WorldWideScience

Sample records for multifrequency vla observations

  1. Multifrequency VLA observations of PKS 0745 - 191 - The archetypal 'cooling flow' radio source?

    Science.gov (United States)

    Baum, S. A.; O'Dea, C. P.

    1991-01-01

    Ninety-, 20-, 6- and 2-cm VLA observations of the high-radio-luminosity cooling-flow radio source PKS 0745 - 191 are presented. The radio source was found to have a core with a very steep spectrum (alpha is approximately -1.5) and diffuse emission with an even steeper spectrum (alpha is approximately -1.5 to -2.3) without clear indications of the jets, hotspots, or double lobes found in the other radio sources of comparable luminosity. It is inferred that the energy to power the radio source comes from the central engine, but the source's structure may be heavily influenced by the past history of the galaxy and the inflowing intracluster medium. It is shown that, while the radio source is energetically unimportant for the cluster as a whole, it is important on the scale of the cooling flow. The mere existence of cosmic rays and magnetic fields within a substantial fraction of the volume inside the cooling radius has important consequences for cooling-flow models.

  2. Multifrequency observations of BL Lacertae

    Science.gov (United States)

    Bregman, Joel N.; Glassgold, A. E.; Huggins, P. J.; Neugebauer, G.; Soifer, B. T.

    1990-01-01

    Optical, IR, and radio monitoring data covering 20 years are presented for BL Lac. Also, four simultaneous multifrequency spectra are given, covering the range 10 to the 9th - 10 to the 18th Hz. These spectra include ground-based observations and data from the Einstein, Exosat, IUE, and IRAS satellites. From the monitoring data, the character of emission variability is determined using structure functions. The multifrequency spectra are used to study the origin of X-ray emission and to determine the physical parameters of emitting regions. The data show that the emitting region is inhomogeneous, with a small inner region of high density and magnetic field that eventually becomes a large, partially opaque radio emitting region with a low density and magnetic fields. Also, the two simple predictions of the synchrotron self-Compton model are reproduced by the multifrequency spectra.

  3. VLA observations of the "water fountain" IRAS 16552-3050

    OpenAIRE

    Suárez, Olga; Gómez, J. F.; Miranda, L. F.

    2008-01-01

    We present Very Large Array (VLA) observations of the water maser emission towards IRAS 16552-3050. The maser emission shows a velocity spread of ~170 km/s, and a bipolar distribution with a separation between the red and blueshifted groups of ~0.08". These observations and the likely post-AGB nature of the source indicate that IRAS 16552-3050 can be considered as a member of the "water fountain" class of sources (evolved stars showing H2O maser emission with a velocity spread $\\ga$ 100 km/s,...

  4. Resolved Multifrequency Radio Observations of GG Tau

    CERN Document Server

    Andrews, Sean M; Isella, Andrea; Birnstiel, Tilman; Rosenfeld, Katherine A; Wilner, David J; Perez, Laura M; Ricci, Luca; Carpenter, John M; Calvet, Nuria; Corder, Stuartt A; Deller, Adam T; Dullemond, Cornelis P; Greaves, Jane S; Harris, Robert J; Henning, Thomas; Kwon, Woojin; Lazio, Joseph; Linz, Hendrik; Mundy, Lee G; Sargent, Anneila I; Storm, Shaye; Testi, Leonardo

    2014-01-01

    We present sub-arcsecond resolution observations of continuum emission associated with the GG Tau quadruple star system at wavelengths of 1.3, 2.8, 7.3, and 50 mm. These data confirm that the GG Tau A binary is encircled by a circumbinary ring at a radius of 235 AU with a FWHM width of ~60 AU. We find no clear evidence for a radial gradient in the spectral shape of the ring, suggesting that the particle size distribution is spatially homogeneous on angular scales of ~0.1". A central point source, likely associated with the primary component (GG Tau Aa), exhibits a composite spectrum from dust and free-free emission. Faint emission at 7.3 mm is observed toward the low-mass star GG Tau Ba, although its origin remains uncertain. Using these measurements of the resolved, multifrequency emission structure of the GG Tau A system, models of the far-infrared to radio spectrum are developed to place constraints on the grain size distribution and dust mass in the circumbinary ring. The non-negligible curvature present ...

  5. Dual frequency observations of flares with the VLA

    Science.gov (United States)

    Dulk, G. A.; Bastian, T. S.; Hurford, G. J.

    1983-01-01

    Observations are presented of two subflares near the limb on 21 and 22 November 1981 and an M7.7 flare on 8 May 1981 made at 5 and 15 GHz using the VLA. One of the November flares produced no 5 GHz radiation, while the 15 GHz radiation in the other flare emanated from a source which was smaller, lower, and displaced from the 5 GHz source. The flare occurring on 8 May was intense and complex, and contained two or more sources at both 5 and 15 GHz. Prior to the peak of the flare, the sources were found to grow in size, after which time only weak subsources were visible to the VLA. These subsources were found to be located between or at the edge of the H-alpha ribbons and the two hard X-ray sources imaged by the Hinotori satellite. Highly polarized, bursty radiation was observed at 1 and 2 GHz, which indicated that an electron-cyclotron maser operated during the flare. The maximum field strength in flaring loops is estimated to be 360-600 gauss.

  6. ALMA and VLA Observations of Proplyd Candidates near Sgr A*

    Science.gov (United States)

    Yusef-Zadeh, Farhad; Cotton, William D.; Royster, Marc; Kunneriath, Devaky; Wardle, M.; Roberts, D. A.; Wootten, Al; Schoedel, R.

    2017-01-01

    Using the VLA, we recently detected a large number of protoplanetary disk (proplyd) candidates lying within a couple of light years of the massive black hole Sgr A*. The bow-shock appearance of proplyd candidates point toward the young massive stars located near Sgr A*. Similar to Orion proplyds, the strong UV radiation from the cluster of massive stars at the Galactic center is expected to photoevaporate and photoionize the circumstellar disks around young, low mass stars, thus allowing detection of the ionized outflows. To confirm this interpretation, ALMA observations detect millimeter emission at 226 GHz from five proplyd candidates that had been detected at 44 and 34 GHz with the VLA. We determine the mass of protoplanetary disks from cool dust emission. These measurements show the presence of on-going star formation with the implication that gas clouds can survive near Sgr A* and the relative importance of high vs low-mass star formation in the strong tidal and radiation fields of the Galactic center.

  7. VLA and VLBI observations of core-dominated quasars

    Energy Technology Data Exchange (ETDEWEB)

    Kollgaard, R.I.

    1989-01-01

    High dynamic range VLA observations of the total intensity and linear polarization of 24 powerful, core dominated quasars have been made at 5 GHz, as well as the first millisecond linear polarization observations of 3C 273. For ten quasars the resolution of the VLA was sufficient to reveal details of the compact extended emission surrounding the bright cores. The former all exhibit one sided jets, and most show evidence of diffuse halos. The luminosity of the extended emission is sufficient for those to be Fanaroff-Riley Class II radio sources. This interpretation is confirmed by the linear polarization structure of the jets and terminal hotspots. If these quasars are similar to powerful lobe dominated sources but are oriented with jet axes close to the line of sight, the large degrees of polarization observed in the hotspots suggest that they are travelling at speeds {upsilon} > 0.5c. The superluminal quasar 3C 345 has been imaged with a variety of resolutions. In spite of the bending on the millisecond scale, the author finds that the jet of 3C 345 is very straight for the first 2 and then has two knots which show an abrupt shift in azimuth. The inferred magnetic field in the jet is offset {approximately}30{degree} from a perpendicular orientation with respect to the jet axis. This quasar also appears to have a faint counter jet, with the jet/counter jet luminosity ratio suggesting jet speeds {upsilon} > 0.56c. There is also an asymmetric diffuse halo. Milliarsecond polarization observations of 3C 273 show that the core (component D) is very weakly polarized. Appreciable polarized flux was detected from five of the superluminal components in the jet, with the fractional polarization increasing with distance from D.

  8. LOFAR, VLA, and Chandra observations of the Toothbrush galaxy cluster

    CERN Document Server

    van Weeren, R J; Brüggen, M; Andrade-Santos, F; Ogrean, G A; Williams, W L; Röttgering, H J A; Dawson, W A; Forman, W R; de Gasperin, F; Hardcastle, M J; Jones, C; Miley, G K; Rafferty, D A; Rudnick, L; Sabater, J; Sarazin, C L; Shimwell, T W; Bonafede, A; Best, P N; Bîrzan, L; Cassano, R; Chyży, K T; Croston, J H; Dijkema, T J; Ensslin, T; Ferrari, C; Heald, G; Hoeft, M; Horellou, C; Jarvis, M J; Kraft, R P; Mevius, M; Intema, H T; Murray, S S; Orrú, E; Pizzo, R; Sridhar, S S; Simionescu, A; Stroe, A; van der Tol, S; White, G J

    2016-01-01

    We present deep LOFAR observations between 120-181 MHz of the "Toothbrush" (RX J0603.3+4214), a cluster that contains one of the brightest radio relic sources known. Our LOFAR observations exploit a new and novel calibration scheme to probe 10 times deeper than any previous study in this relatively unexplored part of the spectrum. The LOFAR observations, when combined with VLA, GMRT, and Chandra X-ray data, provide new information about the nature of cluster merger shocks and their role in re-accelerating relativistic particles. We derive a spectral index of $\\alpha = -0.8 \\pm 0.1$ at the northern edge of the main radio relic, steepening towards the south to $\\alpha \\approx - 2$. The spectral index of the radio halo is remarkably uniform ($\\alpha = -1.16$, with an intrinsic scatter of $\\leq 0.04$). The observed radio relic spectral index gives a Mach number of $\\mathcal{M} = 2.8^{+0.5}_{-0.3}$, assuming diffusive shock acceleration (DSA). However, the gas density jump at the northern edge of the large radio r...

  9. Commensal low frequency observing on the NRAO VLA: VLITE status and future plans

    Science.gov (United States)

    Clarke, Tracy E.; Kassim, Namir E.; Brisken, Walter; Helmboldt, Joseph; Peters, Wendy; Ray, Paul S.; Polisensky, Emil; Giacintucci, Simona

    2016-08-01

    The National Radio Astronomy Observatory's 27 antenna Karl G. Jansky Very Large Array (NRAO VLA) has been successfully transitioned to a broadband system. As part of this transition, the US Naval Research Laboratory (NRL) worked with NRAO to develop, install, and commission a new commensal low frequency system on the VLA. The VLA Low-band Ionosphere and Transient Experiment (VLITE) has dedicated samplers and uses spare NRAO optical fibers to transmit the signal from 10 low band receivers on VLA antennas to a dedicated real-time DiFX correlator. For these 10 antennas, this observing mode provides simultaneous data from both the low frequency receivers through the VLITE correlator and from the VLA higher frequencies receivers (1-50 GHz) through the NRAO WIDAR correlator. During the first 1.5 years of operation, VLITE recorded data at roughly 70% wall-time, providing 64 MHz of bandwidth centered at 352 MHz with 2s sample time and 100 kHz spectral resolution. VLITE operations require no additional resources from the VLA system and greatly expand the capabilities of the VLA through value-added PI science, stand-alone astrophysics, the opening of a new window on transient searches, and serendipity. We present an overview of the VLITE program, discuss the sky coverage and depth obtained during the first 1.5 years of operation, and brie y outline a possible path forward to a full 27 antenna LOw Band Observatory (LOBO) which could run commensally with all VLA operations.

  10. VLA observations of ultraluminous IRAS galaxies active nuclei or starbursts?

    CERN Document Server

    Crawford, T; Partridge, B; Strauss, M; Crawford, Thomas; Marr, Jon; Partridge, Bruce; Strauss, Michael

    1995-01-01

    We employed the Very Large Array (VLA) of the National Radio Astronomy Observatory in C configuration to map 39 ultraluminous IRAS galaxies at 6~cm and 20~cm, at resolutions of ~ 4" and 15", respectively, and 24 sources at 6~cm with in the A configuration with a resolution of ~0.5". Most of the sources have radio spectral indices indicative of synchrotron emission (alpha ~ -0.65). There is one source, however, that shows an inverted spectrum with alpha = +2.1; observations at higher frequencies show that the spectrum peaks between 5 and 8 GHz, as high as any of the ``gigahertz peaked spectrum'' sources studied by O'Dea etal. We discuss the implications of this source for observations of fluctuations in the CMB. Two of the sources show multiple unresolved components, another four are doubles with at least one resolved component, 14 show extended emission which could arise from a disk, and two show arc-second long jets. Our data fit the tight correlation found by Helou etal (1985) between far-infrared and micro...

  11. LOFAR, VLA, and Chandra Observations of the Toothbrush Galaxy Cluster

    Science.gov (United States)

    van Weeren, R. J.; Brunetti, G.; Brüggen, M.; Andrade-Santos, F.; Ogrean, G. A.; Williams, W. L.; Röttgering, H. J. A.; Dawson, W. A.; Forman, W. R.; de Gasperin, F.; Hardcastle, M. J.; Jones, C.; Miley, G. K.; Rafferty, D. A.; Rudnick, L.; Sabater, J.; Sarazin, C. L.; Shimwell, T. W.; Bonafede, A.; Best, P. N.; Bîrzan, L.; Cassano, R.; Chyży, K. T.; Croston, J. H.; Dijkema, T. J.; Enßlin, T.; Ferrari, C.; Heald, G.; Hoeft, M.; Horellou, C.; Jarvis, M. J.; Kraft, R. P.; Mevius, M.; Intema, H. T.; Murray, S. S.; Orrú, E.; Pizzo, R.; Sridhar, S. S.; Simionescu, A.; Stroe, A.; van der Tol, S.; White, G. J.

    2016-02-01

    We present deep LOFAR observations between 120 and 181 MHz of the “Toothbrush” (RX J0603.3+4214), a cluster that contains one of the brightest radio relic sources known. Our LOFAR observations exploit a new and novel calibration scheme to probe 10 times deeper than any previous study in this relatively unexplored part of the spectrum. The LOFAR observations, when combined with VLA, GMRT, and Chandra X-ray data, provide new information about the nature of cluster merger shocks and their role in re-accelerating relativistic particles. We derive a spectral index of α =-0.8+/- 0.1 at the northern edge of the main radio relic, steepening toward the south to α ≈ -2. The spectral index of the radio halo is remarkably uniform (α =-1.16, with an intrinsic scatter of ≤slant 0.04). The observed radio relic spectral index gives a Mach number of { M }={2.8}-0.3+0.5, assuming diffusive shock acceleration. However, the gas density jump at the northern edge of the large radio relic implies a much weaker shock ({ M }≈ 1.2, with an upper limit of { M }≈ 1.5). The discrepancy between the Mach numbers calculated from the radio and X-rays can be explained if either (i) the relic traces a complex shock surface along the line of sight, or (ii) if the radio relic emission is produced by a re-accelerated population of fossil particles from a radio galaxy. Our results highlight the need for additional theoretical work and numerical simulations of particle acceleration and re-acceleration at cluster merger shocks.

  12. Synergy of multifrequency studies from observations of NGC6334I

    CERN Document Server

    Seifahrt, Andreas; Beuther, Henrik; Leurini, Silvia; Brogan, Crystal L; Hunter, Todd R; Menten, Karl M; Stecklum, Bringfried; 10.1088/1742-6596/131/1/012030

    2008-01-01

    We combine multifrequency observations from the millimeter to near infrared wavelengths that demonstrate the spatial distributions of H2, CO, and NH3 emission, which are all manifestations of various shocks driven by outflows of deeply embedded sources in NGC6334I. In addition to the well-known northeast-southwest outflow we detect at least one more outflow in the region by combining observations from APEX, ATCA, SMA, Spitzer and VLT/ISAAC. Potential driving sources will be discussed. NGC6334I exhibits several signs of active star formation and will be a major target for future observatories such as Herschel and ALMA.

  13. Simultaneous multifrequency observations of the BL Lacertae object Markarian 421

    Science.gov (United States)

    Makino, F.; Tanaka, Y.; Matsuoka, M.; Koyama, K.; Inoue, H.; Makishima, K.; Hoshi, R.; Hayakawa, S.; Kondo, Y.

    1987-01-01

    Simultaneous multifrequency observations of the BL Lac object Mrk 421 covering radio through X-ray wavelengths were performed on two occasions separated by 5 weeks in January and March 1984, and each observation was coordinated for about 1 week. Composite multifrequency spectra of the central nonthermal component were obtained at the two epochs after subtracting the optical and infrared light of the underlying galaxy. The spectra show the gradual steepening toward high frequency; the power law indices are about 0.1, about 0.6, and about 1.0 for radio, infrared-optical, and UV bands, respectively. The UV and optical-infrared fluxes decreased by about 20 percent in 5 weeks, while the radio flux remained stable. The X-ray flux decreased by a factor of about 2, and the change was more pronounced at hard X-rays, which suggest that X-ray emission possibly consists of two components. The degree of polarization at the optical band varied on the time scale of a few days, while the position angle remained unchanged. Physical parameters of Mrk 421 are discussed in terms of the synchrotron self-Compton model.

  14. The VLA-COSMOS Survey: V. 324 MHz continuum observations

    CERN Document Server

    Smolcic, Vernesa; Jelic, Vibor; Bondi, Marco; Schinnerer, Eva; Carilli, Chris L; Riechers, Dominik A; Salvato, Mara; Brkovic, Alen; Capak, Peter; Ilbert, Olivier; Karim, Alexander; McCracken, Henry; Scoville, Nick Z

    2014-01-01

    We present 90 cm VLA imaging of the COSMOS field, comprising a circular area of 3.14 square degrees at 8.0"x6.0" angular resolution with an average rms of 0.5 mJy/beam. The extracted catalog contains 182 sources (down to 5.5sigma), 30 of which are multi-component sources. Using Monte Carlo artificial source simulations we derive the completeness of the catalog, and we show that our 90 cm source counts agree very well with those from previous studies. Using X-ray, NUV-NIR and radio COSMOS data to investigate the population mix of our 90 cm radio sample, we find that our sample is dominated by active galactic nuclei (AGN). The average 90-20 cm spectral index (S_nu~nu**alpha, where S_nu is the flux density at frequency nu, and alpha the spectral index) of our 90 cm selected sources is -0.70, with an interquartile range of -0.90 to -0.53. Only a few ultra-steep-spectrum sources are present in our sample, consistent with results in the literature for similar fields. Our data do not show clear steepening of the spe...

  15. Multifrequency observations of the flaring quasar 1156+295

    Science.gov (United States)

    Glassgold, A. E.; Bregman, J. N.; Huggins, P. J.; Kinney, A. L.; Pica, A. J.; Pollock, J. T.; Leacock, R. J.; Smith, A. G.; Webb, J. R.; Wisniewski, W. Z.

    1983-01-01

    A report is presented on the optically violent variable quasar 1156+295, known also as 4C 29.45 and Ton 599. A large outburst of this quasar was discovered in April 1981 in the course of a program to obtain simultaneous multifrequency spectra of variable quasars. Ultraviolet observations taken with the International Ultraviolet Explorer satellite were coordinated with ground-based observations at radio, infrared, and optical wavelengths. Measurements were made at four epochs starting immediately after the outburst was discovered, when the B-magnitude was 14.0, and at intervals of 4 days, 60 days and 1 year. The luminosity integrated only over observed wavelength bands was approximately 3 x 10 to the 48th ergs/sec on the first epoch of observation. Modeling of the source with a synchrotron self-Compton model suggests that the core of the source has a linear dimension of 0.01 pc, a magnetic field strength in the range 0.1-30 gauss, and a bulk relativistic motion in the quasar rest frame characterized by a Lorentz factor in the range 2-8.

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

    Science.gov (United States)

    Willson, Robert F.

    1991-01-01

    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.

  17. High spatial resolution VLA observations of the R Aquarii jet

    Science.gov (United States)

    Kafatos, M.; Hollis, J. M.; Michalitsianos, A. G.

    1983-01-01

    The Very Large Array was used to observe the jet feature of the symbiotic variable R Aquarii. A steady emission at 6 cm was confirmed for the past year, with the jet located 6.4 arcsec from R Aquarii at 29.3 deg PA. A velocity for the jet has been calculated as 40 km/sec, and may be accompanied by an ejection velocity in the range of 760-1800 km/sec. Since R Aquarii is the closest known object with a jet, further monitoring is recommended in order to detect any episodic mass transfer in what may be a binary system. The mass transfer, monitored at various wavelengths, would account for the observed optical and radio properties.

  18. Simultaneous multi-frequency single pulse observations of pulsars

    Science.gov (United States)

    Naidu, A.; Joshi, B. C.; Manoharan, P. K.; KrishnaKumar, M. A.

    2017-08-01

    Aims: We report on simultaneous multi-frequency single pulse observations of a sample of pulsars with previously reported, frequency dependent subpulse drift inferred from non-simultaneous and short observations. We aim to clarify if the frequency dependence is a result of multiple drift modes in these pulsars. Methods: We performed simultaneous observations at 326.5 MHz with the Ooty Radio Telescope and at 326, 610, and 1308 MHz with the Giant Meterwave Radio Telescope for a sample of 12 pulsars, where frequency dependent single pulse behaviour was reported. The single pulse sequences were analysed with three types of fluctuation analysis techniques, namely longitude-resolved fluctuation spectrum technique, two-dimensional fluctuation spectrum technique and sliding two-dimensional fluctuation spectrum technique. The first two techniques are sensitive to average fluctuation properties of the pulses, whereas the last technique is used for examining the temporal behaviour of the pulses. Results: We report subpulse drifting in PSR J0934-5249 for the first time. We also report pulse nulling measurements in PSRs J0934-5249, B1508+55, J1822-2256, B1845-19, and J1901-0906 for the first time. Our measurements of subpulse drifting and pulse nulling for the rest of the pulsars are consistent with previously reported values. Contrary to previous belief, we find no evidence for a frequency dependent drift pattern in PSR B2016+28 as reported in previous studies. In PSRs B1237+25, J1822-2256, J1901-0906, and B2045-16, our longer and more sensitive observations reveal multiple drift rates with distinct P3. We increase the sample of pulsars showing concurrent nulling across multiple frequencies by more than 100 percent, adding four more pulsars to this sample. Our results confirm and further strengthen the understanding that the subpulse drifting and pulse nulling are consistent in the broadband with previous studies and are closely tied to physics of polar gap.

  19. VLA Observations of Solar Decimetric Spike Bursts: Direct Signature of Accelerated Electrons in Reconnection Outflow Region

    Science.gov (United States)

    Chen, B.; Bastian, T.; Gary, D. E.

    2014-12-01

    Solar decimetric spike bursts, which appear in a radio dynamic spectrum as a cluster of short-lived and narrowband brightenings, have been suggested as a possible signature of many, "elementary" particle accelerations at or near a magnetic reconnection site. Their dynamic spectral feature can be potentially used to diagnose important parameters of the reconnection site such as plasma density and spatial size of the fragmentation. Yet direct observational evidence supporting this scenario has been elusive mainly due to the lack of imaging observations. The upgraded Karl G. Jansky Very Large Array (VLA) provides the first opportunity of performing simultaneous radio imaging and dynamic spectroscopy, which allows radio sources to be imaged at every spatio-temporal pixel in the dynamic spectrum. Here we report Jansky VLA observations of decimetric spike bursts recorded during an eruptive solar limb flare. Combined with EUV and X-ray data from SDO and RHESSI, we show that the spike bursts coincide spatially with a loop-top hard X-ray source, which are located in a region where supra-arcade downflows meet the underlying hot, EUV/X-ray loops. We interpret the observed spike bursts as a direct signature of non-thermal electrons accelerated by turbulences and/or shocks in the reconnection outflow region.

  20. ALMA and VLA observations of the outflows in IRAS 16293-2422

    CERN Document Server

    Loinard, Laurent; Rodriguez, Luis F; Pech, Gerardo; Chandler, Claire J; Brogan, Crystal L; Wilner, David J; Ho, Paul T P; Parise, Berengere; Hartmann, Lee W; Zhu, Zhaohuan; Takahashi, Satoko; Trejo, Alfonso

    2012-01-01

    We present ALMA and VLA observations of the molecular and ionized gas at 0.1-0.3 arcsec resolution in the Class 0 protostellar system IRAS 16293-2422. These data clarify the origins of the protostellar outflows from the deeply embedded sources in this complex region. Source A2 is confirmed to be at the origin of the well known large scale north-east--south-west flow. The most recent VLA observations reveal a new ejection from that protostar, demonstrating that it drives an episodic jet. The central compact part of the other known large scale flow in the system, oriented roughly east-west, is well delineated by the CO(6-5) emission imaged with ALMA and is confirmed to be driven from within component A. Finally, a one-sided blueshifted bubble-like outflow structure is detected here for the first time from source B to the north-west of the system. Its very short dynamical timescale (~ 200 yr), low velocity, and moderate collimation support the idea that source B is the youngest object in the system, and possibly...

  1. The Lyman Alpha Reference Sample: III. Properties of the Neutral ISM from GBT and VLA Observations

    CERN Document Server

    Pardy, Stephen A; Östlin, Göran; Hayes, Matthew; Rivera-Thorsen, Thøger; Sandberg, Andreas; Adamo, Angela; Freeland, Emily; Heren, E Christian; Guaita, Lucia; Kunth, Daniel; Laursen, Peter; Mas-Hesse, J M; Melinder, Jens; Orlitová, Ivana; Otí-Floranes, Héctor; Puschnig, Johannes; Schaerer, Daniel; Verhamme, Anne

    2014-01-01

    We present new H I imaging and spectroscopy of the 14 UV-selected star-forming galaxies in the Lyman Alpha Reference Sample (LARS), aimed for a detailed study of the processes governing the production, propagation, and escape of Ly$\\alpha$ photons. New H I spectroscopy, obtained with the 100m Green Bank Telescope (GBT), robustly detects the H I spectral line in 11 of the 14 observed LARS galaxies (although the profiles of two of the galaxies are likely confused by other sources within the GBT beam); the three highest redshift galaxies are not detected at our current sensitivity limits. The GBT profiles are used to derive fundamental H I line properties of the LARS galaxies. We also present new pilot H I spectral line imaging of 5 of the LARS galaxies obtained with the Karl G. Jansky Very Large Array (VLA). This imaging localizes the H I gas and provides a measurement of the total H I mass in each galaxy. In one system, LARS 03 (UGC 8335 or Arp 238), VLA observations reveal an enormous tidal structure that ext...

  2. A Keplerian disk around a Class 0 source: ALMA observations of VLA1623A

    CERN Document Server

    Murillo, Nadia M; Bruderer, Simon; Harsono, Daniel; van Dishoeck, Ewine F

    2013-01-01

    Context: Rotationally supported disks are critical in the star formation process. The questions of when do they form and what factors influence or hinder their formation have been studied but are largely unanswered. Observations of early stage YSOs are needed to probe disk formation. Aims: VLA1623 is a triple non-coeval protostellar system, with a weak magnetic field perpendicular to the outflow, whose Class 0 component, VLA1623A, shows a disk-like structure in continuum with signatures of rotation in line emission. We aim to determine whether this structure is in part or in whole a rotationally supported disk, i.e. a Keplerian disk, and what are its characteristics. Methods: ALMA Cycle 0 Early Science 1.3 mm continuum and C$^{18}$O (2-1) observations in the extended configuration are presented here and used to perform an analysis of the disk-like structure using PV diagrams and thin disk modelling with the addition of foreground absorption. Results: The PV diagrams of the C$^{18}$O line emission suggest the ...

  3. VLA observations of ammonia in high-mass star formation regions

    CERN Document Server

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

    2014-01-01

    We report systematic mapping observations of the NH$_{3}$ (1,1) and (2,2) inversion lines towards 62 high-mass star-forming regions using VLA in its D and DnC array configurations. The VLA images cover a spatial dynamic range from 40$"$ to 3$"$, allowing us to trace gas kinematics from $\\sim$1 pc scales to $\\lesssim$0.1 pc scales. Based on the NH$_3$ morphology and the infrared nebulosity on 1\\,pc scales, we categorize three sub-classes in the sample: filaments, hot cores, and NH$_3$ dispersed sources. The ubiquitous gas filaments found on 1 pc scales have a typical width of $\\sim$0.1\\,pc and often contain regularly spaced fragments along the major axis. The spacing of the fragments and the column densities are consistent with the turbulent supported fragmentation of cylinders. Several sources show multiple filaments that converge toward a center, where the velocity field in the filaments is consistent with gas flows. We derive rotational temperature maps for the entire sample. For the three hot core sources,...

  4. ALMA and VLA Observations: Evidence for Ongoing Low-mass Star Formation near Sgr A*

    Science.gov (United States)

    Yusef-Zadeh, F.; Cotton, W.; Wardle, M.; Royster, M. J.; Kunneriath, D.; Roberts, D. A.; Wootten, A.; Schödel, R.

    2017-01-01

    Using the VLA, we recently detected a large number of protoplanetary disk (proplyd) candidates lying within a couple of light years of the massive black hole Sgr A*. The bow-shock appearance of proplyd candidates point toward the young massive stars located near Sgr A*. Similar to Orion proplyds, the strong UV radiation from the cluster of massive stars at the Galactic center is expected to photoevaporate and photoionize the circumstellar disks around young, low mass stars, thus allowing detection of the ionized outflows from the photoionized layer surrounding cool and dense gaseous disks. To confirm this picture, ALMA observations detect millimeter emission at 226 GHz from five proplyd candidates that had been detected at 44 and 34 GHz with the VLA. We present the derived disk masses for four sources as a function of the assumed dust temperature. The mass of protoplanetary disks from cool dust emission ranges between 0.03 - 0.05 M⊙. These estimates are consistent with the disk masses found in star forming sites in the Galaxy. These measurements show the presence of on-going star formation with the implication that gas clouds can survive near Sgr A* and the relative importance of high vs low-mass star formation in the strong tidal and radiation fields of the Galactic center.

  5. MERLIN and VLA Observations of VII Zw 19: Distant Cousin of M82

    CERN Document Server

    Beck, S C; Turner, J L; Van Dyk, S D

    2004-01-01

    We have observed the starburst dwarf galaxy VII Zw 19 at subarcsecond resolution with the MERLIN and MERLIN+EVN networks at 18 cm, with MERLIN at 6 cm, and with the VLA in A array at 6 and 2 cm. The galaxy is detected at all VLA wavelengths and is resolved. It is also resolved at 18 cm by MERLIN, but is not detected by the EVN nor by MERLIN at 6 cm. VII Zw 19 has a complex structure of nonthermal radio emission at 18 cm extended over ~1200-1800 pc (4-6''). That the EVN did not detect this emission indicates that there are no obvious point sources that could be radio supernovae. The 2 cm emission, predominantly thermal free-free emission, has a markedly different spatial distribution from the nonthermal emission. The radio colors show that the galaxy contains numerous supernova remnants, as well as many young HII regions, many of which are optically thick at 6 cm. Two extended regions of 2 cm emission have little 18 cm flux and are probably emission from young star clusters. VII Zw 19 resembles M82 in its radi...

  6. MERLIN and VLA Observations of VII Zw 19: Distant Cousin of M82

    Science.gov (United States)

    Beck, Sara C.; Garrington, S. T.; Turner, Jean L.; Van Dyk, Schuyler D.

    2004-10-01

    We have observed the starburst dwarf galaxy VII Zw 19 at subarcsecond resolution with MERLIN and MERLIN+European VLBI Network (EVN) at 18 cm, with MERLIN at 6 cm, and with the Very Large Array (VLA) in the A configuration at 6 and 2 cm. The galaxy is detected at all VLA wavelengths and is resolved. It is also resolved at 18 cm by MERLIN but is not detected by the EVN or by MERLIN at 6 cm. VII Zw 19 has a complex structure of nonthermal radio emission at 18 cm extended over ~1200-1800 pc (4"-6"). That the EVN did not detect this emission indicates that there are no obvious point sources that could be radio supernovae. The 2 cm emission, predominantly thermal free-free emission, has a markedly different spatial distribution from the nonthermal emission. The radio colors show that the galaxy contains numerous supernova remnants, as well as many young H II regions, many of which are optically thick at 6 cm. Two extended regions of 2 cm emission have little 18 cm flux and are probably emission from young star clusters. VII Zw 19 resembles M82 in its radio and infrared spectrum, but the starburst region in VII Zw 19 is twice the size of the one in M82 and twice as luminous.

  7. GMRT and VLA Observations at 49 cm and 20 cm of the HII Region near = 24.8°, = 0.1°

    Indian Academy of Sciences (India)

    N. G. Kantharia; W. M. Goss; D. Anish Roshi; Niruj R. Mohan; Francois Viallefond

    2007-03-01

    We report multi-frequency radio continuum and hydrogen radio recombination line observations of HII regions near = 24.8°, = 0.1° using the Giant Metrewave Radio Telescope(GMRT) at 1.28 GHz ( = 172), 0.61 GHz ( = 220) and the Very Large Array (VLA) at 1.42 GHz ( = 166). The region consists of a large number of resolved HII regions and a few compact HII regions as seen in our continuum maps, many of which have associated infrared (IR) point sources. The largest HII region at = 24.8° and = 0.1° is a few arcmins in size and has a shell-type morphology. It is a massive HII region enclosing ∼ 550 M⊙ with a linear size of 7 pc and an rms electron density of ∼ 110 cm-3 at a kinematic distance of 6 kpc. The required ionization can be provided by a single star of spectral type O5.5. We also report detection of hydrogen recombination lines from the HII region at = 24.8° and = 0.1° at all observed frequencies near = 100 km s-1. We model the observed integrated line flux density as arising in the diffuse HII region and find that the best fitting model has an electron density comparable to that derived from the continuum.We also report detection of hydrogen recombination lines from two other HII regions in the field.

  8. Multifrequency observations of the superluminal quasar 3C 345

    Science.gov (United States)

    Bregman, J. N.; Glassgold, A. E.; Huggins, P. J.; Neugebauer, G.; Soifer, B. T.; Matthews, K.; Roellig, T. P. L.; Bregman, J. D.; Witteborn, F. C.; Lester, D. F.

    1986-01-01

    Attention is given to the continuum properties of the superluminal quasar 3C 345, on the basis of radio, optical, IR, and X-ray frequency monitorings, as well as by means of simultaneous multifrequency spectra extending from the radio through the X-ray bands. Radio outbursts, which appear to follow IR-optical outbursts by about one year, first occur at the highest frequencies, as expected from optical depth effects; the peak flux is nevertheless often reached at several frequencies at once. The beginning of outbursts, as defined by mm-measurements, corresponds to the appearance of the three known 'superluminal' components. An increase in the X-ray flux during 1979-1980 corresponds to increased radio flux, while the IR flux changes in the opposite sense.

  9. VLA observations of the wide-angle tailed radio source 1313+073

    Energy Technology Data Exchange (ETDEWEB)

    Patnaik, A.R.; Banhatti, D.G.; Subrahmanya, C.R. (Tata Inst. of Fundamental Research, Bangalore (India). Radio Astronomy Centre)

    1984-12-15

    VLA observations at 20 and 6 cm of the wide-angle tailed source 1313+073 are presented. It has an asymmetric structure with a sharp bend in the eastern tail and a gradual bend in the western. Both tails become diffuse after the bends. Several models are explored to explain this structure and it is concluded that the tails bend because of the motion of the parent cD galaxy through the ICM, which is possible if the cluster containing the source is dynamically young. Examination of the optical fields of 26 similar sources shows that in 20 of them the parent galaxies have a fainter companion (by approx. 2 mag), or are D, cD or db. This indicates that cannibalism may be important in the formation and powering of such sources.

  10. Searching the Nearest Stars for Exoplanetary Radio Emission: VLA and LOFAR Observations

    Science.gov (United States)

    Knapp, Mary; Winterhalter, Daniel; Lazio, Joseph

    2016-10-01

    Six of the eight solar system planets and one moon (Ganymede) exhibit present-day dynamo magnetic fields. To date, however, there are no conclusive detections of exoplanetary magnetic fields. Low frequency radio emission via the cyclotron maser instability (CMI) from interactions between a planet and the solar/stellar wind is the most direct means of detecting and characterizing planetary/exoplanetary magnetic fields. We have undertaken a survey of the very nearest stars in low frequency radio (30 MHz - 4 GHz) in order to search for yet-undiscovered planets. The closest stars are chosen in order to reduce the attenuation of the magnetospheric radio signal by distance dilution, thereby increasing the chances of making a detection if a planet with a strong magnetic field is present. The VLA telescope (P-band: 230-470 MHz, L-band: 1-2 GHz, S-band: 2-4 GHz) and LOFAR telescope (LBA: 30-75 MHz) have been used to conduct this survey.This work focuses on VLA and LOFAR observations of an M-dwarf binary system: GJ 725. We present upper limits on radio flux as a function of frequency. Since the peak emission frequency of CMI-type emission is the local plasma frequency in the emission region, the peak frequency of planetary radio emission is a direct proxy for the magnetic field strength of the planet. Our spectral irradiance upper limits therefore represent upper limits on the magnetic field strengths of any planets in the GJ 725 system.Part of this research was carried out at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration.

  11. The nature of composite LINER/H II galaxies as revealed from high-resolution VLA observations

    NARCIS (Netherlands)

    Filho, ME; Barthel, PD; Ho, LC

    2000-01-01

    A sample of 37 nearby galaxies displaying composite LINER/H II and pure H II spectra was observed with the VLA in an investigation of the nature of their weak radio emission. The resulting radio contour maps overlaid on optical galaxy images are presented here, together with an extensive literature

  12. Simultaneous Chandra, CSO and VLA Observations of Sgr A*: The Nature of Flaring Activity

    CERN Document Server

    Yusef-Zadeh, F; Heinke, C; Dowell, C D; Roberts, D; Baganoff, F K; Bower, G C

    2007-01-01

    Sgr A*, the massive black hole at the center of the Galaxy, varies in radio through X-ray emission on hourly time scales. The flare activity is thought to arise from the innermost region of an accretion flow onto Sgr A*. We present simultaneous light curves of Sgr A* in radio, sub-mm and X-rays that show a possible time delay of 110$\\pm17$ minutes between X-ray and 850 $\\mu$m suggesting that the sub-mm flare emission is optically thick. At radio wavelengths, we detect time lags of of $20.4\\pm6.8, 30\\pm12$ and 20$\\pm6$ minutes between the flare peaks observed at 13 and 7 mm in three different epochs using the VLA. Linear polarization of 1$\\pm0.2$% and 0.7$\\pm0.1$% is detected at 7 and 13 mm, respectively, when averaged over the entire observation on 2006 July 17. A simple picture of an expanding bubble of synchrotron emitting hot plasma can explain the time delay between various wavelengths, the asymmetric shape of the light curves, and the observed polarization of the flare emission at 43 and 22 GHz. The deri...

  13. Wideband VLA Observations of Abell 2256 I: Continuum, Rotation Measure and Spectral Imaging

    CERN Document Server

    Owen, Frazer; Eilek, Jean; Rau, Urvashi; Bhatnagar, Sanjay; Kogan, Leonid

    2014-01-01

    We report new observations of Abell 2256 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 for a single observation to study the spectral index, polarization and Rotation Measure as well as using the associated higher sensitivity to image total intensity features down to ~0.5" resolution. We find the Large Relic, which dominates the cluster, is made up of a complex of filaments which 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,...

  14. Dust properties across the CO snowline in the HD 163296 disk from ALMA and VLA observations

    CERN Document Server

    Guidi, G; Testi, L; de Gregorio-Monsalvo, I; Chandler, C J; Pérez, L; Isella, A; Natta, A; Ortolani, S; Hennings, Th; Corder, S; Linz, H; Andrews, S; Wilner, D; Ricci, L; Carpenter, J; Sargent, A; Mundy, L; Storm, S; Calvet, N; Dullemond, C; Greaves, J; Lazio, J; Deller, A; Kwon, W

    2016-01-01

    To characterize the mechanisms of planet formation it is crucial to investigate the properties and evolution of protoplanetary disks around young stars, where the initial conditions for the growth of planets are set. Our goal is to study grain growth in the disk of the young, intermediate mass star HD163296 where dust processing has already been observed, and to look for evidence of growth by ice condensation across the CO snowline, already identified in this disk with ALMA. Under the hypothesis of optically thin emission we compare images at different wavelengths from ALMA and VLA to measure the opacity spectral index across the disk and thus the maximum grain size. We also use a Bayesian tool based on a two-layer disk model to fit the observations and constrain the dust surface density. The measurements of the opacity spectral index indicate the presence of large grains and pebbles ($\\geq$1 cm) in the inner regions of the disk (inside $\\sim$50 AU) and smaller grains, consistent with ISM sizes, in the outer ...

  15. VLA H53alpha radio recombination line observations of the ultraluminous infrared galaxy Arp~220

    CERN Document Server

    Rodriguez-Rico, C A; Viallefond, F; Zhao, J H; Gómez, Y; Anantharamaiah, K R

    2005-01-01

    We present high angular resolution (0.7'') observations made with the Very Large Array (VLA) of the radio recombination line (RRL) H53alpha and radio continuum emission at 43 GHz from the ultraluminous infrared galaxy (ULIRG) Arp 220. The 43 GHz continuum emission shows a compact structure (~2'') with two peaks separated by ~1'', the East (E) and West (W) components, that correspond to each galactic nucleus of the merger. The spectral indices for both the E and W components, using radio continuum images at 8.3 and 43 GHz are typical of synchrotron emission (alpha ~ -1.0). Our 43 GHz continuum and H53alpha line observations confirm the flux densities predicted by the models proposed by Anantharamaiah et al. This agreement with the models implies the presence of high-density (~ 100,000 cm^-3) compact HII regions (~ 0.1 pc) in Arp~220. The integrated H53alpha line emission is stronger toward the non-thermal radio continuum peaks, which are also coincident with the peaks of molecular emission of the H2CO. The coi...

  16. CHANDRA, KECK, AND VLA OBSERVATIONS OF THE CRAB NEBULA DURING THE 2011-APRIL GAMMA-RAY FLARE

    Energy Technology Data Exchange (ETDEWEB)

    Weisskopf, Martin C.; Tennant, Allyn F.; O' Dell, Stephen L. [NASA Marshall Space Flight Center, Astrophysics Office (ZP12), Huntsville, AL 35812 (United States); Arons, Jonathan [Astronomy Department and Theoretical Astrophysics Center, University of California, Berkeley, 601 Campbell Hall, Berkeley, CA 94720 (United States); Blandford, Roger; Funk, Stefan; Romani, Roger W. [W. W. Hansen Experimental Physics Laboratory, Kavli Institute for Particle Astrophysics and Cosmology, Department of Physics and SLAC National Accelerator Laboratory, Stanford University, Stanford, CA 94305 (United States); Buehler, Rolf [DESY, Platanenallee 6, D-15738 Zeuthen (Germany); Caraveo, Patrizia; De Luca, Andrea [INAF-IASF Milano, via E. Bassini 15, I-20133 Milano (Italy); Cheung, Chi C. [National Research Council Research Associate, National Academy of Sciences, Washington, DC 20001 (United States); Costa, Enrico [INFN Roma Tor Vergata, via della Ricerca Scientifica 1, I-00133 Roma (Italy); Ferrigno, Carlo [ISDC, Data Center for Astrophysics of the University of Geneva, chemin d' cogia 16, CH-1290 Versoix (Switzerland); Fu, Hai [Department of Physics and Astronomy, University of California, Irvine, CA 92697 (United States); Habermehl, Moritz; Horns, Dieter [Institut fuer Experimentalphysik, Universitaet Hamburg, Luruper Chaussee 149, D-22761 Hamburg (Germany); Linford, Justin D. [Department of Physics and Astronomy, University of New Mexico, MSC07 4220, Albuquerque, NM 87131-0001 (United States); Lobanov, Andrei [Max-Planck-Institut fuer Radioastronomie, Auf dem Huegel 69, D-53121 Bonn (Germany); Max, Claire [Department of Astronomy and Astrophysics, University of California, Santa Cruz, CA 95064 (United States); Mignani, Roberto [Mullard Space Science Laboratory, University College London, Holmbury St. Mary Dorking, Surrey RH5 6NT (United Kingdom); and others

    2013-03-01

    We present results from our analysis of Chandra X-Ray Observatory, W. M. Keck Observatory, and Karl G. Jansky Very Large Array (VLA) images of the Crab Nebula that were contemporaneous with the {gamma}-ray flare of 2011 April. Despite hints in the X-ray data, we find no evidence for statistically significant variations that pinpoint the specific location of the flares within the Nebula. The Keck observations extend this conclusion to the 'inner knot', i.e., the feature within an arcsecond of the pulsar. The VLA observations support this conclusion. We also discuss theoretical implications of the {gamma}-ray flares and suggest that the most dramatic {gamma}-ray flares are due to radiation-reaction-limited synchrotron emission associated with sudden, dissipative changes in the current system sustained by the central pulsar.

  17. Multifrequency observations of the BL Lacertae object 0735+178

    Science.gov (United States)

    Bregman, J. N.; Glassgold, A. E.; Huggins, P. J.; Aller, H. D.; Aller, M. F.; Hodge, P. E.; Rieke, G. H.; Lebofsky, M. J.; Pollock, J. T.; Pica, A. J.

    1984-01-01

    In each of the present four simultaneous spectra covering the radio-through-X-ray regimes, the IR-UV synchrotron continuum dominates the total observed power and presumably becomes opague between 10 to the 11th and 10 to the 13th Hz. Nonsimultaneous observations were also conducted, over a longer time period, in order to study long- and short-term variability at X-ray, optical, and radio frequencies. These data indicate that the rapid and dramatic variations evident at IR and optical wavelengths are absent at radio and X-ray frequencies, supporting a view of IR-UV flux emanation from a small region, while the X-rays are produced by the inverse Compton process in the radio-emitting region. Particles, photons and magnetic field may not be far from equipartition in this region. Theoretical suggestions are developed regarding the radial behavior of the electron density and magnetic field.

  18. Multi-frequency radio observations of BAL quasar 1045+352

    CERN Document Server

    Kunert-Bajraszewska, M; Kunert-Bajraszewska, Magdalena; Marecki, Andrzej

    2006-01-01

    Multi-frequency 1.7, 5 and 8.4-GHz VLBA observations of a radio-loud broad absorption line (BAL) quasar 1045+352 are presented. It is a young compact steep spectrum (CSS) object and its asymmetric, two-sided morphology on a scale of several hundred parsecs, extending in two different directions, may suggest intermittent activity. The young age and unusual morphology of 1045+352 are arguments in favour of an evolution scenario for BAL quasars, in which the BAL features appear at a very early stage of their evolution.

  19. VLA and CARMA Observations of Protostars in the Cepheus Clouds: Sub-arcsecond Proto-Binaries Formed via Disk Fragmentation

    CERN Document Server

    Tobin, John J; Wilner, David J; Looney, Leslie W; Loinard, Laurent; Chiang, Hsin-Fang; Hartmann, Lee; Calvet, Nuria; D'Alessio, Paola; Bourke, Tyler L; Kwon, Woojin

    2013-01-01

    We present observations of three Class 0/I protostars (L1157-mm, CB230 IRS1, and L1165-SMM1) using the Karl G. Jansky Very Large Array (VLA) and observations of two (L1165-SMM1 and CB230 IRS1) with the Combined Array for Research in Millimeter-wave Astronomy (CARMA). The VLA observations were taken at wavelengths of $\\lambda = 7.3$ mm, 1.4 cm, 3.3 cm, 4.0 cm, and 6.5 cm with a best resolution of $\\sim$0\\farcs06 (18 AU) at 7.3 mm. The L1165-SMM1 CARMA observations were taken at $\\lambda = 1.3$ mm with a best resolution of $\\sim0\\farcs3$ (100 AU), and the CB230 IRS1 observations were taken at $\\lambda = 3.4$ mm with a best resolution of $\\sim$3\\arcsec\\ (900 AU). We find that L1165-SMM1 and CB230 IRS1 have probable binary companions at separations of $\\sim$0\\farcs3 (100 AU) from detections of secondary peaks at multiple wavelengths. The position angles of these companions are nearly orthogonal to the direction of the observed bipolar outflows, consistent with the expected protostellar disk orientations. We sugge...

  20. VLA and GBT Observations of Orion B (NGC 2024, W12) : Photo-dissociation Region Properties and Magnetic field

    CERN Document Server

    Roshi, D Anish; Jeyakumar, S

    2014-01-01

    We present images of C110$\\alpha$ and H110$\\alpha$ radio recombination line (RRL) emission at 4.8 GHz and images of H166$\\alpha$, C166$\\alpha$ and X166$\\alpha$ RRL emission at 1.4 GHz, observed toward the starforming region NGC 2024. The 1.4 GHz image with angular resolution $\\sim$ 70\\arcsec\\ is obtained using VLA data. The 4.8 GHz image with angular resolution $\\sim$ 17\\arcsec\\ is obtained by combining VLA and GBT data. The similarity of the LSR velocity (10.3 \\kms\\) of the C110$\\alpha$ line to that of lines observed from molecular material located at the far side of the \\HII\\ region suggests that the photo dissociation region (PDR) responsible for C110$\\alpha$ line emission is at the far side. The LSR velocity of C166$\\alpha$ is 8.8 \\kms. This velocity is comparable with the velocity of molecular absorption lines observed from the foreground gas, suggesting that the PDR is at the near side of the \\HII\\ region. Non-LTE models for carbon line forming regions are presented. Typical properties of the foreground...

  1. XMM-Newton and VLA Observations of the Variable Wolf-Rayet Star EZ CMa Evidence for a Close Companion?

    CERN Document Server

    Skinner, S L; Güdel, M; Schmutz, W

    2002-01-01

    We present new X-ray and radio observations of the WR star EZ CMa (HD 50896) obtained with XMM-Newton and the VLA. This WN4 star shows optical/UV variability at a period of 3.76 d whose cause is unknown. VLA flux measurements at five frequencies show the radio spectral energy distribution is well-described by a power law with spectral index +0.69 (+-0.05), as expected for free-free wind emission. The derived ionized mass loss rate allowing for distance uncertainties is M(dot) = 3.8 (+-2.6)e-5 M_sun/yr. The CCD X-ray spectra show prominent Si XIII and S XV emission lines and can be acceptably modeled as an absorbed multi-temperature optically thin plasma. Nonsolar abundances are inferred with Fe notably deficient. The X-ray emission is dominated by cool plasma at kT_cool = 0.6 keV, but a harder component is also detected with a derived temperature kT_hot = 3.0 - 4.2 keV if the emission is thermal. This is too high to be explained by radiative wind shock models and the luminosity of the hard component is 3 orde...

  2. VLA and CARMA observations of protostars in the Cepheus clouds: Sub-arcsecond proto-binaries formed via disk fragmentation

    Energy Technology Data Exchange (ETDEWEB)

    Tobin, John J.; Looney, Leslie W. [National Radio Astronomy Observatory, Charlottesville, VA 22903 (United States); Chandler, Claire J. [National Radio Astronomy Observatory, Socorro, NM (United States); Wilner, David J.; Bourke, Tyler L. [Harvard-Smithsonian Center for Astrophysics, Cambridge, MA 02138 (United States); Loinard, Laurent; D' Alessio, Paola [Centro de Radioastronomía y Astrofísica, UNAM, Apartado Postal 3-72 (Xangari), 58089 Morelia, Michoacán (Mexico); Chiang, Hsin-Fang [Institute for Astronomy and NASA Astrobiology Institute, University of Hawaii at Manoa, Hilo, HI 96720 (United States); Hartmann, Lee; Calvet, Nuria [Department of Astronomy, University of Michigan, Ann Arbor, MI 48109 (United States); Kwon, Woojin, E-mail: jtobin@nrao.edu [SRON Netherlands Institute for Space Research, Landleven 12, 9747 AD Groningen (Netherlands)

    2013-12-20

    We present observations of three Class 0/I protostars (L1157-mm, CB230 IRS1, and L1165-SMM1) using the Karl G. Jansky Very Large Array (VLA) and observations of two (L1165-SMM1 and CB230 IRS1) with the Combined Array for Research in Millimeter-wave Astronomy (CARMA). The VLA observations were taken at wavelengths of λ = 7.3 mm, 1.4 cm, 3.3 cm, 4.0 cm, and 6.5 cm with a best resolution of ∼0.''06 (18 AU) at 7.3 mm. The L1165-SMM1 CARMA observations were taken at λ = 1.3 mm with a best resolution of ∼0.''3 (100 AU) and the CB230 IRS1 observations were taken at λ = 3.4 mm with a best resolution of ∼3'' (900 AU). We find that L1165-SMM1 and CB230 IRS1 have probable binary companions at separations of ∼0.''3 (100 AU) from detections of secondary peaks at multiple wavelengths. The position angles of these companions are nearly orthogonal to the direction of the observed bipolar outflows, consistent with the expected protostellar disk orientations. We suggest that these companions may have formed from disk fragmentation; turbulent fragmentation would not preferentially arrange the binary companions to be orthogonal to the outflow direction. For L1165-SMM1, both the 7.3 mm and 1.3 mm emission show evidence of a large (R > 100 AU) disk. For the L1165-SMM1 primary protostar and the CB230 IRS1 secondary protostar, the 7.3 mm emission is resolved into structures consistent with ∼20 AU radius disks. For the other protostars, including L1157-mm, the emission is unresolved, suggesting disks with radii <20 AU.

  3. Multi-frequency solar observations at Metsähovi Radio Observatory and KAIRA

    Science.gov (United States)

    Kallunki, J.; Uunila, M.; McKay-Bukowski, D.

    2015-08-01

    We describe solar observations carried out for the first time jointly with Kilpisjärvi Atmospheric Imaging Receiver Array (KAIRA) and Aalto University Metsähovi Radio Observatory (MRO). KAIRA is new radio antenna array observing the decimeter and meter wavelength range. It is located near Kilpisjärvi, Finland, and operated by the Sodankylä Geophysical Observatory, University of Oulu. We investigate the feasibility of KAIRA for solar observations, and the additional benefits of carrying out multi-instrument solar observations with KAIRA and the MRO facilities, which are already used for regular solar observations. The data measured with three instruments at MRO, and with KAIRA during time period 2014 April-October were analyzed. One solar radio event, measured on 2014 April 18, was studied in detail. Seven solar flares were recorded with at least two of the three instruments at MRO, and with KAIRA during the chosen time period. KAIRA is a great versatile asset as a new Finnish instrument that can also be used for solar observations. Collaboration observations with MRO instruments and KAIRA enable detailed multi-frequency solar flare analysis. Flare pulsations, flare statistics and radio spectra of single flares can be investigated due to the broad frequency range observations. The Northern locations of both MRO and KAIRA make as long as 15-hour unique solar observations possible during summer time.

  4. VLA observations of Jupiter at 1.3 - 20 cm wavelengths

    Science.gov (United States)

    Depater, Imke

    1986-01-01

    In order to study the vertical distribution of ammonia as a function of Jovian latitude, high resolution images were obtained with the VLA at 1.3, 2, 6 and 20 cm wavelengths. Although the interpretation of the data is quite complicated due to Jupiter's synchrotron radiation, which in fact is the dominant source of radiation at 29 cm, the belt-zone structure is clearly present at 2 and 6 cm wavelengths. At 1.3 cm near the center of the ammonia band, the structure is less pronounced, and at 20 cm it is absent. The data is currently being fitted with model atmosphere calculations. Since one probes in and through the visible cloud layers at these wavelengths (temperatures of 135 to 400 K), and the opacity is likely all provided by ammonia gas, a detailed vertical distribution of this gas can be obtained as a function of Jovian latitude. This ought to give insight in the formation processes of the white cloud layers in the zones and their absence above the belts.

  5. VLA Observations of HI in the Circumstellar Envelopes of Asymptotic Giant Branch Stars

    CERN Document Server

    Matthews, Lynn D; 10.1086/512613

    2008-01-01

    (Abridged) We have used the VLA to search for neutral atomic hydrogen in the circumstellar envelopes of five AGB stars. We have detected HI 21-cm emission coincident in both position and velocity with the semi-regular variable RS Cnc. The emission comprises a compact, slightly elongated feature centered on the star with a mean diameter ~82'' (1.5e17 cm), plus an additional filament extending ~6' to the NW. This filament suggests that a portion of the mass loss is highly asymmetric. We estimate MHI=1.5e-3 Msun and M_dot~1.7e-7 Msun/yr. Toward R Cas, we detect weak emission that peaks at the stellar systemic velocity and overlaps with the location of its circumstellar dust shell and thus is probably related to the star. In the case of IRC+10216, we were unable to confirm the detection of HI in absorption against the cosmic background previously reported by Le Bertre & Gerard. However, we detect arcs of emission at projected distances of r~14'-18' (~2e18 cm) to the NW. A large separation of the emission from...

  6. VLA Observations of the Magnetic Field of the Smith High Velocity Cloud

    Science.gov (United States)

    Betti, Sarah; Hill, Alex S.; Mao, Sui Ann; McClure-Griffiths, Naomi M.; Lockman, Felix J.; Benjamin, Robert A.; Gaensler, Bryan M.

    2017-01-01

    High velocity clouds (HVCs) are hydrogen gas clouds around galaxies with velocities inconsistent with Galactic rotation. HVCs may fuel future star formation and drive galaxy evolution. The Smith Cloud is an HVC with an orbit suggesting it has made at least one passage through the disk. A measured magnetic field suggests how it survived passage through the Galactic halo. The Faraday rotation measure (RM) provides information about the strength and direction of the magnetic field. We use the Karl G. Jansky Very Large Array (VLA) to obtain reliable RMs towards ~950 background point sources to measure the geometry of the magnetic field of the Smith Cloud. These RMs constrain the strength of the magnetic field at the head, tail, and body of the Smith Cloud while RMs directly behind the Smith Cloud suggest there is ionized gas associated with the cloud that has not previously been detected. The confirmation of the magnetic field of the Smith Cloud along with a detailed morphology of the magnetic field structure will constrain how HVCs pass through the Galactic halo without losing their gas and survive the passage through the intergalactic and interstellar media.

  7. Weak and Compact Radio Emission in Early High-Mass Star Forming Regions: I. VLA Observations

    CERN Document Server

    Rosero, V; Claussen, M; Kurtz, S; Cesaroni, R; Araya, E D; Carrasco-González, C; Rodríguez, L F; Menten, K M; Wyrowski, F; Loinard, L; Ellingsen, S P

    2016-01-01

    We present a high sensitivity radio continuum survey at 6 and 1.3$\\,$cm using the Karl G. Jansky Very Large Array towards a sample of 58 high-mass star forming regions. Our sample was chosen from dust clumps within infrared dark clouds with and without IR sources (CMC-IRs, CMCs, respectively), and hot molecular cores (HMCs), with no previous, or relatively weak radio continuum detection at the $1\\,$mJy level. Due to the improvement in the continuum sensitivity of the VLA, this survey achieved map rms levels of $\\sim$ 3-10 $\\mu$Jy beam$^{-1}$ at sub-arcsecond angular resolution. We extracted 70 centimeter continuum sources associated with 1.2$\\,$mm dust clumps. Most sources are weak, compact, and are prime candidates for high-mass protostars. Detection rates of radio sources associated with the mm dust clumps for CMCs, CMC-IRs and HMCs are 6$\\%$, 53$\\%$ and 100$\\%$, respectively. This result is consistent with increasing high-mass star formation activity from CMCs to HMCs. The radio sources located within HMCs...

  8. MAGIC observations and multifrequency properties of the Flat Spectrum Radio Quasar 3C 279 in 2011

    CERN Document Server

    Aleksić, J; Antonelli, L A; Antoranz, P; Babic, A; Bangale, P; de Almeida, U Barres; Barrio, J A; González, J Becerra; Bednarek, W; Berger, K; Bernardini, E; Biland, A; Blanch, O; Bock, R K; Bonnefoy, S; Bonnoli, G; Borracci, F; Bretz, T; Carmona, E; Carosi, A; Fidalgo, D Carreto; Colin, P; Colombo, E; Contreras, J L; Cortina, J; Covino, S; Da Vela, P; Dazzi, F; De Angelis, A; De Caneva, G; De Lotto, B; Mendez, C Delgado; Doert, M; Domínguez, A; Prester, D Dominis; Dorner, D; Doro, M; Einecke, S; Eisenacher, D; Elsaesser, D; Farina, E; Ferenc, D; Fonseca, M V; Font, L; Frantzen, K; Fruck, C; López, R J García; Garczarczyk, M; Terrats, D Garrido; Gaug, M; Giavitto, G; Godinović, N; Muñoz, A González; Gozzini, S R; Hadasch, D; Herrero, A; Hildebrand, D; Hose, J; Hrupec, D; Idec, W; Kadenius, V; Kellermann, H; Knoetig, M L; Kodani, K; Konno, Y; Krause, J; Kubo, H; Kushida, J; La Barbera, A; Lelas, D; Lewandowska, N; Lindfors, E; Lombardi, S; López, M; López-Coto, R; López-Oramas, A; Lorenz, E; Lozano, I; Makariev, M; Mallot, K; Maneva, G; Mankuzhiyil, N; Mannheim, K; Maraschi, L; Marcote, B; Mariotti, M; Martínez, M; Mazin, D; Menzel, U; Meucci, M; Miranda, J M; Mirzoyan, R; Moralejo, A; Munar-Adrover, P; Nakajima, D; Niedzwiecki, A; Nilsson, K; Nishijima, K; Nowak, N; Orito, R; Overkemping, A; Paiano, S; Palatiello, M; Paneque, D; Paoletti, R; Paredes, J M; Paredes-Fortuny, X; Partini, S; Persic, M; Prada, F; Moroni, P G Prada; Prandini, E; Preziuso, S; Puljak, I; Reinthal, R; Rhode, W; Ribó, M; Rico, J; Garcia, J Rodriguez; Rügamer, S; Saggion, A; Saito, T; Saito, K; Salvati, M; Satalecka, K; Scalzotto, V; Scapin, V; Schultz, C; Schweizer, T; Shore, S N; Sillanpää, A; Sitarek, J; Snidaric, I; Sobczynska, D; Spanier, F; Stamatescu, V; Stamerra, A; Steinbring, T; Storz, J; Sun, S; Surić, T; Takalo, L; Takami, H; Tavecchio, F; Temnikov, P; Terzić, T; Tescaro, D; Teshima, M; Thaele, J; Tibolla, O; Torres, D F; Toyama, T; Treves, A; Vogler, P; Wagner, R M; Zandanel, F; Zanin, R; Berdyugin, A; Vornanen, T; Lähteenmäki, A; Tammi, J; Tornikoski, M; Hovatta, T; Max-Moerbeck, W; Readhead, A; Richards, J; Hayashida, M; Sanchez, D A; Fermi-LAT, on behalf of the; Marscher, A; Jorstad, S

    2013-01-01

    We study the multifrequency emission and spectral properties of the quasar 3C 279. We observed 3C 279 in very high energy (VHE, E>100GeV) gamma rays, with the MAGIC telescopes during 2011, for the first time in stereoscopic mode. We combine these measurements with observations at other energy bands: in high energy (HE, E>100MeV) gamma rays from Fermi-LAT, in X-rays from RXTE, in the optical from the KVA telescope and in the radio at 43GHz, 37GHz and 15GHz from the VLBA, Mets\\"ahovi and OVRO radio telescopes and optical polarisation measurements from the KVA and Liverpool telescopes. During the MAGIC observations (February to April 2011) 3C 279 was in a low state in optical, X-ray and gamma rays. The MAGIC observations did not yield a significant detection. These upper limits are in agreement with the extrapolation of the HE gamma-ray spectrum, corrected for extragalactic background light absorption, from Fermi-LAT. The second part of the MAGIC observations in 2011 was triggered by a high activity state in the...

  9. Interferometric Monitoring of Gamma-ray Bright AGNs I: Results of Single-epoch Multifrequency Observations

    CERN Document Server

    Lee, Sang-Sung; Algaba, Juan-Carlos; Zhao, Guang-Yao; Hodgson, Jeffrey A; Kim, Dae-Won; Park, Jongho; Kim, Jae-Young; Miyazaki, Atsushi; Byun, Do-Young; Kang, Sincheol; Kim, Jeong-Sook; Kim, Soon-Wook; Kino, Motoki; Trippe, Sascha

    2016-01-01

    We present results of single-epoch very long baseline interferometry (VLBI) observations of gamma-ray bright active galactic nuclei (AGNs) using the Korean VLBI Network (KVN) at 22, 43, 86, and 129~GHz bands, which are part of a KVN key science program, Interferometric Monitoring of Gamma-ray Bright AGNs (iMOGABA). We selected a total of 34 radio-loud AGNs of which 30 sources are gamma-ray bright AGNs with flux densities of $>6\\times10^{-10}$~ph~cm$^{-2}$~s$^{-1}$. Single-epoch multi-frequency VLBI observations of the target sources were conducted during a 24-hr session on 2013 November 19 and 20. All observed sources were detected and imaged at all frequency bands with or without a frequency phase transfer technique which enabled the imaging of 12 faint sources at 129~GHz, except for one source. Many of the target sources are resolved on milliarcsecond scales, yielding a core-jet structure with the VLBI core dominating the synchrotron emission on the milliarcsecond scale. CLEAN flux densities of the target s...

  10. The alfalfa “almost darks” campaign: Pilot VLA HI observations of five high mass-to-light ratio systems

    Energy Technology Data Exchange (ETDEWEB)

    Cannon, John M.; Martinkus, Charlotte P. [Department of Physics and Astronomy, Macalester College, 1600 Grand Avenue, Saint Paul, MN 55105 (United States); Leisman, Lukas; Haynes, Martha P.; Giovanelli, Riccardo; Hallenbeck, Gregory; Jones, Michael, E-mail: jcannon@macalester.edu, E-mail: cmartink@macalester.edu, E-mail: leisman@astro.cornell.edu, E-mail: haynes@astro.cornell.edu, E-mail: riccardo@astro.cornell.edu, E-mail: hallenbg@union.edu, E-mail: jonesmg@astro.cornell.edu [Center for Radiophysics and Space Research, Space Sciences Building, Cornell University, Ithaca, NY 14853 (United States); and others

    2015-02-01

    We present new Very Large Array (VLA) H i spectral line imaging of five sources discovered by the ALFALFA extragalactic survey. These targets are drawn from a larger sample of systems that were not uniquely identified with optical counterparts during ALFALFA processing, and as such have unusually high H i mass to light ratios. The candidate “Almost Dark” objects fall into four broad categories: (1) objects with nearby H i neighbors that are likely of tidal origin; (2) objects that appear to be part of a system of multiple H i sources, but which may not be tidal in origin; (3) objects isolated from nearby ALFALFA H i detections, but located near a gas-poor early type galaxy; (4) apparently isolated sources, with no object of coincident redshift within ∼400 kpc. Roughly 75% of the 200 objects without identified counterparts in the α.40 database (Haynes et al. 2011) fall into category 1 (likely tidal), and were not considered for synthesis follow-up observations. The pilot sample presented here (AGC193953, AGC208602, AGC208399, AGC226178, and AGC233638) contains the first five sources observed as part of a larger effort to characterize H i sources with no readily identifiable optical counterpart at single dish resolution (3.′5). These objects span a range of H i mass [7.41 < log(M{sub Hi}) < 9.51] and H i mass to B-band luminosity ratios (3 < M{sub Hi}/L{sub B} < 9). We compare the H i total intensity and velocity fields to optical imaging drawn from the Sloan Digital Sky Survey and to ultraviolet imaging drawn from archival GALEX observations. Four of the sources with uncertain or no optical counterpart in the ALFALFA data are identified with low surface brightness optical counterparts in Sloan Digital Sky Survey imaging when compared with VLA H i intensity maps, and appear to be galaxies with clear signs of ordered rotation in the H i velocity fields. Three of these are detected in far-ultraviolet GALEX images, a likely indication of star formation within

  11. Multifrequency radio observations of 3C 28, 76. 1, 186 and 319

    Energy Technology Data Exchange (ETDEWEB)

    Macklin, J.T. (Mullard Radio Astronomy Observatory, Cambridge (UK). Cavendish Lab.)

    1983-04-01

    Multifrequency observations of 3C 28, 76.1, 186 and 319, made with the One-Mile and 5-km telescopes, enable the spectral-index distributions of each source and the polarization properties of 3C 76.1 to be studied. 3C 28 is shown to have the structure of a Fanaroff-Riley class I source, but it is 10 times more luminous than expected for this class. Although 3C 76.1 is also in Fanaroff-Riley class I, it contains a feature which has the properties of a 'hotspot'. The spectral-index distribution in 3C 76.1 is complex; the magnetic field is perpendicular to the axes of the jets, and the polarization properties are consistent with a tangled-field model. The morphology of 3C 186 remains unclear, and 3C 319 is a double source with only one 'hotspot', rather than being a tail source. It is suggested that the different properties of 3C 28 and 76.1 are due to their different environments; this explanation would be consistent with a general scheme which can account for all the observed dependences of source properties on cluster membership.

  12. Retrieval of Precipitation Profiles from Multiresolution, Multifrequency, Active and Passive Microwave Observations

    Science.gov (United States)

    Grecu, Mircea; Olson, William S.; Anagnostou, Emmanouil N.

    2003-01-01

    In this study, a technique for estimating vertical profiles of precipitation from multifrequency, multiresolution active and passive microwave observations is investigated. The technique is applicable to the Tropical Rainfall Measuring Mission (TRMM) observations and it is based on models that simulate high-resolution brightness temperatures as functions of observed reflectivity profiles and a parameter related to the rain drop-size-distribution. The modeled high-resolution brightness temperatures are used to determine normalized brightness temperature polarizations at the microwave radiometer resolution. An optimal estimation procedure is employed to minimize the differences between the simulated and observed normalized polarizations by adjusting the drop-size-distribution parameter. The impact of other unknowns that are not independent variables in the optimal estimation but affect the retrievals is minimized through statistical parameterizations derived from cloud model simulations. The retrieval technique is investigated using TRMM observations collected during the Kwajalein Experiment (KWAJEX). These observations cover an area extending from 5 deg to deg N latitude and 166 deg to 172 deg E longitude from July to September 1999, and are coincident with various ground-based observations, facilitating a detailed analysis of the retrieved precipitation. Using the method developed in this study, precipitation estimates consistent with both the passive and active TRMM observations are obtained. Various parameters characterizing these estimates, i.e. the rain rate, the precipitation water content, the drop-size-distribution intercept, and the mass weighted mean drop diameter, are in good qualitative agreement with independent experimental and theoretical estimates. Combined rain estimates are in general higher than the official TRMM Precipitation Radar (PR) only estimates for the area and the period considered in the study. Ground-based precipitation estimates

  13. An Algorithm for Soil Moisture Retrieval using Multi-frequency Observations for Future the Water Cycle Observation Mission (WCOM)

    Science.gov (United States)

    Chen, Liang; Zhao, Tianjie; Wang, Cheng; Wan, Xiaoyun

    2017-04-01

    Soil moisture is one of the important parts in the global land surface ecosystem, water cycle and energy cycle, which control the water and heat energy exchange between land and atmosphere. Earth observation satellites play a critical role in providing information for understanding the global water cycle, which dominates the Earth-climate system. A new satellite concept of global Water Cycle Observation Mission (WCOM) is proposed in China, aiming to provide higher accuracy and consistent measurements of key elements of water cycle from space, including soil moisture, ocean salinity, freeze-thaw, snow water equivalent and etc. The expected more consistent and accurate datasets would be used to refine existing long-time series of satellite measurements, to constrain hydrological model projections and to detect the trends necessary for global change studies. The WCOM mission concept is a combination of active and passive microwave instruments. There will be three payloads: 1) an L-S-C tri-frequency Full-Polarized Interferometric synthetic aperture microwave Radiometer (FPIR); 2) a Polarized Microwave radiometric Imager (PMI) covering 6.8 GHz to 150 GHz bands; 3) an X-Ku Dual-Frequency Polarized SCATterometer (DFPSCAT). A soil moisture retrieval algorithm using the multi-frequency radiometer measurements is developed in this study. Through analyzing the simulated database of the Advanced Integral Equation Model (AIEM) under WCOM (Water Cycle Observation Mission) sensor configurations, a parameterized surface reflectivity model for multi-frequency Full-Polarized Interferometric synthetic aperture microwave Radiometer (FPIR) and Polarized Microwave radiometric Imager (PMI) are developed. In this model, influences of surface roughness parameters (e.g. RMS height, correlation length and type of autocorrelation function) on surface reflectivity are considered. It is found that the surface roughness and temperature can be cancelled out using the relationship of the multi-frequency

  14. H2O line mapping at high spatial and spectral resolution - Herschel observations of the VLA1623 outflow

    CERN Document Server

    Bjerkeli, P; Larsson, B; Rydbeck, G; Nisini, B; Tafalla, M; Antoniucci, S; Benedettini, M; Bergman, P; Cabrit, S; Giannini, T; Melnick, G; Neufeld, D; Santangelo, G; van Dishoeck, E F

    2012-01-01

    Apart from being an important coolant, H2O is known to be a tracer of high-velocity molecular gas. Recent models predict relatively high abundances behind interstellar shockwaves. The dynamical and physical conditions of the H2O emitting gas, however, are not fully understood yet. We aim to determine the abundance and distribution of H2O, its kinematics and the physical conditions of the gas responsible for the H2O emission. The observed line profile shapes help us understand the dynamics in molecular outflows. We mapped the VLA1623 outflow, in the ground-state transitions of o-H2O, with the HIFI and PACS instruments. We also present observations of higher energy transitions of o-H2O and p-H2O obtained with HIFI and PACS towards selected outflow positions. From comparison with non-LTE radiative transfer calculations, we estimate the physical parameters of the water emitting regions. The observed water emission line profiles vary over the mapped area. Spectral features and components, tracing gas in different ...

  15. EXAMINING THE RADIO-LOUD/RADIO-QUIET DICHOTOMY WITH NEW CHANDRA AND VLA OBSERVATIONS OF 13 UGC GALAXIES

    Energy Technology Data Exchange (ETDEWEB)

    Kharb, P.; Axon, D. J.; Robinson, A. [Physics Department, Rochester Institute of Technology, Rochester, NY 14623 (United States); Capetti, A.; Balmaverde, B. [INAF, Osservatorio Astronomico di Torino, Strada Osservatorio 20, 10025 Pino Torinese (Italy); Chiaberge, M.; Macchetto, D. [Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 (United States); Grandi, P. [INAF, Istituto di Astrofisica Spaziale e Fisica Cosmica, Bologna (Italy); Giovannini, G. [INAF, Istituto di Radioastronomia di Bologna, via Gobetti 101, 40129 Bologna (Italy); Montez, R., E-mail: kharb@cis.rit.edu [Center for Imaging Science, Rochester Institute of Technology, Rochester, NY 14623 (United States)

    2012-04-15

    We present the results from new {approx}15 ks Chandra-ACIS and 4.9 GHz Very Large Array (VLA) observations of 13 galaxies hosting low-luminosity active galactic nuclei (AGNs). This completes the multiwavelength study of a sample of 51 nearby early-type galaxies described in Capetti and Balmaverde and Balmaverde and Capetti. The aim of the three previous papers was to explore the connection between the host galaxies and AGN activity in a radio-selected sample. We detect nuclear X-ray emission in eight sources and radio emission in all but one (viz., UGC 6985). The new VLA observations improve the spatial resolution by a factor of 10: the presence of nuclear radio sources in 12 of the 13 galaxies confirms their AGN nature. As previously indicated, the behavior of the X-ray and radio emission in these sources depends strongly on the form of their optical surface brightness profiles derived from Hubble Space Telescope imaging, i.e., on their classification as 'core', 'power-law', or 'intermediate' galaxies. With more than twice the number of 'power-law' and 'intermediate' galaxies compared to previous work, we confirm with a much higher statistical significance that these galaxies lie well above the radio-X-ray correlation established in Fanaroff-Riley type I radio galaxies and the low-luminosity 'core' galaxies. This result highlights the fact that the 'radio-loud/radio-quiet' dichotomy is a function of the host galaxy's optical surface brightness profile. We present radio-optical-X-ray spectral indices for all 51 sample galaxies. Survival statistics point to significant differences in the radio-to-optical and radio-to-X-ray spectral indices between the 'core' and 'power-law galaxies (Gehan's Generalized Wilcoxon test probability p for the two classes being statistically similar is <10{sup -5}), but not in the optical-to-X-ray spectral indices (p = 0.25). Therefore, the

  16. VizieR Online Data Catalog: CHANG-ES. IV. VLA D-configuration observations (Wiegert+, 2015)

    Science.gov (United States)

    Wiegert, T.; Irwin, J.; Miskolczi, A.; Schmidt, P.; Mora, S. C.; Damas-Segovia, A.; Stein, Y.; English, J.; Rand, R. J.; Santistevan, I.; Walterbos, R.; Krause, M.; Beck, R.; Dettmar, R.-J.; Kepley, A.; Wezgowiec, M.; Wang, Q. D.; Heald, G.; Li, J.; MacGregor, S.; Johnson, M.; Strong, A. W.; Desouza, A.; Porter, T. A.

    2016-04-01

    This is the fourth paper in the series "Continuum Halos in Nearby Galaxies, an EVLA Survey" (CHANG-ES). With CHANG-ES, we have observed 35 nearby edge-on galaxies in the radio continuum in L- and C-bands (centered at approximately 1.5 and 6GHz, respectively), in three array configurations (B, C, D; in the B configuration only L-band was observed) of the Karl G. Jansky Very Large Array (hereafter VLA). We refer to Table1 of Irwin et al. (2012AJ....144...43I; Paper I) for details of the galaxy sample. Two other papers, Irwin et al. (2012AJ....144...44I; Paper II) and Irwin et al. (2013AJ....146..164I; Paper III), present the detailed results of CHANG-ES observations of NGC 4631 and UGC 10288, respectively. In this, the fourth CHANG-ES paper, we present all observations that were carried out in the shortest baseline array configuration, D. The data products (including intensity maps, spectral index maps, and polarization maps) are part of our Data Release 1, located at http://www.queensu.ca/changes. Of the 405hr that were awarded for the entire CHANG-ES project, 65hr were set apart for the D-configuration observations in two frequency bands, L and C. The observations were divided up into 13 scheduling blocks. The bulk of the data were observed during 2011 December. Two scheduling blocks were reobserved in 2013 March. The details of the observations are presented in Table1. (5 data files).

  17. Multi-wave band SMM-VLA observations of an M2 flare and an associated coronal mass ejection

    Science.gov (United States)

    Willson, Robert F.; Lang, Kenneth R.; Schmelz, Joan T.; Gonzalez, Raymond D.; Smith, Kermit L.

    1991-01-01

    Results are presented of observations of an M2 flare and an associated coronal mass ejection CME by instruments on the SMM as well as by the VLA and other ground-based observatories on September 30, 1988. The multiwave band data show a gradual slowly changing event which lasted several hours. The microwave burst emission was found to originate in compact moderately circularly polarized sources located near the sites of bright H-alpha and soft X-ray emission. These data are combined with estimates of an electron temperature of 1.5 x 10 to the 7th K and an emission measure of about 2.0 x 10 to the 49th/cu cm obtained from Ca XIX and Fe XXV spectra to show that the microwave emission can be attributed to thermal gyrosynchrotron radiation in regions where the magnetic field strength is 425-650 G. The CME acceleration at low altitudes is measured on the basis of ground- and space-based coronagraphs.

  18. The Wasp-Waist Nebula: VLA Ammonia Observations of the Molecular Core Envelope In a Unique Class 0 Protostellar System

    Science.gov (United States)

    Wiseman, Jennifer; Barsony, M.; Sahai, R.

    2010-01-01

    The Wasp-Waist Nebula was discovered in the IRAC c2d survey of the Ophiuchus star-forming clouds. It is powered by a well-isolated, low-luminosity, low-mass Class 0 object. Its weak outflow has been mapped in the CO (3-2) transition with the JCMT, in 2.12 micron H2 emission with WIRC (the Wide-Field Infrared Camera) on the Hale 5-meter, and, most recently, in six H2 mid-infrared lines with the IRS (InfraRed Spectrograph) on-board the Spitzer Space Telescope; possible jet twisting structure may be evidence of unique core dynamics. Here, we report results of recent VLA ammonia mapping observations of the dense gas envelope feeding the central core protostellar system. We describe the morphology, kinematics, and angular momentum characteristics of this unique system. The results are compared with the envelope structure deduced from IRAC 8-micron absorption of the PAH (polycyclic aromatic hydrocarbon) background emission from the cloud.

  19. The ALFALFA "Almost Darks" Campaign: Pilot VLA HI Observations of Five High Mass-to-Light Ratio Systems

    CERN Document Server

    Cannon, John M; Leisman, Lukas; Haynes, Martha P; Adams, Elizabeth A K; Giovanelli, Riccardo; Hallenbeck, Gregory; Janowiecki, Steven; Jones, Michael; Józsa, Gyula I G; Koopmann, Rebecca A; Nichols, Nathan; Papastergis, Emmanouil; Rhode, Katherine L; Salzer, John J; Troischt, Parker

    2014-01-01

    We present VLA HI spectral line imaging of 5 sources discovered by ALFALFA. These targets are drawn from a larger sample of systems that were not uniquely identified with optical counterparts during ALFALFA processing, and as such have unusually high HI mass to light ratios. These candidate "Almost Dark" objects fall into 4 categories: 1) objects with nearby HI neighbors that are likely of tidal origin; 2) objects that appear to be part of a system of multiple HI sources, but which may not be tidal in origin; 3) objects isolated from nearby ALFALFA HI detections, but located near a gas-poor early-type galaxy; 4) apparently isolated sources, with no object of coincident redshift within ~400 kpc. Roughly 75% of the 200 objects without identified counterparts in the $\\alpha$.40 database (Haynes et al. 2011) fall into category 1. This pilot sample contains the first five sources observed as part of a larger effort to characterize HI sources with no readily identifiable optical counterpart at single dish resolutio...

  20. ALMA and VLA Observations of Recombination Lines and Continuum toward the Becklin-Neugebauer object in Orion

    CERN Document Server

    Galvan-Madrid, Roberto; Rodriguez, Luis F

    2012-01-01

    Compared to their centimeter-wavelength counterparts, millimeter recombination lines (RLs) are intrinsically brighter and are free from pressure broadening. We report observations of RLs (H30alpha at 231.9 GHz and H53alpha at 42.9 GHz) and the millimeter and centimeter continuum toward the Becklin-Neugebauer (BN) object in Orion, obtained from the Atacama Large Millimeter/submillimeter Array (ALMA) Science Verification archive and the Very Large Array (VLA). The RL emission appears to be arising from the slowly-moving, dense (N_e=8.4x10^6 cm^-3) base of the ionized envelope around BN. This ionized gas has a relatively low electron temperature (T_e<4900 K) and small (<<10 km s^-1) bulk motions. Comparing our continuum measurements with previous (non)detections, we find evidence that BN could have large flux variations in the mm, but only mild (<30 %) variations in the cm. This could be understood if the free-free continuum of BN arises in an unresolved, unconfined ionized region that preserves its ...

  1. TINY SCALE OPACITY FLUCTUATIONS FROM VLBA, MERLIN, AND VLA OBSERVATIONS OF H I ABSORPTION TOWARD 3C 138

    Energy Technology Data Exchange (ETDEWEB)

    Roy, Nirupam; Goss, W. M. [National Radio Astronomy Observatory, 1003 Lopezville Road, Socorro, NM 87801 (United States); Minter, Anthony H. [National Radio Astronomy Observatory, P.O. Box 2, Green Bank, WV 24944 (United States); Brogan, Crystal L. [National Radio Astronomy Observatory, 520 Edgemont Road, Charlottesville, VA 22903 (United States); Lazio, T. J. W., E-mail: nroy@aoc.nrao.edu [Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109 (United States)

    2012-04-20

    The structure function of opacity fluctuations is a useful statistical tool to study tiny scale structures of neutral hydrogen. Here we present high-resolution observation of H I absorption toward 3C 138, and estimate the structure function of opacity fluctuations from the combined VLA, MERLIN, and VLBA data. The angular scales probed in this work are {approx}10-200 mas (about 5-100 AU). The structure function in this range is found to be well represented by a power law S{sub {tau}}(x) {approx} x{sup {beta}} with index {beta} {approx} 0.33 {+-} 0.07 corresponding to a power spectrum P{sub {tau}}(U) {approx} U{sup -2.33}. This is slightly shallower than the earlier reported power-law index of {approx}2.5-3.0 at {approx}1000 AU to few pc scales. The amplitude of the derived structure function is a factor of {approx}20-60 times higher than the extrapolated amplitude from observation of Cas A at larger scales. On the other hand, extrapolating the AU scale structure function for 3C 138 predicts the observed structure function for Cas A at the pc scale correctly. These results clearly establish that the atomic gas has significantly more structures in AU scales than expected from earlier pc scale observations. Some plausible reasons are identified and discussed here to explain these results. The observational evidence of a shallower slope and the presence of rich small-scale structures may have implications for the current understanding of the interstellar turbulence.

  2. The Power of (Near Simultaneous Multi-Frequency Observations for mm-VLBI and Astrometry

    Directory of Open Access Journals (Sweden)

    María J. Rioja

    2017-01-01

    Full Text Available Simultaneous or near-simultaneous observations at multiple frequency bands have the potential to overcome the fundamental limitation imposed by the atmospheric propagation in mm-VLBI observations. The propagation effects place a severe limit in the sensitivity achievable in mm-VLBI, reducing the time over which the signals can be coherently combined, and preventing the use of phase referencing and astrometric measurements. We present two demonstrations of the power of (near simultaneous multi-frequency observations with the KVN and VLBA, and our recently developed analysis strategies to enable new measurements at mm-VLBI. The first case comprises simultaneous observations at 22, 43, 87 and 130 GHz of a group of five AGNs, the weakest of which is ∼200 mJy at 130 GHz, with angular separations ranging from 3.6 to 11 degrees, using the KVN. We analysed this data using the Frequency Phase Transfer (FPT and the Source Frequency Phase Referencing (SFPR techniques, which use the observations at a lower frequency to correct those at a higher frequency. The results of the analysis provide an empirical demonstration of the increase in the coherence times at 130 GHz from a few tens of seconds to about twenty minutes, with FPT, and up to many hours with SFPR. Moreover the astrometric analysis provides high precision relative position measurements between two frequencies, including, for the first time, astrometry at 130 GHz. The second case is a variation of the above, whereby adding dedicated wide-band cm-wavelength observations to measure the ionosphere eliminates the need for a second, calibrator, source. This addresses the scarcity of calibrators at mm-VLBI. We dubbed this technique Multi Frequency Phase Referencing (MFPR. We present bona fide astrometrically aligned VLBA images of BL Lacertae at 22 and 43 GHz using MFPR, which, combined with results from conventional phase referencing at cm-wavelengths, suggests the VLBI core has a recollimation shock

  3. NH$_3$(3,3) and CH$_3$OH near Supernova Remnants: GBT and VLA Observations

    CERN Document Server

    McEwen, Bridget; Sjouwerman, Loránt

    2016-01-01

    We report on Green Bank Telescope 23.87 GHz NH$_3$(3,3), emission observations in five supernova remnants interacting with molecular clouds (G1.4$-$0.1, IC443, W44, W51C, and G5.7$-$0.0). The observations show a clumpy gas density distribution, and in most cases the narrow line widths of $\\sim3-4$\\,km\\,s$^{-1}$ are suggestive of maser emission. Very Large Array observations reveal 36~GHz and/or 44~GHz CH$_3$OH, maser emission in a majority (72\\%) of the NH$_3$, peak positions towards three of these SNRs. This good positional correlation is in agreement with the high densities required for the excitation of each line. Through these observations we have shown that CH$_3$OH, and NH$_3$, maser emission can be used as indicators of high density clumps of gas shocked by supernova remnants, and provide density estimates thereof. Modeling of the optical depth of the NH$_3$(3,3) emission is compared to that of CH$_3$OH, constraining the densities of the clumps to a typical density of the order of $10^5$~cm$^{-3}$ for ...

  4. High dynamic range VLA observations of eight core-dominated quasars

    Energy Technology Data Exchange (ETDEWEB)

    Kollgaard, R.I.; Wardle, J.F.C.; Roberts, D.H. (Brandeis Univ., Waltham, MA (USA))

    1990-10-01

    The Very Large Array has been used at 5 GHz to make high dynamic range observations of eight quasars with prominent cores. All exhibit one-sided jets, and all but one show evidence of diffuse halos. The luminosity of the extended emission by itself is sufficient for these to be Fanaroff-Riley Class II radio sources. This interpretation is confirmed by the polarization of the extended structure: the inferred magnetic field is parallel to the jet axis in all cases, and in all but one instance turns to be nearly perpendicular to the jet at its outer end. These latter structures are identified as classical terminal hot-spots. Both the total intensity data and especially the polarization data strongly support the notion that these quasars are similar to the classical lobe-dominated quasars, but are oriented with jet axes close to the line of sight. If this is so, then the relatively high degrees of polarization observed in the terminal hotspots appear to require that the downstream fluid velocities in the hotspots are mildly relativistic, in the range v/c = 0.2 - 0.8. This, in turn, implies that the jets are at least moderately relativistic over their entire length. 53 refs.

  5. Deep VLA observations of nearby star forming regions I: Barnard 59 and Lupus 1

    Science.gov (United States)

    Dzib, S. A.; Loinard, L.; Medina, S.-N. X.; Rodríguez, L. F.; Mioduszewski, A. J.; Torres, R. M.

    2016-10-01

    Barnard 59 and Lupus 1 are two nearby star-forming regions visible from the southern hemisphere. In this manuscript, we present deep (σ˜15 μJy) radio observations (ν=6 GHz) of these regions, and report the detection of a total of 114 sources. Thirteen of these sources are associated with known young stellar objects, nine in Barnard 59 and four in Lupus 1. The properties of the radio emission (spectral index and, in some cases, polarization) suggest a thermal origin for most young stellar objects. Only for two sources (Sz 65 and Sz 67) are there indications for a possible non-thermal origin. The remaining radio detections do not have counterparts at other wavelengths, and the number of sources detected per unit solid angle is in agreement with extragalactic number counts, suggesting that they are extragalactic sources.

  6. VLA observations of candidate high-mass protostellar objects at 7 mm

    CERN Document Server

    Garay, Guido; de Gregorio-Monsalvo, Itziar

    2007-01-01

    We present radio continuum observations at 7 mm made using the Very Large Array towards three massive star forming regions thought to be in very early stages of evolution selected from the sample of Sridharan et al. (2002). Emission was detected towards all three sources (IRAS 18470-0044, IRAS 19217+1651 and IRAS 23151+5912). We find that in all cases the 7 mm emission corresponds to thermal emission from ionized gas. The regions of ionized gas associated with IRAS 19217+1651 and IRAS 23151+5912 are hypercompact with diameters of 0.009 and 0.0006 pc, and emission measures of 7.0 x 10^8 and 2.3 x 10^9 pc cm^(-6), respectively.

  7. Quasi-simultaneous XMM-Newton and VLA observation of the non-thermal radio emitter HD\\168112 (O5.5III(f^+))

    OpenAIRE

    De Becker, Michaël; Rauw, Grégor; Blomme, Ronny; Waldron, Wayne; Sana, Hugues; Pittard, Julian; Eenens, Philippe; Stevens, Ian Robert; Runacres, Mark; Van Loo, Sven; Pollock, Andy

    2004-01-01

    We report the results of a multiwavelength study of the non-thermal radio emitter HD 168112 (O5.5III(f+)). The detailed analysis of two quasi-simultaneous XMM-Newton and VLA observations reveals strong variability of this star both in the X-ray and radio ranges. The X-ray observations separated by five months reveal a decrease of the X-ray flux of ˜30%. The radio emission on the other hand increases by a factor 5-7 between the two observations obtained roughly simultaneously with the XMM-Newt...

  8. Hydroxyl, water, ammonia, carbon monoxide, and neutral carbon towards the Sagittarius A complex. VLA, Odin, and SEST observations

    Science.gov (United States)

    Karlsson, R.; Sandqvist, Å.; Hjalmarson, Å.; Winnberg, A.; Fathi, K.; Frisk, U.; Olberg, M.

    2013-06-01

    Aims: The Sagittarius A complex in the Galactic centre comprises an ensemble of molecular clouds of different species with a variety of geometrical and kinematic properties. This work aims to study molecular abundances, morphology, and kinematics by comparing hydroxyl, water, carbon monoxide, ammonia, and atomic carbon and some of their isotopologues, in the +50 km s-1 cloud, the circumnuclear disk (CND), the +20 km s-1 cloud, the expanding molecular ring and the line-of-sight spiral arm features, including the Local/Sgr arm, the -30 km s-1 arm, and the 3-kpc arm. Methods: We observed the +50 km s-1 cloud, the CND and the +20 km s-1 cloud, and other selected positions at the Galactic centre with the VLA, and the Odin satellite. The VLA was used to map the 1665 and 1667 MHz OH lambda doublet main lines of the (2Π3/2) state, and the Odin satellite was used to map the 557 GHz H2O (110 - 101) line as well as to observe the 548 GHz H218O (110-101) line, the 572 GHz NH3 (10 - 00) line, the 576 GHz CO J = 5 - 4 line and the 492 GHz C i (3P1-3P0) line. Furthermore, the SEST was used to map a region of the Sgr A complex in the 220 GHz C18O J = 2-1 line. Results: Strong OH absorption, H2O emission and absorption lines were seen at all observed positions, and the H218O line was detected in absorption towards the +50 km s-1 cloud, the CND, the +20 km s-1cloud, the expanding molecular ring, and the 3-kpc arm. Strong CO J = 5-4, C18O J = 2-1, and neutral carbon C i emissions were seen towards the +50 and +20 km s-1 clouds. NH3 was only detected in weak absorption originating in the line-of-sight spiral arm features. The abundances of OH and H2O in the +50 and +20 km s-1 clouds reflect the different physical environments in the clouds, where shocks and star formation prevail in the +50 km s-1 cloud and giving rise to a higher rate of H2O production there than in the +20 km s-1 cloud. In the CND, cloud collisions and shocks are frequent, and the CND is also subject to intense UV

  9. Visual Landing Aids (VLA) Laboratory

    Data.gov (United States)

    Federal Laboratory Consortium — Purpose:The Visual Landing Aids (VLA) Laboratory serves to support fleet VLA systems by maintaining the latest service change configuration of currently deployed VLA...

  10. Quasi-simultaneous XMM-Newton and VLA observation of the non-thermal radio emitter HD\\168112 (O5.5III(f^+))

    CERN Document Server

    De Becker, M; Blomme, R; Waldron, W L; Sana, H; Pittard, J M; Eenens, P; Stevens, I R; Runacres, M C; Van Loo, S; Pollock, A M T

    2004-01-01

    We report the results of a multiwavelength study of the non-thermal radio emitter HD168112 (O5.5III(f^+)). The detailed analysis of two quasi-simultaneous XMM-Newton and VLA observations reveals strong variability of this star both in the X-ray and radio ranges. The X-ray observations separated by five months reveal a decrease of the X-ray flux of ~30%. The radio emission on the other hand increases by a factor 5-7 between the two observations obtained roughly simultaneously with the XMM-Newton pointings. The X-ray data reveal a hard emission that is most likely produced by a thermal plasma at kT ~2-3 keV while the VLA data confirm the non-thermal status of this star in the radio waveband. Comparison with archive X-ray and radio data confirms the variability of this source in both wavelength ranges over a yet ill defined time scale. The properties of HD168112 in the X-ray and radio domain point towards a binary system with a significant eccentricity and an orbital period of a few years. However, our optical s...

  11. Multifrequency observation of the optically violent variable quasar 3C 446

    Science.gov (United States)

    Bregman, Joel N.; Glassgold, A. E.; Huggins, P. J.; Kinney, A. L.; Mchardy, I.

    1988-01-01

    Nearly 20 years of optical and radio monitoring data as well as seven multifrequency spectra of the violently variable quasar 3C 446 are reported. The monitoring data suggest a correlation between the radio and optical outbursts, with the optical flare preceding the radio activity by 400-600 days. Considerable processing occurs in the optical-emitting plasma before it becomes radio-emitting plasma. Within the radio band, outbursts proceed from high to low frequencies. The flat radio spectrum turns over at 3-10 x 10 to the 11th Hz and the continuum steepens with frequency. The X-ray emission lies an order of magnitude above an extrapolation of the optical-UV spectrum and has a harder spectrum. The power is primarily concentrated in the submillimeter and infrared region. The data suggest that the X-rays are produced by the inverse Compton process from an emitting region smaller than but related to the synchrotron-emitting UV-IR region. The characteristic size of the emitting region increases with decreasing frequency.

  12. Multifrequency Observations of the Gamma-Ray Blazar 3C 279 in Low-State during Integral AO-1

    CERN Document Server

    Collmar, W; Burwitz, V; Courvoisier, Thierry J L; Komossa, S; Kretschmar, P; Nieppola, E; Nilsson, K; Ojala, T; Pottschmidt, K; Pasanen, M; Pursimo, T; Sillanpää, A; Takalo, L; Tornikoski, M; Ungerechts, H; Valtaoja, E; Walter, R; Webster, R; Whiting, M; Wiik, K; Wong, I

    2004-01-01

    We report first results of a multifrequency campaign from radio to hard X-ray energies of the prominent gamma-ray blazar 3C 279 during the first year of the INTEGRAL mission. The variable blazar was found at a low activity level, but was detected by all participating instruments. Subsequently a multifrequency spectrum could be compiled. The individual measurements as well as the compiled multifrequency spectrum are presented. In addition, this 2003 broadband spectrum is compared to one measured in 1999 during a high activity period of 3C 279.

  13. Science with a Next-Generation VLA

    Science.gov (United States)

    Murphy, Eric J.; Carilli, Chris Luke; ngVLA Science Working Groups

    2017-01-01

    Inspired by dramatic discoveries from the Jansky VLA and ALMA, a plan has been initiated to pursue a future large area radio interferometer that will open new discovery space from proto-planetary disks to distant galaxies. Building on the superb cm observing conditions and existing infrastructure of the VLA site, the current vision of ngVLA is an interferometric array with more than 10 times the effective collecting area and 10 times higher spatial resolution than the current VLA and the Atacama Large Millimeter Array (ALMA) that will operate at frequencies spanning ~1.2-116GHz. The ngVLA is optimized for observations at wavelengths between the exquisite performance of ALMA at submm wavelengths, and the future SKA-1 at few centimeter and longer wavelengths, thus lending itself to be highly complementary with these facilities. As such, the ngVLA will open a new window on the universe through ultra-sensitive imaging of thermal line and continuum emission down to milliarcecond resolution, as well as deliver unprecedented broad band continuum polarimetric imaging of non-thermal processes. The ngVLA will be the only facility in the world that can tackle a broad range of outstanding scientific questions in modern astronomy by simultaneously delivering the capability to: directly image planet formation in the terrestrial-zone; map dust-obscured star formation and the cosmic baryon cycle down to pc-scales out to the Virgo cluster; take a cosmic census of the molecular gas which fuels star formation back to first light and cosmic reionization; and carry out novel techniques for exploring temporal phenomena from milliseconds to years. In this poster we highlight a number of the tranformative science cases that are driving the design of the ngVLA.

  14. MAGIC gamma-ray and multifrequency observations of flat spectrum radio quasar PKS 1510-089 in early 2012

    CERN Document Server

    Aleksić, J; Antonelli, L A; Antoranz, P; Babic, A; Bangale, P; de Almeida, U Barres; Barrio, J A; González, J Becerra; Bednarek, W; Bernardini, E; Biland, A; Blanch, O; Bonnefoy, S; Bonnoli, G; Borracci, F; Bretz, T; Carmona, E; Carosi, A; Carreto-Fidalgo, D; Colin, P; Colombo, E; Contreras, J L; Cortina, J; Covino, S; Da Vela, P; Dazzi, F; De Angelis, A; De Caneva, G; De Lotto, B; Mendez, C Delgado; Doert, M; Domínguez, A; Prester, D Dominis; Dorner, D; Doro, M; Einecke, S; Eisenacher, D; Elsaesser, D; Farina, E; Ferenc, D; Fonseca, M V; Font, L; Frantzen, K; Fruck, C; López, R J García; Garczarczyk, M; Terrats, D Garrido; Gaug, M; Godinović, N; Muñoz, A González; Gozzini, S R; Hadasch, D; Hayashida, M; Herrera, J; Herrero, A; Hildebrand, D; Hose, J; Hrupec, D; Idec, W; Kadenius, V; Kellermann, H; Kodani, K; Konno, Y; Krause, J; Kubo, H; Kushida, J; La Barbera, A; Lelas, D; Lewandowska, N; Lindfors, E; Lombardi, S; López, M; López-Coto, R; López-Oramas, A; Lorenz, E; Lozano, I; Makariev, M; Mallot, K; Maneva, G; Mankuzhiyil, N; Mannheim, K; Maraschi, L; Marcote, B; Mariotti, M; Martínez, M; Mazin, D; Menzel, U; Meucci, M; Miranda, J M; Mirzoyan, R; Moralejo, A; Munar-Adrover, P; Nakajima, D; Niedzwiecki, A; Nilsson, K; Nishijima, K; Noda, K; Nowak, N; Orito, R; Overkemping, A; Paiano, S; Palatiello, M; Paneque, D; Paoletti, R; Paredes, J M; Paredes-Fortuny, X; Partini, S; Persic, M; Prada, F; Moroni, P G Prada; Prandini, E; Preziuso, S; Puljak, I; Reinthal, R; Rhode, W; Ribó, M; Rico, J; Garcia, J Rodriguez; Rügamer, S; Saggion, A; Saito, T; Saito, K; Satalecka, K; Scalzotto, V; Scapin, V; Schultz, C; Schweizer, T; Shore, S N; Sillanpää, A; Sitarek, J; Snidaric, I; Sobczynska, D; Spanier, F; Stamatescu, V; Stamerra, A; Steinbring, T; Storz, J; Strzys, M; Sun, S; Surić, T; Takalo, L; Takami, H; Tavecchio, F; Temnikov, P; Terzić, T; Tescaro, D; Teshima, M; Thaele, J; Tibolla, O; Torres, D F; Toyama, T; Treves, A; Uellenbeck, M; Vogler, P; Wagner, R M; Zandanel, F; Zanin, R; Lucarelli, F; Pittori, C; Vercellone, S; Verrecchia, F; Buson, S; D'Ammando, F; Stawarz, L; Giroletti, M; Orienti, M; Mundell, C; Steele, I; Zarpudin, B; Raiteri, C M; Villata, M; Sandrinelli, A; Lähteenäki, A; Tammi, J; Tornikoski, M; Hovatta, T; Readhead, A C S; Max-Moerbeck, W; Richards, J L; Jorstad, S; Marscher, A; Gurwell, M A; Larionov, V M; Blinov, D A; Konstantinova, T S; Kopatskaya, E N; Larionova, L V; Larionova, E G; Morozova, D A; Troitsky, I S; Mokrushina, A A; Pavlova, Yu V; Chen, W P; Lin, H C; Panwar, N; Agudo, I; Casadio, C; Gómez, J L; Molina, S N; Kurtanidze, O M; Nikolashvili, M G; Kurtanidze, S O; Chigladze, R A; Acosta-Pulido, J A; Carnerero, M I; Manilla-Robles, A; Ovcharov, E; Bozhilov, V; Metodieva, I; Aller, M F; Aller, H D; Fuhrmann, L; Angelakis, E; Nestoras, I; Krichbaum, T P; Zensus, J A; Ungerechts, H; Sievers, A; Riquelme, D

    2014-01-01

    Among more than fifty blazars detected in very high energy (VHE, E>100GeV) gamma-rays, only three belong to the subclass of Flat Spectrum Radio Quasars (FSRQs). MAGIC observed FSRQ PKS 1510-089 in February-April 2012 during a high activity state in the high energy (HE, E>100 MeV) gamma-ray band observed by AGILE and Fermi. MAGIC observations result in the detection of a source with significance of 6.0 sigma. In agreement with the previous VHE observations of the source, we find no statistically significant variability during the MAGIC observations in daily, weekly or monthly time scales. The other two known VHE FSRQs have shown daily scale to sub-hour variability. We study the multifrequency behaviour of the source at the epoch of MAGIC observation, collecting quasi-simultaneous data at radio and optical (GASP-WEBT and F-Gamma collaborations, REM, Steward, Perkins, Liverpool, OVRO and VLBA telescopes), X-ray (Swift satellite) and HE gamma-ray frequencies. The gamma-ray SED combining AGILE, Fermi and MAGIC dat...

  15. Multi-frequency imaging in VLBI

    CERN Document Server

    Likhachev, S

    2004-01-01

    The new technique, multi-frequency imaging (MFI) is developed. In VLBI, Multi-Frequency Imaging (MFI) consists of multi-frequency synthesis (MFS) and multi-frequency analysis (MFA) of the VLBI data obtained from observations on various frequencies. A set of linear deconvolution MFI algorithms is described. The algorithms make it possible to obtain high quality images interpolated on any given frequency inside any given bandwidth, and to derive reliable estimates of spectral indexes for radio sources with continuum spectrum. Thus MFI approach makes it is possible not only to improve the quality and fidelity of the images and also essentially to derive the morphology of the observed radio sources.

  16. FIRST-based survey of Compact Steep Spectrum sources, IV. Multifrequency VLBA observations of very compact objects

    CERN Document Server

    Kunert-Bajraszewska, M; Thomasson, P; Kunert-Bajraszewska, Magdalena; Marecki, Andrzej; Thomasson, Peter

    2006-01-01

    Evidence has been mounting recently that activity in some radio loud AGNs (RLAGNs) can cease shortly after ignition and that perhaps even a majority of very compact sources may be short-lived phenomena because of a lack of stable fuelling from the black hole. Thus, they can fade out before having evolved to large, extended objects. Re-ignition of the activity in such objects is not ruled out. With the aim of finding more examples of these objects and to investigate if they could be RLAGNs switched off at very early stages of their evolution, multifrequency VLBA observations of six sources with angular sizes significantly less than an arcsecond, yet having steep spectra, have been made. Observations were initially made at 1.65 GHz using the VLBA with the inclusion of Effelsberg telescope. The sources were then re-observed with the VLBA at 5, 8.4 and 15.4 GHz. All the observations were carried out in a snapshot mode with phase referencing. One of the sources studied, 0809+404, is dominated by a compact componen...

  17. New insights from deep VLA data on the potentially recoiling black hole CID-42 in the COSMOS field

    CERN Document Server

    Novak, Mladen; Civano, Francesca; Bondi, Marco; Ciliegi, Paolo; Wang, Xiawei; Loeb, Abraham; Banfield, Julie; Bourke, Stephen; Elvis, Martin; Hallinan, Gregg; Intema, Huib T; Klockner, Hans-Rainer; Mooley, Kunal; Navarrete, Felipe

    2014-01-01

    We present deep 3 GHz VLA observations of the potentially recoiling black hole CID-42 in the COSMOS field. This galaxy shows two optical nuclei in the HST/ACS image and a large velocity offset of ~ 1300 km/s between the broad and narrow H beta emission line although the spectrum is not spacially resolved (Civano et al. 2010). The new 3 GHz VLA data has a bandwidth of 2 GHz and to correctly interpret the flux densities imaging was done with two different methods: multi-scale multi-frequency synthesis and spectral windows stacking. The final resolutions and sensitivities of these maps are 0.7" with rms = 4.6 muJy/beam and 0.9" with rms = 4.8 muJy/beam respectively. With a 7 sigma detection we find that the entire observed 3 GHz radio emission can be associated with the South-Eastern component of CID-42, coincident with the detected X-ray emission. We use our 3 GHz data combined with other radio data from the literature ranging from 320 MHz to 9 GHz, which include the VLA, VLBA and GMRT data, to construct a radi...

  18. Rapid ambiguity resolution over medium-to-long baselines based on GPS/BDS multi-frequency observables

    Science.gov (United States)

    Gong, Xiaopeng; Lou, Yidong; Liu, Wanke; Zheng, Fu; Gu, Shengfeng; Wang, Hua

    2017-02-01

    Medium-long baseline RTK positioning generally needs a long initial time to find an accurate position due to non-negligible atmospheric delay residual. In order to shorten the initial or re-convergence time, a rapid phase ambiguity resolution method is employed based on GPS/BDS multi-frequency observables in this paper. This method is realized by two steps. First, double-differenced un-combined observables (i.e., L1/L2 and B1/B2/B3 observables) are used to obtain a float solution with atmospheric delay estimated as random walk parameter by using Kalman filter. This model enables an easy and consistent implementation for different systems and different frequency observables and can readily be extended to use more satellite navigation systems (e.g., Galileo, QZSS). Additional prior constraints for atmospheric information can be quickly added as well, because atmospheric delay is parameterized. Second, in order to fix ambiguity rapidly and reliably, ambiguities are divided into three types (extra-wide-lane (EWL), wide-lane (WL) and narrow-lane (NL)) according to their wavelengths and are to be fixed sequentially by using the LAMBDA method. Several baselines ranging from 61 km to 232 km collected by Trimble and Panda receivers are used to validate the method. The results illustrate that it only takes approximately 1, 2 and 6 epochs (30 s intervals) to fix EWL, WL and NL ambiguities, respectively. More epochs' observables are needed to fix WL and NL ambiguity around local time 14:00 than other time mainly due to more active ionosphere activity. As for the re-convergence time, the simulated results show that 90% of epochs can be fixed within 2 epochs by using prior atmospheric delay information obtained from previously 5 min. Finally, as for positioning accuracy, meter, decimeter and centimeter level positioning results are obtained according to different ambiguity resolution performances, i.e., EWL, WL and NL fixed solutions.

  19. 3D reconstruction methods of coronal structures by radio observations

    Science.gov (United States)

    Aschwanden, Markus J.; Bastian, T. S.; White, Stephen M.

    1992-01-01

    The ability to carry out the three dimensional (3D) reconstruction of structures in the solar corona would represent a major advance in the study of the physical properties in active regions and in flares. Methods which allow a geometric reconstruction of quasistationary coronal structures (for example active region loops) or dynamic structures (for example flaring loops) are described: stereoscopy of multi-day imaging observations by the VLA (Very Large Array); tomography of optically thin emission (in radio or soft x-rays); multifrequency band imaging by the VLA; and tracing of magnetic field lines by propagating electron beams.

  20. New insights into the evolution of the FR I radio galaxy 3C 270 (NGC 4261) from VLA and GMRT radio observations

    CERN Document Server

    Kolokythas, Konstantinos; Giacintucci, Simona; Raychaudhury, Somak; Ishwara-Chandra, C H; Worrall, Diana M; Birkinshaw, Mark

    2015-01-01

    We present Giant Metrewave Radio Telescope (GMRT) 240 MHz observations of the nearby luminous FR I radio source 3C 270, in the group-central elliptical NGC 4261. Combining these data with reprocessed Very Large Array (VLA) 1.55 and 4.8 GHz observations, we produce spectral index maps that reveal a constant spectral index along the jets and a gradual steepening from the ends of the jets through the lobes towards the nucleus. A Jaffe & Perola (JP) model fitted to the integrated spectrum of the source gives an asymptotic low-frequency index of $\\alpha_{inj}=0.53_{-0.02}^{+0.01}$, while JP models fitted to the observed spectral index trend along the lobes allow us to estimate radiative ages of $\\sim29$ Myr and $\\sim37$ Myr for the west and east lobes respectively. Our age estimates are a factor of two lower than the 75-Myr upper limit derived from X-ray data (O'Sullivan et al. 2011). We find unlikely the scenario of an early supersonic phase in which the lobe expanded into the ISM at approximately Mach 6 (350...

  1. Plasma properties and magnetic field structure of the solar corona, based on coordinated Max 1991 observations from SERTS, the VLA, and magnetographs

    Science.gov (United States)

    Brosius, Jeffrey W.

    1995-01-01

    The purposes of this investigation are to determine the plasma properties and magnetic field structure of the solar corona using coordinated observations obtained with NASA/GSFC's Solar EUV rocket Telescope and Spectrograph (SERTS), the Very Large Array (VLA), and magnetographs. The observations were obtained under the auspices of NASA's Max '91 program. The methods of achieving the stated purposes of this investigation are: (1) to use SERTS spectra and spectroheliograms to determine coronal plasma properties such as temperature, density, and emission measure; (2) to use the coronal plasma properties to calculate the intensity of the thermal bremsstrahlung microwave emission from the coronal plasma (the minimum microwave intensity expected from the emitting plasma); (3) to establish which emission mechanism(s) contribute to the observed microwave emission by comparing the calculated thermal bremsstrahlung intensity with the observed microwave intensity; (4) to derive the coronal magnetic field for regions in which gyroemission contributes to the microwave emission by determining the appropriate harmonic of the local electron gyrofrequency; (5) to derive the coronal magnetic field for regions in which thermal bremsstrahlung emission alone is responsible for the observed microwave emission by calculating the magnetic field which yields the observed microwave polarization; (6) to derive three-dimensional models of the coronal plasma and magnetic field which are consistent with all of the EUV spectra and spectroheliograms, as well as with the intensity and polarization maps at all of the microwave observing frequencies; and (7) to compare the coronal magnetic field derived from the coordinated multiwaveband observations with extrapolations from photospheric magnetograms.

  2. Multi-Frequency Observations of Polar Mesospheric Summer Echoes (PMSE) Under Artificial Electron Heating at EISCAT

    Science.gov (United States)

    La Hoz, C.; Kosch, M.; Senior, A.; Pinedo, H.; Havnes, O.; Rietveld, M. T.; Häggström, I.

    2011-12-01

    In a unique experiment at EISCAT, located in northern Norway and executed in July 2011, Polar Mesospheric Summer Echoes (PMSE) have been observed in the zenith at four different radar frequencies (933, 224, 56 and 7.9 MHz) simultaneously whilst artificially heating the electrons with high-frequency radio waves. Increasing the electron temperature reduces PMSE backscatter power at VHF but may increase it at HF, while the opposite may happen during the relaxation period following heater off. The PMSE backscatter power depends on many parameters, including dust size and charge, radar frequency and electron temperature. By observing the artificially modified PMSE at multiple radar frequencies, it may be possible to uniquely determine dust parameters as a function of altitude. Validation of PMSE theories and its behaviour under electron heating employing this unique set of observations are underway. In addition, high aspect angle observations of the PMSE were obtained at 224 MHz with 66 degrees zenith angle. These clearly show that PMSE can be observed at very high aspect angle, at least for VHF, contrary to results from earlier attempts to investigate PMSE's aspect sensitivity behaviour that has a bearing on the geometry of the electron density irregularities that cause the scattering. Preliminary results from the campaign are presented.

  3. Spitzer observations of Abell 1763 - II: Constraining the nature of activity in the cluster-feeding filament with VLA and XMM-Newton data

    CERN Document Server

    Edwards, Louise O V; Frayer, David T; Neto, Gastao B Lima; Durret, Florence

    2010-01-01

    The Abell 1763 superstructure at z=0.23 contains the first galaxy filament to be directly detected using mid-infrared observations. Our previous work has shown that the frequency of starbursting galaxies, as characterized by 24{\\mu}m emission is much higher within the filament than at either the center of the rich galaxy cluster, or the field surrounding the system. New VLA and XMM-Newton data are presented here. We use the radio and X-ray data to examine the fraction and location of active galaxies, both active galactic nuclei (AGN) and starbursts. The radio far-infrared correlation, X-ray point source location, IRAC colors, and quasar positions are all used to gain an understanding of the presence of dominant AGN. We find very few MIPS-selected galaxies that are clearly dominated by AGN activity. Most radio selected members within the filament are starbursts. Within the supercluster, 3 of 8 spectroscopic members detected both in the radio and in the mid-infrared are radio-bright AGN. They are found at or ne...

  4. Rotational modulation and flares on RS canum Venaticorum and BY Draconis stars. XVI - IUE spectroscopy and VLA observations of Gl 182( = V 1005 Orionis) in October 1983

    Science.gov (United States)

    Mathioudakis, M.; Doyle, J. G.; Byrne, P. B.; Rodono, M.; Gibson, D. M.

    1991-01-01

    A large flare was detected simultaneously with IUE and VLA on Gl 182 on October 5, 1983, this event showing the largest C IV flare enhancement yet observed by IUE. A smaller flare was also detected on October 4, although only with the IUE satellite. Line ratio and emission measure techniques are used to derive various physical parameters of the flares. The radiative losses in the temperature region log T(e) = 4.3-5.4 in the two flares are 2.9 x 10 to the 33rd and 8.4 x 10 to the 32nd ergs, respectively. Total radiative losses over the whole temperature range log T(e) = 4.0-8.0 are estimated to be of the order of 6.4 x 10 to the 34th and 1.1 x 10 to the 34th ergs, respectively. In the October 5, flare, a very strong ultraviolet continuum is present with a total energy of 1.9 x 10 to the 33rd ergs over the wavelength range 1250-1950 A.

  5. Multifrequency radio continuum observations of head-tail galaxies in the Perseus cluster

    NARCIS (Netherlands)

    Sijbring, D; de Bruyn, AG

    1998-01-01

    New observations of head-tail radio galaxies in the Perseus cluster at 21, 49 and 92 cm using the WSRT are presented. Two new head-tail galaxies were discovered bringing the total for the cluster to five. We show total intensity maps for all of them and spectral index distribution and polarization m

  6. Multi-frequency observations of Polar Mesospheric Summer Echoes and their aspect sensitivity at EISCAT

    Science.gov (United States)

    La Hoz, Cesar; Rietveld, Michael; Havnes, Ove; Senior, Andrew; Haggstrom, Ingemar; Kosch, Michael; Pinedo, Henry

    2012-07-01

    In a unique experiment at EISCAT in northern Norway, executed in July 2011, Polar Mesospheric Summer Echoes (PMSE) have been observed in the zenith at four different radar frequencies (933, 224, 56 and 7.9 MHz) simultaneously whilst artificially heating the electrons with high-frequency radio waves. In addition, measurements of the scattering layers were also made for the first time by the EISCAT_3D demonstrator array at 224 MHz located in Kiruna, Sweden, which is 234 km away from the transmitting site and obtains measurements at an aspect angle of 69 degrees. Strong scattering was observed over prolonged periods on several days by the demonstrator array. These measurements are at variance with previous aspect angle measurements that have reported aspect angles no greater than about 15 degrees. These results indicate that the turbulent irregularities that produce the scattering have a high degree of isotropy, which is more in line with Kolmogorov'a hypothesis of a universal scaling of turbulence based precisely on the assumption of homogeneity and isotropy in the inertial regime of turbulence which applies also, naturally, to the Batchelor regime due to large Schmidt numbers which is believed to be the case for PMSE. An interseting question arises, namely, what is the mechanism or process that controls the level of isotropy of the turbulent irregularities in the small scale regime, i.e., inertial or Batchelor, that the radars detect?

  7. Multifrequency radio continuum observations of head-tail galaxies in the Perseus cluster

    Science.gov (United States)

    Sijbring, D.; de Bruyn, A. G.

    1998-03-01

    New observations of head-tail radio galaxies in the Perseus cluster at 21, 49 and 92 cm using the WSRT are presented. Two new head-tail galaxies were discovered bringing the total for the cluster to five. We show total intensity maps for all of them and spectral index distribution and polarization maps for NGC 1265 and IC 310. The observations with high dynamic range, obtained with the WSRT and the redundancy and self-calibration techniques, reveal a large extension of the tail of NGC 1265 both at 49 cm and at 92 cm. The projected tail bends over an angle of almost 360°. There are several clear differences between the bright and the faint part of the radio tail: within a distance of one or two resolution beams the intensity decreases by more than an order of magnitude and the spectral index steepens from -1 to -2. The simplest model for the tail is that it delineates the orbit of the galaxy through the cluster. Because the tail is seen in projection, the faint part of the tail is visible only when it is not superimposed onto the bright part of the tail. It is likely, however, that large scale motions of the hot intracluster medium also help shape the tail. In this respect it is interesting to note that the tails of both NGC 1265 and IC 310, as well as the low brightness emission of NGC 1275 appear to have their faint extensions shifted to the east. The very long tail of NGC 1265 makes it possible to test at low frequencies models of the ageing process of the radiating electrons. In the faint part of the tail the brightness temperature is very low, which either indicates a very weak magnetic field or a large deviation from equipartition between particle and magnetic energy. The most remarkable properties of the faint part of the tail of NGC1265, namely its constant surface brightness and spectral index, are compared with three synchrotron ageing models, making some standard assumptions. All these models disagree with either the data or one of the assumptions. The

  8. Experimental observation of multifrequency patterns in arrays of coupled nonlinear oscillators.

    Science.gov (United States)

    In, Visarath; Kho, Andy; Neff, Joseph D; Palacios, Antonio; Longhini, Patrick; Meadows, Brian K

    2003-12-12

    Frequency-related oscillations in coupled oscillator systems, in which one or more oscillators oscillate at different frequencies than the other oscillators, have been studied using group theoretical methods by Armbruster and Chossat [Phys. Lett. A 254, 269 (1999)] and more recently by Golubitsky and Stewart [in Geometry, Mechanics, and Dynamics, edited by P. Newton, P. Holmes, and A. Weinstein (Springer, New York, 2002), p. 243]. We demonstrate, experimentally, via electronic circuits, the existence of frequency-related oscillations in a network of two arrays of N oscillators, per array, coupled to one another. Under certain conditions, one of the arrays can be induced to oscillate at N times the frequency of the other array. This type of behavior is different from the one observed in a driven system because it is dictated mainly by the symmetry of the coupled system.

  9. Multifrequency observations of a solar microwave burst with two-dimensional spatial resolution

    Science.gov (United States)

    Gary, Dale E.; Hurford, G. J.

    1990-01-01

    Frequency-agile interferometry observations using three baselines and the technique of frequency synthesis were used to obtain two-dimensional positions of multiple microwave sources at several frequency ranges in a solar flare. Source size and brightness temperature spectra were obtained near the peak of the burst. The size spectrum shows that the source size decreases rapidly with increasing frequency, but the brightness temperature spectrum can be well-fitted by gyrosynchrotron emission from a nonthermal distribution of electrons with power-law index of 4.8. The spatial structure of the burst showed several characteristics in common with primary/secondary bursts discussed by Nakajima et al. (1985). A source of coherent plasma emission at low frequencies is found near the secondary gyrosynchrotron source, associated with the leader spots of the active region.

  10. Multi-Frequency Observations of Gamma-Ray Blazar 1633+382

    Indian Academy of Sciences (India)

    S. G. Jorstad; A. P. Marscher; I. Agudo; P. S. Smith; V. M. Larionov; A. Lähteenmäki

    2011-03-01

    We perform monthly monitoring of the quasar 1633+382 (4C+38.41) within a sample of -ray blazars with the VLBA at 43 GHz along with optical photometric and polarimetric observations. We construct the -ray light curve of 1633+382 using data obtained by the Fermi LAT. We find that a high -ray state of the quasar starting in 2009 September is simultaneous with an increase of the flux in the mm-wave VLBI core. We resolve a superluminal feature on the VLBA images that appears to be responsible for the mm-wave flux increase. We find a strong correlation between optical and -ray light curves with a delay of -ray variations of 5 ± 3 days, as well as a strong correlation between optical flux and degree of polarization during the high -ray state. Comparison between the optical polarization position angle and that in the VLBI core supports the idea that in the quasar 1633+382 a high -ray state is connected with processes originating near the mm-VLBI core.

  11. Multi-Frequency Observations of Gamma-Ray Blazar 1633 plus 382

    Science.gov (United States)

    Jorstad, S. G.; Marscher, A. P.; Agudo, I.; Smith, P. S.; Larionov, V. M.; Laehteenmaeki, A.

    2011-01-01

    We perform monthly monitoring of the quasar 1633+382 (4C+38.41) within a sample of gamma-ray blazars with the VLBA at 43 GHz along with optical photometric and polarimetric observations. We construct the gamma-ray light curve of 1633+382 using data obtained by the Fermi LAT. We find that a high gamma-ray state of the quasar starting in 2009 September is simultaneous with an increase of the flux in the mm-wave VLBI core. We resolve a superluminal feature on the VLBA images that appears to be responsible for the mm-wave flux increase. We find a strong correlation between optical and gamma-ray light curves with a delay of gamma-ray variations of 5+/-3 days, as well as a strong correlation between optical flux and degree of polarization during the high gamma-ray state. Comparison between the optical polarization position angle and that in the VLBI core supports the idea that in the quasar 1633+382 a high gamma-ray state is connected with processes originating near the mm-VLBI core.

  12. Multifrequency radio observations of SNR J0536-6735 (N 59B) with associated pulsar

    CERN Document Server

    Bozzetto, L M; Crawford, E J; De Horta, A Y; Stupar, M

    2012-01-01

    We present a study of new Australian Telescope Compact Array (ATCA) observations of supernova remnant, SNR J0536-6735. This remnant appears to follow a shell morphology with a diameter of D=36x29 pc (with 1 pc uncertainty in each direction). There is an embedded Hii region on the northern limb of the remnant which made various analysis and measurements (such as flux density, spectral index and polarisation) difficult. The radio-continuum emission followed the same structure as the optical emission, allowing for extent and flux density estimates at 20 cm. We estimate a surface brightness for the SNR at 1 GHz of 2.55x10^-21 W m^-2 Hz^-1 sr^-1. Also, we detect a distinctive radio-continuum point source which confirms the previous suggestion of this remnant being associated with a pulsar wind nebulae (PWN). The tail of this remnant isn't seen in the radio-continuum images and is only seen in the optical and X-ray images.

  13. Plasma Properties and Magnetic Field Structure of the Solar Corona, Based on Coordinated Max '91 Observations from SERTS, the VLA, and Magnetographs

    Science.gov (United States)

    Brosius, Jeffrey W. (Principal Investigator)

    1996-01-01

    The plasma properties and magnetic field structure of the solar corona were determined using coordinated observations obtained with NASA/GSFC's Solar EUV Rocket Telescope and Spectrograph (SERTS), the Very Large Array (VLA), and Kitt Peak photospheric longitudinal magnetograms. A problem was identified with the SERTS calibration as determined from laboratory measurements. A revised calibration curve was derived by requiring that the numerous available measured line intensity ratios agreed with their respective theoretical values. Densities were derived from line intensity ratios, and active region densities were found to typically exceed quiet Sun densities by factors of only about 2. The active region density was found to remain constant across the SERTS slit, despite the fact that the emission line intensities vary significantly. This indicates that the product of the path length and the volume filling factor must vary significantly from the active region outskirts to the central core. Filling factors were derived and found to range from much less than one to nearly unity. Wavelength shifts were examined along the SERTS slit in the spatially resolved spectra, but no evidence was found for significant Doppler shifts in active region 7563 or in the quiet Sun. The numerical procedure developed by Monsignori-Fossi and Landini was used to derive the active region and quiet sun differential emission measure (DEM) from the spatially averaged spectra. A DEM was estimated for each spatial pixel in the two dimensional active region images by scaling the averaged active region DEM based upon corresponding pixel intensities of SERTS Mg IX, Fe XV, and Fe XVI images. These results, along with density measurements, were used in an IDL computer code which calculated the temperature dependence of the coronal magnetic field in each spatial pixel by minimizing the difference between the observed and calculated 20 and 6 cm microwave brightness temperatures.

  14. The VLA Atmospheric Phase Interferometer

    Science.gov (United States)

    Morris, Keith

    2014-05-01

    The Atmospheric Phase Interferometer (API) is a two-element atmospheric seeing monitor located at the Very Large Array (VLA) site. The instrument measures turbulent refractive index variation through the atmosphere by examining phase differences in a satellite beacon signal detected at two (or more) antennas. With this measurement, the VLA scheduling software is able to consider atmospheric stability when determining which frequency observation to schedule next. We are in the process of extending this two-element interferometer to four elements, which will allow us to measure the turbulence in two dimensions and at multiple length scales. This thesis will look at some statistical properties of turbulence, the effects of atmospheric stability on radio interferometric observations, and discuss details of the instrument and the data that it collects. The thesis will also cover some techniques and principles of signal processing, and an analysis of some data from the instrument. The results demonstrate that other surface atmospheric variables (e.g. windspeed, water vapor pressure) show the same structure function exponent as the atmospheric phase fluctuations. In particular, the structure functions of water vapor partial pressure and wind speed show the same exponent as the phase. Though the agreement between meteorological variables and atmospheric phase is scientifically satisfying, these surface measurements are not nearly as sensitive as the API saturation phase measurement, and therefore cannot be used to schedule telescope time in its stead. What is informative about these results is that the similar structure functions for API and meteorological data are detecting reinforce the claim that both measurements represent turbulent transport, and not instrumental noise. Data from the instrument reveals that measurements are consistent with both Kolmogorov turbulence theory, and with prior observations. The API predominately measures three-dimensional isotropic

  15. Multi-epoch VLA observations of IRAS 16293-2422B and the modeling of its continuum emission

    Science.gov (United States)

    Hernández-Gómez, A.; Quénard, D.; Loinard, L.; Caux, E.

    2017-07-01

    We present multi-epoch interferometric observations of IRAS 16293-2422B taken with the Very Large Array at 0.7, 1, 1.3, 2, 3, 6 and 13 cm. We made continuum maps of the source at these wavelengths and measured a proper motion of -5.7±1.4 mas yr-1 in R.A. and -21.0±1.1 mas yr-1 in Dec. We also measured the spectral energy distribution for the source and found that the emission doesn't show any break in frequency as IRAS16293-2422A does, which is associated with free-free emission. We also observe that the size of this source increases always with the frequency, reaching a maximum of about 200 marcsec at 7 mm. This could indicate us that the emission is coming mostly from dust. We built up a model with a radiative transfer code (GASS-LIME) by considering the dust opacity, and the radial density and temperature profiles for the source. We show a comparison between our model and the continuum maps, proving that we are able to reproduce satisfactorily the continuum emission and the size for all the observations.

  16. Simultaneous Observations of GRS 1758-258 in 1997 by VLA, IRAM, SEST, RXTE and OSSE Spectroscopy and Timing

    CERN Document Server

    Lin, D; Liang, E P; Bridgman, T; Smith, D M; Martí, J; Durouchoux, P; Mirabel, I F; Rodríguez, L F; Durouchoux, Ph.

    1999-01-01

    We report the results of our multi-wavelength observations of GRS 1758-258 made in August 1997. The energy bands include radio, millimeter, X-ray, and gamma-ray. The observations enable us to obtain a complete spectrum of the source over an energy range of 2 - 500 keV. The spectrum shows that GRS 1758-258 was in its hard state. It is well fitted by the Sunyaev-Titarchuk (ST) Compton scattering model. The spectrum is also fit by a power law with an exponential cutoff (PLE) plus a soft black-body component. The temperature of the soft component is about 1.2 keV, and the energy flux is less than 1.5% of the total X- and gamma-ray flux. The deduced hydrogen column density is in the range of (0.93 - 2.0) 10^{22} cm^{-2}. No significant iron lines are detected. The radio emission has a flat energy spectrum. The daily radio, X-ray and gamma-ray light curves show that GRS 1758-258 was stable during the observation period, but was highly variable on smaller time scales in X- and gamma-rays. The power density spectra a...

  17. A glimpse beneath Antarctic sea ice: observation of platelet-layer thickness and ice-volume fraction with multifrequency EM

    Science.gov (United States)

    Hoppmann, Mario; Hunkeler, Priska A.; Hendricks, Stefan; Kalscheuer, Thomas; Gerdes, Rüdiger

    2016-04-01

    In Antarctica, ice crystals (platelets) form and grow in supercooled waters below ice shelves. These platelets rise, accumulate beneath nearby sea ice, and subsequently form a several meter thick, porous sub-ice platelet layer. This special ice type is a unique habitat, influences sea-ice mass and energy balance, and its volume can be interpreted as an indicator of the health of an ice shelf. Although progress has been made in determining and understanding its spatio-temporal variability based on point measurements, an investigation of this phenomenon on a larger scale remains a challenge due to logistical constraints and a lack of suitable methodology. In the present study, we applied a lateral constrained Marquardt-Levenberg inversion to a unique multi-frequency electromagnetic (EM) induction sounding dataset obtained on the ice-shelf influenced fast-ice regime of Atka Bay, eastern Weddell Sea. We adapted the inversion algorithm to incorporate a sensor specific signal bias, and confirmed the reliability of the algorithm by performing a sensitivity study using synthetic data. We inverted the field data for sea-ice and platelet-layer thickness and electrical conductivity, and calculated ice-volume fractions within the platelet layer using Archie's Law. The thickness results agreed well with drillhole validation datasets within the uncertainty range, and the ice-volume fraction yielded results comparable to other studies. Both parameters together enable an estimation of the total ice volume within the platelet layer, which was found to be comparable to the volume of landfast sea ice in this region, and corresponded to more than a quarter of the annual basal melt volume of the nearby Ekström Ice Shelf. Our findings show that multi-frequency EM induction sounding is a suitable approach to efficiently map sea-ice and platelet-layer properties, with important implications for research into ocean/ice-shelf/sea-ice interactions. However, a successful application of this

  18. Multi-frequency observations of seawater carbonate chemistry on the central coast of the western Antarctic Peninsula

    Directory of Open Access Journals (Sweden)

    Julie B. Schram

    2015-07-01

    Full Text Available Assessments of benthic coastal seawater carbonate chemistry in Antarctica are sparse. The studies have generally been short in duration, during the austral spring/summer, under sea ice, or offshore in ice-free water. Herein we present multi-frequency measurements for seawater collected from the shallow coastal benthos on a weekly schedule over one year (May 2012–May 2013, daily schedule over three months (March–May 2013 and semidiurnal schedule over five weeks (March–April 2013. A notable pH increase (max pH = 8.62 occurred in the late austral spring/summer (November–December 2012, coinciding with sea-ice break-out and subsequent increase in primary productivity. We detected semidiurnal variation in seawater pH with a maximum variation of 0.13 pH units during the day and 0.11 pH units during the night. Daily variation in pH is likely related to biological activity, consistent with previous research. We calculated the variation in dissolved inorganic carbon (DIC over each seawater measurement frequency, focusing on the primary DIC drivers in the Palmer Station region. From this, we estimated net biological activity and found it accounts for the greatest variations in DIC. Our seasonal data suggest that this coastal region tends to act as a carbon dioxide source during austral winter months and as a strong sink during the summer. These data characterize present-day seawater carbonate chemistry and the extent to which these measures vary over multiple time scales. This information will inform future experiments designed to evaluate the vulnerability of coastal benthic Antarctic marine organisms to ocean acidification.

  19. Identifying Hidden Supernova Remnants in M83 with the VLA

    Science.gov (United States)

    Cole, Bradley; Stockdale, Christopher; Blair, William P.; Cowan, John J.; Godfrey, Leith; Kuntz, K. D.; Long, Knox S.; Maddox, Larry A.; Plucinsky, Paul P.; Pritchard, Tyler A.; Soria, Roberto; Whitmore, Bradley C.; Winkler, P. Frank

    2017-01-01

    We present results of our analysis of C and L band observations of the grand design spiral galaxy, M83 made with the Karl G. Jansky Very Large Array (VLA). With recent optical (HST) and X-ray (Chandra) observations and utilizing the newly expanded bandwidth of the VLA, we are exploring the radio spectral properties of the historical radio point sources in M83 and have discovered more than 250 discrete radio sources. These observations allow us to probe the evolution of supernova remnants (SNRs) and to find previously undiscovered SNRs. These observations represent the fourth epoch of deep VLA observations of M83. The National Radio Astronomy Observatory is a facility of the National Science Foundation operated under cooperative agreement by Associated Universities.

  20. Insights Into the High-Energy Gamma-ray Emission of Markarian 501 from Extensive Multifrequency Observations in the Fermi Era

    CERN Document Server

    :,; :,; al., J Aleksić et; :,; al., V A Acciari et; partners, multi-wavelength

    2012-01-01

    We report on the gamma-ray activity of the blazar Mrk 501 during the first 480 days of Fermi operation. We find that the average LAT gamma-ray spectrum of Mrk 501 can be well described by a single power-law function with a photon index of 1.78 +/- 0.03. While we observe relatively mild flux variations with the Fermi-LAT (within less than a factor of 2), we detect remarkable spectral variability where the hardest observed spectral index within the LAT energy range is 1.52 +/- 0.14, and the softest one is 2.51 +/- 0.20. These unexpected spectral changes do not correlate with the measured flux variations above 0.3GeV. In this paper, we also present the first results from the 4.5-month-long multifrequency campaign (2009 March 15 - August 1) on Mrk 501, which included the VLBA, Swift, RXTE, MAGIC and VERITAS, the F-GAMMA, GASP-WEBT, and other collaborations and instruments which provided excellent temporal and energy coverage of the source throughout the entire campaign. The average spectral energy distribution of...

  1. Parameter Estimation Using VLA Data

    Science.gov (United States)

    Venter, Willem C.

    The main objective of this dissertation is to extract parameters from multiple wavelength images, on a pixel-to-pixel basis, when the images are corrupted with noise and a point spread function. The data used are from the field of radio astronomy. The very large array (VLA) at Socorro in New Mexico was used to observe planetary nebula NGC 7027 at three different wavelengths, 2 cm, 6 cm and 20 cm. A temperature model, describing the temperature variation in the nebula as a function of optical depth, is postulated. Mathematical expressions for the brightness distribution (flux density) of the nebula, at the three observed wavelengths, are obtained. Using these three equations and the three data values available, one from the observed flux density map at each wavelength, it is possible to solve for two temperature parameters and one optical depth parameter at each pixel location. Due to the fact that the number of unknowns equal the number of equations available, estimation theory cannot be used to smooth any noise present in the data values. It was found that a direct solution of the three highly nonlinear flux density equations is very sensitive to noise in the data. Results obtained from solving for the three unknown parameters directly, as discussed above, were not physical realizable. This was partly due to the effect of incomplete sampling at the time when the data were gathered and to noise in the system. The application of rigorous digital parameter estimation techniques result in estimated parameters that are also not physically realizable. The estimated values for the temperature parameters are for example either too high or negative, which is not physically possible. Simulation studies have shown that a "double smoothing" technique improves the results by a large margin. This technique consists of two parts: in the first part the original observed data are smoothed using a running window and in the second part a similar smoothing of the estimated parameters

  2. VLA-ANGST: A HIGH-RESOLUTION H I SURVEY OF NEARBY DWARF GALAXIES

    Energy Technology Data Exchange (ETDEWEB)

    Ott, Juergen [National Radio Astronomy Observatory, P.O. Box O, 1003 Lopezville Road, Socorro, NM 87801 (United States); Stilp, Adrienne M.; Dalcanton, Julianne J. [Department of Astronomy, Box 351580, University of Washington, Seattle, WA 98195 (United States); Warren, Steven R.; Skillman, Evan D. [Minnesota Institute for Astrophysics, University of Minnesota, 116 Church St. SE, Minneapolis, MN 55455 (United States); Walter, Fabian [Max-Planck-Institut fuer Astronomie, Koenigstuhl 17, D-69117 Heidelberg (Germany); De Blok, W. J. G. [Netherlands Institute for Radio Astronomy, Oude Hoogeveensedijk 4, 7991 PD Dwingeloo (Netherlands); Koribalski, Baerbel [Australia Telescope National Facility, CSIRO Astronomy and Space Science, P.O. Box 76, Epping, NSW 1710 (Australia); West, Andrew A., E-mail: jott@nrao.edu, E-mail: adrienne@astro.washington.edu, E-mail: jd@astro.washington.edu, E-mail: warren@astro.umn.edu, E-mail: skillman@astro.umn.edu, E-mail: walter@mpia.de, E-mail: blok@astron.nl, E-mail: Baerbel.Koribalski@csiro.au, E-mail: aawest@bu.edu [Department of Astronomy, Boston University, 725 Commonwealth Avenue, Boston, MA 02215 (United States)

    2012-10-01

    We present the 'Very Large Array survey of Advanced Camera for Surveys Nearby Galaxy Survey Treasury galaxies (VLA-ANGST)'. VLA-ANGST is a National Radio Astronomy Observatory Large Program consisting of high spectral (0.6-2.6 km s{sup -1}) and spatial ({approx}6'') resolution observations of neutral, atomic hydrogen (H I) emission toward 35 nearby dwarf galaxies from the ANGST survey. ANGST is a systematic Hubble Space Telescope survey to establish a legacy of uniform multi-color photometry of resolved stars for a volume-limited sample of nearby galaxies (D {approx}< 4 Mpc). VLA-ANGST provides VLA H I observations of the sub-sample of ANGST galaxies with recent star formation that are observable from the northern hemisphere and that were not observed in the 'The H I Nearby Galaxy Survey' (THINGS). The overarching scientific goal of VLA-ANGST is to investigate fundamental characteristics of the neutral interstellar medium (ISM) of dwarf galaxies. Here we describe the VLA observations, the data reduction, and the final VLA-ANGST data products. We present an atlas of the integrated H I maps, the intensity-weighted velocity fields, the second moment maps as a measure for the velocity dispersion of the H I, individual channel maps, and integrated H I spectra for each VLA-ANGST galaxy. We closely follow the observational setup and data reduction of THINGS to achieve comparable sensitivity and angular resolution. A major difference between VLA-ANGST and THINGS, however, is the high velocity resolution of the VLA-ANGST observations (0.65 and 1.3 km s{sup -1} for the majority of the galaxies). The VLA-ANGST data products are made publicly available through a dedicated Web site (https://science.nrao.edu/science/surveys/vla-angst). With available star formation histories from resolved stellar populations and lower resolution ancillary observations from the far-infrared to the ultraviolet, VLA-ANGST will enable detailed studies of the

  3. The VLA Low-frequency Sky Survey

    CERN Document Server

    Cohen, A S; Cotton, W D; Kassim, N E; Lazio, T J W; Perley, R A; Condon, J J; Erickson, W C

    2007-01-01

    The Very Large Array (VLA) Low-frequency Sky Survey (VLSS) has imaged 95% of the 3*pi sr of sky north of declination = -30 degrees at a frequency of 74 MHz (4 meter wavelength). The resolution is 80" (FWHM) throughout, and the typical RMS noise level is ~0.1 Jy/beam. The typical point-source detection limit is 0.7 Jy/beam and so far nearly 70,000 sources have been catalogued. This survey used the 74 MHz system added to the VLA in 1998. It required new imaging algorithms to remove the large ionospheric distortions at this very low frequency throughout the entire ~11.9 degree field of view. This paper describes the observation and data reduction methods used for the VLSS and presents the survey images and source catalog. All of the calibrated images and the source catalog are available online (http://lwa.nrl.navy.mil/VLSS) for use by the astronomical community.

  4. VLA-ANGST: A high-resolution HI Survey of Nearby Dwarf Galaxies

    CERN Document Server

    Ott, Juergen; Warren, Steven R; Skillman, Evan D; Dalcanton, Julianne J; Walter, Fabian; de Blok, W J G; Koribalski, Baerbel; West, Andrew A

    2012-01-01

    We present the "Very Large Array survey of Advanced Camera for Surveys Nearby Galaxy Survey Treasury galaxies (VLA-ANGST)." VLA-ANGST is a National Radio Astronomy Observatory Large Program consisting of high spectral (0.6-2.6 km/s) and spatial (~6") resolution observations of neutral, atomic hydrogen (HI) emission toward 35 nearby dwarf galaxies from the ANGST survey. ANGST is a systematic HST survey to establish a legacy of uniform multi-color photometry of resolved stars for a volume-limited sample of nearby galaxies (D\\lesssim4 Mpc). VLA-ANGST provides VLA HI observations of the sub-sample of ANGST galaxies with recent star formation that are observable from the northern hemisphere and that were not observed in the "The HI Nearby Galaxy Survey" (THINGS). The overarching scientific goal of VLA-ANGST is to investigate fundamental characteristics of the neutral interstellar medium (ISM) of dwarf galaxies. Here we describe the VLA observations, the data reduction, and the final VLA-ANGST data products. We pre...

  5. Slow and fast narrow spectra aurora E region echoes during the March 17, 2015 storm at mid latitudes. Multi-static, multi-frequency radar observations

    Science.gov (United States)

    Chau, Jorge; St-Maurice, Jean-Pierre

    2016-07-01

    Coherent E region echoes were observed at midlatitudes during the March 17, 2015 storm. The observations came from multi-static, multi-frequency, wide-field of view radars operating at 32.55 and 36.2 MHz in northern Germany. Each of the three receiver stations used, two in monostatic and one in bistatic modes, allow interferometry. These radars systems are devoted primarily to the measurement of mesospheric winds from specular meteor echoes. However during this storm, the strongest of the current solar cycle, strong Radar Aurora echoes were observed during the day for more than four hours. Here we present the main features observed, with a specific emphasis on echoes presenting narrow spectra with slower (around 180 m/s) and faster (as fast as 1600 m/s) Doppler velocities, than nominal typical ion-acoustic velocity expected to be between 400 and 800 m/s. We find that in both types of echoes the range vs. time slopes are between 800 and 1400 m/s. They agree rather well with the Doppler velocity for the narrow fast types but do not agree at all in the narrow slow spectral case. In both instances, the echoes are organized in localized horizontal structures with a range extent typically between 50 and 80 km. The fast-narrow structures tend to occur at higher altitudes than the well-known Farley-Buneman echoes, while the slow-narrow structures occur at lower altitudes (lower than 95 km). Both echo types come from regions with relatively small flow angles. Moreover the altitude of all echoes went down after 16:15 UT with the small-narrow echoes acquiring even smaller Doppler velocities. In large part thanks to the echo localization made feasible by interferometry, these new features are shedding some new important perspective on our understanding of auroral E-region radar echoes, particularly when it comes to spectra classified in the past as "Type III" and "Type IV" echoes.

  6. Studies of circumstellar shells in AGB stars by multifrequency (sub)mm-VLBI observations of maser emission

    Science.gov (United States)

    Colomer, F.; Desmurs, J. F.; Bujarrabal, V.; Baudry, A.; de Vicente, P.; Soria-Ruiz, R.; Alcolea, J.; Diaz-Pulido, A.; Gómez, M.

    2017-03-01

    VLBI observations of maser emission are a basic tool to study the circumstellar envelopes (CSEs) around evolved stars, mainly around AGB and post-AGB stars. The maser lines of water and silicon monoxide are particularly intense. They provide us with high spatial resolution data on the very inner CSEs around AGB stars, including the pulsating layers previous to grain formation and outer regions where the fast expansion characteristic of such envelopes is already present. The analysis of the pumping mechanism of SiO masers and of the physical conditions in the emitting clumps requires accurate maps of the various lines, which show different excitation requirements. A large observational effort is being done to obtain (quasi-)simultaneous multiline data at the highest spatial resolution, using VLBI techniques, which makes possible to compare the relative distribution of the maser lines. We present the state-of-the-art in the field, and discuss preliminary results of SiO masers observed with the Global Millimeter VLBI Array (GMVA) which provide a new view into the physics of these AGB envelopes. The participation of ALMA in these VLBI arrays will boost the study of these masers, at higher frequencies.

  7. Multifrequency Radio Observations of a SNR in the LMC. The Case of SNR J0527-6549 (DEM l204)

    CERN Document Server

    Bozzetto, L M; Crawford, E J; Bojicić, I S; Mendik, A; Wardlaw, B; Payne, J L; De Horta, A Y

    2010-01-01

    We present a detailed study and results of new Australia Telescope Compact Array (ATCA) observations of supernova remnant, SNR J0527-6549. This Large Magellanic Cloud (LMC) ob ject follows a typical supernova remnant (SNR) horseshoe morphology with a diameter of D=(66x58)+-1 pc which is among the largest SNRs in the LMC. Its relatively large size indicates older age while a steeper than expected radio spectral index of aplha=-0.92+-0.11 is more typical for younger and energetic SNRs. Also, we report detections of regions with a high order of polarization at a peak value of ~54+-17% at 6 cm.

  8. Multi-frequency observations of a superbubble in the LMC: The case of LHA 120-N 70

    CERN Document Server

    De Horta, A Y; Filipović, M D; O'Brien, A; Bozzetto, L M; Collier, J D; Wong, G F; Crawford, E J; Tothill, N F H; Maggi, P; Haberl, F

    2014-01-01

    We present a detailed study of new Australia Telescope Compact Array (ATCA) and XMM-Newton observations of LHA 120-N 70 (hereafter N 70), a spherically shaped object in the Large Magellanic Cloud (LMC) classified as a superbubble (SB). Both archival and new observations were used to produce high quality radio-continuum, X-ray and optical images. The radio spectral index of N 70 is estimated to be $\\alpha=-0.12\\pm 0.06$ indicating that while a supernova or supernovae have occurred in the region at some time in the distant past, N70 is not the remnant of a single specific supernova. N70 exhibits limited polarisation with a maximum fractional polarisation of 9% in a small area of the north west limb. We estimate the size of N 70 to have a diameter of 104 pc ($\\pm 1$ pc). The morphology of N 70 in X-rays closely follows that in radio and optical, with most X-ray emission confined within the bright shell seen at longer wavelengths. Purely thermal models adequately fit the soft X-ray spectrum which lacks harder emi...

  9. Multifrequency radio observations of a SNR in the LMC: The case of SNR J0527-6549 (DEM l204

    Directory of Open Access Journals (Sweden)

    Bozzetto L.M.

    2010-01-01

    Full Text Available We present a detailed study and results of new Australia Telescope Compact Array (ATCA observations of supernova remnant SNR J0527-6549. This Large Magellanic Cloud (LMC object follows a typical supernova remnant (SNR horseshoe morphology with a diameter of D=(66×58±1 pc which is among the largest SNRs in the LMC. Its relatively large size indicates older age while a steeper than expected radio spectral index of α=-0.92±0.11 is more typical of younger and energetic SNRs. Also, we report detections of regions with a high order of polarization at a peak value of ~54%±17% at 6 cm.

  10. Multifrequency Radio Observations of a SNR in the LMC. The Case of SNR J0527-6549 (DEM L204)

    Science.gov (United States)

    Bozzetto, L. M.; Filipovic, M. D.; Crawford, E. J.; Bojicic, I. S.; Payne, J. L.; Medik, A.; Wardlaw, B.; de Horta, A. Y.

    2010-12-01

    We present a detailed study and results of new Australia Telescope Compact Array (ATCA) observations of supernova remnant SNR J0527-6549. This Large Magellanic Cloud (LMC) object follows a typical supernova remnant (SNR) horseshoe morphology with a diameter of D=(66×58)±1 pc which is among the largest SNRs in the LMC. Its relatively large size indicates older age while a steeper than expected radio spectral index of α=- 0.92±0.11 is more typical of younger and energetic SNRs. Also, we report detections of regions with a high order of polarization at a peak value of ˜ 54 per cent ± 17 per cent at 6 cm.

  11. Insights into the High-energy γ-ray Emission of Markarian 501 from Extensive Multifrequency Observations in the Fermi Era

    Science.gov (United States)

    Abdo, A. A.; Ackermann, M.; Ajello, M.; Allafort, A.; Baldini, L.; Ballet, J.; Barbiellini, G.; Baring, M. G.; Bastieri, D.; Bechtol, K.; Bellazzini, R.; Berenji, B.; Blandford, R. D.; Bloom, E. D.; Bonamente, E.; Borgland, A. W.; Bouvier, A.; Brandt, T. J.; Bregeon, J.; Brez, A.; Brigida, M.; Bruel, P.; Buehler, R.; Buson, S.; Caliandro, G. A.; Cameron, R. A.; Cannon, A.; Caraveo, P. A.; Carrigan, S.; Casandjian, J. M.; Cavazzuti, E.; Cecchi, C.; Çelik, Ö.; Charles, E.; Chekhtman, A.; Cheung, C. C.; Chiang, J.; Ciprini, S.; Claus, R.; Cohen-Tanugi, J.; Conrad, J.; Cutini, S.; Dermer, C. D.; de Palma, F.; Silva, E. do Couto e.; Drell, P. S.; Dubois, R.; Dumora, D.; Favuzzi, C.; Fegan, S. J.; Ferrara, E. C.; Focke, W. B.; Fortin, P.; Frailis, M.; Fuhrmann, L.; Fukazawa, 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.; Guillemot, L.; Guiriec, S.; Hayashida, M.; Hays, E.; Horan, D.; Hughes, R. E.; Jóhannesson, G.; Johnson, A. S.; Johnson, W. N.; Kadler, M.; Kamae, T.; Katagiri, H.; Kataoka, J.; Knödlseder, J.; Kuss, M.; Lande, J.; Latronico, L.; Lee, S.-H.; Lemoine-Goumard, M.; Longo, F.; Loparco, F.; Lott, B.; Lovellette, M. N.; Lubrano, P.; Madejski, G. M.; Makeev, A.; Max-Moerbeck, W.; Mazziotta, M. N.; McEnery, J. E.; Mehault, J.; Michelson, P. F.; Mitthumsiri, W.; Mizuno, T.; Moiseev, A. A.; Monte, C.; Monzani, M. E.; Morselli, A.; Moskalenko, I. V.; Murgia, S.; Naumann-Godo, M.; Nishino, 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.; Pavlidou, V.; Pearson, T. J.; Pelassa, V.; Pepe, M.; Pesce-Rollins, M.; Piron, F.; Porter, T. A.; Rainò, S.; Rando, R.; Razzano, M.; Readhead, A.; Reimer, A.; Reimer, O.; Richards, J. L.; Ripken, J.; Ritz, S.; Roth, M.; Sadrozinski, H. F.-W.; Sanchez, D.; Sander, A.; Scargle, J. D.; Sgrò, C.; Siskind, E. J.; Smith, P. D.; Spandre, G.; Spinelli, P.; Stawarz, Ł.; Stevenson, M.; Strickman, M. S.; Sokolovsky, K. V.; Suson, D. J.; Takahashi, H.; Takahashi, T.; 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.; Vandenbroucke, J.; Vasileiou, V.; Vilchez, N.; Vitale, V.; Waite, A. P.; Wang, P.; Wehrle, A. E.; Winer, B. L.; Wood, K. S.; Yang, Z.; Ylinen, T.; Zensus, J. A.; Ziegler, M.; Fermi LAT Collaboration; Aleksić, J.; Antonelli, L. A.; Antoranz, P.; Backes, M.; Barrio, J. A.; Becerra González, J.; Bednarek, W.; Berdyugin, A.; Berger, K.; Bernardini, E.; Biland, A.; Blanch, O.; Bock, R. K.; Boller, A.; Bonnoli, G.; Bordas, P.; Borla Tridon, D.; Bosch-Ramon, V.; Bose, D.; Braun, I.; Bretz, T.; Camara, M.; Carmona, E.; Carosi, A.; Colin, P.; Colombo, E.; Contreras, J. L.; Cortina, J.; Covino, S.; Dazzi, F.; de Angelis, A.; De Cea del Pozo, E.; De Lotto, B.; De Maria, M.; De Sabata, F.; Delgado Mendez, C.; Diago Ortega, A.; Doert, M.; Domínguez, A.; Dominis Prester, D.; Dorner, D.; Doro, M.; Elsaesser, D.; Ferenc, D.; Fonseca, M. V.; Font, L.; García López, R. J.; Garczarczyk, M.; Gaug, M.; Giavitto, G.; Godinovi, N.; Hadasch, D.; Herrero, A.; Hildebrand, D.; Höhne-Mönch, D.; Hose, J.; Hrupec, D.; Jogler, T.; Klepser, S.; Krähenbühl, T.; Kranich, D.; Krause, J.; La Barbera, A.; Leonardo, E.; Lindfors, E.; Lombardi, S.; López, M.; Lorenz, E.; Majumdar, P.; Makariev, E.; Maneva, G.; Mankuzhiyil, N.; Mannheim, K.; Maraschi, L.; Mariotti, M.; Martínez, M.; Mazin, D.; Meucci, M.; Miranda, J. M.; Mirzoyan, R.; Miyamoto, H.; Moldón, J.; Moralejo, A.; Nieto, D.; Nilsson, K.; Orito, R.; Oya, I.; Paoletti, R.; Paredes, J. M.; Partini, S.; Pasanen, M.; Pauss, F.; Pegna, R. G.; Perez-Torres, M. A.; Persic, M.; Peruzzo, J.; Pochon, J.; Prada Moroni, P. G.; Prada, F.; Prandini, E.; Puchades, N.; Puljak, I.; Reichardt, T.; Reinthal, R.; Rhode, W.; Ribó, M.; Rico, J.; Rissi, M.; Rügamer, S.; Saggion, A.; Saito, K.; Saito, T. Y.; Salvati, M.; Sánchez-Conde, M.; Satalecka, K.; Scalzotto, V.; Scapin, V.; Schultz, C.; Schweizer, T.; Shayduk, M.; Shore, S. N.; Sierpowska-Bartosik, A.; Sillanpää, A.; Sitarek, J.; Sobczynska, D.; Spanier, F.; Spiro, S.; Stamerra, A.; Steinke, B.; Storz, J.; Strah, N.; Struebig, J. C.; Suric, T.; Takalo, L. O.; Tavecchio, F.; Temnikov, P.; Terzić, T.; Tescaro, D.; Teshima, M.; Vankov, H.; Wagner, R. M.; Weitzel, Q.; Zabalza, V.; Zandanel, F.; Zanin, R.; MAGIC Collaboration; Acciari, V. A.; Arlen, T.; Aune, T.; Benbow, W.; Boltuch, D.; Bradbury, S. M.; Buckley, J. H.; Bugaev, V.; Cannon, A.; Cesarini, A.; Ciupik, L.; Cui, W.; Dickherber, R.; Errando, M.; Falcone, A.; Finley, J. P.; Finnegan, G.; Fortson, L.; Furniss, A.; Galante, N.; Gall, D.; Gillanders, G. H.; Godambe, S.; Grube, J.; Guenette, R.; Gyuk, G.; Hanna, D.; Holder, J.; Huang, D.; Hui, C. M.; Humensky, T. B.; Kaaret, P.; Karlsson, N.; Kertzman, M.; Kieda, D.; Konopelko, A.; Krawczynski, H.; Krennrich, F.; Lang, M. J.; Maier, G.; McArthur, S.; McCann, A.; McCutcheon, M.; Moriarty, P.; Mukherjee, R.; Ong, R.; Otte, A. N.; Pandel, D.; Perkins, J. S.; Pichel, A.; Pohl, M.; Quinn, J.; Ragan, K.; Reyes, L. C.; Reynolds, P. T.; Roache, E.; Rose, H. J.; Rovero, A. C.; Schroedter, M.; Sembroski, G. H.; Senturk, G. D.; Steele, D.; Swordy, S. P.; Tešić, G.; Theiling, M.; Thibadeau, S.; Varlotta, A.; Vincent, S.; Wakely, S. P.; Ward, J. E.; Weekes, T. C.; Weinstein, A.; Weisgarber, T.; Williams, D. A.; Wood, M.; Zitzer, B.; VERITAS Collaboration; Villata, M.; Raiteri, C. M.; Aller, H. D.; Aller, M. F.; Arkharov, A. A.; Blinov, D. A.; Calcidese, P.; Chen, W. P.; Efimova, N. V.; Kimeridze, G.; Konstantinova, T. S.; Kopatskaya, E. N.; Koptelova, E.; Kurtanidze, O. M.; Kurtanidze, S. O.; Lähteenmäki, A.; Larionov, V. M.; Larionova, E. G.; Larionova, L. V.; Ligustri, R.; Morozova, D. A.; Nikolashvili, M. G.; Sigua, L. A.; Troitsky, I. S.; Angelakis, E.; Capalbi, M.; Carramiñana, A.; Carrasco, L.; Cassaro, P.; de la Fuente, E.; Gurwell, M. A.; Kovalev, Y. Y.; Kovalev, Yu. A.; Krichbaum, T. P.; Krimm, H. A.; Leto, P.; Lister, M. L.; Maccaferri, G.; Moody, J. W.; Mori, Y.; Nestoras, I.; Orlati, A.; Pagani, C.; Pace, C.; Pearson, R., III; Perri, M.; Piner, B. G.; Pushkarev, A. B.; Ros, E.; Sadun, A. C.; Sakamoto, T.; Tornikoski, M.; Yatsu, Y.; Zook, A.

    2011-02-01

    We report on the γ-ray activity of the blazar Mrk 501 during the first 480 days of Fermi operation. We find that the average Large Area Telescope (LAT) γ-ray spectrum of Mrk 501 can be well described by a single power-law function with a photon index of 1.78 ± 0.03. While we observe relatively mild flux variations with the Fermi-LAT (within less than a factor of two), we detect remarkable spectral variability where the hardest observed spectral index within the LAT energy range is 1.52 ± 0.14, and the softest one is 2.51 ± 0.20. These unexpected spectral changes do not correlate with the measured flux variations above 0.3 GeV. In this paper, we also present the first results from the 4.5 month long multifrequency campaign (2009 March 15—August 1) on Mrk 501, which included the Very Long Baseline Array (VLBA), Swift, RXTE, MAGIC, and VERITAS, the F-GAMMA, GASP-WEBT, and other collaborations and instruments which provided excellent temporal and energy coverage of the source throughout the entire campaign. The extensive radio to TeV data set from this campaign provides us with the most detailed spectral energy distribution yet collected for this source during its relatively low activity. The average spectral energy distribution of Mrk 501 is well described by the standard one-zone synchrotron self-Compton (SSC) model. In the framework of this model, we find that the dominant emission region is characterized by a size lsim0.1 pc (comparable within a factor of few to the size of the partially resolved VLBA core at 15-43 GHz), and that the total jet power (sime1044 erg s-1) constitutes only a small fraction (~10-3) of the Eddington luminosity. The energy distribution of the freshly accelerated radiating electrons required to fit the time-averaged data has a broken power-law form in the energy range 0.3 GeV-10 TeV, with spectral indices 2.2 and 2.7 below and above the break energy of 20 GeV. We argue that such a form is consistent with a scenario in which the bulk

  12. VLA Polarimetry of Two Extended Radio Galaxies

    CERN Document Server

    Junor, W; Morganti, R; Padrielli, L

    2000-01-01

    Multi-wavelength VLA observations of two extended radio galaxies, 0235-197and 1203+043 are presented. There is some evidence from earlier studies thatthese two sources exhibit low frequency (<1 GHz) variability. This work showsthat both sources have linear polarizations, if any, below the detection limitsat 320 MHz, so we cannot explain the variability as being due to instrumentalpolarization effects as has been suggested for 3C159. Refractive scintillationmay be the cause of the variability in 0235-197. This would require theexistence of a bright, compact component in one of the hot spots seen in theseobservations. This is not implausible but the resolution of this observationalprogram is insufficent to address that question. The radio source 1203+043lacks any bright compact component thereby ruling out a refractivescintillation mechanism for its variability. Consequently, it is possible thatclaims of variability in this source are spurious. However, the 320 MHz VLAobservations show that 1203+043 has an `...

  13. NRAO Makes Available VLA Sky Survey Maps

    Science.gov (United States)

    1994-06-01

    An original and comprehensive data set potentially full of scientific surprises now is available to astronomers, students and the public through the information superhighway. Radio images of the sky produced by the Very Large Array radio telescope -- one of the premier astronomical instruments in the world -- as part of a massive survey now are stored in an electronic repository avail- able over the Internet computer communications network. "Each of these sensitive new sky maps shows about a thou- sand radio-emitting objects, most of which have never been seen before," said Dr. J. J. Condon, leader of the National Radio As- tronomy Observatory (NRAO) survey team. "We are releasing them as soon as they are completed because they contain more data than we could possibly analyze by ourselves." "By using electronic distribution, we can open this tre- mendous resource of information for computer analysis by all as- tronomers immediately, without waiting for traditional publication," Condon added. The radio images are copyright NRAO/ AUI. Permission is granted for use of the material without charge for scholarly, educational and private non-commercial purposes. "It is entirely conceivable -- even probable -- that valuable discoveries will be made by students or amateur astrono- mers who devote the time to study these maps carefully," said team member Dr. W. D. Cotton. "Making this new information available electronically means that more people can participate in adding to its scientific value." The maps are a product of the NRAO VLA Sky Survey (NVSS), which began its observational phase in September of 1993 and will cover 82 percent of the sky when completed by the end of 1996. The NVSS is expected to produce a catalog of more than two million ra- dio-emitting objects in the sky, and it is the first sky survey sensitive to linearly polarized emission from radio sources beyond our own Milky Way galaxy. "The NVSS is being made as a service to the entire astronomical

  14. A Multifrequency Radiometer System

    DEFF Research Database (Denmark)

    Skou, Niels

    1977-01-01

    A radiometer system having four channels: 5 GHz, l7 GHz, 34 GHz, all vertical polarization, and a 34 GHz sky horn, will be described. The system which is designed for collecting glaciological and oceanographic data is intended for airborne use and imaging is achieved by means of a multifrequency ...... elaborate processing later, using ground facilities. In conjunction with a side looking radar which is under development at present, the radiometers are intended as the remote sensing basis for an all-weather ice reconnaissance service in the Greenland seas....

  15. VLA's Sharpened Vision Shows Details of Still-Forming Star

    Science.gov (United States)

    2001-01-01

    Using a new observing capability of the National Science Foundation's Very Large Array (VLA) radio telescope, astronomers have discovered a solar-system-sized disk of gas and dust feeding material onto a young star with 8 to 10 times the mass of the Sun. This is the first time an inner "accretion disk" has been seen around such a massive star. The VLA images also revealed the inner portion of an energetic outflow of material powered by the accretion disk. Artist's conception "Disks and outflows in young stars increase dramatically in mass and energy as the mass of the young star increases. We don't know if the same process is at work in all young stars or how the disks can both power an outflow that extends more than 15 light-years and also start the process of forming planets," said Debra Shepherd, of the National Radio Astronomy Observatory (NRAO) in Socorro, New Mexico. "By studying the birth of massive young stars, we're pushing the limits of our understanding and trying to learn if there are critical differences between the outflows from high and low mass young stars," she added Shepherd and Mark Claussen, also from the NRAO in Socorro, and Stan Kurtz of the National Autonomous University in Mexico, presented their findings today at the American Astronomical Society's meeting in San Diego, CA. The scientists made the discovery using the VLA connected by a newly- operational fiber-optic link to one of the radio-telescope antennas of the NSF's Very Long Baseline Array (VLBA), located at Pie Town, NM, 32 miles away from the VLA. Linking the VLA to the Pie Town antenna almost doubled the resolving power, or ability to see fine detail, available to the astronomers. "We could not have seen these structures without using the Pie Town antenna connected to the VLA," said Claussen. Work on the VLA-Pie Town fiber-optic link, financed by the NSF and Associated Universities, Inc., which operates NRAO for the NSF, began in late 1997. The linked facilities first were

  16. Multi-frequency excitation

    KAUST Repository

    Younis, Mohammad I.

    2016-03-10

    Embodiments of multi-frequency excitation are described. In various embodiments, a natural frequency of a device may be determined. In turn, a first voltage amplitude and first fixed frequency of a first source of excitation can be selected for the device based on the natural frequency. Additionally, a second voltage amplitude of a second source of excitation can be selected for the device, and the first and second sources of excitation can be applied to the device. After applying the first and second sources of excitation, a frequency of the second source of excitation can be swept. Using the methods of multi- frequency excitation described herein, new operating frequencies, operating frequency ranges, resonance frequencies, resonance frequency ranges, and/or resonance responses can be achieved for devices and systems.

  17. The VLA Low Band Ionospheric and Transient Experiment (VLITE): A Commensal Sky Survey

    CERN Document Server

    Clarke, Tracy; Polisensky, Emil; Peters, Wendy; Giacintucci, Simona; Hyman, Scott D

    2016-01-01

    The US Naval Research Laboratory (NRL) and the National Radio Astronomy Observatory (NRAO) have collaborated to develop, install, and commission a new commensal system on the Karl G. Jansky Very Large Array (VLA). The VLA Low Band Ionospheric and Transient Experiment (VLITE) makes use of dedicated samplers and fibers to tap the signal from 10 VLA low band receivers and correlate those through a real-time DiFX correlator. VLITE allows for the simultaneous use of the VLA to observe primary science using the higher frequencies receivers (1-50 GHz) through the NRAO WIDAR correlator and lower frequencies through the DiFX correlator. VLITE operates during nearly all observing programs and provides 64 MHz of bandwidth centered at 352 MHz. The operation of VLITE requires no additional resources from the VLA system running the primary science and produces an ad-hoc sky survey. The commensal system greatly expands the capabilities of the VLA through value-added PI science, stand-alone astrophysics, the opening of a new...

  18. VLA observations of the OH emission from Comet Wilson (1986) - The value of high resolution in both spatial and velocity coordinates

    Science.gov (United States)

    Palmer, Patrick; De Pater, Imke; Snyder, Lewis E.

    1989-01-01

    In comparison with Comet Halley, the radio OH emission from Comet Wilson behaved very erratically, changing rapidly in position as well as in velocity, while the emission and brightness distribution from Comet Halley displayed apparent stability. A few months later, nearer perihelion, just the opposite behavior was observed at UV wavelengths. Another difference between the two comets is that the OH emission from Comet Halley seemed confined to a region a few times 100.000 km in size, while the emission from Comet Wilson showed up in sporadic blobs, with variable intensities and velocities, at distances as far as 10 to the 6th km from the nucleus. This behavior in Comet Wilson may be associated with the disintegration of the outer frosting associated with new comets and possibly with the fragmentation and ejection of cometesimals from the nucleus. As part of the data analysis, it is demonstrated that lengthening the integration time and lowering the velocity resolution affects the symmetry of the OH images and spectral-line profiles. As a consequence, asymmetric cometary OH line profiles may be more common than previously thought.

  19. The LOFAR Multifrequency Snapshot Sky Survey (MSSS) I. Survey description and first results

    CERN Document Server

    Heald, G H; Orrú, E; Breton, R P; Carbone, D; Ferrari, C; Hardcastle, M J; Jurusik, W; Macario, G; Mulcahy, D; Rafferty, D; Asgekar, A; Brentjens, M; Fallows, R A; Frieswijk, W; Toribio, M C; Adebahr, B; Arts, M; Bell, M R; Bonafede, A; Bray, J; Broderick, J; Cantwell, T; Carroll, P; Cendes, Y; Clarke, A O; Croston, J; Daiboo, S; de Gasperin, F; Gregson, J; Harwood, J; Hassall, T; Heesen, V; Horneffer, A; van der Horst, A J; Iacobelli, M; Jelić, V; Jones, D; Kant, D; Kokotanekov, G; Martin, P; McKean, J P; Morabito, L K; Nikiel-Wroczyński, B; Offringa, A; Pandey, V N; Pandey-Pommier, M; Pietka, M; Pratley, L; Riseley, C; Rowlinson, A; Sabater, J; Scaife, A M M; Scheers, L H A; Sendlinger, K; Shulevski, A; Sipior, M; Sobey, C; Stewart, A J; Stroe, A; Swinbank, J; Tasse, C; Trüstedt, J; Varenius, E; van Velzen, S; Vilchez, N; van Weeren, R J; Wijnholds, S; Williams, W L; de Bruyn, A G; Nijboer, R; Wise, M; Alexov, A; Anderson, J; Avruch, I M; Beck, R; Bell, M E; van Bemmel, I; Bentum, M J; Bernardi, G; Best, P; Breitling, F; Brouw, W N; Brüggen, M; Butcher, H R; Ciardi, B; Conway, J E; de Geus, E; de Jong, A; de Vos, M; Deller, A; Dettmar, R J; Duscha, S; Eislöffel, J; Engels, D; Falcke, H; Fender, R; Garrett, M A; Grießmeier, J; Gunst, A W; Hamaker, J P; Hessels, J W T; Hoeft, M; Hörandel, J; Holties, H A; Intema, H; Jackson, N J; Jütte, E; Karastergiou, A; Klijn, W F A; Kondratiev, V I; Koopmans, L V E; Kuniyoshi, M; Kuper, G; Law, C; van Leeuwen, J; Loose, M; Maat, P; Markoff, S; McFadden, R; McKay-Bukowski, D; Mevius, M; Miller-Jones, J C A; Morganti, R; Munk, H; Nelles, A; Noordam, J E; Norden, M J; Paas, H; Polatidis, A G; Reich, W; Renting, A; Röttgering, H; Schoenmakers, A; Schwarz, D; Sluman, J; Smirnov, O; Stappers, B W; Steinmetz, M; Tagger, M; Tang, Y; ter Veen, S; Thoudam, S; Vermeulen, R; Vocks, C; Vogt, C; Wijers, R A M J; Wucknitz, O; Yatawatta, S; Zarka, P

    2015-01-01

    We present the Multifrequency Snapshot Sky Survey (MSSS), the first northern-sky LOFAR imaging survey. In this introductory paper, we first describe in detail the motivation and design of the survey. Compared to previous radio surveys, MSSS is exceptional due to its intrinsic multifrequency nature providing information about the spectral properties of the detected sources over more than two octaves (from 30 to 160 MHz). The broadband frequency coverage, together with the fast survey speed generated by LOFAR's multibeaming capabilities, make MSSS the first survey of the sort anticipated to be carried out with the forthcoming Square Kilometre Array (SKA). Two of the sixteen frequency bands included in the survey were chosen to exactly overlap the frequency coverage of large-area Very Large Array (VLA) and Giant Metrewave Radio Telescope (GMRT) surveys at 74 MHz and 151 MHz respectively. The survey performance is illustrated within the "MSSS Verification Field" (MVF), a region of 100 square degrees centered at J...

  20. Detecting multiple periodicities in observational data with the multi-frequency periodogram. II. Frequency Decomposer, a parallelized time-series analysis algorithm

    CERN Document Server

    Baluev, Roman V

    2013-01-01

    This is a parallelized algorithm performing a decomposition of a noisy time series into a number of frequency components. The algorithm analyses all suspicious periodicities that can be revealed, including the ones that look like an alias or noise at a glance, but later may prove to be a real variation. After selection of the initial candidates, the algorithm performs a complete pass through all their possible combinations and computes the rigorous multi-frequency statistical significance for each such frequency tuple. The largest combinations that still survived this thresholding procedure represent the outcome of the analysis. The parallel computing on a graphics processing unit (GPU) is implemented through CUDA and brings a significant performance increase. It is still possible to run FREDEC solely on CPU in the traditional single-threaded mode, when no suitable GPU device is available.

  1. Formation and evolution of the water maser outflow event in AFGL 2591 VLA 3-N

    CERN Document Server

    Trinidad, M A; Estalella, R; Cantó, J; Raga, A; Torrelles, J M; Patel, N A; Gómez, J F; Anglada, G; Carrasco-González, C; Rodríguez, L F

    2012-01-01

    In this paper we analyze multi-epoch Very Long Baseline Interferometry (VLBI) water maser observations carried out with the Very Long Baseline Array (VLBA) toward the high-mass star-forming region AFGL 2591. We detected maser emission associated with the radio continuum sources VLA 2 and VLA 3. In addition, a water maser cluster, VLA 3-N, was detected ~ 0.5" north of VLA 3. We concentrate the discussion of this paper on the spatio-kinematical distribution of the water masers towards VLA 3-N. The water maser emission toward the region VLA 3-N shows two bow shock-like structures, Northern and Southern, separated from each other by ~ 100 mas (~ 330 AU). The spatial distribution and kinematics of the water masers in this cluster have persisted over a time span of seven years. The Northern bow shock has a somewhat irregular morphology, while the Southern one has a remarkably smooth morphology. We measured the proper motions of 33 water maser features, which have an average proper motion velocity of ~ 1.3 mas/yr (~...

  2. Computing Architecture for the ngVLA

    Science.gov (United States)

    Kern, Jeffrey S.; Glendenning, Brian; Hiriart, R.

    2017-01-01

    Computing challenges for the Next Generation Very Large Array (ngVLA) are not always the ones that first come to mind. Current design concepts have visibility data rates which allow the permanent storage of the raw visibility data, and although challenging, the calibration and imaging processing for the ngVLA is not beyond the capabilities of existing systems (let alone those that will exist when ngVLA construction is completed). Design goals include a system that supports a wide range of PI-driven projects, end to end data management, and the production of science ready data products. This should be accomplished while minimizing the operating costs of an array consisting of hundreds of elements distributed over an area of nearly 100,000 km2. We discuss a proposed architecture of the computing system, design constraints for a detailed design, and some possible design choices and their implications.

  3. EVOLUTION OF THE WATER MASER EXPANDING SHELL IN W75N VLA 2

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Jeong-Sook; Kim, Sang Joon [School of Space Science, Kyunghee University, Seocheon-dong, Giheung-si, Gyeonggi-do, 446-701 (Korea, Republic of); Kim, Soon-Wook [Korea Astronomy and Space Science Institute, 776 Daedeokdaero, Yuseong, Daejeon 305-348 (Korea, Republic of); Kurayama, Tomoharu [Graduate School of Science and Engineering, Kagoshima University, 1-21-35 Korimoto, Kagoshima, Kagoshima 890-0065 (Japan); Honma, Mareki [National Astronomical Observatory of Japan, 2-21-1 Osawa, Mitaka, Tokyo 181-8588 (Japan); Sasao, Tesuo [Yaeyama Star Club, Ookawa, Ishigaki, Okinawa 904-0022 (Japan); Surcis, Gabriele [Joint Institute for VLBI in Europe, Postbus 2, 7990 AA Dwingeloo (Netherlands); Canto, Jorge [Instituto de Astronomia (UNAM), Apartado 70-264, 04510 Mexico D. F. (Mexico); Torrelles, Jose M., E-mail: evony@kasi.re.kr, E-mail: skim@kasi.re.kr [Instituto de Ciencias del Espacio (CSIC)-UB/IEEC, Universitat de Barcelona, Marti i Franques 1, E-08028 Barcelona (Spain)

    2013-04-10

    We present Very Long Baseline Interferometry (VLBI) observations of 22 GHz H{sub 2}O masers in the high-mass star-forming region of W75N, carried out with VLBI Exploration of Radio Astrometry (VERA) for three epochs in 2007 with an angular resolution of {approx}1 mas. We detected H{sub 2}O maser emission toward the radio jet in VLA 1 and the expanding shell-like structure in VLA 2. The spatial distribution of the H{sub 2}O masers detected with VERA and measured proper motions around VLA 1 and VLA 2 are similar to those found with previous VLBI observations in epochs 1999 and 2005, with the masers in VLA 1 mainly distributed along a linear structure parallel to the radio jet and, on the other hand, forming a shell-like structure around VLA 2. We have made elliptical fits to the VLA 2 H{sub 2}O maser shell-like structure observed in the different epochs (1999, 2005, and 2007), and found that the shell is still expanding eight years after its discovery. From the difference in the size of the semi-major axes of the fitted ellipses in epochs 1999 ({approx_equal}71 {+-} 1 mas), 2005 ({approx_equal}97 {+-} 3 mas), and 2007 ({approx_equal}111 {+-} 1 mas), we estimate an average expanding velocity of {approx}5 mas yr{sup -1}, similar to the proper motions measured in the individual H{sub 2}O maser features. A kinematic age of {approx}20 yr is derived for this structure. In addition, our VERA observations indicate an increase in the ellipticity of the expanding shell around VLA 2 from epochs 1999 to 2007. In fact, the elliptical fit of the VERA data shows a ratio of the minor and major axes of {approx}0.6, in contrast with an almost circular shape for the shell detected in 1999 and 2005 (b/a {approx} 0.9). This suggests that we are probably observing the formation of a jet-driven H{sub 2}O maser structure in VLA2, evolving from a non-collimated pulsed-outflow event during the first stages of evolution of a massive young stellar object (YSO). This may support predictions made

  4. A Multifrequency Study of Five Large Radio Galaxies

    Indian Academy of Sciences (India)

    A. Pirya; S. Nandi; D. J. Saikia; C. Konar; M. Singh

    2011-12-01

    We present the results of GMRT and VLA observations of five large radio sources over a wide frequency range to investigate their structural and spectral asymmetries. The hot-spot brightness ratios suggest intrinsic source asymmetries, while the spectral indices show evidence of re-acceleration of particles.

  5. A Banach Space Regularization Approach for Multifrequency Microwave Imaging

    Directory of Open Access Journals (Sweden)

    Claudio Estatico

    2016-01-01

    Full Text Available A method for microwave imaging of dielectric targets is proposed. It is based on a tomographic approach in which the field scattered by an unknown target (and collected in a proper observation domain is inverted by using an inexact-Newton method developed in Lp Banach spaces. In particular, the extension of the approach to multifrequency data processing is reported. The mathematical formulation of the new method is described and the results of numerical simulations are reported and discussed, analyzing the behavior of the multifrequency processing technique combined with the Banach spaces reconstruction method.

  6. 20 cm VLA Radio-Continuum Study of M31 - Images and Point Source Catalogues DR2: Extraction of a supernova remnant sample

    CERN Document Server

    Galvin, T J

    2014-01-01

    We present Data Release 2 of the Point Source Catalogue created from a series of previously constructed radio-continuum images of M31 at lambda=20 cm (nu=1.4 GHz) from archived VLA observations. In total, we identify a collection of 916 unique discrete radio sources across the field of M31. Comparing these detected sources to those listed by Gelfand et al. (2004) at lambda=92 cm, the spectral index of 98 sources has been derived. The majority (73%) of these sources exhibit a spectral index of alpha <-0.6, indicating that their emission is predominantly non-thermal in nature, which is typical for background objects and Supernova Remnants (SNRs). Additionally, we investigate the presence of radio counterparts for some 156 SNRs and SNR candidates, finding a total of only 13 of these object in our images within a 5 arcsec search area. Auxiliary optical, radio and X-ray catalogs were cross referenced highlighting a small population of SNR and SNR candidates common to multi-frequency domains.

  7. High-Fidelity VLA Imaging of the Radio Structure of 3C273

    CERN Document Server

    Perley, R A

    2016-01-01

    3C273, the nearest bright quasar, comprises a strong nuclear core and a bright, one-sided jet extending ~ 23 arcseconds to the SW. The source has been the subject of imaging campaigns in all wavebands. Extensive observations of this source have been made with the Very Large Array and other telescopes as part of a campaign to understand the jet emission mechanisms. Partial results from the VLA radio campaign have been published, but to date, the complete set of VLA imaging results has not been made available. We have utilized the VLA to determine the radio structure of 3C273 in Stokes I, Q, and U, over the widest possible frequency and resolution range. The VLA observed the source in all four of its configurations, and with all eight of its frequency bands, spanning 73.8 MHz to 43 GHz. The data were taken in a pseudo-spectral line mode to minimize the VLA's correlator errors, and were fully calibrated with subsequent self-calibration techniques to maximise image fidelity. Images in Stokes parameters I, Q, and ...

  8. VLA Discovers Giant Rings Around Galaxy Cluster

    Science.gov (United States)

    2006-11-01

    , thanks to its very high sensitivity and unique capability to make images of exceedingly faint radio-emitting objects," Bagchi said. The scientists also used the European Space Agency's XMM-Newton, the world's most sensitive X-ray observatory, to observe this extraordinary cluster of galaxies. "The advanced technical capabilities of the orbiting XMM-Newton revealed a spectacular bullet-like region of X-ray emission in this dynamically active cluster," said Gastao B. Lima Neto, of the Institute of Astronomy and Geophysics in Sao Paulo, Brazil, a co-author of the research paper. "Our X-ray observations strongly suggest a recent collision and merger of two or more smaller clusters. Such a phenomenon is among the most energetic events in the Universe after the Big Bang. Only a tiny fraction of the total energy of this collision, if transferred to electrons, would cause them to emit the radio waves observed by the VLA. However, the main question is, how this is achieved," said Florence Durret of the Astrophysical Institute of Paris, France, another of the researchers. The scientists calculated that the total energy of the colliding groups of galaxies would be enough to keep our Sun shining for more than 20 sextillion years (2 followed by 22 zeros)! "We think the shock waves that sped up these electrons came from the collision of a smaller group of galaxies with the main body of the larger cluster. When two such massive objects crash into each other at supersonic speed, gigantic ripple-like shock waves are created in the surrounding gas, which race out to the outer regions of the forming cluster at a speed of thousands of kilometers per second," Bagchi said. "You can imagine that each cluster is like a supersonic aircraft, moving faster than the speed of sound in the surrounding gas, and just as you hear a sonic boom when shock waves from an airplane pass by you, we believe that the situation in the Abell 3376 cluster is similar, with ringlike radio structures tracing out the

  9. Connecting Gas Dynamics and Star Formation Histories in Nearby Galaxies: The VLA-ANGST Survey

    CERN Document Server

    Ott, Juergen; Dalcanton, Julianne; Walter, Fabian; Stilp, Adrienne; Koribalski, Baerbel; West, Andrew; Warren, Steven

    2008-01-01

    In recent years, HST revolutionized the field of star formation in nearby galaxies. Due to its high angular resolution it has now become possible to construct star formation histories of individual stellar populations on scales of a few arcseconds spanning a range of up to ~600 Myr. This method will be applied to the ANGST galaxies, a large HST volume limited survey to map galaxies up to distances of 3.5-4.0 Mpc (excluding the Local Group). The ANGST sample is currently followed--up by high, ~6'' resolution VLA observations of neutral, atomic hydrogen (HI) in the context of VLA-ANGST, an approved Large VLA Project. The VLA resolution is well matched to that of the spatially resolved star formation history maps. The combination of ANGST and VLA-ANGST data will provide a new, promising approach to study essential fields of galaxy evolution such as the triggering of star formation, the feedback of massive stars into the interstellar medium, and the structure and dynamics of the interstellar medium.

  10. VizieR Online Data Catalog: VLA-COSMOS 3 GHz Large Project (Smolcic+, 2017)

    Science.gov (United States)

    Smolcic, V.; Novak, M.; Bondi, M.; Ciliegi, P.; Mooley, K. P.; Schinnerer, E.; Zamorani, G.; Navarrete, F.; Bourke, S.; Karim, A.; Vardoulaki, E.; Leslie, S.; Delhaize, J.; Carilli, C. L.; Myers, S. T.; Baran, N.; Delvecchio, I.; Miettinen, O.; Banfield, J.; Balokovic, M.; Bertoldi, F.; Capak, P.; Frail, D. A.; Hallinan, G.; Hao, H.; Herrera Ruiz, N.; Horesh, A.; Ilbert, O.; Intema, H.; Jelic, V.; Klockner, H.-R.; Krpan, J.; Kulkarni, S. R.; McCracken, H.; Laigle, C.; Middleberg, E.; Murphy, E.; Sargent, M.; Scoville, N. Z.; Sheth, K.

    2016-10-01

    The catalog contains sources selected down to a 5σ(σ~2.3uJy/beam) threshold. This catalog can be used for statistical analyses, accompanied with the corrections given in the data & catalog release paper. All completeness & bias corrections and source counts presented in the paper were calculated using this sample. The total fraction of spurious sources in the COSMOS 2 sq.deg. is below 2.7% within this catalog. However, an increase of spurious sources up to 24% at 5.0=5.5 for single component sources (MULTI=0). The total fraction of spurious sources in the COSMOS 2 sq.deg. within such a selected sample is below 0.4%, and the fraction of spurious sources is below 3% even at the lowest S/N (=5.5). Catalog Notes: 1. Maximum ID is 10966 although there are 10830 sources. Some IDs were removed by joining them into multi-component sources. 2. Peak surface brightness of sources [uJy/beam] is not reported, but can be obtained by multiplying SNR with RMS. 3. High NPIX usually indicates extended or very bright sources. 4. Reported positional errors on resolved and extended sources should be considered lower limits. 5. Multicomponent sources have errors and S/N column values set to -99.0 Additional data information: Catalog date: 21-Mar-2016 Source extractor: BLOBCAT v1.2 (http://blobcat.sourceforge.net/) Observations: 384 hours, VLA, S-band (2-4GHz), A+C array, 192 pointings Imaging software: CASA v4.2.2 (https://casa.nrao.edu/) Imaging algorithm: Multiscale multifrequency synthesis on single pointings Mosaic size: 30000x30000 pixels (3.3 GB) Pixel size: 0.2x0.2 arcsec2 Median rms noise in the COSMOS 2 sq.deg.: 2.3uJy/beam Beam is circular with FWHM=0.75 arcsec Bandwidth-smearing peak correction: 0% (no corrections applied) Resolved criteria: Sint/Speak>1+6*snr^(-1.44) Total area covered: 2.6 sq.deg. (1 data file).

  11. Improved analysis of plasmasphere motion using the VLA radio interferometer

    Directory of Open Access Journals (Sweden)

    G. W. Hoogeveen

    Full Text Available Observations using the very large (VLA radio interferometer during the past five years have enabled the discovery of a new type of plasmasphere disturbance, the magnetic eastward-directed wave. Previous work indicated these disturbances were likely frozen to the geomagnetic field as determined from their azimuth distributions. This work provides a method to explain more accurately the azimuth distribution, thereby allowing the calculation of the disturbances' location in the plasmasphere independently of the measured velocity. The measurable velocity due to corotation is calculated and subtracted from the measured trace velocity. This difference, or deviation from corotation, is attributed to electrodynamic convection; the measurement of plasmaspheric convection may lead to the eventual monitoring of mid-latitude electric fields. Disturbances are seen convecting predominantly westward, with the fastest having angular velocities greater than the anticorotating VLA line of sight. The direction of convection and conditions of observations indicate that the disturbances are likely the same phenomenon seen by the Los Alamos satellite beacon array.

  12. VLA-Max '91 tests of high energy flare physics

    Science.gov (United States)

    Lang, Kenneth R.; Willson, Robert F.

    1989-01-01

    The potential for the Very Large Array (VLA) contributions during the coming maximum in solar activity is illustrated by unpublished observations of solar flares on 28 May, 8 June, 24 June, and 30 September 1988. Some of this data appears in the two papers by Willson et al., referenced in this article. The VLA can be used to spatially resolve flaring active regions and their magnetic fields. These results can be compared with simultaneous x ray and gamma ray observations from space. Examples are provided in which spatially separated radio sources are resolved for the pre-burst, impulsive and decay phases of solar flares. The emergence of precursor coronal loops probably triggers the release of stored magnetic energy in adjacent coronal loops. Noise storm enhancements can originate in large-scale coronal loops on opposite sides of the visible solar disk. An interactive feedback mechanism may exist between activity in high-lying 90 cm coronal loops and lower-lying 20 cm ones.

  13. Connecting low- and high-mass star formation: the intermediate-mass protostar IRAS 05373+2349 VLA 2

    CERN Document Server

    Brown, G M; Hoare, M G; Lumsden, S L

    2016-01-01

    Until recently, there have been few studies of the protostellar evolution of intermediate-mass (IM) stars, which may bridge the low- and high-mass regimes. This paper aims to investigate whether the properties of an IM protostar within the IRAS 05373+2349 embedded cluster are similar to that of low- and/or high-mass protostars. We carried out Very Large Array as well as Combined Array for Research in Millimeter Astronomy continuum and 12CO(J=1-0) observations, which uncover seven radio continuum sources (VLA 1-7). The spectral index of VLA 2, associated with the IM protostar is consistent with an ionised stellar wind or jet. The source VLA 3 is coincident with previously observed H2 emission line objects aligned in the north-south direction (P.A. -20 to -12 deg), which may be either an ionised jet emanating from VLA 2 or (shock-)ionised cavity walls in the large-scale outflow from VLA 2. The position angle between VLA 2 and 3 is slightly misaligned with the large-scale outflow we map at ~5-arcsec resolution i...

  14. Saturn's rings resolved by the VLA. [Very Larg Array (VLA)

    Science.gov (United States)

    Depater, I.; Dickel, J. B.

    1982-01-01

    High resolution radio data of Saturn were obtained at 1.3, 2, 6, and 21 cm, at different inclination angles of the ring plane. Results on optical depth measurements in the rings are described. There is no wavelength dependence in the optical depth of the rings between 1.3 and 6 cm. This indicates that there are not many small particles (sizes of a few centimeters) in the B-ring, which ring is responsible for most of the observed obscuration. This result agrees with the Voyager radio occultation experiment.

  15. A VLA Survey of Orion Class 0 Protostars at 30 AU Resolution

    Science.gov (United States)

    Karnath, Nicole; Tobin, John J.; Booker, Joseph J.; Guilfoil Cox, Erin; Diaz-Rodriguez, Ana; Kama, MIHKEL; Li, Zhi-Yun; Looney, Leslie; Melis, Carl; Murillo, Nadia; Persson, Magnus; Reynolds, Nick; Sadavoy, Sarah; Segura-Cox, Dominique; Stephenson, Brian; Megeath, Samuel Thomas

    2017-06-01

    We present initial results from the VANDAM:Orion survey, a VLA survey of Class 0 protostars in Orion. Disks and multiple systems are thought to originate early in the star formation process, when the protostars are deeply embedded in dense envelopes. The VANDAM survey of the Perseus molecular cloud demonstrated that VLA Ka-band (33 GHz) observations can resolve disks and companions around Class 0 protostars, providing the means to study the incidence and separations of companions, and the properties of disks during the first 100,000 years of protostellar evolution. The VANDAM:Orion survey targets 92 Class 0 protostars in the Orion Molecular clouds, the largest population of Class 0 objects within 500 pc of the Sun. These were selected from protostars characterized by the Herschel Orion Protostar Survey, or HOPS, which assembled 1.6-870 micron SEDs of 319 protostars in the Orion A and B molecular clouds. VANDAM:Orion not only triples the number of Class 0 protostars observed with the VLA , as compared to the original VANDAM survey, but also samples the diverse environments found in the Orion clouds. VANDAM:Orion also includes 38 Class I protostars found near the targeted Class 0 objects.VANDAM:Orion initially carried out VLA observations in the C-array to determine their fluxes in the Ka-band (33 GHZ). The subsequent A-array observations then imaged the protostars with a resolution of 0.08”/34 AU. The entire sample has now been observed and reduced. We will overview the detection statistics and show examples of multiple systems and disks around Orion Class 0 protostars. The VLA images will also be compared to images from a recent ALMA 850 micron snapshot survey of all Orion protostars characterized by HOPS. Many sources appear opaque to ALMA at 870 μm, but the dust is optically thin for the VLA, enabling it to detect structure that ALMA cannot. Finally, we will discuss the prospects of VANDAM:Orion for characterizing the role of environment in the formation of

  16. Connecting low- and high-mass star formation: the intermediate-mass protostar IRAS 05373+2349 VLA 2

    Science.gov (United States)

    Brown, G. M.; Johnston, K. G.; Hoare, M. G.; Lumsden, S. L.

    2016-12-01

    Until recently, there have been few studies of the protostellar evolution of intermediate-mass (IM) stars, which may bridge the low- and high-mass regimes. This paper aims to investigate whether the properties of an IM protostar within the IRAS 05373+2349 embedded cluster are similar to that of low- and/or high-mass protostars. We carried out Very Large Array as well as Combined Array for Research in Millimeter Astronomy continuum and 12CO(J=1-0) observations, which uncover seven radio continuum sources (VLA 1-7). The spectral index of VLA 2, associated with the IM protostar is consistent with an ionized stellar wind or jet. The source VLA 3 is coincident with previously observed H2 emission line objects aligned in the north-south direction (P.A. -20 to -12°), which may be either an ionized jet emanating from VLA 2 or (shock-)ionized cavity walls in the large-scale outflow from VLA 2. The position angle between VLA 2 and 3 is slightly misaligned with the large-scale outflow we map at ˜5-arcsec resolution in 12CO (P.A. ˜ 30°), which in the case of a jet suggests precession. The emission from the mm core associated with VLA 2 is also detected; we estimate its mass to be 12-23 M⊙, depending on the contribution from ionized gas. Furthermore, the large-scale outflow has properties intermediate between outflows from low- and high-mass young stars. Therefore, we conclude that the IM protostar within IRAS 05373+2349 is phenomenologically as well as quantitatively intermediate between the low- and high-mass domains.

  17. Imaging Cold Gas to 1 kpc scales in high-redshift galaxies with the ngVLA

    Science.gov (United States)

    Casey, Caitlin; Narayanan, Desika; Dave, Romeel; Hung, Chao-Ling; Champagne, Jaclyn; Carilli, Chris Luke; Decarli, Roberto; Murphy, Eric J.; Popping, Gergo; Riechers, Dominik; Somerville, Rachel S.; Walter, Fabian

    2017-01-01

    The next generation Very Large Array (ngVLA) will revolutionize our understanding of the distant Universe via the detection of cold molecular gas in the first galaxies. Its impact on studies of galaxy characterization via detailed gas dynamics will provide crucial insight on dominant physical drivers for star-formation in high redshift galaxies, including the exchange of gas from scales of the circumgalactic medium down to resolved clouds on mass scales of ~10^5 M_sun. In this study, we employ a series of high-resolution, cosmological, hydrodynamic zoom simulations from the MUFASA simulation suite and a CASA simulator to generate mock ngVLA observations. Based on a direct comparison between the inferred results from our mock observations and the cosmological simulations, we investigate the capabilities of ngVLA to constrain the mode of star formation, dynamical mass, and molecular gas kinematics in individual high-redshift galaxies using cold gas tracers like CO(1-0) and CO(2-1). Using the Despotic radiative transfer code that encompasses simultaneous thermal and statistical equilibrium in calculating the molecular and atomic level populations, we generate parallel mock observations of high-J transitions of CO and C+ from ALMA for comparison. The factor of 100 times improvement in mapping speed for the ngVLA beyond the Jansky VLA and the proposed ALMA Band 1 will make these detailed, high-resolution imaging and kinematic studies routine at z=2 and beyond.

  18. The Multifrequency Campaign on 3C 279 in January 2006

    CERN Document Server

    Collmar, W; Krichbaum, T P; Agudo, I; Bottacini, E; Bremer, M; Burwitz, V; Cuccchiara, A; Grupe, D; Gurwell, M

    2010-01-01

    We present the results of a multifrequency campaign from radio to hard X-ray energies on the blazar 3C 279 during an optical high-state in January 2006. We give the observational results (multifrequency light curves and spectra) and compile an SED. This complements an SED from an optical low-state in June 2003. Surprisingly the two SEDs differ only in their high-energy synchrotron emission (near-IR - UV), while the low-energy inverse-Compton emission (X- to Gamma-rays) remained unchanged. By interpreting with a steady-state leptonic emission model, the variability among the SED can be reproduced by a change solely of the low-energy cutoff of the relativistic electron distribution. In an internal shock model for blazar emission, such a change could e.g. achieved through a varying relative Lorentz factor of colliding shells producing internal shocks in the jet.

  19. Multifrequency Photo-polarimetric WEBT Observation Campaign on the Blazar S5 0716+714: Source Microvariability and Search for Characteristic Timescales

    CERN Document Server

    Bhatta, G; Ostrowski, M; Markowitz, A; Akitaya, H; Arkharov, A A; Bachev, R; Benítez, E; Borman, G A; Carosati, D; Cason, A D; Chanishvili, R; Damljanovic, G; Dhalla, S; Frasca, A; Hiriart, D; Hu, S-M; Itoh, R; Jableka, D; Jorstad, S; Jovanovic, M D; Kawabata, K S; Klimanov, S A; Kurtanidze, O; Larionov, V M; Laurence, D; Leto, G; Marscher, A P; Moody, J W; Moritani, Y; Ohlert, J M; Di Paola, A; Raiteri, C M; Rizzi, N; Sadun, A C; Sasada, M; Sergeev, S; Strigachev, A; Takaki, K; Troitsky, I S; Ui, T; Villata, M; Vince, O; Webb, J R; Yoshida, M; Zola, S

    2016-01-01

    Here we report on the results of the WEBT photo-polarimetric campaign targeting the blazar S5~0716+71, organized in March 2014 to monitor the source simultaneously in BVRI and near IR filters. The campaign resulted in an unprecedented dataset spanning $\\sim 110$\\,h of nearly continuous, multi-band observations, including two sets of densely sampled polarimetric data mainly in R filter. During the campaign, the source displayed pronounced variability with peak-to-peak variations of about $30\\%$ and "bluer-when-brighter" spectral evolution, consisting of a day-timescale modulation with superimposed hourlong microflares characterized by $\\sim 0.1$\\,mag flux changes. We performed an in-depth search for quasi-periodicities in the source light curve; hints for the presence of oscillations on timescales of $\\sim 3$\\,h and $\\sim 5$\\,h do not represent highly significant departures from a pure red-noise power spectrum. We observed that, at a certain configuration of the optical polarization angle relative to the posit...

  20. Multi-frequency observations of SNR J0453-6829 in the LMC; A composite supernova remnant with a pulsar wind nebula

    CERN Document Server

    Haberl, F; Bozzetto, L M; Crawford, E J; Points, S D; Pietsch, W; De Horta, A Y; Tothill, N; Payne, J L; Sasaki, M

    2012-01-01

    The Large Magellanic Cloud (LMC) is rich in supernova remnants (SNRs) which can be investigated in detail with radio, optical and X-ray observations. SNR J0453-6829 is an X-ray and radio-bright remnant in the LMC, within which previous studies revealed the presence of a pulsar wind nebula (PWN), making it one of the most interesting SNRs in the Local Group of galaxies. We study the emission of SNR J0453-6829 to improve our understanding of its morphology, spectrum, and thus the emission mechanisms in the shell and the PWN of the remnant. We obtained new radio data with the Australia Telescope Compact Array and analysed archival XMM-Newton observations of SNR J0453-6829. We studied the morphology of SNR J0453-6829 from radio, optical and X-ray images and investigated the energy spectra in the different parts of the remnant. Our radio results confirm that this LMC SNR hosts a typical PWN. The prominent central core of the PWN exhibits a radio spectral index alpha_Core of -0.04+/-0.04, while in the rest of the S...

  1. Multifrequency Photo-polarimetric WEBT Observation Campaign on the Blazar S5 0716+714: Source Microvariability and Search for Characteristic Timescales

    Science.gov (United States)

    Bhatta, G.; Stawarz, Ł.; Ostrowski, M.; Markowitz, A.; Akitaya, H.; Arkharov, A. A.; Bachev, R.; Benítez, E.; Borman, G. A.; Carosati, D.; Cason, A. D.; Chanishvili, R.; Damljanovic, G.; Dhalla, S.; Frasca, A.; Hiriart, D.; Hu, S.-M.; Itoh, R.; Jableka, D.; Jorstad, S.; Jovanovic, M. D.; Kawabata, K. S.; Klimanov, S. A.; Kurtanidze, O.; Larionov, V. M.; Laurence, D.; Leto, G.; Marscher, A. P.; Moody, J. W.; Moritani, Y.; Ohlert, J. M.; Di Paola, A.; Raiteri, C. M.; Rizzi, N.; Sadun, A. C.; Sasada, M.; Sergeev, S.; Strigachev, A.; Takaki, K.; Troitsky, I. S.; Ui, T.; Villata, M.; Vince, O.; Webb, J. R.; Yoshida, M.; Zola, S.

    2016-11-01

    Here we report on the results of the Whole Earth Blazar Telescope photo-polarimetric campaign targeting the blazar S5 0716+71, organized in 2014 March to monitor the source simultaneously in BVRI and near-IR filters. The campaign resulted in an unprecedented data set spanning ∼110 hr of nearly continuous, multiband observations, including two sets of densely sampled polarimetric data mainly in the R filter. During the campaign, the source displayed pronounced variability with peak-to-peak variations of about 30% and “bluer-when-brighter” spectral evolution, consisting of a day-timescale modulation with superimposed hour-long microflares characterized by ∼0.1 mag flux changes. We performed an in-depth search for quasi-periodicities in the source light curve; hints for the presence of oscillations on timescales of ∼3 and ∼5 hr do not represent highly significant departures from a pure red-noise power spectrum. We observed that, at a certain configuration of the optical polarization angle (PA) relative to the PA of the innermost radio jet in the source, changes in the polarization degree (PD) led the total flux variability by about 2 hr; meanwhile, when the relative configuration of the polarization and jet angles altered, no such lag could be noted. The microflaring events, when analyzed as separate pulse emission components, were found to be characterized by a very high PD (>30%) and PAs that differed substantially from the PA of the underlying background component, or from the radio jet positional angle. We discuss the results in the general context of blazar emission and energy dissipation models. ).

  2. Essential roles of VLA-4 in the hematopoietic system.

    Science.gov (United States)

    Imai, Yoichi; Shimaoka, Motomu; Kurokawa, Mineo

    2010-05-01

    Integrins are one of the major families of adhesion molecules and make various kinds of biological effects by mediating cell-cell and cell-matrix interactions. Among integrins, VLA-4 is expressed on many types of hematopoietic cells including stem/progenitor cells and it is considered as a critical regulator of adult hematopoiesis. Recent studies revealed that VLA-4 is not necessarily required for the development or maintenance of adult hematopoietic cells. On the other hand, it was proved that VLA-4 is essential for homeostasis of distribution of hematopoietic stem/progenitor cells (HSPCs) and mature lymphocytes in the body. The dynamic regulation of VLA-4 function is mediated by its conformational change, which is strictly linked to the interaction between alpha and beta cytoplasmic domains. The study using knockin mice showed that GFFKR sequence, a well-preserved motif in the alpha cytoplasmic domain of VLA-4, is critical for binding of alpha and beta cytoplasmic domains as well as regulation of hematopoietic cell distribution. Small molecules targeting this cytoplasmic interaction or ligand-VLA-4 interaction may become good candidates of new drugs for mobilization of hematopoietic stem cells. Several studies have suggested the impact of VLA-4 on chemotherapy sensitivity and prognosis in hematological malignancies, which awaits further investigations.

  3. Design of multi-frequency CW radars

    CERN Document Server

    Jankiraman, Mohinder

    2007-01-01

    This book deals with the basic theory for design and analysis of Low Probability of Intercept (LPI) radar systems. The design of one such multi-frequency high resolution LPI radar, PANDORA, is covered.

  4. Modelling of multifrequency IRMPD for laser isotope separation

    Indian Academy of Sciences (India)

    Akshaya K Nayak; Sisir K Sarkar

    2002-12-01

    The process of infrared multiple photon dissociation (IRMPD) of molecules is of great fundamental importance and has practical significance, such as isotope separation etc. Unfortunately, a clear insight into the process has been hindered by the bewildering array of important variables affecting MPD. The dissociation probability () i.e. the yield has been found to be a sensitive function of laser fluence along with numerous other parameters like laser frequency, gas pressure etc. We have shown that in single frequency IRMPD, an accurate quantitative characterization of the dissociation probability can be adequately expressed by a `power law’ model with two fitting parameters namely critical fluence, and multiphoton order, . This model was exploited in analysing our MPD results on various systems. However, the small isotope shift encountered in heavy elements and the sticking phenomenon observed in small light molecules restrict respectively the separation factor and the dissociation yield. These problems can effectively be tackled by irradiation with multifrequency laser beams which can be chosen appropriately on the basis of spectroscopic features. Based on our success in single frequency model, multifrequency IRMPD is modelled by a functional form containing the product of power law terms for individual fluences on irradiation frequencies. This model is successfully benchmarked with our experimental results on multifrequency LIS of tritium. Such knowledge can be utilized for appropriate separation process design, evaluation and optimization.

  5. The multifrequency monitoring of microquasars. SS433

    CERN Document Server

    Trushkin, S A; Nizhelskij, N A

    2003-01-01

    The principal results of daily observations with the RATAN-600 radio telescope of X-ray binary with relativistic jets microquasar SS433 in 1986--2003 are presented. We have measured the flux densities at 0.96, 2.3, 3.9, 7.7, 11.2 and 21.7 GHz in different sets, duration from a week to some months. In general there are 940 observations of SS433 and more than 4500 flux density measurements in the period. Observations show that radio spectra are well fitting by a power law. The mean spectral index remained the same, $-0.60\\pm0.14$ during almost 20 years at least, and mean accuracy of the index determination was better than 0.1 in our multi-frequency observations, i.e. it was higher than in the intensive two-frequency monitoring of SS433 with the three-element GBI interferometer. Flux density data and spectra `on-line' plotting are accessible on the CATS data base site: http://cats.sao.ru/.

  6. VLA Measurements of Faraday Rotation through Coronal Mass Ejections

    CERN Document Server

    Kooi, Jason E; Buffo, Jacob J; Spangler, Steven R

    2016-01-01

    Coronal mass ejections (CMEs) are large-scale eruptions of plasma from the Sun that play an important role in space weather. Faraday rotation (FR) is the rotation of the plane of polarization that results when a linearly polarized signal passes through a magnetized plasma such as a CME. FR observations of a source near the Sun can provide information on the plasma structure of a CME shortly after launch. We report on simultaneous white-light and radio observations made of three CMEs in August 2012. We made sensitive Very Large Array (VLA) full-polarization observations using 1 - 2 GHz frequencies of a "constellation" of radio sources through the solar corona at heliocentric distances that ranged from 6 - 15 solar radii. Of the nine sources observed, three were occulted by CMEs: two sources (0842+1835 and 0900+1832) were occulted by a single CME and one source (0843+1547) was occulted by two CMEs. In addition to our radioastronomical observations, which represent one of the first active hunts for CME Faraday r...

  7. The VLA-COSMOS Survey: II. Source Catalog of the Large Project

    CERN Document Server

    Schinnerer, E; Carilli, C L; Bondi, M; Ciliegi, P; Jahnke, K; Scoville, N Z; Aussel, H; Bertoldi, F; Blain, A W; Impey, C D; Koekemoer, A M; Lefèvre, O; Urry, C M

    2006-01-01

    The VLA-COSMOS large project is described and its scientific objective is discussed. We present a catalog of ~ 3,600 radio sources found in the 2deg^2 COSMOS field at 1.4 GHz. The observations in the VLA A and C configuration resulted in a resolution of 1.5''x1.4'' and a mean rms noise of ~ 10.5(15) uJy/beam in the central 1(2)deg^2. 80 radio sources are clearly extended consisting of multiple components, and most of them appear to be double-lobed radio galaxies. The astrometry of the catalog has been thoroughly tested and the uncertainty in the relative and absolute astrometry are 130mas and <55mas, respectively.

  8. Extracellular matrix proteins, integrin receptors (VLA-beta 1, VLA-alpha 2 and VLA-alpha 5) and growth fraction in atypical macroregenerative nodules of the liver: an immunocytochemical case study.

    Science.gov (United States)

    Patriarca, C; Roncalli, M; Viale, G; Alfano, R M; Braidotti, P; Guddo, F; Coggi, G

    1994-08-01

    A case of cirrhotic liver harbouring three atypical macroregenerative nodules and an hepatocellular carcinoma was immunocytochemically investigated for the expression of VLA-beta 1, VLA-alpha 2 and VLA-alpha 5 integrins and for different extracellular matrix (ECM) components (collagen I, collagen IV, laminin, fibronectin and tenascin). In addition, the proliferative activity within the nodules was evaluated, using the MIB 1 monoclonal antibody (MAb). The cirrhotic liver disclosed a continuous staining pattern of the ECM proteins investigated, as well as a "sinusoidal" immunostaining of VLA-beta 1, VLA-alpha 2 and VLA-alpha 5. The macroregenerative nodules showed a discontinued immunoreactivity for ECM proteins while maintaining a VLA-beta 1 sinusoidal immunostaining, coupled with intercellular immunostaining. VLA-alpha 2 and VLA-alpha 5 expression was lacking. The growth fraction was low in both the above pathological conditions. The hepatocellular carcinoma was devoid of any ECM immunostaining. VLA-beta 1 immunoreactivity exhibited a honeycomb pattern of staining, whereas VLA alpha subunits were absent. MIB1 expression was high, being present in 30% of neoplastic nuclei. A possible relationship between atypical macroregenerative nodules and hepatocellular carcinoma is discussed.

  9. Evolution of the Water Maser Expanding Shell in W75N VLA 2

    CERN Document Server

    Kim, Jeong-Sook; Kurayama, Tomoharu; Honma, Mareki; Sasao, Tesuo; Surcis, Gabriele; Canto, Jorge; Torrelles, Jose M; Kim, Sang Joon

    2013-01-01

    We present Very Long Baseline Interferometry (VLBI) observations of 22 GHz H$_2$O masers in the high-mass star-forming region of \\objectname{W75N}, carried out with VLBI Exploration of Radio Astrometry (VERA) for three-epochs in 2007 with an angular resolution of $\\sim$ 1 mas. We detected H$_2$O maser emission toward the radio jet in VLA 1 and the expanding shell-like structure in VLA 2. .......... We have made elliptical fits to the VLA 2 H$_2$O maser shell-like structure observed in the different epochs (1999, 2005, and 2007), and found that the shell is still expanding eight years after its discovery. From the difference in the size of the semi-major axes of the fitted ellipses in the epochs 1999 ($\\simeq$ 71$\\pm$1 mas), 2005 ($\\simeq$ 97$\\pm$3 mas), and 2007 ($\\simeq$ 111$\\pm$1 mas), we estimate an average expanding velocity of $\\sim$ 5 mas yr$^{-1}$, similar to the proper motions measured in the individual H$_2$O maser features. A kinematic age of $\\sim$ 20 yr is derived for this structure. In addition, ...

  10. VLASSICK: The VLA Sky Survey in the Central Kiloparsec

    CERN Document Server

    Mills, E A C; Kruijssen, J M D; Sjouwerman, L; Lang, C C; Mao, S A; Walsh, A; Su, M; Longmore, S N; Zhao, J-H; Meier, D; Morris, M R

    2014-01-01

    At a distance of 8 kpc, the center of our Galaxy is the nearest galactic nucleus, and has been the subject of numerous key projects undertaken by great observatories such as Chandra, Spitzer, and Herschel. However, there are still no surveys of molecular gas properties in the Galactic center with less than 30" (1 pc) resolution. There is also no sensitive polarization survey of this region, despite numerous nonthermal magnetic features apparently unique to the central 300 parsecs. In this paper, we outline the potential the VLASS has to fill this gap. We assess multiple considerations in observing the Galactic center, and recommend a C-band survey with 10 micro-Jy continuum RMS and sensitive to molecular gas with densities greater than 10^4 cm^{-3}, covering 17 square degrees in both DnC and CnB configurations ( resolution ~5"), totaling 750 hours of observing time. Ultimately, we wish to note that the upgraded VLA is not just optimized for fast continuum surveys, but has a powerful correlator capable of simu...

  11. A Sensitive VLA Search for Small-Scale Glycine Emission Toward OMC-1

    Science.gov (United States)

    Hollis, J. M.; Pedelty, J. A.; Snyder, L. E.; Jewell, P. R.; Lovas, F. J.; Palmer, Patrick; Liu, S.-Y.

    2002-01-01

    We have conducted a deep Q-band (lambda-7 mm) search with the Very Large Array (VLA) toward OMC-1 for the lowest energy conformation (conformer I) of glycine (NH2CH2COOH) in four rotational transitions: the 6(sub 15)- 5(sub 14), 6(sub 24)-5(sub 23), 7(sub 17- 6(sub 16), and 7(sub 07)-6(sub 06). Our VLA observations sample the smallest-scale structures to date in the search for glycine toward OMC-1. No glycine emission features were detected. Thus if glycine exists in OMC-1, either it is below our detection limit, or it is more spatially extended than other large molecules in this source, or it is primarily in its high energy form (conformer II). Our VLA glycine fractional abundance limits in OMC-1 are comparable to those determined from previous IRAM 30m measurements -- somewhat better or worse depending on the specific source model -- and the entire approximately 1 foot primary beam of the VLA was searched while sensitive to an areal spatial scale approximately 150 times smaller than the 24 inch beam of the IRAM single-element telescope. In the course of this work, we detected and imaged the 4(sub 14)-3(sub 13) A and E transitions of methyl formate (HCOOCH3) and also the 2(sub 02) - 1(sub 01) transition of formic acid (HCOOH). Since formic acid is a possible precursor to glycine, our glycine limits and formic acid results provide a constraint on this potential formation chemistry route for glycine in OMC-1.

  12. The VLA-COSMOS Survey. IV. Deep Data and Joint Catalog

    CERN Document Server

    Schinnerer, Eva; Bondi, M; Smolcic, V; Datta, A; Carilli, C L; Bertoldi, F; Blain, A; Ciliegi, P; Koekemoer, A M; Scoville, N Z

    2010-01-01

    In the context of the VLA-COSMOS Deep project additional VLA A array observations at 1.4 GHz were obtained for the central degree of the COSMOS field and combined with the existing data from the VLA-COSMOS Large project. A newly constructed Deep mosaic with a resolution of 2.5" was used to search for sources down to 4 sigma with 1 sigma ~ 12 microJy/beam in the central 50'x50'. This new catalog is combined with the catalog from the Large project (obtained at 1.5"x1.4" resolution) to construct a new Joint catalog. All sources listed in the new Joint catalog have peak flux densities of >5 sigma at 1.5" and/or 2.5" resolution to account for the fact that a significant fraction of sources at these low flux levels are expected to be slighty resolved at 1.5" resolution. All properties listed in the Joint catalog such as peak flux density, integrated flux density and source size are determined in the 2.5" resolution Deep image. In addition, the Joint catalog contains 43 newly identified multi-component sources.

  13. Multi-Frequency Resonances in Pure Multiple-Pulse NQR

    Energy Technology Data Exchange (ETDEWEB)

    Furman, G. B., E-mail: gregoryf@bgu.ac.il [Ben-Gurion University (Israel); Kibrik, G. E.; Polyakov, A. Yu. [Perm State University (Russian Federation)

    2004-12-15

    We have observed multi-frequency resonances in a system with a spin 3/2 irradiated simultaneously by a multiple-pulse radiofrequency sequence and a low frequency field swept in the range 0 - 80 kHz. The theoretical description of the effect is presented using both the rotating frame approximation and the Floquet theory. Both approaches give indentical results at the calculation of the resonance frequencies, transition probabilities and shifts of resonance frequency. The calculated magnetization vs. the frequency of the low-frequency field agrees with the obtained experimental data.

  14. A Rotation Measure Gradient on the M87 VLA Jet

    Directory of Open Access Journals (Sweden)

    Algaba Juan Carlos

    2013-12-01

    Full Text Available Rotation measures (RMs have proven to be an excellent tool to study magnetic field structures in AGNs. Here we study RM properties on kiloparsec scales of theM87 jet via stacked multi wavelength polarized VLA observations. Our results show for the first time an indication of the RM gradient transverse to the jet in knot A, and possibly knot C and HST-1. Motivated by the shape of the RM in knots A and B, we discuss that part of it may be a filamentary structure of higher RM due to an external Faraday screen, although we consider this unlikely The data presented here can be easily explained by a helical magnetic field. By combining this result together with polarization direction plus the shape and degree of the fractional polarization across the jet, we can fairly conclude the presence of systematically wrapped, possibly helical, magnetic fields tightly wounded in knots A and C, in agreement with an MHD quad shock model.

  15. Multi-Frequency Band Pyroelectric Sensors

    Directory of Open Access Journals (Sweden)

    Chun-Ching Hsiao

    2014-11-01

    Full Text Available A methodology is proposed for designing a multi-frequency band pyroelectric sensor which can detect subjects with various frequencies or velocities. A structure with dual pyroelectric layers, consisting of a thinner sputtered ZnO layer and a thicker aerosol ZnO layer, proved helpful in the development of the proposed sensor. The thinner sputtered ZnO layer with a small thermal capacity and a rapid response accomplishes a high-frequency sensing task, while the thicker aerosol ZnO layer with a large thermal capacity and a tardy response is responsible for low-frequency sensing tasks. A multi-frequency band pyroelectric sensor is successfully designed, analyzed and fabricated in the present study. The range of the multi-frequency sensing can be estimated by means of the proposed design and analysis to match the thicknesses of the sputtered and the aerosol ZnO layers. The fabricated multi-frequency band pyroelectric sensor with a 1 μm thick sputtered ZnO layer and a 20 μm thick aerosol ZnO layer can sense a frequency band from 4000 to 40,000 Hz without tardy response and low voltage responsivity.

  16. THE VLA NASCENT DISK AND MULTIPLICITY (VANDAM) SURVEY OF PERSEUS PROTOSTARS. RESOLVING THE SUB-ARCSECOND BINARY SYSTEM IN NGC 1333 IRAS2A

    Energy Technology Data Exchange (ETDEWEB)

    Tobin, John J.; Looney, Leslie W. [National Radio Astronomy Observatory, Charlottesville, VA 22903 (United States); Dunham, Michael M. [Harvard-Smithsonian Center for Astrophysics, Cambridge, MA 02138 (United States); Li, Zhi-Yun [Department of Astronomy, University of Virginia, Charlottesville, VA 22903 (United States); Chandler, Claire J.; Perez, Laura M. [National Radio Astronomy Observatory, Socorro, NM 87801 (United States); Segura-Cox, Dominique; Harris, Robert J.; Hull, Charles L. H. [Department of Astronomy, University of Illinois, Urbana, IL 61801 (United States); Sadavoy, Sarah I. [Max-Planck-Institut für Astronomie, D-69117 Heidelberg (Germany); Melis, Carl [Center for Astrophysics and Space Sciences, University of California, San Diego, CA 92093 (United States); Kratter, Kaitlin [Steward Observatory, University of Arizona, Tucson, AZ 85721 (United States); Jørgensen, Jes K. [Niels Bohr Institute, University of Copenhagen, Juliane Maries Vej 30, DK-2100 Copenhagen Ø. (Denmark); Plunkett, Adele L., E-mail: jtobin@nrao.edu, E-mail: jeskj@nbi.dk [Department of Astronomy, Yale University, New Haven, CT 06520 (United States)

    2015-01-01

    We are conducting a Jansky Very Large Array (VLA) Ka-band (8 mm and 1 cm) and C-band (4 cm and 6.4 cm) survey of all known protostars in the Perseus Molecular Cloud, providing resolution down to ∼0.''06 and ∼0.''35 in the Ka band and C band, respectively. Here we present first results from this survey that enable us to examine the source NGC 1333 IRAS2A in unprecedented detail and resolve it into a protobinary system separated by 0.''621 ± 0.''006 (∼143 AU) at 8 mm, 1 cm, and 4 cm. These two sources (IRAS2A VLA1 and VLA2) are likely driving the two orthogonal outflows known to originate from IRAS2A. The brighter source IRAS2A VLA1 is extended perpendicular to its outflow in the VLA data, with a deconvolved size of 0.''055 (∼13 AU), possibly tracing a protostellar disk. The recently reported candidate companions (IRAS2A MM2 and MM3) are not detected in either our VLA data, Combined Array for Research in Millimeter-wave Astronomy (CARMA) 1.3 mm data, or Submillimeter Array (SMA) 850 μm data. SMA CO (J = 3 → 2), CARMA CO (J = 2 → 1), and lower-resolution CARMA CO (J = 1 → 0) observations are used to examine the outflow origins and the nature of the candidate companions to IRAS2A VLA1. The CO (J = 3 → 2) and (J = 2 → 1) data show that IRAS2A MM2 is coincident with a bright CO emission spot in the east-west outflow, and IRAS2A MM3 is within the north-south outflow. In contrast, IRAS2A VLA2 lies at the east-west outflow symmetry point. We propose that IRAS2A VLA2 is the driving source of the east-west outflow and a true companion to IRAS2A VLA1, whereas IRAS2A MM2 and MM3 may not be protostellar.

  17. Measuring H_0 with CLASS B1608+656: The Second Season of VLA Monitoring

    OpenAIRE

    Fassnacht, C. D.; Xanthopoulos, E.; Koopmans, L. V. E.; Pearson, T. J.; A. C. S. Readhead(Cahill Center for Astronomy and Astrophysics, California Institute of Technology, 1200 E California Blvd, Pasadena, CA 91125); Myers, S. T.

    1999-01-01

    The four-component gravitational lens CLASS B1608+656 has been monitored with the VLA for two seasons in order to search for time delays between the components. These time delays can be combined with mass models of the lens system to yield a measurement of H_0. The component light curves show significantly different behavior in the two observing seasons. In the first season the light curves have maximum variations of ~5%, while in the second season the components experienced a nearly monotoni...

  18. Multifrequency Electron Paramagnetic Resonance Theory and Applications

    CERN Document Server

    Misra, Sushil K

    2011-01-01

    Filling the gap for a systematic, authoritative, and up-to-date review of this cutting-edge technique, this book covers both low and high frequency EPR, emphasizing the importance of adopting the multifrequency approach to study paramagnetic systems in full detail by using the EPR method. In so doing, it discusses not only the underlying theory and applications, but also all recent advances -- with a final section devoted to future perspectives.

  19. Deviations from mirroring in interpersonal multifrequency coordination when visual information is occluded.

    Science.gov (United States)

    Gorman, Jamie C; Amazeen, Polemnia G; Crites, Michael J; Gipson, Christina L

    2017-02-10

    In activities such as dancing and sports, people synchronize behaviors in many different ways. Synchronization between people has traditionally been characterized as either perfect mirroring (1:1 in-phase synchronization, spontaneous synchrony, and mimicry) or reflectional mirroring (1:1 antiphase synchronization), but most activities require partners to synchronize more complicated patterns. We asked visually coupled dyads to coordinate finger movements to perform multifrequency ratios (1:1, 2:1, 3:1, 4:1, and 5:1). Because these patterns are coordinated across and not just within individual physiological and motor systems, we based our predictions on frequency-locking dynamics, which is a general coordination principle that is not limited to physiological explanations. Twenty dyads performed five multifrequency ratios under three levels of visual coupling, with half using a subcritical visual information update rate. The dynamical principle was supported, such that multifrequency performance tends to abide by the strictures of frequency locking. However, these constraints are relaxed if the visual information rate is beyond the critical information update rate. An analysis of turning points in the oscillatory finger movements suggested that dyads did not rely on this visual information to stabilize coordination. How the laboratory findings align with naturalistic observations of multifrequency performance in actual sports teams (Double Dutch) is discussed. Frequency-locking accounts not only for the human propensity for perfect mirroring but also for variations in performance when dyads deviate from mirroring.

  20. Multi-frequency axial transmission bone ultrasonometer.

    Science.gov (United States)

    Tatarinov, Alexey; Egorov, Vladimir; Sarvazyan, Noune; Sarvazyan, Armen

    2014-07-01

    The last decade has seen a surge in the development of axial transmission QUS (Quantitative UltraSound) technologies for the assessment of long bones using various modes of acoustic waves. The condition of cortical bones and the development of osteoporosis are determined by numerous mechanical, micro-structural, and geometrical or macro-structural bone properties like hardness, porosity and cortical thickness. Such complex manifestations of osteoporosis require the evaluation of multiple parameters with different sensitivities to the various properties of bone that are affected by the disease. This objective may be achieved by using a multi-frequency ultrasonic examination The ratio of the acoustic wavelength to the cortical thickness can be changed by varying the frequency of the ultrasonic pulse propagating through the long bone that results in the change in composition of the induced wave comprised of a set of numerous modes of guided, longitudinal, and surface acoustic waves. The multi-frequency axial transmission QUS method developed at Artann Laboratories (Trenton, NJ) is implemented in the Bone Ultrasonic Scanner (BUSS). In the current version of the BUSS, a train of ultrasonic pulses with 60, 100, 400, 800, and 1200 kHz frequencies is used. The developed technology was tested on a variety of bone phantoms simulating normal, osteopenic, and osteoporotic bones. The results of this study confirm the feasibility of the multi-frequency approach for the assessment of the processes leading to osteoporosis.

  1. Multi-frequency Study of Intraday Variable Sources

    CERN Document Server

    Cim`o, G; Krichbaum, T P; Beckert, T; Kraus, A L; Witzel, A; Zensus, J A; Cim\\`o, Giuseppe

    2002-01-01

    Intraday variability (IDV) of compact extragalactic radio sources is a complex phenomenon and shows a wavelength dependent mixture of refractive interstellar scintillation (RISS) (dominant at long cm-wavelengths) and source-intrinsic effects (dominant at shorter wavelengths). Detailed investigations of individual sources and new high frequency observations suggest a source-intrinsic contribution to the IDV pattern at least in some sources. However, the sizes of intraday variable sources at cm-wavelength are typically smaller than the scattering size set by the ISM in our galaxy and scintillation must be present, too. We present new IDV observations in different regimes (from cm to sub-mm wavelengths) and show how such multi-frequency study can be used as powerful instrument to describe different aspects of IDV.

  2. A VLA Search for Radio Signals from M31 and M33

    Science.gov (United States)

    Gray, Robert H.; Mooley, Kunal

    2017-03-01

    Observing nearby galaxies would facilitate the search for artificial radio signals by sampling several billions of stars simultaneously, but few efforts have been made to exploit this opportunity. An added attraction is that the Milky Way is the second largest member of the Local Group, so our galaxy might be a probable target for hypothetical broadcasters in nearby galaxies. We present the first relatively high spectral resolution (radio signals of complete galaxies in the Local Group with the Jansky VLA, observing the galaxies M31 (Andromeda) and M33 (Triangulum)—the first and third largest members of the group, respectively—sampling more stars than any prior search of this kind. We used 122 Hz channels over a 1 MHz spectral window in the target galaxy velocity frame of reference, and 15 Hz channels over a 125 kHz window in our local standard of rest. No narrowband signals were detected above a signal-to-noise ratio of 7, suggesting the absence of continuous narrowband flux greater than approximately 0.24 and 1.33 Jy in the respective spectral windows illuminating our part of the Milky Way during our observations in 2014 December and 2015 January. This is also the first study in which the upgraded VLA has been used for SETI.

  3. Multi-frequency recirculating planar magnetrons

    Science.gov (United States)

    Greening, Geoffrey B.; Jordan, Nicholas M.; Exelby, Steven C.; Simon, David H.; Lau, Y. Y.; Gilgenbach, Ronald M.

    2016-08-01

    The multi-frequency recirculating planar magnetron (MFRPM) is the first magnetron capable of simultaneous generation of significantly different output frequencies (1 and 2 GHz) in a single operating pulse. Design and simulation of a prototype MFRPM were followed by hardware fabrication and experimental verification using the Michigan Electron Long Beam Accelerator with a Ceramic insulator at -300 kV, 1-5 kA, and 0.14-0.23 T axial magnetic field. Preliminary results demonstrated simultaneous generation of microwave pulses near 1 GHz and 2 GHz at powers up to 44 MW and 21 MW, respectively, with peak total efficiencies up to 9%.

  4. VLA HI Imaging of the LARS+eLARS Galaxies: Tidally Interacting Systems

    Science.gov (United States)

    Reilly, Bridget; Eisner, Brian Andrew; Cannon, John M.; Hayes, Matthew; Melinder, Jens; Östlin, Göran; Pardy, Stephen; LARS Team

    2017-01-01

    The Lyman Alpha Reference Sample (LARS) and its extension (eLARS) form the most comprehensive effort to date to study the details of Lyman Alpha radiative transfer in galaxies. Direct imaging of Lyman Alpha emission from the Hubble Space Telescope is supplemented by a wealth of multi-wavelength observations designed to probe the complex processes that contribute to the escape or destruction of Lyman Alpha photons as they resonantly scatter in the neutral ISM. The 42 LARS+eLARS galaxies span a range of physical properties, including mass and star formation rate. A companion poster presents VLA HI imaging of 32 LARS+eLARS galaxies. In this work, we present new VLA D-configuration HI imaging of selected LARS+eLARS galaxies that are well-resolved or tidally interacting. HI column density and velocity field images are compared to SDSS imaging. We interpret the results in the context of tidal interactions shifting the HI gas out of resonance and increasing the likelihood of Lyman Alpha photons escaping the galaxy.

  5. VLA-MAC: A Variable Load Adaptive MAC Protocol for Wireless Sensor Networks

    Science.gov (United States)

    Yao, Guoliang; Liu, Hao; Chen, Hao; Shi, Longxin

    This letter presents VLA-MAC, a novel adaptive MAC protocol for wireless sensor networks that can achieve high energy efficiency and low latency in variable load conditions. In VLA-MAC, traffic load is measured online and utilized for adaptive adjustment. VLA-MAC transmits packets via a burst style to alleviate packets accumulation problem and achieve low latency in high load condition. Furthermore, it also saves obvious energy by removing unnecessary listen period in low load condition. Unlike current approach, VLA-MAC does not need to adjust duty-cycle according to load online. Simulation results based on ns-2 show the performance improvements of our protocol.

  6. Analysis of multifrequency langevin composite ultrasonic transducers.

    Science.gov (United States)

    Lin, Shuyu

    2009-09-01

    The multimode coupled vibration of Langevin composite ultrasonic transducers with conical metal mass of large cross-section is analyzed. The coupled resonance and anti-resonance frequency equations are derived and the effective electromechanical coupling coefficient is analyzed. The effect of the geometrical dimensions on the resonance frequency, the anti-resonance frequency, and the effective electromechanical coupling coefficient is studied. It is illustrated that when the radial dimension is large compared with the longitudinal dimension, the vibration of the Langevin transducer becomes a multifrequency multimode coupled vibration. Numerical methods are used to simulate the coupled vibration; the simulated results are in good agreement with those from the analytical results. Some Langevin transducers of large cross-section are designed and manufactured and their resonance frequencies are measured. It can be seen that the resonance frequencies obtained from the coupled resonance frequency equations are in good agreement with the measured results. It is expected that by properly choosing the dimensions, multifrequency Langevin transducers can be designed and used in ultrasonic cleaning, ultrasonic sonochemistry, and other applications.

  7. Preliminary Antenna Concept for the ngVLA

    Science.gov (United States)

    Di Francesco, James; Selina, Robert; Grammer, Wes; McKinnon, Mark M.

    2017-01-01

    The preliminary concept for a Next Generation Very Large Array (ngVLA) calls for an interferometric array having an effective collecting area and spatial resolution that are both 10 times better than that of the current VLA and operating over a frequency range of 1.2-116 GHz. Given the large number of antennas needed to meet the collecting area goal, the ngVLA antenna concept must strike a balance between competing science requirements and the programmatic targets for the array’s life cycle cost.Antenna diameters currently under consideration for the ngVLA are in the range of 12-25 m, with a nominal 18-m diameter aperture used for the conceptual design. Currently, the optimization for operations and construction cost suggests that a smaller number of larger apertures is preferable.The surface accuracy goal for the antennas is 185 µm rms (λ/16 @ 100 GHz) for the primary and subreflector combined under optimal environmental conditions. The subreflector will be optimized for performance above 10 GHz, with some degradation in aperture efficiency accepted at lower frequencies.For high dynamic range imaging, particularly at the low end of the ngVLA’s frequency range, the optimum optical configuration is likely an offset geometry. An unblocked aperture will minimize scattering, spillover, and sidelobe pickup. Both performance and maintenance requirements favor a receiver feedarm on the low side of the reflector.High pointing accuracy will also be necessary to provide the imaging dynamic range required of the system. With an unblocked aperture, variations in the antenna gain pattern are expected to be dominated by pointing errors. Preliminary requirements are for an absolute pointing accuracy of 40” RMS, with referenced pointing of 3” RMS (FWHM/10 at 10 GHz and 120 GHz, respectively, for an 18-m diameter dish).The antenna mount is expected to be a typical altitude-azimuth design. Both pedestal bearing and rail-based azimuth drives are under consideration. If fast

  8. Multifrequency Printed Antennas Loaded with Metamaterial Particles

    Directory of Open Access Journals (Sweden)

    D. Segovia-Vargas

    2009-06-01

    Full Text Available This paper provides a review of printed antennas loaded with metamaterial particles. This novel technique allows developing printed antennas with interesting features such as multifrequency (simultaneous operation over two or more frequency bands and multifunctionality (e. g. radiation pattern diversity. Moreover, compactness is also achieved and the main advantages of conventional printed antennas (light weight, low profile, low cost ... are maintained. Different types of metamaterial-loaded printed antennas are reviewed: printed dipoles and patch antennas. Several prototypes are designed, manufactured and measured showing good results. Furthermore, simple but accurate equivalent models are proposed. These models allow an easy and quick design of metamaterial-loaded printed antennas. Finally, two interesting applications based on the proposed antennas are reviewed: the patch antennas are used as radiating elements of emerging active RFID systems in the microwave band and the metamaterial-loaded printed dipoles are employed to increase the performance of log-periodic arrays.

  9. VLA HI Imaging of the LARS+eLARS Galaxies: Global HI Properties

    Science.gov (United States)

    Eisner, Brian Andrew; Reilly, Bridget; Cannon, John M.; Hayes, Matthew; Melinder, Jens; Östlin, Göran; Pardy, Stephen; LARS Team

    2017-01-01

    The Lyman Alpha Reference Sample (LARS) and its extension (eLARS) form the most comprehensive effort to date to study the details of Lyman Alpha radiative transfer in galaxies. Direct imaging of Lyman Alpha emission from the Hubble Space Telescope is supplemented by a wealth of multi-wavelength observations designed to probe the complex processes that contribute to the escape or destruction of Lyman Alpha photons as they resonantly scatter in the neutral ISM. The 42 LARS+eLARS galaxies span a range of physical properties, including mass and star formation rate. In this work, we present new VLA D-configuration HI imaging of 32 LARS+eLARS galaxies designed to localize the HI gas and to measure the total HI mass. HI column density images and velocity fields are compared to SDSS imaging. Most galaxies are unresolved at this angular resolution; a companion poster presents imaging of interacting galaxies that are well-resolved.

  10. First Science Verification of the VLA Sky Survey Pilot

    Science.gov (United States)

    Cavanaugh, Amy

    2017-01-01

    My research involved analyzing test images by Steve Myers for the upcoming VLA Sky Survey. This survey will cover the entire sky visible from the VLA site in S band (2-4 GHz). The VLA will be in B configuration for the survey, as it was when the test images were produced, meaning a resolution of approximately 2.5 arcseconds. Conducted using On-the-Fly mode, the survey will have a speed of approximately 20 deg2 hr-1 (including overhead). New Python imaging scripts are being developed and improved to process the VLASS images. My research consisted of comparing a continuum test image over S band (from the new imaging scripts) to two previous images of the same region of the sky (from the CNSS and FIRST surveys), as well as comparing the continuum image to single spectral windows (from the new imaging scripts and of the same sky region). By comparing our continuum test image to images from CNSS and FIRST, we tested on-the-Fly mode and the imaging script used to produce our images. Another goal was to test whether individual spectral windows could be used in combination to calculate spectral indices close to those produced over S band (based only on our continuum image). Our continuum image contained 64 sources as opposed to the 99 sources found in the CNSS image. The CNSS image also had lower noise level (0.095 mJy/beam compared to 0.119 mJy/beam). Additionally, when our continuum image was compared to the CNSS image, separation showed no dependence on total flux density (in our continuum image). At lower flux densities, sources in our image were brighter than the same ones in the CNSS image. When our continuum image was compared to the FIRST catalog, the spectral index difference showed no dependence on total flux (in our continuum image). In conclusion, the quality of our images did not completely match the quality of the CNSS and FIRST images. More work is needed in developing the new imaging scripts.

  11. Foreground removal of 21 cm fluctuation with multifrequency fitting

    Institute of Scientific and Technical Information of China (English)

    Li-Ping He

    2009-01-01

    The 21 centimeter (21 cm) line emission from neutral hydrogen in the inter-galactic medium (IGM) at high redshifts is strongly contaminated by foreground sources such as the diffuse Galactic synchrotron emission and free-free emission from the Galaxy, as well as emission from extragalactic radio sources, thus making its observation very complicated. However, the 21 cm signal can be recovered through its structure in fre-quency space, as the power spectrum of the foreground contamination is expected to be smooth over a wide band in frequency space while the 21 cm fluctuations vary signifi-cantly. We use a simple polynomial fitting to reconstruct the 21 cm signal around four frequencies 50, 100, 150 and 200 MHz with an especially small channel width of 20 kHz. Our calculations show that this multifrequency fitting approach can effectively recover the 21 cm signal in the frequency range 100 ~ 200 MHz. However, this method doesn't work well around 50 MHz because of the low intensity of the 21 cm signal at this frequency. We also show that the fluctuation of detector noise can be suppressed to a very low level by taking long integration times, which means that we can reach a sensitivity of ≈ 10 mK at 150 MHz with 40 antennas in 120 hours of observations.

  12. Research on nonlinear characteristics of strata collapse because of the multi-frequency mining

    Institute of Scientific and Technical Information of China (English)

    YANG Fan; HU Zhen-qi; YANG Lun; MA Feng-hai

    2008-01-01

    Based on the complexity of mine stratum and coupling of the multi-frequency for the damage of mine stratum, using the method of on-site inspection and mathematical statistics, the regulation and nonlinear characteristics of strata collapse in mine stratum's multi-frequency mining were put forward and systemically studied. Study result shows that the influence of multi-frequency mining in mine stratum has the feature of multi-frequency incontinuity, multi-characteristic and multi-type nonlinear collapse, strata collapse activation turned worse, presenting an accumulation effect of multi-frequency mining for the strata damage. With the example of multi-frequency mining in the mine, the real characteristics of strata collapse by multi-frequency mining and nonlinear characteristics of accumulative response damage were analyzed. Research achievements about the surface recover and controlling of strata collapse by the multi-frequency mining have instruction meaning.

  13. Multifrequency Study of Giant Radio Pulses from the Crab Pulsar with K5 VLBI Recording Terminal

    CERN Document Server

    Popov, M V; Kondratiev, V I; Bilous, A V; Moshkina, O; Oreshko, V V; Ilyasov, Yu P; Sekido, M; Kondo, T

    2009-01-01

    Simultaneous multifrequency observations of the Crab pulsar giant pulses (GPs) were performed with the 64-m Kalyazin radio telescope at four frequencies 0.6, 1.4, 2.2 and 8.3 GHz using the K5 VLBI recording terminal. K5 terminal provided continuous recording in 16 4-MHz wide frequency channels distributed over 4 frequency bands. Several thousands of GPs were detected during about 6 hours of observations in two successive days in July 2005. Radio spectra of single GPs were analysed at separate frequencies and over whole frequency range. These spectra manifest notable modulation both on large ($\\Delta\

  14. The multi-frequency multi-temporal sky

    CERN Document Server

    Giommi, Paolo

    2013-01-01

    Contemporary astronomy benefits of very large and rapidly growing amounts of data in all bands of the electromagnetic spectrum, from long-wavelength radio waves to high energy gamma-rays. Astronomers normally specialize in data taken in one particular energy window, however the advent of data centers world-wide and of the Virtual Observatory, which provide simple and open access to quality data in all energy bands taken at different epochs, is making multi-frequency and multi-epoch astronomy much more affordable than in the past. New tools designed to combine and analyze these data sets are being developed with the aim of visualizing observational results and extracting information about the physical processes powering cosmic sources in ways that were not possible before. In this contribution blazars, a type of cosmic sources that emit highly variable radiation at all frequencies, are used as an example to describe the possibilities of this type of astronomy today, and the discovery potential for the near fut...

  15. Multifrequency Bayesian compressive sensing methods for microwave imaging.

    Science.gov (United States)

    Poli, Lorenzo; Oliveri, Giacomo; Ding, Ping Ping; Moriyama, Toshifumi; Massa, Andrea

    2014-11-01

    The Bayesian retrieval of sparse scatterers under multifrequency transverse magnetic illuminations is addressed. Two innovative imaging strategies are formulated to process the spectral content of microwave scattering data according to either a frequency-hopping multistep scheme or a multifrequency one-shot scheme. To solve the associated inverse problems, customized implementations of single-task and multitask Bayesian compressive sensing are introduced. A set of representative numerical results is discussed to assess the effectiveness and the robustness against the noise of the proposed techniques also in comparison with some state-of-the-art deterministic strategies.

  16. Fourier method for recovering acoustic sources from multi-frequency far-field data

    Science.gov (United States)

    Wang, Xianchao; Guo, Yukun; Zhang, Deyue; Liu, Hongyu

    2017-03-01

    We consider an inverse source problem of determining a source term in the Helmholtz equation from multi-frequency far-field measurements. Based on the Fourier series expansion, we develop a novel non-iterative reconstruction method for solving the problem. A promising feature of this method is that it utilizes the data from only a few observation directions for each frequency. Theoretical uniqueness and stability analysis are provided. Numerical experiments are conducted to illustrate the effectiveness and efficiency of the proposed method in both two and three dimensions.

  17. Development of a multi-frequency ESR system with high sensitivity

    Energy Technology Data Exchange (ETDEWEB)

    Yashiro, H [KYOKUGEN, Osaka University, 1-3 Machikaneyama, Toyonaka, Osaka 560-8531 (Japan); Kashiwagi, T [KYOKUGEN, Osaka University, 1-3 Machikaneyama, Toyonaka, Osaka 560-8531 (Japan); Horitani, M [Division of Bioengineering, Graduate School of Engineering Science, Osaka University, Toyonaka, Osaka 560-8531 (Japan); Hobo, F [International Graduate School of Arts and Sciences, Yokohama City University, Suehiro 1-7-29, Tsurumi, Yokohama, Kanagawa, 230-0045 (Japan); Hori, H [Division of Bioengineering, Graduate School of Engineering Science, Osaka University, Toyonaka, Osaka 560-8531 (Japan); Hagiwara, M [KYOKUGEN, Osaka University, 1-3 Machikaneyama, Toyonaka, Osaka 560-8531 (Japan)

    2006-11-15

    We have developed a new Multi-Frequency (MF) ESR system for the frequencies between 35 to 130 GHz utilizing TE{sub 011} single mode resonators. Their sensitivities (10{sup 10}spins/G at 1.5 K) are comparable to that of a conventional low frequency ESR resonator and an order of magnitude higher than that of a Fabry Perot resonator which was previously developed by us. Thanks to a newly developed precise and stable matching system, we observed for the first time MFESR spectra of a metalloprotein with an integer spin.

  18. Development of a multi-frequency ESR system with high sensitivity

    Science.gov (United States)

    Yashiro, H.; Kashiwagi, T.; Horitani, M.; Hobo, F.; Hori, H.; Hagiwara, M.

    2006-11-01

    We have developed a new Multi-Frequency (MF) ESR system for the frequencies between 35 to 130 GHz utilizing TE011 single mode resonators. Their sensitivities (1010spins/G at 1.5 K) are comparable to that of a conventional low frequency ESR resonator and an order of magnitude higher than that of a Fabry Perot resonator which was previously developed by us. Thanks to a newly developed precise and stable matching system, we observed for the first time MFESR spectra of a metalloprotein with an integer spin.

  19. Multi-Frequency Blazar Micro-Variability as a Tool to Investigate Relativistic Jets

    Directory of Open Access Journals (Sweden)

    James R. Webb

    2016-08-01

    Full Text Available For the past 12 years we have been studying optical micro-variability of a sample of 15 Blazars. We summarize the results of this study and draw some basic conclusions about the characteristics of micro-variability. The intermittency, the stochastic nature, and the similar profile shapes seen in micro-variations at different times and in different objects have led us to a possible model to explain the observed micro-variations. The model is based on a strong shock propagating down a relativistic jet and encountering turbulence which causes density or magnetic field enhancements. We use the theory of Kirk, Reiger, and Mastichiadis (1998 to describe the pulse of synchrotron emission emanating from individual density enhancements energized by the shock. By fitting these “pulses” to micro-variability observations, we obtain excellent fits to actual micro-variations. The model predicts that the spectral index changes as a function of pulse duration. This effect should be observable in multi-frequency micro-variability data. We present the theoretical model, model fits of our micro-variability light curves, and preliminary multi-frequency micro-variability observations that support this model. A further test that has yet to be carried out involves observing polarization changes in different pulses.

  20. VLA+WSRT HI Imaging of Two "Almost Dark" Galaxies

    Science.gov (United States)

    Ball, Catie; Singer, Quinton; Cannon, John M.; Leisman, Luke; Haynes, Martha P.; Adams, Elizabeth A.; Bernal Neira, David; Giovanelli, Riccardo; Hallenbeck, Gregory L.; Janesh, William; Janowiecki, Steven; Jozsa, Gyula; Rhode, Katherine L.; Salzer, John Joseph

    2017-01-01

    We present sensitive HI imaging of the "Almost Dark" galaxies AGC229385 and AGC229101. Selected from the ALFALFA survey, "Almost Dark" galaxies have significant HI reservoirs but lack an obvious stellar counterpart in survey-depth ground-based optical imaging. Deeper ground- and space-based imaging reveals very low surface brightness optical counterparts in both systems. The resulting M_HI/L_B ratios are among the highest ever measured for individual galaxies. Here we combine VLA and WSRT imaging of these two systems, allowing us to preserve surface brightness sensitivity while working at high angular resolution. The resulting maps of HI mass surface density, velocity field, and velocity dispersion are compared to deep optical and ultraviolet imaging. In both systems the highest column density HI gas is clumpy and resolved into multiple components. In the case of AGC229385, the kinematics are inconsistent with a simple rotating disk and may be the result of either an infall episode or an interaction between two HI-rich disks.Support for this work was provided by NSF grant 1211683 to JMC at Macalester College.

  1. Multifrequency Behaviour of the Gamma-Ray Binary System PSR B1259-63: Modelling the FERMI Flare

    Directory of Open Access Journals (Sweden)

    Brian van Soelen

    2014-12-01

    Full Text Available This paper presents a brief overview of the multifrequency properties of the gamma-ray binary system PSR B1259-63 from radio to very high energy gamma-rays. A summary is also presented of the various models put forward to explain the Fermi "flare" detected in 2011. Initial results are presented of a new turbulence driven model to explain the GeV observations.

  2. Tracing the Baryon Cycle within Nearby Galaxies with a next-generation VLA

    Science.gov (United States)

    Kepley, Amanda A.; Leroy, Adam; Murphy, Eric J.; ngVLA Baryon Cycle Science Working Group

    2017-01-01

    The evolution of galaxies over cosmic time is shaped by the cycling of baryons through these systems, namely the inflow of atomic gas, the formation of molecular structures, the birth of stars, and the expulsion of gas due to associated feedback processes. The best way to study this cycle in detail are observations of nearby galaxies. These systems provide a complete picture of baryon cycling over a wide range of astrophysical conditions. In the next decade, higher resolution/sensitivity observations of such galaxies will fundamentally improve our knowledge of galaxy formation and evolution, allowing us to better interpret higher redshift observations of sources that were rapidly evolving at epochs soon after the Big Bang. In particular, the centimeter-to-millimeter part of the spectrum provides critical diagnostics for each of the key baryon cycling processes and access to almost all phases of gas in galaxies: cool and cold gas (via emission and absorption lines), ionized gas (via free-free continuum and recombination lines), cosmic rays and hot gas (via synchrotron emission and the Sunyaev-Zeldovich effect). This poster highlights a number of key science problems in this area whose solutions require a next-generation radio-mm interferometer such as the next-generation VLA.

  3. XI Multifrequency Behaviour of High Energy Cosmic Sources Workshop

    Science.gov (United States)

    This was the eleventh edition of the series of Frascati Workshops on "Multifrequency Behaviour of High Energy Cosmic Sources" undoubtedly a largely accepted biennial meeting in which an updated experimental and theoretical panorama is depicted. This edition took place on the 31st anniversary of the first historical "multifrequency" workshop about "Multifrequency Behaviour of Galactic Accreting Sources", held in Vulcano in September 1984. This surely renders the Frascati Workshop Series the oldest among the many devoted to "Multifrequency Studies of Cosmic Sources". The study of the physics governing the cosmic sources was the main goal of the workshop. A session devoted to the ongoing and next generation ground- and space-based experiments gave the actual prospects for the first decades of this millennium. The following items have been reviewed: Cosmology: Cosmic Background, Clusters of Galaxies Extragalactic Sources: Active Galaxies, Normal Galaxies Gamma-Rays Burst: Experiments versus Theories Galactic Sources: Pre-Main-Sequence and Main-Sequence Stars, Cataclysmic Variables and Novae, Supernovae and SNRs, X-Ray Binary Systems, Pulsars, Black Holes, Gamma-Ray Sources,Nucleosynthesis. The Astrophysics with the Ongoing and Future Experiments: Space-Based Experiments, Ground-Based Experiments. The workshop included a few 30-minute general review talks to introduce the current problems, and typically 20-minute talks discussing new experimental and theoretical results. A series of 20-minute talks discussed the ongoing and planned ground- and space-based experiments. The cadence of the workshop is biennial. The participation is only by invitation.

  4. The VLA Sky Survey (VLASS): Technical Implementation and Pilot Survey Results

    Science.gov (United States)

    Myers, Steven T.; Baum, Stefi; Chandler, Claire J.; Chatterjee, Shami; Kimball, Amy E.; Lacy, Mark; Law, Casey J.; Schinzel, Frank; Arancibia, Demian; Hiriart, R.; Medlin, Drew; VLA Sky Survey Team; Survey Science Group

    2017-01-01

    The VLA Sky Survey (VLASS) is a 5520 hour project to survey the 33885 square degrees of the sky above Declination -40 degrees from 2-4 GHz at 2.5" angular resolution using the upgraded Karl G. Jansky Very Large Array (VLA). Over the survey duration of 7 years, each area of the sky will be covered in 3 epochs spaced 32 months apart, to a depth of 0.12mJy/beam rms noise per epoch and 0.07mJy/beam for 3 epochs combined. Pilot observations were taken in mid-2016, with the full survey to start in September 2017. The raw data will be available in the NRAO archive immediately with no proprietary period and science data products will be provided to the community in a timely manner. Basic Data Products (BDP) that will be produced by the survey team include: raw and calibrated visibility data, quick-look continuum images, single-epoch images and spectral image cubes, single-epoch basic object catalogs, and cumulative "static sky" images and image cubes and basic object catalogs to the full survey depth. Single-epoch and cumulative images are in intensity and linear polarization (Stokes IQU). In addition to the BDP provided by NRAO and served through the NRAO archive, there are opportunities for Enhanced Data Products and Services that are provided by the community in partnership with the VLASS team.In this presentation we describe the survey design and the Technical Implementation Plan (TIP) for the VLASS, and report on results from the VLASS Pilot observations. The pilot survey covered 2480 unique square degrees, with 2160 square degrees within the SDSS/FIRST footprint. The pilot also covered key deep fields including COSMOS, GOODS-N, CDFS, Elais-N1, and the SDSS Stripe-82. Preliminary imaging and comparisons have been carried out for selected pilot fields as part of early science verification. We also discuss the technical issues and challenges remaining to be addressed before commencing the survey and our plans moving forward. There are also opportunities for community

  5. A VLA (Very Large Array) Search for 5 GHz Radio Transients and Variables at Low Galactic Latitudes

    Science.gov (United States)

    Ofek, E. O.; Frail, D. A.; Breslauer, B.; Kulkarni, S. R.; Chandra, P.; Gal-Yam, A.; Kasliwal, M. M.; Gehrels, N.

    2012-01-01

    We present the results of a 5GHz survey with the Very Large Array (VLA) and the expanded VLA, designed to search for short-lived (approx 1.8mJy) = 0.039(exp +0.13,+0.18) (sub .0.032,.0.038) / sq. deg (1, 2 sigma confidence errors). This areal density is consistent with the sky surface density of transients from the Bower et al. survey extrapolated to 1.8mJy. Our observed transient areal density is consistent with a Neutron Stars (NSs) origin for these events. Furthermore, we use the data to measure the sources variability on days to years time scales, and we present the variability structure function of 5GHz sources. The mean structure function shows a fast increase on approximately 1 day time scale, followed by a slower increase on time scales of up to 10 days. On time scales between 10 - 60 days the structure function is roughly constant. We find that approx > 30% of the unresolved sources brighter than 1.8mJy are variable at the > 4-sigma confidence level, presumably due mainly to refractive scintillation.

  6. Active structural acoustic control of helicopter interior multifrequency noise using input-output-based hybrid control

    Science.gov (United States)

    Ma, Xunjun; Lu, Yang; Wang, Fengjiao

    2017-09-01

    This paper presents the recent advances in reduction of multifrequency noise inside helicopter cabin using an active structural acoustic control system, which is based on active gearbox struts technical approach. To attenuate the multifrequency gearbox vibrations and resulting noise, a new scheme of discrete model predictive sliding mode control has been proposed based on controlled auto-regressive moving average model. Its implementation only needs input/output data, hence a broader frequency range of controlled system is modelled and the burden on the state observer design is released. Furthermore, a new iteration form of the algorithm is designed, improving the developing efficiency and run speed. To verify the algorithm's effectiveness and self-adaptability, experiments of real-time active control are performed on a newly developed helicopter model system. The helicopter model can generate gear meshing vibration/noise similar to a real helicopter with specially designed gearbox and active struts. The algorithm's control abilities are sufficiently checked by single-input single-output and multiple-input multiple-output experiments via different feedback strategies progressively: (1) control gear meshing noise through attenuating vibrations at the key points on the transmission path, (2) directly control the gear meshing noise in the cabin using the actuators. Results confirm that the active control system is practical for cancelling multifrequency helicopter interior noise, which also weakens the frequency-modulation of the tones. For many cases, the attenuations of the measured noise exceed the level of 15 dB, with maximum reduction reaching 31 dB. Also, the control process is demonstrated to be smoother and faster.

  7. Multi-frequency, multi-messenger astrophysics with Swift. The case of blazars

    CERN Document Server

    Giommi, Paolo

    2015-01-01

    During its first 10 years of orbital operations Swift dedicated approximately 11% of its observing time to blazars, carrying out more than 12,000 observations of ~1,600 different objects, for a total exposure time of over 25 million seconds. This is probably the largest contribution to multi-frequency (optical, UV, soft and hard X-rays) and multi-temporal data archives about this type of sources. In this paper I briefly discuss the impact that Swift is having on blazar multi-frequency and time-domain astrophysics, as well as how it is contributing to the opening of the era of multi-messenger astronomy. Finally, I present some preliminary results from a systematic analysis of a very large number of Swift XRT observations of blazars. All the "science ready" data products that are being generated by this project will be publicly released. Specifically, deconvolved X-ray spectra and best fit spectral parameters will be available through the ASDC "SED builder" tool (https://tools.asdc.asi.it/SED) and by means of i...

  8. Multi-frequency bioelectrical impedance analysis (BIA) compared to magnetic resonance imaging (MRI) for estimation of fat-free mass in colorectal cancer patients treated with chemotherapy

    DEFF Research Database (Denmark)

    Palle, Stine Skov; Tang Møllehave, Line; Kadkhoda, Zahra Taheri

    2016-01-01

    undergoing chemotherapy. Design: In an observational, prospective study we examine the relationships between single cross-sectional thighs MRI (T1-weighted (1.5 T) SM compared to FFM BIA (8-electrodes multi-frequency Tanita MC780MA)) and FFM skin-fold thickness (ST) (4-points (Harpenden, Skinfold Caliper...

  9. Multi-Frequency VLBA Studies of the Parsec-Scale Jets in 3C 66A and 3C 66B

    Indian Academy of Sciences (India)

    G.-Y. Zhao; Y.-J. Chen; Z.-Q. Shen; H. Sudou; S. Iguchi; F. Gao; Y. Murata; Y. Taniguchi

    2014-09-01

    We report multi-frequency VLBA phase-referencing observation results of 3C 66A and 3C 66B, including high resolution maps and relative position measurements. The resulting images show similar morphology with that presented in previous works. We find core shift variations in both sources, indicating some physical condition changes in the jets.

  10. Swift observations of unidentified radio sources in the revised Third Cambridge Catalogue

    Science.gov (United States)

    Maselli, A.; Massaro, F.; Cusumano, G.; La Parola, V.; Harris, D. E.; Paggi, A.; Liuzzo, E.; Tremblay, G. R.; Baum, S. A.; O'Dea, C. P.

    2016-08-01

    We have investigated a group of unassociated radio sources included in the Third Cambridge Catalogue (3CR) to increase the multifrequency information on them and possibly obtain an identification. We have carried out an observational campaign with the Swift satellite to observe with the Ultraviolet/Optical Telescope (UVOT) and the X-Ray Telescope (XRT) the field of view of 21 bright NRAO VLA Sky Survey (NVSS) sources within the positional uncertainty region of the 3CR sources. Furthermore, we have searched in the recent AllWISE Source Catalogue for infrared sources matching the position of these NVSS sources. We have detected significant emission in the soft X-ray band for nine of the investigated NVSS sources. To all of them, and in four cases with no soft X-ray association, we have associated a Wide-field Infrared Survey Explorer infrared counterpart. Eight of these infrared candidates have not been proposed earlier in the literature. In the five remaining cases our candidate matches one among a few optical candidates suggested for the same 3CR source in previous studies. No source has been detected in the UVOT filters at the position of the NVSS objects, confirming the scenario that all of them are heavily obscured. With this in mind, a spectroscopic campaign, preferably in the infrared band, will be necessary to establish the nature of the sources that we have finally identified.

  11. VLA survey of the CDFS: the nature of faint radio sources

    CERN Document Server

    Tozzi, P; Fomalont, E; Miller, N; Norman, C; Mainieri, V; Padovani, P; Rosati, P

    2009-01-01

    We present the multiwavelength properties of 266 cataloged radio sources identified with 20 and 6 cm VLA deep observations of the CDFS at a flux density limit of 42 \\mu Jy at the field centre at 1.4 GHz. These new observations probe the faint end of both the star formation and radio galaxy/AGN population. X-ray data, including upper limits, turn out to be a key factor in establishing the nature of faint radio sources. We find that, while the well-known flattening of the radio number counts below 1 mJy is mostly due to star forming galaxies, these sources and AGN make up an approximately equal fraction of the sub--millijansky sky, contrary to some previous results. We have also uncovered a population of distant AGN systematically missing from many previous studies of sub-millijansky radio source identifications. The AGN include radio galaxies, mostly of the low-power, Fanaroff-Riley I type, and a significant radio-quiet component, which amounts to approximately one fifth of the total sample. We also find that ...

  12. Rotation Measures in AGN jets seen by VLA at 21 cm to 6 mm

    CERN Document Server

    Kravchenko, E V; Kovalev, Y Y

    2014-01-01

    We present Faraday Rotation Measure (RM) properties of seven active galactic nuclei (AGN), observed with the NRAO VLA at three epochs in 2012-2014. Data was taken at 1.4, 2.2, 5.0, 8.2, 15.4, 22.4, 33.5 and 43.1 GHz quasi simultaneously in full polarization mode. For the first time RMs were calculated in a range of wavelengths covering more than one order of magnitude: from 21 cm up to 6 mm. We measured RM for each source and showed a tendency to increase its value toward high frequencies according to the law |RM|~f^a with a=1.6+/-0.1. For 0710+439, we observed an increase over the frequency range of 4 orders of magnitude and measured one of the highest RM ever, (-89+/-1)*10^3 rad/m^2. Analysis of different epochs shows variations of the value and the sign of RM on short and long time-scales. This may be caused by changing physical conditions in the compact regions of the AGN jets, e.g. strength of magnetic field, particle density and so on.

  13. A multifrequency MUSIC algorithm for locating small inhomogeneities in inverse scattering

    Science.gov (United States)

    Griesmaier, Roland; Schmiedecke, Christian

    2017-03-01

    We consider an inverse scattering problem for time-harmonic acoustic or electromagnetic waves with sparse multifrequency far field data-sets. The goal is to localize several small penetrable objects embedded inside an otherwise homogeneous background medium from observations of far fields of scattered waves corresponding to incident plane waves with one fixed incident direction but several different frequencies. We assume that the far field is measured at a few observation directions only. Taking advantage of the smallness of the scatterers with respect to wavelength we utilize an asymptotic representation formula for the far field to design and analyze a MUSIC-type reconstruction method for this setup. We establish lower bounds on the number of frequencies and receiver directions that are required to recover the number and the positions of an ensemble of scatterers from the given measurements. Furthermore we briefly sketch a possible application of the reconstruction method to the practically relevant case of multifrequency backscattering data. Numerical examples are presented to document the potentials and limitations of this approach.

  14. The QUIJOTE CMB Experiment: status and first results with the multi-frequency instrument

    CERN Document Server

    López-Caniego, M; Aguiar, M; Génova-Santos, R; Gómez-Reñasco, F; Gutierrez, C; Herreros, J M; Hoyland, R J; López-Caraballo, C; Santos, A E Pelaez; Poidevin, F; Rubiño-Martín, J A; de la Rosa, V Sanchez; Tramonte, D; Vega-Moreno, A; Viera-Curbelo, T; Vignaga, R; Martínez-González, E; Barreiro, R B; Casaponsa, B; Casas, F J; Diego, J M; Fernández-Cobos, R; Herranz, D; Ortiz, D; Vielva, P; Artal, E; Aja, B; Cagigas, J; Cano, J L; de la Fuente, L; Mediavilla, A; Terán, J V; Villa, E; Piccirillo, L; Battye, R; Blackhurst, E; Brown, M; Davies, R D; Davis, R J; Dickinson, C; Grainge, K; Harper, S; Maffei, B; McCulloch, M; Melhuish, S; Pisano, G; Watson, R A; Hobson, M; Lasenby, A; Saunders, R; Scott, P

    2014-01-01

    The QUIJOTE (Q-U-I JOint Tenerife) CMB Experiment is designed to observe the polarization of the Cosmic Microwave Background and other Galactic and extragalactic signals at medium and large angular scales in the frequency range of 10-40 GHz. The first of the two QUIJOTE telescopes and the multi-frequency (10-20 GHz) instrument have been in operation since November 2012. In 2014 a second telescope and a new instrument at 30GHz will be ready for commissioning, and an additional instrument at 40 GHz is in its final design stages. After three years of effective observations, the data obtained by these telescopes and instruments will have the required sensitivity to detect a primordial gravitational-wave component if the tensor-to-scalar ratio is larger than r = 0.05. At the moment, we have completed half of the wide Galactic survey with the multi-frequency instrument covering 18 000 square degrees of the Northern hemisphere. When we finish this survey in early 2014, we shall have reached approximately 14{\\mu}K pe...

  15. A Multiwavelength Study of RZ Cassiopeiae: The XMM-Newton/VLA Campaign

    CERN Document Server

    Audard, M; Güdel, M; Audard, Marc; Donisan, Julius R.; Guedel, Manuel

    2004-01-01

    XMM-Newton and the VLA simultaneously observed the eclipsing Algol-type binary RZ Cassiopeiae in August 2003. The secondary eclipse (K3 IV companion behind the A3 V primary) was placed at the center of the 15-hour radio campaign, while the X-ray satellite monitored a full 1.2-day orbital period. We present results of the X-ray and radio campaigns. The X-ray light curve shows significant modulation probably related to rotational modulation and active region evolution, and even small flares. However, the X-ray eclipse is not deep, implying that the coronal X-ray emitting material is spatially extended. The Reflection Grating Spectrometer (RGS) spectrum shows a variety of bright emission lines from Fe, Ne, O, N. A strong [C/N] depletion probably reflects the surface composition of the secondary which fills its Roche lobe and loses material onto the primary. The O~\\textsc{vii} He-like triplet reflects a low forbidden-to-intercombination ratio; while it generally suggests high electron densities, the ratio is here...

  16. Multi-frequency synthesis algorithm based on Generalized Maximum Entropy Method. Application to 0954+658

    CERN Document Server

    Bajkova, Anisa T

    2011-01-01

    We propose the multi-frequency synthesis (MFS) algorithm with spectral correction of frequency-dependent source brightness distribution based on maximum entropy method. In order to take into account the spectral terms of n-th order in the Taylor expansion for the frequency-dependent brightness distribution, we use a generalized form of the maximum entropy method suitable for reconstruction of not only positive-definite functions, but also sign-variable ones. The proposed algorithm is aimed at producing both improved total intensity image and two-dimensional spectral index distribution over the source. We consider also the problem of frequency-dependent variation of the radio core positions of self-absorbed active galactic nuclei, which should be taken into account in a correct multi-frequency synthesis. First, the proposed MFS algorithm has been tested on simulated data and then applied to four-frequency synthesis imaging of the radio source 0954+658 from VLBA observational data obtained quasi-simultaneously ...

  17. Investigation of the teratogenic potential of VLA-4 antagonist derivatives in rats.

    Science.gov (United States)

    Sakurai, Ken; Matsuoka, Toshiki; Suzuki, Chiharu; Kinoshita, Junzo; Takayama, Gensuke; Shimomura, Kazuhiro

    2014-11-01

    Very late antigen-4 (VLA-4), which is concerned with cell-cell adhesion, plays important roles in development of the heart, and some VLA-4 antagonists cause cardiac anomalies. In this study, we evaluated the teratogenic potential of VLA-4 antagonist derivatives as screening, and investigated the conditions that induce cardiac anomalies. Seventeen compounds were orally administered to pregnant rats throughout the organogenesis period, and fetal examinations were performed. In addition, drug concentrations in the embryos were assayed. As a result, the incidence of ventricular septal defect (VSD) ranged from 0 to 100% depending on the compound. Plasma drug concentrations in the dams were related to increased incidence of VSD; however, these incidences were not increased when the concentration of the compound in the embryos at 24h after dosing was low. It is considered that continuous pharmacological activity in the embryo for more than 24h might disrupt closure of the ventricular septum.

  18. Multi-frequency bioimpedance in equine muscle assessment

    DEFF Research Database (Denmark)

    Harrison, Adrian Paul; Elbrønd (Bibs), Vibeke Sødring; Riis-Olesen, Kiwa

    2015-01-01

    Multi-frequency BIA (mfBIA) equipment has been shown to be a non-invasive and reliable method to assess a muscle as a whole or at fibre level. In the equine world this may be the future method of assessment of training condition or of muscle injury. The aim of this study was to test if mfBIA reli.......g. myofascial release therapy and metabolic diseases, respectively....

  19. A Meliorated Multi-Frequency Band Pyroelectric Sensor.

    Science.gov (United States)

    Hsiao, Chun-Ching; Liu, Sheng-Yi; Siao, An-Shen

    2015-07-06

    This article proposes a meliorated multi-frequency band pyroelectric sensor for detecting subjects with various velocities, namely extending the sensing frequency under good performance from electrical signals. A tactic, gradually increasing thickness of the ZnO layers, is used for redeeming drawbacks of a thicker pyroelectric layer with a tardy response at a high-frequency band and a thinner pyroelectric layer with low voltage responsivity at a low-frequency band. The proposed sensor is built on a silicon substrate with a thermal isolation layer of a silicon nitride film, consisting of four pyroelectric layers with various thicknesses deposited by a sputtering or aerosol deposition (AD) method and top and bottom electrodes. The thinnest ZnO layer is deposited by sputtering, with a low thermal capacity and a rapid response shoulders a high-frequency sensing task, while the thicker ZnO layers are deposited by AD with a large thermal capacity and a tardy response shoulders a low-frequency sensing task. The fabricated device is effective in the range of 1 KHz~10 KHz with a rapid response and high voltage responsivity, while the ZnO layers with thicknesses of about 0.8 μm, 6 μm, 10 μm and 16 μm are used for fabricating the meliorated multi-frequency band pyroelectric sensor. The proposed sensor is successfully designed, analyzed, and fabricated in the present study, and can indeed extend the sensing range of the multi-frequency band.

  20. Advanced multi-frequency radar: Design, preliminary measurements and particle size distribution retrieval

    Science.gov (United States)

    Majurec, Ninoslav

    lower output power of klystron amplifiers (comparing to magnetrons) is compensated by use of pulse compression (linear FM). The problem of range sidelobes (pulse compression artifacts) has been solved by using appropriate windowing functions in the receiver. Satisfactory sidelobe suppression level of 45 dB has been demonstrated in the lab. The currently best achievable range resolution of the AMFR system is 30 m (corresponds to 5 MHz receiver BW, set by the sampling rate of the Analog-to-Digital card). During the design stage, various polarization schemes have been investigated. The polarization scheme analysis showed the switching polarization scheme to be the best suited for the AMFR system. The AMFR subsystems were partially finished in the winter of 2005. Some preliminary tests were conducted in January 2006. Antenna platform was fabricated in summer 2006. The final assembly took place in the fall of 2006. Early results are presented in the dissertation. These results were helpful in revealing of certain problems in the radar system (i.e. immediate processing computer synchronization) that needed to be addressed during system development. Stratiform rain event occurred on December 18 2006 has been analyzed in detail. A number of commonly used theoretical particle size distributions is presented. Furthermore, it is shown that a fully calibrated multi-frequency radar system has capability of separating scattering and attenuation effects. This was accomplished by fitting the theoretical models into the measured data. An alternative method of estimating rain rate that relies on the dual wavelength ratios is also presented. Although not as powerful as theoretical model fitting, it has its merits for off-zenith observations. During January 2007, AMFR system participated in the C3VP experiment (Canadian CloudSat/CALIPSO Validation Project) in south Ontario, Canada. Some of the data obtained during C3VP experiment has been analyzed and presented. Analysis of these two

  1. The jet of the BL Lacertae object PKS 2201+044: MAD near-IR adaptive optics observations and comparison with optical, radio and X-ray data

    Science.gov (United States)

    Liuzzo, E.; Falomo, R.; Treves, A.; Donato, D.; Sambruna, M.; Arcidiacono, C.; Giovannini, G.; Farinato, J.; Moretti, A.; Ragazzoni, R.; Diolaiti, E.; Lombini, M.; Brast, R.; Donaldson, R.; Kolb, J.; Marchetti, E.; Tordo, S.

    2011-04-01

    Context. Relativistic jets are a common feature of radio loud active galactic nuclei. Multifrequency observations are a unique tool to constrain their physics. Aims: We report on a detailed study of the properties of the jet of the nearby BL Lac object PKS 2201+044, one of the rare cases where the jet is detected from radio to X-rays. Methods: We use new adaptive optics near-IR observations of the source, obtained with the ESO multi-conjugated adaptive optics demonstrator (MAD) at the Very Large Telescope. These observations acquired in Ground-Layer Adaptive Optics mode are combined with images previously achieved by HST, VLA and Chandra to perform a morphological and photometric study of the jet. Results: We find a noticeable similarity in the morphology of the jet at radio, near-IR and optical wavelengths. We construct the spectral shape of the main knot of jet that appears dominated by synchrotron radiation. Conclusions: On the basis of the jet morphology and the weak lines spectrum we suggest that PKS 2201+044 belongs to the class of radio sources intermediate between FRIs and FRIIs.

  2. Update on the Commensal VLA Low-band Ionospheric and Transient Experiment (VLITE)

    Science.gov (United States)

    Kassim, Namir E.; Clarke, Tracy E.; Ray, Paul S.; Polisensky, Emil; Peters, Wendy M.; Giacintucci, Simona; Helmboldt, Joseph F.; Hyman, Scott D.; Brisken, Walter; Hicks, Brian; Deneva, Julia S.

    2017-01-01

    The JVLA Low-band Ionospheric and Transient Experiment (VLITE) is a commensal observing system on the NRAO JVLA. The separate optical path of the prime-focus sub-GHz dipole feeds and the Cassegrain-focus GHz feeds provided an opportunity to expand the simultaneous frequency operation of the JVLA through joint observations across both systems. The low-band receivers on 10 JVLA antennas are outfitted with dedicated samplers and use spare fibers to transport the 320-384 MHz band to the VLITE correlator. The initial phase of VLITE uses a custom-designed real-time DiFX software correlator to produce autocorrelations, as well as parallel and cross-hand cross-correlations from the linear dipole feeds. NRL and NRAO have worked together to explore the scientific potential of the commensal low frequency system for ionospheric remote sensing, astrophysics and transients. VLITE operates at nearly 70% wall time with roughly 6200 hours of JVLA time recorded each year.VLITE data are used in real-time for ionospheric research and are transferred daily to NRL for processing in the astrophysics and transient pipelines. These pipelines provide automated radio frequency interference excision, calibration, imaging and self-calibration of data.We will review early scientific results from VLITE across all three science focus areas, including the ionosphere, slow (> 1 sec) transients, and astrophysics. We also discuss the future of the project, that includes its planned expansion to eVLITE including the addition of more antennas, and a parallel capability to search for fast (< 1 sec), dispersed transients, such as Fast Radio Bursts and Rotating Radio Transients. We will also present early results of commissioning tests to utilize VLITE data products to complement NRAO’s 3 GHz VLA Sky Survey (VLASS). Revised pipelines are under development for operation during the on-the-fly operation mode of the sky survey.

  3. Gravitational wave sources in the era of multi-frequency gravitational wave astronomy

    CERN Document Server

    Colpi, Monica

    2016-01-01

    The focus of this Chapter is on describing the prospective sources of the gravitational wave universe accessible to present and future observations, from kHz, to mHz down to nano-Hz frequencies. The multi-frequency gravitational wave universe gives a deep view into the cosmos, inaccessible otherwise. It has as main actors core-collapsing massive stars, neutron stars, coalescing compact object binaries of different flavours and stellar origin, coalescing massive black hole binaries, extreme mass ratio inspirals, and possibly the very early universe itself. Here, we highlight the science aims and describe the gravitational wave signals expected from the sources and the information gathered in it. We show that the observation of gravitational wave sources will play a transformative role in our understanding of the processes ruling the formation and evolution of stars and black holes, galaxy clustering and evolution, the nature of the strong forces in neutron star interiors, and the most mysterious interaction of...

  4. Positioning Precision Analysis of GNSS Multi-frequency Carrier Phase Combinations

    Institute of Scientific and Technical Information of China (English)

    WU Yue; PAN Yong; FAN Yimin; WANG Xiaojun

    2007-01-01

    GPS positioning precision is affected by various error sources, and traditional combinations of GPS carrier phase observations have their own limitations such as the wide-lane, the narrow-lane and the ionospheric-free combinations. To obtain the optimal positioning precision, a new linear combination method is addressed through the variance-covariance (VCV)of the GPS multi-frequency carrier phase combination equations, and the impact of the positioning precision is analyzed with the changing of the observation errors deduced by the law of error propagation. For the high precision positioning with only one carrier phase combination, the optimal combination method is deduced and further validated by an example of a baseline resolution with 60 km length. The result indicates that this method is the simplest, and the positioning precision is the best. Therefore, it is useful for long baseline quick positioning for different precision requirements in various distances.

  5. Increased prevalence of late stage T cell activation antigen (VLA-1) in active juvenile chronic arthritis

    DEFF Research Database (Denmark)

    Ødum, Niels; Morling, Niels; Platz, P;

    1987-01-01

    +) was studied. Twenty patients and six controls were investigated for the capability to stimulate alloreactivated primed lymphocytes. The prevalence of VLA-1 positive, large cells was significantly increased to 5% (median value) in active JCA as compared with JCA in remission (2%, p less than 0.05) and controls...

  6. Properties and environment of radio-emitting galaxies in the VLA-zCOSMOS survey

    NARCIS (Netherlands)

    Bardelli, S.; Schinnerer, E.; Smolčic, V.; Zamorani, G.; Zucca, E.; Mignoli, M.; Halliday, C.; Kovač, K.; Ciliegi, P.; Caputi, K.; Koekemoer, A. M.; Bongiorno, A.; Bondi, M.; Bolzonella, M.; Vergani, D.; Pozzetti, L.; Carollo, C. M.; Contini, T.; Kneib, J.-P.; Le Fèvre, O.; Lilly, S.; Mainieri, V.; Renzini, A.; Scodeggio, M.; Coppa, G.; Cucciati, O.; de la Torre, S.; de Ravel, L.; Franzetti, P.; Garilli, B.; Iovino, A.; Kampczyk, P.; Knobel, C.; Lamareille, F.; Le Borgne, J.-F.; Le Brun, V.; Maier, C.; Pellò, R.; Peng, Y.; Perez-Montero, E.; Ricciardelli, E.; Silverman, J. D.; Tanaka, M.; Tasca, L.; Tresse, L.; Abbas, U.; Bottini, D.; Cappi, A.; Cassata, P.; Cimatti, A.; Guzzo, L.; Leauthaud, A.; Maccagni, D.; Marinoni, C.; McCracken, H. J.; Memeo, P.; Meneux, B.; Oesch, P.; Porciani, C.; Scaramella, R.; Capak, P.; Sanders, D.; Scoville, N.; Taniguchi, Y.; Jahnke, K.

    2010-01-01

    Aims: We investigate the properties and the environment of radio sources with optical counterparts from the combined VLA-COSMOS and zCOSMOS samples. The advantage of this sample is the availability of optical spectroscopic informations, high quality redshifts, and accurate density determination. Met

  7. Gravitational lensing statistics with extragalactic surveys; 2, Analysis of the Jodrell Bank-VLA Astrometric Survey

    NARCIS (Netherlands)

    Helbig, P.; Marlow, D. R.; Quast, R.; Wilkinson, P. N.; Browne, I. W. A.; Koopmans, L. V. E.

    1999-01-01

    Published in: Astron. Astrophys. Suppl. Ser. 136 (1999) no. 2, pp.297-305 citations recorded in [Science Citation Index] Abstract: We present constraints on the cosmological constant $lambda_{0}$ from gravitational lensing statistics of the Jodrell Bank-VLA Astrometric Survey (JVAS). Although this

  8. Gravitational lensing statistics with extragalactic surveys - II. Analysis of the Jodrell Bank-VLA Astrometric Survey

    NARCIS (Netherlands)

    Helbig, P; Marlow, D; Quast, R; Wilkinson, PN; Browne, IWA; Koopmans, LVE

    We present constraints on the cosmological constant lambda(0) from gravitational lensing statistics of the Jodrell Bank-VLA Astrometric Survey (JVAS). Although this is the largest gravitational lens survey which has been analysed, cosmological constraints are only comparable to those from optical

  9. Multi-frequency force-detected electron spin resonance in the millimeter-wave region up to 150 GHz

    Science.gov (United States)

    Ohmichi, E.; Tokuda, Y.; Tabuse, R.; Tsubokura, D.; Okamoto, T.; Ohta, H.

    2016-07-01

    In this article, a novel technique is developed for multi-frequency force-detected electron spin resonance (ESR) in the millimeter-wave region. We constructed a compact ESR probehead, in which the cantilever bending is sensitively detected by a fiber-optic Fabry-Perot interferometer. With this setup, ESR absorption of diphenyl-picrylhydrazyl radical (<1 μg) was clearly observed at multiple frequencies of up to 150 GHz. We also observed the hyperfine splitting of low-concentration Mn2+ impurities(˜0.2%) in MgO.

  10. Multi-frequency force-detected electron spin resonance in the millimeter-wave region up to 150 GHz

    Energy Technology Data Exchange (ETDEWEB)

    Ohmichi, E., E-mail: ohmichi@harbor.kobe-u.ac.jp; Tokuda, Y.; Tabuse, R.; Tsubokura, D.; Okamoto, T. [Graduate School of Science, Kobe University, 1-1 Rokkodai-cho, Nada, Kobe 657-8501 (Japan); Ohta, H. [Molecular Photoscience Research Center, Kobe University, 1-1 Rokkodai-cho, Nada, Kobe 657-8501 (Japan)

    2016-07-15

    In this article, a novel technique is developed for multi-frequency force-detected electron spin resonance (ESR) in the millimeter-wave region. We constructed a compact ESR probehead, in which the cantilever bending is sensitively detected by a fiber-optic Fabry-Perot interferometer. With this setup, ESR absorption of diphenyl-picrylhydrazyl radical (<1 μg) was clearly observed at multiple frequencies of up to 150 GHz. We also observed the hyperfine splitting of low-concentration Mn{sup 2+} impurities(∼0.2%) in MgO.

  11. Fast multifrequency focal beam analysis for 3D seismic acquisition geometry

    NARCIS (Netherlands)

    Wei, W.; Fu, L.; Blacquiere, G.

    2012-01-01

    A method for the efficient computation of multifrequency focal beams for 3D seismic acquisition geometry analysis has been developed. By computing them for all the frequency components of seismic data, single-frequency focal beams can be extended to multifrequency focal beams. However, this

  12. Status of the new multi-frequency ECRH system for ASDEX Upgrade

    DEFF Research Database (Denmark)

    Wagner, D.; Grünwald, G.; Leuterer, F.

    2008-01-01

    Currently, a new multi-frequency ECRH system is under construction at the ASDEX Upgrade tokamak experiment. This system employs, for the first time in a fusion device, multi-frequency gyrotrons, step-tunable in the range 105-140 GHz. The first two gyrotrons, working at 105 and 140 GHz, were...

  13. An Approach to High-Order Cumulants Used to Detect Multifrequency Signals in Telephone Networks

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    In accordance with the detecting process of multi-frequency signals between the offices in telephone networks, and in contrast with the autocorrelation method used to handle the multi-frequency signals, a fast,inexpensive and unbiased of cumulants estimation method is adopted in detecting signals. This detecting method is better for resisting noise performance and more practical than the autocorrelation method.

  14. VLA positions and distributions of H2O masers associated with 15 Mira and semiregular variables

    Science.gov (United States)

    Bowers, P. F.; Johnston, K. J.

    1994-05-01

    Results of VLA observations of 22 GHz H2O masers associated with 15 Mira and semiregular variables are reported. The combination of angular resolution (approximately equals 70 mas), spectral resolution (0.3 km/sec), rms sensitivity (+/- 35 mJy/beam), and hour-angle coverage is the best yet obtained for H2O masers from a significant sample of stars. Comparison of accurate optical positions of the stars with estimates from the masers yields total differences typically less than or equal to 0 sec .15-an improvement over previous comparisons by a factor of about 2. There are indications of some combination of nonuniformities in the density distribution, deviations from sphericity, and anisotropies in the velocity field, but it is difficult to disentangle the effects of these phenomena and achieve unique interpretation. A plausible model is clumps or filaments distributed at radii which vary with direction from the star. From the angular distributions and velocity ranges, there is good evidence that at least some parcels of gas are accelerated to the terminal outflow velocity at rho greater than or equal to 20 AU and that there is a component of outflow at rho approximately equals 10 to 15 AU; some gas probably is fully accelerated at radii less than 10 AU. To illustrate the problems of interpretation, the well-known case of VX Sgr is reexamined. The data do not support a simple model of increasing outflow velocity with increasing maser shell radius. It is proposed that the outflow is weakly bipolar.

  15. Filtering techniques for the detection of Sunyaev-Zel'dovich clusters in multifrequency CMB maps

    CERN Document Server

    Herranz, D; Hobson, M P; Barreiro, R B; Diego-Rodriguez, J M; Martínez-González, E; Lasenby, A N

    2002-01-01

    The problem of detecting Sunyaev-Zel'dovich (SZ) clusters in multifrequency CMB observations is investigated using a number of filtering techniques. A multifilter approach is introduced, which optimizes the detection of SZ clusters on microwave maps. An alternative method is also investigated, in which maps at different frequencies are combined in an optimal manner so that existing filtering techniques can be applied to the single combined map. The SZ profiles are approximated by the circularly-symmetric template $\\tau (x) = [1 +(x/r_c)^2]^{-\\lambda}$, with $\\lambda \\simeq \\tfrac{1}{2}$ and $x\\equiv |\\vec{x}|$, where the core radius $r_c$ and the overall amplitude of the effect are not fixed a priori, but are determined from the data. The background emission is modelled by a homogeneous and isotropic random field, characterized by a cross-power spectrum $P_{\

  16. A Meliorated Multi-Frequency Band Pyroelectric Sensor

    Directory of Open Access Journals (Sweden)

    Chun-Ching Hsiao

    2015-07-01

    Full Text Available This article proposes a meliorated multi-frequency band pyroelectric sensor for detecting subjects with various velocities, namely extending the sensing frequency under good performance from electrical signals. A tactic, gradually increasing thickness of the ZnO layers, is used for redeeming drawbacks of a thicker pyroelectric layer with a tardy response at a high-frequency band and a thinner pyroelectric layer with low voltage responsivity at a low-frequency band. The proposed sensor is built on a silicon substrate with a thermal isolation layer of a silicon nitride film, consisting of four pyroelectric layers with various thicknesses deposited by a sputtering or aerosol deposition (AD method and top and bottom electrodes. The thinnest ZnO layer is deposited by sputtering, with a low thermal capacity and a rapid response shoulders a high-frequency sensing task, while the thicker ZnO layers are deposited by AD with a large thermal capacity and a tardy response shoulders a low-frequency sensing task. The fabricated device is effective in the range of 1 KHz~10 KHz with a rapid response and high voltage responsivity, while the ZnO layers with thicknesses of about 0.8 μm, 6 μm, 10 μm and 16 μm are used for fabricating the meliorated multi-frequency band pyroelectric sensor. The proposed sensor is successfully designed, analyzed, and fabricated in the present study, and can indeed extend the sensing range of the multi-frequency band.

  17. Handbook of multifrequency electron paramagnetic resonance data and techniques

    CERN Document Server

    Misra, Sushil K

    2014-01-01

    This handbook is aimed to deliver an up-to-date account of some of the recently developed experimental and theoretical methods in EPR, as well as a complete up-to-date listing of the experimentally determined values of multifrequency transition-ion spin Hamiltonian parameters by Sushil Misra, reported in the past 20 years, extending such a listing published by him in the Handbook on Electron Spin Resonance, volume 2. This extensive data tabulation makes up roughly 60% of the book`s content. It is complemented by the first full compilation of hyperfine splittings and g-factors for aminoxyl (nit

  18. Multi-frequency bioimpedance in human muscle assessment

    DEFF Research Database (Denmark)

    Bartels, Else Marie; Sørensen, Emma Rudbæk; Harrison, Adrian Paul

    2015-01-01

    Bioimpedance analysis (BIA) is a well-known and tested method for body mass and muscular health assessment. Multi-frequency BIA (mfBIA) equipment now makes it possible to assess a particular muscle as a whole, as well as looking at a muscle at the fiber level. The aim of this study was to test...... healthy human control subjects and three selected cases were examined to demonstrate the extent to which this method may be used clinically, and in relation to training in sport. The electrode setup is shown to affect the mfBIA parameters recorded. Our recommendation is the use of noble metal electrodes...

  19. Multi-frequency klystron designed for high efficiency

    Energy Technology Data Exchange (ETDEWEB)

    Jensen, Aaron

    2017-07-04

    A multi-frequency klystron has an electron gun which generates a beam, a circuit of bunch-align-collect (BAC) tuned cavities that bunch the beam and amplify an RF signal, a collector where the beam is collected and dumped, and a standard output cavity and waveguide coupled to a window to output RF power at a fundamental mode to an external load. In addition, the klystron has additional bunch-align-collect (BAC) cavities tuned to a higher harmonic frequency, and a harmonic output cavity and waveguide coupled via a window to an additional external load.

  20. Retrieval of Aboveground Biomass Using Multi-Frequency SAR

    Science.gov (United States)

    Stelmaszczuk-Gorska, Martyna; Thiel, Christian; Schmullius, Christiane

    2016-08-01

    The objective of this study was to investigate above-ground biomass (AGB) estimation in forests by combining multi-frequency Synthetic Aperture Radar (SAR) L-band and C-band data. An area of Siberian boreal forest was selected for this study. The results demonstrated that relatively high estimation accuracy can be obtained at the spatial resolution of 0.5 ha using the L- and C-band SAR backscatter. Overall, the AGB estimation error was calculated to be approximately 24 t ha-1 using the Random Forests machine learning algorithm.

  1. Multi-frequency bioimpedance in human muscle assessment

    DEFF Research Database (Denmark)

    Bartels, Else Marie; Sørensen, Emma Rudbæk; Harrison, Adrian Paul

    2015-01-01

    Bioimpedance analysis (BIA) is a well-known and tested method for body mass and muscular health assessment. Multi-frequency BIA (mfBIA) equipment now makes it possible to assess a particular muscle as a whole, as well as looking at a muscle at the fiber level. The aim of this study was to test......, contracted state, and cell transport/metabolic activity, which relate to muscle performance. Our findings indicate that mfBIA provides a noninvasive, easily measurable and very precise momentary assessment of skeletal muscles....

  2. High School Students Discover Neutron Star Using Chandra and VLA Data

    Science.gov (United States)

    2000-12-01

    Three high school students, using data from NASA's Chandra X-ray Observatory and the National Science Foundation's Very Large Array (VLA), have found the first evidence of a neutron star in the nearby supernova remnant IC443, a system long studied by professional astronomers. This remarkable discovery has led the team to the national finals and a 1st place finish in the team competition at the Siemens-Westinghouse Science and Technology Competition held today in Washington, DC. Charles Olbert (age 18), Christopher Clearfield (age 18), and Nikolas Williams (age 16), all of the North Carolina School for Science and Mathematics (NCSSM) in Durham, NC, found a point-like source of X rays embedded in the remains of the stellar explosion, or supernova. Based on both the X-ray and radio data, the students determined that the central object in IC443 is most likely a young and rapidly rotating neutron star -- an object known as a "pulsar." "This is a really solid scientific finding," said Bryan Gaensler of the Massachusetts Institute of Technology, a noted pulsar expert who reviewed the paper for the team. "Everyone involved should be really proud of this accomplishment." Taking advantage of Chandra's superior angular resolution, the North Carolina students found the source embedded in IC443, a region known to be emitting particularly high-energy X rays. In a highly unusual situation, the students got access to the Chandra data from their science teacher, Dr. Jonathan Keohane. Keohane applied for the observation time while still associated with NASA's Goddard Space Flight Center. "The students really went through the whole analysis process themselves," said Keohane. "And, they even lived together all summer near the school to complete the research." In order to confirm the evidence from Chandra, the students turned to the National Radio Observatory's Dale Frail who gave the student team VLA data on IC443. While the radio data did not reveal any periodicity, the VLA

  3. SMA observations towards the compact, short-lived bipolar water maser outflow in the LkHα234 region

    Science.gov (United States)

    Girart, J. M.; Torrelles, J. M.; Estalella, R.; Curiel, S.; Anglada, G.; Gómez, J. F.; Carrasco-González, C.; Cantó, J.; Rodríguez, L. F.; Patel, N. A.; Trinidad, M. A.

    2016-10-01

    We present Submillimeter Array (SMA) 1.35 mm subarcsecond angular resolution observations towards the LkHα234 intermediate-mass star-forming region. The dust emission arises from a filamentary structure of ˜5 arcsec (˜4500 au) enclosing VLA 1-3 and MM 1, perpendicular to the different outflows detected in the region. The most evolved objects are located at the southeastern edge of the dust filamentary structure and the youngest ones at the northeastern edge. The circumstellar structures around VLA 1, VLA 3, and MM 1 have radii between ˜200 and ˜375 au and masses in the ˜0.08-0.3 M⊙ range. The 1.35 mm emission of VLA 2 arises from an unresolved (r ≲ 135 au) circumstellar disc with a mass of ˜0.02 M⊙. This source is powering a compact (˜4000 au), low radial velocity (˜7 km s-1) SiO bipolar outflow, close to the plane of the sky. We conclude that this outflow is the `large-scale' counterpart of the short-lived, episodic, bipolar outflow observed through H2O masers at much smaller scales (˜180 au), and that has been created by the accumulation of the ejection of several episodic collimated events of material. The circumstellar gas around VLA 2 and VLA 3 is hot (˜130 K) and exhibits velocity gradients that could trace rotation. There is a bridge of warm and dense molecular gas connecting VLA 2 and VLA 3. We discuss the possibility that this bridge could trace a stream of gas between VLA 3 and VLA 2, increasing the accretion rate on to VLA 2 to explain why this source has an important outflow activity.

  4. A review of errors in multi-frequency EIT instrumentation.

    Science.gov (United States)

    McEwan, A; Cusick, G; Holder, D S

    2007-07-01

    Multi-frequency electrical impedance tomography (MFEIT) was proposed over 10 years ago as a potential spectroscopic impedance imaging method. At least seven systems have been developed for imaging the lung, heart, breast and brain, yet none has yet achieved clinical acceptance. While the absolute impedance varies considerably between different tissues, the changes in the spectrum due to physiological changes are expected to be quite small, especially when measured through a volume. This places substantial requirements on the MFEIT instrumentation to maintain a flat system frequency response over a broad frequency range (dc-MHz). In this work, the EIT measurement problem is described from a multi-frequency perspective. Solutions to the common problems are considered from recent MFEIT systems, and the debate over four-terminal or two-terminal (multiple source) architecture is revisited. An analysis of the sources of MFEIT errors identifies the major sources of error as stray capacitance and common-mode voltages which lead to a load dependence in the frequency response of MFEIT systems. A system that employs active electrodes appears to be the most able to cope with these errors (Li et al 1996). A distributed system with digitization at the electrode is suggested as a next step in MFEIT system development.

  5. A multifrequency view of starburst galaxies

    CERN Document Server

    Becker, J K; Schoeneberg, S

    2011-01-01

    During the past few years, first observations of starburst galaxies at >GeV energies could be made with the Fermi Gamma-ray Space Telescope (GeV range) and Imaging Air Cherenkov Telescopes (TeV range). The two nearest starbursts, M82 and NGC253 were detected, and most recently, the detection of two starburst-Seyfert composites (NGC1068 and NGC4945) were reported. The emission for the two starbursts is best explained by hadronic interactions, and thus providing a first, unique opportunity to study the role of cosmic rays in galaxies. In this paper, the role of cosmic rays for the non-thermal component of galaxies is reviewed by discussing the entire non-thermal frequency range from radio emission to TeV energies. In particular, the interpretation of radio emission arising from electron synchrotron radiation is predicted to be correlated to TeV emission coming from interactions of accelerated hadrons. This is observed for the few objects known at TeV energies, but the correlation needs to be established with si...

  6. The VLA-COSMOS Survey: III. Further Catalog Analysis and the Radio Source Counts

    CERN Document Server

    Bondi, M; Schinnerer, E; Smolcic, V; Jahnke, K; Carilli, C; Zamorani, G

    2008-01-01

    The VLA-COSMOS Large Project has imaged the 2 sq.deg. COSMOS field with a resolution of 1.5 arcsec and a sensitivity of about 11 microJy (1 sigma) yielding to a catalog of about 3600 radio sources. In this paper we present a further analysis of the VLA-COSMOS Large Project catalog of radio sources aimed to: 1) quantify and correct for the effect of bandwidth smearing in the catalog, 2) determine the incompleteness produced by the noise bias and the resolution bias in the new catalog and 3) derive the radio source counts at 1.4 GHz. The effect of bandwidth smearing on the radio sources in the catalog was quantified comparing the peak and total flux densities in the final mosaic and in each of the individual pointings where the source was closest to the center of the field. We find that the peak flux densities in the original VLA-COSMOS Large Project catalog have to be divided by a factor about 0.8 or 0.9, depending on the distance from the mosaic center. The completeness of the radio catalog has been tested us...

  7. Fibronectin and VLA-4 in haematopoietic stem cell-microenvironment interactions

    Science.gov (United States)

    Williams, David A.; Rios, Maribel; Stephens, Carmella; Patel, Vikram P.

    1991-08-01

    THE self-renewal and differentiation of haematopoietic stem cells occurs in vivo and in vitro in direct contact with cells making up the haematopoietic microenvironment1-4. In this study we used adhesive ligands and blocking antibodies to identify stromal cell-derived extracellular matrix proteins involved in promoting attachment of murine haematopoietic stem cells. Here we report that day-12 colony-forming-unit spleen (CFU-S12)5 cells and reconstituting haematopoietic stem cells attach to the C-terminal, heparin-binding fragment of fibronectin by recognizing the CS-1 peptide of the alternatively spliced non-type III connecting segment (IIICS) of human plasma fibronectin. Furthermore, CFU-S12 stem cells express the α4 subunit of the VLA-4 integrin receptor, which is known to be a receptor for the CS-1 sequence, and monoclonal antibodies against the integrin α4 subunit of VLA-4 block adhesion of CFU-S12 stem cells to plates coated with the C-terminal fibronectin fragment. Finally, polyclonal antibodies against the integrin β1 subunit of VLA-4 inhibit the formation of CFU-S12-derived spleen colonies and medullary haematopoiesis in vivo following intravenous infusion of antibody-treated bone marrow cells.

  8. Multi-frequency monitoring of gamma-ray loud blazars: I. Light curves and spectral energy distributions

    CERN Document Server

    Bach, U; Villata, M; Fuhrmann, L; Buemi, C S; Larionov, V M; Leto, P; Arkharov, A A; Coloma, J M; Di Paola, A; Dolci, M; Efimova, N; Forne, E; Ibrahimov, M A; Hagen-Thorn, V; Konstantinova, T; Kopatskaya, E; Lanteri, L; Kurtanidze, O M; Maccaferri, G; Nikolashvili, M G; Orlati, A; Ros, J A; Tosti, G; Trigilio, C; Umana, G

    2006-01-01

    Context: Being dominated by non-thermal emission from aligned relativistic jets, blazars allow us to elucidate the physics of extragalactic jets, and, ltimately, how the energy is extracted from the central black hole in radio-loud active galactic nuclei. Aims: Crucial information is provided by broad-band spectral energy distributions (SEDs), their trends with luminosity and correlated multi-frequency variability. With this study we plan to obtain a database of contemporaneous radio-to-optical spectra of a sample of blazars, which are and will be observed by current and future high-energy satellites. Methods: Since December 2004 we are performing a monthly multi-frequency radio monitoring of a sample of 35 blazars at the antennas in Medicina and Noto. Contemporaneous near-IR and optical observations for all our observing epochs are organised. Results: Until June 2006 about 4000 radio measurements and 5500 near-IR and optical measurements were obtained. Most of the sources show significant variability in all ...

  9. Radio and Optical Observations of DG Tau B

    CERN Document Server

    Rodríguez, Luis F; Loinard, Laurent; Zapata, Luis A; Raga, Alejandro C; Cantó, Jorge; Riera, Angels

    2012-01-01

    DG Tau B is a Class I young stellar source that drives the asymmetric HH 159 bipolar jet. At optical wavelengths it is obscured by circumstellar optically-thick material. Using VLA and JVLA observations, we determine for the first time the proper motions of this source and find them to be consistent, within error, with those of the nearby young star DG Tau. We also discuss an ejection event that is evident in the 1994 VLA data. As the optical and molecular outflows, this ejection traced in the radio continuum is markedly asymmetric and was detected only to the NW of the star. We propose that this knot, no longer detectable in the radio, could be observed in future optical images of DG Tau B. The positions of the VLA source and of a nearby infrared object are not coincident and we suggest that the VLA source traces the exciting object, while the infrared source could be a reflection lobe.

  10. THE ABUNDANCE OF X-SHAPED RADIO SOURCES. I. VLA SURVEY OF 52 SOURCES WITH OFF-AXIS DISTORTIONS

    Energy Technology Data Exchange (ETDEWEB)

    Roberts, David H.; Cohen, Jake P.; Lu, Jing [Department of Physics MS-057, Brandeis University, Waltham, MA 02454-0911 (United States); Saripalli, Lakshmi; Subrahmanyan, Ravi, E-mail: roberts@brandeis.edu [Raman Research Institute, C. V. Raman Avenue, Sadashivanagar, Bangalore 560080 (India)

    2015-09-15

    Cheung identified a sample of 100 candidate X-shaped radio galaxies using the NRAO FIRST survey; these are small-axial-ratio extended radio sources with off-axis emission. Here, we present radio images of 52 of these sources that have been made from archival Very Large Array data with resolution of about 1″. Fifty-one of the 52 were observed at 1.4 GHz, 7 were observed at 1.4 and 5 GHz, and 1 was observed only at 5 GHz. We also present overlays of the Sloan Digital Sky Survey red images for 48 of the sources, and DSS II overlays for the remainder. Optical counterparts have been identified for most sources, but there remain a few empty fields. Our higher resolution VLA images along with FIRST survey images of the sources in the sample reveal that extended extragalactic radio sources with small axial ratios are largely (60%) cases of double radio sources with twin lobes that have off-axis extensions, usually with inversion-symmetric structure. The available radio images indicate that at most 20% of sources might be genuine X-shaped radio sources that could have formed by a restarting of beams in a new direction following an interruption and axis flip. The remaining 20% are in neither of these categories. The implications of this result for the gravitational wave background are discussed in Roberts et al.

  11. The Abundance of X-Shaped Radio Sources I. VLA Survey of 52 Sources With Off-Axis Distortions

    CERN Document Server

    Roberts, David H; Lu, Jing; Saripalli, Lakshmi; Subrahmanyan, Ravi

    2015-01-01

    Cheung (2007) identified a sample of 100 candidate X-shaped radio galaxies using the NRAO FIRST survey; these are small-axial-ratio extended radio sources with off-axis emission. Here we present radio images of 52 of these sources that have been made from archival Very Large Array data with resolution of about 1 arcsec. Fifty-one of the 52 were observed at 1.4 GHz, seven were observed at 1.4 GHz and 5 GHz, and one was observed only at 5 GHz. We also present overlays of the SDSS red images for 41 of the sources, and DSS II overlays for the remainder. Optical counterparts have been identified for most sources, but there remain a few empty fields. Our higher resolution VLA images along with FIRST survey images of the sources in the sample reveal that extended extragalactic radio sources with small axial ratios are largely (60%) cases of double radio sources with twin lobes that have off-axis extensions, usually with inversion-symmetric structure. The available radio images indicate that at most 20% sources might...

  12. A CHANDRA-VLA INVESTIGATION OF THE X-RAY CAVITY SYSTEM AND RADIO MINI-HALO IN THE GALAXY CLUSTER RBS 797

    Energy Technology Data Exchange (ETDEWEB)

    Doria, Alberto [Argelander-Institut fuer Astronomie, Auf dem Huegel 71, D-53121 Bonn (Germany); Gitti, Myriam; Brighenti, Fabrizio [Dipartimento di Astronomia, Universita di Bologna, via Ranzani 1, Bologna 40127 (Italy); Ettori, Stefano [Astronomical Observatory of Bologna-INAF, via Ranzani 1, I-40127 Bologna (Italy); Nulsen, Paul E. J.; McNamara, Brian R. [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States)

    2012-07-01

    We present a study of the cavity system in the galaxy cluster RBS 797 based on Chandra and Very Large Array (VLA) data. RBS 797 (z = 0.35) is one of the most distant galaxy clusters in which two pronounced X-ray cavities have been discovered. The Chandra data confirm the presence of a cool core and indicate a higher metallicity along the cavity directions. This is likely due to the active galactic nucleus outburst, which lifts cool metal-rich gas from the center along the cavities, as seen in other systems. We find indications that the cavities are hotter than the surrounding gas. Moreover, the new Chandra images show bright rims contrasting with the deep, X-ray deficient cavities. The likely cause is that the expanding 1.4 GHz radio lobes have displaced the gas, compressing it into a shell that appears as bright cool arms. Finally, we show that the large-scale radio emission detected with our VLA observations may be classified as a radio mini-halo, powered by the cooling flow, as it nicely follows the trend P{sub radio} versus P{sub CF} predicted by the reacceleration model.

  13. A Chandra - VLA Investigation of the X-ray Cavity System and Radio Mini-Halo in the Galaxy Cluster RBS 797

    CERN Document Server

    Doria, Alberto; Ettori, Stefano; Brighenti, Fabrizio; Nulsen, Paul E J; McNamara, Brian R

    2012-01-01

    We present a study of the cavity system in the galaxy cluster RBS 797 based on Chandra and VLA data. RBS 797 (z = 0.35), is one of the most distant galaxy clusters in which two pronounced X-ray cavities have been discovered. The Chandra data confirm the presence of a cool core and indicate an higher metallicity along the cavity directions. This is likely due to the AGN outburst, which lifts cool metal-rich gas from the center along the cavities, as seen in other systems. We find indications that the cavities are hotter than the surrounding gas. Moreover, the new Chandra images show bright rims contrasting with the deep, X-ray deficient cavities. The likely cause is that the expanding 1.4 GHz radio lobes have displaced the gas, compressing it into a shell that appears as bright cool arms. Finally we show that the large-scale radio emission detected with our VLA observations may be classified as a radio mini-halo, powered by the cooling flow (CF), as it nicely follows the trend P_radio vs. P_CF predicted by the...

  14. MULTIFREQUENCY ALGORITHMS FOR DETERMINING THE MOISTURE CONTENT OF LIQUID EMULSIONS BY THE METHOD OF RESONANCE DIELCOMETRY

    National Research Council Canada - National Science Library

    A. A. Korobko

    2017-01-01

    Purpose. The main attention is paid to the development and investigation of multifrequency algorithms for the realization of the method of resonance dielcometric measurement of the humidity of emulsions of the type...

  15. Multifrequency scanning probe microscopy study of nanodiamond agglomerates

    Science.gov (United States)

    Aravind, Vasudeva; Lippold, Stephen; Li, Qian; Strelcov, Evgheny; Okatan, Baris; Legum, Benjamin; Kalinin, Sergei; Clarion University Team; Oak Ridge National Laboratory Team

    Due to their rich surface chemistry and excellent mechanical properties and non-toxic nature, nanodiamond particles have found applications such as biomedicine, tribology and lubrication, targeted drug delivery systems, tissue scaffolds and surgical implants. Although single nanodiamond particles have diameters about 4-5nm, they tend to form agglomerates. While these agglomerates can be useful for some purposes, many applications of nanodiamonds require single particle, disaggregated nanodiamonds. This work is oriented towards studying forces and interactions that contribute to agglomeration in nanodiamonds. In this work, using multifrequency scanning probe microscopy techniques, we show that agglomerate sizes can vary between 50-100nm in raw nanodiamonds. Extremeties of particles and Interfaces between agglomerates show dissipative forces with scanning probe microscope tip, indicating agglomerates could act as points of increased adhesion, thus reducing lubricating efficiency when nanodiamonds are used as lubricant additives. This research was conducted at the Center for Nanophase Materials Sciences, which is a DOE Office of Science User Facility.

  16. III-V-on-silicon multi-frequency lasers.

    Science.gov (United States)

    Keyvaninia, S; Verstuyft, S; Pathak, S; Lelarge, F; Duan, G-H; Bordel, D; Fedeli, J-M; De Vries, T; Smalbrugge, B; Geluk, E J; Bolk, J; Smit, M; Roelkens, G; Van Thourhout, D

    2013-06-03

    Compact multi-frequency lasers are realized by combining III-V based optical amplifiers with silicon waveguide optical demultiplexers using a heterogeneous integration process based on adhesive wafer bonding. Both devices using arrayed waveguide grating routers as well as devices using ring resonators as the demultiplexer showed lasing with threshold currents between 30 and 40 mA and output powers in the order of a few mW. Laser operation up to 60°C is demonstrated. The small bending radius allowable for the silicon waveguides results in a short cavity length, ensuring stable lasing in a single longitudinal mode, even with relaxed values for the intra-cavity filter bandwidths.

  17. Multifrequency polarimetric microwave scatterometer based on a vector network analyzer

    Science.gov (United States)

    D'Alessio, Angelo C.; Posa, Francesco; Sabatelli, Vincenzo; Casarano, Domenico

    1999-12-01

    In order to test a multi-frequency polarimetric scatterometer based on a Vector Network Analyzer, calibration measurements have been performed over point targets. Two trihedral corner reflectors with different dimensions have been employed. The radar cross sections have been measured at different frequency bands (L, C and X) and for different look angles between 23 degree(s) and 50 degree(s). Satisfactory results have been obtained in all three bands, however in the L-band the electromagnetic smog, due to mobile phones and airport radars, caused some difficulties in the extinction of the radiometric information. Other calibration tests have been planned before using the instrument as a ground-truth data acquisition device on the test-sites envisaged for the spaceborne SRTM and ENVISAT SAR missions.

  18. Investigation of vegetation with multifrequency and multipolarization SAR systems

    Science.gov (United States)

    Winter, Rudolf; Roth, Achim; Bayer, Thomas

    1990-05-01

    Investigations of vegetation is conducted by synergism of different types of digital image data and models. As a standard application, satellite images are digitally coregistered with existant topographical data and stored in the Geographic Information Systems (GIS). The usefulness of multiparametric SAR (Synthetic Aperture Radar) data for vegetation mapping is discussed. The multifrequency aspects requires precise geocoding. Different application fields with recent results are discussed: forest investigations with SIR (Spaceborne Imaging Radar)-B data in the southern Rhine valley ; extraction of landuse categories in landscape units using two geocoded Seasat-SAR scenes in the area of Bonn; relief effects on image gray values in geocoded Seasat-SAR images; the concept of a remote sensing data base for ecological applications.

  19. Dynamics of Microbeams under Multi-Frequency Excitations

    KAUST Repository

    Ibrahim, Alwathiqbellah

    2017-01-24

    This paper presents an investigation of the dynamics of microbeams under multiple harmonic electrostatic excitation frequencies. First, the response of a cantilever microbeam to two alternating current (AC) source excitation is examined. We show by simulations the response of the microbeam at primary resonance (near the fundamental natural frequency) and at secondary resonances (near half, superharmonic, and twice, subharmonic, the fundamental natural frequency). A multimode Galerkin method combined with the Euler-Bernoulli beam equation, accounting for the nonlinear electrostatic force, has been used to develop a reduced order model. The response of the cantilever microbeam to three AC source excitation is also investigated and shown as a promising technique to enhance the bandwidth of resonators. Finally, an experimental study of a clamped-clamped microbeam is conducted, demonstrating the multi-frequency excitation resonances using two, three, and four AC sources.

  20. Dynamics of Microbeams under Multi-Frequency Excitations

    Directory of Open Access Journals (Sweden)

    Alwathiqbellah Ibrahim

    2017-01-01

    Full Text Available This paper presents an investigation of the dynamics of microbeams under multiple harmonic electrostatic excitation frequencies. First, the response of a cantilever microbeam to two alternating current (AC source excitation is examined. We show by simulations the response of the microbeam at primary resonance (near the fundamental natural frequency and at secondary resonances (near half, superharmonic, and twice, subharmonic, the fundamental natural frequency. A multimode Galerkin method combined with the Euler-Bernoulli beam equation, accounting for the nonlinear electrostatic force, has been used to develop a reduced order model. The response of the cantilever microbeam to three AC source excitation is also investigated and shown as a promising technique to enhance the bandwidth of resonators. Finally, an experimental study of a clamped-clamped microbeam is conducted, demonstrating the multi-frequency excitation resonances using two, three, and four AC sources.

  1. Multifrequency acoustics as a probe of mesoscopic blood coagulation dynamics

    Science.gov (United States)

    Ganesan, Adarsh; Rajendran, Gokulnath; Ercole, Ari; Seshia, Ashwin

    2016-08-01

    Coagulation is a complex enzymatic polymerisation cascade. Disordered coagulation is common in medicine and may be life-threatening yet clinical assays are typically bulky and/or provide an incomplete picture of clot mechanical evolution. We present the adaptation of an in-plane acoustic wave device: quartz crystal microbalance with dissipation at multiple harmonics to determine the time-evolution of mesoscale mechanical properties of clot formation in vitro. This approach is sensitive to changes in surface and bulk clot structure in various models of induced coagulopathy. Furthermore, we are able to show that clot formation at surfaces has different kinetics and mechanical strength to that in the bulk, which may have implications for the design of bioprosthetic materials. The "Multifrequency acoustics" approach thus enables unique capability to portray biological processes concerning blood coagulation.

  2. Silicon pin solar cells investigated by multi-frequency EDMR

    Energy Technology Data Exchange (ETDEWEB)

    Meier, Christoph; Teutloff, Christian; Behrends, Jan; Bittl, Robert [Fachbereich Physik, Freie Universitaet Berlin, Arnimallee 14, 14195 Berlin (Germany); Fehr, Matthias; Schnegg, Alexander; Lips, Klaus [Institut fuer Silizium-Photovoltaik, Helmholtz-Zentrum Berlin fuer Materialien und Energie, Kekulestr. 5, 12489 Berlin (Germany)

    2011-07-01

    Electrically detected magnetic resonance (EDMR) can be used to investigate paramagnetic centres influencing charge transport in semiconductors even at concentrations well below the sensitivity threshold of conventional electron paramagnetic resonance (EPR). This technique measures conductivity changes in the sample that occur when spin transitions cause an enhancement or a quenching of currents. EDMR was e.g. successfully employed to microcrystalline Si pin solar cells in X-band (9.7 GHz). We present the application of EDMR to Si pin solar cells at Q-band frequency (34 GHz). We could demonstrate a gain of spectral resolution. With multi-frequency EDMR we distinguished between field-dependent and field-independent interactions. Further, we realized EDMR in a non-resonant setup at 94 GHz (W-band) and show first results.

  3. Distributed multi-frequency image reconstruction for radio-interferometry

    CERN Document Server

    Deguignet, Jérémy; Mary, David; Ferrari, Chiara

    2016-01-01

    The advent of enhanced technologies in radio interferometry and the perspective of the SKA telescope bring new challenges in image reconstruction. One of these challenges is the spatio-spectral reconstruction of large (Terabytes) data cubes with high fidelity. This contribution proposes an alternative implementation of one such 3D prototype algorithm, MUFFIN (MUlti-Frequency image reconstruction For radio INterferometry), which combines spatial and spectral analysis priors. Using a recently proposed primal dual algorithm, this new version of MUFFIN allows a parallel implementation where computationally intensive steps are split by spectral channels. This parallelization allows to implement computationally demanding translation invariant wavelet transforms (IUWT), as opposed to the union of bases used previously. This alternative implementation is important as it opens the possibility of comparing these efficient dictionaries, and others, in spatio-spectral reconstruction. Numerical results show that the IUWT-...

  4. T Cell Costimulation via the Integrin VLA-4 Inhibits the Actin-Dependent Centralization of Signaling Microclusters Containing the Adaptor SLP-76

    National Research Council Canada - National Science Library

    Nguyen, Ken; Sylvain, Nicholas R; Bunnell, Stephen C

    2008-01-01

    .... Costimulatory VLA-4 ligands also prevented the centralization of SLP-76, promoted microcluster persistence, prolonged lateral interactions between SLP-76 and its upstream kinase, ZAP-70, and retained...

  5. A VLA Study of Ultracompact and Hypercompact H II Regions from 0.7 to 3.6 cm

    CERN Document Server

    Sewilo, M; Kurtz, S; Goss, W M; Hofner, P

    2011-01-01

    We report multi-frequency Very Large Array observations of three massive star formation regions (MSFRs) containing radio continuum components that were identified as broad radio recombination line (RRL) sources and hypercompact (HC) H II region candidates in our previous H92alpha and H76alpha study: G10.96+0.01 (component W), G28.20-0.04 (N), and G34.26+0.15 (B). An additional HC H II region candidate, G45.07+0.13, known to have broad H66alpha and H76alpha lines, small size, high electron density and emission measure, was also included. We observed with high spatial resolution (0.9" to 2.3") the H53alpha, H66alpha, H76alpha, and H92alpha RRLs and the radio continuum at the corresponding wavelengths (0.7 to 3.6 cm). The motivation for these observations was to obtain RRLs over a range of principal quantum states to look for signatures of pressure broadening and macroscopic velocity structure. We find that pressure broadening contributes significantly to the line widths, but it is not the sole cause of the broa...

  6. The VLA 1.4GHz Survey of the Extended Chandra Deep Field South: Second Data Release

    CERN Document Server

    Miller, N A; Fomalont, E B; Kellermann, K I; Mainieri, V; Padovani, P; Rosati, P; Tozzi, P; Vattakunnel, S

    2013-01-01

    Deep radio observations at 1.4GHz for the Extended Chandra Deep Field South were performed in June through September of 2007 and presented in a first data release (Miller et al. 2008). The survey was made using six separate pointings of the Very Large Array (VLA) with over 40 hours of observation per pointing. In the current paper, we improve on the data reduction to produce a second data release (DR2) mosaic image. This DR2 image covers an area of about a third of a square degree and reaches a best rms sensitivity of 6 uJy and has a typical sensitivity of 7.4 uJy per 2.8" by 1.6" beam. We also present a more comprehensive catalog, including sources down to peak flux densities of five or more times the local rms noise along with information on source sizes and relevant pointing data. We discuss in some detail the consideration of whether sources are resolved under the complication of a radio image created as a mosaic of separate pointings each suffering some degree of bandwidth smearing, and the accurate eval...

  7. VCAM-1 and VLA-4 modulate dendritic cell IL-12p40 production in experimental visceral leishmaniasis.

    Directory of Open Access Journals (Sweden)

    Amanda C Stanley

    Full Text Available Vascular cell adhesion molecule-1 (VCAM-1 interacts with its major ligand very late antigen-4 (VLA-4 to mediate cell adhesion and transendothelial migration of leukocytes. We report an important role for VCAM-1/VLA-4 interactions in the generation of immune responses during experimental visceral leishmaniasis caused by Leishmania donovani. Our studies demonstrate that these molecules play no direct role in the recruitment of leukocytes to the infected liver, but instead contribute to IL-12p40-production by splenic CD8(+ dendritic cells (DC. Blockade of VCAM-1/VLA-4 interactions using whole antibody or anti-VCAM-1 Fab' fragments reduced IL-12p40 mRNA accumulation by splenic DC 5 hours after L. donovani infection. This was associated with reduced anti-parasitic CD4(+ T cell activation in the spleen and lowered hepatic IFNgamma, TNF and nitric oxide production by 14 days post infection. Importantly, these effects were associated with enhanced parasite growth in the liver in studies with either anti-VCAM-1 or anti-VLA-4 antibodies. These data indicate a role for VCAM-1 and VLA-4 in DC activation during infectious disease.

  8. A Search for H2CO 6cm Emission toward Young Stellar Objects III: VLA Observations

    CERN Document Server

    Araya, E D; Goss, W M; Linz, H; Kurtz, S; Olmi, L

    2008-01-01

    We report the results of our third survey for formaldehyde (H2CO) 6cm maser emission in the Galaxy. Using the Very Large Array, we detected two new H2CO maser sources (G23.01-0.41 and G25.83-0.18), thus increasing the sample of known H2CO maser regions in the Galaxy to seven. We review the characteristics of the G23.01-0.41 and G25.83-0.18 star forming regions. The H2CO masers in G23.01-0.41 and G25.83-0.18 share several properties with the other known H2CO masers, in particular, emission from rich maser environments and close proximity to very young massive stellar objects.

  9. VLA and Swift XRT Observations of PTF12os in NGC 5806

    Science.gov (United States)

    Stockdale, C. J.; Immler, S.; Horesh, A.; Kasliwal, M.; Ryder, S. D.; Weiler, K. W.; Van Dyk, S. D.; Panagia, N.; Bauer, F. E.; Marcaide, J. M.; Pooley, D.; Sramek, R. A.; Williams, C. L.

    2012-01-01

    We report the detection of radio emission near the position of the type-IIb supernova PTF2012os (ATEL #3881) with the Karl G. Jansky Very Large Array radio telescope in the DnC configuration: A flux density of 0.44 ± 0.05 mJy was measured at 5.02 GHz (wavelength 6.0 cm) on 2012 Jan. 22.42 UT. The measured position of the radio emission of R.A. = 14h59m59.s12, Decl. = +01d53m23s.3, equinox 2000.0 is in good agreement with the measured optical position of (ending digits) R.A.

  10. VLA Observations of Z CMa: The Orientation and Origin of the Thermal Jet

    Directory of Open Access Journals (Sweden)

    P. F. Velázquez

    2001-01-01

    Full Text Available Presentamos observaciones sensitivas y de alta resolución angular ( 0``45 hechas a 6 y 3.5 cm con el Conjunto Muy Grande de Radiotelescopios (Very Large Array hacia el chorro térmico asociado con la estrella joven Z CMa. Hemos encontrado que el ángulo de posición del eje del chorro térmico es coincidente dentro del error con la orientación del chorro óptico y con la orientación del flujo bipolar observado en CO. Las estructuras débiles observadas en radio alrededor de Z CMa (principalmente al este de esta fuente podrán ser el resultado de eyecciones periódicas. Se sabe que Z CMa tiene una compañera infrarroja 0:001 al noroeste. Hemos usado nuestros datos de alta resolución angular ( 0:``2 tomados en la configuración A y la posición astrométrica de Hipparcos para establecer que el chorro se origina en la compañera visible.

  11. SEARCH FOR NEW MICROQUASARS CANDIDATES THROUGH VLA/XMM-NEWTON OBSERVATIONS

    Directory of Open Access Journals (Sweden)

    J. A. Combi

    2009-01-01

    Full Text Available In this work we have developed an improved search strategy based on positional cross-identi cation with very restrictive selection criteria to nd new MQs candidate, using more sensitive modern X-ray data. For such purpose, we made combined use of the radio, infrared, and X-ray properties of the sources, using di erent available catalogs. As a result, we nd 86 sources with positional coincidence in the NVSS/XMM catalogs atgalactic latitudes |b| < 10 . For the fully coincident sources, whenever possible, we analyzed color-color and hardness ratio diagrams and found that at least 3 of them display high-mass X-ray binary characteristics. A preliminary study of one of them is presented.

  12. PAGaN I: Multi-Frequency Polarimetry of AGN Jets with KVN

    CERN Document Server

    Kim, Jae-Young; Sohn, Bong Won; Oh, Junghwan; Park, Jong-Ho; Lee, Sang-Sung; Lee, Taeseok; Kim, Daewon

    2015-01-01

    Active Galactic Nuclei (AGN) with bright radio jets offer the opportunity to study the structure of and physical conditions in relativistic outflows. For such studies, multi-frequency polarimetric very long baseline interferometric (VLBI) observations are important as they directly probe particle densities, magnetic field geometries, and several other parameters. We present results from first-epoch data obtained by the Korean VLBI Network (KVN) within the frame of the Plasma Physics of Active Galactic Nuclei (PAGaN) project. We observed seven radio-bright nearby AGN at frequencies of 22, 43, 86, and 129 GHz in dual polarization mode. Our observations constrain apparent brightness temperatures of jet components and radio cores in our sample to $>10^{8.01}$ K and $>10^{9.86}$ K, respectively. Degrees of linear polarization $m_{L}$ are relatively low overall: less than 10%. This indicates suppression of polarization by strong turbulence in the jets. We found an exceptionally high degree of polarization in a jet ...

  13. A Study of Multi-frequency Polarization Pulse Profiles of Millisecond Pulsars

    CERN Document Server

    Dai, S; Manchester, R N; Kerr, M; Shannon, R M; van Straten, W; Mata, A; Bailes, M; Bhat, N D R; Burke-Spolaor, S; Coles, W A; Johnston, S; Keith, M J; Levin, Y; Oslowski, S; Reardon, D; Ravi, V; Sarkissian, J M; Tiburzi, C; Toomey, L; Wang, H G; Wang, J -B; Wen, L; Xu, R X; Yan, W M; Zhu, X -J

    2015-01-01

    We present high signal-to-noise ratio, multi-frequency polarization pulse profiles for 24 millisecond pulsars that are being observed as part of the Parkes Pulsar Timing Array (PPTA) project. The pulsars are observed in three bands, centred close to 730, 1400 and 3100 MHz, using a dual-band 10 cm/50 cm receiver and the central beam of the 20 cm multibeam receiver. Observations spanning approximately six years have been carefully calibrated and summed to produce high S/N profiles. This allows us to study the individual profile components and in particular how they evolve with frequency. We also identify previously undetected profile features. For many pulsars we show that pulsed emission extends across almost the entire pulse profile. The pulse component widths and component separations follow a complex evolution with frequency; in some cases these parameters increase and in other cases they decrease with increasing frequency. The evolution with frequency of the polarization properties of the profile is also n...

  14. CHILES Con Pol: Probing galaxy evolution, the dark Universe, and cosmic magnetism with a deep 1000 hour Jansky VLA survey

    Science.gov (United States)

    Hales, Christopher A.; Chiles Con Pol Collaboration

    2014-04-01

    We recently started a 1000 hour campaign to observe 0.2 square degrees of the COSMOS field in full polarization continuum at 1.4 GHz with the Jansky VLA, as part of a joint program with the spectral line COSMOS HI Large Extragalactic Survey (CHILES). When complete, we expect our CHILES Continuum Polarization (CHILES Con Pol) survey to reach an unprecedented SKA-era sensitivity of 0.7 uJy per 4 arcsecond FWHM beam. Here we present the key goals of CHILES Con Pol, which are to (i) produce a source catalog of legacy value to the astronomical community, (ii) measure differential source counts in total intensity, linear polarization, and circular polarization in order to constrain the redshift and luminosity distributions of source populations, (iii) perform a novel weak lensing study using radio polarization as an indicator of intrinsic alignment to better study dark energy and dark matter, and (iv) probe the unknown origin of cosmic magnetism by measuring the strength and structure of intergalactic magnetic fields in the filaments of large scale structure. The CHILES Con Pol source catalog will be a useful resource for upcoming wide-field surveys by acting as a training set for machine learning algorithms, which can then be used to identify and classify radio sources in regions lacking deep multiwavelength coverage.

  15. The VLA Nascent Disk and Multiplicity Survey of Perseus Protostars (VANDAM). II. Multiplicity of Protostars in the Perseus Molecular Cloud

    CERN Document Server

    Tobin, John J; Li, Zhi-Yun; Chandler, Claire J; Dunham, Michael M; Segura-Cox, Dominique; Sadavoy, Sarah I; Melis, Carl; Harris, Robert J; Kratter, Kaitlin; Perez, Laura

    2016-01-01

    We present a multiplicity study of all known protostars (94) in the Perseus molecular cloud from a Karl G. Jansky Very Large Array (VLA) survey at Ka-band (8 mm and 1 cm) and C-band (4 cm and 6.6 cm). The observed sample has a bolometric luminosity range between 0.1 L$_{\\odot}$ and $\\sim$33 L$_{\\odot}$, with a median of 0.7 L$_{\\odot}$. This multiplicity study is based on the Ka-band data, having a best resolution of $\\sim$0.065" (15 AU) and separations out to $\\sim$43" (10000 AU) can be probed. The overall multiplicity fraction (MF) is found to be of 0.40$\\pm$0.06 and the companion star fraction (CSF) is 0.71$\\pm$0.06. The MF and CSF of the Class 0 protostars are 0.57$\\pm$0.09 and 1.2$\\pm$0.2, and the MF and CSF of Class I protostars are both 0.23$\\pm$0.08. The distribution of companion separations appears bi-modal, with a peak at $\\sim$75 AU and another peak at $\\sim$3000 AU. Turbulent fragmentation is likely the dominant mechanism on $>$1000 AU scales and disk fragmentation is likely to be the dominant mec...

  16. A new VLA/e-MERLIN limit on central images in the gravitational lens system CLASS B1030+074

    CERN Document Server

    Quinn, Jonathan; Tagore, Amitpal; Biggs, Andrew; Birkinshaw, Mark; Chapman, Scott; De Zotti, Gianfranco; McKean, John; Perez-Fournon, Ismael; Scott, Douglas; Serjeant, Stephen

    2016-01-01

    We present new VLA 22-GHz and e-MERLIN 5-GHz observations of CLASS B1030+074, a two-image strong gravitational lens system whose background source is a compact flat-spectrum radio quasar. In such systems we expect a third image of the background source to form close to the centre of the lensing galaxy. The existence and brightness of such images is important for investigation of the central mass distributions of lensing galaxies, but only one secure detection has been made so far in a galaxy-scale lens system. The noise levels achieved in our new B1030+074 images reach 3 microJy/beam and represent an improvement in central image constraints of nearly an order of magnitude over previous work, with correspondingly better resulting limits on the shape of the central mass profile of the lensing galaxy. Simple models with an isothermal outer power law slope now require either the influence of a central supermassive black hole, or an inner power law slope very close to isothermal, in order to suppress the central i...

  17. Adhesion of Human B Cells to Germinal Centers in Vitro Involves VLA-4 and INCAM-110

    Science.gov (United States)

    Freedman, Arnold S.; Munro, J. Michael; Rice, G. Edgar; Bevilacqua, Michael P.; Morimoto, Chikao; McIntyre, Bradley W.; Rhynhart, Kurt; Pober, Jordan S.; Nadler, Lee M.

    1990-08-01

    Human B lymphocytes localize and differentiate within the microenvironment of lymphoid germinal centers. A frozen section binding assay was developed for the identification of those molecules involved in the adhesive interactions between B cells and lymphoid follicles. Activated human B cells and B cell lines were found to selectively adhere to germinal centers. The VLA-4 molecule on the lymphocyte and the adhesion molecule INCAM-110, expressed on follicular dendritic cells, supported this interaction. This cellular interaction model can be used for the study of how B cells differentiate.

  18. The December 2009 gamma-ray flare of 3C 454.3: the multifrequency campaign

    CERN Document Server

    Pacciani, L; Tavani, M; Fiocchi, M T; Vercellone, S; D'Ammando, F; Sakamoto, T; Pian, E; Raiteri, C M; Villata, M; Sasada, M; Itoh, R; Yamanaka, M; Uemura, M; Striani, E; Fugazza, D; Tiengo, A; Krimm, H A; Stroh, M C; Falcone, A D; Curran, P A; Sadun, A C; Lahteenmaki, A; Tornikoski, M; Aller, H D; Aller, M F; Lin, C S; Larionov, V M; Leto, P; Takalo, L O; Berdyugin, A; Gurwell, M A; Bulgarelli, A; Chen, A W; Donnarumma, I; Giuliani, A; Longo, F; Pucella, G; Argan, A; Caraveo, G Barbiellini P; Cattaneo, P W; Cocco, V; Costa, E; De Paris, G; Del Monte, E; Di Cocco, G; Evangelista, Y; Ferrari, A; Feroci, M; Fiorini, M; Fuschino, F; Galli, M; Gianotti, F; Labanti, C; Lapshov, I; Lazzarotto, F; Lipari, P; Marisaldi, M; Mereghetti, S; Morelli, E; Moretti, E; Morselli, A; Pellizzoni, A; Perotti, F; Piano, G; Picozza, P; Pilia, M; Prest, M; Rapisarda, M; Rappoldi, A; Rubini, A; Sabatini, S; Soffitta, P; Trifoglio, M; Trois, A; Vallazza, E; Zanello, D; Colafrancesco, S; Pittori, C; Verrecchia, F; Santolamazza, P; Lucarelli, F; Giommi, P; Salotti, L

    2010-01-01

    During the month of December, 2009 the blazar 3C 454.3 became the brightest gamma-ray source in the sky, reaching a peak flux F ~2000E-8 ph/cm2/s for E > 100 MeV. Starting in November, 2009 intensive multifrequency campaigns monitored the 3C 454 gamma-ray outburst. Here we report the results of a 2-month campaign involving AGILE, INTEGRAL, Swift/XRT, Swift/BAT, RossiXTE for the high-energy observations, and Swift/UVOT, KANATA, GRT, REM for the near-IR/optical/UV data. The GASP/WEBT provided radio and additional optical data. We detected a long-term active emission phase lasting ~1 month at all wavelengths: in the gamma-ray band, peak emission was reached on December 2-3, 2009. Remarkably, this gamma-ray super-flare was not accompanied by correspondingly intense emission in the optical/UV band that reached a level substantially lower than the previous observations in 2007-2008. The lack of strong simultaneous optical brightening during the super-flare and the determination of the broad-band spectral evolution ...

  19. Multifrequency Studies of the Peculiar Quasar 4C +21.35 During the 2010 Flaring Activity

    CERN Document Server

    Ackermann, M; Allafort, A; Antolini, E; Barbiellini, G; Bastieri, D; Bellazzini, R; Bissaldi, E; Bonamente, E; Bregeon, J; Brigida, M; Bruel, P; Buehler, R; Buson, S; Caliandro, G A; Cameron, R A; Caraveo, P A; Cavazzuti, E; Cecchi, C; Chaves, R C G; Chekhtman, A; Chiang, J; Chiaro, G; Ciprini, S; Claus, R; Cohen-Tanugi, J; Conrad, J; Cutini, S; D'Ammando, F; de Palma, F; Dermer, C D; Silva, E do Couto e; Donato, D; Drell, P S; Favuzzi, C; Finke, J; Focke, W B; Franckowiak, A; Fukazawa, Y; Fusco, P; Gargano, F; Gasparrini, D; Gehrels, N; Giglietto, N; Giordano, F; Giroletti, M; Godfrey, G; Grenier, I A; Guiriec, S; Hayashida, M; Hewitt, J W; Horan, D; Hughes, R E; Iafrate, G; Johnson, A S; Knodlseder, 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; Michelson, P F; Mizuno, T; Monzani, M E; Morselli, A; Moskalenko, I V; Murgia, S; Nemmen, R; Nuss, E; Ohsugi, T; Orienti, M; Orlando, E; Perkins, J S; Pesce-Rollins, M; Piron, F; Pivato, G; Porter, T A; Rainò, S; Razzano, M; Reimer, A; Reimer, O; Sanchez, D A; Schulz, A; Sgrò, C; Siskind, E J; Spandre, G; Spinelli, P; Stawarz, L; Takahashi, H; Takahashi, T; Thayer, J G; Thayer, J B; Thompson, D J; Tinivella, M; Torres, D F; Tosti, G; Troja, E; Usher, T L; Vandenbroucke, J; Vasileiou, V; Vianello, G; Vitale, V; Werner, M; Winer, B L; Wood, D L; Wood, K S; Aleksic, J; Ansoldi, S; Antonelli, L A; Antoranz, P; Babic, A; Bangale, P; de Almeida, U Barres; Barrio, J A; Gonzalez, J Becerra; Bednarek, W; Berger, K; Bernardini, E; Biland, A; Blanch, O; Bock, R K; Bonnefoy, S; Bonnoli, G; Borracci, F; Bretz, T; Carmona, E; Carosi, A; Fidalgo, D Carreto; Colin, P; Colombo, E; Contreras, J L; Cortina, J; Covino, S; Da Vela, P; Dazzi, F; De Angelis, A; De Caneva, G; De Lotto, B; Mendez, C Delgado; Doert, M; Dominguez, A; Prester, D Dominis; Dorner, D; Doro, M; Einecke, S; Eisenacher, D; Elsaesser, D; Farina, E; Ferenc, D; Fonseca, M V; Font, L; Frantzen, K; Fruck, C; Lopez, R J Garcia; Garczarczyk, M; Terrats, D Garrido; Gaug, M; Giavitto, G; Godinovic, N; Munoz, A Gonzalez; Gozzini, S R; Hadasch, D; Herrero, A; Hildebrand, D; Hose, J; Hrupec, D; Idec, W; Kadenius, V; Kellermann, H; Knoetig, M L; Kodani, K; Konno, Y; Krause, J; Kubo, H; Kushida, J; La Barbera, A; Lelas, D; Lewandowska, N; Lindfors, E; Lombardi, S; Lopez, M; Lopez-Coto, R; Lopez-Oramas, A; Lorenz, E; Lozano, I; Makariev, M; Mallot, K; Maneva, G; Mankuzhiyil, N; Mannheim, K; Maraschi, L; Marcote, B; Mariotti, M; Martinez, M; Mazin, D; Menzel, U; Meucci, M; Miranda, J M; Mirzoyan, R; Moralejo, A; Munar-Adrover, P; Nakajima, D; Niedzwiecki, A; Nishijima, K; Nilsson, K; Nowak, N; Orito, R; Overkemping, A; Paiano, S; Palatiello, M; Paneque, D; Paoletti, R; Paredes, J M; Paredes-Fortuny, X; Partini, S; Persic, M; Prada, F; Moroni, P G Prada; Prandini, E; Preziuso, S; Puljak, I; Reinthal, R; Rhode, W; Ribo, M; Rico, J; Garcia, J Rodriguez; Rugamer, S; Saggion, A; Saito, T; Saito, K; Salvati, M; Satalecka, K; Scalzotto, V; Scapin, V; Schultz, C; Schweizer, T; Shore, S N; Sillanpaa, A; Sitarek, J; Snidaric, I; Sobczynska, D; Spanier, F; Stamatescu, V; Stamerra, A; Steinbring, T; Storz, J; Sun, S; Suric, T; Takalo, L; Takami, H; Tavecchio, F; Temnikov, P; Terzic, T; Tescaro, D; Teshima, M; Thaele, J; Tibolla, O; Toyama, T; Treves, A; Vogler, P; Wagner, R M; Zandanel, F; Zanin, R; Aller, M F; Angelakis, E; Blinov, D A; Djorgovski, S G; Drake, A J; Efimova, N V; Gurwell, M A; Homan, D C; Jordan, B; Kopatskaya, E N; Kovalev, Y Y; Kurtanidze, O M; Lahteenmaki, A; Larionov, V M; Lister, M L; Nieppola, E; Nikolashvili, M G; Ros, E; Savolainen, T; Sigua, L A; Tornikoski, M; .,

    2014-01-01

    The discovery of rapidly variable Very High Energy (VHE; E > 100 GeV) gamma-ray emission from 4C +21.35 (PKS 1222+216) by MAGIC on 2010 June 17, triggered by the high activity detected by the Fermi Large Area Telescope (LAT) in high energy (HE; E > 100 MeV) gamma-rays, poses intriguing questions on the location of the gamma-ray emitting region in this flat spectrum radio quasar (FSRQ). We present multifrequency data of 4C +21.35 collected from centimeter to VHE during 2010 to investigate the properties of this source and discuss a possible emission model. The first hint of detection at VHE was observed by MAGIC on 2010 May 3, soon after a gamma-ray flare detected by Fermi-LAT that peaked on April 29. The same emission mechanism may therefore be responsible for both the HE and VHE emission during the 2010 flaring episodes. Two optical peaks were detected on 2010 April 20 and June 30, close in time but not simultaneous with the two gamma-ray peaks, while no clear connection was observed between the X-ray an gam...

  20. The Detection of 3He+ in a Planetary Nebula Using the VLA

    CERN Document Server

    Balser, D S; Bania, T M; Rood, R T; Balser, Dana S.; Rood, Robert T.

    2006-01-01

    We used the VLA to search for 3He+ emission from two Galactic planetary nebulae (PNe): NGC6572 and J320}. Standard stellar models predict that the 3He/H abundance ratios for PNe should be 1-2 orders of magnitude higher than the primordial value (3He/H ~ 1e-5 by number) determined from Galactic HII region abundances and confirmed by WMAP cosmic microwave background results. Chemical evolution models suggest that fewer than 5% of all PNe enrich the interstellar medium (ISM) with 3He at the level of standard stellar models. Our target PNe are therefore anomalous in that they were selected from a sample deliberately biased to contain objects with properties that maximized the likelihood of a 3He detection by the VLA. We have detected the 8.665 GHz hyperfine 3He+ transition in J320 at the 4 sigma level. The 3He/H abundance ratio is 1.9e-3 with roughly a factor of two uncertainty. For NGC 6572 we find an upper limit of 3He/H <= 1e-3. This detection of 3He in J320 makes it the second PN known to have an anomalous...

  1. The discovery and potential of N-sulfonylated dipeptide VLA-4 antagonists.

    Science.gov (United States)

    Hagmann, William K

    2004-01-01

    Through a directed screening of a combinatorial library containing carboxylic acids, N-sulfonylated dipeptides were identified as leads in the Merck Research Laboratories VLA-4 antagonist program. Further optimization quickly identified subnanomolar compounds with varying degrees of specificity over the related integrin alpha4beta7. Various metabolic liabilities were identified and addressed. However, the pharmacokinetic properties of nearly all compounds in this class were unacceptable. Other leads were identified with apparent good oral bioavailability, but these were generally associated with very high plasma protein binding and a loss of potency. The mechanism of high plasma clearance was identified in the rat as the organic acid transporter, mrp-2. Compounds were identified that were not substrates of mrp-2, but they still suffered from poor oral bioavailability. Finally, a shift in strategy to identifying VLA-4 antagonists that would be suitable as candidates for inhalation therapy resulted in the preparation of compounds with exception tight binding properties. These compounds were superior to BIO-1211 in the ovalbumin-sensitized mouse model of eosinophil trafficking to the lung. One particular compound had an exceptionally long off-rate with a KD < or = 2 pM. The evolution of the structure activity relationships in our laboratories and strategies for improving potencies and pharmacokinetic profiles are the subject of this review.

  2. Long-term multi-frequency monitoring of microquasars

    CERN Document Server

    Trushkin, Sergei A; Bursov, Nikolaj N

    2008-01-01

    We discuss the results of the radio studies of the X-ray binaries with relativistic jets. We carried out a multi-frequency (1-30 GHz) daily monitoring of the radio flux variability of the microquasars SS433, GRS1915+105, and Cyg X-3 with the RATAN-600 radio telescope during the recent sets from 1 November 2006 to 31 August 2008. From December 2005 radio emission of Cyg X-3 after four years relatively quiescent levels (100-200 mJy) dropped down to $\\sim$20 mJy, and then we detected a lot of bright radio flaring events (1-20 Jy) followed the very variable (from 0 to 0.5 crabs) 15-50 keV X-ray emission, which was monitored in the Swift/BAT ASM program. Again from December 2007 to March 2008 we have daily measured almost quiescent fluxes from Cyg X-3 but in April 2008 a bright radio flare with clear synchrotron self-absorption was detected. We detected several bright short-term flares from GRS 1915+105 which could be associated with active soft X-ray events. In intense measurements of SS433 fluxes (often mutually...

  3. Multi-frequency metal detector in high mineralization

    Science.gov (United States)

    Stamatescu, Laurence; Harmer, Gregory; Nesper, Oliver; Bordean, Dorin; Tkachenko, Yuri

    2009-05-01

    The successful detection and discrimination of mines is very difficult in areas of high soil mineralization. In these areas, the soil can make a significant contribution to the received signal that causes false detections or masks the true mine response. To address this problem, Minelab has developed a continuous wave (CW) multi-frequency digital detector (MFDD). It transmits four frequencies (between 1 kHz and 45 kHz) and each has a high dynamic range that approaches 120 dB. The mineralized soil with high magnetic susceptibility affects the characteristics of the sensor-head, in particular the inductance of the transmitting and receiving windings. These in turn affect the front-end electronics and measuring circuits and can lead to excessive ground noise that makes detection difficult. Minelab has modeled the effect that the soil has on the sensor-head and developed methods to monitor these effects. By having a well calibrated detector, which is demonstrated by the tight agreement of raw ground signals with theoretical ground models, the tasks of ground balance and discrimination become much more reliable and robust.

  4. Multifrequency OFDM SAR in Presence of Deception Jamming

    Directory of Open Access Journals (Sweden)

    Schuerger Jonathan

    2010-01-01

    Full Text Available Orthogonal frequency division multiplexing (OFDM is considered in this paper from the perspective of usage in imaging radar scenarios with deception jamming. OFDM radar signals are inherently multifrequency waveforms, composed of a number of subbands which are orthogonal to each other. While being employed extensively in communications, OFDM has not found comparatively wide use in radar, and, particularly, in synthetic aperture radar (SAR applications. In this paper, we aim to show the advantages of OFDM-coded radar signals with random subband composition when used in deception jamming scenarios. Two approaches to create a radar signal by the jammer are considered: instantaneous frequency (IF estimator and digital-RF-memory- (DRFM- based reproducer. In both cases, the jammer aims to create a copy of a valid target image via resending the radar signal at prescribed time intervals. Jammer signals are derived and used in SAR simulations with three types of signal models: OFDM, linear frequency modulated (LFM, and frequency-hopped (FH. Presented results include simulated peak side lobe (PSL and peak cross-correlation values for random OFDM signals, as well as simulated SAR imagery with IF and DRFM jammers'-induced false targets.

  5. Probing magnetic fields with multi-frequency polarized synchrotron emission

    CERN Document Server

    Thiebaut, Jerome; Pichon, Christophe; Thiébaut, Eric

    2009-01-01

    We investigate the problem of probing the local spatial structure of the magnetic field of the interstellar medium using multi-frequency polarized maps of the synchrotron emission at radio wavelengths. We focus in this paper on the three-dimensional reconstruction of the largest scales of the magnetic field, relying on the internal depolarization (due to differential Faraday rotation) of the emitting medium as a function of electromagnetic frequency. We argue that multi-band spectroscopy in the radio wavelengths, developed in the context of high-redshift extragalactic HI lines, can be a very useful probe of the 3D magnetic field structure of our Galaxy when combined with a Maximum A Posteriori reconstruction technique. When starting from a fair approximation of the magnetic field, we are able to recover the true one by using a linearized version of the corresponding inverse problem. The spectral analysis of this problem allows us to specify the best sampling strategy in electromagnetic frequency and predicts ...

  6. Multifrequency seismic detectability of seasonal thermoclines assessed from ARGO data

    Science.gov (United States)

    Ker, S.; Le Gonidec, Y.; Marié, L.

    2016-08-01

    Seismic oceanography is a developing research topic where new acoustic methods allow high-resolution teledetection of the thermohaline structure of the ocean. First implementations to study the Ocean Surface Boundary Layer have recently been achieved but remain very challenging due to the weakness and shallowness of such seismic reflectors. In this article, we develop a multifrequency seismic analysis of hydrographic data sets collected in a seasonally stratified midlatitude shelf by ARGO network floats to assess the detectability issue of shallow thermoclines. This analysis, for which sensitivity to the data reduction scheme used by ARGO floats for the transmission of the profiles is discussed, allows characterizing both the depth location and the frequency dependency of the dominant reflective feature of such complex structures. This approach provides the first statistical distribution of the range of variability of the frequency-dependent seismic reflection amplitude of the midlatitude seasonal thermoclines. We introduce a new parameter to quantify the overall capability of a multichannel seismic setup, including the source strength, the fold, and the ambient noise level, to detect shallow thermoclines. Seismic source signals are approximated by Ricker wavelets, providing quantitative guidelines to help in the design of seismic experiments targeting such oceanic reflectors. For shallow midlatitude seasonal thermoclines, we show that the detectability is optimal for seismic peak frequencies between 200 and 400 Hz: this means that airgun and Sparker sources are not well suited and that significant improvements of source devices will be necessary before seismic imaging of OSBL structures can be reliably attempted.

  7. What do we understand from multi-frequency monitoring of microquasars?

    CERN Document Server

    Trushkin, S A; Nizhelskij, N A; Majorova, E K; Voitsik, P A

    2006-01-01

    We discuss the results of the monitoring programs of the X-ray binaries with relativistic jets studies. We carried out a multi-frequency (1-30 GHz) daily monitoring of the radio flux variability of the microquasars SS433, GRS1915+105, V4641 Sgr and Cyg X-3 with RATAN-600 radio telescope during the recent sets in 2002-2006. We detected a lot of bright short-time flares from GRS 1915+105 which could be associated with active X-ray events. In 2004 we have detected two flares from V4641 Sgr, which followed after recurrent X-ray activity of the transient. From September 2005 to May 2006 and then in July we have daily measured flux densities from Cyg X-3. In January 2006 we detected a drop down of its quiescent fluxes (from 100 to ~20 mJy), then the 1Jy-flare was detected on 2 February 2006 after 18 days of quenched radio emission. The daily spectra of the flare in the maximum were flat from 2 to 110 GHz, using the quasi-simultaneous observations at 110 GHz with the RT45m telescope and the NMA millimeter array of t...

  8. Multifrequency study of a double-double radio galaxy J1706+4340

    CERN Document Server

    Marecki, A; Machalski, J

    2016-01-01

    We report the outcome of multifrequency radio observations of a double-double radio source J1706+4340 carried out with the Very Large Array and Giant Metrewave Radio Telescope. After supplementing our own data with those available in the literature, we collected a considerable set of radio measurements covering the range from 74 to 8460 MHz. This has enabled us to perform a comprehensive review of physical properties of the source and its dynamical evolution analysis. In particular, we found that, while the age of the large-scale outer lobes is in the range 260-300 Myr, the renewal of the jet activity, which is directly responsible for the double-double structure, took place only about 12 Myr ago after about 27-Myr long period of quiescence. Another important property of J1706+4340 we found is that the injection spectral indices and the jet powers for the inner and the outer doubles are very similar. This implies that it is the spin of the supermassive black hole rather than e.g. an instability of the accreti...

  9. The Sedentary Multi-Frequency Survey; 1, Statistical Identification and Cosmological Properties of HBL BL Lacs

    CERN Document Server

    Giommi, P; Padovani, P

    1999-01-01

    We have assembled a multi-frequency database by cross-correlating the NVSS catalog of radio sources with the RASSBSC list of soft X-ray sources, obtaining optical magnitude estimates from the Palomar and UK Schmidt surveys as provided by the APM and COSMOS on-line services. By exploiting the nearly unique broad-band properties of High-Energy Peaked (HBL) BL Lacs we have statistically identified a sample of 218 objects that is expected to include about 85% of BL Lacs and that is therefore several times larger than all other published samples of HBLs. Using a subset (155 objects) that is radio flux limited and statistically well-defined we have derived the \\vovm distribution and the LogN-LogS of extreme HBLs (fx/fr >= 3E-10 erg/cm2/s/Jansky) down to 3.5 mJy. We find that the LogN-LogS flattens around 20 mJy and that = 0.42 +/- 0.02. This extends to the radio band earlier results, based on much smaller X-ray selected samples, about the anomalous cosmological observational properties of HBL BL Lacs. A comparison...

  10. A frequency based constraint for a multi-frequency linear sampling method

    Science.gov (United States)

    Alqadah, H. F.; Valdivia, N.

    2013-09-01

    The linear sampling method (LSM) has become a well established non-iterative technique for a variety of inverse scattering problems. The method offers a number of advantages over competing inverse scattering methods, mainly it is based on solving a linear problem while being able to account for multi-path effects. Unfortunately under the current framework the method is only effective when using a large number of multi-static data, and therefore may be impractical for many imaging applications. While primarily developed under a single frequency framework, recently the extension of the method to multi-banded data sets has been considered. It is known in general that the availability of multi-frequency data should compensate for reduced spatial diversity, but it is not clear how this can be accomplished for the LSM. In this work we take a step in this direction by considering a frequency based partial variation approach. We first establish that on bands absent of any corresponding Dirichlet eigenvalues the Herglotz density exhibits bounded variation. We then consider a regularization method incorporating this prior knowledge. The proposed approach exhibited a good estimate of the unknown Dirichlet eigenvalues of the obstacle in question when using reduced data. This observation also correlated with higher quality 3D reconstructions.

  11. Development of high-pressure, high-field and multifrequency electron spin resonance system.

    Science.gov (United States)

    Sakurai, T; Taketani, A; Tomita, T; Okubo, S; Ohta, H; Uwatoko, Y

    2007-06-01

    The electron spin resonance (ESR) system which covers the magnetic field region up to 16 T, the quasicontinuous frequency region from 60 to 700 GHz, the temperature region from 1.8 to 4.2 K, and the hydrostatic pressure region up to 1.1 GPa has been developed. This is the first pulsed high-field and multifrequency ESR system with the pressure region over 1 GPa as far as we know. Transmission ESR spectra under hydrostatic pressure can be obtained by combining a piston-cylinder-type pressure cell and the pulsed magnetic field ESR apparatus. The pressure cell consists of a NiCrAl cylinder and sapphire or zirconia inner parts. The use of sapphire or zirconia as inner parts enables us to observe ESR under pressure because these inner parts have high transmittance for the electromagnetic wave with millimeter and submillimeter wavelengths. We have successfully applied this system for the pressure dependence measurements of an isolated spin system NiSnCl(6)6H(2)O up to 1.1 GPa. It was found that the single ion anisotropy parameter D of this compound strongly depends on pressure. The parameter D is approximately proportional to the pressure up to 0.75 GPa, and the relation between D and the pressure can be used for the pressure calibration of this high-field and high-pressure ESR system.

  12. A Multi-Frequency Wide-Swath Spaceborne Cloud and Precipitation Imaging Radar

    Science.gov (United States)

    Li, Lihua; Racette, Paul; Heymsfield, Gary; McLinden, Matthew; Venkatesh, Vijay; Coon, Michael; Perrine, Martin; Park, Richard; Cooley, Michael; Stenger, Pete; hide

    2016-01-01

    Microwave and millimeter-wave radars have proven their effectiveness in cloud and precipitation observations. The NASA Earth Science Decadal Survey (DS) Aerosol, Cloud and Ecosystems (ACE) mission calls for a dual-frequency cloud radar (W band 94 GHz and Ka-band 35 GHz) for global measurements of cloud microphysical properties. Recently, there have been discussions of utilizing a tri-frequency (KuKaW-band) radar for a combined ACE and Global Precipitation Measurement (GPM) follow-on mission that has evolved into the Cloud and Precipitation Process Mission (CaPPM) concept. In this presentation we will give an overview of the technology development efforts at the NASA Goddard Space Flight Center (GSFC) and at Northrop Grumman Electronic Systems (NGES) through projects funded by the NASA Earth Science Technology Office (ESTO) Instrument Incubator Program (IIP). Our primary objective of this research is to advance the key enabling technologies for a tri-frequency (KuKaW-band) shared-aperture spaceborne imaging radar to provide unprecedented, simultaneous multi-frequency measurements that will enhance understanding of the effects of clouds and precipitation and their interaction on Earth climate change. Research effort has been focused on concept design and trade studies of the tri-frequency radar; investigating architectures that provide tri-band shared-aperture capability; advancing the development of the Ka band active electronically scanned array (AESA) transmitreceive (TR) module, and development of the advanced radar backend electronics.

  13. Evaluation of multifrequency range imaging technique implemented on the Chung-Li VHF atmospheric radar

    Science.gov (United States)

    Chen, Jenn-Shyong; Tsai, Shih-Chiao; Su, Ching-Lun; Chu, Yen-Hsyang

    2016-05-01

    The multifrequency range imaging technique (RIM) has been implemented on the Chung-Li VHF array radar since 2008 after its renovation. This study made a more complete examination and evaluation of the RIM technique to facilitate the performance of the radar for atmospheric studies. RIM experiments with various radar parameters such as pulse length, pulse shape, receiver bandwidth, transmitter frequency set, and so on were conducted. The radar data employed for the study were collected from 2008 to 2013. It has been shown that two factors, the range/time delay of the signal traveling in the media and the standard deviation of Gaussian-shaped range-weighting function, play crucial roles in ameliorating the RIM-produced brightness (or power distribution); the two factors are associated with some radar parameters and system characteristics. The range/time delay of the signal was found to increase with time; moreover, it was slightly different for the echoes from the atmosphere with and without the presence of significant precipitation. A procedure of point-by-point correction of range/time delay was thus executed for the presence of precipitation to minimize the bogus brightness discontinuity at range gate boundaries. With the RIM technique, the Chung-Li VHF radar demonstrates its first successful observation of double-layer structures as well as their temporal and spatial variations with time.

  14. Multifrequency magnetic resonance elastography of the brain reveals tissue degeneration in neuromyelitis optica spectrum disorder

    Energy Technology Data Exchange (ETDEWEB)

    Streitberger, Kaspar-Josche [Charite - Universitaetsmedizin Berlin, Department of Radiology, Berlin (Germany); Charite - Universitaetsmedizin Berlin, Department of Neurology with Experimental Neurology, Berlin (Germany); Fehlner, Andreas; Sack, Ingolf [Charite - Universitaetsmedizin Berlin, Department of Radiology, Berlin (Germany); Pache, Florence [Charite - Universitaetsmedizin Berlin, Department of Neurology with Experimental Neurology, Berlin (Germany); Charite - Universitaetsmedizin Berlin, NeuroCure Clinical Research Center, Berlin (Germany); Lacheta, Anna; Papazoglou, Sebastian; Brandt, Alexander [Charite - Universitaetsmedizin Berlin, NeuroCure Clinical Research Center, Berlin (Germany); Bellmann-Strobl, Judith [Max Delbrueck Center for Molecular Medicine and Charite - Universitaetsmedizin Berlin, Experimental and Clinical Research Center, Berlin (Germany); Ruprecht, Klemens [Charite - Universitaetsmedizin Berlin, Department of Neurology with Experimental Neurology, Berlin (Germany); Braun, Juergen [Charite - Universitaetsmedizin Berlin, Institute of Medical Informatics, Berlin (Germany); Paul, Friedemann [Charite - Universitaetsmedizin Berlin, Department of Neurology with Experimental Neurology, Berlin (Germany); Charite - Universitaetsmedizin Berlin, NeuroCure Clinical Research Center, Berlin (Germany); Max Delbrueck Center for Molecular Medicine and Charite - Universitaetsmedizin Berlin, Experimental and Clinical Research Center, Berlin (Germany); Wuerfel, Jens [Charite - Universitaetsmedizin Berlin, NeuroCure Clinical Research Center, Berlin (Germany); Max Delbrueck Center for Molecular Medicine and Charite - Universitaetsmedizin Berlin, Experimental and Clinical Research Center, Berlin (Germany); Medical Image Analysis Center (MIAC AG), Basel (Switzerland)

    2017-05-15

    Application of multifrequency magnetic resonance elastography (MMRE) of the brain parenchyma in patients with neuromyelitis optica spectrum disorder (NMOSD) compared to age matched healthy controls (HC). 15 NMOSD patients and 17 age- and gender-matched HC were examined using MMRE. Two three-dimensional viscoelastic parameter maps, the magnitude G* and phase angle φ of the complex shear modulus were reconstructed by simultaneous inversion of full wave-field data in 1.9-mm isotropic resolution at 7 harmonic drive frequencies from 30 to 60 Hz. In NMOSD patients, a significant reduction of G* was observed within the white matter fraction (p = 0.017), predominantly within the thalamic regions (p = 0.003), compared to HC. These parameters exceeded the reduction in brain volume measured in patients versus HC (p = 0.02 whole-brain volume reduction). Volumetric differences in white matter fraction and the thalami were not detectable between patients and HC. However, phase angle φ was decreased in patients within the white matter (p = 0.03) and both thalamic regions (p = 0.044). MMRE reveals global tissue degeneration with accelerated softening of the brain parenchyma in patients with NMOSD. The predominant reduction of stiffness is found within the thalamic region and related white matter tracts, presumably reflecting Wallerian degeneration. (orig.)

  15. The Double Pulsar Eclipses I: Phenomenology and Multi-frequency Analysis

    CERN Document Server

    Breton, R P; McLaughlin, M A; Lyutikov, M; Kramer, M; Stairs, I H; Ransom, S M; Ferdman, R D; Camilo, F; Possenti, A

    2012-01-01

    The double pulsar PSR J0737-3039A/B displays short, 30 s eclipses that arise around conjunction when the radio waves emitted by pulsar A are absorbed as they propagate through the magnetosphere of its companion pulsar B. These eclipses offer a unique opportunity to probe directly the magnetospheric structure and the plasma properties of pulsar B. We have performed a comprehensive analysis of the eclipse phenomenology using multi-frequency radio observations obtained with the Green Bank Telescope. We have characterized the periodic flux modulations previously discovered at 820 MHz by McLaughlin et al., and investigated the radio frequency dependence of the duration and depth of the eclipses. Based on their weak radio frequency evolution, we conclude that the plasma in pulsar B's magnetosphere requires a large multiplicity factor (~ 10^5). We also found that, as expected, flux modulations are present at all radio frequencies in which eclipses can be detected. Their complex behavior is consistent with the confin...

  16. Information compression and speckle reduction for multifrequency polarimetric SAR images based on kernel PCA

    Institute of Scientific and Technical Information of China (English)

    Li Ying; Lei Xiaogang; Bai Bendu; Zhang Yanning

    2008-01-01

    Multifrequency polarimetric SAR imagery provides a very convenient approach for signal processing and acquisition of radar image. However, the amount of information is scattered in several images, and redundancies exist between different bands and polarizations. Similar to signal-polarimetric SAR image, multifrequency polarimetric SAR image is corrupted with speckle noise at the same time. A method of information compression and speckle reduction for multifrequency polarimetric SAR imagery is presented based on kernel principal component analysis (KPCA). KPCA is a nonlinear generalization of the linear principal component analysis using the kernel trick. The NASA/JPL polarimetric SAR imagery of P, L, and C bands quadpolarizations is used for illustration. The experimental results show that KPCA has better capability in information compression and speckle reduction as compared with linear PCA.

  17. 2WHSP: A multi-frequency selected catalog of VHE gamma-ray blazars and blazar candidates

    Science.gov (United States)

    Chang, Yu Lin; Arsioli, Bruno; Giommi, Paolo; Padovani, Paolo

    2016-08-01

    High Synchrotron Peaked Blazars (HSPs) are extremely important for VHE astronomy. We built the largest existing catalog of High Synchrotron Blazars (2WHSP) based on multi-frequency data. The catalog is an extension of the 1WHSP list. We compared several general properties of HSPs such as the synchrotron peak, the redshift and IR the color-color diagram. We also built the logN-logS for the sources, trying to see the evolution and the deficiency of the catalog. The catalog will provide a unique sample of targets for VHE observations in future since the HSPs are the dominant extra-Galactic sources in VHE sky. This might help find more VHE sources later. In the future, we will use this catalog to estimate other VHE properties of HSPs.

  18. Endothelium adhesion molecules ICAM-1, ICAM-2, VCAM-1 and VLA-4 expression in leprosy.

    Science.gov (United States)

    de Sousa, Juarez; Sousa Aarão, Tinara Leila; Rodrigues de Sousa, Jorge; Hirai, Kelly Emi; Silva, Luciana Mota; Dias, Leonidas Braga; Oliveira Carneiro, Francisca Regina; Fuzii, Hellen Thais; Quaresma, Juarez Antonio Simões

    2017-03-01

    Leprosy triggers a complex relationship between the pathogen and host immune response. Endothelium plays an important role in this immune response by directly influencing cell migration to infected tissues. The objective of this work is to investigate the possible role of endothelium in M. leprae infection, correlating the characteristics of endothelial markers with the expression pattern of cytokines. Thirty-six skin biopsy samples were cut into 5-μm thick sections and stained with hematoxylin-eosin and Ziehl-Neelsen for morphological analysis and then submitted to immunohistochemical analysis using monoclonal antibodies against ICAM-1, ICAM-2, VCAM-1, and VLA-4. Immunostaining for ICAM-1 showed a significantly larger number of stained endothelial cells in the tuberculoid leprosy (9.92 ± 1.11 cells/mm(2)) when compared to lepromatous samples (5.87 ± 1.01 cells/mm(2)) and ICAM-2 revealed no significant difference in the number of endothelial cells expressing this marker between the tuberculoid (13.21 ± 1.27 cells/mm(2)) and lepromatous leprosy (14.3 ± 1.02 cells/mm(2)). VCAM-1-immunostained showed 18.28 ± 1.46/mm(2) cells in tuberculoid leprosy and 10.67 ± 1.25 cells/mm(2) in the lepromatous leprosy. VLA-4 exhibited 22.46 ± 1.38 cells/mm(2) in the tuberculoid leprosy 16.04 ± 1.56 cells/mm(2) in the lepromatous leprosy. Samples with characteristics of the tuberculoid leprosy exhibited a larger number of cells stained with ICAM-1, VCAM-1 and VLA-4, demonstrating the importance of these molecules in the migration and selection of cells that reach the inflamed tissue. Copyright © 2017 Elsevier Ltd. All rights reserved.

  19. Multi-Frequency Monitoring of the Flat Spectrum Radio Quasar PKS 1222+216 in 2008–2015

    Directory of Open Access Journals (Sweden)

    Ivan Troitskiy

    2016-11-01

    Full Text Available We analyze the broadband activity of the flat spectrum radio quasar PKS 1222+216 from 2008 to 2015 using multi-frequency monitoring which involves γ-ray data from the Fermi Large Area Telescope, total intensity and linear polarization observations from different optical telescopes in R band, and imaging of the inner jet structure with the Very Long Baseline Array (VLBA at 43 GHz. During the observations, the source showed several dramatic flares at γ rays and optical bands, with the rising branch of a γ-ray flare accompanied by a rapid rotation of the polarization position angle (EVPA, a fast increase of the degree of polarization in the optical band, brightening of the VLBI core, and appearance of a new superluminal component in the parsec-scale jet. The rapid variability of the optical linear polarization may be explained by a strong turbulence in the jet plasma. We find a correlation between the γ rays, optical R band, and 43 GHz variability on a long-term scale (months and years, and a good general alignment between EVPAs in R band and at 43 GHz, while the correlation between short-term variations (days and weeks is weaker. Synchronous activity across the bands supports the idea that the emission regions responsible for the γ-ray and optical flares are co-spatial and located in the vicinity of the mm-wave core of the parsec-scale jet. However, these connections do not completely explain the challenging behaviour of PKS 1222+216, since there are some γ-ray flares which are not accompanied by jet events, and vice versa. We need a continuation of multi-frequency monitoring along with high resolution imaging of the parsec-scale jet to understand in detail the origin of high energy emission in blazars.

  20. The status of the QUIJOTE multi-frequency instrument

    Science.gov (United States)

    Hoyland, R. J.; Aguiar-González, M.; Aja, B.; Ariño, J.; Artal, E.; Barreiro, R. B.; Blackhurst, E. J.; Cagigas, J.; Cano de Diego, J. L.; Casas, F. J.; Davis, R. J.; Dickinson, C.; Arriaga, B. E.; Fernandez-Cobos, R.; de la Fuente, L.; Génova-Santos, R.; Gómez, A.; Gomez, C.; Gómez-Reñasco, F.; Grainge, K.; Harper, S.; Herran, D.; Herreros, J. M.; Herrera, G. A.; Hobson, M. P.; Lasenby, A. N.; Lopez-Caniego, M.; López-Caraballo, C.; Maffei, B.; Martinez-Gonzalez, E.; McCulloch, M.; Melhuish, S.; Mediavilla, A.; Murga, G.; Ortiz, D.; Piccirillo, L.; Pisano, G.; Rebolo-López, R.; Rubiño-Martin, J. A.; Ruiz, J. Luis; Sanchez de la Rosa, V.; Sanquirce, R.; Vega-Moreno, A.; Vielva, P.; Viera-Curbelo, T.; Villa, E.; Vizcargüenaga, A.; Watson, R. A.

    2012-09-01

    The QUIJOTE-CMB project has been described in previous publications. Here we present the current status of the QUIJOTE multi-frequency instrument (MFI) with five separate polarimeters (providing 5 independent sky pixels): two which operate at 10-14 GHz, two which operate at 16-20 GHz, and a central polarimeter at 30 GHz. The optical arrangement includes 5 conical corrugated feedhorns staring into a dual reflector crossed-draconian system, which provides optimal cross-polarization properties (designed to be < -35 dB) and symmetric beams. Each horn feeds a novel cryogenic on-axis rotating polar modulator which can rotate at a speed of up to 1 Hz. The science driver for this first instrument is the characterization of the galactic emission. The polarimeters use the polar modulator to derive linear polar parameters Q, U and I and switch out various systematics. The detection system provides optimum sensitivity through 2 correlated and 2 total power channels. The system is calibrated using bright polarized celestial sources and through a secondary calibration source and antenna. The acquisition system, telescope control and housekeeping are all linked through a real-time gigabit Ethernet network. All communication, power and helium gas are passed through a central rotary joint. The time stamp is synchronized to a GPS time signal. The acquisition software is based on PLCs written in Beckhoffs TwinCat and ethercat. The user interface is written in LABVIEW. The status of the QUIJOTE MFI will be presented including pre-commissioning results and laboratory testing.

  1. VLA Detection of the Exciting Sources of the HH 288 and HHL59 Outflows

    Directory of Open Access Journals (Sweden)

    Mónica Rodríguez

    2002-01-01

    Full Text Available Presentamos observaciones hechas con el VLA a 3.6 cm hacia tres campos conteniendo flujos moleculares, incluyendo a la región de HHL59, cuyo flujo molecular en CO se reporta en este artículo. Detectamos candidatos para las fuentes excitadoras de los flujos moleculares en los tres campos observados: L1287, HH 288 y HHL59. La fuente excitadora de L1287 se ha reportado anteriormente, pero aquellas hacia HH 288 y HHL59 se presentan aquí por vez primera. Discutimos los parámetros de estas fuentes, así como su relación con fuentes detectadas a otras longitudes de onda.

  2. The environment of radio sources in the VLA-COSMOS Survey field

    CERN Document Server

    Malavasi, Nicola; Ciliegi, Paolo; Ilbert, Olivier; Pozzetti, Lucia; Zucca, Elena

    2016-01-01

    This work studies the correlation among environmental density and radio AGN presence up to $z = 2$. Using data from the photometric COSMOS survey and its radio 1.4 GHz follow-up (VLA-COSMOS), a sample of radio AGNs has been defined. The environment was studied using the richness distributions inside a parallelepiped with base side of 1 Mpc and height proportional to the photometric redshift precision. Radio AGNs are found to be always located in environments significantly richer than those around galaxies with no radio emission. Moreover, a distinction based on radio AGN power shows that the significance of the environmental effect is only maintained for low-power radio sources. The results of this work show that denser environments play a significant role in enhancing the probability that a galaxy hosts a radio AGN and, in particular, low-power ones.

  3. THE DOUBLE PULSAR ECLIPSES. I. PHENOMENOLOGY AND MULTI-FREQUENCY ANALYSIS

    Energy Technology Data Exchange (ETDEWEB)

    Breton, R. P. [Department of Astronomy and Astrophysics, University of Toronto, Toronto, ON M5S 3H4 (Canada); Kaspi, V. M. [Department of Physics, McGill University, Montreal, QC H3A 2T8 (Canada); McLaughlin, M. A. [Department of Physics, West Virginia University, Morgantown, WV 26506 (United States); Lyutikov, M. [Department of Physics, Purdue University, West Lafayette, IN 47907 (United States); Kramer, M. [Max Planck Institut fuer Radioastronomie, Auf dem Huegel 69, 53121 Bonn (Germany); Stairs, I. H. [Department of Physics and Astronomy, University of British Columbia, Vancouver, BC V6T 1Z1 (Canada); Ransom, S. M. [National Radio Astronomy Observatory, Charlottesville, VA 22903 (United States); Ferdman, R. D. [University of Manchester, Jodrell Bank Centre for Astrophysics, Alan Turing Building, Manchester, M13 9PL (United Kingdom); Camilo, F. [Columbia University, New York, NY 10027 (United States); Possenti, A., E-mail: breton@astro.utoronto.ca [INAF-Osservatorio Astronomico di Cagliari, Poggio dei Pini, strada 54, I-09012 Capoterra (Italy)

    2012-03-10

    The double pulsar PSR J0737-3039A/B displays short, 30 s eclipses that arise around conjunction when the radio waves emitted by pulsar A are absorbed as they propagate through the magnetosphere of its companion pulsar B. These eclipses offer a unique opportunity to directly probe the magnetospheric structure and the plasma properties of pulsar B. We have performed a comprehensive analysis of the eclipse phenomenology using multi-frequency radio observations obtained with the Green Bank Telescope. We have characterized the periodic flux modulations previously discovered at 820 MHz by McLaughlin et al. and investigated the radio frequency dependence of the duration and depth of the eclipses. Based on their weak radio frequency evolution, we conclude that the plasma in pulsar B's magnetosphere requires a large multiplicity factor ({approx}10{sup 5}). We also found that, as expected, flux modulations are present at all radio frequencies in which eclipses can be detected. Their complex behavior is consistent with the confinement of the absorbing plasma in the dipolar magnetic field of pulsar B as suggested by Lyutikov and Thompson and such a geometric connection explains that the observed periodicity is harmonically related to pulsar B's spin frequency. We observe that the eclipses require a sharp transition region beyond which the plasma density drops off abruptly. Such a region defines a plasmasphere that would be well inside the magnetospheric boundary of an undisturbed pulsar. It is also two times smaller than the expected standoff radius calculated using the balance of the wind pressure from pulsar A and the nominally estimated magnetic pressure of pulsar B.

  4. In multiple myeloma, only a single stage of neoplastic plasma cell differentiation can be identified by VLA-5 and CD45 expression.

    Science.gov (United States)

    Rawstron, A C; Barrans, S L; Blythe, D; English, A; Richards, S J; Fenton, J A; Davies, F E; Child, J A; Jack, A S; Morgan, G J

    2001-06-01

    The nature of the proliferating fraction in myeloma is still not known and understanding the characteristics of this fraction is central to the development of effective novel therapies. However, myeloma plasma cells typically show a very low rate of proliferation and this complicates accurate analysis. Although the level of CD45 and/or VLA-5 has been reported to identify proliferating 'precursor' plasma cells, there are discrepancies between these studies. We have therefore used a rigorous sequential gating strategy to simultaneously analyse cycle status and immunophenotype with respect to CD45, VLA-5 and a range of other integrin molecules. In 11 presentation myeloma patients, the proliferative fraction was distributed evenly between CD45+ and CD45- cells, however, cycling plasma cells were consistently VLA-5-. There was close correlation between the expression of VLA-5 and a range of other integrin molecules (CD11a, CD11c, CD103), as well as the immunoglobulin-associated molecules CD79a/b (Spearman, n = 10, P < 0.0001). In short-term culture, cells that were initially VLA-5-showed increasing VLA-5 expression with time. However, simultaneous analysis of the DNA-binding dye 7-amino-actinomycin D demonstrated that this was not as a result of differentiation, as VLA-5+ plasma cells were all non-viable. This was confirmed in freshly explanted plasma cells from nine patients. Discrete stages of plasma cell differentiation could not be distinguished by the level of CD45 or VLA-5 expression. The results indicate that there is a single stage of plasma cell differentiation, with the phenotype CD38+CD138+VLA-5-. These findings support the hypothesis that neoplastic bone marrow plasma cells represent an independent, self-replenishing population.

  5. Design and development of a microwave multifrequency polarimetric scatterometer for biosphere remote sensing

    Energy Technology Data Exchange (ETDEWEB)

    Stjernman, A.

    1995-05-01

    The main topic of this research report is the design and development of a multifrequency, polarimetric scatterometer for biosphere remote sensing. The system was developed using a standard HP network analyzer, a crossed log-periodic dipole antenna and a reflector. The scatterometer functions in a linear polarization basis between the L- and X-bands and gathers full-polarimetric information. The standard S-parameter measurements using the network analyzer were related to surface and volume scattering coefficients of rough surface, snow cover and vegetation media. The scatterometer measurements were carried out in the frequency domain to make use of narrow band filters in the receiver chain. The fast Fourier transform was used to convert the frequency domain measurements to the time domain. The range resolution of the system was 20 cm; azimuthal and elevation resolutions are determined by the antenna beam widths. Range side lobes were reduced by making use of appropriate weighting (Kaiser-Bessel window) functions. The accuracy of target characterization depends on the quality of scatterometer calibration. A novel technique to estimate the absolute gain and crosstalk of the radar system was developed. Using a distortion matrix approach, the cross-polarization response of the system was improved by 10 to 25 dB. The radar measurements were validated by comparing point target radar observations with the corresponding theoretical values. Also, measurements of fading decorrelation distance and decorrelation bandwidth or rough surfaces were in good agreement with the theory. Backscatter observations of vegetation and snow cover were comparable to earlier published values for a similar environment. 50 refs, 56 figs, 1 tab.

  6. The LOFAR multi-frequency snapshot sky survey (MSSS) I. survey description and first results

    NARCIS (Netherlands)

    Heald, G.H.; Pizzo, R.F.; Orrú, E.; Breton, R.P.; Carbone, D.; Ferrari, C.; Hardcastle, M.J.; Bentum, M.J.

    2015-01-01

    We present the Multifrequency Snapshot Sky Survey (MSSS), the first northern-sky Low Frequency Array (LOFAR) imaging survey. In this introductory paper, we first describe in detail the motivation and design of the survey. Compared to previous radio surveys, MSSS is exceptional due to its intrinsic m

  7. The LOFAR Multifrequency Snapshot Sky Survey (MSSS). I. Survey description and first results

    NARCIS (Netherlands)

    Heald, G.; Pizzo, R.; et al, not CWI; Scheers, L.H.A.

    2015-01-01

    We present the Multifrequency Snapshot Sky Survey (MSSS), the first northern-sky Low Frequency Array (LOFAR) imaging survey. In this introductory paper, we first describe in detail the motivation and design of the survey. Compared to previous radio surveys, MSSS is exceptional due to its intrinsic m

  8. Single-receiver single-channel multi-frequency GNSS integrity: outliers, slips, and ionospheric disturbances

    NARCIS (Netherlands)

    Teunissen, P.J.G.; De Bakker, P.F.

    2013-01-01

    In this contribution the integrity of single- receiver, single-channel, multi-frequency GNSS models is studied. The uniformly most powerful invariant test statistics for spikes and slips are derived and their detection capabilities are described by means of minimal detectable biases (MDBs). Analytic

  9. Broadband Bioimpedance Spectroscopy Based on a Multifrequency Mixed Excitation and Nuttall Windowed FFT Algorithm

    Directory of Open Access Journals (Sweden)

    Yuxiang Yang

    2014-01-01

    Full Text Available Bioimpedance spectroscopy (BIS has become an important clinical indicator for monitoring the pathological status of biological tissues, and multifrequency simultaneous measurement of BIS may provide more accurate diagnostic information compared with the traditional frequency-sweep measurement technology. This paper proposes a BIS multifrequency simultaneous measurement method based on multifrequency mixed (MFM signal excitation and a Nuttall windowed interpolation FFT algorithm. Firstly, the excitation source adopts the nine-frequency MFM signal f(9,t, which has excellent spectral characteristic and is very suitable for BIS measurement. On this basis, a Nuttall window is adopted to truncate sample data, and an interpolation FFT algorithm based on Nuttall window is built to perform spectral analysis, in which the parameter correction formula is provided based on polynomial approximation. A BIS measurement simulation experiment is performed on an RC three-element equivalent circuit, and results on the 9 primary harmonic frequencies ranging from 3.9 kHz to 1 MHz show a high accuracy with the impedance amplitude relative error |Ez|<0.3%, and the phase absolute error |Ep|<0.1°. This paper validates the feasibility of BIS multifrequency simultaneous measurement method and establishes an algorithm foundation for the development of practical broadband BIS measurement system.

  10. BODY COMPOSITION ASSESSMENT WITH SEGMENTAL MULTIFREQUENCY BIOIMPEDANCE METHOD

    Directory of Open Access Journals (Sweden)

    Jukka A. Salmi

    2003-12-01

    Full Text Available Body composition assessment is an important factor in weight management, exercise science and clinical health care. Bioelectrical impedance analysis (BIA is widely used method for estimating body composition. The purpose of this study was to evaluate segmental multi-frequency bioimpedance method (SMFBIA in body composition assessment with underwater weighing (UWW and whole body dual energy x-ray absorptiometry (DXA in healthy obese middle-aged male subjects. The measurements were carried out at the UKK Institute for Health Promotion Research in Tampere, Finland according to standard procedures of BIA, UWW and DXA. Fifty-eight (n=58 male subjects, aged 36-53 years, body mass index (BMI 24.9-40.7, were studied. Of them forty (n=40 underwent also DXA measurement. Fat mass (FM, fat-percentage (F% and fat free mass (FFM were the primary outcome variables. The mean whole body FM (±SD from UWW was 31.5 kg (±7.3. By DXA it was 29.9 kg (±8.1 and by SMFBIA it was 25.5 kg (±7.6, respectively. The Pearson correlation coefficients (r were 0.91 between UWW and SMFBIA, 0.94 between DXA and SMFBIA and 0.91 between UWW and DXA, respectively. The mean segmental FFM (±SD from DXA was 7.7 kg (±1.0 for arms, 41.7 kg (±4.6 for trunk and 21.9 kg (±2.2 for legs. By SMFBIA, it was 8.5 kg (±0.9, 31.7 kg (±2.5 and 20.3 kg (±1.6, respectively. Pearson correlation coefficients were 0.75 for arms, 0.72 for legs and 0.77 for trunk. This study demonstrates that SMFBIA is usefull method to evaluate fat mass (FM, fat free mass (FFM and fat percentage (F% from whole body. Moreover, SMFBIA is suitable method for assessing segmental distribution of fat free mass (FFM compared to whole body DXA. The results of this study indicate that the SMFBIA method may be particularly advantageous in large epidemiological studies as being a simple, rapid and inexpensive method for field use of whole body and segmental body composition assessment

  11. Novel RF MEMS capacitive switches with design flexibility for multi-frequency operation

    Science.gov (United States)

    Gopalakrishnan, Sarath; DasGupta, Amitava; Nair, Deleep R.

    2017-09-01

    RF MEMS capacitive shunt switches with a dielectric-on-metal (DOM) capacitor, which are widely used for microwave applications in the communication field, suffer from some serious drawbacks. A significant shift is observed in the resonant frequency of these switches due to the reduction in the down-state capacitance caused by the surface roughness of the dielectric layer. In order to achieve accurate down-state capacitance, a thin layer of floating metal is deposited on the dielectric layer converting the DOM switch to a metal-insulator metal (MIM) switch. The MIM switch opens up interesting possibilities in the design, such as achieving flexibility in the operating frequency of the switch. This paper reports a novel method to achieve design flexibility for multi-frequency operation in switches, by effectively utilizing the equipotential nature of the floating metal in the MIM capacitor. Unlike in a DOM switch, the resonant frequency can be varied by changing merely the length of the floating metal, without having to make any other structural modifications. This enables to have switches operating at different frequency on the same wafer. The beams of the switches are also designed in such a way as to provide stress resilience, thereby preventing buckling. This paper presents the design, simulation, fabrication and characterization of a switch that operates in the X-band. The fabricated switches show excellent stress resilience. The characterized switch demonstrates a reduction in the resonant frequency in proportion to an increase in the length of the floating metal, hence validating the design flexibility proposed in this paper.

  12. Multifrequency VLBA polarimetry of the high-redshift GPS quasar OQ172

    Science.gov (United States)

    Liu, Yi; Jiang, D. R.; Gu, Minfeng; Gurvits, L. I.

    2017-07-01

    Multifrequency Very Long Baseline Array (VLBA) polarimetry observation of the GHz-peaked spectrum (GPS) quasar OQ172 (J1445+0958) has been performed at 1.6, 2.2, 4.8, 8.3 and 15.3 GHz in 2005. Core-jet structures are detected in all bands with the jet strongly bent at about 3 mas from the core. The radio emission of the source is polarized at all five bands. We study the Faraday rotation in the core and jet components at all five bands, and find good linear fits of Faraday rotation in the core and jet components at 4.8 and 8.3 GHz. At these two frequencies, the rotation measure (RM) is ˜ 2000 rad m- 2 in the core and ˜ 700 rad m- 2 in the inner jet components and continues to decrease at the outer jet parts. We find that the depolarization at 4.8 and 8.3 GHz might be caused by the internal medium in the source. We investigate consistency of the turnover spectra of VLBI components with the synchrotron self-absorption and free-free absorption models. Although these two models cannot be easily distinguished due to the lack of low-frequency data, the physical parameters can be constrained for each model. We find that the large width of the [O III]_{5007} line is likely caused by a jet interaction with a narrow line region (NLR) medium. The jet bending, significant RM variations, Faraday depolarization, spectral turnover and broad line width of [O III]_{5007} could be closely related, likely caused by the same nucleus medium, presumably NLR.

  13. Tomoelastography of the prostate using multifrequency MR elastography and externally placed pressurized-air drivers.

    Science.gov (United States)

    Dittmann, Florian; Reiter, Rolf; Guo, Jing; Haas, Matthias; Asbach, Patrick; Fischer, Thomas; Braun, Jürgen; Sack, Ingolf

    2017-06-06

    To demonstrate the feasibility of in vivo multifrequency magnetic resonance elastography (MRE) of the prostate using externally placed drivers. Three pressurized-air drivers were used to excite shear waves within the prostate at vibration frequencies of 60, 70, and 80 Hz. Full 3D wave fields were acquired by multislice spin-echo echo-planar imaging in conjunction with tomoelastography wave speed recovery for generating full field-of-view stiffness maps. Twelve healthy volunteers were repeatedly scanned to analyze test-retest reproducibility. Five patients with suspected prostate cancer were investigated to demonstrate the clinical feasibility of the method. In healthy volunteers, the shear wave speed of the entire prostate was 2.24 ± 0.20 m/s with a repeatability coefficient of 0.14 m/s and 88% intraclass correlation coefficient. No significant difference between the peripheral zone (2.27 ± 0.20 m/s) and the central gland (2.22 ± 0.23 m/s) was observed. In patients, wave-speed maps displayed stiff regions consistent with the localization of suspicious masses detected by other imaging markers. The proposed method provides reproducible quantitative maps of tissue stiffness throughout the pelvic region and can easily be integrated into clinical imaging protocols. Clinical stiffness maps display many details of potential interest for cancer diagnosis. Magn Reson Med, 2017. © 2017 International Society for Magnetic Resonance in Medicine. © 2017 International Society for Magnetic Resonance in Medicine.

  14. Low Cost 1.2 to 116 GHz Receivers for the ngVLA

    Science.gov (United States)

    Weinreb, Sander; Soliman, Ahmed; Mani, Hamdi

    2017-01-01

    The next-generation VLA (ngVLA) is a major new radio telescope that is being considered for implementation is the southwest US in the 2020 decade. The general parameters which have been discussed in science and technology workshops in the past 18 months are an array with 10 times the sensitivity and resolution of the current JVLA and operating in the 1.2 to 116 GHz range which is the approximate frequency gap between the SKA and ALMA. This can be implemented with 256 x 18m antennas at fixed locations within a 300km maximum baseline.A major requirement for this instrument is affordable capital and operating cost. This poster addresses a receiver design to minimize these costs. A goal is an operating cost no larger than the current JVLA. An important parameter in the operating cost both for electric power and maintenance is the number of cryogenic coolers and vacuum dewars. The JVLA has 8 such systems on 27 telescopes and our goal is 1 cryogenic dewar on each of the 256 telescopes to give approximately the same total number of cryogenic systems.Key questions are the number and frequency range of the receivers packaged as one system. Much work has been done in the past several years on wideband antenna feeds and low noise amplifiers and the important question is the sensitivity as measured by effective area divided by system noise compared to this figure of merit for narrow band receivers. We consider that the 70-116 GHz range will be covered by one conventional bandwidth receiver, the 50 to 70 GHz range range will be skipped due to atmospheric oxygen absorption, and 1.2 to 50 GHz will be covered by 3 to 5 receivers depending upon performance studies and science needs.This poster presents constraints on the reflector shaped Gregorian optics to allow the feeds to be completely cooled in one package, possible layout of the cryogenic dewar, cooling power requirements, and a current estimate of performance.

  15. The VLA Nascent Disk And Multiplicity (VANDAM) Survey of Perseus Protostars. Resolving the Sub-Arcsecond Binary System in NGC 1333 IRAS2A

    CERN Document Server

    Tobin, John J; Looney, Leslie W; Li, Zhi-Yun; Chandler, Claire J; Segura-Cox, Dominique; Sadavoy, Sarah I; Melis, Carl; Harris, Robert J; Perez, Laura M; Kratter, Kaitlin; Jorgensen, Jes K; Plunkett, Adele L; Hull, Charles L H

    2014-01-01

    We are conducting a Jansky VLA Ka-band (8 mm and 1 cm) and C-band (4 cm and 6.4 cm) survey of all known protostars in the Perseus Molecular Cloud, providing resolution down to $\\sim$0.06'' and $\\sim$0.35" in Ka-band and C-band, respectively. Here we present first results from this survey that enable us to examine the source NGC 1333 IRAS2A in unprecedented detail and resolve it into a proto-binary system separated by 0.621"$\\pm$0.006" ($\\sim$143 AU) at 8 mm, 1 cm, and 4 cm. These 2 sources (IRAS2A VLA1 and VLA2) are likely driving the two orthogonal outflows known to originate from IRAS2A. The brighter source IRAS2A VLA1 is extended perpendicular to its outflow in the VLA data, with a deconvolved size of 0.055" ($\\sim$13 AU), possibly tracing a protostellar disk. The recently reported candidate companions (IRAS2A MM2 and MM3) are not detected in either our VLA data, CARMA 1.3 mm data, or SMA 850 $\\mu$m data. SMA CO ($J=3\\rightarrow2$), CARMA CO ($J=2\\rightarrow1$), and lower resolution CARMA CO ($J=1\\rightarr...

  16. Artificial neural network approach for estimation of surface specific humidity and air temperature using Multifrequency Scanning Microwave Radiometer

    Indian Academy of Sciences (India)

    Randhir Singh; B G Vasudevan; P K Pal; P C Joshi

    2004-03-01

    Microwave sensor MSMR (Multifrequency Scanning Microwave Radiometer) data onboard Oceansat-1 was used for retrieval of monthly averages of near surface specific humidity (a) and air temperature (a) by means of Artificial Neural Network (ANN). The MSMR measures the microwave radiances in 8 channels at frequencies of 6.6, 10.7, 18 and 21 GHz for both vertical and horizontal polarizations. The artificial neural networks (ANN) technique is employed to find the transfer function relating the input MSMR observed brightness temperatures and output (a and a) parameters. Input data consist of nearly 28 months (June 1999 — September 2001) of monthly averages of MSMR observed brightness temperature and surface marine observations of a and a from Comprehensive Ocean- Atmosphere Data Set (COADS). The performance of the algorithm is assessed with independent surface marine observations. The results indicate that the combination of MSMR observed brightness temperatures as input parameters provides reasonable estimates of monthly averaged surface parameters. The global root mean square (rms) differences are 1.0°C and 1.1 g kg−1 for air temperature and surface specific humidity respectively.

  17. Multifrequency observations of extended radio galaxies V - 3C 31, 3C 33.1, 3C 35, 3C 66B, 3C 129, 3C 130, 3C 223, 3C 310, 3C 390.3 and 4C 48.29

    Science.gov (United States)

    van Breugel, W.; Jagers, W.

    1982-08-01

    A sample of 3C radio sources of large angular size has been observed in total and polarized intensity at several wavelengths with the Westerbork Synthesis Radio Telescope. The sources were selected such that their largest angular size was greater than about 200 arcsec and their declination greater than about 25 degrees. Some additional sources with radio jets or peculiar morphology were also included. The name of each source, its structural type classification, wavelength of observation, and data references are given.

  18. The VLA Survey of the Chandra Deep Field South. IV. Source Population

    CERN Document Server

    Padovani, P; Tozzi, P; Kellermann, K I; Fomalont, E B; Miller, N; Rosati, P; Shaver, P

    2008-01-01

    We present a detailed analysis of 256 radio sources from our deep (flux density limit of 42 microJy at the field centre at 1.4 GHz) Chandra Deep Field South 1.4 and 5 GHz VLA survey. The radio population is studied by using a wealth of multi-wavelength information in the radio, optical, and X-ray bands. The availability of redshifts for ~ 80% of the sources in our complete sample allows us to derive reliable luminosity estimates for the majority of the objects. X-ray data, including upper limits, for all our sources turn out to be a key factor in establishing the nature of faint radio sources. Due to the faint optical levels probed by this study, we have uncovered a population of distant Active Galactic Nuclei (AGN) systematically missing from many previous studies of sub-millijansky radio source identifications. We find that, while the well-known flattening of the radio number counts below 1 mJy is mostly due to star forming galaxies, these sources and AGN make up an approximately equal fraction of the sub-m...

  19. The VVDS-VLA Deep Field - IV: Radio-optical properties

    CERN Document Server

    Bardelli, S; Bolzonella, M; Ciliegi, P; Gregorini, L; Zamorani, G; Bondi, M; Zanichelli, A; Tresse, L; Vergani, D; Gavignaud, I; Bongiorno, A; Bottini, D; Garilli, B; Le Brun, V; Le Fèvre, O; MacCagni, D; Scaramella, R; Scodeggio, M; Vettolani, G; Adami, C; Arnouts, S; Cappi, A; Charlot, S; Contini, T; Foucaud, S; Franzetti, P; Guzzo, L; Ilbert, O; Iovino, A; Lamareille, F; McCracken, H J; Marano, B; Marinoni, C; Mazure, A; Meneux, B; Merighi, R; Paltani, S; Pello`, R; Pollo, A; Pozzetti, L; Radovich, M; Abbas, U; Brinchmann, J; Cucciati, O; De la Torre, S; de Ravel, L; Memeo, P; Pérez-Montero, E; Mellier, Y; Merluzzi, P; Temporin, S; De Ruiter, H R; Parma, P

    2008-01-01

    (abridged) We use the 1.4 GHz VIMOS-VLA Deep Survey and the optical VVDS and the CFHT-LS to compare the properties of radio loud galaxies with respect to the whole population of optical galaxies. The availability of multiband photometry and high quality photometric redshifts allows to derive rest frame colors and radio luminosity functions down to a limit of a B rest-frame magnitude of M=-20. Galaxy properties and luminosity functions (LFs) are estimated up to z~1 for radio loud and radio quiet early and late type galaxies. Radio loud late type galaxies are redder than radio quiet objects of the same class and this is an effect related to the presence of more dust in stronger star forming galaxies. Moreover, we estimate optical LFs, stellar masses and star formation rate distributions for radio sources and compare them with those derived for a well defined control sample, finding that the probability for a galaxy to be a radio emitter significantly increases at high values of these parameters. Radio loud earl...

  20. Properties and environment of Radio Emitting Galaxies in the VLA-zCOSMOS survey

    CERN Document Server

    Bardelli, S; Smolcic, V; Zamorani, G; Zucca, E; Mignoli, M; Halliday, C; Kovac, K; Ciliegi, P; Caputi, K; Koekemoer, A M; Bongiorno, A; Bondi, M; Bolzonella, M; Vergani, D; Pozzetti, L; Carollo, C M; Contini, T; Kneib, J -P; LeFevre, O; Lilly, S; Mainieri, V; Renzini, A; Scodeggio, M; Coppa, G; Cucciati, O; delaTorre, S; deRavel, L; Franzetti, P; Garilli, B; Iovino, A; Kampczyk, P; Knobel, C; Lamareille, F; LeBorgne, J -F; Le Brun, V; Maier, C; Pello`, R; Peng, Y; Pérez-Montero, E; Ricciardelli, E; Silverman, J D; Tanaka, M; Tasca, L; Tresse, L; Abbas, U; Bottini, D; Cappi, A; Cassata, P; Cimatti, A; Guzzo, L; Leauthaud, A; MacCagni, D; Marinoni, C; McCracken, H J; Memeo, P; Meneux, B; Oesch, P; Porciani, C; Scaramella, R; Capak, P; Sanders, D; Scoville, N; Taniguchi, Y; Jahnke, K

    2009-01-01

    We investigate the properties and the environment of radio sources with optical counterpart from the combined VLA-COSMOS and zCOSMOS samples. The advantage of this sample is the availability of optical spectroscopic information, high quality redshifts, and accurate density determination. By comparing the star formation rates estimated from the optical spectral energy distribution with those based on the radio luminosity, we divide the radio sources in three families, passive AGN, non-passive AGN and star forming galaxies. These families occupy specific regions of the 8.0-4.5 $\\mu$m infrared color--specific star formation plane, from which we extract the corresponding control samples. Only the passive AGN have a significantly different environment distribution from their control sample. The fraction of radio-loud passive AGN increases from ~2% in underdense regions to ~15% for overdensities (1+delta) greater than 10. This trend is also present as a function of richness of the groups hosting the radio sources. ...

  1. VLA and ALMA Imaging of Intense, Galaxy-Wide Star Formation in z ~ 2 Galaxies

    CERN Document Server

    Rujopakarn, W; Rieke, G H; Ivison, R J; Cibinel, A; Nyland, K; Jagannathan, P; Silverman, J D; Alexander, D M; Biggs, A D; Bhatnagar, S; Ballantyne, D R; Dickinson, M; Elbaz, D; Geach, J E; Hayward, C C; Kirkpatrick, A; McLure, R J; Michalowski, M J; Miller, N A; Narayanan, D; Owen, F N; Pannella, M; Papovich, C; Pope, A; Rau, U; Robertson, B E; Scott, D; Swinbank, A M; van der Werf, P; van Kampen, E; Windhorst, R A

    2016-01-01

    We present $\\simeq$0$.\\!\\!^{\\prime\\prime}4$-resolution extinction-independent distributions of star formation and dust in 11 star-forming galaxies (SFGs) at $z = 1.3-3.0$. These galaxies are selected from sensitive, blank-field surveys of the $2' \\times 2'$ Hubble Ultra-Deep Field at $\\lambda = 5$ cm and 1.3 mm using the Karl G. Jansky Very Large Array (VLA) and Atacama Large Millimeter/submillimeter Array (ALMA). They have star-formation rates (SFRs), stellar masses, and dust properties representative of massive main-sequence SFGs at $z \\sim 2$. Morphological classification performed on spatially-resolved stellar mass maps indicates a mixture of disk and morphologically disturbed systems; half of the sample harbor X-ray active galactic nuclei (AGN), thereby representing a diversity of $z \\sim 2$ SFGs undergoing vigorous mass assembly. We find that their intense star formation most frequently occurs at the location of stellar-mass concentration and extends over an area comparable to their stellar-mass distrib...

  2. A VLA H92alpha Study of the Arched Filament Complex Near the Galactic Center

    CERN Document Server

    Lang, C C; Lang, Cornelia C.

    2001-01-01

    The VLA has been used at 8.3 GHz in the DnC and CnB array configurations to carry out an H92alpha recombination line study (at 8.3 GHz) of the ionized gas in the Arched Filaments H II complex, which defines the western edge of the Galactic center Radio Arc. The H92alpha line properties of the ionized gas are consistent with photoionization from hot stars,and consistent with the physical properties of other Galactic center H II regions. The LTE electron temperatures vary only slightly across the entire extent of the source, and have an average value of 6200 K. The velocity field is very complex, with velocities ranging from +15 to - 70 km/s and the majority of velocities having negative values. Large velocity gradients (2-7 km/s/pc, with gradients in some regions >10 km/s/pc) occur along each of the filaments, with the velocities becoming increasingly negative with decreasing distance from the Galactic center. The magnitudes of the velocity gradient are consistent with the cloud residing on an inner, elongated...

  3. A VLA Survey For Faint Compact Radio Sources in the Orion Nebula Cluster

    CERN Document Server

    Sheehan, Patrick D; Mann, Rita K; Williams, Jonathan P

    2016-01-01

    We present Karl G. Janksy Very Large Array (VLA) 1.3 cm, 3.6 cm, and 6 cm continuum maps of compact radio sources in the Orion Nebular Cluster. We mosaicked 34 square arcminutes at 1.3 cm, 70 square arcminutes at 3.6 cm and 109 square arcminutes at 6 cm, containing 778 near-infrared detected YSOs and 190 HST-identified proplyds (with significant overlap between those characterizations). We detected radio emission from 175 compact radio sources in the ONC, including 26 sources that were detected for the first time at these wavelengths. For each detected source we fit a simple free-free and dust emission model to characterize the radio emission. We extrapolate the free-free emission spectrum model for each source to ALMA bands to illustrate how these measurements could be used to correctly measure protoplanetary disk dust masses from sub-millimeter flux measurements. Finally, we compare the fluxes measured in this survey with previously measured fluxes for our targets, as well as four separate epochs of 1.3 cm ...

  4. Nuevas observaciones de 3C10 con el VLA*: estudio de la expansión

    Science.gov (United States)

    Reynoso, E. M.; Moffett, D. A.:; Dubner, G. M.; Giacani, E. B.; Reynolds, S. P.; Goss, W. M.; Dickel, J.

    Se presentan nuevos resultados sobre la expansión del remanente de la supernova de Tycho a lo largo de un intervalo de 10.9 años, comparando nuevas observaciones tomadas con el VLA a 1375 y 1635 MHz durante 1994 y 1995, con observaciones previas realizadas entre 1983 y 1984 (Dickel y col. ~1991 AJ 101, 2151), usando las mismas configuraciones, anchos de banda, calibradores y tiempos de integración. El coeficiente de expansión se calcula para sectores radiales de 4o de ancho cada uno, ajustando la correlación cruzada de las derivadas de los perfiles promedio para cada época. A partir de la expansión medida, se estima el índice (parámetro de expansión) de la ley potencial R∝ tm como m≡ d ln R/d ln t . Este valor se compara con coeficientes teóricos para diferentes fases evolutivas de remanentes de supernova.

  5. Effect of inter-tissue inductive coupling on multi-frequency imaging of intracranial hemorrhage by magnetic induction tomography

    Science.gov (United States)

    Xiao, Zhili; Tan, Chao; Dong, Feng

    2017-08-01

    Magnetic induction tomography (MIT) is a promising technique for continuous monitoring of intracranial hemorrhage due to its contactless nature, low cost and capacity to penetrate the high-resistivity skull. The inter-tissue inductive coupling increases with frequency, which may lead to errors in multi-frequency imaging at high frequency. The effect of inter-tissue inductive coupling was investigated to improve the multi-frequency imaging of hemorrhage. An analytical model of inter-tissue inductive coupling based on the equivalent circuit was established. A set of new multi-frequency decomposition equations separating the phase shift of hemorrhage from other brain tissues was derived by employing the coupling information to improve the multi-frequency imaging of intracranial hemorrhage. The decomposition error and imaging error are both decreased after considering the inter-tissue inductive coupling information. The study reveals that the introduction of inter-tissue inductive coupling can reduce the errors of multi-frequency imaging, promoting the development of intracranial hemorrhage monitoring by multi-frequency MIT.

  6. Nine years of multi-frequency monitoring of the blazar PKS 0048-097: spectral and temporal variability

    CERN Document Server

    Wierzcholska, Alicja

    2016-01-01

    Blazars are highly variable, radio-loud active galactic nuclei with jets oriented at a small angle to the line of sight. The observed emission of these sources covers the whole electromagnetic spectrum from radio frequencies up to the high or even very high energy gamma-ray range. To understand the complex physics of these objects, multi-wavelength observations and studies on the variability and correlations between different wavelengths are therefore essential. The long-term multi-frequency observations of PKS 0048-097 are analysed here to investigate its spectral and temporal features. The studies includes nine years of observations of the blazar, which is well studied in the optical and radio domain, but not in the other frequencies. Multi-wavelength data collected with OVRO, KAIT, Catalina, Swift/UVOT, Swift/XRT and Fermi/LAT were studied. The performed analysis revealed strong variability in all wavelengths that is most clearly manifested in the X-ray range. The correlation studies do not exhibit any rel...

  7. Multifrequency Magneto-optic Bragg Diffraction and Radio Frequency Signal Parallel Processing

    Institute of Scientific and Technical Information of China (English)

    SHANG Dan; WU Bao-jian; QIU Kun

    2008-01-01

    Magneto-optic(MO) coupling of guided optical waves with microwave magnetostatic waves(MSWs) simultaneously excited by multiple radio frequency(RF) signals can lead to multifrequency diffraction effects and then parallel processing of RF signals can be realized by using of the characteristics that diffraction efficiencies(Des) are approximately in direct proportion to RF signals intensities and diffraction angles are related to frequencies of the corresponding RF signals within linear MO interaction region. In this paper, studied is the multifrequency MO Bragg diffraction in first-order MO interaction approximation, and obtained was the approximate analytical expression for principle diffraction efficiency(PDE). Also, put forward was a parallel imaging method of relative intensity of RF signals based on single-frequency diffraction. By calculation and analysis, it is shown that the relative error is not more than 0.3 dB for the case of three RF signals within the frequency space of 60 MHz.

  8. A 3D tunable and multi-frequency graphene plasmonic cloak

    KAUST Repository

    Farhat, Mohamed

    2013-01-01

    We demonstrate the possibility of cloaking three-dimensional objects at multi-frequencies in the far-infrared part of the spectrum. The proposed cloaking mechanism exploits graphene layers wrapped around the object to be concealed. Graphene layers are doped via a variable external voltage difference permitting continuous tuning of the cloaking frequencies. Particularly, two configurations are investigated: (i) Only one graphene layer is used to suppress the scattering from a dielectric sphere. (ii) Several of these layers biased at different gate voltages are used to achieve a multi-frequency cloak. These frequencies can be set independently. The proposed cloak\\'s functionality is verified by near- and far-field computations. By considering geometry and material parameters that are realizable by practical experiments, we contribute to the development of graphene based plasmonic applications that may find use in disruptive photonic technologies. © 2013 Optical Society of America.

  9. OCT based on multi-frequency sweeping Fizeau interferometer with phase modulating method

    Science.gov (United States)

    Choi, S.; Watanabe, T.; Sasaki, O.; Suzuki, T.

    2013-09-01

    The Multi-frequency sweeping Fizeau-type interferometer (MFS-FI) for optical coherence tomography (OCT) is demonstrated. The multi-frequency sweeping by a variable Fabry-Perot filter permits detection of high-order low-coherence interferometric signals in the Fizeau interferometer. The sinusoidal phase modulation technique was utilized to detect accurate interference amplitude and phase distributions of back scattered light from surfaces of a sample. OCT measurements by the MFS-FI were conducted for vibrating glass plates with a frequency of 1 kHz, and cellular tissues fixed with formalin and embedded in paraffin. The tomographic 3-dimensional volume and cross-sectional surface displacements were detected with an accuracy of nano-meters.

  10. Multifrequency excitation method for rapid and accurate dynamic test of micromachined gyroscope chips.

    Science.gov (United States)

    Deng, Yan; Zhou, Bin; Xing, Chao; Zhang, Rong

    2014-10-17

    A novel multifrequency excitation (MFE) method is proposed to realize rapid and accurate dynamic testing of micromachined gyroscope chips. Compared with the traditional sweep-frequency excitation (SFE) method, the computational time for testing one chip under four modes at a 1-Hz frequency resolution and 600-Hz bandwidth was dramatically reduced from 10 min to 6 s. A multifrequency signal with an equal amplitude and initial linear-phase-difference distribution was generated to ensure test repeatability and accuracy. The current test system based on LabVIEW using the SFE method was modified to use the MFE method without any hardware changes. The experimental results verified that the MFE method can be an ideal solution for large-scale dynamic testing of gyroscope chips and gyroscopes.

  11. Multifrequency Excitation Method for Rapid and Accurate Dynamic Test of Micromachined Gyroscope Chips

    Directory of Open Access Journals (Sweden)

    Yan Deng

    2014-10-01

    Full Text Available A novel multifrequency excitation (MFE method is proposed to realize rapid and accurate dynamic testing of micromachined gyroscope chips. Compared with the traditional sweep-frequency excitation (SFE method, the computational time for testing one chip under four modes at a 1-Hz frequency resolution and 600-Hz bandwidth was dramatically reduced from 10 min to 6 s. A multifrequency signal with an equal amplitude and initial linear-phase-difference distribution was generated to ensure test repeatability and accuracy. The current test system based on LabVIEW using the SFE method was modified to use the MFE method without any hardware changes. The experimental results verified that the MFE method can be an ideal solution for large-scale dynamic testing of gyroscope chips and gyroscopes.

  12. Multi-frequency image reconstruction for radio interferometry. A regularized inverse problem approach

    CERN Document Server

    Ferrari, André; Ferrari, Chiara; Mary, David; Schutz, Antony; Smirnov, Oleg

    2015-01-01

    We describe a "spatio-spectral" deconvolution algorithm for wide-band imaging in radio interferometry. In contrast with the existing multi-frequency reconstruction algorithms, the proposed method does not rely on a model of the sky-brightness spectral distribution. This non-parametric approach can be of particular interest for the new generation of low frequency radiotelescopes. The proposed solution formalizes the reconstruction problem as a convex optimization problem with spatial and spectral regularizations. The efficiency of this approach has been already proven for narrow-band image reconstruction and the present contribution can be considered as its extension to the multi-frequency case. Because the number of frequency bands multiplies the size of the inverse problem, particular attention is devoted to the derivation of an iterative large scale optimization algorithm. It is shown that the main computational bottleneck of the approach, which lies in the resolution of a linear system, can be efficiently ...

  13. Target detection for low angle radar based on multi-frequency order-statistics

    Institute of Scientific and Technical Information of China (English)

    Yunhe Cao∗; Shenghua Wang; Yu Wang; Shenghua Zhou

    2015-01-01

    For radar targets flying at low altitude, multiple pathways produce fade or enhancement relative to the level that would be expected in a free-space environment. In this paper, a new detec-tion method based on a wide-ranging multi-frequency radar for low angle targets is proposed. Sequential transmitting multiple pulses with different frequencies are first applied to decorrelate the cohe-rence of the direct and reflected echoes. After receiving al echoes, the multi-frequency samples are arranged in a sort descending ac-cording to the amplitude. Some high amplitude echoes in the same range cel are accumulated to improve the signal-to-noise ratio and the optimal number of high amplitude echoes is analyzed and given by experiments. Final y, simulation results are presented to verify the effectiveness of the method.

  14. Multi-Frequency Target Detection Techniques for DVB-T Based Passive Radar Sensors

    Directory of Open Access Journals (Sweden)

    Tatiana Martelli

    2016-09-01

    Full Text Available This paper investigates the possibility to improve target detection capability in a DVB-T- based passive radar sensor by jointly exploiting multiple digital television channels broadcast by the same transmitter of opportunity. Based on the remarkable results obtained by such a multi-frequency approach using other signals of opportunity (i.e., FM radio broadcast transmissions, we propose appropriate modifications to the previously devised signal processing techniques for them to be effective in the newly considered scenarios. The resulting processing schemes are extensively applied against experimental DVB-T-based passive radar data pertaining to different surveillance applications. The obtained results clearly show the effectiveness of the proposed multi-frequency approaches and demonstrate their suitability for application in the considered scenarios.

  15. Multifrequency eddy-current inspection of seam weld in steel sheath

    Energy Technology Data Exchange (ETDEWEB)

    Smith, J.H.; Dodd, C.V.; Chitwood, L.D.

    1985-04-01

    Multifrequency eddy-current techniques were used to perform a continuous on-line inspection of the seam weld in the steel jacket for a superconducting cable. The inspection was required to detect both surface and internal weld flaws in the presence of a large, highly conductive central conductor. Raw eddy-current data were recorded on magnetic tape, and test properties such as discontinuity size and weld penetration were determined by mathematically fitting these data to coefficients developed with representative standards. A sophisticated computer-controlled scanning technique was applied, and a unique scanning device was developed to provide full coverage of the weld and heat-affected zone. The techniques used to develop this multifrequency eddy-current examination are described in this report along with the test equipment, test procedures, and computer programs.

  16. Indoor Positioning Using Multi-Frequency RSS with Foot-Mounted INS

    OpenAIRE

    Nilsson, Martin; Rantakokko, Jouni; Skoglund, Martin A.; Hendeby, Gustaf

    2014-01-01

    This paper presents a system which combines a zero-velocity-update-(ZUPT-)aided inertial navigation system (INS), using a foot-mounted inertial measurement unit (IMU), with opportunistic use of multi-frequency received signal strength (RSS) measurements. The system does not rely on maps or pre-collected data from surveys of the radio-frequency (RF) environment. Instead it builds its own database of collected RSS measurements during the course of the operation. New RSS measurements are continu...

  17. Multi-frequency proportional-resonant (MFPR) current controller for PWM VSC under unbalanced supply conditions

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    This letter presents a multi-frequency proportional-resonant (MFPR) current controller developed for PWM voltage source converter (VSC) under the unbalanced supply voltage conditions. The delta operator is used in place of the shift operator for the implementation of MFPR by using a low-cost fixed-point DSP. The experimental results with an alternative control strategy validated the feasibility of the proposed MFPR current controller for the PWM VSC during voltage unbalance.

  18. Multifrequency Acoustic Emissions (AE) for Monitoring the Time Evolution of Microprocesses within Solids

    Science.gov (United States)

    Paparo, Gabriele; Gregori, Giovanni P.

    2003-03-01

    Microprocesses occur like chain reactions where bonds progressively yield. The temporal evolution can be tracked by multifrequency AE. Two principle ideas. One relies on time series of AE of increasingly lower frequency. The second compares time histories of every AE event (fixed frequency) with a lognormal distribution: deviations reveal additional parameters, and the tail results modulated by external effects, envisaging what triggers every AE. Natural environmental phenomena are effective feasibility tests, for subsequent laboratory implementation.

  19. A Novel Tunable Multi-Frequency Hybrid Vibration Energy Harvester Using Piezoelectric and Electromagnetic Conversion Mechanisms

    Directory of Open Access Journals (Sweden)

    Zhenlong Xu

    2016-01-01

    Full Text Available This paper presents a novel tunable multi-frequency hybrid energy harvester (HEH. It consists of a piezoelectric energy harvester (PEH and an electromagnetic energy harvester (EMEH, which are coupled with magnetic interaction. An electromechanical coupling model was developed and numerically simulated. The effects of magnetic force, mass ratio, stiffness ratio, and mechanical damping ratios on the output power were investigated. A prototype was fabricated and characterized by experiments. The measured first peak power increases by 16.7% and 833.3% compared with that of the multi-frequency EMEH and the multi-frequency PEH, respectively. It is 2.36 times more than the combined output power of the linear PEH and linear EMEH at 22.6 Hz. The half-power bandwidth for the first peak power is also broadened. Numerical results agree well with the experimental data. It is indicated that magnetic interaction can tune the resonant frequencies. Both magnetic coupling configuration and hybrid conversion mechanism contribute to enhancing the output power and widening the operation bandwidth. The magnitude and direction of magnetic force have significant effects on the performance of the HEH. This proposed HEH is an effective approach to improve the generating performance of the micro-scale energy harvesting devices in low-frequency range.

  20. Multi-frequency AOM for multi-beam laser scanning exposure system

    Science.gov (United States)

    Shinada, Hidetoshi

    2016-10-01

    Digital printing systems recorded on films or computer to plates (CTPs) have been required to improve their productivity and image quality. Under the circumstance, a printing technology of the multi-beam laser scanning for the drum capstan system, which is almost the same as optics configuration as the flat bed system, was developed using a newly developed multi-frequency acousto-optic modulator (AOM) as a key device instead of ultra-fast scanning devices toward a main scan direction. The multi-frequency AOM was developed with phased array-type transducers, achieving a wider bandwidth of over 160 MHz. The design consisted of a simultaneous three beams generation with interlace scan to avoid the beat effect by adjacent Doppler-shifted beams, which consequently attained the fastest recording speed of 5.0 mm/s compared with 2.0-3.0 mm/s of existing systems in those days. Furthermore, a couple of critical parameters of the multi-frequency AOM are studied, for example, a treatment of third-order intermodulation and also beat effect in connection with photosensitive media. As a result, the necessity of interlaces scanning to obtain good image quality without beat effect and also to allow a lower laser power to apply is proposed.

  1. Observation

    Science.gov (United States)

    Patell, Hilla

    2016-01-01

    In order to achieve the goal of observation, preparation of the adult, the observer, is necessary. This preparation, says Hilla Patell, requires us to "have an appreciation of the significance of the child's spontaneous activities and a more thorough understanding of the child's needs." She discusses the growth of both the desire to…

  2. Observation

    Science.gov (United States)

    Kripalani, Lakshmi A.

    2016-01-01

    The adult who is inexperienced in the art of observation may, even with the best intentions, react to a child's behavior in a way that hinders instead of helping the child's development. Kripalani outlines the need for training and practice in observation in order to "understand the needs of the children and...to understand how to remove…

  3. Relative position determination of a lunar rover using high-accuracy multi-frequency same-beam VLBI

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    Multi-frequency same-beam VLBI means that two explorers with a small separation angle are simultaneously observed with the main beam of receiving antennas. In the same-beam VLBI, the differential phase delay between two explorers and two receiving telescopes can be obtained with a small error of several picoseconds. The differential phase delay, as the observable of the same-beam VLBI, gives the separation angular information of the two explorers in the celestial sphere. The two-dimensional relative position on the plane-of-sky can thus be precisely determined with an error of less than 1 m for a distance of 3.8×105 km far away from the earth, by using the differential phase delay obtained with the four Chinese VLBI stations. The relative position of a lunar rover on the lunar surface can be determined with an error of 10 m by using the differential phase delay data and the range data for the lander when the lunar topography near the rover and the lander can be determined with an error of 10 m.

  4. 20 cm VLA radio-continuum study of M31-images and point source catalogues DR2: Extraction of a supernova remnant sample

    Directory of Open Access Journals (Sweden)

    Galvin T.J.

    2014-01-01

    Full Text Available We present Data Release 2 of the Point Source Catalogue created from a series of previously constructed radio-continuum images of M31 at λ=20 cm (v=1.4 GHz from archived VLA observations. In total, we identify a collection of 916 unique discrete radio sources across the field of M31. Comparing these detected sources to those listed by Gelfand et al. (2004 at λ=92 cm, the spectral index of 98 sources has been derived. The majority (73% of these sources exhibit a spectral index of α<-0.6, indicating that their emission is predominantly non-thermal in nature, which is typical for background objects and Supernova Remnants (SNRs. Additionally, we investigate the presence of radio counterparts for some 156 SNRs and SNR candidates, finding a total of only 13 of these objects in our images within a 500 search area. Auxiliary optical, radio and X-ray catalogues were cross referenced highlighting a small population of SNRs and SNR candidates common to multi frequency domains.

  5. A Wideband Polarization Survey of the Extragalactic Sky at 2-4 GHz: A Science White Paper for the VLA Sky Survey

    CERN Document Server

    Mao, Sui Ann; Gaensler, Bryan; Rudnick, Lawrence; Stil, Jeroen; Purcell, Cormac; Beck, Rainer; Farnes, Jamie; O'Sullivan, Shane; Schnitzeler, Dominic; Willis, Tony; Sun, Xiaohui; Carretti, Ettore; Dolag, Klaus; Sokoloff, Dmitry; Kothes, Roland; Wolleben, Maik; Heald, George; Geisbuesch, Joern; Robishaw, Tim; Afonso, Jose; Magalhães, Antonio Mario; Lundgren, Britt; Haverkorn, Marijke; Oppermann, Niels; Taylor, Russ

    2014-01-01

    A VLA Sky Survey of the extragalactic sky at S band (2-4 GHz) with polarization information can uniquely probe the magneto-ionic medium in a wide range of astrophysical environments over cosmic time. For a shallow all-sky survey, we expect to detect over 4 million sources in total intensity $>$ 0.45 mJy beam$^{-1}$ and over 2.2$\\times$10$^5$ sources in polarized intensity. With these new observations, we expect to discover new classes of polarized radio sources in very turbulent astrophysical environments and those with extreme values of Faraday depth. Moreover, by determining reliable Faraday depths and by modeling depolarization effects, we can derive properties of the magneto-ionic medium associated with AGNs, absorption line systems and galaxies, addressing the following unresolved questions: (1) What is the covering fraction, the degree of turbulence and the origin of absorption line systems? (2) What is the thermal content in AGNs and radio galaxies? (3) How do AGNs and galaxies evolve over cosmic time?...

  6. CHANDRA/VLA Follow-up of TeV J2032+4131, the Only Unidentified TeV Gamma-ray Source

    CERN Document Server

    Butt, Y; Combi, J; Corcoran, M; Dame, T M; Drake, J; Bernado, M M K; Milne, P; Miniati, F; Pohl, M; Reimer, O; Romero, G; Rupen, M P; Butt, Yousaf; Benaglia, Paula; Combi, Jorge; Corcoran, Michael; Dame, Thomas; Drake, Jeremy; Bernado, Marina Kaufman; Milne, Peter; Miniati, Francesco; Pohl, Martin; Reimer, Olaf; Romero, Gustavo; Rupen, Michael

    2003-01-01

    The HEGRA Cherenkov telescope array group recently reported a steady and extended unidentified TeV gamma-ray source lying at the outskirts of Cygnus OB2. This is the most massive stellar association known in the Galaxy, estimated to contain ~2600 OB type members alone. It has been previously argued that the large scale shocks and turbulence in such associations may play a role in accelerating Galactic cosmic rays. Indeed, Cyg OB2 also coincides with the non-variable MeV-GeV range unidentified EGRET source, 3EG 2033+4118. We report on the near-simultaneous follow-up observations of the extended TeV source region with the CHANDRA X-ray Observatory and the Very Large Array (VLA) radio telescope obtained in order to explore this possibility. Analysis of the CO, HI, and IRAS 100 micron emissions shows that the TeV source region coincides with an outlying sub-group of powerful OB stars which have evacuated or destroyed much of the ambient atomic, molecular and dust material, and which may be related to the very hig...

  7. Multifrequency Polarimetry of the Nrao 140 Jet: Possible Detection of a Helical Magnetic Field and Constraints on its Pitch Angle

    CERN Document Server

    Asada, Keiichi; Nakamura, Masanori; Kameno, Seiji; Nagai, Hiroshi

    2008-01-01

    We present results from multifrequency polarimetry of NRAO 140 using the Very Long Baseline Array. These observations allow us to reveal the distributions of both the polarization position angle and the Faraday rotation measure (RM). These distributions are powerful tools to discern the projected and line-of-sight components of the magnetic field, respectively. We find a systematic gradient in the RM distribution, with its sign being opposite at either side of the jet with respect to the jet axis. The sign of the RM changes only with the direction of the magnetic field component along the line of sight, so this can be explained by the existence of helical magnetic components associated with the jet itself. We derive two constraints for the pitch angle of the helical magnetic field from the distributions of the RM and the projected magnetic field; the RM distribution indicates that the helical fields are tightly wound, while that of the projected magnetic field suggests they are loosely wound around the jet ax...

  8. {Interstellar Plasma Weather Effects in Long-term Multi-frequency Timing of Pulsar B1937+21

    CERN Document Server

    Ramachandran, R; Cognard, I; Demorest, P; Lommen, A N

    2006-01-01

    We report here on variable propagation effects in over twenty years of multi-frequency timing analysis of pulsar PSR B1937+21 that determine small-scale properties of the intervening plasma as it drifts through the sight line. The phase structure function derived from the dispersion measure variations is in remarkable agreement with that expected from the Kolmogorov spectrum, with a power law index of $3.66\\pm 0.04$, valid over an inferred scale range of 0.2--50 A.U. The observed flux variation time scale and the modulation index, along with their frequency dependence, are discrepant with the values expected from a Kolmogorov spectrum with infinitismally small inner scale cutoff, suggesting a caustic-dominated regime of interstellar optics. This implies an inner scale cutoff to the spectrum of $\\sim 1.3\\times 10^9$ meters. Our timing solutions indicate a transverse velocity of 9 km sec$^{-1}$ with respect to the solar system barycenter, and 80 km sec$^{-1}$ with respect to the pulsar's LSR. We interpret the f...

  9. Understanding natural semiquinone radicals--multifrequency EPR and relativistic DFT studies of the structure of Hg(II) complexes.

    Science.gov (United States)

    Witwicki, Maciej; Jerzykiewicz, Maria; Ozarowski, Andrzej

    2015-01-01

    Multifrequency EPR spectroscopy and DFT calculations were used to investigate Hg(II) complexes with semiquinone radical ligands formed in a direct reaction between the metal ions and tannic acid (a polyphenol closely related to tannins). Because of the intricate structure of tannic acid a vast array of substituted phenolic compounds were tested to find a structural model mimicking its ability to react with Hg(II) ions. The components of the g matrix (the g tensor) determined from the high field (208 GHz) EPR spectra of the Hg(II) complexes with the radical ligands derived from tannic acid and from the model compounds were analogous, indicating a similar coordination mode in all the studied Hg(II) complexes. Since catechol (1,2-dihydroxybenzene) was the simplest compound undergoing the reaction with Hg(II) it was selected for DFT studies which were aimed at providing an insight into the structural properties of the investigated complexes. Various coordination numbers and different conformations and protonation states of the ligands were included in the theoretical analyses. g Matrices were computed for all the DFT optimized geometries. A good agreement between the theoretical and experimental values was observed only for the model with the Hg(II) ion tetracoordinated by two ligands, one of the ligands being monoprotonated with the unpaired electron mainly localized on it.

  10. RADIO OBSERVATIONS OF THE QUADRUPLE LENS 1608+656

    NARCIS (Netherlands)

    SNELLEN, IAG; DEBRUYN, AG; SCHILIZZI, RT; MILEY, GK; MYERS, ST

    1995-01-01

    VLA observations at 8.4 and 15 GHz of a sample of 119 inverted-spectrum radio sources revealed that one object, 1608+656, consists of four components in a configuration suggestive of gravitational lensing. The maximum separation between individual components is 2''.1. An independent discovery of thi

  11. Radio and Millimeter Observations of the COSMOS Field

    OpenAIRE

    Schinnerer, E.; Bertoldi, F.; Carilli, C.L.; Smolčić, V.; Scoville, N.; K. Menten; Voss, H.; Blain, A; Lutz, D.

    2007-01-01

    The Cosmic Evolution Survey (COSMOS) targets an equatorial two square degree field covering the full electromagnetic spectrum. Here we present first results from observations of the COSMOS field in the millimeter and centimeter regime done with the IRAM 30m/MAMBO array and NRAO's Very Large Array (VLA) at 250GHz and 1.4GHz, respectively.

  12. A simplified view of blazars: comparison with multi-frequency observations

    CERN Document Server

    Giommi, Paolo

    2013-01-01

    We have recently proposed a new scenario where blazars are classified as flat-spectrum radio quasars or BL Lacs according to the prescriptions of unified schemes, and to a varying combination of Doppler boosted radiation from the jet, emission from the accretion disk, the broad line region, and light from the host galaxy. This mix of different components leads to strong selection effects, which are properly taken into account in our scheme. We describe here the main features of our approach, which solves many long-standing issues of blazar research, give the most important results, and discuss its implications and testable predictions.

  13. Tumor necrosis factor-{alpha} enhanced fusions between oral squamous cell carcinoma cells and endothelial cells via VCAM-1/VLA-4 pathway

    Energy Technology Data Exchange (ETDEWEB)

    Song, Kai; Zhu, Fei; Zhang, Han-zhong [The State Key Laboratory Breeding Base of Basic Science of Stomatology (Hubei-MOST), Key Laboratory for Oral Biomedicine Ministry of Education, Wuhan University, Wuhan (China); Shang, Zheng-jun, E-mail: shangzhengjun@hotmail.com [The State Key Laboratory Breeding Base of Basic Science of Stomatology (Hubei-MOST), Key Laboratory for Oral Biomedicine Ministry of Education, Wuhan University, Wuhan (China); First Department of Oral and Maxillofacial Surgery, School and Hospital of Stomatology, Wuhan University, Wuhan (China)

    2012-08-15

    Fusion between cancer cells and host cells, including endothelial cells, may strongly modulate the biological behavior of tumors. However, no one is sure about the driving factors and underlying mechanism involved in such fusion. We hypothesized in this study that inflammation, one of the main characteristics in tumor microenvironment, serves as a prominent catalyst for fusion events. Our results showed that oral cancer cells can fuse spontaneously with endothelial cells in co-culture and inflammatory cytokine tumor necrosis factor-{alpha} (TNF-{alpha}) increased fusion of human umbilical vein endothelium cells and oral cancer cells by up to 3-fold in vitro. Additionally, human oral squamous cell carcinoma cell lines and 35 out of 50 (70%) oral squamous carcinoma specimens express VLA-4, an integrin, previously implicated in fusions between human peripheral blood CD34-positive cells and murine cardiomyocytes. Expression of VCAM-1, a ligand for VLA-4, was evident on vascular endothelium of oral squamous cell carcinoma. Moreover, immunocytochemistry and flow cytometry analysis revealed that expression of VCAM-1 increased obviously in TNF-{alpha}-stimulated endothelial cells. Anti-VLA-4 or anti-VCAM-1 treatment can decrease significantly cancer-endothelial adhesion and block such fusion. Collectively, our results suggested that TNF-{alpha} could enhance cancer-endothelial cell adhesion and fusion through VCAM-1/VLA-4 pathway. This study provides insights into regulatory mechanism of cancer-endothelial cell fusion, and has important implications for the development of novel therapeutic strategies for prevention of metastasis. -- Highlights: Black-Right-Pointing-Pointer Spontaneous oral cancer-endothelial cell fusion. Black-Right-Pointing-Pointer TNF-{alpha} enhanced cell fusions. Black-Right-Pointing-Pointer VCAM-1/VLA-4 expressed in oral cancer. Black-Right-Pointing-Pointer TNF-{alpha} increased expression of VCAM-1 on endothelial cells. Black

  14. Hudba při pohřbech se zaměřením na katolické pohřby ve vlašimském vikariátu

    OpenAIRE

    Jelínková, Lenka

    2012-01-01

    This work speaks about the Vicariate of Vlašim, liturgical music and music used during the catholic funerals in the Vicariate of Vlašim. Work is mainly focused on organists from the vicariate. It writes about personal data of organists like their age, sex and music education and about songs that they usually play during funerals.

  15. VLA-4 integrin concentrates at the peripheral supramolecular activation complex of the immune synapse and drives T helper 1 responses

    Science.gov (United States)

    Mittelbrunn, María; Molina, Ana; Escribese, María M.; Yáñez-Mó, María; Escudero, Ester; Ursa, Ángeles; Tejedor, Reyes; Mampaso, Francisco; Sánchez-Madrid, Francisco

    2004-07-01

    The integrin 41 (VLA-4) not only mediates the adhesion and transendothelial migration of leukocytes, but also provides costimulatory signals that contribute to the activation of T lymphocytes. However, the behavior of 41 during the formation of the immune synapse is currently unknown. Here, we show that 41 is recruited to both human and murine antigen-dependent immune synapses, when the antigen-presenting cell is a B lymphocyte or a dendritic cell, colocalizing with LFA-1 at the peripheral supramolecular activation complex. However, when conjugates are formed in the presence of anti-4 antibodies, VLA-4 colocalizes with the CD3- chain at the center of the synapse. In addition, antibody engagement of 4 integrin promotes polarization toward a T helper 1 (Th1) response in human in vitro models of CD4+ T cell differentiation and naïve T cell priming by dendritic cells. The in vivo administration of anti-4 integrin antibodies also induces an immune deviation to Th1 response that dampens a Th2-driven autoimmune nephritis in Brown Norway rats. These data reveal a regulatory role of 4 integrins on T lymphocyte-antigen presenting cell cognate immune interactions.

  16. Design and verification of wide-band, simultaneous, multi-frequency, tuning circuits for large moment transmitter loops

    Science.gov (United States)

    Dvorak, Steven L.; Sternberg, Ben K.; Feng, Wanjie

    2017-03-01

    In this paper we discuss the design and verification of wide-band, multi-frequency, tuning circuits for large-moment Transmitter (TX) loops. Since these multi-frequency, tuned-TX loops allow for the simultaneous transmission of multiple frequencies at high-current levels, they are ideally suited for frequency-domain geophysical systems that collect data while moving, such as helicopter mounted systems. Furthermore, since multi-frequency tuners use the same TX loop for all frequencies, instead of using separate tuned-TX loops for each frequency, they allow for the use of larger moment TX loops. In this paper we discuss the design and simulation of one- and three-frequency tuned TX loops and then present measurement results for a three-frequency, tuned-TX loop.

  17. SPET monitoring of perfusion changes in auditory cortex following mono- and multi-frequency stimuli

    Energy Technology Data Exchange (ETDEWEB)

    De Rossi, G. [Nuclear Medicine Inst., Policlinico A. Gemelli, Rome (Italy); Paludetti, G. [Otorhinolaryngology Inst., Policlinico A. Gemelli, Rome (Italy); Di Nardo, W. [Otorhinolaryngology Inst., Policlinico A. Gemelli, Rome (Italy); Calcagni, M.L. [Nuclear Medicine Inst., Policlinico A. Gemelli, Rome (Italy); Di Giuda, D. [Nuclear Medicine Inst., Policlinico A. Gemelli, Rome (Italy); Almadori, G. [Otorhinolaryngology Inst., Policlinico A. Gemelli, Rome (Italy); Galli, J. [Otorhinolaryngology Inst., Policlinico A. Gemelli, Rome (Italy)

    1996-08-01

    In order to assess the relationship between auditory cortex perfusion and the frequency of acoustic stimuli, twenty normally-hearing subjects underwent cerebral SPET. In 10 patients a multi-frequency stimulus (250-4000 Hz at 40 dB SL) was delivered, while 10 subjects were stimulated with a 500 Hz pure tone at 40 dB SL. The prestimulation SPET was subtracted from poststimulation study and auditory cortex activation was expressed as percent increments. Contralateral cortex was the most active area with multifrequency and monofrequency stimuli as well. A clear demonstration of a tonotopic distribution of acoustic stimuli in the auditory cortex was achieved. In addition, the accessory role played by homolateral accoustic areas was confirmed. The results of the present research support the hypothesis that brain SPET may be useful to obtain semiquantitative reliable information on low frequency auditory level in profoundly deaf patients. This may be achieved comparing the extension of the cortical areas activated by high-intensity multifrequency stimuli. (orig.) [Deutsch] Zur Aufklaerung der Beziehung von regionaler Perfusion des auditorischen Kortex und Frequenz des akustischen Stimulus wurden 20 Normalpatienten mit Hilfe von Hirn-SPECT untersucht. Bei je 10 Patienten wurde ein Multifrequenzstimulus (250-2000 Hz bei 60 dB) bzw. ein Monofrequenzstimulus (500 Hz bei 60 dB) verwendet. Die vor der Stimulation akquirierten SPECT-Daten wurden jeweils von den nach der Stimulation akquirierten SPECT-Daten abgezogen und die aditorische Kortexaktivation als prozentuale Steigerung ausgedrueckt. Der kontralaterale Kortex war das am staerksten aktivierte Areal sowohl bei der Multifrequenz- als auch bei der Monofrequenzstimulation. Es konnte eine klare tonotopische Verteilung der akustischen Stimuli im auditorischen Koretx demonstriert werden. Zusaetzlich konnte die akzessorische Rolle des homolateralen akustischen Kortex bestaetigt werden. Die Ergebnisse dieser Studie unterstuetzen

  18. Separation of ocean features from multifrequency full-polarization SAR imagery

    Institute of Scientific and Technical Information of China (English)

    YANG Jingsong; XIAO Qingmei; HUANG Weigen; FU Bin; CHEN Peng

    2008-01-01

    Different ocean features usually appear in synthetic aperture radar (SAR) images simultaneously. This makes the image compli- cated and hard to understand. Because of lower signal-to-noise rate , it is much more difficult to separate different ocean features than to separate different land features. A completely novel method is presented to separate ocean features from multifrequency po- larimetric SAR imagery. AIRSAR data from Jet Propulsion Laboratory (JPL), National Aeronautics and Space Administration (NASA) are used in the case studies and good results are achieved.

  19. MULTIFREQUENCY ALGORITHMS FOR DETERMINING THE MOISTURE CONTENT OF LIQUID EMULSIONS BY THE METHOD OF RESONANCE DIELCOMETRY

    Directory of Open Access Journals (Sweden)

    A. A. Korobko

    2017-06-01

    Full Text Available Purpose. The main attention is paid to the development and investigation of multifrequency algorithms for the realization of the method of resonance dielcometric measurement of the humidity of emulsions of the type «nonpolar liquid dielectric-water». Multifrequency algorithms take into account the problem of «uncertainty of varieties» and increase the sensitivity of the dielcometric method. Methodology. Multifrequency algorithms are proposed to solve the problem of «uncertainty of varieties» and improve the metrological characteristics of the resonance dielcometric method. The essence of the algorithms is to use a mathematical model of the emulsion and to determine the permittivity of the dehydrated liquid and the emulsion. The task of developing algorithms is to determine and take into account the influence of the parasitic electrical capacitance of the measuring oscillator and the measuring transducer. The essence of the method consists in alternately determining the resonance frequency of the oscillatory circuit with various configurations, which allows to take into account errors from parasitic parameters. The problem of «uncertainty of varieties» is formulated and solved. The metrological characteristics of the resonance dielcometric method are determined using algorithms. Results. Frequency domains of application of mathematical model of an emulsion are defined. An algorithm in a general form with four frequencies suitable for practical implementation in dielcometric resonance measurements is developed. Partial algorithms with three and two frequencies are developed. The systematic values of simulation errors in the emulsion in the microwave range are determined. Generalized metrological characteristics are obtained. The ways of increasing the sensitivity of the dielcometric method are determined. The problem of «uncertainty of varieties» was solved. Experimental data on determination of humidity for the developed algorithms are

  20. Investigation of a Real-time Processing System for the NASA Multifrequency Microwave Radiometer

    Science.gov (United States)

    1976-01-01

    A study was conducted to investigate the data reduction and processing requirements for the multifrequency microwave radiometer system (MFMR). The objectives were to develop and evaluate algorithms and processing techniques which might provide for dedicated real time or near real time data processing and to develop a configuration design and processor recommendation to accomplish the data reduction. An analysis of the required data reduction and calibration equations was included along with the identification of sources of error which may be present in the (MFMR) data. The definition and evaluation of the significance of effects introduced by aircraft perturbation was given.

  1. Simultaneous multi-frequency topological edge modes between one-dimensional photonic crystals.

    Science.gov (United States)

    Choi, Ka Hei; Ling, C W; Lee, K F; Tsang, Y H; Fung, Kin Hung

    2016-04-01

    We show theoretically that, in the limit of weak dispersion, one-dimensional binary centrosymmetric photonic crystals can support topological edge modes in all photonic bandgaps. By analyzing their bulk band topology, these "harmonic" topological edge modes can be designed in a way that they exist at all photonic bandgaps opened at the center of the Brillouin zone, at all gaps opened at the zone boundaries, or both. The results may suggest a new approach to achieve robust multi-frequency coupled modes for applications in nonlinear photonics, such as frequency upconversion.

  2. Designer cantilevers for even more accurate quantitative measurements of biological systems with multifrequency AFM

    Science.gov (United States)

    Contera, S.

    2016-04-01

    Multifrequency excitation/monitoring of cantilevers has made it possible both to achieve fast, relatively simple, nanometre-resolution quantitative mapping of mechanical of biological systems in solution using atomic force microscopy (AFM), and single molecule resolution detection by nanomechanical biosensors. A recent paper by Penedo et al [2015 Nanotechnology 26 485706] has made a significant contribution by developing simple methods to improve the signal to noise ratio in liquid environments, by selectively enhancing cantilever modes, which will lead to even more accurate quantitative measurements.

  3. Characterization of Decarburization of Steels Using a Multifrequency Electromagnetic Sensor: Experiment and Modeling

    Science.gov (United States)

    Hao, X. J.; Yin, W.; Strangwood, M.; Peyton, A. J.; Morris, P. F.; Davis, C. L.

    2009-04-01

    A potential online nondestructive method using a multifrequency electromagnetic (EM) sensor to measure the decarburization of steels has been proposed and tested. Online (hot) testing was simulated, using composite samples comprised of a 316 stainless steel (paramagnetic) core and a surrounding tube of ferritic steel (ferromagnetic), with thicknesses between 100 and 600 μm. The sensor can detect the decarburization and quantify the depth. Offline (cold) measurement of decarburized high-carbon steel rods was also carried out and compared with the online measurement. The relationship between the sensor output and the decarburized layer type/thickness has been modeled using finite element methods (FEMs).

  4. Design and characterization of a fractal-inspired multi-frequency piezoelectric energy converter

    Directory of Open Access Journals (Sweden)

    Davide Castagnetti

    2013-01-01

    Full Text Available A promising harvesting technique, in terms of simplicity and efficiency, is the conversion of ambient kinetic energy through piezoelectric materials. This work aims to design and investigate a piezoelectric converter conform to a fractal-inspired, multi-frequency structure previously presented by the author. A physical prototype of the converter is built and experimentally examined, up to 120 Hz, in terms of modal response and power output. Three eigenfrequencies are registered and the power output is particularly good at the fundamental eigenfrequency. Also the effect of the resistive load applied to the converter is investigated.

  5. Multi-frequency acoustic metasurface for extraordinary reflection and sound focusing

    Directory of Open Access Journals (Sweden)

    Yi-Fan Zhu

    2016-12-01

    Full Text Available We theoretically and numerically present the design of multi-frequency acoustic metasurfaces (MFAMs with simple structure that can work not only at fundamental frequency, but also at their harmonic frequencies, which breaks the single frequency limitation in conventional resonance-based acoustic metasurfaces. The phase matched condition for achromatic manipulation is discussed. We demonstrate achromatic extraordinary reflection and sound focusing at 1700Hz, 3400Hz, and 5100Hz, that is, they have the same reflection direction and the same focusing position. This significant feature may pave the way to new type of acoustic metasurface, and will also extend acoustic metasurface applications to strongly nonlinear source cases.

  6. A VLA ARCHIVE OBSERVATION OF THE YOUNGEST KNOWN GALACTIC SUPERNOVA REMNANT G1.9+0.3

    Directory of Open Access Journals (Sweden)

    Yolanda Gómez

    2009-01-01

    Full Text Available Presentamos el análisis de una observación de archivo sin publicar hecha con el Very Large Array a 1.49 GHz en 1989 hacia la remanente de supernova G1.9+0.3, la más joven conocida en la Galaxia. Esta observación concuerda con la evolución temporal del tama~no angular reportada anteriormente. Derivamos una tasa de expansión angular de 0:46 +- 0:11% por año y estimamos una edad de 220+-70/45 años comparando las imágenes de 1985 y 1989.

  7. Redox modulation of adjacent thiols in VLA-4 by AS101 converts myeloid leukemia cells from a drug-resistant to drug-sensitive state.

    Science.gov (United States)

    Layani-Bazar, Adi; Skornick, Itai; Berrebi, Alain; Pauker, Maor H; Noy, Elad; Silberman, Alon; Albeck, Michael; Longo, Dan L; Kalechman, Yona; Sredni, Benjamin

    2014-06-01

    Interaction between the integrin VLA-4 on acute myelogenous leukemia (AML) cells with stromal fibronectin is a decisive factor in chemotherapeutic resistance. In this study, we provide a rationale for a drug repositioning strategy to blunt integrin activation in AML cells and restore their sensitivity to chemotherapy. Specifically, we demonstrate that the nontoxic tellurium compound AS101, currently being evaluated in clinical trials, can abrogate the acquired resistance of AML. Mechanistic investigations revealed that AS101 caused redox inactivation of adjacent thiols in the exofacial domain of VLA-4 after its ligation to stromal fibronectin. This effect triggered cytoskeletal conformational changes that decreased PI3K/Akt/Bcl2 signaling, an obligatory step in chemosensitization by AS101. In a mouse xenograft of AML derived from patient leukemic cells with high VLA-4 expression and activity, we demonstrated that AS101 abrogated drug resistance and prolonged survival in mice receiving chemotherapy. Decreased integrin activity was confirmed on AML cells in vivo. The chemosensitizing activity of AS101 persisted in hosts with defective adaptive and innate immunity, consistent with evidence that integrin deactivation was not mediated by heightening immune attack. Our findings provide a mechanistic rationale to reposition the experimental clinical agent, AS101, to degrade VLA-4-mediated chemoresistance and improve clinical responses in patients with AML.

  8. Nonselective excitation of pulsed ELDOR using multi-frequency microwaves

    Science.gov (United States)

    Asada, Yuki; Mutoh, Risa; Ishiura, Masahiro; Mino, Hiroyuki

    2011-12-01

    The use of a polychromatic microwave pulse to expand the pumping bandwidth in pulsed electron-electron double resonance (PELDOR) was investigated. The pumping pulse was applied in resonance with the broad (˜100 mT) electron paramagnetic resonance (EPR) signal of the manganese cluster of photosystem II in the S 2 state. The observation pulses were in resonance with the narrow EPR signal of the tyrosine radical, YDrad . It was found that in the case of the polychromatic pumping pulse containing five harmonics with the microwave frequencies between 8.5 and 10.5 GHz the PELDOR effect corresponding to the dipole interaction between the Mn cluster and YDrad was about 2.9 times larger than that achieved with a monochromatic pulse. In addition to the dipolar modulation, the nuclear modulation effects were observed. The effects could be suppressed by averaging the PELDOR trace over the time interval between the observation microwave pulses. The polychromatic excitation technique described will be useful for improving the PELDOR sensitivity in the measurements of long distances in biological samples, where the pair consists of a radical with a narrow EPR spectrum and slow phase relaxation, and a metal center that has a broad EPR spectrum and a short phase relaxation time.

  9. The Effect of Subcutaneous Fat on Electrical Impedance Myography: Electrode Configuration and Multi-Frequency Analyses.

    Directory of Open Access Journals (Sweden)

    Le Li

    Full Text Available This study investigates the impact of the subcutaneous fat layer (SFL thickness on localized electrical impedance myography (EIM, as well as the effects of different current electrodes, varying in distance and direction, on EIM output. Twenty-three healthy subjects underwent localized multi-frequency EIM on their biceps brachii muscles with a hand-held electrode array. The EIM measurements were recorded under three different configurations: wide (or outer longitudinal configuration 6.8 cm, narrow (or inner longitudinal configuration 4.5 cm, and narrow transverse configuration 4.5 cm. Ultrasound was applied to measure the SFL thickness. Coefficients of determination (R2 of three EIM variables (resistance, reactance, and phase and SFL thickness were calculated. For the longitudinal configuration, the wide distance could reduce the effects of the subcutaneous fat when compared with the narrow distance, but a significant correlation still remained for all three EIM parameters. However, there was no significant correlation between SFL thickness and reactance in the transverse configuration (R2 = 0.0294, p = 0.434. Utilizing a ratio of 50kHz/100kHz phase was found to be able to help reduce the correlation with SFL thickness for all the three configurations. The findings indicate that the appropriate selection of the current electrode distance, direction and the multi-frequency phase ratio can reduce the impact of subcutaneous fat on EIM. These settings should be evaluated for future clinical studies using hand-held localized arrays to perform EIM.

  10. Energy harvesting from a multifrequency response of a tuned bending-torsion system

    Science.gov (United States)

    Abdelkefi, A.; Nayfeh, A. H.; Hajj, M. R.; Najar, F.

    2012-07-01

    We investigate the benefits of tuning the frequencies of an energy harvester to extract more energy from a base excitation that comprises three frequency components. The energy harvester is composed of a unimorph cantilever beam with asymmetric tip masses. By adjusting the asymmetry of the tip masses, we can tune this beam-mass structure to harvest energy from multifrequency components of a base excitation. We model the beam using the Euler-Bernoulli beam theory and use the first three global mode shapes of the harvester in a Galerkin procedure to derive a reduced-order model describing its response. We derive an exact analytical solution for the tip deflection, twisting angle, voltage output, and harvested electrical power. Using this solution, we investigate the advantages of harvesting energy from a response that contains multifrequencies in comparison to a response that contains a single frequency by tuning only the fundamental frequency. The advantages of this bending-torsion energy harvester and the effect of its tuning are investigated for different short- and open-circuit configurations. The results show that, through a proper tuning of this bending-torsion harvester, the harvested power can be increased significantly and it can be made to cover a wide range of electrical load resistances.

  11. The use of Cole-Cole plots to compare two multifrequency bioimpedance instruments.

    Science.gov (United States)

    Stroud, D B; Cornish, B H; Thomas, B J; Ward, L C

    1995-10-01

    Two commercially available multifrequency bioimpedance spectrometers (Xitron 4000B and SEAC SFB3) were compared by performing measurements on a set of electronic circuits and by studying 14 healthy volunteers. Output data were plotted as reactance versus resistance and fitted with a semi-circle using a least squares fitting program. In tests with six electronic circuits both instruments produced impedance loci that were well described by semicircular Cole-Cole plots, though there were some minor discrepancies using the Xitron instrument at frequencies above 150 kHz. When tested on the volunteers the SEAC instrument gave very good fits (RMSE = 1.5 Omega) to a semi-circle from 5-600 kHz on all volunteers. The Xitron instrument gave excellent fits to the semi-circle between 5 and 55 kHz (RMSE = 0.7 Omega) but above 55 kHz the phase measurements stayed constant or even increased, confirming the anomalous behaviour reported by other authors. The conclusions to be drawn are that the semicircular plots predicted by the Cole-Cole theory give a very good description of multifrequency impedance data recorded by the SEAC SFB3 instrument, on human subjects, for frequencies between 5 and 600 kHz. The Xitron 4000B is not able to reproduce the theoretically expected results in humans above 55 kHz.

  12. Multi-frequency spin manipulation using rapidly tunable superconducting coplanar waveguide microresonators

    Science.gov (United States)

    Asfaw, A. T.; Sigillito, A. J.; Tyryshkin, A. M.; Schenkel, T.; Lyon, S. A.

    2017-07-01

    In this work, we demonstrate the use of frequency-tunable superconducting NbTiN coplanar waveguide microresonators for multi-frequency pulsed electron spin resonance (ESR) experiments. By applying a bias current to the center pin, the resonance frequency (˜7.6 GHz) can be continuously tuned by as much as 95 MHz in 270 ns without a change in the quality factor of 3000 at 2 K. We demonstrate the ESR performance of our resonators by measuring donor spin ensembles in silicon and show that adiabatic pulses can be used to overcome magnetic field inhomogeneities and microwave power limitations due to the applied bias current. We take advantage of the rapid tunability of these resonators to manipulate both phosphorus and arsenic spins in a single pulse sequence, demonstrating pulsed double electron-electron resonance. Our NbTiN resonator design is useful for multi-frequency pulsed ESR and should also have applications in experiments where spin ensembles are used as quantum memories.

  13. A multi-frequency impedance analysing instrument for eddy current testing

    Science.gov (United States)

    Yin, W.; Dickinson, S. J.; Peyton, A. J.

    2006-02-01

    This paper presents the design of a high-performance multi-frequency impedance analysing instrument (MFIA) for eddy current testing which has been developed primarily for monitoring a steel production process using an inductive sensor. The system consists of a flexible multi-frequency waveform generator and a voltage/current measurement unit. The impedance of the sensor is obtained by cross-spectral analysis of the current and voltage signals. The system contains high-speed digital-to-analogue, analogue-to-digital converters and dual DSPs with one for control and interface and one dedicated to frequency-spectra analysis using fast Fourier transformation (FFT). The frequency span of the signal that can be analysed ranges from 1 kHz to 8 MHz. The system also employs a high-speed serial port interface (USB) to communicate with a personal computer (PC) and to allow for fast transmission of data and control commands. Overall, the system is capable of delivering over 250 impedance spectra per second. Although the instrument has been developed mainly for use with an inductive sensor, the system is not restricted to inductive measurement. The flexibility of the design architecture is demonstrated with capacitive and resistive measurements by using appropriate input circuitry. Issues relating to optimizing the phase of the spectra components in the excitation waveform are also discussed.

  14. Utilisation of multi-frequency VEMPs improves diagnostic accuracy for Meniere's disease.

    Science.gov (United States)

    Maxwell, Rebecca; Jerin, Claudia; Gürkov, Robert

    2017-01-01

    To determine whether vestibular evoked myogenic potential (VEMP) measurements that combine the VEMP 500/1000 Hz frequency tuning ratio and the inter-aural asymmetry ratio can reliably detect unilateral Meniere's disease ears as compared to healthy controls. Forty-two consecutive patients with certain unilateral Meniere's disease (as confirmed using a locally enhanced inner ear MRI (LEIM)) were assessed. Cervical vestibular evoked myogenic potentials (cVEMP) and ocular vestibular evoked myogenic potentials (oVEMP) were recorded at 500 and 1000 Hz. The VEMP amplitudes, asymmetry ratios, and the 500/1000 Hz amplitude ratios were compared with those of 21 age-matched healthy controls. A multi-frequency VEMPs score that combined: (1) the cVEMP 500/1000 Hz amplitude ratio, (2) the oVEMP 500/1000 Hz amplitude ratio, (3) the 500 Hz cVEMP asymmetry ratio, (4) the 1000 Hz cVEMP asymmetry ratio, produced a ROC curve with an area under the curve (AUC) of 0.814. The inclusion of audiology data further improved the result to 0.906. This score can be used to discriminate with a good degree of clinical accuracy between Meniere's ears (unilateral) and those of healthy controls. Multi-frequency VEMP analysis offers a simple, cost-effective solution to the diagnostic difficulties presented by Meniere's disease.

  15. Study of the Method of Multi-Frequency Signal Detection Based on the Adaptive Stochastic Resonance

    Directory of Open Access Journals (Sweden)

    Zhenyu Lu

    2013-01-01

    Full Text Available Recently, the stochastic resonance effect has been widely used by the method of discovering and extracting weak periodic signals from strong noise through the stochastic resonance effect. The detection of the single-frequency weak signals by using stochastic resonance effect is widely used. However, the detection methods of the multifrequency weak signals need to be researched. According to the different frequency input signals of a given system, this paper puts forward a detection method of multifrequency signal by using adaptive stochastic resonance, which analyzed the frequency characteristics and the parallel number of the input signals, adjusted system parameters automatically to the low frequency signals in the fixed step size, and then measured the stochastic resonance phenomenon based on the frequency of the periodic signals to select the most appropriate indicators in the middle or high frequency. Finally, the optimized system parameters are founded and the frequency of the given signals is extracted in the frequency domain of the stochastic resonance output signals. Compared with the traditional detection methods, the method in this paper not only improves the work efficiency but also makes it more accurate by using the color noise, the frequency is more accurate being extracted from the measured signal. The consistency between the simulation results and analysis shows that this method is effective and feasible.

  16. Interpulse multifrequency electrical impedance measurements during electroporation of adherent differentiated myotubes.

    Science.gov (United States)

    García-Sánchez, Tomás; Azan, Antoine; Leray, Isabelle; Rosell-Ferrer, Javier; Bragós, Ramon; Mir, Lluis M

    2015-10-01

    In this study, electrical impedance spectroscopy measurements are performed during electroporation of monolayers of differentiated myotubes. The time resolution of the system (1 spectrum/ms) enable 860 full spectra (21 frequencies from 5 kHz to 1.3 MHz) to be acquired during the time gap between consecutive pulses (interpulse) of a classical electroporation treatment (8 pulses, 100 μs, 1 Hz). Additionally, the characteristics of the custom microelectrode assembly used allow the experiments to be performed directly in situ in standard 24 multi-well plates. The impedance response dynamics are studied for three different electric field intensities (400, 800 and 1200 V/cm). The multifrequency information, analysed with the Cole model, reveals a short-term impedance recovery after each pulse in accordance with the fast resealing of the cell membrane, and a long-term impedance decay over the complete treatment in accordance with an accumulated effect pulse after pulse. The analysis shows differences between the lowest electric field condition and the other two, suggesting that different mechanisms that may be related with the reversibility of the process are activated. As a result of the multifrequency information, the system is able to measure simultaneously the conductivity variations due to ion diffusion during electroporation. Finally, in order to reinforce the physical interpretation of the results, a complementary electrical equivalent model is used.

  17. Experimental validation of a dual uplink multifrequency dispersive noise calibration scheme for Deep Space tracking

    Science.gov (United States)

    Mariotti, G.; Tortora, P.

    2013-03-01

    We discuss the implementation and effectiveness of a dispersive noise multifrequency calibration scheme for Deep Space tracking. We show that the combination of two phase-coherent links at X band and Ka-band, with two separate uplink carriers, can provide an effective plasma and ionospheric noise removal, in the order of 75% of the plasma noise affecting the Ka-band link. This algorithm, which we refer to as "Dual Uplink, Dual Downlink", shows a modest loss in the radio link stability, if compared to the complete, state-of-the-art calibration achieved by a more complex radio system, which supplements the two separate uplinks and downlinks at X band and Ka-band with an additional "cross-link" (X-up/Ka-down). The calibration accuracy of these two algorithms is thoroughly compared to define their advantages and shortcomings. Finally, Cassini's multifrequency tracking data acquired in 2002 during a General Relativity solar conjunction experiment aimed at the estimation of the parametrized post Newtonian parameter γ were reanalyzed to assess the capability of the Dual Uplink, Dual Downlink calibration algorithm to support accurate radio science experiments.

  18. Dynamic analysis of parametrically excited system under uncertainties and multi-frequency excitations

    Science.gov (United States)

    Wei, Sha; Han, Qinkai; Peng, Zhike; Chu, Fulei

    2016-05-01

    Some system parameters in mechanical systems are always uncertain due to uncertainties in geometric and material properties, lubrication condition and wear. For a more reasonable estimation of dynamic analysis of the parametrically excited system, the effect of uncertain parameters should be taken into account. This paper presents a new non-probabilistic analysis method for solving the dynamic responses of parametrically excited systems under uncertainties and multi-frequency excitations. By using the multi-dimensional harmonic balance method (MHBM) and the Chebyshev inclusion function (CIF), an interval multi-dimensional harmonic balance method (IMHBM) is obtained. To illustrate the accuracy of the proposed method, a time-varying geared system of wind turbine with different kinds of uncertainties is demonstrated. By comparing with the results of the scanning method, it is shown that the presented method is valid and effective for the parametrically excited system with uncertainties and multi-frequency excitations. The effects of some uncertain system parameters including uncertain mesh stiffnesses and uncertain bearing stiffnesses on the frequency responses of the system are also discussed in detail. It is shown that the dynamic responses of the system are insensitive to the uncertain mesh stiffness and bearing stiffnesses of the planetary gear stage. The uncertain bearing stiffnesses of the intermediate and high-speed stages will lead to relatively large uncertainties in the dynamic responses around resonant regions. It will provide valuable guidance for the optimal design and condition monitoring of wind turbine gearboxes.

  19. The multifrequency spectrum of the starburst galaxy NGC 2782

    Science.gov (United States)

    Kinney, A. L.; Bregman, J. N.; Huggins, P. J.; Glassgold, A. E.; Cohen, R. D.

    1984-01-01

    The nuclear region of NGC 2782 has been observed at radio, millimeter, infrared, optical, ultraviolet, and X-ray frequencies to understand the ionization source that gives rise to the narrow emission lines. The continuum is probably caused by a normal galactic population plus considerable numbers of young stars and warm dust. In the ultraviolet and optical spectra, which are powerful diagnostics, no strong lines are detected in the 1200 A-3200 A region aside from L-alpha, and the optical emission lines cover only a narrow ionization range. The line and continuum properties suggest that NGC 2782 is a starburst galaxy, in which young stars photoionize the surrounding gas.

  20. Evaluation of Data from the Multi-frequency Scanning Microwave Radiometer (MSMR) and Its Potential for Soil Moisture Retrieval

    Science.gov (United States)

    Wen, J.; Jackson, T. J.; Bindlish, R.; Su, Z. B.

    2003-12-01

    The Multi-frequency Scanning Microwave Radiometer (MSMR) aboard the India Space Research Organization - Oceansat-1 (IRS-P4) platform measured land surface brightness temperature at low frequencies and provided an opportunity for exploring large-scale soil moisture retrieval during its two years period of observation. Several data issues had to be addressed before using the data. These included geolocation errors, data calibration and anthropogenic Radio-frequency Interference (RFI). Calibration was evaluated by comparisons to the Tropical Rainfall Measuring Mission/Microwave Imager (TRMM/TMI) measured brightness temperatures. A negative bias of 3.4 and 3.6 K were observed for the 10.6 GHz horizontal and vertical polarization bands respectively, negative differences of 14.0 and 10.1 K were found between the MSMR 6.6 GHz and TMI 10.6 GHz horizontal and vertical polarizations over land surface. These results suggested that additional calibration of the MSMR data was required. Comparisons between the MSMR measured brightness temperature and ground measured volumetric soil moisture collected during two field campaigns indicated that the lower frequency and horizontal polarization had higher sensitivity to the ground soil moisture. Using a previously developed soil emission model, multi-temporal soil moisture was retrieved for the continental United States. Comparisons between the MSMR based soil moisture and ground measured volumetric soil moisture indicated an uncertain error of 3.8 percent in the estimated soil moisture. This data may provide a valuable extension to the SMMR and AMSR instruments since it covers a portion of the time between the two missions. Keywords: passive microwave, brightness temperature, soil moisture, satellite remote sensing.

  1. Modeling multi-frequency diurnal backscatter from a walnut orchard

    Science.gov (United States)

    Mcdonald, Kyle C.; Dobson, Myron C.; Ulaby, Fawwaz T.

    1991-01-01

    The Michigan Microwave Canopy Scattering Model (MIMICS) is used to model scatterometer data that were obtained during the August 1987 EOS (Earth Observing System) synergism study. During this experiment, truck-based scatterometers were used to measure radar backscatter from a walnut orchard in Fresno County, California. Multipolarized L- and X-band data were recorded for orchard plots for which dielectric and evapotranspiration characteristics were monitored. MIMICS is used to model a multiangle data set in which a single orchard plot was observed at varying impedance angles and a series of diurnal measurements in which backscatter from this same plot was measured continuously over several 24-h periods. MIMICS accounts for variations in canopy backscatter driven by changes in canopy state that occur diurnally as well as on longer time scales. L-band backscatter is dependent not only on properties of the vegetation but also on properties of the underlying soil surface. The behavior of the X-band backscatter is dominated by properties of the tree crowns.

  2. Multifrequency polarimetry of a complete sample of PACO radio sources

    Science.gov (United States)

    Galluzzi, V.; Massardi, M.; Bonaldi, A.; Casasola, V.; Gregorini, L.; Trombetti, T.; Burigana, C.; De Zotti, G.; Ricci, R.; Stevens, J.; Ekers, R. D.; Bonavera, L.; di Serego Alighieri, S.; Liuzzo, E.; López-Caniego, M.; Mignano, A.; Paladino, R.; Toffolatti, L.; Tucci, M.

    2017-03-01

    We present high-sensitivity polarimetric observations (σP ≃0.6 mJy) in six bands covering the 5.5-38 GHz range of a complete sample of 53 compact extragalactic radio sources brighter than 200 mJy at 20 GHz. The observations, carried out with the Australia Telescope Compact Array, achieved a 91 per cent detection rate (at 5σ). Within this frequency range, the spectra of about 95 per cent of sources are well fitted by double power laws, both in total intensity and in polarization, but the spectral shapes are generally different in the two cases. Most sources were classified as either steep- or peaked-spectrum but less than 50 per cent have the same classification in total and in polarized intensity. No significant trends of the polarization degree with flux density or with frequency were found. The mean variability index in total intensity of steep-spectrum sources increases with frequency for a 4-5 yr lag, while no significant trend shows up for the other sources and for the 8 yr lag. In polarization, the variability index, which could be computed only for the 8 yr lag, is substantially higher than in total intensity and has no significant frequency dependence.

  3. [Study on spectral gain characterization of FWM processes with multi-frequency pumps in photonic crystal fiber].

    Science.gov (United States)

    Hui, Zhan-Qiang

    2011-10-01

    Spectral gain induced by four-wave-mixing with multi-frequency pump was investigated by exploiting the data signal and continue lights co-propagation in dispersion flattened high nonlinear photonic crystal fiber (PCF). The effects of wavelength drift of pump lights, polarization state of orthogonal or parallel of pump lights, polarization mismatch of signal light versus orthogonal pump lights, total power of signal and probe light on the spectrum gain were analyzed. The results show that good FWM gain effects with multi-frequency pump can be obtained in 36.4 nm wavelength range when power ratio of pump to probe light is appropriate and with identical polarization. Furthermore, the gain of FWM with multi-frequency pump is very sensitive to polarization fluctuation and the different idle waves obtain different gain with the variation in signal polarization state. Moreover, the impact of pump numbers was investigated. The obtained results would be helpful for further research on ultrahigh-speed all optical signal processing devices exploiting the FWM with multi-frequency pump in PCF for future photonics network.

  4. Prediction of extracellular water and total body water by multifrequency bio-electrical impedance in a Southeast Asian population

    NARCIS (Netherlands)

    Guricci, S.; Hatriyanti, Y.; Hautvast, J.G.A.J.; Deurenberg, P.

    1999-01-01

    Three different adult Indonesian population groups living on Sumatra (Palembang), Java (Depok) and Sulawesi (Makale) participated in a study on body composition. Body weight, body height and multifrequency bioelectrical impedance (1, 5, 50 and 100 kHz) were measured and in addition total body water

  5. Electrical Impedance Spectroscopic Studies on Broiler Chicken Tissue Suitable for the Development of Practical Phantoms in Multifrequency EIT

    Directory of Open Access Journals (Sweden)

    Tushar Kanti Bera

    2011-06-01

    Full Text Available Phantoms are essential for assessing the system performance in Electrical Impedance Tomography (EIT. Saline phantoms with insulator inhomogeneity fail to mimic the physiological structure of real body tissue in several aspects. Saline or any other salt solutions are purely resistive and hence studying multifrequency EIT systems cannot be assessed with saline phantoms because the response of the purely resistive materials do not change over frequency. Animal tissues show a variable response over a wide band of signal frequency due to their complex physiological and physiochemical structures and hence they can suitably be used as bathing medium and inhomogeneity in the phantoms of multifrequency EIT system. An efficient assessment of a multifrequency EIT system with real tissue phantom needs a prior knowledge of the impedance profile of the bathing medium as well as the inhomogeneity. In this direction Electrical Impedance Spectroscopy (EIS of broiler chicken muscle tissue paste and broiler chicken fat tissue is conducted from 10 Hz to 2 MHz using an impedance analyzer and their impedance profiles are thoroughly studied. Results show that the broiler chicken muscle tissue paste is less resistive than the fat tissue and hence it can be successfully used as the bathing medium of the phantoms for resistivity imaging in multifrequency EIT. Fat tissue is found more resistive than the muscle tissue which makes it more suitable for the inhomogeneity in phantoms of resistivity imaging study. doi:10.5617/jeb.174 J Electr Bioimp, vol. 2, pp. 48-63, 2011

  6. Dual-channel and multifrequency radar system calibration

    Science.gov (United States)

    Stjernman, Anders; Vivekanandan, J.; Nystrom, Anders

    1995-03-01

    Uncertainty in absolute gain and crosstalk factors are the primary sources of error in dual-channel radar measurements. A full two-port calibration technique compensates for the errors introduced due to an imperfect antenna system and improves the isolation between orthogonal polarization channels as long as the observed cross section is above the equivalent system noise cross section. A novel technique for calibrating a dual-polarized network analyzer-based scatterometer system is discussed. Rigorous two-port S-parameter representation is used to describe absolute gain and crosstalk characteristics. Validity of the crosstalk correction is demonstrated by measuring the point target scattering matrix. Correction factors are obtained by measuring the S-parameters of trihedral and dihedral corner reflectors of known sizes. Results of absolute gain of the antenna system are verified using independent test target cross section measurements.

  7. Multifrequency analyses of fish distributions in the northwest Atlantic

    Science.gov (United States)

    Jech, J. Michael

    2004-05-01

    Routine acoustical surveys for estimating Atlantic herring (Clupea harengus) population abundance have been conducted on Georges Bank during the autumn spawning season from 1998 to present. Acoustical data are collected with a Simrad EK500 scientific echo sounder operating at 12 or 18, 38, and 120 kHz, and split-beam (the 12-kHz system is a single beam) transducers. Biological measurements and verification of acoustical scatterers are obtained with a pelagic trawl. Acoustical data are evaluated (scrutinized) manually to remove noise, faulty bottom detections, and to classify acoustical backscattering to species. Species classification is currently subjective, and is based on the experience of the scientists and trawl catches. Objective species classification and automated fish density and abundance estimates are an obvious goal for fisheries surveys using advanced technologies. Classification methods using relationships among frequency-dependent volume backscattering strengths, such as presence-absence and combination-permutation, are described and presented. Results indicate that while classification using these methods and acoustical information alone is not robust, these methods highlight backscattering patterns within aggregations and have the potential to characterize backscattering patterns observed in fisheries acoustics data. [Work supported by NOAA Fisheries and ONR.

  8. Multifrequency radar imaging of ash plumes: an experiment at Stromboli

    Science.gov (United States)

    Donnadieu, Franck; Freret-Lorgeril, Valentin; Delanoë, Julien; Vinson, Jean-Paul; Peyrin, Frédéric; Hervier, Claude; Caudoux, Christophe; Van Baelen, Joël; Latchimy, Thierry

    2016-04-01

    Volcanic ash emissions in the atmosphere are hazardous to aviation while ash fallout affects people and human activities and may cause damage to infrastructures and economic losses. In the framework of the French Government Laboratory of Excellence ClerVolc initiative, an experiment was carried out on Stromboli volcano (Italy), between 28 September and 4 October 2015. The aim was to retrieve various physical properties of the ash plumes, especially the mass loading parameters which are critical for the modelling of ash dispersal. We used a complementary set of cutting edge techniques recording in different bands of the electromagnetic spectrum. The innovative instrument setup consisted in three radars, hyperspectral thermal infrared and dual-band UV cameras, a mini DOAS-Flyspec and a multigas sensor. A drone equipped with differential GPS was flown near the ash plumes with several sensors including SO2, CO2 and particle counter. We mainly focus on radar measurements of over 200 ash plumes and present some preliminary comparisons at three frequencies. The BASTA Doppler radar at 95 GHz, originally designed for atmospheric studies, was deployed at about 2.2 km in slant distance from the eruptive craters. It was configured to observe volumes above one of the active craters with a spatio-temporal resolution of 12.5 m and 1 s. From the same location, a 1.2 GHz volcano Doppler radar (VOLDORAD) was recording the signature of ballistics and small lapilli at 0.15 s in 60 m-deep volumes. In addition, a commercial 24 GHz micro rain Doppler radar (MRR) simultaneously recorded activity from the Rochette station, at 400 to 650 m from the active craters with a sampling rate of 10 s and a resolution of 25 m. The latter was pointing almost perpendicularly to the other radar beams. Reflectivity factors were measured inside the ash plume above the source vent by the BASTA radar (3 mm wavelength) spanning -9 to +21 dBZ. Fallout could sometimes be tracked during several minutes within

  9. Therapeutic effect of all-trans-retinoic acid (at-RA on an autoimmune nephritis experimental model: role of the VLA-4 integrin

    Directory of Open Access Journals (Sweden)

    Lucio-Cazaña Javier

    2007-01-01

    Full Text Available Abstract Background Mercuric chloride (HgCl2 induces an autoimmune nephritis in the Brown Norway (BN rats characterized by anti-glomerular basement membrane antibodies (anti-GBM Ab deposition, proteinuria and a severe interstitial nephritis, all evident at day 13 of the disease. We assessed the effects of all-trans retinoic acid (at-RA in this experimental model. At-RA is a vitamin A metabolite which has shown beneficial effects on several nephropathies, even though no clear targets for at-RA were provided. Methods We separated animals in four different experimental groups (HgCl2, HgCl2+at-RA, at-RA and vehicle. From each animal we collected, at days 0 and 13, numerous biological samples: urine, to measure proteinuria by colorimetry; blood to determine VLA-4 expression by flow citometry; renal tissue to study the expression of VCAM-1 by Western blot, the presence of cellular infiltrates by immunohistochemistry, the IgG deposition by immunofluorescence, and the cytokines expression by RT-PCR. Additionally, adhesion assays to VCAM-1 were performed using K562 α4 transfectant cells. ANOVA tests were used for statistical significance estimation. Results We found that at-RA significantly decreased the serum levels of anti-GBM and consequently its deposition along the glomerular membrane. At-RA markedly reduced proteinuria as well as the number of cellular infiltrates in the renal interstitium, the levels of TNF-α and IL-1β cytokines and VCAM-1 expression in renal tissue. Moreover, we reported here for the first time in an in vivo model that at-RA reduced, to basal levels, the expression of VLA-4 (α4β1 integrin induced by mercury on peripheral blood leukocytes (PBLs. In addition, using K562 α4 stable transfectant cells, we found that at-RA inhibited VLA-4 dependent cell adhesion to VCAM-1. Conclusion Here we demonstrate a therapeutic effect of at-RA on an autoimmune experimental nephritis model in rats. We report a significant reduction of the

  10. Three-dimensional ground penetrating radar imaging using multi-frequency diffraction tomography

    Energy Technology Data Exchange (ETDEWEB)

    Mast, J.E.; Johansson, E.M. [Lawrence Livermore National Lab., CA (United States)

    1994-11-15

    In this talk we present results from a three-dimensional image reconstruction algorithm for impulse radar operating in monostatic pule-echo mode. The application of interest to us is the nondestructive evaluation of civil structures such as bridge decks. We use a multi-frequency diffraction tomography imaging technique in which coherent backward propagations of the received reflected wavefield form a spatial image of the scattering interfaces within the region of interest. This imaging technique provides high-resolution range and azimuthal visualization of the subsurface region. We incorporate the ability to image in planarly layered conductive media and apply the algorithm to experimental data from an offset radar system in which the radar antenna is not directly coupled to the surface of the region. We present a rendering in three-dimensions of the resulting image data which provides high-detail visualization.

  11. Multifrequency excitation of a clamped–clamped microbeam: Analytical and experimental investigation

    KAUST Repository

    Jaber, Nizar

    2016-03-14

    Using partial electrodes and a multifrequency electrical source, we present a large-bandwidth, large-amplitude clamped–clamped microbeam resonator excited near the higher order modes of vibration. We analytically and experimentally investigate the nonlinear dynamics of the microbeam under a two-source harmonic excitation. The first-frequency source is swept around the first three modes of vibration, whereas the second source frequency remains fixed. New additive and subtractive resonances are demonstrated. We illustrated that by properly tuning the frequency and amplitude of the excitation force, the frequency bandwidth of the resonator is controlled. The microbeam is fabricated using polyimide as a structural layer coated with nickel from the top and chromium and gold layers from the bottom. Using the Galerkin method, a reduced order model is derived to simulate the static and dynamic response of the device. A good agreement between the theoretical and experimental data are reported.

  12. Ultra-broadband Terahertz Perfect Absorber Based on Multi-frequency Destructive Interference and Grating Diffraction

    CERN Document Server

    Shi, Cheng; Ji, XueBin; Chen, Lin; Cai, Bin; Zhu, YiMing

    2014-01-01

    High absorption in a wide frequency band has attracted considerable interest since their potential applications in frequency spectrum imaging systems and anti-radar cloaking. In this paper, a polarization-independent, ultra-broadband and omnidirectional terahertz absorber is proposed, fabricated and evaluated. It is experimentally demonstrated that an over 95% absorption can be obtained in the frequency range of 0.75~2.41 THz. Attributing to the multi-frequency destructive interference between the layers and the impedance-matching condition of the grating, five successive absorption peaks at 0.88 THz, 1.20 THz, 1.53 THz, 1.96 THz and 2.23 THz merged into a ultra-broadband absorption spectrum.

  13. Mathematical framework for multi-frequency identification of thin insulating and small conductive inhomogeneities

    Science.gov (United States)

    Ammari, Habib; Seo, Jin Keun; Zhang, Tingting

    2016-10-01

    We are aiming to identify the thin insulating inhomogeneities and small conductive inhomogeneities inside an electrically conducting medium by using multi-frequency electrical impedance tomography. The thin insulating inhomogeneities are considered in the form of a tubular neighborhood of a curve and small conductive inhomogeneities are regarded as circular disks. Taking advantage of the frequency dependent behavior of insulating objects, we give a rigorous derivation of the potential along thin insulating objects at various frequencies. Asymptotic formula is given to analyze relationship between inhomogeneities and boundary potential at different frequencies. In numerical simulations, spectroscopic images are provided to visualize the reconstructed admittivity at various frequencies. For the view of both kinds of inhomogeneities, an integrated reconstructed image based on principal component analysis is provided. Phantom experiments are performed by using Swisstom EIT-Pioneer Set.

  14. Design and characterization of a multi-frequency bioimpedance measurement prototype

    Science.gov (United States)

    Mattia Neto, O. E.; Porto, R. W.; Aya, J. C. C.

    2012-12-01

    A multi-frequency bioimpedance measurement prototype is proposed, validated and characterized. It consists of an Improved Howland Current Source controlled by voltage, a load voltage sensing scheme through a discrete 3-opamp instrumentation amplifier, a phase and quadrature demodulation setup through analog multipliers, and digitization and processing of the signals using a digital benchtop multimeter. The electrical characterization of the measurement channel was done for resistive loads only, on four different circuits. Measurements were made on 10 frequencies, from 100 kHz to 1 MHz, with 10 load resistances, from 100 Ω to 1 kΩ, to obtain linearity, absolute error and frequency response. The best performance among the four circuits was a maximum absolute error of 5.55 %, and -1.93 % of load current variation at the worst case scenario.

  15. Design and optimization of a harmonic probe with step cross section in multifrequency atomic force microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Cai, Jiandong; Zhang, Li [Department of Mechanical and Automation Engineering, The Chinese University of Hong Kong, Shatin, NT (Hong Kong); Wang, Michael Yu, E-mail: michael.wang@nus.edu.sg [Department of Mechanical and Automation Engineering, The Chinese University of Hong Kong, Shatin, NT (Hong Kong); Department of Mechanical Engineering, National University of Singapore, Singapore 117575 (Singapore)

    2015-12-15

    In multifrequency atomic force microscopy (AFM), probe’s characteristic of assigning resonance frequencies to integer harmonics results in a remarkable improvement of detection sensitivity at specific harmonic components. The selection criterion of harmonic order is based on its amplitude’s sensitivity on material properties, e.g., elasticity. Previous studies on designing harmonic probe are unable to provide a large design capability along with maintaining the structural integrity. Herein, we propose a harmonic probe with step cross section, in which it has variable width in top and bottom steps, while the middle step in cross section is kept constant. Higher order resonance frequencies are tailored to be integer times of fundamental resonance frequency. The probe design is implemented within a structural optimization framework. The optimally designed probe is micromachined using focused ion beam milling technique, and then measured with an AFM. The measurement results agree well with our resonance frequency assignment requirement.

  16. Implementation of a graphical user interface for the virtual multifrequency spectrometer: The VMS-Draw tool.

    Science.gov (United States)

    Licari, Daniele; Baiardi, Alberto; Biczysko, Malgorzata; Egidi, Franco; Latouche, Camille; Barone, Vincenzo

    2015-02-15

    This article presents the setup and implementation of a graphical user interface (VMS-Draw) for a virtual multifrequency spectrometer. Special attention is paid to ease of use, generality and robustness for a panel of spectroscopic techniques and quantum mechanical approaches. Depending on the kind of data to be analyzed, VMS-Draw produces different types of graphical representations, including two-dimensional or three-dimesional (3D) plots, bar charts, or heat maps. Among other integrated features, one may quote the convolution of stick spectra to obtain realistic line-shapes. It is also possible to analyze and visualize, together with the structure, the molecular orbitals and/or the vibrational motions of molecular systems thanks to 3D interactive tools. On these grounds, VMS-Draw could represent a useful additional tool for spectroscopic studies integrating measurements and computer simulations.

  17. Quantifying the Effect of Component Covariances in CMB Extraction from Multi-frequency Data

    Science.gov (United States)

    Phillips, Nicholas G.

    2008-01-01

    Linear combination methods provide a global method for component separation of multi-frequency data. We present such a method that allows for consideration of possible covariances between the desired cosmic microwave background signal and various foreground signals that are also present. We also recover information on the foregrounds including the number of foregrounds, their spectra and templates. In all this, the covariances, which we would only expect to vanish 'in the mean' are included as parameters expressing the fundamental uncertainty due to this type of cosmic variance. When we make the reasonable assumption that the CMB is Gaussian, we can compute both a mean recovered CMB map and also an RMS error map, The mean map coincides with WMAP's Internal Linear Combination map.

  18. Low-Profile Fully-Printed Multifrequency Monopoles Loaded with Complementary Metamaterial Transmission Line

    Directory of Open Access Journals (Sweden)

    Xue Li

    2015-04-01

    Full Text Available The design of a new class of multifrequency monopoles by loading a set of resonant-type complementary metamaterial transmission lines (CMTL is firstly presented. Two types of CMTL elements are comprehensively explored: the former is the epsilon negative (ENG one by loading complementary split ring resonators (CSRRs with different configurations on the signal strip, whereas the latter is the double negative (DNG one by incorporating the CSRRs and capacitive gaps. In both cases, the CMTLs are considered with different number of unit cells. By cautiously controlling the geometrical parameters of element structure, five antenna prototypes coving different communication standards (GSM, UMTS, DMB and WiMAX are designed, fabricated and measured. Numerical and experimental results illustrate that the zeroth-order resonance frequencies of the ENG and DNG monopoles are in desirable consistency. Moreover, of all operating frequencies the antennas exhibit fairly good impedance matching performances better than -10dB and quasi-omnidirectional radiation patterns.

  19. Monopole and dipole estimation for multi-frequency sky maps by linear regression

    CERN Document Server

    Wehus, I K; Eriksen, H K; Banday, A J; Dickinson, C; Ghosh, T; Gorski, K M; Lawrence, C R; Leahy, J P; Maino, D; Reich, P; Reich, W

    2014-01-01

    We describe a simple but efficient method for deriving a consistent set of monopole and dipole corrections for multi-frequency sky map data sets, allowing robust parametric component separation with the same data set. The computational core of this method is linear regression between pairs of frequency maps, often called "T-T plots". Individual contributions from monopole and dipole terms are determined by performing the regression locally in patches on the sky, while the degeneracy between different frequencies is lifted when ever the dominant foreground component exhibits a significant spatial spectral index variation. Based on this method, we present two different, but each internally consistent, sets of monopole and dipole coefficients for the 9-year WMAP, Planck 2013, SFD 100 um, Haslam 408 MHz and Reich & Reich 1420 MHz maps. The two sets have been derived with different analysis assumptions and data selection, and provides an estimate of residual systematic uncertainties. In general, our values are...

  20. N Design of an H-shaped Slot Multi-frequency Microstrip Antenna

    Institute of Scientific and Technical Information of China (English)

    YANG Hong; MOU Hong-jiang

    2014-01-01

    Conventional slot microstrip antenna is analyzed, an h-shaped multi-frequency and miniaturization slot microstrip antenna is proposed. Numerical simulation is performed for the characteristics of the antenna with the software HFSS11.0, which is a kind of simulation software based on Finite Element Method, the simulation results shown that the antenna operated at 2.26~2.42GHz, 2.67~2.82GHz , 4.28~4.39GHz and 5.76~5.89GHz when the return loss S1 <-10dB, the size reduced compare to general microstrip antenna, demonstrated the effectiveness of the design scheme. The antenna structure is simple and easily to be implemented, met the wireless LAN 802.11a/b/g/n mobile terminal antenna miniaturization and multi-band requirements.

  1. SU-E-I-52: Validation of Multi-Frequency Electrical Impedance Tomography Using Computed Tomography

    Energy Technology Data Exchange (ETDEWEB)

    Kohli, K; Liu, F; Krishnan, K [BC Cancer Agency, Surrey, BC (United Kingdom)

    2014-06-01

    Purpose: Multi-frequency EIT has been reported to be a potential tool in distinguishing a tissue anomaly from background. In this study, we investigate the feasibility of acquiring functional information by comparing multi-frequency EIT images in reference to the structural information from the CT image through fusion. Methods: EIT data was acquired from a slice of winter melon using sixteen electrodes around the phantom, injecting a current of 0.4mA at 100, 66, 24.8 and 9.9 kHz. Differential EIT images were generated by considering different combinations of pair frequencies, one serving as reference data and the other as test data. The experiment was repeated after creating an anomaly in the form of an off-centered cavity of diameter 4.5 cm inside the melon. All EIT images were reconstructed using Electrical Impedance Tomography and Diffuse Optical Tomography Reconstruction Software (EIDORS) package in 2-D differential imaging mode using one-step Gaussian Newton minimization solver. CT image of the melon was obtained using a Phillips CT Scanner. A segmented binary mask image was generated based on the reference electrode position and the CT image to define the regions of interest. The region selected by the user was fused with the CT image through logical indexing. Results: Differential images based on the reference and test signal frequencies were reconstructed from EIT data. Result illustrated distinct structural inhomogeneity in seeded region compared to fruit flesh. The seeded region was seen as a higherimpedance region if the test frequency was lower than the base frequency in the differential EIT reconstruction. When the test frequency was higher than the base frequency, the signal experienced less electrical impedance in the seeded region during the EIT data acquisition. Conclusion: Frequency-based differential EIT imaging can be explored to provide additional functional information along with structural information from CT for identifying different tissues.

  2. The acoustic spectrophonometer: a novel bioanalytical technique based on multifrequency acoustic devices.

    Science.gov (United States)

    Stevenson, A C; Araya-Kleinsteuber, B; Sethi, R S; Mehta, H M; Lowe, C R

    2003-10-01

    A measurement technique similar to optical absorption spectroscopy but based on evanescent acoustic waves is described in this paper. This format employs a planar spiral coil to vibrate a single crystal of quartz from 6 to 400 MHz, in order to measure multifrequency acoustic spectra. Consistency with the defined Sauerbrey and Kanazawa terms K1 and K2 when applied to multiple frequencies was found for these specific operating conditions in terms of a significant fit between the measured and calculated values: For an IgG surface density of 13.5 ng mm(-2) the measured value of K1 is 22.5 x 10(-6) and the calculated value is 20.4 x 10(-6), whilst for glycerol viscous loadings of 5.131 cP the measured value of K2 is 0.47 and the calculated value is 0.54. Thus for these specific surface loadings the multifrequency data fits to the predictions of the Sauerbrey model to within 10% and to Kanazawa model within 13%. However collective frequency shifts for 5.131 cP solutions of sucrose, dextran and glucose were found to exhibit an unanticipated additional variability (R2 solution was found to be significantly below the other isoviscous solutions, with a substantially reduced frequency shift and K2 value than would be expected from its bulk viscosity. In comparison with these viscous solutions, IgG protein films consistently produced linear frequency shifts with little scatter (R2 > 0.96) that were proportional to the operating frequency, and fully consistent with the Sauerbrey model under these specific conditions. A t-test value of 14.52 was calculated from the variance and mean of the two groups, and demonstrates that the acoustic spectrophonometer can be used to distinguish between the acoustic impedance characteristics of two chemical systems that are not clearly differentiable at a single operating frequency.

  3. Advanced spectral analysis of ionospheric waves observed with sparse arrays

    CERN Document Server

    Helmboldt, Joseph

    2014-01-01

    This paper presents a case study from a single, six-hour observing period to illustrate the application of techniques developed for interferometric radio telescopes to the spectral analysis of observations of ionospheric fluctuations with sparse arrays. We have adapted the deconvolution methods used for making high dynamic range images of cosmic sources with radio arrays to making comparably high dynamic range maps of spectral power of wavelike ionospheric phenomena. In the example presented here, we have used observations of the total electron content (TEC) gradient derived from Very Large Array (VLA) observations of synchrotron emission from two galaxy clusters at 330 MHz as well as GPS-based TEC measurements from a sparse array of 33 receivers located within New Mexico near the VLA. We show that these techniques provide a significant improvement in signal to noise (S/N) of detected wavelike structures by correcting for both measurement inaccuracies and wavefront distortions. This is especially true for the...

  4. HI observations of low surface brightness galaxies : Probing low-density galaxies

    NARCIS (Netherlands)

    deBlok, WJG; McGaugh, SS; vanderHulst, JM

    1996-01-01

    We present Very Large Array (VLA) and Westerbork Synthesis Radio Telescope (WSRT) 21-cm HI observations of 19 late-type low surface brightness (LSB) galaxies. Our main findings are that these galaxies, as well as having low surface brightnesses, have low HI surface densities, about a factor of simil

  5. Role of very-late antigen-4 (VLA-4) in myelin basic protein-primed T cell contact-induced expression of proinflammatory cytokines in microglial cells.

    Science.gov (United States)

    Dasgupta, Subhajit; Jana, Malabendu; Liu, Xiaojuan; Pahan, Kalipada

    2003-06-20

    The presence of neuroantigen-primed T cells recognizing self-myelin antigens within the CNS is necessary for the development of demyelinating autoimmune disease like multiple sclerosis. This study was undertaken to investigate the role of myelin basic protein (MBP)-primed T cells in the expression of proinflammatory cytokines in microglial cells. MBP-primed T cells alone induced specifically the microglial expression of interleukin (IL)-1beta, IL-1alpha tumor necrosis factor alpha, and IL-6, proinflammatory cytokines that are primarily involved in the pathogenesis of MS. This induction was primarily dependent on the contact between MBP-primed T cells and microglia. The activation of microglial NF-kappaB and CCAAT/enhancer-binding protein beta (C/EBPbeta) by MBP-primed T cell contact and inhibition of contact-mediated microglial expression of proinflammatory cytokines by dominant-negative mutants of p65 and C/EBPbeta suggest that MBP-primed T cells induce microglial expression of cytokines through the activation of NF-kappaB and C/EBPbeta. In addition, we show that MBP-primed T cells express very late antigen-4 (VLA-4), and functional blocking antibodies to alpha4 chain of VLA-4 (CD49d) inhibited the ability of MBP-primed T cells to induce microglial proinflammatory cytokines. Interestingly, the blocking of VLA-4 impaired the ability of MBP-primed T cells to induce microglial activation of only C/EBPbeta but not that of NF-kappaB. This study illustrates a novel role of VLA-4 in regulating neuroantigen-primed T cell-induced activation of microglia through C/EBPbeta

  6. Multi-Frequency Measured and Modeled Microwave Backscatter from a Highly Saline Snow Cover on Smooth First-Year Sea Ice

    Science.gov (United States)

    Nandan, V.; Geldsetzer, T.; Islam, T.; Yackel, J.; Gill, J. P. S.; Gunn, G. E.; Duguay, C. R.

    2015-12-01

    Monitoring Arctic sea ice and its snow cover variability is of prime importance in Cryosphere research. Snow cover plays major roles in the energy balance of Arctic sea ice and also required to understand the present condition and future behavior of first-year ice (FYI). Microwave remote sensing provides the most effective means to acquire near-real time thermodynamic information about snow cover on smooth FYI. Microwave interaction with snow-covered sea ice is a function of both snow and ice electro-thermo-physical properties such as shape, size and orientation of scatterers, surface roughness, complex dielectric constant as a function primarily of brine volume, and brine volume as a function of temperature, salinity and density; as well as microwave parameters such as incidence angle, polarization and wavelength. Fluctuations in snow cover thermodynamics affect microwave propagation, attenuation, and scattering through the influence that brine volume exerts on interfacial and volume characteristics of snow and ice layers. Previous studies exhibit reduced penetration depth and inaccurate snow thickness estimates, using a single-frequency approach (C-band), from highly saline snow covers. We present a case study based on an observational (Ku-, X- and C-band surface-based fully-polarimetric microwave scatterometer system) and theoretical multi-frequency approach (using first-order microwave scattering and penetration depth models), to understand the sensitivity of varying snow thermodynamics on microwave scattering and penetration. The study site is a 14cm highly saline snow cover over smooth FYI, near Resolute Bay, Nunavut, Canada (Figure 1), with in-situ snow property measurements acquired from 18th to 20th May 2012, when snow layer temperatures were found to be fluctuating (Figure 2). Preliminary results show variations in observed Ku-, X- and C-band VV backscatter (Figure 3) and penetration (Figure 5) for warm (18th and 20th May) and cold (19th May) snow cases

  7. Radio frequency current-voltage probe for impedance and power measurements in multi-frequency unmatched loads

    Science.gov (United States)

    Lafleur, T.; Delattre, P. A.; Booth, J. P.; Johnson, E. V.; Dine, S.

    2013-01-01

    A broad-band, inline current-voltage probe, with a characteristic impedance of 50 Ω, is presented for the measurement of voltage and current waveforms, impedance, and power in rf systems. The probe, which uses capacitive and inductive sensors to determine the voltage and current, respectively, can be used for the measurement of single or multi-frequency signals into both matched and unmatched loads, over a frequency range of about 1-100 MHz. The probe calibration and impedance/power measurement technique are described in detail, and the calibrated probe results are compared with those obtained from a vector network analyzer and other commercial power meters. Use of the probe is demonstrated with the measurement of power into an unmatched capacitively coupled plasma excited by multi-frequency tailored voltage waveforms.

  8. Radio frequency current-voltage probe for impedance and power measurements in multi-frequency unmatched loads.

    Science.gov (United States)

    Lafleur, T; Delattre, P A; Booth, J P; Johnson, E V; Dine, S

    2013-01-01

    A broad-band, inline current-voltage probe, with a characteristic impedance of 50 Ω, is presented for the measurement of voltage and current waveforms, impedance, and power in rf systems. The probe, which uses capacitive and inductive sensors to determine the voltage and current, respectively, can be used for the measurement of single or multi-frequency signals into both matched and unmatched loads, over a frequency range of about 1-100 MHz. The probe calibration and impedance/power measurement technique are described in detail, and the calibrated probe results are compared with those obtained from a vector network analyzer and other commercial power meters. Use of the probe is demonstrated with the measurement of power into an unmatched capacitively coupled plasma excited by multi-frequency tailored voltage waveforms.

  9. Multi-frequency study of Local Group Supernova Remnants The curious case of the Large Magellanic Cloud SNR J0528-6714

    CERN Document Server

    Crawford, E J; Haberl, F; Pietsch, W; Payne, J L; De Horta, A Y

    2010-01-01

    Aims. Recent ATCA, XMM-Newton and MCELS observations of the Magellanic Clouds (MCs) cover a number of new and known SNRs which are poorly studied, such as SNR J0528-6714 . This particular SNR exhibits luminous radio-continuum emission, but is one of the unusual and rare cases without detectable optical and very faint X-ray emission (initially detected by ROSAT and listed as object [HP99] 498). We used new multi-frequency radio-continuum surveys and new optical observations at H{\\alpha}, [S ii] and [O iii] wavelengths, in combination with XMM-Newton X-ray data, to investigate the SNR properties and to search for a physical explanation for the unusual appearance of this SNR. Methods. We analysed the X-ray and Radio-Continuum spectra and present multi-wavelength morphological studies of this SNR. Results. We present the results of new moderate resolution ATCA observations of SNR J0528-6714. We found that this object is a typical older SNR with a radio spectral index of {\\alpha}=-0.36 \\pm 0.09 and a diameter of D...

  10. Single dish performance of KVN 21-m radio telescopes:Simultaneous observations at 22 and 43 GHz

    CERN Document Server

    Lee, Sang-Sung; Oh, Chung Sik; Han, Seog-Tae; Je, Do-Heung; Kim, Kee-Tae; Wi, Seog-Oh; Cho, Se-Hyung; Sohn, Bong Won; Kim, Jaeheon; Lee, Jeewon; Oh, Se-Jin; Song, Min-Gyu; Kang, Jiman; Jung, Moon-Hee; Lee, Jeong Ae; Oh, Junghwan; Bae, Jae-Han; Yun, So-Young; Lee, Jung-Won; Kim, Bong Gyu; Chung, Hyunsoo; Roh, Duk-Gyoo; Lee, Chang Hoon; Kim, Hyun Goo; Kim, Hyo Ryoung; Yeom, Jae-Hwan; Kurayama, Tomoharu; Jung, Taehyun; Park, Pulun; Kim, Min Joong; Yoon, Dong-Hwan; Kim, Won-Ju

    2011-01-01

    We report simultaneous multi-frequency observing performance at 22 and 43 GHz of the 21-m shaped-Cassegrain radio telescopes of the Korean VLBI Network (KVN). KVN is the first millimeter-dedicated VLBI network in Korea having a maximum baseline length of 480 km. It currently operates at 22 and 43 GHz and planed to operate in four frequency bands, 22, 43, 86, and 129 GHz. The unique quasioptics of KVN enable simultaneous multi-frequency observations based on efficient beam filtering and accuarate antenna-beam alignment at 22 and 43 GHz. We found that the offset of the beams is within 20 degrees.

  11. Optimization of measurement methods for a multi-frequency electromagnetic field from mobile phone base station using broadband EMF meter

    Directory of Open Access Journals (Sweden)

    Paweł Bieńkowski

    2015-10-01

    Full Text Available Background: This paper presents the characteristics of the mobile phone base station (BS as an electromagnetic field (EMF source. The most common system configurations with their construction are described. The parameters of radiated EMF in the context of the access to methods and other parameters of the radio transmission are discussed. Attention was also paid to antennas that are used in this technology. Material and Methods: The influence of individual components of a multi-frequency EMF, most commonly found in the BS surroundings, on the resultant EMF strength value indicated by popular broadband EMF meters was analyzed. The examples of metrological characteristics of the most common EMF probes and 2 measurement scenarios of the multisystem base station, with and without microwave relays, are shown. Results: The presented method for measuring the multi-frequency EMF using 2 broadband probes allows for the significant minimization of measurement uncertainty. Equations and formulas that can be used to calculate the actual EMF intensity from multi-frequency sources are shown. They have been verified in the laboratory conditions on a specific standard setup as well as in real conditions in a survey of the existing base station with microwave relays. Conclusions: Presented measurement methodology of multi-frequency EMF from BS with microwave relays, validated both in laboratory and real conditions. It has been proven that the described measurement methodology is the optimal approach to the evaluation of EMF exposure in BS surrounding. Alternative approaches with much greater uncertainty (precaution method or more complex measuring procedure (sources exclusion method are also presented. Med Pr 2015;66(5:701–712

  12. Multi-frequency accelerating strategy for the contrast source inversion method of ultrasound waveform tomography using pulse data

    Science.gov (United States)

    Lin, Hongxiang; Azuma, Takashi; Qu, Xiaolei; Takagi, Shu

    2017-03-01

    In this work, we construct a multi-frequency accelerating strategy for the contrast source inversion (CSI) method using pulse data in the time domain. CSI is a frequency-domain inversion method for ultrasound waveform tomography that does not require the forward solver through the process of reconstruction. Several prior researches show that the CSI method has a good performance of convergence and accuracy in the low-center-frequency situation. In contrast, utilizing the high-center-frequency data leads to a high-resolution reconstruction but slow convergence on large numbers of grid. Our objective is to take full advantage of all low frequency components from pulse data with the high-center-frequency data measured by the diagnostic device. First we process the raw data in the frequency domain. Then multi-frequency accelerating strategy helps restart CSI in the current frequency using the last iteration result obtained from the lower frequency component. The merit of multi- frequency accelerating strategy is that computational burden decreases at the first few iterations. Because the low frequency component of dataset computes on the coarse grid with assuming a fixed number of points per wavelength. In the numerical test, the pulse data were generated by the K-wave simulator and have been processed to meet the computation of the CSI method. We investigate the performance of the multi-frequency and single-frequency reconstructions and conclude that the multi-frequency accelerating strategy significantly enhances the quality of the reconstructed image and simultaneously reduces the average computational time for any iteration step.

  13. The dust un-biased cosmic star formation history from the 20 cm VLA-COSMOS survey

    CERN Document Server

    Smolcic, V; Zamorani, G; Bell, E F; Bondi, M; Carilli, C L; Ciliegi, P; Mobasher, B; Paglione, T; Scodeggio, M; Scoville, N

    2008-01-01

    We derive the cosmic star formation history (CSFH) out to z=1.3 using a sample of ~350 radio-selected star-forming galaxies, a far larger sample than in previous, similar studies. We attempt to differentiate between radio emission from AGN and star-forming galaxies, and determine an evolving 1.4 GHz luminosity function based on these VLA-COSMOS star forming galaxies. We precisely measure the high-luminosity end of the star forming galaxy luminosity function (SFR>100 M_Sol/yr; equivalent to ULIRGs) out to z=1.3, finding a somewhat slower evolution than previously derived from mid-infrared data. We find that more stars are forming in luminous starbursts at high redshift. We use extrapolations based on the local radio galaxy luminosity function; assuming pure luminosity evolution, we derive $L_* \\propto (1+z)^{2.1 \\pm 0.2}$ or $L_* \\propto (1+z)^{2.5 \\pm 0.1}$, depending on the choice of the local radio galaxy luminosity function. Thus, our radio-derived results independently confirm the ~1 order of magnitude de...

  14. Increasingly complex bimanual multi-frequency coordination patterns are equally easy to perform with on-line relative velocity feedback.

    Science.gov (United States)

    Boyles, Jason; Panzer, Stefan; Shea, Charles H

    2012-02-01

    An experiment was conducted to determine whether multi-frequency continuous bimanual circling movements of varying difficulty (1:2, 2:3, 3:4, and 4:5) could be effectively performed following relatively little practice when on-line continuous relative velocity feedback is provided. The between-subjects results indicate extremely effective bimanual multi-frequency performance for all coordination patterns with relatively stable and continuous movements of both limbs. The findings suggest that the previous performance effects using Lissajous feedback with reciprocal movement can be extended to circling movements using on-line relative velocity feedback. Contrary to the long-held position that these coordination patterns result in increasing difficulty, we failed to find systematic relative velocity error, variability, or bias differences between the participants performing the various multi-frequency coordination patterns. Indeed, coordination error, variability, and biases were remarkably low for each of the tasks. The results clearly indicate the ease with which participants are able to produce bimanual coordination patterns typically considered difficult if not impossible when salient visual information is provided that allows the participants to detect and correct their coordination errors.

  15. On the Design of Radar Corner Reflectors for Deformation Monitoring in Multi-Frequency InSAR

    Directory of Open Access Journals (Sweden)

    Matthew C. Garthwaite

    2017-06-01

    Full Text Available Trihedral corner reflectors are being increasingly used as point targets in deformation monitoring studies using interferometric synthetic aperture radar (InSAR techniques. The frequency and size dependence of the corner reflector Radar Cross Section (RCS means that no single design can perform equally in all the possible imaging modes and radar frequencies available on the currently orbiting Synthetic Aperture Radar (SAR satellites. Therefore, either a corner reflector design tailored to a specific data type or a compromise design for multiple data types is required. In this paper, I outline the practical and theoretical considerations that need to be made when designing appropriate radar targets, with a focus on supporting multi-frequency SAR data. These considerations are tested by performing field experiments on targets of different size using SAR images from TerraSAR-X, COSMO-SkyMed and RADARSAT-2. Phase noise behaviour in SAR images can be estimated by measuring the Signal-to-Clutter ratio (SCR in individual SAR images. The measured SCR of a point target is dependent on its RCS performance and the influence of clutter near to the deployed target. The SCR is used as a metric to estimate the expected InSAR displacement error incurred by the design of each target and to validate these observations against theoretical expectations. I find that triangular trihedral corner reflectors as small as 1 m in dimension can achieve a displacement error magnitude of a tenth of a millimetre or less in medium-resolution X-band data. Much larger corner reflectors (2.5 m or greater are required to achieve the same displacement error magnitude in medium-resolution C-band data. Compromise designs should aim to satisfy the requirements of the lowest SAR frequency to be used, providing that these targets will not saturate the sensor of the highest frequency to be used. Finally, accurate boresight alignment of the corner reflector can be critical to the overall

  16. Evaluation of leg edema using a multifrequency impedance meter in patients with lymphatic obstruction.

    Science.gov (United States)

    Watanabe, R; Miura, A; Inoue, K; Haeno, M; Sakamoto, K; Kanai, H

    1989-06-01

    To evaluate quantitatively local edema, electrical tissue impedance in the leg was measured with a multifrequency impedance meter in 10 patients without edema and in 10 other patients with lymphedema after hysterectomy for uterine cervical cancer (Groups 1 and 2, respectively). Equivalent resistivity of extra- and intracellular fluid (RE, RI, respectively) and the ratio RI/RE were calculated. The difference in mean RE between Groups 1 and 2 was significant (p less than 0.05). In four patients in Group 1 and nine in Group 2, simultaneous measurements were carried out on both legs. The differences between mean RE and RI/RE in Group 2 were significant (p less than 0.05, p less than 0.025, respectively). In these 13 patients, correlation coefficients between the ratio of cross-sectional areas of both legs, and both RE and RI/RE were -0.614 (p less than 0.05) and 0.805 (p less than 0.001), respectively. The results suggest that RE and RI/RE could be used as sensitive indicators of local edema.

  17. Multi-Frequency Polarimetric SAR Classification Based on Riemannian Manifold and Simultaneous Sparse Representation

    Directory of Open Access Journals (Sweden)

    Fan Yang

    2015-07-01

    Full Text Available Normally, polarimetric SAR classification is a high-dimensional nonlinear mapping problem. In the realm of pattern recognition, sparse representation is a very efficacious and powerful approach. As classical descriptors of polarimetric SAR, covariance and coherency matrices are Hermitian semidefinite and form a Riemannian manifold. Conventional Euclidean metrics are not suitable for a Riemannian manifold, and hence, normal sparse representation classification cannot be applied to polarimetric SAR directly. This paper proposes a new land cover classification approach for polarimetric SAR. There are two principal novelties in this paper. First, a Stein kernel on a Riemannian manifold instead of Euclidean metrics, combined with sparse representation, is employed for polarimetric SAR land cover classification. This approach is named Stein-sparse representation-based classification (SRC. Second, using simultaneous sparse representation and reasonable assumptions of the correlation of representation among different frequency bands, Stein-SRC is generalized to simultaneous Stein-SRC for multi-frequency polarimetric SAR classification. These classifiers are assessed using polarimetric SAR images from the Airborne Synthetic Aperture Radar (AIRSAR sensor of the Jet Propulsion Laboratory (JPL and the Electromagnetics Institute Synthetic Aperture Radar (EMISAR sensor of the Technical University of Denmark (DTU. Experiments on single-band and multi-band data both show that these approaches acquire more accurate classification results in comparison to many conventional and advanced classifiers.

  18. High-resolution mechanical imaging of glioblastoma by multifrequency magnetic resonance elastography.

    Directory of Open Access Journals (Sweden)

    Kaspar-Josche Streitberger

    Full Text Available OBJECTIVE: To generate high-resolution maps of the viscoelastic properties of human brain parenchyma for presurgical quantitative assessment in glioblastoma (GB. METHODS: Twenty-two GB patients underwent routine presurgical work-up supplemented by additional multifrequency magnetic resonance elastography. Two three-dimensional viscoelastic parameter maps, magnitude |G*|, and phase angle φ of the complex shear modulus were reconstructed by inversion of full wave field data in 2-mm isotropic resolution at seven harmonic drive frequencies ranging from 30 to 60 Hz. RESULTS: Mechanical brain maps confirmed that GB are composed of stiff and soft compartments, resulting in high intratumor heterogeneity. GB could be easily differentiated from healthy reference tissue by their reduced viscous behavior quantified by φ (0.37±0.08 vs. 0.58±0.07. |G*|, which in solids more relates to the material's stiffness, was significantly reduced in GB with a mean value of 1.32±0.26 kPa compared to 1.54±0.27 kPa in healthy tissue (P = 0.001. However, some GB (5 of 22 showed increased stiffness. CONCLUSION: GB are generally less viscous and softer than healthy brain parenchyma. Unrelated to the morphology-based contrast of standard magnetic resonance imaging, elastography provides an entirely new neuroradiological marker and contrast related to the biomechanical properties of tumors.

  19. Development of a Multi-frequency Interferometer Telescope for Radio Astronomy (MITRA)

    Science.gov (United States)

    Ingala, Dominique Guelord Kumamputu

    2015-03-01

    This dissertation describes the development and construction of the Multi-frequency Interferometer Telescope for Radio Astronomy (MITRA) at the Durban University of Technology. The MITRA station consists of 2 antenna arrays separated by a baseline distance of 8 m. Each array consists of 8 Log-Periodic Dipole Antennas (LPDAs) operating from 200 MHz to 800 MHz. The design and construction of the LPDA antenna and receiver system is described. The receiver topology provides an equivalent noise temperature of 113.1 K and 55.1 dB of gain. The Intermediate Frequency (IF) stage was designed to produce a fixed IF frequency of 800 MHz. The digital Back-End and correlator were implemented using a low cost Software Defined Radio (SDR) platform and Gnu-Radio software. Gnu-Octave was used for data analysis to generate the relevant received signal parameters including total power, real, and imaginary, magnitude and phase components. Measured results show that interference fringes were successfully detected within the bandwidth of the receiver using a Radio Frequency (RF) generator as a simulated source. This research was presented at the IEEE Africon 2013 / URSI Session Mauritius, and published in the proceedings.

  20. Development of a Stair-Step Multifrequency Synchronized Excitation Signal for Fast Bioimpedance Spectroscopy

    Directory of Open Access Journals (Sweden)

    Yuxiang Yang

    2014-01-01

    Full Text Available Wideband excitation signal with finite prominent harmonic components is desirable for fast bioimpedance spectroscopy (BIS measurements. This work introduces a simple method to synthesize and realize a type of periodical stair-step multifrequency synchronized (MFS signal. The Fourier series analysis shows that the p-order MFS signal f(p,t has constant 81.06% energy distributed equally on its p  2nth primary harmonics. The synthesis principle is described firstly and then two examples of the 4-order and 5-order MFS signals, f(4,t and f(5,t, are synthesized. The method to implement the MFS waveform based on a field-programmable gate array (FPGA and a digital to analog converter (DAC is also presented. Both the number and the frequencies of the expected primary harmonics can be adjusted as needed. An impedance measurement experiment on a RC three-element equivalent model is performed, and results show acceptable precision, which validates the feasibility of the MFS excitation.

  1. Development of a Stair-Step Multifrequency Synchronized Excitation Signal for Fast Bioimpedance Spectroscopy

    Science.gov (United States)

    Bian, He; Du, Fangling; Sun, Qiang

    2014-01-01

    Wideband excitation signal with finite prominent harmonic components is desirable for fast bioimpedance spectroscopy (BIS) measurements. This work introduces a simple method to synthesize and realize a type of periodical stair-step multifrequency synchronized (MFS) signal. The Fourier series analysis shows that the p-order MFS signal f(p, t) has constant 81.06% energy distributed equally on its p  2nth primary harmonics. The synthesis principle is described firstly and then two examples of the 4-order and 5-order MFS signals, f(4, t) and f(5, t), are synthesized. The method to implement the MFS waveform based on a field-programmable gate array (FPGA) and a digital to analog converter (DAC) is also presented. Both the number and the frequencies of the expected primary harmonics can be adjusted as needed. An impedance measurement experiment on a RC three-element equivalent model is performed, and results show acceptable precision, which validates the feasibility of the MFS excitation. PMID:24701563

  2. Impurities and electron spin relaxations in nanodiamonds studied by multi-frequency electron spin resonance

    Science.gov (United States)

    Cho, Franklin; Takahashi, Susumu

    2014-03-01

    Nano-sized diamond or nanodiamond is a fascinating material for potential applications of fluorescence imaging and magnetic sensing of biological systems via nitrogen-vacancy defect centers in diamonds. Sensitivity of the magnetic sensing strongly depends on coupling to surrounding environmental noises, thus understanding of the environment is critical to realize the application. In the present study, we employ multi-frequency (X-band, 115 GHz and 230 GHz) continuous-wave (cw) and pulsed electron spin resonance (ESR) spectroscopy to investigate impurity contents and spin relaxation properties in various sizes of nanodiamonds. Spectra taken with our home-built 230/115 GHz cw/pulsed ESR spectrometer shows presence of two major impurity contents; single substitutional nitrogen impurities (P1) also common in bulk diamonds and paramagnetic impurities (denoted as X) unique to nanodiamonds. The ESR measurement also shows a strong dependence of the population ratio between P1 and X on particle size. Furthermore, we will discuss the nature of spin-lattice relaxation time T1 of nanodiamonds studied by pulsed ESR measurements at X-band, 115 GHz and 230 GHz.

  3. Study of body composition in small animals by a multifrequency impedancemeter

    Science.gov (United States)

    Ribbe, E.; Khider, N.; Moreno, M. V.

    2010-04-01

    Bioimpedance is essentially used today to study the body composition in the human body but not really in small animals. The aim of this paper is to develop a model for body composition in rats to help pharmaceutical labs assessing effects of medicine on rats. We propose a non invasive, rapid and scientific method. With a multifrequency impedancemeter, Z-Métrix® (BioparHom© Company France), resistances and reactances are measured at 55 frequencies for a population of 40 rats (males and females). With our model, derived from Cole-Cole model, resistances of extracellular (Re) and total body (Rinf) compartment are extrapolated. Three methods were applied: posterior to posterior leg, anterior to posterior leg on the left and on the right side. Measurements by CT imaging were performed on the anesthetized population to determine Fat Mass (FM), Lean Body Mass (LBM) and Bone Mineral Content (BMC), as our reference measurements. With electrical data, age, sex and weight, equations are created to calculate FM, LBM and BMC with the three methods. Graphs of correlation, between tissue masses calculated by bioimpedance and obtained with scanner, indicate that measurements with posterior to posterior leg are better. Moreover, there is no significantly difference between tissue masses measured by bioimpedance and with the scanner.

  4. Multifrequency simultaneous bioimpedance measurements using multitone burst signals for dynamic tissue characterization

    Science.gov (United States)

    Sanchez, B.; Bragos, R.

    2010-04-01

    In this paper we present the keypoints to perform multifrequency simultaneous bioimpedance measurements using multitone signals. Concerning the frequency distribution, tones are spread over 1kHz to 1MHz range using a custom frequency distribution which we called Bilateral Quasi Logarithmic (BQL). BQL concentrates a higher number of tones around the impedance relaxation and contains a frequency plan algorithm. It minimizes the intermodulation effects due to non-linearities behaviours of the DUT and electrodes by slightly shifting the original tones in order to guarantee a guard bandwith. Regarding the multitone phase distribution, a Genetic Algorithm (GA) has been developed to minimize multitone Crest Factor (CF). This allow us to maximize the resultant Signal to Noise Ratio (SNR) of the acquisition system. This paper also presents the relation between parameters such as sampling frequency and ADC bits with the SNR and the effect in the overall amplitude and phase error when using multitone signals as excitation waveforms. Finally, we present characterization results from a measurement system based on a modular PXI architecture.

  5. Multi-frequency simultaneous measurement of bioimpedance spectroscopy based on a low crest factor multisine excitation.

    Science.gov (United States)

    Yang, Yuxiang; Zhang, Fu; Tao, Kun; Wang, Lianhuan; Wen, He; Teng, Zhaosheng

    2015-03-01

    Bioimpedance spectroscopy (BIS) is becoming a powerful diagnostic tool for a wide variety of medical applications, and the multi-frequency simultaneous (MFS) measurement of BIS can greatly reduce measurement time and record the transient physiological status of a living body compared with traditional frequency-sweep measurement technology. This paper adopts the Van der Ouderaa's multisine, which has 31 equidistant and flat amplitude spectra and a low crest factor of 1.405 as the broadband excitation, and realizes the MFS measurement of BIS by means of spectral analysis using the fast Fourier transform algorithm. The approach to implement the multisine based on a field-programmable gate array and a digital to analog converter is described in detail, and impedance measurement experiments are performed on three resistance-capitance three-element phantoms. Experimental results show a commendable accuracy with a mean relative error of 0.55% for the impedance amplitudes, and a mean absolute error of 0.20° for the impedance phases on the 31 frequencies ranging linearly from 32 to 992 kHz. This paper validates the feasibility of the MFS technology for BIS measurement based on the multisine excitation.

  6. Smart Multi-Frequency Bioelectrical Impedance Spectrometer for BIA and BIVA Applications.

    Science.gov (United States)

    Harder, Rene; Diedrich, Andre; Whitfield, Jonathan S; Buchowski, Macie S; Pietsch, John B; Baudenbacher, Franz J

    2016-08-01

    Bioelectrical impedance analysis (BIA) is a noninvasive and commonly used method for the assessment of body composition including body water. We designed a small, portable and wireless multi-frequency impedance spectrometer based on the 12 bit impedance network analyzer AD5933 and a precision wide-band constant current source for tetrapolar whole body impedance measurements. The impedance spectrometer communicates via Bluetooth with mobile devices (smart phone or tablet computer) that provide user interface for patient management and data visualization. The export of patient measurement results into a clinical research database facilitates the aggregation of bioelectrical impedance analysis and biolectrical impedance vector analysis (BIVA) data across multiple subjects and/or studies. The performance of the spectrometer was evaluated using a passive tissue equivalent circuit model as well as a comparison of body composition changes assessed with bioelectrical impedance and dual-energy X-ray absorptiometry (DXA) in healthy volunteers. Our results show an absolute error of 1% for resistance and 5% for reactance measurements in the frequency range of 3 kHz to 150 kHz. A linear regression of BIA and DXA fat mass estimations showed a strong correlation (r(2)=0.985) between measures with a maximum absolute error of 6.5%. The simplicity of BIA measurements, a cost effective design and the simple visual representation of impedance data enables patients to compare and determine body composition during the time course of a specific treatment plan in a clinical or home environment.

  7. Sonic IR crack detection of aircraft turbine engine blades with multi-frequency ultrasound excitations

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Ding; Han, Xiaoyan [Department of Electrical and Computer Engineering, Wayne State University, Detroit, MI 48202 (United States); Newaz, Golam [Department of Mechanical Engineering, Wayne State University, Detroit, MI 48202 (United States)

    2014-02-18

    Effectively and accurately detecting cracks or defects in critical engine components, such as turbine engine blades, is very important for aircraft safety. Sonic Infrared (IR) Imaging is such a technology with great potential for these applications. This technology combines ultrasound excitation and IR imaging to identify cracks and flaws in targets. In general, failure of engine components, such as blades, begins with tiny cracks. Since the attenuation of the ultrasound wave propagation in turbine engine blades is small, the efficiency of crack detection in turbine engine blades can be quite high. The authors at Wayne State University have been developing the technology as a reliable tool for the future field use in aircraft engines and engine parts. One part of the development is to use finite element modeling to assist our understanding of effects of different parameters on crack heating while experimentally hard to achieve. The development has been focused with single frequency ultrasound excitation and some results have been presented in a previous conference. We are currently working on multi-frequency excitation models. The study will provide results and insights of the efficiency of different frequency excitation sources to foster the development of the technology for crack detection in aircraft engine components.

  8. A multi-frequency EIT system design based on telecommunication signal processors.

    Science.gov (United States)

    Robitaille, Nicolas; Guardo, Robert; Maurice, Isabelle; Hartinger, Alzbeta E; Gagnon, Hervé

    2009-06-01

    A multi-frequency electrical impedance tomography system for cardiopulmonary monitoring has been designed with specialized digital signal processors developed primarily for the telecommunications sector. The system consists of two modules: a scan-head and a base-station. The scan-head, located close to the patient's torso, contains front-end circuits for measuring transfer impedance with a 16-electrode array. The base-station, placed at the bedside, comprises 16 direct digital synthesizers, 32 digital down-converters, digital circuits to control the data acquisition sequence and a USB-2.0 microcontroller. At every step of the scan sequence, the system simultaneously measures four complex variables at eight frequencies. These variables are the potential difference between the selected pair of sense electrodes, the currents applied by the source and sink electrodes, and the current flowing through the ground electrode. Frequencies are programmable from 10 kHz to 2 MHz with a resolution of 2 mHz. Characterization tests were performed with a precision mesh phantom connected to the scan-head. For a 5 Hz frame rate, the mean signal-to-noise ratio and accuracy are, respectively, 43 dB and 95.4% for eight frequencies logarithmically spaced from 70 to 950 kHz. In vitro and in vivo time-difference images have been reconstructed.

  9. Recovering scattering obstacles by multi-frequency phaseless far-field data

    Science.gov (United States)

    Zhang, Bo; Zhang, Haiwen

    2017-09-01

    It is well known that the modulus of the far-field pattern (or phaseless far-field pattern) is invariant under translations of the scattering obstacle if only one plane wave is used as the incident field, so the shape but not the location of the obstacle can be recovered from the phaseless far-field data. This paper aims to devise an approach to break the translation invariance property of the phaseless far-field pattern. To this end, we make use of the superposition of two plane waves rather than one plane wave as the incident field. In this paper, it is mathematically proved that the translation invariance property of the phaseless far-field pattern can indeed be broken if superpositions of two plane waves are used as the incident fields for all wave numbers in a finite interval. Furthermore, a recursive Newton-type iteration algorithm in frequencies is also developed to numerically recover both the location and the shape of the obstacle simultaneously from multi-frequency phaseless far-field data. Numerical examples are also carried out to illustrate the validity of the approach and the effectiveness of the inversion algorithm.

  10. Inversion of Electromagnetic Models for Bare Soil Parameter Estimation from Multifrequency Polarimetric SAR Data

    Directory of Open Access Journals (Sweden)

    Nazzareno Pierdicca

    2008-12-01

    Full Text Available The potentiality of polarimetric SAR data for the estimation of bare soil geophysical parameters (i.e., roughness and soil moisture is investigated in this work. For this purpose, two forward models available in the literature, able to simulate the measurements of a multifrequency radar polarimeter, have been implemented for use within an inversion scheme. A multiplicative noise has been considered in the multidimensional space of the elements of the polarimetric Covariance Matrix, by adopting a complex Wishart distribution to account for speckle effects. An additive error has been also introduced on the simulated measurements to account for calibration and model errors. Maximum a Posteriori Probability and Minimum Variance criteria have been considered to perform the inversion. As for the algorithms to implement the criteria, simple optimization/integration procedures have been used. A Neural Network approach has been adopted as well. A correlation between the roughness parameters has been also supposed in the simulation as a priori information, to evaluate its effect on the estimation accuracy. The methods have been tested on simulated data to compare their performances as function of number of looks, incidence angles and frequency bands, thus identifying the best radar configuration in terms of estimation accuracy. Polarimetric measurements acquired during MAC Europe and SIR-C campaigns, over selected bare soil fields, have been also used as validation data.

  11. Multi-frequency Radio Profiles of PSR B1133+16: radiation location and particle energy

    CERN Document Server

    Ji-Guang, Lu; Long-Fei, Hao; Zhen, Yan; Zhi-Yong, Liu; Ke-Jia, Lee; Guo-Jun, Qiao; Lun-Hua, Shang; Min, Wang; Ren-Xin, Xu; Qi-Jun, Zhi

    2015-01-01

    The pulse profile of PSR B1133+16 is usually regarded as a conal-double structure. However, its multifrequency profiles cannot simply be fitted with two Gaussian functions, and a third component is always needed to fit the bridge region (between two peaks). This would introduce additional, redundant parameters. In this paper, through a comparison of five fitting functions (Gaussian, von Mises, hyperbolic secant, square hyperbolic secant, and Lorentz), it is found that the square hyperbolic secant function can best reproduce the profile, yielding an improved fit. Moreover, a symmetric 2D radiation beam function, instead of a simple 1D Gaussian function, is used to fit the profile. Each profile with either well-resolved or not-so-well-resolved peaks could be fitted adequately using this beam function, and the bridge emission between the two peaks does not need to be a new component. Adopting inclination and impact angles based on polarization measurements, the opening angle ({\\theta}_{\\mu}0) of the radiation be...

  12. Derivation and Solution of Multifrequency Radiation Diffusion Equations for Homogeneous Refractive Lossy Media

    Energy Technology Data Exchange (ETDEWEB)

    Shestakov, A I; Vignes, R M; Stolken, J S

    2010-01-05

    Starting from the radiation transport equation for homogeneous, refractive lossy media, we derive the corresponding time-dependent multifrequency diffusion equations. Zeroth and first moments of the transport equation couple the energy density, flux and pressure tensor. The system is closed by neglecting the temporal derivative of the flux and replacing the pressure tensor by its diagonal analogue. The system is coupled to a diffusion equation for the matter temperature. We are interested in modeling annealing of silica (SiO{sub 2}). We derive boundary conditions at a planar air-silica interface taking account of reflectivities. The spectral dimension is discretized into a finite number of intervals leading to a system of multigroup diffusion equations. Three simulations are presented. One models cooling of a silica slab, initially at 2500 K, for 10 s. The other two are 1D and 2D simulations of irradiating silica with a CO{sub 2} laser, {lambda} = 10.59 {micro}m. In 2D, we anneal a disk (radius = 0.4, thickness = 0.4 cm) with a laser, Gaussian profile (r{sub 0} = 0.5 mm for 1/e decay).

  13. Multifrequency and Multistatic Inverse Synthetic Aperture Radar, with Application to FM Passive Radar

    Directory of Open Access Journals (Sweden)

    Ginolhac Guillaume

    2010-01-01

    Full Text Available This paper deals with the imaging of a moving target using a multifrequency and multistatic radar consisting in one receiver and several narrowband transmitters. Considering two hypotheses about the studied target, we derive two multistatic inverse synthetic aperture radar processors: the first one, which models the target as a set of isotropic points, performs a coherent sum of bistatic images; the second one, which models the target as a set of nonisotropic points, performs an incoherent sum of bistatic images. Numerical simulations are done, which demonstrate the efficiency of the second processor. We also apply both processors to a multistatic passive radar scenario for which the transmitters are FM stations located in a realistic configuration. We study the system performance in terms of resolution and sidelobe levels as a function of the number of transmitters and of the integration time. Both processors are applied to similar complex targets for which the scattered fields are simulated by a numerical electromagnetic code. The resulting multistatic radar images show interesting characteristics that might be used by classification algorithms in future work.

  14. Digital radiography: optimization of image quality and dose using multi-frequency software

    Energy Technology Data Exchange (ETDEWEB)

    Precht, H. [University College Lillebelt, Conrad Research Center, Odense (Denmark); Gerke, O. [Odense University Hospital, Department of Nuclear Medicine, Odense (Denmark); University of Southern Denmark, Research Unit of Health Economics, Odense (Denmark); Rosendahl, K. [Haukeland University Hospital, Section of Pediatric Radiology, Bergen (Norway); University of Bergen, Institute of Surgical Sciences, Bergen (Norway); Tingberg, A. [Skaane University Hospital, Lund University (Sweden); Medical Radiation Physics, Department of Clinical Sciences, Malmoe (Sweden); Waaler, D. [Gjoevik University College, Gjoevik (Norway)

    2012-09-15

    New developments in processing of digital radiographs (DR), including multi-frequency processing (MFP), allow optimization of image quality and radiation dose. This is particularly promising in children as they are believed to be more sensitive to ionizing radiation than adults. To examine whether the use of MFP software reduces the radiation dose without compromising quality at DR of the femur in 5-year-old-equivalent anthropomorphic and technical phantoms. A total of 110 images of an anthropomorphic phantom were imaged on a DR system (Canon DR with CXDI-50 C detector and MLT[S] software) and analyzed by three pediatric radiologists using Visual Grading Analysis. In addition, 3,500 images taken of a technical contrast-detail phantom (CDRAD 2.0) provide an objective image-quality assessment. Optimal image-quality was maintained at a dose reduction of 61% with MLT(S) optimized images. Even for images of diagnostic quality, MLT(S) provided a dose reduction of 88% as compared to the reference image. Software impact on image quality was found significant for dose (mAs), dynamic range dark region and frequency band. By optimizing image processing parameters, a significant dose reduction is possible without significant loss of image quality. (orig.)

  15. a Look at Nitrile Chemistry in SGR B2(N) Using the Combined Power of the GBT and the VLA

    Science.gov (United States)

    Steber, Amanda; Zaleski, Daniel P.; Seifert, Nathan A.; Neill, Justin; Muckle, Matt; Pate, Brooks; Corby, Joanna F.; Remijan, Anthony

    2014-06-01

    Nitriles form the most prolific family of molecules known in the ISM, and laboratory work shows that radical-driven chemistry can account for the formation of a diverse set of nitrile and imine molecules. Broadband reaction screening of nitrile chemistry in a pulsed discharge nozzle coupled to a chirped-pulse Fourier transform rotational spectrometer has enabled detections of several new interstellar species including E- and Z-ethanimine and E-cyanomethanimine. The detections were made by direct comparisons of laboratory broadband rotational spectra with the Robert C. Byrd Green Bank Telescope (GBT) PRebiotic Interstellar MOlecule Survery (PRIMOS) survey towards Sgr B2(N), the most chemically complex interstellar region known. In order to probe nitrile chemistry in Sgr B2, we targeted low energy rotational transitions in the 18-21 GHz range of several nitriles with the Karl G. Jansky Very Large Array (VLA) at ˜1 arcsecond resolution. The data indicate that most nitriles and nitrile derivatives are co-spatial with shell shaped continuum features thought to be expanding ionization fronts. The CH2CN radical and imine species in particular are NOT associated with the hot core known as the "Large Molecule Heimat", where most large organic molecules are thought to reside. This result suggests radical driven nitrile chemistry may be promoted by near-UV radiation in moderate density regions of molecular clouds, and the data will be useful for evaluating possible formation mechanisms. R.A. Loomis et al. Ap. J. L., 765, (L9), 2013. D.P. Zaleski et al. Ap. J. L., 765, (L10), 2013.

  16. Fusion of space-borne multi-baseline and multi-frequency interferometric results based on extended Kalman filter to generate high quality DEMs

    Science.gov (United States)

    Zhang, Xiaojie; Zeng, Qiming; Jiao, Jian; Zhang, Jingfa

    2016-01-01

    Repeat-pass Interferometric Synthetic Aperture Radar (InSAR) is a technique that can be used to generate DEMs. But the accuracy of InSAR is greatly limited by geometrical distortions, atmospheric effect, and decorrelations, particularly in mountainous areas, such as western China where no high quality DEM has so far been accomplished. Since each of InSAR DEMs generated using data of different frequencies and baselines has their own advantages and disadvantages, it is therefore very potential to overcome some of the limitations of InSAR by fusing Multi-baseline and Multi-frequency Interferometric Results (MMIRs). This paper proposed a fusion method based on Extended Kalman Filter (EKF), which takes the InSAR-derived DEMs as states in prediction step and the flattened interferograms as observations in control step to generate the final fused DEM. Before the fusion, detection of layover and shadow regions, low-coherence regions and regions with large height error is carried out because MMIRs in these regions are believed to be unreliable and thereafter are excluded. The whole processing flow is tested with TerraSAR-X and Envisat ASAR datasets. Finally, the fused DEM is validated with ASTER GDEM and national standard DEM of China. The results demonstrate that the proposed method is effective even in low coherence areas.

  17. Multi-Frequency Study of Supernova Remnants in the Large Magellanic Cloud. The case of LMC SNR J0530-7007

    CERN Document Server

    De Horta, A Y; Bozzetto, L M; Maggi, P; Haberl, F; Crawford, E J; Sasaki, M; Urosević, D; Pietsch, W; Gruendl, R; Dickel, J; Tothill, N F H; Chu, Y -H; Payne, J L; Collier, J D

    2012-01-01

    Context: The Supernova Remnants (SNRs) known in the Large Magellanic Cloud (LMC) show a variety of morphological structures in the different wavelength bands. This variety is the product of the conditions in the surrounding medium with which the remnant interacts and the inherent circumstances of the supernova event itself. Aims: This paper performs a multi-frequency study of the LMC SNR J0530-7007 by combining Australia Telescope Compact Array (ATCA), Molonglo Observatory Synthesis Telescope (MOST), R\\"ontgensatellit (ROSAT) and Magellanic Clouds Emission Line Survey (MCELS) observations. Methods: We analysed radio-continuum, X-ray and optical data and present a multi-wavelength morphological study of LMC SNR J0530-7007. Results We find that this object has a shell-type morphology with a size of 215"x180" (52 pc x 44 pc); a radio spectral index (alpha=-0.85+-0.13); with [Sii]/Halpha > 0.4 in the optical; and the presence of non-thermal radio and X-ray emission. Conclusions: We confirmed this object as a bona...

  18. VLA Mapping of the CO(1-0) Line in SMM J14011+0252

    CERN Document Server

    Sharon, Chelsea E; Harris, Andrew I; Thomson, Alasdair P

    2012-01-01

    We present high-resolution CO(1-0) observations of the lensed submillimeter galaxy (SMG) SMM J14011+0252 at z=2.6. Comparison to the previously-detected CO(3-2) line gives an intensity ratio of r_3,1=0.97+/-0.16 in temperature units, larger than is typical for SMGs but within the range seen in the low-z ultraluminous infrared galaxy population. Combining our new data with previous mid-J CO observations, we perform a single-phase large velocity gradient (LVG) analysis to constrain the physical conditions of the molecular gas. Acceptable models have significant degeneracies between parameters, even when we rule out all models that produce optically thin emission, but we find that the bulk of the molecular gas has T_kin=20-60 K, n_{H_2}~10^4-10^5 cm^-3, and N_CO/Delta-v=10^{17.00+/-0.25} cm^-2 km^-1 s. For our best-fit models to self-consistently recover a typical CO-to-H_2 abundance and a plausible degree of virialization, the local velocity gradient in the molecular gas must be substantially larger than its ga...

  19. The VLA-COSMOS Perspective on the IR-Radio Relation. I. New Constraints on Selection Biases and the Non-Evolution of the IR/Radio Properties of Star Forming and AGN Galaxies at Intermediate and High Redshift

    CERN Document Server

    Sargent, Mark T; Murphy, E; Aussel, H; Le Floc'h, E; Frayer, D T; Martínez-Sansigre, A; Oesch, P; Salvato, M; Smolcic, V; Zamorani, G; Brusa, M; Cappelluti, N; Carollo, C M; Ilbert, O; Kartaltepe, J; Koekemoer, A M; Lilly, S J; Sanders, D B; Scoville, N Z

    2010-01-01

    VLA 1.4 GHz (rms noise ~0.012 mJy) and MIPS 24 and 70 micron (rms noise ~0.02 and ~1.7 mJy, respectively) observations covering the 2 square degree COSMOS field are combined with an extensive multi-wavelength data set to study the evolution of the IR-radio relation at intermediate and high redshift. With ~4500 sources -- of which ~30% have spectroscopic redshifts -- the current sample is significantly larger than previous ones used for the same purpose. Both monochromatic IR/radio flux ratios (q24 & q70), as well as the ratio of the total IR and the 1.4 GHz luminosity (qTIR) are used as indicators for the IR/radio properties of star forming galaxies and AGN. Using a sample jointly selected at IR and radio wavelengths in order to reduce selection biases, we provide firm support for previous findings that the IR-radio relation remains unchanged out to at least z~1.4. Moreover, based on data from ~150 objects we also find that the local relation likely still holds at 2.5

  20. Multi-frequency EPR evidence for a binuclear CuA center in cytochrome c oxidase: studies with a 63Cu- and 65Cu-enriched, soluble domain of the cytochrome ba3 subunit II from Thermus thermophilus.

    Science.gov (United States)

    Fee, J A; Sanders, D; Slutter, C E; Doan, P E; Aasa, R; Karpefors, M; Vänngård, T

    1995-07-01

    We have recorded multi-frequency EPR spectra of 63Cu- and 65Cu-labeled, water-soluble CuA-protein from the cytochrome ba3 of T. thermophilus. The spectrum taken at the highest frequency (34.03 GHz) shows no hyperfine structure and is nominally axial with apparent gz approximately 2.18 and gxy approximately 2.00. The spectrum taken at the lowest frequency (3.93 GHz) shows a rich hyperfine structure. Analyses of the spectra show that the observed splitting arises from an interaction of the unpaired electron with two Cu nuclei and support the notion that CuA is a mixed-valent [Cu(II)/Cu(I)] complex in which the unpaired electronic spin is distributed evenly over the two Cu ions.

  1. A multifrequency study of the active star-forming complex NGC 6357 - I. Interstellar structures linked to the open cluster Pis 24

    Science.gov (United States)

    Cappa, C. E.; Barbá, R.; Duronea, N. U.; Vasquez, J.; Arnal, E. M.; Goss, W. M.; Fernández Lajús, E.

    2011-08-01

    We investigate the distribution of gas (ionized, neutral atomic and molecular) and interstellar dust in the complex star-forming region NGC 6357 with the goal of studying the interplay between the massive stars in the open cluster Pis 24 and the surrounding interstellar matter. Our study of the distribution of the ionized gas is based on narrow-band Hα, [S II]and [O III] images obtained with the Curtis-Schmidt Camera at CTIO, Chile, and on radio continuum observations at 1465 MHz taken with the VLA with a synthesized beam of 40 arcsec. The distribution of the molecular gas is analysed using 12CO(1-0) data obtained with the NANTEN radiotelescope, Chile (angular resolution = 2.7 arcmin). The interstellar dust distribution was studied using mid-infrared data from the GLIMPSE survey and far-infrared observations from IRAS. NGC 6357 consists of a large ionized shell and a number of smaller optical nebulosities. The optical, radio continuum, and near- and mid-IR images delineate the distributions of the ionized gas and interstellar dust in the H II regions and in previously unknown wind-blown bubbles linked to the massive stars in Pis 24 revealing surrounding photodissociation regions. The CO line observations allowed us to identify the molecular counterparts of the ionized structures in the complex and to confirm the presence of photodissociation regions. The action of the WR star HD 157504 on the surrounding gas was also investigated. The molecular mass in the complex is estimated to be (4 ± 2) × 105 M⊙. The mean electron densities derived from the radio data suggest electron densities >200 cm-3, indicating that NGC 6357 is a complex formed in a region of high ambient density. The known massive stars in Pis 24 and a number of newly inferred massive stars are mainly responsible for the excitation and photodissociation of the parental molecular cloud.

  2. The NRAO Observing for University Classes Program

    Science.gov (United States)

    Cannon, John M.; Van Moorsel, Gustaaf A.

    2017-01-01

    The NRAO "Observing for University Classes" program is a tremendous resource for instructors of courses in observational astronomy. As a service to the astronomical and educational communities, the NRAO offers small amounts of observing time on the Very Large Array (VLA) and the Very Long Baseline Array to such instructors. The data can be used by students and faculty to demonstrate radio astronomy theory with modern data products. Further, the results may lead to publication; this is a unique opportunity for faculty members to integrate research into the classroom. Previous experience with NRAO facilities is required for instructors; individuals without radio astronomy experience can take advantage of other NRAO educational opportunities (e.g., the Synthesis Imaging Workshop) prior to using the program. No previous experience with radio astronomy data is required for students; this is the primary target audience of the program. To demonstrate concept, this poster describes three different VLA observing programs that have been completed using the "Observing for University Classes" resource at Macalester College; undergraduate students have published the results of all three of these programs. Other recent "Observing for University Classes" programs are also described.

  3. Optical multi-frequency swept sensing for wide-field vibration measurement of interior surfaces in biological tissue

    Science.gov (United States)

    Choi, S.; Nin, F.; Hibino, H.; Suzuki, T.

    2015-12-01

    Multifrequency sensing technique adopting the wide field heterodyne detection technique is demonstrated for interior surface vibration measurements in thick biological tissue. These arrangements allow obtaining not only 3D tomographic images but also various vibration parameters such as spatial amplitude, phase, and frequency, with high temporal and transverse resolutions over a wide field. The axial resolution and the accuracy of vibration amplitude measurement were estimated to be 2.5 μm and 3 nm, respectively. This wide-field tomographic sensing method can be applied for measuring microdynamics of a variety of biological samples, thus contributing to the progress in life sciences research.

  4. Radio continuum of galaxies with H2O megamaser disks: 33 GHz VLA data

    Science.gov (United States)

    Kamali, F.; Henkel, C.; Brunthaler, A.; Impellizzeri, C. M. V.; Menten, K. M.; Braatz, J. A.; Greene, J. E.; Reid, M. J.; Condon, J. J.; Lo, K. Y.; Kuo, C. Y.; Litzinger, E.; Kadler, M.

    2017-09-01

    Context. Galaxies with H2O megamaser disks are active galaxies in whose edge-on accretion disks 22 GHz H2O maser emission has been detected. Because their geometry is known, they provide a unique view into the properties of active galactic nuclei. Aims: The goal of this work is to investigate the nuclear environment of galaxies with H2O maser disks and to relate the maser and host galaxy properties to those of the radio continuum emission of the galaxy. Methods: The 33 GHz (9 mm) radio continuum properties of 24 galaxies with reported 22 GHz H2O maser emission from their disks are studied in the context of the multiwavelength view of these sources. The 29-37 GHz Ka-band observations are made with the Karl Jansky Very Large Array in B, CnB, or BnA configurations, achieving a resolution of 0.2-0.5 arcsec. Hard X-ray data from the Swift/BAT survey and 22 μm infrared data from WISE, 22 GHz H2O maser data and 1.4 GHz data from NVSS and FIRST surveys are also included in the analysis. Results: Eighty-seven percent (21 out of 24) galaxies in our sample show 33 GHz radio continuum emission at levels of 4.5-240σ. Five sources show extended emission (deconvolved source size larger than 2.5 times the major axis of the beam), including one source with two main components and one with three main components. The remaining detected 16 sources (and also some of the above-mentioned targets) exhibit compact cores within the sensitivity limits. Little evidence is found for extended jets (>300 pc) in most sources. Either they do not exist, or our chosen frequency of 33 GHz is too high for a detection of these supposedly steep spectrum features. In NGC 4388, we find an extended jet-like feature that appears to be oriented perpendicular to the H2O megamaser disk. NGC 2273 is another candidate whose radio continuum source might be elongated perpendicular to the maser disk. Smaller 100-300 pc sized jets might also be present, as is suggested by the beam-deconvolved morphology of our

  5. Forming supermassive black hole seeds under the influence of a nearby anisotropic multifrequency source.

    Science.gov (United States)

    Regan, John A; Johansson, Peter H; Wise, John H

    2016-07-01

    The photodissociation of H2 by a nearby anisotropic source of radiation is seen as a critical component in creating an environment in which a direct collapse black hole may form. Employing radiative transfer we model the effect of multifrequency (0.76-60 eV) radiation on a collapsing halo at high redshift. We vary both the shape of the spectrum which emits the radiation and the distance to the emitting galaxy. We use blackbody spectra with temperatures of T = 10(4) K and 10(5) K and a realistic stellar spectrum. We find that an optimal zone exists between 1 and 4 kpc from the emitting galaxy. If the halo resides too close to the emitting galaxy the photoionizing radiation creates a large H ii region which effectively disrupts the collapsing halo, too far from the source and the radiation flux drops below the level of the expected background and the H2 fraction remains too high. When the emitting galaxy is initially placed between 1 and 2 kpc from the collapsing halo, with a spectral shape consistent with a star-forming high-redshift galaxy, then a large central core forms. The mass of the central core is between 5000 and 10 000 M⊙ at a temperature of approximately 1000 K. This core is however surrounded by a reservoir of hotter gas at approximately 8000 K, which leads to mass inflow rates of the order of ∼0.1 M⊙ yr(-1).

  6. Multifrequency high precise subTHz-THz-IR spectroscopy for exhaled breath research

    Science.gov (United States)

    Vaks, Vladimir L.; Domracheva, Elena G.; Pripolzin, Sergey I.; Chernyaeva, Mariya B.

    2016-09-01

    Nowadays the development of analytical spectroscopy with high performance, sensitivity and spectral resolution for exhaled breath research is attended. The method of two-frequency high precise THz spectroscopy and the method of high precise subTHz-THz-IR spectroscopy are presented. Development of a subTHz-THz-IR gas analyzer increases the number of gases that can be identified and the reliability of the detection by confirming the signature in both THz and MIR ranges. The testing measurements have testified this new direction of analytical spectroscopy to open widespread trends of its using for various problems of medicine and biology. First of all, there are laboratory investigations of the processes in exhaled breath and studying of their dynamics. Besides, the methods presented can be applied for detecting intermediate and short time living products of reactions in exhaled breath. The spectrometers have been employed for investigations of acetone, methanol and ethanol in the breath samples of healthy volunteers and diabetes patients. The results have demonstrated an increased concentration of acetone in breath of diabetes patients. The dynamic of changing the acetone concentration before and after taking the medicines is discovered. The potential markers of pre-cancer states and oncological diseases of gastrointestinal tract organs have been detected. The changes in the NO concentration in exhaled breath of cancer patients during radiotherapy as well as increase of the NH3 concentration at gastrointestinal diseases have been revealed. The preliminary investigations of biomarkers in three frequency ranges have demonstrated the advantages of the multifrequency high precise spectroscopy for noninvasive medical diagnostics.

  7. Monopole and dipole estimation for multi-frequency sky maps by linear regression

    Science.gov (United States)

    Wehus, I. K.; Fuskeland, U.; Eriksen, H. K.; Banday, A. J.; Dickinson, C.; Ghosh, T.; Górski, K. M.; Lawrence, C. R.; Leahy, J. P.; Maino, D.; Reich, P.; Reich, W.

    2017-01-01

    We describe a simple but efficient method for deriving a consistent set of monopole and dipole corrections for multi-frequency sky map data sets, allowing robust parametric component separation with the same data set. The computational core of this method is linear regression between pairs of frequency maps, often called T-T plots. Individual contributions from monopole and dipole terms are determined by performing the regression locally in patches on the sky, while the degeneracy between different frequencies is lifted whenever the dominant foreground component exhibits a significant spatial spectral index variation. Based on this method, we present two different, but each internally consistent, sets of monopole and dipole coefficients for the nine-year WMAP, Planck 2013, SFD 100 μm, Haslam 408 MHz and Reich & Reich 1420 MHz maps. The two sets have been derived with different analysis assumptions and data selection, and provide an estimate of residual systematic uncertainties. In general, our values are in good agreement with previously published results. Among the most notable results are a relative dipole between the WMAP and Planck experiments of 10-15μK (depending on frequency), an estimate of the 408 MHz map monopole of 8.9 ± 1.3 K, and a non-zero dipole in the 1420 MHz map of 0.15 ± 0.03 K pointing towards Galactic coordinates (l,b) = (308°,-36°) ± 14°. These values represent the sum of any instrumental and data processing offsets, as well as any Galactic or extra-Galactic component that is spectrally uniform over the full sky.

  8. Multi-frequency harmonic arrays: initial experience with a novel transducer concept for nonlinear contrast imaging.

    Science.gov (United States)

    Forsberg, Flemming; Shi, William T; Jadidian, Bahram; Winder, Alan A

    2004-12-01

    Nonlinear contrast imaging modes such as second harmonic imaging (HI) and subharmonic imaging (SHI) are increasingly important for clinical applications. However, the performance of currently available transducers for HI and SHI is significantly constrained by their limited bandwidth. To bypass this constraint, a novel transducer concept termed multi-frequency harmonic transducer arrays (MFHA's) has been designed and a preliminary evaluation has been conducted. The MFHA may ultimately be used for broadband contrast enhanced HI and SHI with high dynamic range and consists of three multi-element piezo-composite sub-arrays (A-C) constructed so the center frequencies are 4f(A) = 2f(B) = f(C) (specifically 2.5/5.0/10.0 MHz and 1.75/3.5/7.0 MHz). In principle this enables SHI by transmitting on sub-array C receiving on B and, similarly, from B to A as well as HI by transmitting on A receiving on B and, likewise, from B to C. Initially transmit and receive pressure levels of the arrays were measured with the elements of each sub-array wired in parallel. Following contrast administration, preliminary in vitro HI and SHI signal-to-noise ratios of up to 40 dB were obtained. In conclusion, initial design and in vitro characterization of two MFHA's have been performed. They have an overall broad frequency bandwidth of at least two octaves. Due to the special design of the array assembly, the SNR for HI and SHI was comparable to that of regular B-mode and better than commercially available HI systems. However, further research on multi-element MFHA's is required before their potential for in vivo nonlinear contrast imaging can be assessed.

  9. Comparison of total and segmental body composition using DXA and multifrequency bioimpedance in collegiate female athletes.

    Science.gov (United States)

    Esco, Michael R; Snarr, Ronald L; Leatherwood, Matthew D; Chamberlain, Nik A; Redding, Melvenia L; Flatt, Andrew A; Moon, Jordan R; Williford, Henry N

    2015-04-01

    The purpose of this investigation was to determine the agreement between multifrequency bioelectrical impedance analysis (BIA) and dual-energy x-ray absorptiometry (DXA) for measuring body fat percentage (BF%), fat-free mass (FFM), and total body and segmental lean soft tissue (LST) in collegiate female athletes. Forty-five female athletes (age = 21.2 ± 2.0 years, height = 166.1 ± 7.1 cm, weight = 62.6 ± 9.9 kg) participated in this study. Variables measured through BIA and DXA were as follows: BF%, FFM, and LST of the arms (ARMS(LST)), the legs (LEGS(LST)), the trunk (TRUNK(LST)), and the total body (TOTAL(LST)). Compared with the DXA, the InBody 720 provided significantly lower values for BF% (-3.3%, p < 0.001) and significantly higher values for FFM (2.1 kg, p < 0.001) with limits of agreement (1.96 SD of the mean difference) of ±5.6% for BF% and ±3.7 kg for FFM. No significant differences (p < 0.008) existed between the 2 devices (InBody 720-DXA) for ARMS(LST) (0.05 kg), TRUNK(LST) (0.14 kg), LEGS(LST) (-0.4 kg), and TOTAL(LST) (-0.21 kg). The limits of agreement were ±0.79 kg for ARMS(LST), ±2.62 kg for LEGS(LST), ±3.18 kg for TRUNK(LST), and ±4.23 kg for TOTAL(LST). This study found discrepancies in BF% and FFM between the 2 devices. However, the InBody 720 and DXA appeared to provide excellent agreement for measuring total body and segmental LST. Therefore, the InBody 720 may be a rapid noninvasive method to assess LST in female athletes when DXA is not available.

  10. Multi-frequency excitation of stiffened triangular plates for large amplitude oscillations

    Science.gov (United States)

    Askari, H.; Saadatnia, Z.; Esmailzadeh, E.; Younesian, D.

    2014-10-01

    Free and forced vibrations of triangular plate are investigated. Diverse types of stiffeners were attached onto the plate to suppress the undesirable large-amplitude oscillations. The governing equation of motion for a triangular plate, based on the von Kármán theory, is developed and the nonlinear ordinary differential equation of the system using Galerkin approach is obtained. Closed-form expressions for the free undamped and large-amplitude vibration of an orthotropic triangular elastic plate are presented using the two well-known analytical methods, namely, the energy balance method and the variational approach. The frequency responses in the closed-form are presented and their sensitivities with respect to the initial amplitudes are studied. An error analysis is performed and the vibration behavior, as well as the accuracy of the solution methods, is evaluated. Different types of the stiffened triangular plates are considered in order to cover a wide range of practical applications. Numerical simulations are carried out and the validity of the solution procedure is explored. It is demonstrated that the two methods of energy balance and variational approach have been quite straightforward and reliable techniques to solve those nonlinear differential equations. Subsequently, due to the importance of multiple resonant responses in engineering design, multi-frequency excitations are considered. It is assumed that three periodic forces are applied to the plate in three specific positions. The multiple time scaling method is utilized to obtain approximate solutions for the frequency resonance cases. Influences of different parameters, namely, the position of applied forces, geometry and the number of stiffeners on the frequency response of the triangular plates are examined.

  11. Multi-frequency survey of background radiations of the Universe. The "Cosmological Gene" project. First results

    Science.gov (United States)

    Parijskij, Yu. N.; Mingaliev, M. G.; Nizhel'Skii, N. A.; Bursov, N. N.; Berlin, A. B.; Grechkin, A. A.; Zharov, V. I.; Zhekanis, G. V.; Majorova, E. K.; Semenova, T. A.; Stolyarov, V. A.; Tsybulev, P. G.; Kratov, D. V.; Udovitskii, R. Yu.; Khaikin, V. B.

    2011-10-01

    The results of the first stage of the "Cosmological Gene" project of the Russian Academy of Sciences are reported. These results consist in the accumulation of multi-frequency data in 31 frequency channels in the wavelength interval 1-55 cm with maximum achievable statistical sensitivity limited by the noise of background radio sources at all wavelengths exceeding 1.38 cm. The survey region is determined by constraints 00 h microwave background are reported as well as the contribution of these noise components in millimeter-wave experiments to be performed in the nearest years. The role of dipole radio emission of fullerene-type dust nanostructures is shown to be small. The most precise estimates of the role of background radio sources with inverted spectra are given and these sources are shown to create no serious interference in experiments. The average spectral indices of the weakest sources of the NVSS and FIRST catalogs are estimated. The "saturation" data for all wavelengths allowed a constraint to be imposed on the Sunyaev-Zeldovich noise (the SZ noise) at all wavelengths, and made it possible to obtain independent estimates of the average sky temperature from sources, substantially weaker than those listed in the NVSS catalog. These estimates are inconsistent with the existence of powerful extragalactic synchrotron background associated with radio sources. Appreciable "quadrupole" anisotropy in is detected in the distribution of the spectral index of the synchrotron radiation of the Galaxy, and this anisotropy should be taken into account when estimating the polarization of the cosmic microwave background on small l. All the results are compared to the results obtained by foreign researchers in recent years.

  12. Effect of food on pharmacokinetics of an inhaled drug: a case study with a VLA-4 antagonist, HMR1031.

    Science.gov (United States)

    Shah, Bharti; Jensen, Bradford K; Zhang, Jie; Hunt, Thomas; Rohatagi, Shashank

    2003-12-01

    HMR1031 is a potent and specific antagonist of the integrin VLA-4 (alpha4beta1) binding to vascular cell adhesion molecule-1 (VCAM-1) and fibronectin. HMR1031 is an inhaled drug being developed for the treatment of asthma using an Ultrahaler dry-powder inhalation device. A pharmacoscintigraphic study of HMR1031 suggests a lung deposition of approximately 25% and gastrointestinal tract deposition of approximately 75%. Since oral absorption may be contributing to systemic plasma concentrations, the effect of food on HMR1031 was assessed. This was a single-dose (3 mg), open-label, randomized, two-way crossover (fasted vs. fed) study in 8 healthy male subjects. Blood samples were collected at predose and up to 24 hours postdose. Plasma concentrations were determined by the LC/MS/MS method. HMR1031 was rapidly absorbed, with median tmax values of 1.0 and 0.75 hours under fasted and fed conditions, respectively. Under fasted conditions, mean AUCinfinity and Cmax values were 16.4 ng x h/mL and 4.56 ng/mL, respectively. Under fed conditions, mean AUCinfinity and Cmax values decreased to 11.7 ng x h/mL and 2.81 ng/mL, respectively. The mean terminal elimination half-life (t1/2) for both treatment groups was similar (2.7 h). HMR1031 population estimates of the apparent clearance, apparent volume of distribution, and absorption rate were 225 L/h (4.1% coefficient of variation [CV]), 44.5 L (26% CV), and 0.340 h-1 (7.0% CV), respectively. Food is a significant covariate on clearance. These data suggest that food unexpectedly decreases the systemic exposure of inhaled HMR1031 by approximately 30%, probably due to increased liver blood flow and increased biliary excretion. This decrease in systemic exposure is unlikely to affect the topical effect of the drug but may result in increased variability in plasma pharmacokinetics. The disposition and food effect of HMR1031 can be described using mixed-effect modeling.

  13. Fut8基因通过促进VLA-4/VCAM-1表达影响B细胞发育%Fut8 gene affects the development of B cells by regulating the core fucosylation of VLA-4/VCAM-1

    Institute of Scientific and Technical Information of China (English)

    焦鑫艳; 马彪; 王旭; 刘庆平; 李文哲

    2012-01-01

    The aim of this study is to explore the role of fucosyltransferase VIII (Fut8) in VLA -4/VCAM-1 expression and B cell development. Firstly, Fut8 -knockdown 70Z/3 cells and Fut8 -knockdown ST2 cells were established by RNA inference using 70Z/3 cells (pre-B cell line) and ST2 cells. Then Fut8 gene-silencing effects were detected by Western blot. In cell adhesion assays and colony forming tests, we found that the loss of a core fucose in both very late antigen 4 (VLA-4) and vascular cell adhesion molecule 1 (VCAM-1) would lead to a decreased binding between pre-B cells and stromal cells, followed the impaired pre-B cells generation in Fut8+ mice. Flow cytometry analysis revealed that Fut8 expression was extremely required for regulating pre-B cell reproduction. These findings clearly demonstrated that the Fut8 could regulate the VLA-4/VCAM-1 interaction and the proper transition from pro-B to pre-B cells, showing the important role of Fut8 in B cell differentiation and development%目的 探讨核心岩藻糖基化修饰对VLA-4/VCAM-1表达及B细胞发育的影响.方法 通过RNA干扰技术使前B细胞(70Z/3)和基质细胞(ST2)的Fut8基因沉默,免疫沉淀和Western blot检测Fut8基因沉默效率,以细胞黏附实验和克隆形成实验分别研究Fut8基因对VLA-4/VCAM-1之间亲和力和对B细胞分化发育的影响.结果 Fut8基因沉默使VLA-4/VCAM-1之间的亲和力以及前B细胞和基质细胞之间的黏附作用降低,并使前B细胞的克隆形成能力明显下降.流式细胞仪分析结果也表明,Fut8祖B细胞向前B细胞分化过程受阻.结论 本实验揭示了Fut8基因调节VLA-4/VCAM-1之间结合能力以及前B细胞克隆形成的机理,为B细胞分化发育研究提供理论依据.

  14. Removal of Optically Thick Clouds from Multi-Spectral Satellite Images Using Multi-Frequency SAR Data

    Directory of Open Access Journals (Sweden)

    Robert Eckardt

    2013-06-01

    Full Text Available This study presents a method for the reconstruction of pixels contaminated by optical thick clouds in multi-spectral Landsat images using multi-frequency SAR data. A number of reconstruction techniques have already been proposed in the scientific literature. However, all of the existing techniques have certain limitations. In order to overcome these limitations, we expose the Closest Spectral Fit (CSF method proposed by Meng et al. to a new, synergistic approach using optical and SAR data. Therefore, the term Closest Feature Vector (CFV is introduced. The technique facilitates an elegant way to avoid radiometric distortions in the course of image reconstruction. Furthermore the cloud cover removal is independent from underlying land cover types and assumptions on seasonality, etc. The methodology is applied to mono-temporal, multi-frequency SAR data from TerraSAR-X (X-Band, ERS (C-Band and ALOS Palsar (L-Band. This represents a way of thinking about Radar data not as foreign, but as additional data source in multi-spectral remote sensing. For the assessment of the image restoration performance, an experimental framework is established and a statistical evaluation protocol is designed. The results show the potential of a synergistic usage of multi-spectral and SAR data to overcome the loss of data due to cloud cover.

  15. Classification of heavy metal ions present in multi-frequency multi-electrode potable water data using evolutionary algorithm

    Science.gov (United States)

    Karkra, Rashmi; Kumar, Prashant; Bansod, Baban K. S.; Bagchi, Sudeshna; Sharma, Pooja; Krishna, C. Rama

    2016-12-01

    Access to potable water for the common people is one of the most challenging tasks in the present era. Contamination of drinking water has become a serious problem due to various anthropogenic and geogenic events. The paper demonstrates the application of evolutionary algorithms, viz., particle swan optimization and genetic algorithm to 24 water samples containing eight different heavy metal ions (Cd, Cu, Co, Pb, Zn, Ar, Cr and Ni) for the optimal estimation of electrode and frequency to classify the heavy metal ions. The work has been carried out on multi-variate data, viz., single electrode multi-frequency, single frequency multi-electrode and multi-frequency multi-electrode water samples. The electrodes used are platinum, gold, silver nanoparticles and glassy carbon electrodes. Various hazardous metal ions present in the water samples have been optimally classified and validated by the application of Davis Bouldin index. Such studies are useful in the segregation of hazardous heavy metal ions found in water resources, thereby quantifying the degree of water quality.

  16. Improvement of nutritional status as assessed by multifrequency BIA during 15 weeks of refeeding in adolescent girls with anorexia nervosa.

    Science.gov (United States)

    Mika, Claudia; Herpertz-Dahlmann, Beate; Heer, Martina; Holtkamp, Kristian

    2004-11-01

    In patients with anorexia nervosa (AN), an assessment of changes in body composition and nutritional status is crucial for adequate nutritional management during refeeding therapies. Phase-sensitive multifrequency bioelectrical impedance analysis (BIA) is an inexpensive and noninvasive technique with which to determine nutritional status and body composition. We investigated 21 female adolescents with AN (initial BMI 15.5 +/- 1.1 kg/m(2)) 4 times between wk 3 and 15 of inpatient refeeding and 19 normal-weight, age-matched female controls. From wk 3 to 15, BMI, fat mass, body cell mass (BCM), total body water (TBW), intracellular water (ICW) but not extracellular mass (ECM), and extracellular water (ECW) increased significantly. Reactance (Xc), phase angle (PhA), and the ECM/BCM index as parameters of nutritional status improved significantly in patients and no longer differed from controls in wk 15, although the BMI of patients was significantly lower than those of controls. Changes in the ECM/BCM index were due to accretion of BCM, which was associated with an increase of ICW. Multifrequency phase-sensitive BIA seems to be a promising tool for the assessment of changes in nutritional status and body composition in patients with AN. An individually determined and controlled hyperenergetic diet as part of a multidimensional, interdisciplinary treatment program for eating disorders seems to quickly improve the nutritional status of AN patients.

  17. Frozen Gaussian approximation-based two-level methods for multi-frequency Schrödinger equation

    Science.gov (United States)

    Lorin, E.; Yang, X.

    2016-10-01

    In this paper, we develop two-level numerical methods for the time-dependent Schrödinger equation (TDSE) in multi-frequency regime. This work is motivated by attosecond science (Corkum and Krausz, 2007), which refers to the interaction of short and intense laser pulses with quantum particles generating wide frequency spectrum light, and allowing for the coherent emission of attosecond pulses (1 attosecond=10-18 s). The principle of the proposed methods consists in decomposing a wavefunction into a low/moderate frequency (quantum) contribution, and a high frequency contribution exhibiting a semi-classical behavior. Low/moderate frequencies are computed through the direct solution to the quantum TDSE on a coarse mesh, and the high frequency contribution is computed by frozen Gaussian approximation (Herman and Kluk, 1984). This paper is devoted to the derivation of consistent, accurate and efficient algorithms performing such a decomposition and the time evolution of the wavefunction in the multi-frequency regime. Numerical simulations are provided to illustrate the accuracy and efficiency of the derived algorithms.

  18. Multi-frequency radiation hydrodynamics simulations of H2 line emission in primordial, star-forming clouds

    CERN Document Server

    Greif, Thomas H

    2014-01-01

    We investigate the collapse of primordial gas in a minihalo with three-dimensional radiation hydrodynamics simulations that accurately model the transfer of H2 line emission. For this purpose, we have implemented a multi-line, multi-frequency ray-tracing scheme in the moving-mesh code Arepo that is capable of adaptively refining rays based on the Healpix algorithm, as well as a hybrid equilibrium/non-equilibrium primordial chemistry solver. We find that the chemical and thermal evolution of the central gas cloud is similar to the case where an escape probability formalism with a fit to detailed one-dimensional calculations is used, with the exception that the suppression of density perturbations due to the diffusion of radiation is only present in the full radiation hydrodynamics simulations. A multi-frequency treatment of the individual H2 lines is essential, since for high optical depths the smaller cross section in the wings of the lines greatly increases the amount of energy that can escape. The influence...

  19. The Multiwavelength Study of Two Unique Radio Galaxies

    Indian Academy of Sciences (India)

    Nectaria A. B. Gizani; M. A. Garrett; J. P. Leahy

    2002-03-01

    We present the usage of multi-frequency and multi-band radio, VLA, observations as well as X-ray observations in order to study the environment around two powerful radio galaxies, namely Hercules A and 3 C310. We study their environment both in pc- and kpc-scales. We have chosen these two radio galaxies as they present similar and unique characteristics, compared to the ones from our general knowledge about double radio galaxies associated with active galactic nuclei.

  20. SMA observations towards the compact, short-lived bipolar water maser outflow in the LkH{\\alpha} 234 region

    CERN Document Server

    Girart, J M; Estalella, R; Curiel, S; Anglada, G; Gómez, J F; Carrasco-González, C; Cantó, J; Rodríguez, L F; Patel, N A; Trinidad, M A

    2016-01-01

    We present Submillimeter Array (SMA) 1.35 mm subarcsecond angular resolution observations toward the LkH{\\alpha} 234 intermediate-mass star-forming region. The dust emission arises from a filamentary structure of $\\sim$5 arcsec ($\\sim$4500 au) enclosing VLA 1-3 and MM 1, perpendicular to the different outflows detected in the region. The most evolved objects are located at the southeastern edge of the dust filamentary structure and the youngest ones at the northeastern edge. The circumstellar structures around VLA 1, VLA 3, and MM 1 have radii between $\\sim$200 and $\\sim$375 au and masses in the $\\sim$0.08-0.3 M$_{\\odot}$ range. The 1.35 mm emission of VLA 2 arises from an unresolved (r$< 135$ au) circumstellar disk with a mass of $\\sim$0.02 M$_{\\odot}$. This source is powering a compact ($\\sim$4000 au), low radial velocity ($\\sim$7 km s$^{-1}$) SiO bipolar outflow, close to the plane of the sky. We conclude that this outflow is the "large-scale" counterpart of the short-lived, episodic, bipolar outflow ob...

  1. 多频GNSS电离层折射误差修正方法%GNSS Multi-Frequency Correction Methods of Ionospheric Refraction Error

    Institute of Scientific and Technical Information of China (English)

    赵彦珍; 苏建峰

    2016-01-01

    Ionospheric refraction error is relatively large, single frequency refraction error of GPS ( Global Positioning System) and BDS ( BeiDou Navigation Satellite System) is analyzed. Then, different frequencies of GPS and BDS linear combination are researched in this paper. Three multi-frequency cor-rection methods such as dual-frequency of one order, triple-frequency of one order and triple-frequency of two orders are discussed. Ionospheric delay correction will also enlarge the observation noises, so the ob-servation noises of each correction method are analyzed and compared. Besides, a theoretical approach to select the best frequency combinations is proposed.%针对电离层折射误差较大的特点,分别对GPS( Global Positioning System)和BDS( BeiDou Navigation Satellite System)的单一频率的电离层折射误差进行了分析,并将不同频率进行线性组合,计算出组合后的电离层折射误差。此方法修正了双频一阶项、三频一阶项和三频二阶项电离层折射误差。由于电离层延迟修正的同时会放大观测噪声,为此分析比较了不同频率组合修正后的观测噪声,为最佳频率组合的选取提供了理论方法。

  2. Evaluation of body composition in COPD patients using multifrequency bioelectrical impedance analysis

    Science.gov (United States)

    de Blasio, Francesca; de Blasio, Francesco; Miracco Berlingieri, Giulia; Bianco, Andrea; La Greca, Marta; Franssen, Frits M E; Scalfi, Luca

    2016-01-01

    Background Multifrequency bioelectrical impedance analysis (MF-BIA) is a technique that measures body impedance (Z) at different frequencies (5, 10, 50, 100, and 250 kHz). Body composition may be estimated using empirical equations, which include BIA variables or, alternatively, raw BIA data may provide direct information on water distribution and muscle quality. Objectives To compare raw MF-BIA data between COPD patients and controls and to study their relationship with respiratory and functional parameters in COPD patients. Methods MF-BIA was performed (Human Im-Touch analyzer) in 212 COPD patients and 115 age- and BMI-matched controls. Fat-free mass (FFM) and fat mass were estimated from BIA data, and low- to high-frequency (5 kHz/250 kHz) impedance ratio was calculated. Physical fitness, lung function and respiratory muscle strength were also assessed in COPD patients. Results After adjusting for age, weight, and body mass index, FFM and the 5/250 impedance ratio were lower in COPD patients (P<0.001) and were negatively affected by disease severity. In both male and female patients, the 5/250 impedance ratio was significantly correlated mainly with age (r=−0.316 and r=−0.346, respectively). Patients with a 5/250 impedance ratio below median value had lower handgrip strength (P<0.001), 6-minute walk distance (P<0.005), respiratory muscle strength (P<0.005), forced expiratory volume in 1 second (P<0.05) and vital capacity (P<0.005). Finally, the 5/250 impedance ratio was reduced (P<0.05) in patients with Global Initiative for Chronic Obstructive Lung Disease (GOLD) III and IV (compared to those with GOLD I and II) or a BODE index between 6 and 10 points (compared to those with BODE index between 1 and 5 points). Conclusion MF-BIA may be a useful tool for assessing body composition and nutritional status in COPD patients. In particular, the impedance ratio could give valuable information on cellular integrity and muscle quality.

  3. Land subsidence in the Yangtze River Delta, China revealed from multi-frequency SAR Interferometry

    Science.gov (United States)

    Li, Zhenhong; Motagh, Mahdi; Yu, Jun; Gong, Xulong; Wu, Jianqiang; Zhu, Yefei; Chen, Huogen; Zhang, Dengming; Xu, Yulin

    2014-05-01

    of multi-frequency SAR datasets allows a long record (~20 years) of historic deformation to be measured over a large region. Ultimately this should help inform land managers in assessing land subsidence and planning appropriate remedial measures.

  4. Observation of the inverse Doppler effect.

    Science.gov (United States)

    Seddon, N; Bearpark, T

    2003-11-28

    We report experimental observation of an inverse Doppler shift, in which the frequency of a wave is increased on reflection from a receding boundary. This counterintuitive effect has been produced by reflecting a wave from a moving discontinuity in an electrical transmission line. Doppler shifts produced by this system can be varied in a reproducible manner by electronic control of the transmission line and are typically five orders of magnitude greater than those produced by solid objects with kinematic velocities. Potential applications include the development of tunable and multifrequency radiation sources.

  5. Multifrequency permittivity measurements enable on-line monitoring of changes in intracellular conductivity due to nutrient limitations during batch cultivations of CHO cells.

    Science.gov (United States)

    Ansorge, Sven; Esteban, Geoffrey; Schmid, Georg

    2010-01-01

    Lab and pilot scale batch cultivations of a CHO K1/dhfr(-) host cell line were conducted to evaluate on-line multifrequency permittivity measurements as a process monitoring tool. The beta-dispersion parameters such as the characteristic frequency (f(C)) and the permittivity increment (Deltaepsilon(max)) were calculated on-line from the permittivity spectra. The dual-frequency permittivity signal correlated well with the off-line measured biovolume and the viable cell density. A significant drop in permittivity was monitored at the transition from exponential growth to a phase with reduced growth rate. Although not reflected in off-line biovolume measurements, this decrease coincided with a drop in OUR and was probably caused by the depletion of glutamine and a metabolic shift occurring at the same time. Sudden changes in cell density, cell size, viability, capacitance per membrane area (C(M)), and effects caused by medium conductivity (sigma(m)) could be excluded as reasons for the decrease in permittivity. After analysis of the process data, a drop in f(C) as a result of a fall in intracellular conductivity (sigma(i)) was identified as responsible for the observed changes in the dual-frequency permittivity signal. It is hypothesized that the beta-dispersion parameter f(C) is indicative of changes in nutrient availability that have an impact on intracellular conductivity sigma(i). On-line permittivity measurements consequently not only reflect the biovolume but also the physiological state of mammalian cell cultures. These findings should pave the way for a better understanding of the intracellular state of cells and render permittivity measurements an important tool in process development and control.

  6. Preoperative Management of Surgical Patients by “Shortened Fasting Time”: A Study on the Amount of Total Body Water by Multi-Frequency Impedance Method

    Directory of Open Access Journals (Sweden)

    Hideki Taniguchi, Toshio Sasaki, Hisae Fujita

    2012-01-01

    Full Text Available Aim: Preoperative fasting is an established procedure to be practiced for patients before surgery, but optimal preoperative fasting time still remains controversial. The aim of this study was to investigate the effect of “shortened preoperative fasting time” on the change in the amount of total body water (TBW in elective surgical patients. TBW was measured by multi-frequency impedance method.Methods: The patients, who were scheduled to undergo surgery for stomach cancer, were divided into two groups of 15 patients each. Before surgery, patients in the control group were managed with conventional preoperative fasting time, while patients in the “enhanced recovery after surgery (ERAS” group were managed with “shortened preoperative fasting time” and “reduced laxative medication.” TBW was measured on the day before surgery and the day of surgery before entering the operating room. Defecation times and anesthesia-related vomiting and aspiration were monitored.Results: TBW values on the day of surgery showed changes in both groups as compared with those on the day before surgery, but the rate of change was smaller in the ERAS group than in the control group (2.4±6.8% [12 patients] vs. −10.6±4.6% [14 patients], p<0.001. Defecation times were less in the ERAS group. Vomiting and aspiration were not observed in either group.Conclusion: The results suggest that preoperative management with “shorted preoperative fasting time” and “reduced administration of laxatives” is effective in the maintenance of TBW in elective surgical patients.

  7. A new method to separate star forming from AGN galaxies at intermediate redshift: The submillijansky radio population in the VLA-COSMOS survey

    CERN Document Server

    Smolcic, V; Scodeggio, M; Franzetti, P; Aussel, H; Bondi, M; Brusa, M; Carilli, C L; Capak, P; Charlot, S; Ciliegi, P; Ilbert, O; Ivezic, Z; Jahnke, K; McCracken, H J; Obric, M; Salvato, M; Sanders, D B; Scoville, N; Trump, J R; Tremonti, C; Tasca, L; Walcher, C J; Zamorani, G

    2008-01-01

    We explore the properties of the submillijansky radio population at 20 cm by applying a newly developed optical color-based method to separate star forming (SF) from AGN galaxies at intermediate redshifts (z1.3) galaxies. We find, for the composition of the submillijansky radio population, that SF galaxies are not the dominant population at submillijansky flux levels, as previously often assumed, but that they make up an approximately constant fraction of 30-40% in the flux density range of ~50 microJy to 0.7 mJy. In summary, based on the entire VLA-COSMOS radio population at 20 cm, we find that the radio population at these flux densities is a mixture of roughly 30-40% of SF and 50-60% of AGN galaxies, with a minor contribution (~10%) of QSOs.

  8. 马拉开波湖VLA6/9/21油田三元复合驱配方筛选

    Institute of Scientific and Technical Information of China (English)

    Manrique; E.; 谢力

    2002-01-01

    VLA6/9/21油田是一个经过水驱的轻油油藏,位于委内瑞拉西部的马拉开波湖,已开采了40多年 ,在过去几年里,PDVSA勘探与生产公司开展了综合实验室矿物研究来评价新技术和EOR方法,以便提高轴油和中质原油的采收率,碱/表面活性剂/聚合物驱是最近委内瑞拉已经评价的化学驱技术之一。

  9. VLBI observations of T Tauri S

    CERN Document Server

    Smith, K W; Gödel, M; Conway, J; Benz, Arnold O

    2003-01-01

    We report observations of the T Tauri system at 8.4 GHz with a VLBI array comprising the VLBA, VLA and Effelsberg 100m telescopes. We detected a compact source offset approximately 40 mas from the best infrared position of the T Tau Sb component. This source was unresolved, and constrained to be less than 0.5 mas in size, corresponding to 0.07 AU or 15 R$_{\\odot}$ at a distance of 140 pc. The other system components (T Tau Sa, T Tau N) were not detected in the VLBI data. The separate VLA map contains extended flux not accounted for by the compact VLBI source, indicating the presence of extended emission on arcsecond scales. The compact source shows rapid variability, which together with circular polarization and its compact nature indicate that the observed flux arises from a magnetically-dominated region. Brightness temperatures in the MK range point to gyrosynchrotron as the emission mechanism for the steady component. The rapid variations are accompanied by dramatic changes in polarization, and we record a...

  10. Mapping power-law rheology of living cells using multi-frequency force modulation atomic force microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Takahashi, Ryosuke; Okajima, Takaharu, E-mail: okajima@ist.hokudai.ac.jp [Graduate School of Information Science and Technology, Hokkaido University, Kita-ku N14 W9, Sapporo 060-0814 (Japan)

    2015-10-26

    We present multi-frequency force modulation atomic force microscopy (AFM) for mapping the complex shear modulus G* of living cells as a function of frequency over the range of 50–500 Hz in the same measurement time as the single-frequency force modulation measurement. The AFM technique enables us to reconstruct image maps of rheological parameters, which exhibit a frequency-dependent power-law behavior with respect to G{sup *}. These quantitative rheological measurements reveal a large spatial variation in G* in this frequency range for single cells. Moreover, we find that the reconstructed images of the power-law rheological parameters are much different from those obtained in force-curve or single-frequency force modulation measurements. This indicates that the former provide information about intracellular mechanical structures of the cells that are usually not resolved with the conventional force measurement methods.

  11. Systematic cavity design approach for a multi-frequency gyrotron for DEMO and study of its RF behavior

    Science.gov (United States)

    Kalaria, P. C.; Avramidis, K. A.; Franck, J.; Gantenbein, G.; Illy, S.; Pagonakis, I. Gr.; Thumm, M.; Jelonnek, J.

    2016-09-01

    High frequency (>230 GHz) megawatt-class gyrotrons are planned as RF sources for electron cyclotron resonance heating and current drive in DEMOnstration fusion power plants (DEMOs). In this paper, for the first time, a feasibility study of a 236 GHz DEMO gyrotron is presented by considering all relevant design goals and the possible technical limitations. A mode-selection procedure is proposed in order to satisfy the multi-frequency and frequency-step tunability requirements. An effective systematic design approach for the optimal design of a gradually tapered cavity is presented. The RF-behavior of the proposed cavity is verified rigorously, supporting 920 kW of stable output power with an interaction efficiency of 36% including the considerations of realistic beam parameters.

  12. Performance limit of a multi-frequency probe based coherent optical time domain reflectometry caused by nonlinear effects

    Institute of Scientific and Technical Information of China (English)

    Lidong Lü; Yuejiang Song; Fan Zhu; Xuping Zhang

    2012-01-01

    The nonlinear effects that limit the performance of the multi-frequency probe (MFP) based coherent optical time domain reflectometry (C-OTDR) are investigated.Based on theoretical analysis and experimental results,compared with conventional C-OTDR,when the probe pulse has power gradient within the pulse width,self-phase modulation (SPM) and cross-phase modulation (XPM) are strengthened in the new COTDR scheme.The generation of four-wave mixing (FWM) is dependent on SPM and XPM,and with modulation frequency of phase modulator higher than 40 MHz,the stimulated Brillouin scattering (SBS) threshold can be enhanced by more than 5 dB,which benefits the maximum dynamic range of the MFP C-OTDR.

  13. Improvements in design of spectra of multisine and binary excitation signals for multi-frequency bioimpedance measurement.

    Science.gov (United States)

    Land, Raul; Cahill, Brian P; Parve, Toomas; Annus, Paul; Min, Mart

    2011-01-01

    The paper discusses the usability of multi-frequency binary waveforms for broadband excitation in fast measurements of impedance spectrum of biological objects. It is shown that up to 70% of the energy of the amplitude spectrum of such two-level binary signals can be concentrated into the selected separate frequencies. The levels of selected frequency components are controllable in tens and hundreds of times. In this way we can underline the most important frequencies enhancing the corresponding amplitudes in the spectrum of excitation signal. As an implementation example, we consider the impedance spectroscopy in micro-fluidic devices for inline measurement of the conductivity of droplets in segmented flow. We use a thin-walled glass capillary with electrodes contacting the outer surface so that the contactless measurement of conductivity of liquid with biologic cells becomes possible.

  14. Multi-frequency, multi-technique pulsed EPR investigation of the copper binding site of murine amyloid β peptide.

    Science.gov (United States)

    Kim, Donghun; Bang, Jeong Kyu; Kim, Sun Hee

    2015-01-26

    Copper-amyloid peptides are proposed to be the cause of Alzheimer's disease, presumably by oxidative stress. However, mice do not produce amyloid plaques and thus do not suffer from Alzheimer's disease. Although much effort has been focused on the structural characterization of the copper- human amyloid peptides, little is known regarding the copper-binding mode in murine amyloid peptides. Thus, we investigated the structure of copper-murine amyloid peptides through multi-frequency, multi-technique pulsed EPR spectroscopy in conjunction with specific isotope labeling. Based on our pulsed EPR results, we found that Ala2, Glu3, His6, and His14 are directly coordinated with the copper ion in murine amyloid β peptides at pH 8.5. This is the first detailed structural characterization of the copper-binding mode in murine amyloid β peptides. This work may advance the knowledge required for developing inhibitors of Alzheimer's disease.

  15. Radio Band Observations of Blazar Variability

    Indian Academy of Sciences (India)

    Margo F. Aller; Hugh D. Aller; Philip A. Hughes

    2011-03-01

    The properties of blazar variability in the radio band are studied using the unique combination of temporal resolution from single dish monitoring and spatial resolution from VLBA imaging. Such measurements now available in all four Stokes parameters, together with theoretical simulations, identify the origin of radio band variability and probe the characteristics of the radio jet where the broadband blazar emission originates. Outbursts in total flux density and linear polarization in the optical-to-radio bands are attributed to shocks propagating within the jet spine, in part, based on limited modelling invoking transverse shocks; new radiative transfer simulations allowing for shocks at arbitrary angle to the flow direction confirm this picture by reproducing the observed centimeter-band variations observed more generally, and are of current interest since these shocks may play a role in the -ray flaring detected by Fermi. Recent UMRAO multifrequency Stokes V studies of bright blazars identify the spectral variability properties of circular polarization for the first time and demonstrate that polarity flips are relatively common. All-Stokes data are consistent with the production of circular polarization by linear-to-circular mode conversion in a region that is at least partially selfabsorbed. Detailed analysis of single-epoch, multifrequency, all-Stokes VLBA observations of 3C 279 support this physical picture and are best explained by emission from an electron-proton plasma.

  16. Evaluation of body composition in COPD patients using multifrequency bioelectrical impedance analysis

    Directory of Open Access Journals (Sweden)

    de Blasio F

    2016-09-01

    Full Text Available Francesca de Blasio,1 Francesco de Blasio,2,3 Giulia Miracco Berlingieri,2 Andrea Bianco,3,4 Marta La Greca,1 Frits M E Franssen,5 Luca Scalfi1 1Department of Public Health, Medical School, “Federico II” University of Naples, 2Respiratory Medicine and Pulmonary Rehabilitation Section, Clinic Center, Private Hospital, Naples, 3Department of Medicine and Health Sciences “V Tiberio”, University of Molise, Campobasso, 4Department of Cardio-Thoracic and Respiratory Sciences, Second University of Naples, Naples, Italy; 5Department of Research and Education, CIRO, Horn, the NetherlandsBackground: Multifrequency bioelectrical impedance analysis (MF-BIA is a technique that measures body impedance (Z at different frequencies (5, 10, 50, 100, and 250 kHz. Body composition may be estimated using empirical equations, which include BIA variables or, alternatively, raw BIA data may provide direct information on water distribution and muscle quality.Objectives: To compare raw MF-BIA data between COPD patients and controls and to study their relationship with respiratory and functional parameters in COPD patients.Methods: MF-BIA was performed (Human Im-Touch analyzer in 212 COPD patients and 115 age- and BMI-matched controls. Fat-free mass (FFM and fat mass were estimated from BIA data, and low- to high-frequency (5 kHz/250 kHz impedance ratio was calculated. Physical fitness, lung function and respiratory muscle strength were also assessed in COPD patients.Results: After adjusting for age, weight, and body mass index, FFM and the 5/250 impedance ratio were lower in COPD patients (P<0.001 and were negatively affected by disease severity. In both male and female patients, the 5/250 impedance ratio was significantly correlated mainly with age (r=−0.316 and r=−0.346, respectively. Patients with a 5/250 impedance ratio below median value had lower handgrip strength (P<0.001, 6-minute walk distance (P<0.005, respiratory muscle strength (P<0.005, forced

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

    CERN Document Server

    Park, Jihye; Grejner-Brzezinska, Dorota A; von Frese, Ralph R B; Wilson, Thomas

    2013-01-01

    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).

  18. A DVB-RCS Multi-Channel, Multi-Frequency Demodulator Based on a Multi-Tasking Hardware-Software Architecture Using a System on Programmable Chip Technology

    Science.gov (United States)

    van Doninck, A.; Dendoncker, M.; Adriaensen, F.; Delbeke, P.; Rolle, A.; Craey, T.; Krekels, S.

    : This paper highlights a multi-channel, multi-frequency DVB-RCS compatible burst demodulator implementation in a System On Programmable Chip (SOPC) technology. The core of the demodulator architecture is a SOPC device with an ARM processor located internally in FPGA. The ARM processor performs the hard real time signal processing functions and is supported by a COTS standard PC based processor module running Linux/RT-Linux for the non-hard real-time demodulator functions. The implemented architecture differs completely from classic multi-channel solutions, in which the multi- channel functionality is realised by means of a multiple instantiation of the entire demodulator. The paper also discusses the followed methodology for the SOPC design. Keywords: DVB-RCS, multi-channel, multi-frequency, SOPC, FPGA, ARM, RT-Linux

  19. Multifrequency EPR Spectroscopy: A Toolkit for the Characterization of Mono- and Di-nuclear Metal Ion Centers in Complex Biological Systems

    Science.gov (United States)

    Hanson, Graeme R.

    Metalloenzymes are ubiquitous in nature containing complex metal ion cofactors intimately involved in the enzymes' biological function. The application of multifrequency continuous wave and orientation selective pulsed EPR in conjunction with computer simulation and density functional theory calculations has proven to be a powerful toolkit for the geometric and electronic structural characterization of these metal ion cofactors in the resting enzyme, enzyme-substrate and -product complexes, which in turn provides a detailed understanding of the enzymes' catalytic mechanism. In this chapter, a brief description of the multifrequency EPR toolkit used to structurally (geometric and electronic) characterize metal ion binding sites in complex biological systems and its application in the structural characterization of (i) molybdenum containing enzymes and model complexes, (ii) mono- and di-nuclear copper(II) cyclic peptide complexes (marine and synthetic analogues) and (iii) dinuclear metal ion centers in purple acid phosphatases will be presented.

  20. Electrical impedance spectroscopy (EIS)-based evaluation of biological tissue phantoms to study multifrequency electrical impedance tomography (Mf-EIT) systems

    KAUST Repository

    Bera, Tushar Kanti

    2016-03-18

    Abstract: Electrical impedance tomography (EIT) phantoms are essential for the calibration, comparison and evaluation of the EIT systems. In EIT, the practical phantoms are typically developed based on inhomogeneities surrounded by a homogeneous background to simulate a suitable conductivity contrast. In multifrequency EIT (Mf-EIT) evaluation, the phantoms must be developed with the materials which have recognizable or distinguishable impedance variations over a wide range of frequencies. In this direction the impedance responses of the saline solution (background) and a number vegetable and fruit tissues (inhomogeneities) are studied with electrical impedance spectroscopy (EIS) and the frequency responses of bioelectrical impedance and conductivity are analyzed. A number of practical phantoms with different tissue inhomogeneities and different inhomogeneity configurations are developed and the multifrequency impedance imaging is studied with the Mf-EIT system to evaluate the phantoms. The conductivity of the vegetable inhomogeneities reconstructed from the EIT imaging is compared with the conductivity values obtained from the EIS studies. Experimental results obtained from multifrequency EIT reconstruction demonstrate that the electrical impedance of all the biological tissues inhomogenity decreases with frequency. The potato tissue phantom produces better impedance image in high frequency ranges compared to the cucumber phantom, because the cucumber impedance at high frequency becomes lesser than that of the potato at the same frequency range. Graphical Abstract: [Figure not available: see fulltext.] © 2016 The Visualization Society of Japan

  1. VizieR Online Data Catalog: 6GHz JVLA observations of low-z SDSS quasars (Kellermann+, 2016)

    Science.gov (United States)

    Kellermann, K. I.; Condon, J. J.; Kimball, A. E.; Perley, R. A.; Ivezic, Z.

    2017-02-01

    We have reprocessed the VLA observations of a sample of SDSS QSOs discussed in Kimball+ (2011ApJ...739L..29K), and generated a catalog of radio sources associated with each QSO. We detected radio emission at 6GHz from all but two of the 178 color-selected SDSS QSOs contained in our volume-limited sample of QSOs more luminous than M_i=-23 and with redshifts 0.2

  2. Follow up of the CFRS with HST, ISO and VLA the cosmic star formation rate as derived from the FIR luminosity density

    CERN Document Server

    Hammer, F

    1998-01-01

    Properties of CFRS field galaxies up to z=1 are discussed. Estimations of the cosmic star formation rate (SFR) lead to serious problems if they not account for AGN emissions and for light reemitted at IR wavelengths. Deep ISOCAM and VLA photometries on one CFRS field have been performed. Multi-wavelength analyses from UV to Mid-IR and hence to radio allow us to classify sources from their spectral energy distributions. This provides an estimation of the FIR luminosity density related to star formation. The deduced SFR density is free of extinction effects and not contaminated by AGN emissions. About 55+/-20% of the star formation at z<=1 is related to FIR emission. If a non truncated Salpeter IMF is adopted, the derived stellar mass formed from z=0 to z=1 seems too high when compared to the present day stellar mass. An important fraction (30%) of the star formation at z=0.5-1 seems to be related to the rapidly evolving population of compact/Irr galaxies. Larger systems found at z=1, show a slower evolution...

  3. Star-forming galaxies versus low- and high-excitation radio AGN in the VLA-COSMOS 3GHz Large Project

    CERN Document Server

    Baran, N; Novak, M; Delhaize, J; Delvecchio, I; Capak, P; Civano, F; Herrera-Ruiz, N; Ilbert, O; Laigle, C; Marchesi, S; McCracken, H J; Middelberg, E; Salvato, M; Schinnerer, E

    2016-01-01

    We study the composition of the faint radio population selected from the VLA-COSMOS 3GHz Large Project, a radio continuum survey performed at 10 cm wavelength. The survey covers the full 2 square degree COSMOS field with mean $rms\\sim2.3$ $\\mu$Jy/beam, cataloging 10,899 source components above $5\\times rms$. By combining these radio data with UltraVISTA, optical, near-infrared, and Spitzer/IRAC mid-infrared data, as well as X-ray data from the Chandra Legacy, and Chandra COSMOS surveys, we gain insight into the emission mechanisms within our radio sources out to redshifts of $z\\sim5$. From these emission characteristics we classify our souces as star forming galaxies or AGN. Using their multi-wavelength properties we further separate the AGN into sub-samples dominated by radiatively efficient and inefficient AGN, often referred to as high- and low-excitation emission line AGN. We compare our method with other results based on fitting of the sources' spectral energy distributions using both galaxy and AGN spec...

  4. Revolutionizing our View of Protostellar Multiplicity and Disks: The VLA Nascent Disk and Multiplicity (VANDAM) Survey of the Perseus Molecular Cloud

    CERN Document Server

    Tobin, John J; Li, Zhi-Yun; Chandler, Claire J; Dunham, Michael M; Segura-Cox, Dominique; Cox, Erin G; Harris, Robert J; Melis, Carl; Sadavoy, Sarah I; Pérez, Laura; Kratter, Kaitlin

    2016-01-01

    There is substantial evidence for disk formation taking place during the early stages of star formation and for most stars being born in multiple systems; however, protostellar multiplicity and disk searches have been hampered by low resolution, sample bias, and variable sensitivity. We have conducted an unbiased, high-sensitivity Karl G. Jansky Very Large Array (VLA) survey toward all known protostars (n = 94) in the Perseus molecular cloud (d~230 pc), with a resolution of ~15 AU (0.06") at 8 mm. We have detected candidate protostellar disks toward 17 sources (with 12 of those in the Class 0 stage) and we have found substructure on < 50AU scales for three Class 0 disk candidates, possibly evidence for disk fragmentation. We have discovered 16 new multiple systems (or new components) in this survey; the new systems have separations < 500 AU and 3 by < 30 AU. We also found a bi-modal distribution of separations, with peaks at ~75 AU and ~3000 AU, suggestive of formation through two distinct mechanisms...

  5. THE VLA NASCENT DISK AND MULTIPLICITY SURVEY: FIRST LOOK AT RESOLVED CANDIDATE DISKS AROUND CLASS 0 AND I PROTOSTARS IN THE PERSEUS MOLECULAR CLOUD

    Energy Technology Data Exchange (ETDEWEB)

    Segura-Cox, Dominique M.; Harris, Robert J.; Looney, Leslie W. [Department of Astronomy, University of Illinois, Urbana, IL 61801 (United States); Tobin, John J. [Leiden Observatory, Leiden University, P.O. Box 9513, 2000-RA Leiden (Netherlands); Li, Zhi-Yun [Department of Astronomy, University of Virginia, Charlottesville, VA 22903 (United States); Chandler, Claire; Perez, Laura [National Radio Astronomy Observatory, Socorro, NM 87801 (United States); Kratter, Kaitlin [Steward Observatory, University of Arizona, Tucson, AZ 85721 (United States); Dunham, Michael M. [Harvard-Smithsonian Center for Astrophysics, Cambridge, MA 02138 (United States); Sadavoy, Sarah [Max-Planck-Institut für Astronomie, D-69117 Heidelberg (Germany); Melis, Carl, E-mail: segurac2@illinois.edu [Center for Astrophysics and Space Sciences, University of California, San Diego, CA 92093 (United States)

    2016-02-01

    We present the first dust emission results toward a sample of seven protostellar disk candidates around Class 0 and I sources in the Perseus molecular cloud from the VLA Nascent Disk and Multiplicity (VANDAM) survey with ∼0.″05 or 12 AU resolution. To examine the surface brightness profiles of these sources, we fit the Ka-band 8 mm dust-continuum data in the u, v-plane to a simple, parametrized model based on the Shakura–Sunyaev disk model. The candidate disks are well-fit by a model with a disk-shaped profile and have masses consistent with known Class 0 and I disks. The inner-disk surface densities of the VANDAM candidate disks have shallower density profiles compared to disks around more evolved Class II systems. The best-fit model radii of the seven early-result candidate disks are R{sub c} > 10 AU; at 8 mm, the radii reflect lower limits on the disk size since dust continuum emission is tied to grain size and large grains radially drift inwards. These relatively large disks, if confirmed kinematically, are inconsistent with theoretical models where the disk size is limited by strong magnetic braking to <10 AU at early times.

  6. The shape of the blue\\/UV continuum of B3-VLA radio quasars Dependence on redshift, blue\\/UV luminosity and radio power

    CERN Document Server

    Carballo, R; Benn, C R; Sánchez, S F; Vigotti, M

    1999-01-01

    UBVR photometry of a sample of B3-VLA radio quasars, about 80 per cent complete, is used to analyse their spectral energy distribution (SED). The SEDs are generally well fitted with power-laws, with an average slope alpha=-0.39 (S_nu propto nu^alpha). Two quasars appear clearly differenciated, exhibiting redder colours that the rest, and they have redshifts z=0.50 and 1.12. Broad-band composite SEDs in the range 1300-4500 AA were obtained from the remaining quasars and they show the CIV1549 line and a break at around 3000 A, where the SED changes from alpha_blue=0.11+-0.16 at lambda>3000 A to alpha_UV=-0.66+-0.15 at lambda1.2 alpha_UV is more flat, -0.48+-0.12. A similar trend is found between alpha_UV and luminosity at 2400 A, L_2400, with luminous quasars exhibiting a bluer spectrum. In addition, an intrinsic correlation is found between L_2400 and radio power at 408 MHz. The correlations alpha_UV-z, alpha_UV-L_2400 and L_2400-z are consistent with accretion disc models with approximately constant black hol...

  7. Advanced spectral analysis of ionospheric waves observed with sparse arrays

    Science.gov (United States)

    Helmboldt, J. F.; Intema, H. T.

    2014-02-01

    This paper presents a case study from a single, 6h observing period to illustrate the application of techniques developed for interferometric radio telescopes to the spectral analysis of observations of ionospheric fluctuations with sparse arrays. We have adapted the deconvolution methods used for making high dynamic range images of cosmic sources with radio arrays to making comparably high dynamic range maps of spectral power of wavelike ionospheric phenomena. In the example presented here, we have used observations of the total electron content (TEC) gradient derived from Very Large Array (VLA) observations of synchrotron emission from two galaxy clusters at 330MHz as well as GPS-based TEC measurements from a sparse array of 33 receivers located within New Mexico near the VLA. We show that these techniques provide a significant improvement in signal-to-noise ratio (S/N) of detected wavelike structures by correcting for both measurement inaccuracies and wavefront distortions. This is especially true for the GPS data when combining all available satellite/receiver pairs, which probe a larger physical area and likely have a wider variety of measurement errors than in the single-satellite case. In this instance, we found that the peak S/N of the detected waves was improved by more than an order of magnitude. The data products generated by the deconvolution procedure also allow for a reconstruction of the fluctuations as a two-dimensional waveform/phase screen that can be used to correct for their effects.

  8. A wideband high common mode rejection ratio amplifier and phase-locked loop demodulator for multifrequency impedance measurement.

    Science.gov (United States)

    Goovaerts, H G; Faes, T J; Raaijmakers, E; Heethaar, R M

    1998-11-01

    Design considerations and implementation of a multifrequency measuring channel for application in the field of bio-impedance measurement are discussed in this paper. The input amplifier has a differential configuration which is electrically isolated from the remaining circuits. Transformer coupling provides improved common mode rejection when compared to non-isolated input stages. The frequency characteristic of the section between input and demodulator is flat within +/- 0.1 dB between 4 kHz and 1024 kHz. The synchronous demodulator is based on a wideband switched video amplifier. In contrast to commonly used lock--in techniques, the carrier for demodulation is recovered from the input signal by means of a phase-locked loop. This method ensures zero phase shift with respect to the input signal and improves the accuracy of measurement. The system has been developed primarily for thoracic impedance cardiography (TIC) but has also successfully been applied in the field of total body bio-impedance analysis (BIA). At present an electrical impedance tomograph is under development based on the instrumentation described. Results regarding the measurement range and accuracy are given and some recordings of patient data are shown.

  9. System Description and First Application of an FPGA-Based Simultaneous Multi-Frequency Electrical Impedance Tomography.

    Science.gov (United States)

    Aguiar Santos, Susana; Robens, Anne; Boehm, Anna; Leonhardt, Steffen; Teichmann, Daniel

    2016-07-25

    A new prototype of a multi-frequency electrical impedance tomography system is presented. The system uses a field-programmable gate array as a main controller and is configured to measure at different frequencies simultaneously through a composite waveform. Both real and imaginary components of the data are computed for each frequency and sent to the personal computer over an ethernet connection, where both time-difference imaging and frequency-difference imaging are reconstructed and visualized. The system has been tested for both time-difference and frequency-difference imaging for diverse sets of frequency pairs in a resistive/capacitive test unit and in self-experiments. To our knowledge, this is the first work that shows preliminary frequency-difference images of in-vivo experiments. Results of time-difference imaging were compared with simulation results and shown that the new prototype performs well at all frequencies in the tested range of 60 kHz-960 kHz. For frequency-difference images, further development of algorithms and an improved normalization process is required to correctly reconstruct and interpreted the resulting images.

  10. Numerical solution of a coefficient inverse problem with multi-frequency experimental raw data by a globally convergent algorithm

    Science.gov (United States)

    Nguyen, Dinh-Liem; Klibanov, Michael V.; Nguyen, Loc H.; Kolesov, Aleksandr E.; Fiddy, Michael A.; Liu, Hui

    2017-09-01

    We analyze in this paper the performance of a newly developed globally convergent numerical method for a coefficient inverse problem for the case of multi-frequency experimental backscatter data associated to a single incident wave. These data were collected using a microwave scattering facility at the University of North Carolina at Charlotte. The challenges for the inverse problem under the consideration are not only from its high nonlinearity and severe ill-posedness but also from the facts that the amount of the measured data is minimal and that these raw data are contaminated by a significant amount of noise, due to a non-ideal experimental setup. This setup is motivated by our target application in detecting and identifying explosives. We show in this paper how the raw data can be preprocessed and successfully inverted using our inversion method. More precisely, we are able to reconstruct the dielectric constants and the locations of the scattering objects with a good accuracy, without using any advanced a priori knowledge of their physical and geometrical properties.

  11. Development of multi-frequency ESR system for high-pressure measurements up to 2.5 GPa.

    Science.gov (United States)

    Sakurai, T; Fujimoto, K; Matsui, R; Kawasaki, K; Okubo, S; Ohta, H; Matsubayashi, K; Uwatoko, Y; Tanaka, H

    2015-10-01

    A new piston-cylinder pressure cell for electron spin resonance (ESR) has been developed. The pressure cell consists of a double-layer hybrid-type cylinder with internal components made of the ZrO2-based ceramics. It can generate a pressure of 2 GPa repeatedly and reaches a maximum pressure of around 2.5 GPa. A high-pressure ESR system using a cryogen-free superconducting magnet up 10T has also been developed for this hybrid-type pressure cell. The frequency region is from 50 GHz to 400 GHz. This is the first time a pressure above 2 GPa has been achieved in multi-frequency ESR system using a piston-cylinder pressure cell. We demonstrate its potential by showing the results of the high-pressure ESR of the S=1 system with the single ion anisotropy NiSnCl6·6H2O and the S=1/2 quantum spin system CsCuCl3. We performed ESR measurements of these systems above 2 GPa successfully. Copyright © 2015 Elsevier Inc. All rights reserved.

  12. The Multi-Frequency Correlation Between Eua and sCER Futures Prices: Evidence from the Emd Approach

    Science.gov (United States)

    Zhang, Yue-Jun; Huang, Yi-Song

    2015-05-01

    Currently European Union Allowances (EUA) and secondary Certified Emission Reduction (sCER) have become two dominant carbon trading assets for investors and their linkage attracts much attention from academia and practitioners in recent years. Under this circumstance, we use the empirical mode decomposition (EMD) approach to decompose the two carbon futures contract prices and discuss their correlation from the multi-frequency perspective. The empirical results indicate that, first, the EUA and sCER futures price movements can be divided into those triggered by the long-term, medium-term and short-term market impacts. Second, the price movements in the EUA and sCER futures markets are primarily caused by the long-term impact, while the short-term impact can only explain a small fraction. Finally, the long-term (short-term) effect on EUA prices is statistically uncorrelated with the short-term (long-term) effect of sCER prices, and there is a medium or strong lead-and-lag correlation between the EUA and sCER price components with the same time scales. These results may provide some important insights of price forecast and arbitraging activities for carbon futures market investors, analysts and regulators.

  13. Monitoring of labeled antisense oligonucleotides within living cells by using a multifrequency phase/modulation approach for fluorescence lifetime measurements

    Science.gov (United States)

    Kocisova, E.; Sureau, F.; Praus, P.; Rosenberg, I.; Stepanek, J.; Turpin, P.-Y.

    2003-06-01

    A multifrequency phase/modulation method has been developed for our UV confocal laser microspectrofluorimeter (modulation frequency 1-200 MHz) for fluorescence lifetime measurements. This technique enables excited state lifetimes of mixed fluorescent components to be resolved and the fluorescence spectral contribution of each species to be determined without using any model spectra. This approach is very efficient for analyzing intracellular multicomponent fluorescence signals. Our effort is focused on the elucidation of the intracellular behavior of synthetic modified oligonucleotides - potential drugs for antisense and/or antigene strategies of curing viral and malignant diseases. A novel type single stranded dT 15 oligomer analogue containing isopolar, non-isosteric, phosphonate-based internucleotide linkages (3'-O-P-CH 2-O-5'), labeled with tetramethylrhodamine dye at the 3'-end, has been utilized. This method, along with fluorescence micro-imaging, was used to monitor uptake, distribution and stability of our modified oligonucleotide inside living cells. Binding to Escort™ vector leads to an homogeneous intracellular distribution of fluorescent labeled oligonucleotide, including nucleus staining, while point distribution only is achieved for its free form.

  14. Computer-aided design of multifrequency eddy-current tests for layered conductors with multiple property variations

    Energy Technology Data Exchange (ETDEWEB)

    Deeds, W E; Dodd, C V; Scott, G W

    1979-10-01

    Our program is part of a larger project designed to develop multifrequency eddy-current inspection techniques for multilayered conductors with parallel planar boundaries. To reduce the need to specially program each new problem, a family of programs that handle a large class of related problems with only minor editorial and interactive changes were developed. Programs for two types of cylindrical coil probes were developed: the reflection probe, which contains the driver and pickup coils and is used from one side of the specimen, and the through-transmission probe set, which places the driver and pickup coils on opposite sides of the conductor stack. The programs perform the following basic functions: (1) simulation of an ideal instrument's response to specific conductor and defect configurations, (2) control of an eddy-current instrument interfaced to a minicomputer to acquire and record actual instrument responses to test specimens, (3) construction of complex function expansions to relate instrument response to conductor and defect properties by using measured or computed responses and properties, and (4) simulation of a microcomputer on board the instrument by the interfaced minicomputer to test the analytical programming for the microcomputer. The report contains the basic equations for the computations, the main and subroutine programs, instructions for editorial changes and program execution, analyses of the main programs, file requirements, and other miscellaneous aids for the user.

  15. MULTI-FREQUENCY STUDIES OF RADIO RELICS IN THE GALAXY CLUSTERS A4038, A1664, AND A786

    Energy Technology Data Exchange (ETDEWEB)

    Kale, Ruta; Dwarakanath, K. S., E-mail: ruta@iucaa.ernet.in [Raman Research Institute, C. V. Raman Avenue, Sadashivanagar, Bangalore 560 080 (India)

    2012-01-01

    We present a multi-frequency study of radio relics associated with the galaxy clusters A4038, A1664, and A786. Radio images, integrated spectra, spectral index maps, and fits to the integrated spectra in the framework of the adiabatic compression model are presented. Images of the relic in A4038 at 150, 240, and 606 MHz with the Giant Meterwave Radio Telescope have revealed extended ultra-steep spectrum ({alpha} {approx} -1.8 to -2.7) emission of extent 210 Multiplication-Sign 80 kpc{sup 2}. The model of passively evolving radio lobes compressed by a shock fits the integrated spectrum best. The relic with a circular morphology at the outskirts of the cluster A1664 has an integrated spectral index of {approx} - 1.10 {+-} 0.06 and is best fit by the model of radio lobes lurking for {approx}4 Multiplication-Sign 10{sup 7} yr. The relic near A786 has a curved spectrum and is best fit by a model of radio lobes lurking for {approx}3 Multiplication-Sign 10{sup 7} yr. At 4.7 GHz, a compact radio source, possibly the progenitor of the A786 relic, is detected near the center of the radio relic. The A786 radio relic is thus likely a lurking radio galaxy rather than a site of cosmological shock as has been considered in earlier studies.

  16. Multi-frequency studies of galaxies and groups: I. Environmental effect on galaxy stellar mass and morphology

    CERN Document Server

    Poudel, A; Nurmi, P; Teerikorpi, P; Tempel, E; Lietzen, H; Einasto, M

    2016-01-01

    To understand the role of the environment in galaxy formation, evolution, and present-day properties, it is essential to study the multi-frequency behavior of different galaxy populations under various environmental conditions. We crossmatch the SDSS DR10 group catalog with GAMA Data Release 2 and Wide-field Survey Explorer (WISE) data to construct a catalog of 1651 groups and 11436 galaxies containing photometric information in 15 different wavebands ranging from ultraviolet (0.152 {\\mu}m) to mid-infrared (22 {\\mu}m). We perform the spectral energy distribution (SED) fitting of galaxies using the MAGPHYS code and estimate the rest frame luminosities and stellar masses. We use the 1/Vmax method to estimate the galaxy stellar mass and luminosity functions, and the luminosity density field of galaxies to define the large scale environment of galaxies. The stellar mass functions of both central and satellite galaxies in groups are different in low and high density large scale environments. Satellite galaxies in ...

  17. Rapid evaluation of multifrequency EMI data to characterize buried structures at a historical Jesuit Mission in Argentina

    Science.gov (United States)

    Bongiovanni, M. V.; Bonomo, N.; de la Vega, M.; Martino, L.; Osella, A.

    2008-03-01

    We present results from a geophysical prospection at a historical Jesuit Mission, located in San Ignacio (Misiones-Argentina), declared World Monument some years ago. We studied different sectors looking for buried structures; the total area under study covered 36 ha. In this work we will show the results obtained in a sector that at the time of the prospection was at imminent risk of being damaged by a wrong management of the historical resource. To optimize the data acquisition and the preliminary in-situ analysis of the results, we performed an electromagnetic survey using a multifrequency electromagnetic induction device (GEM-2) to have a first insight of the near surface electrical distribution. From 2D and 3D visualization of data, different targets were identified as possible historical structures. Around these anomalous zones, we performed different dipole-dipole profiles, forming high resolution grids for later 3D inversions. Further inversions of the electric and electromagnetic data completed the characterization of the anomalies. One of the main results of this work is that the 3D electric image obtained from 1D inversion of electromagnetic data coincides with the 3D images obtained from resistivity inversion, but at a much less time consuming cost.

  18. System Description and First Application of an FPGA-Based Simultaneous Multi-Frequency Electrical Impedance Tomography

    Directory of Open Access Journals (Sweden)

    Susana Aguiar Santos

    2016-07-01

    Full Text Available A new prototype of a multi-frequency electrical impedance tomography system is presented. The system uses a field-programmable gate array as a main controller and is configured to measure at different frequencies simultaneously through a composite waveform. Both real and imaginary components of the data are computed for each frequency and sent to the personal computer over an ethernet connection, where both time-difference imaging and frequency-difference imaging are reconstructed and visualized. The system has been tested for both time-difference and frequency-difference imaging for diverse sets of frequency pairs in a resistive/capacitive test unit and in self-experiments. To our knowledge, this is the first work that shows preliminary frequency-difference images of in-vivo experiments. Results of time-difference imaging were compared with simulation results and shown that the new prototype performs well at all frequencies in the tested range of 60 kHz–960 kHz. For frequency-difference images, further development of algorithms and an improved normalization process is required to correctly reconstruct and interpreted the resulting images.

  19. Effects of multi-frequency power ultrasound on the enzymolysis of corn gluten meal: Kinetics and thermodynamics study.

    Science.gov (United States)

    Jin, Jian; Ma, Haile; Qu, Wenjuan; Wang, Kai; Zhou, Cunshan; He, Ronghai; Luo, Lin; Owusu, John

    2015-11-01

    The effects of multi-frequency power ultrasound (MPU) pretreatment on the kinetics and thermodynamics of corn gluten meal (CGM) were investigated in this research. The apparent constant (KM), apparent break-down rate constant (kA), reaction rate constants (k), energy of activation (Ea), enthalpy of activation (ΔH), entropy of activation (ΔS) and Gibbs free energy of activation (ΔG) were determined by means of the Michaelis-Menten equation, first-order kinetics model, Arrhenius equation and transition state theory, respectively. The results showed that MPU pretreatment can accelerate the enzymolysis of CGM under different enzymolysis conditions, viz. substrate concentration, enzyme concentration, pH, and temperature. Kinetics analysis revealed that MPU pretreatment decreased the KM value by 26.1% and increased the kA value by 7.3%, indicating ultrasound pretreatment increased the affinity between enzyme and substrate. In addition, the values of k for ultrasound pretreatment were increased by 84.8%, 41.9%, 28.9%, and 18.8% at the temperature of 293, 303, 313 and 323 K, respectively. For the thermodynamic parameters, ultrasound decreased Ea, ΔH and ΔS by 23.0%, 24.3% and 25.3%, respectively, but ultrasound had little change in ΔG value in the temperature range of 293-323 K. In conclusion, MPU pretreatment could remarkably enhance the enzymolysis of CGM, and this method can be applied to protein proteolysis industry to produce peptides.

  20. Measuring body composition in dogs using multifrequency bioelectrical impedance analysis and dual energy X-ray absorptiometry.

    Science.gov (United States)

    Rae, L S; Vankan, D M; Rand, J S; Flickinger, E A; Ward, L C

    2016-06-01

    Thirty-five healthy, neutered, mixed breed dogs were used to determine the ability of multifrequency bioelectrical impedance analysis (MFBIA) to predict accurately fat-free mass (FFM) in dogs using dual energy X-ray absorptiometry (DXA)-measured FFM as reference. A second aim was to compare MFBIA predictions with morphometric predictions. MFBIA-based predictors provided an accurate measure of FFM, within 1.5% when compared to DXA-derived FFM, in normal weight dogs. FFM estimates were most highly correlated with DXA-measured FFM when the prediction equation included resistance quotient, bodyweight, and body condition score. At the population level, the inclusion of impedance as a predictor variable did not add substantially to the predictive power achieved with morphometric variables alone; in individual dogs, impedance predictors were more valuable than morphometric predictors. These results indicate that, following further validation, MFBIA could provide a useful tool in clinical practice to objectively measure FFM in canine patients and help improve compliance with prevention and treatment programs for obesity in dogs.

  1. Multi-frequency studies of radio relics in the galaxy clusters A4038, A1664 and A786

    CERN Document Server

    Kale, Ruta

    2011-01-01

    We present a multi-frequency study of radio relics associated with the galaxy clusters A4038, A1664 and A786. Radio images, integrated spectra, spectral index maps and fits to the integrated spectra in the framework of the adiabatic compression model are presented. Images of the relic in A4038 at 150, 240 and 606 MHz with the Giant Metrewave Radio Telescope have revealed extended ultra-steep spectrum (\\alpha ~ -1.8 to -2.7) emission of an extent 210 x 80 kpc^2. The model of passively evolving radio lobes compressed by a shock best fits the integrated spectrum. The relic with a circular morphology at the outskirts of the cluster A1664 has an integrated spectral index of -1.10+/-0.06 and is best fit by the model of radio lobes lurking for ~ 4x10^7 yr. The relic near A786 has a curved spectrum and is best fit by a model of radio lobes lurking for ~ 3x10^7 yr. At 4.7 GHz, a compact radio source, possibly the progenitor of the A786 relic, is detected near the center of the radio relic. The A786 radio relic is thus...

  2. A new VLA/e-MERLIN limit on central images in the gravitational lens system CLASS B1030+074

    NARCIS (Netherlands)

    Quinn, Jonathan; Jackson, Neal; Tagore, Amitpal; Biggs, Andrew; Birkinshaw, Mark; Chapman, Scott; De Zotti, Gianfranco; McKean, John; Pérez-Fournon, Ismael; Scott, Douglas; Serjeant, Stephen

    2016-01-01

    We present the new Very Large Array 22 GHz and extended Multi-Element Remote-Linked Interferometer Network 5 GHz observations of CLASS B1030+074, a two-image strong gravitational lens system whose background source is a compact flat-spectrum radio quasar. In such systems we expect a third image of

  3. Extremely Red Submillimeter Galaxies: New z ≳ 4-6 Candidates Discovered using ALMA and Jansky VLA

    NARCIS (Netherlands)

    Ikarashi, Soh; Ivison, R. J.; Caputi, Karina I.; Nakanishi, Kouichiro; Lagos, Claudia D. P.; Ashby, M. L. N.; Aretxaga, Itziar; Dunlop, James S.; Hatsukade, Bunyo; Hughes, David H.; Iono, Daisuke; Izumi, Takuma; Kawabe, Ryohei; Kohno, Kotaro; Motohara, Kentaro; Ohta, Kouji; Tamura, Yoichi; Umehata, Hideki; Wilson, Grant W.; Yabe, Kiyoto; Yun, Min S.

    2017-01-01

    We present the detailed characterization of two extremely red submillimeter galaxies (SMGs), ASXDF1100.053.1 and 231.1, with the Atacama Large Millimeter/submillimeter Array (ALMA) and the Jansky Very Large Array. These SMGs were originally selected using AzTEC at 1100 μm, and are observed by Hersch

  4. Radio Band Observations of Blazar Variability

    CERN Document Server

    Aller, Margo F; Hughes, Philip A

    2010-01-01

    The properties of blazar variability in the radio band are studied using the unique combination of temporal resolution from single dish monitoring and spatial resolution from VLBA imaging; such measurements, now available in all four Stokes parameters, together with theoretical simulations, identify the origin of radio band variability and probe the characteristics of the radio jet where the broadband blazar emission originates. Outbursts in total flux density and linear polarization in the optical-to-radio bands are attributed to shocks propagating within the jet spine, in part based on limited modeling invoking transverse shocks; new radiative transfer simulations allowing for shocks at arbitrary angle to the flow direction confirm this picture by reproducing the observed centimeter-band variations observed more generally, and are of current interest since these shocks may play a role in the gamma-ray flaring detected by Fermi. Recent UMRAO multifrequency Stokes V studies of bright blazars identify the spec...

  5. A new VLA/e-MERLIN limit on central images in the gravitational lens system CLASS B1030+074

    Science.gov (United States)

    Quinn, Jonathan; Jackson, Neal; Tagore, Amitpal; Biggs, Andrew; Birkinshaw, Mark; Chapman, Scott; De Zotti, Gianfranco; McKean, John; Pérez-Fournon, Ismael; Scott, Douglas; Serjeant, Stephen

    2016-07-01

    We present the new Very Large Array 22 GHz and extended Multi-Element Remote-Linked Interferometer Network 5 GHz observations of CLASS B1030+074, a two-image strong gravitational lens system whose background source is a compact flat-spectrum radio quasar. In such systems we expect a third image of the background source to form close to the centre of the lensing galaxy. The existence and brightness of such images is important for investigation of the central mass distributions of lensing galaxies, but only one secure detection has been made so far in a galaxy-scale lens system. The noise levels achieved in our new B1030+074 images reach 3 μJy beam-1 and represent an improvement in central image constraints of nearly an order of magnitude over previous work, with correspondingly better resulting limits on the shape of the central mass profile of the lensing galaxy. Simple models with an isothermal outer power-law slope now require either the influence of a central supermassive black hole (SMBH), or an inner power-law slope very close to isothermal, in order to suppress the central image below our detection limit. Using the central mass profiles inferred from light distributions in Virgo galaxies, moved to z = 0.5, and matching to the observed Einstein radius, we now find that 45 per cent of such mass profiles should give observable central images, 10 per cent should give central images with a flux density still below our limit, and the remaining systems have extreme demagnification produced by the central SMBH. Further observations of similar objects will therefore allow proper statistical constraints to be placed on the central properties of elliptical galaxies at high redshift.

  6. Proportional integral plus multi-frequency resonant current controller for grid-connected voltage source converter under imbalanced and distorted supply voltage conditions

    Institute of Scientific and Technical Information of China (English)

    Jia-bing HU; Wei ZHANG; Hong-sheng WANG; Yi-kang HE; Lie XU

    2009-01-01

    This paper proposes a current control scheme for a grid-connected pulse width modulator (PWM) voltage source converter (GC-VSC) under imbalanced and distorted supply voltage conditions. The control scheme is implemented in the positive synchronously rotating reference frame and composed of a single proportional integral (PI) regulator and multi-frequency resonant controllers tuned at the frequencies of 2ω and 6ω, respectively. The experimental results, with the target of eliminating the active power oscillations and current harmonics on a prototype GC-VSC system, validate the feasibility of the proposed current control scheme during supply voltage imbalance and distortion.

  7. Quest for COSMOS submillimeter galaxy counterparts using CARMA and VLA: Identifying three high-redshift starburst galaxies

    CERN Document Server

    Smolcic, V; Aravena, M; Ilbert, O; Yun, M S; Sheth, K; Salvato, M; McCracken, H J; Diener, C; Aretxaga, I; Riechers, D A; Finoguenov, A; Bertoldi, F; Capak, P; Hughes, D; Karim, A; Schinnerer, E; Scoville, N Z; Wilson, G

    2012-01-01

    We report on interferometric observations at 1.3 mm at 2"-3" resolution using the Combined Array for Research in Millimeter-wave Astronomy (CARMA). We identify multi-wavelength counterparts of three submillimeter galaxies (SMGs; F(1mm)>5.5 mJy) in the COSMOS field, initially detected with MAMBO and AzTEC bolometers at low, ~10"-30", resolution. All three sources -- AzTEC/C1, Cosbo-3 and Cosbo-8 -- are identified to coincide with positions of 20 cm radio sources. Cosbo-3, however, is not associated with the most likely radio counterpart, closest to the MAMBO source position, but that further away from it. This illustrates the need for intermediate-resolution (~2") mm-observations to identify the correct counterparts of single-dish detected SMGs. All of our three sources become prominent only at NIR wavelengths, and their mm-to-radio flux based redshifts suggest that they lie at redshifts z>~2. As a proof of concept, we show that photometric redshifts can be well determined for SMGs, and we find photometric-red...

  8. QUEST FOR COSMOS SUBMILLIMETER GALAXY COUNTERPARTS USING CARMA AND VLA: IDENTIFYING THREE HIGH-REDSHIFT STARBURST GALAXIES

    Energy Technology Data Exchange (ETDEWEB)

    Smolcic, V. [European Southern Observatory, Karl-Schwarzschild-Strasse 2, D-85748 Garching b. Muenchen (Germany); Navarrete, F.; Bertoldi, F. [Argelander Institut for Astronomy, Auf dem Huegel 71, Bonn D-53121 (Germany); Aravena, M.; Sheth, K. [National Radio Astronomy Observatory, 520 Edgemont Road, Charlottesville, VA 22903 (United States); Ilbert, O. [Laboratoire d' Astrophysique de Marseille, Universite de Provence, CNRS, BP 8, Traverse du Siphon, F-13376 Marseille Cedex 12 (France); Yun, M. S. [Department of Astronomy, University of Massachusetts, Amherst, MA 01003 (United States); Salvato, M.; Finoguenov, A. [Max-Planck-Institut fuer Extraterrestrische Physik, Giessenbachstrasse, D-85748 Garching (Germany); McCracken, H. J. [Institut d' Astrophysique de Paris, UMR7095 CNRS, Universit Pierre et Marie Curie, 98 bis Boulevard Arago, F-75014 Paris (France); Diener, C. [Institute for Astronomy, ETH Zrich, Wolfgang-Pauli-strasse 27, 8093 Zurich (Switzerland); Aretxaga, I.; Hughes, D.; Wilson, G. [Instituto Nacional de Astrofisica, Optica y Electronica (INAOE), Aptdo. Postal 51 y 216, 72000 Puebla, Pue. (Mexico); Riechers, D. A.; Capak, P.; Scoville, N. Z. [Astronomy Department, California Institute of Technology, MC 249-17, 1200 East California Boulevard, Pasadena, CA 91125 (United States); Karim, A.; Schinnerer, E. [Max Planck Institut fuer Astronomie, Koenigstuhl 17, Heidelberg D-69117 (Germany)

    2012-05-01

    We report on interferometric observations at 1.3 mm at 2''-3'' resolution using the Combined Array for Research in Millimeter-wave Astronomy. We identify multi-wavelength counterparts of three submillimeter galaxies (SMGs; F{sub 1m} > 5.5 mJy) in the COSMOS field, initially detected with MAMBO and AzTEC bolometers at low, {approx}10''-30'', resolution. All three sources-AzTEC/C1, Cosbo-3, and Cosbo-8-are identified to coincide with positions of 20 cm radio sources. Cosbo-3, however, is not associated with the most likely radio counterpart, closest to the MAMBO source position, but with that farther away from it. This illustrates the need for intermediate-resolution ({approx}2'') mm-observations to identify the correct counterparts of single-dish-detected SMGs. All of our three sources become prominent only at NIR wavelengths, and their mm-to-radio flux based redshifts suggest that they lie at redshifts z {approx}> 2. As a proof of concept, we show that photometric redshifts can be well determined for SMGs, and we find photometric redshifts of 5.6 {+-} 1.2, 1.9{sup +0.9}{sub -0.5}, and {approx}4 for AzTEC/C1, Cosbo-3, and Cosbo-8, respectively. Using these we infer that these galaxies have radio-based star formation rates of {approx}> 1000 M{sub Sun} yr{sup -1}and IR luminosities of {approx}10{sup 13} L{sub Sun} consistent with properties of high-redshift SMGs. In summary, our sources reflect a variety of SMG properties in terms of redshift and clustering, consistent with the framework that SMGs are progenitors of z {approx} 2 and today's passive galaxies.

  9. Deep multi-frequency rotation measure tomography of the galaxy cluster A2255

    NARCIS (Netherlands)

    Pizzo, R. F.; de Bruyn, A. G.; Bernardi, G.; Brentjens, M. A.

    Aims. By studying the polarimetric properties of the radio galaxies and the radio filaments belonging to the galaxy cluster Abell 2255, we aim to unveil their 3-dimensional location within the cluster. Methods. We performed WSRT observations of A2255 at 18, 21, 25, 85, and 200 cm. The polarization

  10. VLA High Resolution 1.4 and 8.4 GHz Mapping of the Barred Galaxy NGC 3367

    CERN Document Server

    García-Barreto, J A; Rudnick, L; Franco, Jose; Rudnick, Larry

    2002-01-01

    We report new radio continuum observations with an angular resolution of 2''.1 at 1.4 GHz and 0''.28 at 8.4 GHz of the barred galaxy NGC 3367. In the map at 1.4 GHz the central nuclear region connects to the SW lobe, with a projected structure at a position angle of PA = 230 forming a jet-like structure. The map at 8.4 GHz shows a compact unresolved source (smaller than 65 pc in diameter) associated with emission from the nucleus and several compact sources located within a radius of about 300 pc, forming a circumnuclear structure. The compact core, jet, and lobes form a small, low power counterpart to radio galaxies, with a flow axis that is out of the plane of the galaxy. The flow axis (PA=230) coincides with the PA of the major axis of the galaxy and is thus inclined to the rotation axis of the disk. In addition, the flow axis differs by about 20 deg. from the major axis of the stellar bar. Assuming that the stellar bar rotates counterclockwise (ie. assuming trailing spiral arms), this difference in angle ...

  11. Extremely Red Submillimeter Galaxies: New z ≳ 4-6 Candidates Discovered using ALMA and Jansky VLA

    Science.gov (United States)

    Ikarashi, Soh; Ivison, R. J.; Caputi, Karina I.; Nakanishi, Kouichiro; Lagos, Claudia D. P.; Ashby, M. L. N.; Aretxaga, Itziar; Dunlop, James S.; Hatsukade, Bunyo; Hughes, David H.; Iono, Daisuke; Izumi, Takuma; Kawabe, Ryohei; Kohno, Kotaro; Motohara, Kentaro; Ohta, Kouji; Tamura, Yoichi; Umehata, Hideki; Wilson, Grant W.; Yabe, Kiyoto; Yun, Min S.

    2017-02-01

    We present the detailed characterization of two extremely red submillimeter galaxies (SMGs), ASXDF1100.053.1 and 231.1, with the Atacama Large Millimeter/submillimeter Array (ALMA) and the Jansky Very Large Array. These SMGs were originally selected using AzTEC at 1100 μm, and are observed by Herschel to be faint at 100–500 μm. Their (sub)millimeter colors are as red as—or redder—than known z ≳ 5 SMGs; indeed, ASXDF1100.053.1 is redder than HFLS 3, which lies at z = 6.3. They are also faint and red in the near-/mid-infrared: ∼1 μJy at IRAC 4.5 μm and ALMA maps are ∼1 and ≲0.2 kpc (∼2–3 kpc for 90% of the total flux). Last, their surface infrared luminosity densities, ΣIR, are ∼1 × 1012 and ≳1.5 × 1013 L ⊙ kpc‑2, similar to values seen for local (U)LIRGs. These data suggest that ASXDF1100.053.1 and 231.1 are compact SMGs at z ≳ 4 and can plausibly evolve into z ≳ 3 compact quiescent galaxies.

  12. Multifrequency study of SNR J0533-7202, a new supernova remnant in the LMC

    CERN Document Server

    Bozzetto, L M; Crawford, E J; Sasaki, M; Maggi, P; Haberl, F; Urošević, D; Payne, J L; De Horta, A Y; Stupar, M; Gruendl, R; Dickel, J

    2013-01-01

    We present a detailed study of Australia Telescope Compact Array (ATCA) observations of a newly discovered Large Magellanic Cloud (LMC) supernova remnant (SNR), SNR J0533-7202. This object follows a horseshoe morphology, with a size 37 pc x 28 pc (1-pc uncertainty in each direction). It exhibits a radio spectrum with the intrinsic synchrotron spectral index of alpha= -0.47+-0.06 between 73 and 6 cm. We report detections of regions showing moderately high fractional polarisation at 6 cm, with a peak value of 36+-6% and a mean fractional polarisation of 12+-7%. We also estimate an average rotation measure across the remnant of -591 rad m^-2. The current lack of deep X-ray observation precludes any conclusion about high-energy emission from the remnant. The association with an old stellar population favours a thermonuclear supernova origin of the remnant.

  13. Multi-GNSS and Multi-frequency SNR Multipath Reflectometry of Snow Depth

    Science.gov (United States)

    Tabibi, S.; Geremia-Nievinski, F.; van Dam, T. M.

    2015-12-01

    Global Navigation Satellite System multipath reflectometry (GNSS-MR) uses ground-based signals of opportunity to retrieve snow depth at an intermediate space scale. This technique is based on the signal-to-noise ratio (SNR) of the simultaneously received direct (line-of-sight) and coherently ground reflected signals. In this contribution, forward and inverse modeling of SNR observations is presented for GLONASS-MR, extending GPS-MR to multiple GNSS. The coupling of the surface and antenna responses from short-delay near-grazing incidence multipath from CDMA and FDMA satellite navigation systems are simulated using an electromagnetic forward model. The inverse model is used to estimate parameter corrections responsible for observation residuals to estimate snow depth. The correlation between snow depth retrievals using GPS L2C signal and GLONASS R2-C/A signal is excellent, with r2 value of 0.990. In a related approach, dual-frequency SNR-based GNSS-MR, which is based on linear combination of SNR observables, is used to estimate snow depth. This ionospheric delay free method synthesizes longer carrier wavelengths ("widelaning" or delta-k) to isolate the direct power contribution in environmental retrievals.

  14. f-mode interaction with models of sunspot: near-field scattering and multifrequency effects

    Science.gov (United States)

    Daiffallah, Khalil

    2016-07-01

    We use numerical simulations to investigate the interaction of an f-mode wave packet with small and large models of a sunspot in a stratified atmosphere. While a loose cluster model has been largely studied before, we focus in this study on the scattering from an ensemble of tightly compact tubes. We showed that the small compact cluster produces a slight distorted scattered wave field in the transverse direction, which can be attributed to the simultaneous oscillations of the pairs of tubes within the cluster aligned in a perpendicular direction to the incoming wave. However, no signature of a multiple-scattering regime has been observed from this model, while it has been clearly observable for the large compact cluster model. Furthermore, we pointed out the importance of the geometrical shape of the monolithic model on the interaction of f-mode waves with a sunspot in a high-frequency range (ν = 5 mHz). These results are a contribution to the observational effort to distinguish seismically between different configurations of magnetic flux tubes within sunspots and plage.

  15. THE VLA NASCENT DISK AND MULTIPLICITY SURVEY OF PERSEUS PROTOSTARS (VANDAM). II. MULTIPLICITY OF PROTOSTARS IN THE PERSEUS MOLECULAR CLOUD

    Energy Technology Data Exchange (ETDEWEB)

    Tobin, John J.; Harris, Robert J. [Leiden Observatory, Leiden University, P.O. Box 9513, 2300-RA Leiden (Netherlands); Looney, Leslie W.; Segura-Cox, Dominique [Department of Astronomy, University of Illinois, Urbana, IL 61801 (United States); Li, Zhi-Yun [Department of Astronomy, University of Virginia, Charlottesville, VA 22903 (United States); Chandler, Claire J.; Perez, Laura [National Radio Astronomy Observatory, P.O. Box O, Socorro, NM 87801 (United States); Dunham, Michael M. [Harvard-Smithsonian Center for Astrophysics, 60 Garden St, MS 78, Cambridge, MA 02138 (United States); Sadavoy, Sarah I. [Max-Planck-Institut für Astronomie, D-69117 Heidelberg (Germany); Melis, Carl [Center for Astrophysics and Space Sciences, University of California, San Diego, CA 92093 (United States); Kratter, Kaitlin, E-mail: tobin@strw.leidenuniv.nl [University of Arizona, Steward Observatory, Tucson, AZ 85721 (United States)

    2016-02-10

    We present a multiplicity study of all known protostars (94) in the Perseus molecular cloud from a Karl G. Jansky Very Large Array survey at Ka-band (8 mm and 1 cm) and C-band (4 and 6.6 cm). The observed sample has a bolometric luminosity range between 0.1 L{sub ⊙} and ∼33 L{sub ⊙}, with a median of 0.7 L{sub ⊙}. This multiplicity study is based on the Ka-band data, having a best resolution of ∼0.″065 (15 au) and separations out to ∼43″ (10,000 au) can be probed. The overall multiplicity fraction (MF) is found to be 0.40 ± 0.06 and the companion star fraction (CSF) is 0.71 ± 0.06. The MF and CSF of the Class 0 protostars are 0.57 ± 0.09 and 1.2 ± 0.2, and the MF and CSF of Class I protostars are both 0.23 ± 0.08. The distribution of companion separations appears bi-modal, with a peak at ∼75 au and another peak at ∼3000 au. Turbulent fragmentation is likely the dominant mechanism on >1000 au scales and disk fragmentation is likely to be the dominant mechanism on <200 au scales. Toward three Class 0 sources we find companions separated by <30 au. These systems have the smallest separations of currently known Class 0 protostellar binary systems. Moreover, these close systems are embedded within larger (50–400 au) structures and may be candidates for ongoing disk fragmentation.

  16. A simplified Nyström-tree theory for extended Runge-Kutta-Nyström integrators solving multi-frequency oscillatory systems

    Science.gov (United States)

    Yang, Hongli; Zeng, Xianyang; Wu, Xinyuan; Ru, Zhengliang

    2014-11-01

    In the study of extended Runge-Kutta-Nyström (abbr. ERKN) methods for the integration of multi-frequency oscillatory systems, a quite complicated set of algebraic conditions arises which must be satisfied for a method to achieve some specified order. A theory of tri-colored tree was proposed by Yang et al. (2009), for achieving the order conditions of ERKN methods which are designed specially for multi-frequency and multidimensional perturbed oscillators. The tri-colored tree theory for the order conditions in that paper is useful, but not completely satisfactory due to the existence of redundant trees. In this paper, a simplified tri-colored theory and the order conditions for ERKN integrators are developed by constructing a set of simplified special extended Nyström trees (abbr. SSENT) and defining some real-valued mappings on it. In order to simplify the tri-colored tree theory, two special mappings, the extended elementary differential and the sign mapping for a tree are investigated in detail. This leads to a novel Nyström-tree theory for the order conditions for ERKN methods without any redundant trees, which simplifies the tri-colored theory.

  17. Detecting new γ-ray sources based on multi-frequency data the case of 1WHSPJ031423.9+061956

    Energy Technology Data Exchange (ETDEWEB)

    Arsioli, Bruno [ASI Science Data Center, ASDC, Agenzia Spaziale Italiana, via del Politecnico snc, 00133 Roma (Italy); Sapienza Università di Roma, Dipartimento di Fisica, Piazzale Aldo Moro 5, I-00185 Roma (Italy); ICRANet-Rio, CBPF, Rua Dr. Xavier Sigaud 150, 22290-180 Rio de Janeiro (Brazil); Chang, Yu Ling [ASI Science Data Center, ASDC, Agenzia Spaziale Italiana, via del Politecnico snc, 00133 Roma (Italy); Sapienza Università di Roma, Dipartimento di Fisica, Piazzale Aldo Moro 5, I-00185 Roma (Italy); ICRAnet, P.zza della Repubblica 10, Pescara (Italy)

    2015-12-17

    We use the Fermi Science Tools in an attempt to unveil faint γ-ray blazars that may be above the threshold for detectability with Fermi-LAT and are not identified by automated methods. Our search for new sources in the 100MeV-300GeV band is mainly driven by the 1/2WHSP catalogs, which list high synchrotron peaked blazars expected to be emitters of VHE photons. Here we present the γ-ray detection of 1WHSP J031423.9+061956, modelling its high energy spectrum as a power law. We describe an example where multi-frequency selection, performed at much lower energies (from radio to X-ray), helps to pin-point a high energy source. The 1/2WHSP catalogs are built with the aim of providing a list of TeV targets for the VHE arrays of Cherenkov telescopes. Moreover, these catalogs provide useful seeds for identifying new high energy sources within the raw-data from Fermi. With the aid of multi-frequency data, we can explore the very high energy domain in greater details, improving the description of the γ-ray sky.

  18. Multi-frequency polarimetry of a complete sample of PACO radio sources

    CERN Document Server

    Galluzzi, V; Bonaldi, A; Casasola, V; Gregorini, L; Trombetti, T; Burigana, C; De Zotti, G; Ricci, R; Stevens, J; Ekers, R D; Bonavera, L; Alighieri, S di Serego; Liuzzo, E; Lopez-Caniego, M; Mignano, A; Paladino, R; Toffolatti, L; Tucci, M

    2016-01-01

    We present high sensitivity polarimetric observations in 6 bands covering the 5.5-38 GHz range of a complete sample of 53 compact extragalactic radio sources brighter than 200 mJy at 20 GHz. The observations, carried out with the Australia Telescope Compact Array (ATCA), achieved a 91% detection rate (at 5 sigma). Within this frequency range the spectra of about 95% of sources are well fitted by double power laws, both in total intensity and in polarisation, but the spectral shapes are generally different in the two cases. Most sources were classified as either steep- or peaked-spectrum but less than 50% have the same classification in total and in polarised intensity. No significant trends of the polarisation degree with flux density or with frequency were found. The mean variability index in total intensity of steep-spectrum sources increases with frequency for a 4-5 year lag, while no significant trend shows up for the other sources and for the 8 year lag. In polarisation, the variability index, that could...

  19. Accurate Navigation of Deep Space Probes using Multifrequency Links: the Cassini Breakthrough during Solar Conjunction Experiments

    Science.gov (United States)

    Tortora, P.; Iess, L.; Ekelund, J. E.

    2002-01-01

    (1) transponders, used for both range and range-rate estimation. These devices are characterized by a frequency stability (measured by the Allan deviation) whose typical value never falls below the limit of 10-13, which broadly reflects in a range rate accuracy of about 15.10-4 cm/s. Moreover, for missions in the ecliptic plane, a critical phase is represented by the solar conjunctions which, depending on the spacecraft trajectory, can last up to two weeks. In such conditions the radio data are inherently corrupted by solar plasma noise, which causes a dramatic decay of the obtainable navigation accuracy. As a matter of fact, in the orbit determination process, radio data collected when the line of sight falls within 40 solar radii are usually discarded, leading to long time spans during which navigation cannot rely on actual data. and 2001 solar conjunctions were removed for navigation purposes. While this strategy is widely acceptable and proven during the cruise flight, it is not recommended during critical mission phases, when frequent ground-commanded maneuvers are executed. maneuver, scheduled on July 1st 2004, a few days before a solar conjunction. A significant improvement of the navigation accuracy would be achieved using, for the Orbit Determination process, all radio data collected up to the SOI. science experiments (RSE). The on-board configuration is based on a X/X transponder, which generates a reference signal to the Ka-Band Exciter (KEX) for the X/Ka link; furthermore a coherent frequency translator (KaT) is used for the Ka/Ka link. With this configuration, the sky frequencies in the three bands (X/X, X/Ka, Ka/Ka) can be coherently combined to remove the effects of the solar plasma, the major noise source in the Doppler observable. plasma calibration scheme, has shown an improvement of a factor of 8 over the noise of the bare Ka/Ka observable and a factor of 100 over X/X data. At an impact parameter of about 25 solar radii, the Allan deviation is as

  20. A 20 GHz Bright Sample for Delta > 72 deg - II. Multi-frequency Follow-up

    CERN Document Server

    Ricci, R; Verma, R; Prandoni, I; Carretti, E; Mack, K -H; Massardi, M; Procopio, P; Zanichelli, A; Gregorini, L; Mantovani, F; Gawronski, M P; Peel, M W

    2013-01-01

    We present follow-up observations at 5, 8 and 30 GHz of the K-band Northern Wide Survey (KNoWS) 20 GHz Bright Sample, performed with the 32-m Medicina Radio Telescope and the 32-m Torun Radio Telescope. The KNoWS sources were selected in the Northern Polar Cap (Delta > 72 deg) and have a flux density limit S(20GHz) = 115 mJy. We include NVSS 1.4 GHz measurements to derive the source radio spectra between 1.4 and 30 GHz. Based on optical identifications, 68 per cent of the sources are QSOs, and 27 per cent are radio galaxies. A redshift measurement is available for 58 per cent of the sources. The radio spectral properties of the different source populations are found to be in agreement with those of other high-frequency selected samples.