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  1. Chemical Compositions of RV Tauri Stars and Related Objects

    CERN Document Server

    Rao, S Sumangala

    2013-01-01

    We have undertaken a comprehensive abundance analysis for a sample of relatively unexplored RV Tauri and RV Tauri like stars to further our understanding of post-Asymptotic Giant Branch (post-AGB) evolution. From our study based on high resolution spectra and grid of model atmospheres, we find indications of mild s-processing for V820 Cen and IRAS 06165+3158. On the other hand, SU Gem and BT Lac exhibit the effects of mild dust-gas winnowing. We have also compiled the existing abundance data on RV Tauri objects and find that a large fraction of them are afflicted by dust-gas winnowing and now added by the present work, we find a small group of two RV Tauris showing mild s-process enhancement in our Galaxy. With two out of three reported s-process enhanced objects belonging to RV Tauri spectroscopic class C, these intrinsically metal-poor objects appear to be promising candidates to analyse the possible s-processing in RV Tauri stars.

  2. Dust-grain processing in circumbinary discs around evolved binaries. The RV Tauri spectral twins RU Cen and AC Her

    CERN Document Server

    Gielen, C; Waters, L B F M; Min, M; Dominik, C

    2007-01-01

    Context: We study the structure and evolution of circumstellar discs around evolved binaries and their impact on the evolution of the central system. Aims: To study in detail the binary nature of RUCen and ACHer, as well as the structure and mineralogy of the circumstellar environment. Methods: We combine multi-wavelength observations with a 2D radiative transfer study. Our radial velocity program studies the central stars, while our Spitzer spectra and broad-band SEDs are used to constrain mineralogy, grain sizes and physical structure of the circumstellar environment. Results: We determine the orbital elements of RUCen showing that the orbit is highly eccentric with a rather long period of 1500 days. The infrared spectra of both objects are very similar and the spectral dust features are dominated by Mg-rich crystalline silicates. The small peak-to-continuum ratios are interpreted as being due to large grains. Our model contains two components with a cold midplain dominated by large grains, and the near- an...

  3. A homogeneous distance catalogue for Galactic RV Tauri objects

    CERN Document Server

    Vickers, Shane; Owers, Matt; Parker, Quentin; Bojičić, Ivan

    2016-01-01

    A subset of Post-AGB (PAGB) objects are the highly luminous RV Tauri variables that show similarities to Type-II Cepheids. By using a sample of known RV Tauri stars from the Magellanic Clouds we are able to determine period luminosity relationships (PLRs) in various bands that have been used to determine the luminosities of their Galactic counterparts. We have gathered all available photometry in order to generate an SED for each object and determine the total integrated flux. This total flux combined with a calculated or inferred intrinsic luminosity leads to a distance (Vickers et al. 2015). This distance catalogue has allowed us to begin to constrain the physical parameters of this poorly understood evolutionary phase and to determine links between these physical characteristics as a function of their stellar population.

  4. Establishing binarity amongst Galactic RV Tauri stars with a disc

    CERN Document Server

    Manick, Rajeev; Kamath, Devika; Hillen, Michel; Escorza, Ana

    2016-01-01

    This study is a contribution in comprehending the role of binarity upon late stages of stellar evolution. We determine the binary status of six Galactic RV Tauri stars, namely DY Ori, EP Lyr, HP Lyr, IRAS 17038-4815, IRAS 09144-4933 and TW Cam, which are surrounded by a dusty disc. We also place them on the HR diagram, thereby establishing their evolutionary nature. All the six Galactic RV Tauri stars included in this study are binaries with orbital periods ranging between $\\sim$ 650 and 1700 days and with eccentricities between 0.2 and 0.6. The mass functions range between 0.08 to 0.55 M$_\\odot$ which points to an unevolved low mass companion. In the photometric time series we detect a long-term variation on the time-scale of the orbital period for IRAS 17038-4815, IRAS 09144-4933 and TW Cam. Our derived stellar luminosities obtained from a calibrated PLC relation indicates that all except DY Ori and EP Lyr, are post-AGB stars. DY Ori and EP Lyr are likely examples of the recently discovered dusty post-RGB s...

  5. Establishing binarity amongst Galactic RV Tauri stars with a disc⋆

    Science.gov (United States)

    Manick, Rajeev; Van Winckel, Hans; Kamath, Devika; Hillen, Michel; Escorza, Ana

    2017-01-01

    Context. Over the last few decades it has become more evident that binarity is a prevalent phenomenon amongst RV Tauri stars with a disc. This study is a contribution to comprehend the role of binarity upon late stages of stellar evolution. Aims: In this paper we determine the binary status of six Galactic RV Tauri stars, namely DY Ori, EP Lyr, HP Lyr, IRAS 17038-4815, IRAS 09144-4933, and TW Cam, which are surrounded by a dusty disc. The radial velocities are contaminated by high-amplitude pulsations. We disentangle the pulsations from the orbital signal in order to determine accurate orbital parameters. We also place them on the HR diagram, thereby establishing their evolutionary nature. Methods: We used high-resolution spectroscopic time series obtained from the HERMES and CORALIE spectrographs mounted on the Flemish Mercator and Swiss Leonhard Euler Telescopes, respectively. An updated ASAS/AAVSO photometric time series is analysed to complement the spectroscopic pulsation search and to clean the radial velocities from the pulsations. The pulsation-cleaned orbits are fitted with a Keplerian model to determine the spectroscopic orbital parameters. We also calibrated a PLC relationship using type II cepheids in the LMC and apply the relation to our Galactic sample to obtain accurate distances and hence luminosities. Results: All six of the Galactic RV Tauri stars included in this study are binaries with orbital periods ranging between 650 and 1700 days and with eccentricities between 0.2 and 0.6. The mass functions range between 0.08 to 0.55 M⊙ which points to an unevolved low-mass companion. In the photometric time series we detect a long-term variation on the timescale of the orbital period for IRAS 17038-4815, IRAS 09144-4933, and TW Cam. Our derived stellar luminosities indicate that all except DY Ori and EP Lyr are post-AGB stars. DY Ori and EP Lyr are likely examples of the recently discovered dusty post-RGB stars. Conclusions: The orbital parameters

  6. Chemical depletion in the Large Magellanic Cloud: RV Tauri stars and the photospheric feedback from their dusty discs

    CERN Document Server

    Gielen, C; Reyniers, M; Zijlstra, A; Evans, T Lloyd; Gordon, K D; Kemper, F; Indebetouw, R; Marengo, M; Matsuura, M; Meixner, M; Sloan, G C; Tielens, A G G M; Woods, P M

    2009-01-01

    Aims: By studying the photospheric abundances of 4 RV Tauri stars in the LMC, we test whether the depletion pattern of refractory elements, seen in similar Galactic sources, is also common for extragalactic sources. Since this depletion process probably only occurs through interaction with a stable disc, we investigate the circumstellar environment of these sources. Methods: A detailed photospheric abundance study was performed using high-resolution UVES optical spectra. To study the circumstellar environment we use photometric data to construct the spectral energy distributions of the stars, and determine the geometry of the circumstellar environment, whereas low-resolution Spitzer-IRS infrared spectra are used to trace its mineralogy. Results: Our results show that, also in the LMC, the photospheres of RV Tauri stars are commonly affected by the depletion process, although it can differ significantly in strength from source to source. From our detailed disc modelling and mineralogy study, we find that this ...

  7. High Resolution Spectroscopy of the high galactic latitude RV Tauri star CE Virginis

    CERN Document Server

    Rao, K; Rao, Kameswara; Reddy, Bacham E.

    2004-01-01

    Analysis of the surface composition of the suspected cool RV Tauri star CE Vir shows no systematic trend in depletions of elements with respect to condensation temperature. However, there is a significant depletion of the elements with respect to the first ionization potential of the element. The derived Li abundance of log $\\epsilon$ (Li) = 1.5$\\pm$0.2 indicates production of Li in the star. Near infrared colours indicate sporadic dust formation close to the photosphere.

  8. Revisiting The Brightest RV Tauri Star: First Ionization Potential (FIP) Effect in R Sct

    Science.gov (United States)

    Yolalan, Gizay; Sahin, Timur

    2016-07-01

    We have derived elemental abundances of the brightest RV Tauri star, R Sct. The abundance analysis of the star is based on high resolution and high quality (S/N>300) echelle spectra, mainly obtained for radial velocity study of a large sample of IRAS like RV Tau sample stars, from the McDonald Observatory (R~48,000). Our analysis is based on optical spectra obtained at only one phase of the variation. The standard 1D LTE analysis provided a fresh determination of the atmospheric parameters: Teff=5000 K, logg=1.05 cgs, and a microturbulence velocity ξ=3.4 km/s and [Fe/H] = -0.33. We report on chemical abundances of 10 neutral and ionized species identified over 4800 - 5600 A wavelength region. In an effort to explain observed deficiency in abundances, possible scenarios including FIP is investigated.

  9. Insights on the spectral signatures of RV jitter from PCA

    Science.gov (United States)

    Davis, Allen Bradford; Cisewski, Jessica; Dumusque, Xavier; Fischer, Debra; Ford, Eric B.

    2017-01-01

    Stellar activity features such as spots and faculae can mimic radial velocity (RV) motion by creating spurious time-varying centroid shifts in the stellar spectral lines. This "RV jitter" hinders the detection of large planetary signals (100 m s-1) around young, active stars, and it dominates the Keplerian signals of Earth-analogs (10 to 20 cm s-1) even around quiet stars. However, appropriate statistical techniques may be able to distinguish these phenomena by exploiting the spectral-line dependence and temporal coherence of RV jitter.We produce simulated disk-integrated time-series spectra of a rotating star with a spot, with a facula, or with a planet of various sizes using the SOAP 2.0 code, which uses real high-resolution and high-S/N spectra of the quiet solar photosphere and sunspots as a starting point. Principal component analysis (PCA) is used to identify and quantify the wavelength-dependent intensity variations of the spectra in each of these cases. We find that the PCA signatures of these three phenomena are distinct, suggesting that they can be distinguished in theory. We then lower the resolution and S/N of these simulated spectra and use PCA to quantify their information content. We find that high-resolution (R > 100,000) observations are better able to recover information in the spectra of spots and faculae than would be expected compared to an equivalent increase in S/N. This effect is especially pronounced for large spots and faculae (S ≥ 1%), suggesting that high-resolution spectrographs will be particularly well-suited for characterizing stellar activity.

  10. Spectral Energy Distributions of T Tauri Stars With Passive Circumstellar Disks

    CERN Document Server

    Chiang, E I

    1997-01-01

    We derive hydrostatic, radiative equilibrium models for passive disks surrounding T Tauri stars. Each disk is encased by an optically thin layer of superheated dust grains. This layer re-emits directly to space about half the stellar energy it absorbs. The other half is emitted inward and regulates the interior temperature of the disk. The heated disk flares. As a consequence, it absorbs more stellar radiation, especially at large radii, than a flat disk would. The portion of the spectral energy distribution contributed by the disk is fairly flat throughout the thermal infrared. At fixed frequency, the contribution from the surface layer exceeds that from the interior by about a factor 3 and is emitted at more than an order of magnitude greater radius. Spectral features from dust grains in the superheated layer appear in emission if the disk is viewed nearly face-on.

  11. C2D Spitzer-IRS spectra of disks around T Tauri stars. V. Spectral decomposition

    Science.gov (United States)

    Olofsson, J.; Augereau, J.-C.; van Dishoeck, E. F.; Merín, B.; Grosso, N.; Ménard, F.; Blake, G. A.; Monin, J.-L.

    2010-09-01

    Context. Dust particles evolve in size and lattice structure in protoplanetary disks, due to coagulation, fragmentation and crystallization, and are radially and vertically mixed in disks due to turbulent diffusion and wind/radiation pressure forces. Aims: This paper aims at determining the mineralogical composition and size distribution of the dust grains in planet forming regions of disks around a statistical sample of 58 T Tauri stars observed with Spitzer/IRS as part of the Cores to Disks (c2d) Legacy Program. Methods: We present a spectral decomposition model, named “B2C”, that reproduces the IRS spectra over the full spectral range (5-35 μm). The model assumes two dust populations: a warm component responsible for the 10 μm emission arising from the disk inner regions (≲1 AU) and a colder component responsible for the 20-30 μm emission, arising from more distant regions (≲10 AU). The fitting strategy relies on a random exploration of parameter space coupled with a Bayesian inference method. Results: We show evidence for a significant size distribution flattening in the atmospheres of disks compared to the typical MRN distribution, providing an explanation for the usual flat, boxy 10 μm feature profile generally observed in T Tauri star spectra. We reexamine the crystallinity paradox, observationally identified by Olofsson et al. (2009 , A&A, 507, 327), and we find a simultaneous enrichment of the crystallinity in both the warm and cold regions, while grain sizes in both components are uncorrelated. We show that flat disks tend to have larger grains than flared disk. Finally our modeling results do not show evidence for any correlations between the crystallinity and either the star spectral type, or the X-ray luminosity (for a subset of the sample). Conclusions: The size distribution flattening may suggests that grain coagulation is a slightly more effective process than fragmentation (helped by turbulent diffusion) in disk atmospheres, and that

  12. Spectral variability of classical T Tauri stars accreting in an unstable regime

    CERN Document Server

    Kurosawa, Ryuichi

    2013-01-01

    Classical T Tauri stars (CTTSs) are variable in different time-scales. One type of variability is possibly connected with the accretion of matter through the Rayleigh-Taylor instability that occurs at the interface between an accretion disc and a stellar magnetosphere. In this regime, matter accretes in a several temporarily formed accretion streams or `tongues' which appear in random locations, and produce stochastic photometric and line variability. We use the results of global three-dimensional magnetohydrodynamic simulations of matter flows in both stable and unstable accretion regimes to calculate time-dependent hydrogen line profiles and study their variability behaviours. In the stable regime, some hydrogen lines (e.g. H-beta, H-gamma, H-delta, Pa-beta and Br-gamma) show a redshifted absorption component only during a fraction of a stellar rotation period, and its occurrence is periodic. However, in the unstable regime, the redshifted absorption component is present rather persistently during a whole s...

  13. Herschel GASPS spectral observations of T Tauri stars in Taurus. Unraveling far-infrared line emission from jets and discs

    Science.gov (United States)

    Alonso-Martínez, M.; Riviere-Marichalar, P.; Meeus, G.; Kamp, I.; Fang, M.; Podio, L.; Dent, W. R. F.; Eiroa, C.

    2017-07-01

    Context. At early stages of stellar evolution young stars show powerful jets and/or outflows that interact with protoplanetary discs and their surroundings. Despite the scarce knowledge about the interaction of jets and/or outflows with discs, spectroscopic studies based on Herschel and ISO data suggests that gas shocked by jets and/or outflows can be traced by far-IR (FIR) emission in certain sources. Aims: We want to provide a consistent catalogue of selected atomic ([OI] and [CII]) and molecular (CO, H2O, and OH) line fluxes observed in the FIR, separate and characterize the contribution from the jet and the disc to the observed line emission, and place the observations in an evolutionary picture. Methods: The atomic and molecular FIR (60-190 μm) line emission of protoplanetary discs around 76 T Tauri stars located in Taurus are analysed. The observations were carried out within the Herschel key programme Gas in Protoplanetary Systems (GASPS). The spectra were obtained with the Photodetector Array Camera and Spectrometer (PACS). The sample is first divided in outflow and non-outflow sources according to literature tabulations. With the aid of archival stellar/disc and jet/outflow tracers and model predictions (PDRs and shocks), correlations are explored to constrain the physical mechanisms behind the observed line emission. Results: Outflow sources exhibit brighter atomic and molecular emission lines and higher detection rates than non-outflow sources. The line detection fractions decrease with SED evolutionary status (from Class I to Class III). We find correlations between [OI] 63.18 μm and [OI] 6300 Å, o-H2O 78.74 μm, CO 144.78 μm, OH 79.12+79.18 μm, and the continuum flux at 24 μm. The atomic line ratios can be explain either by fast (Vshock > 50 km s-1) dissociative J-shocks at low densities (n 103 cm-3) occurring along the jet and/or PDR emission (G0 > 102, n 103-106 cm-3). To account for the [CII] absolute fluxes, PDR emission or UV irradiation of

  14. The hot Jupiter of the magnetically active weak-line T Tauri star V830 Tau

    Science.gov (United States)

    Donati, J.-F.; Yu, L.; Moutou, C.; Cameron, A. C.; Malo, L.; Grankin, K.; Hébrard, E.; Hussain, G. A. J.; Vidotto, A. A.; Alencar, S. H. P.; Haywood, R. D.; Bouvier, J.; Petit, P.; Takami, M.; Herczeg, G. J.; Gregory, S. G.; Jardine, M. M.; Morin, J.; MaTYSSE Collaboration

    2017-03-01

    We report results of an extended spectropolarimetric and photometric monitoring of the weak-line T Tauri star V830 Tau and its recently detected newborn close-in giant planet. Our observations, carried out within the MaTYSSE (Magnetic Topologies of Young Stars and the Survival of close-in giant Exoplanets) programme, were spread over 91 d, and involved the ESPaDOnS and Narval spectropolarimeters linked to the 3.6-m Canada-France-Hawaii, the 2-m Bernard Lyot, and the 8-m Gemini-North Telescopes. Using Zeeman-Doppler Imaging, we characterize the surface brightness distributions, magnetic topologies, and surface differential rotation of V830 Tau at the time of our observations, and demonstrate that both distributions evolve with time beyond what is expected from differential rotation. We also report that near the end of our observations, V830 Tau triggered one major flare and two weaker precursors, showing up as enhanced redshifted emission in multiple spectral activity proxies. With three different filtering techniques, we model the radial velocity (RV) activity jitter (of semi-amplitude 1.2 km s-1) that V830 Tau generates, successfully retrieve the 68 ± 11 m s-1 RV planet signal hiding behind the jitter, further confirm the existence of V830 Tau b, and better characterize its orbital parameters. We find that the method based on Gaussian-process regression performs best thanks to its higher ability at modelling not only the activity jitter, but also its temporal evolution over the course of our observations, and succeeds at reproducing our RV data down to an rms precision of 35 m s-1. Our result provides new observational constraints on scenarios of star/planet formation and demonstrates the scientific potential of large-scale searches for close-in giant planets around T Tauri stars.

  15. POST T-Tauri Stars in Galactic Clusters

    Science.gov (United States)

    Haro, G.

    1983-08-01

    spectral type and luminosity: the earlier the spectral type, the shorter the vanishing effect. Therefore, if we look for weakened T Tauri features in stellar aggregates of various ages from which the typical and extreme T Tauri stars have already disappeared, we find that the older the aggregate, the later the spectral type in which the last prominent features are detectable. Everything seems to suggest that it is within these possible evolved T Tauri objects that we can find the so-called post-T Tauri stars, and that a good number of flare stars detected in galactic clusters are among them. These clusters are: the Orion stellar aggregate, NOC 2264, the Pleiades, and possibly the flare stars in stellar aggregates of ages equal or superior to 108 years. As I have in the past, I would like to place special emphasis on the genetic relationship between certain flare stars and their T Tauri ancestors, based not only on the very rapid outbursts of the former but also, and primarily, on the fact that these flare stars show spectroscopic characteristics reminiscent of the T Tauri original stars. In other words, the simple fact that a star presents the "flare" phenomenon does not constitute necessary and sufficient proof that it should be regarded as an evolutionary product of a T Tauri star: in addition to the flare-up the spectral types of the investigated objects must present -during maximum and minimum light- clear and reminiscent spectroscopic evidences of the original T Tauri objects; that is, spectral types as late or later than G and some emission lines, at least in H and Call. There are some flare stars in Orion and NGC 2264 which, even during minimum light, can be classified spectroscopically as typical T Tauri stars. In the case of the Pleiades, where undoubtedly there are no T Tauri stars, many of the flare stars show spectral emission lines (H and Call) of great intensity during maximum and of detectable intensity in slit spectrograms of not high dispersion, during

  16. New circumstellar structure in the T Tauri system. A near-infrared high-contrast imaging study

    Science.gov (United States)

    Kasper, M.; Santhakumari, K. K. R.; Herbst, T. M.; Köhler, R.

    2016-09-01

    Aims: The immediate vicinity of T Tauri was observed with the new high-contrast imaging instrument SPHERE at the VLT to resolve remaining mysteries of the system, such as the putative small edge-on disk around T Tauri Sa and the assignment of the complex outflow patterns to the individual stars. Methods: We used SPHERE IRDIS narrow-band classical imaging in Paβ, Brγ, and the ν = 1-0 S(1) line of H2, as well as in the nearby continua to obtain high spatial resolution and high-contrast images over the near-infrared spectral range. Line maps were created by subtracting the nearby continuum. We also reanalyzed coronagraphic data taken with SPHERE's integral field spectrograph in J- and H-band with the goal of obtaining a precise extinction estimate to T Tauri Sb, and of verifying the recently reported claim of another stellar or substellar object in the system. Results: A previously unknown coiling structure is observed southwest of the stars in reflected light, which points to the vicinity of T Tauri N. We map the circumbinary emission from T Tauri S in J- and H-band scattered light for the first time, showing a morphology that differs significantly from that observed in K-band. Molecular Hydrogen emission is found southwest of the stars, near the coiling structure. We also detect the H2 emitting region T Tauri NW. The motion of T Tauri NW with respect to T Tauri N and S between previous images and our 2014 data provides strong evidence that the southeast-northwest outflow triggering T Tauri NW is likely to be associated with T Tauri S. We also present accurate relative photometry of the stars, which confirms that T Tauri Sa is brightening again. Our analysis rules out the presence of the recently proposed companion to T Tauri N with high confidence.

  17. X-ray photometry and spectroscopy of T Tauri stars

    Science.gov (United States)

    Walter, F. M.; Kuhi, L. V.

    1984-01-01

    Follow-up Einstein X-ray observations of four fields containing pre-main-sequence stars are presented. A search has been made for evidence of variability on time scales of hours and of 1 year. A large, slow flare in AS 205, and the X-ray disappearance of AA Tau are reported. Otherwise, T Tauri stars appear no more variable in X-rays than do active solar-like stars. An attempt has been made to determine spectral parameters for a number of the brighter sources. X-ray absorption column densities are consistent with those inferred from A(v), and T(x) of about 10-million K, in all cases. The importance of these observations for models of T Tauri stars and their coronae is considered.

  18. A Survey and Analysis of Spitzer Infrared Spectrograph Spectra of T Tauri Stars in Taurus

    CERN Document Server

    Furlan, E; Calvet, N; D'Alessio, P; Franco-Hernandez, R; Forrest, W J; Watson, D M; Uchida, K I; Sargent, B; Green, J D; Keller, L D; Herter, T L

    2006-01-01

    We present mid-infrared spectra of T Tauri stars in the Taurus star-forming region obtained with the Spitzer Infrared Spectrograph (IRS). For the first time, the 5-36 micron spectra of a large sample of T Tauri stars belonging to the same star-forming region is studied, revealing details of the mid-infrared excess due to dust in circumstellar disks. We analyze common features and differences in the mid-IR spectra based on disk structure, dust grain properties, and the presence of companions. Our analysis encompasses spectral energy distributions from the optical to the far-infrared, a morphological sequence based on the IRS spectra, and spectral indices in IRS wave bands representative of continuum emission. By comparing the observed spectra to a grid of accretion disk models, we infer some basic disk properties for our sample of T Tauri stars, and find additional evidence for dust settling.

  19. POLARIZATION OF FIR EMISSION FROM T-TAURI DISKS

    Directory of Open Access Journals (Sweden)

    J. Cho

    2009-01-01

    Full Text Available Recent observations of 850 gm sub-mm polarization from T-Tauri disks open up the possibility of studying the magnetic eld structure within protostellar disks. The degree of polarization is around 3% and the direction of polarization is perpendicular to the disk. Since thermal emission from dust grains dominates the spectral energy distribution at sub-mm/far-infrared (FIR wavelengths, dust grains are thought to be the cause of the polarization. We discuss grain alignment by radiation and we explore the efficiency of dust alignment in T-Tauri disks. The calculations show that dust grains located far away from the central proto-star are more efficiently aligned. In the presence of a regular magnetic eld, the aligned grains produce polarized emission in sub-mm/FIR wavelengths. The direction of polarization is perpendicular to the local magnetic eld direction. When we use a recent T-Tauri disk model and take a Mathis-Rumpl-Nordsieck-type distribution with maximum grain size of 500{1000 -m, the degree of polarization is around 2{3% level at wavelengths larger than - 100 gm. Our work indicates that multifrequency infrared polarimetric studies of protostellar disks can provide good insights into the details of their magnetic structure. We also provide predictions for polarize emission for disks viewed at di erent wavelengths and viewing angles.

  20. The hot Jupiter of the magnetically-active weak-line T Tauri star V830 Tau

    CERN Document Server

    Donati, J -F; Moutou, C; Cameron, A C; Malo, L; Grankin, K; Hébrard, E; Hussain, G A J; Vidotto, A A; Alencar, S H P; Haywood, R D; Bouvier, J; Petit, P; Takami, M; Herczeg, G J; Gregory, S G; Jardine, M M; Morin, J

    2016-01-01

    We report results of an extended spectropolarimetric and photometric monitoring of the weak-line T Tauri star V830 Tau and its recently-detected newborn close-in giant planet. Our observations, carried out within the MaTYSSE programme, were spread over 91d, and involved the ESPaDOnS and Narval spectropolarimeters linked to the 3.6m Canada-France-Hawaii, the 2m Bernard Lyot and the 8-m Gemini-North Telescopes. Using Zeeman-Doppler Imaging, we characterize the surface brightness distributions, magnetic topologies and surface differential rotation of V830 Tau at the time of our observations, and demonstrate that both distributions evolve with time beyond what is expected from differential rotation. We also report that near the end of our observations, V830 Tau triggered one major flare and two weaker precursors, showing up as enhanced red-shifted emission in multiple spectral activity proxies. With 3 different filtering techniques, we model the radial velocity (RV) activity jitter (of semi-amplitude 1.2km/s) tha...

  1. A Candidate Young Massive Planet in Orbit around the Classical T Tauri Star CI Tau

    CERN Document Server

    Johns-Krull, Christopher M; Prato, L; Crockett, Christopher J; Jaffe, Daniel T; Hartigan, Patrick M; Beichman, Charles A; Mahmud, Naved I; Chen, Wei; Skiff, B A; Cauley, P Wilson; Jones, Joshua A; Mace, G N

    2016-01-01

    The ~2 Myr old classical T Tauri star CI Tau shows periodic variability in its radial velocity (RV) variations measured at infrared (IR) and optical wavelengths. We find that these observations are consistent with a massive planet in a ~9-day period orbit. These results are based on 71 IR RV measurements of this system obtained over 5 years, and on 26 optical RV measurements obtained over 9 years. CI Tau was also observed photometrically in the optical on 34 nights over ~one month in 2012. The optical RV data alone are inadequate to identify an orbital period, likely the result of star spot and activity induced noise for this relatively small dataset. The infrared RV measurements reveal significant periodicity at ~9 days. In addition, the full set of optical and IR RV measurements taken together phase coherently and with equal amplitudes to the ~9 day period. Periodic radial velocity signals can in principle be produced by cool spots, hot spots, and reflection of the stellar spectrum off the inner disk, in ad...

  2. Doppler Probe of Accretion onto a T Tauri star

    CERN Document Server

    Petrov, Peter P; Herczeg, Gregory J; Stempels, Henricus C; Walter, Frederick M

    2014-01-01

    The YY Ori stars are T Tauri stars with prominent time-variable redshifted absorption components that flank certain emission lines. One of the brightest in this class is S CrA, a visual double star. We have obtained a series of high-resolution spectra of the two components during four nights with the UVES spectrograph at the Very Large Telescope. We followed the spectral changes occurring in S CrA to derive the physical structure of the accreting gas. We found that both stars are very similar with regard to surface temperature, radius, and mass. Variable redshifted absorption components are particularly prominent in the SE component. During one night, this star developed a spectrum unique among the T Tauri stars: extremely strong and broad redshifted absorption components appeared in many lines of neutral and ionized metals, in addition to those of hydrogen and helium. The absorption depths of cooler, low ionization lines peak at low velocities - while more highly ionized lines have peak absorption depths at ...

  3. Profiles of Strong Permitted Lines in Classical T Tauri Stars

    CERN Document Server

    Alencar, S; Alencar, Silvia; Basri, Gibor

    2000-01-01

    We present a spectral analysis of 30 T Tauri stars observed with the Hamilton echelle spectrograph over more than a decade. One goal is to test magnetospheric accretion model predictions. Observational evidence previously published supporting the model, such as emission line asymmetry and a high frequency of redshifted absorption components, are considered. We also discuss the relation between different line forming regions and search for good accretion rate indicators. In this work we confirm several important points of the models, such as the correlation between accretion and outflow, broad emission components that are mostly central or slightly blueshifted and only the occasional presence of redshifted absorption. We also show, however, that the broad emission components supposedly formed in the magnetospheric accretion flow only partially support the models. Unlike the predictions, they are sometimes redshifted, and are mostly found to be symmetric. The published theoretical profiles do not have a strong ...

  4. Periodicities of the RV Tau-type pulsating star DF Cygni: a combination of Kepler data with ground-based observations

    CERN Document Server

    Bódi, A; Kiss, L L

    2016-01-01

    The RV Tauri stars constitute a small group of classical pulsating stars with some dozen known members in the Milky Way. The light variation is caused predominantly by pulsations, but these alone do not explain the full complexity of the light curves. High quality photometry of RV Tau-type stars is very rare. DF Cygni is the only member of this class of stars in the original Kepler field, hence allowing the most accurate photometric investigation of an RV Tauri star to date. The main goal is to analyse the periodicities of the RV Tauri-type star DF Cygni by combining four years of high-quality Kepler photometry with almost half a century of visual data collected by the American Association of Variable Star Observers. Kepler quarters of data have been stitched together to minimize the systematic effects of the space data. The mean levels have been matched with the AAVSO visual data. Both datasets have been submitted to Fourier and wavelet analyses, while the stability of the main pulsations has been studied wi...

  5. Magnetic Accretion Onto T Tauri Stars

    Directory of Open Access Journals (Sweden)

    Christopher M. Johns Krull

    2003-01-01

    Full Text Available Espectroscopía de alta resolución de líneas de absorción fotosfericas, particularmente en el infrarrojo, revelan la presencia de campos magnéticos en las estrellas T Tauri. Espectropolarimetría de alta resolución restringe la geometría de los campos magnéticos estelares de gran escala, que se supone juegan un papel crucial en controlar la acrecion y eyección de vientos en estos sistemas. Revisamos las mas recientes mediciones de campos magnéticos en estrellas T Tauri, que ofrecen evidencia de la importancia de los campos magnéticos estelares en el control de la acrecion de material, y comparamos las mediciones con las predicciones de la teoría.

  6. Disks Around Classical T Tauri Stars

    Directory of Open Access Journals (Sweden)

    P. D`Alessio

    2003-01-01

    Full Text Available En este trabajo explicamos como se pueden cuantificar las propiedades de los discos circunestelares y el polvo en estos, a partir de la comparación de observaciones y las propiedades observables de modelos físicos de discos irradiados por su estrella central. En particular se discuten las indicaciones de una evolución de la población de polvo de los discos alrededor de estrellas T Tauri.

  7. A Portable Ultra-Stable Calibration Source for Precision RV Measurements in NIR

    Science.gov (United States)

    Wang, Ji; Ge, J.; Wan, X.; Delgado, A.; Jakeman, H.

    2011-09-01

    In the next decade, astronomers are aiming at reaching 0.1 m/s RV precision, which will enable discoveries of Earth-like planets around solar-type stars. However, the RV precision is currently limited by stellar activity, the stability and bandwidth of RV calibration sources. We proposed to use an ultra-stable monolithic Michelson interferometer as an RV calibration source. This monolithic interferometer source has several advantages over the conventional RV calibration sources: (1), it produces sinusoidal spectral features which can be easily processed, unlike gas absorption cells or emission lamps, which spectral line distributions are extremely nonuniform; (2), it has a wide spectral coverage from visible to near infrared (NIR); (3), it is designed to be thermal-stable (thermally compensated) so that the thermal induced RV drift is very small; (4), it is also field compensated to ensure a high optical efficiency so that a spatially incoherent continuum light source is suitable for producing bright calibration light (unlike the faint ThAr emission lamp); (5). it is extremely compact ( 10x10x10 cm3) and low cost compared to the bulky (more than 1x1x1 m3) and extremely high cost laser frequency combs. With the help of the proposed RV calibration source, the search of exoplanets around M dwarfs or even L, T dwarfs can be extended to the NIR band. The predicted sub m/s RV calibration precision will enable the discovery of Earth-like planets in the habitable zone around M dwarfs. The proposed calibration source may be quite useful for calibrating future space instruments for possible space RV exoplanet searches in the IR region where RV measurements are free of contamination of the Earth's telluric lines, which is a serious issue for ground-based IR RV observations. We will present our latest results of the calibration source on its application for both Echelle spectrograph and the instrument adopting DFDI method.

  8. Modeling the Circumstellar Disk of $\\zeta$ Tauri

    OpenAIRE

    Carciofi, A. C.; Bjorkman, J. E.

    2004-01-01

    We present a model for the disk of the classical Be star $\\zeta$ Tauri. The model consists of a Keplerian rotating disk with a power-law surface density and a vertical density distribution that follows from the balance between the thermal gas pressure and the z-component of the stellar gravitation. The opening angle of such a disk is not a fixed value but increases with the distance to the star (flared disk). We use a Monte Carlo code that solves simultaneously the thermal equilibrium, the st...

  9. Hot Gas Lines in T Tauri Stars

    CERN Document Server

    Ardila, David R; Gregory, Scott G; Ingleby, Laura; France, Kevin; Brown, Alexander; Edwards, Suzan; Johns-Krull, Christopher; Linsky, Jeffrey L; Yang, Hao; Valenti, Jeff A; Abgrall, Hervé; Alexander, Richard D; Bergin, Edwin; Bethell, Thomas; Brown, Joanna M; Calvet, Nuria; Espaillat, Catherine; Hillenbrand, Lynne A; Hussain, Gaitee; Roueff, Evelyne; Schindhelm, Eric R; Walter, Frederick M

    2013-01-01

    For Classical T Tauri Stars (CTTSs), the resonance lines of N V, Si IV, and C IV, as well as the He II 1640 A line, act as diagnostics of the accretion process. Here we assemble a large high-resolution dataset of these lines in CTTSs and Weak T Tauri Stars (WTTSs). We present data for 35 stars: one Herbig Ae star, 28 CTTSs, and 6 WTTSs. We decompose the C IV and He II lines into broad and narrow Gaussian components (BC & NC). The most common (50 %) C IV line morphology in CTTSs is that of a low-velocity NC together with a redshifted BC. The velocity centroids of the BCs and NCs are such that V_BC > 4 * V_NC, consistent with the predictions of the accretion shock model, in at most 12 out of 22 CTTSs. We do not find evidence of the post-shock becoming buried in the stellar photosphere due to the pressure of the accretion flow. The He II CTTSs lines are generally symmetric and narrow, less redshifted than the CTTSs C IV lines, by ~10 km/sec. The flux in the BC of the He II line is small compared to that of t...

  10. Long-term variability of T Tauri stars using WASP

    CERN Document Server

    Rigon, Laura; Anderson, David; West, Richard

    2016-01-01

    We present a reference study of the long-term optical variability of young stars using data from the WASP project. Our primary sample is a group of well-studied classical T Tauri stars (CTTS), mostly in Taurus-Auriga. WASP lightcurves cover timescales up to 7 years and typically contain 10000-30000 datapoints. We quantify the variability as function of timescale using the time-dependent standard deviation 'pooled sigma'. We find that the overwhelming majority of CTTS has low-level variability with sigma0.3mag) is 21% in our sample and 21% in an unbiased control sample. An even smaller fraction (13% in our sample, 6% in the control) show evidence for an increase in variability amplitude as a function of timescale from weeks to months or years. The presence of long-term variability correlates with the spectral slope at 3-5mu, which is an indicator of inner disk geometry, and with the U-B band slope, which is an accretion diagnostics. This shows that the long-term variations in CTTS are predominantly driven by p...

  11. Locating the Launching Region of T Tauri Winds: The Case of DG Tauri

    Science.gov (United States)

    Anderson, Jeffrey M.; Li, Zhi-Yun; Krasnopolsky, Ruben; Blandford, Roger D.

    2003-06-01

    It is widely believed that T Tauri winds are driven magnetocentrifugally from accretion disks close to the central stars. The exact launching conditions are uncertain. We show that a general relation exists between the poloidal and toroidal velocity components of a magnetocentrifugal wind at large distances and the rotation rate of the launching surface, independent of the uncertain launching conditions. We discuss the physical basis of this relation and verify it by using a set of numerically determined large-scale wind solutions. Both velocity components are in principle measurable from spatially resolved spectra, as has been done for the extended low-velocity component (LVC) of the DG Tauri wind by Bacciotti et al. For this particular source, we infer that the spatially resolved LVC originates from a region on the disk extending from ~0.3 to ~4.0 AU from the star, which is consistent with, and a refinement over, the rough estimate of Bacciotti et al.

  12. Discovery of ``isolated'' co-moving T Tauri stars in Cepheus

    Science.gov (United States)

    Guillout, P.; Frasca, A.; Klutsch, A.; Marilli, E.; Montes, D.

    2010-09-01

    Context. During the course of a large spectroscopic survey of X-ray active late-type stars in the solar neighbourhood, we discovered four lithium-rich stars packed within just a few degrees on the sky. Although located in a sky area rich in CO molecular regions and dark clouds, the Cepheus-Cassiopeia complex, these very young stars are projected several degrees away from clouds in front of an area void of interstellar matter. As such, they are very good “isolated” T Tauri star candidates. Aims: We present optical observations of these stars conducted with 1-2 m class telescopes. We acquired high-resolution optical spectra as well as photometric data allowing us to investigate in detail their nature and physical parameters with the aim of testing the “runaway” and “in-situ” formation scenarios. Their kinematical properties are also analyzed to investigate their possible connection to already known stellar kinematic groups. Methods: We use the cross-correlation technique and other tools developed by us to derive accurate radial and rotational velocities and perform an automatic spectral classification. The spectral subtraction technique is used to infer chromospheric activity level in the Hα line core and clean the spectra of photospheric lines before measuring the equivalent width of the lithium absorption line. Results: Both physical (lithium content, chromospheric, and coronal activities) and kinematical indicators show that all stars are very young, with ages probably in the range 10-30 Myr. In particular, the spectral energy distribution of TYC 4496-780-1 displays a strong near- and far-infrared excess, typical of T Tauri stars still surrounded by an accretion disc. They also share the same Galactic motion, proving that they form a homogeneous moving group of stars with the same origin. Conclusions: The most plausible explanation of how these “isolated” T Tauri stars formed is the “in-situ” model, although accurate distances are needed to

  13. New Circumstellar Structure in the T Tauri System

    CERN Document Server

    Kasper, M; Herbst, T M; Köhler, R

    2016-01-01

    The immediate vicinity of T Tauri was observed with the new high-contrast imaging instrument SPHERE at the VLT to resolve remaining mysteries of the system, such as the putative small edge-on disk around T Tauri Sa, and the assignment of the complex outflow patterns to the individual stars. We used SPHERE IRDIS narrow-band classical imaging in Pa$\\beta$, Br$\\gamma$, and the $\

  14. V471 Tauri, ballerina of the Hyades

    Science.gov (United States)

    Skillman, David R.; Patterson, Joseph

    1988-09-01

    Orbital light curves for V471 Tauri, the red dwarf-white dwarf binary in the Hyades, were obtained for the 1980-1983 observing seasons based on photometric and spectroscopic data. The results reveal the effects of tidal distortion of the secondary and a slow, transient wave which may originate from darker areas on the star's surface. A consistent ephemeris is derived. A Ca II line emission similar to that of rapidly rotating late-type stars and an additional component arising from the stellar region bathed in the white dwarf's UV-radiation field are found. An overall orbital-period decrease is noted which may be due to the strong braking of the K star's rotation by its own stellar wind, coupled with the enforcement of synchronous rotation by the tidal interaction with the white dwarf.

  15. Over-Contact Binary GR Tauri

    Science.gov (United States)

    Snyder, Lee

    2009-05-01

    New times of minima and ephemeredes are presented on the over-contact system GR Tauri. An observed minus calculated (O-C), times of minimum chart was constructed and based on statistical analysis the orbital period of the system is found to be decreasing with a rate of dP/dE = 3.33^-4 seconds Yr^-1 since 1931. Both components are filling their respective critical Roche lobes with fillouts f = 0.11 and 0.95. The light curve displays the O'Connell effect which is discussed on the assumption mass is going from the primary to the secondary creating a hot spot. The TRO, thermal relaxation oscillations (Lucy & Wilson 1979), theory is discussed as an explanation.

  16. Activity Of T Tauri Type Stars And Objects Similar To Them

    Science.gov (United States)

    Ibryamov, Sunay

    2016-06-01

    The main purpose of the dissertation is on the basis of long-term light curves, to be classified the variability of 28 PMS stars and to be draw conclusions about the physical mechanisms initiating observed changes in their brightness. 22 of the investigated stars are located in the dense molecular cloud L935, known as 'Gulf of Mexico' (NGC 7000/IC 5070), and 6 stars are located in the vicinity of the reflection nebula NGC 7129. The multicolour photometric observations that we present were performed from 1993 to 2015 with the 2-m RCC, the 50/70-cm Schmidt and the 60-cm Cassegrain telescopes of the Rozhen NAO (Bulgaria) and the 1.3-m RC telescope of the Skinakas Observatory (Greece). All frames were taken through a standard Johnson-Cousins set of filters. The studied stars were classified as follows: V752 Cyg, V1539 Cyg, V1716 Cyg, FHO 26, FHO 29, LkHα 186, LkHα 187, LkHα 191, [KW97] 53-17, [KW97] 53-22, [KW97] 53-23, V391 Cep, NGC 7129 S V2 and 2MASS J21403576+6635000 show characteristics for classical T Tauri stars; V1538 Cyg, V1929 Cyg, [KW97] 53-20 and NGC 7129 S V1 are probably weak-line T Tauri stars; LkHα 189 and [KW97] 53-11 show characteristics for both type T Tauri stars and spectral observations are needed for their exact classification; V350 Cep shows indications for EXor and/or FUor-type variability; V521 Cyg, FHO 27, FHO 28 and NGC 7129 S V3 show characteristics for UXor-type variability; V1957 Cyg, V2051 Cyg and [KW97] 53-36 likely are evolved PMS stars or post-T Tauri stars. Periodicity was discovered for 3 of the investigated stars. V1716 Cyg indicates 4.15-day period, V1929 Cyg indicates 0.43-day period and LkHα 189 indicates 2.45-day period.

  17. Curved walls: Grain growth, settling, and composition patterns in T Tauri disk dust submlimation fronts

    CERN Document Server

    McClure, M K; Calvet, N; Espaillat, C; Hartmann, L; Sargent, B; Watson, D M; Ingleby, L; Hernandez, J

    2013-01-01

    The dust sublimation walls of disks around T Tauri stars represent a directly observable cross-section through the disk atmosphere and midplane. Their emission properties can probe the grain size distribution and composition of the innermost regions of the disk, where terrestrial planets form. Here we calculate the inner dust sublimation wall properties for four classical T Tauri stars with a narrow range of spectral types and inclination angles and a wide range of mass accretion rates to determine the extent to which the walls are radially curved. Best-fits to the near- and mid-IR excesses are found for curved, 2-layer walls in which the lower layer contains larger, hotter, amorphous pyroxene grains with Mg/(Mg+Fe)=0.6 and the upper layer contains submicron, cooler, mixed amorphous olivine and forsterite grains. As the mass accretion rates decrease from 10^(-8) to 10^(-10) Msol/yr, the maximum grain size in the lower layer decreases from 3 to 0.5 microns. We attribute this to a decrease in fragmentation and ...

  18. The Origins of Fluorescent H2 Emission From T Tauri~Stars

    CERN Document Server

    Herczeg, G J; Johns-Krull, C M; Linsky, J L; Walter, F M; Gahm, Gosta F.; Herczeg, Gregory J.; Johns-Krull, Christopher M.; Linsky, Jeffrey L.; Walter, Frederick M.

    2006-01-01

    We survey fluorescent H2 emission in HST/STIS spectra of the classical T Tauri stars (CTTSs) TW Hya, DF Tau, RU Lupi, T Tau, and DG Tau, and the weak-lined T Tauri star (WTTS) V836 Tau. From each of those sources we detect between 41-209 narrow H2 emission lines, most of which are pumped by strong Ly-alpha emission. H2 emission is not detected from the WTTS V410 Tau. The fluorescent H2 emission appears to be common to circumstellar environments around all CTTSs, but high spectral and spatial resolution STIS observations reveal diverse phenomenon. Blueshifted H2 emission detected from RU Lupi, T Tau, and DG Tau is consistent with an origin in an outflow. The H2 emission from TW Hya, DF Tau, and V836 Tau is centered at the radial velocity of the star and is consistent with an origin in a warm disk surface. The H2 lines from RU Lupi, DF Tau, and T Tau also have excess blueshifted H2 emission that extends to as much as -100 km/s. The strength of this blueshifted component from DF Tau and T Tau depends on the uppe...

  19. Investigating grain growth in disks around southern T Tauri stars at millimetre wavelengths

    CERN Document Server

    Lommen, D; Maddison, S T; Jørgensen, J K; Bourke, T L; Van Dishoeck, E F; Hughes, A; Wilner, D J; Burton, M; Van Langevelde, H J; Lommen, Dave; Wright, Chris M.; Maddison, Sarah T.; Jorgensen, Jes K.; Bourke, Tyler L.; Dishoeck, Ewine F. van; Hughes, Annie; Wilner, David J.; Burton, Michael; Langevelde, Huib Jan van

    2006-01-01

    CONTEXT - Low-mass stars form with disks in which the coagulation of grains may eventually lead to the formation of planets. It is not known when and where grain growth occurs, as models that explain the observations are often degenerate. A way to break this degeneracy is to resolve the sources under study. AIMS - To find evidence for the existence of grains of millimetre sizes in disks around in T Tauri stars, implying grain growth. METHODS - The Australia Telescope Compact Array (ATCA) was used to observe 15 southern T Tauri stars, five in the constellation Lupus and ten in Chamaeleon, at 3.3 millimetre. The five Lupus sources were also observed with the Submillimeter Array (SMA) at 1.4 millimetre. Our new data are complemented with data from the literature to determine the slopes of the spectral energy distributions in the millimetre regime. RESULTS - Ten sources were detected at better than 3sigma with the ATCA, with sigma ~1-2 mJy, and all sources that were observed with the SMA were detected at better t...

  20. Veiling in Orion T Tauri Stars

    Science.gov (United States)

    Hawks, E. L.; Johns-Krull, C. M.; Hamilton, C. M.

    2005-12-01

    We use the cross dispersed echelle spectrometer on the 2.7 m Harlan J. Smith telescope at McDonald Observatory to measure the optical veiling in several classical T Tauri stars with known rotation periods in the Orion star formation region. Veiling is the excess continuum produced as circumstellar matter accretes onto the stellar surface. Pervious studies have generally ignored this excess continuum when analyzing the V, R and I colors to determine stellar and accretion properties of the low mass young stars in Orion. We find for a number of stars that the veiling flux contributes significantly to the V and Ic colors. We use our veiling measurements to correct literature photometric data in order to calculate new extinction values and intrinsic magnitudes for each star. We then use these corrected magnitudes with pre-main sequence evolutionary tracks to obtain new estimates of the stellar luminosity, radius, mass, and age of each star in our sample. Combining these updated parameters with our veiling measurements, we determine accurate accretion rate estimates which we will use to test disk locking theory in the low mass stars of Orion. This research was supported in part by a NASA Origins grant to Rice University.

  1. 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...

  2. CAN T TAURI STARS PRODUCE HIGH-ENERGY RADIATION?

    Directory of Open Access Journals (Sweden)

    M. V. del Valle

    2011-01-01

    Full Text Available Las estrellas T Tauri son estrellas de baja masa de pre-secuencia principal. Estos objetos están rodeados por un disco de acreción y presentan una poderosa actividad magnética. Las estrellas T Tauri son copiosas emisoras de rayos X. Los rayos X se generan en eventos intensos de reconexión magnética. Ondas de choque fuertes pueden estar asociadas con la reconexión masiva del campo magnético. Estas ondas o la propia reconexión pueden acelerar partículas hasta energías relativistas, como se ha observado en el sol. Presentamos un modelo para la radiación de muy alta energía producida en la magnetósfera de las estrellas T Tauri. Discutimos si esta emisión es detectable o no con los telescopios de rayos gamma existentes.

  3. Measurements of magnetic field strength on T Tauri stars

    Science.gov (United States)

    Guenther, Eike W.; Lehmann, Holger; Emerson, James P.; Staude, Jürgen

    1999-01-01

    We have investigated the magnetic field strength of one weak-line and four classical T Tauri stars. The magnetic field strength is derived from the differential change of the equivalent width of photospheric Fe I lines in the presence of a magnetic field, calculated using a full radiative transfer code. The method was successfully tested by applying it to a non-magnetic solar-type star, and to VY Ari which is believed to have a strong magnetic field. For two of the classical T Tauri stars, we find a product of magnetic field strength and filling factor B * f = (2.35+/- 0.15) kG for T Tau, and B * f = (1.1+/- 0.2) kG for LkCa 15. For the classical T Tauri star UX Tau A and the weak-line T Tauri star LkCa 16 the detection is only marginal, indicating magnetic field strengths of the order of 1 kG and possibly of more than 2 kG, respectively. No field could be detected for the classical T Tauri star GW Ori. For the two classical T Tauri stars for which we have detected a field, we find the filling factors to be larger than ~ 0.5, which indicates that the magnetic field covers most of the photosphere. We also show that ignoring a magnetic field can, depending on the lines used, result in errors in effective temperature and underestimates of veiling. Based on observations made with the William Herschel Telescope operated on the island of La Palma by the Royal Greenwich Observatory in the Spanish Observatorio de los Roque de los Muchachos of the Instituto de Astrofisica de Canarias

  4. Photometric data analysis of the eclipsing binary system AH Tauri

    CERN Document Server

    El-Sadek, M A; Essam, A; Rassem, M A

    2014-01-01

    Two sets of photometric observations of the system AH Tauri have been analyzed using the latest version of the Wilson-Devinney code. The results show that AH Tauri may classified as A-type of W-UMa eclipsing binary. The mass ratio of q = 0.81, an over-contact degree of f = 0.095, and a slightly temperature difference between the two components have been obtained. The asymmetry of its light curve explained by the presence of a dark spot on the massive component. The physical, geometrical, and absolute parameters have been derived and compared with previous work.

  5. HOT GAS LINES IN T TAURI STARS

    Energy Technology Data Exchange (ETDEWEB)

    Ardila, David R. [NASA Herschel Science Center, California Institute of Technology, MC 100-22, Pasadena, CA 91125 (United States); Herczeg, Gregory J. [Kavli Institute for Astronomy and Astrophysics, Peking University, Beijing 100871 (China); Gregory, Scott G.; Hillenbrand, Lynne A. [Cahill Center for Astronomy and Astrophysics, California Institute of Technology, MC 249-17, Pasadena, CA 91125 (United States); Ingleby, Laura; Bergin, Edwin; Bethell, Thomas; Calvet, Nuria [Department of Astronomy, University of Michigan, 830 Dennison Building, 500 Church Street, Ann Arbor, MI 48109 (United States); France, Kevin; Brown, Alexander [Center for Astrophysics and Space Astronomy, University of Colorado, Boulder, CO 80309-0389 (United States); Edwards, Suzan [Department of Astronomy, Smith College, Northampton, MA 01063 (United States); Johns-Krull, Christopher [Department of Physics and Astronomy, Rice University, Houston, TX 77005 (United States); Linsky, Jeffrey L. [JILA, University of Colorado and NIST, 440 UCB Boulder, CO 80309-0440 (United States); Yang, Hao [Institute for Astrophysics, Central China Normal University, Wuhan 430079 (China); Valenti, Jeff A. [Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 (United States); Abgrall, Herve [LUTH and UMR 8102 du CNRS, Observatoire de Paris, Section de Meudon, Place J. Janssen, F-92195 Meudon (France); Alexander, Richard D. [Department of Physics and Astronomy, University of Leicester, University Road, Leicester LE1 7RH (United Kingdom); Brown, Joanna M.; Espaillat, Catherine [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, MS 78, Cambridge, MA 02138 (United States); Hussain, Gaitee, E-mail: ardila@ipac.caltech.edu [ESO, Karl-Schwarzschild-Strasse 2, D-85748 Garching bei Muenchen (Germany); and others

    2013-07-01

    For Classical T Tauri Stars (CTTSs), the resonance doublets of N V, Si IV, and C IV, as well as the He II 1640 A line, trace hot gas flows and act as diagnostics of the accretion process. In this paper we assemble a large high-resolution, high-sensitivity data set of these lines in CTTSs and Weak T Tauri Stars (WTTSs). The sample comprises 35 stars: 1 Herbig Ae star, 28 CTTSs, and 6 WTTSs. We find that the C IV, Si IV, and N V lines in CTTSs all have similar shapes. We decompose the C IV and He II lines into broad and narrow Gaussian components (BC and NC). The most common (50%) C IV line morphology in CTTSs is that of a low-velocity NC together with a redshifted BC. For CTTSs, a strong BC is the result of the accretion process. The contribution fraction of the NC to the C IV line flux in CTTSs increases with accretion rate, from {approx}20% to up to {approx}80%. The velocity centroids of the BCs and NCs are such that V{sub BC} {approx}> 4 V{sub NC}, consistent with the predictions of the accretion shock model, in at most 12 out of 22 CTTSs. We do not find evidence of the post-shock becoming buried in the stellar photosphere due to the pressure of the accretion flow. The He II CTTSs lines are generally symmetric and narrow, with FWHM and redshifts comparable to those of WTTSs. They are less redshifted than the CTTSs C IV lines, by {approx}10 km s{sup -1}. The amount of flux in the BC of the He II line is small compared to that of the C IV line, and we show that this is consistent with models of the pre-shock column emission. Overall, the observations are consistent with the presence of multiple accretion columns with different densities or with accretion models that predict a slow-moving, low-density region in the periphery of the accretion column. For HN Tau A and RW Aur A, most of the C IV line is blueshifted suggesting that the C IV emission is produced by shocks within outflow jets. In our sample, the Herbig Ae star DX Cha is the only object for which we find a

  6. A sub-AU outwardly truncated accretion disk around a classical T Tauri star

    CERN Document Server

    McClure, M K; Sargent, B A; Watson, Dan M; Furlan, E; Manoj, P; Tayrien, C; Harrold, S T; Calvet, N; Hartmann, L W

    2008-01-01

    We present the Spitzer Infrared Spectrograph (IRS) spectrum of SR20, a 5--10 AU binary T Tauri system in the rho Ophiuchi star forming region. The spectrum has features consistent with the presence of a disk; however, the continuum slope is steeper than the lambda^{-4/3} slope of an infinite geometrically thin, optically thick disk, indicating that the disk is outwardly truncated. Comparison with photometry from the literature shows large variability from 1993 to 1996. We model the spectral energy distribution and IRS spectrum with a geometrically thin, optically thick irradiated disk, yielding an outer radius of 0.15 AU, much smaller than predicted by models of binary orbits. Using a two temperature chi-squared minimization model to fit the dust composition of the IRS spectrum, we find the disk is comprised of large (5 micron) amorphous olivine grains. These results lead us to conclude that there is likely an unseen companion orbiting close to the primary.

  7. CCD Photometric Study and Period Investigation of AH Tauri

    Science.gov (United States)

    Xiang, Fu-Yuan; Xiao, Ting-Yu; Yu, Yun-Xia

    2015-07-01

    In this paper, we present new CCD photometric observations of AH Tauri in the R band observed in 2006 at the Yunnan Observatory. Two new times of light minima were derived from these observations. We modeled the light curves using the 2003 version of the Wilson-Devinney program. The results show that the variations of the light curves can be expained by a cool spot on the primary star. The fill-out factor is about 6.6%, indicating that AH Tauri is a shallow-contact system. The mass ratio was determined to be about 0.505. In addition, the orbital period variations of AH Tauri were investigated based on all of the photoelectric and CCD light minimum times, including our two new data. It was found that the orbital period exhibits a possible periodic variation with a period of {P}{mod}=54.62\\(+/- 0.20) years and a secular period decrease of {dP}/{dt}=-(1.823+/- 0.215)× {10}-7 {days} {{yr}}-1. Since AH Tauri is an overcontact solar-like system, we discuss three mechanisms of the mass transfer, the light-time effect of the third body, and magnetic activity responsible for the orbital period changes.

  8. RV variable, hot post-AGB stars from the MUCHFUSS project - Classification, atmospheric parameters, formation scenarios

    CERN Document Server

    Reindl, N; Kupfer, T; Bloemen, S; Schaffenroth, V; Heber, U; Barlow, B N; Østensen, R H

    2016-01-01

    In the course of the MUCHFUSS project we have recently discovered four radial velocity (RV) variable, hot (Teff $\\approx$ 80,000 - 110,000 K) post-asymptotic giant branch (AGB) stars. Among them, we found the first known RV variable O(He) star, the only second known RV variable PG 1159 close binary candidate, as well as the first two naked (i.e., without planetary nebula (PN)) H-rich post-AGB stars of spectral type O(H) that show significant RV variations. We present a non-LTE spectral analysis of these stars along with one further O(H)-type star whose RV variations were found to be not significant. We also report the discovery of an far-infrared excess in the case of the PG 1159 star. None of the stars in our sample displays nebular emission lines, which can be explained well in terms of a very late thermal pulse evolution in the case of the PG 1159 star. The "missing" PNe around the O(H)-type stars seem strange, since we find that several central stars of PNe have much longer post-AGB times. Besides the non...

  9. T Tauri Disk Lifetime in the Lupus Association

    Science.gov (United States)

    Galli, P. A. B.; Bertout, C.; Teixeira, R.; Ducourant, C.

    2016-01-01

    In a recent study, we derived individual distances for a sample of pre-main sequence stars that define the comoving association of young stars in the Lupus star-forming region. Here, we use these new distances to investigate the mass and age distributions of Lupus T Tauri stars and derive the average disk lifetime in the Lupus association based on an empirical disk model.

  10. Four Probable T Tauri Stars in MBM 12

    Science.gov (United States)

    Ogura, Katsuo; Sugitani, Koji; Magakian, Tigran Yu.; Movsessian, Tigran A.; Nikogossian, Elena H.; Itoh, Yoichi; Tamura, Motohide

    2003-06-01

    Survey observations were carried out in the MBM 12 (sometimes referred to as Lynds 1457) dark cloud in search of Hα emission stars by using a slitless grism spectrograph on the 2.6-m reflector of Byurakan Astrophysical Observatory, Armenia. Four new Hα stars were detected by the survey and identified as candidate T Tauri stars by follow-up low-dispersion spectroscopy and/or near-infrared photometry.

  11. Probing entrainment of Ostreococcus tauri circadian clock by green and blue light through a mathematical modeling approach.

    Science.gov (United States)

    Thommen, Quentin; Pfeuty, Benjamin; Schatt, Philippe; Bijoux, Amandine; Bouget, François-Yves; Lefranc, Marc

    2015-01-01

    Most organisms anticipate daily environmental variations and orchestrate cellular functions thanks to a circadian clock which entrains robustly to the day/night cycle, despite fluctuations in light intensity due to weather or seasonal variations. Marine organisms are also subjected to fluctuations in light spectral composition as their depth varies, due to differential absorption of different wavelengths by sea water. Studying how light input pathways contribute to circadian clock robustness is therefore important. Ostreococcus tauri, a unicellular picoplanktonic marine green alga with low genomic complexity and simple cellular organization, has become a promising model organism for systems biology. Functional and modeling approaches have shown that a core circadian oscillator based on orthologs of Arabidopsis TOC1 and CCA1 clock genes accounts for most experimental data acquired under a wide range of conditions. Some evidence points at putative light input pathway(s) consisting of a two-component signaling system (TCS) controlled by the only two histidine kinases (HK) of O. tauri. LOV-HK is a blue light photoreceptor under circadian control, that is required for circadian clock function. An involvement of Rhodopsin-HK (Rhod-HK) is also conceivable since rhodopsin photoreceptors mediate blue to green light input in animal circadian clocks. Here, we probe the role of LOV-HK and Rhod-HK in mediating light input to the TOC1-CCA1 oscillator using a mathematical model incorporating the TCS hypothesis. This model agrees with clock gene expression time series representative of multiple environmental conditions in blue or green light, characterizing entrainment by light/dark cycles, free-running in constant light, and resetting. Experimental and theoretical results indicate that both blue and green light can reset O. tauri circadian clock. Moreover, our mathematical analysis suggests that Rhod-HK is a blue-green light receptor and drives the clock together with LOV-HK.

  12. Orbits in the T Tauri triple system observed with SPHERE

    CERN Document Server

    Köhler, R; Herbst, T M; Ratzka, T; Bertrang, G H -M

    2015-01-01

    We present new astrometric measurements of the components in the T Tauri system, and derive new orbits and masses. T Tauri was observed during the science verification time of the new extreme adaptive optics facility SPHERE at the VLT. We combine the new positions with recalibrated NACO-measurements and data from the literature. Model fits for the orbits of T Tau Sa and Sb around each other and around T Tau N yield orbital elements and individual masses of the stars Sa and Sb. Our new orbit for T Tau Sa/Sb is in good agreement with other recent results, which indicates that enough of the orbit has been observed for a reliable fit. The total mass of T Tau S is 2.65+/-0.11 Msun. The mass ratio M_Sb:M_Sa is 0.25+/-0.03, which yields individual masses of M_Sa = 2.12+/-0.10 Msun and M_Sb = 0.53+/-0.06 Msun. If our current knowledge of the orbital motions is used to compute the position of the southern radio source in the T Tauri system, then we find no evidence for the proposed dramatic change in its path.

  13. Magnetic fields of weak line T-Tauri stars

    Science.gov (United States)

    Hill, Colin A.; MaTYSSE Collaboration

    2017-10-01

    T-Tauri stars (TTS) are late-type pre-main-sequence (PMS) stars that are gravitationally contracting towards the MS. Those that possess a massive accretion disc are known as classical T-Tauri stars (cTTSs), and those that have exhausted the gas in their inner discs are known as weak-line T-Tauri stars (wTTSs). Magnetic fields largely dictate the angular momentum evolution of TTS and can affect the formation and migration of planets. Thus, characterizing their magnetic fields is critical for testing and developing stellar dynamo models, and trialling scenarios currently invoked to explain low-mass star and planet formation. The MaTYSSE programme (Magnetic Topologies of Young Stars and the Survival of close-in Exoplanets) aims to determine the magnetic topologies of ~30 wTTSs and monitor the long-term topology variability of ~5 cTTSs. We present several wTTSs that have been magnetically mapped thus far (using Zeeman Doppler Imaging), where we find a much wider range of field topologies compared to cTTSs and MS dwarfs with similar internal structures.

  14. Another deep dimming of the classical T Tauri star RW Aur A

    CERN Document Server

    Petrov, P P; Djupvik, A A; Babina, E V; Artemenko, S A; Grankin, K N

    2015-01-01

    Context. RW Aur A is a classical T Tauri star (CTTS) with an unusually rich emission line spectrum. In 2014 the star faded by ~ 3 magnitudes in the V band and went into a long-lasting minimum. In 2010 the star suffered from a similar fading, although less deep. These events in RW Aur A are very unusual among the CTTS, and have been attributed to occultations by passing dust clouds. Aims. We want to find out if any spectral changes took place after the last fading of RW Aur A with the intention to gather more information on the occulting body and the cause of the phenomenon. Methods. We collected spectra of the two components of RW Aur. Photometry was made before and during the minimum. Results. The overall spectral signatures reflecting emission from accretion flows from disk to star did not change after the fading. However, blue-shifted absorption components related to the stellar wind had increased in strength in certain resonance lines, and the profiles and strengths, but not fluxes, of forbidden lines had...

  15. Discovery of seven T Tauri stars and a brown dwarf candidate in the nearby TW Hydrae Association

    CERN Document Server

    Webb, R A; Platais, I; Patience, J; White, R J; Schwartz, M J; McCarthy, C

    1999-01-01

    We report the discovery of five T Tauri star systems, two of which are resolved binaries, in the vicinity of the nearest known region of recent star formation, the TW Hydrae Association. The newly discovered systems display the same signatures of youth (namely high X-ray flux, large Li abundance and strong chromospheric activity) and the same proper motion as the original five members. These similarities firmly establish the group as a bona fide T Tauri association, unique in its proximity to Earth and its complete isolation from any known molecular clouds. At an age of ~10 Myr and a distance of ~50 pc, the association members are excellent candidates for future studies of circumstellar disk dissipation and the formation of brown dwarfs and planets. Indeed, as an example, our speckle imaging revealed a faint, very likely companion 2" north of CoD-33 7795 (TWA 5). Its color and brightness suggest a spectral type ~M8.5 which, at an age of ~10^7 years, implies a mass ~20 M(Jupiter).

  16. A High-Precision NIR Survey for RV Variable Low-Mass Stars

    CERN Document Server

    Gagné, Jonathan; Gao, Peter; Anglada-Escude, Guillem; Furlan, Elise; Davison, Cassy; Tanner, Angelle; Henry, Todd J; Riedel, Adric R; Brinkworth, Carolyn; Latham, David; Bottom, Michael; White, Russel; Mills, Sean; Beichman, Chas; Johnson, John A; Ciardi, David R; Wallace, Kent; Mennesson, Bertrand; von Braun, Kaspar; Vasisht, Gautam; Prato, Lisa; Kane, Stephen R; Mamajek, Eric E; Walp, Bernie; Crawford, Timothy J; Rougeot, Raphaël; Geneser, Claire S; Catanzarite, Joseph

    2016-01-01

    We present the results of a precise near-infrared (NIR) radial velocity (RV) survey of 32 low-mass stars with spectral types K2-M4 using CSHELL at the NASA IRTF in the $K$-band with an isotopologue methane gas cell to achieve wavelength calibration and a novel iterative RV extraction method. We surveyed 14 members of young ($\\approx$ 25-150 Myr) moving groups, the young field star $\\varepsilon$ Eridani as well as 18 nearby ($<$ 25 pc) low-mass stars and achieved typical single-measurement precisions of 8-15 m s$^{-1}$ with a long-term stability of 15-50 m s$^{-1}$. We obtain the best NIR RV constraints to date on 27 targets in our sample, 19 of which were never followed by high-precision RV surveys. Our results indicate that very active stars can display long-term RV variations as low as $\\sim$ 25-50 m s$^{-1}$ at $\\approx$ 2.3125 $\\mu$m, thus constraining the effect of jitter at these wavelengths. We provide the first multi-wavelength confirmation of GJ 876 bc and independently retrieve orbital parameters...

  17. New CCD Photometry Study of RV UMa

    CERN Document Server

    Tasselli, D

    2015-01-01

    All available CCD observation of RV UMa have been analyzed to obtain an accurate mathematical description of the ligh variation. We discuss in this paper a new study of variable star RV UMa, a short period RRab star, in orther to determine through the light curve and the physical parameters, the presence of "Blazhko effect". The Star were observed for a total of 839 sessions shooting, and exhibits light curve modulation with the shortest modulation Period=0.468002 ever observed. The result detect small but definite modification in temperature and mean radius of the star itself. All results are compared with previously published literature values and discussed.

  18. Teadlase eetika / Magnus Ilmjärv

    Index Scriptorium Estoniae

    Ilmjärv, Magnus, 1961-

    2008-01-01

    Vastukaja art.: Valge, Jaak. Pätsi riigipööret ei inspireeritud väljastpoolt // Postimees (2008) 26. apr., lk. 13. President Konstantin Pätsi kohta leitud uutest arhiivimaterjalidest. Raamatu "Hääletu alistumine" autor, ajaloolane Magnus Ilmjärv peab Jaak Valge kriitikat tema suhtes põhjendamatult suureks

  19. Physical Conditions of Accreting Gas in T Tauri Star Systems

    CERN Document Server

    Bary, Jeffrey S; Skrutskie, Michael F; Wilson, John C; Peterson, Dawn E; Nelson, Matthew J

    2008-01-01

    We present results from a low resolution (R~300) near-infrared spectroscopic variability survey of actively accreting T Tauri stars (TTS) in the Taurus-Auriga star forming region. Paschen and Brackett series H I recombination lines were detected in 73 spectra of 15 classical T Tauri systems. The values of the Pan/PaB, Brn/BrG, and BrG/Pan H I line ratios for all observations exhibit a scatter of < 20% about the weighted mean, not only from source to source, but also for epoch-to-epoch variations in the same source. A representative or `global' value was determined for each ratio in both the Paschen and Brackett series as well as the BrG/Pan line ratios. A comparison of observed line ratio values was made to those predicted by the temperature and electron density dependent models of Case B hydrogen recombination line theory. The measured line ratios are statistically well-fit by a tightly constrained range of temperatures (T < 2000 K) and electron densities 1e9 < n_e < 1e10 cm^-3. A comparison of t...

  20. X-ray Photoevaporation-starved T Tauri Accretion

    CERN Document Server

    Drake, Jeremy J; Flaccomio, Ettore; Micela, Giusi

    2009-01-01

    X-ray luminosities of accreting T Tauri stars are observed to be systematically lower than those of non-accretors. There is as yet no widely accepted physical explanation for this effect, though it has been suggested that accretion somehow suppresses, disrupts or obscures coronal X-ray activity. Here, we suggest that the opposite might be the case: coronal X-rays modulate the accretion flow. We re-examine the X-ray luminosities of T Tauri stars in the Orion Nebula Cluster and find that not only are accreting stars systematically fainter, but that there is a correlation between mass accretion rate and stellar X-ray luminosity. We use the X-ray heated accretion disk models of Ercolano et al. to show that protoplanetary disk photoevaporative mass loss rates are strongly dependent on stellar X-ray luminosity and sufficiently high to be competitive with accretion rates. X-ray disk heating appears to offer a viable mechanism for modulating the gas accretion flow and could be at least partially responsible for the o...

  1. Accretion-related properties of Herbig Ae/Be stars. Comparison with T Tauris

    CERN Document Server

    Mendigutía, I; Montesinos, B; Eiroa, C; Meeus, G; Merín, B; Oudmaijer, R D

    2012-01-01

    We look for trends relating the mass accretion rate (Macc) and the stellar ages (t), spectral energy distributions (SEDs), and disk masses (Mdisk) for a sample of 38 HAeBe stars, comparing them to analogous correlations found for classical T Tauri stars. Our goal is to shed light on the timescale and physical processes that drive evolution of intermediate-mass pre-main sequence objects. Macc shows a dissipation timescale \\tau = 1.3^{+1.0}_{-0.5} Myr from an exponential law fit, while a power law yields Macc(t) \\propto t^{-\\eta}, with \\eta = 1.8^{+1.4}_{-0.7}. This result is based on our whole HAeBe sample (1-6 Msun), but the accretion rate decline most probably depends on smaller stellar mass bins. The near-IR excess is higher and starts at shorter wavelengths (J and H bands) for the strongest accretors. Active and passive disks are roughly divided by 2 x 10^{-7} Msun/yr. The mid-IR excess and the SED shape from the Meeus et al. classification are not correlated with Macc. We find Macc \\propto Mdisk^{1.1 +- 0...

  2. Mid-Infrared Spectroscopy of Disks around Classical T Tauri Stars

    CERN Document Server

    Forrest, W J; Furlan, E; D'Alessio, P; Calvet, N; Hartmann, L; Uchida, K I; Green, J D; Watson, D M; Chen, C H; Markwick-Kemper, F; Keller, L D; Sloan, G C; Herter, T L; Brandl, B R; Houck, J R; Barry, J; Hall, P; Morris, P W; Najita, J; Myers, P C

    2004-01-01

    We present the first Spitzer Infrared Spectrograph (IRS; The IRS was a collaborative venture between Cornell University and Ball Aerospace Corporation funded by NASA through the Jet Propulsion Laboratory and the Ames Research Center.) observations of the disks around classical T Tauri stars: spectra in the 5.2-30 micron range of six stars. The spectra are dominated by emission features from amorphous silicate dust, and a continuous component from 5 to 8 microns that in most cases comprises an excess above the photosphere throughout our spectral range. There is considerable variation in the silicate feature/continuum ratio, which implies variations of inclination, disk flaring, and stellar mass accretion rate. In most of our stars, structure in the silicate feature suggests the presence of a crystalline component. In one, CoKu Tau/4, no excess above the photosphere appears at wavelengths shortward of the silicate features, similar to 10 Myr old TW Hya, Hen 3-600, and HR 4796A. This indicates the optically thic...

  3. The protoplanetary disk of FT Tauri: multi-wavelength data analysis and modeling

    CERN Document Server

    Garufi, Antonio; Kamp, Inga; Ménard, François; Brittain, Sean; Eiroa, Carlos; Montesinos, Benjamin; Alonso-Martinez, Míguel; Thi, Wing-Fai; Woitke, Peter

    2014-01-01

    Investigating the evolution of protoplanetary disks is crucial for our understanding of star and planet formation. Several theoretical and observational studies have been performed in the last decades to advance this knowledge. FT Tauri is a young star in the Taurus star forming region that was included in a number of spectroscopic and photometric surveys. We investigate the properties of the star, the circumstellar disk, and the accretion and ejection processes and propose a consistent gas and dust model also as a reference for future observational studies. We performed a multi-wavelength data analysis to derive the basic stellar and disk properties, as well as mass accretion/outflow rate from TNG-Dolores, WHT-Liris, NOT-Notcam, Keck-Nirspec, and Herschel-Pacs spectra. From the literature, we compiled a complete Spectral Energy Distribution. We then performed detailed disk modeling using the MCFOST and ProDiMo codes. Multi-wavelengths spectroscopic and photometric measurements were compared with the reddened...

  4. Evidence for an FU Orionis Outburst from a Classical T Tauri Star

    CERN Document Server

    Miller, Adam A; Covey, Kevin R; Poznanski, Dovi; Silverman, Jeffrey M; Kleiser, Io K W; Rojas-Ayala, Barbara; Muirhead, Philip S; Cenko, S Bradley; Bloom, Joshua S; Kasliwal, Mansi M; Filippenko, Alexei V; Law, Nicholas M; Ofek, Eran O; Dekany, Richard G; Rahmer, Gustavo; Hale, David; Smith, Roger; Quimby, Robert M; Nugent, Peter; Jacobsen, Janet; Zolkower, Jeff; Velur, Viswa; Walters, Richard; Henning, John; Bui, Khanh; McKenna, Dan; Kulkarni, Shrinivas R; Klein, Christopher R

    2010-01-01

    We present pre- and post-outburst observations of the new FU Orionis-like young stellar object Lk Halpha 188-G4 (also known as HBC 722 and PTF 10qpf). Prior to this outburst, Lk Halpha 188-G4 would have been classified as a classical T Tauri star on the basis of its optical emission-line spectrum superposed on a K8-type photosphere, and photometric variability. The mid-infrared spectral index of Lk Halpha 188-G4 indicates a Class II type object. Lk Halpha 188-G4 exhibited a steady rise by ~1 mag over ~11 months starting in Aug. 2009, before a subsequent more abrupt rise of >3 mag on a time scale of ~2 months. Observations taken during and after eruption exhibit all of the defining characteristics of FU Orionis variables: (i) Lk Halpha 188-G4 increased in brightness by >4 mag, (ii) a bright optical/near-infrared reflection nebula has now appeared (iii) optical spectra in the outburst phase are consistent with a G supergiant and dominated by absorption lines, the only exception being Halpha which is characteriz...

  5. The Temperature and Distribution of Organic Molecules in the Inner Regions of T Tauri Disks

    Science.gov (United States)

    Mandell, Avi

    2012-01-01

    "High-resolution NIR spectroscopic observations of warm molecular gas emission from young circumstellar disks allow us to constrain the temperature and composition of material in the inner planet-forming region. By combining advanced data reduction algorithms with accurate modeling of the terrestrial atmospheric spectrum and a novel double-differencing data analysis technique, we have achieved very high-contrast measurements (S/N approx. 500-1000) of molecular emission at 3 microns. In disks around low-mass stars, we have achieved the first detections of emission from HCN and C2H2 at near-infrared wavelengths from several bright T Tauri stars using the CRIRES spectrograph on the Very Large Telescope and NIRSPEC spectrograph on the Keck Telescope. We spectrally resolve the line shape, showing that the emission has both a Keplerian and non-Keplerian component as observed previously for CO emission. We used a simplified single-temperature local thermal equilibrium (LTE) slab model with a Gaussian line profile to make line identifications and determine a best-fit temperature and initial abundance ratios, and we then compared these values with constraints derived from a detailed disk radiative transfer model assuming LTE excitation but utilizing a realistic temperature and density structure. Abundance ratios from both sets of models are consistent with each other and consistent with expected values from theoretical chemical models, and analysis of the line shapes suggests that the molecular emission originates from within a narrow region in the inner disk (R < 1 AU)."

  6. Rotating molecular outflows: the young T Tauri star in CB26

    CERN Document Server

    Launhardt, R; Gueth, F; Chen, X; Dutrey, A; Guilloteau, S; Henning, T; Pietu, V; Schreyer, K; Semenov, D

    2008-01-01

    The disk-outflow connection is thought to play a key role in extracting excess angular momentum from a forming proto-star. Though jet rotation has been observed in a few objects, no rotation of molecular outflows has been unambiguously reported so far. We report new millimeter-interferometric observations of the edge-on T Tauri star - disk system in the isolated Bok globule CB26. The aim of these observations was to study the disk-outflow relation in this 1Myr old low-mass young stellar object. The IRAM PdBI array was used to observe 12CO(2-1) at 1.3mm in two configurations, resulting in spectral line maps with 1.5 arcsec resolution. We use an empirical parameterized steady-state outflow model combined with 2-D line radiative transfer calculations and chi^2-minimization in parameter space to derive a best-fit model and constrain parameters of the outflow. The data reveal a previously undiscovered collimated bipolar molecular outflow of total length ~2000 AU, escaping perpendicular to the plane of the disk. We...

  7. Magnetically Controlled Accretion on the Classical T Tauri Stars GQ Lupi and TW Hydrae

    CERN Document Server

    Johns-Krull, C M; Valenti, J A; Jeffers, S V; Piskunov, N E; Kuchukhov, O; Makaganiuk, V; Stempels, H C; Snik, F; Keller, C; Rodenhuis, M

    2013-01-01

    We present high spectral resolution ($R\\approx108,000$) Stokes $V$ polarimetry of the Classical T Tauri stars (CTTSs) GQ Lup and TW Hya obtained with the polarimetric upgrade to the HARPS spectrometer on the ESO 3.6 m telescope. We present data on both photospheric lines and emission lines, concentrating our discussion on the polarization properties of the \\ion{He}{1} emission lines at 5876 \\AA\\ and 6678 \\AA. The \\ion{He}{1} lines in these CTTSs contain both narrow emission cores, believed to come from near the accretion shock region on these stars, and broad emission components which may come from either a wind or the large scale magnetospheric accretion flow. We detect strong polarization in the narrow component of the two \\ion{He}{1} emission lines in both stars. We observe a maximum implied field strength of $6.05 \\pm 0.24$ kG in the 5876 \\AA\\ line of GQ Lup, making it the star with the highest field strength measured in this line for a CTTS. We find field strengths in the two \\ion{He}{1} lines that are c...

  8. The Evolution and Simulation of the Outburst from XZ Tauri - A Possible EXor?

    CERN Document Server

    Coffey, D; Ray, T P

    2004-01-01

    We report on multi-epoch HST/WFPC2 images of the XZ Tauri binary, and its outflow, covering the period from 1995 to 2001. Data from 1995 to 1998 have already been published in the literature. Additional images, from 1999, 2000 and 2001 are presented here. These reveal not only further dynamical and morphological evolution of the XZ Tauri outflow but also that the suspected outflow source, XZ Tauri North has flared in EXor-type fashion. In particular our proper motion studies suggests that the recently discovered bubble-like shock, driven by the the XZ Tauri outflow, is slowing down (its tangential velocity decreasing from 146km/s to 117km/s). We also present simulations of the outflow itself, with plausible ambient and outflow parameters, that appear to reproduce not only the dynamical evolution of the flow, but also its shape and emission line luminosity.

  9. PLANETARY SYSTEM FORMATION IN THE PROTOPLANETARY DISK AROUND HL TAURI

    Energy Technology Data Exchange (ETDEWEB)

    Akiyama, Eiji; Hasegawa, Yasuhiro; Hayashi, Masahiko; Iguchi, Satoru, E-mail: eiji.akiyama@nao.ac.jp, E-mail: yasuhiro.hasegawa@nao.ac.jp [National Astronomical Observatory of Japan, 2-21-1 Osawa, Mitaka, Tokyo 181-8588 (Japan)

    2016-02-20

    We reprocess the Atacama Large Millimeter/Submillimeter Array (ALMA) long-baseline science verification data taken toward HL Tauri. Assuming the observed gaps are opened up by currently forming, unseen bodies, we estimate the mass of such hypothetical bodies based on the following two approaches: the Hill radius analysis and a more elaborate approach developed from the angular momentum transfer analysis in gas disks. For the former, the measured gap widths are used for estimating the mass of the bodies, while for the latter, the measured gap depths are utilized. We show that their masses are comparable to or less than the mass of Jovian planets. By evaluating Toomre’s gravitational instability (GI) condition and cooling effect, we find that the GI might be a mechanism to form the bodies in the outer region of the disk. As the disk might be gravitationally unstable only in the outer region of the disk, inward planetary migration would be needed to construct the current architecture of the observed disk. We estimate the gap-opening mass and show that type II migration might be able to play such a role. Combining GIs with inward migration, we conjecture that all of the observed gaps may be a consequence of bodies that might have originally formed at the outer part of the disk, and have subsequently migrated to the current locations. While ALMA’s unprecedented high spatial resolution observations can revolutionize our picture of planet formation, more dedicated observational and theoretical studies are needed to fully understand the HL Tauri images.

  10. Fundamental stellar parameters for selected T-Tauri stars in the Chamaeleon and Rho Ophiuchus star-forming regions

    Science.gov (United States)

    James, D. J.; Aarnio, A. N.; Richert, A. J. W.; Cargile, P. A.; Santos, N. C.; Melo, C. H. F.; Bouvier, J.

    2016-06-01

    We present the results of an optical photometry and high-resolution spectroscopy campaign for a modest sample of X-ray selected stars in the Chamaeleon and Rho Ophiuchus star-forming regions. With R˜ 50 000 optical spectra, we establish kinematic membership of the parent association and confirm stellar youth for each star in our sample. With the acquisition of new standardized BVIc photometry, in concert with near-infrared data from the literature, we derive age and mass from stellar positions in model-dependent Hertzsprung-Russell diagrams. We compare isochronal ages derived using colour-dependent extinction values finding that, within error bars, ages are the same irrespective of whether E(B - V), E(V - Ic), E(J - H) or E(H - K) is used to establish extinction, although model ages tend to be marginally younger for redder Ecolour values. For Cham I and η Cham members, we derive ages of ≲5-6 Myr, whereas our three η Cha candidates are more consistent with a ≳25 Myr post-T Tauri star population. In Rho Ophiuchus, most stars in our sample have isochronal ages 5) in the Two Micron All Sky Survey colour-colour diagram, however in terms of Hα emission, all stars except RXJ1625.6-2613 are consistent with being weak-lined T-Tauri stars. Spectral energy distributions (SEDs) over the range ≃4000 Å <λ < 1000 μm, show that only one Chamaeleon star (RXJ1112.7 -7637) and three Rho Ophiuchus stars (ROXR1 13, RXJ1625.6-2613 & RXJ1627.1-2419) reveal substantial departures from a bare photosphere.

  11. Management of iatrogenic RV injury - RV packing and CPB through PTFE graft attached to femoral artery.

    Science.gov (United States)

    Mangukia, Chirantan V; Agarwal, Saket; Satyarthy, Subodh; Aggarwal, Satish Kumar; Datt, Vishnu; Satsangi, Deepak Kumar

    2015-01-01

    Cardiac injuries during repeat sternotomy are rare. While undergoing debridement for chronic osteomyelitis (post arterial septal defect closure), a 4-year-old girl sustained significant right ventricular (RV) injury. Bleeding from the RV was controlled by packing the injury site, which helped in maintaining stable hemodynamics till arrangements were made for instituting cardiopulmonary bypass (CPB). Since the femoral artery was very small and unsuitable for direct cannulation, a polytetrafluoroethylene (PTFE) graft sutured end-to-side to the femoral artery was used for establishing CPB. The injury was successfully repaired.

  12. Humoral Responses to Rv1733c, Rv0081, Rv1735c, and Rv1737c DosR Regulon-Encoded Proteins of Mycobacterium tuberculosis in Individuals with Latent Tuberculosis Infection

    Directory of Open Access Journals (Sweden)

    Simon G. Kimuda

    2017-01-01

    Full Text Available Latent tuberculosis infection (LTBI is evidence of immunological control of tuberculosis. Dormancy survival regulator (DosR regulon-encoded proteins may have a role in the maintenance of LTBI. T cell responses to Rv1733c, Rv0081, Rv1735c, and Rv1737c DosR regulon-encoded proteins were found to be most frequent among household contacts of TB cases from Uganda compared to other DosR proteins, but antibody responses were not described. We characterized antibody responses to these proteins in individuals from Uganda. Antibodies to Rv1733c, Rv0081, Rv1735c, and Rv1737c DosR regulon-encoded proteins were measured in 68 uninfected individuals, 62 with LTBI, and 107 with active pulmonary tuberculosis (APTB cases. There were no differences in the concentrations of antibodies to Rv0081, Rv1735c, and Rv1737c DosR regulon-encoded proteins between individuals with LTBI and APTB and those who were uninfected. LTBI was associated with higher concentrations of antibodies to Rv1733c in female participants [adjusted geometric mean ratio: 1.812, 95% confidence interval (CI: 1.105 2.973, and p=0.019] but not in males (p value for interaction = 0.060. Antibodies to the four DosR regulon-encoded proteins investigated may not serve as good biomarkers of LTBI in the general population. More of the M.tb proteome needs to be screened to identify proteins that induce strong antibody responses in LTBI.

  13. Molecular analysis of Rv0679c and Rv0180c genes of Mycobacterium tuberculosis from clinical isolates of pulmonary tuberculosis

    Directory of Open Access Journals (Sweden)

    L Rupa

    2016-01-01

    Full Text Available Context: Two novel proteins/genes Rv0679c and Rv0180c of Mycobacterium tuberculosis (MTB H37Rv were classified as a hypothetical membrane and transmembrane proteins which might have a role in the invasion. Molecular analysis of these genes in human clinical isolates of pulmonary tuberculosis (PTB patients was not well characterised. Aims: To assess the molecular diversity of Rv0679c and Rv0180c genes of MTB from clinical isolates of PTB patients. Settings and Design: DNA from 97 clinical isolates was extracted and subjected to amplification using selective primers by polymerase chain reaction (PCR. The PCR product obtained was sequenced commercially. Patients and Methods: Clinical isolates obtained from tuberculosis patients were investigated for polymorphisms in the Rv0679c and Rv0180c genes by PCR and DNA sequencing. Genomic DNA isolated by cetyltrimethylammonium bromide method was used for amplification of genes. Results: Rv0679c gene was highly conserved in 61 out of 65 clinical isolates assessed for sequence homology with wild-type H37Rv gene and was identical using ClustalW. Fifty-five out of 78 (70.5% clinical isolates assessed for Rv0180c were positive for single nucleotide polymorphism (SNP at 258th position where the nucleotide G was replaced with T (G to T. In clinical isolates of untreated cases, the frequency was 54.5% for SNP at 258th position which is low compared to cases undergoing treatment where the frequency was 73.1%. Conclusions: Molecular analysis of Rv0180c in clinical isolates of PTB assessed in this study was the first report, where an SNP at 258th position G to T was identified within the gene. Rv0679c gene was highly conserved (94%, within Indian clinical isolates as compared to reports from other nations.

  14. Evolution of the T Tauri star population in the Lupus association

    CERN Document Server

    Galli, P A B; Teixeira, R; Ducourant, C

    2015-01-01

    Aims: In a recent study, we derived individual distances for 109 pre-main sequence stars that define the Lupus kinematic association of young stars. Here, we use these new distances to derive the masses and ages of Lupus T Tauri stars with the aim of better constraining the lifetime of their circumstellar disks. Methods: Using the photometric and spectroscopic information available in the literature, we computed the photospheric luminosity of 92 T Tauri stars in the Lupus association. Then, we estimated their masses and ages from theoretical evolutionary models. Based on Monte Carlo simulations and statistical tests, we compare the mass and age distribution of the classical T Tauri stars (CTTS) and weak-line T Tauri (WTTS) in our sample. Results: We show that the CTTSs are on average younger than the WTTSs and that the probability that both T~Tauri subclasses are drawn from the same mass and age parental distribution is very low. Our results favor the scenario proposed earlier for the Taurus-Auriga associatio...

  15. High-Resolution Spectroscopy of Winds Associated with T Tauri Stars

    Science.gov (United States)

    Iguchi, Naoto; Itoh, Yoichi

    2016-02-01

    We carried out optical high-resolution spectroscopy of T Tauri stars using the Subaru Telescope. Using archived data from the Keck Telescope and the Very Large Telescope, we detected forbidden lines of [S II] at 4069 Å, in addition to those of [O I] at 5577 Å and 6300 Å, for 13 T Tauri stars. We consider that low-velocity components of these forbidden lines emanate from the wind associated with T Tauri stars. Using two flux ratios of the three lines, we simultaneously determined the hydrogen density and temperature of the winds. The winds of T Tauri stars have a hydrogen density of 2.5 × 106 cm‑3 ‑ 2.5 × 109 cm‑3 and a temperature of 10800 –18 000 K. The mass loss rates by the wind are estimated to lie in the range from 2.0 × 10‑10 M⊙ yr‑1 to 1.4 × 10‑9 M⊙ yr‑1. The mass loss rates are found to increase with increasing mass accretion rates. The ratio of the mass loss rate to the mass accretion rate is 0.001–0.1 for classical T Tauri stars and 0.1–1 for transitional disk objects.

  16. Interpretation of the Veiling of the Photospheric Spectrum for T Tauri Stars in Terms of an Accretion Model

    CERN Document Server

    Dodin, A V

    2012-01-01

    The problem on heating the atmospheres of T Tauri stars by radiation from an accretion shock has been solved. The structure and radiation spectrum of the emerging so-called hot spot have been calculated in the LTE approximation. The emission not only in continuum but also in lines has been taken into account for the first time when calculating the spot spectrum. Comparison with observations has shown that the strongest of these lines manifest themselves as narrow components of helium and metal emission lines, while the weaker ones decrease significantly the depth of photospheric absorption lines, although until now, this effect has been thought to be due to the emission continuum alone. The veiling by lines changes the depth of different photospheric lines to a very different degree even within a narrow spectral range. Therefore, the nonmonotonic wavelength dependence of the degree of veiling r found for some CTTS does not suggest a nontrivial spectral energy distribution of the veiling continuum. In general,...

  17. Rv2031c of Mycobacterium tuberculosis: a master regulator of Rv2028-Rv2031 (HspX operon

    Directory of Open Access Journals (Sweden)

    Khurram eMushtaq

    2015-04-01

    Full Text Available AbstractGenes belonging to the same operon are transcribed as a single mRNA molecule in all prokaryotes. The genes of the same operon are presumed to be involved in similar metabolic and physiological processes. Hence, computational analysis of constituent proteins could provide important clues to the functional relationships within the operonic genes. This tends to be more fruitful in the case of Mycobacterium tuberculosis (Mtb, considering the number of hypothetical genes with unknown functions and interacting partners. Dramatic advances in the past decade have increased our knowledge of the mechanisms that tubercle bacilli employ to survive within the host. But the phenomenon of Mtb latency continues to baffle all. Rv2031c belonging to dormancy regulon of Mtb is predominantly expressed during latency, with myriad immunological roles. Thus we attempted to analyze the operon comprising Rv2031c protein to gain insights into its role during latency. In the current study, we have carried out computational analysis of proteins encoded by genes known to be a part of this operon. Our study includes phylogenetic analysis, modeling of protein 3D structures, and protein interaction network analysis. We describe the mechanistic role in the establishment of latency and regulation of DevS/DevR component system. Additionally, we have identified the probable role of these proteins in carbohydrate metabolism, erythromycin tolerance and nucleotide synthesis. Hence, these proteins can modulate the metabolism of mycobacterium inside the host cells and can be important for its survival in latency. The functional characterization and interactome of this important operon can give insight into its role during latency along with the exploitation of constituent proteins as drug targets and vaccine candidates.

  18. Rv2031c of Mycobacterium tuberculosis: a master regulator of Rv2028–Rv2031 (HspX) operon

    Science.gov (United States)

    Mushtaq, Khurram; Sheikh, Javaid A.; Amir, Mohammed; Khan, Nargis; Singh, Balvinder; Agrewala, Javed N.

    2015-01-01

    Genes belonging to the same operon are transcribed as a single mRNA molecule in all prokaryotes. The genes of the same operon are presumed to be involved in similar metabolic and physiological processes. Hence, computational analysis of constituent proteins could provide important clues to the functional relationships within the operonic genes. This tends to be more fruitful in the case of Mycobacterium tuberculosis (Mtb), considering the number of hypothetical genes with unknown functions and interacting partners. Dramatic advances in the past decade have increased our knowledge of the mechanisms that tubercle bacilli employ to survive within the host. But the phenomenon of Mtb latency continues to baffle all. Rv2031c belonging to dormancy regulon of Mtb is predominantly expressed during latency, with myriad immunological roles. Thus we attempted to analyze the operon comprising Rv2031c protein to gain insights into its role during latency. In the current study, we have carried out computational analysis of proteins encoded by genes known to be a part of this operon. Our study includes phylogenetic analysis, modeling of protein 3D structures, and protein interaction network analysis. We describe the mechanistic role in the establishment of latency and regulation of DevS–DevR component system. Additionally, we have identified the probable role of these proteins in carbohydrate metabolism, erythromycin tolerance, and nucleotide synthesis. Hence, these proteins can modulate the metabolism of Mtb inside the host cells and can be important for its survival in latency. The functional characterization and interactome of this important operon can give insight into its role during latency along with the exploitation of constituent proteins as drug targets and vaccine candidates. PMID:25964780

  19. Indications for Grain Growth and Mass Decrease in Cold Dust Disks around Classical T Tauri Stars in the MBM 12 Young Association

    Science.gov (United States)

    Hogerheijde, Michiel R.; Johnstone, Doug; Matsuyama, Isamu; Jayawardhana, Ray; Muzerolle, James

    2003-08-01

    We report the detection of continuum emission at λ=850 and 450 μm from disks around four classical T Tauri stars in the MBM 12 (L1457) young association. Using a simple model, we infer masses of 0.0014-0.012 Msolar for the disk of LkHα 263 ABC, 0.005-0.021 Msolar for S18 ABab, 0.03-0.18 Msolar for LkHα 264 A, and 0.023-0.23 Msolar for LkHα 262. The disk mass found for LkHα 263 ABC is consistent with the 0.0018 Msolar inferred from the scattered-light image of the edge-on disk around component C. Comparison to earlier 13CO line observations indicates CO depletion by up to a factor of 300 with respect to dark-cloud values. The spectral energy distributions (SEDs) suggest grain growth, possibly to sizes of a few hundred microns, but our spatially unresolved data cannot rule out opacity as an explanation for the SED shape. Our observations show that these T Tauri stars are still surrounded by significant reservoirs of cold material at an age of 1-5 Myr. We conclude that the observed differences in disk mass are likely explained by binary separation affecting the initial value. With available accretion rate estimates we find that our data are consistent with theoretical expectations for viscously evolving disks having decreased their masses by ~30%.

  20. Indications for grain growth and mass decrease in cold dust disks around Classical T Tauri stars in the MBM 12 young association

    CERN Document Server

    Hogerheijde, M R; Matsuyama, I; Jayawardhana, R; Muzerolle, J; Hogerheijde, Michiel R.; Johnstone, Doug; Matsuyama, Isamu; Jayawardhana, Ray; Muzerolle, James

    2003-01-01

    We report detection of continuum emission at 850 and 450 micron from disks around four Classical T Tauri stars in the MBM 12 (L1457) young association. Using a simple model we infer masses of 0.0014-0.012 M_sun for the disk of LkHa 263 ABC, 0.005-0.021 M_sun for S18 ABab, 0.03-0.18 M_sun for LkHa 264 A, and 0.023-0.23 M_sun for LkHa 262. The disk mass found for LkHa 263 ABC is consistent with the 0.0018 M_sun inferred from the scattered light image of the edge-on disk around component C. Comparison to earlier 13CO line observations indicates CO depletion by up to a factor 300 with respect to dark-cloud values. The spectral energy distributions (SED) suggest grain growth, possibly to sizes of a few hundred micron, but our spatially unresolved data cannot rule out opacity as an explanation for the SED shape. Our observations show that these T Tauri stars are still surrounded by significant reservoirs of cold material at an age of 1-5 Myr. We conclude that the observed differences in disk mass are likely explain...

  1. Planetary System Formation in Protoplanetary Disk around HL Tauri

    CERN Document Server

    Akiyama, Eiji; Hayashi, Masahiko; Iguchi, Satoru

    2015-01-01

    We re-process the Atacama Large Millimeter/Submillimeter Array (ALMA) long-baseline science verification data taken toward HL Tauri. As shown by the previous work, we confirm that the high spatial resolution (~ 0."019, corresponding to ~ 2.7 AU) dust continuum images at \\lambda = 0.87, 1.3, and 2.9 mm exhibit a multiple ring-like gap structure in the circumstellar disk. Assuming that the observed gaps are opened up by currently forming, unseen bodies, we estimate the mass of such hypothetical bodies based on following two approaches; the Hill radius analysis and a more elaborated approach developed from the angular momentum transfer analysis in gas disks. For the former, the measured gap widths are used for calibrating the mass of the bodies, while for the latter, the measured gap depths are utilized. We show that their masses are likely comparable to or less than the mass of Jovian planets, and then discuss an origin of the observed gap structure. By evaluating Toomre's gravitational instability (GI) conditi...

  2. SPECTROPOLARIMETRY OF THE CLASSICAL T TAURI STAR BP TAU

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Wei; Johns-Krull, Christopher M., E-mail: wc2@rice.edu, E-mail: cmj@rice.edu [Department of Physics and Astronomy, Rice University, Houston, TX 77005 (United States)

    2013-10-20

    We implement a least-squares deconvolution (LSD) code to study magnetic fields on cool stars. We first apply our code to high-resolution optical echelle spectra of 53 Cam (a magnetic Ap star) and three well-studied cool stars (Arcturus, 61 Cyg A, and ξ Boo A) as well as the Sun (by observing the asteroid Vesta) as tests of the code and the instrumentation. Our analysis is based on several hundred photospheric lines spanning the wavelength range 5000 Å to 9000 Å. We then apply our LSD code to six nights of data on the Classical T Tauri Star BP Tau. A maximum longitudinal field of 370 ± 80 G is detected from the photospheric lines on BP Tau. A 1.8 kG dipole tilted at 129° with respect to the rotation axis and a 1.4 kG octupole tilted at 104° with respect to the rotation axis, both with a filling factor of 0.25, best fit our LSD Stokes V profiles. Measurements of several emission lines (He I 5876 Å, Ca II 8498 Å, and 8542 Å) show the presence of strong magnetic fields in the line formation regions of these lines, which are believed to be the base of the accretion footpoints. The field strength measured from these lines shows night-to-night variability consistent with rotation of the star.

  3. Constraints on the ionizing flux emitted by T Tauri stars

    CERN Document Server

    Alexander, R D; Pringle, J E

    2005-01-01

    We present the results of an analysis of ultraviolet observations of T Tauri Stars (TTS). By analysing emission measures taken from the literature we derive rates of ionizing photons from the chromospheres of 5 classical TTS in the range ~10^41-10^44 photons/s, although these values are subject to large uncertainties. We propose that the HeII/CIV line ratio can be used as a reddening-independent indicator of the hardness of the ultraviolet spectrum emitted by TTS. By studying this line ratio in a much larger sample of objects we find evidence for an ionizing flux which does not decrease, and may even increase, as TTS evolve. This implies that a significant fraction of the ionizing flux from TTS is not powered by the accretion of disc material onto the central object, and we discuss the significance of this result and its implications for models of disc evolution. The presence of a significant ionizing flux in the later stages of circumstellar disc evolution provides an important new constraint on disc photoev...

  4. The Line-Profile Variations of Theta2 Tauri

    Science.gov (United States)

    Kennelly, E. J.; Walker, G. A. H.

    1996-04-01

    With a 5.4-hour time series of high-resolution CFHT spectra, the oscillations of the rapidly-rotating delta Scuti star Theta2 Tauri (A7 IV + A5 V) are investigated. Line-profile variations are discovered and identified with the spectrum of the primary star of this binary system. Radial velocity variations are derived from the data and analyzed to reveal an oscillation frequency near 13.7 cycles day^-1. Variations within the absorption profiles are analyzed with a Fourier-Doppler Imaging (FDI) technique to reveal that high-degree oscillations with a frequency of 16.1 cycles day ^-1 and an apparent degree of about l = 8 are also present in the star. Whereas the low-degree variations of Theta2 Tau have been shown to be consistent with p-modes of radial order n=2 or 3, the identification of the high-degree variations in terms of pressure modes requires confirmation with theoretical models. (SECTION: Stars)

  5. Formation of simple organic molecules in inner T Tauri disks

    CERN Document Server

    Agundez, Marcelino; Goicoechea, Javier R

    2008-01-01

    We present time dependent chemical models for a dense and warm O-rich gas exposed to a strong far ultraviolet field aiming at exploring the formation of simple organic molecules in the inner regions of protoplanetary disks around T Tauri stars. An up-to-date chemical network is used to compute the evolution of molecular abundances. Reactions of H2 with small organic radicals such as C2 and C2H, which are not included in current astrochemical databases, overcome their moderate activation energies at warm temperatures and become very important for the gas phase synthesis of C-bearing molecules. The photodissociation of CO and release of C triggers the formation of simple organic species such as C2H2, HCN, and CH4. In timescales between 1 and 10,000 years, depending on the density and FUV field, a steady state is reached in the model in which molecules are continuously photodissociated but also formed, mainly through gas phase chemical reactions involving H2. The application of the model to the upper layers of i...

  6. Post-T Tauri Stars in the Nearest OB Association

    CERN Document Server

    Mamajek, E E; Liebert, J; Mamajek, Eric E.; Meyer, Michael R.; Liebert, James

    2002-01-01

    We present results of a spectroscopic survey of X-ray- and proper motion-selected samples of late-type stars in the Lower Cen-Cru (LCC) and Upper Cen-Lup (UCL) subgroups of the nearest OB association: Sco-Cen. The primary goals of the survey are to determine the star-formation history of the OB subgroups, and to assess the frequency of accreting stars in a sample dominated by ``post-T Tauri'' pre-MS stars. We investigate two samples: (1) ACT and TRC proper motion candidates with X-ray counterparts in the ROSAT All-Sky Survey BSC, and (2) G and K-type Hipparcos candidate members (de Zeeuw et al. 1999). We obtained optical spectra of 130 candidates with the MSSSO 2.3-m DBS. Pre-MS stars were identified by (1) strong Li 6707A absorption, (2) subgiant surface gravities, (3) proper motions consistent with Sco-Cen membership, and (4) HRD positions consistent with being pre-MS. We demonstrate that measuring the gravity-sensitive band-ratio of Sr II 4077A to Fe I 4071A is a valuable means of discriminating pre-MS and...

  7. The V471 Tauri System: A Multi-datatype Probe

    CERN Document Server

    Vaccaro, Todd R; Van Hamme, Walter; Terrell, Dirk

    2015-01-01

    V471 Tauri, a white dwarf--red dwarf eclipsing binary in the Hyades, is well known for stimulating development of common envelope theory, whereby novae and other cataclysmic variables form from much wider binaries by catastrophic orbit shrinkage. Our evaluation of a recent imaging search that reported negative results for a much postulated third body shows that the object could have escaped detection or may have actually been seen. The balance of evidence continues to favor a brown dwarf companion about 12 AU from the eclipsing binary. A recently developed algorithm finds unified solutions from three datatypes. New radial velocities (RVs) of the red dwarf and BV RCIC light curves are solved simultaneously along with white dwarf and red dwarf RVs from the literature, uvby data, the MOST mission light curve, and 40 years of eclipse timings. Precision-based weighting is the key to proper information balance among the various datasets. Timewise variation of modeled starspots allows unified solution of multiple da...

  8. Modeling Rotational Evolution of Young T Tauri Stars

    Science.gov (United States)

    Aidle Esin, Ann; Baxter, E.; Corrales, L.

    2007-12-01

    Measurements of rotational periods of pre-main sequence stars in several young open clusters reveal a uniform trend. Stars with masses below 0.25 solar show a bimodal period distribution with fast and slow rotators clustered around 2 day and 8 day periods, respectively, while the period distribution of low-mass stars lacks the slow rotating component. In one popular interpretation of this observational result the slow rotators are identified with the "disk locked'' stars whose periods are fixed to the orbital periods at the inner edge of the accretion disk; the fast rotators are then assumed to have lost their connection to the disk. We argue that this scenario can account for observations only if the mass accretion rate in the disk declines with time. We construct a simple model for the period evolution in T Tauri stars that includes realistic prescriptions for the mass accretion rate, radius evolution and a better treatment of the transition between strong and weak accretion disk coupling. Using this model to simulate period distribution for a young cluster, we can qualitatively reproduce the observed results, but only if the accretion is allowed to continue after the disk and the star are no longer locked. This work was supported by the grant from the Research Corporation.

  9. Det Digitale Nærvær

    DEFF Research Database (Denmark)

    Heilesen, Simon

    Computer-medieret kommunikation (CMC – via intranet- og internet, ”allestedsnærværende computing” mm. ), er grundlaget for det informations- og videnssamfund, der begynder at tage form i disse år. CMC er blevet kolossalt udbredt de seneste 10 – 15 år og har forandret den måde vi udsender og søger...... information, kommunikerer med hinanden både privat og i organisationer, samarbejder, underviser og tilegner os viden. Denne bog går tæt på tre udvalgte områder inden for den computer-medierede kommunikation: · Videndeling i formelle og uformelle organisationer, · Netbaseret samarbejde og læring, · Design af...

  10. Mass accretion rates in self-regulated disks of T Tauri stars

    CERN Document Server

    Vorobyov, E I

    2008-01-01

    We have studied numerically the evolution of protostellar disks around intermediate and upper mass T Tauri stars (0.25 M_sun < M_st < 3.0 M_sun) that have formed self-consistently from the collapse of molecular cloud cores. In the T Tauri phase, disks settle into a self-regulated state, with low-amplitude nonaxisymmetric density perturbations persisting for at least several million years. Our main finding is that the global effect of gravitational torques due to these perturbations is to produce disk accretion rates that are of the correct magnitude to explain observed accretion onto T Tauri stars. Our models yield a correlation between accretion rate M_dot and stellar mass M_st that has a best fit M_dot \\propto M_st^{1.7}, in good agreement with recent observations. We also predict a near-linear correlation between the disk accretion rate and the disk mass.

  11. Evolution of the T Tauri star population in the Lupus association

    Science.gov (United States)

    Galli, P. A. B.; Bertout, C.; Teixeira, R.; Ducourant, C.

    2015-08-01

    Aims: In a recent study, we derived individual distances for 109 pre-main sequence stars that define the Lupus kinematic association of young stars. Here, we use these new distances to derive the masses and ages of Lupus T Tauri stars with the aim of better constraining the lifetime of their circumstellar disks. Methods: Using the photometric and spectroscopic information available in the literature, we computed the photospheric luminosity of 92 T Tauri stars in the Lupus association. Then, we estimated their masses and ages from theoretical evolutionary models. Based on Monte Carlo simulations and statistical tests, we compare the mass and age distribution of the classical T Tauri stars (CTTS) and weak-line T Tauri (WTTS) in our sample. Results: We show that the CTTSs are on average younger than the WTTSs and that the probability that both T Tauri subclasses are drawn from the same mass and age parental distribution is very low. Our results favor the scenario proposed earlier for the Taurus-Auriga association, where the CTTSs evolve into WTTSs when their disks are fully accreted by the star. Based on an empirical disk model, we find that the average disk lifetime for the T Tauri stars in the Lupus association is τd = 3 × 106 (M∗/M⊙)0.55 yr. Conclusions: We find evidence that the average lifetime of the circumstellar disks in the Lupus association is shorter than in the Taurus-Auriga association and discuss the implications of this result. Table 1 is available in electronic form at http://www.aanda.org

  12. Mid-infrared interferometric variability of DG Tauri: Implications for the inner-disk structure

    Science.gov (United States)

    Varga, J.; Gabányi, K. É.; Ábrahám, P.; Chen, L.; Kóspál, Á.; Menu, J.; Ratzka, Th.; van Boekel, R.; Dullemond, C. P.; Henning, Th.; Jaffe, W.; Juhász, A.; Moór, A.; Mosoni, L.; Sipos, N.

    2017-08-01

    Context. DG Tau is a low-mass pre-main sequence star, whose strongly accreting protoplanetary disk exhibits a so-far enigmatic behavior: its mid-infrared thermal emission is strongly time-variable, even turning the 10 μm silicate feature from emission to absorption temporarily. Aims: We look for the reason for the spectral variability at high spatial resolution and at multiple epochs. Methods: Infrared interferometry can spatially resolve the thermal emission of the circumstellar disk, also giving information about dust processing. We study the temporal variability of the mid-infrared interferometric signal, observed with the VLTI/MIDI instrument at six epochs between 2011 and 2014. We fit a geometric disk model to the observed interferometric signal to obtain spatial information about the disk. We also model the mid-infrared spectra by template fitting to characterize the profile and time dependence of the silicate emission. We use physically motivated radiative transfer modeling to interpret the mid-infrared interferometric spectra. Results: The inner disk (r 1-3 au) spectra show a crystalline silicate feature in emission, similar to the spectra of comet Hale-Bopp. The striking difference between the inner and outer disk spectral feature is highly unusual among T Tauri stars. The mid-infrared variability is dominated by the outer disk. The strength of the silicate feature changed by more than a factor of two. Between 2011 and 2014 the half-light radius of the mid-infrared-emitting region decreased from 1.15 to 0.7 au. Conclusions: For the origin of the absorption we discuss four possible explanations: a cold obscuring envelope, an accretion heated inner disk, a temperature inversion on the disk surface and a misaligned inner geometry. The silicate emission in the outer disk can be explained by dusty material high above the disk plane, whose mass can change with time, possibly due to turbulence in the disk. Based on observations made with the ESO Very Large

  13. The Bizarre Spectral Variability of Central Stars of Planetary Nebulae

    CERN Document Server

    De Marco, Orsola; Bond, Howard E; Harmer, Dianne

    2007-01-01

    A radial velocity (RV) survey to detect central stars in binary systems was carried out between 2002 and 2004. De Marco et al. (2004) reported that 10 out of 11 monitored stars exhibited strong RV variability, but periods were not detected. Since other mechanisms, such as wind variability, can cause apparent RV variations, we monitored 4 of the 10 RV-variable stars at echelle resolutions to determine the origin of the variability. Although RV changes are confirmed for all four stars, none of them can be ascribed to binarity at this time. However, only for IC4593 is wind variability able to explain most (though not all) spectral variability. For BD+332642, no wind and no pulsations appear to be the origin of the RV changes. Finally, M1-77 and M2-54, both known to be irregular photometric variables, exhibit dramatic RV and line shape variability of the hydrogen and HeI absorption lines, as well as large RV variability of weaker lines, which do not change in shape. There is no satisfactory explanation of this va...

  14. Hydrodynamic Modeling of Accretion Impacts in Classical T Tauri Stars: Radiative Heating of the Pre-shock Plasma

    CERN Document Server

    Costa, G; Peres, G; Argiroffi, C; Bonito, R

    2016-01-01

    Context. It is generally accepted that, in Classical T Tauri Stars, the plasma from the circumstellar disc accretes onto the stellar surface with free fall velocity, and the impact generates a shock. The impact region is expected to contribute to emission in different spectral bands; many studies have confirmed that the X-rays arise from the post-shock plasma but, otherwise, there are no studies in the literature investigating the origin of the observed UV emission which is apparently correlated to accretion. Aims. We investigated the effect of radiative heating of the infalling material by the post-shock plasma at the base of the accretion stream with the aim to identify in which region a significant part of the UV emission originates. Methods. We developed a 1D hydrodynamic model describing the impact of an accretion stream onto the stellar surface; the model takes into account the gravity, the radiative cooling of an optically thin plasma, the thermal conduction, and the heating due to absorption of X-ray ...

  15. A single-dish survey of the HCO+, HCN, and CN emission toward the T Tauri disk population in Taurus

    CERN Document Server

    Salter, D M; van der Burg, R F J; Kristensen, L E; Brinch, C

    2011-01-01

    (Abridged) As the stellar X-ray and UV light penetration of a protoplanetary disk depends sensitively on the dust properties, trace molecular species like HCO+, HCN, and CN are expected to show marked differences from photoprocessing effects as the dust content in the disk evolves. We investigate the evolution of the UV irradiation of the molecular gas in a sample of classical T Tauri stars in Taurus that exhibit a wide range in grain growth and dust settling properties. We obtained HCO+ (J=3-2), HCN (J=3-2), and CN (J=2-1) observations of 13 sources with the JCMT. Our sample has 1.3mm fluxes in excess of 75mJy, indicating the presence of significant dust reservoirs; a range of dust settling as traced through their spectral slopes between 6, 13, and 25 microns; and varying degrees of grain growth as extrapolated from the strength of their 10-micron silicate emission features. We compare the emission line strengths with the sources' continuum flux and infrared features, and use detailed modeling based on two d...

  16. Revealing the inner circumstellar disk of the T Tauri star S CrA N using the VLTI

    CERN Document Server

    Vural, J; Kraus, S; Weigelt, G; Driebe, T; Benisty, M; Dugué, M; Massi, F; Monin, J -L; Vannier, M

    2012-01-01

    Aims: We investigate the structure of the circumstellar disk of the T Tauri star S CrA N and test whether the observations agree with the standard picture proposed for Herbig Ae stars. Methods: Our observations were carried out with the VLTI/AMBER instrument in the H and K bands with the low spectral resolution mode. For the interpretation of our near-infrared AMBER and archival mid-infrared MIDI visibilities, we employed both geometric and temperature-gradient models. Results: To characterize the disk size, we first fitted geometric models consisting of a stellar point source, a ring-shaped disk, and a halo structure to the visibilities. In the H and K bands, we measured ring-fit radii of 0.73 +- 0.03 mas (corresponding to 0.095 +- 0.018 AU for a distance of 130 pc) and 0.85 +- 0.07 mas (0.111 +- 0.026 AU), respectively. This K-band radius is approximately two times larger than the dust sublimation radius of ~0.05 AU expected for a dust sublimation temperature of 1500 K and gray dust opacities, but approxima...

  17. Impacts of fragmented accretion streams onto Classical T Tauri Stars: UV and X-ray emission lines

    CERN Document Server

    Colombo, Salvatore; Peres, Giovanni; Argiroffi, Costanza; Reale, Fabio

    2016-01-01

    Context. The accretion process in Classical T Tauri Stars (CTTSs) can be studied through the analysis of some UV and X-ray emission lines which trace hot gas flows and act as diagnostics of the post-shock downfalling plasma. In the UV band, where higher spectral resolution is available, these lines are characterized by rather complex profiles whose origin is still not clear. Aims. We investigate the origin of UV and X-ray emission at impact regions of density structured (fragmented) accretion streams.We study if and how the stream fragmentation and the resulting structure of the post-shock region determine the observed profiles of UV and X-ray emission lines. Methods. We model the impact of an accretion stream consisting of a series of dense blobs onto the chromosphere of a CTTS through 2D MHD simulations. We explore different levels of stream fragmentation and accretion rates. From the model results, we synthesize C IV (1550 {\\AA}) and OVIII (18.97 {\\AA}) line profiles. Results. The impacts of accreting blob...

  18. The Origin of T Tauri X-ray Emission: New Insights from the Chandra Orion Ultradeep Project

    CERN Document Server

    Preibisch, T; Favata, F; Feigelson, E D; Flaccomio, E; Getman, K; Micela, G; Sciortino, S; Stassun, K G; Stelzer, B; Zinnecker, H; Preibisch, Thomas; Kim, Yong -Cheol; Favata, Fabio; Feigelson, Eric D.; Flaccomio, Ettore; Getman, Konstantin; Micela, Giusi; Sciortino, Salvatore; Stassun, Keivan; Stelzer, Beate; Zinnecker, Hans

    2005-01-01

    We use the data of the Chandra Orion Ultradeep Project (COUP) to study the nearly 600 X-ray sources that can be reliably identified with optically well characterized T Tauri stars (TTS) in the Orion Nebula Cluster. We detect X-ray emission from more than 97% of the optically visible late-type (spectral types F to M) cluster stars. This proofs that there is no ``X-ray quiet'' population of late-type stars with suppressed magnetic activity. All TTS with known rotation periods lie in the saturated or super-saturated regime of the relation between activity and Rossby numbers seen for main-sequence (MS) stars, but the TTS show a much larger scatter in X-ray activity than seen for the MS stars. Strong near-linear relations between X-ray luminosities, bolometric luminosities and mass are present. We also find that the fractional X-ray luminosity rises slowly with mass over the 0.1 - 2 M_sun range. The plasma temperatures determined from the X-ray spectra of the TTS are much hotter than in MS stars, but seem to follo...

  19. Evaluation of cytokine and chemokine response elicited by Rv2204c and Rv0753c to detect latent tuberculosis infection.

    Science.gov (United States)

    Pathakumari, Balaji; Prabhavathi, Maddineni; Raja, Alamelu

    2015-12-01

    Latent TB infection (LTBI) is one of the major contributing factors for the high incidence of TB in India that in turn significantly contributes to the pool of active TB. Hence, identification and treatment of LTBI is of utmost importance. Currently, no specific diagnostic test is available for LTBI. Earlier, in our immunoproteomic analysis, we identified Rv2204c and Rv0753c protein-containing fractions induced significantly higher interferon-gamma (IFN-γ) response in LTBI than in active TB. In this study, we evaluated cytokine and chemokine response against M. tuberculosis antigens for improving LTBI identification. Two M. tb proteins Rv2204c and Rv0753c were cloned, over expressed in E. coli and purified by affinity chromatography. Antigen-specific immune response was evaluated in 39 pulmonary TB patients (PTB) and 35 healthy house-hold contacts (HHC). After whole blood culture for 6 days, the secretion of cytokines and chemokines were quantified in culture supernatants using Enzyme Linked Immune Sorbent Assay (ELISA). Antigen specific cytokines such as interferon gamma (IFN-γ), interleukin-6 (IL-6), IL-8, IL-12p40 and chemokines like monocyte chemotactic proteins MCP-1, MCP-2 were significantly higher in HHC than PTB. In contrast to other cytokines, tumor necrosis factor-alpha (TNF)-α response was significantly increased in PTB compared with HHC. Both Rv2204c and Rv0753c antigen specific IFN-γ response showed 86% positivity in HHC; whereas in PTB, these antigens showed 18% and 21% positivity respectively. Rv2204c antigen-specific IFN-γ/TNF-α response displayed maximum positivity of 91% in HHC and minimum positivity of 10% (4/39) in PTB. Rv2204c and Rv0753c specific IFN-γ and IFN-γ/TNF-α responses showed the most promising accuracy in identifying LTBI.

  20. Temperature and wind speed data from XBT and bucket casts from the R/V OCEANOGRAPHER AND R/V RESEARCHER I (NODC Accession 7700678)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Air temperature, water temperature, and wind speed data were collected using XBT and bucket casts from the R/V OCEANGRAPHER AND R/V RESEARCHER I.

  1. Differential expression of two members of Rv1922-LipD operon in Mycobacterium tuberculosis: Does rv1923 qualify for membership?

    Science.gov (United States)

    Dogra, Nandita; Arya, Stuti; Singh, Kashmir; Kaur, Jagdeep

    2015-07-01

    rv1922 and rv1923 (lipD) are members of Rv1922-LipD operon in the genome of Mycobacterium tuberculosis. rv1922 was expressed under aerobic and stress conditions, whereas rv1923 was not expressed in aerobically grown bacteria but expressed moderately under oxidative stress conditions. Different expression of both the operonic genes under normal and stress conditions posed apprehensions for the inclusion of rv1922 and rv1923 in the same operon. The results from this study indicated that although the genes were expressed in an operonic manner, there existed the possibility of differential regulation for rv1923 which has been supported by in silico analysis for the presence of putative internal regulatory sites in the operon.

  2. Characterization of a nitric oxide synthase from the plant kingdom: NO generation from the green alga Ostreococcus tauri is light irradiance and growth phase dependent.

    Science.gov (United States)

    Foresi, Noelia; Correa-Aragunde, Natalia; Parisi, Gustavo; Caló, Gonzalo; Salerno, Graciela; Lamattina, Lorenzo

    2010-11-01

    The search for a nitric oxide synthase (NOS) sequence in the plant kingdom yielded two sequences from the recently published genomes of two green algae species of the Ostreococcus genus, O. tauri and O. lucimarinus. In this study, we characterized the sequence, protein structure, phylogeny, biochemistry, and expression of NOS from O. tauri. The amino acid sequence of O. tauri NOS was found to be 45% similar to that of human NOS. Folding assignment methods showed that O. tauri NOS can fold as the human endothelial NOS isoform. Phylogenetic analysis revealed that O. tauri NOS clusters together with putative NOS sequences of a Synechoccocus sp strain and Physarum polycephalum. This cluster appears as an outgroup of NOS representatives from metazoa. Purified recombinant O. tauri NOS has a K(m) for the substrate l-Arg of 12 ± 5 μM. Escherichia coli cells expressing recombinant O. tauri NOS have increased levels of NO and cell viability. O. tauri cultures in the exponential growth phase produce 3-fold more NOS-dependent NO than do those in the stationary phase. In O. tauri, NO production increases in high intensity light irradiation and upon addition of l-Arg, suggesting a link between NOS activity and microalgal physiology.

  3. Confirming and Improving Ross Variable Star RV Del

    Science.gov (United States)

    Linder, Tyler R.; Sanchez, Rick; Palser, Sage; Schultze, Kendra; Kenney, Jessica; Thompson, Briana; DeCoster, Richard; Mills, Frank; Osborn, Wayne; Hoette, Vivian L.; Skynet Junior Scholars; Stone Edge Observatory

    2017-01-01

    RV Del is an intrinsic pulsating variable star in the constellation Delphinus, discovered by Ross (1926). The AAVSO list RV Del as a RRAB type of variable star. RV Del has been found to have a magnitude that varies from 12.9 - 14.2 and a period of 11.9553 hours.The purpose of our research of RV Del is to confirm and improve previous results as well as explore different methods to engage middle school students in the scientific method and astronomy. The SKYNET network of telescopes allows students to request images from a group of international research class telescopes. The telescope request process allows students first-hand experience in astronomy while the data analysis allows students to understand advance software systems to produce publishable results. Data is being gathered using the SKYNET network and Stone Edge Observatory to gather photometry of RV Del and create a new light curve. Findings will be presented the January 2017 AAS.

  4. Accretion Rates for T Tauri Stars Using Nearly Simultaneous Ultraviolet and Optical Spectra

    CERN Document Server

    Ingleby, Laura; Herczeg, Gregory; Blaty, Alex; Walter, Frederick; Ardila, David; Alexander, Richard; Edwards, Suzan; Espaillat, Catherine; Gregory, Scott G; Hillenbrand, Lynne; Brown, Alexander

    2013-01-01

    We analyze the accretion properties of 21 low mass T Tauri stars using a dataset of contemporaneous near ultraviolet (NUV) through optical observations obtained with the Hubble Space Telescope Imaging Spectrograph (STIS) and the ground based Small and Medium Aperture Research Telescope System (SMARTS), a unique dataset because of the nearly simultaneous broad wavelength coverage. Our dataset includes accreting T Tauri stars (CTTS) in Taurus, Chamaeleon I, $\\eta$ Chamaeleon and the TW Hydra Association. For each source we calculate the accretion rate by fitting the NUV and optical excesses above the photosphere, produced in the accretion shock, introducing multiple accretion components characterized by a range in energy flux (or density) for the first time. This treatment is motivated by models of the magnetospheric geometry and accretion footprints, which predict that high density, low filling factor accretion spots co-exist with low density, high filling factor spots. By fitting the UV and optical spectra wi...

  5. Mechanical Equilibrium of Hot, Large-Scale Magnetic Loops on T Tauri Stars

    CERN Document Server

    Aarnio, Alicia; Jardine, Moira; Gregory, Scott G

    2011-01-01

    The most extended, closed magnetic loops inferred on T Tauri stars confine hot, X-ray emitting plasma at distances from the stellar surface beyond the the X-ray bright corona and closed large-scale field, distances comparable to the corotation radius. Mechanical equilibrium models have shown that dense condensations, or "slingshot prominences", can rise to great heights due to their density and temperatures cooler than their environs. On T Tauri stars, however, we detect plasma at temperatures hotter than the ambient coronal temperature. By previous model results, these loops should not reach the inferred heights of tens of stellar radii where they likely no longer have the support of the external field against magnetic tension. In this work, we consider the effects of a stellar wind and show that indeed, hot loops that are negatively buoyant can attain a mechanical equilibrium at heights above the typical extent of the closed corona and the corotation radius.

  6. Stellar energetic particle ionization in protoplanetary disks around T Tauri stars

    Science.gov (United States)

    Rab, Ch.; Güdel, M.; Padovani, M.; Kamp, I.; Thi, W.-F.; Woitke, P.; Aresu, G.

    2017-07-01

    Context. Anomalies in the abundance measurements of short lived radionuclides in meteorites indicate that the protosolar nebulae was irradiated by a large number of energetic particles (E ≳ 10 MeV). The particle flux of the contemporary Sun cannot explain these anomalies. However, similar to T Tauri stars the young Sun was more active and probably produced enough high energy particles to explain those anomalies. Aims: We aim to study the interaction of stellar energetic particles with the gas component of the disk (i.e. ionization of molecular hydrogen) and identify possible observational tracers of this interaction. Methods: We used a 2D radiation thermo-chemical protoplanetary disk code to model a disk representative for T Tauri stars. We used a particle energy distribution derived from solar flare observations and an enhanced stellar particle flux proposed for T Tauri stars. For this particle spectrum we calculated the stellar particle ionization rate throughout the disk with an accurate particle transport model. We studied the impact of stellar particles for models with varying X-ray and cosmic-ray ionization rates. Results: We find that stellar particle ionization has a significant impact on the abundances of the common disk ionization tracers HCO+ and N2H+, especially in models with low cosmic-ray ionization rates (e.g. 10-19 s-1 for molecular hydrogen). In contrast to cosmic rays and X-rays, stellar particles cannot reach the midplane of the disk. Therefore molecular ions residing in the disk surface layers are more affected by stellar particle ionization than molecular ions tracing the cold layers and midplane of the disk. Conclusions: Spatially resolved observations of molecular ions tracing different vertical layers of the disk allow to disentangle the contribution of stellar particle ionization from other competing ionization sources. Modelling such observations with a model like the one presented here allows to constrain the stellar particle flux in

  7. Turbulence-driven Polar Winds from T Tauri Stars Energized by Magnetospheric Accretion

    CERN Document Server

    Cranmer, Steven R

    2008-01-01

    Pre-main-sequence stars are observed to be surrounded by both accretion flows and some kind of wind or jet-like outflow. Recent work by Matt and Pudritz has suggested that if classical T Tauri stars exhibit stellar winds with mass loss rates about 0.1 times their accretion rates, the wind can carry away enough angular momentum to keep the stars from being spun up unrealistically by accretion. This paper presents a preliminary set of theoretical models of accretion-driven winds from the polar regions of T Tauri stars. These models are based on recently published self-consistent simulations of the Sun's coronal heating and wind acceleration. In addition to the convection-driven MHD turbulence (which dominates in the solar case), we add another source of wave energy at the photosphere that is driven by the impact of plasma in neighboring flux tubes undergoing magnetospheric accretion. This added energy, determined quantitatively from the far-field theory of MHD wave generation, is sufficient to produce T Tauri-l...

  8. X-ray deficiency on strong accreting T Tauri stars - Comparing Orion with Taurus

    CERN Document Server

    Bustamante, Ignacio; Bouy, Hervé; Manara, Carlo; Ribas, Álvaro; Riviere-Marichalar, Pablo

    2015-01-01

    Depending on whether a T Tauri star accretes material from its circumstellar disk or not, different X-ray emission properties can be found. The accretion shocks produce cool heating of the plasma, contributing to the soft X-ray emission from the star. Using X-ray data from the Chandra Orion Ultra-deep Project and accretion rates that were obtained with the Hubble Space Telescope/WFPC2 photometric measurements in the Orion Nebula Cluster, we studied the relation between the accretion processes and the X-ray emissions of a coherent sample of T Tauri sources in the region. We performed regression and correlation analyses of our sample of T Tauri stars between the X-ray parameters, stellar properties, and the accretion measurements. We find that a clear anti-correlation is present between the residual X-ray luminosity and the accretion rates in our samples in Orion that is consistent with that found on the XMM-Newton Extended Survey of the Taurus molecular cloud (XEST) study. We provide a catalog with X-ray lumin...

  9. A search for the lasts gasps of disk accretion in Orion T Tauri stars

    Science.gov (United States)

    Clark, Catherine; Briceno, Cesar; Calvet, Nuria; Hernandez, Jesus

    2017-01-01

    Using the echelle mode of the Michigan/Magellan Fiber System (M2FS) on the Magellan/Clay telescope at Las Campanas Observatory, we obtained high resolution spectra (R~35000) of a sample of ~4 - 10 Myr old T Tauri stars distributed in ten 0.5 deg diameter fields in the Orion OB1 association.We present here a search for accretion signatures among a sample of weak-line T Tauri stars (WTTS). These are young stars that on the basis of their classification in low-resolution spectra, are assumed to lack a primordial disk and therefore should not be actively accreting. We look for signatures of disk accretion at modest or low levels by measuring the width at 10% height of the H-alpha profile, and looking for a redshifted absorption feature. In parallel, we determine which WTTS among the M2FS sample have infrared excesses indicating a circumstellar disk, to see which disk-bearing WTTS also show indications of accretion. We propose that such WTTS accreting at low levels are T Tauri stars at or nearing the end of their accretion phase. Our goal is to build a large sample of these objects so that we can place statistical contraints on how long the accretion phase lasts in solar-like and low-mass stars.

  10. Imaging the circumstellar environment of the young T Tauri star SU Aurigae

    CERN Document Server

    Jeffers, S V; Canovas, H; Rodenhuis, M; Keller, C U

    2013-01-01

    The circumstellar environments of classical T Tauri stars are challenging to directly image because of their high star-to-disk contrast ratio. One method to overcome this is by using imaging polarimetry where scattered and consequently polarised starlight from the star's circumstellar disk can be separated from the unpolarised light of the central star. We present images of the circumstellar environment of SU Aur, a classical T Tauri star at the transition of T Tauri to Herbig stars. The images directly show that the disk extends out to ~500 au with an inclination angle of $\\sim$ 50$^\\circ$. Using interpretive models, we derived very small grains in the surface layers of its disk, with a very steep size- and surface-density distribution. Additionally, we resolved a large and extended nebulosity in our images that is most likely a remnant of the prenatal molecular cloud. The position angle of the disk, determined directly from our images, rules out a polar outflow or jet as the cause of this large-scale nebulo...

  11. X-ray Diagnostics of Grain Depletion in Matter Accreting onto T Tauri Stars

    CERN Document Server

    Hartmann, J J D P T L

    2005-01-01

    Recent analysis of high resolution Chandra X-ray spectra has shown that the Ne/O abundance ratio is remarkably constant in stellar coronae. Based on this result, we point out the utility of the Ne/O ratio as a discriminant for accretion-related X-rays from T Tauri stars, and for probing the measure of grain-depletion of the accreting material in the inner disk. We apply the Ne/O diagnostic to the classical T Tauri stars BP Tau and TW Hya--the two stars found to date whose X-ray emission appears to originate, at least in part, from accretion activity. We show that TW Hya appears to be accreting material which is significantly depleted in O relative to Ne. In constrast, BP Tau has an Ne/O abundance ratio consistent with that observed for post-T Tauri stars. We interpret this result in terms of the different ages and evolutionary states of the circumstellar disks of these stars. In the young BP Tau disk (age 0.6 Myr) dust is still present near the disk corotation radius and can be ionized and accreted, re-releas...

  12. Multiwavelength study of the magnetically active T Tauri star HD 283447

    Science.gov (United States)

    Feigelson, Eric D.; Welty, Alan D.; Imhoff, Catherine; Hall, Jeffrey C.; Etzel, Paul B.; Phillips, Robert B.; Lonsdale, Colin J.

    1994-01-01

    We observed the luminous T Tauri star HD 283447 = V773 Tauri simultaneously at X-ray, ultraviolet, optical photometric and spectroscopic, and radio wavelengths for several hours on UT 1992 September 11. ROSAT, IUE, Very Large Array (VLA) and an intercontinental Very Long Baseline Interferometry (VLBI) network, and three optical observatories participated in the campaign. The star is known for its unusually high and variable nonthermal radio continuum emission. High levels of soft X-ray and Mg II line emission are discovered, with luminosity L(sub x) = 5.5 x 10(exp 30) ergs/s (0.2 - 2 keV) and L(sub Mg II) = 1 x 10(exp 29) ergs/s, respectively. Optically, the spectrum exhibits rather weak characteristics of `classical' T Tauri stars. A faint, broad emission line component, probably due to a collimated wind or infall, is present. During the campaign, the radio luminosity decreased by a factor of 4, while optical/UV lines and X-ray emission remained strong but constant. The large gyrosynchrotron-emitting regions are therefore decoupled from the chromospheric and coronal emission. Five models for the magnetic geometry around the star are discussed; solar-type activity, dipole magnetosphere, star-disk magnetic coupling, disk magnetic fields, and close binary interaction. The data suggest that two magnetic geometries are simultaneously present: complex multipolar fields like those on the Sun, and a large-scale field possibly associated with the circumstellar disk.

  13. X-ray optical depth diagnostics of T Tauri accretion shocks

    CERN Document Server

    Argiroffi, C; Peres, G; Drake, J J; Santiago, J Lopez; Sciortino, S; Stelzer, B

    2009-01-01

    In classical T Tauri stars, X-rays are produced by two plasma components: a hot low-density plasma, with frequent flaring activity, and a high-density lower temperature plasma. The former is coronal plasma related to the stellar magnetic activity. The latter component, never observed in non-accreting stars, could be plasma heated by the shock formed by the accretion process. However its nature is still being debated. Our aim is to probe the soft X-ray emission from the high-density plasma component in classical T Tauri stars to check whether this is plasma heated in the accretion shock or whether it is coronal plasma. High-resolution X-ray spectroscopy allows us to measure individual line fluxes. We analyze X-ray spectra of the classical T Tauri star MP Muscae and TW Hydrae. Our aim is to evaluate line ratios to search for optical depth effects, which are expected in the accretion-driven scenario. We also derive the plasma emission measure distributions EMD, to investigate whether and how the EMD of accreting...

  14. Modeling the RV jitter of early M dwarfs using tomographic imaging

    CERN Document Server

    Hébrard, É M; Delfosse, X; Morin, J; Moutou, C; Boisse, I

    2016-01-01

    In this paper we show how tomographic imaging (Zeeman Doppler Imaging, ZDI) can be used to characterize stellar activity and magnetic field topologies, ultimately allowing to filter out the radial velocity (RV) activity jitter of M-dwarf moderate rotators. This work is based on spectropolarimetric observations of a sample of five weakly-active early M-dwarfs (GJ 205, GJ 358, GJ 410, GJ479, GJ 846) with HARPS-Pol and NARVAL. These stars have v sin i and RV jitters in the range 1-2 km/s and 2.7-10.0 m/s rms respectively. Using a modified version of ZDI applied to sets of phase-resolved Least-Squares- Decon- volved (LSD) profiles of unpolarized spectral lines, we are able to characterize the distribution of active regions at the stellar surfaces. We find that darks spots cover less than 2% of the total surface of the stars of our sample. Our technique is e cient at modeling the rotationally mod- ulated component of the activity jitter, and succeeds at decreasing the amplitude of this com- ponent by typical facto...

  15. V838 Mon and M31-RV: The Stellar Populations Angle

    CERN Document Server

    Siegel, M H; Siegel, Michael H.; Bond, Howard E.

    2006-01-01

    Insight into the origin of unusual events like the eruption of V838 Mon can be obtained from studies of the stellar populations from which they arise. V838 Mon lies in an intriguing region of the Galaxy, toward the warped outer edge of the disk, with significant contributions from the Galactic thick disk and the recently discovered Monoceros tidal stream. The initial distance measures placed V838 Mon in a jumbled region of the Galaxy but the recent shorter distances make it highly likely that V838 Mon was a thin disk star -- likely in a spiral arm -- consistent with the recent detection of a young cluster in the vicinity. We compare V838 Mon to M31-RV, a red variable that erupted in the bulge of M31 in 1988 and had a peak luminosity and spectral evolution very similar to V838 Mon. Archival HST images show no nebulosity or unusual stars at M31-RV's projected location. Moreover, the only stellar population in the field is a canonic old bulge population. This indicates that whatever the origin of the red novae, ...

  16. Hydrodynamic modelling of accretion impacts in classical T Tauri stars: radiative heating of the pre-shock plasma

    Science.gov (United States)

    Costa, G.; Orlando, S.; Peres, G.; Argiroffi, C.; Bonito, R.

    2017-01-01

    Context. It is generally accepted that, in classical T Tauri stars, the plasma from the circumstellar disc accretes onto the stellar surface with free-fall velocity and the impact generates a shock. The impact region is expected to contribute to emission in different spectral bands; many studies have confirmed that the X-rays arise from the post-shock plasma but, otherwise, there are no studies in the literature investigating the origin of the observed UV emission which is apparently correlated to accretion. Aims: We investigated the effect of radiative heating of the infalling material by the post-shock plasma at the base of the accretion stream, with the aim to identify in which region a significant part of the UV emission originates. Methods: We developed a one-dimensional hydrodynamic model describing the impact of an accretion stream onto the stellar surface; the model takes into account the gravity, the radiative cooling of an optically thin plasma, the thermal conduction, and the heating due to absorption of X-ray radiation. The latter term represents the heating of the infalling plasma due to the absorption of X-rays emitted from the post-shock region. Results: We found that the radiative heating of the pre-shock plasma plays a non-negligible role in the accretion phenomenon. In particular, the dense and cold plasma of the pre-shock accretion column is gradually heated up to a few 105K due to irradiation of X-rays arising from the shocked plasma at the impact region. This heating mechanism does not affect significantly the dynamics of the post-shock plasma. On the other hand, a region of radiatively heated gas (that we consider a precursor) forms in the unshocked accretion column and contributes significantly to UV emission. Our model naturally reproduces the luminosity of UV emission lines correlated to accretion and shows that most of the UV emission originates from the precursor.

  17. Stable and unstable accretion in the classical T Tauri stars IM Lup and RU Lup as observed by MOST

    Science.gov (United States)

    Siwak, Michal; Ogloza, Waldemar; Rucinski, Slavek M.; Moffat, Anthony F. J.; Matthews, Jaymie M.; Cameron, Chris; Guenther, David B.; Kuschnig, Rainer; Rowe, Jason F.; Sasselov, Dimitar; Weiss, Werner W.

    2016-03-01

    Results of the time variability monitoring of the two classical T Tauri stars, RU Lup and IM Lup, are presented. Three photometric data sets were utilized: (1) simultaneous (same field) MOST satellite observations over four weeks in each of the years 2012 and 2013, (2) multicolour observations at the South African Astronomical Observatory in April-May of 2013, (3) archival V-filter All Sky Automated Survey (ASAS) data for nine seasons, 2001-2009. They were augmented by an analysis of high-resolution, public-domain VLT-UT2 Ultraviolet Visual Echelle Spectrograph spectra from the years 2000 to 2012. From the MOST observations, we infer that irregular light variations of RU Lup are caused by stochastic variability of hotspots induced by unstable accretion. In contrast, the MOST light curves of IM Lup are fairly regular and modulated with a period of about 7.19-7.58 d, which is in accord with ASAS observations showing a well-defined 7.247 ± 0.026 d periodicity. We propose that this is the rotational period of IM Lup and is due to the changing visibility of two antipodal hotspots created near the stellar magnetic poles during the stable process of accretion. Re-analysis of RU Lup high-resolution spectra with the broadening function approach reveals signs of a large polar coldspot, which is fairly stable over 13 years. As the star rotates, the spot-induced depression of intensity in the broadening function profiles changes cyclically with period 3.710 58 d, which was previously found by the spectral cross-correlation method.

  18. Impacts of fragmented accretion streams onto classical T Tauri stars: UV and X-ray emission lines

    Science.gov (United States)

    Colombo, S.; Orlando, S.; Peres, G.; Argiroffi, C.; Reale, F.

    2016-10-01

    Context. The accretion process in classical T Tauri stars (CTTSs) can be studied through the analysis of some UV and X-ray emission lines which trace hot gas flows and act as diagnostics of the post-shock downfalling plasma. In the UV-band, where higher spectral resolution is available, these lines are characterized by rather complex profiles whose origin is still not clear. Aims: We investigate the origin of UV and X-ray emission at impact regions of density structured (fragmented) accretion streams. We study if and how the stream fragmentation and the resulting structure of the post-shock region determine the observed profiles of UV and X-ray emission lines. Methods: We modeled the impact of an accretion stream consisting of a series of dense blobs onto the chromosphere of a CTTS through two-dimensional (2D) magnetohydrodynamic (MHD) simulations. We explored different levels of stream fragmentation and accretion rates. From the model results, we synthesize C IV (1550 Å) and O VIII (18.97 Å) line profiles. Results: The impacts of accreting blobs onto the stellar chromosphere produce reverse shocks propagating through the blobs and shocked upflows. These upflows, in turn, hit and shock the subsequent downfalling fragments. As a result, several plasma components differing for the downfalling velocity, density, and temperature are present altoghether. The profiles of C IV doublet are characterized by two main components: one narrow and redshifted to speed ≈ 50 km s-1 and the other broader and consisting of subcomponents with redshift to speed in the range 200-400 km s-1. The profiles of O VIII lines appear more symmetric than C IV and are redshifted to speed ≈ 150 km s-1. Conclusions: Our model predicts profiles of C IV line remarkably similar to those observed and explains their origin in a natural way as due to stream fragmentation. Movies are available at http://www.aanda.org

  19. Ajaloolaste juhiks saab Magnus Ilmjärv

    Index Scriptorium Estoniae

    2006-01-01

    Tallinna Ülikooli Ajaloo Instituudi uueks direktoriks saab ajaloolane Magnus Ilmjärv, kes on tuntuks saanud oma põhjaliku uurimistööga "Hääletu alistumine" Eesti Vabariigi sõjaeelsest välispoliitikast ja riigijuhi Konstantin Pätsi rollist iseseisvuse kaotamisel

  20. Cloning, expression, purification and crystallization of a transcriptional regulatory protein (Rv3291c) from Mycobacterium tuberculosis H37Rv.

    Science.gov (United States)

    Shrivastava, Tripti; Kumar, Sandeep; Ramachandran, Ravishankar

    2004-10-01

    Rv3291c, the translational product of the Mycobacterium tuberculosis Rv3291c gene, is an 18 kDa protein. It is a putative transcriptional regulatory protein belonging to the leucine-responsive regulatory protein/asparagine synthase C (Lrp/AsnC) family, which are proteins that have been identified in archaea and bacteria. Rv3291c probably plays a significant role during the persistent/latent phase of M. tuberculosis, as supported by its up-regulation several-fold during this stage. Orthorhombic crystals of recombinant Rv3291c have been grown from trisodium citrate dihydrate-buffered solutions containing monoammonium dihydrogen phosphate. Diffraction data extending to 2.7 A have been collected from a single crystal with unit-cell parameters a = 99.6, b = 100.7, c = 100.6 A. Assuming an octamer in the asymmetric unit results in a Matthews coefficient (VM) of 1.75 A3 Da(-1), corresponding to a solvent content of about 30%.

  1. RV-Typer: A Web Server for Typing of Rhinoviruses Using Alignment-Free Approach.

    Directory of Open Access Journals (Sweden)

    Pandurang S Kolekar

    Full Text Available Rhinoviruses (RV are increasingly being reported to cause mild to severe infections of respiratory tract in humans. RV are antigenically the most diverse species of the genus Enterovirus and family Picornaviridae. There are three species of RV (RV-A, -B and -C, with 80, 32 and 55 serotypes/types, respectively. Antigenic variation is the main limiting factor for development of a cross-protective vaccine against RV.Serotyping of Rhinoviruses is carried out using cross-neutralization assays in cell culture. However, these assays become laborious and time-consuming for the large number of strains. Alternatively, serotyping of RV is carried out by alignment-based phylogeny of both protein and nucleotide sequences of VP1. However, serotyping of RV based on alignment-based phylogeny is a multi-step process, which needs to be repeated every time a new isolate is sequenced. In view of the growing need for serotyping of RV, an alignment-free method based on "return time distribution" (RTD of amino acid residues in VP1 protein has been developed and implemented in the form of a web server titled RV-Typer. RV-Typer accepts nucleotide or protein sequences as an input and computes return times of di-peptides (k = 2 to assign serotypes. The RV-Typer performs with 100% sensitivity and specificity. It is significantly faster than alignment-based methods. The web server is available at http://bioinfo.net.in/RV-Typer/home.html.

  2. Millimeter-wave Searches for Cold Dust and Molecular Gas around T Tauri Stars in MBM 12

    Science.gov (United States)

    Hogerheijde, Michiel R.; Jayawardhana, Ray; Johnstone, Doug; Blake, Geoffrey A.; Kessler, Jacqueline E.

    2002-12-01

    We report results of a sensitive search for cold dust and molecular gas in the disks around eight T Tauri stars in the high-latitude cloud MBM 12. Interferometric observations of 3 mm continuum emission in five fields containing six of the objects and literature values for the remaining two limit the disk masses to MdiskMBM 12. Our observations can exclude the presence in MBM 12 of T Tauri stars with relatively bright and massive disks such as T Tau, DG Tau, and GG Tau.

  3. CHARACTERIZING THE STELLAR PHOTOSPHERES AND NEAR-INFRARED EXCESSES IN ACCRETING T TAURI SYSTEMS

    Energy Technology Data Exchange (ETDEWEB)

    McClure, M. K.; Calvet, N.; Hartmann, L.; Ingleby, L. [Department of Astronomy, University of Michigan, 500 Church Street, 830 Dennison Building, Ann Arbor, MI 48109 (United States); Espaillat, C. [Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Hernandez, J. [Centro de Investigaciones de Astronomia (CIDA), Merida 5101-A (Venezuela, Bolivarian Republic of); Luhman, K. L. [Department of Astronomy and Astrophysics and the Center for Exoplanets and Habitable Worlds, The Pennsylvania State University, University Park, PA 16802 (United States); D' Alessio, P. [Centro de Radioastronomia y Astrofisica, Universidad Nacional Autonoma de Mexico, 58089 Morelia, Michoacan (Mexico); Sargent, B., E-mail: melisma@umich.edu, E-mail: ncalvet@umich.edu, E-mail: lhartm@umich.edu, E-mail: lingleby@umich.edu, E-mail: cespaillat@cfa.harvard.edu, E-mail: hernandj@cida.ve, E-mail: kluhman@astro.psu.edu, E-mail: p.dalessio@astrosmo.unam.mx, E-mail: baspci@rit.edu [Center for Imaging Science and Laboratory for Multiwavelength Astrophysics, Rochester Institute of Technology, 54 Lomb Memorial Drive, Rochester, NY 14623 (United States)

    2013-05-20

    Using NASA Infrared Telescope Facility SpeX data from 0.8 to 4.5 {mu}m, we determine self-consistently the stellar properties and excess emission above the photosphere for a sample of classical T Tauri stars (CTTS) in the Taurus molecular cloud with varying degrees of accretion. This process uses a combination of techniques from the recent literature as well as observations of weak-line T Tauri stars to account for the differences in surface gravity and chromospheric activity between the T Tauri stars and dwarfs, which are typically used as photospheric templates for CTTS. Our improved veiling and extinction estimates for our targets allow us to extract flux-calibrated spectra of the excess in the near-infrared. We find that we are able to produce an acceptable parametric fit to the near-infrared excesses using a combination of up to three blackbodies. In half of our sample, two blackbodies at temperatures of 8000 K and 1600 K suffice. These temperatures and the corresponding solid angles are consistent with emission from the accretion shock on the stellar surface and the inner dust sublimation rim of the disk, respectively. In contrast, the other half requires three blackbodies at 8000, 1800, and 800 K, to describe the excess. We interpret the combined two cooler blackbodies as the dust sublimation wall with either a contribution from the disk surface beyond the wall or curvature of the wall itself, neither of which should have single-temperature blackbody emission. In these fits, we find no evidence of a contribution from optically thick gas inside the inner dust rim.

  4. Koala retrovirus (KoRV) genotyping analyses reveal a low prevalence of KoRV-A in Victorian koalas and an association with clinical disease.

    Science.gov (United States)

    Legione, Alistair Raymond; Patterson, Jade L S; Whiteley, Pam; Firestone, Simon M; Curnick, Megan; Bodley, Kate; Lynch, Michael; Gilkerson, James R; Sansom, Fiona M; Devlin, Joanne M

    2016-12-28

    Koala retrovirus (KoRV) is currently undergoing endogenisation into the genome of koalas in Australia, providing an opportunity to assess the effect of retrovirus infection on the health of a population. The prevalence of KoRV in north eastern Australia (Queensland and New South Wales) is 100%, whereas previous preliminary investigations in south eastern Australia (Victoria) suggested KoRV is present at a lower prevalence, although the values have varied widely. Here we describe a large study of free ranging koalas in Victoria to estimate the prevalence of KoRV and assess the clinical significance of KoRV infection in wild koalas. Blood or spleen samples from 648 koalas where tested for KoRV provirus using PCRs to detect pol and env genes. The prevalence of KoRV in these Victorian koalas was 24.7% (160/648) (95% confidence interval [CI]: 21.3, 28.1%). KoRV-A was detected in 141/160 cases but KoRV-B, a genotype associated with neoplasia in captive koalas, was not detected. Detection may have been precluded by genomic differences between KoRV in Victoria and type strains. Factors associated with KoRV infection, based on multivariable analysis, were low body condition score, region sampled, and 'wet bottom'(a staining of the fur around the rump associated with chronic urinary incontinence). Koalas with wet bottom were nearly twice as likely to have KoRV provirus detected than those without wet bottom (odds ratio = 1.90, 95% CI 1.21, 2.98). Our findings have important implications for the conservation of this iconic species, particularly in regards to translocation potential.

  5. The kinematic relationship between disk and jet in the DG Tauri system

    CERN Document Server

    Testi, L; Sargent, A I; Ray, T P; Eislöffel, J

    2002-01-01

    We present high angular resolution millimeter wavelength continuum and 13CO(2-1) observations of the circumstellar disk surrounding the TTauri star DG Tauri. We show that the velocity pattern in the inner regions of the disk is consistent with Keplerian rotation about a central 0.67 Msun star. The disk rotation is also consistent with the toroidal velocity pattern in the initial channel of the optical jet, as inferred from HST spectra of the first de-projected 100 AU from the source. Our observations support the tight relationship between disk and jet kinematics postulated by the popular magneto-centrifugal models for jet formation and collimation.

  6. Abundâncias químicas de estrelas T Tauri fracas

    Science.gov (United States)

    Rojas, G. A.; Gregorio-Hetem, J.

    2003-08-01

    Apresentamos resultados do estudo de 44 estrelas pré-seqüência principal, para as quais buscamos realizar uma classificação espectroscópica e determinar parâmetros estelares e abundâncias químicas. A amostra foi escolhida da seguinte maneira : 21 objetos selecionados a partir de catálogos de objetos jovens, como o Pico dos Dias Survey e o Herbig Bell Catalogue, e 23 objetos selecionados a partir de contrapartidas ópticas de fontes de raios X detectadas pelo satélite ROSAT. Dentre 24 objetos previamente classificados como estrelas T Tauri Fracas, apenas 7 revelaram ser realmente pertencentes à essa classe, sendo os demais objetos T Tauri Clássicas ou estrelas evoluídas da pré-seqüência principal. Esse resultado demonstra que o critério mais utilizado para distinguir as T Tauri Clássicas das T Tauri Fracas, baseado na largura equivelente da emissão Ha, não é suficiente para determinar o estágio evolutivo desses objetos. Para o cálculo de parâmetros estelares e abundâncias, foram escolhidas as estrelas que apresentam características ideais para esse tipo de estudo, como ausência de velamento, baixa velocidade de rotação e espectros com razão sinal-ruído adequada. Os parâmetros estelares como temperatura efetiva e gravidade foram determinados através do equilíbrio de excitação e ionização das linhas de Ferro, e as abundâncias químicas foram calculadas utilizando o método de síntese espectral. Serão apresentados os parâmetros estelares e as abundâncias de Lítio para toda a amostra, e abundâncias de vários elementos quimicos para 7 estrelas estudadas em maior detalhe

  7. Comparison of Anyplex II RV16 with the xTAG respiratory viral panel and Seeplex RV15 for detection of respiratory viruses.

    Science.gov (United States)

    Kim, Hyun-Ki; Oh, Sung-Hee; Yun, Kyung Ah; Sung, Heungsup; Kim, Mi-Na

    2013-04-01

    A novel multiplex real-time PCR approach (Anyplex II RV16 [RV16]; Seegene, South Korea) was compared with a multiplex endpoint PCR kit (Seeplex RV15 ACE detection kit [RV15]; Seegene) and a liquid bead-based assay (xTAG respiratory viral panel [xTAG]; Abbott, United States). Of nasopharyngeal swabs or aspirates and bronchoalveolar lavage fluid samples submitted for RV15 testing, 199 retrospectively collected positive specimens and 283 prospectively collected specimens were further tested with RV16 and xTAG. A true-positive result was defined as a positive result from all three methods or RV16 and xTAG or RV15 and xTAG. For specimens with discrepant results, monoplex PCR and sequencing of the target viruses were performed. In total, 300 virus-positive specimens yielded 386 viruses. When the bocavirus results were excluded, the overall sensitivities of RV16, RV15, and xTAG were 95.2%, 93.3%, and 87.2%, respectively (95% confidence intervals, 93.0 to 97.4%, 90.8 to 95.8%, and 83.8 to 90.6%, respectively). RV16 was more sensitive than xTAG for coronavirus OC43/HKU1 (100% versus 26.1%; P < 0.0001) and adenovirus (100% versus 79.5%; P < 0.01) but was less sensitive than xTAG for rhinovirus/enterovirus (89.4% versus 97.9%; P < 0.05). RV16 demonstrated higher sensitivity than RV15 for the detection of adenovirus (100% versus 82.1%; P < 0.05). The specificities of all three methods ranged from 98.6% to 100%. Sequencing analysis of 64 rhinovirus-positive samples revealed that RV16 accurately differentiated between rhinovirus and enterovirus. RV16 most frequently missed rhinovirus C. In conclusion, the overall sensitivity of RV16 was better than that of xTAG. However, improvement of the sensitivity for rhinovirus is required.

  8. Captured at Millimeter Wavelengths: a Flare from the Classical T Tauri Star DQ Tau

    CERN Document Server

    Salter, D M; Blake, G A

    2008-01-01

    For several hours on 2008 April 19 the T Tauri spectroscopic binary DQ Tau was observed to brighten, reaching a maximum detected flux of 468 mJy and likely making it (briefly) the brightest object at 3 mm in the Taurus star-forming region. We present the light curve of a rarely before observed millimeter flare originating in the region around a pre-main-sequence star, and the first from a classical T Tauri star. We discuss the properties and nature of the flaring behavior in the context of pulsed accretion flows (the current picture based largely on studies of this object's optically variable spectrum), as well as magnetospheric re-connection models (a separate theory that predicts millimeter flares for close binaries of high orbital eccentricity). We believe that the flare mechanism is linked to the binary orbit, and therefore periodic. DQ Tau makes a strong case for multi-wavelength follow-up studies, performed in parallel, of future flares to help determine whether magnetospheric and dynamical interactions...

  9. V819 Tau: A Rare Weak-Lined T Tauri Star with a Weak Infrared Excess

    CERN Document Server

    Furlan, E; Sargent, B A; Manoj, P; Kim, K H; Watson, Dan M

    2009-01-01

    We use Spitzer data to infer that the small infrared excess of V819 Tau, a weak-lined T Tauri star in Taurus, is real and not attributable to a "companion" 10 arcsec to the south. We do not confirm the mid-infrared excess in HBC 427 and V410 X-ray 3, which are also non-accreting T Tauri stars in the same region; instead, for the former object, the excess arises from a red companion 9 arcsec to the east. A single-temperature blackbody fit to the continuum excess of V819 Tau implies a dust temperature of 143 K; however, a better fit is achieved when the weak 10 and 20 micron silicate emission features are also included. We infer a disk of sub-micron silicate grains between about 1 AU and several 100 AU with a constant surface density distribution. The mid-infrared excess of V819 Tau can be successfully modeled with dust composed mostly of small amorphous olivine grains at a temperature of 85 K, and most of the excess emission is optically thin. The disk could still be primordial, but gas-poor and therefore shor...

  10. Infrared Spectroscopy and Imaging Polarimetry of the Disk Around the T Tauri Star RNO 91

    Science.gov (United States)

    Weintraub, David A.; Tegler, Stephen C.; Rettig, Terrence

    1994-01-01

    We present 3-5 micrometer spectra and a 2.2 micrometer polarimetric image of the T Tauri star RNO 91. We report the detection of three absorption bands centered at 3250 per cm (3.08 micrometer), 2139 per cm (4.68 micrometer), and 2165 per cm (4.62 micrometer) in spectra of RNO 91. These features are due to frozen H2O, CO, and possibly XCN along the line of sight toward RNO 91. Our 2187-2107 per cm spectrum of RNO 90, the only other T Tauri star in the dark cloud L43, does not show the CO or XCN absorption bands. By comparing our observed polarimetric image with modeled images of scattered light from bipolar nebulae or circumstellar disks as well as with known morphology of the RNO 91 bipolar outflow, we demonstrate that the reflection nebulosity seen in the near-infrared is most likely a circumstellar disklike structure with a radius of approximately 1700 AU. The location of both RNO 90 and RNO 91 in front of or near the front of L43 suggests that the intracloud optical depths toward both stars are small and, therefore, that the frozen H2O, CO, and XCN molecules are located on grains in circumstellar material around RNO 91 at distances from the central star of perhaps 10-1700 AU. This frozen material may represent precometary grains orbiting RNO 91.

  11. Exploring a Simple Method to Estimate Spot Temperatures in Weak-Lined T Tauri Stars

    Science.gov (United States)

    Koen, Chris

    2016-09-01

    The astronomy literature contains a wealth of photometric measurements of the brightness variations of weak-lined T Tauri stars. Comparing observations through two different filters, the brightness changes of the vast majority of these stars trace straight lines in magnitude-magnitude plots. It is plausible that the slope of the line is determined by a fixed mean starspot temperature, and that changing filling factors cause the linear magnitude-magnitude relations to be described. This is exploited to derive an estimator for the starspot temperature in terms of a linear regression slope, valid for modest starspot filling factors. Simulations are used to demonstrate that such regression slopes first need to be corrected for measurement errors, in order to avoid biased results. The theory is applied to a collection of 45 extensive sets of BVR (and in some cases UBVR) observations of weak-lined T Tauri stars taken from the literature. The results are examined critically, and it is pointed out that there are systematic differences between spot temperatures determined respectively from BV and VR data pairs. The reason for this is not known; possible causes are briefly speculated about. There is generally poor agreement with published spot temperatures, which also vary considerably. The simplest explanation is that the mean temperature of starspots is variable.

  12. CSI 2264: Accretion process in classical T Tauri stars in the young cluster NGC 2264

    CERN Document Server

    Sousa, Alana; Bouvier, Jérôme; Stauffer, John; Venuti, Laura; Hillenbrand, Lynne; Cody, Ann Marie; Teixeira, Paula; Guimarães, Marcelo; McGinnis, Pauline; Rebull, Luisa; Flaccomio, Ettore; Fürész, Gabor; Micela, Giuseppina; Gameiro, Jorge

    2016-01-01

    Our goal is to relate the photometric and spectroscopic variability of classical T Tauri stars, of the star-forming cluster NGC 2264, to the physical processes acting in the stellar and circumstellar environment, within a few stellar radii from the star. NGC 2264 was the target of a multiwavelength observational campaign with CoRoT, MOST, Spitzer, and Chandra satellites and observations from the ground. We classified the CoRoT light curves of accreting systems according to their morphology and compared our classification to several accretion diagnostics and disk parameters. The morphology of the CoRoT light curve reflects the evolution of the accretion process and of the inner disk region. Accretion burst stars present high mass-accretion rates and optically thick inner disks. AA Tau-like systems, whose light curves are dominated by circumstellar dust obscuration, show intermediate mass-accretion rates and are located in the transition of thick to anemic disks. Classical T Tauri stars with spot-like light cur...

  13. Comparison between accretion-related properties of Herbig Ae/Be and T Tauri stars

    CERN Document Server

    Mendigutía, I

    2013-01-01

    This paper summarizes several results concerning the comparison between accretion-related properties of cool (T Tauri; T < 7000 K, M < 1 Msun and hot (Herbig Ae/Be; 7000 < T(K) < 13000; 1 < M(Msun) < 6) pre-main sequence (PMS) stars. This comparison gives insight into the analogies/differences in the physics of the star-disk interaction and in the physical mechanisms driving disk dissipation. Several optical and near-IR line luminosities used for low-mass objects are also valid to estimate typical accretion rates for intermediate-mass stars under similar empirical expressions. In contrast, the Halpha width at 10% of peak intensity is used as an accretion tracer for T Tauris, but is not reliable to estimate accretion rates for Herbig Ae/Bes. This can be explained as a consequence of the different stellar rotation rates that characterize both types of stars. In addition, there are similar trends when the accretion rate is related to the near-IR colours and disk masses, suggesting that viscous ...

  14. A New Association of Post-T Tauri Stars Near The Sun

    CERN Document Server

    Torres, C A O; Quast, G R; De la Reza, R; Jilinski, E; Torres, Carlos A. O.; Silva, Licio da; Quast, Germano R.; Reza, Ramiro de la; Jilinski, Evgueni

    2000-01-01

    Observing ROSAT sources in 20 x 25 deg centered at the high latitude active star ER Eri, we found evidences for a new young nearby association (~30Myr at~60pc), the Horologium Association (HorA), formed by at least 10 probable and 6 possible members, some being Post-T Tauri stars. We examine several requirements that characterize a young association and they, together, create a strong evidence for the reality of the HorA. In fact, the Li line intensities are between those of the oldest classical T Tauri stars and the ones of the Local Association stars. The space velocities of the HorA relative to the Sun, U= -9.5+/-1.0, V = -20.9 +/- 1.1, W = -2.1 +/- 1.9, are not far from those of the Local Association. We suggest that some hotter and non-X-ray active stars, with similar space velocities, could be massive members of the HorA, among them, the nearby Be star Achernar. The maximum of the mass distribution function of the HorA is around 0.8 solar masses. At its distance, the projected size of the HorA, ~50 pc, ...

  15. Exploring a simple method to estimate spot temperatures in weak-lined T Tauri stars

    Science.gov (United States)

    Koen, Chris

    2016-12-01

    The astronomy literature contains a wealth of photometric measurements of the brightness variations of weak-lined T Tauri stars. Comparing observations through two different filters, the brightness changes of the vast majority of these stars trace straight lines in magnitude-magnitude plots. It is plausible that the slope of the line is determined by a fixed mean starspot temperature, and that changing filling factors cause the linear magnitude-magnitude relations to be described. This is exploited to derive an estimator for the starspot temperature in terms of a linear regression slope, valid for modest starspot filling factors. Simulations are used to demonstrate that such regression slopes first need to be corrected for measurement errors, in order to avoid biased results. The theory is applied to a collection of 45 extensive sets of BVR (and in some cases UBVR) observations of weak-lined T Tauri stars taken from the literature. The results are examined critically, and it is pointed out that there are systematic differences between spot temperatures determined respectively from BV and VR data pairs. The reason for this is not known; possible causes are briefly speculated about. There is generally poor agreement with published spot temperatures, which also vary considerably. The simplest explanation is that the mean temperature of starspots is variable.

  16. Modelling the RV jitter of early-M dwarfs using tomographic imaging

    Science.gov (United States)

    Hébrard, É. M.; Donati, J.-F.; Delfosse, X.; Morin, J.; Moutou, C.; Boisse, I.

    2016-09-01

    In this paper, we show how tomographic imaging (Zeeman-Doppler imaging, ZDI) can be used to characterize stellar activity and magnetic field topologies, ultimately allowing us to filter out the radial velocity (RV) activity jitter of M dwarf moderate rotators. This work is based on spectropolarimetric observations of a sample of five weakly active early-M dwarfs (GJ 205, GJ 358, GJ 410, GJ 479, GJ 846) with HARPS-Pol and NARVAL. These stars have v sin i and RV jitters in the range 1-2 km s-1 and 2.7-10.0 m s-1 rms, respectively. Using a modified version of ZDI applied to sets of phase-resolved least-squares deconvolved profiles of unpolarized spectral lines, we are able to characterize the distribution of active regions at the stellar surfaces. We find that dark spots cover less than 2 per cent of the total surface of the stars of our sample. Our technique is efficient at modelling the rotationally modulated component of the activity jitter, and succeeds at decreasing the amplitude of this component by typical factors of 2-3 and up to 6 in optimal cases. From the rotationally modulated time series of circularly polarized spectra and with ZDI, we also reconstruct the large-scale magnetic field topology. These fields suggest that bistability of dynamo processes observed in active M dwarfs may also be at work for moderately active M dwarfs. Comparing spot distributions with field topologies suggest that dark spots causing activity jitter concentrate at the magnetic pole and/or equator, to be confirmed with future data on a larger sample.

  17. Understanding the water emission in the mid- and far-IR from protoplanetary disks around T Tauri stars

    NARCIS (Netherlands)

    Antonellini, S.; Kamp, I.; Riviere-Marichalar, P.; Meijerink, R.; Woitke, P.; Thi, W.-F.; Spaans, M.; Aresu, G.; Lee, G.

    2015-01-01

    Aims: We investigate which properties of protoplanetary disks around T Tauri stars affect the physics and chemistry in the regions where mid- and far-IR water lines originate and their respective line fluxes. We search for diagnostics for future observations. Methods: With the code ProDiMo, we build

  18. Spectral Methods

    CERN Document Server

    Shen, Jie; Wang, Li-Lian

    2011-01-01

    Along with finite differences and finite elements, spectral methods are one of the three main methodologies for solving partial differential equations on computers. This book provides a detailed presentation of basic spectral algorithms, as well as a systematical presentation of basic convergence theory and error analysis for spectral methods. Readers of this book will be exposed to a unified framework for designing and analyzing spectral algorithms for a variety of problems, including in particular high-order differential equations and problems in unbounded domains. The book contains a large

  19. MaRV (maneuverable reentry vehicles) PoP (probability of penetration) vs CEP (circular error probability) analysis concept study (MaRV Penetration Study Project)

    Energy Technology Data Exchange (ETDEWEB)

    Morris, J M

    1986-08-01

    The performance analysis of maneuverable reentry vehicles (MaRV) in terms of its probability of penetration (PoP) against terminal engagement with a ballistic missile defense (BMD) system and in terms of its associate circular error probability (CEP), at impact is a very complex problem. A thorough study of this problem under the MaRV Penetration Study Project will require the development of a number of analytical and simulation tools. As a result of a preliminary study, a MaRV PoP vs CEP analysis concept has been formulated to support the MaRV Penetration Study Project. The concept is based on analytical models and techniques and, moreover, exploits the existing knowledge base and is physically intuitive. The analysis concept, as formulated, is applicable to arbitrary MaRV's and BMD systems.

  20. Discussing the low fraction of disk-bearing T Tauri stars discovered near to the Sh2-296 nebula

    Science.gov (United States)

    Gregorio-Hetem, Jane

    2015-08-01

    A multiband study has been developed by our team in the direction of young star clusters associated to the Sh2-296 nebula aiming to unveil the star formation history of this galactic molecular cloud that shows a mixing of different age stellar groups. A sample of 58 pre-main sequence stars has been recently discovered by us in this region (Fernandes et al. 2015, MNRAS in press), based on optical spectral features. Only 41% of the sample shows evidence of IR excess revealing the presence of circumstellar disks. It is interesting to note that the targets were revealed by their strong X-ray emission, typically found in T Tauri stars (TTs) (Santos-Silva et al. 2015, in preparation) . In this case, it would be expected a larger number of disk-bearing stars and also the fraction of circumstellar emission (fc = Ldisk/Ltotal ) should be more significant in these objects. However, we verified that only 12% of the sample has fc > 30%. This low fraction is quite rare compared to most young star-forming regions, suggesting that some external factor has accelerated the disc dissipation. In the present work we explore the circumstellar structure of a subsample of 8 TTs associated to Sh2-296. The TTs were selected on the basis of their high circumstellar emission, which is estimated by SED fitting that uses near- to mid-IR data extracted from available catalogues (WISE, AKARI, MSX). The circumstellar characteristics are confronted to interstellar environment by comparing the stellar spatial distribution with 12CO maps (Nanten Survey, Fukui et al. ). Most of the TTs are projected against moderate molecular emission (33 Jy), but some of them are found in regions of lower levels of gas distribution (3.8 Jy). The similarities and differences found among the studied objects are discussed in order to better understand the formation and evolution of protostellar disks of the selected sample and their role in the star formation scenario nearby Sh2-296

  1. Ülemiste City kvartal Tallinnas / Mattias Agabus, Eero Endjärv, Illimar Truverk...[jt.] ; fotod: Kaido Haagen

    Index Scriptorium Estoniae

    2008-01-01

    asendiplaan, 3 korruste plaani, 3 värv. välisvaadet, restorani Mercado sisevaade; projekteerijad: M. Agabus, E. Endjärv, I.Truverk (Agabus, Endjärv & Truverk Arhitektid); hoonete arhitektuurne osa: E. Endjärv; sisearhitektid: K. Lents, H. Kääramees, T. Aunre (restoran Mercado); konstruktorid: Ü. Suvemaa, A. Lehtla, K. Adoberg; maastikuarhitektuur: Ü. Grišakov, M. Agabus, E. Endjärv

  2. Ülemiste City kvartal Tallinnas / Mattias Agabus, Eero Endjärv, Illimar Truverk...[jt.] ; fotod: Kaido Haagen

    Index Scriptorium Estoniae

    2008-01-01

    asendiplaan, 3 korruste plaani, 3 värv. välisvaadet, restorani Mercado sisevaade; projekteerijad: M. Agabus, E. Endjärv, I.Truverk (Agabus, Endjärv & Truverk Arhitektid); hoonete arhitektuurne osa: E. Endjärv; sisearhitektid: K. Lents, H. Kääramees, T. Aunre (restoran Mercado); konstruktorid: Ü. Suvemaa, A. Lehtla, K. Adoberg; maastikuarhitektuur: Ü. Grišakov, M. Agabus, E. Endjärv

  3. PEMBUATAN PROGRAM INTERFACE UNTUK PENGONTROLAN RV-M1

    Directory of Open Access Journals (Sweden)

    Endra Endra

    2007-10-01

    Full Text Available Article explores the making of interface of RV-M1 hand robot control that replaced the cosiprog program,a program that is able to help student in Mecatronica-1 Practice, and able to control the hand robot by localnetwork by two user or more. The used methods were literature study, and field study, that is design method. Theresearch result are control of hand robot on X,Y,Z axis and point to point, the use of local network to control thehand robot, save certain position, and use several user to control the robot.Keywords: interface program, robot, local network

  4. Ülehomme on õpetajate päev - milline oli teie parim õpetaja? / Toomas Edur, Tauri Tallermaa, Irene Käosaar...[jt.

    Index Scriptorium Estoniae

    2009-01-01

    Küsimusele vastavad Rahvusooper Estonia balleti kunstiline juht Toomas Edur, koolitaja Tauri Tallermaa, haridus- ja teadusministeeriumi osakonnajuhataja Irene Käosaar, Tartu Karlova Gümnaasiumi direktor Undel Kokk ja näitleja Andrus Vaarik

  5. Infection with koala retrovirus subgroup B (KoRV-B), but not KoRV-A, is associated with chlamydial disease in free-ranging koalas (Phascolarctos cinereus).

    Science.gov (United States)

    Waugh, Courtney A; Hanger, Jonathan; Loader, Joanne; King, Andrew; Hobbs, Matthew; Johnson, Rebecca; Timms, Peter

    2017-03-09

    The virulence of chlamydial infection in wild koalas is highly variable between individuals. Some koalas can be infected (PCR positive) with Chlamydia for long periods but remain asymptomatic, whereas others develop clinical disease. Chlamydia in the koala has traditionally been studied without regard to coinfection with other pathogens, although koalas are usually subject to infection with koala retrovirus (KoRV). Retroviruses can be immunosuppressive, and there is evidence of an immunosuppressive effect of KoRV in vitro. Originally thought to be a single endogenous strain, a new, potentially more virulent exogenous variant (KoRV-B) was recently reported. We hypothesized that KoRV-B might significantly alter chlamydial disease outcomes in koalas, presumably via immunosuppression. By studying sub-groups of Chlamydia and KoRV infected koalas in the wild, we found that neither total KoRV load (either viraemia or proviral copies per genome), nor chlamydial infection level or strain type, was significantly associated with chlamydial disease risk. However, PCR positivity with KoRV-B was significantly associated with chlamydial disease in koalas (p = 0.02961). This represents an example of a recently evolved virus variant that may be predisposing its host (the koala) to overt clinical disease when co-infected with an otherwise asymptomatic bacterial pathogen (Chlamydia).

  6. Salmonella abortusovis, strain Rv6, a new vaccinal vehicle for small ruminants.

    Science.gov (United States)

    Bourgogne, A; Sanchis, R; Clément, J M; Pépin, M

    1998-03-31

    Salmonella abortusovis strain Rv6 (Sao Rv6) is a live attenuated vaccine used for a few years to protect ewes against abortive salmonellosis. As Salmonellae, particularly Salmonella aro mutants, have considerable potential as vehicles for the presentation of heterologous vaccine antigens, Sao Rv6 was tested in order to develop a vaccinal vehicle for small ruminants. Five vector plasmids were tested in Sao Rv6; these plasmids, which carry Maltose Binding Protein (MBP) expressed as protein, but differ in their promotors, had been previously tested in S. typhimurium strain SL3261, and were transferred into Sao Rv6. The five plasmids were stable in vitro, and the recombinant Sao Rv6 expressed MBP at various levels. Intraperitoneal infection of OF1 mice with the recombinant bacteria did not modify the characteristics of Sao Rv6; dissemination and infection levels were similar in all groups and all mice developed antibodies to Salmonella antigens as measured by ELISA. In contrast, only animals immunized with Sao Rv6 carrying the pNTE plasmid developed a serum antibody response to MBP. This plasmid was then tested in sheep; following subcutaneous immunization with Sao Rv6-pNTE, dissemination and infection levels were not modified in comparison with sheep immunized with Sao Rv6 lacking plasmid. Antibodies specific to MBP were detected in sera of sheep immunized with Sao Rv6-pNTE, purified MBP, and with S. typhimurium SL3261-pNTE as positive controls. These results demonstrate that Sao Rv6 can be used as a vehicle for heterologous antigens in sheep with pNTE as plasmid vector.

  7. Lack of antiviral antibody response in koalas infected with koala retroviruses (KoRV).

    Science.gov (United States)

    Fiebig, Uwe; Keller, Martina; Möller, Annekatrin; Timms, Peter; Denner, Joachim

    2015-02-16

    Many wild koalas are infected with the koala retrovirus, KoRV, some of which suffer from lymphoma and chlamydial disease. Three subgroups, KoRV-A, KoRV-B and KoRV-J, have so far been described. It is well known that other closely related gammaretroviruses can induce tumours and severe immunodeficiencies in their respective hosts and a possible role for KoRV infection in lymphoma and chlamydial disease in koalas has been suggested. In many wild koalas, KoRV-A has become endogenised, i.e., it is integrated in the germ-line and is passed on with normal cellular genes. In this study, sera from koalas in European zoos and from wild animals in Australia were screened for antibodies against KoRV-A. These naturally infected animals all carry endogenous KoRV-A and two zoo animals are also infected with KoRV-B. The antibody response is generally an important diagnostic tool for detecting retrovirus infections. However, when Western blot analyses were performed using purified virus or recombinant proteins corresponding to KoRV-A, none of the koalas tested positive for specific antibodies, suggesting a state of tolerance. These results have implications for koala vaccination, as they suggest that therapeutic immunisation of animals carrying and expressing endogenous KoRV-A will not be successful. However, it remains unclear whether these animals can be immunised against KoRV-B and immunisation of uninfected koalas could still be worthwhile. Copyright © 2015 Elsevier B.V. All rights reserved.

  8. The Bipolar X-Ray Jet of the Classical T Tauri Star DG Tau

    CERN Document Server

    Guedel, M; Bacciotti, F; Bary, J S; Briggs, K R; Cabrit, S; Carmona, A; Codella, C; Dougados, C; Eisloeffel, J; Gueth, F; Guenther, H M; Herczeg, G; Kundurthy, P; Matt, S P; Mutel, R L; Ray, T; Schmitt, J H M M; Schneider, P C; Skinner, S L; van Boekel, R

    2011-01-01

    We report on new X-ray observations of the classical T Tauri star DG Tau. DG Tau drives a collimated bi-polar jet known to be a source of X-ray emission perhaps driven by internal shocks. The rather modest extinction permits study of the jet system to distances very close to the star itself. Our initial results presented here show that the spatially resolved X-ray jet has been moving and fading during the past six years. In contrast, a stationary, very soft source much closer (~ 0.15-0.2") to the star but apparently also related to the jet has brightened during the same period. We report accurate temperatures and absorption column densities toward this source, which is probably associated with the jet base or the jet collimation region.

  9. Rotation of Jets from T-Tauri Stars New Clues from Hst/stis

    Science.gov (United States)

    Coffey, Deirdre; Woitas, Jens; Francesca, Bacciotti; Ray, Thomas P.; Eisloffel, Jochen

    Whether jets from newly forming stars rotate is a fundamental question in star formation research. Theoretical models propose jet rotation as a means of removing angular momentum from the young star and disk system thus allowing accretion. While widely accepted this idea has not yet been tested observational due to the high resolution requirement of examining jets close to their launching point. Previous findings from the Hubble Space Telescope Imaging Spectrograph (HST/STIS) and Owens Valley Radio Observatory (OVRO) give indications of same sense rotation of the jet (Bacciotti et al 2002) and disk (Testi et al 2002) respectively of T Tauri star DG Tau. We report preliminary findings from HST/STIS data for 3 of 8 sources in a current survey to establish conclusively whether protostellar jets rotate. The results were positive yielding evidence of radial velocity differences about the axis at the base of all three jets of up to 20-30 km/s.

  10. The Disk and Jet of the Classical T Tauri Star AA Tau

    Science.gov (United States)

    Cox, A. W.; Grady, C. A.; Hamel, H.; Hornbeck, Jeremy; Russell, R.; Sitko, M.; Woodgate, B.

    2013-01-01

    Previous studies of the classical T Tauri star AA Tau have interpreted the UX Orionis-like photopolarimetric variability as being due to a warp in the inner disk caused by an inclined stellar magnetic dipolefield. We test that these effects are macroscopically observable in the inclination and alignment of the disk. We use the HST/STIS coronagraphic detection of the disk to measure the outer disk radius and inclination, and find that the inner disk is both misinclined and misaligned with respect to the outer disk. AA Tau drives a faint jet which is also misaligned with respect to the projection of the outer disk minor axis. The jet is also poorly collimated near the star. The measured inclination, 71+/-1deg, is above the inclination range suggested for stars with UX Orionis-like variability, indicating that dust grains in the disk have grown and settled toward the disk midplane.

  11. Wind Dynamics and Circumstellar Extinction Variations in the T Tauri Star RY Tau

    CERN Document Server

    Babina, Elena V; Petrov, Peter P

    2016-01-01

    The wind interaction with the dusty environment of the classical T Tauri star RY Tau has been investigated. During two seasons of 2013-2015 we carried out a spectroscopic and photometric (BVR) monitoring of the star. A correlation between the stellar brightness and the radial velocity of the wind determined from the H-alpha and Na D line profiles has been found for the first time. The irregular stellar brightness variations are shown to be caused by extinction in a dusty disk wind at a distance of about 0.2 AU from the star. We suppose, that variations of the circumstellar extinction results from cyclic rearrangements of the stellar magnetosphere and coronal mass ejections, which affect the dusty disk wind near the inner boundary of the circumstellar disk.

  12. High spatial resolution IR observations of young stellar objects - A possible disk surrounding HL Tauri

    Science.gov (United States)

    Grasdalen, G. L.; Strom, S. E.; Strom, K. M.; Capps, R. W.; Thompson, D.; Castelaz, M.

    1984-01-01

    High spatial resolution images of the T Tauri star HL Tau were obtained at 1.6 microns and 2.2 microns. The original images as well as maximum entropy image reconstructions reveal a circumstellar envelope structure, similar at both wavelenghts, and extended along P.A. = 112 deg; the 10 percent width of the structure is 1.9 sec (300 AU at 160 pc). The extended structure is interpreted as light scattered toward earth by dust in a disk surrounding this young stellar object. Polarization measurements made at 2.2 microns support this hypothesis. The total solid particle mass is, at minimum, 5 x 10 to the -7th solar mass.

  13. V471 Tauri: Examining Eclipse Timing Variations with two Independent Clocks

    Science.gov (United States)

    Vanderbosch, Z. P.; Clemens, J. C.; Dunlap, B. H.; Winget, D. E.

    2017-03-01

    Eclipse timing variations (ETVs) in binary systems can result from a plethora of potential mechanisms, one of which is the interaction of an unseen third body causing a periodic wobble in the system's barycenter. ETVs in the V471 Tauri dK+WD binary system have historically been attributed to such a cause. Using the orbital period of the system (˜12.5-hr) and the spin period (˜9.25-min) of the WD as two independent clocks, we show that a third body interpretation of the ETVs cannot adequately explain the nature of this system. A wobbling barycenter would introduce variations of equal magnitude to both the eclipse timing and the spin period O-C diagrams. We present O-C diagrams for both clocks using photometric data spanning several years, noting a relatively flat line for the spin-period O-C. We then argue for alternative mechanisms causing ETVs, namely the Applegate effect.

  14. X-ray emission from classical T Tauri stars: Accretion shocks and coronae?

    CERN Document Server

    Guenther, H M; Robrade, J; Liefke, C

    2007-01-01

    Classical T Tauri stars (CTTS) are surrounded by actively accreting disks. According to current models material falls along the magnetic field lines from the disk with more or less free-fall velocity onto the star, where the plasma heats up and generates X-rays. We want to quantitatively explain the observed high energy emission and measure the infall parameters from the data. Absolute flux measurements allow to calculate the filling factor and the mass accretion rate.We use a numerical model of the hot accretion spot and solve the conservation equations. A comparison to data from XMM-Newton and Chandra shows that our model reproduces the main features very well. It yields for TW Hya a filling factor of 0.3% and a mass accretion rate 2e-10 M_sun/yr.

  15. Development of Monolithic Michelson Interferometer for RV measurement in IR

    Science.gov (United States)

    Wang, Ji; Wan, Xiaoke; Ge, Jian C.

    2010-07-01

    We present a fixed delay interferometer to be installed in IR-ET (Infra-Red Exoplanets Tracker). We introduce the design, fabrication and testing processes. In particular, we present a new methodology of computing the fundamental limit of radial velocity (RV) measurement given by photon noise for DFDI (Dispersed Fixed Delay Interferometer) method as opposed to conventional echelle method. The new method is later used to determine the optical path difference (OPD) of the IR-ET interferometer. In addition, we introduce a novel method of monitoring the stability of the interferometer for IR-ET in broad-band using fourier-transform white-light scanning interferometry technique. The new method can be potentially expanded and applied to thermo-optic effect measurement if temperature control system is introduced into the experiment. The thermal response of the optical system is 3500 m/s/°C. We find that the RV calibration precision of 'Bracketing' method is 1.74 m/s without temperature control.

  16. SDSS-III MARVELS Planet Candidate RV Follow-up

    Science.gov (United States)

    Ge, Jian; Thomas, Neil; Ma, Bo; Li, Rui; SIthajan, Sirinrat

    2014-02-01

    Planetary systems, discovered by the radial velocity (RV) surveys, reveal strong correlations between the planet frequency and stellar properties, such as metallicity and mass, and a greater diversity in planets than found in the solar system. However, due to the sample sizes of extant surveys (~100 to a few hundreds of stars) and their heterogeneity, many key questions remained to be addressed: Do metal poor stars obey the same trends for planet occurrence as metal rich stars? What is the distribution of giant planets around intermediate- mass stars and binaries? Is the ``planet desert'' within 0.6 AU in the planet orbital distribution of intermediate-mass stars real? The MARVELS survey has produced the largest homogeneous RV measurements of 3300 V=7.6-12 FGK stars. The latest data pipeline effort at UF has been able to remove long term systematic errors suffered in the earlier data pipeline. 18 high confident giant planet candidates have been identified among newly processed data. We propose to follow up these giant planet candidates with the KPNO EXPERT instrument to confirm the detection and also characterize their orbits. The confirmed planets will be used to measure occurrence rates, distributions and multiplicity of giants planets around F,G,K stars with a broad range of mass (~0.6-2.5 M_⊙) and metallicity ([Fe/H]~-1.5-0.5). The well defined MARVELS survey cadence allows robust determinations of completeness limits for rigorously testing giant planet formation theories and constraining models.

  17. The rotation period distributions of 4--10 Myr T Tauri stars in Orion OB1: New constraints on pre-main-sequence angular momentum evolution

    CERN Document Server

    Karim, Md Tanveer; Briceno, Cesar; Vivas, A Katherina; Raetz, Stefanie; Mateu, Cecilia; Downes, Juan Jose; Calvet, Nuria; Hernandez, Jesus; Neuhauser, Ralph; Mugrauer, Markus; Takahashi, Hidenori; Tachihara, Kengo; Chini, Rolf; Cruz-Dias, Gustavo A; Aarnio, Alicia; James, David J; Hackstein, Moritz

    2016-01-01

    Most existing studies of the angular momentum evolution of young stellar populations have focused on the youngest (1-3 Myr) T Tauri stars. In contrast, the angular momentum distributions of older T Tauri stars (4-10 Myr) have been less studied, even though they hold key insight to understanding stellar angular momentum evolution at a time when protoplanetary disks have largely dissipated and when models therefore predict changes in the rotational evolution that can in principle be tested. We present a study of photometric variability among 1,974 confirmed T Tauri members of various sub-regions of the Orion OB1 association, and with ages spanning 4-10 Myr, using optical time-series from three different surveys. For 564 of the stars (~32% of the weak-lined T Tauri stars and ~13% of the classical T Tauri stars in our sample) we detect statistically significant periodic variations which we attribute to the stellar rotation periods, making this one of the largest samples of T Tauri star rotation periods yet publis...

  18. The Rotation Period Distributions of 4-10 Myr T Tauri Stars in Orion OB1: New Constraints on Pre-main-sequence Angular Momentum Evolution

    Science.gov (United States)

    Karim, Md Tanveer; Stassun, Keivan G.; Briceño, César; Vivas, A. Katherina; Raetz, Stefanie; Mateu, Cecilia; José Downes, Juan; Calvet, Nuria; Hernández, Jesús; Neuhäuser, Ralph; Mugrauer, Markus; Takahashi, Hidenori; Tachihara, Kengo; Chini, Rolf; Cruz-Dias, Gustavo A.; Aarnio, Alicia; James, David J.; Hackstein, Moritz

    2016-12-01

    Most existing studies of the angular momentum evolution of young stellar populations have focused on the youngest (≲1-3 Myr) T Tauri stars. In contrast, the angular momentum distributions of older T Tauri stars (˜4-10 Myr) have been less studied, even though they hold key insights to understanding stellar angular momentum evolution at a time when protoplanetary disks have largely dissipated and when models therefore predict changes in the rotational evolution that can in principle be tested. We present a study of photometric variability among 1974 confirmed T Tauri members of various subregions of the Orion OB1 association, and with ages spanning 4-10 Myr, using optical time series from three different surveys. For 564 of the stars (˜32% of the weak-lined T Tauri stars and ˜13% of the classical T Tauri stars in our sample) we detect statistically significant periodic variations, which we attribute to the stellar rotation periods, making this one of the largest samples of T Tauri star rotation periods yet published. We observe a clear change in the overall rotation period distributions over the age range 4-10 Myr, with the progressively older subpopulations exhibiting systematically faster rotation. This result is consistent with angular momentum evolution model predictions of an important qualitative change in the stellar rotation periods starting at ˜5 Myr, an age range for which very few observational constraints were previously available.

  19. Mycobacterium tuberculosis Rv3406 is a type II alkyl sulfatase capable of sulfate scavenging.

    Directory of Open Access Journals (Sweden)

    Kimberly M Sogi

    Full Text Available The genome of Mycobacterium tuberculosis (Mtb encodes nine putative sulfatases, none of which have a known function or substrate. Here, we characterize Mtb's single putative type II sulfatase, Rv3406, as a non-heme iron (II and α-ketoglutarate-dependent dioxygenase that catalyzes the oxidation and subsequent cleavage of alkyl sulfate esters. Rv3406 was identified based on its homology to the alkyl sulfatase AtsK from Pseudomonas putida. Using an in vitro biochemical assay, we confirmed that Rv3406 is a sulfatase with a preference for alkyl sulfate substrates similar to those processed by AtsK. We determined the crystal structure of the apo Rv3406 sulfatase at 2.5 Å. The active site residues of Rv3406 and AtsK are essentially superimposable, suggesting that the two sulfatases share the same catalytic mechanism. Finally, we generated an Rv3406 mutant (Δrv3406 in Mtb to study the sulfatase's role in sulfate scavenging. The Δrv3406 strain did not replicate in minimal media with 2-ethyl hexyl sulfate as the sole sulfur source, in contrast to wild type Mtb or the complemented strain. We conclude that Rv3406 is an iron and α-ketoglutarate-dependent sulfate ester dioxygenase that has unique substrate specificity that is likely distinct from other Mtb sulfatases.

  20. Detection of koala retrovirus subgroup B (KoRV-B) in animals housed at European zoos.

    Science.gov (United States)

    Fiebig, Uwe; Keller, Martina; Denner, Joachim

    2016-12-01

    Many koalas carry an endogenous retrovirus, KoRV-A, in their genome. Recently, a second retrovirus, KoRV-B, was detected in koalas in Japanese and U.S. zoos. However, this virus is not endogenous, differs in the receptor binding site of the surface envelope protein, and uses a receptor different from that of KoRV-A. We describe here a KoRV-B found in koalas at zoos in Germany and Belgium that differs slightly from that found in the Los Angeles zoo.

  1. A hot Jupiter around the very active weak-line T Tauri star TAP 26

    Science.gov (United States)

    Yu, L.; Donati, J.-F.; Hébrard, E. M.; Moutou, C.; Malo, L.; Grankin, K.; Hussain, G.; Collier Cameron, A.; Vidotto, A. A.; Baruteau, C.; Alencar, S. H. P.; Bouvier, J.; Petit, P.; Takami, M.; Herczeg, G.; Gregory, S. G.; Jardine, M.; Morin, J.; Ménard, F.; Matysse Collaboration

    2017-01-01

    We report the results of an extended spectropolarimetric and photometric monitoring of the weak-line T Tauri star TAP 26, carried out within the MaTYSSE programme with the ESPaDOnS spectropolarimeter at the 3.6 m Canada-France-Hawaii Telescope. Applying Zeeman-Doppler Imaging to our observations, concentrating in 2015 November and 2016 January and spanning 72 d in total, 16 d in 2015 November and 13 d in 2016 January, we reconstruct surface brightness and magnetic field maps for both epochs and demonstrate that both distributions exhibit temporal evolution not explained by differential rotation alone. We report the detection of a hot Jupiter (hJ) around TAP 26 using three different methods, two using Zeeman-Doppler Imaging (ZDI) and one Gaussian-Process Regression (GPR), with a false-alarm probability smaller than 6 10-4. However, as a result of the aliasing related to the observing window, the orbital period cannot be uniquely determined; the orbital period with highest likelihood is 10.79±0.14 d followed by 8.99±0.09 d. Assuming the most likely period, and that the planet orbits in the stellar equatorial plane, we obtain that the planet has a minimum mass Msin i of 1.66±0.31 MJup and orbits at 0.0968±0.0032 au from its host star. This new detection suggests that disc type II migration is efficient at generating newborn hJs, and that hJs may be more frequent around young T Tauri stars than around mature stars (or that the MaTYSSE sample is biased towards hJ-hosting stars).

  2. IMAGING THE DISK AND JET OF THE CLASSICAL T TAURI STAR AA TAU

    Energy Technology Data Exchange (ETDEWEB)

    Cox, Andrew W. [Astronomy Department, Villanova University, Villanova, PA 19085 (United States); Grady, Carol A. [Eureka Scientific, 2452 Delmer St., Suite 100, Oakland, CA 96402 (United States); Hammel, Heidi B. [AURA, 1212 New York Ave. NW, Suite 450, Washington, DC 20005 (United States); Hornbeck, Jeremy [Department of Physics and Astronomy, University of Louisville, Louisville, KY 40292 (United States); Russell, Ray W. [The Aerospace Corporation, Los Angeles, CA 90009 (United States); Sitko, Michael L. [Department of Physics, University of Cincinnati, Cincinnati, OH 45221 (United States); Woodgate, Bruce E., E-mail: acox02@villanova.edu [ExoPlanets and Stellar Astrophysics Laboratory, Code 667, NASA' s Goddard Space Flight Center, Greenbelt, MD 20771 (United States)

    2013-01-01

    Previous studies of the classical T Tauri star AA Tau have interpreted the UX-Orionis-like photo-polarimetric variability as being due to a warp in the inner disk caused by an inclined stellar magnetic dipole field. We test that these effects are macroscopically observable in the inclination and alignment of the disk. We use Hubble Space Telescope (HST)/STIS coronagraphic imagery to measure the V magnitude of the star for both STIS coronagraphic observations, compare these data with optical photometry in the literature, and find that, unlike other classical T Tauri stars observed in the same HST program, the disk is most robustly detected in scattered light at stellar optical minimum light. We measure the outer disk radius, 1.''15 {+-} 0.''10, major-axis position angle, and disk inclination and find that the inner disk, as reported in the literature, is both misinclined and misaligned with respect to the outer disk. AA Tau drives a faint jet, detected in both STIS observations and in follow-on Goddard Fabry-Perot imagery, which is also misaligned with respect to the projection of the outer disk minor axis and is poorly collimated near the star, but which can be traced 21'' from the star in data from 2005. The measured outer disk inclination, 71 Degree-Sign {+-} 1 Degree-Sign , is out of the range of inclinations suggested for stars with UX-Orionis-like variability when no grain growth has occurred in the disk. The faintness of the disk, small disk size, and detection of the star despite the high inclination all indicate that the dust disk must have experienced grain growth and settling toward the disk midplane, which we verify by comparing the observed disk with model imagery from the literature.

  3. A hot Jupiter around the very active weak-line T Tauri star TAP 26

    Science.gov (United States)

    Yu, L.; Donati, J.-F.; Hébrard, E. M.; Moutou, C.; Malo, L.; Grankin, K.; Hussain, G.; Collier Cameron, A.; Vidotto, A. A.; Baruteau, C.; Alencar, S. H. P.; Bouvier, J.; Petit, P.; Takami, M.; Herczeg, G.; Gregory, S. G.; Jardine, M.; Morin, J.; Ménard, F.; Matysse Collaboration

    2017-05-01

    We report the results of an extended spectropolarimetric and photometric monitoring of the weak-line T Tauri star TAP 26, carried out within the Magnetic Topologies of Young Stars and the Survival of close-in massive Exoplanets (MaTYSSE) programme with the Echelle SpectroPolarimetric Device for the Observation of Stars (ESPaDOnS) spectropolarimeter at the 3.6-m Canada-France-Hawaii Telescope. Applying Zeeman-Doppler Imaging (ZDI) to our observations, concentrating in 2015 November and 2016 January and spanning 72 d in total, 16 d in 2015 November and 13 d in 2016 January, we reconstruct surface brightness and magnetic field maps for both epochs and demonstrate that both distributions exhibit temporal evolution not explained by differential rotation alone. We report the detection of a hot Jupiter (hJ) around TAP 26 using three different methods, two using ZDI and one Gaussian-process regression (GPR), with a false-alarm probability smaller than 6 × 10-4. However, as a result of the aliasing related to the observing window, the orbital period cannot be uniquely determined; the orbital period with highest likelihood is 10.79 ± 0.14 d followed by 8.99 ± 0.09 d. Assuming the most likely period, and that the planet orbits in the stellar equatorial plane, we obtain that the planet has a minimum mass Msin i of 1.66 ± 0.31 MJup and orbits at 0.0968 ± 0.0032 au from its host star. This new detection suggests that disc type II migration is efficient at generating newborn hJs, and that hJs may be more frequent around young T Tauri stars than around mature stars (or that the MaTYSSE sample is biased towards hJ-hosting stars).

  4. Accretion Rates for T Tauri Stars Using Nearly Simultaneous Ultraviolet and Optical Spectra

    Science.gov (United States)

    Ingleby, Laura; Calvet, Nuria; Herczeg, Gregory; Blaty, Alex; Walter, Frederick; Ardila, David; Alexander, Richard; Edwards, Suzan; Espaillat, Catherine; Gregory, Scott G.; Hillenbrand, Lynne; Brown, Alexander

    2013-04-01

    We analyze the accretion properties of 21 low-mass T Tauri stars using a data set of contemporaneous near-UV (NUV) through optical observations obtained with the Hubble Space Telescope Imaging Spectrograph and the ground-based Small and Medium Aperture Research Telescope System, a unique data set because of the nearly simultaneous broad wavelength coverage. Our data set includes accreting T Tauri stars in Taurus, Chamaeleon I, η Chamaeleon, and the TW Hydra Association. For each source we calculate the accretion rate (\\dot{M}) by fitting the NUV and optical excesses above the photosphere, produced in the accretion shock, introducing multiple accretion components characterized by a range in energy flux (or density) for the first time. This treatment is motivated by models of the magnetospheric geometry and accretion footprints, which predict that high-density, low filling factor accretion spots coexist with low-density, high filling factor spots. By fitting the UV and optical spectra with multiple accretion components, we can explain excesses which have been observed in the near-IR. Comparing our estimates of \\dot{M} to previous estimates, we find some discrepancies; however, they may be accounted for when considering assumptions for the amount of extinction and variability in optical spectra. Therefore, we confirm many previous estimates of the accretion rate. Finally, we measure emission line luminosities from the same spectra used for the \\dot{M} estimates, to produce correlations between accretion indicators (Hβ, Ca II K, C II], and Mg II) and accretion properties obtained simultaneously.

  5. Spectral Analysis

    CERN Document Server

    Cecconi, Jaures

    2011-01-01

    G. Bottaro: Quelques resultats d'analyse spectrale pour des operateurs differentiels a coefficients constants sur des domaines non bornes.- L. Garding: Eigenfuction expansions.- C. Goulaouic: Valeurs propres de problemes aux limites irreguliers: applications.- G. Grubb: Essential spectra of elliptic systems on compact manifolds.- J.Cl. Guillot: Quelques resultats recents en Scattering.- N. Schechter: Theory of perturbations of partial differential operators.- C.H. Wilcox: Spectral analysis of the Laplacian with a discontinuous coefficient.

  6. SEEDS direct imaging of the RV-detected companion to V450 Andromedae, and characterization of the system

    CERN Document Server

    Hełminiak, K G; Mede, K; Brandt, T D; Kandori, R; Suenaga, T; Kusakabe, N; Narita, N; Carson, J C; Currie, T; Kudo, T; Hashimoto, J; Abe, L; Akiyama, E; Brandner, W; Feldt, M; Goto, M; Grady, C A; Guyon, O; Hayano, Y; Hayashi, M; Hayashi, S S; Henning, T; Hodapp, K W; Ishii, M; Iye, M; Janson, M; Knapp, G R; Kwon, J; Matsuo, T; McElwain, M W; Miyama, S; Morino, J -I; Moro-Martin, A; Nishimura, T; Ryu, T; Pyo, T -S; Serabyn, E; Suto, H; Suzuki, R; Takahashi, Y H; Takami, M; Takato, N; Terada, H; Thalmann, C; Turner, E L; Watanabe, M; Wisniewski, J; Yamada, T; Takami, H; Usuda, T; Tamura, M

    2016-01-01

    We report the direct imaging detection of a low-mass companion to a young, moderately active star V450 And, that was previously identified with the radial velocity method. The companion was found in high-contrast images obtained with the Subaru Telescope equipped with the HiCIAO camera and AO188 adaptive optics system. From the public ELODIE and SOPHIE archives we extracted available high-resolution spectra and radial velocity (RV) measurements, along with RVs from the Lick planet search program. We combined our multi-epoch astrometry with these archival, partially unpublished RVs, and found that the companion is a low-mass star, not a brown dwarf, as previously suggested. We found the best-fitting dynamical masses to be $m_1=1.141_{-0.091}^{+0.037}$ and $m_2=0.279^{+0.023}_{-0.020}$ M$_\\odot$. We also performed spectral analysis of the SOPHIE spectra with the iSpec code. The Hipparcos time-series photometry shows a periodicity of $P=5.743$ d, which is also seen in SOPHIE spectra as an RV modulation of the st...

  7. Overexpression, purification, crystallization and preliminary X-ray analysis of Rv2780 from Mycobacterium tuberculosis H37Rv

    Energy Technology Data Exchange (ETDEWEB)

    Tripathi, Sarvind Mani; Ramachandran, Ravishankar, E-mail: r-ravishankar@cdri.res.in [Molecular and Structural Biology Division, Central Drug Research Institute, PO Box 173, Chattar Manzil, Mahatma Gandhi Marg, Lucknow 226001 (India)

    2008-05-01

    Rv2780, an alanine dehydrogenase from M. tuberculosis, has been crystallized in apo and NAD/pyruvate-bound forms. Preliminary crystallographic analysis shows that there is a hexamer and trimer in the asymmetric units of the apo and ternary complex forms, respectively. Rv2780, an alanine dehydrogenase from Mycobacterium tuberculosis (MtAlaDH), catalyzes the NAD-dependent interconversion of alanine and pyruvate. Alanine dehydrogenase is released into the culture medium in substantial amounts by virulent strains of mycobacteria and is not found in the vaccine strain of tuberculosis. Crystals of recombinant MtAlaDH were grown from 2 M ammonium sulfate solution at ∼12 mg ml{sup −1} protein concentration in two crystal forms which occur in the presence and absence of NAD/pyruvate, respectively. Diffraction data extending to 2.6 Å were collected at room temperature from both apo and ternary complex crystals. Crystals of the apoenzyme have unit-cell parameters a = 173.89, b = 127.07, c = 135.95 Å. They are rod-like in shape and belong to space group C2. They contain a hexamer in the asymmetric unit. Crystals of the ternary complex belong to space group P4{sub 3}2{sub 1}2 and have unit-cell parameters a = b = 88.99, c = 373.85 Å. There are three subunits in the asymmetric unit of the holoenzyme crystals.

  8. Increased virulence of Mycobacterium tuberculosis H37Rv overexpressing LipY in a murine model.

    Science.gov (United States)

    Singh, Vipul K; Srivastava, Mrigank; Dasgupta, Arunava; Singh, Mohan P; Srivastava, Ranjana; Srivastava, Brahm S

    2014-05-01

    We have investigated the role of Rv3097c-encoded lipase (LipY) on the virulence of Mycobacterium tuberculosis. It has been shown that the overexpression of LipY in strain H37Rv induced increase in virulence of recombinant H37Rv::LipY strain. Compared to H37Rv, infection with H37Rv::LipY caused enhanced mortality, weight loss, bacterial load in lungs, splenomegaly, worsening lung morphology and pathology. Mice immunized with recombinant LipY antigen were protected against challenge with H37Rv::LipY, which correlated with enhanced survival of challenged mice and striking decrease in pathological features observed in unimmunized mice. To probe the cause of increase in virulence of H37Rv::LipY, the immune status of the host infected with H37Rv and H37Rv::LipY was compared. It was found that overexpression of LipY compromised immune responses resulting in attenuation of Th1 and Th17 responses, significant increase in IL-10, decrease in number of macrophages and T cells, and increase in numbers of Treg, and DCs in the lungs whereas in mice immunized with LipY an increased pool of T cells and DCs was observed. This led us to conclude that the increase in the virulence of H37Rv::LipY was due to downregulation of the host's protective immunity and the Rv3097c encoded LipY lipase is a virulence factor of M. tuberculosis.

  9. Role of local absorption on the X-ray emission from MHD accretion shocks in classical T Tauri stars

    OpenAIRE

    Bonito; Orlando,; Argiroffi; Miceli; Reale,, S; Peres,, Marco A; Matsakos; Stehle; Ibgui

    2014-01-01

    Accretion processes onto classical T Tauri stars (CTTSs) are believed to generate shocks at the stellar surface due to the impact of supersonic downflowing plasma. Although current models of accretion streams provide a plausible global picture of this process, several aspects are still unclear. For example, the observed X-ray luminosity in accretion shocks is, in general, well below the predicted value. A possible explanation discussed in the literature is in terms of significant absorption o...

  10. Spectral Ranking

    CERN Document Server

    Vigna, Sebastiano

    2009-01-01

    This note tries to attempt a sketch of the history of spectral ranking, a general umbrella name for techniques that apply the theory of linear maps (in particular, eigenvalues and eigenvectors) to matrices that do not represent geometric transformations, but rather some kind of relationship between entities. Albeit recently made famous by the ample press coverage of Google's PageRank algorithm, spectral ranking was devised more than fifty years ago, almost exactly in the same terms, and has been studied in psychology and social sciences. I will try to describe it in precise and modern mathematical terms, highlighting along the way the contributions given by previous scholars.

  11. Spectral Tagging

    Energy Technology Data Exchange (ETDEWEB)

    Smartt, Heidi A. [Sandia National Laboratories (United States)

    2003-05-01

    This research examines the feasibility of spectral tagging, which involves modifying the spectral signature of a target, e.g. by mixing an additive with the target's paint. The target is unchanged to the human eye, but the tag is revealed when viewed with a spectrometer. This project investigates a layer of security that is not obvious, and therefore easy to conceal. The result is a tagging mechanism that is difficult to counterfeit. Uniquely tagging an item is an area of need in safeguards and security and non-proliferation. The powdered forms of the minerals lapis lazuli and olivine were selected as the initial test tags due to their availability and uniqueness in the visible to near-infrared spectral region. They were mixed with paints and applied to steel. In order to verify the presence of the tags quantitatively, the data from the spectrometer was input into unmixing models and signal detection algorithms. The mixture with the best results was blue paint mixed with lapis lazuli and olivine. The tag had a 0% probability of false alarm and a 100% probability of detection. The research proved that spectral tagging is feasible, although certain tag/paint mixtures are more detectable than others.

  12. Functional Characterization of PknI-Rv2159c Interaction in Redox Homeostasis of Mycobacterium tuberculosis

    Directory of Open Access Journals (Sweden)

    Arunkumar Venkatesan

    2016-10-01

    Full Text Available Mycobacterium tuberculosis adapts to stress conditions by responding to the signals from its external environment. M. tuberculosis genome encodes 11 eukaryotic like serine/threonine protein kinases (STPK and their importance in regulating the physiology and virulence of the bacteria are being explored. Previous study from our lab identified the M. tuberculosis STPK, PknI interacts with two peroxidase proteins such as Rv2159c and Rv0148. In this study, we have characterized the biological function behind the PknI-Rv2159c interaction in M. tuberculosis. Point mutation of Ala-Gly-Trp motif identified that only Ala49 and Gly50 amino acids of Rv2159c are responsible for interaction and there is no phosphorylation involved in the PknI-Rv2159c interaction. Rv2159c is a member from the carboxymuconolactone decarboxylase family with peroxidase activity. Enzymatic assays with catalytic site point mutants showed that Cys84 of Rv2159c was responsible for its alkylhydroperoxidase activity. Interestingly, interaction with PknI increased its peroxidase activity by several folds. Gene knockdown of Rv2159c in M. tuberculosis showed increased sensitivity to peroxides such as cumene hydroperoxide and hydrogen peroxide. Proteomic analysis of differentially expressing Rv2159c strains by 2D gel electrophoresis and mass spectrometry revealed the differential abundance of 21 proteins. The total absence of oxidoreductase, GuaB1 suggests the essential role of Rv2159c in redox maintenance. Our findings provide new insights on signaling mechanisms of PknI in maintaining the redox homeostasis during oxidative stresses.

  13. Spectral Predictors

    Energy Technology Data Exchange (ETDEWEB)

    Ibarria, L; Lindstrom, P; Rossignac, J

    2006-11-17

    Many scientific, imaging, and geospatial applications produce large high-precision scalar fields sampled on a regular grid. Lossless compression of such data is commonly done using predictive coding, in which weighted combinations of previously coded samples known to both encoder and decoder are used to predict subsequent nearby samples. In hierarchical, incremental, or selective transmission, the spatial pattern of the known neighbors is often irregular and varies from one sample to the next, which precludes prediction based on a single stencil and fixed set of weights. To handle such situations and make the best use of available neighboring samples, we propose a local spectral predictor that offers optimal prediction by tailoring the weights to each configuration of known nearby samples. These weights may be precomputed and stored in a small lookup table. We show that predictive coding using our spectral predictor improves compression for various sources of high-precision data.

  14. Dissecting Mechanisms of Immunodominance to the Common TB Antigens ESAT-6, CFP10, Rv2031c (hspX), Rv2654c (TB7.7) and Rv1038c (EsxJ)1

    Science.gov (United States)

    Arlehamn, Cecilia S. Lindestam; Sidney, John; Henderson, Ryan; Greenbaum, Jason A.; James, Eddie A.; Moutaftsi, Magdalini; Coler, Rhea; McKinney, Denise M.; Park, Daniel; Taplitz, Randy; Kwok, William W.; Grey, Howard; Peters, Bjoern; Sette, Alessandro

    2012-01-01

    Diagnosis of tuberculosis often relies on the ex vivo interferon gamma release assays QuantiFERON-TB Gold In-Tube and T-SPOT.TB. However, understanding of the immunological mechanisms underlying their diagnostic utility is still incomplete. Accordingly, we investigated T cell responses for the TB antigens included in the these assays and other commonly studied antigens; ESAT-6, CFP10, Rv2031c, Rv2654c, and Rv1038c. PBMC from latently infected individuals were tested in ex vivo ELISPOT assays with overlapping peptides spanning the entirety of these antigens. We found striking variations in prevalence and magnitude of ex vivo reactivity, with CFP10 being most dominant, followed by ESAT-6 and Rv2654c being virtually inactive. Rv2031c and Rv1038c were associated with intermediate patterns of reactivity. Further studies showed that low reactivity was not due to lack of HLA binding peptides, and high reactivity was associated with recognition of a few discrete dominant antigenic regions. Different donors recognized the same core sequence in a given epitope. In some cases the identified epitopes were restricted by a single specific common HLA molecule (selective restriction), while in other cases promiscuous restriction of the same epitope by multiple HLA molecules was apparent. Definition of the specific restricting HLA allowed to produce tetrameric reagents and show that epitope-specific T cells recognizing either selectively or promiscuously restricted epitopes were predominantly T effector memory (TEM). In conclusion, these results highlight the feasibility of more clearly defined TB diagnostic reagent. PMID:22504645

  15. Dissecting mechanisms of immunodominance to the common tuberculosis antigens ESAT-6, CFP10, Rv2031c (hspX), Rv2654c (TB7.7), and Rv1038c (EsxJ).

    Science.gov (United States)

    Arlehamn, Cecilia S Lindestam; Sidney, John; Henderson, Ryan; Greenbaum, Jason A; James, Eddie A; Moutaftsi, Magdalini; Coler, Rhea; McKinney, Denise M; Park, Daniel; Taplitz, Randy; Kwok, William W; Grey, Howard; Peters, Bjoern; Sette, Alessandro

    2012-05-15

    Diagnosis of tuberculosis often relies on the ex vivo IFN-γ release assays QuantiFERON-TB Gold In-Tube and T-SPOT.TB. However, understanding of the immunological mechanisms underlying their diagnostic use is still incomplete. Accordingly, we investigated T cell responses for the TB Ags included in the these assays and other commonly studied Ags: early secreted antigenic target 6 kDa, culture filtrate protein 10 kDa, Rv2031c, Rv2654c, and Rv1038c. PBMC from latently infected individuals were tested in ex vivo ELISPOT assays with overlapping peptides spanning the entirety of these Ags. We found striking variations in prevalence and magnitude of ex vivo reactivity, with culture filtrate protein 10 kDa being most dominant, followed by early secreted antigenic target 6 kDa and Rv2654c being virtually inactive. Rv2031c and Rv1038c were associated with intermediate patterns of reactivity. Further studies showed that low reactivity was not due to lack of HLA binding peptides, and high reactivity was associated with recognition of a few discrete dominant antigenic regions. Different donors recognized the same core sequence in a given epitope. In some cases, the identified epitopes were restricted by a single specific common HLA molecule (selective restriction), whereas in other cases, promiscuous restriction of the same epitope by multiple HLA molecules was apparent. Definition of the specific restricting HLA allowed to produce tetrameric reagents and showed that epitope-specific T cells recognizing either selectively or promiscuously restricted epitopes were predominantly T effector memory. In conclusion, these results highlight the feasibility of more clearly defined TB diagnostic reagent.

  16. Geir Hønneland, Russia and the Arctic: Environment, Identity and Foreign Policy & Leif Christian Jensen, International Relations in the Arctic: Norway and the Struggle for Power in the New North (London/New York: IB Tauris, 2016

    Directory of Open Access Journals (Sweden)

    Romain Chuffart

    2017-03-01

    Full Text Available A review of the books: Geir Hønneland, Russia and the Arctic: Environment, Identity and Foreign Policy (London/New York: IB Tauris, 2016; and Leif Christian Jensen, International Relations in the Arctic: Norway and the Struggle for Power in the New North (London/New York: IB Tauris, 2016

  17. Rv3351c, a Mycobacterium tuberculosis gene that affects bacterial growth and alveolar epithelial cell viability.

    Science.gov (United States)

    Pavlicek, Rebecca L; Fine-Coulson, Kari; Gupta, Tuhina; Quinn, Frederick D; Posey, James E; Willby, Melisa; Castro-Garza, Jorge; Karls, Russell K

    2015-12-01

    Despite the interactions known to occur between various lower respiratory tract pathogens and alveolar epithelial cells (AECs), few reports examine factors influencing the interplay between Mycobacterium tuberculosis bacilli and AECs during infection. Importantly, in vitro studies have demonstrated that the M. tuberculosis hbha and esxA gene products HBHA and ESAT6 directly or indirectly influence AEC survival. In this report, we identify Rv3351c as another M. tuberculosis gene that impacts the fate of both the pathogen and AEC host. Intracellular replication of an Rv3351c mutant in the human AEC type II pneumocyte cell line A549 was markedly reduced relative to the complemented mutant and parent strain. Deletion of Rv3351c diminished the release of lactate dehydrogenase and decreased uptake of trypan blue vital stain by host cells infected with M. tuberculosis bacilli, suggesting attenuated cytotoxic effects. Interestingly, an isogenic hbha mutant displayed reductions in AEC killing similar to those observed for the Rv3351c mutant. This opens the possibility that multiple M. tuberculosis gene products interact with AECs. We also observed that Rv3351c aids intracellular replication and survival of M. tuberculosis in macrophages. This places Rv3351c in the same standing as HBHA and ESAT6, which are important factors in AECs and macrophages. Defining the mechanism(s) by which Rv3351c functions to aid pathogen survival within the host may lead to new drug or vaccine targets.

  18. Computational prediction and experimental assessment of secreted/surface proteins from Mycobacterium tuberculosis H37Rv.

    Directory of Open Access Journals (Sweden)

    Carolina Vizcaíno

    2010-06-01

    Full Text Available The mycobacterial cell envelope has been implicated in the pathogenicity of tuberculosis and therefore has been a prime target for the identification and characterization of surface proteins with potential application in drug and vaccine development. In this study, the genome of Mycobacterium tuberculosis H37Rv was screened using Machine Learning tools that included feature-based predictors, general localizers and transmembrane topology predictors to identify proteins that are potentially secreted to the surface of M. tuberculosis, or to the extracellular milieu through different secretory pathways. The subcellular localization of a set of 8 hypothetically secreted/surface candidate proteins was experimentally assessed by cellular fractionation and immunoelectron microscopy (IEM to determine the reliability of the computational methodology proposed here, using 4 secreted/surface proteins with experimental confirmation as positive controls and 2 cytoplasmic proteins as negative controls. Subcellular fractionation and IEM studies provided evidence that the candidate proteins Rv0403c, Rv3630, Rv1022, Rv0835, Rv0361 and Rv0178 are secreted either to the mycobacterial surface or to the extracellular milieu. Surface localization was also confirmed for the positive controls, whereas negative controls were located on the cytoplasm. Based on statistical learning methods, we obtained computational subcellular localization predictions that were experimentally assessed and allowed us to construct a computational protocol with experimental support that allowed us to identify a new set of secreted/surface proteins as potential vaccine candidates.

  19. Systematic Search for Rotation at the Base of Outflows from T Tauri Stars

    Science.gov (United States)

    Bacciotti, Francesca

    2002-07-01

    We wish to search for rotation signatures in the initial portion {first 100 AU} of a sample of outflows emanating from T Tauri stars {TTSs}. This project originates from our detection of systematic transverse radial velocity shifts in STIS spectra of the DG Tau jet {Bacciotti et al., 2002}. The shifts, observed in a region where the flow is already collimated, but has not yet manifestly interacted with its environment, are consistent with the predictions of magneto- centrifugal launching models, and may constitute the first observed indication for rotation in the initial portion of a jet flow. Rotation is a fundamental ingredient in star formation theories, thus we propose to confirm the above result by carrying out a systematic survey in similar flows. We plan to take for each jet a STIS spectrum in the 6300 - 6800 Angstrom range, with the slit perpendicular to the flow direction and at a distance of about 0.''3 from the source {i.e., in our targets, 40 - 70 AU along the jet depending on inclination angle}. Since the flows are resolved transversely with HST, the proposed slit orientation allows for the direct detection of systematic velocity shifts. Where found, we will check for consistency between the sense of rotation observed and that of the underlying disk through CO interferometric measurements. As a by-product, estimates of the excitation conditions across the flow {including ionization fraction} and of the mass outflow rates will be derived.

  20. T Tauri Jet Physics Resolved Near The Launching Region with the Hubble Space Telescope

    CERN Document Server

    Coffey, Deirdre; Podio, Linda

    2008-01-01

    We present an analysis of the gas physics at the base of jets from five T Tauri stars based on high angular resolution optical spectra, using the Hubble Space Telescope Imaging Spectrograph (HST/STIS). The spectra refer to a region within 100 AU of the star, i.e. where the collimation of the jet has just taken place. We form PV images of the line ratios to get a global picture of the flow excitation. We then apply a specialised diagnostic technique to find the electron density, ionisation fraction, electron temperature and total density. Our results are in the form of PV maps of the obtained quantities, in which the gas behaviour is resolved as a function of both radial velocity and distance from the jet axis. They highlight a number of interesting physical features of the jet collimation region, including regions of extremely high density, asymmetries with respect to the axis, and possible shock signatures. Finally, we estimate the jet mass and angular momentum outflow rates, both of which are fundamental pa...

  1. Locating the Launching Region of T Tauri Winds The Case of DG Tau

    CERN Document Server

    Anderson, J M; Krasnopolsky, R; Blandford, R D; Anderson, Jeffrey M.; Li, Zhi-Yun; Krasnopolsky, Ruben; Blandford, Roger

    2003-01-01

    It is widely believed that T Tauri winds are driven magnetocentrifugally from accretion disks close to the central stars. The exact launching conditions are uncertain. We show that a general relation exists between the poloidal and toroidal velocity components of a magnetocentrifugal wind at large distances and the rotation rate of the launching surface, independent of the uncertain launching conditions. We discuss the physical basis of this relation and verify it using a set of numerically-determined large-scale wind solutions. Both velocity components are in principle measurable from spatially resolved spectra, as has been done for the extended low-velocity component (LVC) of the DG Tau wind by Bacciotti et al. For this particular source, we infer that the spatially resolved LVC originates from a region on the disk extending from $\\sim 0.3$ to $\\sim 4.0\\AU$ from the star, which is consistent with, and a refinement over, the previous rough estimate of Bacciotti et al.

  2. Magnetospheric accretion on the fully-convective classical T Tauri star DN Tau

    CERN Document Server

    Donati, JF; Alencar, SHP; Hussain, G; Bouvier, J; Jardine, MM; Menard, F; Dougados, C; Romanova, MM

    2013-01-01

    We report here results of spectropolarimetric observations of the classical T Tauri star DN Tau carried out (at 2 epochs) with ESPaDOnS at the Canada-France-Hawaii Telescope within the `Magnetic Protostars and Planets' programme. We infer that DN Tau, with a photospheric temperature of 3,950+-50 K, a luminosity of 0.8+-0.2 Lsun and a rotation period of 6.32 d, is a ~2Myr-old fully-convective 0.65+-0.05 Msun star with a radius of 1.9+-0.2 Dsun, viewed at an inclination of 35+-10degr. Clear circularly-polarized Zeeman signatures are detected in both photospheric and accretion-powered emission lines, probing longitudinal fields of up to 1.8 kG (in the He1 D3 accretion proxy). Rotational modulation of Zeeman signatures, detected both in photospheric and accretion lines, is different between our 2 runs, providing further evidence that fields of cTTSs are generated by non-stationary dynamos. Using tomographic imaging, we reconstruct maps of the large-scale field, of the photospheric brightness and of the accretion-...

  3. Classical T Tauri stars: magnetic fields, coronae, and star-disc interactions

    CERN Document Server

    Johnstone, C P; Gregory, S G; Donati, J -F; Hussain, G

    2013-01-01

    The magnetic fields of young stars set their coronal properties and control their spin evolution via the star-disc interaction and outflows. Using 14 magnetic maps of 10 classical T Tauri stars (CTTSs) we investigate their closed X-ray emitting coronae, their open wind-bearing magnetic fields, and the geometry of magnetospheric accretion flows. The magnetic fields of all the CTTSs are multipolar. Stars with simpler (more dipolar) large-scale magnetic fields have stronger fields, are slower rotators, and have larger X-ray emitting coronae compared to stars with more complex large-scale magnetic fields. The field complexity controls the distribution of open and closed field regions across the stellar surface, and strongly influences the location and shapes of accretion hot spots. However, the higher order field components are of secondary importance in determining the total unsigned open magnetic flux, which depends mainly on the strength of the dipole component and the stellar surface area. Likewise, the dipol...

  4. On the origin of ionising photons emitted by T Tauri stars

    CERN Document Server

    Alexander, R D; Pringle, J E

    2004-01-01

    We address the issue of the production of Lyman continuum photons by T Tauri stars, in an attempt to provide constraints on theoretical models of disc photoionisation. By treating the accretion shock as a hotspot on the stellar surface we show that Lyman continuum photons are produced at a rate approximately three orders of magnitude lower than that produced by a corresponding black body, and that a strong Lyman continuum is only emitted for high mass accretion rates. When our models are extended to include a column of material accreting on to the hotspot we find that the accretion column is extremely optically thick to Lyman continuum photons. Further, we find that radiative recombination of hydrogen atoms within the column is not an efficient means of producing photons with energies greater than 13.6eV, and find that an accretion column of any conceivable height suppresses the emission of Lyman continuum photons to a level below or comparable to that expected from the stellar photosphere. The photospheric L...

  5. A survey of T Tauri stars with AKARI toward the Taurus-Auriga region

    CERN Document Server

    Takita, Satoshi; Kitamura, Yoshimi; Ishihara, Daisuke; Ita, Yoshifusa; Oyabu, Shinki; Ueno, Munetaka

    2010-01-01

    Aims: We search new T Tauri star (TTS) candidates with the mid-infrared (MIR) part of the AKARI All-Sky Survey at 9 and 18 um wavelengths. Methods: We used the point source catalogue (PSC), obtained by the Infrared Camera (IRC) on board AKARI. We combined the 2MASS PSC and the 3rd version of the USNO CCD Astrograph Catalogue (UCAC) with the AKARI IRC-PSC, and surveyed 517 known TTSs over a 1800-square-degree part of the Taurus-Auriga region to find criteria to extract TTSs. We considered asymptotic giant branch (AGB) stars, post-AGB stars, Planetary Nebulae (PNe), and galaxies, which have similar MIR colours, to separate TTSs from these sources. Results: Of the 517 known TTSs, we detected 133 sources with AKARI. Based on the colour-colour and colour-magnitude diagrams made from the AKARI, 2MASS, and UCAC surveys, we propose the criteria to extract TTS candidates from the AKARI All-Sky data. On the basis of our criteria, we selected 176/14725 AKARI sources as TTS candidates which are located around the Taurus-...

  6. Mapping the Circumstellar Environment of T Tauri with Fluorescent H_2 Emission

    CERN Document Server

    Walter, F M; Brown, A; Ardila, D R; Gahm, G F; Johns-Krull, C M; Lissauer, J J; Simon, M; Valenti, J A; Walter, Frederick M.; Herczeg, Gregory; Brown, Alexander; Ardila, David R.; Gahm, Goesta F.; Johns-Krull, Christopher M.; Lissauer, Jack J.; Simon, Michal; Valenti, Jeff A.

    2003-01-01

    We have obtained three long-slit, far UV spectra of the pre-main sequence system T Tauri. These HST/STIS spectra show a strong and variable on-source spectrum composed of both fluoresced H_2 and stellar chromospheric lines. Extended H_2 emission is seen up to 10" from the T Tau system. The on-source and extended H_2 are both pumped by H I Lyman alpha. The on-source H_2 is pumped by the red wing of a broad, self-absorbed Ly-alpha line, while the progressions seen in the extended gas are pumped from near line center. This suggests that the extended H_2 is pumped locally, and not by the stellar Ly-alpha line. The H_2 to the north and west coincides with the evacuated cavity bounded by the optical reflection nebulosity; to the south the extended H_2 coincides with the HH 255 outflow from the embedded infrared companion T Tau S. The spatial profile of the extended gas shows a prominent dip coincident with the position of T Tau S. This may be absorption by a disk associated with T Tau S. There is no evidence for ab...

  7. A unique homodimeric NAD⁺-linked isocitrate dehydrogenase from the smallest autotrophic eukaryote Ostreococcus tauri.

    Science.gov (United States)

    Tang, Wang-Gang; Song, Ping; Cao, Zheng-Yu; Wang, Peng; Zhu, Guo-Ping

    2015-06-01

    In eukaryotes, NAD(+)-dependent isocitrate dehydrogenase (IDH) is strictly mitochondrial and is a key enzyme in the Krebs cycle. To date, all known NAD(+)-specific IDHs (NAD-IDHs) in the mitochondria are believed to be heteromeric in solution. Here, a unique homodimeric NAD-IDH from Ostreococcus tauri (OtIDH), the smallest autotrophic picoeukaryote, was unveiled. Active OtIDH has a molecular weight of ∼93 kDa with each subunit of 46.7 kDa. In the presence of Mn(2+) and Mg(2+), OtIDH displayed 42-fold and 51-fold preference for NAD(+) over NADP(+), respectively. Interestingly, OtIDH exhibited a sigmoidal kinetic behavior in response to isocitrate unlike other homodimeric homologs, and a remarkably high affinity for isocitrate (S0.5 < 10 μM) unlike other hetero-oligomeric homologs. Furthermore, its coenzyme specificity can be completely converted from NAD(+) (ancient trait) to NADP(+) (adaptive trait) by rational mutagenesis based on the evolutionary trace. Mutants D344R and D344R/M345H displayed a 15-fold and 72-fold preference for NADP(+) over NAD(+), respectively, indicating that D344 and M345 are the determinants of NAD(+) specificity. These findings also suggest that OtIDH may be an ancestral form of type II IDHs (all reported members are NADP(+)-linked enzymes) and may have evolved into NADP(+)-dependent IDH for adaptation to the increased demand of NADPH under carbon starvation.

  8. Star-disk interaction in classical T Tauri stars revealed using wavelet analysis

    CERN Document Server

    Lopez-Santiago, J; Flaccomio, E; Sciortino, S; Micela, G; Reale, F

    2016-01-01

    The extension of the corona of classical T Tauri stars (CTTS) is under discussion. The standard model of magnetic configuration of CTTS predicts that coronal magnetic flux tubes connect the stellar atmosphere to the inner region of the disk. However, differential rotation may disrupt these long loops. The results from Hydrodynamic modeling of X-ray flares observed in CTTS confirming the star-disk connection hypothesis are still controversial. Some authors suggest the presence of the accretion disk prevent the stellar corona to extent beyond the co-rotation radius, while others simply are not confident with the methods used to derive loop lengths. We use independent procedures to determine the length of flaring loops in stars of the Orion Nebula Cluster previously analyzed using Hydrodynamic models. Our aim is to disentangle between the two scenarios proposed. We present a different approach to determine the length of flaring loops based on the oscillatory nature of the loops after strong flares. We use wavele...

  9. MN Lup: X-rays from a weakly accreting T Tauri star

    CERN Document Server

    Guenther, H M; Robrade, J; Wolk, S J

    2013-01-01

    Young T Tauri stars (TTS) are surrounded by an accretion disk, which over time disperses due to photoevaporation, accretion, and possibly planet formation. The accretion shock on the central star produces an UV/optical veiling continuum, line emission, and X-ray signatures. As the accretion rate decreases, the impact on the central star must change. In this article we study MN Lup, a young star where no indications of a disk are seen in IR observations. We present XMM-Newton and VLT/UVES observations, some of them taken simultaneously. The X-ray data show that MN Lup is an active star with L_X/L_bol close to the saturation limit. However, we find high densities (n_e > 3e10 /cm^3) in the X-ray grating spectrum. This can be well fitted using an accretion shock model with an accretion rate of 2e-11 M_sun/yr. Despite the simple Halpha line profile which has a broad component, but no absorption signatures as typically seen on accreting TTS, we find rotational modulation in Ca II K and in photospheric absorption li...

  10. Turbulent mixing layers in supersonic protostellar outflows, with application to DG Tauri

    CERN Document Server

    White, Marc C; Sutherland, Ralph S; Salmeron, Raquel; McGregor, Peter J

    2015-01-01

    Turbulent entrainment processes may play an important role in the outflows from young stellar objects at all stages of their evolution. In particular, lateral entrainment of ambient material by high-velocity, well-collimated protostellar jets may be the cause of the multiple emission-line velocity components observed in the microjet-scale outflows driven by classical T Tauri stars. Intermediate-velocity outflow components may be emitted by a turbulent, shock- excited mixing layer along the boundaries of the jet. We present a formalism for describing such a mixing layer based on Reynolds decomposition of quantities measuring fundamental properties of the gas. In this model, the molecular wind from large disc radii provides a continual supply of material for entrainment. We calculate the total stress profile in the mixing layer, which allows us to estimate the dissipation of turbulent energy, and hence the luminosity of the layer. We utilize MAPPINGS IV shock models to determine the fraction of total emission t...

  11. Tracing Slow Winds from T Tauri Stars via Low Velocity Forbidden Line Emission

    CERN Document Server

    Simon, M N; Edwards, S; Feng, W; Gorti, U; Hollenbach, D; Rigliaco, E; Keane, J T

    2016-01-01

    Using Keck/HIRES spectra {\\Delta}v ~ 7 km/s, we analyze forbidden lines of [O I] 6300 {\\AA}, [O I] 5577 {\\AA} and [S II] 6731 {\\AA} from 33 T Tauri stars covering a range of disk evolutionary stages. After removing a high velocity component (HVC) associated with microjets, we study the properties of the low velocity component (LVC). The LVC can be attributed to slow disk winds that could be magnetically (MHD) or thermally (photoevaporative) driven. Both of these winds play an important role in the evolution and dispersal of protoplanetary material. LVC emission is seen in all 30 stars with detected [O I] but only in 2 out of eight with detected [S II] , so our analysis is largely based on the properties of the [O I] LVC. The LVC itself is resolved into broad (BC) and narrow (NC) kinematic components. Both components are found over a wide range of accretion rates and their luminosity is correlated with the accretion luminosity, but the NC is proportionately stronger than the BC in transition disks. The FWHM of...

  12. The nature of the embedded intermediate-mass T Tauri star DK Cha

    CERN Document Server

    Lopez, Rebeca Garcia; Antoniucci, Simone; Garatti, Alessio Caratti o; Lorenzetti, Dario; Giannini, Teresa; Eislöffel, Jochen; Ray, Tom

    2011-01-01

    Most of our knowledge about star formation is based on studies of low-mass stars, whereas very little is known about the properties of the circumstellar material around young and embedded intermidiate-mass T Tauri stars (IMTTSs). We present an analysis of the excitation and accretion properties of the young IMTTS DK Cha. The nearly face-on configuration of this source allows us to have direct access to the star-disk system through the excavated envelope and outflow cavity. Based on LR optical and IR spectroscopy obtained with SofI/EFOSC2 on the NTT we derive the spectrum of DK Cha from ~0.6 to 2.5 \\mu m. From the detected lines we probe the conditions of the gas that emits the HI IR emission lines. In addition, we derive the mass accretion rate (Macc) from the relationships that connect the luminosity of the Br\\gamma\\ and Pa\\beta\\ lines with the accretion luminosity (Lacc). The observed optical/IR spectrum is extremely rich in forbidden and permitted atomic and molecular emission lines, which makes this sourc...

  13. Constraints to the magnetospheric properties of T Tauri stars - II. The Mg II ultraviolet feature

    Science.gov (United States)

    López-Martínez, Fatima; Gómez de Castro, Ana Inés

    2015-03-01

    The atmospheric structure of T Tauri stars (TTSs) and its connection with the large-scale outflow is poorly known. Neither the effect of the magnetically mediated interaction between the star and the disc is well understood. The Mg II multiplet is a fundamental tracer of TTSs atmospheres and outflows, and is the strongest feature in the near-ultraviolet spectrum of TTSs. The International Ultraviolet Explorer and Hubble Space Telescope data archives provide a unique set to study the main physical compounds contributing to the line profile and to derive the properties of the line formation region. The Mg II profiles of 44 TTSs with resolution 13 000-30 000 are available in these archives. In this work, we use this data set to measure the main observables: flux, broadening, asymmetry, terminal velocity of the outflow, and the velocity of the discrete absorption components. For some few sources repeated observations are available and variability has been studied. There is a warm wind that at sub-au scales absorbs the blue wing of the Mg II profiles. The main result found in this work is the correlation between the line broadening, Mg II flux, terminal velocity of the flow and accretion rate. Both outflow and magnetospheric plasma contribute to the Mg II flux. The flux-flux correlation between Mg II and C IV or He II is confirmed; however, no correlation is found between the Mg II flux and the UV continuum or the H2 emission.

  14. Constraints to the magnetospheric properties of T Tauri stars - II. The Mg II ultraviolet feature

    CERN Document Server

    Lopez-Martinez, Fatima

    2015-01-01

    The atmospheric structure of T Tauri Stars (TTSs) and its connection with the large scale outflow is poorly known. Neither the effect of the magnetically mediated inter- action between the star and the disc in the stellar atmosphere is well understood. The Mg II multiplet is a fundamental tracer of TTSs atmospheres and outflows, and is the strongest feature in the near-ultraviolet spectrum of TTSs. The International Ultraviolet Explorer and Hubble Space Telescope data archives provide a unique set to study the main physical compounds contributing to the line profile and to derive the properties of the line formation region. The Mg II profiles of 44 TTSs with resolution 13,000 to 30,000 are available in these archives. In this work, we use this data set to measure the main observables: flux, broadening, asymmetry, terminal velocity of the outflow, and the velocity of the Discrete Absorption Components. For some few sources repeated observations are available and variability has been studied. There is a warm wi...

  15. Observable Signatures of Classical T Tauri Stars Accreting in an Unstable Regime

    Directory of Open Access Journals (Sweden)

    Kurosawa Ryuichi

    2014-01-01

    Full Text Available We discuss key observational signatures of Classical T Tauri stars (CTTSs accreting through Rayleigh-Taylor instability, which occurs at the interface between an accretion disk and a stellar magnetosphere. In this study, the results of global 3-D MHD simulations of accretion flows, in both stable and unstable regimes, are used to predict the variability of hydrogen emission lines and light curves associated with those two distinctive accretion flow patterns. In the stable regime, a redshifted absorption component (RAC periodically appears in some hydrogen lines, but only during a fraction of a stellar rotation period. In the unstable regime, the RAC is present rather persistently during a whole stellar rotation period, and its strength varies non-periodically. The latter is caused by multiple accreting streams, formed randomly due to the instability, passing across the line of sight to an observer during one stellar rotation. This results in the quasi-stationarity appearance of the RAC because at least one of the accretion stream is almost always in the line of sight to an observer. In the stable regime, two stable hot spots produce a smooth and periodic light curve that shows only one or two peaks per stellar rotation. In the unstable regime, multiple hot spots formed on the surface of the star, produce the stochastic light curve with several peaks per rotation period.

  16. X-Shooter spectroscopy of young stellar objects: V - Slow winds in T Tauri stars

    CERN Document Server

    Natta, A; Alcalá, J M; Rigliaco, E; Covino, E; Stelzer, B; D'Elia, V

    2014-01-01

    Disks around T Tauri stars are known to lose mass, as best shown by the profiles of forbidden emission lines of low ionization species. At least two separate kinematic components have been identified, one characterised by velocity shifts of tens to hundreds km/s (HVC) and one with much lower velocity of few km/s (LVC). The HVC are convincingly associated to the emission of jets, but the origin of the LVC is still unknown. In this paper we analyze the forbidden line spectrum of a sample of 44 mostly low mass young stars in Lupus and $\\sigma$-Ori observed with the X-Shooter ESO spectrometer. We detect forbidden line emission of [OI], [OII], [SII], [NI], and [NII], and characterize the line profiles as LVC, blue-shifted HVC and red-shifted HVC. We focus our study on the LVC. We show that there is a good correlation between line luminosity and both L$_{star}$ and the accretion luminosity (or the mass-accretion rate) over a large interval of values (L$_{star}$ $\\sim 10^{-2} - 1$ L$_\\odot$; L$_{acc}$ $\\sim 10^{-5} ...

  17. Spatially Resolved Molecular Hydrogen Emission in the Inner 200AU Environments of Classical T Tauri Stars

    CERN Document Server

    Beck, Tracy L; Takami, Michihiro; Pyo, Tae-Soo

    2007-01-01

    We present 2.0-2.4micron integral field spectroscopy at adaptive optics spatial resolution (~0.''1) obtained with the Near-infrared Integral Field Spectrograph (NIFS) at Gemini North Observatory of six Classical T Tauri stars: T Tau, DG Tau, XZ Tau, HL Tau, RW Aur and HV Tau C. In all cases, the v=1-0 S(1) (2.12 micron) emission is detected at spatially extended distances from the central stars. The bulk of the H_2 emission is typically not spatially coincident with the location of continuum flux. Multiple transitions detected in the K-band spectra show that H_2 level populations are typical of gas in thermal equilibrium with excitation temperatures in the 1800K-2300 K range. Three of the stars have H_2 velocity profiles that are centered at the stellar radial velocity, and three show velocity shifts with respect to the system. Each of the stars studied here show observed excitation temperatures, spatial extents, and kinematics of the H_2 that are most consistent with shock excited emission from the inner reg...

  18. Identification and characterization of a novel starch branching enzyme from the picoalgae Ostreococcus tauri.

    Science.gov (United States)

    Hedin, Nicolas; Barchiesi, Julieta; Gomez-Casati, Diego F; Iglesias, Alberto A; Ballicora, Miguel A; Busi, María V

    2017-03-15

    Starch branching enzyme is a highly conserved protein from plants to algae. This enzyme participates in starch granule assembly by the addition of α-1,6-glucan branches to the α-1,4-polyglucans. This modification determines the structure of amylopectin thus arranging the final composition of the starch granule. Herein, we describe the function of the Ot01g03030 gene from the picoalgae Ostreococcus tauri. Although in silico analysis suggested that this gene codes for a starch debranching enzyme, our biochemical studies support that this gene encodes a branching enzyme (BE). The resulting 1058 amino acids protein has two in tandem carbohydrate binding domains (CBMs, from the CBM41 and CBM48 families) at the N-terminal (residues 64-403) followed by the C-terminal catalytic domain (residues 426-1058). Analysis of the BE truncated isoforms show that the CBMs bind differentially to whole starch, amylose or amylopectin. Furthermore, both CBMs seem to be essential for BE activity, as no catalytic activity was detected in the truncated enzyme comprising only by the catalytic domain. Our results suggest that the Ot01g03030 gene codifies for a functional BE containing two CBMs from CBM41 and CBM48 families which are critical for enzyme function and regulation. Copyright © 2017. Published by Elsevier Inc.

  19. Photo-reverberation Mapping of a Protoplanetary Accretion Disk around a T Tauri Star

    CERN Document Server

    Meng, Huan Y A; Rieke, George H; Cody, Ann Marie; Güth, Tina; Stauffer, John; Covey, Kevin; Carey, Sean; Ciardi, David; Duran-Rojas, Maria C; Gutermuth, Robert A; Morales-Calderón, María; Rebull, Luisa M; Watson, Alan M

    2016-01-01

    Theoretical models and spectroscopic observations of newborn stars suggest that protoplantary disks have an inner "wall" at a distance set by the disk interaction with the star. Around T Tauri stars, the size of this disk hole is expected to be on a 0.1-AU scale that is unresolved by current adaptive optics imaging, though some model-dependent constraints have been obtained by near-infrared interferometry. Here we report the first measurement of the inner disk wall around a solar-mass young stellar object, YLW 16B in the {\\rho} Ophiuchi star-forming region, by detecting the light travel time of the variable radiation from the stellar surface to the disk. Consistent time lags were detected on two nights, when the time series in H (1.6 {\\mu}m) and K (2.2 {\\mu}m) bands were synchronized while the 4.5 {\\mu}m emission lagged by 74.5 +/- 3.2 seconds. Considering the nearly edge-on geometry of the disk, the inner rim should be 0.084 AU from the protostar on average, with an error of order 0.01 AU. This size is likel...

  20. X-ray impact on the protoplanetary disks around T Tauri stars

    CERN Document Server

    Aresu, G; Meijerink, R; Woitke, P; Thi, W -F; Spaans, M

    2010-01-01

    Context: T Tauri stars have X-ray luminosities ranging from $L_{\\rm X} = 10^{28}-10^{32}\\,\\mathrm{erg\\,s^{-1}}$. These luminosities are similar to UV luminosities ($L_{\\rm UV} \\sim 10^{30}-10^{31} \\rm erg\\,s^{-1}$) and therefore X-rays are expected to affect the physics and chemistry of the upper layers of their surrounding protoplanetary disks. Aim: The effects and importance of X-rays on the chemical and hydrostatic structure of protoplanetary disks are investigated, species tracing X-ray irradiation (for $L_{\\rm X} \\geq 10^{29}\\mathrm{erg \\,s^{-1}}$) are identified and predictions for [O\\,{\\sc i}], [C\\,{\\sc ii}] and [N\\,{\\sc ii}] fine structure line fluxes are provided. Methods: We have implemented X-ray physics and chemistry into the chemo-physical disk code ProDiMo. We include Coulomb heating and $\\mathrm{H_2}$ ionization as heating processes and primary and secondary ionization due to X-rays in the chemistry. Results: X-rays heat up the gas causing it to expand in the optically thin surface layers. Neut...

  1. Accretion and Magnetic Reconnection in the Classical T Tauri Binary DQ Tau

    Science.gov (United States)

    Tofflemire, Benjamin M.; Mathieu, Robert D.; Ardila, David R.; Akeson, Rachel L.; Ciardi, David R.; Johns-Krull, Christopher; Herczeg, Gregory J.; Quijano-Vodniza, Alberto

    2017-01-01

    The theory of binary star formation predicts that close binaries (a archetype for the pulsed accretion theory is the eccentric, short-period, classical T Tauri binary DQ Tau. Low-cadence (∼daily) broadband photometry has shown brightening events near most periastron passages, just as numerical simulations would predict for an eccentric binary. Magnetic reconnection events (flares) during the collision of stellar magnetospheres near periastron could, however, produce the same periodic, broadband behavior when observed at a one-day cadence. To reveal the dominant physical mechanism seen in DQ Tau’s low-cadence observations, we have obtained continuous, moderate-cadence, multiband photometry over 10 orbital periods, supplemented with 27 nights of minute-cadence photometry centered on four separate periastron passages. While both accretion and stellar flares are present, the dominant timescale and morphology of brightening events are characteristic of accretion. On average, the mass accretion rate increases by a factor of five near periastron, in good agreement with recent models. Large variability is observed in the morphology and amplitude of accretion events from orbit to orbit. We argue that this is due to the absence of stable circumstellar disks around each star, compounded by inhomogeneities at the inner edge of the CBD and within the accretion streams themselves. Quasiperiodic apastron accretion events are also observed, which are not predicted by binary accretion theory.

  2. The PTF Orion Project: a Possible Planet Transiting a T-Tauri Star

    CERN Document Server

    van Eyken, Julian C; von Braun, Kaspar; Kane, Stephen R; Plavchan, Peter; Bender, Chad F; Brown, Timothy M; Crepp, Justin; Fulton, Benjamin J; Howard, Andrew W; Howell, Steve B; Mahadevan, Suvrath; Marcy, Geoffrey W; Shporer, Avi; Szkody, Paula; Akeson, Rachel L; Beichman, Charles A; Boden, Andrew F; Gelino, Dawn M; Hoard, D W; Ramírez, Solange V; Rebull, Luisa M; Stauffer, John R; Bloom, Joshua S; Cenko, S Bradley; Kasliwal, Mansi M; Kulkarni, Shrinivas R; Law, Nicholas M; Nugent, Peter E; Ofek, Eran O; Poznanski, Dovi; Quimby, Robert M; Walters, Richard; Grillmair, Carl J; Laher, Russ; Levitan, David B; Sesar, Branimir; Surace, Jason A

    2012-01-01

    We report observations of a possible young transiting planet orbiting a previously known weak-lined T-Tauri star in the 7-10Myr-old Orion-OB1a/25-Ori region. The candidate was found as part of the Palomar Transient Factory (PTF) Orion project. It has a photometric transit period of 0.448413 \\pm 0.000040 days, and appears in both 2009 and 2010 PTF data. Follow-up low-precision radial velocity observations and adaptive-optics imaging suggest that the star is not an eclipsing binary, and that it is unlikely that a background source is blended with the target and mimicking the observed transit. Radial-velocity observations with the Hobby-Eberly and Keck telescopes yield a radial velocity that has the same period as the photometric event, but is offset in phase from the transit center by \\approx -0.22 periods. The amplitude (half range) of the radial velocity variations is 2.4 km/s and is comparable with the expected radial velocity amplitude that stellar spots could induce. The radial velocity curve is likely dom...

  3. Robustness of circadian clocks to daylight fluctuations: hints from the picoeucaryote Ostreococcus tauri.

    Directory of Open Access Journals (Sweden)

    Quentin Thommen

    Full Text Available The development of systemic approaches in biology has put emphasis on identifying genetic modules whose behavior can be modeled accurately so as to gain insight into their structure and function. However, most gene circuits in a cell are under control of external signals and thus, quantitative agreement between experimental data and a mathematical model is difficult. Circadian biology has been one notable exception: quantitative models of the internal clock that orchestrates biological processes over the 24-hour diurnal cycle have been constructed for a few organisms, from cyanobacteria to plants and mammals. In most cases, a complex architecture with interlocked feedback loops has been evidenced. Here we present the first modeling results for the circadian clock of the green unicellular alga Ostreococcus tauri. Two plant-like clock genes have been shown to play a central role in the Ostreococcus clock. We find that their expression time profiles can be accurately reproduced by a minimal model of a two-gene transcriptional feedback loop. Remarkably, best adjustment of data recorded under light/dark alternation is obtained when assuming that the oscillator is not coupled to the diurnal cycle. This suggests that coupling to light is confined to specific time intervals and has no dynamical effect when the oscillator is entrained by the diurnal cycle. This intriguing property may reflect a strategy to minimize the impact of fluctuations in daylight intensity on the core circadian oscillator, a type of perturbation that has been rarely considered when assessing the robustness of circadian clocks.

  4. Organic Molecules and Water in the Inner Disks of T Tauri Stars

    CERN Document Server

    Carr, John S

    2011-01-01

    We report high signal-to-noise Spitzer IRS spectra of a sample of eleven classical T Tauri stars. Molecular emission from rotational transitions of H2O and OH and ro-vibrational bands of simple organic molecules (CO2, HCN, C2H2) is common among the sources in the sample. The gas temperatures (200-800 K) and emitting areas we derive are consistent with the emission originating in a warm disk atmosphere in the inner planet formation region at radii < 2 AU. The H2O emission appears to form under a limited range of excitation conditions, as shown by the similarity in relative strengths of H2O features from star to star and the narrow range in derived temperature and column density. Emission from highly excited rotational levels of OH is present in all stars; the OH emission flux increases with the stellar accretion rate, and the OH/H2O flux ratio shows a relatively small scatter. We interpret these results as evidence for OH production via FUV photo-dissociation of H2O in the disk surface layers. No obvious ex...

  5. Evolution of protoplanetary disks: Constraints from DM Tauri and GM Aurigae

    CERN Document Server

    Hueso, R; Hueso, Ricardo; Guillot, Tristan

    2005-01-01

    We present a one-dimensional model of the formation and viscous evolution of protoplanetary disks. The formation of the early disk is modeled as the result of the gravitational collapse of an isothermal molecular cloud. The disk's viscous evolution is integrated according to two parameterizations of turbulence: The classical $\\alpha$ representation and a $\\beta$ parameterization, representative of non-linear turbulence driven by the keplerian shear. We apply the model to DM Tau and GM Aur, two classical T-Tauri stars with relatively well-characterized disks, retrieving the evolution of their surface density with time. We perform a systematic Monte-Carlo exploration of the parameter space (i.e. values of the $\\alpha$-$\\beta$ parameters, and of the temperature and rotation rate in the molecular cloud) to find the values that are compatible with the observed disk surface density distribution, star and disk mass, age and present accretion rate. We find that the observations for DM Tau require $0.001<\\alpha<...

  6. Discovery of a bipolar X-ray jet from the T Tauri star DG Tau

    CERN Document Server

    Güdel, M; Audard, M; Briggs, K R; Cabrit, S

    2007-01-01

    We have obtained and analyzed Chandra ACIS-S observations of the strongly accreting classical T Tauri star DG Tau. Our principal goals are to map the immediate environment of the star to characterize possible extended X-rays formed in the jet, and to re-visit the anomalous, doubly absorbed X-ray spectrum of DG Tau itself. We combine our new ACIS-S data with a data set previously obtained. The data are superimposed to obtain flux and hardness images. Separate X-ray spectra are extracted for DG Tau and areas outside its point spread function. We detect a prominent X-ray jet at a position angle of PA ~225 deg (tentatively suggested by Guedel et al. 2005), coincident with the optical jet axis. We also identify a counter jet at PA = 45 deg. The X-ray jets are detected out to a distance of ~5" from the star, their sources being extended at the ACIS-S resolution. The jet spectra are soft, with a best-fit electron temperature of 3.4 MK. We find evidence for excess absorption of the counter jet. The spectrum of the DG...

  7. XMM-Newton X-ray spectroscopy of classical T Tauri stars

    CERN Document Server

    Robrade, J

    2006-01-01

    We present results from a comparative study of XMM-Newton observations of four classical T Tauri stars (CTTS), namely BP Tau, CR Cha, SU Aur and TW Hya. In these objects coronal, i.e. magnetic, activity and as recently shown, magnetically funneled accretion are the processes likely to be responsible for the generation of X-ray emission. Variable X-ray emission with luminosities in the order of $10^{30}$ erg/s is observed for all targets. We investigate light curves as well as medium and high-resolution X-ray spectra to determine the plasma properties of the sample CTTS and to study the origin of their X-ray emission and its variability. The emission measure distributions and observed temperatures differ significantly and the targets are dominated either by plasma at high densities as produced by accretion shocks or by predominantly hotter plasma of coronal origin. Likewise the variability of the X-ray luminosity is found to be generated by both mechanisms. Cool plasma at high densities is found in all stars w...

  8. CO and H2 Absorption in the AA Tauri Circumstellar Disk

    CERN Document Server

    France, Kevin; Herczeg, Gregory J; Schindhelm, Eric; Yang, Hao; Abgrall, Herve; Roueff, Evelyne; Brown, Alexander; Brown, Joanna; Linsky, Jeffrey L

    2011-01-01

    The direct study of molecular gas in inner protoplanetary disks is complicated by uncertainties in the spatial distribution of the gas, the time-variability of the source, and the comparison of observations across a wide range of wavelengths. Some of these challenges can be mitigated with far-ultraviolet spectroscopy. Using new observations obtained with the HST-Cosmic Origins Spectrograph, we measure column densities and rovibrational temperatures for CO and H2 observed on the line-of-sight through the AA Tauri circumstellar disk. CO A-X absorption bands are observed against the far-UV continuum. The CO absorption is characterized by log(N(^{12}CO)) = 17.5 +/- 0.5 cm^{-2} and T_rot(CO) = 500$^{+500}_{-200} K, although this rotational temperature may underestimate the local kinetic temperature of the CO-bearing gas. We also detect ^{13}CO in absorption with an isotopic ratio of ~20. We do not observe H2 absorption against the continuum; however, hot H2 (v > 0) is detected in absorption against the LyA emissio...

  9. Faint disks around classical T Tauri stars: small but dense enough to form planets?

    CERN Document Server

    Piétu, V; di Folco, E; Dutrey, A; Boehler, Y

    2014-01-01

    (abridged) Most Class II sources (of nearby star forming regions) are surrounded by disks with weak millimeter continuum emission. These "faint" disks may hold clues to the disk dissipation mechanism. We attempt to determine the characteristics of such faint disks around classical T Tauri stars, and to explore the link between disk faintness and the proposed disk dispersal mechanisms (accretion, viscous spreading, photo-evaporation, planetary system formation). We performed high-angular resolution (0.3") imaging of a small sample of disks (9 sources) with low 1.3mm continuum flux (mostly <30 mJy) with the IRAM Plateau de Bure interferometer and simultaneously searched for 13CO (or CO) J=2-1 line emission. Using a simple parametric disk model, we determine characteristic sizes of the disks, in dust and gas, and we constrain surface densities in the central 50 AU. All disks are much smaller than the bright disks imaged so far, both in continuum and 13CO lines (5 detections). In continuum, half of the disks a...

  10. Near-Infrared, Adaptive Optics Observations of the T Tauri Multiple-Star System

    CERN Document Server

    Furlan, E; Watson, D M; Uchida, K I; Brandl, B R; Keller, L D; Herter, T L

    2003-01-01

    With high-angular-resolution, near-infrared observations of the young stellar object T Tauri at the end of 2002, we show that, contrary to previous reports, none of the three infrared components of T Tau coincide with the compact radio source that has apparently been ejected recently from the system (Loinard, Rodriguez, and Rodriguez 2003). The compact radio source and one of the three infrared objects, T Tau Sb, have distinct paths that depart from orbital or uniform motion between 1997 and 2000, perhaps indicating that their interaction led to the ejection of the radio source. The path that T Tau Sb took between 1997 and 2003 may indicate that this star is still bound to the presumably more massive southern component, T Tau Sa. The radio source is absent from our near-infrared images and must therefore be fainter than K = 10.2 (if located within 100 mas of T Tau Sb, as the radio data would imply), still consistent with an identity as a low-mass star or substellar object.

  11. OCCULTATION OF THE T TAURI STAR RW AURIGAE A BY ITS TIDALLY DISRUPTED DISK

    Energy Technology Data Exchange (ETDEWEB)

    Rodriguez, Joseph E.; Stassun, Keivan G. [Department of Physics, Fisk University, 1000 17th Avenue North, Nashville, TN 37208 (United States); Pepper, Joshua; Siverd, Robert J.; Cargile, Phillip [Department of Physics and Astronomy, Vanderbilt University, 6301 Stevenson Center, Nashville, TN 37235 (United States); Beatty, Thomas G.; Gaudi, B. Scott [Department of Astronomy, The Ohio State University, Columbus, OH 43210 (United States)

    2013-11-01

    RW Aur A is a classical T Tauri star, believed to have undergone a reconfiguration of its circumstellar environment as a consequence of a recent flyby of its stellar companion, RW Aur B. This interaction stripped away part of the circumstellar disk of RW Aur A, leaving a tidally disrupted ''arm'' and a short truncated circumstellar disk. We present photometric observations of the RW Aur system from the Kilodegree Extremely Little Telescope survey showing a long and deep dimming that occurred from 2010 September until 2011 March. The dimming has a depth of ∼2 mag, a duration of ∼180 days, and was confirmed by archival observations from American Association of Variable Star Observers. We suggest that this event is the result of a portion of the tidally disrupted disk occulting RW Aur A, specifically a fragment of the tidally disrupted arm. The calculated transverse linear velocity of the occulter is in excellent agreement with the measured relative radial velocity of the tidally disrupted arm. Using simple kinematic and geometric arguments, we show that the occulter cannot be a feature of the RW Aur A circumstellar disk, and we consider and discount other hypotheses. We also place constraints on the thickness and semimajor axis of the portion of the arm that occulted the star.

  12. Purification, crystallization and preliminary X-ray crystallographic studies of Rv3705c from Mycobacterium tuberculosis

    Energy Technology Data Exchange (ETDEWEB)

    Lu, Feifei [East China University of Science and Technology, 130 Meilong Road, Shanghai 200237, People’s Republic of (China); Gao, Feng [Institute of Biophysics, Chinese Academy of Sciences, Beijing 100101, People’s Republic of (China); Li, Honglin [East China University of Science and Technology, 130 Meilong Road, Shanghai 200237, People’s Republic of (China); Gong, Weimin [Institute of Biophysics, Chinese Academy of Sciences, Beijing 100101, People’s Republic of (China); Zhou, Lin, E-mail: gdtb-bg@vip.163.com [Center for Tuberculosis Control of Guangdong Province, Guangzhou, People’s Republic of (China); Bi, Lijun, E-mail: gdtb-bg@vip.163.com [East China University of Science and Technology, 130 Meilong Road, Shanghai 200237, People’s Republic of (China)

    2014-07-23

    The cloning, expression, purification, crystallization and preliminary X-ray diffraction analysis of Rv3705c from M. tuberculosis are described. The conserved protein Rv3705c from Mycobacterium tuberculosis has been cloned, expressed, purified and crystallized by the sitting-drop vapour-diffusion method using PEG 3350 as a precipitant. The Rv3705c crystals exhibited space group P6{sub 1}22 or P6{sub 5}22, with unit-cell parameters a = b = 198.0, c = 364.1 Å, α = β = 90, γ = 120°, and diffracted to a resolution of 3.3 Å.

  13. 22. Comparison of conventional echocardiographic parameters of rv systolic function with cardiac magnetic resonance imaging

    Directory of Open Access Journals (Sweden)

    H. Shamsan

    2016-07-01

    Full Text Available Nowadays, cardiac magnetic resonance (CMR imaging is considered the gold standard for quantification of RV size and function. Multiple 2D Echocardiography (echo parameters are recommended for quantification of systolic RV function including Fractional Area Change (FAC%, tricuspid annular plane systolic excursion (TAPSE and Tissue Doppler velocity (TDI of tricuspid annulus. The aim of our study was to compare the conventional 2-D echocardiographic parameters of RV systolic function with CMR derived RVEF and stroke volume (SV. The echo and cardiac magnetic parameters to assess the right ventricular function are different. Consecutive patients referred to CMR for RV assessment from January 2011 to December 2014 were screened. 69 patients with CMR and adequate echo were selected. 20 subjects with normal CMR were enrolled as a control group. Quantitative 2-D echo measures were compared with CMR RVEF (% and SV (ml. The comparison was made using linear correlation for the echo variables with CMR variables. The mean age of patients was 38.2 + 5.4 (51% females were enrolled. 84.1% of patients had normal RVEF by CMR. In patients, FAC% but not TAPSE or annular TDI, correlated with CMR derived RVEF (R = 0.45, p = 0.0001 with fair agreement (kappa 0.43. However, FAC% did not correlate with CMR RV stroke volume. In contrast, in normal subjects, TAPSE had the best correlation with CMR derived RVEF (R = 0.67, p = 0.0001. In patients, CMR reclassified RV function assessed by FAC% in 11 (16%. 6 (8% patients who had abnormal RV function by FAC% were reclassified as normal while 5 (7% with normal RV function by FAC% were reclassified as abnormal. In normal subjects, however, only one with abnormal RV function by TAPSE was reclassified as normal by CMR. The current quantitative 2-D echo parameters of RV systolic function assessment correlate poorly with CMR measured RVEF and SV and behave differently in comparison with CMR in patients with normal and

  14. Incomplete RV Remodeling After Transcatheter ASD Closure in Pediatric Age.

    Science.gov (United States)

    Agha, Hala M; El-Saiedi, Sonia A; Shaltout, Mohamed F; Hamza, Hala S; Nassar, Hayat H; Abdel-Aziz, Doaa M; Tantawy, Amira Esmat El

    2015-10-01

    Published data showing the intermediate effect of transcatheter device closure of atrial septal defect (ASD) in the pediatric age-group are scarce. The objective of the study was to assess the effects of transcatheter ASD closure on right and left ventricular functions by tissue Doppler imaging (TDI). The study included 37 consecutive patients diagnosed as ASD secundum by transthoracic echocardiography and TEE and referred for transcatheter closure at Cairo University Specialized Pediatric Hospital, Egypt, from October 2010 to July 2013. Thirty-seven age- and sex-matched controls were selected. TDI was obtained using the pulsed Doppler mode, interrogating the right cardiac border (the tricuspid annulus) and lateral mitral annulus, and myocardial performance index (MPI) was calculated at 1-, 3-, 6- and 12-month post-device closure. Transcatheter closure of ASD and echocardiographic examinations were successfully performed in all patients. There were no significant differences between two groups as regards the age, gender, weight or BSA. TDI showed that patients with ASD had significantly prolonged isovolumetric contraction, relaxation time and MPI compared with control group. Decreased tissue Doppler velocities of RV and LV began at one-month post-closure compared with the controls. Improvement in RVMPI and LVMPI began at 1-month post-closure, but they are still prolonged till 1 year. Reverse remodeling of right and left ventricles began 1 month after transcatheter ASD closure, but did not completely normalize even after 1 year of follow-up by tissue Doppler imaging.

  15. [RV polymorphism of the chromosomes in newborn infants].

    Science.gov (United States)

    Krachunova, M; Tsancheva, M; Lozanova, T

    1980-01-01

    The authors examined the routine variants (RV) of the karyotype of 100 clinically healthy newborns--49 girls and 51 boys. Secondary constriction of the long arm of one of the homologues of the chromosome I was found in 2% of the newborns; of the chromosome 9--in 4% of the chromosome 16--in 3%. Secondary constriction in both homologues was observed in the chromosome I in 1%; in the chromosome 9--in 1% and in the chromosome 16--4%. Secondary constriction of the short arm of both homologues was found only in the chromosome 16 in 3%. The large acrocentric chromosomes showed extended proximal area (p5) in 34%, but diminished (pI)--in 8%. The small acrocentrics with p5 were found in 14% of the newborns, but with pI--in 7%. Enlarged satelites were observed in 1% in the both groups of acrocentrics. Difference between the homologues in respect to the short arms was observed in 32,3% of the pairs of the great acrocentrics and in 47,5% of the small acrocentrics. Distribution of the Y chromosome according to the size in 51 boys was of Gaus character q1--0%, q2--29,4%, q3--33,3%, q4--25,5% and q5--11,7%. It is possible that Y chromosome with a size of q1 could be connected with definite pathology.

  16. The MarR family transcription factor Rv1404 coordinates adaptation of Mycobacterium tuberculosis to acid stress via controlled expression of Rv1405c, a virulence-associated methyltransferase.

    Science.gov (United States)

    Healy, Claire; Golby, Paul; MacHugh, David E; Gordon, Stephen V

    2016-03-01

    Coordinated regulation of gene expression is essential for pathogen adaptation in vivo. Understanding the control of these virulence circuits in the TB pathogen Mycobacterium tuberculosis is a key challenge if we are to increase our basic understanding of how this organism establishes infection. In this study we focused on the transcriptional regulator Rv1404 that shows similarity to the MarR family of transcriptional repressors. Rv1404 derepresses a set of genes in vivo that have been implicated in virulence and may therefore allow adaptation of M. tuberculosis to the intracellular environment. We used a combination of ChIP-qPCR and Electromobility Band Shift Assays (EMSA) to show that Rv1404 coordinates gene expression in response to stresses such as low pH in M. tuberculosis. Two genes regulated by Rv1404, rv1403c and rv1405c, encode putative SAM-dependent methyltransferases. To elucidate gene function, M. tuberculosis rv1403c and rv1405c mutants were constructed. The mutants showed attenuated growth in response to in vitro stress conditions that mimic the intracellular milieu. Our data sheds new light on the function of a novel regulon controlled by Rv1404 that coordinates adaptation of M. tuberculosis to the in vivo environment and reveals the Rv1405c and Rv1403c methyltransferases as playing a role in this adaptive process.

  17. Crystallization and preliminary X-ray analysis of Rv1674c from Mycobacterium tuberculosis

    Science.gov (United States)

    Li, Jincheng; Wang, Xudong; Gong, Weimin; Niu, Chunyan; Zhang, Min

    2015-01-01

    Adaptations to hypoxia play an important role in Mycobacterium tuberculosis pathogenesis. Rv0324, which contains an HTH DNA-binding domain and a rhodanese domain, is one of the key transcription regulators in response to hypoxia. M. tuberculosis Rv1674c is a homologue of Rv0324. To understand the interdomain interaction and regulation of the HTH domain and the rhodanese domain, recombinant Rv1674c protein was purified and crystallized by the vapour-diffusion method. The crystals diffracted to 2.25 Å resolution. Preliminary diffraction analysis suggests that the crystals belonged to space group P3121 or P3221, with unit-cell parameters a = b = 67.8, c = 174.5 Å, α = β = 90, γ = 120°. The Matthews coefficient was calculated to be 2.44 Å3 Da−1, assuming that the crystallographic asymmetric unit contains two protein molecules. PMID:25760714

  18. Cellular and molecular basis of RV hypertrophy in congenital heart disease.

    Science.gov (United States)

    Iacobazzi, D; Suleiman, M-S; Ghorbel, M; George, S J; Caputo, M; Tulloh, R M

    2016-01-01

    RV hypertrophy (RVH) is one of the triggers of RV failure in congenital heart disease (CHD). Therefore, improving our understanding of the cellular and molecular basis of this pathology will help in developing strategic therapeutic interventions to enhance patient benefit in the future. This review describes the potential mechanisms that underlie the transition from RVH to RV failure. In particular, it addresses structural and functional remodelling that encompass contractile dysfunction, metabolic changes, shifts in gene expression and extracellular matrix remodelling. Both ischaemic stress and reactive oxygen species production are implicated in triggering these changes and will be discussed. Finally, RV remodelling in response to various CHDs as well as the potential role of biomarkers will be addressed.

  19. Automatic right ventricle (RV) segmentation by propagating a basal spatio-temporal characterization

    Science.gov (United States)

    Atehortúa, Angélica; Zuluaga, María. A.; Martínez, Fabio; Romero, Eduardo

    2015-12-01

    An accurate right ventricular (RV) function quantification is important to support the evaluation, diagnosis and prognosis of several cardiac pathologies and to complement the left ventricular function assessment. However, expert RV delineation is a time consuming task with high inter-and-intra observer variability. In this paper we present an automatic segmentation method of the RV in MR-cardiac sequences. Unlike atlas or multi-atlas methods, this approach estimates the RV using exclusively information from the sequence itself. For so doing, a spatio-temporal analysis segments the heart at the basal slice, segmentation that is then propagated to the apex by using a non-rigid-registration strategy. The proposed approach achieves an average Dice Score of 0:79 evaluated with a set of 48 patients.

  20. ATOMIC DECOMPOSITION FOR B-VALUED R.V. SEQUENCE SPACES

    Institute of Scientific and Technical Information of China (English)

    Li Yufan; Liu Peide

    2009-01-01

    In this article, atomic decompositions and the duals of some B-valued r.v. sequence spaces are investigated. The results show that it closely depends on the geometrical properties of the sequence that take values in.

  1. rvær i pædagogisk praksis

    DEFF Research Database (Denmark)

    skoler og daginstitutioner, som arbejder med nærvær og viser eksempler på, hvordan man konkret kan skabe øget nærvær i undervisning og andre pædagogiske sammenhænge. Forfatterne beskriver forskellige øvelser som fx kropslig/sanselig opmærksomhed, vejrtræknings- og afslapningsøvelser samt massage og yoga...

  2. rvær i pædagogisk praksis

    DEFF Research Database (Denmark)

    skoler og daginstitutioner, som arbejder med nærvær og viser eksempler på, hvordan man konkret kan skabe øget nærvær i undervisning og andre pædagogiske sammenhænge. Forfatterne beskriver forskellige øvelser som fx kropslig/sanselig opmærksomhed, vejrtræknings- og afslapningsøvelser samt massage og yoga...

  3. IN and CCN Measurements on RV Polarstern and Cape Verde

    Science.gov (United States)

    Welti, André; Herenz, Paul; Henning, Silvia; Stratmann, Frank

    2016-04-01

    Two field campaigns, one situated on RV Polarstern (Oct. - Dec. 2015) and one on the Cape Verde islands (Jan. - Feb. 2016) measuring ice nuclei (IN) and cloud condensation nuclei (CCN) concentrations as a function of supersaturation and temperature are presented. The Polarstern cruise from Bremerhaven to Cape Town yields a cross section of IN and CCN concentrations from 54°N to 35°S and passes the Cape Verde Islands at 15°N. Measurements were conducted using the commercial CCNC and SPIN instruments from DMT. During both campaigns, a comprehensive set of aerosol characterization data including size distribution, optical properties and chemical information were measured in parallel. The ship based measurements provide a measure of variability in IN/CCN concentration with geographic position. As an example a clear influence on IN and CCN number concentration of the Saharan desert dust outflow between the Canary Islands and Cape Verde or the continental aerosol from Europe and South Africa was observed. The measurements on Cape Verde provide information on the temporal variability at a fixed position varying between clean marine and dust influenced conditions. Both datasets are related to auxiliary data of aerosol size distribution and chemical composition. The datasets are used to distinguish the influence of local sources and background concentration of IN/CCN. By combining of the geographically fix measurements with the geographical cross section, typical ranges of IN and CCN concentration are derived. The datasets will be part of the BACCHUS database thereby providing valuable input for future climate modeling activities.

  4. Mycobacterium tuberculosislpdC, Rv0462, induces dendritic cell maturation and Th1 polarization

    Energy Technology Data Exchange (ETDEWEB)

    Heo, Deok Rim [Department of Microbiology and Immunology, School of Medicine, Pusan National University, Beom-eo Ri, Mulgum Eop, Yangsan, Gyeongsangnam-do 626-770 (Korea, Republic of); Shin, Sung Jae; Kim, Woo Sik [Department of Microbiology, College of Medicine, Chungnam National University, Munwha-Dong, Jung-Ku, Daejeon 301-747 (Korea, Republic of); Noh, Kyung Tae; Park, Jin Wook; Son, Kwang Hee [Department of Microbiology and Immunology, School of Medicine, Pusan National University, Beom-eo Ri, Mulgum Eop, Yangsan, Gyeongsangnam-do 626-770 (Korea, Republic of); Park, Won Sun [Department of Physiology, Kangwon National University, School of Medicine, Chuncheon 200-701 (Korea, Republic of); Lee, Min-Goo [Department of Physiology, Korea University, College of Medicine, Anam-dong, Sungbuk-Gu, Seoul 136-705 (Korea, Republic of); Kim, Daejin [Department of Anatomy, Chung-Ang University, College of Medicine, 221 Heuksuk-Dong, Dongjak-Ku, Seoul 156-756 (Korea, Republic of); Shin, Yong Kyoo [Department of Pharmacology, Chung-Ang University, College of Medicine, 221 Heuksuk-Dong, Dongjak-Ku, Seoul 156-756 (Korea, Republic of); Jung, In Duk, E-mail: jungid@pusan.ac.kr [Department of Microbiology and Immunology, School of Medicine, Pusan National University, Beom-eo Ri, Mulgum Eop, Yangsan, Gyeongsangnam-do 626-770 (Korea, Republic of); Research Institute of Convergence of Biomedical Science and Technology, Pusan National University Yangsan Hospital, Beom-eo Ri, Mulgum Eop, Yangsan, Gyeongsangnam-do 626-770 (Korea, Republic of); Park, Yeong-Min, E-mail: immunpym@pusan.ac.kr [Department of Microbiology and Immunology, School of Medicine, Pusan National University, Beom-eo Ri, Mulgum Eop, Yangsan, Gyeongsangnam-do 626-770 (Korea, Republic of); Research Institute of Convergence of Biomedical Science and Technology, Pusan National University Yangsan Hospital, Beom-eo Ri, Mulgum Eop, Yangsan, Gyeongsangnam-do 626-770 (Korea, Republic of)

    2011-08-05

    Highlights: {yields} Treatment with Rv0462 induces the expression of surface molecules and the production of cytokines in DCs. {yields} Rv0462 induces the activation of MAPKs. {yields} Rv0462-treated DCs enhances the proliferation of CD4{sup +} T cells. -- Abstract: Mycobacterium tuberculosis, the etiological factor of pulmonary tuberculosis, causes significant morbidity and mortality worldwide. Activation of host immune responses for containment of mycobacterial infections involves participation of innate immune cells, such as dendritic cells (DCs). In this study, we demonstrated that the gene encoding lipoamide dehydrogenase C (lpdC) from M. tuberculosis, Rv0462, induce maturation and activation of DCs involved in the MAPKs signaling pathway. Moreover, Rv0462-treated DCs activated naive T cells, polarized CD4{sup +} and CD8{sup +} T cells to secrete IFN-{gamma} in syngeneic mixed lymphocyte reactions, which would be expected to contribute to Th1 polarization of the immune response. Our results suggest that Rv0462 can contribute to the innate and adaptive immune responses during tuberculosis infection, and thus modulate the clinical course of tuberculosis.

  5. Mycobacterium tuberculosis Rv1987 induces Th2 immune responses and enhances Mycobacterium smegmatis survival in mice.

    Science.gov (United States)

    Sha, Shanshan; Shi, Xiaoxia; Deng, Guoying; Chen, Lina; Xin, Yi; Ma, Yufang

    2017-04-01

    Mycobacterium tuberculosis can interfere with host immune response and escape clearance through its specific antigens. M. tuberculosis Rv1987 encoded by region of difference (RD)-2 gene is a secretory protein with immunogenic potency. Here, we investigated the impact of Rv1987 on host cytokine responses and T cell polarization in mouse aerosol model. A recombinant M. smegmatis mc(2)155 strain that overexpressed Rv1987 protein (named MS1987) was constructed and used to infect C57BL/6 mice. The mc(2)155 harbored the empty vector (named MSVec) was as a control. The results showed that MS1987 challenged mice promoted Th2-biased cytokine responses with lower secretion of IFN-γ but higher production of IL-4 and Rv1987-specific IgG antibody compared to MSVec infected mice. Neutrophilic inflammation and high bacterial burden were observed in the lung tissues of MS1987 infected mice probably own to the failed Th1 cell immunity. Besides, subcutaneous injection of Rv1987 protein could mediate the Th1 cytokine responses caused by M. bovis BCG in mice. These results indicated that M. tuberculosis Rv1987 protein could modulate host immune response towards Th2 profile, which probably contributed to the immune evasion of bacteria from host elimination. Copyright © 2017 Elsevier GmbH. All rights reserved.

  6. EVIDENCE OF HOT HIGH VELOCITY PHOTOIONIZED PLASMA FALLING ON ACTIVELY ACCRETING T TAURI STARS

    Energy Technology Data Exchange (ETDEWEB)

    Gómez de Castro, Ana Ines [Grupo de Investigación Complutense AEGORA and S.D. Astronomía y Geodesia, Fac. de CC Matemáticas, Universidad Complutense, E-28040 Madrid (Spain)

    2013-10-01

    The He II (1640 Å) line and the resonance doublet of N V (UV1) provide a good diagnostic tool to constrain the excitation mechanism of hot (T{sub e} > 40,000 K) atmospheric/magnetospheric plasmas in T Tauri stars (TTSs). Making use of the data available in the Hubble Space Telescope archive, this work shows that there are at least two distinct physical components contributing to the radiation in these tracers: the accretion flow sliding on the magnetosphere and the atmosphere. The N V profiles in most sources are symmetric and at rest with respect to the star. The velocity dispersion of the profile increases from non-accreting (σ = 40 km s{sup –1}) to accreting (σ = 120 km s{sup –1}) TTSs, suggesting that the macroturbulence field in the line formation region decreases as the stars approach the main sequence. Evidence of the N V line being formed in a hot solar-like wind has been found in RW Aur, HN Tau, and AA Tau. The He II profile has a strong narrow component that dominates the line flux; the dispersion of this component ranges from 20 to 60 km s{sup –1}. Current data suggest that both accretion shocks and atmospheric emission might contribute to the line flux. In some sources, the He II line shows a broad and redward-shifted emission component often accompanied by semiforbidden O III] emission that has a critical electron density of ∼3.4 × 10{sup 10} cm{sup 3}. In spite of their different origins (inferred from the kinematics of the line formation region), N V and He II fluxes are strongly correlated, with only the possible exception of some of the heaviest accretors.

  7. The absence of sub-minute periodicity in classical T Tauri stars

    Science.gov (United States)

    Günther, H. M.; Lewandowska, N.; Hundertmark, M. P. G.; Steinle, H.; Schmitt, J. H. M. M.; Buckley, D.; Crawford, S.; O'Donoghue, D.; Vaisanen, P.

    2010-07-01

    Context. Classical T Tauri stars (CTTS) are young, late-type objects, that still accrete matter from a circumstellar disk. Analytical treatments and numerical simulations predict instabilities of the accretion shock on the stellar surface. Aims: We search for variability on timescales below a few minutes in the CTTS TW Hya and AA Tau. Methods: TW Hya was observed with SALTICAM on the Southern African Large Telescope (SALT) in narrow-band filters around the Balmer jump. The observations were performed in slit mode, which provides a time resolution of about 0.1 s. For AA Tau we obtained observations with OPTIMA, a single photon-counting device with even better time resolution. Results: Small-scale variability typically lasts a few seconds, however, no significant periodicity is detected. We place a 99% confidence upper limit on the pulsed fraction of the lightcurves. The relative amplitude is below 0.001 for TW Hya in the frequency range 0.02-3 Hz in the 340 nm filter and 0.1-3 Hz in the 380 nm filter. The corresponding value for AA Tau is an amplitude of 0.005 for 0.02-50 Hz. Conclusions: The relevant timescales indicate that shock instabilites should not be seen directly in our optical and UV observations, but the predicted oscialltions would induce observable variations in the reddening. We discuss how the magnetic field could stabilise the accretion shock. Based on observations obtained at the Southern African Large Telescope (SALT) and Skinakas observatory, Greece. unknown author type, collab unknown author type, collab unknown author type, collab unknown author type, collab unknown author type, collab unknown author type, collab

  8. Polycyclic Aromatic Hydrocarbons in Protoplanetary Disks around Herbig Ae/Be and T Tauri Stars

    Science.gov (United States)

    Seok, Ji Yeon; Li, Aigen

    2017-02-01

    A distinct set of broad emission features at 3.3, 6.2, 7.7, 8.6, 11.3, and 12.7 μm, is often detected in protoplanetary disks (PPDs). These features are commonly attributed to polycyclic aromatic hydrocarbons (PAHs). We model these emission features in the infrared spectra of 69 PPDs around 14 T Tauri and 55 Herbig Ae/Be stars in terms of astronomical PAHs. For each PPD, we derive the size distribution and the charge state of the PAHs. We then examine the correlations of the PAH properties (i.e., sizes and ionization fractions) with the stellar properties (e.g., stellar effective temperature, luminosity, and mass). We find that the characteristic size of the PAHs tends to correlate with the stellar effective temperature ({T}{eff}) and interpret this as the preferential photodissociation of small PAHs in systems with higher {T}{eff} of which the stellar photons are more energetic. In addition, the PAH size shows a moderate correlation with the red-ward wavelength shift of the 7.7 μm PAH feature that is commonly observed in disks around cool stars. The ionization fraction of PAHs does not seem to correlate with any stellar parameters. This is because the charging of PAHs depends on not only the stellar properties (e.g., {T}{eff}, luminosity) but also their spatial distribution in the disks. The marginally negative correlation between PAH size and stellar age suggests that continuous replenishment of PAHs via the outgassing of cometary bodies and/or the collisional grinding of planetesimals and asteroids is required to maintain the abundance of small PAHs against complete destruction by photodissociation.

  9. The 2RE J0241-525: A Nearby Post T-Tauri Visual Binary System

    Science.gov (United States)

    Jeffries, R. D.; Buckley, D. A. H.; James, D. J.; Stauffer, J. R.

    1995-01-01

    We present high spatial resolution X-ray observations, photometry and spectroscopy of the two low mass, active stars proposed as optical counterparts to the extreme ultraviolet source 2RE J0241-525 (equal to EUVE J0241-530). It is confirmed that both stars, which are of types dK7e and dM3e and separated by 22 arcsecs, are sources of soft X-ray emission and exhibit substantial chromospheric activity. Radial velocity measurements indicate that the two components are physically associated and most probably single. The projected equatorial velocities are measured as (75 +/- 3) km/s and (11.7 +/- 0.7) km/s for the hotter and cooler components, respectively, and whilst the hotter component has a relatively high photospheric lithium abundance, log N(Li) equal to 1.5 +/- 0.2, we are unable to detect any lithium in the cooler star. Isochrone fitting to this 'mini-cluster' yields an age of (3-70) Myr and a distance of (19-60) pc. An empirical comparison of the lithium abundances with those for similar stars in young clusters and associations narrows this age range to (5-30) Myr and a corresponding distance of (26-50) pc. We conclude that this object is a nearby post T-Tauri system, but we cannot locate any possible birth site. It appears unlikely that the system can have been ejected from a nearby open cluster in a two or three body encounter.

  10. Spectroscopic characterization of a (6-4) photolyase from the green alga Ostreococcus tauri.

    Science.gov (United States)

    Usman, Anwar; Brazard, Johanna; Martin, Monique M; Plaza, Pascal; Heijde, Marc; Zabulon, Gérald; Bowler, Chris

    2009-07-17

    The cofactor content of OtCPF1, a (6-4) photolyase isolated from the green marine alga Ostreococcus tauri, was characterized by steady-state absorption and fluorescence spectroscopy. The heterologously expressed, GST-fused, purified protein (MW: 89kDa) is non-covalently bound to flavin adenine dinucleotide (FAD), with a flavin to apoprotein molecular ratio of 64%. No light-harvesting chromophore was found in this protein. In freshly purified OtCPF1, FAD is present in three different redox states: the fully oxidized form (FAD(ox), 82%), the neutral semiquinone (FADH*, 14%) and the fully reduced anion (FADH-, 4%). Keeping the sample in the dark, at 5 degrees C, yields oxidation of FADH* and FADH-, partial release of FAD to the solution and slow degradation of the protein. Upon steady-state blue-light irradiation of OtCPF1 at 450nm, photoreduction processes leading to an accumulation of stable FADH* and FADH- species are observed. We demonstrate that this accumulation is due to the presence of an external electron donor agent in the purification buffer. Composition changes observed under steady-state photoexcitation are interpreted in terms of photoinduced reductions of FAD(ox) and FADH* states and competitive back reactions. Specific irradiation by red light at 620 nm shows both photoreduction of FADH* to FADH- and irreversible oxidation of FADH* to FAD(ox). The photoinduced oxidation reaction is believed to be indirectly caused by the external donor agent present in the buffer. Photoexcitation is also shown to stabilize the binding of FAD to the protein. We suggest this effect to be due to slight changes in the protein conformation, possibly strengthening the hydrogen-bonding network surrounding FAD.

  11. Cloning and characterization of a novel PE_PGRS60 protein (Rv3652) of Mycobacterium tuberculosis H37 Rv exhibit fibronectin-binding property.

    Science.gov (United States)

    Meena, Laxman S; Meena, Jaishree

    2016-07-01

    The binding of pathogenic bacteria to extracellular matrix components enhances adhesion and invasion of host cells. The host receptor proteins such as fibronectin (Fn) targeted to pathogenic ligands that have clinical importance. In the present study, we cloned, expressed, purified, and identified a novel Fn-binding protein from PE_PGRS60 (Rv3652) of Mycobacterium tuberculosis H37 Rv. The protein product of Rv3652 showed optimum binding efficiency to 10 ng Fn at 0.2 µg purified protein of PE_PGRS60 and 20 ng Fn at 0.2 µg concentrations, respectively. PE_PGRS60 protein (primary sequences) of different pathogenic mycobacterium species retrieved from NCBI exhibited complete homology at the 104 residues on multiple sequence alignment. The primary sequence of protein from H37 Rv was further used to predict cleavage signals. The secondary structure prediction method revealed a number of residues responsible for alpha helices formation and percentage of residues participating in the random coils and extended strands. In addition, online prediction tools such as B- and T-cell epitopes showed the surface probability scale and antigenic propensity scale. The current finding opens new opportunity to mycobacterial survival and pathogenesis research of PE-polymorphic GC-rich repetitive sequences (PE-PGRS) family proteins.

  12. Structure of the heterodimeric neurotoxic complex viperotoxin F (RV-4/RV-7) from the venom of Vipera russelli formosensis at 1.9 A resolution.

    Science.gov (United States)

    Perbandt, Markus; Tsai, Inn-Ho; Fuchs, Annemarie; Banumathi, Sankaran; Rajashankar, Kanagalaghata R; Georgieva, Dessislava; Kalkura, Narayana; Singh, Tej P; Genov, Nicolay; Betzel, Christian

    2003-10-01

    The presynaptic viperotoxin F is the major lethal component of the venom of Vipera russelli formosensis (Taiwan viper). It is a heterodimer of two highly homologous (65% identity) but oppositely charged subunits: a basic and neurotoxic PLA(2) (RV-4) and an acidic non-toxic component with a very low enzymatic activity (RV-7). The crystal structure of the complex has been determined by molecular replacement and refined to 1.9 A resolution and an R factor of 22.3% with four RV-4/RV-7 complexes in the asymmetric unit, which do not exhibit any local point-group symmetry. The complex formation decreases the accessible surface area of the two subunits by approximately 1425 A(2). Both PLA(2)s are predicted to have very low, if any, anticoagulant activity. The structure of viperotoxin F is compared with that of the heterodimeric neurotoxin vipoxin from the venom of another viper, V. ammodytes meridionalis. The structural basis for the differences between the pharmacological activities of the two toxins is discussed. The neutralization of the negative charge of the major ligand for Ca(2+), Asp49, by intersubunit salt bridges is probably a common mechanism of self-stabilization of heterodimeric Viperinae snake-venom neurotoxins in the absence of bound calcium.

  13. Mycobacterium tuberculosis universal stress protein Rv2623 regulates bacillary growth by ATP-Binding: requirement for establishing chronic persistent infection.

    Directory of Open Access Journals (Sweden)

    Joshua E Drumm

    2009-05-01

    Full Text Available Tuberculous latency and reactivation play a significant role in the pathogenesis of tuberculosis, yet the mechanisms that regulate these processes remain unclear. The Mycobacterium tuberculosisuniversal stress protein (USP homolog, rv2623, is among the most highly induced genes when the tubercle bacillus is subjected to hypoxia and nitrosative stress, conditions thought to promote latency. Induction of rv2623 also occurs when M. tuberculosis encounters conditions associated with growth arrest, such as the intracellular milieu of macrophages and in the lungs of mice with chronic tuberculosis. Therefore, we tested the hypothesis that Rv2623 regulates tuberculosis latency. We observed that an Rv2623-deficient mutant fails to establish chronic tuberculous infection in guinea pigs and mice, exhibiting a hypervirulence phenotype associated with increased bacterial burden and mortality. Consistent with this in vivo growth-regulatory role, constitutive overexpression of rv2623 attenuates mycobacterial growth in vitro. Biochemical analysis of purified Rv2623 suggested that this mycobacterial USP binds ATP, and the 2.9-A-resolution crystal structure revealed that Rv2623 engages ATP in a novel nucleotide-binding pocket. Structure-guided mutagenesis yielded Rv2623 mutants with reduced ATP-binding capacity. Analysis of mycobacteria overexpressing these mutants revealed that the in vitro growth-inhibitory property of Rv2623 correlates with its ability to bind ATP. Together, the results indicate that i M. tuberculosis Rv2623 regulates mycobacterial growth in vitro and in vivo, and ii Rv2623 is required for the entry of the tubercle bacillus into the chronic phase of infection in the host; in addition, iii Rv2623 binds ATP; and iv the growth-regulatory attribute of this USP is dependent on its ATP-binding activity. We propose that Rv2623 may function as an ATP-dependent signaling intermediate in a pathway that promotes persistent infection.

  14. Mycobacterium tuberculosis Universal Stress Protein Rv2623 Regulates Bacillary Growth by ATP Binding: Requirement for Establishing Chronic Persistent Infection

    Energy Technology Data Exchange (ETDEWEB)

    Drumm, J.; Mi, K; Bilder, P; Sun, M; Lim, J; Bielefeldt-Ohmann, H; Basaraba, R; So, M; Zhu, G; et. al.

    2009-01-01

    Tuberculous latency and reactivation play a significant role in the pathogenesis of tuberculosis, yet the mechanisms that regulate these processes remain unclear. The Mycobacterium tuberculosisuniversal stress protein (USP) homolog, rv2623, is among the most highly induced genes when the tubercle bacillus is subjected to hypoxia and nitrosative stress, conditions thought to promote latency. Induction of rv2623 also occurs when M. tuberculosis encounters conditions associated with growth arrest, such as the intracellular milieu of macrophages and in the lungs of mice with chronic tuberculosis. Therefore, we tested the hypothesis that Rv2623 regulates tuberculosis latency. We observed that an Rv2623-deficient mutant fails to establish chronic tuberculous infection in guinea pigs and mice, exhibiting a hypervirulence phenotype associated with increased bacterial burden and mortality. Consistent with this in vivo growth-regulatory role, constitutive overexpression of rv2623 attenuates mycobacterial growth in vitro. Biochemical analysis of purified Rv2623 suggested that this mycobacterial USP binds ATP, and the 2.9-A-resolution crystal structure revealed that Rv2623 engages ATP in a novel nucleotide-binding pocket. Structure-guided mutagenesis yielded Rv2623 mutants with reduced ATP-binding capacity. Analysis of mycobacteria overexpressing these mutants revealed that the in vitro growth-inhibitory property of Rv2623 correlates with its ability to bind ATP. Together, the results indicate that i M. tuberculosis Rv2623 regulates mycobacterial growth in vitro and in vivo, and ii Rv2623 is required for the entry of the tubercle bacillus into the chronic phase of infection in the host; in addition, iii Rv2623 binds ATP; and iv the growth-regulatory attribute of this USP is dependent on its ATP-binding activity. We propose that Rv2623 may function as an ATP-dependent signaling intermediate in a pathway that promotes persistent infection.

  15. Mid-IR Observations of T Tauri stars: Probing the Star-Disk Connection in Rotational Evolution

    CERN Document Server

    Kundurthy, P; Robberto, M; Beckwith, S V W; Herbst, T; Kundurthy, Praveen; Meyer, Michael R.; Robberto, Massimo; Beckwith, Steven V.W.; Herbst, Tom

    2006-01-01

    We present mid-IR N-band $(\\lambda_{eff} = 10.2\\micron)$ photometry of a carefully selected sample of T Tauri stars thought to be single from the Taurus-Auriga molecular cloud. Infrared excesses in these stars are generally attributed to circumstellar dust-disks. Combining observations at 2.16$\\micron$ (K$_{s}$-band) and 10.2$\\micron$ (N-band) we probe a region in the circumstellar dust-disk from a few stellar radii through the terrestrial planet zone (0.02-1.0AU). By analyzing the distribution of the $(K_{s}-N)$ color index with respect to previously measured photometric rotation periods we investigate what role circumstellar disks play in the rotational evolution of the central star. The resulting positive correlation between these two variables is consistent with the notion that a star-disk interaction facilitates the regulation of angular momentum during the T Tauri stage. We also demonstrate, how including non-single stars in such an analysis will \\textit{weaken} any correlation in the relation between $...

  16. Millimeter-wave Searches for Cold Dust and Molecular Gas around T Tauri Stars in MBM 12

    CERN Document Server

    Hogerheijde, M R; Johnstone, D; Blake, G A; Kessler, J E; Hogerheijde, Michiel R.; Jayawardhana, Ray; Johnstone, Doug; Blake, Geoffrey A.; Kessler, Jacqueline E.

    2002-01-01

    We report results of a sensitive search for cold dust and molecular gas in the disks around 8 T Tauri stars in the high-latitude cloud MBM 12. Interferometric observations of 3 mm continuum emission in 5 fields containing 6 of the objects, and literature values for the remaining two, limit the disk masses to M_disk (N=5) < 0.03 M_sun. Simultaneous observation of the CS J=2-1 and the N2H+ 1-0 lines show no emission. Single-dish observations of the 13CO 2-1 line limit the disk mass to (5 - 10) * 10^-4 M_sun for a standard CO abundance of 2 * 10^-4. Depletion of CO by up to two orders of magnitude, through freezing out or photodissociation, can reconcile these limits. These mass limits lie within the range found in the Taurus-Auriga and rho Oph star-forming regions (0.001 - 0.3 M_sun), and preclude conclusions about possible decrease in disk mass over the 1 - 2 Myr age range spanned by the latter two regions and MBM 12. Our observations can exclude the presence in MBM 12 of T Tauri stars with relatively brigh...

  17. The Secreted Protein Rv1860 of Mycobacterium tuberculosis Stimulates Human Polyfunctional CD8+ T Cells.

    Science.gov (United States)

    Satchidanandam, Vijaya; Kumar, Naveen; Biswas, Sunetra; Jumani, Rajiv S; Jain, Chandni; Rani, Rajni; Aggarwal, Bharti; Singh, Jaya; Kotnur, Mohan Rao; Sridharan, Anand

    2016-04-01

    We previously reported that Rv1860 protein from Mycobacterium tuberculosis stimulated CD4(+)and CD8(+)T cells secreting gamma interferon (IFN-γ) in healthy purified protein derivative (PPD)-positive individuals and protected guinea pigs immunized with a DNA vaccine and a recombinant poxvirus expressing Rv1860 from a challenge with virulent M. tuberculosis We now show Rv1860-specific polyfunctional T (PFT) cell responses in the blood of healthy latently M. tuberculosis-infected individuals dominated by CD8(+) T cells, using a panel of 32 overlapping peptides spanning the length of Rv1860. Multiple subsets of CD8(+) PFT cells were significantly more numerous in healthy latently infected volunteers (HV) than in tuberculosis (TB) patients (PAT). The responses of peripheral blood mononuclear cells (PBMC) from PAT to the peptides of Rv1860 were dominated by tumor necrosis factor alpha (TNF-α) and interleukin-10 (IL-10) secretions, the former coming predominantly from non-T cell sources. Notably, the pattern of the T cell response to Rv1860 was distinctly different from those of the widely studied M. tuberculosis antigens ESAT-6, CFP-10, Ag85A, and Ag85B, which elicited CD4(+) T cell-dominated responses as previously reported in other cohorts. We further identified a peptide spanning amino acids 21 to 39 of the Rv1860 protein with the potential to distinguish latent TB infection from disease due to its ability to stimulate differential cytokine signatures in HV and PAT. We suggest that a TB vaccine carrying these and other CD8(+) T-cell-stimulating antigens has the potential to prevent progression of latent M. tuberculosis infection to TB disease.

  18. Universal stress protein Rv2624c alters abundance of arginine and enhances intracellular survival by ATP binding in mycobacteria

    Science.gov (United States)

    Jia, Qiong; Hu, Xinling; Shi, Dawei; Zhang, Yan; Sun, Meihao; Wang, Jianwei; Mi, Kaixia; Zhu, Guofeng

    2016-01-01

    The universal stress protein family is a family of stress-induced proteins. Universal stress proteins affect latency and antibiotic resistance in mycobacteria. Here, we showed that Mycobacterium smegmatis overexpressing M. tuberculosis universal stress protein Rv2624c exhibits increased survival in human monocyte THP-1 cells. Transcriptome analysis suggested that Rv2624c affects histidine metabolism, and arginine and proline metabolism. LC-MS/MS analysis showed that Rv2624c affects the abundance of arginine, a modulator of both mycobacteria and infected THP-1 cells. Biochemical analysis showed that Rv2624c is a nucleotide-binding universal stress protein, and an Rv2624c mutant incapable of binding ATP abrogated the growth advantage in THP-1 cells. Rv2624c may therefore modulate metabolic pathways in an ATP-dependent manner, changing the abundance of arginine and thus increasing survival in THP-1 cells. PMID:27762279

  19. 1.55 Å resolution X-ray crystal structure of Rv3902c from Mycobacterium tuberculosis

    Energy Technology Data Exchange (ETDEWEB)

    Reddy, Bharat G.; Moates, Derek B. [University of Alabama at Birmingham, 1025 18th Street South, Birmingham, AL 35233 (United States); Kim, Heung-Bok [Los Alamos National Laboratory, Los Alamos, NM 87545 (United States); Green, Todd J. [University of Alabama at Birmingham, 1025 18th Street South, Birmingham, AL 35233 (United States); Kim, Chang-Yub; Terwilliger, Thomas C. [Los Alamos National Laboratory, Los Alamos, NM 87545 (United States); DeLucas, Lawrence J., E-mail: duke2@uab.edu [University of Alabama at Birmingham, 1025 18th Street South, Birmingham, AL 35233 (United States)

    2014-03-25

    The 1.55 Å resolution X-ray crystal structure of Rv3902c from M. tuberculosis reveals a novel fold. The crystallographic structure of the Mycobacterium tuberculosis (TB) protein Rv3902c (176 residues; molecular mass of 19.8 kDa) was determined at 1.55 Å resolution. The function of Rv3902c is unknown, although several TB genes involved in bacterial pathogenesis are expressed from the operon containing the Rv3902c gene. The unique structural fold of Rv3902c contains two domains, each consisting of antiparallel β-sheets and α-helices, creating a hand-like binding motif with a small binding pocket in the palm. Structural homology searches reveal that Rv3902c has an overall structure similar to that of the Salmonella virulence-factor chaperone InvB, with an r.m.s.d. for main-chain atoms of 2.3 Å along an aligned domain.

  20. Altered Immune Cytokine Expression Associated with KoRV B Infection and Season in Captive Koalas.

    Science.gov (United States)

    Maher, Iona E; Higgins, Damien P

    2016-01-01

    Koala (Phascolarctos cinereus) populations are increasingly vulnerable and one of the main threats is chlamydial infection. Koala retrovirus (KoRV) has been proposed as an underlying cause of the koala's susceptibility to infection with Chlamydia and high rates of lymphoid neoplasia; however, the regionally ubiquitous, endogenous nature of this virus suggests that KoRV A infection is not sufficient for immune suppression to occur. A recently discovered exogenous variant of KoRV, KoRV B, has several structural elements that cause increased pathogenicity in related retroviruses and was associated with lymphoid neoplasia in one study. The present study assesses whether KoRV B infection is associated with alterations in immune function. Cytokine gene expression by mitogen stimulated lymphocytes of KoRV B positive (n = 5-6) and negative (n = 6-7) captive koalas was evaluated by qPCR four times (April 2014-February 2015) to control for seasonal variation. Key immune genes in the Th1 pathway (IFNγ, TNFα), Th2 pathway (IL 10, IL4, IL6) and Th17 pathway (IL17A), along with CD4:CD8 ratio, were assessed. KoRV B positive koalas showed significantly increased up-regulation of IL17A and IL10 in three out of four sampling periods and IFNγ, IL6, IL4 and TNFα in two out of four. IL17A is an immune marker for chlamydial pathogenesis in the koala; increased expression of IL17A in KoRV B positive koalas, and concurrent immune dysregulation, may explain the differences in susceptibility to chlamydial infection and severity of disease seen between individuals and populations. There was also marked seasonal variation in up-regulation for most of the cytokines and the CD4:CD8 ratio. The up-regulation in both Th1 and Th2 cytokines mirrors changes associated with immune dysregulation in humans and felids as a result of retroviral infections. This is the first report of altered immune expression in koalas infected by an exogenous variant of KoRV and also the first report of seasonal

  1. Magnetospheric accretion and spin-down of the prototypical classical T Tauri star AA Tau

    Science.gov (United States)

    Donati, J.-F.; Skelly, M. B.; Bouvier, J.; Gregory, S. G.; Grankin, K. N.; Jardine, M. M.; Hussain, G. A. J.; Ménard, F.; Dougados, C.; Unruh, Y.; Mohanty, S.; Aurière, M.; Morin, J.; Farès, R.; MAPP Collaboration

    2010-12-01

    From observations collected with the ESPaDOnS spectropolarimeter at the Canada-France-Hawaii Telescope (CFHT) and with the NARVAL spectropolarimeter at the Télescope Bernard Lyot (TBL), we report the detection of Zeeman signatures on the prototypical classical T Tauri star AA Tau, both in photospheric lines and accretion-powered emission lines. Using time series of unpolarized and circularly polarized spectra, we reconstruct at two epochs maps of the magnetic field, surface brightness and accretion-powered emission of AA Tau. We find that AA Tau hosts a 2-3 kG magnetic dipole tilted at ≃20° to the rotation axis, and of presumably dynamo origin. We also show that the magnetic poles of AA Tau host large cool spots at photospheric level and accretion regions at chromospheric level. The accretion rate at the surface of AA Tau at the time of our observations (estimated from the emission in the He I D3 line mainly) is strongly variable, ranging from -9.6 to -8.5 and equal to -9.2 in average (in logarithmic scale and in M⊙ yr-1); this is an order of magnitude smaller than the disc accretion rate at which the magnetic truncation radius (below which the disc is disrupted by the stellar magnetic field) matches the corotation radius (where the Keplerian period equals the stellar rotation period) - a necessary condition for accretion to occur. It suggests that AA Tau is largely in the propeller regime, with most of the accreting material in the inner disc regions being expelled outwards and only a small fraction accreted towards the surface of the star. The strong variability in the observed surface mass accretion rate and the systematic time-lag of optical occultations (by the warped accretion disc) with respect to magnetic and accretion-powered emission maxima also support this conclusion. Our results imply that AA Tau is being actively spun-down by the star/disc magnetic coupling and appears as an ideal laboratory for studying angular momentum losses of forming suns

  2. Mycobacterium tuberculosis Rv0198c, a putative matrix metalloprotease is involved in pathogenicity.

    Science.gov (United States)

    Muttucumaru, D G Niranjala; Smith, Debbie A; McMinn, Elizabeth J; Reese, Valerie; Coler, Rhea N; Parish, Tanya

    2011-03-01

    We are interested in the role of proteases in the biology of the global human pathogen, Mycobacterium tuberculosis. We have focused on a putative matrix metalloprotease, Rv0198c. In order to investigate its role we constructed an unmarked chromosomal deletion of the gene and analysed the phenotype of the resulting mutant. No differences in growth in axenic culture were seen and there was no measurable change in overall protease activity in cell-free extracts. Transcriptome analysis revealed a small number of changes in gene expression in aerobic growth, with Rv2488c and Rv1971 being over 40-fold up-regulated and qor (Rv1454c) being 20-fold down-regulated; in addition, changes were seen in members of the heat shock regulon. Virulence assays demonstrated that the mutant was able to replicate in human macrophage-like cells (THP-1 cell line) to a comparable degree with the wild-type. However, the mutant was hyper-virulent in the SCID and C57BL/6 mouse models. Our data suggest that Rv0198c plays a role during infection. Copyright © 2010 Elsevier Ltd. All rights reserved.

  3. AT-RvD1 Promotes Resolution of Inflammation in NOD/ShiLtJ mice

    Science.gov (United States)

    Wang, Ching-Shuen; Maruyama, Christina L.; Easley, Justin T.; Trump, Bryan G.; Baker, Olga J.

    2017-01-01

    Sjögren’s syndrome (SS) is a chronic inflammatory autoimmune disease characterized by diminished secretory function of the exocrine glands. Treatments for hyposalivation are limited to the use of saliva substitutes and medications that provide only temporary relief. In light of the high degree of need and the limitations of current therapies, development of alternative treatments to restore functioning is essential. Resolvins (Rv), which are highly potent lipid mediators, offer a viable alternative for better treating inflammatory diseases such as SS. The goal of this study was to determine whether systemic preventive treatment with Aspirin-triggered RvD1 (AT-RvD1) reduces inflammation and preserves secretory functioning in NOD/ShiLtJ SS-like mice. Our results indicate that systemic treatment with AT-RvD1 diminishes the progression of the disease in salivary epithelium from female mice as follows: (a) improves secretory function, (b) reduces pro-inflammatory molecule gene expression, (c) increases anti-inflammatory molecule gene expression and (d) induces M2 macrophage polarization. Finally, AT-RvD1 decreases lymphocytic infiltration into the salivary glands when used with small doses of the steroid, dexamethasone, and promotes the tissue healing process. PMID:28361884

  4. Functional analysis of TPM domain containing Rv2345 of Mycobacterium tuberculosis identifies its phosphatase activity.

    Science.gov (United States)

    Sinha, Avni; Eniyan, Kandasamy; Sinha, Swati; Lynn, Andrew Michael; Bajpai, Urmi

    2015-07-01

    Mycobacterium tuberculosis (Mtb) is the causal agent of tuberculosis, the second largest infectious disease. With the rise of multi-drug resistant strains of M. tuberculosis, serious challenge lies ahead of us in treating the disease. The availability of complete genome sequence of Mtb has improved the scope for identifying new proteins that would not only further our understanding of biology of the organism but could also serve to discover new drug targets. In this study, Rv2345, a hypothetical membrane protein of M. tuberculosis H37Rv, which is reported to be a putative ortholog of ZipA cell division protein has been assigned function through functional annotation using bioinformatics tools followed by experimental validation. Sequence analysis showed Rv2345 to have a TPM domain at its N-terminal region and predicted it to have phosphatase activity. The TPM domain containing region of Rv2345 was cloned and expressed using pET28a vector in Escherichia coli and purified by Nickel affinity chromatography. The purified TPM domain was tested in vitro and our results confirmed it to have phosphatase activity. The enzyme activity was first checked and optimized with pNPP as substrate, followed by using ATP, which was also found to be used as substrate by the purified protein. Hence sequence analysis followed by in vitro studies characterizes TPM domain of Rv2345 to contain phosphatase activity.

  5. A spectral invariant representation of spectral reflectance

    Science.gov (United States)

    Ibrahim, Abdelhameed; Tominaga, Shoji; Horiuchi, Takahiko

    2011-03-01

    Spectral image acquisition as well as color image is affected by several illumination factors such as shading, gloss, and specular highlight. Spectral invariant representations for these factors were proposed for the standard dichromatic reflection model of inhomogeneous dielectric materials. However, these representations are inadequate for other characteristic materials like metal. This paper proposes a more general spectral invariant representation for obtaining reliable spectral reflectance images. Our invariant representation is derived from the standard dichromatic reflection model for dielectric materials and the extended dichromatic reflection model for metals. We proof that the invariant formulas for spectral images of natural objects preserve spectral information and are invariant to highlights, shading, surface geometry, and illumination intensity. It is proved that the conventional spectral invariant technique can be applied to metals in addition to dielectric objects. Experimental results show that the proposed spectral invariant representation is effective for image segmentation.

  6. Rv2607 from Mycobacterium tuberculosis is a pyridoxine 5'-phosphate oxidase with unusual substrate specificity.

    Directory of Open Access Journals (Sweden)

    Ellene H Mashalidis

    Full Text Available Despite intensive effort, the majority of the annotated Mycobacterium tuberculosis genome consists of genes encoding proteins of unknown or poorly understood function. For example, there are seven conserved hypothetical proteins annotated as homologs of pyridoxine 5'-phosphate oxidase (PNPOx, an enzyme that oxidizes pyridoxine 5'-phosphate (PNP or pyridoxamine 5'-phosphate (PMP to form pyridoxal 5'-phosphate (PLP. We have characterized the function of Rv2607 from Mycobacterium tuberculosis H37Rv and shown that it encodes a PNPOx that oxidizes PNP to PLP. The k(cat and K(M for this reaction were 0.01 s(-1 and 360 µM, respectively. Unlike many PNPOx enzymes, Rv2607 does not recognize PMP as a substrate.

  7. Identification of Rv0222 from RD4 as a novel serodiagnostic target for tuberculosis

    DEFF Research Database (Denmark)

    Rosenkrands, Ida; Aagaard, Claus; Weldingh, Karin;

    2008-01-01

    Forty-seven Mycobacterium tuberculosis genes from the 'regions of difference' RD2-7, RD9-13 and RD15 were cloned and expressed, and the purified recombinant proteins were screened for their serodiagnostic potential. Evaluation of six selected proteins in serum samples from Danish resident...... Uganda. The highest overall sensitivity was observed for Rv0222 compared to BCG-vaccinated non-endemic healthy controls as well as symptomatic endemic controls. Importantly, Rv0222 identified human immuno deficiency (HIV) virus-positive patients and HIV-negative patients with the same overall sensitivity....... The results emphasize the importance of cut-off values in TB endemic regions based on endemic control individuals to diagnose active TB, and identify Rv0222 as a promising new antigen for serodiagnosis of TB in both HIV-negative and HIV-positive patients....

  8. Spectral Decomposition Algorithm (SDA)

    Data.gov (United States)

    National Aeronautics and Space Administration — Spectral Decomposition Algorithm (SDA) is an unsupervised feature extraction technique similar to PCA that was developed to better distinguish spectral features in...

  9. Synthetic Long Peptide Derived from Mycobacterium tuberculosis Latency Antigen Rv1733c Protects against Tuberculosis.

    Science.gov (United States)

    Coppola, Mariateresa; van den Eeden, Susan J F; Wilson, Louis; Franken, Kees L M C; Ottenhoff, Tom H M; Geluk, Annemieke

    2015-09-01

    Responsible for 9 million new cases of active disease and nearly 2 million deaths each year, tuberculosis (TB) remains a global health threat of overwhelming dimensions. Mycobacterium bovis BCG, the only licensed vaccine available, fails to confer lifelong protection and to prevent reactivation of latent infection. Although 15 new vaccine candidates are now in clinical trials, an effective vaccine against TB remains elusive, and new strategies for vaccination are vital. BCG vaccination fails to induce immunity against Mycobacterium tuberculosis latency antigens. Synthetic long peptides (SLPs) combined with adjuvants have been studied mostly for therapeutic cancer vaccines, yet not for TB, and proved to induce efficient antitumor immunity. This study investigated an SLP derived from Rv1733c, a major M. tuberculosis latency antigen which is highly expressed by "dormant" M. tuberculosis and well recognized by T cells from latently M. tuberculosis-infected individuals. In order to assess its in vivo immunogenicity and protective capacity, Rv1733c SLP in CpG was administered to HLA-DR3 transgenic mice. Immunization with Rv1733c SLP elicited gamma interferon-positive/tumor necrosis factor-positive (IFN-γ(+)/TNF(+)) and IFN-γ(+) CD4(+) T cells and Rv1733c-specific antibodies and led to a significant reduction in the bacterial load in the lungs of M. tuberculosis-challenged mice. This was observed both in a pre- and in a post-M. tuberculosis challenge setting. Moreover, Rv1733c SLP immunization significantly boosted the protective efficacy of BCG, demonstrating the potential of M. tuberculosis latency antigens to improve BCG efficacy. These data suggest a promising role for M. tuberculosis latency antigen Rv1733c-derived SLPs as a novel TB vaccine approach, both in a prophylactic and in a postinfection setting.

  10. Mechanism of DNA Recognition by the Restriction Enzyme EcoRV

    Energy Technology Data Exchange (ETDEWEB)

    Zahran, Mai [ORNL; Daidone, Isabella [University of Heidelberg; Smith, Jeremy C [ORNL; Imhof, Petra [University of Heidelberg

    2010-08-01

    EcoRV, a restriction enzyme in Escherichia coli, destroys invading foreign DNA by cleaving it at the center step of a GATATC sequence. In the EcoRV-cognate DNA crystallographic complex, a sharp kink of 50 degrees has been found at the center base-pair step (TA). Here, we examine the interplay between the intrinsic propensity of the cognate sequence to kink and the induction by the enzyme by performing all-atom molecular dynamics simulations of EcoRV unbound and interacting with three DNA sequences: the cognate sequence, GATATC (TA); the non-cognate sequence, GAATTC (AT); and with the cognate sequence methylated on the first adenine GA(CH(3))TATC (TA-CH(3)). In the unbound EcoRV, the cleft between the two C-terminal subdomains is found to be open. Binding to AT narrows the cleft and forms a partially bound state. However, the intrinsic bending propensity of AT is insufficient to allow tight binding. In contrast, the cognate TA sequence is easier to bend, allowing specific, high-occupancy hydrogen bonds to form in the complex. The absence of cleavage for this methylated sequence is found to arise from the loss of specific hydrogen bonds between the first adenine of the recognition sequence and Asn185. On the basis of the results, we suggest a three-step recognition mechanism. In the first step, EcoRV, in an open conformation, binds to the DNA at a random sequence and slides along it. In the second step, when the two outer base pairs, GAxxTC, are recognized, the R loops of the protein become more ordered, forming strong hydrogen-bonding interactions, resulting in a partially bound EcoRV-DNA complex. In the third step, the flexibility of the center base pair is probed, and in the case of the full cognate sequence the DNA bends, the complex strengthens and the protein and DNA interact more closely, allowing cleavage.

  11. Determining Type Ia Supernovae Host galaxy extinction probabilities and a statistical approach to estimating the absorption-to-reddening ratio $R_V$

    CERN Document Server

    Cikota, Aleksandar; Marleau, Francine

    2016-01-01

    We investigate limits on the extinction values of Type Ia supernovae to statistically determine the most probable color excess, E(B-V), with galactocentric distance, and use these statistics to determine the absorption-to-reddening ratio, $R_V$, for dust in the host galaxies. We determined pixel-based dust mass surface density maps for 59 galaxies from the Key Insight on Nearby Galaxies: a Far-Infrared Survey with \\textit{Herschel} (KINGFISH, Kennicutt et al. (2011)). We use Type Ia supernova spectral templates (Hsiao et al. 2007) to develop a Monte Carlo simulation of color excess E(B-V) with $R_V$ = 3.1 and investigate the color excess probabilities E(B-V) with projected radial galaxy center distance. Additionally, we tested our model using observed spectra of SN 1989B, SN 2002bo and SN 2006X, which occurred in three KINGFISH galaxies. Finally, we determined the most probable reddening for Sa-Sap, Sab-Sbp, Sbc-Scp, Scd-Sdm, S0 and Irregular galaxy classes as a function of $R/R_{25}$. We find that the larges...

  12. Registration of cytoplasmic male-sterile oilseed sunflower genetic stocks CMS GIG2 and CMS GIG2-RV, and fertility restoration lines RF GIG2-MAX 1631 and RF GIG2-MAX 1631-RV

    Science.gov (United States)

    Two cytoplasmic male-sterile (CMS) oilseed sunflower (Helianthus annuus L.) genetic stocks, CMS GIG2 (Reg. No. xxx, PI xxxx), and CMS GIG2-RV (Reg. No. xxx, PI xxxx), and corresponding fertility restoration lines RF GIG2-MAX 1631 (Reg. No. xxx, PI xxxx) and RF GIG2-MAX 1631-RV (Reg. No. xxx, PI xxx...

  13. Evidence of large-scale structures in the atmosphere of the active K-dwarf component of V471 Tauri

    Science.gov (United States)

    Guinan, E. F.; Raymond, J. C.; Raymond, J. C.; Raymond, J. C.; Raymond, J. C.

    1986-01-01

    Contemporaneous IUE ultraviolet spectra and visible photoelectric data of the eclipsing binary V471 Tauri (K2V + DA) between 1979 and 1985 was analyzed. The combined data detail the three-dimensional structure of atmospheric loops and their associated starspots on the K dwarf. The distribution of starspot regions on the surface of the K star was inferred from the visible photometry. When spots are located near the limb of the K dwarf prior to and shortly after the total eclipse of the white dwarf, absorption lines such as C II, C III, c IV, and Si IV appear superimposed on the continuum of the white dwarf. These absorption lines are likely caused by cool coronal loops overlying the spots in the atmosphere of the K dwarf. The loops can extend nearly one stellar radius above the surface of the K2V star.

  14. Detection of a Radio Flare at Millimeter-Wavelengths from the X-ray T Tauri Star V773 Tau

    Science.gov (United States)

    Umemoto, T.; Saito, M.; Nakanishi, K.; Kuno, N.; Tsuboi, M.

    2009-08-01

    We present the results of multi-frequency observations of a radio flare in the young stellar object (YSO) V773 Tau, which is probably a weak-line T Tauri star. We carried out radio continuum observations at 22 GHz, 43 GHz and 86 GHz, using the Nobeyama 45 m telescope, and detected a radio flare at all frequencies. The radio flare occurred near periastron passage, and the flux density became 4 to 10 times higher, then rapidly decreased at 43 and 86 GHz within a few hours. The radio spectrum was rising (brighter at higher frequency) during the flare. On the other hand, the radio continuum at 22 GHz was detected even 28 hours later at more than 2 mJy. Thus, the active phase is surprisingly long at 22 GHz.. V773 Tau is the most promising target for detailed imaging of the magnetosphere with the next space VLBI project VSOP-2.

  15. Robust and flexible response of the Ostreococcus tauri circadian clock to light/dark cycles of varying photoperiod.

    Science.gov (United States)

    Thommen, Quentin; Pfeuty, Benjamin; Corellou, Florence; Bouget, François-Yves; Lefranc, Marc

    2012-09-01

    The green microscopic alga Ostreococcus tauri has recently emerged as a promising model for understanding how circadian clocks, which drive the daily biological rhythms of many organisms, synchronize to the day/night cycle in changing weather and seasons. Here, we analyze translational reporter time series data for the central clock genes CCA1 and TOC1 for a wide range of daylight durations (photoperiods). The variation of temporal expression profiles with day duration is complex, with the two protein peaks tracking different times of the day. Nevertheless, all profiles are accurately reproduced by a simple two-gene transcriptional loop model whose parameters depend on light only through the photoperiod value. We show that this non-intuitive behavior allows the circadian clock to combine flexibility and robustness with respect to daylight fluctuations.

  16. CSI 2264: Probing the inner disks of AA Tauri-like systems in NGC 2264

    Science.gov (United States)

    McGinnis, P. T.; Alencar, S. H. P.; Guimarães, M. M.; Sousa, A. P.; Stauffer, J.; Bouvier, J.; Rebull, L.; Fonseca, N. N. J.; Venuti, L.; Hillenbrand, L.; Cody, A. M.; Teixeira, P. S.; Aigrain, S.; Favata, F.; Fűrész, G.; Vrba, F. J.; Flaccomio, E.; Turner, N. J.; Gameiro, J. F.; Dougados, C.; Herbst, W.; Morales-Calderón, M.; Micela, G.

    2015-05-01

    Context. The classical T Tauri star (CTTS) AA Tau has presented photometric variability that was attributed to an inner disk warp, caused by the interaction between the inner disk and an inclined magnetosphere. Previous studies of the young cluster NGC 2264 have shown that similar photometric behavior is common among CTTS. Aims: The goal of this work is to investigate the main causes of the observed photometric variability of CTTS in NGC 2264 that present AA Tau-like light curves, and verify if an inner disk warp could be responsible for their observed variability. Methods: In order to understand the mechanism causing these stars' photometric behavior, we investigate veiling variability in their spectra and u - r color variations and estimate parameters of the inner disk warp using an occultation model proposed for AA Tau. We also compare infrared Spitzer IRAC and optical CoRoT light curves to analyze the dust responsible for the occultations. Results: AA Tau-like variability proved to be transient on a timescale of a few years. We ascribe this variability to stable accretion regimes and aperiodic variability to unstable accretion regimes and show that a transition, and even coexistence, between the two is common. We find evidence of hot spots associated with occultations, indicating that the occulting structures could be located at the base of accretion columns. We find average values of warp maximum height of 0.23 times its radial location, consistent with AA Tau, with variations of on average 11% between rotation cycles. We also show that extinction laws in the inner disk indicate the presence of grains larger than interstellar grains. Conclusions: The inner disk warp scenario is consistent with observations for all but one star with AA Tau-like variability in our sample. AA Tau-like systems are fairly common, comprising 14% of CTTS observed in NGC 2264, though this number increases to 35% among systems of mass 0.7 M⊙ ≲ M ≲ 2.0 M⊙. Assuming random

  17. Avastatud maa-alune järv võib lõpetada Darfuri kodusõja / Karin Volmer

    Index Scriptorium Estoniae

    Volmer, Karin

    2007-01-01

    Ilmunud ka: Postimees : na russkom jazõke, 23. juuli 2007, lk. 6. Teadlaste hinnangul võib Darfuri konflikti lõpetada Darfuris avastatud maa-alune järv, sest kodusõda araablastest karjakasvatajate ja põlluharijatest põliselanike vahel võib tingitud olla veepuudusest. Kaart: Darfuri maa-alune järv. Lisa: Darfuri konflikt

  18. Millises olukorras on teie linna lasteaiad? / Jane Mets, Kristi Aavakivi, Priit Metsjärv ... [jt.

    Index Scriptorium Estoniae

    2012-01-01

    Küsimusele vastavad Pärnu abilinnapea Jane Mets, Võru linnavalitsuse haridusspetsialist Kristi Aavakivi, Tartu linnavalitsuse ehitusteenistuse juhataja Priit Metsjärv, Viljandi abilinnapea Ardo Agasild, Rakvere abilinnapea Ain Suurkaev ja Valga linna haridus- ja kultuuriameti juhataja Anneli Rants

  19. Millises olukorras on teie linna lasteaiad? / Jane Mets, Kristi Aavakivi, Priit Metsjärv ... [jt.

    Index Scriptorium Estoniae

    2012-01-01

    Küsimusele vastavad Pärnu abilinnapea Jane Mets, Võru linnavalitsuse haridusspetsialist Kristi Aavakivi, Tartu linnavalitsuse ehitusteenistuse juhataja Priit Metsjärv, Viljandi abilinnapea Ardo Agasild, Rakvere abilinnapea Ain Suurkaev ja Valga linna haridus- ja kultuuriameti juhataja Anneli Rants

  20. Piret Hiisjärv tõi mehed kooli / Sirje Tohver

    Index Scriptorium Estoniae

    Tohver, Sirje, 1948-

    2006-01-01

    Õismäe Humanitaargümnaasiumi direktor Piret Hiisjärv kutsus tundi andma kümmekond isa (Heiki Sibul, Richard Snait, Mike Wahl, Väino Reintamm, Aleksei Turovski, Andres Elmisto, Gert Laanemaa, Mihkel Klemantsov). Tingimuseks oli, et usust ja poliitikast rääkida ei tohi

  1. Hydrogen production by co-cultures of Lactobacillus and a photosynthetic bacterium, Rhodobacter sphaeroides RV

    Energy Technology Data Exchange (ETDEWEB)

    Asada, Yasuo; Ishimi, Katsuhiro [Department of General Education, College of Science and Technology, Nihon University, Narashinodai, Chiba 274-8501 (Japan); Tokumoto, Masaru; Aihara, Yasuyuki; Oku, Masayo; Kohno, Hideki [Department of Applied Molecular Chemistry, College of Industrial Technology, Nihon University, Izumi-cho, Chiba 275-8575 (Japan); Wakayama, Tatsuki; Miyake, Jun [Research Institute for Cell Engineering, National Institute of Advanced Industrial Science and Technology, Nakoji, Amagasaki, Hyogo 661-0974 (Japan); Tomiyama, Masamitsu [Genetic Diversity Department, National Institute of Agrobiological Science, Tsukuba, Ibaraki 305-8602 (Japan)

    2006-09-15

    Hydrogen production with glucose by using co-immobilized cultures of a lactic acid bacterium, Lactobacillus delbrueckii NBRC13953, and a photosynthetic bacterium, Rhodobacter sphaeroides RV, in agar gels was studied. Glucose was converted to hydrogen gas in a yield of 7.1mol of hydrogen per mole of glucose at a maximum under illuminated conditions. (author)

  2. Heat Flow Data Cruise MD72 RV Marion Dufresne over the Mascarene Ridge

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Data were gathered by the R/V Marion Dufresne in May and June of 1992 over the Mascarene Ridge in the Indian Ocean on cruise MD72/MASCAFLUX. Heat flow measurements...

  3. Hydrogen Production by Co-cultures of Rhizopus oryzae and a Photosynthetic Bacterium, Rhodobacter sphaeroides RV

    Science.gov (United States)

    Asada, Yasuo; Ishimi, Katsuhiro; Nagata, Yoko; Wakayama, Tatsuki; Miyake, Jun; Kohno, Hideki

    Hydrogen production with glucose by using co-immobilized cultures of a fungus, Rhizopus oryzae NBRC5384, and a photosynthetic bacterium, Rhodobacter sphaeroides RV, in agar gels was studied. The co-immobilized cultures converted glucose to hydrogen via lactate in a high molar yield of about 8moles of hydrogen per glucose at a maximum under illuminated conditions.

  4. Quantum Spectral Symmetries

    Science.gov (United States)

    Hamhalter, Jan; Turilova, Ekaterina

    2017-02-01

    Quantum symmetries of spectral lattices are studied. Basic properties of spectral order on A W ∗-algebras are summarized. Connection between projection and spectral automorphisms is clarified by showing that, under mild conditions, any spectral automorphism is a composition of function calculus and Jordan ∗-automorphism. Complete description of quantum spectral symmetries on Type I and Type II A W ∗-factors are completely described.

  5. 结核分枝杆菌Rv2031c基因在P815细胞中的高效表达%The high efficiency expression of Rv2031c gene of Mycobacterium tuberculosis in P815 Cells

    Institute of Scientific and Technical Information of China (English)

    尚淑琴; 王丽梅; 张薇; 曾令城; 陈宝忠

    2012-01-01

    目的 构建结核分枝杆菌Rv2031c基因的真核表达载体,并在P815细胞中高效表达.方法 应用PCR扩增Rv2031c基因,克隆人原核表达载体后进行测序,测序正确的序列克隆人真核表达载体pcDNA3.1(-);重组质粒pcDNA-Rv2031c转染P815真核细胞;以RT-PCR方法 检测结核分枝杆菌Rv2031c在真核细胞内mRNA表达,以间接免疫荧光技术检测目的 蛋白的表达.结果 Rv2031c基因成功克隆人真核表达载体pcDNA3.1(-),并可在P815细胞高效表达.结论 成功构建了真核表达重组质粒pcDNA-Rv2031c,为进一步研究Rv2031c的功能奠定了坚实基础.%Objective To construct eukaryotic expression vector encoding Mycobacterium tuberculosis Rv2031c gene and highly express the protein in P815 cells. Methods The Rv2031c gene segments were amplified by PCR and sequenced after cloned into prokaryotic expression vector, then the correct sequences were cloned into eukaryotic expression vector pcDNA3.1 (-). The recombinant plasmid pcDNA -Rv2031c was transfected into P815 cells. The expressions of mRNA and the expressed of proteins encoded by this gene were detected with RT-PCR and indirect immunofluorescence respectively. Results Rv2031c gene was cloned into pcDNA3.1 (-) correctly and can highly expressed in P815 cells. Conclusion Eukaryotic recombinant plas-mids encoding Rv2031c were constructed successfully, which established the basis for further study of the function of Rv2031c.

  6. The Spectral Shift Function and Spectral Flow

    Science.gov (United States)

    Azamov, N. A.; Carey, A. L.; Sukochev, F. A.

    2007-11-01

    At the 1974 International Congress, I. M. Singer proposed that eta invariants and hence spectral flow should be thought of as the integral of a one form. In the intervening years this idea has lead to many interesting developments in the study of both eta invariants and spectral flow. Using ideas of [24] Singer’s proposal was brought to an advanced level in [16] where a very general formula for spectral flow as the integral of a one form was produced in the framework of noncommutative geometry. This formula can be used for computing spectral flow in a general semifinite von Neumann algebra as described and reviewed in [5]. In the present paper we take the analytic approach to spectral flow much further by giving a large family of formulae for spectral flow between a pair of unbounded self-adjoint operators D and D + V with D having compact resolvent belonging to a general semifinite von Neumann algebra {mathcal{N}} and the perturbation V in {mathcal{N}} . In noncommutative geometry terms we remove summability hypotheses. This level of generality is made possible by introducing a new idea from [3]. There it was observed that M. G. Krein’s spectral shift function (in certain restricted cases with V trace class) computes spectral flow. The present paper extends Krein’s theory to the setting of semifinite spectral triples where D has compact resolvent belonging to {mathcal{N}} and V is any bounded self-adjoint operator in {mathcal{N}} . We give a definition of the spectral shift function under these hypotheses and show that it computes spectral flow. This is made possible by the understanding discovered in the present paper of the interplay between spectral shift function theory and the analytic theory of spectral flow. It is this interplay that enables us to take Singer’s idea much further to create a large class of one forms whose integrals calculate spectral flow. These advances depend critically on a new approach to the calculus of functions of non

  7. Prevention of pneumonic plague in mice, rats, guinea pigs and non-human primates with clinical grade rV10, rV10-2 or F1-V vaccines

    Science.gov (United States)

    Quenee, Lauriane E.; Ciletti, Nancy A.; Elli, Derek; Hermanas, Timothy M.; Schneewind, Olaf

    2012-01-01

    Yersinia pestis causes plague, a disease with high mortality in humans that can be transmitted by fleabite or aerosol. A US Food and Drug Administration (FDA)-licensed plague vaccine is currently not available. Vaccine developers have focused on two subunits of Y. pestis: LcrV, a protein at the tip of type III secretion needles, and F1, the fraction 1 pilus antigen. F1-V, a hybrid generated via translational fusion of both antigens, is being developed for licensure as a plague vaccine. The rV10 vaccine is a non-toxigenic variant of LcrV lacking residues 271–300. Here we developed Current Good Manufacturing Practice (cGMP) protocols for rV10. Comparison of clinical grade rV10 with F1-V did not reveal significant differences in plague protection in mice, guinea pigs or cynomolgus macaques. We also developed cGMP protocols for rV10-2, a variant of rV10 with an altered affinity tag. Immunization with rV10-2 adsorbed to aluminum hydroxide elicited antibodies against LcrV and conferred pneumonic plague protection in mice, rats, guinea pigs, cynomolgus macaques and African Green monkeys. The data support further development of rV10-2 for FDA Investigational New Drug (IND) authorization review and clinical testing. PMID:21763383

  8. Crystal Structure of Mycobacterium tuberculosis H37Rv AldR (Rv2779c), a Regulator of the ald Gene: DNA BINDING AND IDENTIFICATION OF SMALL MOLECULE INHIBITORS.

    Science.gov (United States)

    Dey, Abhishek; Shree, Sonal; Pandey, Sarvesh Kumar; Tripathi, Rama Pati; Ramachandran, Ravishankar

    2016-06-03

    Here we report the crystal structure of M. tuberculosis AldR (Rv2779c) showing that the N-terminal DNA-binding domains are swapped, forming a dimer, and four dimers are assembled into an octamer through crystal symmetry. The C-terminal domain is involved in oligomeric interactions that stabilize the oligomer, and it contains the effector-binding sites. The latter sites are 30-60% larger compared with homologs like MtbFFRP (Rv3291c) and can consequently accommodate larger molecules. MtbAldR binds to the region upstream to the ald gene that is highly up-regulated in nutrient-starved tuberculosis models and codes for l-alanine dehydrogenase (MtbAld; Rv2780). Further, the MtbAldR-DNA complex is inhibited upon binding of Ala, Tyr, Trp and Asp to the protein. Studies involving a ligand-binding site G131T mutant show that the mutant forms a DNA complex that cannot be inhibited by adding the amino acids. Comparative studies suggest that binding of the amino acids changes the relative spatial disposition of the DNA-binding domains and thereby disrupt the protein-DNA complex. Finally, we identified small molecules, including a tetrahydroquinoline carbonitrile derivative (S010-0261), that inhibit the MtbAldR-DNA complex. The latter molecules represent the very first inhibitors of a feast/famine regulatory protein from any source and set the stage for exploring MtbAldR as a potential anti-tuberculosis target.

  9. Identification of novel adhesins of M. tuberculosis H37Rv using integrated approach of multiple computational algorithms and experimental analysis.

    Science.gov (United States)

    Kumar, Sanjiv; Puniya, Bhanwar Lal; Parween, Shahila; Nahar, Pradip; Ramachandran, Srinivasan

    2013-01-01

    Pathogenic bacteria interacting with eukaryotic host express adhesins on their surface. These adhesins aid in bacterial attachment to the host cell receptors during colonization. A few adhesins such as Heparin binding hemagglutinin adhesin (HBHA), Apa, Malate Synthase of M. tuberculosis have been identified using specific experimental interaction models based on the biological knowledge of the pathogen. In the present work, we carried out computational screening for adhesins of M. tuberculosis. We used an integrated computational approach using SPAAN for predicting adhesins, PSORTb, SubLoc and LocTree for extracellular localization, and BLAST for verifying non-similarity to human proteins. These steps are among the first of reverse vaccinology. Multiple claims and attacks from different algorithms were processed through argumentative approach. Additional filtration criteria included selection for proteins with low molecular weights and absence of literature reports. We examined binding potential of the selected proteins using an image based ELISA. The protein Rv2599 (membrane protein) binds to human fibronectin, laminin and collagen. Rv3717 (N-acetylmuramoyl-L-alanine amidase) and Rv0309 (L,D-transpeptidase) bind to fibronectin and laminin. We report Rv2599 (membrane protein), Rv0309 and Rv3717 as novel adhesins of M. tuberculosis H37Rv. Our results expand the number of known adhesins of M. tuberculosis and suggest their regulated expression in different stages.

  10. Identification of novel adhesins of M. tuberculosis H37Rv using integrated approach of multiple computational algorithms and experimental analysis.

    Directory of Open Access Journals (Sweden)

    Sanjiv Kumar

    Full Text Available Pathogenic bacteria interacting with eukaryotic host express adhesins on their surface. These adhesins aid in bacterial attachment to the host cell receptors during colonization. A few adhesins such as Heparin binding hemagglutinin adhesin (HBHA, Apa, Malate Synthase of M. tuberculosis have been identified using specific experimental interaction models based on the biological knowledge of the pathogen. In the present work, we carried out computational screening for adhesins of M. tuberculosis. We used an integrated computational approach using SPAAN for predicting adhesins, PSORTb, SubLoc and LocTree for extracellular localization, and BLAST for verifying non-similarity to human proteins. These steps are among the first of reverse vaccinology. Multiple claims and attacks from different algorithms were processed through argumentative approach. Additional filtration criteria included selection for proteins with low molecular weights and absence of literature reports. We examined binding potential of the selected proteins using an image based ELISA. The protein Rv2599 (membrane protein binds to human fibronectin, laminin and collagen. Rv3717 (N-acetylmuramoyl-L-alanine amidase and Rv0309 (L,D-transpeptidase bind to fibronectin and laminin. We report Rv2599 (membrane protein, Rv0309 and Rv3717 as novel adhesins of M. tuberculosis H37Rv. Our results expand the number of known adhesins of M. tuberculosis and suggest their regulated expression in different stages.

  11. Análisis transcripcional de la región genética RvD1 de Mycobacterium bovis Transcriptional analysis of genetic region RvD1 of Mycobacterium bovis

    Directory of Open Access Journals (Sweden)

    del Portillo Patricia

    2004-12-01

    Full Text Available Mycobacterium bovis comparte una identidad del 99,9% con los genomas de M. tuberculosis, M. africanum y M. microti. Dentro del 0,1% de esta diferencia se encuentran dos regiones genéticas propias de M. bovis: RvD1 y RvD2, las cuales se encuentran delecionadas del genoma de M. tuberculosis H37Rv y, según el análisis bioin-formático, contienen probables marcos abiertos de lectura (Open Reading Frames: ORF. Con el fin de deter­minar si la región RvD1, transcribe los ORF predichos por bioinformática: ORF1, ORF2 y Rv2024, se extrajeron muestras de ARN total de M. bovis BCG Pasteur, en diferentes puntos de una curva de crecimiento micobacteriano, las cuales fueron analizadas mediante la técnica de Transcripción Reversa y Reacción en Ca­dena de la Polimerasa (RTq-PCR en tiempo real. Los hallazgos obtenidos en esta cinética de transcripción por RTq-PCR en tiempo real demostraron que los probables marcos de lectura abiertos ORF1, ORF2 y Rv2024 de la región RvD1 de M. bovis, sí se transcriben y lo hacen de manera constitutiva, hecho que no había sido repor­tado. Los resultados de esta investigación sirven como un primer paso para determinar la función que desem­peña la región RvD1 de M. bovis, y su posible papel en la patogénesis y en la interacción huésped-patógeno de la tuberculosis bovina y humana. Palabras clave: Mycobacterium bovis, BCG, RNA, RT-PCR, RvD1.Mycobacterium bovis, shares 99.9% of genomic identity with M. tuberculosis, M. africanum and M. microti. Within this 0.1 % of difference, there are two genetic regions characteristics of M. bovis that are deleted in M. tuberculo­sis H37Rv: RvD1 and RvD2. According to bioinformatic analysis, these regions contain Open Reading Frames (ORFs. With the purpose of determining if the RvD1 region transcribes the ORFs predicted by bioinformatics (ORF1, ORF2 and Rv2024; total RNA was extracted from a culture of M. bovis BCG Pasteur, at different time points along the growth curve

  12. Overview of errors in the reference sequence and annotation of Mycobacterium tuberculosis H37Rv, and variation amongst its isolates

    KAUST Repository

    Köser, Claudio U.

    2012-06-01

    Since its publication in 1998, the genome sequence of the Mycobacterium tuberculosis H37Rv laboratory strain has acted as the cornerstone for the study of tuberculosis. In this review we address some of the practical aspects that have come to light relating to the use of H37Rv throughout the past decade which are of relevance for the ongoing genomic and laboratory studies of this pathogen. These include errors in the genome reference sequence and its annotation, as well as the recently detected variation amongst isolates of H37Rv from different laboratories. © 2011 Elsevier B.V..

  13. Machine learning methods enable predictive modeling of antibody feature:function relationships in RV144 vaccinees.

    Directory of Open Access Journals (Sweden)

    Ickwon Choi

    2015-04-01

    Full Text Available The adaptive immune response to vaccination or infection can lead to the production of specific antibodies to neutralize the pathogen or recruit innate immune effector cells for help. The non-neutralizing role of antibodies in stimulating effector cell responses may have been a key mechanism of the protection observed in the RV144 HIV vaccine trial. In an extensive investigation of a rich set of data collected from RV144 vaccine recipients, we here employ machine learning methods to identify and model associations between antibody features (IgG subclass and antigen specificity and effector function activities (antibody dependent cellular phagocytosis, cellular cytotoxicity, and cytokine release. We demonstrate via cross-validation that classification and regression approaches can effectively use the antibody features to robustly predict qualitative and quantitative functional outcomes. This integration of antibody feature and function data within a machine learning framework provides a new, objective approach to discovering and assessing multivariate immune correlates.

  14. Magistritööd : [Merike Angerjärv jt.

    Index Scriptorium Estoniae

    2000-01-01

    TPÜ kasvatusteaduste ja pedagoogika magistritööde kaitsmisnõukogu koosolekul kaitsmisele tulevad magistritööd: 30. nov. 2000 Merike Angerjärv "5-7-aastaste laste vanemate kasvatuskultuur ja koolitusvajadus" ja Marianne Martinson "Õpiraskused ja õpetaja toimetulekuvõimalusi õpiraskustega õpilastel"; 14. dets. Heli Maajärv "Teabekirjanduse kasutamise võimalusi põhikooli keemia tundides" ja Nelli Leosk "Õpitingimuste loomine haigestunud õpilastele"; 15. dets. Kristi Kiilu "Diferentseeritud muusikaline tegevus eelkooliealiste laste muusikatunnis" ja Krista Savitsch "Algkooliõpilase elukeskkond toimetuleku tegurina". 15. dets. 2000 kaitsevad Tiina Kukkes TPÜ kasvatusteaduste (kutseõpetuse ja reaalainete didaktika) magistritööde kaitsmisnõukogu koosolekul magistritööd "Inglise keele ja erialaõpetuse integratsiooni tagamine õdede koolituses" ja Viia Parve magistritööd "Teooria ja praktika seose ning õenduskeskuse realiseerimine õppematerjali sisus (nakkushaiguste õppematerjali näitel)"

  15. Selgusid kirjanduse aastapreemiate saajad / Rein Veidemann ; komment. Karl Martin Sinijärv, Viivi Luik

    Index Scriptorium Estoniae

    Veidemann, Rein, 1946-

    2006-01-01

    Eesti Kultuurkapitali aastapreemiad: Kristiina Ehini luulekogu "Kaitseala" ja Jürgen Rooste luulekogu "Ilusaks inimeseks", Piret Raud "Sanna ja salakütid", Merle Karusoo näidend "Misjonärid", Madis Kõivu artiklikogumik "Luhta-minek". Tõlkepreemiad tõlkijatele Anu Saluäär, Heili Einasto, Lembi Loigu, Veronika Kivisilla, Risto Järv. Vabaauhind Käbi Laretei. Artiklipreemia Aare Pilv. Venekeelse autori kirjandusauhind Gohar Markosjan-Käsper, Svetlan Semenenko

  16. Mindfulness og nærværende opmærksomhed i skole og daginstitution

    DEFF Research Database (Denmark)

    Nielsen, Anne Maj; Herskind, Mia

    Mindfulness og nærværende opmærksomhed i skole og daginstitution Vi præsenterer resultater fra undersøgelser af, hvordan lærere og pædagoger lærer mindfulness og hvordan det får betydning for deres praksis og forholdemåder i pædagogik og undervisning. Undersøgelserne er kvalitative og i...

  17. New structural forms of a mycobacterial adenylyl cyclase Rv1625c

    Directory of Open Access Journals (Sweden)

    Deivanayaga Barathy

    2014-09-01

    Full Text Available Rv1625c is one of 16 adenylyl cyclases encoded in the genome of Mycobacterium tuberculosis. In solution Rv1625c exists predominantly as a monomer, with a small amount of dimer. It has been shown previously that the monomer is active and the dimeric fraction is inactive. Both fractions of wild-type Rv1625c crystallized as head-to-head inactive domain-swapped dimers as opposed to the head-to-tail dimer seen in other functional adenylyl cyclases. About half of the molecule is involved in extensive domain swapping. The strain created by a serine residue located on a hinge loop and the crystallization condition might have led to this unusual domain swapping. The inactivity of the dimeric form of Rv1625c could be explained by the absence of the required catalytic site in the swapped dimer. A single mutant of the enzyme was also generated by changing a phenylalanine predicted to occur at the functional dimer interface to an arginine. This single mutant exists as a dimer in solution but crystallized as a monomer. Analysis of the structure showed that a salt bridge formed between a glutamate residue in the N-terminal segment and the mutated arginine residue hinders dimer formation by pulling the N-terminal region towards the dimer interface. Both structures reported here show a change in the dimerization-arm region which is involved in formation of the functional dimer. It is concluded that the dimerization arm along with other structural elements such as the N-terminal region and certain loops are vital for determining the oligomeric nature of the enzyme, which in turn dictates its activity.

  18. Office of Naval Research (ONR) Support for R/V Point Sur Ship Operations

    Science.gov (United States)

    2014-08-20

    Yoneda "^ Lead Enterprise Program Analyst San Jose State University Research Foundation Subject: ONR Pt Sur RV Award N00014-13-1-0581 Enclosed is...the SF298 along with the final summary report which was sent previously. SF298 is enclosed per your office’s request to Mr. Robert T. Schnoor, ONR...instrumented bottom tripods, and drifting GPS -tracked wave-resolving buoys in ebb and flood currents in the Columbia River Mouth. Bottom tripods with

  19. Mindfulness og nærværende opmærksomhed i skole og daginstitution

    DEFF Research Database (Denmark)

    Nielsen, Anne Maj; Herskind, Mia

    Mindfulness og nærværende opmærksomhed i skole og daginstitution Vi præsenterer resultater fra undersøgelser af, hvordan lærere og pædagoger lærer mindfulness og hvordan det får betydning for deres praksis og forholdemåder i pædagogik og undervisning. Undersøgelserne er kvalitative og i...

  20. Modeling Phenotypic Metabolic Adaptations of Mycobacterium tuberculosis H37Rv under Hypoxia

    Science.gov (United States)

    2012-09-13

    Tuberculosis in humans and its epidemiology , diagnosis and treatment in the United States. Int J Tuberc Lung Dis 14: 1226–1232. 4. Horsburgh CR, Jr., Rubin...Modeling Phenotypic Metabolic Adaptations of Mycobacterium tuberculosis H37Rv under Hypoxia Xin Fang, Anders Wallqvist, Jaques Reifman* DoD... tuberculosis , the causative agent of tuberculosis (TB), to successfully infect human hosts. Adaptations allow the organism to evade the host immune

  1. Ship Operations, Maintenance, Repair and Upgrade for the R/V KILO MOANA

    Science.gov (United States)

    2017-07-20

    upgrade the research vessel Kilo Moana, a ship owned by the federal government, operated by University of Hawaii under charter agreement with the...Office of Naval Research . 15. SUBJECT TERMS Research vessel, operation , maintenance, repair. 16. SECURITY CLASSIFICATION OF: 17. LIMITATION OF a...University of Hawaii University of Hawaii operates Research Vessel (R/V) Kilo Moana (AGOR 26), a SWATH vessel owned by the federal government and

  2. Comprehensive Sieve Analysis of Breakthrough HIV-1 Sequences in the RV144 Vaccine Efficacy Trial

    Science.gov (United States)

    Edlefsen, Paul T.; Rolland, Morgane; Hertz, Tomer; Tovanabutra, Sodsai; Gartland, Andrew J.; deCamp, Allan C.; Magaret, Craig A.; Ahmed, Hasan; Gottardo, Raphael; Juraska, Michal; McCoy, Connor; Larsen, Brendan B.; Sanders-Buell, Eric; Carrico, Chris; Menis, Sergey; Bose, Meera; Arroyo, Miguel A.; O’Connell, Robert J.; Nitayaphan, Sorachai; Pitisuttithum, Punnee; Kaewkungwal, Jaranit; Rerks-Ngarm, Supachai; Robb, Merlin L.; Kirys, Tatsiana; Georgiev, Ivelin S.; Kwong, Peter D.; Scheffler, Konrad; Pond, Sergei L. Kosakovsky; Carlson, Jonathan M.; Michael, Nelson L.; Schief, William R.; Mullins, James I.; Kim, Jerome H.; Gilbert, Peter B.

    2015-01-01

    The RV144 clinical trial showed the partial efficacy of a vaccine regimen with an estimated vaccine efficacy (VE) of 31% for protecting low-risk Thai volunteers against acquisition of HIV-1. The impact of vaccine-induced immune responses can be investigated through sieve analysis of HIV-1 breakthrough infections (infected vaccine and placebo recipients). A V1/V2-targeted comparison of the genomes of HIV-1 breakthrough viruses identified two V2 amino acid sites that differed between the vaccine and placebo groups. Here we extended the V1/V2 analysis to the entire HIV-1 genome using an array of methods based on individual sites, k-mers and genes/proteins. We identified 56 amino acid sites or “signatures” and 119 k-mers that differed between the vaccine and placebo groups. Of those, 19 sites and 38 k-mers were located in the regions comprising the RV144 vaccine (Env-gp120, Gag, and Pro). The nine signature sites in Env-gp120 were significantly enriched for known antibody-associated sites (p = 0.0021). In particular, site 317 in the third variable loop (V3) overlapped with a hotspot of antibody recognition, and sites 369 and 424 were linked to CD4 binding site neutralization. The identified signature sites significantly covaried with other sites across the genome (mean = 32.1) more than did non-signature sites (mean = 0.9) (p vaccine immunogens and because most of the associations were insignificant following correction for multiple testing, we predict that few of the genetic differences are strongly linked to the RV144 vaccine-induced immune pressure. In addition to presenting results of the first complete-genome analysis of the breakthrough infections in the RV144 trial, this work describes a set of statistical methods and tools applicable to analysis of breakthrough infection genomes in general vaccine efficacy trials for diverse pathogens. PMID:25646817

  3. Identification of Rv3852 as an Agrimophol-Binding Protein in Mycobacterium tuberculosis.

    Directory of Open Access Journals (Sweden)

    Nan Zhao

    Full Text Available Mycobacterial tuberculosis (Mtb is able to preserve its intrabacterial pH (pHIB near neutrality in the acidic phagosomes of immunologically activated macrophages and to cause lethal pathology in immunocompetent mice. In contrast, when its ability to maintain pHIB homeostasis is genetically compromised, Mtb dies in acidic phagosomes and is attenuated in the mouse. Compounds that phenocopy the genetic disruption of Mtb's pHIB homeostasis could serve as starting points for drug development in their own right or through identification of their targets. A previously reported screen of a natural product library identified a phloroglucinol, agrimophol, that lowered Mtb's pHIB and killed Mtb at an acidic extrabacterial pH. Inability to identify agrimophol-resistant mutants of Mtb suggested that the compound may have more than one target. Given that polyphenolic compounds may undergo covalent reactions, we attempted an affinity-based method for target identification. The structure-activity relationship of synthetically tractable polyhydroxy diphenylmethane analogs with equivalent bioactivity informed the design of a bioactive agrimophol alkyne. After click-chemistry reaction with azido-biotin and capture on streptavidin, the biotinylated agrimophol analog pulled down the Mtb protein Rv3852, a predicted membrane protein that binds DNA in vitro. A ligand-protein interaction between agrimophol and recombinant Rv3852 was confirmed by isothermal calorimetry (ITC and led to disruption of Rv3852's DNA binding function. However, genetic deletion of rv3852 in Mtb did not phenocopy the effect of agrimophol on Mtb, perhaps because of redundancy of its function.

  4. Potential Mechanism of Action of meso-Dihydroguaiaretic Acid on Mycobacterium tuberculosis H37Rv

    Directory of Open Access Journals (Sweden)

    Aldo F. Clemente-Soto

    2014-12-01

    Full Text Available The isolation and characterization of the lignan meso-dihydroguaiaretic acid (MDGA from Larrea tridentata and its activity against Mycobacterial tuberculosis has been demonstrated, but no information regarding its mechanism of action has been documented. Therefore, in this study we carry out the gene expression from total RNA obtained from M. tuberculosis H37Rv treated with MDGA using microarray technology, which was validated by quantitative real time polymerase chain reaction. Results showed that the alpha subunit of coenzyme A transferase of M. tuberculosis H37Rv is present in both geraniol and 1-and 2-methylnaphthalene degradation pathways, which are targeted by MDGA. This assumption was supported by molecular docking which showed stable interaction between MDGA with the active site of the enzyme. We propose that inhibition of coenzyme A transferase of M. tuberculosis H37Rv results in the accumulation of geraniol and 1-and 2-methylnaphtalene inside bacteria, causing membrane destabilization and death of the pathogen. The natural product MDGA is thus an attractive template to develop new anti-tuberculosis drugs, because its target is different from those of known anti-tubercular agents.

  5. Potential mechanism of action of meso-dihydroguaiaretic acid on Mycobacterium tuberculosis H37Rv.

    Science.gov (United States)

    Clemente-Soto, Aldo F; Balderas-Rentería, Isaías; Rivera, Gildardo; Segura-Cabrera, Aldo; Garza-González, Elvira; del Rayo Camacho-Corona, María

    2014-12-02

    The isolation and characterization of the lignan meso-dihydroguaiaretic acid (MDGA) from Larrea tridentata and its activity against Mycobacterial tuberculosis has been demonstrated, but no information regarding its mechanism of action has been documented. Therefore, in this study we carry out the gene expression from total RNA obtained from M. tuberculosis H37Rv treated with MDGA using microarray technology, which was validated by quantitative real time polymerase chain reaction. Results showed that the alpha subunit of coenzyme A transferase of M. tuberculosis H37Rv is present in both geraniol and 1-and 2-methylnaphthalene degradation pathways, which are targeted by MDGA. This assumption was supported by molecular docking which showed stable interaction between MDGA with the active site of the enzyme. We propose that inhibition of coenzyme A transferase of M. tuberculosis H37Rv results in the accumulation of geraniol and 1-and 2-methylnaphtalene inside bacteria, causing membrane destabilization and death of the pathogen. The natural product MDGA is thus an attractive template to develop new anti-tuberculosis drugs, because its target is different from those of known anti-tubercular agents.

  6. Orbital Solutions and Absolute Elements of the Massive Algol Binary ET Tauri

    Science.gov (United States)

    Williamon, Richard M.; Dale, Horace; Evavold, Charles L.; Langoussis, Alexander; Fekel, Francis C.; Muterspaugh, Matthew W.; Williams, Stephen; Napier, Kate; Sowell, James R.

    2016-12-01

    We acquired differential UBV photoelectric photometry and radial velocities of the relatively bright, understudied, massive Algol binary ET Tau and utilized the Wilson-Devinney (WD) analysis program to obtain a simultaneous solution of these observations. To improve the orbital ephemeris, the V measurements from the ASAS program were also analyzed. Because of the very rapid rotation of the significantly more massive and hotter component (B2/3 spectral class), only radial velocities of the secondary component, which has a ˜B7 spectral class, could be measured. We derive masses of {M}1=14.34+/- 0.28 {M}⊙ and {M}2=6.339+/- 0.117 {M}⊙ and equal-volume radii of {R}1=6.356+/- 0.056 {R}⊙ and {R}2=11.84+/- 0.10 {R}⊙ for the primary and secondary, respectively. The secondary is filling its Roche lobe, so the system is semi-detached. The effective temperature of the secondary was held fixed at 15,000 K, and the primary's temperature was found to be {30,280}+/- 109 K. The system, which has a period of 5.996883 ± 0.000002 days, is assumed to have a circular orbit and is seen at an inclination of 79\\buildrel{\\circ}\\over{.} 55+/- 0\\buildrel{\\circ}\\over{.} 05.

  7. Perfil de temperatura dos funis magnetosféricos de estrelas T Tauri com aquecimento alfvênico

    Science.gov (United States)

    Vasconcelos, M. J.

    2003-08-01

    Estrelas T Tauri Clássicas são objetos jovens circundados por discos de gás e poeira e que apresentam uma intensa atividade magnética. Seu espectro mostra linhas de emissão alargadas que são razoavelmente reproduzidas nos modelos de acresção magnetosférica. No entanto, o perfil de temperatura dos funis magnéticos é desconhecido. Aquecimento magnético compressional e difusão ambipolar foram considerados para estas estruturas, porém as temperaturas obtidas não são suficientes para explicar as observações. Neste trabalho, examinamos o aquecimento gerado pelo amortecimento de ondas Alfvén através de quatro mecanismos, os amortecimentos não-linear, turbulento, viscoso-resistivo e colisional como função da freqüência da onda. Inicialmente, a temperatura é ajustada para reproduzir as observações e o grau de turbulência requerido para que o mecanismo seja viável é calculado. Os resultados mostram que este é compatível com os dados observacionais. Apresentam-se, também, resultados preliminares do cálculo auto-consistente do perfil de temperatura dos funis, levando-se em conta fontes de aquecimento Alfvênica e fontes de resfriamento.

  8. Origin of the wide-angle hot H2 in DG Tauri: New insight from SINFONI spectro-imaging

    CERN Document Server

    Agra-Amboage, Vanessa; Dougados, C; Kristensen, L E; Ibgui, L; Reunanen, J

    2014-01-01

    We wish to test the origins proposed for the extended hot H2 at 2000K around the atomic jet from the T Tauri star DGTau, in order to constrain the wide-angle wind structure and the possible presence of an MHD disk wind. We present flux calibrated IFS observations in H2 1-0 S(1) obtained with SINFONI/VLT. Thanks to spatial deconvolution by the PSF and to accurate correction for uneven slit illumination, we performed a thorough analysis and modeled the morphology, kinematics, and surface brightness. We also compared our results with studies in [FeII], [OI], and FUV-pumped H2. The limb-brightened H2 emission in the blue lobe is strikingly similar to FUV-pumped H2 imaged 6yr later, confirming that they trace the same hot gas and setting an upper limit of 12km/s on any expansion proper motion. The wide-angle H2 rims are at lower blueshifts than probed by narrow long-slit spectra. We confirm that they extend to larger angle and to lower speed the onion-like velocity structure observed in optical atomic lines. The l...

  9. Understanding the water emission in the mid- and far-IR from protoplanetary disks around T~Tauri stars

    CERN Document Server

    Antonellini, S; Riviere-Marichalar, P; Meijerink, R; Woitke, P; Thi, W -F; Spaans, M; Aresu, G; Lee, G

    2015-01-01

    We investigate which properties of protoplanetary disks around T Tauri stars affect the physics and chemistry in the regions where mid- and far-IR water lines originate and their respective line fluxes. We search for diagnostics for future observations. With the code ProDiMo, we build a series of models exploring a large parameter space, computing rotational and rovibrational transitions of water in nonlocal thermodynamic equilibrium (non-LTE). We select a sample of transitions in the mid- IR regime and the fundamental ortho and para water transitions in the far-IR. We investigate the chemistry and the local physical conditions in the line emitting regions. We calculate Spitzer spectra for each model and compare far-IR and mid-IR lines. In addition, we use mid-IR colors to tie the water line predictions to the dust continuum. Parameters affecting the water line fluxes in disks by more than a factor of three are : the disk gas mass, the dust-to-gas mass ratio, the dust maximum grain size, ISM(InterStellarMediu...

  10. Multi-Wavelength Photometry of the T Tauri Binary V582 Mon (KH 15D): A New Epoch of Occultations

    CERN Document Server

    Windemuth, Diana

    2013-01-01

    We present multi-wavelength (VRIJHK) observations of KH 15D obtained in 2012/13, as well as a master table of standard photometry spanning the years 1967 to 2013. The system is a close, eccentric T Tauri binary embedded in an inclined precessing circumbinary (CB) ring. The most recent data show the continued rise of star B with respect to the trailing edge of the occulting horizon as the system's maximum brightness steadily increases. The wealth of data in time and wavelength domains allows us to track the long-term CCD color evolution of KH 15D. We find that the V-I behavior is consistent with direct and scattered light from the composite color of two stars with slightly different temperatures. There is no evidence for any reddening or bluing associated with extinction or scattering by ISM-sized dust grains. Furthermore, we probe the system's faint phase behavior at near-infrared wavelengths in order to investigate extinction properties of the ring and signatures of a possible shepherding planet sometimes in...

  11. Temperaments of young stars: Rapid mass-accretion rate changes in T Tauri and Herbig Ae stars

    CERN Document Server

    Costigan, Gráinne; Scholz, Aleks; Ray, Tom; Testi, Leonardo

    2014-01-01

    Variability in emission lines is a characteristic feature in young stars and can be used as a tool to study the physics of the accretion process. Here we present a study of H{\\alpha} variability in 15 T Tauri and Herbig Ae stars (K7-B2) over a wide range of time windows, from minutes, to hours, to days, and years. We assess the variability using linewidth measurements and the time series of line profiles. All objects show gradual, slow profile changes on time-scales of days. In addition, in three cases there is evidence for rapid variations in H{\\alpha} with typical time-scales of 10 min, which occurs in 10% of the total covered observing time. The mean accretion-rate changes, inferred from the line fluxes,are 0.01-0.07 dex for time-scales of < 1 hour, 0.04-0.4 dex for time-scales of days, and 0.13-0.52 dex for time-scales of years. In Costigan et al. 2012 we derived an upper limit finding that the intermediate (days) variability dominated over longer (years) variability. Here our new results, based on muc...

  12. Role of local absorption on the X-ray emission from MHD accretion shocks in classical T Tauri stars

    Directory of Open Access Journals (Sweden)

    Bonito

    2014-01-01

    Full Text Available Accretion processes onto classical T Tauri stars (CTTSs are believed to generate shocks at the stellar surface due to the impact of supersonic downflowing plasma. Although current models of accretion streams provide a plausible global picture of this process, several aspects are still unclear. For example, the observed X-ray luminosity in accretion shocks is, in general, well below the predicted value. A possible explanation discussed in the literature is in terms of significant absorption of the emission due to the thick surrounding medium. Here we consider a 2D MHD model describing an accretion stream propagating through the atmosphere of a CTTS and impacting onto its chromosphere. The model includes all the relevant physics, namely the gravity, the thermal conduction, and the radiative cooling, and a realistic description of the unperturbed stellar atmosphere (from the chromosphere to the corona. From the model results, we synthesize the X-ray emission emerging from the hot slab produced by the accretion shock, exploring different configurations and strengths of the stellar magnetic field. The synthesis includes the local absorption by the thick surrounding medium and the Doppler shift of lines due to the component of plasma velocity along the line-of-sight. We explore the effects of absorption on the emerging X-ray spectrum, considering different inclinations of the accretion stream with respect to the observer. Finally we compare our results with the observations.

  13. A Spitzer IRS Study of Infrared Variability in Transitional and Pre-Transitional Disks around T Tauri Stars

    CERN Document Server

    Espaillat, C; D'Alessio, P; Sargent, B; Nagel, E; Calvet, N; Watson, Dan M; Muzerolle, J

    2010-01-01

    We present a Spitzer IRS study of variability in 14 T Tauri stars in the Taurus and Chamaeleon star-forming regions. The sample is composed of transitional and pre-transitional objects which contain holes and gaps in their disks. We detect variability between 5-38 microns in all but two of our objects on timescales of 2-3 years. Most of the variability observed can be classified as seesaw behavior, whereby the emission at shorter wavelengths varies inversely with the emission at longer wavelengths. For many of the objects we can reasonably reproduce the observed variability using irradiated disk models, particularly by changing the height of the inner disk wall by ~20%. When the inner wall is taller, the emission at the shorter wavelengths is higher since the inner wall dominates the emission at 2-8 microns. The taller inner wall casts a larger shadow on the outer disk wall, leading to less emission at wavelengths beyond 20 microns where the outer wall dominates. We discuss how the possible presence of planet...

  14. Evidence for Accretion High-Resolution X-ray Spectroscopy of the Classical T Tauri Star TW Hydrae

    CERN Document Server

    Kästner, J H; Schulz, N S; Canizares, C R; Weintraub, D A; Kastner, Joel H.; Huenemoerder, David P.; Schulz, Norbert S.; Canizares, Claude R.; Weintraub, David A.

    2002-01-01

    We present high resolution X-ray spectra of the X-ray bright classical T Tauri star, TW Hydrae, covering the wavelength range of 1.5-25 AA. The differential emission measure derived from fluxes of temperature-sensitive emission lines shows a plasma with a sharply peaked temperature distribution, peaking at log T = 6.5. Abundance anomalies are apparent, with iron very deficient relative to oxygen, while neon is enhanced relative to oxygen. Density-sensitive line ratios of Ne IX and O VII indicate densities near log n_e = 13. A flare with rapid (~1 ks) rise time was detected during our 48 ksec observation; however, based on analysis of the emission-line spectrum during quiescent and flaring states, the derived plasma parameters do not appear strongly time-dependent. The inferred plasma temperature distribution and densities are consistent with a model in which the bulk of the X-ray emission from TW Hya is generated via mass accretion from its circumstellar disk. Assuming accretion powers the X-ray emission, our...

  15. Fundamental stellar parameters for selected T-Tauri stars in the Chamaeleon and Rho Ophiuchus star-forming regions

    CERN Document Server

    James, David; Richert, Alexander; Cargile, Phillip; Santo, Nuno; Melo, Claudio; Bouvier, Jerome

    2016-01-01

    We present the results of an optical photometry and high-resolution spectroscopy campaign for a modest sample of X-ray selected stars in the Chamaeleon and Rho Ophiuchus star forming regions. With R~50000 optical spectra, we establish kinematic membership of the parent association and confirm stellar youth for each star in our sample. With the acquisition of new standardized BVIc photometry, in concert with near-infrared data from the literature, we derive age and mass from stellar positions in model-dependent Hertzsprung-Russell diagrams. We compare isochronal ages derived using colour-dependent extinction values finding that, within error bars, ages are the same irrespective of whether E(B-V), E(V-Ic), E(J-H) or E(H-K) is used to establish extinction, although model ages tend to be marginally younger for redder Ecolour values. For Cham I and Eta Cham members we derive ages of ~ 25 Myr post-T Tauri star population. In Rho Ophiuchus, most stars in our sample have isochronal ages 5) in the 2MASS colour colour ...

  16. Stable and unstable accretion in the classical T Tauri stars IM Lup and RU Lup as observed by MOST

    CERN Document Server

    Siwak, Michal; Rucinski, Slavek M; Moffat, Anthony F J; Matthews, Jaymie M; Cameron, Chris; Guenther, David B; Kuschnig, Rainer; Rowe, Jason F; Sasselov, Dimitar; Weiss, Werner W

    2015-01-01

    Results of the time variability monitoring of the two classical T Tauri stars, RU Lup and IM Lup, are presented. Three photometric data sets were utilised: (1) simultaneous (same field) MOST satellite observations over four weeks in each of the years 2012 and 2013, (2) multicolour observations at the SAAO in April - May of 2013, (3) archival V-filter ASAS data for nine seasons, 2001 - 2009. They were augmented by an analysis of high-resolution, public-domain VLT-UT2 UVES spectra from the years 2000 to 2012. From the MOST observations, we infer that irregular light variations of RU Lup are caused by stochastic variability of hot spots induced by unstable accretion. In contrast, the MOST light curves of IM Lup are fairly regular and modulated with a period of about 7.19 - 7.58 d, which is in accord with ASAS observations showing a well defined 7.247+/-0.026 d periodicity. We propose that this is the rotational period of IM Lup and is due to the changing visibility of two antipodal hot spots created near the ste...

  17. Chandra and XMM-Newton X-ray Observations of the Hyperactive T Tauri Star RY Tau

    CERN Document Server

    Skinner, Stephen L; Guedel, Manuel

    2016-01-01

    We present results of pointed X-ray observations of the accreting jet-driving T Tauri star RY Tau using Chandra and XMM-Newton. We obtained high-resolution grating spectra and excellent-quality CCD spectra and light curves with the objective of identifying the physical mechanisms underlying RY Tau's bright X-ray emission. Grating spectra reveal numerous emission lines spanning a broad range of temperature superimposed on a hot continuum. The X-ray emission measure distribution is dominated by very hot plasma at T_hot ~ 50 MK but higher temperatures were present during flares. A weaker cool plasma component is also present as revealed by low-temperature lines such as O VIII. X-ray light curves show complex variability consisting of short-duration (~hours) superhot flares accompanied by fluorescent Fe emission at 6.4 keV superimposed on a slowly-varying (~one day) component that may be tied to stellar rotation. The hot flaring component is undoubtedly of magnetic (e.g. coronal) origin. Soft and hard-band light ...

  18. Recurring millimeter flares as evidence for star-star magnetic reconnection events in the DQ Tauri PMS binary system

    CERN Document Server

    Salter, D M; Getman, K V; Hogerheijde, M R; van Kempen, T A; Carpenter, J M; Blake, G A; Wilner, D

    2010-01-01

    Observations of the T Tauri spectroscopic binary DQ Tau in April 2008 captured an unusual flare at 3 mm, which peaked at an observed max flux of 0.5 Jy (about 27x the quiescent value). Here we present follow-up mm observations that demonstrate a periodicity to the phenomenon. While monitoring 3 new periastron encounters, we detect flares within 17.5 hrs (or 4.6%) of the orbital phase of the first reported flare, and we constrain the main emitting region to a stellar height of 3.7-6.8 Rstar. The recorded activity is consistent with the proposed picture for synchrotron emission initiated by a magnetic reconnection event when the two stellar magnetospheres of the highly eccentric (e=0.556) binary are believed to collide near periastron as the stars approach a minimum separation of 8 Rstar (~13 Rsolar). The similar light curve decay profiles allow us to estimate an average flare duration of 30 hrs. Assuming one mm flare per orbit, DQ Tau could spend approximately 8% of its 15.8-d orbital period in an elevated flu...

  19. Simulations of Winds of Weak-Lined T Tauri Stars. II.: The Effects of a Tilted Magnetosphere and Planetary Interactions

    CERN Document Server

    Vidotto, A A; Jatenco-Pereira, V; Gombosi, T I

    2010-01-01

    Based on our previous work (Vidotto et al. 2009a), we investigate the effects on the wind and magnetospheric structures of weak-lined T Tauri stars due to a misalignment between the axis of rotation of the star and its magnetic dipole moment vector. In such configuration, the system loses the axisymmetry presented in the aligned case, requiring a fully 3D approach. We perform 3D numerical MHD simulations of stellar winds and study the effects caused by different model parameters. The system reaches a periodic behavior with the same rotational period of the star. We show that the magnetic field lines present an oscillatory pattern and that by increasing the misalignment angle, the wind velocity increases. Our wind models allow us to study the interaction of a magnetized wind with a magnetized extra-solar planet. Such interaction gives rise to reconnection, generating electrons that propagate along the planet's magnetic field lines and produce electron cyclotron radiation at radio wavelengths. We find that a cl...

  20. The Magnetic Topology of the Weak-Lined T Tauri Star V410 - A Simultaneous Temperature and Magnetic Field Inversion

    CERN Document Server

    Carroll, T A; Rice, J B; Kuenstler, A

    2012-01-01

    We present a detailed temperature and magnetic investigation of the T Tauri star V410 Tau by means of a simultaneous Doppler- and Zeeman-Doppler Imaging. Moreover we introduce a new line profile reconstruction method based on a singular value decomposition (SVD) to extract the weak polarized line profiles. One of the key features of the line profile reconstruction is that the SVD line profiles are amenable to radiative transfer modeling within our Zeeman-Doppler Imaging code iMap. The code also utilizes a new iterative regularization scheme which is independent of any additional surface constraints. To provide more stability a vital part of our inversion strategy is the inversion of both Stokes I and Stokes V profiles to simultaneously reconstruct the temperature and magnetic field surface distribution of V410 Tau. A new image-shear analysis is also implemented to allow the search for image and line profile distortions induced by a differential rotation of the star. The magnetic field structure we obtain for ...

  1. Herschel-PACS observation of the 10 Myr old T Tauri disk TW Hya: Constraining the disk gas mass

    CERN Document Server

    Thi, W F; Ménard, F; Woitke, P; Meeus, G; Riviere-Marichalar, P; Pinte, C; Howard, C D; Roberge, A; Sandell, G; Pascucci, I; Riaz, B; Grady, C A; Dent, W R F; Kamp, I; Duchêne, G; Augereau, J C; Pantin, E; Vandenbussche, B; Tilling, I; Williams, J P; Eiroa, C; Barrado, D; Alacid, J M; Andrews, S; Ardila, D R; Aresu, G; Brittain, S; Ciardi, D R; Danchi, W; Fedele, D; de Gregorio-Monsalvo, I; Heras, A; Huelamo, N; Krivov, A; Lebreton, J; Liseau, R; Martin-Zaidi, C; Mendigutía, I; Montesinos, B; Mora, A; Morales-Calderon, M; Nomura, H; Phillips, N; Podio, L; Poelman, D R; Ramsay, S; Rice, K; Solano, E; Walker, H; White, G J; Wright, G

    2010-01-01

    Planets are formed in disks around young stars. With an age of ~10 Myr, TW Hya is one of the nearest T Tauri stars that is still surrounded by a relatively massive disk. In addition a large number of molecules has been found in the TW Hya disk, making TW Hya the perfect test case in a large survey of disks with Herschel-PACS to directly study their gaseous component. We aim to constrain the gas and dust mass of the circumstellar disk around TW Hya. We observed the fine-structure lines of [OI] and [CII] as part of the Open-time large program GASPS. We complement this with continuum data and ground-based 12CO 3-2 and 13CO 3-2 observations. We simultaneously model the continuum and the line fluxes with the 3D Monte-Carlo code MCFOST and the thermo-chemical code ProDiMo to derive the gas and dust masses. We detect the [OI] line at 63 micron. The other lines that were observed, [OI] at 145 micron and [CII] at 157 micron, are not detected. No extended emission has been found. Preliminary modeling of the photometric...

  2. Observations of T Tauri Disks at Sub-AU Radii: Implications for Magnetospheric Accretion and Planet Formation

    CERN Document Server

    Eisner, J A; White, R J; Akeson, R L; Sargent, A I

    2005-01-01

    We determine inner disk sizes and temperatures for four solar-type (1-2 M$_{\\odot}$) classical T Tauri stars (AS 207A, V2508 Oph, AS 205A, and PX Vul) using 2.2 $\\mu$m observations from the Keck Interferometer. Nearly contemporaneous near-IR adaptive optics imaging photometry, optical photometry, and high-dispersion optical spectroscopy are used to distinguish contributions from the inner disks and central stars in the interferometric observations. In addition, the spectroscopic and photometric data provide estimates of stellar properties, mass accretion rates, and disk co-rotation radii. We model our interferometric and photometric data in the context of geometrically flat accretion disk models with inner holes, and flared disks with puffed-up inner walls. Models incorporating puffed-up inner disk walls generally provide better fits to the data, similar to previous results for higher-mass Herbig Ae stars. Our measured inner disk sizes are larger than disk truncation radii predicted by magnetospheric accretio...

  3. Calibration of Seismic Sources during a Test Cruise with the new RV SONNE

    Science.gov (United States)

    Engels, M.; Schnabel, M.; Damm, V.

    2015-12-01

    During autumn 2014, several test cruises of the brand new German research vessel SONNE were carried out before the first official scientific cruise started in December. In September 2014, BGR conducted a seismic test cruise in the British North Sea. RV SONNE is a multipurpose research vessel and was also designed for the mobile BGR 3D seismic equipment, which was tested successfully during the cruise. We spend two days for calibration of the following seismic sources of BGR: G-gun array (50 l @ 150 bar) G-gun array (50 l @ 207 bar) single GI-gun (3.4 l @ 150 bar) For this experiment two hydrophones (TC4042 from Reson Teledyne) sampling up to 48 kHz were fixed below a drifting buoy at 20 m and 60 m water depth - the sea bottom was at 80 m depth. The vessel with the seismic sources sailed several up to 7 km long profiles around the buoy in order to cover many different azimuths and distances. We aimed to measure sound pressure level (SPL) and sound exposure level (SEL) under the conditions of the shallow North Sea. Total reflections and refracted waves dominate the recorded wave field, enhance the noise level and partly screen the direct wave in contrast to 'true' deep water calibration based solely on the direct wave. Presented are SPL and RMS power results in time domain, the decay with distance along profiles, and the somehow complicated 2D sound radiation pattern modulated by topography. The shading effect of the vessel's hull is significant. In frequency domain we consider 1/3 octave levels and estimate the amount of energy in frequency ranges not used for reflection seismic processing. Results are presented in comparison of the three different sources listed above. We compare the measured SPL decay with distance during this experiment with deep water modeling of seismic sources (Gundalf software) and with published results from calibrations with other marine seismic sources under different conditions: E.g. Breitzke et al. (2008, 2010) with RV Polarstern

  4. Mycobacterium tuberculosis Rv3802c encodes a phospholipase/thioesterase and is inhibited by the antimycobacterial agent tetrahydrolipstatin.

    Directory of Open Access Journals (Sweden)

    Sarah K Parker

    Full Text Available The cell wall of M. tuberculosis is central to its success as a pathogen. Mycolic acids are key components of this cell wall. The genes involved in joining the alpha and mero mycolates are located in a cluster, beginning with Rv3799c and extending at least until Rv3804c. The role of each enzyme encoded by these five genes is fairly well understood, except for Rv3802c. Rv3802 is one of seven putative cutinases encoded by the genome of M. tuberculosis. In phytopathogens, cutinases hydrolyze the waxy layer of plants, cutin. In a strictly mammalian pathogen, such as M. tuberculosis, it is likely that these proteins perform a different function. Of the seven, we chose to focus on Rv3802c because of its location in a mycolic acid synthesis gene cluster, its putative essentiality, its ubiquitous presence in actinomycetes, and its conservation in the minimal genome of Mycobacterium leprae. We expressed Rv3802 in Escherichia coli and purified the enzymatically active form. We probed its activities and inhibitors characterizing those relevant to its possible role in mycolic acid biosynthesis. In addition to its reported phospholipase A activity, Rv3802 has significant thioesterase activity, and it is inhibited by tetrahydrolipstatin (THL. THL is a described anti-tuberculous compound with an unknown mechanism, but it reportedly targets cell wall synthesis. Taken together, these data circumstantially support a role for Rv3802 in mycolic acid synthesis and, as the cell wall is integral to M. tuberculosis pathogenesis, identification of a novel cell wall enzyme and its inhibition has therapeutic and diagnostic implications.

  5. Mycobacterium tuberculosis EsxO (Rv2346c) promotes bacillary survival by inducing oxidative stress mediated genomic instability in macrophages.

    Science.gov (United States)

    Mohanty, Soumitra; Dal Molin, Michael; Ganguli, Geetanjali; Padhi, Avinash; Jena, Prajna; Selchow, Petra; Sengupta, Srabasti; Meuli, Michael; Sander, Peter; Sonawane, Avinash

    2016-01-01

    Mycobacterium tuberculosis (Mtb) survives inside the macrophages by modulating the host immune responses in its favor. The 6-kDa early secretory antigenic target (ESAT-6; esxA) of Mtb is known as a potent virulence and T-cell antigenic determinant. At least 23 such ESAT-6 family proteins are encoded in the genome of Mtb; however, the function of many of them is still unknown. We herein report that ectopic expression of Mtb Rv2346c (esxO), a member of ESAT-6 family proteins, in non-pathogenic Mycobacterium smegmatis strain (MsmRv2346c) aids host cell invasion and intracellular bacillary persistence. Further mechanistic studies revealed that MsmRv2346c infection abated macrophage immunity by inducing host cell death and genomic instability as evident from the appearance of several DNA damage markers. We further report that the induction of genomic instability in infected cells was due to increase in the hosts oxidative stress responses. MsmRv2346c infection was also found to induce autophagy and modulate the immune function of macrophages. In contrast, blockade of Rv2346c induced oxidative stress by treatment with ROS inhibitor N-acetyl-L-cysteine prevented the host cell death, autophagy induction and genomic instability in infected macrophages. Conversely, MtbΔRv2346c mutant did not show any difference in intracellular survival and oxidative stress responses. We envision that Mtb ESAT-6 family protein Rv2346c dampens antibacterial effector functions namely by inducing oxidative stress mediated genomic instability in infected macrophages, while loss of Rv2346c gene function may be compensated by other redundant ESAT-6 family proteins. Thus EsxO plays an important role in mycobacterial pathogenesis in the context of innate immunity.

  6. Physical and chemical data collected by bottle and CTD in the Gulf of Mexico from the R/V Gyre and R/V Pelican, April 2004 - July 2009 to help resolve the dominant oceanographic processes that control the timing, duration, and severity of hypoxia of the region (NCEI Accession 0088164)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Physical and chemical oceanographic observational data collected by bottle and CTD in the Gulf of Mexico from the R/V Gyre and R/V Pelican, April 2004 - July 2009....

  7. Nutrients and physical data from the R/V Thomas Washington and the R/V Oshoru Maru using bottle and CTD casts as part of the Inner Shelf Transport and Recycling (ISHTAR) project from 12 June 1986 to 19 October 1988 (NODC Accession 0000333)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Nutrients and physical data were collected from the R/V THOMAS WASHINGTON and R/V OSHORU MARU from June 12, 1986 to October 19, 1988. Data were submitted by...

  8. Radiative transfer modeling of three T Tauri stars: selecting candidates for studying circumstellar disk evolution

    Institute of Scientific and Technical Information of China (English)

    Yao Liu; Hong-Chi Wang; Sebastian Wolf; David Madlener

    2013-01-01

    We present modeling work on three young stellar objects that are promising targets for future high-resolution observations to investigate circumstellar disk evolution.The currently available data comprise the spectral energy distribution from optical to millimeter wavelengths which allow constraining the structure of the circumstellar disk using self-consistent radiative transfer models.The results suggest that the assumption of well-mixed dust and gas leads to overestimation of flux in the far-infrared.Observational and theoretical arguments suggest that an overall decrease in far-infrared excess can be explained by dust settling towards the midplane.A new disk model is hence employed to take the effect of dust sedimentation into account.The extended model satisfactorily reproduces all existing observations.The three targets studied here therefore deserve follow-up observations to reveal the evolutionary state of their protoplanetary disks.

  9. Interferometric Observations of the T Tauri Stars in the MBM 12 Cloud

    Science.gov (United States)

    Itoh, Yoichi; Sugitani, Koji; Fukuda, Naoya; Nakanishi, Kouichiro; Ogura, Katsuo; Tamura, Motohide; Marui, Kazuko; Fujita, Kenta; Oasa, Yumiko; Fukagawa, Misato

    2003-04-01

    We have carried out a millimeter interferometric continuum survey toward seven young stellar objects (YSOs) in the MBM 12 cloud. Thermal emissions associated with two YSOs were detected above the 3 σ level at 2.1 mm, and one also showed a 1.3 mm thermal emission. Another object was marginally detected at 2.1 mm. Spectral energy distributions of the YSOs are well fitted by a simple power-law disk model. Masses of the circumstellar disks are estimated to be of the order of 0.05 Msolar. The circumstellar disks in the MBM 12 cloud have properties in common with the disks in nearby star-forming regions, in terms of disk parameters, such as disk mass, as well as an infrared excess.

  10. Interferometric Observations of the T Tauri Stars in the MBM 12 Cloud

    CERN Document Server

    Itoh, Y; Fukuda, N; Nakanishi, K; Ogura, K; Tamura, M; Marui, K; Fujita, K; Oasa, Y; Fukagawa, M; Itoh, Yoichi; Sugitani, Koji; Fukuda, Naoya; Nakanishi, Kouichiro; Ogura, Katsuo; Tamura, Motohide; Marui, Kazuko; Fujita, Kenta; Oasa, Yumiko; Fukagawa, Misato

    2003-01-01

    We have carried out a millimeter interferometric continuum survey toward 7 YSOs in the MBM 12 cloud. Thermal emissions associated with 2 YSOs were detected above the 3-$\\sigma$ level at 2.1 mm, and one also showed a 1.3 mm thermal emission. Another object was marginally detected at 2.1 mm. Spectral energy distributions of the YSOs are well fitted by a simple power-law disk model. Masses of the circumstellar disks are estimated to be an order of $0.05 M_{\\sun}$. The circumstellar disks in the MBM 12 cloud have properties in common with the disks in nearby star-forming regions, in terms of disk parameters such as a disk mass, as well as an infrared excess.

  11. NEAR-ULTRAVIOLET EXCESS IN SLOWLY ACCRETING T TAURI STARS: LIMITS IMPOSED BY CHROMOSPHERIC EMISSION

    Energy Technology Data Exchange (ETDEWEB)

    Ingleby, Laura; Calvet, Nuria; Bergin, Edwin; McClure, Melissa [Department of Astronomy, University of Michigan, 830 Dennison Building, 500 Church Street, Ann Arbor, MI 48109 (United States); Herczeg, Gregory [Max-Planck-Institut fuer Extraterrestriche Physik, Postfach 1312, D-85741 Garching (Germany); Brown, Alexander; France, Kevin [Center for Astrophysics and Space Astronomy, University of Colorado, Boulder, CO 80309-0389 (United States); Alexander, Richard [Department of Physics and Astronomy, University of Leicester, University Road, Leicester LE1 7RH (United Kingdom); Edwards, Suzan [Department of Astronomy, Smith College, Northampton, MA 01063 (United States); Espaillat, Catherine; Brown, Joanna [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, MS-78, Cambridge, MA 02138 (United States); Gregory, Scott G.; Hillenbrand, Lynne [Department of Astrophysics, California Institute of Technology, MC 249-17, Pasadena, CA 91125 (United States); Roueff, Evelyne; Abgrall, Herve [LUTH and UMR 8102 du CNRS, Observatoire de Paris, Section de Meudon, Place J. Janssen, F-92195 Meudon (France); Valenti, Jeff [Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 (United States); Walter, Frederick [Department of Physics and Astronomy, Stony Brook University, Stony Brook, NY 11794-3800 (United States); Johns-Krull, Christopher [Department of Physics and Astronomy, Rice University, Houston, TX 77005 (United States); Linsky, Jeffrey [JILA, University of Colorado and NIST, 440 UCB Boulder, CO 80309-0440 (United States); Ardila, David, E-mail: lingleby@umich.edu, E-mail: ncalvet@umich.edu, E-mail: gregoryh@mpe.mpg.de [NASA Herschel Science Center, California Institute of Technology, Mail Code 100-22, Pasadena, CA 91125 (United States); and others

    2011-12-20

    Young stars surrounded by disks with very low mass accretion rates are likely in the final stages of inner disk evolution and therefore particularly interesting to study. We present ultraviolet (UV) observations of the {approx}5-9 Myr old stars RECX-1 and RECX-11, obtained with the Cosmic Origins Spectrograph and Space Telescope Imaging Spectrograph on the Hubble Space Telescope, as well as optical and near-infrared spectroscopic observations. The two stars have similar levels of near-UV emission, although spectroscopic evidence indicates that RECX-11 is accreting and RECX-1 is not. The line profiles of H{alpha} and He I {lambda}10830 in RECX-11 show both broad and narrow redshifted absorption components that vary with time, revealing the complexity of the accretion flows. We show that accretion indicators commonly used to measure mass accretion rates, e.g., U-band excess luminosity or the Ca II triplet line luminosity, are unreliable for low accretors, at least in the middle K spectral range. Using RECX-1 as a template for the intrinsic level of photospheric and chromospheric emission, we determine an upper limit of 3 Multiplication-Sign 10{sup -10} M{sub Sun} yr{sup -1} for RECX-11. At this low accretion rate, recent photoevaporation models predict that an inner hole should have developed in the disk. However, the spectral energy distribution of RECX-11 shows fluxes comparable to the median of Taurus in the near-infrared, indicating that substantial dust remains. Fluorescent H{sub 2} emission lines formed in the innermost disk are observed in RECX-11, showing that gas is present in the inner disk, along with the dust.

  12. Compressive Spectral Renormalization Method

    CERN Document Server

    Bayindir, Cihan

    2016-01-01

    In this paper a novel numerical scheme for finding the sparse self-localized states of a nonlinear system of equations with missing spectral data is introduced. As in the Petviashivili's and the spectral renormalization method, the governing equation is transformed into Fourier domain, but the iterations are performed for far fewer number of spectral components (M) than classical versions of the these methods with higher number of spectral components (N). After the converge criteria is achieved for M components, N component signal is reconstructed from M components by using the l1 minimization technique of the compressive sampling. This method can be named as compressive spectral renormalization (CSRM) method. The main advantage of the CSRM is that, it is capable of finding the sparse self-localized states of the evolution equation(s) with many spectral data missing.

  13. V4046 Sgr: Touchstone to Investigate Spectral Type Discrepancies for Pre-main Sequence Stars

    CERN Document Server

    Kastner, Joel H; Sargent, Benjamin; Smith, C T; Rayner, John

    2014-01-01

    Determinations of the fundamental properties (e.g., masses and ages) of late-type, pre-main sequence (pre-MS) stars are complicated by the potential for significant discrepancies between the spectral types of such stars as ascertained via optical vs. near-infrared observations. To address this problem, we have obtained near-IR spectroscopy of the nearby, close binary T Tauri system V4046 Sgr AB with the NASA Infrared Telescope Facility (IRTF) SPEX spectrometer. The V4046 Sgr close binary (and circumbinary disk) system provides an important test case for spectral type determination thanks to the stringent observational constraints on its component stellar masses (i.e., ~0.9 Msun each) as well as on its age (12-21 Myr) and distance (73 pc). Analysis of the IRTF data indicates that the composite near-IR spectral type for V4046 Sgr AB lies in the range M0-M1, i.e., significantly later than the K5+K7 composite type previously determined from optical spectroscopy. However, the K5+K7 composite type is in better agre...

  14. The other spectral flow

    CERN Document Server

    Gato-Rivera, Beatriz; Gato-Rivera, Beatriz; Rosado, Jose Ignacio

    1995-01-01

    Recently we showed that the spectral flow acting on the N=2 twisted topological theories gives rise to a topological algebra automorphism. Here we point out that the untwisting of that automorphism leads to a spectral flow on the untwisted N=2 superconformal algebra which is different from the usual one. This "other" spectral flow does not interpolate between the chiral ring and the antichiral ring. In particular, it maps the chiral ring into the chiral ring and the antichiral ring into the antichiral ring. We discuss the similarities and differences between both spectral flows. We also analyze their action on null states.

  15. The crystal structure of the Rv0301-Rv0300 VapBC-3 toxin-antitoxin complex from M. tuberculosis reveals a Mg2+ ion in the active site and a putative RNA-binding site

    Energy Technology Data Exchange (ETDEWEB)

    Min, Andrew B; Miallau, Linda; Sawaya, Michael R; Habel, Jeff; Cascio, Duilio; Eisenberg, David [UCLA; (UCB)

    2013-01-10

    VapBC pairs account for 45 out of 88 identified toxin-antitoxin (TA) pairs in the Mycobacterium tuberculosis (Mtb) H37Rv genome. A working model suggests that under times of stress, antitoxin molecules are degraded, releasing the toxins to slow the metabolism of the cell, which in the case of VapC toxins is via their RNase activity. Otherwise the TA pairs remain bound to their promoters, autoinhibiting transcription. The crystal structure of Rv0301-Rv0300, an Mtb VapBC TA complex determined at 1.49 Å resolution, suggests a mechanism for these three functions: RNase activity, its inhibition by antitoxin, and its ability to bind promoter DNA. The Rv0301 toxin consists of a core of five parallel beta strands flanked by alpha helices. Three proximal aspartates coordinate a Mg2+ ion forming the putative RNase active site. The Rv0300 antitoxin monomer is extended in structure, consisting of an N-terminal beta strand followed by four helices. The last two helices wrap around the toxin and terminate near the putative RNase active site, but with different conformations. In one conformation, the C-terminal arginine interferes with Mg2+ ion coordination, suggesting a mechanism by which the antitoxin can inhibit toxin activity. At the N-terminus of the antitoxin, two pairs of Ribbon-Helix-Helix (RHH) motifs are related by crystallographic twofold symmetry. The resulting hetero-octameric complex is similar to the FitAB system, but the two RHH motifs are about 30 Å closer together in the Rv0301-Rv0300 complex, suggesting either a different span of the DNA recognition sequence or a conformational change.

  16. X-rays from jet-driving protostars and T Tauri stars

    CERN Document Server

    Güdel, M; Audard, M; Skinner, S L; Briggs, K R; Palla, F; Dougados, C; Dougados, Catherine

    2006-01-01

    (abridged:) We study X-rays from jet-driving protostars and T Tau stars. We seek soft spectral components that may be due to shock emission, and shock-induced emission displaced from the stellar position. Two stellar samples are used, the first consisting of lightly absorbed T Tau stars with strong jets, the other containing protostars with disks seen nearly edge-on. The former sample was observed in the XMM-Newton Extended Survey of the Taurus Molecular Cloud (XEST), while Chandra archival data provided observations of the latter. We confirm the previously identified peculiar spectrum of DG Tau A and find similar phenomenology in GV Tau and DP Tau, suggesting a new class of X-ray spectra. These consist of a lightly absorbed, very soft component and a strongly absorbed, very hard component. The latter is flaring while little variability is detected in the former. The absorption of the harder component is about an order of magnitude higher than expected from the optical extinction assuming a standard gas-to-du...

  17. Herschel-PACS observation of the 10 Myr old T Tauri disk TW Hya. Constraining the disk gas mass

    Science.gov (United States)

    Thi, W.-F.; Mathews, G.; Ménard, F.; Woitke, P.; Meeus, G.; Riviere-Marichalar, P.; Pinte, C.; Howard, C. D.; Roberge, A.; Sandell, G.; Pascucci, I.; Riaz, B.; Grady, C. A.; Dent, W. R. F.; Kamp, I.; Duchêne, G.; Augereau, J.-C.; Pantin, E.; Vandenbussche, B.; Tilling, I.; Williams, J. P.; Eiroa, C.; Barrado, D.; Alacid, J. M.; Andrews, S.; Ardila, D. R.; Aresu, G.; Brittain, S.; Ciardi, D. R.; Danchi, W.; Fedele, D.; de Gregorio-Monsalvo, I.; Heras, A.; Huelamo, N.; Krivov, A.; Lebreton, J.; Liseau, R.; Martin-Zaidi, C.; Mendigutía, I.; Montesinos, B.; Mora, A.; Morales-Calderon, M.; Nomura, H.; Phillips, N.; Podio, L.; Poelman, D. R.; Ramsay, S.; Rice, K.; Solano, E.; Walker, H.; White, G. J.; Wright, G.

    2010-07-01

    Planets are formed in disks around young stars. With an age of ~10 Myr, TW Hya is one of the nearest T Tauri stars that is still surrounded by a relatively massive disk. In addition a large number of molecules has been found in the TW Hya disk, making TW Hya the perfect test case in a large survey of disks with Herschel-PACS to directly study their gaseous component. We aim to constrain the gas and dust mass of the circumstellar disk around TW Hya. We observed the fine-structure lines of [O i] and [C ii] as part of the open-time large program GASPS. We complement this with continuum data and ground-based 12 CO 3-2 and 13CO 3-2 observations. We simultaneously model the continuum and the line fluxes with the 3D Monte-Carlo code MCFOST and the thermo-chemical code ProDiMo to derive the gas and dust masses. We detect the [O i] line at 63 μm. The other lines that were observed, [O i] at 145 μm and [C ii] at 157 μm, are not detected. No extended emission has been found. Preliminary modeling of the photometric and line data assuming [ 12CO] /[ 13CO] = 69 suggests a dust mass for grains with radius <1 mm of ~1.9 × 10-4 M⊙ (total solid mass of 3 × 10-3 M⊙) and a gas mass of (0.5-5) × 10-3 M⊙. The gas-to-dust mass may be lower than the standard interstellar value of 100. Herschel is an ESA space observatory with science instruments provided by Principal Investigator consortia. It is open for proposals for observing time from the worldwide astronomical community.Appendix is only available in electronic form at http://www.aanda.org

  18. The pre-main-sequence star V1184 Tauri (CB 34V) at the end of prolonged eclipse

    Science.gov (United States)

    Semkov, E. H.; Peneva, S. P.; Ibryamov, S. I.

    2015-10-01

    Aims: V1184 Tau (CB 34V) lies in the field of the Bok globule CB 34 and was discovered as a large amplitude variable in 1993. According to the first hypothesis of the variability of the star, it is a FU Orionis candidate erupted between 1951 and 1993. During subsequent observations, the star manifests large amplitude variability interpreted as obscuration from circumstellar clouds of dust. We included V1184 Tau (CB 34V) in our target list of highly variable pre-main-sequence stars to determine the reasons for the variations in the brightness of this object. Methods: Data from BVRI photometric observations of the young stellar object V1184 Tau, obtained in the period 2008-2015, are presented in the paper. These data are a continuation of our optical photometric monitoring of the star began in 2000 and continuing to date. The photometric observations of V1184 Tau were performed in two observatories with two medium-sized and two small telescopes. Results: Our results indicate that during periods of maximum light the star shows characteristics typical of T Tauri stars. During the observed deep minimum in brightness, however, V1184 Tau is rather similar to UX Orionis objects. The deep drop in brightness began in 2003 ended in 2015 as the star has returned to maximum light. The light curve during the drop is obviously asymmetric as the decrease in brightness lasts two times longer than the rise. The observed colour reverse on the colour-magnitude diagrams is also confirmation of obscuration from circumstellar clouds of dust as a reason for the large amplitude variability in the brightness. Appendix A is available in electronic form at http://www.aanda.org

  19. NARROW Na AND K ABSORPTION LINES TOWARD T TAURI STARS: TRACING THE ATOMIC ENVELOPE OF MOLECULAR CLOUDS

    Energy Technology Data Exchange (ETDEWEB)

    Pascucci, I.; Simon, M. N. [Lunar and Planetary Laboratory, The University of Arizona, Tucson, AZ 85721 (United States); Edwards, S. [Five College Astronomy Department, Smith College, Northampton, MA 01063 (United States); Heyer, M. [Department of Astronomy, University of Massachusetts, Amherst, MA 01003-9305 (United States); Rigliaco, E. [Institute for Astronomy, ETH Zurich, Wolfgang-Pauli-Strasse 27, CH-8093 Zurich (Switzerland); Hillenbrand, L. [Department of Astronomy, California Institute of Technology, Pasadena, CA 91125 (United States); Gorti, U.; Hollenbach, D., E-mail: pascucci@lpl.arizona.edu [SETI Institute, Mountain View, CA 94043 (United States)

    2015-11-20

    We present a detailed analysis of narrow Na i and K i absorption resonance lines toward nearly 40 T Tauri stars in Taurus with the goal of clarifying their origin. The Na i λ5889.95 line is detected toward all but one source, while the weaker K i λ7698.96 line is detected in about two-thirds of the sample. The similarity in their peak centroids and the significant positive correlation between their equivalent widths demonstrate that these transitions trace the same atomic gas. The absorption lines are present toward both disk and diskless young stellar objects, which excludes cold gas within the circumstellar disk as the absorbing material. A comparison of Na i and CO detections and peak centroids demonstrates that the atomic gas and molecular gas are not co-located, the atomic gas being more extended than the molecular gas. The width of the atomic lines corroborates this finding and points to atomic gas about an order of magnitude warmer than the molecular gas. The distribution of Na i radial velocities shows a clear spatial gradient along the length of the Taurus molecular cloud filaments. This suggests that absorption is associated with the Taurus molecular cloud. Assuming that the gradient is due to cloud rotation, the rotation of the atomic gas is consistent with differential galactic rotation, whereas the rotation of the molecular gas, although with the same rotation axis, is retrograde. Our analysis shows that narrow Na i and K i absorption resonance lines are useful tracers of the atomic envelope of molecular clouds. In line with recent findings from giant molecular clouds, our results demonstrate that the velocity fields of the atomic and molecular gas are misaligned. The angular momentum of a molecular cloud is not simply inherited from the rotating Galactic disk from which it formed but may be redistributed by cloud–cloud interactions.

  20. Orbital Period Changes and Their Evolutionary Status for the Weak-Contact Binaries. III. AO Camelopardalis and AH Tauri

    Science.gov (United States)

    Yang, Y.-G.; Wei, J.-Y.; Kreiner, J. M.; Li, H.-L.

    2010-01-01

    In this paper, we presented multicolor photometric observations for two eclipsing binaries, AO Camelopardalis and AH Tauri, obtained on 2008 December 16 and 17. Using the Wilson-Devinney Code, the photometric solution of AH Tau was determined from our new CCD data. The mass ratio and the fill-out factor are q = 0.503(±0.003) and f = 10.8%(±0.1%), respectively. This indicates that AH Tau is in weak contact. For the weak-contact binary AO Cam, BVI light curves clearly show a difference in the heights of the maxima (i.e., the O'Connell effect), which may be explained by spot activity. By analyzing the O - C curves for AO Cam and AH Tau, it is found that the orbital periods appear to show a secular period decrease with a cyclic variation. The observed period modulation is ΔP/P ~ 10-6. For AO Cam, the cyclic oscillation with a short period of 7.63(±0.07) yr and a low amplitude of 0fd0019(±0fd0003) may be preferably attributed to the cyclic magnetic activity. The period and amplitude of the cyclic variation for AH Tau are 45.8(±1.1) yr and 0fd0171(±0fd0005), which may more likely result from the light-time effect via a third body. The secular period decrease rates are dP/dt = -1.26(±0.04) × 10-7 days yr -1 for AO Cam and dP/dt = -6.98(±0.07) × 10-8 days yr -1 for AH Tau. This kind of period decrease can be plausibly explained by the mass transfer from the primary to the secondary, and may result in the system evolving into a deep contact configuration.

  1. THE CLOSE T TAURI BINARY SYSTEM V4046 Sgr: ROTATIONALLY MODULATED X-RAY EMISSION FROM ACCRETION SHOCKS

    Energy Technology Data Exchange (ETDEWEB)

    Argiroffi, C. [Dipartimento di Fisica, Universita di Palermo, Piazza del Parlamento 1, I-90134 Palermo (Italy); Maggio, A.; Damiani, F. [INAF-Osservatorio Astronomico di Palermo, Piazza del Parlamento 1, I-90134 Palermo (Italy); Montmerle, T. [Institut d' Astrophysique de Paris, 98bis bd Arago, FR-75014 Paris (France); Huenemoerder, D. P. [MIT, Kavli Institute for Astrophysics and Space Research, 77 Massachusetts Avenue, Cambridge, MA 02139 (United States); Alecian, E. [Observatoire de Paris, LESIA, 5, place Jules Janssen, F-92195 Meudon Principal Cedex (France); Audard, M. [ISDC Data Center for Astrophysics, University of Geneva, Ch. d' Ecogia 16, CH-1290 Versoix (Switzerland); Bouvier, J. [UJF-Grenoble 1/CNRS-INSU, Institut de Planetologie et d' Astrophysique de Grenoble (IPAG) UMR 5274, F-38041, Grenoble (France); Donati, J.-F. [IRAP-UMR 5277, CNRS and Universite de Toulouse, 14 Av. E. Belin, F-31400 Toulouse (France); Gregory, S. G. [Astronomy Department, California Institute of Technology, MC 249-17, Pasadena, CA 91125 (United States); Guedel, M. [Department of Astronomy, University of Vienna, Trkenschanzstrasse 17, A-1180 Vienna (Austria); Hussain, G. A. J. [ESO, Karl-Schwarzschild-Strasse 2, D-85748 Garching bei Muenchen (Germany); Kastner, J. H.; Sacco, G. G., E-mail: argi@astropa.unipa.it [Center for Imaging Science, Rochester Institute of Technology, 54 Lomb Memorial Drive, Rochester, NY 14623 (United States)

    2012-06-20

    We report initial results from a quasi-simultaneous X-ray/optical observing campaign targeting V4046 Sgr, a close, synchronous-rotating classical T Tauri star (CTTS) binary in which both components are actively accreting. V4046 Sgr is a strong X-ray source, with the X-rays mainly arising from high-density (n{sub e}{approx} 10{sup 11}-10{sup 12} cm{sup -3}) plasma at temperatures of 3-4 MK. Our multi-wavelength campaign aims to simultaneously constrain the properties of this X-ray-emitting plasma, the large-scale magnetic field, and the accretion geometry. In this paper, we present key results obtained via time-resolved X-ray-grating spectra, gathered in a 360 ks XMM-Newton observation that covered 2.2 system rotations. We find that the emission lines produced by this high-density plasma display periodic flux variations with a measured period, 1.22 {+-} 0.01 d, that is precisely half that of the binary star system (2.42 d). The observed rotational modulation can be explained assuming that the high-density plasma occupies small portions of the stellar surfaces, corotating with the stars, and that the high-density plasma is not azimuthally symmetrically distributed with respect to the rotational axis of each star. These results strongly support models in which high-density, X-ray-emitting CTTS plasma is material heated in accretion shocks, located at the base of accretion flows tied to the system by magnetic field lines.

  2. An IUE Atlas of Pre-Main-Sequence Stars. II. Far-Ultraviolet Accretion Diagnostics in T Tauri Stars

    Science.gov (United States)

    Johns-Krull, Christopher M.; Valenti, Jeff A.; Linsky, Jeffrey L.

    2000-08-01

    We use our ultraviolet (UV) atlas of pre-main-sequence stars constructed from all useful, short-wavelength, low-resolution spectra in the International Ultraviolet Explorer (IUE) satellite Final Archive to analyze the short-wavelength UV properties of 49 T Tauri stars (TTSs). We compare the line and continuum fluxes in these TTSs with each other and with previously published parameters of these systems, including rotation rate, infrared excess, and mass accretion rate. The short-wavelength continuum in the classical TTSs (CTTSs) appears to originate in a ~10,000 K optically thick plasma, while in the naked TTSs (NTTSs-stars without dusty disks) the continuum appears to originate in the stellar atmosphere. We show that all of the TTSs in our sample lie in the regime of ``saturated'' magnetic activity due to their small Rossby numbers. However, while some of the TTSs show emission line surface fluxes consistent with this saturation level, many CTTSs show significantly stronger emission than predicted by saturation. In these stars, the emission line luminosity in the high ionization lines present in the spectrum between 1200 and 2000 Å correlates well with the mass accretion rate. Therefore, we conclude that the bulk of the short-wavelength emission seen in CTTSs results from accretion related processes and not from dynamo-driven magnetic activity. Using CTTSs with known mass accretion rates, we calibrate the relationship between M and LC IV to derive the mass accretion rate for some CTTSs which for various reasons have never had their mass accretion rates measured. Finally, several of the CTTSs show strong emission from molecular hydrogen. While emission from H2 cannot form in gas at a temperature of ~105 K, the strength of the molecular hydrogen emission is nevertheless well correlated with all the other emissions displayed in the IUE short-wavelength bandpass. This suggests that the H2 emission is in fact fluorescent emission pumped by the emission (likely Ly

  3. Detailed optical study of HH 32 and the highly collimated outflow from the T Tauri star AS 353A

    Energy Technology Data Exchange (ETDEWEB)

    Hartigan, P.; Mundt, R.; Stocke, J.

    1986-06-01

    The T Tauri star AS 353A and its highly collimated bipolar outflow have been studied using medium- and high-resolution spectroscopy and deep emission-line CCD imagery. We report the discovery of a linear emission jet in the redshifted part of the flow, and present spectra of the HH objects (HH 32A--D) that confirm the bipolarity of the flow. Despite widely varying line profiles, all four HH objects have similar extremely broad emission linewidths and maximum radial velocities (approx.400 km/s) as well as nearly constant number density as a function of radial velocity. Three of the four objects (HH 32D is the possible exception) possess prominent double-peaked emission-line profiles, and in HH 32A and HH 32C the high-velocity component is situated closer to the star than the low-velocity component. The line profile of (O III) lambda5007 differs markedly from the profiles of lower-excitation lines for HH 32A. These characteristics are examined in the light of two physical models: HH objects as strongly radiating shocks in outflowing jets or as single bow shocks around dense clumps in the outflow. Both are successful in explaining the majority of characteristics observed, but both models encounter some difficulties. The stellar wind has been studied through examination of the star's emission and absorption lines, and we find that the wind is already accelerated to 300 km/s close to the star, and reaches a terminal velocity in excess of 350 km/s. The blueshifted component of the H..cap alpha.. profile of AS 353A is highly variable, and the profiles of different lines have quite dissimilar characteristics. The P Cygni line profiles are discussed briefly in terms of two wind models. There is evidence that the flow collimation occurs at distances greater than two stellar radii.

  4. On Longitudinal Spectral Coherence

    DEFF Research Database (Denmark)

    Kristensen, Leif

    1979-01-01

    It is demonstrated that the longitudinal spectral coherence differs significantly from the transversal spectral coherence in its dependence on displacement and frequency. An expression for the longitudinal coherence is derived and it is shown how the scale of turbulence, the displacement between...

  5. Spectral geometry of spacetime

    CERN Document Server

    Kopf, T

    2000-01-01

    Spacetime, understood as a globally hyperbolic manifold, may be characterized by spectral data using a 3+1 splitting into space and time, a description of space by spectral triples and by employing causal relationships, as proposed earlier. Here, it is proposed to use the Hadamard condition of quantum field theory as a smoothness principle.

  6. Hydrocarbon Spectral Database

    Science.gov (United States)

    SRD 115 Hydrocarbon Spectral Database (Web, free access)   All of the rotational spectral lines observed and reported in the open literature for 91 hydrocarbon molecules have been tabulated. The isotopic molecular species, assigned quantum numbers, observed frequency, estimated measurement uncertainty and reference are given for each transition reported.

  7. Comprehensive sieve analysis of breakthrough HIV-1 sequences in the RV144 vaccine efficacy trial.

    Directory of Open Access Journals (Sweden)

    Paul T Edlefsen

    2015-02-01

    Full Text Available The RV144 clinical trial showed the partial efficacy of a vaccine regimen with an estimated vaccine efficacy (VE of 31% for protecting low-risk Thai volunteers against acquisition of HIV-1. The impact of vaccine-induced immune responses can be investigated through sieve analysis of HIV-1 breakthrough infections (infected vaccine and placebo recipients. A V1/V2-targeted comparison of the genomes of HIV-1 breakthrough viruses identified two V2 amino acid sites that differed between the vaccine and placebo groups. Here we extended the V1/V2 analysis to the entire HIV-1 genome using an array of methods based on individual sites, k-mers and genes/proteins. We identified 56 amino acid sites or "signatures" and 119 k-mers that differed between the vaccine and placebo groups. Of those, 19 sites and 38 k-mers were located in the regions comprising the RV144 vaccine (Env-gp120, Gag, and Pro. The nine signature sites in Env-gp120 were significantly enriched for known antibody-associated sites (p = 0.0021. In particular, site 317 in the third variable loop (V3 overlapped with a hotspot of antibody recognition, and sites 369 and 424 were linked to CD4 binding site neutralization. The identified signature sites significantly covaried with other sites across the genome (mean = 32.1 more than did non-signature sites (mean = 0.9 (p < 0.0001, suggesting functional and/or structural relevance of the signature sites. Since signature sites were not preferentially restricted to the vaccine immunogens and because most of the associations were insignificant following correction for multiple testing, we predict that few of the genetic differences are strongly linked to the RV144 vaccine-induced immune pressure. In addition to presenting results of the first complete-genome analysis of the breakthrough infections in the RV144 trial, this work describes a set of statistical methods and tools applicable to analysis of breakthrough infection genomes in general vaccine

  8. Recent cruise onboard R/V Sonne to the Carlsberg Ridge and the Andaman Sea

    Digital Repository Service at National Institute of Oceanography (India)

    KameshRaju, K.A.

    analysis was carried out for pH, dissolved oxygen, and sio4 . Water samples were collected in specially designed copper tubes for the analysis of helium . Many of the results from this cruise were reported at a special session at the aoGs 2008 meeting...R) and the andaman backarc spreading center (absc; fig . 1) . The cruise was conducted onboard the German research vessel R/V Sonne (fig . 2) chartered by the national Institute of oceanography (nIo) . We also collaborated with the Hawaii Mapping Research Group...

  9. Identification of Rv0222 from RD4 as a novel serodiagnostic target for tuberculosis

    DEFF Research Database (Denmark)

    Rosenkrands, Ida; Aagaard, Claus; Weldingh, Karin;

    2008-01-01

    Forty-seven Mycobacterium tuberculosis genes from the 'regions of difference' RD2-7, RD9-13 and RD15 were cloned and expressed, and the purified recombinant proteins were screened for their serodiagnostic potential. Evaluation of six selected proteins in serum samples from Danish resident tubercu....... The results emphasize the importance of cut-off values in TB endemic regions based on endemic control individuals to diagnose active TB, and identify Rv0222 as a promising new antigen for serodiagnosis of TB in both HIV-negative and HIV-positive patients....

  10. Identification of Rv0222 from RD4 as a novel serodiagnostic target for tuberculosis

    DEFF Research Database (Denmark)

    Rosenkrands, I.; Aagaard, C.; Weldingh, K.;

    2008-01-01

    Forty-seven Mycobacterium tuberculosis genes from the 'regions of difference' RD2-7, RD9-13 and RD15 were cloned and expressed, and the purified recombinant proteins were screened for their serodiagnostic potential. Evaluation of six selected proteins in serum samples from Danish resident tubercu....... The results emphasize the importance of cut-off values in TB endemic regions based on endemic control individuals to diagnose active TB, and identify Rv0222 as a promising new antigen for serodiagnosis of TB in both HIV-negative and HIV-positive patients Udgivelsesdato: 2008/7...

  11. Ultraviolet exposure of Gafchromic XR-RV3 and XR-SP2 films.

    Science.gov (United States)

    Katsuda, Toshizo; Gotanda, Rumi; Gotanda, Tatsuhiro; Akagawa, Takuya; Tanki, Nobuyoshi; Kuwano, Tadao; Yabunaka, Kouichi

    2015-09-08

    Gafchromic film has been used for X-ray dose measurement in diagnostic examinations. Their use has been initiated for three-dimensional X-ray dose measurement by using the high-resolution characteristics of Gafchromic films in computed tomography. However, it is necessary to solve the problem of nonuniform thickness in the active layers of Gafchromic films. A double exposure technique using X-rays is performed in therapeutic radiology; it is difficult to use in a diagnostic examination because of the heel effect. Therefore, it is suggested that ultraviolet (UV) rays be substituted for X-rays. However, the appropriate UV wavelength is unknown. In this study, we aimed to determine which UV wavelengths are effective to expose Gafchromic XR-RV3 and XR-SP2. UV lamps with peak wavelengths of 245 nm, 310 nm, and 365 nm were used. The three UV wavelengths were used to irradiate Gafchromic XR-RV3 and XR-SP2 films for 60 min, and irradiation was repeated every 60 min for 600 min thereafter. Films were scanned after each irradiation period on a flatbed scanner. The images were split into their red-green-blue components, and red images were stored using ImageJ version 1.44o image analysis software. Regions of interest (ROI), 0.5 inches in diameter, were placed at the centers of the subtracted Gafchromic film images, and graphs of UV irradiation duration and mean pixel values were plotted. There were reactions to UV-A on both Gafchromic XR-RV3 and XR-SP2; those to UV-B were moderate. However, UV-C demonstrated few reactions with Gafchromic XR-RV3 and XR-SP2. From these results, irradiation with UV-A may be able to correct nonuniformity errors. Uniform UV-A irradiation of Gafchromic films with large areas is possible, and UV rays can be used as a substitute for X-rays in the double exposure technique.

  12. [Identification and evaluation of T cell epitopes of Rv0585c from Mycobacterium tuberculosis].

    Science.gov (United States)

    Wang, X X; Chen, X; Li, Y Q; Xiao, T Y; Jiang, Y; Li, M C; Liu, H C; Wan, K L

    2017-05-10

    Objective: To investigate the human T cell epitopes of Mycobacterium (M.) tuberculosis Rv0585c protein antigen and their immunogenicity and provide evidence for the development of specific tuberculosis immune diagnostic techniques and tuberculosis vaccine. Methods: We synthesized peptides from M. tuberculosis Rv0585c protein antigen predicted by TE-predict and IEDB human T cell epitope prediction tool. The cellular immunoreactivity of the predicted peptides was evaluated through ELISpot assay with the peripheral blood monouclear cells (PBMC) of clinical tuberculosis patients. In animal experiments, BALB/c mice were respectively immunized with high dose (100 μg/mice) and low dose (50 μg/mice) of the peptides of Rv0585c, at the same time, high dose (50 μg/mice) and low dose (20 μg/mice) of Ag85B protein were used in positive control group. The levels of IFN-γ, IL-2, IL-4 and IL-10 were tested with ELISA kit respectively. Results: By means of bioinformatics technique, 66 human T cell epitopes of Rv0585c were predicted, from which9 peptides concentrated epitopes were synthesized for the animal immune experiments. Peptides P10110, P10112 and P10117 were confirmed to be antigenic. The sensitivity and specificity of P10110, P10112 and P10117 were 14.00%, 12.00%, 6.00% and 100.00%, 100.00%, 97.96% respectively when they were used as diagnostic reagents of tuberculosis. The sensitivity and specificity were 22.00% and 97.96% when the epitopes were combined together. The results of animal immunity test showed that high levels of cytokines IFN-γ, IL-2, IL-4 and IL-10 were induced by high and low dose of P10110, and high levels of IFN-γ、IL-2 and IL-10 were induced by high and low dose of P10112, which were much higher than that in negative controls, respectively (Ptuberculosis and the development of new type of tuberculosis vaccine.

  13. Spectral Geometry and Causality

    CERN Document Server

    Kopf, T

    1996-01-01

    For a physical interpretation of a theory of quantum gravity, it is necessary to recover classical spacetime, at least approximately. However, quantum gravity may eventually provide classical spacetimes by giving spectral data similar to those appearing in noncommutative geometry, rather than by giving directly a spacetime manifold. It is shown that a globally hyperbolic Lorentzian manifold can be given by spectral data. A new phenomenon in the context of spectral geometry is observed: causal relationships. The employment of the causal relationships of spectral data is shown to lead to a highly efficient description of Lorentzian manifolds, indicating the possible usefulness of this approach. Connections to free quantum field theory are discussed for both motivation and physical interpretation. It is conjectured that the necessary spectral data can be generically obtained from an effective field theory having the fundamental structures of generalized quantum mechanics: a decoherence functional and a choice of...

  14. Snapshot spectral imaging system

    Science.gov (United States)

    Arnold, Thomas; De Biasio, Martin; McGunnigle, Gerald; Leitner, Raimund

    2010-02-01

    Spectral imaging is the combination of spectroscopy and imaging. These fields are well developed and are used intensively in many application fields including industry and the life sciences. The classical approach to acquire hyper-spectral data is to sequentially scan a sample in space or wavelength. These acquisition methods are time consuming because only two spatial dimensions, or one spatial and the spectral dimension, can be acquired simultaneously. With a computed tomography imaging spectrometer (CTIS) it is possible to acquire two spatial dimensions and a spectral dimension during a single integration time, without scanning either spatial or spectral dimensions. This makes it possible to acquire dynamic image scenes without spatial registration of the hyperspectral data. This is advantageous compared to tunable filter based systems which need sophisticated image registration techniques. While tunable filters provide full spatial and spectral resolution, for CTIS systems there is always a tradeoff between spatial and spectral resolution as the spatial and spectral information corresponding to an image cube is squeezed onto a 2D image. The presented CTIS system uses a spectral-dispersion element to project the spectral and spatial image information onto a 2D CCD camera array. The system presented in this paper is designed for a microscopy application for the analysis of fixed specimens in pathology and cytogenetics, cell imaging and material analysis. However, the CTIS approach is not limited to microscopy applications, thus it would be possible to implement it in a hand-held device for e.g. real-time, intra-surgery tissue classification.

  15. Mycobacterium tuberculosis DosR regulon gene Rv0079 encodes a putative, 'dormancy associated translation inhibitor (DATIN'.

    Directory of Open Access Journals (Sweden)

    Ashutosh Kumar

    Full Text Available Mycobacterium tuberculosis is a major human pathogen that has evolved survival mechanisms to persist in an immune-competent host under a dormant condition. The regulation of M. tuberculosis metabolism during latent infection is not clearly known. The dormancy survival regulon (DosR regulon is chiefly responsible for encoding dormancy related functions of M. tuberculosis. We describe functional characterization of an important gene of DosR regulon, Rv0079, which appears to be involved in the regulation of translation through the interaction of its product with bacterial ribosomal subunits. The protein encoded by Rv0079, possibly, has an inhibitory role with respect to protein synthesis, as revealed by our experiments. We performed computational modelling and docking simulation studies involving the protein encoded by Rv0079 followed by in vitro translation and growth curve analysis experiments, involving recombinant E. coli and Bacille Calmette Guérin (BCG strains that overexpressed Rv0079. Our observations concerning the interaction of the protein with the ribosomes are supportive of its role in regulation/inhibition of translation. We propose that the protein encoded by locus Rv0079 is a 'dormancy associated translation inhibitor' or DATIN.

  16. Koala retrovirus genotyping analyses reveal a low prevalence of KoRV-A in Victorian koalas and an association with clinical disease.

    Science.gov (United States)

    Legione, Alistair R; Patterson, Jade L S; Whiteley, Pam; Firestone, Simon M; Curnick, Megan; Bodley, Kate; Lynch, Michael; Gilkerson, James R; Sansom, Fiona M; Devlin, Joanne M

    2017-02-01

    Koala retrovirus (KoRV) is undergoing endogenization into the genome of koalas in Australia, providing an opportunity to assess the effect of retrovirus infection on the health of a population. The prevalence of KoRV in north-eastern Australia (Queensland and New South Wales) is 100 %, whereas previous preliminary investigations in south-eastern Australia (Victoria) suggested KoRV is present at a lower prevalence, although the values have varied widely. Here, we describe a large study of free-ranging koalas in Victoria to estimate the prevalence of KoRV and assess the clinical significance of KoRV infection in wild koalas. Blood or spleen samples from 648 koalas where tested for KoRV provirus, and subsequently genotyped, using PCRs to detect the pol and env genes respectively. Clinical data was also recorded where possible and analysed in comparison to infection status. The prevalence of KoRV was 24.7 % (160/648). KoRV-A was detected in 141/160 cases, but KoRV-B, a genotype associated with neoplasia in captive koalas, was not detected. The genotype in 19 cases could not be determined. Genomic differences between KoRV in Victoria and type strains may have impacted genotyping. Factors associated with KoRV infection, based on multivariable analysis, were low body condition score, region sampled, and 'wet bottom' (a staining of the fur around the rump associated with chronic urinary incontinence). Koalas with wet bottom were nearly twice as likely to have KoRV provirus detected than those without wet bottom (odds ratio=1.90, 95 % confidence interval 1.21, 2.98). Our findings have important implications for the conservation of this iconic species, particularly regarding translocation potential of Victorian koalas.

  17. Herbig-Haro jets in 3D: the HL/XZ Tauri region

    Science.gov (United States)

    Movsessian, T. A.; Magakian, T. Yu.; Bally, J.; Smith, M. D.; Moiseev, A. V.; Dodonov, S. N.

    2007-08-01

    Context: Jets and outflows from young stellar objects (YSOs) can be identified and traced through the distribution and structure of shocked emission-line features. To understand the formation of these regions requires kinematic data at high spectral resolution and with full spatial coverage. Aims: In this work, we investigate the environment of HL/XZ Tau, which contains a compact and very active nest of YSOs. We explore the kinematic properties of the close association of jets in this region and study the interaction of jets with the ambient medium, as well as the outflows with each other. Methods: We present scanning Fabry-Perót interferometry of the HL/XZ Tau region in Hα and [S ii] 6716 Å emission. We also measure the proper motions of the knots in the outflows, as derived from images obtained in 1997 and 2001, to achieve the full 3D kinematic picture. Results: Radial velocities of the HL Tau jet indicate a fast spine of low excitation surrounded by a slower sheared sheath of higher excitation. Proper motions range from 200-220 km s-1 in the HL Tau jet and are aligned within 10 degrees of the jet spine. In combination, the proper motions and radial velocities indicate that three outflows in this region may be interacting with each other. Evidence of an outflow associated with LkHα 358 is found, and we suggest it is a source of Herbig-Haro (HH) knots that lie to the southeast of HL Tau and HH 265. Conclusions: We conclude that the southern lobe of the XZ Tau wind disrupts the eastern lobe of the collimated outflow from LkHα 358. The jet emerging from HL Tau is deflected by the northern lobe of the wind from XZ Tau. We propose several probable explanations for the unusual structure of the HL Tau jet. It is plausible that the shocks in the jet spine are maintained by the ram pressure of a low-density crosswind from XZ Tau. The crosswind interacts to form a sheath of entrained gas. Based partly on observations collected with the 6 m telescope of the Special

  18. Longer duration of asthma is significantly associated with increased RV/TLC ratio.

    Science.gov (United States)

    Tiwari, Anupama; Rahman, Kazi; Abejie, Belayneh; Jain, Vipul V; Vempilly, Jose Joseph

    2017-03-01

    Although FEV1/FVC ratio has been shown to be negatively associated with longer duration of asthma; an association between RV/TLC ratio and longer duration of asthma has not been explored. Patients with established asthma for more than a year and met inclusion and exclusion criteria were recruited. Data obtained by questionnaire after informed consent was obtained, Pulmonary function tests and laboratory results were collected through chart review. Correlation and multiple linear regressions were used to analyze the data. Among the 93 subjects, 61 were women. The mean age of patients was 58 ± 15 years, and the mean duration of asthma was 21 ± 18 years. The ethnic composition included: Caucasians 64%, Hispanics 28% and other groups 8%. The FEV1/FVC ratio was not significantly associated with duration of asthma (R2 = 0.15, p = 0.05). However, the RV/TLC ratio was significantly associated with duration of asthma (R2 = 0.46, p TLC ratio may be a better indicator than FEV1/FVC ratio to detect airway obstruction related to longer duration of asthma. Lung volume measurements should be done in addition to spirometry to detect changes related to airway obstruction in patients with longer duration of asthma. Copyright © 2017 Elsevier Ltd. All rights reserved.

  19. 5-HT2B Receptor Antagonists Inhibit Fibrosis and Protect from RV Heart Failure

    Directory of Open Access Journals (Sweden)

    Wiebke Janssen

    2015-01-01

    Full Text Available Objective. The serotonin (5-HT pathway was shown to play a role in pulmonary hypertension (PH, but its functions in right ventricular failure (RVF remain poorly understood. The aim of the current study was to investigate the effects of Terguride (5-HT2A and 2B receptor antagonist or SB204741 (5-HT2B receptor antagonist on right heart function and structure upon pulmonary artery banding (PAB in mice. Methods. Seven days after PAB, mice were treated for 14 days with Terguride (0.2 mg/kg bid or SB204741 (5 mg/kg day. Right heart function and remodeling were assessed by right heart catheterization, magnetic resonance imaging (MRI, and histomorphometric methods. Total secreted collagen content was determined in mouse cardiac fibroblasts isolated from RV tissues. Results. Chronic treatment with Terguride or SB204741 reduced right ventricular fibrosis and showed improved heart function in mice after PAB. Moreover, 5-HT2B receptor antagonists diminished TGF-beta1 induced collagen synthesis of RV cardiac fibroblasts in vitro. Conclusion. 5-HT2B receptor antagonists reduce collagen deposition, thereby inhibiting right ventricular fibrosis. Chronic treatment prevented the development and progression of pressure overload-induced RVF in mice. Thus, 5-HT2B receptor antagonists represent a valuable novel therapeutic approach for RVF.

  20. 5-HT2B receptor antagonists inhibit fibrosis and protect from RV heart failure.

    Science.gov (United States)

    Janssen, Wiebke; Schymura, Yves; Novoyatleva, Tatyana; Kojonazarov, Baktybek; Boehm, Mario; Wietelmann, Astrid; Luitel, Himal; Murmann, Kirsten; Krompiec, Damian Richard; Tretyn, Aleksandra; Pullamsetti, Soni Savai; Weissmann, Norbert; Seeger, Werner; Ghofrani, Hossein Ardeschir; Schermuly, Ralph Theo

    2015-01-01

    The serotonin (5-HT) pathway was shown to play a role in pulmonary hypertension (PH), but its functions in right ventricular failure (RVF) remain poorly understood. The aim of the current study was to investigate the effects of Terguride (5-HT2A and 2B receptor antagonist) or SB204741 (5-HT2B receptor antagonist) on right heart function and structure upon pulmonary artery banding (PAB) in mice. Seven days after PAB, mice were treated for 14 days with Terguride (0.2 mg/kg bid) or SB204741 (5 mg/kg day). Right heart function and remodeling were assessed by right heart catheterization, magnetic resonance imaging (MRI), and histomorphometric methods. Total secreted collagen content was determined in mouse cardiac fibroblasts isolated from RV tissues. Chronic treatment with Terguride or SB204741 reduced right ventricular fibrosis and showed improved heart function in mice after PAB. Moreover, 5-HT2B receptor antagonists diminished TGF-beta1 induced collagen synthesis of RV cardiac fibroblasts in vitro. 5-HT2B receptor antagonists reduce collagen deposition, thereby inhibiting right ventricular fibrosis. Chronic treatment prevented the development and progression of pressure overload-induced RVF in mice. Thus, 5-HT2B receptor antagonists represent a valuable novel therapeutic approach for RVF.

  1. VizieR Online Data Catalog: Kepler-10 RV measurements by HARPS-N (Dumusque+, 2014)

    Science.gov (United States)

    Dumusque, X.; Bonomo, A. S.; Haywood, R. D.; Malavolta, L.; Segransan, D.; Buchhave, L. A.; Collier, Cameron A.; Latham, D. W.; Molinari, E.; Pepe, F.; Udry, S.; Charbonneau, D.; Cosentino, R.; Dressing, C. D.; Figueira, P.; Fiorenzano, A. F. M.; Gettel, S.; Harutyunyan, A.; Horne, K.; Lopez-Morales, M.; Lovis, C.; Mayor, M.; Micela, G.; Motalebi, F.; Nascimbeni, V.; Phillips, D. F.; Piotto, G.; Pollacco, D.; Queloz, D.; Rice, K.; Sasselov, D.; Sozzetti, A.; Szentgyorgyi, A.; Watson, C.

    2017-03-01

    We monitored the RV variation of Kepler-10 with the HARPS-N spectrograph installed on the 3.57-m Telescopio Nazionale Galileo at the Spanish Observatorio del Roque de los Muchachos, La Palma Island, Spain (Cosentino et al. 2012SPIE.8446E..1VC). This instrument is an updated version of the original HARPS planet hunter installed on the 3.6-m telescope at the European Southern Observatory on La Silla, Chile (Mayor et al. 2003Msngr.114...20M). Just like its older brother, the HARPS-N instrument is an ultra-stable fiber-fed high-resolution (R = 115,000) optical echelle spectrograph optimized for the measurement of very precise RVs. The use of a more modern monolithic 4kx4k CCD enclosed in a more temperature stable cryostat, and the use of octagonal fibers for a better scrambling of the incoming light fed into the spectrograph should improve the precision of the instrument compared to HARPS. Scientific operations began at HARPS-N in 2012 August. Over the first two observing seasons, we obtained 157 RV measurements of Kepler-10. Four observations that were obtained during bad weather conditions had very low signal to noise (S/N, <10) and were rejected. (1 data file).

  2. A Large X-ray Flare from a Single Weak-lined T Tauri Star TWA-7 Detected with MAXI GSC

    CERN Document Server

    Uzawa, Akiko; Morii, Mikio; Yamazaki, Kyohei; Kawai, Nobuyuki; Matsuoka, Masaru; Nakahira, Satoshi; Serino, Motoko; Matsumura, Takanori; Mihara, Tatehiro; Tomida, Hiroshi; Ueda, Yoshihiro; Sugizaki, Mutsumi; Ueno, Shiro; Daikyuji, Arata; Ebisawa, Ken; Eguchi, Satoshi; Hiroi, Kazuo; Ishikawa, Masaki; Isobe, Naoki; Kawasaki, Kazuyoshi; Kimura, Masashi; Kitayama, Hiroki; Kohama, Mitsuhiro; Kotani, Taro; Nakagawa, Yujin E; Nakajima, Motoki; Negoro, Hitoshi; Ozawa, Hiroshi; Shidatsu, Megumi; Sootome, Tetsuya; Sugimori, Kousuke; Suwa, Fumitoshi; Tsunemi, Hiroshi; Usui, Ryuichi; Yamamoto, Takayuki; Yamaoka, Kazutaka; Yoshida, Atsumasa

    2011-01-01

    We present a large X-ray flare from a nearby weak-lined T Tauri star TWA-7 detected with the Gas Slit Camera (GSC) on the Monitor of All-sky X-ray Image (MAXI). The GSC captured X-ray flaring from TWA-7 with a flux of $3\\times10^{-9}$ ergs cm$^{-2}$ s$^{-1}$ in 2--20 keV band during the scan transit starting at UT 2010-09-07 18:24:30.The estimated X-ray luminosity at the scan in the energy band is 3$\\times10^{32}$ ergs s$^{-1}$,indicating that the event is among the largest X-ray flares fromT Tauri stars.Since MAXI GSC monitors a target only during a scan transit of about a minute per 92 min orbital cycle, the luminosity at the flare peak might have been higher than that detected. At the scan transit, we observed a high X-ray-to-bolometric luminosity ratio, log $L_{\\rm X}/L_{\\rm bol}$ = $-0.1^{+0.2}_{-0.3}$; i.e., the X-ray luminosity is comparable to the bolometric luminosity. Since TWA-7 has neither an accreting disk nor a binary companion, the observed event implies that none of those are essential to gene...

  3. Magnetic activity and hot Jupiters of young Suns: the weak-line T Tauri stars V819 Tau and V830 Tau

    CERN Document Server

    Donati, JF; Hussain, G; Moutou, C; Malo, L; Grankin, K; Vidotto, AA; Alencar, SHP; Gregory, SG; Jardine, MM; Herczeg, G; Morin, J; Fares, R; Ménard, F; Bouvier, J; Delfosse, X; Doyon, R; Takami, M; Figueira, P; Petit, P; Boisse, I

    2015-01-01

    We report results of a spectropolarimetric and photometric monitoring of the weak-line T Tauri stars (wTTSs) V819 Tau and V830 Tau within the MaTYSSE programme, involving the ESPaDOnS spectropolarimeter at the Canada-France-Hawaii Telescope. At ~3 Myr, both stars dissipated their discs recently and are interesting objects for probing star and planet formation. Profile distortions and Zeeman signatures are detected in the unpolarized and circularly-polarized lines, whose rotational modulation we modelled using tomographic imaging, yielding brightness and magnetic maps for both stars. We find that the large-scale magnetic fields of V819 Tau and V830 Tau are mostly poloidal and can be approximated at large radii by 350-400 G dipoles tilted at ~30 degrees to the rotation axis. They are significantly weaker than the field of GQ Lup, an accreting classical T Tauri star (cTTS) with similar mass and age which can be used to compare the magnetic properties of wTTSs and cTTSs. The reconstructed brightness maps of both ...

  4. The Spitzer c2d Survey of Weak-Line T Tauri Stars. III. The Transition from Primordial Disks to Debris Disks

    CERN Document Server

    Wahhaj, Zahed; Stapelfeldt, Karl R; Padgett, Deborah L; Koerner, David W; Case, April; Keller, James R; Merín, Bruno; Evans, Neal J; Harvey, Paul; Sargent, Anneila; van Dishoeck, Ewine F; Allen, Lori; Blake, Geoff; Brooke, Tim; Chapman, Nicholas; Mundy, Lee; Myers, Philip C

    2010-01-01

    We present 3.6 to 70 {\\mu}m Spitzer photometry of 154 weak-line T Tauri stars (WTTS) in the Chamaeleon, Lupus, Ophiuchus and Taurus star formation regions, all of which are within 200 pc of the Sun. For a comparative study, we also include 33 classical T Tauri stars (CTTS) which are located in the same star forming regions. Spitzer sensitivities allow us to robustly detect the photosphere in the IRAC bands (3.6 to 8 {\\mu}m) and the 24 {\\mu}m MIPS band. In the 70 {\\mu}m MIPS band, we are able to detect dust emission brighter than roughly 40 times the photosphere. These observations represent the most sensitive WTTS survey in the mid to far infrared to date, and reveal the frequency of outer disks (r = 3-50 AU) around WTTS. The 70 {\\mu}m photometry for half the c2d WTTS sample (the on-cloud objects), which were not included in the earlier papers in this series, Padgett et al. (2006) and Cieza et al. (2007), are presented here for the first time. We find a disk frequency of 19% for on-cloud WTTS, but just 5% for...

  5. Detection of Strong Millimeter Emission from the Circumstellar Dust Disk Around V1094 Sco: Cold and Massive Disk around a T Tauri Star in a Quiescent Accretion Phase?

    CERN Document Server

    Tsukagoshi, Takashi; Kitamura, Yoshimi; Momose, Munetake; Shimajiri, Yoshito; Hiramatsu, Masaaki; Ikeda, Norio; Kamegai, Kazuhisa; Wilson, Grant; Yun, Min S; Scott, Kimberly; Austermann, Jay; Perera, Thushara; Hughes, David; Aretxaga, Itziar; Mauskopf, Philip; Ezawa, Hajime; Kohno, Kotaro; Kawabe, Ryohei

    2010-01-01

    We present the discovery of a cold massive dust disk around the T Tauri star V1094 Sco in the Lupus molecular cloud from the 1.1 millimeter continuum observations with AzTEC on ASTE. A compact ($r\\lesssim$320 AU) continuum emission coincides with the stellar position having a flux density of 272 mJy which is largest among T Tauri stars in Lupus. We also present the detection of molecular gas associated with the star in the five-point observations in $^{12}$CO J=3--2 and $^{13}$CO J=3--2. Since our $^{12}$CO and $^{13}$CO observations did not show any signature of a large-scale outflow or a massive envelope, the compact dust emission is likely to come from a disk around the star. The observed SED of V1094 Sco shows no distinct turnover from near infrared to millimeter wavelengths, which can be well described by a flattened disk for the dust component, and no clear dip feature around 10 $\\micron$ suggestive of absence of an inner hole in the disk. We fit a simple power-law disk model to the observed SED. The es...

  6. c2d Spitzer IRS Spectra of Disks around T Tauri Stars. III. [Ne II], [Fe I], and H_2 gas-phase lines

    CERN Document Server

    Lahuis, Fred; Blake, Geoffrey A; Evans, Neal J; Kessler-Silacci, Jacqueline E; Pontoppidan, Klaus M

    2007-01-01

    We present a survey of mid-infrared gas-phase lines toward a sample of 76 circumstellar disks around low mass pre-main sequence stars from the Spitzer "Cores to Disks" legacy program. We report the first detections of [Ne II] and [Fe I] toward classical T Tauri stars in ~20% respectively ~9% of our sources. The observed [Ne II] line fluxes and upper limits are consistent with [Ne II] excitation in an X-ray irradiated disk around stars with X-ray luminosities L_X=10^{29}-10^{31} erg s^{-1}. [Fe I] is detected at ~10^-5-10^-4 L_Sun, but no [S I] or [Fe II] is detected down to ~10^{-6} L_Sun. The [Fe I] detections indicate the presence of gas-rich disks with masses of >~0.1 M_J. No H_2 0-0 S(0) and S(1) disk emission is detected, except for S(1) toward one source. These data give upper limits on the warm (T~100-200K) gas mass of a few Jovian masses, consistent with recent T Tauri disk models which include gas heating by stellar radiation. Compact disk emission of hot (T>~500K) gas is observed through the H_2 0-0...

  7. Modelling the magnetic activity & filtering radial velocity curves of young Suns: the weak-line T Tauri star LkCa 4

    CERN Document Server

    Donati, J -F; Hussain, G; Moutou, C; Grankin, K; Boisse, I; Morin, J; Gregory, S G; Vidotto, A A; Bouvier, J; Alencar, S H P; Delfosse, X; Doyon, R; Takami, M; Jardine, M M; Fares, R; Cameron, A C; Menard, F; Dougados, C; Herczeg, G

    2014-01-01

    We report results of a spectropolarimetric and photometric monitoring of the weak-line T Tauri star LkCa4 within the MaTYSSE programme, involving ESPaDOnS at the Canada-France-Hawaii Telescope. Despite an age of only 2Myr and a similarity with prototypical classical T Tauri stars, LkCa4 shows no evidence for accretion and probes an interesting transition stage for star and planet formation. Large profile distortions and Zeeman signatures are detected in the unpolarized and circularly-polarized lines of LkCa4 using Least-Squares Deconvolution (LSD), indicating the presence of brightness inhomogeneities and magnetic fields at the surface of LkCa4. Using tomographic imaging, we reconstruct brightness and magnetic maps of LkCa4 from sets of unpolarized and circularly-polarized LSD profiles. The large-scale field is strong and mainly axisymmetric, featuring a ~2kG poloidal component and a ~1kG toroidal component encircling the star at equatorial latitudes - the latter making LkCa4 markedly different from classical...

  8. Pre-Main Sequence variables in the VMR-D : identification of T Tauri-like accreting protostars through Spitzer-IRAC variability

    CERN Document Server

    Giannini, T; Elia, D; Strafella, F; De Luca, M; Fazio, G; Marengo, M; Nisini, B; Smith, H A

    2009-01-01

    We present a study of the infrared variability of young stellar objects by means of two Spitzer-IRAC images of the Vela Molecular Cloud D (VMR-D) obtained in observations separated in time by about six months. By using the same space-born IR instrumentation, this study eliminates all the unwanted effects usually unavoidable when comparing catalogs obtained from different instruments. The VMR-D map covers about 1.5 square deg. of a site where star formation is actively ongoing. We are interested in accreting pre-main sequence variables whose luminosity variations are due to intermittent events of disk accretion (i.e. active T Tauri stars and EXor type objects). The variable objects have been selected from a catalog of more than 170,000 sources detected at a S/N ratio > 5. We searched the sample of variables for ones whose photometric properties are close to those of known EXor's. These latter are monitored in a more systematic way than T Tauri stars and the mechanisms that regulate the observed phenomenology a...

  9. A NusG paralogue from Mycobacterium tuberculosis, Rv0639, has evolved to interact with ribosomal protein S10 (Rv0700) but not to function as a transcription elongation-termination factor.

    Science.gov (United States)

    Kalyani, B Sudha; Kunamneni, Radhika; Wal, Megha; Ranjan, Amitabh; Sen, Ranjan

    2015-01-01

    NusG, a well-conserved protein in all the three forms of life, is involved in transcription elongation and termination, as well as in the process of transcription-translation coupling. The existence of species-specific functional, as well as conformational, divergences in NusG makes it an attractive transcription factor to study, especially if it originates from a pathogen. Here, we report functional and conformational characterizations of the Mycobacterium tuberculosis (Mtb) protein Rv0639 that has been annotated as a homologue of Escherichia coli NusG. Rv0639 failed to complement the in vivo functions of E. coli NusG (Ec NusG) and did not exhibit any signature of a transcription elongation-termination factor. However, it retained the ability to bind to its cognate ribosomal protein S10 (Rv0700). Compared with Ec NusG, Rv0639 possesses unique conformational features characterized by altered secondary structures in the C-terminal domain (CTD), an unusually long and disordered linker region between the N-terminal domain (NTD) and CTD, and a folding of its NTD over its CTD. This unusual folded conformation could have imparted specialized functions to this protein, required to adapt the physiology of Mtb. We speculate that in the absence of a bona fide RfaH, a NusG paralogue that is involved in pathogenicity in E. coli, Rv0639 functions as an RfaH-like factor and is involved in pathogenicity using unidentified ops-like sequences in the Mtb genome. And hence, we reannotate Rv0639 as a paralogue of NusG, instead of a homologue.

  10. Spectral radius of graphs

    CERN Document Server

    Stevanovic, Dragan

    2015-01-01

    Spectral Radius of Graphs provides a thorough overview of important results on the spectral radius of adjacency matrix of graphs that have appeared in the literature in the preceding ten years, most of them with proofs, and including some previously unpublished results of the author. The primer begins with a brief classical review, in order to provide the reader with a foundation for the subsequent chapters. Topics covered include spectral decomposition, the Perron-Frobenius theorem, the Rayleigh quotient, the Weyl inequalities, and the Interlacing theorem. From this introduction, the

  11. Conserved hypothetical protein Rv1977 in Mycobacterium tuberculosis strains contains sequence polymorphisms and might be involved in ongoing immune evasion.

    Science.gov (United States)

    Jiang, Yi; Liu, Haican; Wang, Xuezhi; Li, Guilian; Qiu, Yan; Dou, Xiangfeng; Wan, Kanglin

    2015-01-01

    Host immune pressure and associated parasite immune evasion are key features of host-pathogen co-evolution. A previous study showed that human T cell epitopes of Mycobacterium tuberculosis are evolutionarily hyperconserved and thus it was deduced that M. tuberculosis lacks antigenic variation and immune evasion. Here, we selected 151 clinical Mycobacterium tuberculosis isolates from China, amplified gene encoding Rv1977 and compared the sequences. The results showed that Rv1977, a conserved hypothetical protein, is not conserved in M. tuberculosis strains and there are polymorphisms existed in the protein. Some mutations, especially one frameshift mutation, occurred in the antigen Rv1977, which is uncommon in M.tb strains and may lead to the protein function altering. Mutations and deletion in the gene all affect one of three T cell epitopes and the changed T cell epitope contained more than one variable position, which may suggest ongoing immune evasion.

  12. Unmixing of spectrally similar minerals

    CSIR Research Space (South Africa)

    Debba, Pravesh

    2009-01-01

    Full Text Available -bearing oxide/hydroxide/sulfate minerals in complex mixtures be obtained using hyperspectral data? Debba (CSIR) Unmixing of spectrally similar minerals MERAKA 2009 3 / 18 Method of spectral unmixing Old method: problem Linear Spectral Mixture Analysis (LSMA...

  13. Vowel Inherent Spectral Change

    CERN Document Server

    Assmann, Peter

    2013-01-01

    It has been traditional in phonetic research to characterize monophthongs using a set of static formant frequencies, i.e., formant frequencies taken from a single time-point in the vowel or averaged over the time-course of the vowel. However, over the last twenty years a growing body of research has demonstrated that, at least for a number of dialects of North American English, vowels which are traditionally described as monophthongs often have substantial spectral change. Vowel Inherent Spectral Change has been observed in speakers’ productions, and has also been found to have a substantial effect on listeners’ perception. In terms of acoustics, the traditional categorical distinction between monophthongs and diphthongs can be replaced by a gradient description of dynamic spectral patterns. This book includes chapters addressing various aspects of vowel inherent spectral change (VISC), including theoretical and experimental studies of the perceptually relevant aspects of VISC, the relationship between ar...

  14. Temporal Lorentzian spectral triples

    Science.gov (United States)

    Franco, Nicolas

    2014-09-01

    We present the notion of temporal Lorentzian spectral triple which is an extension of the notion of pseudo-Riemannian spectral triple with a way to ensure that the signature of the metric is Lorentzian. A temporal Lorentzian spectral triple corresponds to a specific 3 + 1 decomposition of a possibly noncommutative Lorentzian space. This structure introduces a notion of global time in noncommutative geometry. As an example, we construct a temporal Lorentzian spectral triple over a Moyal-Minkowski spacetime. We show that, when time is commutative, the algebra can be extended to unbounded elements. Using such an extension, it is possible to define a Lorentzian distance formula between pure states with a well-defined noncommutative formulation.

  15. Spectral recognition of graphs

    Directory of Open Access Journals (Sweden)

    Cvetković Dragoš

    2012-01-01

    Full Text Available At some time, in the childhood of spectral graph theory, it was conjectured that non-isomorphic graphs have different spectra, i.e. that graphs are characterized by their spectra. Very quickly this conjecture was refuted and numerous examples and families of non-isomorphic graphs with the same spectrum (cospectral graphs were found. Still some graphs are characterized by their spectra and several mathematical papers are devoted to this topic. In applications to computer sciences, spectral graph theory is considered as very strong. The benefit of using graph spectra in treating graphs is that eigenvalues and eigenvectors of several graph matrices can be quickly computed. Spectral graph parameters contain a lot of information on the graph structure (both global and local including some information on graph parameters that, in general, are computed by exponential algorithms. Moreover, in some applications in data mining, graph spectra are used to encode graphs themselves. The Euclidean distance between the eigenvalue sequences of two graphs on the same number of vertices is called the spectral distance of graphs. Some other spectral distances (also based on various graph matrices have been considered as well. Two graphs are considered as similar if their spectral distance is small. If two graphs are at zero distance, they are cospectral. In this sense, cospectral graphs are similar. Other spectrally based measures of similarity between networks (not necessarily having the same number of vertices have been used in Internet topology analysis, and in other areas. The notion of spectral distance enables the design of various meta-heuristic (e.g., tabu search, variable neighbourhood search algorithms for constructing graphs with a given spectrum (spectral graph reconstruction. Several spectrally based pattern recognition problems appear in many areas (e.g., image segmentation in computer vision, alignment of protein-protein interaction networks in bio

  16. Enhanced propagation of fish nodaviruses in BF-2 cells persistently infected with snakehead retrovirus (SnRV).

    Science.gov (United States)

    Nishizawa, Toyohiko; Kokawa, Yuki; Wakayama, Takako; Kinoshita, Shinichi; Yoshimizu, Mamoru

    2008-03-01

    Fish nodaviruses are causative agents of viral nervous necrosis causing high mortality in cultured marine fishes around the world. The first successful isolation of fish nodavirus was made with SSN-1 cells, which are persistently infected with snakehead retrovirus (SnRV). In the present study, a BF-2 cell line persistently infected with SnRV (PI-BF-2) was established to evaluate the influence of SnRV on the production of fish nodavirus. The PI-BF-2 cells were slightly more slender than BF-2 cells, but no difference was observed in propagation rate between both cell lines. No difference was observed in production of SnRV between PI-BF-2 and SSN-1 cell lines. Although both PI-BF-2 and BF-2 cell lines showed no cytopathic effect (CPE) after inoculation of striped jack nervous necrosis virus (SJNNV) and redspotted grouper nervous necrosis virus (RGNNV), these fish nodaviruses could be amplified in BF-2 cells, and moreover, production of fish nodaviruses in the PI-BF-2 cell line was more than 40 times higher than in BF-2 cells. Thus, it was concluded that BF-2 cell permissiveness to fish nodaviruses was enhanced by persistent infection with SnRV. Furthermore, homologous cDNA to genomic RNA of SJNNV was detected from both PI-BF-2 and SSN-1 cell lines persistently infected with SnRV. The amount of nodavirus cDNA in SJNNV-inoculated PI-BF-2 cells was clearly lower than that in SJNNV-inoculated SSN-1 cells.

  17. Spectrally selective glazings

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1998-08-01

    Spectrally selective glazing is window glass that permits some portions of the solar spectrum to enter a building while blocking others. This high-performance glazing admits as much daylight as possible while preventing transmission of as much solar heat as possible. By controlling solar heat gains in summer, preventing loss of interior heat in winter, and allowing occupants to reduce electric lighting use by making maximum use of daylight, spectrally selective glazing significantly reduces building energy consumption and peak demand. Because new spectrally selective glazings can have a virtually clear appearance, they admit more daylight and permit much brighter, more open views to the outside while still providing the solar control of the dark, reflective energy-efficient glass of the past. This Federal Technology Alert provides detailed information and procedures for Federal energy managers to consider spectrally selective glazings. The principle of spectrally selective glazings is explained. Benefits related to energy efficiency and other architectural criteria are delineated. Guidelines are provided for appropriate application of spectrally selective glazing, and step-by-step instructions are given for estimating energy savings. Case studies are also presented to illustrate actual costs and energy savings. Current manufacturers, technology users, and references for further reading are included for users who have questions not fully addressed here.

  18. Thermophotovoltaic Spectral Control

    Energy Technology Data Exchange (ETDEWEB)

    DM DePoy; PM Fourspring; PF Baldasaro; JF Beausang; EJ Brown; MW Dashiel; KD Rahner; TD Rahmlow; JE Lazo-Wasem; EJ Gratrix; B Wemsman

    2004-06-09

    Spectral control is a key technology for thermophotovoltaic (TPV) direct energy conversion systems because only a fraction (typically less than 25%) of the incident thermal radiation has energy exceeding the diode bandgap energy, E{sub g}, and can thus be converted to electricity. The goal for TPV spectral control in most applications is twofold: (1) Maximize TPV efficiency by minimizing transfer of low energy, below bandgap photons from the radiator to the TPV diode. (2) Maximize TPV surface power density by maximizing transfer of high energy, above bandgap photons from the radiator to the TPV diode. TPV spectral control options include: front surface filters (e.g. interference filters, plasma filters, interference/plasma tandem filters, and frequency selective surfaces), back surface reflectors, and wavelength selective radiators. System analysis shows that spectral performance dominates diode performance in any practical TPV system, and that low bandgap diodes enable both higher efficiency and power density when spectral control limitations are considered. Lockheed Martin has focused its efforts on front surface tandem filters which have achieved spectral efficiencies of {approx}83% for E{sub g} = 0.52 eV and {approx}76% for E{sub g} = 0.60 eV for a 950 C radiator temperature.

  19. Imunogenicidade da cepa avirulenta RV194-2 do vírus rábico em camundongos

    Directory of Open Access Journals (Sweden)

    Rugimar Marcovistz

    1996-12-01

    Full Text Available O vírus rábico RV194-2, uma variante avirulenta da cepa CVS (Challenge Vírus Standard, produz uma infecção inaparente quando inoculado intracerebralmente em camundongos adultos. Sugerindo que a resposta imunológica do hospedeiro permite a eliminação do vírus do sistema nervoso central. Por esta razão foram estudadas a indução de interferon e a resposta imune humoral em camundongos BALB/c inoculados com vírus RV194-2. Durante a infecção, estes camundongos apresentaram elevados níveis de interferon no plasma e no cérebro com altos títulos de anticorpos neutralizantes anti-rábicos. A 2-5A sintetase. um marcador da ação dos interferons,foi também analisada no cérebro destes animais. Sua atividade, aumentou, paralelamente, á produção de interferon, demonstrando que este interferon é bioquímicamente ativo. O vírus RV194-2 também induziu, 45 dias após sua inoculação, proteção aos animais quando desafiados com a cepa virulenta CVS. Estes resultados demonstram que a cepa RV194-2possui um alto nível imunogênico.RV194-2 rabies virus, an avirulent mutant of CVS strain, induces an inapparent infection limited to the central nervous system (CNS in adult mice inoculated intracerebrally. This fact suggest that immune response of the host is able to eliminate the virus in CNS. For this reason, we have studied the induction of interferon and the humoral immune responses in BALB/c mice after RV194-2 inoculation. These mice presented high levels of interferon in the plasma and in the brain, with elevated levels of neutralizing antirabies antibodies. The 2-5A synthetase, an enzyme marker of interferon action, was analyzed in the brain of inoculated animals. Its enhancement in parallel to the interferon production in the brain, showed biochemical evidence that this interferon is active. Forty five days after RV194-2 virus inoculation, mice were protected against a challenge with the CVS virulent strain. The results presented

  20. ξTauri: a unique laboratory to study the dynamic interaction in a compact hierarchical quadruple system

    Science.gov (United States)

    Nemravová, J. A.; Harmanec, P.; Brož, M.; Vokrouhlický, D.; Mourard, D.; Hummel, C. A.; Cameron, C.; Matthews, J. M.; Bolton, C. T.; Božić, H.; Chini, R.; Dembsky, T.; Engle, S.; Farrington, C.; Grunhut, J. H.; Guenther, D. B.; Guinan, E. F.; Korčáková, D.; Koubský, P.; Kříček, R.; Kuschnig, R.; Mayer, P.; McCook, G. P.; Moffat, A. F. J.; Nardetto, N.; Prša, A.; Ribeiro, J.; Rowe, J.; Rucinski, S.; Škoda, P.; Šlechta, M.; Tallon-Bosc, I.; Votruba, V.; Weiss, W. W.; Wolf, M.; Zasche, P.; Zavala, R. T.

    2016-10-01

    Context. Compact hierarchical systems are important because the effects caused by the dynamical interaction among its members occur ona human timescale. These interactions play a role in the formation of close binaries through Kozai cycles with tides. One such system is ξ Tauri: it has three hierarchical orbits: 7.14 d (eclipsing components Aa, Ab), 145 d (components Aa+Ab, B), and 51 yr (components Aa+Ab+B, C). Aims: We aim to obtain physical properties of the system and to study the dynamical interaction between its components. Methods: Our analysis is based on a large series of spectroscopic photometric (including space-borne) observations and long-baseline optical and infrared spectro-interferometric observations. We used two approaches to infer the system properties: a set of observation-specific models, where all components have elliptical trajectories, and an N-body model, which computes the trajectory of each component by integrating Newton's equations of motion. Results: The triple subsystem exhibits clear signs of dynamical interaction. The most pronounced are the advance of the apsidal line and eclipse-timing variations. We determined the geometry of all three orbits using both observation-specific and N-body models. The latter correctly accounted for observed effects of the dynamical interaction, predicted cyclic variations of orbital inclinations, and determined the sense of motion of all orbits. Using perturbation theory, we demonstrate that prominent secular and periodic dynamical effects are explainable with a quadrupole interaction. We constrained the basic properties of all components, especially of members of the inner triple subsystem and detected rapid low-amplitude light variations that we attribute to co-rotating surface structures of component B. We also estimated the radius of component B. Properties of component C remain uncertain because of its low relative luminosity. We provide an independent estimate of the distance to the system

  1. Rapid spectral analysis for spectral imaging.

    Science.gov (United States)

    Jacques, Steven L; Samatham, Ravikant; Choudhury, Niloy

    2010-07-15

    Spectral imaging requires rapid analysis of spectra associated with each pixel. A rapid algorithm has been developed that uses iterative matrix inversions to solve for the absorption spectra of a tissue using a lookup table for photon pathlength based on numerical simulations. The algorithm uses tissue water content as an internal standard to specify the strength of optical scattering. An experimental example is presented on the spectroscopy of portwine stain lesions. When implemented in MATLAB, the method is ~100-fold faster than using fminsearch().

  2. 波动率度量方法的比较分析——基于LHAR-RV-EVT风险管理%A Comparative Study of Volatility Measures:Based on VaR of LHAR-RV-EVT

    Institute of Scientific and Technical Information of China (English)

    刘广应; 蔡则祥; 张新生

    2013-01-01

    在比较分析已实现波动率(RV)、双幂变差已实现波动率(BPV)、截断双幂变差已实现波动率(TB-PV)、两尺度已实现波动率(TRSV)以及已实现核波动率(RKV)五种高频数据波动率度量方法的理论性质基础上,结合异质自回归已实现波动率(HAR-RV)和GJR-GARCH思想,本文构建LHAR-RV-EVT模型对VaR进行预测,并使用上证指数1分钟数据进行实证分析,结果表明LHAR-RV-EVT能够较为准确地预测VaR、TBPV和BPV优于其他三种波动率度量方法.

  3. Archive of Digitized Analog Boomer and Minisparker Seismic Reflection Data Collected from the Alabama-Mississippi-Louisiana Shelf During Cruises Onboard the R/V Carancahua and R/V Gyre, April and July, 1981

    Science.gov (United States)

    Sanford, Jordan M.; Harrison, Arnell S.; Wiese, Dana S.; Flocks, James G.

    2009-01-01

    In April and July of 1981, the U.S. Geological Survey (USGS) conducted geophysical surveys to investigate the shallow geologic framework of the Alabama-Mississippi-Louisiana Shelf in the northern Gulf of Mexico. Work was conducted onboard the Texas A&M University R/V Carancahua and the R/V Gyre to develop a geologic understanding of the study area and to locate potential hazards related to offshore oil and gas production. While the R/V Carancahua only collected boomer data, the R/V Gyre used a 400-Joule minisparker, 3.5-kilohertz (kHz) subbottom profiler, 12-kHz precision depth recorder, and two air guns. The authors selected the minisparker data set because, unlike with the boomer data, it provided the most complete record. This report is part of a series to digitally archive the legacy analog data collected from the Mississippi-Alabama SHelf (MASH). The MASH data rescue project is a cooperative effort by the USGS and the Minerals Management Service (MMS). This report serves as an archive of high-resolution scanned Tagged Image File Format (TIFF) and Graphics Interchange Format (GIF) images of the original boomer and minisparker paper records, navigation files, trackline maps, Geographic Information System (GIS) files, cruise logs, and formal Federal Geographic Data Committee (FGDC) metadata.

  4. Role of Magnesium Ions in DNA Recognition by the EcoRV Restriction Endonuclease

    Energy Technology Data Exchange (ETDEWEB)

    Zahran, Mai [ORNL; Berezniak, Tomasz [University of Heidelberg; Imhof, Petra [University of Heidelberg; Smith, Jeremy C [ORNL

    2011-01-01

    The restriction endonuclease EcoRV binds two magnesium ions. One of these ions, Mg2+A, binds to the phosphate group where the cleavage occurs and is required for catalysis, but the role of the other ion, Mg2+B is debated. Here, multiple independent molecular dynamics simulations suggest that Mg2+B is crucial for achieving a tightly bound protein DNA complex and stabilizing a conformation that allows cleavage. In the absence of Mg2+B in all simulations the protein DNA hydrogen bond network is significantly disrupted and the sharp kink at the central base pair step of the DNA, which is observed in the two-metal complex, is not present. Also, the active site residues rearrange in such a way that the formation of a nucleophile, required for DNA hydrolysis, is unlikely.

  5. The R/V Folger a Floating Laboratory: Teaching Marine Science Skills on Lake Champlain (Invited)

    Science.gov (United States)

    Manley, P.; Manley, T.

    2013-12-01

    Undergraduate senior work has been required at Middlebury College as far back as 1960's and hands-on experiential learning was and still is the mode for our geology courses. The history of Middlebury College having a research vessel started in the 1970's when Dave Folger started the marine component of our curriculum and obtained the first Middlebury College's research vessel - a coast guard rescue surf boat (Bruno Schmidt). The second Middlebury College research vessel, the R/V Baldwin was purchased in 1985 and was used exclusively in a river-like setting due to its open cockpit and minimal research equipment. In 1990, Middlebury College received a grant from NSF-MRI to upgrade the vessel, to a then state-of the-art small oceanographic vessel including new equipment (CTD, side-scan sonar, ROV, met station, coring devices, computers and navigation). Middlebury College contributed monies to enclose the wheelhouse, install safer diesel engines, as well as a winch and an A-frame to haul in equipment. Over 600+ students used the Baldwin in a variety of geology courses; mainly Oceanography and Marine Geology. In 2010, Middlebury College received an NSF -ARRA grant (American Recovery and Reinvestment Act) to replace the ailing R/V Baldwin with a floating state-of-the art laboratory with the specific goals of increasing 1) access to lake research for Middlebury faculty and students in the biological, chemical, and environmental sciences, 2) the scope of lake research by reducing transit times over this 100km long lake, 3) stability for broad-lake research, 4) improve and expand research capabilities on Lake Champlain, 5) the carrying capacity (both equipment and people), and 6) instructional capability and overnight capabilities. The newly built R/V Folger is a sophisticated research vessel with advanced capabilities that provides a greater capacity to the research infrastructure on Lake Champlain, enhancing interdisciplinary inquiry not only for Middlebury College, but

  6. EXPRES: A Next Generation RV Spectrograph in the Search for Earth-like Worlds

    CERN Document Server

    Jurgenson, C; McCracken, T; Sawyer, D; Szymkowiak, A; Davis, A B; Muller, G; Santoro, F

    2016-01-01

    The EXtreme PREcision Spectrograph (EXPRES) is an optical fiber fed echelle instrument being designed and built at the Yale Exoplanet Laboratory to be installed on the 4.3-meter Discovery Channel Telescope operated by Lowell Observatory. The primary science driver for EXPRES is to detect Earth-like worlds around Sun-like stars. With this in mind, we are designing the spectrograph to have an instrumental precision of 15 cm/s so that the on-sky measurement precision (that includes modeling for RV noise from the star) can reach to better than 30 cm/s. This goal places challenging requirements on every aspect of the instrument development, including optomechanical design, environmental control, image stabilization, wavelength calibration, and data analysis. In this paper we describe our error budget, and instrument optomechanical design.

  7. Association of cGH EcoRV Gene with Production in Tolaki Chicken

    Directory of Open Access Journals (Sweden)

    Muhammad Amrullah Pagala

    2017-02-01

    Full Text Available cGH (Chicken Growth Hormone gene plays a crucial role in production responses of chicken. The objective of the research was to investigate the association of cGH gene with production in Tolaki chicken. Tolaki chicken is native chickens from Southeast Sulawesi Province of Indonesian. cGH gene was genotyped in 58 Tolaki chicken with PCR-RFLP. PCR was used to amplify genomic DNA for GH gene (399 bp. The amplicon was cutted by EcoRV and produced three genotypes: AA, AG, and GG and two alleles: A and G allele. The study showed the association of GH gene polymorphism with Production traits. GG genotype have better production (daily weight gain and feed conversion than AG genotype in Tolaki chicken, providing evidence that GH gene might be an important candidate gene for production traits.

  8. Perspective on sequence evolution of microsatellite locus (CCGn in Rv0050 gene from Mycobacterium tuberculosis

    Directory of Open Access Journals (Sweden)

    Jin Ruiliang

    2011-08-01

    Full Text Available Abstract Background The mycobacterial genome is inclined to polymerase slippage and a high mutation rate in microsatellite regions due to high GC content and absence of a mismatch repair system. However, the exact molecular mechanisms underlying microsatellite variation have not been fully elucidated. Here, we investigated mutation events in the hyper-variable trinucleotide microsatellite locus MML0050 located in the Rv0050 gene of W-Beijing and non-W-Beijing Mycobacterium tuberculosis strains in order to gain insight into the genomic structure and activity of repeated regions. Results Size analysis indicated the presence of five alleles that differed in length by three base pairs. Moreover, nucleotide gains occurred more frequently than loses in this trinucleotide microsatellite. Mutation frequency was not completely related with the total length, though the relative frequency in the longest allele was remarkably higher than that in the shortest. Sequence analysis was able to detect seven alleles and revealed that point mutations enhanced the level of locus variation. Introduction of an interruptive motif correlated with the total allele length and genetic lineage, rather than the length of the longest stretch of perfect repeats. Finally, the level of locus variation was drastically different between the two genetic lineages. Conclusion The Rv0050 locus encodes the bifunctional penicillin-binding protein ponA1 and is essential to mycobacterial survival. Our investigations of this particularly dynamic genomic region provide insights into the overall mode of microsatellite evolution. Specifically, replication slippage was implicated in the mutational process of this microsatellite and a sequence-based genetic analysis was necessary to determine that point mutation events acted to maintain microsatellite size integrity while providing genomic diversity.

  9. FCGR2C polymorphisms associate with HIV-1 vaccine protection in RV144 trial

    Science.gov (United States)

    Li, Shuying S.; Gilbert, Peter B.; Tomaras, Georgia D.; Kijak, Gustavo; Ferrari, Guido; Thomas, Rasmi; Pyo, Chul-Woo; Zolla-Pazner, Susan; Montefiori, David; Liao, Hua-Xin; Nabel, Gary; Pinter, Abraham; Evans, David T.; Gottardo, Raphael; Dai, James Y.; Janes, Holly; Morris, Daryl; Fong, Youyi; Edlefsen, Paul T.; Li, Fusheng; Frahm, Nicole; Alpert, Michael D.; Prentice, Heather; Rerks-Ngarm, Supachai; Pitisuttithum, Punnee; Kaewkungwal, Jaranit; Nitayaphan, Sorachai; Robb, Merlin L.; O’Connell, Robert J.; Haynes, Barton F.; Michael, Nelson L.; Kim, Jerome H.; McElrath, M. Juliana; Geraghty, Daniel E.

    2014-01-01

    The phase III RV144 HIV-1 vaccine trial estimated vaccine efficacy (VE) to be 31.2%. This trial demonstrated that the presence of HIV-1–specific IgG-binding Abs to envelope (Env) V1V2 inversely correlated with infection risk, while the presence of Env-specific plasma IgA Abs directly correlated with risk of HIV-1 infection. Moreover, Ab-dependent cellular cytotoxicity responses inversely correlated with risk of infection in vaccine recipients with low IgA; therefore, we hypothesized that vaccine-induced Fc receptor–mediated (FcR-mediated) Ab function is indicative of vaccine protection. We sequenced exons and surrounding areas of FcR-encoding genes and found one FCGR2C tag SNP (rs114945036) that associated with VE against HIV-1 subtype CRF01_AE, with lysine at position 169 (169K) in the V2 loop (CRF01_AE 169K). Individuals carrying CC in this SNP had an estimated VE of 15%, while individuals carrying CT or TT exhibited a VE of 91%. Furthermore, the rs114945036 SNP was highly associated with 3 other FCGR2C SNPs (rs138747765, rs78603008, and rs373013207). Env-specific IgG and IgG3 Abs, IgG avidity, and neutralizing Abs inversely correlated with CRF01_AE 169K HIV-1 infection risk in the CT- or TT-carrying vaccine recipients only. These data suggest a potent role of Fc-γ receptors and Fc-mediated Ab function in conferring protection from transmission risk in the RV144 VE trial. PMID:25105367

  10. Heave Compensated GLAD800 Coring from the R/V Knorr: a Progress Report

    Science.gov (United States)

    Nielson, D.; Mountain, G.; Pardey, M.; Austin, J.; Alexander, C.

    2001-12-01

    Despite potential applications to studies of stratal architecture, sea-level history, land-sea interaction, and rapid climate change, scientific drilling with high core recovery in shallow marine settings has been thwarted by several challenges. Among these has been the problem of maintaining hole stability while penetrating unconsolidated lithologies from a floating, open-ocean platform. We report on progress in overcoming this barrier. The GLAD800 coring system, originally developed as a joint venture between the International Scientific Drilling Program and DOSECC to collect long, high-resolution cores in modern lakes, has been adapted for deploying from the R/V Knorr. As in lake-based operations, the drilling system can continuously sample sediments of different composition and stiffness to a total depth of 800m below the rig floor using HWT drill rods and riser pipe. Core is collected in standard ODP-size plastic liners. A modular design provides inexpensive and easily transportable operations. The latest advance is the installation of an active heave compensation (AHC) system that accommodates as much as 8 feet of vertical rig motion. This minimizes excursions in the total weight of the bit at the cutting face, a major concern in achieving the high core recovery needed for scientific purposes. We show results of testing this AHC-equipped GLAD800 rig during a 5-day operation in November. We drilled through the existing 'moon pool' of the R/V Knorr on the outer shelf south of Martha's Vineyard. This technological development and ship time is funded by the Office of Naval Research, and if successful, will be extended to core numerous drill holes 10's to 100's of meters into the New Jersey shelf during 2002.

  11. Bipolar spectral associative memories.

    Science.gov (United States)

    Spencer, R G

    2001-01-01

    Nonlinear spectral associative memories are proposed as quantized frequency domain formulations of nonlinear, recurrent associative memories in which volatile network attractors are instantiated by attractor waves. In contrast to conventional associative memories, attractors encoded in the frequency domain by convolution may be viewed as volatile online inputs, rather than nonvolatile, off-line parameters. Spectral memories hold several advantages over conventional associative memories, including decoder/attractor separability and linear scalability, which make them especially well suited for digital communications. Bit patterns may be transmitted over a noisy channel in a spectral attractor and recovered at the receiver by recurrent, spectral decoding. Massive nonlocal connectivity is realized virtually, maintaining high symbol-to-bit ratios while scaling linearly with pattern dimension. For n-bit patterns, autoassociative memories achieve the highest noise immunity, whereas heteroassociative memories offer the added flexibility of achieving various code rates, or degrees of extrinsic redundancy. Due to linear scalability, high noise immunity and use of conventional building blocks, spectral associative memories hold much promise for achieving robust communication systems. Simulations are provided showing bit error rates for various degrees of decoding time, computational oversampling, and signal-to-noise ratio.

  12. Noncomputable Spectral Sets

    CERN Document Server

    Teutsch, J

    2007-01-01

    It is possible to enumerate all computer programs. In particular, for every partial computable function, there is a shortest program which computes that function. f-MIN is the set of indices for shortest programs. In 1972, Meyer showed that f-MIN is Turing equivalent to 0'', the halting set with halting set oracle. This paper generalizes the notion of shortest programs, and we use various measures from computability theory to describe the complexity of the resulting "spectral sets." We show that under certain Godel numberings, the spectral sets are exactly the canonical sets 0', 0'', 0''', ... up to Turing equivalence. This is probably not true in general, however we show that spectral sets always contain some useful information. We show that immunity, or "thinness" is a useful characteristic for distinguishing between spectral sets. In the final chapter, we construct a set which neither contains nor is disjoint from any infinite arithmetic set, yet it is 0-majorized and contains a natural spectral set. Thus ...

  13. Parametric Explosion Spectral Model

    Energy Technology Data Exchange (ETDEWEB)

    Ford, S R; Walter, W R

    2012-01-19

    Small underground nuclear explosions need to be confidently detected, identified, and characterized in regions of the world where they have never before occurred. We develop a parametric model of the nuclear explosion seismic source spectrum derived from regional phases that is compatible with earthquake-based geometrical spreading and attenuation. Earthquake spectra are fit with a generalized version of the Brune spectrum, which is a three-parameter model that describes the long-period level, corner-frequency, and spectral slope at high-frequencies. Explosion spectra can be fit with similar spectral models whose parameters are then correlated with near-source geology and containment conditions. We observe a correlation of high gas-porosity (low-strength) with increased spectral slope. The relationship between the parametric equations and the geologic and containment conditions will assist in our physical understanding of the nuclear explosion source.

  14. Photovoltaic spectral responsivity measurements

    Energy Technology Data Exchange (ETDEWEB)

    Emery, K.; Dunlavy, D.; Field, H.; Moriarty, T. [National Renewable Energy Lab., Golden, CO (United States)

    1998-09-01

    This paper discusses the various elemental random and nonrandom error sources in typical spectral responsivity measurement systems. The authors focus specifically on the filter and grating monochrometer-based spectral responsivity measurement systems used by the Photovoltaic (PV) performance characterization team at NREL. A variety of subtle measurement errors can occur that arise from a finite photo-current response time, bandwidth of the monochromatic light, waveform of the monochromatic light, and spatial uniformity of the monochromatic and bias lights; the errors depend on the light source, PV technology, and measurement system. The quantum efficiency can be a function of he voltage bias, light bias level, and, for some structures, the spectral content of the bias light or location on the PV device. This paper compares the advantages and problems associated with semiconductor-detector-based calibrations and pyroelectric-detector-based calibrations. Different current-to-voltage conversion and ac photo-current detection strategies employed at NREL are compared and contrasted.

  15. On the Existence and Uniqueness of Rv-Generalized Solution for Dirichlet Problem with Singularity on All Boundary

    Directory of Open Access Journals (Sweden)

    V. Rukavishnikov

    2014-01-01

    Full Text Available The existence and uniqueness of the Rv-generalized solution for the first boundary value problem and a second order elliptic equation with coordinated and uncoordinated degeneracy of input data and with strong singularity solution on all boundary of a two-dimensional domain are established.

  16. The SecB-like chaperone Rv1957 from Mycobacterium tuberculosis: crystallization and X-ray crystallographic analysis.

    Science.gov (United States)

    Lu, Zuokun; Wang, Han; Yu, TingTing

    2016-06-01

    Protein export is important in all bacteria, and bacteria have evolved specialized export machineries to fulfil this task. In Mycobacterium tuberculosis, the causative agent of tuberculosis, the general secretion pathway (Sec pathway) is conserved and is essential in performing the export of proteins. The bacterial Sec pathway post-translationally exports unfolded proteins out of the cytoplasm, and the core of the Sec pathway is composed of a heterotrimeric membrane-embedded channel, SecYEG, and two cytosolic components, SecA and SecB. SecB functions by stabilizing unfolded proteins, maintaining them in an export-competent state. Although SecB is mainly found in Proteobacteria, a SecB-like protein, Rv1957, that controls a stress-response toxin-antitoxin system, is found in M. tuberculosis. Rv1957 can also functionally replace the Escherichia coli SecB chaperone both in vivo and in vitro. In this work, the production, crystallization and X-ray crystallographic analysis of Rv1957 are reported. Notably, diffraction-quality crystals were obtained only at high concentrations of dimethyl sulfoxide, i.e. about 12%(v/v). The crystals of Rv1957 belonged to space group P212121, with unit-cell parameters a = 64.5, b = 92.0, c = 115.4 Å.

  17. The potential impact of RV144-like vaccines in rural South Africa: A study using the STDSIM microsimulation model

    NARCIS (Netherlands)

    J.A.C. Hontelez (Jan); N.J.D. Nagelkerke (Nico); T. Bärnighausen (Till); R. Bakker (Roel); F. Tanser (Frank); M.L. Newell (Marie Louise); M.N. Lurie (Mark N.); R.M.P.M. Baltussen (Rob); S.J. de Vlas (Sake)

    2011-01-01

    textabstractBackground: The only successful HIV vaccine trial to date is the RV144 trial of the ALVAC/AIDSVAX vaccine in Thailand, which showed an overall incidence reduction of 31%. Most cases were prevented in the first year, suggesting a rapidly waning efficacy. Here, we predict the population

  18. The potential impact of RV144-like vaccines in rural South Africa: a study using the STDSIM microsimulation model.

    NARCIS (Netherlands)

    Hontelez, J.A.; Nagelkerke, N.; Barnighausen, T.; Bakker, R.; Tanser, F.; Newell, M.L.; Lurie, M.N.; Baltussen, R.M.P.M.; Vlas, S.J. de

    2011-01-01

    BACKGROUND: The only successful HIV vaccine trial to date is the RV144 trial of the ALVAC/AIDSVAX vaccine in Thailand, which showed an overall incidence reduction of 31%. Most cases were prevented in the first year, suggesting a rapidly waning efficacy. Here, we predict the population level impact

  19. VizieR Online Data Catalog: WASP 127, 136 and 138 RV and light curves (Lam+, 2017)

    Science.gov (United States)

    Lam, K. W. F.; Faedi, F.; Brown, D. J. A.; Anderson, D. R.; Delrez, L.; Gillon, M.; Hebrard, G.; Lendl, M.; Mancini, L.; Southworth, J.; Smalley, B.; Triaud, A. H. M.; Turner, O. D.; Hay, K. L.; Armstrong, D. J.; Barros, S. C. C.; Bonomo, A. S.; Bouchy, F.; Boumis, P.; Collier, Cameron A.; Doyle, A. P.; Hellier, C.; Henning, T.; Jehin, E.; King, G.; Kirk, J.; Louden, T.; Maxted, P. F. L.; McCormac, J. J.; Osborn, H. P.; Palle, E.; Pepe, F.; Pollacco, D.; Prieto-Arranz, J.; Queloz, D.; Rey, J.; Segransan, D.; Udry, S.; Walker, S.; West, R. G.; Wheatley, P. J.

    2016-11-01

    Photometric time-series obtained for the WASP-127, WASP-136, and WASP-138, and RV time-series obtained for the three systems. The photometric time-series were obtained using the TRAPPIST and Euler-Swiss telescopes. The RVs were obtained using the Euler/CORALIE spectrograph. (6 data files).

  20. Stringent homology-based prediction of H. sapiens-M. tuberculosis H37Rv protein-protein interactions.

    Science.gov (United States)

    Zhou, Hufeng; Gao, Shangzhi; Nguyen, Nam Ninh; Fan, Mengyuan; Jin, Jingjing; Liu, Bing; Zhao, Liang; Xiong, Geng; Tan, Min; Li, Shijun; Wong, Limsoon

    2014-04-08

    H. sapiens-M. tuberculosis H37Rv protein-protein interaction (PPI) data are essential for understanding the infection mechanism of the formidable pathogen M. tuberculosis H37Rv. Computational prediction is an important strategy to fill the gap in experimental H. sapiens-M. tuberculosis H37Rv PPI data. Homology-based prediction is frequently used in predicting both intra-species and inter-species PPIs. However, some limitations are not properly resolved in several published works that predict eukaryote-prokaryote inter-species PPIs using intra-species template PPIs. We develop a stringent homology-based prediction approach by taking into account (i) differences between eukaryotic and prokaryotic proteins and (ii) differences between inter-species and intra-species PPI interfaces. We compare our stringent homology-based approach to a conventional homology-based approach for predicting host-pathogen PPIs, based on cellular compartment distribution analysis, disease gene list enrichment analysis, pathway enrichment analysis and functional category enrichment analysis. These analyses support the validity of our prediction result, and clearly show that our approach has better performance in predicting H. sapiens-M. tuberculosis H37Rv PPIs. Using our stringent homology-based approach, we have predicted a set of highly plausible H. sapiens-M. tuberculosis H37Rv PPIs which might be useful for many of related studies. Based on our analysis of the H. sapiens-M. tuberculosis H37Rv PPI network predicted by our stringent homology-based approach, we have discovered several interesting properties which are reported here for the first time. We find that both host proteins and pathogen proteins involved in the host-pathogen PPIs tend to be hubs in their own intra-species PPI network. Also, both host and pathogen proteins involved in host-pathogen PPIs tend to have longer primary sequence, tend to have more domains, tend to be more hydrophilic, etc. And the protein domains from both

  1. Spectral Networks and Snakes

    CERN Document Server

    Gaiotto, Davide; Neitzke, Andrew

    2012-01-01

    We apply and illustrate the techniques of spectral networks in a large collection of A_{K-1} theories of class S, which we call "lifted A_1 theories." Our construction makes contact with Fock and Goncharov's work on higher Teichmuller theory. In particular we show that the Darboux coordinates on moduli spaces of flat connections which come from certain special spectral networks coincide with the Fock-Goncharov coordinates. We show, moreover, how these techniques can be used to study the BPS spectra of lifted A_1 theories. In particular, we determine the spectrum generators for all the lifts of a simple superconformal field theory.

  2. Spectral library searching in proteomics.

    Science.gov (United States)

    Griss, Johannes

    2016-03-01

    Spectral library searching has become a mature method to identify tandem mass spectra in proteomics data analysis. This review provides a comprehensive overview of available spectral library search engines and highlights their distinct features. Additionally, resources providing spectral libraries are summarized and tools presented that extend experimental spectral libraries by simulating spectra. Finally, spectrum clustering algorithms are discussed that utilize the same spectrum-to-spectrum matching algorithms as spectral library search engines and allow novel methods to analyse proteomics data.

  3. Novel vaccine potential of Rv3131, a DosR regulon-encoded putative nitroreductase, against hyper-virulent Mycobacterium tuberculosis strain K

    Science.gov (United States)

    Kwon, Kee Woong; Kim, Woo Sik; Kim, Hongmin; Han, Seung Jung; Hahn, Mi-Young; Lee, Jong Seok; Nam, Ki Taek; Cho, Sang-Nae; Shin, Sung Jae

    2017-01-01

    Accumulating evidence indicates that latency-associated Mycobacterium tuberculosis (Mtb)-specific antigens from the dormancy survival regulator regulon (DosR) may be promising novel vaccine target antigens for the development of an improved tuberculosis vaccine. After transcriptional profiling of DosR-related genes in the hyper-virulent Beijing Mtb strain K and the reference Mtb strain H37Rv, we selected Rv3131, a hypothetical nitroreductase, as a vaccine antigen and evaluated its vaccine efficacy against Mtb K. Mtb K exhibited stable and constitutive up-regulation of rv3131 relative to Mtb H37Rv under three different growth conditions (at least 2-fold induction) including exponential growth in normal culture conditions, hypoxia, and inside macrophages. Mice immunised with Rv3131 formulated in GLA-SE, a well-defined TLR4 adjuvant, displayed enhanced Rv3131-specific IFN-γ and serum IgG2c responses along with effector/memory T cell expansion and remarkable generation of Rv3131-specific multifunctional CD4+ T cells co-producing TNF-α, IFN-γ and IL-2 in both spleen and lung. Following challenge with Mtb K, the Rv3131/GLA-SE-immunised group exhibited a significant reduction in bacterial number and less extensive lung inflammation accompanied by the obvious persistence of Rv3131-specific multifunctional CD4+ T cells. These results suggest that Rv3131 could be an excellent candidate for potential use in a multi-antigenic Mtb subunit vaccine, especially against Mtb Beijing strains. PMID:28272457

  4. RV Myocardial Strain During Pre-Load Augmentation Is Associated With Exercise Capacity in Patients With Chronic HF.

    Science.gov (United States)

    Kusunose, Kenya; Yamada, Hirotsugu; Nishio, Susumu; Ishii, Ayumi; Hirata, Yukina; Seno, Hiromitsu; Saijo, Yoshihito; Ise, Takayuki; Yamaguchi, Koji; Yagi, Shusuke; Soeki, Takeshi; Wakatsuki, Tetsuzo; Sata, Masataka

    2017-07-13

    The aim of this study was to assess the relationship between right ventricular (RV) function during pre-load augmentation and exercise tolerance. Peak oxygen uptake (VO2) is a strong predictor of mortality in chronic heart failure. Cardiac function during pre-load augmentation is an important part of the phenomenon in the evaluation of exercise capacity. We prospectively performed echocardiographic studies in 68 chronic heart failure patients with cardiopulmonary exercise testing (mean age 60 ± 12 years; 69% male). After resting evaluations, echocardiographic parameters were repeated during leg positive pressure (LPP). Exercise capacity was assessed by peak VO2 in all patients (left ventricular ejection fraction: 43 ± 15%). Patients with severely reduced exercise capacity (peak VO2 <14 ml/kg/min) had significantly lower stroke volume index, left ventricular global longitudinal strain and RV strain and higher filling pressure (E/e' and pulmonary arterial systolic pressure) than the remainder. Stroke volume index (β = 0.49), global longitudinal strain (β = -0.61), E/e' (β = -0.32), pulmonary arterial systolic pressure (β = -0.57), and RV strain (β = -0.66) during LPP were independently correlated to peak VO2 (all p < 0.01). RV strain during LPP was the most powerful predictor in identifying patients with severely reduced exercise capacity (cut off value: -17%; sensitivity: 81%; specificity: 88%; areas under the curve: 0.88, p < 0.001) compared with other variables including resting parameters. RV strain during pre-load augmentation correlated independently to peak VO2 and was a powerful predictor in identifying patients with severely reduced exercise capacity. Copyright © 2017 American College of Cardiology Foundation. Published by Elsevier Inc. All rights reserved.

  5. Mycobacterium tuberculosis PPE68 and Rv2626c genes contribute to the host cell necrosis and bacterial escape from macrophages.

    Science.gov (United States)

    Danelishvili, Lia; Everman, Jamie; Bermudez, Luiz E

    2016-01-01

    Alveolar macrophages are the main line of innate immune response against M. tuberculosis (Mtb) infection. However, these cells serve as the major intracellular niche for Mtb enhancing its survival, replication and, later on, cell-to-cell spread. Mtb-associated cytotoxicity of macrophages has been well documented, but limited information exists about mechanisms by which the pathogen induces cell necrosis. To identify virulence factors involved in the induction of necrosis, we screened 5,000 transposon mutants of Mtb for clones that failed to promote the host cell necrosis in a similar manner as the wild-type bacterium. Five Mtb mutants were identified as potential candidates inducing significantly lower levels of THP-1 cell damage in contrast to the H37Rv wild-type infection. Reduced levels of the cell damage by necrosis deficient mutants (NDMs) were also associated with delayed damage of mitochondrial membrane permeability when compared with the wild-type infection over time. Two knockout mutants of the Rv3873 gene, encoding a cell wall PPE68 protein of RD1 region, were identified out of 5 NDMs. Further investigation lead to the observation that PPE68 protein interacts and exports several unknown or known surface/secreted proteins, among them Rv2626c is associated with the host cell necrosis. When the Rv2626c gene is deleted from the genome of Mtb, the bacterium displays significantly less necrosis in THP-1 cells and, conversely, the overexpression of Rv2626c promotes the host cell necrosis at early time points of infections in contrast to the wild-type strain.

  6. SU-E-T-599: Patient Safety Enhancements Through a Study of R&V System Override Data

    Energy Technology Data Exchange (ETDEWEB)

    Hendrickson, K; Vimolchalao, S [University of Washington, Seattle, WA (United States)

    2015-06-15

    Purpose: Record and verify (R&V) software systems include safety checks that compare actual machine parameters with prescribed values for a patient’s treatment, such as treatment couch position, linac, energy, and MUs. The therapist is warned of a mismatch with a pop-up and prompted to approve an override in order to continue without changes. Override approval is often legitimate, but the pop-up can also genuinely indicate a problem that would Result in the wrong treatment. When there are numerous pop-up warnings, human nature leads us to approve any override without careful reading, undermining the effectiveness of the safety mechanism. Methods: Override data was collected from our R&V system for all patients treated between October 8 and 29, 2012, on four linacs and entered into a spreadsheet. Additional data collected included treatment technique, disease site, immobilization, time, linac, and whether localization images were obtained. Data were analyzed using spreadsheet tools to reveal trends, patterns and associations that might suggest appropriate process changes that could decrease the total number of overrides. Results: 76 out of 113 patients had overrides. Out of the 944 treatments, 599 override items were generated. The majority were due to couch positions. 74 of the 84 overrides on a linac equipped with a 6D couch were due to the use of the rotational corrections and the fact that the 6D couch control does not communicate with the R&V system; translations required to rotate the couch appear to the R&V system as translations outside the tolerance range. Conclusion: Many findings were interesting but did not suggest a process change. Proposed process changes include creating site-specific instead of just technique-specific tolerance tables for couch shifts. Proposed improvements to the vendor are to facilitate direct communication between the 6D couch and the R&V system to eliminate those override warnings related to lack of communication.

  7. Coupled evolutions of the stellar obliquity, orbital distance, and planet's radius due to the Ohmic dissipation induced in a diamagnetic hot Jupiter around a magnetic T Tauri star

    CERN Document Server

    Chang, Yu-Ling; Gu, Pin-Gao

    2012-01-01

    We revisit the calculation of the Ohmic dissipation in a hot Jupiter presented in Laine et al. (2008) by considering more realistic interior structures, stellar obliquity, and the resulting orbital evolution. In this simplified approach, the young hot Jupiter of one Jupiter mass is modelled as a diamagnetic sphere with a finite resistivity, orbiting across tilted stellar magnetic dipole fields in vacuum. Since the induced Ohmic dissipation occurs mostly near the planet's surface, we find that the dissipation is unable to significantly expand the young hot Jupiter. Nevertheless, the planet inside a small co-rotation orbital radius can undergo orbital decay by the dissipation torque and finally overfill its Roche lobe during the T Tauri star phase. The stellar obliquity can evolve significantly if the magnetic dipole is parallel/anti-parallel to the stellar spin. Our results are validated by the general torque-dissipation relation in the presence of the stellar obliquity. We also run the fiducial model in Laine...

  8. Magnetohydrodynamic modeling of the accretion shocks in classical T Tauri stars: the role of local absorption on the X-ray emission

    CERN Document Server

    Bonito, R; Argiroffi, C; Miceli, M; Peres, G; Matsakos, T; Stehle, C; Ibgui, L

    2014-01-01

    We investigate the properties of X-ray emission from accretion shocks in classical T Tauri stars (CTTSs), generated where the infalling material impacts the stellar surface. Both observations and models of the accretion process reveal several aspects that are still unclear: the observed X-ray luminosity in accretion shocks is below the predicted value, and the density versus temperature structure of the shocked plasma, with increasing densities at higher temperature, deduced from the observations, is at odds with that proposed in the current picture of accretion shocks. To address these open issues we investigate whether a correct treatment of the local absorption by the surrounding medium is crucial to explain the observations. To this end, we describe the impact of an accretion stream on a CTTS by considering a magnetohydrodynamic model. From the model results we synthesize the X-ray emission from the accretion shock by producing maps and spectra. We perform density and temperature diagnostics on the synthe...

  9. Blue spectral inflation

    CERN Document Server

    Schunck, Franz E

    2008-01-01

    We reconsider the nonlinear second order Abel equation of Stewart and Lyth, which follows from a nonlinear second order slow-roll approximation. We find a new eigenvalue spectrum in the blue regime. Some of the discrete values of the spectral index n_s have consistent fits to the cumulative COBE data as well as to recent ground-base CMB experiments.

  10. Large Spectral Library Problem

    Energy Technology Data Exchange (ETDEWEB)

    Chilton, Lawrence K.; Walsh, Stephen J.

    2008-10-03

    Hyperspectral imaging produces a spectrum or vector at each image pixel. These spectra can be used to identify materials present in the image. In some cases, spectral libraries representing atmospheric chemicals or ground materials are available. The challenge is to determine if any of the library chemicals or materials exist in the hyperspectral image. The number of spectra in these libraries can be very large, far exceeding the number of spectral channels collected in the ¯eld. Suppose an image pixel contains a mixture of p spectra from the library. Is it possible to uniquely identify these p spectra? We address this question in this paper and refer to it as the Large Spectral Library (LSL) problem. We show how to determine if unique identi¯cation is possible for any given library. We also show that if p is small compared to the number of spectral channels, it is very likely that unique identi¯cation is possible. We show that unique identi¯cation becomes less likely as p increases.

  11. Quarkonium Spectral Functions

    Energy Technology Data Exchange (ETDEWEB)

    Mocsy, Agnes [Department of Mathematics and Science, Pratt Institute, Brooklyn, NY 11205 (United States)

    2009-11-01

    In this talk I summarize the progress achieved in recent years on the understanding of quarkonium properties at finite temperature. Theoretical studies from potential models, lattice QCD, and effective field theories are discussed. I also highlight a bridge from spectral functions to experiment.

  12. Spectral representation of fingerprints

    NARCIS (Netherlands)

    Xu, Haiyun; Bazen, Asker M.; Veldhuis, Raymond N.J.; Kevenaar, Tom A.M.; Akkermans, Anton H.M.

    2007-01-01

    Most fingerprint recognition systems are based on the use of a minutiae set, which is an unordered collection of minutiae locations and directions suffering from various deformations such as translation, rotation and scaling. The spectral minutiae representation introduced in this paper is a novel m

  13. Extended Magnetospheres in Pre-main-sequence Evolution: From T Tauri Stars to the Brown Dwarf Limit

    Science.gov (United States)

    Gómez de Castro, Ana I.; Marcos-Arenal, Pablo

    2012-04-01

    Low-mass pre-main-sequence stars, i.e., T Tauri stars (TTSs), strongly radiate at high energies, from X-rays to the ultraviolet (UV). This excess radiation with respect to main-sequence cool stars (MSCSs) is associated with the accretion process, i.e., it is produced in the extended magnetospheres, in the accretion shocks on the stellar surface, and in the outflows. Although evidence of accretion shocks and outflow contribution to the high-energy excess have been recently addressed, there is not an updated revision of the magnetospheric contribution. This article addresses this issue. The UV observations of the TTSs in the well-known Taurus region have been analyzed together with the XMM-Newton observations compiled in the XEST survey. For the first time the high sensitivity of the Hubble Space Telescope UV instrumentation has allowed measurement of the UV line fluxes of TTSs to M8 type. UV- and X-ray-normalized fluxes have been determined to study the extent and properties of the TTS magnetospheres as a class. They have been compared with the atmospheres of the MSCSs. The main results from this analysis are (1) the normalized fluxes of all the tracers are correlated; this correlation is independent of the broad mass range and the hardness of the X-ray radiation field; (2) the TTS correlations are different than the MSCS correlations; (3) there is a very significant excess emission in O I in the TTSs compared with MSCSs that seems to be caused by recombination radiation from the disk atmosphere after photoionization by extreme UV radiation; the Fe II/Mg II recombination continuum has also been detected in several TTSs and most prominently in AA Tau; and (4) the normalized flux of the UV tracers anticorrelates with the strength of the X-ray flux, i.e., the stronger the X-ray surface flux is, the weaker the observed UV flux. This last behavior is counterintuitive within the framework of stellar dynamo theory and suggests that UV emission can be produced in the

  14. Spectral-collocation variational integrators

    Science.gov (United States)

    Li, Yiqun; Wu, Boying; Leok, Melvin

    2017-03-01

    Spectral methods are a popular choice for constructing numerical approximations for smooth problems, as they can achieve geometric rates of convergence and have a relatively small memory footprint. In this paper, we introduce a general framework to convert a spectral-collocation method into a shooting-based variational integrator for Hamiltonian systems. We also compare the proposed spectral-collocation variational integrators to spectral-collocation methods and Galerkin spectral variational integrators in terms of their ability to reproduce accurate trajectories in configuration and phase space, their ability to conserve momentum and energy, as well as the relative computational efficiency of these methods when applied to some classical Hamiltonian systems. In particular, we note that spectrally-accurate variational integrators, such as the Galerkin spectral variational integrators and the spectral-collocation variational integrators, combine the computational efficiency of spectral methods together with the geometric structure-preserving and long-time structural stability properties of symplectic integrators.

  15. Role of Mutations in Dihydrofolate Reductase DfrA (Rv2763c) and Thymidylate Synthase ThyA (Rv2764c) in Mycobacterium tuberculosis Drug Resistance

    KAUST Repository

    Koser, C. U.

    2010-09-17

    We would like to comment on a number of recent reports in this journal (6, 8, 12, 18) concerning Mycobacterium tuberculosis dihydrofolate reductase (DHFR), encoded by dfrA (Rv2763c). Around 36% of phenotypically para-aminosalicylic acid (PAS)-resistant M. tuberculosis strains harbor mutations in thyA (Rv2764c), which encodes a thymidylate synthase (20). In their effort to elucidate the remaining unknown resistance mechanism(s), Mathys et al. extended their sequence analysis to a number of additional genes, including dfrA (12). It was unclear whether the three dfrA mutations they identified in the PAS-resistant strains P-693 and P-3158 could contribute to PAS resistance on their own. Nonetheless, these findings are notable for two reasons. First, isoniazid (INH) has been shown to inhibit M. tuberculosis DHFR in vitro (1). Whether the same holds true for ethionamide, which shares a number of common resistance mechanisms with INH, was not tested (J. Blanchard, personal communication). In any case, the clinical relevance of DHFR-mediated INH resistance remains enigmatic. To date, only Ho et al. have addressed this question, but they did not identify any dfrA mutations in a screen of 127 INH-resistant clinical isolates (8). Consequently, Mathys et al. remain the first to describe mutations in this target (12). However, given that isolates with mutated DHFR are members of a cluster with baseline INH resistance, the importance of these mutations with respect to INH resistance remains unclear. Irrespective of their relevance in INH resistance, these dfrA mutations are noteworthy for a second reason. Contrary to previous wisdom, Forgacs et al. recently showed that M. tuberculosis is sensitive to the drug combination trimethoprim-sulfamethoxazole (TMP-SMX) (6, 18). DHFR is competitively inhibited by TMP, and consequently, mutations therein lead to resistance in a variety of organisms (9, 16, 19). The crystal structures of the wild-type M. tuberculosis DHFR in complex with

  16. Wavelength conversion based spectral imaging

    DEFF Research Database (Denmark)

    Dam, Jeppe Seidelin

    There has been a strong, application driven development of Si-based cameras and spectrometers for imaging and spectral analysis of light in the visible and near infrared spectral range. This has resulted in very efficient devices, with high quantum efficiency, good signal to noise ratio and high...... resolution for this spectral region. Today, an increasing number of applications exists outside the spectral region covered by Si-based devices, e.g. within cleantech, medical or food imaging. We present a technology based on wavelength conversion which will extend the spectral coverage of state of the art...... visible or near infrared cameras and spectrometers to include other spectral regions of interest....

  17. Variability of stellar granulation and convective blueshift with spectral type and magnetic activity. I. K and G main sequence stars

    Science.gov (United States)

    Meunier, N.; Lagrange, A.-M.; Mbemba Kabuiku, L.; Alex, M.; Mignon, L.; Borgniet, S.

    2017-01-01

    Context. In solar-type stars, the attenuation of convective blueshift by stellar magnetic activity dominates the RV (radial velocity) variations over the low amplitude signal induced by low mass planets. Models of stars that differ from the Sun will require a good knowledge of the attenuation of the convective blueshift to estimate its impact on the variations. Aims: It is therefore crucial to precisely determine not only the amplitude of the convective blueshift for different types of stars, but also the dependence of this convective blueshift on magnetic activity, as these are key factors in our model producing the RV. Methods: We studied a sample of main sequence stars with spectral types from G0 to K2 and focused on their temporally averaged properties: the activity level and a criterion allowing to characterise the amplitude of the convective blueshift. This criterion is derived from the dependence of the convective blueshift with the intensity at the bottom of a large set of selected spectral lines. Results: We find the differential velocity shifts of spectral lines due to convection to depend on the spectral type, the wavelength (this dependence is correlated with the Teff and activity level), and on the activity level. This allows us to quantify the dependence of granulation properties on magnetic activity for stars other than the Sun. We are indeed able to derive a significant dependence of the convective blueshift on activity level for all types of stars. The attenuation factor of the convective blueshift appears to be constant over the considered range of spectral types. We derive a convective blueshift which decreases towards lower temperatures, with a trend in close agreement with models for Teff lower than 5800 K, but with a significantly larger global amplitude. Differences also remain to be examined in detail for larger Teff. We finally compare the observed RV variation amplitudes with those that could be derived from our convective blueshift using

  18. Boosting of HIV envelope CD4 binding site antibodies with long variable heavy third complementarity determining region in the randomized double blind RV305 HIV-1 vaccine trial

    Science.gov (United States)

    Ackerman, Margaret; Saunders, Kevin O.; Pollara, Justin; Vandergrift, Nathan; Parks, Rob; Michael, Nelson L.; O’Connell, Robert J.; Vasan, Sandhya; Rerks-Ngarm, Supachai; Kaewkungwal, Jaranit; Pitisuttithum, Punnee; Nitayaphan, Sorachai; Sinangil, Faruk; Phogat, Sanjay; Alam, S. Munir; Liao, Hua-Xin; Ferrari, Guido; Seaman, Michael S.; Montefiori, David C.; Harrison, Stephen C.; Haynes, Barton F.

    2017-01-01

    The canary pox vector and gp120 vaccine (ALVAC-HIV and AIDSVAX B/E gp120) in the RV144 HIV-1 vaccine trial conferred an estimated 31% vaccine efficacy. Although the vaccine Env AE.A244 gp120 is antigenic for the unmutated common ancestor of V1V2 broadly neutralizing antibody (bnAbs), no plasma bnAb activity was induced. The RV305 (NCT01435135) HIV-1 clinical trial was a placebo-controlled randomized double-blinded study that assessed the safety and efficacy of vaccine boosting on B cell repertoires. HIV-1-uninfected RV144 vaccine recipients were reimmunized 6–8 years later with AIDSVAX B/E gp120 alone, ALVAC-HIV alone, or a combination of ALVAC-HIV and AIDSVAX B/E gp120 in the RV305 trial. Env-specific post-RV144 and RV305 boost memory B cell VH mutation frequencies increased from 2.9% post-RV144 to 6.7% post-RV305. The vaccine was well tolerated with no adverse events reports. While post-boost plasma did not have bnAb activity, the vaccine boosts expanded a pool of envelope CD4 binding site (bs)-reactive memory B cells with long third heavy chain complementarity determining regions (HCDR3) whose germline precursors and affinity matured B cell clonal lineage members neutralized the HIV-1 CRF01 AE tier 2 (difficult to neutralize) primary isolate, CNE8. Electron microscopy of two of these antibodies bound with near-native gp140 trimers showed that they recognized an open conformation of the Env trimer. Although late boosting of RV144 vaccinees expanded a novel pool of neutralizing B cell clonal lineages, we hypothesize that boosts with stably closed trimers would be necessary to elicit antibodies with greater breadth of tier 2 HIV-1 strains. Trial Registration: ClinicalTrials.gov NCT01435135 PMID:28235027

  19. SU-E-T-215: A Technique for Treating Patients outside the Mosaiq R&V System for TrueBeam Users (or 4DTC).

    Science.gov (United States)

    Nelson, C; Gifford, K; Kisling, K; Kirsner, S

    2012-06-01

    When the record and verify (R&V) system (Mosaiq, Elekta Medical Systems) is unavailable to send information to the treatment console of the linear accelerator (Varian Clinac, Varian Medical Systems), treatment is manually delivered by entering parameters into the treatment console and loading backed up MLC files. The new linear accelerator, the TrueBeam (Varian Medical Systems) lacks the ability to manually deliver treatment by entering machine parameters into the treatment console. The TrueBeam can only deliver treatments using the R&V system or loading DICOM RT plan files directly in File Mode. Every time a prescription site is sent from the R&V system to the accelerator, a DICOM RT plan file is created by the R&V system. A script was created that reads the headers of these files, copies them to the treatment console and renames them in an identifiable form. At the end of each treatment day, the script is executed transferring only the DICOM RT plan files created that treatment day. A contingency report is then generated from the R&V system, which contains machine parameters for all fields for all patients under treatment. When the R&V system is unavailable the RT plan files are opened in file mode, and the machine parameters are verified using the contingency report before delivery. This system was tested on a cohort of patients. Each patient's plan was opened in file mode and the machine parameters were verified against the patient's planned treatment in the R&V system. All files opened in file mode were identical to the information stored in the R&V system. This was tested both on the TrueBeam and accelerators having the 4DTC. Our technique was validated and is an alternative method for delivering treatment when the R&V system is unavailable. © 2012 American Association of Physicists in Medicine.

  20. Boosting of HIV envelope CD4 binding site antibodies with long variable heavy third complementarity determining region in the randomized double blind RV305 HIV-1 vaccine trial.

    Science.gov (United States)

    Easterhoff, David; Moody, M Anthony; Fera, Daniela; Cheng, Hao; Ackerman, Margaret; Wiehe, Kevin; Saunders, Kevin O; Pollara, Justin; Vandergrift, Nathan; Parks, Rob; Kim, Jerome; Michael, Nelson L; O'Connell, Robert J; Excler, Jean-Louis; Robb, Merlin L; Vasan, Sandhya; Rerks-Ngarm, Supachai; Kaewkungwal, Jaranit; Pitisuttithum, Punnee; Nitayaphan, Sorachai; Sinangil, Faruk; Tartaglia, James; Phogat, Sanjay; Kepler, Thomas B; Alam, S Munir; Liao, Hua-Xin; Ferrari, Guido; Seaman, Michael S; Montefiori, David C; Tomaras, Georgia D; Harrison, Stephen C; Haynes, Barton F

    2017-02-01

    The canary pox vector and gp120 vaccine (ALVAC-HIV and AIDSVAX B/E gp120) in the RV144 HIV-1 vaccine trial conferred an estimated 31% vaccine efficacy. Although the vaccine Env AE.A244 gp120 is antigenic for the unmutated common ancestor of V1V2 broadly neutralizing antibody (bnAbs), no plasma bnAb activity was induced. The RV305 (NCT01435135) HIV-1 clinical trial was a placebo-controlled randomized double-blinded study that assessed the safety and efficacy of vaccine boosting on B cell repertoires. HIV-1-uninfected RV144 vaccine recipients were reimmunized 6-8 years later with AIDSVAX B/E gp120 alone, ALVAC-HIV alone, or a combination of ALVAC-HIV and AIDSVAX B/E gp120 in the RV305 trial. Env-specific post-RV144 and RV305 boost memory B cell VH mutation frequencies increased from 2.9% post-RV144 to 6.7% post-RV305. The vaccine was well tolerated with no adverse events reports. While post-boost plasma did not have bnAb activity, the vaccine boosts expanded a pool of envelope CD4 binding site (bs)-reactive memory B cells with long third heavy chain complementarity determining regions (HCDR3) whose germline precursors and affinity matured B cell clonal lineage members neutralized the HIV-1 CRF01 AE tier 2 (difficult to neutralize) primary isolate, CNE8. Electron microscopy of two of these antibodies bound with near-native gp140 trimers showed that they recognized an open conformation of the Env trimer. Although late boosting of RV144 vaccinees expanded a novel pool of neutralizing B cell clonal lineages, we hypothesize that boosts with stably closed trimers would be necessary to elicit antibodies with greater breadth of tier 2 HIV-1 strains. ClinicalTrials.gov NCT01435135.

  1. Context Dependent Spectral Unmixing

    Science.gov (United States)

    2014-08-01

    International Geoscience and Remote Sensing Symposium (IGARSS), Cape Town, South Africa , July 2009. HONORS AND AWARDS: 1. IEEE Outstanding CECS Student Award...COMMEND on the Usgs1C2M3 data across the 25 runs and at all noise levels: (a) SME , (b) SMAE, (c) AME. . . . . . . . . . . . . . 59 6.10 True (solid lines...identifying multiple sets of endmembers. In other words, the unmixing process is adapted to different regions of the spectral space. Another challenge with most

  2. The Teachers at Sea program during the CIRCEA cruise of the R/V Marion Dufresne

    Science.gov (United States)

    Laj, Carlo; Sanchez Morante, Ana; Kissel, Catherine; Leau, Hélène

    2015-04-01

    With the support of the French Polar Institute (IPEV) and EGU, two teachers from Spain and France were able to participate to the CIRCEA (CIRCulation in East Asian seas) cruise of the R/V Marion Dufresne in the South China Sea, departing and arriving in Singapore. On board, the two teachers participated to all the scientific activities, including together with the scientists and technicians, to two 4-hours shifts per day (8h total per day). During these shifts, they were involved in every step of the process of obtaining the cores, cutting, opening and labelling them, archiving, and measuring some of the physical parameters, and finally sediment description. It was possible to establish almost daily reports of the scientific progress of the cruise and to send regular logs to the participating land-based teachers in different schools mainly in Europe and in the USA, taking advantage of a list of addresses of teachers having participated to the Geosciences Information for teachers (GIFT) workshops of the European Geosciences Union. This should bring authentic science in the classroom, and indeed we received enthusiastic responses from many teachers. Also, a video report of the different aspects of the life on board was realized by Ana Morante (the teacher from Spain) and Carlo Laj (Chair of the Committee on Education of EGU) which will be shown during the GIFT workshop and during the General Assembly of EGU at the IPEV booth.

  3. Evaluation of 1-phase, 3-phase and Lightning Faults on Wind Farms using EMTP-RV

    Directory of Open Access Journals (Sweden)

    Saber Arabi Nowdeh

    2014-12-01

    Full Text Available Since the development of wind power plants installation is growing, problems which are related to network connecting, stability and voltage effects become more important. On the other hand, wind farms are often open to lightning because of their long height and specific appearance. In this paper, modeling and simulation of 1-phase, 3-phase and lightning faults in a wind farm consisting of 40 wind turbines and faults impact on wind farm and the network is investigated in EMTP-RV environment. In this field, it’s necessary to develop a precise modeling out of wind power plant in order to evaluate the effects of these power plants on dynamical behavior of the power system. These models can be used in designing new protection systems, new protection algorithms, and new strategies for power plants exploitation improvement. Each wind unit in the farm is connected to the whole units that are connected to the network using a doubly fed induction generator (DFIG.

  4. Genetic parameters for resistance to the Salmonella abortusovis vaccinal strain Rv6 in sheep

    Directory of Open Access Journals (Sweden)

    Bouix Jacques

    2003-03-01

    Full Text Available Abstract An experimental population (1216 lambs from 30 sires of the Inra401 sheep was created in an Inra flock to allow QTL detection for susceptibility to Salmonella infection, wool and carcass traits. The Inra401 is a sheep composite line developed from two breeds: Berrichon du Cher and Romanov. At 113 days of age on average, the lambs were inoculated intravenously with 108 Salmonella abortusovis Rv6 (vaccinal strain. They were slaughtered 10 days after the inoculation. Several traits were measured at inoculation and/or slaughtering to estimate the genetic resistance of the lambs to Salmonella infection: specific IgM and IgG1 antibody titres, body weight loss, spleen and pre-scapular node weights and counts of viable Salmonella persisting in these organs. This paper presents a quantitative analysis of the genetic variability of the traits related to salmonellosis susceptibility. The heritabilities of the traits varied between 0.10 and 0.64 (significantly different from zero. Thus, in sheep as well as in other species, the determinism of resistance to Salmonella infection is under genetic control. Moreover, the correlations between the traits are in agreement with the known immune mechanisms. The genetic variability observed should help QTL detection.

  5. Current meter and other data collected using current meter casts from R/V RESEARCHER and R/V CALANUS in the Atlantic and Pacific Ocean as part of the Eastern Pacific Ocean Circulation Study (EPOCS) and Subtropical Atlantic Current Study (STACS), 23 March 1983 - 19 November 1986 (NODC Accession 8700226)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Current meter and other data were collected using current meter casts from R/V RESEARCHER and R/V CALANUS in the Atlantic and Pacific Ocean from March 23, 1983 to...

  6. Temperature, salinity, and other data from CTD and bottle casts from the Oregon Coast (NE Pacific limit-180) from the R/V WECOMA and R/V MC ARTHUR from 17 February 1999 to 12 September 2000 (NODC Accession 0000471)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — CTD, bottle, and other data were collected from the Oregon Coast from the R/V WECOMA and R/V MC ARTHUR from 17 February 1999 to 12 September 2000. Data include...

  7. Benthic data from bottom grabs from Prince William Sound in support of Exxon Valdez Oil Spill Restoration Project from the R/V DAVIDSON and R/V BIG VALLEY from 03 July 1990 to 25 June of 1991 (NODC Accession 0000447)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Benthic samples and other data were collected from the R/V DAVIDSON and R/V BIG VALLEY from the Prince William Sound from 03 July 1990 to 25 June of 1991 . Data were...

  8. Tracking of Single Quantum Dot Labeled EcoRV Sliding along DNA Manipulated by Double Optical Tweezers

    OpenAIRE

    Biebricher, Andreas; Wende, Wolfgang; Escudé, Christophe; Pingoud, Alfred; Desbiolles, Pierre

    2009-01-01

    Fluorescence microscopy provides a powerful method to directly observe single enzymes moving along a DNA held in an extended conformation. In this work, we present results from single EcoRV enzymes labeled with quantum dots which interact with DNA manipulated by double optical tweezers. The application of quantum dots facilitated accurate enzyme tracking without photobleaching whereas the tweezers allowed us to precisely control the DNA extension. The labeling did not affect the biochemical a...

  9. VizieR Online Data Catalog: WASP78 and WASP79 RV and photometric data (Smalley+, 2012)

    Science.gov (United States)

    Smalley, B.; Anderson, D. R.; Collier-Cameron, A.; Doyle, A. P.; Fumel, A.; Gillon, M.; Hellier, C.; Jehin, E.; Lendl, M.; Maxted, P. F. L.; Pepe, F.; Pollacco, D.; Queloz, D.; Segransan, D.; Smith, A. M. S.; Southworth, J.; Triaud, A. H. M. J.; Udry, S.; West, R. G.

    2012-10-01

    File rv.dat contains the Radial velocity and line bisector span measurements of WASP-78 and WASP-79 obtained using the CORALIE spectrograph. Files phot.dat contains the transit photometry of WASP-78 obtained using the Trappist Telescope through a blue-blocking filter on 2011 November 8, 2011 December 15 and 2012 January 8, respectively, and the z' band transit photometry of WASP-79 obtained using the Trappist Telescope on 2011 September 26. (2 data files).

  10. VizieR Online Data Catalog: WASP41 and WASP47 photometric and RV data (Neveu-VanMalle+, 2016)

    Science.gov (United States)

    Neveu-Vanmalle, M.; Queloz, D.; Anderson, D. R.; Brown, D. J. A.; Collier-Cameron, A.; Delrez, L.; Diaz, R. F.; Gillon, M.; Hellier, C.; Jehin, E.; Lister, T.; Pepe, F.; Rojo, P.; Segransan, D.; Triaud, A. H. M. J.; Turner, O. D.; Udry, S.

    2015-10-01

    Photometric time-series obtained during transits of the hot Jupiter WASP-47b, and RV time-series obtained on WASP-41 and WASP-47. The photometric time-series were obtained using the LCOGT's Faulkes Telescope South, the TRAPPIST telescope and the 1.54-m Danish telescope. The RVs were obtained using the Euler/CORALIE and the ESO/HARPS spectrographs. (7 data files).

  11. Molecular characterization of eight segments of Scylla serrata reovirus (SsRV) provides the complete genome sequence.

    Science.gov (United States)

    Chen, Jigang; Xiong, Juan; Cui, Bojing; Yang, Jifang; Li, Wenchen; Mao, Zhijuan

    2012-08-01

    Scylla serrata reovirus (SsRV) is one of the most prevalent viral pathogens of mud crabs (S. serrata). Of the 12 double-stranded RNA (dsRNA) genomic segments (S1-S12), the three largest (S1-S3) and S7 were sequenced previously and were shown to have no or only low sequence homology to known members within the family Reoviridae. The sequences of the remaining segments, S4-S6 and S8-S12, are reported here. With the exception of S4, all have single open reading frames (ORFs) on their positive strands, and the terminal sequences 5'-AUAAA(U)/(C) (A)/(U)…G(A)/(G) (A)/(U) (A)/(C)AAC(G)/(U)AU-3' are conserved among currently and previously sequenced segments. S4 contains two out-of-phase ORFs on the positive strand, suggesting that this segment is bicistronic. The ORFs of segments S4-S6 and S8-S12 have low or no homology to other reovirus genes, with the exception that all of the SsRV segments have high sequence similarity to those of mud crab reovirus (MCRV) and share the same 5'- and 3'-terminal nucleotide sequences, suggesting that the two viruses belong to the same species in the family Reoviridae. Analysis of virion proteins revealed that SsRV contains at least eight structural proteins, with sizes ranging from 25 to 160 kDa.

  12. The Extinction Curve in the Visible and the Value of Rv. Part II: Addendum to AN 333, 160

    CERN Document Server

    Zagury, Frederic

    2012-01-01

    This paper corrects and completes a previous study of the shape of the extinction curve in the visible and the value of Rv. A continuous visible/infrared extinction law proportional to 1/{\\lambda}^p with p close to 1 ({\\pm}0.4) is indistinguishable from a perfectly linear law (p = 1) in the visible within observational precision, but the shape of the curve in the infrared can be substantially modified. Values of p slightly larger than 1 would account for the increase of extinction (compared to the p = 1 law) reported for {\\lambda} > 1{\\mu}m and deeply affect the value of Rv. In the absence of gray extinction Rv must be 4.04 if p = 1. It becomes 3.14 for p = 1.25, 3.00 for p = 1.30, and 2.76 for p = 1.40. Values of p near 1.3 are also attributed to extinction by atmospheric aerosols, which indicates that both phenomena may be governed by similar particle size distributions. A power extinction law may harmonize visible and infrared data into a single, continuous, and universal, interstellar extinction law.

  13. Rv1458c: a new diagnostic marker for identification of Mycobacterium tuberculosis complex in a novel duplex PCR assay.

    Science.gov (United States)

    Shrivastava, Kamal; Garima, Kushal; Narang, Anshika; Bhattacharyya, Kausik; Vishnoi, Ekta; Singh, Roshan Kumar; Chaudhry, Anil; Prasad, Rajendra; Bose, Mridula; Varma-Basil, Mandira

    2017-03-01

    We explored the efficiency of Rv1458c, the gene encoding a putative ABC drug transporter specific for the Mycobacterium tuberculosis complex (MTBC), as a diagnostic marker. A 190 bp region of Rv1458c and a 300 bp region of hsp65 were targeted in a novel duplex PCR assay and the results were compared with those for PCR restriction analysis(PRA) using the restriction enzymes NruI and BamHI. Species identification of a subset of the isolates (n=50) was confirmed by sequencing. Clinical isolates of M. tuberculosis (n=426) obtained from clinically suspected patients of pulmonary tuberculosis and mycobacterial (n=13) and non-mycobacterial (n=8) reference strains were included in the study. The duplex PCR assay correctly identified 320/426 isolates as MTBC and 106/426 isolates as non-tuberculous mycobacteria(NTM). The test was 100 % specific and sensitive when compared with NruI/BamHI PCR restriction analysis and highlighted the use of Rv1458c as a diagnostic marker for MTBC. The duplex PCR assay could be developed for use as a screening test to identify MTBC in clinical specimens in peripheral laboratories with limited resources.

  14. Mechanistic analysis of Mycobacterium tuberculosis Rv1347c, a lysine Nepsilon-acyltransferase involved in mycobactin biosynthesis.

    Science.gov (United States)

    Frankel, Brenda A; Blanchard, John S

    2008-09-15

    Mycobactin acylation plays a crucial role in the ability of Mycobacterium tuberculosis to acquire intracellular iron during infection. M. tuberculosis Rv1347c, the lysine N(epsilon)-acyltransferase responsible for mycobactin acylation, represents a valid target for the development of novel anti-tubercular agents. Here we investigate the substrate specificity of Rv1347c, evaluate its kinetic mechanism and probe the contributions of active-site residues to catalysis. Our results confirm that Rv1347c demonstrates a preference for longer acyl-chains and suggest that mycobactin acylation occurs subsequent to mycobactin core assembly. Steady-state bisubstrate kinetics and dead-end inhibitor studies support a random sequential kinetic mechanism. Analysis of the pH dependence of k(cat)/K(m) revealed the presence of two groups that must be deprotonated for efficient catalysis. Mutagenesis of His(130) and Asp(168) indicated that both residues are critical for acyltransferase activity and suggests that His(130) is responsible for general base activation of the epsilon-amino group of lysine.

  15. Untangling the Near-IR Spectral Features in the Protoplanetary Environment of KH 15D

    CERN Document Server

    Arulanantham, Nicole A; Gilmore, Martha S; Cauley, P Wilson; Leggett, S K

    2016-01-01

    We report on Gemini/GNIRS observations of the binary T Tauri system V582 Mon (KH 15D) at three orbital phases. These spectra allow us to untangle five components of the system: the photosphere and magnetosphere of star B, the jet, scattering properties of the ring material, and excess near-IR radiation previously attributed to a possible self-luminous planet. We confirm an early-K subgiant classification for star B and show that the magnetospheric He I emission line is variable, possibly indicating increased mass accretion at certain times. As expected, the H$_2$ emission features associated with the inner part of the jet show no variation with orbital phase. We show that the reflectance spectrum for the scattered light has a distinctive blue slope and spectral features consistent with scattering and absorption by a mixture of water and methane ice grains in the 1-50 $\\mu$m size range. This suggests that the methane frost line is closer than $\\sim$5 AU in this system, requiring that the grains be shielded fro...

  16. Variability of stellar granulation and convective blueshift with spectral type and magnetic activity. I. K and G main sequence stars

    CERN Document Server

    Meunier, N; Kabuiku, L Mbemba; Alex, M; Mignon, L; Borgniet, S

    2016-01-01

    In solar-type stars, the attenuation of convective blueshift by stellar magnetic activity dominates the RV variations over the low amplitude signal induced by low mass planets. Models of stars that differ from the Sun will require a good knowledge of the attenuation of the convective blueshift to estimate its impact on the variations. It is therefore crucial to precisely determine not only the amplitude of the convective blueshift for different types of stars, but also the dependence of this convective blueshift on magnetic activity, as these are key factors in our model producing the RV. We studied a sample of main sequence stars with spectral types from G0 to K2 and focused on their temporally averaged properties: the activity level and a criterion allowing to characterise the amplitude of the convective blueshift. We find the differential velocity shifts of spectral lines due to convection to depend on the spectral type, the wavelength (this dependence is correlated with the Teff and activity level), and o...

  17. Temperature profile data from the R/V LITTLE DIPPER using CTD casts from 19 January 2000 to 23 February 2000 (NODC Accession 0000401)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Temperature profile data were collected from the R/V LITTLE DIPPER from January 19, 2000 to February 23, 2000. Data were submitted by University of Alaska -...

  18. CTD observations off Oregon and California : R/V Wecoma, W8201B, 28 January to 6 February 1982 (NODC Accession 8300065)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Temperature profile were collected using CTD casts from the R.V. WECOMA and other platforms in the coastal waters of Oregon and California from 28 January 1982 to 04...

  19. Eesti muinasjutud jõuavad laia maailma. Aga meile? / Piret Päär, Veronika Kivisilla, Risto Järv ; interv. Jürgen Rooste

    Index Scriptorium Estoniae

    Päär, Piret

    2005-01-01

    Raamatust "Estonian folktales. The heavenly wedding" (Varrak, 2005, koostajad Piret Päär ja Anne Türnpu, tõlkijad Heili Einasto, Lembi Loigu, Veronika Kivisilla, Risto Järv). Lühidalt ka Kadri Roosi illustratsioonidest

  20. 2002 EM1002 and EM120 Multibeam Sonar Data from Cruise R/V Kilo Moana KM-02-06 - Northwestern Hawaiian Islands

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — EM1002 and EM120 multibeam Data were collected in October/November 2002 aboard R/V Kilo Moana between Kauai Island and Lisianski Island in the Northwestern Hawaiian...

  1. Oceanographic profile temperature and salinity measurements collected using CTD from R/V Hecla in the North Atlantic during 1996 (NODC Accession 0046839)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Oceanographic profile temperature and salinity measurements collected using CTD from R/V Hecla in the North Atlantic during 1996. Data submitted by Garry Dawson...

  2. Eesti muinasjutud jõuavad laia maailma. Aga meile? / Piret Päär, Veronika Kivisilla, Risto Järv ; interv. Jürgen Rooste

    Index Scriptorium Estoniae

    Päär, Piret

    2005-01-01

    Raamatust "Estonian folktales. The heavenly wedding" (Varrak, 2005, koostajad Piret Päär ja Anne Türnpu, tõlkijad Heili Einasto, Lembi Loigu, Veronika Kivisilla, Risto Järv). Lühidalt ka Kadri Roosi illustratsioonidest

  3. Water temperature, salinity, nutrients and other variables from bottle casts by R/V MELVILLE From NE Pacific (limit-180) from 19850816 to 19850906 (NODC Accession 8700138)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Data from thirty five bottle casts from the R/V MELVILLE for the ALCYONE cruise Leg 3 (cruise 275) in NODC standard C100/SD2 format.

  4. Water physics and chemistry data from bottle casts from the MICMAC R/V from the 28 January 1970 to 21 April 1970 (NODC Accession 7100666)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Water physics and chemistry data were collected from bottle casts from the MICMAC Stanford R/V from 28 January 1970 to 21 April 1970. Data were submitted by the...

  5. Spectral signatures of chirality

    DEFF Research Database (Denmark)

    Pedersen, Jesper Goor; Mortensen, Asger

    2009-01-01

    We present a new way of measuring chirality, via the spectral shift of photonic band gaps in one-dimensional structures. We derive an explicit mapping of the problem of oblique incidence of circularly polarized light on a chiral one-dimensional photonic crystal with negligible index contrast...... to the formally equivalent problem of linearly polarized light incident on-axis on a non-chiral structure with index contrast. We derive analytical expressions for the first-order shifts of the band gaps for negligible index contrast. These are modified to give good approximations to the band gap shifts also...

  6. Spectral Variability of FSRQs

    Indian Academy of Sciences (India)

    Minfeng Gu; Y. L. Ai

    2011-03-01

    The optical variability of 29 flat spectrum radio quasars in SDSS Stripe 82 region are investigated by using DR7 released multi-epoch data. All FSRQs show variations with overall amplitude ranging from 0.24 mag to 3.46 mag in different sources. About half of FSRQs show a bluer-when-brighter trend, which is commonly observed for blazars. However, only one source shows a redder-when-brighter trend, which implies it is rare in FSRQs. In this source, the thermal emission may be responsible for the spectral behaviour.

  7. Spectrally encoded confocal microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Tearney, G.J.; Webb, R.H.; Bouma, B.E. [Wellman Laboratories of Photomedicine, Massachusetts General Hospital, 50 Blossom Street, BAR 703, Boston, Massachusetts 02114 (United States)

    1998-08-01

    An endoscope-compatible, submicrometer-resolution scanning confocal microscopy imaging system is presented. This approach, spectrally encoded confocal microscopy (SECM), uses a quasi-monochromatic light source and a transmission diffraction grating to detect the reflectivity simultaneously at multiple points along a transverse line within the sample. Since this method does not require fast spatial scanning within the probe, the equipment can be miniaturized and incorporated into a catheter or endoscope. Confocal images of an electron microscope grid were acquired with SECM to demonstrate the feasibility of this technique. {copyright} {ital 1998} {ital Optical Society of America}

  8. Recombinant Lipoprotein Rv1016c Derived from Mycobacterium tuberculosis Is a TLR-2 Ligand that Induces Macrophages Apoptosis and Inhibits MHC II Antigen Processing.

    Science.gov (United States)

    Su, Haibo; Zhu, Shenglin; Zhu, Lin; Huang, Wei; Wang, Honghai; Zhang, Zhi; Xu, Ying

    2016-01-01

    TLR2-dependent cellular signaling in Mycobacterium tuberculosis-infected macrophages causes apoptosis and inhibits class II major histocompatibility complex (MHC-II) molecules antigen processing, leading to evasion of surveillance. Mycobacterium tuberculosis (MTB) lipoproteins are an important class of Toll-like receptor (TLR) ligand, and identified as specific components that mediate these effects. In this study, we identified and characterized MTB lipoprotein Rv1016c (lpqT) as a cell wall associated-protein that was exposed on the cell surface and enhanced the survival of recombinants M. smegmatis_Rv1016c under stress conditions. We found that Rv1016c lipoprotein was a novel TLR2 ligand and able to induce macrophage apoptosis in a both dose- and time-dependent manner. Additionally, apoptosis induced by Rv1016c was reserved in THP-1 cells blocked with anti-TLR-2 Abs or in TLR2(-/-) mouse macrophages, indicating that Rv1016c-induced apoptosis is dependent on TLR2. Moreover, we demonstrated that Rv1016c lipoprotein inhibited IFN-γ-induced MHC-II expression and processing of soluble antigens in a TLR2 dependent manner. Class II transactivator (CIITA) regulates MHC II expression. In this context, Rv1016c lipoprotein diminished IFN-γ-induced expression of CIITA IV through TLR2 and MAPK Signaling. TLR2-dependent apoptosis and inhibition of MHC-II Ag processing induced by Rv1016c during mycobacteria infection may promote the release of residual bacilli from apoptotic cells and decrease recognition by CD4(+) T cells. These mechanisms may allow intracellular MTB to evade immune surveillance and maintain chronic infection.

  9. The rv1184c locus encodes Chp2, an acyltransferase in Mycobacterium tuberculosis polyacyltrehalose lipid biosynthesis.

    Science.gov (United States)

    Touchette, Megan H; Holsclaw, Cynthia M; Previti, Mary L; Solomon, Viven C; Leary, Julie A; Bertozzi, Carolyn R; Seeliger, Jessica C

    2015-01-01

    Trehalose glycolipids are found in many bacteria in the suborder Corynebacterineae, but methyl-branched acyltrehaloses are exclusive to virulent species such as the human pathogen Mycobacterium tuberculosis. In M. tuberculosis, the acyltransferase PapA3 catalyzes the formation of diacyltrehalose (DAT), but the enzymes responsible for downstream reactions leading to the final product, polyacyltrehalose (PAT), have not been identified. The PAT biosynthetic gene locus is similar to that of another trehalose glycolipid, sulfolipid 1. Recently, Chp1 was characterized as the terminal acyltransferase in sulfolipid 1 biosynthesis. Here we provide evidence that the homologue Chp2 (Rv1184c) is essential for the final steps of PAT biosynthesis. Disruption of chp2 led to the loss of PAT and a novel tetraacyltrehalose species, TetraAT, as well as the accumulation of DAT, implicating Chp2 as an acyltransferase downstream of PapA3. Disruption of the putative lipid transporter MmpL10 resulted in a similar phenotype. Chp2 activity thus appears to be regulated by MmpL10 in a relationship similar to that between Chp1 and MmpL8 in sulfolipid 1 biosynthesis. Chp2 is localized to the cell envelope fraction, consistent with its role in DAT modification and possible regulatory interactions with MmpL10. Labeling of purified Chp2 by an activity-based probe was dependent on the presence of the predicted catalytic residue Ser141 and was inhibited by the lipase inhibitor tetrahydrolipstatin (THL). THL treatment of M. tuberculosis resulted in selective inhibition of Chp2 over PapA3, confirming Chp2 as a member of the serine hydrolase superfamily. Efforts to produce in vitro reconstitution of acyltransferase activity using straight-chain analogues were unsuccessful, suggesting that Chp2 has specificity for native methyl-branched substrates.

  10. PE11 (Rv1169c Selectively Altering Fatty Acid Components of Mycobacterium smegmatis and Host interleukin-6 Level Accompany with Cell Death

    Directory of Open Access Journals (Sweden)

    Wanyan eDeng

    2015-06-01

    Full Text Available PE/PPE family proteins, named after their conserved PE (Pro-Glu and PPE (Pro-Pro-Glu domains of N-terminal, are most intriguing aspects of pathologic mycobacterial genome. The roles of most members of this family remain unknown, although selected genes of this family are related to the virulence of Mycobacterium tuberculosis. In order to decipher the role of Rv1169c, the Mycobacterium smegmatis strain heterologously expressed this ORF was constructed and identified that Rv1169c was a cell wall associated protein with a novel function in modifying the cell wall fatty acid component.. The growth of Rv1169c expressing strain was affected under surface stress, acidic condition and antibiotics norfloxacin and rifampicin treatment. M. smegmatis expressing Rv1169c induced necrotic cell death of macrophage after infection and significantly decreased interlukin-6 production compared to controls. In general, these results underscore a proposing role of Rv1169c in virulence of M. tuberculosis, as it’s role in the susceptibility of anti-mycobacteria factors caused by modified cell wall fatty acid, and the induced necrotic cell death by Rv1169c is crucial for M. tuberculosis virulence during infection.

  11. The T Tauri star RY Tau as a case study of the inner regions of circumstellar dust disks

    CERN Document Server

    Schegerer, A A; Ratzka, Th; Leinert, Ch

    2007-01-01

    We study the inner region of the circumstellar disk around the TTauri star RY Tau. Our aim is to find a physical description satisfying the available interferometric data, obtained with the mid-infrared interferometric instrument at the Very Large Telescope Interferometer, as well as the spectral energy distribution. We also compare the findings with the results of similar studies, including those of intermediate-mass stars. Our analysis is done within the framework of a passive circumstellar disk, which is optionally supplemented by the effects of accretion and an added envelope. To achieve a more consistent and realistic model, we used our continuum transfer code MC3D. In addition, we studied the shape of the 10um silicate emission feature in terms of the underlying dust population, both for single-dish and for interferometric measurements. We show that a modestly flaring disk model with accretion can explain both the observed spectral energy distribution and the mid-infrared visibilities obtained with the ...

  12. Rectangular spectral collocation

    KAUST Repository

    Driscoll, Tobin A.

    2015-02-06

    Boundary conditions in spectral collocation methods are typically imposed by removing some rows of the discretized differential operator and replacing them with others that enforce the required conditions at the boundary. A new approach based upon resampling differentiated polynomials into a lower-degree subspace makes differentiation matrices, and operators built from them, rectangular without any row deletions. Then, boundary and interface conditions can be adjoined to yield a square system. The resulting method is both flexible and robust, and avoids ambiguities that arise when applying the classical row deletion method outside of two-point scalar boundary-value problems. The new method is the basis for ordinary differential equation solutions in Chebfun software, and is demonstrated for a variety of boundary-value, eigenvalue and time-dependent problems.

  13. Spectral disentangling with Spectangular

    Science.gov (United States)

    Sablowski, Daniel P.; Weber, Michael

    2017-01-01

    The paper introduces the software Spectangular for spectral disentangling via singular value decomposition with global optimisation of the orbital parameters of the stellar system or radial velocities of the individual observations. We will describe the procedure and the different options implemented in our program. Furthermore, we will demonstrate the performance and the applicability using tests on artificial data. Additionally, we use high-resolution spectra of Capella to demonstrate the performance of our code on real-world data. The novelty of this package is the implemented global optimisation algorithm and the graphical user interface (GUI) for ease of use. We have implemented the code to tackle SB1 and SB2 systems with the option of also dealing with telluric (static) lines. Based in part on data obtained with the STELLA robotic telescope in Tenerife, an AIP facility jointly operated by AIP and IAC.

  14. Spectral Classification Beyond M

    CERN Document Server

    Leggett, S K; Burgasser, A J; Jones, H R A; Marley, M S; Tsuji, T

    2004-01-01

    Significant populations of field L and T dwarfs are now known, and we anticipate the discovery of even cooler dwarfs by Spitzer and ground-based infrared surveys. However, as the number of known L and T dwarfs increases so does the range in their observational properties, and difficulties have arisen in interpreting the observations. Although modellers have made significant advances, the complexity of the very low temperature, high pressure, photospheres means that problems remain such as the treatment of grain condensation as well as incomplete and non-equilibrium molecular chemistry. Also, there are several parameters which control the observed spectral energy distribution - effective temperature, grain sedimentation efficiency, metallicity and gravity - and their effects are not well understood. In this paper, based on a splinter session, we discuss classification schemes for L and T dwarfs, their dependency on wavelength, and the effects of the parameters T_eff, f_sed, [m/H] and log g on optical and infra...

  15. Spectral Animation Compression

    Institute of Scientific and Technical Information of China (English)

    Chao Wang; Yang Liu; Xiaohu Guo; Zichun Zhong; Binh Le; Zhigang Deng

    2015-01-01

    This paper presents a spectral approach to compress dynamic animation consisting of a sequence of homeomor-phic manifold meshes. Our new approach directly compresses the field of deformation gradient defined on the surface mesh, by decomposing it into rigid-body motion (rotation) and non-rigid-body deformation (stretching) through polar decompo-sition. It is known that the rotation group has the algebraic topology of 3D ring, which is different from other operations like stretching. Thus we compress these two groups separately, by using Manifold Harmonics Transform to drop out their high-frequency details. Our experimental result shows that the proposed method achieves a good balance between the reconstruction quality and the compression ratio. We compare our results quantitatively with other existing approaches on animation compression, using standard measurement criteria.

  16. Spectral disentangling with Spectangular

    CERN Document Server

    Sablowski, Daniel P

    2016-01-01

    The paper introduces the software Spectangular for spectral disentangling via singular value decomposition with global optimisation of the orbital parameters of the stellar system or radial velocities of the individual observations. We will describe the procedure and the different options implemented in our program. Furthermore, we will demonstrate the performance and the applicability using tests on artificial data. Additionally, we use high-resolution spectra of Capella to demonstrate the performance of our code on real-world data. The novelty of this package is the implemented global optimisation algorithm and the graphical user interface (GUI) for ease of use. We have implemented the code to tackle SB1 and SB2 systems with the option of also dealing with telluric (static) lines.

  17. Spectral proper orthogonal decomposition

    CERN Document Server

    Sieber, Moritz; Paschereit, Christian Oliver

    2015-01-01

    The identification of coherent structures from experimental or numerical data is an essential task when conducting research in fluid dynamics. This typically involves the construction of an empirical mode base that appropriately captures the dominant flow structures. The most prominent candidates are the energy-ranked proper orthogonal decomposition (POD) and the frequency ranked Fourier decomposition and dynamic mode decomposition (DMD). However, these methods fail when the relevant coherent structures occur at low energies or at multiple frequencies, which is often the case. To overcome the deficit of these "rigid" approaches, we propose a new method termed Spectral Proper Orthogonal Decomposition (SPOD). It is based on classical POD and it can be applied to spatially and temporally resolved data. The new method involves an additional temporal constraint that enables a clear separation of phenomena that occur at multiple frequencies and energies. SPOD allows for a continuous shifting from the energetically ...

  18. SPECTRAL ANALYSIS OF RADIOXENON

    Energy Technology Data Exchange (ETDEWEB)

    Cooper, Matthew W.; Bowyer, Ted W.; Hayes, James C.; Heimbigner, Tom R.; Hubbard, Charles W.; McIntyre, Justin I.; Schrom, Brian T.

    2008-09-23

    Monitoring changes in atmospheric radioxenon concentrations is a major tool in the detection of an underground nuclear explosion. Ground based systems like the Automated Radioxenon Sampler /Analyzer (ARSA), the Swedish Unattended Noble gas Analyzer (SAUNA) and the Automatic portable radiometer of isotopes Xe (ARIX), can collect and detect several radioxenon isotopes by processing and transferring samples into a high efficiency beta-gamma coincidence detector. The high efficiency beta-gamma coincidence detector makes these systems highly sensitive to the radioxenon isotopes 133Xe, 131mXe, 133mXe and 135Xe. The standard analysis uses regions of interest (ROI) to determine the amount of a particular radioxenon isotope present. The ROI method relies on the peaks of interest falling within energy limits of the ROI. Some potential problems inherent in this method are the reliance on stable detector gains and a fixed resolution for each energy peak. In addition, when a high activity sample is measured there will be more interference among the ROI, in particular within the 133Xe, 133mXe, and 131mXe regions. A solution to some of these problems can be obtained through spectral fitting of the data. Spectral fitting is simply the fitting of the peaks using known functions to determine the number and relative peak positions and widths. By knowing this information it is possible to determine which isotopes are present. Area under each peak can then be used to determine an overall concentration for each isotope. Using the areas of the peaks several key detector characteristics can be determined: efficiency, energy calibration, energy resolution and ratios between interfering isotopes (Radon daughters).

  19. Molecular characterization of tlyA gene product, Rv1694 of Mycobacterium tuberculosis: A non-conventional hemolysin and a ribosomal RNA methyl transferase

    Directory of Open Access Journals (Sweden)

    Ahmed Neesar

    2010-09-01

    Full Text Available Abstract Background Mycobacterium tuberculosis is a virulent bacillus causing tuberculosis, a disease responsible for million deaths each year worldwide. In order to understand its mechanism of pathogenesis in humans and to help control tuberculosis, functions of numerous Mycobacterium tuberculosis genes are being characterized. In this study we report the dual functionality of tlyA gene product of Mycobacterium tuberculosis annotated as Rv1694, a 268 amino acid long basic protein. Results The recombinant purified Rv1694 protein was found to exhibit hemolytic activity in vitro. It showed concentration and time-dependent hemolysis of rabbit and human erythrocytes. Multiple oligomeric forms (dimers to heptamers of this protein were seen on the membranes of the lysed erythrocytes. Like the oligomers of conventional, well-known, pore-forming toxins, the oligomers of Rv1694 were found to be resistant to heat and SDS, but were susceptible to reducing agents like β-mercaptoethanol as it had abolished the hemolytic activity of Rv1694 indicating the role of disulfide bond(s. The Rv1694 generated de novo by in vitro transcription and translation also exhibited unambiguous hemolysis confirming the self assembly and oligomerization properties of this protein. Limited proteolytic digestion of this protein has revealed that the amino terminus is susceptible while in solution but is protected in presence of membrane. Striking feature of Rv1694 is its presence on the cell wall of E. coli as visualized by confocal microscopy. The surface expression is consistent with the contact dependent haemolytic ability of E. coli expressing this protein. Also, immune serum specific to this protein inhibits the contact dependent hemolysis. Moreover, Rv1694 protein binds to and forms stable oligomers on the macrophage phagosomal membranes. In addition to all these properties, E. coli expressing Rv1694 was found to be susceptible to the antibiotic capreomycin as its growth

  20. Spectral unmixing: estimating partial abundances

    CSIR Research Space (South Africa)

    Debba, Pravesh

    2009-01-01

    Full Text Available of spectral unmixing 3 End-member spectra and synthetic mixtures 4 Results 5 Conclusions Debba (CSIR) Spectral Unmixing LQM 2009 2 / 22 Background and Research Question If research could be as easy as eating a chocolate cake . . . Figure: Can you guess... the ingredients for this chocolate cake? Debba (CSIR) Spectral Unmixing LQM 2009 3 / 22 Background and Research Question Ingredients Quantity unsweetened chocolate unsweetened cocoa powder boiling water flour baking powder baking soda salt unsalted...

  1. VLBA determination of the distance to nearby star-forming regions I. The distance to T Tauri with 0.4% accuracy

    CERN Document Server

    Loinard, Laurent; Mioduszewski, Amy J; Rodriguez, Luis F; Gonzalez-Lopezlira, Rosa A; Lachaume, Regis; Vazquez, Virgilio; Gonzalez, Erandy

    2007-01-01

    In this article, we present the results of a series of twelve 3.6-cm radio continuum observations of T Tau Sb, one of the companions of the famous young stellar object T Tauri. The data were collected roughly every two months between September 2003 and July 2005 with the Very Long Baseline Array (VLBA). Thanks to the remarkably accurate astrometry delivered by the VLBA, the absolute position of T Tau Sb could be measured with a precision typically better than about 100 micro-arcseconds at each of the twelve observed epochs. The trajectory of T Tau Sb on the plane of the sky could, therefore, be traced very precisely, and modeled as the superposition of the trigonometric parallax of the source and an accelerated proper motion. The best fit yields a distance to T Tau Sb of 147.6 +/- 0.6 pc. The observed positions of T Tau Sb are in good agreement with recent infrared measurements, but seem to favor a somewhat longer orbital period than that recently reported by Duchene et al. (2006) for the T Tau Sa/T Tau Sb sy...

  2. 弱发射线T Tauri型星的高色散光谱观测%High-dispersion Spectroscopy of Weak-line T Tauri Stars

    Institute of Scientific and Technical Information of China (English)

    邢丽峰; 马晓春; 张晓冬

    2013-01-01

    应用国家天文台兴隆观测基地2.16 m望远镜及其高色散光谱仪,对6颗弱发射线T Tauri型星(Weak-line T Tauri Stars,简称WTTS)进行了高色散光谱观测,计算了这些弱发射线T Tauri型星的锂元素丰度,讨论了这些弱发射线TTauri型星锂丰度和恒星自转周期、光变幅度的关系,研究发现:自转较快的弱发射线T Tauri型星锂丰度小于自转较慢的弱发射线T Tauri型星锂丰度;但是这些弱发射线TTauri型星,其锂丰度与恒星在V波段的光变幅度并没有明显的相关性.

  3. The Spitzer c2d Survey of Weak-line T Tauri Stars II: New Constraints on the Timescale for Planet Building

    CERN Document Server

    Cieza, Lucas; Stapelfeldt, Karl R; Augereau, Jean-Charles; Harvey, Paul; Evans, Neal J; II,; Merin, Bruno; Koerner, David W; Sargent, Anneila; van Dishoeck, Ewine F; Allen, Lori; Blake, G A; Brooke, Timothy; Chapman, Nicholas; Huard, Tracy; Lai, Shih-Ping; Mundy, Lee; Myers, Philip C; Spiesman, William; Wahhaj, Zahed

    2007-01-01

    One of the central goals of the Spitzer Legacy Project ``From Molecular Cores to Planet-forming Disks'' (c2d) is to determine the frequency of remnant circumstellar disks around weak-line T Tauri stars (wTTs) and to study the properties and evolutionary status of these disks. Here we present a census of disks for a sample of over 230 spectroscopically identified wTTs located in the c2d IRAC (3.6, 4.5, 4.8, and 8.0 um) and MIPS (24 um) maps of the Ophiuchus, Lupus, and Perseus Molecular Clouds. We find that ~20% of the wTTs in a magnitude limited subsample have noticeable IR-excesses at IRAC wavelengths indicating the presence of a circumstellar disk. The disk frequencies we find in these 3 regions are ~3-6 times larger than that recently found for a sample of 83 relatively isolated wTTs located, for the most part, outside the highest extinction regions covered by the c2d IRAC and MIPS maps. The disk fractions we find are more consistent with those obtained in recent Spitzer studies of wTTs in young clusters s...

  4. Simulations of Winds of Weak-Lined T Tauri Stars: The Magnetic Field Geometry and The Influence of the Wind on Giant Planet Migration

    CERN Document Server

    Vidotto, A A; Jatenco-Pereira, V; Gombosi, T I

    2009-01-01

    By means of numerical simulations, we investigate magnetized stellar winds of pre-main-sequence stars. In particular we analyze under which circumstances these stars will present elongated magnetic features (e.g., helmet streamers, slingshot prominences, etc). We focus on weak-lined T Tauri stars, as the presence of the tenuous accretion disk is not expected to have strong influence on the structure of the stellar wind. We show that the plasma-beta parameter (the ratio of thermal to magnetic energy densities) is a decisive factor in defining the magnetic configuration of the stellar wind. Using initial parameters within the observed range for these stars, we show that the coronal magnetic field configuration can vary between a dipole-like configuration and a configuration with strong collimated polar lines and closed streamers at the equator (multi-component configuration for the magnetic field). We show that elongated magnetic features will only be present if the plasma-beta parameter at the coronal base is ...

  5. Coupled Evolutions of the Stellar Obliquity, Orbital Distance, and Planet's Radius due to the Ohmic Dissipation Induced in a Diamagnetic Hot Jupiter around a Magnetic T Tauri Star

    Science.gov (United States)

    Chang, Yu-Ling; Bodenheimer, Peter H.; Gu, Pin-Gao

    2012-10-01

    We revisit the calculation of the ohmic dissipation in a hot Jupiter presented by Laine et al. by considering more realistic interior structures, stellar obliquity, and the resulting orbital evolution. In this simplified approach, the young hot Jupiter of one Jupiter mass is modeled as a diamagnetic sphere with a finite resistivity, orbiting across tilted stellar magnetic dipole fields in vacuum. Since the induced ohmic dissipation occurs mostly near the planet's surface, we find that the dissipation is unable to significantly expand the young hot Jupiter. Nevertheless, the planet inside a small corotation orbital radius can undergo orbital decay by the dissipation torque and finally overfill its Roche lobe during the T Tauri star phase. The stellar obliquity can evolve significantly if the magnetic dipole is parallel/antiparallel to the stellar spin. Our results are validated by the general torque-dissipation relation in the presence of the stellar obliquity. We also run the fiducial model of Laine et al. and find that the planet's radius is sustained at a nearly constant value by the ohmic heating, rather than being thermally expanded to the Roche radius as suggested by the authors.

  6. MAGNETOHYDRODYNAMIC MODELING OF THE ACCRETION SHOCKS IN CLASSICAL T TAURI STARS: THE ROLE OF LOCAL ABSORPTION IN THE X-RAY EMISSION

    Energy Technology Data Exchange (ETDEWEB)

    Bonito, R.; Argiroffi, C.; Peres, G. [Dip. di Fisica e Chimica, Università di Palermo, P.zza del Parlamento 1, I-90134 Palermo (Italy); Orlando, S.; Miceli, M.; Ibgui, L. [INAF-Osservatorio Astronomico di Palermo, P.zza del Parlamento 1, I-90134 Palermo (Italy); Matsakos, T. [Department of Astronomy and Astrophysics, The University of Chicago, Chicago, IL 60637 (United States); Stehle, C., E-mail: sbonito@astropa.unipa.it [LERMA, Observatoire de Paris, Université Pierre et Marie Curie, Ecole Normale Superieure, Universite Cergy-Pontoise, CNRS, F-75014 Paris (France)

    2014-11-10

    We investigate the properties of X-ray emission from accretion shocks in classical T Tauri stars (CTTSs), generated where the infalling material impacts the stellar surface. Both observations and models of the accretion process reveal several aspects that are still unclear: the observed X-ray luminosity in accretion shocks is below the predicted value, and the density versus temperature structure of the shocked plasma, with increasing densities at higher temperature, deduced from the observations, is at odds with that proposed in the current picture of accretion shocks. To address these open issues, we investigate whether a correct treatment of the local absorption by the surrounding medium is crucial to explain the observations. To this end, we describe the impact of an accretion stream on a CTTS by considering a magnetohydrodynamic model. From the model results, we synthesize the X-ray emission from the accretion shock by producing maps and spectra. We perform density and temperature diagnostics on the synthetic spectra, and we directly compare the results with observations. Our model shows that the X-ray fluxes inferred from the emerging spectra are lower than expected because of the complex local absorption by the optically thick material of the chromosphere and of the unperturbed stream. Moreover, our model, including the effects of local absorption, explains in a natural way the apparently puzzling pattern of density versus temperature observed in the X-ray emission from accretion shocks.

  7. High spatial resolution optical imaging of the multiple T Tauri system LkH{\\alpha} 262/LkH{\\alpha} 263

    CERN Document Server

    Velasco, S; Oscoz, A; Mackay, C; Labadie, L; Garrido, A Pérez; Crass, J; Díaz-Sánchez, A; Femenía, B; González-Escalera, V; King, D L; López, R L; Puga, M; Rodríguez-Ramos, L F; Zuther, J

    2016-01-01

    We report high spatial resolution i' band imaging of the multiple T Tauri system LkH$\\alpha$ 262/LkH$\\alpha$ 263 obtained during the first commissioning period of the Adaptive Optics Lucky Imager (AOLI) at the 4.2 m William Herschel Telescope, using its Lucky Imaging mode. AOLI images have provided photometry for each of the two components LkH$\\alpha$ 263 A and B (0.41 arcsec separation) and marginal evidence for an unresolved binary or a disc in LkH$\\alpha$ 262. The AOLI data combined with previously available and newly obtained optical and infrared imaging show that the three components of LkH$\\alpha$ 263 are co-moving, that there is orbital motion in the AB pair, and, remarkably, that LkH$\\alpha$ 262-263 is a common proper motion system with less than 1 mas/yr relative motion. We argue that this is a likely five-component gravitationally bounded system. According to BT-settl models the mass of each of the five components is close to 0.4 M$_{\\odot}$ and the age is in the range 1-2 Myr. The presence of discs...

  8. X-ray to NIR emission from AA Tauri during the dim state - Occultation of the inner disk and gas-to-dust ratio of the absorber

    CERN Document Server

    Schneider, P C; Günther, H M; Herczeg, G J; Robrade, J; Bouvier, J; McJunkin, M; Schmitt, J H M M

    2015-01-01

    AA Tau is a well-studied, nearby classical T Tauri star, which is viewed almost edge-on. A warp in its inner disk periodically eclipses the central star, causing a clear modulation of its optical light curve. The system underwent a major dimming event beginning in 2011 caused by an extra absorber, which is most likely associated with additional disk material in the line of sight toward the central source. We present new XMM-Newton X-ray, Hubble Space Telescope FUV, and ground based optical and near-infrared data of the system obtained in 2013 during the long-lasting dim phase. The line width decrease of the fluorescent H$_2$ disk emission shows that the extra absorber is located at $r>1\\,$au. Comparison of X-ray absorption ($N_H$) with dust extinction ($A_V$), as derived from measurements obtained one inner disk orbit (eight days) after the X-ray measurement, indicates that the gas-to-dust ratio as probed by the $N_H$ to $A_V$ ratio of the extra absorber is compatible with the ISM ratio. Combining both result...

  9. Initial Results From the new Long Coring System of RV Knorr

    Science.gov (United States)

    Curry, W.; Keigwin, L.; Broda, J.; Mountain, G.; Pisias, N.

    2008-12-01

    A new long piston coring system has been designed and built for RV Knorr. The system is capable of deploying core lengths up to 46 m and weights of ~25000 lbs. With suitable modifications to other ships, a slightly smaller system could be deployed from other large UNOLS vessels. The handling system was designed around a hybrid rope blend of Vectran and Plasma braided with a torque-balanced, non- rotating construction. The rope is 7500 m long with a breaking strength (~360,000 lbs) more than 10 times greater than the pullout tensions experienced by the coring system. The high breaking strength limits stretching during coring operations, which minimizes rebound of the rope and movement of the piston during core penetration. An accelerometer placed on the release system documented that rope rebound was less than 2 m after the release of a ~15000 lb core at a water depth of 4585 m. The handling system for the new core includes a new A-frame mounted with a load transfer winch and a vertically-mounted rigging boom; a new stern-mounted grapple for transferring the corer from starboard to stern; a new deck-mounted traction winch for the Vectran-Plasma rope; and three new computer-controlled davit cranes along the starboard rail to raise and lower the corer between horizontal and vertical orientations. During testing at Bermuda Rise, core recovery exceeded 38 m, with cores generally filling 85% to 90% of the piston core barrel length. The test location has been cored many times before and stratigraphic correlation of the new cores with ODP Site 1063 shows that the new system recovered sediments without stretching. Three cores exhibit some evidence of compression at about 30 mbsf, while two others do not. These two cores were collected with a reduced-diameter core cutter, minimizing internal friction and enhancing core recovery. Four of the new cores completely recovered the last 150,000 years of sedimentation at Bermuda Rise with an average sedimentation rate of greater

  10. In situ measurements of IO and reactive iodine aboard the RV Sonne during SHIVA

    Science.gov (United States)

    Heard, Dwayne; Walker, Hannah; Ingham, Trevor; Huang, Ru-Jin; Wittrock, Folker

    2013-04-01

    Halogenated very short-lived substances (VSLS) are emitted from the oceans by marine species such as macroalgae and phytoplankton and contribute to halogen loading in the troposphere and lower stratosphere. The SHIVA (Stratospheric Ozone: Halogen Impacts in a Varying Atmosphere) project combined ship-borne, aircraft-based and ground-based measurements in and over the South China Sea and the Sulu Sea, and around the coast of Malaysian Borneo. In this paper we present measurements of IO radicals in coastal and open ocean regions made onboard the German research vessel RV Sonne in November 2011 between Singapore and Manila, via the northern coast of Malaysian Borneo (South China Sea) and the Sulu Sea. In situ measurements of IO were made on 12 days by the University of Leeds laser-induced fluorescence (LIF) instrument, with a detection limit of 0.3 pptv for a 30 minute averaging period. The cruise average IO concentration was found to be 1.2 pptv, with a maximum concentration of 2.4 pptv in the middle of the Sulu Sea, an area known for high biological activity. Only a weak diurnal profile was observed, with IO detected above the detection limit on 10 out of the 11 nights when the LIF instrument was operational. Measurements of IO at night in the open ocean have not previously been reported and indicate the presence of gas phase or heterogeneous mechanisms that recycle iodine species without requiring light. There was reasonable agreement for IO concentrations measured by the University of Leeds LIF and the University of Bremen MAX-DOAS instruments, for which a comparison will be presented. I2, ICl and HOI were measured by the University of Mainz using a coupled diffusion denuder system followed by analysis using gas chromatography coupled with ion trap mass spectroscopy, with a detection of 0.17 pptv for 30 mins (I2). The cruise average I2 concentration was found to be 2.0 pptv, with a maximum concentration observed during one night of 12.7 pptv on the northern coast

  11. The Mycobacterium tuberculosis Rv2540c DNA sequence encodes a bifunctional chorismate synthase

    Directory of Open Access Journals (Sweden)

    Santos Diógenes S

    2008-04-01

    Full Text Available Abstract Background The emergence of multi- and extensively-drug resistant Mycobacterium tuberculosis strains has created an urgent need for new agents to treat tuberculosis (TB. The enzymes of shikimate pathway are attractive targets to the development of antitubercular agents because it is essential for M. tuberculosis and is absent from humans. Chorismate synthase (CS is the seventh enzyme of this route and catalyzes the NADH- and FMN-dependent synthesis of chorismate, a precursor of aromatic amino acids, naphthoquinones, menaquinones, and mycobactins. Although the M. tuberculosis Rv2540c (aroF sequence has been annotated to encode a chorismate synthase, there has been no report on its correct assignment and functional characterization of its protein product. Results In the present work, we describe DNA amplification of aroF-encoded CS from M. tuberculosis (MtCS, molecular cloning, protein expression, and purification to homogeneity. N-terminal amino acid sequencing, mass spectrometry and gel filtration chromatography were employed to determine identity, subunit molecular weight and oligomeric state in solution of homogeneous recombinant MtCS. The bifunctionality of MtCS was determined by measurements of both chorismate synthase and NADH:FMN oxidoreductase activities. The flavin reductase activity was characterized, showing the existence of a complex between FMNox and MtCS. FMNox and NADH equilibrium binding was measured. Primary deuterium, solvent and multiple kinetic isotope effects are described and suggest distinct steps for hydride and proton transfers, with the former being more rate-limiting. Conclusion This is the first report showing that a bacterial CS is bifunctional. Primary deuterium kinetic isotope effects show that C4-proS hydrogen is being transferred during the reduction of FMNox by NADH and that hydride transfer contributes significantly to the rate-limiting step of FMN reduction reaction. Solvent kinetic isotope effects and

  12. Performance Evaluation of INMARSAT Fleet 77 Services Aboard the R/V Ewing

    Science.gov (United States)

    Schmidt, V. E.; Chayes, D. N.; Gold, E.

    2002-12-01

    In late 2001, the R/V Ewing was asked to conduct a trial installation of the Thrane and Thrane [of Denmark] F77 antennae [TT-3084A Capsat] and the newest IMNARSAT communications channel, INMARSAT F. Branded as "Fleet F77 Service" by INMARSAT, the service provides ISDN 64kbps and 56kbps high quality voice and data connections as well as Mobile Packet Data Service which allows an "always on" connection under which users pay for the packets they send rather than the time they are connected. Fleet F77 also allows low bandwidth [2.4kbps] "Mini-M" voice and fax services. While not currently available, the Capsat antennae also is prepared to take advantage of 4th Generation Inm-IV satellites [expected in 2004] allowing LAN speeds up to 432kbps. The F77 antenna consists of two units, the TT-3084A antenna and a single "Below Deck Unit". The Capsat antennae radome is a mere 84 cm in diameter - considerably smaller than that typically associated with INMARSAT A or B. It was mounted above the forward port corner of the pilot house atop a reinforced mast. Below deck electronics consist of a single unit containing three analog RJ-11 interfaces, a single ISDN interface, two RS-232 serial interfaces, a USB interface [not functional on our test unit] and a standard Handset. This was mounted in the pilot house electronics space. The Capsat antennae and associated electronics were installed in Guam in mid February 2002 and the system began operational trials during the following cruise on February 24th. Tests of the Fleet 77 system consisted of Mini-M voice and fax both to and from the ship, 64kbs voice to and from the ship, MPDS connects to shore, and operational tests with the INMARSAT Command Center. The trial period completed May 12th after which the F77 became an integral part of the Ewing's communication suite. Results of these tests as well as latency and packet loss measurements made over various data connection types will be presented.

  13. [Review of digital ground object spectral library].

    Science.gov (United States)

    Zhou, Xiao-Hu; Zhou, Ding-Wu

    2009-06-01

    A higher spectral resolution is the main direction of developing remote sensing technology, and it is quite important to set up the digital ground object reflectance spectral database library, one of fundamental research fields in remote sensing application. Remote sensing application has been increasingly relying on ground object spectral characteristics, and quantitative analysis has been developed to a new stage. The present article summarized and systematically introduced the research status quo and development trend of digital ground object reflectance spectral libraries at home and in the world in recent years. Introducing the spectral libraries has been established, including desertification spectral database library, plants spectral database library, geological spectral database library, soil spectral database library, minerals spectral database library, cloud spectral database library, snow spectral database library, the atmosphere spectral database library, rocks spectral database library, water spectral database library, meteorites spectral database library, moon rock spectral database library, and man-made materials spectral database library, mixture spectral database library, volatile compounds spectral database library, and liquids spectral database library. In the process of establishing spectral database libraries, there have been some problems, such as the lack of uniform national spectral database standard and uniform standards for the ground object features as well as the comparability between different databases. In addition, data sharing mechanism can not be carried out, etc. This article also put forward some suggestions on those problems.

  14. Untangling the Near-IR Spectral Features in the Protoplanetary Environment of KH 15D

    Science.gov (United States)

    Arulanantham, Nicole A.; Herbst, William; Gilmore, Martha S.; Cauley, P. Wilson; Leggett, S. K.

    2017-01-01

    We report on Gemini/GNIRS observations of the binary T Tauri system V582 Mon (KH 15D) at three orbital phases. These spectra allow us to untangle five components of the system: the photosphere and magnetosphere of star B, the jet, scattering properties of the ring material, and excess near-infrared (near-IR) radiation previously attributed to a possible self-luminous planet. We confirm an early-K subgiant classification for star B and show that the magnetospheric He i emission line is variable, possibly indicating increased mass accretion at certain times. As expected, the H2 emission features associated with the inner part of the jet show no variation with orbital phase. We show that the reflectance spectrum for the scattered light has a distinctive blue slope and spectral features consistent with scattering and absorption by a mixture of water and methane ice grains in the 1–50 μm size range. This suggests that the methane frost line is closer than ∼5 au in this system, requiring that the grains be shielded from direct radiation. After correcting for features from the scattered light, jet, magnetosphere, and photosphere, we confirm the presence of leftover near-IR light from an additional source, detectable near minimum brightness. A spectral emission feature matching the model spectrum of a 10 MJ, 1 Myr old planet is found in the excess flux, but other expected features from this model are not seen. Our observations, therefore, tentatively support the picture that a luminous planet is present within the system, although they cannot yet be considered definitive.

  15. Millimeter Spectral Indices and Dust Trapping By Planets in Brown Dwarf Disks

    Science.gov (United States)

    Pinilla, P.; Quiroga-Nuñez, L. H.; Benisty, M.; Natta, A.; Ricci, L.; Henning, Th.; van der Plas, G.; Birnstiel, T.; Testi, L.; Ward-Duong, K.

    2017-09-01

    Disks around brown dwarfs (BDs) are excellent laboratories to study the first steps of planet formation in cold and low-mass disk conditions. The radial-drift velocities of dust particles in BD disks higher than in disks around more massive stars. Therefore, BD disks are expected to be more depleted in millimeter-sized grains compared to disks around T Tauri or Herbig Ae/Be stars. However, recent millimeter observations of BD disks revealed low millimeter spectral indices, indicating the presence of large grains in these disks and challenging models of dust evolution. We present 3 mm photometric observations carried out with the IRAM/Plateau de Bure Interferometer (PdBI) of three BD disks in the Taurus star-forming region, which have been observed with ALMA at 0.89 mm. The disks were not resolved and only one was detected with enough confidence (∼3.5σ) with PdBI. Based on these observations, we obtain the values and lower limits of the spectral index and find low values (α mm ≲ 3.0). We compare these observations in the context of particle trapping by an embedded planet, a promising mechanism to explain the observational signatures in more massive and warmer disks. We find, however, that this model cannot reproduce the current millimeter observations for BD disks, and multiple-strong pressure bumps globally distributed in the disk remain as a favorable scenario to explain observations. Alternative possibilities are that the gas masses in the BD disk are very low (∼2 × 10‑3 M Jup) such that the millimeter grains are decoupled and do not drift, or fast growth of fluffy aggregates.

  16. The formation and evolution of planetary systems: Grain growth and chemical processing of dust in T Tauri systems

    CERN Document Server

    Bouwman, J; Hillenbrand, L A; Meyer, M R; Pascucci, I; Carpenter, J; Hines, D; Kim, J S; Silverstone, M D; Hollenbach, D; Wolf, S

    2008-01-01

    This paper is one in a series presenting results obtained within the Formation and Evolution of Planetary Systems (FEPS) Legacy Science Program on the Spitzer Space Telescope. Here we present a study of dust processing and growth in seven protoplanetary disks. Our spectra indicate that the circumstellar silicate dust grains have grown to sizes at least 10 times larger than observed in the interstellar medium, and show evidence for a non-negligible (~5 % in mass fractions) contribution from crystalline species. These results are similar to those of other studies of protoplanetary disks. In addition, we find a correlation between the strength of the amorphous silicate feature and the shape of the spectral energy distribution. This latter result is consistent with the growth and subsequent gravitational settling of dust grains towards the disk mid-plane. Further, we find a change in the relative abundance of the different crystalline species: more enstatite relative to forsterite is observed in the inner warm du...

  17. Mycobacterium tuberculosis DosR Regulon Gene Rv2004c Encodes a Novel Antigen with Pro-inflammatory Functions and Potential Diagnostic Application for Detection of Latent Tuberculosis

    Directory of Open Access Journals (Sweden)

    Sankara Narayana Doddam

    2017-06-01

    Full Text Available Approximately 1.7 billion people in the world harbor latent Mycobacterium tuberculosis (Mtb with a substantial risk of progression to clinical outcome. Containment of these seed beds of Mtb is essential to eliminate tuberculosis completely in high burden settings such as India. Hence, there is an urgent need for the identification of new serological markers for detection or vaccine candidates to prevent latent tuberculosis infection (LTBI. DosR regulon antigens of Mtb might serve as attractive targets for LTBI diagnosis or vaccine development as they are specifically expressed and are upregulated during latent phase. In this study, we investigated the role of Rv2004c, a member of DosR regulon (exclusive to Mtb complex, in host–pathogen interaction and its immunogenic potential in LTBI, active TB, and healthy control cohorts. Rv2004c elicited strong antibody response in individuals with LTBI compared to active TB patients and healthy cohorts. Recombinant Rv2004c induced pro-inflammatory cytokine response in human peripheral blood mononuclear cells and THP-1 cells via NF-κB phosphorylation. Interaction of Rv2004c with toll-like receptor (TLR-2 was confirmed using HEK-Blue hTLR-2 and pull-down assays. Rv2004c enhanced the surface expression of TLR-2 at mRNA and protein levels in THP-1 cells. Our findings revealed that Rv2004c induces strong humoral and cell mediated immune responses. Given these observations, we propose Rv2004c to be a potential diagnostic marker or an attractive vaccine candidate that can be useful against LTBI.

  18. Genome Sequence Analysis of CsRV1: A Pathogenic Reovirus that Infects the Blue Crab Callinectes sapidus Across Its Trans-Hemispheric Range.

    Science.gov (United States)

    Flowers, Emily M; Bachvaroff, Tsvetan R; Warg, Janet V; Neill, John D; Killian, Mary L; Vinagre, Anapaula S; Brown, Shanai; Almeida, Andréa Santos E; Schott, Eric J

    2016-01-01

    The blue crab, Callinectes sapidus Rathbun, 1896, which is a commercially important trophic link in coastal ecosystems of the western Atlantic, is infected in both North and South America by C. sapidus Reovirus 1 (CsRV1), a double stranded RNA virus. The 12 genome segments of a North American strain of CsRV1 were sequenced using Ion Torrent technology. Putative functions could be assigned for 3 of the 13 proteins encoded in the genome, based on their similarity to proteins encoded in other reovirus genomes. Comparison of the CsRV1 RNA-dependent RNA polymerase (RdRP) sequence to genomes of other crab-infecting reoviruses shows that it is similar to the mud crab reovirus found in Scylla serrata and WX-2012 in Eriocheir sinensis, Chinese mitten crab, and supports the idea that there is a distinct "Crabreo" genus, different from Seadornavirus and Cardoreovirus, the two closest genera in the Reoviridae. A region of 98% nucleotide sequence identity between CsRV1 and the only available sequence of the P virus of Macropipus depurator suggests that these two viruses may be closely related. An 860 nucleotide region of the CsRV1 RdRP gene was amplified and sequenced from 15 infected crabs collected from across the geographic range of C. sapidus. Pairwise analysis of predicted protein sequences shows that CsRV1 strains in Brazil can be distinguished from those in North America based on conserved residues in this gene. The sequencing, annotation, and preliminary population metrics of the genome of CsRV1 should facilitate additional studies in diverse disciplines, including structure-function relationships of reovirus proteins, investigations into the evolution of the Reoviridae, and biogeographic research on the connectivity of C. sapidus populations across the Northern and Southern hemispheres.

  19. Genome sequence analysis of CsRV1, a pathogenic reovirus that infects the blue crab Callinectes sapidus across its trans-hemispheric range

    Directory of Open Access Journals (Sweden)

    Emily Maya Flowers

    2016-02-01

    Full Text Available The blue crab, Callinectes sapidus (Rathbun 1896, which is a commercially important trophic link in coastal ecosystems of the western Atlantic, is infected in both North and South America by C. sapidus Reovirus 1 (CsRV1, a double stranded RNA virus. The 12 genome segments of a North American strain of CsRV1 were sequenced using Ion Torrent technology. Putative functions could be assigned for 3 of the 13 proteins encoded in the genome, based on their similarity to proteins encoded in other reovirus genomes. Comparison of the CsRV1 RNA dependent RNA polymerase (RdRP sequence to genomes of other crab-infecting reoviruses shows that it is similar to the MCRV virus found in Scylla serrata, mud crab, and WX-2012 in Eriocheir sinensis, Chinese mitten crab, and supports the idea that there is a distinct Crabreo genus, different from Seadornavirus and Cardoreovirus, the two closest genera in the Reoviridae. A region of 98% nucleotide sequence identity between CsRV1 and the only available sequence of the P virus of Macropipus depurator suggests that these two viruses may be closely related. An 860 nucleotide region of the CsRV1 RdRP gene was amplified and sequenced from 15 infected crabs collected from across the geographic range of C. sapidus. Pairwise analysis of predicted protein sequences shows that CsRV1 strains in Brazil can be distinguished from those in North America based on conserved residues in this gene. The sequencing, annotation, and preliminary population metrics of the genome of CsRV1 should facilitate additional studies in diverse disciplines, including structure-function relationships of reovirus proteins, investigations into the evolution of the Reoviridae, and biogeographic research on the connectivity of C. sapidus populations across the Northern and Southern hemispheres.

  20. Trichosanthes kirilowii Exerts Androgenic Activity via Regulation of PSA and KLK2 in 22Rv1 Prostate Cancer Cells

    Science.gov (United States)

    Jeong, Soo-Jin; Choi, Ji-Yoon; Dong, Mi-Sook; Seo, Chang-Seob; Shin, Hyeun-Kyoo

    2017-01-01

    Background: The androgen comprises a group of hormones that play roles in male reproductive activity as well as personal characteristics. Objective: We investigated the androgenic activity of various herbal medicines in human prostate cancer 22Rv1 cells. Materials and Methods: Herbal extracts of Trichosanthes kirilowii (TK), Asarum sieboldii (AS), Sanguisorba officinalis (SO), and Xanthium strumarium (XS) were selected to have androgenic effects based on a preliminary in vitro screening system. Results: TK, AS, SO, and XS enhanced the proliferation of 22Rv1 cells without having cytotoxic effects. All tested herbal extracts increased androgen receptor (AR)-induced transcriptional activity in the absence or presence of dihydrotestosterone (DHT). In an AR-binding assay, TK, but not AS, SO, or XS, produced a significant inhibition of AR binding activity, indicating it has androgenic activity. Additionally, TK treatment positively regulated mRNA expression of the AR-related molecular targets prostate-specific antigen (PSA) and kallikrein 2 (KLK2) compared with untreated control. Conclusion: Taken together, TK-enhanced AR-mediated transcriptional activity might be an attractive candidate drug for treating androgen-related diseases. SUMMARY Trichosantheskirilowii (TK), Asarumsieboldii (AS), Sanguisorbaofficinalis (SO), and Xanthium strumarium (XS) enhanced the proliferation of 22Rv1 cells without having cytotoxic effects.TK, AS, SO, and XS increased androgen receptor (AR)-induced transcriptional activity.TK, but not AS, SO, or XS, produced a significant inhibition against AR-binding activity.TK treatment positively regulated mRNA expression of the AR-related molecular targets prostate-specific antigen and kallikrein 2. Abbreviations used: BPH: benign prostatic hyperplasia; AR: androgen receptor; DHT: dihydrotestosterone; PSA: prostate-specific antigen; TK: Trichosanthes kirilowii; AS: Asarum sieboldii; SO: Sanguisorba officinalis; XS: Xanthium strumarium; ATCC: American

  1. The PE16 (Rv1430 of Mycobacterium tuberculosis is an esterase belonging to serine hydrolase superfamily of proteins.

    Directory of Open Access Journals (Sweden)

    Rafiya Sultana

    Full Text Available The PE and PPE multigene families, first discovered during the sequencing of M. tuberculosis H37Rv genome are responsible for antigenic variation and have been shown to induce increased humoral and cell mediated immune response in the host. Using the bioinformatics tools, we had earlier reported that the 225 amino acid residue PE-PPE domain (Pfam: PF08237 common to some PE and PPE proteins has a "serine α/β hydrolase" fold and conserved Ser, Asp and His catalytic triad characteristic of lipase, esterase and cutinase activities. In order to prove experimentally that PE-PPE domain is indeed a serine hydrolase, we have cloned the full-length Rv1430 and its PE-PPE domain into pET-28a vector, expressed the proteins in E. coli and purified to homogeneity. The activity assays of both purified proteins were carried out using p-nitrophenyl esters of aliphatic carboxylic acids with varying chain length (C2-C16 to study the substrate specificity. To characterize the active site of the PE-PPE domain, we mutated the Ser199 to Ala. The activity of the protein in the presence of serine protease inhibitor- PMSF and the mutant protein were measured. Our results reveal that Rv1430 and its PE-PPE domain possess esterase activity and hydrolyse short to medium chain fatty acid esters with the highest specific activity for pNPC6 at 37°C, 38°C and pH 7.0, 8.0. The details of this work and the observed results are reported in this manuscript.

  2. Definition of novel cell envelope associated proteins in Triton X-114 extracts of Mycobacterium tuberculosis H37Rv

    Directory of Open Access Journals (Sweden)

    Søfteland Tina

    2010-04-01

    Full Text Available Abstract Background Membrane- and membrane-associated proteins are important for the pathogenicity of bacteria. We have analysed the content of these proteins in virulent Mycobacterium tuberculosis H37Rv using Triton X-114 detergent-phase separation for extraction of lipophilic proteins, followed by their identification with high resolution mass spectrometry. Results In total, 1417 different proteins were identified. In silico analysis of the identified proteins revealed that 248 proteins had at least one predicted trans-membrane region. Also, 64 of the identified proteins were predicted lipoproteins, and 54 proteins were predicted as outer membrane proteins. Three-hundred-and-ninety-five of the observed proteins, including 91 integral membrane proteins were described for the first time. Comparison of abundance levels of the identified proteins was performed using the exponentially modified protein abundance index (emPAI which takes into account the number of the observable peptides to the number of experimentally observed peptide ions for a given protein. The outcome showed that among the membrane-and membrane-associated proteins several proteins are present with high relative abundance. Further, a close examination of the lipoprotein LpqG (Rv3623 which is only detected in the membrane fractions of M. tuberculosis but not in M. bovis, revealed that the homologous gene in M. bovis lack the signal peptide and lipobox motif, suggesting impaired export to the membrane. Conclusions Altogether, we have identified a substantial proportion of membrane- and membrane-associated proteins of M. tuberculosis H37Rv, compared the relative abundance of the identified proteins and also revealed subtle differences between the different members of the M. tuberculosis complex.

  3. Definition of novel cell envelope associated proteins in Triton X-114 extracts of Mycobacterium tuberculosis H37Rv.

    Science.gov (United States)

    Målen, Hiwa; Pathak, Sharad; Søfteland, Tina; de Souza, Gustavo A; Wiker, Harald G

    2010-04-29

    Membrane- and membrane-associated proteins are important for the pathogenicity of bacteria. We have analysed the content of these proteins in virulent Mycobacterium tuberculosis H37Rv using Triton X-114 detergent-phase separation for extraction of lipophilic proteins, followed by their identification with high resolution mass spectrometry. In total, 1417 different proteins were identified. In silico analysis of the identified proteins revealed that 248 proteins had at least one predicted trans-membrane region. Also, 64 of the identified proteins were predicted lipoproteins, and 54 proteins were predicted as outer membrane proteins. Three-hundred-and-ninety-five of the observed proteins, including 91 integral membrane proteins were described for the first time. Comparison of abundance levels of the identified proteins was performed using the exponentially modified protein abundance index (emPAI) which takes into account the number of the observable peptides to the number of experimentally observed peptide ions for a given protein. The outcome showed that among the membrane-and membrane-associated proteins several proteins are present with high relative abundance. Further, a close examination of the lipoprotein LpqG (Rv3623) which is only detected in the membrane fractions of M. tuberculosis but not in M. bovis, revealed that the homologous gene in M. bovis lack the signal peptide and lipobox motif, suggesting impaired export to the membrane. Altogether, we have identified a substantial proportion of membrane- and membrane-associated proteins of M. tuberculosis H37Rv, compared the relative abundance of the identified proteins and also revealed subtle differences between the different members of the M. tuberculosis complex.

  4. Spectral Analysis of Markov Chains

    OpenAIRE

    2007-01-01

    The paper deals with the problem of a statistical analysis of Markov chains connected with the spectral density. We present the expressions for the function of spectral density. These expressions may be used to estimate the parameter of the Markov chain.

  5. SPECTRAL ANALYSIS OF EXCHANGE RATES

    Directory of Open Access Journals (Sweden)

    ALEŠA LOTRIČ DOLINAR

    2013-06-01

    Full Text Available Using spectral analysis is very common in technical areas but rather unusual in economics and finance, where ARIMA and GARCH modeling are much more in use. To show that spectral analysis can be useful in determining hidden periodic components for high-frequency finance data as well, we use the example of foreign exchange rates

  6. Miniature spectrally selective dosimeter

    Energy Technology Data Exchange (ETDEWEB)

    Adams, R.R.; Macconochie, I.O.; Poole, B.D.

    1983-02-08

    The present invention discloses a miniature spectrally selective dosimeter capable of measuring selected bandwidths of radiation exposure on small mobile areas. This is achieved by the combination of photovoltaic detectors, electrochemical integrators (e-cells) and filters in a small compact case which can be easily attached in close proximity to and substantially parallel to the surface being measured. In one embodiment two photovoltaic detectors, two e-cells and three filters are packaged in a small case with attaching means consisting of a safety pin. In another embodiment, two detectors, one e-cell and three filters are packaged in a small case with attaching means consisting of a clip to clip over a side piece of an eye glass frame in a further embodiment, the electro-optic elements a packaged in a wristwatch case with attaching means being a watchband. The filters in all embodiments allow only selected wavelengths of radiation to be detected by the photovoltaic detectors and then integrated by the e-cells.

  7. Spectral numbers in Floer theories

    CERN Document Server

    Usher, Michael

    2007-01-01

    The chain complexes underlying Floer homology theories typically carry a real-valued filtration, allowing one to associate to each Floer homology class a spectral number defined as the infimum of the filtration levels of chains representing that class. These spectral numbers have been studied extensively in the case of Hamiltonian Floer homology by Oh, Schwarz, and others. We prove that the spectral number associated to any nonzero Floer homology class is always finite, and that the infimum in the definition of the spectral number is always attained. In the Hamiltonian case, this implies that what is known as the "nondegenerate spectrality" axiom holds on all closed symplectic manifolds. Our proofs are entirely algebraic and rather elementary, and apply to any Floer-type theory (including Novikov homology) satisfying certain standard formal properties provided that one works with coefficients in a Novikov ring whose degree-zero part \\Lambda_0 is a field. The key ingredient is a theorem about linear transforma...

  8. High level of IFN-γ released from whole blood of human tuberculosis infections following stimulation with Rv2073c of Mycobacterium tuberculosis.

    Science.gov (United States)

    Tan, Kun; Zhang, Jingyan; Teng, Xindong; Liang, Jinping; Wang, Xiaochun; Yuan, Xuefeng; Tian, Maopeng; Fan, Xionglin

    2015-07-01

    More efficacious and specific biomarkers are urgently needed for better control of tuberculosis (TB), the second leading infectious cause of mortality worldwide. The region of difference 9 (RD9) presents the genome of the causative pathogen Mycobacterium tuberculosis rather than other species of the genus Mycobacterium, which might be promising targets for specific diagnosis, vaccine development and pathogenesis. In this study, two proteins Rv2073c and Rv2074, encoded by the RD9 were expressed and purified from Escherichia coli system. Following stimulation with both proteins, the levels of IFN-γ secreted by T cells from a total of 49 whole blood samples obtained from clinically diagnosed active TB patients, patients with latent TB infections (LTBIs), and healthy donors, were compared with those of the incubation with recombinant fusion protein of CFP21 and MPT64 (rCM). Our results demonstrated that only Rv2073c could induce a higher level of IFN-γ in TB infections than healthy controls and there was a positive correlation between Rv2073c- and rCM-specific IFN-γ levels in TB infections and healthy donors, respectively. These findings indicate that Rv2073c might be a promising antigen for specific diagnostic reagents and vaccine candidates of TB.

  9. The influence of reduced oxygen availability on gene expression in laboratory (H37Rv) and clinical strains (S7 and S10) of Mycobacterium tuberculosis.

    Science.gov (United States)

    Devasundaram, Santhi; Khan, Imran; Kumar, Neeraj; Das, Sulochana; Raja, Alamelu

    2015-09-20

    Mycobacterium tuberculosis has the ability to persist within the host in a dormant stage. One important condition believed to contribute to dormancy is reduced access to oxygen known as hypoxia. However, the response of M. tuberculosis to such hypoxia condition is not fully characterized. Virtually all dormant models against tuberculosis tested in animals used laboratory strain H37Rv or Erdman strain. But major outbreaks of tuberculosis (TB) occur with the strains that have widely different genotypes and phenotypes compared to H37Rv. In this study, we used a custom oligonucleotide microarray to determine the overall transcriptional response of laboratory strain (H37Rv) and most prevalent clinical strains (S7 and S10) of M. tuberculosis from South India to hypoxia. Analysis of microarray results revealed that a total of 1161 genes were differentially regulated (≥1.5 fold change) in H37Rv, among them 659 genes upregulated and 502 genes down regulated. Microarray data of clinical isolates showed that a total of 790 genes were differentially regulated in S7 among which 453 genes were upregulated and 337 down regulated. Interestingly, numerous genes were also differentially regulated in S10 (total 2805 genes) of which 1463 genes upregulated and 1342 genes down regulated during reduced oxygen condition (Wayne's model). One hundred and thirty-four genes were found common and upregulated among all three strains (H37Rv, S7, and S10) and can be targeted for drug/vaccine development against TB.

  10. The 1600 Å Emission Bump in Protoplanetary Disks: A Spectral Signature of H2O Dissociation

    Science.gov (United States)

    France, Kevin; Roueff, Evelyne; Abgrall, Hervé

    2017-08-01

    The FUV continuum spectrum of many accreting pre-main sequence stars, Classical T Tauri Stars (CTTSs), does not continue smoothly from the well-studied Balmer continuum emission in the NUV, suggesting that additional processes contribute to the short-wavelength emission in these objects. The most notable spectral feature in the FUV continuum of some CTTSs is a broad emission approximately centered at 1600 Å, which has been referred to as the “1600 Å Bump.” The origin of this feature remains unclear. In an effort to better understand the molecular properties of planet-forming disks and the UV spectral properties of accreting protostars, we have assembled archival FUV spectra of 37 disk-hosting systems observed by the Hubble Space Telescope-Cosmic Origins Spectrograph. Clear 1600 Å Bump emission is observed above the smooth, underlying 1100-1800 Å continuum spectrum in 19/37 Classical T Tauri disks in the HST-COS sample, with the detection rate in transition disks (8/8) being much higher than that in primordial or non-transition sources (11/29). We describe a spectral deconvolution analysis to separate the Bump (spanning 1490-1690 Å) from the underlying FUV continuum, finding an average Bump luminosity L(Bump) ≈ 7 × 1029 erg s-1. Parameterizing the Bump with a combination of Gaussian and polynomial components, we find that the 1600 Å Bump is characterized by a peak wavelength λ o = 1598.6 ± 3.3 Å, with FWHM = 35.8 ± 19.1 Å. Contrary to previous studies, we find that this feature is inconsistent with models of H2 excited by electron -impact. We show that this Bump makes up between 5%-50% of the total FUV continuum emission in the 1490-1690 Å band and emits roughly 10%-80% of the total fluorescent H2 luminosity for stars with well-defined Bump features. Energetically, this suggests that the carrier of the 1600 Å Bump emission is powered by Lyα photons. We argue that the most likely mechanism is Lyα-driven dissociation of H2O in the inner disk, r

  11. Measured and parameterized energy fluxes estimated for Atlantic transects of RV Polarstern

    Science.gov (United States)

    Bumke, Karl; Macke, Andreas; Kalisch, John; Kleta, Henry

    2013-04-01

    Even to date energy fluxes over the oceans are difficult to assess. As an example the relative paucity of evaporation observations and the uncertainties of currently employed empirical approaches lead to large uncertainties of evaporation products over the ocean (e.g. Large and Yeager, 2009). Within the frame of OCEANET (Macke et al., 2010) we performed such measurements on Atlantic transects between Bremerhaven (Germany) and Cape Town (South Africa) or Punta Arenas (Chile) onboard RV Polarstern during the recent years. The basic measurements of sensible and latent heat fluxes are inertial-dissipation (e.g. Dupuis et al., 1997) flux estimates and measurements of the bulk variables. Turbulence measurements included a sonic anemometer and an infrared hygrometer, both mounted on the crow's nest. Mean meteorological sensors were those of the ship's operational measurement system. The global radiation and the down terrestrial radiation were measured on the OCEANET container placed on the monkey island. At least about 1000 time series of 1 h length were analyzed to derive bulk transfer coefficients for the fluxes of sensible and latent heat. The bulk transfer coefficients were applied to the ship's meteorological data to derive the heat fluxes at the sea surface. The reflected solar radiation was estimated from measured global radiation. The up terrestrial radiation was derived from the skin temperature according to the Stefan-Boltzmann law. Parameterized heat fluxes were compared to the widely used COARE-parameterization (Fairall et al., 2003), the agreement is excellent. Measured and parameterized heat and radiation fluxes gave the total energy budget at the air sea interface. As expected the mean total flux is positive, but there are also areas, where it is negative, indicating an energy loss of the ocean. It could be shown that the variations in the energy budget are mainly due to insolation and evaporation. A comparison between the mean values of measured and

  12. CCN Spectral Measurements

    Energy Technology Data Exchange (ETDEWEB)

    Hudson, James G.

    2009-02-27

    Detailed aircraft measurements were made of cloud condensation nuclei (CCN) spectra associated with extensive cloud systems off the central California coast in the July 2005 MASE project. These measurements include the wide supersaturation (S) range (2-0.01%) that is important for these polluted stratus clouds. Concentrations were usually characteristic of continental/anthropogenic air masses. The most notable feature was the consistently higher concentrations above the clouds than below. CCN measurements are so important because they provide a link between atmospheric chemistry and cloud-climate effects, which are the largest climate uncertainty. Extensive comparisons throughout the eleven flights between two CCN spectrometers operated at different but overlapping S ranges displayed the precision and accuracy of these difficult spectral determinations. There are enough channels of resolution in these instruments to provide differential spectra, which produce more rigorous and precise comparisons than traditional cumulative presentations of CCN concentrations. Differential spectra are also more revealing than cumulative spectra. Only one of the eleven flights exhibited typical maritime concentrations. Average below cloud concentrations over the two hours furthest from the coast for the 8 flights with low polluted stratus was 614?233 at 1% S, 149?60 at 0.1% S and 57?33 at 0.04% S cm-3. Immediately above cloud average concentrations were respectively 74%, 55%, and 18% higher. Concentration variability among those 8 flights was a factor of two. Variability within each flight excluding distances close to the coast ranged from 15-56% at 1% S. However, CN and probably CCN concentrations sometimes varied by less than 1% over distances of more than a km. Volatility and size-critical S measurements indicated that the air masses were very polluted throughout MASE. The aerosol above the clouds was more polluted than the below cloud aerosol. These high CCN concentrations from

  13. The R/V EL PUMA and JUSTO SIERRA impact on the development of oceanography in Mexico

    Science.gov (United States)

    Gracia, A.

    2007-05-01

    The acquisition of the two research vessels (R/V EL PUMA AND R/V JUSTO SIERRA) of the Universidad Nacional Autónoma de México represented a milestone for the development of oceanography and capacity building in Mexico. These boats were designed to conduct multi and interdisciplinary research in the Economic Exclusive Zone of Mexico in the main areas of oceanography (Physics, Geology, Chemistry and Biology). Its use, by different institutions, resulted in a substantial advancement of the knowledge of Marine ecosystems of Mexico. About 460 oceanographic campaigns, with more than 8700 participants, have been conducted since the boats arrived. These covered a wide array of topics of the marine ecosystem from the inner shelf to deep sea. Extensive research was done on current patterns, primary productivity and pollution monitoring of the Mexican Pacific, Sea of Cortez, Gulf of Mexico and Caribbean sea. Marine biodiversity studies were also carried which discovered more than 180 new species in Mexican seas. Ecological characterization and paleo-oceanographic research from continental shelf to deep sea also registered a substantial advance. The vessels are now renewed with hi-tech equipment for sea bottom, water column and navigation that increased their research capacity, representing again a new milestone in the history of oceanography in Mexico. This improved capacity is very promising and opens new and sound opportunities for carrying modern oceanographic in order to improve knowledge of the Mexican Economic Exclusive Zone.

  14. Effects of Calorie Restriction and IGF-1 Receptor Blockade on the Progression of 22Rv1 Prostate Cancer Xenografts

    Directory of Open Access Journals (Sweden)

    Colette Galet

    2013-07-01

    Full Text Available Calorie restriction (CR inhibits prostate cancer progression, partially through modulation of the IGF axis. IGF-1 receptor (IGF-1R blockade reduces prostate cancer xenograft growth. We hypothesized that combining calorie restriction with IGF-1R blockade would have an additive effect on prostate cancer growth. Severe combined immunodeficient mice were subcutaneously injected with 22Rv1 cells and randomized to: (1 Ad libitum feeding/intraperitoneal saline (Ad-lib; (2 Ad-lib/20 mg/kg twice weekly, intraperitoneal ganitumab [anti-IGF-1R antibody (Ad-lib/Ab]; (3 40% calorie restriction/intraperitoneal saline (CR; (4 CR/ intraperitoneal ganitumab, (CR/Ab. CR and ganitumab treatment were initiated one week after tumor injection. Euthanasia occurred 19 days post treatment. Results showed that CR alone decreased final tumor weight, plasma insulin and IGF-1 levels, and increased apoptosis. Ganitumab therapy alone reduced tumor growth but had no effect on final tumor weight. The combination therapy (CR/Ab further decreased final tumor weight and proliferation, increased apoptosis in comparison to the Ad-lib group, and lowered plasma insulin levels relative to the Ad-lib and Ad-lib/Ab groups. Tumor AKT activation directly correlated with plasma IGF-1 levels. In conclusion, whereas ganitumab therapy modestly affected 22Rv1 tumor growth, combining IGF-1R blockade with calorie restriction resulted in a significant decrease in final tumor weight and improved metabolic profile.

  15. Structure of pyrR (Rv1379) from Mycobacterium tuberculosis: A persistence gene and protein drug target

    Energy Technology Data Exchange (ETDEWEB)

    Kantardjieff, K A; Vasquez, C; Castro, P; Warfel, N M; Rho, B; Lekin, T; Kim, C; Segelke, B W; Terwilliger, T C; Rupp, B

    2004-09-24

    The 1.9 {angstrom} native structure of pyrimidine biosynthesis regulatory protein encoded by the Mycobacterium tuberculosis pyrR gene (Rv1379) is reported. Because pyrimidine biosynthesis is an essential step in the progression of TB, pyrR is an attractive antitubercular drug target. The Mycobacterium tuberculosis pyrR gene (Rv1379) encodes a protein that regulates expression of pyrimidine nucleotide biosynthesis (pyr) genes in a UMP-dependent manner. Because pyrimidine biosynthesis is an essential step in the progression of TB, the gene product pyrR is an attractive antitubercular drug target. We report the 1.9 {angstrom} native structure of Mtb pyrR determined by the TB Structural Genomics Consortium facilities (PDB entry 1W30) in trigonal space group P3{sub 1}21, with cell dimensions at 120K of a = 66.64 {angstrom}, c = 154.72 {angstrom}, and two molecules in the asymmetric unit. The 3D structure and residual uracil phosphoribosyltransferase activity point to a common PRTase ancestor for pyrR. However, while PRPP and UMP binding sites have been retained in Mtb pyrR, a novel dimer interaction among subunits creates a deep, positively charged cleft capable of binding pyr mRNA. In silico screening of pyrimidine nucleoside analogs has revealed a number of potential leads compounds that, if bound to Mtb pyrR, could facilitate transcriptional attenuation, particularly cyclopentenyl nucleosides.

  16. Palaeolimnological assessment of environmental change over the last two centuries in oligotrophic Lake Nohipalu Valgjärv, southern Estonia

    Directory of Open Access Journals (Sweden)

    Heinsalu, Atko

    2009-06-01

    Full Text Available The main objectives of this study were to reconstruct the environmental conditions for a small oligotrophic lake during the last two centuries, to determine if the environment of the lake was anthropogenically mediated, and to assess the pre-impact reference conditions with palaeolimnological techniques. A short sediment core from Lake Nohipalu Valgjärv was analysed in detail for diatom assemblages as well as for loss-on-ignition measurements. Accurate chronology of the sediment core was established and evaluated by different independent approaches – 210Pb, 137Cs, and 241Am dating, and the distribution of spheroidal fly-ash particles in sediments. Quantitative inference models based on sedimentary diatoms were applied to reconstruct changes in past lake water pH. Before the mid-19th century, Nohipalu Valgjärv was an oligotrophic lake with clear water continuously transparent down to the bottom and with rich benthic diatom flora. Since the early second half of the 19th century, presumably as a result of forest logging around the lake, water transparency decreased and benthic diatom productivity diminished, and the lake did not recover any more to natural baseline conditions. Due to peat mining activities in the Meenikunno bog, the quality of lake water has changed during the last two decades. The lowered lake level, deteriorated light climate, and decreased pH are the most important environmental variables that have influenced the lake ecosystem.

  17. Chromospheric activity and rotational modulation of the RS Canum Venaticorum binary V711 Tauri during 1998-2004

    Science.gov (United States)

    Cao, Dongtao; Gu, Shenghong

    2015-05-01

    We present long-term high-resolution spectroscopic observations of the very active RS Canum Venaticorum-type star V711 Tau, obtained during several observing runs from 1998 to 2004, and study its chromospheric activity. Using the spectral subtraction technique, several optical chromospheric activity indicators [including the He I D3, Na I D1, D2, Hα and Ca II infrared triplet (IRT) lines] formed at different atmospheric heights are analysed. Strong chromospheric emission supports earlier results that indicate that V711 Tau is a very active system. Two large optical flares were detected during our observations. The results suggest that the main part of chromospheric emission is attributed to the primary star of the system. The secondary also presents weak emission but is less active. The ratios of EW8542/EW8498 indicate that Ca II IRT emission arises predominantly from plage-like regions. We have found rotational modulation of chromospheric activity in the Hα and Ca II IRT lines, which suggests the presence of the chromospheric active longitudes over the surface of V711 Tau. Two active longitudes separated by about 180° were observed to dominate the activity, and the so-called flip-flop phenomenon was seen during our observations. Moreover, the chromospheric activity level shows a long-term variation that gradually increases from a deep minimum near the year 2002. A close spatial connection of photospheric spots and chromospheric active regions in both short and long timescales was found for V711 Tau.

  18. Discovery and Observations of ASASSN-13db, an EXor Accretion Event on a Low-Mass T Tauri Star

    CERN Document Server

    Holoien, Thomas W -S; Stanek, Krzysztof Z; Kochanek, Christopher S; Shappee, B J; Zhu, Z; Sicilia-Aguilar, A; Grupe, D; Croxall, K; Adams, J; Simon, J D; McGraw, N Morell S M; Wagner, R M; Basu, U; Beacom, J F; Bersier, D; Brimacombe, J; Jencson, J; Pojmanski, G; Starrfield, S G; Szczygieł, D M; Woodward, C E

    2014-01-01

    We discuss ASASSN-13db, an EXor accretion event on the young stellar object (YSO) SDSS J051011.01$-$032826.2 (hereafter SDSSJ0510) discovered by the All-Sky Automated Survey for SuperNovae (ASAS-SN). Using archival photometric data of SDSSJ0510 we construct a pre-outburst spectral energy distribution (SED) and find that it is consistent with a low-mass class II YSO near the Orion star forming region ($d \\sim 420$ pc). We present follow-up photometric and spectroscopic observations of the source after the $\\Delta V \\sim-$3.7 mag outburst that began in September 2013. These data indicate an increase in temperature and luminosity consistent with an accretion rate of $\\sim10^{-7}$ $\\rm{M}_\\odot$ yr$^{-1}$, three-to-five orders of magnitude greater than in quiescence. Spectroscopic observations show a forest of narrow emission lines dominated by neutral metallic lines from Fe I and some low-ionization lines. The properties of ASASSN-13db are similar to those of the EXor prototype EX~Lupi in late 2008 during its st...

  19. AT-RvD1 Modulates CCL-2 and CXCL-8 Production and NF-κB, STAT-6, SOCS1, and SOCS3 Expression on Bronchial Epithelial Cells Stimulated with IL-4

    Directory of Open Access Journals (Sweden)

    Jhony Robison de Oliveira

    2015-01-01

    Full Text Available Bronchial epithelial cells represent the first line of defense against microorganisms and allergens in the airways and play an important role in chronic inflammatory processes such as asthma. In an experimental model, both RvD1 and AT-RvD1, lipid mediators of inflammation resolution, ameliorated some of the most important phenotypes of experimental asthma. Here, we extend these results and demonstrate the effect of AT-RvD1 on bronchial epithelial cells (BEAS-2B stimulated with IL-4. AT-RvD1 (100 nM decreased both CCL2 and CXCL-8 production, in part by decreasing STAT6 and NF-κB pathways. Furthermore, the effects of AT-RvD1 were ALX/FRP2 receptor dependent, as the antagonist of this receptor (BOC1 reversed the inhibition of these chemokines by AT-RvD1. In addition, AT-RvD1 decreased SOCS1 and increased SOCS3 expression, which play important roles in Th1 and Th17 modulation, respectively. In conclusion, AT-RvD1 demonstrated significant effects on the IL-4-induced activation of bronchial epithelial cells and consequently the potential to modulate neutrophilic and eosinophilic airway inflammation in asthma. Taken together, these findings identify AT-RvD1 as a potential proresolving therapeutic agent for allergic responses in the airways.

  20. spectral-cube: Read and analyze astrophysical spectral data cubes

    Science.gov (United States)

    Robitaille, Thomas; Ginsburg, Adam; Beaumont, Chris; Leroy, Adam; Rosolowsky, Erik

    2016-09-01

    Spectral-cube provides an easy way to read, manipulate, analyze, and write data cubes with two positional dimensions and one spectral dimension, optionally with Stokes parameters. It is a versatile data container for building custom analysis routines. It provides a uniform interface to spectral cubes, robust to the wide range of conventions of axis order, spatial projections, and spectral units that exist in the wild, and allows easy extraction of cube sub-regions using physical coordinates. It has the ability to create, combine, and apply masks to datasets and is designed to work with datasets too large to load into memory, and provide basic summary statistic methods like moments and array aggregates.

  1. Timescale Analysis of Spectral Lags

    Institute of Scientific and Technical Information of China (English)

    Ti-Pei Li; Jin-Lu Qu; Hua Feng; Li-Ming Song; Guo-Qiang Ding; Li Chen

    2004-01-01

    A technique for timescale analysis of spectral lags performed directly in the time domain is developed. Simulation studies are made to compare the time domain technique with the Fourier frequency analysis for spectral time lags. The time domain technique is applied to studying rapid variabilities of X-ray binaries and γ-ray bursts. The results indicate that in comparison with the Fourier analysis the timescale analysis technique is more powerful for the study of spectral lags in rapid variabilities on short time scales and short duration flaring phenomena.

  2. Aquecimento alfvênico viscoso-resistivo em discos de acresção ao redor de estrelas T Tauri clássicas

    Science.gov (United States)

    Santana, W. M.; Vasconcelos, M. J.

    2003-08-01

    Com a crescente disponibilidade de dados observacionais sobre estrelas T Tauri, a busca por modelos mais precisos vem se tornando cada vez maior. Estes modelos devem explicar, entre outras coisas, o mecanismo dissipativo responsável pelo transporte de momento angular no disco de acresção que acredita-se, circunda estas estrelas. O mecanismo mais viável, do ponto de vista teórico, é uma instabilidade MHD conhecida como "instabilidade magnetorotacional ou Balbus-Hawley" (IBH). Esta instabilidade veio mostrar que o campo magnético desempenha um papel importante na evolução destes objetos mas requer, no entanto, um acoplamento mínimo entre o gás e o campo magnético no disco que não é atingido para os valores de temperatura obtidos do modelo padrão. Contudo, alguns mecanismos de aquecimento para o disco precisam ser examinados. Neste trabalho, propomos a dissipação de ondas Alfvén como uma fonte de aquecimento para o disco. Se o gás apresentar uma condutividade elétrica finita e viscosidade, teremos um tipo de amortecimento para as ondas denominado amortecimento viscoso-resistivo que será aqui considerado. Este mecanismo é aplicado ao modelo de disco em camadas. Calculam-se as taxas de aquecimento Alfvênico, a temperatura efetiva do disco bem como as taxas de ionização decorrentes deste aquecimento e do aquecimento gerado pela absorção de raios cósmicos. Comparações com os dados observacionais de Kitamura et. al. (2001) são efetuadas, ressaltando-se os pontos comuns entre suas observações e nossos dados teóricos.

  3. Cell death of THP-1 induced by puried Rv3671c protein of tuberculosis and the detection of TNF-α and IL-1β in Mycobacterium tuberculosis%结核分枝杆菌Rv3671c蛋白诱导人巨噬细胞死亡及TNF-α和IL-1β水平检测

    Institute of Scientific and Technical Information of China (English)

    蒯守刚; 裴豪; 黄利华; 刘忠华; 麦广良; 刘君; 崔振玲

    2013-01-01

    Objective To assess the response in THP-1 treated with Rv3671c protein in Mycobacterium tuberculosis (M.tuberculosis).Methods The gene encoding Rv3671 c protein of M.tuberculosis was cloned into pET-28a vector and then expressed in Escherichia coli.The Rv3671c was purified with Ni-NTA affinity and ion exchange chromatography.The detection of protein concentration was by Lowry method.THP-1 cell was stimulated with Rv3671c protein and cells were analyzed by Hochest staining under fluorescence microscopy to assay cell death (apoptosis and necrosis).TNF-α and IL-1β were detected by ELISA at each stimulating time.Results The Rv3671c protein of M.tuberculosis was successfully expressed in Escherichia coli.The purity of recombinant Rv3671c protein was 95%,and the protein concentration was up to 0.4 mg/ml.The nucleus of THP-1 was isolated and necrosis-like under fluorescence when cells were stimulated by Rv3671c protein.The levels of TNF-α and IL-1β in supernatant were 19 000 and 16 500 pg/ml respectively,and were significantly higher than control cells with the levels of 2100 and 3800 pg/ml separately.Conclusion The necrosis of THP-1 cells could be stimulated by Rv3671c protein of M.tuberculosis and it was probably associated with high cytokines TNF-α and IL-13 levels.%目的 评价MTB Rv3671 c蛋白对人巨噬细胞(THP-1)的影响及机制.方法 将编码MTB Rv3671c蛋白的基因克隆到pET-28a质粒,并在大肠埃希菌中进行表达,采用镍亲和层析和离子层析法纯化重组Rv3671c蛋白,Lowry法测定蛋白浓度,并用纯化蛋白刺激分化成熟巨噬细胞,采用Hochest染色法观察细胞的转归(凋亡及坏死)情况,同时取上清液用ELISA法检测TNF-α和IL-1β 的浓度.结果 MTB Rv3671c蛋白在大肠埃希菌中成功表达,层析纯化获得纯度为95.0%的重组Rv3671c蛋白,蛋白浓度可达0.4 mg/ml.Rv3671c蛋白刺激下经Hochest染色可见巨噬细胞核以坏死状多见,上清液中TNF-α和IL-13

  4. Interplay between Intravitreal RvD1 and Local Endogenous Sirtuin-1 in the Protection from Endotoxin-Induced Uveitis in Rats

    Directory of Open Access Journals (Sweden)

    S. Rossi

    2015-01-01

    Full Text Available Rat endotoxin-induced uveitis (EIU is a well-established model of human uveitis. In this model, intravitreal injection of resolvin D1 (RvD1, 10–100–1000 ng/kg 1 hour after subcutaneous treatment of Sprague-Dawley rats with lipopolysaccharide (LPS, 200 μg/rat significantly prevented the development of uveitis into the eye. RvD1 dose-dependently increased the expression of sirtuin-1 (SIRT1 within the eye, while it decreased the expression of acetyl-p53 and acetyl-FOXO1. These effects were accompanied by local downregulation of some microRNAs related to the expression and activity of SIRT1. These were miR-195-5p, miR-200a-3p, miR-34a-5p, and miR-145-5p. An increase of manganese superoxide dismutase and decrease of caspase 3 were evident after RvD1 treatment. In another set of experiments, the protective effects of RvD1 (1000 ng/kg were partly abolished by the pretreatment of the rats with EX527 (10 mg/kg/day, i.p., a specific inhibitor of SIRT1 activity, for 7 days prior to the induction of EIU in rats. Similarly, the effects of RvD1 (1000 ng/kg on the SIRT1 protein expression were abolished by Boc2, N-t-butoxycarbonyl-PLPLP, a specific formyl-peptide receptor type 2/lipoxin A receptor antagonist. Therefore, an interplay of the SIRT1 activity on the RvD1 mediated resolution of EIU is argued.

  5. A Study on the Marketing Strategy of RV Travel in China%国内房车旅游营销策略研究

    Institute of Scientific and Technical Information of China (English)

    梁磊

    2011-01-01

    With the advent of experience economy, RV travel is increasingly welcomed as a fashionable way to travel. At present, the domestic RV tourism development is far behind the developed countries, and there exist such problems as delayed construction of camping and related facilities, the inadequate consumption capacity, the inadequate RV tourism marketing and delayed tourism facilities and services. To solve these problems, this paper puts forward some marketing strategies, including carrying out camp marketing, subdividing RV tourism market, strengthening cooperation among related industries and enterprises, improving ways and means of RV tourism information dissemination, and promoting the construction of RV rental network.%随着体验经济时代的到来,房车旅游作为一种时尚的旅游方式日益受到人们的青睐。当前,国内房车旅游发展远远落后于发达国家,并存在露营地及相关设施建设滞后、居民消费能力不足、房车旅游营销力度不够和房车旅游设施及服务滞后的问题,针对这些问题,提出开展营地营销、细分房车旅游市场、加强房车旅游相关行业企业之间的合作、优化房车旅游信息传播方式和手段、加强房车租赁网络建设的房车旅游具体营销策略。

  6. Broadband Advanced Spectral System Project

    Data.gov (United States)

    National Aeronautics and Space Administration — NovaSol proposes to develop an advanced hyperspectral imaging system for earth science missions named BRASS (Broadband Advanced Spectral System). BRASS combines...

  7. Matched Spectral Filter Imager Project

    Data.gov (United States)

    National Aeronautics and Space Administration — OPTRA proposes the development of an imaging spectrometer for greenhouse gas and volcanic gas imaging based on matched spectral filtering and compressive imaging....

  8. Spectral Methods for Numerical Relativity

    CERN Document Server

    Grandclément, Philippe

    2007-01-01

    Equations arising in General Relativity are usually to complicated to be solved analytically and one has to rely on numerical methods to solve sets of coupled, partial differential, equations. Amongst the possible choices, this paper focuses on a class called spectral methods where, typically, the various functions are expanded onto sets of orthogonal polynomials or functions. A theoretical introduction on spectral expansion is first given and a particular emphasize is put on the fast convergence of the spectral approximation. We present then different approaches to solve partial differential equations, first limiting ourselves to the one-dimensional case, with one or several domains. Generalization to more dimensions is then discussed. In particular, the case of time evolutions is carefully studied and the stability of such evolutions investigated. One then turns to results obtained by various groups in the field of General Relativity by means of spectral methods. First, works which do not involve explicit t...

  9. Substitution dynamical systems spectral analysis

    CERN Document Server

    Queffélec, Martine

    2010-01-01

    This volume mainly deals with the dynamics of finitely valued sequences, and more specifically, of sequences generated by substitutions and automata. Those sequences demonstrate fairly simple combinatorical and arithmetical properties and naturally appear in various domains. As the title suggests, the aim of the initial version of this book was the spectral study of the associated dynamical systems: the first chapters consisted in a detailed introduction to the mathematical notions involved, and the description of the spectral invariants followed in the closing chapters. This approach, combined with new material added to the new edition, results in a nearly self-contained book on the subject. New tools - which have also proven helpful in other contexts - had to be developed for this study. Moreover, its findings can be concretely applied, the method providing an algorithm to exhibit the spectral measures and the spectral multiplicity, as is demonstrated in several examples. Beyond this advanced analysis, many...

  10. Spectral Theory and Mirror Symmetry

    CERN Document Server

    Marino, Marcos

    2015-01-01

    Recent developments in string theory have revealed a surprising connection between spectral theory and local mirror symmetry: it has been found that the quantization of mirror curves to toric Calabi-Yau threefolds leads to trace class operators, whose spectral properties are conjecturally encoded in the enumerative geometry of the Calabi-Yau. This leads to a new, infinite family of solvable spectral problems: the Fredholm determinants of these operators can be found explicitly in terms of Gromov-Witten invariants and their refinements; their spectrum is encoded in exact quantization conditions, and turns out to be determined by the vanishing of a quantum theta function. Conversely, the spectral theory of these operators provides a non-perturbative definition of topological string theory on toric Calabi-Yau threefolds. In particular, their integral kernels lead to matrix integral representations of the topological string partition function, which explain some number-theoretic properties of the periods. In this...

  11. The glycosylated Rv1860 protein of Mycobacterium tuberculosis inhibits dendritic cell mediated TH1 and TH17 polarization of T cells and abrogates protective immunity conferred by BCG.

    Science.gov (United States)

    Satchidanandam, Vijaya; Kumar, Naveen; Jumani, Rajiv S; Challu, Vijay; Elangovan, Shobha; Khan, Naseem A

    2014-06-01

    We previously reported interferon gamma secretion by human CD4⁺ and CD8⁺ T cells in response to recombinant E. coli-expressed Rv1860 protein of Mycobacterium tuberculosis (MTB) as well as protection of guinea pigs against a challenge with virulent MTB following prime-boost immunization with DNA vaccine and poxvirus expressing Rv1860. In contrast, a Statens Serum Institute Mycobacterium bovis BCG (BCG-SSI) recombinant expressing MTB Rv1860 (BCG-TB1860) showed loss of protective ability compared to the parent BCG strain expressing the control GFP protein (BCG-GFP). Since Rv1860 is a secreted mannosylated protein of MTB and BCG, we investigated the effect of BCG-TB1860 on innate immunity. Relative to BCG-GFP, BCG-TB1860 effected a significant near total reduction both in secretion of cytokines IL-2, IL-12p40, IL-12p70, TNF-α, IL-6 and IL-10, and up regulation of co-stimulatory molecules MHC-II, CD40, CD54, CD80 and CD86 by infected bone marrow derived dendritic cells (BMDC), while leaving secreted levels of TGF-β unchanged. These effects were mimicked by BCG-TB1860His which carried a 6-Histidine tag at the C-terminus of Rv1860, killed sonicated preparations of BCG-TB1860 and purified H37Rv-derived Rv1860 glycoprotein added to BCG-GFP, but not by E. coli-expressed recombinant Rv1860. Most importantly, BMDC exposed to BCG-TB1860 failed to polarize allogeneic as well as syngeneic T cells to secrete IFN-γ and IL-17 relative to BCG-GFP. Splenocytes from mice infected with BCG-SSI showed significantly less proliferation and secretion of IL-2, IFN-γ and IL-17, but secreted higher levels of IL-10 in response to in vitro restimulation with BCG-TB1860 compared to BCG-GFP. Spleens from mice infected with BCG-TB1860 also harboured significantly fewer DC expressing MHC-II, IL-12, IL-2 and TNF-α compared to mice infected with BCG-GFP. Glycoproteins of MTB, through their deleterious effects on DC may thus contribute to suppress the generation of a TH1- and TH17-dominated

  12. The glycosylated Rv1860 protein of Mycobacterium tuberculosis inhibits dendritic cell mediated TH1 and TH17 polarization of T cells and abrogates protective immunity conferred by BCG.

    Directory of Open Access Journals (Sweden)

    Vijaya Satchidanandam

    2014-06-01

    Full Text Available We previously reported interferon gamma secretion by human CD4⁺ and CD8⁺ T cells in response to recombinant E. coli-expressed Rv1860 protein of Mycobacterium tuberculosis (MTB as well as protection of guinea pigs against a challenge with virulent MTB following prime-boost immunization with DNA vaccine and poxvirus expressing Rv1860. In contrast, a Statens Serum Institute Mycobacterium bovis BCG (BCG-SSI recombinant expressing MTB Rv1860 (BCG-TB1860 showed loss of protective ability compared to the parent BCG strain expressing the control GFP protein (BCG-GFP. Since Rv1860 is a secreted mannosylated protein of MTB and BCG, we investigated the effect of BCG-TB1860 on innate immunity. Relative to BCG-GFP, BCG-TB1860 effected a significant near total reduction both in secretion of cytokines IL-2, IL-12p40, IL-12p70, TNF-α, IL-6 and IL-10, and up regulation of co-stimulatory molecules MHC-II, CD40, CD54, CD80 and CD86 by infected bone marrow derived dendritic cells (BMDC, while leaving secreted levels of TGF-β unchanged. These effects were mimicked by BCG-TB1860His which carried a 6-Histidine tag at the C-terminus of Rv1860, killed sonicated preparations of BCG-TB1860 and purified H37Rv-derived Rv1860 glycoprotein added to BCG-GFP, but not by E. coli-expressed recombinant Rv1860. Most importantly, BMDC exposed to BCG-TB1860 failed to polarize allogeneic as well as syngeneic T cells to secrete IFN-γ and IL-17 relative to BCG-GFP. Splenocytes from mice infected with BCG-SSI showed significantly less proliferation and secretion of IL-2, IFN-γ and IL-17, but secreted higher levels of IL-10 in response to in vitro restimulation with BCG-TB1860 compared to BCG-GFP. Spleens from mice infected with BCG-TB1860 also harboured significantly fewer DC expressing MHC-II, IL-12, IL-2 and TNF-α compared to mice infected with BCG-GFP. Glycoproteins of MTB, through their deleterious effects on DC may thus contribute to suppress the generation of a TH1- and TH

  13. Nanocatalytic resonance scattering spectral analysis

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    The resonance scattering spectral technique has been established using the synchronous scanning technique on spectrofluorometry.Because of its advantages of simplicity,rapidity and sensitivity,it has been widely applied to analyses of proteins,nucleic acids and inorganic ions.This paper summarizes the application of immunonanogold and aptamer modified nanogold(AptAu) catalytic resonance scattering spectral technique in combination with the work of our group,citing 53 references.

  14. Spectral Conditions for Positive Maps

    Science.gov (United States)

    Chruściński, Dariusz; Kossakowski, Andrzej

    2009-09-01

    We provide partial classification of positive linear maps in matrix algebras which is based on a family of spectral conditions. This construction generalizes the celebrated Choi example of a map which is positive but not completely positive. It is shown how the spectral conditions enable one to construct linear maps on tensor products of matrix algebras which are positive but only on a convex subset of separable elements. Such maps provide basic tools to study quantum entanglement in multipartite systems.

  15. Prym varieties of spectral covers

    CERN Document Server

    Hausel, Tamás

    2010-01-01

    Given a possibly reducible and non-reduced spectral cover X over a smooth projective complex curve C we determine the group of connected components of the Prym variety Prym(X/C). We also describe the sublocus of characteristics a for which the Prym variety Prym(X_a/C) is connected. These results extend special cases of work of Ng\\^o who considered integral spectral curves.

  16. Magnetotelluric (MT) data smoothing based on B-Spline algorithm and qualitative spectral analysis

    Science.gov (United States)

    Handyarso, Accep; Grandis, Hendra

    2017-07-01

    Data processing is one of the essential steps to obtain optimum response function of the Earth's subsurface. The MT Data processing is based on the Fast Fourier Transform (FFT) algorithm which converts the time series data into its frequency domain counterpart. The FFT combined with statistical algorithm constitute the Robust Processing algorithm which is widely implemented in MT data processing software. The Robust Processing has three variants, i.e. No Weight (NW), Rho Variance (RV), and Ordinary Coherency (OC). The RV and OC options allow for denoising the data but in many cases the Robust Processing still results in not so smooth sounding curve due to strong noise presence during measurement, such that the Crosspower (XPR) analysis must be conducted in the data processing. The XPR analysis is very time consuming step within the data processing. The collaboration of B-Spline algorithm and Qualitative Spectral Analysis in the frequency domain could be of advantages as an alternative for these steps. The technique is started by using the best coherency from the Robust Processing results. In the Qualitative Spectral Analysis one can determine which part of the data based on frequency that is more or less reliable, then the next process invokes B-Spline algorithm for data smoothing. This algorithm would select the best fit of the data trend in the frequency domain. The smooth apparent resistivity and phase sounding curves can be considered as more appropriate to represent the subsurface. This algorithm has been applied to the real MT data from several survey and give satisfactory results.

  17. Evaluation of the in vivo efficacy of novel monosubstituted sulfonylureas against H37Rv and extensively drug-resistant tuberculosis.

    Science.gov (United States)

    Liu, Yu; Bao, Pengtao; Wang, Di; Li, Zhengming; Li, Yun; Tang, Liping; Zhou, Yi; Zhao, Weiguo

    2014-01-01

    Sulfonylureas have been regarded as potential drug candidates against tuberculosis (TB) because they can inhibit the biosynthesis of branched-chain amino acids by targeting acetohydroxyacid synthase (AHAS). We demonstrated previously that novel monosubstituted sulfonylureas showed potent in vitro activities against TB. In the current study, we further explored the anti-TB activity of monosubstituted sulfonylureas in a mouse model. Compounds 30 and 31 exhibited the most efficacy: a single intragastric administration at a dose of 250 mg/kg led to a reduced lung bacterial count, and the dose of 500 mg/kg achieved a >99% reduction in bacterial load for both H37Rv and extensively drug-resistant isolates. These results indicate that these compounds are more potent than commercial sulfonylureas in vivo and may provide insight into the potential implications for the design of novel drugs to combat TB by targeting AHAS.

  18. Overproduction, purification and preliminary X-ray diffraction analysis of a sulfotransferase from Mycobacterium tuberculosis H37Rv

    Energy Technology Data Exchange (ETDEWEB)

    Tanaka, Shotaro; Moriizumi, Yuuji; Kimura, Makoto; Kakuta, Yoshimitsu, E-mail: kakuta@agr.kyushu-u.ac.jp [Laboratory of Biochemistry, Department of Bioscience and Biotechnology, Faculty of Agriculture, Graduate School, Kyushu University, Hakozaki 6-10-1, Higashi-ku, Fukuoka 812-8581 (Japan)

    2005-01-01

    A sulfotransferase from M. tuberculosis was crystallized and preliminarily analyzed using X-ray diffraction. Sulfotransferase STF1 from the Mycobacterium tuberculosis H37Rv genome was overproduced in Escherichia coli, purified and crystallized using the hanging-drop vapour-diffusion method. The crystals diffract to 1.5 Å resolution using synchrotron radiation at SPring-8. The crystals are monoclinic and belong to space group P2{sub 1}, with unit-cell parameters a = 40.86, b = 95.76, c = 48.04 Å, β = 106.43°. The calculated Matthews coefficient is approximately 2.1 Å{sup 3} Da{sup −1} assuming the presence of one molecule of STF1 in the asymmetric unit. A substrate-binding assay using a PAP–agarose column suggests that STF1 exhibits sulfotransferase activity.

  19. Rv0989c encodes a novel (E)-geranyl diphosphate synthase facilitating decaprenyl diphosphate biosynthesis in Mycobacterium tuberculosis.

    Science.gov (United States)

    Mann, Francis M; Thomas, Jill A; Peters, Reuben J

    2011-02-04

    Mycobacterium tuberculosis (Mtb) has a highly complex cell wall, which is required for both bacterial survival and infection. Cell wall biosynthesis is dependent on decaprenyl diphosphate as a glyco-carrier, which is hence an essential metabolite in this pathogen. Previous biochemical studies indicated (E)-geranyl diphosphate (GPP) is required for the synthesis of decaprenyl diphosphate. Here we demonstrate that Rv0989c encodes the "missing" GPP synthase, representing the first such enzyme to be characterized from bacteria, and which presumably is involved in decaprenyl diphosphate biosynthesis in Mtb. Our investigation also has revealed previously unrecognized substrate plasticity of the farnesyl diphosphate synthases from Mtb, resolving previous discrepancies between biochemical and genetic studies of cell wall biosynthesis.

  20. Carbon Dioxide, Hydrographic, and Chemical Data Obtained During the R/V Thomas G. Thompson Cruise in the Pacific Ocean

    Energy Technology Data Exchange (ETDEWEB)

    Sabine, C.L.; Key, R.M.; Hall, M.; Kozyr, A.

    1999-08-01

    This data documentation discusses the procedures and methods used to measure total carbon dioxide (TCO2), total alkalinity (TALK), and radiocarbon (delta 14C), at hydrographic stations, as well as the underway partial pressure of CO2 (pCO2) during the R/V Thomas G. Thompson oceanographic cruise in the Pacific Ocean (Section P10). Conducted as part of the World Ocean Circulation Experiment (WOCE), the cruise began in Suva, Fiji, on October 5, 1993, and ended in Yokohama, Japan, on November 10, 1993. Measurements made along WOCE Section P10 included pressure, temperature, salinity [measured by conductivity temperature, and depth sensor (CTD)], bottle salinity, bottle oxygen, phosphate, nitrate, silicate, chlorofluorocarbons (CFC-11, CFC-12), TCO2, TALK, delta 14C, and underway pCO2.