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1

Two-dimensional flow through large numbers of circular inhomogeneities  

Microsoft Academic Search

An implicit analytic solution is presented for two-dimensional groundwater flow through a large number of non-intersecting circular inhomogeneities in the hydraulic conductivity. The locations, sizes and conductivity of the inhomogeneities may be arbitrarily selected. The influence of each inhomogeneity is expanded in a series that satisfies the Laplace equation exactly. The unknown coefficients in this expansion are related to the

R. Barnes; I. Jankovi?

1999-01-01

2

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

3

Large Scale Quantum Coherence of Nearly Circular Wavepackets  

SciTech Connect

We demonstrate that the quantum coherence of mesoscopic very-high-n, n {approx} 305, Rydberg wave packets travelling along nearly circular orbits can be maintained on microsecond time scales corresponding to hundreds of classical orbital periods. The coherence is probed through collapses and revivals of periodic oscillations in the average electron position. The temporal interferences of spatially separated Schroedinger cat-like wave packets are also observed. A novel hybrid quantum-classical trajectory method is employed to simulate the wave packet dynamics.

Reinhold, Carlos O [ORNL; Yoshida, S. [Vienna University of Technology, Austria; Burgdorfer, J. [Vienna University of Technology, Austria; Wyker, B. [Rice University; Mestayer, J. J. [Rice University; Dunning, F. B. [Rice University

2009-01-01

4

Observation of circular dichroism in photoelectron angular distributions  

SciTech Connect

The first observations of dichroic effects in photoelectron angular distributions are reported for photoionization of aligned molecular excited states with circularly polarized light. Photoelectron angular distributions resulting from the two-color, (2+1) REMPI of NO via the A /sup 2/summation/sup +/, v = 0, J = 3/2,5/2 excited states exhibit significant left--right asymmetry. The experimental CD angular distributions are found to be well described by the general theoretical framework recently developed by Dubs, Dixit, and McKoy and are in good qualitative agreement with their calculated REMPI--CD distributions.

Appling, J.R.; White, M.G.; Orlando, T.M.; Anderson, S.L.

1986-12-01

5

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

6

Circular Base Plates with a Gap under Large Eccentric Load  

Microsoft Academic Search

Circular base plates are commonly used for cylindrical columns; such as pylons in cabled-stayed bridges, lighting poles, electric power line posts, and even buildings. In some structures and conditions, a little gap is considered between base plate and foundation. In this case, the whole forces are transmitted to the foundation via bolts. There are several explicit methods for design of

A. A. Gholampour; M. Naghipour; A. Sobati

2012-01-01

7

Circular mitochondrial genome of Candida albicans contains a large inverted duplication.  

PubMed Central

The mitochondrial DNA (mtDNA) of the dimorphic fungus Candida albicans has a molecular size of 41 kilobase pairs as judged by summation of the fragment sizes produced by digestion with restriction endonucleases EcoRI, PvuII, and a combination of both enzymes. Five of the six EcoRI fragments comprising the mitochondrial genome have been cloned into the plasmid vector, pBR322. Restriction mapping revealed a circular map as predicted by previous observations with the electron microscope. The use of nick-translated, purified mtDNA to probe digests of mtDNA from other strains of C. albicans revealed a common restriction pattern. Use of nick-translated, cloned EcoRI fragments to probe digests of mtDNA revealed a large (at least 5 kilobase pairs), inverted duplication as well as a smaller (less than 0.4 kilobase pairs) region of related sequences. Images

Wills, J W; Troutman, W B; Riggsby, W S

1985-01-01

8

Electromagnetic Response of a Large Circular Loop Source on a Layered Earth: A New Computation Method  

Microsoft Academic Search

— Integral expressions of electromagnetic (EM) field components due to a large circular loop source carrying an alternating (ac) current and placed on or above the surface of a layered earth model are transformed to such suitable forms that facilitate numerical computation of field response in quasi-static as well as non-quasi-static regions. The improper integrals occurring in expressions of EM

Nagendra Pratap Singh; Toru Mogi

2005-01-01

9

Circular, linear, and curvilinear vection in a large-screen virtual environment with floor projection  

Microsoft Academic Search

Vection is defined as the compelling sensation of illusory self-motion elicited by a moving sensory, usually visual, stimulus. This paper presents collected introspective data, user discomfort and perceived speed data for the experience of linear, circular, and curvilinear vection in a large-screen, immersive, virtual environment. As a first step we evaluated the effectiveness of a floor projection on the perception

Laura C. Trutoiu; Betty J. Mohler; Jörg Schulte-Pelkum; Heinrich H. Bülthoff

2009-01-01

10

Numerical and modeling influences on large eddy simulations for the flow past a circular cylinder  

Microsoft Academic Search

In the present work the turbulent flow past a circular cylinder (Re=3900) was computed by large eddy simulation (LES). The objective was not to investigate the physical phenomena of this flow in detail but to study numerical as well as modeling aspects which influence the quality of LES solutions. Concerning the numerical method the most important component is the discretization

Michael Breuer

1998-01-01

11

Circular, linear, and curvilinear vection in a large-screen virtual environment with floor projection  

Microsoft Academic Search

Vection is defined as the compelling sensation of illusory self-motion elicited by a moving sensory, usually visual, stimulus. This paper presents collected introspective data, user discomfort and perceived speed data for the experience of linear, circular, and curvilinear vection in a large-screen, immersive, virtual environment. As a first step we evaluated the effectiveness of a floor projection on the perception

Laura C. Trutoiu; Betty J. Mohler; Heinrich H. Bulthoff; Max Planck

12

An Electrically Large Metallic Cavity Antenna With Circular Polarization for Satellite Applications  

Microsoft Academic Search

An electrically large metallic cavity antenna with circular polarization (CP) is proposed in this letter. The aim is to increase the size of satellite antennas working in the Ku-band and other higher-frequency bands through low cost and easy fabrication. A brass C-band antenna prototype is designed, fabricated, and measured for concept verification. The overall dimensions of the antenna are $0.67\\\\lambda_{0}\\\\times

Yang Zhao; Zhijun Zhang; Zhenghe Feng

2011-01-01

13

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

NASA Astrophysics Data System (ADS)

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

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

2002-12-01

14

Observations of Kelvin-Helmholtz instability at the air-water interface in a circular domain  

NASA Astrophysics Data System (ADS)

We present an analysis of Kelvin-Helmholtz instability in a circular domain in the limit of the azimuthal integer wavenumber, n --> ? which reproduces the classical results for a rectilinear geometry at the rim, provided that the additional condition that the surface current to surface wind ratio is (?1/?2)1/2 where ?1 and ?2 are respectively the densities of air and water, is satisfied. Experiments were carried out in a circular rig of radius 0.19 m in which a family of unstable waveforms with n ~ 60 were observed with properties (including the additional condition) in approximate agreement with theory. The additional condition is consistent with the absence of a surface shear stress in the instability process.

Bye, John A. T.; Ghantous, Malek

2012-03-01

15

Fermi Observations of the Large Magellanic Cloud  

NASA Astrophysics Data System (ADS)

We report on observations of the Large Magellanic Cloud (LMC) with the Fermi Gamma-Ray Space Telescope. The LMC is clearly detected with the Large Area Telescope (LAT) and for the first time the emission is spatially well resolved in gamma-rays. Our observations reveal that the bulk of the gamma-ray emission arises from the 30 Doradus region. We discuss this result in light of the massive star populations that are hosted in this area and address implications for cosmic ray physics. We conclude by exploring the scientific potential of the ongoing Fermi observations on the study of high-energy phenomena in massive stars.

Knödlseder, J.

2010-05-01

16

Large-scale structures in the wake of a circular cylinder  

NASA Astrophysics Data System (ADS)

The authors have reported (1984) that the two-dimensional Karman vortices behind a circular cylinder with diameter d are broken into lengths of about 8(d) and they form chains of spoon-shaped vortex couples. In the present experiment, disks were attached to the cylinder so that the Karman vortices were artificially cut to fixed lengths of 4(d), 6(d), 8(d), and 10(d). The structures with 8(d) were most stable forming a vortex chain with least irregularities, and the wake was much wider than without the disks, while the neighboring vortices with a length 4(d) merged to a scale of 8(d). These results show that the length 8(d) is a unique scale in the deformation of the Karman vortices to a three-dimensional large scale structure.

Yamane, Ryuichiro; Mochimaru, Yoshihiro; Yagita, Miki; Tanaka, Yutaka; Shirakashi, Masataka

1986-11-01

17

Capacity of the circular plate condenser: analytical solutions for large gaps between the plates  

NASA Astrophysics Data System (ADS)

A solution of Love's integral equation (Love E R 1949 Q. J. Mech. Appl. Math. 2 428), which forms the basis for the analysis of the electrostatic field due to two equal circular co-axial parallel conducting plates, is considered for the case when the ratio, ?, of distance of separation to radius of the plates is greater than 2. The kernel of the integral equation is expanded into an infinite series in odd powers of 1/? and an approximate kernel accurate to {\\cal O}(\\tau^{-(2N+1)}) is deduced therefrom by terminating the series after an arbitrary but finite number of terms, N. The approximate kernel is rearranged into a degenerate form and the integral equation with this kernel is reduced to a system of N linear equations. An explicit analytical solution is obtained for N = 4 and the resulting analytical expression for the capacity of the circular plate condenser is shown to be accurate to {\\cal O}(\\tau^{-9}) . Analytical expressions of lower orders of accuracy with respect to 1/? are deduced from the four-term (i.e., N = 4) solution and predictions (of capacity) from the expressions of different orders of accuracy (with respect to 1/?) are compared with very accurate numerical solutions obtained by solving the linear system for large enough N. It is shown that the {\\cal O}(\\tau^{-9}) approximation predicts the capacity extremely well for any ? >= 2 and an {\\cal O}(\\tau^{-3}) approximation gives, for all practical purposes, results of adequate accuracy for ? >= 4. It is further shown that an approximate solution, applicable for the case of large distances of separation between the plates, due to Sneddon (Sneddon I N 1966 Mixed Boundary Value Problems in Potential Theory (Amsterdam: North-Holland) pp 230-46) is accurate to {\\cal O}(\\tau^{-6}) for ? >= 2.

Rao, T. V.

2005-11-01

18

Linking Very Large Telescope asteroid observations  

NASA Astrophysics Data System (ADS)

A novel method for the preliminary identification of asteroids at discovery and a few days thereafter is being developed in Helsinki. Having two different sets of asteroid observations, the goal is to identify all possible pairs of objects between the sets. An arbitrary asteroid can either remain unidentified, or be preliminary linked to one or more asteroids. In the case of ambiguity, the final decision must usually be based on additional observations. We use a multistep approach, during which possible pairs of objects are first selected by comparing ephemerides that have been generated for three common epochs. The method has been successfully tested using both Very Large Telescope observations, and simulated observations of near-Earth and main-belt objects. Identification results of simulated observations indicate that the observing strategy promoted by the Minor Planet Center might not be the best one, at least for the purposes of identification. The ultimate goal is to produce a real-time asteroid identification tool for ESA's astrometric space observatory Gaia, the Lowell Observatory Near-Earth-Object Search, the Near-Earth Space Surveillance mission, and the Nordic Near-Earth Object Network. The tool could also benefit large-scale surveys done with the Large Synoptic Survey Telescope, and the Discovery Channel Telescope.

Granvik, M.; Muinonen, K.; Virtanen, J.; Delbó, M.; Saba, L.; de Sanctis, G.; Morbidelli, R.; Cellino, A.; Tedesco, E.

2005-02-01

19

GEOMECHANICAL OBSERVATIONS DURING THE LARGE BLOCK TEST  

SciTech Connect

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

STEPHEN C. BLAIR AND STEPHANIE A. WOOD

1998-04-10

20

Infrasonic observations of large scale HE events  

SciTech Connect

The Los Alamos Infrasound Program has been operating since about mid-1982, making routine measurements of low frequency atmospheric acoustic propagation. Generally, we work between 0.1 Hz to 10 Hz; however, much of our 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. This discussion will concentrate on measurements of large, high explosive (HE) events at ranges of 250 km to 5330 km. Because the equipment is well suited for mobile deployments, it can easily establish temporary observing sites for special events. The measurements in this report are from our permanent sites, as well as from various temporary sites. In this short report will not give detailed data from all sites for all events, but rather will present a few observations that are typical of the full data set. The Defense Nuclear Agency sponsors these large explosive tests as part of their program to study airblast effects. A wide variety of experiments are fielded near the explosive by numerous Department of Defense (DOD) services and agencies. This measurement program is independent of this work; use is made of these tests as energetic known sources, which can be measured at large distances. Ammonium nitrate and fuel oil (ANFO) is the specific explosive used by DNA in these tests. 6 refs., 6 figs.

Whitaker, R.W.; Mutschlecner, J.P.; Davidson, M.B.; Noel, S.D.

1990-01-01

21

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...

22

Local circular polarization observed in surface vortices of optical near-fields.  

PubMed

We demonstrate local circular polarization in surface vortices of an optical near-field generated by superposing two cross-propagating evanescent waves with transverse electric fields on a planar dielectric surface. The circularly rotating local electric fields are converted into circularly polarized propagating light waves in free space via a near-field interaction with a sub-wavelength size local probe. The results show that optical near-fields generated under the influence of a material environment with local rotational symmetry carry angular pseudo-momentum with respect to the symmetry axis. The local circular polarization is of fundamental significance in spin-related and magneto-optical phenomena in nanophotonics. PMID:18542376

Ohdaira, Y; Inoue, T; Hori, H; Kitahara, K

2008-03-01

23

A new frequency formula for closed circular cylindrical shells for a large variety of boundary conditions  

Microsoft Academic Search

A new formula for the natural frequencies of circular cylindrical shells is presented for modes in which transverse deflections dominate. It is valid for all boundary conditions for which the roots of the analogous beam problem can be obtained. Good agreement with experimental data for a variety of boundary conditions is shown.

W. Scedel

1980-01-01

24

Modular hybrid architecture for a large aperture circularly polarized shaped-beam antenna  

Microsoft Academic Search

In this work the design, manufacturing procedure, and testing of a 6.4 meter long antenna for X-band airport surveillance radar applications is presented. This antenna operates with circular polarisation and produces a cosecant-squared shaped beam pattern in the elevation plane. To reduce manufacturing costs, the antenna has a modular architecture consisting of a number of identical microstrip subarray panels connected

Giacomo Guarnieri; Giuseppe Mauriello; Guido Biffi Gentili; Andrea Vallecchi

2009-01-01

25

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

NASA Astrophysics Data System (ADS)

Surface hardness tests such as Shore hardness (SH) and Schmidt hammer rebound hardness (SR) may provide a quick and inexpensive measure of rock hardness, which may be widely used for estimating the mechanical properties of rock material such as strength, sawability, drillability and cuttability. In the marble industry, circular sawing with diamond sawblades constitutes a major cost in the processing. Therefore, several models based on the relations between hourly slab production ( P hs), rock surface hardness (SH and SR) and mineral grain size ( S cr) were developed using the data obtained from field and laboratory measurements on five different marbles quarried in the Mugla Province of Turkey. The models which include surface hardness and crystal size may as well be used for the prediction of sawability (hourly slab production) of carbonate rocks using large-diameter circular saws.

Güney, Avni

2011-05-01

26

Observation of Spin Helicity Using Nonresonant Circularly Polarized X-ray Diffraction Analysis  

NASA Astrophysics Data System (ADS)

We have successfully detected spin chirality in prototypical multiferroic MnWO4 wherein the helical magnetic order induces ferroelectricity using a nonresonant circularly polarized X-ray diffraction technique. The intensity of the magnetic reflection from MnWO4 shows a clear difference between the right- and left-handed circular polarizations of the incident X-ray beam. The ratio of these intensities is in good agreement with theoretical predictions. The results clearly show that this technique is suitable for the investigation of spin chirality. Finally, we studied the spin chirality of another multiferroic material, DyMnO3. Possible applications of this technique are also discussed.

Sagayama, Hajime; Abe, Nobuyuki; Taniguchi, Kouji; Arima, Taka-hisa; Yamasaki, Yuichi; Okuyama, Daisuke; Tokura, Yoshinori; Sakai, Souichiro; Morita, Takeshi; Komesu, Takashi; Ohsumi, Hiroyuki; Takata, Masaki

2010-04-01

27

Visual Observations of the Flow past a Circular Cylinder Performing a Rotatory Oscillation  

Microsoft Academic Search

The flow around a circular cylinder performing a rotatory oscillation about its axis in a uniform flow has been investigated experimentally by means of flow visualization methods at Reynolds numbers between 30 and 300 and Strouhal numbers between 0 and 55. It has been found that the dead water region is reduced as the frequency of the oscillation is increased,

Sadatoshi Taneda

1978-01-01

28

Compressible turbulent flows in long circular cross-section diffusers of large area ratio  

NASA Astrophysics Data System (ADS)

A computational method based on the boundary-layer concept is proposed for calculating compressible, turbulent flows in circular cross-section diffusers. The present work overcomes the limitations of older methods. Its effectiveness in predicting diffuser flows is mainly due to the application of the Cebeci-Smith turbulence model in conjunction with the use of the Coles velocity profiles. The influence of the basic flow parameters on flow separation is discussed. An extensive comparison with experiment is presented; this includes pressure distributions, boundary-layer properties, velocity profiles in different cross sections and, in the case of a recent experiment, turbulent shear stresses.

Stock, H.-W.

1985-06-01

29

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

Microsoft Academic Search

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

Delong Zuo; Nicholas P. Jones

2009-01-01

30

Forced convection flow past a circular cylinder and a sphere in a Darcian fluid at large Peclet numbers  

SciTech Connect

Heat transfer in saturated porous media has received considerable attention in recent years because of its important applications in geophysics and energy related engineering problems. These include the control of pollutant spread in groundwater, compact heat exchangers, solar power collectors, and high performance insulation for buildings and many more. Here, an analysis is made for the steady heat transfer from a circular cylinder and a sphere embedded in a fluid-saturated porous medium. Analytical solutions for large Peclet numbers are obtained when the cylinder and the sphere are maintained at constant temperatures. The solutions are compared with known results from open literature and found to be in excellent agreement.

Pop, I. [Univ. of Cluj (Romania). Faculty of Mathematics; Yan, B. [Univ. of East Anglia, Norwich (United Kingdom). School of Mathematics

1998-02-01

31

A large circular minichromosome of Schizosaccharomyces pombe requires a high dose of type II DNA topoisomerase for its stabilization  

Microsoft Academic Search

We have constructed circular minichromosomes, ranging in size from 36 to 110 kb, containing the centromeric repeats of Schizosaccharomyces pombe cen3. Comparison of their mitotic stability showed that the circular minichromosomes became more unstable with increasing in size, however, a linear cen3 minichromosome, which is almost the same size as the largest circular one tested, does not show such instability.

Shin Murakami; Mitsuhiro Yanagida; Osami Niwa

1995-01-01

32

The characteristic negative Cotton effect of ganglioside lactones observed by circular dichroism spectrometry.  

PubMed

Circular dichroism spectrometry was applied to gangliosides and their lactones and revealed that the lactones have a characteristic strong negative Cotton effect around 235 nm. Four monolactones and two dilactones, which were formed from GM4, GD3, and GD1b, gave molar ellipticities at the wavelength in magnitude of 10(4), while their parent gangliosides, along with other gangliosides such as GM3, GM1, GD1a, GT1b, and GQ1b, showed no distinct feature. Two ganglioside esters, GM4-methyl ester and O-Ac-GT1b did not show the Cotton effect. The molar ellipticities had an additivity with respect to the number of lactone rings. The Cotton effect was attributed to the carbonyl group on the lactone ring. PMID:1514681

Terabayashi, T; Tsuda, M; Kawanishi, Y

1992-07-01

33

Observation of magnetic moments at the interface region in magnetic tunnel junctions using depth-resolved x-ray magnetic circular dichroism  

NASA Astrophysics Data System (ADS)

The depth-resolved x-ray magnetic circular dichroism (XMCD) technique was applied to observe the interfacial and inner magnetic moments in CoFe/MgO and Co2MnSi(CMS)/MgO. The magnetic moments of the real interface region (two monolayers from the interface) and the inner layers were separately analyzed using the XMCD sum rules. The observed interfacial moments of Co at the CMS/MgO interface show a remarkable reduction from that in the inner layers compared with the CoFe/MgO structure, suggesting small exchange stiffness in the CMS at the MgO interface. The weak exchange stiffness of Co is a possible reason for the large temperature dependence of tunnel magnetoresistance in CMS-based magnetic tunnel junctions.

Tsunegi, S.; Sakuraba, Y.; Amemiya, K.; Sakamaki, M.; Ozawa, E.; Sakuma, A.; Takanashi, K.; Ando, Y.

2012-05-01

34

Centimeter Band Observations of Circular Polarization in Flaring Blazars from the Effelsberg and Michigan Programs  

NASA Astrophysics Data System (ADS)

A program to study the centimeter-band spectral variability in Stokes V with the Michigan 26-meter radio telescope (Astrophys. Sp. Sc., 288, 17, 2003) has provided evidence for polarity changes and wavelength-dependent variability; this work has been restricted to time-averaged data for a small subset of strong sources because of the low levels of circularly polarized emission. A new calibration technique has recently been developed which yields high-accuracy full-Stokes data from measurements obtained with the Effelsberg 100-m radio telescope (Astron. Astrophys., 498, 591, 2009). This capability is important since it permits study of Stokes V emission from a wide range of sources and a search for variations on rapid time scales. As a test of the achieved accuracy, we have compared coeval 5 GHz measurements obtained in 2007 from the two radio telescopes. We present multi-epoch data for three program sources -- 3C84, 3C279, and 2145+067 -- which illustrate that excellent agreement in polarity and amplitude is attained. UMRAO is supported in part by NSF grant AST-0607523 and by funds from the University of Michigan. E. C. is supported by a grant from the EU Framework 6 Marie Curie Early Training Programme under contract MEST-CT-2005-19669``ESTRELA''.

Aller, Margo F.; Aller, H. D.; Cenacchi, E.; Kraus, A.; Mack, K. H.; Krichbaum, T. P.

2010-01-01

35

Multiplex amplification enabled by selective circularization of large sets of genomic DNA fragments  

Microsoft Academic Search

We present a method to specifically select large sets of DNA sequences for parallel amplification by PCR using target-specific oligonucleotide constructs, so-called selectors. The selectors are oligonucleotide duplexes with single-stranded target-complementary end-sequences that are linked by a general sequence motif. In the selection process, a pool of selectors is combined with denatured restriction digested DNA. Each selector hybridizes to its

Fredrik Dahl; Mats Gullberg; Johan Stenberg; Ulf Landegren; Mats Nilsson

2005-01-01

36

Fast Na+ current in circular smooth muscle cells of the large intestine.  

PubMed

Whole-cell voltage clamp was carried out on freshly dispersed single smooth muscle cells from adult rat and human colons to investigate the regulation of the Ca2+ channels. In this study, we unexpectedly discovered the existence of a fast Na+ channel current. With normal physiological salt solution (PSS) plus 4-amino-pyridine (3 mM) in the bath and high-Cs+ solution in the pipette to inhibit outward K+ currents, an inward current possessing fast and slow components was observed when the cell membrane was depolarized to a value more positive than -20 mV from a holding potential of -100 mV. When Ca2+ ions were removed from the PSS, or when nifedipine (10 microM) and Ni2+ (30 microM) were simultaneously applied, the slow component disappeared and the fast component remained. The fast current component became almost completely inactivated within 10 ms. This fast component was dependent on extracellular Na+ concentration and was inhibited by tetrodotoxin (TTX) dose dependently (IC50 of 130 nM in rat and 14 nM in human). These results suggest that the slow component of inward current was a Ca2+ channel current, whereas the fast component was a TTX-sensitive fast Na+ channel current. The threshold voltage, the voltage for peak current, and the reversal potential for the fast Na+ current were, respectively, about -50, -20, and +50 mV in rats, and -40, 0, and +60 mV in humans. The incidence of cells possessing fast Na+ currents depended on the region of the colon.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:8394569

Xiong, Z; Sperelakis, N; Noffsinger, A; Fenoglio-Preiser, C

1993-06-01

37

Observation of x-ray absorption magnetic circular dichroism in well-characterized iron-cobalt-platinum multilayers  

SciTech Connect

Magnetic circular dichroism in the Fe 2p x-ray absorption is observed in multilayers of(Fe9.5{Angstrom}/Pt9.5{Angstrom}){sub 92}. The magnetization and helicity are both in the plane of this multilayer which is prepared by magnetron sputter deposition. This sample is part of a study to examine magnetization in the ternary multilayer system of FeCo/Pt. Lattice and layer pair spacings are measured using x-ray scattering. The atomic concentration profiles of the multilayer films are characterized using Auger electron spectroscopy coupled with depth profiling. Conventional and high resolution transmission electron microscopy are used to examine the thin film, growth morphology and atomic structure.

Jankowski, A.F.; Waddill, G.D.; Tobin, J.G.

1993-04-01

38

Very Large Array (V.L.A.) Observations of Solar Active Regions.  

National Technical Information Service (NTIS)

High resolution radio wavelength observations of solar active regions indicate ever present, fine scale features whose high degree of circular polarization reflects the magnetic field structure in the solar corona. Changes in this structure may trigger ma...

K. R. Lang

1979-01-01

39

Very large array observations of solar active regions  

Microsoft Academic Search

Observations of solar active regions with the Very Large Array have led to a new understanding of the origin and prediction of the solar bursts which disrupt communication systems and interfere with high-flying aircraft. The detailed temperature, density and magnetic structure of coronal loops have been investigated by using observations at 20 cm wavelength. By studying loop evolution on time

K. R. Lang

1984-01-01

40

Observations of the Large Magellanic Cloud with Fermi  

Microsoft Academic Search

Context. The Large Magellanic Cloud (LMC) is to date the only normal external galaxy that has been detected in high-energy gamma rays. High-energy gamma rays trace particle acceleration processes and gamma-ray observations allow the nature and sites of acceleration to be studied. Aims: We characterise the distribution and sources of cosmic rays in the LMC from analysis of gamma-ray observations.

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

2010-01-01

41

Design of Circular Base Plate under Large Bending Moment Which There Is a Little Gap between Base Plate and Foundation  

Microsoft Academic Search

Circular base plates are commonly used for cylindrical columns; such as pylons in cabled-stayed bridges, lighting poles, electric power line posts, and even buildings. In some structures a little gap is considered between base plate and foundation. In this case compressive bolts which transmit compressive forces to the foundation are also considered in design of base plate. The purpose of

A. A. Gholampour; M. Naghipour; A. Sobati

2010-01-01

42

The Atacama Large Millimeter Array: Observing the Distant Universe  

Microsoft Academic Search

Observations at millimeter and submillimeter wavelengths will be crucial for understanding galaxy formation and evolution in the early universe. Much of the star formation in the cosmos occurs in galaxies heavily obscured by dust, where optical and ultraviolet energy from young stars and AGNs is absorbed and re-emitted at far infrared\\/submillimeter wavelengths. When complete around 2012, the Atacama Large Millimeter

S. J. E. Radford

2005-01-01

43

Large scale testing and analysis of hybrid concrete\\/composite tubes for circular beam-column applications  

Microsoft Academic Search

Concrete-filled fiber reinforced polymer (FRP) circular tubes provide an effective structural system for a variety of applications such as piles, columns, overhead sign structures and utility poles. This paper discusses the behavior of concrete-filled Glass-FRP tubes ranging in diameter from 90 to 942 mm, using test results of eight beams, five columns and ten beam-column specimens. The effects of concrete

Amir Fam; Sami Rizkalla

2003-01-01

44

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

Microsoft Academic Search

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

Avni Güney

2011-01-01

45

High-resolution mesospheric sodium observations for extremely large telescopes  

NASA Astrophysics Data System (ADS)

Variations in density structure and altitude of mesospheric sodium impact the performance of adaptive optics systems employing sodium laser guide stars. The associated wave-front errors grow as the square of the telescope aperture and will be very significant for the next generation of large-aperture ground-based optical/infrared telescopes. To support the adaptive optics program for the Thirty Meter Telescope and European Extremely Large Telescope, we are conducting a program of sodium monitoring using a high-resolution sodium lidar system on the 6-meter Large Zenith Telescope (LZT). Located at 49°N latitude, the LZT lidar system provides density profiles with spatial and temporal resolution sampling of 4.8 m and 20 ms. In this paper we report highlights of results obtained over two years of observations.

Pfrommer, Thomas; Hickson, Paul

2010-07-01

46

FAST satellite observations of large-amplitude solitary structures  

Microsoft Academic Search

We report observations of ``fast solitary waves'' that are ubiquitous in downward current regions of the mid-altitude auroral zone. The single-period structures have large amplitudes (up to 2.5 V\\/m), travel much faster than the ion acoustic speed, carry substantial potentials (up to ~100 Volts), and are associated with strong modulations of energetic electron fluxes. The amplitude and speed of the

R. E. Ergun; C. W. Carlson; J. P. McFadden; F. S. Mozer; G. T. Delory; W. Peria; C. C. Chaston; M. Temerin; I. Roth; L. Muschietti; R. Elphic; R. Strangeway; R. Pfaff; C. A. Cattell; D. Klumpar; E. Shelley; W. Peterson; E. Moebius; L. Kistler

1998-01-01

47

Thinking big: large-scale collaborative research in observational epidemiology  

Microsoft Academic Search

Efforts to identify risk factors for chronic diseases have tended to involve observational studies characterised by relatively\\u000a few disease outcomes. In the absence of individual studies of sufficiently large size, synthesis of available evidence from\\u000a multiple smaller studies can help enhance statistical power and aid appropriate interpretation. While meta-analyses of published\\u000a findings can help prioritize research hypotheses, they are inherently

Alexander Thompson

2009-01-01

48

The microwave radiation of the corona above a large single sunspot in right- and left-circular polarization  

NASA Astrophysics Data System (ADS)

Results of a study of the corona above a large sunspot in the active region NOAA 10105 with a penumbra size of ˜70? observed in September 2002 are reported. Maps of the active region and emission spectra were constructed using observational data from the NoRH, SSRT, and RATAN-600 telescopes. The sizes and brightness temperatures of the microwave emission above the sunspot are determined. SOHO/MDI and Kitt Peak magnetograms, as well as CaII K line images obtained at the Meudon Observatory, are compared. The derived characteristics are interpreted as cyclotron emission of thermal plasma, assuming a dipole structure for themagnetic field. A stable darkening at the sunspot center observed at short wavelengths and only in the ordinary emission mode was detected. A jump-like change was observed in the structure of the sunspot source in the ordinary emission mode, due to an increase in the size and spectral flux density. These results demand a fundamental correction of model concepts about cyclotron emission sources above sunspots, since they are at variance with the initial assumptions. It is suggested that, at the top of the transition region, the cyclotron emission source may be represented only by the third gyrolevel, but is observed in the extraordinary and ordinary emission modes (in contrast to the generally accepted model, which has a combination of the second and third gyrolevels). Taking into account the new observational data may allow us to refine model distributions of the main parameters of the coronal plasma above sunspots (the electron temperature and density) and information about the character of the magnetic field.

Topchilo, N. A.; Peterova, N. G.; Borisevich, T. P.

2010-01-01

49

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

50

Probing large-scale structure with radio observations  

NASA Astrophysics Data System (ADS)

This thesis focuses on detecting magnetized relativistic plasma in the intergalactic medium (IGM) of filamentary large-scale structure (LSS) by observing synchrotron emission emitted by structure formation shocks. Little is known about the IGM beyond the largest clusters of galaxies, and synchrotron emission holds enormous promise as a means of probing magnetic fields and relativistic particle populations in these low density regions. I'll first report on observations taken at the Very Large Array and the Westerbork Synthesis Radio Telescope of the diffuse radio source 0809+39. I use these observations to demonstrate that 0809+39 is likely the first "radio relic" discovered that is not associated with a rich |"X-ray emitting cluster of galaxies. I then demonstrate that an unconventional reprocessing of the NVSS polarization survey can reveal structures on scales from 15' to hundreds of degrees, far larger than the nominal shortest-baseline scale. This yields hundreds of new diffuse sources as well as the identification of a new nearby galactic loop . These observations also highlight the major obstacle that diffuse galactic foreground emission poses for any search for large-scale, low surface- brightness extragalactic emission. I therefore explore the cross-correlation of diffuse radio emission with optical tracers of LSS as a means of statistically detecting the presence of magnetic fields in the low-density regions of the cosmic web. This initial study with the Bonn 1.4 GHz radio survey yields an upper limit of 0.2 mG for large-scale filament magnetic fields. Finally, I report on new Green Bank Telescope and Westerbork Synthesis Radio Telescope observations of the famous Coma cluster of galaxies. Major findings include an extension to the Coma cluster radio relic source 1253+275 which makes its total extent ~2 Mpc, as well as a sharp edge, or "front", on the Western side of the radio halo which shows a strong correlation with merger activity associated with an infalling sub-cluster. This front is just interior to a temperature jump derived from XMM-Newton observations, and may be related to shocked infalling gas.

Brown, Shea D.

51

Observation of x-ray magnetic circular dichroism at the Ru K edge in Co-Ru alloys  

SciTech Connect

X-ray magnetic circular dichroism spectra have been measured from dilute Ru alloys of Co at the Ru K edge, evidencing the induced magnetization on Ru in contact with ferromagnetic Co. This was made possible using circularly polarized probing beams of approximately 22 keV in energy obtained from a germanium Laue-reflection phase retarder at a synchrotron source. The Ru dichroism is quite small with a main peak of -3x10{sup -4} in flipping ratio at about 6 eV above the K absorption edge. The spectrum has a very similar profile to the one of the Co K-edge dichroism. Ab initio calculations indicate that the Ru dichroism is generated by the p-orbital magnetic moment on the core-hole site, which is induced through the p-d hybridization between Co and Ru.

Hashizume, H.; Ishiji, K.; Lang, J. C.; Haskel, D.; Srajer, G.; Minar, J.; Ebert, H. [Photon Factory, KEK, Tsukuba 305-0801 (Japan); Advanced Photon Source, Argonne National Laboratory, Argonne, Illinois 60439 (United States); Department Chemie und Biochemie, Physikalische Chemie, Universitaet Muenchen, Muenchen D-81377 (Germany)

2006-06-01

52

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.

Snyder, Lewis E.

2006-01-01

53

Satellite observations of large power plants and megacities from GOSAT  

NASA Astrophysics Data System (ADS)

Fossil fuel CO2 emissions are a major source of CO2 to the global carbon cycle over decadal time scales and international efforts to curb those missions are required for mitigating climate change. Although emissions from nations are estimated and reported to help monitor their compliance of emission reductions, we still lack an objective method to monitor emissions directly. Future carbon-observing space missions are thus expected to provide an independent tool for directly measuring emissions. We proposed and have implemented satellite observations specifically over intense large point sources (LPS), including large fossil-fueled power plants and megacities, worldwide (N > 300) using the Japanese Greenhouse Gases Observing SATelllite (GOSAT). Our target LPS sites have been occasionally included in the observation schedule of GOSAT and the measurements are made using the target observation mode. This proposal was officially accepted by the GOSAT project office and we have attempted to use these data to detect signatures of man-made greenhouse gas emissions. We have submitted our locations of interest on a monthly basis two month prior to observation. We calculated the X_CO2 concentration enhancement due to the LPS emissions. We analyzed GOSAT X_CO2 retrievals from four research groups (five products total): the National Institute for Environmental Studies (NIES) (both the NIES standard Level 2 and NIES-PPDF products), the NASA Atmospheric CO2 from Space (ACOS) team (ACOS Level 2 product), the Netherlands Institute for Space Research (SRON)/Karlsruhe Institute of Technology, Germany (RemoTeC), and the University of Leicester, UK (Full-Physics CO2 retrieval dataset). Although we obtained fewer retrieved soundings relative to what we requested (probably due to geophysical difficulties in the retrievals), we did obtain statistically significant enhancements at some LPS sites where weather condition were ideal for viewing. We also implemented simulations of enhanced X_CO2 using a global Eulerian-Lagrangian coupled atmospheric transport model (GELCA) and a high-resolution fossil fuel emissions dataset (Odiac). Odiac includes emissions information on the power plants requested in our target observations. Our model simulations tend to underestimate the enhancements, but showed good correlation with observed enhancements.

Oda, Tom; Maksyutov, Shamil; Boesch, Hartmut; Butz, Andre; Ganshin, Alexander; Guerlet, Sandrine; Parker, Robert; O'Dell, Chris; Oshchepkov, Sergey; Yoshida, Yukio; Zhuravlev, Ruslan; Yokota, Tatsuya

2013-04-01

54

Observations of the Large Magellanic Cloud with Fermi  

NASA Astrophysics Data System (ADS)

Context. The Large Magellanic Cloud (LMC) is to date the only normal external galaxy that has been detected in high-energy gamma rays. High-energy gamma rays trace particle acceleration processes and gamma-ray observations allow the nature and sites of acceleration to be studied. Aims: We characterise the distribution and sources of cosmic rays in the LMC from analysis of gamma-ray observations. Methods: We analyse 11 months of continuous sky-survey observations obtained with the Large Area Telescope aboard the Fermi Gamma-Ray Space Telescope and compare it to tracers of the interstellar medium and models of the gamma-ray sources in the LMC. Results: The LMC is detected at 33? significance. The integrated >100 MeV photon flux of the LMC amounts to (2.6 ± 0.2) × 10-7 ph cm-2 s-1 which corresponds to an energy flux of (1.6 ± 0.1) × 10-10 erg cm-2 s-1, with additional systematic uncertainties of ?16%. The analysis reveals the massive star forming region 30 Doradus as a bright source of gamma-ray emission in the LMC in addition to fainter emission regions found in the northern part of the galaxy. The gamma-ray emission from the LMC shows very little correlation with gas density and is rather correlated to tracers of massive star forming regions. The close confinement of gamma-ray emission to star forming regions suggests a relatively short GeV cosmic-ray proton diffusion length. Conclusions: The close correlation between cosmic-ray density and massive star tracers supports the idea that cosmic rays are accelerated in massive star forming regions as a result of the large amounts of kinetic energy that are input by the stellar winds and supernova explosions of massive stars into the interstellar medium.

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.; Blandford, R. D.; Bloom, E. D.; Bonamente, E.; Borgland, A. W.; Bregeon, J.; Brez, A.; Brigida, M.; Bruel, P.; Burnett, T. H.; Buson, S.; Caliandro, G. A.; Cameron, R. A.; Caraveo, P. A.; Casandjian, J. M.; Cecchi, C.; Çelik, Ö.; Chekhtman, A.; Cheung, C. C.; Chiang, J.; Ciprini, S.; Claus, R.; Cohen-Tanugi, J.; Cominsky, L. R.; Conrad, J.; Cutini, S.; Dermer, C. D.; de Angelis, A.; de Palma, F.; Digel, S. W.; Silva, E. Do Couto E.; Drell, P. S.; Dubois, R.; Dumora, D.; Farnier, C.; Favuzzi, C.; Fegan, S. J.; Focke, W. B.; Fortin, P.; Frailis, M.; Fukazawa, Y.; Fusco, P.; Gargano, F.; Gasparrini, D.; Gehrels, N.; Germani, S.; Giavitto, G.; Giebels, B.; Giglietto, N.; Giordano, F.; Glanzman, T.; Godfrey, G.; Gotthelf, E. V.; Grenier, I. A.; Grondin, M.-H.; Grove, J. E.; Guillemot, L.; Guiriec, S.; Hanabata, Y.; Harding, A. K.; Hayashida, M.; Hays, E.; Horan, D.; Hughes, R. E.; Jackson, M. S.; Jean, P.; Jóhannesson, G.; Johnson, A. S.; Johnson, R. P.; Johnson, T. J.; Johnson, W. N.; Kamae, T.; Katagiri, H.; Kataoka, J.; Kawai, N.; Kerr, M.; Knödlseder, J.; Kocian, M. L.; Kuss, M.; Lande, J.; Latronico, L.; Lemoine-Goumard, M.; Longo, F.; Loparco, F.; Lott, B.; Lovellette, M. N.; Lubrano, P.; Madejski, G. M.; Makeev, A.; Marshall, F.; Martin, P.; Mazziotta, M. N.; McConville, W.; McEnery, J. E.; Meurer, C.; Michelson, P. F.; Mitthumsiri, W.; Mizuno, T.; Moiseev, A. A.; Monte, C.; Monzani, M. E.; Morselli, A.; Moskalenko, I. V.; Murgia, S.; Nolan, P. L.; Norris, J. P.; Nuss, E.; Ohsugi, T.; Omodei, N.; Orlando, E.; Ormes, J. F.; Paneque, D.; 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.; Ritz, S.; Rodriguez, A. Y.; Romani, R. W.; Roth, M.; Ryde, F.; Sadrozinski, H. F.-W.; Sanchez, D.; Sander, A.; Saz Parkinson, P. M.; Scargle, J. D.; Sellerholm, A.; Sgrò, C.; Siskind, E. J.; Smith, D. A.; Smith, P. D.; Spandre, G.; Spinelli, P.; Starck, J.-L.; Strickman, M. S.; Strong, A. W.; Suson, D. J.; Tajima, H.; 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.; Venter, C.; Vilchez, N.; Vitale, V.; Waite, A. P.; Wang, P.; Weltevrede, P.; Winer, B. L.; Wood, K. S.; Ylinen, T.; Ziegler, M.

2010-03-01

55

Observation of circular dichroism in (001)-oriented P-I-N InGaAs/GaAs quantum wells without magnetic field  

NASA Astrophysics Data System (ADS)

The (001)-oriented P-I-N InGaAs/GaAs quantum wells (QWs) are studied by means of helicity dependent spin photocurrent. We have observed an unexpected circular dichroism effect along [001] direction in the QWs without an applied magnetic field. The circular polarization rate can be linearly tuned by the applied DC current flowing along [001] direction, and its value is enhanced more than one order in an InGaAs/GaAs vertical-cavity surface-emitting laser with distributed Bragg reflectors than that in a common InGaAs/GaAs QWs. This experiment indicates a type of spin-splitting in (001)-grown P-I-N InGaAs/GaAs quantum wells induced by space inversion asymmetry introduced by residual strain which is previously overlooked.

Yu, J. L.; Chen, Y. H.; Liu, Y.; Jiang, C. Y.; Ma, H.; Zhu, L. P.; Qin, X. D.

2013-02-01

56

Very large array observations of solar active regions  

NASA Astrophysics Data System (ADS)

Observations of solar active regions with the Very Large Array have led to a new understanding of the origin and prediction of the solar bursts which disrupt communication systems and interfere with high-flying aircraft. The detailed temperature, density and magnetic structure of coronal loops have been investigated by using observations at 20 cm wavelength. By studying loop evolution on time scales as short as 10 seconds and as long as days, we have obtained new information about preburst temperature enhancements and changes in the magnetic field topology which account for the release and source of burst energy. Multiple wavelength observations were carried out and combined to specify the three dimensional structure of the temperature, density and magnetic field in the solar atmosphere above active regions. This has helped resolve uncertainties in the coronal magnetic field strength, the temperature of the solar atmosphere above sunspots, the physical nature of the coronal loops, and the dominant radiation mechanisms at different levels in the solar atmosphere. We have also specified the positions, size evolution and magnetic structure of solar bursts, thereby obtaining new information about preburst heating, changing magnetic field configurations, and thes nearly simultaneous excitation of bursts at widely separated areas on the solar surface.

Lang, K. R.

1984-01-01

57

Magnetospheric observation of large sub-auroral electric fields  

SciTech Connect

An example of large sub-auroral poleward electric fields, similar to those observed on OGO-6, S3-2 and AE-C (recently referred to as SAID) has been found in the magnetosphere near L = 4 and 2300 MLT using ISEE-1 electric field data. The event is located adjacent to and outside the plasmapause and occurs 1 1/2 hours into a substorm. The event is accompanied by a significant penetration of the convection electric field inside the plasmasphere. Data from similar regions on the next orbit occurring near the beginning of a substorm did not exhibit these effects. Recent theoretical models predict SAID to occur in the trough regions, where substorm dynamics force currents to flow in regions of low conductivity: These models provide a first-order interpretation of this phenomena; however, the overall picture is more complex.

Maynard, N.C.; Aggson, T.L.; Heppner, J.P.

1980-11-01

58

Experimental observation of very large magnetoconductance in microbial nanowires  

NASA Astrophysics Data System (ADS)

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

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

2011-03-01

59

Land Surface Albedo of Large Urban Agglomerations from Landsat Observations  

NASA Astrophysics Data System (ADS)

The world's urban population is expected to rise to 5 billion by the year 2030 and urban climates are expected to have a growing influence on surface energy budgets at regional-to-global scales. A key component of surface energy balance is shortwave reflectivity or albedo, which can be measured and modeled with optical satellite imagery such as Landsat. In this study, we processed Landsat ETM+ imagery of world's 20 largest urban areas as of the early 2000s. To derive robust albedo estimates for each urban area, we applied an atmospheric correction and BRDF modeling using the 6s atmospheric radiative transfer model as well as an empirically based narrow-to-broadband conversion involving ETM+ bands 2, 4, and 7. A spatial analysis of the resultant albedo images was performed using various statistical and geostatistical methods. The results reveal moderate variability of land-surface albedo values among the various urban areas with mean values for urban land surfaces ranging between 0.12 for Cairo to 0.23 for Buenos Aires. As expected, in most instances we found that the albedo of these large urban areas was less than what we observed for nearby non-urban land cover types. The absolute differences in albedo between urban areas and adjacent non-urban areas within each ETM+ scene ranged from large (0.21 for Cairo) to very small (0.02 for Shanghai). Our preliminary conclusion is that the albedo difference (or the "urban albedo effect") between urban and adjacent non-urban land surfaces was greater for cities situated in arid environments than "green" cities that are situated in mesic, temperate regions.

Fuller, D. O.; Roy, S. S.; Cohen, A.

2006-05-01

60

Large breast compressions: Observations and evaluation of simulations  

SciTech Connect

Purpose: Several methods have been proposed to simulate large breast compressions such as those occurring during x-ray mammography. However, the evaluation of these methods against real data is rare. The aim of this study is to learn more about the deformation behavior of breasts and to assess a simulation method. Methods: Magnetic resonance (MR) images of 11 breasts before and after applying a relatively large in vivo compression in the medial direction were acquired. Nonrigid registration was employed to study the deformation behavior. Optimal material properties for finite element modeling were determined and their prediction performance was assessed. The realism of simulated compressions was evaluated by comparing the breast shapes on simulated and real mammograms. Results: Following image registration, 19 breast compressions from 8 women were studied. An anisotropic deformation behavior, with a reduced elongation in the anterior-posterior direction and an increased stretch in the inferior-superior direction was observed. Using finite element simulations, the performance of isotropic and transverse isotropic material models to predict the displacement of internal landmarks was compared. Isotropic materials reduced the mean displacement error of the landmarks from 23.3 to 4.7 mm, on average, after optimizing material properties with respect to breast surface alignment and image similarity. Statistically significantly smaller errors were achieved with transverse isotropic materials (4.1 mm, P=0.0045). Homogeneous material models performed substantially worse (transverse isotropic: 5.5 mm; isotropic: 6.7 mm). Of the parameters varied, the amount of anisotropy had the greatest influence on the results. Optimal material properties varied less when grouped by patient rather than by compression magnitude (mean: 0.72 vs 1.44). Employing these optimal materials for simulating mammograms from ten MR breast images of a different cohort resulted in more realistic breast shapes than when using established material models. Conclusions: Breasts in the prone position exhibited an anisotropic compression behavior. Transverse isotropic materials with an increased stiffness in the anterior-posterior direction improved the prediction of these deformations and produced more realistic mammogram simulations from MR images.

Tanner, Christine; White, Mark; Guarino, Salvatore; Hall-Craggs, Margaret A.; Douek, Michael; Hawkes, David J. [Centre of Medical Image Computing, UCL, London WC1E 6BT, United Kingdom and Computer Vision Laboratory, ETH Zuerich, 8092 Zuerich (Switzerland); Centre of Medical Image Computing, UCL, London WC1E 6BT (United Kingdom); Department of Surgery, UCL, London W1P 7LD (United Kingdom); Department of Imaging, UCL Hospital, London NW1 2BU (United Kingdom); Department of Surgery, UCL, London W1P 7LD (United Kingdom); Centre of Medical Image Computing, UCL, London WC1E 6BT (United Kingdom)

2011-02-15

61

Large anisotropic Fe orbital moments in perpendicularly magnetized Co2FeAl Heusler alloy thin films revealed by angular-dependent x-ray magnetic circular dichroism  

NASA Astrophysics Data System (ADS)

Perpendicular magnetic anisotropy (PMA) in Heusler alloy Co2FeAl thin films sharing an interface with a MgO layer is investigated by angular-dependent x-ray magnetic circular dichroism. Orbital and spin magnetic moments are deduced separately for Fe and Co 3d electrons. In addition, the PMA energies are estimated using the orbital magnetic moments parallel and perpendicular to the film surfaces. We found that PMA in Co2FeAl is determined mainly by the contribution of Fe atoms with large orbital magnetic moments, which are enhanced at the interface between Co2FeAl and MgO. Furthermore, element specific magnetization curves of Fe and Co are found to be similar, suggesting the existence of ferromagnetic coupling between Fe and Co PMA directions.

Okabayashi, Jun; Sukegawa, Hiroaki; Wen, Zhenchao; Inomata, Koichiro; Mitani, Seiji

2013-09-01

62

Ground-water levels in Alabama. For observation wells measured periodically, August 1952-July 1977. Circular 105  

SciTech Connect

A systematic observation well network in Alabama was started in 1940. This report summarizes the general relationship between geology and groundwater availability. Unpublished water-level data collected periodically since 1952 at 254 observation wells are listed along with the location description and general information on construction of the observation wells. Publications containing water-level data from selected observation wells are also listed.

Davis, M.E.

1981-03-05

63

Large Scale Surface Radiation Budget from Satellite Observation  

NASA Astrophysics Data System (ADS)

During the current reporting period, the focus of our work was on preparing and testing an improved version of our Surface Radiation Budget algorithm for processing the ISCCP D1 data routinely at the SRB Satellite Data Analysis Center (SDAC) at NASA Langley Research Center. The major issues addressed are related to gap filling and to testing whether observations made from ERBE could be used to improve current procedures of converting narrowband observations, as available from ISCCP, into broadband observations at the TOA. The criteria for selecting the optimal version are to be based on results of intercomparison with ground truth.

Pinker, R. T.

1995-12-01

64

Censored regression analysis in large samples with many zero observations  

Microsoft Academic Search

With the advent of improved data collection techniques, the applied econometrician can nowadays have access to very large data bases. Sometimes, however, these can have fairly low informational content. For example, a typical response rate in direct mailings is below 1%. Given the small fraction of respondents, one could be tempted to omit the larger part of the nonrespondents from

Ph. H. B. F. Franses; E. Slagter; J. S. Cramer

1999-01-01

65

Online Performance Observation of Large-Scale Parallel Applications  

Microsoft Academic Search

Parallel performance tools oer insights into the execution behavior of an application and are a valuable component in the cycle of application development, deployment, and optimization. However, most tools do not work well with large-scale parallel applications where the performance data gener- ated comes from upwards of thousands of processes. As parallel computer systems increase in size, the scaling of

Allen D. Malony; Sameer Shende; Robert Bell

2003-01-01

66

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

67

Accumulation of large non-circular forms of the chromosome in recombination-defective mutants of Escherichia coli  

PubMed Central

Background Double-strand breakage of chromosomal DNA is obviously a serious threat to cells because various activities of the chromosome depend on its integrity. However, recent experiments suggest that such breakage may occur frequently during "normal" growth in various organisms – from bacteria through vertebrates, possibly through arrest of a replication fork at some endogenous DNA damage. Results In order to learn how the recombination processes contribute to generation and processing of the breakage, large (> 2000 kb) linear forms of Escherichia coli chromosome were detected by pulsed-field gel electrophoresis in various recombination-defective mutants. The mutants were analyzed in a rich medium, in which the wild-type strain showed fewer of these huge broken chromosomes than in a synthetic medium, and the following results were obtained: (i) Several recB and recC null mutants (in an otherwise rec+ background) accumulated these huge linear forms, but several non-null recBCD mutants (recD, recC1001, recC1002, recC1003, recC1004, recC2145, recB2154, and recB2155) did not. (ii) In a recBC sbcA background, in which RecE-mediated recombination is active, recA, recJ, recQ, recE, recT, recF, recO, and recR mutations led to their accumulation. The recJ mutant accumulated many linear forms, but this effect was suppressed by a recQ mutation. (iii) The recA, recJ, recQ, recF and recR mutations led to their accumulation in a recBC sbcBC background. The recJ mutation showed the largest amount of these forms. (iv) No accumulation was detected in mutants affecting resolution of Holliday intermediates, recG, ruvAB and ruvC, in any of these backgrounds. Conclusion These results are discussed in terms of stepwise processing of chromosomal double-strand breaks.

Handa, Naofumi; Kobayashi, Ichizo

2003-01-01

68

Large-Distance Effects on Spin Observables at Rhic  

NASA Astrophysics Data System (ADS)

The impact of large-distance contributions on the behaviour of the slopes of the spin-non-flip and of the spin-flip amplitudes is analysed. It is shown that the long tail of the hadron potential in impact parameter space leads to a larger value of the slope for the spin-flip amplitude (without the kinematic factor ? {|t|} ) than for the spin-non-flip amplitude. This effect is taken into account in the calculation of the analysing power in proton-nucleus reactions at high energies.

Selyugin, O. V.; Cudell, J.; Predazzi, E.

2005-08-01

69

The large-scale environment of Betelgeuse from radio observations  

NASA Astrophysics Data System (ADS)

We present HI data obtained with the Nançay Radiotelescope and with the Very Large Array (VLA) on the red supergiant ? Ori (Betelgeuse). The high spectral resolution allows us to identify three components emitting in narrow spectral lines (FWHM ˜ 3 km s^{-1}). By selecting different ranges of baselines from the VLA data, it is possible to obtain images revealing different structures in the environment of ? Ori. The confusion arising from the emission by the interstellar medium on the same line of sight can also be identified and thus be mitigated by filtering short spacings. The HI data reveal a quasi-stationary detached shell of neutral atomic hydrogen ˜4' in diameter (˜0.24 pc at 200 pc), and also atomic hydrogen emission associated with the 6' radius far-infrared arc discovered by IRAS and with a newly discovered far-ultraviolet emitting arc.

Le Bertre, T.; Matthews, L. D.; Gérard, E.

2012-12-01

70

Large-scale convection patterns observed by DMSP  

SciTech Connect

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

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

1994-03-01

71

Modelling of Astrophysical Observables for the Very Large Telescope Interferometer  

NASA Astrophysics Data System (ADS)

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

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

2001-05-01

72

FERMI LARGE AREA TELESCOPE OBSERVATION OF SUPERNOVA REMNANT S147  

SciTech Connect

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

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

2012-06-20

73

Parallel Large-Scale Computation of an Oldroyd-B Fluid Past a Confined Circular Cylinder in a Rectangular Channel using an Unstructured Finite Volume Method  

NASA Astrophysics Data System (ADS)

A new stable unstructured finite volume method is presented for parallel large-scale simulation of viscoelastic fluid flows. The numerical method based on side-centered finite volume method where the velocity vector components are defined at the mid-point of each cell face, while the pressure term and the extra stress tensor are defined at element centroids. The present arrangement of the primitive variables leads to a stable numerical scheme and it does not require any ad-hoc modifications in order to enhance the pressure-velocity-stress coupling. The log-conformation representation has been implemented in order improve the limiting Weissenberg numbers in the proposed finite volume method. The time stepping algorithm used decouples the calculation of the extra stresses from the evaluation of the velocity and pressure fields by solving a generalised Stokes problem. The present numerical method is verified for the three-dimensional flow of an Oldroyd-B fluid past a confined sphere in a cylindrical tube. Then the method is applied to the three-dimensional flow of an Oldroyd-B fluid past a confined circular cylinder in a rectangular channel. The computed results at relatively high Weissenberg numbers are discussed and compared to those obtained for Newtonian fluids.

Sahin, Mehmet

2010-11-01

74

Observations of large scale ion conic generation with DE-1  

SciTech Connect

Data from Dynamics Explorer 1 were analyzed to investigate the phenomena that are associated with the occurrence of upward conical ion distributions in the nightside auroral oval. In a single pass through the boundary plasma sheet (BPS) and central plasma sheet (CPS) at altitudes near 1 R/sub E/ and MLT of about 19 hrs, it was found that the angular morphology of the conics contained distinct signatures of the parallel and perpendicular flow velocities that were determined from calculated moments of the ion-distribution functions. In addition to the expected presence of field-aligned currents and waves in the <100-Hz frequency range, the CPS conic region, where the highest-energy conics were observed, contained a population of upward-streaming electrons with temperatures between 1 and 2 eV. It is suggested that the upward-streaming electrons may be the primary source of free energy for ion conic generation.

Winningham, J.D.; Burch, J.L.

1984-01-01

75

Non-circular scans and image reconstruction for breast CT  

NASA Astrophysics Data System (ADS)

Current dedicated, cone-beam breast CT scanners generally use a circular scanning configuration largely because it is relatively easy to implement mechanically. It is also well-known, however, that a circular scanning configuration produces insufficient cone-beam data for reconstrucing accurate 3D breast images. Approximate algorithms, such as FDK has been widely applied to reconstruct images from circular cone-beam data. In the FDK reconstruction, it is possible to observe artifacts such as intensity decay for locations that are not within the plane containing the circular source trajectory. Such artifacts may potentially lead to false positive and/or false negative diagnosis of breast cancer. Non-circular imaging configurations may provide data sufficient for accurate image reconstruction. In this work, we implement, investigate innovative, non-circular scanning configurations such as helical and saddle configurations for data acquisition on a dedicated, cone-beam breast CT scanner, and develop novel algorithms to reconstruct accurate 3D images from these data. A dedicated, cone-beam breast CT scanner capable of performing non-circular scanning configurations was used in this research. We have investigated different scanning configurations, including helical and saddle configurations. A Defrise disk phantom and a dead mouse were scanned by use of these configurations. For each configuration, cone-beam data were acquired at 501 views over each turn. We have reconstructed images using our BPF algorithm from data acquired with the helical scanning configuration.

Bian, Junguo; Packard, Nathan J.; Yang, Kai; Xia, Dan; Boone, John M.; Pan, Xiaochuan

2008-04-01

76

Gravitational waves from a compact star in a circular, inspiral orbit, in the equatorial plane of a massive, spinning black hole, as observed by LISA  

NASA Astrophysics Data System (ADS)

Results are presented from high-precision computations of the orbital evolution and emitted gravitational waves for a stellar-mass object spiraling into a massive black hole in a slowly shrinking, circular, equatorial orbit. The focus of these computations is inspiral near the innermost stable circular orbit (isco)-more particularly, on orbits for which the angular velocity ? is 0.03<~?/?isco<=1.0. The computations are based on the Teuksolsky-Sasaki-Nakamura formalism, and the results are tabulated in a set of functions that are of order unity and represent relativistic corrections to low-orbital-velocity formulas. These tables can form a foundation for future design studies for the LISA space-based gravitational-wave mission. A first survey of applications to LISA is presented: Signal to noise ratios S/N are computed and graphed as functions of the time-evolving gravitational-wave frequency for the lowest three harmonics of the orbital period, and for various representative values of the hole's mass M and spin a and the inspiraling object's mass ?, with the distance to Earth chosen to be ro=1 Gpc. These S/N's show a very strong dependence on the black-hole spin, as well as on M and ?. Graphs are presented showing the range of the \\{M,a,?\\} parameter space, for which S/N>10 at r0=1 Gpc during the last year of inspiral. The hole's spin a has a factor of ~10 influence on the range of M (at fixed ?) for which S/N>10, and the presence or absence of a white-dwarf-binary background has a factor of ~3 influence. A comparison with predicted event rates shows strong promise for detecting these waves, but not beyond about 1 Gpc if the inspiraling object is a white dwarf or neutron star. This argues for a modest lowering of LISA's noise floor. A brief discussion is given of the prospects for extracting information from the observed waves.

Finn, Lee Samuel; Thorne, Kip S.

2000-12-01

77

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

78

Large P(T) jets observed in Chacaltaya gamma ray families  

Microsoft Academic Search

Large PT jets in high-energy gamma-ray families observed in Chacaltaya emulsion chambers at Sigma-E(gamma) = 100-1,000 TeV are studied. Through jet-cluster analysis it is found that families with large PT jets exist which cannot be from random jet production, but must be from interaction of exotic type with large PT.

H. Semba

1983-01-01

79

Circular inferences in schizophrenia.  

PubMed

A considerable number of recent experimental and computational studies suggest that subtle impairments of excitatory to inhibitory balance or regulation are involved in many neurological and psychiatric conditions. The current paper aims to relate, specifically and quantitatively, excitatory to inhibitory imbalance with psychotic symptoms in schizophrenia. Considering that the brain constructs hierarchical causal models of the external world, we show that the failure to maintain the excitatory to inhibitory balance results in hallucinations as well as in the formation and subsequent consolidation of delusional beliefs. Indeed, the consequence of excitatory to inhibitory imbalance in a hierarchical neural network is equated to a pathological form of causal inference called 'circular belief propagation'. In circular belief propagation, bottom-up sensory information and top-down predictions are reverberated, i.e. prior beliefs are misinterpreted as sensory observations and vice versa. As a result, these predictions are counted multiple times. Circular inference explains the emergence of erroneous percepts, the patient's overconfidence when facing probabilistic choices, the learning of 'unshakable' causal relationships between unrelated events and a paradoxical immunity to perceptual illusions, which are all known to be associated with schizophrenia. PMID:24065721

Jardri, Renaud; Denève, Sophie

2013-09-24

80

Simultaneous Chandra and Very Large Array Observations of Young Stars and Protostars in ? Ophiuchus Cloud Core A  

NASA Astrophysics Data System (ADS)

A 96 ks Chandra X-ray observation of ? Ophiuchus cloud core A detected 87 sources, of which 60 were identified with counterparts at other wavelengths. The X-ray detections include 12 of 14 known classical T Tauri stars (CTTSs) in the field, 15 of 17 known weak-lined TTSs (WTTSs), and 4 of 15 brown dwarf candidates. The X-ray detections are characterized by hard, heavily absorbed emission. Most X-ray detections have visual extinctions in the range AV~10-20 mag, but several sources with visual absorptions as high as AV~40-56 mag were detected. The mean photon energy of a typical source is ~3 keV, and more than half of the detections are variable. Prominent X-ray flares were detected in the unusual close binary system Oph S1, the X-ray-bright WTTS DoAr 21, and the brown dwarf candidate GY 31 (M5.5). Time-resolved spectroscopic analysis of the DoAr 21 flare clearly reveals a sequence of secondary flares during the decay phase that may have reheated the plasma. We find that the X-ray luminosity distributions and spectral hardnesses of CTTSs and WTTSs are similar. We also conclude that the X-ray emission of detected brown dwarf candidates is less luminous than TTSs, but spectroscopically similar. Simultaneous multifrequency Very Large Array (VLA) observations detected 31 radio sources at 6 cm, of which 10 were also detected by Chandra. We report new radio detections of the optically invisible IR source WLY 2-11 and the faint H? emission line star Elias 24 (class II). We confirm circular polarization in Oph S1 and report a new detection of circular polarization in DoAr 21. We find no evidence that X-ray and radio luminosities are correlated in the small sample of TTSs detected simultaneously with Chandra and the VLA. We describe a new nonparametric method for estimating X-ray spectral properties from unbinned photon event lists that is applicable to both faint and bright X-ray sources. The method is used to generate fX, logT, and LX light curves. In addition, we provide a publicly available electronic database containing multiwavelength data for 345 known X-ray, IR, and radio sources in the core A region.

Gagné, Marc; Skinner, Stephen L.; Daniel, Kathryne J.

2004-09-01

81

OBSERVATION OF LARGE TRANSIENT FIELD ENHANCEMENTS IN PHOTOCONDUCTIVE ZnSe SWITCHES  

Microsoft Academic Search

Photoconductive switching using polycrystalline ZnSe with transparent liquid electrolytic electrode under pulsed bias was investigated. Nonlinear optical transmission which is due to high internal electric fields of this switch under moderate biases was observed. The temporal behavior of the optical transmission shows large transient field-induced optical absorption followed by an increase of optical trunsmission. From the optical transmission measurements, large

Pak S. Cho; Julius Goldhar; Chi H. Lee

1993-01-01

82

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

SciTech Connect

A burst of eight neutrino events 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 six seconds and have visible energies in the range 20--40 MeV.

Bionta, R.M.; Blewitt, G.; Bratton, C.B.; Casper, D.; Ciocio, A.; Claus, R.; Cortez, B.; Crouch, M.; Dye, S.T.; Errede, S.

1987-04-06

83

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

NASA Astrophysics Data System (ADS)

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

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

2010-12-01

84

Experimental Observation of Large-Scale Electron Vortex Structures in the Electrostatic Plasma Lens  

Microsoft Academic Search

We describe here the first experimental results of the observation of electron vortex structures in electrostatic plasma lens caused both by unremovable radial gradients of magnetic field and the high radial gradient of electron density. Anharmonic large-amplitude potential waves propagating in azimuth direction are observed. The results of the measurement of electric field distributions enable to establish that electron bunches

Yu. Chekh; A. Goncharov; I. Protsenko

2006-01-01

85

Very Large Array observations of solar active regions. Interim scientific report 1 Jan30 Dec 83  

Microsoft Academic Search

Observations of solar active regions with the Very Large Array have led to a new understanding of the origin and prediction of the solar bursts which disrupt communication systems and interfere with high-flying aircraft. The detailed temperature, density and magnetic structure of coronal loops have been investigated by using observations at 20 cm wavelength. By studying loop evolution on time

Lang

1984-01-01

86

Large scale evaluation of soil moisture retrievals from passive microwave observations  

Technology Transfer Automated Retrieval System (TEKTRAN)

For several years passive microwave observations have been used to retrieve surface soil moisture from the Earth’s surface. Several satellite sensors such as the Advanced Microwave Scanning Radiometer-EOS (AMSR-E) and WindSat have been used for this purpose using multi-channel observations. Large sc...

87

OBSERVATIONS ON HIGH ENERGY JETS AND GAMMA-RAYS WITH LARGE EMULSION CHAMBER  

Microsoft Academic Search

S>Large emulsion chambers of several square meters were constructed and ; exposed to cosmic rays to study the high energy jets and the gamma spectra. ; About 1000 gamma rays with energy higher than 10¹² were observed, and the ; spectrunn showed the gradual increase of the exponent with increasing energy. ; Direct observations were also made for the high

M. Akashi; K. Shimizu; Z. Watanabe; T. Ogata; N. Ogita; A. Misaki; I. Mito; S. Oyama; S. Tokunaga; M. Tamura; Y. Fujimoto; S. Hasegawa; J. Nishimura; K. Yokoi

1961-01-01

88

SPITZER, VERY LARGE TELESCOPE, AND VERY LARGE ARRAY OBSERVATIONS OF THE GALACTIC LUMINOUS BLUE VARIABLE CANDIDATE HD 168625  

SciTech Connect

We present mid-IR and radio observations of the Galactic luminous blue variables (LBVs) candidate HD 168625 and its associated nebula. We obtained mid-IR spectroscopic observations using the Infrared Spectrograph on board the Spitzer Space Telescope, and performed mid-IR and radio imaging observations using VISIR on the Very Large Telescope and the Very Large Array with comparable angular resolution. Our spectroscopic observations detected spectral features attributable to polycyclic aromatic hydrocarbons (PAHs) and therefore indicate the presence of a photodissociation region (PDR) around the ionized nebula. This result increases the number of LBVs and LBV candidates where a PDR has been found, confirming the importance of such a component in the total mass-loss budget of the central object during this elusive phase of massive star evolution. We have analyzed and compared the mid-IR and radio maps, and derive several results concerning the associated nebula. There is evidence for grain distribution variations across the nebula, with a predominant contribution from bigger grains in the northern part of the nebula while PAH and smaller grains are more concentrated in the southern part. A compact radio component located where there is a lack of thermal dust grains corroborates the presence of a shock in the southern nebula, which could arise as a consequence of the interaction of a fast outflow with the slower, expanding dusty nebula. Such a shock would be a viable means for PAH production as well as for changes in the grain size distribution. Finally, from the detection of a central radio component probably associated with the wind from the central massive supergiant, we derive a current mass-loss rate of M-dot =(1.46{+-}0.15)x10{sup -6} M{sub sun} yr{sup -1}.

Umana, G.; Buemi, C. S.; Trigilio, C.; Leto, P. [INAF-Osservatorio Astrofisico di Catania, Via S. Sofia 78, 95123 Catania (Italy); Hora, J. L. [Harvard-Smithsonian Center for Astrophysics, 60 Garden St. MS-65, Cambridge, MA 02138-1516 (United States)

2010-08-01

89

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

2010-03-29

90

Circular configuration of the genome of ascoviruses  

Microsoft Academic Search

A circular configuration of genomic DNA was observed in ascoviruses isolated from two species of insects of the family Noctuidae (fall armyworm (Spodoptera frugiperda) and cotton bollworm (Helicoverpa zea)) using restriction endonuclease (REN) digestion, conventional gel electrophoresis, pulsed-field gel electrophoresis and Southern hybridization analysis. This circular configuration of ascovirus genomic DNA was established based on the difference between linear and

Xiao-Wen Cheng; Gerald R. Carner; Thomas M. Brown

1999-01-01

91

Observation of a large spin-dependent transport length in organic spin valves at room temperature  

NASA Astrophysics Data System (ADS)

The integration of organic semiconductors and magnetism has been a fascinating topic for fundamental scientific research and future applications in electronics, because organic semiconductors are expected to possess a large spin-dependent transport length based on weak spin-orbit coupling and weak hyperfine interaction. However, to date, this length has typically been limited to several nanometres at room temperature, and a large length has only been observed at low temperatures. Here we report on a novel organic spin valve device using C60 as the spacer layer. A magnetoresistance ratio of over 5% was observed at room temperature, which is one of the highest magnetoresistance ratios ever reported. Most importantly, a large spin-dependent transport length of approximately 110?nm was experimentally observed for the C60 layer at room temperature. These results provide insights for further understanding spin transport in organic semiconductors and may strongly advance the development of spin-based organic devices.

Zhang, Xianmin; Mizukami, Shigemi; Kubota, Takahide; Ma, Qinli; Oogane, Mikihiko; Naganuma, Hiroshi; Ando, Yasuo; Miyazaki, Terunobu

2013-01-01

92

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

PubMed

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

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

2010-06-01

93

An improved in vitro bioassay for the study of 5-HT(4) receptors in the human isolated large intestinal circular muscle.  

PubMed

Recently, it was demonstrated that 5-HT induces relaxation of human colon circular muscle through activation of 5-HT(4) receptors and 5-HT(7) receptors. The aim of the current study was to develop a new in vitro bioassay of human colon that would facilitate the pharmacological analysis of 5-HT responses mediated solely by 5-HT(4) receptors. Contracting circular muscle strips with KCl (80 mM) yielded a stable contractile tension and, in contrast to muscarinic cholinoceptor agonists and histamine, a profound reduction of spontaneous contractility. This allowed the establishment of reproducible, fully-defined, agonist concentration-response curves by cumulative dosing. Under these conditions, 5-HT induced a concentration-dependent relaxation (pEC(50) 7.31, Hill slope 0.91). Neither methysergide (10 microM) nor granisetron (1 microM) affected the 5-HT-induced relaxation, suggesting that 5-HT(1), 5-HT(2), 5-HT(3), 5-ht(5), 5-HT(6) or 5-HT(7) receptors are not involved. The lack of effect of tetrodotoxin (0.3 microM) indicated a direct effect of 5-HT on the smooth muscle. The selective 5-HT(4) receptor antagonists GR 113808, GR 125487 and RS 39604 competitively antagonized the 5-HT-induced relaxation (pK(B) 9.43, 10.12 and 8.53, respectively). SB 204070 (1 nM) produced a rightward shift (pA(2) 10.34) and depression of the 5-HT curve. These affinity estimates are similar to those previously reported for 5-HT(4) receptors. The selective 5-HT(4) receptor agonists, prucalopride and R076186, induced relaxations (pEC(50) 7.50 and 7.57, respectively), that were blocked by GR 113808 (3 nM), yielding pA(2) estimates of 9.31 and 9.21, respectively. To summarise, in KCl (80 mM)-contracted muscle strips, 5-HT induces relaxation through activation of a homogeneous smooth muscle 5-HT(4) receptor population. This new bioassay allows the focused, pharmacological characterization of human colonic 5-HT(4) receptors in vitro. PMID:10780964

Prins, N H; Shankley, N P; Welsh, N J; Briejer, M R; Lefebvre, R A; Akkermans, L M; Schuurkes, J A

2000-04-01

94

An improved in vitro bioassay for the study of 5-HT4 receptors in the human isolated large intestinal circular muscle  

PubMed Central

Recently, it was demonstrated that 5-HT induces relaxation of human colon circular muscle through activation of 5-HT4 receptors and 5-HT7 receptors. The aim of the current study was to develop a new in vitro bioassay of human colon that would facilitate the pharmacological analysis of 5-HT responses mediated solely by 5-HT4 receptors.Contracting circular muscle strips with KCl (80?mM) yielded a stable contractile tension and, in contrast to muscarinic cholinoceptor agonists and histamine, a profound reduction of spontaneous contractility. This allowed the establishment of reproducible, fully-defined, agonist concentration-response curves by cumulative dosing. Under these conditions, 5-HT induced a concentration-dependent relaxation (pEC50 7.31, Hill slope 0.91).Neither methysergide (10??M) nor granisetron (1??M) affected the 5-HT-induced relaxation, suggesting that 5-HT1, 5-HT2, 5-HT3, 5-ht5, 5-HT6 or 5-HT7 receptors are not involved. The lack of effect of tetrodotoxin (0.3??M) indicated a direct effect of 5-HT on the smooth muscle.The selective 5-HT4 receptor antagonists GR 113808, GR 125487 and RS 39604 competitively antagonized the 5-HT-induced relaxation (pKB 9.43, 10.12 and 8.53, respectively). SB 204070 (1?nM) produced a rightward shift (pA2 10.34) and depression of the 5-HT curve. These affinity estimates are similar to those previously reported for 5-HT4 receptors.The selective 5-HT4 receptor agonists, prucalopride and R076186, induced relaxations (pEC50 7.50 and 7.57, respectively), that were blocked by GR 113808 (3?nM), yielding pA2 estimates of 9.31 and 9.21, respectively.To summarise, in KCl (80?mM)-contracted muscle strips, 5-HT induces relaxation through activation of a homogeneous smooth muscle 5-HT4 receptor population. This new bioassay allows the focused, pharmacological characterization of human colonic 5-HT4 receptors in vitro.

Prins, N H; Shankley, N P; Welsh, N J; Briejer, M R; Lefebvre, R A; Akkermans, L M A; Schuurkes, J A J

2000-01-01

95

Observations of large-amplitude, narrowband whistlers at stream interaction regions  

Microsoft Academic Search

We present the first solar wind observations of large-amplitude, narrowband waveforms in the frequency range 10–100 Hz, consistent with the whistler mode. These whistlers are only observable in high time resolution electric field waveform data provided by the Time Domain Sampler (TDS) instrument on STEREO. Amplitudes range from a few to >40 mV\\/m peak-to-peak, one to three orders of magnitude

A. Breneman; C. Cattell; S. Schreiner; K. Kersten; L. B. Wilson III; P. Kellogg; K. Goetz; Lan K. Jian

2010-01-01

96

Coherent structure in the turbulent wake behind a circular cylinder  

Microsoft Academic Search

A wake behind a circular cylinder at Reynolds number 850-1700 was visualized by the smoke-wire method. The observations of the How together with the results of quantitative measurements, such as various velocity correlation coefficients, illustrated the formation process of spoon-shaped large eddies in the region 90 <= x\\/d <= 230 attained through the deformation and rearrangement of the regular Karman

Masataka Shirakashi; Shuichi Yamaguchi; Yoshihiro Mochimaru; Ryuichiro Yamane

1988-01-01

97

Direct observation of large chiral domains in chloroplast thylakoid membranes by differential polarization microscopy.  

PubMed

Long-range chiral organization of the pigment-protein complexes in mature granal chloroplasts has been established by differential polarization imaging and local circular dichroism spectra. Linear and circular dichroism images of oriented chloroplasts were obtained in a confocal differential polarization microscope. The circular dichroism images display signals of opposite signs emerging from discrete regions with local dichroic values much larger than anticipated, indicating domains in the thylakoid membranes having long-range chiral organization. These domains are associated with positive and negative circular dichroism bands obtained at specific locations on the chloroplasts. Surprisingly, the local circular dichroism spectra do not display the excitonic shape of spectra obtained for macroscopic suspensions, but the latter can be produced by superposition of two local spectra of opposite sign. These data are evidence for the existence of long-range chiral order of the pigment-protein complexes in thylakoid membranes. The possible role of the long-range chiral domains in the efficiency of energy delocalization through the thylakoid membranes is discussed. PMID:2813422

Finzi, L; Bustamante, C; Garab, G; Juang, C B

1989-11-01

98

Observations and Large-Eddy Simulations of Entrainment in the Sheared Sahelian Boundary Layer  

NASA Astrophysics Data System (ADS)

At the top of the planetary boundary layer, the entrainment of air, which incorporates dry and warm air from the free troposphere into the boundary layer, is a key process for exchanges with the free troposphere since it controls the growth of the boundary layer. Here, we focus on the semi-arid boundary layer where the entrainment process is analyzed using aircraft observations collected during the African Monsoon Multidisciplinary Analysis experiment and large-eddy simulations. The role of the entrainment is specifically enhanced in this region where very large gradients at the planetary boundary-layer top can be found due to the presence of the moist, cold monsoon flow on which the dry, warm Harmattan flow is superimposed. A first large-eddy simulation is designed based on aircraft observations of 5 June 2006 during the transition period between dry conditions and the active monsoon phase. The simulation reproduces the boundary-layer development and dynamics observed on this day. From this specific case, sensitivity tests are carried out to cover a range of conditions observed during seven other flights made in the same transition period in order to describe the entrainment processes in detail. The combination of large-eddy simulations and observations allows us to test the parametrization of entrainment in a mixed-layer model with zero-order and first-order approximations for the entrainment zone. The latter representation of the entrainment zone gives a better fit with the conditions encountered in the Sahelian boundary layer during the transition period because large entrainment thicknesses are observed. The sensitivity study also provides an opportunity to highlight the contribution of shear stress and scalar jumps at the top of the boundary layer in the entrainment process, and to test a relevant parametrization published in the recent literature for a mixed-layer model.

Canut, Guylaine; Couvreux, Fleur; Lothon, Marie; Pino, David; Saïd, Frédérique

2012-01-01

99

Interactions of Large Meteoroids and Small Interplanetary Bodies with the Earth's Atmosphere: Theories and Observational Constraints  

NASA Astrophysics Data System (ADS)

Problems of hypervelocity interaction of large bodies with the Earth's atmosphere has attracted more attention during last few years. Several new concepts of dynamical explosive fragmentation of strong interplanetary bodies at extremely low heights under dynamic pressures of hundreds of Mdyn/cm2 were published. Comparison of these theoretical models with precise observations has not yet been done, because data on atmospheric penetration of large bodies are not available. Single body theory with sudden gross-fragmentation was successfully applied to photographic observations of fireballs. The largest bodies observed have sizes up to several meters. The highest dynamic pressure acting on these observed bodies reached slightly over 100 Mdyn/cm2. All these photographed fireballs follow theoretical concepts of motion of either the single-body or the single-body with gross-fragmentation under dynamic pressures in the range from 1 to 12 Mdyn/cm2. When this theory has been applied to photographic observations, typical standard deviation of the distance flown in the trajectory has been found in a range of 10 to 30 m for one observed distance corresponding also to the geometrical precision of the observations. This model can explain all good observations of atmospheric trajectories of meteoroids up to initial sizes of several meters with high precision. Also the three photographed and one videorecorded meteorite falls fit to this concept completely. The most important phenomenon of atmospheric motion of meteoroids up to several meters in size is the ablation with final stage of hot vapor from ablated material. Spectral records of meteoroids up to several meters in size, down to a height of 16 km and for various velocities show overwhelming radiation of rather low excited metalic atoms (several eV; temperatures 3000 to 5000 K) in the pass-band of visible light. Radiation from high excited atoms of either atmospheric or ablational origin forms only an insignificant part of visible radiation. Contrary to this regime, theories of very large bodies contain ablation mostly in the form of explosive fragmentation. Ablation at higher heights is negligible. This absence of “classical” ablation and fragmentation at low dynamic pressures for large bodies (contrary to observations of smaller bodies) brings the body to lower heights without too much change of size and makes thus the dynamic pressure much higher than in reality. In any case the change of body dynamics and radiation going from sizes of several meters (observed regime) to sizes of several tens of meters (hypothetical regime) may be crucial for our understanding of dynamics and radiation of large body penetration through the low atmosphere to the Earth's surface. Observations of atmospheric trajectory of these bodies with sufficiently high precision are extremely needed.

Ceplecha, Z.

1995-01-01

100

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

National Technical Information Service (NTIS)

We report the observation of amplification of a probe laser beam (I (le) 1 (times) 10(sup 14) W/cm(sup 2)) in a large scale ((approximately) 1 mm) plasma by interaction with a pumping laser beam (I = 2 (times) 10(sup 15) W/cm(sup 2)) and a stimulated Lang...

R. Kirkwood

1997-01-01

101

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

Microsoft Academic Search

The Millennium simulation is the largest numerical simulation of how minor fluctuations in the density of the universe's dark matter distribution are amplified by gravity to develop into the large scale structures(LSS) and galaxy clusters seen today(Springel et al. 2005). Although the simulations have been compared with the astronomical observations of the local universe, the simulations have not been widely

G. Li; N. Z. Scoville

2009-01-01

102

Observations of TeV gamma rays from Markarian 501 at large zenith angles  

Microsoft Academic Search

TeV gamma rays from the blazar Markarian 501 have been detected with the University of Durham Mark 6 atmospheric Cerenkov telescope using the imaging technique at large zenith angles. Observations were made at zenith angles in the range 70-73 during July and August 1997 when Markarian 501 was undergoing a prolonged and strong flare.

P M Chadwick; K Lyons; T J L McComb; K J Orford; J L Osborne; S M Rayner; S E Shaw; K E Turver

1999-01-01

103

Vertical distributions of sulfur species simulated by large scale atmospheric models in COSAM: Comparison with observations  

Microsoft Academic Search

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

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

2001-01-01

104

Testing coupled dark energy with next-generation large-scale observations  

NASA Astrophysics Data System (ADS)

Coupling dark energy to dark matter provides one of the simplest way to effectively modify gravity at large scales without strong constraints from local (i.e. Solar System) observations. Models of coupled dark energy have been studied several times in the past and are already significantly constrained by cosmic microwave background experiments. In this paper we estimate the constraints that future large-scale observations will be able to put on the coupling and in general on all the parameters of the model. We combine cosmic microwave background, tomographic weak lensing, redshift distortions and power spectrum probes. We show that next-generation observations can improve the current constraint on the coupling to dark matter by two orders of magnitude; this constraint is complementary to the current Solar System bounds on a coupling to baryons.

Amendola, Luca; Pettorino, Valeria; Quercellini, Claudia; Vollmer, Adrian

2012-05-01

105

Petermann Glacier, North Greenland: Large Ice-Discharge Episodes from 20 Years of Satellite Observations  

NASA Astrophysics Data System (ADS)

The major marine-terminating outlet glaciers of Greenland can undergo large mass losses through calving of icebergs and bottom melting from floating ice tongues. Recent observations of outlet glaiers around Greenland have shown that large and rapid changes in solid-ice fluxes are possible. The Petermann glacier in remote northern Greenland is the region’s largest floating-tongue glacier (~70 km by 10 km). In summer 2008 a large calving event was observed, as well as large cracks upstream of the remaining calving front, portending a more massive near-term loss. These observations may herald extraordinary and unprecedented change. However, the long-term variability of calving events and ice velocities are poorly known. Our research goal here is to identify the temporal variability and possible trends in solid-ice flux indicators - variability of the calving front and ice velocity - for Petermann glacier. The methodological approach is observational, based primarily on analysis of 20 years of repetitive satellite data over a period starting from 1990, together with sporadic earlier observations. The multisensor data range from high-resolution optical images from Landsat, SPOT and Terra ASTER and high-resolution synthetic aperture radar (SAR) images from ERS and ENVISAT. These disparate data have been imported, geo-registered and analysed within a Geographic Information System. The following measurements are made: (1) delineating changes in the calving front, (2) estimating the area of glacial ice loss during calving events, and (3) estimating the ice-surface velocity using sequential satellite images. We find evidence of a number of previous calving episodes of similar magnitude to the summer 2008. The ice-velocity estimates compare well with other estimates for particular years, and moreover are relatively consistent during the 20-year period. These findings suggest business-as-usual for Petermann glacier; however, a near-term calving event exceeding those observed over the past 20 years cannot be ruled out.

Babiker, M.; Johannessen, O. M.; Miles, M. W.; Miles, V. V.

2009-12-01

106

Arrival Time Calculation for Interplanetary Coronal Mass Ejections with Circular Fronts and Application to STEREO Observations of the 2009 February 13 Eruption  

NASA Astrophysics Data System (ADS)

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

Möstl, C.; Rollett, T.; Lugaz, N.; Farrugia, C. J.; Davies, J. A.; Temmer, M.; Veronig, A. M.; Harrison, R. A.; Crothers, S.; Luhmann, J. G.; Galvin, A. B.; Zhang, T. L.; Baumjohann, W.; Biernat, H. K.

2011-11-01

107

Observed vertical structure of tropical oceanic clouds sorted in large-scale regimes  

NASA Astrophysics Data System (ADS)

The CloudSat cloud water content (CWC) profiles are sorted by a number of large-scale parameters obtained from reanalysis and satellite observations, including 500 hPa vertical velocity, sea surface temperature and its gradient, surface divergence, precipitation, water vapor path, convective available potential energy and lower tropospheric static stability. The sorting is physics-based and phenomenon-oriented. We find different degrees of clustering of cloud vertical structure in various large-scale regimes. The dominant modes are the deep and shallow clouds with peak CWC above 7 km and below 2 km, respectively, corresponding to distinctly different large-scale regimes. A middle-level peak of CWC around 5-7 km is discernible associated with the large-scale conditions similar to the shallow clouds. This study provides the first quantitative and comprehensive view of tropical CWC distributions in large-scale regimes. These results offer insights into cloud parameterizations and serve as new observational metrics for evaluation of cloud simulations in models.

Su, Hui; Jiang, Jonathan H.; Vane, Deborah G.; Stephens, Graeme L.

2008-12-01

108

GLAST Large Area Telescope Multiwavelength Studies: An Invitation to Coordinated Observations  

NASA Astrophysics Data System (ADS)

High-energy gamma-ray sources are inherently nonthermal, multiwavelength objects. With the launch of the Gamma-ray Large Area Space Telescope (GLAST) less than a year away, the GLAST Large Area Telescope (LAT) Collaboration invites cooperative efforts from observers at all wavelengths. Among the many topics where multiwavelength studies will maximize the scientific understanding, three stand out for particular emphasis: (1) Active Galactic Nuclei. The study of AGN gamma-ray jets can help link the accretion processes close to the black hole with the large-scale interaction of the AGN with its environment. Gamma-ray AGN are also important in the study of absorption effects of extragalactic background light at high redshifts; (2) Unidentified Gamma-ray Sources. New gamma-ray sources need first to be identified with known objects by position, spectrum, or time variability, and then multiwavelength studies can be used to explore the astrophysical implications of high-energy radiation from these sources; (3) Pulsar Timing. The LAT will be capable of some blind searches for new gamma-ray pulsars, but the deepest studies of these rotating neutron stars will come from having known timing solutions. The need for long LAT observations calls for timing solutions valid (at least piecewise) over years. Observers interested in providing coordinated observations should contact one of the authors. The LAT is an international project with U.S. support from NASA and the Department of Energy. K.S. Wood acknowledges support from the Office of Naval Research.

Wood, Kent S.; Thompson, D. J.; Cameron, R. A.; GLAST Collaboration

2006-12-01

109

A tool to estimate the Fermi Large Area Telescope background for short-duration observations  

NASA Astrophysics Data System (ADS)

The proper estimation of the background is a crucial component of data analyses in astrophysics, such as source detection, temporal studies, spectroscopy, and localization. For the case of the Large Area Telescope (LAT) on board the Fermi spacecraft, approaches to estimate the background for short (?1000 s duration) observations fail if they ignore the strong dependence of the LAT background on the continuously changing observational conditions. We present a (to be) publicly available background-estimation tool created and used by the LAT Collaboration in several analyses of Gamma Ray Bursts. This tool can accurately estimate the expected LAT background for any observational conditions, including, for example, observations with rapid variations of the Fermi spacecraft's orientation occurring during automatic repointings.

Vasileiou, Vlasios

2013-08-01

110

Theoretical explanation of the large observed cosmic ray parallel mean free paths in the solar system  

NASA Astrophysics Data System (ADS)

In recent observations large parallel mean free paths of charged cosmic rays which interact with the solar wind plasma have been discovered. The traditional approach to reproduce these measurements theoretically is the assumption that a large part of the magnetic fluctuations is in so-called 2D modes which are expected to be ineffective in scattering. By considering very recent results of particle scattering studies is is argued in this article that the assumption that 2D modes are ineffective in scattering is ruther questionable. By replacing the standard form of the wavespectrum of the magnetic fluctuations by a more realistic model an alternative explanation of observed cosmic ray parallel mean free paths in the solar system is provided by this article.

Shalchi, A.

2007-07-01

111

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

NASA Astrophysics Data System (ADS)

On April 5, 2010 around 09 UT, the NOAA Geosynchronous Operational Environmental Satellites (GOES) observed a large reconfiguration of the magnetospheric magnetic field in the midnight to dawn local time sector. Specifically, near midnight, the GOES-11 Hp (north-south) magnetic field increased by approximately 100 nT in 15 minutes. This is one of the largest dipolarizations of Earth’s field ever observed by GOES. At the same time, there were large increases in the flux of energetic electrons and protons and large ground magnetic perturbations. While the auroral electrojet index (AL) was extreme, being less than -2000 nT during this event, the preliminary, real-time Dst storm index was only on the order of -30 nT during the event (although it reached somewhat more intense values during the following day). The Active Magnetosphere and Planetary Electrodynamics Response Experiment (AMPERE) monitored currents at low altitude during this event, and these observations can be used to place the localized measurements at geosynchronous orbit in a global context. Additional measurements were made by the Time History of Events and Macroscale Interactions during Substorms (THEMIS) spacecraft just tailward of the GOES satellites. Minutes after the initiation of this intense substorm, at 0948 UT, Galaxy 15, located at geosynchronous orbit, just a few degrees away from GOES-11, suffered a serious anomaly and to date, contact has not been restored. At the time, it was reported that this anomaly was likely related to the solar generated event; however, the anomaly is still under investigation. The purpose of this presentation is not to evaluate the anomaly, but rather to describe the large response of the magnetosphere and ionosphere system to the solar and solar wind conditions that caused this extremely large substorm.

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

2010-12-01

112

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

Microsoft Academic Search

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.

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

2010-01-01

113

Recovery of visual field defects: A large clinical observational study using vision restoration therapy  

Microsoft Academic Search

Abstract. Purpose: In small experimental trials, vision restoration therapy (VRT), a home-based rehabilitation method, has shown,to enlarge the visual field and improve,reaction times in patients with lesion involving the CNS. We now,evaluated the outcome,of VRT in a large sample,of clinical patients and studied factors contributing to subjective and objective measures,of visual field alterations. Methods: Clinical observational analysis of visual fields

Iris Mueller; Henning Mast; Bernhard A. Sabel

114

Satellite and ground observations for large-scale air pollution transport in the Yellow Sea region  

Microsoft Academic Search

Large-scale air pollution transport (LSAPT) in the Yellow Sea region and their inflow onto the Korean Peninsula were observed\\u000a through satellite images and ground measurements. LSAPT includes regional continental air-masses saturated with pollutants\\u000a originating from China and subsequently landing on or passing through the Korean Peninsula. It is also possible to identify\\u000a the distribution and transport patterns of LSAPT over

Hak-Sung Kim; Yong-Seung Chung

2008-01-01

115

Observations of CO2 and CH4 enhancements over large point sources using GOSAT  

NASA Astrophysics Data System (ADS)

We present the first results of the effort to directly monitor GHG emissions from intense sources such as large power plants and populated cities (large point sources, LPS) using Greenhouse gas Observing SATellite (GOSAT). National GHG emissions are calculated according to the local activity statistics by sector and their inventories are compiled and reported on annual basis by country. Such inventories are presently the only measure of national emissions, although these might not accurate due to statistical data quality and calculation methods. Towards monitoring of emission reductions an independent method to monitor emissions and verify emission inventories is required. Since August 2009 till December 2009, we have requested targeted mode measurements every 6 days over more than 300 LPS observation sites worldwide. The number is limited by GOSAT targeted mode observation allocation to one research project. Observation points include large power plants selected from CARMA (Carbon Monitoring and Action) global power plant database by emission intensity, and cities selected by population ranking. During 5 months, 154 XCO2 measurements over 74 LPS sites and 170 XCH4 measurements over 80 LPS sites were successfully retrieved. The observed concentrations at LPS sites were compared to zonal mean concentrations and local background values, which were calculated using GOSAT observational data. We also perfomed point-wise model simulations for XCO2 using high resolution (1 km x 1 km) emission dataset and an Eulerian-Lagrangian coupled atmospheric transport model. The majority of the observation over LPS were higher than zonal mean concentrations, and also higher than background values on average. The average CO2 and CH4 enhancements for whole period were +0.51 ± 0.30 ppm (std. 3.51) for CO2 and +2.65 ± 0.78 ppb (std.15.8) for CH4. We can expect lower errors with the use of later versions of the retrieval (The versions of GOSAT L2 product use in this study are V00.03 and V00.10). The observed CO2 enhancement appeared to be close to model simulations (+0.78 ppm ± 0.10 ppm, std. 1.23), suggesting the observation data are in realistic range and there is only minor contamination by aerosols and clouds. Better results were obtained for countries with large percentage of the clear sky observations like Mexico and South Africa, where we observe good correlation between the model predictions and observations for CO2 on country average level. The level of uncertainty at this point (61% for CO2 and 29% for CH4 of the mean value) is still close to the level of the value itself, however a simple estimate suggests that it could be reduced to about 12% for CO2 and 5.9% for CH4 for whole 5-year operation of GOSAT with reasonably improved retrieval. These results demonstrate feasibility of observing man-made CO2 and CH4 emissions from space, which is being actively discussed in context of the planned satellite mission such as OCO-II and CarbonSat.

Oda, T.; Maksyutov, S.; Saito, M.; Valsala, V.; Ganshin, A.; Andres, R. J.; Yoshida, Y.; Yokota, T.

2010-12-01

116

Vortex Rossby waves on smooth circular vortices  

Microsoft Academic Search

A complete theory of the linear initial-value problem for Rossby waves on a class of smooth circular vortices in both f-plane and polar-region geometries is presented in the limit of small and large Rossby deformation radius. Although restricted to the interior region of barotropically stable circular vortices possessing a single extrema in tangential wind, the theory covers all azimuthal wavenumbers.

Gilbert Brunet; Michael T. Montgomeryb

2002-01-01

117

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

118

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

NASA Astrophysics Data System (ADS)

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

Li, G.; Scoville, N. Z.

2009-10-01

119

Circular Extinction Contrast Imaging Microscope.  

National Technical Information Service (NTIS)

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

B. Kahr W. Kaminsky

2004-01-01

120

Circular Intronic Long Noncoding RNAs.  

PubMed

We describe the identification and characterization of circular intronic long noncoding RNAs in human cells, which accumulate owing to a failure in debranching. The formation of such circular intronic RNAs (ciRNAs) can be recapitulated using expression vectors, and their processing depends on a consensus motif containing a 7 nt GU-rich element near the 5' splice site and an 11 nt C-rich element close to the branchpoint site. In addition, we show that ciRNAs are abundant in the nucleus and have little enrichment for microRNA target sites. Importantly, knockdown of ciRNAs led to the reduced expression of their parent genes. One abundant such RNA, ci-ankrd52, largely accumulates to its sites of transcription, associates with elongation Pol II machinery, and acts as a positive regulator of Pol II transcription. This study thus suggests a cis-regulatory role of noncoding intronic transcripts on their parent coding genes. PMID:24035497

Zhang, Yang; Zhang, Xiao-Ou; Chen, Tian; Xiang, Jian-Feng; Yin, Qing-Fei; Xing, Yu-Hang; Zhu, Shanshan; Yang, Li; Chen, Ling-Ling

2013-09-12

121

Circular Polarization in Scattered Light and the Process of Light Scattering in OMC1  

NASA Astrophysics Data System (ADS)

Large linear (pl) and circular (pc) polarization observed in star forming regions is believed to be due to scattering and/or extinction by aligned grains, although specific details of the process are not well known. We investigate the properties of polarization in scattered light by aligned ellipsoidal grains with the Fredholm integral equation method (FIM) and the T-matrix method (Tmat), and we apply the results to the observed circular polarization in a region south-east of the BN object (SEBN) in OMC1. The observed large circular polarization, pc?0.15, can be explained by silicate grains, if their size is 0.15-1.5 ?m, and they are well aligned, i.e. R > 0.5 where R is the Rayleigh reduction factor. If the grains are composed of silicates and ices, our model predicts that the degree of circular polarization pc decreases in the 3 ?m ice feature, while that of linear polarization increases. Since this wavelength dependence is different from that in a process of extinction, linear and circular polarimetry of the 3 ?m ice band in SEBN should be important to investigate the details of the scattering process.

Matsumura, M.; Bastien, P.

2011-11-01

122

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

ERIC Educational Resources Information Center

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

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

2012-01-01

123

Strongly sheared stratocumulus convection: an observationally based large-eddy simulation study  

NASA Astrophysics Data System (ADS)

Unusually large wind shears across the inversion in the stratocumulus-topped marine boundary layer (MBL) were frequently observed during VOCALS-REx. To investigate the impact of wind shear on the MBL turbulence structure, a large-eddy simulation (LES) model is used to simulate the strongly sheared MBL observed from Twin-Otter RF 18 on 13 November 2008. The LES simulated turbulence statistics agree in general with those derived from the measurements, with the MBL exhibiting a decoupled structure characterized by an enhanced entrainment and a turbulence intensity minimum just below the clouds. Sensitivity simulations show that the shear tends to reduce the dynamic stability of the inversion, enhance the entrainment mixing, and decrease the cloud water. Consequently, the turbulence intensity in the MBL is significantly weakened by the intense wind shear. The inversion thickens considerably and the MBL top separates from the cloud top, creating a finite cloud-free sublayer of 10-50 m thickness within the inversion, depending on the shear intensity. The wind shear enhances the turbulence buoyant consumption within the inversion, and simultaneously weakens the buoyant production in the cloud layer. These effects may result in different heating rates between the cloud and subcloud layer, leading to a process that tends to decouple the cloud from the subcloud layer. The decoupling process occurs even without solar radiation in the case of an intense wind shear similar to the observations.

Wang, S.; Zheng, X.; Jiang, Q.

2012-02-01

124

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

125

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

126

The Large-Scale Cosmic-Ray Anisotropy as Observed with Milagro  

NASA Astrophysics Data System (ADS)

Results are presented of a harmonic analysis of the large-scale cosmic-ray (CR) anisotropy as observed by the Milagro observatory. We show a two-dimensional display of the sidereal anisotropy projections in right ascension (R.A.) 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 CRs with a median energy of 6 TeV. The dominant feature is a deficit region of depth (2.49 ± 0.02 stat. ± 0.09 sys.) ×10-3 in the direction of the Galactic north pole centered at 189 deg R.A. We observe a steady increase in the magnitude of the signal over seven years.

Abdo, A. A.; Allen, B. T.; Aune, T.; Berley, D.; Casanova, S.; Chen, C.; Dingus, B. L.; Ellsworth, R. W.; Fleysher, L.; Fleysher, R.; Gonzalez, 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.; Nemethy, P.; Noyes, D.; Pretz, J.; 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.

2009-06-01

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

Circular configuration of the genome of ascoviruses.  

PubMed

A circular configuration of genomic DNA was observed in ascoviruses isolated from two species of insects of the family Noctuidae [fall armyworm (Spodoptera frugiperda) and cotton bollworm (Helicoverpa zea)] using restriction endonuclease (REN) digestion, conventional gel electrophoresis, pulsed-field gel electrophoresis and Southern hybridization analysis. This circular configuration of ascovirus genomic DNA was established based on the difference between linear and circular DNA in the numbers of fragments resolved on agarose gel electrophoresis after single and double REN digestion. Genomic DNA of ascoviruses was found to be sheared after purification. PMID:10374973

Cheng, X W; Carner, G R; Brown, T M

1999-06-01

129

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

130

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

SciTech Connect

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

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

2011-09-20

131

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

NASA Astrophysics Data System (ADS)

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

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

2012-10-01

132

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

SciTech Connect

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

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

2011-09-20

133

Observations of whistler-mode chorus in a large range of radial distances  

NASA Astrophysics Data System (ADS)

Whistler-mode chorus emissions are known for their capacity to interact with energetic electrons. We use data collected by the Cluster mission after 2005, when the orbit of the four Cluster spacecraft changed, thus facilitating the analysis of chorus in a large range of different radial distances from the Earth. We concentrate our analysis on the equatorial source region of chorus. We use multipoint measurements of the WBD and STAFF-SA instruments to characterize propagation and spectral properties of the observed waves. We show that intense whistler-mode emissions are found at large radial distances up to the dayside magnetopause. These emissions either have the form of hiss or they contain the typical structure of chorus wave packets. This result is supported by case studies as well as by statistical results, using the unprecedented database of Cluster measurements.

Santolik, O.; Macusova, E.; Gurnett, D. A.; Pickett, J. S.; Cornilleau-Wehrlin, N.

2011-12-01

134

Observation of large electric polarization in orthorhombic TmMnO3 thin films  

NASA Astrophysics Data System (ADS)

High-quality orthorhombic (OT) TmMnO3 (TMO) thin films with a-axis perpendicular to the film surface are grown epitaxially on Nb-doped SrTiO3(110) substrates using pulsed laser deposition. The structural, magnetic, and electric properties of OT-TMO films are measured. We found that a strong coupling between the magnetic structure and the electric polarization. Our experimental results also show that ferroelectricity in OT-TMO thin films below 32 K. Furthermore, the large electric polarization up to 0.45 ?C/cm2 is observed at 10 K, supporting a theoretical prediction of large polarization in the E-type spin structure in this system.

Han, T. C.; Chao, H. H.

2010-12-01

135

The distance to the Large Magellanic Cloud from observations of SN1987A  

NASA Astrophysics Data System (ADS)

The distance to the Large Magellanic Cloud (LMC), although of basic importance to astrophysics, is still not known very well. The latest review (van den Bergh 1989) quotes mo-M = 18.45 +/- 0.1 or 49.0 +/- 2.2 kpc as a result of many methods applied to thousands of objects. Here we present a distance determination which attains comparable accuracy using only one object, SN1987A. The radius of the photosphere of SN1987A, calculated from luminosity Lbol and temperature Teff is distance-dependent. Spectroscopic radii, calculated from observed Doppler shifts, are distance-independent. Comparison of rph with rsp yields the distance.

Schmidt-Kaler, Theodor

136

Fermi Large Area Telescope Observations of the Cosmic-Ray Induced  

SciTech Connect

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

Abdo, A.

2012-02-29

137

Fermi Large Area Telescope Observations of Supernova Remnants Interacting with Molecular Clouds  

NASA Astrophysics Data System (ADS)

We report the detection of ?-ray emission coincident with four supernova remnants (SNRs) using data from the Large Area Telescope on board the Fermi Gamma-ray Space Telescope. G349.7+0.2, CTB 37A, 3C 391, and G8.7-0.1 are SNRs known to be interacting with molecular clouds, as evidenced by observations of hydroxyl (OH) maser emission at 1720 MHz in their directions. SNR shocks are expected to be sites of cosmic-ray acceleration, and clouds of dense material can provide effective targets for production of ?-rays from ?0 decay. The observations reveal unresolved sources in the direction of G349.7+0.2, CTB 37A, and 3C 391, and a possibly extended source coincident with G8.7-0.1, all with significance levels greater than 10?.

Castro, Daniel; Slane, Patrick

2010-07-01

138

Observation of visible forbidden lines from highly charged tungsten ions at the large helical device  

NASA Astrophysics Data System (ADS)

Visible line emission from highly charged tungsten ions has been observed at the large helical device (LHD) using a tracer encapsulated solid pellet. One of the measured lines is assigned to a magnetic-dipole (M1) line of the ground-term fine-structure transition of W26+. The other line is unidentified but probably due to a highly charged tungsten ion. Photon emission was observed at 40 lines of sight divided along the vertical direction of a horizontally elongated poloidal cross section of the LHD plasma. The line-integrated intensity of the M1 line along each line of sight indicates a peaked profile at the plasma center where the electron temperatures are high enough so that tungsten ions are highly ionized.

Kato, D.; Goto, M.; Morita, S.; Murakami, I.; Sakaue, H. A.; Ding, X. B.; Sudo, S.; Suzuki, C.; Tamura, N.; Nakamura, N.; Watanabe, H.; Koike, F.

2013-09-01

139

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

140

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

141

Marine Stratocumulus during VOCALS: Comparing Microphysical Observations to Large-Eddy Simulation Results  

NASA Astrophysics Data System (ADS)

Large-eddy simulation (LES) is a tool capable of resolving cloud-scale processes and has been used extensively for study of the stratocumulus-topped boundary layer. Understanding the strengths and deficiencies of LES is crucial if we are to use it effectively. The ability of LES to accurately represent detailed microphysics has been sparsely investigated (Khairoutdinov and Kogan, 1999), and we seek to advance knowledge in this area. Here we study how well LES coupled with an explicit binned resolving model can simulate daytime observations of stratocumulus dynamics and microphysics during VOCALS. Our observations were acquired from the CIRPAS Twin Otter on October 19th, 2008 centered around 20 S, 72 W. During this day a well-mixed, non-drizzling stratus-topped boundary layer of ~300m thickness was observed. The cloud top height, thermodynamic profile, and wind profile all remained relatively stationary throughout the observation period. Potential temperature and moisture content jumps were 15.2 K and -6.55 g/kg, respectively. The Passive Cavity Aerosol Spectrometer Probe (PCASP) showed aerosol concentrations elevated (~600 cm^-3) from what is expected for clean maritime conditions. The Twin Otter was outfitted an airborne phase Doppler Interferometer (PDI) providing detailed microphysical information about the cloud layer. The PDI data show a monomodal drop size distribution that exhibits little change in shape with change in liquid water content (LWC), consistent with extreme inhomogeneous mixing of air parcels. For our numerical model we employ the Regional Atmospheric Modeling System (RAMS, Cotton et al., 2001) in LES mode. So that the results of our LES best matched the detailed microphysical data from the PDI, we coupled a binned microphysical model to our LES (Feingold et al., 1996; Tzivion et al., 1987). Our LES cloud top height after model spin-up then matches the observations while model cloud base is 25 m than observations. Comparisons between probability distribution functions of LWC at matched heights in the observations and the LES results show reasonable agreement. The strength of simulated boundary-layer circulations is substantially weaker than what the observations suggest. These weak circulations are associated with a somewhat decoupled cloud layer in the LES which was not evident in our daytime observations. We suggest that this decoupling could be related to modeled overentrainment of free tropospheric air. Our model cloud top increases by 10 m over one hour of simulation, while no cloud top height increase was observed. For large LWCs (0.3 g/kg or greater) LES predicts drop size distribution remarkably well. For lower LWCs, the LES shows a substantial tail to smaller drop sizes not present in the observations. We attribute this discrepancy to the assumption of purely homogeneous mixing in the LES model. The LES also predicts a substantial number of small cloud droplets (~ 2 micron diameter) that are not observed by the PDI.

Petters, J.; Rossiter, D. L.; Feingold, G.; Jiang, H.; Chuang, P. Y.

2010-12-01

142

Observing cataclysmic variables with the Southern African Large Telescope (SALT): new capabilities and new insights  

NASA Astrophysics Data System (ADS)

The Southern African Large Telescope (SALT) - a 10-m segmented mirror telescope - has recently (as of Sept 2011) begun science operations following a period of recommissioning during which two major problems (image quality and spectrograph throughput) were succesfully addressed. SALT and its First Generation science instruments provide a variety of capabilities which can be fully exploited in observing CVs and related objects. These include good UV performance (to the atmospheric cutoff at ˜310-320nm), high time resolution (0.1 sec) observations in many modes, full polarimetric capabilities (imaging & spectroscopy) and a 100% queue scheduling mode which is well suited to target of opportunity and synoptic observations of CVs. In this paper I present some initial results from commissioning science programs which highlight these capabilities. Examples include exquisite high time resloution eclipse light curves of Polars, which fully resolve the accretion hots spots. SALT observations of the recent outburst of the recurrent nova T Pyx have provided new insights by virtue of two capabilities: UV spectroscopy, revealing the Bowen flourescence lines, and spectropolarimetry showing line depolarization and little interstellar polarization.

Buckley, D. A. H.

143

Color Observations of Large Trans-Neptunian Objects as a Function of Rotational Phase  

NASA Astrophysics Data System (ADS)

Observationally there is widespread interest in comparing different classes of TNOs in color space. Currently, there are claims of color differences and trends among different classes of TNOs (Jewitt & Luu 2001, Boehnhardt et al. 2001, Davies et al. 2000, Tegler & Romanishin 2000). However, the number of TNOs with reliable dynamical classifications and colors as a function of rotational phase are still small (e.g. 1996 TO_66, Hainaut et al. 2000). We propose to observe colors of several bright (V brighter than 21.5 mag) trans-Neptunian objects (TNOs) as a function of rotational phase, therefore complementing ongoing programs at bigger telescopes which primarily observe fainter objects. This approach is necessary because many TNOs show large peak to peak variations in their lightcurves and measured colors of the same objects from different authors (see Jewitt & Luu 2001) often lie outside the formal errors of each other. We will concentrate on the scattered disk objects, which have fewer color observations than other TNO dynamical classes and are the most diagnostic for distinguishing theories for the migration of giant planets (e.g. Hahn & Malhotra 1999).

Mueller, Beatrice E. A.; Samarasinha, Nalin H.

2003-02-01

144

Circular Polarization of Galilean Satellites of Jupiter  

NASA Astrophysics Data System (ADS)

We present the results of circular polarization measurements of Jupiter Galilean satellites carried out during Jupiter oppositions of 2005, 2007-2009 and 2010 in phase angle range ? = 0.14°-11.0°. It has given us a possibility to compose phase-angle dependences of circular polarization for Galilean satellites Io, Europa, Ganymede and Callisto in the entire range of phase angles accessible to ground-based observations.

Velichko, F. P.; Psarev, V. A.; Rikhtehgar, A.

2012-03-01

145

Boston University Physics Applets: Vertical Circular Motion  

NSDL National Science Digital Library

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

Duffy, Andrew

2008-08-01

146

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

NASA Astrophysics Data System (ADS)

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 moment, the predictability of these systems remains limited. Due to the scarcity of conventional observations, use is made of NOAA/MetOp satellite observations, for which advantage can be taken of the time coverage differences between the platforms that carry it, to give a very complete temporal description of the disturbances. A combination of AMSU-B (Advanced Microwave Sounding Unit-B)/MHS (Microwave Humidity Sounder) observations permit to investigate precipitation associated with these systems while coincident AMSU-A (Advanced Microwave Sounding Unit-A) observations give insights into the larger synoptic-scale environment in which they occur. Three different cases (in terms of intensity, location, trajectory, duration, and periods of the year - May, September and December, respectively) were investigated. Throughout these time periods, AMSU-A observations show that the persisting deep outflow of cold air over the sea together with an upper-level trough upstream constituted a favourable environment for the development of medicanes. AMSU-B/MHS based diagnostics show that convection and precipitation areas are large in the early stage of the low, but significantly reduced afterwards. Convection is maximum just after the upper-level trough, located upstream of cold mid-tropospheric air, reached its maximum intensity and acquired a cyclonic orientation.

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

2010-10-01

147

Estimation of large scale daily evapotranspiration using geostationary meteorological satellite observations  

NASA Astrophysics Data System (ADS)

Accurate estimate of daily evapotranspiration over large areas is important both for understanding hydrological processes on the earth and for water resources management. Remote sensing observations of land surface have been used to estimate evapotranspiration (ET) over large areas, when point measurements cannot provide such information efficiently because of insufficient coverage density. Conventional methods to estimate regional daily ET are based on extrapolation of instantaneous ET estimates usually from polar-orbiting satellite observations at clear sky moments and assuming clear sky conditions prevailing throughout the day. However, such methods are unable to overcome uncertainties caused by eventual cloud interference along a day course. The new generations of geostationary meteorological satellites having frequent temporal sampling and relatively higher spatial resolution than older generations, carries the promise of solving the problem of time integration to estimate daily ET. Such observations at high temporal resolution are particularly helpful in capturing the diurnal variation of land surface temperature, the most critical land surface parameter in determining the energy partitioning between sensible heat flux and latent heat flux. However, cloud-free measurements during a day may be sparse and not simultaneous for different pixels. A time series analysis technique using Fourier transfer analysis as described in Harmonic Analyze of Time Series (HANTS) is therefore needed to fill the gaps in sparse satellite observations due to clouds contamination. In this research, instantaneous latent heat flux in turn the evapotranspiration is calculated from an energy balance based model SEBS (Surface Energy Balance System) firstly using a set of land surface parameters provided by LandSAF products retrieved from observations of SEVIRI (Spinning Enhanced Visible and Infrared Imager) onboard Meteosat Second Generation (MSG). Secondly, HANTS algorithm is used to reconstruct gap-filled time series of instantaneous ET along a day. In the end, daily evapotranspiration is calculated from the reconstructed gap-filled time series of instantaneous estimation of evapotranspiration. The algorithm validation was done using data from limited number of flux tower sites of CarboEurope project in Europe by comparing the energy balance flux components estimated by SEBS with tower flux measurements. Analyses of daily variation of estimated surface heat fluxes show that the proposed method is able to generate large scale net radiation, sensible, latent, and soil heat fluxes that follow closely daily variation of the courses of these flux components as observed by ground measurements. It was found that abnormal values in the estimated latent heat flux are observed near cloudy pixels. It indicates that pixels close to cloudy pixels may be affected by clouds but not masked in the MSG land surface temperature product. In general, reconstruction of evapotranspiration time-series using HANTS algorithm is demonstrated to be a promising technique to overcome the interference of clouds and preserve inherent trends of evapotranspiration process over a day when applied to a large-scale. HANTS reconstruction is capable to maintain daily variation of evapotranspiration on less cloudy days by keeping good correlation with the ground measurements. However, the technique has proven to be limited to areas with cloud cover less than 60% along a day course. Comparison of the daily total ET estimated from SEBS/MSG/HANTS technique with daily ET calculated using conventional method (using one-time measurements of a day and assuming clear sky throughout a day) has shown that the former is less affected by the intensity of cloud interference along the day.

Jia, L.; Daamen, M.

2009-04-01

148

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

NASA Astrophysics Data System (ADS)

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

Berger, T.

2012-12-01

149

Strongly sheared stratocumulus convection: an observationally based large-eddy simulation study  

NASA Astrophysics Data System (ADS)

Unusually large wind shears across the inversion in the stratocumulus-topped marine boundary layer (MBL) were frequently observed during VOCALS-REx. To investigate the impact of wind shear on the MBL turbulence structure, a large-eddy simulation (LES) model is used to simulate the strongly sheared MBL observed from Twin-Otter RF 18 on 13 November 2008. The LES simulated turbulence statistics agree in general with those derived from the measurements, with the MBL exhibiting a decoupled structure characterized by an enhanced entrainment and a turbulence intensity minimum just below the clouds. Sensitivity simulations show that the shear forcing tends to reduce the dynamic stability of the inversion, characterized by the bulk (or gradient) Richardson number. This decrease enhances the entrainment mixing, leading to reduced cloud water. Consequently, the turbulence intensity in the MBL is significantly weakened by the intense wind shear. The inversion thickens considerably and the MBL top separates from the cloud top, creating a finite cloud-free sublayer of 10-50 m thickness within the inversion, depending on the Richardson number. The weakened inversion tends to enhance the turbulence buoyant consumption and simultaneously lead to a reduced buoyant production in the cloud layer due to less radiative cooling. These effects may result in a decoupling process that creates the different heating/moistening rates between the cloud and subcloud layer, leading to a two-layered structure in the strongly sheared stratocumulus-topped MBL.

Wang, S.; Zheng, X.; Jiang, Q.

2012-06-01

150

Strong circular photogalvanic effect in ZnO epitaxial films  

SciTech Connect

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

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

2011-12-23

151

Interpreting observed Arctic snow trends with large ensembles of climate simulations  

NASA Astrophysics Data System (ADS)

In response to increasing greenhouse gas concentrations, Northern Hemisphere snow cover extent is predicted to decrease while snowfall is predicted to decrease at midlatitudes but increase at high latitudes. Accurately forecasting both global and regional changes in the coming decades is predicated on the ability to properly simulate historical changes and the ability to separate forced signals from the large amount of natural variability. In this context, we analyze Northern Hemisphere snow trends and trend variability as simulated by coupled and uncoupled configurations of a single comprehensive global climate model, the National Center for Atmospheric Research's Community Earth System Model (CESM). We compare two 40-member ensembles with one another and against observational data products over the historical period, 1981-2010. The model is able to reproduce the observed climatology and variability of snow cover extent and snow water equivalent (albeit the latter to a lesser degree of fidelity). Despite this success, in either ensemble internal climate noise generates widely different spatial patterns of snow trends in a given climate realization. These patterns are related in an intuitive way to the long-term temperature, precipitation and circulation trends of the given realization. For springtime snow cover, the mean trends of both ensembles have decreasing trends, consistent with observations but of weaker magnitude. In contrast the wintertime trends in snow cover are much stronger in the coupled model than the uncoupled model; such a large decrease in wintertime snow is not seen in the observations. We demonstrate that the difference in the wintertime trend magnitudes is ultimately related to differences in the pattern of sea surface temperature trends in the respective ensembles. The ensemble-mean of the coupled configuration has a shallow northern Pacific temperature gradient that leads to a strong decreasing snow signal over North America. However, a subset of realizations from this experiment shows better correlation with the historical SSTs, and correspondingly shows similar trends in snow cover and snow water equivalent to the ensemble mean of the uncoupled model. These results support the idea that historical SST patterns have played a large role in determining the amount of warming and snow cover trends over North America in the last thirty years.

Kushner, Paul; Mudryk, Lawrence

2013-04-01

152

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

2011-03-06

153

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

NASA Astrophysics Data System (ADS)

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

Bronfman, L.; Merello, M.

2013-10-01

154

Large-scale quasiperiodic plasma bubbles: C/NOFS observations and causal mechanism  

NASA Astrophysics Data System (ADS)

Large-scale periodic plasma bubbles are often observed by ionospheric radars and satellites. The seeding effect of atmospheric gravity waves has been widely used to explain the generation of periodic plasma bubbles. However, it has not been well understood where the seeding process occurs and how a series of plasma bubbles is triggered. In this study, we present the observations of equatorial plasma bubbles by the Communication/Navigation Outage Forecasting System (C/NOFS) satellite. We show examples of quasiperiodic plasma bubbles in the post-midnight sector, with nearly equal distance of 800-1000 km between adjacent bubbles, in 2008 under deep solar minimum conditions. The bubble chain covered a longitudinal range of ~7000 km between 00:00 and 04:00 LT. Quasiperiodic plasma bubbles were also measured by C/NOFS in the evening sector in 2011 during the ascending phase of the solar activity, and the longitudinal distance between adjacent bubbles was ~500 km. We propose a causal mechanism to explain the generation of quasiperiodic plasma bubbles. In this scenario, atmospheric gravity waves are generated near the sunset terminator and initiate the Rayleigh-Taylor instability there. The spatial (longitudinal) periodicity of plasma bubbles is determined by the temporal periodicity of the seeding gravity waves. A period of 15-30 min of the seeding gravity waves corresponds to a longitudinal separation of 500-1000 km between adjacent bubbles. This mechanism provides a reasonable explanation of the observed quasiperiodic plasma bubbles.

Huang, Chao-Song; La BeaujardièRe, O.; Roddy, P. A.; Hunton, D. E.; Ballenthin, J. O.; Hairston, M. R.; Pfaff, R. F.

2013-06-01

155

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

NASA Astrophysics Data System (ADS)

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

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

2013-07-01

156

Broad range of 2050 warming from an observationally constrained large climate model ensemble  

NASA Astrophysics Data System (ADS)

Incomplete understanding of three aspects of the climate system--equilibrium climate sensitivity, rate of ocean heat uptake and historical aerosol forcing--and the physical processes underlying them lead to uncertainties in our assessment of the global-mean temperature evolution in the twenty-first century. Explorations of these uncertainties have so far relied on scaling approaches, large ensembles of simplified climate models, or small ensembles of complex coupled atmosphere-ocean general circulation models which under-represent uncertainties in key climate system properties derived from independent sources. Here we present results from a multi-thousand-member perturbed-physics ensemble of transient coupled atmosphere-ocean general circulation model simulations. We find that model versions that reproduce observed surface temperature changes over the past 50 years show global-mean temperature increases of 1.4-3K by 2050, relative to 1961-1990, under a mid-range forcing scenario. This range of warming is broadly consistent with the expert assessment provided by the Intergovernmental Panel on Climate Change Fourth Assessment Report, but extends towards larger warming than observed in ensembles-of-opportunity typically used for climate impact assessments. From our simulations, we conclude that warming by the middle of the twenty-first century that is stronger than earlier estimates is consistent with recent observed temperature changes and a mid-range `no mitigation' scenario for greenhouse-gas emissions.

Rowlands, Daniel J.; Frame, David J.; Ackerley, Duncan; Aina, Tolu; Booth, Ben B. B.; Christensen, Carl; Collins, Matthew; Faull, Nicholas; Forest, Chris E.; Grandey, Benjamin S.; Gryspeerdt, Edward; Highwood, Eleanor J.; Ingram, William J.; Knight, Sylvia; Lopez, Ana; Massey, Neil; McNamara, Frances; Meinshausen, Nicolai; Piani, Claudio; Rosier, Suzanne M.; Sanderson, Benjamin M.; Smith, Leonard A.; Stone, Dáithí A.; Thurston, Milo; Yamazaki, Kuniko; Hiro Yamazaki, Y.; Allen, Myles R.

2012-04-01

157

A new analysis of the ESO Very Large Telescope (VLT) observations of Titan  

NASA Astrophysics Data System (ADS)

In this presentation, we report a new analysis of ESO Very Large Telescope (VLT) observations of Titan at about 2 m, in the methane band and window. The VLT data consists in two north-south cuts of Titan's disk with about twenty points in resolution, each point being a spectrum. To analyze this observation, we use the atmospheric properties of Titan recently measured by Huygens, the methane coefficients proposed by Boudon et al. (2006), while the description of the haze layer is from a database derived from the simulations of the Titan Global Climate of the IPSL. We used the radiative transfer model SHDOMPP developed by Evans. This work is hence a significant improvement over the previous analysis by Negrão et al. (2007) In this work, we essentially focus on the distribution of the airborn scatterers (e.g, haze aerosols, clouds, mist). In a first step, we compute the outgoing intensity using the prediction of the GCM database for the haze, and we compare the results with the VLT observations. These comparisons allow us to check the validity of the haze layer provided by the GCM database. In a second step, we modify the haze properties and we include a layer of bright scatterers in the troposphere (liquid droplets as observed by DISR) to improve the fit. This work yields a latitude-altitude map of Titan's haze from the VLT data, and we estimate the impact of the haze and the cloud layer on the surface albedo retrieval. 1) Boudon, V., M. Rey, and M. Loete (2006), The Vibrational Levels of Methane Obtained from Analyses of High- Resolution Spectra, J. Quant Spectrosc., 98, 394-404. 2) Negrão, A., Hirtzig, M., Coustenis, A., Gendron, E., Drossart, P., Rannou, Combes, M., Boudon, V. (2007), 2-micron spectroscopy of Huygens' landing site on Titan with VLT/NACO. J. Geophys. Res. Planets, 112, E02S92.

Cours, T.; Rannou, P.; Coustenis, A.; Negrao, A.; Hirtzig, M.

2009-04-01

158

Observing strongly interacting vector boson systems at the CERN Large Hadron Collider  

SciTech Connect

We explore the potential of the CERN Large Hadron Collider to access a strongly interacting electroweak symmetry breaking sector via weak boson scattering with W{sup +}W{sup -}jj, ZZjj, and W{sup {+-}}Zjj final states. As examples of models with scalar or vector resonances we concentrate on a scenario with a heavy Higgs boson and on a warped Higgsless Kaluza-Klein model of narrow spin-one resonances. The signal and the most prominent background processes are evaluated using exact tree-level matrix elements including full off-shell and finite width effects for final states with two tagging jets and four leptons. Using double forward jet-tagging techniques, we derive dedicated cuts on the observable jets and charged leptons to suppress standard model backgrounds. We demonstrate that the LHC has substantial sensitivity to strong interactions in the electroweak symmetry breaking sector.

Englert, C.; Zeppenfeld, D. [ITP, Universitaet Karlsruhe, 76128 Karlsruhe (Germany); Jaeger, B. [Institut fuer Theoretische Physik und Astrophysik, Universitaet Wuerzburg, 97074 Wuerzburg (Germany); KEK Theory Division, 305-0801 Tsukuba (Japan); Worek, M. [ITP, Universitaet Karlsruhe, 76128 Karlsruhe (Germany); Institute of Physics, University of Silesia, 40-007 Katowice (Poland)

2009-08-01

159

Observation of a large reaction cross section in the drip-line nucleus 22C.  

PubMed

Reaction cross sections (sigma(R)) for 19C, 20C and the drip-line nucleus 22C on a liquid hydrogen target have been measured at around 40A MeV by a transmission method. A large enhancement of sigma(R) for 22C compared to those for neighboring C isotopes was observed. Using a finite-range Glauber calculation under an optical-limit approximation the rms matter radius of 22C was deduced to be 5.4+/-0.9 fm. It does not follow the systematic behavior of radii in carbon isotopes with N < or = 14, suggesting a neutron halo. It was found by an analysis based on a few-body Glauber calculation that the two-valence neutrons in 22C preferentially occupy the 1s(1/2) orbital. PMID:20366816

Tanaka, K; Yamaguchi, T; Suzuki, T; Ohtsubo, T; Fukuda, M; Nishimura, D; Takechi, M; Ogata, K; Ozawa, A; Izumikawa, T; Aiba, T; Aoi, N; Baba, H; Hashizume, Y; Inafuku, K; Iwasa, N; Kobayashi, K; Komuro, M; Kondo, Y; Kubo, T; Kurokawa, M; Matsuyama, T; Michimasa, S; Motobayashi, T; Nakabayashi, T; Nakajima, S; Nakamura, T; Sakurai, H; Shinoda, R; Shinohara, M; Suzuki, H; Takeshita, E; Takeuchi, S; Togano, Y; Yamada, K; Yasuno, T; Yoshitake, M

2010-02-08

160

Observation of a Large Reaction Cross Section in the Drip-Line Nucleus C22  

NASA Astrophysics Data System (ADS)

Reaction cross sections (?R) for C19, C20 and the drip-line nucleus C22 on a liquid hydrogen target have been measured at around 40AMeV by a transmission method. A large enhancement of ?R for C22 compared to those for neighboring C isotopes was observed. Using a finite-range Glauber calculation under an optical-limit approximation the rms matter radius of C22 was deduced to be 5.4±0.9fm. It does not follow the systematic behavior of radii in carbon isotopes with N?14, suggesting a neutron halo. It was found by an analysis based on a few-body Glauber calculation that the two-valence neutrons in C22 preferentially occupy the 1s1/2 orbital.

Tanaka, K.; Yamaguchi, T.; Suzuki, T.; Ohtsubo, T.; Fukuda, M.; Nishimura, D.; Takechi, M.; Ogata, K.; Ozawa, A.; Izumikawa, T.; Aiba, T.; Aoi, N.; Baba, H.; Hashizume, Y.; Inafuku, K.; Iwasa, N.; Kobayashi, K.; Komuro, M.; Kondo, Y.; Kubo, T.; Kurokawa, M.; Matsuyama, T.; Michimasa, S.; Motobayashi, T.; Nakabayashi, T.; Nakajima, S.; Nakamura, T.; Sakurai, H.; Shinoda, R.; Shinohara, M.; Suzuki, H.; Takeshita, E.; Takeuchi, S.; Togano, Y.; Yamada, K.; Yasuno, T.; Yoshitake, M.

2010-02-01

161

Observation of a Large Reaction Cross Section in the Drip-Line Nucleus {sup 22}C  

SciTech Connect

Reaction cross sections ({sigma}{sub R}) for {sup 19}C, {sup 20}C and the drip-line nucleus {sup 22}C on a liquid hydrogen target have been measured at around 40A MeV by a transmission method. A large enhancement of {sigma}{sub R} for {sup 22}C compared to those for neighboring C isotopes was observed. Using a finite-range Glauber calculation under an optical-limit approximation the rms matter radius of {sup 22}C was deduced to be 5.4+-0.9 fm. It does not follow the systematic behavior of radii in carbon isotopes with N<=14, suggesting a neutron halo. It was found by an analysis based on a few-body Glauber calculation that the two-valence neutrons in {sup 22}C preferentially occupy the 1s{sub 1/2} orbital.

Tanaka, K.; Aoi, N.; Baba, H.; Kubo, T.; Kurokawa, M.; Michimasa, S.; Motobayashi, T.; Sakurai, H.; Takeshita, E.; Takeuchi, S.; Yamada, K. [RIKEN Nishina Center, Saitama 351-0198 (Japan); Yamaguchi, T.; Suzuki, T.; Kobayashi, K.; Komuro, M.; Nakajima, S.; Shinoda, R.; Yoshitake, M. [Department of Physics, Saitama University, Saitama 338-8570 (Japan); Ohtsubo, T.; Aiba, T. [Department of Physics, Niigata University, Niigata 950-2181 (Japan)

2010-02-12

162

Validation of the Systemic Lupus Erythematosus Activity Questionnaire in a Large Observational Cohort  

PubMed Central

Objective To examine the reliability, construct validity, and responsiveness of the Systemic Lupus Erythematosus Activity Questionnaire (SLAQ) in a large observational cohort of persons with systemic lupus erythematosus (SLE). Methods We evaluated the reliability of the SLAQ using Cronbach's alpha and principal factor analysis and ascertained construct validity by studying the association of the SLAQ with other clinically relevant, validated patient assessments of health. We estimated responsiveness by calculating standardized response means and analyzing the association of changes in SLAQ scores with changes in other patient assessments of health. Results The SLAQ had excellent reliability, as reflected by Cronbach's alpha (0.87) and principal factor analysis (one factor accounted for 92% of the variance). SLAQ scores were strongly correlated with other health indices, including the Short Form 12 Physical Component Summary and the Short Form 36 Physical Functioning subscale. Scores were significantly higher for respondents reporting a flare, more disease activity, hospitalization in the last year, concurrent use of immunosuppressive medication, and work disability. The SLAQ demonstrated a small to moderate degree of responsiveness; standardized response means were 0.66 and ?0.37 for those reporting clinical worsening and improvement, respectively. Across a range of other patient assessments of disease status, the SLAQ had a response in the direction predicted by these other measures. Conclusion The SLAQ demonstrates adequate reliability, construct validity, and responsiveness in our large, community-based cohort and appears to represent a promising tool for studies of SLE outside the clinical setting.

Yazdany, Jinoos; Yelin, Edward H.; Panopalis, Pantelis; Trupin, Laura; Julian, Laura; Katz, Patricia P.

2013-01-01

163

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

NASA Astrophysics Data System (ADS)

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

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

2013-03-01

164

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

165

FERMI LARGE AREA TELESCOPE OBSERVATIONS OF PSR J1836+5925  

SciTech Connect

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

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

2010-04-01

166

Circular Ribbon Flares and Homologous Jets  

NASA Astrophysics Data System (ADS)

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? 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

2012-12-01

167

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

168

SDO/AIA OBSERVATIONS OF LARGE-AMPLITUDE LONGITUDINAL OSCILLATIONS IN A SOLAR FILAMENT  

SciTech Connect

We present the first Solar Dynamics Observatory/Atmospheric Imaging Assembly observations of the large-amplitude longitudinal (LAL) oscillations in the south and north parts (SP and NP) of a solar filament on 2012 April 7. Both oscillations are triggered by flare activities close to the filament. The period varies with filamentary threads, ranging from 44 to 67 minutes. The oscillations of different threads are out of phase, and their velocity amplitudes vary from 30 to 60 km s{sup -1}, with a maximum displacement of about 25 Mm. The oscillations of the SP repeat for about four cycles without any significant damping and then a nearby C2.4 flare causes the transition from the LAL oscillations of the filament to its later eruption. The filament eruption is also associated with a coronal mass ejection and a B6.8 flare. However, the oscillations of the NP damp with time and die out at last. Our observations show that the activated part of the SP repeatedly shows a helical motion. This indicates that the magnetic structure of the filament is possibly modified during this process. We suggest that the restoring force is the coupling of the magnetic tension and gravity.

Li Ting; Zhang Jun, E-mail: liting@nao.cas.cn, E-mail: zjun@nao.cas.cn [Key Laboratory of Solar Activity, National Astronomical Observatories, Chinese Academy of Sciences, Beijing 100012 (China)

2012-11-20

169

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

170

Observations of galaxies at z>6. The properties of large, spectroscopic samples  

NASA Astrophysics Data System (ADS)

Observed properties of spectroscopically confirmed galaxies at z5 and z6 based on selection from deep, multi-wavelength wide-field samples provide a picture of the current status of the properties of high-redshift galaxies and their evolution to yet higher redshifts. In the current presentation, we use results of deep, wide-field spectroscopy with the multi-object Deimos spectrograph on Keck in combination with deep, wide-field multi-color imaging studies using the SuprimeCam CCD camera of Subaru for a number of fields, to evaluate the luminosity function of high-redshift galaxies and its evolution at z>6. High-redshift candidates are selected using both narrow-band Lyman alpha emission and broad-band colors with a high success-rate from a number of SuprimeCam (0.5 degree FOV) fields. Luminosity functions and Lyman? emission line profiles and equivalent widths appear similar between samples at z5.7 and z6.5, and the galaxy distribution is structured both spatially and in redshift. A large amount of cosmic variance is seen in the distribution of z6 galaxies from field to field. The observed properties are discussed in relationship to their impact on strategies for complementary optical surveys of high-redshift galaxies, and in relationship to surveys at very different wavelengths (X-ray, far-infrared, and submillimeter) that cover the same regions.

Hu, Esther M.; Cowie, Lennox L.; Kakazu, Yuko

2007-08-01

171

Observations of Galaxies at z>6 - The Properties of Large, Spectroscopic Samples  

NASA Astrophysics Data System (ADS)

Observed properties of spectroscopically confirmed galaxies at z>>5 and z>>6 based on selection from deep, multi-wavelength wide-field samples provide a picture of the current status of the properties of high-redshift galaxies and their evolution to yet higher redshifts. In the current presentation, we use results of deep, wide-field spectroscopy with the multi-object DEIMOS spectrograph on Keck in combination with deep, wide-field multi-color imaging studies using the SuprimeCam CCD camera of Subaru for a number of fields, to evaluate the luminosity function of high-redshift galaxies and its evolution at z>6. High-redshift candidates are selected using both narrow-band Lyman alpha emission and broad-band colors with a high success-rate from a number of SuprimeCam (0.5 degree FOV) fields. Luminosity functions and Lyman alpha emission line profiles and equivalent widths appear similar between samples at z~5.7 and z~6.5, and the galaxy distribution is structured both spatially and in redshift. A large amount of cosmic variance is seen in the distribution of z>>6 galaxies from field to field. The observed properties are discussed in relationship to their impact on strategies for complementary optical surveys of high-redshift galaxies, and in relationship to surveys at very different wavelengths (X-ray, far-infrared, and submillimeter) that cover the same regions.

Hu, E. M.; Cowie, L. L.; Kakazu, Y.

2006-08-01

172

Very Large Array Observations of Circumstellar Envelopes in the H I 21-cm Line  

NASA Astrophysics Data System (ADS)

The H I 21-cm line is a powerful tool for probing the circumstellar envelopes of asymptotic giant branch (AGB) stars, as it is able to trace envelope kinematics up to 1 pc from the star and thus envelope interactions with the interstellar medium (ISM). We present Very Large Array D-configuration 21-cm line data of the circumstellar envelopes of three AGB stars, X Her, R Peg, and Y UMa. H I emission had previously been detected in single-dish observations of all three stars. The observed envelope morphologies are complex and diverse. X Her's envelope appears to be swept back into a "cometary” tail by motion through the ISM; R Peg displays an arc- or "horseshoe"-like shape; and Y UMa has an "s"-shaped envelope. The detected H I envelopes have extents of 0.1-1 pc and masses of 0.8 x 10-3 to 6 x 10-3 MSun. These new results strengthen earlier indications that circumstellar envelope morphologies can be significantly influenced by their environments, and may have implications for the morphologies displayed by planetary nebulae. This project was supported through an NSF/REU grant at MIT Haystack Observatory.

Johnson, Marshall C.; Matthews, L. D.

2010-01-01

173

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

NASA Astrophysics Data System (ADS)

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

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

2013-06-01

174

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

NASA Astrophysics Data System (ADS)

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

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

2013-07-01

175

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

NASA Astrophysics Data System (ADS)

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

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

2009-12-01

176

Modeling and surface observations of arsenic dispersion from a large Cu-smelter in southwestern Europe  

NASA Astrophysics Data System (ADS)

Arsenic is a toxic element for human health. Consequently, a mean annual target level for arsenic at 6 ng m-3 in PM10 was established by the European Directive 2004/107/CE to take effect January 2013. Cu-smelters can contribute to one-third of total emissions of arsenic in the atmosphere. Surface observations taken near a large Cu-smelter in the city of Huelva (Spain) show hourly arsenic concentrations in the range of 0-20 ng m-3. The arsenic peaks of 20 ng m-3 are higher than values normally observed in urban areas around Europe by a factor of 10. The Hybrid Single Particle Lagrangian Integrated Trajectory (HYSPLIT) model has been employed to predict arsenic emissions, transport, and dispersion from the Cu-smelter. The model utilized outputs from different meteorological models and variations in the model physics options to simulate the uncertainty in the dispersion of the arsenic plume. Modeling outputs from the physics ensemble for each meteorological model driving HYSPLIT show the same number of arsenic peaks. HYSPLIT coupled with the Weather Research and Forecasting (WRF-ARW) meteorological output predicted the right number of peaks for arsenic concentration at the observation site. The best results were obtained when the WRF simulation used both four-dimensional data assimilation and surface analysis nudging. The prediction was good in local sea breeze circulations or when the flow was dominated by the synoptic scale prevailing winds. However, the predicted peak was delayed when the transport and dispersion was under the influence of an Atlantic cyclone. The calculated concentration map suggests that the plume from the Cu-smelter can cause arsenic pollution events in the city of Huelva as well as other cities and tourist areas in southwestern Spain.

Chen, Bing; Stein, Ariel F.; Castell, Nuria; de la Rosa, Jesus D.; Sanchez de la Campa, Ana M.; Gonzalez-Castanedo, Yolanda; Draxler, Roland R.

2012-03-01

177

Fermi Large Area Telescope Observations of a Candidate Young Radio Source  

NASA Astrophysics Data System (ADS)

Using 19 months of Fermi LAT data, we investigate the gamma-ray properties of the radio-loud active galaxy 4C+55.17 (z=0.896) and re-examine its classification as a quasar-hosted blazar, considering instead its possible nature as a gamma-ray emitting young radio source. The active galaxy 4C+55.17 has a history of gamma-ray observations dating back to the EGRET era. Commonly classified as a Flat Spectrum Radio Quasar (FSRQ) due to its radio spectral shape and broad optical emission lines, the association of the EGRET source with 4C+55.17 remained tentative at the time, as the source exhibited spectral and morphological properties that were unlike any of the other bright gamma-ray blazars. With the improved angular resolution and sensitivity of the Large Area Telescope on board the Fermi Gamma-ray Space Telescope, the association of the gamma-ray source with 4C+55.17 is now confirmed due to the precise gamma-ray localization. An investigation of the gamma-ray properties of this source has revealed it to be an atypical member of the gamma-ray emitting FSRQ's, with an unusually hard and non-variable gamma-ray spectrum which extends up to the observed photon energies of 145 GeV despite its considerably high redshift for a very-high energy (>100 GeV) emitter. We further show that the high energy (>100 MeV) spectrum of this source may be formally extrapolated into the detectable range of ground-based Cherenkov telescopes, making it a compelling candidate for very-high energy observations, and in particular for future studies of the extragalactic background light.

McConville, William; Ostorero, L.; Moderski, R.; Stawarz, L.; Cheung, C. C.; Fermi LAT Collaboration

2011-01-01

178

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

179

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

180

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

181

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

182

Circular dichroism of peptides.  

PubMed

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

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

2014-01-01

183

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

184

Isolation of circular yeast artificial chromosomes for synthetic biology and functional genomics studies  

Microsoft Academic Search

Circular yeast artificial chromosomes (YACs) provide significant advantages for cloning and manipulating large segments of genomic DNA in Saccharomyces cerevisiae. However, it has been difficult to exploit these advantages, because circular YACs are difficult to isolate and purify. Here we describe a method for purification of large circular YACs that is more reliable compared with previously described protocols. This method

Vladimir N Noskov; Daniel G Gibson; Sun-Hee Leem; Vladimir Larionov; Ray-Yuan Chuang; Natalay Kouprina

2010-01-01

185

Chemical synthesis of circular proteins.  

PubMed

Circular proteins, once thought to be rare, are now commonly found in plants. Their chemical synthesis, once thought to be difficult, is now readily achievable. The enabling methodology is largely due to the advances in entropic chemical ligation to overcome the entropy barrier in coupling the N- and C-terminal ends of large peptide segments for either intermolecular ligation or intramolecular ligation in end-to-end cyclization. Key elements of an entropic chemical ligation consist of a chemoselective capture step merging the N and C termini as a covalently linked O/S-ester intermediate to permit the subsequent step of an intramolecular O/S-N acyl shift to form an amide. Many ligation methods exploit the supernucleophilicity of a thiol side chain at the N terminus for the capture reaction, which makes cysteine-rich peptides ideal candidates for the entropy-driven macrocyclization. Advances in desulfurization and modification of the thiol-containing amino acids at the ligation sites to other amino acids add extra dimensions to the entropy-driven ligation methods. This minireview describes recent advances of entropy-driven ligation to prepare circular proteins with or without a cysteinyl side chain. PMID:22700959

Tam, James P; Wong, Clarence T T

2012-06-14

186

Chemical Synthesis of Circular Proteins*  

PubMed Central

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

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

2012-01-01

187

Observing Recent Changes in the Large-Scale Arctic Energy Budget  

NASA Astrophysics Data System (ADS)

Changes in the large-scale energy budget of the Arctic are examined using a variety of next-generation reanalysis and observational data. An effort is made to construct a best-guess of the current arctic energy budget using a variety of atmospheric data. For the period of 2000-2005, monthly means from the Clouds and the Earth's Radiant Energy System (CERES) data represents the current most-reliable top of atmosphere radiation budget. The remaining components of the energy budget system in the arctic polar cap (defined as 70 degrees North latitude circle), comprising of the vertically-integrated storage and horizontal transports of energy, and net heat transfers between the atmosphere and the subsurface column, are diagnosed using the Japanese 25-year Reanalysis Project (JRA-25) and the NCEP/NCAR Reanalysis (NRA). The as then record-setting minimum sea-ice extent during the 2005 melt season is used as a marker of recent changes occurring in the arctic climate system. However, changes in each reanalysis differs than the satellite observations. In one example, when compared to the 2000-2005 climatology, CERES shows a shift in the peak TOA radiation from July to June in 2005, a change that is absent in the reanalyses and directly attributable to the early and pronounced albedo reduction. An earlier peak in TOA radiation can strongly modulate the flux energy convergence from lower latitudes through circulation changes. Here, the energy budget framework provides a simplified view of the pathway through which changes of key component parings occur.

Porter, D. F.; Serreze, M.; Cassano, J.

2008-12-01

188

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

NASA Astrophysics Data System (ADS)

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

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

2012-04-01

189

Relations among neutrino observables in the light of a large ? 13 angle  

NASA Astrophysics Data System (ADS)

The recent T2K and MINOS indications for a "large" ? 13 neutrino mixing angle can be accommodated in principle by an infinite number of Yukawa flavour structures in the seesaw model. Without considering any explicit flavour symmetry, there is an instructive exercise one can do: to determine the simplest flavour structures which can account for the data with a minimum number of parameters, simply assuming these parameters to be uncorrelated. This approach points towards a limited number of simple structures which show the minimum complexity a neutrino mass model must generally involve to account for the data. These basic structures essentially lead to only 4 relations between the neutrino observables. We emphasize that 2 of these relations, | {sin {?_{{13}}}} | = {tan {?_{{23}}}}/{\\cos ? }{1 - tan {?_{{12}}}}/{1 + tan {?_{{12}}}} and | {{ sin }{?_{{{13}}}}} | = { sin }{?_{{{12}}}}{R^{{{1}/{4}}}} , with R equiv ? m_{{21}}^2/? m_{{32}}^2 , have several distinctive properties. First, they hold not only with a minimum number of parameters, but also for complete classes of more general models. Second, any value of ? 13 within the T2K and MINOS ranges can be obtained from these relations by taking into account small perturbations. Third, they turn out to be the pivot relations of models with approximate conservation of lepton number, which allow the seesaw interactions to induce observable flavour violating processes, such as ? ? e? and ? ? ??. Finally, in specific cases of this kind, these structures have the rather unique property to allow a full reconstruction of the seesaw Lagrangian from low energy data.

Chu, Xiaoyong; Dhen, Mikaël; Hambye, Thomas

2011-11-01

190

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

191

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

NASA Astrophysics Data System (ADS)

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

Lovkaya, M. N.

2012-06-01

192

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

NASA Astrophysics Data System (ADS)

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

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

2011-12-01

193

Large-scale structure and dynamics of solar active regions observed in the far ultraviolet  

NASA Astrophysics Data System (ADS)

In this thesis high resolution Dopplergrams in CIV (1548) are examined for the purpose of understanding the large scale dynamics of solar active regions and the closely related problem of magnetic structure. The Dopplergrams are compared with photospheric magnetograms and Halpha filtergrams in order to determine the relationship of the flows to the overall magnetic field topology. These observations sample three different heights in the atmosphere and can potentially be used to map the field from the photosphere up through the transition region. Vector properties of the flow and field are inferred from center-to-limb variations in the measured Doppler shift and longitudinal field component. It was found that spatial correlations between features seen in Dopplegrams, magnetograms, and filtergrams are quite close, and that active regions can be naturally divided into three basic parts; strong field regions, weak field corridors between opposite polarities, and surrounding weak field areas. Sizable uncertainties in the Dopplergram interpretation have prevented the description of the transition region flows unambiguously. Two possible scenarios that are consistent with the data are identified. In the most likely of the two, the flows vanish within corridors and surrounding areas, and they produce constant (across the disk) absolute red shifts of about 18 km/s within strong field regions.

Klimchuk, J. A.

194

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.

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

2010-01-01

195

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

196

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

197

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

198

Compact dual-band circular polarizer using twisted Hilbert-shaped chiral metamaterial.  

PubMed

We propose a kind of chiral metamaterial inspired from the fractal concept. The Hilbert fractal perturbation in the twisted split ring resonator element results in compact metamaterial and breaking mirror symmetry, which readily forms chirality over triple bands. The discrepancy between co-polarization conversion and cross-polarization conversion over multiple bands can be explored for multifunctional devices. A multiband circular polarizer is then numerically and experimentally studied in the X band based on the bilayered twisted Hilbert resonator with mutual 90° rotation. The ability of transforming linearly polarized incident waves to circularly polarized waves is unambiguously demonstrated with high conversion efficiency and large polarization extinction ratio of more than 20 dB across dual bands. Moreover, exceptionally strong optical activity and circular dichroism are also observed. PMID:24150334

Xu, He-Xiu; Wang, Guang-Ming; Qi, Mei Qing; Cai, Tong; Cui, Tie Jun

2013-10-21

199

Influence of Slip on the Flow Past Superhydrophobic Circular Cylinders  

Microsoft Academic Search

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

Jonathan Rothstein; Robert Daniello; Nangelie Ferrer; Pranesh Muralidhar

2010-01-01

200

On the pre-main sequence circularization period  

NASA Astrophysics Data System (ADS)

In this paper we present an updated compilation of the currently known pre-main sequence (PMS) spectroscopic binaries (SB) for which orbital elements have been determined. In particular we report our results for and discuss the case of the bona-fide PMS system RX J1603.9-3938, which has a circular orbit and a period of 7.56 days. This is the longest orbital period for a circular orbit found among the bona-fide PMS spectroscopic binaries so far, and we suggest that this system may be thus considered to now set the PMS circularization period. The longer period is compatible with the circularization periods already known for older binary populations such as the Hyades and Praesepe. When considered in the context of the circularization periods for other binary populations of different ages, the new PMS circularization period strongly supports the suggestion of Mathieu et al. (\\cite{M92}) that a hybrid scenario (tidal circularization occurring on both PMS phase and on MS phase) could explain the observed circularization periods as a function of age. The apparently circular orbit observed in another PMS system, RX J1301.0-7654a, with an orbital period of nearly 13 days, may perhaps change this picture when the orbit is improved and the system is better understood. Based on observations carried out at the Swiss Euler Telescope at ESO, La Silla, Chile.

Melo, C. H. F.; Covino, E.; Alcalá, J. M.; Torres, G.

2001-11-01

201

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.

2008-01-01

202

EXPANDED VERY LARGE ARRAY OBSERVATIONS OF THE RADIO EVOLUTION OF SN 2011dh  

SciTech Connect

We report on Expanded Very Large Array observations of the Type IIb supernova 2011dh, performed over the first 100 days of its evolution and spanning 1-40 GHz in frequency. The radio emission is well described by the self-similar propagation of a spherical shockwave, generated as the supernova ejecta interact with the local circumstellar environment. Modeling this emission with a standard synchrotron self-absorption (SSA) model gives an average expansion velocity of v Almost-Equal-To 0.1c, supporting the classification of the progenitor as a compact star (R{sub *} Almost-Equal-To 10{sup 11} cm). We find that the circumstellar density is consistent with a {rho}{proportional_to}r{sup -2} profile. We determine that the progenitor shed mass at a constant rate of Almost-Equal-To 3 Multiplication-Sign 10{sup -5} M{sub Sun} yr{sup -1}, assuming a wind velocity of 1000 km s{sup -1} (values appropriate for a Wolf-Rayet star), or Almost-Equal-To 7 Multiplication-Sign 10{sup -7} M{sub Sun} yr{sup -1} assuming 20 km s{sup -1} (appropriate for a yellow supergiant [YSG] star). Both values of the mass-loss rate assume a converted fraction of kinetic to magnetic energy density of {epsilon}{sub B} = 0.1. Although optical imaging shows the presence of a YSG, the rapid optical evolution and fast expansion argue that the progenitor is a more compact star-perhaps a companion to the YSG. Furthermore, the excellent agreement of the radio properties of SN 2011dh with the SSA model implies that any YSG companion is likely in a wide, non-interacting orbit.

Krauss, M. I.; Chomiuk, L.; Brunthaler, A.; Rupen, M. [National Radio Astronomy Observatory, Socorro, NM 87801 (United States); Soderberg, A. M.; Zauderer, B. A. [Harvard-Smithsonian Center for Astrophysics, 60 Garden St., Cambridge, MA 02138 (United States); Bietenholz, M. F. [Department of Physics and Astronomy, York University, Toronto, M3J 1P3, Ontario (Canada); Chevalier, R. A. [Astronomy Department, University of Virginia, Charlottesville, VA 22904 (United States); Fransson, C. [Department of Astronomy, The Oskar Klein Centre, Stockholm University, 106 91 Stockholm (Sweden)

2012-05-10

203

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

NASA Astrophysics Data System (ADS)

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

Yang, Bin; Lucey, Paul; Glotch, Timothy

2013-03-01

204

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

Microsoft Academic Search

We report on measurements of the cosmic-ray induced -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 6.4x10 photons with energies >100 MeV and 250 hours

A. A. Abdo; M. Ackermann; M. Ajello; K. Bechtol; B. Berenji; E. D. Bloom; A. W. Borgland; A. Bouvier; R. Buehler; R. A. Cameron; E. Charles; J. Chiang; R. Claus; S. W. Digel; E. do Couto e Silva; P. S. Drell; R. Dubois; W. B. Focke; S. Funk; T. Glanzman

2009-01-01

205

Peculiarity of formation of doubly charged ions upon multiphoton ionization of barium atoms by linearly and circularly polarized radiation  

Microsoft Academic Search

The process of formation of doubly charged ions upon multiphoton ionization of barium atoms by linearly and circularly polarized radiation of dye lasers is studied in the frequency range from 16 600 to 17 900 cm-1. A large number of resonance maxima in the yield of Ba+ and Ba2+ ions were observed upon tuning the radiation frequency. It is unambiguously

V. V. Suran; I. I. Bondar

2007-01-01

206

Circular DNA and Splicing Systems  

Microsoft Academic Search

Circular strings representing DNA molecules and certain recombinant behaviour are formalized. Various actions of splicing schemes on linear and circular DNA molecules are examined. It is shown that there is a difference in the regularity result of Culik and Harju [1] between the linear and circular strings. A consequence of this result is that a conjecture of Head [4] that

Rani Siromoney; K. G. Subramanian; V. Rajkumar Dare

1992-01-01

207

The 2-D Curvature of Large Angle Interplanetary MHD Discontinuity Surfaces: IMP8 and WIND Observations  

Microsoft Academic Search

This study examines the degree of 2-D curvature of solar wind directional discontinuity (DD) surfaces at 1 AU using magnetic field, density, and velocity data from the WIND and IMP-8 spacecraft for a large number (N = 134) of carefully selected events having large ``discontinuity angles\\

R. P. Lepping; C. Wu; K. McClernan

2002-01-01

208

Hypercomplete circular harmonic pyramids  

NASA Astrophysics Data System (ADS)

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

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

1996-10-01

209

Circular ARC solar concentrator  

Microsoft Academic Search

A solar energy concentrator and collector having a concentrator made up of one or more anticlastic panels that feature a non-developable doubly curved surface. The panels are concave in the north-south direction and convex in the east-west direction. In one embodiment, the panels are formed to have parallel circular arcs in the north-south direction of increasing radius from the center

D. W. Townsend; E. E. Routery

1985-01-01

210

Very Large Array Observations of the Infrared Dark Cloud G19.30+0.07  

NASA Astrophysics Data System (ADS)

We present Very Large Array observations of ammonia (NH3) (1,1), (2,2), and dicarbon sulfide (CCS) (21-10) emission toward the infrared dark cloud (IRDC) G19.30+0.07 at ~22 GHz. The NH3 emission closely follows the 8 ?m extinction. The NH3 (1,1) and (2,2) lines provide diagnostics of the temperature and density structure within the IRDC, with typical rotation temperatures of ~10-20 K and NH3 column densities of ~1015 cm-2. The estimated total mass of G19.30+0.07 is ~1130 M sun. The cloud comprises four compact NH3 clumps of mass ~30-160 M sun. Two coincide with 24 ?m emission, indicating heating by protostars, and show evidence of outflow in the NH3 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 NH3 emission, we find that G19.30+0.07 is composed of three distinct velocity components or "subclouds." One velocity component contains the two 24 ?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 NH3 and CCS emission from G19.30+0.07 is highly anti-correlated, with the NH3 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.; Chandler, C. J.; Brogan, C.; Churchwell, E.; Indebetouw, R.; Shirley, Y.; Borg, K. J.

2011-05-01

211

Energetic ion driven MHD instabilities observed in the heliotron\\/torsatron devices Compact Helical System and Large Helical Device  

Microsoft Academic Search

Recent results of energetic ion driven MHD instabilities observed in the heliotron\\/torsatron devices Compact Helical System (CHS) and Large Helical Device (LHD) are presented. Alfvén eigenmodes (AEs) and fishbone-like burst modes (FBs) destabilized by energetic ions were observed in NBI heated plasmas of CHS. The AEs are toroidicity induced Alfvén eigenmodes (TAEs) and global Alfvén eigenmodes (GAEs), where the identified

K. Toi; M. Takechi; M. Isobe; N. Nakajima; M. Osakabe; S. Takagi; T. Kondo; G. Matsunaga; K. Ohkuni; M. Sasao; S. Yamamoto; S. Ohdachi; S. Sakakibara; H. Yamada; K. Y. Watanabe; D. S. Darrow; A. Fujisawa; M. Goto; K. Ida; H. Idei; H. Iguchi; S. Lee; S. Kado; S. Kubo; O. Kaneko; K. Kawahata; K. Matsuoka; T. Minami; S. Morita; O. Motojima; K. Narihara; S. Nishimura; N. Ohyabu; Y. Oka; S. Okamura; T. Ozaki; K. Sato; M. Sato; A. Shimizu; T. Shimozuma; Y. Takeiri; K. Tanaka; T. Tokuzawa; K. Tsumori; I. Yamada; Y. Yoshimura; LHD Experimental Groups

2000-01-01

212

Direct observation of large quantum interference effect in anthraquinone solid-state junctions.  

PubMed

Quantum interference in cross-conjugated molecules embedded in solid-state devices was investigated by direct current-voltage and differential conductance transport measurements of anthraquinone (AQ)-based large area planar junctions. A thin film of AQ was grafted covalently on the junction base electrode by diazonium electroreduction, while the counter electrode was directly evaporated on top of the molecular layer. Our technique provides direct evidence of a large quantum interference effect in multiple CMOS compatible planar junctions. The quantum interference is manifested by a pronounced dip in the differential conductance close to zero voltage bias. The experimental signature is well developed at low temperature (4 K), showing a large amplitude dip with a minimum >2 orders of magnitude lower than the conductance at higher bias and is still clearly evident at room temperature. A temperature analysis of the conductance curves revealed that electron-phonon coupling is the principal decoherence mechanism causing large conductance oscillations at low temperature. PMID:23805821

Rabache, Vincent; Chaste, Julien; Petit, Philippe; Della Rocca, Maria Luisa; Martin, Pascal; Lacroix, Jean-Christophe; McCreery, Richard L; Lafarge, Philippe

2013-07-09

213

Observations of large scale F-region irregularities using airflow emissions at 7774 deg A and 6300 deg A  

Microsoft Academic Search

The measurements were made with a two-channel photometer which permitted scanning observations both along and across the magnetic meridian. Observations at 7774 A can detect large scale irregularities near the F-region peak height, whereas observations at 6300 A detect such irregularities at an altitude about 50 km to 100 km lower, depending on the F-region height. On several nights, during

Y. Sahai; J. A. Bittencourt; N. R. Teixeira; H. Takahashi

1981-01-01

214

Photoinduced circular anisotropy in a photochromic W -shaped-molecule-doped polymeric liquid crystal film  

Microsoft Academic Search

Photoinduced circular anisotropy has been demonstrated in thin films of a main-chain polymeric liquid crystal (PLC) system doped with photochromic W -shaped molecules containing two azobenzene groups by irradiating with circularly polarized light (CPL). Reversible photoinduced circular dichroism (CD) was observed with sign relevant to the handedness of the CPL. The experimentally observed CD spectra were analyzed using the DeVoe

Suk-Won Choi; N. Y. Ha; Kazuaki Shiromo; Nandiraju V. S. Rao; Manoj Kr. Paul; Takehiro Toyooka; Suzushi Nishimura; J. W. Wu; Yoichi Takanishi; Ken Ishikawa; Hideo Takezoe

2006-01-01

215

Circular polarization memory in single Quantum Dots  

SciTech Connect

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

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

2010-01-04

216

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

NASA Astrophysics Data System (ADS)

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 of mV/m) whistler mode waves are common during magnetically active periods. The large-amplitude whistler mode waves are usually nondispersive and obliquely propagating, with a large longitudinal electric field and significant parallel electric field. These characteristics are different than those of typical chorus, though it remains to be seen whether the large-amplitude whistler mode waves are a subpopulation of chorus or something else entirely. 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 electron energization by many MeV and/or scattering by large pitch 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, C. A.; Breneman, A.; Goetz, K.; Kellogg, P. J.; Kersten, K.; Wygant, J. R.; Wilson, L. B., III; Looper, M. D.; Blake, J. B.; Roth, I.

2012-12-01

217

Daily observations of a large period jump of the VELA pulsar  

Microsoft Academic Search

The decay and recovery of the pulse arrival times of signals from the Vela pulsar PSRO833-45 are analyzed for indications of the structure of the object. A 102 nsec decrease was found to occur over a day's observations at 646 MHz. Six weeks of relatively continuous observations showed that a recovery from the decay occurred. Time constants for an exponential

P. M. McCulloch; P. A. Hamilton; G. W. R. Royle; R. N. Manchester

1983-01-01

218

Incoherent scatter observations of the ionospheric response to a large solar flare  

Microsoft Academic Search

Incoherent scatter observations at Millstone Hill were made during the ; importance 3B solar flare which occurred at 15:00 UT on 7 August 1972. ; Measurements were obtained of the electron density profile over the height range ; 125 to 1200 km, together with observations of the electron temperature, ion ; temperature, and vertical drift velocity above 225 km. The

Michael Mendillo; John V. Evans

1974-01-01

219

Etude Comparee des Coefficients Aerodynamiques Mesures sur des Maquettes de Section Circulaire ou Carree de Grand Allongement en Ecoulement Supersonique (Comparison Study of the Aerodynamic Coefficients Measured on Models with Circular or Squared Section and Large Elongation in Supersonic Flow).  

National Technical Information Service (NTIS)

Aerodynamic coefficients of ogives are measured for the Mach numbers 1.7 and 3.02. The Reynolds number was based on the caliber and the maximal incidence was 30 deg. It is shown that the linearized theory is a good approximation for models of circular cro...

B. Gautier A. Koeneke J. Duperoux E. Cattin

1989-01-01

220

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

Microsoft Academic Search

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

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

1997-01-01

221

Opportunity to observe a large-scale hole in the ionosphere  

Microsoft Academic Search

Since the earliest days of the U.S. Space Program, concerns have been raised regarding the atmospheric perturbations that might be caused by the exhaust products of large rocket engines. In 1964 a comprehensive review of the subject was published by Kellogg [1964] in which the space science community was alerted to the many possible ways that rocket `pollutants' could have

Michael Mendillo; Jeffrey Baumgardner; John A. Klobuchar

1979-01-01

222

MAPTIP observations of large aerosol in the lowest 10 meters above waves  

NASA Astrophysics Data System (ADS)

This paper addresses the question of what is the structure of the aerosol concentration profile close to the sea surface during high wind and whitecapping conditions. EO energy must pass through this layer on long horizontal trajectories because of the curvature of the earth. This is also a region of the marine atmosphere where very little is known during high wind conditions. The paper discusses the profile of large aerosol size distribution data obtained from rotorod devices during the MAPTIP experiment. These devices were lowered from an overhang on the Dutch tower, Meetpost Noordwijk, MPN (located about 9 kilometers off the Dutch shore). Altitudes of from 10 meters to just above the wave tops were investigated in calm and high wind conditions. In addition to aerosol size data, relative humidity profiles and other pertinent meteorological measurements were made throughout the MAPTIP experiment and utilized in the analysis. The wind speed dependence of the structure of very large aerosol in the surface layer above the sea is derived from this data. This analysis shows that the turbulence produced by the high wind speed (required to build up the sea state) also mixes the large aerosol in the lowest 10 meters of the atmosphere. This causes any vertical structure in the aerosol spectrum to disappear while the net amount of large aerosol increases non-linearly with the wind speed.

Gathman, Stuart G.

1996-10-01

223

Sedimentary stylolite connectivity: Large-scale field observations and implications for strain and compaction  

NASA Astrophysics Data System (ADS)

Stylolites, which constitute surfaces of localized rock dissolution and compaction, have a documented impact on porosity and permeability, and are important for the evolution of sedimentary basins and for accomodating compactive strain. We present here a meso-scale field study on sedimentary stylolites in carbonates, characterizing large scale distributions of stylolite, including measurements conducted on more than 1 km long stylolites, the largest stylolite lateral distribution ever reported in the literature. Our field study suggests that on large-scales connections between stylolites become important both to compactive strain accomodation and to transport properties of the rocks, indicating that large-scale analysis may require a new characterization scheme for "stylolites populations" based on their connectivity. We thus divide stylolite populations into three end-member types: long-parallel stylolites (where stylolites never connect since they are parallel), interconnected stylolite networks (where stylolites connect by merging and anastamosing or via fractures and veins), and isolated stylolites (where stylolites terminate before connecting). We suggest characterizing the different populations by different statistical parameters and measures. Using schematic mechanistic models for the evolution of the 3 end-member connectivity classes, we discuss how each of the end-member types accommodates large scale strain and how the different connectivity classes affect fluid flow.

Aharonov, Einat; Laronne Ben-Itzhak, Leehee; Karcz, Zvi; Kaduri, Maor; Toussaint, Renaud

2013-04-01

224

Theoretical performance of solar coronagraphs using sharp-edged or apodized circular external occulters  

NASA Astrophysics Data System (ADS)

Context. This study focuses on an instrument able to monitor the corona close to the solar limb. Aims: We study the performance of externally occulted solar coronagraphs. We compute the shape of the umbra and penumbra produced by the occulter at the entrance aperture of the telescope and compare levels of rejection obtained for a circular occulter with a sharp or smooth transmission at the edge. Methods: We show that the umbral pattern in an externally occulted coronagraph can be written as a convolution product between the occulter diffraction pattern and an image of the Sun. We then focus on the analysis to circular symmetric occulters. We first derive an analytical expression using two Lommel series for the Fresnel diffraction pattern produced by a sharp-edged circular occulter. Two different expressions are used for inside and outside the occulter's geometric shadow. We verify that a numerical approach that directly solves the Huygens-Fresnel integral gives the same result. This suggests that the numerical computation can be used for a circular occulter with any variable transmission. Results: With the objective of observing the solar corona a few minutes from limb, a sharp-edged circular occulter of a few meters cannot produce an umbra darker than 10-4 of the direct sunlight. The same occulter, having an apodization zone of a few percent of the diameter (3 cm for a 1.5 m occulter), darkers the umbra down to 10-8 of the direct sunlight for linear transmission and to 10-12 for Sonine or cosine bell transmissions. An investigation for an apodized occulter with manufacturing defaults is quickly performed. Conclusions: It has been possible to numerically demonstrate the large superiority of apodized circular occulters with respect to the sharp-edged ones. These occulters allow the theoretical observation of the very limb-close corona with not yet obtained contrast ratios.

Aime, C.

2013-10-01

225

Melt Production in Large-Scale Impact Events: Planetary Observations and Implications.  

National Technical Information Service (NTIS)

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...

M. J. Cintala R. A. F. Grieve

1992-01-01

226

Acidic Precipitation and Large-Scale Transport of Air Pollutants Observed in Korea  

Microsoft Academic Search

Acid rain at a rural site in Chongwon (KHN), central Korea has been under observation since 1990. To substantiate the 10-year observations, rain samples from six other sites were also collected and analyzed. Results show that acid rain occurred frequently at all sites. At KHN, seasonal and annual variability of pH values had a 10-year VWM value of 4.67 and

Yong-Seung Chung; Hak-Sung Kim; Kie-Hyun Park

2001-01-01

227

Observing Light-by-Light Scattering at the Large Hadron Collider  

NASA Astrophysics Data System (ADS)

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

d'Enterria, David; da Silveira, Gustavo G.

2013-08-01

228

Observing Light-by-Light Scattering at the Large Hadron Collider.  

PubMed

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

d'Enterria, David; da Silveira, Gustavo G

2013-08-22

229

Observing strongly interacting vector boson systems at the CERN Large Hadron Collider  

Microsoft Academic Search

We explore the potential of the CERN Large Hadron Collider to access a strongly interacting electroweak symmetry breaking sector via weak boson scattering with W+W-jj, ZZjj, and W±Zjj final states. As examples of models with scalar or vector resonances we concentrate on a scenario with a heavy Higgs boson and on a warped Higgsless Kaluza-Klein model of narrow spin-one resonances.

C. Englert; B. Jäger; M. Worek; D. Zeppenfeld

2009-01-01

230

STARE observations of a Pc 5 pulsation with large azimuthal wave number  

Microsoft Academic Search

The Scandinavian Twin Auroral Radar Experiment is used to analyze a new type of Pc 5 pulsation which occurred during local magnetic afternoon. It had an amplitude of less than about 5 mV\\/m in the ionosphere, a 220-385 sec period, and an azimuthal wave number that was large, at approximately 35, and varied in a way that kept the azimuthal

W. Allan; E. M. Poulter; E. Nielsen

1982-01-01

231

Large gamma anisotropy observed in the 252Cf spontaneous-fission process  

NASA Astrophysics Data System (ADS)

The energy spectrum and the angular dependence relative to the fission direction of photons in the energy region between 2 and 40 MeV have been measured for the spontaneous fission of 252Cf. A large anisotropy was found in the energy region 8 to 12 MeV implying that photons in this region are emitted from a nuclear system which is highly elongated along the fission axis.

van der Ploeg, H.; Postma, R.; Bacelar, J. C.; van den Berg, T.; Iacob, V.; Jongman, J.; van der Woude, A.

1992-05-01

232

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

233

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

Microsoft Academic Search

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

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

2005-01-01

234

Observations on sediment mobility in a large gravel-bed river  

Microsoft Academic Search

This study investigates sediment mobility in a large gravel-bed river (Tagliamento River, northeastern Italy). Field data were used to identify the morphological effectiveness of a range of flows (floods with recurrence interval <1 to 3.5 year) and for a detailed analysis of the partial transport condition. The analyses were carried out on three cross sections where a number of areas representative

Luca Mao; Nicola Surian

2010-01-01

235

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

NASA Astrophysics Data System (ADS)

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 rest were head echoes, which was quite contrary to expectation. The smaller number of meteors detected by the VHF system and its wider beam width show that UHF meteors are far smaller than the VHF meteors. We estimate that VHF head echoes have a typical effective scattering cross section of the order of 10-3m2, while the accompanying UHF echoes have an effective scattering cross section of the order of 10-6m2. The paucity of VHF trail echoes observed leads us to suggest that the ratio of head echo power to the trail echo power increases with decreasing meteor size. When a meteor is too small, a radar can observe the head echo but not the trail echo. Of the 145 meteors observed by both radars, the powers received by the two systems were not correlated. Although antenna beam pattern contributes to the lack of correlation, it is also possible that UHF and VHF echoes may be enhanced by different scattering mechanisms.

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

236

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

237

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.

2012-01-15

238

AQUAPORINS ARE OBSERVED IN THE DUCT EPITHELIA OF THE EPIDIDYMAL REGION OF THE LARGE WHITE TURKEY  

Technology Transfer Automated Retrieval System (TEKTRAN)

The cellular and molecular mechanisms regulating the re-uptake of the testicular fluid supporting sperm exiting the testes is not known in the bird. The presence of aquaporin, a protein involved in the transmembrane water transport, was investigated. Observations were limited to the ductuli efferent...

239

Solar wind structure at large heliocentric distances: An interpretation of Pioneer 10 observations  

Microsoft Academic Search

Examination of hourly values of the solar wind speed observed by the Pioneer 10 spacecraft beyond a heliocentric distance of 4 AU reveals (1) a prevalent 'sawtoothlike' speed-time profile, most speed fluctuations displaying a rapid rise and a much slower decline, and (2) the nearly universal appearance of abrupt (on the 1-hour time resolution of these data) changes in the

A. J. Hundhausen; J. T. Gosling

1976-01-01

240

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

241

Class IIc or Circular Bacteriocins  

Microsoft Academic Search

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

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

242

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

243

High Resolution WRF Modeling of the Western USA: Comparisons with Observations and large scale Gridded Data  

NASA Astrophysics Data System (ADS)

Meso- and micro-scale atmospheric features are often not captured in GCMs due to the coarse model resolution. These features could be very important in modifying the regional- and local-scale climate. For example sea breezes, urbanization, irrigation, and mountain/valley circulations can modify the local climate and potentially upscale to larger scales. In this study we evaluate the mesoscale Weather Research and Forecast (WRF) Model against station observations, gridded observations, and reanalysis data over the western states of the USA. Simulations are compared for summer (JJA) 2010 at resolutions of 4, 25 and 50kms with each grid covering the entire Western USA. Observations of July surface temperature, relative humidity, and wind speed and direction are compared with model results at the three resolutions. Results showed that 4km WRF most closely matched point observations of the daytime 10m wind speeds and direction, while 50km WRF showed the largest biases. However, 4km WRF showed larger daytime surface temperature and humidity biases, while agreement with observed nighttime temperature and humidity was generally high for all resolutions. Comparisons of 4km WRF and 4km gridded PRISM data showed a warm bias in the Central Valley of California and the southern part of the Western USA domain. These biases were small in June and larger in July and August, and are associated with deficit of moisture from irrigation in the Central Valley and deficit of monsoon rainfall in the southern domain. Finally, comparisons between 4km WRF forced by global (NCEP) and regional (NARR) reanalysis was undertaken. Results showed warm biases in coastal California when 4km WRF was nested within the global reanalysis, and that these coastal biases did not occur 4km WRF was nested within the regional reanalysis. These results will be used in evaluations of the need for high resolution non-hydrostatic WRF and its performance against observations. It will also be used for quantifying the biased for further research of meso-scale phenomenon in the region.

Lebassi-Habtezion, B.; Diffenbaugh, N. S.

2011-12-01

244

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

NASA Astrophysics Data System (ADS)

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

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

2013-09-01

245

ESO Large Program on physical studies of Trans-Neptunian objects and Centaurs: Final results of the visible spectrophotometric observations  

Microsoft Academic Search

The Large Program on physical studies of TNOs and Centaurs, started at ESO Cerro Paranal on April 2001, has recently been concluded. This project was devoted to the investigation of the surface properties of these icy bodies through photometric and spectroscopic observations. In this paper we present the latest results on these pristine bodies obtained from the spectrophotometric investigation in

S. Fornasier; A. Doressoundiram; G. P. Tozzi; M. A. Barucci; H. Boehnhardt; C. de Bergh; A. Delsanti; J. Davies; E. Dotto

2004-01-01

246

Observation of high-energy jet showers and high-energy gamma-rays by means of large emulsion chamber  

Microsoft Academic Search

Two large emulsion chambers were constructed and exposed to cosmic ; radiation at the Mt. Norikura Laboratory (2740 ml from Sept. 1958 to Feb. 1959. ; Basic design of the chambers is shown and the results of observations on high-; energy jet showers and gamma rays are discussed. (W.D.M.);

Y. Fujimoto; S. Hasegawa; M. Kazuno; J. Nishimura; K. Niu; N. Ogita

1960-01-01

247

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

248

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

Microsoft Academic Search

We are developing a new balloon-borne instrument (PoGO), to measure polarization of soft gamma rays (25-200 keV) using asymmetry in azimuth angle distribution of Compton scattering. PoGO will detect 10% polarization in 100mCrab sources in a 6-8 hour observation and bring a new dimension to studies on gamma ray emission\\/transportation mechanism in pulsars, AGNs, black hole binaries, and neutron star

Blanford

2005-01-01

249

Coherent structure in the turbulent wake behind a circular cylinder  

NASA Astrophysics Data System (ADS)

A wake behind a circular cylinder at Reynolds number 850-1700 was visualized by the smoke-wire method. The observations of the How together with the results of quantitative measurements, such as various velocity correlation coefficients, illustrated the formation process of spoon-shaped large eddies in the region 90 <= x/d <= 230 attained through the deformation and rearrangement of the regular Karman vortices. A spoon vortex was likely to pair with the counterpart on the opposite side of the wake. The large-scale bulges of the turbulent and non-turbulent interface of the wake were shown to correspond to these spoon vortices. These results indicate that some coherent structures are organized by rearrangement and deformation of initially regular vortices in turbulent flow. Translated from Nagare, Journal of Japan Society of Fluid Mechanics 3 (1984) 128-138

Shirakashi, Masataka; Yamaguchi, Shuichi; Mochimaru, Yoshihiro; Yamane, Ryuichiro

1988-07-01

250

Large Magellanic Cloud Distance and Structure from Near-Infrared Red Clump Observations  

NASA Astrophysics Data System (ADS)

We have applied the Infrared Survey Facility Magellanic Clouds Point-Source Catalog to the mapping of the red clump (RC) distance modulus across the Large Magellanic Cloud (LMC). Using the J- (1.25 ?m) and H- (1.63 ?m) band data to derive a reddening free luminosity function and a theoretical RC absolute magnitude from stellar evolution libraries, we estimate a distance modulus to the LMC of ? = 18.54 ± 0.06. The best fitting plane inclination, i, and the position angle of the line of nodes, phi, have little dependence on the assumed RC absolute magnitude; we find i = 23fdg5 ± 0fdg4 and phi = 154fdg6 ± 1fdg2. It was also noted that many fields included a significant asymptotic giant branch bump population that must be accounted for.

Koerwer, Joel F.

2009-07-01

251

Design method for circular and non-circular sewer sections  

Microsoft Academic Search

An analytical method is presented for the determination of hydraulic and geometric elements of partly full flowing circular and non-circular sections with known parameters being discharge, depth of flow, bed slope and Manning's roughness coefficient. This method will eliminate the application of tabular and graphical form of hydraulic elements for partly full flow conditions, which provide relationships between partly full

Ashok K. Sharma; Prabhata K. Swamee

2008-01-01

252

Dual-spacecraft observation of large-scale magnetic flux ropes in the Martian ionosphere  

NASA Astrophysics Data System (ADS)

We here report the first dual-spacecraft detection of planetary flux ropes in the ionosphere of Mars. The Mars Advanced Radar for Subsurface and Ionosphere Sounding (MARSIS), on board Mars Express, can measure the magnetic field magnitude near the spacecraft. Typically, these measurements track the known crustal magnetic field strength very well; however, occasionally, MARSIS detects transient, intense magnetic fields that deviate significantly from the known crustal fields. Two such magnetic field enhancements occur in near-coincidence with flux rope detections by the Mars Global Surveyor Magnetometer and Electron Reflectometer, which provides vector magnetic field measurements, allowing us to clearly identify the enhancements as flux ropes. The flux ropes detected are quasi-stable for at least a half hour, have peak magnetic field strengths of ˜50 and 90 nT, and are ˜650-700 km in diameter. Both occur downstream of the region of strong crustal fields. In addition, MARSIS has detected 13 other magnetic enhancements over a 5 year period, which we infer to be flux ropes. These structures have peak field strengths up to 130 nT and measured horizontal dimensions of several hundred to over a thousand kilometers. They are clustered around the intense crustal fields in the southern hemisphere of Mars. The large spatial scale of these flux ropes distinguishes them from small-scale flux ropes, with diameters of tens of kilometers, that have been seen in the ionospheres of Venus and Mars. These large-scale flux ropes are believed to be caused by solar wind stretching and shearing of the Martian crustal fields.

Morgan, D. D.; Gurnett, D. A.; Akalin, F.; Brain, D. A.; Leisner, J. S.; Duru, F.; Frahm, R. A.; Winningham, J. D.

2011-02-01

253

HERSCHEL OBSERVATIONS OF A NEWLY DISCOVERED UX Ori STAR IN THE LARGE MAGELLANIC CLOUD  

SciTech Connect

The LMC star, SSTISAGE1C J050756.44-703453.9, was first noticed during a survey of EROS-2 light curves for stars with large irregular brightness variations typical of the R Coronae Borealis (RCB) class. However, the visible spectrum showing emission lines including the Balmer and Paschen series as well as many Fe II lines is emphatically not that of an RCB star. This star has all of the characteristics of a typical UX Ori star. It has a spectral type of approximately A2 and has excited an H II region in its vicinity. However, if it is an LMC member, then it is very luminous for a Herbig Ae/Be star. It shows irregular drops in brightness of up to 2 mag, and displays the reddening and 'blueing' typical of this class of stars. Its spectrum, showing a combination of emission and absorption lines, is typical of a UX Ori star that is in a decline caused by obscuration from the circumstellar dust. SSTISAGE1C J050756.44-703453.9 has a strong IR excess and significant emission is present out to 500 {mu}m. Monte Carlo radiative transfer modeling of the spectral energy distribution requires that SSTISAGE1C J050756.44-703453.9 have both a dusty disk as well as a large extended diffuse envelope to fit both the mid- and far-IR dust emission. This star is a new member of the UX Ori subclass of the Herbig Ae/Be stars and only the second such star to be discovered in the LMC.

Clayton, Geoffrey C. [Department of Physics and Astronomy, Louisiana State University, Baton Rouge, LA 70803 (United States); Sargent, B.; Boyer, M. L.; Meixner, M.; Roman-Duval, J.; Sewilo, M., E-mail: gclayton@fenway.phys.lsu.ed, E-mail: duval@stsci.ed, E-mail: mboyer@stsci.ed, E-mail: meixner@stsci.ed, E-mail: mmsewilo@stsci.ed, E-mail: sargent@stsci.ed [Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 (United States)

2010-10-20

254

Oseen Flow past a Circular Cylinder  

Microsoft Academic Search

Oseen flow past a circular cylinder is studied for the whole range of the Reynolds number R on the basis of an integral equation. Approximate analytical solutions are obtained for both small and large R. A non-trivial solution of the associated homogeneous equation is noticed and discussed. The integral equation is also solved numerically for R{=}0.2, 2, 20, 200, 2000

Tosio Miyagi

1974-01-01

255

A statistical model of magnetic islands in a large current layer: validation from Hall MHD simulations and Cluster FTE observations  

NASA Astrophysics Data System (ADS)

Magnetic islands have been observed in large current layers for various space plasmas, including the magnetopause and solar corona. Since the direct simulation of very large systems is not possible, we have developed a statistical model which describes the formation, growth, convection and coalescence of these magnetic islands. An integral-differential equation is derived for the island distribution function, which characterizes islands by the flux they contain ? and the area they enclose A. This evolution equation therefore scales the behavior of magnetic islands observed in kinetic simulations up to global scales. We use Hall MHD simulations to validate the model and to benchmark its parameters. The steady-state solution of the evolution equation predicts a distribution of islands. A database of 1,098 flux transfer events observed by Cluster between 2001 and 2003 is shown to be consistent with the model's predictions.

Fermo, R. L.; Drake, J. F.; Swisdak, M. M.; Hwang, K.; Wang, Y.

2010-12-01

256

A Large Sample of Magnetically-Active Stars Observed With Kepler  

NASA Astrophysics Data System (ADS)

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

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

2013-01-01

257

Condensation of circular DNA.  

PubMed

A simple model of a circularly closed double-stranded DNA in a poor solvent is considered as an example of a semi-flexible polymer with self-attraction. To find the ground states, the conformational energy is computed as a sum of the bending and torsional elastic components and the effective self-attraction energy. The model includes a relative orientation or sequence dependence of the effective attraction forces between different pieces of the polymer chain. Two series of conformations are analysed: a multicovered circle (a toroid) and a multifold two-headed racquet. The results are presented as a diagram of state. It is suggested that the stability of particular conformations may be controlled by proper adjustment of the primary structure. Application of the model to other semi-flexible polymers is considered. PMID:23635167

Starostin, E L

2013-04-28

258

Occasional large emissions of nitrous oxide and methane observed in stormwater biofiltration systems.  

PubMed

Designed, green infrastructures are becoming a customary feature of the urban landscape. Sustainable technologies for stormwater management, and biofilters in particular, are increasingly used to reduce stormwater runoff volumes and peaks as well as improve the water quality of runoff discharged into urban water bodies. Although a lot of research has been devoted to these technologies, their effect in terms of greenhouse gas fluxes in urban areas has not been yet investigated. We present the first study aimed at quantifying greenhouse gas fluxes between the soil of stormwater biofilters and the atmosphere. N2O, CH4, and CO2 were measured periodically over a year in two operational vegetated biofiltration cells at Monash University in Melbourne, Australia. One cell had a saturated zone at the bottom, and compost and hardwood mulch added to the sandy loam filter media. The other cell had no saturated zone and was composed of sandy loam. Similar sedges were planted in both cells. The biofilter soil was a small N2O source and a sink for CH4 for most measurement events, with occasional large emissions of both N2O and CH4 under very wet conditions. Average N2O fluxes from the cell with the saturated zone were almost five-fold greater (65.6?g N2O-Nm(-2)h(-1)) than from the other cell (13.7?g N2O-Nm(-2)h(-1)), with peaks up to 1100?g N2O-Nm(-2)h(-1). These N2O fluxes are of similar magnitude to those measured in other urban soils, but with larger peak emissions. The CH4 sink strength of the cell with the saturated zone (-3.8?g CH4-Cm(-2)h(-1)) was lower than the other cell (-18.3?g CH4-Cm(-2)h(-1)). Both cells of the biofilter appeared to take up CH4 at similar rates to other urban lawn systems; however, the biofilter cells displayed occasional large CH4 emissions following inflow events, which were not seen in other urban systems. CO2 fluxes increased with soil temperature in both cells, and in the cell without the saturated zone CO2 fluxes decreased as soil moisture increased. Other studies of CO2 fluxes from urban soils have found both similar and larger CO2 emissions than those measured in the biofilter. The results of this study suggest that the greenhouse gas footprint of stormwater treatment warrant consideration in the planning and implementation of engineered green infrastructures. PMID:23399408

Grover, Samantha P P; Cohan, Amanda; Chan, Hon Sen; Livesley, Stephen J; Beringer, Jason; Daly, Edoardo

2013-02-09

259

Provision of preventive health care in systemic lupus erythematosus: data from a large observational cohort study  

PubMed Central

Introduction Cancer and infections are leading causes of mortality in systemic lupus erythematosus (SLE) after diseases of the circulatory system, and therefore preventing these complications is important. In this study, we examined two categories of preventive services in SLE: cancer surveillance (cervical, breast, and colon) and immunizations (influenza and pneumococcal). We compared the receipt of these services in SLE to the general population, and identified subgroups of patients who were less likely to receive these services. Methods We compared preventive services reported by insured women with SLE enrolled in the University of California, San Francisco Lupus Outcomes Study (n = 685) to two representative samples derived from a statewide health interview survey, a general population sample (n = 18,013) and a sample with non-rheumatic chronic conditions (n = 4,515). In addition, using data from the cohort in both men and women (n = 742), we applied multivariate regression analyses to determine whether characteristics of individuals (for example, sociodemographic and disease factors), health systems (for example, number of visits, involvement of generalists or rheumatologists in care, type of health insurance) or neighborhoods (neighborhood poverty) influenced the receipt of services. Results The receipt of preventive care in SLE was similar to both comparison samples. For cancer surveillance, 70% of eligible respondents reported receipt of cervical cancer screening and mammography, and 62% reported colon cancer screening. For immunizations, 59% of eligible respondents reported influenza immunization, and 60% reported pneumococcal immunization. In multivariate regression analyses, several factors were associated with a lower likelihood of receiving preventive services, including younger age and lower educational attainment. We did not observe any effects by neighborhood poverty. A higher number of physician visits and involvement of generalist providers in care was associated with a higher likelihood of receiving most services. Conclusions Although receipt of cancer screening procedures and immunizations in our cohort was comparable to the general population, we observed significant variability by sociodemographic factors such as age and educational attainment. Further research is needed to identify the physician, patient or health system factors contributing to this observed variation in order to develop effective quality improvement interventions.

2010-01-01

260

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).

Kastens, Kim; Ishikawa, Toru

261

Improved Resolution and Image Separation (IRIS) Satellite: astronomical observations with a large occulting satellite  

NASA Astrophysics Data System (ADS)

Natural occultations have long been used to study sources on small angular scales, while coronographs have been used to study high contrast sources. We propose launching the Improved Resolution and Image Selection (IRIS) Satellite, a large steerable occulting satellite. IRIS will have several advantages over standard occulting bodies. IRIS woudl block over 99.8 percent of the visible light from an occulted point source. Because the occultation occurs outside both the telescope and the atmosphere, seeing and optical imperfections do not degrade this performance. If placed in Earth orbit, integration times of 160-1600 s can be achieved from most major telescope sites for objects in over 90 percent of the sky. Alternately, IRIS could be combined with a 2-4 meter space telescope at the Earth-Sun L2 point to yield very long integration times. Applications for IRIS include direct imaging of planets around nearby stars, and resolution of micro-lensed images of LMC and Galactic bulge stars into distinct image pairs. Resolution of microlensed stars would greatly improve our understanding of the massive compact halo objects comprising 20-90 percent of the mass of our galaxy. Direct imaging of planets, would enhance our understanding of star formation, formation of planetary systems, and perhaps ultimately help evaluate the probability of extraterrestrial life.

Copi, Craig J.; Starkman, Glenn D.

1998-08-01

262

Observations of Energetic High Magnetic Field Pulsars with the Fermi Large Area Telescope  

NASA Astrophysics Data System (ADS)

We report the detection of ?-ray pulsations from the high-magnetic-field rotation-powered pulsar PSR J1119-6127 using data from the Fermi Large Area Telescope. The ?-ray light curve of PSR J1119-6127 shows a single, wide peak offset from the radio peak by 0.43 ± 0.02 in phase. Spectral analysis suggests a power law of index 1.0 ± 0.3+0.4 - 0.2 with an energy cutoff at 0.8 ± 0.2+2.0 - 0.5 GeV. The first uncertainty is statistical and the second is systematic. We discuss the emission models of PSR J1119-6127 and demonstrate that despite the object's high surface magnetic field—near that of magnetars—the field strength and structure in the ?-ray emitting zone are apparently similar to those of typical young pulsars. Additionally, we present upper limits on the ?-ray pulsed emission for the magnetically active PSR J1846-0258 in the supernova remnant Kesteven 75 and two other energetic high-B pulsars, PSRs J1718-3718 and J1734-3333. We explore possible explanations for the non-detection of these three objects, including peculiarities in their emission geometry.

Parent, D.; Kerr, M.; den Hartog, P. R.; Baring, M. G.; DeCesar, M. E.; Espinoza, C. M.; Gotthelf, E. V.; Harding, A. K.; Johnston, S.; Kaspi, V. M.; Livingstone, M.; Romani, R. W.; Stappers, B. W.; Watters, K.; Weltevrede, P.; Abdo, A. A.; Burgay, M.; Camilo, F.; Craig, H. A.; Freire, P. C. C.; Giordano, F.; Guillemot, L.; Hobbs, G.; Keith, M.; Kramer, M.; Lyne, A. G.; Manchester, R. N.; Noutsos, A.; Possenti, A.; Smith, D. A.

2011-12-01

263

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

264

Fermi Large Area Telescope Observations of the Cygnus Loop Supernova Remnant  

SciTech Connect

We present an analysis of the gamma-ray measurements by the Large Area Telescope (LAT) onboard the Fermi Gamma-ray Space Telescope in the region of the supernova remnant (SNR) Cygnus Loop (G74.0-8.5). We detect significant gamma-ray emission associated with the SNR in the energy band 0.2-100 GeV. The gamma-ray spectrum shows a break in the range 2-3 GeV. The gamma-ray luminosity is {approx} 1 x 10{sup 33} erg s{sup -1} between 1-100 GeV, much lower than those of other GeV-emitting SNRs. The morphology is best represented by a ring shape, with inner/outer radii 0{sup o}.7 {+-} 0{sup o}.1 and 1{sup o}.6 {+-} 0{sup o}.1. Given the association among X-ray rims, H{alpha} filaments and gamma-ray emission, we argue that gamma rays originate in interactions between particles accelerated in the SNR and interstellar gas or radiation fields adjacent to the shock regions. The decay of neutral pions produced in nucleon-nucleon interactions between accelerated hadrons and interstellar gas provides a reasonable explanation for the gamma-ray spectrum.

Katagiri, H.; /Ibaraki U., Mito; Tibaldo, L.; /INFN, Padua /Padua U. /Paris U., VI-VII; Ballet, J.; /Paris U., VI-VII; Giordano, F.; /Bari U. /Bari Polytechnic /INFN, Bari; Grenier, I.A.; /Paris U., VI-VII; Porter, T.A.; /Stanford U., HEPL /KIPAC, Menlo Park /SLAC; Roth, M.; /Washington U., Seattle; Tibolla, O.; /Wurzburg U.; Uchiyama, Y.; /Stanford U., HEPL /KIPAC, Menlo Park /SLAC; Yamazaki, R.; /Sagamihara, Aoyama Gakuin U.

2011-11-08

265

VERY LARGE ARRAY OBSERVATIONS OF AMMONIA IN INFRARED-DARK CLOUDS. II. INTERNAL KINEMATICS  

SciTech Connect

Infrared-dark clouds (IRDCs) are believed to be the birthplaces of rich clusters and thus contain the earliest phases of high-mass star formation. We use the Green Bank Telescope and Very Large Array maps of ammonia (NH{sub 3}) in six IRDCs to measure their column density and temperature structure (Paper 1), and here, we investigate the kinematic structure and energy content. We find that IRDCs overall display organized velocity fields, with only localized disruptions due to embedded star formation. The local effects seen in NH{sub 3} emission are not high-velocity outflows but rather moderate (few km s{sup -1}) increases in the linewidth that exhibit maxima near or coincident with the mid-infrared emission tracing protostars. These linewidth enhancements could be the result of infall or (hidden in NH{sub 3} emission) outflow. Not only is the kinetic energy content insufficient to support the IRDCs against collapse, but also the spatial energy distribution is inconsistent with a scenario of turbulent cloud support. We conclude that the velocity signatures of the IRDCs in our sample are due to active collapse and fragmentation, in some cases augmented by local feedback from stars.

Ragan, Sarah E.; Bergin, Edwin A. [Department of Astronomy, University of Michigan, 830 Dennison Building, 500 Church Street, Ann Arbor, MI 48109 (United States); Heitsch, Fabian [Department of Physics and Astronomy, University of North Carolina-Chapel Hill, CB 3255 Phillips Hall, Chapel Hill, NC 27599 (United States); Wilner, David, E-mail: ragan@mpia.de [Smithsonian Center for Astrophysics, Mail Stop 42, 60 Garden Street, Cambridge, MA 02138 (United States)

2012-02-20

266

VLA observations of a solar noise storm  

Microsoft Academic Search

The first Very Large Array (VLA) observations of the sun at 92 cm wavelength (328 MHz) are presented. A 3-hr solar noise storm was detected; it consisted of burst-like spikes superimposed on a slowly varying background, and both storm components were 95 + or - 5 percent right-hand circularly polarized. A long duration soft X ray event preceeded the radio

Kenneth R. Lang; Robert F. Willson

1987-01-01

267

Observation of large CP violation in the neutral B meson system.  

PubMed

We present a measurement of the standard model CP violation parameter sin2 phi(1) based on a 29.1 fb(-1) data sample collected at the Upsilon(4S) resonance with the Belle detector at the KEKB asymmetric-energy e(+)e(-) collider. One neutral B meson is fully reconstructed as a J/psi K(S), psi(2S)K(S), chi(c1)K(S), eta(c)K(S), J/psi K(L), or J/psi 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 phi(1) = 0.99+/-0.14(stat)+/-0.06(syst). We conclude that we have observed CP violation in the neutral B meson system. PMID:11531561

Abe, K; Abe, K; Abe, R; Adachi, I; Ahn, B S; 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, H; Kim, H J; Kim, H; 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; Stanic, S; Sugi, A; Sugiyama, A; Sumisawa, K; Sumiyoshi, T; Suzuki, J; 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; Zontar, D

2001-08-14

268

Idiopathic generalized epilepsy: Phenotypic and electroencephalographic observations in a large cohort from South India  

PubMed Central

Purpose: We studied the phenotype and electroencephalographic (EEG) features, and therapeutic aspects of idiopathic generalized epilepsies (IGEs) in South Indian population. Patients and Methods: This prospective cross-sectional hospital-based study was carried out on non-consecutive 287 patients (age 22.2 ± 7.7 years; M:F = 139:148) with IGE syndrome. Their clinical and EEG observations were analyzed. Results: Majority of the patients had onset of seizures <20 years of age (n = 178; 62%). Thirty one patients (10.8%) had family history of epilepsy. Nearly half of them (49.9%) had <5 years of duration of seizures. The type of IGEs included Juvenile myoclonic epilepsy (JME): 115 (40.1%); IGE with generalized tonic-clonic seizures (GTCS) only: 102 (39.02%); childhood absence epilepsy (CAE): 35 (12.2%); GTCS on awakening: 15 (5.2%); Juvenile absence epilepsy (JAE): 11 (3.8%); and unclassified seizures: 9 (3.1%). The triggering factors noted in 45% were sleep deprivation (20%), non-compliance and stress in 5% each. The EEG (n = 280) showed epileptiform discharges in about 50% of patients. Epileptiform discharges during activation was observed in 40/249 patients (16.1%): Hyperventilation in 32 (12.8%) and photic stimulation in 19 (7.6%). The seizures were well controlled with anti-epileptic drugs (AEDs) in 232 (80.8%) patients and among them, 225 (78.4%) patients were on monotherapy. Valproate (n = 131) was the most frequently prescribed as monotherapy. Conclusions: This is one of the largest cohort of patients with IGE. This study reiterates the importance of segregating IGE syndrome and such analysis will aid to the current understanding and management.

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

2013-01-01

269

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/ R p > ˜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

270

Optical circular polarization in quasars  

Microsoft Academic Search

We present new optical circular polarization measurements with typical uncertainties 3sigma) circular polarization in two blazars with high linear polarization and discuss the implications of this result for quasar physics. In particular, the recorded polarization degrees may be indicative of magnetic fields as strong as 1 kG or a significant contribution of inverse Compton scattering to the optical continuum. Based

D. Hutsemékers; B. Borguet; D. Sluse; R. Cabanac; H. Lamy

2010-01-01

271

Understanding and measuring circular polarization  

Microsoft Academic Search

Many modern satellite and terrestrial point-to-point communications systems use circular polarization (CP) wave propagation in order to maximize the polarization efficiency component of the link budget. Therefore, in an undergraduate electromagnetics syllabus, an introduction to the topic of circular polarization is necessary to promote an understanding of the propagation aspects of modern communications system design. Students new to the antennas

Bee Yen Toh; Robert Cahill; Vincent F. Fusco

2003-01-01

272

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

273

Seismic observations of large-scale deformation at the bottom of fast-moving plates  

NASA Astrophysics Data System (ADS)

We present a new tomographic model of azimuthal anisotropy in the upper mantle, DR2012, and discuss in details the geodynamical causes of this anisotropy. Our model improves upon DKP2005 seismic model (Debayle et al., 2005) through a larger dataset (expanded by a factor ˜3.7) and a new approach which allows us to better extract fundamental and higher-mode information. Our results confirm that on average, azimuthal anisotropy is only significant in the uppermost 200-250 km of the upper mantle where it decreases regularly with depth. We do not see a significant difference in the amplitude of anisotropy beneath fast oceanic plates, slow oceanic plates or continents. The anisotropy projected onto the direction of present plate motion shows a very specific relation with the plate velocity; it peaks in the asthenosphere around 150 km depth, it is very weak for plate velocities smaller than 3 cmyr, increases significantly between 3 and 5 cmyr, and saturates for plate velocities larger than 5 cmyr. Plate-scale present-day deformation is remarkably well and uniformly recorded beneath the fastest-moving plates (India, Coco, Nazca, Australia, Philippine Sea and Pacific plates). Beneath slower plates, plate-motion parallel anisotropy is only observed locally, which suggests that the mantle flow below these plates is not controlled by the lithospheric motion (a minimum plate velocity of around 4 cmyr is necessary for a plate to organize the flow in its underlying asthenosphere). The correlation of oceanic anisotropy with the actual plate motion in the shallow lithosphere is very weak. A better correlation is obtained with the fossil accretion velocity recorded by the gradient of local seafloor age. The transition between frozen-in and active anisotropy occurs across the typical ?{age} isotherm that defines the bottom of the thermal lithosphere around 1100°C. Under fast continents (mostly under Australia and India), the present-day velocity orients also the anisotropy in a depth range around 150-200 km depth which is not deeper than what is observed under oceans.

Debayle, Eric; Ricard, Yanick

2013-08-01

274

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

SciTech Connect

We are developing a new balloon-borne instrument (PoGO), to measure polarization of soft gamma rays (30-200 keV) using asymmetry in azimuth angle distribution of Compton scattering. PoGO is designed to detect 10% polarization in 100mCrab sources in a 6-8 hour observation and bring a new dimension to studies on gamma ray emission/transportation mechanism in pulsars, AGNs, black hole binaries, and neutron star surface. The concept is an adaptation to polarization measurements of well-type phoswich counter consisting of a fast plastic scintillator (the detection part), a slow plastic scintillator (the active collimator) and a BGO scintillator (the bottom anti-counter). PoGO consists of close-packed array of 217 hexagonal well-type phoswich counters and has a narrow field-of-view ({approx} 5 deg{sup 2}) to reduce possible source confusion. A prototype instrument has been tested in the polarized soft gamma-ray beams at Advanced Photon Source (ANL) and at Photon Factory (KEK). On the results, the polarization dependence of EGS4 has been validated and that of Geant4 has been corrected.

Andersson, V.; Chen, P.; Kamae, T.; Madejski, G.; Mizuno, T.; Ng, J.; Tajima, H.; Thurston, T.; /SLAC; Bogaert, G.; /Ecole Polytechnique; Fukazawa, Y.; /Hiroshima U.; Saito, Y.; Takahashi, T.; /Sagamihara, Inst. Space Astron. Sci.; Barbier, L.; Bloser, P.; Harding, A.; Hunter, S.; Krizmanic, J.; Mitchell, J.; Streitmatter, R.; Fernholz, R.; Groth, E.; /NASA, Goddard /Princeton U. /Royal Inst. Tech., Kista /Stockholm U. /Tokyo Inst. Tech. /Yamagata U.

2005-06-30

275

Simple large-scale synthesis of hydroxyapatite nanoparticles: in situ observation of crystallization process.  

PubMed

The noble synthesis method for hydroxyapatite (HAp) nanoparticles was exploited using a fairly simple reaction of Ca(OH)(2) and H(3)PO(4), which does not generate residual harmful anions and consequently does not need an additional washing process. HAp nanoparticles were found to yield from dicalcium phosphate dehydrate (DCPD) as the only intermediate phase, which was monitored by in situ observation study using X-ray diffraction (XRD), Fourier transform infrared (FT-IR), (1)H and (31)P magic-angle spinning (MAS) NMR. Furthermore, we found that the phase evolution of HAp was preceded by heteronucleation of HAp onto the DCPD surface. The combination of scanning electron microscopy (SEM) and inductively coupled plasma atomic emission spectroscopy (ICP-ES) analysis gave more information on the HAp crystallization process, which was found to be retarded by the residual Ca(OH)(2) and slow diffusion process of Ca ions into the interface between HAp and DCPD. These results demonstrate that the synthesis of pure HAp nanoparticles with high throughput can be achieved by controlling the residual Ca(OH)(2) and diffusion process of Ca ions. PMID:19810677

Kim, Dong Wook; Cho, In-Sun; Kim, Jin Young; Jang, Hae Lin; Han, Gill Sang; Ryu, Hyun-Seung; Shin, Heungsoo; Jung, Hyun Suk; Kim, Hyungtak; Hong, Kug Sun

2010-01-01

276

Mapping observations of large organic molecules in massive star-forming regions  

NASA Astrophysics Data System (ADS)

We carried out mapping observations of O-bearing molecules (CH3OH, C2H5OH etc) and NH-/NH2-bearing molecules (CH2NH, CH3NH2 etc). Such a molecule, which is saturated or nearly saturated, has been believed to be prodcued on dust grain. We found difference between distributions of O-bearing molecules and those of NH-/NH2-bearing molecules. O-bearing molecules are concentrated to H II regions. If these molecules are produced on the dust grain, many embedded OB-stars in H II regions can heat the dust grain, and produced molecules can be evaporated. This indicates that dust chemistry may be important for formation mechanisms of these molecules. On the other hand, intensity peaks of NH-/NH2-bearing molecules are shifted to the west of H II regions. This resut indicates that formation mechanisms of NH-/NH2-bearing molecules may be different from those of O-bearing molecules.

Ikeda, M.; Ohishi, M.

277

Observation of electron plasma waves inside large amplitude electromagnetic pulses in a temporally growing plasma  

SciTech Connect

Observation of electron plasma waves excited inside high power ({approx}10 kW) short pulse ({approx}20 {mu}s) electromagnetic (em) waves interacting with a gaseous medium (argon) in the pressure range 0.2-2.5 mTorr is reported. The waves have long wavelength ({approx}13 cm) and get damped at time scales slower ({approx}3 {mu}s) than the plasma period (0.1-0.3 {mu}s), the energy conveyed to the medium lead to intense ionization (ion density n{sub i} {approx} 10{sup 11} cm{sup -3} and electron temperature T{sub e} {approx} 6-8 eV) and rapid growth of the plasma ({approx}10{sup 5} s{sup -1}) beyond the waves. Time frequency analysis of the generated oscillations indicate the presence of two principal frequencies centered around 3.8 MHz and 13.0 MHz with a spread {Delta}f {approx} 4 MHz, representing primarily two population of electrons in the plasma wave. The experimental results are in reasonable agreement with a model that considers spatiotemporal forces of the em wave on the medium, space charges and diffusion.

Pandey, Shail; Bhattacharjee, Sudeep; Sahu, Debaprasad [Department of Physics, Indian Institute of Technology, Kanpur-208016 (India)

2012-01-15

278

FERMI LARGE AREA TELESCOPE OBSERVATIONS OF MARKARIAN 421: THE MISSING PIECE OF ITS SPECTRAL ENERGY DISTRIBUTION  

SciTech Connect

We report on the {gamma}-ray activity of the high-synchrotron-peaked BL Lacertae object Markarian 421 (Mrk 421) during the first 1.5 years of Fermi operation, from 2008 August 5 to 2010 March 12. We find that the Large Area Telescope (LAT) {gamma}-ray spectrum above 0.3 GeV can be well described by a power-law function with photon index {Gamma} = 1.78 {+-} 0.02 and average photon flux F(> 0.3 GeV) = (7.23 {+-} 0.16) x 10{sup -8} ph cm{sup -2} s{sup -1}. Over this time period, the Fermi-LAT spectrum above 0.3 GeV was evaluated on seven-day-long time intervals, showing significant variations in the photon flux (up to a factor {approx}3 from the minimum to the maximum flux) but mild spectral variations. The variability amplitude at X-ray frequencies measured by RXTE/ASM and Swift/BAT is substantially larger than that in {gamma}-rays measured by Fermi-LAT, and these two energy ranges are not significantly correlated. We also present the first results from the 4.5 month long multifrequency campaign on Mrk 421, which included the VLBA, Swift, RXTE, MAGIC, the F-GAMMA, GASP-WEBT, and other collaborations and instruments that provided excellent temporal and energy coverage of the source throughout the entire campaign (2009 January 19 to 2009 June 1). During this campaign, Mrk 421 showed a low activity at all wavebands. The extensive multi-instrument (radio to TeV) data set provides an unprecedented, complete look at the quiescent spectral energy distribution (SED) for this source. The broadband SED was reproduced with a leptonic (one-zone synchrotron self-Compton) and a hadronic model (synchrotron proton blazar). Both frameworks are able to describe the average SED reasonably well, implying comparable jet powers but very different characteristics for the blazar emission site.

Abdo, A. A. [National Research Council Research Associate, National Academy of Sciences, Washington, DC 20001 (United States); Ackermann, M.; Ajello, M.; Bechtol, K.; Berenji, B.; Blandford, R. D.; Bloom, E. D.; Borgland, A. W.; Buehler, R. [W. W. Hansen Experimental Physics Laboratory, Kavli Institute for Particle Astrophysics and Cosmology, Department of Physics and SLAC National Accelerator Laboratory, Stanford University, Stanford, CA 94305 (United States); Baldini, L.; Bellazzini, R.; Bregeon, J.; Brez, A. [Istituto Nazionale di Fisica Nucleare, Sezione di Pisa, I-56127 Pisa (Italy); Ballet, J. [Laboratoire AIM, CEA-IRFU/CNRS/Universite Paris Diderot, Service d'Astrophysique, CEA Saclay, 91191 Gif sur Yvette (France); Barbiellini, G. [Istituto Nazionale di Fisica Nucleare, Sezione di Trieste, I-34127 Trieste (Italy); Bastieri, D. [Istituto Nazionale di Fisica Nucleare, Sezione di Padova, I-35131 Padova (Italy); Bonamente, E. [Istituto Nazionale di Fisica Nucleare, Sezione di Perugia, I-06123 Perugia (Italy); Bouvier, A. [Santa Cruz Institute for Particle Physics, Department of Physics and Department of Astronomy and Astrophysics, University of California at Santa Cruz, Santa Cruz, CA 95064 (United States); Brigida, M. [Dipartimento di Fisica 'M. Merlin' dell'Universita e del Politecnico di Bari, I-70126 Bari (Italy); Bruel, P., E-mail: dpaneque@mppmu.mpg.de, E-mail: anita.reimer@uibk.ac.at, E-mail: georgano@umbc.edu, E-mail: justin.finke@nrl.navy.mil, E-mail: diegot@ifae.es [Laboratoire Leprince-Ringuet, Ecole polytechnique, CNRS/IN2P3, Palaiseau (France)

2011-08-01

279

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

280

Circular chemiresistors for microchemical sensors  

DOEpatents

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

Ho, Clifford K. (Albuquerque, NM)

2007-03-13

281

Observations of large-amplitude internal wave of the second mode in Luzon Strait  

NASA Astrophysics Data System (ADS)

Among the regions of the World Ocean where intense internal waves occur, the South China Sea is known as an area where the largest internal waves can be met. Comprehensive studies of internal waves, which were carried out there during the last decade, reveal the substantial effects of both the first and second modes. The place where the record amplitude waves are generated is Luzon Strait. In May, 2006, we performed the studies in Luzon Strait, aboard the "Ocean Researcher 1" vessel of the National Taiwan University. In those experiments, we could detect a passage of a solitary internal wave of the second mode in deep water, and to measure its parameters. The observations were carried out at a calm sea, after some days of the passage of a big typhoon Chanchu through the South China Sea. In the measurements, a 150-kHz acoustic Doppler current profiler, the EK 500 echo-sounder, radar that registered the pattern of the sea surface, and a neutral-buoyancy body with temperature and depth sensors were used. In addition, ambient underwater noises were measured by a hydrophone. On May 23, a solitary internal wave passed under the vessel, with a height of 50 m and apparent features of the second mode, was found. The undersurface 200-m water layer suffered from an elevation. At the same time, the deep water layers were depressed. The internal wave moved with an extraordinarily high speed of more than 3 m/s in the north-west direction. The passage of the internal wave was accompanied by a wide rip band that was detected by the vessel radar and the digital camera. The passage also caused the underwater noise. This work was supported by National Science Council of Taiwan in Taiwan-Russia two-side research projects (No. NSC96-2923-E-002-002-MYZ) and by Russian Foundation for Basic Research.

Serebryany, A. N.; Liu, C.-T.

2012-04-01

282

Large area balloon borne Polarized Gamma ray Observer ( PoGO)  

NASA Astrophysics Data System (ADS)

Polarimetry has proven to be a powerful diagnostic tool in optical and radio astronomy. In the X-ray range, a wide variety of compact objects is expected to provide polarization between a few per cent to 50 per cent, with polarization measurements providing insights on the geometry of accreting sources, the effects of intense magnetic fields, and tests of general relativity. PoGO is an instrument designed to detect 10% polarization of a bright source (100 mCrab) in the energy range 25-200 keV within a single 6 hour balloon flight. Prime targets for PoGO will be super massive black holes, galactic binaries, accreting neutron stars, pulsars, and Seyfert galaxies. In one flight PoGO will be able to determine the Crab pulsar polarization at a 20 sigma level according to a detailed simulation of the instrument. The instrument uses Compton scattering and photo-absorption in an array of 400 well-type phoswich detectors. Its passive and active collimators select a 5 square degree observation cone, and suppress the background down to 10 mCrab. A ``proof of principle'' prototype detector segment has been built and tested at Argonne National Laboratory. The prototype behaved as predicted by simulation and gave a modulation factor of 41% at 60 keV. Two possible designs of PoGO are being studied, aiming for a first balloon flight in 2007. PoGO has been selected by NASA as a Research Opportunity in Space Science Program.

Bogaert, G.; Pogo Collaboration

283

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

SciTech Connect

We are developing a new balloon-borne instrument (PoGO), to measure polarization of soft gamma rays (25-200 keV) using asymmetry in azimuth angle distribution of Compton scattering. PoGO will detect 10% polarization in 100mCrab sources in a 6-8 hour observation and bring a new dimension to studies on gamma ray emission/transportation mechanism in pulsars, AGNs, black hole binaries, and neutron star surface. The concept is an adaptation to polarization measurements of well-type phoswich counter technology used in balloon-borne experiments (Welcome-1) and AstroE2 Hard X-ray Detector. PoGO consists of close-packed array of 397 hexagonal well-type phoswich counters. Each unit is composed of a long thin tube (well) of slow plastic scintillator, a solid rod of fast plastic scintillator, and a short BGO at the base. A photomultiplier coupled to the end of the BGO detects light from all 3 scintillators. The rods with decay times < 10 ns, are used as the active elements; while the wells and BGOs, with decay times {approx}250 ns are used as active anti-coincidence. The fast and slow signals are separated out electronically. When gamma rays entering the field-of-view (fwhm {approx} 3deg{sup 2}) strike a fast scintillator, some are Compton scattered. A fraction of the scattered photons are absorbed in another rod (or undergo a second scatter). A valid event requires one clean fast signal of pulse-height compatible with photo-absorption (> 20keV) and one or more compatible with Compton scattering (< 10keV). Studies based on EGS4 (with polarization features) and Geant4 predict excellent background rejection and high sensitivity.

Blanford, R.

2005-04-06

284

Fermi Large Area Telescope Observations of the Supernova Remnant W28 (G6.4-0.1)  

NASA Astrophysics Data System (ADS)

We present detailed analysis of two gamma-ray sources, 1FGL J1801.3-2322c and 1FGL J1800.5-2359c, that have been found toward the supernova remnant (SNR) W28 with the Large Area Telescope (LAT) on board the Fermi Gamma-ray Space Telescope. 1FGL J1801.3-2322c is found to be an extended source within the boundary of SNR W28, and to extensively overlap with the TeV gamma-ray source HESS J1801-233, which is associated with a dense molecular cloud interacting with the SNR. The gamma-ray spectrum measured with the LAT from 0.2 to 100 GeV can be described by a broken power-law function with a break at ~1 GeV and photon indices of 2.09 ± 0.08 (stat) ± 0.28 (sys) below the break and 2.74 ± 0.06 (stat) ± 0.09 (sys) above the break. Given the clear association between HESS J1801-233 and the shocked molecular cloud and a smoothly connected spectrum in the GeV-TeV band, we consider the origin of the gamma-ray emission in both GeV and TeV ranges to be the interaction between particles accelerated in the SNR and the molecular cloud. The decay of neutral pions produced in interactions between accelerated hadrons and dense molecular gas provides a reasonable explanation for the broadband gamma-ray spectrum. 1FGL J1800.5-2359c, located outside the southern boundary of SNR W28, cannot be resolved. An upper limit on the size of the gamma-ray emission was estimated to be ~16' using events above ~2 GeV under the assumption of a circular shape with uniform surface brightness. It appears to coincide with the TeV source HESS J1800-240B, which is considered to be associated with a dense molecular cloud that contains the ultra compact H II region W28A2 (G5.89-0.39). We found no significant gamma-ray emission in the LAT energy band at the positions of TeV sources HESS J1800-230A and HESS J1800-230C. The LAT data for HESS J1800-230A combined with the TeV data points indicate a spectral break between 10 GeV and 100 GeV.

Abdo, A. A.; Ackermann, M.; 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.; Bouvier, A.; Brandt, T. J.; Bregeon, J.; Brigida, M.; Bruel, P.; Buehler, R.; Buson, S.; Caliandro, G. A.; Cameron, R. A.; Caraveo, P. A.; Carrigan, S.; Casandjian, J. M.; Cecchi, C.; Çelik, Ö.; Chekhtman, A.; Chiang, J.; Ciprini, S.; Claus, R.; Cohen-Tanugi, J.; Conrad, J.; Dermer, C. D.; de Palma, F.; Silva, E. do Couto e.; Drell, P. S.; Dubois, R.; Dumora, D.; Farnier, C.; Favuzzi, C.; Fegan, S. J.; Fukazawa, Y.; Fukui, Y.; Funk, S.; Fusco, P.; Gargano, F.; Gehrels, N.; Germani, S.; Giglietto, N.; Giordano, F.; Glanzman, T.; Godfrey, G.; Grenier, I. A.; Grove, J. E.; Guiriec, S.; Hadasch, D.; Hanabata, Y.; Harding, A. K.; Hays, E.; Horan, D.; Hughes, R. E.; Jóhannesson, G.; Johnson, A. S.; Johnson, W. N.; Kamae, T.; Katagiri, H.; Kataoka, J.; Knödlseder, J.; Kuss, M.; Lande, J.; Latronico, L.; Lee, S.-H.; Lemoine-Goumard, M.; Llena Garde, M.; Longo, F.; Loparco, F.; Lovellette, M. N.; Lubrano, P.; Makeev, A.; Mazziotta, M. N.; Michelson, P. F.; Mitthumsiri, W.; Mizuno, T.; Moiseev, A. A.; Monte, C.; Monzani, M. E.; Morselli, A.; Moskalenko, I. V.; Murgia, S.; Nakamori, T.; Nolan, P. L.; Norris, J. P.; Nuss, E.; Ohno, M.; Ohsugi, T.; Omodei, N.; Orlando, E.; Ormes, J. F.; Ozaki, M.; 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.; Rodriguez, A. Y.; Roth, M.; Sadrozinski, H. F.-W.; Sander, A.; Saz Parkinson, P. M.; Sgrò, C.; Siskind, E. J.; Smith, D. A.; Smith, P. D.; Spandre, G.; Spinelli, P.; Strickman, M. S.; Suson, D. J.; Tajima, H.; Takahashi, H.; Takahashi, T.; Tanaka, T.; Thayer, J. B.; Thayer, J. G.; Thompson, D. J.; Tibaldo, L.; Tibolla, O.; Torres, D. F.; Tosti, G.; Uchiyama, Y.; Uehara, T.; Usher, T. L.; Vasileiou, V.; Vilchez, N.; Vitale, V.; Waite, A. P.; Wang, P.; Winer, B. L.; Wood, K. S.; Yamamoto, H.; Yamazaki, R.; Yang, Z.; Ylinen, T.; Ziegler, M.

2010-07-01

285

Large-scale interplanetary magnetic fields: Voyager 1 and 2 observations between 1 AU and 9. 5 AU  

SciTech Connect

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.

1984-04-01

286

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

SciTech Connect

We report on measurements of the cosmic-ray induced {gamma}-ray emission of Earth's atmosphere by the Large Area Telescope on board the Fermi Gamma-ray Space Telescope. The Large Area Telescope has observed the Earth during its commissioning phase and with a dedicated Earth limb following observation in September 2008. These measurements yielded {approx}6.4x10{sup 6} photons with energies >100 MeV and {approx}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 {gamma}=2.79{+-}0.06.

Abdo, A. A. [Space Science Division, Naval Research Laboratory, Washington, D.C. 20375 (United States); National Academy of Sciences, Washington, D.C. 20001 (United States); Ackermann, M.; Ajello, M.; Bechtol, K.; Berenji, B.; Bloom, E. D.; Borgland, A. W.; Bouvier, A.; Buehler, R.; Cameron, R. A.; Charles, E.; Chiang, J.; Claus, R.; Digel, S. W.; Couto e Silva, E. do; Drell, P. S.; Dubois, R.; Focke, W. B.; Funk, S.; Glanzman, T. [W. W. Hansen Experimental Physics Laboratory, Kavli Institute for Particle Astrophysics and Cosmology, Department of Physics and SLAC National Accelerator Laboratory, Stanford University, Stanford, California 94305 (United States)] (and others)

2009-12-15

287

A statistical model of magnetic islands in a large current layer: validation from Hall MHD simulations and Cluster FTE observations  

NASA Astrophysics Data System (ADS)

Magnetic islands have been observed in large current layers for various space plasmas, including the magnetopause and solar corona. Since the direct simulation of very large systems is not possible, we have developed a statistical model which describes the formation, growth, convection and coalescence of these magnetic islands. An integral- differential equation is derived for the island distribution function, which characterizes islands by the flux they contain ? and the area they enclose A. We use Hall MHD simulations to validate the model and to benchmark its parameters. The steady- state solution of the evolution equation predicts a distribution of islands. A database of 1,098 flux transfer events observed by Cluster between 2001 and 2003 is shown to be consistent with the model's predictions.

Fermo, Raymond; Drake, James; Swisdak, Marc; Hwang, Kyoung-Joo; Wang, Yongli

2010-11-01

288

Entropic derivation of F = m a for circular motion  

NASA Astrophysics Data System (ADS)

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 = m a 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.

Duncan, Michael; Myrzakulov, Ratbay; Singleton, Douglas

2011-09-01

289

Large-scale, prospective, observational studies in patients with psoriasis and psoriatic arthritis: A systematic and critical review  

Microsoft Academic Search

Background  Observational studies, if conducted appropriately, play an important role in the decision-making process providing invaluable\\u000a information on effectiveness, patient-reported outcomes and costs in a real-world environment. We conducted a systematic review\\u000a of large-scale, prospective, cohort studies with the aim of (a) summarising design characteristics, the interventions or aspects\\u000a of the disease studied and the outcomes measured and (b) investigating methodological

Sue Langham; Julia Langham; Hans-Peter Goertz; Mark Ratcliffe

2011-01-01

290

Fermi-Large Area Telescope Observations of the Exceptional Gamma-ray Outbursts of 3C 273 in 2009 September  

Microsoft Academic Search

We present the light curves and spectral data of two exceptionally luminous gamma-ray outbursts observed by the Large Area Telescope experiment on board the Fermi Gamma-ray Space Telescope from 3C 273 in 2009 September. During these flares, having a duration of a few days, the source reached its highest gamma-ray flux ever measured. This allowed us to study, in some

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; T. H. Burnett; 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; C. C. Cheung; J. Chiang; S. Ciprini; R. Claus; J. Cohen-Tanugi; J. Conrad; L. Costamante; C. D. Dermer; A. de Angelis; F. de Palma; E. do Couto e. Silva; P. S. Drell; R. Dubois; D. Dumora; C. Farnier; C. Favuzzi; S. J. Fegan; W. B. Focke; M. Frailis; Y. Fukazawa; S. Funk; P. Fusco; F. Gargano; D. Gasparrini; N. Gehrels; S. Germani; N. Giglietto; P. Giommi; F. Giordano; T. Glanzman; G. Godfrey; I. A. Grenier; M.-H. Grondin; S. Guiriec; M. Hayashida; E. Hays; A. B. Hill; D. Horan; R. E. Hughes; G. Jóhannesson; A. S. Johnson; W. N. Johnson; T. Kamae; H. Katagiri; J. Kataoka; N. Kawai; J. Knödlseder; M. Kuss; J. Lande; S. Larsson; L. Latronico; M. Lemoine-Goumard; M. Llena Garde; F. Longo; F. Loparco; B. Lott; M. N. Lovellette; P. Lubrano; G. M. Madejski; A. Makeev; O. Mansutti; E. Massaro; M. N. Mazziotta; W. McConville; J. E. McEnery; C. Meurer; P. F. Michelson; W. Mitthumsiri; T. Mizuno; A. A. Moiseev; C. Monte; M. E. Monzani; A. Morselli; I. V. Moskalenko; S. Murgia; P. L. Nolan; J. P. Norris; E. Nuss; T. Ohsugi; N. Omodei; E. Orlando; J. F. Ormes; D. Paneque; J. H. Panetta; V. Pelassa; M. Pepe; M. Pesce-Rollins; F. Piron; T. A. Porter; S. Rainò; R. Rando; M. Razzano; A. Reimer; O. Reimer; S. Ritz; A. Y. Rodriguez; R. W. Romani; M. Roth; F. Ryde; H. F.-W. Sadrozinski; A. Sander; J. D. Scargle; T. L. Schalk; C. Sgrò; E. J. Siskind; P. D. Smith; G. Spandre; P. Spinelli; J.-L. Starck; M. S. Strickman; D. J. Suson; H. Tajima; H. Takahashi; T. Takahashi; T. Tanaka; J. B. Thayer; J. G. Thayer; D. J. Thompson; L. Tibaldo; D. F. Torres; G. Tosti; A. Tramacere; Y. Uchiyama; T. L. Usher; V. Vasileiou; N. Vilchez; V. Vitale; A. P. Waite; P. Wang; A. E. Wehrle; B. L. Winer; K. S. Wood; Z. Yang; T. Ylinen; M. Ziegler

2010-01-01

291

Observations and simulations of quasiperiodic ionospheric oscillations and large-scale traveling ionospheric disturbances during the December 2006 geomagnetic storm  

NASA Astrophysics Data System (ADS)

A numerical simulation was performed to investigate quasiperiodic ionospheric oscillations that were observed with periods of 4-5 h by the ionosonde network (Okinawa, Yamagawa, Kokubunji, and Wakkanai) in Japan during the 15 December 2006 magnetic storm. This simulation used the Coupled Magnetosphere Ionosphere Thermosphere (CMIT) 2.0 model. The CMIT model reproduced the main characteristics of the observed ionospheric oscillations, although it remains a challenging task to simulate the observations in a quantitative sense. Term analysis of the ion continuity equation demonstrated that the ionospheric oscillations in this event were mainly induced by the disturbed neutral winds, which were associated with the large scale thermospheric circulation and traveling atmospheric disturbances (TADs) during the storm. The TADs simulated from the model were then compared with those observed by the GPS Earth Observation Network (GEONET) in Japan to validate the simulation results. A prominent northward propagating large-scale traveling ionospheric disturbance (LSTID) during daytime, seen by the GEONET total electron content (TEC) data, was captured by the CMIT model. Two southward LSTIDs observed by GEONET GPS network were also reproduced by the CMIT model. However, the model gave faster phase speeds for the southward propagating LSTID occurred during 0620-0800 UT and the northward propagating LSTID; furthermore, the model missed the LSTID seen in the TEC perturbation data during 0140-0220 UT. Finally, both observations and simulations showed a strong hemispheric asymmetry for the TAD propagation that occurred during 0000-0400 UT, which may be associated with the hemispheric asymmetry of the change of Joule heating at high latitude.

Lei, Jiuhou; Burns, Alan G.; Tsugawa, Takuya; Wang, Wenbin; Solomon, Stanley C.; Wiltberger, Michael

2008-06-01

292

Z-DNA: vacuum ultraviolet circular dichroism.  

PubMed

In concentrated salt or ethanolic solutions, the self-complementary copolymer poly(dG-dC).poly(dG-dC) forms a left-handed double-helical structure that has been termed "Z-DNA." The first evidence for this structure came from changes observed in the circular dichroism (CD) spectrum between 230 and 300 nm for low- and high-salt solutions (Pohl, F. M. & Jovin, T. M. (1972) J. Mol. Biol. 67, 675-696). In 3 M NaCl, the CD spectrum is approximately inverted compared to the B-form spectrum observed in low-salt solution. We measured the vacuum ultraviolet CD spectrum of poly(dG-dC).poly(dG-dC) down to 180 nm under conditions in which the 230- to 300-nm spectrum is inverted. Below 200 nm, where the B form exhibits the large positive peak at 187 nm that is characteristic of right-handed double-helical DNAs, the Z form exhibits a large negative peak at 194 nm and a positive band below 186 nm. Therefore, the Z-form vacuum ultraviolet CD spectrum resembles an inverted and red-shifted B-form spectrum. The magnitudes of the differences observed between the B and Z forms in the CD spectrum below 200 nm are about 10 times greater than those observed between 230 and 300 nm. The vacuum ultraviolet CD spectrum of poly(dG-dC).poly(dG-dC) in 3 M Cs2SO4 also is inverted compared to the B-form spectrum; however, between 230 and 300 nm, it is nonconservative with a negative maximum at 290 nm and a weak positive CD signal above 300 nm, presumably reflecting differential light scattering and indicating the existence of molecular aggregates. Our results suggest that the vacuum ultraviolet CD spectrum is sensitive to the handedness of double-helical DNA structures. The CD spectrum in this region should complement other spectroscopic methods in relating the structures of poly(dG-dC).poly(dG-dC) existing in solution to those determined in the solid state by x-ray crystallography. PMID:6946428

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

1981-08-01

293

Circular nodes in neural networks.  

PubMed

In the usual construction of a neural network, the individual nodes store and transmit real numbers that lie in an interval on the real line; the values are often envisioned as amplitudes. In this article we present a design for a circular node, which is capable of storing and transmitting angular information. We develop the forward and backward propagation formulas for a network containing circular nodes. We show how the use of circular nodes may facilitate the characterization and parameterization of periodic phenomena in general. We describe applications to constructing circular self-maps, periodic compression, and one-dimensional manifold decomposition. We show that a circular node may be used to construct a homeomorphism between a trefoil knot in R3 and a unit circle. We give an application with a network that encodes the dynamic system on the limit cycle of the Kuramoto-Sivashinsky equation. This is achieved by incorporating a circular node in the bottleneck layer of a three-hidden-layer bottleneck network architecture. Exploiting circular nodes systematically offers a neural network alternative to Fourier series decomposition in approximating periodic or almost periodic functions. PMID:8581887

Kirby, M J; Miranda, R

1996-02-15

294

Very Large Array observations of solar active regions. IV Structure and evolution of radio bursts from 20 centimeter loops  

NASA Astrophysics Data System (ADS)

It is pointed out that centimeter wavelength (2 or 6 cm) observations with the Very Large Array (VLA) at high angular resolution and moderate time resolution have provided new insights into the physics of solar radio bursts. However, there have been comparatively few VLA observations of solar bursts at the longer 20 cm wavelength. The present investigation is concerned with a VLA analysis of six bursts from 20 cm loops. The Very Large Array was used to observe the active region AR 3804 on July 12-20, 1982 at 1380 MHz, 1540 MHz, or 1705 MHz. Attention is given to time profiles and 10 s snapshot maps which describe the evolution of the 20 cm bursts, preburst heating, and changes in magnetic structure before and during the bursts. The observations presented provide new insight into the evolution of solar microwave bursts and the physical processes which may trigger them. In one case, the intense components of multiple bursts originated in different sources, suggesting that a number of loops may have become successively activated like some complex X-ray bursts.

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

1984-04-01

295

Coordinated ground-based and Cluster observations of large amplitude global magnetospheric oscillations during a fast solar wind speed interval  

NASA Astrophysics Data System (ADS)

We present magnetospheric observations of very large amplitude global scale ULF waves, from 9 and 10 December 2000 when the upstream solar wind speed exceeded 600 km/s. We characterise these ULF waves using ground-based magnetometer, radar and optical instrumentation on both the dawn and dusk flanks; we find evidence to support the hypothesis that discrete frequency field line resonances (FLRs) were being driven by magnetospheric waveguide modes. During the early part of this interval, Cluster was on an outbound pass from the northern dusk side magnetospheric lobe into the magnetosheath, local-time conjugate to the Canadian sector. In situ magnetic fluctuations, observed by Cluster FGM, show evidence of quasi-periodic motion of the magnetosheath boundary layer with the same period as the ULF waves seen on the ground. Our observations represent the first simultaneous magnetometer, radar and optical observations of the characteristics of FLRs, and confirm the potential importance of ULF waves for magnetosphere-ionosphere coupling, particularly via the generation and modulation of electron precipitation into the ionosphere. The in situ Cluster measurements support the hypothesis that, during intervals of fast solar wind speed, the Kelvin-Helmholtz instability (KHI) can excite magnetospheric waveguide modes which bathe the flank magnetosphere with discrete frequency ULF wave power and drive large amplitude FLRs.

Mann, I. R.; Voronkov, I.; Dunlop, M.; Donovan, E.; Yeoman, T. K.; Milling, D. K.; Wild, J.; Kauristie, K.; Amm, O.; Bale, S. D.; Balogh, A.; Viljanen, A.; Opgenoorth, H. J.

2002-04-01

296

SWAP Observations of the Long-term, Large-scale Evolution of the Extreme-ultraviolet Solar Corona  

NASA Astrophysics Data System (ADS)

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; Shearer, Paul; Berghmans, David; Nicula, Bogdan

2013-11-01

297

Themis Observations of Long-lived Regions of Large-Amplitude Whistler Waves in the Inner Magnetosphere  

NASA Astrophysics Data System (ADS)

The Themis mission, with multiple satellites in near-equatorial orbits, offers an excellent opportunity to observe the large-amplitude whistler waves (>100 mV/m) that can exist in the radiation belts. We use data from the Electric Field Instrument (EFI) to assess several statistical properties of these waves, including the occurrence frequency, spatial extent and longevity of regions of large-amplitude whistlers. We show that the probability distribution of wave activity in the dawn-side radiation belts, especially near L-shells from 3.5 to 5.5, has a significant high-amplitude tail and is hence not well-described by long-term time averages. Regions of enhanced wave activity exhibit four-second averaged wave power above 1 mV/m and sub-second bursts up to several hundred mV/m. These regions are spatially localized to at most several hours of local time azimuthally, but can persist in the same location for several days. These observations of persistent, bursty, large-amplitude waves support the importance of the emerging nonlinear theories of electron acceleration in the radiation belts.

Cully, C. M.; Bonnell, J. W.; Ergun, R. E.

2008-12-01

298

Cluster Analysis of Large Scale Dynamics of Growing and Dissipating Cirrus Events Observed by A-Train and Geostationary Satellite  

NASA Astrophysics Data System (ADS)

Knowledge of how large-scale dynamics are coupled with microphysical properties is useful for understanding cloud behavior and necessary for parameterizing cirrus in models. Atlantic cirrus events observed by CloudSat and the SEVIRI Imager on the Meteosat satellite are classified based on six large-scale dynamical parameters: 300mb relative humidity, 300mb omega, 300mb moisture flux convergence, 500mb omega, 500mb absolute vorticity advection, and 850mb temperature advection. A k-means clustering algorithm is used to identify different types of cirrus occurring in the tropics and mid-latitudes. Composite histograms of pressure and radar reflectivity are created for each cirrus cluster to examine differences in vertical structure. To characterize the tendencies of cirrus events within the dynamical regimes, observations from geostationary satellite data are used to track the cirrus events in time by following patterns of 6.2?m brightness temperature. Cirrus events are classified as growing if the average brightness temperature is decreasing in time. Using NCEP/NCAR reanalysis data, the composite dynamics of each cirrus cluster are investigated to determine how the large-scale meteorology plays a role in the evolution of the cirrus events. Differences in the vertical structure of the cirrus cloud microphysics are revealed with composite profiles of total water content from cloud base to cloud top.

Dupont, E. J.; Mace, G. G.; Minnis, P.; Palikonda, R.

2009-12-01

299

THEMIS observations of long-lived regions of large-amplitude whistler waves in the inner magnetosphere  

NASA Astrophysics Data System (ADS)

Recent reports of large-amplitude whistler waves (>100 mV/m) in the radiation belts have intensified interest in the role of whistler waves in accelerating radiation belt electrons to MeV energies. Several critical parameters for addressing this issue have not previously been observed, including the occurrence frequency, spatial extent and longevity of regions of large-amplitude whistlers. The THEMIS mission, with multiple satellites in a near-equatorial orbit, offers an excellent opportunity to study these waves. We use data from the Electric Field Instrument (EFI) to show that in the dawn-side radiation belts, especially near L-shells from 3.5 to 5.5, the probability distribution of wave activity has a significant high-amplitude tail and is hence not well-described by long-term time averages. Regions of enhanced wave activity exhibit four-second averaged wave power above 1 mV/m and sub-second bursts up to several hundred mV/m. These regions are spatially localized to at most several hours of local time azimuthally, but can persist in the same location for several days. With large regions of space persistently covered by bursty, large-amplitude waves, the mechanisms and rates of radiation belt electron acceleration may need to be reconsidered.

Cully, C. M.; Bonnell, J. W.; Ergun, R. E.

2008-06-01

300

Astronomic Circular No. 605, 1971.  

National Technical Information Service (NTIS)

The report contains a translation of the following titles, contained in Astronomic Circular No. 605; On the problem of small eccentricities in the theory of satellite motion; On comet and minor planets collision; and, Hypsometry of the moon's surface. (Au...

I. E. Zalkalne V. V. Terentev Y. N. Lipskii Z. F. Rodionova

1972-01-01

301

Biological Synthesis of Circular Polypeptides*  

PubMed Central

Here, we review the use of different biochemical approaches for biological synthesis of circular or backbone-cyclized proteins and peptides. These methods allow the production of circular polypeptides either in vitro or in vivo using standard recombinant DNA expression techniques. Protein circularization can significantly impact protein engineering and research in protein folding. Basic polymer theory predicts that circularization should lead to a net thermodynamic stabilization of a folded protein by reducing the entropy associated with the unfolded state. Protein cyclization also provides a valuable tool for exploring the effects of topology on protein folding kinetics. Furthermore, the biological production of cyclic polypeptides makes possible the production of cyclic polypeptide libraries. The generation of such libraries, which was previously restricted to the domain of synthetic chemists, now offers biologists access to highly diverse and stable molecular libraries for probing protein structure and function.

Aboye, Teshome L.; Camarero, Julio A.

2012-01-01

302

Comparison of a statistical model for magnetic islands in large current layers with Hall MHD simulations and Cluster FTE observations  

NASA Astrophysics Data System (ADS)

Magnetic islands have been observed in long current layers for various space plasmas, including the magnetopause and solar corona. In previous work exploring these magnetic islands, a statistical model was developed that described their formation, growth, convection, and coalescence in very large systems, for which simulations prove inadequate. An integro-differential equation was derived for the island distribution function, which characterized islands by the flux they contain ? and the cross-sectional area they enclose A. The steady-state solution of the evolution equation predicted a distribution of islands. Here, we use a Hall MHD (magnetohydrodynamic) simulation of a very long current sheet with large numbers of magnetic islands to explore their dynamics, specifically their growth via two distinct mechanisms: quasi-steady reconnection and merging. We then use the simulation to validate the statistical model and benchmark its parameters. A database of 1,098 flux transfer events (FTEs) observed by Cluster between 2001 and 2003 is also compared with the model's predictions. In both simulations and observations, island merging plays a significant role. This suggests that the magnetopause is populated by many FTEs too small to be recognized by spacecraft instrumentation.

Fermo, R. L.; Drake, J. F.; Swisdak, M.; Hwang, K.-J.

2011-09-01

303

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

304

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.

2013-10-01

305

Optical observations of comet Hale-Bopp (C/1995 O1) at large heliocentric distances before perihelion.  

PubMed

The activity of comet Hale-Bopp (C/1995 O1) was monitored monthly by optical imaging and long-slit spectroscopy of its dust and gas distribution over heliocentric distances of 4.6 to 2.9 astronomical units. The observed band intensities of the NH2 radical and the H2O+ ion cannot be explained by existing models of fluorescence excitation, warranting a reexamination of the corresponding production rates, at least at large heliocentric distances. Comparing the production rate of the CN radical to its proposed parent, HCN, shows no evidence for the need of a major additional source for CN in Hale-Bopp at large heliocentric distances. The dust and CN production rates are consistent with a significant amount of sublimation occurring from icy dust grains surrounding Hale-Bopp. PMID:9072962

Rauer, H; Arpigny, C; Boehnhardt, H; Colas, F; Crovisier, J; Jorda, L; Küppers, M; Manfroid, J; Rembor, K; Thomas, N

1997-03-28

306

Observations of a high-latitude stable electron auroral emission at ˜16 MLT during a large substorm  

NASA Astrophysics Data System (ADS)

During an interval when the interplanetary magnetic field was large and primarily duskward and southward, a stable region of auroral emission was observed on 17 August 2001 by IMAGE at ˜16 magnetic local time, poleward of the main aurora, for 1 h, from before the onset of a large substorm through the recovery phase. In a region where ions showed the energy dispersion expected for the cusp, strong field-aligned currents and Poynting flux were observed by Polar (at 1.8 RE in the Southern Hemisphere) as it transited field lines mapping to the auroral spot in the Northern Hemisphere. The data are consistent with the hypothesis that the long-lasting electron auroral spot maps to the magnetopause region where reconnection was occurring. Under the assumption of conjugacy between the Northern and Southern hemispheres on these field lines, the Polar data suggest that the electrons on these field lines were accelerated by Alfvén waves and/or a quasi-static electric field, primarily at altitudes below a few RE since the in situ Poynting flux (mapped to 100 km) is comparable to the energy flux of the emission while the mapped in situ electron energy flux is much smaller. This event provides the first example of an emission due to electrons accelerated at low altitudes at the foot point of a region of quasi-steady dayside reconnection. Cluster data in the magnetotail indicate that the Poynting flux from the reconnection region during this substorm is large enough to account for the observed nightside aurora.

Cattell, C.; Dombeck, J.; Preiwisch, A.; Thaller, S.; Vo, P.; Wilson, L. B., III; Wygant, J.; Mende, S. B.; Frey, H. U.; Ilie, R.; Lu, G.

2011-07-01

307

SIMULTANEOUS OBSERVATIONS OF A LARGE-SCALE WAVE EVENT IN THE SOLAR ATMOSPHERE: FROM PHOTOSPHERE TO CORONA  

SciTech Connect

For the first time, we report a large-scale wave that was observed simultaneously in the photosphere, chromosphere, transition region, and low corona layers of the solar atmosphere. Using the high temporal and high spatial resolution observations taken by the Solar Magnetic Activity Research Telescope at Hida Observatory and the Atmospheric Imaging Assembly (AIA) on board Solar Dynamic Observatory, we find that the wave evolved synchronously at different heights of the solar atmosphere, and it propagated at a speed of 605 km s{sup -1} and showed a significant deceleration (-424 m s{sup -2}) in the extreme-ultraviolet (EUV) observations. During the initial stage, the wave speed in the EUV observations was 1000 km s{sup -1}, similar to those measured from the AIA 1700 A (967 km s{sup -1}) and 1600 A (893 km s{sup -1}) observations. The wave was reflected by a remote region with open fields, and a slower wave-like feature at a speed of 220 km s{sup -1} was also identified following the primary fast wave. In addition, a type-II radio burst was observed to be associated with the wave. We conclude that this wave should be a fast magnetosonic shock wave, which was first driven by the associated coronal mass ejection and then propagated freely in the corona. As the shock wave propagated, its legs swept the solar surface and thereby resulted in the wave signatures observed in the lower layers of the solar atmosphere. The slower wave-like structure following the primary wave was probably caused by the reconfiguration of the low coronal magnetic fields, as predicted in the field-line stretching model.

Shen, Yuandeng; Liu, Yu, E-mail: ydshen@ynao.ac.cn [Yunnan Astronomical Observatory, Chinese Academy of Sciences, Kunming 650011 (China)

2012-06-20

308

Observation of ultra-narrow band plasmon induced transparency based on large-area hybrid plasmon-waveguide systems  

NASA Astrophysics Data System (ADS)

We report the observation of an ultra-narrow band plasmon induced transparency resonance which is realized in a large area hybrid plasmon-waveguide system consisting of a gold nanowire array embedded in a slab waveguide. Due to the destructive interference between optical modes supported by the hybrid system, an ultra-narrow plasmon induced transparency resonance with a bandwidth of 8 nm at the wavelength of 966 nm was obtained (i.e., ~1/120 of the peak wavelength at the incident angle of 60°). The group velocity is estimated to be ~76, which is promising for miniaturized slow-light components.

Zhang, Jing; Bai, Wenli; Cai, Likang; Xu, Yun; Song, Guofeng; Gan, Qiaoqiang

2011-10-01

309

Flow Past a Circular Cylinder on a beta Plane  

Microsoft Academic Search

With a view to obtaining a fuller understanding of the interactions between topography and large-scale geophysical flows, a series of laboratory investigations have been performed on the flow past a right circular cylinder in a rotating water channel. For large-scale flows on a spherical Earth the variation of the Coriolis parameter, F = 2Omega sin phi , with latitude, phi

D. L. Boyer; P. A. Davies

1982-01-01

310

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

SciTech Connect

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 {+-} 1.7(stat.) x 10{sup -4} and (8.9 {+-} 12.1(stat.)){sup o}, and at 11 TeV are 3.8 {+-} 0.5(stat.) x 10{sup -4} and (27.2 {+-} 7.2(stat.)){sup o}.

de Jong, J.K.

2012-01-01

311

Spatial Seismology of a Large Coronal Loop Arcade from TRACE and EIT Observations of its Transverse Oscillations  

NASA Astrophysics Data System (ADS)

We present a study of transverse loop oscillations in a large coronal loop arcade, using observations from the Transition Region And Coronal Explorer (TRACE) and Extreme-ultraviolet Imaging Telescope (EIT). For the first time we reveal the presence of long-period transverse oscillations with periods between 24 minutes and 3 hr. One loop bundle, 690 Mm long and with an oscillation period of 40 minutes, is analyzed in detail and its oscillation characteristics are determined in an automated manner. The oscillation quality factor is similar to what has been found earlier for oscillations in much shorter loops. This indicates that the damping mechanism of transverse loop oscillations is independent of loop length or period. The displacement profile along the whole length of the oscillating loop is determined for the first time and consistently between TRACE and EIT. By comparing the observed profile with models of the three-dimensional geometry of the equilibrium and perturbed loop, we test the effect of longitudinal structuring (spatial seismology) and find that the observations cannot unambiguously distinguish between structuring and non-planarity of the equilibrium loop. Associated intensity variations with a similar periodicity are explained in terms of variations in the line-of-sight column depth. Also, we report intensity oscillations at the loop footpoint, which are in anti-phase with respect to the intensity oscillations in the loop body. Lastly, this observation offers the first opportunity to use the transverse oscillations of the arcade to model the Alfvén speed profile in the global corona.

Verwichte, E.; Foullon, C.; Van Doorsselaere, T.

2010-07-01

312

SPATIAL SEISMOLOGY OF A LARGE CORONAL LOOP ARCADE FROM TRACE AND EIT OBSERVATIONS OF ITS TRANSVERSE OSCILLATIONS  

SciTech Connect

We present a study of transverse loop oscillations in a large coronal loop arcade, using observations from the Transition Region And Coronal Explorer (TRACE) and Extreme-ultraviolet Imaging Telescope (EIT). For the first time we reveal the presence of long-period transverse oscillations with periods between 24 minutes and 3 hr. One loop bundle, 690 Mm long and with an oscillation period of 40 minutes, is analyzed in detail and its oscillation characteristics are determined in an automated manner. The oscillation quality factor is similar to what has been found earlier for oscillations in much shorter loops. This indicates that the damping mechanism of transverse loop oscillations is independent of loop length or period. The displacement profile along the whole length of the oscillating loop is determined for the first time and consistently between TRACE and EIT. By comparing the observed profile with models of the three-dimensional geometry of the equilibrium and perturbed loop, we test the effect of longitudinal structuring (spatial seismology) and find that the observations cannot unambiguously distinguish between structuring and non-planarity of the equilibrium loop. Associated intensity variations with a similar periodicity are explained in terms of variations in the line-of-sight column depth. Also, we report intensity oscillations at the loop footpoint, which are in anti-phase with respect to the intensity oscillations in the loop body. Lastly, this observation offers the first opportunity to use the transverse oscillations of the arcade to model the Alfven speed profile in the global corona.

Verwichte, E.; Foullon, C.; Van Doorsselaere, T., E-mail: Erwin.Verwichte@warwick.ac.u [Centre for Fusion, Space and Astrophysics, Department of Physics, University of Warwick, Coventry CV4 7AL (United Kingdom)

2010-07-01

313

H? Line Impact Linear Polarization Observed in the 23 July 2002 Flare with the Large Solar Vacuum Telescope (LSVT)  

NASA Astrophysics Data System (ADS)

We present the results of studying the proton flare 2B/X4.8 on 23 July 2002, observed with the Large Solar Vacuum Telescope (LSVT) at the Baikal Astrophysical Observatory in spectropolarimetric mode with high spatial and spectral resolution. We have found some evidence for H? line impact linear polarization, predominantly during the initial moments of the flare. For the H? line 606 cuts were made along the dispersion in 53 spectrograms, and a polarization signal was found more or less confidently in 60 cuts (13 spectrograms). Polarization was mainly observed in one of the kernels of the flare. A particular feature of this kernel was that the H? line was observed to show a reversal in the central part of this kernel, which created a dip in the kernel center in the photometric cut. The size of these dips and the size of the sites with the linear polarization coincide and are equal to 3 - 6 arcsec. The maximum polarization degree in this kernel reached 15 %. The direction of the polarization in the kernel is radial, except for the first two frames, where the direction of the polarization was both radial and tangential. Furthermore, we found an analogy between the effects observed at the chromospheric level in this kernel (polarization and depression in H? line) and the temporal variation of the HXR sources.

Firstova, N. M.; Polyakov, V. I.; Firstova, A. V.

2012-08-01

314

Regulated Large-Scale Shutdown of Amazonian Isoprene Emissions Inferred From GOME and SCIAMACHY Observations of HCHO Columns  

NASA Astrophysics Data System (ADS)

We perform Empirical Orthogonal Function analysis on 12 years of global GOME and SCIAMACHY formaldehyde (HCHO) column observations, to determine the most significant spatial and temporal HCHO variations. In most regions, we find that HCHO variability is predominantly driven by seasonal variations of biogenic emissions and biomass burning. However, unusually low HCHO columns are consistently observed over western Amazonia, during the transition from the wet-to-dry seasons. We present top-down isoprene emissions over western Amazonia during 1997-2001 inferred GOME HCHO columns, the GEOS-Chem chemistry transport model and the MEGAN (Model of Emissions of Gases and Aerosols from Nature) bottom- up isoprene inventory. The seasonal variation of GOME isoprene emissions is broadly consistent with MEGAN, with the smallest emissions during the wet-to-dry transitional period. The largest isoprene emissions are during the dry season, when the observed variability is consistent with prior knowledge of temperature dependence. We use MODIS Leaf Area Index and Enhanced Vegetation Index data, to show variations in vegetation are remarkably consistent (correlations of 0.69 and 0.67, respectively) with the observed decrease in HCHO during the wet-to-dry period. Based on this evidence, we suggest isoprene emitters experience widespread leaf flushing prior to the dry season, resulting in a large-scale annual shutdown of Amazonian isoprene emissions.

Barkley, M. P.; Palmer, P. I.

2008-12-01

315

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

316

Surface Faring Using Circular Highlight Lines  

Microsoft Academic Search

We herein propose a novel method for removing irregularities of B-spline surfaces via smoothing circular highlight lines. A circular highlight line is defined as a set of points on a surface such that the distance between a circular light source and an extended surface normal to be zero. Circular highlight lines allow us to capture the surface fairness in all

Yu Nishiyama; Yoh Nishimura; Takayuki Sasaki; Takashi Maekawa

2007-01-01

317

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

NASA Astrophysics Data System (ADS)

Frequency-banded electromagnetic VLF waves up to 2000 Hz are observed concurrently with warm (10 s to 10,000 s of eV) energy-banded ions in the low latitude auroral and sub-auroral zones during every large geomagnetic storm encountered by the FAST and DEMETER satellites. The banded ions and waves persist for several FAST or DEMETER orbits, lasting up to 12 h, in both dawn and dusk sectors, in both the northern and southern hemispheres. If the waves are generated at harmonics of the proton gyrofrequency, the inferred source region would be ?4000 km altitude. Previous investigations have shown that such waves can propagate from this source region to the locations of both spacecraft. An investigation into the growth of waves at harmonics of fci in the inferred source region suggests that these emissions could be generated by ion bands similar to those observed at the same time as the waves. Magnetospheric waves such as these play a role in energy transfer between distinct particle populations and may contribute to ion heating and ion outflow as well as electron energization. All of these phenomena occur during the strongest magnetic storms. The appearance of the banded ions and associated wave activity suggests that there may be distinct changes in the geospace system that characterize large magnetic storms.

Colpitts, Christopher A.; Cattell, Cynthia A.; Kozyra, Janet U.; Parrot, Michel

2012-10-01

318

Lightning NOx influence on large scale NOy and O3 plumes observed over the northern mid-latitudes  

NASA Astrophysics Data System (ADS)

Nitrogen species (NOy) play a major role in the tropospheric chemistry by controlling ozone distributions and the oxidizing capacity of the atmosphere. In the upper troposphere, NOy is principally emitted on the form of NOx through aircraft and surface emissions, stratospheric intrusions and lightning activity. This last one is particularly active over North America through large convective systems. This study aims to assess lightning NOx influence on large scale NOy and O3 plumes (> 300km) over the northern midlatitudes. We use 5 years (2001-2005) of aircraft observations (NOy, CO, O3, Relative Humidity) from the MOZAIC programme to discriminate those plumes. Ground-based and satellite-based observations of clouds (GOES) and lightning (NLDN, LIS), combined with systematic simulations of the Lagrangian FLEXPART model are used to assess the impact of the lightning and convective activity on the NOy and O3 distributions over the North Atlantic upper troposphere. Two case studies of continental and maritime convection are analyzed in order to give an estimation of NOy and O3 production per lightning flash.

Sauvage, B.; Cammas, J.; Defer, E.; Volz-Thomas, A.; Vouzelaud, J.; Thomas, K.; Holle, R. L.; Smit, H. M.

2010-12-01

319

Observations of Large Amplitude Electrostatic Waves Associated with Magnetic Ramp Substructure at Earth's Bow Shock by Polar  

NASA Astrophysics Data System (ADS)

We present Polar-EFI observations of electrostatic (ES) waves at high frequency (100 Hz < f < 4000 Hz) at Earth's bow shock under extreme solar wind conditions. Polar-EFI provides the first 3-axis measurements of electric fields across the shock layer, allowing for a better evaluation of the electric field properties than previous missions. The ES waveforms are of large amplitude (as large as 20-100 mV/m), and have both parallel and perpendicular components. Although we have observed solitary waves, the most prevalent structures in the magnetic ramp are large amplitude ES wave packets usually lasting from 10-30 cycles. These structures have wavelengths of a few hundred meters (e.g., ~ 10 Debeye Lengths) and are convecting by the spacecraft at speeds from 50 km/s to > 800 km/s. In the events presented, the ES wave power is generally well correlated with maxima in the magnetic ramp substructure, suggesting that these local maxima are important sites for the generation of these waves. These waveforms are not consistent with the classical ion acoustic wave description, since they occur under conditions where T_e~ T_i at local magnetic field maxima as opposed to the gradient and they propagate at oblique angles to the magnetic field. The fact that these waves are collocated with magnetic maxima is suggestive that the free-energy source of these waves may be from phase-space holes in the electron distribution, as a result of the acceleration of the low energy part of electron phase space by the shock DC electric field.

Hull, A. J.; Larson, D.; Mozer, F.; Wilber, M.; Bale, S.; Scudder, J.; Russell, C.

2005-12-01

320

Large-Scale Ozone and Aerosol Variations Observed Over the Pacific Ocean During the INTEX-B Field Experiment  

NASA Astrophysics Data System (ADS)

Large-scale distributions of ozone and aerosols were measured with a differential absorption lidar (DIAL) on the NASA DC-8 aircraft during the second part of the Intercontinental Chemical Transport Experiment - Phase B (INTEX-B) field experiment conducted over the Pacific Ocean from 17 April to 15 May 2006. Remote ozone and aerosol profiles were simultaneously measured below and above the DC-8 to provide information from near the surface to above the tropopause along the flight track. Multiple-wavelength aerosol backscatter measurements were made to estimate the relative size of the aerosols, and simultaneous aerosol depolarization measurements were made to detect the presence of nonspherical aerosols, such as mineral dust. In situ measurements of ozone were also made onboard the DC-8, and these were used to constrain the interpolation of the nadir and zenith ozone lidar measurements, which then provided an estimate of the entire tropospheric ozone profile along the flight track. Large-scale measurements of tropospheric ozone and aerosol distributions were obtained on all INTEX-B flights over the Pacific, and the long-range transport of aged and relatively fresh Asian pollution was often observed in the free troposphere in eastern Pacific. Comparisons have been made between the measured ozone cross sections and results from chemical transport models, which show general agreement in the atmospheric structure and pollution layer features. Average latitudinal and longitudinal variations of ozone and aerosols have also been derived from the remote and in situ ozone data for INTEX-B, and these results are compared to previous field experiments. The contribution of stratosphere-troposphere exchange to the latitudinal variation of ozone over the Pacific has also been examined. This paper discusses these results and relates them to chemical and dynamical processes that produce the observed large-scale variations in ozone and aerosols over the Pacific.

Browell, E. V.; Hair, J. W.; Butler, C. F.; Fenn, M. A.; Notari, A.; Kooi, S. A.; Ismail, S.; Avery, M. A.; Pierce, R. B.

2007-12-01

321

EXPANDED VERY LARGE ARRAY OBSERVATIONS OF THE H66{alpha} AND He66{alpha} RECOMBINATION LINES TOWARD MWC 349A  

SciTech Connect

We have used the greatly enhanced spectral capabilities of the Expanded Very Large Array to observe both the 22.3 GHz continuum emission and the H66{alpha} recombination line toward the well-studied Galactic emission-line star MWC 349A. The continuum flux density is found to be 411 {+-} 41 mJy in good agreement with previous determinations. The H66{alpha} line peak intensity is about 25 mJy, and the average line-to-continuum flux ratio is about 5%, as expected for local thermodynamic equilibrium conditions. This shows that the H66{alpha} recombination line is not strongly masing as had previously been suggested, although a moderate maser contribution could be present. The He66{alpha} recombination line is also detected in our observations; the relative strengths of the two recombination lines yield an ionized helium to ionized hydrogen abundance ratio y {sup +} = 0.12 {+-} 0.02. The ionized helium appears to share the kinematics of the thermally excited ionized hydrogen gas, so the two species are likely to be well mixed. The electron temperature of the ionized gas in MWC 349A deduced from our observations is 6300 {+-} 600 K.

Loinard, Laurent; Rodriguez, Luis F., E-mail: l.loinard@crya.unam.m [Centro de Radioastronomia y Astrofisica, Universidad Nacional Autonoma de Mexico, Apartado Postal 3-72, 58090, Morelia, Michoacan (Mexico)

2010-10-10

322

Lightning NOx influence on large scale NOy and O3 plumes observed over the northern mid-latitudes  

NASA Astrophysics Data System (ADS)

Nitrogen species (NOy) play a major role in the tropospheric chemistry by controlling ozone concentrations and the oxidizing capacity of the atmosphere. In the upper troposphere, NOy is principally emitted on the form of NOx through aircraft and surface emissions, stratospheric intrusions and lightning activity. This study investigates lightning NOx influence on large scale plumes (LSPs) of NOy and O3 (> 300km) over the northern mid-latitudes. We use 5 years (2001-2005) of aircraft observations (NOy, CO, O3, Relative Humidity) from the MOZAIC programme, ground-based and satellite-based observations of clouds (GOES) and lightning (NLDN, LIS) and systematic simulations with Lagrangian FLEXPART model to analyse the seasonal distributions and the origin of those lightning-related LSPs. Most of the LSPs (72%) are observed downwind of the convective and lightning activity occurring over North America, leading to a negative (positive) west to east zonal gradient of NOy (O3). Three case studies of lightning-related LSPs related to continental convection allow to give an estimation of the global annual nitrogen production of 2.2-4.6 Tg N yr-1, and of the NOy and O3 production (0.25-0.65 ppbv / d and 1-7 ppbv / d respectively). Finally we give an estimation of the NOy and O3 aging using the LSPs MOZAIC dataset, with a general decrease (increase) of NOy (O3) with -0.1/-0.4 ppbv/d (+0.2 /+16.3 ppbv/d).

Sauvage, B.; Cammas, J.; Defer, E.; Volz-Thomas, A.; Thomas, K.; Holle, R. L.

2011-12-01

323

A Chandra X-ray detection of the L dwarf binary Kelu-1. Simultaneous Chandra and Very Large Array observations  

NASA Astrophysics Data System (ADS)

Context: Magnetic activity in ultracool dwarfs, as measured in X-rays and H?, shows a steep decline after spectral type M7-M8. So far, no L dwarf has been detected in X-rays. In contrast, L dwarfs may have higher radio activity than M dwarfs. Aims: We observe L and T dwarfs simultaneously in X-rays and radio to determine their level of magnetic activity in the context of the general decline of magnetic activity with cooler effective temperatures. Methods: The field L dwarf binary Kelu-1 was observed simultaneously with Chandra and the Very Large Array. Results: Kelu-1AB was detected in X-rays with LX = 2.9-1.3+1.8 × 1025 erg s-1, while it remained undetected in the radio down to a 3 ? limit of LR ? 1.4 × 1013 erg s-1 Hz-1. We argue that, whereas the X-ray and H? emissions decline in ultracool dwarfs with decreasing effective temperature, the radio luminosity stays (more or less) constant across M and early-L dwarfs. The radio surface flux or the luminosity may better trace magnetic activity in ultracool dwarfs than the ratio of the luminosity to the bolometric luminosity. Conclusions: Deeper radio observations (and at short frequencies) are required to determine if and when the cut-off in radio activity occurs in L and T dwarfs, and what kind of emission mechanism takes place in ultracool dwarfs.

Audard, M.; Osten, R. A.; Brown, A.; Briggs, K. R.; Güdel, M.; Hodges-Kluck, E.; Gizis, J. E.

2007-09-01

324

Observation of large Zeeman splitting in GaGdN/AlGaN ferromagnetic semiconductor double quantum well superlattices  

NASA Astrophysics Data System (ADS)

Symmetric GaGdN/AlGaN (Gd concentration: 2%) and GaN/AlGaN double quantum well superlattices (DQW-SLs) were grown by radio-frequency plasma-assisted molecular-beam epitaxy on GaN (0001) templates. Atomic steps were observed on all the sample surfaces by atomic force microscope. X-ray diffraction ?/2? scan curves exhibited well-defined satellite structures. Room temperature ferromagnetism was confirmed for the GaGdN/AlGaN DQW-SL samples by using alternating gradient magnetometer. Strong photoluminescence was observed from both GaGdN and GaN QWs at higher energy side of GaN excitonic peak. Magneto-photoluminescence spectra for GaGdN/AlGaN DQW-SL samples showed a large magnetic field dependence of the excitonic energy by applying a magnetic field up to 7 T. The observed strong redshift of excitonic PL indicated an enhancement of Zeeman splitting of the free carrier energy levels in magnetic GaGdN/AlGaN DQW-SL. Enhanced g-factor was estimated to be about 60 for GaGdN/AlGaN DQW-SL sample with QW thickness of 1 nm.

Zhou, YiKai; Almokhtar, Mohamed; Kubo, Hitoshi; Mori, Nobuya; Emura, Shuichi; Hasegawa, Shigehiko; Asahi, Hajime

2012-07-01

325

Interaction between longitudinal and circular muscle in intestine of cat  

PubMed Central

1. Slow waves recorded from isolated longitudinal muscle averaged 13 mV and had slow rate of rise (0.04 V/sec) whereas when recorded from intact segments the amplitude averaged 27 mV and the rate of rise was more rapid (0.09 V/sec), often with a notch between the initial peak and the plateau. Membrane potentials of longitudinal muscle were similar in isolated and intact preparations (- 66 mV). Resting potentials of circular muscle averaged - 67 mV. 2. Small bundles of circular muscle tested in the double sucrose gap produced activity, either spontaneously or in response to stimulation, which fell into three categories: fast spikes (50-200 msec duration), slow spikes (1-5 sec duration), and small graded responses. The duration of fast spikes could be increased severalfold by the addition of TEA; the graded responses were converted to full-sized spikes by TEA. 3. Treatment of circular muscle with Ca-free Krebs solution eliminated spikes, and in intact preparations reduced the amplitude and rate of rise of slow waves and eliminated the notch on slow waves. 4. Current—voltage curves of longitudinal muscle show delayed rectification in the depolarizing quadrant; similar curves of circular muscle show anomalous rectification, i.e. a region where a very small current causes a large voltage change. 5. Non-polarized electrotonic coupling between longitudinal and circular layers indicates low-resistance pathways. Apparent space constants of longitudinal muscle are greater when attached to circular muscle than when isolated. 6. It is concluded that small slow potentials originate rhythmically in longitudinal muscle, that these spread passively to circular muscle where a regenerative amplification occurs which depends on Ca conductance and the amplified slow waves spread back to the longitudinal layer. In the intact intestine pacemaking is, therefore, separate from propagation and the circular muscle provides the bulk of depolarizing current for propagation.

Connor, J. A.; Kreulen, David; Prosser, C. L.; Weigel, R.

1977-01-01

326

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

327

Energetic Ions Accelerated during the large solar flare of 24 May 1990: high energy gamma-ray observations  

NASA Astrophysics Data System (ADS)

The large flare of 24 May 1990 (GOES X9.3, N36 W76) was observed at X-ray/gamma-ray energies by PHEBUS aboard GRANAT (Talon et al., 1993, Solar Phys., 147,137) and described in detail in Debrunner et al., 1997 (ApJ, 479,997). The flare comprised an impulsive phase detected at gamma-ray energies up to 75 MeV, followed by a long duration tail at high energies. The long lasting emission was dominated by high energy gamma-ray continuum and by > 500 MeV neutrons. Here we combine the observations of the gamma-ray continuum in the 10-100 MeV photon energy range with calculations of pion-decay gamma-ray radiation to constrain the accelerated interacting ion distributions at energies above 300 MeV. We compare this information with the numbers previously obtained for this event (Debrunner et al., 1997), for ions above 30 MeV from the de-excitation gamma-ray line emission as well as from the observations of neutrons from ground-based monitors. We find that the complete set of gamma-ray observations cannot be reproduced with a single power law ion spectrum extending from gamma-ray line emitting energies to those characteristic of pion decay emission. Similar ion energy distribution behaviour has been reported for the energetic flare of 15 June 1991, and we discuss our results in the light of this previous finding. Finally we comment on the different characteristics found for interacting and escaping protons.

Vilmer, N. R.; MacKinnon, A. L.; Trottet, G.; Barat, C.

2001-12-01

328

Observation of energetic-ion losses induced by various MHD instabilities in the Large Helical Device (LHD)  

SciTech Connect

Energetic-ion losses induced by toroidicity-induced Alfven eigenmodes (TAEs) and resistive interchange modes (RICs) were observed in neutral-beam heated plasmas of the Large Helical Device (LHD) at a relatively low toroidal magnetic field level (<= 0.75 T). The energy and pitch angle of the lost ions are detected using a scintillator-based lost-fast ion probe. Each instability increases the lost ions having a certain energy/pitch angle. TAE bursts preferentially induce energetic beam ions in co-passing orbits having energy from the injection energy E = 190keV down to 130 keV, while RICs expel energetic ions of E = 190 keV down to similar to 130 keV in passing-toroidally trapped boundary orbits. Loss fluxes induced by these instabilities increase with different dependences on the magnetic fluctuation amplitude: nonlinear and linear dependences for TAEs and RICs, respectively.

Ogawa, K. [Nagoya University, Japan; Isobe, M. [National Institute for Fusion Science, Toki, Japan; Toi, K. [National Institute for Fusion Science, Toki, Japan; Watanabe, F. [Kyoto University, Japan; Spong, Donald A [ORNL; Shimizu, A. [National Institute for Fusion Science, Toki, Japan; Osakabe, M. [National Institute for Fusion Science, Toki, Japan; Ohdachi, S. [National Institute for Fusion Science, Toki, Japan; Sakakibara, S. [National Institute for Fusion Science, Toki, Japan

2010-01-01

329

Observation of enhancement of stopping power and possible hydrodynamic shock behavior in penetration of large molecules in solids  

SciTech Connect

Measurements of the stopping power of large multiply charged ions were made by determining energy losses in thin aluminum films directly coated on solid-state detectors. With initial projectile velocities in the range of (1--5)[times]10[sup 7] cm/sec, the stopping power per amu of albumin (molecular weight [ital M][similar to]66290) and cytochrome [ital c] ([ital M][similar to]12400) increases quadratically in velocity to a maximum value of seven times that estimated for isolated atomic nitrogen moving with the same velocity. The observed velocity dependence of the stopping power is in qualitative agreement with the one derived from a one-dimensional shock model. Pressures estimated from the measured stopping power using the model are hundreds of megabars. The results show evidence of the collective interaction that results possibly from hydrodynamic'' shock behavior in plasmas formed by the coherent collision of high-velocity biopolymer atoms with target atoms.

Bae, Y.K.; Chu, Y.Y.; Friedman, L. (Department of Chemistry, Brookhaven National Laboratory, Upton, New York 11973 (United States))

1995-03-01

330

The observation of nonlinear ion cyclotron wave excitation during high-harmonic fast wave heating in the large helical device.  

PubMed

A wave detector, a newly designed magnetic probe, is installed in the large helical device (LHD). This wave detector is a 100-turn loop coil with electrostatic shield. Comparing a one-loop coil to this detector, this detector has roughly constant power coupling in the lower frequency range of 40 MHz, and it can easily detect magnetic wave in the frequency of a few megahertz. During high-harmonic fast wave heating, lower frequency waves (<10 MHz) were observed in the LHD for the first time, and for the power density threshold of lower frequency wave excitation (7.5 MHz) the power density of excited pumped wave (38.47 MHz) was approximately -46 dBmHz. These lower frequencies are kept constant for electron density and high energy particle distribution, and these lower frequency waves seem to be ion cyclotron waves caused by nonlinear wave-particle interaction, for example, parametric decay instability. PMID:19044539

Kasahara, H; Seki, T; Kumazawa, R; Saito, K; Mutoh, T; Kubo, S; Shimozuma, T; Igami, H; Yoshimura, Y; Takahashi, H; Yamada, I; Tokuzawa, T; Ohdachi, S; Morita, S; Nomura, G; Shimpo, F; Komori, A; Motojima, O; Oosako, T; Takase, Y; Zhao, Y; Kwak, J

2008-10-01

331

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

332

Spectra of strong scintillation caused by large-scale anisotropic stratospheric irregularities, in spacecraft-based observations  

NASA Astrophysics Data System (ADS)

Numerical methods are used to investigate one- and two-dimentional spectra of strong scintillation caused by atmospheric irregularities associated with the internal gravity waves. Calculations are based on the model of statistically uniform phase screen. The irregularities possess specific features: their spectra are anisotropic and they are much larger than the size of a Fresnel zone in the observation plane. The conditions are specified under which the theory of small perturbations can be applied to calculate weak-scintillation spectra. It is shown that large-scale part of the scintillation spectra can be appropriately described using the theory of perturbations even for strong scintillation, when the rms value of the relative intensity fluctuations ?0 , calculated with the perturbations method, equals 10. At the same time, the perturbations method is not applicable for the description of the small-scale portion of scintillation spectra even at ?0 >0.3. It was found that the product of 1-D spectral density and a wave number has a "plateau" interval. The level of this plateau depends only on the parameter ?0 , provided that this parameter is smaller than one-third of the squared anisotropy coefficient. Within the interval of large wave numbers, the maximum point of the scintillation spectra is formed, with the value of 0.242. The conditions are formulated for small-scale part of the spectrum to become normal; under these conditions, the scintillation spectrum is equal to that of the squared coherence function on the phase screen.

Fedorova, O. V.; Marakasov, D. A.; Vorob'ev, V. V.

2006-11-01

333

Circular Differential Scattering Is an Important Part of the Circular Dichroism of Macromolecules.  

National Technical Information Service (NTIS)

Differential scattering of incident left and right circularly polarized light is an important contribution to the circular dichroism of macromolecules. In principle both differential absorption and differential scattering of circularly polarized light con...

C. Bustamante I. Tinoco M. F. Maestre

1982-01-01

334

Constraints on Lorentz invariance violation from Fermi-Large Area Telescope observations of gamma-ray bursts  

NASA Astrophysics Data System (ADS)

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 where LIV-inducing QG effects become strong, EQG) 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% C.L.) are obtained from GRB 090510 and are EQG,1>7.6 times the Planck energy (EPl) and EQG,2>1.3×1011GeV 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 ˜2. Our results disfavor any class of models requiring EQG,1?EPl.

Vasileiou, V.; Jacholkowska, A.; Piron, F.; Bolmont, J.; Couturier, C.; Granot, J.; Stecker, F. W.; Cohen-Tanugi, J.; Longo, F.

2013-06-01

335

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

336

Texture effects of circularly ordered fibers.  

PubMed

Powder samples can show pronounced texture effects in X-ray scattering. Here, texture effects are described theoretically for circularly ordered fibers and shown experimentally for a special type of these fibers based on nanostructured silica. The systematic diffraction peak intensity dependences, observed with the tilting of the samples, fit well with the theoretical model proposed and can be used as an efficient detection method for circulite-type mesopore organization. Our investigations clearly emphasize the difficulties encountered in the interpretation of peak intensities in the X-ray scattering analyses because of pronounced texture effects. PMID:15945108

Marlow, Frank; Kleitz, Freddy; Wilczok, Ursula; Schmidt, Wolfgang; Leike, Ines

2005-07-11

337

Circular array radar technical and applications  

NASA Astrophysics Data System (ADS)

A new type circular array radar is introduced in this paper. First, the working theory of this radar is introduced, as well as the signal processing method. The characteristics and advancements of this type of radar are detailed analyzed, and the key technology of the circular array radar is proposed. Second, two applications of circular array radar are introduced; they are VHF circular array long-range surveillance radar and L band mini circular array radar. Finally, the potential prospect of this circular array radar is proposed.

Xu, Chengfa; Wang, Chonghui; Hong, Yongbin

2013-03-01

338

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

339

Viscous Flow Past Circular Cylinders.  

National Technical Information Service (NTIS)

Accurate and efficient calculations of the flow around a circular cylinder are presented for Reynolds numbers from 1 to 40 (based on the diameter). The semi-analytical method of series truncation is used to express the stream function and the vorticity in...

F. Nieuwstadt H. B. Keller

1972-01-01

340

Development of the Large-Scale Statistical Analysis System of Satellites Observations Data with Grid Datafarm Architecture  

NASA Astrophysics Data System (ADS)

In the Solar-Terrestrial Physics (STP) field, the amount of satellite observation data has been increasing every year. It is necessary to solve the following three problems to achieve large-scale statistical analyses of plenty of data. (i) More CPU power and larger memory and disk size are required. However, total powers of personal computers are not enough to analyze such amount of data. Super-computers provide a high performance CPU and rich memory area, but they are usually separated from the Internet or connected only for the purpose of programming or data file transfer. (ii) Most of the observation data files are managed at distributed data sites over the Internet. Users have to know where the data files are located. (iii) Since no common data format in the STP field is available now, users have to prepare reading program for each data by themselves. To overcome the problems (i) and (ii), we constructed a parallel and distributed data analysis environment based on the Gfarm reference implementation of the Grid Datafarm architecture. The Gfarm shares both computational resources and perform parallel distributed processings. In addition, the Gfarm provides the Gfarm filesystem which can be as virtual directory tree among nodes. The Gfarm environment is composed of three parts; a metadata server to manage distributed files information, filesystem nodes to provide computational resources and a client to throw a job into metadata server and manages data processing schedulings. In the present study, both data files and data processes are parallelized on the Gfarm with 6 file system nodes: CPU clock frequency of each node is Pentium V 1GHz, 256MB memory and40GB disk. To evaluate performances of the present Gfarm system, we scanned plenty of data files, the size of which is about 300MB for each, in three processing methods: sequential processing in one node, sequential processing by each node and parallel processing by each node. As a result, in comparison between the number of files and the elapsed time, parallel and distributed processing shorten the elapsed time to 1/5 than sequential processing. On the other hand, sequential processing times were shortened in another experiment, whose file size is smaller than 100KB. In this case, the elapsed time to scan one file is within one second. It implies that disk swap took place in case of parallel processing by each node. We note that the operation became unstable when the number of the files exceeded 1000. To overcome the problem (iii), we developed an original data class. This class supports our reading of data files with various data formats since it converts them into an original data format since it defines schemata for every type of data and encapsulates the structure of data files. In addition, since this class provides a function of time re-sampling, users can easily convert multiple data (array) with different time resolution into the same time resolution array. Finally, using the Gfarm, we achieved a high performance environment for large-scale statistical data analyses. It should be noted that the present method is effective only when one data file size is large enough. At present, we are restructuring the new Gfarm environment with 8 nodes: CPU is Athlon 64 x2 Dual Core 2GHz, 2GB memory and 1.2TB disk (using RAID0) for each node. Our original class is to be implemented on the new Gfarm environment. In the present talk, we show the latest results with applying the present system for data analyses with huge number of satellite observation data files.

Yamamoto, K.; Murata, K.; Kimura, E.; Honda, R.

2006-12-01

341

Polarimetry of young stellar objects - II. Circular polarization ofGSS 30  

Microsoft Academic Search

We present results from the first imaging polarimetry measurements of circularly polarized light. These observations, towards the outflow source GSS 30, show degrees of circular polarization in the K_n band of as much as -1.7 per cent, measured in the outflow region, and ~-0.5 per cent towards the source of the outflow, IRS 1. No circular polarization is measured towards

Antonio Chrysostomou; Francois Menard; T. M. Gledhill; Stuart Clark; J. H. Hough; Alan McCall; Motohide Tamura

1997-01-01

342

Experimental investigation of the performance of an annular aperture and a circular aperture on the same very-small-aperture laser facet  

NASA Astrophysics Data System (ADS)

A very-small-aperture laser (VSAL) with a circular aperture has a trade-off between the spot size and the output power. A nanometric annular aperture is fabricated to overcome this difficulty. The advantages of the annular aperture are demonstrated by measuring and comparing its near-field intensity distribution with that of a circular aperture. These apertures are fabricated on the same VSAL to ensure that they are under the same illumination conditions. The experimental results indicate that an annular aperture produces a smaller spot size and a higher peak intensity than a circular aperture. The confinement effect and the enhancement effect are attributed to the convergence of the power flow that passes through the annular aperture. The observed enhancement effect decreases when the distance from the VSAL facet is increased, but it does not vanish even when the distance is as large as 3.5 ?m.

Gai, Hongfeng; Wang, Jia; Tian, Qian; Xia, Wei; Xu, Xiangang

2007-09-01

343

EXPANDED VERY LARGE ARRAY OBSERVATIONS OF GALACTIC SUPERNOVA REMNANTS: WIDE-FIELD CONTINUUM AND SPECTRAL-INDEX IMAGING  

SciTech Connect

The radio continuum emission from the Galaxy has a rich mix of thermal and non-thermal emission. This very richness makes its interpretation challenging since the low radio opacity means that a radio image represents the sum of all emission regions along the line of sight. These challenges make the existing narrowband radio surveys of the Galactic plane difficult to interpret: e.g., a small region of emission might be a supernova remnant (SNR) or an H II region, or a complex combination of both. Instantaneous wide bandwidth radio observations in combination with the capability for high-resolution spectral-index mapping can be directly used to disentangle these effects. Here we demonstrate simultaneous continuum and spectral-index imaging capability at the full continuum sensitivity and resolution using newly developed wide-band wide-field imaging algorithms. Observations were conducted in the L and C bands with a total bandwidth of 1 and 2 GHz, respectively. We present preliminary results in the form of a full-field continuum image covering the wide-band sensitivity pattern of the EVLA centered on a large but poorly studied SNR (G55.7 + 3.4) and relatively narrower field continuum and spectral-index maps of three fields containing SNR and diffused thermal emission. We demonstrate that spatially resolved spectral-index maps differentiate regions with emission of different physical origins (spectral-index variation across composite SNRs and separation of thermal and non-thermal emission), superimposed along the line of sight. The wide-field image centered on the SNR G55.7+3.4 also demonstrates the excellent wide-field wide-band imaging capability of the EVLA.

Bhatnagar, S.; Rau, U.; Rupen, M. P. [National Radio Astronomy Observatory, Socorro, NM 87801 (United States); Green, D. A., E-mail: sbhatnag@nrao.edu, E-mail: rurvashi@nrao.edu, E-mail: mrupen@nrao.edu, E-mail: dag9@cam.ac.uk [Astrophysics Group, Cavendish Laboratory, Cambridge CB3 0HE (United Kingdom)

2011-09-20

344

Circular polarization memory effect in low-coherence enhanced backscattering of light  

Microsoft Academic Search

We experimentally study the propagation of circularly polarized light in the subdiffusion regime by exploit- ing enhanced backscattering ((EBS), also known as coherent backscattering) of light under low spatial co- herence illumination. We demonstrate for the first time, to the best of our knowledge, that a circular polar- ization memory effect exists in EBS over a large range of scatterers'

Young L. Kim; Prabhakar Pradhan; Min H. Kim; Vadim Backman

2006-01-01

345

A Theoretical Study of the Sea and Land Breezes of Circular Islands  

Microsoft Academic Search

The axisymmetric sea and land breezes of circular islands are studied. First we show, from the equation of turbulent energy, that the marked horizontal convergence of the sea breeze intensifies the turbulence in the flow and that this conclusion affects the equations that model the turbulence. Next, the equations of motion are integrated numerically for two circular islands: a `large'

J. Neumann; Y. Mahrer

1974-01-01

346

An air-supported wideband circularly polarized patch antenna  

Microsoft Academic Search

An air-supported circularly polarized square patch antenna with three dimensional (3D) suspended feeding strips is designed. With 3D feeding strips, and the use of air as dielectric, large impedance bandwidth is achieved. A microstrip feeding network is designed to excite the patch antenna in phase quadrature. Radiation pattern measurement results verify the design of the proposed feeding network and the

Basit Ali Zeb; Peter Meincke

2009-01-01

347

ANALYSIS OF CIRCULAR SYMMETRIC COUPLED STRIP AND MICROSTRIP TRANSMISSION LINES  

Microsoft Academic Search

In this paper, a new kind of coupled line called circular symmetric coupled strip or microstrip transmission line is introduced. These kind of coupled lines are less sensitive to external electromagnetic interference and can also be designed for large scale and low crosstalk interconnects. First, an exact expression of capacitance and inductance matrices (both for strip and microstrip structures) is

M. KHALAJ AMIRHOSSEINI; A. CHELDAVI

348

STABILITY ANALYSIS OF A CIRCULARLY TOWED CABLE–BODY SYSTEM  

Microsoft Academic Search

This paper investigates the dynamic response of a circularly towed cable-body system with fluid drag loading. The system model includes non-linear steady state equations and linear vibrational equations about steady state. The steady state equations are linearized using Galerkin's method. Numerical results show the existence of multiple steady state solutions for fluid drag, large end mass, or high rotation speed.

F. Zhu; C. D. Rahn

1998-01-01

349

The inward solidification of spheres and circular cylinders  

Microsoft Academic Search

An analytical study is presented of the inward freezing of a sphere or a circular cylinder, initially molten and at the fusion temperature, when the outside surface is suddenly cooled. The treatment assumes, among other things, constant thermal properties and that the parameter beta, the ratio of the latent heat to the sensible heat of the substance, is large. Basic

D. S. Riley; F. T. Smith; G. Poots

1974-01-01

350

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

351

Observations of Gamma-Ray Bursts at high energies by the Fermi Large Area Telescope--two years review  

NASA Astrophysics Data System (ADS)

The Large Area Telescope (LAT) onboard the Fermi Gamma-ray Space Telescope is a pair-conversion detector of high-energy ? rays of energies ranging from 20 MeV to more than 300 GeV. It operates in synergy with the Gamma-ray Burst Monitor (GBM), which covers the entire unocculted sky and is designed for ?-ray transients' detection and spectroscopy between 8 keV and 40 MeV. Since July 2008, the GBM detected over 500 Gamma-Ray Bursts (GRB), 21 of them had a significant emission in LAT data. The present proceeding is an overview of the features revealed in the GBM/LAT combined analyses of these GRB: additional spectral components, searches for spectral cutoffs at the highest energies, delays between low- and high-energy ?-ray emissions, long-lived emissions at GeV energies. Finally, we will discuss some implications of these observations: emission mechanisms, limits on the jet's bulk Lorentz factor from opacity constraints, limits on Lorentz invariance violation models.

Pelassa, Véronique

2011-08-01

352

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

353

X-ray observations of the Large Magellanic Cloud pulsar PSR B0540-69 and its pulsar wind nebula  

NASA Astrophysics Data System (ADS)

PSR B0540-69 is a young pulsar in the Large Magellanic Cloud that has similar properties with respect to the Crab Pulsar, and is embedded in a pulsar wind nebula (PWN). We have analysed the complete archival Rossi X-Ray Timing Explorer (RXTE) data set of observations of this source, together with new Swift/XRT (X-Ray Telescope) and International Gamma-Ray Astrophysics Laboratory (INTEGRAL)/IBIS (Imager on Board INTEGRAL Satellite) data. Accurate light curves are produced in various energy bands between 2 and 60 keV, showing no significant energy variations of the pulse shape. The spectral analysis shows that the pulsed spectrum is curved, and is best fitted up to 100 keV by a log-parabolic model: this strengthens the similarities with the Crab Pulsar, and is discussed in the light of a phenomenologic multicomponent model. The total emission from this source is studied, the relative contributions of the pulsar and the PWN emission are derived and discussed in the context of other INTEGRAL-detected pulsar/PWN systems.

Campana, R.; Mineo, T.; de Rosa, A.; Massaro, E.; Dean, A. J.; Bassani, L.

2008-09-01

354

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

355

POLARIMETRIC IMAGING OF LARGE CAVITY STRUCTURES IN THE PRE-TRANSITIONAL PROTOPLANETARY DISK AROUND PDS 70: OBSERVATIONS OF THE DISK  

SciTech Connect

We present high-resolution H-band polarized intensity (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 resolved 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 spectral energy distribution 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 of {approx}30 to {approx}50 M{sub J} on the mass of companions within the gap. Taking into account 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. [National Astronomical Observatory of Japan, 2-21-1 Osawa, Mitaka, Tokyo 181-8588 (Japan); Dong, R.; Zhu, Z.; Brandt, T. [Department of Astrophysical Sciences, Princeton University, Princeton, NJ 08544 (United States); Kudo, T.; Egner, S.; Guyon, O.; Hayano, Y. [Subaru Telescope, 650 North A'ohoku Place, Hilo, HI 96720 (United States); Honda, M. [Kanagawa University, 2946 Tsuchiya, Hiratsuka, Kanagawa 259-1293 (Japan); McClure, M. K. [Department of Astronomy, University of Michigan, 500 Church Street, 830 Dennison Building, Ann Arbor, MI 48109 (United States); Muto, T. [Division of Liberal Arts, Kogakuin University, 1-24-2, Nishi-Shinjuku, Shinjuku-ku, Tokyo 163-8677 (Japan); Wisniewski, J. [University of Washington, Seattle, WA 98195 (United States); Abe, L. [Laboratoire Hippolyte Fizeau, UMR6525, Universite de Nice Sophia-Antipolis, 28, avenue Valrose, F-06108 Nice Cedex 02 (France); Brandner, W.; Carson, J.; Feldt, M. [Max Planck Institute for Astronomy, D-69117 Heidelberg (Germany); Fukagawa, M. [Osaka University, 1-1, Machikaneyama, Toyonaka, Osaka 560-0043 (Japan); Goto, M. [Universitaets-Sternwarte Muenchen, Scheinerstr. 1, D-81679 Munich (Germany); Grady, C. A., E-mail: jun.hashimoto@nao.ac.jp [Exoplanets and Stellar Astrophysics Laboratory, Code 667, Goddard Space Flight Center, Greenbelt, MD 20771 (United States); and others

2012-10-10

356

Compact Circularly Polarized Rectenna With Unbalanced Circular Slots  

Microsoft Academic Search

A novel rectifying antenna (rectenna) using a compact circularly polarized (CP) patch antenna with RF-to-DC power conversion part at 2.45 GHz is introduced, in which the unbalanced slots structure is adopted for size reduction and 2nd harmonic rejection. To contribute a rectenna for RF power conversion, the back side of the CP antenna is the doubler rectifier circuit with 3rd

Tzong-Chee Yo; Chien-Ming Lee; Chen-Ming Hsu; Ching-Hsing Luo

2008-01-01

357

SUZAKU OBSERVATION OF A1689: ANISOTROPIC TEMPERATURE AND ENTROPY DISTRIBUTIONS ASSOCIATED WITH THE LARGE-SCALE STRUCTURE  

SciTech Connect

We present results of new, deep Suzaku X-ray observations (160 ks) of the intracluster medium (ICM) in A1689 out to its virial radius, combined with complementary data sets of the projected galaxy distribution obtained from the SDSS catalog and the projected mass distribution from our recent comprehensive weak and strong lensing analysis of Subaru/Suprime-Cam and Hubble Space Telescope/Advanced Camera for Surveys observations. Faint X-ray emission from the ICM around the virial radius (r{sub vir} {approx} 15.'6) is detected at 4.0{sigma} significance, thanks to the low and stable particle background of Suzaku. The Suzaku observations reveal anisotropic gas temperature and entropy distributions in cluster outskirts of r{sub 500} {approx_lt} r {approx_lt} r{sub vir} correlated with large-scale structure of galaxies in a photometric redshift slice around the cluster. The high temperature ({approx}5.4 keV) and entropy region in the northeastern (NE) outskirts is apparently connected to an overdense filamentary structure of galaxies outside the cluster. The gas temperature and entropy profiles in the NE direction are in good agreement, out to the virial radius, with that expected from a recent XMM-Newton statistical study and with an accretion shock heating model of the ICM, respectively. On the contrary, the other outskirt regions in contact with low-density void environments have low gas temperatures ({approx}1.7 keV) and entropies, deviating from hydrostatic equilibrium. These anisotropic ICM features associated with large-scale structure environments suggest that the thermalization of the ICM occurs faster along overdense filamentary structures than along low-density void regions. We find that the ICM density distribution is fairly isotropic, with a three-dimensional density slope of -2.29 {+-} 0.18 in the radial range of r{sub 2500} {approx_lt} r {approx_lt} r{sub 500}, and with -1.24{sup +0.23}{sub -0.56} in r{sub 500} {approx_lt} r {approx_lt} r{sub vir}, which, however, is significantly shallower than the Navarro, Frenk, and White universal matter density profile in the outskirts, {rho} {proportional_to} r {sup -3}. A joint X-ray and lensing analysis shows that the hydrostatic mass is lower than the spherical-lensing one ({approx}60%-90%), but comparable to a triaxial halo mass within errors, at intermediate radii of 0.6r{sub 2500} {approx_lt} r {approx_lt} 0.8r{sub 500}. On the other hand, the hydrostatic mass within 0.4r{sub 2500} is significantly biased as low as {approx_lt}60%, irrespective of mass models. The thermal gas pressure within r{sub 500} is, at most, {approx}50%-60% of the total pressure to balance fully the gravity of the spherical-lensing mass, and {approx}30%-40% around the virial radius. Although these constitute lower limits when one considers the possible halo triaxiality, these small relative contributions of thermal pressure would require additional sources of pressure, such as bulk and/or turbulent motions.

Kawaharada, Madoka [RIKEN - Institute of Physical and Chemical Research, 2-1 Hirosawa, Wako, Saitama 351-0198 (Japan); Okabe, Nobuhiro; Umetsu, Keiichi [Institute of Astronomy and Astrophysics, Academia Sinica, P.O. Box 23-141, Taipei 10617, Taiwan (China); Takizawa, Motokazu [Department of Physics, Yamagata University, Yamagata 990-8560 (Japan); Matsushita, Kyoko [Department of Physics, Tokyo University of Science, 1-3 Kagurazawa, Shinjuku-ku, Tokyo 162-8601 (Japan); Fukazawa, Yasushi [Deparment of Physical Science, Hiroshima University, 1-3-1 Kagamiyama, Higashi-Hiroshima, Hiroshima 739-8526 (Japan); Hamana, Takashi; Miyazaki, Satoshi [National Astronomical Observatory of Japan, Mitaka, Tokyo 181-8588 (Japan); Nakazawa, Kazuhiro [Department of Physics, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033 (Japan); Ohashi, Takaya, E-mail: kawahard@crab.riken.j [Department of Physics, Tokyo Metropolitan University, 1-1 Minami-Osawa, Hachioji, Tokyo 192-0397 (Japan)

2010-05-01

358

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

PubMed

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/cm(2). 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. PMID:12648953

Noble, Marlene A; Xu, J P

359

Dealing with circular correlation effects  

NASA Astrophysics Data System (ADS)

Discrete Fourier transforms (DFTs) are typically used to compute correlations and implementing correlation filters (CFs). Because of the properties of DFTs, resulting correlations are actually circular (also known as periodic) correlations. Using current CF design techniques, it is not possible to design a CF that produces exactly the desired linear correlation output. There are several techniques that may be used to reduce the effects of circular correlation. In this paper, we describe these techniques and provide some experimental results that compare these techniques. This work is sponsored by the Air Force Research Laboratory (AFRL). The views and conclusions contained in this document are those of the authors and should not be interpreted as representing offcial policies, either expressed or implied, of AFRL, or the U.S. Government. The U.S. Government is authorized to reproduce and distribute reprints for Government purposes notwithstanding any copyright notation herein. This document is approved for public released via PA#: 88ABW-2013-1359.

Rodriguez, Andres; Vijaya Kumar, B. V. K.

2013-05-01

360

Two reactions of Haloferax volcanii RNA splicing enzymes: Joining of exons and circularization of introns  

PubMed Central

Archaeal RNA splicing involves at least two protein enzymes, a specific endonuclease and a specific ligase. The endonuclease recognizes and cleaves within a characteristic bulge-helix-bulge (BHB) structure formed by pairing of the regions near the two exon–intron junctions, producing 2‘,3?-cyclic phosphate and 5?-hydroxyl termini. The ligase joins the exons and converts the cyclic phosphate into junction phosphate. The ligated product contains a seven-base hairpin loop, in which the splice junction is in between the two 3? terminal residues of the loop. Archaeal splicing endonucleases are also involved in rRNA processing, cutting within the BHB structures formed by pairing of the 5? and 3? flanking regions of the rRNAs. Large free introns derived from pre-rRNAs have been observed as stable and abundant circular RNAs in certain Crenarchaeota, a kingdom in the domain Archaea. In the present study, we show that the cells of Haloferax volcanii, a Euryarchaeote, contain circular RNAs formed by 3?,5?-phosphodiester linkage between the two termini of the introns derived from their pre-tRNAs. H. volcanii ligase, in vitro, can also circularize both endonuclease-cleaved introns, and non-endonuclease-produced substrates. Exon joining and intron circularization are mechanistically similar ligation reactions that can occur independently. The size of the ligated hairpin loop and position of the splice junction within this loop can be changed in in vitro ligation reactions. Overall, archaeal RNA splicing seems to involve two sets of two symmetric transesterification reactions each.

SALGIA, SHILPA R.; SINGH, SANJAY K.; GURHA, PRIYATANSH; GUPTA, RAMESH

2003-01-01

361

Circular dichroism in magnesium sulfite hexahydrate doped with cobalt  

NASA Astrophysics Data System (ADS)

The new nonlinear crystal of magnesium sulfite hexahydrate (MgSO3.6H2O) belongs to the rare crystallographic class C3 (without a symmetry centre), the other known only representative being sodium periodate (NaIO4). There are some scarce data in the scientific papers about magnesium sulfite hexahydrate's physical properties. Single crystals of significant sizes (up to 40-50 mm) of MgSO3.6H2O as well as such, doped with Ni, Co, and Zn, for the time being are grown only by our own method developed in the Laboratory for Crystal growth at the Faculty of Physics of Sofia University. Recently we have observed the supposed presence of optical activity. Circular dichroism is not observed in pure MgSO3.6H2O. The results of the first ever investigations are presented, which demonstrate the presence of circular dichroism in MgSO3.6H2O doped with Co. The circular dichroism appears in the spectral range from 420 nm to 580 nm. The spectrum of circular dichroism demonstrates a well expressed structure - an isolated maximum at 470 nm and a combination of two overlapped maxima at ~ 495 nm and 520 nm respectively. The spectrum of the circular dichroism is compared with the absorption spectrum of MgSO3.6H2O:Co, along the direction (0001) and with the linear dichroism spectrum measured in direction(1210). It is shown in this way that the circular dichroism appears only in the spectral range of the optical absorption structure due to Co dopant. In the same spectral range can be observed also the linear dichroism determined by Co presence in MgSO3.6H2O.

Bunzarov, Zh.; Iliev, I.; Dimov, T.; Petkova, P.; Kovachev, Tz.; Lyutov, L.; Tzoukrovski, Y.

2009-10-01

362

Anomalous Circular Polarization Profiles in Sunspot Chromospheres  

NASA Astrophysics Data System (ADS)

This paper presents a detailed description, analysis, and interpretation of the spectropolarimetric observations recently reported by Socas-Navarro, Trujillo Bueno, & Ruiz Cobo. These observations consist of time series of Stokes I and V profiles above a sunspot umbra. The spectral lines observed simultaneously are the Ca II chromospheric lines at 8498 and 8542 Å and the photospheric Fe I line at 8497 Å. These spectropolarimetric observations unveil an intriguing time-dependent behavior of the Stokes V profiles in the chromospheric lines. This behavior should be considered as an observational reference for future radiation magnetohydrodynamic simulations of sunspot chromospheres. The analysis of the observed time series shows that a ``normal,'' nearly antisymmetric V profile rapidly evolves toward an ``anomalous,'' completely asymmetric profile, returning later to the normal state. The occurrence of such anomalous circular polarization profiles repeats itself with a periodicity of ~150 s. After giving arguments to discard other scenarios, we are able to interpret the anomalous V profiles as a consequence of the development of a second unresolved atmospheric component. This unresolved component seems to be the same that produces the umbral flashes observed in other sunspots, where it is present with a larger filling factor. Based on observations obtained with the Gregory Coudé Telescope, operated on the island of Tenerife by the Observatory of Göttingen University, in the Spanish Observatorio del Teide of the Instituto de Astrofísica de Canarias.

Socas-Navarro, H.; Trujillo Bueno, J.; Ruiz Cobo, B.

2000-12-01

363

Circular magnetoplasmonic modes in gold nanoparticles.  

PubMed

The quest for efficient ways of modulating localized surface plasmon resonance is one of the frontiers in current research in plasmonics; the use of a magnetic field as a source of modulation is among the most promising candidates for active plasmonics. Here we report the observation of magnetoplasmonic modes on colloidal gold nanoparticles detected by means of magnetic circular dichroism (MCD) spectroscopy and provide a model that is able to rationalize and reproduce the experiment with unprecedented qualitative and quantitative accuracy. We believe that the steep slope observed at the plasmon resonance in the MCD spectrum can be very efficient in detecting changes in the refractive index of the surrounding medium, and we give a simple proof of principle of its possible implementation for magnetoplasmonic refractometric sensing. PMID:24050533

Pineider, Francesco; Campo, Giulio; Bonanni, Valentina; Fernández, César de Julián; Mattei, Giovanni; Caneschi, Andrea; Gatteschi, Dante; Sangregorio, Claudio

2013-09-24

364

Giant polygons and circular graben in western Utopia basin, Mars: Exploring possible formation mechanisms  

NASA Astrophysics Data System (ADS)

Large-scale fracture systems surrounding the Utopia basin include giant polygons and circular graben. Data covering the northern Utopia basin now allow high-resolution mapping of these features in all regions of the basin. Giant polygons to the north and south of the basin are different in both size and morphology, leading to the polygon classifications (1) S-style, (2) subdued S-style, (3) northern S-style and (4) N-style. Also, ten circular graben have been identified to the north of the Utopia basin. These have generally larger diameters than southern circular graben, and their fracture morphology is similar to N-style giant polygons. As with southern circular graben, the surface relief of the depression inside the northern circular graben scales directly with diameter. However, northern circular graben have less steep trend slopes, larger average diameters and greater ring spacing compared to southern circular graben of the same diameter and similar distance to the center of the Utopia basin. Both the giant polygons and circular graben of Utopia Planitia are consistent with formation by volumetric compaction of a fine-grained sedimentary material covering an uneven buried surface. Giant polygon size variations can be explained by the material being wet to the south but frozen or partially frozen to the north, while differences between northern and southern circular graben may be attributed to changes in cover thickness. Differences in fracture morphology can be explained by subsequent alteration of the northern troughs due to polar processes.

Buczkowski, Debra L.; Seelos, Kim D.; Cooke, Michele L.

2012-08-01

365

Circular plumes in Lake Pontchartrain estuary under wind straining  

Microsoft Academic Search

Circular shaped density plumes of low turbidity, low fecal indicator (Escherichia coli and enterococci) concentrations, and high salinity have been observed near the Industrial Canal in Lake Pontchartrain, north of the City of New Orleans. A conceptual model in polar coordinates and a numerical model are developed, together with data analysis, to illustrate the dense plume. It is demonstrated that

Chunyan Li; Nan Walker; Aixin Hou; Ioannis Georgiou; Harry Roberts; Ed Laws; J. Alex McCorquodale; Xiaofeng Li; Jessica Crochet

2008-01-01

366

Circular orbits and relative strains in Schwarzschild space-time  

Microsoft Academic Search

The equation of the relative strain is analyzed in tetrad form with respect to a family of observers moving on spatially circular orbits, in the Schwarzschild space-time. We select a field of tetrads, which we term phase locking frames, and explicitly calculate how, in the equatorial plane, the orbital acceleration, its gradient and the Fermi drag add together to compensate

F. de Felice; S. Usseglio-Tomasset

1992-01-01

367

Some radar observations of meteors and aurorae at 300 and 500 Mc\\/s using a large radio telescope--II Observations of the aurora borealis  

Microsoft Academic Search

Radar echoes from the aurora borealis have been obtained at frequencies of 300 and 500 Mc\\/s using a 250 ft radio telescope. Strong echoes detected during the afternoon hours originated from a layer of ionization at a mean height of 110 km and less than a few kilometres thick. Isolated weak echoes observed at other times originated from localized regions

D. Barber; H. K. Sutcliffe; C. D. Watkins

1962-01-01

368

Rectenna composed of a circular microstrip antenna  

SciTech Connect

One of the big problems in the SPS system is reradiation of the harmonic waves generated by the rectifying diode. The authors proposed the use of a circular microstrip antenna (CMSA), since the CMSA has no higher resonance-harmonic of integer multiple of the dominant resonance frequency. However, characteristics of a large rectenna array of CMSA's have not been clarified. This paper is concerned with the absorption efficiency of the rectenna composed of the CMSA. The efficiency is estimated explicitly using an infinite array model. The results show that the absorption efficiency of the infinite rectenna array composed of the CMSA is 100%. Also, this paper considers the effect of the losses of the composed of the CMSA is 100%. Also, this paper considers the effect of the losses of the CMSA. 4 references, 4 figures.

Itoh, K.; Ohgane, T.; Ogawa, Y.

1986-01-01

369

The VIMOS-VLT Deep Survey First Epoch observations: evolution of galaxies, large scale structures and AGNs over 90% of the current age of the Universe  

Microsoft Academic Search

THE VIMOS VLT DEEP SURVEY (VVDS) IS A MAJOR REDSHIFT SURVEY OF THE DISTANT UNIVERSE, AIMED AT STUDYING THE EVOLUTION OF GALAXIES, LARGE SCALE STRUCTURES AND AGNS OVER MORE THAN 90% OF THE AGE OF THE UNIVERSE. A TOTAL OF 41000 SPECTRA HAVE BEEN OBSERVED SO FAR. FROM THE FIRST EPOCH OBSERVATIONS CONDUCTED WITH VIMOS, WE HAVE ASSEMBLED ~11000 REDSHIFTS

O. Le Fèvre; G. Vettolani; D. Bottini; B. Garilli; V. Le Brun; D. Maccagni; J.-P. Picat; R. Scaramella; M. Scodeggio; L. Tresse; A. Zanichelli; C. Adami; M. Arnaboldi; S. Arnouts; S. Bardelli; M. Bolzonella; A. Cappi; S. Charlot; P. Ciliegi; T. Contini; P. Franzetti; S. Foucaud; I. Gavignaud; L. Guzzo; O. Ilbert; A. Iovino; H.-J. McCracken; B. Marano; C. Marinoni; A. Mazure; B. Meneux; R. Merighi; S. Paltani; R. Pellò; A. Pollo; L. Pozzetti; M. Radovich; G. Zamorani; E. Zucca; M. Bondi; A. Bongiorno; G. Busarello; F. Lamareille; G. Mathez; Y. Mellier; P. Merluzzi; V. Ripepi; D. Rizzo

2005-01-01

370

Effectiveness of TeV ?-ray observations at large zenith angles with a stereoscopic system of imaging atmospheric Cerenkov telescopes  

NASA Astrophysics Data System (ADS)

The sensitivity of imaging atmospheric Cerenkov telescopes (IACTs) in TeV ?-ray observations reaches its maximum at small zenith angles (SZAs) (? ? 30o) which provides the minimum attainable energy threshold of an instrument. However, for a specific telescope site a number of ?-ray sources, or source candidates, can only be observed at much larger zenith angles (LZAs) (? ? 60o). Moreover, the observations at LZAs allow us to extend the observation time window for any object seen at SZAs, as well as to enlarge the dynamic energy range of an instrument towards the highest observable energies of ?-rays. Based on Monte Carlo simulations we present the results on the sensitivity of a stereoscopic system of five IACTs in observations at LZAs. We point out some important parameters of the telescope design which could substantially improve the efficiency of such observations with forthcoming IACT arrays like CANGAROO III, HESS and VERITAS.

Konopelko, A.; Aharonian, F.; Hemberger, M.; Hofmann, W.; Kettler, J.; Pühlhofer, G.; Völk, H. J.

1999-09-01

371

Comparison Between Low Circular and Elliptical Inclined Orbits for Small Satellites Communication Applications.  

National Technical Information Service (NTIS)

Some results of a system study concerning the performance of large constellations of small satellites in low circular and inclined elliptical orbits for real time communications are presented. Performances are evaluated in terms of visibility and mutual c...

G. Perrotta

1991-01-01

372

Local infrasound observations of large ash explosions at Augustine Volcano, Alaska, during January 11-28, 2006  

Microsoft Academic Search

We present and interpret acoustic waveforms associated with a sequence of large explosion events that occurred during the initial stages of the 2006 eruption of Augustine Volcano, Alaska. During January 11-28, 2006, 13 large explosion events created ash-rich plumes that reached up to 14 km a.s.l., and generated atmospheric pressure waves that were recorded on scale by a microphone located

Tanja Petersen; Silvio De Angelis; Guy Tytgat; Stephen R. McNutt

2006-01-01

373

Local infrasound observations of large ash explosions at Augustine Volcano, Alaska, during January 11–28, 2006  

Microsoft Academic Search

We present and interpret acoustic waveforms associated with a sequence of large explosion events that occurred during the initial stages of the 2006 eruption of Augustine Volcano, Alaska. During January 11–28, 2006, 13 large explosion events created ash-rich plumes that reached up to 14 km a.s.l., and generated atmospheric pressure waves that were recorded on scale by a microphone located

Tanja Petersen; Silvio De Angelis; Guy Tytgat; Stephen R. McNutt

2006-01-01

374

Circular on controlling the outflow of labourers, March 1989.  

PubMed

In early March 1989, China's General Office of the State Council issued an urgent Circular demanding that various local governmental bodies "do a good job in strictly controlling the blind outflow of laborers." The circular pointed out that "since the Spring Festival, large numbers of laborers from Sichuan, Henan, Hubei, Shandong, Shaanxi, Jiangsu, Zhejiang, Anhui, and other provinces have concentrated in large numbers in regions such as the northwest, the northwest, and Guangdong Province, causing a huge increase in railroad passenger traffic. There has been a large pile-up of passengers on some main railroad lines and stations, and trains have been seriously overcrowded. This has put tremendous pressure on railroad transport. After arriving in the above mentioned regions, some of these laborers hang around the streets because they cannot find work, and their life is extremely difficult. The large influx of laborers into these regions has caused confusion in local social order." In order to resolve this problem satisfactorily, the circular makes the following demands: "The people's government at all levels must rapidly get under control the blind outflow of laborers and their assembly in large numbers for moving elsewhere. It is necessary to organize forces to admonish and stop those laborers who have already assembled at the railroad stations, so that they will not blindly move elsewhere. They should also be mobilized to return to their home towns." PMID:12344256

1989-01-01

375

Combining Linear and Circular Polarization in Remote Sensing of Cosmic Dust and Planetary Aerosols  

NASA Astrophysics Data System (ADS)

Scattering of light by any type of cosmic dust and planetary aerosols always produces some linear polarization. Its degree and polarization plane are sensitive to the characteristics of the scattering particles, specifically their size, shape and composition. Circular polarization arises from more special conditions, namely, when the scatterers or the scattering medium are characterized by a lack of mirror symmetry. Most common sources of circular polarization are multiple scattering in asymmetric media (e.g. nonspherical nebulae), alignment of elongated dust particles, or their optical activity (circular birefringence and dichroism). The last case is of special interest as optical activity is typical for life-related molecules due to their homochirality, and, thus, circular polarization can indicate presence of biological or pre-biological organics. There are numerous observations of circular polarization, e.g. in molecular clouds and comets, and in the future we may expect to see it when studying the atmospheres of extrasolar planets. In all cases it is important to determine the cause of the circular polarization, specifically to prove or disprove its biological origin. We explore how this can be done by combining linear and circular polarization. Correlations between linear and circular polarization are discussed for cosmic dust and planetary aerosols. The discussion is based on spectral and angular dependence of linear and circular polarizations obtained using computer modeling of light scattering by complex, including optically active, particles and with laboratory measurements of light scattering by biological objects.

Kolokolova, L.; Nagdimunov, L.; Sparks, W.

2012-04-01

376

Cascade mechanism of formation of doubly charged ions upon multiphoton ionization of barium atoms by linearly and circularly polarized radiation (? = 16800–18700 cm ?1 )  

Microsoft Academic Search

The process of formation of doubly charged ions upon multiphoton ionization of barium atoms by linearly and circularly polarized\\u000a radiation of dye lasers is studied in the frequency range from 16800 to 18700 cm?1. A large number of resonance maxima in the yield of Ba+ and Ba2+ ions were observed upon tuning the radiation frequency. It is unambiguously proved that

V. V. Suran; I. I. Bondar

2005-01-01

377

Longitudinal motion in circular accelerators  

SciTech Connect

A general description is given of the longitudinal motion of an idealized synchronous particle, exactly in step with the radiofrequency field of a circular accelerator, and a domain in phase and energy, called a bucket, around this particle within which particles are focused around the synchronous particle. This general picture is then made more precise and quantitative. The equations of longitudinal motion and their solutions and the resulting motion are discussed, followed by applications and amplication of the theory. 7 refs., 8 figs. (LEW)

Cole, F.T.

1985-01-01

378

Circular strings, wormholes, and minimum size  

SciTech Connect

The quantization of circular strings in an anti{endash}de Sitter background spacetime is performed, obtaining a discrete spectrum for the string mass. A comparison with a four-dimensional homogeneous and isotropic spacetime coupled to a conformal scalar field shows that the string radius and the scale factor have the same classical solutions and that the quantum theories of these two models are formally equivalent. However, the physically relevant observables of these two systems have different spectra, although they are related to each other by a specific one-to-one transformation. We finally obtain a discrete spectrum for the spacetime size of both systems, which presents a nonvanishing lower bound. {copyright} {ital 1997} {ital The American Physical Society}

Garay, L.J.; Gonzalez-Diaz, P.F.; Mena Marugan, G.A.; Raya, J.M. [Centro de Fisica Miguel A. Catalan, Instituto de Matematicas y Fisica Fundamental, CSIC Serrano 121, 28006 Madrid (Spain)

1997-06-01

379

NEAR-ULTRAVIOLET PROPERTIES OF A LARGE SAMPLE OF TYPE Ia SUPERNOVAE AS OBSERVED WITH THE Swift UVOT  

SciTech Connect

We present ultraviolet (UV) and optical photometry of 26 Type Ia supernovae (SNe Ia) observed from 2005 March to 2008 March with the NASA Swift Ultraviolet and Optical Telescope (UVOT). The dataset consists of 2133 individual observations, making it by far the most complete study of the UV emission from SNe Ia to date. Grouping the SNe into three subclasses as derived from optical observations, we investigate the evolution of the colors of these SNe, finding a high degree of homogeneity within the normal subclass, but dramatic differences between that group and the subluminous and SN 2002cx-like groups. For the normal events, the redder UV filters on UVOT (u, uvw1) show more homogeneity than do the bluer UV filters (uvm2, uvw2). Searching for purely UV characteristics to determine existing optically based groupings, we find the peak width to be a poor discriminant, but we do see a variation in the time delay between peak emission and the late, flat phase of the light curves. The UV light curves peak a few days before the B band for most subclasses (as was previously reported by Jha et al.), although the SN 2002cx-like objects peak at a very early epoch in the UV. That group also features the bluest emission observed among SNe Ia. As the observational campaign is ongoing, we discuss the critical times to observe, as determined by this study, in order to maximize the scientific output of future observations.

Milne, Peter A. [Steward Observatory, University of Arizona, 933 North Cherry Avenue, Tucson, AZ 85719 (United States); Brown, Peter J.; Roming, Peter W. A.; Vanden Berk, Daniel [Department of Astronomy and Astrophysics, Pennsylvania State University, University Park, PA 16802 (United States); Holland, Stephen T.; Immler, Stefan; Bufano, Filomena; Gehrels, Neil [NASA-Goddard Space Flight Center, Astrophysics Science Division, Codes 660.1 and 662, Greenbelt, MD 20771 (United States); Filippenko, Alexei V.; Ganeshalingam, Mohan; Li Weidong [Department of Astronomy, University of California, Berkeley, CA 94720-3411 (United States); Stritzinger, Maximilian; Phillips, Mark M. [Las Campanas Observatory, Carnegie Observatories, Casilla 601, La Serena (Chile); Hicken, Malcolm; Kirshner, Robert P.; Challis, Peter J. [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Mazzali, Paolo [INAF, Observatorio Astronomico di Padova, Vicolo dell'Osservatorio 5, I-35122 Padova (Italy); Schmidt, Brian P. [Mount Stromlo Observatory, The Research School of Astronomy and Astrophysics, Australian National University, Weston Creek, ACT 2611 (Australia)

2010-10-01

380

Large Rotary Vacuum Seal  

Microsoft Academic Search

A seal is described which permits rotation of large circular sections or ; ports in the walls of a vacuum chamber. The seal is an unlubricated Tec-Ring (a ; Teflon O-ring with a core of rubber), and the friction is low even at large ; diameters. The behavior of such a seal is compared with that of a lubricated ;

D. E. Armstrong; Normand Blais

1963-01-01

381

A Dynamic Measure of Controllability and Observability for the Placement of Actuators and Sensors on Large Space Structures.  

National Technical Information Service (NTIS)

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 st...

W. E. Vandervelde C. R. Carignan

1982-01-01

382

THE INFRARED SPECTRA OF VERY LARGE IRREGULAR POLYCYCLIC AROMATIC HYDROCARBONS (PAHs): OBSERVATIONAL PROBES OF ASTRONOMICAL PAH GEOMETRY, SIZE, AND CHARGE  

SciTech Connect

The mid-infrared (IR) spectra of six large, irregular polycyclic aromatic hydrocarbons (PAHs) with formulae (C{sub 84}H{sub 24}-C{sub 120}H{sub 36}) have been computed using density functional theory (DFT). Trends in the dominant band positions and intensities are compared to those of large, compact PAHs as a function of geometry, size, and charge. Irregular edge moieties that are common in terrestrial PAHs, such as bay regions and rings with quartet hydrogens, are shown to be uncommon in astronomical PAHs. As for all PAHs comprised solely of C and H reported to date, mid-IR emission from irregular PAHs fails to produce a strong CC{sub str} band at 6.2 {mu}m, the position characteristic of the important, class A astronomical PAH spectra. Earlier studies showed that inclusion of nitrogen within a PAH shifts this to 6.2 {mu}m for PAH cations. Here we show that this band shifts to 6.3 {mu}m in nitrogenated PAH anions, close to the position of the CC stretch in class B astronomical PAH spectra. Thus, nitrogenated PAHs may be important in all sources and the peak position of the CC stretch near 6.2 {mu}m appears to directly reflect the PAH cation to anion ratio. Large irregular PAHs exhibit features at 7.8 {mu}m but lack them near 8.6 {mu}m. Hence, the 7.7 {mu}m astronomical feature is produced by a mixture of small and large PAHs while the 8.6 {mu}m band can only be produced by large compact PAHs. As with the CC{sub str}, the position and profile of these bands reflect the PAH cation to anion ratio.

Bauschlicher, Charles W. [NASA-Ames Research Center, Space Technology Division, Mail Stop 230-3, Moffet Field, CA 94035 (United States); Peeters, Els [Department of Physics and Astronomy, University of Western Ontario, London, ON N6A 3K7 (Canada); Allamandola, Louis J. [NASA-Ames Research Center, Space Science Division, Mail Stop 245-6, Moffet Field, CA 94035 (United States)], E-mail: Charles.W.Bauschlicher@nasa.gov, E-mail: epeeters@uwo.ca, E-mail: Louis.J.Allamandola@nasa.gov

2009-05-20

383

Hubble Space Telescope Observations of the Windblown Nebula NGC 7635  

Microsoft Academic Search

We present Hubble Space Telescope observations of the northern part of NGC 7635, a circular shell around the O6.5 IIIf star BD +60°2522. The nebula, which lies within the large emission-line region S162, is notable not only for its symmetric shell, but also for a complex of ``cometary'' knots close to the central star. Our observations include spectra taken with

Brian D. Moore; Donald K. Walter; J. Jeff Hester; Paul A. Scowen; Reginald J. Dufour; Brent A. Buckalew

2002-01-01

384

Molecular alignment using circularly polarized laser pulses  

NASA Astrophysics Data System (ADS)

We show that circularly polarized femtosecond laser pulses produce field-free alignment in linear and planar molecules. We study the rotational wavepacket evolution of O2 and benzene created by circularly polarized light. For benzene, we align the molecular plane to the plane of polarization. For O2, we demonstrate that circular polarization yields a net alignment along the laser propagation axis at certain phases of the evolution. Circular polarization gives us the ability to control alignment of linear molecules outside the plane of polarization, providing new capabilities for molecular imaging.

Smeenk, C. T. L.; Corkum, P. B.

2013-10-01

385

Spatial and Temporal Variation of the Fish Assemblage on a Large Artificial Reef Assessed Using MultiplePoint Stationary Observations  

Microsoft Academic Search

\\u000a Over the past decade, the sizes of artificial reefs in Japan have increased, with heights reaching 30 m or more. However,\\u000a there are few studies about the efficiency of the high-rise artificial reefs, and it is not clear how effectively these reefs\\u000a gather and nurse fish resources. In these large artificial reefs, it is difficult for divers to view entire

Hideyuki Takahashi; Akihiko Matsuda; Tomonari Akamatsu; Norimasa Takagi

386

Decadal Variability in the Large-Scale Sea Surface Height Field of the South Pacific Ocean: Observations and Causes  

Microsoft Academic Search

Large-scale sea surface height (SSH) changes in the extraequatorial South Pacific Ocean are investigated using satellite altimetry data of the past 12 yr. The decadal SSH signals in the 1990s were dominated by an increasing trend in the 30°-50°S band and a decreasing trend in the central South Pacific Ocean poleward of 50°S. In recent years since 2002 there has

Bo Qiu; Shuiming Chen

2006-01-01

387

Observation of artificial spread-F and large region ionization enhancement in an HF heating experiment at HAARP  

Microsoft Academic Search

A large-scale ionospheric modification by HF heaters was explored via HAARP digisonde operated in a fast mode. The results show that the ionogram virtual heights and the height spread of the ordinary-wave sounding echoes were changed significantly by the O-mode heater; the X-mode heater imposed no noticeable effect on the ionograms. The enhanced virtual height spread exceeds 40 km, more

Spencer Kuo; Arnold Snyder

2010-01-01

388

Observations of large scale F-region irregularities using airglow emissions at 7774 A and 6300 A  

Microsoft Academic Search

The dynamics of low-latitude large scale F-region irregularities were investigated based on simultaneous scanning measurements of the atomic oxygen 7774 A and 6300 A emissions carried out at Cachoeira Paulista (geographic coordinates 22.7 deg S, 45.0 deg W; geomagnetic latitude 11.95 deg S), Brazil, during the period October-November, 1980. A two-channel photometer was used for the measurements, which allowed scanning

Y. Sahai; J. A. Bittencourt; N. R. Teixeira; H. Takahashi

1983-01-01

389

A mass-flux cumulus parameterization scheme for large-scale models: description and test with observations  

Microsoft Academic Search

A simple mass-flux cumulus parameterization scheme suitable for large-scale atmospheric models is presented. The scheme is\\u000a based on a bulk-cloud approach and has the following properties: (1) Deep convection is launched at the level of maximum moist\\u000a static energy above the top of the boundary layer. It is triggered if there is positive convective available potential energy\\u000a (CAPE) and relative

Tongwen Wu

2011-01-01

390

Observations of wild hunting behaviour and bioluminescence of a large deep-sea, eight-armed squid, Taningia danae.  

PubMed

Our newly developed underwater high definition video camera system took the first live images of adults of the mesopelagic large squid, Taningia danae, between 240 and 940 m deep off Ogasawara Islands, western North Pacific. The resulting footage includes attacking and bioluminescence behaviours, and reveals that T. danae is far from the sluggish neutrally buoyant deep-sea squid previously suspected. It can actively swim both forward and backward freely by flapping its large muscular triangular fins and changes direction quickly through bending its flexible body. It can attain speeds of 2-2.5 ms(-1) (7.2-9 km h(-1)) when attacking bait rigs. They emitted short bright light flashes from their large arm-tip photophores before final assault, which might act as a blinding flash for prey as well as a means of measuring target distance in a dark deep-sea environment. They also emitted long and short glows separated by intervals while wandering around the double torch lights attached to the bait rig, suggestive of potential courtship behaviours during mating. PMID:17301020

Kubodera, Tsunemi; Koyama, Yasuhiro; Mori, Kyoichi

2007-04-22

391

Observations of wild hunting behaviour and bioluminescence of a large deep-sea, eight-armed squid, Taningia danae  

PubMed Central

Our newly developed underwater high definition video camera system took the first live images of adults of the mesopelagic large squid, Taningia danae, between 240 and 940?m deep off Ogasawara Islands, western North Pacific. The resulting footage includes attacking and bioluminescence behaviours, and reveals that T. danae is far from the sluggish neutrally buoyant deep-sea squid previously suspected. It can actively swim both forward and backward freely by flapping its large muscular triangular fins and changes direction quickly through bending its flexible body. It can attain speeds of 2–2.5?m?s?1 (7.2–9?km?h?1) when attacking bait rigs. They emitted short bright light flashes from their large arm-tip photophores before final assault, which might act as a blinding flash for prey as well as a means of measuring target distance in a dark deep-sea environment. They also emitted long and short glows separated by intervals while wandering around the double torch lights attached to the bait rig, suggestive of potential courtship behaviours during mating.

Kubodera, Tsunemi; Koyama, Yasuhiro; Mori, Kyoichi

2007-01-01

392

A large hydrothermal reservoir beneath Taal Volcano (Philippines) revealed by magnetotelluric observations and its implications to the volcanic activity.  

PubMed

Taal Volcano is one of the most active volcanoes in the Philippines. The magnetotelluric 3D forward analyses indicate the existence of a large high resistivity anomaly (?100 ?·m) with a volume of at least 3 km × 3 km × 3 km, which is capped by a conductive layer (?10 ?·m), beneath the Main Crater. This high resistivity anomaly is hypothesized to be a large hydrothermal reservoir, consisting of the aggregate of interconnected cracks in rigid and dense host rocks, which are filled with hydrothermal fluids coming from a magma batch below the reservoir. The hydrothermal fluids are considered partly in gas phase and liquid phase. The presence of such a large hydrothermal reservoir and the stagnant magma below may have influences on the volcano's activity. Two possibilities are presented. First, the 30 January 1911 explosion event was a magmatic hydrothermal eruption rather than a base-surge associated with a phreato-magmatic eruption. Second, the earlier proposed four eruption series may be better interpreted by two cycles, each consisting of series of summit and flank eruptions.(Communicated by Seiya Uyeda, M.J.A.). PMID:24126286

Alanis, Paul K B; Yamaya, Yusuke; Takeuchi, Akihiro; Sasai, Yoichi; Okada, Yoshihiro; Nagao, Toshiyasu

2013-01-01

393

Instrument Design of the Large Aperture Solar UV Visible and IR Observing Telescope (SUVIT) for the SOLAR-C Mission  

NASA Astrophysics Data System (ADS)

We present an instrumental design of one major solar observation payload planned for the SOLAR-C mission: the Solar Ultra-violet Visible and near IR observing Telescope (SUVIT). The SUVIT is designed to provide high-angular-resolution investigation of the lower solar atmosphere, from the photosphere to the uppermost chromosphere, with enhanced spectroscopic and spectro-polarimetric capability in wide wavelength regions from 280 nm (Mg II h&k lines) to 1100 nm (He I 1083 nm line) with 1.5 m class aperture and filtergraphic and spectrographic instruments.

Suematsu, Y.; Katsukawa, Y.; Shimizu, T.; Ichimoto, K.; Takeyama, N.

2012-12-01

394

Accuracy of Biopsy Gleason Scores from a Large Uropathology Laboratory: Use of a Diagnostic Protocol to Minimize Observer Variability  

Microsoft Academic Search

Objectives. To examine the correlation of biopsy Gleason scores with radical prostatectomy specimens from a laboratory that uses protocols designed to minimize observer variability. This protocol mandates consensus case review of all nonbenign cases.Methods. Between August 24, 1993 and June 26, 1997, 106 patients who underwent radical prostatectomy at Johns Hopkins Hospital, Baltimore, Maryland had their prostate cancer diagnosed and

Grant D Carlson; Christina B Calvanese; Hillel Kahane; Jonathan I Epstein

1998-01-01

395

Spectra of strong scintillation caused by large-scale anisotropic stratospheric irregularities, in spacecraft-based observations  

Microsoft Academic Search

Numerical methods are used to investigate one- and two-dimentional spectra of strong scintillation caused by atmospheric irregularities associated with the internal gravity waves. Calculations are based on the model of statistically uniform phase screen. The irregularities possess specific features: their spectra are anisotropic and they are much larger than the size of a Fresnel zone in the observation plane. The

O. V. Fedorova; D. A. Marakasov; V. V. Vorob'ev

2006-01-01