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Sample records for bl lac object

  1. Clustering environments of BL Lac objects

    Science.gov (United States)

    Wurtz, Ronald; Ellingson, Erica; Stocke, John T.; Yee, H. K. C.

    1993-01-01

    We report measurements of the amplitude of the BL Lac galaxy spatial covariance function, B(gb), for the fields of five BL Lacertae objects. We present evidence for rich clusters around MS 1207+39 and MS 1407+59, and confirm high richness for the cluster containing H0414+009. We discuss the ease of 3C 66 A and find evidence for a poor cluster based on an uncertain redshift of z = 0.444. These data suggest that at least some BL Lac objects are consistent with being FR 1 radio galaxies in rich clusters.

  2. Evolutionary behaviour of BL Lac objects

    OpenAIRE

    Beckmann, Volker

    1998-01-01

    We present analysis of a new flux limited sample of 72 X-ray selected BL Lacertae objects with known redshifts for 59 of them. We find the more X-ray dominated BL Lac having negative evolution with redshift, while intermediate objects show no evolution at all. X-ray dominated objects show higher X-ray luminosities and flatter X-ray spectra than the intermediate ones. We were also able to determine the redshift of 1517+656, which is part of our sample and is the optically most luminous X-ray s...

  3. New extreme synchrotron BL Lac objects

    International Nuclear Information System (INIS)

    We report on the BeppoSAX observations of four 'extreme' BL Lacs, selected to have high synchrotron peak frequencies. All have been detected also in the PDS band. For 1ES 0120+340, PKS 0548-322 and H 2356-309 the spectrum is well fitted by a convex broken power-law, thus locating the synchrotron peak around 1-4 keV. 1ES 1426+428 presents a flat energy spectral index (αx=0.92) up to ∼100 keV, thus constraining the synchrotron peak to lie near or above that value. For their extreme properties, all sources could be strong TeV emitters

  4. Radio Detection of 18 RASS BL Lac Objects

    Directory of Open Access Journals (Sweden)

    Anderson M. W. B.

    2009-12-01

    Full Text Available We present the radio detection of 18 BL Lac objects from oursurvey of over 575 deg$^2$ of sky. These 18 objects are located within$20arcsec$ of the X-ray position, of which 11 have a measuredred-shift. All candidates are radio emitters above $sim$1 mJy and fall within the range of existing samples on the two colour, $alpha _mathrm{RO}$ vs $alpha _mathrm{OX}$, diagram with a transitional population of three evident. Two unusual sources have been identified, a candidate radio quiet BL Lac, RX J0140.9-4130, and an extreme HBL, RX J0109.9-4020, with $log( u _mathrm{peak}approx 19.2$. The BL Lac $log(N-log(S$ relation is consistent with other samples and indicates the ROSAT All Sky Survey (RASS could contain ($2000{pm}400$ BL Lac objects.

  5. The fraction of BL Lac objects in groups of galaxies

    CERN Document Server

    Muriel, Hernán

    2016-01-01

    Context: BL Lac objects are a rare class of active galactic nuclei that typically show featureless optical spectra that make it difficult to estimate the redshift. A novel method for estimating the redshift of BL Lac objects has recently been proposed which assumes that these objects typically reside in groups of galaxies. Aims: The aim of this work is to estimate the fraction of BL Lac objects that reside in groups of galaxies. Methods: We use a sample of groups (M12 catalogue) selected by applying a friends-of-friends algorithm in the SDSS DR12. Galaxies in the M12 sample were cross-correlated with the sample of blazars in the BZCAT. Results: We found that 121 galaxies in the M12 catalogue are blazars in the BZCAT sample, all but one are BL Lac objects, and a large fraction are classified as BL Lac-galaxy dominated. Analysing the fraction of galaxies in groups as a function of redshift we have estimated a correction factor that takes into account the typical incompleteness of the catalogues based on the fri...

  6. Diffuse γ-ray emission from unresolved BL Lac objects

    International Nuclear Information System (INIS)

    Blazars, active galactic nuclei with a jet pointing toward the Earth, represent the most abundant class of high-energy extragalactic γ-ray sources. The subset of blazars known as BL Lac objects is on average closer to Earth (i.e., younger) and characterized by harder spectra at high energy than the whole sample. The fraction of BL Lacs that is too dim to be detected and resolved by current γ-ray telescopes is therefore expected to contribute to the high-energy isotropic diffuse γ-ray background (IGRB). The IGRB has been recently measured over a wide energy range by the Large Area Telescope (LAT) on board the Gamma-ray Space Telescope (Fermi). We present a new prediction of the diffuse γ-ray flux due to the unresolved BL Lac blazar population. The model is built upon the spectral energy distribution and the luminosity function derived from the fraction of BL Lacs detected (and spectrally characterized) in the γ-ray energy range. We focus our attention on the O(100) GeV energy range, predicting the emission up to the TeV scale and taking into account the absorption on the extragalactic background light. In order to better shape the BL Lac spectral energy distribution, we combine the Fermi-LAT data with Imaging Atmospheric Cerenkov Telescope measurements of the most energetic sources. Our analysis is carried on separately for low- and intermediate-synchrotron-peaked BL Lacs on the one hand and high-synchrotron-peaked BL Lacs on the other hand: we find in fact statistically different features for the two. The diffuse emission from the sum of both BL Lac classes increases from about 10% of the measured IGRB at 100 MeV to ∼100% of the data level at 100 GeV. At energies greater than 100 GeV, our predictions naturally explain the IGRB data, accommodating their softening with increasing energy. Uncertainties are estimated to be within of a factor of two of the best-fit flux up to 500 GeV.

  7. Imaging redshift estimates for Fermi BL Lac objects

    Energy Technology Data Exchange (ETDEWEB)

    Stadnik, Matt; Romani, Roger W., E-mail: mstadnik@stanford.edu, E-mail: rwr@astro.stanford.edu [Dept. of Physics/KIPAC, Stanford University, Stanford, CA 94305-4060 (United States)

    2014-04-01

    We have obtained WIYN and SOAR i' images of BL Lacertae objects and used these to detect or constrain the flux of the host galaxy. Under common standard candle assumptions, these data provide estimates of, or lower bounds on, the redshift. Our targets are a set of flat-spectrum radio counterparts of high flux Fermi Large Area Telescope sources, with sensitive spectral observations showing them to be continuum-dominated BL Lac objects. In this sample, 5 of 11 BL Lac objects yielded significant host detections, with standard candle redshifts z = 0.13-0.58. Our estimates and lower bounds are generally in agreement with other redshifts estimates, although our z = 0.374 estimate for J0543–5532 implies a significantly sub-luminous host.

  8. BL Lac Objects and Blazars Past, Present, and Future

    CERN Document Server

    Urry, C M

    1998-01-01

    The past 20 years have seen phenomenal progress in our understanding of BL Lac objects. They form part of the blazar class, which are radio-loud AGN whose relativistic jets are aligned along our line of sight. Several critical milestones have helped establish this picture, first proposed at the Pittsburgh BL Lac meeting 20 years ago, most recently the EGRET and TeV detections of beamed gamma-ray emission. The spectral energy distributions are double peaked and follow a self-similar sequence in luminosity, which can be explained by electron cooling on ambient photons. This simple paradigm has yet to be tested, and further questions remain, notably about physical conditions in blazar jets --- the kinetic power, magnetic energy density, acceleration time scales, proton content, etc. --- and how this energy is transported in the innermost regions. Some clues are available from multiwavelength monitoring campaigns although better sampling over longer periods is clearly called for. Recent work on the host galaxies ...

  9. Optical polarization of high-energy BL Lac objects

    CERN Document Server

    Hovatta, T; Blinov, D; Pavlidou, V; Nilsson, K; Kiehlmann, S; Angelakis, E; Ramazani, V Fallah; Liodakis, I; Myserlis, I; Panopoulou, G V; Pursimo, T

    2016-01-01

    We investigate the optical polarization properties of high-energy BL Lac objects using data from the RoboPol blazar monitoring program and the Nordic Optical Telescope. We wish to understand if there are differences in the BL Lac objects that are detected with the current-generation TeV instruments compared to those that have not yet been detected. The mean polarization fraction of the TeV-detected BL Lacs is 5% while the non-TeV sources show a higher mean polarization fraction of 7%. This difference in polarization fraction disappears when the dilution by the unpolarized light of the host galaxy is accounted for. The TeV sources show somewhat lower fractional polarization variability amplitudes than the non-TeV sources. Also the fraction of sources with a smaller spread in the Q/I - U/I -plane and a clumped distribution of points away from the origin, possibly indicating a preferred polarization angle, is larger in the TeV than in the non-TeV sources. These differences between TeV and non-TeV samples seems t...

  10. Broad band energy distribution of UV-bright BL Lac objects

    International Nuclear Information System (INIS)

    IUE satellite data in the 1200-2000 and 1900-3200 A intervals of BL Lac objects are analyzed in terms of two discernible groups. A total of 25 BL Lac objects were observed, with differences between groups displayed in terms of the power slope of the energy of the UV emissions, i.e., slopes of 1 and 2. Comparisons of the spectra with those of quasars showed that quasars have a small spectral index in the 1000-6000 A band and no correlation exists between the spectral index and UV flux of the BL Lac objects. The comparisons underscore the lack of a thermal component for BL Lac objects. Steep spectral components in both BL Lac objects and highly polarized quasars emissions could both be due to synchrotron emission. Compton scattering of relativistic electrons off synchrotron photons could produce the X ray emissions. 44 references

  11. Extraordinary Activity in the BL Lac Object OJ~287

    CERN Document Server

    Hughes, P A; Aller, M F; Hughes, Philip A.; Aller, Hugh D.; Aller, Margo F.

    1998-01-01

    We use a continuous wavelet transform to analyze more than two decades of data for the BL~Lac object OJ~287 acquired as part of the UMRAO variability program. We find clear evidence for a persistent modulation of the total flux and polarization with period $\\sim 1.66$ years, and for another signal that dominates activity in the 1980s with period $\\sim 1.12$ years. The relationship between these two variations can be understood in terms of a `shock-in-jet' model, in which the longer time scale periodicity is associated with an otherwise quiescent jet, and the shorter time scale activity is associated with the passage of a shock; the different periodicities of these two components may reflect different internal conditions of the two flow domains, leading to different wave speeds, or different contractions of a single underlying periodicity, due to the different Doppler factors of the two flow components. We suggest that the modulation arises from a wave driven by some asymmetric disturbance close to the central...

  12. Absorption in the spectra of quasi stellar objects and BL Lac objects

    International Nuclear Information System (INIS)

    An extensive review is given of the observations of absorption in the spectra of QSOs and BL Lac objects. In Table Ia we summarize all of the information available up to May 1, 1978 on objects which show absorption. Following discussion of the observations in Section II, possible interpretations are critically discussed. (orig.)

  13. Gamma-ray Emission from the γ-ray-loud BL Lac Objects

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    Using the HST observation data of BL Lac objects by Urry et al. and γγ-ray observation data, we find that there is a correlation between Fγ and FO nucleifor γ-ray-loud BL Lac objects (correlation coefficients: γ = 0.63,p = 4.0 × 10-2),but no correlation between Fγ and Fohost, where FO nuclei and Fohost are the fluxes ofnuclei and host galaxy in V-band. For 19 γ-ray-loud BL Lac objects with observedspectral index in multi-wavebands, the spectral index correlations between any twobands are as follow: (1) there is a strong correlation between αγ and αK for 15 BLLac objects(γ = 0.84,p = 3.11 × 10-4); (2) the correlation between αγ and αo for12 BL Lac objects is γ = 0.82,p = 1.5 × 10-3; (3) there is no correlation betweenαγ and αx for 16 BL Lac objects. The results, together with characteristic double-humped shape of their SEDs, show that the synchrotron self-Compton mechanismmight be a main mechanism for the γ-ray emission of the BL Lac objects. Theelectrons emitting IR and optical radiation via synchrotron are also responsible forupscattering these photons to γ-rays, and a variability in IR-optical regime shouldbe accompanied by a change in the γ-rays.

  14. Multiband optical polarimetry of BL Lac objects with the Nordic Optical Telescope

    CERN Document Server

    Tommasi, L; Pian, E; Piirola, V; Poretti, E; Scaltriti, F; Sillanpää, A; Takalo, L; Treves, A

    2001-01-01

    Optical polarization of seven selected BL Lac objects in UBVRI bands was studied with the Nordic Optical Telescope from December 10-14, 1999. Two of them, 3C 66A and PKS 0735+178, were monitored for 4 nights for a total integration time of 4.75 and 5.5 hours, respectively. Other objects (1Jy 0138-097, H 0414+009, PKS 0823-223, OJ287 and BL Lac) were observed sparsely during the run. Apart from PKS 0823-223 (more polarized than observed in the past), the sources show levels of flux and polarization consistent with results at previous epochs. 3C 66A and PKS 0735+178 were intensively observed during December 11 and 12 and exhibited variability of polarization, both on internight and intranight time scales. Wavelength dependence of polarization has been investigated, as well as circular polarization. The results are discussed within the standard model for BL Lacs.

  15. Multi-wavelength studies of TeV γ-ray emitting BL Lac objects

    International Nuclear Information System (INIS)

    The discovery of TeV γ-ray emission of BL Lac objects gave new insights in the particle acceleration and the emission processes of the highly relativistic jets. To shed light on the conditions in the high energetic jets of the TeV γ-ray emitting BL Lac objects, I have studied in great detail the spectral energy distribution (SED) of sources with different characteristics. BL Lac objects with exceptional very high energy spectra (soft and hard spectra) and with large differences in the emission peak frequencies, to cover the different classes of BL Lac objects, have been chosen. The basic aim of this thesis was, to study with new, simultaneous multi- avelength (MWL) observations, if the emission processes of these extreme cases of TeV BL Lac objects can be explained by the synchrotron Self-Compton (SSC) model which is well established for the class of BL Lac objects at lower energies. We proposed MWL observations in the optical, UV and X-ray regime, to be conducted simultaneous to very high energy observations with the H.E.S.S. experiment, to study the emission processes. Simultaneous observations are crucial, since BL Lac objects are variable at all wavebands. I have analysed the MWL observations and conducted detailed variability and spectral studies in each wavelength range. The different kind of absorption at each wavelength as well as the influence of the host galaxy of the AGN has been considered to obtain the intrinsic jet spectrum. I have then applied the commonly used theoretical jet model, the SSC model, to the SED. I conducted a MWL campaign on a BL Lac object with the softest TeV spectrum, PKS 2005-489, during which it was observed in a very bright X-ray state. The good spectral coverage of the emission peaks allowed a detailed study of the SSC model. The extreme BL Lac object 1ES 0229+200 exhibits a hard intrinsic TeV spectrum. With my MWL campaign I found a clear cut-off in the optical range and therefore a high minimum Lorentz factor is needed to

  16. Statistical analysis of optical variability in the Perugia monitoring sample of BL Lac objects.

    Science.gov (United States)

    Fiorucci, M.; Tosti, G.; Luciani, M.

    The authors present a statistical analysis of optical variability in a sample of 25 BL Lac objects observed at the Perugia University Observatory in the last years. The light curves did not show clear periodic behaviors and are a combination of flicker and shot noise.

  17. Dynamical black hole masses of BL Lac objects from the Sloan Digital Sky Survey

    NARCIS (Netherlands)

    R.M. Plotkin; S. Markoff; S.C. Trager; S.F. Anderson

    2011-01-01

    We measure black hole masses for 71 BL Lac objects from the Sloan Digital Sky Survey with redshifts out to z∼ 0.4. We perform spectral decompositions of their nuclei from their host galaxies and measure their stellar velocity dispersions. Black hole masses are then derived from the black hole mass -

  18. Dynamical black hole masses of BL Lac objects from the Sloan Digital Sky Survey

    NARCIS (Netherlands)

    Plotkin, R. M.; Markoff, S.; Trager, S. C.; Anderson, S. F.

    2011-01-01

    We measure black hole masses for 71 BL Lac objects from the Sloan Digital Sky Survey with redshifts out to z similar to 0.4. We perform spectral decompositions of their nuclei from their host galaxies and measure their stellar velocity dispersions. Black hole masses are then derived from the black h

  19. Dynamical Black Hole Masses of BL Lac Objects from the Sloan Digital Sky Survey

    NARCIS (Netherlands)

    Plotkin, Richard M.; Markoff, Sera; Trager, Scott C.; Anderson, Scott F.

    2012-01-01

    We measure black hole masses for 71 BL Lac objects from the Sloan Digital Sky Survey (SDSS) with redshifts out to z ∼ 0.4. We perform spectral decompositions of their nuclei from their host galaxies and measure their stellar velocity dispersions. Black hole masses are then derived from the black hol

  20. The colours of BL Lac objects: a new approach to their classification

    CERN Document Server

    Massaro, Enrico; Piranomonte, Silvia

    2012-01-01

    We selected a sample of 437 BL Lac objects, taken from the RomaBZCat catalogue, for which spectroscopic information and SDSS photometry is available. We propose a new classification of BL Lacs in which the sources' type is not defined only on the basis of the peak frequency of the synchrotron component in their Spectral Energy Distribution (types L and H), but also on the relevance of this component with respect to the brightness of the host galaxy (types N and G, for nuclear or galaxy dominated sources). We found that the SDSS colour index u-r=1.4 is a good separator between these two types. We used multiband colour-colour plots to study the properties of the BL Lac classes and found that in the X-ray to radio flux ratio vs u-r plot most of the N (blue) sources are located in a rather narrow strip, while the G-sources (red) are spread in a large area, and most of them are located in galaxy clusters or interacting systems, suggesting that their X-ray emission is not from a genuine BL Lac nucleus but it is rel...

  1. Exploring the bulk of the BL Lac object population: parsec scale radio properties and gamma ray emission

    Directory of Open Access Journals (Sweden)

    Giovannini G.

    2013-12-01

    Full Text Available BL Lac objects have been found to be the largest population of emitters in gamma-ray band. However, since they are relatively weak radio sources, their parsec scale structure and most of their radio properties are poorly known. To increase our knowledge of the BL Lac object population, we selected a sample of BL Lacs from the BZ Cat at low redshift (z < 0.2, with no constrain on the radio flux density and gamma-ray activity. We present here the results of a first VLBA observation at 8 and 15 GHz and shortly discuss their properties

  2. Black hole mass and binary model for BL Lac object OJ 287

    OpenAIRE

    Liu, F. K.; Wu, Xue-Bing

    2002-01-01

    Recent intensive observations of the BL Lac object OJ 287 raise a lot of questions on the models of binary black holes, processing jets, rotating helical jets and thermal instability of slim accretion disks. After carefully analyzing their radio flux and polarization data, Valtaoja et al. (\\cite{valtaoja00}) propose a new binary model. Based on the black hole mass of $4 \\times 10^8 {\\rm M_\\odot}$ estimated with the tight correlations of the black hole masses and the bulge luminosity or centra...

  3. Modelling the IDV Emissions of the BL Lac Objects with a Langevin Type Stochastic Differential Equation

    Indian Academy of Sciences (India)

    C. S. Leung; J. Y. Wei; T. Harko; Z. Kovacs

    2011-03-01

    In this paper, we introduce a simplified model for explaining the observations of optical intra-day variability (IDV) of the BL Lac Objects. We assume that the source of the IDV are the stochastic oscillations of an accretion disk around a supermassive black hole. The stochastic fluctuations on the vertical direction of the accretion disk are described by using a Langevin type equation with a damping term and a random, white noise type force. Furthermore, preliminary numerical simulation results are presented, which are based on the numerical analysis of the Langevin stochastic differential equation.

  4. An Analysis of Periodic Components in BL Lac Object S5 0716 +714 with MUSIC Method

    Science.gov (United States)

    Tang, J.

    2012-01-01

    Multiple signal classification (MUSIC) algorithms are introduced to the estimation of the period of variation of BL Lac objects.The principle of MUSIC spectral analysis method and theoretical analysis of the resolution of frequency spectrum using analog signals are included. From a lot of literatures, we have collected a lot of effective observation data of BL Lac object S5 0716 + 714 in V, R, I bands from 1994 to 2008. The light variation periods of S5 0716 +714 are obtained by means of the MUSIC spectral analysis method and periodogram spectral analysis method. There exist two major periods: (3.33±0.08) years and (1.24±0.01) years for all bands. The estimation of the period of variation of the algorithm based on the MUSIC spectral analysis method is compared with that of the algorithm based on the periodogram spectral analysis method. It is a super-resolution algorithm with small data length, and could be used to detect the period of variation of weak signals.

  5. Observation of X-Ray Variability in the BL Lac Object 1ES1959+65

    International Nuclear Information System (INIS)

    This paper reports X-ray spectral observations of a relatively nearby (z = 0.048) BL Lacertae (BL Lac) object 1ES1959+65, which is a potential TeV emitter. The observations include 31 short pointings made by the Unconventional Stellar Aspect (USA) Experiment on board the Advanced Research and Global Observation Satellite (ARGOS), and 17 pointings by the PCA on board the Rossi X-ray Timing Explorer (RXTE). Most of these observations were spaced by less than 1 day. 1ES1959+65 was detected by the ARGOS USA detector in the range 1-16 keV, and by the PCA in the 2-16 keV range but at different times. During the closely spaced RXTE observations beginning on 2000 July 28, an ending of one flare and a start of another are visible, associated with spectral changes, where the photon index Λ ranges between ∼ 1.4 and 1.7, and the spectrum is harder when the source is brighter. This implies that 1ES1959+65 is an XBL-type blazar, with the X-ray emission likely to originate via the synchrotron process. The USA observations reveal another flare that peaked on 2000 November 14 and doubled the flux within a few days, again associated with spectral changes of the same form. The spectral variability correlated with the flux and timing characteristics of this object that are similar to those of other nearby BL Lacs, and suggest relativistic beaming with a Doppler factor (delta) (ge) 1.6 and magnetic fields of the order of a few mG. We also suggest that the steady component of the X-ray emission--present in this object as well as in other XBLs--may be due to the large-scale relativistic jet (such as measured by Chandra in many radio-loud AGN), but pointing very closely to our line of sight

  6. Analysis of Optical Variations of BL Lac Object AO 0235+164

    Indian Academy of Sciences (India)

    Wang Hong-tao

    2014-03-01

    Historical optical BVRI band data are combined on the BL Lac object AO 0235 + 164. In order to examine the possible existence of lags and correlations between variations in different optical bands from this source, a statistical analysis is performed through the Discrete Correlation Function (DCF) method. Monte Carlo simulations called Flux Redistribution/Random Subset Selection (FR/RSS) are performed to obtain statistically meaningful values for the cross-correlation time lags and their related uncertainties. The analysis confirms that the variations in different optical light curves are strongly correlated, with no or very weak lag within the errors. Long term variability of color indices are also analysed. No color variabilities are found.

  7. Contemporaneous broadband observations of three high-redshift BL Lac Objects

    OpenAIRE

    Ackermann, Markus; Ajello, M.; Bregeon, J.; Troja, E.; Vianello, G.; Wood, K. S.; Wood, M; Fermi-LAT Collaboration; Britto, R. J.; Bruel, P.; Buehler, R.; Caliandro, G. A.; Cameron, R. A.; Caragiulo, M.; Caraveo, P. A.

    2016-01-01

    We have collected broadband spectral energy distributions (SEDs) of three BL Lac objects 3FGL J0022.1−1855 (z = 0.689), 3FGL J0630.9−2406 ($z\\quad \\gtrsim $ 1.239), and 3FGL J0811.2−7529 (z = 0.774), detected by Fermi with relatively flat gigaelectronvolt spectra. By observing simultaneously in the near-infrared to hard X-ray band, we can well characterize the high end of the synchrotron component of the SED. Thus, fitting the SEDs to synchro-Compton models of the dominant emission from the r...

  8. Discovery of very high energy gamma-ray emission from the low-frequency peaked BL Lac object BL Lacertae

    CERN Document Server

    Albert, J; Anderhub, H; Antoranz, P; Armada, A; Baixeras, C; Barrio, J A; Bartko, H; Bastieri, D; Becker, J K; Bednarek, W; Berger, K; Bigongiari, C; Biland, A; Böck, R K; Bordas, P; Bosch-Ramon, V; Bretz, T; Britvitch, I; Camara, M; Carmona, E; Chilingarian, A; Coarasa, J A; Commichau, S; Contreras, J L; Cortina, J; Costado, M T; Curtef, V; Danielyan, V; Dazzi, F; Deangelis, A; Delgado, C; Delosreyes, R; Delotto, B; Domingo-Santamaria, E; Dorner, D; Doro, M; Errando, M; Fagiolini, M; Ferenc, D; Fernndez, E; Firpo, R; Flix, J; Fonseca, M V; Font, L; Fuchs, M; Galante, N; Garca-Lopez, R; Garczarczyk, M; Gaug, M; Giller, M; Göbel, F; Hakobyan, D; Hayashida, M; Hengstebeck, T; Herrero, A; Höhne, D; Hose, J; Hsu, C C; Jacon, P; Jogler, T; Kosyra, R; Kranich, D; Kritzer, R; Laille, A; Lindfors, E; Lombardi, S; Longo, F; López, J; López, M; Lorenz, E; Majumdar, P; Maneva, G; Mannheim, K; Mansutti, O; Mariotti, M; Martínez, M; Mazin, D; Merck, C; Meucci, M; Meyer, M; Miranda, J M; Mirzoyan, R; Mizobuchi, S; Moralejo, A; Nilsson, K; Ninkovic, J; Oa-Wilhelmi, E; Otte, N; Oya, I; Paneque, D; Panniello, M; Paoletti, R; Paredes, J M; Pasanen, M; Pascoli, D; Pauss, F; Pegna, R; Persic, M; Peruzzo, L; Piccioli, A; Poller, M; Puchades, N; Prandini, E; Raymers, A; Rhode, W; Rib, M; Rico, J; Rissi, M; Robert, A; Rugamer, S; Saggion, A; Sánchez, A; Sartori, P; Scalzotto, V; Scapin, V; Schmitt, R; Schweizer, T; Shayduk, M; Shinozaki, K; Shore, S N; Sidro, N; Sillanp, A; Sobczynska, D; Stamerra, A; Stark, L S; Takalo, L; Temnikov, P; Tescaro, D; Teshima, M; Tonello, N; Torres, D F; Turini, N; Vankov, H; Vitale, V; Wagner, R M; Wibig, T; Wittek, W; Zandanel, F; Zanin, R; Zapatero, J

    2007-01-01

    The low-frequency peaked BL Lac (LBL) object BL Lacertae was observed with the MAGIC telescope from August to December 2005 (22.2 hrs), and from July to September 2006 (26.0 hrs). A very high energy (VHE) gamma-ray signal was discovered with a 5.1 sigma excess in the 2005 data. Above 200 GeV, an integral flux of (0.6+-0.2)x10^{-11} cm^{-2} s^{-1} was measured, corresponding to approximate by 3 of the Crab flux. The differential spectrum between 150 and 900 GeV is rather steep, with a photon index of -3.6+-0.5. For the first time, a clear detection of VHE gamma-ray emission from an LBL object was obtained with a signal below previous upper limits. During the observation, the light curve shows no large fluctuation. On the contrary, the 2006 data show no significant excess. This drop in flux follows the observed trend in optical activity.

  9. Optical and Radio variability of the Northern VHE gamma-ray emitting BL Lac objects

    CERN Document Server

    Lindfors, E J; Nilsson, K; Reinthal, R; Ramazani, V Fallah; Pavlidou, V; Max-Moerbeck, W; Richards, J; Berdyugin, A; Takalo, L; Sillanpää, A; Readhead, A C S

    2016-01-01

    We compare the variability properties of very high energy gamma-ray emitting BL Lac objects in the optical and radio bands. We use the variability information to distinguish multiple emission components in the jet, to be used as a guidance for spectral energy distribution modelling. Our sample includes 32 objects in the Northern sky that have data for at least 2 years in both bands. We use optical R-band data from the Tuorla blazar monitoring program and 15 GHz radio data from the Owens Valley Radio Observatory blazer monitoring program. We estimate the variability amplitudes using the intrinsic modulation index, and study the time-domain connection by cross-correlating the optical and radio light curves assuming power law power spectral density. Our sample objects are in general more variable in the optical than radio. We find correlated flares in about half of the objects, and correlated long-term trends in more than 40% of the objects. In these objects we estimate that at least 10%-50% of the optical emiss...

  10. The Luminosity Function of the Host Galaxies of QSOs and BL Lac Objects

    CERN Document Server

    Carangelo, N; Treves, A

    2001-01-01

    A clear insight of the galaxies hosting active galactic nuclei is of fundamental importance for understanding the processes of galaxies and nuclei formation and their cosmic evolution. A good characterization of the host galaxies properties requires images of excellent quality in order to disentangle the light of the galaxy from that of the bright nucleus. To this aim HST has provided a major improvement of data on QSOs (Disney et al. 1995; Bahcall et al. 1996, 1997; Boyce et al. 1998; McLure et al. 1999; Hamilton et al. 2000; Kukula et al. 2001) and BL Lacs (Scarpa et al. 2000, Urry et al. 2000). We present a comparative study of low redshift QSO and BL Lac host galaxy luminosity function (HGLF). To this aim we have considered samples of BL Lacs (Urry et al. 2000) and QSOs (Bahcall et al. 1997; Boyce et al. 1998; McLure et al. 1999) that have been well resolved by images obtained with WFPC2 on board of HST.

  11. Discovery of VHE gamma-rays from the BL Lac object PKS 0548-322

    CERN Document Server

    Akhperjanian, A G; de Almeida, U Barres; Bazer-Bachi, A R; Becherini, Y; Behera, B; Benbow, W; Bernlöhr, K; Bochow, A; Boisson, C; Bolmont, J; Borrel, V; Brucker, J; Brun, F; Brun, P; Bühler, R; Bulik, T; Büsching, I; Boutelier, T; Chadwick, P M; Charbonnier, A; Chaves, R C G; Cheesebrough, A; Chounet, L -M; Clapson, A C; Coignet, G; Dalton, M; Daniel, M K; Davids, I D; Degrange, B; Deil, C; Dickinson, H J; Djannati-Ataï, A; Domainko, W; Drury, L O'C; Dubois, F; Dubus, G; Dyks, J; Dyrda, M; Egberts, K; Emmanoulopoulos, D; Espigat, P; Farnier, C; Feinstein, F; Fiasson, A; Förster, A; Fontaine, G; Füssling, M; Gabici, S; Gallant, Y A; Gérard, L; Gerbig, D; Giebels, B; Glicenstein, J F; Glück, B; Goret, P; Göring, D; Hauser, D; Hauser, M; Heinz, S; Heinzelmann, G; Henri, G; Hermann, G; Hinton, J A; Hoffmann, A; Hofmann, W; Holleran, M; Hoppe, S; Horns, D; Jacholkowska, A; deJager, O C; Jahn, C; Jung, I; Katarzyński, K; Katz, U; Kaufmann, S; Kendziorra, E; Kerschhagg, M; Khangulyan, D; Khélifi, B; Keogh, D; Kluźniak, W; Kneiske, T; Komin, Nu; Kosack, K; Lamanna, G; Lenain, J -P; Lohse, T; Marandon, V; Martin, J M; Martineau-Huynh, O; Marcowith, A; Masbou, J; Maurin, D; McComb, T J L; Medina, M C; Moderski, R; Moulin, E; Naumann-Godo, M; deNaurois, M; Nedbal, D; Nekrassov, D; Nicholas, B; Niemiec, J; Nolan, S J; Ohm, S; Olive, J-F; Wilhelm, E de Oña; Orford, K J; Ostrowski, M; Panter, M; Arribas, M Paz; Pedaletti, G; Pelletier, G; Petrucci, P -O; Pita, S; Pühlhofer, G; Punch, M; Quirrenbach, A; Raubenheimer, B C; Raue, M; Rayner, S M; Renaud, M; Rieger, F; Ripken, J; Rob, L; Rosier-Lees, S; Rowell, G; Rudak, B; Rulten, C B; Ruppel, J; Sahakian, V; Santangelo, A; Schlickeiser, R; Schöck, F M; Schröder, R; Schwanke, U; Schwarzburg, S; Schwemmer, S; Shalchi, A; Sikora, M; Skilton, J L; Sol, H; Spangler, D; Stawarz, L; Steenkamp, R; Stegmann, C; Stinzing, F; Superina, G; Szostek, A; Tam, P H; Tavernet, J -P; Terrier, R; Tibolla, O; Tluczykont, M; vanEldik, C; Vasileiadis, G; Venter, C; Venter, L; Vialle, J P; Vincent, P; Vivier, M; Völk, H J; Volp, F; Wagner, S J; Ward, M; Zdziarski, A A; Zech, A

    2010-01-01

    PKS 0548-322 (z=0.069) is a ``high-frequency-peaked'' BL Lac object and a candidate very high energy (VHE, E>100 GeV) gamma-ray emitter, due to its high X-ray and radio flux. Observations at the VHE band provide insights into the origin of very energetic particles present in this source and the radiation processes at work. We report observations made between October 2004 and January 2008 with the H.E.S.S. array, a four imaging atmospheric-Cherenkov telescopes. Contemporaneous UV and X-ray observations with the Swift satellite in November 2006 are also reported. PKS 0548-322 is detected for the first time in the VHE band with H.E.S.S. We measure an excess of 216 gamma-rays corresponding to a significance of 5.6 standard deviations. The photon spectrum of the source is described by a power-law, with a photon index of Gamma=2.86 +/- 0.34 (stat) +/- 0.10 (sys). The integral flux above 200 GeV is 1.3 % of the flux of the Crab Nebula, and is consistent with being constant in time. Contemporaneous Swift/XRT observat...

  12. X-RAY AND TeV EMISSIONS FROM HIGH-FREQUENCY-PEAKED BL LAC OBJECTS

    International Nuclear Information System (INIS)

    The majority of the extragalactic sources yet detected at TeV photon energies belong to the class of 'high-frequency-peaked BL Lac objects' (HBLs) that exhibit a spectral energy distribution with a lower peak in the X-ray band. Such spectra are well described in terms of a log-parabolic shape with considerable curvature, and widely interpreted as synchrotron emission from ultrarelativistic electrons outflowing in a relativistic jet; these are expected to radiate also in γ-rays through the inverse Compton process. Recently, we have compared the X-ray spectral parameter distributions of TeV detected HBLs (TBLs) with those undetected (UBLs), and found that the distributions of the peak energies Ep are similarly symmetric around a value of a few keVs for both subclasses, while the X-ray spectra are broader for TBLs than for UBLs. Here we propose an acceleration scenario to interpret both the Ep and the spectral curvature distributions in terms of a coherent and a stochastic acceleration mechanisms, respectively. We show how the curvature parameter b ≅ 0.3-0.7 of the synchrotron X-rays, which depends only on the latter acceleration component, can be related to the inverse Compton luminosity in γ-rays, thus introducing a link between the X-ray and the TeV observations of HBLs.

  13. VERITAS Observations of the BL Lac Object PG 1553+113

    CERN Document Server

    Aliu, E; Aune, T; Barnacka, A; Behera, B; Beilicke, M; Benbow, W; Berger, K; Bird, R; Buckley, J H; Bugaev, V; Byrum, K; Cardenzana, J V; Cerruti, M; Chen, X; Ciupik, L; Connolly, M P; Cui, W; Dickinson, H J; Dumm, J; Eisch, J D; Errando, M; Falcone, A; Federici, S; Feng, Q; Finley, J P; Fortin, P; Fortson, L; Furniss, A; Galante, N; Gillanders, G H; Griffin, S; Griffiths, S T; Grube, J; Gyuk, G; Håkansson, N; Hanna, D; Holder, J; Hughes, G; Humensky, T B; Johnson, C A; Kaaret, P; Kertzman, P Kar M; Khassen, Y; Kieda, D; Krawczynski, H; Krennrich, F; Kumar, S; Lang, M J; Madhavan, A; McArthur, S; McCann, A; Meagher, K; Millis, J; Moriarty, P; Nieto, D; de Bhróithe, A O'Faoláin; Ong, R A; Orr, M; Otte, A N; Park, N; Perkins, J S; Pohl, M; Popkow, A; Prokoph, H; Pueschel, E; Quinn, J; Ragan, K; Rajotte, J; Reyes, L C; Reynolds, P T; Richards, G T; Roache, E; Sembroski, G H; Shahinyan, K; Staszak, D; Telezhinsky, I; Tucci, J V; Tyler, J; Varlotta, A; Vassiliev, V V; Wakely, S P; Weinstein, A; Welsing, R; Wilhelm, A; Williams, D A; Zitzer, B

    2014-01-01

    We present results from VERITAS observations of the BL Lac object PG 1553+113 spanning the years 2010, 2011, and 2012. The time-averaged spectrum, measured between 160 and 560\\,GeV, is well described by a power law with a spectral index of $4.33 \\pm 0.09$. The time-averaged integral flux above $200\\,$GeV measured for this period was $(1.69 \\pm 0.06) \\times 10^{-11} \\, \\mathrm{ph} \\, \\mathrm{cm}^{-2} \\, \\mathrm{s}^{-1}$, corresponding to 6.9\\% of the Crab Nebula flux. We also present the combined $\\gamma$-ray spectrum from the Fermi Large Area Telescope and VERITAS covering an energy range from 100~MeV to 560~GeV. The data are well fit by a power law with an exponential cutoff at $\\rm {101.9 \\pm 3.2 \\, \\mathrm{GeV}} $. The origin of the cutoff could be intrinsic to PG~1553+113 or be due to the $\\gamma$-ray opacity of our universe through pair production off the extragalactic background light (EBL). Given lower limits to the redshift of $\\rm z \

  14. Observations of the high-frequency-peaked BL Lac object 1ES 1218+304 with VERITAS

    CERN Document Server

    Fortin, Pascal

    2007-01-01

    The VERITAS collaboration has observed the high-frequency-peaked BL Lac object 1ES 1218+304 using an array of several imaging Cherenkov telescopes located at the Fred Lawrence Whipple Observatory in Southern Arizona. A gamma-ray signal was detected with high significance for the observations taken during several months in the 2006-2007 observing season. Here we present the detection of 1ES 1218+304 in very-high-energy gamma rays.

  15. New detection of high-energy gamma-ray sources associated with BL Lac objects above 10 GeV

    CERN Document Server

    Campana, R; Bernieri, E

    2015-01-01

    We report the detection of 19 new high-energy gamma-ray sources closely associated with BL Lac objects at energies higher than 10 GeV in the 6.3 years Fermi-Large Area Telescope sky, selected using the Minimum Spanning Tree (MST) clustering method. Photon clusters with good selection parameters were found matching the positions of known blazars in the fifth Roma-BZCAT catalogue. A brief summary of the properties of these sources is presented.

  16. Dust in BL Lac objects and Fanaroff-Riley radio galaxies: infrared region

    Science.gov (United States)

    Seal Braun, P.

    2015-12-01

    Here 28 BL Lac objects, 18 FR I type radio galaxies, 4 FR I/II type radio galaxies and 10 FR II type radio galaxies are studied from FIR (far infrared) to optical region (180 μm to 0.44 μm) to understand the nature of infrared emission from these objects and the physical properties of dust in the emitting region. Using the flux densities from 2MASS, IRAS, ISO, SCUBA (40 % samples), WISE All-sky Data, AKARI (10 % samples) data and optical (B) observations, the spectral energy distributions are constructed. FIR and NIR spectral indices (α_{FIR} and α_{NIR}) are estimated. The dust temperatures and dust masses of all the samples are estimated from FIR flux densities. The SEDs of most of the samples (90 %) show steep slopes from FIR to optical region and about 10 % of the samples show flat continuous spectra from FIR to NIR region. The SEDs of 80 % FR I type radio galaxies and 1 out of 4 FR I/II type radio galaxies and two RBLs show a bump in the NIR to optical region. The SEDs of these sources are compared with Radiative transfer models. From FIR to MIR region, the SEDs of 90 % of the objects studied here can be fitted to the models with luminosities L˜ 10^{9.5} L0, considering uncertainty from 10 % to 20 %. But the observable fluxes in the NIR region are higher and can be fitted to other models with higher L˜ 10^{12.5} L0. Since there is a difference in emission in NIR region, mainly for FR I radio galaxies, so the variation of apparent K magnitudes with logarithm of redshift z is also studied. The WISE colours, (W1 - W2) and (W2 - W3) are compared with isodensity contours. Comparing with radiative transfer models it can be suggested that, in the FIR and MIR region the infrared emission is from the dust containing large grains, small graphites and PAHs at temperature ˜50 K-100 K. In the NIR region hot dust is mainly due to small grains at temperature ˜1200 K and the emission is mainly from synchrotron radiation produced in the inner part of the relativistic

  17. VERITAS OBSERVATIONS OF THE BL LAC OBJECT PG 1553+113

    Energy Technology Data Exchange (ETDEWEB)

    Aliu, E. [Department of Physics and Astronomy, Barnard College, Columbia University, NY 10027 (United States); Archer, A.; Beilicke, M.; Buckley, J. H.; Bugaev, V. [Department of Physics, Washington University, St. Louis, MO 63130 (United States); Aune, T. [Department of Physics and Astronomy, University of California, Los Angeles, CA 90095 (United States); Barnacka, A. [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Behera, B.; Chen, X. [DESY, Platanenallee 6, 15738 Zeuthen (Germany); Benbow, W.; Cerruti, M. [Fred Lawrence Whipple Observatory, Harvard-Smithsonian Center for Astrophysics, Amado, AZ 85645 (United States); Berger, K. [Department of Physics and Astronomy and the Bartol Research Institute, University of Delaware, Newark, DE 19716 (United States); Bird, R. [School of Physics, University College Dublin, Belfield, Dublin 4 (Ireland); Byrum, K. [Argonne National Laboratory, 9700 South Cass Avenue, Argonne, IL 60439 (United States); Cardenzana, J. V; Dickinson, H. J. [Department of Physics and Astronomy, Iowa State University, Ames, IA 50011 (United States); Ciupik, L. [Astronomy Department, Adler Planetarium and Astronomy Museum, Chicago, IL 60605 (United States); Connolly, M. P. [School of Physics, National University of Ireland Galway, University Road, Galway (Ireland); Cui, W. [Department of Physics and Astronomy, Purdue University, West Lafayette, IN 47907 (United States); Dumm, J. [School of Physics and Astronomy, University of Minnesota, Minneapolis, MN 55455 (United States); and others

    2015-01-20

    We present results from VERITAS observations of the BL Lac object PG 1553+113 spanning the years 2010, 2011, and 2012. The time-averaged spectrum, measured between 160 and 560 GeV, is well described by a power law with a spectral index of 4.33 ± 0.09. The time-averaged integral flux above 200 GeV measured for this period was (1.69 ± 0.06) × 10{sup –11} photons cm{sup –2} s{sup –1}, corresponding to 6.9% of the Crab Nebula flux. We also present the combined γ-ray spectrum from the Fermi Large Area Telescope and VERITAS covering an energy range from 100 MeV to 560 GeV. The data are well fit by a power law with an exponential cutoff at 101.9 ± 3.2 GeV. The origin of the cutoff could be intrinsic to PG 1553+113 or be due to the γ-ray opacity of our universe through pair production off the extragalactic background light (EBL). Given lower limits to the redshift of z > 0.395 based on optical/UV observations of PG 1553+113, the cutoff would be dominated by EBL absorption. Conversely, the small statistical uncertainties of the VERITAS energy spectrum have allowed us to provide a robust upper limit on the redshift of PG 1553+113 of z ≤ 0.62. A strongly elevated mean flux of (2.50 ± 0.14) × 10{sup –11} photons cm{sup –2} s{sup –1} (10.3% of the Crab Nebula flux) was observed during 2012, with the daily flux reaching as high as (4.44±0.71)×10{sup −11} photons cm{sup −2} s{sup −1} (18.3% of the Crab Nebula flux) on MJD 56048. The light curve measured during the 2012 observing season is marginally inconsistent with a steady flux, giving a χ{sup 2} probability for a steady flux of 0.03%.

  18. Synchrotron and Compton Components and their Variability in BL Lac Objects

    OpenAIRE

    Giommi, P.; Ghisellini, G.; Padovani, P.; Tagliaferri, G.

    2000-01-01

    BL Lacertae objects are extreme extragalactic sources characterized by the emission of strong and rapidly variable nonthermal radiation over the entire electromagnetic spectrum. Synchrotron emission followed by inverse Compton scattering in a relativistic beaming scenario is generally thought to be the mechanism powering these objects. ...

  19. Multi-wavelength study of flaring activity in BL Lac object S5 0716+714 during 2015 outburst

    OpenAIRE

    Chandra, Sunil; Zhang, Haocheng; Kushwaha, Pankaj; Singh, K.P.; Bottcher, M.; Kaur, Navpreet; Baliyan, K. S.

    2015-01-01

    We present a detailed investigation of the flaring activity observed from a BL Lac object, S5 0716+714 , during its brightest ever optical state in the second half of January 2015. Observed almost simultaneously in the optical, X-rays and {\\gamma}-rays, a significant change in the degree of optical polarization (PD) and a swing in the position angle (PA) of polarization were recorded. A detection in the TeV (VHE) was also reported by the MAGIC consortium during this flaring episode. Two promi...

  20. Computing Optical Variable Periods of BL Lac Object S5 0716+714 with Period04 Analysis Method

    Indian Academy of Sciences (India)

    Junping Fu; Xiong Zhang; Dingrong Xiong

    2014-09-01

    From a large volume of literature, we have collected effective observation of BL Lac object S5 0716+714 in the optical band, and constructed its long-term light curve from 1994 to 2006 AD. The light curve shows that S5 0716+714 is very active and exhibits very complicated non-sinusoidal variations. We used Period04 to analyse the period of light curve variation. Our results show that for S5 0716+714, the long-term period of variation is 3.3 yr which is consistent with the result of Raiter et al. (2003).

  1. An Analysis of Light Periods of BL Lac Object S5 0716+714 with the MUSIC Algorithm

    Science.gov (United States)

    Tang, Jie

    2012-07-01

    The multiple signal classification (MUSIC) algorithm is introduced to the estimation of light periods of BL Lac objects. The principle of the MUSIC algorithm is given, together with a testing on its spectral resolution by using a simulative signal. From a lot of literature, we have collected a large number of effective observational data of the BL Lac object S5 0716+714 in the three optical wavebands V, R, and I from 1994 to 2008. The light periods of S5 0716+714 are obtained by means of the MUSIC algorithm and average periodogram algorithm, respectively. It is found that there exist two major periodic components, one is the period of (3.33±0.08) yr, another is the period of (1.24±0.01) yr. The comparison of the performances of periodicity analysis of two algorithms indicates that the MUSIC algorithm has a smaller requirement on the sample length, as well as a good spectral resolution and anti-noise ability, to improve the accuracy of periodicity analysis in the case of short sample length.

  2. The jet of the BL Lac object PKS 0521 -365 in the near-IR : MAD adaptive optics observations

    CERN Document Server

    Falomo, R; Treves, A; Giovannini, G; Venturi, T; Moretti, A; Arcidiacono, C; Farinato, J; Ragazzoni, R; Diolaiti, E; Lombini, M; Tavecchio, F; Brast, R; Marchetti, E; Tordo, S

    2009-01-01

    BL Lac objects are low--power active nuclei exhibiting a variety of peculiar properties that are caused by the presence of a relativistic jet and orientation effects. We present here adaptive optics near-IR images at high spatial resolution of the nearby BL Lac object PKS 0521-365, which is known to display a prominent jet both at radio and optical frequencies. The observations were obtained in Ks--band using the ESO multi-conjugated adaptive optics demonstrator at the Very Large Telescope. This allowed us to obtain images with 0.1 arcsec effective resolution. We performed a detailed analysis of the jet and its related features from the near-IR images, and combined them with images previously obtained with HST in the R band and by a re-analysis of VLA radio maps. We find a remarkable similarity in the structure of the jet at radio, near-IR, and optical wavelengths. The broad--band emission of the jet knots is dominated by synchrotron radiation, while the nucleus also exhibits a significant inverse Compton com...

  3. Connection between inner jet kinematics and broadband flux variability in the BL Lac object S5 0716+714

    CERN Document Server

    Rani, B; Marscher, A P; Hodgson, J A; Fuhrmann, L; Angelakis, E; Britzen, S; Zensus, J A

    2015-01-01

    We present a high-frequency very long baseline interferometry (VLBI) kinematical study of the BL Lac object S5 0716+714 over the time period of September 2008 to October 2010. The aim of the study is to investigate the relation of the jet kinematics to the observed broadband flux variability. We find significant non-radial motions in the jet outflow of the source. In the radial direction, the highest measured apparent speed is \\sim37 c, which is exceptionally high, especially for a BL Lac object. Patterns in the jet flow reveal a roughly stationary feature \\sim0.15 mas downstream of the core. The long-term fits to the component trajectories reveal acceleration in the sub-mas region of the jet. The measured brightness temperature, T_{B}, follows a continuous trend of decline with distance, T_B \\propto r_{jet}^{-(2.36\\pm0.41)}, which suggests a gradient in Doppler factor along the jet axis. Our analysis suggest that a moving disturbance (or a shock wave) from the base of the jet produces the high-energy (optica...

  4. Discovery of VHE gamma-rays from the high-frequency-peaked BL Lac object RGB J0152+017

    CERN Document Server

    Aharonian, F; Barresde Almeida, U; Bazer-Bachi, A R; Behera, B; Beilicke, M; Benbow, W; Bernlöhr, K; Boisson, C; Borrel, V; Braun, I; Brion, E; Brucker, J; Buhler, R; Bulik, T; Büsching, I; Boutelier, T; Carrigan, S; Chadwick, P M; Chaves, R C G; Chounet, L M; Clapson, A C; Coignet, G; Cornils, R; Costamante, L; Dalton, M; Degrange, B; Dickinson, H J; Djannati-Ata, A; Domainko, i W; O'Connor-Drury, L; Dubois, F; Dubus, G; Dyks, J; Egberts, K; Emmanoulopoulos, D; Espigat, P; Farnier, C; Feinstein, F; Fiasson, A; Förster, A; Fontaine, G; Fuling, M; Gabici, S; Gallant, Y A; Giebels, B; Glicenstein, J F; Glück, B; Goret, P; Hadjichristidis, C; Hauser, D; Hauser, M; Heinzelmann, G; Henri, G; Hermann, G; Hinton, J A; Hoffmann, A; Hofmann, W; Holleran, M; Hoppe, S; Horns, D; Jacholkowska, A; De Jager, O C; Jung, I; Katarzynski, K; Kaufmann, S; Kendziorra, E; Kerschhaggl, M; Khelifi, B; Keogh, D; Komin, Nu; Kosack, K; Lamanna, G; Latham, I J; Lenain, J P; Lohse, D Khangulyan T; Martin, J M; Martineau-Huynh, O; Marcowith, A; Masterson, C; Maurin, D; McComb, T J L; Moderski, R; Moulin, E; Naumann-Godo, M; De Naurois, Mathieu; Nedbal, D; Nekrassov, D; Nolan, S J; Ohm, S; Olive, J P; de Ona Wilhelmi, E; Orford, K J; Osborne, J L; Ostrowski, M; Panter, M; Pedaletti, G; Pelletier, G; Petrucci, P O; Pita, S; Pühlhofer, G; Punch, M; Quirrenbach, Andreas G; Raubenheimer, B C; Raue, M; Rayner, S M; Renaud, M; Rieger, F; Ripken, J; Rob, L; Rosier-Lees, S; Rowell, G; Rudak, B; Ruppel, J; Sahakian, V V; Santangelo, A; Schlickeiser, R; Schock, F M; Schroder, R; Schwanke, U; Schwarzburg, S; Schwemmer, S; Shalchi, A; Sol, H; Spangler, D; Stawarz, L; Steenkamp, R; Stegmann, C; Superina, G; Tam, P H; Tavernet, J P; Terrier, R; Van Eldik, C; Vasileiadis, G; Venter, C; Vialle, J P; Vincent, P; Vivier, M; Völk, H J; Volpe, F; Wagner, S J; Ward, M; Zdziarski, A A; Zech, A

    2008-01-01

    Aims: The BL Lac object RGB J0152+017 (z=0.080) was predicted to be a very high-energy (VHE; > 100 GeV) gamma-ray source, due to its high X-ray and radio fluxes. Our aim is to understand the radiative processes by investigating the observed emission and its production mechanism using the High Energy Stereoscopic System (H.E.S.S.) experiment. Methods: We report recent observations of the BL Lac source RGB J0152+017 made in late October and November 2007 with the H.E.S.S. array consisting of four imaging atmospheric Cherenkov telescopes. Contemporaneous observations were made in X-rays by the Swift and RXTE satellites, in the optical band with the ATOM telescope, and in the radio band with the Nancay Radio Telescope. Results: A signal of 173 gamma-ray photons corresponding to a statistical significance of 6.6 sigma was found in the data. The energy spectrum of the source can be described by a powerlaw with a spectral index of 2.95+/-0.36stat+/-0.20syst. The integral flux above 300 GeV corresponds to ~2% of the ...

  5. EVN Observations of HESS J1943+213: Evidence for an Extreme TeV BL Lac Object

    Science.gov (United States)

    Akiyama, Kazunori; Stawarz, Łukasz; Tanaka, Yasuyuki T.; Nagai, Hiroshi; Giroletti, Marcello; Honma, Mareki

    2016-06-01

    We report on the 1.6 GHz (18 cm) very long baseline interferometry (VLBI) observations of the unresolved, steady TeV source HESS J1943+213 located in the Galactic plane, performed with the European VLBI Network (EVN) in 2014. Our new observations with a nearly full EVN array provide the deepest image of HESS J1943+213 at the highest resolution ever achieved, enabling us to resolve the long-standing issues of the source identification. The milliarcsecond-scale structure of HESS J1943+213 has a clear asymmetric morphology consisting of a compact core and a diffuse jet-like tail. This is broadly consistent with the previous e-EVN observations of the source performed in 2011 and re-analyzed in this work. The core component is characterized by the brightness temperature of ≳ 1.8× {10}9 K, which is typical for low-luminosity blazars in general. Overall, the radio properties of HESS J1943+213 are consistent with the source classification as an “extreme high-frequency-peaked BL Lac object.” Remarkably, we note that because HESS J1943+213 does not reveal any optical or infrared signatures of the active galactic nucleus activity, it would never be recognized and identified as a BL Lac object if not for its location close to the Galactic plane where the High Energy Stereoscopic System surveyed for and the follow-up dedicated X-ray and radio studies triggered by the source detection in the TeV range. Our results suggest, therefore, a presence of an unrecognized, possibly very numerous population of particularly extreme HBLs and simultaneously demonstrate that the low-frequency VLBI observations with high angular resolution are indispensable for a proper identification of such objects.

  6. Are some BL Lacs artefacts of gravitational lensing?

    International Nuclear Information System (INIS)

    We suggested in 1985 that a significant fraction of BL Lacertae objects, a kind of lineless quasar, seen in nearby galaxies are in fact images, gravitationally lensed and substantially amplified by stars in the nearby galaxy, of background objects, optically violent variable (OVV) quasars at redshifts z>1. This hypothesis was made on the basis of certain general similarities between BL Lacs and OVVs, but for two recently observed BL Lacs a strong case can be made that the accompanying elliptical galaxy is a foreground object. In addition, we argue that the distribution of BL Lac redshifts is hard to understand without gravitational lensing, unless we happen to be at a very local maximum of the spatial cosmic distribution of BL Lacs. Our analysis also indicates that the galaxies whose stars are likely to act as microlenses will be found in two peaks, one nearby, with redshift 0.05-0.10, and the other near the distant quasar. (author)

  7. Long term lightcurve of the BL Lac object 1ES 0229+200 at TeV energies

    CERN Document Server

    Cologna, Gabriele; Wagner, Stefan J; Wierzcholska, Alicja; Romoli, Carlo; Kurtanidze, Omar

    2015-01-01

    The high-frequency peaked BL Lac object 1ES 0229+200 (z = 0.14) was first detected in very high energy (VHE, E > 100 GeV) $\\gamma$-rays by the H.E.S.S. (High Energy Stereoscopic System) collaboration in 2006. No flux variability was reported in the initial study and its spectral characteristics have been used to derive constraints on the extragalactic background light (EBL) and on the intergalactic magnetic field (IGMF). 1ES 0229+200 has been observed with H.E.S.S. for $\\sim$130 hours from 2004 to 2013: the full dataset analysed with a more sensitive method will be presented here. The results indicate that the source is not constant and displays flux variability on yearly and monthly timescales. The existence of flux variability affects the derivation of the constraints on the IGMF. The H.E.S.S. observations cover several simultaneous multi-frequency campaigns and the VHE variations are compared with those reported in different bands.

  8. Discovery of high and very high-energy emission from the BL Lac object SHBL J001355.9-185406

    CERN Document Server

    :,; Acero, F; Aharonian, F; Akhperjanian, A G; Angüner, E; Anton, G; Balenderan, S; Balzer, A; Barnacka, A; Becherini, Y; Tjus, J Becker; Bernlöhr, K; Birsin, E; Bissaldi, E; Biteau, J; Boisson, C; Bolmont, J; Bordas, P; Brucker, J; Brun, F; Brun, P; Bulik, T; Carrigan, S; Casanova, S; Cerruti, M; Chadwick, P M; Chalme-Calvet, R; Chaves, R C G; Cheesebrough, A; Chrétien, M; Colafrancesco, S; Cologna, G; Conrad, J; Couturier, C; Dalton, M; Daniel, M K; Davids, I D; Degrange, B; Deil, C; deWilt, P; Dickinson, H J; Djannati-Ataï, A; Domainko, W; Drury, L O'C; Dubus, G; Dutson, K; Dyks, J; Dyrda, M; Edwards, T; Egberts, K; Eger, P; Espigat, P; Farnier, C; Fegan, S; Feinstein, F; Fernandes, M V; Fernandez, D; Fiasson, A; Fontaine, G; Förster, A; Füßling, M; Gajdus, M; Gallant, Y A; Garrigoux, T; Gast, H; Giebels, B; Glicenstein, J F; Göring, D; Grondin, M -H; Grudzińska, M; Häffner, S; Hague, J D; Hahn, J; Harris, J; Heinzelmann, G; Henri, G; Hermann, G; Hervet, O; Hillert, A; Hinton, J A; Hofmann, W; Hofverberg, P; Holler, M; Horns, D; Jacholkowska, A; Jahn, C; Jamrozy, M; Janiak, M; Jankowsky, F; Jung, I; Kastendieck, M A; Katarzyński, K; Katz, U; Kaufmann, S; Khélifi, B; Kieffer, M; Klepser, S; Klochkov, D; Kluźniak, W; Kneiske, T; Kolitzus, D; Komin, Nu; Kosack, K; Krakau, S; Krayzel, F; Krüger, P P; Laffon, H; Lamanna, G; Lefaucheur, J; Lemoine-Goumard, M; Lenain, J -P; Lennarz, D; Lohse, T; Lopatin, A; Lu, C -C; Marandon, V; Marcowith, A; Maurin, G; Maxted, N; Mayer, M; McComb, T J L; Medina, M C; Méhault, J; Menzler, U; Meyer, M; Moderski, R; Mohamed, M; Moulin, E; Murach, T; Naumann, C L; de Naurois, M; Nedbal, D; Niemiec, J; Nolan, S J; Oakes, L; Ohm, S; Wilhelmi, E de O\; Opitz, B; Ostrowski, M; Oya, I; Panter, M; Parsons, R D; Arribas, M Paz; Pekeur, N W; Pelletier, G; Perez, J; Petrucci, P -O; Peyaud, B; Pita, S; Poon, H; Pühlhofer, G; Punch, M; Quirrenbach, A; Raab, S; Raue, M; Reimer, A; Reimer, O; Renaud, M; Reyes, R de los; Rieger, F; Rob, L; Rosier-Lees, S; Rowell, G; Rudak, B; Rulten, C B; Sahakian, V; Sanchez, D A; Santangelo, A; Schlickeiser, R; Schüssler, F; Schulz, A; Schwanke, U; Schwarzburg, S; Schwemmer, S; Sol, H; Spengler, G; Spieß, F; Stawarz, {Ł }; Steenkamp, R; Stegmann, C; Stinzing, F; Stycz, K; Sushch, I; Szostek, A; Tavernet, J -P; Terrier, R; Tluczykont, M; Trichard, C; Valerius, K; van Eldik, C; Vasileiadis, G; Venter, C; Viana, A; Vincent, P; Völk, H J; Volpe, F; Vorster, M; Wagner, S J; Wagner, P; Ward, M; Weidinger, M; White, R; Wierzcholska, A; Willmann, P; Wörnlein, A; Wouters, D; Zacharias, M; Zajczyk, A; Zdziarski, A A; Zech, A; Zechlin, H -S

    2013-01-01

    The detection of the high-frequency peaked BL Lac object (HBL) SHBL J001355.9-185406 ($z$=0.095) at high (HE; 100 MeV$100\\,{\\rm GeV}$) with the \\fer\\ Large Area Telescope (LAT) and the High Energy Stereoscopic System (H.E.S.S.) is reported. Dedicated observations have been performed with the H.E.S.S. telescopes, leading to a detection at the $5.5\\,\\sigma$ significance level. The measured flux above 310 GeV is $(8.3 \\pm 1.7_{\\rm{stat}}\\pm 1.7_{\\rm{sys}})\\times 10^{-13}$ photons \\cms\\ (about 0.6% of that of the Crab Nebula), and the power law spectrum has a photon index of \\indexHESS. Using 3.5 years of publicly available \\fla\\ data, a faint counterpart has been detected in the LAT data at the $5.5\\,\\sigma$ significance level, with an integrated flux above 300 MeV of $(9.3 \\pm 3.4_{\\rm stat} \\pm 0.8_{\\rm sys})\\times 10^{-10}$ photons \\cms\\ and a photon index of $\\Gamma = 1.96 \\pm 0.20_{\\rm stat} \\pm 0.08_{\\rm sys}$. X-ray observations with \\textit{Swift}-XRT allow the synchrotron peak energy in $\

  9. Discovery of hard-spectrum \\gamma-ray emission from the BL Lac object 1ES 0414+009

    CERN Document Server

    Abramowski, A; Aharonian, F; Akhperjanian, A G; Anton, G; Balzer, A; Barnacka, A; de Almeida, U Barres; Becherini, Y; Becker, J; Behera, B; Bernlöhr, K; Birsin, E; Biteau, J; Bochow, A; Boisson, C; Bolmont, J; Bordas, P; Brucker, J; Brun, F; Brun, P; Bulik, T; Büsching, I; Carrigan, S; Casanova, S; Cerruti, M; Chadwick, P M; Charbonnier, A; Chaves, R C G; Cheesebrough, A; Chounet, L -M; Clapson, A C; Coignet, G; Cologna, G; Conrad, J; Dalton, M; Daniel, M K; Davids, I D; Degrange, B; Deil, C; Dickinson, H J; Djannati-Ataï, A; Domainko, W; Drury, L O'C; Dubois, F; Dubus, G; Dutson, K; Dyks, J; Dyrda, M; Egberts, K; Eger, P; Espigat, P; Fallon, L; Farnier, C; Feinstein, F; Fernandes, M V; Fiasson, A; Fontaine, G; Förster, A; Füßling, M; Gallant, Y A; Gast, H; Gérard, L; Gerbig, D; Giebels, B; Glicenstein, J F; Glück, B; Goret, P; Göring, D; Häffner, S; Hague, J D; Hampf, D; Hauser, M; Heinz, S; Heinzelmann, G; Henri, G; Hermann, G; Hinton, J A; Hoffmann, A; Hofmann, W; Hofverberg, P; Holler, M; Horns, D; Jacholkowska, A; de Jager, O C; Jahn, C; Jamrozy, M; Jung, I; Kastendieck, M A; Katarzynski, K; Katz, U; Kaufmann, S; Keogh, D; Khangulyan, D; Khélifi, B; Kluźniak, D Klochkov W; Kneiske, T; Komin, Nu; Kosack, K; Kossakowski, R; Laffon, H; Lamanna, G; Lennarz, D; Lohse, T; Lopatin, A; Lu, C -C; Marandon, V; Marcowith, A; Masbou, J; Maurin, D; Maxted, N; Mayer, M; McComb, T J L; Medina, M C; Méhault, J; Moderski, R; Moulin, E; Naumann, C L; Naumann-Godo, M; de Naurois, M; Nedbal, D; Nekrassov, D; Nguyen, N; Nicholas, B; Niemiec, J; Nolan, S J; Ohm, S; Wilhelmi, E de Ona; Opitz, B; Ostrowski, M; Oya, I; Panter, M; Arribas, M Paz; Pedaletti, G; Pelletier, G; Petrucci, P -O; Pita, S; Pühlhofer, G; Punch, M; Quirrenbach, A; Raue, M; Rayner, S M; Reimer, A; Reimer, O; Renaud, M; Reyes, R de los; Rieger, F; Ripken, J; Rob, L; Rosier-Lees, S; Rowell, G; Rudak, B; Rulten, C B; Ruppel, J; Sahakian, V; Sanchez, D A; Santangelo, A; Schlickeiser, R; Schöck, F M; Schulz, A; Schwanke, U; Schwarzburg, S; Schwemmer, S; Sheidaei, F; Sikora, M; Skilton, J L; Sol, H; Spengler, G; Stawarz, L; Steenkamp, R; Stegmann, C; Stinzing, F; Stycz, K; Sushch, I; Szostek, A; Tavernet, J -P; Terrier, R; Tluczykont, M; Valerius, K; van Eldik, C; Vasileiadis, G; Venter, C; Vialle, J P; Viana, A; Vincent, P; Völk, H J; Volpe, F; Vorobiov, S; Vorster, M; Wagner, S J; Ward, M; White, R; Wierzcholska, A; Zacharias, M; Zajczyk, A; Zdziarski, A A; Zech, A; Zechlin, H -S; Costamante, L; Fegan, S; Ajello, M

    2012-01-01

    1ES 0414+009 (z = 0.287) is a distant high-frequency-peaked BL Lac object, and has long been considered a likely emitter of very-high energy (VHE, E>100 GeV) gamma-rays due to its high X-ray and radio flux. Observations in the VHE gamma-ray band and across the electromagnetic spectrum can provide insights into the origin of highly energetic particles present in the source and the radiation processes at work. Because of the distance of the source, the gamma-ray spectrum might provide further limits on the level of the Extragalactic Background Light (EBL). We report observations made between October 2005 and December 2009 with H.E.S.S., an array of four imaging atmospheric Cherenkov telescopes. Observations at high energies (HE, 100 MeV - 100 GeV) with the Fermi-LAT instrument in the first 20 months of its operation are also reported. To complete the multi-wavelength picture, archival UV and X-ray observations with the Swift satellite and optical observations with the ATOM telescope are also used. Based on the ...

  10. On the redshift of the very high-energy gamma-ray BL Lac object S2 0109+22

    Science.gov (United States)

    Paiano, S.; Landoni, M.; Falomo, R.; Scarpa, R.; Treves, A.

    2016-05-01

    The determination of the redshift of extragalactic gamma-ray sources is of fundamental importance for the interpretation of their emission models and extragalactic population studies, active galactic nuclei classification schemes, and to study the interaction with the extragalactic background light. Here we focus on the BL Lac S2 0109+22, recently detected at very high energies. We obtained a high signal-to-noise optical spectrum at Gran Telescopio Canarias for the source over the spectral range 4000-10 000 Å, to search for spectral features of the host galaxy and/or of the nuclear source and it was compared with previous observations in order to confirm and/or dispute its redshift determination. We find the S2 0109+22 optical spectrum is well represented by a power-law continuum without any absorption or emission feature of equivalent width >0.1 Å. Based on the new optical spectrum, we are able to set a redshift lower limit z > 0.35, assuming the source is hosted by a massive elliptical galaxy typical for this class of sources. The redshift z = 0.265 proposed in the literature for this object is most probably referred to a r = 18.3 galaxy at 15 arcsec from S2 0109. This galaxy could belong to a group of faint galaxies located at z ˜ 0.26.

  11. Multi-wavelength study of flaring activity in BL Lac object S5 0716+714 during 2015 outburst

    CERN Document Server

    Chandra, Sunil; Kushwaha, Pankaj; Singh, K P; Bottcher, M; Kaur, Navpreet; Baliyan, K S

    2015-01-01

    We present a detailed investigation of the flaring activity observed from a BL Lac object, S5 0716+714 , during its brightest ever optical state in the second half of January 2015. Observed almost simultaneously in the optical, X-rays and {\\gamma}-rays, a significant change in the degree of optical polarization (PD) and a swing in the position angle (PA) of polarization were recorded. A detection in the TeV (VHE) was also reported by the MAGIC consortium during this flaring episode. Two prominent sub-flares, peaking about 5-days apart, were seen in almost all the energy bands. The multi-wavelength light-curves, spectral energy distribution (SED) and polarization are modeled using the time-dependent code developed by Zhang et al. (2014). This model assumes a straight jet threaded by large scale helical magnetic fields taking into account the light travel time effects, incorporating synchrotron flux and polarization in 3D geometry. The rapid variation in PD and rotation in PA are most likely due to re-connectio...

  12. EVN Observations of HESS J1943+213: Evidence for an Extreme TeV BL Lac Object

    CERN Document Server

    Akiyama, Kazunori; Tanaka, Yasuyuki T; Nagai, Hiroshi; Giroletti, Marcello; Honma, Mareki

    2016-01-01

    We report on the 1.6 GHz (18 cm) VLBI observations of the unresolved, steady TeV source HESS J1943+213 located in the Galactic plane, performed with the European VLBI Network (EVN) in 2014. Our new observations with a nearly full EVN array provide the deepest image of HESS J1943+213 at the highest resolution ever achieved, enabling us to resolve the long-standing issues of the source identification. The milliarcsecond-scale structure of HESS J1943+213 has a clear asymmetric morphology, consisting of a compact core and a diffuse jet-like tail. This is broadly consistent with the previous e-EVN observations of the source performed in 2011, and re-analyzed in this work. The core component is characterized by the brightness temperature of $\\gtrsim1.8 \\times 10^9$ K, which is typical for low-luminosity blazars in general. Overall, radio properties of HESS J1943+213 are consistent with the source classification as an "extreme high-frequency-peaked BL Lac object". Remarkably, we note that since HESS J1943+213 does n...

  13. Chaotic Behaviour of Intra-Day Variability of BL Lac Object S5 0716+714

    Indian Academy of Sciences (India)

    Shuhong Li; Jianwen Ou; Zheng Liu

    2014-06-01

    An optical monitoring shows Blazar object S5 0716+714 has complex Intra-Day Variability (IDV) behaviour. In this paper, we introduce a method of non-linear time series analysis, and calculate the correlation dimension of the IDV light curves of S5 0716+714 over seven nights in the December of 2006. According to our calculations, the correlation dimension ≈ 1.993-5.178 for all of the observed data, it is implied that the IDV behaviour may be a chaotic system with some additional noise.

  14. Active Galactic Nuclei, Quasars, BL Lac Objects and X-Ray Background

    Science.gov (United States)

    Mushotzky, Richard (Technical Monitor); Elvis, Martin

    2005-01-01

    The XMM COSMOS survey is producing the large surface density of X-ray sources anticipated. The first batch of approx. 200 sources is being studied in relation to the large scale structure derived from deep optical/near-IR imaging from Subaru and CFHT. The photometric redshifts from the opt/IR imaging program allow a first look at structure vs. redshift, identifying high z clusters. A consortium of SAO, U. Arizona and the Carnegie Institute of Washington (Pasadena) has started a large program using the 6.5meter Magellan telescopes in Chile with the prime objective of identifying the XMM X-ray sources in the COSMOS field. The first series of observing runs using the new IMACS multi-slit spectrograph on Magellan will take place in January and February of 2005. Some 300 spectra per field will be taken, including 70%-80% of the XMM sources in each field. The four first fields cover the center of the COSMOS field. A VLT consortium is set to obtain bulk redshifts of the field galaxies. The added accuracy of the spectroscopic redshifts over the photo-z's will allow much lower density structures to be seen, voids and filaments. The association of X-ray selected AGNs, and quasars with these filaments, is a major motivation for our studies. Comparison to the deep VLA radio data now becoming available is about to begin.

  15. Observation of the BL Lac objects 1ES 1215+303 and 1ES 1218+304 with the MAGIC telescopes

    OpenAIRE

    Colin, Pierre; Gonzalez, Josefa Becerra; Lindfors, Elina; Lombardi, Saverio; Sitarek, Julian; Stamera, Antonio; collaboration, for the MAGIC

    2011-01-01

    The two BL Lac objects 1ES 1215+303 and 1ES 1218+304, separated by 0.8 deg, were observed with the MAGIC telescopes in 2010 and 2011. The 20 hours of data registered in January 2011 resulted in the first detection at Very High Energy (>100 GeV) of 1ES 1215+303 (also known as ON-325). This observation was triggered by a high optical state of the source reported by the Tuorla blazar monitoring program. Comparison with the 25 hours of data carried out from January to May 2010 suggests that 1ES 1...

  16. Fermi-LAT detection of hard spectrum and enhanced gamma-ray emission from the BL Lac object PKS 1717+177

    Science.gov (United States)

    Ciprini, Stefano

    2015-12-01

    The Large Area Telescope (LAT), one of two instruments on the Fermi Gamma-ray Space Telescope, has observed a gamma-ray flare from a source positionally consistent with the BL Lac object PKS 1717+177 (also known as S3 1717+17, OT 129, and 3FGL J1719.2+1744, Acero et al. 2015, ApJS, 218, 23), with radio coordinates (J2000.0), R.A.: 259.804368 deg, Dec.: 17.751788 deg (Johnston et al. 1995, AJ, 110, 880).

  17. MAGIC detection of short-term variability of the high-peaked BL Lac object 1ES 0806+524

    CERN Document Server

    Aleksić, J; Antonelli, L A; Antoranz, P; Babic, A; Bangale, P; Barrio, J A; González, J Becerra; Bednarek, W; Bernardini, E; Biasuzzi, B; Biland, A; Blanch, O; Bonnefoy, S; Bonnoli, G; Borracci, F; Bretz, T; Carmona, E; Carosi, A; Colin, P; Colombo, E; Contreras, J L; Cortina, J; Covino, S; Da Vela, P; Dazzi, F; De Angelis, A; De Caneva, G; De Lotto, B; Wilhelmi, E de O na; Mendez, C Delgado; Di Pierro, F; Prester, D Dominis; Dorner, D; Doro, M; Einecke, S; Eisenacher, D; Elsaesser, D; Fernández-Barral, A; Fidalgo, D; Fonseca, M V; Font, L; Frantzen, K; Fruck, C; Galindo, D; López, R J García; Garczarczyk, M; Terrats, D Garrido; Gaug, M; Godinović, N; noz, A González Mu; Gozzini, S R; Hadasch, D; Hanabata, Y; Hayashida, M; Herrera, J; Hose, J; Hrupec, D; Idec, W; Kadenius, V; Kellermann, H; Knoetig, M L; Kodani, K; Konno, Y; Krause, J; Kubo, H; Kushida, J; La Barbera, A; Lelas, D; Lewandowska, N; Lindfors, E; Lombardi, S; Longo, F; López, M; López-Coto, R; López-Oramas, A; Lorenz, E; Lozano, I; Makariev, M; Mallot, K; Maneva, G; Mannheim, K; Maraschi, L; Marcote, B; Mariotti, M; Martínez, M; Mazin, D; Menzel, U; Miranda, J M; Mirzoyan, R; Moralejo, A; Munar-Adrover, P; Nakajima, D; Neustroev, V; Niedzwiecki, A; Rosillo, M Nievas; Nilsson, K; Nishijima, K; Noda, K; Orito, R; Overkemping, A; Paiano, S; Palatiello, M; Paneque, D; Paoletti, R; Paredes, J M; Paredes-Fortuny, X; Persic, M; Poutanen, J; Moroni, P G Prada; Prandini, E; Puljak, I; Reinthal, R; Rhode, W; Ribó, M; Rico, J; Garcia, J Rodriguez; Saito, T; Saito, K; Satalecka, K; Scalzotto, V; Scapin, V; Schultz, C; Schweizer, T; Shore, S N; Sillanpää, A; Sitarek, J; Snidaric, I; Sobczynska, D; Stamerra, A; Steinbring, T; Strzys, M; Takalo, L; Takami, H; Tavecchio, F; Temnikov, P; Terzić, T; Tescaro, D; Teshima, M; Thaele, J; Torres, D F; Toyama, T; Treves, A; Vogler, P; Will, M; Zanin, R; Berger, K; Buson, S; D'Ammando, F; Gasparrini, D; Hovatta, T; Max-Moerbeck, W; Readhead, A; Richards, J

    2015-01-01

    The high-frequency-peaked BL Lac (HBL) 1ES 0806+524 (z = 0.138) was discovered in VHE $\\gamma$ rays in 2008. Until now, the broad-band spectrum of 1ES 0806+524 has been only poorly characterized, in particular at high energies. We analysed multiwavelength observations from $\\gamma$ rays to radio performed from 2011 January to March, which were triggered by the high activity detected at optical frequencies. These observations constitute the most precise determination of the broad-band emission of 1ES 0806+524 to date. The stereoscopic MAGIC observations yielded a $\\gamma$-ray signal above 250 GeV of $(3.7 \\pm 0.7)$ per cent of the Crab Nebula flux with a statistical significance of 9.9 $\\sigma$. The multiwavelength observations showed significant variability in essentially all energy bands, including a VHE $\\gamma$-ray flare that lasted less than one night, which provided unprecedented evidence for short-term variability in 1ES 0806+524. The spectrum of this flare is well described by a power law with a photon...

  18. Discovery of VHE gamma-ray emission from the BL Lac object B3 2247+381 with the MAGIC telescopes

    CERN Document Server

    Aleksić, J; Antonelli, L A; Antoranz, P; Asensio, M; Backes, M; Barrio, J A; Bastieri, D; González, J Becerra; Bednarek, W; Berdyugin, A; Berger, K; Bernardini, E; Biland, A; Blanch, O; Bock, R K; Boller, A; Bonnoli, G; Tridon, D Borla; Braun, I; Bretz, T; Cañellas, A; Carmona, E; Carosi, A; Colin, P; Colombo, E; Contreras, J L; Cortina, J; Cossio, L; Covino, S; Dazzi, F; De Angelis, A; De Caneva, G; del Pozo, E De Cea; De Lotto, B; Mendez, C Delgado; Ortega, A Diago; Doert, M; Domínguez, A; Prester, D Dominis; Dorner, D; Doro, M; Elsaesser, D; Ferenc, D; Fonseca, M V; Font, L; Fruck, C; López, R J García; Garczarczyk, M; Garrido, D; Giavitto, G; Godinović, N; Hadasch, D; Häfner, D; Herrero, A; Hildebrand, D; Höhne-Mönch, D; Hose, J; Hrupec, D; Huber, B; Jogler, T; Kellermann, H; Klepser, S; Krähenbühl, T; Krause, J; La Barbera, A; Lelas, D; Leonardo, E; Lindfors, E; Lombardi, S; López, M; López-Oramas, A; Lorenz, E; Makariev, M; Maneva, G; Mankuzhiyil, N; Mannheim, K; Maraschi, L; Mariotti, M; Martínez, M; Mazin, D; Meucci, M; Miranda, J M; Mirzoyan, R; Miyamoto, H; Moldón, J; Moralejo, A; Munar-Adrover, P; Nieto, D; Nilsson, K; Orito, R; Oya, I; Paneque, D; Paoletti, R; Pardo, S; Paredes, J M; Partini, S; Pasanen, M; Pauss, F; Perez-Torres, M A; Persic, M; Peruzzo, L; Pilia, M; Pochon, J; Prada, F; Moroni, P G Prada; Prandini, E; Puljak, I; Reichardt, I; Reinthal, R; Rhode, W; Ribó, M; Rico, J; Rügamer, S; Saggion, A; Saito, K; Saito, T Y; Salvati, M; Satalecka, K; Scalzotto, V; Scapin, V; Schultz, C; Schweizer, T; Shayduk, M; Shore, S N; Sillanpää, A; Sitarek, J; Snidaric, I; Sobczynska, D; Spanier, F; Spiro, S; Stamatescu, V; Stamerra, A; Steinke, B; Storz, J; Strah, N; Surić, T; Takalo, L; Takami, H; Tavecchio, F; Temnikov, P; Terzić, T; Tescaro, D; Teshima, M; Tibolla, O; Torres, D F; Treves, A; Uellenbeck, M; Vankov, H; Vogler, P; Wagner, R M; Weitzel, Q; Zabalza, V; Zandanel, F; Zanin, R; Kadenius, V; Weidinger, M; Buson, S

    2012-01-01

    We study the non-thermal jet emission of the BL Lac object B3 2247+381 during a high optical state. The MAGIC telescopes observed the source during 13 nights between September 30th and October 30th 2010, collecting a total of 14.2 hours of good quality very high energy (VHE) $\\gamma$-ray data. Simultaneous multiwavelength data was obtained with X-ray observations by the Swift satellite and optical R-band observations at the KVA-telescope. We also use high energy $\\gamma$-ray (HE, 0.1 GeV-100 GeV) data from the Fermi satellite. The BL Lac object B3 2247+381 (z=0.119) was detected, for the first time, at VHE $\\gamma$-rays at a statistical significance of 5.6 $\\sigma$. A soft VHE spectrum with a photon index of -3.2 $\\pm$ 0.6 was determined. No significant short term flux variations were found. We model the spectral energy distribution using a one-zone SSC-model, which can successfully describe our data.

  19. MAGIC detection of short-term variability of the high-peaked BL Lac object 1ES 0806+524

    Science.gov (United States)

    Aleksić, J.; Ansoldi, S.; Antonelli, L. A.; Antoranz, P.; Babic, A.; Bangale, P.; Barrio, J. A.; Becerra González, J.; Bednarek, W.; Bernardini, E.; Biasuzzi, B.; Biland, A.; Blanch, O.; Bonnefoy, S.; Bonnoli, G.; Borracci, F.; Bretz, T.; Carmona, E.; Carosi, A.; Colin, P.; Colombo, E.; Contreras, J. L.; Cortina, J.; Covino, S.; Da Vela, P.; Dazzi, F.; De Angelis, A.; De Caneva, G.; De Lotto, B.; de Oña Wilhelmi, E.; Delgado Mendez, C.; Di Pierro, F.; Dominis Prester, D.; Dorner, D.; Doro, M.; Einecke, S.; Eisenacher, D.; Elsaesser, D.; Fernández-Barral, A.; Fidalgo, D.; Fonseca, M. V.; Font, L.; Frantzen, K.; Fruck, C.; Galindo, D.; García López, R. J.; Garczarczyk, M.; Garrido Terrats, D.; Gaug, M.; Godinović, N.; González Muñoz, A.; Gozzini, S. R.; Hadasch, D.; Hanabata, Y.; Hayashida, M.; Herrera, J.; Hose, J.; Hrupec, D.; Idec, W.; Kadenius, V.; Kellermann, H.; Knoetig, M. L.; Kodani, K.; Konno, Y.; Krause, J.; Kubo, H.; Kushida, J.; La Barbera, A.; Lelas, D.; Lewandowska, N.; Lindfors, E.; Lombardi, S.; Longo, F.; López, M.; López-Coto, R.; López-Oramas, A.; Lorenz, E.; Lozano, I.; Makariev, M.; Mallot, K.; Maneva, G.; Mannheim, K.; Maraschi, L.; Marcote, B.; Mariotti, M.; Martínez, M.; Mazin, D.; Menzel, U.; Miranda, J. M.; Mirzoyan, R.; Moralejo, A.; Munar-Adrover, P.; Nakajima, D.; Neustroev, V.; Niedzwiecki, A.; Nievas Rosillo, M.; Nilsson, K.; Nishijima, K.; Noda, K.; Orito, R.; Overkemping, A.; Paiano, S.; Palatiello, M.; Paneque, D.; Paoletti, R.; Paredes, J. M.; Paredes-Fortuny, X.; Persic, M.; Poutanen, J.; Prada Moroni, P. G.; Prandini, E.; Puljak, I.; Reinthal, R.; Rhode, W.; Ribó, M.; Rico, J.; Rodriguez Garcia, J.; Saito, T.; Saito, K.; Satalecka, K.; Scalzotto, V.; Scapin, V.; Schultz, C.; Schweizer, T.; Shore, S. N.; Sillanpää, A.; Sitarek, J.; Snidaric, I.; Sobczynska, D.; Stamerra, A.; Steinbring, T.; Strzys, M.; Takalo, L.; Takami, H.; Tavecchio, F.; Temnikov, P.; Terzić, T.; Tescaro, D.; Teshima, M.; Thaele, J.; Torres, D. F.; Toyama, T.; Treves, A.; Vogler, P.; Will, M.; Zanin, R.; Berger, K.; Buson, S.; D'Ammando, F.; Gasparrini, D.; Hovatta, T.; Max-Moerbeck, W.; Readhead, A.; Richards, J.

    2015-07-01

    The high-frequency-peaked BL Lac (HBL) 1ES 0806+524 (z = 0.138) was discovered in very high energy (VHE) γ-rays in 2008. Until now, the broad-band spectrum of 1ES 0806+524 has been only poorly characterized, in particular at high energies. We analysed multiwavelength observations from γ-rays to radio performed from 2011 January to March, which were triggered by the high activity detected at optical frequencies. These observations constitute the most precise determination of the broad-band emission of 1ES 0806+524 to date. The stereoscopic Major Atmospheric Gamma-Ray Imaging Cherenkov (MAGIC) observations yielded a γ-ray signal above 250 GeV of (3.7 ± 0.7) per cent of the Crab Nebula flux with a statistical significance of 9.9σ. The multiwavelength observations showed significant variability in essentially all energy bands, including a VHE γ-ray flare that lasted less than one night, which provided unprecedented evidence for short-term variability in 1ES 0806+524. The spectrum of this flare is well described by a power law with a photon index of 2.97 ± 0.29 between ˜150 GeV and 1 TeV and an integral flux of (9.3 ± 1.9) per cent of the Crab nebula flux above 250 GeV. The spectrum during the non-flaring VHE activity is compatible with the only available VHE observation performed in 2008 with VERITAS when the source was in a low optical state. The broad-band spectral energy distribution can be described with a one-zone synchrotron self-Compton model with parameters typical for HBLs, indicating that 1ES 0806+524 is not substantially different from the HBLs previously detected.

  20. Swift XRT and UVOT deep observations of the high energy peaked BL Lac object PKS 0548-322 close to its brightest state

    CERN Document Server

    Perri, M; Giommi, P; Massaro, E; Nesci, R; Tramacere, A; Capalbi, M; Cusumano, G; Chincarini, G; Tagliaferri, G; Burrows, D N; Vanden Berk, D E; Gehrels, N; Sambruna, R M

    2006-01-01

    We present the results of a spectral analysis of 5 Swift XRT and UVOT observations of the BL Lac object PKS 0548-322 carried out over the period April-June 2005. The X-ray flux of this high energy peaked BL Lac (HBL) source was found to be approximately constant at a level of F(2-10 keV) ~ 4x10^-11 erg cm^-2 s^-1, a factor of 2 brighter than when observed by BeppoSAX in 1999 and close to the maximum intensity reported in the Einstein Slew Survey. The very good statistics obtained in the 0.3-10 keV Swift X-ray spectrum allowed us to detect highly significant deviations from a simple power law spectral distribution. A log-parabolic model describes well the X-ray data and gives a best fit curvature parameter of 0.18 and peak energy in the Spectral Energy Distribution of about 2 keV. The UV spectral data from Swift UVOT join well with a power law extrapolation of the soft X-ray data points suggesting that the same component is responsible for the observed emission in the two bands. The combination of synchrotron ...

  1. Properties of optically selected BL Lac candidates from the SDSS

    CERN Document Server

    Kügler, S D; Heidt, J; Esser, J; Schultz, T

    2014-01-01

    \\textbf{Context.} Deep optical surveys open the avenue for find large numbers of BL Lac objects that are hard to identify because they lack the unique properties classifying them as such. While radio or X-ray surveys typically reveal dozens of sources, recent compilations based on optical criteria alone have increased the number of BL Lac candidates considerably. However, these compilations are subject to biases and may contain a substantial number of contaminating sources. \\textbf{Aims.} In this paper we extend our analysis of 182 optically selected BL Lac object candidates from the SDSS with respect to an earlier study. The main goal is to determine the number of bona fide BL Lac objects in this sample. \\textbf{Methods.} We examine their variability characteristics, determine their broad-band radio-UV SEDs, and search for the presence of a host galaxy. In addition we present new optical spectra for 27 targets with improved S/N with respect to the SDSS spectra. \\textbf{Results.} At least 59% of our targets h...

  2. On the magnetization of BL Lac jets

    CERN Document Server

    Tavecchio, F

    2015-01-01

    The current paradigm foresees that relativistic jets are launched as magnetically dominated flows, whose magnetic power is progressively converted to kinetic power of of the matter of the jet, until equipartition is reached. Therefore, at the end of the acceleration phase, the jet should still carry a substantial fraction ($\\approx$ half) of its power in the form of a Poynting flux. It has been also argued that, in these conditions, the best candidate particle acceleration mechanism is efficient reconnection of magnetic field lines, for which it is predicted that magnetic field and accelerated relativistic electron energy densities are in equipartition.Through the modeling of the jet non--thermal emission, we explore if equipartition is indeed possible in BL Lac objects, i.e. low-power blazars with weak or absent broad emission lines. We find that one-zone models (for which only one region is involved in the production of the radiation we observe) the particle energy density is largely dominating (by 1-2 orde...

  3. VERITAS detection of $\\gamma$-ray flaring activity from the BL Lac object 1ES 1727+502 during bright moonlight observations

    CERN Document Server

    Archambault, S; Beilicke, M; Benbow, W; Bird, R; Biteau, J; Bouvier, A; Bugaev, V; Cardenzana, J V; Cerruti, M; Chen, X; Ciupik, L; Connolly, M P; Cui, W; Dickinson, H J; Dumm, J; Eisch, J D; Errando, M; Falcone, A; Feng, Q; Finley, J P; Fleischhack, H; Fortin, P; Fortson, L; Furniss, A; Gillanders, G H; Griffin, S; Griffiths, S T; Grube, J; Gyuk, G; Håkansson, N; Hanna, D; Holder, J; Humensky, T B; Johnson, C A; Kaaret, P; Kar, P; Kertzman, M; Khassen, Y; Kieda, D; Krause, M; Krennrich, F; Kumar, S; Lang, M J; Maier, G; McArthur, S; McCann, A; Meagher, K; Millis, J; Moriarty, P; Mukherjee, R; Nieto, D; de Bhróithe, A O'Faoláin; Ong, R A; Otte, A N; Park, N; Pohl, M; Popkow, A; Prokoph, H; Pueschel, E; Quinn, J; Ragan, K; Reyes, L C; Reynolds, P T; Richards, G T; Roache, E; Santander, M; Sembroski, G H; Shahinyan, K; Smith, A W; Staszak, D; Telezhinsky, I; Tucci, J V; Tyler, J; Varlotta, A; Vincent, S; Wakely, S P; Weinstein, A; Welsing, R; Wilhelm, A; Williams, D A; Zitzer, B; Hughes, Z D

    2015-01-01

    During moonlit nights, observations with ground-based Cherenkov telescopes at very high energies (VHE, $E>100$ GeV) are constrained since the photomultiplier tubes (PMTs) in the telescope camera are extremely sensitive to the background moonlight. Observations with the VERITAS telescopes in the standard configuration are performed only with a moon illumination less than 35$\\%$ of full moon. Since 2012, the VERITAS collaboration has implemented a new observing mode under bright moonlight, by either reducing the voltage applied to the PMTs (reduced-high-voltage configuration, RHV), or by utilizing UV-transparent filters. While these operating modes result in lower sensitivity and increased energy thresholds, the extension of the available observing time is useful for monitoring variable sources such as blazars and sources requiring spectral measurements at the highest energies. In this paper we report the detection of $\\gamma$-ray flaring activity from the BL Lac object 1ES 1727+502 during RHV observations. Thi...

  4. A Large Sample of BL Lacs from SDSS and FIRST

    CERN Document Server

    Plotkin, Richard M; Hall, Patrick B; Margon, Bruce; Voges, Wolfgang; Schneider, Donald P; Stinson, Gregory; York, Donald G

    2008-01-01

    We present a large sample of 501 radio-selected BL Lac candidates from the combination of the Sloan Digital Sky Survey (SDSS) Data Release 5 optical spectroscopy and from the Faint Images of the Radio Sky at Twenty-Centimeters (FIRST) radio survey; this is one of the largest BL Lac samples yet assembled, and each object emerges with homogeneous data coverage. Each candidate is detected in the radio from FIRST and confirmed in SDSS optical spectroscopy to have: (1) no emission feature with measured rest equivalent width larger than 5 Angstroms; and (2) no measured Ca II H/K depression larger than 40%. We subdivide our sample into 426 higher confidence candidates and 75 lower confidence candidates. We argue that contamination from other classes of objects that formally pass our selection criteria is small, and we identify a few very rare radio AGN with unusual spectra that are probably related to broad absorption line quasars. About one-fifth of our sample were known BL Lacs prior to the SDSS. A preliminary ana...

  5. Multi-Epoch VLBA Observations of EGRET-Detected Quasars and BL Lac Objects Superluminal Motion of Gamma-Ray Bright Blazars

    CERN Document Server

    Jorstad, S G; Mattox, J R; Wehrle, A E; Bloom, S D; Yurchenko, A V; Jorstad, Svetlana G; Marscher, Alan P; Mattox, John R; Wehrle, Ann E; Bloom, Steven D; Yurchenko, Alexei V

    2001-01-01

    We present the results of a program to monitor the structure of the radio emission in 42 $\\gamma$-ray bright blazars (31 quasars and 11 BL Lac objects) with the VLBA at 43, 22, and occasionally 15 and 8.4 GHz, over the period from November 1993 to July 1997. We determine proper motions in 33 sources and find that the apparent superluminal motions in $\\gamma$-ray sources are much faster than for the general population of bright compact radio sources. This follows the strong dependence of the $\\gamma$-ray flux on the level of relativistic beaming for both external-radiation Compton and synchrotron self-Compton emission. There is a positive correlation (correlation coefficient $r$=0.45) between the flux density of the VLBI core and the $\\gamma$-ray flux and a moderate correlation (partial correlation coefficient $r$=0.31) between $\\gamma$-ray apparent luminosity and superluminal velocities of jet components, as expected if the $\\gamma$-ray emission originates in a very compact region of the relativistic jet and ...

  6. Discovery of very high energy gamma-ray emission from the BL Lac object PKS 0301-243 with H.E.S.S

    CERN Document Server

    Abramowski, A; Aharonian, F; Ait, F; Akhperjanian, A G; Angüner, E; Anton, G; Balenderan, S; Balzer, A; Barnacka, A; Becherini, Y; Becker, J; Bernlöhr, K; Birsin, E; Bissaldi, E; Biteau, J; Böttcher, M; Boisson, C; Bolmont, J; Bordas, P; Brucker, J; Brun, F; Brun, P; Bulik, T; Carrigan, S; Casanova, S; Cerruti, M; Chadwick, P M; Chalme-Calvet, R; Chaves, R C G; Cheesebrough, A; Chrétien, M; Colafrancesco, S; Cologna, G; Conrad, J; Couturier, C; Dalton, M; Daniel, M K; Davids, I D; Degrange, B; Deil, C; deWilt, P; Dickinson, H J; Djannati-Ataï, A; Domainko, W; Drury, L O'C; Dubus, G; Dutson, K; Dyks, J; Dyrda, M; Edwards, T; Egberts, K; Eger, P; Espigat, P; Farnier, C; Fegan, S; Feinstein, F; Fernandes, M V; Fernandez, D; Fiasson, A; Fontaine, G; Förster, A; Füssling, M; Gajdus, M; Gallant, Y A; Garrigoux, T; Giebels, B; Glicenstein, J F; Grondin, M -H; Grudzìnska, M; Häffner, S; Hague, J D; Hahn, J; Harris, J; Heinzelmann, G; Henri, G; Hermann, G; Hervet, O; Hillert, A; Hinton, J A; Hofmann, W; Hofverberg, P; Holler, M; Horns, D; Jacholkowska, A; Jahn, C; Jamrozy, M; Janiak, M; Jankowsky, F; Jung, I; Kastendieck, M A; Katarzyński, K; Katz, U; Kaufmann, S; Khélifi, B; Kieffer, M; Klepser, S; Klochkov, D; Kluźniak, W; Kneiske, T; Kolitzus, D; Komin, Nu; Kosack, K; Krakau, S; Krayzel, F; Krüger, P P; Laffon, H; Lamanna, G; Lefaucheur, J; Lemoine-Goumard, M; Lenain, J -P; Lennarz, D; Lohse, T; Lopatin, A; Lu, C -C; Marandon, V; Marcowith, A; Marx, R; Maurin, G; Maxted, N; Mayer, M; McComb, T J L; Medina, M C; Méhault, J; Menzler, U; Meyer, M; Moderski, R; Mohamed, M; Moulin, E; Murach, T; Naumann, C L; de Naurois, M; Nedbal, D; Niemiec, J; Nolan, S J; Oakes, L; Ohm, S; Wilhelmi, E de Oña; Opitz, B; Ostrowski, M; Oya, I; Panter, M; Parsons, R D; Arribas, M Paz; Pekeur, N W; Pelletier, G; Perez, J; Petrucci, P -O; Peyaud, B; Pita, S; Poon, H; Pühlhofer, G; Punch, M; Quirrenbach, A; Raab, S; Raue, M; Reimer, A; Reimer, O; Renaud, M; Reyes, R de los; Rieger, F; Rob, L; Rosier-Lees, S; Rowell, G; Rudak, B; Rulten, C B; Sahakian, V; Sanchez, D A; Santangelo, A; Schlickeiser, R; Schüssler, F; Schulz, A; Schwanke, U; Schwarzburg, S; Schwemmer, S; Sol, H; Spengler, G; Spies, F; Stawarz, L; Steenkamp, R; Stegmann, C; Stinzing, F; Stycz, K; Sushch, I; Szostek, A; Tavernet, J -P; Terrier, R; Tluczykont, M; Trichard, C; Valerius, K; van Eldik, C; Vasileiadis, G; Venter, C; Viana, A; Vincent, P; Völk, H J; Volpe, F; Vorster, M; Wagner, S J; Wagner, P; Ward, M; Weidinger, M; Weitzel, Q; White, R; Wierzcholska, A; Willmann, P; Wörnlein, A; Wouters, D; Zacharias, M; Zajczyk, A; Zdziarski, A A; Zech, A; Zechlin, H -S

    2013-01-01

    The active galactic nucleus PKS 0301-243 (z=0.266) is a high-synchrotron-peaked BL Lac object that is detected at high energies (HE, 100 MeV 100 GeV) by the High Energy Stereoscopic System (H.E.S.S.) from observations between September 2009 and December 2011 for a total live time of 34.9 hours. Gamma rays above 200 GeV are detected at a significance of 9.4{\\sigma}. A hint of variability at the 2.5{\\sigma} level is found. An integral flux I(E > 200 GeV) = (3.3 +/- 1.1_stat +/- 0.7_syst)e-12 ph cm^-2s^-1 and a photon index {\\Gamma} = 4.6 +/- 0.7_stat +/- 0.2_syst are measured. Multi-wavelength light curves in HE, X-ray and optical bands show strong variability, and a minimal variability timescale of eight days is estimated from the optical light curve. A single-zone leptonic synchrotron self-Compton scenario satisfactorily reproduces the multi-wavelength data. In this model, the emitting region is out of equipartition and the jet is particle dominated. Because of its high redshift compared to other sources obse...

  7. Discovery of VHE \\gamma-ray emission and multi-wavelength observations of the BL Lac object 1RXS J101015.9-311909

    CERN Document Server

    Abramowski, A; Aharonian, F; Akhperjanian, A G; Anton, G; Balzer, A; Barnacka, A; Becherini, Y; Becker, J; Bernlöhr, K; Birsin, E; Biteau, J; Bochow, A; Boisson, C; Bolmont, J; Bordas, P; Brucker, J; Brun, F; Brun, P; Bulik, T; Büsching, I; Carrigan, S; Casanova, S; Cerruti, M; Chadwick, P M; Charbonnier, A; Chaves, R C G; Cheesebrough, A; Cologna, G; Conrad, J; Dalton, M; Daniel, M K; Davids, I D; Degrange, B; Deil, C; Dickinson, H J; Djannati-Ataï, A; Domainko, W; Drury, L O'C; Dubus, G; Dutson, K; Dyks, J; Dyrda, M; Egberts, K; Eger, P; Espigat, P; Fallon, L; Fegan, S; Feinstein, F; Fernandes, M V; Fiasson, A; Fontaine, G; Förster, A; Füßling, M; Gallant, Y A; Gast, H; Gérard, L; Gerbig, D; Giebels, B; Glicenstein, J F; Glück, B; Göring, D; Häffner, S; Hague, J D; Hahn, J; Hampf, D; Harris, J; Hauser, M; Heinz, S; Heinzelmann, G; Henri, G; Hermann, G; Hillert, A; Hinton, J A; Hofmann, W; Hofverberg, P; Holler, M; Horns, D; Jacholkowska, A; de Jager, O C; Jahn, C; Jamrozy, M; Jung, I; Kastendieck, M A; Katarzyński, K; Katz, U; Kaufmann, S; Keogh, D; Khélifi, B; Klochkov, D; Kluźniak, W; Kneiske, T; Komin, Nu; Kosack, K; Kossakowski, R; Krayzel, F; Laffon, H; Lamanna, G; Lenain, J -P; Lennarz, D; Lohse, T; Lopatin, A; Lu, C -C; Marandon, V; Marcowith, A; Masbou, J; Maxted, N; Mayer, M; McComb, T J L; Medina, M C; Méhault, J; Moderski, R; Mohamed, M; Moulin, E; Naumann, C L; Naumann-Godo, M; de Naurois, M; Nedbal, D; Nekrassov, D; Nguyen, N; Nicholas, B; Niemiec, J; Nolan, S J; Ohm, S; Wilhelmi, E de Oña; Opitz, B; Ostrowski, M; Oya, I; Panter, M; Arribas, M Paz; Pekeur, N W; Pelletier, G; Perez, J; Petrucci, P -O; Peyaud, B; Pita, S; Pühlhofer, G; Punch, M; Quirrenbach, A; Raue, M; Rayner, S M; Reimer, A; Reimer, O; Renaud, M; Reyes, R de los; Rieger, F; Ripken, J; Rob, L; Rosier-Lees, S; Rowell, G; Rudak, B; Rulten, C B; Sahakian, V; Sanchez, D A; Santangelo, A; Schlickeiser, R; Schulz, A; Schwanke, U; Schwarzburg, S; Schwemmer, S; Sheidaei, F; Skilton, J L; Sol, H; Spengler, G; Stawarz, Ł; Steenkamp, R; Stegmann, C; Stinzing, F; Stycz, K; Sushch, I; Szostek, A; Tavernet, J -P; Terrier, R; Tluczykont, M; Valerius, K; van Eldik, C; Vasileiadis, G; Venter, C; Viana, A; Vincent, P; Völk, H J; Volpe, F; Vorobiov, S; Vorster, M; Wagner, S J; Ward, M; White, R; Wierzcholska, A; Zacharias, M; Zajczyk, A; Zdziarski, A A; Zech, A; Zechlin, H -S

    2012-01-01

    1RXS J101015.9-311909 is a galaxy located at a redshift of z=0.14 hosting an active nucleus belonging to the class of bright BL Lac objects. Observations at high (HE, E > 100 MeV) and very high (VHE, E > 100 GeV) energies provide insights into the origin of very energetic particles present in such sources and the radiation processes at work. We report on results from VHE observations performed between 2006-10 with H.E.S.S. H.E.S.S. data have been analysed with enhanced analysis methods, making the detection of faint sources more significant. VHE emission at a position coincident with 1RXS J101015.9-311909 is detected with H.E.S.S. for the first time. In a total good-quality livetime of about 49 h, we measure 263 excess counts, corresponding to a significance of 7.1\\sigma. The photon spectrum above 0.2 TeV can be described by a power-law with a photon index of \\Gamma\\ = 3.08\\pm0.42_{stat}\\pm0.20_{sys}. The integral flux above 0.2 TeV is about 0.8% of the flux of the Crab nebula and shows no significant variabi...

  8. The WEBT campaign on the BL Lac object PG 1553+113 in 2013. An analysis of the enigmatic synchrotron emission

    CERN Document Server

    Raiteri, C M; Villata, M; Larionov, V M; Acosta-Pulido, J A

    2015-01-01

    A multifrequency campaign on the BL Lac object PG 1553+113 was organized by the Whole Earth Blazar Telescope (WEBT) in 2013 April-August, involving 19 optical, two near-IR, and three radio telescopes. The aim was to study the source behaviour at low energies during and around the high-energy observations by the Major Atmospheric Gamma-ray Imaging Cherenkov (MAGIC) telescopes in April-July. We also analyse the UV and X-ray data acquired by the Swift and XMM-Newton satellites in the same period. The WEBT and satellite observations allow us to detail the synchrotron emission bump in the source spectral energy distribution (SED). In the optical we found a general bluer-when-brighter trend. The X-ray spectrum remained stable during 2013, but a comparison with previous observations suggests that it becomes harder when the X-ray flux increases. The long XMM-Newton exposure reveals a curved X-ray spectrum. In the SED, the XMM-Newton data show a hard near-UV spectrum, while Swift data display a softer shape that is co...

  9. Perplexing correlations between Gamma-ray emission and parsec-scale jet orientation variations in the BL Lac object S5 0716+714

    CERN Document Server

    Rani, B; Marscher, A P; Jorstad, S G; Hodgson, J A; Fuhrmann, L; Zensus, J A

    2015-01-01

    The analysis of $\\gamma$-ray flux variability along with the parsec-scale jet kinematics suggests that the high-energy radiation in the BL Lac object S5 0716+714 has a significant correlation with the mm-VLBI core flux density and with the local orientation of the inner jet flow. For the first time in any blazar, we report a significant correlation between the $\\gamma$-ray flux variations and the variations in the local orientation of the jet outflow (position angle). We find that the $\\gamma$-ray flux variations lead the 7~mm VLBI core flux variations by 82$\\pm$32~days, which suggests that the high-energy emission in S5 0716+714 is coming from a region located 3.8$\\pm$1.9~parsecs closer to the central black hole than the "core" seen on the mm-VLBI images. The results imply a strong physical and casual connection between $\\gamma$-ray emission and the inner jet morphology in the source.

  10. BL Lacertae objects

    International Nuclear Information System (INIS)

    The properties of BL Lacertae objects are discussed including their spectra, variability, and brightness. The historical development of observation, and the conclusion that these objects are possibly quasar-related objects rather than variable stars as originally supposed are treated. The possible mechanisms for the unusual luminosity of these objects are considered

  11. Extreme BL Lacs: probes for cosmology and UHECR candidates

    CERN Document Server

    Tavecchio, F

    2015-01-01

    High-energy observations of extreme BL Lac objects, such as 1ES0229+200 or 1ES 0347-121, recently focused interest both for blazar and jet physics and for the implication on the extragalactic background light and intergalactic magnetic field estimate. Moreover, their enigmatic properties have been interpreted in a scenario in which their primary high- energy output is through a beam of high-energy hadrons. However, despite their possible important role in all these topics, the number of these extreme highly peaked BL Lac objects (EHBL) is still rather small. Aiming at increase their number, we selected a group of EHBL candidates considering those undetected (or only barely detected) by the LAT onboard Fermi and characterized by a high X-ray versus radio flux ratio. We assembled the multi-wavelength spectral energy distribution of the resulting 9 sources, using available archival data of Swift, GALEX, and Fermi satellites, confirming their nature. Through a simple one-zone synchrotron self-Compton model we est...

  12. Testing the blazar sequence with the least luminous BL Lacs

    CERN Document Server

    Raiteri, Claudia M

    2015-01-01

    In a previous paper, we proposed a new method to select low-power BL Lacs (LPBLs) based on mid-infrared emission and flux contrast through the Ca II spectral break; that study led to the selection of a complete sample formed by 34 LPBLs with 0.05BL Lacs. We find that the ratios between the X-ray and radio luminosities range from ~20 to ~30000 and that the synchrotron peak frequencies span a wide energy interval, from log(nu_peak)~13.5 to ~20 [Hz]. This indicates a broad variety of SED shapes and a mixture of BL Lac flavors. Indeed, although the majority of our LPBLs are high-energy peaked BL Lacs (HBLs), we find that a quarter of them are low-energy peaked BL Lacs (LBLs), despite the fact that the sample is biased against the selection of LBLs. The analysis of the median LPBL SED con...

  13. Application of the MST clustering to the high energy γ-ray sky. I—New possible detection of high-energy γ-ray emission associated with BL Lac objects

    Science.gov (United States)

    Campana, R.; Massaro, E.; Bernieri, E.; D'Amato, Q.

    2015-12-01

    In this paper we show an application of the Minimum Spanning Tree (MST) clustering method to the high-energy γ-ray sky observed at energies higher than 10 GeV in 6.3 years by the Fermi-Large Area Telescope. We report the detection of 19 new high-energy γ-ray clusters with good selection parameters whose centroid coordinates were found matching the positions of known BL Lac objects in the 5th Edition of the Roma-BZCAT catalogue. A brief summary of the properties of these sources is presented.

  14. Detection of Possible Quasi-periodic Oscillations in the Long-term Optical Light Curve of the BL Lac Object OJ 287

    CERN Document Server

    Bhatta, G; Stawarz, Ł; Ostrowski, M; Winiarski, M; Ogłoza, W; Dróżdz, M; Siwak, M; Liakos, A; Kozieł-Wierzbowska, D; Gazeas, K; Debski, B; Kundera, T; Stachowski, G; Paliya, V S

    2016-01-01

    Detection of periodicity in the broad-band non-thermal emission of blazars has so far been proven to be elusive. However, there are a number of scenarios which could lead to quasi-periodic variations in blazar light curves. For example, orbital or thermal/viscous period of accreting matter around central supermassive black holes could, in principle, be imprinted in the multi-wavelength emission of small-scale blazar jets, carrying as such crucial information about plasma conditions within the jet launching regions. In this paper, we present the results of our time series analysis of $\\sim 9.2$ year-long, and exceptionally well-sampled optical light curve of the BL Lac OJ 287. The study primarily uses the data from our own observations performed at the Mt. Suhora and Krak\\'ow Observatories in Poland, and at the Athens Observatory in Greece. Additionally, SMARTS observations were used to fill in some of the gaps in the data. The Lomb-Scargle Periodogram and the Weighted Wavelet Z-transform methods were employed...

  15. Intranight optical variability of radio-quiet BL Lacertae objects

    CERN Document Server

    Liu, Yuan; Zhang, Shuang Nan

    2015-01-01

    Aims: The intranight variation (or microvariation) is a common phenomenon of radio-loud BL Lac objects. However, it is not clear whether the recently found radio-quiet BL Lac objects have the same properties. The occurrence rate of intranight variation is helpful in distinguishing the mechanism of the continuum of radio-quiet BL Lac objects. Methods: We conducted a photometric monitoring of 8 radio-quiet BL Lac objects by Xinglong 2.16m and Lijiang 2.4m telescopes. The differential light curves are calculated between each target and two comparison stars. To qualify the variation, the significance of variation is examined by scaled $F$-test. Results: No significant variation is found in the 11 sessions of light curves of 8 radio-quiet BL Lac objects (one galactic source is excluded). The lack of microvariation in radio-quiet BL Lac objects is consistent with the detection rate of microvariation in normal radio-quiet AGNs, but much lower than that of radio-loud AGNs. This result indicates that the continua of t...

  16. Hard synchrotron BL Lacs: the case of 1ES 1101-232

    OpenAIRE

    Wolter, Anna; Ghisellini, Gabriele; Tagliaferri, Gianpiero; Tavecchio, Fabrizio; Caccianiga, Alessandro

    2000-01-01

    The bright X-ray selected BL Lac object 1ES1101--232 shows a flat X-ray spectrum, making it detectable with high statistics over the wide BeppoSAX energy range. We have observed it in two different epochs with BeppoSAX, and found a variation of the flux of about 30% that can be explained by a change in the spectral index above the synchrotron peak. We present here the data and infer limits on the strength of the magnetic field based on models of emission for High-frequency peaked BL Lacs.

  17. The hard synchrotron X-ray spectrum of the TeV BL Lac 1ES 1426+428

    CERN Document Server

    Wolter, A; Ghisellini, G; Tavecchio, F; Maraschi, L; Costamante, L; Celotti, A; Ghirlanda, G

    2007-01-01

    We have observed 1ES 1426+428 with INTEGRAL detecting it up to $\\sim$150 keV. The spectrum is hard, confirming that this source is an extreme BL Lac object, with a synchrotron component peaking, in a $\

  18. Period of Light Variability in BL Lac ON 231

    Indian Academy of Sciences (India)

    Xu Yun Bing; Zhang Hao Jing; Zhang Xiong; Mao Wei Ming; Dong Fu Tong

    2011-03-01

    In this paper, the authors have compiled the data of about 100 years in B-band of the BL Lac ON 231 and used this database to analyze periodicity signals in the optical light curve. Two different methods were applied: the wavelet analysis and the Discrete Correlation Function (DCF) method. We revealed the existence of periods of 13.5 years in the source variability.

  19. BeppoSAX Spectral Survey of BL Lacs - new spectra and results

    OpenAIRE

    Beckmann, V.; Wolter, A.; Celotti, A.; Costamante, L.; Ghisellini, G.; Maccacaro, T.; Tagliaferri, G.

    2001-01-01

    We present BeppoSAX LECS, MECS, and PDS spectra of eleven X-ray selected BL Lacertae objects. Combining these sources with the ones presented elsewhere we have a sample of 21 BL Lacs from the Einstein Medium Sensitivity and Einstein Slew Survey. The sample shows strong correlations of several physical parameters with the peak frequency of the synchrotron branch of the spectral energy distribution. In particular the peak frequency is correlated to the X-ray spectral shape: objects with the pea...

  20. Exploring the magnetic field configuration in BL Lac using GMVA

    CERN Document Server

    Rani, B; Hodgson, J; Koyama, S; Zensus, J A; Fuhrmann, L; Marscher, A P; Jorstad, S G

    2016-01-01

    The high radio frequency polarization imaging of non-thermal emission from active galactic nuclei (AGN) is a direct way to probe the magnetic field strength and structure in the immediate vicinity of supermassive black holes (SMBHs) and is crucial in testing the jet-launching scenario. To explore the the magnetic field configuration at the base of jets in blazars, we took advantage of the full polarization capabilities of the Global Millimeter VLBI Array (GMVA). With an angular resolution of $\\sim$50 micro-arcseconds ($\\mu$as) at 86 GHz, one could resolve scales up to $\\sim$450 gravitational radii (for a 10$^9$ solar mass black hole at a redshift of 0.1). We present here the preliminary results of our study on the blazar BL~Lac. Our results suggest that on sub-mas scales the core and the central jet of BL Lac are significantly polarized with two distinct regions of polarized intensity. We also noted a great morphological similarity between the 7mm/3mm VLBI images at very similar angular resolution.

  1. The REX survey as a tool to test the beaming model for BL Lacs

    CERN Document Server

    Caccianiga, A; MacCacaro, T; Wolter, A; Gioia, I M

    1999-01-01

    In the context of the beaming model (BM) BL Lac and FR I radio galaxies are thought to be the same class of sources seen at different angles. If this picture is correct, we expect to find some transition objects with intermediate properties between the two classes. To date, this intermediate population of objects is missing, probably due to the limiting fluxes of the current X-ray/radio surveys and/or to the criteria used to separate BL Lacs from normal elliptical galaxies. As pointed out by Browne and Marcha (1993), the detection of the transition objects requires particular attention since the "weak" BL Lac nucleus is hidden by the light of the host elliptical galaxy. A useful criterion often used to assess the presence of a non-thermal source, in addition to the stellar emission of the host galaxy, is the Ca contrast at 4000 AA (K/sub 4000/). This quantity, which is defined as the relative depression of the spectrum across 4000 AA, is a typical feature observed in a "normal" elliptical galaxy; the samples ...

  2. THE LACK OF TORUS EMISSION FROM BL LACERTAE OBJECTS: AN INFRARED VIEW OF UNIFICATION WITH WISE

    International Nuclear Information System (INIS)

    We use data from the Wide-Field Infrared Survey Explorer (WISE) to perform a statistical study on the mid-infrared (IR) properties of a large number (∼102) of BL Lac objects—low-luminosity active galactic nuclei (AGNs) with a jet beamed toward the Earth. As expected, many BL Lac objects are so highly beamed that their jet synchrotron emission dominates their IR spectral energy distributions. In other BL Lac objects, however, the jet is not strong enough to completely dilute the rest of the AGN emission. We do not see observational signatures of the dusty torus from these weakly beamed BL Lac objects. The lack of observable torus emission is consistent with suggestions that BL Lac objects are fed by radiatively inefficient accretion disks. Implications for the 'nature versus nurture' debate for FR I and FR II radio galaxies are briefly discussed. Our study supports the notion that, beyond orientation, accretion rate plays an important role in AGN unification.

  3. Is BZB J1450+5201 the most distant $\\gamma$-ray BL Lacertae object?

    OpenAIRE

    Liao, N. H.; Bai, J. M.; Wang, J. G.; Liu, H.T.; Zhang, J. J.; Jiang, Ning; Yuan, Z. L.; Chen, Liang

    2013-01-01

    BL Lacertae (BL Lac) objects at high redshifts ($z\\geq 2$) are rarely detected. Through careful analysis of the SDSS spectrum, BZB J1450+5201 is confirmed to be a high-$z$ BL Lac object with $z\\geq$ 2.471 by identifying the Ly$\\alpha$ 1216 and CIV 1548/1550 absorption lines. This indicates that BZB J1450+5201 is the most distant BL Lac object discovered to date. Careful analysis of the five-year \\fermi data of 2FGL J1451.0+5159 shows that its $\\gamma$-ray emission is robust with confidence le...

  4. Relativistic Beaming and Orientation Effects in BL Lacertae Objects

    Indian Academy of Sciences (India)

    F. C. Odo; A. A. Ubachukwu; A. E. Chukwude

    2012-09-01

    We use the correlation between the core-to-lobe radio luminosity ratio () and the linear size () of a sample of BL Lacertae objects to investigate the relativistic beaming and radio source orientation paradigm for high peaked and low-peaked BL Lacs (X-ray and radio selected BL Lacs respectively) and to constrain relativistic beaming model for this extreme class of active galactic nuclei. We show that the - distributions of the BL Lac populations contradict blazar orientation sequence, with the X-ray selected BL Lacs (XBLs) being more consistent with the beaming and orientation model. On the premise that Fanaroff-Riley Type I radio galaxies are the unbeamed parent population of these objects, we derive the bulk Lorentz factor of the jets, ∼ 7-20 corresponding to a critical cone angle for optimum boosting, c of ∼ 1° - 4°, while on average, these objects are inclined at 5° - 12° to the line-of-sight. The implications of these results for the blazar unification sequence are discussed.

  5. The milliarcsecond polarization structure of six BL Lacertae objects

    International Nuclear Information System (INIS)

    Milliarcsecond resolution total intensity and linear polarization maps at GHz are presented for the BL Lacertae objects 0235 + 164, 0454 + 844, 1749 + 096, 1823 + 568, and 2200 + 420 (BL Lac). Maps of 1807 + 698 (3C 371), which has in the past been classified either as a BL Lacertae object or an N galaxy, are also presented. Appreciable polarization structure is found in 0454 + 844, 1823 + 568, and BL Lac; in each the polarization position angle in the knots lies within about 10 deg of the structural direction of the VLBI jet, suggesting that plane perpendicular shock waves may be common in these objects. The polarization of 3C 371 is weak, and is quite atypical of BL Lacertae objects. Superluminal motion in 1823 + 568 is suggested. Similar comparison for 0454 + 844 over four epochs confirms proper motion at mu about 0.14 mas/yr. Systematic differences in the VLBI polarization structures of BL Lacertae objects and quasars rule out the possibility that a significant fraction of BL Lacertae objects are gravitationally microlensed quasars. 87 refs

  6. On the relationship between BL Lacertae objects and radio galaxies

    CERN Document Server

    Landt, Hermine

    2008-01-01

    We present deep radio images at 1.4 GHz of a large and complete sample of BL Lacertae objects (BL Lacs) selected from the Deep X-ray Radio Blazar Survey (DXRBS). We have observed 24 northern sources with the Very Large Array (VLA) in both its A and C configurations and 15 southern sources with the Australia Telescope Compact Array (ATCA) in its largest configuration. We find that in the DXRBS, as in the 1-Jy survey, which has a radio flux limit roughly ten times higher than the DXRBS, a considerable number (about a third) of BL Lacs can be identified with the relativistically beamed counterparts of Fanaroff-Riley type II (FR II) radio galaxies. We attribute the existence of FR II-BL Lacs, which is not accounted for by current unified schemes, to an inconsistency in our classification scheme for radio-loud active galactic nuclei (AGN). Taking the extended radio power as a suitable measure of intrinsic jet power, we find similar average values for low- (LBL) and high-energy peaked BL Lacs (HBL), contrary to the...

  7. The Lack of Torus Emission from BL Lacertae Objects: An Infrared View of Unification with WISE

    OpenAIRE

    Plotkin, Richard M.; Anderson, Scott F.; Brandt, W. N.; Markoff, Sera; Shemmer, Ohad; Wu, Jianfeng

    2011-01-01

    We use data from the Wide-Field Infrared Survey Explorer (WISE) to perform a statistical study on the mid-infrared (IR) properties of a large number ($\\sim10^2$) of BL Lac objects --- low-luminosity Active Galactic Nuclei (AGN) with a jet beamed toward the Earth. As expected, many BL Lac objects are so highly beamed that their jet synchrotron emission dominates their IR spectral energy distributions. In other BL Lac objects, however, the jet is not strong enough to completely dilute the rest ...

  8. Redshift measurement of the BL-Lac gamma-ray blazar PKS 1424+240

    CERN Document Server

    Rovero, A C; Pichel, A; Muriel, H

    2015-01-01

    PKS 1424+240 is a BL-Lac blazar with unknown redshift detected at high-energy gamma rays by Fermi-LAT with a hard spectrum. It was first detected at very-high-energy by VERITAS and latter confirmed by MAGIC. Attempts to find limits on its redshift include three estimations by modeling gamma-ray observations, and one obtained by analyzing Lyb and Lyg absorption lines observed in the far-UV spectra (from HST/COS) caused by absorbing gas along the line of sight. They allowed to constrain the redshift range to 0:6BL-Lac objects are difficult to achieve. We have found that redshift of blazars can be determined by its association to a galaxy group or cluster. To explore this possibility for PKS 1424+240, we have carried out spectroscopic measurements with the Gemini North telescope of galaxies in its field of view...

  9. X-ray spectroscopy of five BL Lacertae objects

    Science.gov (United States)

    Urry, C. M.; Mushotzky, R. F.; Holt, S. S.

    1986-01-01

    Five X-ray bright BL Lacertae objects were observed in the energy range 0.6-4.5 keV with the solid state spectrometer (SSS) of the Einstein Observatory. The 14 SSS spectra obtained represent most of the X-ray spectra of BL Lac objects with resolution better than approximately 3. These data do not reveal the presence of large amounts of thermal gas, with upper limits for the equivalent width of individual spectral features typically less that about 100 eV. However, the SSS spectra are the first set of X-ray data to indicate low-energy absorption in excess of that caused by the cold interstellar matter in the Galaxy. Comparison with contemporaneous, lower energy X-ray data implies that this absorption does not arise in cold neutral material, but in hotter, highly ionized material, probably intrinsic to the source. All five BL Lac objects have X-ray continua that are well fitted by power-law models, with power-law energy indices usually greater than about 1. In a few cases, a flattening at higher energies is observed; these and other data suggest that two-component X-ray spectra, steep at low energies and flat at high energies, are a common feature of BL Lac objects. Three of the five sources clearly vary between SSS observations, with time scales ranging from days to years. A historical synopsis of the X-ray spectral data confirms the tendency for BL Lacertae objects to be highly variable in the X-ray band but reveals no correlation between spectral and intensity changes.

  10. Rapid Tev Gamma-ray Variability Of Bl Lac

    Science.gov (United States)

    Feng, Qi

    2011-09-01

    Recent VERITAS observations of BL Lacertae revealed rapid gamma-ray flaring of the object at TeV energies (Ong, 2011, ATel #3459). Here, we present preliminary results from the observations. The flaring activity was observed during a 20-minute exposure, when the flux above 200 GeV reached a peak of about 3x10^-6 m^-2s^-1 (roughly one and a half times the Crab Nebula flux). The light curve shows that the observations missed the rising phase of the flare but covered the decaying phase almost in its entirety. The decay time of the flare is about 4 minutes, making it one of the most rapid gamma-ray flares seen for any TeV blazars. Compared to several other blazars that are known to produce gamma-ray flares on a timescale of minutes, BL Lacertae produces the bulk of its radiation at much lower frequencies. The measured gamma-ray spectrum appears to be as soft as that of the non-flaring state, when compared with the published MAGIC spectrum of the source. We will discuss the implications of the results. VERITAS research is supported by grants from the U.S. Department of Energy, the U.S. National Science Foundation, the Smithsonian Institution, by NSERC in Canada, by STFC in the U.K. and by Science Foundation Ireland.

  11. Does black hole spin play a key role in the FSRQ/BL Lac dichotomy?

    Science.gov (United States)

    Bhattacharya, Debbijoy; Sreekumar, Parameswaran; Mukhopadhyay, Banibrata; Tomar, Ishan

    2016-04-01

    Blazars are characterized by large intensity and spectral variations across the electromagnetic spectrum It is believed that jets emerging from them are almost aligned with the line-of-sight. The majority of identified extragalactic sources in γ-ray catalogs of EGRET and Fermi are blazars. Observationally, blazars can be divided into two classes: flat spectrum radio quasars (FSRQs) and BL Lacs. BL Lacs usually exhibit lower γ-ray luminosity and harder power law spectra at γ-ray energies than FSRQs. We attempt to explain the high energy properties of FSRQs and BL Lacs from Fermi γ-ray space telescope observations. It was argued previously that the difference in accretion rates is mainly responsible for the large mismatch in observed luminosity in γ-ray. However, when intrinsic luminosities are derived by correcting for beaming effects, this difference in γ-ray luminosity between the two classes is significantly reduced. In order to explain this difference in intrinsic luminosities, we propose that spin plays an important role in the luminosity distribution dichotomy of BL Lacs and FSRQs. As the outflow power of a blazar increases with increasing spin of a central black hole, we suggest that the spin plays a crucial role in making BL Lac sources low luminous and slow rotators compared to FSRQ sources.

  12. The Lack of Torus Emission from BL Lacertae Objects: An Infrared View of Unification with WISE

    CERN Document Server

    Plotkin, Richard M; Brandt, W N; Markoff, Sera; Shemmer, Ohad; Wu, Jianfeng

    2011-01-01

    We use data from the Wide-Field Infrared Survey Explorer (WISE) to perform a statistical study on the mid-infrared (IR) properties of a large number ($\\sim10^2$) of BL Lac objects --- low-luminosity Active Galactic Nuclei (AGN) with a jet beamed toward the Earth. As expected, many BL Lac objects are so highly beamed that their jet synchrotron emission dominates their IR spectral energy distributions. In other BL Lac objects, however, the jet is not strong enough to completely dilute the rest of the AGN emission. We do not see observational signatures of the dusty torus from these weakly beamed BL Lac objects. The lack of observable torus emission is consistent with suggestions that BL Lac objects are fed by radiatively inefficient accretion disks. Implications for the "nature vs. nurture" debate for FR I and FR II radio galaxies are briefly discussed. Our study supports the notion that, beyond orientation, accretion rate plays an important role in AGN unification.

  13. The Connection between X-ray- and Radio-Selected BL Lacertae Objects

    OpenAIRE

    Padovani, Paolo; Giommi, Paolo

    1994-01-01

    We explain the properties of X-ray selected BL Lacertae objects, under the assumption that they constitute the small minority of the BL Lac population with energy cutoff located in the UV/X-ray band, as suggested by their multifrequency spectra. In particular, we derive their X-ray luminosity function, log N-log S, and radio flux distribution starting from radio selected BL Lacs using a method that does not require any free parameters. Our hypothesis is at variance with the most common explan...

  14. RATAN-600 multi-frequency data for the BL Lacertae objects

    Science.gov (United States)

    Mingaliev, M. G.; Sotnikova, Yu. V.; Udovitskiy, R. Yu.; Mufakharov, T. V.; Nieppola, E.; Erkenov, A. K.

    2014-12-01

    Aims: We present a new catalogue of the RATAN-600 multi-frequency measurements for BL Lac objects. The purpose of this catalogue is to compile the BL Lac multi-frequency data that is acquired with the RATAN-600 simultaneously at several frequencies. The BL Lac objects emit a strongly variable and polarized non-thermal radiation across the entire electromagnetic spectrum from radio to γ rays and represent about 1% of known AGNs. They belong to the blazar population and differ from other blazars' featureless optical spectrum, which sometimes have absorption lines, or have weak and narrow emission lines. One of the most effective ways of studying the physics of BL Lacs is the use of simultaneous multi-frequency data. Methods: The multi-frequency broadband radio spectrum was obtained simultaneously with an accuracy of up to 1-2 min for four to six frequencies: 1.1, 2.3, 4.8, 7.7, 11.2, and 21.7 GHz. The catalogue is based on the RATAN-600 observations and on the data from: equatorial coordinate and redshift, R-band magnitude, synchrotron peak frequency, SED classes, and object type literature. Results: The present version of the catalogue contains RATAN-600 flux densities measurements over nine years (2006-2014), radio spectra at different epochs, and their parameters of the catalogue for more than 300 BL Lacs objects and candidates. The BL Lacs list is constantly updated with new observational data of RATAN-600. The catalogue is presented in interactive form and available at Special Astrophysical Observatory of the Russian Academy of Sciences website http://www.sao.ru/blcat/

  15. Simultaneous Multifrequency Observations of the BL Lac MS 0205.7+3509

    CERN Document Server

    Watson, D; McBreen, B; Smith, N; Tashiro, M; Foley, A R; Metcalfe, L; Beckmann, V; Sánchez, S F; Teraesranta, H

    1999-01-01

    Radio and optical observations of the possible microlensed BL Lac source MS 0205.7+3509 were obtained simultaneously with ASCA x-ray measurements in February 1997. A single power law model, with a photon index of 2.61, is an adequate fit to the ASCA data, once hydrogenic absorption in excess of the Galactic value is permitted, confirming a previous ROSAT measurement. On the basis of our simultaneous data we have determined MS 0205.7+3509 to be a typical x--ray selected BL Lac, with alpha_xox=-0.82. There is no indication of an inverse Compton (IC) component in the ASCA spectrum up to 10 keV. No evidence for variability on hour-long timescales is present in either the x-ray or the optical data. We discuss these results in the context of a gravitational microlensing scenario for MS 0205.7+3509.

  16. Discovery of a new BL Lacertae object /1E 1402.3 + 0416/ with the Einstein Observatory

    Science.gov (United States)

    Stocke, J.; Liebert, J.; Stockman, H.; Danziger, J.; Lub, J.; Maccacaro, T.; Griffiths, R.; Giommi, P.

    1982-01-01

    It is noted that only one BL Lac object, designated 1E 1402.3 + 0416, has so far been discovered as part of an optical identification program for a complete sample of faint X-ray sources detected with the Einstein Observatory. Consistent with previously X-ray-discovered BL Lacs, this object is blue and radio weak (17 mJy at 6 cm). It is pointed out that the percentage of BL Lacs in the faint extragalactic X-ray sample (2%) is smaller than the percentage at higher X-ray fluxes (6%). Over the same range in X-ray flux, the percentage of emission-line active galaxy nuclei (QSO + Seyferts) rises from 40% to 74%). This is seen as suggesting that BL Lacs do not evolve in a manner similar to quasars and are, therefore, not substantial contributors to the X-ray background.

  17. MAGIC discovery and multiwavelength observations of the BL Lac 1ES 1727+502

    CERN Document Server

    Berger, K; Lindfors, E; Lombardi, S; Stamerra, A

    2013-01-01

    Blazars, active galactic nuclei whose jet axis is pointed towards the observer, constitute the most numerous class of extragalactic very high energy (VHE, E > 100\\, GeV) gamma-ray emitters. The MAGIC experiment, a system of two Imaging Atmospheric Cherenkov Telescopes located in the Canary Island of La Palma (Northern hemisphere), with an energy threshold of 50 GeV, is a well suited experiment for observations of such objects. Here we present the discovery of the BL Lac 1ES 1727+502 (z = 0.055) as VHE source. This object was identified as a promising TeV candidate based on archival data and the observation that lead to this detection was not triggered by any high state alert in other wavebands. The MAGIC observations are complemented by other observations are lower frequencies: optical data from the KVA telescope, UV, optical and X-ray archival data taken with the instruments on board the Swift satellite and high energy (HE, 300 MeV < E < 100 GeV) data from the \\textit{Fermi}-LAT instrument. We studied ...

  18. Why are some BL Lacs detected by \\fermi, but others not ?

    CERN Document Server

    Wu, Zhongzu; Gu, Minfeng; Chen, Liang

    2014-01-01

    By cross-correlating an archival sample of 170 BL Lacs with 2 year \\fermilat AGN sample, we have compiled a sample of 100 BL Lacs with \\fermi detection (FBLs), and a sample of 70 non-\\fermi BL Lacs (NFBLs). We compared various parameters of FBLs with those of NFBLs, including the redshift, the low frequency radio luminosity at 408 MHz ($L_{\\rm 408MHz}$), the absolute magnitude of host galaxies ($M_{\\rm host}$), the polarization fraction from NVSS survey ($P_{\\rm NVSS}$), the observed arcsecond scale radio core flux at 5 GHz ($F_{\\rm core}$) and jet Doppler factor; all the parameters are directly \\textbf{measured} or derived from available data from literatures. We found that the Doppler factor is on average larger in FBLs than in NFBLs, and the $Fermi~ \\gamma$-ray detection rate is higher in sources with higher Doppler factor. In contrast, there are no significant differences in terms of the intrinsic parameters of redshift, $ L_{\\rm 408MHz}$, $ M_{\\rm host}$ and $ P_{\\rm NVSS}$. FBLs seem to have a higher pr...

  19. The stellar content of low redshift BL Lac host galaxies from multicolour imaging

    Directory of Open Access Journals (Sweden)

    T. Hyvönen

    2008-01-01

    Full Text Available Presentamos imágenes en las bandas UBV de 18 objetos BL Lac de bajo corrimiento al rojo (z ≤ 0.3. Estos datos se usan para investigar los colores rojo-azul-infrarrojo y gradientes de color de galaxias huésped. La distribución del color integrado azul/cercano-infrarrojo y el gradiente de color de las galaxias huésped de objetos BL Lac es más amplia que la que tienen las elípticas no-activas, y la mayoría de los objetos BL Lac tienen galaxias huésped más azules y gradientes de color más empinados que los de las elípticas no-activas. Los colores azules parecen ser causados por una componente de la población estelar joven, e indican una conexión entre la formación estelar causada por un evento de interacción/fusión, y el encendido de la actividad nuclear. Este resultado es apoyado por los modelos de población estelar, que indican que existe una población estelar joven/intermedia en la mayoría de los objetos de la muestra.

  20. Discovery of VHE gamma-rays from the distant BL Lac 1ES 0347-121

    CERN Document Server

    Aharonian, F; Barres de Almeida, U; Bazer-Bachi, A R; Behera, B; Beilicke, M; Benbow, W; Bernlöhr, K; Boisson, C; Bolz, O; Borrel, V; Braun, I; Brion, E; Brown, A M; Buhler, R; Bulik, T; Büsching, I; Boutelier, T; Carrigan, S; Chadwick, P M; Chounet, L M; Clapson, A C; Coignet, G; Cornils, R; Costamante, L; Dalton, M; Degrange, B; Dickinson, H J; Djannati-Ata:, A; Domainko, W; O'Connor-Drury, L; Dubois, F; Dubus, G; Dyks, J; Egberts, K; Emmanoulopoulos, D; Espigat, P; Farnier, C; Feinstein, F; Fiasson, A; Förster, A; Fontaine, G; Funk, Seb; Fuling, M; Gallant, Y A; Giebels, B; Glicenstein, J F; Glück, B; Goret, P; Hadjichristidis, C; Hauser, D; Hauser, M; Heinzelmann, G; Henri, G; Hermann, G; Hinton, J A; Hoffmann, A; Hofmann, W; Holleran, M; Hoppe, S; Horns, D; Jacholkowska, A; De Jager, O C; Jung, I; Katarzynski, K; Kendziorra, E; Kerschhaggl, M; Khelifi, B; Keogh, D; Komin, Nu; Kosack, K; Lamanna, G; Latham, I J; Lemiere, A; Lemoine-Goumard, M; Lenain, J P; Lohse, T; Martin, J M; Martineau-Huynh, O; Marcowith, A; Masterson, C; Maurin, D; Maurin, G; McComb, T J L; Moderski, R; Moulin, E; De Naurois, Mathieu; Nedbal, D; Nolan, S J; Ohm, S; Olive, J P; De Ona Wilhelmi, E; Orford, K J; Osborne, J L; Ostrowski, M; Panter, M; Pedaletti, G; Pelletier, G; Petrucci, P O; Pita, S; Pühlhofer, G; Punch, M; Ranchon, S; Raubenheimer, B C; Raue, M; Rayner, S M; Renaud, M; Ripken, J; Rob, L; Rolland, L; Rosier-Lees, S; Rowell, G; Rudak, B; Ruppel, J; Sahakian, V V; Santangelo, A; Schlickeiser, R; Schock, F; Schroder, R; Schwanke, U; Schwarzburg, S; Schwemmer, S; Shalchi, A; Sol, H; Spangler, D; Stawarz,; Steenkamp, R; Stegmann, C; Superina, G; Tam, P H; Tavernet, J P; Terrier, R; Van Eldik, C; Vasileiadis, G; Venter, C; Vialle, J P; Vincent, P; Vivier, M; Völk, H J; Volpe, F; Wagner, S J; Ward, M; Zdziarski, A A; Zech, A

    2007-01-01

    Aims: Our aim is to study the production mechanism for very-high-energy (VHE; >100GeV) gamma-rays in distant active galactic nuclei (AGN) and use the observed VHE spectrum to derive limits on the Extragalactic Background Light (EBL). We also want to determine physical quantities through the modeling of the object's broad-band spectral energy distribution (SED). Methods: VHE observations (~25h live time) of the BL Lac 1ES 0347-121 (redshift z=0.188) were conducted with the High Energy Stereoscopic System (H.E.S.S.) between August and December 2006. Contemporaneous X-ray and UV/optical observations from the SWIFT satellite are used to interpret the SED of the source in terms of a synchrotron self Compton (SSC) model. Results: An excess of 327 events, corresponding to a statistical significance of 10.1 standard deviations, is detected from 1ES 0347-121. Its photon spectrum, ranging from ~250GeV to ~3TeV, is well described by a power law with a photon index of Gamma = 3.10 +/- 0.23_stat +/- 0.10_sys. The integral...

  1. The Connection among Gamma-ray Burst Host-Galaxies, BL Lacs and Quasars

    OpenAIRE

    Rej, A.

    1999-01-01

    A possible connection among host-galaxies of gamma-ray bursts, BL Lacs and quasars is analysed. It is believed that the gamma-ray bursts, which do not show radio or infrared emission, occur in faint blue dwarf galaxies, that are seen around radio-quiet quasars, which lie in clusters. The GRB counterparts, which show radio emission, may be associated with more evolved starbursting environments, and arise from red galaxies, that are observed around some radio-loud quasars lying in richer cluste...

  2. Polarization and Variations of BL Lacertae Objects

    OpenAIRE

    Fan, J.H.; Cheng, K. S.; Zhang, L.

    1999-01-01

    BL Lacertae objects are an extreme subclass of AGNs showing rapid and large-amplitude variability, high and variable polarization, and core-dominated radio emissions. If a strong beaming effect is the cause of the extreme observation properties, one would expect that these properties would be correlated with each other. Based on the relativistic beaming model, relationships between the polarization and the magnitude variation in brightness, as well as the core- dominance parameter are derived...

  3. Search for Cross-Correlations of Ultra--High-Energy Cosmic Rays with BL Lacertae Objects

    CERN Document Server

    Abbasi, R U; Amman, J F; Archbold, G; Atkins, R; Bellido, J A; Belov, K; Belz, J W; Ben-Zvi, S Y; Bergman, D R; Burt, G W; Cao, Z; Clay, R W; Connolly, B C; Deng, W; Dawson, B R; Fedorova, Y; Findlay, J; Finley, C B; Hanlon, W F; Hoffman, C M; Hughes, G A; Holzscheiter, M H; Hüntemeyer, P; Jui, C C H; Kim, K; Kirn, M A; Loh, E C; Maestas, M M; Manago, N; Marek, L J; Martens, K; Matthews, J A J; Matthews, J N; O'Neill, A; Painter, C A; Perera, L P; Reil, K; Riehle, R; Roberts, M; Sasaki, M; Schnetzer, S R; Simpson, K M; Sinnis, G; Smith, J D; Snow, R; Sokolsky, P; Song, C; Springer, R W; Stokes, B T; Thomas, J R; Thomas, S B; Thomson, G B; Tupa, D; Westerhoff, S; Wiencke, L R; Zech, A

    2005-01-01

    Data taken in stereo mode by the High Resolution Fly's Eye (HiRes) air fluorescence experiment are analyzed to search for correlations between the arrival directions of ultra--high-energy cosmic rays with the positions of BL Lacertae objects. Several previous claims of significant correlations between BL Lacs and cosmic rays observed by other experiments are tested. These claims are not supported by the HiRes data. However, we verify a recent analysis of correlations between HiRes events and a subset of confirmed BL Lacs from the 10th Veron Catalog, and we study this correlation in detail. Due to the a posteriori nature of the search, the significance level cannot be reliably estimated and the correlation must be tested independently before any claim can be made. We identify the precise hypotheses that will be tested with statistically independent data.

  4. Multi-Wave Luminosity of High-Synchrotron-Peaked TeV BL Lacs Detected by Fermi LAT

    Indian Academy of Sciences (India)

    Dingrong Xiong; Xiong Zhang; Yonggang Zheng

    2014-09-01

    We have studied the correlations between luminosities (R, IR, ) in the radio, near-infrared and -ray wave bands for HSP TeV BL Lacs. The results show that there are significant intrinsic correlations between R and and between IR and in all states (high/average/low), and suggest that for HSP TeV BL Lacs, the Synchrotron Self-Compton radiation (SSC) is the main mechanism of high energy -ray emission, and the inverse Compton scattering of circum-nuclear dust is likely to be an important complementary mechanism.

  5. The BL-Lac gamma-ray blazar PKS 1424+240 associated with a group of galaxies at z=0.6010

    CERN Document Server

    Rovero, A C; Donzelli, C; Pichel, A

    2016-01-01

    PKS 1424+240 is a BL-Lac blazar with unknown redshift that was detected at high-energy gamma rays by Fermi-LAT with a hard spectrum. At VHE, it was first detected by VERITAS and later confirmed by MAGIC. Its spectral energy distribution is highly attenuated at VHE gamma rays, which is coherent with distant sources. Several estimations enabled the redshift to be constrained to the range 0.6 < z < 1.3. These results place PKS 1424+240 in the very interesting condition of being probably the most distant blazar that has been detected at VHE. The ambiguity in the redshift is still large enough to prevent precise studies of the EBL and the intrinsic blazar spectrum. Given the difficulty of measuring spectroscopic redshifts for BL-Lac objects directly, we aim to establish a reliable redshift value for this blazar by finding its host group of galaxies. Elliptical galaxies are associated with groups, and BL-Lac objects are typically hosted by them, so we decided to search for the host group of the blazar. For th...

  6. Seven-Year Multi-Colour Optical Monitoring of BL Lacertae Object S5 0716+714

    Indian Academy of Sciences (India)

    Jianghua Wu; Yan Dai; Xu Zhou; Jun Ma

    2014-09-01

    We monitored the BL Lac object S5 0716+714 in five intermediate optical passbands from 2004 September to 2011 April. The object was active most of the time and intra-day variability was frequently observed. The total variation amplitude tended to decrease with decreasing frequency. Strong bluer-when-brighter chromatism was observed on both long and short timescales.

  7. Rapid X-ray Variability of the BL Lacertae Object PKS 2155-304

    OpenAIRE

    Zhang, Y.H.; Celotti, A.; Treves, A.; Chiappetti, L.; Ghisellini, G.; L. Maraschi(INAF National Institute for Astrophysics, I-00136 Rome, Italy); Pian, E.; Tagliaferri, G.; Tavecchio, F.; C. M. Urry

    1999-01-01

    (Abridged) We present a detailed power density spectrum and cross-correlation analysis of the X-ray light curves of the BL Lac object PKS 2155-304, observed with BeppoSAX in 1997 and 1996, aimed at exploring the rapid variability properties and the inter-band cross correlations in the X-rays. We also perform the same analysis on the (archival) X-ray light curve obtained with ASCA in 1994.

  8. Infrared Polarization and Beaming Effect for BL Lac Objects

    Institute of Scientific and Technical Information of China (English)

    MEI Dong-Cheng; XIE Guang-Zhong

    2001-01-01

    With the idea of the beaming models, we derive a relation between the observed polarization and Dopplercorrected magnitude; that is, the observed polarization is in anti-correlation with the Doppler-corrected magnitude. Making use of the infrared data observed simultaneously by Impey et al. [Mon. Not. R. Astron. Soc.200 (1982) 19; 209 (1984) 245] and Holmes et al. [ibid. 210 (1984) 961] we found that: (1) there is a significant correlation between the observed maximum polarization and Doppler-corrected magnitude but the polarization is not in anti-correlation with the Doppler-corrected magnitude; (2) the maximum infrared polarization is strongly correlated with the maximum optical polarization. Our conclusion is that the infrared polarization depends only on the degree of ordering of the magnetic field in the synchrotron emission regions and not on the beaming effect.Both infrared and optical emissions originate from the synchrotron radiation.

  9. X-ray Emission of Low-Energy-Peaked BL Lacertae Objects

    International Nuclear Information System (INIS)

    Presented here is an analysis of X-ray observations of the following seven low-energy-peaked BL Lacertae objects: BL Lacertae, S5 0716+71, W Comae, 3C 66A, S4 0954+65, OJ 287, and AO 0235+16. The spectral data for these objects were taken from observations by the XMM-Newton and/or Chandra X-ray observatories. These objects are being analyzed in an effort to reanalyze all XMM-Newton and Chandra data of low-energy BL Lacs, similar to the efforts of Perlman et al.[4] for high energy BL Lacs. The objects were studied in an effort to understand the nature of the X-ray and multi-waveband emissions in these objects, study the shape of the spectra, and compare the observations of low-energy-peaked BL Lacs to previous observations of these objects and also to observations of high-energy-peaked BL Lacs. Light curves and spectra were analyzed to look for evidence of spectral variability in the objects and as a comparison to previous research on these objects. Most data shows both synchrotron and Inverse-Compton emission, though only little correlation was seen between the emission strength and the spectral slope. Our data is generally well-fitted to a broken power law model with distinct bimodality seen in the first spectral index (six observations with Γ1∼0.4 and four observations with Γ1∼3.0), a break in energy between 0.6 and 1.4 keV, and a second spectral index Γ2∼2.0. None of the observations showed spectral lines, which is consistent with past results. For S5 0716+71 the XMM-Newton X-ray and optical data, along with radio data obtained from the University of Michigan Radio Astronomy Observatory (UMRAO), a spectral energy distribution was created and peak frequencies were estimated.

  10. Evidence for VHE Gamma-ray Emission from the Distant BL Lac PG 1553+113

    CERN Document Server

    Aharonian, F; Bazer-Bachi, A R; Beilicke, M; Benbow, W; Berge, D; Bernlöhr, K; Boisson, C; Bolz, O; Borrel, V; Braun, I; Breitling, F; Brown, A M; Buhler, R; Carrigan, S; Chadwick, P M; Chounet, L M; Cornils, R; Costamante, L; Degrange, B; Dickinson, H J; Djannati-Ata, A; O'Connor-Drury, L; Dubus, G; Egberts, K; Emmanoulopoulos, D; Espigat, P; Feinstein, F; Fontaine, G; Funk, S; Gallant, Y A; Giebels, B; Glicenstein, J F; Goret, P; Hadjichristidis, C; Hauser, D; Hauser, M; Heinzelmann, G; Henri, G; Hermann, G; Hinton, J A; Hofmann, W; Holleran, M; Horns, D; Jacholkowska, A; De Jager, O C; Khelifi, B; Komin, Nu; Konopelko, A; Latham, I J; Le Gallou, R; Lemiere, A; Lemoine-Goumard, M; Lohse, T; Martin, J M; Martineau-Huynh, O; Marcowith, A; Masterson, C; McComb, T J L; De Naurois, Mathieu; Nedbal, D; Nolan, S J; Noutsos, A; Orford, K J; Osborne, J L; Ouchrif, M; Panter, M; Pelletier, G; Pita, S; Pühlhofer, G; Punch, M; Raubenheimer, B C; Raue, M; Rayner, S M; Reimer, A; Reimer, O; Ripken, J; Rob, L; Rolland, L; Rowell, G; Sahakian, V V; Sauge, L; Schlenker, S; Schlickeiser, R; Schuster, C; Schwanke, U; Siewert, M; Sol, H; Spangler, D; Steenkamp, R; Stegmann, C; Superina, G; Tavernet, J P; Terrier, R; Theoret, C G; Tluczykont, M; Van Eldik, C; Vasileiadis, G; Venter, C; Vincent, P; Völk, H J; Wagner, S J; Ward, M

    2006-01-01

    The high-frequency peaked BL Lac PG 1553+113 was observed in 2005 with the H.E.S.S. stereoscopic array of imaging atmospheric-Cherenkov telescopes in Namibia. Using the H.E.S.S. standard analysis, an excess was measured at the 4.0 sigma level in these observations (7.6 hours live time). Three alternative, lower-threshold analyses yield >5 sigma excesses. The observed integral flux above 200 GeV is (4.8 +/- 1.3_{stat} +/- 1.0_{syst}) x10^{-12} cm^{-2} s^{-1}, and shows no evidence for variability. The measured energy spectrum is characterized by a very soft power law (photon index of Gamma=4.0 +/- 0.6). Although the redshift of PG 1553+113 is unknown, there are strong indications that it is greater than z=0.25 and possibly larger than z=0.78. The observed spectrum is interpreted in the context of VHE gamma-ray absorption by the Extragalactic Background Light, and is used to place an upper limit on the redshift of z<0.74.

  11. 3C84, BL Lac. Earth based VLBI test for the RADIOASTRON project

    CERN Document Server

    Chuprikov, Andrey; Chibisov, Andrey; Kostenko, Vladimir; Kovalev, Yuri; Graham, Dave; Lobanov, Andrew; Giovannini, Gabriele

    2011-01-01

    Results of processing of data of a VLBI experiment titled RAPL01 are presented. These VLBI observations were made on 4th February, 2010 at 6.28 cm between the 100-m antenna of the Max Planck Institute (Effelsberg, Germany), Puschino 22-m antenna (Astro Space Center (ASC), Russia), and two 32-m antennas of the Istituto di Radioastronomia di Bologna (Bologna, Italy) in Noto and Medicina. 2 well-known sources, 3C84 (0316+413), and BL Lac (2200+420) were included in the schedule of observations. Each of them was observed during 1 hour at all the stations. The Mark-5A registration system was used at 3 European antennae. The alternative registration system known as RDR (RADIOASTRON Data Recorder) was used in Puschino. The Puschino data were recorded in format RDF (RADIOASTRON Data Format). Two standard recording modes designed as 128-4-1 (one bit), and 256-4-2 (two bit) were used in the experiment. All the Mark-5A data from European antennae were successfully converted into the RDF format. Then, the correlation fun...

  12. Observations of low and intermediate-frequency-peaked BL Lacs above 100 GeV with VERITAS

    Directory of Open Access Journals (Sweden)

    Errando M.

    2013-12-01

    Full Text Available Most of the ~ 50 blazars detected to date at TeV energies (E > 0.1 TeV are high-frequency-peaked BL Lacs (HBLs. Only a handful episodic detections of low- and intermediate-frequency-peaked BL Lacs (LBL/IBLs, with synchrotron peak frequencies in the infrared and optical regime have been reported by ground-based gamma-ray telescopes, typically during high-flux states. The VERITAS array located in southern Arizona has observed five known TeV LBL/IBLs since 2009: 3C 66A, WComae, PKS 1424+240, S5 0716+714 and BL Lacertae, with exposures of 5-10 hours/year, which so far resulted in the detection of a bright, sub-hour timescale gamma-ray flare of BL Lacertae in June 2011. We also report the detection and characterization of two new IBLs: VER J0521+211 and B2 1215+30.

  13. Baryon Loading Efficiency and Particle Acceleration Efficiency of Relativistic Jets: Cases for Low Luminosity BL Lacs

    Science.gov (United States)

    Inoue, Yoshiyuki; Tanaka, Yasuyuki T.

    2016-09-01

    Relativistic jets launched by supermassive black holes, so-called active galactic nuclei (AGNs), are known as the most energetic particle accelerators in the universe. However, the baryon loading efficiency onto the jets from the accretion flows and their particle acceleration efficiencies have been veiled in mystery. With the latest data sets, we perform multi-wavelength spectral analysis of quiescent spectra of 13 TeV gamma-ray detected high-frequency-peaked BL Lacs (HBLs) following one-zone static synchrotron self-Compton (SSC) model. We determine the minimum, cooling break, and maximum electron Lorentz factors following the diffusive shock acceleration (DSA) theory. We find that HBLs have {P}B/{P}e˜ 6.3× {10}-3 and the radiative efficiency {ɛ }{{rad,jet}}˜ 6.7× {10}-4, where P B and P e is the Poynting and electron power, respectively. By assuming 10 leptons per one proton, the jet power relates to the black hole mass as {P}{{jet}}/{L}{{Edd}}˜ 0.18, where {P}{{jet}} and {L}{{Edd}} is the jet power and the Eddington luminosity, respectively. Under our model assumptions, we further find that HBLs have a jet production efficiency of {η }{{jet}}˜ 1.5 and a mass loading efficiency of {ξ }{{jet}}≳ 5× {10}-2. We also investigate the particle acceleration efficiency in the blazar zone by including the most recent Swift/BAT data. Our samples ubiquitously have particle acceleration efficiencies of {η }g˜ {10}4.5, which is inefficient to accelerate particles up to the ultra-high-energy-cosmic-ray (UHECR) regime. This implies that the UHECR acceleration sites should not be the blazar zones of quiescent low power AGN jets, if one assumes the one-zone SSC model based on the DSA theory.

  14. Discovery of a BL Lacertae object (EXO 055625 - 3838.6) in the error box of H0557 - 385

    International Nuclear Information System (INIS)

    X-ray and optical data are presented of a new BL Lacertae type object (EXO 055625 - 3838.6) which has been serendipitously discovered in an EXOSAT CMA image and is located within the error box of HO557-385 (4U0557 - 38, 3A0557 - 383), a hard X-ray source previously identified with a Seyfert 1 galaxy. Although the soft X-ray flux of the BL Lac is 10 times higher than that of the Seyfert and the EXOSAT data are fully consistent with the BL Lac being the only counterpart of HO557 - 385, a substantial contribution to the hard X-ray flux from the Seyfert galaxy cannot be excluded. (author)

  15. BL Lacertae objects and radio-loud quasars within an evolutionary unified scheme

    International Nuclear Information System (INIS)

    On the basis of a joint radio-optical analysis, different amounts of cosmological luminosity evolution in the optical band for flat- and steep-spectrum radio-loud quasars are found. Specifically, a slower evolution for the flat-spectrum quasars, evidence of a sluggish beamed component in the optical band additional to the canonical isotropic continuum is shown. The persistence of the beamed component in terms of a spectral evolution with the Doppler factor increasing somewhat in cosmic time is interpreted. The BL Lacertae objects are placed into this framework and an evolutionary unified scheme is proposed maintaining spectral and statistical continuity of BL Lacs with flat-spectrum quasars. Supportive observational evidence, and clues for the parent population, are discussed. 57 refs

  16. Multifrequency-spectral behavior of the BL Lacertae objects OI 90.4 and 3C 66A

    Science.gov (United States)

    Worrall, D. M.; Rodriguez-Espinosa, J. M.; Puschell, J. J.; Bruhweiler, F. C.; Miller, H. R.; Aller, M. F.; Aller, H. D.

    1984-01-01

    Single-epoch multifrequency data for the BL Lac objects OI 90.4 and 3C 66A, spanning radio through ultraviolet wavelengths, are presented, as well as other measurements relevant to intensity and spectral-shape variability. Both BL Lac objects exhibit spectral curvature in the infrared-to-ultraviolet region, a properity that is inferred to be usual for this object class. Variability in the ultraviolet spectral index of OI 90.4 is found, whereas the spectral index of 3C 66A is the same in two observations 17 months apart. A synchrotron self-Compton jet model is applied to each BL Lac object. The OI 90.4 data are found to be best satisfied by a jet with a relatively high degree of relativistic beaming, but emission at frequencies below about 50 GHz is not described by the model. Furthermore, 3C 66A may not always undergo strong relativistic beaming, and the model may incorporate the small fraction of the total radio emission below about 20 GHz that is from within about 1.5 milliarcsec of the core.

  17. BROAD Lyα EMISSION FROM THREE NEARBY BL LACERTAE OBJECTS

    International Nuclear Information System (INIS)

    We present far-UV HST/COS spectra of four nearby BL Lac objects. BL Lac spectra are dominated by a smooth, power-law continuum which arises in a relativistic jet. However, the spectra are not necessarily featureless; weak, broad- and/or narrow-line emission is sometimes seen in high-quality optical spectra. We present detections of Lyα emission in HST/COS spectra of Mrk 421 (z = 0.030) and PKS 2005-489 (z = 0.071) as well as an archival HST/GHRS observation of Mrk 501 (z = 0.0337). Archival HST/STIS observations of PKS 2155-304 (z = 0.116) show no Lyα emission to a very low upper limit. Using the assumption that the broad-line region (BLR) clouds are symmetrically placed around the active galactic nucleus (AGN), we use these measured Lyα emission features to constrain either the relativistic Γ values for the ionizing continuum produced by the jet (in the ionization-bounded case) or the mass of warm gas (in the density-bounded case). While realistic Γ values can be obtained for all four cases, the values for Mrk 421 and PKS 2155-304 are high enough to suggest that covering factors of BLR clouds of ∼1%-2% might be required to provide consistency with earlier values of Doppler boosting and viewing angles suggested for this class of BL Lacs. This discrepancy also exists in the case of M 87, where the amount of Doppler boosting in our direction is expected to be minimal, again suggestive of a small covering factor of BLR clouds. If, as these small covering factors might suggest, the assumptions of a density-bounded model could be more correct, then the observed Lyα luminosities require that BL Lac/FR 1 nuclei possess very little warm gas (10-4 to 10-5 Msun) as suggested by Guilbert et al. If these clouds are in pressure balance with a hotter (∼106 K) gas, the BLR contains too little mass to power the AGN by accretion alone.

  18. On the Absence of Core Luminosity–Core-Dominance Parameter (C - ) Correlation in Radio Galaxies and BL Lacs

    Indian Academy of Sciences (India)

    J. A. Alhassan; A. A. Ubachukwu; F. C. Odo

    2013-03-01

    We have presented an alternative interpretation for the absence of correlation in the relationship between the core radio power (C) and core-dominance parameter () for a sample of BL Lacs and radio galaxies found in Fan & Zhang (Astron. Astrophys. 407, 899 (2003)). This is contrary to the predictions of the relativistic beaming and radio source orientation models in which the core luminosity is expected to be Doppler-boosted relative to the extended luminosity which is generally assumed to be isotropic. Our analysis of the C - data indicates a strong luminosity selection effect (reminiscent of bright source samples due to Malmquist bias) in the sample. In particular, we showed that a strong C - correlation exists above some redshift cut-off which may correspond to the flux limit of the sample used.

  19. An HST/COS observation of broad Lyα emission and associated absorption lines of the BL Lacertae object H 2356-309

    Energy Technology Data Exchange (ETDEWEB)

    Fang, Taotao [Department of Astronomy and Institute of Theoretical Physics and Astrophysics, Xiamen University, Xiamen, Fujian 361005 (China); Danforth, Charles W.; Stocke, John T.; Shull, J. Michael [CASA, Department of Astrophysical and Planetary Sciences, University of Colorado, 389-UCB, Boulder, CO 80309 (United States); Buote, David A. [Department of Physics and Astronomy, 4129 Frederick Reines Hall, University of California, Irvine, CA 92697 (United States); Canizares, Claude R. [Department of Physics and Kavli Institute for Astrophysics and Space Research, Massachusetts Institute of Technology, Cambridge, MA 02139 (United States); Gastaldello, Fabio, E-mail: fangt@xmu.edu.cn [IASF-Milano, INAF, via Bassini 15, Milan I-20133 (Italy)

    2014-11-01

    Weak spectral features in BL Lacertae objects (BL Lacs) often provide a unique opportunity to probe the inner region of this rare type of active galactic nucleus. We present a Hubble Space Telescope/Cosmic Origins Spectrograph observation of the BL Lac H 2356-309. A weak Lyα emission line was detected. This is the fourth detection of a weak Lyα emission feature in the ultraviolet (UV) band in the so-called high-energy peaked BL Lacs, after Stocke et al. Assuming the line-emitting gas is located in the broad line region (BLR) and the ionizing source is the off-axis jet emission, we constrain the Lorentz factor (Γ) of the relativistic jet to be ≥8.1 with a maximum viewing angle of 3.°6. The derived Γ is somewhat larger than previous measurements of Γ ≈ 3-5, implying a covering factor of ∼3% of the line-emitting gas. Alternatively, the BLR clouds could be optically thin, in which case we constrain the BLR warm gas to be ∼10{sup –5} M {sub ☉}. We also detected two H I and one O VI absorption lines that are within |Δv| < 150 km s{sup –1} of the BL Lac object. The O VI and one of the H I absorbers likely coexist due to their nearly identical velocities. We discuss several ionization models and find a photoionization model where the ionizing photon source is the BL Lac object that can fit the observed ion column densities with reasonable physical parameters. This absorber can either be located in the interstellar medium of the host galaxy or in the BLR.

  20. The Optical Microvariability and Spectral Changes of the BL Lacertae Object S5 0716+714

    Indian Academy of Sciences (India)

    H. Poon; J. H. Fan; J. N. Fu

    2011-03-01

    The BL Lac object S5 0716+714 was monitored in the optical band during October 2008, December 2008 and February 2009. We achieved a best temporal resolution of about 5 min in the bands. The source was active during the whole monitoring campaign. It showed microvariability in 13 days out of 14 days of observation. Four fast flares were observed with amplitudes ranging from 0.3–0.75 mag. The overall amplitude changes during the whole campaign are ∼ 0. 89, ∼ 0. 80, ∼ 0. 73, and ∼ 0. 51. On internight time scales, strong bluer-when-brighter chromatism was found while different spectral behaviours were found on intranight time scales.

  1. VizieR Online Data Catalog: Multiwavelength obs. of BL Lac in 2012-2013 (Wehrle+, 2016)

    Science.gov (United States)

    Wehrle, A. E.; Grupe, D.; Jorstad, S. G.; Marscher, A. P.; Gurwell, M.; Balokovic, M.; Hovatta, T.; Madejski, G. M.; Harrison, F. H.; Stern, D.

    2016-03-01

    Our Herschel target of opportunity observations began on 2012 October 29 (MJD 56229) and continued for the three-month visibility window. We arranged for daily Swift pointings starting on 2012 October 27 through 2013 February 1. We also arranged for two intense periods of every-orbit Swift monitoring on 2012 December 11-12 and 2013 January 11-12. We obtained target of opportunity observations with NuSTAR on 2012 December 11-12. Observations of BL Lac every two to four days were carried out at the SMA on Mauna Kea, HI during the Herschel observation window, and intermittently thereafter. Monitoring observations with CARMA at 3mm were already underway. VLBA monitoring continued throughout the time range reported here as part of the ongoing Boston University (BU) γ-ray blazar monitoring program. Observations at other wavebands were already underway by other collaborations, e.g., the Whole Earth Blazar Telescope. In addition, roughly weekly Swift observations have been carried out for several years by A. Falcone and M. Stroh (Stroh & Falcone 2013ApJS..207...28S). Herschel SPIRE and PACS FIR observations of BL Lac are presented in table 1 and sections 2.2 and 2.5. SMA millimeter and submillimeter observations are presented in tables 1, 2 and 3 and sections 2.3 and 2.5. Millimeter observations with CARMA are presented in table 4 and sections 2.4 and 2.5. Swift optical, UV and X-ray observations are presented in tables 5 and 6 and section 2.6. Hard X-ray observations with NuSTAR are presented in section 2.7. γ-ray observations with Fermi are presented in section 2.8. The 7mm band observations are presented in section 2.9. The BU group obtained 2.4-10keV X-ray fluxes with the RXTE PCA three times per week from 2005 March 3 to 2011 December 31; see table 10 and Appendix. (7 data files).

  2. Infrared Variation of Radio Selected BL Lacertae Objects

    OpenAIRE

    Fan, J. H.; Lin, R. G.

    1999-01-01

    In this paper, the historical infrared (JHK) data compiled from the published literature are presented in electronic form for 40 radio selected BL Lacertae objects (RBLs) for the first time. Largest variations are found and compared with the largest optical variation. Relations between color index and magnitude and between color-color indices are discussed individually. For the color-magnitude relation, some objects (0048-097, 0735+178, 0851+202, 1215+303, 1219+285, 1749+096, and perhaps 0219...

  3. Are both BL Lacs and pulsar wind nebulae the astrophysical counterparts of IceCube neutrino events?

    CERN Document Server

    Padovani, P

    2014-01-01

    IceCube has recently reported the discovery of high-energy neutrinos of astrophysical origin. These are the highest energy particles produced in cosmic ray interactions ever detected, opening up the possibility of investigating the PeV (10^15 eV) sky. Because of their rather large positional uncertainties, these events have so far not been associated to any astrophysical source. We have found plausible counterparts in the GeV - TeV band by using joint spatial and energetic information. Namely, we looked for sources in the available high-energy gamma-ray catalogues (TeVCat, WHSP, 1FHL) within the median error circles of the IceCube events. We then built the spectral energy distribution of these sources and compared it with the energy and flux of the corresponding neutrino events. The likely counterparts include "classic" BL Lacs, such as MKN 421 and PG 1553+113, as well as Galactic pulsar wind nebulae, namely MGRO J1908+06 and HESS J1809-193. This might indicate the emerging of a mixed scenario of Galactic and...

  4. BeppoSAX observations of 1 Jy BL Lacertae objects

    International Nuclear Information System (INIS)

    Preliminary results on BeppoSAX LECS and MECS observations of BL Lacertae objects selected from the 1 Jy sample are presented. All sources of the LBL type, that is, characterized by a peak in their multifrequency spectra at infrared/optical energies, seem to show a relatively flat (αx ∼ 0.7 - 0.8) X-ray spectrum. This is in agreement with the supposed dominance of inverse Compton emission in the X-ray band of these sources

  5. High-energy emitting BL Lacs and high-energy neutrinos - Prospects for the direct association with IceCube and KM3NeT

    CERN Document Server

    Righi, Chiara; Guetta, Dafne

    2016-01-01

    The origin of the high-energy flux of neutrinos detected by IceCube is still unknown. Recent works report the evidence for a possible positional correlation between the reconstructed neutrino arrival directions and the positions in the sky of low power, high-energy emitting BL Lac objects (HBL). Assuming that $\\gamma$-ray emitting HBL form the bulk of the sources of high-energy neutrinos above 100 TeV, we intend to calculate the number of events expected to be detected for each source by IceCube and KM3NeT. Based on a simple theoretically-motivated framework inspired by the structured jet scenario for these sources, we postulate a direct proportionality between high-energy $\\gamma$-ray and neutrino fluxes. We calculate the expected neutrino event rate for the HBL sources of the Second Fermi-LAT Catalog of High-Energy Sources (2FHL) for IceCube and the presently under construction KM3NeT using declination-dependent and exposure-weighted effective areas. We provide a list of 2FHL HBL with the calculated number ...

  6. Longterm Optical Monitoring of Bright BL Lacertae Objects with ATOM: Spectral Variability and Multiwavelength Correlations

    CERN Document Server

    Wierzcholska, Alicja; Stawarz, Łukasz; Wagner, Stefan; Hauser, Marcus

    2014-01-01

    Blazars are the established sources of an intense and variable non-thermal radiation extending from radio wavelengths up to HE and VHE gamma-rays. Understanding the spectral evolution of blazars in selected frequency ranges, as well as multi-frequency correlations in various types of blazar sources, is of a primary importance for constraining the blazar physics. Here we present the results of a long-term optical monitoring of a sample of 30 blazars of the BL Lac type. We study the optical color-magnitude correlation patterns emerging in the analyzed sample, and compare the optical properties of the targets with the high-energy gamma-ray and high-frequency radio data. The optical observations were carried out in R and B filters using ATOM telescope. Each object was observed during at least 20 nights in the period 2007-2012. We find significant global color-magnitude correlations in 40 % of the sample. The sources which do not display any clear chromatism often do exhibit bluer-when-brighter (bwb) behavior but ...

  7. Gamma-ray and multiwaveband emission from gamma-ray-loud BL Lacertae objects

    International Nuclear Information System (INIS)

    We have collected 18 γ-ray-loud BL Lac with observed data in multiwaveband, we find that γ-ray flux densities correlate better with the near-IR flux densities than those with the optical or x-ray flux densities. There is no correlation between γ-ray and radio flux densities. Possible constraints on the γ-ray emission mechanism are discussed. We suggest that the main γ-ray radiation mechanism is probably the synchrotron self-Compton process. The inverse Compton scattering of the radiation from hot circumscribe dust, by beamed ultrarelativistic electrons, is likely to be an important complementary mechanism

  8. Discovery of VHE γ-ray emission from the very distant BL Lac KUV 00311-1938 by H.E.S.S

    International Nuclear Information System (INIS)

    The observed spectra of very-high-energy (VHE) blazars may be deformed by γ-γ absorption onto the Extra-galactic Background Light (EBL) or, more speculatively, by photon-axion oscillations. As the resulting imprint on observed spectral characteristics may be redshift-dependent, it is important to enrich the catalogue of VHE high-redshift blazars. HESS-II, with its low energy threshold and enhanced E ≥ 100 GeV sensitivity, will be a major instrument in this field of study. While awaiting this new phase of the experiment, H.E.S.S. observed the very distant BL Lac KUV00311-1938 in a multi-year campaign, leading to the discovery of its VHE γ-ray emission with a significance of 5.1 standard deviations. The detection of this source has been possible thanks to an enhanced low-energy sensitivity of recent developed analysis techniques for IACTs (Paris-MVA) and a full refurbishment which markedly lowered the overall analysis threshold. The evaluation of the redshift of this source is difficult, due to the weakness of the absorption lines in the optical spectrum. A first attempt to evaluate this redshift was performed, where a value of 0.61 was quoted with a question mark. More recently, the data from the X-Shooter spectrograph operating on the VLT have been used to estimate a solid lower limit on the redshift of the source of z ≥ 0.506, confirming that KUV00311-1938 is the farthest BL Lac ever detected at VHE. (authors)

  9. The HST Survey of BL Lacertae Objects: Morphological Properties of Low redshift Host Galaxies

    CERN Document Server

    Falomo, R; Treves, A; Urry, C M; 10.1086/317044

    2009-01-01

    We report on the optical properties of a sample of 30 BL Lac host galaxies in the redshift range $0.03BL Lac nucleus is well centered in the main body of its host galaxy, a result that argues strongly against the microlensing hypothesis for any significant fraction of the population. A search for faint sub-structures in the host galaxies has not revealed notable signatures of tidal distortions or sub-components (faint disks, bars, X features, etc.), and with only one exception, there are no prominent dusty features in the central regions. Instead, the B...

  10. An active state of the BL Lac Object Markarian 421 detected by INTEGRAL in April 2013

    CERN Document Server

    Pian, E; Fiocchi, M; Bazzano, A; Foschini, L; Tavecchio, F; Bianchin, V; Boissay, R; Castignani, G; Ferrigno, C; Raiteri, C M; Villata, M; Beckmann, V; D'Ammando, F; Hudec, R; Malaguti, G; Maraschi, L; Pursimo, T; Romano, P; Soldi, S; Stamerra, A; Treves, A; Ubertini, P; Vercellone, S; Walter, R

    2013-01-01

    (abridged) Multi-wavelength variability of blazars offers effective insight into the mechanisms through which energy is propagated from the center down the jet. In this context, we activated INTEGRAL observations of the blazar Markarian 421 in an active state on 16-21 April 2013, and complemented them with Fermi-LAT data. We obtained well sampled optical, soft and hard X-ray light curves that show the presence of two flares, the first one reaching a brighter maximum than the second one at X-rays. The average flux in the 20-100 keV range is 9.1e-11 cgs and the nuclear average apparent magnitude, corrected for Galactic extinction, is V ~ 12.2. In the time-resolved JEMX+IBIS spectra we see a change of spectral slope at an energy that correlates with flux, as expected in refreshed energy injections in a population of electrons that cool thereafter via synchrotron radiation. During the observation, the variability level increases monotonically from the optical to the hard X-rays, and the cross-correlation analysis...

  11. Fractal Property in the Light Curve of BL Lac Object S5 0716+714

    Indian Academy of Sciences (India)

    J. W. Ou; Y. G. Zheng

    2014-09-01

    In this paper, we compile the historical R-band data of S5 0716+714 from literature and obtain its fractal dimension by using a fractal method and then simulate the data with the Weierstrass–Mandelbrot (W–M) function. It is considered that the light curve has a fractal property.

  12. Discovery of VHE γ-ray emission from the BL Lacertae object B3 2247+381 with the MAGIC telescopes

    Science.gov (United States)

    Aleksić, J.; Alvarez, E. A.; Antonelli, L. A.; Antoranz, P.; Asensio, M.; Backes, M.; Barrio, J. A.; Bastieri, D.; Becerra González, J.; Bednarek, W.; Berdyugin, A.; Berger, K.; Bernardini, E.; Biland, A.; Blanch, O.; Bock, R. K.; Boller, A.; Bonnoli, G.; Borla Tridon, D.; Braun, I.; Bretz, T.; Cañellas, A.; Carmona, E.; Carosi, A.; Colin, P.; Colombo, E.; Contreras, J. L.; Cortina, J.; Cossio, L.; Covino, S.; Dazzi, F.; de Angelis, A.; de Caneva, G.; de Cea Del Pozo, E.; de Lotto, B.; Delgado Mendez, C.; Diago Ortega, A.; Doert, M.; Domínguez, A.; Dominis Prester, D.; Dorner, D.; Doro, M.; Elsaesser, D.; Ferenc, D.; Fonseca, M. V.; Font, L.; Fruck, C.; García López, R. J.; Garczarczyk, M.; Garrido, D.; Giavitto, G.; Godinović, N.; Hadasch, D.; Häfner, D.; Herrero, A.; Hildebrand, D.; Höhne-Mönch, D.; Hose, J.; Hrupec, D.; Huber, B.; Jogler, T.; Kellermann, H.; Klepser, S.; Krähenbühl, T.; Krause, J.; La Barbera, A.; Lelas, D.; Leonardo, E.; Lindfors, E.; Lombardi, S.; López, M.; López-Oramas, A.; Lorenz, E.; Makariev, M.; Maneva, G.; Mankuzhiyil, N.; Mannheim, K.; Maraschi, L.; Mariotti, M.; Martínez, M.; Mazin, D.; Meucci, M.; Miranda, J. M.; Mirzoyan, R.; Miyamoto, H.; Moldón, J.; Moralejo, A.; Munar-Adrover, P.; Nieto, D.; Nilsson, K.; Orito, R.; Oya, I.; Paneque, D.; Paoletti, R.; Pardo, S.; Paredes, J. M.; Partini, S.; Pasanen, M.; Pauss, F.; Perez-Torres, M. A.; Persic, M.; Peruzzo, L.; Pilia, M.; Pochon, J.; Prada, F.; Prada Moroni, P. G.; Prandini, E.; Puljak, I.; Reichardt, I.; Reinthal, R.; Rhode, W.; Ribó, M.; Rico, J.; Rügamer, S.; Saggion, A.; Saito, K.; Saito, T. Y.; Salvati, M.; Satalecka, K.; Scalzotto, V.; Scapin, V.; Schultz, C.; Schweizer, T.; Shayduk, M.; Shore, S. N.; Sillanpää, A.; Sitarek, J.; Snidaric, I.; Sobczynska, D.; Spanier, F.; Spiro, S.; Stamatescu, V.; Stamerra, A.; Steinke, B.; Storz, J.; Strah, N.; Surić, T.; Takalo, L.; Takami, H.; Tavecchio, F.; Temnikov, P.; Terzić, T.; Tescaro, D.; Teshima, M.; Tibolla, O.; Torres, D. F.; Treves, A.; Uellenbeck, M.; Vankov, H.; Vogler, P.; Wagner, R. M.; Weitzel, Q.; Zabalza, V.; Zandanel, F.; Zanin, R.; Kadenius, V.; Weidinger, M.; Buson, S.

    2012-03-01

    Aims: We study the non-thermal jet emission of the BL Lac object B3 2247+381 during a high optical state. Methods: The MAGIC telescopes observed the source during 13 nights between September 30th and October 30th 2010, collecting a total of 14.2 h of good quality very high energy (VHE) γ-ray data. Simultaneous multiwavelength data was obtained with X-ray observations by the Swift satellite and optical R-band observations at the KVA-telescope. We also use high energy γ-ray (HE, 0.1-100 GeV) data from the Fermi satellite. Results: The BL Lac object B3 2247+381 (z = 0.119) was detected, for the first time, at VHE γ-rays at a statistical significance of 5.6σ. A soft VHE spectrum with a photon index of -3.2 ± 0.6 was determined. No significant short term flux variations were found. We model the spectral energy distribution using a one-zone SSC-model, which can successfully describe our data.

  13. Soft X-ray spectrum of BL Lacertae object AO 0235+164 as a tracer of elemental abundances at z approximately 0.5

    Science.gov (United States)

    Madejski, Greg

    1994-01-01

    We report the soft X-ray spectrum of BL Lac object AO 0235+164, observed with the Einstein Observatory Imaging Proportional Counter (IPC). This object (z = 0.94) has an intervening galaxy (or a protogalactic disk) at z = 0.524 present in the line of sight, producing both radio and optical absorption lines in the background BL Lac continuum. The X-ray spectrum exhibits a substantial soft X-ray cutoff, corresponding to several times that expected from our own Galaxy; we interpret that excess cutoff as due to the intervening galaxy. The comparison of the hydrogen column density inferred from the 21 cm radio data and the X-ray absorption allows, in principle, the determination of the elemental abundances in the intervening galaxy. However, the uncertainties in both the H I spin temperature and X-ray spectral parameters only loosely restrict these abundances to be 2 +/- 1 solar, which even at the lower limit appears higher than that inferred from studies of samples of optical absoprtion-line systems.

  14. Variability of fluxes extragalactic radio sources 3С120, 3С273, BL Lac, OJ 287 , its "spectrums periods" and VLBI data on the centimeters waves

    Science.gov (United States)

    Donskykh, Ann; Ryabov, Mikhail; Sukharev, Artem

    We analyzed long and short term monitoring of data fluxes of extragalactic sources 3C120, 3C273, BL Lac, OJ 287 obtained at frequencies of 14.5 GHz (1974-2011), 8 GHz (1971-2011), 4.8GHz and (1979-2010), on the RT-26, University of Michigan, USA. Variability of the flux of the radio source was investigated by applying wavelet analysis. There were identified long-period and short components at all studied frequencies and it was determined the time of their existence. The "spectra periods" for each year of observation were built to assess the contribution of individual periods in the formation of the most powerful phase of activity of the radio sources. The dynamics of the manifestations of active periods at different frequencies was observed. The obtained data was compared with the results of MOJAVE VLBI monitoring for the period of 1995-2012 years at a frequency of 15.4 GHz. It allowed to investigate the structure of emissions during periods of manifestation activity maxima.

  15. First NuSTAR observations of the BL Lac - type blazar PKS~2155-304: constraints on the jet content and distribution of radiating particles

    CERN Document Server

    Madejski, G M; Madsen, K K; Chiang, J; Baloković, M; Paneque, D; Furniss, A K; Hayashida, M; Urry, C M; Sikora, M; Ajello, M; Blandford, R D; Harrison, F A; Sanchez, D; Giebels, B; Stern, D; Alexander, D M; Barret, D; Boggs, S E; Christensen, F E; Craig, W W; Forster, K; Giommi, P; Grefenstette, B; Hailey, C; Hornstrup, A; Kitaguchi, T; Koglin, J E; Mao, P H; Miyasaka, H; Mori, K; Perri, M; Pivovaroff, M J; Puccetti, S; Rana, V; Westergaard, N J; Zhang, W W; Zoglauer, A

    2016-01-01

    We report the first hard X-ray observations with NuSTAR of the BL Lac type blazar PKS 2155-304, augmented with soft X-ray data from XMM-Newton and gamma-ray data from the Fermi Large Area Telescope, obtained in April 2013 when the source was in a very low flux state. A joint NuSTAR and XMM spectrum, covering the energy range 0.5 - 60 keV, is best described by a model consisting of a log-parabola component with curvature beta = 0.3(+0.2,-0.1) and a (local) photon index 3.04 +/- 0.15 at photon energy of 2 keV, and a hard power-law tail with photon index 2.2 +/- 0.4. The hard X-ray tail can be smoothly joined to the quasi-simultaneous gamma-ray spectrum by a synchrotron self-Compton component produced by an electron distribution with index p = 2.2. Assuming that the power-law electron distribution extends down to the minimum electron Lorentz factor gamma_min = 1 and that there is one proton per electron, an unrealistically high total jet power L_p of roughly 10^47 erg/s is inferred. This can be reduced by two or...

  16. Possible links between BL Lacertae objects and quasars from very long baseline interferometry radio data.

    Science.gov (United States)

    Gabuzda, D C

    1995-01-01

    Systematic differences in the very long baseline interferometry (VLBI) radio polarization structure and average VLBI component speeds of BL Lacertae objects and quasars support the view that the observational distinction between these classes, based in large part on the strength of their optical line emission, is meaningful; in other words, this distinction reflects significant differences in the physical conditions in these sources. Possible models providing a link between the optical and VLBI properties of BL Lacertae objects and quasars are discussed. Most VLBI polarization observations to date have been global observations made at 6 cm; recent results suggest that the VLBI polarization structure of some sources may change dramatically on scales smaller than those probed by these 6-cm observations. PMID:11607606

  17. Radio-loud Active Galaxies in the Northern ROSAT All-Sky Survey. III. New Spectroscopic Identifications from the RASS endash Green Bank BL Lacertae Survey

    International Nuclear Information System (INIS)

    We present new spectroscopic identifications for 169 objects in the RASS endash Green Bank (RGB) catalog of radio- and X-ray endash emitting active galactic nuclei (AGNs). The data presented here significantly increase the fraction of bright RGB objects with classifications. Specifically, we report and discuss the classification of 57 radio-loud quasars, eight radio-quiet quasars (QSOs), 53 BL Lacs, 32 broad-line radio galaxies, five narrow-line radio galaxies, three Seyfert I galaxies, and 11 galaxies or galaxies in clusters. Over 78% of the identifications we present here are the first published classifications for these sources. The observations we report were undertaken as part of our targeted search program to identify a new, large unbiased sample of BL Lac objects, and we therefore discuss the BL Lac sample extensively. Unlike many previous surveys, we impose no selection criteria based on optical morphology, color, or broadband spectral energy distribution. Our classifications are based solely on a carefully defined set of self-consistent spectroscopic classification criteria. These criteria are then carefully evaluated, and particular attention is paid to issues involving the classification and description of BL Lacs. The criteria yielded BL Lac classifications for 53 RGB objects, 38 of which were are newly discovered BL Lacs. We show these RGB BL Lacs exhibit transitional properties between normal galaxies and BL Lacs discovered in previous radio and X-ray surveys. We briefly discuss the broadband flux distributions of these new RGB BL Lacs and the range of Ca ii H and K break contrasts (Br4000) they exhibit. We show that there is no clear separation in Br4000 between BL Lacs and galaxies detected in the RGB survey, with the distribution of break strengths varying smoothly between 0% and 50%. We also present and use a simple method based on the break strength to estimate the contribution of both the host galaxy and AGN to the 4000 Angstrom flux. We also

  18. Long-Term Optical Spectra Variability of BL Lacertae Object S5 0716+714

    Indian Academy of Sciences (India)

    Zhang Hao Jing; Zhao Gang; Zhang Xiong; Bai Jing Ming; Tang Ling; Xu Yun Bing

    2011-03-01

    Based on the long-term data from observations, we present an evidence for its spectral index variability behaviour in optical bands for BL Lacertae object S5 0716+714.We find that the spectral index variability period is in agreement with the flux variability period of about 1180 days in optical bands.We also find that the spectral index variability has periods of about 71 and 60 days which cannot be compared with the amplitude of long-term variability.

  19. Upper limits from hard X-ray observations of five BL Lacertae objects

    Science.gov (United States)

    Bezler, M.; Gruber, D. E.; Rothschild, R. E.

    1988-01-01

    Results are presented from hard X-ray observations of the five brightest X-ray BL Lacertae objects: PKS 0548-322, Mrk 421 (=1101+384), 2A 1219+305, Mrk 501 (=1652+398), and PKS 2155-304. The observations covered the energy range 15-165 keV from August 1977 to December 1978. The results are compared with previous studies.

  20. QUANTITATIVE EVALUATION OF THE HYPOTHESIS THAT BL LACERTAE OBJECTS ARE QSO REMNANTS

    Energy Technology Data Exchange (ETDEWEB)

    Borra, E. F. [Centre d' Optique, Photonique et Lasers, Département de Physique, Université Laval, Quebec (Canada)

    2014-11-20

    We evaluate with numerical simulations the hypothesis that BL Lacertae objects (BLLs) are the remnants of quasi-stellar objects. This hypothesis is based on their highly peculiar redshift evolution. They have a comoving space density that increases with decreasing redshift, contrary to all other active galactic nuclei. We assume that relativistic jets are below detection in young radio-quiet quasars and increase in strength with cosmic time so that they eventually are detected as BLLs. Our numerical simulations fit very well the observed redshift distributions of BLLs. There are strong indications that only the high-synchrotron-peaked BLLs could be QSO remnants.

  1. Host galaxy subtraction of TeV candidate BL Lacertae objects

    OpenAIRE

    Nilsson, K.; Pasanen, M.; Takalo, L. O.; Lindfors, E.; Berdyugin, A.; Ciprini, S.; Pforr, J.

    2007-01-01

    We have derived R-band host galaxy fluxes of 20 TeV candidate BL Lacertae objects as a function of aperture radius and FWHM. The results are given as correction tables, that list the fluxes (in mJy) of all ``contaminating'' sources (host galaxy + significant nearby objects) as a function of aperture radius and FWHM. We found that the derived fluxes depend strongly on aperture radius, but the FWHM has only a minor effect (a few percent). We also discuss the implications of our findings to opti...

  2. VERITAS and Multiwavelength Observations of the BL Lacertae Object 1ES 1741+196

    Science.gov (United States)

    Abeysekara, A. U.; Archambault, S.; Archer, A.; Benbow, W.; Bird, R.; Biteau, J.; Buchovecky, M.; Buckley, J. H.; Bugaev, V.; Byrum, K.; Cardenzana, J. V.; Cerruti, M.; Chen, X.; Christiansen, J. L.; Ciupik, L.; Connolly, M. P.; Cui, W.; Dickinson, H. J.; Dumm, J.; Eisch, J. D.; Errando, M.; Falcone, A.; Feng, Q.; Finley, J. P.; Fleischhack, H.; Flinders, A.; Fortin, P.; Fortson, L.; Furniss, A.; Gillanders, G. H.; Griffin, S.; Grube, J.; Gyuk, G.; Huetten, M.; Hanna, D.; Holder, J.; Humensky, T. B.; Johnson, C. A.; Kaaret, P.; Kar, P.; Kelley-Hoskins, N.; Kertzman, M.; Kieda, D.; Krause, M.; Krennrich, F.; Lang, M. J.; Maier, G.; McArthur, S.; McCann, A.; Meagher, K.; Moriarty, P.; Mukherjee, R.; Nieto, D.; O'Brien, S.; de Bhróithe, A. O'Faoláin; Ong, R. A.; Otte, A. N.; Park, N.; Pelassa, V.; Petrashyk, A.; Petry, D.; Pohl, M.; Popkow, A.; Pueschel, E.; Quinn, J.; Ragan, K.; Ratliff, G.; Reyes, L. C.; Reynolds, P. T.; Reynolds, K.; Richards, G. T.; Roache, E.; Rulten, C.; Santander, M.; Sembroski, G. H.; Shahinyan, K.; Smith, A. W.; Staszak, D.; Telezhinsky, I.; Tucci, J. V.; Tyler, J.; Vincent, S.; Wakely, S. P.; Weiner, O. M.; Weinstein, A.; Wilhelm, A.; Williams, D. A.; Zitzer, B.

    2016-04-01

    We present results from multiwavelength observations of the BL Lacertae object 1ES 1741+196, including results in the very-high-energy γ-ray regime using the Very Energetic Radiation Imaging Telescope Array System (VERITAS). The VERITAS time-averaged spectrum, measured above 180 GeV, is well-modelled by a power law with a spectral index of 2.7 ± 0.7stat ± 0.2syst. The integral flux above 180 GeV is (3.9 ± 0.8stat ± 1.0syst) × 10-8 m-2 s-1, corresponding to 1.6% of the Crab Nebula flux on average. The multiwavelength spectral energy distribution of the source suggests that 1ES 1741+196 is an extreme-high-frequency-peaked BL Lacertae object. The observations analysed in this paper extend over a period of six years, during which time no strong flares were observed in any band. This analysis is therefore one of the few characterizations of a blazar in a non-flaring state.

  3. VERITAS and Multiwavelength Observations of the BL Lacertae Object 1ES 1741+196

    CERN Document Server

    Abeysekara, A U; Archer, A; Benbow, W; Bird, R; Biteau, J; Buchovecky, M; Buckley, J H; Bugaev, V; Byrum, K; Cardenzana, J V; Cerruti, M; Chen, X; Christiansen, J L; Ciupik, L; Connolly, M P; Cui, W; Dickinson, H J; Dumm, J; Eisch, J D; Errando, M; Falcone, A; Feng, Q; Finley, J P; Fleischhack, H; Flinders, A; Fortin, P; Fortson, L; Furniss, A; Gillanders, G H; Griffin, S; Grube, J; Gyuk, G; Hütten, M; Hanna, D; Holder, J; Humensky, T B; Johnson, C A; Kaaret, P; Kar, P; Kelley-Hoskins, N; Kertzman, M; Kieda, D; Krause, M; Krennrich, F; Kumar, S; Lang, M J; Maier, G; McArthur, S; McCann, A; Meagher, K; Moriarty, P; Mukherjee, R; Nieto, D; O'Brien, S; de Bhróithe, A O'Faoláin; Ong, R A; Otte, A N; Park, N; Pelassa, V; Petrashyk, A; Pohl, M; Popkow, A; Pueschel, E; Quinn, J; Ragan, K; Ratliff, G; Reyes, L C; Reynolds, P T; Richards, G T; Roache, E; Rulten, C; Santander, M; Sembroski, G H; Shahinyan, K; Smith, A W; Staszak, D; Telezhinsky, I; Tucci, J V; Tyler, J; Vincent, S; Wakely, S P; Weiner, O M; Weinstein, A; Wilhelm, A; Williams, D A; Zitzer, B

    2016-01-01

    We present results from multiwavelength observations of the BL Lacertae object 1ES 1741+196, including results in the very-high-energy $\\gamma$-ray regime using the Very Energetic Radiation Imaging Telescope Array System (VERITAS). The VERITAS time-averaged spectrum, measured above 180 GeV, is well-modelled by a power law with a spectral index of $2.7\\pm0.7_{\\mathrm{stat}}\\pm0.2_{\\mathrm{syst}}$. The integral flux above 180 GeV is $(3.9\\pm0.8_{\\mathrm{stat}}\\pm1.0_{\\mathrm{syst}})\\times 10^{-8}$ m$^{-2}$ s$^{-1}$, corresponding to 1.6% of the Crab Nebula flux on average. The multiwavelength spectral energy distribution of the source suggests that 1ES 1741+196 is an extreme-high-frequency-peaked BL Lacertae object. The observations analysed in this paper extend over a period of six years, during which time no strong flares were observed in any band. This analysis is therefore one of the few characterizations of a blazar in a non-flaring state.

  4. The Binary Black Hole Scenario for the BL Lacertae Object AO 0235+16

    Institute of Scientific and Technical Information of China (English)

    G. E. Romero; Jun-Hui Fan; S. E. Nuza

    2003-01-01

    Recent analysis of the long term radio light curve of the extremely variable BL Lacertae object AO 0235t16 by Raiteri et al. have revealed the presence of recurrent outbursts with a period of ~ 5.7 ± 0.5yr. Periodicity analysis of the optical light curve also shows evidence for a shorter period. Here we discuss whether such a behavior can be explained by a binary black hole model where the accretion disk of one of the supermassive black holes is precessing due to the tidal effects of the companion. We estimate the mass of the accreting hole and analyze constraints on the secondary mass and the orbital parameters of the system. It is possible to provide a viable interpretation of the available multiwavelength data.

  5. EVN Observations of HESS J1943+213: Evidence for an Extreme TeV BL Lac Object

    OpenAIRE

    Akiyama, Kazunori; Stawarz, Łukasz; Tanaka, Yasuyuki T.; Nagai, Hiroshi; Giroletti, Marcello; Honma, Mareki

    2016-01-01

    We report on the 1.6 GHz (18 cm) VLBI observations of the unresolved, steady TeV source HESS J1943+213 located in the Galactic plane, performed with the European VLBI Network (EVN) in 2014. Our new observations with a nearly full EVN array provide the deepest image of HESS J1943+213 at the highest resolution ever achieved, enabling us to resolve the long-standing issues of the source identification. The milliarcsecond-scale structure of HESS J1943+213 has a clear asymmetric morphology, consis...

  6. VizieR Online Data Catalog: VRI LCs of BL Lac object Mrk 501 from 2010 to 2015 (Xiong+, 2016)

    Science.gov (United States)

    Xiong, D.; Zhang, H.; Zhang, X.; Yi, T.; Bai, J.; Wang, F.; Liu, H.; Zhen, Y.

    2016-03-01

    Our optical monitoring program of Mrk 501 was carried out with the 1.02m optical telescope located at the the Yunnan Astronomical Observatory of China. Our monitoring program for Mrk 501 was divided into five periods. The first period was from 2010 April 1-3, the second was from 2012 April 22-25, the third was from 2013 April 1-4, the fourth was from 2014 April 17-May 8, and the fifth was from 2015 April 6-May 25. Excluding the nights with bad weather and those devoted to other targets, the actual number of observations for Mrk 501 is 29 nights. The standard Johnson broadband filters were used. The typical integration times were 150-300s for the I and R filters and 400s for the V filter. (3 data files).

  7. IDV Observations of BL0716+714 at 5 GHz

    Indian Academy of Sciences (India)

    H.-G Song; X. Liu; J. Liu; N. Marchili; T. P. Krichbaum

    2011-03-01

    A selected sample of intra-day variable AGN had been observed for 3–4 days per month at the Urumqi Observatory. The sample includes 7 target sources and 7 calibrators. The BL Lac object B0716+714 shows prominent intraday and long term variations.

  8. Discovery and characterization of the first low-peaked and intermediate-peaked BL Lacertae objects in the very high energy {gamma}-ray regime

    Energy Technology Data Exchange (ETDEWEB)

    Berger, Karsten

    2009-12-19

    20 years after the discovery of the Crab Nebula as a source of very high energy {gamma}-rays, the number of sources newly discovered above 100 GeV using ground-based Cherenkov telescopes has considerably grown, at the time of writing of this thesis to a total of 81. The sources are of different types, including galactic sources such as supernova remnants, pulsars, binary systems, or so-far unidentified accelerators and extragalactic sources such as blazars and radio galaxies. The goal of this thesis work was to search for {gamma}-ray emission from a particular type of blazars previously undetected at very high {gamma}-ray energies, by using the MAGIC telescope. Those blazars previously detected were all of the same type, the so-called high-peaked BL Lacertae objects. The sources emit purely non-thermal emission, and exhibit a peak in their radio-to-X-ray spectral energy distribution at X-ray energies. The entire blazar population extends from these rare, low-luminosity BL Lacertae objects with peaks at X-ray energies to the much more numerous, high-luminosity infrared-peaked radio quasars. Indeed, the low-peaked sources dominate the source counts obtained from space-borne observations at {gamma}-ray energies up to 10 GeV. Their spectra observed at lower {gamma}-ray energies show power-law extensions to higher energies, although theoretical models suggest them to turn over at energies below 100 GeV. This opened the quest for MAGIC as the Cherenkov telescope with the currently lowest energy threshold. In the framework of this thesis, the search was focused on the prominent sources BL Lac, W Comae and S5 0716+714, respectively. Two of the sources were unambiguously discovered at very high energy {gamma}-rays with the MAGIC telescope, based on the analysis of a total of about 150 hours worth of data collected between 2005 and 2008. The analysis of this very large data set required novel techniques for treating the effects of twilight conditions on the data quality

  9. Discovery and characterization of the first low-peaked and intermediate-peaked BL Lacertae objects in the very high energy γ-ray regime

    International Nuclear Information System (INIS)

    20 years after the discovery of the Crab Nebula as a source of very high energy γ-rays, the number of sources newly discovered above 100 GeV using ground-based Cherenkov telescopes has considerably grown, at the time of writing of this thesis to a total of 81. The sources are of different types, including galactic sources such as supernova remnants, pulsars, binary systems, or so-far unidentified accelerators and extragalactic sources such as blazars and radio galaxies. The goal of this thesis work was to search for γ-ray emission from a particular type of blazars previously undetected at very high γ-ray energies, by using the MAGIC telescope. Those blazars previously detected were all of the same type, the so-called high-peaked BL Lacertae objects. The sources emit purely non-thermal emission, and exhibit a peak in their radio-to-X-ray spectral energy distribution at X-ray energies. The entire blazar population extends from these rare, low-luminosity BL Lacertae objects with peaks at X-ray energies to the much more numerous, high-luminosity infrared-peaked radio quasars. Indeed, the low-peaked sources dominate the source counts obtained from space-borne observations at γ-ray energies up to 10 GeV. Their spectra observed at lower γ-ray energies show power-law extensions to higher energies, although theoretical models suggest them to turn over at energies below 100 GeV. This opened the quest for MAGIC as the Cherenkov telescope with the currently lowest energy threshold. In the framework of this thesis, the search was focused on the prominent sources BL Lac, W Comae and S5 0716+714, respectively. Two of the sources were unambiguously discovered at very high energy γ-rays with the MAGIC telescope, based on the analysis of a total of about 150 hours worth of data collected between 2005 and 2008. The analysis of this very large data set required novel techniques for treating the effects of twilight conditions on the data quality. This was successfully achieved

  10. Six-year Optical Monitoring of BL Lacertae Object 1ES 0806+52.4

    CERN Document Server

    Man, Zhongyi; Wu, Jianghua; Zhou, Xu; Yuan, Qirong

    2014-01-01

    We present the results of the first systematic long-term multi-color optical monitoring of the BL Lacertae object 1ES 0806+52.4. The monitoring was performed in multiple passbands with a 60/90 cm Schmidt telescope from December 2005 to February 2011. The overall brightness of this object decreased from 2005 December to 2008 December, and regained after that. A sharp outburst probably occurred around the end of our monitoring program. Overlapped on the long-term trend are some short-term small-amplitude oscillations. No intra-night variability was found in the object, which is in accord with the historical observations before 2005. By investigating the color behavior, we found strong bluer-when-brighter chromatism for the long-term variability of 1ES 0806+52.4. The total amplitudes at the c, i and o bands are 1.18, 1.12, and 1.02 mags, respectively. The amplitudes tend to increase toward shorter wavelength, which may be the major cause of bluer-when-brighter. Such bluer-when-brighter is also found in other bla...

  11. KEPLER OBSERVATIONS OF RAPID OPTICAL VARIABILITY IN THE BL LACERTAE OBJECT W2R1926+42

    International Nuclear Information System (INIS)

    We present the first Kepler monitoring of a strongly variable BL Lac, W2R1926+42. The light curve covers 181 days with ∼0.2% errors, 30 minute sampling and >90% duty cycle, showing numerous δI/I > 25% flares over timescales as short as a day. The flux distribution is highly skewed and non-Gaussian. The variability shows a strong rms-flux correlation with the clearest evidence to date for nonlinearity in this relation. We introduce a method to measure periodograms from the discrete autocorrelation function, an approach that may be well-suited to a wide range of Kepler data. The periodogram is not consistent with a simple power-law, but shows a flattening at frequencies below 7 × 10–5 Hz. Simple models of the power spectrum, such as a broken power law, do not produce acceptable fits, indicating that the Kepler blazar light curve requires more sophisticated mathematical and physical descriptions than currently in use.

  12. KEPLER OBSERVATIONS OF RAPID OPTICAL VARIABILITY IN THE BL LACERTAE OBJECT W2R1926+42

    Energy Technology Data Exchange (ETDEWEB)

    Edelson, R.; Mushotzky, R. [Department of Astronomy, University of Maryland, College Park, MD 20742-2421 (United States); Vaughan, S. [X-ray and Observational Astronomy Group, Department of Physics and Astronomy, University of Leicester, University Road, Leicester LE1 7RH (United Kingdom); Scargle, J. [Astrobiology and Space Science Division, NASA Ames Research Center, Moffet Field, CA 94035 (United States); Gandhi, P. [Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency, 3-1-1 Yoshinodai, chuo-ku, Sagamihara, Kanagawa 252-5210 (Japan); Malkan, M. [Department of Physics and Astronomy, University of California Los Angeles, Los Angeles, CA 90095-1547 (United States); Baumgartner, W., E-mail: redelson@astro.umd.edu [Laboratory for High Energy Astrophysics, NASA/GSFC, Code 662, Greenbelt, MD 20771 (United States)

    2013-03-20

    We present the first Kepler monitoring of a strongly variable BL Lac, W2R1926+42. The light curve covers 181 days with {approx}0.2% errors, 30 minute sampling and >90% duty cycle, showing numerous {delta}I/I > 25% flares over timescales as short as a day. The flux distribution is highly skewed and non-Gaussian. The variability shows a strong rms-flux correlation with the clearest evidence to date for nonlinearity in this relation. We introduce a method to measure periodograms from the discrete autocorrelation function, an approach that may be well-suited to a wide range of Kepler data. The periodogram is not consistent with a simple power-law, but shows a flattening at frequencies below 7 Multiplication-Sign 10{sup -5} Hz. Simple models of the power spectrum, such as a broken power law, do not produce acceptable fits, indicating that the Kepler blazar light curve requires more sophisticated mathematical and physical descriptions than currently in use.

  13. Variability of the BL Lacertae objects PKS 2155 - 304 and OJ 287 in the far-ultraviolet

    International Nuclear Information System (INIS)

    All the ultraviolet spectra of the two bright BL Lacertae objects PKS 2155 - 304 and OJ 287 taken with the International Ultraviolet Explorer in the period 1978-1984 are examined. For each spectrum the best-fitting power law is determined and a correlation between spectral slope and intensity is searched for. The correlation, if present, is weak. This is discussed in terms of models of the continuum emission of active galactic nuclei. 31 references

  14. CLUSTERING OF γ-RAY-SELECTED 2LAC FERMI BLAZARS

    Energy Technology Data Exchange (ETDEWEB)

    Allevato, V.; Finoguenov, A. [Department of Physics, University of Helsinki, Gustaf Hällströmin katu 2a, FI-00014 Helsinki (Finland); Cappelluti, N. [University of Maryland, Baltimore County, 1000 Hilltop Circle, Baltimore, MD 21250 (United States)

    2014-12-20

    We present the first measurement of the projected correlation function of 485 γ-ray-selected blazars, divided into 175 BL Lacertae (BL Lacs) and 310 flat-spectrum radio quasars (FSRQs) detected in the 2 year all-sky survey by the Fermi-Large Area Telescope. We find that Fermi BL Lacs and FSRQs reside in massive dark matter halos (DMHs) with log M{sub h} = 13.35{sub −0.14}{sup +0.20} and log M{sub h} = 13.40{sub −0.19}{sup +0.15} h {sup –1} M {sub ☉}, respectively, at low (z ∼ 0.4) and high (z ∼ 1.2) redshift. In terms of clustering properties, these results suggest that BL Lacs and FSRQs are similar objects residing in the same dense environment typical of galaxy groups, despite their different spectral energy distributions, power, and accretion rates. We find no difference in the typical bias and hosting halo mass between Fermi blazars and radio-loud active galactic nuclei (AGNs), supporting the unification scheme simply equating radio-loud objects with misaligned blazar counterparts. This similarity in terms of the typical environment they preferentially live in, suggests that blazars tend to occupy the center of DMHs, as already pointed out for radio-loud AGNs. This implies, in light of several projects looking for the γ-ray emission from DM annihilation in galaxy clusters, a strong contamination from blazars to the expected signal from DM annihilation.

  15. Short Timescale Photometric and Polarimetric Behavior of two BL Lacertae Type Objects

    CERN Document Server

    Covino, S; Foschini, L; Sandrinelli, A; Tavecchio, F; Treves, A; Zhang, H; de Almeida, U Barres; Bonnoli, G; Boettcher, M; Cecconi, M; D'Ammando, F; di Fabrizio, L; Giarrusso, M; Leone, F; Lindfors, E; Lorenzi, V; Molinari, E; Paiano, S; Prandini, E; Raiteri, C M; Stamerra, A; Tagliaferri, G

    2015-01-01

    Blazars are astrophysical sources whose emission is dominated by non-thermal processes, typically interpreted as synchrotron and inverse Compton emission. Although the general picture is rather robust and consistent with observations, many aspects are still unexplored. Polarimetric monitoring can offer a wealth of information about the physical processes in blazars. Models with largely different physical ingredients can often provide almost indistinguishable predictions for the total flux, but usually are characterized by markedly different polarization properties. We explore, with a pilot study, the possibility to derive structural information about the emitting regions of blazars by means of a joint analysis of rapid variability of the total and polarized flux at optical wavelengths. Short timescale (from tens of seconds to a couple of minutes) optical linear polarimetry and photometry for two blazars, BL Lacertae and PKS 1424+240, was carried out with the PAOLO polarimeter at the 3.6m Telescopio Nazionale ...

  16. Short timescale photometric and polarimetric behavior of two BL Lacertae type objects

    International Nuclear Information System (INIS)

    Context. Blazars are astrophysical sources whose emission is dominated by non-thermal processes, typically interpreted as synchrotron and inverse Compton emission. Although the general picture is rather robust and consistent with observations, many aspects are still unexplored. Aims. Polarimetric monitoring can offer a wealth of information about the physical processes in blazars. Models with largely different physical ingredients can often provide almost indistinguishable predictions for the total flux, but usually are characterized by markedly different polarization properties. We explore, with a pilot study, the possibility to derive structural information about the emitting regions of blazars by means of a joint analysis of rapid variability of the total and polarized flux at optical wavelengths. Methods. Short timescale (from tens of seconds to a couple of minutes) optical linear polarimetry and photometry for two blazars, BL Lacertae and PKS 1424+240, was carried out with the PAOLO polarimeter at the 3.6 m Telescopio Nazionale Galileo. Several hours of almost continuous observations were obtained for both sources. Results. Our intense monitoring allowed us to draw strongly different scenarios for BL Lacertae and PKS 1424+240, with the former characterized by intense variability on time-scales from hours to a few minutes and the latter practically constant in total flux. Essentially the same behavior is observed for the polarized flux and the position angle. The variability time-scales turned out to be as short as a few minutes, although involving only a few percent variation of the flux. The polarization variability time-scale is generally consistent with the total flux variability. Total and polarized flux appear to be essentially uncorrelated. However, even during our relatively short monitoring, different regimes can be singled out. Conclusions. No simple scenario is able to satisfactorily model the very rich phenomenology exhibited in our data. As a

  17. The collective emission of electromagnetic waves from astrophysical jets - Luminosity gaps, BL Lacertae objects, and efficient energy transport

    Science.gov (United States)

    Baker, D. N.; Borovsky, Joseph E.; Benford, Gregory; Eilek, Jean A.

    1988-01-01

    A model of the inner portions of astrophysical jets is constructed in which a relativistic electron beam is injected from the central engine into the jet plasma. This beam drives electrostatic plasma wave turbulence, which leads to the collective emission of electromagnetic waves. The emitted waves are beamed in the direction of the jet axis, so that end-on viewing of the jet yields an extremely bright source (BL Lacertae object). The relativistic electron beam may also drive long-wavelength electromagnetic plasma instabilities (firehose and Kelvin-Helmholtz) that jumble the jet magnetic field lines. After a sufficient distance from the core source, these instabilities will cause the beamed emission to point in random directions and the jet emission can then be observed from any direction relative to the jet axis. This combination of effects may lead to the gap turn-on of astrophysical jets. The collective emission model leads to different estimates for energy transport and the interpretation of radio spectra than the conventional incoherent synchrotron theory.

  18. The disk-jet connection of Fermi 2LAC blazars

    Science.gov (United States)

    Du, L. M.; Xie, Zh. H.; Yi, T. F.; Xue, R.; Xu, Y. B.; Liu, W. G.; Wang, X. H.

    2016-07-01

    In this article, an estimator of the radiative power for blazars is proposed and is used in the study of the link between the accretion disk power and jet power. The results lend support to the disk-jet symbiosis. Since the blazars are strongly beamed sources, our results suggest that the Doppler enhancement of the sources needs to be removed to obtain physically reasonable results in the disk-jet connection study. The results after de-beaming suggest that FSRQs are accreting in the radiatively efficient regime, while the BL Lac population shows a flatter dependence between jet power and disk power, possibly due to a mixture of sources in the radiatively efficient (the broad lined BL Lacs) and inefficient (the bulk of the BL Lac population) regimes.

  19. The underluminous Type Ia Supernova 2005bl and the class of objects similar to SN 1991bg

    OpenAIRE

    Taubenberger, S.; Hachinger, S.; Pignata, G.; Mazzali, P. A.; Contreras, C.; Valenti, S.; Pastorello, A.; Elias-Rosa, N.; Bärnbantner, O.; Barwig, H.; Benetti, S.; Dolci, M.; Fliri, J.; Folatelli, G.; Freedman, W. L.

    2007-01-01

    Optical observations of the Type Ia supernova (SN Ia) 2005bl in NGC 4070, obtained from -6 to +66 d with respect to the B-band maximum, are presented. The photometric evolution is characterised by rapidly-declining light curves and red colours at peak and soon thereafter. With M_B,max = -17.24 the SN is an underluminous SN Ia, similar to the peculiar SNe 1991bg and 1999by. This similarity also holds for the spectroscopic appearance, the only remarkable difference being the likely presence of ...

  20. BL Lacertae complex spectral variability and rapid synchrotron flare detected with BeppoSAX

    CERN Document Server

    Ravasio, M; Ghisellini, G; Giommi, P; Nesci, R; Massaro, E; Chiappetti, L; Celotti, A; Costamante, L; Maraschi, L; Tavecchio, F; Tosti, G; Treves, A; Wolter, A; Balonek, T; Carini, M; Kato, T; Kurtanidze, O M; Montagni, F; Nikolashvili, M M; Noble, J; Nucciarelli, G; Raiteri, C M; Sclavi, S; Uemura, M; Villata, M

    2002-01-01

    We report on two BeppoSAX observations of BL Lac (2200+420) performed respectively in June and December 1999, as part of a ToO program to monitor blazars in high states of activity. During both runs the source has been detected up to 100 keV, but it showed quite different spectra: in June it was concave with a very hard component above 5-6 keV (alpha_1 ~ 1.6; alpha_2 ~ 0.15); in December it was well fitted by a single power law (alpha ~ 0.6). During the first BeppoSAX observation BL Lac showed an astonishing variability episode: the 0.3 - 2 keV flux doubled in ~ 20 minutes, while the flux above 4 keV was almost constant. This frequency-dependent event is one of the shortest ever recordered for BL Lac objects and places lower limits on the dimension and the magnetic field of the emitting region and on the energy of the synchrotron radiating electrons. A similar but less extreme behaviour is detected also in optical light curves, that display non-simultaneous, smaller fluctuations of ~ 20% in 20 min. We fit the...

  1. Optical variability of the BL Lacertae object GC 0109+224. Multiband behaviour and time scales from a 7-years monitoring campaign

    CERN Document Server

    Ciprini, S; Raiteri, C M; Villata, M; Ibrahimov, M A; Nucciarelli, G; Lanteri, L

    2003-01-01

    We present the most continuous data base of optical $BVR_{c}I_{c}$ observations ever published on the BL Lacertae object GC 0109+224, collected mainly by the robotic telescope of the Perugia University Observatory in the period November 1994-February 2002. These observations have been complemented by data from the Torino Observatory, collected in the period July 1995-January 1999, and Mt. Maidanak Observatory (December 2000). GC 0109+224 showed rapid optical variations and six major outbursts were observed at the beginning and end of 1996, in fall 1998, at the beginning and at the end of 2000, and at the beginning of 2002. Fast and large-amplitude drops characterized its flux behaviour. The $R_c$ magnitude ranged from 13.3 (16.16 mJy) to 16.46 (0.8 mJy), with a mean value of 14.9 (3.38 mJy). In the periods where we collected multi-filter observations, we analyzed colour and spectral indexes, and the variability patterns during some flares. The long-term behaviour seems approximatively achromatic, but during s...

  2. On the Location of the Gamma-ray Emission in the 2008 Outburst in the BL Lacertae Object AO 0235+164 through Observations across the Electromagnetic Spectrum

    CERN Document Server

    Agudo, Ivan; Jorstad, Svetlana G; Larionov, Valeri M; Gomez, Jose L; Lahteenmaki, Anne; Smith, Paul S; Nilsson, Kari; Readhead, Anthony C S; Aller, Margo F; Heidt, Jochen; Gurwell, Mark; Thum, Clemens; Wehrle, Ann E; Aller, Hugh D; Benitez, Erika; Blinov, Dmitriy A; Hagen-Thorn, Vladimir A; Hiriart, David; Jannuzi, Buell T; Joshi, Manasvita; Lindfors, Elina; Molina, Sol N; Morozova, Daria A; Nieppola, Elina; Olmstead, Alice R; Reinthal, Riho; Roca--Sogorb, Mar; Schmidt, Gary D; Sillanpaa, Aimo; Takalo, Leo; Taylor, Brian; Tornikoski, Merja; Troitsky, Ivan S; Zook, Alma C; Wiesemeyer, Helmut

    2011-01-01

    We present observations of a major outburst at centimeter, millimeter, optical, X-ray, and gamma-ray wavelengths of the BL Lacertae object AO 0235+164. We analyze the timing of multi-waveband variations in the flux and linear polarization, as well as changes in Very Long Baseline Array (VLBA) images at 7mm with 0.15 milliarcsecond resolution. The association of the events at different wavebands is confirmed at high statistical significance by probability arguments and Monte-Carlo simulations. A series of sharp peaks in optical linear polarization, as well as a pronounced maximum in the 7 mm polarization of a superluminal jet knot, indicate rapid fluctuations in the degree of ordering of the magnetic field. These results lead us to conclude that the outburst occurred in the jet both in the quasi-stationary "core" and in the superluminal knot, both parsecs downstream of the supermassive black hole. We interpret the outburst as a consequence of the propagation of a disturbance, elongated along the line of sight ...

  3. Des Lacs National Wildlife Refuge Water Management Plan 1966

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — The Des Lacs National Wildlife Refuge Water Management Plan has been developed to meet the station objectives set forth in the Master Plan. The purpose of this plan...

  4. Des Lacs National Wildlife Refuge Water Management Plan 1961

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — The Des Lacs National Wildlife Refuge Water Management Plan has been developed to meet the station objectives set forth in the Master Plan. The purpose of this plan...

  5. Des Lacs National Wildlife Refuge Water Management Plan 1958

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — The Des Lacs National Wildlife Refuge Water Management Plan has been developed to meet the station objectives set forth in the Master Plan. The purpose of this plan...

  6. Des Lacs National Wildlife Refuge Water Management Plan 1968

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — The Des Lacs National Wildlife Refuge Water Management Plan has been developed to meet the station objectives set forth in the Master Plan. The purpose of this plan...

  7. Des Lacs National Wildlife Refuge Water Management Plan 2013

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — The Des Lacs NWR Water Management Plan has been developed to meet the station objectives set forth in the Master Plan. The purpose of this plan is to establish a...

  8. Des Lacs National Wildlife Refuge Water Management Plan 1993

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — The Des Lacs National Wildlife Refuge Water Management Plan has been developed to meet the station objectives set forth in the Master Plan. The purpose of this plan...

  9. Des Lacs National Wildlife Refuge Water Management Plan 1965

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — The Des Lacs National Wildlife Refuge Water Management Plan has been developed to meet the station objectives set forth in the Master Plan. The purpose of this plan...

  10. Des Lacs National Wildlife Refuge Water Management Plan 1957

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — The Des Lacs National Wildlife Refuge Water Management Plan has been developed to meet the station objectives set forth in the Master Plan. The purpose of this plan...

  11. Des Lacs National Wildlife Refuge Water Management Plan 1964

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — The Des Lacs National Wildlife Refuge Water Management Plan has been developed to meet the station objectives set forth in the Master Plan. The purpose of this plan...

  12. Des Lacs National Wildlife Refuge Water Management Plan 1970

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — The Des Lacs National Wildlife Refuge Water Management Plan has been developed to meet the station objectives set forth in the Master Plan. The purpose of this plan...

  13. Des Lacs National Wildlife Refuge Water Management Plan 1962

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — The Des Lacs National Wildlife Refuge Water Management Plan has been developed to meet the station objectives set forth in the Master Plan. The purpose of this plan...

  14. Des Lacs National Wildlife Refuge Water Management Plan 2008

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — The Des Lacs NWR Water Management Plan has been developed to meet the station objectives set forth in the Master Plan. The purpose of this plan is to establish a...

  15. Des Lacs National Wildlife Refuge Water Management Plan 1969

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — The Des Lacs National Wildlife Refuge Water Management Plan has been developed to meet the station objectives set forth in the Master Plan. The purpose of this plan...

  16. Des Lacs National Wildlife Refuge Water Management Plan 2014

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — The Des Lacs NWR Water Management Plan has been developed to meet the station objectives set forth in the Master Plan. The purpose of this plan is to establish a...

  17. Des Lacs National Wildlife Refuge Water Management Plan 2012

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — The Des Lacs NWR Water Management Plan has been developed to meet the station objectives set forth in the Master Plan. The purpose of this plan is to establish a...

  18. Des Lacs National Wildlife Refuge Water Management Plan 1967

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — The Des Lacs National Wildlife Refuge Water Management Plan has been developed to meet the station objectives set forth in the Master Plan. The purpose of this plan...

  19. Des Lacs National Wildlife Refuge Water Management Plan 1963

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — The Des Lacs National Wildlife Refuge Water Management Plan has been developed to meet the station objectives set forth in the Master Plan. The purpose of this plan...

  20. Des Lacs National Wildlife Refuge Water Management Plan 1956

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — The Des Lacs National Wildlife Refuge Water Management Plan has been developed to meet the station objectives set forth in the Master Plan. The purpose of this plan...

  1. Des Lacs National Wildlife Refuge Water Management Plan 2010

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — The Des Lacs NWR Water Management Plan has been developed to meet the station objectives set forth in the Master Plan. The purpose of this plan is to establish a...

  2. Des Lacs National Wildlife Refuge Water Management Plan 1960

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — The Des Lacs National Wildlife Refuge Water Management Plan has been developed to meet the station objectives set forth in the Master Plan. The purpose of this plan...

  3. Des Lacs National Wildlife Refuge Water Management Plan 2009

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — The Des Lacs NWR Water Management Plan has been developed to meet the station objectives set forth in the Master Plan. The purpose of this plan is to establish a...

  4. Des Lacs National Wildlife Refuge Water Management Plan 2011

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — The Des Lacs NWR Water Management Plan has been developed to meet the station objectives set forth in the Master Plan. The purpose of this plan is to establish a...

  5. Des Lacs National Wildlife Refuge Water Management Plan 2007

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — The Des Lacs NWR Water Management Plan has been developed to meet the station objectives set forth in the Master Plan. The purpose of this plan is to establish a...

  6. Des Lacs National Wildlife Refuge Water Management Plan 1996

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — The Des Lacs National Wildlife Refuge Water Management Plan has been developed to meet the station objectives set forth in the Master Plan. The purpose of this plan...

  7. Des Lacs National Wildlife Refuge Water Management Plan 1998

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — The Des Lacs National Wildlife Refuge Water Management Plan has been developed to meet the station objectives set forth in the Master Plan. This plan contains...

  8. Des Lacs National Wildlife Refuge Water Management Plan 1999

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — The Des Lacs National Wildlife Refuge Water Management Plan has been developed to meet the station objectives set forth in the Master Plan. This plan contains...

  9. Des Lacs National Wildlife Refuge Water Management Plan 2006

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — The Des Lacs National Wildlife Refuge Water Management Plan has been developed to meet the station objectives set forth in the Master Plan. This plan contains 2005...

  10. Des Lacs National Wildlife Refuge Water Management Plan 1997

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — The Des Lacs National Wildlife Refuge Water Management Plan has been developed to meet the station objectives set forth in the Master Plan. This plan contains...

  11. Des Lacs National Wildlife Refuge Water Management Plan 2002

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — The Des Lacs National Wildlife Refuge Water Management Plan has been developed to meet the station objectives set forth in the Master Plan. This plan contains 2001...

  12. Des Lacs National Wildlife Refuge Water Management Plan 2016

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — The Des Lacs National Wildlife Refuge Water Management Plan has been developed to meet the station objectives set forth in the Master Plan. This plan contains 2015...

  13. Very high-resolution observations of the radio sources NRAO 150, OJ 287, 3C 273, M87, 1633+38, BL Lacertae, and 3C 454. 3

    Energy Technology Data Exchange (ETDEWEB)

    Kellermann, K.I. (National Radio Astronomy Observatory, Green Bank, WV); Shaffer, D.B.; Purcell, G.H.

    1977-02-01

    Very long baseline interferometer observations made at a wavelength of 2 and 2.8 cm with baselines ranging from 54 to 291 million wavelengths show a number of radio sources with only slightly resolved components, even on the longest baselines; the quasars 1633 + 38 and 3C 454.3, the objects OJ 287 and BL Lac, and the nucleus of M87 (Virgo A, 3C 274) all contain components < or approximately 0.4 milli-arcsec. The smallest component observed is in the core of 3C 454.3, which contains about 50% of the total flux density and is < or approximately 0.2 milli-arcsec in diameter. The compact component in the nucleus of M87 is < or approximately 1.5 light-months across, and contains about one-third of the total flux density of the nucleus at 2.8 cm. NRAO 150 and BL Lac are double: the components of NRAO 150 are separated by 0.6 milli-arcsec, while BL Lac has an elongated structure consisting of a large (1.4 milli-arcsec) component separated by 1.25 milli-arcsec from a smaller (0.5 milli-arcsec) variable one. The present data on 3C 273 are consistent with triple models similar to those discussed previously, but with a somewhat greater apparent separation of components.

  14. Optical behaviour of BL Lacertae during the great 1997 outburst.

    Science.gov (United States)

    Tosti, G.; Luciani, M.; Fiorucci, M.; Massaro, E.; Nesci, R.; Maesano, M.; Montagni, F.; Villata, M.; Raiteri, C. M.; de Francesco, G.; Sobrito, G.; Takalo, L. O.; Sillanpää, A.; Katajainen, S.; Pursimo, T.; Kurtanidze, O. M.; Nikolashvili, M. G.

    The authors report here optical observations of BL Lac performed during its large outburst in 1997. During this monitoring the source reached the brightest magnitude observed in the last 25 years, showing a variability pattern characterized by rapid flares lasting from few hours to days.

  15. Nucleotide sequence of Klebsiella pneumoniae lac genes.

    OpenAIRE

    Buvinger, W E; Riley, M

    1985-01-01

    The nucleotide sequences of the Klebsiella pneumoniae lacI and lacZ genes and part of the lacY gene were determined, and these genes were located and oriented relative to one another. The K. pneumoniae lac operon is divergent in that the lacI and lacZ genes are oriented head to head, and complementary strands are transcribed. Besides base substitutions, the lacZ genes of K. pneumoniae and Escherichia coli have suffered short distance shifts of reading frame caused by additions or deletions or...

  16. Study of gamma-ray and near-infrared emission of gamma-ray-loud Blazars object

    International Nuclear Information System (INIS)

    The authors have collected 29 gamma-ray-loud Blazars (16 BL Lac objects and 13 flat-spectrum radio quasars) with both observed near-IR and γ-ray flux densities, with the following main results: (1) there is a very strong correlation between Fγ and FIR in the low state, and a weaker but also significant correlation between Fγ and FIR in the high state for 23 objects with both high and low state fluxes; (2) there is a very significant correlation between Fγ and FIR in the low state, and a weak correlation between Fγ and FIR in the high state for 29 sources; (3) there is a correlation between Fγ and Fx, but not between Fγ and FO, and FR for both the low and high state of 26 sources; (4) there is a strong correlation between Fγ and FIR in the low and high states for 15 BL Lac objects, but not for 11 flat-spectrum radio quasars. Possible constraints on the γ-ray emission mechanism are discussed. The authors suggest that the main gamma-ray radiation mechanism is probably the synchrotron self-Compton process. The inverse Compton scattering of the radiation from hot circumnuclear dust with Tg = 2000 K, which is located within the region of r ≅ 3pc, by beamed ultrarelativistic electrons is likely to be an important complementary mechanism. In addition, the γ-ray emission may be somewhat different for BL Lac objects and flat-spectrum radio quasars

  17. Very high-resolution observations of the radio sources NRAO 150, OJ 287, 3C 273, M87, 1633+38, BL Lacertae, and 3C 454.3

    International Nuclear Information System (INIS)

    Very long baseline interferometer observations made at a wavelength of 2 and 2.8 cm with baselines ranging from 54 to 291 million wavelengths show a number of radio sources with only slightly resolved components, even on the longest baselines; the quasars 1633 + 38 and 3C 454.3, the objects OJ 287 and BL Lac, and the nucleus of M87 (Virgo A, 3C 274) all contain components < or approximately 0.4 milli-arcsec. The smallest component observed is in the core of 3C 454.3, which contains about 50% of the total flux density and is < or approximately 0.2 milli-arcsec in diameter. The compact component in the nucleus of M87 is < or approximately 1.5 light-months across, and contains about one-third of the total flux density of the nucleus at 2.8 cm. NRAO 150 and BL Lac are double: the components of NRAO 150 are separated by 0.6 milli-arcsec, while BL Lac has an elongated structure consisting of a large (1.4 milli-arcsec) component separated by 1.25 milli-arcsec from a smaller (0.5 milli-arcsec) variable one. The present data on 3C 273 are consistent with triple models similar to those discussed previously, but with a somewhat greater apparent separation of components

  18. LacR is a repressor of lacABCD and LacT is an activator of lacTFEG, constituting the lac gene cluster in Streptococcus pneumoniae.

    Science.gov (United States)

    Afzal, Muhammad; Shafeeq, Sulman; Kuipers, Oscar P

    2014-09-01

    Comparison of the transcriptome of Streptococcus pneumoniae strain D39 grown in the presence of either lactose or galactose with that of the strain grown in the presence of glucose revealed the elevated expression of various genes and operons, including the lac gene cluster, which is organized into two operons, i.e., lac operon I (lacABCD) and lac operon II (lacTFEG). Deletion of the DeoR family transcriptional regulator lacR that is present downstream of the lac gene cluster revealed elevated expression of lac operon I even in the absence of lactose. This suggests a function of LacR as a transcriptional repressor of lac operon I, which encodes enzymes involved in the phosphorylated tagatose pathway in the absence of lactose or galactose. Deletion of lacR did not affect the expression of lac operon II, which encodes a lactose-specific phosphotransferase. This finding was further confirmed by β-galactosidase assays with PlacA-lacZ and PlacT-lacZ in the presence of either lactose or glucose as the sole carbon source in the medium. This suggests the involvement of another transcriptional regulator in the regulation of lac operon II, which is the BglG-family transcriptional antiterminator LacT. We demonstrate the role of LacT as a transcriptional activator of lac operon II in the presence of lactose and CcpA-independent regulation of the lac gene cluster in S. pneumoniae. PMID:24951784

  19. The Evolving Radio Jet in BL Lacerta

    Science.gov (United States)

    Aller, H. D.; Hughes, P. A.; Aller, M. F.

    1994-05-01

    During the past 15 years, there have been at least ten outbursts at centimeter wavelengths in this extragalactic object. We describe here the flux density and linear polarization variations observed at 4.8, 8.0 and 14.5 GHz with the Michigan 26-meter telescope during the series of outbursts since 1987. The recent bursts are somewhat different from the highly polarized bursts in the early 1980s, which provided a successful quantitative test of a source model based on propagating transverse shocks in a relativistic jet. The most notable change is that the polarization position angle during polarized outbursts has increased by approximately 10 degrees. This is approximately the same shift as found in a comparison of VLBI maps taken during the same time periods by Mutel, Denn and Dryer (1994, NRAO Workshop on Compact Extragalactic Radio Sources, ed. Zensus and Kellermann, p. 191), and supports their conclusion that the orientation of the radio emitting jet in BL Lac has changed over time. Our preliminary analysis further suggests that a simple scaling of the physical parameters which gave quantitatively good fits to both the 1982 and 1983 bursts will not accurately describe the recent, relatively isolated, burst in 1991. We also note that while some bursts (e.g. in 1982, 1983 and 1991) exhibit degrees of linear polarization in excess of ten percent, other bursts (e.g. in 1980 and 1990) exhibit a very low degree of linear polarization. A common characteristic of the low polarization events is that they all exhibit high internal synchrotron self absorption (as indicated by the flux density spectra of the outbursts). This research has been supported in part by NSF grant AST-9120224.

  20. Fifty years fused to lac.

    Science.gov (United States)

    Beckwith, Jonathan

    2013-01-01

    I recount the history of how I became interested in the use of gene fusions for studying biological problems. Initially, selections for mutations that would restore function to an inactivated lac operon unexpectedly yielded fusions in which lac was expressed from the controlling elements of upstream genes. Subsequently, by chance, I generated strains in which the lac operon was transposed from its normal position on the chromosome to a position close to the trp operon, thus facilitating sets of useful fusions of the two operons. The development of a more generalized technique for obtaining fusions by my student Malcolm Casadaban opened up a much broader set of biological problems that could be approached with fusions. Work on these problems included the study of protein translocation across membranes, the analysis of membrane protein topology, and the discovery of the pathway of electron transfer that leads to disulfide bond formation in proteins. PMID:24024632

  1. Location of gamma-ray Flare Emission in the Jet of the BL Lacertae Object OJ287 more than 14pc from the Central Engine

    CERN Document Server

    Agudo, Ivan; Marscher, Alan P; Larionov, Valeri M; Gomez, Jose L; Lahteenmaki, Anne; Gurwell, Mark A; Smith, Paul S; Wiesemeyer, Helmut; Thum, Clemens; Heidt, Jochen; Blinov, Dmitriy A; D'Arcangelo, Francesca D; Hagen-Thorn, Vladimir A; Morozova, Daria A; Nieppola, Elina; Roca-Sogorb, Mar; Schmidt, Gary D; Taylor, Brian; Tornikoski, Merja; Troitsky, Ivan S

    2010-01-01

    We combine time-dependent multi-waveband flux and linear polarization observations with sub-milliarcsecond-scale polarimetric images at lambda=7mm of the BL Lacertae-type blazar OJ287 to locate the gamma-ray emission in prominent flares in the jet of the source >14pc from the central engine. We demonstrate a highly significant correlation between the strongest gamma-ray and millimeter-wave flares through Monte-Carlo simulations. The two reported gamma-ray peaks occurred near the beginning of two major mm-wave outbursts, each of which is associated with a linear polarization maximum at millimeter wavelengths. Our Very Long Baseline Array observations indicate that the two mm-wave flares originated in the second of two features in the jet that are separated by >14 pc. The simultaneity of the peak of the higher-amplitude gamma-ray flare and the maximum in polarization of the second jet feature implies that the gamma-ray and mm-wave flares are co-spatial and occur >14 pc from the central engine. We also associate...

  2. Program Evaluation of Community College Learning Assistance Centers: What Do LAC Directors Think?

    Science.gov (United States)

    Franklin, Doug; Blankenberger, Bob

    2016-01-01

    Objective: This study seeks to determine the nature of current program evaluation practices for learning assistance centers (LACs), the practices being used for program evaluation, and whether LAC directors believe their practices are appropriate for evaluating program effectiveness. Method: We conducted a survey (n = 61) of community college LAC…

  3. LOCATION OF γ-RAY FLARE EMISSION IN THE JET OF THE BL LACERTAE OBJECT OJ287 MORE THAN 14 pc FROM THE CENTRAL ENGINE

    International Nuclear Information System (INIS)

    We combine time-dependent multi-waveband flux and linear polarization observations with submilliarcsecond-scale polarimetric images at λ = 7 mm of the BL Lacertae type blazar OJ287 to locate the γ-ray emission in prominent flares in the jet of the source >14 pc from the central engine. We demonstrate a highly significant correlation between the strongest γ-ray and millimeter-wave flares through Monte Carlo simulations. The two reported γ-ray peaks occurred near the beginning of two major millimeter-wave outbursts, each of which is associated with a linear polarization maximum at millimeter wavelengths. Our very long baseline array observations indicate that the two millimeter-wave flares originated in the second of two features in the jet that are separated by >14 pc. The simultaneity of the peak of the higher-amplitude γ-ray flare and the maximum in polarization of the second jet feature implies that the γ-ray and millimeter-wave flares are cospatial and occur >14 pc from the central engine. We also associate two optical flares, accompanied by sharp polarization peaks, with the two γ-ray events. The multi-waveband behavior is most easily explained if the γ-rays arise from synchrotron self-Compton scattering of optical photons from the flares. We propose that flares are triggered by interaction of moving plasma blobs with a standing shock. The γ-ray and optical emission is quenched by inverse Compton losses as synchrotron photons from the newly shocked plasma cross the emission region. The millimeter-wave polarization is high at the onset of a flare, but decreases as the electrons emitting at these wavelengths penetrate less polarized regions.

  4. Optical spectroscopy of SDSS J004054.65-0915268: three possible scenarios for the classification. A z \\sim 5 BL Lacertae, blue FSRQ or a weak emission line quasar

    CERN Document Server

    Landoni, M; Bianco, A; Tavecchio, F; Bonnoli, G; Ghisellini, G

    2015-01-01

    The haunt of high redshift BL Lacerate objects is day by day more compelling, to firmly understand their intrinsic nature and evolution. SDSS J004054.65-0915268 is, at the moment, one of the most distant BL Lac candidate at z \\sim 5 (Plotkin et al 2010). We present a new optical-near IR spectrum obtained with ALFOSC-NOT with a new, custom designed dispersive grating aimed to detect broad emission lines that could disprove this classification. In the obtained spectra we do not detect any emission features and we provide an upper limit to the luminosity of the C IV broad emission line. Therefore, the nature of the object is then discussed, building the overall spectral energy distribution and fitting it with three different models. Our fits, based on the SED modeling with different possible scenarios, cannot rule out the possibility that this source is indeed a BL Lac object although, the absence of optical variability and lack of strong radio flux, they seems to suggest that the observed optical emission origi...

  5. A synchrotron self-Compton scenario for the very high energyγ-ray emission of the intermediate BL Lacertae object W Comae

    Institute of Scientific and Technical Information of China (English)

    Jin Zhang

    2009-01-01

    W Comae has significant variability in multi-wavelengthes, from radio to gamma-ray bands. A bright outburst in optical and X-ray bands was observed in 1998, and most recently, a strong TeV flare was detected by VERITAS in 2008. It is the first TeV intermediate-frequency-peaked BL Lacertae source. I find that both the broadband spectral energy distributions (SEDs) which were quasi-simultaneously obtained during the TeV flare and during the optical/X-ray outburst are well fit by using a single-zone synchrotron + synchrotron-self-Compton model. The satisfactory fitting requires a large beaming factor, i.e., δ~25 and δ~20 for the TeV flare and the optical/X-ray outburst, respectively, suggesting that both the optical/X-ray outburst and the TeV flare are from a relativistic jet. The size of the emission region of the TeV flare is three times larger than that of the optical/X-ray outburst, and the strength of the magnetic field for the TeV flare is~14 times smaller than that of the X-ray/optical outburst, likely indicating that the region of the TeV flare is more distant from the core than that of the X-ray/optical outburst. The inverse Compton component of the TeV flare peaks around 1.3 GeV, but it is around 0 MeV for the X-ray/optical outburst, lower than that for the TeV flare by two orders of magnitude. The model predicts that the optical/X-ray outburst might be accompanied by a strong MeV/GeV emission, but the TeV flare may be not associated with the X-ray/optical outburst. The GeV emission is critical for characterizing the SEDs of the optical/X-ray outburst and the TeV flare. The predicted GeV flux is above the sensitivity of Fermi/LAT, and it could be verified with the observations by Fermi/LAT in the near future.

  6. LacR Is a Repressor of lacABCD and LacT Is an Activator of lacTFEG, Constituting the lac Gene Cluster in Streptococcus pneumoniae

    OpenAIRE

    Afzal, Muhammad; Shafeeq, Sulman; Kuipers, Oscar P

    2014-01-01

    Comparison of the transcriptome of Streptococcus pneumoniae strain D39 grown in the presence of either lactose or galactose with that of the strain grown in the presence of glucose revealed the elevated expression of various genes and operons, including the lac gene cluster, which is organized into two operons, i.e., lac operon I (lacABCD) and lac operon II (lacTFEG). Deletion of the DeoR family transcriptional regulator lacR that is present downstream of the lac gene cluster revealed elevate...

  7. Examination of the hippocampal contribution to serotonin 5-HT2A receptor-mediated facilitation of object memory in C57BL/6J mice.

    Science.gov (United States)

    Zhang, Gongliang; Cinalli, David; Cohen, Sarah J; Knapp, Kristina D; Rios, Lisa M; Martínez-Hernández, José; Luján, Rafael; Stackman, Robert W

    2016-10-01

    The rodent hippocampus supports non-spatial object memory. Serotonin 5-HT2A receptors (5-HT2AR) are widely expressed throughout the hippocampus. We previously demonstrated that the activation of 5-HT2ARs enhanced the strength of object memory assessed 24 h after a limited (i.e., weak memory) training procedure. Here, we examined the subcellular distribution of 5-HT2ARs in the hippocampal CA1 region and underlying mechanisms of 5-HT2AR-mediated object memory consolidation. Analyses with immuno-electron microscopy revealed the presence of 5-HT2ARs on the dendritic spines and shafts of hippocampal CA1 neurons, and presynaptic terminals in the CA1 region. In an object recognition memory procedure that places higher demand on the hippocampus, only post-training systemic or intrahippocampal administration of the 5-HT2AR agonist TCB-2 enhanced object memory. Object memory enhancement by TCB-2 was blocked by the 5-HT2AR antagonist, MDL 11,937. The memory-enhancing dose of systemic TCB-2 increased extracellular glutamate levels in hippocampal dialysate samples, and increased the mean in vivo firing rate of hippocampal CA1 neurons. In summary, these data indicate a pre- and post-synaptic distribution of 5-HT2ARs, and activation of 5-HT2ARs selectively enhanced the consolidation of object memory, without affecting encoding or retrieval. The 5-HT2AR-mediated facilitation of hippocampal memory may be associated with an increase in hippocampal neuronal firing and glutamate efflux during a post-training time window in which recently encoded memories undergo consolidation. PMID:27114257

  8. High-Level Expression of Bacillus naganoensis Pullulanase from Recombinant Escherichia coli with Auto-Induction: Effect of lac Operator

    Science.gov (United States)

    Xu, Yan; Chen, Wen Bo; Mu, Xiao Qing; Wang, Xinye; Xiao, Rong

    2013-01-01

    Pullulanase plays an important role in specific hydrolysis of branch points in amylopectin and is generally employed as an important enzyme in starch-processing industry. So far, however, the production level of pullulanase is still somewhat low from wide-type strains and even heterologous expression systems. Here the gene encoding Bacillus naganoensis pullulanase was amplified and cloned. For expression of the protein, two recombinant systems, Escherichia coli BL21(DE3)/pET-20b(+)-pul and E. coli BL21(DE3)/pET-22b(+)-pul, were constructed, both bearing T7 promoter and signal peptide sequence, but different in the existance of lac operator and lacI gene encoding lac repressor. Recombinant pullulanase was initially expressed with the activity of up to 14 U/mL by E. coli BL21(DE3)/pET-20b(+)-pul with IPTG induction in LB medium, but its expression level reduced continually with the extension of cryopreservation time and basal expression was observed. However, E. coli BL21(DE3)/pET-22b(+)-pul , involving lac operator downstream of T7 promoter to regulate foreign gene transcription, exhibited pullulanase activity consistently without detected basal expression. By investigating the effect of lac operator, basal expression of foreign protein was found to cause expression instability and negative effect on production of target protein. Thus double-repression strategy was proposed that lac operators in both chromosome and plasmid were bound with lac repressor to repress T7 RNA polymerase synthesis and target protein expression before induction. Consequently, the total activity of pullulanase was remarkably increased to 580 U/mL with auto-induction by lac operator-involved E. coli BL21(DE3)/pET-22b(+)-pul. When adding 0.6% glycine in culture, the extracellular production of pullulanase was significantly improved with the extracellular activity of 502 U/mL, which is a relatively higher level achieved to date for extracellular production of pullulanase. The successful

  9. High-level expression of Bacillus naganoensis pullulanase from recombinant Escherichia coli with auto-induction: effect of lac operator.

    Directory of Open Access Journals (Sweden)

    Yao Nie

    Full Text Available Pullulanase plays an important role in specific hydrolysis of branch points in amylopectin and is generally employed as an important enzyme in starch-processing industry. So far, however, the production level of pullulanase is still somewhat low from wide-type strains and even heterologous expression systems. Here the gene encoding Bacillus naganoensis pullulanase was amplified and cloned. For expression of the protein, two recombinant systems, Escherichia coli BL21(DE3/pET-20b(+-pul and E. coli BL21(DE3/pET-22b(+-pul, were constructed, both bearing T7 promoter and signal peptide sequence, but different in the existance of lac operator and lacI gene encoding lac repressor. Recombinant pullulanase was initially expressed with the activity of up to 14 U/mL by E. coli BL21(DE3/pET-20b(+-pul with IPTG induction in LB medium, but its expression level reduced continually with the extension of cryopreservation time and basal expression was observed. However, E. coli BL21(DE3/pET-22b(+-pul , involving lac operator downstream of T7 promoter to regulate foreign gene transcription, exhibited pullulanase activity consistently without detected basal expression. By investigating the effect of lac operator, basal expression of foreign protein was found to cause expression instability and negative effect on production of target protein. Thus double-repression strategy was proposed that lac operators in both chromosome and plasmid were bound with lac repressor to repress T7 RNA polymerase synthesis and target protein expression before induction. Consequently, the total activity of pullulanase was remarkably increased to 580 U/mL with auto-induction by lac operator-involved E. coli BL21(DE3/pET-22b(+-pul. When adding 0.6% glycine in culture, the extracellular production of pullulanase was significantly improved with the extracellular activity of 502 U/mL, which is a relatively higher level achieved to date for extracellular production of pullulanase. The

  10. High-level expression of Bacillus naganoensis pullulanase from recombinant Escherichia coli with auto-induction: effect of lac operator.

    Science.gov (United States)

    Nie, Yao; Yan, Wei; Xu, Yan; Chen, Wen Bo; Mu, Xiao Qing; Wang, Xinye; Xiao, Rong

    2013-01-01

    Pullulanase plays an important role in specific hydrolysis of branch points in amylopectin and is generally employed as an important enzyme in starch-processing industry. So far, however, the production level of pullulanase is still somewhat low from wide-type strains and even heterologous expression systems. Here the gene encoding Bacillus naganoensis pullulanase was amplified and cloned. For expression of the protein, two recombinant systems, Escherichia coli BL21(DE3)/pET-20b(+)-pul and E. coli BL21(DE3)/pET-22b(+)-pul, were constructed, both bearing T7 promoter and signal peptide sequence, but different in the existance of lac operator and lacI gene encoding lac repressor. Recombinant pullulanase was initially expressed with the activity of up to 14 U/mL by E. coli BL21(DE3)/pET-20b(+)-pul with IPTG induction in LB medium, but its expression level reduced continually with the extension of cryopreservation time and basal expression was observed. However, E. coli BL21(DE3)/pET-22b(+)-pul , involving lac operator downstream of T7 promoter to regulate foreign gene transcription, exhibited pullulanase activity consistently without detected basal expression. By investigating the effect of lac operator, basal expression of foreign protein was found to cause expression instability and negative effect on production of target protein. Thus double-repression strategy was proposed that lac operators in both chromosome and plasmid were bound with lac repressor to repress T7 RNA polymerase synthesis and target protein expression before induction. Consequently, the total activity of pullulanase was remarkably increased to 580 U/mL with auto-induction by lac operator-involved E. coli BL21(DE3)/pET-22b(+)-pul. When adding 0.6% glycine in culture, the extracellular production of pullulanase was significantly improved with the extracellular activity of 502 U/mL, which is a relatively higher level achieved to date for extracellular production of pullulanase. The successful

  11. Estradiol-Induced Enhancement of Object Memory Consolidation Involves NMDA Receptors and Protein Kinase A in the Dorsal Hippocampus of Female C57BL/6 Mice

    OpenAIRE

    Michael C. Lewis; Kerr, Kristin M.; Orr, Patrick T.; Frick, Karyn M.

    2008-01-01

    This study examined the role of dorsal hippocampal NMDA receptors and PKA activation in 17β-estradiol (E2)-induced enhancement of object memory consolidation. Mice explored two identical objects during training, after which they immediately received intraperitoneal injections of 0.2 mg/kg E2, and bilateral dorsal hippocampal infusions of Vehicle, the NMDA receptor antagonist APV (2.5 μg/side), or the cAMP inhibitor Rp-cAMPS (18.0 μg/side). Retention was tested 48 hours later. The enhanced obj...

  12. Radiation-induced point mutations, deletions and micronuclei in lacI transgenic mice

    International Nuclear Information System (INIS)

    The development of transgenic mutagenesis systems has now made it possible to study the effects of ionizing radiation at both the molecular and chromosomal levels in the same animal. In this report we present preliminary data on the response of Big BlueTM lacI transgenic mice to ionizing radiation as measured by lacI mutations and micronuclei. C57Bl/6 transgenic mice were irradiated with 137Cs γ-rays at doses ranging from 0.1 to 14 Gy, and expression times ranging from 2 to 14 days. Dose-related increases in the mutant frequency were observed after irradiations with longer expression times. Mutant plaques were analyzed by restriction enzyme digestion to detect large structural changes in the target sequence. Of 34 γ-ray- induced mutations analyzed, 4 were large-scale rearrangements. Three of these rearrangements were deletions within the lacI gene characterized by the presence of short regions of homology at the breakpoint junctions. The fourth rearrangement was a deletion that extended from within the αlacZ gene into downstream sequences and that had 43 bp of homology at the junction. These data indicate that the Big BlueTM lacI transgenic mouse system is sensitive to the types of mutations induced by ionizing radiation. To determine whether the presence of the transgene affects micronucleus induction we compared the response of nontransgenic to hemizygous transgenic B6C3F1 mice and the response of nontransgenic to hemizygous and homozygous transgenic C57Bl/6 mice. The presence or absence of the lacI transgene had no effect on spontaneous micronucleus frequencies for either strain. However, radiation-induced micronucleus frequencies were significantly higher in hemizygous lacI B6C3F1 mice than in nontransgenic litter mates; the converse was true in C57Bl/6 mice. These data suggest that the lacI transgene does not cause chromosome instability as measured by spontaneous micronucleus levels. However, the response of these transgenic mice to a variety of

  13. Observations of BL Lacertae with MAGIC telescope

    Directory of Open Access Journals (Sweden)

    E. J. Lindfors

    2008-01-01

    Full Text Available BL Lacertae fue observado con el telescopio MAGIC de agosto a diciembre de 2005 (22.2 horas y de julio a septiembre de 2006 (26.0 horas. En 2005 se detectó, con un nivel de significación 5.1 σ, una fuerte emisión de rayos γ de muy alta energía (VHE. BL Lacertae es el primer objeto BL Lac con un pico de emisión a bajas frecuencias, en el cual se detecta este tipo de emisión. En los datos de 2006, no hay detección en la región de los rayos γ, lo que se atribuye a un menor nivel de flujo en este periodo. En este trabajo mostramos que también se observa una caida en el flujo óptico y milimétrico, lo cual sugiere una conexión entre estas tres bandas de emisión.

  14. Learning Vector Quantization for Classifying Astronomical Objects

    Institute of Scientific and Technical Information of China (English)

    2003-01-01

    The sizes of astronomical surveys in different wavebands are increas-ing rapidly. Therefore, automatic classification of objects is becoming ever moreimportant. We explore the performance of learning vector quantization (LVQ) inclassifying multi-wavelength data. Our analysis concentrates on separating activesources from non-active ones. Different classes of X-ray emitters populate distinctregions of a multidimensional parameter space. In order to explore the distributionof various objects in a multidimensional parameter space, we positionally cross-correlate the data of quasars, BL Lacs, active galaxies, stars and normal galaxiesin the optical, X-ray and infrared bands. We then apply LVQ to classify them withthe obtained data. Our results show that LVQ is an effective method for separatingAGNs from stars and normal galaxies with multi-wavelength data.

  15. Present research on the composition and application of lac

    Institute of Scientific and Technical Information of China (English)

    Wang Xia; Li Jian-zhang; Fan Yong-ming; Jin Xiao-juan

    2006-01-01

    Lac is a natural polymer with atoxigenic, renewable, and naturally degradable characteristics. Nowadays, more and more attentions are paid to environment protection and resource conservation, so it has great significance to study the composition and application of lac. The paper summarizes the research of lac composition and emphasizes on the present research of lac resin. The applications of lac are also introduced. In addition, some suggestions are proposed, which is expected to provide some scientific references for further studies of lac.

  16. Transcriptional and functional analysis of galactooligosaccharide uptake by lacS in Lactobacillus acidophilus.

    Science.gov (United States)

    Andersen, Joakim M; Barrangou, Rodolphe; Abou Hachem, Maher; Lahtinen, Sampo; Goh, Yong Jun; Svensson, Birte; Klaenhammer, Todd R

    2011-10-25

    Probiotic microbes rely on their ability to survive in the gastrointestinal tract, adhere to mucosal surfaces, and metabolize available energy sources from dietary compounds, including prebiotics. Genome sequencing projects have proposed models for understanding prebiotic catabolism, but mechanisms remain to be elucidated for many prebiotic substrates. Although β-galactooligosaccharides (GOS) are documented prebiotic compounds, little is known about their utilization by lactobacilli. This study aimed to identify genetic loci in Lactobacillus acidophilus NCFM responsible for the transport and catabolism of GOS. Whole-genome oligonucleotide microarrays were used to survey the differential global transcriptome during logarithmic growth of L. acidophilus NCFM using GOS or glucose as a sole source of carbohydrate. Within the 16.6-kbp gal-lac gene cluster, lacS, a galactoside-pentose-hexuronide permease-encoding gene, was up-regulated 5.1-fold in the presence of GOS. In addition, two β-galactosidases, LacA and LacLM, and enzymes in the Leloir pathway were also encoded by genes within this locus and up-regulated by GOS stimulation. Generation of a lacS-deficient mutant enabled phenotypic confirmation of the functional LacS permease not only for the utilization of lactose and GOS but also lactitol, suggesting a prominent role of LacS in the metabolism of a broad range of prebiotic β-galactosides, known to selectively modulate the beneficial gut microbiota. PMID:22006318

  17. Is BL Lacertae an "orphan" AGN? Multiband and spectroscopic constraints on the parent population

    CERN Document Server

    Capetti, Alessandro; Buttiglione, Sara; ),

    2010-01-01

    We have analysed optical spectra of BL Lacertae, the prototype of its class, to verify the presence and possible flux variations of its broad Ha line. We used the spectroscopic information also to investigate the question of its parent population. Four spectra were acquired at the TNG in 2007-2008, when the source was in a relatively faint state. In three cases we were able to measure the broad Ha and several narrow emission lines. A comparison with previous results suggests that the broad Ha has increased by ~50% in ten years, a change not unusual for Broad Lined AGN. We estimated a black hole mass for BL Lac of 4-6 10^8 solar masses from its relation with the bulge luminosity. The virial mass estimated from the spectroscopic data is instead 20-30 times smaller. We suggest that this discrepancy is due to the BL Lac BLR being underluminous. Finally, we addressed the problem of the BL Lac parent population, comparing its isotropic quantities with those of other AGN classes. From the point of view of the narrow...

  18. Mutagenesis in the lacI gene target of E. coli: improved analysis for lacI(d) and lacO mutants.

    Science.gov (United States)

    Swerdlow, Sarah J; Schaaper, Roel M

    2014-12-01

    The lacI gene of Escherichia coli has been a highly useful target for studies of mutagenesis, particularly for analysis of the specificity (spectrum) of mutations generated under a variety of conditions and in various genetic backgrounds. The gene encodes the repressor of the lac operon, and lacI-defective mutants displaying constitutive expression of the operon are readily selected. DNA sequencing of the lacI mutants has often been confined to the N-terminal region of the protein, as it presents a conveniently short target with a high density of detectably mutable sites. Mutants in this region are easily selected due to their dominance in a genetic complementation test (lacI(d) mutants). A potential complication in these studies is that constitutive expression of lac may also arise due to mutations in the lac operator (lacO mutants). Under some conditions, for example when analyzing spontaneous mutations, lacO mutants can comprise a very high fraction of the constitutive mutants due to a strong base-substitution hotspot in the lac operator. Such mutational hot spots diminish the return of the sequencing effort and do not yield significant new information. For this reason, a procedure to eliminate the lacO mutants prior to DNA sequencing is desirable. Here, we report a simple method that allows screening out of lacO mutants. This method is based on the lack of resistance of lacO mutants to kanamycin under conditions when the kan gene is expressed from a plasmid under control of the lac promoter-operator (lacPO). We show data validating the new approach with sets of known lacI(d) and lacO mutants, and further apply it to the generation of a new collection of spontaneous mutations, where lacO mutants have historically been a significant contributor. PMID:25771873

  19. Optimized expression and purification of biophysical quantities of Lac repressor and Lac repressor regulatory domain.

    Science.gov (United States)

    Stetz, Matthew A; Carter, Marie V; Wand, A Joshua

    2016-07-01

    The recombinant production of Lac repressor (LacI) in Escherichia coli is complicated by its ubiquitous use as a regulatory element in commercially-available expression vectors and host strains. While LacI-regulated expression systems are often used to produce recombinant LacI, the product can be heterogeneous and unsuitable for some studies. Alternative approaches include using unregulated vectors which typically suffer from low yield or vectors with promoters induced by metabolically active sugars which can dilute isotope labels necessary for certain biophysical studies. Here, an optimized expression system and isolation protocol for producing various constructs of LacI is introduced which eliminates these complications. The expression vector is an adaptation of the pASK backbone wherein expression of the lacI gene is regulated by an anhydrotetracyline inducible tetA promoter and the host strain lacks the lacI gene. Typical yields in highly deuterated minimal medium are nearly 2-fold greater than those previously reported. Notably, the new expression system is also able to produce the isolated regulatory domain of LacI without co-expression of the full-length protein and without any defects in cell viability, eliminating the inconvenient requirement for strict monitoring of cell densities during pre-culturing. Typical yields in highly deuterated minimal medium are significantly greater than those previously reported. Characterization by solution NMR shows that LacI constructs produced using this expression system are highly homogenous and functionally active. PMID:27064119

  20. CCC/WPA study : Des Lacs NWR

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — Summary of the Civilian Conservation Corps (CCC) camp at Des Lacs National Wildlife Refuge from July 1935-May 1942 to carry on restoration and development of Des...

  1. Regulatory region of the divergent Klebsiella pneumoniae lac operon.

    OpenAIRE

    Buvinger, W E; Riley, M

    1985-01-01

    The chromosomal DNA that lies between the lacI and lacZ genes of Klebsiella pneumoniae constitutes a 196-base pair intercistronic region that contains regulatory sequences for both genes. The probable locations of specific regulatory elements for both lacI and lacZ genes were determined by analogy with the corresponding Escherichia coli sequences. A recombinational event in ancestral DNA evidently has inverted the transcriptional direction of lacI in K. pneumoniae relative to the transcriptio...

  2. The Coronae of AR Lac

    CERN Document Server

    Huenemoerder, D P; Drake, J J; Sanz-Forcada, J; Canizares, Claude R.; Drake, Jeremy J.; Huenemoerder, David P.; Sanz-Forcada, Jorge

    2003-01-01

    We observed the coronally active eclipsing binary, AR Lac, with the High Energy Transmission Grating on Chandra for a total of 97 ks, spaced over five orbits, at quadratures and conjunctions. Contemporaneous and simultaneous EUV spectra and photometry were also obtained with the Extreme Ultraviolet Explorer. Significant variability in both X-ray and EUV fluxes were observed, dominated by at least one X-ray flare and one EUV flare. We saw no evidence of primary or secondary eclipses. X-ray flux modulation was largest at high temperature, indicative of flare heating of coronal plasma. Line widths interpreted in terms of Doppler broadening suggest that both binary stellar components are active. From line fluxes obtained from total integrated spectra, we have modeled the emission measure and abundance distributions. A strong maximum was found in the differential emission measure, characterized by peaks at log T = 6.9 and 7.4, together with a weak but significant cooler maximum near log T=6.2, and a moderately str...

  3. Modification of natural matrix lac-bagasse for matrix composite films

    Science.gov (United States)

    Nurhayati, Nanik Dwi; Widjaya, Karna; Triyono

    2016-02-01

    Material technology continues to be developed in order to a material that is more efficient with composite technology is a combination of two or more materials to obtain the desired material properties. The objective of this research was to modification and characterize the natural matrix lac-bagasse as composite films. The first step, natural matrix lac was changed from solid to liquid using an ethanol as a solvent so the matrix homogenly. Natural matrix lac was modified by adding citric acid with concentration variation. Secondly, the bagasse delignification using acid hydrolysis method. The composite films natural matrix lac-bagasse were prepared with optimum modified the addition citric acid 5% (v/v) and delignification bagasse optimum at 1,5% (v/v) in hot press at 80°C 6 Kg/cm-1. Thirdly, composite films without and with modification were characterized functional group analysis using FTIR spectrophotometer and mechanical properties using Universal Testing Machine. The result of research showed natural matrix lac can be modified by reaction with citric acid. FTIR spectra showed without and with modification had functional groups wide absorption 3448 cm-1 group -OH, C=O ester strong on 1712 cm-1 and the methylene group -CH2 on absorption 1465 cm-1. The mechanical properties showed tensile strength 0,55 MPa and elongation at break of 0,95 %. So that composite films natural matrix lac can be made with reinforcement bagasse for material application.

  4. 3BL hotel management

    OpenAIRE

    MALECHOVÁ, Vendula

    2013-01-01

    The work is dedicated to Corporate Social Responsibility (CSR) and its application in the hotel. Part of this work are interviews with representatives of hotels representing the CSR best practices and interviews with other selected subjects. Comparison of the information reflects the current status of implementation of CSR in hotel management in the Czech Republic. The output of work is created CSR matrix. According the principles of 3 BL management matrix visualizes the organization current ...

  5. The radiation experiment for Lac insects

    International Nuclear Information System (INIS)

    Two kinds of lac insect (Kerria chinensis, K.lacca) were radiated in this radiation experiment. The different stage of lac insect (larva, adult) are radiated by several dosages of Co 60. Tests showed that lac insects in the second stage are all dead after radiation of 500-2 000 rad, female insect of K.chinensis with pregnancy egg time 2-3 stage radiated by 1000 rad can produce new generation. Female insect of K.lacca with pregnancy egg time 5-6 stage radiated by 11 000 rad occasionally produce new generation. The egg amount and amount of secreting lac are similar to those of the normal, effective production and sex ratio are higher than those of the normal, group density on branch is lower than the normal in the generation of K.lacca after radiation. The sex ratio of the female, group density on branch are higher than those of the normal, egg amount and amount of secreting lac are normal in the generation of K.chinensis arter radiation. (author)

  6. The comparison between LAC and ALA

    Directory of Open Access Journals (Sweden)

    Tzu-heng Chiu

    2000-12-01

    Full Text Available A good library association serves its members, improves the librarianship, and helps library institutions achieving their missions. This article describes the history, missions and goals, organization structure, membership, financial sources, professional activities, publication, and website of the Library Association of China (LAC and American Library Association (ALA, respectively. Considering social / cultural / political differences between Taiwan and the United Sates, the author then compares these two library associations from the eight factors mentioned above. At the end, suggestions for the LAC are proposed.[Article content in Chinese

  7. Spectral energy distributions of the BL Lac PKS 2155-304 from XMM-Newton

    CERN Document Server

    Bhagwan, Jai; Papadakis, I E; Wiita, Paul J

    2014-01-01

    We have used all 20 archival XMM-Newton observations of PKS 2155-304 with simultaneous X-ray and UV/optical data to study its long term flux and spectral variability. We find significant variations, in all bands, on time-scales of years with an rms amplitude of ~ 35-45 per cent, through the optical/UV variations are not correlated with those in the X-ray. We constructed SEDs that span more than three orders of magnitude in frequency and we first fitted them with a log-parabolic model; such models have been applied many times in the past for this, and other, blazars. These fits were poor, so we then examined combined power-law and log-parabolic fits that are improvements. These models indicate that the optical/UV and X-ray flux variations are mainly driven by model normalization variations, but the X-ray band flux is also affected by spectral variations, as parametrized with the model 'curvature' parameter, b. Overall, the energy at which the emitted power is maximum correlates positively with the total flux. ...

  8. Arcsecond-Scale Radio Jets of Ultra-High-Energy Synchrotron Peak BL Lacs (UHBLs)

    Indian Academy of Sciences (India)

    Zhongzu Wu; Shengxu Yang; Minfeng Gu

    2014-09-01

    We present the arcsecond-scale jet structure and related radio properties for a sample of 9 UHBLs selected from Nieppola et al. (2006) with log(peak/Hz) > 20. Our preliminary results show that most of the UHBLs have compact structures, and their core dominance parameters are much larger than FR-I radio galaxies, suggesting that beaming may be prevalent in the jets of these sources.

  9. Baryon Loading Efficiency and Particle Acceleration Efficiency of Relativistic Jets: Cases For Low Luminosity BL Lacs

    CERN Document Server

    Inoue, Yoshiyuki

    2016-01-01

    Relativistic jets launched by SMBHs are the most energetic particle accelerators in the universe. However, the baryon mass loading efficiency onto the jets from the accretion and the particle acceleration efficiency in the jets have been veiled in mystery. With the latest data sets, we perform multi-wavelength spectral analysis of quiescent spectra of 13 TeV gamma-ray detected HBLs following one-zone synchrotron-self-Compton (SSC) model. We determine the minimum, cooling break, and maximum electron Lorentz factors following the diffusive shock acceleration (DSA) theory. We find that HBLs have $P_B/P_e\\sim0.025$ where $P_B$ and $P_e$ is the Poynting and electron power, respectively. The radiative efficiency of the jets is found to be $P_{\\rm rad}/P_{\\rm jet}\\sim0.026$. $P_{\\rm rad}$ and $P_{\\rm jet}$ is the radiative and total jet power, respectively. We find that the jet power relates to the black hole mass as $P_{\\rm jet}/L_{\\rm Edd}\\sim0.036$. We further find that HBLs have the mass loading efficiency of $\\...

  10. The three operators of the lac operon cooperate in repression.

    OpenAIRE

    Oehler, S; Eismann, E R; Krämer, H; Müller-Hill, B

    1990-01-01

    We tested the effect of systematic destruction of all three lac operators of the chromosomal lac operon of Escherichia coli on repression by Lac repressor. Absence of just one 'pseudo-operator' O2 or O3 decreases repression by wild-type tetrameric Lac repressor approximately 2- to 3-fold; absence of both 'pseudo-operators' decreases repression greater than 50-fold. O1 alone represses under these conditions only approximately 20-fold. Dimeric active Lac repressor (iadi) represses the wild-type...

  11. Variability of Extragalactic Objects in Relation to Redshift, Color, Radio Spectral Index and Absorption Lines

    Indian Academy of Sciences (India)

    D. Basu

    2001-12-01

    Optical variability of extragalactic objects, viz., QSOs, BL Lacs and Seyfert galaxies has been monitored systematically over an appreciable period of time and a large amount of data have accumulated. The present work reports results of investigations involving statistical analysis of updated data on relationships between variability and various observed properties of the objects, viz., redshift, color indices, radio spectral index and absorption lines. It is found that at high frequencies (rest frame) radio spectral index does not change significantly with the degree of variability. However, the degree of variability depends on redshifts. On the other hand, presence or absence of absorption lines is significantly associated with variability for QSOs with larger redshifts ( > 1.0), while no such relationship exists for QSOs at smaller redshifts ( < 1.0 or other objects. Correlation between color indices and redshifts depends on the degree of variability and the sample chosen for the color index.

  12. Mutagenesis in the lacI gene target of E. coli: improved analysis for lacId and lacO mutants

    OpenAIRE

    Swerdlow, Sarah J.; Schaaper, Roel M.

    2014-01-01

    The lacI gene of E. coli has been a highly useful target for studies of mutagenesis, particularly for analysis of the specificity (spectrum) of mutations generated under a variety of conditions and in various genetic backgrounds. The gene encodes the repressor of the lac operon, and lacI-defective mutants displaying constitutive expression of the operon are readily selected. DNA sequencing of the lacI mutants has often been confined to the N-terminal region of the protein, as it presents a co...

  13. Lac Courte Oreilles Energy Analysis Project

    Energy Technology Data Exchange (ETDEWEB)

    Leslie Isham; Denise Johnson

    2009-04-01

    The Lac Courte Oreilles Tribe applied for first step funding in 2007 and was awarded in October of that year. We wanted to perform an audit to begin fulfilling two commitments we made to our membership and resolutions that we adopted. One was the Kyoto Protocol and reduce our carbon emissions by 25% and to produce 25% of our energy by sustainable means. To complete these goals we needed to begin with first assessing what our carbon emissions are and begin taking the steps to conserve on the energy we currently use. The First Step Grant gave us the opportunity to do this. Upon funding the Energy Project was formed under the umbrella of the LCO Public Works Department and Denise Johnson was hired as the coordinator. She quickly began fulfilling the objectives of the project. Denise began by contact the LCO College and hiring interns who were able to go to each Tribal entity and perform line logging to read and document the energy used for each electrical appliance. Data was also gathered for one full year from each entity for all their utility bills (gasoline, electric, natural gas, fuel oil, etc.). Relationships were formed with the Green Team and other Green Committees in the area that could assist us in this undertaking. The Energy Task Force was of great assistance as well recommending other committees and guidance to completing our project. The data was gathered, compiled and placed into spreadsheets that would be understandable for anyone who didn't have a background in Renewable Resources. While gathering the data Denise was also looking for ways to conserve energy usage, policies changes to implement and any possible viable renewable energy resources. Changes in the social behaviors of our members and employees will require further education by workshops, energy fairs, etc.. This will be looked into and done in coordination with our schools. The renewable resources seem most feasible are wind resources as well as Bio Mass both of which need further

  14. Isolation and characterization of the lacA gene encoding beta-galactosidase in Bacillus subtilis and a regulator gene, lacR.

    OpenAIRE

    Daniel, R.A.; Haiech, J.; Denizot, F; Errington, J

    1997-01-01

    We have isolated transposon insertions in the lacA gene encoding an endogenous beta-galactosidase of Bacillus subtilis. Upstream of the putative operon containing lacA is a negative regulator, lacR, which encodes a product related to a family of regulators that includes the lactose repressor, lacI, of Escherichia coli. New strains with insertions in the lacA gene should be of use in studies using lacZ fusions in B. subtilis.

  15. Integration and gene replacement in the Lactococcus lactis lac operon: induction of a cryptic phospho-beta-glucosidase in LacG-deficient strains.

    OpenAIRE

    Simons, G.; Nijhuis, M.; de Vos, W M

    1993-01-01

    Insertions, replacement mutations, and deletions were introduced via single or double crossover recombination into the lacE (enzyme IIlac) and lacG (phospho-beta-galactosidase) genes of the Lactococcus lactis chromosomal lacABCDFEGX operon. LacG production was abolished in strains missing the lacG gene or carrying multicopy insertions in the lacE gene that affected expression of the lacG gene. However, these LacG-deficient strains could still ferment lactose slowly and were found to contain a...

  16. Acquisition of the lac operon by Salmonella enterica

    OpenAIRE

    Leonard, Susan R.; Lacher, David W.; Lampel, Keith A.

    2015-01-01

    Background Classical bacteriological characteristics of Salmonella enterica indicate that the members of this species are unable to utilize lactose as a carbon source. However, lactose-fermenting (Lac+) strains of several Salmonella serovars have been isolated from different foodborne outbreaks as well as different geographical regions worldwide. In the present study, we sequenced the genomes of 13 Lac + S. enterica isolates and characterized the lac region, comparing it to the lac region in ...

  17. The Energy Landscape of Hyperstable LacI-DNA Loops

    Science.gov (United States)

    Kahn, Jason

    2009-03-01

    The Escherichia coli LacI protein represses transcription of the lac operon by blocking access to the promoter through binding at a promoter-proximal DNA operator. The affinity of tetrameric LacI (and therefore the repression efficiency) is enhanced by simultaneous binding to an auxiliary operator, forming a DNA loop. Hyperstable LacI-DNA loops were previously shown to be formed on DNA constructs that include a sequence-directed bend flanked by operators. Biochemical experiments showed that two such constructs (9C14 and 11C12) with different helical phasing between the operators and the DNA bend form different DNA loop shapes. The geometry and topology of the loops and the relevance of alternative conformations suggested by probable flexible linkers in LacI remain unclear. Bulk and single molecule fluorescence resonance energy transfer (SM-FRET, with D. English) experiments on a dual fluorophore-labeled 9C14-LacI loop demonstrate that it adopts a single, stable, rigid closed-form loop conformation. Here, we characterize the LacI-9C14 loop by SM-FRET as a function of inducer isopropyl-β,D-thiogalactoside (IPTG) concentration. Energy transfer measurements reveal partial but incomplete destabilization of loop formation by IPTG. Surprisingly, there is no change in the energy transfer efficiency of the remaining looped population. Models for the regulation of the lac operon often assume complete disruption of LacI-operator complexes upon inducer binding to LacI. Our work shows that even at saturating IPTG there is still a significant population of LacI-DNA complexes in a looped state, in accord with previous in vivo experiments that show incomplete induction (with J. Maher). Finally, we will report progress on characterizing the ``energy landscape'' for DNA looping upon systematic variation of the DNA linkers between the operators and the bending locus. Rod mechanics simulations (with N. Perkins) provide testable predictions on loop stability, topology, and FRET.

  18. Blått vann

    OpenAIRE

    Jensen, Poul Johannes

    2013-01-01

    Verket består av to "blå vann" i høybrent porselæn som er plassert i en sansehage. Et rundt "vann" med diameter 350 cm og retangulært "vann" på 125 x 700 cm. Begge "vann" er belyst med ledlys som kan skifte fargetemperatur/farge. Her er brukt blå porselensfliser for å gi en følelse av vann. Flisene som er ca. 23 x 23 cm er etter 1. brenning dekorert med vannløselige keramiske farger som tildels glir i hverandre og veksler i farge og nyanse, fra blått til grønt ettersom hvilke farge som ...

  19. Applications of lac dye using different mordants on leather

    International Nuclear Information System (INIS)

    Lac dye aleuritic acid extracted from seed lac. when applied onto leather, using post-mordanting process showed good results. Among acetic acid, formic acid and alum, acetic acid at 0.1 M concentration proved to be the best mordant and gave excellent colour fastness to washing, light and rubbing and good tensile strength. (author)

  20. DNA supercoiling, a critical signal regulating the basal expression of the lac operon in Escherichia coli

    OpenAIRE

    Geraldine Fulcrand; Samantha Dages; Xiaoduo Zhi; Prem Chapagain; Bernard S. Gerstman; David Dunlap; Fenfei Leng

    2016-01-01

    Escherichia coli lac repressor (LacI) is a paradigmatic transcriptional factor that controls the expression of lacZYA in the lac operon. This tetrameric protein specifically binds to the O1, O2 and O3 operators of the lac operon and forms a DNA loop to repress transcription from the adjacent lac promoter. In this article, we demonstrate that upon binding to the O1 and O2 operators at their native positions LacI constrains three (−) supercoils within the 401-bp DNA loop of the lac promoter and...

  1. Den Blå Drage

    DEFF Research Database (Denmark)

    Ingerslev, Gitte Holten

    Denne publikation i serien Læselyst tjener tre formål. Den evaluerer læseprojektet Den blå drage i efteråret 2004 på Byskolen i Svendborg ? et projekt ledet af forfatteren Josefine Ottesen. Desuden gøres der rede for nogle af de teorier der støtter og begrunder arbejdsmåde og resultater i projektet...

  2. DNA supercoiling, a critical signal regulating the basal expression of the lac operon in Escherichia coli.

    Science.gov (United States)

    Fulcrand, Geraldine; Dages, Samantha; Zhi, Xiaoduo; Chapagain, Prem; Gerstman, Bernard S; Dunlap, David; Leng, Fenfei

    2016-01-01

    Escherichia coli lac repressor (LacI) is a paradigmatic transcriptional factor that controls the expression of lacZYA in the lac operon. This tetrameric protein specifically binds to the O1, O2 and O3 operators of the lac operon and forms a DNA loop to repress transcription from the adjacent lac promoter. In this article, we demonstrate that upon binding to the O1 and O2 operators at their native positions LacI constrains three (-) supercoils within the 401-bp DNA loop of the lac promoter and forms a topological barrier. The stability of LacI-mediated DNA topological barriers is directly proportional to its DNA binding affinity. However, we find that DNA supercoiling modulates the basal expression from the lac operon in E. coli. Our results are consistent with the hypothesis that LacI functions as a topological barrier to constrain free, unconstrained (-) supercoils within the 401-bp DNA loop of the lac promoter. These constrained (-) supercoils enhance LacI's DNA-binding affinity and thereby the repression of the promoter. Thus, LacI binding is superhelically modulated to control the expression of lacZYA in the lac operon under varying growth conditions. PMID:26763930

  3. DNA sequence of the lactose operon: the lacA gene and the transcriptional termination region.

    OpenAIRE

    Hediger, M A; Johnson, D F; Nierlich, D P; Zabin, I

    1985-01-01

    The lac operon of Escherichia coli spans approximately 5300 base pairs and includes the lacZ, lacY, and lacA genes in addition to the operator, promoter, and transcription termination regions. We report here the sequence of the lacA gene and the region distal to it, confirming the sequence of thiogalactoside transacetylase and completing the sequence of the lac operon. The lacA gene is characterized by use of rare codons, suggesting an origin from a plasmid, transposon, or virus gene. UUG is ...

  4. 1951 gill net studies : Des Lacs National Wildlife Refuge

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — Report on the gill net studies conducted on Des Lacs National Wildlife Refuge lakes. The net studies indicated that severe, if not complete, winter kill was...

  5. Preliminary fishery management report : Des Lacs National Wildlife Refuge

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — A study of fishery management at Des Lacs National Wildlife Refuge was conducted from June 18 to 20, 1952. This brief preliminary report will serve to highlight the...

  6. [Wildlife inventory plan : Des Lacs National Wildlife Refuge

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — This wildlife inventory plan describes methods for collecting migratory birds, upland birds, big game, predator, and small mammal surveys at Des Lacs National...

  7. Narrative report calendar year 1969 Des Lacs National Wildlife Refuge

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — This annual narrative report for Des Lacs National Wildlife Refuge outlines Refuge accomplishments during the 1969 calendar year. The report begins by summarizing...

  8. Narrative report calendar year 1970 Des Lacs National Wildlife Refuge

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — This annual narrative report for Des Lacs National Wildlife Refuge outlines Refuge accomplishments during the 1970 calendar year. The report begins by summarizing...

  9. Monthly narrative reports for the Des Lacs Wildlife Refuge, 1937

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — This narrative report for Des Lacs and Lostwood Migratory Waterfowl Refuges outlines Refuge accomplishments from January through April of 1937. The report begins by...

  10. 76 FR 68124 - Television Broadcasting Services; Fond du Lac, WI

    Science.gov (United States)

    2011-11-03

    ... From the Federal Register Online via the Government Publishing Office FEDERAL COMMUNICATIONS COMMISSION 47 CFR Part 73 Television Broadcasting Services; Fond du Lac, WI AGENCY: Federal Communications Commission. ACTION: Proposed rule. SUMMARY: In this document, the Commission denies a petition...

  11. Land use plan : Des Lacs National Wildlife Refuge

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — The purpose of this land use plan for Des Lacs National Wildlife Refuge is to outline the principal practices and procedures necessary to establish a reasonable...

  12. Narrative report calendar year 1967 Des Lacs National Wildlife Refuge

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — This annual narrative report for Des Lacs National Wildlife Refuge outlines Refuge accomplishments during the 1967 calendar year. The report begins by summarizing...

  13. Narrative report calendar year 1965 Des Lacs National Wildlife Refuge

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — This annual narrative report for Des Lacs National Wildlife Refuge outlines Refuge accomplishments during the 1965 calendar year. The report begins by summarizing...

  14. Narrative report calendar year 1964 Des Lacs National Wildlife Refuge

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — This annual narrative report for Des Lacs National Wildlife Refuge outlines Refuge accomplishments during the 1964 calendar year. The report begins by summarizing...

  15. Narrative report calendar year 1966 Des Lacs National Wildlife Refuge

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — This annual narrative report for Des Lacs National Wildlife Refuge outlines Refuge accomplishments during the 1966 calendar year. The report begins by summarizing...

  16. The use of lac-type promoters in control analysis

    DEFF Research Database (Denmark)

    Jensen, Peter Ruhdal; Westerhoff, H. v.; Michelsen, Ole

    1993-01-01

    , the tacI promoter when the latter is high. The endogenous lac operon is placed under the control of a second copy of the lacUV5 promoter and a lacYam mutation (eliminating lactose permease, the transport system for the inducer isopropyl-thio-beta-D-galactoside) is introduced. The method was...... demonstrated experimentally by constructing E. coli strains, in which the chromosomal atp operon is transcribed from the lacUV5 and the tacI promoter. We measured the concentration of the c subunit of H+-ATPase, and found that the expression of this enzyme could be modulated between non-detectable levels and...... up to five times the wild-type level. Thus, in the absence of inducer, no expression of atp genes could be detected when the atp operon was controlled by the lacUV5 promoter, and we estimate that the expression was less than 0.0025 times the wild-type level. We show that the introduction of a lac Y...

  17. The use of lac-type promoters in control analysis

    DEFF Research Database (Denmark)

    Jensen, Peter Ruhdal; Westerhoff, H. v.; Michelsen, Ole

    1993-01-01

    For control analysis, it is necessary to modulate the activity of an enzyme around its normal level and measure the changes in steady-state fluxes or concentrations. We describe an improved method for effecting the modulation, as elaborated for Escherichia coli. The chromosomal gene, encoding the...... enzyme of interest, is put under the control of a lacUV5 or a tacI promoter. The alternative use of the two promoters leads to an expression range which should make it suitable for the use in control analysis of many enzymes. The lacUV5 promoter should be used when the wild-type expression level is low......, the tacI promoter when the latter is high. The endogenous lac operon is placed under the control of a second copy of the lacUV5 promoter and a lacYam mutation (eliminating lactose permease, the transport system for the inducer isopropyl-thio-beta-D-galactoside) is introduced. The method was...

  18. Parsec-scale jet precession in BL Lacertae (2200+420)

    CERN Document Server

    Caproni, Anderson; Monteiro, Hektor

    2012-01-01

    BL Lacertae is the prototype of the BL Lac class of active galactic nuclei, exhibiting intensive activity on parsec (pc) scales, such as intense core variability and multiple ejections of jet components. In particular, in previous works the existence of precession motions in the pc-scale jet of BL Lacertae has been suggested. In this work we revisit this issue, investigating temporal changes of the observed right ascension and declination offsets of the jet knots in terms of our relativistic jet-precession model. The seven free parameters of our precession model were optimized via a heuristic cross-entropy method, comparing the projected precession helix with the positions of the jet components on the plane of the sky and imposing constraints on their maximum and minimum superluminal velocities. Our optimized best model is compatible with a jet having a bulk velocity of 0.9824c, which is precessing with a period of about 12.1 yr in the observer's reference frame and changing its orientation in relation to the...

  19. Lac du Flambeau Band of Lake Superior Chippewa Indians Strategic Energy Plan

    Energy Technology Data Exchange (ETDEWEB)

    Bryan Hoover

    2009-11-16

    This plan discusses the current energy use on the Lac du Flambeau Reservation, the current status of the Tribe's energy program, as well as the issues and concerns with energy on the reservation. This plan also identifies and outlines energy opportunities, goals, and objectives for the Tribe to accomplish. The overall goal of this plan is to address the energy situation of the reservation in a holistic manner for the maximum benefit to the Tribe. This plan is an evolving document that will be re-evaluated as the Tribe's energy situation changes.

  20. Dynamic model of gene regulation for the lac operon

    International Nuclear Information System (INIS)

    Gene regulatory network is a collection of DNA which interact with each other and with other matter in the cell. The lac operon is an example of a relatively simple genetic network and is one of the best-studied structures in the Escherichia coli bacteria. In this work we consider a deterministic model of the lac operon with a noise term, representing the stochastic nature of the regulation. The model is written in terms of a system of simultaneous first order differential equations with delays. We investigate an analytical and numerical solution and analyse the range of values for the parameters corresponding to a stable solution.

  1. Dynamic model of gene regulation for the lac operon

    Science.gov (United States)

    Angelova, Maia; Ben-Halim, Asma

    2011-03-01

    Gene regulatory network is a collection of DNA which interact with each other and with other matter in the cell. The lac operon is an example of a relatively simple genetic network and is one of the best-studied structures in the Escherichia coli bacteria. In this work we consider a deterministic model of the lac operon with a noise term, representing the stochastic nature of the regulation. The model is written in terms of a system of simultaneous first order differential equations with delays. We investigate an analytical and numerical solution and analyse the range of values for the parameters corresponding to a stable solution.

  2. Dynamic model of gene regulation for the lac operon

    OpenAIRE

    Angelova, Maia; Ben-Halim, Asma

    2011-01-01

    Gene regulatory network is a collection of DNA which interact with each other and with other matter in the cell. The lac operon is an example of a relatively simple genetic network and is one of the best-studied structures in the Escherichia coli bacteria. In this work we consider a deterministic model of the lac operon with a noise term, representing the stochastic nature of the regulation. The model is written in terms of a system of simultaneous first order differential equations with dela...

  3. In vivo expression of the lacY gene in two segments leads to functional lac permease

    International Nuclear Information System (INIS)

    The lacY gene of Escherichia coli was cut into two approximately equal-size fragments with Afl II and subcloned individually or together under separate lac operator/promoters in plasmid pT7-5. Under these conditions, lac permease is expressed in two portions: (i) the N-terminal portion (the N terminus, the first six putative transmembrane helices, and most of putative loop 7) and (ii) the C-terminal portion (the last six putative transmembrane helices and the C terminus). Cells harboring pT7-5 encoding both fragments transport lactose at about 30% the rate of cells expressing intact permease to a comparable steady-state level of accumulation. In contrast, cells expressing either half of the permease independently do not transport lactose. As judged by [35S]methionine labeling and immunoblotting, intact permease in completely absent from the membrane of cells expressing lacY fragments either individually or together. Thus, transport activity must result from an association between independently synthesized pieces of lac permease. When the gene fragments are expressed individually, the N-terminal portion of the permease is observed inconsistently, and the C-terminal portion is not observed. When the gene fragments are expressed together, polypeptides identified as the N- and C-terminal moieties of the permease are found in the membrane. It is concluded that the N- or C-terminal halves of lac permease are proteolyzed when synthesized independently and that association between the two complementing polypeptides leads to a more stable, catalytically active complex

  4. Isolation and characterization of purine regulatory mutants of Salmonella typhimurium with an episomal purE-lac fusion.

    OpenAIRE

    Thomulka, K W; Gots, J S

    1982-01-01

    Expression of the purE operon of Salmonella typhimurium was analyzed by using an Escherichia coli F' episome containing a purE-lac fusion. The fusion removes the lacOP and part of the lacZ genes of the lac operon and places the intact lacY and lacA genes under control of the purE operon as shown by inhibition of growth on melibiose (lacY) and repression of thiogalactoside transacetylase (lacA) by various purines. Two classes of regulatory-deficient mutants were found among those resistant to ...

  5. Plasmid insertion mutagenesis and lac gene fusion with mini-mu bacteriophage transposons.

    OpenAIRE

    Castilho, B A; Olfson, P; Casadaban, M J

    1984-01-01

    Small bacteriophage Mu transposable elements containing the lac operon structural genes were constructed to facilitate the isolation and use of Mu insertions and lac gene fusions. These mini-Mu elements have selectable genes for either ampicillin or kanamycin resistance and can be used to form both transcriptional and translational lac gene fusions. Some of the mini-Mu-lac elements constructed are deleted for the Mu A and B transposition genes and form stable insertions that cannot undergo tr...

  6. Structural explanation for allolactose (lac operon inducer) synthesis by lacZ β-galactosidase and the evolutionary relationship between allolactose synthesis and the lac repressor.

    Science.gov (United States)

    Wheatley, Robert W; Lo, Summie; Jancewicz, Larisa J; Dugdale, Megan L; Huber, Reuben E

    2013-05-01

    β-Galactosidase (lacZ) has bifunctional activity. It hydrolyzes lactose to galactose and glucose and catalyzes the intramolecular isomerization of lactose to allolactose, the lac operon inducer. β-Galactosidase promotes the isomerization by means of an acceptor site that binds glucose after its cleavage from lactose and thus delays its exit from the site. However, because of its relatively low affinity for glucose, details of this site have remained elusive. We present structural data mapping the glucose site based on a substituted enzyme (G794A-β-galactosidase) that traps allolactose. Various lines of evidence indicate that the glucose of the trapped allolactose is in the acceptor position. The evidence includes structures with Bis-Tris (2,2-bis(hydroxymethyl)-2,2',2″-nitrilotriethanol) and L-ribose in the site and kinetic binding studies with substituted β-galactosidases. The site is composed of Asn-102, His-418, Lys-517, Ser-796, Glu-797, and Trp-999. Ser-796 and Glu-797 are part of a loop (residues 795-803) that closes over the active site. This loop appears essential for the bifunctional nature of the enzyme because it helps form the glucose binding site. In addition, because the loop is mobile, glucose binding is transient, allowing the release of some glucose. Bioinformatics studies showed that the residues important for interacting with glucose are only conserved in a subset of related enzymes. Thus, intramolecular isomerization is not a universal feature of β-galactosidases. Genomic analyses indicated that lac repressors were co-selected only within the conserved subset. This shows that the glucose binding site of β-galactosidase played an important role in lac operon evolution. PMID:23486479

  7. LOBI-BL-40: an approach to the SGTR phenomenology in a one loop PWR

    International Nuclear Information System (INIS)

    The aim of the ''LOBI-BL-40'' project is to study the phenomena and the recovery techniques involved in Steam Generator Tube Rupture (SGTR) events in a commercial single-loop PWR plant. Experimental support for the project will be provided by the BL-40 experiment, to be carried out at the LOBI installation (JRC, Ispra-Varese, Italy). This paper describes the project, its objectives, the activities involved and the progress made, with special attention to specification of the BL-40 experiments. The work is being undertaken by the Spanish utility UNION-FENOSA. (author)

  8. A single mutation in the core domain of the lac repressor reduces leakiness

    NARCIS (Netherlands)

    Gatti-Lafranconi, Pietro; Dijkman, Willem; Devenish, Sean RA; Hollfelder, Florian

    2013-01-01

    The lac operon provides cells with the ability to switch from glucose to lactose metabolism precisely when necessary. This metabolic switch is mediated by the lac repressor (LacI), which in the absence of lactose binds to the operator DNA sequence to inhibit transcription. Allosteric rearrangements

  9. [Monopolization of honeydew sources by Crematogaster macaoensis and its effects on lac production].

    Science.gov (United States)

    Wang, Si-Ming; Chen, You-Qing; Lu, Zhi-Xing; Liu, Chun-Ju; Zhang, Wei; Guo, Zu-Xue

    2011-01-01

    From October 2008 to May 2010, an investigation was made in a lac plantation in Yayi region of Mojiang County, Yunnan Province, China, aimed to understand the behavior of the monopolization of honeydew sources by ant Crematogaster macaoensis, and its effects on the sex ratio, mortality, fecundity, and lac production of Yunnan lac insect Kerria yunnanensis. The results showed that C. macaoensis fed and monopolized the honeydews around the clock during the whole life cycle of K. yunnanensis on the stick-lac, and the average number of visiting C. macaoensis ranged from 16.8 +/- 2.3 to 39.3 +/- 10.0 per 10 cm length of the stick-lac. C. macaoensis constructed shelters to prevent other animals from visiting the lac insect. C. macaoensis monopolization reduced the lac production of individual K. yunnanensi significantly, but had no significant effects on the lac production of whole lac insect colony. In addition, C. macaoensis monopolization reduced the mortality of K. yunnanensis significantly, and increased the percentage of K. yunnanensis females and the adult female fecundity. It was concluded that ant monopolization of the lac insect honeydew seemed to be beneficial to the lac production by the Yunnan lac insect. PMID:21548313

  10. Development of a Lac Operon Concept Inventory (LOCI).

    Science.gov (United States)

    Stefanski, Katherine M; Gardner, Grant E; Seipelt-Thiemann, Rebecca L

    2016-01-01

    Concept inventories (CIs) are valuable tools for educators that assess student achievement and identify misconceptions held by students. Results of student responses can be used to adjust or develop new instructional methods for a given topic. The regulation of gene expression in both prokaryotes and eukaryotes is an important concept in genetics and one that is particularly challenging for undergraduate students. As part of a larger study examining instructional methods related to gene regulation, the authors developed a 12-item CI assessing student knowledge of the lac operon. Using an established protocol, the authors wrote open-ended questions and conducted in-class testing with undergraduate microbiology and genetics students to discover common errors made by students about the lac operon and to determine aspects of item validity. Using these results, we constructed a 12-item multiple-choice lac operon CI called the Lac Operon Concept Inventory (LOCI), The LOCI was reviewed by two experts in the field for content validity. The LOCI underwent item analysis and was assessed for reliability with a sample of undergraduate genetics students (n = 115). The data obtained were found to be valid and reliable (coefficient alpha = 0.994) with adequate discriminatory power and item difficulty. PMID:27252300

  11. Modeling network dynamics: the lac operon, a case study

    OpenAIRE

    Vilar, J. M. G.; Guet, C. C.; Leibler, S

    2004-01-01

    We use the lac operon in Escherichia coli as a prototype system to illustrate the current state, applicability, and limitations of modeling the dynamics of cellular networks. We integrate three different levels of description -molecular, cellular, and that of cell population- into a single model, which seems to capture many experimental aspects of the system.

  12. Development of a Lac Operon Concept Inventory (LOCI)

    Science.gov (United States)

    Stefanski, Katherine M.; Gardner, Grant E.; Seipelt-Thiemann, Rebecca L.

    2016-01-01

    Concept inventories (CIs) are valuable tools for educators that assess student achievement and identify misconceptions held by students. Results of student responses can be used to adjust or develop new instructional methods for a given topic. The regulation of gene expression in both prokaryotes and eukaryotes is an important concept in genetics and one that is particularly challenging for undergraduate students. As part of a larger study examining instructional methods related to gene regulation, the authors developed a 12-item CI assessing student knowledge of the lac operon. Using an established protocol, the authors wrote open-ended questions and conducted in-class testing with undergraduate microbiology and genetics students to discover common errors made by students about the lac operon and to determine aspects of item validity. Using these results, we constructed a 12-item multiple-choice lac operon CI called the Lac Operon Concept Inventory (LOCI), The LOCI was reviewed by two experts in the field for content validity. The LOCI underwent item analysis and was assessed for reliability with a sample of undergraduate genetics students (n = 115). The data obtained were found to be valid and reliable (coefficient alpha = 0.994) with adequate discriminatory power and item difficulty. PMID:27252300

  13. GENERALIZED FUZZY FILTERS OF BL-ALGEBRAS

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    The concept of quasi-coincidence of a fuzzy interval value with an interval valued fuzzy set is considered. In fact, this is a generalization of quasi-coincidence of a fuzzy point with a fuzzy set. By using this new idea, the notion of interval valued (∈, ∈∨q)-fuzzy filters in BL-algebras which is a generalization of fuzzy filters of BL-algebras, is defined, and related properties are investigated. In particular, the concept of a fuzzy subgroup with thresholds is extended to the concept of an interval valued fuzzy filter with thresholds in BL-algebras.

  14. Galactic membership of BL Her type variable stars

    CERN Document Server

    Jurkovic, Monika I; Ninković, Slobodan

    2016-01-01

    As the RR Lyrae stars evolve on the Hertzsprung-Russell diagram they are believed to become short period Type II Cepheids, known as BL Her type (with a pulsation period from $1$ to $3-8$ days). Assuming that their mass is around $0.5 - 0.6 {\\rm M}_{\\odot}$, and that they are low metallicity objects, they were thought to belong to the halo of the Milky Way. We investigated seven Galactic short period Type II Cepheids (BL Her, SW Tau, V553 Cen, DQ And, BD Cas, V383 Cyg, and KT Com) in order to establish their membership within the Galactic structure using the kinematic approach. $Gaia$ should provide us with more data needed to conduct the study of the whole sample.

  15. Phosphorylation of Streptococcus salivarius Lactose Permease (LacS) by HPr(His∼P) and HPr(Ser-P)(His∼P) and Effects on Growth

    Science.gov (United States)

    Lessard, Christian; Cochu, Armelle; Lemay, Jean-Dominique; Roy, Denis; Vaillancourt, Katy; Frenette, Michel; Moineau, Sylvain; Vadeboncoeur, Christian

    2003-01-01

    The oral bacterium Streptococcus salivarius takes up lactose via a transporter called LacS that shares 95% identity with the LacS from Streptococcus thermophilus, a phylogenetically closely related organism. S. thermophilus releases galactose into the medium during growth on lactose. Expulsion of galactose is mediated via LacS and stimulated by phosphorylation of the transporter by HPr(His∼P), a phosphocarrier of the phosphoenolpyruvate:sugar phosphotransferase transport system (PTS). Unlike S. thermophilus, S. salivarius grew on lactose without expelling galactose and took up galactose and lactose concomitantly when it is grown in a medium containing both sugars. Analysis of the C-terminal end of S. salivarius LacS revealed a IIA-like domain (IIALacS) almost identical to the IIA domain of S. thermophilus LacS. Experiments performed with purified proteins showed that S. salivarius IIALacS was reversibly phosphorylated on a histidine residue at position 552 not only by HPr(His∼P) but also by HPr(Ser-P)(His∼P), a doubly phosphorylated form of HPr present in large amounts in rapidly growing S. salivarius cells. Two other major S. salivarius PTS proteins, IIABLMan and IIABHMan, were unable to phosphorylate IIALacS. The effect of LacS phosphorylation on growth was studied with strain G71, an S. salivarius enzyme I-negative mutant that cannot synthesize HPr(His∼P) or HPr(Ser-P)(His∼P). These results indicated that (i) the wild-type and mutant strains had identical generation times on lactose, (ii) neither strain expelled galactose during growth on lactose, (iii) both strains metabolized lactose and galactose concomitantly when grown in a medium containing both sugars, and (iv) the growth of the mutant was slightly reduced on galactose. PMID:14617640

  16. Transcription and decay of the lac messenger: role of an intergenic terminator.

    OpenAIRE

    Murakawa, G J; Kwan, C; Yamashita, J; Nierlich, D P

    1991-01-01

    Prior work has indicated that the polycistronic lacZYA mRNA of Escherichia coli is cleaved during decay at approximately intergenic sites (L. W. Lim and D. Kennell, J. Mol. Biol. 135: 369-390, 1979). In this work, we characterized the products by using probes specific for the different cistrons. This analysis indicated that six lac mRNA species are present in the following order of decreasing abundance: lacZ, -A, -ZYA, -ZY, -YA, and -Y. Very little lacYA and lacY mRNAs were present, whereas i...

  17. Expression of lacZ from the Promoter of the Escherichia coli spc Operon Cloned into Vectors Carrying the W205 trp-lac Fusion

    OpenAIRE

    Liang, Sung-Tzu; Dennis, Patrick P.; Bremer, Hans

    1998-01-01

    The expression of lacZ has been analyzed and compared in a series of promoter cloning vectors by measuring the amount of lacZ mRNA by hybridization and the amount of β-galactosidase by standard enzymatic assay. Expression was driven by the promoter, Pspc, of the spc ribosomal protein operon. The vectors contained either the standard W205 trp-lac fusion with the trp operon transcription terminator, trpt, located in the lacZ leader sequence, or a deletion derivative that functionally inactivate...

  18. The lac operon of Lactobacillus casei contains lacT, a gene coding for a protein of the Bg1G family of transcriptional antiterminators.

    OpenAIRE

    Alpert, C A; Siebers, U

    1997-01-01

    The 5' region of the lac operon of Lactobacillus casei has been investigated. An open reading frame of 293 codons, designated lacT, was identified upstream of lacE. The gene product encoded by lacT is related to the family of transcriptional antiterminator proteins, which includes BglG from Escherichia coli, ArbG from Erwinia chrysanthemi, SacT, SacY, and LicT from Bacillus subtilis, and BglR from Lactococcus lactis. Amino acid sequence identities range from 35 to 24%, while similarities rang...

  19. Varieties Generated by Standard BL-algebras

    Czech Academy of Sciences Publication Activity Database

    Haniková, Zuzana

    2014-01-01

    Roč. 31, č. 1 (2014), s. 15-33. ISSN 0167-8094 R&D Projects: GA ČR GAP202/10/1826 Institutional research plan: CEZ:AV0Z10300504 Institutional support: RVO:67985807 Keywords : substructural logic * fuzzy logic * BL * standard BL- algebra * variety of algebra s Subject RIV: BA - General Mathematics Impact factor: 0.621, year: 2014

  20. Comparative genomics and experimental evolution of Escherichia coli BL21(DE3) strains reveal the landscape of toxicity escape from membrane protein overproduction.

    Science.gov (United States)

    Kwon, Soon-Kyeong; Kim, Seong Keun; Lee, Dae-Hee; Kim, Jihyun F

    2015-01-01

    Achieving sufficient yields of proteins in their functional form represents the first bottleneck in contemporary bioscience and biotechnology. To accomplish successful overexpression of membrane proteins in a workhorse organism such as E. coli, defined and rational optimization strategies based on an understanding of the genetic background of the toxicity-escape mechanism are desirable. To this end, we sequenced the genomes of E. coli C41(DE3) and its derivative C43(DE3), which were developed for membrane protein production. Comparative analysis of their genomes with those of their ancestral strain E. coli BL21(DE3) revealed various genetic changes in both strains. A series of E. coli variants that are able to tolerate transformation with or overexpression of membrane proteins were generated by in vitro evolution. Targeted sequencing of the evolved strains revealed the mutational hotspots among the acquired genetic changes. By these combinatorial approaches, we found non-synonymous changes in the lac repressor gene of the lac operon as well as nucleotide substitutions in the lacUV5 promoter of the DE3 region, by which the toxic effect to the host caused by overexpression of membrane proteins could be relieved. A mutation in lacI was demonstrated to be crucial for conferring tolerance to membrane protein overexpression. PMID:26531007

  1. Long-term optical and radio variability of BL Lacertae

    Science.gov (United States)

    Guo, Y. C.; Hu, S. M.; Xu, C.; Liu, C. Y.; Chen, X.; Guo, D. F.; Meng, F. Y.; Xu, M. T.; Xu, J. Q.

    2015-04-01

    Well-sampled optical and radio light curves of BL Lacertae in B, V, R, I bands and 4.8, 8.0, 14.5 GHz from 1968 to 2014 were presented in this paper. A possible 1.26 ± 0.05 yr period in optical bands and a 7.50 ± 0.15 yr period in radio bands were detected based on discrete correlation function, structure function as well as Jurkevich method. Correlations among different bands were also analyzed and no reliable time delay was found between optical bands. Very weak correlations were detected between V band and radio bands. However, in radio bands the variation at low frequency lagged that at high frequency obviously. The spectrum of BL Lacertae turned mildly bluer when the object turned brighter, and stronger bluer-when-brighter trends were found for short flares. A scenario including a precessing helical jet and periodic shocks was put forward to interpret the variation characteristics of BL Lacertae.

  2. Direct observation of a 91 bp LacI-mediated, negatively supercoiled DNA loop by atomic force microscope.

    Science.gov (United States)

    Fulcrand, Geraldine; Chapagain, Prem; Dunlap, David; Leng, Fenfei

    2016-03-01

    Escherichia coli lactose repressor (LacI), a tetrameric protein, is a paradigmatic transcriptional factor that controls the expression of lacZYA in the lac operon. It specifically binds to the O1, O2, and O3 operators of the lac promoter, forms DNA loops, and regulates transcription of the lac operon. In this article, utilizing combined techniques of DNA-nicking assay and AFM imaging, we directly observed a 91 bp LacI-mediated, negatively supercoiled DNA loop mimicking the DNA loop between the O1 and O3 operators in the lac promoter. PMID:26878689

  3. Evolution and Biophysics of the Escherichia coli lac Operon

    Science.gov (United States)

    Ray, J. Christian; Igoshin, Oleg; Quan, Selwyn; Monds, Russell; Cooper, Tim; Balázsi, Gábor

    2011-03-01

    To understand, predict, and control the evolution of living organisms, we consider biophysical effects and molecular network architectures. The lactose utilization system of E. coli is among the most well-studied molecular networks in biology, making it an ideal candidate for such studies. Simulations show how the genetic architecture of the wild-type operon attenuates large metabolic intermediate fluctuations that are predicted to occur in an equivalent system with the component genes on separate operons. Quantification of gene expression in the lac operon evolved in growth conditions containing constant lactose, alternating with glucose, or constant glucose, shows characteristic gene expression patterns depending on conditions. We are simulating these conditions to show context-dependent biophysical sources and costs of different lac operon architectures.

  4. Positive and Negative Control of the Lac Operon

    Science.gov (United States)

    Qaddour, Jihad S.; Werman, Steven D.; Misra, Prasanta K.

    1997-03-01

    We present a mathematical model for the positive and negative control of lac operon. We investigate a steady state solution for the coupled nonlinear differential equations representing the dynamic behaviors of the repressor-inducer components of negative control as well as the cyclic AMP receptor components of the positive control. A dimensionless derivation of the lac operon system is employed to produce singularly perturbed models. The first model represents the dynamical behavior of the operator while the slow model represents the dynamical behaviors of the inducer and the repressor. We use the singular perturbation theory to show that the behavior of the system can be described as a rapid on-off switch of structural gene transformation.

  5. Wind Resource Assessment Report: Mille Lacs Indian Reservation, Minnesota

    Energy Technology Data Exchange (ETDEWEB)

    Jimenez, A. C.

    2013-12-01

    The U.S. Environmental Protection Agency (EPA) launched the RE-Powering America's Land initiative to encourage development of renewable energy on potentially contaminated land and mine sites. EPA collaborated with the U.S. Department of Energy's (DOE's) National Renewable Energy Laboratory (NREL) and the Mille Lacs Band of Chippewa Indians to evaluate the wind resource and examine the feasibility of a wind project at a contaminated site located on the Mille Lacs Indian Reservation in Minnesota. The wind monitoring effort involved the installation of a 60-m met tower and the collection of 18 months of wind data at multiple heights above the ground. This report focuses on the wind resource assessment, the estimated energy production of wind turbines, and an assessment of the economic feasibility of a potential wind project sited this site.

  6. A geological survey of the Lac du Bonnet batholith, Manitoba

    International Nuclear Information System (INIS)

    This report presents the results of a geological survey of the Lac du Bonnet batholith in Manitoba. The survey consisted of field mapping of the lithologies and the joint systems throughout the batholith, and the examination of lineaments identified on aerial photographs and Landsat imagery. Petrographic descriptions and a map of the lithologies, an analysis of the fracture systems and a lineament map are presented. The results of various regional geophysical surveys were used as an aid to the interpretation of the batholith's contacts and in the interpretation of lineaments as possible faults. A comparison of the Lac du Bonnet Batholith with the Eye-Dashwa Lakes Pluton near Atikokan, Ontario is also presented

  7. Lac Courte Oreilles Hydro Dam Assessment

    Energy Technology Data Exchange (ETDEWEB)

    Weaver, Jason [Lac Courte Oreilles, Hayward, WI (United States); Meyers, Amy [Kiser Hydro, LLC, Norway, MI (United States)

    2014-12-31

    The main objective of this project was to investigate upgrading the existing hydro power generating system at the Winter Dam. The tribe would like to produce more energy and receive a fair market power purchase agreement so the dam is no longer a drain on our budget but a contributor to our economy. We contracted Kiser Hydro, LLC Engineering for this project and received an engineering report that includes options for producing more energy with cost effective upgrades to the existing turbines. Included in this project was a negotiation of energy price sales negotiations.

  8. Induction of the lac carrier and an associated membrane protein in Escherichia coli

    International Nuclear Information System (INIS)

    Induction of the lac operon in wild type Escherichia coli strains results in synthesis of a 16 kilodalton inner membrane protein in addition to the known products of the lacZ, lacY and lacA genes. Cells carrying the lacY gene on a plasmid over produce this 16 kilodalton polypeptide as well as the Lac carrier, the membrane protein product of the lacY gene. However, [35S]methionine labeling of minicells carrying the lacY plasmid shows that the 16 kDa protein is not synthesized from the plasmid DNA. The 16 kDa protein was purified and partially characterized. It is an acidic membrane protein of apparent molecular weight 15,800 whose amino terminal sequence (NH2-Met-Arg-Asn-Phe-Asp-Leu-) does not correspond to any nucleotide sequence known in lac operon DNA. Using antibody prepared to the purified 16 kDa protein, a quantitative analysis of conditions under which this protein is made was accomplished, and reveals that the amount of 16 kDa protein which appears in the membrane is proportional to lac operon expression. Hybridization of a synthetic oligonucleotide probe complementary to the 5' end of 16 kDa protein mRNA shows that its synthesis is regulated at the level of transcription. A description of attempts to clone this gene is given. Possible functional roles for the 16 kDa protein are discussed

  9. Du Lac de Geneve au Lac Baikal: deux metropoles en construction

    Directory of Open Access Journals (Sweden)

    Guy Mettan

    2006-08-01

    Full Text Available En apparence, Geneve et Irkutsk n'ont rien en commun. A part une amitie reciproque et la proximite d'un lac, il est difficile de trouver des points communs entre la Suisse francophone, dont Geneve est la ville le plus importante, et la Siberie centrale, dont Irkutsk, est la capitale. Et pourtant les deux regions, malgre les differences de taille, de densite de la population, de climat, d'economie et de traditions culturelles, sont confrontees au meme probleme: elles sont trop petites et trop limitees pour assurer, avec leurs seuls moyens, leur avenir et elles doivent imperativement s'unir a des villes voisines pour renforcer leur statut de metropole regionale et s'imposer face aux regions et aux pays concurrents.C'est ainsi qu'Irkutsk projette de s'unir aux villes voisines d'Angarsk et de Chelekhov pour constituer une megapole au c?ur de la Siberie, tandis qu'a Geneve le debat fait rage pour trouver des solutions a l'exiguite geographique et a l'insuffisance des moyens face aux grandes regions metropolitaines de France, d'Italie et d'Allemagne.Ce debat est propre a toute la Suisse. Malgre sa petitesse, la Suisse est divisee en 26 cantons. Ces unites administratives sont jugees trop couteuses, trop petites, trop lourdes et trop compliquees pour assurer l'avenir economique et meme politique du pays. De nombreux groupes de reflexion proposent donc de reduire ce nombre a 3, 5 ou 10 grandes provinces selon les cas. En Suisse, romande, il y a dix ans, des mouvements politiques ont meme lance l'idee de fusionner les cantons de Vaud (dont Lausanne est la capitale et de Geneve. Mais l'echec a ete fracassant : le peuple des deux cantons a refuse cette option a 80% des voix. On cherche donc d'autres solutions.Les discussions s'orientent desormais autour de la constitution d'une grande metropole lemanique qui regrouperait les deux grandes villes de Geneve et Lausanne et les villes plus petites de Montreux, Vevey, Nyon ainsi que la ville francaise d

  10. THE FIRST FERMI MULTIFREQUENCY CAMPAIGN ON BL LACERTAE: CHARACTERIZING THE LOW-ACTIVITY STATE OF THE EPONYMOUS BLAZAR

    International Nuclear Information System (INIS)

    We report on observations of BL Lacertae during the first 18 months of Fermi LAT science operations and present results from a 48 day multifrequency coordinated campaign from 2008 August 19 to 2008 October 7. The radio to gamma-ray behavior of BL Lac is unveiled during a low-activity state thanks to the coordinated observations of radio-band (Metsaehovi and VLBA), near-IR/optical (Tuorla, Steward, OAGH, and MDM), and X-ray (RXTE and Swift) observatories. No variability was resolved in gamma rays during the campaign, and the brightness level was 15 times lower than the level of the 1997 EGRET outburst. Moderate and uncorrelated variability has been detected in UV and X-rays. The X-ray spectrum is found to be concave, indicating the transition region between the low- and high-energy components of the spectral energy distribution (SED). VLBA observation detected a synchrotron spectrum self-absorption turnover in the innermost part of the radio jet appearing to be elongated and inhomogeneous, and constrained the average magnetic field there to be less than 3 G. Over the following months, BL Lac appeared variable in gamma rays, showing flares (in 2009 April and 2010 January). There is no evidence for the correlation of gamma rays with the optical flux monitored from the ground in 18 months. The SED may be described by a single-zone or a two-zone synchrotron self-Compton (SSC) model, but a hybrid SSC plus external radiation Compton model seems to be preferred based on the observed variability and the fact that it provides a fit closest to equipartition.

  11. Chaos in hydrodynamic BL Herculis models

    CERN Document Server

    Smolec, R

    2014-01-01

    We present non-linear, convective, BL Her-type hydrodynamic models that show complex variability characteristic for deterministic chaos. The bifurcation diagram reveals a rich structure, with many phenomena detected for the first time in hydrodynamic models of pulsating stars. The phenomena include not only period doubling cascades en route to chaos (detected in earlier studies) but also periodic windows within chaotic band, type-I and type-III intermittent behaviour, interior crisis bifurcation and others. Such phenomena are known in many textbook chaotic systems, from the simplest discrete logistic map, to more complex systems like Lorenz equations. We discuss the physical relevance of our models. Although except of period doubling such phenomena were not detected in any BL Her star, chaotic variability was claimed in several higher luminosity siblings of BL Her stars - RV Tau variables, and also in longer-period, luminous irregular pulsators. Our models may help to understand these poorly studied stars. Pa...

  12. Chemo-enzymatic modification of poly-N-acetyllactosamine (LacNAc oligomers and N,N-diacetyllactosamine (LacDiNAc based on galactose oxidase treatment

    Directory of Open Access Journals (Sweden)

    Christiane E. Kupper

    2012-05-01

    Full Text Available The importance of glycans in biological systems is highlighted by their various functions in physiological and pathological processes. Many glycan epitopes on glycoproteins and glycolipids are based on N-acetyllactosamine units (LacNAc; Galβ1,4GlcNAc and often present on extended poly-LacNAc glycans ([Galβ1,4GlcNAc]n. Poly-LacNAc itself has been identified as a binding motif of galectins, an important class of lectins with functions in immune response and tumorigenesis. Therefore, the synthesis of natural and modified poly-LacNAc glycans is of specific interest for binding studies with galectins as well as for studies of their possible therapeutic applications. We present the oxidation by galactose oxidase and subsequent chemical or enzymatic modification of terminal galactose and N-acetylgalactosamine residues of poly-N-acetyllactosamine (poly-LacNAc oligomers and N,N-diacetyllactosamine (LacDiNAc by galactose oxidase. Product formation starting from different poly-LacNAc oligomers was characterised and optimised regarding formation of the C6-aldo product. Further modification of the aldehyde containing glycans, either by chemical conversion or enzymatic elongation, was established. Base-catalysed β-elimination, coupling of biotin–hydrazide with subsequent reduction to the corresponding hydrazine linkage, and coupling by reductive amination to an amino-functionalised poly-LacNAc oligomer were performed and the products characterised by LC–MS and NMR analysis. Remarkably, elongation of terminally oxidised poly-LacNAc glycans by β3GlcNAc- and β4Gal-transferase was also successful. In this way, a set of novel, modified poly-LacNAc oligomers containing terminally and/or internally modified galactose residues were obtained, which can be used for binding studies and various other applications.

  13. Use of lac regulatory elements for gene expression in Lactobacillus casei

    OpenAIRE

    Gosalbes, María; Pérez-Arellano, Isabel; Esteban, Carlos; GalÁn, José; Pérez-Martínez, Gaspar

    2001-01-01

    Usage des éléments régulateurs de l'opéron lactose pour l'expression de gènes chez Lactobacillus casei . Les gènes du lactose Lactobacillus casei ssp. casei ATCC393 [ pLZ15$^-$] sont regroupés dans un même opéron, lacTEGF, codant pour un antiterminateur (LacT), pour les éléments spécifiques du transport du lactose par le système phosphotransferase dépendant du phosphoénolpyruvate (PTS) (LacE et LacF) et pour une phospho-$\\beta$-galactosidase (LacG). L'opéron lac est soumis à une répression pa...

  14. Cloning and expression of human papilloma virus type 6b-L1 gene

    Directory of Open Access Journals (Sweden)

    Lie-hua DENG

    2011-03-01

    Full Text Available Objective To investigate the expression of green fluorescent protein plasmid of human papilloma virus 6b L1 gene(HPV6bL1 in eukaryotic cells.Methods The L1 gene of PQE40-HPV6bL1 was amplified by PCR,purified by restriction enzyme digestion,and then connected to eukaryotic expression plasmid PEGFP-C1.The recombinant expression vector was then transformed into E.coli DH5a,which was identified by BamH Ⅰ and Hand Ⅲ digestion and the positive vector was selected.The recombinant plasmid PEGFP-HPV6bL1 was transfected into COS-7 cells by liposomal transfection technique and the expression of fusion protein was observed under fluorescence microscope.The generation of HPV6bL1 mRNA was detected by RT-PCR.Results Identification of PEGFP-HPV6bL1 by enzyme digestion and sequencing showed that the length,direction and inserted location of target,which was inserted into the recombinant,was correct and the expression of EGFP in transfected cell was observed.Conclusions A new type of green fluorescent HPV6bL1 eukaryotic expression system has been established.It may provide a research foundation for the study of the protein.

  15. Quality and position of the three lac operators of E. coli define efficiency of repression.

    OpenAIRE

    Oehler, S; Amouyal, M; Kolkhof, P.; von Wilcken-Bergmann, B; Müller-Hill, B

    1994-01-01

    Repression of the lac promoter may be achieved in two different ways: either by interference with the action of RNA polymerase or by interference with CAP activation. We investigated cooperative repression of the Escherichia coli lac operon by systematic conversion of its three natural operators (O1, O2 and O3) on the chromosome. We find that cooperative repression by tetrameric Lac repressor increases with both quality and proximity of the interacting operators. A short distance of 92 bp all...

  16. Aspartoacylase-lacZ knockin mice: an engineered model of Canavan disease.

    Directory of Open Access Journals (Sweden)

    Nadine Mersmann

    Full Text Available Canavan Disease (CD is a recessive leukodystrophy caused by loss of function mutations in the gene encoding aspartoacylase (ASPA, an oligodendrocyte-enriched enzyme that hydrolyses N-acetylaspartate (NAA to acetate and aspartate. The neurological phenotypes of different rodent models of CD vary considerably. Here we report on a novel targeted aspa mouse mutant expressing the bacterial β-Galactosidase (lacZ gene under the control of the aspa regulatory elements. X-Gal staining in known ASPA expression domains confirms the integrity of the modified locus in heterozygous aspa lacZ-knockin (aspa(lacZ/+ mice. In addition, abundant ASPA expression was detected in Schwann cells. Homozygous (aspa(lacZ/lacZ mutants are ASPA-deficient, show CD-like histopathology and moderate neurological impairment with behavioural deficits that are more pronounced in aspa(lacZ/lacZ males than females. Non-invasive ultrahigh field proton magnetic resonance spectroscopy revealed increased levels of NAA, myo-inositol and taurine in the aspa(lacZ/lacZ brain. Spongy degeneration was prominent in hippocampus, thalamus, brain stem, and cerebellum, whereas white matter of optic nerve and corpus callosum was spared. Intracellular vacuolisation in astrocytes coincides with axonal swellings in cerebellum and brain stem of aspa(lacZ/lacZ mutants indicating that astroglia may act as an osmolyte buffer in the aspa-deficient CNS. In summary, the aspa(lacZ mouse is an accurate model of CD and an important tool to identify novel aspects of its complex pathology.

  17. Allostery in the LacI/GalR Family: Variations on a Theme

    OpenAIRE

    Swint-Kruse, Liskin; Matthews, Kathleen S.

    2009-01-01

    The lactose repressor protein (LacI) was among the very first genetic regulatory proteins discovered, and more than 1000 members of the bacterial LacI/GalR family are now identified. LacI has been the prototype for understanding how transcription is controlled using small metabolites to modulate protein association with specific DNA sites. This understanding has been greatly expanded by the study of other LacI/GalR homologues. A general picture emerges in which the conserved fold provides a s...

  18. Mapping DNA-Lac repressor interaction with ultra-fast optical tweezers

    Science.gov (United States)

    Monico, Carina; Tempestini, Alessia; Vanzi, Francesco; Pavone, Francesco S.; Capitanio, Marco

    2015-03-01

    The lac operon is a well-known example of gene expression regulation, based on the specific interaction of Lac repressor protein (LacI) with its target DNA sequence (operator). We recently developed an ultrafast force-clamp laser trap technique capable of probing molecular interactions with sub-ms temporal resolution, under controlled pN-range forces. With this technique, we tested the interaction of LacI with different DNA constructs. Based on position along the DNA sequence, the observed interactions can be interpreted as specific binding to operator sequences and transient interactions with nonspecific sequences.

  19. Expression of Ty-lacZ fusions in Saccharomyces cerevisiae.

    OpenAIRE

    Bowen, B A; Fulton, A.M.; Tuite, M F; Kingsman, S M; Kingsman, A J

    1984-01-01

    We have determined the nucleotide sequence of about 520 bp spanning the 5' delta regions (Figure 1) of two Tyl elements. There is an open reading frame running out of the deltas for at least 180 nucleotides into the internal region of each element. The functional significance of these open reading frames has been tested by fusing them to a defective E.coli lacZ gene. Expression of B-galactosidase in yeast transformants containing these fusions shows that Tyl elements contain functional transl...

  20. A mutant Ebg enzyme that converts lactose into an inducer of the lac operon.

    OpenAIRE

    Rolseth, S J; Fried, V A; Hall, B G

    1980-01-01

    Lactose is not itself an inducer of the lac operon, nor is it converted to an inducer by ebg+ beta-galactosidase of Escherichia coli. We report here the isolation of a mutant Ebg beta-galactosidase which is capable of converting lactose into an inducer of the lac operon.

  1. Mu dX, a derivative of Mu d1 (lac Apr) which makes stable lacZ fusions at high temperature.

    OpenAIRE

    Baker, T A; Howe, M M; Gross, C A

    1983-01-01

    We describe defective Mu phage Mu dX (Mu d1 Bx::Tn9 [lac Apr Cmr]) which is useful for insertion mutagenesis and for construction of lac operon fusions in vivo. Mu dX retains the insertion properties of Mu d1 but produces temperature-resistant lysogens and transposes at a reduced frequency. A method is described to convert existing Mu d1 insertions to Mu dX.

  2. Deterministic and stochastic population-level simulations of an artificial lac operon genetic network

    OpenAIRE

    Zygourakis Kyriacos; Stamatakis Michail

    2011-01-01

    Abstract Background The lac operon genetic switch is considered as a paradigm of genetic regulation. This system has a positive feedback loop due to the LacY permease boosting its own production by the facilitated transport of inducer into the cell and the subsequent de-repression of the lac operon genes. Previously, we have investigated the effect of stochasticity in an artificial lac operon network at the single cell level by comparing corresponding deterministic and stochastic kinetic mode...

  3. Characterization of the Lactococcus lactis lactose operon promoter: contribution of flanking sequences and LacR repressor to promoter activity.

    OpenAIRE

    van Rooijen, R J; Gasson, M. J.; de Vos, W M

    1992-01-01

    We determined the location, activity, and regulation of the promoter of the Lactococcus lactis 8-kb lactose operon (lacABCDFEGX), which encodes the enzymes of the lactose phosphotransferase system and the tagatose 6-phosphate pathway. The lac promoter sequence corresponds closely to the consensus promoter described for gram-positive bacteria and is located in a back-to-back configuration with the promoter of the divergently transcribed lacR gene, which encodes the LacR repressor. The transcri...

  4. Nucleotide and deduced amino acid sequences of the lacR, lacABCD, and lacFE genes encoding the repressor, tagatose 6-phosphate gene cluster, and sugar-specific phosphotransferase system components of the lactose operon of Streptococcus mutans.

    OpenAIRE

    Rosey, E L; Stewart, G. C.

    1992-01-01

    The complete nucleotide sequences of lacRABCDF and partial nucleotide sequence of lacE from the lactose operon of Streptococcus mutans are presented. Comparison of the streptococcal lac determinants with those of Staphylococcus aureus and Lactococcus lactis indicate exceptional protein and nucleotide identity. The deduced polypeptides also demonstrate significant, but lower, sequence similarity with the corresponding lactose proteins of Lactobacillus casei. Additionally, LacR has sequence hom...

  5. The gBL transport equations

    International Nuclear Information System (INIS)

    The transport equations arising from the ''generalized Balescu- Lenard'' (gBL) collision operator are obtained, and some of their properties examined. The equations contain neoclassical and turbulent transport as two special cases, having the same structure. The resultant theory offers potential explanation for a number of results not well understood, including the anomalous pinch, observed ratios of Q/ΓT on TFTR, and numerical reproduction of ASDEX profiles by a model for turbulent transport invoked without derivation, but by analogy to neoclassical theory. The general equations are specialized to consideration of a number of particular transport mechanisms of interest. 10 refs

  6. lac Repressor Is an Antivirulence Factor of Salmonella enterica: Its Role in the Evolution of Virulence in Salmonella

    OpenAIRE

    Sandeepa M Eswarappa; Karnam, Guruswamy; Nagarajan, Arvindhan G; Chakraborty, Sangeeta; Chakravortty, Dipshikha

    2009-01-01

    The genus Salmonella includes many pathogens of great medical and veterinary importance. Bacteria belonging to this genus are very closely related to those belonging to the genus Escherichia. lacZYA operon and lacI are present in Escherichia coli, but not in Salmonella enterica. It has been proposed that Salmonella has lost lacZYA operon and lacI during evolution. In this study, we have investigated the physiological and evolutionary significance of the absence of lacI in Salmonella e...

  7. Oxygen-regulated stimulons of Salmonella typhimurium identified by Mu d(Ap lac) operon fusions.

    OpenAIRE

    Aliabadi, Z; Warren, F; Mya, S; Foster, J. W.

    1986-01-01

    Using the technique of Mu d1(Ap lac)-directed lacZ operon fusions, several oxygen-regulated genetic loci were identified in Salmonella typhimurium. Thirteen anaerobically inducible and six aerobically inducible operon fusions were identified. Based on control by the oxrA and oxrB regulatory loci, the anti-lacZ fusions were grouped into three classes: class I loci were regulated by both oxr loci, class II genes were regulated by oxrA only, and class III loci were not affected by either regulat...

  8. Thermodynamics Study of Lac Dyeing of Silk Yarn Coated with Chitosan

    Directory of Open Access Journals (Sweden)

    Montra CHAIRAT

    2009-01-01

    Full Text Available A thermodynamic study of lac dyeing of silk pretreated with chitosan at pH 3.0 was investigated in a batch system. It was found that the adsorption of lac dye on silk pretreated with chitosan could be described by the Langmuir isotherm. The results showed that the pretreatment of silk with chitosan provided an enhancement of dye uptake on silk and also decreased the dye desorption from silk yarn compared with the results in the absence of chitosan. The negative value of the enthalpy change (DHº for the adsorption of lac dye on silk pretreated with chitosan indicated that the adsorption process was an exothermic one.

  9. A lacZ reporter gene expression atlas for 313 adult KOMP mutant mouse lines

    OpenAIRE

    West, David B.; Pasumarthi, Ravi K.; Baridon, Brian; Djan, Esi; Trainor, Amanda; Stephen M Griffey; Engelhard, Eric K.; Rapp, Jared; LI, BOWEN; de Jong, Pieter J.; Lloyd, K. C. Kent

    2015-01-01

    Expression of the bacterial beta-galactosidase reporter gene (lacZ) in the vector used for the Knockout Mouse Project (KOMP) is driven by the endogenous promoter of the target gene. In tissues from KOMP mice, histochemical staining for LacZ enzyme activity can be used to determine gene expression patterns. With this technique, we have produced a comprehensive resource of gene expression using both whole mount (WM) and frozen section (FS) LacZ staining in 313 unique KOMP mutant mouse lines. Of...

  10. lac repressor is an antivirulence factor of Salmonella enterica: its role in the evolution of virulence in Salmonella.

    Directory of Open Access Journals (Sweden)

    Sandeepa M Eswarappa

    Full Text Available The genus Salmonella includes many pathogens of great medical and veterinary importance. Bacteria belonging to this genus are very closely related to those belonging to the genus Escherichia. lacZYA operon and lacI are present in Escherichia coli, but not in Salmonella enterica. It has been proposed that Salmonella has lost lacZYA operon and lacI during evolution. In this study, we have investigated the physiological and evolutionary significance of the absence of lacI in Salmonella enterica. Using murine model of typhoid fever, we show that the expression of LacI causes a remarkable reduction in the virulence of Salmonella enterica. LacI also suppresses the ability of Salmonella enterica to proliferate inside murine macrophages. Microarray analysis revealed that LacI interferes with the expression of virulence genes of Salmonella pathogenicity island 2. This effect was confirmed by RT-PCR and Western blot analysis. Interestingly, we found that SBG0326 of Salmonella bongori is homologous to lacI of Escherichia coli. Salmonella bongori is the only other species of the genus Salmonella and it lacks the virulence genes of Salmonella pathogenicity island 2. Overall, our results demonstrate that LacI is an antivirulence factor of Salmonella enterica and suggest that absence of lacI has facilitated the acquisition of virulence genes of Salmonella pathogenicity island 2 in Salmonella enterica making it a successful systemic pathogen.

  11. Optical and Radio Variability of BL Lacertae

    CERN Document Server

    Gaur, Haritma; Bachev, R; Strigachev, A; Semkov, E; Wiita, Paul J; Volvach, A E; Gu, Minfeng; Agarwal, A; Agudo, I; Aller, M F; Aller, H D; Kurtanidze, O M; Kurtanidze, S O; Lahteenmaki, A; Peneva, S; Nikolashvili, M G; Sigua, L A; Tornikoski, M; Volvach, L N

    2015-01-01

    We observed the prototype blazar, BL Lacertae, extensively in optical and radio bands during an active phase in the period 2010--2013 when the source showed several prominent outbursts. We searched for possible correlations and time lags between the optical and radio band flux variations using multifrequency data to learn about the mechanisms producing variability. During an active phase of BL Lacertae, we searched for possible correlations and time lags between multifrequency light curves of several optical and radio bands. We tried to estimate any possible variability timescales and inter-band lags in these bands. We performed optical observations in B, V, R and I bands from seven telescopes in Bulgaria, Georgia, Greece and India and obtained radio data at 36.8, 22.2, 14.5, 8 and 4.8 GHz frequencies from three telescopes in Ukraine, Finland and USA. Significant cross-correlations between optical and radio bands are found in our observations with a delay of cm-fluxes with respect to optical ones of ~250 days...

  12. Studies of the Jet in BL Lacertae. II. Superluminal Alfv\\'en Waves

    CERN Document Server

    Cohen, M H; Arshakian, T G; Clausen-Brown, E; Homan, D C; Hovatta, T; Kovalev, Y Y; Lister, M L; Pushkarev, A B; Richards, J L; Savolainen, T

    2014-01-01

    Ridge lines on the pc-scale jet of the active galactic nucleus BL Lac display transverse patterns that move superluminally downstream. The patterns are not ballistic, but are analogous to waves on a whip. Their apparent speeds $\\beta_\\mathrm{app}$ (units of $c$) range from 4.2 to 13.5, corresponding to $\\beta_\\mathrm{wave}^\\mathrm{gal}= 0.981 - 0.998$ in the galaxy frame. We show that the magnetic field in the jet is well-ordered with a strong transverse component, and assume that it is helical and that the transverse patterns are longitudinal Alfv\\'en waves. The wave-induced transverse speed of the jet is non-relativistic ($\\beta_\\mathrm{tr}^\\mathrm{gal}\\sim 0.09$) and in agreement with our assumption of low-amplitude waves. In 2010 the wave activity subsided and the jet displayed a mild wiggle that had a complex oscillatory behavior. The waves are excited by changes in the position angle of the recollimation shock, in analogy to exciting a wave on a whip by shaking it. Simple models of the system are presen...

  13. Object and Objective Lost?

    DEFF Research Database (Denmark)

    Lopdrup-Hjorth, Thomas

    2015-01-01

    of this organization-phobia, the paper argues that OT has become increasingly incapable of speaking about its core object. I show how organizations went from being conceptualized as entities of major importance to becoming theoretically deconstructed and associated with all kinds of ills. Through this history...

  14. The first Fermi multifrequency campaign on BL Lacertae: characterizing the low-activity state of the eponymous blazar

    CERN Document Server

    Abdo, A A

    2011-01-01

    We report on observations of BL Lacertae during the first 18 months of Fermi-LAT science operations and present results from a 48-day multifrequency coordinated campaign from 2008 August 19 to 2008 October 7. The radio to gamma-ray behavior of BL Lac is unveiled during a low activity state thanks to the coordinated observations of radio-band (Metsahovi and VLBA), near-IR/optical (Tuorla, Steward, OAGH and MDM) and X-ray (RXTE and Swift) observatories. No variability was resolved in gamma-rays during the campaign, and the brightness level was 15 times lower than the level of the 1997 EGRET outburst. Moderate and uncorrelated variability has been detected in UV and X-rays. The X-ray spectrum is found to be concave indicating the transition region between the low and high energy component of the spectral energy distribution (SED). VLBA observation detected a synchrotron spectrum self-absorption turnover in the innermost part of the radio jet appearing to be elongated and inhomogeneous, and constrained the averag...

  15. 1956 Progress report : Fishery management program : Des Lacs National Wildlife Refuge

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — Progress report for the fishery management program at Des Lacs National Wildlife Refuge. This report is a result of a site visit to continue fish population studies...

  16. 1954 Progress report : Fishery management program : Des Lacs National Wildlife Refuge

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — Progress report for the fishery management program at Des Lacs National Wildlife Refuge. This report is a result of a site visit to continue fish population studies...

  17. Rice Lake National Wildlife Refuge : Mille Lacs National Wildlife Refuge : Sandstone Unit : Fiscal year 2003

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — This annual narrative report for Rice Lake including the Sandstone Unit and Mille Lacs National Wildlife Refuges outlines Refuge accomplishments during the 2003...

  18. Des Lacs Migratory Waterfowl Refuge Quarterly narrative report : November, 1938; December, 1938; & January, 1939

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — This narrative report for Des Lacs and Lostwood Migratory Waterfowl Refuges outlines Refuge accomplishments from November 1938 through January of 1939. The report...

  19. Des Lacs Migratory Waterfowl Refuge Quarterly narrative report : May, June, & July, 1939

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — This narrative report for Des Lacs Migratory Waterfowl Refuge outlines Refuge accomplishments from May through July of 1939. The report begins by summarizing the...

  20. Integrated Pest Management Plan 2005-2010 Des Lacs National Wildlife Refuge Complex

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — The purpose of the Integrated Pest Management Plan is to provide a comprehensive, environmentally sensitive approach to managing pests on the Des Lacs NWRC. The...

  1. Preliminary report of the biological development of the Des Lacs, Upper Souris, and Lostwood Refuges

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — Preliminary report on the development of Des Lacs National Wildlife Refuge, Lostwood National Wildlife Refuge, and Upper Souris National Wildlife Refuge. This...

  2. Narrative report May, June, July, August, 1946 Des Lacs National Wildlife Refuge & Easement Refuges - District IV

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — This narrative report for Des Lacs National Wildlife Refuge outlines Refuge accomplishments from May through August of 1946. The report begins by summarizing the...

  3. Narrative report May, June, July, August, 1949, Des Lacs National Wildlife Refuge & Easement Refuges - District IV

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — This narrative report for Des Lacs National Wildlife Refuge outlines Refuge accomplishments from May through August of 1949. The report begins by summarizing the...

  4. [Draft letter to President: Mille Lacs and Rice Lake National Wildlife Refuge

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — This document is a draft letter from the Secretary of the Interior to the President regarding the establishment of the Mille Lacs and Rice Lake Wilderness area. The...

  5. Des Lacs National Wildlife Refuge : Annual Narrative Report : Calendar Year 1980

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — This narrative report for Des Lacs National Wildlife Refuge outlines Refuge accomplishments during the 1980 calendar year. The report begins with an introduction to...

  6. Des Lacs National Wildlife Refuge : Annual Narrative Report : Calendar Year 1976

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — This narrative report for Des Lacs National Wildlife Refuge outlines Refuge accomplishments during the 1976 calendar year. The report begins with an introduction to...

  7. Des Lacs National Wildlife Refuge: Annual narrative report: Calendar year 1993

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — This annual narrative report for Des Lacs National Wildlife Refuge outlines Refuge accomplishments during the 1993 calendar year. The report begins with a summary...

  8. Des Lacs National Wildlife Refuge: Annual narrative report: Calendar year 1994

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — This annual narrative report for Des Lacs National Wildlife Refuge outlines Refuge accomplishments during the 1994 calendar year. The report begins with a summary...

  9. Des Lacs National Wildlife Refuge[: Annual narrative report: Calendar year 1995

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — This annual narrative report for Des Lacs National Wildlife Refuge outlines Refuge accomplishments during the 1995 calendar year. The report begins with a summary...

  10. Narrative report for September, October, November and December 1943 Des Lacs National Wildlife Refuge

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — This narrative report for Des Lacs National Wildlife Refuge outlines Refuge accomplishments from September through December of 1943. The report begins by...

  11. Narrative report for January, February, March and April 1945 Des Lacs National Wildlife Refuge

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — This narrative report for Des Lacs National Wildlife Refuge outlines Refuge accomplishments from January through April of 1945. The report begins by summarizing the...

  12. Narrative report May, June, July, August, 1948 Des Lacs National Wildlife Refuge & Easement Refuges - District IV

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — This narrative report for Des Lacs National Wildlife Refuge outlines Refuge accomplishments from May through August of 1948. The report begins by summarizing the...

  13. Narrative report September, October, November, December, 1950 Des Lacs National Wildlife Refuge & Easement Refuges - District IV

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — This narrative report for Des Lacs National Wildlife Refuge outlines Refuge accomplishments from September through December of 1950. The report begins by...

  14. Narrative report for September, October, November and December 1944 Des Lacs National Wildlife Refuge

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — This narrative report for Des Lacs National Wildlife Refuge outlines Refuge accomplishments from September through December of 1944. The report begins by...

  15. Narrative report January, February, March, April, 1946 Des Lacs National Wildlife Refuge & Easement Refuges - District IV

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — This narrative report for Des Lacs National Wildlife Refuge outlines Refuge accomplishments from January through April of 1946. The report begins by summarizing the...

  16. Narrative report January, February, March, April, 1948 Des Lacs National Wildlife Refuge & Easement Refuges - District IV

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — This narrative report for Des Lacs National Wildlife Refuge outlines Refuge accomplishments from January through April of 1948. The report begins by summarizing the...

  17. Narrative report January, February, March, April, 1949 Des Lacs National Wildlife Refuge & Easement Refuges - District IV

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — This narrative report for Des Lacs National Wildlife Refuge and Ilo Lake National Wildlife Refuge outlines Refuge accomplishments from January through April of...

  18. Narrative report September, October, November, December, 1947 Des Lacs National Wildlife Refuge & Easement Refuges - District IV

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — This narrative report for Des Lacs National Wildlife Refuge outlines Refuge accomplishments from September through December of 1947. The report begins by...

  19. Narrative report September, October, November, December, 1946 Des Lacs National Wildlife Refuge & Easement Refuges - District IV

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — This narrative report for Des Lacs National Wildlife Refuge outlines Refuge accomplishments from September through December of 1946. The report begins by...

  20. Narrative report May, June, July, August, 1947 Des Lacs National Wildlife Refuge & Easement Refuges - District IV

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — This narrative report for Des Lacs National Wildlife Refuge outlines Refuge accomplishments from May through August of 1947. The report begins by summarizing the...

  1. Narrative report January, February, March, April, 1947 Des Lacs National Wildlife Refuge & Easement Refuges - District IV

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — This narrative report for Des Lacs National Wildlife Refuge outlines Refuge accomplishments from January through April of 1947. The report begins by summarizing the...

  2. Winter report on biological projects : Des Lacs and Lostwood Migratory Bird Refuge : 1935-1936

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — Report on biological projects taking place during the winter of 1935-1936 on Des Lacs National Wildlife Refuge and Lostwood National Wildlife Refuge. Activities...

  3. Rice Lake National Wildlife Refuge (including Mille Lacs and Sandstone): Annual narrative report: Calendar year 1985

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — This annual narrative report for Rice Lake NWR and Mille Lacs NWR outlines Refuge accomplishments during the 1985 calendar year. The report begins with a summary of...

  4. Rice Lake National Wildlife Refuge : Mille Lacs National Wildlife Refuge : Sandstone Unit : Fiscal year 2004

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — This annual narrative report for Rice Lake (including the Sandstone Unit) and Mille Lacs National Wildlife Refuges outlines Refuge accomplishments during the 2004...

  5. Des Lacs National Wildlife Refuge: Annual narrative report: Calendar year 1998

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — This annual narrative report for Des Lacs National Wildlife Refuge summarizes Refuge activities during the 1998 calendar year. The report begins with a summary of...

  6. Sustaining the natural and economical resources of the Lac Courte Oreilles, Leslie Isham; Jason Weaver

    Energy Technology Data Exchange (ETDEWEB)

    Isham, Leslie; Weaver, Jason

    2013-09-30

    The Lac Courte Oreilles Band of Lake Superior Chippewa Indians, located in northwest Wisconsin has developed a project, entitled Sustaining the Natural and Economic Resources of the LCO Ojibwe. This technical report is a summary of the project.

  7. Rice Lake National Wildlife Refuge, Mille Lacs Refuge, Sandstone Unit: [Narrative report]: 1972

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — This annual narrative report for Rice Lake NWR and Mille Lacs NWR outlines Refuge accomplishments during the 1972 calendar year. The report begins by summarizing...

  8. Quarterly narrative report for Des Lacs National Wildlife Refuge [May-July, 1941

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — This narrative report for Des Lacs Migratory Waterfowl Refuge outlines Refuge accomplishments from May through July of 1941. The report begins by summarizing the...

  9. Fact sheet : Wilderness proposal : Rice Lake - Mille Lacs National Wildlife Refuges

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — This document is a fact sheet of information about the Rice Lake and Mille Lacs National wildlife Refuges. Pertinent information such as the area of the refuge,...

  10. Rice Lake National Wildlife Refuge (including Mille Lacs and Sandstone): Annual narrative report: Calendar year 1987

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — This annual narrative report for Rice Lake NWR and Mille Lacs NWR outlines Refuge accomplishments during the 1987 calendar year. The report begins with a summary of...

  11. Des Lacs National Wildlife Refuge : Annual narrative report : Calendar year 2002

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — This annual narrative report for Des Lacs National Wildlife Refuge summarizes Refuge activities during the 2002 calendar year. The report begins with a summary of...

  12. Des Lacs National Wildlife Refuge : Annual Narrative Report : Calendar Year 1984

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — This annual narrative report for Des Lacs National Wildlife Refuge outlines Refuge accomplishments during the 1984 calendar year. The report begins with a summary...

  13. Des Lacs National Wildlife Refuge : Annual Narrative Report : Calendar Year 1985

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — This annual narrative report for Des Lacs National Wildlife Refuge outlines Refuge accomplishments during the 1985 calendar year. The report begins with a summary...

  14. Des Lacs National Wildlife Refuge : Annual Narrative Report : Calendar Year 1986

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — This annual narrative report for Des Lacs National Wildlife Refuge outlines Refuge accomplishments during the 1986 calendar year. The report begins with a summary...

  15. Des Lacs National Wildlife Refuge : Annual Narrative Report : Calendar Year 1983

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — This annual narrative report for Des Lacs National Wildlife Refuge outlines Refuge accomplishments during the 1983 calendar year. The report begins with a summary...

  16. Des Lacs National Wildlife Refuge : Annual Narrative Report : Calendar Year 1988

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — This annual narrative report for Des Lacs National Wildlife Refuge outlines Refuge accomplishments during the 1988 calendar year. The report begins with a summary...

  17. Des Lacs National Wildlife Refuge : Annual Narrative Report : Calendar Year 1987

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — This annual narrative report for Des Lacs National Wildlife Refuge outlines Refuge accomplishments during the 1987 calendar year. The report begins with a summary...

  18. Des Lacs National Wildlife Refuge: Annual narrative report: Calendar year 2000

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — This annual narrative report for Des Lacs National Wildlife Refuge summarizes Refuge activities during the 2000 calendar year. The report begins with a summary of...

  19. [Development of Matt Welch's land : Unit #2 at Des Lacs National Wildlife Refuge

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — Memorandum to the Acting Regional Director from Des Lacs National Wildlife Refuge concenring the proposed work to improve and developm the pasture area on Matt...

  20. Mille Lacs lake islands and Rice Lake National Wildlife Refuges : Wilderness study summary [draft

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — This document is a draft summary of a wilderness study done of Mille Lacs and Rice Lake National Wildlife Refuges pursuant to the Wilderness Act of 1964. It...

  1. Mille Lacs and Rice Lake National Wildlife Refuges Wilderness study summary

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — This document is a summary of a wilderness study done of Mille Lacs and Rice Lake National Wildlife Refuges pursuant to the Wilderness Act of 1964. It provides...

  2. Des Lacs National Wildlife Refuge : Annual Narrative Report : Calendar Year 1982

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — This annual narrative report for Des Lacs National Wildlife Refuge outlines Refuge accomplishments during the 1982 calendar year. The report begins with a summary...

  3. Des Lacs Nat'l Wildlife Refuge : Narrative Report for Calendar Year 1972

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — This annual narrative report for Des Lacs National Wildlife Refuge outlines Refuge accomplishments during the 1972 calendar year. The report begins by summarizing...

  4. Narrative Report : Des Lacs National Wildlife Refuge Complex for Fiscal Year 1975 [including July - December 1975

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — This annual narrative report for Des Lacs National Wildlife Refuge outlines Refuge accomplishments during the 1975 fiscal and calendar year. The report begins by...

  5. Des Lacs National Wildlife Refuge : Annual Narrative Report : Calendar Year 1979

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — This narrative report for Des Lacs National Wildlife Refuge outlines Refuge accomplishments during the 1979 calendar year. The report begins with an introduction to...

  6. Des Lacs National Wildlife Refuge : Annual Narrative Report : Calendar Year 1981

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — This annual narrative report for Des Lacs National Wildlife Refuge outlines Refuge accomplishments during the 1981 calendar year. The report begins with a summary...

  7. Des Lacs National Wildlife Refuge : Annual Narrative Report : Calendar Year 1978

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — This narrative report for Des Lacs National Wildlife Refuge outlines Refuge accomplishments during the 1978 calendar year. The report begins with an introduction to...

  8. Des Lacs National Wildlife Refuge : Annual Narrative Report : Calendar Year 1977

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — This narrative report for Des Lacs National Wildlife Refuge outlines Refuge accomplishments during the 1977 calendar year. The report begins with an introduction to...

  9. Narrative Report : Fiscal Year 1974 : Des Lacs National Wildlife Refuge Complex

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — This annual narrative report for Des Lacs National Wildlife Refuge outlines Refuge accomplishments during the 1974 fiscal year. The report begins by summarizing the...

  10. Optical and radio variability of BL Lacertae

    Science.gov (United States)

    Gaur, H.; Gupta, A. C.; Bachev, R.; Strigachev, A.; Semkov, E.; Wiita, P. J.; Volvach, A. E.; Gu, M. F.; Agarwal, A.; Agudo, I.; Aller, M. F.; Aller, H. D.; Kurtanidze, O. M.; Kurtanidze, S. O.; Lähteenmäki, A.; Peneva, S.; Nikolashvili, M. G.; Sigua, L. A.; Tornikoski, M.; Volvach, L. N.

    2015-10-01

    Context. We extensively observed the prototype blazar, BL Lacertae, in optical and radio bands during an active phase in the period 2010-2013 when the source showed several prominent outbursts. We searched for possible correlations and time lags between the optical and radio band flux variations using multi-frequency data to learn about the mechanisms producing variability. Aims: During an active phase of BL Lacertae, we searched for possible correlations and time lags between multi-frequency light curves of several optical and radio bands. We tried to estimate any possible variability timescales and inter-band lags in these bands. Methods: We performed optical observations in B, V, R, and I-bands from seven telescopes in Bulgaria, Georgia, Greece, and India and obtained radio data at 36.8, 22.2, 14.5, 8, and 4.8 GHz frequencies from three telescopes in Crimea, Finland, and USA. Results: Significant cross-correlations between optical and radio bands are found in our observations with a delay of cm-fluxes with respect to optical bands of ~250 days. The optical and radio light curves do not show any significant timescales of variability. BL Lacertae showed many optical "mini-flares" on short timescales. Variations on longer term timescales are mildly chromatic with the superposition of many strong optical outbursts. In radio bands, the amplitude of variability is frequency dependent. Flux variations at higher radio frequencies lead the lower frequencies by days or weeks. Conclusions: The optical variations are consistent with being dominated by a geometric scenario where a region of emitting plasma moves along a helical path in a relativistic jet. The frequency dependence of the variability amplitude supports an origin of the observed variations intrinsic to the source. Tables of the light curves are only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/582/A103

  11. Fusions of flagellar operons to lactose genes on a mu lac bacteriophage.

    OpenAIRE

    Komeda, Y

    1982-01-01

    Previous studies have defined 29 genes necessary for synthesis of the Escherichia coli flagellar apparatus. This study analyzed the transcriptional control of flagellar genes, using Mu d (Apr lac) phage to generate flagellar mutants by insertion. These mutants contained operon fusions of flagellar genes to the lac genes of the Mu d phage and allowed the measurement of flagellar operon expression by detection of beta-galactosidase activity. These fusion mutants expressed the enzyme activity co...

  12. Quantitative approaches to the study of bistability in the lac operon of Escherichia coli

    OpenAIRE

    Santillán, Moisés; Mackey, Michael C.

    2008-01-01

    In this paper, the history and importance of the lac operon in the development of molecular and systems biology are briefly reviewed. We start by presenting a description of the regulatory mechanisms in this operon, taking into account the most recent discoveries. Then we offer a survey of the history of the lac operon, including the discovery of its main elements and the subsequent influence on the development of molecular and systems biology. Next the bistable behaviour of the operon is dis...

  13. Comparison of Deterministic and Stochastic Models of the lac Operon Genetic Network

    OpenAIRE

    Stamatakis, M.; Mantzaris, N. V.

    2009-01-01

    The lac operon has been a paradigm for genetic regulation with positive feedback, and several modeling studies have described its dynamics at various levels of detail. However, it has not yet been analyzed how stochasticity can enrich the system's behavior, creating effects that are not observed in the deterministic case. To address this problem we use a comparative approach. We develop a reaction network for the dynamics of the lac operon genetic switch and derive corresponding deterministic...

  14. Use of bio-lac fusion strains to study regulation of biotin biosynthesis in Escherichia coli.

    OpenAIRE

    Barker, D F; Campbell, A M

    1980-01-01

    The technique developed by Casadaban (M. J. Casadaban, J. Mol. Biol. 104: 541-555, 1976) has been employed to construct Escherichia coli K-12 derivatives in which the genes determining lactose utilization are fused to the regulatory region of the biotin operon. Fusions of the lac genes to either arm of this divergently transcribed operon have been isolated. When the operon is derepressed, expression of the lac genes is sufficient to permit growth on lactose minimal medium. Repressing conditio...

  15. Network Topology as a Driver of Bistability in the lac Operon

    OpenAIRE

    Stigler, Brandilyn; Veliz-Cuba, Alan

    2008-01-01

    The lac operon in Escherichia coli has been studied extensively and is one of the earliest gene systems found to undergo both positive and negative control. The lac operon is known to exhibit bistability, in the sense that the operon is either induced or uninduced. Many dynamical models have been proposed to capture this phenomenon. While most are based on complex mathematical formulations, it has been suggested that for other gene systems network topology is sufficient to produce the desired...

  16. In Silico Evolved lac Operons Exhibit Bistability for Artificial Inducers, but Not for Lactose

    OpenAIRE

    van Hoek, M. J. A.; Hogeweg, P.

    2006-01-01

    Bistability in the lac operon of Escherichia coli has been widely studied, both experimentally and theoretically. Experimentally, bistability has been observed when E. coli is induced by an artificial, nonmetabolizable, inducer. However, if the lac operon is induced with lactose, the natural inducer, bistability has not been demonstrated. We derive an analytical expression that can predict the occurrence of bistability both for artificial inducers and lactose. We find very different condition...

  17. Site-specific mutagenesis of histidine residues in the lac permease of Escherichia coli.

    OpenAIRE

    Padan, E; Sarkar, H K; Viitanen, P V; Poonian, M S; Kaback, H R

    1985-01-01

    The lacY gene of Escherichia coli, which encodes the lac permease, has been modified by oligonucleotide-directed, site-specific mutagenesis such that each of the four histidine residues in the molecule is replaced with an arginine residue. Replacement of histidine-35 and histidine-39 with arginine has no apparent effect on permease activity. In contrast, replacement of either histidine-205 or histidine-322 by arginine causes a dramatic loss of transport activity, although the cells contain a ...

  18. Preliminary fish survey of Lac Tseny in northwestern Madagascar

    Directory of Open Access Journals (Sweden)

    Noromalala Raminosoa

    2011-12-01

    Full Text Available We surveyed the fish fauna of Lac Tseny, in the Sofia Region of northwestern Madagascar, during October 2010 by observing commercial catches and targeted netting of areas used by endemic species. We recorded seven native fish species at the lake, including three endemic cichlids, a herring and a catfish. We confirmed the continued survival of the Critically Endangered Paretroplus menarambo, as well as the presence of a Paretroplus taxon that may be new to science. The commercial fishery in the lake is sustained by introduced tilapiines and the native Savagella robusta. The three endemic cichlids (Paretroplus spp. were not targeted by commercial fishermen, but when caught in small numbers were retained for domestic consumption. Submerged trees in the west of the lake restrict fishing with nets and probably provide important habitat for P. menarambo. Priority next steps at the lake include (i additional surveys and biological studies of the endemic fish species and the Critically Endangered Madagascar big-headed turtle, Erymnochelys madagascariensis, (ii clarification of the taxonomic status of Paretroplus cf. kieneri and, should it prove a new taxon, its formal scientific description, and (iii continued engagement with fishing communities and authorities to promote practices that benefit livelihoods and the survival of threatened fish species.

  19. eLac - Conceptual Model for Flood Management

    Science.gov (United States)

    Rata, Marius; Florentin Draghia, Aurelian; Drobot, Radu; Matreata, Marius; Corbus, Ciprian

    2015-04-01

    This article reviews the conceptual model of the decision support system (DSS) for flood management activities introduced in the scope of e-LAC project. Following the general system architecture which has an emphasize on the water management decision processes, hydrologic and hydraulic models are introduced and discussed according to their specific DSS integration potential. Three directions are discussed in dedicated sections corresponding to the main modules defined in the conceptual model : the Water Basin Management Module (mainly implements the management decision flow, but manages also data exchange between hydrologic modeling module and hydraulic modeling module, allow real time visualization for hydrological data), the Hydrologic Modeling Module (manages all the modeling functionalities of rainfalls - runoff processes, providing continuous hydrologic forecasts with a variable time-step depending on the actual basin situation) and the Hydraulic Modeling Module (computes the flood's waves routing having as boundary upstream conditions the discharge hydrographs, generated both by catchment's upper area, river tributaries and inter-basins, respectively the rating curves, water level hydrograph or water surface slope as downstream condition). The GIS concepts are contextually reviewed based on their use as geospatial database for water management modeling, integration within hydrologic time courses, hydraulic modeling (from both software and management perspective), expert knowledge or mathematical modeling results (knowledge database, rules).

  20. Regulation of endothelial-specific transgene expression by the LacI repressor protein in vivo.

    Directory of Open Access Journals (Sweden)

    Susan K Morton

    Full Text Available Genetically modified mice have played an important part in elucidating gene function in vivo. However, conclusions from transgenic studies may be compromised by complications arising from the site of transgene integration into the genome and, in inducible systems, the non-innocuous nature of inducer molecules. The aim of the present study was to use the vascular system to validate a technique based on the bacterial lac operon system, in which transgene expression can be repressed and de-repressed by an innocuous lactose analogue, IPTG. We have modified an endothelium specific promoter (TIE2 with synthetic LacO sequences and made transgenic mouse lines with this modified promoter driving expression of mutant forms of connexin40 and an independently translated reporter, EGFP. We show that tissue specificity of this modified promoter is retained in the vasculature of transgenic mice in spite of the presence of LacO sequences, and that transgene expression is uniform throughout the endothelium of a range of adult systemic and cerebral arteries and arterioles. Moreover, transgene expression can be consistently down-regulated by crossing the transgenic mice with mice expressing an inhibitor protein LacI(R, and in one transgenic line, transgene expression could be de-repressed rapidly by the innocuous inducer, IPTG. We conclude that the modified bacterial lac operon system can be used successfully to validate transgenic phenotypes through a simple breeding schedule with mice homozygous for the LacI(R protein.

  1. Loss of the lac operon contributes to Salmonella invasion of epithelial cells through derepression of flagellar synthesis.

    Science.gov (United States)

    Jiang, Lingyan; Ni, Zhiwei; Wang, Lei; Feng, Lu; Liu, Bin

    2015-03-01

    Salmonella, a genus that is closely related to Escherichia coli, includes many pathogens of humans and other animals. A notable feature that distinguishes Salmonella from E. coli is lactose negativity, because the lac operon is lost in most Salmonella genomes. Here, we expressed the lac operon in Salmonella enterica serovar Typhimurium and compared the virulence of the Lac(+) strain to that of the wild-type strain in a murine model, invasion assays, and macrophage replication assays. We showed that the Lac(+) strain is attenuated in vivo and the attenuation of virulence is caused by its defect in epithelial cell invasion. However, the invasion-defective phenotype is unrelated to lactose utilization. Through sequencing and the comparison of the transcriptome profile between the Lac(+) and wild-type strains during invasion, we found that most flagellar genes were markedly downregulated in the Lac(+) strain, while other genes associated with invasion, such as the majority of genes encoded in Salmonella pathogenicity island 1, were not differentially expressed. Moreover, we discovered that lacA is the major repressor of flagellar gene expression in the lac operon. In conclusion, these data demonstrate that the lac operon decreases Salmonella invasion of epithelial cells through repression of flagellar biosynthesis. As the ability to invade epithelial cells is a critical virulence determinant of Salmonella, our results provide important evidence that the loss of the lac operon contributes to the evolution of Salmonella pathogenicity. PMID:25362512

  2. Genotype to phenotype mapping and the fitness landscape of the E. coli lac promoter.

    Directory of Open Access Journals (Sweden)

    Jakub Otwinowski

    Full Text Available Genotype-to-phenotype maps and the related fitness landscapes that include epistatic interactions are difficult to measure because of their high dimensional structure. Here we construct such a map using the recently collected corpora of high-throughput sequence data from the 75 base pairs long mutagenized E. coli lac promoter region, where each sequence is associated with its phenotype, the induced transcriptional activity measured by a fluorescent reporter. We find that the additive (non-epistatic contributions of individual mutations account for about two-thirds of the explainable phenotype variance, while pairwise epistasis explains about 7% of the variance for the full mutagenized sequence and about 15% for the subsequence associated with protein binding sites. Surprisingly, there is no evidence for third order epistatic contributions, and our inferred fitness landscape is essentially single peaked, with a small amount of antagonistic epistasis. There is a significant selective pressure on the wild type, which we deduce to be multi-objective optimal for gene expression in environments with different nutrient sources. We identify transcription factor (CRP and RNA polymerase binding sites in the promotor region and their interactions without difficult optimization steps. In particular, we observe evidence for previously unexplored genetic regulatory mechanisms, possibly kinetic in nature. We conclude with a cautionary note that inferred properties of fitness landscapes may be severely influenced by biases in the sequence data.

  3. IUE observations of extragalactic objects

    Science.gov (United States)

    Boksenberg, A.; Snijders, M. A. J.; Wilson, R.; Benvenuti, P.; Clavell, J.; Macchetto, F.; Penston, M.; Boggess, A.; Gull, T. R.; Gondhalekar, P.

    1978-01-01

    During the commissioning phase of IUE several extragalactic objects were observed spectrally at low dispersion in the UV range lambda lambda 1150-3200: the Seyfert galaxies NGC4151 and NGC1068, the QSO 3C273, the BL Lacertae object B2 1101+38, the giant elliptical galaxy M87 and the spiral galaxy M81. The results obtained are presented and a preliminary analysis given for all six objects, discussing the continuous spectrum, extinction, emission line spectrum and absorption line spectrum, where possible for each case. Several new or confirmatory astrophysical results are obtained.

  4. IUE observations of extragalactic objects

    International Nuclear Information System (INIS)

    During the commissioning phase of the International Ultraviolet Explorer several extragalactic objects were observed spectrally at low dispersion in the UV range lambdalambda1150-3200: the Seyfert galaxies NGC4151 and NGC1068, the QSO 3C273, the BL Lacertae object B2 1101 + 38, the giant eliptical galaxy M87 and the spiral galaxy M81. The results obtained are presented and a preliminary analysis given for all six objects, discussing the continuous spectrum, extinction, emission line spectrum and absorption line spectrum, where possible for each case. Several new or confirmatory astrophysical results are obtained. (author)

  5. Isolation and analysis of aroFo mutants by using an aroF-lac operon fusion.

    OpenAIRE

    Cobbett, C S; Morrison, S.; Pittard, J

    1984-01-01

    The lac structural genes were fused to the regulatory region of the aroF-tyrA operon so that the expression of beta-galactosidase was regulated by the tyrR+ gene product. Transducing phage carrying the aroF-lac fusion were isolated, and a lambda aroF-lac lysogen was used to select for aroFo mutants. A plasmid vector was constructed onto which the aroFo mutations were transferred by recombination in vivo.

  6. République de Djibouti : lac Assal [بحيرة عسل

    OpenAIRE

    Pouyllau, Stéphane

    2009-01-01

    Vue des berges sud-est du lac Assal (République de Djibouti) le 11 novembre 2009. Le Lac Assal est un lac salé endoréique situé au fond du golfe du Ghoubbet-el-Kharab. D'une superficie de 54 km2 et fermé de la mer par le volcan Ardoukôba, sont altitude est de -153m sous le niveau de la mer.

  7. Delivery system for creation of one-step in vivo lac gene fusions in Pseudomonas spp. involved in biological control.

    OpenAIRE

    O'Sullivan, D J; O'Gara, F

    1988-01-01

    The suicide plasmid pVA838 carrying the operon fusion transposon Tn5-lac was used as a delivery system to introduce Tn5-lac into Pseudomonas sp. strain M114. Random, in vivo lac gene fusions were successfully isolated in a one-step conjugation approach with this vector system. Tn5-lac-containing exconjugants were recovered at a frequency of approximately 10(-7) per recipient. However, when the mating temperature was increased from the normal growth temperature (28 degrees C) to 34 degrees C, ...

  8. opp-lac Operon fusions and transcriptional regulation of the Escherichia coli trp-linked oligopeptide permease.

    OpenAIRE

    Andrews, J C; Short, S. A.

    1986-01-01

    The transcriptional regulation of the Escherichia coli trp-linked opp operon that encodes the oligopeptide permease was investigated by using lambda plac Mu51-generated lac operon fusions. Synthesis of beta-galactosidase by strains harboring oppA-lac, oppB-lac, and oppD-lac fusions occurred at a basal level when the fusion-containing strains were grown in minimal medium. The addition of L-leucine or L-alanine to exponentially growing, aerobic cultures or shifting the aerobic fusion-containing...

  9. Lactose metabolism by Staphylococcus aureus: characterization of lacABCD, the structural genes of the tagatose 6-phosphate pathway.

    OpenAIRE

    Rosey, E L; Oskouian, B; Stewart, G. C.

    1991-01-01

    The nucleotide and deduced amino acid sequences of the lacA and lacB genes of the Staphylococcus aureus lactose operon (lacABCDFEG) are presented. The primary translation products are polypeptides of 142 (Mr = 15,425) and 171 (Mr = 18,953) amino acids, respectively. The lacABCD loci were shown to encode enzymes of the tagatose 6-phosphate pathway through both in vitro studies and complementation analysis in Escherichia coli. A serum aldolase assay, modified to allow detection of the tagatose ...

  10. Construction of a recombinant plasmid pGEX-Sj26GST of Schistosoma japonicum and expression in Escherichia coli BL21( DE3)

    Institute of Scientific and Technical Information of China (English)

    张丽

    2014-01-01

    Objective To construct and express a recombinant plasmid pGEX-Sj26GST of Schistosoma japonicum(Sj)in Escherichia coli(E.coli)BL21(DE3).Methods Total RNA was extracted from Sj adult worms by RNeasy Mini kit,26 kilodalton glutathione-S-transferases of Schistosoma japonicum(Sj26GST)antigen gene was amplified by real-time PCR(RT-PCR)from the total RNA,then cloned into a prokaryotic expression plasmid pGEX-1λT and transformed into E.coli BL21(DE3)to construct pGEX-Sj26GST;BL21(pGEX-

  11. Solving a discrete model of the lac operon using Z3

    Science.gov (United States)

    Gutierrez, Natalia A.

    2014-05-01

    A discrete model for the Lcac Operon is solved using the SMT-solver Z3. Traditionally the Lac Operon is formulated in a continuous math model. This model is a system of ordinary differential equations. Here, it was considerated as a discrete model, based on a Boolean red. The biological problem of Lac Operon is enunciated as a problem of Boolean satisfiability, and it is solved using an STM-solver named Z3. Z3 is a powerful solver that allows understanding the basic dynamic of the Lac Operon in an easier and more efficient way. The multi-stability of the Lac Operon can be easily computed with Z3. The code that solves the Boolean red can be written in Python language or SMT-Lib language. Both languages were used in local version of the program as online version of Z3. For future investigations it is proposed to solve the Boolean red of Lac Operon using others SMT-solvers as cvc4, alt-ergo, mathsat and yices.

  12. Lac repressor: Crystallization of intact tetramer and its complexes with inducer and operator DNA

    International Nuclear Information System (INIS)

    The intact lac repressor tetramer, which regulates expression of the lac operon in Escherichia coli, has been crystallized in the native form, with an inducer, and in a ternary complex with operator DNA and an anti-inducer. The crystals without DNA diffract to better than 3.5 angstrom. They belong to the monoclinic space group C2 and have cell dimensions a = 164.7 angstrom, b = 75.6 angstrom, and c = 161.2 angstrom, with α = γ = 90 degree and β = 125.5 degree. Cocrystals have been obtained with a number of different lac operator-related DNA fragments. The complex with a blunt-ended 16-base-pair strand yielded tetragonal bipyramids that diffract to 6.5 angstrom. These protein-DNA cocrystals crack upon exposure to the gratuitous inducer isopropyl β-D-thiogalactoside, suggesting a conformational change in the repressor-operator complex

  13. A computational systems biology study of the lambda-lac mutants

    CERN Document Server

    Werner, Maria

    2007-01-01

    We present a comprehensive computational study of some 900 possible "lambda-lac" mutants of the lysogeny maintenance switch in phage lambda, of which up to date 19 have been studied experimentally (Atsumi & Little, PNAS 103: 4558-4563, (2006)). We clarify that these mutants realise regulatory schemes quite different from wild-type lambda, and can therefore be expected to behave differently, within the conventional mechanistic setting in which this problem has often been framed. We verify that indeed, within this framework, across this wide selection of mutants the lambda-lac mutants for the most part either have no stable lytic states, or should only be inducible with difficulty. In particular, the computational results contradicts the experimental finding that four lambda-lac mutants both show stable lysogeny and are inducible. This work hence suggests either that the four out of 900 mutants are special, or that lambda lysogeny and inducibility are holistic effects involving other molecular players or ot...

  14. The clean development mechanism (CDM) an international perspective and implications for the LAC region

    International Nuclear Information System (INIS)

    This paper addresses activity a) an analysis of international CDM experiences and its potential contribution to the LAC region. The paper begins with a section describing the basic principles of the CDM and retrieves the lessons learned from the first two years of the CDM operation. This is followed by a more detailed review in section 2 of the on-going baseline and monitoring methodology approval process. In section 3, the development value of the CDM is explored. Section 4 describes the current CDM markets, while section 5 reviews the response of host countries to the CDM outside the LAC region. Section 6 describes the various capacity building programs established by Annex 1 countries to support the CDM. In each of the first 6 sections, implications for the LAC region are identified. Section 7 brings these conclusions together into a concise summary. (The author)

  15. A lacZ reporter gene expression atlas for 313 adult KOMP mutant mouse lines.

    Science.gov (United States)

    West, David B; Pasumarthi, Ravi K; Baridon, Brian; Djan, Esi; Trainor, Amanda; Griffey, Stephen M; Engelhard, Eric K; Rapp, Jared; Li, Bowen; de Jong, Pieter J; Lloyd, K C Kent

    2015-04-01

    Expression of the bacterial beta-galactosidase reporter gene (lacZ) in the vector used for the Knockout Mouse Project (KOMP) is driven by the endogenous promoter of the target gene. In tissues from KOMP mice, histochemical staining for LacZ enzyme activity can be used to determine gene expression patterns. With this technique, we have produced a comprehensive resource of gene expression using both whole mount (WM) and frozen section (FS) LacZ staining in 313 unique KOMP mutant mouse lines. Of these, ∼ 80% of mutants showed specific staining in one or more tissues, while ∼ 20% showed no specific staining, ∼ 13% had staining in only one tissue, and ∼ 25% had staining in >6 tissues. The highest frequency of specific staining occurred in the brain (∼ 50%), male gonads (42%), and kidney (39%). The WM method was useful for rapidly identifying whole organ and some substructure staining, while the FS method often revealed substructure and cellular staining specificity. Both staining methods had >90% repeatability in biological replicates. Nonspecific LacZ staining occurs in some tissues due to the presence of bacteria or endogenous enzyme activity. However, this can be effectively distinguished from reporter gene activity by the combination of the WM and FS methods. After careful annotation, LacZ staining patterns in a high percentage of mutants revealed a unique structure-function not previously reported for many of these genes. The validation of methods for LacZ staining, annotation, and expression analysis reported here provides unique insights into the function of genes for which little is currently known. PMID:25591789

  16. STRUCTURAL ASPECTS REGARDING TO THE IMAGE OF ICE HOTEL BALEA LAC BREND

    Directory of Open Access Journals (Sweden)

    Marian ZAHARIA

    2008-06-01

    Full Text Available Applying a poll-based survey provides important information regarding the tourist offer particulars in Bâlea Lac area. On the day the survey is performed its main advantage is also outlined: the fact that this information display a good accuracy, are obtained in a short time span and involving relatively low expenses. Data collection and centralization of the answers provided by interviewed tourists regarding tourism practice in the Bâlea Lac area have led to drawing up distributions that are presented in the paper. Based on the respective information, statistics methods adequate to the study of tourist opinion on the Bâlea Lac Ice Hotel brand image. Several issues have been outlined, regarding the types of respondents based on their category, Romanian or foreigners, from Romania and based on destination countries, function of: the type of stay; the means of information; their answers referring to their first arrival at Bâlea Lac; the degree of destination assessment; their opinion on host reception; their preference for Bâlea Lac; appreciating value for money; age groups; gender; social and professional standing. The image created through the attractions and services provided in the Bâlea Lac tourist area by tourism activities closely related to the Ice Hotel is well appreciated, so that they have opened up a rather favourable expectancy for those willing to come back and for those tempted to try and spend their holidays in the presented hotel.

  17. Premiers effets des barrages du fleuve Sénégal sur le lac de Guiers

    OpenAIRE

    Cogels, François-Xavier; Thiam, A.; Gac, Jean-Yves

    1993-01-01

    La récente mise en fonction de deux barrages a régularisé le cycle hydrologique du fleuve Senegal, et le fonctionnement du lac de Guiers, qui en est un défluent, a été complètement modifié. La disponibilité permanente d'eau douce fluviale permet de meilleurs remplissages annuels et une plus grande stabilité du niveau du lac. Ces nouvelles conditions empêchent l'exondation annuelle d'une importante frange de rivage comme c'était le cas auparavant. Elles ont aussi induit l'adoucissement progres...

  18. Isolation of behavioral mutants of Azospirillum brasilense by using Tn5 lacZ.

    OpenAIRE

    van Rhijn, P; Vanstockem, M; Vanderleyden, J.; De Mot, R

    1990-01-01

    Tn5 lacZ mutants were generated with Azospirillum brasilense 7030 by mating that strain with Escherichia coli strains carrying suicide plasmid pCIB100 or pCIB110. Kanamycin-resistant Azospirillum colonies were obtained with a maximum frequency of 10(-6) per recipient cell. The potential of Tn5 lacZ for random transposon mutagenesis coupled to transcription analysis in A. brasilense 7030 was demonstrated. Sixty percent of all Kmr A. brasilense 7030 mutants expressed beta-galactosidase activity...

  19. Synthesis of tetravalent LacNAc-glycoclusters as high-affinity cross-linker against Erythrina cristagalli agglutinin.

    Science.gov (United States)

    Ogata, Makoto; Chuma, Yasushi; Yasumoto, Yoshinori; Onoda, Takashi; Umemura, Myco; Usui, Taichi; Park, Enoch Y

    2016-01-01

    Four kinds of tetravalent double-headed glycoclusters [(LacNAc)4-DHGs] were designed with linkers of varying lengths consisting of alkanedioic carboxyamido groups (C6, C12, C18 and C24) between two bi-antennary LacNAc-glycosides. These glycoclusters served as high-affinity cross-linking ligands for the LacNAc-binding lectin Erythrina cristagalli agglutinin (ECA). The binding activity and cross-linking between each ligand and ECA were characterized by a hemagglutination inhibition (HI) assay, isothermal titration calorimetry (ITC), a quantitative precipitation assay and dynamic light scattering (DLS). For the precipitation assay and DLS measurement, the synthesized (LacNAc)4-DHGs were found to be capable of binding and precipitating the ECA as multivalent ligands. ITC analysis indicated the binding of (LacNAc)4-DHGs was driven by a favorable enthalpy change. Furthermore, the entropy penalty from binding (LacNAc)4-DHGs clearly decreased in a spacer length-dependent manner. The binding affinities of flexible (LacNAc)4-DHGs (C18 and C24) with long spacers were found to be more favorable than those of the clusters having short spacers (C6 and C12). These results were supported by molecular dynamics simulations with explicit water molecules for the tetravalent glycoclusters with ECA. We concluded that the subtle modification in the epitope-presenting scaffolds exerts the significant effect in the recognition efficiency involved in the LacNAc moieties by ECA. PMID:26672510

  20. Radium-226 in certified uranium reference ores DL-1a, BL-4a, DH-1a and BL-5

    International Nuclear Information System (INIS)

    Radium-226 radioactivity in uranium reference ores BL-4a and BL-5 and uranium-thorium reference ores DL-1a and DH-1a was determined in an interlaboratory program. Twelve of thirteen participants used certified radium solutions from the United States National Bureau of Standards (NBS) for calibration purposes. Recommended values of sup(226)Ra activity and associated parameters were calculated by statistical treatment of the results. In all cases, the recommended values are within 2 percent of activities predicted assuming secular equilibrium in the sup(238)U decay series. The recommended values for radium activity are 1.40, 15.5, 31.5 and 857 Bq/ for DL-1a, BL-4a, DH-1a and BL-5, respectively

  1. Regulation of gene expression in mammalian cells using the lac repressor

    International Nuclear Information System (INIS)

    The study describes the construction of a one step inducible lac repressor/operator mammalian expression system within the context of DNA mediated vaccination (naked DNA). It is novel in that it contains, on a single vector (pSO1), all the cis and trans controlling elements necessary to manipulate (switch on/off) and control the expression of a reporter gene in a mammalian cell. The enhanced green fluorescent protein (EGFP) gene was cloned downstream of the cytomegalovirus immediate-early enhancer promoter (PCMV IE) and a lac operator (LacO), which was in turn regulated by the expression of the lac repressor under the control of a second PCMV IE. The number of cells fluorescing were greatly increased following isopropyl B-D thiogalactoside (IPTG) induction. In the repressed state, fewer pSO1 transfected cells expressed the EGFP, and the fluorescence intensity was also lower than that observed for the induced pSO1 transfected cells. Observation by microscopy was quantified by FACScan analysis on the different populations of cells. There was always a significant difference between the induced and repressed pSO1 transfected cells in terms of the percentage of the population of cells fluorescing and the intensity of the fluorescence. Of the repressed pSO1 transfected HeLa cells, only about 10% showed fluorescence at 507 nm wavelength. However, of the induced pSO1 transfected HeLa cells, 68% showed fluorescence at 24 h, 51% at 48 h and 46% at 72 h post-transfection. To demonstrate this system's ability to be manipulated, two experiments were conducted in parallel. Almost 40% of the pSO1 transfected HeLa cells (24 h repressed, followed by 24 h induced) responded to the induction and expressed EGFP. A similar result was obtained for pSO1 transfected HeLa cells (48 h repressed, followed by 24 h induced); 36% of the cells responded and expressed EGFP. Alternatively, there was a decrease in the number of EGFP expressing cells when pSO1 transfected HeLa cells were induced for

  2. Deterministic and stochastic population-level simulations of an artificial lac operon genetic network

    Directory of Open Access Journals (Sweden)

    Zygourakis Kyriacos

    2011-07-01

    Full Text Available Abstract Background The lac operon genetic switch is considered as a paradigm of genetic regulation. This system has a positive feedback loop due to the LacY permease boosting its own production by the facilitated transport of inducer into the cell and the subsequent de-repression of the lac operon genes. Previously, we have investigated the effect of stochasticity in an artificial lac operon network at the single cell level by comparing corresponding deterministic and stochastic kinetic models. Results This work focuses on the dynamics of cell populations by incorporating the above kinetic scheme into two Monte Carlo (MC simulation frameworks. The first MC framework assumes stochastic reaction occurrence, accounts for stochastic DNA duplication, division and partitioning and tracks all daughter cells to obtain the statistics of the entire cell population. In order to better understand how stochastic effects shape cell population distributions, we develop a second framework that assumes deterministic reaction dynamics. By comparing the predictions of the two frameworks, we conclude that stochasticity can create or destroy bimodality, and may enhance phenotypic heterogeneity. Conclusions Our results show how various sources of stochasticity act in synergy with the positive feedback architecture, thereby shaping the behavior at the cell population level. Further, the insights obtained from the present study allow us to construct simpler and less computationally intensive models that can closely approximate the dynamics of heterogeneous cell populations.

  3. Elastic Rod Model of a DNA Loop in the Lac Operon

    Science.gov (United States)

    Balaeff, Alexander; Mahadevan, L.; Schulten, Klaus

    1999-12-01

    We use the theory of elasticity to compute the shape of the DNA loop bridging the gap in the crystal structure of the lac repressor-DNA complex. The Kirchhoff system of equations with boundary conditions derived from the crystal structure is solved using a continuation method. This approach can be applied effectively to find coarse-grained conformational minima of DNA loops.

  4. Fusions of bacteriophage P22 late genes to the Escherichia coli lacZ gene.

    OpenAIRE

    Riggs, P D; Botstein, D

    1987-01-01

    The late genes of bacteriophage P22 were fused to lacZ to study their differential expression from the late operon transcript. No instances of posttranscriptional regulation were uncovered, thus supporting the model that the late genes are expressed, by and large, in fixed ratios based on their translational efficiency and message stability.

  5. Determining the bistability parameter ranges of artificially induced lac operon using the root locus method.

    Science.gov (United States)

    Avcu, N; Alyürük, H; Demir, G K; Pekergin, F; Cavas, L; Güzeliş, C

    2015-06-01

    This paper employs the root locus method to conduct a detailed investigation of the parameter regions that ensure bistability in a well-studied gene regulatory network namely, lac operon of Escherichia coli (E. coli). In contrast to previous works, the parametric bistability conditions observed in this study constitute a complete set of necessary and sufficient conditions. These conditions were derived by applying the root locus method to the polynomial equilibrium equation of the lac operon model to determine the parameter values yielding the multiple real roots necessary for bistability. The lac operon model used was defined as an ordinary differential equation system in a state equation form with a rational right hand side, and it was compatible with the Hill and Michaelis-Menten approaches of enzyme kinetics used to describe biochemical reactions that govern lactose metabolism. The developed root locus method can be used to study the steady-state behavior of any type of convergent biological system model based on mass action kinetics. This method provides a solution to the problem of analyzing gene regulatory networks under parameter uncertainties because the root locus method considers the model parameters as variable, rather than fixed. The obtained bistability ranges for the lac operon model parameters have the potential to elucidate the appearance of bistability for E. coli cells in in vivo experiments, and they could also be used to design robust hysteretic switches in synthetic biology. PMID:25864166

  6. Logistics, Transport and Food Prices in LAC : Policy Guidance for Improving Efficiency and Reducing Costs

    OpenAIRE

    Schwartz, Jordan; Guasch, Jose Luis; Wilmsmeier, Gordon; Stokenberga, Aiga

    2009-01-01

    This introductory section explains the rationale for the guidance note, reflecting on the relevance of food prices in Latin America and the Caribbean (LAC), their impact on the poor and the effect that logistics and transport costs have on those prices. Based upon that framework, the note provides an overview of the logistics and transport hurdles faced by importers and consumers in the re...

  7. 77 FR 27245 - Big Stone National Wildlife Refuge, Big Stone and Lac Qui Parle Counties, MN

    Science.gov (United States)

    2012-05-09

    ... Register (73 FR 76677) on December 17, 2008. For more about the initial process and the history of this... Fish and Wildlife Service Big Stone National Wildlife Refuge, Big Stone and Lac Qui Parle Counties, MN... comprehensive conservation plan (CCP) and environmental assessment (EA) for Big Stone National Wildlife...

  8. Multiple Lac-mediated loops revealed by Bayesian statistics and tethered particle motion

    CERN Document Server

    Johnson, Stephanie; Phillips, Rob; Wiggins, Chris H; Lindén, Martin

    2014-01-01

    The bacterial transcription factor LacI loops DNA by binding to two separate locations on the DNA simultaneously. Despite being one of the best-studied model systems for transcriptional regulation, the number and conformations of loop structures accessible to LacI remain unclear, though the importance of multiple co-existing loops has been implicated in interactions between LacI and other cellular regulators of gene expression. To probe this issue, we have developed a new analysis method for tethered particle motion (TPM), a versatile and commonly-used in vitro single-molecule technique. Our method, vbTPM, is based on a variational Bayes treatment of hidden Markov models. It learns the number of distinct states (i.e., DNA-protein conformations) directly from TPM data with better resolution than existing methods, while easily correcting for common experimental artifacts. Studying short (roughly 100 bp) LacI-mediated loops, we are able to resolve three distinct loop structures, more than previously reported at ...

  9. Function, Structure, and Evolution of the Major Facilitator Superfamily: The LacY Manifesto

    Directory of Open Access Journals (Sweden)

    M. Gregor Madej

    2014-01-01

    Full Text Available The major facilitator superfamily (MFS is a diverse group of secondary transporters with members found in all kingdoms of life. A paradigm for MFS is the lactose permease (LacY of Escherichia coli, which couples the stoichiometric translocation of a galactopyranoside and an H+ across the cytoplasmic membrane. LacY has been the test bed for the development of many methods applied for the analysis of transport proteins. X-ray structures of an inward-facing conformation and the most recent structure of an almost occluded conformation confirm many conclusions from previous studies. Although structure models are critical, they are insufficient to explain the catalysis of transport. The clues to understanding transport are based on the principles of enzyme kinetics. Secondary transport is a dynamic process—static snapshots of X-ray crystallography describe it only partially. However, without structural information, the underlying chemistry is virtually impossible to conclude. A large body of biochemical/biophysical data derived from systematic studies of site-directed mutants in LacY suggests residues critically involved in the catalysis, and a working model for the symport mechanism that involves alternating access of the binding site is presented. The general concepts derived from the bacterial LacY are examined for their relevance to other MFS transporters.

  10. Expression of Porcine Interleukin-2 and Porcine Interleukin-6 and Their Adjuvant Effects on Gene Deleted Vaccine of Pseudorabies Virus (TK-/gG-/LacZ+)

    Institute of Scientific and Technical Information of China (English)

    YAN Lin; HE Qi-gai; CHEN Huan-chun; XIAO Shao-bo; WU Mei-zhou; LU Jian-qiang; HAN Li

    2003-01-01

    Porcine interleukin-2 and porcine interleukin-6 cDNA sequences were cloned into the expressing vectors pET-28a and pGEX-KG respectively. They were expressed in E.coli BL21 (DE3) with high-level production. The gene deleted vaccine of pseudorabies virus Ea strain (TK-/gG-/LacZ+) was mixed with the two different purified recombinant proteins each, or both, with the doses of 2, 5 or 10 μg ml-1. Ten groups of pseudorabies negative antibody swines were immuned twice with tested vaccines with different doses, or control vaccine, respectively. The antibody titers of the test groups were detected by neutralization test, and the daily weight gains of swines were calculated and analyzed statistically. In the study, all the neutralizing antibody titers in test groups were higher than the control group, and the recombinant proteins appeared a dose dependent adjuvant effect. The tested vaccines with 2 μg ml-1 pIL-2 and with 10 μg ml-1 pIL-2/pIL-6 got significant and extremely significant differences, compared with the vaccines without pILs. The difference of the daily weight gain indicated the potential positive influence of pIL-2 and pIL-6 on immune protection.

  11. Dicty_cDB: FC-BL14 [Dicty_cDB

    Lifescience Database Archive (English)

    Full Text Available /dictycdb.biol.tsukuba.ac.jp/CSM/FC/FC-BL/FC-BL14Q.Seq.d/ Representative seq. ID ...FC-BL14Z (Link to Original site) Representative DNA sequence >FC-BL14 (FC-BL14Q) /CSM/FC/FC-BL/FC-BL14Q.Seq....SVWIGGSILASLSTFQQMWISKEEYDESGPSIVHRKCF *tiktsdesashtnkyi*mynnnki*lflmvvdlyptikkkkk Translated Amino Acid sequence (All Frames...DIRKDLYGNVVLSGGTTMFPGIADRMNK ELTALAPSTMKIKIIAPPERKYSVWIGGSILASLSTFQQMWISKEEYDESGPSIVHRKCF *tiktsdesashtnkyi*...mynnnki*lflmvvdlyptikkkkk Homology vs CSM-cDNA Score E Sequences producing significant alignments: (bits) Va

  12. Positive control of lac operon expression in vitro by guanosine 5'-diphosphate 3'-diphosphate.

    Science.gov (United States)

    Primakoff, P; Artz, S W

    1979-04-01

    Maximal expression of the Escherichia coli lactose operon in a coupled in vitro transcription-translation system from a Salmonella typhimurium relA mutant was strongly dependent upon addition of guanosine 5'-diphosphate 3'-diphosphate (ppGpp). Without added ppGpp, at saturating 3',5'-cyclic AMP (cAMP) concentrations, synthesis of beta-galactosidase (beta-D-galactoside galactohydrolase, EC 3.2.1.23) was reproducibly only 5-7% of that which can be obtained with 0.5-0.8 mM ppGpp. Experiments in which transcription was uncoupled from translation indicated that this 14- to 20-fold stimulation by ppGpp occurred at the level of transcription. When coupled beta-galactosidase synthesis was primed with a template containing a well-characterized mutant lac promoter (lacP(r)L8UV5), the dependence on ppGpp was greatly reduced. This result provides an important experimental control previously unavailable for verifying the significance of ppGpp effects on gene regulation in vitro; it indicates that activation of lacP(+) expression by ppGpp is specifically an effect of increased transcription initiations. Furthermore, the large ppGpp stimulation of lacP(+) DNA enabled the level of expression of this template to approach that of lacP(r)L8UV5 DNA, an observation expected from results in vivo but not obtained with other transcription-translation systems in vitro. The importance of these results is considered with respect to previous ideas on the physiological role of ppGpp as a supercontrol molecule in bacterial regulation. PMID:109832

  13. R-parity Conserving Minimal SUSY $B-L$ Model

    CERN Document Server

    Okada, Nobuchika

    2016-01-01

    We propose a simple gauged U(1)$_{B-L}$ extension of the minimal supersymmetric Standard Model (MSSM), where R-parity is conserved as usual in the MSSM. The global $B-L$ (baryon number minus lepton number) symmetry in the MSSM is gauged and three MSSM gauge-singlet chiral multiplets with a unit $B-L$ charge are introduced, ensuring the model free from gauge and gravitational anomalies. We assign an odd R-parity for two of the new chiral multiplets and hence they are identified with the right-handed neutrino superfields, while an even R-parity is assigned to the other one ($\\Phi$). The scalar component of $\\Phi$ plays the role of a Higgs field to break the U(1)$_{B-L}$ symmetry through its negative mass squared, which is radiatively generated by the renormalization group running of soft supersymmetry (SUSY) breaking parameters from a high energy. This radiative U(1)$_{B-L}$ symmetry breaking leads to its breaking scale being at the TeV naturally. Because of our novel R-parity assignment, three light neutrinos ...

  14. Unifying the electroweak and B-L interactions

    CERN Document Server

    Dong, P V

    2015-01-01

    We argue that the gauge symmetry which includes SU(3)_L as a higher weak-isospin symmetry is manifestly given by SU(3)_C\\otimes SU(3)_L\\otimes U(1)_X\\otimes U(1)_N, where the last two factors determine the electric charge and B-L, respectively. This theory not only provides a consistent unification of the electroweak and B-L interactions, but also gives insights in dark matter, neutrino masses, and inflation. The dark matter belongs to a class of new particles that have wrong B-L numbers, and is stabilized due to a newly-realized W-parity as residual gauge symmetry. The B-L breaking field is important to define the W-parity, seesaw scales, and inflaton. Furthermore, the number of fermion generations and the electric charge quantization are explained naturally. We also show that the previous 3-3-1 models are only an effective theory as the B-L charge and the unitarity argument are violated. This work substantially generalizes our recently-proposed 3-3-1-1 model.

  15. Polarimetry and photometry of active quasars at visual and near-infrared wavelengths

    International Nuclear Information System (INIS)

    The optical and near-infrared continua of highly luminous BL Lacertae (BL Lac) objects and optically violent variable (OVV) quasars are studied through simultaneous broad-band photometry and linear polarimetry. Nineteen BL Lacs and OVVs were monitored during a ∼1 1/2-year period, with the major aim of characterizing the wavelength-dependent polarization exhibited by these objects. Optical (UBVRI) observations were conducted at the UCSD/U. Minn. 1.5-m telescope on Mt. Lemmon, Arizona. Simultaneous (within 1 hr.) near-infrared (JHK) measurements were made using the KPNO 2.1-m telescope. Most of the BL Lac objects exhibit large variations in polarization and brightness on time scale of less than a week. The degree of fractional linear polarization (P) is not observed to be related to brightness or optical spectral index. Most BL Lacs did not show a preferred polarization position angle (theta). Wavelength-dependent P and theta are observed in almost all BL Lacs, but not always simultaneously. The OVV quasar 1156 + 295 shows behavior very similar to the BL Lac objects. 3C 345 Exhibited polarization properties that are quite different from those of the BL Lacs. This object showed a clear correlation between brightness and P

  16. 云县紫胶虫相关特性及放养技术对紫胶生产的影响%Effects of Relevant Characteristics of Yunxian Lac Insect and Stocking Technology on Lac Production

    Institute of Scientific and Technical Information of China (English)

    严世葵

    2013-01-01

    According to the morphological characteristics of the lac insect, living habits, biological characteristics and pupae scattered law, various technical aspects of the lac stocking and post-stocking management and harvesting were elaborated, which lay a foundation for lac production.%根据紫胶虫的形态特征、生活习性、生物学特性及蛹散规律,阐述了紫胶虫放养中的各个技术环节及放养后的管理和紫胶的采收,为紫胶生产奠定了基础.

  17. P-Element repression in Drosophila melanogaster by variegating clusters of P-lacZ-white transgenes.

    Science.gov (United States)

    Ronsseray, S; Boivin, A; Anxolabéhère, D

    2001-12-01

    In Drosophila, clusters of P transgenes (P-lac-w) display a variegating phenotype for the w marker. In addition, X-ray-induced rearrangements of chromosomes bearing such clusters may lead to enhancement of the variegated phenotype. Since P-lacZ transgenes in subtelomeric heterochromatin have some P-element repression abilities, we tested whether P-lac-w clusters also have the capacity to repress P-element activity in the germline. One cluster (T-1), located on a rearranged chromosome (T2;3) and derived from a line bearing a variegating tandem array of seven P-lac-w elements, partially represses the dysgenic sterility (GD sterility) induced by P elements. This cluster also strongly represses in trans the expression of P-lacZ elements in the germline. This latter suppression shows a maternal effect. Finally, the combination of variegating P-lac-w clusters and a single P-lacZ reporter inserted in subtelomeric heterochromatic sequences at the X chromosome telomere (cytological site 1A) leads to strong repression of dysgenic sterility. These results show that repression of P-induced dysgenic sterility can be elicited in the absence of P elements encoding a polypeptide repressor and that a transgene cluster can repress the expression of a single homologous transgene at a nonallelic position. Implications for models of transposable element silencing are discussed. PMID:11779802

  18. HESS J1943+213: a candidate extreme BL Lacertae object

    CERN Document Server

    Abramowski, A; Aharonian, F; Akhperjanian, A G; Anton, G; Balzer, A; Barnacka, A; de Almeida, U Barres; Bazer-Bachi, A R; Becherini, Y; Becker, J; Behera, B; Bernlöhr, K; Bochow, A; Boisson, C; Bolmont, J; Bordas, P; Borrel, V; Brucker, J; Brun, F; Brun, P; Bulik, T; Büsching, I; Carrigan, S; Casanova, S; Cerruti, M; Chadwick, P M; Charbonnier, A; Chaves, R C G; Cheesebrough, A; Chounet, L -M; Clapson, A C; Coignet, G; Colom, P; Conrad, J; Dalton, M; Daniel, M K; Davids, I D; Degrange, B; Deil, C; Dickinson, H J; Djannati-Ataï, A; Domainko, W; Drury, L O'C; Dubois, F; Dubus, G; Dyks, J; Dyrda, M; Egberts, K; Eger, P; Espigat, P; Fallon, L; Farnier, C; Fegan, S; Feinstein, F; Fernandes, M V; Fiasson, A; Fontaine, G; Förster, A; Fü\\ssling, M; Gallant, Y A; Gast, H; Gérard, L; Gerbig, D; Giebels, B; Glicenstein, J F; Glück, B; Goret, P; Göring, D; Häffner, S; Hague, J D; Hampf, D; Hauser, M; Heinz, S; Heinzelmann, G; Henri, G; Hermann, G; Hinton, J A; Hoffmann, A; Hofmann, W; Hofverberg, P; Holler, M; Horns, D; Jacholkowska, A; de Jager, O C; Jahn, C; Jamrozy, M; Jung, I; Kastendieck, M A; Katarzyński, K; Katz, U; Kaufmann, S; Keogh, D; Khangulyan, D; Khélifi, B; Klochkov, D; Kluźniak, W; Kneiske, T; Komin, Nu; Kosack, K; Kossakowski, R; Laffon, H; Lamanna, G; Lennarz, D; Lohse, T; Lopatin, A; Lu, C -C; Marandon, V; Marcowith, A; Masbou, J; Maurin, D; Maxted, N; McComb, T J L; Medina, M C; Méhault, J; Nguyen, N; Moderski, R; Moulin, E; Naumann, C L; Naumann-Godo, M; de Naurois, M; Nedbal, D; Nekrassov, D; Nicholas, B; Niemiec, J; Nolan, S J; Ohm, S; Olive, J-F; Wilhelmi, E de Oña; Opitz, B; Ostrowski, M; Panter, M; Arribas, M Paz; Pedaletti, G; Pelletier, G; Petrucci, P -O; Pita, S; Pühlhofer, G; Punch, M; Quirrenbach, A; Raue, M; Rayner, S M; Reimer, A; Reimer, O; Renaud, M; Reyes, R de los; Rieger, F; Ripken, J; Rob, L; Rosier-Lees, S; Rowell, G; Rudak, B; Rulten, C B; Ruppel, J; Ryde, F; Sahakian, V; Santangelo, A; Schlickeiser, R; Schöck, F M; Schönwald, A; Schulz, A; Schwanke, U; Schwarzburg, S; Schwemmer, S; Shalchi, A; Sikora, M; Skilton, J L; Sol, H; Spengler, G; Stawarz, \\L; Steenkamp, R; Stegmann, C; Stinzing, F; Stycz, K; Sushch, I; Szostek, A; Tavernet, J -P; Terrier, R; Tibolla, O; Tluczykont, M; Valerius, K; van Eldik, C; Vasileiadis, G; Venter, C; Vialle, J P; Viana, A; Vincent, P; Vivier, M; Völk, H J; Volpe, F; Vorobiov, S; Vorster, M; Wagner, S J; Ward, M; Wierzcholska, A; Zajczyk, A; Zdziarski, A A; Zech, A; Zechlin, H -S; Burnett, T H; Hill, A B

    2011-01-01

    We report on a newly detected point-like source, HESS J1943+213 located in the Galactic plane. This source coincides with an unidentified hard X-ray source IGR J19443+2117, which was proposed to have radio and infrared counterparts. HESS J1943+213 is detected at the significance level of 7.9 \\sigma (post-trials) at RA(J2000)=19h 43m 55s +- 1s (stat) +- 1s (sys), DEC(J2000) = +21deg 18' 8" +- 17" (stat) +- 20" (sys). The source has a soft spectrum with photon index Gamma = 3.1 +- 0.3 (stat) +- 0.2 (sys) and a flux above 470 GeV of 1.3 +- 0.2 (stat) +- 0.3 (sys) x 10^{-12} cm^{-2} s^{-1}. There is no Fermi/LAT counterpart down to a flux limit of 6 x 10^{-9} cm^{-2} s^{-1} in the 0.1-100 GeV energy range (95% confidence upper limit calculated for an assumed power-law model with a photon index Gamma=2.0). The data from radio to VHE gamma-rays do not show any significant variability. We combine new H.E.S.S., Fermi/LAT and Nancay Radio Telescope observations with pre-existing non-simultaneous multi-wavelength obser...

  19. Isolation and analysis of two Escherichia coli K-12 ilv attenuator deletion mutants with high-level constitutive expression of an ilv-lac fusion operon.

    OpenAIRE

    Bennett, D C; Umbarger, H E

    1984-01-01

    A lysogenizing lambda phage, lambda dilv-lac11, was constructed to carry an ilvD-lac operon fusion. Expression from the phage of the ilvE and lacZ genes is controlled by an intact ilv control region also carried by this phage. Two spontaneous mutants of lambda dilv-lac11 that have high-level constitutive expression of the ilv-lac fusion operon were isolated by growth on a beta-chloroalanine selective medium. The mutants were shown by nucleotide sequence determination to contain large deletion...

  20. Statistical analysis of the temporal properties of BL Lacertae

    Science.gov (United States)

    Guo, Yu Cheng; Hu, Shao Ming; Li, Yu Tong; Chen, Xu

    2016-08-01

    A comprehensive temporal analysis has been performed on optical light curves of BL Lacertae in the B, V and R bands. The light curves were denoised by Gaussian smoothing and decomposed into individual flares using an exponential profile. The asymmetry, duration, peak flux and equivalent energy output of flares were measured and the frequency distributions presented. Most optical flares of BL Lacertae are highly symmetric, with a weak tendency towards gradual rises and rapid decays. The distribution of flare durations is not random, but consistent with a gamma distribution. Peak fluxes and energy outputs of flares all follow a log-normal distribution. A positive correlation is detected between flare durations and peak fluxes. The temporal properties of BL Lacertae provide evidence of the stochastic magnetohydrodynamic process in the accretion disc and jet.The results presented here can serve as constraints on physical models attempting to interpret blazar variations.

  1. Statistical Analysis on Temporal Properties of BL Lacertae

    Science.gov (United States)

    Guo, Yu Cheng; Hu, Shao Ming; Li, Yu Tong; Chen, Xu

    2016-04-01

    A comprehensive temporal analysis has been performed on optical light curves of BL Lacertae in B, V and R bands. The light curves were denoised by Gaussian smoothing and decomposed into individual flares using an exponential profile. Asymmetry, duration, peak flux and equivalent energy output of flares were measured and the frequency distributions are presented. Most optical flares of BL Lacertae are highly symmetric, with a weak tendency towards gradual rises and rapid decays. The distribution of flare durations is not random but consistent with a gamma distribution. Peak fluxes and energy outputs of flares all follow lognormal distribution. A positive correlation is detected between flare durations and peak fluxes. The temporal properties of BL Lacertae provide evidence of the stochastic magnetohydrodynamic process in accretion disk and jet. Results presented here can serve as constraints on physical models attempting to interpreting blazar variations.

  2. Measurement of the proton motive force in Rhizobium meliloti with the Escherichia coli lacY gene product.

    OpenAIRE

    Gober, J W; Kashket, E R

    1985-01-01

    An Escherichia coli lac operon constitutive for lacY was subcloned into the EcoRI site of a wide-host-range plasmid of the Q incompatibility group, and the resulting recombinant plasmid was introduced into Tn5-generated Lac- mutants of Rhizobium meliloti. The R. meliloti transconjugants accumulated lactose about 1,000-fold, equivalent to a proton motive force of -170 to -180 mV, not significantly different from the values calculated from the distributions of weak acids and lipophilic cations.

  3. Majorana Dark matter with B+L gauge symmetry

    OpenAIRE

    Chao, Wei; Guo, Huai-Ke; Zhang, Yongchao

    2016-01-01

    We present a new model that extends the Standard Model (SM) with the local B+L symmetry, and point out that the lightest new fermion $\\zeta$, introduced to cancel anomalies and stabilized automatically by the B+L symmetry, can serve as the cold dark matter candidate. We study constraints on the model from Higgs measurements, electroweak precision measurements as well as the relic density and direct detections of the dark matter. Numerical results reveal that the pseudo-vector coupling of $\\ze...

  4. Elevated Optical Luminosity for Gamma-ray Blazar BL Lacertae

    Science.gov (United States)

    Furniss, A.; Fumagalli, M.; Hogan, M.; Kaplan, K.; Prochaska, P. X.; Williams, D. A.

    2012-06-01

    We report on the increased optical luminosity of BL Lacertae (RA=22h02m43.29s, dec=42d16m39.98s), a low-frequency-peaked gamma-ray emitting blazar at a redshift of 0.068 (3EG J2202+4225, 2FGL J2202.8+4216). We have collected regular R-band exposures for BL Lacertae as part of a larger optical monitoring program of gamma-ray-bright blazars using the Super-LOTIS (Livermore Optical Transient Imaging System) robotic telescope at the Steward Observatory on Kitt Peak, near Tucson Arizona.

  5. Von Blüten, Göttern und Gelehrten

    OpenAIRE

    Zotter, Astrid

    2013-01-01

    Der Sanskrittext Puṣpacintāmaṇi (PuCi) behandelt Blüten als Darbringungen (upacāra) im wichtigsten hinduistischen Verehrungsritual, der pūjā. In ca. 400 Strophen werden über 200 Namen von Blüten genannt und für verschiedene Gottheiten und pūjās als geeignete oder ungeeignete Gaben vorgeschrieben. Der Text ist eine Kompilation (Nibandha), in der die Inhalte aus 47 namentlich genannten Quellentexten referiert werden. Ziel der Dissertation ist es nicht nur, diesen Text, der 1966 zum ersten Ma...

  6. Kartlegging av marin bløtbunnsfauna - Metodeutvikling i hydrolittoralsonen

    OpenAIRE

    Haugen, Grethe Sundet

    2016-01-01

    Det er gjort få kvalitative undersøkelser på bløtbunnssamfunnet i hydrolittoralen i Norge. I denne studien ble artssammensetningen i littoralsonen fra tre forskjellige bløtbunnsstrender i Sør-Trøndelag undersøkt ved en enkel innsamlingsmetode. Innsamlingsmetoden hadde fokus på å observere og registrere fysiske miljøvariabler som bølgeeksponering og kornstørrelse, samt å observere å samle inn epi- og infauna som var tilstede i fjæra ved lavvann. Erfaringer fra felt- og laboratoriearbeidet har ...

  7. MULTIPLE OBJECTS

    Directory of Open Access Journals (Sweden)

    A. A. Bosov

    2015-04-01

    Full Text Available Purpose. The development of complicated techniques of production and management processes, information systems, computer science, applied objects of systems theory and others requires improvement of mathematical methods, new approaches for researches of application systems. And the variety and diversity of subject systems makes necessary the development of a model that generalizes the classical sets and their development – sets of sets. Multiple objects unlike sets are constructed by multiple structures and represented by the structure and content. The aim of the work is the analysis of multiple structures, generating multiple objects, the further development of operations on these objects in application systems. Methodology. To achieve the objectives of the researches, the structure of multiple objects represents as constructive trio, consisting of media, signatures and axiomatic. Multiple object is determined by the structure and content, as well as represented by hybrid superposition, composed of sets, multi-sets, ordered sets (lists and heterogeneous sets (sequences, corteges. Findings. In this paper we study the properties and characteristics of the components of hybrid multiple objects of complex systems, proposed assessments of their complexity, shown the rules of internal and external operations on objects of implementation. We introduce the relation of arbitrary order over multiple objects, we define the description of functions and display on objects of multiple structures. Originality.In this paper we consider the development of multiple structures, generating multiple objects.Practical value. The transition from the abstract to the subject of multiple structures requires the transformation of the system and multiple objects. Transformation involves three successive stages: specification (binding to the domain, interpretation (multiple sites and particularization (goals. The proposed describe systems approach based on hybrid sets

  8. Use of urea and glycine betaine to quantify coupled folding and probe the burial of DNA phosphates in lac repressor-lac operator binding.

    Science.gov (United States)

    Hong, Jiang; Capp, Mike W; Saecker, Ruth M; Record, M Thomas

    2005-12-27

    Thermodynamic analysis of urea-biopolymer interactions and effects of urea on folding of proteins and alpha-helical peptides shows that urea interacts primarily with polar amide surface. Urea is therefore predicted to be a quantitative probe of coupled folding, remodeling, and other large-scale changes in the amount of water-accessible polar amide surface in protein processes. A parallel analysis indicates that glycine betaine [N,N,N-trimethylglycine (GB)] can be used to detect burial or exposure of anionic (carboxylate, phosphate) biopolymer surface. To test these predictions, we have investigated the effects of these solutes (0-3 m) on the formation of 1:1 complexes between lac repressor (LacI) and its symmetric operator site (SymL) at a constant KCl molality. Urea reduces the binding constant K(TO) [initial slope dlnK(TO)/dm(urea) = -1.7 +/- 0.2], and GB increases K(TO) [initial slope dlnK(TO)/dm(GB) = 2.1 +/- 0.2]. For both solutes, this derivative decreases with an increase in solute concentration. Analysis of these initial slopes predicts that (1.5 +/- 0.3) x 10(3) A2 of polar amide surface and (4.5 +/- 1.0) x 10(2) A2 of anionic surface are buried in the association process. Analysis of published structural data, together with modeling of unfolded regions of free LacI as extended chains, indicates that 1.5 x 10(3) A2 of polar amide surface and 6.3 x 10(2) A2 of anionic surface are buried in complexation. Quantitative agreement between structural and thermodynamic results is obtained for amide surface (urea); for anionic surface (GB), the experimental value is approximately 70% of the structural value. For LacI-SymL binding, two-thirds of the structurally predicted change in amide surface (1.0 x 10(3) A2) occurs outside the protein-DNA interface in protein-protein interfaces formed by folding of the hinge helices and interactions of the DNA binding domain (DBD) with the core of the repressor. Since urea interacts principally with amide surface, it is

  9. PENURUNAN KADAR SIANIDA SINGKONG PAHIT PADA PROSES FERMENTASI CAIR BAKTERI BREVIBACTERIUM LACTOFERMENTEMUM BL-1M76

    Directory of Open Access Journals (Sweden)

    Suryana Purawisastra

    2012-11-01

    Full Text Available THE REDUCTION OF THE CYANIDE CONTENT OF BITIER CASSAVA BY THE PROCESS OF LIQUID FERMENTATION USING BREVIBACTERIUM LACTOFERMENTUM BL-1M76.Background: Cassava is one of the important source of carbohydrate in tropical countries, that easliy grows in any kind of soil. However, there is a kind of cassava containing cyanide substance, which is toxic for human consumption. This kind of cassava known as bitter cassava contains more starch, but it can't be used as food directly. Usually, people uses this cassava as raw material for producing starch known as 'tapioka' by the traditional method. The cyanide substance in cassava can be degraded by bacteria known as Brevibacterium sp R312 that is capable to degrade about 80% of the cyianide content in cassava, since this bacteria produces some enzymes namely E glucosidase, nitrilhydratase, and amidase, which degrade this cyanide substance. In our laboratory, has another strain of this bacteria, Brevibacterium fermentum BL-1M76, which Is not harmful and has potential capability in producing amino acid of lysine. Objectives: The study was conducted to investigate the potential of the bacteria Brevibacterium fermentum BL-1M76 in reducting of the cyanide substance of bitter cassava using the process of liquid fermentation. Materials and Methods: This experiment used four kinds of bitter cassava obtained from the Balai Penelitian Bioteknologi Tanaman Pangan, Departemen Pertanian (The Research Station of Biotechnology for Food Crops. Those cassavas are known as Adira II, Adria IV, 39.1.1 code, and 46.8 code. The liquid fermentation was conducted in the erlenmeyer flask 250 ml containing 10 ml of 10% cassava medium. The process of fermentation was done in two steps. The first step was to decide the maxmium volume and concentration cell of bacteria suspension, and the duration time of the incubation at the 28°C. The observation was done to the changes content of cyanide, and protein of the cassava medium due

  10. Bistability of the lac operon during growth of Escherichia coli on lactose and lactose+glucose.

    Science.gov (United States)

    Narang, Atul; Pilyugin, Sergei S

    2008-05-01

    The lac operon of Escherichia coli can exhibit bistability. Early studies showed that bistability occurs during growth on TMG/succinate and lactose+glucose, but not during growth on lactose. More recently, studies with lacGFP-transfected cells show bistability during growth on TMG/succinate, but not during growth on lactose and lactose+glucose. In the literature, these results are invariably attributed to variations in the destabilizing effect of the positive feedback generated by induction. Specifically, during growth on TMG/succinate, lac induction generates strong positive feedback because the permease stimulates the accumulation of intracellular TMG, which in turn, promotes the synthesis of even more permease. This positive feedback is attenuated during growth on lactose because hydrolysis of intracellular lactose by beta-galactosidase suppresses the stimulatory effect of the permease. It is attenuated even more during growth on lactose + glucose because glucose inhibits the uptake of lactose. But it is clear that the stabilizing effect of dilution also changes dramatically as a function of the medium composition. For instance, during growth on TMG/succinate, the dilution rate of lac permease is proportional to its activity, e, because the specific growth rate is independent of e (it is completely determined by the concentration of succinate). However, during growth on lactose, the dilution rate of the permease is proportional to e2 because the specific growth rate is proportional to the specific lactose uptake rate, which in turn, proportional to e. We show that: (a) This dependence on e2 creates such a strong stabilizing effect that bistability is virtually impossible during growth on lactose, even in the face of the intense positive feedback generated by induction. (b) This stabilizing effect is weakened during growth on lactose+glucose because the specific growth rate on glucose is independent of e, so that the dilution rate once again contains a term that

  11. Object theatre

    DEFF Research Database (Denmark)

    Ryöppy, Merja; Heiberg, Andreas

    2015-01-01

    This paper investigates how four perspectives from Object Theatre can enhance interaction design in the early stages of a product design process. We propose these perspectives as a playful approach for designers to gain embodied understanding and perception of objects to enable new design...... possibilities to emerge. We present a study in which the Object Theatre approach is applied to redesign socially shared everyday products that are located in public places. This project demonstrates how Object Theatre offers a broad perspective form which to explore and present product interactions. In...

  12. The gravitational wave spectrum from cosmological B-L breaking

    International Nuclear Information System (INIS)

    Cosmological B-L breaking is a natural and testable mechanism to generate the initial conditions of the hot early universe. If B-L is broken at the grand unification scale, the false vacuum phase drives hybrid inflation, ending in tachyonic preheating. The decays of heavy B-L Higgs bosons and heavy neutrinos generate entropy, baryon asymmetry and dark matter and also control the reheating temperature. The different phases in the transition from inflation to the radiation dominated phase produce a characteristic spectrum of gravitational waves. We calculate the complete gravitational wave spectrum due to inflation, preheating and cosmic strings, which turns out to have several features. The production of gravitational waves from cosmic strings has large uncertainties, with lower and upper bounds provided by Abelian Higgs strings and Nambu-Goto strings, implying ΩGWh2 ∼ 10−13–10−8, much larger than the spectral amplitude predicted by inflation. Forthcoming gravitational wave detectors such as eLISA, advanced LIGO, ET, BBO and DECIGO will reach the sensitivity needed to test the predictions from cosmological B-L breaking

  13. Proteomic Analysis on Acetate Metabolism in Citrobacter sp. BL-4

    Directory of Open Access Journals (Sweden)

    Young-Man Kim, Sung-Eun Lee, Byeoung-Soo Park, Mi-Kyung Son, Young-Mi Jung, Seung-Ok Yang, Hyung-Kyoon Choi, Sung-Ho Hur, Jong Hwa Yum

    2012-01-01

    Full Text Available Mass production of glucosamine (GlcN using microbial cells is a worthy approach to increase added values and keep safety problems in GlcN production process. Prior to set up a microbial cellular platform, this study was to assess acetate metabolism in Citrobacter sp. BL-4 (BL-4 which has produced a polyglucosamine PGB-2. The LC-MS analysis was conducted after protein separation on the 1D-PAGE to accomplish the purpose of this study. 280 proteins were totally identified and 188 proteins were separated as acetate-related proteins in BL-4. Acetate was converted to acetyl-CoA by acetyl-CoA synthetase up-regulated in the acetate medium. The glyoxylate bypass in the acetate medium was up-regulated with over-expression of isocitrate lyases and 2D-PAGE confirmed this differential expression. Using 1H-NMR analysis, the product of isocitrate lyases, succinate, increased about 15 times in the acetate medium. During acetate metabolism proteins involved in the lipid metabolism and hexosamine biosynthesis were over-expressed in the acetate medium, while proteins involved in TCA cycle, pentose phosphate cycle and purine metabolism were down-regulated. Taken together, the results from the proteomic analysis can be applied to improve GlcN production and to develop metabolic engineering in BL-4.

  14. The gravitational wave spectrum from cosmological B-L breaking

    Energy Technology Data Exchange (ETDEWEB)

    Buchmueller, W.; Domcke, V.; Kamada, K. [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany); Schmitz, K. [Tokyo Univ., Kashiwa (Japan). Kavli IPMU (WPI)

    2013-05-15

    Cosmological B-L breaking is a natural and testable mechanism to generate the initial conditions of the hot early universe. If B-L is broken at the grand unification scale, the false vacuum phase drives hybrid inflation, ending in tachyonic preheating. The decays of heavy B-L Higgs bosons and heavy neutrinos generate entropy, baryon asymmetry and dark matter and also control the reheating temperature. The different phases in the transition from inflation to the radiation dominated phase produce a characteristic spectrum of gravitational waves. We calculate the complete gravitational wave spectrum due to inflation, preheating and cosmic strings, which turns out to have several features. The production of gravitational waves from cosmic strings has large uncertainties, with lower and upper bounds provided by Abelian Higgs strings and Nambu-Goto strings, implying {Omega}{sub GW}h{sup 2}{proportional_to}10{sup -13}-10{sup -8}, much larger than the spectral amplitude predicted by inflation. Forthcoming gravitational wave detectors such as eLISA, advanced LIGO and BBO/DECIGO will reach the sensitivity needed to test the predictions from cosmological B-L breaking.

  15. Probing classically conformal $B-L$ model with gravitational waves

    CERN Document Server

    Jinno, Ryusuke

    2016-01-01

    We study the cosmological history of the classical conformal $B-L$ gauge extension of the standard model, in which the physical scales are generated via the Coleman-Weinberg-type symmetry breaking. Especially, we consider the thermal phase transition of the U$(1)_{B-L}$ symmetry in the early universe and resulting gravitational-wave production. Due to the classical conformal invariance, the phase transition tends to be a first-order one with ultra-supercooling, which enhances the strength of the produced gravitational waves. We show that, requiring (1) U$(1)_{B-L}$ is broken after the reheating, (2) the $B-L$ gauge coupling does not blow up below the Planck scale, (3) the thermal phase transition completes in almost all the patches in the universe, the gravitational wave spectrum can be as large as $\\Omega_{\\rm GW} \\sim 10^{-8}$ at the frequency $f \\sim 0.01$-$1$Hz for some model parameters, and a vast parameter region can be tested by future interferometer experiments such as eLISA, LISA, BBO and DECIGO.

  16. The gravitational wave spectrum from cosmological B-L breaking

    Energy Technology Data Exchange (ETDEWEB)

    Buchmüller, W.; Domcke, V.; Kamada, K. [Deutsches Elektronen-Synchrotron DESY, 22607 Hamburg (Germany); Schmitz, K., E-mail: buchmuwi@mail.desy.de, E-mail: valerie.domcke@desy.de, E-mail: kohei.kamada@desy.de, E-mail: kai.schmitz@ipmu.jp [Kavli IPMU (WPI), University of Tokyo, Kashiwa 277-8583 (Japan)

    2013-10-01

    Cosmological B-L breaking is a natural and testable mechanism to generate the initial conditions of the hot early universe. If B-L is broken at the grand unification scale, the false vacuum phase drives hybrid inflation, ending in tachyonic preheating. The decays of heavy B-L Higgs bosons and heavy neutrinos generate entropy, baryon asymmetry and dark matter and also control the reheating temperature. The different phases in the transition from inflation to the radiation dominated phase produce a characteristic spectrum of gravitational waves. We calculate the complete gravitational wave spectrum due to inflation, preheating and cosmic strings, which turns out to have several features. The production of gravitational waves from cosmic strings has large uncertainties, with lower and upper bounds provided by Abelian Higgs strings and Nambu-Goto strings, implying Ω{sub GW}h{sup 2} ∼ 10{sup −13}–10{sup −8}, much larger than the spectral amplitude predicted by inflation. Forthcoming gravitational wave detectors such as eLISA, advanced LIGO, ET, BBO and DECIGO will reach the sensitivity needed to test the predictions from cosmological B-L breaking.

  17. Department of the Interior : Draft Environmental Statement : DES 73-40 : Proposed Rice Lake and Mille Lacs Islands Wilderness Areas

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — This document is a draft of an analysis of the environmental impact wilderness designation would pose for the Rice Lake and Mille Lacs Islands Wilderness Areas....

  18. Rice Lake National Wildlife Refuge, Mille Lacs Refuge, Sandstone Unit [Narrative report]: July 1, 1974 to June 30, 1975

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — This annual narrative report for Rice Lake NWR and Mille Lacs NWR outlines Refuge accomplishments during the 1975 fiscal year. The report begins by summarizing the...

  19. Rice Lake National Wildlife Refuge and Mille Lacs National Wildlife Refuge: Comprehensive Conservation Plan and Environmental Assessment

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — This Comprehensive Conservation Plan (CCP) was written to guide management on Rice Lake and Mille Lacs NWRs for the next 15 years. This plan outlines the refuges'...

  20. Narrative report for May, June, July, August, 1945 Des Lacs National Wildlife Refuge & Easement Refuge in District IV

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — This narrative report for Des Lacs National Wildlife Refuge outlines Refuge accomplishments from May through August of 1945. The report begins by summarizing the...

  1. Narrative report for September, October, November, December, 1945 Des Lacs National Wildlife Refuge and Easement Refuges in District IV

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — This narrative report for Des Lacs National Wildlife Refuge outlines Refuge accomplishments from September through December of 1945. The report begins by...

  2. Narrative report for May, June, July and August 1944 Des Lacs National Wildlife Refuge & Easement Refuges in District IV

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — This narrative report for Des Lacs National Wildlife Refuge outlines Refuge accomplishments from May through August of 1944. The report begins by summarizing the...

  3. Archive of Geosample Data and Information from the University of Minnesota National Lacustrine Core Repository (LacCore)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The National Lacustrine Core Repository (LacCore), operated by the University of Minnesota is a partner in the Index to Marine and Lacustrine Geological Samples...

  4. Etude du comportement biogéochimique du carbone dans le lac Kivu au nord-ouest du Rwanda

    OpenAIRE

    Rwabuhungu Rwatangabo, Digne

    2008-01-01

    RésuméLe Rift Est-Africain comprend plusieurs grands lacs, dont le lac Kivu situé entre 1°34’et 2°30’ de latitude Sud et compris entre 28°50’ et 29°23’ de longitude Est. Ce lac,localisé au nord-ouest du Rwanda à la frontière avec la République Démocratique duCongo, présente une spécificité unique au monde: ses eaux profondes contiennentune gigantesque quantité de gaz dissous (3/4 de dioxyde de carbone (CO2), 1/4 degaz méthane (CH4)).Les études antérieures indiquent que les eaux du lac Kivu pr...

  5. Rôle et place du riz pluvial dans les exploitations du lac Alaotra

    OpenAIRE

    Penot, E.; Domas, R.; Andriamalala, H.; Hyac, P.; Dupin, B.; Durand, C; Nave, S.; Rabenandro, T. H.; Rasolomanjaka, J.

    2009-01-01

    International audience La région de l'Alaotra repose sur un plateau situé à 750 mètres d'altitude avec au cœur de la plaine le lac Alaotra. La surface cultivée en riziculture est estimée à 148 500 ha en 2000 (FAO/UPDR, 2000), dont 75-80 000 ha dans la cuvette du Lac et plus de 65-70 000 ha au sud et dans les zones en périphérie, qui constitue 10% de la surface rizicole nationale pour seulement 4% des riziculteurs malgaches. Cette région réalise 33% de la valeur ajoutée de l'ensemble de la ...

  6. Escherichia coli catabolite gene activator protein mutants defective in positive control of lac operon transcription.

    OpenAIRE

    Eschenlauer, A C; Reznikoff, W S

    1991-01-01

    We isolated three Escherichia coli catabolite gene activator protein mutants that are defective in the positive control of transcription initiation from the lac operon promoter region yet retain negative control of transcription from other promoters. One mutant has a substitution of valine for glutamate at residue 72, which lies in the cyclic AMP binding domain and contacts cyclic AMP. The other two mutants have substitutions of asparagine and cysteine for glycine 162, which lies in a surface...

  7. Influence of Catabolite Repression and Inducer Exclusion on the Bistable Behavior of the lac Operon

    OpenAIRE

    Santillán, Moisés; Mackey, Michael C.

    2004-01-01

    A mathematical model of the lac operon which includes all of the known regulatory mechanisms, including external-glucose-dependent catabolite repression and inducer exclusion, as well as the time delays inherent to transcription and translation, is presented. With this model we investigate the influence of external glucose, by means of catabolite repression and the regulation of lactose uptake, on the bistable behavior of this system.

  8. Bistable Behavior in a Model of the lac Operon in Escherichia coli with Variable Growth Rate

    OpenAIRE

    Santillán, M.

    2007-01-01

    This work is a continuation from another study previously published in this journal. Both the former and the present works are dedicated to investigating the bistable behavior of the lac operon in Escherichia coli from a mathematical modeling point of view. In the previous article, we developed a detailed mathematical model that accounts for all of the known regulatory mechanisms in this system, and studied the effect of inducing the operon with lactose instead of an artificial inducer. In th...

  9. Monitoring of the Lac Bam Wetland Extent Using Dual-Polarized X-Band SAR Data

    OpenAIRE

    Linda Moser; Andreas Schmitt; Anna Wendleder; Achim Roth

    2016-01-01

    Wetlands in semi-arid Africa are vital as water resource for local inhabitants and for biodiversity, but they are prone to strong seasonal fluctuations. Lac Bam is the largest natural freshwater lake in Burkina Faso, its water is mixed with patches of floating or flooded vegetation, and very turbid and sediment-rich. These characteristics as well as the usual cloud cover during the rainy season can limit the suitability of optical remote sensing data for monitoring purposes. This study demons...

  10. MINNESOTA V. MILLE LACS: GATEWAY TO TRIBAL/STATE RESOURCE MANAGEMENT

    OpenAIRE

    Gonzalez, Mark J.

    2000-01-01

    Minnesota v. Mille Lacs Band of Chippewa Indians is the United States Supreme Court's most recent decision to focus on the continued existence of tribal off-reservation hunting, fishing, and gathering rights (usufructuary rights) as guaranteed by 19th century treaties entered into between the Lake Superior Chippewa and the federal government. This paper addresses three issues. First, a fundamental flaw with the Petitioner's position is a misconceptualization of the legal theory that governs I...

  11. Development of Mammalian Cell Lines with lac Operator-Tagged Chromosomes

    OpenAIRE

    sprotocols

    2014-01-01

    Authors: Yuri G. Strukov and Andrew S. Belmont This protocol was adapted from “Development of Mammalian Cell Lines with lac Operator-Tagged Chromosomes,” Chapter 25, in[ *Live Cell Imaging* ](http://www.cshlpress.com/link/livecelp.htm)(eds. Goldman and Spector). Cold Spring Harbor Laboratory Press, Cold Spring Harbor, NY, USA, 2005. ### INTRODUCTION The discovery and use of fluorescent proteins to label chromosomal proteins has yielded basic structural information as well as insig...

  12. Engineering a portable riboswitch-LacP hybrid device for two-way gene regulation.

    Science.gov (United States)

    Jin, Ye; Huang, Jian-Dong

    2011-10-01

    Riboswitches are RNA-based regulatory devices that mediate ligand-dependent control of gene expression. However, there has been limited success in rationally designing riboswitches. Moreover, most previous riboswitches are confined to a particular gene and only perform one-way regulation. Here, we used a library screening strategy for efficient creation of ON and OFF riboswitches of lacI on the chromosome of Escherichia coli. We then engineered a riboswitch-LacP hybrid device to achieve portable gene control in response to theophylline and IPTG. Moreover, this device regulated target expression in a 'two-way' manner: the default state of target expression was ON; the expression was switched off by adding theophylline and restored to the ON state by adding IPTG without changing growth medium. We showcased the portability and two-way regulation of this device by applying it to the small RNA CsrB and the RpoS protein. Finally, the use of the hybrid device uncovered an inhibitory role of RpoS in acetate assimilation, a function which is otherwise neglected using conventional genetic approaches. Overall, this work establishes a portable riboswitch-LacP device that achieves sequential OFF-and-ON gene regulation. The two-way control of gene expression has various potential scientific and biotechnological applications and helps reveal novel gene functions. PMID:21803790

  13. The variable V381 Lac and its possible connection with the R CrB phenomenon

    CERN Document Server

    Rossi, Corinne; Di Paola, Andrea; Gigoyan, Kamo S; Nesci, Roberto

    2015-01-01

    We have performed new medium resolution spectroscopy, optical and near infrared photometry to monitor the variability of the AGB carbon star V 381 Lac. Our observations revealed rapid and deep changes in the spectrum and extreme variability in the optical and near infrared bands. Most notably we observed the change of NaI D lines from deep absorption to emission, and the progressive growing of the [N II] doublet 6548-6584 A emission, strongly related to the simultaneous photometric fading. V381 Lac occupies regions of 2MASS and WISE colour-colour diagrams typical of stars with dust formation in the envelope. The general framework emerging from the observations of V381 Lac is that of a cool AGB carbon star undergoing episodes of high mass ejection and severe occultation of the stellar photosphere reminiscent of those characterising the RCB phenomenon. Comparing the Spectral Energy Distribution obtained with the theoretical model for AGB evolution with dust in the circumstellar envelope, we can identify V381 La...

  14. AlloRep: A Repository of Sequence, Structural and Mutagenesis Data for the LacI/GalR Transcription Regulators.

    Science.gov (United States)

    Sousa, Filipa L; Parente, Daniel J; Shis, David L; Hessman, Jacob A; Chazelle, Allen; Bennett, Matthew R; Teichmann, Sarah A; Swint-Kruse, Liskin

    2016-02-22

    Protein families evolve functional variation by accumulating point mutations at functionally important amino acid positions. Homologs in the LacI/GalR family of transcription regulators have evolved to bind diverse DNA sequences and allosteric regulatory molecules. In addition to playing key roles in bacterial metabolism, these proteins have been widely used as a model family for benchmarking structural and functional prediction algorithms. We have collected manually curated sequence alignments for >3000 sequences, in vivo phenotypic and biochemical data for >5750 LacI/GalR mutational variants, and noncovalent residue contact networks for 65 LacI/GalR homolog structures. Using this rich data resource, we compared the noncovalent residue contact networks of the LacI/GalR subfamilies to design and experimentally validate an allosteric mutant of a synthetic LacI/GalR repressor for use in biotechnology. The AlloRep database (freely available at www.AlloRep.org) is a key resource for future evolutionary studies of LacI/GalR homologs and for benchmarking computational predictions of functional change. PMID:26410588

  15. Trusted Objects

    Energy Technology Data Exchange (ETDEWEB)

    CAMPBELL,PHILIP L.; PIERSON,LYNDON G.; WITZKE,EDWARD L.

    1999-10-27

    In the world of computers a trusted object is a collection of possibly-sensitive data and programs that can be allowed to reside and execute on a computer, even on an adversary's machine. Beyond the scope of one computer we believe that network-based agents in high-consequence and highly reliable applications will depend on this approach, and that the basis for such objects is what we call ''faithful execution.''

  16. Radar imaging of binary near-Earth asteroid (357439) 2004 BL86

    Science.gov (United States)

    Benner, Lance A. M.; Brozovic, Marina; Giorgini, Jon D.; Taylor, Patrick A.; Howell, Ellen S.; Busch, Michael W.; Nolan, Michael C.; Jao, Joseph S.; Lee, Clement G.; Ford, H. Alyson; Ghigo, Frank D.

    2015-11-01

    We report radar imaging of near-Earth asteroid 2004 BL86 obtained at Goldstone, Arecibo, Green Bank, and elements of the Very Long Baseline Array between 2015 January 26-31. 2004 BL86 approached within 0.0080 au on January 26, the closest known approach by any object with an absolute magnitude brighter than ~19 until 2027. Prior to the encounter, virtually nothing was known about its physical properties other than its absolute magnitude of 19, which suggested a diameter within a factor of two of 500 m. 2004 BL86 was a very strong radar target that provided an outstanding opportunity for radar imaging and physical characterization. Delay-Doppler images with range resolutions as fine as 3.75 m placed thousands of pixels on the object and confirmed photometric results reported by Pravec et al. (2015, CBET 4063) that 2004 BL86 is a binary system. During the observations, the asteroid moved more than 90 deg and provided a range of viewing geometries. The bandwidth was relatively narrow on Jan. 26, reached a maximum on Jan. 27, and then narrowed on Jan. 28, a progression indicating that the subradar latitude moved across the equator during those days. The images reveal a rounded primary with an equatorial diameter of ~350 m, evidence for ridges, possible boulders, and a pronounced angular feature ~100 m in diameter near one of the poles. Images from Jan. 26 show arcs of radar-bright pixels on the approaching and receding limbs that extend well behind the trailing edge in the middle of the echo. This is the delay-Doppler signature of an oblate shape seen at least a few tens of degrees off the equator. A rough estimate for the diameter of the secondary is ~70 m and its narrow bandwidth is consistent with the 14-h orbital period reported by Pravec et al. (2015). The images are suitable for 3D shape, pole, orbit, and mass estimation. The observations utilized new data taking equipment at Green Bank to receive X-band (8560 MHz, 3.5 cm) transmissions from the 70 m DSS-14

  17. Fashion Objects

    DEFF Research Database (Denmark)

    Andersen, Bjørn Schiermer

    2009-01-01

    This article attempts to create a framework for understanding modern fashion phenomena on the basis of Durkheim's sociology of religion. It focuses on Durkheim's conception of the relation between the cult and the sacred object, on his notion of 'exteriorisation', and on his theory of the social...... symbol in an attempt to describe the peculiar attraction of the fashion object and its social constitution. However, Durkheim's notions of cult and ritual must undergo profound changes if they are to be used in an analysis of fashion. The article tries to expand the Durkheimian cult, radically enlarging...... of the enlargement of the cult into individual behaviour....

  18. Setting Objectives

    Science.gov (United States)

    Elkins, Aaron J.

    1977-01-01

    The author questions the extent to which educators have relied on "relevance" and learner participation in objective-setting in the past decade. He describes a useful approach to learner-oriented evaluation in which content relevance was not judged by participants until after they had been exposed to it. (MF)

  19. RISING beamline (BL28XU) for rechargeable battery analysis

    International Nuclear Information System (INIS)

    The BL28XU beamline, dedicated to rechargeable battery analysis, is described. The newly installed BL28XU beamline at SPring-8 is dedicated to in situ structural and electronic analysis of rechargeable batteries. It supports the time range (1 ms to 100 s) and spatial range (1 µm to 1 mm) needed for battery analysis. Electrochemical apparatus for battery charging and discharging are available in experimental hutches and in a preparation room. Battery analysis can be carried out efficiently and effectively using X-ray diffraction, X-ray absorption fine-structure analysis and hard X-ray photoelectron spectroscopy. Here, the design and performance of the beamline are described, and preliminary results are presented

  20. Majorana Dark matter with B+L gauge symmetry

    CERN Document Server

    Chao, Wei; Zhang, Yongchao

    2016-01-01

    We present a new model that extends the Standard Model (SM) with the local B+L symmetry, and point out that the lightest new fermion $\\zeta$, introduced to cancel anomalies and stabilized automatically by the B+L symmetry, can serve as the cold dark matter candidate. We study constraints on the model from Higgs measurements, electroweak precision measurements as well as the relic density and direct detections of the dark matter. Numerical results reveal that the pseudo-vector coupling of $\\zeta$ with $Z$ and the Yukawa coupling with the SM Higgs are highly constrained by the latest results of LUX, while there are viable parameter space that could satisfy all the constraints and give testable predictions.

  1. Asymmetric Gepner models III. B-L lifting

    Energy Technology Data Exchange (ETDEWEB)

    Gato-Rivera, B. [NIKHEF Theory Group, Kruislaan 409, 1098 SJ Amsterdam (Netherlands); Instituto de Fisica Fundamental, CSIC, Serrano 123, Madrid 28006 (Spain); Schellekens, A.N., E-mail: t58@nikhef.n [NIKHEF Theory Group, Kruislaan 409, 1098 SJ Amsterdam (Netherlands); Instituto de Fisica Fundamental, CSIC, Serrano 123, Madrid 28006 (Spain); IMAPP, Radboud Universiteit, Nijmegen (Netherlands)

    2011-06-21

    In the same spirit as heterotic weight lifting, B-L lifting is a way of replacing the superfluous and ubiquitous U(1){sub B-L} with something else with the same modular properties, but different conformal weights and ground state dimensions. This method works in principle for all variants of (2,2) constructions, such as orbifolds, Calabi-Yau manifolds, free bosons and fermions and Gepner models, since it only modifies the universal SO(10)xE{sub 8} part of the CFT. However, it can only yield chiral spectra if the 'internal' sector of the theory provides a simple current of order 5. Here we apply this new method to Gepner models. Including exceptional invariants, 86 of them have the required order 5 simple current, and 69 of these yield chiral spectra. Three family spectra occur abundantly.

  2. Asymmetric Gepner Models III. B-L Lifting

    CERN Document Server

    Gato-Rivera, B

    2010-01-01

    In the same spirit as heterotic weight lifting, B-L lifting is a way of replacing the superfluous and ubiquitous U(1)_{B-L} with something else with the same modular properties, but different conformal weights and ground state dimensions. This method works in principle for all variants of (2,2) constructions, such as orbifolds, Calabi-Yau manifolds, free bosons and fermions and Gepner models, since it only modifies the universal SO(10) x E_8 part of the CFT. However, it can only yield chiral spectra if the ``internal" sector of the theory provides a simple current of order 5. Here we apply this new method to Gepner models. Including exceptional invariants, 86 of them have the required order 5 simple current, and 69 of these yield chiral spectra. Three family spectra occur abundantly.

  3. Period doubling and Blazhko modulation in BL Herculis hydrodynamic models

    CERN Document Server

    Smolec, R

    2012-01-01

    We present the hydrodynamic BL Herculis-type models which display a long-term modulation of pulsation amplitudes and phases. The modulation is either strictly periodic or it is quasi-periodic, with the modulation period and modulation pattern varying from one cycle to the other. Such behaviour has not been observed in any BL Her variable so far, however, it is a common property of their lower luminosity siblings - RR Lyrae variables showing the Blazhko effect. These models provide a support for the recent mechanism proposed by Buchler & Kollath to explain this still mysterious phenomenon. In their model, a half-integer resonance that causes the period doubling effect, discovered recently in the Blazhko RR Lyrae stars, is responsible for the modulation of the pulsation as well. Although our models are more luminous than is appropriate for RR Lyrae stars, they clearly demonstrate, through direct hydrodynamic computation, that the mechanism can indeed be operational. Of great importance are models which show...

  4. 普通小麦-簇毛麦易位系T6BS·6BL-2VS的选育%Identification of Triticum aestivum-Haynaldia villosa Translocation Line T6BS·6BL-2VS

    Institute of Scientific and Technical Information of China (English)

    陈全战; 张边江; 周峰; 吴梅; 李华春

    2008-01-01

    [Objective] The aim of experiment was to provide a new germplasm for wheat breeding by further using desirable genes in 2V chromosome of Haynaldia villosa.[Method] Through hybridization between common wheat(Triticum aestivum)-Haynaldia villosa disomic substitution line and common wheat Nonglin26-3C chromosome of Aegilops triuncialis disomic addition line, the analysis methods such as chromosome C-banding, genomic in situ hybridization and molecular marker technique were comprehensively applied and combined characters investigation.[Result] The wheat-Haynaldia villosa translocation line(T6BS·6BL-2VS) was selected from hybrid progenies to conduct characters investigation,which found some bristles on glume ridge of T6BS·6BL-2VS.[Conclusion] The translocation line induced by gametocidal chromosome was a small segment translocation line and the gene of bristle on glume ridge of Haynaldia villosa was located between the middle and the terminal of 2VS.

  5. Substitutions at Auxiliary Operator O3 Enhance Repression by Nitrate-Responsive Regulator NarL at Synthetic lac Control Regions in Escherichia coli K-12▿

    OpenAIRE

    Stewart, Valley; Bledsoe, Peggy J.

    2007-01-01

    We constructed monocopy lac operon control regions in which the operators O1-lac and O3-lac were replaced by NarL and NarP binding sites from the nirB or napF operon control regions. The results support the hypothesis that DNA-bound dimers of phospho-NarL can participate in higher-order cooperative interactions.

  6. Objective thermomechanics

    OpenAIRE

    Fülöp, Tamás

    2015-01-01

    An irreversible thermodynamical theory of solids is presented where the kinematic quantities are defined in an automatically objective way. Namely, auxiliary elements like reference frame, reference time and reference configuration are avoided by formulating the motion of the continuum on spacetime directly. Solids are distinguished from fluids by possessing not only an instantaneous metric tensor but also a relaxed metric. The elastic state variable is defined through comparing these two met...

  7. Objective Morality

    OpenAIRE

    Allott, Robin

    1991-01-01

    An objective basis for morality can be found in an evolutionary account of its origin and development. Morality is a key factor in the success of human groups in competition or co-existence with each other.A group's moral code represents an increasingly rational pattern of behaviour derived from the collective experience of the group handed down from generation to generation. Group selection is a controversial idea for animal evolution but it is inescapable in accounting for human evolution u...

  8. Distinct Transcriptional Signatures of Bone Marrow-Derived C57BL/6 and DBA/2 Dendritic Leucocytes Hosting Live Leishmania amazonensis Amastigotes

    OpenAIRE

    Giraud, Emilie; Lecoeur, Hervé; Soubigou, Guillaume; Coppée, Jean-Yves; Milon, Geneviève; Prina, Eric; Lang, Thierry

    2012-01-01

    Background/Objectives The inoculation of a low number (104) of L. amazonensis metacyclic promastigotes into the dermis of C57BL/6 and DBA/2 mouse ear pinna results in distinct outcome as assessed by the parasite load values and ear pinna macroscopic features monitored from days 4 to 22-phase 1 and from days 22 to 80/100-phase 2. While in C57BL/6 mice, the amastigote population size was increasing progressively, in DBA/2 mice, it was rapidly controlled. This latter rapid control did not preven...

  9. Acupuncture of Weizhong (BL 40) and Zusanli (ST 36) on the study of brain function by PET/CT imaging

    International Nuclear Information System (INIS)

    Objective: To explore the correlation between acupuncture of the points and certain functional areas of brain by PET/CT imaging. Methods: Twelve healthy volunteers were acupunctured separately in the point Weizhong (BL 40, right leg) and Zusanli(ST 36, right leg), and 5 consecutive PET/CT images were taken, statistical parameter map (SPM) paired t-test was analyzed between the different activated brain PET/CT imagings. Results: Changes of PET/CT imaging were found in acupuncture of the point Weizhong (BL 40) and Zusanli(ST 36) in 12 healthy volunteers. High metabolic areas were demonstrated in multiple brain regions, the data of two groups had significant difference between 2 points (t>4.03, P< 0.01). Conclusion: Acupuncturing the different point resulted activation of the glucose metabolism in different brain areas. (authors)

  10. Brain plasticity and cognitive functions after ethanol consumption in C57BL/6J mice.

    Science.gov (United States)

    Stragier, E; Martin, V; Davenas, E; Poilbout, C; Mongeau, R; Corradetti, R; Lanfumey, L

    2015-01-01

    Acute or chronic administrations of high doses of ethanol in mice are known to produce severe cognitive deficits linked to hippocampal damage. However, we recently reported that chronic and moderate ethanol intake in C57BL/6J mice induced chromatin remodeling within the Bdnf promoters, leading to both enhanced brain-derived neurotrophic factor (BDNF) expression and hippocampal neurogenesis under free-choice protocol. We performed here a series of cellular and behavioral studies to analyze the consequences of these modifications. We showed that a 3-week chronic free-choice ethanol consumption in C57BL/6J mice led to a decrease in DNA methylation of the Bdnf gene within the CA1 and CA3 subfields of the hippocampus, and upregulated hippocampal BDNF signaling pathways mediated by ERK, AKT and CREB. However, this activation did not affect long-term potentiation in the CA1. Conversely, ethanol intake impaired learning and memory capacities analyzed in the contextual fear conditioning test and the novel object recognition task. In addition, ethanol increased behavioral perseveration in the Barnes maze test but did not alter the mouse overall spatial capacities. These data suggested that in conditions of chronic and moderate ethanol intake, the chromatin remodeling leading to BDNF signaling upregulation is probably an adaptive process, engaged via epigenetic regulations, to counteract the cognitive deficits induced by ethanol. PMID:26670281

  11. BL_Wiener Denoising Method for Removal of Speckle Noise in Ultrasound Image

    Directory of Open Access Journals (Sweden)

    Suhaila Sari

    2015-02-01

    Full Text Available Medical imaging techniques are extremely important tools in medical diagnosis. One of these important imaging techniques is ultrasound imaging. However, during ultrasound image acquisition process, the quality of image can be degraded due to corruption by speckle noise. The enhancement of ultrasound images quality from the 2D ultrasound imaging machines is expected to provide medical practitioners more reliable medical images in their patients’ diagnosis. However, developing a denoising technique which could remove noise effectively without eliminating the image’s edges and details is still an ongoing issue. The objective of this paper is to develop a new method that is capable to remove speckle noise from the ultrasound image effectively. Therefore, in this paper we proposed the utilization of Bilateral Filter and Adaptive Wiener Filter (BL_Wiener denoising method for images corrupted by speckle noise. Bilateral Filter is a non-linear filter effective in removing noise, while Adaptive Wiener Filter balances the tradeoff between inverse filtering and noise smoothing by removing additive noise while inverting blurring. From our simulation results, it is found that the BL_Wiener method has improved between 0.89 [dB] to 3.35 [dB] in terms of PSNR for test images in different noise levels in comparison to conventional methods.

  12. The SOS-LUX-LAC-FLUORO-Toxicity-test on the International Space Station (ISS)

    Science.gov (United States)

    Rabbow, E.; Rettberg, P.; Baumstark-Khan, C.; Horneck, G.

    In the 21 st century, an increasing number of astronauts will visit the International Space Station (ISS) for prolonged times. Therefore it is of utmost importance to provide necessary basic knowledge concerning risks to their health and their ability to work on the station and during extravehicular activities (EVA) in free space. It is the aim of one experiment of the German project TRIPLE-LUX (to be flown on the ISS) to provide an estimation of health risk resulting from exposure of the astronauts to the radiation in space inside the station as well as during extravehicular activities on one hand, and of exposure of astronauts to unavoidable or as yet unknown ISS-environmental genotoxic substances on the other. The project will (i) provide increased knowledge of the biological action of space radiation and enzymatic repair of DNA damage, (ii) uncover cellular mechanisms of synergistic interaction of microgravity and space radiation and (iii) examine the space craft milieu with highly specific biosensors. For these investigations, the bacterial biosensor SOS-LUX-LAC-FLUORO-Toxicity-test will be used, combining the SOS-LUX-Test invented at DLR Germany (Patent) with the commercially available LAC-FLUORO-Test. The SOS-LUX-Test comprises genetically modified bacteria transformed with the pBR322-derived plasmid pPLS-1. This plasmid carries the promoterless lux operon of Photobacterium leiognathi as a reporter element under control of the DNA-damage dependent SOS promoter of ColD as sensor element. This system reacts to radiation and other agents that induce DNA damages with a dose dependent measurable emission of bioluminescence of the transformed bacteria. The analogous LAC-FLUORO-Test has been developed for the detection of cellular responses to cytotoxins. It is based on the constitutive expression of green fluorescent protein (GFP) mediated by the bacterial protein expression vector pGFPuv (Clontech, Palo Alto, USA). In response to cytotoxic agents, this system

  13. Hydrogeologic Characterization of the U-3bl Collapse Zone

    International Nuclear Information System (INIS)

    The U-3bl collapse crater was formed by an underground nuclear test in August 1962. This crater and the adjoining U-3ax crater were subsequently developed and used as a bulk low-level radioactive waste disposal cell (U-3ax/bl), which is part of the Area 3 Radioactive Waste Management Site at the Nevada Test Site (NTS). Various investigations have been conducted to assess the hydrogeologic characteristics and properties in the vicinity of the U-3ax/bl waste disposal cell. This report presents data from one of these investigations, conducted in 1996. Also included in this report is a review of pertinent nuclear testing records, which shows that the testing operations and hydrogeologic setting of the U-3ax/bl site were typical for the period and location of testing. Borehole U-3bl-D2 is a 45-degree-angle hole drilled from the edge of the crater under the waste cell to intercept the U-3bl collapse zone, the disturbed alluvium between the crater (surface collapse sink) and the nuclear test cavity. A casing-advance system with an air percussion hammer was used to drill the borehole, and air was used as the drilling fluid. Properties of the U-3bl crater collapse zone were determined from cores collected within the interval, 42.1 to 96.6 meters (138 to 317 feet) below the ground surface. Selected core samples were analyzed for particle density, particle size, bulk density, water retention, hydraulic conductivity, water content, water potential, chloride, carbonate, stable isotopes, and tritium. Physical and hydraulic properties were typical of alluvial valley sediments at the NTS. No visual evidence of preferential pathways for water transport was observed in the core samples. Soil parameters showed no trends with depth. Volumetric water content values ranged from 0.08 to 0.20 cubic meters per cubic meter, and tended to increase with depth. Water-retention relations were typical for soils of similar texture. Water potentials ranged from -1.9 MegaPascals at a depth of 42

  14. Quantum Objects

    CERN Document Server

    Mansouri, Alireza; Karbasizadeh, Amir Ehsan

    2013-01-01

    In this paper, we suggest an alternative interpretation for the quantum state vector, which, by considering temporal parts for physical objects, aims to give an intelligible account of measurement problem in quantum mechanics. We examine the capacity of this interpretation as for explaining three measurement problems: the problem of outcome, the problem of statistics and the problem of effect. We argue that, this interpretation of the state vector, while providing a satisfactory account, as rationally plausible as its rivals, for the measurement problem, shows yet another limitation of our perceptual experience, i.e. our inability to perceive unsharp reality.

  15. Wow!: objects

    OpenAIRE

    Freitas, Paulo Sérgio da Silva

    2008-01-01

    Nowadays computers have advanced beyond the desktop into many parts of everyday life and objects. To achieve this we have to make the computer invisible, and making a computer invisible is not a matter of size of the hardware, it’s all about how the human perceives the computer. To make this possible, the interaction with the computer has to be done in an alternative way, such that the user doesn’t notice the usual computer interfaces (mouse and keyboard) when using it. Therefore this t...

  16. The effect of stochasticity on the lac operon: an evolutionary perspective.

    Directory of Open Access Journals (Sweden)

    Milan van Hoek

    2007-06-01

    Full Text Available The role of stochasticity on gene expression is widely discussed. Both potential advantages and disadvantages have been revealed. In some systems, noise in gene expression has been quantified, in among others the lac operon of Escherichia coli. Whether stochastic gene expression in this system is detrimental or beneficial for the cells is, however, still unclear. We are interested in the effects of stochasticity from an evolutionary point of view. We study this question in the lac operon, taking a computational approach: using a detailed, quantitative, spatial model, we evolve through a mutation-selection process the shape of the promoter function and therewith the effective amount of stochasticity. We find that noise values for lactose, the natural inducer, are much lower than for artificial, nonmetabolizable inducers, because these artificial inducers experience a stronger positive feedback. In the evolved promoter functions, noise due to stochasticity in gene expression, when induced by lactose, only plays a very minor role in short-term physiological adaptation, because other sources of population heterogeneity dominate. Finally, promoter functions evolved in the stochastic model evolve to higher repressed transcription rates than those evolved in a deterministic version of the model. This causes these promoter functions to experience less stochasticity in gene expression. We show that a high repression rate and hence high stochasticity increases the delay in lactose uptake in a variable environment. We conclude that the lac operon evolved such that the impact of stochastic gene expression is minor in its natural environment, but happens to respond with much stronger stochasticity when confronted with artificial inducers. In this particular system, we have shown that stochasticity is detrimental. Moreover, we demonstrate that in silico evolution in a quantitative model, by mutating the parameters of interest, is a promising way to unravel

  17. Analysis and Remediation of the 2013 LAC-MÉGANTIC Train Derailment

    Science.gov (United States)

    Brunke, Suzanne; Aubé, Guy; Legaré, Serge; Auger, Claude

    2016-06-01

    On July 6, 2013 a train owned by Montréal, Maine & Atlantic Railway (MMA) Company derailed in Lac-Mégantic, Quebec, Canada triggering the explosion of the tankers carrying crude oil. Several buildings in the downtown core were destroyed. The Sûreté du Québec confirmed the death of 47 people in the disaster. Through the Canadian Space Agency (CSA) Rapid Information Products and Services (RIPS) program, MDA developed value-added products that allowed stakeholders and all levels of government (municipal, provincial and federal) to get an accurate picture of the disaster. The goal of this RIPS Project was to identify the contribution that remote sensing technology can provide to disasters such as the train derailment and explosion at Lac-Mégantic through response and remediation monitoring. Through monitoring and analysis, the Lac-Mégantic train derailment response and remediation demonstrated how Earth observation data can be used for situational awareness in a disaster and in documenting the remediation process. Both high resolution optical and RADARSAT-2 SAR image products were acquired and analyzed over the disaster remediation period as each had a role in monitoring. High resolution optical imagery provided a very clear picture of the current state of remediation efforts, however it can be difficult to acquire due to cloud cover and weather conditions. The RADARSAT-2 SAR images can be acquired in all weather conditions at any time of day making it ideal for mission critical information gathering. MDA's automated change detection processing enabled rapid delivery of advanced information products.

  18. What makes the lac-pathway switch: identifying the fluctuations that trigger phenotype switching in gene regulatory systems.

    Science.gov (United States)

    Bhogale, Prasanna M; Sorg, Robin A; Veening, Jan-Willem; Berg, Johannes

    2014-10-01

    Multistable gene regulatory systems sustain different levels of gene expression under identical external conditions. Such multistability is used to encode phenotypic states in processes including nutrient uptake and persistence in bacteria, fate selection in viral infection, cell-cycle control and development. Stochastic switching between different phenotypes can occur as the result of random fluctuations in molecular copy numbers of mRNA and proteins arising in transcription, translation, transport and binding. However, which component of a pathway triggers such a transition is generally not known. By linking single-cell experiments on the lactose-uptake pathway in E. coli to molecular simulations, we devise a general method to pinpoint the particular fluctuation driving phenotype switching and apply this method to the transition between the uninduced and induced states of the lac-genes. We find that the transition to the induced state is not caused only by the single event of lac-repressor unbinding, but depends crucially on the time period over which the repressor remains unbound from the lac-operon. We confirm this notion in strains with a high expression level of the lac-repressor (leading to shorter periods over which the lac-operon remains unbound), which show a reduced switching rate. Our techniques apply to multistable gene regulatory systems in general and allow to identify the molecular mechanisms behind stochastic transitions in gene regulatory circuits. PMID:25245949

  19. Induction kinetics of the lac operon : Studied by single molecule methods

    OpenAIRE

    Hedén Gynnå, Arvid

    2014-01-01

    The repression of the E. coli lac operon seems to be more efficient than the current theoretical model allows for. Specifically, it is more quiet than expected during the replication of the chromosome. I have induced cells during short periods and counted the number of protein products from the operon to determine if there is a delay in activation of transcription that could account for the discrepancy. The results are compatible with a delay of 10-20 s, but the delay could not be conclusivel...

  20. Thermal cracking in Lac du Bonnet granite during slow heating to 205 degrees celsius

    International Nuclear Information System (INIS)

    Acoustic emissions (AE) were recorded as drill core samples of Lac du Bonnet granite were slowly heated to between 66 and 205 degrees celsius to evaluate the effects of temperature on the properties of rock samples. Longitudinal and shear velocities of the samples were measured, and Young's moduli, shear moduli and Poisson's ratios were calculated. No significant AE activity was detected until temperatures reached approximately 73-80 degrees celsius. Above this 'threshold' temperature, calculated rock properties decreased, and at 205 degrees celsius calculated Young's modulus, shear modulus, and Poisson's ratio were reduced by 30, 26, and 29% respectively

  1. The diluvial rains of Saguenay-Lac-Saint-Jean : status one year after

    International Nuclear Information System (INIS)

    The status of damages and reconstruction in the Saguenay-Lac-Saint-Jean region, one year after the catastrophic torrential rain storm of July 1996 was presented. Numerous detailed maps and photographs of the principal washed-out, destroyed and damaged regions were presented, along with maps and photographs of the same areas after reconstruction, repair and landscaping. The maps show the different river beds, urban, and rural districts that were subjected to the catastrophic washouts, landslides and soil collapses. The report also includes a summary of the repair costs by municipal regions and the financial aid received by the region to help in the reconstruction effort. tabs., figs

  2. In vivo role of the relA+ gene in regulation of the lac operon.

    OpenAIRE

    Primakoff, P

    1981-01-01

    Under conditions of amino acid limitation, beta-galactosidase was produced at a 70-fold higher rate in a relA+ strain than in an isogenic relA strain of Escherichia coli K-12. Under identical conditions with the relA+ and relA strains carrying various lac promoter mutations, rates of beta-galactosidase synthesis in relA+ (relative to relA) ranged from 26-fold higher (promoter mutant Pr 13) to only 5-fold higher (promoter mutant PrL8uv5). This promoter specificity was independent of strain bac...

  3. Objective thermomechanics

    CERN Document Server

    Fülöp, Tamás

    2015-01-01

    An irreversible thermodynamical theory of solids is presented where the kinematic quantities are defined in an automatically objective way. Namely, auxiliary elements like reference frame, reference time and reference configuration are avoided by formulating the motion of the continuum on spacetime directly, utilizing the Weyl-Matolcsi description of spacetime. This restricts the range of definable kinematic quantities heavily. Solids are distinguished from fluids by possessing not only an instantaneous metric tensor but a relaxed metric, too, that represents the natural geometric structure of the solid. The comparison of the instantaneous metric to the relaxed one is the basis of the definition of the elastic state variable, the elastic deformedness tensor. Thermal expansion is conceived as the temperature dependence of the relaxed metric. As opposed to this reversible type of change, plasticity means an irreversible change in the relaxed metric, and is describable via a plastic change rate tensor. The relat...

  4. Adeno-associated Virus Mediated LacZ Gene Transfect to Cultured Human Iris Pigment Epithelium Cells

    Institute of Scientific and Technical Information of China (English)

    Chun Zhang; Shibo Tang; Yan Luo; Xiaoling Liang; Jing Ma; Shaofen Lin

    2003-01-01

    Purpose: To study the feasibility of adeno-associated virus mediated gene transfection tocultured human iris pigment epithelium (IPE) cells in vitro.Methods: Recombinant replication deficient adeno-associated viruses (AAV) expressingLacZ gene were produced without helper virus. The LacZ gene was transduced into culturedhuman IPE cells.Results: Cultured human IPE cells stained positively anticytokeratin, The titer ofrAAV-LacZ was 2.1 × 108 virus particles/ml, 42% cultured human IPE cells expressedβ-galactosidase 7 days after transfection and 67% after 14 days.Conclusions: Recombined AAV produced without helper virus can transfer a foreign geneinto human IPE cells with high efficiency in vitro.

  5. Hydrogeologic characteristics of domains of sparsely fractured rock in the granitic Lac Du Bonnet Batholith, southeastern Manitoba, Canada

    International Nuclear Information System (INIS)

    The hydrogeologic characteristics of the granitic Lac du Bonnet batholith in southeastern Manitoba have been studied since 1978, as part of AECL's program to assess the concept of disposing of Canada's nuclear fuel waste deep within plutonic rocks of the Canadian Shield (Davison et al. 1994a). These studies have included an extensive program of drilling, logging, testing, sampling and monitoring in 19 deep surface boreholes drilled at Grid areas located across the Lac du Bonnet batholith, at the Whiteshell Laboratory (WL), and in surface and underground boreholes at the Underground Research Laboratory (URL). Based on these investigations domains of low permeability, sparsely fractured rock (SFR) have been identified in the Lac du Bonnet batholith

  6. Ozone measurement in EXAFS beam line BL-08 of INDUS-2

    International Nuclear Information System (INIS)

    Ozone measurement in experimental hutch of Extended X-ray Absorption Fine Structure (EXAFS) beam line (BL-08) of INDUS-2 is carried out with the objectives of measuring ozone build-up profile at various locations inside the hutch, to check the effectiveness of the existing exhaust blower used to remove the ozone from the hutch and to determine the ozone decay time to reach the safe limit of 0.1 ppm. The results show that the ozone level is less than 0.1 ppm in all measured locations. This paper describes the methodology, experimental set-up and the results of the experiment done in June 2010 at RRCAT. (author)

  7. Dynamics and bistability in a reduced model of the lac operon

    Science.gov (United States)

    Yildirim, Necmettin; Santillán, Moisés; Horike, Daisuke; Mackey, Michael C.

    2004-06-01

    It is known that the lac operon regulatory pathway is capable of showing bistable behavior. This is an important complex feature, arising from the nonlinearity of the involved mechanisms, which is essential to understand the dynamic behavior of this molecular regulatory system. To find which of the mechanisms involved in the regulation of the lac operon is the origin of bistability, we take a previously published model which accounts for the dynamics of mRNA, lactose, allolactose, permease and β-galactosidase involvement and simplify it by ignoring permease dynamics (assuming a constant permease concentration). To test the behavior of the reduced model, three existing sets of data on β-galactosidase levels as a function of time are simulated and we obtain a reasonable agreement between the data and the model predictions. The steady states of the reduced model were numerically and analytically analyzed and it was shown that it may indeed display bistability, depending on the extracellular lactose concentration and growth rate.

  8. Evolution in Binary and Triple Stars, with an application to SS Lac

    CERN Document Server

    Eggleton, P P; Eggleton, Peter P.; Kiseleva-Eggleton, Ludmila

    2001-01-01

    We present equations governing the way in which both the orbit and the intrinsic spins of stars in a close binary should evolve subject to a number of perturbing forces, including the effect of a third body in a possibly inclined wider orbit. We illustrate the solutions in some binary-star and triple-star situations: tidal friction in a wide but eccentric orbit of a radio pulsar about a B star, the Darwin and eccentricity instabilities in a more massive but shorter-period massive X-ray binary, and the interaction of tidal friction with Kozai cycles in a triple such as Algol (beta-Per), at an early stage in that star's life when all 3 components were ZAMS stars. We also attempt to model in some detail the interesting triple system SS Lac, which stopped eclipsing in about 1950. We find that our model of SS Lac is quite constrained by the relatively good observational data of this system, and leads to a specific inclination (29 deg) of the outer orbit relative to the inner orbit at epoch zero (1912). Although th...

  9. In vitro transcription accurately predicts lac repressor phenotype in vivo in Escherichia coli

    Directory of Open Access Journals (Sweden)

    Matthew Almond Sochor

    2014-07-01

    Full Text Available A multitude of studies have looked at the in vivo and in vitro behavior of the lac repressor binding to DNA and effector molecules in order to study transcriptional repression, however these studies are not always reconcilable. Here we use in vitro transcription to directly mimic the in vivo system in order to build a self consistent set of experiments to directly compare in vivo and in vitro genetic repression. A thermodynamic model of the lac repressor binding to operator DNA and effector is used to link DNA occupancy to either normalized in vitro mRNA product or normalized in vivo fluorescence of a regulated gene, YFP. An accurate measurement of repressor, DNA and effector concentrations were made both in vivo and in vitro allowing for direct modeling of the entire thermodynamic equilibrium. In vivo repression profiles are accurately predicted from the given in vitro parameters when molecular crowding is considered. Interestingly, our measured repressor–operator DNA affinity differs significantly from previous in vitro measurements. The literature values are unable to replicate in vivo binding data. We therefore conclude that the repressor-DNA affinity is much weaker than previously thought. This finding would suggest that in vitro techniques that are specifically designed to mimic the in vivo process may be necessary to replicate the native system.

  10. Lightning Detection by LAC Onboard the Japanese Venus Climate Orbiter, Planet-C

    Science.gov (United States)

    Takahashi, Y.; Yoshida, J.; Yair, Y.; Imamura, T.; Nakamura, M.

    2008-06-01

    Lightning activity in Venus has been a mystery for a long period, although many studies based on observations both by spacecraft and by ground-based telescope have been carried out. This situation may be attributed to the ambiguity of these evidential measurements. In order to conclude this controversial subject, we are developing a new type of lightning detector, LAC (Lightning and Airglow Camera), which will be onboard Planet-C (Venus Climate Orbiter: VCO). Planet-C will be launched in 2010 by JAXA. To distinguish an optical lightning flash from other pulsing noises, high-speed sampling at 50 kHz for each pixel, that enables us to investigate the time variation of each lightning flash phenomenon, is adopted. On the other hand, spatial resolution is not the first priority. For this purpose we developed a new type of APD (avalanche photo diode) array with a format of 8×8. A narrow band interference filter at wavelength of 777.4 nm (OI), which is the expected lightning color based on laboratory discharge experiment, is chosen for lightning measurement. LAC detects lightning flash with an optical intensity of average of Earth’s lightning or less at a distance of 3 Rv. In this paper, firstly we describe the background of the Venus lightning study to locate our spacecraft project, and then introduce the mission details.

  11. Another look at the BL Lacertae flux and spectral variability

    OpenAIRE

    Raiteri, C. M.; Villata, M.; BRUSCHINI, L.; Capetti, A.; Kurtanidze, O. M.; Larionov, V. M.; Romano, P; Vercellone, S.; Agudo, I.; Aller, H. D.; Aller, M. F.; Arkharov, A. A.; Bach, U.; Berdyugin, A.; Blinov, D. A.

    2010-01-01

    The GLAST-AGILE Support Program (GASP) of the Whole Earth Blazar Telescope (WEBT) monitored BL Lacertae in 2008-2009 at radio, near-IR, and optical frequencies. During this period, high-energy observations were performed by XMM-Newton, Swift, and Fermi. We analyse these data with particular attention to the calibration of Swift UV data, and apply a helical jet model to interpret the source broad-band variability. The GASP-WEBT observations show an optical flare in 2008 February-March, and osc...

  12. Reduction of forecast uncertainty in the context of hydropower production: a case study for two catchment in Lac-St-Jean, Canada

    Science.gov (United States)

    Brisson, Cathy; Boucher, Marie-Amélie; Latraverse, Marco

    2014-05-01

    This research focuses on the improvement of streamflow forecasts for two subcatchments in the Lac-St-Jean area, a northern part of the province of Quebec in Canada. Those two subcatchments, named Manouane and Passes-Dangereuses, are part of a bigger system, which comprises many reservoirs and six hydropower plants. This system is managed by Rio Tinto Alcan, an aluminium producer who needs this energy for its processes. Optimal management of the hydropower plants highly depends on the reliability of the inflow forecasts to the reservoirs and also on the reliability of observed streamflow. The latter are not directly measured, but rather deduced from the computation of a water balance. This water balance includes streamflow computation based on rating curves for river sections and upstream reservoirs and a modelling process using CEQUEAU hydrological model (Morin et al., 1981). In addition, mostly during the winter, the model has to account for a transfer of water from Lac Manouane reservoir to Passes-Dangereuses through Bonnard channel. Winter flow though Bonnard channel is controlled by a spillway, and represented in CEQUEAU by a transfer function and a fixed time delay (2 days). However, it is suspected that the evacuation function, as it is currently computed, is inaccurate. The main objective of this work is to reduce predictive uncertainty for Lac Manouane and Passes-Dangereuses catchment, for the one-day ahead horizon. This objective is twofold. First, the uncertainty related to the parameterization of the hydrological model had never been evaluated. It was to be investigated whether it is better to spatialize the calibration of the hydrological model. In its actual form, the calibration of the hydrological model CEQUEAU (Morin et al., 1981) is based exclusively on the downstream outflow. There is, however, intermediate streamflow measurements data available for an intermediate location. Our study shows that calibrating the model using streamflows for both

  13. Capric Acid Reduces Body Weight in C57BL/6J Mice Fed a High Fat Diet

    Institute of Scientific and Technical Information of China (English)

    Ying-hua LIU; Yong ZHANG; Qing XU; Xin-sheng ZHANG; Jin WANG; Xiao-ming YU; Xue-yan YANG; Chang-yong XUE

    2014-01-01

    Objective To compare the body weight reducing effect of two medium-chain fatty acids (MCFA), capric acid and caprylic acid, and the potential underlying mechanisms in C57BL/6J mice fed a high fat diet.Methods Obese C57BL/6J mice were developed on a high-fat diet containing 2% caprylic acid (C8:0), 2% capric acid (C10:0), or 2% oleic acid (C18:1). Body weight and diet intake were monitored twice a week. After 8 weeks of feeding, body fat composition and the protein or mRNA expression of lipolysis-related genes in the white adipose tissue (WAT) were analyzed.Results In the capric acid group, significant reductions were observed in body weight gain, Lee's index, BMI, and epididymal adipose tissue weight, while increased levels of adipose triglyceride lipase (ATGL), hormone-sensitive lipase (HSL), cyclic adenosine monophosphate (cAMP) and beta 3 adrenergic receptor (β3-AR) were found in the adipose tissue, compared to the oleic acid group. No significant differences in these parameters were found between caprylic acid and oleic acid groups.Conclusion Capric acid, but not caprylic acid, is effective in reducing body weight in obese C57BL/6J mice,possibly due to up-regulation of β3-AR, ATGL, and HSL in WAT.

  14. The labeling of C57BL/6j derived embryonic stem cells with enhanced green fluorescent protein

    Institute of Scientific and Technical Information of China (English)

    滕路; 张崇本; 尤洁芳; 尚克刚; 顾军

    2003-01-01

    Objective To labele MESPU35, a embryonic stem (ES) cell line derived from C57BL/6j mouse, with enhanced green fluorescent protein (EGFP) for further application.Methods The EGFP gene was controlled by the hybrid CA promoter/enhancer (CMV enhancer/ chicken beta-actin promoter/ beta-actin intron) to construct the vector of the transgene, pCA-EGFP. The vector was transfected into MESPU35 by electroporation.Results We generated EGFP expressing ES cells demonstrating normal properties. The green fluorescence of EGFP expressing cells was maintained in propagation of the ES cells for more than 30 passages as well as in differentiated cells. Cultured in suspension, the "green" ES cells aggregated, and formed embryoid bodies maintaining the green fluorescence at varying developmental stages. The "green" embryoid bodies could expand and differentiate into various types of cells, exhibiting ubiquitous green fluorescence. Conclusions The hybrid CA promoter/enhancer used to control the EGFP expressing ES cells, resulted in more intense and ubiquitous activity. The EGFP transfected cells yield bright green fluorescence, which can be visualized in real time and in situ. In addition, the ES cells, MESPU35, are derived from C57BL/6j mice, which are the most widely used in oncology, physiology and genetics. Compared to 129 substrains, C57BL/6j mice avoid a number of potential problems apparent in the other strains.

  15. Long-term artificial sweetener acesulfame potassium treatment alters neurometabolic functions in C57BL/6J mice.

    Directory of Open Access Journals (Sweden)

    Wei-na Cong

    Full Text Available With the prevalence of obesity, artificial, non-nutritive sweeteners have been widely used as dietary supplements that provide sweet taste without excessive caloric load. In order to better understand the overall actions of artificial sweeteners, especially when they are chronically used, we investigated the peripheral and central nervous system effects of protracted exposure to a widely used artificial sweetener, acesulfame K (ACK. We found that extended ACK exposure (40 weeks in normal C57BL/6J mice demonstrated a moderate and limited influence on metabolic homeostasis, including altering fasting insulin and leptin levels, pancreatic islet size and lipid levels, without affecting insulin sensitivity and bodyweight. Interestingly, impaired cognitive memory functions (evaluated by Morris Water Maze and Novel Objective Preference tests were found in ACK-treated C57BL/6J mice, while no differences in motor function and anxiety levels were detected. The generation of an ACK-induced neurological phenotype was associated with metabolic dysregulation (glycolysis inhibition and functional ATP depletion and neurosynaptic abnormalities (dysregulation of TrkB-mediated BDNF and Akt/Erk-mediated cell growth/survival pathway in hippocampal neurons. Our data suggest that chronic use of ACK could affect cognitive functions, potentially via altering neuro-metabolic functions in male C57BL/6J mice.

  16. Long-term artificial sweetener acesulfame potassium treatment alters neurometabolic functions in C57BL/6J mice.

    Science.gov (United States)

    Cong, Wei-na; Wang, Rui; Cai, Huan; Daimon, Caitlin M; Scheibye-Knudsen, Morten; Bohr, Vilhelm A; Turkin, Rebecca; Wood, William H; Becker, Kevin G; Moaddel, Ruin; Maudsley, Stuart; Martin, Bronwen

    2013-01-01

    With the prevalence of obesity, artificial, non-nutritive sweeteners have been widely used as dietary supplements that provide sweet taste without excessive caloric load. In order to better understand the overall actions of artificial sweeteners, especially when they are chronically used, we investigated the peripheral and central nervous system effects of protracted exposure to a widely used artificial sweetener, acesulfame K (ACK). We found that extended ACK exposure (40 weeks) in normal C57BL/6J mice demonstrated a moderate and limited influence on metabolic homeostasis, including altering fasting insulin and leptin levels, pancreatic islet size and lipid levels, without affecting insulin sensitivity and bodyweight. Interestingly, impaired cognitive memory functions (evaluated by Morris Water Maze and Novel Objective Preference tests) were found in ACK-treated C57BL/6J mice, while no differences in motor function and anxiety levels were detected. The generation of an ACK-induced neurological phenotype was associated with metabolic dysregulation (glycolysis inhibition and functional ATP depletion) and neurosynaptic abnormalities (dysregulation of TrkB-mediated BDNF and Akt/Erk-mediated cell growth/survival pathway) in hippocampal neurons. Our data suggest that chronic use of ACK could affect cognitive functions, potentially via altering neuro-metabolic functions in male C57BL/6J mice. PMID:23950916

  17. Regulation of proline utilization in Salmonella typhimurium: characterization of put::Mu d(Ap, lac) operon fusions.

    OpenAIRE

    Maloy, S R; Roth, J R

    1983-01-01

    The genes for proline utilization were fused to the structural genes of the lac operon by use of the hybrid Mu phage derivative Mu d(Ap lac). Stable deletion derivatives of these fusions were selected and used to study the transcriptional regulation of the put genes. Analysis of these fusions showed that the putA gene product, a bifunctional oxidase-dehydrogenase, also serves to negatively control transcription of the putA and putP genes. Transcription of the put genes is repressed only in pu...

  18. Large Inversion in Escherichia Coli K-12 1485in between Inversely Oriented Is3 Elements near Lac and Cdd

    OpenAIRE

    Komoda, Y.; Enomoto, M.; Tominaga, A

    1991-01-01

    A companion study has shown that the inversion carried by strain 1485IN has one terminus between lac and proC and the other between his and cdd of the normal strain. Starting with this mapping data, we have done molecular work demonstrating that the inversion occurred by recombination between inversely oriented two IS3 elements, one present near lac and the other near the cdd locus; i.e., the inversion is IN(is3B-is3E). Evidence supporting this conclusion includes: (i) Normal and inversion st...

  19. A fire history derived from Pinus resinosa Ait. for the Islands of Eastern Lac La Croix, Minnesota, USA.

    Science.gov (United States)

    Johnson, Lane B; Kipfmueller, Kurt F

    2016-06-01

    We reconstructed fire occurrence near a fur-trade era canoe travel corridor (used ca. 1780-1802) in the Quetico-Superior region west of Lake Superior to explore the possibility of human influence on pre-fire suppression rates of fire occurrence. Our research objectives were to (1) examine the spatial and temporal patterns of fire in the study area, (2) test fires' strength of association with regional drought, and (3) assess whether reconstructed fire frequencies could be explained by observed rates of lightning fire ignition over the modern period of record. We developed a 420-year fire history for the eastern portion of Lac La Croix in the Boundary Waters Canoe Area Wilderness (BWCAW). Seventy-one fire-scarred samples were collected from remnant Pinus resinosa Ait. (red pine) stumps and logs from thirteen distinct island and three mainland forest stands. Collectively these samples contained records of 255 individual fire scars representing 79 fire events from 1636 to 1933 (study area mean fire intervals [MFI] 3.8 yr). Reconstructed fires were spatially and temporally asynchronous and not strongly associated with regional drought (P > 0.05). When compared to the conservative, tree-ring reconstructed estimate of historical fire occurrence and modern lightning-caused fires (1929-2012), a noticeable change in the distribution and frequency of fires within the study area was evident with only two lightning-ignited island fires since 1934 in the study area. Our results suggest a high likelihood that indigenous land use contributed to surface fire ignitions within our study area and highlights the importance of examining the potential effects of past indigenous land use when determining modern approaches to fire and wilderness management in fire-adapted ecosystems. PMID:27509746

  20. Use of cir-lac operon fusions to study transcriptional regulation of the colicin Ia receptor in Escherichia coli K-12.

    OpenAIRE

    Worsham, P L; Konisky, J

    1981-01-01

    We describe cir-lac operon fusions constructed by using phage Mu d(Apr lac). Expression of beta-galactosidase in these fusion strains is analogous to known regulatory properties of cir gene expression. It is concluded that the observed regulation by iron of the cir gene is under transcriptional control.