokushuku; S. Yamada; Y. Yamazaki; M. Chiba; R. Hamatsu; T. Hirose; K. Homma

1995-01-01

135

Survey of the ionospheric disturbances related with large seismic events in multi-satellite ionospheric observations  

NASA Astrophysics Data System (ADS)

We survey the ionospheric disturbances in the plasma and electro-magnetic wave measurements during the simultaneous observation period of DEMETER (Detection of Electro-Magnetic Emissions Transmitted from Earthquake Regions), CHAMP (CHAllenging Minisatellite Payload) and DMSP(Defense Meteorological Satellite Program) missions. The multi-satellite observation around three large earthquakes that occurred between 2004 and 2005 were investigated. The observational evidences of the earth-quake precursory phenomena and the recent progress of physical modeling of the ionospheric disturbances caused by the coupling of the stressed rock, Earth surface charges, atmosphere, and ionosphere system are reviewed. Then, we focus on identifying the precursory disturbances from the well-studied plasma disturbances in the ionosphere, which are known to originate from various physical mechanism other than the seismic activities. Electron density/temperature, ion density/temperature, and electro-magnetic field/wave data measured by various instruments equipped in the satellites were analyzed in finding specific examples of anomaly caused by large seismic activities. Finally, the possibility of forecasting or predicting large earthquakes using the plasma measurements of LEO (low earth orbit) satellites will be discussed.

Ryu, K.; Chae, J.; Lee, E.; Kil, H.

2013-12-01

136

Radiometer requirements for Earth-observation systems using large space antennas  

NASA Technical Reports Server (NTRS)

Requirements are defined for Earth observation microwave radiometry for the decade of the 1990's by using large space antenna (LSA) systems with apertures in the range from 50 to 200 m. General Earth observation needs, specific measurement requirements, orbit mission guidelines and constraints, and general radiometer requirements are defined. General Earth observation needs are derived from NASA's basic space science program. Specific measurands include soil moisture, sea surface temperature, salinity, water roughness, ice boundaries, and water pollutants. Measurements are required with spatial resolution from 10 to 1 km and with temporal resolution from 3 days to 1 day. The primary orbit altitude and inclination ranges are 450 to 2200 km and 60 to 98 deg, respectively. Contiguous large scale coverage of several land and ocean areas over the globe dictates large (several hundred kilometers) swaths. Radiometer measurements are made in the bandwidth range from 1 to 37 GHz, preferably with dual polarization radiometers with a minimum of 90 percent beam efficiency. Reflector surface, root mean square deviation tolerances are in the wavelength range from 1/30 to 1/100.

Keafer, L. S., Jr.; Harrington, R. F.

1983-01-01

137

Bridging the Gap between Large-Scale Simulations and Observations of Star Forming Cores  

NASA Astrophysics Data System (ADS)

Numerical simulations and observations of star forming cores are topics that both see a lot of progress these years. MHD simulations of molecular clouds have reached a level, where it is possible to evolve the cloud on parsec scale, while simultaneously resolving the neighbourhood around the individual protostars on AU scale. At the same time interferometers such as ALMA, with its increased sensitivity and resolving capabilities, are making it possible to zoom in on the protostellar cores in their earliest stages and map their gas and dust content. The advances in simulations and observations also open the possibility of comparing the two directly. I will present synthetic observations of a large number of protostellar cores, created from the high resolution numerical simulations of Haugbølle, Padoan and Nordlund in prep (see Padoan et al 2012 for similar lower resolution models). The synthetic observations are compared directly to real observations obtained from a range of different submm telescopes. The motivation for comparing real and synthetic observations is twofold. It enables us to test the validity of the simulations by ensuring that the synthetic observations agree with the real ones, and in the cases where they differ to identify the issues. In addition to this, through the simulations we are able to gain additional insight into the physics behind the observations. I will present several cases where synthetic and real observations have been compared. In one example of this we used 24 ?m Spitzer maps, and 850 ?m SCUBA maps from Perseus and Ophiuchus to calculate the distribution of distances between protostars and their parental cores (Jørgensen et. al. 2007, 2008). Both real and synthetic observations produce a centrally peaked distribution (HWHM smaller than the typical core radius). This indicates that on average newly formed protostars do not migrate far away from their parental core.

Frimann, Søren; Jørgensen, Jes Kristian

2014-07-01

138

Circular Well Model  

NSDL National Science Digital Library

The Circular Well model displays the 2D energy eigenstates of a particle trapped in a very deep two-dimensional circular well.  Because the Schrödinger equation for this system is separable into radial and angular differential equations, the solution can be expressed as a product of a Bessel function and and a complex exponential. The Circular Well model is distributed as a ready-to-run (compiled) Java archive. Double clicking the ejs_qm_CircularWell.jar file will run the program if Java is installed. You can modify this simulation if you have EJS installed by right-clicking within the plot and selecting âOpen EJS Modelâ from the pop-up menu item.

Christian, Wolfgang

2009-11-12

139

Simultaneous Solar Maximum Mission (SMM) and Very Large Array (VLA) observations of solar active regions  

NASA Technical Reports Server (NTRS)

Very Large Array observations at 20 cm wavelength can detect the hot coronal plasma previously observed at soft x ray wavelengths. Thermal cyclotron line emission was detected at the apex of coronal loops where the magnetic field strength is relatively constant. Detailed comparison of simultaneous Solar Maximum Mission (SMM) Satellite and VLA data indicate that physical parameters such as electron temperature, electron density, and magnetic field strength can be obtained, but that some coronal loops remain invisible in either spectral domain. The unprecedent spatial resolution of the VLA at 20 cm wavelength showed that the precursor, impulsive, and post-flare components of solar bursts originate in nearby, but separate loops or systems of loops.. In some cases preburst heating and magnetic changes are observed from loops tens of minutes prior to the impulsive phase. Comparisons with soft x ray images and spectra and with hard x ray data specify the magnetic field strength and emission mechanism of flaring coronal loops. At the longer 91 cm wavelength, the VLA detected extensive emission interpreted as a hot 10(exp 5) K interface between cool, dense H alpha filaments and the surrounding hotter, rarefield corona. Observations at 91 cm also provide evidence for time-correlated bursts in active regions on opposite sides of the solar equator; they are attributed to flare triggering by relativistic particles that move along large-scale, otherwise-invisible, magnetic conduits that link active regions in opposite hemispheres of the Sun.

Willson, Robert F.

1991-01-01

140

Estimating the Concentration of Large Raindrops from Polarimetric Radar and Disdrometer Observations  

NASA Technical Reports Server (NTRS)

Estimation of rainfall integral parameters, including radar observables, and empirical relations between them are sensitive to the truncation of the drop size distribution (DSD), particularly at the large drop end. The sensitivity of rainfall integral parameters to the maximum drop diameter (D(sub max)) is exacerbated at C-band since resonance effects are pronounced for large drops in excess of 5 mm diameter (D). Due to sampling limitations, it is often difficult to reliably estimate D(sub max) with disdrometers. The resulting uncertainties in D(sub max0 potentially increase errors in radar retrieval methods, particularly at C-band, that rely on disdrometer observations for DSD input to radar models. In fact, D(sub max) is typically an assumed DSD parameter in the development of radar retrieval methods. Because of these very uncertainties, it is difficult to independently confirm disdrometer estimates of D(sub max) with polarimetric radar observations. A couple of approaches can be taken to reduce uncertainty in large drop measurement. Longer integration times can be used for the collection of larger disdrometer samples. However, integration periods must be consistent with a radar resolution volume (RRV) and the temporal and spatial scales of the physical processes affecting the DSD therein. Multiple co-located disdrometers can be combined into a network to increase the sample size within a RRV. However, over a reasonable integration period, a single disdrometer sample volume is many orders of magnitudes less than a RRV so it is not practical to devise a network of disdrometers that has an equivalent volume to a typical RRV. Since knowledge of DSD heterogeneity and large drop occurrence in time and space is lacking, the specific accuracy or even general representativeness of disdrometer based D(sub max) and large drop concentration estimates within a RRV are currently unknown. To address this complex issue, we begin with a simpler question. Is the frequency of occurrence of large rain drops (D > 5 mm) in disdrometer observations, either stand alone or networked, generally representative and consistent with polarimetric radar observations? We first show from simulations that the concentration of large (D > 5 mm) rain drops (N(sub T5)) can be estimated from polarimetric observations of specific differential phase (K(sub dp)) and differential reflectivity (Z(sub dr)), N(sub T5)=F(K(sub dp),Z(sub dr)), or horizontal reflectivity (Z(sub h)) and Z(sub dr), N(sub T5)=(Z(sub h),Z(sub dr)). We assess the error associated with polarimetric retrieval of N(sub T5), including sensitivity to D(sub max) parameterization assumptions and measurement error in the radar simulations. Polarimetric measurements at S-band and C-band will then be used to retrieve estimates of N(sub T5) and compared to disdrometer estimates of N(sub T5). After careful consideration of retrieval error, we will check consistency between disdrometer and polarimetric radar estimates of N(sub T5) and the frequency of occurrence of large rain drops in a variety of precipitating regimes using data from NASA's Global Precipitation Measurement (GPM) Ground Validation (GV) program, including field campaigns such as MC3E (Oklahoma) and IFloodS (Iowa) and extended measurements over Huntsville, Alabama and NASA Wallops Flight Facility in coastal Virginia.

Carey, Lawrence D.; Petersen, Walter A; Gatlink, Patrick N.

2013-01-01

141

Phased array simulation using circular patch radiators  

NASA Astrophysics Data System (ADS)

The circuit properties of a circular patch with center short-circuit pin is investigated in a rectangular grid array. It is found that feed probe direct radiation produces large variations in element-to-element coupling coefficients in the E-plane. For the investigated pairwise arrangement of feed probe positions, the additional effect is unsymmetric E-plane coupling with respect to the direction toward the coupled element; this leads to unsymmetric E-plane scanning-induced impedance variation. The principal method of investigation is the small-array method using an 8 x 8 element array, but two waveguide simulators are used to check the results. It is concluded that the small array calculation provides reliable results for scanning angles greater than 60 deg off broadside. Active element match is observed to vary from -8.5 dB at broadside to about -20 dB on a 60 deg scanning cone.

Solbach, K.

1986-08-01

142

Squaring a Circular Segment  

ERIC Educational Resources Information Center

Consider a circular segment (the smaller portion of a circle cut off by one of its chords) with chord length c and height h (the greatest distance from a point on the arc of the circle to the chord). Is there a simple formula involving c and h that can be used to closely approximate the area of this circular segment? Ancient Chinese and Egyptian…

Gordon, Russell

2008-01-01

143

Simultaneous Solar Maximum Mission (SMM) and very large array observations of solar active regions  

NASA Technical Reports Server (NTRS)

The research deals mainly with Very Large Array and Solar Maximum Mission observations of the ubiquitous coronal loops that dominate the structure of the low corona. As illustrated, the observations of thermal cyclotron lines at microwave wavelengths provide a powerful new method of accurately specifying the coronal magnetic field strength. Processes are delineated that trigger solar eruptions from coronal loops, including preburst heating and the magnetic interaction of coronal loops. Evidence for coherent burst mechanisms is provided for both the Sun and nearby stars, while other observations suggest the presence of currents that may amplify the coronal magnetic field to unexpectedly high levels. The existence is reported of a new class of compact, variable moving sources in regions of apparently weak photospheric field.

Lang, K. R.

1986-01-01

144

Simultaneous Solar Maximum Mission (SMM) and very large array observations of solar active regions  

NASA Astrophysics Data System (ADS)

The research deals mainly with Very Large Array and Solar Maximum Mission observations of the ubiquitous coronal loops that dominate the structure of the low corona. As illustrated, the observations of thermal cyclotron lines at microwave wavelengths provide a powerful new method of accurately specifying the coronal magnetic field strength. Processes are delineated that trigger solar eruptions from coronal loops, including preburst heating and the magnetic interaction of coronal loops. Evidence for coherent burst mechanisms is provided for both the Sun and nearby stars, while other observations suggest the presence of currents that may amplify the coronal magnetic field to unexpectedly high levels. The existence is reported of a new class of compact, variable moving sources in regions of apparently weak photospheric field.

Lang, K. R.

1986-10-01

145

Observation of shock waves in a large Bose-Einstein condensate  

SciTech Connect

We observe the formation of shock waves in a Bose-Einstein condensate containing a large number of sodium atoms. The shock wave is initiated with a repulsive blue-detuned light barrier, intersecting the Bose-Einstein condensate, after which two shock fronts appear. We observe breaking of these waves when the size of these waves approaches the healing length of the condensate. At this time, the wave front splits into two parts and clear fringes appear. The experiment is modeled using an effective one-dimensional Gross-Pitaevskii-like equation and gives excellent quantitative agreement with the experiment, even though matter waves with wavelengths two orders of magnitude smaller than the healing length are present. In these experiments, no significant heating or particle loss is observed.

Meppelink, R.; Koller, S. B.; Vogels, J. M.; Straten, P. van der; Ooijen, E. D. van; Heckenberg, N. R.; Rubinsztein-Dunlop, H.; Haine, S. A.; Davis, M. J. [Atom Optics and Ultrafast Dynamics, Utrecht University, 3508 TA Utrecht (Netherlands); School of Mathematics and Physics, University of Queensland, Queensland 4072 (Australia); School of Mathematics and Physics, ARC Centre of Excellence for Quantum-Atom Optics, University of Queensland, Queensland 4072 (Australia)

2009-10-15

146

Boston University Physics Applets: Vertical Circular Motion  

NSDL National Science Digital Library

This web page is an interactive physics simulation relating to circular motion. An object on a vertical circular pathway is shown, accompanied by an animated free-body diagram. Users may view the motion in steps to observe the net force as the object changes speed due to gravitation. This item is part of a collection of similar simulation-based activities developed for students of introductory physics.

Duffy, Andrew

2008-08-01

147

Estimating the impact of SWOT observations on the predictability of large-scale hydraulic models  

NASA Astrophysics Data System (ADS)

The proposed NASA/CNES Surface Water Ocean Topography (SWOT) satellite mission would provide unprecedented measurements of hydraulic variables globally. This paper investigates the impact of different SWOT-like observations on the capability to model and predict hydrodynamics over large scales. In order to achieve this, the Ensemble Sensitivity (ET) method was adopted, examining the cost functional between two 'models' run on a 40,000 km2 area of the Ohio basin. The ET method is similar to the adjoint method but uses an ensemble of model perturbations to calculate the sensitivity to observations. The experiment consists of two configurations of the LISFLOOD-FP hydraulic model. The first (baseline) simulation represents a calibrated 'best effort' model based on a sub-grid channel structure using observations for parameters and boundary conditions, whereas the second (background) simulation consists of estimated parameters and SRTM-based boundary conditions. Using accurate SWOT-like observations such as water level, water surface width and slope in an Ensemble Sensitivity framework allowed us to assess the true impact of SWOT observables over different temporal and spatial scales on our current capabilities to model and predict hydrodynamic characteristics at a potentially global scale. Estimating the model sensitivity to observations could also allow the identification of errors in the model structure and parameterizations, as well as facilitate the derivation of a SWOT data product with optimal characteristics (e.g. reach-averaging).

Schumann, G. J.; Andreadis, K.

2012-12-01

148

Comparison Between Simulated and Observational Results of Galaxy Formation for Large Scale Structures  

NASA Astrophysics Data System (ADS)

The Millennium simulation is the largest numerical simulation of how minor fluctuations in the density of the universe's dark matter distribution are amplified by gravity to develop into the large scale structures(LSS) and galaxy clusters seen today(Springel et al. 2005). Although the simulations have been compared with the astronomical observations of the local universe, the simulations have not been widely compared with high redshift, early universe observations. In our study we compare the simulation data(Wang et al. 2008; Guo et al. 2008(in preparation)) for the first time with observations from the COSMOS survey(Scoville et al. 2006). Three quantities are proposed to characterize the structures and the structures distribution, namely the percent area occupied by LSS at each redshift, the average area of LSS and the shapes as characterized by the square root of the area divided by the circumference. We calculate these quantities for both the observations and the simulations, and quantify discrepancies between the existing simulations and observations. In particular, the simulations exhibit earlier development of dense structures than is seen in the observational data.

Li, G.; Scoville, N. Z.

2009-10-01

149

Strong circular photogalvanic effect in ZnO epitaxial films  

SciTech Connect

A strong circular photogalvanic effect (CPGE) in ZnO epitaxial films was reported under interband excitation. It was observed that CPGE current is as large as 100 nA/W in ZnO, which is about one order in magnitude higher than that in InN film while the CPGE currents in GaN films are not detectable. The possible reasons for the above observations are the strong spin orbit coupling in ZnO or the inversed valence band structure of ZnO.

Zhang, Q.; Wang, X. Q.; Yin, C. M.; Shen, B. [State Key Laboratory of Artificial Microstructure and Mesoscopic Physics, School of Physics, Peking University, Beijing 100871 (China); Chen, Y. H.; Chang, K. [Laboratory of Semiconductor Materials Science, Institute of Semiconductors, CAS, Beijing 100083 (China); Ge, W. K. [Department of Physics, Tsinghua University, Beijing 100871 (China)

2011-12-23

150

Using SDO/HMI Observations to Detect Pre-emergence Signatures of Large Active Regions  

NASA Astrophysics Data System (ADS)

It was shown that large active regions can be detected by helioseismology in the deep convection zone before they become visible in the photosphere. The detection method is based on computations of cross-covariances between oscillation signals observed at pairs of locations on the solar surface. We present in this study the results of a thorough helioseismic investigation of large emerging active regions observed with SDO/HMI. For each one of these regions, we monitor the subsurface acoustic perturbations at various depths up to about 75 Mm and for several days before the emergence of magnetic field in the photosphere. The same set of measurements is also applied to quiet regions to obtain estimates of the noise level and evaluate the statistical significance of the perturbations measured in emerging-flux regions. We show examples of positive detection with the corresponding confidence levels, and we discuss perspectives of using this method with near real-time data from SDO/HMI to forecast the emergence of large active regions.

Ilonidis, Stathis; Zhao, Junwei

2014-06-01

151

Observations of structured and long-range transport in a large volume dusty (complex) plasma experiment  

NASA Astrophysics Data System (ADS)

DUPLEX-the DUsty PLasma EXperiment at the Naval Research Laboratory-is a large volume dc glow discharge plasma device. The DUPLEX chamber is a transparent polycarbonate cylinder that is 40 cm in radius and 80 cm in height. Argon dc glow discharge plasmas are generated between a grounded cathode and a biased anode. The anode and cathode are separated by 15 to 20 cm. Clouds of 1 ?m diameter alumina microparticles are suspended in the plasma-with the highest density directly above the cathode. However, particles have been detected throughout the entire plasma volume. This article reports on previously unidentified, and possibly unknown, phenomena observed in a dusty plasma. Two specific features will be the focus of this article. First, large microparticle clouds-up to 15 cm in diameter in some locations-with highly complex internal structures are identified. Second, long range-20 to 30 cm distances-periodic transport of microparticles from one region of the plasma to another is identified. It is believed that the large size and nonconducting boundary of the DUPLEX chamber facilitates the observation of these phenomena.

Thomas, Edward; Amatucci, William E.; Compton, Christopher; Christy, Brian

2002-07-01

152

EXPANDED VERY LARGE ARRAY CONTINUUM OBSERVATIONS TOWARD HOT MOLECULAR CORE CANDIDATES  

SciTech Connect

We have used the Expanded Very Large Array (EVLA) with two 1 GHz wide bands to obtain K-band (1.3 cm) continuum observations toward the following five hot molecular core candidates: IRAS 18151 - 1208, IRAS 18182 - 1433, IRAS 18345 - 0641, IRAS 18470 - 0044, and IRAS 19012 + 0536. The sources were selected from the 2002 list of Sridharan et al. and are characterized by high FIR luminosity, dense molecular and dust condensations, massive large-scale CO flows, and the absence of strong cm continuum emission. These properties are indicative of massive star-forming regions in an evolutionary phase prior to ultra- or hypercompact H II regions. We detect a total of 10 individual 1.3 cm continuum sources toward this sample, and derive in-band spectral indices between 19.3 and 25.5 GHz consistent with thermal free-free emission, for all sources except component A in IRAS 18182 - 1433, which has a negative spectral index indicative of synchrotron emission. We suggest that in most cases the 1.3 cm sources are due to shock-induced ionization, rather than direct photoionization by massive objects. The momentum rate present in these ionized flows is sufficient to drive the large-scale molecular flows. We discuss a number of morphological features supporting this hypothesis. The present observations demonstrate that the EVLA has sufficient sensitivity to study the regions near very young massive stars in the cm continuum.

Hofner, P. [Physics Department, New Mexico Tech, 801 Leroy Pl., Socorro, NM 87801 (United States); Kurtz, S.; Loinard, L.; RodrIguez, L. F. [Centro de RadioastronomIa y Astrofisica, P.O. Box 3-72 Universidad Nacional Autonoma de Mexico, Morelia 58090 (Mexico); Ellingsen, S. P. [School of Mathematics and Physics, University of Tasmania, Private Bag 37, Hobart, Tasmania 7001 (Australia); Menten, K. M.; Wyrowski, F. [Max-Planck-Institut fuer Radioastronomie, Auf dem Huegel 69, 53121 Bonn (Germany); Araya, E. D. [Physics Department, Western Illinois University, 1 University Circle, Macomb, IL 61455 (United States); Cesaroni, R. [INAF, Osservatorio Astrofisico di Arcetri, Largo E. Fermi 5, 50125 Firenze (Italy)

2011-09-20

153

Observations of Neutrons in Association with the Large Solar Flare of 6 November 1997  

NASA Astrophysics Data System (ADS)

Solar neutrons were detected by the Mt. Chacaltaya neutron detector in Bolivia (S E, 5250 m above sea level) in association with solar flares on 1997 November 6th. A clear signal was observed in association with a C4.7 solar flare which occurred at about 10 minutes before the X9.4 large solar flare. Previously, there have been no observation of solar neutrons in association with C class solar flares. Moreover, the signal was detected at early in the morning(7:41 Local Time). Therefore, solar neutrons which arrive at the earth must travel through a thick atmosphere to reach the detector because of large incident angle (?) to the atmosphere. In the thick atmosphere, it has been believed that solar neutrons could not arrive at the detector if we applied the usual attenuation model. However, calculations based on a new attenuation model for solar neutrons in the atmosphere, which takes account of multiple and/or large scattering, gives us a new possibility for us detecting solar neutrons under extreme conditions.

Tsuchiya, H.; Matsubara, Y.; Muraki, Y.; Murakami, K.; Sako, T.; Kakimoto, F.; Ogio, S.; Tsunesada, Y.; Tokuno, H.; Yoshii, H.; Tajima, N.; Martinic, N.; Miranda, P.; Ticona, R.; Velarde, A.

2001-08-01

154

Rater Calibration when Observational Assessment Occurs at Large Scale: Degree of Calibration and Characteristics of Raters Associated with Calibration  

ERIC Educational Resources Information Center

Observational assessment is used to study program and teacher effectiveness across large numbers of classrooms, but training a workforce of raters that can assign reliable scores when observations are used in large-scale contexts can be challenging and expensive. Limited data are available to speak to the feasibility of training large numbers of…

Cash, Anne H.; Hamre, Bridget K.; Pianta, Robert C.; Myers, Sonya S.

2012-01-01

155

Large-Amplitude Oscillation of an Erupting Filament as Seen in EUV, H?, and Microwave Observations  

NASA Astrophysics Data System (ADS)

We present multiwavelength observations of a large-amplitude oscillation of a polar-crown filament on 15 October 2002, which has been reported by Isobe and Tripathi ( Astron. Astrophys. 449, L17, 2006). The oscillation occurred during the slow rise (?1 km s-1) of the filament. It completed three cycles before sudden acceleration and eruption. The oscillation and following eruption were clearly seen in observations recorded by the Extreme-Ultraviolet Imaging Telescope (EIT) onboard the Solar and Heliospheric Observatory (SOHO). The oscillation was seen only in a part of the filament, and it appears to be a standing oscillation rather than a propagating wave. The amplitudes of velocity and spatial displacement of the oscillation in the plane of the sky were about 5 km s-1 and 15 000 km, respectively. The period of oscillation was about two hours and did not change significantly during the oscillation. The oscillation was also observed in H? by the Flare Monitoring Telescope at the Hida Observatory. We determine the three-dimensional motion of the oscillation from the H? wing images. The maximum line-of-sight velocity was estimated to be a few tens of kilometers per second, although the uncertainty is large owing to the lack of line-profile information. Furthermore, we also identified the spatial displacement of the oscillation in 17-GHz microwave images from Nobeyama Radio Heliograph (NoRH). The filament oscillation seems to be triggered by magnetic reconnection between a filament barb and nearby emerging magnetic flux as was evident from the MDI magnetogram observations. No flare was observed to be associated with the onset of the oscillation. We also discuss possible implications of the oscillation as a diagnostic tool for the eruption mechanisms. We suggest that in the early phase of eruption a part of the filament lost its equilibrium first, while the remaining part was still in an equilibrium and oscillated.

Isobe, H.; Tripathi, D.; Asai, A.; Jain, R.

2007-11-01

156

Observation of three-dimensional motion of the pellet ablatant in the Large Helical Device  

NASA Astrophysics Data System (ADS)

Application of two-point stereoscopic diagnostics using a fast camera and bundled fibre has enabled the observation of the three-dimensional nature of the pellet trajectory in the Large Helical Device. It has been observed that the pellet trajectory deviates from its injection direction, toroidally and vertically depending on the direction of the tangentially applied neutral beams. The magnitude of the toroidal deviation is similar in the clockwise as well as counter-clockwise neutral beam directions and is of 15-20 cm with a deflection speed of up to 400 m s-1. In contrast, an asymmetry in trajectory deflection has been observed in the vertical direction. Experimental results also indicate that the starting radius of the pellet trajectory bending in the counter-clockwise neutral beam case is more inward to that of the plasma. Collectively this leads to less penetration of the pellet inside the plasma and is prominent in the case of the clockwise neutral beam. Additionally, this fact supports evidence that the fast ion plays an important role in the pellet ablation process in the Large Helical Device. The pellet deflection is explained by the rocket effect due to unilateral ablation by the fast ions. The possible cause of the difference in the vertical deflection is explained by considering the geometrical aspects of the magnetic field structure.

Mishra, J. S.; Sakamoto, R.; Matsuyama, A.; Motojima, G.; Yamada, H.; LHD Experiment Group

2011-08-01

157

CONTEMPORANEOUS VLBA 5 GHz OBSERVATIONS OF LARGE AREA TELESCOPE DETECTED BLAZARS  

SciTech Connect

The radio properties of blazars detected by the Large Area Telescope (LAT) on board the Fermi Gamma-ray Space Telescope have been observed contemporaneously by the Very Long Baseline Array (VLBA). In total, 232 sources were observed with the VLBA. Ninety sources that were previously observed as part of the VLBA Imaging and Polarimetry Survey (VIPS) have been included in the sample, as well as 142 sources not found in VIPS. This very large, 5 GHz flux-limited sample of active galactic nuclei (AGNs) provides insights into the mechanism that produces strong {gamma}-ray emission. In particular, we see that {gamma}-ray emission is related to strong, uniform magnetic fields in the cores of the host AGN. Included in this sample are non-blazar AGNs such as 3C84, M82, and NGC 6251. For the blazars, the total VLBA radio flux density at 5 GHz correlates strongly with {gamma}-ray flux. The LAT BL Lac objects tend to be similar to the non-LAT BL Lac objects, but the LAT flat-spectrum radio quasars (FSRQs) are significantly different from the non-LAT FSRQs. Strong core polarization is significantly more common among the LAT sources, and core fractional polarization appears to increase during LAT detection.

Linford, J. D.; Taylor, G. B. [Department of Physics and Astronomy, University of New Mexico, MSC07 4220, Albuquerque, NM 87131-0001 (United States); Romani, R. W. [Department of Physics, Stanford University, Stanford, CA 94305 (United States); Helmboldt, J. F. [Naval Research Laboratory, Code 7213, 4555 Overlook Avenue SW, Washington, DC 20375 (United States); Readhead, A. C. S.; Reeves, R.; Richards, J. L. [Astronomy Department, California Institute of Technology, Mail Code 247-17, 1200 East California Boulevard, Pasadena, CA 91125 (United States)

2012-01-10

158

EXPANDED VERY LARGE ARRAY OBSERVATIONS OF THE BARNARD 5 STAR-FORMING CORE: EMBEDDED FILAMENTS REVEALED  

SciTech Connect

We present {approx}6.'5 x 8' Expanded Very Large Array (EVLA) mosaic observations of the NH{sub 3} (1,1) emission in the Barnard 5 region in Perseus, with an angular resolution of 6''. This map covers the coherent region, where the dense gas presents subsonic non-thermal motions (as seen from single dish observations with the Green Bank Telescope, GBT). The combined EVLA and GBT observations reveal, for the first time, a striking filamentary structure (20'' wide or 5000 AU at the distance of Perseus) in this low-mass star-forming region. The integrated intensity profile of this structure is consistent with models of an isothermal filament in hydrostatic equilibrium. The observed separation between the B5-IRS1 young stellar object (YSO), in the central region of the core, and the northern starless condensation matches the Jeans length of the dense gas. This suggests that the dense gas in the coherent region is fragmenting. The observed region displays a narrow velocity dispersion, where most of the gas shows evidence for subsonic turbulence and where little spatial variations are present. It is only close to the YSO where an increase in the velocity dispersion is found, but still displaying subsonic non-thermal motions.

Pineda, Jaime E.; Longmore, Steven [ESO, Karl Schwarzschild Street 2, 85748 Garching bei Munchen (Germany); Goodman, Alyssa A. [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Arce, Hector G. [Department of Astronomy, Yale University, P.O. Box 208101, New Haven, CT 06520-8101 (United States); Caselli, Paola [School of Physics and Astronomy, University of Leeds, Leeds LS2 9JT (United Kingdom); Corder, Stuartt, E-mail: jaime.pineda@manchester.ac.uk [North American ALMA Science Center, 520 Edgemont Road, Charlottesville, VA 22903 (United States)

2011-09-20

159

Interstellar Chemistry Special Feature: Interferometric observations of large biologically interesting interstellar and cometary molecules  

NASA Astrophysics Data System (ADS)

Interferometric observations of high-mass regions in interstellar molecular clouds have revealed hot molecular cores that have substantial column densities of large, partly hydrogen-saturated molecules. Many of these molecules are of interest to biology and thus are labeled "biomolecules." Because the clouds containing these molecules provide the material for star formation, they may provide insight into presolar nebular chemistry, and the biomolecules may provide information about the potential of the associated interstellar chemistry for seeding newly formed planets with prebiotic organic chemistry. In this overview, events are outlined that led to the current interferometric array observations. Clues that connect this interstellar hot core chemistry to the solar system can be found in the cometary detection of methyl formate and the interferometric maps of cometary methanol. Major obstacles to understanding hot core chemistry remain because chemical models are not well developed and interferometric observations have not been very sensitive. Differentiation in the molecular isomers glycolaldehdye, methyl formate, and acetic acid has been observed, but not explained. The extended source structure for certain sugars, aldehydes, and alcohols may require nonthermal formation mechanisms such as shock heating of grains. Major advances in understanding the formation chemistry of hot core species can come from observations with the next generation of sensitive, high-resolution arrays. biomolecules | comets | chemistry

Snyder, Lewis E.

2006-08-01

160

Fermi Large Area Telescope Observations of Two Gamma-Ray Emission Components from the Quiescent Sun  

NASA Astrophysics Data System (ADS)

We report the detection of high-energy ?-rays from the quiescent Sun with the Large Area Telescope on board the Fermi Gamma-Ray Space Telescope (Fermi) during the first 18 months of the mission. These observations correspond to the recent period of low solar activity when the emission induced by cosmic rays (CRs) is brightest. For the first time, the high statistical significance of the observations allows clear separation of the two components: the point-like emission from the solar disk due to CR cascades in the solar atmosphere and extended emission from the inverse Compton (IC) scattering of CR electrons on solar photons in the heliosphere. The observed integral flux (>=100 MeV) from the solar disk is (4.6 ± 0.2[statistical error]+1.0 - 0.8[systematic error]) × 10-7 cm-2 s-1, which is ~7 times higher than predicted by the "nominal" model of Seckel et al. In contrast, the observed integral flux (>=100 MeV) of the extended emission from a region of 20° radius centered on the Sun, but excluding the disk itself, (6.8 ± 0.7[stat.]+0.5 - 0.4[syst.]) × 10-7 cm-2 s-1, along with the observed spectrum and the angular profile, is in good agreement with the theoretical predictions for the IC emission.

Abdo, A. A.; Ackermann, M.; Ajello, M.; Baldini, L.; Ballet, J.; Barbiellini, G.; Bastieri, D.; Bechtol, K.; Bellazzini, R.; Berenji, B.; Bonamente, E.; Borgland, A. W.; Bouvier, A.; Bregeon, J.; Brez, A.; Brigida, M.; Bruel, P.; Buehler, R.; Buson, S.; Caliandro, G. A.; Cameron, R. A.; Caraveo, P. A.; Casandjian, J. M.; Cecchi, C.; Charles, E.; Chekhtman, A.; Chiang, J.; Ciprini, S.; Claus, R.; Cohen-Tanugi, J.; Conrad, J.; Cutini, S.; de Angelis, A.; de Palma, F.; Dermer, C. D.; Digel, S. W.; Silva, E. do Couto e.; Drell, P. S.; Dubois, R.; Favuzzi, C.; Fegan, S. J.; Focke, W. B.; Fortin, P.; Frailis, M.; Funk, S.; Fusco, P.; Gargano, F.; Gasparrini, D.; Gehrels, N.; Germani, S.; Giglietto, N.; Giordano, F.; Giroletti, M.; Glanzman, T.; Godfrey, G.; Grenier, I. A.; Grillo, L.; Guiriec, S.; Hadasch, D.; Hays, E.; Hughes, R. E.; Iafrate, G.; Jóhannesson, G.; Johnson, A. S.; Johnson, T. J.; Kamae, T.; Katagiri, H.; Kataoka, J.; Knödlseder, J.; Kuss, M.; Lande, J.; Latronico, L.; Lee, S.-H.; Lionetto, A. M.; Longo, F.; Loparco, F.; Lott, B.; Lovellette, M. N.; Lubrano, P.; Makeev, A.; Mazziotta, M. N.; McEnery, J. E.; Mehault, J.; Michelson, P. F.; Mitthumsiri, W.; Mizuno, T.; Moiseev, A. A.; Monte, C.; Monzani, M. E.; Morselli, A.; Moskalenko, I. V.; Murgia, S.; Nakamori, T.; Naumann-Godo, M.; Nolan, P. L.; Norris, J. P.; Nuss, E.; Ohsugi, T.; Okumura, A.; Omodei, N.; Orlando, E.; Ormes, J. F.; Ozaki, M.; Paneque, D.; Pelassa, V.; Pesce-Rollins, M.; Pierbattista, M.; Piron, F.; Porter, T. A.; Rainò, S.; Rando, R.; Razzano, M.; Reimer, A.; Reimer, O.; Reposeur, T.; Ritz, S.; Sadrozinski, H. F.-W.; Schalk, T. L.; Sgrò, C.; Share, G. H.; Siskind, E. J.; Smith, P. D.; Spandre, G.; Spinelli, P.; Strickman, M. S.; Strong, A. W.; Takahashi, H.; Tanaka, T.; Thayer, J. G.; Thayer, J. B.; Thompson, D. J.; Tibaldo, L.; Torres, D. F.; Tosti, G.; Tramacere, A.; Troja, E.; Uchiyama, Y.; Usher, T. L.; Vandenbroucke, J.; Vasileiou, V.; Vianello, G.; Vilchez, N.; Vitale, V.; Vladimirov, A. E.; Waite, A. P.; Wang, P.; Winer, B. L.; Wood, K. S.; Yang, Z.; Ziegler, M.

2011-06-01

161

FERMI LARGE AREA TELESCOPE OBSERVATIONS OF TWO GAMMA-RAY EMISSION COMPONENTS FROM THE QUIESCENT SUN  

SciTech Connect

We report the detection of high-energy {gamma}-rays from the quiescent Sun with the Large Area Telescope on board the Fermi Gamma-Ray Space Telescope (Fermi) during the first 18 months of the mission. These observations correspond to the recent period of low solar activity when the emission induced by cosmic rays (CRs) is brightest. For the first time, the high statistical significance of the observations allows clear separation of the two components: the point-like emission from the solar disk due to CR cascades in the solar atmosphere and extended emission from the inverse Compton (IC) scattering of CR electrons on solar photons in the heliosphere. The observed integral flux ({>=}100 MeV) from the solar disk is (4.6 {+-} 0.2[statistical error]{sup +1.0}{sub -0.8}[systematic error]) x 10{sup -7} cm{sup -2} s{sup -1}, which is {approx}7 times higher than predicted by the 'nominal' model of Seckel et al. In contrast, the observed integral flux ({>=}100 MeV) of the extended emission from a region of 20 deg. radius centered on the Sun, but excluding the disk itself, (6.8 {+-} 0.7[stat.]{sup +0.5}{sub -0.4}[syst.]) x 10{sup -7} cm{sup -2} s{sup -1}, along with the observed spectrum and the angular profile, is in good agreement with the theoretical predictions for the IC emission.

Abdo, A. A. [Center for Earth Observing and Space Research, College of Science, George Mason University, Fairfax, VA 22030 (United States); Ackermann, M.; Ajello, M.; Bechtol, K.; Berenji, B.; Borgland, A. W.; Buehler, R. [Department of Physics and SLAC National Accelerator Laboratory, W. W. Hansen Experimental Physics Laboratory, Kavli Institute for Particle Astrophysics and Cosmology, Stanford University, Stanford, CA 94305 (United States); Baldini, L.; Bellazzini, R.; Bregeon, J.; Brez, A. [Istituto Nazionale di Fisica Nucleare, Sezione di Pisa, I-56127 Pisa (Italy); Ballet, J. [Laboratoire AIM, CEA-IRFU/CNRS/Universite Paris Diderot, Service d'Astrophysique, CEA Saclay, 91191 Gif sur Yvette (France); Barbiellini, G. [Istituto Nazionale di Fisica Nucleare, Sezione di Trieste, I-34127 Trieste (Italy); Bastieri, D.; Buson, S. [Istituto Nazionale di Fisica Nucleare, Sezione di Padova, I-35131 Padova (Italy); Bonamente, E. [Istituto Nazionale di Fisica Nucleare, Sezione di Perugia, I-06123 Perugia (Italy); Bouvier, A. [Santa Cruz Institute for Particle Physics, Department of Physics and Department of Astronomy and Astrophysics, University of California at Santa Cruz, Santa Cruz, CA 95064 (United States); Brigida, M. [Dipartimento di Fisica 'M. Merlin' dell'Universita e del Politecnico di Bari, I-70126 Bari (Italy); Bruel, P. [Laboratoire Leprince-Ringuet, Ecole polytechnique, CNRS/IN2P3, Palaiseau (France); Caliandro, G. A., E-mail: imos@stanford.edu, E-mail: eorlando@stanford.edu, E-mail: brigida@ba.infn.it, E-mail: nico.giglietto@ba.infn.it [Institut de Ciencies de l'Espai (IEEC-CSIC), Campus UAB, 08193 Barcelona (Spain)

2011-06-20

162

Expanded Very Large Array Nova Project Observations of the Classical NovaV1723 Aquilae  

NASA Technical Reports Server (NTRS)

We present radio light curves and spectra of the classical nova VI723 Aql obtained with the Expanded Very Large Array (EVLA). This is the first paper to showcase results from the EVLA Nova Project, which comprises a team of observers and theorists utilizing the greatly enhanced sensitivity and frequency coverage of EVLA radio observations, along with observations at other wavelengths, to reach a deeper understanding of the energetics, morphology, and temporal characteristics of nova explosions. Our observations of VI723 Aql span 1-37 GHz in frequency, and we report on data from 14 to 175 days following the time of the nova explosion. The broad frequency coverage and frequent monitoring show that the radio behavior of VI723 Aql does not follow the classic Hubble-flow model of homologous spherically expanding thermal ejecta. The spectra are always at least partially optically thin, and the flux rises on faster timescales than can be reproduced with linear expansion. Therefore, any description of the underlying physical processes must go beyond this simple picture. The unusual spectral properties and light curve evolution might be explained by multiple emitting regions or shocked material. Indeed, X-ray observations from Swift reveal that shocks are likely present.

Krauss, Miriam I.; Chomiuk, Laura; Rupen, Michael; Roy, Nirupam; Mioduszewski, Amy J.; Sokoloski, J. L.; Nelson, Thomas; Mukai, Koji; Bode, M. F.; Eyres, S. P. S.; OBrien, T. J.

2011-01-01

163

Bursts of energetic electron induced large surface charging observed by Chang'E-1  

NASA Astrophysics Data System (ADS)

A relationship between surface charging and bursts of energetic electron (BEE) event is presented in this paper. In a 200 km lunar polar orbit, during quiet time, 0.1-2.0 MeV BEE events were observed by High Energetic Particles Detectors (HPD) on board Chang'E-1, on December 22, 2007, when the spacecraft was within the inner terrestrial magnetosheath. At the same time, a large surface charging of ˜-5.4 kV was observed by Chang'E-1, which was evidenced by increasing the ions energy observed by Solar Wind Ion Detectors (SWIDs). We found that the surface charging is strongly correlated with BEE events, and the potentials of spacecraft surface charging was experientially expressed as U?3.6×10-5·fT (kV). The BEE events did occur in the solar wind, geomagnetic tail and magnetosheath alternately, whereas the surface charging during the BEE events is in the magnetosheath or transition region of boundaries. Though the observed surface charging was fewer than the BEE events, it is expected that the occurrence of the charging events caused by the bursts of energetic electrons should be more frequent than the Chang'E-1 observations. Meanwhile, the spacecraft charging indicates the lunar surface can be charged to negative kilovolt-scale by the BEE events even in quiet times.

Wang, X. Y.; Zhang, A. B.; Zhang, X. G.; Reme, H.; Kong, L. G.; Zhang, S. Y.; Yu, D. J.; Wang, S. J.; Zhu, G. W.

2012-10-01

164

EXPANDED VERY LARGE ARRAY NOVA PROJECT OBSERVATIONS OF THE CLASSICAL NOVA V1723 AQUILAE  

SciTech Connect

We present radio light curves and spectra of the classical nova V1723 Aql obtained with the Expanded Very Large Array (EVLA). This is the first paper to showcase results from the EVLA Nova Project, which comprises a team of observers and theorists utilizing the greatly enhanced sensitivity and frequency coverage of EVLA radio observations, along with observations at other wavelengths, to reach a deeper understanding of the energetics, morphology, and temporal characteristics of nova explosions. Our observations of V1723 Aql span 1-37 GHz in frequency, and we report on data from 14 to 175 days following the time of the nova explosion. The broad frequency coverage and frequent monitoring show that the radio behavior of V1723 Aql does not follow the classic Hubble-flow model of homologous spherically expanding thermal ejecta. The spectra are always at least partially optically thin, and the flux rises on faster timescales than can be reproduced with linear expansion. Therefore, any description of the underlying physical processes must go beyond this simple picture. The unusual spectral properties and light curve evolution might be explained by multiple emitting regions or shocked material. Indeed, X-ray observations from Swift reveal that shocks are likely present.

Krauss, Miriam I.; Chomiuk, Laura; Rupen, Michael; Roy, Nirupam; Mioduszewski, Amy J., E-mail: mkrauss@nrao.edu, E-mail: lchomiuk@nrao.edu, E-mail: mrupen@nrao.edu, E-mail: nroy@nrao.edu [National Radio Astronomy Observatory, Socorro, NM 87801 (United States)

2011-09-20

165

Large Amplitude Dynamic Events Near the Mesopause Observed in Na Lidar Measured Wind, Temperature, and Density  

NASA Astrophysics Data System (ADS)

Large amplitude dynamic events are frequently observed in the 85-105 km altitude region in data from Starfire, NM, Maui, HA, and Urbana, IL. Similar events at Maui have been analyzed by Larsen et al., [2004, J. Geophys. Res., 109, doi:10.1029/2002JF003067] and Hurd et al. [CEDAR poster, Utah, 2008] from Na lidar data. The events have a vertical extent of large temperature anomalies over 4-6 km, with a period of 3- 6 hours. All the events consist of a cold (upwelling) followed by a warm (downwelling) phase. Na density enhancements and depletions above the events as well as the horizontal winds provide insights into the cause for specific events (i.e. Li et al. , 2007, Investigation of a "wall" wave event, J. Geophys. Res., 112, doi10.1029/2006JD007213).

Swenson, G. R.; Liu, A.; Carlson, C.; Lu, X.; Mangognia, T.; Li, Z.

2008-12-01

166

Observing trans-Planckian ripples in the primordial power spectrum with future large scale structure probes  

SciTech Connect

We revisit the issue of ripples in the primordial power spectra caused by trans-Planckian physics, and the potential for their detection by future cosmological probes. We find that for reasonably large values of the first slow-roll parameter {epsilon} ({approx}>0.001), a positive detection of trans-Planckian ripples can be made even if the amplitude is as low as 10{sup -4}. Data from the Large Synoptic Survey Telescope (LSST) and the proposed future 21 cm survey with the Fast Fourier Transform Telescope (FFTT) will be particularly useful in this regard. If the scale of inflation is close to its present upper bound, a scale of new physics as high as {approx}0.2 M{sub P} could lead to observable signatures.

Hamann, Jan [LAPTH (Laboratoire d'Annecy-le-Vieux de Physique Theorique, CNRS UMR5108 and Universite de Savoie), BP 110, F-74941 Annecy-le-Vieux Cedex (France)] [LAPTH (Laboratoire d'Annecy-le-Vieux de Physique Theorique, CNRS UMR5108 and Universite de Savoie), BP 110, F-74941 Annecy-le-Vieux Cedex (France); Hannestad, Steen; Sloth, Martin S [Department of Physics and Astronomy, University of Aarhus, Ny Munkegade, DK-8000 Aarhus C (Denmark)] [Department of Physics and Astronomy, University of Aarhus, Ny Munkegade, DK-8000 Aarhus C (Denmark); Wong, Yvonne Y Y, E-mail: hamann@lapp.in2p3.fr, E-mail: sth@phys.au.dk, E-mail: sloth@phys.au.dk, E-mail: ywong@mppmu.mpg.de [Max-Planck-Institut fuer Physik (Werner-Heisenberg-Institut), Foehringer Ring 6, D-80805 Muenchen (Germany)

2008-09-15

167

Proposal for Environmental Observation System for Large Scale Gas Pipeline Networks Using Unmanned Airship  

NASA Astrophysics Data System (ADS)

Construction of a large scale natural gas pipeline network system in the Northeast Asian area has been proposed by several researchers, including Prof. Masaru Hirata, which will extend over tens of thousands of kilometers. To monitor the gas leakage, and to cope with any other hazardous problems, continuous surveillance of the network will be required. For this purpose, an environmental observation system for the large scale pipeline network is proposed. In this system unmanned airships are used as platforms for various environmental diagnostics. The unmanned airship is routed along the pipeline with the aid of GPS. Propulsion power of the air ship is transmitted from the ground bases by microwave; the microwave power stations are located every 100-200km along the pipeline. This paper describes the unmanned airships, environmental diagnostic systems, microwave generation tubes, and microwave powering system.

Shiho, Makoto; Horioka, Kazuhiko; Inoue, Gen; Onda, Masahiko; Leighty, William C.; Yokoo, Kuniyoshi; Ono, Shoichi; Ohashi, Kazuhiko; Hirata, Masaru

2004-03-01

168

Rotating Toroidal Dust Clouds in the NRL Large Volume Dusty Plasma Experiment: I. Initial Observations  

NASA Astrophysics Data System (ADS)

Large volume toroidal dust cloud structures that rotate in both the azimuthal (i.e., about the cylindrical axis) and poloidal (i.e., about the toroidal axis) directions have been observed in the Naval Research Laboratory's Large Volume Dusty Plasma Experiment (DUPLEX). The DUPLEX plasma is an argon dc glow discharge operated at pressures ranging from 50 to 250 mtorr and voltages ranging from 500 to 1000 V. Detailed measurements of the rotational velocities of the 1 micron alumina particles are made using the Auburn University Particle Image Velocity (PIV) laser system [E. Thomas, Jr., Phys. Plasmas, 6, 2672 (1999)]. The size, shape, and rotational characteristics of the toroidal cloud depend sensitively on the neutral pressure and discharge voltage. Examples illustrating the morphology, formation of central voids, and disruption of the cloud will be presented.

Compton, C. S.; Amatucci, W. E.; Thomas, E. E., Jr.; Christy, B. J.

2001-10-01

169

The direct observations of large aerosol radiative forcing in the Himalayan region  

NASA Astrophysics Data System (ADS)

We show here that absorbing aerosols have led to a large reduction of surface solar radiation during winter over the Himalayan region. Our results are based on radiometric, aerosol and Lidar observations made at three sites in Nepal during winter 2003. The monthly mean aerosol optical depth (AOD) ranged from 0.2 to 0.34 and the TERRA satellite MODIS data reveal that AODs measured over these sites were typical of the entire Himalayan region. The near-surface aerosol single scattering albedo was in the range from 0.7 to 0.9. The presence of strongly absorbing aerosols resulted in a relatively large diurnal mean aerosol surface radiative forcing efficiency of -73 Wm-2 (per unit optical depth). The seasonal mean reduction in solar flux was as high as 25 Wm-2 and aerosol heating as much as 1 K per day within the first two kilometers.

Ramana, M. V.; Ramanathan, V.; Podgorny, I. A.; Pradhan, Bidya B.; Shrestha, Basanta

2004-03-01

170

Large scale evaluation of soil moisture retrievals from passive microwave observations  

NASA Astrophysics Data System (ADS)

For several years passive microwave observations have been used to retrieve surface soil moisture from the Earth's surface. Several satellite sensors such as the Advanced Microwave Scanning Radiometer-EOS (AMSR-E) and WindSat have been used for this purpose using multi-channel observations. Large scale validation of these retrievals is generally hampered by a lack of ground-based observation networks with sufficient spatial density to be accurately up-scaled to the resolution of satellite-based soil moisture retrievals. In response to this challenge, two new global evaluation techniques have been proposed which circumvent the need for extensive ground-based soil moisture observations. The first technique (Rvalue) is based on calculating the correlation coefficient between known rainfall errors and Kalman filter analysis increments realized during the assimilation of remotely sensed soil moisture into an antecedent precipitation index. The second technique is based on a so-called Triple Collocation (TC) analysis, which is a statistical tool for estimating the root mean square error (RMSE) of a set of three linearly related data sources with independent error structures. These two newly-developed, large-scale soil moisture evaluation techniques are applied for cross-verification on a global scale. Both techniques are also used to determine the sensitivity of soil moisture retrievals to land surface temperature estimates by artificially degrading the satellite signal used for the retrieval of this important parameter. Instead of coincident land surface temperature observations from the same satellite, external sources for land surface temperature are also evaluated using the same evaluation techniques. Finally, both day- and night-time observations are evaluated separately to determine the impact of the different physical conditions during day- and night-time. The evaluation results produced by the Rvalue and TC soil moisture verification approaches show a high mutual consistency (R2 = 0.95), which lends confidence to their interpretation as robust evaluation techniques. They show that the quality of soil moisture retrievals has a strong link with density of the vegetation cover of the observed area. This link was also found when evaluating the different scenarios for the land surface temperature input and when comparing soil moisture retrievals from day- and night-time observations. This study could be used as a framework to evaluate retrievals from the recent Soil Moisture and Ocean Salinity (SMOS) and future Soil Moisture Active and Passive (SMAP) missions.

Parinussa, R.; Holmes, T. R.; Crow, W. T.; De Jeu, R. A.

2011-12-01

171

Interpreting Observed Northern Hemisphere Snow Trends with Large Ensembles of Climate Simulations  

NASA Astrophysics Data System (ADS)

Simulated variability and trends in Northern Hemisphere seasonal snow cover are analyzed in large ensembles of climate integrations of the National Center for Atmospheric Research's Community Earth System Model. Two 40-member ensembles driven by historical radiative forcings are generated, one coupled to a dynamical ocean and the other driven by observed sea surface temperatures (SSTs) over the period 1981-2010. The simulations reproduce many aspects of the observed climatology and variability of snow cover extent as characterized by the NOAA snow chart climate data record. Major features of the simulated snow water equivalent (SWE) also agree with observations (GlobSnow Northern Hemisphere SWE data record), although with a lesser degree of fidelity. Ensemble spread in the climate response quantifies the impact of natural climate variability in the presence and absence of coupling to the ocean. Both coupled and uncoupled ensembles indicate an overall decrease in springtime snow cover that is consistent with observations, although springtime trends in most climate realizations are weaker than observed. In the coupled ensemble, a tendency towards excessive warming in wintertime leads to a strong wintertime snow cover loss that is not found in observations. The wintertime warming bias and snow cover reduction trends are reduced in the uncoupled ensemble with observed SSTs. Natural climate variability generates widely different regional patterns of snow trends across realizations; these patterns are related in an intuitive way to temperature, precipitation and circulation trends in individual realizations. In particular, regional snow loss over North America in individual realizations is strongly influenced by North Pacific SST trends (manifested as Pacific Decadal Oscillation variability) and by sea level pressure trends in the North Pacific/North Atlantic sectors.

Mudryk, Lawrence; Kushner, Paul; Derksen, Chris

2014-05-01

172

Circular free-electron laser  

DOEpatents

A high efficiency, free electron laser utilizing a circular relativistic electron beam accelerator and a circular whispering mode optical waveguide for guiding optical energy in a circular path in the circular relativistic electron beam accelerator such that the circular relativistic electron beam and the optical energy are spatially contiguous in a resonant condition for free electron laser operation. Both a betatron and synchrotron are disclosed for use in the present invention. A free electron laser wiggler is disposed around the circular relativistic electron beam accelerator for generating a periodic magnetic field to transform energy from the circular relativistic electron beam to optical energy.

Brau, Charles A. (Los Alamos, NM); Kurnit, Norman A. (Santa Fe, NM); Cooper, Richard K. (Los Alamos, NM)

1984-01-01

173

Circular free-electron laser  

DOEpatents

A high efficiency, free electron laser is described utilizing a circular relativistic electron beam accelerator and a circular whispering mode optical waveguide for guiding optical energy in a circular path in the circular relativistic electron beam accelerator such that the circular relativistic electron beam and the optical energy are spatially contiguous in a resonant condition for free electron laser operation. Both a betatron and synchrotron are disclosed for use in the present invention. A free electron laser wiggler is disposed around the circular relativistic electron beam accelerator for generating a periodic magnetic field to transform energy from the circular relativistic electron beam to optical energy.

Brau, C.A.; Kurnit, N.A.; Cooper, R.K.

1982-01-26

174

High-resolution sounding rocket observations of large-amplitude Alfven waves  

NASA Technical Reports Server (NTRS)

Shear Alfven waves with amplitudes greater than 100 mV/m were observed on two recent sounding rocket flights. The largest waveforms are best described as a series of step functions, rather than as broadband noise or as single frequency waves. Complete two-dimensional E and B measurements at 4-ms time resolution were made, showing a downward propagation direction and implying insignificant reflection from the ionosphere at frequencies greater than 1 Hz. Intense, field-aligned, low-energy electron fluxes accompany the waves. Acceleration of these electrons by the Alfven waves is shown to be feasible. The waves in at least one case have a sufficently large ponderomotive potential to generate the observed density fluctuations of order one.

Boehm, M. H.; Carlson, C. W.; Mcfadden, J. P.; Clemmons, J. H.; Mozer, F. S.

1990-01-01

175

Fermi Large Area Telescope Observations of the Cosmic-Ray Induced  

SciTech Connect

We report on measurements of the cosmic-ray induced {gamma}-ray emission of Earth's atmosphere by the Large Area Telescope onboard the Fermi Gamma-ray Space Telescope. The LAT has observed the Earth during its commissioning phase and with a dedicated Earth-limb following observation in September 2008. These measurements yielded {approx} 6.4 x 10{sup 6} photons with energies > 100 MeV and {approx} 250 hours total livetime for the highest quality data selection. This allows the study of the spatial and spectral distributions of these photons with unprecedented detail. The spectrum of the emission - often referred to as Earth albedo gamma-ray emission - has a power-law shape up to 500 GeV with spectral index {Lambda} = 2.79 {+-} 0.06.

Abdo, A.

2012-02-29

176

Large amplitude whistlers in the magnetosphere observed with Wind-Waves  

NASA Astrophysics Data System (ADS)

We describe the results of a statistical survey of Wind-Waves data motivated by the recent STEREO/Waves discovery of large-amplitude whistlers in the inner magnetosphere. Although Wind was primarily intended to monitor the solar wind, the spacecraft spent 47 h inside 5 RE and 431 h inside 10 RE during the 8 years (1994-2002) that it orbited the Earth. Five episodes were found when whistlers had amplitudes comparable to those of Cattell et al. (2008), i.e., electric fields of 100 mV/m or greater. The whistlers usually occurred near the plasmapause. The observations are generally consistent with the whistlers observed by STEREO. In contrast with STEREO, Wind-Waves had a search coil, so magnetic measurements are available, enabling determination of the wave vector without a model. Eleven whistler events with useable magnetic measurements were found. The wave vectors of these are distributed around the magnetic field direction with angles from 4 to 48°. Approximations to observed electron distribution functions show a Kennel-Petschek instability which, however, does not seem to produce the observed whistlers. One Wind episode was sampled at 120,000 samples s-1, and these events showed a signature that is interpreted as trapping of electrons in the electrostatic potential of an oblique whistler. Similar waveforms are found in the STEREO data. In addition to the whistler waves, large amplitude, short duration solitary waves (up to 100 mV/m), presumed to be electron holes, occur in these passes, primarily on plasma sheet field lines mapping to the auroral zone.

Kellogg, P. J.; Cattell, C. A.; Goetz, K.; Monson, S. J.; Wilson, L. B., III

2011-09-01

177

Observation of large anomalous orientational nonlinear response in dye-doped liquid crystals at 1320 nm  

NASA Astrophysics Data System (ADS)

IR z-scan and conoscopic measurements have been performed on dye-doped nematic liquid crystal samples to investigate the influence of the dopant on the orientational nonlinear response of the liquid crystalline material, and the result compared to undyed samples. Both the dye-doped and undyed samples were prepared utilizing a surface treatment which produces homeotropic alignment in the undyed, glass-substrate samples. For samples constructed with non-conducting substrates, the dopant only slightly strengthens the nonlinear response of the host material, and the response in all cases is less than half that observed in samples with ITO- coated substrates. Undyed samples displayed no response at normal incidence for the laser intensities used, regardless of substrate, while doped samples displayed significant self- limiting at all angles of incidence. Increasing the dopant concentration further enhances the observed responses, but the time required to achieve the initial alignment state of the nematic increases more rapidly than the response, and significant delays in response to pulsed inputs are also observed. Laser polarization strongly effects the response characteristics, as expected. Z-scan and conoscopic measurements are used to determine the origin of the unusually large response in the ITO-coated samples Initial efforts with conoscopic techniques have found no evidence of pre-tilt in the director orientation, though more sensitive measurements are in process. The presence of a large nonlinear absorption contribution due to the dopant has been observed, though why only ITO-substrate samples may be affected is still under investigation.

Lopresti, Peter G.; Hemphill, Daniel A.

1997-10-01

178

Large Amplitude Whistlers in the Magnetosphere Observed with Wind-Waves  

NASA Technical Reports Server (NTRS)

We describe the results of a statistical survey of Wind-Waves data motivated by the recent STEREO/Waves discovery of large-amplitude whistlers in the inner magnetosphere. Although Wind was primarily intended to monitor the solar wind, the spacecraft spent 47 h inside 5 R(sub E) and 431 h inside 10 R(sub E) during the 8 years (1994-2002) that it orbited the Earth. Five episodes were found when whistlers had amplitudes comparable to those of Cattell et al. (2008), i.e., electric fields of 100 m V/m or greater. The whistlers usually occurred near the plasmapause. The observations are generally consistent with the whistlers observed by STEREO. In contrast with STEREO, Wind-Waves had a search coil, so magnetic measurements are available, enabling determination of the wave vector without a model. Eleven whistler events with useable magnetic measurements were found. The wave vectors of these are distributed around the magnetic field direction with angles from 4 to 48deg. Approximations to observed electron distribution functions show a Kennel-Petschek instability which, however, does not seem to produce the observed whistlers. One Wind episode was sampled at 120,000 samples/s, and these events showed a signature that is interpreted as trapping of electrons in the electrostatic potential of an oblique whistler. Similar waveforms are found in the STEREO data. In addition to the whistler waves, large amplitude, short duration solitary waves (up to 100 mV/m), presumed to be electron holes, occur in these passes, primarily on plasma sheet field lines mapping to the auroral zone.

Kellogg, P. J.; Cattell, C. A.; Goetz, K.; Monson, S. J.; Wilson, L. B., III

2011-01-01

179

Very Large Array Observations of DG Tau's Radio Jet: A Highly Collimated Thermal Outflow  

NASA Astrophysics Data System (ADS)

The active young protostar DG Tau has an extended jet that has been well studied at radio, optical, and X-ray wavelengths. We report sensitive new Very Large Array (VLA) full-polarization observations of the core and jet between 5 GHz and 8 GHz. Our high angular resolution observation at 8 GHz clearly shows an unpolarized inner jet with a size of 42 AU (0.''35) extending along a position angle similar to the optical-X ray outer jet. Using our nearly coeval 2012 VLA observations, we find a spectral index ? = +0.46 ± 0.05, which combined with the lack of polarization is consistent with bremsstrahlung (free-free) emission, with no evidence for a non-thermal coronal component. By identifying the end of the radio jet as the optical depth unity surface, and calculating the resulting emission measure, we find that our radio results are in agreement with previous optical line studies of electron density and consequent mass-loss rate. We also detect a weak radio knot at 5 GHz located 7'' from the base of the jet, coincident with the inner radio knot detected by Rodríguez et al. in 2009 but at lower surface brightness. We interpret this as due to expansion of post-shock ionized gas in the three years between observations.

Lynch, C.; Mutel, R. L.; Güdel, M.; Ray, T.; Skinner, S. L.; Schneider, P. C.; Gayley, K. G.

2013-03-01

180

VERY LARGE ARRAY OBSERVATIONS OF DG TAU'S RADIO JET: A HIGHLY COLLIMATED THERMAL OUTFLOW  

SciTech Connect

The active young protostar DG Tau has an extended jet that has been well studied at radio, optical, and X-ray wavelengths. We report sensitive new Very Large Array (VLA) full-polarization observations of the core and jet between 5 GHz and 8 GHz. Our high angular resolution observation at 8 GHz clearly shows an unpolarized inner jet with a size of 42 AU (0.''35) extending along a position angle similar to the optical-X ray outer jet. Using our nearly coeval 2012 VLA observations, we find a spectral index {alpha} = +0.46 {+-} 0.05, which combined with the lack of polarization is consistent with bremsstrahlung (free-free) emission, with no evidence for a non-thermal coronal component. By identifying the end of the radio jet as the optical depth unity surface, and calculating the resulting emission measure, we find that our radio results are in agreement with previous optical line studies of electron density and consequent mass-loss rate. We also detect a weak radio knot at 5 GHz located 7'' from the base of the jet, coincident with the inner radio knot detected by Rodriguez et al. in 2009 but at lower surface brightness. We interpret this as due to expansion of post-shock ionized gas in the three years between observations.

Lynch, C.; Mutel, R. L.; Gayley, K. G. [Department of Physics and Astronomy, University of Iowa, Iowa City, Iowa 52240 (United States)] [Department of Physics and Astronomy, University of Iowa, Iowa City, Iowa 52240 (United States); Guedel, M. [Department of Astrophysics, University of Vienna, A-1180 Vienna (Austria)] [Department of Astrophysics, University of Vienna, A-1180 Vienna (Austria); Ray, T. [Astronomy and Astrophysics Section, Dublin Institute for Advanced Studies, 31 Fitzwilliam Place, Dublin 2 (Ireland)] [Astronomy and Astrophysics Section, Dublin Institute for Advanced Studies, 31 Fitzwilliam Place, Dublin 2 (Ireland); Skinner, S. L. [Center for Astrophysics and Space Astronomy, University of Colorado, Boulder, CO 80309 (United States)] [Center for Astrophysics and Space Astronomy, University of Colorado, Boulder, CO 80309 (United States); Schneider, P. C. [Hamburger Sternwarte, Gojenbergsweg 112, D-21029 Hamburg (Germany)] [Hamburger Sternwarte, Gojenbergsweg 112, D-21029 Hamburg (Germany)

2013-03-20

181

BATSE Observations of the Large-Scale Isotropy of Gamma-Ray Bursts  

NASA Technical Reports Server (NTRS)

We use dipole and quadrupole statistics to test the large-scale isotropy of the first 1005 gamma-ray bursts observed by the Burst and Transient Source Experiment (BATSE). In addition to the entire sample of 1005 gamma-ray bursts, many subsets are examined. We use a variety of dipole and quadrupole statistics to search for Galactic and other predicted anisotropies and for anisotropies in a coordinate-system independent manner. We find the gamma-ray burst locations to be consistent with isotropy, e.g., for the total sample the observed Galactic dipole moment (cos theta) differs from the value predicted for isotropy by 0.9 sigma and the observed Galactic quadrupole moment (sin(exp 2) b - 1/3) by 0.3 sigma. We estimate for various models the anisotropies that could have been detected. If one-half of the locations were within 86 deg of the Galactic center, or within 28 deg of the Galactic plane, the ensuing dipole or quadrupole moment would have typically been detected at the 99% confidence level. We compare the observations with the dipole and quadrupole moments of various Galactic models. Several Galactic gamma-ray bursts models have moments within 2 sigma of the observations; most of the Galactic models proposed to date are no longer in acceptable agreement with the data. Although a spherical dark matter halo distribution could be consistent with the data, the required core radius is larger than the core radius of the dark matter halo used to explain the Galaxy's rotation curve. Gamma-ray bursts are much more isotropic than any observed Galactic population, strongly favoring but not requiring an origin at cosmological distances.

Briggs, Michael S.; Paciesas, William S.; Pendleton, Geoffrey N.; Meegan, Charles A.; Fishman, Gerald J.; Horack, John M.; Brock, Martin N.; Kouveliotou, Chryssa; Hartmann, Dieter H.; Hakkila, Jon

1996-01-01

182

Satellite observations of energy-banded ions during large geomagnetic storms  

NASA Astrophysics Data System (ADS)

Energy-banded ions from 10's to 10000's of eV are observed coincident with frequency-banded waves in the low latitude auroral and sub-auroral zones during every large (minimum DST <-150 nT) geomagnetic storm encountered by the FAST satellite. The banded ions persist for several FAST orbits, lasting up to 12 hours, in both the northern and southern hemispheres. The energy-banded ions often have more than six distinct bands, and the O+, He+ and H+ bands are often observed at the same energies. The bands are seen on the both the dayside and nightside and are also extensive in latitude (~50-75 degrees on the dayside, often extending to 45 degrees). The distributions are peaked in the perpendicular direction (locally mirroring) at the altitudes of the FAST satellite (~4000 km). We present both case studies and statistical studies of the banded ions. These bands are new phenomenon associated with all large storms, which are distinctly different from other banded populations, and are not readily interpreted using previous models for particle sources, transport and loss. The energy-banded ions are an energetically important component of the inner magnetosphere during the most intense magnetic storms. Evidence suggests that the banded ions may be the energy or particle source for many previously reported but unexplained phenomena during superstorms, including unusually intense stable auroral red (SAR) arcs, intense midlatitude ion-atom auroras, and the enhanced low energy (< 30 keV) component of the ring.

Dombeck, J. P.; Colpitts, C. A.; Cattell, C. A.; Kozyra, J. U.

2012-12-01

183

A fast-propagating, large-scale atmospheric gravity wave observed in the WAVE2004 campaign  

NASA Astrophysics Data System (ADS)

The Waves in Airglow Campaign in 2004 (WAVE2004), which aimed to elucidate the formation process of waves in airglow structures from both dynamical and chemical perspectives, was conducted using rocket-borne and ground-based instruments in Japan on 17 January 2004. In this experiment, we observed a large-scale atmospheric gravity wave (AGW), which appeared in both the vertical profiles of sodium density obtained by a Na lidar and the horizontal distributions of airglow emission obtained by an all-sky imager (ASI). Vertical propagation of the AGW accompanied by a shortening of its vertical wavelength was clearly visualized using the Na lidar data. The horizontal wavelength, horizontal phase velocity, period, and propagation direction of the AGW were estimated from the ASI data as 673-774 km, 107-122 m/s, ˜1.75 hours, and north-northeastward, respectively. Using these parameters and the MF radar wind, vertical wavelengths of the wave were calculated from the dispersion relation of gravity waves. The calculated vertical wavelengths were comparable at altitudes of 85.5 km and 93.25 km to those estimated from the variation of the sodium density. Using a simple ray tracing technique, the AGW was traced back to the southern edge of the distorted jet stream near tropopause. This result strongly suggests that an unstable baroclinic wave associated with ageostrophic motions in the jet stream was the wave source of the large-scale AGW observed in the WAVE2004.

Kubota, Minoru; Kawamura, Seiji; Abo, Makoto; Koizumi, Yoshiko; Murayama, Yasuhiro; Yamamori, Miho; Shiokawa, Kazuo; Otsuka, Yuichi; Uchiumi, Michihiro; Igarashi, Kiyoshi; Abe, Takumi; Oyama, Koh-Ichiro; Iwagami, Naomoto

2006-11-01

184

A Large Biogenic Source of Formic Acid Revealed From Space Observations  

NASA Astrophysics Data System (ADS)

Formic acid (HCOOH) is a ubiquitous trace gas in ambient air and a major contributor to acidic rain in remote environments. Its sources, however, are far from being fully understood. Along with direct emissions from human activities, vegetation fires and green plants, its major and most uncertain source is photochemical, and predominantly biogenic. Severe underpredictions of observed formic acid concentrations by large scale models in earlier studies pointed to the existence of missing sources. New insights into our understanding of the formic acid budget are brought forward by recent measurements of global tropospheric columns of formic acid retrieved from the thermal infrared IASI satellite sensor. In this communication, we use the IASI observations as input to an advanced source inversion algorithm coupled with a global chemistry transport model to build constraints on the formic acid budget. We deduce an annual formic acid source much higher than estimated from known sources, with a biogenic contribution of about 90%, mostly from tropical and boreal forests. We evaluate the derived fluxes against an extensive compilation of independent formic acid measurements, and investigate the implications of the large formic acid source on precipitation acidity on the global scale.

Stavrakou, T.; Muller, J. J.; Peeters, J.; Razavi, A.; Clarisse, L.; Clerbaux, C.; Coheur, P.; Hurtmans, D.

2011-12-01

185

Biochemical abnormalities observed in serum of dogs infected with large Babesia in Warsaw (Poland).  

PubMed

Biochemical abnormalities observed in canine babesiosis are related to the severity of the disease. The primary biochemical abnormalities found in affected dogs are: increase of the serum activity of transaminases and alkaline phosphatase, azotemia, and hypoglycemia. The purposes of this study were: 1) to estimate biochemical abnormalities in dogs infected with large Babesia in Warsaw and 2) to evaluate statistically changes observed during canine babesiosis in dogs from Warsaw. Samples of serum were collected from dogs naturally infected with large Babesia. Among 2023 positive samples, 202 were randomly selected. Alanine aminotransferase (ALT), aspartate aminotransferase (AST), alkaline phosphatase (ALP), creatinine, blood urea nitrogen (BUN), total serum protein (TSP), albumin and blood glucose concentration were determined with a clinical chemistry analyser. Elevated activity of ALT, AST and ALP was detected accordingly in: 64.9, 92.6 and 31.7% of dogs. Elevated creatinine concentration and BUN were detected accordingly in 30.7 and 62.4% of dogs. Decrease of TSP, albumin, BUN, and hypoglycemia was detected accordingly in: 19.8, 32.7, 1.5 and 18.3% of dogs. The most common biochemical abnormalities found in affected dogs were: increase of activity of transaminases and ALP, elevated creatinine concentration, hypoalbuminemia and hypoglycemia. These abnormalities resulted from hepatopathy, renal failure and fasting. PMID:18198540

Zygner, W; Rapacka, G; Gójska-Zygner, O; D?ugosz, E; Wedrychowicz, H

2007-01-01

186

Science with Large Solar Telescopes: Addressing Key Science Questions with New Observing Modes  

NASA Astrophysics Data System (ADS)

We review the capabilities of existing and future large solar telescopes with an emphasis on the key science questions that these instruments must address. Large solar telescopes coming online now, as well as the 4-meter ATST coming online in 2018 are tasked with extending high resolution and polarimetric investigations from the lower atmospheric regions into the higher regions and connecting the dynamics between the two. The overall goal is to understand the interaction of flows and magnetic fields in the convection zone down to O(10) km scales and the magnetohydrodynamic transport, storage, and release of energy in the upper atmosphere leading to coronal heating and eruptive events. The ATST in particular will have unique opportunities to address this goal with new observations of the infrared atmosphere at very high spatial resolution and with coronagraphic capabilities. We discuss some of the multi-instrument ATST observing programs that will investigate such topics as small-scale magnetoconvection and energetic events in the lower atmosphere and energy release in filament eruptions.

Berger, T.

2012-12-01

187

Observations of large-scale traveling ionospheric disturbances using GPS networks  

NASA Astrophysics Data System (ADS)

~~~The generation and propagation mechanisms of large-scale traveling ionospheric disturbances (LSTIDs) were studied using the total electron content (TEC) data derived from GPS earth observation network (GEONET), international GPS service (IGS), and Continuously Operating Reference Stations (CORS). A dense and wide-area GPS network in Japan, GEONET, has about 1,000 GPS receivers and provides GPS data every 30 seconds. With GEONET, it is possible to reveal spatial structures and temporal variations of LSTIDs in detail over Japan. The GPS data of the global network, IGS, and a regional network, CORS, enable to clarify the global-scale characteristics of the propagation. ~~~In this study, LSTIDs during a large geomagnetic storm on September 22, 1999 were investigated in detail. Two LSTIDs were seen to travel southward in the dawn region from 0730 to 0900 LT (from 2230 to 2400 UT) and were dissipated as they traveled over Japan. Their damping rates were larger at mid latitudes than at high latitudes. In the afternoon region, several LSTIDs were observed around 1300 LT (2100 UT) and their damping rate is higher than that in the dawn region. LSTIDs were observed in these two regions. No LSTID was, however, detected in the night region, despite the geomagnetic activities in the auroral night region were very large. ~~~The dissipation of the LSTIDs was more intense at lower latitudes and in the afternoon region than at higher latitudes and in the dawn region. In the regions where the LSTIDs were rapidly damped, the values of background TEC found to be larger than those in the other regions. This feature indicates that the intense dissipation is caused by the ion drag effect that is proportional to the background TEC. It is also noted that the LSTIDs were not always generated when the geomagnetic activities are large in the auroral region. We believe that the other ionospheric conditions also contributes to the generation of the LSTIDs. >http://www-step.kugi.kyoto- u.ac.jp/~tsug/study/study_e.html

Tsugawa, T.; Saito, A. Q.; Otsuka, Y.

2001-12-01

188

Large 0/12 GMT Differences of US Vaisala RS80 Observations  

NASA Technical Reports Server (NTRS)

The daily differences between the temperatures and heights taken at 0 GMT and 12 GMT by Vaisala RS80 rawinsondes have been calculated. The observations were obtained during selected months from 1998 - 2002 over North America, Europe and Australia. The daily differences are defined by the formula, Delta T = Delta T(sub 0) - 0.5(T(sub -12) - T(sub +12)) where AT is the 0/12 GMT difference, T(sub 0) is the 0 GMT observation and T(sub -12) and T(sub +12) are the 12 GMT observations taken just prior and after the 0 GMT synoptic time. If T(sub +12) is missing then Delta T = T(sub 0) - T(sub -12). A similar expression is used if T(sub -12) is missing. Monthly averages of the increments at each station that launch RS80 rawinsondes are then calculated. The results show positive systematic differences in the stratosphere with values as high as 5 K and 150 m at 10 hPa over the central United States. The values remain generally positive and gradually decrease as the levels descend into the upper troposphere but are still significant. In addition, the maximum at each level is just westward of 90 W at the highest levels and just eastward in the troposphere with smaller values along both coasts. In Canada as well as in Europe and Australia the differences are much smaller with no systematic patterns similar to those that exist over the contiguous United States. Time-series plots of the temperatures and heights at select stations in the United States show that the observed values taken at 0 GMT are consistently higher than those at 12 GMT. Over Canada the differences become much less apparent and some cases non-existent. The observations were obtained through National Centers for Environmental Prediction (NCEP) but were checked with data from other sources to verify that no modifications were made other than those at the stations. Since the data from outside the the United States exhibit no large systematic differences, the preliminary conclusion is that the large differences are artificial and probably originate from the post-processing software at the observing stations.

Redder, Chris; Atlas, Robert (Technical Monitor)

2002-01-01

189

Circular Well Superposition Model  

NSDL National Science Digital Library

The Circular Well Superposition model displays the time evolution of the position-space wave function in an deep 2D circular well. The default configuration shows the first excited state with zero angular momentum. Additional eigenstates can be added using a button in the eigenstate coefficient table. A description of the quantum system and eigenstates, with questions for the students, are included. Circular Well Superpostion model was created using the Easy Java Simulations (Ejs) modeling tool. It is distributed as a ready-to-run (compiled) Java archive. Double clicking the ejs_qm_Superposition2DCircularWell.jar file will run the program if Java is installed. Ejs is a part of the Open Source Physics Project and is designed to make it easier to access, modify, and generate computer models. Additional Open Source Physics programs for quantum mechanics are available. They can be found by searching ComPADRE for Open Source Physics, OSP, or EJS.

Christian, Wolfgang

2008-11-21

190

Observational Requirements for Ly? Forest Tomographic Mapping of Large-scale Structure at z ~ 2  

NASA Astrophysics Data System (ADS)

The z >~ 2 Ly? forest traces the underlying dark matter distribution on large scales and, given sufficient sightlines, can be used to create three-dimensional (3D) maps of large-scale structures. We examine the observational requirements to construct such maps and estimate the signal-to-noise as a function of exposure time and sightline density. Sightline densities at z = 2.25 are n los ? [360, 1200, 3300] deg-2 at limiting magnitudes of g = [24.0, 24.5, 25.0], resulting in transverse sightline separations of langd rang ? [3.6, 1.9, 1.2] h -1 Mpc, which roughly sets the reconstruction scale. We simulate these reconstructions using mock spectra with realistic noise properties and find that spectra with S/N ? 4 per angstrom can be used to generate maps that clearly trace the underlying dark matter at overdensities of ?/lang?rang ~ 1. For the VLT/VIMOS spectrograph, exposure times t exp = [4, 6, 10] hr are sufficient for maps with spatial resolution epsilon3D = [5.0, 3.2, 2.3] h -1 Mpc. Assuming ~250 h -1 Mpc is probed along the line of sight, 1 deg2 of survey area would cover a comoving volume of ?106 h -3 Mpc3 at langzrang ~ 2.3, enabling the efficient mapping of large volumes with 8-10 m telescopes. These maps could be used to study galaxy environments, the topology of large-scale structures at high z, and to detect proto-clusters.

Lee, Khee-Gan; Hennawi, Joseph F.; White, Martin; Croft, Rupert A. C.; Ozbek, Melih

2014-06-01

191

Design of a large low-scattered light telescope for solar observations  

NASA Astrophysics Data System (ADS)

This paper is an interim report of a feasibility study which is in progress for a large 400 cm aperture solar telescope (`CLEAR'). Unlike other large solar telescopes constructed in the last three decades, CLEAR does not use the concept of evacuated telescopes to eliminate internal seeing. The requirement for full access to the far infrared spectral region (> 2.5 micrometers ), and for low scattered light, eliminates the use of the entrance window which evacuated telescopes require. Instead, CLEAR avoids internal seeing by carefully controlling the internal thermal environment of the telescope by a number of means: (1) thermal control of the primary mirror; (2) flow of ambient air over the primary mirror surface and in the telescope; (3) locating the primary focus outside the telescope beam and enclosure where the heating resulting in concentrated sunlight can be managed better (this requires the use of an off-axis primary mirror); and (4) the use of a prime focus heat stop/absorber. In addition to controlling the internal seeing, such a configuration produces a telescope with very low scattered light characteristics, allowing quality observation of regions outside the solar limb and of sunspots. By eliminating the need for a large entrance window, the CLEAR concept therefore opens up the possibility of larger aperture solar telescopes. Notwithstanding its off-axis configuration, the Gregorian telescope produces excellent images (< 0.1 arcsec) over a 5 arcminute diameter field-of-view at the f/130 Gregorian focus. In addition to the four instrumentation stations near the Gregorian focus (i.e., direct Gregorian, Nasmyth, two `folded Gregorian'), the design provides for extensive instrumentation locations in a coude area. By means of a 3- level rotating coude platform, large instruments can be located at respectively f/30, f/45 and f/60 foci.

Beckers, Jacques M.

1998-08-01

192

Sky surface brightness at Mount Graham II. First JHKs science observations with the Large Binocular Telescope  

NASA Astrophysics Data System (ADS)

We studied the near-infrared sky-brightness at J, H and Ks-bands as derived from the data taken during the first year and a half of routine science operations of the Large Binocular Telescope (LBT). This is the first comprehensive study of the near-infrared night sky-brightness ever conducted at the Mount Graham International Observatory (MGIO), based on a large dataset comprising 4699 near-infrared images taken in 52 nights. We analyzed the dependency of the near-infrared night sky-brightness with the airmass, the season and the moon phase and distance. The average night sky-brightnesses (dispersion) in the J, H and Ks bands scaled to the zenith is 15.82 mag/arcsec2 (0.21), 14.29 mag/arcsec2 (0.26) and 13.42 mag/arcsec2 (0.32) respectively. Those values were derived for the first time at this observatory. At the J-band we found a tendency of the sky background to get darker by ˜0.35 mag at the end of the night with respect to the evening twilight. Also in the J-band we found that the sky background can be up to ˜0.11 mag brighter when observing at 10° distance from the full moon. A correlation was also found between the night sky-brightness in the Ks-band and the air temperature with a gradient of -0.06 mag per 1°C of temperature increase. If we compare the average sky brightness of the major observing sites we find that, at J-band, Mt. Graham is quite similar to the major sites but it quickly becomes the second darkest place at the H-band and definitely the darkest observing site at the Ks-band together with Mauna Kea.

Pedani, M.

2014-04-01

193

Large Eddy Simulations of Continental Boundary Layer Clouds Observed during the RACORO Field Campaign  

NASA Astrophysics Data System (ADS)

Three cases of boundary layer clouds are analyzed in the FAst-physics System TEstbed and Research (FASTER) project, based on continental boundary-layer-cloud observations during the RACORO Campaign [Routine Atmospheric Radiation Measurement (ARM) Aerial Facility (AAF) Clouds with Low Optical Water Depths (CLOWD) Optical Radiative Observations] at the ARM Climate Research Facility's Southern Great Plains (SGP) site. The three 60-hour case study periods are selected to capture the temporal evolution of cumulus, stratiform, and drizzling boundary-layer cloud systems under a range of conditions, intentionally including those that are relatively more mixed or transitional in nature versus being of a purely canonical type. Multi-modal and temporally varying aerosol number size distribution profiles are derived from aircraft observations. Large eddy simulations (LESs) are performed for the three case study periods using the GISS Distributed Hydrodynamic Aerosol and Radiative Modeling Application (DHARMA) model and the WRF-FASTER model, which is the Weather Research and Forecasting (WRF) model implemented with forcing ingestion and other functions to constitute a flexible LES. The two LES models commonly capture the significant transitions of cloud-topped boundary layers in the three periods: diurnal evolution of cumulus layers repeating over multiple days, nighttime evolution/daytime diminution of thick stratus, and daytime breakup of stratus and stratocumulus clouds. Simulated transitions of thermodynamic structures of the cloud-topped boundary layers are examined by balloon-borne soundings and ground-based remote sensors. Aircraft observations are then used to statistically evaluate the predicted cloud droplet number size distributions under varying aerosol and cloud conditions. An ensemble approach is used to refine the model configuration for the combined use of observations with parallel LES and single-column model simulations. See Lin et al. poster for single-column model investigation.

Endo, S.; Fridlind, A. M.; Lin, W.; Vogelmann, A. M.; Toto, T.; Liu, Y.

2013-12-01

194

From Large Scale Surveys of the Galaxy to High Resolution Observations with ALMA  

NASA Astrophysics Data System (ADS)

A CS(2-1) survey of OB star forming regions provides statistics of their distribution in the Galaxy. The complete scenario of massive star formation for one particular GMC, at a distance of 1.6 kpc, is revealed through 1.2 mm continuum observations for spatial scales from 1 pc to 50 pc. Using large scale CO and C18O maps from NANTEN at 2.5' resolution, we identified toward the peak of C18O one of the most luminous regions of high-mass star formation in the Galaxy, G331.5, toward the tangent of Norma spiral arm, at a distance of 7.5 kpc. Observations at 1.2 mm continuum emission with SIMBA at SEST reveal the presence of a cluster of six massive millimeter clumps, with high bolometric luminosity, making G331.5 one of the most densely populated GMC cores known so far. High density molecular tracers reveal the presence, in the center of the most massive clump, of a compact, highly massive and energetic molecular outflow, with a velocity width reaching 160 km s-1 (fwzp). Further interferometric continuum observations at 3.6 cm and 6 cm shows that this powerful outflow is associated with a compact radio continuum source, likely producing highly ionized stellar wind. ALMA observations were carried in band 7 to this unresolved molecular outflow. SiO and H13CO+ observations unveil a shell-like structure toward the ambient velocity of the source, evidence of an isotropic high speed wind. The derived crossing time for this source indicates that the molecular outflow in G331.5 is one of the youngest outflow found around an OB star.

Bronfman, L.; Merello, M.

2013-10-01

195

Circular dichroism of peptides.  

PubMed

Circular dichroism measures the difference between the absorbance of left- and right-handed circularly polarized light, and can be used to monitor the secondary structure of peptides (far UV) and the tertiary structure of larger polypeptides (near UV). This technique is especially useful for helix-coil transitions and other aspects of structural alterations. Data from several low-resolution spectroscopic techniques, including CD, can be combined to generate an overall picture of peptide structure as a function of environmental conditions. PMID:24146409

Bakshi, Kunal; Liyanage, Mangala R; Volkin, David B; Middaugh, C Russell

2014-01-01

196

Spectral Decay Characteristics in High Frequency Range of Observed Records from Crustal Large Earthquakes (Part 2)  

NASA Astrophysics Data System (ADS)

Spectral decay characteristics in high frequency range of observed records from crustal large earthquakes occurred in Japan is examined. It is very important to make spectral decay characteristics clear in high frequency range for strong ground motion prediction in engineering purpose. The authors examined spectral decay characteristics in high frequency range of observed records among three events, the 2003 Miyagi-Ken Hokubu earthquake (Mw 6.1), the 2005 Fukuoka-Ken Seiho-oki earthquake (Mw 6.6), and the 2008 Iwate-Miyagi Nairiku earthquake (Mw 6.9) in previous study [Tsurugi et al.(2010)]. Target earthquakes in this study are two events shown below. *EQ No.1 Origin time: 2011/04/11 17:16, Location of hypocenter: East of Fukushima pref., Mj: 7.0, Mw: 6.6, Fault type: Normal fault *EQ No.2 Origin time: 2011/03/15 22:31, Location of hypocenter: East of Shizuoka pref., Mj: 6.4, Mw: 5.9, Fault type: Strike slip fault The borehole data of each event are used in the analysis. The Butterworth type high-cut filter with cut-off frequency, fmax and its power coefficient of high-frequency decay, s [Boore(1983)], are assumed to express the high-cut frequency characteristics of ground motions. The four parameters such as seismic moment, corner frequency, cut-off frequency and its power coefficient of high-frequency decay are estimated by comparing observed spectra at rock sites with theoretical spectra. The theoretical spectra are calculated based on the omega squared source characteristics convolved with propagation-path effects and high-cut filter shapes. In result, the fmax's of the records from the earthquakes are estimated 8.0Hz for EQ No.1 and 8.5Hz for EQ No.2. These values are almost same with those of other large crustal earthquakes occurred in Japan. The power coefficient, s, are estimated 0.78 for EQ No.1 and 1.65 for EQ No.2. The value for EQ No.2 is notably larger than those of other large crustal earthquakes. It is seems that the value of the power coefficient, s, became large under the effect of complex ground structure and volcanic front. The obtained results may contribute to strong ground motion prediction in high frequency range for crustal earthquakes. Acknowledgement: This study commissioned by Japan Nuclear Energy Safety Organization. We thank the National Research Institute for Earth Science Disaster Prevention to provide the strong-motion data. References: Hanks,T.C. : fmax, Bulletin of Seismological Society of America, 72, 1867-1879, 1982. Boore,D.M. : Stochastic simulation of high-frequency ground motion based on seismological models of the radiated spectra, Bulletin of Seismological Society of America, 73, 1865-1894, 1983. Tsurugi,M., Kagawa,T., and Irikura,K. : Spectral Decay Characteristics in High Frequency Range of Observed Records from Crustal Large Earthquakes, AGU Fall Meeting, 2010.

Tsurugi, M.; Kagawa, T.; Irikura, K.

2012-12-01

197

Reduction of Cloud Water in Ship Tracks: Observations and Large-Eddy Simulations  

NASA Technical Reports Server (NTRS)

Ship tracks represent a natural laboratory to study the effects of aerosols on clouds. A number of observations and simulations have shown that increased droplet concentrations in ship tracks increase their total cross-sectional area, thereby enhancing cloud albedo and providing a negative radiative forcing at the surface and the top of the atmosphere. In some cases, cloud water has been found to be enhanced in ship tracks, which has been attributed to suppression of drizzle and implies an enhanced susceptibility of cloud albedo to droplet concentrations. However, more recently compiled observations indicate that cloud water is instead reduced in daytime ship tracks on average. Such a response is consistent with cloud-burning due to solar absorption by soot (the semi-direct radiative forcing of aerosols), recently suggested to be suppressing trade cumulus cloud coverage over the Indian Ocean. We will summarize observational evidence and present large-eddy simulations that consider these competing mechanisms in the effects of aerosols on cloud albedo.

Ackerman, A. S.; Stevens, D. E.; Toon, O. B.; Coakley, J. A., Jr.; Gore, Warren J. (Technical Monitor)

2001-01-01

198

Sensitivity of Stratocumulus Optical Depths to Droplet Concentrations: Satellite Observations and Large-Eddy Simulations  

NASA Technical Reports Server (NTRS)

A number of observations and simulations have shown that increased droplet concentrations in ship tracks increase their total cross-sectional area, thereby enhancing cloud albedo and providing a negative (cooling) radiative forcing at the surface and the top of the atmosphere. In some cases cloud water has been found to be enhanced in ship tracks, which has been attributed to suppression of drizzle and implies an enhanced susceptibility of cloud albedo to droplet concentrations. However, observations from aircraft and satellite indicate that on average cloud water is instead reduced in daytime ship tracks. Such a reduction in liquid water may be attributable to cloud-burning caused by solar heating by soot within the ship exhaust, or by increased precipitation resulting from giant nuclei in the ship exhaust. We will summarize the observational evidence and present results from large-eddy simulations that evaluate these mechanisms. Along the way we will present our insights into the interpretation of satellite retrievals of cloud microphysical properties.

Ackerman, A. S.; Stevens, D. E.; Toon, O. B.; Coakley, J. A., Jr.; Gore, Warren J. (Technical Monitor)

2002-01-01

199

Ionospheric observations of underground nuclear explosions (UNE) using GPS and the Very Large Array  

NASA Astrophysics Data System (ADS)

Observations from Global Positioning System (GPS) receivers and the Very Large Array (VLA) radio telescope recorded traveling ionospheric disturbances (TID) from underground nuclear explosions (UNEs), detonated in September 1992. The slant TEC (STEC) data derived from GPS observations were processed for all ray paths to isolate TIDs. For the TIDs from the Hunters Trophy test on 18 September 1992 and the Divider test on 23 September 1992, the propagated mean velocities of the TIDs were about 573 m/s and 740 m/s with standard deviations of 85 m/s and 135 m/s, respectively. For the VLA observations, the spectral analysis produced three-dimensional fluctuation spectral cubes for the Hunters Trophy event. The arrival time of the TID at the VLA implied a propagation speed of 570-710 m/s. This study suggests the global availability of GNSS tracking networks and new low-frequency (VHF) radio telescopes may offer a method of UNE detection and characterization, which could complement the International Monitoring System (IMS).

Park, Jihye; Helmboldt, Joseph; Grejner-Brzezinska, Dorota A.; Frese, Ralph R. B.; Wilson, Thomas L.

2013-07-01

200

Geophysical characterization of two circular structures at Bajada del Diablo (Patagonia, Argentina): Indication of impact origin  

NASA Astrophysics Data System (ADS)

An impact origin has been proposed for the circular structures found in Bajada del Diablo, Patagonia, Argentina. Taking into account its extension and the number of impact structures, Bajada del Diablo would be the largest meteoritic impact areas known on Earth, being an extremely interesting area for the research of impact events and processes. Moreover, the global distribution of known impact structures shows a surprising asymmetry. Particularly, South America has only seven described areas. It is evident that this situation is an artifact, highlighting the importance of intensifying the research in the least studied areas such as Argentina. Circular structures in Bajada del Diablo have been identified on two rock types: the Quiñelaf eruptive complex and Pampa Sastre Formation. In the first case, circular structures are placed in olivine basalts. On the other hand, Pampa Sastre Formation (late Pliocene/early Pleistocene) corresponds to conglomerate layers with basalt clasts boulder and block in size in a coarse sandy matrix. With the aim of further the investigation of the proposed impact origin for these circular structures, we carried out detailed topographic, magnetic and electromagnetic ground surveys in two circular structures ("8" and "A") found in Pampa Sastre conglomerates. Both circular structures are simple, bowl-shaped with rim diameters of 300 m and maximum depths of 10 m. They have been partially filled in by debris flows from the rims and wind-blown sands. Two preliminary magnetic profiles have also been carried out in circular structure "G" found in Quiñelaf basalts. The magnetic anomalies show a circular pattern with a slightly negative and relatively flat signal in the circular structures' bases. Furthermore in the circular structures' rims, high-amplitude, conspicuous and localized (short wavelength) anomalies are observed. Such large amplitude and short wavelength anomalies are not detected outside the circular structures. For all used frequencies, the electromagnetic profiles show lower apparent electrical conductivities in the circular structures' base, while the rims present notably higher values. Curvature attributes, analytic signal, horizontal gradient and Euler solutions were calculated for the magnetic data. 2.5D magnetic models were developed across the studied circular structures. Our results suggest that in the circular structures' bases up to 12 m of Pampa Sastre conglomerate would have been removed. On the contrary, the circular structures' rims exhibit high-amplitude, localized magnetic anomalies and higher apparent electrical conductivities, which would be related to the anomalous accumulation of basalt boulders and blocks remanently magnetized. Such high-amplitude anomalies are not present outside the surveyed circular structures. The geomorphological, geological and geophysical features of the studied circular structures can only be explained by means of an extra-terrestrial projectile impact. We conclude that, considering the results obtained to date, Bajada del Diablo should be envisaged as a focus of further research, which could provide novel information about impact events, associated processes and their evidences. Particularly, the data produced in this study could represent one of the first documented geophysical signatures of the impact of a comet nucleus on Earth.

Prezzi, Claudia B.; Orgeira, María Julia; Acevedo, Rogelio D.; Ponce, Juan Federico; Martinez, Oscar; Rabassa, Jorge O.; Corbella, Hugo; Vásquez, Carlos; González-Guillot, Mauricio; Subías, Ignacio

2012-02-01

201

{gamma}-RAY SPECTRAL EVOLUTION OF NGC 1275 OBSERVED WITH FERMI LARGE AREA TELESCOPE  

SciTech Connect

We report on a detailed investigation of the high-energy {gamma}-ray emission from NGC 1275, a well-known radio galaxy hosted by a giant elliptical located at the center of the nearby Perseus cluster. With the increased photon statistics, the center of the {gamma}-ray-emitting region is now measured to be separated by only 0.46 arcmin from the nucleus of NGC 1275, well within the 95% confidence error circle with radius {approx_equal}1.5 arcmin. Early Fermi Large Area Telescope (LAT) observations revealed a significant decade-timescale brightening of NGC 1275 at GeV photon energies, with a flux about 7 times higher than the one implied by the upper limit from previous EGRET observations. With the accumulation of one year of Fermi-LAT all-sky-survey exposure, we now detect flux and spectral variations of this source on month timescales, as reported in this paper. The average >100 MeV {gamma}-ray spectrum of NGC 1275 shows a possible deviation from a simple power-law shape, indicating a spectral cutoff around an observed photon energy of {epsilon}{sub {gamma}} = 42.2 {+-} 19.6 GeV, with an average flux of F{sub {gamma}} = (2.31 {+-} 0.13) x 10{sup -7} photons cm{sup -2} s{sup -1} and a power-law photon index, {Gamma}{sub {gamma}} = 2.13 {+-} 0.02. The largest {gamma}-ray flaring event was observed in 2009 April-May and was accompanied by significant spectral variability above {epsilon}{sub {gamma} {approx}}> 1-2 GeV. The {gamma}-ray activity of NGC 1275 during this flare can be described by a hysteresis behavior in the flux versus photon index plane. The highest energy photon associated with the {gamma}-ray source was detected at the very end of the observation, with the observed energy of {epsilon}{sub {gamma}} = 67.4 GeV and an angular separation of about 2.4 arcmin from the nucleus. In this paper we present the details of the Fermi-LAT data analysis, and briefly discuss the implications of the observed {gamma}-ray spectral evolution of NGC 1275 in the context of {gamma}-ray blazar sources in general.

Kataoka, J. [Research Institute for Science and Engineering, Waseda University, 3-4-1, Okubo, Shinjuku, Tokyo 169-8555 (Japan); Stawarz, L. [Institute of Space and Astronautical Science, JAXA, 3-1-1, Yoshinodai, Sagamihara, Kanagawa 252-5210 (Japan); Cheung, C. C. [NRC Research Associate, Space Science Division, Naval Research Laboratory, Washington, DC 20375 (United States); Tosti, G. [Istituto Nazionale di Fisica Nucleare, Sezione di Perugia, I-06123 Perugia (Italy); Cavazzuti, E. [Agenzia Spaziale Italiana (ASI) Science Data Center, I-00044 Frascati, Roma (Italy); Celotti, A. [Scuola Internazionale Superiore di Studi Avanzati (SISSA), 34014 Trieste (Italy); Nishino, S.; Fukazawa, Y. [Department of Physical Sciences, Hiroshima University, Higashi-Hiroshima, Hiroshima 739-8526 (Japan); Thompson, D. J.; McConville, W. F. [NASA Goddard Space Flight Center, Greenbelt, MD 20771 (United States)

2010-05-20

202

Determination of interface preference by observation of linear-to-circular polarization conversion under optical orientation of excitons in type-II GaAs/AlAs superlattices  

NASA Astrophysics Data System (ADS)

A comprehensive investigation of exciton optical orientation and alignment in type-II GaAs/AlAs(001) superlattices in longitudinal and transverse magnetic fields is presented. We observe the previously predicted type-II orientation-to-alignment conversion induced by a longitudinal field due to the anisotropic exchange splitting of the localized-exciton radiative doublet. A theory of polarized exciton photoluminescence under polarized excitation is developed, that takes into account the fine structure of the excitonic quartet, the exciton spin relaxation, and the difference in the lifetimes of electric-dipole-active and inactive states. By comparing experimental and theoretical curves, the main parameters characterizing the level splitting, the recombination rates, and the spin relaxation of localized excitons are deduced. Field-induced polarization conversion provides an effective method to measure the interface preference, i.e., the difference between the fractions of excitons localized on AlAs/GaAs and GaAs/AlAs interfaces. We have also observed the field-induced transformation from [100] to [110] linear polarization, which is direct evidence of exciton cascade kinetics.

Dzhioev, R. I.; Gibbs, H. M.; Ivchenko, E. L.; Khitrova, G.; Korenev, V. L.; Tkachuk, M. N.; Zakharchenya, B. P.

1997-11-01

203

Changes in the Molar Ellipticities of HEWL Observed by Circular Dichroism and Quantitated by Time Resolved Fluorescence Anisotropy Under Crystallizing Conditions  

NASA Technical Reports Server (NTRS)

Fluid models for simple colloids predict that as the protein concentration is increased, crystallization should occur at some sufficiently high concentration regardless of the strength of attraction. However, empirical measurements do not fully support this assertion. Measurements of the second virial coefficient (B22) indicate that protein crystallization occurs only over a discrete range of solution parameters. Furthermore, observations of a strong correlation between protein solubility and B22, has led to an ongoing debate regarding the relationship between the two. Experimental work in our lab, using Hen Egg White Lysozyme (HEWL), previously revealed that the rotational anisotropy of the protein under crystallizing conditions changes systematically with pH, ionic strength and temperature. These observations are now supported by recent work revealing that small changes in the molar ellipticity also occur systematically with changes in ionic strength and temperature. This work demonstrates that under crystallization conditions, the protein native state is characterized by a conformational heterogeneity that may prove fundamental to the relationship between protein crystallization and protein solubility.

Sumida, John

2002-01-01

204

Laminar circular hydraulic jumps without separation  

NASA Astrophysics Data System (ADS)

The traditional inviscid criterion for the occurrence of a planar, standing hydraulic jump is to have the Froude number decrease downstream and go through a value of 1 at some location. Here, upstream propagating, small-amplitude, long, non-dispersive gravity waves are trapped, and non-linear steepening is said to result in a near-discontinuous height profile, but it is not clear how. Such a condition on the Froude number is shown in the present axisymmetric Navier-Stokes computations to hold for a circular jump as well. The relevance of non-linear steepening to a circular jump is therefore a question we wish to answer. In circular jumps, moreover, a region of recirculation is usually observed underneath the jump, underlining the importance of viscosity in this process. This led Tani (J. Phys. Soc. Japan, 1949) to hypothesise that boundary-layer separation was the cause of the circular jump. This hypothesis has been debated extensively and the possibility of circular jumps without separation hinted at. In our simulations, we are able to obtain circular hydraulic jumps without any flow separation. This, and the necessity or otherwise of viscosity in jump formation will be discussed.

Dasgupta, Ratul; Tomar, Gaurav; Govindarajan, Rama

2009-11-01

205

Production and trapping of cold circular Rydberg atoms  

NASA Astrophysics Data System (ADS)

Cold circular Rydberg atoms are produced and magnetically trapped. The trap is characterized by direct spatial imaging of ion distributions, ion counting, and state-selective field ionization. At room temperature, we observe about 70% of the trapped atoms remaining after 6 ms. We measure a trap oscillation frequency increase of the circular Rydberg atom trap relative to the ground-state atom trap due to the larger magnetic moment of the circular Rydberg atoms. Simulations of the center-of-mass and internal-state evolution of circular states in our magnetic trap are performed and results are in good agreement with experimental observations.

Anderson, D. A.; Schwarzkopf, A.; Sapiro, R. E.; Raithel, G.

2013-09-01

206

Large Barkhausen jumps observed in Nd-Fe-B sintered magnets at very low temperatures  

SciTech Connect

The authors discuss the demagnetization process for Nd/sub 15/Fe/sub 77/B/sub 8/ sintered magnets studied by precise loop measurements below 50 K. A zigazg variation of coercivity with temperature was observed below about 18 K. In this temperature range, the magnetization reverses with large discontinuous magnetization jumps. The temperature of 18 K coincides with the Curie temperature of the B-rich Nd/sub 1.11/Fe/sub 4/B/sub 4/ phases segregated in the Nd/sub 15/Fe/sub 77/B/sub 8/ magnet. This behavior may be related to the soft magnetic properties of the B-rich phase and the demagnetizing field in the Nd/sub 15/Fe/sub 77/B/sub 8/ magnet.

Otani, Y.; Miyajima, H.; Chikazumi, S. (Keio Univ., Yokohama (Japan). Faculty of Science and Technology)

1989-09-01

207

Observation of the saturation of Langmuir waves driven by ponderomotive force in a large scale plasma  

SciTech Connect

We report the observation of amplification of a probe laser beam (I {le} 1 {times} 10{sup 14} W/cm{sup 2}) in a large scale ({approximately} 1 mm) plasma by interaction with a pumping laser beam (I = 2 {times} 10{sup 15} W/cm{sup 2}) and a stimulated Langmuir wave. When the plasma density is adjusted to allow the Langmuir wave dispersion to match the difference frequency and wave number of the two beams, amplification factors as high as {times} 2.5 result. Interpretation of this amplification as scattering of pump beam energy by the Langmuir wave that is produced by the ponderomotive force of the two beams, allows the dependence of Langmuir wave amplitude on ponderomotive force to be measured. It is found that the Langmuir wave amplitude saturates at a level that depends on ion wave damping, and is generally consistent with secondary ion wave instabilities limiting its growth. 20 refs., 4 figs.

Kirkwood, R. K.; Moody, J. D.; MacGowan, B. J.; Glenzer, S. H.; Kruer, W. L.; Estabrook, K. G.; Wharton, K. B.; Williams, E. A.; Berger, R. L. [University of California, Lawrence Livermore National Lab., CA (United States)

1997-06-22

208

Observations of O vi Absorption from the Superbubbles of the Large Magellanic Cloud  

NASA Astrophysics Data System (ADS)

We have presented the observations of O VI absorption at 1032 Å towards 22 sightlines in 10 superbubbles (SBs) of the Large Magellanic Cloud (LMC) using the data obtained from the Far Ultraviolet Spectroscopic Explorer (FUSE). The estimated abundance of O VI in the SBs varies from a minimum of (1.09 +/-0.22)×1014 atoms/cm2 in SB N206 to a maximum of (3.71+/-0.23)×1014 atoms/cm2 in SB N70. We find about a 46% excess in the abundance of O VI in the SBs compared to the non-SB lines of sight. Even inside a SB, O VI column density (N(O VI)) varies by about a factor of 2 to 2.5. These data are useful in understanding the nature of the hot gas in SBs.

Pradhan, Ananta C.; Pathak, Amit; Murthy, Jayant; Ojha, D. K.

2014-01-01

209

Chemical Synthesis of Circular Proteins*  

PubMed Central

Circular proteins, once thought to be rare, are now commonly found in plants. Their chemical synthesis, once thought to be difficult, is now readily achievable. The enabling methodology is largely due to the advances in entropic chemical ligation to overcome the entropy barrier in coupling the N- and C-terminal ends of large peptide segments for either intermolecular ligation or intramolecular ligation in end-to-end cyclization. Key elements of an entropic chemical ligation consist of a chemoselective capture step merging the N and C termini as a covalently linked O/S-ester intermediate to permit the subsequent step of an intramolecular O/S-N acyl shift to form an amide. Many ligation methods exploit the supernucleophilicity of a thiol side chain at the N terminus for the capture reaction, which makes cysteine-rich peptides ideal candidates for the entropy-driven macrocyclization. Advances in desulfurization and modification of the thiol-containing amino acids at the ligation sites to other amino acids add extra dimensions to the entropy-driven ligation methods. This minireview describes recent advances of entropy-driven ligation to prepare circular proteins with or without a cysteinyl side chain.

Tam, James P.; Wong, Clarence T. T.

2012-01-01

210

Large NAT particle formation by mother clouds: Analysis of SOLVE/THESEO-2000 observations  

NASA Astrophysics Data System (ADS)

During the SOLVE/THESEO-2000 Arctic stratospheric campaign in the winter 1999/2000 widespread occurrences of very large HNO3-containing particles, probably composed of nitric acid trihydrate (NAT), were observed in situ by instruments on board the ER-2 stratospheric research aircraft. These large NAT particles were found with low number densities (n ~ 10-4 cm-3) in vast regions, in air generally supersaturated with respect to NAT. Within the same campaign other instruments have performed airborne and ground-based measurements of polar stratospheric clouds (PSCs), often showing the existence of type 1a and type 1a-enh clouds. Such PSCs often occur on the mesoscale with particle number densities n >~ 10-2cm-3 and are also most likely composed of NAT. We use forward trajectories for the path of NAT particles, which are advected by winds based on ECMWF analyses and sediment due to gravity, to show that high number density NAT PSCs (mother clouds) could give rise to low number density NAT particle populations several days downstream.

Fueglistaler, S.; Luo, B. P.; Buss, S.; Wernli, H.; Voigt, C.; Müller, M.; Neuber, R.; Hostetler, C. A.; Poole, L. R.; Flentje, H.; Fahey, D. W.; Northway, M. J.; Peter, Th.

2002-06-01

211

Observation of Impurity Accumulation After Hydrogen Multi-Pellet Injection in Large Helical Device  

NASA Astrophysics Data System (ADS)

Impurity accumulation is studied for neutral beam-heated discharges after hydrogen multi-pellet injection in Large Helical Device (LHD). Iron density profiles are derived from radial profiles of EUV line emissions of FeXV-XXIV with the help of the collisional-radiative model. A peaked density profile of Fe23+ is simulated by using one-dimensional impurity transport code. The result indicates a large inward velocity of -6 m/s at the impurity accumulation phase. However, the discharge is not entirely affected by the impurity accumulation, since the concentration of iron impurity, estimated to be 3.3 × 10-5 to the electron density, is considerably small. On the other hand, a flat profile is observed for the carbon density of C6+, which is derived from the Zeff profile, indicating a small inward velocity of -1 m/s. These results suggest atomic number dependence in the impurity accumulation of LHD, which is similar to the tokamak result.

Dong, Chunfeng; Shigeru, Morita; Motoshi, Goto; Wang, Erhui; Gen, Motojiama; Izumi, Murakami; Ryuichi, Sakamoto; Norimasa, Yamamoto

2013-03-01

212

H.E.S.S. Observations of The Large Magellanic Cloud  

NASA Astrophysics Data System (ADS)

With an angular resolution of less than 0.1 degree and a sensitivity to detect less than 1% of the Crab flux in fifty hours, the H.E.S.S. telescopes have the potential to detect and separate very-high-energy (VHE) gamma-ray sources in nearby galaxies. The Large Magellanic Cloud (LMC), at a moderate distance and hosting the largest star forming region in the Local Group, is the most promising target to search for extragalactic VHE gamma-ray emitters of stellar-mass scale systems. The LMC has an extraordinarily high supernova rate per unit mass compared with the Milky Way galaxy. Studying cosmic-ray accelerators in such a dierent environment is of considerable interest. The H.E.S.S. observations of nearly two hundred hours cover a large portion of the LMC. Within the eld of view lie various types of expected gamma-ray emitters, i.e. pulsar wind nebulae, supernova remnants, superbubbles and the unique object SN 1987A, a very young supernova remnant. The results will be reported.

Lu, Chia-Chun; Aharonian, Felix; Brun, Francois; Chaves, Ryan; Domainko, Wilfried; Hofmann, Werner; Komin, Nukri; Lohse, Thomas; Mayer, Michael; Ohm, Stefan; Renaud, Matthieu; Stegmann, Christian; Vink, Jacco; Voelk, Heinrich

2014-08-01

213

Rapid formation of large aggregates during the spring bloom of Kerguelen Island: observations and model comparisons  

NASA Astrophysics Data System (ADS)

We recorded vertical profiles of particle size distributions (PSD, sizes ranging from 0.052 to several mm in equivalent spherical diameter) in the natural iron-fertilized bloom southeast of Kerguelen Island (Southern Ocean) from pre-bloom to early bloom stage. PSD were measured by the Underwater Vision Profiler during the Kerguelen Ocean and Plateau Compared Study cruise 2 (KEOPS 2, October-November 2011). The total particle numerical abundance was more than 4 fold higher during the early bloom phase compared to pre-bloom conditions as a result of the 2-weeks bloom development. We witnessed the rapid formation of large particles and their accumulation at the base of the mixed layer within a two days period, as indicated by changes in total particle volume (VT) and particle size distribution. The VT profiles suggest sinking of particles from the mixed layer to 200 m, but little export deeper than 200 m during the observation period. The results of a one dimensional particles dynamic model support coagulation as the mechanism responsible for the rapid aggregate formation and the development of the VT subsurface maxima. Comparison with KEOPS1, which investigated the same area during late summer, and previous iron fertilization experiments highlights physical aggregation as the primary mechanism for large particulate production during the earlier phase of iron fertilized bloom and its export from the surface mixed layer.

Jouandet, M.-P.; Jackson, G. A.; Carlotti, F.; Picheral, M.; Stemmann, L.; Blain, S.

2014-03-01

214

FERMI LARGE AREA TELESCOPE OBSERVATIONS OF PSR J1836+5925  

SciTech Connect

The discovery of the gamma-ray pulsar PSR J1836+5925, powering the formerly unidentified EGRET source 3EG J1835+5918, was one of the early accomplishments of the Fermi Large Area Telescope (LAT). Sitting 25{sup 0} off the Galactic plane, PSR J1836+5925 is a 173 ms pulsar with a characteristic age of 1.8 million years, a spindown luminosity of 1.1 x 10{sup 34} erg s{sup -1}, and a large off-peak (OP) emission component, making it quite unusual among the known gamma-ray pulsar population. We present an analysis of one year of LAT data, including an updated timing solution, detailed spectral results, and a long-term light curve showing no indication of variability. No evidence for a surrounding pulsar wind nebula is seen and the spectral characteristics of the OP emission indicate it is likely magnetospheric. Analysis of recent XMM-Newton observations of the X-ray counterpart yields a detailed characterization of its spectrum, which, like Geminga, is consistent with that of a neutron star showing evidence for both magnetospheric and thermal emission.

Abdo, A. A. [Space Science Division, Naval Research Laboratory, Washington, DC 20375 (United States); Ackermann, M.; Ajello, M.; Bechtol, K.; Berenji, B.; Blandford, R. D.; Bloom, E. D.; Borgland, A. W. [W. W. Hansen Experimental Physics Laboratory, Kavli Institute for Particle Astrophysics and Cosmology, Department of Physics and SLAC National Accelerator Laboratory, Stanford University, Stanford, CA 94305 (United States); Atwood, W. B.; Belfiore, A. [Santa Cruz Institute for Particle Physics, Department of Physics and Department of Astronomy and Astrophysics, University of California at Santa Cruz, Santa Cruz, CA 95064 (United States); Baldini, L.; Bellazzini, R.; Bregeon, J.; Brez, A. [Istituto Nazionale di Fisica Nucleare, Sezione di Pisa, I-56127 Pisa (Italy); Ballet, J. [Laboratoire AIM, CEA-IRFU/CNRS/Universite Paris Diderot, Service d'Astrophysique, CEA Saclay, 91191 Gif sur Yvette (France); Barbiellini, G. [Istituto Nazionale di Fisica Nucleare, Sezione di Trieste, I-34127 Trieste (Italy); Baring, M. G. [Department of Physics and Astronomy, Rice University, MS-108, P.O. Box 1892, Houston, TX 77251 (United States); Bastieri, D. [Istituto Nazionale di Fisica Nucleare, Sezione di Padova, I-35131 Padova (Italy); Bonamente, E. [Istituto Nazionale di Fisica Nucleare, Sezione di Perugia, I-06123 Perugia (Italy); Brigida, M., E-mail: olr@slac.stanford.ed, E-mail: pablo@scipp.ucsc.ed, E-mail: nkawai@phys.titech.ac.j [Dipartimento di Fisica 'Merlin' dell'Universita e del Politecnico di Bari, I-70126 Bari (Italy)

2010-04-01

215

Wiimote Experiments: Circular Motion  

ERIC Educational Resources Information Center

The advent of new sensor technologies can provide new ways of exploring fundamental physics. In this paper, we show how a Wiimote, which is a handheld remote controller for the Nintendo Wii video game system with an accelerometer, can be used to study the dynamics of circular motion with a very simple setup such as an old record player or a…

Kouh, Minjoon; Holz, Danielle; Kawam, Alae; Lamont, Mary

2013-01-01

216

Hypercomplete circular harmonic pyramids  

Microsoft Academic Search

In this contribution we present a steerable pyramid based on a particular set of complex wavelets named circular harmonic wavelets (CHW). The proposed CHWs set constitutes a generalization of the smoothed edge wavelets introduced by Mallat, consisting of extending the local differential representation of a signal image from the first order to a generic n-th order. The key feature of

Giovanni Jacovitti; A. Manca; Alessandro Neri

1996-01-01

217

The Right Circular Cone  

NSDL National Science Digital Library

This learning object from Wisc-Online covers the right circular cone, examining the properties and components of the shape. The lesson uses the geometric formulas for finding the volume and surface area of the shape. Practice questions are also included.

Jensen, Douglas; Reed, Allen

2005-01-01

218

Wiimote Experiments: Circular Motion  

NASA Astrophysics Data System (ADS)

The advent of new sensor technologies can provide new ways of exploring fundamental physics. In this paper, we show how a Wiimote, which is a handheld remote controller for the Nintendo Wii video game system with an accelerometer, can be used to study the dynamics of circular motion with a very simple setup such as an old record player or a bicycle wheel.

Kouh, Minjoon; Holz, Danielle; Kawam, Alae; Lamont, Mary

2013-03-01

219

Changes in the Observing System Contributing To Perceived Changes in Large Scale Circulation  

NASA Astrophysics Data System (ADS)

Ocean surface wind observations have transitioned from purely in situ systems to satellite dominated systems. Reanalyses treat satellite winds as physically identical to in situ winds (albeit with different error characteristics). However, there are systematic differences between satellite and in situ winds. Prior work has shown that this wind observing system change causes trends in latent heat flux that are consistent with trends in analyses, both in spatial pattern and magnitude. These physical differences have also been confirmed in comparisons of research vessel and scatterometer winds (May and Bourassa, 2011), and have been shown to be quite large on weather time scales (Kara et al. 2007). For the published example for 0Z on January 1, 2005, the change in wind shear (U10 - Usfc) was modified by from -15% to +10%, and the monthly average was changed by from -10% to +5%. The differences do to waves and currents are examined herein. The vector differences in seasonal averages are determined from the modern data record, and used to infer systematic changes from the purely in situ system to a satellite-based system. These differences are examined in terms of biases to long term changes in Walker circulation and Hadley circulation. While the changes in wind speed are small compared to the wind speed, they are substantial in comparison to long term trends.

Bourassa, M. A.

2012-12-01

220

Mechanical and hydrologic basis for the rapid motion of a large tidewater glacier. 1: Observations  

NASA Technical Reports Server (NTRS)

Measurements of glacier flow velocity and basal water pressure at two sites on Columbia Glacier, Alaska, are combined with meteorological and hydrologic data to provide an observational basis for assessing the role of water storage and basal water pressure in the rapid movement of this large glacier. During the period from July 5 to August 31, 1987, coordinated observations were made of glacier surface motion and of water level in five boreholes drilled to (or in one case near to) the glacier bed at two sites, 5 and 12 km from the terminus. Glacier velocities increased downglacier in this reach from about 4 m/d to about 7 m/d. Three types of time variation in velocity and other variables were revealed: (1) Diurnal fluctuation in water input/output, borehole water level, and ice velocity (fluctuation amplitude 5 to 8%); (2) Speed-up events in glacier motion (15-30% speed-up), lasting about three days, and ocurring at times of enhanced input of water, in some cases from rain and in others from ice ablation enhanced by strong, warm winds; (3) 'Extra-slowdown' events, in which, after a speed-up event, the ice velocity decreased in about 3 days to a level consistently lower than that prior to the speed-up event. All of the time variations were due, directly or indirectly, to variations in water input to the glacier.

Meier, Mark; Lundstrom, Scott; Stone, Dan; Kamb, Barclay; Engelhardt, Hermann; Humphrey, Neil; Dunlap, William W.; Fahnestock, Mark; Krimmel, Robert M.; Walters, Roy

1994-01-01

221

Microwave observations of late-type stars with the Very Large Array  

NASA Technical Reports Server (NTRS)

The Very Large Array was used to search for microwave emission from 32 stars of late spectral type including RS CVn type stars, dwarf M stars, and stars with active chromospheres, coronae, or intense magnetic fields. The RS CVn stars were detected at 6 cm wavelength, and upper limits are established for another six. Radio emission was detected from three dwarf M flare stars, UV Cet, EQ Peg and YZ CMi. Both impulsive (no more than 20 s) and more gradual (at least ten minutes) bursts were observed from the flare star YZ CMi. Radio emission was not confirmed at 6 cm from the solar type star Chi(1) Ori, with an upper limit that is three times lower than the detections reported by other observers. Microwave emission could not be detected from any other solar type star of spectral class F to K. The quiescent radio emission from dwarf M flare stars was interpreted as nonthermal gyrosynchrotron emission by mildly relativistic electrons accelerated more or less continuously in the magnetic fields of starspots.

Pallavicini, R.; Willson, R. F.; Lang, K. R.

1985-01-01

222

The topology of large-scale structure. III - Analysis of observations. [in universe  

NASA Technical Reports Server (NTRS)

A recently developed algorithm for quantitatively measuring the topology of large-scale structures in the universe was applied to a number of important observational data sets. The data sets included an Abell (1958) cluster sample out to Vmax = 22,600 km/sec, the Giovanelli and Haynes (1985) sample out to Vmax = 11,800 km/sec, the CfA sample out to Vmax = 5000 km/sec, the Thuan and Schneider (1988) dwarf sample out to Vmax = 3000 km/sec, and the Tully (1987) sample out to Vmax = 3000 km/sec. It was found that, when the topology is studied on smoothing scales significantly larger than the correlation length (i.e., smoothing length, lambda, not below 1200 km/sec), the topology is spongelike and is consistent with the standard model in which the structure seen today has grown from small fluctuations caused by random noise in the early universe. When the topology is studied on the scale of lambda of about 600 km/sec, a small shift is observed in the genus curve in the direction of a 'meatball' topology.

Gott, J. Richard, III; Weinberg, David H.; Miller, John; Thuan, Trinh X.; Schneider, Stephen E.

1989-01-01

223

SEISMOLOGY OF A LARGE SOLAR CORONAL LOOP FROM EUVI/STEREO OBSERVATIONS OF ITS TRANSVERSE OSCILLATION  

SciTech Connect

The first analysis of a transverse loop oscillation observed by both Solar TErrestrial RElations Observatories (STEREO) spacecraft is presented, for an event on the 2007 June 27 as seen by the Extreme Ultraviolet Imager (EUVI). The three-dimensional loop geometry is determined using a three-dimensional reconstruction with a semicircular loop model, which allows for an accurate measurement of the loop length. The plane of wave polarization is found from comparison with a simulated loop model and shows that the oscillation is a fundamental horizontally polarized fast magnetoacoustic kink mode. The oscillation is characterized using an automated method and the results from both spacecraft are found to match closely. The oscillation period is 630 {+-} 30 s and the damping time is 1000 {+-} 300 s. Also, clear intensity variations associated with the transverse loop oscillations are reported for the first time. They are shown to be caused by the effect of line-of-sight integration. The Alfven speed and coronal magnetic field derived using coronal seismology are discussed. This study shows that EUVI/STEREO observations achieve an adequate accuracy for studying long-period, large-amplitude transverse loop oscillations.

Verwichte, E.; Van Doorsselaere, T.; Foullon, C.; Nakariakov, V. M. [Centre for Fusion, Space and Astrophysics, Department of Physics, University of Warwick, Coventry CV4 7AL (United Kingdom); Aschwanden, M. J. [Lockheed Martin Advanced Technology Center, Solar and Astrophysics Laboratory, Organization ADBS, Building 252, 3251 Hanover Street, Palo Alto, CA 94304 (United States)], E-mail: Erwin.Verwichte@warwick.ac.uk

2009-06-10

224

Using large scale 2D modeling to explain driven vortex motion observed by STM  

NASA Astrophysics Data System (ADS)

We studied vortex matter in NbSe2, a type II superconductor, at magnetic fields of 0.25 - 0.75 T and temperatures of 4.2 K. At these fields the vortices form an Abrikosov lattice. Due to a small residual resistance in our superconducting magnet the applied magnetic field slowly decayed, driving the vortex lattice. The velocity was low enough to allow acquiring highly resolved time series using a low temperature scanning tunneling microscopy (STM). From the images we where able to extract the lattice constant as well as time series of the average vortex position (path) and velocity. The data was compared to a large scale 2D molecular dynamic type model of over 10000 vortices. Different configurations were examined to match the observed behaviour concerning vortex tracks, velociy vs. time and lattice constant vs. time. The data is detailed enough two distinguish small loops in the vortex tracks most likely caused by lattice dislocations. The focus of this presentation lies in matching simulation to the observed time evolution of the average velocity and lattice constant. We would like to thank Eva Andrej and Helmut Berger for providing NbSe2 samples.

Dreyer, Michael; Lee, Jonghee; Wang, Hui; Barker, Barry

2010-03-01

225

Vertical Distributions of Sulfur Species Simulated by Large Scale Atmospheric Models in COSAM: Comparison with Observations  

SciTech Connect

A comparison of large-scale models simulating atmospheric sulfate aerosols (COSAM) was conducted to increase our understanding of global distributions of sulfate aerosols and precursors. Earlier model comparisons focused on wet deposition measurements and sulfate aerosol concentrations in source regions at the surface. They found that different models simulated the observed sulfate surface concentrations mostly within a factor of two, but that the simulated column burdens and vertical profiles were very different amongst different models. In the COSAM exercise, one aspect is the comparison of sulfate aerosol and precursor gases above the surface. Vertical profiles of SO2, SO42-, oxidants and cloud properties were measured by aircraft during the North Atlantic Regional Experiment (NARE) experiment in August/September 1993 off the coast of Nova Scotia and during the Second Eulerian Model Evaluation Field Study (EMEFSII) in central Ontario in March/April 1990. While no single model stands out as being best or worst, the general tendency is that those models simulating the full oxidant chemistry tend to agree best with observations although differences in transport and treatment of clouds are important as well.

Lohmann, U.; Leaitch, W. R.; Barrie, Leonard A.; Law, K.; Yi, Y.; Bergmann, D.; Bridgeman, C.; Chin, M.; Christensen, J.; Easter, Richard C.; Feichter, J.; Jeuken, A.; Kjellstrom, E.; Koch, D.; Land, C.; Rasch, P.; Roelofs, G.-J.

2001-11-01

226

Large-Field CO(J = 1?0) Observations of the Starburst Galaxy M 82  

NASA Astrophysics Data System (ADS)

We present large-field (15.7 × 16.9 arcmin2) CO(J = 1?0) observations of the starburst galaxy M 82, at an angular resolution of 22" with the NRO 45-m telescope. The CO emission was detected in the galactic disk, outflow (driven by the galactic wind) up to ˜2 kpc above the galactic plane in the halo, and in tidal streams. The kinematics of the outflow (including CO line splitting) suggests that it has the shape of a cylinder that is diverging outwards. The mass and kinetic energy of the molecular gas outflow are estimated to be (0.26-1.0) × 109 M? and (1-4) × 1056 erg. A clump of CO gas was discovered 3.5 kpc above the galactic plane; it coincides with a dark lane previously found in X-ray observations, and a peak in H I emission. A comparison with H I, hot molecular hydrogen and dust suggests that the molecular gas shows signatures of warm and cool components in the outflow and tidal streams, respectively.

Salak, Dragan; Nakai, Naomasa; Miyamoto, Yusuke; Yamauchi, Aya; Tsuru, Takeshi G.

2013-06-01

227

Benchmarking global land surface models against the observed mean annual runoff from 150 large basins  

NASA Astrophysics Data System (ADS)

SummaryUsing the observed mean annual runoff for 1986-1995 from 150 large basins globally, we evaluate the performance of the 14 global land surface models (LSMs) and six Budyko-type hydrological models that are forced by the meteorological data from the second phase of the Global Soil Wetness Project (GSWP-2). The results show that both the 14 LSMs and six Budyko-type models can explain 55-70% of the spatial variations of mean annual runoff across the selected 150 basins. However, the 14 LSMs show larger biases in the simulated mean annual runoff than the Budyko-type models. The LSMs biases are caused by errors in forcing data, model structure and model parameterisation. The errors in the precipitation forcing data are found to be the main cause for biases in the simulated mean annual runoffs by the Budyko-types models, and most likely for biases in the 14 global land surface models too. The GSWP-2 precipitation is noticeably overestimated at Northern high-latitudes, which causes large positive biases for the LSMs in simulating mean annual runoff in these regions. The most LSMs show large biases in the regions with low mean annual precipitation. Underestimation of the GSWP-2 precipitation in Amazon and Orinoco basins results in significant underestimation in the simulated mean annual runoff by all LSMs and Budyko-type models for these regions. The LSMs with smaller biases generally show larger baseflow ratio in wet basins than in dry basins while the LSMs with larger biases generally show smaller baseflow ratio in wet basins than in dry basins. This indicates that errors in model structure can result in large biases in the simulated runoff. Several parameter sensitivity experiments for one LSM are carried out to investigate impacts on simulated mean runoff. The result indicates that ±20% changes in five key model parameters have relatively smaller impacts on the simulated mean annual runoff across the 150 basins, compared to errors in model structure.

Zhou, Xinyao; Zhang, Yongqiang; Wang, Yingping; Zhang, Huqiang; Vaze, Jai; Zhang, Lu; Yang, Yonghui; Zhou, Yanchun

2012-11-01

228

Large-scale inhomogeneities of the intracluster medium: improving mass estimates using the observed azimuthal scatter  

NASA Astrophysics Data System (ADS)

Achieving a robust determination of the gas density profile in the outskirts of clusters is a crucial step for measuring their baryonic content and using them as cosmological probes. The difficulty in obtaining this measurement lies not only in the low surface brightness of the intracluster medium (ICM), but also in the inhomogeneities of the gas associated with clumps, asymmetries and accretion patterns. Using a set of hydrodynamical simulations of 62 galaxy clusters and groups we study these kinds of inhomogeneities, focusing on the ones on large scales, which, unlike clumps, are difficult to identify. For this purpose we introduce the concept of the residual clumpiness, CR, which quantifies the large-scale inhomogeneity of the ICM. After showing that this quantity can be robustly defined for relaxed systems, we characterize how it varies with radius, and with the mass and dynamical state of the halo. Most importantly, we observe that it introduces an overestimate in the determination of the density profile from the X-ray emission, which translates into a systematic overestimate of 6 (12) per cent in the measurement of Mgas at R200 for our relaxed (perturbed) cluster sample. At the same time, the increase of CR with radius introduces a ˜2 per cent systematic underestimate in the measurement of the hydrostatic-equilibrium mass (Mhe), which adds to the previous one, generating a systematic overestimate of ˜8.5 per cent in fgas in our relaxed sample. Because the residual clumpiness of the ICM is not directly observable, we study its correlation with the azimuthal scatter in the X-ray surface brightness of the halo, a quantity that is well constrained by current measurements, and in the y-parameter profiles, which will be obtained in the forthcoming Sunyaev-Zeldovich (SZ) experiments. We find that their correlation is highly significant (rS = 0.6-0.7), allowing us to define the azimuthal scatter measured in the X-ray surface brightness profile and in the y-parameter as robust proxies of CR. After providing a function that connects the two quantities, we find that correcting the observed gas density profiles using the azimuthal scatter eliminates the bias in the measurement of Mgas for relaxed objects, which becomes 0 ± 2 per cent up to 2R200, and reduces it by a factor of 3 for perturbed ones. This method also allows us to eliminate the systematics on the measurements of Mhe and fgas, although a significant halo-to-halo scatter remains.

Roncarelli, M.; Ettori, S.; Borgani, S.; Dolag, K.; Fabjan, D.; Moscardini, L.

2013-07-01

229

FIRST OBSERVATIONS OF A DOME-SHAPED LARGE-SCALE CORONAL EXTREME-ULTRAVIOLET WAVE  

SciTech Connect

We present first observations of a dome-shaped large-scale extreme-ultraviolet coronal wave, recorded by the Extreme Ultraviolet Imager instrument on board STEREO-B on 2010 January 17. The main arguments that the observed structure is the wave dome (and not the coronal mass ejection, CME) are (1) the spherical form and sharpness of the dome's outer edge and the erupting CME loops observed inside the dome; (2) the low-coronal wave signatures above the limb perfectly connecting to the on-disk signatures of the wave; (3) the lateral extent of the expanding dome which is much larger than that of the coronal dimming; and (4) the associated high-frequency type II burst indicating shock formation low in the corona. The velocity of the upward expansion of the wave dome (v {approx} 650 km s{sup -1}) is larger than that of the lateral expansion of the wave (v {approx} 280 km s{sup -1}), indicating that the upward dome expansion is driven all the time, and thus depends on the CME speed, whereas in the lateral direction it is freely propagating after the CME lateral expansion stops. We also examine the evolution of the perturbation characteristics: first the perturbation profile steepens and the amplitude increases. Thereafter, the amplitude decreases with r {sup -2.5{+-}0.3}, the width broadens, and the integral below the perturbation remains constant. Our findings are consistent with the spherical expansion and decay of a weakly shocked fast-mode MHD wave.

Veronig, A. M.; Muhr, N.; Kienreich, I. W.; Temmer, M. [Institute of Physics, University of Graz, Universitaetsplatz 5, A-8010 Graz (Austria); Vrsnak, B., E-mail: asv@igam.uni-graz.a [Hvar Observatory, Faculty of Geodesy, Kaciceva 26, 1000 Zagreb (Croatia)

2010-06-10

230

OBSERVATION OF SUPERNOVA REMNANT IC 443 WITH THE FERMI LARGE AREA TELESCOPE  

SciTech Connect

We report observation of the supernova remnant (SNR) IC 443 (G189.1+3.0) with the Fermi Gamma-ray Space Telescope Large Area Telescope (LAT) in the energy band between 200 MeV and 50 GeV. IC 443 is a shell-type SNR with mixed morphology located off the outer Galactic plane where high-energy emission has been detected in the X-ray, GeV and TeV gamma-ray bands. Past observations suggest IC 443 has been interacting with surrounding interstellar matter. Proximity between dense shocked molecular clouds and GeV-TeV gamma-ray emission regions detected by EGRET, MAGIC, and VERITAS suggests an interpretation that cosmic-ray (CR) particles are accelerated by the SNR. With the high gamma-ray statistics and broad energy coverage provided by the LAT, we accurately characterize the gamma-ray emission produced by the CRs accelerated at IC 443. The emission region is extended in the energy band with theta{sub 68} = 0.{sup 0}27 +- 0.{sup 0}01(stat) +- 0.{sup 0}03(sys) for an assumed two-dimensional Gaussian profile and overlaps almost completely with the extended source region of VERITAS. Its centroid is displaced significantly from the known pulsar wind nebula (PWN) which suggests the PWN is not the major contributor in the present energy band. The observed spectrum changes its power-law slope continuously and continues smoothly to the MAGIC and VERITAS data points. The combined gamma-ray spectrum (200 MeV

Abdo, A. A. [Space Science Division, Naval Research Laboratory, Washington, DC 20375 (United States); Ackermann, M.; Ajello, M.; Bechtol, K.; Berenji, B.; Blandford, R. D.; Bloom, E. D.; Borgland, A. W. [W. W. Hansen Experimental Physics Laboratory, Kavli Institute for Particle Astrophysics and Cosmology, Department of Physics and SLAC National Accelerator Laboratory, Stanford University, Stanford, CA 94305 (United States); Baldini, L.; Bellazzini, R.; Bregeon, J.; Brez, A. [Istituto Nazionale di Fisica Nucleare, Sezione di Pisa, I-56127 Pisa (Italy); Ballet, J. [Laboratoire AIM, CEA-IRFU/CNRS/Universite Paris Diderot, Service d'Astrophysique, CEA Saclay, 91191 Gif sur Yvette (France); Barbiellini, G. [Istituto Nazionale di Fisica Nucleare, Sezione di Trieste, I-34127 Trieste (Italy); Bastieri, D. [Istituto Nazionale di Fisica Nucleare, Sezione di Padova, I-35131 Padova (Italy); Baughman, B. M. [Department of Physics, Center for Cosmology and Astro-Particle Physics, The Ohio State University, Columbus, OH 43210 (United States); Bonamente, E. [Istituto Nazionale di Fisica Nucleare, Sezione di Perugia, I-06123 Perugia (Italy); Brigida, M. [Dipartimento di Fisica 'M. Merlin' dell'Universita e del Politecnico di Bari, I-70126 Bari (Italy); Bruel, P. [Laboratoire Leprince-Ringuet, Ecole polytechnique, CNRS/IN2P3, Palaiseau (France); Burnett, T. H., E-mail: kamae@slac.stanford.ed, E-mail: shia520@stanford.ed, E-mail: francesco.giordano@ba.infn.i, E-mail: dtorres@ieec.uab.e, E-mail: arodrig@ieec.uab.e [Department of Physics, University of Washington, Seattle, WA 98195-1560 (United States)

2010-03-20

231

VERY LARGE ARRAY OH ZEEMAN OBSERVATIONS OF THE STAR-FORMING REGION S88B  

SciTech Connect

We present observations of the Zeeman effect in OH thermal absorption main lines at 1665 and 1667 MHz taken with the Very Large Array toward the star-forming region S88B. The OH absorption profiles toward this source are complicated, and contain several blended components toward a number of positions. Almost all of the OH absorbing gas is located in the eastern parts of S88B, toward the compact continuum source S88B-2 and the eastern parts of the extended continuum source S88B-1. The ratio of 1665/1667 MHz OH line intensities indicates the gas is likely highly clumped, in agreement with other molecular emission line observations in the literature. S88-B appears to present a similar geometry to the well-known star-forming region M17, in that there is an edge-on eastward progression from ionized to molecular gas. The detected magnetic fields appear to mirror this eastward transition; we detected line-of-sight magnetic fields ranging from 90 to 400 {mu}G, with the lowest values of the field to the southwest of the S88B-1 continuum peak, and the highest values to its northeast. We used the detected fields to assess the importance of the magnetic field in S88B by a number of methods; we calculated the ratio of thermal to magnetic pressures, we calculated the critical field necessary to completely support the cloud against self-gravity and compared it to the observed field, and we calculated the ratio of mass to magnetic flux in terms of the critical value of this parameter. All these methods indicated that the magnetic field in S88B is dynamically significant, and should provide an important source of support against gravity. Moreover, the magnetic energy density is in approximate equipartition with the turbulent energy density, again pointing to the importance of the magnetic field in this region.

Sarma, A. P.; Eftimova, M. [Physics Department, DePaul University, 2219 N. Kenmore Ave., Byrne Hall 211, Chicago, IL 60614 (United States)] [Physics Department, DePaul University, 2219 N. Kenmore Ave., Byrne Hall 211, Chicago, IL 60614 (United States); Brogan, C. L. [National Radio Astronomy Observatory, Charlottesville, VA 22903 (United States)] [National Radio Astronomy Observatory, Charlottesville, VA 22903 (United States); Bourke, T. L. [Harvard-Smithsonian Center for Astrophysics, Cambridge, MA 02138 (United States)] [Harvard-Smithsonian Center for Astrophysics, Cambridge, MA 02138 (United States); Troland, T. H., E-mail: asarma@depaul.edu [Department of Physics and Astronomy, University of Kentucky, Lexington, KY 40506 (United States)

2013-04-10

232

Simultaneous observations of large-scale traveling ionospheric disturbances on the nightside and dayside middle latitude  

NASA Astrophysics Data System (ADS)

In this paper, we present further observational evidence for the transpolar propagation of large-scale traveling ionospheric disturbances (LSTIDs) from their nightside source region to the dayside reported by Cai et al. (2011). Slant total electron content (STEC) observed by longitudinally aligned GPS receiver chains in North American and European sectors was analyzed to demonstrate presences of LSTIDs at both nightside and dayside mid-latitude. Signatures of TID were inferred from phase difference in time series of STEC perturbations (TECP) derived from measurements of ground-based GPS receivers, which are separated by hundreds of kilometers longitudinally. Periods of the daytime and nighttime ionospheric disturbances were estimated to be around 128 min, being in good agreement with that of the transpolar AGW (atmospheric gravity wave) recorded by EISCAT (European Incoherent Scatter Scientific Association)/ESR (EISCAT Svalbard Radar) radars. On the dayside, the LSTID moved equatorward with an average phase speed of ~440 m s-1. In North American sector, however, southward speed of the nighttime LSTID was much slower, being around 160 m s-1. We suggest that the observed daytime and nighttime mid-latitude LSTIDs are likely to have the same source region, being located somewhere at nighttime auroral latitude. Having been launched on the nightside, the waves propagate simultaneously equatorward and poleward. The equatorward-moving waves are recorded by GPS receiver chain in North American sector. The poleward-moving waves, however, cross the polar cap from nightside to dayside and then are detected consecutively at high and mid-latitudes by EISCAT/ESR radars and GPS receiver chains, respectively.

Cai, H. T.; Yin, F.; Ma, S. Y.; Xu, J. S.; Liu, Y. W.

2012-12-01

233

Nonlinear Site Response Due to Large Ground Acceleration: Observation and Computer Simulation  

NASA Astrophysics Data System (ADS)

We studied nonlinear site response due to large ground acceleration during the 2003 off-Miyagi Earthquake (Mw7.0) in Japan by means of horizontal-to-vertical spectral ratio analysis of S-wave motion. The results were then confirmed by finite-difference method (FDM) simulation of nonlinear seismic wave propagation. A nonlinear site response is often observed at soft sediment sites, and even at hard bedrock sites which are covered by thin soil layers. Nonlinear site response can be induced by strong ground motion whose peak ground acceleration (PGA) exceeds about 100 cm/s/s, and seriously affects the amplification of high frequency ground motion and PGA. Noguchi and Sasatani (2008) developed an efficient technique for quantitative evaluation of nonlinear site response using the horizontal-to-vertical spectral ratio of S-wave (S-H/V) derived from strong ground motion records, based on Wen et al. (2006). We applied this technique to perform a detailed analysis of the properties of nonlinear site response based on a large amount of data recorded at 132 K-NET and KiK-net strong motion stations in Northern Japan during the off-Miyagi Earthquake. We succeeded in demonstrating a relationship between ground motion level, nonlinear site response and surface soil characteristics. For example, the seismic data recorded at KiK-net IWTH26 showed obvious characteristics of nonlinear site response when the PGA exceeded 100 cm/s/s. As the ground motion level increased, the dominant peak of S-H/V shifted to lower frequency, the high frequency level of S-H/V dropped, and PGA amplification decreased. On the other hand, the records at MYGH03 seemed not to be affected by nonlinear site response even for high ground motion levels in which PGA exceeds 800 cm/s/s. The characteristics of such nonlinear site amplification can be modeled by evaluating Murnaghan constants (e.g. McCall, 1994), which are the third-order elastic constants. In order to explain the observed characteristics of nonlinear site response, we conducted FDM simulations of nonlinear seismic wavefield using finite strain formulation and Murnaghan constants that describe the nonlinear properties of surface soil. The nonlinear FDM simulation of ground motion is based on the work of Xu et al. (2000). Our present simulation model is in 2D, but it can be extended to 3D very easy. The Murnaghan constants for this simulation can be determined from a relationship between these constants and S-H/V deformation, which is derived from comparison of the observed S-H/V and that from FDM simulation with different values of these constants. The results of this simulation indicated a dramatic change occurring in the frequency-dependent amplification properties as the strain level near the surface increases. The predominant peak in the Fourier spectra of the S-wave gradually moved to the lower frequency band as the strain level increased from 10^-8 to 10^-6, and high frequency components showed a significant drop. These results correspond well with the observed data mentioned above. This demonstrates the effectiveness of nonlinear FDM simulation for an estimation of actual ground motion and frequency contents in an expected large earthquake.

Noguchi, S.; Furumura, T.; Sasatani, T.

2009-12-01

234

Influence of Slip on the Flow Past Superhydrophobic Circular Cylinders  

Microsoft Academic Search

Superhydrophobic surfaces have been shown to produce significant drag reduction for both laminar and turbulent flows of water through large and small-scale channels. In this presentation a series of experiments will be presented which investigate the effect of superhydrophobic-induced slip on the flow past a circular cylinder. In these experiments, circular cylinders are coated with a series of superhydrophobic surfaces

Jonathan Rothstein; Robert Daniello; Nangelie Ferrer; Pranesh Muralidhar

2010-01-01

235

Circular analysis in systems neuroscience: the dangers of double dipping  

Microsoft Academic Search

A neuroscientific experiment typically generates a large amount of data, of which only a small fraction is analyzed in detail and presented in a publication. However, selection among noisy measurements can render circular an otherwise appropriate analysis and invalidate results. Here we argue that systems neuroscience needs to adjust some widespread practices to avoid the circularity that can arise from

W Kyle Simmons; Patrick S F Bellgowan; Nikolaus Kriegeskorte; Chris I Baker

2009-01-01

236

A Summary of Large Raindrop Observations from GPM GV Field Campaigns  

NASA Technical Reports Server (NTRS)

NASA's Global Precipitation Measurement Mission (GPM) has conducted as series of Ground Validation (GV) studies to assist algorithm development for the GPM core satellite. Characterizing the drop size distribution (DSD) for different types of precipitation systems is critical in order to accurately estimate precipitation across the majority of the planet. Thus far, GV efforts have sampled DSDs in a variety of precipitation systems from Finland to Oklahoma. This dataset consists of over 33 million raindrops sampled by GPM GV's two-dimensional video disdrometers (2DVD) and includes RSD observations from the LPVEx, MC3E, GCPEx, HyMEx and IFloodS campaigns as well as from GV sites in Huntsville, AL and Wallops Island, VA. This study focuses on the larger end of the raindrop size spectrum, which greatly influences radar reflectivity and has implications for moment estimation. Thus knowledge of the maximum diameter is critical to GPM algorithm development. There are over 24,000 raindrops exceeding 5 mm in diameter contained within this disdrometer dataset. The largest raindrops in the 2DVD dataset (>7-8 mm in diameter) are found within intense convective thunderstorms, and their origins are believed to be hailstones. In stratiform rainfall, large raindrops have also been found to fall from lower and thicker melting layers. The 2DVD dataset will be combined with that collected by dual-polarimetric radar and aircraft particle imaging probes to "follow" the vertical evolution of the DSD tail (i.e., retrace the large drops from the surface to their origins aloft).

Gatlin, Patrick N.; Petersen, Walter; Tokay, Ali; Thurai, Merhala; Bringi, V. N.; Carey, Lawrence; Wingo, Matthew

2013-01-01

237

Large format heterodyne arrays for observing far-infrared lines with SOFIA  

NASA Astrophysics Data System (ADS)

In the wavelength regime between 60 and 300 microns there are a number of atomic and molecular emission lines that are key diagnostic probes of the interstellar medium. These include transitions of [CII], [NII], [OI], HD, H2D+, OH, CO, and H2O, some of which are among the brightest global and local far-infrared lines in the Galaxy. In Giant Molecular Clouds (GMCs), evolved star envelopes, and planetary nebulae, these emission lines can be extended over many arc minutes and possess complicated, often self absorbed, line profiles. High spectral resolution (R> 105) observations of these lines at sub-arcminute angular resolution are crucial to understanding the complicated interplay between the interstellar medium and the stars that form from it. This feedback is central to all theories of galactic evolution. Large format heterodyne array receivers can provide the spectral resolution and spatial coverage to probe these lines over extended regions. The advent of large format (~100 pixel) spectroscopic imaging cameras in the far-infrared (FIR) will fundamentally change the way astronomy is performed in this important wavelength regime. While the possibility of such instruments has been discussed for more than two decades, only recently have advances in mixer and local oscillator technology, device fabrication, micromachining, and digital signal processing made the construction of such instruments tractable. These technologies can be implemented to construct a sensitive, flexible, heterodyne array facility instrument for SOFIA. The instrument concept for StratoSTAR: Stratospheric Submm/THz Array Receiver includes a common user mounting, control system, IF processor, spectrometer, and cryogenic system. The cryogenic system will be designed to accept a frontend insert. The frontend insert and associated local oscillator system/relay optics would be provided by individual user groups and reflect their scientific interests. Rapid technology development in this field makes SOFIA the ideal platform to operate such a modular, continuously evolving instrument.

Walker, C.; Kulesa, C.; Kloosterman, J.; Lesser, D.; Cottam, T.; Groppi, C.; Zmuidzinas, J.; Edgar, M.; Radford, S.; Goldsmith, P.; Langer, W.; Yorke, H.; Kawamura, J.; Mehdi, I.; Hollenbach, D.; Stutzki, J.; Huebers, H.; Gao, J. R.; Martin, C.

2010-07-01

238

Small Earth Observing Satellites Flying with Large Satellites in the A-Train  

NASA Technical Reports Server (NTRS)

This paper/poster presents a real-life example of the benefits of flying small satellites with other satellites, large or small, and vice versa. Typically, most small satellites fly payloads consisting of one or two instruments and fly in orbits that are independent from that of other satellites. The science data from these satellites are either used in isolation or correlated with instrument data from other satellites. Data correlation with other satellites is greatly improved when the measurements of the same point or air mass are taken at approximately the same time. Scientists worldwide are beginning to take advantage of the opportunities for improved data correlation, or coincidental science, offered by the international Earth Observing Constellation known as the A-Train (sometimes referred to as the Afternoon Constellation). Most of the A-Train satellites are small - the A-Train is anchored by two large NASA satellites (EOS-Aqua and EOS-Aura), but consists also of 5 small satellites (CloudSat, CALIPSO, PARASOL, OCO and Glory these last two will join in 2009). By flying in a constellation, each mission benefits from coincidental observations from instruments on the other satellites in the constellation. Essentially, from a data point of view, the A-Train can be envisioned as a single, virtual science platform with multiple instruments. Satellites in the A-Train fly at 705 km in sun-synchronous orbits. Their mean local times at the equator are within seconds to a few minutes of each other. This paper describes the challenges of operating an international constellation of independent satellites from the U.S. and Europe to maximize the coincidental science opportunities while at the same time minimizing the level of operational interactions required between team members. The A-Train mission teams have been able to demonstrate that flying as members of an international constellation does not take away the flexibility to accommodate new requirements. Specific examples will be cited, including CloudSat's relocation (to accommodate a new viewing angle for the CALIPSO satellite), Glory's replan to move closer to PARASOL, and OCO's long term plans to minimize on-orbit operations costs while maintaining safety. In all cases, safety is ensured, science returns are enhanced, and operational flexibility is retained to the maximum extent possible.

Kelly, Angelita C.; Loverro, Adam; Case, Warren F.; Queruel, Nadege; Marechal, Chistophe; Barroso, Therese

2009-01-01

239

Observation and analysis of nonlinear vibrational relaxation of large molecules in shock waves  

SciTech Connect

We report the observation of highly nonlinear vibrational relaxation for a number of large molecules in shock waves, together with an attempt at a master-equation modeling of this phenomenon. In all these molecules laser-schlieren measurements show a clear and often well-resolved local maximum in the density gradient, indicating a similar maximum in the rate of energy transfer. This unexpected phenomenon is seen in the relaxation of benzene (C{sub 6}H{sub 6}), cubane (C{sub 8}H{sub 8}), cyclopropane (C{sub 3}H{sub 6}), furan (C{sub 4}H{sub 4}O), norbornadiene (C{sub 7}H{sub 8}), oxirane (C{sub 2}H{sub 4}O), and quadricyclane (C{sub 7}H{sub 8}). It has also been detected in cyclopentadiene (C{sub 5}H{sub 6}) and pyrazine (C{sub 4}N{sub 2}H{sub 4}), as well as CF{sub 3}Br and CF{sub 3}Cl but in these was not well resolved. The phenomenon thus seems nearly ubiquitous; of the ''large'' molecules where relaxation could be resolved, only norbornene (at C{sub 7}H{sub 10} the largest such molecule) exhibits a fully linear relaxation. The gradients are clearly and solely from vibrational relaxation; integrated gradients are in good agreement with thermodynamic calculations of total density change, and near-equilibrium relaxation times in pure cyclopropane and oxirane are fully consistent with overlapping ultrasonic results. It appears we are seeing a delay in the development of series coupling in these experiments. An attempt is made to model the process using a linear master equation with exponential gap probabilities having an {alpha}({approx}<{delta}E>{sub down}) linear in energy. Although this does introduce sufficient nonlinearity through the rate coefficients to produce maxima, these and the overall gradients are consistently too small. It is suggested that inclusion of a true nonlinearity through VV transfer will be needed to explain the observations, and a possible mechanism for this is proposed. (c) 2000 American Institute of Physics.

Kiefer, John H. [Department of Chemical Engineering, University of Illinois at Chicago, Chicago, Illinois 60680 (United States)] [Department of Chemical Engineering, University of Illinois at Chicago, Chicago, Illinois 60680 (United States); Buzyna, Leonid L. [Department of Chemical Engineering, University of Illinois at Chicago, Chicago, Illinois 60680 (United States)] [Department of Chemical Engineering, University of Illinois at Chicago, Chicago, Illinois 60680 (United States); Dib, Amal [Department of Chemical Engineering, University of Illinois at Chicago, Chicago, Illinois 60680 (United States)] [Department of Chemical Engineering, University of Illinois at Chicago, Chicago, Illinois 60680 (United States); Sundaram, Sekhar [Department of Chemical Engineering, University of Illinois at Chicago, Chicago, Illinois 60680 (United States)] [Department of Chemical Engineering, University of Illinois at Chicago, Chicago, Illinois 60680 (United States)

2000-07-01

240

Circular Compositional Reasoning about Liveness  

Microsoft Academic Search

. Compositional proofs about systems of many components often involve apparently circulararguments. That is, correctness of component A must be assumed when verifying component B, andvice versa. The apparent circularity of such arguments can be resolved by induction over time. However,previous methods for such circular compositional reasoning apply only to safety properties. This paperpresents a method of circular compositional reasoning

Kenneth L. Mcmillan; Cadence Berkeley Labs

1999-01-01

241

Satellite Observation of Large Scale Changes in Climate and Land Use in the Caspian Sea Basin  

NASA Astrophysics Data System (ADS)

The Caspian Sea Basin (catchments) area occupies the vast European and Asian territory between approx. 330-580 N latitude and 300-620 E longitude. In comparison with other world great natural lakes, the Caspian Sea ranks first in watershed area (3660,000 km2) and also in a total annual rivers runoff (340 km3/year - long-term average value). The Caspian is a closed basin with the largest landlocked water body in the world in its center. As a result, the water and biogeochemical cycles over the sea and surrounding lands are intimately linked. Any changes in the hydrologic regime over land and any major shifts in land use and land ecosystem health will directly impact the overall water and energy cycle of the basin, as well as the water quality and aquatic biology of the Sea. The basin being a closed system, it can also exhibit feedback processes that reinforce excursions from normal and lead to large impacts on the surrounding regions. In this paper, we present results of the analysis of climate and vegetation observations over the past 30 years over the Caspian Sea Basin to document the changes of climate, and land use, the regional vegetation response. We focus our analysis using data from AVHRR, MODIS, QSCAT, and TRMM. The results indicate that the region has gone through major changes in land use accompanied by anomalies of temperature and rainfall that in turn has suppressed the vegetation cover and phenology. The results are corroborated by data from socio-economic changes in the region and ground observation of climate and vegetation.

Saatchi, S.; Nouri, A.; Asefi, S.; Shiklomanov, A.; Entekhabi, D.; Mohammadi, S.; Hedjazi, B.

2012-04-01

242

Large scale patterns of auroral ionospheric convection observed with the Chatanika radar  

SciTech Connect

Ionospheric convection at auroral latitudes has been examined during a series of long duration experiments with the Chatanika, Alaska, incoherent scatter radar. These experiments have been carefully designed to obtain maximum latitudinal coverage (56 /sup 0/..lambda.. to 75 /sup 0/..lambda..) while maintaining a temporal resolution of 30 min in order to resolve the effects of individual substorms on the convection pattern. Design criteria for the experiments are described together with presentation of observational data acquired during 400 hr of radar operations during various levels of geophysical disturbance. The data accentuate the repeatability of the gross features of the auroral convection and its basic conformity to the two0cell pattern predicted from the large-scale magnetospheric circulation. For moderate to active geomagnetic conditions uniform sunward convection with velocities of 800 to 1200 m/s spans the 62 /sup 0/..lambda.. to 72 /sup 0/..lambda.. latitude band at both dawn and dusk. In quieter circumstances the sunward convection continues in this region, but has smaller speeds and is centered at higher latitudes. Little evidence of a throat in the dayside convection pattern is seen at latitudes below 75 /sup 0/..lambda.. except in very disturbed circumstances. During several experiments coordinated operation of the Chatanika and Millstone Hill, Massachusetts, radars permitted the simultaneous observation of the auroral convection pattern at two different local times. substorms affect the convection at all local times and appears to generally enhance the rate of convection without seriously changing its direction. Near midnight, latitudinal displacements and expansions of the convection pattern during substorms may result in a local rotation or reversal of the direction of convection, while near dawn and dusk, convection velocities are enhanced and the region of sunward flow expands to lower latitudes.

Foster, J.C.; Doupnik, J.R.; Stiles, G.S.

1981-12-01

243

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

NASA Technical Reports Server (NTRS)

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

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

2013-01-01

244

Observational and Model Studies of Large-Scale Mixing Processes in the Stratosphere  

NASA Technical Reports Server (NTRS)

The following is the final technical report for grant NAGW-3442, 'Observational and Model Studies of Large-Scale Mixing Processes in the Stratosphere'. Research efforts in the first year concentrated on transport and mixing processes in the polar vortices. Three papers on mixing in the Antarctic were published. The first was a numerical modeling study of wavebreaking and mixing and their relationship to the period of observed stratospheric waves (Bowman). The second paper presented evidence from TOMS for wavebreaking in the Antarctic (Bowman and Mangus 1993). The third paper used Lagrangian trajectory calculations from analyzed winds to show that there is very little transport into the Antarctic polar vortex prior to the vortex breakdown (Bowman). Mixing is significantly greater at lower levels. This research helped to confirm theoretical arguments for vortex isolation and data from the Antarctic field experiments that were interpreted as indicating isolation. A Ph.D. student, Steve Dahlberg, used the trajectory approach to investigate mixing and transport in the Arctic. While the Arctic vortex is much more disturbed than the Antarctic, there still appears to be relatively little transport across the vortex boundary at 450 K prior to the vortex breakdown. The primary reason for the absence of an ozone hole in the Arctic is the earlier warming and breakdown of the vortex compared to the Antarctic, not replenishment of ozone by greater transport. Two papers describing these results have appeared (Dahlberg and Bowman; Dahlberg and Bowman). Steve Dahlberg completed his Ph.D. thesis (Dahlberg and Bowman) and is now teaching in the Physics Department at Concordia College. We also prepared an analysis of the QBO in SBUV ozone data (Hollandsworth et al.). A numerical study in collaboration with Dr. Ping Chen investigated mixing by barotropic instability, which is the probable origin of the 4-day wave in the upper stratosphere (Bowman and Chen). The important result from this paper is that even in the presence of growing, unstable waves, the mixing barriers around

Bowman, Kenneth P.

1997-01-01

245

Hypercomplete circular harmonic pyramids  

NASA Astrophysics Data System (ADS)

In this contribution we present a steerable pyramid based on a particular set of complex wavelets named circular harmonic wavelets (CHW). The proposed CHWs set constitutes a generalization of the smoothed edge wavelets introduced by Mallat, consisting of extending the local differential representation of a signal image from the first order to a generic n-th order. The key feature of the proposed representation is the use of complex operators leading to an expansion in series of polar separable complex functions, which are shown to possess the space-scale representability of the wavelets. The resulting tool is highly redundant, and for this reason is called hypercomplete circular harmonic pyramid (HCHP), but presents some interesting aspects in terms of flexibility, being suited for many image processing applications. In the present contribution the main theoretical aspects of the HCHPs are discussed along with some introductory applications.

Jacovitti, Giovanni; Manca, A.; Neri, Alessandro

1996-10-01

246

How do We Choose, Use and Interpret Data From Large Scale Observing Arrays?  

NASA Astrophysics Data System (ADS)

This is a poster presentation of a "website under construction" that will provide free-ware access to spatial analysis modules for Kalman Filtering, Kriging, Neural Networks, Splines, Empirical Orthogonal Function Analysis, and Spatial Objective Analysis. The website is being designed to aid scientists, educators and students with the analysis of data which is generally sparse and irregularly spaced, for which the geographic locations of the observing points are essential inputs to the analyses. Sections for each of the state-of-the-art methodologies will include: 1) Discussion of the objectives for which it was originally developed; 2) Examples of applications to large data sets; 3) Mathematical foundations; 4) References to relevant scientific and mathematical literature; 5) E-links to software for data analysis, with explanations for its use; 6) E-links to data sets for exercise of the technology. Modular construction will permit use of any of the above technologies, independent of others. This "workshop presentation" invites creative input that can contribute to the utility of the final product, from all viewers/potential users.

Thiebaux, H.

2005-12-01

247

Observations of short large-amplitude magnetic structures at a quasi-parallel shock  

NASA Technical Reports Server (NTRS)

Results of a detailed analysis of short large-amplitude magnetic structures (SLAMS) observed at an encounter of the quasi-parallel blow shock by the AMPTE UKS and IRM satellites are presented. Isolated SLAMS, surrounded by solar wind conditions, and embedded SLAMS, which lie within or form the boundary with regions of significant heating and deceleration, are identified. The duration, polarization, and other characteristics of SLAMS are all consistent with their growth directly out of the ULF wave field, including the common occurrence of an attached whistler as found in ULF shocklets. The plasma rest frame propagation speeds and two-spacecraft time delays for all cases show that the SLAMS attempt to propagate upstream against the oncoming flow, but are convected back downstream. The speeds and delays vary systematically with SLAMS amplitude in the way anticipated from nonlinear wave theory, as do their polarization features. Inter-SLAMS regions and boundary regions with solar wind contain hot deflected ions of lesser density than within the SLAMS.

Schwartz, Steven J.; Burgess, David; Wilkinson, William P.; Kessel, Ramona L.; Dunlop, Malcolm; Luehr, Herman

1992-01-01

248

Expanded Very Large Array Observations of the Radio Evolution of SN 2011dh  

NASA Astrophysics Data System (ADS)

We report on Expanded Very Large Array observations of the Type IIb supernova 2011dh, performed over the first 100 days of its evolution and spanning 1-40 GHz in frequency. The radio emission is well described by the self-similar propagation of a spherical shockwave, generated as the supernova ejecta interact with the local circumstellar environment. Modeling this emission with a standard synchrotron self-absorption (SSA) model gives an average expansion velocity of v ? 0.1c, supporting the classification of the progenitor as a compact star (R sstarf ? 1011 cm). We find that the circumstellar density is consistent with a ?vpropr -2 profile. We determine that the progenitor shed mass at a constant rate of ?3 × 10-5 M ? yr-1, assuming a wind velocity of 1000 km s-1 (values appropriate for a Wolf-Rayet star), or ?7 × 10-7 M ? yr-1 assuming 20 km s-1 (appropriate for a yellow supergiant [YSG] star). Both values of the mass-loss rate assume a converted fraction of kinetic to magnetic energy density of epsilon B = 0.1. Although optical imaging shows the presence of a YSG, the rapid optical evolution and fast expansion argue that the progenitor is a more compact star—perhaps a companion to the YSG. Furthermore, the excellent agreement of the radio properties of SN 2011dh with the SSA model implies that any YSG companion is likely in a wide, non-interacting orbit.

Krauss, M. I.; Soderberg, A. M.; Chomiuk, L.; Zauderer, B. A.; Brunthaler, A.; Bietenholz, M. F.; Chevalier, R. A.; Fransson, C.; Rupen, M.

2012-05-01

249

Colorimetry of two large flares of EV Lac according to UBVRI observations in 1996-1998  

NASA Astrophysics Data System (ADS)

According to the data of fast UBVRI photometry of the red flaring dwarf star EV Lac obtained in the course of international cooperative observations, a fine temporal structure of two large flares (15 Oct 1996 and 10 Oct 1998) with amplitudes of 3.73 and 2.72 magnitudes in the U band have been studied. A detailed colorimetric analysis allowed us to trace variations in the flare plasma characteristics such as the optical thickness, electron density, and temperature during the development of the flare. It was revealed that, in the time period up to the maximum brightness, both flares are in the state of hydrogen plasma, which is optically thin in the Balmer continuum. In the region of the brightness maximum, both flares emit for about 1 min as an absolutely black body (ABB), the temperature of which varies from 20000 to 12000 K and 16000 to 14000 K, respectively. Then, these flares pass to the plasma state, is optically thick in the Balmer continuum. At the brightness maximum, the flares emitted as an ABB with a temperature of about 15000 and 16000 K. In the ABB approximation, the linear sizes of the flares are approximately 5 and 3% of the stellar radius at luminosity maximum. The area is 5.1 × 1018 cm2 and 1.6 × 1018 cm2.

Lovkaya, M. N.

2012-06-01

250

Search for Large Extra Dimensions via Observations of Neutron Stars with Fermi--LAT  

NASA Astrophysics Data System (ADS)

Large extra dimensions (LED) have been proposed to account for the apparent weakness of gravitation. These theories also indicate that the postulated massive Kaluza-Klein (KK) gravitons may be produced by nucleon-nucleon bremsstrahlung in the course of core collapse of supernovae. Hannestad and Raffelt have predicted energy spectra of gamma ray emission from the decay of KK gravitons trapped by the gravity of the remnant neutron stars (NS). These and other authors have used EGRET data on NS to obtain stringent limits on LED. Fermi-LAT is observing radio pulsar positions obtained from radio and x-ray catalogs. NS with certain characteristics are unlikely emitter of gamma rays, and emit in radio and perhaps x-rays. This talk will focus on the blind analysis we plan to perform, which has been developed using the 1^st 2 months of all sky data and Monte Carlo simulations, to obtain limits on LED based on about 1 year of Fermi-LAT data. Preliminary limits from this analysis using these first 2 months of data will be also be discussed.

Berenji, Bijan; Bloom, Elliott

2009-05-01

251

Inferred Cosmic-Ray Spectrum from Fermi Large Area Telescope ?-Ray Observations of Earth's Limb  

NASA Astrophysics Data System (ADS)

Recent accurate measurements of cosmic-ray (CR) species by ATIC-2, CREAM, and PAMELA reveal an unexpected hardening in the proton and He spectra above a few hundred GeV, a gradual softening of the spectra just below a few hundred GeV, and a harder spectrum of He compared to that of protons. These newly discovered features may offer a clue to the origin of high-energy CRs. We use the Fermi Large Area Telescope observations of the ?-ray emission from Earth's limb for an indirect measurement of the local spectrum of CR protons in the energy range ˜90 GeV-6 TeV (derived from a photon energy range 15 GeV-1 TeV). Our analysis shows that single power law and broken power law spectra fit the data equally well and yield a proton spectrum with index 2.68±0.04 and 2.61±0.08 above ˜200 GeV, respectively.

Ackermann, M.; Ajello, M.; Albert, A.; Allafort, A.; Baldini, L.; Barbiellini, G.; Bastieri, D.; Bechtol, K.; Bellazzini, R.; Blandford, R. D.; Bloom, E. D.; Bonamente, E.; Bottacini, E.; Bouvier, A.; Brandt, T. J.; Brigida, M.; Bruel, P.; Buehler, R.; Buson, S.; Caliandro, G. A.; Cameron, R. A.; Caraveo, P. A.; Cecchi, C.; Charles, E.; Chaves, R. C. G.; Chekhtman, A.; Chiang, J.; Chiaro, G.; Ciprini, S.; Claus, R.; Cohen-Tanugi, J.; Conrad, J.; Cutini, S.; Dalton, M.; D'Ammando, F.; de Angelis, A.; de Palma, F.; Dermer, C. D.; Digel, S. W.; Di Venere, L.; do Couto e Silva, E.; Drell, P. S.; Drlica-Wagner, A.; Favuzzi, C.; Fegan, S. J.; Ferrara, E. C.; Focke, W. B.; Franckowiak, A.; Fukazawa, Y.; Funk, S.; Fusco, P.; Gargano, F.; Gasparrini, D.; Germani, S.; Giglietto, N.; Giordano, F.; Giroletti, M.; Glanzman, T.; Godfrey, G.; Gomez-Vargas, G. A.; Grenier, I. A.; Grove, J. E.; Guiriec, S.; Gustafsson, M.; Hadasch, D.; Hanabata, Y.; Harding, A. K.; Hayashida, M.; Hayashi, K.; Hewitt, J. W.; Horan, D.; Hou, X.; Hughes, R. E.; Inoue, Y.; Jackson, M. S.; Jogler, T.; Jóhannesson, G.; Johnson, A. S.; Kamae, T.; Kawano, T.; Knödlseder, J.; Kuss, M.; Lande, J.; Larsson, S.; Latronico, L.; Longo, F.; Loparco, F.; Lovellette, M. N.; Lubrano, P.; Mayer, M.; Mazziotta, M. N.; McEnery, J. E.; Mehault, J.; Michelson, P. F.; Mitthumsiri, W.; Mizuno, T.; Moiseev, A. A.; Monte, C.; Monzani, M. E.; Morselli, A.; Moskalenko, I. V.; Murgia, S.; Nemmen, R.; Nuss, E.; Ohsugi, T.; Okumura, A.; Orienti, M.; Orlando, E.; Ormes, J. F.; Paneque, D.; Panetta, J. H.; Perkins, J. S.; Pesce-Rollins, M.; Piron, F.; Pivato, G.; Porter, T. A.; Rainò, S.; Rando, R.; Razzano, M.; Razzaque, S.; Reimer, A.; Reimer, O.; Ritz, S.; Roth, M.; Schaal, M.; Schulz, A.; Sgrò, C.; Siskind, E. J.; Spandre, G.; Spinelli, P.; Strong, A. W.; Takahashi, H.; Takeuchi, Y.; Thayer, J. G.; Thayer, J. B.; Thompson, D. J.; Tibaldo, L.; Tinivella, M.; Torres, D. F.; Tosti, G.; Troja, E.; Tronconi, V.; Usher, T. L.; Vandenbroucke, J.; Vasileiou, V.; Vianello, G.; Vitale, V.; Werner, M.; Winer, B. L.; Wood, K. S.; Wood, M.; Yang, Z.; Fermi LAT Collaboration

2014-04-01

252

Inferred cosmic-ray spectrum from Fermi large area telescope ?-ray observations of Earth's limb.  

PubMed

Recent accurate measurements of cosmic-ray (CR) species by ATIC-2, CREAM, and PAMELA reveal an unexpected hardening in the proton and He spectra above a few hundred GeV, a gradual softening of the spectra just below a few hundred GeV, and a harder spectrum of He compared to that of protons. These newly discovered features may offer a clue to the origin of high-energy CRs. We use the Fermi Large Area Telescope observations of the ?-ray emission from Earth's limb for an indirect measurement of the local spectrum of CR protons in the energy range ?90??GeV-6??TeV (derived from a photon energy range 15 GeV-1 TeV). Our analysis shows that single power law and broken power law spectra fit the data equally well and yield a proton spectrum with index 2.68±0.04 and 2.61±0.08 above ?200??GeV, respectively. PMID:24785023

Ackermann, M; Ajello, M; Albert, A; Allafort, A; Baldini, L; Barbiellini, G; Bastieri, D; Bechtol, K; Bellazzini, R; Blandford, R D; Bloom, E D; Bonamente, E; Bottacini, E; Bouvier, A; Brandt, T J; Brigida, M; Bruel, P; Buehler, R; Buson, S; Caliandro, G A; Cameron, R A; Caraveo, P A; Cecchi, C; Charles, E; Chaves, R C G; Chekhtman, A; Chiang, J; Chiaro, G; Ciprini, S; Claus, R; Cohen-Tanugi, J; Conrad, J; Cutini, S; Dalton, M; D'Ammando, F; de Angelis, A; de Palma, F; Dermer, C D; Digel, S W; Di Venere, L; do Couto e Silva, E; Drell, P S; Drlica-Wagner, A; Favuzzi, C; Fegan, S J; Ferrara, E C; Focke, W B; Franckowiak, A; Fukazawa, Y; Funk, S; Fusco, P; Gargano, F; Gasparrini, D; Germani, S; Giglietto, N; Giordano, F; Giroletti, M; Glanzman, T; Godfrey, G; Gomez-Vargas, G A; Grenier, I A; Grove, J E; Guiriec, S; Gustafsson, M; Hadasch, D; Hanabata, Y; Harding, A K; Hayashida, M; Hayashi, K; Hewitt, J W; Horan, D; Hou, X; Hughes, R E; Inoue, Y; Jackson, M S; Jogler, T; Jóhannesson, G; Johnson, A S; Kamae, T; Kawano, T; Knödlseder, J; Kuss, M; Lande, J; Larsson, S; Latronico, L; Longo, F; Loparco, F; Lovellette, M N; Lubrano, P; Mayer, M; Mazziotta, M N; McEnery, J E; Mehault, J; Michelson, P F; Mitthumsiri, W; Mizuno, T; Moiseev, A A; Monte, C; Monzani, M E; Morselli, A; Moskalenko, I V; Murgia, S; Nemmen, R; Nuss, E; Ohsugi, T; Okumura, A; Orienti, M; Orlando, E; Ormes, J F; Paneque, D; Panetta, J H; Perkins, J S; Pesce-Rollins, M; Piron, F; Pivato, G; Porter, T A; Rainò, S; Rando, R; Razzano, M; Razzaque, S; Reimer, A; Reimer, O; Ritz, S; Roth, M; Schaal, M; Schulz, A; Sgrò, C; Siskind, E J; Spandre, G; Spinelli, P; Strong, A W; Takahashi, H; Takeuchi, Y; Thayer, J G; Thayer, J B; Thompson, D J; Tibaldo, L; Tinivella, M; Torres, D F; Tosti, G; Troja, E; Tronconi, V; Usher, T L; Vandenbroucke, J; Vasileiou, V; Vianello, G; Vitale, V; Werner, M; Winer, B L; Wood, K S; Wood, M; Yang, Z

2014-04-18

253

ASCA observations of the Large Magellanic Cloud supernova remnant sample: Typing supernovae from their remnants  

NASA Technical Reports Server (NTRS)

We present our first results from a study of the supernova remnants (SNRs) in the Large Magellanic Cloud (LMC) using data from ASCA. The three remnants we have analyzed to date, 0509-67.5, 0519-69.0, and N103B, are among the smallest, and presumably also the youngest, in the Cloud. The X-ray spectra of these SNRs show strong K alpha emission lines of silicon, sulfur, argon, and calcium with no evidence for corresponding lines of oxygen, neon, or magnesium. The dominant feature in the spectra is a broad blend of emission lines around 1 keV which we attribute to L-shell emission lines of iron. Model calculations (Nomoto, Thielemann, & Yokoi 1984) show that the major products of nucleosynthesis in Type Ia supernovae (SNs) are the elements from silicon to iron, as observed here. The calculated nucleosynthetic yields from Type Ib and II SNs are shown to be qualitatively inconsistent with the data. We conclude that the SNs which produced these remnants were of Type Ia. This finding also confirms earlier suggestions that the class of Balmer-dominated remnants arise from Type Ia SN explosions. Based on these early results from the LMC SNR sample, we find that roughly one-half of the SNRs produced in the LMC within the last approximately 1500 yr came from Type Ia SNs.

Hughes, John P.; Hayashi, Ichizo; Helfand, David; Hwang, Una; Itoh, Masayuki; Kirshner, Robert; Koyama, Katsuji; Markert, Thomas; Tsunemi, Hiroshi; Woo, Jonathan

1995-01-01

254

Search for Large Extra Dimensions Based on Observations of Neutron Stars with the Fermi-LAT  

SciTech Connect

Large extra dimensions (LED) have been proposed to account for the apparent weakness of gravitation. These theories also indicate that the postulated massive Kaluza-Klein (KK) gravitons may be produced by nucleon-nucleon bremsstrahlung in the course of core collapse of supernovae. Hannestad and Raffelt have predicted energy spectra of gamma ray emission from the decay of KK gravitons trapped by the gravity of the remnant neutron stars (NS). These and other authors have used EGRET data on NS to obtain stringent limits on LED. Fermi-LAT is observing radio pulsar positions obtained from radio and x-ray catalogs. NS with certain characteristics are unlikely emitter of gamma rays, and emit in radio and perhaps x-rays. This talk will focus on the blind analysis we plan to perform, which has been developed using the 1st 2 months of all sky data and Monte Carlo simulations, to obtain limits on LED based on about 1 year of Fermi-LAT data. Preliminary limits from this analysis using these first 2 months of data will be also be discussed.

Berenji, Bijan; /Stanford U., Appl. Phys. Dept. /SLAC

2012-09-19

255

Observations of short large-amplitude magnetic structures at a quasi-parallel shock  

NASA Astrophysics Data System (ADS)

Results of a detailed analysis of short large-amplitude magnetic structures (SLAMS) observed at an encounter of the quasi-parallel blow shock by the AMPTE UKS and IRM satellites are presented. Isolated SLAMS, surrounded by solar wind conditions, and embedded SLAMS, which lie within or form the boundary with regions of significant heating and deceleration, are identified. The duration, polarization, and other characteristics of SLAMS are all consistent with their growth directly out of the ULF wave field, including the common occurrence of an attached whistler as found in ULF shocklets. The plasma rest frame propagation speeds and two-spacecraft time delays for all cases show that the SLAMS attempt to propagate upstream against the oncoming flow, but are convected back downstream. The speeds and delays vary systematically with SLAMS amplitude in the way anticipated from nonlinear wave theory, as do their polarization features. Inter-SLAMS regions and boundary regions with solar wind contain hot deflected ions of lesser density than within the SLAMS.

Schwartz, Steven J.; Burgess, David; Wilkinson, William P.; Kessel, Ramona L.; Dunlop, Malcolm; Luehr, Herman

1992-04-01

256

Interactive Browsing, Filtering, Visualization, and Retrieval from Large Collections of Near Real-Time Satellite Observations  

NASA Astrophysics Data System (ADS)

The recent availability of vast quantities of near real-time, global satellite observations through the NASA/GSFC Land Atmospheres Near real-time Capability for EOS (LANCE) has provided a compelling opportunity to use that data to improve response to natural hazards and disasters. Given the sheer volume of data (40+ image-based products, 90+ total) and their associated application areas (14 currently identified), this prototype framework provides a web-based user interface to enable efficient browsing, filtering, visualization, and retrieval of the most relevant products available for a given scenario. While this large number of available products can initially be reduced by selecting an application area, the remainder of the user workflow generally follows Shneiderman's visual information seeking mantra, "overview first, zoom and filter, then details-on-demand." In this case, "overview first" and "zoom" capabilities are provided by standard mapping tools such as Google Earth and OpenLayers. Once a region of interest is found, an overlaid custom interface displays all relevant data products for that region from the past week, facilitating a rapid visual "filtering" and selection by the user of the most suitable product and time step. That selected solution then can be further analyzed (e.g., with "before/after" comparisons) and downloaded in the subsequent "details-on-demand" phase. Once complete, the product and time step are applied to the initial global view for broader analyses, enabling a restart or refinement of the investigative process.

Boller, R. A.; Murphy, K. J.; Teague, M.; Schmaltz, J. E.; Ilavajhala, S.; Davies, D.

2011-12-01

257

Rain Characteristics and Large-Scale Environment Associated with Extreme Precipitation Events Based on TRMM Observations  

NASA Astrophysics Data System (ADS)

This study utilizes the Precipitation Feature (PF) database developed at the University of Utah to analyze extreme precipitation events from 13-year TRMM observations. Characteristics of instantaneous extreme volumetric PFs, their geophysical distributions and diurnal variations are examined and compared to those of intermediate and small systems. It is found that the instantaneous PF exhibits much larger scale range than daily gridded precipitation, with those at top 1% of PFs two orders of magnitude greater than the medium PF but contributing to over 50% of instantaneous rainfall. The study shows that extreme PFs are significantly larger, deeper and colder than the lower 80% of the PFs. NCEP reanalysis shows a systematic increase in surface moist static energy (MSE) with larger PFs but convective available potential energy (CAPE) levels off for extremely large systems. Mid-level relative humidity and total precipitable water increase consistently for increasingly heavy precipitation events, suggesting a potential role of increasing moisture in a warming climate in producing extreme precipitation events.

Zhou, Y.; Lau, W. K.

2012-12-01

258

Soft X-ray observations of large-scale coronal active region brightenings  

NASA Technical Reports Server (NTRS)

One hundred fifty-six large-scale enhancements of X-ray emission from solar active regions were studied on full-disk filterheliograms to determine characteristic morphology and expansion rates for heated coronal plasma. The X-ray photographs were compared with H-alpha observations of flares, sudden filament disappearances, sprays, and loop prominence systems (LPS). Eighty-one percent of the X-ray events were correlated with H-alpha filament activity, but only 44% were correlated with reported H-alpha flares. The X-ray enhancements took the form of loops or arcades of loops ranging in length from 60,000 km to 520,000 km and averaging 15,000 km in width. Lifetimes ranged from at least 3 hr to more than 24 hr. The event frequency was approximately 1.4 per day. X-ray loop arcades evolved from sharp-edged clouds in cavities vacated by rising H-alpha filaments. Expansion velocities of the loops were about 50 km/s immediately after excitation and 1-10 km/s several hours later. These long-lived loop arcades are identified with LPS, and it is suggested that the loops outlined magnetic fields which were reconnecting after filament eruptions. Another class of X-ray-enhanced loops stretched outside active regions and accompanied sprays or lateral filament ejections. It is suggested that these loops outlined closed magnetic fields guiding slow-mode shocks from flares and filament eruptions.

Rust, D. M.; Webb, D. F.

1977-01-01

259

Progress in circular dichroism laser mass spectrometry.  

PubMed

Circular dichroism in ion yield has promising new potentials for chiral analysis. Our progress of its development is described here. Circular dichroism in ion yield is achieved by resonance-enhanced multiphoton ionization. The feasibility of circular dichroism spectroscopy and quantitative determination of circular dichroism by this method is demonstrated. Several excitation schemes have been applied using different types of lasers, which vary in wavelength and repetition rate. Progress to improve the statistical error and thus the lower limit of measurable circular dichroism is described. This is achieved by adding achiral compounds or racemic mixtures of chiral compounds to the sample gas as reference substances and ionizing them by the same laser pulse. Therefore, in the mass spectrum of every single laser pulse, ion signals of sample and reference species appear both being subject to the same kind of instrumental fluctuations (in particular of laser pulse energy). In another approach, a laser repetition rate of 200 Hz allowed averaging of large numbers of laser pulses. PMID:19636544

Logé, Christoph; Bornschlegl, Alexander; Boesl, Ulrich

2009-11-01

260

Observed and Aogcm Simulated Relationships Between us Wind Speeds and Large Scale Modes of Climate Variability  

NASA Astrophysics Data System (ADS)

Previous research has indicated that large-scale modes of climate variability, such as El Niño - Southern Oscillation (ENSO), the Arctic Oscillation (AO) and the Pacific-North American pattern (PNA), influence the inter-annual and intra-annual variability of near-surface and upper-level wind speeds over the United States. For example, we have shown that rawinsonde derived wind speeds indicate that 90th percentile of wind speeds at 700 hPa over the Pacific Northwest and Southwestern USA are significantly higher under the negative phase of the PNA, and the Central Plains experiences higher wind speeds at 850 hPa under positive phase Southern Oscillation index while the Northeast exhibits higher wind speeds at 850 hPa under positive phase NAO. Here, we extend this research by further investigating these relationships using both reanalysis products and output from coupled atmosphere-ocean general circulation models (AOGCMs) developed for the 5th Phase of the Coupled Model Intercomparison Project (CMIP5). The research presented has two specific goals. First, we evaluate the AOGCM simulations in terms of their ability to represent the temporal and spatial representations of ENSO, the AO, and the PNA pattern relative to historical observations. The diagnostics used include calculation of the power spectra (and thus representation of the fundamental frequencies of variability) and Taylor diagrams (for comparative assessment of the spatial patterns and their intensities). Our initial results indicate that most AOGCMs produce modes that are qualitatively similar to those observed, but that differ slightly in terms of the spatial pattern, intensity of specific centers of action, and variance explained. Figure 1 illustrates an example of the analysis of the frequencies of variability of two climate modes for the NCEP-NCAR reanalysis (NNR) and a single AOGCM (BCC CSM1). The results show a high degree of similarity in the power spectra but for this AOGCM the variance of the PNA associated with high frequencies are amplified relative to those in NNR. Second, we quantify the observed and AOGCM-simulated relationships between ENSO, AO, and PNA indices and zonal and meridional wind components at multiple levels for the contiguous United States. The results are presented in form of maps displaying the strength of the relationship at different timescales, from daily to annual, and at multiple atmospheric levels, from 10m to 500 mb. The results of the analysis are used to provide context for regional wind climate projections based on 21st century AOGCM simulations.

Schoof, J. T.; Pryor, S. C.; Barthelmie, R. J.

2013-12-01

261

Large rivers in sedimentary basins: Morphology and form observed from satellite imagery  

NASA Astrophysics Data System (ADS)

Preservation of the deposits of big rivers, like any other river, can only occur where the river crosses an area of net aggradation in a sedimentary basin. Many of the world’s big rivers are systems that transfer sediment load from erosional realms to the sea, depositing fluvial successions only where there is accommodation on the coastal plain. However, many of the big rivers (e.g., Parana, Paraguay, Brahmaputra, Ganges, Indus, and Yukon Rivers) also cross continental sedimentary basins (e.g., sedimentary basins with minimal marine influence that lie inside continents) on their way to the oceans. We use satellite imagery to observe the large-scale morphology of big rivers in these continental sedimentary basins. As with other rivers, big rivers lose confinement of their valleys and form distributive fluvial systems (DFS) as they enter the continental sedimentary basins. Commonly, channel size decreases down-DFS, either through infiltration, bifurcation, or evaporation. Several active and/or old channels radiate outward from a DFS apex, and where the river is incised into its DFS, several paleochannel deposits are visible radiating outward from the DFS apex. Between and adjacent to channels, a significant amount of fine-grained sediment is deposited across the DFS surface, leaving high potential for preservation of floodplain deposits, even on large river DFS dominated by braided river systems. Commonly, the big rivers become the axial river in the sedimentary basin, continuing along strike of the basin. In this position, the river becomes confined between opposing DFS or between transverse DFS and the basin edge. In several examples, the river morphology changes upon reaching the sedimentary basin and across the DFS and this morphology may change once again at the toe of the DFS where the river takes the axial position in the basin. For example, the Brahamaputra River upstream from the sedimentary basin is a relatively narrow, single thread channel that is confined in its valley. Upon entering the sedimentary basin, the Brahmaputra River develops a DFS and becomes broadly braided in form. Distally on the DFS, the braided system bifurcates, leaving relatively large areas where floodplain deposits may be preserved. At the toe of the DFS, the Brahmaputra River becomes the axial system for this portion of the foreland basin. In this axial position, it is held between opposing DFS, thus the channel system migrates back and forth between these DFS and fills this portion of the basin with coarse-grained material. Other large rivers show similar change as they enter a continental sedimentary basin. In areal extent, DFS from smaller rivers occupy more of the modern continental sedimentary basins than the big rivers (either in axial or DFS position), therefore deposits of all rivers in sedimentary basins must be considered in order to fully interpret the rock record.

Weissmann, G. S.; Hartley, A. J.; Scuderi, L. A.; Nichols, G. J.; Davidson, S. K.

2010-12-01

262

Felyx : A Free Open Software Solution for the Analysis of Large Earth Observation Datasets  

NASA Astrophysics Data System (ADS)

GHRSST project, by assembling large collections of earth observation data from various sources and agencies, has also raised the need for providing the user community with tools to inter-compare them, assess and monitor their quality. The ESA /Medspiration project, which implemented the first operating node of GHRSST system for Europe, also paved the way successfully towards such generic analytics tools by developing the High Resolution Diagnostic Dataset System (HR-DDS) and Satellite to In situ Multi-sensor Match-up Databases. Building on this heritage, ESA is now funding the development by IFREMER, PML and Pelamis of felyx, a web tool merging the two capabilities into a single software solution. It will consist in a free open software solution, written in python and javascript, whose aim is to provide Earth Observation data producers and users with an open-source, flexible and reusable tool to allow the quality and performance of data streams (satellite, in situ and model) to be easily monitored and studied. The primary concept of Felyx is to work as an extraction tool, subsetting source data over predefined target areas (which can be static or moving) : these data subsets, and associated metrics, can then be accessed by users or client applications either as raw files, automatic alerts and reports generated periodically, or through a flexible web interface enabling statistical analysis and visualization. Felyx presents itself as an open-source suite of tools, written in python and javascript, enabling : * subsetting large local or remote collections of Earth Observation data over predefined sites (geographical boxes) or moving targets (ship, buoy, hurricane), storing locally the extracted data (refered as miniProds). These miniProds constitute a much smaller representative subset of the original collection on which one can perform any kind of processing or assessment without having to cope with heavy volumes of data. * computing statistical metrics over these miniProds using for instance a set of usual statistical operators (mean, median, rms, ...), fully extensible and applicable to any variable of a dataset. These metrics are stored in a fast search engine, queryable by humans and automated applications. * reporting or alerting, based on user-defined inference rules, through various media (emails, twitter feeds,..) and devices (phones, tablets). * analysing miniProds and metrics through a web interface allowing to dig into this base of information and extracting useful knowledge through multidimensional interactive display functions (time series, scatterplots, histograms, maps). The services provided by felyx will be generic, deployable at users own premises and adaptable enough to integrate any kind of parameters. Users will be able to operate their own felyx instance at any location, on datasets and parameters of their own interest, and the various instances will be able to interact with each other, creating a web of felyx systems enabling aggregation and cross comparison of miniProds and metrics from multiple sources. Initially two instances will be operated simultaneously during a 6 months demonstration phase, at IFREMER - on sea surface temperature (for GHRSST community) and ocean waves datasets - and PML - on ocean colour. We will present results from the Felyx project, demonstrate how the GHRSST community can exploit Felyx and demonstrate how the wider community can make use of the GHRSST data within Felyx.

Piolle, Jean-Francois; Shutler, Jamie; Poulter, David; Guidetti, Veronica; Donlon, Craig

2014-05-01

263

Polarization variablity among Wolf-Rayet stars. IV. A complete lack of circular polarization in the optical continuum  

SciTech Connect

Quasi-simultaneous blue and red, broadband optical monitoring in linear and circular polarization and in intensity has been carried out over an interval of three weeks for several Wolf-Rayet stars that show relatively large Delta P variations in linear polarization. No significant varying Delta V component of circular polarization is detected in any of these stars. The lower upper limit Delta V/Delta P implies that the intrinsic linearly polarized light which does vary cannot be produced by electrons gyrating in a magnetic field, unless they are ultrarelativistic - a rather unlikely situation. The low mean circular polarization typically observed is probably interstellar in origin. Lack of periodicity in the observed variations of linear polarization implies that even weak magnetic field loops are unlikely to be involved in confining pockets of wind plasma. The observed linear polarization variations are related mainly to electron scattering. 25 refs.

Robert, C.; Moffat, A.F.J. (Montreal Universite (Canada))

1989-08-01

264

Improved frequency characteristics of large Rogowski coil using lightning surges observation  

Microsoft Academic Search

A large Rogowski coil is applied to measure the lightning surge current of large objects such as telecommunications towers and building pillars. A large Rogowski coil was constructed with several short Rogowski coils to improve its frequency characteristics. The frequency characteristics were calculated using SPICE and measured. The calculated results agree closely with the measured results and indicate improved frequency

Jun Kato; T. Tominaga; N. Kuwabara

1999-01-01

265

Identification of the replication region of a 111-kb circular plasmid from Rhodococcus opacus B-4 by ? Red recombination-based deletion analysis.  

PubMed

The replication region of the 111-kb circular plasmid pKNR from Rhodococcus opacus B-4 was identified. A PCR-based deletion analysis using the ? Red recombination technique followed by restriction digestion and PCR-amplification analyses revealed that a 2.5-kb fragment covering one putative open reading frame (ORF) was involved in the replication of pKNR. The product of this ORF showed significant similarity to a functionally unknown protein encoded in the replication region of the 70-kb circular plasmid of Clavibacter michiganensis and to ones in other bacterial large circular plasmids. These observations suggest that the product of the identified ORF and its orthologs can serve as novel replication proteins for large circular bacterial plasmids. PMID:23006580

Honda, Kohsuke; Imura, Makoto; Okano, Kenji; Omasa, Takeshi; Kato, Junichi; Ohtake, Hisao

2012-01-01

266

Z-DNA Vacuum ultraviolet circular dichroism  

SciTech Connect

In concentrated salt or ethanolic solutions, the self-complementary copolymer poly(dG-dC).poly(dG-dC) forms a left-handed double-helical structure that has been termed ZDNA. The first evidence for this structure came from changes observed in the circular dichroism (CD) spectrum between 230 and 300 nm for low- and high-salt solutions (Pohl, F.M. and Jovin, T.M. (1972) J. Mol. Biol. 67, 675-696). In 3 M NaCl, the CD spectrum is approximately inverted compared to the B-form spectrum observed in low-salt solution. We measured the vacuum ultraviolet CD spectrum of poly(dG-dC).poly(dG-dC) down to 180 nm under conditions in which the 230 to 300 nm spectrum is inverted. Below 200 nm, where the B form exhibits the large positive peak at 187 nm that is characteristic of right-handed double-helical DNAs, the Z form exhibits a large negative peak at 194 nm and a positive band below 186 nm. Therefore, the Z-form vacuum ultraviolet CD spectrum resembles an inverted and red-shifted B-form spectrum. The magnitudes of the differences observed between the Band Z forms in the CD spectrum below 200 nm are about 10 times greater than those observed between 230 and 300 nm. The vacuum ultraviolet CD spectrum of poly(dG-dC).poly(dG-dC) in 3 M Cs/sub 2/SO/sub 4/ also is inverted compared to the B-form spectrum; however, between 230 and 300 nm, it is nonconservative with a negative maximum at 290 nm and a weak positive CD signal above 300 nm, presumably reflecting differential light scattering and indicating the existence of molecular aggregates. Our results suggest that the vacuum ultraviolet CD spectrum is sensitive to the handedness of double-helical DNA structures.

Sutherland, J.C.; Griffin, K.P.; Keck, P.C.; Takacs, P.Z.

1981-08-01

267

Z-DNA: vacuum ultraviolet circular dichroism  

SciTech Connect

In concentrated salt or ethanolic solutions, the self-complementary copolymer poly(dG-dC)-poly(dG-dC) forms a left-handed double-helical structure that has been termed Z-DNA. The first evidence for this structure came from changes observed in the circular dichroism (CD) spectrum between 230 and 300 nm for low- and high-salt solutions. In 3 M NaCl, the CD spectrum is approximately inverted compared to the B-form spectrum observed in low salt solution. We measured the vacuum ultraviolet CD spectrum of poly(dG-dC)-poly(dG-dC) down to 180 nm under conditions in which the 230- to 300-nm spectrum is inverted. Below 200 nm, where the B form exhibits the large positive peak at 187 nm that is characteristic of right-handed double-helical DNAs, the Z form exhibits a large negative peak at 194 nm and a positive band below 186 nm. Therefore, the Z-form vacuum ultraviolet CD spectrum resembles an inverted and red-shifted B-form spectrum. The magnitudes of the differences observed between the B and Z forms in the CD spectrum below 200 nm are about 10 times greater than those observed between 230 and 300 nm. The vacuum ultraviolet CD spectrum of poly(dG-dC)-poly(dG-dC) is 3 M C/sub 2/O/sub 4/ also is inverted compared to the B-form spectrum; however, between 230 and 300 nm, it is nonconservative with a negative maximum at 290 nm and a weak positive CD signal above 300 nm, presumably reflecting differential light scattering and indicating the existence of molecular aggregates. Our results suggest that the vacuum ultraviolet CD spectrum is sensitive to the handedness of doublehelical DNA structures.

Sutherland, J.C.; Griffin, K.P.; Keck, P.C.; Takacs, P.Z.

1981-08-01

268

Dynamics of sediment transport in large tropical tidal rivers via observations in the Mekong and Amazon  

NASA Astrophysics Data System (ADS)

Of the ten largest-discharge river systems worldwide, freshwater delivery to the ocean from tropical rivers comprises approximately 72% of the total. Tropical-river suspended-sediment loads make up about 45% of the total among the same ten largest rivers. In this context, flow and sediment dynamics of tropical river systems are crucial to a comprehensive understanding of global river budgets. The processes by which sediment is eroded, transported, trapped, and ultimately exported from tidal rivers--where tides propagate but oceanic salinity is absent or only ephemerally present--are poorly understood, even though previous research suggests up to one-third of riverine sediment loads may be trapped within tidal rivers. In an effort to better understand these processes, we present and contrast results from several campaigns along two large tropical tidal rivers: the Mekong and Amazon. Under conditions of high and low seasonal discharge, three cross-sections within the Mekong tidal river were each occupied for a 25-hour tidal cycle, during which ADCP and CTD transects were completed every 15-30 minutes. In this transitional environment between fluvial and estuarine conditions, flow reversed throughout the water column during both low and high flow at all locations, and a strongly sheared flow was present during lesser flood tides. Salinity was spatially variable over seasons: during low flow, salinity in excess of 10 PSU was observed 30 km upstream during maximum flood, while at the same location during high flow, salinity was less than 0.5 PSU at all times. Conditions were partially stratified during low flow. When present, stratification was in the form of a salt wedge during high flow. Suspended sediment was well mixed or exhibited a Rouse-like profile in fresh regions; suspended-sediment concentration within the salt wedge was generally less, except during periods of strong near-bottom flow within the salt-wedge water mass. During both seasons and at all locations, distinct, preferential pathways of water and sediment within the cross-sections were present through the tidal cycles, which may foster development of the rapidly prograding islands within the tidal river. Data collected from seasonal cruises along the geographically vast Amazon tidal river provide context for more spatially constrained studies on the Mekong tidal river and highlight the contrasts between these two large tropical river systems. Ongoing work in these two systems provides a basis for improved understanding of sediment-transport processes within the tidal reach and ultimate quantity, timing, and character of sediment delivered to the ocean.

Nowacki, D. J.; Ogston, A. S.; Nittrouer, C. A.; Fricke, A. T.; Van, P.; Souza Filho, P. W.; Silva, M. S.

2013-12-01

269

Observations and Large-Eddy Simulations of Wave-Induced Boundary-Layer Separation  

NASA Astrophysics Data System (ADS)

Wave-induced boundary-layer separation in flow over orography has received significant attention in recent years, especially in relation to the formation of atmospheric rotors. Traditionally depicted as horizontal eddies in the lee of mountain ranges, rotors are characterized by intense turbulence and pose a known threat to aviation. This study focuses on the first observationally documented case of wave-induced boundary-layer separation, which occurred on Jan 26 2006 in the lee of the Medicine Bow Mountains in SE Wyoming. Observations from the University of Wyoming King Air (UWKA) aircraft, in particular, the remote sensing measurements with the dual-Doppler Wyoming Cloud Radar (WCR), indicate strong wave activity, downslope winds in excess of 30 m s-1 within 200 m above the ground, and near-surface flow reversal in the lee of the mountain range. The fine resolution of WCR data (on the order of 40x40 m2 for two-dimensional velocity fields) reveals fine-scale coherent vortical structures which are embedded within the rotor zone and whose intensity contributes to the severity of turbulence therein. A series of semi-idealized three-dimensional large-eddy simulations of the Medicine Bow case was carried out using the CM1 model. Simulations represent the flow of an air mass with invariant profiles of wind speed and potential temperature over an isolated mountain ridge: the atmospheric soundings match the available observations and the ridge has the same size and shape as the Medicine Bow range. Model runs consider a simplified two-dimensional geometry where the complex topographic obstacle is represented as a smooth linear mountain ridge, but they are fully three-dimensional allowing for realistic turbulence dynamics. The simulated flow field is strikingly similar to the observed, with the simulations reproducing strong downslope flow detaching from the ground, with a patch of considerably lower wind intensities and embedded reverse flow further downstream. The near-surface rotor circulation is associated with an undular bore near the mountain top level that is triggered by breaking of a hydrostatic mountain wave aloft, at an altitude between 2000 and 5000 m. Once separated from the ground, the thin sheet of positive horizontal vorticity breaks down into several small vortices within the rotor region. Several phenomena of interest can be discerned in the simulated flow, including non-steadiness in the position of boundary-layer separation and shooting downslope flow, the latter associated with Kelvin-Helmholtz instability developing upstream of the obstacle along a stable shear layer above the mountain top height. A set of sensitivity experiments with increasing surface friction have been carried out to assess the impact of surface friction on the onset of BLS, through the deceleration of the surface flow and reduction of the wave amplitudes downstream of the obstacle.

Grubisic, V.; Serafin, S.; Strauss, L.

2011-12-01

270

Circular polarization memory in single Quantum Dots  

SciTech Connect

Under quasi-resonant circularly polarized optical excitation, charged quantum dots may emit polarized light. We measured various transitions with either positive, negative or no circular-polarization memory. We explain these observations and quantitatively calculate the polarization spectrum. Our model use the full configuration-interaction method, including the electron-hole exchange interaction, for calculating the quantum dot's confined many-carrier states, along with one assumption regarding the spin relaxation of photoexcited carriers: Electrons maintain their initial spin polarization, while holes do not.

Khatsevich, S.; Poem, E.; Benny, Y.; Marderfeld, I.; Gershoni, D. [Physics Department and Solid State Institute, Technion, Haifa 32000 (Israel); Badolato, A.; Petroff, P. M. [Materials Department, University of California Santa Barbara, Santa Barbara, California 93106 (United States)

2010-01-04

271

Helically corrugated circular waveguides as antenna feeders  

Microsoft Academic Search

Rotation of the plane of polarization of the TE(11)-mode is predicted and observed in a helically corrugated circular waveguide. Rotation is suppressed by a longitudinal deformation produced on the corrugation. This modified structure can be used as an antenna feeder with low losses.

F. Jecko; A. Papiernik

1983-01-01

272

Helically corrugated circular waveguides as antenna feeders  

NASA Astrophysics Data System (ADS)

Rotation of the plane of polarization of the TE(11)-mode is predicted and observed in a helically corrugated circular waveguide. Rotation is suppressed by a longitudinal deformation produced on the corrugation. This modified structure can be used as an antenna feeder with low losses.

Jecko, F.; Papiernik, A.

1983-07-01

273

Polarimetry of young stellar objects - III. Circular polarimetry of OMC-1  

Microsoft Academic Search

We present the first imaging circular polarimetry of the Orion Molecular Cloud, OMC-1. The observations, taken in the J, H, Kn and nbL bands, reveal a complex pattern of circular polarization. Globally, there is a background circular polarization of the order of +\\/-2per cent in the Kn band, conforming to the typical quadrupolar patterns that have been observed in other

Antonio Chrysostomou; T. M. Gledhill; François Ménard; J. H. Hough; Motohide Tamura; Jeremy Bailey

2000-01-01

274

FERMI LARGE AREA TELESCOPE OBSERVATIONS OF THE CRAB PULSAR AND NEBULA  

SciTech Connect

We report on gamma-ray observations of the Crab Pulsar and Nebula using 8 months of survey data with the Fermi Large Area Telescope (LAT). The high quality light curve obtained using the ephemeris provided by the Nancay and Jodrell Bank radio telescopes shows two main peaks stable in phase with energy. The first gamma-ray peak leads the radio main pulse by (281 +- 12 +- 21) mus, giving new constraints on the production site of non-thermal emission in pulsar magnetospheres. The first uncertainty is due to gamma-ray statistics, and the second arises from the rotation parameters. The improved sensitivity and the unprecedented statistics afforded by the LAT enable precise measurement of the Crab Pulsar spectral parameters: cut-off energy at E{sub c} = (5.8 +- 0.5 +- 1.2) GeV, spectral index of GAMMA = (1.97 +- 0.02 +- 0.06) and integral photon flux above 100 MeV of (2.09 +- 0.03 +- 0.18) x 10{sup -6} cm{sup -2} s{sup -1}. The first errors represent the statistical error on the fit parameters, while the second ones are the systematic uncertainties. Pulsed gamma-ray photons are observed up to approx 20 GeV which precludes emission near the stellar surface, below altitudes of around 4-5 stellar radii in phase intervals encompassing the two main peaks. A detailed phase-resolved spectral analysis is also performed: the hardest emission from the Crab Pulsar comes from the bridge region between the two gamma-ray peaks while the softest comes from the falling edge of the second peak. The spectrum of the nebula in the energy range 100 MeV-300 GeV is well described by the sum of two power laws of indices GAMMA{sub sync} = (3.99 +- 0.12 +- 0.08) and GAMMA{sub IC} = (1.64 +- 0.05 +- 0.07), corresponding to the falling edge of the synchrotron and the rising edge of the inverse Compton (IC) components, respectively. This latter, which links up naturally with the spectral data points of Cherenkov experiments, is well reproduced via IC scattering from standard magnetohydrodynamic nebula models, and does not require any additional radiation mechanism.

Abdo, A. A. [Space Science Division, Naval Research Laboratory, Washington, DC 20375 (United States); Ackermann, M.; Ajello, M.; Bechtol, K.; Berenji, B.; Blandford, R. D.; Bloom, E. D.; Borgland, A. W. [W. W. Hansen Experimental Physics Laboratory, Kavli Institute for Particle Astrophysics and Cosmology, Department of Physics and SLAC National Accelerator Laboratory, Stanford University, Stanford, CA 94305 (United States); Atwood, W. B. [Santa Cruz Institute for Particle Physics, Department of Physics and Department of Astronomy and Astrophysics, University of California at Santa Cruz, Santa Cruz, CA 95064 (United States); Axelsson, M. [Department of Astronomy, Stockholm University, SE-106 91 Stockholm (Sweden); Baldini, L.; Bellazzini, R.; Bregeon, J.; Brez, A. [Istituto Nazionale di Fisica Nucleare, Sezione di Pisa, I-56127 Pisa (Italy); Ballet, J. [Laboratoire AIM, CEA-IRFU/CNRS/Universite Paris Diderot, Service d'Astrophysique, CEA Saclay, 91191 Gif sur Yvette (France); Barbiellini, G. [Istituto Nazionale di Fisica Nucleare, Sezione di Trieste, I-34127 Trieste (Italy); Baring, M. G. [Department of Physics and Astronomy, Rice University, MS-108, P.O. Box 1892, Houston, TX 77251 (United States); Bastieri, D. [Istituto Nazionale di Fisica Nucleare, Sezione di Padova, I-35131 Padova (Italy); Bonamente, E. [Istituto Nazionale di Fisica Nucleare, Sezione di Perugia, I-06123 Perugia (Italy); Brigida, M., E-mail: loparco@ba.infn.i, E-mail: mazziotta@ba.infn.i, E-mail: grondin@cenbg.in2p3.f, E-mail: lemoine@cenbg.in2p3.f [Dipartimento di Fisica 'M. Merlin' dell'Universita e del Politecnico di Bari, I-70126 Bari (Italy)

2010-01-10

275

Effects of large-scale moisture transport and mesoscale processes on precipitation isotope ratios observed at Sumatera, Indonesia  

Microsoft Academic Search

Isotopic and meteorological observations in November 2006 on the west coast of Sumatera, Indonesia during the intense observation period of the Hydrometeorological ARray for Intraseasonal Variation-Monsoon AUtomonitoring (HARIMAU2006), revealed the impacts of large-scale moisture transport and mesoscale processes on precipitation isotope ratios. Intraseasonal changes in the precipitation d2H in November had large variability ranging from þ10 to 65 per mil,

Hironori Fudeyasu; Kimpei Ichiyanagi; Kei Yoshimura; Shuichi Mori; Hamada Jun-Ichi; Namiko SAKURAI; Manabu D. Yamanaka; Jun Matsumoto; Fadli Syamsudin

2011-01-01

276

Fermi large area telescope observations of the cosmic-ray induced gamma-ray emission of the Earth's atmosphere  

Microsoft Academic Search

We report on measurements of the cosmic-ray induced gamma-ray emission of Earth's atmosphere by the Large Area Telescope on board the Fermi Gamma-ray Space Telescope. The Large Area Telescope has observed the Earth during its commissioning phase and with a dedicated Earth limb following observation in September 2008. These measurements yielded ˜6.4×106 photons with energies >100MeV and ˜250 hours total

A. A. Abdo; M. Ackermann; M. Ajello; W. B. Atwood; L. Baldini; J. Ballet; G. Barbiellini; D. Bastieri; B. M. Baughman; K. Bechtol; R. Bellazzini; B. Berenji; E. D. Bloom; E. Bonamente; A. W. Borgland; A. Bouvier; J. Bregeon; A. Brez; M. Brigida; P. Bruel; R. Buehler; T. H. Burnett; S. Buson; G. A. Caliandro; R. A. Cameron; P. A. Caraveo; J. M. Casandjian; C. Cecchi; Ö. Çelik; E. Charles; A. Chekhtman; J. Chiang; S. Ciprini; R. Claus; J. Cohen-Tanugi; J. Conrad; F. de Palma; S. W. Digel; E. Do Couto E Silva; P. S. Drell; R. Dubois; D. Dumora; C. Farnier; C. Favuzzi; S. J. Fegan; W. B. Focke; P. Fortin; M. Frailis; Y. Fukazawa; S. Funk; P. Fusco; F. Gargano; N. Gehrels; S. Germani; B. Giebels; N. Giglietto; F. Giordano; T. Glanzman; G. Godfrey; I. A. Grenier; M.-H. Grondin; J. E. Grove; L. Guillemot; S. Guiriec; E. Hays; D. Horan; R. E. Hughes; G. Jóhannesson; A. S. Johnson; T. J. Johnson; W. N. Johnson; T. Kamae; H. Katagiri; J. Kataoka; N. Kawai; M. Kerr; J. Knödlseder; M. Kuss; J. Lande; L. Latronico; M. Lemoine-Goumard; F. Longo; F. Loparco; B. Lott; M. N. Lovellette; P. Lubrano; A. Makeev; M. N. Mazziotta; J. E. McEnery; C. Meurer; P. F. Michelson; W. Mitthumsiri; T. Mizuno; C. Monte; M. E. Monzani; A. Morselli; I. V. Moskalenko; S. Murgia; P. L. Nolan; J. P. Norris; E. Nuss; T. Ohsugi; A. Okumura; N. Omodei; E. Orlando; J. F. Ormes; D. Paneque; J. H. Panetta; D. Parent; V. Pelassa; M. Pepe; M. Pesce-Rollins; F. Piron; T. A. Porter; S. Rainò; R. Rando; M. Razzano; A. Reimer; O. Reimer; T. Reposeur; L. S. Rochester; A. Y. Rodriguez; M. Roth; H. F.-W. Sadrozinski; A. Sander; P. M. Saz Parkinson; C. Sgrò; G. H. Share; E. J. Siskind; D. A. Smith; P. D. Smith; G. Spandre; P. Spinelli; M. S. Strickman; D. J. Suson; H. Takahashi; T. Tanaka; J. B. Thayer; J. G. Thayer; D. J. Thompson; L. Tibaldo; D. F. Torres; G. Tosti; A. Tramacere; Y. Uchiyama; T. L. Usher; V. Vasileiou; N. Vilchez; V. Vitale; A. P. Waite; P. Wang; B. L. Winer; K. S. Wood; T. Ylinen; M. Ziegler

2009-01-01

277

Gamma-Ray Observations of the Orion Molecular Clouds with the Fermi Large Area Telescope  

NASA Technical Reports Server (NTRS)

We report on the gamma-ray observations of giant molecular clouds Orion A and B with the Large Area Telescope (LAT) on board the Fermi Gamma-ray Space Telescope. The gamma-ray emission in the energy band between approx 100 MeV and approx 100 GeV is predicted to trace the gas mass distribution in the clouds through nuclear interactions between the Galactic cosmic rays (CRs) and interstellar gas. The gamma-ray production cross-section for the nuclear interaction is known to approx 10% precision which makes the LAT a powerful tool to measure the gas mass column density distribution of molecular clouds for a known CR intensity. We present here such distributions for Orion A and B, and correlate them with those of the velocity-integrated CO intensity (W(sub CO)) at a 1 deg 1 deg pixel level. The correlation is found to be linear over a W(sub CO) range of approx 10-fold when divided in three regions, suggesting penetration of nuclear CRs to most of the cloud volumes. The W(sub CO)-to-mass conversion factor, X(sub CO), is found to be approx 2.3 10(exp 20) / sq cm (K km/s)(exp -1) for the high-longitude part of Orion A (l > 212 deg), approx 1.7 times higher than approx 1.3 10(exp 20) found for the rest of Orion A and B. We interpret the apparent high X(sub CO) in the high-longitude region of Orion A in the light of recent works proposing a nonlinear relation between H2 and CO densities in the diffuse molecular gas.W(sub CO) decreases faster than the H2 column density in the region making the gas "darker" to W(sub CO).

Ackermann, M.; Ajello, M.; Allafort, A.; Antolini, E.; Baldini, L.; Ballet, J.; Barbiellini, G.; Bastieri, D.; Bechtol, K.; Bellazzini, R.; Berenji, B.; Blandford, R. D.; Bloom, E. D.; Bonamente, E.; Borgland, A. W.; Bottacini, E.; Brandt, T. J.; Bregeon, J.; Brigida, M.; Bruel, P.; Buehler, R.; Buson, S.; Ferrara, E. C.; Harding, A. K.; Troja, E.

2012-01-01

278

Fermi Large Area Telescope observations of the supernova remnant HESS J1731-347  

NASA Astrophysics Data System (ADS)

Context. HESS J1731-347 has been identified as one of the few TeV-bright shell-type supernova remnants (SNRs). These remnants are dominated by nonthermal emission, and the nature of TeV emission has been continuously debated for nearly a decade. Aims: We carry out the detailed modeling of the radio to ?-ray spectrum of HESS J1731-347 to constrain the magnetic field and energetic particles sources, which we compare with those of the other TeV-bright shell-type SNRs explored before. Methods: Four years of data from Fermi Large Area Telescope (LAT) observations for regions around this remnant are analyzed, leading to no detection correlated with the source discovered in the TeV band. The Markov chain Monte Carlo method is used to constrain parameters of one-zone models for the overall emission spectrum. Results: Based on the 99.9% upper limits of fluxes in the GeV range, one-zone hadronic models with an energetic proton spectral slope greater than 1.8 can be ruled out, which favors a leptonic origin for the ?-ray emission, making this remnant a sibling of the brightest TeV SNR RX J1713.7-3946, the Vela Junior SNR RX J0852.0-4622, and RCW 86. The best-fit leptonic model has an electron spectral slope of 1.8 and a magnetic field of ~30 ?G, which is at least a factor of 2 higher than those of RX J1713.7-3946 and RX J0852.0-4622, posing a challenge to the distance estimate and/or the energy equipartition between energetic electrons and the magnetic field of this source. A measurement of the shock speed will address this challenge and has implications on the magnetic field evolution and electron acceleration driven by shocks of SNRs.

Yang, Rui-zhi; Zhang, Xiao; Yuan, Qiang; Liu, Siming

2014-07-01

279

Are large Trojan asteroids salty? An observational, theoretical, and experimental study  

NASA Astrophysics Data System (ADS)

With a total mass similar to the main asteroid belt, the jovian Trojan asteroids are a major feature in the Solar System. Based upon the thermal infrared spectra of the largest Trojans obtained with the Spitzer space telescope, Emery et al. (Emery, J.P., Cruikshank, D.P., van Cleve, J. [2006]. Icarus 182, 496) suggested that the surfaces of these Trojans may consist of fine-grained silicates suspended in a transparent matrix. To explore the transparent matrix hypothesis, we adopted a modified radiative transfer model to fit the Trojan spectra simultaneously both in the near and the thermal infrared regions. Our model shows that the Trojan spectra over a wide wavelength range can be consistently explained by fine grained silicates (1-5 wt.%) and highly absorbing material (e.g. carbon or iron, 2-10 wt.%) suspended in a transparent matrix. The matrix is consistent with a deposit of salt on the surfaces of the large Trojans. However, this consistency is not an actual detection of salt and other alternatives may still be possible. We suggest that early in the Solar System history, short-lived radionuclides heated ice-rich Trojans and caused melting, internal circulation of water and dissolution of soluble materials. Briny water volcanism were facilitated by internal volatiles and a possibly global sill of frozen brine was formed beneath the cold primitive crust. The frozen brine layer was likely to be evacuated by impact erosions and evaporation of the exposed brines eventually left a lag deposit of salt. Over the Solar System's history, fine dust from comets or impacts contaminated and colored these salty surfaces of the Trojans to produce the spectral properties observed today.

Yang, Bin; Lucey, Paul; Glotch, Timothy

2013-03-01

280

Gamma-Ray Observations of the Orion Molecular Clouds with the Fermi Large Area Telescope  

NASA Astrophysics Data System (ADS)

We report on the gamma-ray observations of giant molecular clouds Orion A and B with the Large Area Telescope (LAT) on board the Fermi Gamma-ray Space Telescope. The gamma-ray emission in the energy band between ~100 MeV and ~100 GeV is predicted to trace the gas mass distribution in the clouds through nuclear interactions between the Galactic cosmic rays (CRs) and interstellar gas. The gamma-ray production cross-section for the nuclear interaction is known to ~10% precision which makes the LAT a powerful tool to measure the gas mass column density distribution of molecular clouds for a known CR intensity. We present here such distributions for Orion A and B, and correlate them with those of the velocity-integrated CO intensity (W CO) at a 1° × 1° pixel level. The correlation is found to be linear over a W CO range of ~10-fold when divided in three regions, suggesting penetration of nuclear CRs to most of the cloud volumes. The W CO-to-mass conversion factor, X CO, is found to be ~2.3 × 1020 cm-2(K km s-1)-1 for the high-longitude part of Orion A (l > 212°), ~1.7 times higher than ~1.3 × 1020 found for the rest of Orion A and B. We interpret the apparent high X CO in the high-longitude region of Orion A in the light of recent works proposing a nonlinear relation between H2 and CO densities in the diffuse molecular gas. W CO decreases faster than the H2 column density in the region making the gas "darker" to W CO.

Ackermann, M.; Ajello, M.; Allafort, A.; Antolini, E.; Baldini, L.; Ballet, J.; Barbiellini, G.; Bastieri, D.; Bechtol, K.; Bellazzini, R.; Berenji, B.; Blandford, R. D.; Bloom, E. D.; Bonamente, E.; Borgland, A. W.; Bottacini, E.; Brandt, T. J.; Bregeon, J.; Brigida, M.; Bruel, P.; Buehler, R.; Buson, S.; Caliandro, G. A.; Cameron, R. A.; Caraveo, P. A.; Cecchi, C.; Chekhtman, A.; Chiang, J.; Ciprini, S.; Claus, R.; Cohen-Tanugi, J.; Conrad, J.; D'Ammando, F.; de Angelis, A.; de Palma, F.; Dermer, C. D.; Silva, E. do Couto e.; Drell, P. S.; Drlica-Wagner, A.; Enoto, T.; Falletti, L.; Favuzzi, C.; Fegan, S. J.; Ferrara, E. C.; Focke, W. B.; Fukazawa, Y.; Fukui, Y.; Fusco, P.; Gargano, F.; Gasparrini, D.; Germani, S.; Giglietto, N.; Giordano, F.; Giroletti, M.; Glanzman, T.; Godfrey, G.; Guiriec, S.; Hadasch, D.; Hanabata, Y.; Harding, A. K.; Hayashida, M.; Hayashi, K.; Horan, D.; Hou, X.; Hughes, R. E.; Jackson, M. S.; Jóhannesson, G.; Johnson, A. S.; Kamae, T.; Katagiri, H.; Kataoka, J.; Kerr, M.; Knödlseder, J.; Kuss, M.; Lande, J.; Larsson, S.; Lee, S.-H.; Longo, F.; Loparco, F.; Lovellette, M. N.; Lubrano, P.; Makishima, K.; Mazziotta, M. N.; Mehault, J.; Mitthumsiri, W.; Moiseev, A. A.; Monte, C.; Monzani, M. E.; Morselli, A.; Moskalenko, I. V.; Murgia, S.; Nakamori, T.; Naumann-Godo, M.; Nishino, S.; Norris, J. P.; Nuss, E.; Ohno, M.; Ohsugi, T.; Okumura, A.; Orienti, M.; Orlando, E.; Ormes, J. F.; Ozaki, M.; Paneque, D.; Panetta, J. H.; Parent, D.; Pelassa, V.; Pesce-Rollins, M.; Pierbattista, M.; Piron, F.; Pivato, G.; Porter, T. A.; Rainò, S.; Razzano, M.; Reimer, A.; Reimer, O.; Roth, M.; Sadrozinski, H. F.-W.; Sgrò, C.; Siskind, E. J.; Spandre, G.; Spinelli, P.; Strong, A. W.; Takahashi, H.; Takahashi, T.; Tanaka, T.; Thayer, J. G.; Thayer, J. B.; Tibolla, O.; Tinivella, M.; Torres, D. F.; Tramacere, A.; Troja, E.; Uchiyama, Y.; Usher, T. L.; Vandenbroucke, J.; Vasileiou, V.; Vianello, G.; Vitale, V.; Waite, A. P.; Wang, P.; Winer, B. L.; Wood, K. S.; Yang, Z.; Zimmer, S.

2012-09-01

281

Multiple self-controlled case series for large-scale longitudinal observational databases.  

PubMed

Characterization of relationships between time-varying drug exposures and adverse events (AEs) related to health outcomes represents the primary objective in postmarketing drug safety surveillance. Such surveillance increasingly utilizes large-scale longitudinal observational databases (LODs), containing time-stamped patient-level medical information including periods of drug exposure and dates of diagnoses for millions of patients. Statistical methods for LODs must confront computational challenges related to the scale of the data, and must also address confounding and other biases that can undermine efforts to estimate effect sizes. Methods that compare on-drug with off-drug periods within patient offer specific advantages over between patient analysis on both counts. To accomplish these aims, we extend the self-controlled case series (SCCS) for LODs. SCCS implicitly controls for fixed multiplicative baseline covariates since each individual acts as their own control. In addition, only exposed cases are required for the analysis, which is computationally advantageous. The standard SCCS approach is usually used to assess single drugs and therefore estimates marginal associations between individual drugs and particular AEs. Such analyses ignore confounding drugs and interactions and have the potential to give misleading results. In order to avoid these difficulties, we propose a regularized multiple SCCS approach that incorporates potentially thousands or more of time-varying confounders such as other drugs. The approach successfully handles the high dimensionality and can provide a sparse solution via an L? regularizer. We present details of the model and the associated optimization procedure, as well as results of empirical investigations. PMID:24117144

Simpson, Shawn E; Madigan, David; Zorych, Ivan; Schuemie, Martijn J; Ryan, Patrick B; Suchard, Marc A

2013-12-01

282

Very Large Array Observations of Ammonia in High-mass Star Formation Regions  

NASA Astrophysics Data System (ADS)

We report systematic mapping observations of the NH3 (1, 1) and (2, 2) inversion lines toward 62 high-mass star-forming regions using the Very Large Array (VLA) in its D and DnC array configurations. The VLA images cover a spatial dynamic range from 40'' to 3'', allowing us to trace gas kinematics from ~1 pc scales to lsim0.1 pc scales. Based on the NH3 morphology and the infrared nebulosity on 1 pc scales, we categorize three subclasses in the sample: filaments, hot cores, and NH3-dispersed sources. The ubiquitous gas filaments found on 1 pc scales have a typical width of ~0.1 pc and often contain regularly spaced fragments along the major axis. The spacing of the fragments and the column densities is consistent with the turbulent supported fragmentation of cylinders. Several sources show multiple filaments that converge toward a center where the velocity field in the filaments is consistent with gas flows. We derive rotational temperature maps for the entire sample. For the three hot core sources, we find a projected radial temperature distribution that is best fit by power-law indices from –0.18 to –0.35. We identify 174 velocity-coherent ~0.1 pc scale dense cores from the entire sample. The mean physical properties for these cores are 1.1 km s–1 in intrinsic linewidth, 18 K in NH3 rotational temperature, 2.3 × 1015 cm–2 in NH3 gas column density, and 67 M ? in molecular mass. The dense cores identified from the filamentary sources are closer to being virialized. Dense cores in the other two categories of sources appear to be dynamically unstable.

Lu, Xing; Zhang, Qizhou; Liu, Hauyu Baobab; Wang, Junzhi; Gu, Qiusheng

2014-08-01

283

Large-scale stable interacting dark energy model: Cosmological perturbations and observational constraints  

NASA Astrophysics Data System (ADS)

Dark energy might interact with cold dark matter in a direct, nongravitational way. However, the usual interacting dark energy models (with constant w) suffer from some catastrophic difficulties. For example, the Q ??c model leads to an early-time large-scale instability, and the Q ??de model gives rise to the future unphysical result for cold dark matter density (in the case of a positive coupling). In order to overcome these fatal flaws, we propose in this paper an interacting dark energy model (with constant w) in which the interaction term is carefully designed to realize that Q ??de at the early times and Q ??c in the future, simultaneously solving the early-time superhorizon instability and future unphysical ?c problems. The concrete form of the interaction term in this model is Q=3?H?de?c/?de+?c, where ? is the dimensionless coupling constant. We show that this model is actually equivalent to the decomposed new generalized Chaplygin gas (NGCG) model, with the relation ?=-?w. We calculate the cosmological perturbations in this model in a gauge-invariant way and show that the cosmological perturbations are stable during the whole expansion history provided that ?>0. Furthermore, we use the Planck data in conjunction with other astrophysical data to place stringent constraints on this model (with eight parameters), and we find that indeed ?>0 is supported by the joint constraint at more than 1? level. The excellent theoretical features and the support from observations all indicate that the decomposed NGCG model deserves more attention and further investigation.

Li, Yun-He; Zhang, Xin

2014-04-01

284

DEEP AUSTRALIA TELESCOPE LARGE AREA SURVEY RADIO OBSERVATIONS OF THE EUROPEAN LARGE AREA ISO SURVEY S1/SPITZER WIDE-AREA INFRARED EXTRAGALACTIC FIELD  

SciTech Connect

We have conducted sensitive (1 {sigma} < 30 {mu}Jy) 1.4 GHz radio observations with the Australia Telescope Compact Array of a field largely coincident with infrared observations of the Spitzer Wide-Area Extragalactic Survey. The field is centered on the European Large Area ISO Survey S1 region and has a total area of 3.9 deg. We describe the observations and calibration, source extraction, and cross-matching to infrared sources. Two catalogs are presented: one of the radio components found in the image and another of radio sources with counterparts in the infrared and extracted from the literature. 1366 radio components were grouped into 1276 sources, 1183 of which were matched to infrared sources. We discover 31 radio sources with no infrared counterpart at all, adding to the class of Infrared-Faint Radio Sources.

Middelberg, Enno [Astronomisches Institut der Universitaet Bochum, Universitaetsstr. 150, 44801 Bochum (Germany); Norris, Ray P.; Cornwell, Tim J.; Voronkov, Maxim A.; Boyle, Brian J.; Jackson, Carole A. [Australia Telescope National Facility, PO Box 76, Epping NSW 1710 (Australia); Siana, Brian D.; Huynh, Minh T. [Spitzer Science Center, California Institute of Technology, MS 220-6, Pasadena, CA 91125 (United States); Ciliegi, Paolo [INAF, Osservatorio Astronomico di Bologna, Via Ranzani 1, I-40127 Bologna (Italy); Berta, Stefano; Rubele, Stefano [Max-Planck-Institut fuer extraterrestrische Physik, Giessenbachstrasse, 85748 Garching (Germany); Lonsdale, Carol J. [Center for Astrophysics and Space Sciences, University of California at San Diego, 9500 Gilman Drive, La Jolla, CA 92093-0424 (United States); Ivison, Rob J. [UK Astronomy Technology Centre, Royal Observatory, Blackford Hill, Edinburgh EH9 3HJ (United Kingdom); Smail, Ian [Institute for Computational Cosmology, Durham University, South Road, Durham DH1 3LE (United Kingdom)], E-mail: middelberg@astro.rub.de

2008-04-15

285

Observations of the Earth's polar cleft at large radial distances with the Hawkeye 1 magnetometer  

Microsoft Academic Search

Based on 364-spacecraft passes through the dayside region, the position of the polar cleft at large redial distances was determined with the magnetometer flown on Hawkeye 1. This data set represents one of the largest to investigate the high-latitude region at large radial distances, making it ideal for the study of the cusp and cleft region. Identification of the cleft

W. M. Farrell; J. A. Van Allen

1990-01-01

286

VERY LARGE ARRAY OBSERVATIONS OF THE INFRARED DARK CLOUD G19.30+0.07  

SciTech Connect

We present Very Large Array observations of ammonia (NH{sub 3}) (1,1), (2,2), and dicarbon sulfide (CCS) (2{sub 1}-1{sub 0}) emission toward the infrared dark cloud (IRDC) G19.30+0.07 at {approx}22 GHz. The NH{sub 3} emission closely follows the 8 {mu}m extinction. The NH{sub 3} (1,1) and (2,2) lines provide diagnostics of the temperature and density structure within the IRDC, with typical rotation temperatures of {approx}10-20 K and NH{sub 3} column densities of {approx}10{sup 15} cm{sup -2}. The estimated total mass of G19.30+0.07 is {approx}1130 M{sub sun}. The cloud comprises four compact NH{sub 3} clumps of mass {approx}30-160 M{sub sun}. Two coincide with 24 {mu}m emission, indicating heating by protostars, and show evidence of outflow in the NH{sub 3} emission. We report a water maser associated with a third clump; the fourth clump is apparently starless. A non-detection of 8.4 GHz emission suggests that the IRDC contains no bright H II regions and places a limit on the spectral type of an embedded zero-age main-sequence star to early-B or later. From the NH{sub 3} emission, we find that G19.30+0.07 is composed of three distinct velocity components or 'subclouds'. One velocity component contains the two 24 {mu}m sources and the starless clump, another contains the clump with the water maser, while the third velocity component is diffuse, with no significant high-density peaks. The spatial distribution of NH{sub 3} and CCS emission from G19.30+0.07 is highly anti-correlated, with the NH{sub 3} predominantly in the high-density clumps and the CCS tracing lower-density envelopes around those clumps. This spatial distribution is consistent with theories of evolution for chemically young low-mass cores, in which CCS has not yet been processed to other species and/or depleted in high-density regions.

Devine, K. E.; Churchwell, E. [Department of Astronomy, University of Wisconsin, 475 N. Charter Street, Madison, WI 53703 (United States); Chandler, C. J.; Borg, K. J. [National Radio Astronomy Observatory, P.O. Box O, Socorro, NM 87801 (United States); Brogan, C.; Indebetouw, R. [National Radio Astronomy Observatory, 520 Edgemont Road, Charlottesville, VA 22903 (United States); Shirley, Y., E-mail: kdevine@collegeofidaho.edu [Steward Observatory, University of Arizona, 933 N. Cherry Ave., Tucson, AZ 85721 (United States)

2011-05-20

287

Large scale IRAM 30 m CO-observations in the giant molecular cloud complex W43  

NASA Astrophysics Data System (ADS)

We aim to fully describe the distribution and location of dense molecular clouds in the giant molecular cloud complex W43. It was previously identified as one of the most massive star-forming regions in our Galaxy. To trace the moderately dense molecular clouds in the W43 region, we initiated W43-HERO, a large program using the IRAM 30 m telescope, which covers a wide dynamic range of scales from 0.3 to 140 pc. We obtained on-the-fly-maps in 13CO (2-1) and C18O (2-1) with a high spectral resolution of 0.1 km s-1 and a spatial resolution of 12''. These maps cover an area of ~1.5 square degrees and include the two main clouds of W43 and the lower density gas surrounding them. A comparison to Galactic models and previous distance calculations confirms the location of W43 near the tangential point of the Scutum arm at approximately 6 kpc from the Sun. The resulting intensity cubes of the observed region are separated into subcubes, which are centered on single clouds and then analyzed in detail. The optical depth, excitation temperature, and H2 column density maps are derived out of the 13CO and C18O data. These results are then compared to those derived from Herschel dust maps. The mass of a typical cloud is several 104 M? while the total mass in the dense molecular gas (>102 cm-3) in W43 is found to be ~1.9 × 106 M?. Probability distribution functions obtained from column density maps derived from molecular line data and Herschel imaging show a log-normal distribution for low column densities and a power-law tail for high densities. A flatter slope for the molecular line data probability distribution function may imply that those selectively show the gravitationally collapsing gas. Appendices are available in electronic form at http://www.aanda.orgThe final datacubes (13CO and C18O) for the entire survey are only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/560/A24

Carlhoff, P.; Nguyen Luong, Q.; Schilke, P.; Motte, F.; Schneider, N.; Beuther, H.; Bontemps, S.; Heitsch, F.; Hill, T.; Kramer, C.; Ossenkopf, V.; Schuller, F.; Simon, R.; Wyrowski, F.

2013-12-01

288

Class IIc or Circular Bacteriocins  

Microsoft Academic Search

\\u000a The circular bacteriocins produced by Gram-positive bacteria represent a diverse class of antimicrobial peptides. These bacteriocins\\u000a display enhanced stability compared to linear bacteriocins, which arises from their characteristic circular backbone. Currently,\\u000a eight unique circular bacteriocins have been identified, and analysis of their gene clusters indicates that they likely utilize\\u000a complex mechanisms for maturation and secretion, as well as for immunity.

Leah A. Martin-Visscher; Marco J. van Belkum; John C. Vederas

289

Circular Dichroism in Biological Photonic Crystals and Cubic Chiral Nets  

NASA Astrophysics Data System (ADS)

Nature provides impressive examples of chiral photonic crystals, with the notable example of the cubic so-called srs network (the label for the chiral degree-three network modeled on SrSi2) or gyroid structure realized in wing scales of several butterfly species. By a circular polarization analysis of the band structure of such networks, we demonstrate strong circular dichroism effects: The butterfly srs microstructure, of cubic I4132 symmetry, shows significant circular dichroism for blue to ultraviolet light, that warrants a search for biological receptors sensitive to circular polarization. A derived synthetic structure based on four like-handed silicon srs nets exhibits a large circular polarization stop band of a width exceeding 30%. These findings offer design principles for chiral photonic devices.

Saba, M.; Thiel, M.; Turner, M. D.; Hyde, S. T.; Gu, M.; Grosse-Brauckmann, K.; Neshev, D. N.; Mecke, K.; Schröder-Turk, G. E.

2011-03-01

290

Direct observational evidence for a heliospheric magnetic field with large excursions in latitude  

Microsoft Academic Search

Fisk has pointed out that the heliospheric magnetic field in fast solar wind, that is, at the higher heliographic latitudes, may undergo large excursions in heliographic latitudes, and thus that the field will deviate from the expected Archimedes spiral pattern. These excursions result from the interplay between the nonradial expansion of the solar wind in rigidly rotating coronal holes, and

T. H. Zurbuchen; N. A. Schwadron; L. A. Fisk

1997-01-01

291

Tempo and mode of modern bird evolution observed with large-scale taxonomic sampling  

Microsoft Academic Search

Macroevolutionists continue to disagree about the evolutionary history of birds. Their debate centers on the apparent discrepancy between molecular- and fossil-derived times of certain events. In this study we will show that there is much more agreement than discrepancy. We do it by simultaneously using both molecules (DNA hybridization and DNA sequence) and fossils to study a large set of

M. van Tuinen; T. A. Stidham; E. A. Hadly

2006-01-01

292

Survey of large branchiopods on Aruba and observations on taxonomic characters in Leptestheria (Spinicaudata)  

Microsoft Academic Search

A survey of more than 60 ephemeral pools during March 1989 resulted in finding three large branchiopods not previously known to occur on the Caribbean Island of Aruba. These were two Anostraca, Dendrocephalus spartaenovae Margalef, 1967 and Thamnocephalus venezuelensis Belk & Pereira, 1982, and one Spinicaudata, Leptestheria venezuelica Daday, 1923. The notostracan previously reported from Aruba, Triops longicaudatus (LeConte, 1846),

Denton Belk; Mary Schug Belk; K. A. L. Reading

2002-01-01

293

Simultaneous meteor echo observations by large-aperture VHF and UHF radars  

Microsoft Academic Search

We report simultaneous meteor echo observations using the Arecibo 430- MHz and 46.8-MHz radars. Using identical data-taking and meteor selection criteria, 1868 and 367 meteors were found in the 430-MHz and 46.8-MHz beams, respectively, while 145 were found in both beams during the 7 hours of observation. Of the 367 VHF echoes, there were only 10 trail echoes, while the

Q. H. Zhou; P. Perillat; J. Y. N. Cho; J. D. Mathews

1998-01-01

294

Observations and Implications of the Star Formation History of the Large Magellanic Cloud  

Microsoft Academic Search

We present derivations of star formation histories based on color-magnitude diagrams of three fields in the LMC from HST\\/WFPC2 observations. One field is located in the LMC bar and the other two are in the outer disk. We find that a significant component of stars older than 4 Gyr is required to match the observed color-magnitude diagrams. Models with a

Jon A. Holtzman; John S. Gallagher III; Andrew A. Cole; Jeremy R. Mould; Carl J. Grillmair; Gilda E. Ballester; Christopher J. Burrows; John T. Clarke; David Crisp; Robin W. Evans; Richard E. Griffiths; J. Jeff Hester; John G. Hoessel; Paul A. Scowen; Karl R. Stapelfeldt; John T. Trauger; Alan M. Watson

1999-01-01

295

Large Amplitude Whistler Waves and Electron Acceleration in the Earth's Radiation Belts: A Review of STEREO and Wind Observations  

NASA Technical Reports Server (NTRS)

One of the critical problems for understanding the dynamics of Earth's radiation belts is determining the physical processes that energize and scatter relativistic electrons. We review measurements from the Wind/Waves and STEREO S/Waves waveform capture instruments of large amplitude whistler-mode waves. These observations have provided strong evidence that large amplitude (100s mV/m) whistler-mode waves are common during magnetically active periods. The large amplitude whistlers have characteristics that are different from typical chorus. They are usually nondispersive and obliquely propagating, with a large longitudinal electric field and significant parallel electric field. We will also review comparisons of STEREO and Wind wave observations with SAMPEX observations of electron microbursts. Simulations show that the waves can result in energization by many MeV and/or scattering by large angles during a single wave packet encounter due to coherent, nonlinear processes including trapping. The experimental observations combined with simulations suggest that quasilinear theoretical models of electron energization and scattering via small-amplitude waves, with timescales of hours to days, may be inadequate for understanding radiation belt dynamics.

Cattell, Cynthia; Breneman, A.; Goetz, K.; Kellogg, P.; Kersten, K.; Wygant, J.; Wilson, L. B., III; Looper, Mark D.; Blake, J. Bernard; Roth, I.

2012-01-01

296

Condensation of circular DNA  

NASA Astrophysics Data System (ADS)

A simple model of a circularly closed double-stranded DNA in a poor solvent is considered as an example of a semi-flexible polymer with self-attraction. To find the ground states, the conformational energy is computed as a sum of the bending and torsional elastic components and the effective self-attraction energy. The model includes a relative orientation or sequence dependence of the effective attraction forces between different pieces of the polymer chain. Two series of conformations are analysed: a multicovered circle (a toroid) and a multifold two-headed racquet. The results are presented as a diagram of state. It is suggested that the stability of particular conformations may be controlled by proper adjustment of the primary structure. Application of the model to other semi-flexible polymers is considered.

Starostin, E. L.

2013-04-01

297

Observing light-by-light scattering at the Large Hadron Collider.  

PubMed

Elastic light-by-light scattering (?????) is open to study at the Large Hadron Collider thanks to the large quasireal photon fluxes available in electromagnetic interactions of protons (p) and lead (Pb) ions. The ????? cross sections for diphoton masses m(??)>5 GeV amount to 12 fb, 26 pb, and 35 nb in p-p, p-Pb, and Pb-Pb collisions at nucleon-nucleon center-of-mass energies ?(s(NN))=14, 8.8, and 5.5 TeV, respectively. Such a measurement has no substantial background in Pb-Pb collisions where one expects about 20 signal events per run, after typical detector acceptance and reconstruction efficiency selections. PMID:24010419

d'Enterria, David; da Silveira, Gustavo G

2013-08-23

298

Observing the Large Scale CMB Polarization using Variable-delay Polarization Modulators  

NASA Astrophysics Data System (ADS)

Variable-delay polarization modulators (VPM) will be deployed on two upcoming cosmic microwave background (CMB) polarization experiments, CLASS and PIPER, whose goal is to recover the large angular scale polarization of the CMB. We investigate the effects that this VPM will have on analysis of CMB polarization data. We look at the ability of the VPM to extract the large scale cosmological signal from systematics generated by the VPM and within the telescope. The systematic effects investigated are grid misalignment, grid emission, temperature variation of the VPM, and a time varying differential gain. The systematics are modeled when simulating timestreams and propagated through map-making to measurements of both the EE and BB power spectra. We show that we can separate the systematics from the sky polarization during map-making to a level below the BB power spectrum corresponding to a tensor-to-scalar ratio of r=0.01.

Miller, Nathan; Chuss, D. T.; Wollack, E.; Marriage, T.

2014-01-01

299

Evaluation of Large-Eddy Simulations via Observations of Nocturnal Marine Stratocumulus  

Microsoft Academic Search

Data from the first research flight (RF01) of the second Dynamics and Chemistry of Marine Stratocumulus (DYCOMS-II) field study are used to evaluate the fidelity with which large-eddy simulations (LESs) can represent the turbulent structure of stratocumulus-topped boundary layers. The initial data and forcings for this case placed it in an interesting part of parameter space, near the boundary where

Bjorn Stevens; Chin-Hoh Moeng; Andrew S. Ackerman; Christopher S. Bretherton; Andreas Chlond; Stephan de Roode; James Edwards; Jean-Christophe Golaz; Hongli Jiang; Marat Khairoutdinov; Michael P. Kirkpatrick; David C. Lewellen; Adrian Lock; Frank Müller; David E. Stevens; Eoin Whelan; Ping Zhu

2005-01-01

300

Comparisons of volume-imaging radar observations of atmospheric boundary layer turbulence with large eddy simulations  

Microsoft Academic Search

The Turbulent Eddy Profiler (TEP) is a volume-imaging 915 MHz radar designed for atmospheric boundary-layer turbulence studies. The TEP system is a pulsed, phased-array radar that uses digital beamforming techniques in order to provide four-dimensional images of Cn 2 fluctuations and wind vectors on grid scales comparable to those of large-eddy simulations (LES). In this paper the authors present results

Brian D. Pollard; Stephen J. Frasier; Robert E. McIntosh

1997-01-01

301

Large-Scale Observations of Galactic Star Forming Regions with the Midcourse Space Experiment  

Microsoft Academic Search

We have imaged seven nearby star forming regions with the infrared telescope on the Midcourse Space Experiment (MSX) at 18 arcsec resolution at 8.3,12.1, 14.7, and 21.3 mum: the Rosette nebula, the Orion nebula (A and B), W 3, the Pleiades, S 263, G159.6-18.5, and G300.2-16.8. The large scale of the regions imaged (7.2-50 square degrees) makes this dataset unique

K. E. Kraemer; S. D. Price; R. F. Shipman; D. R. Mizuno; T. Kuchar; S. J. Carey

2004-01-01

302

Laboratory observation of coherent structures beneath microscale and large-scale breaking waves under wind action  

Microsoft Academic Search

This study presents the results of an experimental investigation of coherent structures generated beneath microscale and large-scale spilling breaking waves. By analyzing PIV velocity data of wind-generated waves that are acquired at three different wind speeds, the similarity and difference in spatio-temporal evolving characteristics of the coherent structures according to the occurrence of the two types of wave breaking are

Sang-Ho Oh; Natsuki Mizutani; Kyung-Duck Suh

2008-01-01

303

Fermi Large Area Telescope Observations of PSR J1836+5925  

Microsoft Academic Search

The discovery of the gamma-ray pulsar PSR J1836+5925, powering the formerly unidentified EGRET source 3EG J1835+5918, was one of the early accomplishments of the Fermi Large Area Telescope (LAT). Sitting 25° off the Galactic plane, PSR J1836+5925 is a 173 ms pulsar with a characteristic age of 1.8 million years, a spindown luminosity of 1.1 × 1034 erg s-1, and

A. A. Abdo; M. Ackermann; M. Ajello; W. B. Atwood; L. Baldini; J. Ballet; G. Barbiellini; M. G. Baring; D. Bastieri; K. Bechtol; A. Belfiore; R. Bellazzini; B. Berenji; R. D. Blandford; E. D. Bloom; E. Bonamente; A. W. Borgland; J. Bregeon; A. Brez; M. Brigida; P. Bruel; T. H. Burnett; S. Buson; G. A. Caliandro; R. A. Cameron; F. Camilo; P. A. Caraveo; S. Carrigan; J. M. Casandjian; C. Cecchi; Ö. Çelik; E. Charles; A. Chekhtman; C. C. Cheung; J. Chiang; S. Ciprini; R. Claus; J. Cohen-Tanugi; J. Conrad; A. de Angelis; A. de Luca; F. de Palma; S. W. Digel; M. Dormody; E. do Couto e. Silva; P. S. Drell; R. Dubois; D. Dumora; Y. Edmonds; C. Farnier; C. Favuzzi; S. J. Fegan; W. B. Focke; P. Fortin; M. Frailis; Y. Fukazawa; S. Funk; P. Fusco; F. Gargano; D. Gasparrini; N. Gehrels; S. Germani; G. Giavitto; N. Giglietto; F. Giordano; T. Glanzman; G. Godfrey; I. A. Grenier; M.-H. Grondin; J. E. Grove; L. Guillemot; S. Guiriec; C. Gwon; D. Hadasch; A. K. Harding; E. Hays; D. Horan; R. E. Hughes; M. S. Jackson; G. Jóhannesson; A. S. Johnson; R. P. Johnson; T. J. Johnson; W. N. Johnson; T. Kamae; Y. Kanai; H. Katagiri; J. Kataoka; N. Kawai; M. Kerr; J. Knödlseder; M. Kuss; J. Lande; L. Latronico; M. Lemoine-Goumard; F. Longo; F. Loparco; B. Lott; M. N. Lovellette; P. Lubrano; G. M. Madejski; A. Makeev; M. Marelli; M. N. Mazziotta; J. E. McEnery; C. Meurer; P. F. Michelson; W. Mitthumsiri; T. Mizuno; A. A. Moiseev; C. Monte; M. E. Monzani; A. Morselli; I. V. Moskalenko; S. Murgia; P. L. Nolan; J. P. Norris; E. Nuss; T. Ohsugi; N. Omodei; E. Orlando; J. F. Ormes; D. Paneque; J. H. Panetta; D. Parent; V. Pelassa; M. Pepe; M. Pesce-Rollins; M. Pierbattista; F. Piron; T. A. Porter; S. Rainò; R. Rando; S. M. Ransom; P. S. Ray; M. Razzano; N. Rea; A. Reimer; O. Reimer; T. Reposeur; L. S. Rochester; A. Y. Rodriguez; R. W. Romani; M. Roth; F. Ryde; H. F.-W. Sadrozinski; A. Sander; P. M. Saz Parkinson; J. D. Scargle; C. Sgrò; E. J. Siskind; D. A. Smith; P. D. Smith; G. Spandre; P. Spinelli; M. S. Strickman; D. J. Suson; H. Takahashi; T. Tanaka; J. B. Thayer; J. G. Thayer; D. J. Thompson; S. E. Thorsett; L. Tibaldo; O. Tibolla; D. F. Torres; G. Tosti; A. Tramacere; T. L. Usher; A. Van Etten; V. Vasileiou; C. Venter; N. Vilchez; V. Vitale; A. P. Waite; P. Wang; K. Watters; B. L. Winer; M. T. Wolff; K. S. Wood; T. Ylinen; M. Ziegler

2010-01-01

304

Fermi Large Area Telescope Observations of Markarian 421: The Missing Piece of its Spectral Energy Distribution  

Microsoft Academic Search

We report on the gamma-ray activity of the high-synchrotron-peaked BL Lacertae object Markarian 421 (Mrk 421) during the first 1.5 years of Fermi operation, from 2008 August 5 to 2010 March 12. We find that the Large Area Telescope (LAT) gamma-ray spectrum above 0.3 GeV can be well described by a power-law function with photon index Gamma = 1.78 ±

A. A. Abdo; M. Ackermann; M. Ajello; L. Baldini; J. Ballet; G. Barbiellini; D. Bastieri; K. Bechtol; R. Bellazzini; B. Berenji; R. D. Blandford; E. D. Bloom; E. Bonamente; A. W. Borgland; A. Bouvier; J. Bregeon; A. Brez; M. Brigida; P. Bruel; R. Buehler; S. Buson; G. A. Caliandro; R. A. Cameron; A. Cannon; P. A. Caraveo; S. Carrigan; J. M. Casandjian; E. Cavazzuti; C. Cecchi; Ö. Çelik; E. Charles; A. Chekhtman; J. Chiang; S. Ciprini; R. Claus; J. Cohen-Tanugi; J. Conrad; S. Cutini; A. de Angelis; F. de Palma; C. D. Dermer; E. do Couto e. Silva; P. S. Drell; R. Dubois; D. Dumora; L. Escande; C. Favuzzi; S. J. Fegan; J. Finke; W. B. Focke; P. Fortin; M. Frailis; L. Fuhrmann; Y. Fukazawa; T. Fukuyama; S. Funk; P. Fusco; F. Gargano; D. Gasparrini; N. Gehrels; M. Georganopoulos; S. Germani; B. Giebels; N. Giglietto; P. Giommi; F. Giordano; M. Giroletti; T. Glanzman; G. Godfrey; I. A. Grenier; S. Guiriec; D. Hadasch; M. Hayashida; E. Hays; D. Horan; R. E. Hughes; G. Jóhannesson; A. S. Johnson; W. N. Johnson; M. Kadler; T. Kamae; H. Katagiri; J. Kataoka; J. Knödlseder; M. Kuss; J. Lande; L. Latronico; S.-H. Lee; F. Longo; F. Loparco; B. Lott; M. N. Lovellette; P. Lubrano; G. M. Madejski; A. Makeev; W. Max-Moerbeck; M. N. Mazziotta; J. E. McEnery; J. Mehault; P. F. Michelson; W. Mitthumsiri; T. Mizuno; C. Monte; M. E. Monzani; A. Morselli; I. V. Moskalenko; S. Murgia; T. Nakamori; M. Naumann-Godo; S. Nishino; P. L. Nolan; J. P. Norris; E. Nuss; T. Ohsugi; A. Okumura; N. Omodei; E. Orlando; J. F. Ormes; M. Ozaki; D. Paneque; J. H. Panetta; D. Parent; V. Pavlidou; T. J. Pearson; V. Pelassa; M. Pepe; M. Pesce-Rollins; M. Pierbattista; F. Piron; T. A. Porter; S. Rainò; R. Rando; M. Razzano; A. Readhead; A. Reimer; O. Reimer; L. C. Reyes; J. L. Richards; S. Ritz; M. Roth; H. F.-W. Sadrozinski; D. Sanchez; A. Sander; C. Sgrò; E. J. Siskind; P. D. Smith; G. Spandre; P. Spinelli; L. Stawarz; M. Stevenson; M. S. Strickman; D. J. Suson; H. Takahashi; T. Takahashi; T. Tanaka; J. G. Thayer; J. B. Thayer; D. J. Thompson; L. Tibaldo; D. F. Torres; G. Tosti; A. Tramacere; E. Troja; T. L. Usher; J. Vandenbroucke; V. Vasileiou; G. Vianello; N. Vilchez; V. Vitale; A. P. Waite; P. Wang; A. E. Wehrle; B. L. Winer; K. S. Wood; Z. Yang; Y. Yatsu; T. Ylinen; J. A. Zensus; M. Ziegler; J. Aleksic; L. A. Antonelli; P. Antoranz; M. Backes; J. A. Barrio; J. Becerra González; W. Bednarek; A. Berdyugin; K. Berger; E. Bernardini; A. Biland; O. Blanch; R. K. Bock; A. Boller; G. Bonnoli; P. Bordas; D. Borla Tridon; V. Bosch-Ramon; D. Bose; I. Braun; T. Bretz; M. Camara; E. Carmona; A. Carosi; P. Colin; E. Colombo; J. L. Contreras; J. Cortina; S. Covino; F. Dazzi; E. De Cea del Pozo; C. Delgado Mendez; B. De Lotto; M. De Maria; F. De Sabata; A. Diago Ortega; M. Doert; A. Domínguez; D. Dominis Prester; D. Dorner; M. Doro; D. Elsaesser; D. Ferenc; M. V. Fonseca; R. J. García López; M. Garczarczyk; M. Gaug; G. Giavitto; N. Godinovi; A. Herrero; D. Hildebrand; D. Höhne-Mönch; J. Hose; D. Hrupec; T. Jogler; S. Klepser; T. Krähenbühl; D. Kranich; J. Krause; A. La Barbera; E. Leonardo; E. Lindfors; S. Lombardi; M. López; E. Lorenz; P. Majumdar; E. Makariev; G. Maneva; N. Mankuzhiyil; K. Mannheim; L. Maraschi; M. Mariotti; M. Martínez; D. Mazin; M. Meucci; J. M. Miranda; R. Mirzoyan; H. Miyamoto; J. Moldón; A. Moralejo; D. Nieto; K. Nilsson; R. Orito; I. Oya; R. Paoletti; J. M. Paredes; S. Partini; M. Pasanen; F. Pauss; R. G. Pegna; M. A. Perez-Torres; M. Persic; J. Peruzzo; J. Pochon; F. Prada; P. G. Prada Moroni; E. Prandini; N. Puchades; I. Puljak; T. Reichardt; W. Rhode; M. Ribó; J. Rico; M. Rissi; S. Rügamer; A. Saggion; K. Saito; T. Y. Saito; M. Salvati; M. Sánchez-Conde; K. Satalecka; V. Scalzotto; V. Scapin; C. Schultz; T. Schweizer; M. Shayduk; S. N. Shore; A. Sierpowska-Bartosik; A. Sillanpää; J. Sitarek; D. Sobczynska; F. Spanier; S. Spiro; A. Stamerra; B. Steinke; J. Storz; N. Strah; J. C. Struebig; T. Suric; L. O. Takalo; F. Tavecchio; P. Temnikov; T. Terzic; D. Tescaro; M. Teshima; H. Vankov; R. M. Wagner; Q. Weitzel; V. Zabalza; F. Zandanel; R. Zanin; M. Villata; C. Raiteri; H. D. Aller; M. F. Aller; W. P. Chen; B. Jordan; E. Koptelova; O. M. Kurtanidze; A. Lähteenmäki; B. McBreen; V. M. Larionov; C. S. Lin; M. G. Nikolashvili; R. Reinthal; E. Angelakis; M. Capalbi; A. Carramiñana; L. Carrasco; P. Cassaro; A. Cesarini; A. Falcone; M. A. Gurwell; T. Hovatta; Yu. A. Kovalev; Y. Y. Kovalev; T. P. Krichbaum; H. A. Krimm; M. L. Lister; J. W. Moody; G. Maccaferri; Y. Mori; I. Nestoras; A. Orlati; C. Pace; C. Pagani; R. Pearson; M. Perri; B. G. Piner; E. Ros; A. C. Sadun; T. Sakamoto; J. Tammi; A. Zook

2011-01-01

305

Observation of jet production in deep inelastic scattering with a large rapidity gap at HERA  

Microsoft Academic Search

Events with a large rapidity gap in deep inelastic scattering with Q2 >= 10 GeV2 have been studied in the ZEUS detector. The properties of these events with W > 140 GeV are consistent with a leading twist diffractive production mechanism. In the laboratory frame, with ETjet >= 4 GeV, 15% of the events are of the 1-jet type with

M. Derrick; D. Krakauer; S. Magill; B. Musgrave; J. Repond; J. Schlereth; R. Stanek; R. L. Talaga; J. Thron; F. Arzarello; R. Ayad; G. Bari; M. Basile; L. Bellagamba; D. Boscherini; A. Bruni; G. Bruni; P. Bruni; G. Cara Romeo; G. Castellini; M. Chiarini; L. Cifarelli; F. Cindolo; F. Ciralli; A. Contin; S. D'Auria; C. del Papa; F. Frasconi; P. Giusti; G. Iacobucci; G. Laurenti; G. Levi; G. Maccarrone; A. Margotti; T. Massam; R. Nania; C. Nemoz; F. Palmonari; G. Sartorelli; R. Timellini; Y. Zamora Garcia; A. Zichichi; A. Bargende; J. Crittenden; K. Desch; B. Diekmann; T. Doeker; L. Feld; A. Frey; M. Geerts; G. Geitz; H. Hartmann; D. Haun; K. Heinloth; E. Hilger; H.-P. Jakob; U. F. Katz; S. Kramarczyk; A. Mass; S. Mengel; J. Mollen; E. Paul; Ch. Rembser; R. Schattevoy; J.-L. Schneider; D. Schramm; J. Stamm; R. Wedemeyer; S. Campbell-Robson; A. Cassidy; N. Dyce; B. Foster; S. George; R. Gilmore; G. P. Heath; H. F. Heath; T. J. Llewellyn; C. J. S. Morgado; D. J. P. Norman; J. A. O'Mara; R. J. Tapper; S. S. Wilson; R. Yoshida; R. R. Rau; M. Arneodo; M. Schioppa; G. Susinno; A. Bernstein; A. Caldwell; I. Gialas; J. A. Parsons; S. Ritz; F. Sciulli; P. B. Straub; L. Wai; S. Yang; P. Borzemski; J. Chwastowski; A. Eskreys; K. Piotrzkowski; M. Zachara; L. Zawiejski; L. Adamczyk; B. Bednarek; K. Eskreys; K. Jelen; D. Kisielewska; T. Kowalski; E. Rulikowska-Zarebska; L. Suszycki; J. Zajc; T. Kedzierski; A. Kotanski; M. Przybycien; L. A. T. Bauerdick; U. Behrens; J. K. Bienlein; S. Böttcher; C. Coldewey; G. Drews; M. Flasinski; I. Fleck; D. J. Gilkinson; P. Göttlicher; B. Gutjahr; T. Haas; L. Hagge; W. Hain; D. Hassell; H. Heßling; H. Hultschig; P. Joos; M. Kasemann; R. Klanner; W. Koch; L. Köpke; U. Kötz; H. Kowalski; W. Kröger; J. Krüger; J. Labs; A. Ladage; B. Löhr; M. Löwe; D. Lüke; J. Mainusch; O. Manczak; J. S. T. Ng; S. Nickel; D. Notz; K. Ohrenberg; M. Rohde; J. Roldán; U. Schneekloth; J. Schroeder; W. Schulz; F. Selonke; E. Stiliaris; T. Tsurugai; W. Vogel; D. Westphal; G. Wolf; C. Youngman; H. J. Grabosch; J. Leich; A. Meyer; C. Rethfeldt; S. Schlenstedt; G. Barbagli; M. Nuti; P. Pelfer; G. Anzivino; S. de Pasquale; S. Qian; L. Votano; A. Bamberger; A. Freidhof; T. Poser; S. Söldner-Rembold; G. Theisen; T. Trefzger; N. H. Brook; P. J. Bussey; A. T. Doyle; J. R. Forbes; V. A. Jamieson; C. Raine; D. H. Saxon; M. Stavrianakou; A. S. Wilson; A. Dannemann; U. Holm; D. Horstmann; H. Kammerlocher; B. Krebs; T. Neumann; R. Sinkus; K. Wick; E. Badura; B. D. Burow; A. Fürtjes; E. Lohrmann; J. Milewski; M. Nakahata; N. Pavel; G. Poelz; W. Schott; J. Terron; F. Zetsche; T. C. Bacon; R. Beuselinck; I. Butterworth; E. Gallo; V. L. Harris; K. R. Long; D. B. Miller; P. Morawitz; A. Prinias; J. K. Sedgbeer; A. Vorvolakos; A. Whitfield; T. Bienz; H. Kreutzmann; U. Mallik; E. McCliment; M. Roco; M. Z. Wang; P. Cloth; D. Filges; S. H. An; S. M. Hong; C. O. Kim; T. Y. Kim; S. W. Nam; S. K. Park; M. H. Suh; S. H. Yon; R. Imlay; S. Kartik; H.-J. Kim; R. R. McNeil; W. Metcalf; V. K. Nadendla; F. Barreiro; G. Cases; R. Graciani; J. M. Hernández; L. Hervás; L. Labarga; J. del Peso; J. Puga; J. F. de Trocóniz; F. Ikraiam; J. K. Mayer; G. R. Smith; F. Corriveau; D. S. Hanna; J. Hartmann; L. W. Hung; J. N. Lim; C. G. Matthews; J. W. Mitchell; P. M. Patel; L. E. Sinclair; D. G. Stairs; M. St. Laurent; R. Ullmann; V. Bashkirov; B. A. Dolgoshein; A. Stifutkin; G. L. Bashindzhagyan; P. F. Ermolov; L. K. Gladilin; Y. A. Golubkov; V. D. Kobrin; V. A. Kuzmin; E. N. Kuznetsov; A. A. Savin; A. N. Solomin; A. G. Voronin; N. P. Zotov; S. Bentvelsen; M. Botje; F. Chlebana; A. Dake; J. Engelen; P. de Jong; M. de Kamps; P. Kooijman; A. Kruse; V. O'dell; A. Tenner; H. Tiecke; W. Verkerke; M. Vreeswijk; L. Wiggers; E. de Wolf; R. van Woudenberg; D. Acosta; B. Bylsma; L. S. Durkin; K. Honscheid; C. Li; T. Y. Ling; K. W. McLean; W. N. Murray; I. H. Park; T. A. Romanowski; R. Seidlein; D. S. Bailey; G. A. Blair; A. Byrne; R. J. Cashmore; A. M. Cooper-Sarkar; D. Daniels; R. C. E. Devenish; N. Harnew; M. Lancaster; P. E. Luffman; J. McFall; C. Nath; A. Quadt; H. Uijterwaal; R. Walczak; F. F. Wilson; T. Yip; G. Abbiendi; A. Bertolin; R. Brugnera; R. Carlin; F. dal Corso; M. de Giorgi; U. Dosselli; F. Gasparini; S. Limentani; M. Morandin; M. Posocco; L. Stanco; R. Stroili; C. Voci; J. Bulmahn; J. M. Butterworth; R. G. Feild; B. Y. Oh; J. J. Whitmore; G. D'Agostini; M. Guida; M. Iori; S. M. Mari; G. Marini; M. Mattioli; A. Nigro; J. C. Hart; N. A. McCubbin; K. Prytz; T. P. Shah; T. L. Short; E. Barberis; N. Cartiglia; C. Heusch; M. van Hook; B. Hubbard; W. Lockman; H. F.-W. Sadrozinski; A. Seiden; D. Zer-Zion; J. Biltzinger; R. J. Seifert; A. H. Walenta; G. Zech; H. Abramowicz; S. Dagan; A. Levy; T. Hasegawa; M. Hazumi; T. Ishii; M. Kuze; S. Mine; Y. Nagasawa; T. Nagira; M. Nakao; I. Suzuki; K. Tokushuku

1994-01-01

306

The MACHO Project: Microlensing Results from 5.7 Years of Large Magellanic Cloud Observations  

Microsoft Academic Search

We report on our search for microlensing toward the Large Magellanic Cloud (LMC). Analysis of 5.7 yr of photometry on 11.9 million stars in the LMC reveals 13-17 microlensing events. A detailed treatment of our detection efficiency shows that this is significantly more than the ~2-4 events expected from lensing by known stellar populations. The timescales (t) of the events

C. Alcock; R. A. Allsman; D. R. Alves; T. S. Axelrod; A. C. Becker; D. P. Bennett; K. H. Cook; N. Dalal; A. J. Drake; K. C. Freeman; M. Geha; K. Griest; M. J. Lehner; S. L. Marshall; D. Minniti; C. A. Nelson; P. Popowski; M. R. Pratt; P. J. Quinn; C. W. Stubbs; W. Sutherland; A. B. Tomaney; T. Vandehei; D. Welch

2000-01-01

307

Observations and Implications of Large-Amplitude LongitudinalOscillations in a Solar Filament  

NASA Astrophysics Data System (ADS)

On 20 August 2010 an energetic disturbance triggered large-amplitude longitudinal oscillations in a large fraction of a nearby filament. The triggering mechanism appears to be episodic jets connecting the energetic event with the filament threads. We analyzed this periodic motion to characterize the underlying physics of the oscillation as well as the filament properties. The results support our previous theoretical conclusions that the restoring force of large-amplitude longitudinal oscillations is solar gravity, and the damping mechanism is the ongoing accumulation of mass onto the oscillating threads. Based on our previous work, we used the fitted parameters to determine the magnitude and radius of curvature of the dipped magnetic field along the filament, as well as the mass accretion rate onto the filament threads. These derived properties are nearly uniform along the filament, indicating a remarkable degree of homogeneity throughout the filament channel. Moreover, the estimated mass accretion rate implies that the footpoint heating responsible for the thread formation, according to the thermal nonequilibrium model, agrees with previous coronal heating estimates. We also estimated the magnitude of the energy released in the nearby event by studying the dynamic response of the filament threads, and concluded that the initiating event is likely to be a microflare. We will present the results of this investigation and discuss their implications for filament structure and heating. This work was supported by NASA’s H-SR program.

Karpen, Judith T.; Luna, Manuel; Knizhnik, Kalman J.; Muglach, Karin; Gilbert, Holly; Kucera, Therese A.; Uritsky, Vadim

2014-06-01

308

High-Resolution ?=1 mm CARMA Observations of Large Molecules in Orion-KL  

NASA Astrophysics Data System (ADS)

We present high-resolution Combined Array for Research in Millimeter-Wave Astronomy (CARMA) ?=1 mm observations of several molecular species toward Orion-KL. These are the highest spatial and spectral resolution 1 mm observations of these molecules to date. Our observations show that ethyl cyanide [C2H5CN] and vinyl cyanide [C2H3CN] originate from multiple cores near the Orion hot core and IRc7. In addition we show that dimethyl ether [(CH3)2O] and methyl formate [HCOOCH3] originate from IRc5 and IRc6 and that acetone [(CH3)2CO] originates only from areas where both N-bearing and O-bearing species are present.

Friedel, D. N.; Snyder, L. E.

2008-01-01

309

Placement of the dam for the no. 2 kambaratinskaya HPP by large-scale blasting: some observations  

SciTech Connect

Results of complex instrument observations of large-scale blasting during construction of the dam for the No. 2 Kambaratinskaya HPP on the Naryn River in the Republic of Kirgizia are analyzed. The purpose of these observations was: to determine the actual parameters of the seismic process, evaluate the effect of air and acoustic shock waves, and investigate the kinematics of the surface formed by the blast in its core region within the mass of fractured rocks.

Shuifer, M. I.; Argal, E. S. [JSC 'SPII Gidroproekt' (Russian Federation)

2011-11-15

310

Circular Vibration Planing of Inconel 718  

NASA Astrophysics Data System (ADS)

Circular vibration milling (CVM) is achieved by vibrating a milling cutter about the machine tool spindle axis in a circular path, in addition to its rotary motion. CVM has been proven capable of producing better surface finishes on difficult to cut materials. However, the CVM process is far slower than conventional milling process. In circular vibration planing (CVP) process, the cutting tool is clamped without rotation and fed at a speed comparable to the feed speed of conventional milling. By superimposing circular vibration motion, necessary cutting speed could be achieved keeping the feed speed at realistic values. Inconel 718 was machined by CVP and conventional milling at a similar feed rate. It was observed that CVP could reduce tool wear and hence produce better surface finishes than conventional milling. A geometric simulation showed a major difference between uncut chip shapes of the two processes. The difference of uncut chip shapes suggests that in CVP process, less rubbing occurs between tool flank face and work before the tool penetrates in to the work to form a chip. The reduced rubbing of the flank face is proposed as the reson for reduced tool wear in CVP when compared with conventional milling.

Hettiarachchi, Nandita Kalyanakumara; Moriwaki, Toshimichi; Shibasaka, Toshiro; Nakamoto, Keiichi

311

Volcanic activity before and after large tectonic earthquakes: Observations and statistical significance  

Microsoft Academic Search

The study of volcanic triggering and interaction with the tectonic surroundings has received special attention in recent years, using both direct field observations and historical descriptions of eruptions and earthquake activity. Repeated reports of clustered eruptions and earthquakes may imply that interaction is important in some subregions. However, the subregions likely to suffer such clusters have not been systematically identified,

Silke Eggert; Thomas R. Walter

2009-01-01

312

Circular chemiresistors for microchemical sensors  

DOEpatents

A circular chemiresistor for use in microchemical sensors. A pair of electrodes is fabricated on an electrically insulating substrate. The pattern of electrodes is arranged in a circle-filling geometry, such as a concentric, dual-track spiral design, or a circular interdigitated design. A drop of a chemically sensitive polymer (i.e., chemiresistive ink) is deposited on the insulating substrate on the electrodes, which spreads out into a thin, circular disk contacting the pair of electrodes. This circularly-shaped electrode geometry maximizes the contact area between the pair of electrodes and the polymer deposit, which provides a lower and more stable baseline resistance than with linear-trace designs. The circularly-shaped electrode pattern also serves to minimize batch-to-batch variations in the baseline resistance due to non-uniform distributions of conductive particles in the chemiresistive polymer film.

Ho, Clifford K. (Albuquerque, NM)

2007-03-13

313

Limits on large extra dimensions based on observations of neutron stars with the Fermi-LAT  

NASA Astrophysics Data System (ADS)

We present limits for the compactification scale in the theory of Large Extra Dimensions (LED) proposed by Arkani-Hamed, Dimopoulos, and Dvali. We use 11 months of data from the Fermi Large Area Telescope (Fermi-LAT) to set gamma ray flux limits for 6 gamma-ray faint neutron stars (NS). To set limits on LED we use the model of Hannestad and Raffelt (HR) that calculates the Kaluza-Klein (KK) graviton production in supernova cores and the large fraction subsequently gravitationally bound around the resulting NS. The predicted decay of the bound KK gravitons to ?? should contribute to the flux from NSs. Considering 2 to 7 extra dimensions of the same size in the context of the HR model, we use Monte Carlo techniques to calculate the expected differential flux of gamma-rays arising from these KK gravitons, including the effects of the age of the NS, graviton orbit, and absorption of gamma-rays in the magnetosphere of the NS. We compare our Monte Carlo-based differential flux to the experimental differential flux using maximum likelihood techniques to obtain our limits on LED. Our limits are more restrictive than past EGRET-based optimistic limits that do not include these important corrections. Additionally, our limits are more stringent than LHC based limits for 3 or fewer LED, and comparable for 4 LED. We conclude that if the effective Planck scale is around a TeV, then for 2 or 3 LED the compactification topology must be more complicated than a torus.

Fermi-LAT Collaboration; Ajello, M.; Baldini, L.; Barbiellini, G.; Bastieri, D.; Bechtol, K.; Bellazzini, R.; Berenji, B.; Bloom, E. D.; Bonamente, E.; Borgland, A. W.; Bregeon, J.; Brigida, M.; Bruel, P.; Buehler, R.; Buson, S.; Caliandro, G. A.; Cameron, R. A.; Caraveo, P. A.; Casandjian, J. M.; Cecchi, C.; Charles, E.; Chekhtman, A.; Chiang, J.; Ciprini, S.; Claus, R.; Cohen-Tanugi, J.; Conrad, J.; Cutini, S.; de Angelis, A.; de Palma, F.; Dermer, C. D.; Silva, E. do Couto e.; Drell, P. S.; Drlica-Wagner, A.; Enoto, T.; Favuzzi, C.; Fegan, S. J.; Ferrara, E. C.; Fukazawa, Y.; Fusco, P.; Gargano, F.; Gasparrini, D.; Germani, S.; Giglietto, N.; Giordano, F.; Giroletti, M.; Glanzman, T.; Godfrey, G.; Graham, P.; Grenier, I. A.; Guiriec, S.; Gustafsson, M.; Hadasch, D.; Hayashida, M.; Hughes, R. E.; Johnson, A. S.; Kamae, T.; Katagiri, H.; Kataoka, J.; Knödlseder, J.; Kuss, M.; Lande, J.; Latronico, L.; Lionetto, A. M.; Longo, F.; Loparco, F.; Lovellette, M. N.; Lubrano, P.; Mazziotta, M. N.; Michelson, P. F.; Mitthumsiri, W.; Mizuno, T.; Monte, C.; Monzani, M. E.; Morselli, A.; Moskalenko, I. V.; Murgia, S.; Norris, J. P.; Nuss, E.; Ohsugi, T.; Okumura, A.; Orlando, E.; Ormes, J. F.; Ozaki, M.; Paneque, D.; Pesce-Rollins, M.; Pierbattista, M.; Piron, F.; Pivato, G.; Rainò, S.; Razzano, M.; Ritz, S.; Roth, M.; Saz Parkinson, P. M.; Scargle, J. D.; Schalk, T. L.; Sgrò, C.; Siskind, E. J.; Spandre, G.; Spinelli, P.; Suson, D. J.; Tajima, H.; Takahashi, H.; Tanaka, T.; Thayer, J. G.; Thayer, J. B.; Tibaldo, L.; Tinivella, M.; Torres, D. F.; Troja, E.; Uchiyama, Y.; Usher, T. L.; Vandenbroucke, J.; Vasileiou, V.; Vianello, G.; Vitale, V.; Waite, A. P.; Winer, B. L.; Wood, K. S.; Wood, M.; Yang, Z.; Zimmer, S.

2012-02-01

314

Limits on Large Extra Dimensions Based on Observations of Neutron Stars with the Fermi-LAT  

NASA Technical Reports Server (NTRS)

We present limits for the compactification scale in the theory of Large Extra Dimensions (LED) proposed by Arkani-Hamed, Dimopoulos, and Dvali. We use 11 months of data from the Fermi Large Area Telescope (Fermi-LAT) to set gamma ray flux limits for 6 gamma-ray faint neutron stars (NS). To set limits on LED we use the model of Hannestad and Raffelt (HR) that calculates the Kaluza-Klein (KK) graviton production in supernova cores and the large fraction subsequently gravitationally bound around the resulting NS. The predicted decay of the bound KK gravitons to should contribute to the flux from NSs. Considering 2 to 7 extra dimensions of the same size in the context of the HR model, we use Monte Carlo techniques to calculate the expected differential flux of gamma-rays arising from these KK gravitons, including the effects of the age of the NS, graviton orbit, and absorption of gamma-rays in the magnetosphere of the NS. We compare our Monte Carlo-based differential flux to the experimental differential flux using maximum likelihood techniques to obtain our limits on LED. Our limits are more restrictive than past EGRET-based optimistic limits that do not include these important corrections. Additionally, our limits are more stringent than LHC based limits for 3 or fewer LED, and comparable for 4 LED. We conclude that if the effective Planck scale is around a TeV, then for 2 or 3 LED the compactification topology must be more complicated than a torus.

Ferrara, E. C.; Scargle, J. D.; Troja, E.

2012-01-01

315

Limits on Large Extra Dimensions Based on Observations of Neutron Stars with the Fermi-LAT  

SciTech Connect

We present limits for the compactification scale in the theory of Large Extra Dimensions (LED) proposed by Arkani-Hamed, Dimopoulos, and Dvali. We use 11 months of data from the Fermi Large Area Telescope (Fermi-LAT) to set gamma ray flux limits for 6 gamma-ray faint neutron stars (NS). To set limits on LED we use the model of Hannestad and Raffelt (HR) that calculates the Kaluza-Klein (KK) graviton production in supernova cores and the large fraction subsequently gravitationally bound around the resulting NS. The predicted decay of the bound KK gravitons to {gamma}{gamma} should contribute to the flux from NSs. Considering 2 to 7 extra dimensions of the same size in the context of the HR model, we use Monte Carlo techniques to calculate the expected differential flux of gamma-rays arising from these KK gravitons, including the effects of the age of the NS, graviton orbit, and absorption of gamma-rays in the magnetosphere of the NS. We compare our Monte Carlo-based differential flux to the experimental differential flux using maximum likelihood techniques to obtain our limits on LED. Our limits are more restrictive than past EGRET-based optimistic limits that do not include these important corrections. Additionally, our limits are more stringent than LHC based limits for 3 or fewer LED, and comparable for 4 LED. We conclude that if the effective Planck scale is around a TeV, then for 2 or 3 LED the compactification topology must be more complicated than a torus.

Ajello, M.; /SLAC /KIPAC, Menlo Park; Baldini, L.; /INFN, Pisa; Barbiellini, G.; /INFN, Trieste /Trieste U.; Bastieri, D.; /INFN, Padua /Padua U.; Bechtol, K.; /SLAC /KIPAC, Menlo Park; Bellazzini, R.; /INFN, Pisa; Berenji, B.; /SLAC /KIPAC, Menlo Park; Bloom, E.D.; /SLAC /KIPAC, Menlo Park; Bonamente, E.; /INFN, Perugia /Perugia U.; Borgland, A.W.; /SLAC /KIPAC, Menlo Park; Bregeon, J.; /INFN, Pisa; Brigida, M.; /Bari Polytechnic /INFN, Bari; Bruel, P.; /Ecole Polytechnique; Buehler, R.; /SLAC /KIPAC, Menlo Park; Buson, S.; /INFN, Padua /Padua U.; Caliandro, G.A.; /CSIC, Catalunya; Cameron, R.A.; /SLAC /KIPAC, Menlo Park; Caraveo, P.A.; /Brera Observ.; Casandjian, J.M.; /AIM, Saclay; Cecchi, C.; /INFN, Perugia /Perugia U.; Charles, E.; /SLAC /KIPAC, Menlo Park /Naval Research Lab, Wash., D.C. /SLAC /KIPAC, Menlo Park /ASDC, Frascati /Perugia U. /SLAC /KIPAC, Menlo Park /Montpellier U. /Stockholm U. /Stockholm U., OKC /Royal Swedish Acad. Sci. /ASDC, Frascati /Udine U. /INFN, Trieste /Bari Polytechnic /INFN, Bari /Naval Research Lab, Wash., D.C. /SLAC /KIPAC, Menlo Park /SLAC /KIPAC, Menlo Park /SLAC /KIPAC, Menlo Park /SLAC /KIPAC, Menlo Park /Bari Polytechnic /INFN, Bari /Ecole Polytechnique /NASA, Goddard /Hiroshima U. /Bari Polytechnic /INFN, Bari /INFN, Bari /ASDC, Frascati /INFN, Perugia /Perugia U. /Bari Polytechnic /INFN, Bari /Bari Polytechnic /INFN, Bari /Bologna Observ. /SLAC /KIPAC, Menlo Park /SLAC /KIPAC, Menlo Park /SLAC /KIPAC, Menlo Park /AIM, Saclay /Alabama U., Huntsville /INFN, Padua; /more authors..

2012-08-17

316

Observable T{sub 7} Lepton Flavor Symmetry at the Large Hadron Collider  

SciTech Connect

More often than not, models of flavor symmetry rely on the use of nonrenormalizable operators (in the guise of flavons) to accomplish the phenomenologically successful tribimaximal mixing of neutrinos. We show instead how a simple renormalizable two-parameter neutrino mass model of tribimaximal mixing can be constructed with the non-Abelian discrete symmetry T{sub 7} and the gauging of B-L. This is also achieved without the addition of auxiliary symmetries and particles present in almost all other proposals. Most importantly, it is verifiable at the Large Hadron Collider.

Cao Qinghong [High Energy Division, Argonne National Laboratory, Argonne, Illinois 60439 (United States); Enrico Fermi Institute, University of Chicago, Chicago, Illinois 60637 (United States); Khalil, Shaaban [Centre for Theoretical Physics, British University in Egypt, El Sherouk City, Postal No. 11837, P.O. Box 43 (Egypt); Department of Mathematics, Ain Shams University, Faculty of Science, Cairo 11566 (Egypt); Ma, Ernest [Department of Physics and Astronomy, University of California, Riverside, California 92521 (United States); Okada, Hiroshi [Centre for Theoretical Physics, British University in Egypt, El Sherouk City, Postal No. 11837, P.O. Box 43 (Egypt)

2011-04-01

317

Observable T{sub 7] lepton flavor symmetry at the large hadron collider.  

SciTech Connect

More often than not, models of flavor symmetry rely on the use of nonrenormalizable operators (in the guise of flavons) to accomplish the phenomenologically successful tribimaximal mixing of neutrinos. We show instead how a simple renormalizable two-parameter neutrino mass model of tribimaximal mixing can be constructed with the non-Abelian discrete symmetry T{sub 7} and the gauging of B-L. This is also achieved without the addition of auxiliary symmetries and particles present in almost all other proposals. Most importantly, it is verifiable at the Large Hadron Collider.

Cao, Q.-H.; Khalil, S.; Ma, E.; Okada, H. (High Energy Physics); (Univ. of Chicago); (British Univ. in Egypt); (Ain Shams Univ.); (Univ. of California at Riverside)

2011-03-29

318

Do Fermi-LAT observations really imply very large Lorentz factors in GRB outflows?  

NASA Astrophysics Data System (ADS)

Recent detections of GeV photons in a few GRBs by Fermi-LAT have led to strong constraints on the bulk Lorentz factor in GRB outflows. To avoid a large ?? optical depth, minimum values of the Lorentz factor are estimated to be as high as 800-1200 in some bursts. Here we present a detailed calculation of the ?? optical depth taking into account both the geometry and the dynamics of the jet. In the framework of the internal shock model, we compute lightcurves in different energy bands and the corresponding spectrum and we show how the limits on the Lorentz factor can be significantly lowered compared to previous estimates.

Hascoët, R.; Vennin, V.; Daigne, F.; Mochkovitch, R.

2011-08-01

319

Observations of large electric fields near the plasmasheet boundary by ISEE-1  

NASA Technical Reports Server (NTRS)

Large electric field spikes of up to about 80 mV/m, at distances of seven to 23 earth radii, were detected within one minute of encountering the high-altitude plasma sheet boundary, as identified by energetic particle detectors. If these high-altitude events, whose strong electric fields occur in enhanced low-frequency turbulence and field-aligned current flow regions and are individually well-correlated with small-scale gradients in particle fluxes and small-scale currents, are mappings of the low-altitude electrostatic shocks, these data may be taken as evidence that poleward auroral field lines map to the boundary of the plasma sheet.

Cattell, C. A.; Kim, M.; Lin, R. P.; Mozer, F. S.

1982-01-01

320

Observation of large photonic band gaps and defect modes in one-dimensional networked waveguides  

NASA Astrophysics Data System (ADS)

The photonic band structures and transmission spectra of serial loop structures (SLSs), made of loops pasted together with segments of finite length, are investigated experimentally and theoretically. These monomode structures, composed of one-dimensional dielectric materials, may exhibit large stop bands where the propagation of electromagnetic waves is forbidden. The width of these band gaps depends on the geometrical and compositional parameters of the structure and may be drastically increased in a tandem geometry made up of several successive SLSs which differ in their physical characteristics. These SLSs may have potential applications as ultrawide-band filters.

Mir, A.; Akjouj, A.; Vasseur, J. O.; Djafari-Rouhani, B.; Fettouhi, N.; El Boudouti, E. H.; Dobrzynski, L.; Zemmouri, J.

2003-03-01

321

Observations of large-amplitude MHD waves in Jupiter's foreshock in connection with a quasi-perpendicular shock structure  

NASA Technical Reports Server (NTRS)

Plasma and magnetic field observations performed onboard the Voyager 2 spacecraft have been used to investigate Jupiter's foreshock. Large-amplitude waves have been detected in association with the quasi-perpendicular structure of the Jovian bow shock, thus proving that the upstream turbulence is not a characteristic signature of the quasi-parallel shock.

Bavassano-Cattaneo, M. B.; Moreno, G.; Scotto, M. T.; Acuna, M.

1987-01-01

322

CARIBIC DOAS observations of nitrous acid and formaldehyde in a large convective cloud  

NASA Astrophysics Data System (ADS)

The CARIBIC (Civil Aircraft for the Regular Investigation of the atmosphere Based on an Instrument Container) flying laboratory measures once per month the chemical composition at cruise altitude (10...12 km) during 4 consecutive Lufthansa flights. Here we present a case study of enhanced nitrogen oxides (NOx), nitrous acid (HONO), and formaldehyde (HCHO) in a thunderstorm cloud over the Caribbean islands of Guadeloupe in August 2011. Nitrous acid is an important reservoir gas for OH radicals, and only few observations of HONO at cruise altitude exist. CARIBIC is designed as a long period atmospheric observation system, the actual system has been flying almost monthly since 8 yr now. During this period only very few similar events (one since 2008) were observed. Due to multiple scattering the light path inside clouds is enhanced, thereby lowering the detection limit of the DOAS instrument. Under background conditions the detection limits are 46 ppt for HONO, 387 ppt for \\chem{HCHO}, and 100 ppt for NO2 and are roughly three times lower inside the cloud. Based on radiative transfer simulations we estimate the path length to 90{ldots}100 km and the cloud top height to ?15 km. The inferred mixing ratios of HONO, HCHO and NO2 are 37 ppt, 400 ppt and 170 ppt, respectively. Bromine monoxide (BrO) remained below the detection limit of 1 ppt. Because the uplifted air masses originated from the remote marine boundary layer and lightning was observed in the area by the World Wide Lightning Location Network several hours prior to the measurement, the NO (?1.5 ppb) enhancement was in all likelihood caused by lightning. The main source for the observed HCHO is probably updraught from the boundary layer, because the chemical formation of formaldehyde due to methane oxidation is too weak. Besides HCHO also CH3OOH and isoprene are considered as precursors. The chemical box model CAABA is used to estimate the \\chem{NO} and HCHO source strengths, which are necessary to explain our measurements. For NO a source strength of 8.25 × 109 molec cm-2 s-1 km-1 is found, which corresponds to the lightning activity as observed by the World Wide Lightning Location network and a lightning emission of 4.2 × 1025 NO molec/flash. The HCHO updraught is of the order of 121 × 109 molec cm-2 s-1 km-1. Also isoprene and CH3OOH as possible HCHO sources were studied and similar source strengths were found.

Heue, K.-P.; Riede, H.; Walter, D.; Brenninkmeijer, C. A. M.; Wagner, T.; Frieß, U.; Platt, U.; Zahn, A.; Stratmann, G.; Ziereis, H.

2013-09-01

323

Limits on Large Extra Dimensions Based on Observations of Neutron Stars with the Fermi-LAT  

NASA Astrophysics Data System (ADS)

We present limits for the compactification scale in the theory of Large Extra Dimensions (LED) of Arkani-Hamed, Dimopoulos, and Dvali. We use 11-months of Fermi-LAT data to set ?-ray flux limits for 6 gamma-ray faint neutron stars (NS). To set limits on LED, we use the model of Hannestad and Raffelt (HR) that calculates the Kaluza-Klein graviton (GKK) production in supernova cores and the large fraction subsequently gravitationally bound around the resulting NS. The decays GKK->?? should contribute to the flux from NSs. For n=2,3,...,7 LED of the same size in the context of the HR model, we use MC techniques to calculate the expected differential flux of gamma-rays arising from these KK gravitons, including the effects of the age of the NS, graviton orbit, and absorption of gamma-rays in the magnetosphere of the NS. We compare our MC differential flux to the experimental differential flux using maximum likelihood techniques, and obtain limits on LED that are more restrictive than past EGRET-based optimistic limits that do not include these important corrections. Additionally, our limits are more stringent than collider limits for 3 or fewer LED. If the effective Planck scale is around a TeV, then with n=2,3, the LED topology is non-toroidal.

Berenji, Bijan; Bloom, Elliott; Cohen-Tanugi, Johann

2011-11-01

324

Observation of Helicity-Induced Alfvén Eigenmodes in Large-Helical-Device Plasmas Heated by Neutral-Beam Injection  

NASA Astrophysics Data System (ADS)

The helicity-induced Alfvén eigenmodes (HAEs) with the toroidal mode number n=2 and 3 are observed for the first time in the Large Helical Device plasmas heated by neutral beam injection. The observed mode frequency is about 8 times higher than that of the observed toroidicity-induced Alfvén eigenmodes, and is proportional to the Alfvén velocity. The modes are excited when the ratio of the beam velocity to the Alfvén velocity exceeds about unity. The frequency lies just above the lower bound of the HAE gap in the plasma edge region of ?>0.7 (?: normalized minor radius).

Yamamoto, S.; Toi, K.; Nakajima, N.; Ohdachi, S.; Sakakibara, S.; Watanabe, K. Y.; Goto, M.; Ikeda, K.; Kaneko, O.; Kawahata, K.; Masuzaki, S.; Morisaki, T.; Morita, S.; Murakami, S.; Narihara, K.; Oka, Y.; Osakabe, M.; Takeiri, Y.; Tanaka, K.; Tokuzawa, T.; Tsumori, K.; Yamada, H.; Yamada, I.; Yamazaki, K.

2003-12-01

325

Fermi Large Area Telescope Observations of Blazar 3C 279 Occultations by the Sun  

NASA Astrophysics Data System (ADS)

Observations of occultations of bright ?-ray sources by the Sun may reveal predicted pair halos around blazars and/or new physics, such as, e.g., hypothetical light dark matter particles—axions. We use Fermi Gamma-Ray Space Telescope (Fermi) data to analyze four occultations of blazar 3C 279 by the Sun on October 8 each year from 2008 to 2011. A combined analysis of the observations of these occultations allows a point-like source at the position of 3C 279 to be detected with significance of ?3?, but does not reveal any significant excess over the flux expected from the quiescent Sun. The likelihood ratio test rules out complete transparency of the Sun to the blazar ?-ray emission at a 3? confidence level.

Barbiellini, G.; Bastieri, D.; Bechtol, K.; Bellazzini, R.; Blandford, R. D.; Borgland, A. W.; Bregeon, J.; Bruel, P.; Buehler, R.; Buson, S.; Caliandro, G. A.; Cameron, R. A.; Caraveo, P. A.; Cavazzuti, E.; Cecchi, C.; Chaves, R. C. G.; Chekhtman, A.; Cheung, C. C.; Chiang, J.; Ciprini, S.; Claus, R.; Cohen-Tanugi, J.; D'Ammando, F.; de Angelis, A.; Dermer, C. D.; Digel, S. W.; Silva, E. do Couto e.; Drell, P. S.; Drlica-Wagner, A.; Favuzzi, C.; Focke, W. B.; Franckowiak, A.; Fukazawa, Y.; Fusco, P.; Gargano, F.; Gasparrini, D.; Germani, S.; Giglietto, N.; Giommi, P.; Giordano, F.; Giroletti, M.; Glanzman, T.; Godfrey, G.; Grenier, I. A.; Grove, J. E.; Guiriec, S.; Hadasch, D.; Hayashida, M.; Hays, E.; Hughes, R. E.; Jackson, M. S.; Jogler, T.; Knödlseder, J.; Kuss, M.; Lande, J.; Larsson, S.; Longo, F.; Loparco, F.; Lovellette, M. N.; Lubrano, P.; Mazziotta, M. N.; Mehault, J.; Michelson, P. F.; Mizuno, T.; Moiseev, A. A.; Monte, C.; Monzani, M. E.; Morselli, A.; Moskalenko, I. V.; Murgia, S.; Nemmen, R.; Nuss, E.; Ohsugi, T.; Omodei, N.; Orienti, M.; Orlando, E.; Paneque, D.; Perkins, J. S.; Piron, F.; Pivato, G.; Prokhorov, D.; Rainò, S.; Razzano, M.; Razzaque, S.; Reimer, A.; Reimer, O.; Ritz, S.; Romoli, C.; Sánchez-Conde, M.; Sanchez, D. A.; Sgrò, C.; Siskind, E. J.; Spandre, G.; Spinelli, P.; Takahashi, H.; Tanaka, T.; Tibaldo, L.; Tinivella, M.; Tosti, G.; Troja, E.; Usher, T. L.; Vandenbroucke, J.; Vasileiou, V.; Vianello, G.; Vitale, V.; Waite, A. P.; Winer, B. L.; Wood, K. S.; Yang, Z.

2014-04-01

326

Very Large Baseline Array observations of Mrk 6: probing the jet-lobe connection  

NASA Astrophysics Data System (ADS)

We present the results of high-resolution VLBI (very long baseline interferometry) observations at 1.6 and 4.9 GHz of the radio-loud Seyfert galaxy, Mrk 6. These observations are able to detect a compact radio core in this galaxy for the first time. The core has an inverted spectral index (? ^{1.6}_{4.9} = +1.0 ± 0.2) and a brightness temperature of 1 × 108 K. Three distinct radio components, which resemble jet elements and/or hotspots, are also detected. The position angles of these elongated jet elements point not only to a curved jet in Mrk 6, but also towards a connection between the AGN and the kpc-scale radio lobes/bubbles in this galaxy. Firmer constraints on the star formation rate provided by new Herschel observations (SFR < 0.8 M? yr-1) make the starburst-wind-powered bubble scenario implausible. From plasma speeds, obtained via prior Chandra X-ray observations, and ram pressure balance arguments for the interstellar medium and radio bubbles, the north-south bubbles are expected to take 7.5 × 106 yr to form, and the east-west bubbles 1.4 × 106 yr. We suggest that the jet axis has changed at least once in Mrk 6 within the last ?107 yr. A comparison of the nuclear radio-loudness of Mrk 6 and a small sample of Seyfert galaxies with a subset of low-luminosity FR I radio galaxies reveals a continuum in radio properties.

Kharb, P.; O'Dea, C. P.; Baum, S. A.; Hardcastle, M. J.; Dicken, D.; Croston, J. H.; Mingo, B.; Noel-Storr, J.

2014-06-01

327

Large-scale characteristics of interstellar dust from COBE DIRBE observations  

Microsoft Academic Search

Observations from the COBE Diffuse Infrared Background Experiment of the 140 and 240 micrometer emissions from the Galatic plane region (absolute value of b less than 10 deg) are combined with radio surveys that trace the molecular (H2), neutral atomic (H I), and extended low-density (ne approximately 10 to 100\\/cm3) ionized (H II) gas phases of the interstellar medium to

T. J. Sodroski; C. Bennett; N. Boggess; E. Dwek; B. A. Franz; M. G. Hauser; T. Kelsall; S. H. Moseley; N. Odegard; R. F. Silverberg; J. L. Weiland

1994-01-01

328

STEREO quadrature observations of the large-scale EUV wave of Feb 13th, 2009  

NASA Astrophysics Data System (ADS)

The event on Feb 13th, 2009 was the first case of a global coronal wave observed by the STEREO twin satellites in quadrature. The wave's initiation site was at the disk center in EUVI STEREO-B and precisely at the limb in STEREO-A. Therefore it was possible to determine the wave's on-disk as well as edge-on kinematics and to study its three-dimensional structure. From the two STEREO observations we derive the height of propagation of the wave, which was found to be in the range between 80-100 Mm above the photosphere. Comparison of the early phases of the contemporaneous CME and the wave's kinematics suggest that the wave is set off by the CME lateral expansion. The wave propagates globally over the whole hemisphere with a constant velocity 263 16 km s-1, which is close to the fast magnetosonic speed in the quiet solar corona. Thus we conclude that the observed EUV wave is consistent with a MHD fast-mode wave.

Ines Kienreich, Mag.; Veronig, Astrid; Temmer, Manuela

329

Recent Large Reduction in Sulfur Dioxide Emissions from Chinese Power Plants Observed by the Ozone Monitoring Instrument  

NASA Technical Reports Server (NTRS)

The Ozone Monitoring Instrument (OMI) aboard NASA's Aura satellite observed substantial increases in total column SO2 and tropospheric column NO2 from 2005 to 2007, over several areas in northern China where large coal-fired power plants were built during this period. The OMI-observed SO2/NO2 ratio is consistent with the SO2/ NO2, emissions estimated from a bottom-up approach. In 2008 over the same areas, OMI detected little change in NO2, suggesting steady electricity output from the power plants. However, dramatic reductions of S0 2 emissions were observed by OMI at the same time. These reductions confirm the effectiveness of the flue-gas desulfurization (FGD) devices in reducing S02 emissions, which likely became operational between 2007 and 2008. This study further demonstrates that the satellite sensors can monitor and characterize anthropogenic emissions from large point sources.

Li, Can; Zhang, Qiang; Krotkov, Nickolay A.; Streets, David G.; He, Kebin; Tsay, Si-Chee; Gleason, James F.

2010-01-01

330

Recent large reduction in sulfur dioxide emissions from Chinese power plants observed by the Ozone Monitoring Instrument  

NASA Astrophysics Data System (ADS)

The Ozone Monitoring Instrument (OMI) aboard NASA's Aura satellite observed substantial increases in total column SO2 and tropospheric column NO2 from 2005 to 2007, over several areas in northern China where large coal-fired power plants were built during this period. The OMI-observed SO2/NO2 ratio is consistent with the SO2/NOx emissions estimated from a bottom-up approach. In 2008 over the same areas, OMI detected little change in NO2, suggesting steady electricity output from the power plants. However, dramatic reductions of SO2 emissions were observed by OMI at the same time. These reductions confirm the effectiveness of the flue-gas desulfurization (FGD) devices in reducing SO2 emissions, which likely became operational between 2007 and 2008. This study further demonstrates that the satellite sensors can monitor and characterize anthropogenic emissions from large point sources.

Li, Can; Zhang, Qiang; Krotkov, Nickolay A.; Streets, David G.; He, Kebin; Tsay, Si-Chee; Gleason, James F.

2010-04-01

331

Observations and modeling of GIC in the Chinese large-scale high-voltage power networks  

NASA Astrophysics Data System (ADS)

During geomagnetic storms, the geomagnetically induced currents (GIC) cause bias fluxes in transformers, resulting in half-cycle saturation. Severely distorted exciting currents, which contain significant amounts of harmonics, threaten the safe operation of equipment and even the whole power system. In this paper, we compare GIC data measured in transformer neutrals and magnetic recordings in China, and show that the GIC amplitudes can be quite large even in mid-low latitude areas. The GIC in the Chinese Northwest 750 kV Power Grid are modeled based on the plane wave assumption. The results show that GIC flowing in some transformers exceed 30 A/phase during strong geomagnetic storms. GIC are thus not only a high-latitude problem but networks in middle and low latitudes can be impacted as well, which needs careful attention.

Liu, Chunming; Li, Yunlong; Pirjola, Risto

2014-01-01

332

Large-range movements of neotropical orchid bees observed via radio telemetry.  

PubMed

Neotropical orchid bees (Euglossini) are often cited as classic examples of trapline-foragers with potentially extensive foraging ranges. If long-distance movements are habitual, rare plants in widely scattered locations may benefit from euglossine pollination services. Here we report the first successful use of micro radio telemetry to track the movement of an insect pollinator in a complex and forested environment. Our results indicate that individual male orchid bees (Exaerete frontalis) habitually use large rainforest areas (at least 42-115 ha) on a daily basis. Aerial telemetry located individuals up to 5 km away from their core areas, and bees were often stationary, for variable periods, between flights to successive localities. These data suggest a higher degree of site fidelity than what may be expected in a free living male bee, and has implications for our understanding of biological activity patterns and the evolution of forest pollinators. PMID:20520813

Wikelski, Martin; Moxley, Jerry; Eaton-Mordas, Alexander; López-Uribe, Margarita M; Holland, Richard; Moskowitz, David; Roubik, David W; Kays, Roland

2010-01-01

333

Concrete-filled circular steel tubes subjected to pure bending  

Microsoft Academic Search

Current design codes and standards provide little information on the flextural behaviour of circular concrete filled tubes (CFT) as there have been few experimental studies. There are significant differences in d\\/t-limits recommended in various codes for CFT under bending. This paper presents an experimental investigation of the flexural behaviour of circular CFT subjected to large deformation pure bending where d\\/t=12

M. Elchalakani; X. L. Zhao; R. H. Grzebieta

2001-01-01

334

Observation of large-angle quasimonoenergetic electrons from a laser wakefield.  

PubMed

A relativistically intense laser pulse is focused into a helium jet and quasimonoenergetic electrons emitted at a 40 degrees angle with respect to the laser axis are observed. The average electron energy is between 1 and 2 MeV and the total accelerated charge is about 1 nC emitted in a 10 degrees cone angle. Three dimensional particle-in-cell simulations reproduce key features of the experimental results and show that the interaction between ionization heating and nonlinear cavitation wakefields is responsible for the acceleration. PMID:18518612

Kaganovich, D; Gordon, D F; Ting, A

2008-05-30

335

A spool pattern tool for circular braiding  

Microsoft Academic Search

Circular Braiding is a composite material preform manufacturing process that is used to manufacture bi- and\\u000atriaxial braids. A procedure is presented for relating braid patterns to spool patterns. The procedure is based\\u000aon the observation that physical removal of a bias spool from the machine corresponds to removal of a row or\\u000acolumn of intersections from the braid pattern

Ravenhorst van J. H; R. Akkerman

2011-01-01

336

X-ray observations of a large sample of cataclysmic variable stars using the Einstein Observatory  

NASA Technical Reports Server (NTRS)

This paper presents the results of an X-ray survey of 31 known or suspected cataclysmic variables. Eighteen of these close binary systems are detected with inferred luminosities in the 0.1-4.0 keV band of between 10 to the 30th and 10 to the 32nd erg/sec. The majority have relatively hard X-ray spectra (kT greater than 2 keV) irrespective of luminosity state. Of seven dwarf novae observed during optical outbursts only U Gem exhibited enhanced ultrasoft X-ray emission (kT of about 10 eV) in addition to weak, hard X-ray emission. Variability of the X-ray flux is observed in many of these stars, on time-scales ranging from tens of seconds to hours. The contribution to the flux from extended X-ray emission is investigated for SU UMa and GK Per. Several possibilities for the origin of the hard X-rays are considered.

Cordova, F. A.; Mason, K. O.

1984-01-01

337

The Spitzer c2d Survey of Large, Nearby, Interstellar Clouds. VIII. Serpens Observed with MIPS  

NASA Astrophysics Data System (ADS)

We present maps of 1.5 deg2 of the Serpens dark cloud at 24, 70, and 160 ?m observed with the Spitzer Space Telescope MIPS camera. We describe the observations and briefly discuss the data processing carried out by the c2d team on these data. More than 2400 compact sources have been extracted at 24 ?m, nearly 100 at 70 ?m, and four at 160 ?m. We estimate completeness limits for our 24 ?m survey from Monte Carlo tests with artificial sources inserted into the Spitzer maps. We compare source counts, colors, and magnitudes in the Serpens cloud to two reference data sets: a 0.50 deg 2 set on a low-extinction region near the dark cloud, and a 5.3 deg2 subset of the SWIRE ELAIS N1 data that was processed through our pipeline. These results show that there is an easily identifiable population of young stellar object candidates in the Serpens cloud that is not present in either of the reference data sets. We also show a comparison of visual extinction and cool dust emission illustrating a close correlation between the two and find that the most embedded YSO candidates are located in the areas of highest visual extinction.

Harvey, Paul M.; Rebull, Luisa M.; Brooke, Tim; Spiesman, William J.; Chapman, Nicholas; Huard, Tracy L.; Evans, Neal J., II; Cieza, Lucas; Lai, Shih-Ping; Allen, Lori E.; Mundy, Lee G.; Padgett, Deborah L.; Sargent, Anneila I.; Stapelfeldt, Karl R.; Myers, Philip C.; van Dishoeck, Ewine F.; Blake, Geoffrey A.; Koerner, David W.

2007-07-01

338

Observations of Pulsar Wind Nebulae with the Fermi-Large Area Telescope  

NASA Astrophysics Data System (ADS)

Prior to the Fermi Gamma-ray Space Telescope, only six pulsars and one associated pulsar wind nebula, the Crab Nebula, had been detected in gamma-rays by EGRET. Since then, Fermi has significantly increased the number of detected pulsars in the 100 MeV to 30 GeV energy range. These gamma-ray pulsars can power pulsar wind nebulae potentially detectable by the LAT, as it has already been done for the Crab and Vela-X. However, their emission can only be observed in the off-pulse windows due to the dominating pulsed emission in the total phase interval. A systematic analysis was performed using 15 months of Fermi-LAT data to detect these weak and steady sources. When no significant detection was observed, flux upper limits were derived to constrain model parameters and provide a first population study of gamma-ray pulsar wind nebulae. In this presentation, we will review the results obtained so far on all pulsar wind nebulae, including the very famous Crab Nebula, Vela-X and MSH 15-52, and give a general overview of the constraints provided by Fermi-LAT non-detection.

Lemoine-Goumard, Marianne; Grondin, Marie-Helene

339

A Large Sample of Magnetically-Active Stars Observed With Kepler  

NASA Astrophysics Data System (ADS)

We have observed about 325 stars in our Kepler Guest Observer programs (Cycles 1 through 4). For most of these targets, we are analyzing extremely high-precision light curves that have been continuously sampled every 30 minutes for up to 3 years. Our sample of candidate magnetically-active stars was selected primarily using GALEX colors. Starspots, pulsations, and variations due to eclipsing and contact binaries combine to produce a rich variety of light curves. We have developed semi-automated procedures to characterize this variability and thus to classify the targets and identify the physical mechanisms that dominate their Kepler light curves. We will describe these procedures and discuss the range of physical properties covered by our final classification scheme. We are using this Kepler database of variability over timescales of minutes to years to provide diagnostics of flares, starspot formation, evolution, migration, and ultimately of stellar cycles in general. This work contains results obtained using the NASA Kepler satellite and from the Apache Point Observatory, the MMT (using NOAO community access time), and the Hobby-Eberly Telescope. Funding is provided by NASA Kepler grants NNX10AC51G, NNX11AC79G, and NNX12AC85G to the University of Colorado, by NSF grant AST-1109695 to the College of Charleston, and by a grant from the South Carolina Space Grant consortium.

Wells, Mark; Neff, J. E.; Brown, A.; Ayres, T. R.; Basri, G. S.; Berdyugina, S.; Harper, G.; Hawley, S. L.; Korhonen, H.; Kowalski, A.; Micela, G.; Piskunov, N. E.; Ramsey, L. W.; Saar, S. H.; Walkowicz, L. M.

2013-01-01

340

Nuclear spin circular dichroism  

NASA Astrophysics Data System (ADS)

Recent years have witnessed a growing interest in magneto-optic spectroscopy techniques that use nuclear magnetization as the source of the magnetic field. Here we present a formulation of magnetic circular dichroism (CD) due to magnetically polarized nuclei, nuclear spin-induced CD (NSCD), in molecules. The NSCD ellipticity and nuclear spin-induced optical rotation (NSOR) angle correspond to the real and imaginary parts, respectively, of (complex) quadratic response functions involving the dynamic second-order interaction of the electron system with the linearly polarized light beam, as well as the static magnetic hyperfine interaction. Using the complex polarization propagator framework, NSCD and NSOR signals are obtained at frequencies in the vicinity of optical excitations. Hartree-Fock and density-functional theory calculations on relatively small model systems, ethene, benzene, and 1,4-benzoquinone, demonstrate the feasibility of the method for obtaining relatively strong nuclear spin-induced ellipticity and optical rotation signals. Comparison of the proton and carbon-13 signals of ethanol reveals that these resonant phenomena facilitate chemical resolution between non-equivalent nuclei in magneto-optic spectra.

Vaara, Juha; Rizzo, Antonio; Kauczor, Joanna; Norman, Patrick; Coriani, Sonia

2014-04-01

341

Nuclear spin circular dichroism.  

PubMed

Recent years have witnessed a growing interest in magneto-optic spectroscopy techniques that use nuclear magnetization as the source of the magnetic field. Here we present a formulation of magnetic circular dichroism (CD) due to magnetically polarized nuclei, nuclear spin-induced CD (NSCD), in molecules. The NSCD ellipticity and nuclear spin-induced optical rotation (NSOR) angle correspond to the real and imaginary parts, respectively, of (complex) quadratic response functions involving the dynamic second-order interaction of the electron system with the linearly polarized light beam, as well as the static magnetic hyperfine interaction. Using the complex polarization propagator framework, NSCD and NSOR signals are obtained at frequencies in the vicinity of optical excitations. Hartree-Fock and density-functional theory calculations on relatively small model systems, ethene, benzene, and 1,4-benzoquinone, demonstrate the feasibility of the method for obtaining relatively strong nuclear spin-induced ellipticity and optical rotation signals. Comparison of the proton and carbon-13 signals of ethanol reveals that these resonant phenomena facilitate chemical resolution between non-equivalent nuclei in magneto-optic spectra. PMID:24712776

Vaara, Juha; Rizzo, Antonio; Kauczor, Joanna; Norman, Patrick; Coriani, Sonia

2014-04-01

342

Very Large Array Observations of H I in the Circumstellar Envelopes of Asymptotic Giant Branch Stars  

NASA Astrophysics Data System (ADS)

We have used the Very Large Array to search for neutral atomic hydrogen (H I) in the circumstellar envelopes of five asymptotic giant branch stars. We have detected H I 21 cm emission coincident in both position and velocity with the S-type semiregular variable star RS Cnc. The emission comprises a compact, slightly elongated feature centered on the star with a mean diameter of ~82" (1.5×1017 cm), plus an additional filament extending ~6' to the northwest. If this filament is associated with RS Cnc, it would imply that a portion of its mass loss is highly asymmetric. We estimate MHI~1.5×10-3 Msolar and a mass-loss rate M?~1.7×10-7 Msolar yr-1. Toward three other stars (IRC+10216, EP Aqr, R Cas) we have detected arcminute-scale H I emission features at velocities consistent with the circumstellar envelopes, but spatially offset from the stellar positions. Toward R Cas, the emission is weak but peaks at the stellar systemic velocity and overlaps with the location of its circumstellar dust shell and thus is probably related to the star. In the case of IRC+10216, we were unable to confirm the detection of H I in absorption against the cosmic background previously reported by Le Bertre & Gérard. However, we detect arcs of emission at projected distances of r~14'-18' (~2×1018 cm) to the northwest of the star. The large separation of the emission from the star is plausible, given its advanced evolutionary status, although it is unclear if the asymmetric distribution and complex velocity structure are consistent with a circumstellar origin. For EP Aqr, the detected H I emission comprises multiple clumps redward of the systemic velocity, but we are unable to determine unambiguously whether the emission arises from the circumstellar envelope or from interstellar clouds along the line of sight. Regardless of the adopted distance for the H I clumps, their inferred H I masses are at least an order of magnitude smaller than their individual gravitational binding masses. We did not detect any H I emission from our fifth target, R Aqr (a symbiotic binary), but measured a 1.4 GHz continuum flux density of 18.8+/-0.7 mJy. R Aqr is a previously known radio source, and the 1.4 GHz emission likely arises primarily from free-free emission from an ionized circumbinary envelope.

Matthews, Lynn D.; Reid, Mark J.

2007-05-01

343

Melt production in large-scale impact events: Implications and observations at terrestrial craters  

NASA Technical Reports Server (NTRS)

The volume of impact melt relative to the volume of the transient cavity increases with the size of the impact event. Here, we use the impact of chondrite into granite at 15, 25, and 50 km s(sup -1) to model impact-melt volumes at terrestrial craters in crystalline targets and explore the implications for terrestrial craters. Figures are presented that illustrate the relationships between melt volume and final crater diameter D(sub R) for observed terrestrial craters in crystalline targets; also included are model curves for the three different impact velocities. One implication of the increase in melt volumes with increasing crater size is that the depth of melting will also increase. This requires that shock effects occurring at the base of the cavity in simple craters and in the uplifted peaks of central structures at complex craters record progressively higher pressures with increasing crater size, up to a maximum of partial melting (approx. 45 GPa). Higher pressures cannot be recorded in the parautochthonous rocks of the cavity floor as they will be represented by impact melt, which will not remain in place. We have estimated maximum recorded pressures from a review of the literature, using such observations as planar features in quartz and feldspar, diaplectic glasses of feldspar and quartz, and partial fusion and vesiculation, as calibrated with estimates of the pressures required for their formation. Erosion complicates the picture by removing the surficial (most highly shocked) rocks in uplifted structures, thereby reducing the maximum shock pressures observed. In addition, the range of pressures that can be recorded is limited. Nevertheless, the data define a trend to higher recorded pressures with crater diameter, which is consistent with the implications of the model. A second implication is that, as the limit of melting intersects the base of the cavity, central topographic peaks will be modified in appearance and ultimately will not occur. That is, the peak will first develop a central depression, due to the flow of low-strength melted materials, when the melt volume begins to intersect the transient-cavity base.

Grieve, Richard A. F.; Cintala, Mark J.

1992-01-01

344

Melt production in large-scale impact events: Implications and observations at terrestrial craters  

NASA Astrophysics Data System (ADS)

The volume of impact melt relative to the volume of the transient cavity increases with the size of the impact event. Here, we use the impact of chondrite into granite at 15, 25, and 50 km s(sup -1) to model impact-melt volumes at terrestrial craters in crystalline targets and explore the implications for terrestrial craters. Figures are presented that illustrate the relationships between melt volume and final crater diameter D(sub R) for observed terrestrial craters in crystalline targets; also included are model curves for the three different impact velocities. One implication of the increase in melt volumes with increasing crater size is that the depth of melting will also increase. This requires that shock effects occurring at the base of the cavity in simple craters and in the uplifted peaks of central structures at complex craters record progressively higher pressures with increasing crater size, up to a maximum of partial melting (approx. 45 GPa). Higher pressures cannot be recorded in the parautochthonous rocks of the cavity floor as they will be represented by impact melt, which will not remain in place. We have estimated maximum recorded pressures from a review of the literature, using such observations as planar features in quartz and feldspar, diaplectic glasses of feldspar and quartz, and partial fusion and vesiculation, as calibrated with estimates of the pressures required for their formation. Erosion complicates the picture by removing the surficial (most highly shocked) rocks in uplifted structures, thereby reducing the maximum shock pressures observed. In addition, the range of pressures that can be recorded is limited. Nevertheless, the data define a trend to higher recorded pressures with crater diameter, which is consistent with the implications of the model. A second implication is that, as the limit of melting intersects the base of the cavity, central topographic peaks will be modified in appearance and ultimately will not occur. That is, the peak will first develop a central depression, due to the flow of low-strength melted materials, when the melt volume begins to intersect the transient-cavity base.

Grieve, Richard A. F.; Cintala, Mark J.

1992-09-01

345

VERY LARGE ARRAY OBSERVATIONS OF AMMONIA IN INFRARED-DARK CLOUDS. II. INTERNAL KINEMATICS  

SciTech Connect

Infrared-dark clouds (IRDCs) are believed to be the birthplaces of rich clusters and thus contain the earliest phases of high-mass star formation. We use the Green Bank Telescope and Very Large Array maps of ammonia (NH{sub 3}) in six IRDCs to measure their column density and temperature structure (Paper 1), and here, we investigate the kinematic structure and energy content. We find that IRDCs overall display organized velocity fields, with only localized disruptions due to embedded star formation. The local effects seen in NH{sub 3} emission are not high-velocity outflows but rather moderate (few km s{sup -1}) increases in the linewidth that exhibit maxima near or coincident with the mid-infrared emission tracing protostars. These linewidth enhancements could be the result of infall or (hidden in NH{sub 3} emission) outflow. Not only is the kinetic energy content insufficient to support the IRDCs against collapse, but also the spatial energy distribution is inconsistent with a scenario of turbulent cloud support. We conclude that the velocity signatures of the IRDCs in our sample are due to active collapse and fragmentation, in some cases augmented by local feedback from stars.

Ragan, Sarah E.; Bergin, Edwin A. [Department of Astronomy, University of Michigan, 830 Dennison Building, 500 Church Street, Ann Arbor, MI 48109 (United States); Heitsch, Fabian [Department of Physics and Astronomy, University of North Carolina-Chapel Hill, CB 3255 Phillips Hall, Chapel Hill, NC 27599 (United States); Wilner, David, E-mail: ragan@mpia.de [Smithsonian Center for Astrophysics, Mail Stop 42, 60 Garden Street, Cambridge, MA 02138 (United States)

2012-02-20

346

Sleeping Patterns of Afghan Unaccompanied Asylum-Seeking Adolescents: A Large Observational Study  

PubMed Central

Unaccompanied asylum-seeking children (UASC) have experienced multiple traumas and are a high-risk group for posttraumatic stress disorder (PTSD). The effects of trauma are known to be associated with sleep problems; indeed sleeping problems are core features of PTSD. However, there has been no systematic research examining the sleep of this high risk group of children. This study presents the first evidence on the sleeping patterns of Afghan UASC living in the UK. A total of 222 male Afghan children, aged 13–18, were interviewed using validated self-report questionnaires measuring sleeping patterns and PTSD. Overall, UASC patterns for bed time and rise time appear acculturated to the country of asylum. Mean UASC sleep onset latency scores were approximately 20 minutes greater compared with normative scores, which may be a reflection of UASC pre-migration and post-migration experiences. As expected, UASC who screened above the clinical cut-off for PTSD reported significantly greater sleep onset latency, increased nightmares, and less total sleep time compared to the non-PTSD group. The results may be of particular interest to clinicians given that, compared to screening for PTSD, screening for sleep problems may be a less culturally disputed form of initial assessment indicating distress in UASC. Similarly, the field of UASC and refugee child interventions is largely focused on trauma, yet sleep may provide a novel avenue for equally or more effective treatment.

Bronstein, Israel; Montgomery, Paul

2013-01-01

347

Coordinated phenotype switching with large-scale chromosome flip-flop inversion observed in bacteria.  

PubMed

Genome inversions are ubiquitous in organisms ranging from prokaryotes to eukaryotes. Typical examples can be identified by comparing the genomes of two or more closely related organisms, where genome inversion footprints are clearly visible. Although the evolutionary implications of this phenomenon are huge, little is known about the function and biological meaning of this process. Here, we report our findings on a bacterium that generates a reversible, large-scale inversion of its chromosome (about half of its total genome) at high frequencies of up to once every four generations. This inversion switches on or off bacterial phenotypes, including colony morphology, antibiotic susceptibility, hemolytic activity, and expression of dozens of genes. Quantitative measurements and mathematical analyses indicate that this reversible switching is stochastic but self-organized so as to maintain two forms of stable cell populations (i.e., small colony variant, normal colony variant) as a bet-hedging strategy. Thus, this heritable and reversible genome fluctuation seems to govern the bacterial life cycle; it has a profound impact on the course and outcomes of bacterial infections. PMID:22645353

Cui, Longzhu; Neoh, Hui-min; Iwamoto, Akira; Hiramatsu, Keiichi

2012-06-19

348

Electric fields with a large parallel component observed by the Freja spacecraft: Artifacts or real signals?  

NASA Astrophysics Data System (ADS)

Using plasma wave data sampled by the Freja spacecraft from the topside ionosphere during auroral conditions, the possible existence of electric fields with an intense parallel component (a few tens of millivolts per meter) with respect to the Earth's magnetic field is discussed. When Freja crosses large-amplitude solitary electromagnetic structures (?E~100mV/m and ?B~10nT, identified as being solitary kinetic Alfvén waves), strong electric spikes are sometimes detected along a direction almost parallel to the static magnetic field. The possible sources of errors due to the plasma inhomogeneities and/or to the magnetic connection between the electric probe and the spacecraft body are reviewed and discussed. In particular, using an indirect technique based on the reconstruction of the electric field hodograms, it is shown that these sources of errors have no influence on our conclusions. Unless unknown mechanisms strongly affect the validity of double-probe measurements in some circumstances, it is then concluded that an electric field with a parallel component 2-3 orders of magnitude larger than expected from the theory of kinetic Alfvén waves can develop in the topside ionosphere.

Chust, Thomas; Louarn, Philippe; Volwerk, Martin; de Feraudy, Hervé; Roux, Alain; Wahlund, Jan-Erik; Holback, Bengt

1998-01-01

349

Fermi Large Area Telescope Observations of the Cygnus Loop Supernova Remnant  

SciTech Connect

We present an analysis of the gamma-ray measurements by the Large Area Telescope (LAT) onboard the Fermi Gamma-ray Space Telescope in the region of the supernova remnant (SNR) Cygnus Loop (G74.0-8.5). We detect significant gamma-ray emission associated with the SNR in the energy band 0.2-100 GeV. The gamma-ray spectrum shows a break in the range 2-3 GeV. The gamma-ray luminosity is {approx} 1 x 10{sup 33} erg s{sup -1} between 1-100 GeV, much lower than those of other GeV-emitting SNRs. The morphology is best represented by a ring shape, with inner/outer radii 0{sup o}.7 {+-} 0{sup o}.1 and 1{sup o}.6 {+-} 0{sup o}.1. Given the association among X-ray rims, H{alpha} filaments and gamma-ray emission, we argue that gamma rays originate in interactions between particles accelerated in the SNR and interstellar gas or radiation fields adjacent to the shock regions. The decay of neutral pions produced in nucleon-nucleon interactions between accelerated hadrons and interstellar gas provides a reasonable explanation for the gamma-ray spectrum.

Katagiri, H.; /Ibaraki U., Mito; Tibaldo, L.; /INFN, Padua /Padua U. /Paris U., VI-VII; Ballet, J.; /Paris U., VI-VII; Giordano, F.; /Bari U. /Bari Polytechnic /INFN, Bari; Grenier, I.A.; /Paris U., VI-VII; Porter, T.A.; /Stanford U., HEPL /KIPAC, Menlo Park /SLAC; Roth, M.; /Washington U., Seattle; Tibolla, O.; /Wurzburg U.; Uchiyama, Y.; /Stanford U., HEPL /KIPAC, Menlo Park /SLAC; Yamazaki, R.; /Sagamihara, Aoyama Gakuin U.

2011-11-08

350

Observations of Energetic High Magnetic Field Pulsars with the Fermi Large Area Telescope  

NASA Technical Reports Server (NTRS)

We report the detection of gamma-ray pulsations from the high-magnetic-field rotation-powered pulsar PSR J1119.6127 using data from the Fermi Large Area Telescope. The gamma-ray light curve of PSR J1119.6127 shows a single, wide peak offset from the radio peak by 0.43 +/- 0.02 in phase. Spectral analysis suggests a power law of index 1.0 +/- 0.3(+0.4 -0.2) with an energy cut-off at 0.8 +/- 0.2(+2.0 -0.5) GeV. The first uncertainty is statistical and the second is systematic. We discuss the emission models of PSR J1119.6127 and demonstrate that despite the object's high surface magnetic field--near that of magnetars -- the field strength and structure in the gamma-ray emitting zone are apparently similar to those of typical young pulsars. Additionally, we present upper limits on the gamma-ray pulsed emission for the magnetically active PSR J1846.0258 in the supernova remnant Kesteven 75 and two other energetic high-Beta pulsars, PSRs J1718.3718 and J1734.3333. We explore possible explanations for the non-detection of these three objects, including peculiarities in their emission geometry.

Parent, D.; Kerr, M.; DenHartog, P. R.; Baring, M. G.; DeCesar, M. E.; Espinoza, C. M.; Harding, A. K.; Romani, R. W.; Stappers, B. W.; Watters, K.; Weltevrde, P.; Abdo, A. A.; Craig, H. A.; Kramer, M.; Lyne, A. G.

2011-01-01

351

Observational Study of Large Amplitude Longitudinal Oscillations in a Solar Filament  

NASA Astrophysics Data System (ADS)

On 20 August 2010 an energetic disturbance triggered damped large-amplitude longitudinal (LAL) oscillations in almost an entire filament. In the present work we analyze this periodic motion in the filament to characterize the damping and restoring mechanism of the oscillation. Our method involves placing slits along the axis of the filament at different angles with respect to the spine of the filament, finding the angle at which the oscillation is clearest, and fitting the resulting oscillation pattern to decaying sinusoidal and Bessel functions. These functions represent the equations of motion of a pendulum damped by mass accretion. With this method we determine the period and the decaying time of the oscillation. Our preliminary results support the theory presented by Luna and Karpen (2012) that the restoring force of LAL oscillations is solar gravity in the tubes where the threads oscillate, and the damping mechanism is the ongoing accumulation of mass onto the oscillating threads. Following an earlier paper, we have determined the magnitude and radius of curvature of the dipped magnetic flux tubes hosting a thread along the filament, as well as the mass accretion rate of the filament threads, via the fitted parameters.

Knizhnik, Kalman; Luna, Manuel; Muglach, Karin; Gilbert, Holly; Kucera, Therese; Karpen, Judith

2014-01-01

352

Phase Coherence of Large Amplitude MHD Waves in the Earth's Foreshock: Geotail Observations  

NASA Astrophysics Data System (ADS)

Large amplitude MHD turbulence is commonly found in the earth's foreshock region. It can be represented as a superposition of Fourier modes with characteristic frequency, amplitude, and phase. Nonlinear interactions between the Fourier modes are likely to produce finite correlation among the wave phases. For discussions of various transport processes of energetic particles, it is fundamentally important to determine whether the wave phases are randomly distributed (as assumed in quasi-linear theories) or they have a finite coherence. However, naive inspection of wave phases does not reveal anything, as the wave phase is sensitively related to the choice of origin of the coordinate, which should be arbitrary. Using a method based on a surrogate data technique and a fractal analysis, we analyzed Geotail magnetic field data to evaluate the phase coherence among the MHD waves in the earth's foreshock region. We show that the correlation of wave phases does exist, indicating that the nonlinear interactions between the waves is in progress. Furthermore, by introducing an index to represent the degree of the phase coherence, we discuss that the wave phases become more coherent as the turbulence amplitude increases, and also as the propagation angle of the most dominant wave mode becomes oblique. Details of the analysis as well as implications of the present results to transport processes of energetic particles will be discussed.

Hada, Tohru; Yamamoto, Eiko; Koga, Daiki

2003-06-01

353

THE FAINTEST RADIO SOURCE YET: EXPANDED VERY LARGE ARRAY OBSERVATIONS OF THE GRAVITATIONAL LENS SDSS J1004+4112  

SciTech Connect

We present new radio observations of the large-separation gravitationally lensed quasar SDSS J1004+4112, taken in a total of 6 hr of observations with the Expanded Very Large Array. The maps reach a thermal noise level of approximately 4 {mu}Jy. We detect four of the five lensed images at the 15-35 {mu}Jy level, representing a source of intrinsic flux density, after allowing for lensing magnification, of about 1 {mu}Jy, intrinsically probably the faintest radio source yet detected. This reinforces the utility of gravitational lensing in potentially allowing us to study nJy-level sources before the advent of the Square Kilometre Array. In an optical observation taken three months after the radio observation, image C is the brightest image, whereas the radio map shows flux density ratios consistent with previous optical observations. Future observations separated by a time delay will give the intrinsic flux ratios of the images in this source.

Jackson, N. [Jodrell Bank Centre for Astrophysics, School of Physics and Astronomy, University of Manchester, Alan Turing Building, Oxford Road, Manchester M13 9PL (United Kingdom)

2011-09-20

354

The large coronal transient of 10 June 1973. I - Observational description  

NASA Technical Reports Server (NTRS)

Ground-based and Skylab coronagraph observations are used to trace a coronal loop transient from its inception near the surface to a distance of 5 solar radii. Events in the lower solar atmosphere associated with this feature are outlined chronologically, and its physical appearance is described. The densities, mass, and energy of the transient are estimated, its shape is determined, and its typical and atypical characteristics are noted. It is inferred that this transient was caused by the emergence of an active region. It is shown that it was not immediately preceded by a flare and that the material at its leading edge did not decelerate appreciably, even at approximately 5 solar radii.

Hildner, E.; Gosling, J. T.; Macqueen, R. M.; Munro, R. H.; Poland, A. I.; Ross, C. L.

1975-01-01

355

Idiopathic generalized epilepsy: Phenotypic and electroencephalographic observations in a large cohort from South India  

PubMed Central

Purpose: We studied the phenotype and electroencephalographic (EEG) features, and therapeutic aspects of idiopathic generalized epilepsies (IGEs) in South Indian population. Patients and Methods: This prospective cross-sectional hospital-based study was carried out on non-consecutive 287 patients (age 22.2 ± 7.7 years; M:F = 139:148) with IGE syndrome. Their clinical and EEG observations were analyzed. Results: Majority of the patients had onset of seizures <20 years of age (n = 178; 62%). Thirty one patients (10.8%) had family history of epilepsy. Nearly half of them (49.9%) had <5 years of duration of seizures. The type of IGEs included Juvenile myoclonic epilepsy (JME): 115 (40.1%); IGE with generalized tonic-clonic seizures (GTCS) only: 102 (39.02%); childhood absence epilepsy (CAE): 35 (12.2%); GTCS on awakening: 15 (5.2%); Juvenile absence epilepsy (JAE): 11 (3.8%); and unclassified seizures: 9 (3.1%). The triggering factors noted in 45% were sleep deprivation (20%), non-compliance and stress in 5% each. The EEG (n = 280) showed epileptiform discharges in about 50% of patients. Epileptiform discharges during activation was observed in 40/249 patients (16.1%): Hyperventilation in 32 (12.8%) and photic stimulation in 19 (7.6%). The seizures were well controlled with anti-epileptic drugs (AEDs) in 232 (80.8%) patients and among them, 225 (78.4%) patients were on monotherapy. Valproate (n = 131) was the most frequently prescribed as monotherapy. Conclusions: This is one of the largest cohort of patients with IGE. This study reiterates the importance of segregating IGE syndrome and such analysis will aid to the current understanding and management.

Sinha, Sanjib; Pramod, M. N.; Dilipkumar, S.; Satishchandra, P.

2013-01-01

356

Fermi Large Area Telescope Observations of Markarian 421: The Missing Piece of its Spectral Energy Distribution  

NASA Astrophysics Data System (ADS)

We report on the ?-ray activity of the high-synchrotron-peaked BL Lacertae object Markarian 421 (Mrk 421) during the first 1.5 years of Fermi operation, from 2008 August 5 to 2010 March 12. We find that the Large Area Telescope (LAT) ?-ray spectrum above 0.3 GeV can be well described by a power-law function with photon index ? = 1.78 ± 0.02 and average photon flux F(> 0.3 GeV) = (7.23 ± 0.16) × 10-8 ph cm-2 s-1. Over this time period, the Fermi-LAT spectrum above 0.3 GeV was evaluated on seven-day-long time intervals, showing significant variations in the photon flux (up to a factor ~3 from the minimum to the maximum flux) but mild spectral variations. The variability amplitude at X-ray frequencies measured by RXTE/ASM and Swift/BAT is substantially larger than that in ?-rays measured by Fermi-LAT, and these two energy ranges are not significantly correlated. We also present the first results from the 4.5 month long multifrequency campaign on Mrk 421, which included the VLBA, Swift, RXTE, MAGIC, the F-GAMMA, GASP-WEBT, and other collaborations and instruments that provided excellent temporal and energy coverage of the source throughout the entire campaign (2009 January 19 to 2009 June 1). During this campaign, Mrk 421 showed a low activity at all wavebands. The extensive multi-instrument (radio to TeV) data set provides an unprecedented, complete look at the quiescent spectral energy distribution (SED) for this source. The broadband SED was reproduced with a leptonic (one-zone synchrotron self-Compton) and a hadronic model (synchrotron proton blazar). Both frameworks are able to describe the average SED reasonably well, implying comparable jet powers but very different characteristics for the blazar emission site.

Abdo, A. A.; Ackermann, M.; Ajello, M.; Baldini, L.; Ballet, J.; Barbiellini, G.; Bastieri, D.; Bechtol, K.; Bellazzini, R.; Berenji, B.; Blandford, R. D.; Bloom, E. D.; Bonamente, E.; Borgland, A. W.; Bouvier, A.; Bregeon, J.; Brez, A.; Brigida, M.; Bruel, P.; Buehler, R.; Buson, S.; Caliandro, G. A.; Cameron, R. A.; Cannon, A.; Caraveo, P. A.; Carrigan, S.; Casandjian, J. M.; Cavazzuti, E.; Cecchi, C.; Çelik, Ö.; Charles, E.; Chekhtman, A.; Chiang, J.; Ciprini, S.; Claus, R.; Cohen-Tanugi, J.; Conrad, J.; Cutini, S.; de Angelis, A.; de Palma, F.; Dermer, C. D.; Silva, E. do Couto e.; Drell, P. S.; Dubois, R.; Dumora, D.; Escande, L.; Favuzzi, C.; Fegan, S. J.; Finke, J.; Focke, W. B.; Fortin, P.; Frailis, M.; Fuhrmann, L.; Fukazawa, Y.; Fukuyama, T.; Funk, S.; Fusco, P.; Gargano, F.; Gasparrini, D.; Gehrels, N.; Georganopoulos, M.; Germani, S.; Giebels, B.; Giglietto, N.; Giommi, P.; Giordano, F.; Giroletti, M.; Glanzman, T.; Godfrey, G.; Grenier, I. A.; Guiriec, S.; Hadasch, D.; Hayashida, M.; Hays, E.; Horan, D.; Hughes, R. E.; Jóhannesson, G.; Johnson, A. S.; Johnson, W. N.; Kadler, M.; Kamae, T.; Katagiri, H.; Kataoka, J.; Knödlseder, J.; Kuss, M.; Lande, J.; Latronico, L.; Lee, S.-H.; Longo, F.; Loparco, F.; Lott, B.; Lovellette, M. N.; Lubrano, P.; Madejski, G. M.; Makeev, A.; Max-Moerbeck, W.; Mazziotta, M. N.; McEnery, J. E.; Mehault, J.; Michelson, P. F.; Mitthumsiri, W.; Mizuno, T.; Monte, C.; Monzani, M. E.; Morselli, A.; Moskalenko, I. V.; Murgia, S.; Nakamori, T.; Naumann-Godo, M.; Nishino, S.; Nolan, P. L.; Norris, J. P.; Nuss, E.; Ohsugi, T.; Okumura, A.; Omodei, N.; Orlando, E.; Ormes, J. F.; Ozaki, M.; Paneque, D.; Panetta, J. H.; Parent, D.; Pavlidou, V.; Pearson, T. J.; Pelassa, V.; Pepe, M.; Pesce-Rollins, M.; Pierbattista, M.; Piron, F.; Porter, T. A.; Rainò, S.; Rando, R.; Razzano, M.; Readhead, A.; Reimer, A.; Reimer, O.; Reyes, L. C.; Richards, J. L.; Ritz, S.; Roth, M.; Sadrozinski, H. F.-W.; Sanchez, D.; Sander, A.; Sgrò, C.; Siskind, E. J.; Smith, P. D.; Spandre, G.; Spinelli, P.; Stawarz, ?.; Stevenson, M.; Strickman, M. S.; Suson, D. J.; Takahashi, H.; Takahashi, T.; Tanaka, T.; Thayer, J. G.; Thayer, J. B.; Thompson, D. J.; Tibaldo, L.; Torres, D. F.; Tosti, G.; Tramacere, A.; Troja, E.; Usher, T. L.; Vandenbroucke, J.; Vasileiou, V.; Vianello, G.; Vilchez, N.; Vitale, V.; Waite, A. P.; Wang, P.; Wehrle, A. E.; Winer, B. L.; Wood, K. S.; Yang, Z.; Yatsu, Y.; Ylinen, T.; Zensus, J. A.; Ziegler, M.; Fermi LAT Collaboration; Aleksi?, J.; Antonelli, L. A.; Antoranz, P.; Backes, M.; Barrio, J. A.; Becerra González, J.; Bednarek, W.; Berdyugin, A.; Berger, K.; Bernardini, E.; Biland, A.; Blanch, O.; Bock, R. K.; Boller, A.; Bonnoli, G.; Bordas, P.; Borla Tridon, D.; Bosch-Ramon, V.; Bose, D.; Braun, I.; Bretz, T.; Camara, M.; Carmona, E.; Carosi, A.; Colin, P.; Colombo, E.; Contreras, J. L.; Cortina, J.; Covino, S.; Dazzi, F.; de Angelis, A.; De Cea del Pozo, E.; Delgado Mendez, C.; De Lotto, B.; De Maria, M.; De Sabata, F.; Diago Ortega, A.; Doert, M.; Domínguez, A.; Dominis Prester, D.; Dorner, D.; Doro, M.; Elsaesser, D.; Ferenc, D.; Fonseca, M. V.; Font, L.; García López, R. J.; Garczarczyk, M.; Gaug, M.; Giavitto, G.; Godinovi, N.; Hadasch, D.; Herrero, A.; Hildebrand, D.; Höhne-Mönch, D.; Hose, J.; Hrupec, D.; Jogler, T.; Klepser, S.; Krähenbühl, T.; Kranich, D.; Krause, J.; La Barbera, A.; Leonardo, E.; Lindfors, E.; Lombardi, S.; López, M.; Lorenz, E.; Majumdar, P.; Makariev, E.; Maneva, G.; Mankuzhiyil, N.; Mannheim, K.; Maraschi, L.; Mariotti, M.; Martínez, M.; Mazin, D.; Meucci, M.; Miranda, J. M.; Mirzoyan, R.; Miyamoto, H.; Moldón, J.; Moralejo, A.; Nieto, D.; Nilsson, K.; Orito, R.; Oya, I.; Paoletti, R.; Paredes, J. M.; Partini, S.; Pasanen, M.; Pauss, F.; Pegna, R. G.; Perez-Torres, M. A.; Persic, M.; Peruzzo, J.; Pochon, J.; Prada, F.; Prada Moroni, P. G.; Prandini, E.; Puchades, N.; Puljak, I.; Reichardt, T.; Rhode, W.; Ribó, M.; Rico, J.; Rissi, M.; Rügamer, S.; Saggion, A.; Saito, K.; Saito, T. Y.; Salvati, M.; Sánchez-Conde, M.; Satalecka, K.; Scalzotto, V.; Scapin, V.; Schultz, C.; Schweizer, T.; Shayduk, M.; Shore, S. N.; Sierpowska-Bartosik, A.; Sillanpää, A.; Sitarek, J.; Sobczynska, D.; Spanier, F.; Spiro, S.; Stamerra, A.; Steinke, B.; Storz, J.; Strah, N.; Struebig, J. C.; Suric, T.; Takalo, L. O.; Tavecchio, F.; Temnikov, P.; Terzi?, T.; Tescaro, D.; Teshima, M.; Vankov, H.; Wagner, R. M.; Weitzel, Q.; Zabalza, V.; Zandanel, F.; Zanin, R.; MAGIC Collaboration; Villata, M.; Raiteri, C.; Aller, H. D.; Aller, M. F.; Chen, W. P.; Jordan, B.; Koptelova, E.; Kurtanidze, O. M.; Lähteenmäki, A.; McBreen, B.; Larionov, V. M.; Lin, C. S.; Nikolashvili, M. G.; Reinthal, R.; Angelakis, E.; Capalbi, M.; Carramiñana, A.

2011-08-01

357

Seismic observations of large-scale deformation at the bottom of fast-moving plates  

NASA Astrophysics Data System (ADS)

We present a new tomographic model of azimuthal anisotropy in the upper mantle, DR2012, and discuss in details the geodynamical causes of this anisotropy. Our model improves upon DKP2005 seismic model (Debayle et al., 2005) through a larger dataset (expanded by a factor ˜3.7) and a new approach which allows us to better extract fundamental and higher-mode information. Our results confirm that on average, azimuthal anisotropy is only significant in the uppermost 200-250 km of the upper mantle where it decreases regularly with depth. We do not see a significant difference in the amplitude of anisotropy beneath fast oceanic plates, slow oceanic plates or continents. The anisotropy projected onto the direction of present plate motion shows a very specific relation with the plate velocity; it peaks in the asthenosphere around 150 km depth, it is very weak for plate velocities smaller than 3 cmyr, increases significantly between 3 and 5 cmyr, and saturates for plate velocities larger than 5 cmyr. Plate-scale present-day deformation is remarkably well and uniformly recorded beneath the fastest-moving plates (India, Coco, Nazca, Australia, Philippine Sea and Pacific plates). Beneath slower plates, plate-motion parallel anisotropy is only observed locally, which suggests that the mantle flow below these plates is not controlled by the lithospheric motion (a minimum plate velocity of around 4 cmyr is necessary for a plate to organize the flow in its underlying asthenosphere). The correlation of oceanic anisotropy with the actual plate motion in the shallow lithosphere is very weak. A better correlation is obtained with the fossil accretion velocity recorded by the gradient of local seafloor age. The transition between frozen-in and active anisotropy occurs across the typical age isotherm that defines the bottom of the thermal lithosphere around 1100°C. Under fast continents (mostly under Australia and India), the present-day velocity orients also the anisotropy in a depth range around 150-200 km depth which is not deeper than what is observed under oceans.

Debayle, Eric; Ricard, Yanick

2013-08-01

358

Seismic observations of large-scale deformation at the bottom of fast-moving plates  

NASA Astrophysics Data System (ADS)

We present a new tomographic model of azimuthal anisotropy in the upper mantle and discuss in details the geodynamical causes of this anisotropy. Our model improves upon DKP2005 seismic model (Debayle et al., 2005) through a larger dataset (expanded by a factor ~ 4) and a new approach which allows us to better extract fundamental and higher mode information. Our results confirm that on average, azimuthal anisotropy is only significant in the uppermost 200-250 km of the upper mantle where it decreases regularly with depth. We do not see a significant difference in the amplitude of anisotropy beneath fast oceanic plates, slow oceanic plates or continents. The anisotropy projected onto the direction of present plate motion shows a very specific relation with the plate velocity; it peaks in the asthenosphere around 150 km depth, it is very weak for plate velocities smaller than 3 cm yr-1, increases significantly between 3 and 5 cm yr-1, and saturates for plate velocities larger than 5 cm yr-1. Plate-scale present-day deformation is remarkably well and uniformly recorded beneath the fastest moving plates (India, Coco, Nazca, Australia, Philippine Sea and Pacific plates). Beneath slower plates, plate-motion parallel anisotropy is only observed locally, which suggests that the mantle flow below these plates is not controlled by the lithospheric motion (a minimum plate velocity of around 4 cm yr-1 is necessary for a plate to organize the flow in its underlying asthenosphere). The correlation of oceanic anisotropy with the actual plate motion in the shallow lithosphere is very weak. A better correlation is obtained with the fossil accretion velocity recorded by the gradient of local seafloor age. The transition between frozen-in and active anisotropy occurs across the typical age- isotherm that defines the bottom of the thermal lithosphere around 1100 °C. Under fast continents (mostly under Australia and India), the present day velocity orients also the anisotropy in a depth range around 150-200 km depth which is not deeper than what is observed under oceans.

Debayle, Eric; Ricard, Yanick

2014-05-01

359

Observation of electron plasma waves inside large amplitude electromagnetic pulses in a temporally growing plasma  

SciTech Connect

Observation of electron plasma waves excited inside high power ({approx}10 kW) short pulse ({approx}20 {mu}s) electromagnetic (em) waves interacting with a gaseous medium (argon) in the pressure range 0.2-2.5 mTorr is reported. The waves have long wavelength ({approx}13 cm) and get damped at time scales slower ({approx}3 {mu}s) than the plasma period (0.1-0.3 {mu}s), the energy conveyed to the medium lead to intense ionization (ion density n{sub i} {approx} 10{sup 11} cm{sup -3} and electron temperature T{sub e} {approx} 6-8 eV) and rapid growth of the plasma ({approx}10{sup 5} s{sup -1}) beyond the waves. Time frequency analysis of the generated oscillations indicate the presence of two principal frequencies centered around 3.8 MHz and 13.0 MHz with a spread {Delta}f {approx} 4 MHz, representing primarily two population of electrons in the plasma wave. The experimental results are in reasonable agreement with a model that considers spatiotemporal forces of the em wave on the medium, space charges and diffusion.

Pandey, Shail; Bhattacharjee, Sudeep; Sahu, Debaprasad [Department of Physics, Indian Institute of Technology, Kanpur-208016 (India)

2012-01-15

360

Data Curation for the Exploitation of Large Earth Observation Products Databases - The MEA system  

NASA Astrophysics Data System (ADS)

National Space Agencies under the umbrella of the European Space Agency are performing a strong activity to handle and provide solutions to Big Data and related knowledge (metadata, software tools and services) management and exploitation. The continuously increasing amount of long-term and of historic data in EO facilities in the form of online datasets and archives, the incoming satellite observation platforms that will generate an impressive amount of new data and the new EU approach on the data distribution policy make necessary to address technologies for the long-term management of these data sets, including their consolidation, preservation, distribution, continuation and curation across multiple missions. The management of long EO data time series of continuing or historic missions - with more than 20 years of data available already today - requires technical solutions and technologies which differ considerably from the ones exploited by existing systems. Several tools, both open source and commercial, are already providing technologies to handle data and metadata preparation, access and visualization via OGC standard interfaces. This study aims at describing the Multi-sensor Evolution Analysis (MEA) system and the Data Curation concept as approached and implemented within the ASIM and EarthServer projects, funded by the European Space Agency and the European Commission, respectively.

Mantovani, Simone; Natali, Stefano; Barboni, Damiano; Cavicchi, Mario; Della Vecchia, Andrea

2014-05-01

361

Suomi-NPP OMPS Observations of Large-Scale Air Pollution Events over China  

NASA Astrophysics Data System (ADS)

Severe smog episodes over China in January 2013 received worldwide attention. This air pollution is distinguished by high concentrations of gaseous pollutants (SO2 and NO2) and heavy loadings of fine particulate matter. To characterize these episodes, we employed the Ozone Mapping and Profiler Suite, Nadir Mapper (OMPS NM), a hyper-spectral UV spectrometer flying on the Suomi National Polar-orbiting Partnership (SNPP) spacecraft since October 2011. We developed an advanced algorithm to detect and quantify SO2 and NO2 in the lower atmosphere, and applied it to the OMPS NM observations. Here we report retrievals of SO2 and NO2, as well as UV aerosol index data for these pollution events. The columns of SO2 and NO2 and the areas covered by high pollutant concentrations are quantified; the results reveal for the first time the full extent (an area of ~10^6 km^2 containing up to 60 kt of SO2) of these episodes.

Yang, K.; Dickerson, R. R.; Carn, S. A.; Wang, J.; Ge, G.

2013-12-01

362

Large-Area Balloon-Borne Polarized Gamma Ray Observer (PoGO)  

SciTech Connect

We are developing a new balloon-borne instrument (PoGO), to measure polarization of soft gamma rays (30-200 keV) using asymmetry in azimuth angle distribution of Compton scattering. PoGO is designed to detect 10% polarization in 100mCrab sources in a 6-8 hour observation and bring a new dimension to studies on gamma ray emission/transportation mechanism in pulsars, AGNs, black hole binaries, and neutron star surface. The concept is an adaptation to polarization measurements of well-type phoswich counter consisting of a fast plastic scintillator (the detection part), a slow plastic scintillator (the active collimator) and a BGO scintillator (the bottom anti-counter). PoGO consists of close-packed array of 217 hexagonal well-type phoswich counters and has a narrow field-of-view ({approx} 5 deg{sup 2}) to reduce possible source confusion. A prototype instrument has been tested in the polarized soft gamma-ray beams at Advanced Photon Source (ANL) and at Photon Factory (KEK). On the results, the polarization dependence of EGS4 has been validated and that of Geant4 has been corrected.

Andersson, V.; Chen, P.; Kamae, T.; Madejski, G.; Mizuno, T.; Ng, J.; Tajima, H.; Thurston, T.; /SLAC; Bogaert, G.; /Ecole Polytechnique; Fukazawa, Y.; /Hiroshima U.; Saito, Y.; Takahashi, T.; /Sagamihara, Inst. Space Astron. Sci.; Barbier, L.; Bloser, P.; Harding, A.; Hunter, S.; Krizmanic, J.; Mitchell, J.; Streitmatter, R.; Fernholz, R.; Groth, E.; /NASA, Goddard /Princeton U. /Royal Inst. Tech., Kista /Stockholm U. /Tokyo Inst. Tech. /Yamagata U.

2005-06-30

363

NEAR-INFRARED CIRCULAR POLARIZATION IMAGES OF NGC 6334-V  

SciTech Connect

We present results from deep imaging linear and circular polarimetry of the massive star-forming region NGC 6334-V. These observations show high degrees of circular polarization (CP), as much as 22% in the K{sub s} band, in the infrared nebula associated with the outflow. The CP has an asymmetric positive/negative pattern and is very extended ({approx}80'' or 0.65 pc). Both the high CP and its extended size are larger than those seen in the Orion CP region. Three-dimensional Monte Carlo light-scattering models are used to show that the high CP may be produced by scattering from the infrared nebula followed by dichroic extinction by an optically thick foreground cloud containing aligned dust grains. Our results show not only the magnetic field orientation of around young stellar objects, but also the structure of circumstellar matter such as outflow regions and their parent molecular cloud along the line of sight. The detection of the large and extended CP in this source and the Orion nebula may imply the CP origin of the biological homochirality on Earth.

Kwon, Jungmi; Tamura, Motohide; Hashimoto, Jun; Kusakabe, Nobuhiko; Kandori, Ryo [National Astronomical Observatory of Japan, 2-21-1 Osawa, Mitaka, Tokyo 181-8588 (Japan); Lucas, Phil W.; Hough, James H. [Centre for Astrophysics Research, University of Hertfordshire, College Lane, Hatfield AL10 9AB (United Kingdom); Nakajima, Yasushi [Center of Information and Communication Technology, Hitotsubashi University, 2-1 Naka, Kunitachi, Tokyo 186-8601 (Japan); Nagayama, Takahiro [Department of Astrophysics, Nagoya University, Nagoya 464-8602 (Japan); Nagata, Tetsuya, E-mail: jungmi.kwon@nao.ac.jp [Department of Astronomy, Kyoto University, Kyoto 606-8502 (Japan)

2013-03-01

364

Fermi Large Area Telescope Observations of the Supernova Remnant G8.7-0.1  

NASA Astrophysics Data System (ADS)

We present a detailed analysis of the GeV gamma-ray emission toward the supernova remnant (SNR) G8.7-0.1 with the Large Area Telescope (LAT) on board the Fermi Gamma-ray Space Telescope. An investigation of the relationship between G8.7-0.1 and the TeV unidentified source HESS J1804-216 provides us with an important clue on diffusion process of cosmic rays if particle acceleration operates in the SNR. The GeV gamma-ray emission is extended with most of the emission in positional coincidence with the SNR G8.7-0.1 and a lesser part located outside the western boundary of G8.7-0.1. The region of the gamma-ray emission overlaps spatially connected molecular clouds, implying a physical connection for the gamma-ray structure. The total gamma-ray spectrum measured with LAT from 200 MeV-100 GeV can be described by a broken power-law function with a break of 2.4 ± 0.6 (stat) ± 1.2 (sys) GeV, and photon indices of 2.10 ± 0.06 (stat) ± 0.10 (sys) below the break and 2.70 ± 0.12 (stat) ± 0.14 (sys) above the break. Given the spatial association among the gamma rays, the radio emission of G8.7-0.1, and the molecular clouds, the decay of ?0s produced by particles accelerated in the SNR and hitting the molecular clouds naturally explains the GeV gamma-ray spectrum. We also find that the GeV morphology is not well represented by the TeV emission from HESS J1804-216 and that the spectrum in the GeV band is not consistent with the extrapolation of the TeV gamma-ray spectrum. The spectral index of the TeV emission is consistent with the particle spectral index predicted by a theory that assumes energy-dependent diffusion of particles accelerated in an SNR. We discuss the possibility that the TeV spectrum originates from the interaction of particles accelerated in G8.7-0.1 with molecular clouds, and we constrain the diffusion coefficient of the particles.

Ajello, M.; Allafort, A.; Baldini, L.; Ballet, J.; Barbiellini, G.; Bastieri, D.; Bechtol, K.; Bellazzini, R.; Berenji, B.; Blandford, R. D.; Bloom, E. D.; Bonamente, E.; Borgland, A. W.; Bregeon, J.; Brigida, M.; Bruel, P.; Buehler, R.; Buson, S.; Caliandro, G. A.; Cameron, R. A.; Caraveo, P. A.; Casandjian, J. M.; Cecchi, C.; Charles, E.; Chekhtman, A.; Ciprini, S.; Claus, R.; Cohen-Tanugi, J.; Cutini, S.; de Angelis, A.; de Palma, F.; Dermer, C. D.; Silva, E. do Couto e.; Drell, P. S.; Drlica-Wagner, A.; Dubois, R.; Favuzzi, C.; Fegan, S. J.; Ferrara, E. C.; Focke, W. B.; Frailis, M.; Fukazawa, Y.; Fukui, Y.; Fusco, P.; Gargano, F.; Gasparrini, D.; Germani, S.; Giglietto, N.; Giommi, P.; Giordano, F.; Giroletti, M.; Glanzman, T.; Godfrey, G.; Grove, J. E.; Guiriec, S.; Hadasch, D.; Hanabata, Y.; Harding, A. K.; Hayashi, K.; Hays, E.; Itoh, R.; Jóhannesson, G.; Johnson, A. S.; Kamae, T.; Katagiri, H.; Kataoka, J.; Knödlseder, J.; Kubo, H.; Kuss, M.; Lande, J.; Latronico, L.; Lee, S.-H.; Lionetto, A. M.; Longo, F.; Loparco, F.; Lovellette, M. N.; Lubrano, P.; Mazziotta, M. N.; Mehault, J.; Michelson, P. F.; Mizuno, T.; Moiseev, A. A.; Monte, C.; Monzani, M. E.; Morselli, A.; Moskalenko, I. V.; Murgia, S.; Nakamori, T.; Naumann-Godo, M.; Nishino, S.; Nolan, P. L.; Norris, J. P.; Nuss, E.; Ohno, M.; Ohsugi, T.; Okumura, A.; Omodei, N.; Orlando, E.; Ormes, J. F.; Paneque, D.; Parent, D.; Pelassa, V.; Pesce-Rollins, M.; Pierbattista, M.; Piron, F.; Porter, T. A.; Rainò, S.; Rando, R.; Reimer, A.; Reimer, O.; Reposeur, T.; Roth, M.; Sadrozinski, H. F.-W.; Sgrò, C.; Siskind, E. J.; Smith, P. D.; Spandre, G.; Spinelli, P.; Suson, D. J.; Tajima, H.; Takahashi, H.; Tanaka, T.; Thayer, J. G.; Thayer, J. B.; Tibaldo, L.; Tibolla, O.; Torres, D. F.; Tosti, G.; Tramacere, A.; Troja, E.; Uchiyama, Y.; Uehara, T.; Usher, T. L.; Vandenbroucke, J.; Van Etten, A.; Vasileiou, V.; Vianello, G.; Vilchez, N.; Vitale, V.; Waite, A. P.; Wang, P.; Winer, B. L.; Wood, K. S.; Yamamoto, H.; Yamazaki, R.; Yang, Z.; Yasuda, H.; Ziegler, M.; Zimmer, S.

2012-01-01

365

GeV Observations of Star-forming Galaxies with the Fermi Large Area Telescope  

NASA Astrophysics Data System (ADS)

Recent detections of the starburst galaxies M82 and NGC 253 by gamma-ray telescopes suggest that galaxies rapidly forming massive stars are more luminous at gamma-ray energies compared to their quiescent relatives. Building upon those results, we examine a sample of 69 dwarf, spiral, and luminous and ultraluminous infrared galaxies at photon energies 0.1-100 GeV using 3 years of data collected by the Large Area Telescope (LAT) on the Fermi Gamma-ray Space Telescope (Fermi). Measured fluxes from significantly detected sources and flux upper limits for the remaining galaxies are used to explore the physics of cosmic rays in galaxies. We find further evidence for quasi-linear scaling relations between gamma-ray luminosity and both radio continuum luminosity and total infrared luminosity which apply both to quiescent galaxies of the Local Group and low-redshift starburst galaxies (conservative P-values <~ 0.05 accounting for statistical and systematic uncertainties). The normalizations of these scaling relations correspond to luminosity ratios of log (L 0.1-100 GeV/L 1.4 GHz) = 1.7 ± 0.1(statistical) ± 0.2(dispersion) and log (L 0.1-100 GeV/L 8-1000 ?m) = -4.3 ± 0.1(statistical) ± 0.2(dispersion) for a galaxy with a star formation rate of 1 M ? yr-1, assuming a Chabrier initial mass function. Using the relationship between infrared luminosity and gamma-ray luminosity, the collective intensity of unresolved star-forming galaxies at redshifts 0 < z < 2.5 above 0.1 GeV is estimated to be 0.4-2.4 × 10-6 ph cm-2 s-1 sr-1 (4%-23% of the intensity of the isotropic diffuse component measured with the LAT). We anticipate that ~10 galaxies could be detected by their cosmic-ray-induced gamma-ray emission during a 10 year Fermi mission.

Ackermann, M.; Ajello, M.; Allafort, A.; Baldini, L.; Ballet, J.; Bastieri, D.; Bechtol, K.; Bellazzini, R.; Berenji, B.; Bloom, E. D.; Bonamente, E.; Borgland, A. W.; Bouvier, A.; Bregeon, J.; Brigida, M.; Bruel, P.; Buehler, R.; Buson, S.; Caliandro, G. A.; Cameron, R. A.; Caraveo, P. A.; Casandjian, J. M.; Cecchi, C.; Charles, E.; Chekhtman, A.; Cheung, C. C.; Chiang, J.; Cillis, A. N.; Ciprini, S.; Claus, R.; Cohen-Tanugi, J.; Conrad, J.; Cutini, S.; de Palma, F.; Dermer, C. D.; Digel, S. W.; Silva, E. do Couto e.; Drell, P. S.; Drlica-Wagner, A.; Favuzzi, C.; Fegan, S. J.; Fortin, P.; Fukazawa, Y.; Funk, S.; Fusco, P.; Gargano, F.; Gasparrini, D.; Germani, S.; Giglietto, N.; Giordano, F.; Glanzman, T.; Godfrey, G.; Grenier, I. A.; Guiriec, S.; Gustafsson, M.; Hadasch, D.; Hayashida, M.; Hays, E.; Hughes, R. E.; Jóhannesson, G.; Johnson, A. S.; Kamae, T.; Katagiri, H.; Kataoka, J.; Knödlseder, J.; Kuss, M.; Lande, J.; Longo, F.; Loparco, F.; Lott, B.; Lovellette, M. N.; Lubrano, P.; Madejski, G. M.; Martin, P.; Mazziotta, M. N.; McEnery, J. E.; Michelson, P. F.; Mizuno, T.; Monte, C.; Monzani, M. E.; Morselli, A.; Moskalenko, I. V.; Murgia, S.; Nishino, S.; Norris, J. P.; Nuss, E.; Ohno, M.; Ohsugi, T.; Okumura, A.; Omodei, N.; Orlando, E.; Ozaki, M.; Parent, D.; Persic, M.; Pesce-Rollins, M.; Petrosian, V.; Pierbattista, M.; Piron, F.; Pivato, G.; Porter, T. A.; Rainò, S.; Rando, R.; Razzano, M.; Reimer, A.; Reimer, O.; Ritz, S.; Roth, M.; Sbarra, C.; Sgrò, C.; Siskind, E. J.; Spandre, G.; Spinelli, P.; Stawarz, ?ukasz; Strong, A. W.; Takahashi, H.; Tanaka, T.; Thayer, J. B.; Tibaldo, L.; Tinivella, M.; Torres, D. F.; Tosti, G.; Troja, E.; Uchiyama, Y.; Vandenbroucke, J.; Vianello, G.; Vitale, V.; Waite, A. P.; Wood, M.; Yang, Z.

2012-08-01

366

Fermi Large Area Telescope Observations of the Supernova Remnant GS.7-0.1  

NASA Technical Reports Server (NTRS)

We present a detailed analysis of the GeV gamma-ray emission toward the supernova remnant (SNR) G8.7-0.1 with the Large Area Telescope (LAT) onboard the Fermi Gamma-ray Space Telescope. An investigation of the relationship among G8.7-0.1 and the TeV unidentified source HESS J1804-216 provides us with an important clue on diffusion process of cosmic rays if particle acceleration operates in the SNR. The GeV gamma-ray emission is extended with most of the emission in positional coincidence with the SNR G8.7-0.1 and a lesser part located outside the western boundary of G8.7-0.1. The region of the gamma-ray emission overlaps spatially-connected molecular clouds, implying a physical connection for the gamma-ray structure. The total gamma-ray spectrum measured with LAT from 200 MeV-100 GeV can be described by a broken power-law function with a break of 2.4 +/- 0.6 (stat) +/- 1.2 (sys) GeV, and photon indices of2.10 +/- 0.06 (stat) +/- 0.10 (sys) below the break and 2.70 +/- 0.12 (stat) +/- 0.14 (sys) above the break. Given the spatial association among the gamma rays, the radio emission ofG8.7-0.1, and the molecular clouds, the decay of pions produced by particles accelerated in the SNR and hitting the molecular clouds naturally explains the GeV gamma-ray spectrum. We also find that the GeV morphology is not well represented by the TeV emission from HESS Jl804-2l6 and that the spectrum in the Ge V band is not consistent with the extrapolation of the TeV gamma-ray spectrum. The spectral index of the TeV emission is consistent with the particle spectral index predicted by a theory that assumes energy-dependent diffusion of particles accelerated in an SNR. We discuss the possibility that the TeV-spectrum originates from the interaction of particles accelerated in G8.7-0.l with molecular clouds, and we constrain the diffusion coefficient of the particles.

Ferrara, E. C.; Hays, E.; Troja, E.; Moiseev, A. A.

2012-01-01

367

Fermi Large Area Telescope Observations of the Supernova Remnant GS.7-0.1  

NASA Technical Reports Server (NTRS)

We present a detailed analysis of the GeV gamma-ray emission toward the supernova remnant (SNR) G8.7-0.1 with the Large Area Telescope (LAT) on board the Fermi Gamma-ray Space Telescope. An investigation of the relationship among G8.7-0.l and the TeV unidentified source HESS J1804-216 provides us with an important clue on diffusion process of cosmic rays if particle acceleration operates in the SNR. The GeV gamma-ray emission is extended with most of the emission in positional coincidence with the SNR G8.7-0.l and a lesser part located outside the western boundary of G8.7-0.l. The region of the gamma-ray emission overlaps spatially-connected molecular clouds, implying a physical connection for the gamma-ray structure. The total gamma-ray spectrum measured with LAT from 200 MeV-100 GeV can be described by a broken power-law function with a break of 2.4 +/- 0.6 (stat) +/- 1.2 (sys) GeV, and photon indices of 2.10 +/- 0.06 (stat) +/- 0.10 (sys) below the break and 2.70 +/- 0.12 (stat) +/- 0.l4 (sys) above the break. Given the spatial association among the gamma rays, the radio emission of G8.7-0.1, and the molecular clouds, the decay of 1IoS produced by particles accelerated in the SNR and hitting the molecular clouds naturally explains the GeV gamma-ray spectrum. We also find that the GeV morphology is not well represented by the TeV emission from HESS J1804-216 and that the spectrum in the GeV band is not consistent with the extrapolation of the TeV gamma-ray spectrum. The spectral index of the TeV emission is consistent with the particle spectral index predicted by a theory that assumes energy-dependent diffusion of particles accelerated in an SNR. We discuss the possibility that the TeV spectrum originates from the interaction of particles accelerated in G8.7-0.1 with molecular clouds, and we constrain the diffusion coefficient of the particles.

Ajello, M.; Allafort, A.; Baldini, L.; Ballet, J.; Barbiellini, G.; Bastieri, D.; Bechtol, K.; Bellazzini, R.; Berenji, B.; Blandford, R. D.; Bloom, E. D.; Bonamente, E.; Borgland, A. W.; Bregeon, J.; Brigida, M.; Bruel, P.; Buehler, R.; Buson, S.; Caliandro, G. A.; Cameron, R. A.; Ferrara, E. C.; Harding, A. K.; Hays, E.; Moiseev, A. A.; Troja, E.

2011-01-01

368

FERMI LARGE AREA TELESCOPE OBSERVATIONS OF THE SUPERNOVA REMNANT G8.7-0.1  

SciTech Connect

We present a detailed analysis of the GeV gamma-ray emission toward the supernova remnant (SNR) G8.7-0.1 with the Large Area Telescope (LAT) on board the Fermi Gamma-ray Space Telescope. An investigation of the relationship between G8.7-0.1 and the TeV unidentified source HESS J1804-216 provides us with an important clue on diffusion process of cosmic rays if particle acceleration operates in the SNR. The GeV gamma-ray emission is extended with most of the emission in positional coincidence with the SNR G8.7-0.1 and a lesser part located outside the western boundary of G8.7-0.1. The region of the gamma-ray emission overlaps spatially connected molecular clouds, implying a physical connection for the gamma-ray structure. The total gamma-ray spectrum measured with LAT from 200 MeV-100 GeV can be described by a broken power-law function with a break of 2.4 {+-} 0.6 (stat) {+-} 1.2 (sys) GeV, and photon indices of 2.10 {+-} 0.06 (stat) {+-} 0.10 (sys) below the break and 2.70 {+-} 0.12 (stat) {+-} 0.14 (sys) above the break. Given the spatial association among the gamma rays, the radio emission of G8.7-0.1, and the molecular clouds, the decay of {pi}{sup 0}s produced by particles accelerated in the SNR and hitting the molecular clouds naturally explains the GeV gamma-ray spectrum. We also find that the GeV morphology is not well represented by the TeV emission from HESS J1804-216 and that the spectrum in the GeV band is not consistent with the extrapolation of the TeV gamma-ray spectrum. The spectral index of the TeV emission is consistent with the particle spectral index predicted by a theory that assumes energy-dependent diffusion of particles accelerated in an SNR. We discuss the possibility that the TeV spectrum originates from the interaction of particles accelerated in G8.7-0.1 with molecular clouds, and we constrain the diffusion coefficient of the particles.

Ajello, M.; Allafort, A.; Bechtol, K.; Berenji, B.; Blandford, R. D.; Bloom, E. D.; Borgland, A. W.; Buehler, R.; Cameron, R. A. [W. W. Hansen Experimental Physics Laboratory, Kavli Institute for Particle Astrophysics and Cosmology, Department of Physics and SLAC National Accelerator Laboratory, Stanford University, Stanford, CA 94305 (United States); Baldini, L.; Bellazzini, R.; Bregeon, J. [Istituto Nazionale di Fisica Nucleare, Sezione di Pisa, I-56127 Pisa (Italy); Ballet, J. [Laboratoire AIM, CEA-IRFU/CNRS/Universite Paris Diderot, Service d'Astrophysique, CEA Saclay, 91191 Gif sur Yvette (France); Barbiellini, G. [Istituto Nazionale di Fisica Nucleare, Sezione di Trieste, I-34127 Trieste (Italy); Bastieri, D.; Buson, S. [Istituto Nazionale di Fisica Nucleare, Sezione di Padova, I-35131 Padova (Italy); Bonamente, E. [Istituto Nazionale di Fisica Nucleare, Sezione di Perugia, I-06123 Perugia (Italy); Brigida, M. [Dipartimento di Fisica 'M. Merlin' dell'Universita e del Politecnico di Bari, I-70126 Bari (Italy); Bruel, P. [Laboratoire Leprince-Ringuet, Ecole polytechnique, CNRS/IN2P3, Palaiseau (France); Caliandro, G. A., E-mail: hanabata@hep01.hepl.hiroshima-u.ac.jp, E-mail: katagiri@mx.ibaraki.ac.jp [Institut de Ciencies de l'Espai (IEEE-CSIC), Campus UAB, 08193 Barcelona (Spain); and others

2012-01-01

369

FERMI LARGE AREA TELESCOPE OBSERVATIONS OF MARKARIAN 421: THE MISSING PIECE OF ITS SPECTRAL ENERGY DISTRIBUTION  

SciTech Connect

We report on the {gamma}-ray activity of the high-synchrotron-peaked BL Lacertae object Markarian 421 (Mrk 421) during the first 1.5 years of Fermi operation, from 2008 August 5 to 2010 March 12. We find that the Large Area Telescope (LAT) {gamma}-ray spectrum above 0.3 GeV can be well described by a power-law function with photon index {Gamma} = 1.78 {+-} 0.02 and average photon flux F(> 0.3 GeV) = (7.23 {+-} 0.16) x 10{sup -8} ph cm{sup -2} s{sup -1}. Over this time period, the Fermi-LAT spectrum above 0.3 GeV was evaluated on seven-day-long time intervals, showing significant variations in the photon flux (up to a factor {approx}3 from the minimum to the maximum flux) but mild spectral variations. The variability amplitude at X-ray frequencies measured by RXTE/ASM and Swift/BAT is substantially larger than that in {gamma}-rays measured by Fermi-LAT, and these two energy ranges are not significantly correlated. We also present the first results from the 4.5 month long multifrequency campaign on Mrk 421, which included the VLBA, Swift, RXTE, MAGIC, the F-GAMMA, GASP-WEBT, and other collaborations and instruments that provided excellent temporal and energy coverage of the source throughout the entire campaign (2009 January 19 to 2009 June 1). During this campaign, Mrk 421 showed a low activity at all wavebands. The extensive multi-instrument (radio to TeV) data set provides an unprecedented, complete look at the quiescent spectral energy distribution (SED) for this source. The broadband SED was reproduced with a leptonic (one-zone synchrotron self-Compton) and a hadronic model (synchrotron proton blazar). Both frameworks are able to describe the average SED reasonably well, implying comparable jet powers but very different characteristics for the blazar emission site.

Abdo, A. A. [National Research Council Research Associate, National Academy of Sciences, Washington, DC 20001 (United States); Ackermann, M.; Ajello, M.; Bechtol, K.; Berenji, B.; Blandford, R. D.; Bloom, E. D.; Borgland, A. W.; Buehler, R. [W. W. Hansen Experimental Physics Laboratory, Kavli Institute for Particle Astrophysics and Cosmology, Department of Physics and SLAC National Accelerator Laboratory, Stanford University, Stanford, CA 94305 (United States); Baldini, L.; Bellazzini, R.; Bregeon, J.; Brez, A. [Istituto Nazionale di Fisica Nucleare, Sezione di Pisa, I-56127 Pisa (Italy); Ballet, J. [Laboratoire AIM, CEA-IRFU/CNRS/Universite Paris Diderot, Service d'Astrophysique, CEA Saclay, 91191 Gif sur Yvette (France); Barbiellini, G. [Istituto Nazionale di Fisica Nucleare, Sezione di Trieste, I-34127 Trieste (Italy); Bastieri, D. [Istituto Nazionale di Fisica Nucleare, Sezione di Padova, I-35131 Padova (Italy); Bonamente, E. [Istituto Nazionale di Fisica Nucleare, Sezione di Perugia, I-06123 Perugia (Italy); Bouvier, A. [Santa Cruz Institute for Particle Physics, Department of Physics and Department of Astronomy and Astrophysics, University of California at Santa Cruz, Santa Cruz, CA 95064 (United States); Brigida, M. [Dipartimento di Fisica 'M. Merlin' dell'Universita e del Politecnico di Bari, I-70126 Bari (Italy); Bruel, P., E-mail: dpaneque@mppmu.mpg.de, E-mail: anita.reimer@uibk.ac.at, E-mail: georgano@umbc.edu, E-mail: justin.finke@nrl.navy.mil, E-mail: diegot@ifae.es [Laboratoire Leprince-Ringuet, Ecole polytechnique, CNRS/IN2P3, Palaiseau (France)

2011-08-01

370

FERMI LARGE AREA TELESCOPE OBSERVATIONS OF THE SUPERNOVA REMNANT W28 (G6.4-0.1)  

SciTech Connect

We present detailed analysis of two gamma-ray sources, 1FGL J1801.3-2322c and 1FGL J1800.5-2359c, that have been found toward the supernova remnant (SNR) W28 with the Large Area Telescope (LAT) on board the Fermi Gamma-ray Space Telescope. 1FGL J1801.3-2322c is found to be an extended source within the boundary of SNR W28, and to extensively overlap with the TeV gamma-ray source HESS J1801-233, which is associated with a dense molecular cloud interacting with the SNR. The gamma-ray spectrum measured with the LAT from 0.2 to 100 GeV can be described by a broken power-law function with a break at {approx}1 GeV and photon indices of 2.09 {+-} 0.08 (stat) {+-} 0.28 (sys) below the break and 2.74 {+-} 0.06 (stat) {+-} 0.09 (sys) above the break. Given the clear association between HESS J1801-233 and the shocked molecular cloud and a smoothly connected spectrum in the GeV-TeV band, we consider the origin of the gamma-ray emission in both GeV and TeV ranges to be the interaction between particles accelerated in the SNR and the molecular cloud. The decay of neutral pions produced in interactions between accelerated hadrons and dense molecular gas provides a reasonable explanation for the broadband gamma-ray spectrum. 1FGL J1800.5-2359c, located outside the southern boundary of SNR W28, cannot be resolved. An upper limit on the size of the gamma-ray emission was estimated to be {approx}16' using events above {approx}2 GeV under the assumption of a circular shape with uniform surface brightness. It appears to coincide with the TeV source HESS J1800-240B, which is considered to be associated with a dense molecular cloud that contains the ultra compact H II region W28A2 (G5.89-0.39). We found no significant gamma-ray emission in the LAT energy band at the positions of TeV sources HESS J1800-230A and HESS J1800-230C. The LAT data for HESS J1800-230A combined with the TeV data points indicate a spectral break between 10 GeV and 100 GeV.

Abdo, A. A. [Space Science Division, Naval Research Laboratory, Washington, DC 20375 (United States); Ackermann, M.; Ajello, M.; Allafort, A.; Bechtol, K.; Berenji, B.; Blandford, R. D.; Bloom, E. D.; Borgland, A. W.; Bouvier, A. [W. W. Hansen Experimental Physics Laboratory, Kavli Institute for Particle Astrophysics and Cosmology, Department of Physics and SLAC National Accelerator Laboratory, Stanford University, Stanford, CA 94305 (United States); Baldini, L.; Bellazzini, R.; Bregeon, J. [Istituto Nazionale di Fisica Nucleare, Sezione di Pisa, I-56127 Pisa (Italy); Ballet, J. [Laboratoire AIM, CEA-IRFU/CNRS/Universite Paris Diderot, Service d'Astrophysique, CEA Saclay, 91191 Gif sur Yvette (France); Barbiellini, G. [Istituto Nazionale di Fisica Nucleare, Sezione di Trieste, I-34127 Trieste (Italy); Bastieri, D. [Istituto Nazionale di Fisica Nucleare, Sezione di Padova, I-35131 Padova (Italy); Bonamente, E. [Istituto Nazionale di Fisica Nucleare, Sezione di Perugia, I-06123 Perugia (Italy); Brandt, T. J. [Centre d'Etude Spatiale des Rayonnements, CNRS/UPS, BP 44346, F-30128 Toulouse Cedex 4 (France); Brigida, M. [Dipartimento di Fisica 'M. Merlin' dell'Universita e del Politecnico di Bari, I-70126 Bari (Italy); Bruel, P., E-mail: htajima@slac.stanford.ed, E-mail: ttanaka@slac.stanford.ed, E-mail: uchiyama@slac.stanford.ed, E-mail: katagiri@hep01.hepl.hiroshima-u.ac.j [Laboratoire Leprince-Ringuet, Ecole polytechnique, CNRS/IN2P3, Palaiseau (France)

2010-07-20

371

Large area balloon borne Polarized Gamma ray Observer ( PoGO)  

NASA Astrophysics Data System (ADS)

Polarimetry has proven to be a powerful diagnostic tool in optical and radio astronomy. In the X-ray range, a wide variety of compact objects is expected to provide polarization between a few per cent to 50 per cent, with polarization measurements providing insights on the geometry of accreting sources, the effects of intense magnetic fields, and tests of general relativity. PoGO is an instrument designed to detect 10% polarization of a bright source (100 mCrab) in the energy range 25-200 keV within a single 6 hour balloon flight. Prime targets for PoGO will be super massive black holes, galactic binaries, accreting neutron stars, pulsars, and Seyfert galaxies. In one flight PoGO will be able to determine the Crab pulsar polarization at a 20 sigma level according to a detailed simulation of the instrument. The instrument uses Compton scattering and photo-absorption in an array of 400 well-type phoswich detectors. Its passive and active collimators select a 5 square degree observation cone, and suppress the background down to 10 mCrab. A ``proof of principle'' prototype detector segment has been built and tested at Argonne National Laboratory. The prototype behaved as predicted by simulation and gave a modulation factor of 41% at 60 keV. Two possible designs of PoGO are being studied, aiming for a first balloon flight in 2007. PoGO has been selected by NASA as a Research Opportunity in Space Science Program.

Bogaert, G.; Pogo Collaboration

372

Large-Area Balloon-Borne Polarized Gamma Ray Observer (PoGO)  

SciTech Connect

We are developing a new balloon-borne instrument (PoGO), to measure polarization of soft gamma rays (25-200 keV) using asymmetry in azimuth angle distribution of Compton scattering. PoGO will detect 10% polarization in 100mCrab sources in a 6-8 hour observation and bring a new dimension to studies on gamma ray emission/transportation mechanism in pulsars, AGNs, black hole binaries, and neutron star surface. The concept is an adaptation to polarization measurements of well-type phoswich counter technology used in balloon-borne experiments (Welcome-1) and AstroE2 Hard X-ray Detector. PoGO consists of close-packed array of 397 hexagonal well-type phoswich counters. Each unit is composed of a long thin tube (well) of slow plastic scintillator, a solid rod of fast plastic scintillator, and a short BGO at the base. A photomultiplier coupled to the end of the BGO detects light from all 3 scintillators. The rods with decay times < 10 ns, are used as the active elements; while the wells and BGOs, with decay times {approx}250 ns are used as active anti-coincidence. The fast and slow signals are separated out electronically. When gamma rays entering the field-of-view (fwhm {approx} 3deg{sup 2}) strike a fast scintillator, some are Compton scattered. A fraction of the scattered photons are absorbed in another rod (or undergo a second scatter). A valid event requires one clean fast signal of pulse-height compatible with photo-absorption (> 20keV) and one or more compatible with Compton scattering (< 10keV). Studies based on EGS4 (with polarization features) and Geant4 predict excellent background rejection and high sensitivity.

Blanford, R.

2005-04-06

373

Fermi large area telescope observations of the cosmic-ray induced ?-ray emission of the Earth’s atmosphere  

Microsoft Academic Search

We report on measurements of the cosmic-ray induced gamma-ray emission of\\u000aEarth's atmosphere by the Large Area Telescope onboard the Fermi Gamma-ray\\u000aSpace Telescope. The LAT has observed the Earth during its commissioning phase\\u000aand with a dedicated Earth-limb following observation in September 2008. These\\u000ameasurements yielded 6.4 x 10^6 photons with energies >100MeV and ~250hours\\u000atotal livetime for the

A. A. Abdo; M. Ackermann; M. Ajello; W. B. Atwood; L. Baldini; J. Ballet; G. Barbiellini; D. Bastieri; B. M. Baughman; K. Bechtol; R. Bellazzini; B. Berenji; E. D. Bloom; E. Bonamente; A. W. Borgland; A. Bouvier; J. Bregeon; A. Brez; M. Brigida; P. Bruel; R. Buehler; T. H. Burnett; S. Buson; G. A. Caliandro; R. A. Cameron; P. A. Caraveo; J. M. Casandjian; C. Cecchi; Ö. Çelik; E. Charles; A. Chekhtman; J. Chiang; S. Ciprini; R. Claus; J. Cohen-Tanugi; J. Conrad; F. de Palma; S. W. Digel; E. do Couto e Silva; P. S. Drell; R. Dubois; D. Dumora; C. Farnier; C. Favuzzi; S. J. Fegan; W. B. Focke; P. Fortin; M. Frailis; Y. Fukazawa; S. Funk; P. Fusco; F. Gargano; N. Giglietto; S. Germani; B. Giebels; F. Giordano; T. Glanzman; G. Godfrey; I. A. Grenier; M.-H. Grondin; J. E. Grove; L. Guillemot; S. Guiriec; E. Hays; D. Horan; R. E. Hughes; G. Jóhannesson; A. S. Johnson; T. J. Johnson; W. N. Johnson; T. Kamae; H. Katagiri; J. Kataoka; N. Kawai; M. Kerr; J. Knödlseder; M. Kuss; J. Lande; L. Latronico; M. Lemoine-Goumard; F. Longo; F. Loparco; B. Lott; M. N. Lovellette; P. Lubrano; A. Makeev; M. N. Mazziotta; J. E. McEnery; C. Meurer; P. F. Michelson; W. Mitthumsiri; T. Mizuno; C. Monte; M. E. Monzani; A. Morselli; I. V. Moskalenko; S. Murgia; P. L. Nolan; J. P. Norris; E. Nuss; T. Ohsugi; A. Okumura; N. Omodei; E. Orlando; J. F. Ormes; D. Paneque; J. H. Panetta; D. Parent; V. Pelassa; M. Pepe; M. Pesce-Rollins; F. Piron; T. A. Porter; S. Rainò; R. Rando; M. Razzano; A. Y. Rodriguez; O. Reimer; T. Reposeur; L. S. Rochester; M. Roth; H. F.-W. Sadrozinski; A. Sander; P. M. Saz Parkinson; C. Sgrò; G. H. Share; E. J. Siskind; D. A. Smith; P. D. Smith; G. Spandre; P. Spinelli; M. S. Strickman; D. J. Suson; H. Takahashi; T. Tanaka; J. B. Thayer; J. G. Thayer; D. J. Thompson; L. Tibaldo; D. F. Torres; G. Tosti; A. Tramacere; Y. Uchiyama; T. L. Usher; V. Vasileiou; N. Vilchez; V. Vitale; A. P. Waite; P. Wang; B. L. Winer; K. S. Wood; T. Ylinen; M. Ziegler

2009-01-01

374

Fermi large area telescope observations of the cosmic-ray induced ?-ray emission of the Earth's atmosphere  

NASA Astrophysics Data System (ADS)

We report on measurements of the cosmic-ray induced ?-ray emission of Earth’s atmosphere by the Large Area Telescope on board the Fermi Gamma-ray Space Telescope. The Large Area Telescope has observed the Earth during its commissioning phase and with a dedicated Earth limb following observation in September 2008. These measurements yielded ˜6.4×106 photons with energies >100MeV and ˜250 hours total live time for the highest quality data selection. This allows the study of the spatial and spectral distributions of these photons with unprecedented detail. The spectrum of the emission—often referred to as Earth albedo gamma-ray emission—has a power-law shape up to 500 GeV with spectral index ?=2.79±0.06.

Abdo, A. A.; Ackermann, M.; Ajello, M.; Atwood, W. B.; Baldini, L.; Ballet, J.; Barbiellini, G.; Bastieri, D.; Baughman, B. M.; Bechtol, K.; Bellazzini, R.; Berenji, B.; Bloom, E. D.; Bonamente, E.; Borgland, A. W.; Bouvier, A.; Bregeon, J.; Brez, A.; Brigida, M.; Bruel, P.; Buehler, R.; Burnett, T. H.; Buson, S.; Caliandro, G. A.; Cameron, R. A.; Caraveo, P. A.; Casandjian, J. M.; Cecchi, C.; Çelik, Ö.; Charles, E.; Chekhtman, A.; Chiang, J.; Ciprini, S.; Claus, R.; Cohen-Tanugi, J.; Conrad, J.; de Palma, F.; Digel, S. W.; Do Couto E Silva, E.; Drell, P. S.; Dubois, R.; Dumora, D.; Farnier, C.; Favuzzi, C.; Fegan, S. J.; Focke, W. B.; Fortin, P.; Frailis, M.; Fukazawa, Y.; Funk, S.; Fusco, P.; Gargano, F.; Gehrels, N.; Germani, S.; Giebels, B.; Giglietto, N.; Giordano, F.; Glanzman, T.; Godfrey, G.; Grenier, I. A.; Grondin, M.-H.; Grove, J. E.; Guillemot, L.; Guiriec, S.; Hays, E.; Horan, D.; Hughes, R. E.; Jóhannesson, G.; Johnson, A. S.; Johnson, T. J.; Johnson, W. N.; Kamae, T.; Katagiri, H.; Kataoka, J.; Kawai, N.; Kerr, M.; Knödlseder, J.; Kuss, M.; Lande, J.; Latronico, L.; Lemoine-Goumard, M.; Longo, F.; Loparco, F.; Lott, B.; Lovellette, M. N.; Lubrano, P.; Makeev, A.; Mazziotta, M. N.; McEnery, J. E.; Meurer, C.; Michelson, P. F.; Mitthumsiri, W.; Mizuno, T.; Monte, C.; Monzani, M. E.; Morselli, A.; Moskalenko, I. V.; Murgia, S.; Nolan, P. L.; Norris, J. P.; Nuss, E.; Ohsugi, T.; Okumura, A.; Omodei, N.; Orlando, E.; Ormes, J. F.; Paneque, D.; Panetta, J. H.; Parent, D.; Pelassa, V.; Pepe, M.; Pesce-Rollins, M.; Piron, F.; Porter, T. A.; Rainò, S.; Rando, R.; Razzano, M.; Reimer, A.; Reimer, O.; Reposeur, T.; Rochester, L. S.; Rodriguez, A. Y.; Roth, M.; Sadrozinski, H. F.-W.; Sander, A.; Saz Parkinson, P. M.; Sgrò, C.; Share, G. H.; Siskind, E. J.; Smith, D. A.; Smith, P. D.; Spandre, G.; Spinelli, P.; Strickman, M. S.; Suson, D. J.; Takahashi, H.; Tanaka, T.; Thayer, J. B.; Thayer, J. G.; Thompson, D. J.; Tibaldo, L.; Torres, D. F.; Tosti, G.; Tramacere, A.; Uchiyama, Y.; Usher, T. L.; Vasileiou, V.; Vilchez, N.; Vitale, V.; Waite, A. P.; Wang, P.; Winer, B. L.; Wood, K. S.; Ylinen, T.; Ziegler, M.

2009-12-01

375

Beam rounders for circular colliders  

SciTech Connect

By means of linear optics, an arbitrary uncoupled beam can be locally transformed into a round (rotation-invariant) state and then back. This provides an efficient way to round beams in the interaction region of circular colliders.

A. Burov and S. Nagaitsev

2002-12-10

376

Biological Synthesis of Circular Polypeptides*  

PubMed Central

Here, we review the use of different biochemical approaches for biological synthesis of circular or backbone-cyclized proteins and peptides. These methods allow the production of circular polypeptides either in vitro or in vivo using standard recombinant DNA expression techniques. Protein circularization can significantly impact protein engineering and research in protein folding. Basic polymer theory predicts that circularization should lead to a net thermodynamic stabilization of a folded protein by reducing the entropy associated with the unfolded state. Protein cyclization also provides a valuable tool for exploring the effects of topology on protein folding kinetics. Furthermore, the biological production of cyclic polypeptides makes possible the production of cyclic polypeptide libraries. The generation of such libraries, which was previously restricted to the domain of synthetic chemists, now offers biologists access to highly diverse and stable molecular libraries for probing protein structure and function.

Aboye, Teshome L.; Camarero, Julio A.

2012-01-01

377

Prevalence of joint replacement surgery in rheumatoid arthritis patients: cross-sectional analysis in a large observational cohort in Japan  

Microsoft Academic Search

The purpose of this study was to describe the prevalence of total joint arthroplasty (TJA) in Japanese rheumatoid arthritis\\u000a (RA) patients undergoing conventional drug treatment in a large observational cohort in Japan. A total of 5,177 RA patients\\u000a were studied for the prevalence of TJA, who were enrolled in the NinJa database during the fiscal year of 2006. The cases

Jinju Nishino; Sakae Tanaka; Toshihiro Matsui; Toshihito Mori; Keita Nishimura; Yoshito Eto; Atsushi Kaneko; Koichiro Saisho; Masayuki Yasuda; Noriyuki Chiba; Yasuhiko Yoshinaga; Yukihiko Saeki; Atsuhito Seki; Shigeto Tohma

2009-01-01

378

Large-scale, prospective, observational studies in patients with psoriasis and psoriatic arthritis: A systematic and critical review  

Microsoft Academic Search

Background  Observational studies, if conducted appropriately, play an important role in the decision-making process providing invaluable\\u000a information on effectiveness, patient-reported outcomes and costs in a real-world environment. We conducted a systematic review\\u000a of large-scale, prospective, cohort studies with the aim of (a) summarising design characteristics, the interventions or aspects\\u000a of the disease studied and the outcomes measured and (b) investigating methodological

Sue Langham; Julia Langham; Hans-Peter Goertz; Mark Ratcliffe

2011-01-01