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1

Large natural circular dichroism in photoionization  

NASA Astrophysics Data System (ADS)

Circular dichroism in the photoionization of nanometer-sized aerosol particles from the chiral amino acid tyrosine is investigated. The Kuhn anisotropy factor in photoionization reaches values of 10%. This value is twenty times larger than previous results. We show that it strongly depends on properties of the particles. The largest anisotropies are obtained for highly ordered particles. The enhancement can be explained by an exiton-coupling mechanism between neighbouring molecules geometrically fixed in the crystal lattice. Implications of this large effect in the context of the origin of biological homochirality and for the construction of a bioaerosol sensor are discussed.

Paul, Johannes; Siegmann, Konstantin

1999-04-01

2

Impedance of a large circular loop antenna in a magnetoplasma  

SciTech Connect

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

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

1986-08-01

3

Impedance of a large circular loop antenna in a magnetoplasma  

Microsoft Academic Search

The input impedance of a large circular loop antenna with arbitrary orientation in a cold magnetoplasma is calculated by using a transmission line theory. New impedance resonances for antennas of finite size in a magnetoplasma in the frequency region below and near the electron cyclotron frequency are indicated theoretically. The resonance peak of the impedance at the lower hybrid resonance

S. Ohnuki; K. Sawaya; S. Adachi

1986-01-01

4

Input susceptance of an arbitrarily large, circular loop antenna  

Microsoft Academic Search

This paper is presenting a very efficient technique for the computation of the input susceptance of an arbitrarily large, circular loop antenna. The Moment Method, in conjunction with point matching, is applied to Pockligton¿s integral equation, and the resulting matrix is inverted analytically, due to its circulant property. A magnetic frill excitation, in lieu of the commonly used delta gap

Hristos T. Anastassiu

2006-01-01

5

Large-amplitude circularly polarized electromagnetic waves in magnetized plasma  

SciTech Connect

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

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

2014-05-15

6

Large quasi-circular features beneath frost on Triton  

NASA Technical Reports Server (NTRS)

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

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

1992-01-01

7

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

SciTech Connect

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

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

2013-08-01

8

Large-eddy simulation of flow past a circular cylinder  

NASA Technical Reports Server (NTRS)

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

Mittal, R.

1995-01-01

9

Fast, simple and accurate computation of the currents on an arbitrarily large circular loop antenna  

Microsoft Academic Search

This paper is presenting a very efficient method for computing the currents on a circular loop antenna with arbitrarily large size. Pocklington's integral equation is formulated for the circular loop geometry, and the method of moments with point matching is applied to cast the equation's discrete counterpart. The basis functions are chosen in such a way that the relevant square

Hristos T. Anastassiu

2006-01-01

10

PHYSICAL REVIEW B 85, 205407 (2012) Circular polarization dependent cyclotron resonance in large-area graphene  

E-print Network

.67 m, we studied cyclotron resonance in large-area graphene grown by chemical vapor depositionPHYSICAL REVIEW B 85, 205407 (2012) Circular polarization dependent cyclotron resonance in large-area-field studies therefore allow for a clear identification of cyclotron resonance features in large-area, low

Kono, Junichiro

11

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

ERIC Educational Resources Information Center

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

Mendle, Gillian, Comp.

12

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

E-print Network

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

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

2007-03-09

13

Evaluation of displacement demands on large circular universal expansion joints  

SciTech Connect

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

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

1996-12-01

14

Evidence of 3-D Reconnection at Null Point from the Observations of Circular Flares and Homologous Jets  

NASA Astrophysics Data System (ADS)

In recent studies by Pariat, Antiochos and DeVore (2009, 2010), fan-separatrix topology and magnetic reconnection at the null-point were simulated and found to produce homologous jets. This motivates us to search for axisymmetric magnetic structure and associated flaring/jetting activity. Using high-resolution ( 0.15" per pixel) and high-cadence ( 15 s) H-alpha center/offband observations obtained from the recently digitized films of Big Bear Solar Observatory, we were able to identify five large circular flares with associated surges. All the events exhibit a central parasite magnetic field surrounded by opposite polarity, forming a circular polarity inversion line (PIL). Consequently, a compact flare kernel at the center is surrounded by a circular ribbon, and together with the upward ejecting dark surge, these seem to depict a dome-like magnetic structure. Very interestingly, (1) the circular ribbon brightens sequentially rather than simultaneously, (2) the central compact flare kernel shows obvious motion, and (3) a remote elongated, co-temporal flare ribbon at a region with the same polarity as the central parasite site is seen in the series of four homologous events on 1991 March 17 and 18. The remote ribbon is 120" away from the jet location. Moreover, magnetic reconnection across the circular PIL is evident from the magnetic flux cancellation. These rarely observed homologous surges with circular as well as central and remote flare ribbons provide valuable evidence concerning the dynamics of magnetic reconnection in a null-point topology. This study is dedicated to Professor Hal Zirin, the founder of Big Bear Solar Observatory, who passed away on January 3, 2012.

Wang, Haimin; Liu, C.

2012-05-01

15

Far field of large circular loop antennas: Theoretical and experimental results  

Microsoft Academic Search

Far field patterns of large circular loop antennas of circumferences up to two and one-half wavelengths were calculated using Storer's theory for the current distribution on the antenna. To verify the theory, radiation pattern measurements were made at 3 GHz; the experimental results are in good qualitative agreement with theory.

B. Rao

1968-01-01

16

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

NASA Technical Reports Server (NTRS)

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

Rohrkaste, G. R.

1990-01-01

17

Pseudo-linearization procedure of nonlinear ordinary differential equations for large deflection problem of circular plates  

Microsoft Academic Search

The large deflection problem of the circular plate is considered in this paper. Generally, there are some nonlinear terms in the ordinary differential equation resulted. For example, one term takes the form (dw\\/dr)2, where w(r) is the deflection function and r is the radial coordinate. Different from the previously suggested procedures, an alternative procedure is suggested in this paper. In

Y. Z. Chen; K. Y. Lee

2003-01-01

18

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

NASA Technical Reports Server (NTRS)

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

Nedoluha, Gerald E.; Watson, William D.

1994-01-01

19

Experimental study of noise emitted by circular cylinders with large roughness  

NASA Astrophysics Data System (ADS)

The aerodynamic noise generated by high Reynolds number flow around a bluff body with large surface roughness was investigated. This is a relevant problem in many applications, in particular aircraft landing gear noise. A circular cylinder in cross-flow and a zero-pressure-gradient turbulent boundary layer with various types of roughness was tested in a series of wind tunnel experiments. It has been shown that distributed roughness covering a circular cylinder affects the spectra over the entire frequency range. Roughness noise is dominant at high frequencies, and the peak frequency is well described by Howe's roughness noise model when scaled with the maximum outer velocity. There are differences between hemispherical and cylindrical roughness elements for both the circular cylinder and the zero-pressure-gradient turbulent boundary layer cases, indicating a dependence on roughness shape, not described by the considered roughness noise models. Cylindrical roughness generates higher noise levels at the highest frequencies, especially for the zero-pressure-gradient turbulent boundary layer case. Cable-type roughness aligned with the mean flow does not generate roughness noise, and its spectrum has been found to collapse with the smooth cylinder at medium and high frequencies. At low and medium frequencies the noise spectra have the same features as the smooth cylinder, but with higher shedding peak levels and fall-off levels, despite the decrease in spanwise correlation length. Roughness induces early separation, and thus a shift of the spectra to lower frequencies.

Alomar, Antoni; Angland, David; Zhang, Xin; Molin, Nicolas

2014-12-01

20

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

NASA Astrophysics Data System (ADS)

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

Aydin, Tayfun Besim

21

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

SciTech Connect

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

Faccioli, L; Alcock, C; Cook, K

2007-11-20

22

An experimental approach to measure particle deposition in large circular ventilation ducts.  

PubMed

The topic of this study is related to airborne particle dynamics in indoor environments. Lab-scale experiments have been performed to investigate particle deposition velocity to six different surfaces orientations (with respect to gravity) for fully developed turbulent flow in horizontal large circular ventilation ducts. Monodispersed aerosol particles (1-6 ?m) were used in the deposition experiments. A very low particle mass (40 ng) was measured reliably above background level on duct surfaces by a means of a nondestructive stencil technique associated with fluorescence analysis. For 2-6 ?m particles (diffusion and impaction regime), deposition rates to floors were much greater than rates to the ceiling and greater than rates to the wall. For 1-?m particles, the effect of surface orientation to particle deposition was not significant. Results were compared to the very few similar and published studies. This work was conducted in the frame of the CleanAirNet project which aimed at producing new knowledge, models, and techniques to help controlling the safety food stuffs, through a better control of aerosol particle (bioaerosols) transport and deposition in the ventilation networks of the food industry. PMID:24756675

Da, Guillaume; Géhin, Evelyne; Ben-Othmane, Mourad; Havet, Michel; Solliec, Camille; Motzkus, Charles

2015-04-01

23

Nonlinear characteristics of a circular plate piezoelectric harvester with relatively large deflection near resonance.  

PubMed

Based on the von Karman thin circular plate theory, we report in this paper the analysis of the nonlinear behavior of a power harvester consisting of a circular piezoelectric plate and an electric resistance. Dependence of the output power of the harvester upon driving frequency for different electric loads and different applied forces is obtained. Numerical results show that the output power exhibits multi-valuedness and a jump phenomenon near resonance. PMID:18986906

Xue, Huan; Hu, Hongping

2008-09-01

24

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...

25

Global ICRF modeling in large non-circular tokamak plasmas with finite temperature  

SciTech Connect

Full wave ICRF coupling calculations in two- and three dimensions have been extended to treat tokamaks with non-circular flux surfaces and conducting boundaries. The magnetic field configuration is derived from a Solovev equilibriium with finite poloidal magnetic fields. The conducting boundary may be of arbitrary shape. The mode conversion model is that of Colestock et al., in which the fourth order finite temperature wave equation is reduced to a second order equation which describes the effects of mode conversion on the fast wave but neglects the detailed structure of the ion Bernstein wave. Results show the effect of non-circular cross section on excitation, wave propagation, and absorption in Doublet III-D and JET. Also, in the limit of circular cross section, toroidal phasing of the resonant double loop antenna design for TFTR is studied.

Jaeger, E.F.; Batchelor, D.B.; Weitzner, H.; Colestock, P.L.

1987-01-01

26

Life Cycle of a Mesoscale Circular Gust Front Observed by a C-Band Doppler Radar in West Africa  

E-print Network

Life Cycle of a Mesoscale Circular Gust Front Observed by a C-Band Doppler Radar in West Africa that occur in West Africa during the boreal summer are often associated with Afri- can easterly waves (AEWs the land surface of West Africa, with substantial surface heating leading to deep boundary layers

Guichard, Francoise

27

Observations of large transient magnetospheric electric fields  

NASA Technical Reports Server (NTRS)

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

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

1977-01-01

28

Direct observation of depth profile of magnetic moment by magnetic circular dichroism  

NASA Astrophysics Data System (ADS)

The magnetic properties at the interface between Fe and Cr wedge layers are investigated with a new depth-resolved soft x-ray photoemission spectroscopy (SXPS)[1], combined with magnetic circular dichroism (MCD). The layers of Fe (10 A)/ Cr (50 A wedge- shaped) are grown on a periodic multilayer (B 4 C(22.5A)/W(17.1 A)) _40, which provides the strong standing wave effects of 40 The unique angular dependence of photoelectron intensity of Fe and Cr has been observed at each different Cr wedge thickness and show excellent agreement with the theoretical calculation. To maximize the enhancement and contrast of standing wave effect inside of sample, the sample position is tuned to the Bragg angle position, at which the MCD measurement with SXPS along the different thickness of Cr wedge layer provides the depth profile of the magnetic moment of Fe and Cr. A strong antiparallel coupling across the interface of Cr magnetic moment is clearly resolved while the apparent reduction of Fe magnetic moment is observed near the interface. This observation is consistent with the other works on the same system [2] and even describes how the magnetic moment behaves inside of the sample from the top surface to the interface in one single sample preparation. In this experiment, a new depth-resolved SXPS has been successfully implemented to magnetic multilayer system and prove to be powerful technique to study the buried interface of magnetic system, as proposed by our former work [1]. [1] S.-H. Yang, B. S. Mun, A.W. Kay, S.-K. Kim, J. B. Kortright , J.H. Underwood, Z. Hussain, C. S. Fadley, Surf. Sci. 461 L557-L564 (2000) [2] G. Panaccione, F. Sirotti, E. Narducci, and G. Rossi, Phys. Rev. B 55, 389 (1997)

Mun, Bongjin Simon; Yang, See-Hun; Mannella, Norman; Kay, Alex W.; Kim, Sang-Koog; Kortright, Jeffrey B.; Underwood, Jim H.; Hussain, Zahid; Fadley, Charles S.

2001-03-01

29

Method of moments analysis of electrically large circular-loop antennas: non-uniform currents  

Microsoft Academic Search

In this paper, a method of moments analysis is carried out so as to obtain in closed form the non-uniform current distributions, and their resulted radiation patterns in both the near and far zones, of circular loop antennas with electrically larger circumferences. An oblique incident field in its general form is considered in the formulation of the non-uniform current distributions.

Le-Wei Li; Chan-Ping Lim; Mook-Seng Leong

1999-01-01

30

Nonlinear Torsional Vibration of a Circular Cylindrical Piezoelectric Rod with Relatively Large Shear Deformation  

Microsoft Academic Search

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

Yang Jiashi

2007-01-01

31

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

PubMed

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

Yang, Jiashi

2007-07-01

32

Large-scale structures in the wake of a circular cylinder  

Microsoft Academic Search

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

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

1986-01-01

33

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

Microsoft Academic Search

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

Günter Schewe

1985-01-01

34

Experimental observations on the relationship between stagnation region flow oscillations and eddy shedding for circular cylinder  

NASA Technical Reports Server (NTRS)

Measurements indicate a direct coupling between the dominant frequencies of flow oscillations at the leading-edge stagnation region, laminar-separation unsteadiness, and the vortex shedding. An array of surface mounted, micro-thin hot-films were used to simultaneously determine the state of the boundary layer along the surfaced of a circular cylinder, and vortex shedding was monitored by a hot wire placed in its wake.

Mangalam, S. M.; Kubendran, L. R.

1990-01-01

35

An Observation of a Circular Motion using Ordinary Appliances: Train Toy, Digital Camera, and Android based Smartphone  

E-print Network

Using a digital camera (Sony DSC-S75) in its video mode and a smartphone (Samsung GT-N700) equipped with an acceleration sensor, observation of a uniform circular motion of a toy train (Thomas & Friends, Player World, CCF No. 2277-13) is conducted. From the first observation average centripetal acceleration about 0.154 m/s2 is obtained, while the second gives 0.350 m/s2 of average centripetal acceleration by assuming ideal condition, where measured accelerations in z direction is not interpreted.

Viridi, Sparisoma; Nasri, Meldawati

2013-01-01

36

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

NASA Astrophysics Data System (ADS)

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

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

2013-04-01

37

Uniform asymptotic solution for the radiation from a magnetic source on a large dielectric coated circular cylinder: Nonparaxial region  

NASA Astrophysics Data System (ADS)

An accurate uniform asymptotic technique to calculate the radiated field from a magnetic current moment situated on the surface of a circular cylinder coated with a thin dielectric layer has been developed. Using the Watson transform, a slowly convergent radially propagating series representation for the fields is converted into a rapidly convergent circumferentially propagating series representation. An asymptotic shadow region solution is then obtained by employing the method of steepest descent. By modifying the shadow region solution in an appropriate manner, a uniform lit region solution is obtained that reduces to the geometrical optics solution in the deep-lit region. The asymptotic solution is valid for large cylinders away from the paraxial region and can be used to calculate the radiation pattern and the scattering from waveguide-fed apertures. Numerical results are compared to an eigenfunction solution, and a very good accuracy is achieved within the expected region of validity.

Thors, B.; Rojas, R. G.

2003-10-01

38

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

NASA Technical Reports Server (NTRS)

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

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

1973-01-01

39

Stochastic fluid—structure interaction of large circular floating islands during wind waves and seaquakes  

Microsoft Academic Search

The dynamic responses of an artificial large floating island subjected to wind waves and seaquakes are evaluated using both long-term and short-term stochastic descriptions of loading and stochastic response analysis of the linearized dynamic model. The short-term description is represented by the power spectral density functions of the load time history during each load intensity, whereas the long-term description is

Takuji Hamamoto

1995-01-01

40

Circular Coinduction  

NASA Technical Reports Server (NTRS)

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

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

2001-01-01

41

Observability Analysis Of Large Bus - System Using Matlab Simulation  

NASA Astrophysics Data System (ADS)

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

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

2013-03-01

42

Observations of Galaxies and Large Scale Structure at High Redshifts  

E-print Network

Observations of Galaxies and Large Scale Structure at High Redshifts Charles C. Steidel Palomar progress in the collection of empirical data on galaxies and their large-scale distribution at high (z >> 1 matter. 1 Introduction It is diÃ?cult to know exactly where a discussion of such a mundane topic as galaxy

Steidel, Chuck

43

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

PubMed Central

Several species of tsetse flies can be infected by the Glossina pallidipes salivary gland hypertrophy virus (GpSGHV). Infection causes salivary gland hypertrophy and also significantly reduces the fecundity of the infected flies. To better understand the molecular basis underlying the pathogenesis of this unusual virus, we sequenced and analyzed its genome. The GpSGHV genome is a double-stranded circular DNA molecule of 190,032 bp containing 160 nonoverlapping open reading frames (ORFs), which are distributed equally on both strands with a gene density of one per 1.2 kb. It has a high A+T content of 72%. About 3% of the GpSGHV genome is composed of 15 sequence repeats, distributed throughout the genome. Although sharing the same morphological features (enveloped rod-shaped nucleocapsid) as baculoviruses, nudiviruses, and nimaviruses, analysis of its genome revealed that GpSGHV differs significantly from these viruses at the level of its genes. Sequence comparisons indicated that only 23% of GpSGHV genes displayed moderate homologies to genes from other invertebrate viruses, principally baculoviruses and entomopoxviruses. Most strikingly, the GpSGHV genome encodes homologues to the four baculoviral per os infectivity factors (p74 [pif-0], pif-1, pif-2, and pif-3). The DNA polymerase encoded by GpSGHV is of type B and appears to be phylogenetically distant from all DNA polymerases encoded by large double-stranded DNA viruses. The majority of the remaining ORFs could not be assigned by sequence comparison. Furthermore, no homologues to DNA-dependent RNA polymerase subunits were detected. Taken together, these data indicate that GpSGHV is the prototype member of a novel group of insect viruses. PMID:18272583

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

2008-01-01

44

Tradeoffs when Multiple Observer Siting on Large Terrain Cells  

E-print Network

Tradeoffs when Multiple Observer Siting on Large Terrain Cells W. Randolph Franklin1 and Christian: terrain visibility, viewshed, line of sight, siting, multiple observers, intervisibility 1 Introduction many applications. A cell phone provider wishes to install multiple towers so that at least one tower

Franklin, W. Randolph

45

Large-scale structure observables in general relativity  

NASA Astrophysics Data System (ADS)

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

Jeong, Donghui; Schmidt, Fabian

2015-02-01

46

The high power large aperture radar method for meteor observations  

NASA Astrophysics Data System (ADS)

The high power large aperture (HPLA) radar meteor method is presented. It is compared to the classical meteor radar method in terms of working frequency ranges, beam widths and power densities at meteor altitudes to show the basic differences. The classical meteor radars are sensitive to perpendicular meteor trails. The large aperture radars, with higher working frequencies and higher transmitted power, observe the meteoroid-atmosphere interaction at all look-angles. Due to the narrow beams, these radars mainly observe the population of numerous very small sporadic background particles. Almost no shower-related increase in fluxes has been observed in the EISCAT Geminid, Perseid and Leonid observations. Simultaneously with the meteor mode, the HPLA radars can operate in their usual incoherent scatter modes to observe the electron density variations in the background ionosphere. Thus evolution of sporadic E layers, their average ion composition and their relation to meteor activity can be monitored.

Pellinen-Wannberg, Asta

2001-11-01

47

Study of Separated Flow Past a Circular Cylinder at Re= 13,400 Using Implicit Large Eddy Simulation Technique  

Microsoft Academic Search

Flow past a circular cylinder is investigated for Re = 13,400 using ILES. There are two objectives in choosing this value of Re. First, for this Re, the low-pressure turbine cascade, a problem of present interest, experiences separation. The second objective is to check if the ILES technique can perform well at higher Re where a subgrid scale model may

Pavan Kumar Mutnuri; Karman Ghia; Urmila Ghia; Hugh Thornburgh

2003-01-01

48

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

NASA Astrophysics Data System (ADS)

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

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

2014-09-01

49

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

50

Large deployable reflectors for telecom and earth observation applications  

NASA Astrophysics Data System (ADS)

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

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

2013-12-01

51

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

PubMed

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

Logé, Christoph; Boesl, Ulrich

2012-12-21

52

35 cm observations of a sample of large supernova remnants  

NASA Astrophysics Data System (ADS)

We present radio maps of ten large-diameter supernova remnants observed at 35 cm wavelength with the Effelsberg 100-m telescope. The angular resolution is 14farcm5 . The sources are G126.2+1.6, G127.1+0.5, HB3, HB9, S147, IC 443, Cygnus Loop, W63 and HB21. For each object we give an integrated flux density and improved spectra when necessary. We also present a map of G213.0-0.6, which we tentatively identify as a new large supernova remnant with a very low surface brightness, apparently interacting with the H Ii region S284. Based on observations with the Effelsberg 100-m telescope operated by the Max-Planck-Institut für Radioastronomie (MPIfR), Bonn, Germany.

Reich, W.; Zhang, X.; Fürst, E.

2003-09-01

53

On tidal tilt corrections to large ring laser gyroscope observations  

NASA Astrophysics Data System (ADS)

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

Tian, Wei

2014-01-01

54

Observation and analysis of large-scale human motion  

Microsoft Academic Search

Many team sports include complex human movement, which can be observed at different levels of detail. Some aspects of the athlete's motion can be studied in detail using commercially available high-speed, high-accuracy biomechanical measurement systems. However, due to their limitations, these devices are not appropriate for studying large-scale motion during a game (for example, the motion of a player running

Janez Perš; Marta Bon; Stanislav Kova?i?; Marko Šibila; Branko Dežman

2002-01-01

55

Fermi Large Area Telescope Observations of the Vela Pulsar  

Microsoft Academic Search

The Vela pulsar is the brightest persistent source in the GeV sky and thus is the traditional first target for new gamma-ray observatories. We report here on initial Fermi Large Area Telescope observations during verification phase pointed exposure and early sky survey scanning. We have used the Vela signal to verify Fermi timing and angular resolution. The high-quality pulse profile,

A. A. Abdo; M. Ackermann; W. B. Atwood; R. Bagagli; L. Baldini; J. Ballet; D. L. Band; G. Barbiellini; M. G. Baring; J. Bartelt; D. Bastieri; B. M. Baughman; K. Bechtol; F. Bellardi; R. Bellazzini; B. Berenji; D. Bisello; R. D. Blandford; E. D. Bloom; J. R. Bogart; E. Bonamente; A. W. Borgland; A. Bouvier; J. Bregeon; A. Brez; M. Brigida; P. Bruel; T. H. Burnett; G. A. Caliandro; R. A. Cameron; F. Camilo; P. A. Caraveo; J. M. Casandjian; M. Ceccanti; C. Cecchi; E. Charles; A. Chekhtman; C. C. Cheung; J. Chiang; S. Ciprini; R. Claus; I. Cognard; J. Cohen-Tanugi; L. R. Cominsky; J. Conrad; R. Corbet; L. Corucci; S. Cutini; D. S. Davis; M. DeKlotz; C. D. Dermer; A. de Angelis; F. de Palma; S. W. Digel; M. Dormody; E. do Couto e. Silva; P. S. Drell; R. Dubois; D. Dumora; C. Espinoza; C. Farnier; C. Favuzzi; D. L. Flath; P. Fleury; W. B. Focke; M. Frailis; P. C. C. Freire; Y. Fukazawa; S. Funk; P. Fusco; F. Gargano; D. Gasparrini; N. Gehrels; S. Germani; R. Giannitrapani; 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; G. Haller; A. K. Harding; P. A. Hart; R. C. Hartman; E. Hays; G. Hobbs; R. E. Hughes; G. Jóhannesson; A. S. Johnson; R. P. Johnson; T. J. Johnson; W. N. Johnson; S. Johnston; T. Kamae; G. Kanbach; V. M. Kaspi; H. Katagiri; J. Kataoka; A. Kavelaars; N. Kawai; H. Kelly; M. Kerr; B. Kiziltan; W. Klamra; J. Knödlseder; M. Kramer; F. Kuehn; M. Kuss; J. Lande; D. Landriu; L. Latronico; B. Lee; S.-H. Lee; M. Lemoine-Goumard; M. Livingstone; F. Longo; F. Loparco; B. Lott; M. N. Lovellette; P. Lubrano; A. G. Lyne; G. M. Madejski; A. Makeev; R. N. Manchester; B. Marangelli; M. Marelli; M. N. Mazziotta; J. E. McEnery; S. McGlynn; M. A. McLaughlin; N. Menon; C. Meurer; P. F. Michelson; T. Mineo; N. Mirizzi; W. Mitthumsiri; T. Mizuno; A. A. Moiseev; M. Mongelli; C. Monte; M. E. Monzani; E. Moretti; A. Morselli; I. V. Moskalenko; S. Murgia; T. Nakamori; P. L. Nolan; A. Noutsos; E. Nuss; T. Ohsugi; N. Omodei; E. Orlando; J. F. Ormes; M. Ozaki; A. Paccagnella; D. Paneque; J. H. Panetta; D. Parent; M. Pearce; M. Pepe; M. Perchiazzi; M. Pesce-Rollins; L. Pieri; M. Pinchera; F. Piron; T. A. Porter; S. Rainò; R. Rando; S. M. Ransom; E. Rapposelli; M. Razzano; A. Reimer; O. Reimer; T. Reposeur; L. C. Reyes; S. Ritz; L. S. Rochester; A. Y. Rodriguez; R. W. Romani; M. Roth; F. Ryde; A. Sacchetti; H. F.-W. Sadrozinski; N. Saggini; D. Sanchez; A. Sander; P. M. Saz Parkinson; K. N. Segal; A. Sellerholm; C. Sgrò; E. J. Siskind; D. A. Smith; P. D. Smith; G. Spandre; P. Spinelli; M. Stamatikos; J.-L. Starck; F. W. Stecker; T. E. Stephens; M. S. Strickman; A. W. Strong; D. J. Suson; H. Tajima; H. Takahashi; T. Takahashi; T. Tanaka; A. Tenze; J. B. Thayer; J. G. Thayer; G. Theureau; D. J. Thompson; S. E. Thorsett; L. Tibaldo; O. Tibolla; D. F. Torres; A. Tramacere; M. Turri; T. L. Usher; L. Vigiani; N. Vilchez; V. Vitale; A. P. Waite; P. Wang; K. Watters; P. Weltevrede; B. L. Winer; K. S. Wood; T. Ylinen; M. Ziegler

2009-01-01

56

SDO AIA Observations of Large-Scale Coronal Propagating Fronts  

NASA Astrophysics Data System (ADS)

The discovery of "EIT waves" rekindled interests in what used to be called flare waves, which had been typically observed in H-alpha. In addition to Moreton waves, first observed at the Lockheed Solar Observatory, other manifestations of shock waves propagating in the corona include type II radio bursts and filament oscillations away from flare sites. Identification of EIT waves with the postulated fast-mode MHD shock waves in the corona has been questioned, however, largely because of their low speeds (e.g., 200-400 km/s). EIT's 10-20 minute cadence could be a contributing factor for this, and we need to find how fast large-scale coronal propagating fronts are in higher-cadence EUV images. It is clear that AIA on SDO is the best instrument at the moment for this type of work. With the availability of high-cadence full-disk images, we now can compare propagating fronts in different directions, and determine the highest speed of each event on AIA images more objectively and accurately than on EIT (and STEREO EUVI) images. In a large number of EIT wave events, we have measured speeds of propagating fronts using AIA's 193 A images. Before the fronts are deflected by the discontinuities, e.g., active regions and coronal holes, the mean and median speeds are 620 km/s and 600 km/s, respectively, and many exceed 800 km/s. Higher speeds are often seen in events that accompany a type II burst, strong flare or energetic CME, but the distribution of the speed with these attributes is broad. We also find that the speeds of the large-scale coronal propagating fronts are not well correlated with those of the associated CMEs. Given that large-scale coronal propagating fronts at large distances represent freely propagating MHD waves, we discuss how to understand their nature close to their origins.

Nitta, Nariaki; Schrijver, C. J.; Title, A. M.; Liu, W.

2013-07-01

57

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

58

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.

59

Interferometric observations of large biologically interesting interstellar and cometary molecules  

PubMed Central

Interferometric observations of high-mass regions in interstellar molecular clouds have revealed hot molecular cores that have substantial column densities of large, partly hydrogen-saturated molecules. Many of these molecules are of interest to biology and thus are labeled “biomolecules.” Because the clouds containing these molecules provide the material for star formation, they may provide insight into presolar nebular chemistry, and the biomolecules may provide information about the potential of the associated interstellar chemistry for seeding newly formed planets with prebiotic organic chemistry. In this overview, events are outlined that led to the current interferometric array observations. Clues that connect this interstellar hot core chemistry to the solar system can be found in the cometary detection of methyl formate and the interferometric maps of cometary methanol. Major obstacles to understanding hot core chemistry remain because chemical models are not well developed and interferometric observations have not been very sensitive. Differentiation in the molecular isomers glycolaldehdye, methyl formate, and acetic acid has been observed, but not explained. The extended source structure for certain sugars, aldehydes, and alcohols may require nonthermal formation mechanisms such as shock heating of grains. Major advances in understanding the formation chemistry of hot core species can come from observations with the next generation of sensitive, high-resolution arrays. PMID:16894168

Snyder, Lewis E.

2006-01-01

60

Observation of Large Amplitude Electromagnetic Wave at the Dipolarization Front  

NASA Astrophysics Data System (ADS)

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

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

2013-12-01

61

Infrasonic observations of large-scale HE events  

NASA Technical Reports Server (NTRS)

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

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

1990-01-01

62

New FUSE Stellar Observations in the Large Magellanic Cloud  

NASA Astrophysics Data System (ADS)

We propose FUSE observations of a select set of stars in the Large Magellanic Cloud to build on and improve earlier work in significant ways. A set of 22 stars has been pared to 12 in Phase 2 to fit into the TAC allocation. We propose 6 new sight lines in close proximity to previously observed stars to provide more detailed sampling of coherent sub-structures in the LMC such as bubbles or shells. A set of 4 sight lines to stars in the previously unobserved superbubble N70 will provide a detailed study of this region. Also, building on our earlier detailed analyses of LMC sightlines, we will re-observe 2 objects whose current LWRS aperture data sets are contaminated by nearby stars and are useless for ISM work. Using MDRS will isolate the stars of interest and will provide ``new'' sight lines in the important 30 Doradus region. Observing these new sight lines will leverage the much larger LMC data set by providing better studies of ISM sub-structures.

Blair, W.

63

Radio polarization observations of large supernova remnants at ?6 cm  

NASA Astrophysics Data System (ADS)

We have observed 79 supernova remnants (SNRs) with the Urumqi 25 m telescope at ?6 cm during the Sino-German ?6 cm polarization survey of the Galactic plane. We measured flux densities of SNRs at ?6 cm, some of which are the first ever measured or the measurements at the highest frequency, so that we can determine or improve spectra of SNRs. Our observations have ruled out spectral breaks or spectral flattening that were suggested for a few SNRs, and confirmed the spectral break of S147. By combining our ?6 cm maps with ?11 cm and ?21 cm maps from the Effelsberg 100 m telescope, we calculated the spectral index maps of several large SNRs. For many remnants we obtained for the first time polarization images, which show the intrinsic magnetic field structures at ?6 cm. We disapproved three objects as being SNRs, OA184, G192.8-1.1 and G16.8-1.1, which show a thermal spectrum and no polarization. We have discovered two large supernova remnants, G178.2-4.2 and G25.1-2.3., in the survey maps.

Han, J. L.; Gao, X. Y.; Sun, X. H.; Reich, W.; Xiao, L.; Reich, P.; Xu, J. W.; Shi, W. B.; Fürst, E.; Wielebinski, R.

2014-01-01

64

Large Scale Multi-transition CO observations of GMCs  

NASA Astrophysics Data System (ADS)

Multi-transition molecular line observations have given us good indication of the range of physical conditions in dense cloud cores around massive protostars. There is little information, however, about conditions in the surrounding GMC's, on scales of 5-25 pc, where the bulk of the molecular material resides. We present large scale observations of 12CO6 ? 5, 4 ? 3, 3 ? 2, and 2 ? 1; 13CO J = 2 ? 1; C18O J = 2 ? 1; and [CI] 3P1 ? 3P0 in 6 GMC's. Using current PDR models and radiative transfer codes, we derive estimates of density and the interstellar radiation field for positions both close to the dense cores and in more diffuse outer regions of the clouds. We find that the 12CO J = 6 ? 5 line is much more sensitive to changes in physical conditions (even with larger calibration uncertainties) than lower-J lines commonly used to obtain large-scale temperatures and densities in the outer regions of GMC's.

Allers, Katelyn N.; Jaffe, Daniel T.; Evans, Neal J., II; Plume, René; van Dishoeck, Ewine F.

65

Evaluation of forest fire models on a large observation database  

NASA Astrophysics Data System (ADS)

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

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

2014-11-01

66

The Flux of Large Meteoroids Observed with Lunar Impact Monitoring  

NASA Technical Reports Server (NTRS)

The flux of large meteoroids is not well determined due to relatively low number statistics, due mainly to the lack of collecting area available to meteor camera systems (10(2)-10(5) km2). Larger collecting areas are needed to provide reasonable statistics for flux calculations. The Moon, with millions of square kilometers of lunar surface, can be used as a detector for observing the population of large meteoroids in the tens of grams to kilogram mass range. This is accomplished by observing the flash of light produced when a meteoroid impacts the lunar surface, converting a portion of its kinetic energy to visible light detectable from Earth. A routine monitoring program at NASA's Marshall Space Flight Center has recorded over 300 impact flashes since early 2006. The program utilizes multiple 0.35 m (14 inch) Schmidt-Cassegrain telescopes, outfitted with video cameras using the 1/2 inch Sony EXview HAD CCDTM chip, to perform simultaneous observations of the earthshine hemisphere of the Moon when the lunar phase is between 0.1 and 0.5. This optical arrangement permits monitoring of approximately 3.8x10(6) km2 of lunar surface. A selection of 126 flashes recorded in 266.88 hours of photometric skies was analyzed, creating the largest and most homogeneous dataset of lunar impact flashes to date. Standard CCD photometric techniques outlined in [1] were applied to the video to determine the luminous energy, kinetic energy, and mass for each impactor, considering a range of luminous efficiencies. The flux to a limiting energy of 2.5x10(-6) kT TNT or 1.05×10(7) J is 1.03×10(-7) km(-2) hr(-1) and the flux to a limiting mass of 30 g is 6.14×10(-10) m(-2) yr(-1). Comparisons made with measurements and models of the meteoroid population indicate that the flux of objects in this size range is slightly lower (but within the error bars) than the power law distribution determined for the near Earth object population by [2].

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

2014-01-01

67

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

68

Observing Planetary Nebulae with JWST and Extremely Large Telescopes  

NASA Astrophysics Data System (ADS)

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

Sahai, Raghvendra

2015-01-01

69

Elliptic and circular wormholes  

E-print Network

Two new exact analytical solutions of the euclidean Einstein equations for a minimal massless scalar field and negative cosmological constant have been obtained. These solutions are given in terms of Jacobian elliptic or circular functions, rather than hyperbolic functions, connect large asymptotic regions of maximally-symmetric anti-DeSitter metrics through a microscopic throat, and correspond to negative definite components of the Ricci tensor. Therefore, they describe wormhole-like changes of topology driven by nucleation of baby universes. The quantum state of such elliptic and circular wormholes or handles is discussed in the most interesting inner and asymptotic regions.

P. F. González-Díaz

1993-06-25

70

Observations Regarding Small Eolian Dunes and Large Ripples on Mars  

NASA Technical Reports Server (NTRS)

Eolian bedforms occur at the interface between a planetary surface and its atmosphere; they present a proxy record of the influence of climate, expressed in sediment transport, over that surface. High resolution images (1.5 - 12 m/pixel) from the Mars Global Surveyor (MGS) Mars Orbiter Camera provide glimpses of the most recent events shaping the martian landscape. Thousands of images exhibit small transverse dunes or large eolian ripples that have crest-to-crest spacings of 10 to 60 m, heights of a few to 10 m. Bedforms of the size and patterns seen in the Mars photographs are rarely described among Earth's eolian landforms; in terms of size and morphology, most of these fall between traditional definitions of "ripples" and "dunes". Dunes are composed chiefly of materials transported by saltation, ripples are smaller forms moved along by the impact of saltating grains (traction). The largest reported eolian ripples on Earth (granule ripples, megaripples) are typically smaller than the bedforms observed on Mars; likewise, most dunes are typically larger. The small dunes and large ripples on Mars come in a variety of relative albedos, despite an early MGS impression that they are all of high albedo. Some ripples occur on the surfaces of sand dunes; these are most likely true granule ripples. However, most of these bedforms occur in troughs, pits, craters, and on deflated plains. Despite impressions early in the MGS mission, they do not occur everywhere (e.g., they are rare on the northern plains) but they do occur at a range of elevations from the highest volcanoes to the deepest basins. Where they occur on a hard substrate among larger sand dunes, the big dunes have over-ridden the smaller bedforms, indicating that the smaller features are older and perhaps indurated or very coarse-grained. At other locales, the small bedforms have been mantled by material settled from suspension, in other cases they are being exhumed and may be lithified. Still other examples are peppered with small impact craters, implying considerable age. These bedforms present a complicated record of the geologically-recent past, one that has involved changes in climate, sediment transport capabilities, and sediment sources and sinks over time.

Edgett, Kenneth S.

2001-01-01

71

Observations regarding small eolian dunes and large ripples on Mars  

NASA Astrophysics Data System (ADS)

Eolian bedforms occur at the interface between a planetary surface and its atmosphere; they present a proxy record of the influence of climate, expressed in sediment transport, over that surface. High resolution images (1.5-12 m/pixel) from the Mars Global Surveyor (MGS) Mars Orbiter Camera provide glimpses of the most recent events shaping the martian landscape. Thousands of images exhibit small transverse dunes or large eolian ripples that have crest-to-crest spacings of 10 to 60 m, heights of a few to 10 m. Bedforms of the size and patterns seen in the Mars photographs are rarely described among Earth's eolian landforms; in terms of size and morphology, most of these fall between traditional definitions of "ripples" and "dunes". Dunes are composed chiefly of materials transported by saltation, ripples are smaller forms moved along by the impact of saltating grains (traction). The largest reported eolian ripples on Earth (granule ripples, megaripples) are typically smaller than the bedforms observed on Mars; likewise, most dunes are typically larger. The small dunes and large ripples on Mars come in a variety of relative albedos, despite an early MGS impression that they are all of high albedo. Some ripples occur on the surfaces of sand dunes; these are most likely true granule ripples. However, most of these bedforms occur in troughs, pits, craters, and on deflated plains. Despite impressions early in the MGS mission, they do not occur everywhere (e.g., they are rare on the northern plains) but they do occur at a range of elevations from the highest volcanoes to the deepest basins. Where they occur on a hard substrate among larger sand dunes, the big dunes have over-ridden the smaller bedforms, indicating that the smaller features are older and perhaps indurated or very coarse-grained. At other locales, the small bedforms have been mantled by material settled from suspension, in other cases they are being exhumed and may be lithified. Still other examples are peppered with small impact craters, implying considerable age. These bedforms present a complicated record of the geologically-recent past, one that has involved changes in climate, sediment transport capabilities, and sediment sources and sinks over time.

Edgett, K. S.

2001-11-01

72

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

PubMed

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

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

2014-06-19

73

Cold Rydberg atoms in circular states  

NASA Astrophysics Data System (ADS)

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

Anderson, David; Schwarzkopf, Andrew; Raithel, Georg

2012-06-01

74

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

NASA Astrophysics Data System (ADS)

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

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

2011-07-01

75

Life Cycle of a Mesoscale Circular Gust Front Observed by a C-Band Doppler Radar in West Africa  

E-print Network

On 10 July 2006, during the Special Observation Period (SOP) of the African Monsoon Multidisciplinary Analysis (AMMA) campaign, a small convective system initiated over Niamey and propagated westward in the vicinity of ...

Lothon, Marie

76

Spatial seismology of a large coronal loop arcade from TRACE & EIT observations of its transverse oscillations  

E-print Network

Spatial seismology of a large coronal loop arcade from TRACE & EIT observations of its transverse seismology) and find that the observations cannot unambigiously distinguish between structuring and non

Verwichte, Erwin

77

SEARCH Workshop on Large-Scale Atmosphere/Cryosphere Observations  

NASA Technical Reports Server (NTRS)

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

2002-01-01

78

Storm induced large scale TIDs observed in GPS derived TEC  

Microsoft Academic Search

This work is a first statistical analysis of large scale traveling ionospheric disturbances (LSTID) in Europe using total electron content (TEC) data derived from GNSS measurements. The GNSS receiver network in Europe is dense enough to map the ionospheric perturbation TEC with high horizontal resolution. The derived perturbation TEC maps are analysed studying the effect of space weather events on

C. Borries; N. Jakowski; V. Wilken

2009-01-01

79

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

80

MESSENGER Observations of Large Flux Transfer Events at Mercury  

NASA Technical Reports Server (NTRS)

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

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

2010-01-01

81

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

82

Sufficient observables for large-scale structure in galaxy surveys  

NASA Astrophysics Data System (ADS)

Beyond the linear regime, the power spectrum and higher order moments of the matter field no longer capture all cosmological information encoded in density fluctuations. While non-linear transforms have been proposed to extract this information lost to traditional methods, up to now, the way to generalize these techniques to discrete processes was unclear; ad hoc extensions had some success. We pointed out in Carron and Szapudi's paper that the logarithmic transform approximates extremely well the optimal `sufficient statistics', observables that extract all information from the (continuous) matter field. Building on these results, we generalize optimal transforms to discrete galaxy fields. We focus our calculations on the Poisson sampling of an underlying lognormal density field. We solve and test the one-point case in detail, and sketch out the sufficient observables for the multipoint case. Moreover, we present an accurate approximation to the sufficient observables in terms of the mean and spectrum of a non-linearly transformed field. We find that the corresponding optimal non-linear transformation is directly related to the maximum a posteriori Bayesian reconstruction of the underlying continuous field with a lognormal prior as put forward in the paper of Kitaura et al.. Thus, simple recipes for realizing the sufficient observables can be built on previously proposed algorithms that have been successfully implemented and tested in simulations.

Carron, J.; Szapudi, I.

2014-03-01

83

Negative circular polarization as a universal property of quantum dots  

NASA Astrophysics Data System (ADS)

This paper shows that negative circular polarization, a spin flip of polarized carriers resulting in emission of opposite helicity, can be observed in undoped, n-doped, and p-doped InAs/GaAs quantum dots. These results contradict the usual interpretation of the effect. We show using power dependent and time resolved spectroscopy that the generation of negative circular polarization correlates with excited state emission. Furthermore, a longer spin lifetime of negatively polarized excitons is observed where emission is largely ground state in character.

Taylor, Matthew W.; Spencer, Peter; Murray, Ray

2015-03-01

84

IRAS observations of a large sample of normal irregular galaxies  

NASA Technical Reports Server (NTRS)

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

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

1989-01-01

85

Cosmological parameter estimation with large scale structure observations  

NASA Astrophysics Data System (ADS)

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

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

2014-01-01

86

Interactive analysis of a large aperture Earth observations satellite  

NASA Technical Reports Server (NTRS)

A system level design and analysis has been conducted on an Earth Observation Satellite (EOS) system using the Interactive Design and Evaluation of Advanced Spacecraft (IDEAS) computer-aided design and analysis program. The IDEAS program consists of about 40 user-friendly technical modules and an interactive graphics display. The reflector support system and feed mast of the EOS spacecraft are constructed with box-truss structural concept, a lattice configuration which can be packaged for delivery in a single Shuttle flight and deployed in orbit. The deployed spacecraft consists of a 120-m by 60-m parabolic focal axis. The spacecraft was modeled for structural, thermal, and control systems analysis and structural elements were designed. On-orbit dynamic and thermal loading analyses were conducted; spacecraft weights and developmental and first unit costs were determined.

Wright, R. L.; Deryder, D. D.; Ferebee, M. J., Jr.; Smith, J. C.

1983-01-01

87

FERMI LARGE AREA TELESCOPE OBSERVATIONS OF MISALIGNED ACTIVE GALACTIC NUCLEI  

SciTech Connect

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

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

2010-09-01

88

Large-scale Observations of the Magnetopause by Cluster (Invited)  

NASA Astrophysics Data System (ADS)

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

Foullon, C.

2013-12-01

89

Large-scale Observations of the Magnetopause by Cluster  

NASA Astrophysics Data System (ADS)

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

Foullon, Claire

2014-05-01

90

Observation of Events with a Large Rapidity Gap in Deep Inelastic Scattering at HERA  

E-print Network

Observation of Events with a Large Rapidity Gap in Deep Inelastic Scattering at HERA ZEUS s = 296 GeV, we observe in the ZEUS detector events with a large rapidity gap in the hadronic final state. These ``large rapidity gap'' events are not described by standard QCD inspired fragmentation models [3

91

The Formaldehyde Masers in Sgr B2: Very Long Baseline Array and Very Large Array Observations  

E-print Network

Observations of two of the formaldehyde (H2CO) masers (A and D) in Sgr B2 using the VLBA+Y27 (resolution ~0.01") and the VLA (resolution ~9") are presented. The VLBA observations show compact sources (10^8 K. The maser sources are partially resolved in the VLBA observations. The flux densities in the VLBA observations are about 1/2 those of the VLA; and, the linewidths are about 2/3 of the VLA values. The applicability of a core-halo model for the emission distribution is demonstrated. Comparison with earlier H2CO absorption observations and with ammonia (NH3) observations suggests that H2CO masers form in shocked gas. Comparison of the integrated flux densities in current VLA observations with those in previous observations indicates that (1) most of the masers have varied in the past 20 years, and (2) intensity variations are typically less than a factor of two compared to the 20-year mean. No significant linear or circular polarization is detected with either instrument.

Ian M. Hoffman; W. M. Goss; Patrick Palmer

2006-09-28

92

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

NASA Astrophysics Data System (ADS)

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

Sawyer, R. F.

2015-01-01

93

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

94

Real time observation of proteolysis with Fourier transform infrared (FT-IR) and UV-circular dichroism spectroscopy: Watching a protease eat a protein  

NASA Astrophysics Data System (ADS)

Fourier transform infrared (FT-IR)- and UV-circular dichroism (UV-CD) spectroscopy have been used to study real-time proteolytic digestion of ?-lactoglobulin (?-LG) and ?-casein (?-CN) by trypsin at various substrate/enzyme ratios in D 2O-buffer at 37 °C. Both techniques confirm that protein substrate looses its secondary structure upon conversion to the peptide fragments. This perturbation alters the backbone of the protein chain resulting in conformational changes and degrading of the intact protein. Precisely, the most significant spectral changes which arise from digestion take place in the amide I and amide II regions. The FT-IR spectra for the degraded ?-LG show a decrease around 1634 cm -1, suggesting a decrease of ?-sheet structure in the course of hydrolysis. Similarly, the intensity around the 1654 cm -1 band decreases for ?-CN digested by trypsin, indicating a reduction in the ?-helical part. On the other hand, the intensity around ˜1594 cm -1 and ˜1406 cm -1 increases upon enzymatic breakdown of both substrates, suggesting an increase in the antisymmetric and symmetric stretching modes of free carboxylates, respectively, as released digestion products. Observation of further H/D exchange in the course of digestion manifests the structural opening of the buried groups and accessibility to the core of the substrate. On the basis of the UV-CD spectra recorded for ?-LG and ?-CN digested by trypsin, the unordered structure increases concomitant with a decrease in the remaining structure, thus, revealing breakdown of the intact protein into smaller fragments. This model study in a closed reaction system may serve as a basis for the much more complex digestion processes in an open reaction system such as the stomach.

Güler, Günnur; Džafi?, Enela; Vorob'ev, Mikhail M.; Vogel, Vitali; Mäntele, Werner

2011-06-01

95

There are no hydrological monsters, just models and observations with large uncertainties!  

E-print Network

1 There are no hydrological monsters, just models and observations with large uncertainties! George) There are no hydrological monsters, just models and observations with large uncertainties! Hydrol. Sci. J. 55(6), xxx ignored or treated simplistically, these errors develop into monsters that destroy our ability to model

Paris-Sud XI, Université de

96

Observation and analysis of large-scale human Janez Pers a,,1,2  

E-print Network

Observation and analysis of large-scale human motion Janez Pers a,,1,2 , Marta Bon b,2 , Stanislav. Bon, S. Kovacic, M. Sibila, B. Dezman: "Observation and Analysis of Large-scale Human Motion", Human, SI-1000 Ljubljana, Slovenia Abstract Many team sports include complex human movement, which can

Kovacic, Stanislav

97

Large-scale structure and coronal dynamics from joint radio, SOHO/EIT and coronagraph observations  

E-print Network

Large-scale structure and coronal dynamics from joint radio, SOHO/EIT and coronagraph observations;Large-Scale Structure and Coronal Dynamics from Joint Radio, SOHO/EITand Coronagraph Observations M of an 'halo' coronal mass ejection from the EIT telescope and LASCO coronagraphs on SOHO, from the Nangay

98

"Circularization" vs. Accretion -- What Powers Tidal Disruption Events?  

E-print Network

A tidal disruption event (TDE) takes place when a star passes near enough to a massive black hole to be disrupted. About half the star's matter is given elliptical trajectories with large apocenter distances, the other half is unbound. To "circularize", i.e., to form an accretion flow, the bound matter must lose a significant amount of energy, with the actual amount depending on the characteristic scale of the flow measured in units of the black hole's gravitational radius ($\\sim 10^{51} (R/1000R_g)^{-1}$~erg). Recent numerical simulations \\citep{Shiokawa+2015} have revealed that the circularization scale is close to the scale of the most-bound initial orbits, $\\sim 10^3 M_{BH,6.5}^{-2/3} R_g \\sim 10^{15} M_{BH,6.5}^{1/3}$~cm from the black hole, and the corresponding circularization energy dissipation rate is $\\sim 10^{44} M_{BH,6.5}^{-1/6}$~erg/s. We suggest that the energy liberated during circularization, rather then energy liberated by accretion onto the black hole, powers the observed optical TDE candidates. The observed rise times, luminosities, temperatures, emission radii, and line widths seen in these TDEs \\citep[e.g.][]{Arcavi+2014} are all more readily explained in terms of heating associated with circularization than in terms of accretion.

Tsvi Piran; Gilad Svirski; Julian Krolik; Roseanne M. Cheng; Hotaka Shiokawa

2015-04-07

99

"Circularization" vs. Accretion -- What Powers Tidal Disruption Events?  

E-print Network

A tidal disruption event (TDE) takes place when a star passes near enough to a massive black hole to be disrupted. About half the star's matter is given elliptical trajectories with large apocenter distances, the other half is unbound. To "circularize", i.e., to form an accretion flow, the bound matter must lose a significant amount of energy, with the actual amount depending on the characteristic scale of the flow measured in units of the black hole's gravitational radius (~ 10^{51} (R/1000R_g)^{-1} erg). Recent numerical simulations (Shiokawa et al., 2015) have revealed that the circularization scale is close to the scale of the most-bound initial orbits, ~ 10^3 M_{BH,6.5}^{-2/3} R_g ~ 10^{15} M_{BH,6.5}^{1/3} cm from the black hole, and the corresponding circularization energy dissipation rate is $\\sim 10^{44} M_{BH,6.5}^{-1/6}$~erg/s. We suggest that the energy liberated during circularization, rather then energy liberated by accretion onto the black hole, powers the observed optical TDE candidates (e.g.Arcavi et al. 2014). The observed rise times, luminosities, temperatures, emission radii, and line widths seen in these TDEs are all more readily explained in terms of heating associated with circularization than in terms of accretion.

Tsvi Piran; Gilad Svirski; Julian Krolik; Roseanne M. Cheng; Hotaka Shiokawa

2015-02-20

100

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

E-print Network

Observation of jet production in deep inelastic scattering with a large rapidity gap at HERA ZEUS Collaboration 11 April 1994 Abstract Events with a large rapidity gap in deep inelastic scattering with Q 2 â?? 10 interactions that give rise to large rapidity gap events. #12; 1 Introduction In a recent publication [1], we

101

Observation of hard scattering in photoproduction events with a large rapidity  

E-print Network

Observation of hard scattering in photoproduction events with a large rapidity gap at HERA ZEUS COLLABORATION FINAL VERSION -- October 18, 1994 Abstract Events with a large rapidity gap and total transverse evidence for events with a large rapidity gap in deep inelastic scattering (DIS). The energy dependence

102

Synthetic-Aperture Coherent Imaging From A Circular Path  

NASA Technical Reports Server (NTRS)

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

Jin, Michael Y.

1995-01-01

103

Asteroids and Comets: the Prospect for Observations with a Large Millimetre Array  

E-print Network

Asteroids and Comets: the Prospect for Observations with a Large Millimetre Array Jacques Crovisier Observatoire de Paris­Meudon, F­92195 Meudon, France Abstract. Radio continuum observations of asteroids will review here the current status and future prospect of radio astronomical observations of asteroids

Demoulin, Pascal

104

The Cluster Galaxy Circular Velocity Function  

Microsoft Academic Search

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

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

2002-01-01

105

Spectra of circularly polarized radiation from astrophysical OH masers  

NASA Technical Reports Server (NTRS)

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

Nedoluha, Gerald E.; Watson, William D.

1990-01-01

106

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

Microsoft Academic Search

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

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

1987-01-01

107

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...

108

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

E-print Network

Are large Trojan asteroids salty? An observational, theoretical, and experimental study Bin Yang a: Trojan asteroids Infrared observations Asteroids, surfaces a b s t r a c t With a total mass similar to the main asteroid belt, the jovian Trojan asteroids are a major feature in the Solar System. Based upon

Glotch, Timothy D.

109

Coordinated Observation of Large-scale TIDs by SuperDARN and GEONET  

Microsoft Academic Search

We present results of the multi-event analysis of the relationship between mid-latitude large-scale traveling ionospheric disturbances (LSTIDs) observed by the GPS receiver network in Japan (GEONET), which have a period of 30 to 120 minutes and longer than 1000 km wavelengths, and the high-latitude ionospheric disturbances observed by the SuperDARN radars. Among the mid-latitude LSTID events observed by GEONET between

N. Nishitani; T. Ogawa; T. Kikuchi; T. Tsugawa; A. Saito; Y. Otsuka; W. A. Bristow; N. Sato

2004-01-01

110

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

NASA Astrophysics Data System (ADS)

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

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

2014-08-01

111

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

Microsoft Academic Search

During the SOLVE\\/THESEO-2000 Arctic stratospheric campaign in the winter 1999\\/2000 widespread occurrences of very large HNO3-containing particles, probably composed of nitric acid trihydrate (NAT), were observed in situ by instruments on board the ER-2 stratospheric research aircraft. These large NAT particles were found with low number densities (n ~ 10-4 cm-3) in vast regions, in air generally supersaturated with respect

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

2002-01-01

112

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

SciTech Connect

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

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

2014-02-28

113

Large-amplitude electrostatic waves observed at a supercritical interplanetary shock  

Microsoft Academic Search

We present the first observations at an interplanetary shock of large-amplitude (> 100 mV\\/m pk-pk) solitary waves and large-amplitude (?30 mV\\/m pk-pk) waves exhibiting characteristics consistent with electron Bernstein waves. The Bernstein-like waves show enhanced power at integer and half-integer harmonics of the cyclotron frequency with a broadened power spectrum at higher frequencies, consistent with the electron cyclotron drift instability.

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

2010-01-01

114

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

E-print Network

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

Eric Gawiser

2000-05-24

115

Scintillation-Induced Circular Polarization in Pulsars and Quasars  

E-print Network

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

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

2000-07-28

116

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

NASA Astrophysics Data System (ADS)

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

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

2014-07-01

117

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

Microsoft Academic Search

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

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

1993-01-01

118

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

NASA Astrophysics Data System (ADS)

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

Kikuchi, Akihiro; Higuchi, Arika; Ida, Shigeru

2014-12-01

119

Direct Observation of High-Spin States in Manganese Dimer and Trimer Cations by X-ray Magnetic Circular Dichroism Spectroscopy in an Ion Trap  

E-print Network

The electronic structure and magnetic moments of free Mn$_2^+$ and Mn$_3^+$ are characterized by $2p$ x-ray absorption and x-ray magnetic circular dichroism spectroscopy in a cryogenic ion trap that is coupled to a synchrotron radiation beamline. Our results show directly that localized magnetic moments of 5 $\\mu_B$ are created by $3d^5 (^6\\mathrm{S})$ states at each ionic core, which are coupled in parallel to form molecular high-spin states via indirect exchange that is mediated in both cases by a delocalized valence electron in a singly-occupied $4s$ derived orbital with an unpaired spin. This leads to total magnetic moments of 11 $\\mu_B$ for Mn$_2^+$ and 16 $\\mu_B$ for Mn$_3^+$, with no contribution of orbital angular momentum.

Zamudio-Bayer, Vicente; Langenberg, Andreas; Kossick, Martin; ?awicki, Arkadiusz; Terasaki, Akira; von Issendorff, Bernd; Lau, J Tobias

2015-01-01

120

Seismology of a large solar coronal loop from EUVI/STEREO observations of its transverse oscillation  

E-print Network

Seismology of a large solar coronal loop from EUVI/STEREO observations of its transverse-of-sight integration. The Alfv´en speed and coronal magnetic field derived using coronal seismology are discussed Doorsselaere et al. 2008c). Through the application of the technique of coronal seismology (for a review see

Verwichte, Erwin

121

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

E-print Network

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

Guo, Zaoyang

122

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

Microsoft Academic Search

A case study of a large-amplitude orographic gravity wave occurring over the Antarctic Peninsula is presented, based on observations from the Vorcore balloon campaign and on mesoscale numerical simulations. The Vorcore campaign (September 2005 to February 2006) consisted in the flight of 27 superpressure balloons in the core of the Southern Hemisphere stratospheric polar vortex at altitudes of 16–19 km,

R. Plougonven; A. Hertzog; H. Teitelbaum

2008-01-01

123

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

Microsoft Academic Search

A case study of a large-amplitude orographic gravity wave occurring over the Antarctic Peninsula is presented, based on observations from the Vorcore balloon campaign and on mesoscale numerical simulations. The Vorcore campaign (September 2005 to February 2006) consisted in the flight of 27 superpressure balloons in the core of the Southern Hemisphere stratospheric polar vortex at altitudes of 16-19 km,

R. Plougonven; A. Hertzog; H. Teitelbaum

2008-01-01

124

Fermi Large Area Telescope Observations of the Crab Pulsar And Nebula  

Microsoft Academic Search

We report on gamma-ray observations of the Crab Pulsar and Nebula using 8 months of survey data with the Fermi Large Area Telescope (LAT). The high quality light curve obtained using the ephemeris provided by the Nançay and Jodrell Bank radio telescopes shows two main peaks stable in phase with energy. The first gamma-ray peak leads the radio main pulse

A. A. Abdo; M. Ackermann; M. Ajello; W. B. Atwood; M. Axelsson; L. Baldini; J. Ballet; G. Barbiellini; M. G. Baring; D. Bastieri; 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; G. A. Caliandro; R. A. Cameron; F. Camilo; P. A. Caraveo; J. M. Casandjian; C. Cecchi; Ö. Çelik; A. Chekhtman; C. C. Cheung; J. Chiang; S. Ciprini; R. Claus; I. Cognard; J. Cohen-Tanugi; L. R. Cominsky; J. Conrad; C. D. Dermer; A. de Angelis; A. de Luca; F. de Palma; S. W. Digel; E. do Couto e. Silva; P. S. Drell; R. Dubois; D. Dumora; C. Espinoza; C. Farnier; C. Favuzzi; S. J. Fegan; E. C. Ferrara; W. B. Focke; M. Frailis; P. C. C. Freire; 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; E. Hays; R. E. Hughes; G. Jóhannesson; A. S. Johnson; R. P. Johnson; T. J. Johnson; W. N. Johnson; S. Johnston; T. Kamae; H. Katagiri; J. Kataoka; N. Kawai; M. Kerr; J. Knödlseder; M. L. Kocian; M. Kramer; F. Kuehn; M. Kuss; J. Lande; L. Latronico; S.-H. Lee; M. Lemoine-Goumard; F. Longo; F. Loparco; B. Lott; M. N. Lovellette; P. Lubrano; A. G. Lyne; A. Makeev; M. Marelli; M. N. Mazziotta; J. E. McEnery; C. Meurer; P. F. Michelson; W. Mitthumsiri; T. Mizuno; A. A. Moiseev; C. Monte; M. E. Monzani; E. Moretti; A. Morselli; I. V. Moskalenko; S. Murgia; T. Nakamori; P. L. Nolan; J. P. Norris; A. Noutsos; E. Nuss; T. Ohsugi; N. Omodei; E. Orlando; J. F. Ormes; M. Ozaki; D. Paneque; J. H. Panetta; D. Parent; V. Pelassa; M. Pepe; M. Pesce-Rollins; M. Pierbattista; F. Piron; T. A. Porter; S. Rainò; R. Rando; P. S. Ray; M. Razzano; A. Reimer; O. Reimer; T. Reposeur; S. Ritz; 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; B. W. Stappers; M. S. Strickman; D. J. Suson; H. Tajima; H. Takahashi; T. Tanaka; J. B. Thayer; J. G. Thayer; G. Theureau; D. J. Thompson; S. E. Thorsett; L. Tibaldo; D. F. Torres; G. Tosti; A. Tramacere; Y. Uchiyama; T. L. Usher; A. Van Etten; V. Vasileiou; N. Vilchez; V. Vitale; A. P. Waite; E. Wallace; P. Wang; K. Watters; P. Weltevrede; B. L. Winer; K. S. Wood; T. Ylinen; M. Ziegler

2010-01-01

125

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

126

Wideband Very Large Array Observations of A2256. I. Continuum, Rotation Measure, and Spectral Imaging  

NASA Astrophysics Data System (ADS)

We report new observations of A2256 with the Karl G. Jansky Very Large Array (VLA) at frequencies between 1 and 8 GHz. These observations take advantage of the 2:1 bandwidths available during a single observation to study the spectral index, polarization, and rotation measure as well as using the associated higher sensitivity per unit time to image total intensity features down to ~0.''5 resolution. We find that the Large Relic, which dominates the cluster, is made up of a complex of filaments that show correlated distributions in intensity, spectral index, and fractional polarization. The rotation measure varies across the face of the Large Relic but is not well correlated with the other properties of the source. The shape of individual filaments suggests that the Large Relic is at least 25 kpc thick. We detect a low surface brightness arc connecting the Large Relic to the Halo and other radio structures, suggesting a physical connection between these features. The center of the F-complex is dominated by a very steep-spectrum, polarized, ring-like structure, F2, without an obvious optical identification, but the entire F-complex does have interesting morphological similarities to the radio structure of NGC 1265. Source C, the Long Tail, is unresolved in width near the galaxy core and is <~ 100 pc in diameter there. This morphology suggests either that C is a one-sided jet or that the bending of the tails takes place very near the core, consistent with the parent galaxy having undergone extreme stripping. Overall it seems that many of the unusual phenomena can be understood in the context of A2256 being near the pericenter of a slightly off-axis merger between a cluster and a smaller group. Given the lack of evidence for a strong shock associated with the Large Relic, other models should be considered, such as reconnection between two large-scale magnetic domains.

Owen, Frazer N.; Rudnick, Lawrence; Eilek, Jean; Rau, Urvashi; Bhatnagar, Sanjay; Kogan, Leonid

2014-10-01

127

Large-Amplitude Electrostatic Waves Observed at a Supercritical Interplanetary Shock  

NASA Technical Reports Server (NTRS)

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

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

2010-01-01

128

Observation of diffraction with the CMS experiment at the Large Hadron Collider  

E-print Network

A clear evidence of inclusive diffraction observed by the CMS detector at the Large Hadron Collider in minimum bias events at $\\sqrt{s}=$0.9 TeV, 2.36 TeV is presented. The observed diffractive signal is dominated by inclusive single-diffractive dissociation and can be identified by the presence of a Large Rapidity Gap that extends over the forward region of the CMS detector. A comparison of the data with Monte Carlo predictions provided by PYTHIA6 and PHOJET generators is given. In addition, first observation of the single-diffractive production of di-jets at $\\sqrt{s}=$7 TeV is presented.

Dmytro Volyanskyy

2011-02-03

129

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

SciTech Connect

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

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

2011-11-01

130

Taming of the Slew: Optimization of the Large Scale X-Ray Surveys with Observing Strategy  

NASA Technical Reports Server (NTRS)

We will discuss simulations intended to address the relative efficiency of observing large areas with a slew observing strategy as opposed to pointing at fields individually. We will emphasize observing with the Wide Field X-ray Telescope (WFXT) but will also discuss optimization of observing strategy with the IXO Wide-Field Imager (WFI) and eRosita. The slew survey simulation is being implemented by translating the point direction along an arbitrary direction which addresses the impact of smoothing the telescope response during a given slew. However the simulation software is being designed to also allow the visibility of the sky to also be incorporated, in which case long-term observing plans could be developed to optimize the total sky coverage at a given depth and spatial resolution.

Ptak, Andrew

2010-01-01

131

"Circularization" vs. Accretion -- What Powers Tidal Disruption Events?  

E-print Network

A tidal disruption event (TDE) takes place when a star passes near enough to a massive black hole to be disrupted. About half the star's matter is given elliptical trajectories with large apocenter distances, the other half is unbound. To "circularize", i.e., to form an accretion flow, the bound matter must lose a significant amount of energy, with the actual amount depending on the characteristic scale of the flow measured in units of the black hole's gravitational radius (~ 10^{51} (R/1000R_g)^{-1} erg). Recent numerical simulations (Shiokawa et al., 2015) have revealed that the circularization scale is close to the scale of the most-bound initial orbits, ~ 10^3 M_{BH,6.5}^{-2/3} R_g ~ 10^{15} M_{BH,6.5}^{1/3} cm from the black hole, and the corresponding circularization energy dissipation rate is $\\sim 10^{44} M_{BH,6.5}^{-1/6}$~erg/s. We suggest that the energy liberated during circularization, rather then energy liberated by accretion onto the black hole, powers the observed optical TDE candidates (e.g.A...

Piran, Tsvi; Krolik, Julian; Cheng, Roseanne M; Shiokawa, Hotaka

2015-01-01

132

The importance of large-amplitude motions for the interpretation of mid-infrared vibrational absorption and circular dichroism spectra: 6,6'-dibromo-[1,1'-binaphthalene]-2,2'-diol in dimethyl sulfoxide.  

PubMed

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

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

2014-07-01

133

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

NASA Astrophysics Data System (ADS)

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

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

2013-12-01

134

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

NASA Technical Reports Server (NTRS)

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

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

2012-01-01

135

Circular A-110 CIRCULAR A-110  

E-print Network

the Duties of the Office of Management and Budget and the Domestic Policy Council in the Executive Office Agreements with State and Local Governments," and the Federal agencies' grants management common rule which this Circular may be obtained by contacting the Office of Federal Financial Management, Office of Management

Weston, Ken

136

Observation of cladding modes spatio-spectral distribution in large mode area photonic crystal fiber  

NASA Astrophysics Data System (ADS)

We report the observation of spatio-spectral distribution in cladding modes of a single-mode large mode area photonic crystal fiber. The cladding modes excitation was achieved without any external fiber exposure. The optical field patterns of the cladding modes within different pump wavelength are investigated. To the best of knowledge the spatio- spectral distribution in cladding modes of large mode photonic crystal fiber is demonstrated for the first time. The results are of immediate interest in applications demanding devices based on core and cladding mode coupling in photonic crystal fibers.

Leonov, Stanislav O.; Lazarev, Vladimir A.; Borisova, Alina V.; Demidov, Vladimir V.; Pryamikov, Andrey D.

2015-01-01

137

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

NASA Technical Reports Server (NTRS)

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

Wilson, Lynn B., III

2010-01-01

138

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

NASA Technical Reports Server (NTRS)

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

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

2002-01-01

139

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

Microsoft Academic Search

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

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

2007-01-01

140

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

Microsoft Academic Search

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

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

1995-01-01

141

Large-scale laboratory observations of wave breaking turbulence over an evolving beach  

Microsoft Academic Search

Wave breaking turbulence over an evolving beach was observed in a large-scale laboratory flume, as part of the CROss-Shore Sediment Transport EXperiment (CROSSTEX). The data set included comprehensive measurements of water surface elevation, fluid velocity, and morphology for irregular waves under erosive and accretive wave conditions. For the both conditions, the beach reached a quasi-equilibrium state, defined as when the

Hyun-Doug Yoon; Daniel T. Cox

2010-01-01

142

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

Microsoft Academic Search

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

Rene Plume; D. T. Jaffe; Jocelyn Keene

1994-01-01

143

Radiometer requirements for Earth-observation systems using large space antennas  

NASA Technical Reports Server (NTRS)

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

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

1983-01-01

144

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

NASA Astrophysics Data System (ADS)

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

Frimann, Søren; Jørgensen, Jes Kristian

2014-07-01

145

Considerations for observational research using large data sets in radiation oncology.  

PubMed

The radiation oncology community has witnessed growing interest in observational research conducted using large-scale data sources such as registries and claims-based data sets. With the growing emphasis on observational analyses in health care, the radiation oncology community must possess a sophisticated understanding of the methodological considerations of such studies in order to evaluate evidence appropriately to guide practice and policy. Because observational research has unique features that distinguish it from clinical trials and other forms of traditional radiation oncology research, the International Journal of Radiation Oncology, Biology, Physics assembled a panel of experts in health services research to provide a concise and well-referenced review, intended to be informative for the lay reader, as well as for scholars who wish to embark on such research without prior experience. This review begins by discussing the types of research questions relevant to radiation oncology that large-scale databases may help illuminate. It then describes major potential data sources for such endeavors, including information regarding access and insights regarding the strengths and limitations of each. Finally, it provides guidance regarding the analytical challenges that observational studies must confront, along with discussion of the techniques that have been developed to help minimize the impact of certain common analytical issues in observational analysis. Features characterizing a well-designed observational study include clearly defined research questions, careful selection of an appropriate data source, consultation with investigators with relevant methodological expertise, inclusion of sensitivity analyses, caution not to overinterpret small but significant differences, and recognition of limitations when trying to evaluate causality. This review concludes that carefully designed and executed studies using observational data that possess these qualities hold substantial promise for advancing our understanding of many unanswered questions of importance to the field of radiation oncology. PMID:25195986

Jagsi, Reshma; Bekelman, Justin E; Chen, Aileen; Chen, Ronald C; Hoffman, Karen; Shih, Ya-Chen Tina; Smith, Benjamin D; Yu, James B

2014-09-01

146

Nystagmus induced by circular head shaking in normal human subjects.  

PubMed

We recorded three-dimensional eye and head movements during circular, horizontal, vertical, and torsional head shaking in six human subjects with normal vestibular function. With circular head shaking, the stimulation of the canals by the termination of the head movement is similar to that following a step in velocity about the naso-occipital axis. A large torsional nystagmus with slow phase eye velocity of about 20 degrees/s was observed upon cessation of circular head shaking. The three-dimensional eye movements expected from stimulation of the semicircular canals by the head-shaking maneuvers were calculated. The predicted activation of the canals was determined by projecting the head velocity (in head coordinates) into the canal planes and then processing the signal with the transfer function of the canals. The torsional eye velocity components predicted by the stimulation of the canals matched the recorded ones. We observed small horizontal eye velocities that could not be predicted by the stimulation of the canals alone. No eye movements were observed after the end of head shaking about a fixed horizontal or vertical axis. The eye velocities following the termination of head oscillations in the roll plane were small. The analysis methods developed for this study may be useful in the investigation of eye movements elicited by other types of three-dimensional head movements. PMID:9928786

Haslwanter, T; Minor, L B

1999-01-01

147

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

148

The deterioration of Circular Mausoleum, Roman Necropolis of Carmona, Spain.  

PubMed

The Circular Mausoleum tomb in the Roman Necropolis of Carmona was carved on a calcarenite sequence in an ancient quarry located in the town of Carmona, Southern Spain. This rock-cut tomb, representative of Roman burial practices, currently suffers from serious deterioration. A detailed survey over several years permitted the identification of the main tomb's pathologies and damaging processes, which include loss of material (scaling, flaking, granular disintegration), surface modifications (efflorescences, crusts and deposits) and extensive biological colonization. The results obtained in this study indicated that anthropogenic changes were largely responsible and enhanced the main alteration mechanisms observed in the Circular Mausoleum. Based on the deterioration diagnosis, effective corrective actions were proposed. This study shows that any conservative intervention in the interior of the tomb should be preceded by accurate in situ measurements and laboratory analyses to ascribe the source of the deterioration damages and thus designing effective treatments. PMID:25747366

Cañaveras, Juan C; Fernandez-Cortes, Angel; Elez, Javier; Cuezva, Soledad; Jurado, Valme; Miller, Ana Zelia; Rogerio-Candelera, Miguel A; Benavente, David; Hernandez-Marine, Mariona; Saiz-Jimenez, Cesareo; Sanchez-Moral, Sergio

2015-06-15

149

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

NASA Technical Reports Server (NTRS)

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

Willson, Robert F.

1991-01-01

150

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

NASA Astrophysics Data System (ADS)

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

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

1993-06-01

151

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

NASA Technical Reports Server (NTRS)

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

Lang, K. R.

1986-01-01

152

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

153

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

NASA Technical Reports Server (NTRS)

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

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

2013-01-01

154

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

NASA Astrophysics Data System (ADS)

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

Schumann, G. J.; Andreadis, K.

2012-12-01

155

Very Large Array and Jansky Very Large Array Observations of the Compact Radio Sources in M8  

NASA Astrophysics Data System (ADS)

We analyze high-resolution Very Large Array continuum observations of the M8 region carried out at several epochs that span a period of 30 yr. Our maps reveal two compact sources. One is associated with Her 36 SE, a possible companion of the O7 luminous massive star Her 36, and the other is associated with G5.97-1.17, whose proplyd nature was previously established. Using the analyzed data, we do not find significant time variability in any of these sources. The derived spectral index of >=0.1 for Her 36 SE, the marginal offset of the radio emission with the previous infrared detection, and the associated X-ray emission previously reported suggest the presence of an unresolved interaction region between the strong winds of Her 36 and Her 36 SE. This region would contribute non-thermal contamination to the global wind emission of Her 36, flattening its spectral index. On the other hand, the emission of G5.97-1.17 can also be explained by a mixture of thermal and non-thermal emission components, with different relative contributions of both emission mechanisms along the proplyd. We argue that the shock created by the photo-evaporation flow of the proplyd with the collimated stellar wind of Her 36 accelerates charged particles in G5.97-1.17, producing considerable synchrotron emission. On the contrary, an electron density enhancement at the southwest of G5.97-1.17 makes the thermal emission dominant over this region.

Masqué, Josep M.; Dzib, Sergio; Rodríguez, Luis F.

2014-12-01

156

VizieR Online Data Catalog: VLTI/MIDI AGN Large Program observations (Burtscher+, 2013)  

NASA Astrophysics Data System (ADS)

All interferometric observations were carried out with MIDI, the MID-infrared interferometric Instrument at the European Southern Observatory's (ESO's) Very Large Telescope Interferometer (VLTI) on Cerro Paranal, Chile. The MIDI AGN Large Program (ESO program number 184.B-0832) consisted of 13.1 nights of Visitor Mode observations. Between December 2009 and August 2011, in total 228 science fringe track observations of 15 AGNs have been observed in this program. For this paper, we also include from the archive 159 previously observed tracks for these sources, 156 fringe tracks of other weak AGNs and 132 tracks for the two mid-IR brightest AGNs (NGC 1068 and the Circinus galaxy). The observing logs of each galaxy can be upload in the subdirectory log. OIFITS is the standard for the exchange of reduced optical interferometry data. It is an IAU accepted standard and defined in Pauls et al. (2005PASP..117.1255P). Since we use a special observing technique, detailed in the paper, our primary observable is not the visibility but the "correlated flux". This is not yet part of the OIFITS specification (version 1), but is currently discussed for OIFITS version 2.0 (http://ipag.obs.ujf-grenoble.fr/twiki/bin/view/Jmmc/OIFITSTwoProject# Proposalforcorrelated_flux). For the attached data I include both the standard VISAMP/VISAMPERR fields which is the corr. flux divided by the spectrum used for this source (from VISIR, if available, for all sources except Mrk 1239, see the paper) and also new CFLUX/CFLUXERR fields that are proposed for OIFITS version 2.0. These fields comply with the FITS standard and are ignored by strict OIFITS viewers; less strict OIFITS readers like MIA+EWS's oirgetvis() routine will read these fields. For NGC 1068, I have downsampled the early GRISM observations to PRISM resolution so that they can be combined in one file. The total flux can be retrieved from CFLUX/VISAMP and its error from flux * sqrt((VISAMPERR/VISAMP)2 - (CFLUXERR/CFLUX)2). (5 data files).

Burtscher, L.; Meisenheimer, K.; Tristram, K. R. W.; Jaffe, W.; Honig, S. F.; Davies, R. I.; Kishimoto, M.; Pott, J.-U.; Rottgering, H.; Schartmann, M.; Weigelt, G.; Wolf, S.

2013-10-01

157

Squaring a Circular Segment  

ERIC Educational Resources Information Center

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

Gordon, Russell

2008-01-01

158

EXPANDED VERY LARGE ARRAY CONTINUUM OBSERVATIONS TOWARD HOT MOLECULAR CORE CANDIDATES  

SciTech Connect

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

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

2011-09-20

159

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

NASA Astrophysics Data System (ADS)

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

Ilonidis, Stathis; Zhao, Junwei

2014-06-01

160

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

161

SWAP Observations of the Long-Term, Large-Scale Evolution of the EUV Solar Corona  

E-print Network

The Sun Watcher with Active Pixels and Image Processing (SWAP) EUV solar telescope on board the Project for On-Board Autonomy 2 (PROBA2) spacecraft has been regularly observing the solar corona in a bandpass near 17.4 nm since February 2010. With a field-of-view of 54x54 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 (PSF) 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 persiste...

Seaton, Daniel B; Shearer, Paul; Berghmans, David; Nicula, Bogdan

2013-01-01

162

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

163

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

164

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

165

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

NASA Technical Reports Server (NTRS)

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

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

2011-01-01

166

Observations of two peculiar emission objects in the Large Magellanic Cloud  

NASA Technical Reports Server (NTRS)

Ultraviolet and visual wavelength spectra were obtained of two peculiar emission objects, Henize S63 and Sanduleak's star in the Large Magellanic Cloud. Previously not observed in the near- or far-ultraviolet, both objects exhibit strong permitted and semiforbidden line emissions. Estimates based on the absolute continuum flux of the hot companion star in Hen S63 indicate that it rivals the luminosity of the carbon star primary. The emission-line profile structure in both objects does not suggest Wolf-Rayet type emission. Carbon in Sanduleak's star (LMC anonymous) is conspicuously absent, while N V, semiforbidden N IV, and semiforbidden N III dominate the UV emission-line spectrum. Nitrogen is overabundant with respect to carbon and oxygen in both objects. The large overabundance of nitrogen in Sanduleak's star suggests evidence for CNO processes material similar to that seen in Nu Car.

Kafatos, M.; Michalitsianos, A. G.; Allen, D. A.; Stencel, R. E.

1983-01-01

167

Interpreting observed northern hemisphere snow trends with large ensembles of climate simulations  

NASA Astrophysics Data System (ADS)

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

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

2014-07-01

168

Observation of EUV spectra from gadolinium and neodymium ions in the Large Helical Device  

NASA Astrophysics Data System (ADS)

We have observed extreme ultraviolet (EUV) spectra from highly charged gadolinium and neodymium ions in optically thin plasmas produced in the Large Helical Device at the National Institute for Fusion Science. Time evolutions of EUV spectra in the 6-9 nm region following injection of a solid pellet into a hydrogen plasma were measured by a grazing incidence spectrometer with a frame rate of 0.2 s. Three different types of spectral features have been observed depending on the electron temperature. Discrete spectral lines of Ni- and Cu-like gadolinium and neodymium ions were identified when the peak electron temperature was around 2 keV, while some lines of Ag-like gadolinium ions were found in the plasma with temperatures below 240 eV when an unusual hollow plasma was formed. Under the intermediate temperature, a quasi-continuum spectral feature arising from an unresolved transition array from open 4p/4d subshell ions is predominant.

Suzuki, C.; Koike, F.; Murakami, I.; Tamura, N.; Sudo, S.

2012-07-01

169

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

170

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

E-print Network

Events with a large rapidity gap and total transverse energy greater than 5 GeV have been observed in quasi-real photoproduction at HERA with the ZEUS detector. The distribution of these events as a function of the $\\gamma p$ centre of mass energy is consistent with diffractive scattering. For total transverse energies above 12 GeV, the hadronic final states show predominantly a two-jet structure with each jet having a transverse energy greater than 4 GeV. For the two-jet events, little energy flow is found outside the jets. This observation is consistent with the hard scattering of a quasi-real photon with a colourless object in the proton.

ZEUS Collaboration

1995-01-25

171

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

172

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

173

Generation of bright circularly-polarized extreme ultraviolet high harmonics for magnetic circular dichroism spectroscopy  

E-print Network

Circularly-polarized extreme UV and X-ray radiation provides valuable access to the structural, electronic and magnetic properties of materials. To date, such experiments have been possible only using large-scale free-electron lasers or synchrotrons. Here we demonstrate the first bright extreme UV circularly-polarized high harmonics and use this new light source for magnetic circular dichroism measurements at the M-shell absorption edges of cobalt. This work paves the way towards element-specific imaging and spectroscopy of multiple elements simultaneously in magnetic and other chiral media with very high spatio-temporal resolution, all on a tabletop.

Kfir, Ofer; Turgut, Emrah; Knut, Ronny; Zusin, Dmitriy; Popmintchev, Dimitar; Popmintchev, Tenio; Nembach, Hans; Shaw, Justin M; Fleicher, Avner; Kapteyn, Henry; Murnane, Margaret; Cohen, Oren

2014-01-01

174

Interpreting Observed Arctic Snow Trends with Large Ensembles of Climate Simulations  

NASA Astrophysics Data System (ADS)

Snow is a key element of the Northern Hemisphere's energy budget, water balance, and climate sensitivity. While Northern Hemisphere mean snowfall and snow accumulation are expected to decrease as a result of warming caused by greenhouse gas emissions, combined changes in the temperature and precipitation patterns are complex enough to cause marked regional variations of either sign. Accurately predicting such regional changes in the coming decades is predicated on being able to properly simulate historical changes and being able to separate forced signals from climate noise. We present an analysis of Northern Hemisphere snow and temperature trends using large ensembles (20+ members) of the Community Earth System Model. We have generated two such large ensembles forced with historical emissions of greenhouse gases, aerosols and ozone during the period 1981-2010. The first ensemble uses a coupled ocean-atmosphere setup with a freely evolving ocean; the second uses the same atmospheric model forced by observed sea surface temperatures. Our results show that while the model is able to reproduce the observed climatology and variability of snow cover extent (as well as snow water equivalent to a lesser degree of fidelity), internal climate noise generates different spatial patterns of snow trends in different climate realizations. These patterns are related in an intuitive way to the temperature and circulation. While both ensembles capture the overall decreasing trend in snow cover extent observed during the spring season, there are differences in their magnitudes and spatial distribution. Following Shin and Sardeshmukh [2010], we discuss the role of the magnitude and spatial pattern of the sea surface temperature trends as they relate to the resulting snow trends. These connections promise to aid in interpretation of observations.

Mudryk, L. R.; Kushner, P. J.

2012-12-01

175

Large Amplitude Whistlers in the Magnetosphere Observed with Wind-Waves  

NASA Technical Reports Server (NTRS)

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

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

2011-01-01

176

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

SciTech Connect

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

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

2013-03-20

177

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

NASA Astrophysics Data System (ADS)

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

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

2014-11-01

178

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

179

The circular internal hydraulic jump  

NASA Astrophysics Data System (ADS)

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

Thorpe, S. A.; Kavcic, I.

180

Confronting the relaxation mechanism for a large cosmological constant with observations  

SciTech Connect

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

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

2012-01-01

181

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

NASA Technical Reports Server (NTRS)

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

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

2013-01-01

182

Large 0/12 GMT Differences of US Vaisala RS80 Observations  

NASA Technical Reports Server (NTRS)

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

Redder, Chris; Atlas, Robert (Technical Monitor)

2002-01-01

183

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

NASA Technical Reports Server (NTRS)

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

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

2014-01-01

184

Forthcoming Coronal Mass Ejection Observations with the Very Large Array (VLA)  

NASA Astrophysics Data System (ADS)

It is widely recognized that measurement of Faraday rotation through a coronal mass ejection (CME) provides unique information on the internal plasma structure of the CME, particularly the form of the magnetic field. The Faraday rotation measure is proportional to the path integral through the CME of the electron density and the line-of-sight component of the magnetic field. In spite of this importance, there are relatively few measurements of Faraday rotation produced by a CME. The Very Large Array (VLA) of the National Radio Astronomy Observatory is an outstanding instrument for measurement of Faraday rotation, and its capabilities have been greatly improved by an upgrade over the past decade. In the case of VLA observations, the trans-coronal sources of radio waves are radio galaxies and quasars. A difficulty in measuring Faraday rotation of a CME is the unpredictability of the CME phenomenon. It is difficult to predict whether a given line of sight to a background source will be occulted by a CME on a given day. We have received approval to carry out ``triggered'' CME observations with the VLA in the summer of 2015. In these observations, we will rely on coronagraph detections of a CME to initiate VLA observations of select background sources. This observing mode will improve on one previously used, in which a decision to observe had to be made a day or more in advance. The goal of these observations will be to secure Faraday rotation measurements on one or more lines of sight that pass through critical parts of a CME. In this paper, we will describe our planned triggering scheme, the selection of background sources, choice of observing frequency and selection of lines of sight that can best determine the plasma structure of a CME. Our planning also depends on prior experience in measurement of coronal Faraday rotation, and Faraday rotation ``transients'' associated with CMEs. This work was supported at the University of Iowa by grant ATM09-56901 from the National Science Foundation.

Spangler, Steven R.; Kooi, Jason E.; Sink, Joseph R.

2015-04-01

185

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

NASA Astrophysics Data System (ADS)

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

Czakon, Nicole G.

186

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

NASA Astrophysics Data System (ADS)

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

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

2014-06-01

187

Ionospheric observations of Underground Nuclear Explosions (UNE) using GPS and the Very Large Array  

E-print Network

Observations from 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 573m/s and 740m/s with standard deviations of 85m/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; Grejner-Brzezinska, Dorota A; von Frese, Ralph R B; Wilson, Thomas

2013-01-01

188

Very Large Telescope observations of Gomez's Hamburger: Insights into a young protoplanet candidate  

E-print Network

Planets are thought to form in the gas and dust disks around young stars. In particular, it has been proposed that giant planets can form via gravitational instability of massive extended disks around intermediate mass stars. However, direct observations to constrain this mechanism lack. We have spatially resolved the 8.6 and 11.2 $\\mu$m emission of a massive edge on protoplanetary disk around an A star, Gomez's Hamburger (GoHam), using VISIR at the Very Large Telescope. A compact region situated at a projected distance of $350\\pm50$ AU South of the central star is found to have a reduced emission. This asymmetry is fully consistent with the presence of a cold density structure, or clump, identified in earlier CO observations, and we derive physical characteristics consistent with those observations: a mass of 0.8-11.4 Jupiter masses (for a dust to gas mass ratio of 0.01), a radius of the order of 10$^2$ astronomical units, a local density of the order of $10^{7}$ cm$^{-3}$. Based on this evidence, we argue t...

Berne, O; Pantin, E; Bujarrabal, V; Baruteau, C; Pilleri, P; Habart, E; Menard, F; Cernicharo, J; Tielens, A; Joblin, C

2015-01-01

189

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

190

Simultaneous radio interferometer and optical observations of ionospheric structure at the Very Large Array  

NASA Astrophysics Data System (ADS)

Radio astronomers are searching the cosmos for new scientific discoveries at increasingly lower radio frequencies and with larger antenna arrays, but their observations of the sky are blurred by the dynamic ionosphere. At the same time, ionospheric scientists are seeking to understand, at increasingly higher spatial and temporal resolutions, the dynamics that drive the ionosphere and its effects on technological systems. Advancements in radio astronomy at the Very Large Array (VLA) are leading to advancements in ionospheric physics and vice versa. We review some of the ionospheric observations made by the VLA at low frequency. Results from a 2003 summer campaign at the VLA are discussed, during which an all-sky optical camera was used to monitor ionospheric structure during VLA 74-MHz operations. The camera and additional off-site sensors, including ionosondes and incoherent scatter radar, were used to identify the dominant, summer nighttime ionospheric phenomena contributing to VLA signal distortion. Knowledge of the specific phenomena, including their spatial and temporal characteristics, can be used to improve low-frequency, astronomical imaging. Similarly, the VLA observations can be used to investigate ionospheric phenomena in great detail, leading to an improved understanding of ionospheric physics. Key to these findings is the identification of specific ionospheric phenomena using support sensors. Implications for the development of the Long Wavelength Array are discussed.

Coker, Clayton; Thonnard, Stefan E.; Dymond, Kenneth F.; Lazio, T. Joseph W.; Makela, Jonathan J.; Loughmiller, Pamela J.

2009-07-01

191

Enhanced light extraction from circular Bragg grating coupled microcavities  

NASA Astrophysics Data System (ADS)

A sevenfold enhancement of light extraction over a 130nm bandwidth from a semiconductor at room temperature was achieved using circular Bragg gratings (CBGs) etched around the periphery of a vertical-cavity light-emitting structure. The CBG defined an in-plane circular cavity for light trapped in guided modes. Maximum enhancement was observed with CBGs that efficiently coupled circular cavity modes into resonant extracted modes of the vertical cavity. The enhancement factor corresponded to a 41% external efficiency.

Su, Mark Y.; Mirin, Richard P.

2006-07-01

192

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. PMID:22700959

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

2012-01-01

193

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

SciTech Connect

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

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

1997-06-22

194

Two-dimensional curvature of large angle interplanetary MHD discontinuity surfaces: IMP-8 and WIND observations  

NASA Astrophysics Data System (ADS)

This study examines the degree of two-dimensional 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" of 90° or greater. The discontinuity angle (?) is measured in the DD's current sheet, the normal (n) to which is estimated by field variance analysis. The fundamental analysis depends on estimates of these DD surface normals at the two spacecraft and the DD's center-times and positions. On average, the transit time from one DD sighting to the other was 36 minutes, and the associated distance along the normal direction was 137 RE. The transition-interval lengths across the DDs are translated into thicknesses and examined for the amount of change between the two spacecraft observing points. The average thickness is relatively large, 14 RE.; the most probable thickness is ?6 RE. All relevant quantities are examined statistically to establish their distributions, average, and degree of change. A weighted average of the radius of curvature is estimated to be 380 RE, but its most probable value is 290 RE. The average ? is 140° with a relatively large spread (? = 28°). The average direction of propagation is: longitude (?n) = 194° and latitude (?n) = 7° (but = 27°), where ?n = 0° is sunward and ?n = 0° is the ecliptic plane. Various parameters are studied with respect to DD type, i.e., rotational or tangential discontinuity (RD or TD), defined in terms of the "ratio" (in percent) of speed of propagation to net speed of the DD surface, where the net speed is the sum of the convection velocity (along n) plus the propagation speed. The RD %-ratio is moderately small, but the TD ratio is very small or zero. The results by this definition of type are favorably compared to those from the more conventional method, which depends on the absolute strength of the normal component of the magnetic field. There is little difference in any average parameter value according to type. However, the average appears to depend slightly on type with the for the RDs being smaller. The discontinuity type was shown to change commonly in either direction (TD to RD or RD to TD) between the two observing positions, i.e., ?40% of the time. It is not clear if these type-changes are spatial or temporal. Shortcomings of the analysis are (1) the need to impose an upper limit on the angular difference of the DD normals between the two observing positions (which eliminated most surfaces of very small radii of curvature), and (2) the inability to distinguish real curvature from shorter-scale surface variations, from only two spacecraft data sets. The results of the study should help to caution us as to the simplistic use of the planar DD surface assumption in projecting, to the distance of Earth's magnetosphere, a distantly observed DD surface (e.g., one near L1), especially for studies that depend on accurately predicting the timing and characteristics of magnetospheric events.

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

2003-07-01

195

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

NASA Astrophysics Data System (ADS)

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

Lonsdale, Carol J.; Hacking, Perry B.

1989-04-01

196

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

NASA Astrophysics Data System (ADS)

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

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

2014-07-01

197

Large Angular Jump Mechanism Observed for Hydrogen Bond Exchange in Aqueous Perchlorate Solution  

SciTech Connect

The mechanism for hydrogen bond (H-bond) switching in solution has remained subject to debate despite extensive experimental and theoretical studies. We have applied polarization-selective multidimensional vibrational spectroscopy to investigate the H-bond exchange mechanism in aqueous NaClO{sub 4} solution. The results show that a water molecule shifts its donated H-bonds between water and perchlorate acceptors by means of large, prompt angular rotation. Using a jump-exchange kinetic model, we extract an average jump angle of 49 {+-} 4{sup o}, in qualitative agreement with the jump angle observed in molecular dynamics simulations of the same aqueous NaClO{sub 4} solution.

Ji, Minbiao; /SLAC, PULSE /Stanford U., Phys. Dept.; Odelius3, Michael; /Stockholm U.; Gaffney1, K.J.; /aff SLAC, PULSE

2010-06-11

198

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

NASA Technical Reports Server (NTRS)

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

Lonsdale, Carol J.; Hacking, Perry B.

1989-01-01

199

Merged interaction regions and large-scale magnetic field fluctuations during 1991: Voyager 2 observations  

NASA Technical Reports Server (NTRS)

This paper analyzes Voyager 2 observations of the magnetic field between 33.6 AU and 36.2 AU during 1991 when extraordinary events were observed on the Sun and in the heliosphere. The magnetic field strength signal B(t) has the unusual form of two large transient merged interaction regions (MIRs) on a fluctuating background. The two MIRs moved past the spacecraft in 32 days and 18 days, respectively. The mean field strength in each transient MIR was approx. equals 2.6 times the mean field during the remaining part of the year (0.11 nT). Each of the MIRs is related to a fast stream. The magnetic field is strong throughout each stream, suggesting that the strong fields are carried by the streams as well as produced by shock and stream compression. The fluctuations in B(t) during 1991 are not multifractal, and the MIRs cannot be approximated as multifractal clusters of intense magnetic fields. The distribution of the hour-averaged magnetic field strengths is approximately lognormal over 90% of its intermediate range, and it has an exponential tail for B greater than the average magnetic field strength. The elevation angles of B have a normal distribution with a standard deviation of 16 deg +/- 4 deg. The distributions of the azimuthal angles of B in the ranges 1 deg - 180 deg and 180 deg - 360 deg are approximately normal over a more limited range, and non-Gaussian tails associated with nearly radial magnetic fields; the standard deviations are approx. equal to 40 deg. Individual sectors are present throughout most of the interval, even in the MIRs, but there is no recurrent sector pattern. A model of the large-scale fluctuations in 1991 will have to include both determinaistic and statistical factors.

Burlaga, L. F.; Ness, N. F.

1994-01-01

200

Observing the Moon at Microwave Frequencies Using a Large-Diameter Deep Space Network Antenna  

NASA Astrophysics Data System (ADS)

The Moon radiates energy at infrared and microwave wavelengths, in addition to reflecting sunlight at optical wavelengths. As a result, an antenna pointed at or near the Moon will result in an increase in system operating noise temperature, which needs to be accounted for in RF telecommunications, radio science or radiometric link calculations. The NASA Deep Space Network (DSN) may use its large-diameter antennas in future lunar robotic or human missions, and thus it is important to understand the nature of this temperature incre ase as a function of observing frequency, lunar phase, and angular position of the antenna beam on the lunar disk. This paper reports on a comprehensive lunar noise temperature measurement campaign and associated theoretical treatment for a 34-m diameter Deep Space Network antenna observing an extended source such as the Moon. A set of measurements over a wide range of lunar phase angles was acquired at DSS-13, a 34-m diameter beam waveguide antenna (BWG) located at Goldstone, California at 2.3 GHz (S-band), 8.4 GHz (X-band) and 32 GHz (Ka-band). For validation purposes, independent predictions of noise temperature increase were derived using a physical optics characterization of the 34-m diameter antenna gain patterns and Apollo model-based brightness temperature maps of the Moon as input. The model-based predictions of noise temperature increase were compared with the measurements at all three frequencies. In addition, a methodology is presented that relates noise temperature increase due to the Moon to disk-centered or disk-averaged brightness temperature of the Moon at the microwave frequencies of interest. Comparisons were made between the measurements and models in the domain of lunar disk-centered and disk-averaged brightness temperatures. It is anticipated that the measurements and associated theoretical development will be useful in developing telecommunications strategies for future high-rate Ka-band communications where large diameter DSN antennas will be required.

Morabito, David D.; Imbriale, William; Keihm, Stephen

2008-03-01

201

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

NASA Astrophysics Data System (ADS)

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

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

2014-08-01

202

An interactive environment for the analysis of large Earth observation and model data sets  

NASA Technical Reports Server (NTRS)

Envision is an interactive environment that provides researchers in the earth sciences convenient ways to manage, browse, and visualize large observed or model data sets. Its main features are support for the netCDF and HDF file formats, an easy to use X/Motif user interface, a client-server configuration, and portability to many UNIX workstations. The Envision package also provides new ways to view and change metadata in a set of data files. It permits a scientist to conveniently and efficiently manage large data sets consisting of many data files. It also provides links to popular visualization tools so that data can be quickly browsed. Envision is a public domain package, freely available to the scientific community. Envision software (binaries and source code) and documentation can be obtained from either of these servers: ftp://vista.atmos.uiuc.edu/pub/envision/ and ftp://csrp.tamu.edu/pub/envision/. Detailed descriptions of Envision capabilities and operations can be found in the User's Guide and Reference Manuals distributed with Envision software.

Bowman, Kenneth P.; Walsh, John E.; Wilhelmson, Robert B.

1994-01-01

203

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

NASA Astrophysics Data System (ADS)

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

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

2014-05-01

204

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

NASA Technical Reports Server (NTRS)

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

Sumida, John

2002-01-01

205

Circular analysis in systems neuroscience: the dangers of double dipping  

Microsoft Academic Search

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

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

2009-01-01

206

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

SciTech Connect

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

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

2009-06-10

207

Observations of energetic particles with STEREO: events with large longitudinal spread  

NASA Astrophysics Data System (ADS)

The two STEREO spacecraft perform Earth-like orbits around the Sun with an increasing longitudinal separation to the Earth of ~22 degrees per year. A 360 degree view of the Sun was reached in February 2011, providing multi-point in-situ and remote-sensing observations of unprecedented quality. Together with close to Earth measurements, the STEREO spacecraft build an optimal platform to study solar energetic particles (SEPs) and its longitudinal variations with minimal radial gradient effects. While solar activity finally began to rise after the very deep minimum in 2010 to 2011, the STEREO spacecraft had reached a sufficient longitudinal separation to detect and investigate events with large longitudinal spreads. The mechanisms producing these unexpected wide particle spreads are subject to recent research. Comprehensive observations and modeling tools are put forth to disentangle source and transport processes. The efficiency of perpendicular diffusion in the interplanetary medium versus coronal transport, as well as the role of coronal shocks, EUV waves, and CMEs will be discussed.

Dresing, Nina; Droege, Wolfgang; Kartavykh, Yulia; Klassen, Andreas; Malandraki, Olga; Gomez-Herrero, Raul; Heber, Bernd

208

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

NASA Astrophysics Data System (ADS)

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

Bourassa, M. A.

2012-12-01

209

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

NASA Astrophysics Data System (ADS)

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

Wilhelmus, Monica M.; Dabiri, John O.

2014-10-01

210

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

NASA Technical Reports Server (NTRS)

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

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

1989-01-01

211

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

212

Circular Motion and Forces  

NSDL National Science Digital Library

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

Wolfgang Christian

213

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

214

Wiimote Experiments: Circular Motion  

NASA Astrophysics Data System (ADS)

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

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

2013-03-01

215

The Right Circular Cylinder  

NSDL National Science Digital Library

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

2010-12-02

216

The Right Circular Cone  

NSDL National Science Digital Library

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

2011-01-18

217

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

218

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

SciTech Connect

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

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

2013-04-10

219

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

220

Exploring the origin of a large cavity in Abell 1795 using deep Chandra observations  

NASA Astrophysics Data System (ADS)

We examine deep stacked Chandra observations of the galaxy cluster Abell 1795 (over 700 ks) to study in depth a large (34 kpc radius) cavity in the X-ray emission. Curiously, despite the large energy required to form this cavity (4PV = 4 × 1060 erg), there is no obvious counterpart to the cavity on the opposite side of the cluster, which would be expected if it has formed due to jets from the central active galactic nucleus (AGN) inflating bubbles. There is also no radio emission associated with the cavity, and no metal enhancement or filaments between it and the brightest cluster galaxy, which are normally found for bubbles inflated by AGN which have risen from the core. One possibility is that this is an old ghost cavity, and that gas sloshing has dominated the distribution of metals around the core. Projection effects, particularly the long X-ray bright filament to the south-east, may prevent us from seeing the companion bubble on the opposite side of the cluster core. We calculate that such a companion bubble would easily have been able to uplift the gas in the southern filament from the core. Interestingly, it has recently been found that inside the cavity is a highly variable X-ray point source coincident with a small dwarf galaxy. Given the remarkable spatial correlation of this point source and the X-ray cavity, we explore the possibility that an outburst from this dwarf galaxy in the past could have led to the formation of the cavity, but find this to be an unlikely scenario.

Walker, S. A.; Fabian, A. C.; Kosec, P.

2014-12-01

221

Infrared circular dichroism and linear dichroism spectrophotometer.  

PubMed

An instrument for the measurement of circular dichroism (CD) between 5000 cm(-1) and 750 cm(-1) is described. This instrument also can perform high precision linear dichroism measurements in the same wavelength range. A germanium photoelastic modulator having a large linear and angular aperture is used to vary the polarization of monochromatic ir light between left- and right-circularly polarized at 8 kHz. This polarization-modulated light traverses the sample and falls onto a cooled InSb or HgCdTe detector. Phase-sensitive demodulation yields the CD of the sample to a precision of 4 x 10(-6) o.d. units near 3000 cm(-1). The instrument has been used to study ir circular dichroism arising from molecular vibrations in cholesteric liquid crystals, crystals, and fluids. CD arising from low-lying electronic transitions of metal complexes and linear dichroism of polymer films have also been studied. PMID:20134906

Chabay, I; Holzwarth, G

1975-02-01

222

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

NASA Technical Reports Server (NTRS)

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

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

2009-01-01

223

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

SciTech Connect

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

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

2000-07-01

224

Progress in circular dichroism laser mass spectrometry.  

PubMed

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

Logé, Christoph; Bornschlegl, Alexander; Boesl, Ulrich

2009-11-01

225

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

226

Solar Observations with the Atacama Large Millimeter/submillimeter Array (ALMA)  

NASA Astrophysics Data System (ADS)

The Atacama Large Millimeter/Submillimeter Array (ALMA) is a joint North American, European, and East Asian project that opens the mm-submm wavelength part of the electromagnetic spectrum for general astrophysical exploration, providing high-resolution imaging in frequency bands currently ranging from 84 GHz to 950 GHz (300 microns to 3 mm). Despite being a general purpose instrument, provisions have been made to enable solar observations with ALMA. Radiation emitted at ALMA wavelengths originates mostly from the chromosphere, which plays an important role in the transport of matter and energy, and the in heating the outer layers of the solar atmosphere. Despite decades of research, the solar chromosphere remains a significant challenge: both to observe, owing to the complicated formation mechanisms of currently available diagnostics; and to understand, as a result of the complex nature of the structure and dynamics of the chromosphere. ALMA has the potential to change the scene substantially as it serves as a nearly linear thermometer at high spatial and temporal resolution, enabling us to study the complex interaction of magnetic fields and shock waves and yet-to-be-discovered dynamical processes. Moreover, ALMA will play an important role in the study of energetic emissions associated with solar flares at sub-THz frequencies.In this paper we describe recent efforts to ensure that ALMA can be usefully exploited by the scientific community to address outstanding questions in solar physics. We summarize activities by the ALMA solar development team comprised of scientists from the East Asia, North America, and Europe. These activities include instrument testing, development of calibration and imaging strategies, software requirements development, and science simulations. Opportunities for the wider community to contribute to these efforts will be highlighted.

Bastian, Timothy S.

2015-04-01

227

Multiwavelength observation of a large-scale flux rope eruption above a kinked small filament  

NASA Astrophysics Data System (ADS)

We analyzed multiwavelength observations of a western limb flare (C3.9) that occurred in AR NOAA 111465 on 30 April 2012. The high-resolution images recorded by SDO/AIA 304, 1600 Å and Hinode/SOT H? show the activation of a small filament (rising speed ~40 km s-1) associated with a kink instability and the onset of a C-class flare near the southern leg of the filament. The first magnetic reconnection occurred at one of the footpoints of the filament and caused the breaking of its southern leg. The filament shows unwinding motion of the northern leg and apex in counterclockwise direction and failed to erupt. A flux-rope structure (visible only in hot channels, i.e., AIA 131 and 94 Å and Hinode/SXT) appeared along the neutral line during the second magnetic reconnection that occurred above the kinked filament. The formation of the RHESSI hard X-ray source (12-25 keV) above the kinked filament and the simultaneous appearance of the hot 131 Å loops associated with photospheric brightenings (AIA 1700 Å) indicates the particle acceleration along these loops from the top of the filament. In addition, extreme ultraviolet disturbances or waves observed above the filament in 171 Å also show a close association with magnetic reconnection. The flux rope rises slowly (~100 km s-1), which produces a very large twisted structure possibly through reconnection with the surrounding sheared magnetic fields within ~15-20 min, and showed an impulsive acceleration reaching a height of about 80-100 Mm. AIA 171 and SWAP 174 Å images reveal a cool compression front (or coronal mass ejection frontal loop) surrounding the hot flux rope structure. Movies associated with Figs. 2 and 7 are available in electronic form at http://www.aanda.org

Kumar, Pankaj; Cho, Kyung-Suk

2014-12-01

228

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

NASA Technical Reports Server (NTRS)

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

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

2013-01-01

229

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

NASA Technical Reports Server (NTRS)

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

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

1994-01-01

230

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

SciTech Connect

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

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

2012-09-19

231

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

NASA Technical Reports Server (NTRS)

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

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

1995-01-01

232

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

PubMed Central

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

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

2010-01-01

233

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

SciTech Connect

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

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

1989-04-01

234

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

PubMed

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

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

2014-04-18

235

Satellite and ground based observations of a large-scale electron precipitation event  

NASA Astrophysics Data System (ADS)

In order to describe how geomagnetic storms couple to the upper atmosphere, and hence to atmospheric chemistry and dynamics, measurements are required of energetic electron precipitation into the atmosphere. However, satellite observations are currently poorly suited to providing measurements of energetic and relativistic electron precipitation. The AARDDVARK network (Antarctic-Arctic Radiation-belt (Dynamic) Deposition - VLF Atmospheric Research Konsortium) provides continuous long-range observations of ionisation levels from ~30-85 km altitude, with the goal of increasing the understanding of energy coupling between the Earth's atmosphere, Sun, and Space. In this study we combine AARDDVARK subionospheric VLF measurements with DEMETER electron spectra using modelling techniques to study >100 keV energetic and relativistic electron precipitation into the atmosphere for the 24-hour period beginning 0600UT 19 January during the 17-21 January 2005 geomagnetic storms. The study augments large-scale regional observations using VLF measurements of multiple subionospheric paths to our receiver at Sodankylä, Finland (67.4°N, 26.6°E, L=5.31), combined with detailed in situ measurements from the DEMETER satellite to allow the spatial extent, flux, and energy distribution of the precipitation to be determined. In contrast to other satellites, DEMETER’s electron spectrometer has excellent energy resolution. The DEMETER-measured precipitation spectrum is used to infer an altered electron density profile, modelled using a simple ionospheric electron model. This altered electron profile is then used in a subionospheric VLF model and compared with AARDDVARK VLF results. Matching model results with subionospheric VLF measurements allows calculation of both the intensity and geographic extent (in L) of the precipitation region required to produce such an effect. We find that a flux of 7000 elec.cm-2s-1 >100 keV electrons precipitates into the atmosphere over an L range of 3.5-4.0. An error analysis is also included. By providing a better picture of both the intensity and size of the precipitation region, we obtain a more complete picture of the net impact that such a precipitation event has on the upper atmosphere. The results of this analysis will become primary inputs to chemical modelling of the impact that this precipitation has on the neutral atmosphere.

Gamble, R. J.; Rodger, C. J.; Clilverd, M.; Thomson, N. R.; Ulich, T.; Parrot, M.; Sauvaud, J.; Berthelier, J.

2010-12-01

236

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

NASA Astrophysics Data System (ADS)

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

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

2013-12-01

237

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

Microsoft Academic Search

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

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

2009-01-01

238

Magnetic Moment Coupling to Circularly Polarized Photons  

E-print Network

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

O. V. Kibis

2009-01-30

239

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

NASA Astrophysics Data System (ADS)

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

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

2014-05-01

240

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

241

Circular Ribbon Flares and Homologous Jets  

E-print Network

Solar flare emissions in the chromosphere often appear as elongated ribbons on both sides of the magnetic polarity inversion line (PIL), and this has been regarded as evidence of a typical configuration of magnetic reconnection. However, flares having a closed 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 \\ha blue wing observations obtained from the recently digitized films of Big Bear Solar Observatory (BBSO). In all the events, a central parasitic magnetic field is encompassed by the opposite magnetic polarity, forming a circular PIL that is also 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 bright...

Wang, Haimin

2012-01-01

242

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

NASA Astrophysics Data System (ADS)

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

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

2013-12-01

243

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

NASA Astrophysics Data System (ADS)

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

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

2014-07-01

244

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

NASA Technical Reports Server (NTRS)

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

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

2012-01-01

245

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

NASA Astrophysics Data System (ADS)

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

Li, Yun-He; Zhang, Xin

2014-04-01

246

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

247

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

248

European heatwave in July 2006: Observations and modeling showing how local processes amplify conducive large-scale conditions  

NASA Astrophysics Data System (ADS)

July 2006 was particularly warm in Europe. The consistency of this kind of anomaly with large-scale circulation conditions or local processes is a key issue for regional climate evolution. Using observations from space and ground-based observatory, together with simulations from regional model, shows that two concomitant but disconnected drivers explain this heatwave. The first driver corresponds to large-scale conditions (specific atmospheric condition with advection of continental air favoring clear sky). The second condition relates to local processes (dry soil, amplifying surface temperature in heatwave for first 5 days, and making this event warm enough to induce a monthly mean anomaly). This large-scale event is studied at a site in northern France, where comprehensive observation data carefully reanalyzed are available. A regional model is able to produce the amplitude of the event, for both temperature and cloud large-scale anomalies. Coupling model and observations allow discriminating the surface contribution to the temperature anomaly.

Chiriaco, Marjolaine; Bastin, Sophie; Yiou, Pascal; Haeffelin, Martial; Dupont, Jean-Charles; Stéfanon, Marc

2014-08-01

249

Simultaneous SOHO and Ground-Based Observations of a Large Eruptive Prominence and Coronal Mass Ejection  

Microsoft Academic Search

Coronal mass ejections (CMEs) are frequently associated with erupting prominences near the solar surface. A spectacular eruption of the southern polar crown prominence was observed on 2 June 1998, accompanied by a CME that was well-observed by the LASCO coronagraphs on SOHO. The prominence was observed in its quiescent state and was followed throughout its eruption by the SOHO EIT and

S. P. Plunkett; A. Vourlidas; S. Šimberová; M. Karlický; P. Kotrc; P. Heinzel; Yu. A. Kupryakov; W. P. Guo; S. T. Wu

2000-01-01

250

Observation of large-scale traveling ionospheric disturbances of auroral origin by global GPS networks  

Microsoft Academic Search

The intention in this paper is to investigate the form and dynamics of large-scale traveling ionospheric disturbances (LS TIDs) of auroral origin. We have devised a technique for determining LS TID parameters using GPS arrays whose elements can be selected from a large set of GPS stations forming part of the international GPS network. The method was used to determine

Edward L. Afraimovich; Eugene A. Kosogorov; Ludmila A. Leonovich; Kirill S. Palamartchouk; Natalia P. Perevalova; Olga M. Pirog

251

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

SciTech Connect

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

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

2011-05-20

252

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

NASA Astrophysics Data System (ADS)

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

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

2013-12-01

253

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

2013-07-17

254

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.

Michael R. Gallis

2013-10-07

255

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

NASA Technical Reports Server (NTRS)

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

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

2012-01-01

256

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

257

Discovery of Circularly Polarized Radio Emission from SS 433.  

PubMed

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

Fender; Rayner; Norris; Sault; Pooley

2000-02-10

258

Integrated observations of processes and products of large scale cratering experiments  

NASA Astrophysics Data System (ADS)

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

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

2013-12-01

259

Radar Observation of Large Attenuation in Convective Storms: Implications for the Dropsize Distribution  

NASA Technical Reports Server (NTRS)

Airborne meteorological radars typically operate at attenuating wavelengths. The path integrated attenuation (PIA) can be estimated using the surface reference technique (SRT). In this method, an initial value is determined for the radar cross section of the earth surface in a rain-free area in relatively close proximity to the rain cloud. During subsequent observations of precipitation any decrease 'in the observed surface cross section from the reference value s assumed to be a result of the two-way attenuation along the propagation path. In this paper we present selected instances of high PIA observed over land by an airborne radar. The observations were taken in Brazil and Florida during TRMM (Tropical Rainfall Measurement Mission) field campaigns. We compared these observations with collocated and nearly simultaneous ground-based radar observations by an S-band radar that is not subject to significant attenuation. In this preliminary evaluation, a systematic difference in the attenuation in the two storms is attributed to a difference in the raindrop size distributions; this is supported by observations of ZDR (differential reflectivity).

Tian, Lin; Heymsfield, G. M.; Srivastava, R. C.

2000-01-01

260

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

Microsoft Academic Search

We present multiwavelength observations of a large-amplitude oscillation of a polar-crown filament on 15 October 2002, which\\u000a has been reported by Isobe and Tripathi (Astron. Astrophys.\\u000a 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\\u000a were clearly seen in observations recorded

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

2007-01-01

261

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

SciTech Connect

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

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

2011-11-15

262

Circularly polarized conical patterns from circular microstrip antennas  

NASA Technical Reports Server (NTRS)

A method is presented for generating circularly polarized conical patterns from circular microstrip antennas. These antennas are excited at higher order modes and require different feed arrangements for different mode excitations. It is determined that the peak direction of the conical pattern can be varied over a wide angular range. Modal expansion technique is employed to calculate the radiation patterns of these antennas.

Huang, J.

1984-01-01

263

Loop equation analysis of the circular ? ensembles  

NASA Astrophysics Data System (ADS)

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

Witte, N. S.; Forrester, P. J.

2015-02-01

264

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

E-print Network

More studies on the dynamics of marine stratus and stratocumulus clouds have been performed than comparable studies on continental stratocumulus. Therefore, to increase the number of observations of continental stratocumulus and to compare marine...

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

2010-10-01

265

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

Microsoft Academic Search

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

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

1998-01-01

266

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

E-print Network

functionality such as indexing, concurrency control, and storage managers, thereby often reinventing the wheel, efficient support for extracting rectangular cutouts and performing raster operations such as zooming. Having said this, relevant knowledge about large- scale MDD management has been collected in the disci

Baumann, Peter

267

Predicting Large Hadron Collider Observations using Kazuo Kondo's Mass Quantum Cascade  

E-print Network

The late Kazuo Kondo left a hitherto unknown a priori particle theory which provides predictions of massive particles which may be detected by the Large Hadron Collider (LHC). This article briefly introduces Kondo's work and documents the derivation and masses of his expected hyper-mesons, hyper-hadrons, heavy leptons and massive neutrinos. Several particles in these classes may have already been detected.

Grenville J. Croll

2008-04-27

268

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

NASA Astrophysics Data System (ADS)

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

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

2014-11-01

269

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

270

Circularly polarized microstrip antennas  

NASA Technical Reports Server (NTRS)

A simple microstrip antenna can be made to radiate EM waves of any polarization, in particular, the circular polarization (CP) without any phasing network and power divider. A simple and accurate theory for this family of antennas was developed. However, the CP bandwidth, (CPBW) the bandwidth in which the axial ratio (AR) is less than a certain specified value, is very small. Most of the experimental designs were made for a feed placed along the diagonal of the patch. It is shown that there are practically infinitely many possible designs with different feed location. The speculation that other designs might give a wider bandwidth is clarified and an effective method for broadening the bandwidth is shown.

Lo, Y. T.; Engst, B.; Lee, R. Q. H.

1985-01-01

271

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

E-print Network

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

Norris, Ray

272

Observations of the electric field fine structure associated with the westward traveling surge and large-scale auroral spirals  

Microsoft Academic Search

The characteristics of the fine scale electric field associated with the westward traveling surge and large-scale auroral spirals and surges are investigated using high-resolution electric field, magnetic field, particle and UV imager observations from four eveningside auroral oval crossings by the Freja satellite. Three of the crossings were associated with signatures of auroral substorms and one crossing went directly through

G. T. Marklund; T. Karlsson; L. G. Blomberg; P.-A. Lindqvist; C.-G. Fälthammar; M. L. Johnson; J. S. Murphree; L. Andersson; L. Eliasson; H. J. Opgenoorth; L. J. Zanetti

1998-01-01

273

Special configuration of a very large Schmidt telescope for extensive astronomical spectroscopic observation.  

PubMed

A special reflecting Schmidt telescope is used to observe celestial objects. The telescope has an aperture of 4m, f ratio of 5, and a 5° field of view. Its optical axis is fixed and tilted 25° to the horizontal that runs from south to north. The celestial objects were observed for 1.5 h as they passed through the meridian. The shape of the reflecting Schmidt plate has to be changed with each different declination ? and in the tracking process. This is achieved with active optics. The sky area to be observed is -10° ? ? ? +90°. There are plans to place ~4000 optical fibers on the telescope focal surface that will lead to a dozen spectrographs. PMID:21102950

Wang, S G; Su, D Q; Chu, Y Q; Cui, X; Wang, Y N

1996-09-01

274

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

NASA Astrophysics Data System (ADS)

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

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

2014-11-01

275

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

PubMed

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

d'Enterria, David; da Silveira, Gustavo G

2013-08-23

276

Direct Observation of Inward Electron Flux being Blocked in the Large Helical Device  

NASA Astrophysics Data System (ADS)

We present a particle transport phenomenon caused by a hydrogen ice pellet injection (PI) into the Large Helical Device. The electron density (ne) profile evolution after a PI was measured by using a 200-channel Thomson scattering diagnostic. The highly hollow ne-profile caused by a PI faded out as time elapsed with a very slight increase in the ne at the core region, giving a direct evidence for the inward electron flux being almost completely blocked in the core region.

Narihara, Kazumichi; Sakamoto, Ryuichi; Yamada, Ichihiro; Funaba, Hisamichi; Shoji, Mamoru; Yokoyama, Masayuki; Hayashi, Hiroshi; LHD Experimental Group

277

Large-Eddy Simulations and Observations of Atmospheric Marine Boundary Layers above Nonequilibrium Surface Waves  

Microsoft Academic Search

Winds and waves in marine boundary layers are often in an unsettled state when fast-running swell generated by distant storms propagates into local regions and modifies the overlying turbulent fields. A large-eddy simulation (LES) model with the capability to resolve a moving sinusoidal wave at its lower boundary is developed to investigate this low-wind\\/fast-wave regime. It is used to simulate

Peter P. Sullivan; James B. Edson; Tihomir Hristov; James C. McWilliams

2008-01-01

278

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

Microsoft Academic Search

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

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

1994-01-01

279

Some observations on the history of large philanthropic foundations in Britain and the United States  

Microsoft Academic Search

Large philanthropic foundations such as those which first developed in the United States in the late nineteenth and early\\u000a twentieth century had four characteristics: (a) the aim of contributing to the public good; (b) applying science and scientific\\u000a method to human affairs, interpreting science broadly; (c) using great wealth to pursue these purposes; and (d) seeking public\\u000a recognition of their

Martin Bulmer

1995-01-01

280

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

281

Fermi Large Area Telescope Observations of PSR J1836+5925  

Microsoft Academic Search

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

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

2010-01-01

282

Observations of residual ULF signals from the Parkfield magnetometer surrounding large Earthquakes  

NASA Astrophysics Data System (ADS)

We use long-term (1999-2004) ULF data (<10 Hz) from a triaxial search-coil magnetometer located in Parkfield, California, to construct signal statistical quantities parametrized according to time of day, frequency range, coil orientation, season, and geomagnetic activity (Kp index). For each such parameter bin, we compute statistical quantities such as mean, variance, median and quartiles of the magnetic signal, and use these quantities as the baseline values from which signals are assumed to deviate. We then examine time periods surrounding those of large, nearby Earthquakes, and subtract the average and median signal values from the absolute signal values to obtain signal `residues'. Results show that this technique can be effective in reducing large background variations and thereby increasing the signal to noise ratio (SNR), allowing much lower amplitude signals of local origin to be detected. To further increase the SNR, we superpose a number of large earthquake periods and discuss the results in light of possible seismogenic ULF signal sources.

Bortnik, J.; Cutler, J. W.; Dunson, C.; Bleier, T.

2005-12-01

283

ELECTRON MICROSCOPIC OBSERVATIONS ON THE LARGE SUBUNIT OF THE RAT LIVER RIBOSOME  

PubMed Central

Active large subunits obtained by urea treatment of rat liver ribosomes, 59S, were compared with large subunits in intact ribosomes and with the 50S subunits obtained by EDTA treatment. For electron microscopy the specimens were negatively stained or shadow cast. The negatively stained 59S subunits had a slightly ovoidal form; their average dimensions, 244 ± 17 x 207 ± 18 A, were very close to the dimensions of the large subunits in intact ribosomes, and lay between the theoretical dimensions for anhydrous and fully hydrated particles that were calculated from the physical properties of the subunits in solution. The shadow-cast preparations showed particles of similar shape. The 50S subunits, which had lost their 5S RNA, were shadow cast at the same time. They appeared to be more spread out than the 59S subunits and had threadlike extensions. In the positively stained regions of uranyl oxalate-stained preparations the 50S particles varied greatly in shape and size, with average dimensions of 330 ± 21 x 276 ± 33 A, and showed threadlike extensions like those of the shadow-cast particles. For 50S particles in solution the frictional drag of these extensions probably accounts for their low sedimentation coefficient. PMID:4105038

Haga, J. Y.; Hamilton, M. G.; Petermann, M. L.

1970-01-01

284

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

NASA Astrophysics Data System (ADS)

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

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

2014-06-01

285

Entropic derivation of F=ma for circular motion  

E-print Network

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

Michael Duncan; Ratbay Myrzakulov; Douglas Singleton

2011-08-11

286

MIC-Large Scale Magnetically Inflated Cable Structures for Space Power, Propulsion, Communications and Observational Applications  

NASA Astrophysics Data System (ADS)

A new approach for the erection of rigid large scale structures in space-MIC (Magnetically Inflated Cable)-is described. MIC structures are launched as a compact payload of superconducting cables and attached tethers. After reaching orbit, the superconducting cables are energized with electrical current. The magnet force interactions between the cables cause them to expand outwards into the final large structure. Various structural shapes and applications are described. The MIC structure can be a simple flat disc with a superconducting outer ring that supports a tether network holding a solar cell array, or it can form a curved mirror surface that concentrates light and focuses it on a smaller region-for example, a high flux solar array that generates electric power, a high temperature receiver that heats H2 propellant for high Isp propulsion, and a giant primary reflector for a telescope for astronomy and Earth surveillance. Linear dipole and quadrupole MIC structures are also possible. The linear quadrupole structure can be used for magnetic shielding against cosmic radiation for astronauts, for example. MIC could use lightweight YBCO superconducting HTS (High Temperature Superconductor) cables, that can operate with liquid N2 coolant at engineering current densities of ~105 amp/cm2. A 1 kilometer length of MIC cable would weigh only 3 metric tons, including superconductor, thermal insulations, coolant circuits, and refrigerator, and fit within a 3 cubic meter compact package for launch. Four potential MIC applications are described: Solar-thermal propulsion using H2 propellant, space based solar power generation for beaming power to Earth, a large space telescope, and solar electric generation for a manned lunar base. The first 3 applications use large MIC solar concentrating mirrors, while the 4th application uses a surface based array of solar cells on a magnetically levitated MIC structure to follow the sun. MIC space based mirrors can be very large and light in weight. A 300 meter diameter MIC mirror in orbit for example, would weigh 20 metric tons and MIC structures can be easily developed and tested on Earth at small scale in existing evacuated chambers followed by larger scale tests in the atmosphere, using a vacuum tight enclosure on the small diameter superconducting cable to prevent air leakage into the evacuated thermal insulation around the superconducting cable.

Powell, James; Maise, George; Rather, John

2010-01-01

287

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

NASA Technical Reports Server (NTRS)

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

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

2010-01-01

288

Non-axisymmetric flexural vibrations of free-edge circular silicon wafers  

NASA Astrophysics Data System (ADS)

Non-axisymmetric flexural vibrations of circular silicon (111) wafers are investigated. The modes with azimuthal index 2?k?30 are electrostatically excited and monitored by a capacitive sensor. The splitting of the mode frequencies associated with imperfection of the wafer is observed. The measured loss factors for the modes with 6?k?26 are close to those calculated according to the thermoelastic damping theory, while clamping losses likely dominate for k?6, and surface losses at the level of inverse Q-factor Q-1?4×10-6 prevail for the modes with large k. The modes demonstrate nonlinear behavior of mainly geometrical origin at large amplitudes.

Dmitriev, A. V.; Gritsenko, D. S.; Mitrofanov, V. P.

2014-02-01

289

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

E-print Network

amplitude oscillation of a polar crown filament on 15 October 2002, which has been reported by Isobe & Tri clearly seen in observations recored by the Extreme-Ultraviolet Imaging Telescope (EIT) on board the Solar in H by the Flare Monitoring Telescope at Hida Observatory. We determine the three-dimensional motion

Li, Yi

290

Large-Scale Plasma Structure in the Polar and Auroral Ionosphere: Experimental Observations and Modelling  

Microsoft Academic Search

Radiotomography provides observations of ionospheric electron density structure on horizontal scales of tens to hundreds of kilometres. Routine measurements over extended periods of time and geographic areas have the potential for parameterising the structure of the polar and auroral ionosphere. Averaged electron densities characteristic of different ionospheric features, locations, local times, Universal Times, seasons, geomagnetic activity and solar conditions can

S. E. Pryse; H. R. Middleton; K. L. Dewis; A. G. Wood; E. L. Whittick; R. L. Balthazor

291

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

292

Post-stroke depression: research methodology of a large multicentre observational study (DESTRO)  

Microsoft Academic Search

The heterogeneity of published data regarding post-stroke depression (PSD) prompted an Italian multicenter observational study (DESTRO), which took place in 2000–2003. The investigation involved 53 Italian neurology centers: of these, 50 treat acute patients and 3 provide rehabilitation care; 21 centres are in Northern Italy, 20 are in Central Italy, and 12 are in Southern Italy. The time schedule was

V. Toso; C. Gandolfo; S. Paolucci; L. Provinciali; R. Torta; N. Grassivaro

2004-01-01

293

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...

294

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

295

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

NASA Astrophysics Data System (ADS)

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

Andreadis, Konstantinos; Schumann, Guy

2014-05-01

296

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

297

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 ?? 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.; Bechtol, K.; Berenji, B.; Bloom, E.D.; Borgland, A.W.; Buehler, R.; Cameron, R.A. [W.W. Hansen Experimental Physics Laboratory, Kavli Institute for Particle Astrophysics and Cosmology, Department of Physics and SLAC National Accelerator Laboratory, Stanford University, Stanford, CA 94305 (United States); Baldini, L.; Bellazzini, R.; Bregeon, J. [INFN — Sezione di Pisa, I-56127 Pisa (Italy); Barbiellini, G. [INFN — Sezione di Trieste, I-34127 Trieste (Italy); Bastieri, D.; Buson, S. [INFN — Sezione di Padova, I-35131 Padova (Italy); Bonamente, E.; Cecchi, C. [INFN — Sezione di Perugia, I-06123 Perugia (Italy); Brigida, M. [Dipartimento di Fisica 'M. Merlin' dell'Università e del Politecnico di Bari, I-70126 Bari (Italy); Bruel, P. [Laboratoire Leprince-Ringuet, École polytechnique, CNRS/IN2P3, Palaiseau (France); Caliandro, G.A. [Institut de Ciències de l'Espai (IEEE-CSIC), Campus UAB, 08193 Barcelona (Spain); Caraveo, P.A. [INAF-Istituto di Astrofisica Spaziale e Fisica Cosmica, I-20133 Milano (Italy); Casandjian, J.M., E-mail: bijanb@alumni.stanford.edu, E-mail: elliott@slac.stanford.edu, E-mail: johann.cohen-tanugi@lupm.in2p3.fr [Laboratoire AIM, CEA-IRFU/CNRS/Université Paris Diderot, Service d'Astrophysique, CEA Saclay, 91191 Gif sur Yvette (France); Collaboration: Fermi-LAT collaboration; and others

2012-02-01

298

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

NASA Technical Reports Server (NTRS)

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

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

2012-01-01

299

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

NASA Astrophysics Data System (ADS)

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

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

2014-11-01

300

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

SciTech Connect

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

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

2011-04-01

301

Satellite Observed Widespread Decline in Mongolian Grasslands Largely Due to Overgrazing  

NASA Technical Reports Server (NTRS)

The Mongolian Steppe is one of the largest remaining grassland ecosystems. Recent studies have reported widespread decline of vegetation across the steppe and about 70 percent of this ecosystem is now considered degraded. Among the scientific community there has been an active debate about whether the observed degradation is related to climate, or overgrazing, or both. Here, we employ a new atmospheric correction and cloud screening algorithm (MAIAC) to investigate trends in satellite observed vegetation phenology. We relate these trends to changes in climate and domestic animal populations. A series of harmonic functions is fitted to MODIS observed phenological curves to quantify seasonal and inter-annual changes in vegetation. Our results show a widespread decline (of about 12 percent on average) in MODIS observed NDVI across the country but particularly in the transition zone between grassland and the Gobi desert, where recent decline was as much as 40 percent below the 2002 mean NDVI. While we found considerable regional differences in the causes of landscape degradation, about 80 percent of the decline in NDVI could be attributed to increase in livestock. Changes in precipitation were able to explain about 30 percent of degradation across the country as a whole but up to 50 percent in areas with denser vegetation cover (p0.05). Temperature changes, while significant, played only a minor role (r20.10, p0.05). Our results suggest that the cumulative effect of overgrazing is a primary contributor to the degradation of the Mongolian steppe and is at least partially responsible for desertification reported in previous studies.

Hilker, Thomas; Natsagdorj, Enkhjargal; Waring, Richard H.; Lyapustin, Alexei; Wang, Yujie

2014-01-01

302

Pan-Chromatic Observations of the Remarkable Nova Large Magellanic Cloud 2012  

NASA Astrophysics Data System (ADS)

We present the results of an intensive multiwavelength campaign on nova LMC 2012. This nova evolved very rapidly in all observed wavelengths. The time to fall two magnitudes in the V band was only 2 days. In X-rays the super soft phase began 13 ± 5 days after discovery and ended around day 50 after discovery. During the super soft phase, the Swift/XRT and Chandra spectra were consistent with the underlying white dwarf (WD) being very hot, ?1 MK, and luminous, ?1038 erg s?1. The UV, optical, and near-IR photometry showed a periodic variation after the initial and rapid fading had ended. Timing analysis revealed a consistent 19.24 ± 0.03 hr period in all UV, optical, and near-IR bands with amplitudes of ?0.3 mag which we associate with the orbital period of the central binary. No periods were detected in the corresponding X-ray data sets. A moderately high inclination system, i = 60 ± 10{\\circ{}}, was inferred from the early optical emission lines. The HST/STIS UV spectra were highly unusual with only the N v (1240 Å) line present and superposed on a blue continuum. The lack of emission lines and the observed UV and optical continua from four epochs can be fit with a low mass ejection event, ?10?6 {{M}? }, from a hot and massive WD near the Chandrasekhar limit. The WD, in turn, significantly illuminated its subgiant companion which provided the bulk of the observed UV/optical continuum emission at the later dates. The inferred extreme WD characteristics and low mass ejection event favor nova LMC 2012 being a recurrent nova of the U Sco subclass. Based on observations with the NASA/ESA Hubble Space Telescope obtained at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Incorporated, under NASA contract NAS5-26555.

Schwarz, Greg J.; Shore, Steven N.; Page, Kim L.; Osborne, Julian P.; Beardmore, Andrew P.; Walter, Frederick M.; Bode, Michael F.; Drake, Jeremy J.; Ness, Jan-Uwe; Starrfield, Sumner; Van Rossum, Daniel R.; Woodward, Charles E.

2015-03-01

303

THE FAINTEST RADIO SOURCE YET: EXPANDED VERY LARGE ARRAY OBSERVATIONS OF THE GRAVITATIONAL LENS SDSS J1004+4112  

SciTech Connect

We present new radio observations of the large-separation gravitationally lensed quasar SDSS J1004+4112, taken in a total of 6 hr of observations with the Expanded Very Large Array. The maps reach a thermal noise level of approximately 4 {mu}Jy. We detect four of the five lensed images at the 15-35 {mu}Jy level, representing a source of intrinsic flux density, after allowing for lensing magnification, of about 1 {mu}Jy, intrinsically probably the faintest radio source yet detected. This reinforces the utility of gravitational lensing in potentially allowing us to study nJy-level sources before the advent of the Square Kilometre Array. In an optical observation taken three months after the radio observation, image C is the brightest image, whereas the radio map shows flux density ratios consistent with previous optical observations. Future observations separated by a time delay will give the intrinsic flux ratios of the images in this source.

Jackson, N. [Jodrell Bank Centre for Astrophysics, School of Physics and Astronomy, University of Manchester, Alan Turing Building, Oxford Road, Manchester M13 9PL (United Kingdom)

2011-09-20

304

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

NASA Astrophysics Data System (ADS)

The study of volcanic triggering and interaction with the tectonic surroundings has received special attention in recent years, using both direct field observations and historical descriptions of eruptions and earthquake activity. Repeated reports of clustered eruptions and earthquakes may imply that interaction is important in some subregions. However, the subregions likely to suffer such clusters have not been systematically identified, and the processes responsible for the observed interaction remain unclear. We first review previous works about the clustered occurrence of eruptions and earthquakes, and describe selected events. We further elaborate available databases and confirm a statistically significant relationship between volcanic eruptions and earthquakes on the global scale. Moreover, our study implies that closed volcanic systems in particular tend to be activated in association with a tectonic earthquake trigger. We then perform a statistical study at the subregional level, showing that certain subregions are especially predisposed to concurrent eruption-earthquake sequences, whereas such clustering is statistically less significant in other subregions. Based on this study, we argue that individual and selected observations may bias the perceptible weight of coupling. The activity at volcanoes located in the predisposed subregions (e.g., Japan, Indonesia, Melanesia), however, often unexpectedly changes in association with either an imminent or a past earthquake.

Eggert, Silke; Walter, Thomas R.

2009-06-01

305

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

NASA Technical Reports Server (NTRS)

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

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

2012-01-01

306

NEAR-INFRARED CIRCULAR POLARIZATION IMAGES OF NGC 6334-V  

SciTech Connect

We present results from deep imaging linear and circular polarimetry of the massive star-forming region NGC 6334-V. These observations show high degrees of circular polarization (CP), as much as 22% in the K{sub s} band, in the infrared nebula associated with the outflow. The CP has an asymmetric positive/negative pattern and is very extended ({approx}80'' or 0.65 pc). Both the high CP and its extended size are larger than those seen in the Orion CP region. Three-dimensional Monte Carlo light-scattering models are used to show that the high CP may be produced by scattering from the infrared nebula followed by dichroic extinction by an optically thick foreground cloud containing aligned dust grains. Our results show not only the magnetic field orientation of around young stellar objects, but also the structure of circumstellar matter such as outflow regions and their parent molecular cloud along the line of sight. The detection of the large and extended CP in this source and the Orion nebula may imply the CP origin of the biological homochirality on Earth.

Kwon, Jungmi; Tamura, Motohide; Hashimoto, Jun; Kusakabe, Nobuhiko; Kandori, Ryo [National Astronomical Observatory of Japan, 2-21-1 Osawa, Mitaka, Tokyo 181-8588 (Japan); Lucas, Phil W.; Hough, James H. [Centre for Astrophysics Research, University of Hertfordshire, College Lane, Hatfield AL10 9AB (United Kingdom); Nakajima, Yasushi [Center of Information and Communication Technology, Hitotsubashi University, 2-1 Naka, Kunitachi, Tokyo 186-8601 (Japan); Nagayama, Takahiro [Department of Astrophysics, Nagoya University, Nagoya 464-8602 (Japan); Nagata, Tetsuya, E-mail: jungmi.kwon@nao.ac.jp [Department of Astronomy, Kyoto University, Kyoto 606-8502 (Japan)

2013-03-01

307

Scattering matrix of infrared radiation by ice finite circular cylinders.  

PubMed

Scattering matrix characteristics of polydisperse, randomly oriented, small ice crystals modeled by finite circular cylinders with various ratios of the length to diameter (L/D) ratio are calculated by use of the exact T-matrix approach, with emphasis on the thermal infrared spectral region that extends from the atmospheric short-wave IR window to the far-IR wavelengths to as large as 30 microm. The observed ice crystal size distribution and the well-known power-law distribution are considered. The results of the extensive calculations show that the characteristics of scattering matrix elements of small ice circular cylinders depend strongly on wavelengths and refractive indices, particle size distributions, and the L/D ratios. The applicability of the power-law distribution and particle shapes for light scattering calculations for small ice crystals is discussed. The effects of the effective variance of size distribution on light scattering characteristics are addressed. It seems from the behavior of scattering matrix elements of small ice crystals that the combination of 25 and 3.979 microm has some advantages and potential applications for remote sensing of cirrus and other ice clouds. PMID:12003228

Xu, Lisheng; Ding, Jilie; Cheng, Andrew Y S

2002-04-20

308

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

NASA Technical Reports Server (NTRS)

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

Norbury, John W.

1992-01-01

309

Fermi Large Area Telescope observations of high-energy gamma-ray emission from solar flares  

NASA Astrophysics Data System (ADS)

With the current solar cycle reaching its maximum, the Fermi observatory has proven to play an active role in the study of solar flares. The Large Area Telescope (LAT) on-board Fermi has detected >30 MeV gamma-ray emission associated with GOES M-class and X-class X-ray flares accompanied by coronal mass ejections and solar energetic particle events. These detections include both the impulsive and the long duration phases including the ~20 hours of extended emission from the 2012 March 7 X-class flares. Accurate localization with the Fermi LAT of the gamma-ray production site(s) coincide with the solar active region from which X-ray emissions associated with the 2012 March 7 X-class flares originated. In this talk I present an overview of the Fermi solar flare detections over the past five years of operation.

Pesce-Rollins, Melissa; Omodei, N.; Petrosian, V.; Fermi LAT Collaboration

2014-01-01

310

Line-of-sight observations at 86 GHz with a very large and a small antenna  

NASA Technical Reports Server (NTRS)

Amplitude variations over a 12.9 km terrestrial line-of-sight path were measured simultaneously on a 1400 lambda and a 29 lambda antenna at 86.16 GHz. Clear atmosphere data from two occasions with considerably different meteorological conditions are presented. Both sets have statistical and spectral parameters in good agreement with turbulence theory. Some of the data taken after a thunderstorm front passage show a slow gain reduction of the large antenna of up to 2 dB and an increase in variance to a level above that of the small antenna. The power spectral density of these data reveals that the excess fluctuation power is in the region of the spectrum which turbulence theory predicts to be flat. It shows an approximate 1/f dependence. It is attributed to refractive bending of up to 0.025 deg. Gain reductions due to turbulence or turbulence induced angle-of-arrival variations were estimated to be negligible.

Vogel, W. J.; Davis, J. H.; Mayer, C. E.

1984-01-01

311

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

NASA Astrophysics Data System (ADS)

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

Liu, Chunming; Li, Yunlong; Pirjola, Risto

2014-01-01

312

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

NASA Astrophysics Data System (ADS)

The study of volcanic triggering and coupling to the tectonic surroundings has received special attention in recent years, using both direct field observations and historical descriptions of eruptions and earthquake activity. Repeated reports of volcano-earthquake interactions in, e.g., Europe and Japan, may imply that clustered occurrence is important in some regions. However, the regions likely to suffer clustered eruption-earthquake activity have not been systematically identified, and the processes responsible for the observed interaction are debated. We first review previous works about the correlation of volcanic eruptions and earthquakes, and describe selected local clustered events. Following an overview of previous statistical studies, we further elaborate the databases of correlated eruptions and earthquakes from a global perspective. Since we can confirm a relationship between volcanic eruptions and earthquakes on the global scale, we then perform a statistical study on the regional level, showing that time and distance between events follow a linear relationship. In the time before an earthquake, a period of volcanic silence often occurs, whereas in the time after, an increase in volcanic activity is evident. Our statistical tests imply that certain regions are especially predisposed to concurrent eruption-earthquake pairs, e.g., Japan, whereas such pairing is statistically less significant in other regions, such as Europe. Based on this study, we argue that individual and selected observations may bias the perceptible weight of coupling. Volcanoes located in the predisposed regions (e.g., Japan, Indonesia, Melanesia), however, indeed often have unexpectedly changed in association with either an imminent or a past earthquake.

Eggert, S.; Walter, T. R.

2009-04-01

313

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

PubMed Central

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

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

2013-01-01

314

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

NASA Astrophysics Data System (ADS)

We statistically analyzed the kinematical evolution and wave pulse characteristics of 60 strong large-scale EUV wave events that occurred during January 2007 to February 2011 with the STEREO twin spacecraft. For the start velocity, the arithmetic mean is 312±115 km s-1 (within a range of 100 - 630 km s-1). For the mean (linear) velocity, the arithmetic mean is 254±76 km s-1 (within a range of 130 - 470 km s-1). 52 % of all waves under study show a distinct deceleration during their propagation ( a?-50 m s-2), the other 48 % are consistent with a constant speed within the uncertainties (-50? a?50 m s-2). The start velocity and the acceleration are strongly anticorrelated with c?-0.8, i.e. initially faster events undergo stronger deceleration than slower events. The (smooth) transition between constant propagation for slow events and deceleration in faster events occurs at an EUV wave start-velocity of v?230 km s-1, which corresponds well to the fast-mode speed in the quiet corona. These findings provide strong evidence that the EUV waves under study are indeed large-amplitude fast-mode MHD waves. This interpretation is also supported by the correlations obtained between the peak velocity and the peak amplitude, impulsiveness, and build-up time of the disturbance. We obtained the following association rates of EUV wave events with other solar phenomena: 95 % are associated with a coronal mass ejection (CME), 74 % to a solar flare, 15 % to interplanetary type II bursts, and 22 % to coronal type II bursts. These findings are consistent with the interpretation that the associated CMEs are the driving agents of the EUV waves.

Muhr, N.; Veronig, A. M.; Kienreich, I. W.; Vršnak, B.; Temmer, M.; Bein, B. M.

2014-12-01

315

Large scale image projection setup for observation of flocculation in heavy oil/water emulsions  

NASA Astrophysics Data System (ADS)

A heavy oil-in-water emulsion is heated by a continuous wave laser beam, thus producing an ascending thermoconvective liquid flow. Once at the open free surface the oil particles are directly heated by the incoming laser beam, which gives rise to flocculation and eventually to coalescence. A bright, enlarged image of the heated region is formed in a projection screen using the backscattered light of their own laser beam. The device thus allows direct observation and high speed photographic recording of the flocculation process as a function of the sample temperature, which is monitored by means of a thermographic camera.

Da Costa, Germán

2005-09-01

316

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

NASA Technical Reports Server (NTRS)

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

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

1984-01-01

317

Circular on family planning, 1988.  

PubMed

This Hubei, China, Circular, issued near the end of 1988, provides the following: "The population growth situation in our country is grim. Since 1986, the natural population growth rate has risen continuously. To draw the prompt attention of the whole party and the entire people to the issue of our population, all localities must seriously unfold the activities of publicizing family planning (FP) this winter and next spring, in coordination with education in current affairs. It is necessary to publicize FP in an all-around way and with accuracy, and the activities of publicizing must be carried out effectively in a solid and deep-going way. In the rural areas, stress must be placed on areas where FP work is not carried out well and where there is a prevailing tendency toward early marriage, early child-bearing, and extra-budgetary births. In cities, publicity and education must be conducted especially among the transient population, individual households, and jobless households. During the period of publicity, large-scale street-corner publicity activities must be carried out in cities and towns so as to create strong public opinion and to combine the endeavor to publicize current affairs and policies with the effort to popularize knowledge about contraception and birth-control, to execute measures of contraception and birth control, and to establish FP associations in the countryside." PMID:12289626

1988-01-01

318

Nuclear spin circular dichroism  

SciTech Connect

Recent years have witnessed a growing interest in magneto-optic spectroscopy techniques that use nuclear magnetization as the source of the magnetic field. Here we present a formulation of magnetic circular dichroism (CD) due to magnetically polarized nuclei, nuclear spin-induced CD (NSCD), in molecules. The NSCD ellipticity and nuclear spin-induced optical rotation (NSOR) angle correspond to the real and imaginary parts, respectively, of (complex) quadratic response functions involving the dynamic second-order interaction of the electron system with the linearly polarized light beam, as well as the static magnetic hyperfine interaction. Using the complex polarization propagator framework, NSCD and NSOR signals are obtained at frequencies in the vicinity of optical excitations. Hartree-Fock and density-functional theory calculations on relatively small model systems, ethene, benzene, and 1,4-benzoquinone, demonstrate the feasibility of the method for obtaining relatively strong nuclear spin-induced ellipticity and optical rotation signals. Comparison of the proton and carbon-13 signals of ethanol reveals that these resonant phenomena facilitate chemical resolution between non-equivalent nuclei in magneto-optic spectra.

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

2014-04-07

319

Melt production in large-scale impact events: Implications and observations at terrestrial craters  

NASA Technical Reports Server (NTRS)

The volume of impact melt relative to the volume of the transient cavity increases with the size of the impact event. Here, we use the impact of chondrite into granite at 15, 25, and 50 km s(sup -1) to model impact-melt volumes at terrestrial craters in crystalline targets and explore the implications for terrestrial craters. Figures are presented that illustrate the relationships between melt volume and final crater diameter D(sub R) for observed terrestrial craters in crystalline targets; also included are model curves for the three different impact velocities. One implication of the increase in melt volumes with increasing crater size is that the depth of melting will also increase. This requires that shock effects occurring at the base of the cavity in simple craters and in the uplifted peaks of central structures at complex craters record progressively higher pressures with increasing crater size, up to a maximum of partial melting (approx. 45 GPa). Higher pressures cannot be recorded in the parautochthonous rocks of the cavity floor as they will be represented by impact melt, which will not remain in place. We have estimated maximum recorded pressures from a review of the literature, using such observations as planar features in quartz and feldspar, diaplectic glasses of feldspar and quartz, and partial fusion and vesiculation, as calibrated with estimates of the pressures required for their formation. Erosion complicates the picture by removing the surficial (most highly shocked) rocks in uplifted structures, thereby reducing the maximum shock pressures observed. In addition, the range of pressures that can be recorded is limited. Nevertheless, the data define a trend to higher recorded pressures with crater diameter, which is consistent with the implications of the model. A second implication is that, as the limit of melting intersects the base of the cavity, central topographic peaks will be modified in appearance and ultimately will not occur. That is, the peak will first develop a central depression, due to the flow of low-strength melted materials, when the melt volume begins to intersect the transient-cavity base.

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

1992-01-01

320

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

Microsoft Academic Search

We report on measurements of the cosmic-ray induced gamma-ray emission of\\u000aEarth's atmosphere by the Large Area Telescope onboard the Fermi Gamma-ray\\u000aSpace Telescope. The LAT has observed the Earth during its commissioning phase\\u000aand with a dedicated Earth-limb following observation in September 2008. These\\u000ameasurements yielded 6.4 x 10^6 photons with energies >100MeV and ~250hours\\u000atotal livetime for the

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

2009-01-01

321

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-N m(-2) h(-1)) than from the other cell (13.7 ?g N2O-N m(-2) h(-1)), with peaks up to 1100 ?g N2O-N m(-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-C m(-2) h(-1)) was lower than the other cell (-18.3 ?g CH4-C m(-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

2013-11-01

322

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

NASA Astrophysics Data System (ADS)

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

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

2014-01-01

323

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

NASA Astrophysics Data System (ADS)

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

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

1992-09-01

324

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

NASA Technical Reports Server (NTRS)

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

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

1992-01-01

325

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

NASA Astrophysics Data System (ADS)

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

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

2015-01-01

326

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

NASA Astrophysics Data System (ADS)

We report on measurements of the cosmic-ray induced ?-ray emission of Earth’s atmosphere by the Large Area Telescope on board the Fermi Gamma-ray Space Telescope. The Large Area Telescope has observed the Earth during its commissioning phase and with a dedicated Earth limb following observation in September 2008. These measurements yielded ˜6.4×106 photons with energies >100MeV and ˜250 hours total live time for the highest quality data selection. This allows the study of the spatial and spectral distributions of these photons with unprecedented detail. The spectrum of the emission—often referred to as Earth albedo gamma-ray emission—has a power-law shape up to 500 GeV with spectral index ?=2.79±0.06.

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

2009-12-01

327

Wideband probe-fed circularly polarised circular loop antenna  

E-print Network

of the printed loops was chosen to be w ¼ 4r0. The antenna was initially designed using a method-of-moment based software, NEC 1.1, and optimised by a full-wave (transmission-line matrix method based) design toolWideband probe-fed circularly polarised circular loop antenna R.L. Li, J. Laskar and M.M. Tentzeris

Tentzeris, Manos

328

Large amplitude wave packets observed in the ionosphere in association with transverse ion acceleration  

NASA Technical Reports Server (NTRS)

Very short duration, large amplitude bursts of monochromatic waves ('spikelets') were detected by the electric field experiment on the sounding rocket MARIE, launched in February 1985 from Churchill, Manitoba. About 35 events were detected, with an average time scale of 5 ms and an average amplitude of 100-150 mV/m. Their frequency varied between 7 and 18 kHz, and there is some evidence that the frequency is a decreasing function of altitude. The bursts are not correlated with any events on the payload, and their occurrence is not related to the rocket's spin or coning. The events were confined to the altitude range 450-650 kilometers. This coincides exactly with the altitude range for which perpendicular (90 deg) ion conics were detected by the particle experiment on the same payload. The 'spikelets' were also correlated one-to-one with small (10-100 mV/m) double-layerlike or shocklike features of similar time scale in the dc electric field data.

Labelle, J.; Kintner, P. M.; Yau, A. W.; Whalen, B. A.

1986-01-01

329

Ensemble learning of inverse probability weights for marginal structural modeling in large observational datasets.  

PubMed

Inverse probability weights used to fit marginal structural models are typically estimated using logistic regression. However, a data-adaptive procedure may be able to better exploit information available in measured covariates. By combining predictions from multiple algorithms, ensemble learning offers an alternative to logistic regression modeling to further reduce bias in estimated marginal structural model parameters. We describe the application of two ensemble learning approaches to estimating stabilized weights: super learning (SL), an ensemble machine learning approach that relies on V-fold cross validation, and an ensemble learner (EL) that creates a single partition of the data into training and validation sets. Longitudinal data from two multicenter cohort studies in Spain (CoRIS and CoRIS-MD) were analyzed to estimate the mortality hazard ratio for initiation versus no initiation of combined antiretroviral therapy among HIV positive subjects. Both ensemble approaches produced hazard ratio estimates further away from the null, and with tighter confidence intervals, than logistic regression modeling. Computation time for EL was less than half that of SL. We conclude that ensemble learning using a library of diverse candidate algorithms offers an alternative to parametric modeling of inverse probability weights when fitting marginal structural models. With large datasets, EL provides a rich search over the solution space in less time than SL with comparable results. PMID:25316152

Gruber, Susan; Logan, Roger W; Jarrín, Inmaculada; Monge, Susana; Hernán, Miguel A

2015-01-15

330

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

NASA Astrophysics Data System (ADS)

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

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

2014-08-01

331

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

NASA Technical Reports Server (NTRS)

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

Parent, D.; Kerr, M.; DenHartog, P. R.; Baring, M. G.; DeCesar, M. E.; Espinoza, C. M.; Harding, A. K.; Romani, R. W.; Stappers, B. W.; Watters, K.; Weltevrde, P.; Abdo, A. A.; Craig, H. A.; Kramer, M.; Lyne, A. G.

2011-01-01

332

Sleeping Patterns of Afghan Unaccompanied Asylum-Seeking Adolescents: A Large Observational Study  

PubMed Central

Unaccompanied asylum-seeking children (UASC) have experienced multiple traumas and are a high-risk group for posttraumatic stress disorder (PTSD). The effects of trauma are known to be associated with sleep problems; indeed sleeping problems are core features of PTSD. However, there has been no systematic research examining the sleep of this high risk group of children. This study presents the first evidence on the sleeping patterns of Afghan UASC living in the UK. A total of 222 male Afghan children, aged 13–18, were interviewed using validated self-report questionnaires measuring sleeping patterns and PTSD. Overall, UASC patterns for bed time and rise time appear acculturated to the country of asylum. Mean UASC sleep onset latency scores were approximately 20 minutes greater compared with normative scores, which may be a reflection of UASC pre-migration and post-migration experiences. As expected, UASC who screened above the clinical cut-off for PTSD reported significantly greater sleep onset latency, increased nightmares, and less total sleep time compared to the non-PTSD group. The results may be of particular interest to clinicians given that, compared to screening for PTSD, screening for sleep problems may be a less culturally disputed form of initial assessment indicating distress in UASC. Similarly, the field of UASC and refugee child interventions is largely focused on trauma, yet sleep may provide a novel avenue for equally or more effective treatment. PMID:23457517

Bronstein, Israel; Montgomery, Paul

2013-01-01

333

Geomagnetic conjugate observation of nighttime medium-scale and large-scale traveling ionospheric disturbances: FRONT3 campaign  

Microsoft Academic Search

The third FRONT (F-region Radio and Optical measurement of Nighttime TID) campaign was carried out during the new-moon period of May–June 2003, in order to investigate the geomagnetic conjugacy of medium-scale and large-scale traveling ionospheric disturbances (MSTIDs\\/LSTIDs) at midlatitudes. Seven all-sky airglow imagers were operated in Japan and Australia. For almost all clear-sky nights, we observed MSTIDs in the 630-nm

K. Shiokawa; Y. Otsuka; T. Tsugawa; T. Ogawa; A. Saito; K. Ohshima; M. Kubota; T. Maruyama; T. Nakamura; M. Yamamoto; P. Wilkinson

2005-01-01

334

Geomagnetic conjugate observation of nighttime medium-scale and large-scale traveling ionospheric disturbances: FRONT3 campaign  

Microsoft Academic Search

The third FRONT (F-region Radio and Optical measurement of Nighttime TID) campaign was carried out during the new-moon period of May-June 2003, in order to investigate the geomagnetic conjugacy of medium-scale and large-scale traveling ionospheric disturbances (MSTIDs\\/LSTIDs) at midlatitudes. Seven all-sky airglow imagers were operated in Japan and Australia. For almost all clear-sky nights, we observed MSTIDs in the 630-nm

K. Shiokawa; Y. Otsuka; T. Tsugawa; T. Ogawa; A. Saito; K. Ohshima; M. Kubota; T. Maruyama; T. Nakamura; M. Yamamoto; P. Wilkinson

2005-01-01

335

Observation of large parity-change-induced dispersion in triangular-lattice photonic crystal waveguides using phase sensitive techniques  

Microsoft Academic Search

We experimentally studied W1 triangular-lattice photonic crystal waveguides (PCWs) fabricated on semiconductor-on-insulator substrates using phase-sensitive lock-in techniques. In addition to the improved signal-to-noise ratio for power transmission measurements, we observed two large group delay peaks at frequencies corresponding to the photonic mode gap and parity changes of Bloch modes inside the PCWs.

Jiandong Huang; Charles M. Reinke; Aliakbar Jafarpour; Babak Momeni; Mohammad Soltani; Ali Adibi

2006-01-01

336

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

337

Laser mass spectrometry with circularly polarized light: circular dichroism of cold molecules in a supersonic gas beam.  

PubMed

An experiment on chiral molecules that combines circular dichroism (CD) spectroscopy, mass-selective detection by laser mass spectrometry (MS), and cooling of molecules by using a supersonic beam is presented. The combination of the former two techniques (CD-laser-MS) is a new method to investigate chiral molecules and is now used by several research groups. Cooling in a supersonic beam supplies a substantial increase in spectroscopic resolution, a feature that has not yet been used in CD spectroscopy. In the experiments reported herein, a large variation in the electronic CD of carbonyl 3-methylcyclopentanone was observed depending on the excited vibrational modes in the n ? ?* transition. This finding should be of interest for the detection of chiral molecules and for the theoretical understanding of the CD of vibronic bands. It is expected that this effect will show up in other chiral carbonyls because the n ? ?* transition is typical for the carbonyl group. PMID:25044352

Titze, Katharina; Zollitsch, Tilo; Heiz, Ulrich; Boesl, Ulrich

2014-09-15

338

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

NASA Astrophysics Data System (ADS)

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

Sjouwerman, Loránt O.; Chandler, Claire J.

2014-05-01

339

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

NASA Astrophysics Data System (ADS)

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

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

2011-03-01

340

Advances in fish harvest technologies for circular tanks  

Microsoft Academic Search

Improved equipment and husbandry practices are required to effectively grade and harvest fish in large land-based culture tanks. The objective of our work was to develop and evaluate several types of relatively inexpensive, portable, and efficient fish handling equipment to reduce the labor requirement for grading and harvesting fish from large circular culture tanks. This equipment and husbandry practices also

Steven T. Summerfelt; John Davidson; Grover Wilson; Thomas Waldrop

2009-01-01

341

Experimental and numerical investigation of a forced circular shear layer  

Microsoft Academic Search

A previous article introduced a dissipative circular geometry in which stationary states of the shear flow instability were obtained. It is shown here that the dynamical behavior of this flow depends strongly on the aspect ratio of the cell. In large cells, where the number of vortices is large, transitions from a mode with m vortices to a mode with

J. M. Chomaz; M. Rabaud; C. Basdevant; Y. Couder

1988-01-01

342

Multiwavelength observation of a large-scale flux rope eruption above kinked mini-filament  

E-print Network

We analyse multiwavelength observations of a western limb flare (C3.9) occurred in AR NOAA 111465 on 30 April 2012. The high resolution images recorded by SDO/AIA 304, 1600 \\AA\\ and Hinode/SOT H$\\alpha$ show the activation of a mini-filament (rising speed$\\sim$40 km s$^{-1}$) associated with kink instability and the onset of a C-class flare near the southern leg of the filament. The first magnetic reconnection occurred at one of the footpoints of the filament causing the breaking of its southern leg. The filament shows unwinding motion of the northern leg and apex in the counterclockwise direction and failed to erupt. A flux-rope (visible only in hot channels, i.e., AIA 131 and 94 \\AA\\ channels and Hinode/SXT) structure was appeared along the neutral line during the second magnetic reconnection taking place above the kinked filament. Formation of the RHESSI hard X-ray source (12-25 keV) above the kinked filament and simultaneous appearance of the hot 131 \\AA\\ loops associated with photospheric brightenings (A...

Kumar, Pankaj

2014-01-01

343

Suomi-NPP OMPS Observations of Large-Scale Air Pollution Events over China  

NASA Astrophysics Data System (ADS)

Severe smog episodes over China in January 2013 received worldwide attention. This air pollution is distinguished by high concentrations of gaseous pollutants (SO2 and NO2) and heavy loadings of fine particulate matter. To characterize these episodes, we employed the Ozone Mapping and Profiler Suite, Nadir Mapper (OMPS NM), a hyper-spectral UV spectrometer flying on the Suomi National Polar-orbiting Partnership (SNPP) spacecraft since October 2011. We developed an advanced algorithm to detect and quantify SO2 and NO2 in the lower atmosphere, and applied it to the OMPS NM observations. Here we report retrievals of SO2 and NO2, as well as UV aerosol index data for these pollution events. The columns of SO2 and NO2 and the areas covered by high pollutant concentrations are quantified; the results reveal for the first time the full extent (an area of ~10^6 km^2 containing up to 60 kt of SO2) of these episodes.

Yang, K.; Dickerson, R. R.; Carn, S. A.; Wang, J.; Ge, G.

2013-12-01

344

Observation of energetic electron confinement in a largely stochastic reversed-field pinch plasma  

SciTech Connect

Runaway electrons with energies >100 keV are observed with the appearance of an m=1 magnetic island in the core of otherwise stochastic Madison Symmetric Torus [Dexter et al., Fusion Technol. 19, 131 (1991)] reversed-field-pinch plasmas. The island is associated with the innermost resonant tearing mode, which is usually the largest in the m=1 spectrum. The island appears over a range of mode spectra, from those with a weakly dominant mode to those, referred to as quasi single helicity, with a strongly dominant mode. In a stochastic field, the rate of electron loss increases with electron parallel velocity. Hence, high-energy electrons imply a region of reduced stochasticity. The global energy confinement time is about the same as in plasmas without high-energy electrons or an island in the core. Hence, the region of reduced stochasticity must be localized. Within a numerical reconstruction of the magnetic field topology, high-energy electrons are substantially better confined inside the island, relative to the external region. Therefore, it is deduced that the island provides a region of reduced stochasticity and that the high-energy electrons are generated and well confined within this region.

Clayton, D. J.; Chapman, B. E.; O'Connell, R.; Almagri, A. F.; Burke, D. R.; Forest, C. B.; Goetz, J. A.; Kaufman, M. C. [Department of Physics, University of Wisconsin-Madison, Madison, Wisconsin 53706 (United States); Bonomo, F.; Franz, P.; Gobbin, M.; Piovesan, P. [Consorzio RFX, Euratom-ENEA Association, Corso Stati Uniti, 4 35127 Padova (Italy)

2010-01-15

345

Observation of energetic electron confinement in a largely stochastic reversed-field pinch plasma  

NASA Astrophysics Data System (ADS)

Runaway electrons with energies >100 keV are observed with the appearance of an m =1 magnetic island in the core of otherwise stochastic Madison Symmetric Torus [Dexter et al., Fusion Technol. 19, 131 (1991)] reversed-field-pinch plasmas. The island is associated with the innermost resonant tearing mode, which is usually the largest in the m =1 spectrum. The island appears over a range of mode spectra, from those with a weakly dominant mode to those, referred to as quasi single helicity, with a strongly dominant mode. In a stochastic field, the rate of electron loss increases with electron parallel velocity. Hence, high-energy electrons imply a region of reduced stochasticity. The global energy confinement time is about the same as in plasmas without high-energy electrons or an island in the core. Hence, the region of reduced stochasticity must be localized. Within a numerical reconstruction of the magnetic field topology, high-energy electrons are substantially better confined inside the island, relative to the external region. Therefore, it is deduced that the island provides a region of reduced stochasticity and that the high-energy electrons are generated and well confined within this region.

Clayton, D. J.; Chapman, B. E.; O'Connell, R.; Almagri, A. F.; Burke, D. R.; Forest, C. B.; Goetz, J. A.; Kaufman, M. C.; Bonomo, F.; Franz, P.; Gobbin, M.; Piovesan, P.

2010-01-01

346

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

NASA Astrophysics Data System (ADS)

We are developing a new balloon-borne instrument (PoGO), to measure polarization of soft gamma rays (30-200 keV) using asymmetry in azimuth angle distribution of Compton scattering. PoGO is designed to detect 10 % polarization in 100mCrab sources in a 6-8 hour observation and bring a new dimension to studies on gamma ray emission/transportation mechanism in pulsars, AGNs, black hole binaries, and neutron star surface. The concept is an adaptation to polarization measurements of well-type phoswich counter consisting of a fast plastic scintillator (the detection part), a slow plastic scintillator (the active collimator) and a BGO scintillator (the bottom anti-counter). PoGO consists of close-packed array of 217 hexagonal well-type phoswich counters and has a narrow field-of-view (~ 5 deg2) to reduce possible source confusion. A prototype instrument has been tested in the polarized soft gamma-ray beams at Advanced Photon Source (ANL) and at Photon Factory (KEK). On the results, the polarization dependence of EGS4 has been validated and that of Geant4 has been corrected.

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

347

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

NASA Astrophysics Data System (ADS)

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

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

2015-02-01

348

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

349

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,; 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

350

Fermi Large Area Telescope Observations of the Supernova Remnant G8.7-0.1  

NASA Astrophysics Data System (ADS)

We present a detailed analysis of the GeV gamma-ray emission toward the supernova remnant (SNR) G8.7-0.1 with the Large Area Telescope (LAT) on board the Fermi Gamma-ray Space Telescope. An investigation of the relationship between G8.7-0.1 and the TeV unidentified source HESS J1804-216 provides us with an important clue on diffusion process of cosmic rays if particle acceleration operates in the SNR. The GeV gamma-ray emission is extended with most of the emission in positional coincidence with the SNR G8.7-0.1 and a lesser part located outside the western boundary of G8.7-0.1. The region of the gamma-ray emission overlaps spatially connected molecular clouds, implying a physical connection for the gamma-ray structure. The total gamma-ray spectrum measured with LAT from 200 MeV-100 GeV can be described by a broken power-law function with a break of 2.4 ± 0.6 (stat) ± 1.2 (sys) GeV, and photon indices of 2.10 ± 0.06 (stat) ± 0.10 (sys) below the break and 2.70 ± 0.12 (stat) ± 0.14 (sys) above the break. Given the spatial association among the gamma rays, the radio emission of G8.7-0.1, and the molecular clouds, the decay of ?0s produced by particles accelerated in the SNR and hitting the molecular clouds naturally explains the GeV gamma-ray spectrum. We also find that the GeV morphology is not well represented by the TeV emission from HESS J1804-216 and that the spectrum in the GeV band is not consistent with the extrapolation of the TeV gamma-ray spectrum. The spectral index of the TeV emission is consistent with the particle spectral index predicted by a theory that assumes energy-dependent diffusion of particles accelerated in an SNR. We discuss the possibility that the TeV spectrum originates from the interaction of particles accelerated in G8.7-0.1 with molecular clouds, and we constrain the diffusion coefficient of the particles.

Ajello, M.; Allafort, A.; Baldini, L.; Ballet, J.; Barbiellini, G.; Bastieri, D.; Bechtol, K.; Bellazzini, R.; Berenji, B.; Blandford, R. D.; Bloom, E. D.; Bonamente, E.; Borgland, A. W.; Bregeon, J.; Brigida, M.; Bruel, P.; Buehler, R.; Buson, S.; Caliandro, G. A.; Cameron, R. A.; Caraveo, P. A.; Casandjian, J. M.; Cecchi, C.; Charles, E.; Chekhtman, A.; Ciprini, S.; Claus, R.; Cohen-Tanugi, J.; Cutini, S.; de Angelis, A.; de Palma, F.; Dermer, C. D.; Silva, E. do Couto e.; Drell, P. S.; Drlica-Wagner, A.; Dubois, R.; Favuzzi, C.; Fegan, S. J.; Ferrara, E. C.; Focke, W. B.; Frailis, M.; Fukazawa, Y.; Fukui, Y.; Fusco, P.; Gargano, F.; Gasparrini, D.; Germani, S.; Giglietto, N.; Giommi, P.; Giordano, F.; Giroletti, M.; Glanzman, T.; Godfrey, G.; Grove, J. E.; Guiriec, S.; Hadasch, D.; Hanabata, Y.; Harding, A. K.; Hayashi, K.; Hays, E.; Itoh, R.; Jóhannesson, G.; Johnson, A. S.; Kamae, T.; Katagiri, H.; Kataoka, J.; Knödlseder, J.; Kubo, H.; Kuss, M.; Lande, J.; Latronico, L.; Lee, S.-H.; Lionetto, A. M.; Longo, F.; Loparco, F.; Lovellette, M. N.; Lubrano, P.; Mazziotta, M. N.; Mehault, J.; Michelson, P. F.; Mizuno, T.; Moiseev, A. A.; Monte, C.; Monzani, M. E.; Morselli, A.; Moskalenko, I. V.; Murgia, S.; Nakamori, T.; Naumann-Godo, M.; Nishino, S.; Nolan, P. L.; Norris, J. P.; Nuss, E.; Ohno, M.; Ohsugi, T.; Okumura, A.; Omodei, N.; Orlando, E.; Ormes, J. F.; Paneque, D.; Parent, D.; Pelassa, V.; Pesce-Rollins, M.; Pierbattista, M.; Piron, F.; Porter, T. A.; Rainò, S.; Rando, R.; Reimer, A.; Reimer, O.; Reposeur, T.; Roth, M.; Sadrozinski, H. F.-W.; Sgrò, C.; Siskind, E. J.; Smith, P. D.; Spandre, G.; Spinelli, P.; Suson, D. J.; Tajima, H.; Takahashi, H.; Tanaka, T.; Thayer, J. G.; Thayer, J. B.; Tibaldo, L.; Tibolla, O.; Torres, D. F.; Tosti, G.; Tramacere, A.; Troja, E.; Uchiyama, Y.; Uehara, T.; Usher, T. L.; Vandenbroucke, J.; Van Etten, A.; Vasileiou, V.; Vianello, G.; Vilchez, N.; Vitale, V.; Waite, A. P.; Wang, P.; Winer, B. L.; Wood, K. S.; Yamamoto, H.; Yamazaki, R.; Yang, Z.; Yasuda, H.; Ziegler, M.; Zimmer, S.

2012-01-01

351

Fermi Large Area Telescope Observations of the Supernova Remnant GS.7-0.1  

NASA Technical Reports Server (NTRS)

We present a detailed analysis of the GeV gamma-ray emission toward the supernova remnant (SNR) G8.7-0.1 with the Large Area Telescope (LAT) onboard the Fermi Gamma-ray Space Telescope. An investigation of the relationship among G8.7-0.1 and the TeV unidentified source HESS J1804-216 provides us with an important clue on diffusion process of cosmic rays if particle acceleration operates in the SNR. The GeV gamma-ray emission is extended with most of the emission in positional coincidence with the SNR G8.7-0.1 and a lesser part located outside the western boundary of G8.7-0.1. The region of the gamma-ray emission overlaps spatially-connected molecular clouds, implying a physical connection for the gamma-ray structure. The total gamma-ray spectrum measured with LAT from 200 MeV-100 GeV can be described by a broken power-law function with a break of 2.4 +/- 0.6 (stat) +/- 1.2 (sys) GeV, and photon indices of2.10 +/- 0.06 (stat) +/- 0.10 (sys) below the break and 2.70 +/- 0.12 (stat) +/- 0.14 (sys) above the break. Given the spatial association among the gamma rays, the radio emission ofG8.7-0.1, and the molecular clouds, the decay of pions produced by particles accelerated in the SNR and hitting the molecular clouds naturally explains the GeV gamma-ray spectrum. We also find that the GeV morphology is not well represented by the TeV emission from HESS Jl804-2l6 and that the spectrum in the Ge V band is not consistent with the extrapolation of the TeV gamma-ray spectrum. The spectral index of the TeV emission is consistent with the particle spectral index predicted by a theory that assumes energy-dependent diffusion of particles accelerated in an SNR. We discuss the possibility that the TeV-spectrum originates from the interaction of particles accelerated in G8.7-0.l with molecular clouds, and we constrain the diffusion coefficient of the particles.

Ferrara, E. C.; Hays, E.; Troja, E.; Moiseev, A. A.

2012-01-01

352

Fermi Large Area Telescope Observations of the Supernova Remnant GS.7-0.1  

NASA Technical Reports Server (NTRS)

We present a detailed analysis of the GeV gamma-ray emission toward the supernova remnant (SNR) G8.7-0.1 with the Large Area Telescope (LAT) on board the Fermi Gamma-ray Space Telescope. An investigation of the relationship among G8.7-0.l and the TeV unidentified source HESS J1804-216 provides us with an important clue on diffusion process of cosmic rays if particle acceleration operates in the SNR. The GeV gamma-ray emission is extended with most of the emission in positional coincidence with the SNR G8.7-0.l and a lesser part located outside the western boundary of G8.7-0.l. The region of the gamma-ray emission overlaps spatially-connected molecular clouds, implying a physical connection for the gamma-ray structure. The total gamma-ray spectrum measured with LAT from 200 MeV-100 GeV can be described by a broken power-law function with a break of 2.4 +/- 0.6 (stat) +/- 1.2 (sys) GeV, and photon indices of 2.10 +/- 0.06 (stat) +/- 0.10 (sys) below the break and 2.70 +/- 0.12 (stat) +/- 0.l4 (sys) above the break. Given the spatial association among the gamma rays, the radio emission of G8.7-0.1, and the molecular clouds, the decay of 1IoS produced by particles accelerated in the SNR and hitting the molecular clouds naturally explains the GeV gamma-ray spectrum. We also find that the GeV morphology is not well represented by the TeV emission from HESS J1804-216 and that the spectrum in the GeV band is not consistent with the extrapolation of the TeV gamma-ray spectrum. The spectral index of the TeV emission is consistent with the particle spectral index predicted by a theory that assumes energy-dependent diffusion of particles accelerated in an SNR. We discuss the possibility that the TeV spectrum originates from the interaction of particles accelerated in G8.7-0.1 with molecular clouds, and we constrain the diffusion coefficient of the particles.

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

2011-01-01

353

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

354

The Spitzer c2d Survey of Large, Nearby, Interstellar Clouds. III. Perseus Observed with IRAC  

E-print Network

We present observations of 3.86 sq. deg. of the Perseus molecular cloud complex with the Spitzer Space Telescope Infrared Array Camera (IRAC). The maps show strong extended emission arising from shocked H2 in outflows in the region and from polycyclic aromatic hydrocarbon features. More than 120,000 sources are extracted toward the cloud. Based on their IRAC colors and comparison to off-cloud and extragalactic fields, we identify 400 candidate young stellar objects. About two thirds of these are associated with the young clusters IC348 and NGC1333, while the last third is distributed over the remaining cloud. We classify the young stellar objects according to the traditional scheme based on the slope of their spectral energy distributions. Significant differences are found for the numbers of embedded Class I objects relative to more evolved Class II objects in IC348, NGC1333 and the remaining cloud with the embedded Class I and "flat spectrum" YSOs constituting 14%, 36% and 47% of the total number of YSOs identified in each of these regions. The high number of Class I objects in the extended cloud (61% of the Class I objects in the entire cloud) suggests that a significant fraction of the current star formation is occuring outside the two main clusters. Finally we discuss a number of outflows and identify their driving sources, including the known deeply embedded Class 0 sources outside the two major clusters. The Class 0 objects are found to be detected by Spitzer and have very red [3.6]-[4.5] colors but do not show similarly red [5.8]-[8.0] colors. The Class 0 objects are easily identifiable in color-color diagrams plotting these two colors but are problematic to extract automatically due to the extended emission from shocked gas or scattered light in cavities related to the associated outflows.

Jes K. Jorgensen; Paul M. Harvey; Neal J. Evans II; Tracy L. Huard; Lori E. Allen; Alicia Porras; Geoffrey A. Blake; Tyler L. Bourke; Nicholas Chapman; Lucas Cieza; David W. Koerner; Shih-Ping Lai; Lee G. Mundy; Philip C. Myers; Deborah L. Padgett; Luisa Rebull; Anneila I. Sargent; William Spiesman; Karl R. Stapelfeldt; Ewine F. van Dishoeck; Zahed Wahhaj; Kaisa E. Young

2006-03-21

355

Cover Image: USGS Circular 1381  

USGS Multimedia Gallery

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

356

Circularly-Polarized Microstrip Antenna  

NASA Technical Reports Server (NTRS)

Microstrip construction compact for mobile applications. Circularly polarized microstrip antenna made of concentric cylindrical layers of conductive and dielectric materials. Coaxial cable feedlines connected to horizontal and vertical subelements from inside. Vertical subelement acts as ground for horizontal subelement.

Stanton, P. H.

1985-01-01

357

Correlated particle and magnetic field observations of a large-scale magnetic loop structure behind an interplanetary shock  

NASA Technical Reports Server (NTRS)

From a survey of observations on ISEE-3, an example of correlated particle and magnetic field observations of a large-scale magnetic loop structure is presented. Bidirectional proton fluxes were observed for a period of 40 hours in the energy range 35-1600 keV approximately 12 hours after the passage of the interplanetary shock of December 11, 1980, and directly after the passage of a discontinuity. For each of the eight logarithmically spaced energy channels, a three-dimensional anisotropy analysis reveals streaming along both directions of the magnetic field. The magnetic field rotated slowly but steadily through approximately 180 deg during this same 40-hour period; this is consistent with the existence of a large-scale loop with extent greater than 0.5 AU. The observations suggest that the particles are being injected into the loop sunward of the spacecraft; they appear as bidirectional fluxes in the outermost regions of the loop arising from a combination of focusing and near scatter-free transport.

Sanderson, T. R.; Marsden, R. G.; Reinhard, R.; Wenzel, K.-P.; Smith, E. J.

1983-01-01

358

Observations of a large-scale vortex-like structure in the deep-tail plasma sheet boundary layer  

NASA Technical Reports Server (NTRS)

ISEE-3 observations of a large-scale vortexlike structure in the deep tail of the magnetosphere at X(GSM) = -217 earth radii are reported. The structure is characterized by two clockwise rotations of the energetic-ion anisotropy vector. Variations in the magnetic-field vector approximately 180 deg out of phase with the ion variations are observed. This structure is most likely the signature within the magnetosphere of a surface wave at the magnetopause driven by a Kelvin-Helmholtz instability. Conditions inside and outside of the magnetosphere, as observed by ISEE-3 and ISEE-2, respectively, are examined; these conditions suggest that the surface wave is most likely propagating in the slow mode.

Sanderson, T. R.; Daly, P.; Wenzel, K.-P.; Hones, E. W., Jr.; Smith, E. J.

1986-01-01

359

Positions of equilibrium points for dust particles in the circular restricted three-body problem with radiation  

NASA Astrophysics Data System (ADS)

For a body with negligible mass moving in the gravitational field of a star with one planet in a circular orbit (the circular restricted three-body problem), five equilibrium points exist and are known as the Lagrangian points. The positions of the Lagrangian points are not valid for dust particles because in the derivation of the Lagrangian points it is assumed that no other forces besides the gravitation act on the body with negligible mass. Here, we determined positions of the equilibrium points for the dust particles in the circular restricted three-body problem with radiation. The equilibrium points are located on curves connecting the Lagrangian points in the circular restricted three-body problem. The equilibrium points for Jupiter are distributed in large interval of heliocentric distances due to its large mass. The equilibrium points for the Earth explain a cloud of dust particles trailing the Earth observed with the Spitzer Space Telescope. The dust particles moving in the equilibrium points are distributed in interplanetary space according to their properties.

Pástor, P.

2014-11-01

360

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

361

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

SciTech Connect

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

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

2013-11-01

362

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

NASA Astrophysics Data System (ADS)

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

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

2014-12-01

363

Merged interaction regions and large-scale fluctuations observed by the Voyager 2 in the distant heliosphere  

NASA Technical Reports Server (NTRS)

The merged interaction regions (MIRs) and large-scale fluctuations of the heliospheric magnetic field play a major role in the dynamics of the solar wind, the position and motion of the termination shock and heliopause, the triggering of radio emissions, and the modulation of cosmic rays. The structure of MIRs and large-scale fluctuations varies with distance from the sun and with solar activity. Here we compare Voyager 2 observations near the maximum of solar activity (1989 through 1991) with those during the declining phase of solar activity (1992 thorough 1994). Global MIRs with strong magnetic fields, preceded by a strong shock, were observed near solar maximum. During the declining phase of the solar cycle, the MIRs had significantly weaker magnetic fields. In both cases the pickup protons, identified by an analysis of pressure balanced structures, play a major role in the dynamical evolution of the MIRs beyond 30 AU. The large-scale magnetic field fluctuations have significantly greater amplitudes near solar maximum than during the declining phase of the solar cycle.

Burlaga, L. F.; Ness, N. F.

1995-01-01

364

Circular forms of Uukuniemi virion RNA: an electron microscopic study.  

PubMed Central

Because the ribonucleoprotein forms of the segments of the Uukuniemi virus genome have previously been characterized as circular, we examined the isolated RNAs by electron microscopy under conditions of increasing denaturation. After spreading under moderately denaturing conditions (50 or 60% formamide), 50 to 70% of the molecules were circular. Increasing the formamide concentration to 70 and 85% decreased the number of circular forms, and only linear forms were observed after incubation of the RNA at 60 degrees C for 15 min in 99% formamide. When spread from 4 M urea-80% formamide--another condition known to denature RNA--only 5 to 30% circular molecules were observed. Pretreatment of the RNA with 0.5 M glyoxal at 37 degrees C for 15 min prior to spreading from 50% formamide gave less than 5% cirucular forms. Length measurement of the molecules showed that they were not significantly degraded by any of the methods employed. The circular molecules were destroyed by treatment with pancreatic RNase, but were unaffected by DNase or proteinase K treatment. After complete denaturation of the RNA, the circles could be reformed under reannealing conditions. We conclude that the three size classes of RNA that comprise the Uukuniemi virus genome are circular molecules probably maintained in that form by base pairing between inverted complementary sequences at the 3' and 5' ends of linear molecules. Images PMID:850304

Hewlett, M J; Pettersson, R F; Baltimore, D

1977-01-01

365

Circular High-Impedance Surfaces Characterization  

Microsoft Academic Search

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

Julien Sarrazin; Anne-Claire Lepage; Xavier Begaud

2012-01-01

366

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

NASA Astrophysics Data System (ADS)

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

Hui, M.-T.

2013-12-01

367

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

NASA Astrophysics Data System (ADS)

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

Hui, Man-To

2014-11-01

368

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

369

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

370

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

NASA Astrophysics Data System (ADS)

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

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

2012-12-01

371

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

372

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

E-print Network

We present multiwavelength observations of a large-amplitude oscillation of a polar crown filament on 15 October 2002. The oscillation occurred during the slow rise (about 1 km/s) 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 onboard 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 period of oscillation was about two hours and did not change significantly during the oscillation. We also identified the oscillation as a "winking filament" in the H-alpha images taken by the Flare Monitoring Telescope, and as a spatial displacement 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.

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

2007-11-26

373

Insights into the nature of northwest-to-southeast aligned ionospheric wavefronts from contemporaneous Very Large Array and ionosondes observations  

E-print Network

The results of contemporaneous summer nighttime observations of midlatitude medium scale traveling ionospheric disturbances (MSTIDs) with the Very Large Array (VLA) in New Mexico and nearby ionosondes in Texas and Colorado are presented. Using 132, 20-minute observations, several instances of MSTIDs were detected, all having wavefronts aligned northwest to southeast and mostly propagating toward the southwest, consistent with previous studies of MSTIDs. However, some were also found to move toward the northeast. It was found that both classes of MSTIDs were only found when sporadic-E (Es) layers of moderate peak density (1.53 MHz that was not present when 1.5observed either before midnight or when the F-region height was increasing at a relatively high rate, even when these Es layers were observed. Combining this result with AE indices which were relatively high at the time (an average of about 300 nT and maximum of nearly 700 nT), it is inferred that both the lack of MSTIDs ...

Helmboldt, J F

2012-01-01

374

Large-scale traveling ionospheric disturbances observed using GPS receivers over high-latitude and equatorial regions  

NASA Astrophysics Data System (ADS)

This paper presents the first results of large-scale traveling ionospheric disturbances (LSTIDs) observation during two moderate magnetic storm events on 28 May 2011 (SYM-H? -94 nT and Dst?-80 nT) and 6 August 2011 (SYM-H?-126 nT and Dst?-113 nT) over the high-latitude region in Russia, Sweden, Norway, Iceland and Greenland and equatorial region in the Peninsular Malaysia using vertical total electron content (VTEC) from the Global Positioning System (GPS) observations measurement. The propagation of the LSTID signatures in the GPS TEC measurements over Peninsular Malaysia was also investigated using VTEC map. The LSTIDs were found to propagate both equatorward and poleward directions during these two events. The results showed that the LSTIDs propagated faster at high-latitude region with an average phase velocity of 1074.91 m/s than Peninsular Malaysia with an average phase velocity of 604.84 m/s. The LSTIDs at the high-latitude region have average periods of 150 min whereas the ones observed over Peninsular Malaysia have average periods of 115 min. The occurrences of these LSTIDs were also found to be the subsequent effects of substorm activities in the auroral region. To our knowledge, this is the first result of observation of LSTIDs over Peninsular Malaysia during the 24th solar cycle.

Idrus, Intan Izafina; Abdullah, Mardina; Hasbi, Alina Marie; Husin, Asnawi; Yatim, Baharuddin

2013-09-01

375

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

376

Statistical analysis of the large-scale structure of the Universe using observational data and numerical modeling  

NASA Astrophysics Data System (ADS)

The statistical properties of elements of the large-scale structure of the Universe are studied using the SDSS DR7 galaxy catalog and a dark-matter halo catalog obtained via numerical modeling using MultiDark Run1. The minimum spanning tree technique is used to distinguish the large-scale structure, and the Core Sampling method is used to analyze its properties. As a result, the SDSS DR7 and MultiDark Run1 catalogs are divided into subcatalogs of two-dimensonal walls and one-dimensional filaments. Some statistical properties of these subcatalogs are compared with theoretical predictions. The mean separation between the walls is measured using both the observations and numerical modeling results (50-60 Mpc/ h) and the distribution of the wall surface density is derived. The fraction of the SDSS DR7 galaxy clusters thought to have been distorted by the observational effect called "fingers of God" is estimated. Dense clusters for which this effect is most appreciable constitute ˜15% of the analyzed clusters. The influence of these clusters on the final result is eliminated by fitting the orientation of test cylinders in the Core Sampling method.

Semenov, V. A.

2013-07-01

377

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

NASA Technical Reports Server (NTRS)

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

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

1981-01-01

378

[Family Planning Circular of 1990].  

PubMed

In 1990, the government of Guangdong issued a Family Planning Circular demanding that the people of Guangdong take immediate actions to push ahead with Guangdong's family planning (FP) work. The Circular provides that, despite the fact that Guangdong has achieved gratifying results in its FP work this year, it has failed to fulfill its FP quotas and check excessive population growth for 4 successive years in the 7th 5-Year period. The Circular also provides that, in view of this rigorous situation, the Government demands that people's governments at all levels in Guangdong immediately formulate specific plans aimed at fully implementing to the FP quotas and an FP-oriented responsibility system at all levels. All concerned departments and mass organizations in Guangdong are required actively to cooperate and coordinate with one another in carrying out FP work. PMID:12317499

1990-05-10

379

Multi-spacecraft Study of Three Large NR Electron Events Observed by ACE and Ulysses: Injection Histories 70 Degrees Apart  

NASA Astrophysics Data System (ADS)

We present a sample of three large near-relativistic (NR; >50 keV) electron events observed in 2001 by both the ACE and the Ulysses spacecraft, when Ulysses was at high-northern latitudes and close to 2 AU. All three events are associated with large solar flares, strong decametric type II radio bursts and accompanied by wide (> 212 deg) and fast (> 1400 km/s) coronal mass ejections (CMEs). We use advanced interplanetary transport simulations and make use of the directional intensities observed in-situ by the spacecraft, to infer the electron injection profiles close to the Sun and the interplanetary transport conditions. For the three selected events, we find similar interplanetary transport conditions at low and at high latitudes, with values of the mean free path ranging from 0.05 AU to 0.27 AU. Despite the similar solar origin signatures, we find differences in the injection profiles inferred for each spacecraft. The injection timescales seem to be ordered by the heliospheric current sheet (HCS) sector boundaries; that is, extended injection profiles (associated with coronal shocks) are found if the footpoint of the spacecraft laid in the flare magnetic sector, while intermittent spare injection episodes appear when the spacecraft footpoint is in the opposite sector or a wrap in the HCS bounded the CME structure. Our results suggest that the large-scale coronal magnetic field might play a role in the expansion of coronal shocks and support an scenario in which reconnection processes during restructuring of coronal magnetic fields contribute to solar energetic particle release.

Agueda, N.; Lario, D.; Dalla, S.; Sanahuja, B.; Vainio, R. O.

2012-12-01

380

Large-scale Desert Dust Deposition on the Himalayan Snow Cover: A Climatological Perspective from Satellite Observations  

NASA Astrophysics Data System (ADS)

The Himalaya-Tibetan Plateau (HTP) has a profound influence on the Asian climate. The HTP are also among the largest snow/ice-covered regions on the Earth and provide major freshwater resource to the downstream densely-populated regions of Asia. Recent studies indicate climate warming over the HTP amplified by atmospheric heating and deposition of absorbing aerosols (e.g. dust and soot) over the HTP snowpack and glaciers. Recently, greater attention has focused on the effects of soot deposition on accelerated snowmelt and glacier retreat in the HTP, associated with increasing anthropogenic emissions in Asia. On the other hand, the role of transported dust affecting snow albedo/melt is not well understood over the HTP, in spite of the large annual cycle of mineral dust loading, particularly over the northern parts of south Asia during pre-monsoon season. This study addresses the large-scale effects of dust deposition on snow albedo in the elevated HTP from a satellite observational perspective. Dust aerosol transport, from southwest Asian arid regions, is observed in satellite imagery as darkening of the Himalayan snowpack. Additionally, multi-year spaceborne lidar observations, from CALIPSO, also show dust advected to elevated altitudes (~5km) over the Himalayan foothills, and episodically reaching the top of the western Himalaya. Spectral surface reflectance analysis of dust-laden snow cover (from MODIS) indicates enhanced absorption in the shorter visible wavelengths, yielding a significant gradient in the visible-nearIR reflectance spectrum. While soot in snow is difficult to distinguish from remote sensing, our spectral reflectance analysis of dust detection in the snowpack is consistent with theoretical simulations of snow darkening due to dust impurity. We find that the western HTP, in general, is influenced by enhanced dust deposition due to its proximity to major dust sources (and prevailing dust transport pathways), compared to the eastern HTP. Coinciding with the snowmelt period, dust deposition appears to further cause snow reflectance reduction, i.e. snow darkening, from spring to summer months. Among the entire HTP, we show that the western Himalaya and the Hindu-Kush snowpack are subjected to greater dust deposition and snow albedo reduction. Thus, our satellite-based observational study addresses the spatial variability of large-scale dust deposition on snow cover in the extensive HTP. A climatological and inter-annual perspective of the spatial variability of dust-induced snow darkening over the HTP will be presented, using ~10 years of MODIS spectral reflectance data (at high spatial resolution of ~1km). Results from this study provide insight into the particular role of desert dust towards accelerated seasonal snowmelt in the HTP.

Gautam, R.; Hsu, N. C.; Lau, W. K.

2013-12-01

381

Circular Bioassay Platforms for Applications in Microwave-Accelerated Techniques  

PubMed Central

In this paper, we present the design of four different circular bioassay platforms, which are suitable for homogeneous microwave heating, using theoretical calculations (i.e., COMSOL™ multiphysics software). Circular bioassay platforms are constructed from poly(methyl methacrylate) (PMMA) for optical transparency between 400–800 nm, has multiple sample capacity (12, 16, 19 and 21 wells) and modified with silver nanoparticle films (SNFs) to be used in microwave-accelerated bioassays (MABs). In addition, a small monomode microwave cavity, which can be operated with an external microwave generator (100 W), for use with the bioassay platforms in MABs is also developed. Our design parameters for the circular bioassay platforms and monomode microwave cavity during microwave heating were: (i) temperature profiles, (ii) electric field distributions, (iii) location of the circular bioassay platforms inside the microwave cavity, and (iv) design and number of wells on the circular bioassay platforms. We have also carried out additional simulations to assess the use of circular bioassay platforms in a conventional kitchen microwave oven (e.g., 900 W). Our results show that the location of the circular bioassay platforms in the microwave cavity was predicted to have a significant effect on the homogeneous heating of these platforms. The 21-well circular bioassay platform design in our monomode microwave cavity was predicted to offer a homogeneous heating pattern, where inter-well temperature was observed to be in between 23.72–24.13°C and intra-well temperature difference was less than 0.21°C for 60 seconds of microwave heating, which was also verified experimentally. PMID:25568813

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

2014-01-01

382

Direct observation of dopant atom diffusion in a bulk semiconductor crystal enhanced by a large size mismatch.  

PubMed

Diffusion is one of the fundamental processes that govern the structure, processing, and properties of materials and it plays a crucial role in determining device lifetimes. However, direct observations of diffusion processes have been elusive and limited only to the surfaces of materials. Here we use an aberration-corrected electron microscope to locally excite and directly image the diffusion of single Ce and Mn dopants inside bulk wurtzite-type AlN single crystals, identifying correlated vacancy-dopant and interstitial-dopant kick-out mechanisms. Using a 200 kV electron beam to supply energy, we observe a higher frequency of dopant jumps for the larger and heavier Ce atoms than the smaller Mn atoms. These observations confirm density-functional-theory-based predictions of a decrease in diffusion barrier for large substitutional atoms. The results show that combining depth sensitive microscopy with theoretical calculations represents a new methodology to investigate diffusion mechanisms, not restricted to surface phenomena, but within bulk materials. PMID:25375721

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

2014-10-10

383

Dual-frequency circularly polarized antennas based on stacked monofilar square spirals  

Microsoft Academic Search

Two radiating spirals stacked on a foam substrate are used in the design of a circularly polarized antenna designed to respect new bandwidth constraints resulting from the emergence of multimedia services in satellite communications. Orthogonal circular polarizations are required for up and down links over large frequency bandwidths. In the single antenna, 4 to 5% axial ratio (AR) bandwidths are

Jean-Marc Laheurte

2003-01-01

384

Flat plate boundary layer transition induced by a controlled near-wall circular cylinder wake  

NASA Astrophysics Data System (ADS)

The flat plate boundary layer transition induced by the wake of a circular cylinder close to the wall is experimentally investigated using particle image velocimetry (PIV) and hydrogen bubble visualization techniques. The wake of the circular cylinder is controlled by a slot synthetic jet at the rear stagnation point of the circular cylinder. It is found that when the synthetic jet is actuated, the wake can be greatly modified. When the excitation frequency of the synthetic jet is set at the natural shedding frequency of the cylinder wake, the symmetrical shedding pattern can be observed. While the excitation frequency increases to be twice of the natural shedding frequency, the wake appears to be antisymmetrical again, but with the shedding frequency locked onto half of the excitation frequency. Flow visualizations show that spanwise secondary vortices can be induced in the near wall region by these large scale vortices in the wake. It is found that the secondary vortices destabilize into streamwise stretched ? vortices as they convect downstream. After the introduction of the synthetic jet, the destabilization process is promoted. By investigating the disturbance growth inside the boundary layer, it reveals that the synthetic jet can cause earlier initialization of the disturbance growth, thus promoting the transition process of the boundary layer. An explanation is provided that the low frequency components of the wake disturbances, which interact with the boundary layer, are enhanced by the introduction of the synthetic jet. Therefore, the destabilization of the secondary vortices is promoted, and disturbance growth in the boundary layer initiates earlier.

He, Guo-Sheng; Wang, Jin-Jun

2015-02-01

385

Radiometric errors caused by diffraction from circular apertures - Edge effects  

Microsoft Academic Search

The diffraction corrections associated with a point source and a circular diffracting aperture are calculated for the case where the detector aperture diameter is nearly equal to that of the illuminated area. It is found that the diffraction corrections are relatively large near the center and near the edge, even using white light and detectors with very extended spectral sensitivities.

L. P. Boivin

1977-01-01

386

Plasma rotation in toroidal devices with circular cross-sections  

Microsoft Academic Search

The plasma rotation is theoretically investigated in toroidal devices. The dependence of magnetic axis curvature and torsion on the longitudinal coordinate and magnetic field ripples are taken into account. The calculations are carried out within the large aspect ratio and circular magnetic surfaces approximation. General equations for the relaxation of poloidal and toroidal velocities are obtained. The analysis of these

V. S. Tsypin; A. B. Mikhailovskii; R. M. O. Galvão; I. C. Nascimento; M. Tendler; C. A. de Azevedo; A. S. de Assis

1998-01-01

387

Broadband circular polarizer formed by stacked plasmonic metasurfaces  

Microsoft Academic Search

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

Yang Zhao; Andrea Alù

2011-01-01

388

Fourier transform vibrational circular dichroism and the artifact problem  

Microsoft Academic Search

FTIR vibrational circular dichroism spectra ofß-pinene are presented as an example of the artifact reduction capability of our new instrument design. The key to this advance is the incorporation of a lens after the sample to focus onto a relatively large detector. Baseline correction with just solvent becomes possible in some cases.

Petr Malon; Timothy A. Keiderling

1988-01-01

389

Chandra, Extreme Ultraviolet Explorer, and Very Large Array Observations of the Active Binary System ?2 Coronae Borealis  

NASA Astrophysics Data System (ADS)

We present the results of a coordinated observing campaign on the short-period RS CVn binary ?2 Coronae Borealis (F6V+G0V Porb=1.14 days) with the Very Large Array, the Extreme Ultraviolet Explorer, and the Chandra X-Ray Observatory High-Energy Transmission Grating Spectrometer. The radio emission is consistent with previously determined quiescent gyrosynchrotron properties. Multiple flares were seen with Extreme Ultraviolet Explorer, five occurring within two consecutive orbital periods. The first of these flares was observed with Chandra. The Chandra observations of ?2 CrB showed no systematic variations of line fluxes, widths, or Doppler shifts with orbital phase, nor any response in line width or offset due to the flare. This is consistent with both stars being equally active coronal emitters. We have developed a self-consistent method of spectral analysis to derive information from the line and continuum emissions concerning the distribution of plasma with temperature and elemental abundances. A bimodal temperature distribution is appropriate for both quiescent and flare intervals, with a stable peak at 6-8 MK and another variable enhancement at higher temperatures, with evidence for significant contribution from temperatures up to 50 MK during the flare, compared to 30 MK during quiescence. The iron abundance is subsolar during quiescence but is enriched by about a factor of 2 during a large flare seen with Chandra. The noble gas elements neon and argon show elevated abundances with respect to iron, but there is no clear evidence for any first ionization potential-based abundance pattern during quiescence or the flare. We have determined coronal electron densities from the helium-like ions O VII, Ne IX, Mg XI, and Si XIII, which imply densities >=1010 cm-3. There is a small enhancement in the electron densities derived for the flare, but it is not statistically significant. We call attention to electron temperature constraints provided by the ratios of 1s2 1S0-1snp 1P1 transitions of the helium-like ions O VII, Ne IX, Mg XI, and Si XIII. The derived coronal electron pressures change by 1-2 orders of magnitude over a 25% change in temperature, implying nonisobaric coronal conditions. We find no evidence for significant departures from the effectively thin coronal assumption. The electron densities inferred from the soft X-ray spectra are inconsistent with cospatial gyrosynchrotron emission; further observations are necessary to discriminate the relative locations of the radio and soft X-ray-emitting plasma.

Osten, Rachel A.; Ayres, Thomas R.; Brown, Alexander; Linsky, Jeffrey L.; Krishnamurthi, Anita

2003-01-01

390

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

391

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

PubMed

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

2012-12-21

392

Observations of the Young Supernova Remnant RX J1713.7-3946 with the Fermi Large Area Telescope  

NASA Astrophysics Data System (ADS)

We present observations of the young supernova remnant (SNR) RX J1713.7-3946 with the Fermi Large Area Telescope (LAT). We clearly detect a source positionally coincident with the SNR. The source is extended with a best-fit extension of 0fdg55 ± 0fdg04 matching the size of the non-thermal X-ray and TeV gamma-ray emission from the remnant. The positional coincidence and the matching extended emission allow us to identify the LAT source with SNR RX J1713.7-3946. The spectrum of the source can be described by a very hard power law with a photon index of ? = 1.5 ± 0.1 that coincides in normalization with the steeper H.E.S.S.-detected gamma-ray spectrum at higher energies. The broadband gamma-ray emission is consistent with a leptonic origin as the dominant mechanism for the gamma-ray emission.

Abdo, A. A.; Ackermann, M.; Ajello, M.; Allafort, A.; Baldini, L.; Ballet, J.; Barbiellini, G.; Baring, M. G.; Bastieri, D.; 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.; Casandjian, J. M.; Cecchi, C.; Chaty, S.; Chekhtman, A.; Cheung, C. C.; Chiang, J.; Cillis, A. N.; Ciprini, S.; Claus, R.; Cohen-Tanugi, J.; Conrad, J.; Corbel, S.; Cutini, S.; de Angelis, A.; de Palma, F.; Dermer, C. D.; Digel, S. W.; Silva, E. do Couto e.; Drell, P. S.; Drlica-Wagner, A.; Dubois, R.; Dumora, D.; Favuzzi, C.; Ferrara, E. C.; Fortin, P.; Frailis, M.; Fukazawa, Y.; Fukui, Y.; Funk, S.; Fusco, P.; Gargano, F.; Gasparrini, D.; Gehrels, N.; Germani, S.; Giglietto, N.; Giordano, F.; Giroletti, M.; Glanzman, T.; Godfrey, G.; Grenier, I. A.; Grondin, M.-H.; Guiriec, S.; Hadasch, D.; Hanabata, Y.; Harding, A. K.; Hayashida, M.; Hayashi, K.; Hays, E.; Horan, D.; Jackson, M. S.; Jóhannesson, G.; Johnson, A. S.; 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.; Lovellette, M. N.; Lubrano, P.; Madejski, G. M.; Makeev, A.; Mazziotta, M. N.; McEnery, J. E.; Michelson, P. F.; Mignani, R. P.; 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.; Orlando, E.; Ormes, J. F.; Paneque, D.; Parent, D.; Pelassa, V.; Pesce-Rollins, M.; Pierbattista, M.; Piron, F.; Pohl, M.; Porter, T. A.; Rainò, S.; Rando, R.; Razzano, M.; Reimer, O.; Reposeur, T.; Ritz, S.; Romani, R. W.; Roth, M.; Sadrozinski, H. F.-W.; Saz Parkinson, P. M.; Sgrò, C.; Smith, D. A.; Smith, P. D.; Spandre, G.; Spinelli, P.; Strickman, M. S.; Tajima, H.; Takahashi, H.; Takahashi, T.; Tanaka, T.; Thayer, J. G.; Thayer, J. B.; Thompson, D. J.; Tibaldo, L.; Tibolla, O.; Torres, D. F.; Tosti, G.; Tramacere, A.; Troja, E.; Uchiyama, Y.; Vandenbroucke, J.; Vasileiou, V.; Vianello, G.; Vilchez, N.; Vitale, V.; Waite, A. P.; Wang, P.; Winer, B. L.; Wood, K. S.; Yamamoto, H.; Yamazaki, R.; Yang, Z.; Ziegler, M.

2011-06-01

393

Observations of large mass-independent fractionation occurring in MC-ICPMS: implications for determination of accurate isotope amount ratios.  

PubMed

Multicollector inductively coupled plasma mass spectrometry (MC-ICPMS) suffers large bias in isotope amount ratio determinations which has to be properly accounted for. The choice of the proper discrimination model is crucial. Over the last few decades, the exponential mass-bias correction model (Russell's law) has become a standard curriculum in isotope amount ratio measurements. In nature, however, isotopic fractionation that deviates significantly from the exponential model has been known for a long time. Recently, such fractionation was also observed in MC-ICPMS. This phenomenon is termed mass-independent fractionation. In this study, significant departure from the mass-dependent fractionation model is reported for germanium and lead with the most dramatic occurring for germanium-73 and lead-204 isotopes wherein, on average, close to a half percent bias was evidenced from the Russell's law. PMID:22023716

Yang, Lu; Mester, Zoltán; Zhou, Lian; Gao, Shan; Sturgeon, Ralph E; Meija, Juris

2011-12-01

394

Benchmarking Electron-Cloud Build-Up and Heat-Load Simulations against Large-Hadron-Collider Observations  

E-print Network

After reviewing the basic features of electron clouds in particle accelerators, the pertinent vacuum-chamber surface properties, and the electron-cloud simulation tools in use at CERN, we report recent observations of electron-cloud phenomena at the Large Hadron Collider (LHC) and ongoing attempts to benchmark the measured LHC vacuum pressure increases and heat loads against electron-cloud build-up simulations aimed at determining the actual surface parameters and at monitoring the so-called scrubbing process. Finally, some other electron-cloud studies related to the LHC are mentioned, and future study plans are described. Presented at MulCoPim2011, Valencia, Spain, 21-23 September 2011.

Dominguez, O; Maury, H; Rumolo, G; Zimmermann, F

2011-01-01

395

Circular polarized leaky wave surface  

NASA Astrophysics Data System (ADS)

A circular polarized (CP) infrared (IR) leaky wave surface design is presented. The metasurface consists of an array of rectangular patches connected by microstrip and operating over the long-wave infrared (LWIR) spectrum with directional wave emission and absorption. The surface is composed of periodically aligned arrays of sub-wavelength metal patches separated from a ground plane by a dielectric slab. The design combines the features of the conventional patch and leaky wave antenn