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1

GRAIN ALIGNMENT IN OMC1 AS DEDUCED FROM OBSERVED LARGE CIRCULAR POLARIZATION  

SciTech Connect

The properties of polarization in scattered light by aligned ellipsoidal grains are investigated with the Fredholm integral equation method and the T-matrix method, and the results are applied to the observed circular polarization in OMC1. We assume that the grains are composed of silicates and are ellipsoidal (oblate, prolate, or triaxial ellipsoid) in shape with a typical axial ratio of 2:1. The angular dependence of circular polarization p{sub c} on directions of incident and scattered light is investigated with spherical harmonics and associated Legendre polynomials. The degree of circular polarization p{sub c} also depends on the Rayleigh reduction factor R, which is a measure of imperfect alignment. We find that p{sub c} is approximately proportional to R for grains with |m|x {sub eq} {approx}< 3 - 5, where x {sub eq} is the dimensionless size parameter and m is the refractive index of the grain. Models that include those grains can explain the observed large circular polarization in the near-infrared, {approx}15%, in the southeast region of the BN object in OMC1, if the directions of incidence and scattering of light is optimal, and if grain alignment is strong, i.e., R {approx}> 0.5. Such a strong alignment cannot be explained by the Davis-Greenstein mechanism; we prefer instead an alternative mechanism driven by radiative torques. If the grains are mixed with silicates and ice, the degree of circular polarization p{sub c} decreases in the 3 {mu}m ice feature, while that of linear polarization increases. This wavelength dependence is different from that predicted in a process of dichroic extinction.

Matsumura, M. [Faculty of Education, Kagawa University, Takamatsu, Kagawa 760-8522 (Japan); Bastien, P. [Departement de physique and Centre de recherche en astrophysique du Quebec, Universite de Montreal, C.P.6128, Succursale Centre-ville, Montreal, Quebec, H3C 3J7 (Canada)], E-mail: matsu@ed.kagawa-u.ac.jp

2009-05-20

2

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

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  

SciTech Connect

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., E-mail: vaskoiy@gmail.com; Artemyev, A. V.; Zelenyi, L. M. [Space Research Institute, RAS, Moscow (Russian Federation)] [Space Research Institute, RAS, Moscow (Russian Federation)

2014-05-15

5

Large quasi-circular features beneath frost on Triton  

NASA Technical Reports Server (NTRS)

Specially processed Voyager 2 images of Neptune's largest moon, Triton, reveal three large quasi-circular features ranging in diameter from 280 to 935 km within Triton's equatorial region. The largest of these features contains a central irregularly shaped area of comparatively low albedo about 380 km in diameter, surrounded by crudely concentric annuli of higher albedo materials. None of the features exhibit significant topographic expression, and all appear to be primarily albedo markings. The features are located within a broad equatorial band of anomalously transparent frost that renders them nearly invisible at the large phase angles (alpha greater than 90 deg) at which Voyager obtained its highest resolution coverage of Triton. The features can be discerned at smaller phase angles (alpha = 66 deg) at which the frost only partially masks underlying albedo contrasts. The origin of the features is uncertain but may have involved regional cryovolcanic activity.

Helfenstein, Paul; Veverka, Joseph; Mccarthy, Derek; Lee, Pascal; Hillier, John

1992-01-01

6

An improved upper limit to the CMB circular polarization at large angular scales  

NASA Astrophysics Data System (ADS)

Circular polarization of the Cosmic Microwave Background (CMB) offers the possibility of detecting rotations of the universe and magnetic fields in the primeval universe or in distant clusters of galaxies. We used the Milano Polarimeter (MIPOL) installed at the Testa Grigia Observatory, on the italian Alps, to improve the existing upper limits to the CMB circular polarization at large angular scales. We obtain 95% confidence level upper limits to the degree of the CMB circular polarization ranging between 5.0?10-4 and 0.7?10-4 at angular scales between 8° and 24°, improving by one order of magnitude preexisting upper limits at large angular scales. Our results are still far from the nK region where today expectations place the amplitude of the V Stokes parameter used to characterize circular polarization of the CMB but improve the preexisting limit at similar angular scales. Our observations offered also the opportunity of characterizing the atmospheric emission at 33 GHz at the Testa Grigia Observatory.

Mainini, R.; Minelli, D.; Gervasi, M.; Boella, G.; Sironi, G.; Baú, A.; Banfi, S.; Passerini, A.; De Lucia, A.; Cavaliere, F.

2013-08-01

7

An improved upper limit to the CMB circular polarization at large angular scales  

SciTech Connect

Circular polarization of the Cosmic Microwave Background (CMB) offers the possibility of detecting rotations of the universe and magnetic fields in the primeval universe or in distant clusters of galaxies. We used the Milano Polarimeter (MIPOL) installed at the Testa Grigia Observatory, on the italian Alps, to improve the existing upper limits to the CMB circular polarization at large angular scales. We obtain 95% confidence level upper limits to the degree of the CMB circular polarization ranging between 5.0?10{sup ?4} and 0.7?10{sup ?4} at angular scales between 8° and 24°, improving by one order of magnitude preexisting upper limits at large angular scales. Our results are still far from the nK region where today expectations place the amplitude of the V Stokes parameter used to characterize circular polarization of the CMB but improve the preexisting limit at similar angular scales. Our observations offered also the opportunity of characterizing the atmospheric emission at 33 GHz at the Testa Grigia Observatory.

Mainini, R.; Minelli, D.; Gervasi, M.; Boella, G.; Sironi, G.; Baú, A.; Banfi, S.; Passerini, A.; Lucia, A. De [Physics Department, University of Milano Bicocca, Milano, I20126 (Italy); Cavaliere, F., E-mail: roberto.mainini@mib.infn.it, E-mail: daniele.minelli@gmail.com, E-mail: massimo.gervasi@mib.infn.it, E-mail: giuliano.boella@unimib.it, E-mail: giorgio.sironi@mib.infn.it, E-mail: bau@mib.infn.it, E-mail: stefano.banfi@mib.infn.it, E-mail: andrea.passerini@mib.infn.it, E-mail: antonio.delucia@unimib.it, E-mail: francesco.cavaliere@fisica.unimi.it [Physics Department, University of Milano, Milano, I20133 (Italy)

2013-08-01

8

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

9

Reading Materials in Large Print: A Resource Guide. Reference Circular No. 97-02.  

ERIC Educational Resources Information Center

This reference circular contains information about large-print materials. Section 1 is an annotated list of selected sources of large-print materials available for purchase or loan. The sources are publishers or distributors, specialized libraries, and associations for persons with visual impairments. Several of these sources also provide general…

Mendle, Gillian, Comp.

10

Circular polarization in comets: Observations of Comet C/1999 S4 (LINEAR) and tentative interpretation  

E-print Network

Comet C/1999 S4 (LINEAR) was exceptional in many respects. Its nucleus underwent multiple fragmentations culminating in the complete disruption around July 20, 2000. We present circular polarization measurements along the cuts through the coma and nucleus of the comet during three separate observing runs, in June 28 - July 2, July 8 - 9, and July 21 - 22, 2000. The circular polarization was detected at a rather high level, up to 0.8%. The left-handed as well as right-handed polarization was observed over the coma with the left circularly polarized light systematically observed in the sunward part of the coma. During our observations the phase angle of the comet varied from 61 up to 122 deg., which allowed us to reveal variations of circular polarization with the phase angle. Correlation between the degree of circular polarization, visual magnitude, water production rate, and linear polarization of Comet C/1999 S4 (LINEAR) during its final fragmentation in July 2000 was found. The mechanisms that may produce circular polarization in comets and specifically in Comet C/1999 S4 (LINEAR) are discussed and some tentative interpretation is presented.

Vera Rosenbush; Ludmilla Kolokolova; Alexander Lazarian; Nikolai Shakhovskoyd; Nikolai Kiselev

2007-03-09

11

Evaluation of displacement demands on large circular universal expansion joints  

SciTech Connect

In 1989 a seismic upgrade was completed at a facility to minimize any disruption of the enriching operations that could result from a major seismic event. Expansion joint modifications were a major part of this upgrade. Large diameter universal expansion joints (bellows) have been employed in facilities at locations where the piping is routed across building joints between structural units. These expansion joints are intended to permit differential displacement of the structural units without introducing excessive loadings into the piping system as well as alleviate thermal loadings. Reanalysis of the building to meet current seismic requirements have resulted in displacements at the building joints that exceed those considered during the initial design. These new seismic building displacements were usually larger than the values used to procure the bellows assemblies. To ensure a confidence in the evaluation of the existing bellows to the new design displacement, a walkdown was performed on a sample population and these results were used to determine any required modifications. This paper presents the bellows critical attributes for inspection, the evaluation process, the additional concern of the universal spool piece dynamic contribution, and an evaluation example. The expansion joints are primarily subjected to thermal displacements and differential movement between building units.

Buchanan, L.P.; Barnhart, J.A. [Parsons Power Corp., Oak Ridge, TN (United States)

1996-12-01

12

Mutual admittance between circular waveguide-fed apertures for large spacing  

NASA Technical Reports Server (NTRS)

A closed-form asymptotic expression for the mutual admittance between two circular waveguide-fed apertures is developed for large element spacings. A comparison with calculations obtained by a numerical integration method indicated that the present analysis gives good results for spacings greater than two wavelengths.

Bailey, M. C.

1977-01-01

13

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

14

All-optical circular polarization switching phenomenon observed in photo chemically etched silicon  

Microsoft Academic Search

We demonstrate an all-optical circular polarization switching (AOCPS) phenomenon by using the storing polarization effect in a photo chemically etched silicon (PCE Si). The luminescence, structural and, chemical characteristics of the PCE Si are also observed, and are compared with the porous silicon (PS). In addition, the mechanism of an AOCPS phenomenon is discussed in terms of interaction between spinning

Naokatsu Yamamoto

2003-01-01

15

Intensity-dependent circular polarization and circumstellar magnetic fields from the observation of SiO masers  

NASA Technical Reports Server (NTRS)

A new aspect of the propagation of astrophysical maser radiation in the presence of a magnetic field is described in which circular polarization is created. The resulting antisymmetric spectral line profile for this circular polarization resembles that produced by the ordinary Zeeman effect when the Zeeman splittings are much less than the spectral line breadth. It is caused by the change, with increasing maser intensity, in the axis of symmetry for the molecular quantum states from a direction that is parallel to the magnetic field to a direction that is parallel to the direction of propagation. When the maser is radiatively saturated, and the rate for stimulated emission is within an order of magnitude of the Zeeman splitting in frequency units, this 'intensity-dependent circular polarization' is greater than that due to the ordinary Zeeman effect by factors as large as 1000. The circular polarization that is observed in the spectra of circumstellar SiO (J = 1-0) masers associated with late-type giants and supergiants may then be caused by magnetic fields as weak as about 10 mG. With the standard Zeeman interpretation of the observations, magnetic fields of 10-100 G are indicated. The lower fields are similar to the limits obtained from the observation of the 22 GHz water masers which are typically somewhat further from the central star. The observed tendency for the fractional linear polarization of SiO masers to increase with increasing angular momentum of the molecular state is shown to be a likely result of anisotropic pumping. Errors are identified that invalidate a recent conflicting claim in the literature about the basic theory of maser polarization in the regime that is relevant here.

Nedoluha, Gerald E.; Watson, William D.

1994-01-01

16

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

17

Linear and circular polarimetry of recent comets: Observational results for eight comets  

NASA Astrophysics Data System (ADS)

We present the results of polarimetric observations for a number of recent comets carried out at the 6-m telescope of the Special Astrophysical Observatory (Russia) and the 2.6-m telescope of the Crimean Astrophysical Observatory (Ukraine) during 2011--2013. Comets 103P/Hartley 2, C/2009 P1 (Garradd), C/2011 L4 (PANSTARRS), C/2012 S1 (ISON), C/2013 R1 (Lovejoy), 29P/Schwassmann-Wachmann 1, C/2010 S1 (LINEAR), and C/2011 R1 (McNaught) were observed at different distances from the Sun (0.9--6.3 au) and at different phase angles (6.2--83.5 deg). The results obtained are compared with the phase-angle dependencies of linear polarization typical for the high-polarization and low-polarization comets. The linear polarization of comet S1 (LINEAR) and Schwassmann-Wachmann 1 are the first ever measured at the heliocentric distances larger than 6 au. The maps of circular polarization over the coma and its variations with the distance from the nucleus of comets P1 (Garradd), L4 (PANSTARRS), R1 (McNaught), and Schwassmann-Wachmann 1 are obtained. In all cases, left-handed circular polarization is detected and its value is within the range from -0.04 % up to -0.3 %. Detection of left-handed circular polarization in these comets has confirmed our previous conclusion that circular polarization of comets is predominantly left-handed. We will discuss the possible reasons for the diversity and similarity of linear and circular polarization in comets.

Rosenbush, V.; Ivanova, A.; Kiselev, N.; Afanasiev, V.; Kolesnikov, S.; Shakhovskoy, D.

2014-07-01

18

Controlling the near-wake of a circular cylinder with a single, large-scale tripwire  

NASA Astrophysics Data System (ADS)

Control of the flow past a circular cylinder using a single tripwire on its surface has been studied experimentally as a function of the wire angular location for different wire-to-cylinder diameter ratios (0.029 ? d/D ? 0.059) and Reynolds numbers (5,000 ? Re D ? 30,000). The use of an endplate with a sharp leading edge on each end of the cylinder yields adequate level of quasi two-dimensionality in the near wake. For each Reynolds number and wire size considered, two types of critical angular locations for the implementation of the large-scale wire on the cylinder surface were shown to exist based on the changes in the flow features in accord with the existing literature. At the first critical wire angle, the vortex shedding ceases for the majority of the time during which the vortex formation length extends, and there exists short time intervals where regular shedding resumes similar to the smooth cylinder. The second critical wire angle is found to encompass a range of angles (50° to 70°) where significant increase in spectral amplitude of Karman frequency is observed together with contraction of the near-wake. The angular location of the first critical wire angle decreases with the wire size, and increases with Reynolds number up to ReD = 15,000, after which it remains unaffected by the Reynolds number. Furthermore, the variations of the Strouhal number and the coherency of Karman vortex shedding are found to be, roughly, inversely related with each other. This investigation explains the relationship between different sets of critical wire angles previously defined by other researchers. Finally, a model is established for the estimation of the Strouhal number as a function of the wire angle. This model requires only the wire size (d), cylinder diameter (D), and Reynolds number (Re D) as inputs, and, therefore, is applicable without any prior knowledge on the flow structures. It yields a low average error (<6.2%) when compared with the experimental data.

Aydin, Tayfun Besim

19

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

20

Nonlinear evolution of a large-amplitude circularly polarized Alfven wave: Low beta  

NASA Technical Reports Server (NTRS)

The nature of turbulent cascades arising from the parametric instabilities of a monochromatic field-aligned large-amplitude circularly polarized Alfven wave is investigated via direct numerical simulation for the case of low plasma Beta and no wave dispersion. The magnetohydrodynamic code permits nonlinear couplings in the parallel direction to the ambient magnetic field and one perpendicular direction. Compressibility is included in the form of a polytropic equation of state. Anisotropic turbulent cascades, similar to those found in early incompressible two-dimensional simulations, occur after nonlinear saturation of the parallel propagating decay instability. The turbulent spectrum can be divided into three regimes: the lowest wave numbers are dominated by lower sideband remnants of the parametric process, intermediate wave numbers display nearly incompressible dynamics, and the highest wave numbers are dominated by acoustic turbulence.

Ghosh, S.; Goldstein, M. L.

1994-01-01

21

Nonlinear evolution of a large-amplitude circularly polarized Alfven wave: High beta  

NASA Technical Reports Server (NTRS)

The nonlinear dynamics following saturation of the parametric instabilities of a monochromatic field-aligned large-amplitude circularly polarized Alfven wave is investigated via direct numerical simulation in the case of high plasma beta and no wave dispersion. The magnetohydrodynamic (MHD) code permits nonlinear couplings in the parallel direction to the ambient magnetic field and one perpendicular direction. Compressibility is included in the form of a polytropic equation of state. Turbulent cascades develop after saturation of two coupled oblique three-wave parametric instabilities; one of which is an oblique filamentationlike instability reported earlier. Remnants of the parametric processes, as well as of the original Alfven pump wave, persist during late nonlinear times. Nearly incompressible MHD features such as spectral anisotropies appear as well.

Ghosh, S.; Vinas, A. F.; Goldstein, M. L.

1994-01-01

22

Sidewall-box airlift pump provides large flows for aeration, CO2 stripping, and water rotation in large dual-drain circular tanks  

Technology Transfer Automated Retrieval System (TEKTRAN)

Conventional gas transfer technologies for aquaculture systems occupy a large amount of space, require a considerable capital investment, and can contribute to high electricity demand. In addition, diffused aeration in a circular culture tank can interfere with the hydrodynamics of water rotation a...

23

Circular High-Q Resonating Isotropic Strain Sensors with Large Shift of Resonance Frequency under Stress  

PubMed Central

We present circular architecture bioimplant strain sensors that facilitate a strong resonance frequency shift with mechanical deformation. The clinical application area of these sensors is for in vivo assessment of bone fractures. Using a rectangular geometry, we obtain a resonance shift of 330 MHz for a single device and 170 MHz for its triplet configuration (with three side-by-side resonators on chip) under an applied load of 3,920 N. Using the same device parameters with a circular isotropic architecture, we achieve a resonance frequency shift of 500 MHz for the single device and 260 MHz for its triplet configuration, demonstrating substantially increased sensitivity. PMID:22303132

Melik, Rohat; Unal, Emre; Perkgoz, Nihan Kosku; Puttlitz, Christian; Demir, Hilmi Volkan

2009-01-01

24

Experimental observation of the ``golden section'' in flow round a circular cylinder  

Microsoft Academic Search

The state of flow round a circular cylinder as a function of the Reynolds number can be characterized by the nondimensionalized vortex shedding frequency (Strouhal number Sr). It was found experimentally that the ratio of Strouhal numbers belonging to the different stable states of the Karman vortex street corresponds approximately to the ``golden section''.

Günter Schewe

1985-01-01

25

Circular Patterns over Large Areas from The Self-Assembly of Block Copolymers Guided by Shallow Trenches  

Microsoft Academic Search

We report the fabrication of ultra-dense circular nanoarrays of block copolymer (BCP) microdomains over macroscopic areas. These arrays were generated by the directed self-assembly of BCPs on the topographically patterned substrates, where the trenches with circular shape are patterned on a flat substrate. The width of circular trench and the distance between circular trenches are varied for commensurability issues, and

Sung Woo Hong; Xiaodan Gu; June Huh; Shuaigang Xiao; Thomas Russell

2011-01-01

26

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

27

Supersonic flow about circular cones at large angles of attack - A floating discontinuity approach  

NASA Technical Reports Server (NTRS)

The technique of floating shock fitting is adapted to the computation of the inviscid flowfield about circular cones in a supersonic free stream at angles of attack that exceed the cone half-angle. In those regions in which the governing conical equations are mixed elliptic-hyperbolic, the fully hyperbolic form is obtained by the addition of the temporal derivative. The resulting equations are applicable over the complete range of free-stream Mach numbers, angles of attack and cone half-angles for which the bow shock is attached. An explicit finite-difference algorithm is used to obtain the solution by an unsteady relaxation approach. The bow shock, embedded crossflow shock, and vortical singularity in the leeward symmetry plane are all treated as floating discontinuities in a fixed computational mesh. The method yields excellent results for the bow and embedded shocks, however, the solution in the leeward symmetry plane exhibits viscous-like effects and does not appear to adequately predict the behavior of the vortical singularity.

Daywitt, J.; Kutler, P.; Anderson, D.

1977-01-01

28

Large-scale laboratory experiment on erosion of sand beds by moving circular vertical jets  

Microsoft Academic Search

This study investigates the topographic deformation due to the erosion of a sand bed impinged by a moving submerged turbulent round jet in a large-scale laboratory. The test conditions represent the case of discharges beneath a vessel while operating in water with a limited clearance such as a shallow navigation channel. The jet moves horizontally and discharges water vertically downward

Po-Hung Yeh; Kuang-An Chang; John Henriksen; Billy Edge; Peter Chang; Andrew Silver; Abel Vargas

2009-01-01

29

A model for simulating the influence of a spatial distribution of large circular macropores on surface runoff  

NASA Astrophysics Data System (ADS)

This paper reports the development and test, at the scale of 1 m2, of an event- based model that aims at simulating the influence of a spatial distribution of large circular macropores on surface runoff. The main originality of this model is that it focuses on the way macropores are supplied with water at the soil surface, by coupling an original model for water interception by individual macropores to a high-resolution spatialized overland flow model. A three-step evaluation of the model was carried out, involving (1) an experimental test of the model for water interception by macropores; (2) a sensitivity analysis of the model to time and space discretization; and (3) a comparison between numerical and field results in the case of runoff on a crusted soil surface with a population of large macropores made by termites in the Sahel. The model was found to accurately simulate the effect of a spatial distribution of large macropores on runoff, and it showed that small heterogeneities, like macropores or areas where a crust has been destroyed, which cover a very limited proportion of the soil surface, can have a high impact on runoff.

Léonard, J.; Perrier, E.; de Marsily, G.

2001-12-01

30

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

31

Measurement of nonlinear observables in the Large Hadron Collider using kicked beams  

NASA Astrophysics Data System (ADS)

The nonlinear dynamics of a circular accelerator such as the Large Hadron Collider (LHC) may significantly impact its performance. As the LHC progresses to more challenging regimes of operation it is to be expected that the nonlinear single particle dynamics in the transverse planes will play an increasing role in limiting the reach of the accelerator. As such it is vital that the nonlinear sources are well understood. The nonlinear fields of a circular accelerator may be probed through measurement of the amplitude detuning: the variation of tune with single particle emittance. This quantity may be assessed experimentally by exciting the beam to large amplitudes with kicks, and obtaining the tunes and actions from turn-by-turn data at Beam Position Monitors. The large amplitude excitations inherent to such a measurement also facilitate measurement of the dynamic aperture from an analysis of beam losses following the kicks. In 2012 these measurements were performed on the LHC Beam 2 at injection energy (450 GeV) with the nominal magnetic configuration. Nonlinear coupling was also observed. A second set of measurements were performed following the application of corrections for b4 and b5 errors. Analysis of the experimental results, and a comparison to simulation are presented herein.

Maclean, E. H.; Tomás, R.; Schmidt, F.; Persson, T. H. B.

2014-08-01

32

Structural Analysis of Large Networks: Observations and Applications  

E-print Network

these behaviors, and apply these findings to real-world problems. We examined graphs of size up to 16 millionStructural Analysis of Large Networks: Observations and Applications Mary McGlohon December 2010 CMU-ML-10-111 #12;#12;Structural Analysis of Large Networks: Observations and Applications Mary Mc

33

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

34

Circular Polarization Mapping of Protostellar Environments: Searching for Aligned Grains  

NASA Astrophysics Data System (ADS)

We have mapped the linear and circular polarization in several protostars. The polarization maps are being compared to Monte Carlo radiative transfer models including the effects of scattering from aligned grains. A definitive test of grain alignment comes from resolved circular polarization maps of protostars. Aligned grains produce large values of circular polarization across the cloud, up to 25-40% in the models, whereas nonaligned grains produce maximum polarizations of only a few percent. To date, very few protostars have been observed at high spatial resolution for circular polarization. If grains are aligned, models of the linear and circular polarization maps can probe the alignment geometry and therefore the magnetic field structure. None of the four protostars observed showed circular polarization at a level above ˜ 1-2 % (3 ?).

Clayton, G. C.; Whitney, B. A.; Wolff, M. J.; Smith, P.; Gordon, K. D.

2005-12-01

35

SEARCH Workshop on Large-Scale Atmosphere/Cryosphere Observations  

E-print Network

SEARCH Workshop on Large-Scale Atmosphere/Cryosphere Observations Contribution 2452 from NOAA ADMINISTRATION U.S.D E PARTMENT OF COM M E R CE #12;NOAA OAR Special Report SEARCH Workshop on Large-Scale Richter-Menge John Walsh Pacific Marine Environmental Laboratory 7600 Sand Point Way NE Seattle, WA 98115

36

Large-scale structure observables in general relativity  

NASA Astrophysics Data System (ADS)

We review recent studies that rigorously define several key observables of the large-scale structure of the Universe in a general relativistic context. Specifically, we consider (i) redshift perturbation of cosmic clock events; (ii) distortion of cosmic rulers, including weak lensing shear and magnification; and (iii) observed number density of tracers of the large-scale structure. We provide covariant and gauge-invariant expressions of these observables. Our expressions are given for a linearly perturbed flat Friedmann–Robertson–Walker metric including scalar, vector, and tensor metric perturbations. While we restrict ourselves to linear order in perturbation theory, the approach can be straightforwardly generalized to higher order.

Jeong, Donghui; Schmidt, Fabian

2015-02-01

37

Large-amplitude, Circularly Polarized, Compressive, Obliquely Propagating Electromagnetic Proton Cyclotron Waves Throughout the Earth's Magnetosheath: Low Plasma ? Conditions  

NASA Astrophysics Data System (ADS)

During 1999 August 18, both Cassini and WIND were in the Earth's magnetosheath and detected transverse electromagnetic waves instead of the more typical mirror-mode emissions. The Cassini wave amplitudes were as large as ~14 nT (peak to peak) in a ~55 nT ambient magnetic field B 0. A new method of analysis is applied to study these waves. The general wave characteristics found were as follows. They were left-hand polarized and had frequencies in the spacecraft frame (f scf) below the proton cyclotron frequency (fp ). Waves that were either right-hand polarized or had f scf > fp are shown to be consistent with Doppler-shifted left-hand waves with frequencies in the plasma frame fpf < fp . Thus, almost all waves studied are consistent with their being electromagnetic proton cyclotron waves. Most of the waves (~55%) were found to be propagating along B 0 (\\theta _{kB_{0}}<30^{\\circ}), as expected from theory. However, a significant fraction of the waves were found to be propagating oblique to B 0. These waves were also circularly polarized. This feature and the compressive ([B max - B min]/B max, where B max and B min are the maximum and minimum field magnitudes) nature (ranging from 0.27 to 1.0) of the waves are noted but not well understood at this time. The proton cyclotron waves were shown to be quasi-coherent, theoretically allowing for rapid pitch-angle transport of resonant protons. Because Cassini traversed the entire subsolar magnetosheath and WIND was in the dusk-side flank of the magnetosheath, it is surmised that the entire region was filled with these waves. In agreement with past theory, it was the exceptionally low plasma ? (0.35) that led to the dominance of the proton cyclotron wave generation during this interval. A high-speed solar wind stream (langVsw rang = 598 km s-1) was the source of this low-? plasma.

Remya, B.; Tsurutani, B. T.; Reddy, R. V.; Lakhina, G. S.; Falkowski, B. J.; Echer, E.; Glassmeier, K.-H.

2014-09-01

38

Large deployable reflectors for telecom and earth observation applications  

NASA Astrophysics Data System (ADS)

Large deployable antennas are one of the key components for advanced missions in the fields of telecom and earth observation. In the recent past, missions have taken on board large deployable reflector (LDR) up to 22 m of diameter and several missions have already planned embarking large reflectors, such as the 12 m of INMARSAT XL or BIOMASS. At the moment, no European LDR providers are available and the market is dominated by Northrop-Grumman and Harris. Consequently, the development of European large reflector technology is considered a key step to maintain commercial and strategic competitiveness (ESA Large Reflector Antenna Working Group Final Report, TEC-EEA/2010.595/CM, 2010). In this scenario, the ESA General Study Project RESTEO (REflector Synergy between Telecom and Earth Observation), starting from the identification of future missions needs, has identified the most promising reflector concepts based on European heritage/technology, able to cover the largest range of potential future missions for both telecom and earth observation. This paper summarizes the activities and findings of the RESTEO Study.

Scialino, L.; Ihle, A.; Migliorelli, M.; Gatti, N.; Datashvili, L.; 't Klooster, K.; Santiago Prowald, J.

2013-12-01

39

Surface Water Temperature Observations of Large Lakes by Optimal Estimation  

E-print Network

Surface Water Temperature Observations of Large Lakes by Optimal Estimation Stuart N MacCallum(1 cloud screening have been developed to provide Lake Surface Water Temperature (LSWT) estimates from radiances. Therefore, the OE retrieval scheme developed is generic ­ i.e., applicable to all lakes. LSWTs

Merchant, Chris

40

Structural Analysis of Large Networks: Observations and Applications  

E-print Network

these behaviors, and apply these findings to real-world problems. We examined graphs of size up to 16 millionStructural Analysis of Large Networks: Observations and Applications Mary McGlohon December 2010, of any sponsoring institution, the U.S. government or any other entity. #12;Keywords: Social networks

41

FERMI LARGE AREA TELESCOPE OBSERVATIONS OF GRB 110625A  

SciTech Connect

Gamma-ray bursts (GRBs) that emit photons at GeV energies form a small but significant population of GRBs. However, the number of GRBs whose GeV-emitting period is simultaneously observed in X-rays remains small. We report {gamma}-ray observations of GRB 110625A using Fermi's Large Area Telescope in the energy range 100 MeV-20 GeV. Gamma-ray emission at these energies was clearly detected using data taken between 180 s and 580 s after the burst, an epoch after the prompt emission phase. The GeV light curve differs from a simple power-law decay, and probably consists of two emission periods. Simultaneous Swift X-Ray Telescope observations did not show flaring behaviors as in the case of GRB 100728A. We discuss the possibility that the GeV emission is the synchrotron self-Compton radiation of underlying ultraviolet flares.

Tam, P. H. T.; Kong, A. K. H. [Institute of Astronomy and Department of Physics, National Tsing Hua University, Hsinchu 30013, Taiwan (China); Fan Yizhong, E-mail: phtam@phys.nthu.edu.tw [Purple Mountain Observatory, Chinese Academy of Sciences, Nanjing 210008 (China)

2012-08-01

42

Interferometric observations of large biologically interesting interstellar and cometary molecules.  

PubMed

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. PMID:16894168

Snyder, Lewis E

2006-08-15

43

Interferometric observations of large biologically interesting interstellar and cometary molecules  

PubMed Central

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. PMID:16894168

Snyder, Lewis E.

2006-01-01

44

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

45

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

46

Observation of large-amplitude magnetosonic waves at dipolarization fronts  

NASA Astrophysics Data System (ADS)

plasma waves have been observed in the vicinity of dipolarization fronts (DFs) and the rarefaction regions behind them. It was suggested that these waves not only play crucial roles in regulating particle kinetics at the DFs but also may potentially affect the large-scale dynamics of the magnetotail. In this paper, we present the observations of large-amplitude electromagnetic waves at DFs that occurred during magnetospheric substorms. The DFs were embedded in either the tailward or earthward flows in the near-Earth magnetotail. The wave frequencies were near the local proton cyclotron frequency. The waves propagated at highly oblique angles with respect to the ambient magnetic field (~80°-100°). Their corresponding wavelengths were on the order of the local ion gyroradii. The major magnetic field fluctuations were along the background magnetic field, while the electric field fluctuations were predominantly perpendicular to the background magnetic field. The waves were compressional waves as there was an anticorrelation between the plasma density and the wave magnetic field strength. The electric potential associated with the waves reached to more than half of the electron temperature, indicating the waves are nonlinear. We suggest that the waves were magnetosonic or ion Bernstein mode waves driven by the ion ring distribution. The waves were able to provide significant anomalous resistivity at the front, with major contributions from the electric field fluctuations. The effects of these waves on the electron pitch angle scattering and energy diffusion are also discussed.

Zhou, Meng; Ni, Binbin; Huang, Shiyong; Deng, Xiaohua; Ashour-Abdalla, Maha; Nishimura, Yukitoshi; Yuan, Zhigang; Pang, Ye; Li, Huimin

2014-06-01

47

Circularity-Measuring System  

NASA Technical Reports Server (NTRS)

Shape gauge and associated computer constitute system measuring deviations of large cylinders from roundness. Shaped and held somewhat like crossbow, measures relative locations of three points on surface of large, round object. By making connected series of measurements around periphery technician using gauge determines deviation of object from perfect circularity. Used to measure straightness, roundness, or complicated shapes of such large geometrical objects as surfaces of aircraft and hulls of ships.

WHIPPO. WALTER B.; Rohrkaste, G. R.; Miller, John E.

1989-01-01

48

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

49

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 four 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 run as first guesses with no tuning for any of the models or cases. This approach leads to a wide range of simulation performance, including some of the bad simulation results to be expected in an operational context. Disregarding 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 codes used for this paper are freely available to the community.

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

2014-11-01

50

The flux of large meteoroids observed with lunar impact monitoring  

NASA Astrophysics Data System (ADS)

The flux of large meteoroids is not well determined due to relatively low number statistics, due mainly to the lack of collecting area available to meteor camera systems (10^2-10^5 km^2). Larger collecting areas are needed to provide reasonable statistics for flux calculations. The Moon, with millions of square kilometers of lunar surface, can be used as a detector for observing the population of large meteoroids in the tens of grams to kilogram mass range. This is accomplished by observing the flash of light produced when a meteoroid impacts the lunar surface, converting a portion of its kinetic energy to visible light detectable from the Earth. A routine monitoring program at NASA's Marshall Space Flight Center has recorded over 300 impact flashes since early 2006. The program utilizes multiple 0.35-m (14-inch) Schmidt-Cassegrain telescopes, outfitted with video cameras using the 1?2 inch Sony EXview HAD CCDTM chip, to perform simultaneous observations of the earthshine hemisphere of the Moon when the lunar phase is between 0.1 and 0.5. This optical arrangement permits monitoring of approximately 3.8×10^6 km^2 of lunar surface. A selection of 126 flashes recorded in 266.88 hours of photometric skies was analyzed, creating the largest and most homogeneous dataset of lunar impact flashes to date. Standard CCD photometric techniques outlined in [1] were applied to the video to determine the luminous energy, kinetic energy, and mass for each impactor, considering a range of luminous efficiencies. The flux to a limiting energy of 2.5×10^{-6} kT TNT or 1.05×10^7 J is 1.03×10^{-7} km^{-2} hr^{-1} and the flux to a limiting mass of 30 g is 6.14×10^{-10} m^{-2} yr^{-1}. Comparisons made with measurements and models of the meteoroid population indicate that the flux of objects in this size range is slightly lower (but within the error bars) than the power law distribution determined for the near-Earth-object population by [2].

Cooke, W.; Suggs, R.; Moser, D.; Suggs, R. J.

2014-07-01

51

Observing Planetary Nebulae with JWST and Extremely Large Telescopes  

NASA Astrophysics Data System (ADS)

Most stars in the Universe that leave the main sequence in a Hubble time will end their lives evolving through the Planetary Nebula (PN) evolutionary phase. The heavy mass loss which occurs during the preceding AGB phase is important across astrophysics, dramatically changing the course of stellar evolution, dominantly contributing to the dust content of the interstellar medium, and influencing its chemical composition. The evolution from the AGB phase to the PN phases remains poorly understood, especially the dramatic transformation that occurs in the morphology of the mass-ejecta as AGB stars and their round circumstellar envelopes evolve into mostly PNe, the majority of which deviate strongly from spherical symmetry. In addition, although the PN [OIII] luminosity function (PNLF) has been used as a standard candle (on par with distance indicators such as Cepheids), we do not understand why it works. It has been argued that the resolution of these issues may be linked to binarity and associated processes such as mass transfer and common envelope evolution.Thus, understanding the formation and evolution of PNe is of wide astrophysical importance. PNe have long been known to emit across a very large span of wavelengths, from the radio to X-rays. Extensive use of space-based observatories at X-ray (Chandra/ XMM-Newton), optical (HST) and far-infrared (Spitzer, Herschel) wavelengths in recent years has produced significant new advances in our knowledge of these objects. Given the expected advent of the James Webb Space Telescope in the near future, and ground-based Extremely Large Telescope(s) somewhat later, this talk will focus on future high-angular-resolution, high-sensitivity observations at near and mid-IR wavelengths with these facilities that can help in addressing the major unsolved problems in the study of PNe.

Sahai, Raghvendra

2015-01-01

52

Detection of Circular Polarization in M81*  

E-print Network

We report the detection of circular polarization in the compact radio jet of the nearby spiral galaxy M81 (M81*). The observations were made with the Very Large Array at 4.8 and 8.4 GHz and circular polarization was detected at both frequencies. We estimate a value of $m_{c}=0.54\\pm0.06\\pm0.07%$ at 8.4 GHz and $m_{c}=0.27\\pm0.06\\pm0.07%$ at 4.8 GHz for the fractional circular polarization. The errors are separated into statistical and systematic terms. The spectrum of the circular polarization is possibly inverted which would be unusual for AGN. We also detected no linear polarization in M81* at a level of 0.1% implying that the source has a very high circular-to-linear polarization ratio as found so far only in Sgr A*, the central radio source in our Galaxy. This further supports the idea that M81* is a scaled-up version of Sgr A* and suggests that the polarization properties are intrinsic to the two sources and are not caused by a foreground screen in the Galaxy.

A. Brunthaler; G. C. Bower; H. Falcke; R. R. Mellon

2001-09-11

53

SPITZER SAGE Observations of Large Magellanic Cloud Planetary Nebulae  

E-print Network

We present IRAC and MIPS images and photometry of a sample of previously known planetary nebulae (PNe) from the SAGE survey of the Large Magellanic Cloud (LMC) performed with the Spitzer Space Telescope. Of the 233 known PNe in the survey field, 185 objects were detected in at least two of the IRAC bands, and 161 detected in the MIPS 24 micron images. Color-color and color-magnitude diagrams are presented using several combinations of IRAC, MIPS, and 2MASS magnitudes. The location of an individual PN in the color-color diagrams is seen to depend on the relative contributions of the spectral components which include molecular hydrogen, polycyclic aromatic hydrocarbons (PAHs), infrared forbidden line emission from the ionized gas, warm dust continuum, and emission directly from the central star. The sample of LMC PNe is compared to a number of Galactic PNe and found to not significantly differ in their position in color-color space. We also explore the potential value of IR PNe luminosity functions (LFs) in the LMC. IRAC LFs appear to follow the same functional form as the well-established [O III] LFs although there are several PNe with observed IR magnitudes brighter than the cut-offs in these LFs.

J. L. Hora; M. Cohen; R. G. Ellis; M. Meixner; R. D. Blum; W. B. Latter; B. A. Whitney; M. R. Meade; B. L. Babler; R. Indebetouw; K. Gordon; C. W. Engelbracht; B. -Q. For; M. Block; K. Misselt; U. Vijh; C. Leitherer

2007-11-01

54

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

55

Cold Rydberg atoms in circular states  

NASA Astrophysics Data System (ADS)

Circular-state Rydberg atoms are interesting in that they exhibit a unique combination of extraordinary properties; long lifetimes (˜n^5), large magnetic moments (l=|m|=n-1) and no first order Stark shift. Circular states have found applications in cavity quantum electrodynamics and precision measurements [1,2], among other studies. In this work we present the production of circular states in an atom trapping apparatus using an adiabatic state-switching method (the crossed-field method [3]). To date, we have observed lifetimes of adiabatically prepared states of several milliseconds. Their relatively large ionization electric fields have been verified by time-of-flight signatures of ion trajectories. We intend to explore the magnetic trapping of circular state Rydberg atoms, as well as their production and interaction properties in ultra-cold and degenerate samples.[4pt] [1] P. Bertet et al., Phys. Rev. Lett., 88, 14 (2002)[0pt] [2] M. Brune et al., Phys. Rev. Lett., 72, 21 (1994)[0pt] [3] D. Delande and J.C. Gay, Europhys. Lett., 5, 303-308 (1988).

Anderson, David; Schwarzkopf, Andrew; Raithel, Georg

2012-06-01

56

Cluster observations of hot flow anomalies with large flow deflections  

NASA Astrophysics Data System (ADS)

Case and statistical studies have been performed to investigate hot flow anomalies (HFAs) with large flow deflections using the Cluster-C1 spacecraft data from 2003 to 2009. We have selected 87 events with Vy or Vz in GSE coordinates larger than 200 km\\ s-1. Observations of these HFAs indicate a "Location Dependent Deflection": Vy or Vz deflects to a positive value when the event is located in the positive Y or Z side relative to the sub-solar point, and to a negative value when it is located in the negative Y or Z side relative to the sub-solar point; the amplitude of the deflection increases with the increasing distance in Y or Z direction; the decrease in Vx at the event center is larger when the location is closer to the Sun-Earth line. The "Location Dependent Deflection" might be due to a near-specularly reflection of ions at the Earth's bow shock. The results also suggest that HFAs can be formed at both quasi-parallel and quasi-perpendicular shocks. The HFAs studied in this paper are close to the bow shock with the distance from the event to the bow shock ranging from 0.03 to 3.51 RE, which might help the reflected ions remain as a coherent near-specular reflected beam. In addition, HFAs with both edges at quasi-perpendicular shocks are closer to the bow shock than those with both edges at quasi-parallel shocks. This might help the reflected ions at a quasi-perpendicular shock interact with the incident solar wind immediately after the reflection and increase the possibility of HFA formation. The HFAs with both the leading and trailing edges at quasi-perpendicular shocks show a high gyration velocity and a high fast magneto-sonic Mach number, increasing the gyro-radius and the possibility of pitch angle scattering, which might help the ions escape from the bow shock and move upstream.

Wang, S.; Zong, Q.; Zhang, H.

2012-12-01

57

Phase separation in thermoelectric delafossite CuFe1-xNixO2 observed by soft x-ray magnetic circular dichroism  

NASA Astrophysics Data System (ADS)

Electronic structures of Ni-doped CuFe1-xNixO2 delafossite oxides (0 ? x ? 0.03) have been investigated by employing soft x-ray magnetic circular dichroism (XMCD). Finite XMCD signals are observed for Fe, Ni, and Cu 2p states, and valence states of Cu, Fe, and Ni ions are nearly monovalent (Cu+), trivalent (Fe3+), and divalent (Ni2+), respectively, for all x ? 0.03. Tiny magnetic impurities could be detected by employing XMCD. Fe and Ni 2p XMCD signals are identified due to ferrimagnetic spinel impurities of CuFe2O4 and NiFe2O4. XMCD signals for Cu 2p states arise from divalent Cu2+ ions. Thermoelectrical properties are found to be very sensitive to the very little impurity phase present in delafossite oxides.

Kang, J.-S.; Kim, D. H.; Hwang, Jihoon; Lee, Eunsook; Nozaki, T.; Hayashi, K.; Kajitani, T.; Park, B.-G.; Kim, J.-Y.; Min, B. I.

2011-07-01

58

Circular RNA Is Expressed across the Eukaryotic Tree of Life  

PubMed Central

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

59

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

60

Circular code motifs in transfer RNAs.  

PubMed

In 1996, a trinucleotide circular code X is identified in genes of prokaryotes and eukaryotes (Arquès and Michel, 1996). In 2012, X motifs are identified in the transfer RNA (tRNA) Phe and 16S ribosomal RNA (Michel, 2012). A statistical analysis of X motifs in all available tRNAs of prokaryotes and eukaryotes in the genomic tRNA database (September 2012, http://lowelab.ucsc.edu/GtRNAdb/, Lowe and Eddy, 1997) is carried out here. For this purpose, a search algorithm of X motifs in a DNA sequence is developed. Two definitions allow to determine the occurrence probabilities of X motifs and the circular codes X, X1=P(X) and X2=P(2)(X) (P being a circular permutation map applied on X) in a population of tRNAs. This approach identifies X motifs in the 5' and/or 3' regions of 16 isoaccepting tRNAs (except for the tRNAs Arg, His, Ser and Trp). The statistical analyses are performed on different and large tRNA populations according to the taxonomy (prokaryotes and eukaryotes), tRNA length and tRNA score. Finally, a circular code property observed in genes of prokaryotes and eukaryotes is identified in the 3' regions of 19 isoaccepting tRNAs of prokaryotes and eukaryotes (except for the tRNA Leu). The identification of X motifs and a gene circular code property in tRNAs strengthens the concept proposed in Michel (2012) of a possible translation (framing) code based on a circular code. PMID:23727957

Michel, Christian J

2013-08-01

61

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

62

Direct observation of large temperature fluctuations during DNA thermal denaturation  

E-print Network

In this paper we report direct measurement of large low frequency temperature fluctuations in double stranded (ds) DNA when it undergoes thermal denaturation transition. The fluctuation, which occurs only in the temperature range where the denaturation occurs, is several orders more than the expected equilibrium fluctuation. It is absent in single stranded (ss) DNA of the same sequence. The fluctuation at a given temperature also depends on the wait time and vanishes in a scale of few hours. It is suggested that the large fluctuation occurs due to coexisting denaturated and closed base pairs that are in dynamic equilibrium due to transition through a potential barrier in the scale of 25-30k_{B}T_{0}(T_{0}=300K).

K. S. Nagapriya; A. K. Raychaudhuri; Dipankar Chatterji

2006-02-10

63

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 (M1 and M2). For M1 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 IMF 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 determine FTE 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

64

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

65

Very Large Array observations of Uranus at 2. 0 cm  

SciTech Connect

Radio observations of Uranus obtained at 2.0 cm with the B configuration of the VLA during April 1985 are reported. The calibration and data-reduction procedures are described in detail, and the results are presented in tables, maps, and graphs and compared with IRIS 44-micron observations (Hanel et al., 1986). Features discussed include highest brightness centered on the pole rather than on the subearth point, a decrease in brightness temperature (by up to 9 K) at latitudes between -20 and -50 deg (well correlated with the IRIS data), and disk-center position (corrected for the observed radio asymmetry) in good agreement with that found on the basis of the outer contours of the image. 15 references.

Berge, G.L.; Muhleman, D.O.; Linfield, R.P.

1988-07-01

66

IRAS observations of a large sample of normal irregular galaxies  

NASA Technical Reports Server (NTRS)

IRAS 12, 25, 60, and 100 micron data are presented for a sample of Irr galaxies which span a large range in star-formation activity. It is found that the dwarf, giant, and amorphous Irr's generally have similar IR properties. The typical L(IR)/L(H-alpha) ratios of most classes of Irr's, except for many of the luminous blue galaxies, are low compared with those of spiral galaxies and are consistent with the Irr's being relatively transparent systems without large amounts of optically hidden star formation. Compared with spiral galaxies, the Irr's have similar L(IR)/L(B) ratios, warmer S(100)/S(60) ratios, cooler S(25)/S(12) ratios, and lower dust-to-H I gas mass ratios. The temperature, dust-to-H I gas mass ratios, and L(IR)/L(B) ratios do not correlate with the metallicity of the ionized gas of the Irr's. A correlation between the IR fluxes and both the H-alpha and the blue stellar fluxes is found for the Irr's.

Hunter, Deidre A.; Gallagher, John S., III; Rice, Walter L.; Gillett, Fred C.

1989-01-01

67

Solar wind stream structure at large heliocentric distances Pioneer observations  

NASA Technical Reports Server (NTRS)

Time profiles and histograms of plasma data from Pioneers 10 and 11 are examined for the period between 1975 and 1983. During this time, Pioneer 10 traveled between a heliocentric distance of 8.7 and 30.4 AU. The velocity structure of the solar wind at these heliocentric distances is found to have one of two distinct forms: approximately 70 percent of the time the solar wind has a nearly flat velocity profile. Occasionally, this flat velocity profile is accompanied by quasi-periodic variations in density and in thermal speed consistent with the concept that the 'corotating interaction regions' which are produced by the interaction of high- and low-speed streams at intermediate heliocentric distances are replaced by 'pressure regions' in the outer heliosphere. The remaining 30 percent of the time the solar wind is marked by large (50-200 km/s) long-term (30-120 days) shifts in the average solar wind velocity.

Gazis, P. R.

1987-01-01

68

Cosmological Parameter Estimation with Large Scale Structure Observations  

E-print Network

We estimate the sensitivity of future galaxy surveys to cosmological parameters, using the redshift dependent angular power spectra of galaxy number counts, $C_\\ell(z_1,z_2)$, calculated with all relativistic corrections at first order in perturbation theory. We pay special attention to the redshift dependence of the non-linearity scale and present Fisher matrix forecasts for Euclid-like and DES-like galaxy surveys. We compare the standard $P(k)$ analysis with the new $C_\\ell(z_1,z_2)$ method. We show that for surveys with photometric redshifts the new analysis performs significantly better than the $P(k)$ analysis. For spectroscopic redshifts, however, the large number of redshift bins which would be needed to fully profit from the redshift information, is severely limited by shot noise. We also identify surveys which can measure the lensing contribution and we study the monopole, $C_0(z_1,z_2)$.

Di Dio, Enea; Durrer, Ruth; Lesgourgues, Julien

2014-01-01

69

Cosmological parameter estimation with large scale structure observations  

NASA Astrophysics Data System (ADS)

We estimate the sensitivity of future galaxy surveys to cosmological parameters, using the redshift dependent angular power spectra of galaxy number counts, Cl(z1,z2), calculated with all relativistic corrections at first order in perturbation theory. We pay special attention to the redshift dependence of the non-linearity scale and present Fisher matrix forecasts for Euclid-like and DES-like galaxy surveys. We compare the standard P(k) analysis with the new Cl(z1,z2) method. We show that for surveys with photometric redshifts the new analysis performs significantly better than the P(k) analysis. For spectroscopic redshifts, however, the large number of redshift bins which would be needed to fully profit from the redshift information, is severely limited by shot noise. We also identify surveys which can measure the lensing contribution and we study the monopole, C0(z1,z2).

Di Dio, Enea; Montanari, Francesco; Durrer, Ruth; Lesgourgues, Julien

2014-01-01

70

Observation of a turbulence-induced large scale magnetic field.  

PubMed

An axisymmetric magnetic field is applied to a spherical, turbulent flow of liquid sodium. An induced magnetic dipole moment is measured which cannot be generated by the interaction of the axisymmetric mean flow with the applied field, indicating the presence of a turbulent electromotive force. It is shown that the induced dipole moment should vanish for any axisymmetric laminar flow. Also observed is the production of toroidal magnetic field from applied poloidal magnetic field (the omega effect). Its potential role in the production of the induced dipole is discussed. PMID:16486942

Spence, E J; Nornberg, M D; Jacobson, C M; Kendrick, R D; Forest, C B

2006-02-10

71

Pulsar Observations with the Fermi Large Area Telescope  

E-print Network

The Large Area Telescope (LAT) on Fermi, launched on 2008 June 11, is a space telescope to explore the high energy gamma-ray universe. The instrument covers the energy range from 20 MeV to 300 GeV with greatly improved sensitivity and ability to localize gamma-ray point sources. It detects gamma-rays through conversion to electron-positron pairs and measurement of their direction in a tracker and their energy in a calorimeter. This thesis presents the gamma-ray light curves and the phase-resolved spectral measurements of radio-loud gamma-ray pulsars detected by the LAT. The measurement of pulsar spectral parameters (i.e. integrated flux, spectral index, and energy cut-off) depends on the instrument response functions (IRFs). A method developed for the on-orbit validation of the effective area is presented using the Vela pulsar. The cut efficiencies between the real data and the simulated data are compared at each stage of the background rejection. The results are then propagated to the IRFs, allowing the syst...

Parent, Damien

2010-01-01

72

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

73

The effects of large vibration amplitudes on the axisymmetric mode shapes and natural frequencies of clamped thin isotropic circular plates. Part I: iterative and explicit analytical solution for non-linear transverse vibrations  

NASA Astrophysics Data System (ADS)

The effects of large vibration amplitudes on the first two axisymmetric mode shapes of clamped thin isotropic circular plates are examined. The theoretical model based on Hamilton's principle and spectral analysis developed previously by Benamar et al. for clamped-clamped beams and fully clamped rectangular plates is adapted to the case of circular plates using a basis of Bessel's functions. The model effectively reduces the large-amplitude free vibration problem to the solution of a set of non-linear algebraic equations. Numerical results are given for the first and second axisymmetric non-linear mode shapes for a wide range of vibration amplitudes. For each value of the vibration amplitude considered, the corresponding contributions of the basic functions defining the non-linear transverse displacement function and the associated non-linear frequency are given. The non-linear frequencies associated to the fundamental non-linear mode shape predicted by the present model were compared with numerical results from the available published literature and a good agreement was found. The non-linear mode shapes exhibit higher bending stresses near to the clamped edge at large deflections, compared with those predicted by linear theory. In order to obtain explicit analytical solutions for the first two non-linear axisymmetric mode shapes of clamped circular plates, which are expected to be very useful in engineering applications and in further analytical developments, the improved version of the semi-analytical model developed by El Kadiri et al. for beams and rectangular plates, has been adapted to the case of clamped circular plates, leading to explicit expressions for the higher basic function contributions, which are shown to be in a good agreement with the iterative solutions, for maximum non-dimensional vibration amplitude values of 0.5 and 0.44 for the first and second axisymmetric non-linear mode shapes, respectively.

Haterbouch, M.; Benamar, R.

2003-07-01

74

Photon-photon interactions as a source of cosmic microwave background circular polarization  

NASA Astrophysics Data System (ADS)

Photon-photon interactions, as described with the standard Heisenberg-Euler interaction, can transform plane polarization of the CMB into circular polarization, in the period right after last scattering. We estimate the distribution of the resulting circular polarization parameters, as constrained by confining observations to very small angular regions of large plane polarization, and find results of the order of 1 0-9 for the Stokes parameter V in some of these regions.

Sawyer, R. F.

2015-01-01

75

Circular polarization ratio characteristics of impact craters from Mini-RF observations and implications for ice detection at the polar regions of the Moon  

NASA Astrophysics Data System (ADS)

In an attempt to reduce the ambiguity on radar detection of water ice at the permanently shadowed regions near the lunar poles, radar echo strength and circular polarization ratio (CPR) of impact craters are analyzed using the Miniature Radio Frequency (Mini-RF) radar data from the Lunar Reconnaissance Orbiter mission. Eight typical craters, among over 70 craters, are selected and classified into four categories based on their locations and CPR characteristics: polar anomalous, polar fresh, nonpolar anomalous, and nonpolar fresh. The influences on CPR caused by surface slope, rocks, and dielectric constant are analyzed quantitatively using high-resolution topography data and optical images. A two-component mixed model for CPR that consists of a normal surface and a rocky surface is developed to study the effect of rocks that are perched on lunar surface and buried in regolith. Our analyses show that inner wall of a typical bowl-shaped crater can give rise to a change of about 30° in local incidence angle of radar wave, which can further result in a CPR difference of about 0.2. There is a strong correlation between Mini-RF CPR and rock abundance that is obtained from high-resolution optical images, and predictions from the two-component mixed model match well with the observed CPRs and the estimated rock abundances. Statistical results show that there is almost no apparent difference in CPR characteristics between the polar and nonpolar anomalous craters, or between the polar and nonpolar fresh craters. The enhanced CPR in the interior of anomalous craters is most probably caused by rocks that are perched on lunar surface or buried in regolith, instead of ice deposits as suggested in previous studies.

Fa, Wenzhe; Cai, Yuzhen

2013-08-01

76

Observation of very large and steep internal waves of elevation near the Massachusetts coast  

E-print Network

Observation of very large and steep internal waves of elevation near the Massachusetts coast Oceanography: Physical: Internal and inertial waves; 4219 Oceanography: General: Continental shelf processes and dynamics. Citation: Scotti, A., and J. Pineda (2004), Observation of very large and steep internal waves

Pineda, Jesús

77

Earth Observations for rapid response to large earthquakes Supervisors: Dr Zhenhong Li (1)  

E-print Network

hazards are growing: there were 4 large earthquakes (Mw > 7) in 2010 alone, and many earthquakes occur. This study will look at global large continental earthquakes (Mw > 7.0) occurring in the next 3 yearsEarth Observations for rapid response to large earthquakes Supervisors: Dr Zhenhong Li (1) , Prof

Glasgow, University of

78

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

79

Spectra of circularly polarized radiation from astrophysical OH masers  

NASA Technical Reports Server (NTRS)

A striking feature of astrophysical masers is the tendency for either one or the other of the circular polarizations to dominate in the radiation from the strong, widely observed masing transitions of OH at 18 cm. Spectral line profiles are calculated for polarized maser radiation due to the combined effects of a velocity gradient and, as is indicated for these transitions, a Zeeman splitting that is at least comparable with the thermal contributions to the breadths of the spectral lines. The resulting spectral features are similar in appearance, including the presence of large net circular polarization and narrow line breadths, to the commonly observed spectra of OH masers in molecular clouds. The calculations presented here are performed as a function of frequency without making the approximations of a large velocity gradient. Rapid cross relaxation, which has been advocated by others for the OH masers, is assumed.

Nedoluha, Gerald E.; Watson, William D.

1990-01-01

80

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. PMID:16658498

Faludi-Dániel, Ágnes; Demeter, S.; Garay, A. S.

1973-01-01

81

Observations of a Large-Amplitude Internal Wave Train and Its Reflection off a Steep Slope  

E-print Network

Observations of a Large-Amplitude Internal Wave Train and Its Reflection off a Steep Slope DANIEL, short, and large- amplitude internal wave train off a steep slope are presented and interpreted the parameter space examined in previous laboratory and numerical experiments on internal solitary wave

82

Observation of a neutrino burst in coincidence with supernova 1987A in the Large Magellanic Cloud  

Microsoft Academic Search

A burst of eight neutrino events a preceding the optical detection of the supernova in the Large Magellanic Cloud has been observed in a large underground water Cherenkov detector. The events span an interval of 6 s and have visible energies in the range 20-40 MeV.

R. M. Bionta; G. Blewitt; C. B. Bratton; D. Casper; A. Ciocio; R. Claus; B. Cortez; M. Crouch; S. T. Dye; S. Errede; G. Foster; W. Gajewski; K. Ganezer; M. Goldhaber; T. Haines; T. Jones; D. Kielczewska; W. Kropp; J. Learned; J. LoSecco; J. Matthews; R. Miller; M. Mudan; L. Price; F. Reines; J. Schultz; S. Seidel; E. Shumard; D. Sinclair; H. Sobel; J. Stone; L. Sulak; R. Svoboda; G. Thornton; J. van der Velde; C. Wuest

1987-01-01

83

Observing resilience within a large technical system Jean Christophe Le Coze, Romuald Prinet1  

E-print Network

Observing resilience within a large technical system Jean Christophe Le Coze, Romuald Périnet1 a combination of anticipation and resilience obtained by a `mixture' of individual expertise, team coordination developments) model of resilience, inferred from observations and interviews, and inspired from the literature

Paris-Sud XI, Université de

84

Large amplitude oscillation of an erupting filament as seen in EUV, H and microwave observations  

E-print Network

Large amplitude oscillation of an erupting filament as seen in EUV, H and microwave observations H Radio Heliograph (NoRH). The filament oscillation seems to be triggered by magnetic reconnection between a filament barb and a nearby emerging magnetic flux as was evident from the MDI magnetogram observations

Li, Yi

85

A LEKID-based CMB instrument design for large-scale observations in Greenland  

NASA Astrophysics Data System (ADS)

We present the results of a feasibility study, which examined deployment of a ground-based millimeter-wave polarimeter, tailored for observing the cosmic microwave background (CMB), to Isi Station in Greenland. The instrument for this study is based on lumped-element kinetic inductance detectors (LEKIDs) and an F/2.4 catoptric, crossed-Dragone telescope with a 500 mm aperture. The telescope is mounted inside the receiver and cooled to < 4 K by a closed-cycle 4He refrigerator to reduce background loading on the detectors. Linearly polarized signals from the sky are modulated with a metal-mesh half-wave plate that is rotated at the aperture stop of the telescope with a hollow-shaft motor based on a superconducting magnetic bearing. The modular detector array design includes at least 2300 LEKIDs, and it can be configured for spectral bands centered on 150 GHz or greater. Our study considered configurations for observing in spectral bands centered on 150, 210 and 267 GHz. The entire polarimeter is mounted on a commercial precision rotary air bearing, which allows fast azimuth scan speeds with negligible vibration and mechanical wear over time. A slip ring provides power to the instrument, enabling circular scans (360 degrees of continuous rotation). This mount, when combined with sky rotation and the latitude of the observation site, produces a hypotrochoid scan pattern, which yields excellent cross-linking and enables 34% of the sky to be observed using a range of constant elevation scans. This scan pattern and sky coverage combined with the beam size (15 arcmin at 150 GHz) makes the instrument sensitive to 5 < ` < 1000 in the angular power spectra.

Araujo, D. C.; Ade, P. A. R.; Bond, J. R.; Bradford, K. J.; Chapman, D.; Che, G.; Day, P. K.; Didier, J.; Doyle, S.; Eriksen, H. K.; Flanigan, D.; Groppi, C. E.; Hillbrand, Seth N.; Johnson, B. R.; Jones, G.; Limon, Michele; Miller, A. D.; Mauskopf, P.; McCarrick, H.; Mroczkowski, T.; Reichborn-Kjennerud, B.; Smiley, B.; Sobrin, Joshua; Wehus, I. K.; Zmuidzinas, J.

2014-08-01

86

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

NASA Astrophysics Data System (ADS)

The demagnetization dynamics of the Heusler alloy Co2MnSi 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 Co2MnSi, which is predicted to be half-metallic. A universal demagnetization time constant was measured across a range of pump power levels.

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.

2010-04-01

87

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

88

Scintillation-Induced Circular Polarization in Pulsars and Quasars  

E-print Network

We present a physical interpretation for the generation of circular polarization resulting from the propagation of radiation through a magnetized plasma in terms of a rotation measure gradient, or `Faraday wedges'. Criteria for the observability of scintillation-induced circular polarization are identified. Application of the theory to the circular polarization in pulsars and compact extragalactic sources is discussed.

J. -P. Macquart; D. B. Melrose

2000-07-28

89

Observation of large magnetocaloric effect in HoRu{sub 2}Si{sub 2}  

SciTech Connect

Detailed magnetic, magnetotransport, and magnetocaloric measurements on HoRu{sub 2}Si{sub 2} have been performed. In this Letter, we report presence of spin reorientation transition below paramagnetic to antiferromagnetic transition temperature (T{sub N}?=?19?K). Large magnetic entropy change 9.1?J/kg K and large negative magnetoresistance ?21% in a magnetic field of 5?T has been observed around T{sub N}, which is associated with field induced spin-flip metamagnetic transition.

Paramanik, Tapas, E-mail: tapas.paramanik@saha.ac.in; Das, Kalipada; Das, I. [CMP Division, Saha Institute of Nuclear Physics, 1/AF, Bidhannagar, Kolkata 700 064 (India); Samanta, Tapas [Department of Physics and Astronomy, Louisiana State University, Baton Rouge, Louisiana 70803 (United States)

2014-02-28

90

Study of a prototypical convective boundary layer observed during BLLAST: contributions by large-scale forcings  

NASA Astrophysics Data System (ADS)

We study the disturbances of CBL dynamics due to large-scale atmospheric contributions for a representative day observed during the Boundary Layer Late Afternoon and Sunset Turbulence (BLLAST) campaign. We first reproduce the observed boundary-layer dynamics by combining the Dutch Atmospheric Large-Eddy Simulation (DALES) model with a mixed-layer theory based model. We find that by only taking surface and entrainment fluxes into account, the boundary-layer height is overestimated by 70%. If we constrain our numerical experiments with the BLLAST comprehensive data set, we are able to quantify the contributions of advection of heat and moisture, and subsidence. We find that subsidence has a clear diurnal pattern. Supported by the presence of a nearby mountain range, this pattern suggests that not only synoptic scales exert their influence on the boundary layer, but also mesoscale circulations. Finally, we study whether the vertical and temporal evolution of turbulent variables are influenced by these large-scale forcings. Our model results show good correspondence of the vertical structure of turbulent variables with observations. Our findings further indicate that when large-scale advection and subsidence are applied, the values for turbulent kinetic are lower than without these large-scale forcings. We conclude that the prototypical CBL can still be used as a valid representation of the boundary-layer dynamics near regions characterized by complex topography and small-scale surface heterogeneity, provided that surface- and large-scale forcings are well characterized.

Pietersen, H.; Vilà-Guerau de Arellano, J.; Augustin, P.; de Coster, O.; Delbarre, H.; Durand, P.; Fourmentin, M.; Gioli, B.; Hartogensis, O.; Lothon, M.; Lohou, F.; Pino, D.; Ouwersloot, H. G.; Reuder, J.; van de Boer, A.

2014-07-01

91

Time resolved ultrafast demagnetization of Co2MnSi observed by X-ray magnetic circular dichroism and an ultrafast streak camera  

NASA Astrophysics Data System (ADS)

The demagnetization dynamics of the Heusler alloy Co2MnSi and a ferromagnetic metal Ni was studied using picosecond time-resolved X-ray Magnetic Circular Dichroism. Femtosecond (fs) laser pulses were used to generate a magnetic phase transition in the samples and their demagnetization time constants compared in order to investigate the effect of electronic density of states (DOS) on the demagnetization mechanisms. In contrast to the sub-picosecond demagnetization of the metal ferromagnet Ni, a substantially slower demagnetization time constant of 3.5+/-0.5 ps was measured for the Heusler alloy, implying that the half metallic character of Co2MnSi inhibits spin-flip scattering of hot electrons. As a result, a bottleneck must be created and a new demagnetization process used in the transfer of angular momentum between the spin system and the lattice.

Opachich, Yekaterina P.

92

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

93

Keck Observations of Solar System Objects: Perspectives for Extremely Large Telescopes  

Microsoft Academic Search

From differential tracking techniques, required for appulse observations of KBOs with Laser Guide Star Adaptive Optics (LGSAO),\\u000a to developing methods for collecting spectra at the precise moment of a predicted impact, each Solar System observation conducted\\u000a on a large telescope presents a unique set of challenges. We present operational details and some key science results from\\u000a our science program, adaptive

A. R. Conrad; R. W. Goodrich; R. D. Campbell; W. J. Merline; J. D. Drummond; C. Dumas; B. Carry

2009-01-01

94

Orbital Circularization of a Planet Accreting Disk Gas: The Formation of Distant Jupiters in Circular Orbits Based on a Core Accretion Model  

NASA Astrophysics Data System (ADS)

Recently, gas giant planets in nearly circular orbits with large semimajor axes (a ~ 30-1000 AU) have been detected by direct imaging. We have investigated orbital evolution in a formation scenario for such planets, based on a core accretion model. (1) Icy cores accrete from planetesimals at <~ 30 AU, (2) they are scattered outward by an emerging nearby gas giant to acquire highly eccentric orbits, and (3) their orbits are circularized through the accretion of disk gas in outer regions, where they spend most of their time. We analytically derived equations to describe the orbital circularization through gas accretion. Numerical integrations of these equations show that the eccentricity decreases by a factor of more than 5 while the planetary mass increases by a factor of 10. Because runaway gas accretion increases planetary mass by ~10-300, the orbits are sufficiently circularized. On the other hand, a is reduced at most only by a factor of two, leaving the planets in the outer regions. If the relative velocity damping by shock is considered, the circularization slows down, but is still efficient enough. Therefore, this scenario potentially accounts for the formation of observed distant jupiters in nearly circular orbits. If the apocenter distances of the scattered cores are larger than the disk sizes, their a shrink to a quarter of the disk sizes; the a-distribution of distant giants could reflect the outer edges of the disks in a similar way that those of hot jupiters may reflect inner edges.

Kikuchi, Akihiro; Higuchi, Arika; Ida, Shigeru

2014-12-01

95

THE SPITZER c2d SURVEY OF LARGE, NEARBY, INTERSTELLAR CLOUDS. IV. LUPUS OBSERVED WITH MIPS  

E-print Network

THE SPITZER c2d SURVEY OF LARGE, NEARBY, INTERSTELLAR CLOUDS. IV. LUPUS OBSERVED WITH MIPS Nicholas June 11 ABSTRACT We present maps of 7.78 deg2 of the Lupus molecular cloud complex at 24, 70, and 160 m cover three separate regions in Lupus, denoted I, III, and IV. We discuss the c2d pipeline and how our

96

A Large-Scale CO2 Observing Plan: In Situ Oceans and Atmosphere (LSCOP)  

E-print Network

A Large-Scale CO2 Observing Plan: In Situ Oceans and Atmosphere (LSCOP) A Report of the In Situ show the composite NASA SeaWiFS Vegetation Index. The ocean colors show the climatological mean air network. The SeaWiFS data were provided courtesy of the NASA SeaWiFS Project Office and ORBIMAGE

Stephens, Britton B.

97

Earth Observations for rapid response to large earthquakes Supervisors: Dr Zhenhong Li and Prof Trevor Hoey  

E-print Network

Earth Observations for rapid response to large earthquakes Supervisors: Dr Zhenhong Li and Prof Trevor Hoey School of Geographical and Earth Sciences, University of Glasgow, UK Earthquakes, together of the earth system; they are messengers of the fundamental processes that shape the surface of the Earth

Guo, Zaoyang

98

Observation of the ``Self-Healing'' of an Error Field Island in the Large Helical Device  

Microsoft Academic Search

It was observed that the vacuum magnetic island produced by an external error magnetic field in the large helical device shrank in the presence of plasma. This was evidenced by the disappearance of flat regions in the electron temperature profile obtained by Thomson scattering. This island behavior depended on the magnetic configuration in which the plasmas were produced.

K. Narihara; K. Y. Watanabe; I. Yamada; T. Morisaki; K. Tanaka; S. Sakakibara; K. Ida; R. Sakamoto; N. Ohyabu; N. Ashikawa; M. Emoto; H. Funaba; M. Goto; H. Hayashi; H. Idei; K. Ikeda; S. Inagaki; N. Inoue; O. Kaneko; K. Kawahata; T. Kobuchi; A. Komori; S. Kubo; R. Kumazawa; S. Masuzaki; J. Miyazawa; S. Morita; O. Motojima; S. Murakami; S. Muto; T. Mutoh; Y. Nagayama; Y. Nakamura; H. Nakanishi; K. Nishimura; N. Noda; T. Notake; S. Ohdachi; Y. Oka; K. Ohkubo; M. Osakabe; S. Ozaki; B. J. Peterson; A. Sagara; K. Saito; H. Sasao; M. Sasao; K. Sato; M. Sato; T. Seki; T. Shimozuma; C. Shoji; S. Sudo; H. Suzuki; A. Takayama; M. Takechi; Y. Takeiri; N. Tamura; K. Toi; N. Tokuzawa; Y. Torii; K. Tsumori; T. Watari; H. Yamada; S. Yamaguchi; S. Yamamoto; K. Yamazaki; Y. Yoshimura

2001-01-01

99

Observation of Plasma Flow at the Magnetic Island in the Large Helical Device  

Microsoft Academic Search

Radial profiles of ion temperature and plasma flow are measured at the n\\/m = 1\\/1 magnetic island produced by external perturbation coils in the Large Helical Device. The sheared poloidal flows and sheared radial electric field are observed at the boundaries of the magnetic island, because the poloidal flow vanishes inside the static magnetic island. When the width of the

K. Ida; N. Ohyabu; T. Morisaki; Y. Nagayama; S. Inagaki; K. Itoh; Y. Liang; K. Narihara; A. Yu. Kostrioukov; B. J. Peterson; K. Tanaka; T. Tokuzawa; K. Kawahata; H. Suzuki; A. Komori

2002-01-01

100

ATLAS: Australia Telescope Large Area Survey: Deep Radio Observations of the CDFS-SWIRE field  

E-print Network

ATLAS: Australia Telescope Large Area Survey: Deep Radio Observations of the CDFS-SWIRE field 1/UDF The Australia Telescope Compact Array used to make the radio images in this paper. CDF-S SWIRE ESO CTIO Las. Overview · We are imaging the CDFS and ELAIS-S1 SWIRE fields at 20 cm. Combining radio data with other

Norris, Ray

101

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

102

2. Northwest circular bastion, seen from edge of southwest circular ...  

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

2. Northwest circular bastion, seen from edge of southwest circular bastion wall. Metal roof beams extend up to form peak. World War II gun installation at right. - Fort Hamilton, Northwest Circular Bastion, Rose Island, Newport, Newport County, RI

103

Numerical simulation of non-circular jets  

Microsoft Academic Search

Results are presented of numerical simulations of spatially developing, three-dimensional jets issued from circular and non-circular nozzles of identical equivalent diameters. Elliptic, rectangular and triangular jets are considered with aspect-ratios of 1:1 and 2:1. Flow visualization results show that large scale coherent structures are formed in both cornered and non-cornered jets. The axis-switching phenomenon is captured in all non-unity aspect-ratio

R. S. Miller; C. K. Madnia; P. Givi

1995-01-01

104

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

105

The x ray properties of a large, uniform QSO sample: Einstein observations of the LBQS  

NASA Technical Reports Server (NTRS)

Although there are large numbers of Quasi Stellar Objects (QSO's) now observed in X rays, extensive X-ray observations of uniformly selected, 'complete' QSO samples are more rare. The Large Bright QSO Survey (LBQS) consists of about 1000 objects with well understood properties, most brighter than B = 18.8 and thus amenable to X-ray detections in relatively brief exposures. The sample is thought to be highly complete in the range 0.2 less than z less than 3.3, a significantly broader interval than many other surveys. The Einstein IPC observed 150 of these objects, mostly serendipitously, during its lifetime. We report the results of an analysis of these IPC data, considering not only the 20 percent of the objects we find to have positive X-ray detections, but also the ensemble X-ray properties derived by 'image stacking'.

Margon, B.; Anderson, S. F.; Xu, X.; Green, P. J.; Foltz, C. B.

1992-01-01

106

A simple active corrector for liquid mirror telescopes observing at large zenith angles  

NASA Astrophysics Data System (ADS)

We investigate a corrector system, having a single spherical active secondary, that compensates the large aberrations of a liquid mirror observing at large angles from the zenith. This simple system gives subarcsecond images in small subregions within a 20 degree field. Although the performance is insufficient for imagery, it would be useful for high-resolution spectroscopy of compact objects. Adding adaptive optics to the system would greatly improve its performance, extending its accessible field and rendering it useful for high-resolution imagery.

Wang, G.; Moretto, E. F.; Borra, G.; Lemaitre, M.

1994-05-01

107

Gravity inversion of horizontal circular discs and vertical circular cylinders  

NASA Astrophysics Data System (ADS)

Inversion schemes are designed for automatic inversion of gravity anomalies of circular discs and vertical circular cylinders. The maximum anomaly is located on the anomaly profile and the distances between point pairs of one-quarter, one-half, and three-quarters the maximum anomaly are measured and used to calculate the initial values of the radius and depth to the center of the disc or depths to top and bottom of the cylinder. These initial values are improved iteratively until a best fit is obtained between the observed and calculated anomaly values by the Ridge regression method. Two FORTRAN 77 programs, GDISCIN and GCYLININ, are presented for routine use on personal computers.

Radhakrishna Murthy, I. V.; Jagannadha Rao, S.

1994-06-01

108

Very Large Telescope Interferometer observations of the dust geometry around R Coronae Borealis stars  

NASA Astrophysics Data System (ADS)

We are investigating the formation and evolution of dust around the hydrogen-deficient supergiants known as R Coronae Borealis (RCB) stars. We aim to determine the connection between the probable merger past of these stars and their current dust-production activities. We carried out high angular resolution interferometric observations of three RCB stars, namely RY Sgr, V CrA and V854 Cen, with the mid-infrared interferometer (MIDI) on the Very Large Telescope Interferometer (VLTI), using two telescope pairs. The baselines ranged from 30 to 60 m, allowing us to probe the dusty environment at very small spatial scales (˜50 mas or 400R?). The observations of the RCB star dust environments were interpreted using both geometrical models and one-dimensional radiative transfer codes. From our analysis, we find that asymmetric circumstellar material is apparent in RY Sgr, may also exist in V CrA and is possible for V854 Cen. Overall, we find that our observations are consistent with dust forming in clumps ejected randomly around the RCB star so that over time they create a spherically symmetric distribution of dust. However, we conclude that the determination of whether there is a preferred plane of dust ejection must wait until a time series of observations are obtained. Based on observations made with the Very Large Telescope Interferometer at Paranal Observatory under programme 079.D-0415.

Bright, S. N.; Chesneau, O.; Clayton, G. C.; De Marco, O.; Leão, I. C.; Nordhaus, J.; Gallagher, J. S.

2011-06-01

109

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

110

IMAGE-EUV Observation of Large Scale Standing Wave Pattern in the Nightside Plasmasphere  

NASA Technical Reports Server (NTRS)

We present analyses of a nightside plasmaspheric pattern of bifurcated, filamentary He(+) 30.4-nm emission enhancements observed by IMAGE EUV between approximately 19:40-22:13 UT on 28 June 2000 that indicate the presence of a large-scale, global ULF standing wave pattern. Analysis of coincident IMAGE magnetometer chain data reveals that these ULF waves extend across the magnetic latitude-longitude range of the chain and possess multiple spectral features between 0.6-5-mHz (3-30 minute period). Additionally, analysis of ACE SWE data reveals similarly structured spectral components in the solar wind. Collectively, these analyses lead to the conclusion that the observed large-scale ULF wave pattern is the result of solar wind pressure pulses 'ringing' the inner-magnetosphere.

Six, N. Frank (Technical Monitor); Gallagher, D. L.; Adrian, M. L.; Sandel, B. R.

2002-01-01

111

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

112

Observations of Gamma-ray Bursts with the Fermi Large Area Telescope  

NASA Astrophysics Data System (ADS)

The Fermi observatory, with its Gamma-ray Bursts Monitor (GBM) and Large Area Telescope (LAT), is observing Gamma-ray Bursts (GRBs) with a very large spectral coverage and unprecedented sensitivity, from ~10 keV to >300 GeV. In the first 3 years of the mission it observed emission above 100 MeV from 35 GRBs. In this paper we review the main results obtained on such a sample, highlighting also the relationships with the low-energy spectral and temporal features (as measured by the GBM). Some recent results on high energy photons from GRBs obtained with the preliminary Pass 8 new event-level reconstruction will be discussed.

Longo, Francesco; Vianello, Giacomo; Omodei, Nicola; Piron, Frederic; Vasilieou, Vlasios; Razzaque, Soebur

2014-04-01

113

Photometric and spectroscopic observations of (2060) Chiron at the ESO Very Large Telescope  

Microsoft Academic Search

Photometric and spectroscopic observations of Centaur Chiron have been obtained at the ESO\\/Very Large Telescope (VLT), both in optical and near-infrared spectral ranges, on 12-14 June 2001. Photometric optical data reveal that Chiron had reached a high activity level at that time. No absorption feature could be seen on the spectra; especially, no water ice could be detected. Based on

J. Romon-Martin; C. Delahodde; M. A. Barucci; C. de Bergh; N. Peixinho

2003-01-01

114

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

115

Constraints on large scale inhomogeneities from WMAP-5 and SDSS: confrontation with recent observations  

E-print Network

Measurements of the SNe Ia Hubble diagram which suggest that the universe is accelerating due to the effect of dark energy may be biased because we are located in a 200-300 Mpc underdense "void" which is expanding 20-30% faster than the average rate. With the smaller global Hubble parameter, the WMAP-5 data on cosmic microwave background anisotropies can be fitted without requiring dark energy if there is some excess power in the spectrum of primordial perturbations on 100 Mpc scales. The SDSS data on galaxy clustering can also be fitted if there is a small component of hot dark matter in the form of 0.5 eV mass neutrinos. We show however that if the primordial fluctuations are gaussian, the expected variance of the Hubble parameter and the matter density are far too small to allow such a large local void. Nevertheless many such large voids have been identified in the SDSS LRG survey in a search for the late-ISW effect due to dark energy. The observed CMB temperature decrements imply that they are nearly empty, thus these real voids too are in gross conflict with the concordance LCDM model. The recently observed high peculiar velocity flow presents another challenge for the model. Therefore whether a large local void actually exists must be tested through observations and cannot be dismissed a priori.

Paul Hunt; Subir Sarkar

2009-09-06

116

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

117

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

118

Circular Membrane Modes Model  

NSDL National Science Digital Library

The Circular Membrane Modes model displays the analytical wave equation solution for an ideal circular membrane with a fixed boundary. The solution is described by two integers m and n where n is a positive integer that counts the number of radial nodes and m counts the number of azimuthal (angular) nodes. The model shows a time-dependent animation of the membrane displacement and Chladni-like nodal pattern. The Circular Membrane Modes model is a supplemental simulation for the article "Chladni Patterns on Drumheads: A Physics of Music Experiment" by Randy Worland in The Physics Teacher 49(1), 24-27 (2011) and has been approved by the authors and The Physics Teacher editor. The model was developed using the Easy Java Simulations (EJS) modeling tool. It is distributed as a ready-to-run (compiled) Java archive. Double clicking the ejs_mech_CircularMembraneModes.jar file will run the program if Java is installed.

Christian, Wolfgang

2010-10-11

119

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

120

Simulating observations with HARMONI: the integral field spectrograph for the European Extremely Large Telescope  

NASA Astrophysics Data System (ADS)

With the next generation of extremely large telescopes commencing construction, there is an urgent need for detailed quantitative predictions of the scientific observations that these new telescopes will enable. Most of these new telescopes will have adaptive optics fully integrated with the telescope itself, allowing unprecedented spatial resolution combined with enormous sensitivity. However, the adaptive optics point spread function will be strongly wavelength dependent, requiring detailed simulations that accurately model these variations. We have developed a simulation pipeline for the HARMONI integral field spectrograph, a first light instrument for the European Extremely Large Telescope. The simulator takes high-resolution input data-cubes of astrophysical objects and processes them with accurate atmospheric, telescope and instrumental effects, to produce mock observed cubes for chosen observing parameters. The output cubes represent the result of a perfect data reduc- tion process, enabling a detailed analysis and comparison between input and output, showcasing HARMONI's capabilities. The simulations utilise a detailed knowledge of the telescope's wavelength dependent adaptive op- tics point spread function. We discuss the simulation pipeline and present an early example of the pipeline functionality for simulating observations of high redshift galaxies.

Zieleniewski, Simon; Thatte, Niranjan; Kendrew, Sarah; Houghton, Ryan; Tecza, Matthias; Clarke, Fraser; Fusco, Thierry; Swinbank, Mark

2014-07-01

121

High-resolution infrared maps from IRAS observations of large galaxies.  

NASA Astrophysics Data System (ADS)

A sample of 18 large optical galaxies from the Large Galaxy Catalog, has been studied for structural properties by processing the IR images taken by IRAS pointed observations. Survey detectors (POSD) observations at 12, 25, 60, and 100 microns, as well as the Chopped Photometric Channel observations (CPC) at 50 and 100 microns, have been used for IRAS pointed observations. High angular resolution intensity maps of several of these galaxies have been obtained using a self-adaptive dynamically controlled image deconvolution scheme based on the maximum entropy method. From a comparative study of the processed CPC and POSD maps in the FIR, it has been shown that the CPC maps do give new reliable structural information, although only for sufficiently strong sources. The flux densities as well as the color temperatures correlate quite well. The POSD intensity maps have been additionally used to obtain maps of interband temperature and optical depth. From the optical depth maps at 25, 60, and 100 microns, it is found that for most of these cases the peaks are close to the galactic nuclei.

Ghosh, S. K.; Verma, R. P.; Rengarajan, T. N.; Das, B.; Saraiya, H. T.

1993-06-01

122

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

123

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

124

Large zenith angle observations with the high-resolution GRANITE III camera  

E-print Network

The GRANITE III camera of the Whipple Cherenkov Telescope at the Fred Lawrence Whipple Observatory on Mount Hopkins, Arizona (2300 m a.s.l.) has the highest angular resolution of all cameras used on this telescope so far. The central region of the camera has 379 pixels with an individual angular diameter of 0.12 degrees. This makes the instrument especially suitable for observations of gamma-induced air-showers at large zenith angles since the increase in average distance to the shower maximum leads to smaller shower images in the focal plane of the telescope. We examine the performance of the telescope for observations of gamma-induced air-showers at zenith angles up to 63 degrees based on observations of Mkn 421 and using Monte Carlo Simulations. An improvement to the standard data analysis is suggested.

D. Petry; the VERITAS Collaboration

2001-08-06

125

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

126

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

127

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

128

The Large Scale Cosmic-Ray Anisotropy as Observed with Milagro  

E-print Network

Results are presented of a harmonic analysis of the large scale cosmic-ray anisotropy as observed by the Milagro observatory. We show a two-dimensional display of the sidereal anisotropy pro jections in right ascension generated by the fitting of three harmonics to 18 separate declination bands. The Milagro observatory is a water Cherenkov detector located in the Jemez mountains near Los Alamos, New Mexico. With a high duty cycle and large field-of-view, Milagro is an excellent instrument for measuring this anisotropy with high sensitivity at TeV energies. The analysis is conducted using a seven year data sample consisting of more than 95 billion events, the largest such data set in existence. We observe an anisotropy with a magnitude around 0.1% for cosmic rays with a median energy of 6 TeV. The dominant feature is a deficit region of depth (2.49 +/- 0.02 stat. +/- 0.09 sys.)x10^(-3) in the direction of the Galactic North Pole centered at 189 degrees right ascension. We observe a steady increase in the magnitude of the signal over seven years.

A. A. Abdo; B. T. Allen; T. Aune; D. Berley; S. Casanova; C. Chen; B. L. Dingus; R. W. Ellsworth; L. Fleysher; R. Fleysher; M. M. Gonzalez; J. A. Goodman; C. M. Hoffman; B. Hopper; P. H. Hüntemeyer; B. E. Kolterman; C. P. Lansdell; J. T. Linnemann; J. E. McEnery; A. I. Mincer; P. Nemethy; D. Noyes; J. Pretz; J. M. Ryan; P. M. Saz Parkinson; A. Shoup; G. Sinnis; A. J. Smith; G. W. Sullivan; V. Vasileiou; G. P. Walker; D. A. Williams; G. B. Yodh

2008-06-13

129

The Large Scale Cosmic-Ray Anisotropy as Observed with Milagro  

E-print Network

Results are presented of a harmonic analysis of the large scale cosmic-ray anisotropy as observed by the Milagro observatory. We show a two-dimensional display of the sidereal anisotropy projections in right ascension generated by the fitting of three harmonics to 18 separate declination bands. The Milagro observatory is a water Cherenkov detector located in the Jemez mountains near Los Alamos, New Mexico. With a high duty cycle and large field-of-view, Milagro is an excellent instrument for measuring this anisotropy with high sensitivity at TeV energies. The analysis is conducted using a seven year data sample consisting of more than 95 billion events. We observe an anisotropy with a magnitude around 0.1% for cosmic rays with a median energy of 6 TeV. The dominant feature is a deficit region of depth (-2.85 +/- 0.06 stat. +/- 0.08 syst.)x10^(-3) in the direction of the Galactic North Pole with a range in declination of -10 to 45 degrees and 150 to 225 degrees in right ascension. We observe a steady increase ...

Abdo, A A; Aune, T; Berley, D; Casanova, S; Chen, C; Dingus, B L; Ellsworth, R W; Fleysher, L; Fleysher, R; González, M M; Goodman, J A; Hoffman, C M; Hopper, B; Hüntemeyer, P H; Kolterman, B E; Lansdell, C P; Linnemann, J T; McEnery, J E; Mincer, A I; Némethy, P; Noyes, D; Ryan, J M; Parkinson, P M Saz; Shoup, A; Sinnis, G; Smith, A J; Sullivan, G W; Vasileiou, V; Walker, G P; Williams, D A; Yodh, G B

2008-01-01

130

The Large Aperture Gamma Ray Observatory as an Observational Alternative at High Altitude  

NASA Astrophysics Data System (ADS)

Although satellite observations have revealed some mysteries about the origin and location of cosmic rays at low energies, questions remain to be resolved in higher energy ranges (>1 GeV). However, the flow of particles at high energies is very low, large sensitive areas are necessary, so that the detection of secondary particles from observatories on the surface of the earth is a technically viable solution. While the Pierre Auger Observatory has such capacity given its 16000 m^2 of detectors, low height above sea level greatly reduces its detection capability. The Large Aperture Gamma Ray Observatory (LAGO) is an observational alternative that attempts to overcome this limitation. This project was started in 2005, placing water Cherenkov Detectors at high altitude. Observation sites have been selected with some basic requirements: altitude, academic and technical infrastructure, existence of a research group responsible for assembly and maintenance of the detectors and the analysis, visualization, divulgation and data storage. This paper presents the general status of the observatories of Sierra Negra-México, Chacaltaya-Bolívia, Marcapomacocha-Perú, Mérida-Venezuela and Bucaramanga-Colombia.

Rosales, M.

2011-10-01

131

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

132

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

133

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

134

CIRCULAR RIBBON FLARES AND HOMOLOGOUS JETS  

SciTech Connect

Solar flare emissions in the chromosphere often appear as elongated ribbons on both sides of the magnetic polarity inversion line (PIL), which has been regarded as evidence of a typical configuration of magnetic reconnection. However, flares having a circular ribbon have rarely been reported, although it is expected in the fan-spine magnetic topology involving reconnection at a three-dimensional (3D) coronal null point. We present five circular ribbon flares with associated surges, using high-resolution and high-cadence H{alpha} blue wing observations obtained from the recently digitized films of Big Bear Solar Observatory. In all the events, a central parasitic magnetic field is encompassed by the opposite polarity, forming a circular PIL traced by filament material. Consequently, a flare kernel at the center is surrounded by a circular flare ribbon. The four homologous jet-related flares on 1991 March 17 and 18 are of particular interest, as (1) the circular ribbons brighten sequentially, with cospatial surges, rather than simultaneously, (2) the central flare kernels show an intriguing 'round-trip' motion and become elongated, and (3) remote brightenings occur at a region with the same magnetic polarity as the central parasitic field and are co-temporal with a separate phase of flare emissions. In another flare on 1991 February 25, the circular flare emission and surge activity occur successively, and the event could be associated with magnetic flux cancellation across the circular PIL. We discuss the implications of these observations combining circular flare ribbons, homologous jets, and remote brightenings for understanding the dynamics of 3D magnetic restructuring.

Wang Haimin; Liu Chang, E-mail: haimin.wang@njit.edu [Space Weather Research Laboratory, Center for Solar-Terrestrial Research, New Jersey Institute of Technology, University Heights, Newark, NJ 07102-1982 (United States)

2012-12-01

135

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

136

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, L. R.; Kushner, P. J.; Derksen, C.

2014-07-01

137

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

138

Observations and simulations of a large-amplitude mountain wave breaking over the Antarctic Peninsula  

NASA Astrophysics Data System (ADS)

A case study of a large-amplitude orographic gravity wave occurring over the Antarctic Peninsula is presented, based on observations from the Vorcore balloon campaign and on mesoscale numerical simulations. The Vorcore campaign (September 2005 to February 2006) consisted in the flight of 27 superpressure balloons in the core of the Southern Hemisphere stratospheric polar vortex at altitudes of 16-19 km, from September 2005 to February 2006. On 7 October 2005, one of the balloons exploded as it was flying above the Antarctic Peninsula. The observations collected by another balloon that was flying during the same time period above the peninsula suggest the presence of a very intense gravity wave (peak-to-peak amplitude of the order of 25-30 m s-1 in zonal and meridional velocity disturbances). The wave packet is likely undersampled in the balloon observations because of its high intrinsic frequency, but the balloon data set is complemented with high-resolution numerical simulations carried out with the Weather Research and Forecast Model. The simulations are validated by comparison with the balloon measurements and show that the wave was breaking in the lower stratosphere at the time and height where the balloon exploded. The simulations highlight several consequences of the mountain wave on the stratosphere: forcing of the mean flow, generation of secondary inertia-gravity waves, and turbulence and mixing. In particular, the momentum fluxes are calculated and are found to compare well with the estimates from balloon measurements. The large values found are likely extreme values, which raises the issue of their representativity. To discuss this, the balloon measurements are used in conjunction with operational analyses to estimate the frequency of such large-amplitude gravity waves, i.e., to provide an estimate of their intermittency.

Plougonven, R.; Hertzog, A.; Teitelbaum, H.

2008-08-01

139

Identification of Very Large Scale Velocity Structures on the Solar Surface Using Mt Wilson Synoptic Observations  

NASA Astrophysics Data System (ADS)

The possible existance of very large velocity structures on the solar surface is important for our understanding of the solar dynamo. A goal of the Mt. Wilson synoptic program has been to measure low amplitude but large scale velocity features. Beginning in 1986 the continuing magnetic synoptic program was enhanced by the addition of a fast-scan program aimed at improving the quality of the large scale velocity measurements by averaging out the smaller scale noise produced by the five-minute oscillations and supergranulation (one program's noise is another program's signal; this well-known adage certainly applies here). The fast-scan program has now been in operation for more than one solar cycle and the resulting data base is well suited to the search for large scale features. The velocity analysis of the Mt. Wilson data proceeds in two steps: (1) The velocity at each point in each observation is correlated with the central meridian angle ?. We find the average of sin(?) ? vlos where ? vlos is the the deviation of the local line-of-sight velocity from the rotational velocity. This average includes all available observations for which a particular position on the solar surface is visible. The average is proportional to the deviation in local rotation rate. (2) A frequency analysis is carried out on the rotation rate deviations using the time of central meridian crossing as the measure of time. This produces a power spectrum in which time is measured in inverse rotation periods P-1. We have carried out the above sequence of operations and studied the resulting power specta. Due to the differential rotation rate, each latitude has a different period. We have compensated for this by expressing the frequency ? in terms of the local rotation rate for each latitude. This process detects structures which are carried across the apparent solar disk for at least more than one rotation. The longitudinal structure can be described in terms of its Fourier compnents each of which has a form Re (i 2 pi m ? t+ phi0) where phi0 is a phase angle offset. To the extent that peaks are seen in the power spectrum at integer multiples of the local inverse rotation period, these represent repeating large scale patterns superimposed on the rotation velocity. Although the peaks for individual latitude strips are somewhat irregular, when all available data for the twelve years of fast-scan observations are averaged together, a very regular pattern emerges of steadily decreasing peak power up to a maximum frequency of 8 inverse rotation periods. Evidently structures of scale larger than roughly 45-circ longitude are present on the solar surface and have lifetimes of several rotation periods.

Ulrich, R. K.

140

The genome of Oryctes rhinoceros nudivirus provides novel insight into the evolution of nuclear arthropod-specific large circular double-stranded DNA viruses.  

PubMed

The Oryctes rhinoceros nudivirus (OrNV) is a dsDNA virus with enveloped, rod-shaped virions. Its genome is 127,615 bp in size and contains 139 predicted protein-coding open reading frames (ORFs). In-depth genome sequence comparisons revealed a varying number of shared gene homologues, not only with other nudiviruses (NVs) and baculoviruses, but also with other arthropod-specific large dsDNA viruses, including the so-called Monodon baculovirus (MBV), the salivary gland hypertrophy viruses (SGHVs) and white spot syndrome virus (WSSV). Nudivirus genomes contain 20 baculovirus core gene homologues associated with transcription (p47, lef-8, lef-9, lef-4, vlf-1, and lef-5), replication (dnapol and helicase), virus structure (p74, pif-1, pif-2, pif-3, 19kda/pif-4, odv-e56/pif-5, vp91, vp39, and 38K), and unknown functions (ac68, ac81, and p33). Most strikingly, a set of homologous genes involved in peroral infection (p74, pif-1, pif-2, and pif-3) are common to baculoviruses, nudiviruses, SGHVs, and WSSV indicating an ancestral mode of infection in these highly diverged viruses. A gene similar to polyhedrin/granulin encoding the baculovirus occlusion body protein was identified in non-occluded NVs and in Musca domestica SGHV evoking the question of the evolutionary origin of the baculovirus polyhedrin/granulin gene. Based on gene homologies, we further propose that the shrimp MBV is an occluded member of the nudiviruses. We conclude that baculoviruses, NVs and the shrimp MBV, the SGHVs and WSSV share the significant number of conserved genetic functions, which may point to a common ancestry of these viruses. PMID:21380757

Wang, Yongjie; Bininda-Emonds, Olaf R P; van Oers, Monique M; Vlak, Just M; Jehle, Johannes A

2011-06-01

141

Experimental control of microdynamic events observed during the testing of a large deployable optical structure  

NASA Astrophysics Data System (ADS)

This paper presents experimental results relating to the Air Force Research Laboratory Precision Deployable Optics System (PDOS) ground demonstration. The PDOS experiment represents a sub-scale experimental test-bed for the demonstration of science and technology related to a large-aperture deployable space-based telescope systems. A description of the experimental test-bed is included. A description of microdynamic phenomena, referred to as `events' or `microlurches', observed during the test phase of the ground demonstration is presented. The performance of a three input, three output, high bandwidth structural controller operating in the presence of these events is presented and compared to the performance of the uncontrolled system.

Moser, Ruth L.; Erwin, R. Scott; Schrader, Karl N.; Bell, Kevin D.; Griffin, Steven F.; Powers, Michael K.

2000-07-01

142

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

143

The circular internal hydraulic jump  

NASA Astrophysics Data System (ADS)

Circular hydraulic jumps are familiar in single layers. Here we report the discovery of similar jumps in two-layer flows. A thin jet of fluid impinging vertically onto a rigid horizontal plane surface submerged in a deep layer of less-dense miscible fluid spreads radially, and a near-circular internal jump forms within a few centimetres from the point of impact with the plane surface. A jump is similarly formed as a jet of relatively less-dense fluid rises to the surface of a deep layer of fluid, but it appears less stable or permanent in form. Several experiments are made to examine the case of a downward jet onto a horizontal plate, the base of a square or circular container. The inlet Reynolds numbers, Re, of the jet range from 112 to 1790. Initially jumps have an undular, laminar form with typically 2-4 stationary waves on the interface between the dense and less-dense layers but, as the depth of the dense layer beyond the jump increases, the transitions become more abrupt and turbulent, resulting in mixing between the two layers. During the transition to a turbulent regime, single and sometimes moving multiple cusps are observed around the periphery of jumps. A semi-empirical model is devised that relates the parameters of the laboratory experiment, i.e. flow rate, inlet nozzle radius, kinematic viscosity and reduced gravity, to the layer depth beyond the jump and the radius at which an undular jump occurs. The experiments imply that surface tension is not an essential ingredient in the formation of circular hydraulic jumps and demonstrate that stationary jumps can exist in stratified shear flows which can be represented as two discrete layers. No stationary circular undular jumps are found, however, in the case of a downward jet of dense fluid when the overlying, less-dense, fluid is stratified, but a stationary turbulent transition is observed. This has implications for the existence of stationary jumps in continuously stratified geophysical flows: results based on two-layer models may be misleading. It is shown that the Froude number at which a transition of finite width occurs in a radially diverging flow may be less than unity.

Thorpe, S. A.; Kavcic, I.

144

The Expanded Very Large Array: Current Status and Shared Risk Observations  

NASA Astrophysics Data System (ADS)

After more than 20 years, the Very Large Array (VLA) remains one of the premier radio telescopes in the world, offering a unique combination of flexibility and sensitivity. The Expanded VLA (EVLA; Perley et al. 2009: arXiv:0909.1585v1) provides order-of-magnitude gains in sensitivity and spectral capabilities, as well as continuous frequency coverage from 1 to 50 GHz. The project is on track for completion in 2012, and is poised to meet or exceed all key technical and scientific requirements. All 28 antennas will be converted to EVLA status by mid-2010, and installation of the eight new cryogenically cooled wideband receiver system proceeds apace. Shared-risk scientific observations with the new WIDAR correlator will begin in early 2010, giving early access to the new wide bandwidths and superb spectral resolution. Here I summarize the rapidly expanding capabilities of the EVLA, emphasizing the latest test results and details of the shared risk observing programs.

Rupen, Michael P.

2010-01-01

145

Observing Growth and Division of Large Numbers of Individual Bacteria by Image Analysis  

PubMed Central

We describe a method that enabled us to observe large numbers of individual bacterial cells during a long period of cell growth and proliferation. We designed a flow chamber in which the cells attached to a transparent solid surface. The flow chamber was mounted on a microscope equipped with a digital camera. The shear force of the flow removed the daughter cells, making it possible to monitor the consecutive divisions of a single cell. In this way, kinetic parameters and their distributions, as well as some physiological characteristics of the bacteria, could be analyzed based on more than 1,000 single-cell observations. The method which we developed enabled us to study the history effect on the distribution of the lag times of single cells. PMID:14766541

Elfwing, A.; LeMarc, Y.; Baranyi, J.; Ballagi, A.

2004-01-01

146

Zero-level problem of solar magnetographs and observations of large-scale magnetic fields  

NASA Astrophysics Data System (ADS)

This paper discusses some aspects of the zero-level problem of solar magnetographs which is particularly important for observations of large-scale magnetic fields on the Sun. Experiments at the STOP telescope of the Sayan Solar Observatory (SSO) showed that in addition to the adjustment errors of the polarization analyzer, the focusing errors of the spectrograph, and the linear polarization of the light (these mechanisms were known previously [5]), “spurious” signals of the magnetograph are brought about by polarization effects in the optical details preceding the polarization analyzer (coelostat mirrors and the objective) and aberration errors of the spectrograph. Disadvantages of the method of monitoring the zero level from the nonmagnetic line ? 512.37 nm FeI are pointed out. A correlation was made between the observations of the solar mean magnetic field in the SSO and WSO (Wilcox Solar Observatory, Stanford, USA) — the observatories which use the different methods of zero-level monitoring.

Demidov, M. L.

1996-10-01

147

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

148

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

NASA Astrophysics Data System (ADS)

Large-scale hydraulic models are able to predict flood characteristics, and are being used in forecasting applications. In this work, the potential value of satellite observations to initialize hydraulic forecasts is explored, using the Ensemble Sensitivity method. The impact estimation is based on the Local Ensemble Transform Kalman Filter, allowing for the forecast error reductions to be computed without additional model runs. The experimental design consisted of two configurations of the LISFLOOD-FP model over the Ohio River basin: a baseline simulation represents a 'best effort' model using observations for parameters and boundary conditions, whereas the second simulation consists of erroneous parameters and boundary conditions. Results showed that the forecast skill was improved for water heights up to lead times of 11 days (error reductions ranged from 0.2 to 0.6 m/km), while even partial observations of the river contained information for the entire river's water surface profile and allowed forecasting 5 to 7 days ahead. Moreover, water height observations had a negative impact on discharge forecasts for longer lead times although they did improve forecast skill for 1 and 3 days (up to 60 m3 / s / km). Lastly, the inundated area forecast errors were reduced overall for all examined lead times. Albeit, when examining a specific flood event the limitations of predictability were revealed suggesting that model errors or inflows were more important than initial conditions.

Andreadis, Konstantinos M.; Schumann, Guy J.-P.

2014-11-01

149

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

150

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

151

THEMIS Observations of the Magnetopause Electron Diffusion Region: Large Amplitude Waves and Heated Electrons  

NASA Technical Reports Server (NTRS)

We present the first observations of large amplitude waves in a well-defined electron diffusion region based on the criteria described by Scudder et al at the subsolar magnetopause using data from one Time History of Events and Macroscale Interactions during Substorms (THEMIS) satellite. These waves identified as whistler mode waves, electrostatic solitary waves, lower hybrid waves, and electrostatic electron cyclotron waves, are observed in the same 12 s waveform capture and in association with signatures of active magnetic reconnection. The large amplitude waves in the electron diffusion region are coincident with abrupt increases in electron parallel temperature suggesting strong wave heating. The whistler mode waves, which are at the electron scale and which enable us to probe electron dynamics in the diffusion region were analyzed in detail. The energetic electrons (approx. 30 keV) within the electron diffusion region have anisotropic distributions with T(sub e(right angle))/T(sub e(parallel)) > 1 that may provide the free energy for the whistler mode waves. The energetic anisotropic electrons may be produced during the reconnection process. The whistler mode waves propagate away from the center of the "X-line" along magnetic field lines, suggesting that the electron diffusion region is a possible source region of the whistler mode waves.

Tang, Xiangwei; Cattell, Cynthia; Dombeck, John; Dai, Lei; Wilson, Lynn B. III; Breneman, Aaron; Hupack, Adam

2013-01-01

152

Confronting the relaxation mechanism for a large cosmological constant with observations  

SciTech Connect

In order to deal with a large cosmological constant a relaxation mechanism based on modified gravity has been proposed recently. By virtue of this mechanism the effect of the vacuum energy density of a given quantum field/string theory (no matter how big is its initial value in the early universe) can be neutralized dynamically, i.e. without fine tuning, and hence a Big Bang-like evolution of the cosmos becomes possible. Remarkably, a large class (F{sup n}{sub m}) of models of this kind, namely capable of dynamically adjusting the vacuum energy irrespective of its value and size, has been identified. In this paper, we carefully put them to the experimental test. By performing a joint likelihood analysis we confront these models with the most recent observational data on type Ia supernovae (SNIa), the Cosmic Microwave Background (CMB), the Baryonic Acoustic Oscillations (BAO) and the high redshift data on the expansion rate, so as to determine which ones are the most favored by observations. We compare the optimal relaxation models F{sup n}{sub m} found by this method with the standard or concordance ?CDM model, and find that some of these models may appear as almost indistinguishable from it. Interestingly enough, this shows that it is possible to construct viable solutions to the tough cosmological fine tuning problem with models that display the same basic phenomenological features as the concordance model.

Basilakos, Spyros; Bauer, Florian; Solà, Joan, E-mail: svasil@academyofathens.gr, E-mail: fbauerphysik@eml.cc, E-mail: sola@ecm.ub.es [High Energy Physics Group, Dept. ECM, Univ. de Barcelona, Av. Diagonal 647, E-08028 Barcelona, Catalonia (Spain)

2012-01-01

153

The characteristics of quasistatic electric field perturbations observed by DEMETER satellite before large earthquakes  

NASA Astrophysics Data System (ADS)

This paper presents new results after processing the ULF electric field (DC-15 Hz) observed by DEMETER satellite (h = 660-710 km). Typical perturbations were picked up in quasistatic electric field around some large earthquakes in 2010 at first. And then, 27 earthquakes were selected to be analyzed on quasistatic electric field in two seismic regions of Indonesia and Chile at equatorial and middle latitude area respectively. Three-component electric field data related to earthquakes were collected along all the up-orbits (in local nighttime) in a limited distance of 2000 km to the epicenters during 9 days with 7 days before and 1 day after those cases, and totally 57 perturbations were found around them. All the results show that the amplitude of quasistatic electric field perturbations varies from 1.5 to 16 mV/m in the upper ionosphere, mostly smaller than 10 mV/m. And the perturbations were mainly located just over the epicentral area or at the end of seismic faults constructed by a series of earthquakes where electromagnetic emissions may be easily formed during preparation and development processes of seismic sequences. Among all 27 cases, there are 10 earthquakes with perturbations occurring just one day before, which demonstrates the close correlation in time domain between quasistatic electric field in ionosphere and large earthquakes. Finally, combined with in situ observation of plasma parameters, the coupling mechanism of quasistatic electric field in different earth spheres was discussed.

Zhang, X.; Shen, X.; Zhao, S.; Yao, Lu; Ouyang, X.; Qian, J.

2014-01-01

154

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

155

Very Large Rain Drops from 2D Video Disdrometers and Concomitant Polarimetric Radar Observations  

NASA Technical Reports Server (NTRS)

Drop size distribution (DSD) measurements using ground-based disdrometers (point measurements) have often been used to derive equations to relate radar observations to the integral rainfall parameters (Atlas et al. 1999, Bringi et al., 2003, Kozu et al., 2006, Tokay and Short, 1996, Ajayi and Owolabi, 1987, Battan, 1973). Disdrometers such as JWD, MRR and several others have a major limitation in measuring drops with equi-volume diameters (D(sub eq)) larger than 5 mm because they often rely on the velocity-diameter relationship which plateaus beyond this diameter range (Atlas et al., 1973, Gunn & Kinzer, 1949). Other disdrometers such as Parsivel also lack accuracy beyond this diameter range. The 2D video disdrometer (2DVD: Schönhuber et al., 2008) on the other hand gives drop-shape contours and velocities for each individual drop/hydrometeor falling through its sensor area; this provides a unique opportunity to study the role of very-large drops on radar measurements in particular those with polarimetric radar capability where DSDs with a significant component of very large drops may require special consideration given that the differential reflectivity and other polarimetric radar parameters including attenuation-correction methods will be sensitive to the concentrations of these large drops. A recent study on the occurrence of large drops by Gatlin et al. (2014) has compiled a large and diverse set of measurements made with the 2D video disdrometers from many locations around the globe. Some of the largest drops found in this study were 9 mm D(sub eq) and larger, and in this paper, we report on three such events, with maximum D(sub eq's) of 9.0, 9.1 and 9.7 mm, which occurred in Colorado, Northern Alabama, and Oklahoma, respectively. Detailed examination of the 2DVD data - in terms of shapes and fall velocities - has confirmed that these are fully-melted hydrometeors, although for the last case in Oklahoma, a bigger and non-fully-melted hydrometeor was also observed. All three events were also captured by polarimetric radars, namely the S-band CHILL radar operated by Colorado State University (Brunkow et al., 2000), the C-band ARMOR radar (Petersen et al., 2007) operated by University of Alabama in Huntsville, and NEXRADKVNX, operated by the US National Weather Service, respectively. For the last event, several other radar observations were also made, including two X-band radars operated by the US Dept. of Energy. Analyses of 2DVD data in conjunction with the corresponding radar observations are presented, along with some discussion on sampling issues related to the measurements of such large rain drops. The latter is addressed using maximum diameter D(sub max) measurements from 1-minute DSDs using two collocated 2DVDs for 37 events in Huntsville.

Thurai, Merhala; Gatlin, Patrick; Bringi, V. N.; Carey, Lawrence

2014-01-01

156

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

157

Circular Fibonacci gratings.  

PubMed

We introduce circular Fibonacci gratings (CFGs) that combine the concept of circular gratings and Fibonacci structures. Theoretical analysis shows that the diffraction pattern of CFGs is composed of fractal distributions of impulse rings. Numerical simulations are performed with two-dimensional fast Fourier transform to reveal the fractal behavior of the diffraction rings. Experimental results are also presented and agree well with the numerical results. The fractal nature of the diffraction field should be of great theoretical interest, and shows potential to be further developed into practical applications, such as in laser measurement with wideband illumination. PMID:22086040

Gao, Nan; Zhang, Yuchao; Xie, Changqing

2011-11-01

158

Sunyaev-Zel'dovich Observations Using Large-Format Millimeter Arrays  

NASA Astrophysics Data System (ADS)

Galaxy clusters are the largest gravitationally bound objects in the observable universe, and they are formed from the largest perturbations of the primordial matter power spectrum. During initial cluster collapse, matter is accelerated to supersonic velocities, and the baryonic component is heated as it passes through accretion shocks. This process stabilizes when the pressure of the bound matter prevents further gravitational collapse. Galaxy clusters are useful cosmological probes, because their formation progressively freezes out at the epoch when dark energy begins to dominate the expansion and energy density of the universe. A diverse set of observables, from radio through X-ray wavelengths, are sourced from galaxy clusters, and this is useful for self-calibration. The distributions of these observables trace a cluster's dark matter halo, which represents more than 80% of the cluster's gravitational potential. One such observable is the Sunyaev-Zel'dovich effect (SZE), which results when the ionized intercluster medium blueshifts the cosmic microwave background via Compton scattering. Great technical advances in the last several decades have made regular observation of the SZE possible. Resolved SZE science, such as is explored in this analysis, has benefitted from the construction of large-format camera arrays consisting of highly sensitive millimeter-wave detectors, such as Bolocam. Bolocam is a submillimeter camera, sensitive to 140 GHz and 268 GHz radiation, located at one of the best observing sites in the world: the Caltech Submillimeter Observatory on Mauna Kea in Hawaii. Bolocam fielded 144 of the original spider web NTD bolometers used in an entire generation of ground-based, balloon-borne, and satellite-borne millimeter wave instrumention. Over approximately six years, our group at Caltech has developed a mature galaxy cluster observational program with Bolocam. This thesis describes the construction of the instrument's full cluster catalog: BOXSZ. Using this catalog, I have scaled the Bolocam SZE measurements with X-ray mass approximations in an effort to characterize the SZE signal as a viable mass probe for cosmology. This work has confirmed the SZE to be a low-scatter tracer of cluster mass. The analysis has also revealed how sensitive the SZE-mass scaling is to small biases in the adopted mass approximation. Future Bolocam analysis efforts are set on resolving these discrepancies by approximating cluster mass jointly with different observational probes.

Czakon, Nicole G.

159

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

NASA Astrophysics Data System (ADS)

While production of aggregates and their subsequent sinking is known to be one pathway for the downward movement of organic matter from the euphotic zone, the rapid transition from non-aggregated to aggregated particles has not been reported previously. We made one vertical profile of particle size distributions (PSD; sizes ranging from 0.052 to several millimeters in equivalent spherical diameter) at pre-bloom stage and seven vertical profiles 3 weeks later over a 48 h period at early bloom stage using the Underwater Vision Profiler during the Kerguelen Ocean and Plateau Compared Study cruise 2 (KEOPS2, October-November 2011). In these naturally iron-fertilized waters southeast of Kerguelen Island (Southern Ocean), the total particle numerical abundance increased by more than fourfold within this time period. A massive total volume increase associated with particle size distribution changes was observed over the 48 h survey, showing the rapid formation of large particles and their accumulation at the base of the mixed layer. The results of a one-dimensional particle dynamics model support coagulation as the mechanism responsible for the rapid aggregate formation and the development of the VT subsurface maxima. The comparison of VT profiles between early bloom stage and pre-bloom stage indicates an increase of particulate export below 200 m when bloom has developed. These results highlight the role of coagulation in forming large particles and triggering carbon export at the early stage of a naturally iron-fertilized bloom, while zooplankton grazing may dominate later in the season. The rapid changes observed illustrate the critical need to measure carbon export flux with high sampling temporal resolution. Our results are the first published in situ observations of the rapid accumulation of marine aggregates and their export and the general agreement of this rapid event with a model of phytoplankton growth and coagulation.

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

2014-08-01

160

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

161

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

162

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

163

Spitzer SAGE Observations of Young Stellar Objects in the Large Magellanic Cloud  

NASA Astrophysics Data System (ADS)

We have identified thousands of new Young Stellar Objects (YSOs) in the Large Magellanic Cloud. The observations were made with the Spitzer Space Telescope as part of the SAGE Legacy project. The YSOs were selected from the SAGE point source catalog by locating regions of color-magnitude space unoccupied by known sources such as galaxies and evolved stars. Our YSO list is not complete, since those with similar colors and magnitudes to other populations are not included. However, our initial goal is to produce a list that is dominated by YSOs. The spatial distribution of the YSOs correlates with CO, H I, and especially 3 cm observations. We will show analysis of the YSOs based on radiation transfer models. This work is based on observations made with the Spitzer Space Telescope, which is operated by the Jet Propulsion Laboratory, California Institute of Technology under a contract with NASA. Support for this work was provided by NASA through an award issued by JPL/Caltech.

Whitney, Barbara; Sewilo, M.; Indebetouw, R.; Robitaille, T.; Meixner, M.; Vijh, U.; Srinivasan, S.; Meade, M.; Babler, B.; Churchwell, E.; Hora, J.; Gordon, K.; Engelbracht, C.; For, B.; Block, M.; Misselt, K.; Leitherer, C.; Kawamura, A.; Onishi, T.; Mizuno, A.; Fukui, Y.

2006-12-01

164

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

165

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

166

Circular Motion and Forces  

NSDL National Science Digital Library

A heavy ball is attached to a string and swung in a circular path in a horizontal plane as shown in the animation. At the point indicated the string suddenly breaks at the ball. Four animations represent possible results when the string breaks at point P.

Christian, Wolfgang; Belloni, Mario

2006-01-14

167

FISH RECIPES CIRCULAR 201  

E-print Network

sought and made their fortunes in the lake trout, whitefish, and sturgeon from these cold, pure watersFISH RECIPES #12;CIRCULAR 201 S ince the days of the voyageurs and copper miners, the Great Lakes caught with spears and crude nets in the rivers that connected the Lakes. These vast inland seas soon

168

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

169

The Right Circular Cylinder  

NSDL National Science Digital Library

This learning object from Wisc-Online covers the right circular cylinder, 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

170

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

171

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

NASA Astrophysics Data System (ADS)

The chemistry in large thunderstorm clouds is influenced by local lightning-NOx production and uplift of boundary layer air. Under these circumstances trace gases like nitrous acid (HONO) or formaldehyde (HCHO) are expected to be formed or to reach the tropopause region. However, up to now only few observations of HONO at this altitude have been reported. Here we report on a case study where enhancements in HONO, HCHO and nitrogen oxides (NOx) were observed by the CARIBIC flying laboratory (Civil Aircraft for the Regular Investigation of the atmosphere Based on an Instrument Container). The event took place in a convective system over the Caribbean Sea in August 2011. Inside the cloud the light path reaches up to 100 km. Therefore the DOAS instrument on CARIBIC was very sensitive to the tracers inside the cloud. Based on the enhanced slant column densities of HONO, HCHO and NO2, average mixing ratios of 37, 468 and 210 ppt, respectively, were calculated. These data represent averages for constant mixing ratios inside the cloud. However, a large dependency on the assumed profile is found; for HONO a mixing ratio of 160 ppt is retrieved if the total amount is assumed to be situated in the uppermost 2 km of the cloud. The NO in situ instrument measured peaks up to 5 ppb NO inside the cloud; the background in the cloud was about 1.3 ppb, and hence clearly above the average outside the cloud (? 150 ppt). The high variability and the fact that the enhancements were observed over a pristine marine area led to the conclusion that, in all likelihood, the high NO concentrations were caused by lighting. This assumption is supported by the number of flashes that the World Wide Lightning Location Network (WWLLN) counted in this area before and during the overpass. The chemical box model CAABA is used to estimate the NO and HCHO source strengths which are necessary to explain our measurements. For NO a source strength of 10 × 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 lightning emissions of 5 × 1025 NO molec flash-1 (2.3-6.4 × 1025). The uncertainties are determined by a change of the input parameters in the box model, the cloud top height and the flash density. The emission rate per flash is scaled up to a global scale and 1.9 (1.4-2.5) tg N a-1 is estimated. The HCHO updraught is of the order of 120 × 109 molec cm-2 s-1 km-1. Also isoprene and CH3OOH as possible HCHO sources are discussed.

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

2014-07-01

172

Galaxy evolution and large-scale structure in the far-infrared. I - IRAS pointed observations  

NASA Technical Reports Server (NTRS)

Redshifts for 66 galaxies were obtained from a sample of 93 60-micron sources detected serendipitously in 22 IRAS deep pointed observations, covering a total area of 18.4 sq deg. The flux density limit of this survey is 150 mJy, 4 times fainter than the IRAS Point Source Catalog (PSC). The luminosity function is similar in shape with those previously published for samples selected from the PSC, with a median redshift of 0.048 for the fainter sample, but shifted to higher space densities. There is evidence that some of the excess number counts in the deeper sample can be explained in terms of a large-scale density enhancement beyond the Pavo-Indus supercluster. In addition, the faintest counts in the new sample confirm the result of Hacking et al. (1989) that faint IRAS 60-micron source counts lie significantly in excess of an extrapolation of the PSC counts assuming no luminosity or density evolution.

Lonsdale, Carol J.; Hacking, Perry B.

1989-01-01

173

Tracking progress: monitoring observing statistics and telescope usage at the Southern African Large telescope  

NASA Astrophysics Data System (ADS)

Monitoring the performance of a facility is critical to successful scientific operations, and even more so, for queue based telescopes such as SALT. We highlight the steps that have been undertaken in order to monitor the performance of the Southern African Large Telescope from proposal submission to on-sky observations, and finally to publication. A suite of dedicated software tools has been produced in order to monitor the performance of the telescope, weather conditions, and scientific productivity. We report on some of the key metrics for SALT since the start of science operations to provide a baseline for its current performance. After taking account that science operations only began in September 2011, the number of papers produced by SALT since that time is similar to other 8m class observatories at the beginning of their operations.

Crawford, Steven M.; Koeslag, Anthony; Romero Colmenero, Encarni; Buckley, David A. H.; Koen, Thea; Marang, Fred; Van Wyk, Veronica; Bennett, Samantha

2014-07-01

174

Observation of collision and oscillation of microdroplets with extremely large shear deformation  

NASA Astrophysics Data System (ADS)

We measured the viscosity and surface tension of various liquids under large (˜106 s-1) shear deformation. Oscillation of a 10-?m size microdroplet is brought about by the head-on collision of two droplets. Since the Reynolds number is as small as 100, the motion of the liquid is stable and the dynamic image is obtained with high reproducibility by the stroboscopic method. By observing and evaluating the mechanical oscillation of the microdroplet, of which frequency ranges typically in 100 - 300 kHz, we found that the viscosity of ethylene glycol and diethylene glycol is smaller than the known literature value, which is considered to be the viscosity at zero-frequency. This phenomena can be attributed to the slow viscous relaxation of associated liquids due to the re-combination dynamics of the network of H-bonds.

Yamada, Tatsuya; Sakai, Keiji

2012-02-01

175

Experimental Observations of Large-Scale Motions in the Turbulent Boundary Layer  

NASA Astrophysics Data System (ADS)

Particle image velocimetry is used to measure instantaneous u and v velocity components in the x-y plane of a zero-pressure gradient turbulent boundary layer. Approximately 50 realizations are performed at each of 2 Reynolds numbers, Re_?=1015 and 7705, capturing a field of view of ? 3 ? streamwise and over ? wall-normal. The data confirms observations of uniform u-momentum zones of fluid often containing packets of hairpin-like vortices( Meinhart and Adrian, 1997). Near-wall packets may concatenate to form low-speed streaks, containing up to ? 10 vortices and extending over 2.5 ? streamwise. If undisturbed, groups of packets may grow to the outer regions of the boundary layer. These large-scale motions typically grow linearly with the streamwise coordinate at angles of 4 to 24 degrees, and may reach heights of ? 0.8 ?.

Tomkins, Christopher D.; Adrian, Ronald J.

1997-11-01

176

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

177

LARGE-AMPLITUDE ALFVEN WAVE IN INTERPLANETARY SPACE: THE WIND SPACECRAFT OBSERVATIONS  

SciTech Connect

We present, for the first time, measurements of arc-polarized velocity variations together with magnetic field variations associated with a large-amplitude Alfven wave as observed by the Wind satellite. The module of the magnetic field variance is larger than the magnitude of the average magnetic field, indicating the large amplitude of these fluctuations. When converting to the deHoffman-Teller frame, we find that the magnetic field and velocity vector components, in the plane perpendicular to the minimum-variance direction of the magnetic field, are arc-polarized, and their tips almost lie on the same circle. We also find that the normalized cross helicity and Alfven ratio of the wave are both nearly equal to unity, a result which has not been reported in previous studies at 1 AU. It is worthy to stress here that pure Alfven waves can also exist in the solar wind even near the Earth at 1 AU, but not only near 0.3 AU. Further study could be done to help us know more about the properties of pure Alfven wave at 1 AU that could not be figured out easily before because of the contaminations (e.g., Alfven waves propagating in different directions, magnetic structures, and other compressional waves) on previously reported Alfven wave cases.

Wang Xin; He Jiansen; Tu Chuanyi; Zhang Lei [School of Earth and Space Sciences, Peking University, Beijing 100871 (China); Marsch, Eckart [Max-Planck-Institut fuer Sonnensystemforschung, 37191 Katlenburg-Lindau (Germany); Chao, Jih-Kwin, E-mail: wangxinpku0209@gmail.com [Institute of Space Science, National Central University, Chung-Li 32054, Taiwan (China)

2012-02-20

178

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

179

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

180

Plasma signatures in large Martian magnetic flux ropes: MARSIS/ASPERA-3 observations  

NASA Astrophysics Data System (ADS)

Cylindrical structures of highly twisted magnetic field (flux ropes) have been observed at Mars, using measurements by the MAG-ER magnetometer-electron reflectometer onboard Mars Global Surveyor (MGS) and by the MARSIS radar sounder onboard Mars Express (MEX). Signatures of flux ropes are spikes of magnetic field strength and magnetic field rotations. Both small scale flux ropes (diameters of a few tens of km) and large scale flux ropes (diameters of around 100 km) have been found at Mars. We look at times of presumed flux ropes on the dayside of Mars, detected in the local magnetic field strength given by MARSIS. The signatures in MARSIS are magnetic field strength increases (peak strength reaches several tens to hundred nT) for several minutes (size of hundreds of km along the spacecraft track), found outside but near crustal magnetic field regions. Although we cannot determine the presence of a magnetic field rotation because of the lack of a magnetometer onboard MEX, we assume that these magnetic field increases are large flux ropes. There are indeed large flux ropes with similar characteristics which were established by the magnetometer data from MGS, and thought to form by stretching and reconnection of crustal magnetic field by the solar wind. On the other hand, MEX possesses in situ ion measurements, unlike MGS. We will use the ion and electron data from the ASPERA-3 particle instrument onboard MEX in order to characterize the plasma (ionospheric only or mixing with shocked plasma?) inside the flux ropes, which will give hints on their origin.

Diéval, Catherine; Morgan, David; Duru, Firdevs; Gurnett, Donald

2014-05-01

181

The Circular Velocity Function of Group Galaxies  

NASA Astrophysics Data System (ADS)

A robust prediction of ?CDM cosmology is the halo circular velocity function (CVF), a dynamical cousin of the halo mass function. The correspondence between theoretical and observed CVFs is uncertain, however: cluster galaxies are reported to exhibit a power-law CVF consistent with N-body simulations, but that of the field is distinctly Schechter-like, flattened compared to ?CDM expectations at circular velocities v c <~ 200 km s-1. Groups offer a powerful probe of the role environment plays in this discrepancy as they bridge the field and clusters. Here, we construct the CVF for a large, mass- and multiplicity-complete sample of group galaxies from the Sloan Digital Sky Survey. Using independent photometric v c estimators, we find no transition from field to ?CDM-shaped CVF above v c = 50 km s-1 as a function of group halo mass. All groups with 12.4 <~ log M halo/M ? <~ 15.1 (Local Group analogs to rich clusters) display similar Schechter-like CVFs marginally suppressed at low v c compared to that of the field. Conversely, some agreement with N-body results emerges for samples saturated with late-type galaxies, with isolated late-types displaying a CVF similar in shape to ?CDM predictions. We conclude that the flattening of the low-v c slope in groups is due to their depressed late-type fractions—environment affecting the CVF only to the extent that it correlates with this quantity—and that previous cluster analyses may suffer from interloper contamination. These results serve as useful benchmarks for cosmological simulations of galaxy formation.

Abramson, Louis E.; Williams, Rik J.; Benson, Andrew J.; Kollmeier, Juna A.; Mulchaey, John S.

2014-09-01

182

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

183

Observations of large-scale fluid transport by laser-guided plankton aggregationsa)  

NASA Astrophysics Data System (ADS)

Diel vertical migration of plankton has been proposed to affect global ocean circulation to a degree comparable to winds and tides. This biomixing process has never been directly observed, however, due to the inability to predict its occurrence in situ or to reproduce it in a laboratory setting. Furthermore, it has been argued that the energy imparted to the ocean by plankton migrations occurs at the scale of individual organisms, which is too small to impact ocean mixing. We describe the development of a multi-laser guidance system that leverages the phototactic abilities of plankton to achieve controllable vertical migrations concurrently with laser velocimetry of the surrounding flow. Measurements in unstratified fluid show that the hydrodynamic interactions between neighboring swimmers establish an alternate energy transfer route from the small scales of individually migrating plankton to significantly larger scales. Observations of laser-induced vertical migrations of Artemia salina reveal the appearance of a downward jet, which triggers a Kelvin-Helmholtz instability that results in the generation of eddy-like structures with characteristic length scales much larger than the organisms. The measured energy spectrum is consistent with these findings and indicates energy input at large scales, despite the small individual size of the organisms. These results motivate the study of biomixing in the presence of stratification to assess the contribution of migrating zooplankton to local and global ocean dynamics. The laser control methodology developed here enables systematic study of the relevant processes.

Wilhelmus, Monica M.; Dabiri, John O.

2014-10-01

184

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

185

VCD -Vibrational Circular Dichroism Applications  

E-print Network

VCD - Vibrational Circular Dichroism Applications Secondary structure of proteins and peptides Purity of enantiomers Absolute structure Method The abbreviation "VCD" derives from "Vibrational Circular to vibrational excitation with nonpolarized IR radiation, in case of VCD spectroscopy the difference

Wells, Mathew G. - Department of Physical and Environmental Sciences, University of Toronto

186

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

187

EXPANDED VERY LARGE ARRAY OBSERVATIONS OF THE NEBULA AROUND G79.29+0.46  

SciTech Connect

We have observed the radio nebula surrounding the Galactic luminous blue variable candidate G79.29+0.46 with the Expanded Very Large Array (EVLA) at 6 cm. These new radio observations allow a morphological comparison between the radio emission, which traces the ionized gas component, and the mid-IR emission, a tracer of the dust component. The InfraRed Array Camera (8 {mu}m) and the Multiband Imaging Photometer for Spitzer (24 {mu}m and 70 {mu}m) images have been reprocessed and compared with the EVLA map. We confirm the presence of a second shell at 24 {mu}m and also provide evidence for its detection at 70 {mu}m. The differences between the spatial morphology of the radio and mid-IR maps indicate the existence of two dust populations, the cooler one emitting mostly at longer wavelengths. Analysis of the two dusty, nested shells have provided us with an estimate of the characteristic timescales for shell ejection, providing important constraints for stellar evolutionary models. Finer details of the ionized gas distribution can be appreciated thanks to the improved quality of the new 6 cm image, most notably the highly structured texture of the nebula. Evidence of interaction between the nebula and the surrounding interstellar medium can be seen in the radio map, including brighter features that delineate regions where the shell structure is locally modified. In particular, the brighter filaments in the southwest region appear to frame the shocked southwestern clump reported from CO observations.

Umana, G.; Buemi, C. S.; Trigilio, C.; Leto, P. [INAF-Osservatorio Astrofisico di Catania, Via S. Sofia 78, 95123 Catania (Italy); Agliozzo, C.; Ingallinera, A. [Department of Physics and Astronomy, Universita di Catania and INAF-Osservatorio Astrofisico di Catania, Via S. Sofia 78, 95123 Catania (Italy); Noriega-Crespo, A. [Spitzer Science Center, California Institute of Technology, Mail Code 314-6, Pasadena, CA 91125 (United States); Hora, J. L., E-mail: Grazia.Umana@oact.inaf.it [Harvard-Smithsonian Center for Astrophysics, 60 Garden St. MS-65, Cambridge, MA 02138-1516 (United States)

2011-09-20

188

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

189

Characteristics of large-scale wave structure observed from African and Southeast Asian longitudinal sectors  

NASA Astrophysics Data System (ADS)

spatial large-scale wave structure (LSWS) at the base of F layer is the earliest manifestation of seed perturbation for Rayleigh-Taylor instability, hence, found to play a deterministic role in the development of Equatorial Plasma Bubbles (EPBs). Except for a few case studies, a comprehensive investigation has not been conducted on the characteristics of LSWS because of the complexity involved in detecting the LSWS, particularly, in spatial domain. In this scenario, a comprehensive study is carried out, for the first time, on the spatial and temporal characteristics of LSWS observed in spatial domain over African and Southeast Asian longitudinal sectors during the year 2011. The observations indicate that these wave structures can be detected a few degrees west of E region sunset terminator and found to grow significantly at longitudes past the sunset terminator. The phase fronts of these spatial structures are found to align with the geomagnetic field (B?) lines over a latitudinal belt for at least 5-6° (~500-600 km) centered on dip equator. The zonal wavelengths of these structures are found to vary from 100 to 700 km, which is consistent with the earlier reports, and the EPBs were consistently observed when the amplitudes of LSWS were grown to sufficient strengths. These results would provide better insights on the underlying physical processes involved in excitation of LSWS in terms of important roles being played by E region electrical loading and polarization electric fields induced via spatially varying dynamo current due to neutral wind perturbations associated with atmospheric gravity waves.

Tulasi Ram, S.; Yamamoto, M.; Tsunoda, R. T.; Chau, H. D.; Hoang, T. L.; Damtie, B.; Wassaie, M.; Yatini, C. Y.; Manik, T.; Tsugawa, T.

2014-03-01

190

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

191

Evolving outer heliosphere: Large-scale stability and time variations observed by the Interstellar Boundary Explorer  

NASA Astrophysics Data System (ADS)

The first all-sky maps of Energetic Neutral Atoms (ENAs) from the Interstellar Boundary Explorer (IBEX) exhibited smoothly varying, globally distributed flux and a narrow “ribbon” of enhanced ENA emissions. In this study we compare the second set of sky maps to the first in order to assess the possibility of temporal changes over the 6 months between views of each portion of the sky. While the large-scale structure is generally stable between the two sets of maps, there are some remarkable changes that show that the heliosphere is also evolving over this short timescale. In particular, we find that (1) the overall ENA emissions coming from the outer heliosphere appear to be slightly lower in the second set of maps compared to the first, (2) both the north and south poles have significantly lower (˜10-15%) ENA emissions in the second set of maps compared to the first across the energy range from 0.5 to 6 keV, and (3) the “knot” in the northern portion of the ribbon in the first maps is less bright and appears to have spread and/or dissipated by the time the second set was acquired. Finally, the spatial distribution of fluxes in the southernmost portion of the ribbon has evolved slightly, perhaps moving as much as 6° (one map pixel) equatorward on average. The observed large-scale stability and these systematic changes at smaller spatial scales provide important new information about the outer heliosphere and its global interaction with the galaxy and help inform possible mechanisms for producing the IBEX ribbon.

McComas, D. J.; Bzowski, M.; Frisch, P.; Crew, G. B.; Dayeh, M. A.; DeMajistre, R.; Funsten, H. O.; Fuselier, S. A.; Gruntman, M.; Janzen, P.; Kubiak, M. A.; Livadiotis, G.; Möbius, E.; Reisenfeld, D. B.; Schwadron, N. A.

2010-09-01

192

Circular Membrane Applet  

NSDL National Science Digital Library

This applet simulates a circular membrane which can be 'poked' or 'struck' with the mouse. Normal modes, one or several, can be selected. The membrane can be viewed in 2-D or 3-D, with color or without, solid or wireframe. Simulation speed, damping and base frequency for sound are adjustable. The sound version of the applet only works in Windows and with Microsoft Java VM. A second applet is available for Netscape/Sun Java.

Falstad, Paul

2004-07-23

193

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

194

Magnetic Moment Coupling to Circularly Polarized Photons  

E-print Network

Exact stationary solutions of the wave equation are obtained to describe the interaction between magnetic moment of elementary particle and circularly polarized photons. The obtained solutions substantially modify the conventional model of field-matter interaction. It follows from them that magnetic moment couples to photons, and this coupling leads to bound particle-photon states with different energies for different orientations of magnetic moment. As a consequence, the interaction splits particle states differing by directions of total angular momentum. Stationary spin splitting, induced by photons, and concomitant effects can be observed for particles exposed to a laser-generated circularly polarized electromagnetic wave.

O. V. Kibis

2009-01-30

195

Cluster observations of hot flow anomalies with large flow deflections: 1. Velocity deflections  

NASA Astrophysics Data System (ADS)

Case and statistical studies have been performed to investigate hot flow anomalies (HFAs) with large flow deflections using data from the Cluster-C1 spacecraft from 2003 to 2009. We have selected 87 events with Vy or Vz in GSE coordinates larger than 200 km s-1. Observations of these HFAs indicate a "location-dependent deflection": Vy or Vz deflect to a positive value when the event is located in the positive Y or Z side relative to the subsolar point and to a negative value when it is located in the negative Y or Z side relative to the subsolar point. The amplitude of the deflection increases with increasing distance in Y or Z direction. The decrease in Vx at the event center is larger when the location is closer to the Sun-Earth line. The location-dependent deflection might be due to a near-specular reflection of ions at the Earth's bow shock. The HFAs studied in this paper are close to the bow shock with the distance of the event location to the bow shock ranging from 0.03 to 3.51 RE, which might cause the reflected ions to remain as a coherent near-specular reflected beam.

Wang, Shan; Zong, Qiugang; Zhang, Hui

2013-02-01

196

Gamma-ray observations of the Orion Molecular Clouds with the Fermi Large Area Telescope  

E-print Network

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 \\sim100 MeV and \\sim100 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 \\sim10% 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 (WCO) at a 1{\\deg} \\times1{\\deg} pixel level. The correlation is found to be linear over a WCO range of ~10 fold when divided in 3 regions, suggesting penetration of nuclear CRs to most of the cloud volumes. The Wco-to-mass conversion factor, Xco, is found to be \\sim2.3\\times1...

Ackermann, 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

2012-01-01

197

Galaxy evolution and large-scale structure in the far-infrared. I. IRAS pointed observations  

SciTech Connect

Redshifts for 66 galaxies were obtained from a sample of 93 60-micron sources detected serendipitously in 22 IRAS deep pointed observations, covering a total area of 18.4 sq deg. The flux density limit of this survey is 150 mJy, 4 times fainter than the IRAS Point Source Catalog (PSC). The luminosity function is similar in shape with those previously published for samples selected from the PSC, with a median redshift of 0.048 for the fainter sample, but shifted to higher space densities. There is evidence that some of the excess number counts in the deeper sample can be explained in terms of a large-scale density enhancement beyond the Pavo-Indus supercluster. In addition, the faintest counts in the new sample confirm the result of Hacking et al. (1989) that faint IRAS 60-micron source counts lie significantly in excess of an extrapolation of the PSC counts assuming no luminosity or density evolution. 81 refs.

Lonsdale, C.J.; Hacking, P.B.

1989-04-01

198

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

199

Observation of the low to high confinement transition in the large helical device  

SciTech Connect

The low to high confinement transition has been observed on the large helical device [A. Iiyoshi, A. Komori, A. Ejiri et al., Nucl. Fusion 39, 1245 (1999)], exhibiting rapid increase in edge electron density with sharp depression of H{sub {alpha}} emission. The transition occurs in low toroidal field (B{sub t}=0.5-0.75 T) discharges and are heated by high power neutral beam injection. The plasma thus has a relatively high value ({approx}1.5%) of the volume averaged {beta} value. The electron temperature and density profiles have steep gradients at the edge region which has high magnetic shear but is at a magnetic hill. Formation of the edge transport barrier leads to enhanced activities of the interchange type of modes with m=2/n=3 (m,n are the poloidal and toroidal mode numbers) in the edge region. At present, these magnetohydrodynamic activities limit the rise of the stored energy; the resultant increment of the stored energy remains modest.

Toi, K.; Ohdachi, S.; Yamamoto, S.; Sakakibara, S.; Narihara, K.; Tanaka, K.; Morita, S.; Morisaki, T.; Goto, M.; Takagi, S.; Watanabe, F.; Nakajima, N.; Watanabe, K.Y.; Ida, K.; Ikeda, K.; Inagaki, S.; Kaneko, O.; Kawahata, K.; Komori, A.; Masuzaki, S. [National Institute for Fusion Science, Toki 509-5292 (Japan); Department of Energy Engineering and Science, Nagoya University, Nagoya 464-8603 (Japan); National Institute for Fusion Science, Toki 509-5292 (Japan); Department of Energy Engineering and Science, Nagoya University, Nagoya 464-8603 (Japan); National Institute for Fusion Science, Toki 509-5292 (Japan)] [and others

2005-02-01

200

WFPC2 observations of the double cluster NGC 1850 in the Large Magellanic Cloud  

NASA Technical Reports Server (NTRS)

Hubble Space Telescope-Wide Field/Planetary Camera-2 (HST-WFPC2) optical and ultraviolet imaging observations of the young double cluster NGC 1850 in the Large Magellanic Cloud (LMC) are presented. The main cluster, NGC 1850A, is a globular-like cluster and has an age of 50 +/- 10 Myr, while the subcluster, NGC 1850B, which is more loosely distributed, is very young at 4.3 +/- 0.9 Myr. Its young age is confirmed by the detection of a pre-main-sequence population of stars associated to it. The two clusters have considerably different IMF slopes, with the main cluster having a flat slope (f(m) proportional to m(exp -1.4 +/- 0.2)) and the young cluster a much steeper one (f(m) proportional to m(exp -2.6 +/- -0.1)). The LMC field star population displays a broad range of ages, from approximately 0.5 Gyr up to more than 4 Gyr.

Gilmozzi, R.; Kinney, E. K.; Ewald, S. P.; Panagia, N.; Romaniello, M.

1994-01-01

201

Large volume collapse observed in the phase transition in cubic PbCrO3 perovskite  

PubMed Central

When cubic PbCrO3 perovskite (Phase I) is squeezed up to ?1.6 GPa at room temperature, a previously undetected phase (Phase II) has been observed with a 9.8% volume collapse. Because the structure of Phase II can also be indexed into a cubic perovskite as Phase I, the transition between Phases I and II is a cubic to cubic isostructural transition. Such a transition appears independent of the raw materials and synthesizing methods used for the cubic PbCrO3 perovskite sample. In contrast to the high-pressure isostructural electronic transition that appears in Ce and SmS, this transition seems not related with any change of electronic state, but it could be possibly related on the abnormally large volume and compressibility of the PbCrO3 Phase I. The physical mechanism behind this transition and the structural and electronic/magnetic properties of the condensed phases are the interesting issues for future studies. PMID:20660782

Xiao, Wansheng; Tan, Dayong; Xiong, Xiaolin; Liu, Jing; Xu, Jian

2010-01-01

202

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

203

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

204

Tests on Stiffened Circular Cylinders  

NASA Technical Reports Server (NTRS)

Compressive tests were made of two series of stiffened circular cylindrical shells under axial load. All the shells were 16 inches in diameter by 24 inches in length and were made of aluminum-alloy sheet curved to the proper radius and welded with one longitudinal weld. The ratios of diameter to thickness of shell wall in the two series of specimens were 258 and 572. Strains were measured with Huggenberger tensometers at a number of gage lines on the stiffeners and shell. The results of these tests indicate that a spacing of circumferential stiffeners equal to 0.67 times the radius is too great to strengthen the shell wall appreciably. The results are not inclusive enough to show the optimum in stiffeners. Plain cylinders without stiffeners developed ultimate strengths approximately half as great as the buckling strengths computed by the equation resulting from the classical theory and slightly greater than those computed by Donnell's large deflection theory.

Holt, Marshall

1941-01-01

205

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

206

Maternal caffeine intake during pregnancy and risk of fetal growth restriction: a large prospective observational study  

PubMed Central

Objective To examine the association of maternal caffeine intake with fetal growth restriction. Design Prospective longitudinal observational study. Setting Two large UK hospital maternity units. Participants 2635 low risk pregnant women recruited between 8-12 weeks of pregnancy. Investigations Quantification of total caffeine intake from 4 weeks before conception and throughout pregnancy was undertaken with a validated caffeine assessment tool. Caffeine half life (proxy for clearance) was determined by measuring caffeine in saliva after a caffeine challenge. Smoking and alcohol were assessed by self reported status and by measuring salivary cotinine concentrations. Main outcome measures Fetal growth restriction, as defined by customised birth weight centile, adjusted for alcohol intake and salivary cotinine concentrations. Results Caffeine consumption throughout pregnancy was associated with an increased risk of fetal growth restriction (odds ratios 1.2 (95% CI 0.9 to 1.6) for 100-199 mg/day, 1.5 (1.1 to 2.1) for 200-299 mg/day, and 1.4 (1.0 to 2.0) for >300 mg/day compared with <100 mg/day; test for trend P<0.001). Mean caffeine consumption decreased in the first trimester and increased in the third. The association between caffeine and fetal growth restriction was stronger in women with a faster compared to a slower caffeine clearance (test for interaction, P=0.06). Conclusions Caffeine consumption during pregnancy was associated with an increased risk of fetal growth restriction and this association continued throughout pregnancy. Sensible advice would be to reduce caffeine intake before conception and throughout pregnancy. PMID:18981029

2008-01-01

207

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

208

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

209

Deep Australia Telescope Large Area Survey Radio Observations of the European Large Area ISO Survey S1/Spitzer Wide-Area Infrared Extragalactic Field  

NASA Astrophysics Data System (ADS)

We have conducted sensitive (1 ? < 30 ?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°. 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; Norris, Ray P.; Cornwell, Tim J.; Voronkov, Maxim A.; Siana, Brian D.; Boyle, Brian J.; Ciliegi, Paolo; Jackson, Carole A.; Huynh, Minh T.; Berta, Stefano; Rubele, Stefano; Lonsdale, Carol J.; Ivison, Rob J.; Smail, Ian

2008-04-01

210

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

211

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

212

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

213

Simple Circular Motion Model  

NSDL National Science Digital Library

This simulation is a simple model of rides like an amusement park Merry-Go-Round. The rotational speed and radial distance are controlled with sliders at the bottom of the applet, while net horizontal force on the riders is monitored in the accompanying graph in terms of g-force experienced by riders. The 3D formatting allows viewing from a variety of vantage points. Students discover how rotational speed and radial distance interact to create a more thrilling ride. Don't miss the page link to "Physiological impact of g-forces". Students will learn that setting the speed and radial distance at the highest points will result in g-forces that exceed space shuttle re-entry and fighter jets at high speed. See Related Materials for an interactive tutorial on circular motion, appropriate for high school and lower-level undergraduate studies. The Simple Circular Motion 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 jar file will run the program if Java is installed.

Gallis, Michael R.

2013-10-07

214

Spin-wave quantization and dynamic coupling in micron-size circular magnetic dots  

NASA Astrophysics Data System (ADS)

We report on the observation of spin-wave quantization in square arrays of micron-size circular magnetic Ni80Fe20 dots by means of Brillouin light-scattering spectroscopy. For a large wave-vector interval several discrete, dispersionless modes with a frequency splitting of up to 2.5 GHz were observed. The modes are identified as magnetostatic surface spin waves laterally quantized due to in-plane confinement in each single dot. The frequencies of the lowest observed modes decrease with increasing distance between the dots, thus indicating an essential dynamic magnetic dipole interaction between the dots at small interdot distances.

Jorzick, J.; Demokritov, S. O.; Hillebrands, B.; Bartenlian, B.; Chappert, C.; Decanini, D.; Rousseaux, F.; Cambril, E.

1999-12-01

215

Observations and numerical simulations of large-eddy circulation in the ocean surface mixed layer  

NASA Astrophysics Data System (ADS)

near-surface dye releases were mapped on scales of minutes to hours temporally, meters to order 1 km horizontally, and 1-20 m vertically using a scanning, depth-resolving airborne lidar. In both cases, dye evolved into a series of rolls with their major axes approximately aligned with the wind and/or near-surface current. In both cases, roll spacing was also of order 5-10 times the mixed layer depth, considerably larger than the 1-2 aspect ratio expected for Langmuir cells. Numerical large-eddy simulations under similar forcing showed similar features, even without Stokes drift forcing. In one case, inertial shear driven by light winds induced large aspect ratio large-eddy circulation. In the second, a preexisting lateral mixed layer density gradient provided the dominant forcing. In both cases, the growth of the large-eddy structures and the strength of the resulting dispersion were highly dependent on the type of forcing.

Sundermeyer, Miles A.; Skyllingstad, Eric; Ledwell, James R.; Concannon, Brian; Terray, Eugene A.; Birch, Daniel; Pierce, Stephen D.; Cervantes, Brandy

2014-11-01

216

Discovery of Circularly Polarized Radio Emission from SS 433.  

PubMed

We report the discovery of circularly polarized radio emission from the radio-jet X-ray binary SS 433 with the Australia Telescope Compact Array. The flux density spectrum of the circular polarization, clearly detected at four frequencies between 1 and 9 GHz, is of the form V~nu-0.9+/-0.1. Multiple components in the source and a lack of very high spatial resolution do not allow a unique determination of the origin of the circular polarization or of the spectrum of fractional polarization. However, we argue that the emission is likely to arise in the inner regions of the binary, possibly via propagation-induced conversion of linear to circular polarization, and the fractional circular polarization of these regions may be as high as 10%. Observations such as these have the potential to help us investigate the composition, whether pairs or baryonic, of the ejecta from X-ray binaries. PMID:10642198

Fender; Rayner; Norris; Sault; Pooley

2000-02-10

217

Gravity field determination for Mars Observer  

Microsoft Academic Search

Mars Observer will be the first near circular, low altitude and short-periodic orbiter of Mars. From previous Mars orbiters, such as Mariner 9 and Vikings 1 and 2, a large gravitational oblateness and in general a gravity field ten times stronger than the earth's field have been determined. Because of these, the gravity field will dominate the evolution of the

Pasquale B. Esposito; Stuart Demcak; Duane Roth

1990-01-01

218

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

219

Loop Equation Analysis of the Circular $ ?$ Ensembles  

E-print Network

We construct a hierarchy of loop equations for invariant circular ensembles. These are valid for general classes of potentials and for arbitrary inverse temperatures $ {\\rm Re}\\,\\beta>0 $ and number of eigenvalues $ N $. Using matching arguments for the resolvent functions of linear statistics $ f(\\zeta)=(\\zeta+z)/(\\zeta-z) $ in a particular asymptotic regime, the global regime, we systematically develop the corresponding large $ N $ expansion and apply this solution scheme to the Dyson circular ensemble. Currently we can compute the second resolvent function to ten orders in this expansion and also its general Fourier coefficient or moment $ m_{k} $ to an equivalent length. The leading large $ N $, large $ k $, $ k/N $ fixed form of the moments can be related to the small wave-number expansion of the structure function in the bulk, scaled Dyson circular ensemble, known from earlier work. From the moment expansion we conjecture some exact partial fraction forms for the low $ k $ moments. For all of the forgoing results we have made a comparison with the exactly soluble cases of $ \\beta = 1,2,4 $, general $ N $ and even, positive $ \\beta $, $ N=2,3 $.

N. S. Witte; P. J. Forrester

2014-11-07

220

Integrated observations of processes and products of large scale cratering experiments  

NASA Astrophysics Data System (ADS)

Detailed analysis of volcanic craters and ballistic deposits can provide insight into eruption dynamics and evolution. As fully exposed craters and associated unmodified deposits are rarely preserved, the dynamics involved can only be inferred. Large-scale blast experiments conducted at the University at Buffalo Geohazards Field Station produced deposits from single and multiple subsurface explosions at individual craters, along with a range of observational data, and provide a unique opportunity to link dynamics with geologic structures and deposits. Meter-scale craters were produced through repeated blasts using chemical explosives in 15 cm thick strata constructed of compacted aggregates (e.g. sands and gravels). Each experiment had 1-3 individual explosions with the same epicenter to form a single crater, with a total of 12 blasts and five craters. Three craters were produced through a series of shallow blasts (34-75 cm depth, six blasts) and two additional craters were produced by deeper blasts (75-100 cm, six blasts). The experiments successfully reproduced crater structures similar to those of maar volcanoes, which are the product of one or more subsurface explosions resulting from the interaction of magma with groundwater. Deep explosion tests successfully reproduced mixing and structures similar to maar-diatremes. The ballistics produced were collected in sample boxes up to 18 m from the blast center. The pits were later excavated and the vertical structures and deposits were described and sampled. Deposits can be described as bedded-diatreme (fallback/inter-crater deposits), unbedded diatreme (disturbed subsurface material), tephra ring (debris on the pre-blast surface) and distal extra-crater deposits. Granulometry and componentry were acquired for all samples. The diatreme structures and deposit componentry were interpreted using high-speed video recordings of the blasts. A comparison of ballistic source depth and collection location revealed the importance of multiple blasts in the excavation of deeper layers, suggesting that componentry of extra-crater deposits does not accurately indicate the depth of explosions, and would yield underestimates of the depth of activity. Additionally, material derived from the surface/shallow depths is deposited farther from the crater than deeper-derived material, suggesting an important lateral control on deposition from explosions at depth. Fallback deposits are critical to interpreting the evolution of the diatreme and crater, because only with the shallowest blasts does material escape the crater. Sampling of deposits from multiple blasts revealed mixing of subsurface material, and the influence of early fallback deposits and a pre-blast crater on the deposits preserved below, within and outside of the crater. Experiments such as these reveal links between explosions and their deposits unattainable from geological studies, and advance our ability to reconstruct processes of real eruptions from their deposits.

Graettinger, A. H.; Sonder, I.; Valentine, G.; Ross, P.; White, J. D.; Taddeucci, J.; Zimanowski, B.; Lube, G.; Kueppers, U.; Bowman, D. C.

2013-12-01

221

Elliptical vs Circular Orbit  

NSDL National Science Digital Library

Find the contrast between a highly exaggerated earth elliptical orbit and circular orbit depicted in .mov format. It should be mentioned to students that in reality the earth's elliptical orbit around the sun would hardly be noticeable if viewed from this distance. Taken alone, the video could unfortunately perpetuate the misconception that earth sun distance is responsible for the seasons. Still, the video is useful for pointing out that the earth's speed around the sun is not constant, with the earth moving fastest in January and slowest in July. This phenomenon helps explain why summer is longer in the Northern Hemisphere and for the analemma. The animation can be paused and rewound to emphasize important points.

Bob Urschel

222

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

223

Large Fields of Sub-circular Depressions On The Carnegie Ridge Flanks Discovered During The French German Salieri Cruise (r/v Sonne, 22-08/16-09 2001)  

NASA Astrophysics Data System (ADS)

During the SALIERI Cruise offshore Ecuador, multibeam bathymetry was collected with the Simrad EM120 of the R/V SONNE. The most conspicuous features discov- ered on the Carnegie Ridge are fields of circular closed depressions distributed along the mid-slope of the ridge northern and southern flanks at depths of 1500 to 2600 m. These circular depressions are 1-4 km wide and typically 100-300 m deep. Most are flat floored and some are so densely packed that they look like a honeycomb pattern. Mud penetrator data indicate that the depressions were carved into the ridge sedimen- tary blanket, although the influence of pre-existing topography in the volcanic base- ment cannot be excluded. On the mid-slope of the southern flank more than 400 m of nannofossil chalk ooze and chalk dated from upper Miocene to upper Pleistocene were recovered at Site 157 of DSDP 16 indicating that the depressions formed in these calcareous deposits. From conventional bathymetry, these circular depressions were previously identified as canyons and gullies and the hypothesis of their erosional origin in relation to either a past emergence of the ridge or bottom currents was first proposed by van Andel et al. (1971) (van Andel et al., 1973). Although we cannot exclude the effects of currents to produce sub-circular depressions, other alternatives including both marine and subaerial karstic origins will be discussed. Van Andel et al., 1971,Tectonics of the Panama Basin, Bull. Geol. Soc. Am., 82 (6) 1489. Van Andel et al., 1973, DSDP 16, Site 157, pp. 53-150.

Michaud, F.; Collot, J. Y.; Gutscher, M. A.; Charvis, P.; Flüh, E.; Santana, E.

224

Large-Eddy Observation of Post-Cold-Frontal Continental Stratocumulus  

E-print Network

United States on 8 April 2006. The stratocumulus occurred in cold-air and dry-air advection behind a surface cold front. LEOs were obtained from millimeter-wavelength cloud radar and micropulse lidar, whereas traditional meteorological observations...

Mechem, David B.; Kogan, Yefim L.; Schultz, David M.

2010-10-01

225

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

226

Circularly polarized metallic EBG antenna  

Microsoft Academic Search

This letter describes the concept and the realization of a directive and circularly polarized antenna using an electromagnetic band gap material whose circular polarization is generated by the structure itself. Experimental and simulated results are presented for an antenna operating at 5GHz.

Michael Diblanc; Emmanuel Rodes; Eric Arnaud; Marc Thevenot; Thierry Monediere; Bernard Jecko

2005-01-01

227

Circularly polarized microstrip fractal antennas  

Microsoft Academic Search

A miniaturized circularly polarized antenna based on the Sierpinski gasket is presented. In exchange for size reduction, minimum axial ratio and the bandwidth of this antenna are degraded. An additional new microstrip fractal antenna named the crown square antenna is also introduced and illustrated to have circular polarization when its feed location is near to the center of the antenna.

P. Dehkhoda; A. Tavakoli

2004-01-01

228

A Circular Po Rectangular R  

E-print Network

of Electronic Science and Technology of China Chengdu, Sichuan, China, 611731 liyaanem@gmail.com Abstract--In this paper, a compact hybrid-integ rectangular ring antenna with circular polariz for RFID reader. By integrating a cross-slotted p a rectangular ring antenna in the same plan antenna has the features of circular

Leung, Ka-Cheong

229

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

230

Arcuate and circular structures in the Tharsis region: Evidence of coronae on Mars  

NASA Technical Reports Server (NTRS)

Arcuate and circular structures are evident in the Tharsis region of Mars. They involve concentric graben and fracture systems and are often associated with volcanic centers. The most prominent example is Alba Patera, a low relief volcanotectonic center. It is surrounded by a graben system comprised of the Alba and Tantalus Fossae and part of the Ceranius Fossae system that are thought to have formed during the Early Amazonian. The graben concentric to Alba Patera form an annulus that is 600 km in diameter. The similarity between Alba Patera and coronae on Venus was observed prior to the Magellan mission. Magellan imagery of Venusian coronae has revealed a number of striking similarities between these structures, Alba Patera, and the other circular structures on Mars. Coronae on Venus are circular to ovoidal volcanotectonic features that range in diameter from 60 to over 1000 km. Concentric graben form partial to complete tectonic annuli. More regionally extensive graben systems are deflected toward, and in many cases merge with, the concentric graben. Volcanic flows and domes dominate the surface enclosed within the concentric graben. However, distinctive differences exist between coronae on Venus and the structures on Mars. Circular structures on Mars lack radial graben crosscut by concentric graben. There is also no evidence of the complex topography associated with coronae on Venus. The differences between coronae on Venus and the suspected coronae on Mars may be largely due to the difference in the thickness of the elastic lithosphere on the two planets. The topographic expression of the interaction between the diapir and the lithosphere would be expected to be greatly subdued on Mars because of the large difference in lithospheric thickness. The lack of circular structures with diameters below 200 km suggests a lower limit to the size that coronae could form on Mars.

Watters, T. R.; Zimbelman, J. R.; Scott, D. H.

1993-01-01

231

Entropic derivation of F=ma for circular motion  

E-print Network

We examine the entropic picture of Newton's second law for the case of circular motion. It is shown that one must make modifications to the derivation of F=ma due to a change in the effective Unruh temperature for circular motion. These modifications present a challenge to the entropic derivation of Newton's second law, but also open up the possibility to experimentally test and constrain this model for large centripetal accelerations.

Michael Duncan; Ratbay Myrzakulov; Douglas Singleton

2011-03-09

232

Large-scale sea ice drift and deformation: Comparison between models and observations in the western Weddell Sea during 1992  

Microsoft Academic Search

Statistical comparisons between numerical sea ice models and an observed large-scale strain array in the western Weddell Sea during 1992 are used to evaluate the performance of three of the more generally utilized sea ice rheology formulations. Results show that sea ice velocity is reproduced with relatively high accuracy (90% coherence, >80% normalized cross correlation) in models having high-quality atmospheric

Cathleen A. Geiger; William D. Hibler; Stephen F. Ackley

1998-01-01

233

ATLAS: Australia Telescope Large Area Survey: Deep Radio Observations of the CDFS-SWIRE and ELAIS-S1 fields  

E-print Network

ATLAS: Australia Telescope Large Area Survey: Deep Radio Observations of the CDFS-SWIRE and ELAIS: University of Durham, UK. GOODS The Australia Telescope Compact Array used to make the radio images-S1 fields 1. Overview · We are imaging the CDFS and ELAIS-S1 SWIRE fields at 20 cm. Combining radio

Norris, Ray

234

Aperiodic Large-Scale Disturbances in the Lower Ionosphere. Ionosonde Observation Results  

NASA Astrophysics Data System (ADS)

We present the observed disturbances of the parameters of the ionosphere affected by high-power radio waves from the SURA heating facility. Ionosondes located in Nizhny Novgorod and Moscow (Russia), Kharkov (Ukraine), and Pruhonice (Czechia) were used for the observations. The diagnostic tools were from 560 to 2200 km away from SURA. Additional ionization layers with a cutoff frequency of 2.6-3.4 MHz were occasionally observed on the ionograms of the Nizhny Novgorod and Moscow stations. The effective altitude of these layers was 120-160 km and the true altitude was about 110-130 km. The occurrence of additional ionization layers below 100-130 km was controlled by an increase in the minimum observable frequency (MOF). For the Moscow station, the MOF increased by about 1 MHz in the daytime and almost did not change in the night time. MOF variations on the ionograms of the Kharkov and Pruhonice stations were less significant (0.3-0.4 MHz) in all time of the day. The observed effects are most probably due to the midlatitude precipitation of electrons from the inner radiation belt, which increased the electron number density in the ionosphere, absorption of the sounding radio waves, and the MOF. Estimated particle flux density was 108-109 m-2 ·s-1. The electron number density in the daytime increased by a factor of 2-3.

Chernogor, L. F.; Frolov, V. L.; Barabash, V. V.

2014-07-01

235

Observation of collisionless shocks in a large current-free laboratory plasma  

NASA Astrophysics Data System (ADS)

We report the first measurements of the formation and structure of a magnetized collisionless shock by a laser-driven magnetic piston in a current-free laboratory plasma. This new class of experiments combines a high-energy laser system and a large magnetized plasma to transfer energy from a laser plasma plume to the ambient ions through collisionless coupling, until a self-sustained MA˜ 2 magnetosonic shock separates from the piston. The ambient plasma is highly magnetized, current free, and large enough (17 m × 0.6 m) to support Alfvén waves. Magnetic field measurements of the structure and evolution of the shock are consistent with two-dimensional hybrid simulations, which show Larmor coupling between the debris and ambient ions and the presence of reflected ions, which provide the dissipation. The measured shock formation time confirms predictions from computational work.

Niemann, C.; Gekelman, W.; Constantin, C. G.; Everson, E. T.; Schaeffer, D. B.; Bondarenko, A. S.; Clark, S. E.; Winske, D.; Vincena, S.; Van Compernolle, B.; Pribyl, P.

2014-11-01

236

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

237

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

238

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

E-print Network

We present high resolution, Combined Array for Research in Millimeter-Wave Astronomy (CARMA), $\\lambda$=1mm observations of several molecular species toward Orion-KL. These are the highest spatial and spectral resolution 1mm observations of these molecules to date. Our observations show that ethyl cyanide [C$_2$H$_5$CN] and vinyl cyanide [C$_2$H$_3$CN] originate from multiple cores near the Orion hot core and IRc7. Additionally we show that dimethyl ether [(CH$_3$)$_2$O] and methyl formate [HCOOCH$_3$] originate from IRc5 and IRc6 and that acetone [(CH$_3$)$_2$CO] originates only from areas where both N-bearing and O-bearing species are present.

D. N. Friedel; L. E. Snyder

2007-09-20

239

Observation and analysis of high-speed human motion with frequent occlusion in a large area  

NASA Astrophysics Data System (ADS)

The use of computer vision technology in collecting and analyzing statistics during sports matches or training sessions is expected to provide valuable information for tactics improvement. However, the measurements published in the literature so far are either unreliably documented to be used in training planning due to their limitations or unsuitable for studying high-speed motion in large area with frequent occlusions. A sports annotation system is introduced in this paper for tracking high-speed non-rigid human motion over a large playing area with the aid of motion camera, taking short track speed skating competitions as an example. The proposed system is composed of two sub-systems: precise camera motion compensation and accurate motion acquisition. In the video registration step, a distinctive invariant point feature detector (probability density grads detector) and a global parallax based matching points filter are used, to provide reliable and robust matching across a large range of affine distortion and illumination change. In the motion acquisition step, a two regions' relationship constrained joint color model and Markov chain Monte Carlo based joint particle filter are emphasized, by dividing the human body into two relative key regions. Several field tests are performed to assess measurement errors, including comparison to popular algorithms. With the help of the system presented, the system obtains position data on a 30 m × 60 m large rink with root-mean-square error better than 0.3975 m, velocity and acceleration data with absolute error better than 1.2579 m s-1 and 0.1494 m s-2, respectively.

Wang, Yuru; Liu, Jiafeng; Liu, Guojun; Tang, Xianglong; Liu, Peng

2009-12-01

240

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

241

Observation of Stable Superdense Core Plasmas in the Large Helical Device  

Microsoft Academic Search

In reduced recycling discharges in the Large Helical Device, a super dense core plasma develops when a series of pellets are injected. A core region with density as high as 4.5×1020m-3 and temperature of 0.85 keV is maintained by an internal diffusion barrier with very high-density gradient. These results may extrapolate to a scenario for fusion ignition at very high

N. Ohyabu; T. Morisaki; S. Masuzaki; R. Sakamoto; M. Kobayashi; J. Miyazawa; M. Shoji; A. Komori; O. Motojima

2006-01-01

242

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

243

Applications of magnetic line ratio method to magnetographic observations of large-scale solar magnetic fields  

Microsoft Academic Search

We interpret Measurements of the large-scale magnetic field strength, obtained with the magnetograph of the STOP telescope at the Sayan observatory, in terms of a two-component model. Theoretical magnetic field strength ratios for used spectral lines are calculated. For this purpose, the Stokes-V parameters are derived by solving the radiative transfer equations for four flux tube models. By means of

R. M. Veretsky; M. L. Demidov

2002-01-01

244

Selecting, Scheduling and Carrying Out Observing Programmes at the Large Binocular Telescope  

NASA Astrophysics Data System (ADS)

The diverse LBT partnership allocates time through various partner-based mechanisms. Each of the four major partner groups receives blocks of observing time, with the fraction of the total proportional to its share of investment in the Observatory. The allocation is currently about one week per lunation per partner, but the week centered on full moon is for technical time devoted to commissioning of telescope and new instrumentation. The partners typically observe their own programs in queue fashion, with strong support from LBTO astronomers.

Green, Richard F.

2013-01-01

245

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

246

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

247

Large-Area Balloon-Borne Polarized Gamma Ray Observer (PoGO) V. Andersson  

E-print Network

-ray observation of extra-solar objects, po- larization has been measured only once, by an ex- ploratory and yet below 10 keV, is based on tracking of the photoelectron from X-ray absorption in a micron- scale()max - R()min)/(R()max + R()min) The other choice, the photoelectron tracking, operates 22nd Texas

Haviland, David

248

Mediterranean hurricanes: large-scale environment and convective and precipitating areas from satellite microwave observations  

Microsoft Academic Search

Subsynoptic scale vortices that have been likened to tropical cyclones or polar lows (medicanes) are occasionally observed over the Mediterranean Sea. Generated over the sea, they are usually associated with strong winds and heavy precipitation and thus can be highly destructive in islands and costal areas. Only an accurate forecasting of such systems could mitigate these effects. However, at the

C. Claud; B. Alhammoud; B. M. Funatsu; J.-P. Chaboureau

2010-01-01

249

The Spitzer c2d Survey of Large, Nearby, Interstellar Clouds. VI. Perseus Observed with MIPS  

Microsoft Academic Search

We present observations of 10.6 deg2 of the Perseus molecular cloud at 24, 70, and 160 mum with Spitzer MIPS. The images show prominent, complex extended emission dominated by illuminating B stars on the east side of the cloud and by cold filaments of 160 mum emission on the west side. Of 3950 point sources identified at 24 mum, 1141

L. M. Rebull; K. R. Stapelfeldt; N. J. Evans II; J. K. Jørgensen; P. M. Harvey; T. Y. Brooke; T. L. Bourke; D. L. Padgett; N. L. Chapman; S.-P. Lai; W. J. Spiesman; A. Noriega-Crespo; B. Merín; T. Huard; L. E. Allen; G. A. Blake; T. Jarrett; D. W. Koerner; L. G. Mundy; P. C. Myers; A. I. Sargent; E. F. van Dishoeck; Z. Wahhaj; K. E. Young

2007-01-01

250

Estimating the impact of satellite observations on large-scale river flood forecasting  

NASA Astrophysics Data System (ADS)

Floods are one of the costliest natural disasters, posing severe risks to human population. Hydraulic models are able to predict flood characteristics, such as water surface elevations and inundated area, and are being used for forecasting operationally although there are many uncertainties. In this work, the potential value of satellite observations to initialize these hydraulic models (and their forecasts correspondingly) is explored. The Ensemble Sensitivity method is adapted to evaluate the impact of potential satellite observations on the forecasting of flood characteristics. The estimation of the impact is based on the Local Ensemble Transform Kalman Filter, allowing for the forecast error reductions to be computed without additional model runs. The study area was located in the Ohio River basin, and the model used was the LISFLOOD-FP hydrodynamic model. The experimental design consisted of two configurations of the LISFLOOD-FP 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. Results showed that the forecast skill was improved for water heights up to lead times of 11 days, while even partial observations of the river contained information for the entire river's water surface profile and allowed forecasting 5 to 7 days ahead. On the other hand, discharge forecasts were not improved as much when assimilating water height observations although forecast errors were reduced. Finally, the potential for identifying errors in the model structure and parameterizations via the ensemble sensitivity method is discussed.

Andreadis, Konstantinos; Schumann, Guy

2014-05-01

251

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

252

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

253

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

254

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

255

Observable T7 lepton flavor symmetry at the Large Hadron Collider.  

PubMed

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(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. PMID:21517373

Cao, Qing-Hong; Khalil, Shaaban; Ma, Ernest; Okada, Hiroshi

2011-04-01

256

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

257

A stacked analysis of brightest cluster galaxies observed with the Fermi Large Area Telescope  

NASA Astrophysics Data System (ADS)

We present the results of a search for high-energy ?-ray emission from a large sample of galaxy clusters sharing the properties of three existing Fermi Large Area Telescope detections (in Perseus, Virgo and A3392), namely a powerful radio source within their brightest cluster galaxy (BCG). From a parent, X-ray flux-limited sample of 863 clusters, we select 114 systems with a core-dominated BCG radio flux above 50/75 mJy (in the National Radio Astronomy Observatory Very Large Array Sky Survey and the Sydney University Molonglo Sky Survey, respectively), stacking data from the first 45 months of the Fermi mission in three energy bands, to determine statistical limits on the ?-ray fluxes of the ensemble of candidate sources. For a >300 MeV selection, the distribution of detection significance across the sample is consistent with that across control samples for significances <3?, but has a tail extending to higher values, including three >4? signals which are not associated with previously identified ?-ray emission. Modelling of the data in these fields results in the detection of four non-2FGL Fermi sources, though none of these appear to be unambiguously associated with the BCG candidate. Only one is sufficiently close to be a plausible counterpart (RXC J0132.6-0804) and the remaining three appear to be background active galactic nuclei. A search at energies >3 GeV hints at emission from the BCG in A2055, which hosts a BL Lac object. There is no evidence for a signal in the stacked data, and the upper limit derived on the ?-ray flux of an average radio-bright BCG in each band is at least an order of magnitude more constraining than that calculated for individual objects. F1 GeV/F1.4 GHz for an average BCG in the sample is <15, compared with ?120 for NGC 1275 in Perseus, which might indicate a special case for those objects detected at high energies. The tentative suggestion that point-like beamed emission from member galaxies comprise the dominant bright ?-ray sources in clusters implies searches for evidence of dark matter annihilation or large-scale merger shock signatures, for example, need to account for a significant level of contamination from within each cluster that is both highly stochastic and varies significantly over time.

Dutson, K. L.; White, R. J.; Edge, A. C.; Hinton, J. A.; Hogan, M. T.

2013-03-01

258

Spacewatch Observations of Asteroids and Comets Supporting the Large-Scale Surveys  

NASA Astrophysics Data System (ADS)

We specialize in followup astrometry of Near-Earth Objects (NEOs) of high priority while they are faint, including recently discovered objects on the MPC's Confirmation Page, objects with potential close encounters with Earth, NEOs for which NEOWISE determined albedos and diameters, targets of radar, potential destinations for spacecraft, and special requests by the MPC or JPL. The present era of Spacewatch observations began on 2011 Oct 15 with a new imaging camera on our 1.8-meter telescope. From then, the MPC has been accepting an annual average of 8,492 lines of astrometry of 1,018 different NEOs from Spacewatch, including 177 different PHAs per year. Thus we observe half of all such objects that are observed by anyone in the same interval. We make twice as many measurements of PHAs while they are fainter than V=22 than the next most productive astrometry group. We have contributed to the removal of half of the objects that were retired from JPL's impact risk list. Per year we observe about 35 radar targets, 50 NEOs that were measured by NEOWISE, and 100 potential rendezvous destinations. We also average 400 observations of comets per year. Since 2004 we have increased our efficiency by a factor of six in terms of observations per unit personnel work year by means of new hardware, software, and the automation of the 0.9-m telescope. Last year we received a grant to upgrade our 0.9-m telescope and develop a public archive of image data dating back to 1990. New grants from the NEOO Program now support our use of telescopes larger than the 1.8-meter of Spacewatch and improvement of the efficiency of the Spacewatch 1.8-m. Support of Spacewatch was/is from JPL subcontract 100319 (2010-2011), NASA/NEOO grants NNG06GJ42G, NNX11AB52G, NNX12AG11G, NNX13AP99G, NNX14AL13G, and NNX14AL14G, the Lunar and Planetary Laboratory, Steward Observatory, the Brinson Foundation of Chicago, IL, the estates of R. S. Vail and R. L. Waland, and other private donors. We are also indebted to the MPC of the IAU for their web services.

McMillan, Robert S.; Bressi, Terrence H.; Scotti, James V.; Larsen, Jeffrey A.; Mastaler, Ronald A.

2014-11-01

259

RHESSI Observations of a Simple Large X-ray Flare on 11-03-2003  

E-print Network

We present data analysis and interpretation of a simple X-class flare observed with RHESSI on November 3, 2003. In contrast to other X-class flares observed previously, this flare shows a very simple morphology with well defined looptop (LT) and footpoint (FP) sources. The almost monotonic upward motion of the LT source and increase in separation of the two FP sources are consistent with magnetic reconnection models proposed for solar flares. In addition, we find that the source motions are relatively slower during the more active phases of hard X-ray emission; the emission centroid of the LT source shifts toward higher altitudes with the increase of energy; the separation between the LT emission centroids at two different photon energies is anti-correlated with the FP flux. Non-uniformity of the reconnecting magnetic fields could be a possible explanation of these features.

Wei Liu; Yan Wei Jiang; Siming Liu; Vahe' Petrosian

2004-06-16

260

VLA observations of stellar planetary nebulae. [using Very Large Array at National Radio Astronomy Observatory  

NASA Technical Reports Server (NTRS)

Coordinates, dimensions, 4885-MHz flux densities, and brightness temperatures of K3-2, NGC 6833, Ps 1, II 5117, Me 2-2, Hb 12, Vy 1-1, and M1-5 are reported. In two other cases, H3-29 and H3-75, confused extended structure was detected in which the nebula could not be identified with certainty. He 2-467, M1-2, and Peterson's H-alpha object in M15 were also included in the observations but not detected with an upper limit of less than 10 mJy. The observations are compared with some of the previous optical and radio data, such as log S(H-beta). Distances are computed from the present data with standard assumptions. Corresponding linear radii range below 0.1 pc, among the smallest in previous distributions of radius.

Johnson, H. M.; Balick, B.; Thompson, A. R.

1979-01-01

261

The Spitzer c2d Survey of Large, Nearby, Interstellar Clouds. VII. Ophiuchus Observed with MIPS  

Microsoft Academic Search

We present maps of 14.4 deg2 of the Ophiuchus dark clouds observed by the Spitzer Space Telescope Multiband Imaging Photometer for Spitzer (MIPS). These high-quality maps depict both numerous point sources and extended dust emission within the star-forming and non-star-forming portions of these clouds. Using PSF-fitting photometry, we detect 5779 sources at 24 mum and 81 sources at 70 mum

Deborah L. Padgett; Luisa M. Rebull; Karl R. Stapelfeldt; Nicholas L. Chapman; Shih-Ping Lai; Lee G. Mundy; Neal J. Evans II; Timothy Y. Brooke; Lucas A. Cieza; William J. Spiesman; Alberto Noriega-Crespo; Caer-Eve McCabe; Lori E. Allen; Geoffrey A. Blake; Paul M. Harvey; Tracy L. Huard; Jes K. Jørgensen; David W. Koerner; Philip C. Myers; Annelia I. Sargent; Peter Teuben; Ewine F. van Dishoeck; Zahed Wahhaj; Kaisa E. Young

2008-01-01

262

Constraints on the Galactic Population of TEV Pulsar Wind Nebulae Using Fermi Large Area Telescope Observations  

E-print Network

Pulsar wind nebulae (PWNe) have been established as the most populous class of TeV gamma-ray emitters. Since launch, the Fermi Large Area Telescope (LAT)identified five high-energy (100MeV large number of PWNe candidates, all powered by young and energetic pulsars. The wealth of multi-wavelength data available and the new results provided by Fermi-LAT give us an opportunity to find new PWNe and to explore the radiative processes taking place in known ones. The TeV gamma-ray unidentifiedsources (UNIDs) are the best candidates for finding new PWNe. Using 45 months of Fermi-LAT data for energies above 10 GeV, an analysis was performed near the position of 58TeV PWNe and UNIDs within 5deg of the Galactic Plane to establish new constraints on PWNe properties and find new clues on the nature of UNIDs. Of the 58 sources, 30 were detected, and this work provides their gamma-rayfluxes for energies above 10 GeV. The spectral energy distributions (SED) anduppe...

Acero, F; Ajello, M; Allafort, A; Baldini, L; Ballet, J; Barbiellini, G; Bastieri, D; Bechtol, K; Bellazzini, R; Blandford, R D; Bloom, E D; Bonamente, E; 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; 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 Palma, F; Dermer, C D; Di Venere, L; Silva, E do Couto e; Drell, P S; Drlica-Wagner, A; Falletti, L; Favuzzi, C; Fegan, S J; Ferrara, E C; Focke, W B; Franckowiak, A; Fukazawa, Y; Funk, S; Fusco, P; Gargano, F; Gasparrini, D; Giglietto, N; Giordano, F; Giroletti, M; Glanzman, T; Godfrey, G; Grégoire, T; Grenier, I A; Grondin, M -H; Grove, J E; Guiriec, S; Hadasch, D; Hanabata, Y; Harding, A K; Hayashida, M; Hayashi, K; Hays, E; Hewitt, J; Hill, A B; Horan, D; Hou, X; Hughes, R E; Inoue, Y; Jackson, M S; Jogler, T; Jóhannesson, G; Johnson, A S; Kamae, T; Kawano, T; Kerr, M; Knödlseder, J; Kuss, M; Lande, J; Larsson, S; Latronico, L; Lemoine-Goumard, M; Longo, F; Loparco, F; Lovellette, M N; Lubrano, P; Marelli, M; Massaro, F; Mayer, M; 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; 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; Reimer, A; Reimer, O; Reposeur, T; Ritz, S; Roth, M; Rousseau, R; Parkinson, P M Saz; Schulz, A; Sgrò, C; Siskind, E J; Smith, D A; Spandre, G; Spinelli, P; Suson, D J; Takahashi, H; Takeuchi, Y; Thayer, J G; Thayer, J B; Thompson, D J; Tibaldo, L; Tibolla, O; Tinivella, M; Torres, D F; Tosti, G; Troja, E; Uchiyama, Y; Vandenbroucke, J; Vasileiou, V; Vianello, G; Vitale, V; Werner, M; Winer, B L; Wood, K S; Yang, Z

2013-01-01

263

MESSENGER Orbital Observations of Large-Amplitude Kelvin-Helmholtz Waves at Mercury's Magnetopause  

NASA Technical Reports Server (NTRS)

We present a survey of Kelvi\\ n-Helmholtz (KH) waves at Mercury's magnetopause during MESSENGER's first Mercury year in orb it. The waves were identified on the basis of the well-established sawtooth wave signatures that are associated with non-linear KH vortices at the magnetopause. MESSENGER frequently observed such KH waves in the dayside region of the magnetosphere where the magnetosheath flow velocity is still sub -sonic, which implies that instability growth rates at Mercury's magnetopau are much larger than at Earth. We attribute these greater rates to the limited wave energy dissipation in Mercury's highly resistive regolith. The wave amplitude was often on the order of ' 00 nT or more, and the wave periods were - 10- 20 s. A clear dawn-dusk asymmetry is present in the data, in that all of the observed wave events occurred in the post-noon and dusk-side sectors of the magnetopause. This asymmetry is like ly related to finite Larmor-radius effects and is in agreement with results from particle-in-cell simulations of the instability. The waves were observed almost exclusively during periods when the north-south component of the magnetosheath magnetic field was northward, a pattern similar to that for most terrestrial KH wave events. Accompanying plasma measurements show that the waves were associated with the transport of magnetosheath plasma into the magnetosphere.

Sundberg, Torbjorn; Boardsen, Scott A.; Slavin, James A.; Anderson, Brian J.; Korth, Haje; Zurbuchen, Thomas H.; Raines, Jim M.; Solomon, Sean C.

2012-01-01

264

Nuclear spin circular dichroism  

SciTech Connect

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, E-mail: juha.vaara@iki.fi [NMR Research Group, Department of Physics, University of Oulu, P.O. Box 3000, FIN-90014 Oulu (Finland)] [NMR Research Group, Department of Physics, University of Oulu, P.O. Box 3000, FIN-90014 Oulu (Finland); Rizzo, Antonio [Istituto per i Processi Chimico-Fisici del Consiglio Nazionale delle Ricerche (IPCF-CNR), Area della Ricerca, via G. Moruzzi 1, I-56124 Pisa (Italy)] [Istituto per i Processi Chimico-Fisici del Consiglio Nazionale delle Ricerche (IPCF-CNR), Area della Ricerca, via G. Moruzzi 1, I-56124 Pisa (Italy); Kauczor, Joanna; Norman, Patrick [Department of Physics, Chemistry and Biology, Linköping University, S-58183 Linköping (Sweden)] [Department of Physics, Chemistry and Biology, Linköping University, S-58183 Linköping (Sweden); Coriani, Sonia, E-mail: coriani@units.it [Dipartimento di Scienze Chimiche e Farmaceutiche, Università degli Studi di Trieste, Via L. Giorgieri 1, I-34127 Trieste (Italy)] [Dipartimento di Scienze Chimiche e Farmaceutiche, Università degli Studi di Trieste, Via L. Giorgieri 1, I-34127 Trieste (Italy)

2014-04-07

265

Circular Scan Streak Tube Development  

NASA Technical Reports Server (NTRS)

A streak tube having circular scan was designed, built and tested. Continuous circular scan, easily derived from out of phase sine waves applied to the conventional deflection plates, permits the timing of pulses traveling long baselines. At the tube's output a circular array of 720 elements is scanned to provide 30 to 40 picosecond resolution. Initial difficulties with electron bombarded silicon arrays were circumvented by using microchannel plates within the streak tube to provide the needed electronic amplification and digital sensitivity and coupling the 720 element arrays to the electron beam by means of a phosphor on a fiber optics. Two ceramic body tubes with S-20 photocathodes were tested and delivered.

Nevin, S.

1980-01-01

266

Do recent observations of very large electromagnetic dissociation cross sections signify a transition towards non-perturbative QED?  

NASA Technical Reports Server (NTRS)

The very large electromagnetic dissociation (EMD) cross section recently observed by Hill, Wohn, Schwellenbach, and Smith do not agree with Weizsacker-Williams (WW) theory or any simple modification thereof. Calculations are presented for the reaction probabilities for this experiment and the entire single and double nucleon removal EMD data set. It is found that for those few reactions where theory and experiment disagree, the probabilities are exceptionally large. This indicates that WW theory is not valid for these reactions and that one must consider higher order corrections and perhaps even a non-perturbative approach to quantum electrodynamics (QED).

Norbury, John W.

1992-01-01

267

Spitzer/SAGE Observations of Planetary Nebulae in the Large Magellanic Cloud  

NASA Astrophysics Data System (ADS)

We present initial results of a program to determine the properties of Planetary Nebulae (PNe) in the Spitzer SAGE survey of the Large Magellanic Cloud (LMC). We have constructed IRAC mosaics of a sample of previously identified PNe in the LMC. Of the 233 PNe in the SAGE survey area, we found 213 that had IRAC sources within 1.5 arcsec of the catalog positions, and 118 had detections in all four IRAC bands. The IRAC colors of the PNe span a similar range as a sample of Galactic PNe. IRS spectra of the LMC PNe reveal several classes of spectral types, including ones dominated by warm dust continuum, PAH features, or emission lines from the ionized gas, including [Ne VI] at 7.65 microns. Several of the PNe are resolved with IRAC, and we compare the images to previous HST imaging at optical wavelengths. We present color-color plots and IRAC images of the detected PNe.

Hora, Joseph L.; Cohen, M.; Meixner, M.; Blum, R. D.; Whitney, B.; Ellis, R. G.; Meade, M.; Babler, B.; Indebetouw, R.; Gordon, K.; Engelbracht, C.; For, B.; Block, M.; Misselt, K.; Vijh, U.; Leitherer, C.

2006-12-01

268

Large Millimeter Telescope Observations of Extremely Luminous High Redshift Infrared Galaxies Detected by the Planck Survey  

NASA Astrophysics Data System (ADS)

We present 8??resolution, 1.1mm, continuum imaging and CO spectroscopic redshift measurements of extremely bright sub-millimeter galaxies identified from the Planck and Herschel surveys, taken with the Large Millimeter Telescope's AzTEC and Redshift Search Receiver instruments. Due to their exceedingly high flux density in the Herschel/SPIRE 250, 350, and 500 micron bands (S_250 ~ S_350 ~ S_500 > 100 mJy), these sources are likely to be strongly lensed dusty galaxies at high redshift. We compiled this target list of lens candidates after cross-correlating the Planck Surveyor mission's highest frequency channel (857 GHz/350 ?m, FWHM = 4.5?) data with archival data taken with the Herschel Spectral and Photometric Imaging Receiver (SPIRE). Every Planck-Herschel counterpart found within a 150??radius is further examined using the higher angular resolution Herschel and WISE images to identify only dusty, high-z starburst galaxies.

Corneilus Harrington, Kevin; Yun, Min Su; Cybulski, John R.; Wilson, Grant; Large Millimeter Telescope (LMT) Team

2015-01-01

269

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

270

Large Millimeter Telescope Observations of Extremely Luminous High Redshift Infrared Galaxies Detected by the Planck Survey  

NASA Astrophysics Data System (ADS)

We present 8?? resolution, 1.1mm, continuum imaging and CO spectroscopic redshift measurements of extremely bright sub-millimeter galaxies identified from the Planck and Herschel surveys, taken with the Large Millimeter Telescope’s AzTEC and Redshift Search Receiver instruments. Due to their exceedingly high flux density in the Herschel/SPIRE 250, 350, and 500 micron bands (S_250 ~ S_350 ~ S_500 > 100 mJy), these sources are likely to be strongly lensed dusty galaxies at high redshift. We compiled this target list of lens candidates after cross-correlating the Planck Surveyor mission’s highest frequency channel (857 GHz/350 ?m, FWHM = 4.5?) data with archival data taken with the Herschel Spectral and Photometric Imaging Receiver (SPIRE). Every Planck-Herschel counterpart found within a 150?? radius is further examined using the higher angular resolution Herschel and WISE images to identify only dusty, high-z starburst galaxies.

Millimeter Telescope, Large

2015-01-01

271

Implementation and management of a biomedical observation dictionary in a large healthcare information system  

PubMed Central

Objective This study shows the evolution of a biomedical observation dictionary within the Assistance Publique Hôpitaux Paris (AP-HP), the largest European university hospital group. The different steps are detailed as follows: the dictionary creation, the mapping to logical observation identifier names and codes (LOINC), the integration into a multiterminological management platform and, finally, the implementation in the health information system. Methods AP-HP decided to create a biomedical observation dictionary named AnaBio, to map it to LOINC and to maintain the mapping. A management platform based on methods used for knowledge engineering has been put in place. It aims at integrating AnaBio within the health information system and improving both the quality and stability of the dictionary. Results This new management platform is now active in AP-HP. The AnaBio dictionary is shared by 120 laboratories and currently includes 50?000 codes. The mapping implementation to LOINC reaches 40% of the AnaBio entries and uses 26% of LOINC records. The results of our work validate the choice made to develop a local dictionary aligned with LOINC. Discussion and Conclusions This work constitutes a first step towards a wider use of the platform. The next step will support the entire biomedical production chain, from the clinician prescription, through laboratory tests tracking in the laboratory information system to the communication of results and the use for decision support and biomedical research. In addition, the increase in the mapping implementation to LOINC ensures the interoperability allowing communication with other international health institutions. PMID:23635601

Vandenbussche, Pierre-Yves; Cormont, Sylvie; André, Christophe; Daniel, Christel; Delahousse, Jean; Charlet, Jean; Lepage, Eric

2013-01-01

272

Observation of large-angle quasi-monoenergetic electrons from a laser wakefield  

NASA Astrophysics Data System (ADS)

A relativistically intense laser pulse is focused into a gas jet and quasi-monoenergetic electrons emitted at a 37 degree angle with respect to the laser axis are observed. The average energy of the electrons was between 1 and 2 MeV and the total accelerated charge was about 1 nC emitted into a 10 degree cone angle. The electron characteristics were sensitive to plasma density. The results are compared with three dimensional particle-in-cell simulations. This electron acceleration mechanism might be useful as a source of injection electrons in a laser wakefield accelerator.

Kaganovich, Dmitri; Gordon, Daniel; Ting, Antonio; Milioutina, Natalie; Sprangle, Phillip

2007-11-01

273

Observation of large-angle quasi-monoenergetic electrons from a laser wakefield  

NASA Astrophysics Data System (ADS)

A relativistically intense laser pulse is focused into a gas jet and quasi-monoenergetic electrons emitted at a 40 degree angle with respect to the laser axis are observed. The average energy of the electrons was between 1 and 2 MeV and the total accelerated charge was about 1 nC emitted into a 10 degree cone angle. The electron characteristics were sensitive to plasma density. The results are compared with three dimensional particle-in-cell simulations. This electron acceleration mechanism might be useful as a source of injection electrons in a laser wakefield accelerator.

Kaganovich, Dmitri; Gordon, Daniel; Ting, Antonio

2008-11-01

274

Observation and analysis of a large amplitude mountain wave event over the Antarctic peninsula  

NASA Astrophysics Data System (ADS)

We use measurements from the Atmospheric Infrared Sounder (AIRS) on the AQUA satellite to observe the 3-dimensional structure of a gravity wave event over the Antarctic peninsula, and determine the horizontal and vertical wavelengths, propagation direction, and temperature amplitude, and from these we estimate wave momentum flux. Using theoretical knowledge of the weighting functions and radiative transfer for AIRS radiance measurements at temperature sensitive channels in the infrared, we derive a method of estimating wave temperature amplitude directly from the radiance measurements. Comparison of the radiance-based temperature amplitudes to the temperature amplitude in AIRS retrieved temperature fields shows close agreement. Because the radiances have 3-times better horizontal resolution than the retrievals, our analysis suggests we can routinely observe important geophysical properties of waves with horizontal wavelengths as short as 80 km using AIRS radiances. We further analyze a nearly identical wave event appearing in the European Centre for Medium Range Forecasts (ECMWF) temperature and wind fields from both assimilation and forecast data. Analysis of the ECMWF data and nearby radiosonde wind profiles allows the interpretation as a mountain wave event forced by flow over the topography of the Antarctic peninsula.

Alexander, M. Joan; Teitelbaum, Hector

2007-11-01

275

An analysis of observed large air-sea temperature differences in tropical cyclones  

SciTech Connect

At high wind speeds over the sea, the lower part of the atmospheric boundary layer becomes filled with spray. In recent years, much attention has been devoted to the question of whether the evaporation from these droplets contributes significantly to the total sea-air evaporative flux under such conditions. Direct observations of turbulent fluxes of heat, moisture and momentum over the sea at moderately high wind speeds were taken during HEXOS Main Experiment (HEXMAX). (HEXOS is the Humidity Exchange Over the Sea program.) An analysis of these results shows that the neutral transfer coefficient is nearly constant with wind speed, up to about 18 m/s, albeit with considerable scatter about the mean. Here the author describes a preliminary investigation of the possible effects evaporation of sea spray could have on the vertical structure of the atmospheric boundary layer at high wind speeds. The remainder of the paper consists of a brief discussion of a radiosonde ascent launched from a ship during a tropical cyclone, a description of the turbulent closure model used to investigate the role of the various physical processes, followed by a discussion of the model results and their relationship to the observation.

Kepert, J.D. [Bureau of Meteorology Research Centre, Melbourne (Australia)

1994-12-31

276

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

277

Large-scale interplanetary magnetic fields: Voyager 1 and 2 observations between 1 AU and 9.5 AU  

NASA Technical Reports Server (NTRS)

The large-scale radial and temporal variations of the interplanetary magnetic field strength B observed by Voyagers 1 and 2 are discussed. Two components of the magnetic field strength were considered: (1) an average component, B sub zero, based on solar rotation averages, and (2) a fluctuation component, delta B, expressed by 10- or 24-hour averages of B normalized by the best-fit average field for the corresponding time and distance. Observations of the sector structure, interfaces, and shocks are presented to further describe magnetic field strength.

Burlaga, L. F.; Klein, L. W.; Lepping, R. P.; Behannon, K. W.

1984-01-01

278

Diffuse Optical Intracluster Light as a Measure of Stellar Tidal Stripping: The Cluster CL0024+17 at z ~ 0.4 Observed at the Large Binocular Telescope  

NASA Astrophysics Data System (ADS)

We have evaluated the diffuse intracluster light (ICL) in the central core of the galaxy cluster CL0024+17 at z ~ 0.4 observed with the prime focus camera (Large Binocular Camera) at the Large Binocular Telescope. The measure required an accurate removal of the galaxies' light within ~200 kpc from the center. The residual background intensity has then been integrated in circular apertures to derive the average ICL intensity profile. The latter shows an approximate exponential decline as expected from theoretical cold dark matter models where the ICL is due to the integrated contribution of light from stars that are tidally stripped from the halo of their host galaxies due to encounters with other galaxies in the cluster cold dark matter (CDM) potential. The radial profile of the ICL over the galaxies intensity ratio (ICL fraction) is increasing with decreasing radius, but near the cluster center it starts to bend and then decreases where the overlap of the halos of the brightest cluster galaxies becomes dominant. Theoretical expectations in a simplified CDM scenario show that the ICL fraction profile can be estimated from the stripped over galaxy stellar mass ratio in the cluster. It is possible to show that the latter quantity is almost independent of the properties of the individual host galaxies but mainly depends on the average cluster properties. The predicted ICL fraction profile is thus very sensitive to the assumed CDM profile, total mass, and concentration parameter of the cluster. Adopting values very similar to those derived from the most recent lensing analysis in CL0024+17, we find a good agreement with the observed ICL fraction profile. The galaxy counts in the cluster core have then been compared with that derived from composite cluster samples in larger volumes, up to the clusters virial radius. The galaxy counts in the CL0024+17 core appear flatter and the amount of bending with respect to the average cluster galaxy counts imply a loss of total emissivity in broad agreement with the measured ICL fraction. The present analysis shows that the measure of the ICL fraction in clusters can quantitatively account for the stellar stripping activity in their cores and can be used to probe their CDM distribution and evolutionary status. Observations have been carried out using the Large Binocular Telescope at Mt. Graham, AZ. The LBT is an international collaboration among institutions in the United States, Italy, and Germany. LBT Corporation partners are the University of Arizona on behalf of the Arizona university system; Istituto Nazionale di Astrofisica, Italy; LBT Beteiligungsgesellschaft, Germany, representing the Max-Planck Society, the Astrophysical Institute Potsdam, and Heidelberg University; the Ohio State University; and The Research Corporation, on behalf of the University of Notre Dame, University of Minnesota, and University of Virginia.

Giallongo, E.; Menci, N.; Grazian, A.; Gallozzi, S.; Castellano, M.; Fiore, F.; Fontana, A.; Pentericci, L.; Boutsia, K.; Paris, D.; Speziali, R.; Testa, V.

2014-01-01

279

Observation of Large CP Violation in the Neutral B Meson System  

NASA Astrophysics Data System (ADS)

We present a measurement of the standard model CP violation parameter sin2?1 based on a 29.1 fb-1 data sample collected at the ?(4S) resonance with the Belle detector at the KEKB asymmetric-energy e+e- collider. One neutral B meson is fully reconstructed as a J/?KS, ?(2S)KS, ?c1KS, ?cKS, J/?KL, or J/?K*0 decay and the flavor of the accompanying B meson is identified from its decay products. From the asymmetry in the distribution of the time intervals between the two B meson decay points, we determine sin2?1 = 0.99+/-0.14(stat)+/-0.06(syst). We conclude that we have observed CP violation in the neutral B meson system.

Abe, K.; Abe, K.; Abe, R.; Adachi, I.; Ahn, Byoung Sup; Aihara, H.; Akatsu, M.; Alimonti, G.; Asai, K.; Asai, M.; Asano, Y.; Aso, T.; Aulchenko, V.; Aushev, T.; Bakich, A. M.; Banas, E.; Behari, S.; Behera, P. K.; Beiline, D.; Bondar, A.; Bozek, A.; Browder, T. E.; Casey, B. C.; Chang, P.; Chao, Y.; Chen, K.-F.; Cheon, B. G.; Chistov, R.; Choi, S.-K.; Choi, Y.; Dong, L. Y.; Dragic, J.; Drutskoy, A.; Eidelman, S.; Eiges, V.; Enari, Y.; Enomoto, R.; Everton, C. W.; Fang, F.; Fujii, H.; Fukunaga, C.; Fukushima, M.; Gabyshev, N.; Garmash, A.; Gershon, T. J.; Gordon, A.; Gotow, K.; Guler, H.; Guo, R.; Haba, J.; Hamasaki, H.; Hanagaki, K.; Handa, F.; Hara, K.; Hara, T.; Hastings, N. C.; Hayashii, H.; Hazumi, M.; Heenan, E. M.; Higasino, Y.; Higuchi, I.; Higuchi, T.; Hirai, T.; Hirano, H.; Hojo, T.; Hokuue, T.; Hoshi, Y.; Hoshina, K.; Hou, S. R.; Hou, W.-S.; Hsu, S.-C.; Huang, H.-C.; Igarashi, Y.; Iijima, T.; Ikeda, H.; Ikeda, K.; Inami, K.; Ishikawa, A.; Ishino, H.; Itoh, R.; Iwai, G.; Iwasaki, H.; Iwasaki, Y.; Jackson, D. J.; Jalocha, P.; Jang, H. K.; Jones, M.; Kagan, R.; Kakuno, H.; Kaneko, J.; Kang, J. H.; Kang, J. S.; Kapusta, P.; Katayama, N.; Kawai, H.; Kawai, H.; Kawakami, Y.; Kawamura, N.; Kawasaki, T.; Kichimi, H.; Kim, D. W.; Kim, Heejong; Kim, H. J.; Kim, Hyunwoo; Kim, S. K.; Kim, T. H.; Kinoshita, K.; Kobayashi, S.; Koishi, S.; Konishi, H.; Korotushenko, K.; Krokovny, P.; Kulasiri, R.; Kumar, S.; Kuniya, T.; Kurihara, E.; Kuzmin, A.; Kwon, Y.-J.; Lange, J. S.; Leder, G.; Lee, M. H.; Lee, S. H.; Leonidopoulos, C.; Lin, Y.-S.; Liventsev, D.; Lu, R.-S.; MacNaughton, J.; Marlow, D.; Matsubara, T.; Matsui, S.; Matsumoto, S.; Matsumoto, T.; Mikami, Y.; Misono, K.; Miyabayashi, K.; Miyake, H.; Miyata, H.; Moffitt, L. C.; Moloney, G. R.; Moorhead, G. F.; Mori, S.; Mori, T.; Murakami, A.; Nagamine, T.; Nagasaka, Y.; Nagashima, Y.; Nakadaira, T.; Nakamura, T.; Nakano, E.; Nakao, M.; Nakazawa, H.; Nam, J. W.; Natkaniec, Z.; Neichi, K.; Nishida, S.; Nitoh, O.; Noguchi, S.; Nozaki, T.; Ogawa, S.; Ohshima, T.; Ohshima, Y.; Okabe, T.; Okazaki, T.; Okuno, S.; Olsen, S. L.; Ozaki, H.; Pakhlov, P.; Palka, H.; Park, C. S.; Park, C. W.; Park, H.; Peak, L. S.; Peters, M.; Piilonen, L. E.; Prebys, E.; Rodriguez, J. L.; Root, N.; Rozanska, M.; Rybicki, K.; Ryuko, J.; Sagawa, H.; Sakai, Y.; Sakamoto, H.; Satapathy, M.; Satpathy, A.; Schrenk, S.; Semenov, S.; Senyo, K.; Settai, Y.; Sevior, M. E.; Shibuya, H.; Shwartz, B.; Sidorov, A.; Stani?, S.; Sugi, A.; Sugiyama, A.; Sumisawa, K.; Sumiyoshi, T.; Suzuki, J.-I.; Suzuki, K.; Suzuki, S.; Suzuki, S. Y.; Swain, S. K.; Tajima, H.; Takahashi, T.; Takasaki, F.; Takita, M.; Tamai, K.; Tamura, N.; Tanaka, J.; Tanaka, M.; Taylor, G. N.; Teramoto, Y.; Tomoto, M.; Tomura, T.; Tovey, S. N.; Trabelsi, K.; Tsuboyama, T.; Tsukamoto, T.; Uehara, S.; Ueno, K.; Unno, Y.; Uno, S.; Ushiroda, Y.; Vahsen, S. E.; Varvell, K. E.; Wang, C. C.; Wang, C. H.; Wang, J. G.; Wang, M.-Z.; Watanabe, Y.; Won, E.; Yabsley, B. D.; Yamada, Y.; Yamaga, M.; Yamaguchi, A.; Yamamoto, H.; Yamanaka, T.; Yamashita, Y.; Yamauchi, M.; Yanaka, S.; Yashima, J.; Yokoyama, M.; Yoshida, K.; Yusa, Y.; Yuta, H.; Zhang, C. C.; Zhang, J.; Zhao, H. W.; Zheng, Y.; Zhilich, V.; Žontar, D.

2001-08-01

280

Melt production in large-scale impact events: Planetary observations and implications  

NASA Technical Reports Server (NTRS)

Differences in scaling relationships for crater formation and the generation of impact melt should lead to a variety of observable features and phenomena. These relationships infer that the volume of the transient cavity (and final crater) relative to the volume of impact melt (and the depth to which melting occurs) decreases as the effects of gravity and impact velocity increase. Since planetary gravity and impact velocity are variables in the calculation of cavity and impact-melt volumes, the implications of the model calculation will vary between planetary bodies. Details of the model calculations of impact-melt generation as a function of impact and target physical conditions were provided elsewhere, as were attempts to validate the model through ground-truth data on melt volumes, shock attenuation, and morphology from terrestrial impact craters.

Cintala, Mark J.; Grieve, Richard A. F.

1992-01-01

281

The Spitzer c2d Survey of Large, Nearby, Interstellar Clouds: VII. Ophiuchus Observed with MIPS  

E-print Network

We present maps of 14.4 deg^2 of the Ophiuchus dark clouds observed by the Spitzer Space Telescope Multiband Imaging Photometer for Spitzer (MIPS). These high quality maps depict both numerous point sources as well as extended dust emission within the star-forming and non-star-forming portions of these clouds. Using PSF-fitting photometry, we detect 5779 sources at 24 um and 81 sources at 70 um at the 10 sigma level of significance. Three hundred twenty-three candidate young stellar objects (YSOs) were identified according to their positions on the MIPS/2MASS K versus K$-$[24] color-magnitude diagrams as compared to 24 um detections in the SWIRE extragalactic survey. We find that more than half of the YSO candidates, and almost all the ones with protostellar Class I spectral energy distributions, are confined to the known cluster and aggregates.

Padgett, Deborah L; Stapelfeldt, Karl R; Chapman, Nicholas L; Lai, Shih-Ping; Mundy, Lee G; Evans, Neal J; Brooke, Timothy Y; Cieza, Lucas A; Spiesman, William J; Noriega-Crespo, Alberto; McCabe, Caer-Eve; Allen, Lori E; Blake, Geoffrey A; Harvey, Paul M; Huard, Tracy L; Jorgensen, Jes K; Koerner, David W; Myers, Philip C; Sargent, Anneila I; Teuben, Peter; van Dishoeck, Ewine F; Wahhaj, Zahed; Young, Kaisa E

2007-01-01

282

Concurrent observations of auroral activity and a large sporadic sodium layer event during ANLC-93  

NASA Astrophysics Data System (ADS)

Prominent sporadic sodium (Nas) layers, apparently associated with intense auroral activity, were observed during the 1993 Arctic Noctilucent Cloud Campaign (ANLC-93) with an airborne sodium lidar on the August 6 flight near 51°N latitude. The peak density of the Nas layer reached 74,500 cm-3. The zonal extent of the Nas layers exceeded 1600 km. Strong auroral emissions were recorded with an all-sky imager on the aircraft. A Michelson Interferometer was used to measure the intensity of OH nightglow between 85-90 km. OH rotational temperature exhibited no obvious correlation with the Nas layer peak density near 94 km. The data suggest a connection between the Nas layers and auroral electron precipitations. The data also support the conjecture that dust and smoke particles may play a crucial role in the Nas layer formation.

Gu, Y. Y.; Qian, J.; Papen, G. C.; Swenson, G. R.; Espy, P. J.

283

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. PMID:23956556

Sinha, Sanjib; Pramod, M. N.; Dilipkumar, S.; Satishchandra, P.

2013-01-01

284

Mining Cancer-Specific Disease Comorbidities from a Large Observational Health Database  

PubMed Central

Cancer comorbidities often reflect the complex pathogenesis of cancers and provide valuable clues to discover the underlying genetic mechanisms of cancers. In this study, we systematically mine and analyze cancer-specific comorbidity from the FDA Adverse Event Reporting System. We stratified 3,354,043 patients based on age and gender, and developed a network-based approach to extract comorbidity patterns from each patient group. We compared the comorbidity patterns among different patient groups and investigated the effect of age and gender on cancer comorbidity patterns. The results demonstrated that the comorbidity relationships between cancers and non-cancer diseases largely depend on age and gender. A few exceptions are depression, anxiety, and metabolic syndrome, whose comorbidity relationships with cancers are relatively stable among all patients. Literature evidences demonstrate that these stable cancer comorbidities reflect the pathogenesis of cancers. We applied our comorbidity mining approach on colorectal cancer and detected its comorbid associations with metabolic syndrome components, diabetes, and osteoporosis. Our results not only confirmed known cancer comorbidities but also generated novel hypotheses, which can illuminate the common pathophysiology between cancers and their co-occurring diseases. PMID:25392682

Chen, Yang; Xu, Rong

2014-01-01

285

Rotation Periods of Binary Asteroids with Large Separations - Confronting the Escaping Ejecta Binaries Model with Observations  

E-print Network

Durda et al. (2004), using numerical models, suggested that binary asteroids with large separation, called Escaping Ejecta Binaries (EEBs), can be created by fragments ejected from a disruptive impact event. It is thought that six binary asteroids recently discovered might be EEBs because of the high separation between their components (~100 > a/Rp > ~20). However, the rotation periods of four out of the six objects measured by our group and others and presented here show that these suspected EEBs have fast rotation rates of 2.5 to 4 hours. Because of the small size of the components of these binary asteroids, linked with this fast spinning, we conclude that the rotational-fission mechanism, which is a result of the thermal YORP effect, is the most likely formation scenario. Moreover, scaling the YORP effect for these objects shows that its timescale is shorter than the estimated ages of the three relevant Hirayama families hosting these binary asteroids. Therefore, only the largest (D~19 km) suspected astero...

Polishook, D; Prialnik, D

2010-01-01

286

Mentally Visualizing Large Geologic Structures from Field Observations: A Behavioral Study  

NSDL National Science Digital Library

We construct artificial outcrops out of plywood on the Lamont campus that together would form a large geologic structure, part of which is eroded or covered by dirt and vegetation. One structure is an elongate basin, and another is an anticline. Participants are expert geoscientists and novice learners. They will be guided by an experimenter around a set of outcrops and take notes while walking around. When they finished walking around the outcrops, they will be asked to choose among an array of scale models of possible geologic structures the one that they think best represents the buried structure. Then they will orient the model so that it is aligned with the actual structure in the real world. They will be asked to "think aloud" while choosing and orienting the model; this process is videotaped so that we can analyze their thought processes and develop strategy-training methods. As individual differences measures, they will also be asked to take standard spatial tests and a questionnaire assessing their learning style (verbal vs. spatial).

Kim Kastens

287

Statistical Analysis of Large-scale EUV Waves Observed by STEREO/EUVI  

E-print Network

We present a statistical analysis of 60 strong large-scale EUV wave events that occurred during January 2007 to February 2011 with the STEREO twin spacecraft regarding their kinematical evolution and wave pulse characteristics. For the start velocity, we obtain for the arithmetic mean $312\\pm115$ km s$^{-1}$ (within a range of 100$-$630 km s$^{-1}$). For the mean (linear) velocity, the arithmetic mean is $254\\pm76$ km s$^{-1}$ (within a range of 130$-$470 km s$^{-1}$). 52 % of all waves under study show a distinct deceleration during their propagation ($a\\leq-50$ m s$^{-2}$), the other 48 % are consistent with a constant speed within the uncertainties ($-50\\leq a\\leq50$ m s$^{-2}$). The start velocity and the acceleration show a strong anticorrelation with $c\\approx-0.8$, \\textit i.e initially faster events undergo stronger deceleration than slower events. The (smooth) transition between constant propagation for slow events and deceleration in faster events occurs at an EUV wave start velocity of $v\\approx230...

Muhr, Nicole; Kienreich, Ines Waltraud; Vrsnak, Bojan; Temmer, Manuela; Bein, Bianca Maria

2014-01-01

288

XMM-Newton observations of 30 Dor C in the Large Magellanic Cloud  

NASA Astrophysics Data System (ADS)

The 30 Dor C superbubble (SB) in the Large Magellanic Cloud is notable for its bright shell of non-thermal X-ray emission. The southeastern region is also known to exhibit significant thermal emission with metal enhancements indicating the presence of a supernova remnant (SNR). However, a detailed treatment and characterisation of the thermal emission has not yet been performed. In this work, we present the analysis of the ample XMM-Newton data available for 30 Dor C (flare-filtered exposure times of 420 ks EPIC-pn, 556 ks EPIC-MOS1, 614 ks EPIC-MOS2) to attempt to isolate and identify any X-ray emission due to an SNR. In addition, an analysis of the non-thermal emission will be presented and discussed in the context of emission mechanisms previously suggested in the literature (i.e., non-thermal bremsstrahlung and synchrotron). Two SNRs were found to be contributing to the thermal emission in 30 Dor C. The most apparent is manifest as a prominent arc in the 1-2 keV energy range, which shows strong emission lines of ?-process elements in its spectrum, consistent with a core-collapse remnant. Its X-ray morphology points to a location outside the SB. The second SNR is likely an interior SNR interacting with the shell wall.

Kavanagh, P.; Sasaki, M.; Bozzetto, L.; Filipovi?, M.; Haberl, F.; Maggi, P.; Points, S.

2014-07-01

289

Observation of abnormally large radii of nuclei in excited states in the vicinity of neutron thresholds  

SciTech Connect

Differential cross sections for inelastic scattering leading to the excitation of some nuclear states situated near neutron-emission thresholds were analyzed. With the aid of a modified diffraction model, abnormally large radii were found for the 1/2{sub 1}{sup +} state of the {sup 13}C nucleus at 3.09 MeV, for the first levels of positive-parity rotational bands in the {sup 9}Be (1/2{sup +} level at 1.68 MeV and 5/2{sup +} level at 3.05 MeV) and {sup 11}Be (5/2{sup +} level at 1.78 MeV and 3/2{sup +} level at 3.41 MeV) nuclei, and for the 2{sub 1}{sup +} state of the {sup 14}Be nucleus at 1.54 MeV and 1{sub 1}{sup -} state of the {sup 12}Be nucleus at 2.7 MeV. All of these states possess signatures typical of neutron halos.

Ogloblin, A. A., E-mail: ogloblina@bk.ru; Danilov, A. N. [Russian Research Centre Kurchatov Institute (Russian Federation); Belyaeva, T. L. [Universidad Nacional Autonoma de Mexico (UNAM) (Mexico); Demyanova, A. S. [Russian Research Centre Kurchatov Institute (Russian Federation); Goncharov, S. A. [Moscow State University, Skobeltsyn Institute of Nuclear Physics (Russian Federation); Trzaska, W. [University of Jyvaeskylae (Finland)

2011-11-15

290

Infrasonic interferometry applied to microbaroms observed at the Large Aperture Infrasound Array in the Netherlands  

NASA Astrophysics Data System (ADS)

We present the results of infrasonic interferometry applied to microbaroms, obtained from ambient noise. For this purpose the "Large Aperture Infrasound Array" (LAIA) was used, which has been installed in the Netherlands. Preprocessing appeared to be an essential step in enhancing the microbarom signals from ambient noise that strongly influences the results of the interferometry. Both the state of the atmosphere and the noise characteristics are taken into account to assess the strength of the cross correlation. The delay time of the microbaroms between two stations is determined through cross correlating the recordings. By calculating the cross correlations between all 55 station pairs of LAIA, we are able to find the delay time of microbaroms up to a interstation distance of 40.6 km. Using the strength of the cross correlations, we are able to show that the coherence of the microbaroms along the direction of arrival is higher than orthogonal to it. A comparison of the atmospheric state, with a cross correlation, over a period of 10 days, reveals that the infrasound propagation over the array is correlated with the tropospheric temperature and wind. Based on the cross correlations between the three closest stations, we are able to passively estimate the effective sound speed and the wind speed as a function of time.

Fricke, J. T.; Evers, L. G.; Smets, P. S. M.; Wapenaar, K.; Simons, D. G.

2014-08-01

291

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

292

Report on the analysis of the large propagation velocities observed in the full-length SSC (Superconducting Super Collider) dipoles  

SciTech Connect

Very large propagation velocities have been observed in the Superconducting Super Collider (SSC) 17-m dipoles: from 75 m/s to 225 m/s, depending on the current. These velocities are much larger than those predicted by the classical conduction theory of normal zone propagation. A plausible explanation for such rapid propagation is hydrodynamic mechanism called thermal hydraulic quenchback (THQ) that has been proposed by Luongo et al. This report supplies an approximate analytic theory of THQ, which is used to analyze the data taken on the SSC 17-m dipoles. It is concluded that THQ in the helium in the interstices of the cable can explain the large propagation velocities observed. Additional experiments are proposed to test the hydrodynamic explanation. 17 refs., 5 figs.

Dresner, L.; Lue, J.W.; Lubell, M.

1990-09-01

293

Observing large-scale temporal variability of ocean currents by satellite altimetry - With application to the Antarctic circumpolar current  

NASA Technical Reports Server (NTRS)

A new method is developed for studying large-scale temporal variability of ocean currents from satellite altimetric sea level measurements at intersections (crossovers) of ascending and descending orbit ground tracks. Using this method, sea level time series can be constructed from crossover sea level differences in small sample areas where altimetric crossovers are clustered. The method is applied to Seasat altimeter data to study the temporal evolution of the Antarctic Circumpolar Current (ACC) over the 3-month Seasat mission (July-October 1978). The results reveal a generally eastward acceleration of the ACC around the Southern Ocean with meridional disturbances which appear to be associated with bottom topographic features. This is the first direct observational evidence for large-scale coherence in the temporal variability of the ACC. It demonstrates the great potential of satellite altimetry for synoptic observation of temporal variability of the world ocean circulation.

Fu, L.-L.; Chelton, D. B.

1985-01-01

294

Potential of a Future Large Aperture UVOIR Space Observatory for Breakthrough Observations of Star and Planet Formation  

NASA Astrophysics Data System (ADS)

A future large aperture space observatory operating from the UV to the near-infrared with a diameter between 10 and 15 meters will provide a unique opportunity for observations of star and planet formation, from nearby moving groups and associations to star formation in galaxies in the local universe. Our newly formed working group will examine the unique opportunities that such a telescope will give observers in a post-JWST/WFIRST-AFTA era that includes extremely large ground-based observatories such as the TMT, E-ELT, ALMA, and the VLTI. Given a potential suite of instruments for this observatory we will discuss some of the key areas of star and planet formation science where breakthroughs might occur.

Danchi, William C.; Grady, Carol A.; Padgett, Deborah

2015-01-01

295

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

296

Cover Image: USGS Circular 1381  

USGS Multimedia Gallery

Cover image: USGS Circular 1381. View of Boulder Basin, Lake Mead, at sunset looking east. The flat topped mountain in the background is Fortification Hill, a well-known landmark in the viewshed from Hoover Dam....

297

Monitoring observations of the interaction between Sgr A* and G2 with the Karl G. Jansky Very Large Array  

NASA Astrophysics Data System (ADS)

We report on an ongoing community service observing program to follow the expected encounter of the G2 cloud with the black hole Sgr A* in 2013. The NRAO Karl G. Jansky Very Large Array (VLA) has been observing the Sgr A region since 2012 October on roughly a bi-monthly interval, each for two hours, cycling through eight observing bands at their default continuum frequencies, using 2 GHz of bandwidth. The data from the monitoring program are publicly available through the NRAO data archive immediately after observing has completed, and the flux densities are published by NRAO staff as soon as the data are reduced. The cumulative results of the monitoring effort are posted on the service observing web page observing" xlink:type="simple">https://science.nrao.edu/science/service-observing and so far do not indicate a significant brightening of the emission from the direction of Sgr A* over the period 2012 October to 2013 September, within the calibration uncertainties.

Sjouwerman, Loránt O.; Chandler, Claire J.

2014-05-01

298

Rotation periods of binary asteroids with large separations - Confronting the Escaping Ejecta Binaries model with observations  

NASA Astrophysics Data System (ADS)

Durda et al. (Durda, D.D., Bottke, W.F., Enke, B.L., Merline, W.J., Asphaug, E., Richardson, D.C., Leinhardt, Z.M. [2004]. Icarus 170, 243-257), using numerical models, suggested that binary asteroids with large separation, called Escaping Ejecta Binaries (EEBs), can be created by fragments ejected from a disruptive impact event. It is thought that six binary asteroids recently discovered might be EEBs because of the high separation between their components (?100 > a/Rp > ?20). However, the rotation periods of four out of the six objects measured by our group and others and presented here show that these suspected EEBs have fast rotation rates of 2.5-4 h. Because of the small size of the components of these binary asteroids, linked with this fast spinning, we conclude that the rotational-fission mechanism, which is a result of the thermal YORP effect, is the most likely formation scenario. Moreover, scaling the YORP effect for these objects shows that its timescale is shorter than the estimated ages of the three relevant Hirayama families hosting these binary asteroids. Therefore, only the largest (D ? 19 km) suspected asteroid, (317) Roxane, could be, in fact, the only known EEB. In addition, our results confirm the triple nature of (3749) Balam by measuring mutual events on its lightcurve that match the orbital period of a nearby satellite in addition to its distant companion. Measurements of (1509) Esclangona at different apparitions show a unique shape of the lightcurve that might be explained by color variations.

Polishook, D.; Brosch, N.; Prialnik, D.

2011-03-01

299

Observations of the Large Magellanic Cloud in high-energy gamma rays  

NASA Technical Reports Server (NTRS)

The LMC provides a valuable site to study gamma-ray production, intensity, and distribution in an external galaxy. Using 4 weeks of data from the Energetic Gamma Ray Experiment Telescope (EGRET) aboard the Compton Gamma Ray Observatory, high-energy gamma-ray emission was detected for the first time from the LMC region. These gamma rays are believed to be produced primarily through the interaction of cosmic rays with interstellar matter. Hence, combined with a knowledge of the interstellar matter distribution, they can provide a direct measure of the cosmic-ray density in an external galaxy. The results obtained from EGRET observations indicate that the level of cosmic rays in the LMC is comparable to that in our Galaxy. The integrated flux above 100 MeV is (1.9 +/- 0.4) x 10 exp -7 photons/(sq cm s). The measured flux suggests a cosmic-ray density level consistent with that expected from a quasi-stable equilibrium model. This is the first detection of a normal galaxy outside the Milky Way in high-energy gamma rays.

Sreekumar, P.; Bertsch, D. L.; Dingus, B. L.; Fichtel, C. E.; Hartman, R. C.; Hunter, S. D.; Kanbach, G.; Kniffen, D. A.; Lin, Y. C.; Mattox, J. R.

1992-01-01

300

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

301

Observation of the Mold-Filling Process of a Large Hydro-Turbine Guide Vane Casting  

NASA Astrophysics Data System (ADS)

The mold-filling process has a determining effect on the quality of castings, and it has always been a hot but difficult research topic. The authors developed a wireless monitoring system for the mold-filling process of castings based on a contact time method and an observation system based on heat-resistant high-speed cameras. By using these two systems, the filling process of a turbine guide vane casting with a stepped gating system was investigated. The filling profile of the casting was recorded, and the filling time of nine typical positions was acquired. These results show that at the beginning, the liquid steel flowed out from the top ingate, which was designed to be the last to fill. The numerical simulation of the filling of the guide vane was performed, and the outflow from the top ingate were predicted. Finally, the gating system of the casting was improved with enlarged sprue. The new design features bigger sprue to ingate ratio; therefore, it could avoid the overflow from the top ingate and realize stable filling.

Kang, Jinwu; Long, Haimin; Li, Yongjie; You, Rui; Hao, Xiaokun; Nie, Gang; Wang, Tianjiao; Zhang, Chengchun

2015-02-01

302

Large-Area Balloon-Borne Polarized Gamma Ray Observer (PoGO)  

NASA Astrophysics Data System (ADS)

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 (~ 5 deg2) 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. S. T.; Suhonen, M.; Tajima, H.; Thurston, T.; Bogaert, G.; Fukazawa, Y.; Saito, Y.; Takahashi, T.; Barbier, L.; Bloser, P.; Cline, T.; Harding, A.; Hunter, S.; Krizmanic, J.; Mitchell, J.; Streitmatter, R.; Fernholz, R.; Groth, E.; Marlow, D.; Carlson, P.; Klamra, W.; Pearce, M.; Bjornsson, C.-I.; Fransson, C.; Larsson, S.; Ryde, F.; Arimoto, M.; Ikagawa, T.; Kanai, Y.; Kataoka, J.; Kawai, N.; Yatsu, Y.; Gunji, S.; Sakurai, H.; Yamashita, Y.

303

Observation of the Mold-Filling Process of a Large Hydro-Turbine Guide Vane Casting  

NASA Astrophysics Data System (ADS)

The mold-filling process has a determining effect on the quality of castings, and it has always been a hot but difficult research topic. The authors developed a wireless monitoring system for the mold-filling process of castings based on a contact time method and an observation system based on heat-resistant high-speed cameras. By using these two systems, the filling process of a turbine guide vane casting with a stepped gating system was investigated. The filling profile of the casting was recorded, and the filling time of nine typical positions was acquired. These results show that at the beginning, the liquid steel flowed out from the top ingate, which was designed to be the last to fill. The numerical simulation of the filling of the guide vane was performed, and the outflow from the top ingate were predicted. Finally, the gating system of the casting was improved with enlarged sprue. The new design features bigger sprue to ingate ratio; therefore, it could avoid the overflow from the top ingate and realize stable filling.

Kang, Jinwu; Long, Haimin; Li, Yongjie; You, Rui; Hao, Xiaokun; Nie, Gang; Wang, Tianjiao; Zhang, Chengchun

2014-10-01

304

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

305

Large-scale variations of the low-latitude ionosphere during the October-November 2003 superstorm: Observational results  

NASA Astrophysics Data System (ADS)

The GPS-derived total electron content (TEC), ion drift measurements from the ROCSAT-1 spacecraft at around 600 km altitude, and far-ultraviolet airglow measured by the Global Ultraviolet Imager (GUVI) carried on board the NASA TIMED satellite are utilized for studying large disturbances of the low-latitude ionosphere during the October-November 2003 superstorm period. Two chains of GPS receivers, one in the American sector (˜70°W) and the other in the Asian/Australian sector (˜120°E), are used to simultaneously observe the daytime equatorial ionization anomaly (EIA) during the entire storm period. It is found from the GPS-TEC measurements that the EIA expanded to very high latitudes with large increases of TEC right after the storm started. The large expansion of the EIA was associated with strong upward E × B drifts measured from the Ionospheric Plasma and Electrodynamics Instrument (IPEI) on board the ROCSAT-1, providing evidence of a penetration electric field and a strong plasma fountain effect. Suppression of the EIA was observed during the storm recovery, associated with downward E × B drifts that were observed by the ROCSAT-1. Significant negative storm effects in the southern hemisphere were also observed in the GPS-TEC during the first day of the recovery phase. The areas of negative storm effects are in good agreement with reductions in the [O]/[N2] density ratio inferred from the ratio of OI (135.6 nm) to LBH emissions measured from GUVI. An enhancement of the EIA was observed on the day, 1 November, that the storm was about to fully recover.

Lin, C. H.; Richmond, A. D.; Liu, J. Y.; Yeh, H. C.; Paxton, L. J.; Lu, G.; Tsai, H. F.; Su, S.-Y.

2005-09-01

306

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

307

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

308

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 p0s 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.; /Stanford U., HEPL /KIPAC, Menlo Park /SLAC; Baldini, L.; /INFN, Pisa; Ballet, J.; /AIM, Saclay; Barbiellini, G.; /INFN, Trieste /Trieste U.; Bastieri, D.; /INFN, Padua /Padua U.; Bechtol, K.; /Stanford U., HEPL /KIPAC, Menlo Park /SLAC; Bellazzini, R.; /INFN, Pisa; Berenji, B.; Blandford, R.D.; Bloom, E.D.; /Stanford U., HEPL /KIPAC, Menlo Park /SLAC; Bonamente, E.; /INFN, Perugia /Perugia U.; Borgland, A.W.; /Stanford U., HEPL /KIPAC, Menlo Park /SLAC; Bregeon, J.; /INFN, Pisa; Brigida, M.; /Bari Polytechnic /INFN, Bari; Bruel, P.; /Ecole Polytechnique; Buehler, R.; /Stanford U., HEPL /KIPAC, Menlo Park /SLAC; Buson, S.; /INFN, Padua /Padua U.; Caliandro, G.A.; /CSIC, Catalunya; Cameron, R.A.; /Stanford U., HEPL /KIPAC, Menlo Park /SLAC; Caraveo, P.A.; /IASF, Milan /AIM, Saclay /INFN, Perugia /Perugia U. /Stanford U., HEPL /KIPAC, Menlo Park /SLAC /Unlisted, US /Naval Research Lab, Wash., D.C. /Perugia U. /ASDC, Frascati /Stanford U., HEPL /KIPAC, Menlo Park /SLAC /Montpellier U. /ASDC, Frascati /Udine U. /INFN, Trieste /Bari Polytechnic /INFN, Bari /Naval Research Lab, Wash., D.C. /Stanford U., HEPL /KIPAC, Menlo Park /SLAC /Bari Polytechnic /INFN, Bari /Ecole Polytechnique /NASA, Goddard /Stanford U., HEPL /KIPAC, Menlo Park /SLAC /Udine U. /INFN, Trieste /Trieste Observ. /Hiroshima U. /Nagoya U. /Bari Polytechnic /INFN, Bari /INFN, Bari /ASDC, Frascati /INFN, Perugia /Perugia U. /Bari Polytechnic /INFN, Bari /ASDC, Frascati /Bari Polytechnic /INFN, Bari /Bologna Observ. /Stanford U., HEPL /KIPAC, Menlo Park /SLAC /Naval Research Lab, Wash., D.C. /Alabama U., Huntsville /CSIC, Catalunya /Hiroshima U. /NASA, Goddard /Hiroshima U.; /more authors..

2012-09-14

309

Circular High-Impedance Surfaces Characterization  

Microsoft Academic Search

In this letter, characterization of circular high-impedance surfaces (HISs) is investigated. The reflection phase characterization used for rectangular HISs is here extended to circular lattices. Circular HISs discussed in this letter present a 2-D periodicity, and consequently the phase diagram is determined for concentric and radial polarizations. The effect of mapping a rectangular HIS into a circular one is investigated

Julien Sarrazin; Anne-Claire Lepage; Xavier Begaud

2012-01-01

310

Angular momentum-induced circular dichroism in non-chiral nanostructures.  

PubMed

Circular dichroism, that is, the differential absorption of a system to left and right circularly polarized light, is one of the only techniques capable of providing morphological information of certain samples. In biology, for instance, circular dichroism spectroscopy is widely used to study the structure of proteins. More recently, it has also been used to characterize metamaterials and plasmonic structures. Typically, circular dichorism can only be observed in chiral objects. Here we present experimental results showing that a non-chiral sample such as a subwavelength circular nanoaperture can produce giant circular dichroism when a vortex beam is used to excite it. These measurements can be understood by studying the symmetries of the sample and the total angular momentum that vortex beams carry. Our results show that circular dichroism can provide a wealth of information about the sample when combined with the control of the total angular momentum of the input field. PMID:25215603

Zambrana-Puyalto, Xavier; Vidal, Xavier; Molina-Terriza, Gabriel

2014-01-01

311

Circular dichroism techniques: biomolecular and nanostructural analyses- a review.  

PubMed

This paper reviews the best known techniques using circular dichroism spectroscopy such as conventional circular dichroism (i.e. electronic circular dichroism), magnetic circular dichroisms (magnetic vibrational circular dichroism, x-ray magnetic circular dichroism), fluorescence detected circular dichroism, near-infrared circular dichroism, vibrational circular dichroism, Fourier transform infrared circular dichroism, high pressure liquid chromatography circular dichroism, stopped-flow circular dichroism, and synchrotron radiation circular dichroism. Also, we have described here the most important applications of circular dichroism spectroscopy in structural biochemistry and nanoscience. PMID:19566697

Ranjbar, Bijan; Gill, Pooria

2009-08-01

312

SWAP OBSERVATIONS OF THE LONG-TERM, LARGE-SCALE EVOLUTION OF THE EXTREME-ULTRAVIOLET SOLAR CORONA  

SciTech Connect

The Sun Watcher with Active Pixels and Image Processing (SWAP) EUV solar telescope on board the Project for On-Board Autonomy 2 spacecraft has been regularly observing the solar corona in a bandpass near 17.4 nm since 2010 February. With a field of view of 54 × 54 arcmin, SWAP provides the widest-field images of the EUV corona available from the perspective of the Earth. By carefully processing and combining multiple SWAP images, it is possible to produce low-noise composites that reveal the structure of the EUV corona to relatively large heights. A particularly important step in this processing was to remove instrumental stray light from the images by determining and deconvolving SWAP's point-spread function from the observations. In this paper, we use the resulting images to conduct the first-ever study of the evolution of the large-scale structure of the corona observed in the EUV over a three year period that includes the complete rise phase of solar cycle 24. Of particular note is the persistence over many solar rotations of bright, diffuse features composed of open magnetic fields that overlie polar crown filaments and extend to large heights above the solar surface. These features appear to be related to coronal fans, which have previously been observed in white-light coronagraph images and, at low heights, in the EUV. We also discuss the evolution of the corona at different heights above the solar surface and the evolution of the corona over the course of the solar cycle by hemisphere.

Seaton, Daniel B.; De Groof, Anik; Berghmans, David; Nicula, Bogdan [Royal Observatory of Belgium-SIDC, Avenue Circulaire 3, B-1180 Brussels (Belgium); Shearer, Paul [Department of Mathematics, 2074 East Hall, University of Michigan, 530 Church Street, Ann Arbor, MI 48109-1043 (United States)

2013-11-01

313

Fluctuations in the ionosphere related to Honshu Twin Large Earthquakes of September 2004 observed by the DEMETER and CHAMP satellites  

NASA Astrophysics Data System (ADS)

While investigating possible precursory signatures of large earthquakes in the ionospheric data measured by the DEMETER and CHAMP satellites, we found ionospheric disturbances related to large earthquakes (M=7.2 and 7.4) that occurred on September 2004 near the south coast of Honshu, Japan. The satellite data were statistically compared with an empirical model and local averages of the large set of data in the study period. A fluctuation in the electron density above the epicenter was observed roughly 2 weeks before the main earthquakes. Surveys of the space weather and geomagnetic activities suggest that these fluctuations were not caused by changes in space conditions or by a geomagnetic storm. The features were also distinct from well-known natural ionospheric anomalies. In addition, a peak-like profile in the ion temperature and lowered O+ density around the region of the epicenter was observed a week before the main earthquakes along the satellite passes whose longitudes are close to the epicenter. The features are more apparent when they are compared with the data more distant from the epicenter, suggesting that the disturbances occur along the geomagnetic field lines. The concurrent measurements of the ion drift velocity suggest the fluctuations were triggered by the vertical plasma drift. The observed anomalies disappeared ? 2 weeks after the quakes. According to the current theories on the seismo-ionospheric coupling, the horizontal electric field at the lower boundary of the ionosphere should have been strengthened by the seismic activity in order for the ionospheric plasma movements above the epicenter and its geomagnetic conjugate regions to trigger the observed ionospheric anomalies.

Ryu, Kwangsun; Chae, Jang-Soo; Lee, Ensang; Parrot, Michel

2014-12-01

314

Circular Harmonic Decomposition Approach for Numerical Inversion of Circular Radon Transforms  

E-print Network

Circular Harmonic Decomposition Approach for Numerical Inversion of Circular Radon Transforms Gaël@num.uni-sb.de ABSTRACT Numerical inversions via circular harmonic decomposition for two classes of circular Radon transforms are established. The first class deals with the Radon transform (RT) de- fined on circular arcs

Paris-Sud XI, Université de

315

325 MHz VERY LARGE ARRAY OBSERVATIONS OF ULTRACOOL DWARFS TVLM 513-46546 AND 2MASS J0036+1821104  

SciTech Connect

We present 325 MHz (90 cm wavelength) radio observations of ultracool dwarfs TVLM 513-46546 and 2MASS J0036+1821104 using the Very Large Array (VLA) in 2007 June. Ultracool dwarfs are expected to be undetectable at radio frequencies, yet observations at 8.5 GHz (3.5 cm) and 4.9 GHz (6 cm) have revealed sources with >100 {mu}Jy quiescent radio flux and >1 mJy pulses coincident with stellar rotation. The anomalous emission is likely a combination of gyrosynchrotron and cyclotron maser processes in a long-duration, large-scale magnetic field. Since the characteristic frequency for each process scales directly with the magnetic field magnitude, emission at lower frequencies may be detectable from regions with weaker field strength. We detect no significant radio emission at 325 MHz from TVLM 513-46546 or 2MASS J0036+1821104 over multiple stellar rotations, establishing 2.5{sigma} total flux limits of 795 {mu}Jy and 942 {mu}Jy, respectively. Analysis of an archival VLA 1.4 GHz observation of 2MASS J0036+1821104 from 2005 January also yields a non-detection at the level of <130 {mu}Jy. The combined radio observation history (0.3 GHz to 8.5 GHz) for these sources suggests a continuum emission spectrum for ultracool dwarfs that is either flat or inverted below 2-3 GHz. Further, if the cyclotron maser instability is responsible for the pulsed radio emission observed on some ultracool dwarfs, our low-frequency non-detections suggest that the active region responsible for the high-frequency bursts is confined within two stellar radii and driven by electron beams with energies less than 5 keV.

Jaeger, T. R.; Kassim, N. [US Naval Research Laboratory, Washington, DC 20375 (United States); Osten, R. A. [Space Telescope Science Institute, Baltimore, MD 21218 (United States); Lazio, T. J. [Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109 (United States); Mutel, R. L., E-mail: ted.jaeger.ctr@nrl.navy.mil [Department of Astronomy, University of Iowa, Iowa City, IA 52242 (United States)

2011-12-15

316

Large-eddy simulation of mesoscale dynamics and entrainment around a pocket of open cells observed in VOCALS RF06  

NASA Astrophysics Data System (ADS)

Large-eddy simulations of a pocket of open cells (POC) based on VOCALS Regional Experiment (REx) Research Flight 06 are analyzed and compared with aircraft observations. A doubly-periodic domain 192 km × 24 km with 125 m horizontal resolution and 5 m vertical resolution near the capping inversion is used. The POC is realized in the model as a fixed 96 km wide region of reduced cloud droplet number concentration (Nc) based on observed values; initialization and forcing are otherwise uniform across the domain. The model reproduces aircraft-observed differences in boundary-layer structure and precipitation organization between a well-mixed overcast region and a decoupled POC with open-cell precipitating cumuli, although the simulated cloud cover is too large in the POC. A sensitivity study in which Nc is allowed to advect following the turbulent flow gives nearly identical results over the 16 h length of the simulation (which starts at night and goes into the next afternoon). The simulated entrainment rate is nearly a factor of two smaller in the less turbulent POC than in the more turbulent overcast region. However, the inversion rises at a nearly uniform rate across the domain because powerful buoyancy restoring forces counteract horizontal inversion height gradients. A secondary circulation sets up that diverts subsiding free-tropospheric air away from the POC into the surrounding overcast region, counterbalancing the weaker entrainment in the POC with locally weaker subsidence.

Berner, A. H.; Bretherton, C. S.; Wood, R.

2011-05-01

317

Observations of Comet P/2003 T12 = 2012 A3 (SOHO) at large phase angle in STEREO-B  

NASA Astrophysics Data System (ADS)

Comet P/2003 T12 = 2012 A3 (SOHO) was observed by the satellite STEREO-B during the period 2012 January 13-27. During its apparition, it ventured into the highest phase angle ever observed for a comet, and the forward-scattering enhancement in brightness was marked, as large as ˜8.5 mag. Therefore, it provided a precious opportunity to examine the compound Henyey-Greenstein (HG) comet-dust light-scattering model and it also offered valuable polarization data under an unprecedented observing geometry. Our analysis reveals that the compound HG model fits the observations very well until the phase angle exceeds ˜173°, where the brightness surge of the comet was obviously steeper than the prediction by the model. We have found that the reason for the greater steepness cannot be explained by contaminations from the proximal tail. Instead, the model of Mie spheres with radii greater than 1 ?m, having a power-law distribution of power index ˜3, matches the observation very well, providing a best-fitting complex refractive index ? = 1.38 + i 0.006. The dust size was found to be consistent with the analysis of the comet's syndyne lines. The debiased polarization of the coma was ˜0 per cent in the phase angle range from 172.9° to 177.6°. . No convincing evidence of temporal variation of the polarization was detected.

Hui, M.-T.

2013-12-01

318

Observations of Comet P/2003 T12 = 2012 A3 (SOHO) at large phase angle in STEREO-B  

NASA Astrophysics Data System (ADS)

Comet P/2003 T12 = 2012 A3 (SOHO) was observed by the satellite STEREO-B during the period 2012 January 13-27. During its apparition, it ventured into the highest phase angle ever observed for a comet, and the forward-scattering enhancement in brightness was marked, as large as ?8.5 mag. Therefore, it provided a precious opportunity to examine the compound Henyey-Greenstein (HG) comet-dust light-scattering model and it also offered valuable polarization data under an unprecedented observing geometry. Our analysis reveals that the compound HG model fits the observations very well until the phase angle exceeds ?173°, where the brightness surge of the comet was obviously steeper than the prediction by the model. We have found that the reason for the greater steepness cannot be explained by contaminations from the proximal tail. Instead, the model of Mie spheres with radii greater than 1 ?m, having a power-law distribution of power index ?3, matches the observation very well, providing a best-fitting complex refractive index ? = 1.38 + i 0.006. The dust size was found to be consistent with the analysis of the comet's syndyne lines. The debiased polarization of the coma was ?0 per cent in the phase angle range from 172.9° to 177.6°. No convincing evidence of temporal variation of the polarization was detected.

Hui, Man-To

2014-11-01

319

Detection of Circular Polarization in the Galactic Center Black Hole Candidate Sagittarius A*  

E-print Network

We report here the detection of circular polarization in the Galactic Center black hole candidate, Sagittarius A*. The detection was made at 4.8 GHz and 8.4 GHz with the Very Large Array. We find that the fractional circular polarization at 4.8 GHz is $m_c=-0.36 \\pm 0.05%$ and that the spectral index of the circular polarization is $\\alpha=-0.6 \\pm 0.3$ ($m_c \\propto \

Geoffrey C. Bower; Heino Falcke; Donald C. Backer

1999-07-16

320

APPROXIMATING THE PATH OF A CELESTIAL BODY WITH A CIRCULAR ORBIT FROM TWO  

E-print Network

1 APPROXIMATING THE PATH OF A CELESTIAL BODY WITH A CIRCULAR ORBIT FROM TWO CLOSE OBSERVATIONS elliptical orbit. Using ecliptic longitudes from only two close observations, we try to compute a circle that approximates the elliptical orbit. Our calculations result in not one, but two circular orbits. In some cases

Osler, Thomas

321

Circular dichroism in x-ray photoemission from core levels of nonmagnetic species  

NASA Astrophysics Data System (ADS)

Circular dichroism in the angular distribution of photoelectrons (CDAD) has been observed in core-level photoemission from spherically symmetric initial states of nonmagnetic species utilizing circularly polarized soft-x-ray radiation from BESSY. Up to now, CDAD was predicted and observed only for aligned initial states. The data for oriented CO molecules prove that circular x-ray dichroism in photoemission from core levels is a general phenomenon that is not restricted to ferromagnets. High asymmetries of 50% suggest future applications as an effective circular x-ray analyzer.

Bansmann, J.; Ostertag, Ch.; Scho?nhense, G.; Fegel, F.; Westphal, C.; Getzlaff, M.; Scha?fers, F.; Petersen, H.

1992-11-01

322

Observations of Large Scale Sidereal Anisotropy in 1 and 11 TeV cosmic rays from the MINOS experiment  

E-print Network

The MINOS Near and Far Detectors are two large, functionally-identical, steel-scintillating sampling calorimeters located at depths of 220 mwe and 2100 mwe respectively. The detectors observe the muon component of hadronic showers produced from cosmic ray interactions with nuclei in the earth's atmosphere. From the arrival direction of these muons, the anisotropy in arrival direction of the cosmic ray primaries can be determined. The MINOS Near and Far Detector have observed anisotropy on the order of 0.1% at 1 and 11 TeV respectively. The amplitude and phase of the first harmonic at 1 TeV are 8.2$\\pm$1.7(stat.)$\\times 10^{-4}$ and (8.9$\\pm$12.1(stat.))$^{\\circ}$, and at 11 TeV are 3.8$\\pm$0.5(stat.)$\\times 10^{-4}$ and (27.2$\\pm$7.2(stat.))$^{\\circ}$.

J. K. de Jong; for the MINOS Collaboration

2011-11-11

323

Mass balance modeling of a large glacier with sparse ground observations, and comparison to three remote sensing techniques  

NASA Astrophysics Data System (ADS)

Like many mountain ranges in Alaska, the Central Alaska Range is a highly glacierized but sparsely monitored region in terms of glacier mass balance and meteorological ground observations. The Kahiltna Glacier, a large (522 km2), remote mountain glacier with a wide range of altitudes and few in-situ measurements, is a challenge for traditional melt models that rely heavily on input of accurate melt gradients, air temperatures and lapse rates, and spatial distribution of snowfall. In order to supplement historical measurements from a single National Park Service mass balance stake, extensive campaigns of field observations were carried out on the glacier in 2010 and 2011, and remaining spatial and temporal gaps have been filled using available climate data products. Here we present a method for modeling twenty years of glacier-wide mass balance evolution for the Kahiltna Glacier, by expanding on sparse ground observations from a single site. We use NCEP-NCAR reanalysis time series' of air temperature and precipitation adjusted to on-glacier conditions, and characterize the spatial distribution of precipitation by sampling a gridded climate product (PRISM) along the glacier centerline. These data serve as input into a fully distributed degree-day melt model. To assess the model results, mass balance estimates obtained from this method are also compared to those derived from several other techniques: DEM differencing, repeat laser altimetry, and regionally downscaled GRACE gravimetry. As well as providing a method for modeling mass balance for a large glacier with a broad elevation range and sparse observational data, this multidisciplinary study will help bridge the gap between modeling and remote sensing techniques for estimating glacier mass balance.

Young, J. C.; Arendt, A. A.; Hock, R. M.; Motyka, R. J.

2012-12-01

324

Circular birefringence of banded spherulites.  

PubMed

Crystal optical properties of banded spherulites of 21 different compounds--molecular crystals, polymers, and minerals--with helically twisted fibers were analyzed with Mueller matrix polarimetry. The well-established radial oscillations in linear birefringence of many polycrystalline ensembles is accompanied by oscillations in circular birefringence that cannot be explained by the natural optical activity of corresponding compounds, some of which are centrosymmetric in the crystalline state. The circular birefringence is shown to be a consequence of misoriented, overlapping anisotropic lamellae, a kind of optical activity associated with the mesoscale stereochemistry of the refracting components. Lamellae splay as a consequence of space constraints related to simultaneous twisting of anisometric lamellae. This mechanism is supported by quantitative simulations of circular birefringence arising from crystallite twisting and splaying under confinement. PMID:24625095

Cui, Xiaoyan; Shtukenberg, Alexander G; Freudenthal, John; Nichols, Shane; Kahr, Bart

2014-04-01

325

Circular dichroism of biological macromolecules.  

PubMed

Circular dichroism, the unequal absorption of right and left circularly polarized light, is a manifestation of optical activity in the vicinity of absorption bands. To the experimental scientist interested in the conformation of macromolecules and in the sensitive response of optical activity to conformational alteration, it offers a relatively new and powerful means of understanding the environment of chromophoric residues. As a tool in the elucidation of electronic spectra, it should be useful to the theoretical scientist in identifying weakly allowed absorption bands as well as in providing rotational parameters which can be compared with the developing theory of optical activity. I have stressed application of circular dichroism, to experimental aspects of protein and nucleic acid conformation in solution. Much is still uncertain in particular quantitative details. However, even these early results shed new light and yield new information on the conformation of these molecules. PMID:5332570

Beychok, S

1966-12-01

326

TWO EPOCHS OF VERY LARGE ARRAY OBSERVATIONS OF WATER MASER EMISSION IN THE ACTIVE GALAXY NGC 6240  

SciTech Connect

Studies of 22 GHz H{sub 2}O maser emission from the merging galaxy NGC 6240 with double nuclei are presented. Two epochs of Very Large Array (VLA) observations in the A-configuration in spectral-line mode were carried out at 0.1 arcsec resolution by covering the redshifted velocity range of {approx}300 km s{sup -1} with respect to the systemic velocity of the galaxy. The purpose of these new observations is twofold: to detect an H{sub 2}O maser that an earlier VLA observation pinpointed in the southern nucleus in the northern nucleus as well to clarify the kinematics of the double nuclei, and to understand the origin of the maser in the galaxy. In the second epoch, one velocity feature peaking at V{sub LSR} = 7491.1 km s{sup -1}, redshifted by {approx}200 km s{sup -1} relative to the systemic velocity, was detected only toward the southern nucleus. The detection of an H{sub 2}O maser feature at or near this velocity had never been reported in earlier observations. However, including the known velocity features at redshifted velocities, no other velocity features were observed toward either nuclei throughout these epochs. The maser remains unresolved at an angular resolution of {approx}0.''1, corresponding to a linear size of less than about 45 pc. The two epochs of VLA observations show that the maser intensity is variable on timescales of at least three months, while the correlation between the maser intensity and the radio continuum intensity is not certain from our data. It is plausible that the maser in NGC 6240 is associated with the activity of an active galactic nucleus in the southern nucleus. Alternatively, the maser can be explained by star-forming activity at the site of massive star formation in the galaxy.

Hagiwara, Yoshiaki [National Astronomical Observatory of Japan, 2-21-1 Osawa, Mitaka, Tokyo 181-8588 (Japan)

2010-12-15

327

Circular Bioassay Platforms for Applications in Microwave-Accelerated Techniques  

PubMed Central

In this paper, we present the design of four different circular bioassay platforms, which are suitable for homogeneous microwave heating, using theoretical calculations (i.e., COMSOL™ multiphysics software). Circular bioassay platforms are constructed from poly(methyl methacrylate) (PMMA) for optical transparency between 400–800 nm, has multiple sample capacity (12, 16, 19 and 21 wells) and modified with silver nanoparticle films (SNFs) to be used in microwave-accelerated bioassays (MABs). In addition, a small monomode microwave cavity, which can be operated with an external microwave generator (100 W), for use with the bioassay platforms in MABs is also developed. Our design parameters for the circular bioassay platforms and monomode microwave cavity during microwave heating were: (i) temperature profiles, (ii) electric field distributions, (iii) location of the circular bioassay platforms inside the microwave cavity, and (iv) design and number of wells on the circular bioassay platforms. We have also carried out additional simulations to assess the use of circular bioassay platforms in a conventional kitchen microwave oven (e.g., 900 W). Our results show that the location of the circular bioassay platforms in the microwave cavity was predicted to have a significant effect on the homogeneous heating of these platforms. The 21-well circular bioassay platform design in our monomode microwave cavity was predicted to offer a homogeneous heating pattern, where inter-well temperature was observed to be in between 23.72–24.13°C and intra-well temperature difference was less than 0.21°C for 60 seconds of microwave heating, which was also verified experimentally.

Mohammed, Muzaffer; Clement, Travis C.; Aslan, Kadir

2014-01-01

328

Complementary sequence-mediated exon circularization.  

PubMed

Exon circularization has been identified from many loci in mammals, but the detailed mechanism of its biogenesis has remained elusive. By using genome-wide approaches and circular RNA recapitulation, we demonstrate that exon circularization is dependent on flanking intronic complementary sequences. Such sequences and their distribution exhibit rapid evolutionary changes, showing that exon circularization is evolutionarily dynamic. Strikingly, exon circularization efficiency can be regulated by competition between RNA pairing across flanking introns or within individual introns. Importantly, alternative formation of inverted repeated Alu pairs and the competition between them can lead to alternative circularization, resulting in multiple circular RNA transcripts produced from a single gene. Collectively, exon circularization mediated by complementary sequences in human introns and the potential to generate alternative circularization products extend the complexity of mammalian posttranscriptional regulation. PMID:25242744

Zhang, Xiao-Ou; Wang, Hai-Bin; Zhang, Yang; Lu, Xuhua; Chen, Ling-Ling; Yang, Li

2014-09-25

329

Large-scale variations of the interplanetary magnetic field: Voyager 1 and 2 observations between 1-5 AU  

NASA Technical Reports Server (NTRS)

Observations by the Voyager 1 and 2 spacecraft of the interplanetary magnetic field between 1 and 5 AU were used to investigate the large scale structure of the IMF in a period of increasing solar activity. The Voyager spacecraft found notable deviations from the Parker axial model. These deviations are attributed both to temporal variations associated with increasing solar activity, and to the effects of fluctuations of the field in the radial direction. The amplitude of the latter fluctuations were found to be large relative to the magnitude of the radial field component itself beyond approximately 3 AU. Both Voyager 1 and Voyager 2 observed decreases with increasing heliocentric distance in the amplitude of transverse fluctuations in the averaged field strength (B) which are consistent with the presence of predominantly undamped Alfven waves in the solar wind, although and necessarily implying the presence of them. Fluctuations in the strength of B (relative to mean field strength) were found to be small in amplitude, with a RMS which is approximately one third of that for the transverse fluctuations and they are essentially independent of distance from the Sun.

Burlaga, L. F.; Lepping, R. P.; Behannon, K. W.; Klein, L. W.; Neubauer, F. M.

1981-01-01

330

THEMIS observations of the magnetopause electron diffusion region and magnetospheric separatrix: Large amplitude waves and heated particles  

NASA Astrophysics Data System (ADS)

We present the first observations of large amplitude waves in a well-defined electron diffusion region based on the criteria described by Scudder et al. [2012] at the subsolar magnetopause [Tang et al., 2013] as well as near the magnetospheric separatrix using data from the THEMIS satellites. A wide range of wave modes identified as whistler mode waves, electrostatic solitary waves, lower hybrid waves, electrostatic electron cyclotron waves and electrostatic ion harmonic waves are often simultaneously observed in association with signatures of active magnetic reconnection. The large amplitude waves in the electron diffusion region are coincident with abrupt increases in electron parallel temperature suggesting strong wave heating. Evidence of perpendicular ion heating (< 100 eV) by the electrostatic ion harmonic waves has been found near the magnetospheric separatrix. The whistler mode waves, which are at the electron scale and enable us to probe electron dynamics in the diffusion region were analyzed in detail. The energetic electrons (˜30 keV) within the electron diffusion region have anisotropic distributions with Te?/Te? > 1 that may provide the free energy for the whistler mode waves. The energetic anisotropic electrons may be produced during the reconnection process. The whistler mode waves propagate away from the center of the 'X-line' along magnetic field lines, suggesting that the electron diffusion region is a possible source region of the whistler mode waves.

Tang, X.; Cattell, C. A.; Wilson, L. B., III

2013-12-01

331

Detecting potential safety issues in large clinical or observational trials by Bayesian screening when event counts arise from poisson distributions.  

PubMed

Patients in large clinical trials and in studies employing large observational databases report many different adverse events, most of which will not have been anticipated at the outset. Conventional hypothesis testing of between group differences for each adverse event can be problematic: Lack of significance does not mean lack of risk, the tests usually are not adjusted for multiplicity, and the data determine which hypotheses are tested. This article describes a Bayesian screening approach that does not test hypotheses, is self-adjusting for multiplicity, provides a direct assessment of the likelihood of no material drug-event association, and quantifies the strength of the observed association. The criteria for assessing drug-event associations can be determined by clinical or regulatory considerations. In contrast to conventional approaches, the diagnostic properties of this new approach can be evaluated analytically. Application of the method to findings from a vaccine trial yields results similar to those found by methods using a false discovery rate argument or a hierarchical Bayes approach. [Supplemental materials are available for this article. Go to the publisher's online edition of Journal of Biopharmaceutical Statistics for the following free supplemental resource: Appendix R: Code for calculations.]. PMID:23786257

Gould, A Lawrence

2013-01-01

332

Initial Fe/O Enhancements in Large, Gradual, Solar Energetic Particle Events: Observations from Wind and Ulysses  

NASA Astrophysics Data System (ADS)

Shocks driven by fast coronal mass ejections (CMEs) are the dominant particle accelerators in large, "gradual" solar energetic particle (SEP) events. In these events, the event-integrated value of the iron-to-oxygen ratio (Fe/O) is typically ˜ 0.1, at least at energies of a few MeV/nucleon. However, at the start of some gradual events, when intensities are low and growing, initially Fe/O is ˜ 1. This value is also characteristic of small, "impulsive" SEP events, in which particle acceleration is due to magnetic reconnection. These observations suggested that SEPs in gradual events also include a direct contribution from the flare that accompanied the CME launch. If correct, this interpretation is of critical importance: it indicates a clear path to interplanetary space for particles from the reconnection region beneath the CME. A key issue for the flare origin is "magnetic connectedness", i.e., proximity of the flare site to the solar footpoint of the observer's magnetic field line. We present two large gradual events observed in 2001 by Wind at L1 and by Ulysses, when it was located at > 60? heliolatitude and beyond 1.6 AU. In these events, transient Fe/O enhancements at 5 - 10 MeV/nucleon were seen at both spacecraft, even though one or both is not "well-connected" to the flare. These observations demonstrate that an initial Fe/O enhancement cannot be cited as evidence for a direct flare component. Instead, initial Fe/O enhancements are better understood as a transport effect, driven by the different mass-to-charge ratios of Fe and O. We further demonstrate that the time-constant of the roughly exponential decay of the Fe/O ratio scales as R 2, where R is the observer's radial distance from the Sun. This behavior is consistent with radial diffusion. These observations thus also provide a potential constraint on models in which SEPs reach high heliolatitudes by cross-field diffusion.

Tylka, Allan J.; Malandraki, Olga E.; Dorrian, Gareth; Ko, Yuan-Kuen; Marsden, Richard G.; Ng, Chee K.; Tranquille, Cecil

2013-07-01

333

FERMI LARGE AREA TELESCOPE OBSERVATION OF A GAMMA-RAY SOURCE AT THE POSITION OF ETA CARINAE  

SciTech Connect

The Large Area Telescope (LAT) on board the Fermi Gamma-ray Space Telescope detected a {gamma}-ray source that is spatially consistent with the location of Eta Carinae. This source has been persistently bright since the beginning of the LAT survey observations (from 2008 August to 2009 July, the time interval considered here). The {gamma}-ray signal is detected significantly throughout the LAT energy band (i.e., up to {approx}100 GeV). The 0.1-100 GeV energy spectrum is well represented by a combination of a cutoff power-law model (<10 GeV) and a hard power-law component (>10 GeV). The total flux (>100 MeV) is 3.7{sup +0.3}{sub -0.1} x 10{sup -7} photons s{sup -1} cm{sup -2}, with additional systematic uncertainties of 10%, and consistent with the average flux measured by AGILE. The light curve obtained by Fermi is consistent with steady emission. Our observations do not confirm the presence of a {gamma}-ray flare in 2008 October, as reported by Tavani et al., although we cannot exclude that a flare lasting only a few hours escaped detection by the Fermi LAT. We also do not find any evidence for {gamma}-ray variability that correlates with the large X-ray variability of Eta Carinae observed during 2008 December and 2009 January. We are thus not able to establish an unambiguous identification of the LAT source with Eta Carinae.

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.; 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: Jurgen.Knodlseder@cesr.f, E-mail: hirotaka@hep01.hepl.hiroshima-u.ac.j [Laboratoire Leprince-Ringuet, Ecole polytechnique, CNRS/IN2P3, Palaiseau (France)

2010-11-01

334

NOVEL FRACTAL ANTENNA ARRAYS FOR SATELLITE NETWORKS: CIRCULAR RING SIERPINSKI CARPET ARRAYS OPTIMIZED BY GENETIC ALGORITHMS  

Microsoft Academic Search

A novel fractal antenna-array type is proposed. The design is based on the Sierpinski rectangular carpet concept. However, the generator is a circular ring area, fllled with radiating elements, so the higher stages of the fractal development produce large arrays of circular rings which, besides the high directivity, have the advantage of the almost uniform azimuthal radiation pattern, attribute that

Katherine Siakavara

2010-01-01

335

Direct Observation of Dopant Atom Diffusion in a Bulk Semiconductor Crystal Enhanced by a Large Size Mismatch  

NASA Astrophysics Data System (ADS)

Diffusion is one of the fundamental processes that govern the structure, processing, and properties of materials and it plays a crucial role in determining device lifetimes. However, direct observations of diffusion processes have been elusive and limited only to the surfaces of materials. Here we use an aberration-corrected electron microscope to locally excite and directly image the diffusion of single Ce and Mn dopants inside bulk wurtzite-type AlN single crystals, identifying correlated vacancy-dopant and interstitial-dopant kick-out mechanisms. Using a 200 kV electron beam to supply energy, we observe a higher frequency of dopant jumps for the larger and heavier Ce atoms than the smaller Mn atoms. These observations confirm density-functional-theory-based predictions of a decrease in diffusion barrier for large substitutional atoms. The results show that combining depth sensitive microscopy with theoretical calculations represents a new methodology to investigate diffusion mechanisms, not restricted to surface phenomena, but within bulk materials.

Ishikawa, Ryo; Mishra, Rohan; Lupini, Andrew R.; Findlay, Scott D.; Taniguchi, Takashi; Pantelides, Sokrates T.; Pennycook, Stephen J.

2014-10-01

336

Circular Symmetry of Pinwheel Diffraction  

Microsoft Academic Search

.  A method is given for explicitly determining the autocorrelation of the pinwheel tiling by use of the substitution system\\u000a generating the tiling. Using this a new proof of the circular symmetry of the diffraction of the pinwheel tiling is given.\\u000a \\u000a Communicated by Jean Bellissard

Robert V. Moody; Derek Postnikoff; Nicolae Strungaru

2006-01-01

337

Circularly polarized fractal slot antenna  

Microsoft Academic Search

A circularly polarized fractal slot antenna is proposed in this paper. The design is based on the Sierpinski shape. The conductors and nonconductors configurations have been exchanged to produce a Sierpinski slot antenna configuration. Then, four versions of the developed Sierpinski slot antenna are placed at right angles to each other to form a symmetrical structure in the form of

A. R. El-Damak; H. Ghali; H. F. Ragaie

2005-01-01

338

Optimal Clocking of Circular Pipelines  

Microsoft Academic Search

A timing model for circular pipelines is presented and used to obtain the minimum cycle time in terms of circuit delays and clock skews. The model accounts for short- and long-path delays, the effects of clock skew, and the use of both latches and flip-flops as synchronizing elements. The formulation and implementation of algorithms to find the minimum cycle time

Karem A. Sakallah; Trevor N. Mudge; Timothy M. Burkst; Edward S. Davidson

1991-01-01

339

Circular polarized leaky wave surface  

NASA Astrophysics Data System (ADS)

A circular polarized (CP) infrared (IR) leaky wave surface design is presented. The metasurface consists of an array of rectangular patches connected by microstrip and operating over the long-wave infrared (LWIR) spectrum with directional wave emission and absorption. The surface is composed of periodically aligned arrays of sub-wavelength metal patches separated from a ground plane by a dielectric slab. The design combines the features of the conventional patch and leaky wave antenna leading to a metasurface that preferentially emits CP IR radiation by use of axial asymmetrical unit cells. This is a deviation from reported structures that mainly employ a phase shifter to combine linearly polarized waves in order to attain circular polarization. The performance of this leaky wave surface is verified through full-wave simulation using the ANSYS HFSS finite element analysis tool. The leaky wave phenomenon is demonstrated by the frequency and angular dependence of the absorption while circular polarization is characterized via stokes parameters. The main beam of this surface can be steered continuously by varying the frequency while maintaining circular polarization within the main beam direction. A CP leaky wave at 10.6 ?m with a scanning angle of 30° is demonstrated. Metasurfaces exhibiting spectral and polarization selectivity in absorption/emission hold the potential for impact in IR applications including detection, imaging, thermal management, energy harvesting and tagging.

Manene, Franklin; Lail, Brian A.; Kinzel, Edward C.

2014-09-01

340

Class IIc or Circular Bacteriocins  

NASA Astrophysics Data System (ADS)

The circular bacteriocins produced by Gram-positive bacteria represent a diverse class of antimicrobial peptides. These bacteriocins display enhanced stability compared to linear bacteriocins, which arises from their characteristic circular backbone. Currently, eight unique circular bacteriocins have been identified, and analysis of their gene clusters indicates that they likely utilize complex mechanisms for maturation and secretion, as well as for immunity. These bacteriocins target the cytoplasmic membrane of sensitive cells, leading to pore formation that results in loss of ions, dissipation of membrane potential, and ultimately, cell death. Structural studies suggest that despite variation in their sequences, most of these bacteriocins likely adopt a common three-dimensional architecture, consisting of four or five tightly packed helices encompassing a hydrophobic core. There are many mysteries surrounding the biosynthesis of these peptides, particularly in regard to the mechanism by which they are cyclized. Elucidation of such a mechanism may provide exciting new approaches to the bioengineering of new, stable, and antimicrobially active circular peptides.

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

341

Broadband circular polarizer formed by stacked plasmonic metasurfaces  

Microsoft Academic Search

Recent ideas involving plasmonic metamaterials have been put forward to enhance the overall bandwidth of operation of quarter-wave plates for circular polarization detection. The proposed metamaterial geometries are inherently complex to realize and difficult to scale beyond the near-infrared frequencies. Here, we show how proper stacks of lithographically printed plasmonic metasurfaces with simple patterns may provide large extinction ratios for

Yang Zhao; Andrea Alù

2011-01-01

342

Experimental Realization of Efficient, Room Temperature Single-Photon Sources with Definite Circular and Linear Polarizations  

NASA Astrophysics Data System (ADS)

In this thesis I present experimental demonstrations of room-temperature, single-photon sources with definite linear and circular polarizations. Definite photon polarization increases the efficiency of quantum communication systems. In contrast with cryogenic-temperature single-photon sources based on epitaxial quantum dots requiring expensive MBE and nanofabrication, my method utilizes a mature liquid crystal technology, which I made consistent with single-emitter fluorescence microscopy. The structures I have prepared are planar-aligned cholesteric liquid crystals forming 1-D photonic bandgaps for circularly-polarized light, which were used to achieve definite circularly-polarized fluorescence of single emitters doped in this environment. I also used planar-aligned nematic liquid crystals to align single molecules with linear dipole moments and achieved definite linearly-polarized fluorescence. I used single nanocrystal quantum dots, single nanodiamond color-centers, rare-earth-doped nanocrystals, and single terrylene and DiIC18(3) dye molecules as emitters. For nanocrystal quantum dots I observed circular polarization dissymmetry factors as large as ge = --1.6. In addition, I observed circularly-polarized resonances in the fluorescence of emitters within a cholesteric microcavity, with cavity quality factors of up to Q ˜ 250. I also showed that the fluorescence of DiIC18(3) dye molecules in planar-aligned nematic cells exhibits definite linear polarization, with a degree of polarization of rho = --0.58 +/- 0.03. Distributed Bragg reflectors form another type of microcavity that can be used to realize a single-photon source. I characterized the fluorescence from nanocrystal quantum dots doped in the defect layers of such microcavites, both organic and inorganic. Finally, to demonstrate the single-photon properties of single-emitter-doped cholesteric and nematic liquid crystal structures and distributed Bragg reflector microcavities, I present observations of photon antibunching from emitters doped in each of these structures. These experimental observations include photon antibunching from: nanocrystal quantum dots and nanodiamond color-centers doped in a cholesteric microcavity; terrylene and DiIC 18(3) dye molecules doped in nematic structures, and nanocrystal quantum dots doped in the distributed Bragg reflector microcavity. A value of the zero-time second-order coherence as low as g(2)(0) = 0.001 +/- 0.03 was measured. These results represent an important step forward in the realization of room temperature single-photon sources with definite polarization for secure quantum communication.

Boutsidis, Christos

343

The present-day flux of large meteoroids on the lunar surface—A synthesis of models and observational techniques  

NASA Astrophysics Data System (ADS)

Monitoring the lunar surface for impacts is a highly rewarding approach to study small asteroids and large meteoroids encountering the Earth-Moon System. The various effects of meteoroids impacting the Moon are described and results from different detection and study techniques are compared. While the traditional statistics of impact craters allow us to determine the cumulative meteoroid flux on the lunar surface, the recent successful identification of fresh craters in orbital imagery has the potential to directly measure the cratering rate of today. Time-resolved recordings, e.g., seismic data of impacts and impact flash detections clearly demonstrate variations of the impact flux during the lunar day. From the temporal/spatial distribution of impact events, constraints can be obtained on the meteoroid approach trajectories and velocities. The current monitoring allows us to identify temporal clustering of impacts and to study the different meteoroid showers encountering the Earth-Moon system. Though observational biases and deficiencies in our knowledge of the scaling laws are severe, there appears to be an order-of-magnitude agreement in the observed flux within the error limits. Selenographic asymmetries in the impact flux (e.g., for equatorial vs. polar areas) have been predicted. An excess of impacts on the lunar leading hemisphere can be demonstrated in current data. We expect that future missions will allow simultaneous detections of seismic events and impact flashes. The known locations and times of the flashes will allow us to constrain the seismic solutions. While the numbers of flash detections are still limited, coordinated world-wide observations hold great potential for exploiting this observation technique. The potential for identification of fresh craters in high-resolution orbital image data has just barely been tapped, but should improve significantly with the LRO extended mission.

Oberst, J.; Christou, A.; Suggs, R.; Moser, D.; Daubar, I. J.; McEwen, A. S.; Burchell, M.; Kawamura, T.; Hiesinger, H.; Wünnemann, K.; Wagner, R.; Robinson, M. S.

2012-12-01

344

A particle consistent with the Higgs boson observed with the ATLAS detector at the Large Hadron Collider.  

PubMed

Nearly 50 years ago, theoretical physicists proposed that a field permeates the universe and gives energy to the vacuum. This field was required to explain why some, but not all, fundamental particles have mass. Numerous precision measurements during recent decades have provided indirect support for the existence of this field, but one crucial prediction of this theory has remained unconfirmed despite 30 years of experimental searches: the existence of a massive particle, the standard model Higgs boson. The ATLAS experiment at the Large Hadron Collider at CERN has now observed the production of a new particle with a mass of 126 giga-electron volts and decay signatures consistent with those expected for the Higgs particle. This result is strong support for the standard model of particle physics, including the presence of this vacuum field. The existence and properties of the newly discovered particle may also have consequences beyond the standard model itself. PMID:23258888

2012-12-21

345

A Particle Consistent with the Higgs Boson Observed with the ATLAS Detector at the Large Hadron Collider  

NASA Astrophysics Data System (ADS)

Nearly 50 years ago, theoretical physicists proposed that a field permeates the universe and gives energy to the vacuum. This field was required to explain why some, but not all, fundamental particles have mass. Numerous precision measurements during recent decades have provided indirect support for the existence of this field, but one crucial prediction of this theory has remained unconfirmed despite 30 years of experimental searches: the existence of a massive particle, the standard model Higgs boson. The ATLAS experiment at the Large Hadron Collider at CERN has now observed the production of a new particle with a mass of 126 giga-electron volts and decay signatures consistent with those expected for the Higgs particle. This result is strong support for the standard model of particle physics, including the presence of this vacuum field. The existence and properties of the newly discovered particle may also have consequences beyond the standard model itself.

ATLAS Collabortion; Aad, G.; Abajyan, T.; Abbott, B.; Abdallah, J.; Abdel Khalek, S.; Abdelalim, A. A.; Abdinov, O.; Aben, R.; Abi, B.; Abolins, M.; AbouZeid, O. S.; Abramowicz, H.; Abreu, H.; Acharya, B. S.; Adamczyk, L.; Adams, D. L.; Addy, T. N.; Adelman, J.; Adomeit, S.; Adragna, P.; Adye, T.; Aefsky, S.; Aguilar-Saavedra, J. A.; Agustoni, M.; Aharrouche, M.; Ahlen, S. P.; Ahles, F.; Ahmad, A.; Ahsan, M.; Aielli, G.; Akdogan, T.; Åkesson, T. P. A.; Akimoto, G.; Akimov, A. V.; Alam, M. S.; Alam, M. A.; Albert, J.; Albrand, S.; Aleksa, M.; Aleksandrov, I. N.; Alessandria, F.; Alexa, C.; Alexander, G.; Alexandre, G.; Alexopoulos, T.; Alhroob, M.; Aliev, M.; Alimonti, G.; Alison, J.; Allbrooke, B. M. M.; Allport, P. P.; Allwood-Spiers, S. E.; Almond, J.; Aloisio, A.; Alon, R.; Alonso, A.; Alonso, F.; Altheimer, A.; Alvarez Gonzalez, B.; Alviggi, M. G.; Amako, K.; Amelung, C.; Ammosov, V. V.; Amor Dos Santos, S. P.; Amorim, A.; Amram, N.; Anastopoulos, C.; Ancu, L. S.; Andari, N.; Andeen, T.; Anders, C. F.; Anders, G.; Anderson, K. J.; Andreazza, A.; Andrei, V.; Andrieux, M.-L.; Anduaga, X. S.; Angelidakis, S.; Anger, P.; Angerami, A.; Anghinolfi, F.; Anisenkov, A.; Anjos, N.; Annovi, A.; Antonaki, A.; Antonelli, M.; Antonov, A.; Antos, J.; Anulli, F.; Aoki, M.; Aoun, S.; Aperio Bella, L.; Apolle, R.; Arabidze, G.; Aracena, I.; Arai, Y.; Arce, A. T. H.; Arfaoui, S.; Arguin, J.-F.; Arik, E.; Arik, M.; Armbruster, A. J.; Arnaez, O.; Arnal, V.; Arnault, C.; Artamonov, A.; Artoni, G.; Arutinov, D.; Asai, S.; Ask, S.; Åsman, B.; Asquith, L.; Assamagan, K.; Astbury, A.; Atkinson, M.; Aubert, B.; Auge, E.; Augsten, K.; Aurousseau, M.; Avolio, G.; Avramidou, R.; Axen, D.; Azuelos, G.; Azuma, Y.; Baak, M. A.; Baccaglioni, G.; Bacci, C.; Bach, A. M.; Bachacou, H.; Bachas, K.; Backes, M.; Backhaus, M.; Backus Mayes, J.; Badescu, E.; Bagnaia, P.; Bahinipati, S.; Bai, Y.; Bailey, D. C.; Bain, T.; Baines, J. T.; Baker, O. K.; Baker, M. D.; Baker, S.; Balek, P.; Banas, E.; Banerjee, P.; Banerjee, Sw.; Banfi, D.; Bangert, A.; Bansal, V.; Bansil, H. S.; Barak, L.; Baranov, S. P.; Barbaro Galtieri, A.; Barber, T.; Barberio, E. L.; Barberis, D.; Barbero, M.; Bardin, D. Y.; Barillari, T.; Barisonzi, M.; Barklow, T.; Barlow, N.; Barnett, B. M.; Barnett, R. M.; Baroncelli, A.; Barone, G.; Barr, A. J.; Barreiro, F.; Barreiro Guimarães da Costa, J.; Barrillon, P.; Bartoldus, R.; Barton, A. E.; Bartsch, V.; Basye, A.; Bates, R. L.; Batkova, L.; Batley, J. R.; Battaglia, A.; Battistin, M.; Bauer, F.; Bawa, H. S.; Beale, S.; Beau, T.; Beauchemin, P. H.; Beccherle, R.; Bechtle, P.; Beck, H. P.; Becker, A. K.; Becker, S.; Beckingham, M.; Becks, K. H.; Beddall, A. J.; Beddall, A.; Bedikian, S.; Bednyakov, V. A.; Bee, C. P.; Beemster, L. J.; Begel, M.; Behar Harpaz, S.; Behera, P. K.; Beimforde, M.; Belanger-Champagne, C.; Bell, P. J.; Bell, W. H.; Bella, G.; Bellagamba, L.; Bellomo, M.; Belloni, A.; Beloborodova, O.; Belotskiy, K.; Beltramello, O.; Benary, O.; Benchekroun, D.; Bendtz, K.; Benekos, N.; Benhammou, Y.; Benhar Noccioli, E.; Benitez Garcia, J. A.; Benjamin, D. P.; Benoit, M.; Bensinger, J. R.; Benslama, K.; Bentvelsen, S.; Berge, D.; Bergeaas Kuutmann, E.; Berger, N.; Berghaus, F.; Berglund, E.; Beringer, J.; Bernat, P.; Bernhard, R.; Bernius, C.; Bernlochner, F. U.; Berry, T.; Bertella, C.; Bertin, A.; Bertolucci, F.; Besana, M. I.; Besjes, G. J.; Besson, N.; Bethke, S.; Bhimji, W.; Bianchi, R. M.; Bianco, M.; Biebel, O.; Bieniek, S. P.; Bierwagen, K.; Biesiada, J.; Biglietti, M.; Bilokon, H.; Bindi, M.; Binet, S.; Bingul, A.; Bini, C.; Biscarat, C.; Bittner, B.; Black, K. M.; Blair, R. E.; Blanchard, J.-B.; Blanchot, G.; Blazek, T.; Bloch, I.; Blocker, C.; Blocki, J.; Blondel, A.; Blum, W.; Blumenschein, U.; Bobbink, G. J.; Bobrovnikov, V. B.; Bocchetta, S. S.; Bocci, A.; Boddy, C. R.; Boehler, M.; Boek, J.; Boelaert, N.; Bogaerts, J. A.; Bogdanchikov, A.; Bogouch, A.; Bohm, C.; Bohm, J.; Boisvert, V.; Bold, T.; Boldea, V.; Bolnet, N. M.; Bomben, M.; Bona, M.; Boonekamp, M.; Bordoni, S.; Borer, C.; Borisov, A.; Borissov, G.; Borjanovic, I.; Borri, M.; Borroni, S.; Bortolotto, V.; Bos, K.; Boscherini, D.; Bosman, M.; Boterenbrood, H.; Bouchami, J.; Boudreau, J.; Bouhova-Thacker, E. V.; Boumediene, D.; Bourdarios, C.; Bousson, N.; Boveia, A.; Boyd, J.; Boyko, I. R.; Bozovic-Jelisavcic, I.; Bracinik, J.; Branchini, P.; Brandenburg, G. W.; Brandt, A.; Brandt, G.; Brandt, O.; Bratzler, U.; Brau, B.; Brau, J. E.; Braun, H. M.; Brazzale, S. F.; Brelier, B.; Bremer, J.; Brendlinger, K.; Brenner, R.; Bressler, S.; Britton, D.; Brochu, F. M.; Brock, I.; Brock, R.; Broggi, F.; Bromberg, C.; Bronner, J.; Brooijmans, G.; Brooks, T.; Brooks, W. K.; Brown, G.; Brown, H.; Bruckman de Renstrom, P. A.; Bruncko, D.

2012-12-01

346

A dynamic measure of controllability and observability for the placement of actuators and sensors on large space structures  

NASA Technical Reports Server (NTRS)

The degree of controllability of a large space structure is found by a four step procedure: (1) finding the minimum control energy for driving the system from a given initial state to the origin in the prescribed time; (2) finding the region of initial state which can be driven to the origin with constrained control energy and time using optimal control strategy; (3) scaling the axes so that a unit displacement in every direction is equally important to control; and (4) finding the linear measurement of the weighted "volume" of the ellipsoid in the equicontrol space. For observability, the error covariance must be reduced toward zero using measurements optimally, and the criterion must be standardized by the magnitude of tolerable errors. The results obtained using these methods are applied to the vibration modes of a free-free beam.

Vandervelde, W. E.; Carignan, C. R.

1982-01-01

347

Observations of the refraction of microbaroms generated by large maritime storms by the wind field of the generating storm  

NASA Astrophysics Data System (ADS)

Microbaroms are a continuous infrasonic signal in the 0.15 to 0.3 Hz band caused by the collision of oceanic surface waves of equal period. Such signals are often generated by large maritime storms. Current formulation of the generation mechanism predicts that the microbarom source location due to a large maritime storm in the open ocean is generally located several hundreds of kilometers from the eye of the storm. Assuming such a source location to be correct, propagation of the microbaroms along paths which pass near the storm center as well as those which propagate away from the storm structure have been examined using geometric acoustics. Microbarom propagation paths which pass near the storm center are refracted by the storm winds and are found to have back azimuths directed toward a virtual source around the storm center. Microbarom propagation paths which do not pass near the storm center are found to have back azimuths directed toward the actual source region. To validate these predictions, data from microbarom signals generated by hurricanes in the Atlantic Ocean have been collected along the east coast of the United States during the 2010 and 2011 Atlantic hurricane seasons. Data from several storm events are presented here for comparison with model predictions. In general, the observations are in agreement with the predictions of the propagation model.

Blom, Philip; Waxler, Roger; Frazier, Wm. Garth; Talmadge, Carrick

2014-06-01

348

Morphologic observation of mucosa-associated lymphoid tissue in the large intestine of Bactrian camels (Camelus bactrianus).  

PubMed

The structure and distribution of the mucosa-associated lymphoid tissue (MALT) throughout the large intestine of 10 Bactrian camels were comparatively studied by anatomical and histological methods. The results showed that Peyer's patches (PPs) were mainly located on the mucosal surfaces of the entire ileocecal orifice, the beginning of the cecum and the first third of the colon. The shape of PPs gradually changed from "scrotiform" to "faviform" along the large intestine with the scrotiform PP as the major type in the ileocecal orifice. The distribution density also gradually decreased from the ileocecal orifice to the colon. The histological observations further revealed that the MALT in the form of PPs or isolated lymphoid follicles (ILF) and lamina propria lymphocytes was mainly present in the lamina propria and submucosa from the entire ileocecal orifice, where the muscularis mucosa is usually incomplete, to the colonic forepart. In addition, lymphoid tissue was much more abundant in the lamina propria and submucosa of the ileocecal orifice as compared to the cecum and colon. Statistically, the MALT of the ileocecal orifice contained a higher number of lymphoid follicles (37.7/10 mm(2) ) than that of the cecum, colon, or rectum (P?large intestine of the Bactrian camel; and that scrotiform PPs are likely to the result of long-term adaptation of the Bactrian camel to the harsh living environment. PMID:24820911

ZhaXi, Yingpai; Wang, Wenhui; Zhang, Wangdong; Gao, Qiang; Guo, Minggang; Jia, Shuai

2014-07-01

349

Suppression of Supercontinuum Generation with Circularly Polarized Light  

E-print Network

Controlling a nonlinear process like supercontinuum generation (SG) with the polarization-state of laser is an important demonstration of laser selectivity. We show that the threshold for SG and the total amount of supercontinuum generated depends on incident laser polarization for isotropic samples. Irrespective of the nature of the samples chosen, SG efficiency decreases as the incident laser polarization changes from linear to circular and thus, provides the first experimental demonstration of the suppression of SG with circularly polarized light. The ratio of the overall SG between the linear and circular polarization (i.e., measure of suppression) undergoes an intensity dependent decrease from large initial values to asymptotic limits, irrespective of samples.

Singh-Sandhu, A; Goswami, D Y; Sandhu, Arvinder S.; Banerjee, Sudeep; Goswami, Debabrata

2000-01-01

350

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

E-print Network

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

:,; Albert, A; Anderson, B; Baldini, L; Ballet, J; Barbiellini, G; Bastieri, D; Bechtol, K; Bellazzini, R; Bissaldi, E; Bloom, E D; Bonamente, E; Bouvier, A; Brandt, T J; Bregeon, J; Brigida, M; Bruel, P; Buehler, R; Buson, S; Caliandro, G A; Cameron, R A; Caragiulo, M; Caraveo, P A; Cecchi, C; Charles, E; Chekhtman, A; Chiang, J; Ciprini, S; Claus, R; Cohen-Tanugi, J; Conrad, J; D'Ammando, F; de Angelis, A; Dermer, C D; Digel, S W; Silva, E do Couto e; Drell, P S; Drlica-Wagner, A; Essig, R; Favuzzi, C; Ferrara, E C; Franckowiak, A; Fukazawa, Y; Funk, S; Fusco, P; Gargano, F; Gasparrini, D; Giglietto, N; Giroletti, M; Godfrey, G; Gomez-Vargas, G A; Grenier, I A; Guiriec,; Gustafsson, M; Hayashida, M; Hays, E; Hewitt, J; Hughes, R E; Jogler, T; Kamae, T; Knödlseder, J; Kocevski, D; Kuss, M; Larsson,; Latronico, L; Garde, M Llena; Longo, F; Loparco, F; Lovellette, M N; Lubrano, P; Martinez, G; Mayer, M; Mazziotta, M N; Michelson, P F; Mitthumsiri, W; Mizuno, T; Moiseev, A A; Monzani, M E; Morselli, A; Moskalenko, I V; Murgia, S; Nemmen, R; Nuss, E; Ohsugi, T; Orlando, E; Ormes, J F; Perkins, J S; Piron, F; Pivato, G; Porter, T A; Rainò, S; Rando, R; Razzano, M; Razzaque, S; Reimer, A; Reimer, O; Ritz, S; Sànchez-Conde, M; Sehgal, N; Sgrò, C; Siskind, E J; Spinelli, P; Strigari, L; Suson, D J; Tajima, H; Takahashi, H; Thayer, J B; Tibaldo, L; Tinivella, M; Torres, D F; Uchiyama, Y; Usher, T L; Vandenbroucke, J; Vianello, G; Vitale, V; Werner, M; Winer, B L; Wood, K S; Wood, M; Zaharijas, G; Zimmer, S

2013-01-01

351

THE VELA-X PULSAR WIND NEBULA REVISITED WITH FOUR YEARS OF FERMI LARGE AREA TELESCOPE OBSERVATIONS  

SciTech Connect

The Vela supernova remnant (SNR) is the closest SNR to Earth containing an active pulsar, the Vela pulsar (PSR B0833-45). This pulsar is an archetype of the middle-aged pulsar class and powers a bright pulsar wind nebula (PWN), Vela-X, spanning a region of 2 Degree-Sign Multiplication-Sign 3 Degree-Sign south of the pulsar and observed in the radio, X-ray, and very high energy {gamma}-ray domains. The detection of the Vela-X PWN by the Fermi Large Area Telescope (LAT) was reported in the first year of the mission. Subsequently, we have reinvestigated this complex region and performed a detailed morphological and spectral analysis of this source using 4 yr of Fermi-LAT observations. This study lowers the threshold for morphological analysis of the nebula from 0.8 GeV to 0.3 GeV, allowing for the inspection of distinct energy bands by the LAT for the first time. We describe the recent results obtained on this PWN and discuss the origin of the newly detected spatial features.

Grondin, M.-H. [Max-Planck-Institut fuer Kernphysik, P.O. Box 103980, D-69029 Heidelberg (Germany); Romani, R. 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); Lemoine-Goumard, M.; Reposeur, T. [Universite Bordeaux 1, CNRS/IN2p3, Centre d'Etudes Nucleaires de Bordeaux Gradignan, F-33175 Gradignan (France); Guillemot, L. [Max-Planck-Institut fuer Radioastronomie, Auf dem Huegel 69, D-53121 Bonn (Germany); Harding, A. K., E-mail: mgrondin@irap.omp.eu [NASA Goddard Space Flight Center, Greenbelt, MD 20771 (United States)

2013-09-10

352

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

E-print Network

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

The Fermi-LAT Collaboration; :; M. Ackermann; A. Albert; B. Anderson; L. Baldini; J. Ballet; G. Barbiellini; D. Bastieri; K. Bechtol; R. Bellazzini; E. Bissaldi; E. D. Bloom; E. Bonamente; A. Bouvier; T. J. Brandt; J. Bregeon; M. Brigida; P. Bruel; R. Buehler; S. Buson; G. A. Caliandro; R. A. Cameron; M. Caragiulo; P. A. Caraveo; C. Cecchi; E. Charles; A. Chekhtman; J. Chiang; S. Ciprini; R. Claus; J. Cohen-Tanugi; J. Conrad; F. D'Ammando; A. de Angelis; C. D. Dermer; S. W. Digel; E. do Couto e Silva; P. S. Drell; A. Drlica-Wagner; R. Essig; C. Favuzzi; E. C. Ferrara; A. Franckowiak; Y. Fukazawa; S. Funk; P. Fusco; F. Gargano; D. Gasparrini; N. Giglietto; M. Giroletti; G. Godfrey; G. A. Gomez-Vargas; I. A. Grenier; S. Guiriec; M. Gustafsson; M. Hayashida; E. Hays; J. Hewitt; R. E. Hughes; T. Jogler; T. Kamae; J. Knödlseder; D. Kocevski; M. Kuss; . Larsson; L. Latronico; M. Llena Garde; F. Longo; F. Loparco; M. N. Lovellette; P. Lubrano; G. Martinez; M. Mayer; M. N. Mazziotta; P. F. Michelson; W. Mitthumsiri; T. Mizuno; A. A. Moiseev; M. E. Monzani; A. Morselli; I. V. Moskalenko; S. Murgia; R. Nemmen; E. Nuss; T. Ohsugi; E. Orlando; J. F. Ormes; J. S. Perkins; F. Piron; G. Pivato; T. A. Porter; S. Rainò; R. Rando; M. Razzano; S. Razzaque; A. Reimer; O. Reimer; S. Ritz; M. Sànchez-Conde; N. Sehgal; C. Sgrò; E. J. Siskind; P. Spinelli; L. Strigari; D. J. Suson; H. Tajima; H. Takahashi; J. B. Thayer; L. Tibaldo; M. Tinivella; D. F. Torres; Y. Uchiyama; T. L. Usher; J. Vandenbroucke; G. Vianello; V. Vitale; M. Werner; B. L. Winer; K. S. Wood; M. Wood; G. Zaharijas; S. Zimmer

2014-02-19

353

Dark matter constraints from observations of 25 Milky Way satellite galaxies with the Fermi Large Area Telescope  

NASA Astrophysics Data System (ADS)

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

Ackermann, M.; Albert, A.; Anderson, B.; Baldini, L.; Ballet, J.; Barbiellini, G.; Bastieri, D.; Bechtol, K.; Bellazzini, R.; Bissaldi, E.; Bloom, E. D.; Bonamente, E.; Bouvier, A.; Brandt, T. J.; Bregeon, J.; Brigida, M.; Bruel, P.; Buehler, R.; Buson, S.; Caliandro, G. A.; Cameron, R. A.; Caragiulo, M.; Caraveo, P. A.; Cecchi, C.; Charles, E.; Chekhtman, A.; Chiang, J.; Ciprini, S.; Claus, R.; Cohen-Tanugi, J.; Conrad, J.; D'Ammando, F.; de Angelis, A.; Dermer, C. D.; Digel, S. W.; do Couto e Silva, E.; Drell, P. S.; Drlica-Wagner, A.; Essig, R.; Favuzzi, C.; Ferrara, E. C.; Franckowiak, A.; Fukazawa, Y.; Funk, S.; Fusco, P.; Gargano, F.; Gasparrini, D.; Giglietto, N.; Giroletti, M.; Godfrey, G.; Gomez-Vargas, G. A.; Grenier, I. A.; Guiriec, S.; Gustafsson, M.; Hayashida, M.; Hays, E.; Hewitt, J.; Hughes, R. E.; Jogler, T.; Kamae, T.; Knödlseder, J.; Kocevski, D.; Kuss, M.; Larsson, S.; Latronico, L.; Llena Garde, M.; Longo, F.; Loparco, F.; Lovellette, M. N.; Lubrano, P.; Martinez, G.; Mayer, M.; Mazziotta, M. N.; Michelson, P. F.; Mitthumsiri, W.; Mizuno, T.; Moiseev, A. A.; Monzani, M. E.; Morselli, A.; Moskalenko, I. V.; Murgia, S.; Nemmen, R.; Nuss, E.; Ohsugi, T.; Orlando, E.; Ormes, J. F.; Perkins, J. S.; Piron, F.; Pivato, G.; Porter, T. A.; Rainò, S.; Rando, R.; Razzano, M.; Razzaque, S.; Reimer, A.; Reimer, O.; Ritz, S.; Sánchez-Conde, M.; Sehgal, N.; Sgrò, C.; Siskind, E. J.; Spinelli, P.; Strigari, L.; Suson, D. J.; Tajima, H.; Takahashi, H.; Thayer, J. B.; Tibaldo, L.; Tinivella, M.; Torres, D. F.; Uchiyama, Y.; Usher, T. L.; Vandenbroucke, J.; Vianello, G.; Vitale, V.; Werner, M.; Winer, B. L.; Wood, K. S.; Wood, M.; Zaharijas, G.; Zimmer, S.; Fermi-LAT Collaboration

2014-02-01

354

The VELA-X-Pulsar Wind Nebula Revisited with Four Years of Fermi Large Area Telescope Observations  

NASA Technical Reports Server (NTRS)

The Vela supernova remnant (SNR) is the closest SNR to Earth containing an active pulsar, the Vela pulsar (PSR B0833-45). This pulsar is an archetype of the middle-aged pulsar class and powers a bright pulsar wind nebula (PWN), Vela-X, spanning a region of 2deg × 3deg south of the pulsar and observed in the radio, X-ray, and very high energy ?-ray domains. The detection of the Vela-X PWN by the Fermi Large Area Telescope (LAT) was reported in the first year of the mission. Subsequently, we have reinvestigated this complex region and performed a detailed morphological and spectral analysis of this source using 4 yr of Fermi-LAT observations. This study lowers the threshold for morphological analysis of the nebula from 0.8 GeV to 0.3 GeV, allowing for the inspection of distinct energy bands by the LAT for the first time. We describe the recent results obtained on this PWN and discuss the origin of the newly detected spatial features.

Grondin, M. -H.; Romani, R. W.; Lemoine-Goumard, M.; Guillemot, L.; Harding, Alice K.; Reposeur, T.

2013-01-01

355

Circularly Polarized Microstrip Antenna for Cordless Phones  

E-print Network

Circularly Polarized Microstrip Antenna for Cordless Phones By: Rachael Moore, Maria-Carmen Parejo;RESULTS Radiation Pattern of Right Handed Circularly Polarized Antenna #12;RESULTS Radiation Pattern of Left Handed Circularly Polarized Antenna #12;DISCUSSION OF RESULTS Axial ratios of right and left

356

Fermi Large Area Telescope observations of Local Group galaxies: detection of M 31 and search for M 33  

NASA Astrophysics Data System (ADS)

Context. Cosmic rays (CRs) can be studied through the galaxy-wide gamma-ray emission that they generate when propagating in the interstellar medium. The comparison of the diffuse signals from different systems may inform us about the key parameters in CR acceleration and transport. Aims: We aim to determine and compare the properties of the cosmic-ray-induced gamma-ray emission of several Local Group galaxies. Methods: We use 2 years of nearly continuous sky-survey observations obtained with the Large Area Telescope aboard the Fermi Gamma-ray Space Telescope to search for gamma-ray emission from M 31 and M 33. We compare the results with those for the Large Magellanic Cloud, the Small Magellanic Cloud, the Milky Way, and the starburst galaxies M 82 and NGC 253. Results: We detect a gamma-ray signal at 5? significance in the energy range 200 MeV-20 GeV that is consistent with originating from M 31. The integral photon flux above 100 MeV amounts to (9.1 ± 1.9stat ± 1.0sys) × 10-9 ph cm-2 s-1. We find no evidence for emission from M 33 and derive an upper limit on the photon flux >100 MeV of 5.1 × 10-9 ph cm-2 s-1 (2?). Comparing these results to the properties of other Local Group galaxies, we find indications of a correlation between star formation rate and gamma-ray luminosity that also holds for the starburst galaxies. Conclusions: The gamma-ray luminosity of M 31 is about half that of the Milky Way, which implies that the ratio between the average CR densities in M 31 and the Milky Way amounts to ? = 0.35 ± 0.25. The observed correlation between gamma-ray luminosity and star formation rate suggests that the flux of M 33 is not far below the current upper limit from the LAT observations. Appendix A is only available in electronic form at http://www.aanda.org

Abdo, A. A.; Ackermann, M.; Ajello, M.; Allafort, A.; Atwood, W. B.; 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.; Brandt, T. J.; Bregeon, J.; Brigida, M.; Bruel, P.; Buehler, R.; Burnett, T. H.; Buson, S.; Caliandro, G. A.; Cameron, R. A.; Cannon, 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.; Dermer, C. D.; de Angelis, A.; de Palma, F.; Digel, S. W.; Silva, E. Do Couto E.; Drell, P. S.; Drlica-Wagner, A.; Dubois, R.; Favuzzi, C.; Fegan, S. J.; Fortin, P.; Frailis, M.; Fukazawa, Y.; Funk, S.; Fusco, P.; Gargano, F.; Germani, S.; Giglietto, N.; Giordano, F.; Giroletti, M.; Glanzman, T.; Godfrey, G.; Grenier, I. A.; Grondin, M.-H.; Guiriec, S.; Gustafsson, M.; Hadasch, D.; Harding, A. K.; Hayashi, K.; Hayashida, M.; Hays, E.; Healey, S. E.; Jean, P.; Jóhannesson, G.; Johnson, A. S.; Johnson, R. P.; Johnson, T. J.; Kamae, T.; Katagiri, H.; Kataoka, J.; Kerr, M.; Knödlseder, J.; Kuss, M.; Lande, J.; Latronico, L.; Lee, S.-H.; Lemoine-Goumard, M.; Longo, F.; Loparco, F.; Lott, B.; Lovellette, M. N.; Lubrano, P.; Madejski, G. M.; Makeev, A.; Martin, P.; Mazziotta, M. N.; Mehault, J.; Michelson, P. F.; Mitthumsiri, W.; Mizuno, T.; Moiseev, A. A.; Monte, C.; Monzani, M. E.; Morselli, A.; Moskalenko, I. V.; Murgia, S.; 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.; Panetta, J. H.; Parent, D.; Pepe, M.; Persic, M.; Pesce-Rollins, M.; Piron, F.; Porter, T. A.; Rainò, S.; Rando, R.; Razzano, M.; Reimer, A.; Reimer, O.; Ritz, S.; Romani, R. W.; Sadrozinski, H. F.-W.; Saz Parkinson, P. M.; Sgrò, C.; Siskind, E. J.; Smith, D. A.; Smith, P. D.; Spandre, G.; Spinelli, P.; Strickman, M. S.; Strigari, L.; Strong, A. W.; Suson, D. J.; Takahashi, H.; Takahashi, T.; Tanaka, T.; Thayer, J. B.; Thompson, D. J.; Tibaldo, L.; Torres, D. F.; Tosti, G.; Tramacere, A.; Uchiyama, Y.; Usher, T. L.; Vandenbroucke, J.; Vianello, G.; Vilchez, N.; Vitale, V.; Waite, A. P.; Wang, P.; Winer, B. L.; Wood, K. S.; Yang, Z.; Ziegler, M.

2010-11-01

357

Oscillation-induced sand ripples in a circular geometry Germain Rousseaux*  

E-print Network

Oscillation-induced sand ripples in a circular geometry Germain Rousseaux* Laboratoire J; published 7 July 2008 This study deals with the observation of sand ripples in a circular geometry under.57.Gc, 47.20.Ma, 47.54.De Ripples are sand patterns which are built by the to and fro motion induced

Wesfreid, José Eduardo

358

Laser-beam intensity dependent, optical circular birefringence in crystals  

Microsoft Academic Search

Using a phenomenological approach, the optical circular birefringence of crystals in the presence of intense laser light is shown to be the sum of natural gyration, self-induced optical rotation (exhibited by optically inactive bodies), and a self-induced nonlinear variation in the natural gyration. These effects are discussed for all crystallographic classes and the conditions for the separate observation of each

Stanislaw Kielich; Roman Zawodny

1975-01-01

359

Far-Ultraviolet Stopped-Flow Circular Dichroism  

Microsoft Academic Search

A stopped-flow circular dichroism instrument, with a total accessible wavelength range of 200 to 750 nanometers, has been constructed and provides a spectroscopic method for kinetic investigations of a wide array of fast reactions in which optical activity changes in absorbing regions are involved. An important biochemical application depends on the far-ultraviolet capability, which allows observation of the rapid alterations

J. Luchins; S. Beychok

1978-01-01

360

Vibration characteristics of circular nanoplates  

NASA Astrophysics Data System (ADS)

This article deals with free vibration of circular nanoplates with consideration of surface properties due to high surface to volume ratio. Classical laminated plate is employed with inclusion of surface elasticity and surface residual stress effects. Solution of the resulting differential equation leads to size dependent behavior of natural frequencies and mode shapes of vibration to be demonstrated. Deviation of the results from conventional theories is shown to be due to changes in the arguments of Bessel functions in the corresponding characteristic equations.

Assadi, Abbas; Farshi, Behrooz

2010-10-01

361

Circular polarization in star- formation regions: implications for biomolecular homochirality  

PubMed

Strong infrared circular polarization resulting from dust scattering in reflection nebulae in the Orion OMC-1 star-formation region has been observed. Circular polarization at shorter wavelengths might have been important in inducing chiral asymmetry in interstellar organic molecules that could be subsequently delivered to the early Earth by comets, interplanetary dust particles, or meteors. This could account for the excess of L-amino acids found in the Murchison meteorite and could explain the origin of the homochirality of biological molecules. PMID:9685254

Bailey; Chrysostomou; Hough; Gledhill; McCall; Clark; Menard; Tamura

1998-07-31

362

Far-ultraviolet stopped-flow circular dichroism.  

PubMed

A stopped-flow circular dichroism instrument, with a total accessible wavelength range of 200 to 750 nanometers, has been constructed and provides a spectroscopic method for kinetic investigations of a wide array of fast reactions in which optical activity changes in absorbing regions are involved. An important biochemical application depends on the far-ultraviolet capability, which allows observation of the rapid alterations in backbone conformation associated with folding and unfolding reactions of proteins. Results obtained by following two such reactions at 222 nanometers represent direct monitoring by circular dichroism of rapid secondary structure changes in proteins. PMID:619462

Luchins, J; Beychok, S

1978-01-27

363

Dynamic scheduling and planning parallel observations on large Radio Telescope Arrays with the Square Kilometre Array in mind  

NASA Astrophysics Data System (ADS)

Scheduling, the task of producing a time table for resources and tasks, is well-known to be a difficult problem the more resources are involved (a NP-hard problem). This is about to become an issue in Radio astronomy as observatories consisting of hundreds to thousands of telescopes are planned and operated. The Square Kilometre Array (SKA), which Australia and New Zealand bid to host, is aiming for scales where current approaches -- in construction, operation but also scheduling -- are insufficent. Although manual scheduling is common today, the problem is becoming complicated by the demand for (1) independent sub-arrays doing simultaneous observations, which requires the scheduler to plan parallel observations and (2) dynamic re-scheduling on changed conditions. Both of these requirements apply to the SKA, especially in the construction phase. We review the scheduling approaches taken in the astronomy literature, as well as investigate techniques from human schedulers and today's observatories. The scheduling problem is specified in general for scientific observations and in particular on radio telescope arrays. Also taken into account is the fact that the observatory may be oversubscribed, requiring the scheduling problem to be integrated with a planning process. We solve this long-term scheduling problem using a time-based encoding that works in the very general case of observation scheduling. This research then compares algorithms from various approaches, including fast heuristics from CPU scheduling, Linear Integer Programming and Genetic algorithms, Branch-and-Bound enumeration schemes. Measures include not only goodness of the solution, but also scalability and re-scheduling capabilities. In conclusion, we have identified a fast and good scheduling approach that allows (re-)scheduling difficult and changing problems by combining heuristics with a Genetic algorithm using block-wise mutation operations. We are able to explain and eradicate two problems in the literature: The inability of a GA to properly improve schedules and the generation of schedules with frequent interruptions. Finally, we demonstrate the scheduling framework for several operating telescopes: (1) Dynamic re-scheduling with the AUT Warkworth 12m telescope, (2) Scheduling for the Australian Mopra 22m telescope and scheduling for the Allen Telescope Array. Furthermore, we discuss the applicability of the presented scheduling framework to the Atacama Large Millimeter/submillimeter Array (ALMA, in construction) and the SKA. In particular, during the development phase of the SKA, this dynamic, scalable scheduling framework can accommodate changing conditions.

Buchner, Johannes

2011-12-01

364

Engineering strictosidine synthase: rational design of a small, focused circular permutation library of the ?-propeller fold enzyme.  

PubMed

Strictosidine synthases catalyze the formation of strictosidine, a key intermediate in the biosynthesis of a large variety of monoterpenoid indole alkaloids. Efforts to utilize these biocatalysts for the preparation of strictosidine analogs have however been of limited success due to the high substrate specificity of these enzymes. We have explored the impact of a protein engineering approach called circular permutation on the activity of strictosidine synthase from the Indian medicinal plant Rauvolfia serpentina. To expedite the discovery process, our study departs from the usual process of creating a random protein library, followed by extensive screening. Instead, a small, focused library of circular permutated variants of the six bladed ?-propeller protein was prepared, specifically probing two regions which cover the enzyme active site. The observed activity changes suggest important roles of both regions in protein folding, stability and catalysis. PMID:24996997

Fischereder, Eva; Pressnitz, Desiree; Kroutil, Wolfgang; Lutz, Stefan

2014-10-15

365

Circular polarization of light scattered by asymmetrical particles  

NASA Astrophysics Data System (ADS)

We present calculations of the degree of circular polarization of light singly scattered by some kinds of asymmetrical particles in random orientation as a function of the scattering angle, using the T-matrix method. To clarify the possible contribution of asymmetry of particles to circular polarization we considered aggregates of optically inactive homogeneous identical spheres. We analysed the effect of changing the size of the monomers and the refractive index. We also performed calculations for two different geometries. The values of the computed degree of circular polarization are generally in the range of the observed ones for light scattered by dust particles in comets P/Halley, C/1995 O1 (Hale-Bopp) and C/1999 S4 (LINEAR), in the interplanetary medium and in the interstellar medium of our galaxy.

Guirado, D.; Hovenier, J. W.; Moreno, F.

2007-07-01

366

Medical and Endovascular Treatment of Patients with Large Vessel Occlusion Presenting with Mild Symptoms: An Observational Multicenter Study.  

PubMed

Background: A significant proportion of stroke patients presenting with mild symptoms does not have a successful recovery, especially when a large vessel is occluded. IV thrombolysis is safe and may benefit patients presenting with mild symptoms. In this study, we tested whether endovascular therapy (ET) is superior to medical therapy in these patients. Methods: Observational, prospectively collected, multicenter study of 78 consecutive patients admitted from 2009 to 2012 within 6 h of stroke, with NIHSS ?5 at presentation or during initial diagnostic work-up and large vessel occlusion. Data for patients undergoing ET and/or IV thrombolysis were taken from the SONIIA registry of reperfusion therapies in Catalonia, or from our local stroke registry if no reperfusion therapy was delivered. We compared risk factors, clinical course, collateral circulation, revascularization rates, hemorrhagic complications, infarct volume, and the functional outcome at 3 months of patients treated with ET and those not receiving ET. Ordinal regression was used to assess the independent effect of ET on functional outcome. Results: Baseline characteristics were similar for ET (n = 34) and medically (n = 44) treated patients, except for older age in the latter. The occlusions were located in the terminal internal carotid artery (1%), M1 segment of the middle cerebral artery (33%), M2 segment (30%), posterior circulation (31%), and 5% of the patients had tandem lesions, with no significant differences between groups. Most patients in both treatment groups had good collateral flow. The rate of successful revascularization (91.2 vs. 63.4%; p = 0.006) and the risk of symptomatic intracranial hemorrhage (11.8 vs. 0%; p = 0.033) were higher in the ET group. The NIHSS scores were similar at hospital arrival, after initial neuroimaging, and at 24 h in both treatment groups and there were no significant differences in the infarct volume in a follow-up MRI. At 3 months, 35.9% of the patients had some disability. The functional outcome was similar in both treatment groups in univariate analysis and also in models adjusted for age and initial NIHSS or for variables associated to functional outcome on univariate comparison. Conversely, IV thrombolysis was associated with significantly greater chances of full recovery after adjusting for baseline differences (OR 3.70, p = 0.015). Conclusions: One third of stroke patients with mild symptoms and large vessel occlusions do not have a successful recovery. ET is effective to recanalize the occluded vessel but increases the risk of serious bleeding significantly without improving the functional outcome, and is therefore not justified routinely in these patients. © 2014 S. Karger AG, Basel. PMID:25472576

Urra, Xabier; San Román, Luis; Gil, Francisco; Millán, Mónica; Cánovas, David; Roquer, Jaume; Cardona, Pere; Ribó, Marc; Martí-Fàbregas, Joan; Abilleira, Sònia; Chamorro, Angel

2014-12-01

367

Circular dichroism in molecular-frame photoelectron angular distributions in the dissociative photoionization of H2 and D2 molecules  

NASA Astrophysics Data System (ADS)

The presence of net circular dichroism in the photoionization of nonchiral homonuclear molecules has been put in evidence recently through the measurement of molecular-frame photoelectron angular distributions in dissociative photoionization of H2 [Dowek et al., Phys. Rev. Lett. 104, 233003 (2010), 10.1103/PhysRevLett.104.233003]. In this work we present a detailed study of circular dichroism in the photoelectron angular distributions of H2 and D2 molecules, oriented perpendicularly to the propagation vector of the circularly polarized light, at different photon energies (20, 27, and 32.5 eV). Circular dichroism in the angular distributions at 20 and to a large extent 27 eV exhibits the usual pattern in which inversion symmetry is preserved. In contrast, at 32.5 eV, the inversion symmetry breaks down, which eventually leads to total circular dichroism after integration over the polar emission angle. Time-dependent ab initio calculations support and explain the observed results for H2 in terms of quantum interferences between direct photoionization and delayed autoionization from the Q1 and Q2 doubly excited states into ionic states (1 s ?g and 2 p ?u ) of different inversion symmetry. Nevertheless, for D2 at 32.5 eV, there is a particular case where theory and experiment disagree in the magnitude of the symmetry breaking: when D+ ions are produced with an energy of around 5 eV. This reflects the subleties associated to such simple molecules when exposed to this fine scrutiny.

Pérez-Torres, J. F.; Sanz-Vicario, J. L.; Veyrinas, K.; Billaud, P.; Picard, Y. J.; Elkharrat, C.; Poullain, S. Marggi; Saquet, N.; Lebech, M.; Houver, J. C.; Martín, F.; Dowek, D.

2014-10-01

368

Discovery of Optical Circular Polarization of the Crab Pulsar  

NASA Astrophysics Data System (ADS)

Nearly 50 years ago at the Lick 3-m Shane telescope, Wampler et al. (1969) discovered optical linear depolarization of the Crab pulsar's main pulse and interpulse regions, which led to the interpretation of synchrotron radiation as the source of pulsed emission. We present phase-resolved, simultaneous linear and circular polarization of the Crab pulsar using the POLISH2 aperture-integrated, optical polarimeter at the Lick 3-m telescope. The two photoelastic modulators in this instrument, used instead of waveplates, AC couple incident Stokes Q, U, and V to unique, independent frequencies between 10 and 200 kHz. Stokes I is measured from the time-averaged intensity of the beam. Thus, this instrument is capable of simultaneous measurement of Q/I, U/I, and V/I in 20 microsecond temporal bins with part-per-million nightly sensitivity on naked eye stars. From just one hour of observations, we confirm linear depolarization of the main pulse and interpulse regions, and we also discover significant optical circular polarization at all pulsar phases. Furthermore, we observe circular depolarization of the main pulse and interpulse regions with respect to the off-pulse region. Observations of strongly polarized calibration stars, as well as lamp observations with a linear polarizer inserted upstream of the modulators, demonstrate that circular polarization results obtained on the Crab pulsar are not due to spurious, instrumental conversion of linear to circular polarization. Therefore, using novel instrumentation, our observations shed new light on this enigmatic object, and we demonstrate that the Lick 3-m Shane telescope still remains at the cutting edge for optical polarimetry.

Wiktorowicz, Sloane; Ramirez-Ruiz, Enrico; Illing, Rainer M. E.; Nofi, Larissa

2015-01-01

369

Lupus I Observations from the 2010 Flight of the Balloon-borne Large Aperture Submillimeter Telescope for Polarimetry  

E-print Network

The Balloon-borne Large Aperture Submillimeter Telescope for Polarimetry (BLASTPol) was created by adding polarimetric capability to the BLAST experiment that was flown in 2003, 2005, and 2006. BLASTPol inherited BLAST's 1.8 m primary and its Herschel/SPIRE heritage focal plane that allows simultaneous observation at 250, 350, and 500 {\\mu}m. We flew BLASTPol in 2010 and again in 2012. Both were long duration Antarctic flights. Here we present polarimetry of the nearby filamentary dark cloud Lupus I obtained during the 2010 flight. Despite limitations imposed by the effects of a damaged optical component, we were able to clearly detect submillimeter polarization on degree scales. We compare the resulting BLASTPol magnetic field map with a similar map made via optical polarimetry (The optical data were published in 1998 by J. Rizzo and collaborators.). The two maps partially overlap and are reasonably consistent with one another. We compare these magnetic field maps to the orientations of filaments in Lupus I,...

Matthews, Tristan G; Angilè, Francesco E; Benton, Steven J; Chapin, Edward L; Chapman, Nicholas L; Devlin, Mark J; Fissel, Laura M; Fukui, Yasuo; Gandilo, Natalie N; Gundersen, Joshua O; Hargrave, Peter C; Klein, Jeffrey; Korotkov, Andrei L; Moncelsi, Lorenzo; Mroczkowski, Tony K; Netterfield, Calvin B; Novak, Giles; Nutter, David; Olmi, Luca; Pascale, Enzo; Poidevin, Frédérick; Savini, Giorgio; Scott, Douglas; Shariff, Jamil A; Soler, Juan Diego; Tachihara, Kengo; Thomas, Nicholas E; Truch, Matthew D P; Tucker, Carole E; Tucker, Gregory S; Ward-Thompson, Derek

2013-01-01

370

The Spitzer c2d Survey of Large, Nearby, Interstellar Clouds. XI. Lupus Observed With IRAC and MIPS  

E-print Network

We present c2d Spitzer/IRAC observations of the Lupus I, III and IV dark clouds and discuss them in combination with optical and near-infrared and c2d MIPS data. With the Spitzer data, the new sample contains 159 stars, 4 times larger than the previous one. It is dominated by low- and very-low mass stars and it is complete down to M $\\approx$ 0.1M$_\\odot$. We find 30-40 % binaries with separations between 100 to 2000 AU with no apparent effect in the disk properties of the members. A large majority of the objects are Class II or Class III objects, with only 20 (12%) of Class I or Flat spectrum sources. The disk sample is complete down to ``debris''-like systems in stars as small as M $\\approx$ 0.2 M$_\\odot$ and includes sub-stellar objects with larger IR excesses. The disk fraction in Lupus is 70 -- 80%, consistent with an age of 1 -- 2 Myr. However, the young population contains 20% optically thick accretion disks and 40% relatively less flared disks. A growing variety of inner disk structures is found for l...

Merin, Bruno; Spezzi, Loredana; Alcala, Juan M; Evans, Neal J; Harvey, Paul M; Chapman, Nicholas; Huard, Tracy; van Dishoeck, Ewine F; Comeron, Fernando

2008-01-01

371

OBSERVATIONS OF THE YOUNG SUPERNOVA REMNANT RX J1713.7-3946 WITH THE FERMI LARGE AREA TELESCOPE  

SciTech Connect

We present observations of the young supernova remnant (SNR) RX J1713.7-3946 with the Fermi Large Area Telescope (LAT). We clearly detect a source positionally coincident with the SNR. The source is extended with a best-fit extension of 0.{sup 0}55 {+-} 0.{sup 0}04 matching the size of the non-thermal X-ray and TeV gamma-ray emission from the remnant. The positional coincidence and the matching extended emission allow us to identify the LAT source with SNR RX J1713.7-3946. The spectrum of the source can be described by a very hard power law with a photon index of {Gamma} = 1.5 {+-} 0.1 that coincides in normalization with the steeper H.E.S.S.-detected gamma-ray spectrum at higher energies. The broadband gamma-ray emission is consistent with a leptonic origin as the dominant mechanism for the gamma-ray 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.; Allafort, A.; 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. [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, 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); 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); Brandt, T. J. [CNRS, IRAP, F-31028 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: markusa@slac.stanford.edu, E-mail: funk@slac.stanford.edu, E-mail: uchiyama@slac.stanford.edu [Laboratoire Leprince-Ringuet, Ecole polytechnique, CNRS/IN2P3, Palaiseau (France)

2011-06-10

372

Polarimetric Imaging of Large Cavity Structures in the Pre-transitional Protoplanetary Disk around PDS 70: Observations of the Disk  

NASA Technical Reports Server (NTRS)

We present high resolution H-band polarized intensity (PI; FWHM = 0."1: 14 AU) and L'-band imaging data (FWHM = 0."11: 15 AU) of the circumstellar disk around the weak-lined T Tauri star PDS 70 in Centaurus at a radial distance of 28 AU (0."2) up to 210 AU (1."5). In both images, a giant inner gap is clearly resolvro for the first time, and the radius of the gap is approx 70 AU. Our data show that the geometric center of the disk shifts by approx 6 AU toward the minor axis. We confirm that the brown dwarf companion candidate to the north of PDS 70 is a background star based on its proper motion. As a result of SED fitting by Monte Carlo radiative transfer modeling, we infer the existence of an optically thick inner disk at a few AU. Combining our observations and modeling, we classify the disk of PDS 70 as a pre-transitional disk. Furthermore, based on the analysis of L'-band imaging data, we put an upper limit mass of companions at approx 30 to approx 50M(sub J) within the gap. Taking account of the presence of the large and sharp gap, we suggest that the gap could be formed by dynamical interactions of sub-stellar companions or multiple unseen giant planets in the gap.

Hashimoto, J.; Hayashi, M.; Iye, M.; Kandori, R.; Kusakabe,N.; Morino, J.-I.; Suto, H.; Suzuki, R.; Tamura, M.; Serabyn, G.; McElwain, M. W.; Dong, R.; Zhu, Z.; Brandt, T.; Janson, M.; Knapp G.; Turner, E. L.

2012-01-01

373

Gamma-Ray Observations of the Supernova Remnant RX J0852.0-4622 with the Fermi Large Area Telescope  

NASA Technical Reports Server (NTRS)

We report on gamma-ray observations of the supernova remnant (SNR) RX J0852.04622 with the Large Area Telescope (LAT) on board the Fermi Gamma-ray Space Telescope. In the Fermi-LAT data, we find a spatially extended source at the location of the SNR. The extension is consistent with the SNR size seen in other wavelengths such as X-rays and TeV gamma rays, leading to the identification of the gamma-ray source with the SNR. The spectrum is well described as a power law with a photon index of = 1.85 0.06 (stat)+0.18 0.19 (sys), which smoothly connects to the H.E.S.S. spectrum in the TeV energy band. We discuss the gamma-ray emission mechanism based on multiwavelength data. The broadband data can be fit well by a model in which the gamma rays are of hadronic origin. We also consider a scenario with inverse Compton scattering of electrons as the emission mechanism of the gamma rays. Although the leptonic model predicts a harder spectrum in the Fermi-LAT energy range, the model can fit the data considering the statistical and systematic errors.

Tanaka, T.; Allafort, A.; Ballet, J.; Funk, S.; Giordano, F.; Hewitt, J.; Lemoine-Goumard, M.; Tajima, H.; Tibolla, O.; Uchiyama, Y.

2011-01-01

374

Large volume collapse observed in the phase transition in cubic PbCrO[subscript 3] perovskite  

SciTech Connect

When cubic PbCrO{sub 3} perovskite (Phase I) is squeezed up to {approx}1.6 GPa at room temperature, a previously undetected phase (Phase II) has been observed with a 9.8% volume collapse. Because the structure of Phase II can also be indexed into a cubic perovskite as Phase I, the transition between Phases I and II is a cubic to cubic isostructural transition. Such a transition appears independent of the raw materials and synthesizing methods used for the cubic PbCrO{sub 3} perovskite sample. In contrast to the high-pressure isostructural electronic transition that appears in Ce and SmS, this transition seems not related with any change of electronic state, but it could be possibly related on the abnormally large volume and compressibility of the PbCrO{sub 3} Phase I. The physical mechanism behind this transition and the structural and electronic/magnetic properties of the condensed phases are the interesting issues for future studies.

Xiao, Wansheng; Tan, Dayong; Xiong, Xiaolin; Liu, Jing; Xu, Jian (Chinese Aca. Sci.)

2010-08-27

375

Hubble Space Telescope and Very Large Array Observations of the H2O Gigamaser Galaxy TXS 2226-184.  

PubMed

We present Hubble Space Telescope/Wide-Field and Planetary Camera 2 images in Halpha + [N ii] lambdalambda6548, 6583 lines and continuum radiation and a VLA map at 8 GHz of the H2O gigamaser galaxy TXS 2226-184. This galaxy has the most luminous H2O maser emission known to date. Our red continuum images reveal a highly elongated galaxy with a dust lane crossing the nucleus. The surface brightness profile is best fitted by a bulge plus exponential disk model, favoring classification as a highly inclined spiral galaxy (i=70&j0;). The color map confirms that the dust lane is aligned with the galaxy major axis and is crossing the putative nucleus. The Halpha + [N ii] map exhibits a gaseous, jetlike structure perpendicular to the nuclear dust lane and the galaxy major axis. The radio map shows compact, steep spectrum emission that is elongated in the same direction as the Halpha + [N ii] emission. By analogy with Seyfert galaxies, we therefore suspect that this alignment reflects an interaction between the radio jet and the interstellar medium. The axes of the nuclear dust disk, the radio emission, and the optical line emission apparently define the axis of the active galactic nucleus. The observations suggest that in this galaxy the nuclear accretion disk, obscuring torus, and large-scale molecular gas layer are roughly coplanar. Our classification of the host galaxy strengthens the trend for megamasers to be found preferentially in highly inclined spiral galaxies. PMID:10642194

Falcke; Wilson; Henkel; Brunthaler; Braatz

2000-02-10

376

CASE STUDY OF FOUR HOMOLOGOUS LARGE-SCALE CORONAL WAVES OBSERVED ON 2010 APRIL 28 AND 29  

SciTech Connect

On 2010 April 28 and 29, the Solar TErrestrial Relations Observatory B/Extreme Ultraviolet Imager observed four homologous large-scale coronal waves, the so-called EIT-waves, within 8 hr. All waves emerged from the same source active region, were accompanied by weak flares and faint coronal mass ejections, and propagated into the same direction at constant velocities in the range of {approx}220-340 km s{sup -1}. The last of these four coronal wave events was the strongest and fastest, with a velocity of 337 {+-} 31 km s{sup -1} and a peak perturbation amplitude of {approx}1.24, corresponding to a magnetosonic Mach number of M{sub ms} {approx} 1.09. The magnetosonic Mach numbers and velocities of the four waves are distinctly correlated, suggestive of the nonlinear fast-mode magnetosonic wave nature of the events. We also found a correlation between the magnetic energy buildup times and the velocity and magnetosonic Mach number.

Kienreich, I. W.; Veronig, A. M.; Muhr, N.; Temmer, M. [Institute of Physics, University of Graz, Universitaetsplatz 5, A-8010 Graz (Austria); Vrsnak, B. [Hvar Observatory, Faculty of Geodesy, Kaciceva 26, 1000 Zagreb (Croatia); Nitta, N., E-mail: ines.kienreich@uni-graz.at [LMSAL, 3251 Hanover Street, Palo Alto, CA 94304 (United States)

2011-02-01

377

Observation of an impurity hole in a plasma with an ion internal transport barrier in the Large Helical Device  

SciTech Connect

Extremely hollow profiles of impurities (denoted as 'impurity hole') are observed in the plasma with a steep gradient of the ion temperature after the formation of an internal transport barrier (ITB) in the ion temperature transport in the Large Helical Device [A. Iiyoshi et al., Nucl. Fusion 39, 1245 (1999)]. The radial profile of carbon becomes hollow during the ITB phase and the central carbon density keeps dropping and reaches 0.1%-0.3% of plasma density at the end of the ion ITB phase. The diffusion coefficient and the convective velocity of impurities are evaluated from the time evolution of carbon profiles assuming the diffusion and the convection velocity are constant in time after the formation of the ITB. The transport analysis gives a low diffusion of 0.1-0.2 m{sup 2}/s and the outward convection velocity of {approx}1 m/s at half of the minor radius, which is in contrast to the tendency in tokamak plasmas for the impurity density to increase due to an inward convection and low diffusion in the ITB region. The outward convection is considered to be driven by turbulence because the sign of the convection velocity contradicts the neoclassical theory where a negative electric field and an inward convection are predicted.

Ida, K.; Yoshinuma, M.; Osakabe, M.; Nagaoka, K.; Yokoyama, M.; Funaba, H.; Suzuki, C.; Ido, T.; Shimizu, A.; Murakami, I.; Tamura, N.; Kasahara, H.; Takeiri, Y.; Ikeda, K.; Tsumori, K.; Kaneko, O.; Morita, S.; Goto, M.; Tanaka, K.; Narihara, K. [National Institute for Fusion Sciences, Toki, Gifu 509-5292 (Japan)] (and others)

2009-05-15

378

ASTE observations in the 345 GHz window towards the HII region N113 of the Large Magellanic Cloud  

NASA Astrophysics Data System (ADS)

Aims: The HII region N113 is located in the central part of the Large Magellanic Cloud (LMC) with an associated molecular cloud that is very rich in molecular species. Most of the previously observed molecular lines cover the frequency range 85-270 GHz. Thus, a survey and study of lines at the 345 GHz window is required for a more complete understanding of the chemistry and excitation conditions of this region. Methods: We mapped a region of 2.´5 × 2.´5 centred at N113 using the Atacama Submillimeter Telescope Experiment in the 13CO J = 3-2 line with an angular and spectral resolution of 22'' and 0.11 km s-1. In addition, we observed 16 molecular lines as single pointings towards its centre. Results: From the 13CO J = 3-2 map we estimate the local thermodynamic equilibrium (LTE) and virial masses in about 1 × 104 and 4.5 × 104M? for the molecular cloud associated with N113. From the dust continuum emission at 500 ?m we additionally obtain a mass of gas of 7 × 103M?. Towards the cloud centre we detected emission from 12CO, 13CO, C18O (3-2), HCN, HNC, HCO+, C2H (4-3), and CS (7-6); these are the first reported detections of the HCN, HNC, and C2H (4-3) lines from this region. We confirm the detection of CS (7-6), which was previously tentatively detected. From analysing the HCN, HNC, and C2H lines we suggest that they might be emitted from a photodissociation region (PDR). Moreover, we suggest that the chemistry involving the C2H lines in N113 is probably similar to that in Galactic PDRs. We analysed the HCN J = 4-3, J = 3-2, and J = 1-0 lines with the code RADEX and we conclude that we observe very high density gas, between some 105 and 107 cm-3.

Paron, S.; Ortega, M. E.; Cunningham, M.; Jones, P. A.; Rubio, M.; Fariña, C.; Komugi, S.

2014-12-01

379

Astronomical sources of circularly polarized light and the origin of homochirality.  

PubMed

Possible astronomical sources of ultraviolet circularly polarized light (UVCPL) which might be responsible for enantiomeric selection in interstellar organic molecules are considered, Synchrotron radiation from magnetic neutron stars has been suggested as a possible source of UVCPL. However, synchrotron radiation in these situations is not predicted to be strongly circularly polarized. Very few such sources show optical synchrotron radiation and in the few that do circular polarization has not been observed. Magnetic white dwarfs and white dwarf binaries (Polars) can be highly circularly polarized but any effect on molecular clouds and star formation regions must rely on rare chance encounters. Recent observations show that substantial levels of circular polarization are present in reflection nebulae in star formation regions. This mechanism produces polarized light exactly when and where it is needed in regions where star formation is occurring and organic molecules are known to be present. PMID:11296520

Bailey, J

2001-01-01

380

Observations of large-amplitude cross-shore internal bores near the shelf break, Santa Monica Bay, CA  

USGS Publications Warehouse

Two sets of moorings were deployed along a cross-shelf transect in central Santa Monica bay for four months in the winter of 1998-1999. Both sites had an array of instruments attached to tripods set on the seafloor to monitor currents over the entire water column, surface waves, near-bed temperature, water clarity and suspended sediment. A companion mooring had temperature sensors spaced approximately 10 m apart to measure temperature profiles between the surface and the seafloor. One array was deployed in 70 m of water at a site adjacent to the shelf break, just northwest of a major ocean outfall. The other was deployed on the mid shelf in 35 m of water approximately 6 km from the shelf break site. The subtidal currents in the region flowed parallel to the isobaths with fluctuating time scales around 10 days, a typical coastal-ocean pattern. However, during the falling phase of the barotropic spring tide, sets of large-amplitude, sheared cross-shore current pulses with a duration of 2-5 h were observed at the shelf break site. Currents in these pulses flowed exclusively offshore in a thin layer near the bed with amplitudes reaching 30-40 cm/s. Simultaneously, currents with amplitudes around 15-20 cm/s flowed exclusively onshore in the thicker layer between the offshore flow layer and the sea surface. The net offshore transport was about half the onshore transport. Near-surface isotherms were depressed 30-40 m. These pulses were likely internal bores generated by tidal currents. Bed stresses associated with these events exceeded 3 dynes/cm2. These amplitudes are large enough to resuspend and transport not only fine-grained material, but also medium to coarse sands from the shelf toward the slope. Consequently, the seafloor over the shelf break was swept clear of fine sediments. The data suggest that the internal bores dissipate and are reduced in amplitude as they propagate across this relatively narrow shelf. There is evidence that they reach the 35 m site, but other coastal ocean processes obscure their distinctive characteristics.

Noble, M.A.; Xu, J.P.

2003-01-01

381

Fluid forces on circular cylinders  

E-print Network

and ~ia force and, several 1'orce anomalies which sx'ise frdm tbe flow conditions imposed by the flaM boundaries. The surface anomaly, 4Fs is the fame anomaly 4us to penetration of the cyl1nder through ths air-fluid interface and is the remelt of bow... of WuZZR OF SCINNCZ l4sy 19+ l4aJor Subject - Physical Oceanography FLUID FORCES CIRCULAR CYLIEDERS A Thesis Ry Robert G. Dean Approved as to style and oontent bye Cha n of Coaaittee Read of De n Contents Introduction Apparatus Procedure...

Dean, Robert G

1956-01-01

382

Evidence from Impact Crater Observations for Few Large Impacts on the Moon 0.8-1.7 Ga  

NASA Astrophysics Data System (ADS)

Our Moon is a keystone for understanding the inner solar system impact flux through time, because it is the only body for which we have crater size-frequency distributions (SFDs) through most of bombardment history and radiometric ages of probable associated terrains. Even so, the bombardment rate over the last 3.5 Gyr is poorly understood. According to the spatial density of sub-km craters on dated lunar terrains, the lunar impact flux has been roughly constant over this interval [e.g., 1 and references therein]. If so, one may expect that craters with diameter (D) > 50 km should also be equally dispersed in time over the last 3.5 Gyr. Surprisingly, our new work indicates this may not be so. We have compiled SFDs for small, superposed craters with D~0.6-15 km on the original floors of several previously designated Copernican and Eratothenian craters (USGS Geological Atlas of the Moon and [2]) with D > 50 km using JMARS. Using these data we compute the large craters' formation model ages with the Model Production Function chronology developed by Marchi et al. [3]. Many of these craters, especially on the farside (e.g., Sharnov, Birkeland), can now be suitably examined only because of the excellent LROC imaging (we use the Wide Angle Camera mosaic). As a test of our methods, we calculated the model age of the 55 km crater Aristillus (34°N, 1°E), a relatively young crater thought to have showered the Apollo 15 landing site with ejecta. Interestingly, our model age of 2.2 ± 0.6 Ga is surprisingly consistent with a 2.1 Ga-old impact-derived clast (radiometric age) returned by the Apollo 15 astronauts [4]. We find that nearly all of our computed ages for the large craters are older than indicated by previous work, with very few having ages younger than 3 Ga. Reasons for these discrepancies include (i) use of poor resolution Lunar Orbiter images (especially away from the near side) and (ii) application of the unreliable "DL" method, which involves simplified assumptions about how craters degrade. In addition, when our crater ages are combined with others determined (e.g., Copernicus, Tycho, King; [5-9]), we preliminarily observe a relative lull in lunar impact cratering for ~0.8-1.7 Ga. Intriguingly, this interval appears to roughly coincide with a period on Earth called the "boring billion" [10], when the evolution of life appears to have been stagnant and oceans were euxinic (poorly mixed, largely starved of oxygen). We speculate that absence of major terrestrial impacts may have surprising implications for the history of life and our biosphere. References: [1] Neukum, G., et al. (2001) SSR 96, 55-86. [2] Wilhelms, D.E. (1987) Geologic History of the Moon USGS, Paper 1348. [3] Marchi, S., et al. (2009) AJ 137, 4936-4948. [4] Ryder, G., et al. (1991) Geology 19, 143-146. [5] Neukum, G. and B. König (1976). Lunar Sci. VII. Proc., 2867-2881. [6] Hiesinger, H., et al. (2012) JGR 117, E00H10, doi: 10.1029/2011je003935. [7] van der Bogert, C.H., et al. (2010). LPSC XLI. Abst. #2165. [8] McEwen, A.S., et al. (1993) JGR 98, 17207-17231. [9] Ashley, J.W., et al. (2011). 42nd LPSC, Abst. #2437. [10] Holland, H.D. (2006) Phil. Trans. R. Soc. B 361, 903-915.

Kirchoff, M. R.; Bottke, W. F.; Marchi, S.; Chapman, C. R.; Enke, B.

2012-12-01

383

The Spitzer c2d Survey of Large, Nearby, Interstellar Clouds. XI. Lupus Observed With IRAC and MIPS  

E-print Network

We present c2d Spitzer/IRAC observations of the Lupus I, III and IV dark clouds and discuss them in combination with optical and near-infrared and c2d MIPS data. With the Spitzer data, the new sample contains 159 stars, 4 times larger than the previous one. It is dominated by low- and very-low mass stars and it is complete down to M $\\approx$ 0.1M$_\\odot$. We find 30-40 % binaries with separations between 100 to 2000 AU with no apparent effect in the disk properties of the members. A large majority of the objects are Class II or Class III objects, with only 20 (12%) of Class I or Flat spectrum sources. The disk sample is complete down to ``debris''-like systems in stars as small as M $\\approx$ 0.2 M$_\\odot$ and includes sub-stellar objects with larger IR excesses. The disk fraction in Lupus is 70 -- 80%, consistent with an age of 1 -- 2 Myr. However, the young population contains 20% optically thick accretion disks and 40% relatively less flared disks. A growing variety of inner disk structures is found for larger inner disk clearings for equal disk masses. Lupus III is the most centrally populated and rich, followed by Lupus I with a filamentary structure and by Lupus IV, where a very high density core with little star-formation activity has been found. We estimate star formation rates in Lupus of 2 -- 10 M$_\\odot$ Myr$^{-1}$ and star formation efficiencies of a few percent, apparently correlated with the associated cloud masses.

Bruno Merin; Jes Jorgensen; Loredana Spezzi; Juan M. Alcala; Neal J. Evans II; Paul M. Harvey; Nicholas Chapman; Tracy Huard; Ewine F. van Dishoeck; Fernando Comeron

2008-03-10

384

The large-scale spatio-temporal variability of precipitation over Sweden observed from the weather radar network  

NASA Astrophysics Data System (ADS)

Using measurements from the national network of 12 weather radar stations for the last decade (2000-2010), we investigate the large-scale spatio-temporal variability of precipitation over Sweden. These statistics provide useful information to evaluate regional climate models as well as for hydrology and energy applications. A strict quality control is applied to filter out noise and artifacts from the radar data. We focus on investigating four distinct aspects namely, the diurnal cycle of precipitation and its seasonality, the dominant time scale (diurnal vs. seasonal) of variability, precipitation response to different wind directions, and the correlation of precipitation events with the North Atlantic Oscillation (NAO) and the Arctic Oscillation (AO). When classified based on their intensity, moderate to high intensity events (precipitation > 0.34 mm (3 h)-1) peak distinctly during late afternoon over the majority of radar stations in summer and during late night or early morning in winter. Precipitation variability is highest over the southwestern parts of Sweden. It is shown that the high intensity events (precipitation > 1.7mm (3 h)-1) are positively correlated with NAO and AO (esp. over northern Sweden), while the low intensity events are negatively correlated (esp. over southeastern parts). It is further observed that southeasterly winds often lead to intense precipitation events over central and northern Sweden, while southwesterly winds contribute most to the total accumulated precipitation for all radar stations. Apart from its operational applications, the present study demonstrates the potential of the weather radar data set for studying climatic features of precipitation over Sweden.

Devasthale, A.; Norin, L.

2013-12-01

385

The large-scale spatio-temporal variability of precipitation over Sweden observed from the weather radar network  

NASA Astrophysics Data System (ADS)

Using measurements from the national network of 12 weather radar stations for the 11-year period 2000-2010, we investigate the large-scale spatio-temporal variability of precipitation over Sweden. These statistics provide useful information to evaluate regional climate models as well as for hydrology and energy applications. A strict quality control is applied to filter out noise and artifacts from the radar data. We focus on investigating four distinct aspects: the diurnal cycle of precipitation and its seasonality, the dominant timescale (diurnal versus seasonal) of variability, precipitation response to different wind directions, and the correlation of precipitation events with the North Atlantic Oscillation (NAO) and the Arctic Oscillation (AO). When classified based on their intensity, moderate- to high-intensity events (precipitation > 0.34 mm/3 h) peak distinctly during late afternoon over the majority of radar stations in summer and during late night or early morning in winter. Precipitation variability is highest over the southwestern parts of Sweden. It is shown that the high-intensity events (precipitation > 1.7 mm/3 h) are positively correlated with NAO and AO (esp. over northern Sweden), while the low intensity events are negatively correlated (esp. over southeastern parts). It is further observed that southeasterly winds often lead to intense precipitation events over central and northern Sweden, while southwesterly winds contribute most to the total accumulated precipitation for all radar stations. Apart from its operational applications, the present study demonstrates the potential of the weather radar data set for studying climatic features of precipitation over Sweden.

Devasthale, A.; Norin, L.

2014-06-01

386

Topography within Circular Grabens: Implications for Polygon Origin, Utopia Planitia, Mars  

NASA Technical Reports Server (NTRS)

Very large, fracture-bounded polygons occur in Acidalia and Utopia Planitiae, Mars. Two models for the origin of these large polygons postulate drape folding of a sedimentary cover material over an uneven buried surface, with the strain enhancement needed to explain the large size due to differential compaction. Throughout the polygonal terrain are circular grabens inferred to overlie buried crater rims. Drape folding models predict that (1) these circular grabens will bound topographic lows and (2) the surface relief and percent compaction within circular grabens will be proportional to ring diameters. Relief and compaction within 8 circular grabens have been determined by gridding MOLA data in ArcView. All 8 fulfill the first prediction, and 7 of them fulfill the second prediction. These results support a sedimentary origin for polygonal terrain materials, and thus are consistent with the past existence of an 'ocean' in the martian lowland.

Buczkowski, Debra L.; McGill, George E.

2002-01-01

387

SEARCH FOR A MAGNETIC FIELD VIA CIRCULAR POLARIZATION IN THE WOLF-RAYET STAR EZ CMa  

SciTech Connect

We report on the first deep, direct search for a magnetic field via the circular polarization of Zeeman splitting in a Wolf-Rayet (W-R) star. Using the highly efficient ESPaDOnS spectropolarimeter at the Canada-France-Hawaii Telescope, we observed at three different epochs one of the best W-R candidates in the sky expected to harbor a magnetic field, the bright, highly variable WN4 star EZ CMa = WR6 = HD 50896. We looked for the characteristic circular polarization (Stokes V) pattern in strong emission lines that would arise as a consequence of a global, rotating magnetic field with a split monopole configuration. We also obtained nearly simultaneous linear polarization spectra (Stokes Q and U), which are dominated by electron scattering, most likely from a flattened wind with large-scale corotating structures. As the star rotates with a period of 3.766 days, our view of the wind changes, which in turn affects the value of the linear polarization in lines versus continuum at the {approx}0.2% level. Depending on the epoch of observation, our Stokes V data were affected by significant crosstalk from Stokes Q and U to V. We removed this spurious signal from the circular polarization data and experimented with various levels of spectral binning to increase the signal-to-noise ratio of our data. In the end, no magnetic field is unambiguously detected in EZ CMa. Assuming that the star is intrinsically magnetic and harbors a split monopole configuration, we find an upper limit of B {approx} 100 G for the intensity of its field in the line-forming regions of the stellar wind.

De la Chevrotiere, A.; St-Louis, N.; Moffat, A. F. J. [Departement de Physique, Universite de Montreal and Centre de Recherche en Astrophysique du Quebec (CRAQ), C. P. 6128, succ. centre-ville, Montreal (Quebec) H3C 3J7 (Canada)] [Departement de Physique, Universite de Montreal and Centre de Recherche en Astrophysique du Quebec (CRAQ), C. P. 6128, succ. centre-ville, Montreal (Quebec) H3C 3J7 (Canada); Collaboration: MiMeS Collaboration

2013-02-20

388

Numerical Studies of Flow Past Two Side-by-Side Circular Cylinders  

NASA Astrophysics Data System (ADS)

Multiple circular cylindrical configurations are widely used in engineering applications. The fluid dynamics of the flow around two identical circular cylinders in side-by-side arrangement has been investigated by both experiments and numerical simulations. The center-to-center transverse pitch ratio T/D plays an important role in determining the flow features. It is observed that for 1 < T/D < 1.1 to 1.2, a single vortex street is formed; for 1.2< T/D < 2 to 2.2, bi-stable narrow and wide wakes are formed; for 2.7< T/D < 4 or 5, anti-phase or in-phase vortex streets are formed. In the current study, the vortex structures of turbulent flows past two slightly heated side-by-side circular cylinders are investigated employing the large eddy simulation (LES). Simulations are performed using a commercial CFD software, FLUENT. The Smagorinsky-Lilly subgrid-scale model is employed for the large eddy simulation. The Reynolds number based on free-stream velocity and cylinder diameter is 5 800, which is in the subcritical regime. The transverse pitch ratio T/D = 3 is investigated. Laminar boundary layer, transition in shear layer, flow separation, large vortex structures and flow interference in the wake are all involved in the flow. Such complex flow features make the current study a challenging task. Both flow field and temperature field are investigated. The calculated results are analyzed and compared with experimental data. The simulation results are qualitatively in accordance with experimental observations. Two anti-phase vortex streets are obtained by the large-eddy simulation, which agrees with the experimental observation. At this transverse pitch ratio, these two cylinders behave as independent, isolated single cylinder in cross flow. The time-averaged streamwise velocity and temperature at x/D=10 are in good agreement with the experimental data. Figure1 displays the instantaneous spanwise vorticity at the center plane.

Shao, J.; Zhang, C.

389

Properties of circularly polarized vortex beams.  

PubMed

The properties of circularly polarized vortex beams in cylindrical polarization bases are studied. A circularly polarized vortex beam is decomposed into radial and azimuthal polarization. With the proper combination of vortex charge and the handedness of the circular polarization, a focal field with an extremely strong longitudinal component as well as a flat-topped profile can be obtained. The cylindrical decomposition also sheds light on the connections between orbital angular momentum and the spin of the light beams. PMID:16599194

Zhan, Qiwen

2006-04-01

390

Element-specific magnetic hysteresis measurements, a new application of circularly polarized soft x-rays  

SciTech Connect

Element-specific magnetic hysteresis measurements on heteromagnetic materials have been achieved by using circularly polarized soft-x- rays. Dramatically different Fe and Co hysteresis curves of Fe/Cu/Co trilayers were obtained by recording the magnetic circular dichroism (MCD) at their respective L{sub 3} white lines as a function of applied magnetic field. The data resolve the complicated hysteresis curves, observed by conventional magnetometry, and determine the individual magnetic moments for the Fe and Co layers. Fine hysteresis features, imperceptible in the conventional curves, were also observed, demonstrating a new application of circularly polarized soft-x-rays in the investigation of magnetic systems.

Lin, H.J.; Chen, C.T.; Meigs, G. [AT and T Bell Labs., Murray Hill, NJ (United States); Idzerda, Y.U.; Chaiken, A.; Prinz, G.A. [Naval Research Lab., Washington, DC (United States); Ho, G.H. [Pennsylvania Univ., Philadelphia, PA (United States). Dept. of Physics

1993-09-07

391

Circular permutant GFP insertion folding reporters  

DOEpatents

Provided are methods of assaying and improving protein folding using circular permutants of fluorescent proteins, including circular permutants of GFP variants and combinations thereof. The invention further provides various nucleic acid molecules and vectors incorporating such nucleic acid molecules, comprising polynucleotides encoding fluorescent protein circular permutants derived from superfolder GFP, which polynucleotides include an internal cloning site into which a heterologous polynucleotide may be inserted in-frame with the circular permutant coding sequence, and which when expressed are capable of reporting on the degree to which a polypeptide encoded by such an inserted heterologous polynucleotide is correctly folded by correlation with the degree of fluorescence exhibited.

Waldo, Geoffrey S. (Santa Fe, NM); Cabantous, Stephanie (Los Alamos, NM)

2011-06-14

392

Circular permutant GFP insertion folding reporters  

SciTech Connect

Provided are methods of assaying and improving protein folding using circular permutants of fluorescent proteins, including circular permutants of GFP variants and combinations thereof. The invention further provides various nucleic acid molecules and vectors incorporating such nucleic acid molecules, comprising polynucleotides encoding fluorescent protein circular permutants derived from superfolder GFP, which polynucleotides include an internal cloning site into which a heterologous polynucleotide may be inserted in-