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Sample records for delta scuti star

  1. Four new Delta Scuti stars

    Science.gov (United States)

    Schutt, R. L.

    1991-01-01

    Four new Delta Scuti stars are reported. Power, modified into amplitude, spectra, and light curves are used to determine periodicities. A complete frequency analysis is not performed due to the lack of a sufficient time base in the data. These new variables help verify the many predictions that Delta Scuti stars probably exist in prolific numbers as small amplitude variables. Two of these stars, HR 4344 and HD 107513, are possibly Am stars. If so, they are among the minority of variable stars which are also Am stars.

  2. The MACHO Project Sample of Galactic Bulge High-Amplitude {delta} Scuti Stars: Pulsation Behavior and Stellar Properties

    Energy Technology Data Exchange (ETDEWEB)

    Alcock, C.; Allsman, R. A.; Alves, D. R.; Axelrod, T. S.; Becker, A. C.; Bennett, D. P.; Cook, K. H.; Freeman, K. C.; Geha, M.; Griest, K. (and others)

    2000-06-20

    We have detected 90 objects with periods and light-curve structures similar to those of field {delta} Scuti stars using the Massive Compact Halo Object (MACHO) Project database of Galactic bulge photometry. If we assume similar extinction values for all candidates and absolute magnitudes similar to those of other field high-amplitude {delta} Scuti stars (HADS), the majority of these objects lie in or near the Galactic bulge. At least two of these objects are likely foreground {delta} Scuti stars, one of which may be an evolved nonradial pulsator, similar to other evolved, disk-population {delta} Scuti stars. We have analyzed the light curves of these objects and find that they are similar to the light curves of field {delta} Scuti stars and the {delta} Scuti stars found by the Optical Gravitational Lens Experiment (OGLE). However, the amplitude distribution of these sources lies between those of low- and high-amplitude {delta} Scuti stars, which suggests that they may be an intermediate population. We have found nine double-mode HADS with frequency ratios ranging from 0.75 to 0.79, four probable double- and multiple-mode objects, and another four objects with marginal detections of secondary modes. The low frequencies (5-14 cycles day-1) and the observed period ratios of {approx}0.77 suggest that the majority of these objects are evolved stars pulsating in fundamental or first overtone radial modes. (c) 2000 The American Astronomical Society.

  3. A survey for southern delta Scuti variable stars

    International Nuclear Information System (INIS)

    McInally, C.J.; Austin, R.R.D.

    1978-01-01

    Twenty-nine field stars have been tested photoelectrically for short-period variability. Eighteen of these stars have spectral types between A2 and F5 and are not Am stars; of these, six have been discovered to be variable and one is a suspected variable. HD 185969, with a period of 0.361 day, has the longest known period for a star of the delta Scuti type. The predominance of discovered variables with amplitudes close to the detection limit is suggestive of most stars in the instability strip being pulsators. (author)

  4. Empirical P-L-C relations for delta Scuti stars

    International Nuclear Information System (INIS)

    Gupta, S.K.

    1978-01-01

    Separate P-L-C relations have been empirically derived by sampling the delta Scuti stars according to their pulsation modes. The results based on these relations have been compared with those estimated from the model based P-L-C relations and the other existing empirical P-L-C relations. It is found that a separate P-L-C relation for each pulsation mode provides a better correspondence with observations. (Auth.)

  5. Pulsations of delta Scuti stars

    International Nuclear Information System (INIS)

    Cox, A.N.

    1990-01-01

    In this paper the authors give a general review of the pulsating δ Scuti variables, including the observed light curves and positions of the stars in the Hertzsprung-Russell diagram. Theoretical interpretations from evolution and pulsation calculations give their masses, radii, luminosities, and even their approximate internal compositions. Then we discuss three models of these stars, and use them to study the nonlinear hydrodynamic behavior of these stars, after which the authors outline the hydrodynamic equations and the Stellingwerf method for obtaining strictly periodic solutions. The authors also present the problems of allowing for time-dependent convection and its great sensitivity to temperature and density. Tentative results to data do not show any tendency for amplitudes to grow to large unobserved amplitudes, in disagreement with an earlier suggestion by Stellingwerf. Finally, the authors find that the very small growth rates of the pulsations may even be too small to be useful in seeking a periodic solution. The δ Scuti variables are the most common type of variable star in our galaxy except for the white dwarfs. This is because stars in the mass range from just over one M circle-dot up to at least several M circle-dot pass through the yellow giant instability strip in the Hertzsprung-Russell diagram as they evolve off the main sequence to the red. Actually, stars up to the maximum main sequence mass also evolve through this region at higher luminosities, but there are so few of them, and they evolve so rapidly to the red, that they are almost unknown. At the higher luminosity, they probably would be called first-instability strip-crossing Cepheids anyway. Such cepheids are difficult to separate from those that are on the second blueward instability strip crossing that is much slower. Really, the δ Scuti variables are just low-luminosity Cepheids

  6. The MACHO Project Sample of Galactic Bulge High-Amplitude Scuti Stars: Pulsation Behavior and Stellar Properties

    International Nuclear Information System (INIS)

    Bennett, D.P.; Cook, K.H.; Freeman, K.C.; Geha, M.; Griest, K.; Lehner, M.J.; Marshall, S.L.; McNamara, B.J.; Minniti, D.; Nelson, C.; Peterson, B.A.; Popowski, P.; Pratt, M.R.; Quinn, P.J.; Rodgers, A.W.; Sutherland, W.; Templeton, M.R.; Vandehei, T.; Welch, D.L.

    1999-01-01

    We have detected 90 objects with periods and lightcurve structure similar to those of field(delta) Scuti stars, using the Massive Compact Halo Object (MACHO) Project database of Galactic bulge photometry. If we assume similar extinction values for all candidates and absolute magnitudes similar to those of other field high-amplitude(delta) Scuti stars (HADS), the majority of these objects lie in or near the Galactic bulge. At least two of these objects are likely foreground(delta) Scuti stars, one of which may be an evolved nonradial pulsator, similar to other evolved, disk-population(delta) Scuti stars. We have analyzed the light curves of these objects and find that they are similar to the light curves of field(delta) Scuti stars and the(delta) Scuti stars found by the Optical Gravitational Lens Experiment (OGLE). However, the amplitude distribution of these sources lies between those of low- and high-amplitude(delta) Scuti stars, which suggests that they may be an intermediate population. We have found nine double-mode HADS with frequency ratios ranging from 0.75 to 0.79, four probable double- and multiple-mode objects, and another four objects with marginal detections of secondary modes. The low frequencies (5-14 cycles d(sup -1)) and the observed period ratios of(approx)0.77 suggest that the majority of these objects are evolved stars pulsating in fundamental or first overtone radial modes

  7. STATISTICAL PROPERTIES OF GALACTIC δ SCUTI STARS: REVISITED

    International Nuclear Information System (INIS)

    Chang, S.-W.; Kim, D.-W.; Byun, Y.-I.; Protopapas, P.

    2013-01-01

    We present statistical characteristics of 1578 δ Scuti stars including nearby field stars and cluster member stars within the Milky Way. We obtained 46% of these stars (718 stars) from work by Rodríguez and collected the remaining 54% of stars (860 stars) from other literature. We updated the entries with the latest information of sky coordinates, color, rotational velocity, spectral type, period, amplitude, and binarity. The majority of our sample is well characterized in terms of typical period range (0.02-0.25 days), pulsation amplitudes (<0.5 mag), and spectral types (A-F type). Given this list of δ Scuti stars, we examined relations between their physical properties (i.e., periods, amplitudes, spectral types, and rotational velocities) for field stars and cluster members, and confirmed that the correlations of properties are not significantly different from those reported in Rodríguez's work. All the δ Scuti stars are cross-matched with several X-ray and UV catalogs, resulting in 27 X-ray and 41 UV-only counterparts. These counterparts are interesting targets for further study because of their uniqueness in showing δ Scuti-type variability and X-ray/UV emission at the same time. The compiled catalog can be accessed through the Web interface http://stardb.yonsei.ac.kr/DeltaScuti.

  8. Pulsations of delta Scuti stars

    International Nuclear Information System (INIS)

    Cox, A.N.

    1989-01-01

    A general review of the pulsating δ Scuti variables is given including the observed light curves and positions of the stars in the Hertzsprung-Russell diagram. Theoretical interpretations from evolution and pulsation calculations give their masses, radii, luminosities, and even their approximate internal compositions. Three models of these stars are discussed and used to study the nonlinear hydrodynamic behavior of these stars. The hydrodynamic equations and the Stellingwerf method for obtaining strictly periodic solutions are outlined. Problems of allowing for time-dependent convection and its great sensitivity to temperature and density are presented. Tentative results to date do not show any tendency for amplitudes to grow to large unobserved amplitudes, in disagreement with an earlier suggestion by Stellingwerf. It is found that the very small growth rates of the pulsations may even be too small to be useful in seeking a periodic solution. 15 refs., 8 figs., 3 tabs

  9. Metallicism and pulsation: an analysis of the delta Delphini stars

    International Nuclear Information System (INIS)

    Kurtz, D.W.

    1976-01-01

    Fine abundance analyses of seven delta Delphini stars and one delta Scuti star relative to four comparison standards are presented. Five of the delta Del stars are shown to have abundances most similar to the evolved Am stars. It is argued that these abundances are different from the classical Am star and Ap star abundances and that similarities to the Ba II star abundances are coincidental. We suggest that the anomalous abundance delta Del stars are evolved metallic line stars on the basis of their abundances, position in the β, M/sub v/ plane, inferred rotational velocities, and perhaps their binary incidence. Some of the delta Del stars are delta Scuti pulsators. We argue that pulsation and metallicism are mutually exclusive among the classical Am stars but may coexist in other stars related to the classical Am stars. A preference for the diffusion hypothesis model for the metallic line stars is stated and supported and the implications of the coexistence of pulsation and diffusion are discussed

  10. Delta Scuti variables. Lecture 6

    International Nuclear Information System (INIS)

    Cox, A.N.

    1983-01-01

    The class of variables near or on the upper main sequence, the delta Scuti variables, are not only the usual ones about the masses, radii, and luminosities, but also the age, rotation, element diffusion to change the surface layer composition, the occurance of convection and the presence of radial and nonradial pulsation modes

  11. Asteroseismology of Scuti Stars

    Indian Academy of Sciences (India)

    Abstract. We briefly outline the state-of-the-art seismology of Scuti stars from a theoretical point of view: why is it so difficult a task? The recent theoretical advances in the field that these difficulties have influenced are also discussed.

  12. What CoRoT tells us about δ Scuti stars

    Directory of Open Access Journals (Sweden)

    Michel Eric

    2017-01-01

    Full Text Available Inspired by the so appealing example of red giants, where going from a handful of stars to thousands revealed the structure of the eigenspectrum, we inspected a large homogeneous set of around 1860 δ Scuti stars observed with CoRoT. This unique data set reveals a common regular pattern which appears to be in agreement with island modes featured by theoretical non-perturbative treatments of fast rotation. The comparison of these data with models and linear stability calculations suggests that spectra can be fruitfully characterized to first order by a few parameters which might play the role of seismic indices for δ Scuti stars, as Δv and vmax do for red giants. The existence of this pattern offers an observational support for guiding further theoretical works on fast rotation. It also provides a framework for further investigation of the observational material collected by CoRoT ([1] and Kepler ([2]. Finally, it sketches out the perspective of using δ Scuti stars pulsations for ensemble asteroseismology

  13. The Delta Scuti star 38 Eri from the ground and from space

    Science.gov (United States)

    Paparó, M.; Kolláth, Z.; Shobbrook, R. R.; Matthews, J. M.; Antoci, V.; Benkő, J. M.; Park, N.-K.; Mirtorabi, M. T.; Luedeke, K.; Kusakin, A.; Bognár, Zs; Sódor, Á.; García-Hernández, A.; Pe na, J. H.; Kuschnig, R.; Moffat, A. F. J.; Rowe, J.; Rucinski, S. M.; Sasselov, D.; Weiss, W. W.

    2018-04-01

    We present and discuss the pulsational characteristics of the Delta Scuti star 38 Eri from photometric data obtained at two widely spaced epochs, partly from the ground (1998) and partly from space (MOST, 2011). We found 18 frequencies resolving the discrepancy among the previously published frequencies. Some of the frequencies appeared with different relative amplitudes at two epochs, however, we carried out investigation for amplitude variability for only the MOST data. Amplitude variability was found for one of three frequencies that satisfy the necessary frequency criteria for linear-combination or resonant-mode coupling. Checking the criteria of beating and resonant-mode coupling we excluded them as possible reason for amplitude variability. The two recently developed methods of rotational-splitting and sequence-search were applied to find regular spacings based only on frequencies. Doublets or incomplete multiplets with l = 1, 2 and 3 were found in the rotational splitting search. In the sequence search method we identified four sequences. The averaged spacing, probably a combination of the large separation and the rotational frequency, is 1.724 ± 0.092 d-1. Using the spacing and the scaling relation \\bar{ρ }= [0.0394, 0.0554] gcm-3 was derived. The shift of the sequences proved to be the integer multiple of the rotational splitting spacing. Using the precise MOST frequencies and multi-colour photometry in a hybrid way, we identified four modes with l = 1, two modes with l = 2, two modes with l = 3, and two modes as l = 0 radial modes.

  14. Comparing the asteroseismic properties of pulsating extremely low-mass pre-white dwarf stars and δ Scuti stars

    Directory of Open Access Journals (Sweden)

    Arias J.P.Sánchez

    2017-01-01

    Full Text Available We present the first results of a detailed comparison between the pulsation properties of pulsating Extremely Low-Mass pre-white dwarf stars (the pre-ELMV variable stars and δ Scuti stars. The instability domains of these very different kinds of stars nearly overlap in the log Teff vs. log g diagram, leading to a degeneracy in the classification of the stars. Our aim is to provide asteroseismic tools for their correct classification.

  15. Asteroseismology of δ Scuti Stars: Problems and Prospects M.-J ...

    Indian Academy of Sciences (India)

    overshoot, time dependent convection, rotation interaction with oscillation and with convection. 2.2 Oscillations δ Scuti stars are pulsating with periods of a few hours. The mechanism which excites the observed modes is similar to that of a thermal machine or heat engine in that, energy is stored in some peculiar region of ...

  16. Convection and Overshoot in Models of Doradus and Scuti Stars

    International Nuclear Information System (INIS)

    Lovekin, Catherine C.

    2017-01-01

    We investigate the pulsation properties of stellar models that are representative of δ Scuti and γ Doradus variables. Here we have calculated a grid of stellar models from 1.2 to 2.2 M ⊙, including the effects of both rotation and convective overshoot using MESA, and we investigate the pulsation properties of these models using GYRE. We discuss the observable patterns in the frequency spacing for p modes and the period spacings for g modes. Using the observable patterns in the g mode period spacings, it may be possible to observationally constrain the convective overshoot and rotation of a model. We also calculate the pulsation constant (Q) for all models in our grid and investigate the variation with convective overshoot and rotation. The variation in the Q values of the radial modes can be used to place constraints on the convective overshoot and rotation of stars in this region. Finally, as a test case, we apply this method to a sample of 22 High-Amplitude δ Scuti stars (HADS) and provide estimates for the convective overshoot of the sample.

  17. Discovery of a magnetic field in the δ Scuti F2m star ρ Pup

    Science.gov (United States)

    Neiner, C.; Wade, G. A.; Sikora, J.

    2017-06-01

    ρ Pup is a δ Scuti F2 pulsator, known to host a main radial mode as well as non-radial pulsations, with chemical peculiarities typical of evolved Am stars. We present a high-precision spectropolarimetric observations of this star, obtained with ESPaDOnS at the Canada-France-Hawaii Telescope in the frame of the BRITE spectropolarimetric survey. A magnetic field is clearly detected in ρ Pup, with a longitudinal field strength below 1 G. This makes ρ Pup the second known magnetic δ Scuti discovered, after HD 188774, and a possible cool evolved counterpart of the recently discovered ultraweakly magnetic Am family.

  18. KEPLER ECLIPSING BINARIES WITH DELTA SCUTI/GAMMA DORADUS PULSATING COMPONENTS. I. KIC 9851944

    Energy Technology Data Exchange (ETDEWEB)

    Guo, Zhao; Gies, Douglas R.; Matson, Rachel A. [Center for High Angular Resolution Astronomy and Department of Physics and Astronomy, Georgia State University, P.O. Box 5060, Atlanta, GA 30302-5060 (United States); Hernández, Antonio García, E-mail: guo@chara.gsu.edu, E-mail: gies@chara.gsu.edu, E-mail: rmatson@chara.gssu.edu, E-mail: agh@astro.up.pt [Instituto de Astrofísica e Ciências do Espaco, Universidade do Porto, CAUP, Rua das Estrelas, PT4150-762 Porto (Portugal)

    2016-07-20

    KIC 9851944 is a short-period ( P = 2.16 days) eclipsing binary in the Kepler field of view. By combining the analysis of Kepler photometry and phase-resolved spectra from Kitt Peak National Observatory and Lowell Observatory, we determine the atmospheric and physical parameters of both stars. The two components have very different radii (2.27 R {sub ⊙}, 3.19 R {sub ⊙}) but close masses (1.76 M {sub ⊙}, 1.79 M {sub ⊙}) and effective temperatures (7026, 6902 K), indicating different evolutionary stages. The hotter primary is still on the main sequence (MS), while the cooler and larger secondary star has evolved to the post-MS, burning hydrogen in a shell. A comparison with coeval evolutionary models shows that it requires solar metallicity and a higher mass ratio to fit the radii and temperatures of both stars simultaneously. Both components show δ Scuti-type pulsations, which we interpret as p -modes and p and g mixed modes. After a close examination of the evolution of δ Scuti pulsational frequencies, we make a comparison of the observed frequencies with those calculated from MESA/GYRE.

  19. A Study of Chemical Composition of δ Scuti-Type Stars Based on the Observations with the BTA and RTT-150

    Science.gov (United States)

    Galeev, A. I.; Berdnikova, V. M.; Ivanova, D. V.; Kudryavtsev, D. O.; Shimanskaya, N. N.; Shimansky, V. V.; Balashova, M. O.

    2017-06-01

    The results of a study of a sample of δ Scuti-type stars obtained from the observations with the BTA and RTT-150 are presented. Based on photometric data, we measured and analyzed the fundamental parameters of all the studied stars. For eight stars (for two of them for the first time), the fundamental parameters of the atmospheres (Teff, log g, [Fe/H]) and the chemical composition for 29 elements in the LTE-approximation are received using spectroscopic observations. The chemical composition analysis demonstrates both the solar abundances of chemical elements and the anomalies of chemical composition typical of Am stars in the studied sample of δ Scuti-type stars.

  20. Precise surface gravities of δ Scuti stars from asteroseismology

    Science.gov (United States)

    García Hernández, A.; Suárez, J. C.; Moya, A.; Monteiro, M. J. P. F. G.; Guo, Z.; Reese, D. R.; Pascual-Granado, J.; Barceló Forteza, S.; Martín-Ruiz, S.; Garrido, R.; Nieto, J.

    2017-10-01

    The work reported here demonstrates that it is possible to accurately determine surface gravities of δ Scuti (δ Sct) stars using the frequency content from high-precision photometry and a measurement of the parallax. Using a sample of 10 eclipsing binary systems with a δ Sct component and the unique δ Sct star discovered with a transiting planet, WASP-33, we were able to refine the Δν-\\bar{ρ } relation. Using this relation and parallaxes, we obtained independent values for the masses and radii, allowing us to calculate the surface gravities without any constraints from spectroscopic or binary analysis. A remarkably good agreement was found between our results and those published, extracted from the analysis of the radial velocities and light curves of the systems. This reinforces the potential of Δν as a valuable observable for δ Sct stars and settles the degeneracy problem for the log g determination through spectroscopy.

  1. Chemical composition of δ Scuti stars: 1. AO CVn, CP Boo, KW Aur

    Science.gov (United States)

    Galeev, A. I.; Ivanova, D. V.; Shimansky, V. V.; Bikmaev, I. F.

    2012-11-01

    We used high-resolution echelle spectra acquired with the 1.5-m Russian-Turkish Telescope to determine the fundamental atmospheric parameters and abundances of 30 chemical elements for three δ Scuti stars: AOCVn, CP Boo, and KWAur. The chemical compositions we find for these stars are similar to those for Am-star atmospheres, though some anomalies of up to 0.6-0.7 dex are observed for light and heavy elements. We consider the effect of the adopted stellar parameters (effective temperature, log g, microturbulent velocity) and the amplitude of pulsational variations on the derived elemental abundances.

  2. The role of turbulent pressure as a coherent pulsational driving mechanism: the case of the δ Scuti star HD 187547

    Energy Technology Data Exchange (ETDEWEB)

    Antoci, V.; Houdek, G.; Kjeldsen, H.; Trampedach, R.; Arentoft, T. [Stellar Astrophysics Centre, Aarhus University, Ny Munkegade 120, DK-8000 Aarhus C (Denmark); Cunha, M. [Centro de Astrofísca e Faculdade de Ciências, Universidade do Porto, Rua das Estrelas 4150-762 (Portugal); Handler, G. [Copernicus Astronomical Center, Bartycka 18, 00-716 Warsaw (Poland); Lüftinger, T. [Institute for Astronomy, University of Vienna, Türkenschanzstr. 17, A-1180 Vienna (Austria); Murphy, S., E-mail: antoci@phys.au.dk [Sydney Institute for Astronomy (SIfA), School of Physics, University of Sydney, Sydney, NSW 2006 (Australia)

    2014-12-01

    HD 187547 was the first candidate that led to the suggestion that solar-like oscillations are present in δ Scuti stars. Longer observations, however, show that the modes interpreted as solar-like oscillations have either very long mode lifetimes, longer than 960 days, or are coherent. These results are incompatible with the nature of 'pure' stochastic excitation as observed in solar-like stars. Nonetheless, one point is certain: the opacity mechanism alone cannot explain the oscillation spectrum of HD 187547. Here we present new theoretical investigations showing that convection dynamics can intrinsically excite coherent pulsations in the chemically peculiar δ Scuti star HD 187547. More precisely, it is the perturbations of the mean Reynold stresses (turbulent pressure) that drives the pulsations and the excitation takes place predominantly in the hydrogen ionization zone.

  3. Photometric studies of δ Scuti stars. I. IP Virginis

    Science.gov (United States)

    Joner, Michael D.; Hintz, Eric G.; Collier, Matthew W.

    1998-01-01

    We report 15 new times of maximum light for the δ Scuti star IP Virginis (formerly known as SA 106‐1024). An analysis of all times of maximum light indicates that IP Vir has been decreasing in period at a constant rate of − days day−1. Evidence is also presented that IP Vir is a double‐mode variable with a period ratio of . This period ratio predicts a [Fe/H] value of −0.3. From photometric (uvbyβ) observations, we find a foreground reddening of .008 mag and a metallicity of [Fe/H] = +0.05. It is shown that [Fe/H] = −0.3 is most likely the correct value. Intrinsic ‐ and c1‐values, plotted in a model atmosphere grid, indicate a mean effective temperature, K, and a mean surface gravity, . All of these physical parameters support Landolt's initial conclusion that IP Vir is an ordinary δ Sct star.

  4. Kepler observations of the high-amplitude δ Scuti star V2367 Cyg

    DEFF Research Database (Denmark)

    Balona, L. A.; Lenz, P.; Antoci, V.

    2012-01-01

    We analyse Kepler observations of the high-amplitude δ Scuti (HADS) star V2367 Cyg (KIC 9408694). The variations are dominated by a mode with frequency f1= 5.6611 d−1. Two other independent modes with f2= 7.1490 d−1 and f3= 7.7756 d−1 have amplitudes an order of magnitude smaller than f1. Nearly...... all the light variation is due to these three modes and their combination frequencies, but several hundred other frequencies of very low amplitude are also present. The amplitudes of the principal modes may vary slightly with time. The star has twice the projected rotational velocity of any other HADS...... star, which makes it unusual. We find a correlation between the phases of the combination frequencies and their pulsation frequencies, which is not understood. Since modes of highest amplitude in HADS stars are normally radial modes, we assumed that this would also be true in this star. However...

  5. The Role of Turbulent Pressure as a Coherent Pulsational Driving Mechanism: The Case of the δ Scuti Star HD 187547

    DEFF Research Database (Denmark)

    Antoci, V.; Cunha, M.; Houdek, G.

    2014-01-01

    are incompatible with the nature of "pure" stochastic excitation as observed in solar-like stars. Nonetheless, one point is certain: the opacity mechanism alone cannot explain the oscillation spectrum of HD 187547. Here we present new theoretical investigations showing that convection dynamics can intrinsically......HD 187547 was the first candidate that led to the suggestion that solar-like oscillations are present in δ Scuti stars. Longer observations, however, show that the modes interpreted as solar-like oscillations have either very long mode lifetimes, longer than 960 days, or are coherent. These results...... excite coherent pulsations in the chemically peculiar δ Scuti star HD 187547. More precisely, it is the perturbations of the mean Reynold stresses (turbulent pressure) that drives the pulsations and the excitation takes place predominantly in the hydrogen ionization zone....

  6. Amplitude Modulation of Pulsation Modes in Delta Scuti Stars

    Science.gov (United States)

    Bowman, Dominic M.

    2017-10-01

    The pulsations in δ Sct stars are excited by a heat engine driving mechanism caused by increased opacity in their surface layers, and have pulsation periods of order a few hours. Space based observations in the last decade have revealed a diverse range of pulsational behaviour in these stars, which is investigated using an ensemble of 983 δ Sct stars observed continuously for 4 yr by the Kepler Space Telescope. A statistical search for amplitude modulation of pulsation modes is carried out and it is shown that 61.3 per cent of the 983 δ Sct stars exhibit significant amplitude modulation in at least a single pulsation mode, and that this is uncorrelated with effective temperature and surface gravity. Hence, the majority of δ Sct stars exhibit amplitude modulation, with time-scales of years and longer demonstrated to be significant in these stars both observationally and theoretically. An archetypal example of amplitude modulation in a δ Sct star is KIC 7106205, which contains only a single pulsation mode that varies significantly in amplitude whilst all other pulsation modes stay constant in amplitude and phase throughout the 4-yr Kepler data set. Therefore, the visible pulsational energy budget in this star, and many others, is not conserved over 4 yr. Models of beating of close-frequency pulsation modes are used to identify δ Sct stars with frequencies that lie closer than 0.001 d^{-1}, which are barely resolved using 4 yr of Kepler observations, and maintain their independent identities over 4 yr. Mode coupling models are used to quantify the strength of coupling and distinguish between non-linearity in the form of combination frequencies and non-linearity in the form of resonant mode coupling for families of pulsation modes in several stars. The changes in stellar structure caused by stellar evolution are investigated for two high amplitude δ Sct (HADS) stars in the Kepler data set, revealing a positive quadratic change in phase for the fundamental and

  7. Kepler observations of rapidly oscillating Ap, δ Scuti and γ Doradus pulsations in Ap stars

    DEFF Research Database (Denmark)

    Balona, Luis A.; Cunha, Margarida S.; Kurtz, Donald W.

    2011-01-01

    Observations of the A5p star KIC 8677585 obtained during the Kepler 10-d commissioning run with 1-min time resolution show that it is a rapidly oscillating Ap (roAp) star with several frequencies with periods near 10 min. In addition, a low frequency at 3.142 d−1 is also clearly present....... Multiperiodic γ Doradus (γ Dor) and δ Scuti (δ Sct) pulsations, never before seen in any Ap star, are present in Kepler observations of at least three other Ap stars. Since γ Dor pulsations are seen in Ap stars, it is likely that the low frequency in KIC 8677585 is also a γ Dor pulsation. The simultaneous...... presence of both γ Dor and roAp pulsations and the unexpected detection of δ Sct and γ Dor pulsations in Ap stars present new opportunities and challenges for the interpretation of these stars. Since it is easy to confuse Am and Ap stars at classification dispersions, the nature of these Ap stars...

  8. Delta isobars in neutron stars

    Directory of Open Access Journals (Sweden)

    Pagliara Giuseppe

    2015-01-01

    Full Text Available The appearance of delta isobars in beta-stable matter is regulated by the behavior of the symmetry energy at densities larger than saturation density. We show that by taking into account recent constraints on the density derivative of the symmetry energy and the theoretical and experimental results on the excitations of delta isobars in nuclei, delta isobars are necessary ingredients for the equations of state used for studying neutron stars. We analyze the effect of the appearance of deltas on the structure of neutron stars: as in the case of hyperons, matter containing delta is too soft for allowing the existence of 2M⊙ neutron stars. Quark stars on the other hand, could reach very massive configurations and they could form from a process of conversion of hadronic stars in which an initial seed of strangeness appears through hyperons.

  9. Gravity Modes Reveal the Internal Rotation of a Post-mass-transfer Gamma Doradus/Delta Scuti Hybrid Pulsator in Kepler Eclipsing Binary KIC 9592855

    Science.gov (United States)

    Guo, Z.; Gies, D. R.; Matson, R. A.

    2017-12-01

    We report the discovery of a post-mass-transfer Gamma Doradus/Delta Scuti hybrid pulsator in the eclipsing binary KIC 9592855. This binary has a circular orbit, an orbital period of 1.2 days, and contains two stars of almost identical masses ({M}1=1.72 {M}⊙ ,{M}2=1.71 {M}⊙ ). However, the cooler secondary star is more evolved ({R}2=1.96 {R}⊙ ), while the hotter primary is still on the zero-age-main-sequence ({R}1=1.53 {R}⊙ ). Coeval models from single-star evolution cannot explain the observed masses and radii, and binary evolution with mass-transfer needs to be invoked. After subtracting the binary light curve, the Fourier spectrum shows low-order pressure-mode pulsations, and more dominantly, a cluster of low-frequency gravity modes at about 2 day-1. These g-modes are nearly equally spaced in period, and the period spacing pattern has a negative slope. We identify these g-modes as prograde dipole modes and find that they stem from the secondary star. The frequency range of unstable p-modes also agrees with that of the secondary. We derive the internal rotation rate of the convective core and the asymptotic period spacing from the observed g-modes. The resulting values suggest that the core and envelope rotate nearly uniformly, i.e., their rotation rates are both similar to the orbital frequency of this synchronized binary.

  10. Eclipsing binary stars with a delta Scuti component

    Czech Academy of Sciences Publication Activity Database

    Alicavus, F.K.; Soydugan, E.; Smalley, B.; Kubát, Jiří

    2017-01-01

    Roč. 470, č. 1 (2017), s. 915-931 ISSN 0035-8711 R&D Projects: GA ČR(CZ) GA16-01116S Institutional support: RVO:67985815 Keywords : stars * eclipsing binaries * fundamental parameters Subject RIV: BN - Astronomy, Celestial Mechanics, Astrophysics OBOR OECD: Astronomy (including astrophysics,space science) Impact factor: 4.961, year: 2016

  11. Pulsating stars in the region of Carina Nebula

    Energy Technology Data Exchange (ETDEWEB)

    Steslicki, Marek [Astronomical Institute, University of Wroclaw (Poland)], E-mail: steslicki@astro.uni.wroc.p1

    2008-10-15

    We present the results of a search for pulsating stars in the region of Carina Nebula which includes three very young open clusters: Trumpler 14, 15 and 16. The search was made with the Wide Field Imager (WFI) on the MPG/ESO 2.2-m telescope in La Silla (Chile). In total, about 16,000 stars have been analyzed using classical Fourier techniques. We found over 20 pulsating {delta}-Scuti type stars in this region. Most of them are probable members of open clusters at the pre-main sequence evolutionary stage.

  12. VizieR Online Data Catalog: Frequency spacing of δ Scuti stars. II. (Paparo+, 2016)

    Science.gov (United States)

    Paparo, M.; Benko, J. M.; Hareter, M.; Guzik, J. A.

    2016-07-01

    The CoRoT satellite was launched in 2006. LRa01, the first long run in the direction of anti-center, started on 2007 October 15 and finished on 2008 March 3, resulting in a ΔT=131d time span. Both chromatic and monochromatic data were obtained on the EXO field with a regular sampling of 8 minutes, although for some stars an oversampling mode (32s) was applied. We systematically searched in the CoRoT data archive all light curves in the EXO field for δ Scuti and γ Doradus light curves (Hareter M., 2013, PhD thesis Univ. Vienna). (2 data files).

  13. The envelope of the power spectra of over a thousand δ Scuti stars. The T̅eff - νmax scaling relation

    Science.gov (United States)

    Barceló Forteza, S.; Roca Cortés, T.; García, R. A.

    2018-06-01

    CoRoT and Kepler high-precision photometric data allowed the detection and characterization of the oscillation parameters in stars other than the Sun. Moreover, thanks to the scaling relations, it is possible to estimate masses and radii for thousands of solar-type oscillating stars. Recently, a Δν - ρ relation has been found for δ Scuti stars. Now, analysing several hundreds of this kind of stars observed with CoRoT and Kepler, we present an empiric relation between their frequency at maximum power of their oscillation spectra and their effective temperature. Such a relation can be explained with the help of the κ-mechanism and the observed dispersion of the residuals is compatible with they being caused by the gravity-darkening effect. Table A.1 is only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (http://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/614/A46

  14. Pulsations of the High-Amplitude δ Scuti star YZ Bootis

    Science.gov (United States)

    Yang, Tao-Zhi; Esamdin, Ali; Fu, Jian-Ning; Niu, Hu-Biao; Feng, Guo-Jie; Song, Fang-Fang; Liu, Jin-Zhong; Ma, Lu

    2018-01-01

    We present a study on pulsations of the high-amplitude δ Scuti star YZ Boo based on photometric observations in Johnson V and R bands with both the Nanshan 1-m telescope of Xinjiang AstronomicalObservatory (XAO) and the Xinglong 85-cmtelescope of NationalAstronomical Observatories, Chinese Academy of Sciences (NAOC). Fourier analysis of the light curves reveals the fundamental radial mode and its five harmonics, with the fourth and fifth being newly detected. Thirty-nine new times of maximum light are determined from the light curves, and combined with those in the literature, we construct the O ‑ C diagram, derive a new ephemeris and determine a new value for the updated period of 0.104091579(2). In addition, the O ‑ C diagram reveals an increasing rate of period change for YZ Boo. Theoretical models are calculated and constrained with the observationally determined parameters of YZ Boo. The mass and age of YZ Boo are hence derived as M = 1.61±0.05 M ⊙ and age = (1.44±0.14)×109 yr, respectively.With both the frequency of the fundamental radial mode and the rate of period change, YZ Boo is located at the post main sequence stage.

  15. Hybrid γ Doradus–δ Scuti Pulsators: New Insights into the Physics of the Oscillations from Kepler Observations

    DEFF Research Database (Denmark)

    Grigahcène, A.; Antoci, V.; Balona, L.

    2010-01-01

    Observations of the pulsations of stars can be used to infer their interior structure and test theoretical models. The main-sequence γ Doradus (Dor) and δ Scuti (Sct) stars with masses 1.2–2.5 M are particularly useful for these studies. The γ Dor stars pulsate in high-order g-modes with periods...

  16. Oscillations in roAp and & Scuti Stars : Theory and observations

    OpenAIRE

    Pinheiro, Fernando Jorge Gutiérrez

    1999-01-01

    As estrelas d Scuti e as estrelas roAp encontram-se na região da Faixa de Instabilidade das Cefeides que é atravessada pela Sequência principal. Cada tipo de estrelas apresenta frequências de oscilação que o outro género de estrelas não apresenta. Estas oscilações dependem da estrutura das estrelas, e podem ser descritas pelos modelos apropriados.De modo inverso, podemos a partir de observações obter as características de uma estrela, usando os modelos adequados.Discutiremos os modos de obter...

  17. Impact of gaps in the asteroseismic characterization of pulsating stars. I. The efficiency of pre-whitening

    Science.gov (United States)

    Pascual-Granado, J.; Suárez, J. C.; Garrido, R.; Moya, A.; Hernández, A. García; Rodón, J. R.; Lares-Martiz, M.

    2018-06-01

    Context. It is known that the observed distribution of frequencies in CoRoT and Kepler δ Scuti stars has no parallelism with any theoretical model. Pre-whitening is a widespread technique in the analysis of time series with gaps from pulsating stars located in the classical instability strip, such as δ Scuti stars. However, some studies have pointed out that this technique might introduce biases in the results of the frequency analysis. Aims: This work aims at studying the biases that can result from pre-whitening in asteroseismology. The results will depend on the intrinsic range and distribution of frequencies of the stars. The periodic nature of the gaps in CoRoT observations, only in the range of the pulsational frequency content of the δ Scuti stars, is shown to be crucial to determining their oscillation frequencies, the first step in performing asteroseismology of these objects. Hence, here we focus on the impact of pre-whitening on the asteroseismic characterization of δ Scuti stars. Methods: We select a sample of 15 δ Scuti stars observed by the CoRoT satellite, for which ultra-high-quality photometric data have been obtained by its seismic channel. In order to study the impact on the asteroseismic characterization of δ Scuti stars we perform the pre-whitening procedure on three datasets: gapped data, linearly interpolated data, and data with gaps interpolated using Autoregressive and Moving Average models (ARMA). Results: The different results obtained show that at least in some cases pre-whitening is not an efficient procedure for the deconvolution of the spectral window. Therefore, in order to reduce the effect of the spectral window to a minimum, in addition to performing a pre-whitening of the data, it is necessary to interpolate with an algorithm that is aimed to preserve the original frequency content. Tables 5-49 are only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (http://130.79.128.5) or via http

  18. The excitation of solar-like oscillations in a δ Sct star by efficient envelope convection

    DEFF Research Database (Denmark)

    Antoci, V.; Handler, G.; Kallinger, T.

    2011-01-01

    Delta Scuti (δSct) stars are opacity-driven pulsators with masses of 1.5-2.5Msolar, their pulsations resulting from the varying ionization of helium. In less massive stars such as the Sun, convection transports mass and energy through the outer 30per cent of the star and excites a rich spectrum...... of resonant acoustic modes. Based on the solar example, with no firm theoretical basis, models predict that the convective envelope in δSct stars extends only about 1per cent of the radius, but with sufficient energy to excite solar-like oscillations. This was not observed before the Kepler mission, so...... the presence of a convective envelope in the models has been questioned. Here we report the detection of solar-like oscillations in the δSct star HD187547, implying that surface convection operates efficiently in stars about twice as massive as the Sun, as the ad hoc models predicted....

  19. Discovery of multiple pulsations in the new δ Scuti star HD 92277: Asteroseismology from Dome A, Antarctica

    International Nuclear Information System (INIS)

    Zong, Weikai; Fu, Jian-Ning; Niu, Jia-Shu; Zhu, Zonghong; Charpinet, S.; Vauclair, G.; Ashley, Michael C. B.; Lawrence, Jon S.; Luong-Van, Daniel; Cui, Xiangqun; Gong, Xuefei; Feng, Longlong; Wang, Lifan; Yuan, Xiangyan; Zhu, Zhenxi; Liu, Qiang; Wang, Lingzhi; Zhou, Xu; Pennypacker, Carl R.; York, Donald G.

    2015-01-01

    We report the discovery of low-amplitude oscillations in the star HD 92277 from long, continuous observations in the r and g bands using the CSTAR telescopes in Antarctica. A total of more than 1950 hours of high-quality light curves were used to categorize HD 92277 as a new member of the δ Scuti class. We have detected 21 (20 frequencies are independent and one is the linear combination) and 14 (13 frequencies are independent and one is the linear combination) pulsation frequencies in the r and g bands, respectively, indicating a multi-periodic pulsation behavior. The primary frequency f 1 = 10.810 days −1 corresponds to a period of 0.0925 days and is an l = 1 mode. We estimate a B − V index of 0.39 and derive an effective temperature of 6800 K for HD 92277. We conclude that long, continuous and uninterrupted time-series photometry can be performed from Dome A, Antarctica, and that this is especially valuable for asteroseismology where multi-color observations (often not available from space-based telescopes) assist with mode identification.

  20. VARIABLE STARS IN LARGE MAGELLANIC CLOUD GLOBULAR CLUSTERS. II. NGC 1786

    International Nuclear Information System (INIS)

    Kuehn, Charles A.; Smith, Horace A.; De Lee, Nathan; Catelan, Márcio; Pritzl, Barton J.; Borissova, Jura

    2012-01-01

    This is the second in a series of papers studying the variable stars in Large Magellanic Cloud globular clusters. The primary goal of this series is to study how RR Lyrae stars in Oosterhoff-intermediate systems compare to their counterparts in Oosterhoff I/II systems. In this paper, we present the results of our new time-series B–V photometric study of the globular cluster NGC 1786. A total of 65 variable stars were identified in our field of view. These variables include 53 RR Lyraes (27 RRab, 18 RRc, and 8 RRd), 3 classical Cepheids, 1 Type II Cepheid, 1 Anomalous Cepheid, 2 eclipsing binaries, 3 Delta Scuti/SX Phoenicis variables, and 2 variables of undetermined type. Photometric parameters for these variables are presented. We present physical properties for some of the RR Lyrae stars, derived from Fourier analysis of their light curves. We discuss several different indicators of Oosterhoff type which indicate that the Oosterhoff classification of NGC 1786 is not as clear cut as what is seen in most globular clusters.

  1. Discovery of multiple pulsations in the new δ Scuti star HD 92277: Asteroseismology from Dome A, Antarctica

    Energy Technology Data Exchange (ETDEWEB)

    Zong, Weikai; Fu, Jian-Ning; Niu, Jia-Shu; Zhu, Zonghong [Department of Astronomy, Beijing Normal University, Beijing 100875 (China); Charpinet, S.; Vauclair, G. [Université de Toulouse, UPS-OMP, IRAP, F-31400 Toulouse (France); Ashley, Michael C. B.; Lawrence, Jon S.; Luong-Van, Daniel [School of Physics, University of New South Wales, Sydney, NSW 2052 (Australia); Cui, Xiangqun; Gong, Xuefei [Nanjing Institute of Astronomical Optics and Technology, Nanjing 210042 (China); Feng, Longlong; Wang, Lifan; Yuan, Xiangyan; Zhu, Zhenxi [Purple Mountain Observatory, Chinese Academy of Sciences, Nanjing 210008 (China); Liu, Qiang; Wang, Lingzhi; Zhou, Xu [National Astronomical Observatories, Chinese Academy of Sciences, Beijing 100012 (China); Pennypacker, Carl R. [Center for Astrophysics, Lawrence Berkeley National Laboratory, Berkeley, CA (United States); York, Donald G., E-mail: jnfu@bnu.edu.cn [Department of Astronomy and Astrophysics and Enrico Fermi Institute, University of Chicago, Chicago, IL 60637 (United States)

    2015-02-01

    We report the discovery of low-amplitude oscillations in the star HD 92277 from long, continuous observations in the r and g bands using the CSTAR telescopes in Antarctica. A total of more than 1950 hours of high-quality light curves were used to categorize HD 92277 as a new member of the δ Scuti class. We have detected 21 (20 frequencies are independent and one is the linear combination) and 14 (13 frequencies are independent and one is the linear combination) pulsation frequencies in the r and g bands, respectively, indicating a multi-periodic pulsation behavior. The primary frequency f{sub 1} = 10.810 days{sup −1} corresponds to a period of 0.0925 days and is an l = 1 mode. We estimate a B − V index of 0.39 and derive an effective temperature of 6800 K for HD 92277. We conclude that long, continuous and uninterrupted time-series photometry can be performed from Dome A, Antarctica, and that this is especially valuable for asteroseismology where multi-color observations (often not available from space-based telescopes) assist with mode identification.

  2. Theoretical pulsation of metallic-line stars

    International Nuclear Information System (INIS)

    Cox, A.N.; King, D.S.; Hodson, S.W.

    1979-01-01

    The linear-theory radial-pulsation stability of low-helium delta Scuti variable models (1.0--2.5 Msun) has been investigated to see if metallicism and pulsation can occur simultaneously. Metallicism, which occurs in slowly rotating stars after the gravitational settling of He and the loss of the He II convection zone and its deep mixing for Y< or approx. =0.1, can then be established rapidly compared with the evolution time scale. Pulsation can still occur with driving due to the residual helium and the enhanced hydrogen. With the reduced helium giving no connection zone, the pulsation instability strip, whose blue and edges are estimated in this paoer, is about half as wide as with a normal helium abundance. Zero helium in the surface driving regions, however, produces blue edges so red that probably no instability strip exists at all. The red edge, predicted theoretically on the basis of the importance of convection in the outer zone, agrees well with the observational one. Cool, low-helium and metallic-line stars are then predicted to pulsate in a 200--500 K wide strip that is widest between the main-sequence luminosity of 5 Lsun and 15 Lsun. This strip reasonably includes the observed pulsating delta Del and mild Am stars, but there may be conflicts. Since blue edges for varying ionization-zone helium content occur across the entire instability strip, bluer first and higher overtone pulsations are also predicted everywhere from less than 7000 K to over 8000 K, the redder ones probably showing metallicism

  3. Protoneutron star formation with delta-resonance matter and trapped neutrinos

    International Nuclear Information System (INIS)

    Oliveira, Jose Carlos Teixeira de; Souza, Ana Graice de; Duarte, Sergio Barbosa; Rodrigues, Hilario

    2009-01-01

    Full text: We discuss the proto-neutron star structure including delta-matter in its composition, and comparing the result with the same mass post-cooling compact object formed. The maximum mass values and corresponding configurations to pre and post-cooling situation are calculated and discussed face to variations in the coupling constants of delta-resonance with the mesons sigma, omega and rho in the context of the Relativistic Mean Field Theory (RMFT). The complete spin-1/2 sector is included solved consistently with the presence of the 3/2-spin delta-resonance quartet. (author)

  4. Pulsations and period variations of the δ Scuti star AN Lyncis in a possible three-body system

    Science.gov (United States)

    Li, Gang; Fu, Jianning; Su, Jie; Fox-Machado, Lester; Michel, Raul; Guo, Zhen; Liu, Jinzhong; Feng, Guojie

    2018-01-01

    Observations for the δ Scuti star AN Lyn have been made between 2008 and 2016 with the 85-cm telescope at Xinglong station of National Astronomical Observatories of China, the 84-cm telescope at SPM Observatory of Mexico and the Nanshan One metre Wide field Telescope of Xinjiang Observatory of China. Data in V in 50 nights and in R in 34 nights are obtained in total. The bi-site observations from both Xinglong Station and SPM Observatory in 2014 are analysed with Fourier Decomposition to detect pulsation frequencies. Two independent frequencies are resolved, including one non-radial mode. A number of stellar model tracks are constructed with the MESA code and the fit of frequencies leads to the best-fitting model with the stellar mass of M = 1.70 ± 0.05 M⊙, the metallicity abundance of Z = 0.020 ± 0.001, the age of 1.33 ± 0.01 billion years and the period change rate 1/P · dP/dt = 1.06 × 10-9 yr-1, locating the star at the evolutionary stage close to the terminal age main sequence. The O-C diagram provides the period change rate of (1/P)(dP/dt) = 4.5(8) × 10-7 yr-1. However, the period change rate calculated from the models is smaller in two orders than the one derived from the O-C diagram. Together with the sinusoidal function signature, the period variations are regarded to be dominated by the light-travel time effect of the orbital motion of a three-body system with two low-luminosity components, rather than the stellar evolutionary effect.

  5. Hyperon-meson and delta-meson coupling to protoneutron stars structure using the nonlinear Walecka model

    International Nuclear Information System (INIS)

    Souto, W A; Oliveira, J C T; Rodrigues, H; Duarte, S B; Chiapparini, M

    2015-01-01

    In this work we determine the equation of state and the population of baryons and leptons and discuss the effects of the hyperon-meson coupling constants to the formation of delta resonances in the stellar medium. We also discuss the structure of the protoneutron stars including the delta matter in their composition, and compared the results of a cooled neutron star, after escape of neutrinos. For protoneutron stars structure and composition, the neutrinos are considered trapped. (paper)

  6. Real And Reactive Power Saving In Three Phase Induction Machine Using Star-Delta Switching Schemes

    Directory of Open Access Journals (Sweden)

    Ramesh Daravath

    2017-04-01

    Full Text Available Induction machines are the most commonly used industrial drives for variety of applications. It has been estimated that induction motors consumes approximately 50 of all the electric energy generated. Further in the area of renewable energy sources such as wind or bio-mass energy induction machines have been found suitable for functioning as generators. In this context it may be mentioned that a star-delta switching is common for the starting of three-phase induction motor. Now it is proposed to use this star-delta switching for energy conservation of induction machines i.e. at times of reduced loads the machine switched back to star connection. Using a three-phase 400 V 50 Hz 4-pole induction machine it has been demonstrated that the star-delta switching of stator winding of three-phase induction machine motor generator operations reconnected in star at suitable reduced loads with a switching arrangement can result in improved efficiency and power factor as compared to a fixed delta or star connection. The predetermined values along with the experimental results have also been presented in this report. A simulation program has been developed for the predetermination of performance of the three-phase induction machine using exact equivalent circuit. A case study on a 250 kW 400 V 4-pole three-phase induction machine operated with different load cycles reveals the significant real and reactive power savings that could be obtained in the present proposal.

  7. Eclipsing binary stars with a δ Scuti component

    Science.gov (United States)

    Kahraman Aliçavuş, F.; Soydugan, E.; Smalley, B.; Kubát, J.

    2017-09-01

    Eclipsing binaries with a δ Sct component are powerful tools to derive the fundamental parameters and probe the internal structure of stars. In this study, spectral analysis of six primary δ Sct components in eclipsing binaries has been performed. Values of Teff, v sin I, and metallicity for the stars have been derived from medium-resolution spectroscopy. Additionally, a revised list of δ Sct stars in eclipsing binaries is presented. In this list, we have only given the δ Sct stars in eclipsing binaries to show the effects of the secondary components and tidal-locking on the pulsations of primary δ Sct components. The stellar pulsation, atmospheric and fundamental parameters (e.g. mass, radius) of 92 δ Sct stars in eclipsing binaries have been gathered. Comparison of the properties of single and eclipsing binary member δ Sct stars has been made. We find that single δ Sct stars pulsate in longer periods and with higher amplitudes than the primary δ Sct components in eclipsing binaries. The v sin I of δ Sct components is found to be significantly lower than that of single δ Sct stars. Relationships between the pulsation periods, amplitudes and stellar parameters in our list have been examined. Significant correlations between the pulsation periods and the orbital periods, Teff, log g, radius, mass ratio, v sin I and the filling factor have been found.

  8. Linear nonradial pulsation theory. Lecture 7

    International Nuclear Information System (INIS)

    Cox, A.N.

    1983-01-01

    Many of the upper main-sequence stars pulsate in spheroidal nonradial modes. We know this to be true in numerous cases, as we have tabulated for the #betta# Cephei and delta Scuti variables in previous lectures. However, we cannot identify the actual mode for any star except for the low-order pressure p and f modes of our sun. It remains a great challenge to clearly state what really is occurring, in the process we learn more about how stars evolve and pulsate

  9. Period--luminosity--color relations and pulsation modes of pulsating variable stars

    International Nuclear Information System (INIS)

    Breger, M.; Bregman, J.N.

    1975-01-01

    The periods of delta Scuti, RR Lyrae, dwarf Cepheid, and W Virginis variables have been investigated for their dependence on luminosity, color, mass, and pulsation modes. A maximum-likelihood method, which includes consideration of the observational errors in each coordinate, has been applied to obtain observational period-luminosity-color (P-L-C) relations

  10. Results of a search for γ Dor and δ SCT stars with the Kepler spacecraft

    Energy Technology Data Exchange (ETDEWEB)

    Bradley, P. A.; Miles, L. F. [XCP-6, MS F-699 Los Alamos National Laboratory, Los Alamos, NM 87545 (United States); Guzik, J. A. [XTD-NTA, MS T-086 Los Alamos National Laboratory, Los Alamos, NM 87545 (United States); Uytterhoeven, K. [Instituto de Astrofisica de Canarias, 38200 La Laguna, Tenerife, Spain and Departamento de Astrofisica, Universidad de La Laguna, E-38200 La Laguna, Tenerife (Spain); Jackiewicz, J. [New Mexico State University, Las Cruces, NM 88003 (United States); Kinemuchi, K., E-mail: pbradley@lanl.gov [Apache Point Observatory, Sunspot, NM 88349 (United States)

    2015-02-01

    The light curves of 2768 stars with effective temperatures and surface gravities placing them near the gamma Doradus (γ Dor)/delta Scuti (δ Sct) instability region were observed as part of the Kepler Guest Observer program from Cycles 1 through 5. The light curves were analyzed in a uniform manner to search for γ Dor, δ Sct, and hybrid star pulsations. The γ Dor, δ Sct, and hybrid star pulsations extend asteroseismology to stars slightly more massive (1.4–2.5 M{sub ⊙}) than our Sun. We find 207 γ Dor, 84 δ Sct, and 32 hybrid candidate stars. Many of these stars are cooler than the red edge of the γ Dor instability strip as determined from ground-based observations made before Kepler. A few of our γ Dor candidate stars lie on the hot side of the ground-based γ Dor instability strip. The hybrid candidate stars cover the entire region between 6200 K and the blue edge of the ground-based δ Sct instability strip. None of our candidate stars are hotter than the hot edge of the ground-based δ Sct instability strip. Our discoveries, coupled with the work of others, show that Kepler has discovered over 2000 γ Dor, δ Sct, and hybrid star candidates in the 116 square degree Kepler field of view. We found relatively few variable stars fainter than magnitude 15, which may be because they are far enough away to lie between spiral arms in our Galaxy, where there would be fewer stars.

  11. Results of a search for γ Dor and δ SCT stars with the Kepler spacecraft

    International Nuclear Information System (INIS)

    Bradley, P. A.; Miles, L. F.; Guzik, J. A.; Uytterhoeven, K.; Jackiewicz, J.; Kinemuchi, K.

    2015-01-01

    The light curves of 2768 stars with effective temperatures and surface gravities placing them near the gamma Doradus (γ Dor)/delta Scuti (δ Sct) instability region were observed as part of the Kepler Guest Observer program from Cycles 1 through 5. The light curves were analyzed in a uniform manner to search for γ Dor, δ Sct, and hybrid star pulsations. The γ Dor, δ Sct, and hybrid star pulsations extend asteroseismology to stars slightly more massive (1.4–2.5 M ⊙ ) than our Sun. We find 207 γ Dor, 84 δ Sct, and 32 hybrid candidate stars. Many of these stars are cooler than the red edge of the γ Dor instability strip as determined from ground-based observations made before Kepler. A few of our γ Dor candidate stars lie on the hot side of the ground-based γ Dor instability strip. The hybrid candidate stars cover the entire region between 6200 K and the blue edge of the ground-based δ Sct instability strip. None of our candidate stars are hotter than the hot edge of the ground-based δ Sct instability strip. Our discoveries, coupled with the work of others, show that Kepler has discovered over 2000 γ Dor, δ Sct, and hybrid star candidates in the 116 square degree Kepler field of view. We found relatively few variable stars fainter than magnitude 15, which may be because they are far enough away to lie between spiral arms in our Galaxy, where there would be fewer stars.

  12. Metal-rich RRc Stars in the Carnegie RR Lyrae Survey

    Science.gov (United States)

    Sneden, Christopher; Preston, George W.; Kollmeier, Juna A.; Crane, Jeffrey D.; Morrell, Nidia; Prieto, José L.; Shectman, Stephen A.; Skowron, Dorota M.; Thompson, Ian B.

    2018-01-01

    We describe and employ a stacking procedure to investigate abundances derived from the low signal-to-noise ratio spectra obtained in the Carnegie RR Lyrae Survey (CARRS). We find iron metallicities that extend from [Fe/H] ∼ ‑2.5 to values at least as large as [Fe/H] ∼ ‑0.5 in the 274-spectrum CARRS RRc data set. We consider RRc sample contamination by high amplitude solar metallicity δ Scuti stars (HADS) at periods less than 0.3 days, where photometric discrimination between RRc and δ Scuti stars has proven to be problematic. We offer a spectroscopic discriminant, the well-marked overabundance of heavy elements, principally [Ba/H], that is a common, if not universal, characteristic of HADS of all periods and axial rotations. No bona fide RRc stars known to us have verified heavy-element overabundances. Three out of 34 stars in our sample with [Fe/H] > ‑0.7 exhibit anomalously strong features of Sr, Y, Zr, Ba, and many rare earths. However, carbon is not enhanced in these three stars, and we conclude that their elevated n-capture abundances have not been generated in interior neutron-capture nucleosynthesis. Contamination by HADS appears to be unimportant, and metal-rich RRc stars occur in approximately the same proportion in the Galactic field as do metal-rich RRab stars. An apparent dearth of metal-rich RRc is probably a statistical fluke. Finally, we show that RRc stars have a similar inverse period–metallicity relationship as has been found for RRab stars.

  13. New Variable Stars Discovered by Data Mining Images Taken during Recent Asteroid Photometric Observations. II. Results from July 2015 through December 2016

    Science.gov (United States)

    Papini, R.; Marchini, A.; Salvaggio, F.; Agnetti, D.; Bacci, P.; Banfi, M.; Bianciardi, G.; Collina, M.; Franco, L.; Galli, G.; Milani, M. G. A.; Lopresti, C.; Marino, G.; Rizzuti, L.; Ruocco, N.; Quadri, U.

    2017-12-01

    This paper follows the previous publication of new variables discovered at Astronomical Observatory, DSFTA, University of Siena, while observing asteroids in order to determine their rotational periods. Usually, this task requires time series images acquisition on a single field for as long as possible on a few nights not necessarily consecutive. Checking continually this "goldmine" allowed us to discover 57 variable stars not yet listed in catalogues or databases. While most of the new variables are eclipsing binaries, a few belong to the RR Lyrae or delta Scuti class. Since asteroid work is definitely a time-consuming activity, coordinated campaigns of follow-up with other observatories have been fundamental in order to determine the elements of the ephemeris and sometimes the right subclass of variability. Further observations of these new variables are therefore strongly encouraged in order to better characterize these stars, especially pulsating ones whose data combined with those taken during professional surveys seem to suggest the presence of light curve amplitude and period variations.

  14. Semi-empirical seismic relations of A-F stars from COROT and Kepler legacy data

    Science.gov (United States)

    Moya, A.; Suárez, J. C.; García Hernández, A.; Mendoza, M. A.

    2017-10-01

    Asteroseismology is witnessing a revolution, thanks to high-precise asteroseismic space data (MOST, COROT, Kepler, BRITE) and their large ground-based follow-up programs. Those instruments have provided an unprecedented large amount of information, which allows us to scrutinize its statistical properties in the quest for hidden relations among pulsational and/or physical observables. This approach might be particularly useful for stars whose pulsation content is difficult to interpret. This is the case of intermediate-mass classical pulsating stars (I.e. γ Dor, δ Scuti, hybrids) for which current theories do not properly predict the observed oscillation spectra. Here, we establish a first step in finding such hidden relations from data mining techniques for these stars. We searched for those hidden relations in a sample of δ Scuti and hybrid stars observed by COROT and Kepler (74 and 153, respectively). No significant correlations between pairs of observables were found. However, two statistically significant correlations emerged from multivariable correlations in the observed seismic data, which describe the total number of observed frequencies and the largest one, respectively. Moreover, three different sets of stars were found to cluster according to their frequency density distribution. Such sets are in apparent agreement with the asteroseismic properties commonly accepted for A-F pulsating stars.

  15. Investigation of the binary fraction among candidate A-F type hybrid stars detected by Kepler

    Directory of Open Access Journals (Sweden)

    Lampens P.

    2015-01-01

    Full Text Available We are currently monitoring up to 40 Kepler candidate δ Scuti-γ Doradus (resp. γ Doradus-δ Scuti hybrid stars in radial velocity in order to identify the physical cause behind the low frequencies observed in the periodograms based on the ultra-high accuracy Kepler space photometry. The presence of low frequency variability in unevolved or slightly evolved oscillating A/F-type stars can generally be explained in three ways: either 1 the star is an (undetected binary or multiple system, or 2 the star is a g-mode pulsator (i.e. a genuine hybrid, or 3 the star’s atmosphere displays an asymmetric intensity distribution (caused by spots, i.e. chemical anomalies, or by (very high rotation, which is detected through rotational modulation. Our targets were selected from the globally characterized variable A/F-type stars of the Kepler mission [7]. We observe each star at least 4 times unevenly spread over a time lapse up to 2 months with the HERMES spectrograph [6]. In the case of composite, multiple-lined spectra, these observations also provide the atmospheric properties of each component. Our principal goal is to estimate the fraction of short-period, spectroscopic systems in the sample.

  16. HYBRID γ DORADUS-δ SCUTI PULSATORS: NEW INSIGHTS INTO THE PHYSICS OF THE OSCILLATIONS FROM KEPLER OBSERVATIONS

    International Nuclear Information System (INIS)

    Grigahcene, A.; Monteiro, M. J. P. F. G.; Antoci, V.; Handler, G.; Houdek, G.; Balona, L.; Catanzaro, G.; Daszynska-Daszkiewicz, J.; Guzik, J. A.; Kurtz, D. W.; Marconi, M.; Ripepi, V.; Moya, A.; Suarez, J.-C.; Uytterhoeven, K.; Borucki, W. J.; Brown, T. M.; Christensen-Dalsgaard, J.; Gilliland, R. L.; Jenkins, J. M.

    2010-01-01

    Observations of the pulsations of stars can be used to infer their interior structure and test theoretical models. The main-sequence γ Doradus (Dor) and δ Scuti (Sct) stars with masses 1.2-2.5 M sun are particularly useful for these studies. The γ Dor stars pulsate in high-order g-modes with periods of order 1 day, driven by convective blocking at the base of their envelope convection zone. The δ Sct stars pulsate in low-order g- and p-modes with periods of order 2 hr, driven by the κ mechanism operating in the He II ionization zone. Theory predicts an overlap region in the Hertzsprung-Russell diagram between instability regions, where 'hybrid' stars pulsating in both types of modes should exist. The two types of modes with properties governed by different portions of the stellar interior provide complementary model constraints. Among the known γ Dor and δ Sct stars, only four have been confirmed as hybrids. Now, analysis of combined Quarter 0 and Quarter 1 Kepler data for hundreds of variable stars shows that the frequency spectra are so rich that there are practically no pure δ Sct or γ Dor pulsators, i.e., essentially all of the stars show frequencies in both the δ Sct and the γ Dor frequency range. A new observational classification scheme is proposed that takes into account the amplitude as well as the frequency and is applied to categorize 234 stars as δ Sct, γ Dor, δ Sct/γ Dor or γ Dor/δ Sct hybrids.

  17. Possibilities of saving energy by using intelligent star-delta switches; Energiesparmoeglichkeiten mit intelligenten Stern-Dreieckschaltern

    Energy Technology Data Exchange (ETDEWEB)

    Gloor, R.

    2006-07-01

    This final report published by the Swiss Federal Office of Energy (SFOE) presents the results of a study made on so-called intelligent switches that switch an induction motor automatically into star configuration when at low load and, when higher loading returns, back again into the delta configuration. The results of theoretical calculations and measurements made in practice are discussed. The results are presented for various application areas including hydraulics, dynamic converters and standard applications. Also, the use of switches in applications such as wood-cutters, transport systems and stone-crushers are looked at. The results are discussed and the possible risks involved in the use of star-delta switches are looked at. Conclusions are drawn on their use from the economical point of view.

  18. GSC4813-0981 = V921 Mon, a new low-amplitude δ Scuti star with variable amplitude

    Science.gov (United States)

    Galeev, A.; Bikmaev, I.; Shimansky, V.; Deminova, N.

    2014-11-01

    GSC 4813-0981 = V921 Mon is a low-amplitude δ Scuti-type variable with an amplitude of 0.018^m-0.027^m in different bands and a period of 48.5 minutes. The fundamental parameters of the atmosphere and physical characteristics, determined from medium-resolution spectra, are: T_{eff}=8700 K, log g=3.95 dex, [M/H]=0, M=1.7 M_{⊙}, R=2.3 R_{⊙}. We performed a long-term analysis of the variations using a ten-year data set of CCD observations (2003-2013) acquired in BVR with the 1.5-m Russian-Turkish telescope (RTT150, TUBITAK National Observatory). A preliminary result is that the amplitude of the variability changes; it was decreasing during 2003-2008, but is now increasing.

  19. Variable Stars in Large Magellanic Cloud Globular Clusters. II. NGC 1786

    Science.gov (United States)

    Kuehn, Charles A.; Smith, Horace A.; Catelan, Márcio; Pritzl, Barton J.; De Lee, Nathan; Borissova, Jura

    2012-12-01

    This is the second in a series of papers studying the variable stars in Large Magellanic Cloud globular clusters. The primary goal of this series is to study how RR Lyrae stars in Oosterhoff-intermediate systems compare to their counterparts in Oosterhoff I/II systems. In this paper, we present the results of our new time-series B-V photometric study of the globular cluster NGC 1786. A total of 65 variable stars were identified in our field of view. These variables include 53 RR Lyraes (27 RRab, 18 RRc, and 8 RRd), 3 classical Cepheids, 1 Type II Cepheid, 1 Anomalous Cepheid, 2 eclipsing binaries, 3 Delta Scuti/SX Phoenicis variables, and 2 variables of undetermined type. Photometric parameters for these variables are presented. We present physical properties for some of the RR Lyrae stars, derived from Fourier analysis of their light curves. We discuss several different indicators of Oosterhoff type which indicate that the Oosterhoff classification of NGC 1786 is not as clear cut as what is seen in most globular clusters. Based on observations taken with the SMARTS 1.3 m telescope operated by the SMARTS Consortium and observations taken at the Southern Astrophysical Research (SOAR) telescope, which is a joint project of the Ministério da Ciência, Tecnologia, e Inovação (MCTI) da República Federativa do Brasil, the U.S. National Optical Astronomy Observatory (NOAO), the University of North Carolina at Chapel Hill (UNC), and Michigan State University (MSU).

  20. Faint (and bright variable stars in the satellites of the Milky Way

    Directory of Open Access Journals (Sweden)

    Vivas A. Katherina

    2017-01-01

    Full Text Available I describe two ongoing projects related with variable stars in the satellites of the MilkyWay. In the first project, we are searching for dwarf Cepheid stars (a.k.a δ Scuti and/or SX Phe in some of the classical dwarf spheroidal galaxies. Our goal is to characterize the population of these variable stars under different environments (age, metallicity in order to study their use as standard candles in systems for which the metallicity is not necessarily known. In the second project we search for RR Lyrae stars in the new ultra-faint satellite galaxies that have been discovered around the Milky Way in recent years.

  1. The Nainital Cape Survey Project : A Search for Pulsation in Chemically Peculiar Stars

    Science.gov (United States)

    Chakradhari, Nand Kumar; Joshi, Santosh

    2018-04-01

    The Nainital-Cape Survey is a dedicated search programme initiated in 1999 in the coordination of astronomers from SAAO South Africa, ARIES Nainital and ISRO Bangalore. Over the last 17 years a total of 345 chemically peculiar stars were monitored for photometric variability, making it one of the longest ground-based survey to search for pulsation in chemically peculiar stars in terms of both time span and sample size. Under this survey, we discovered rapid pulsation in the Ap star HD12098 while δ Scuti-type pulsations were detected in seven Am stars. Those stars in which pulsations were not detected have also been tabulated along with their detailed astrophysical parameters for further investigation.

  2. Tracing early stellar evolution with asteroseismology: pre-main sequence stars in NGC 2264

    Directory of Open Access Journals (Sweden)

    Zwintz Konstanze

    2015-01-01

    Full Text Available Asteroseismology has been proven to be a successful tool to unravel details of the internal structure for different types of stars in various stages of their main sequence and post-main sequence evolution. Recently, we found a relation between the detected pulsation properties in a sample of 34 pre-main sequence (pre-MS δ Scuti stars and the relative phase in their pre-MS evolution. With this we are able to demonstrate that asteroseismology is similarly powerful if applied to stars in the earliest stages of evolution before the onset of hydrogen core burning.

  3. PEMANFAATAN RELAI TUNDA WAKTU DAN KONTAKTOR PADA PANEL HUBUNG BAGI (PHB UNTUK PRAKTEK PENGHASUTAN STARTING MOTOR STAR DELTA

    Directory of Open Access Journals (Sweden)

    I Gede Siden Sudaryana

    2015-07-01

    Full Text Available Tujuan dari pemanfaatan relai tunda watu selanjutnya disebut TDR (Time Delay Relay dan kontaktor adalah sebagai salah satu modul pembelajaran mahasiswa di Laboratorium Teknik Tenaga Listrik sebagai pendukung mata kuliah Panel Hubung Bagi (PHB. Selama ini pemahaman yang dimiliki mahasiswa mengenai sistem kerja TDR dan kontaktor belum maksimal, yang menyebabkan mahasiswa belum siap diterjunkan ke lapangan dunia industri, dikarenakan kurangnya modul praktek di Laboratorium. Berdasarkan hal tersebut perlu dirancang dan dibuat suatu alat berupa Modul Praktek sebagai media pembelajaran tentang pengoperasian TDR dan kontaktor. Modul Praktek ini disusun dalam bentuk modul pembelajaran yang berisi uraian materi, tentang operasi sistem kunci rangakaian Otomatisasi Lampu Taman, sistem Direct On Line (DOL, sistem Interlock hidup secara bergantian, Interlock hidup berurutan, Putar balik Motor, penghasutan/starting motor Star-Delta. Pada kesempatan ini akan dibahas tentang pemanfaatan TDR dan Kontaktor dimana komponen-komponen tersebut adalah sebagai rangkaian kontrol yang dipergunakan pada pengendali sistem penghasutan starting motor star-delta. Sistem hidup berurutan saat push button ON ditekan yaitu rangkaian kontaktor K1 dan K2 yang akan menghubungkan rangkaian motor star, sedang rangkaian kontaktor K1 dan K3 yang akan menghubungkan rangkaian motor menjadi delta. Operasi kontaktor K2 dan K3 bekerja secara berurutan/bergantian. Jika push button OFF ditekan maka semua kontaktor akan terputus. Sistem hidup bergantian menggunakan sistem Interlock dimana K2 dan K3 tidak boleh hidup bersamaan, dimana K3 akan mengalami penundaan waktu selama 5 detik setelah K2 bekerja, sedangkan kontaktor K1 tetap bekerja dengan sistem Direct On Line (DOL. Penundaan waktu bekerjanya kontaktor K3 setelah K2 terputus secara automatis, dengan menggunakan komponen TDR (Time Delay Relay. Hasilnya, dengan pemanfaatan TDR pada rangkaian star-delta mahasiswa lebih mengerti cara kerja

  4. The Kepler characterization of the variability among A- and F-type stars. I. General overview

    DEFF Research Database (Denmark)

    Uytterhoeven, K.; Moya, A.; Grigahcène, A.

    2011-01-01

    candidate A-F type stars, and observationally investigate the relation between γ Doradus (γ Dor), δ Scuti (δ Sct), and hybrid stars. Methods: We compile a database of physical parameters for the sample stars from the literature and new ground-based observations. We analyse the Kepler light curve of each...... no clear periodic variability. 23% of the stars (171 stars) are hybrid stars, which is a much higher fraction than what has been observed before. We characterize for the first time a large number of A-F type stars (475 stars) in terms of number of detected frequencies, frequency range, and typical...... constructed variables, "efficiency" and "energy", as a means to explore the relation between γ Dor and δ Sct stars. Conclusions: Our results suggest a revision of the current observational instability strips of δ Sct and γ Dor stars and imply an investigation of pulsation mechanisms to supplement the κ...

  5. MASCARA-1 b. A hot Jupiter transiting a bright mV = 8.3 A-star in a misaligned orbit

    Science.gov (United States)

    Talens, G. J. J.; Albrecht, S.; Spronck, J. F. P.; Lesage, A.-L.; Otten, G. P. P. L.; Stuik, R.; Van Eylen, V.; Van Winckel, H.; Pollacco, D.; McCormac, J.; Grundahl, F.; Fredslund Andersen, M.; Antoci, V.; Snellen, I. A. G.

    2017-10-01

    We report the discovery of MASCARA-1 b, which is the first exoplanet discovered with the Multi-site All-Sky CAmeRA (MASCARA). This exoplanet is a hot Jupiter orbiting a bright mV = 8.3, rapidly rotating (vsini⋆ > 100 km s-1) A8 star with a period of 2.148780 ± 8 × 10-6 days. The planet has a mass and radius of 3.7 ± 0.9 MJup and 1.5 ± 0.3 RJup, respectively. As with most hot Jupiters transiting early-type stars, we find a misalignment between the planet orbital axis and the stellar spin axis, which may be a signature of the formation and migration histories of this family of planets. MASCARA-1 b has a mean density of 1.5 ± 0.9 g cm-3 and an equilibrium temperature of 2570+50-30K, that is one of the highest temperatures known for a hot Jupiter to date. The system is reminiscent of WASP-33, but the host star lacks apparent delta-scuti variations, making the planet an ideal target for atmospheric characterization. We expect this to be the first of a series of hot Jupiters transiting bright early-type stars that will be discovered by MASCARA. Tables of the photometry and the reduced spectra as FITS files are only available at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/606/A73

  6. Double-mode pulsation

    International Nuclear Information System (INIS)

    Cox, A.N.

    1982-01-01

    Double mode pulsation is a very pervasive phenomenon in stars all over the Hertzsprung-Russell diagram. In order of increasing radius, examples are: ZZ Ceti stars, the sun, the delta Scuti stars, RR Lyrae variables, the β Cephei variables and those related to them, Cepheids, and maybe even the Mira stars. These many modes have been interpreted as both radial and nonradial modes, but in many cases the actual mode has not been clearly identified. Yellow giants seem to be the most simple pulsators with a large majority of the RR Lyrae variables and Cepheids showing only one pulsation period. We limit this review to those very few cases for classical Cepheids and RR Lyrae variables which display two modes. For these we know many facts about these stars, but the actual cause of the pulsation in two modes simultaneously remains unknown

  7. Variable stars in the field of open cluster NGC 2126

    International Nuclear Information System (INIS)

    Liu Shunfang; Wu Zhenyu; Zhang Xiaobin; Wu Jianghua; Ma Jun; Jiang Zhaoji; Chen Jiansheng; Zhou Xu

    2009-01-01

    We report the results of a time-series CCD photometric survey of variable stars in the field of open cluster NGC 2126. In about a one square degree field covering the cluster, a total of 21 variable candidates are detected during this survey, of which 16 are newly found. The periods, classifications and spectral types of 14 newly discovered variables are discussed, which consist of six eclipsing binary systems, three pulsating variable stars, three long period variables, one RS CVn star, and one W UMa or δ Scuti star. In addition, there are two variable candidates, the properties of which cannot be determined. By a method based on fitting observed spectral energy distributions of stars with theoretical ones, the membership probabilities and the fundamental parameters of this cluster are determined. As a result, five variables are probably members of NGC 2126. The fundamental parameters of this cluster are determined as: metallicity to be 0.008 Z o-dot , age log(t) = 8.95, distance modulus (m - M) 0 = 10.34 and reddening value E (B - V) = 0.55 mag.

  8. Regularities in frequency spacings of δ Scuti stars: the Kepler star KIC 9700322

    DEFF Research Database (Denmark)

    Breger, M.; Balona, L.; Lenz, P.

    2011-01-01

    In the faint star KIC 9700322 observed by the Kepler satellite, 76 frequencies with amplitudes from 14 to 29 000 ppm were detected. The two dominant frequencies at 9.79 and 12.57 d-1 (113.3 and 145.5 μHz), interpreted to be radial modes, are accompanied by a large number of combination frequencie...... with the Hobby-Eberly Telescope, which is a joint project of the University of Texas at Austin, the Pennsylvania State University, Stanford University, Ludwig-Maximilians-Universität München and Georg-August-Universität Göttingen....

  9. The Taiwanese-American occultation survey project stellar variability. III. Detection of 58 new variable stars

    Energy Technology Data Exchange (ETDEWEB)

    Ishioka, R.; Wang, S.-Y.; Zhang, Z.-W.; Lehner, M. J.; Cook, K. H.; King, S.-K.; Lee, T.; Marshall, S. L.; Schwamb, M. E.; Wang, J.-H.; Wen, C.-Y. [Institute of Astronomy and Astrophysics, Academia Sinica, 11F of Astronomy-Mathematics Building, National Taiwan University, No. 1, Sec. 4, Roosevelt Road, Taipei 10617, Taiwan (China); Alcock, C.; Protopapas, P. [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Axelrod, T. [Steward Observatory, 933 North Cherry Avenue, Room N204, Tucson, AZ 85721 (United States); Bianco, F. B. [Center for Cosmology and Particle Physics, New York University, 4 Washington Place, New York, NY 10003 (United States); Byun, Y.-I. [Department of Astronomy and University Observatory, Yonsei University, 134 Shinchon, Seoul 120-749 (Korea, Republic of); Chen, W. P.; Ngeow, C.-C. [Institute of Astronomy, National Central University, No. 300, Jhongda Road, Jhongli City, Taoyuan County 320, Taiwan (China); Kim, D.-W. [Max Planck Institute for Astronomy, Königstuhl 17, D-69117 Heidelberg (Germany); Rice, J. A., E-mail: ishioka@asiaa.sinica.edu.tw [Department of Statistics, University of California Berkeley, 367 Evans Hall, Berkeley, CA 94720 (United States)

    2014-04-01

    The Taiwanese-American Occultation Survey project is designed for the detection of stellar occultations by small-size Kuiper Belt Objects, and it has monitored selected fields along the ecliptic plane by using four telescopes with a 3 deg{sup 2} field of view on the sky since 2005. We have analyzed data accumulated during 2005-2012 to detect variable stars. Sixteen fields with observations of more than 100 epochs were examined. We recovered 85 variables among a total of 158 known variable stars in these 16 fields. Most of the unrecovered variables are located in the fields observed less frequently. We also detected 58 variable stars which are not listed in the International Variable Star Index of the American Association of Variable Star Observers. These variable stars are classified as 3 RR Lyrae, 4 Cepheid, 1 δ Scuti, 5 Mira, 15 semi-regular, and 27 eclipsing binaries based on the periodicity and the profile of the light curves.

  10. Identification and period investigation of pulsation variable star UY Camelopardalis, an RR Lyrae star in binary system

    Science.gov (United States)

    Li, Lin-Jia; Qian, Sheng-Bang; Voloshina, Irina; Metlov, Vladimir G.; Zhu, Li-Ying; Liao, Wen-Ping

    2018-06-01

    We present photometric measurements of the short period variable star UY Cam, which has been classified as a δ Scuti or c-type RR Lyrae (RRc) variable in different catalogs. Based on the analyses on Fourier coefficients and (NUV - V)0, we find that UY Cam is probably an RRc star. We obtain 58 new times of light maximum for UY Cam based on several sky surveys and our observations. Combining these with the times of light maximum in literature, a total of 154 times of light maximum are used to analyze the O - C diagram of UY Cam. The results show that the O - C pattern can be described by a downward parabolic component with a rate of -6.86 ± 0.47 × 10-11 d d-1, and a cyclic variation with a period of 65.7 ± 2.4 yr. We suppose these components are caused by the stellar evolution and the light travel time effect (LiTE) of a companion in elliptical orbit, respectively. By calculation, the minimum mass of the potential companion is about 0.17 M⊙, and its mass should be less than or equal to the pulsation primary star when the inclination i > 22.5°D. Therefore, the companion should be a low-mass star, like a late-type main-sequence star or a white dwarf. Due to the unique property of UY Cam, we suggest that more observations and studies on UY Cam and other RRc stars are needed to check the nature of these stars, including the pulsations and binarities.

  11. The High Angular Resolution Multiplicity of Massive Stars

    Science.gov (United States)

    2009-02-01

    binaries: visual – stars: early-type – stars: individual ( iota Ori, delta Ori, delta Sco) – techniques: interferometric Online-only material...STATEMENT Approved for public release; distribution unlimited 13. SUPPLEMENTARY NOTES 14. ABSTRACT 15. SUBJECT TERMS 16. SECURITY

  12. Variable Stars Observed in the Galactic Disk by AST3-1 from Dome A, Antarctica

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Lingzhi; Ma, Bin; Hu, Yi; Liu, Qiang; Shang, Zhaohui [Key Laboratory of Optical Astronomy, National Astronomical Observatories, Chinese Academy of Sciences, Beijing 100012 (China); Li, Gang; Fu, Jianning [Department of Astronomy, Beijing Normal University, Beijing, 100875 (China); Wang, Lifan; Cui, Xiangqun; Du, Fujia; Gong, Xuefei; Li, Xiaoyan; Li, Zhengyang; Yuan, Xiangyan; Zhou, Jilin [Chinese Center for Antarctic Astronomy, Nanjing 210008 (China); Ashley, Michael C. B. [School of Physics, University of New South Wales, NSW 2052 (Australia); Pennypacker, Carl R. [Center for Astrophysics, Lawrence Berkeley National Laboratory, Berkeley, CA (United States); York, Donald G., E-mail: wanglingzhi@bao.ac.cn [Department of Astronomy and Astrophysics and Enrico Fermi Institute, University of Chicago, Chicago, IL 60637 (United States)

    2017-03-01

    AST3-1 is the second-generation wide-field optical photometric telescope dedicated to time-domain astronomy at Dome A, Antarctica. Here, we present the results of an i -band images survey from AST3-1 toward one Galactic disk field. Based on time-series photometry of 92,583 stars, 560 variable stars were detected with i magnitude ≤16.5 mag during eight days of observations; 339 of these are previously unknown variables. We tentatively classify the 560 variables as 285 eclipsing binaries (EW, EB, and EA), 27 pulsating variable stars ( δ Scuti, γ Doradus, δ Cephei variable, and RR Lyrae stars), and 248 other types of variables (unclassified periodic, multiperiodic, and aperiodic variable stars). Of the eclipsing binaries, 34 show O’Connell effects. One of the aperiodic variables shows a plateau light curve and another variable shows a secondary maximum after peak brightness. We also detected a complex binary system with an RS CVn-like light-curve morphology; this object is being followed-up spectroscopically using the Gemini South telescope.

  13. EVIDENCE FOR GRANULATION IN EARLY A-TYPE STARS

    International Nuclear Information System (INIS)

    Kallinger, Thomas; Matthews, Jaymie M.

    2010-01-01

    Stars with spectral types earlier than about F0 on (or close) to the main sequence have long been believed to lack observable surface convection, although evolutionary models of A-type stars do predict very thin surface convective zones. We present evidence for granulation in two δ Scuti stars of spectral type A2: HD 174936 and HD 50844. Recent analyses of space-based CoRoT data revealed up to some 1000 frequencies in the photometry of these stars. The frequencies were interpreted as individual pulsation modes. If true, there must be large numbers of nonradial modes of very high degree l which should suffer cancellation effects in disk-integrated photometry (even of high space-based precision). The p-mode interpretation of all the frequencies in HD 174936 and HD 50844 depends on the assumption of white (frequency-independent) noise. Our independent analyses of the data provide an alternative explanation: most of the peaks in the Fourier spectra are the signature of non-white granulation background noise, and less than about 100 of the frequencies are actual stellar p-modes in each star. We find granulation timescales which are consistent with scaling relations that describe cooler stars with known surface convection. If the granulation interpretation is correct, the hundreds of low-amplitude Fourier peaks reported in recent studies are falsely interpreted as independent pulsation modes and a significantly lower number of frequencies are associated with pulsation, consistent with only modes of low degree.

  14. Binarity and Variable Stars in the Open Cluster NGC 2126

    Science.gov (United States)

    Chehlaeh, Nareemas; Mkrtichian, David; Kim, Seung-Lee; Lampens, Patricia; Komonjinda, Siramas; Kusakin, Anatoly; Glazunova, Ljudmila

    2018-04-01

    We present the results of an analysis of photometric time-series observations for NGC 2126 acquired at the Thai National Observatory (TNO) in Thailand and the Mount Lemmon Optical Astronomy Observatory (LOAO) in USA during the years 2004, 2013 and 2015. The main purpose is to search for new variable stars and to study the light curves of binary systems as well as the oscillation spectra of pulsating stars. NGC 2126 is an intermediate-age open cluster which has a population of stars inside the δ Scuti instability strip. Several variable stars are reported including three eclipsing binary stars, one of which is an eclipsing binary star with a pulsating component (V551 Aur). The Wilson-Devinney technique was used to analyze its light curves and to determine a new set of the system’s parameters. A frequency analysis of the eclipse-subtracted light curve was also performed. Eclipsing binaries which are members of open clusters are capable of delivering strong constraints on the cluster’s properties which are in turn useful for a pulsational analysis of their pulsating components. Therefore, high-resolution, high-quality spectra will be needed to derive accurate component radial velocities of the faint eclipsing binaries which are located in the field of NGC 2126. The new Devasthal Optical Telescope, suitably equipped, could in principle do this.

  15. DISCOVERY OF 14 NEW SLOWLY PULSATING B STARS IN THE OPEN CLUSTER NGC 7654

    International Nuclear Information System (INIS)

    Luo, Y. P.; Han, Z. W.; Zhang, X. B.; Deng, L. C.

    2012-01-01

    We carried out time-series BV CCD photometric observations of the open cluster NGC 7654 (Messier 52) to search for variable stars. Eighteen slowly pulsating B (SPB) stars have been detected, among which 14 candidates are newly discovered, three known ones are confirmed, and a previously found δ Scuti star is also identified as an SPB candidate. Twelve SPBs are probable cluster members based on membership analysis. This makes NGC 7654 the richest galactic open cluster in terms of SPB star content. It is also a new discovery that NGC 7654 hosts three γ Dor star candidates. We found that all these stars (18 SPB and 3 γ Dor stars) have periods longer than their corresponding fundamental radial mode. With such a big sample of g-mode pulsators in a single cluster, it is clear that multi-mode pulsation is more common in the upper part of the main sequence than in the lower part. All the stars span a narrow strip on the period-luminosity plane, which also includes the γ Dor stars at the low-luminosity extension. This result implies that there may be a single period-luminosity relation applicable to all g-mode main-sequence pulsators. As a by-product, three EA-type eclipsing binaries and an EW-type eclipsing binary are also discovered.

  16. Astrometric Observation of Delta Cepheus

    Science.gov (United States)

    Warren, Naomi; Wilson, Betsie; Estrada, Chris; Crisafi, Kim; King, Jackie; Jones, Stephany; Salam, Akash; Warren, Glenn; Collins, S. Jananne; Genet, Russell

    2012-04-01

    Members of a Cuesta College astronomy research seminar used a manually-controlled 10-inch Newtonian Reflector telescope to determine the separation and position angle of the binary star Delta Cepheus. It was observed on the night of Saturday, October 29, 2011, at Star Hill in Santa Margarita, California. Their values of 40.2 arc seconds and 192.4 degrees were similar to those reported in the WDS (1910).

  17. A radio-pulsing white dwarf binary star.

    Science.gov (United States)

    Marsh, T R; Gänsicke, B T; Hümmerich, S; Hambsch, F-J; Bernhard, K; Lloyd, C; Breedt, E; Stanway, E R; Steeghs, D T; Parsons, S G; Toloza, O; Schreiber, M R; Jonker, P G; van Roestel, J; Kupfer, T; Pala, A F; Dhillon, V S; Hardy, L K; Littlefair, S P; Aungwerojwit, A; Arjyotha, S; Koester, D; Bochinski, J J; Haswell, C A; Frank, P; Wheatley, P J

    2016-09-15

    White dwarfs are compact stars, similar in size to Earth but approximately 200,000 times more massive. Isolated white dwarfs emit most of their power from ultraviolet to near-infrared wavelengths, but when in close orbits with less dense stars, white dwarfs can strip material from their companions and the resulting mass transfer can generate atomic line and X-ray emission, as well as near- and mid-infrared radiation if the white dwarf is magnetic. However, even in binaries, white dwarfs are rarely detected at far-infrared or radio frequencies. Here we report the discovery of a white dwarf/cool star binary that emits from X-ray to radio wavelengths. The star, AR Scorpii (henceforth AR Sco), was classified in the early 1970s as a δ-Scuti star, a common variety of periodic variable star. Our observations reveal instead a 3.56-hour period close binary, pulsing in brightness on a period of 1.97 minutes. The pulses are so intense that AR Sco's optical flux can increase by a factor of four within 30 seconds, and they are also detectable at radio frequencies. They reflect the spin of a magnetic white dwarf, which we find to be slowing down on a 10 7 -year timescale. The spin-down power is an order of magnitude larger than that seen in electromagnetic radiation, which, together with an absence of obvious signs of accretion, suggests that AR Sco is primarily spin-powered. Although the pulsations are driven by the white dwarf's spin, they mainly originate from the cool star. AR Sco's broadband spectrum is characteristic of synchrotron radiation, requiring relativistic electrons. These must either originate from near the white dwarf or be generated in situ at the M star through direct interaction with the white dwarf's magnetosphere.

  18. ISO-SWS spectrophotometry of galactic Wolf-Rayet stars: preliminary results.

    NARCIS (Netherlands)

    van der Hucht, K. A.; Morris, P. W.; Williams, P. M.; Setia Gunawan, D. Y. A.; Beintema, D. A.; Boxhoorn, D. R.; de Graauw, T.; Heras, A.; Kester, D. J. M.; Lahuis, F.; Leech, K. J.; Roelfsema, P. R.; Salama, A.; Valentijn, E. A.; Vandenbussche, B.

    1996-01-01

    ISO-SWS spectra of seven late-type galactic Wolf-Rayet stars are discussed. A high resolution spectrum (2.3-29.6μm, λ/{DELTA}λ=~820-1700) of the WC8 star WR11 (γ^2^ Vel) is shown and its Ne abundance is discussed. Medium resolution spectra (λ/{DELTA}λ=~250-600) of the WC8-9 stars WR48a, WR98a,

  19. Neutron stars in relativistic mean field theory with isovector scalar meson

    Energy Technology Data Exchange (ETDEWEB)

    Kubis, S.; Kutschera, M.; Stachniewicz, S. [H. Niewodniczanski Institute of Nuclear Physics, Cracow (Poland)

    1998-03-01

    We study the equation of state (EOS) of {beta}-stable dense matter and models of neutron stars in the relativistic mean field (RMF) theory with the isovector scalar mean field corresponding to the {delta}-meson (a{sub 0}(980)). A range of values of the {delta}-meson coupling compatible with the Bonn potentials is explored. Parameters of the model in the isovector sector are constrained to fit the nuclear symmetry energy, E{sub s}{approx}30 MeV. We find that the quantity most sensitive to the {delta}-meson coupling is the proton fraction of neutron star matter. It increases significantly in the presence of the {delta}-field. The energy per baryon also increases but the effect is smaller. The EOS becomes slightly stiffer and the maximum neutron star mass increases for stronger {delta}-meson coupling. (author) 8 refs, 6 figs, 2 tabs

  20. Further observations of the lambda 10830 He line in stars and their significance as a measure of stellar activity

    International Nuclear Information System (INIS)

    Zirin, H.

    1975-11-01

    Measurements of the lambda 10830 He line in 198 stars are given along with data on other features in that spectral range. Nearly 80% of all G and K stars show some lambda 10830; of these, half are variable and 1/4 show emission. It was confirmed that lambda 10830 is not found in M stars, is weak in F stars, and is particularly strong in close binaries. The line is found in emission in extremely late M and S stars, along with P gamma, but P gamma is not in emission in G and K stars with lambda 10830 emissions. Variable He emission and Ti I emission are found in the RV Tauri variables R Scuti and U Mon. In R Aqr the Fe XIII coronal line lambda 10747 and a line at lambda 11012, which may be singlet He or La II, are found, as well as lambda 10830 and P gamma. The nature of coronas or hot chromospheres in the various stars is discussed. It was concluded that the lambda 10830 intensity must be more or less proportional to the energy deposited in the chromosphere corona by non-thermal processes

  1. LASR-Guided Variability Subtraction: The Linear Algorithm for Significance Reduction of Stellar Seismic Activity

    Science.gov (United States)

    Horvath, Sarah; Myers, Sam; Ahlers, Johnathon; Barnes, Jason W.

    2017-10-01

    Stellar seismic activity produces variations in brightness that introduce oscillations into transit light curves, which can create challenges for traditional fitting models. These oscillations disrupt baseline stellar flux values and potentially mask transits. We develop a model that removes these oscillations from transit light curves by minimizing the significance of each oscillation in frequency space. By removing stellar variability, we prepare each light curve for traditional fitting techniques. We apply our model to $\\delta$-Scuti KOI-976 and demonstrate that our variability subtraction routine successfully allows for measuring bulk system characteristics using traditional light curve fitting. These results open a new window for characterizing bulk system parameters of planets orbiting seismically active stars.

  2. Neutron stars in relativistic mean field theory with isovector scalar meson

    Energy Technology Data Exchange (ETDEWEB)

    Kubis, S.; Kutschera, M.; Stachniewicz, S. [Institute of Nuclear Physics, Cracow (Poland)

    1996-12-01

    We study the equation of state (EOS) of neutron star matter in a relativistic mean field (RMF) theory with the isovector scalar mean field corresponding to the {delta}-meson [a{sub 0}(980)]. A range of values of the {delta}-meson coupling compatible with the Bonn potentials is explored. Parameters of the model in the isovector sector are constrained to fit the nuclear symmetry energy, E{sub s} {approx} 30 MeV. We find that proton fraction of neutron star matter is higher in the presence of the {delta}-field whereas the energy per particle is lower. The EOS becomes slightly stiffer and the maximum mass of the neutron star increased with increasing {delta}meson coupling. The effect is stronger for soft EOS. (author). 7 refs, 6 figs, 1 tab.

  3. Excitation of Stellar Pulsations

    DEFF Research Database (Denmark)

    Houdek, G.

    2012-01-01

    In this review I present an overview of our current understanding of the physical mechanisms that are responsible for the excitation of pulsations in stars with surface convection zones. These are typically cooler stars such as the δ Scuti stars, and stars supporting solar-like oscillations....

  4. Investigation of Υ Dor - δ Sct hybrid stars based on high precission space photometry and complementary ground based spectroscopy

    International Nuclear Information System (INIS)

    Hareter, M.

    2013-01-01

    Stellar pulsation carries information on the physical condition within the star. While pressure modes (p modes) probe the outer layers of a star, gravity modes (g modes) penetrate deep into the radiative zone and thus carry valuable information on the physical conditions there. gamma Dor stars are stars that pulsate in such modes, apart from white dwarfs and slowly pulsating B (SPB) stars. Therefore, these stars are important test benches for stellar evolution and pulsation theory. delta Sct - gamma Dor hybrids are stars that pulsate like gamma Dor stars with g modes but also with p modes as the delta Sct stars do. This makes them even more suited for asteroseismology. The CoRoT long runs offer a great opportunity to analyse a large sample of stars observed homogeneously, uninterrupted and long time base of about 150 days, which is practically unachievable with ground based observation. Since space missions avoid the scintillation caused by the Earth's atmosphere, they allow to detect stellar oscillations on a sub-millimagnitude level even for stars as faint as 15th magnitude. The photometric data is supplemented by AAOmega classification spectroscopy, allowing to determine effective tem- peratures and surface gravity. With these data a statistical approach was adopted to describe the pulsation behaviour gamma Dor and delta Sct - gamma Dor hybrid stars. A temperature - period relation was found for gamma Dor and delta Sct stars, but none for delta Sct - gamma Dor hybrid stars, when considering their strongest g mode or p mode, respectively. The instability domain of hybrid stars is equal to that of delta Sct stars and is not con- fined to the overlapping region of the delta Sct and gamma Dor IS in the Hertzsprung- Russell diagram. Hybrid stars behave differently in the g mode regime than gamma Dor stars, which poses a serious question on how to define properly a delta Sct - gamma Dor hybrid. The convective flux blocking mechanism is supposed to work for stars

  5. Kepler red-clump stars in the field and in open clusters

    DEFF Research Database (Denmark)

    Bossini, D.; Miglio, A.; Salaris, M.

    2017-01-01

    Convective mixing in helium-core-burning (HeCB) stars is one of the outstanding issues in stellar modelling. The precise asteroseismic measurements of gravity-mode period spacing (Delta Pi(1)) have opened the door to detailed studies of the near-core structure of such stars, which had not been...... possible before. Here, we provide stringent tests of various core-mixing scenarios against the largely unbiased population of red-clump stars belonging to the old-open clusters monitored by Kepler, and by coupling the updated precise inference on Delta Pi(1) in thousands of field stars with spectroscopic...... constraints. We find that models with moderate overshooting successfully reproduce the range observed of Delta Pi(1) in clusters. In particular, we show that there is no evidence for the need to extend the size of the adiabatically stratified core, at least at the beginning of the HeCB phase. This conclusion...

  6. The radii and masses of dwarf Cepheids

    International Nuclear Information System (INIS)

    Fernley, J.A.; Jameson, R.F.; Sherrington, M.R.; Skillen, I.

    1987-01-01

    The authors present VJK photometry for the dwarf Cepheids CY Aqr, YZ Boo and VZ Cnc, and a radial velocity curve for CY Aqr. Using these data, plus radial velocity curves taken from the literature, Wesselink-type radii, and hence absolute magnitudes and masses, are derived for the three stars. Using these results, plus previously published work, a mean 'pulsation' mass for dwarf Cepheids of 1.2 +-0.3M solar mass is determined. If dwarf Cepheids are early post-main-sequence stars this is less than their 'evolutionary' mass by the ratio Msub(puls)/Msub(evol)approx.0.75. Previously published data on period changes show an order of magnitude larger than predicted by early post-main-sequence evolutionary tracks. The possibility that these stars are at a more advanced evolutionary state is briefly discussed. The properties of fundamental and possible/probable overtone pulsators are compared. Finally attention is drawn to the small cycle-to-cycle variations in dwarf Cepheid light curves noted by many observers and the possible link between these variations and delta Scuti behaviour. (author)

  7. A NEW CENSUS OF THE VARIABLE STAR POPULATION IN THE GLOBULAR CLUSTER NGC 2419

    International Nuclear Information System (INIS)

    Di Criscienzo, M.; Greco, C.; Ripepi, V.; Dall' Ora, M.; Marconi, M.; Musella, I.; Clementini, G.; Federici, L.; Di Fabrizio, L.

    2011-01-01

    We present B, V, and I CCD light curves for 101 variable stars belonging to the globular cluster NGC 2419, 60 of which are new discoveries, based on data sets obtained at the Telescopio Nazionale Galileo, the Subaru telescope, and the Hubble Space Telescope. The sample includes 75 RR Lyrae stars (38 RRab, 36 RRc, and one RRd), one Population II Cepheid, 12 SX Phoenicis variables, two δ Scuti stars, three binary systems, five long-period variables, and three variables of uncertain classification. The pulsation properties of the RR Lyrae variables are close to those of Oosterhoff type II clusters, consistent with the low metal abundance and the cluster horizontal branch morphology, disfavoring (but not totally ruling out) an extragalactic hypothesis for the origin of NGC 2419. The observed properties of RR Lyrae and SX Phoenicis stars are used to estimate the cluster reddening and distance, using a number of different methods. Our final value is μ 0 (NGC 2419) = 19.71 ± 0.08 mag (D = 87.5 ± 3.3 kpc), with E(B - V) = 0.08 ± 0.01 mag, [Fe/H] = -2.1 dex on the Zinn and West metallicity scale, and a value of M V that sets μ 0 (LMC) = 18.52 mag. This value is in good agreement with the most recent literature estimates of the distance to NGC 2419.

  8. Fulltext PDF

    Indian Academy of Sciences (India)

    Asteroseismology ofγ Scuti Stars: Problems and Prospects (M.-J. Goupil, M. A. Dupret,. R. Samadi, T. Boehm, E. Alecian, J. C. Suarez, Y. Lebreton & C. Catala), 249. Pulsations in Subdwarf B Stars (C. Simon Jeffery), 261. Lessons for Asteroseismology from White Dwarf Stars (Travis S. Metcalfe), 273. On the Analysis of Light ...

  9. Constraints on stellar evolution from pulsations

    International Nuclear Information System (INIS)

    Cox, A.N.

    1984-01-01

    Consideration of the many types of intrinsic variable stars, that is, those that pulsate, reveals that perhaps a dozen classes can indicate some constraints that affect the results of stellar evolution calculations, or some interpretations of observations. Many of these constraints are not very strong or may not even be well defined yet. The author discusses the case for six classes: classical Cepheids with their measured Wesselink radii, the observed surface effective temperatures of the known eleven double-mode Cepheids, the pulsation periods and measured surface effective temperatures of three R CrB variables, the delta Scuti variable VZ Cnc with a very large ratio of its two observed periods, the nonradial oscillations of the Sun, and the period ratios of the newly discovered double-mode RR Lyrae variables. (Auth.)

  10. Student Observations of Double Star Delta Orionis (STFA 14 AC)

    Science.gov (United States)

    Estrada, Reed; Aguilera, Sophia; Bowden, Sam; Gillette, Travis; Givens, Jalynn; Reder, Gabriel; Rhoades, Breauna; Sharpe, Scott; Shattles, Jenna; Cha, Brendon; Do, Vicky; Ewing, Malachi; Kiamco, Alex Junior; Nelms, Brenda; Peña, Emilie; Maricarmen, Richard; Thielen, Austin

    2018-01-01

    A group of eight eighth graders and eight high schoolers studied the double star STFA 14 AC. They used the procedure from Argyle's book to get the separation and position angle for the double star. The students used a Celestron C8 Schmidt-Cassegrain telescope with a Baader Planetarium microguide eyepiece with similar markings to a Celestron Eyepiece. The students determined the separation to be 56 arcseconds and the position angle to be 4.19°. They compared their results to the Washington Double Star Catalog and found that they had a 2.88 arcseconds difference in separation and a 2.19° in position angle.

  11. The potential energy of an infinite system of nucleons and delta resonances

    International Nuclear Information System (INIS)

    Goodwin, N.H.

    1980-01-01

    The nature and properties of the delta resonance, Δ (1236), in infinite nuclear and neutron matter are investigated. Calculations of the potential energy of a system of separate Fermi seas of nucleons and delta resonances have been performed using Jastrow lowest-order constrained variational techniques. Using the Reid soft-core nucleon-nucleon interaction and a model, consistent, energy-dependent, static one-pion- and one-rho-meson-exchange nucleon-delta potential, a significant reduction in the potential energy of the system is found at densities above nuclear matter density (0.17 fm -3 ) when deltas are present. The density at which the formation of a separate Fermi sea of deltas is favourable is estimated and the consequences for the possible formation of a pion condensate and the properties of neutron star matter are discussed. (author)

  12. The Nainital–Cape Survey: A Search for Variability in Ap and Am ...

    Indian Academy of Sciences (India)

    Abstract. The “Nainital–Cape Survey” program for searching photo- metric variability in chemically peculiar (CP) stars was initiated in 1997 at ARIES, Nainital. We present here the results obtained to date. The Am stars HD 98851, HD 102480, HD 13079 and HD 113878 were discovered to exhibit δ Scuti type variability.

  13. Hot subluminous star: HDE 283048

    International Nuclear Information System (INIS)

    Laget, M.; Vuillemin, A.; Parsons, S.B.; Henize, K.G.; Wray, J.D.

    1978-01-01

    The star HDE 283048, located at α = 3/sup h/50/sup m/.3, delta = +25 0 36', shows a strong ultraviolet continuum. Ground-based observations indicate a hot-dominated composite spectrum. Several lines of evidence suggest that the hot component is a hot subdwarf. 2 figures

  14. Pulsating variables

    International Nuclear Information System (INIS)

    1989-01-01

    The study of stellar pulsations is a major route to the understanding of stellar structure and evolution. At the South African Astronomical Observatory (SAAO) the following stellar pulsation studies were undertaken: rapidly oscillating Ap stars; solar-like oscillations in stars; 8-Scuti type variability in a classical Am star; Beta Cephei variables; a pulsating white dwarf and its companion; RR Lyrae variables and galactic Cepheids. 4 figs

  15. Analisis espectroscopico de estrellas variables Delta Scuti

    Science.gov (United States)

    Solano Marquez, Enrique

    The rampant success of quantum theory is the result of applications of the 'new' quantum mechanics of Schrodinger and Heisenberg (1926-7), the Feynman-Schwinger-Tomonaga Quantum Electro-dynamics (1946-51), the electro-weak theory of Salaam, Weinberg, and Glashow (1967-9), and Quantum Chromodynamics (1973-); in fact, this success of 'the' quantum theory has depended on a continuous stream of brilliant and quite disparate mathematical formulations. In this carefully concealed ferment there lie plenty of unresolved difficulties, simply because in churning out fabulously accurate calculational tools there has been no sensible explanation of all that is going on. It is even argued that such an understanding is nothing to do with physics. A long-standing and famous illustration of this is the paradoxical thought-experiment of Einstein, Podolsky and Rosen (1935). Fundamental to all quantum theories, and also their paradoxes, is the location of sub-microscopic objects; or, rather, that the specification of such a location is fraught with mathematical inconsistency. This project encompasses a detailed, critical survey of the tangled history of Position within quantum theories. The first step is to show that, contrary to appearances, canonical quantum mechanics has only a vague notion of locality. After analysing a number of previous attempts at a 'relativistic quantum mechanics', two lines of thought are considered in detail. The first is the work of Wan and students, which is shown to be no real improvement on the iisu.al 'nonrelativistic' theory. The second is based on an idea of Dirac's - using backwards-in-time light-cones as the hypersurface in space-time. There remain considerable difficulties in the way of producing a consistent scheme here. To keep things nicely stirred up, the author then proposes his own approach - an adaptation of Feynman's QED propagators. This new approach is distinguished from Feynman's since the propagator or Green's function is not obtained by Feynman's rule. The type of equation solved is also different: instead of an initial-value problem, a solution that obeys a time-symmetric causality criterion is found for an inhomogeneous partial differential equation with homogeneous boundary conditions. To make the consideration of locality more precise, some results of Fourier transform theory are presented in a form that is directly applicable. Somewhat away from the main thrust of the thesis, there is also an attempt to explain, the manner in which quantum effects disappear as the number of particles increases in such things as experimental realisations of the EPR and de Broglie thought experiments.

  16. Two new pulsating low-mass pre-white dwarfs or SX Phoenicis stars?

    Science.gov (United States)

    Corti, M. A.; Kanaan, A.; Córsico, A. H.; Kepler, S. O.; Althaus, L. G.; Koester, D.; Sánchez Arias, J. P.

    2016-03-01

    Context. The discovery of pulsations in low-mass stars opens an opportunity to probe their interiors and determine their evolution by employing the tools of asteroseismology. Aims: We aim to analyse high-speed photometry of SDSS J145847.02+070754.46 and SDSS J173001.94+070600.25 and discover brightness variabilities. In order to locate these stars in the Teff - log g diagram, we fit optical spectra (SDSS) with synthetic non-magnetic spectra derived from model atmospheres. Methods: To carry out this study, we used the photometric data we obtained for these stars with the 2.15 m telescope at CASLEO, Argentina. We analysed their light curves and applied the discrete Fourier transform (FT) to determine the pulsation frequencies. Finally, we compare both stars in the Teff - log g diagram, with two known pre-white dwarfs and seven pulsating pre-ELM white dwarf stars, δ Scuti, and SX Phe stars Results: We report the discovery of pulsations in SDSS J145847.02+070754.46 and SDSS J173001.94+070600.25. We determine their effective temperature and surface gravity to be Teff = 7972 ± 200 K, log g = 4.25 ± 0.5 and Teff = 7925 ± 200 K, log g = 4.25 ± 0.5, respectively. With these parameters, these new pulsating low-mass stars can be identified with either ELM white dwarfs (with ~0.17 M⊙) or more massive SX Phe stars. We identified pulsation periods of 3278.7 and 1633.9 s for SDSS J145847.02+070754.46 and a pulsation period of 3367.1 s for SDSS J173001.94+070600.25. These two new objects, together with those of Maxted et al. (2013, 2014), indicate the possible existence of a new instability domain towards the late stages of evolution of low-mass white dwarf stars, although their identification with SX Phe stars cannot be discarded. Visiting Astronomer, Complejo Astronómico El Leoncito operated under agreement between the Consejo Nacional de Investigaciones Científicas y Técnicas de la República Argentina and the National Universities of La Plata, Córdoba, and San Juan.

  17. LOOKING FOR A CONNECTION BETWEEN THE Am PHENOMENON AND HYBRID {delta} Sct -{gamma} Dor PULSATION: DETERMINATION OF THE FUNDAMENTAL PARAMETERS AND ABUNDANCES OF HD 114839 AND BD +18 4914

    Energy Technology Data Exchange (ETDEWEB)

    Hareter, M.; Weiss, W. [Department of Astronomy, University of Vienna, Tuerkenschanzstrasse 17, A-1180 Wien (Austria); Fossati, L. [Department of Physics and Astronomy, Open University, Walton Hall, Milton Keynes MK6 7AA (United Kingdom); Suarez, J. C. [Instituto de Astrofisica de Andalucia (CSIC), Glorieta de la Astronomia S/N, 18008, Granada (Spain); Uytterhoeven, K. [Kiepenheuer-Institut fuer Sonnenphysik, Schoeneckstr. 6, D-79104 Freiburg (Germany); Rainer, M.; Poretti, E., E-mail: hareter@astro.univie.ac.at [INAF-Osservatorio Astronomico di Brera, Via E. Bianchi 46, 23807, Merate (Saint Lucia) (Italy)

    2011-12-20

    {delta} Sct-{gamma} Dor hybrids pulsate simultaneously in p- and g-modes, which carry information on the structure of the envelope as well as to the core. Hence, they are key objects for investigating A and F type stars with asteroseismic techniques. An important requirement for seismic modeling is small errors in temperature, gravity, and chemical composition. Furthermore, we want to investigate the existence of an abundance indicator typical for hybrids, something that is well established for the roAp stars. Previous to the present investigation, the abundance pattern of only one hybrid and another hybrid candidate has been published. We obtained high-resolution spectra of HD 114839 and BD +18 4914 using the SOPHIE spectrograph of the Observatoire de Haute-Provence and the HARPS spectrograph at ESO La Silla. For each star we determined fundamental parameters and photospheric abundances of 16 chemical elements by comparing synthetic spectra with the observations. We compare our results to that of seven {delta} Sct and nine {gamma} Dor stars. For the evolved BD +18 4914 we found an abundance pattern typical for an Am star, but could not confirm this peculiarity for the less evolved star HD 114839, which is classified in the literature as uncertain Am star. Our result supports the concept of evolved Am stars being unstable. With our investigation we nearly doubled the number of spectroscopically analyzed {delta} Sct-{gamma} Dor hybrid stars, but did not yet succeed in identifying a spectroscopic signature for this group of pulsating stars. A statistically significant spectroscopic investigation of {delta} Sct- {gamma} Dor hybrid stars is still missing, but would be rewarding considering the asteroseismological potential of this group.

  18. Delta-Connected Cascaded H-Bridge Multilevel Converters for Large-Scale Photovoltaic Grid Integration

    DEFF Research Database (Denmark)

    Yu, Yifan; Konstantinou, Georgios; Townsend, Christopher D.

    2017-01-01

    The cascaded H-bridge (CHB) converter is becoming a promising candidate for use in next generation large-scale photovoltaic (PV) power plants. However, solar power generation in the three converter phase-legs can be significantly unbalanced, especially in a large geographically-dispersed plant....... The power imbalance between the three phases defines a limit for the injection of balanced three-phase currents to the grid. This paper quantifies the performance of, and experimentally confirms, the recently proposed delta-connected CHB converter for PV applications as an alternative configuration...... for large-scale PV power plants. The required voltage and current overrating for the converter is analytically developed and compared against the star-connected counterpart. It is shown that the delta-connected CHB converter extends the balancing capabilities of the star-connected CHB and can accommodate...

  19. Ultraviolet spectrophotometry from Gemini 11 of stars in Orion

    International Nuclear Information System (INIS)

    Morgan, T.H.; Spear, G.G.; Kondo, Y.; Henize, K.G.

    1975-01-01

    Ultraviolet spectrophotometry in the wavelength region 2600--3600 A is reported for the bright early-type stars β, eta, γ, delta, iota, epsilon, sigma, xi, and kappa Ori. The results are in good agreement with other observations, and with the possible exception of the supergiants, are in good agreement with recent line-blanketed model atmospheres. There is evidence that the supergiants possess a small ultraviolet deficiency shortward of 3000 A relative to main-sequence stars of similar spectral type. The most extreme example of this phenomenon is the star kappa Ori

  20. The scenario of two families of compact stars. Pt. 1. Equations of state, mass-radius relations and binary systems

    Energy Technology Data Exchange (ETDEWEB)

    Drago, Alessandro; Pagliara, Giuseppe [Ferrara Univ. (Italy). Dipt. di Fisica e Scienze della Terra; INFN, Ferrara (Italy); Lavagno, Andrea; Pigato, Daniele [Politecnico di Torino (Italy). Dept. of Applied Science and Technology; INFN, Torino (Italy)

    2016-02-15

    We present several arguments which favor the scenario of two coexisting families of compact stars: hadronic stars and quark stars. Besides the well-known hyperon puzzle of the physics of compact stars, a similar puzzle exists also when considering delta resonances. We show that these particles appear at densities close to twice saturation density and must be therefore included in the calculations of the hadronic equation of state. Such an early appearance is strictly related to the value of the L parameter of the symmetry energy that has been found, in recent phenomenological studies, to lie in the range 40 < L < 62 MeV. We discuss also the threshold for the formation of deltas and hyperons for hot and lepton-rich hadronic matter. Similarly to the case of hyperons, also delta resonances cause a softening of the equation of state, which makes it difficult to obtain massive hadronic stars. Quark stars, on the other hand, can reach masses up to 2.75M {sub CircleDot} as predicted by perturbative QCD calculations. We then discuss the observational constraints on the masses and the radii of compact stars. The tension between the precise measurements of high masses and the indications of the existence of very compact stellar objects (with radii of the order of 10 km) is relieved when assuming that very massive compact stars are quark stars and very compact stars are hadronic stars. Finally, we discuss recent interesting measurements of the eccentricities of the orbits of millisecond pulsars in low mass X-ray binaries. The high values of the eccentricities found in some cases could be explained by assuming that the hadronic star, initially present in the binary system, converts to a quark star due to the increase of its central density. (orig.)

  1. Effect of mass loss on the chemical yields from massive stars

    Energy Technology Data Exchange (ETDEWEB)

    Chiosi, C; Caimmi, R [Padua Univ. (Italy). Istituto di Astronomia

    1979-01-01

    Recent results on the calculation of the chemical yields from massive stars, are rediscussed by taking into account the occurrence of mass loss by stellar wind during the core H- and He-burning phases. The new yields are found to be compatible with the observed distribution of chemical abundances in the solar system, except for He. The net enrichment of several elements over the galaxy's lifetime is found to be consistent with the current estimate of the star formation rate, if we adopt a two phase process of galaxy formation (halodisk). The relative He to heavy element enrichment rate ..delta..Y/..delta..Z turns out to agree with the observational value when mass loss by stellar wind is taken into account.

  2. The EB factory project. I. A fast, neural-net-based, general purpose light curve classifier optimized for eclipsing binaries

    International Nuclear Information System (INIS)

    Paegert, Martin; Stassun, Keivan G.; Burger, Dan M.

    2014-01-01

    We describe a new neural-net-based light curve classifier and provide it with documentation as a ready-to-use tool for the community. While optimized for identification and classification of eclipsing binary stars, the classifier is general purpose, and has been developed for speed in the context of upcoming massive surveys such as the Large Synoptic Survey Telescope. A challenge for classifiers in the context of neural-net training and massive data sets is to minimize the number of parameters required to describe each light curve. We show that a simple and fast geometric representation that encodes the overall light curve shape, together with a chi-square parameter to capture higher-order morphology information results in efficient yet robust light curve classification, especially for eclipsing binaries. Testing the classifier on the ASAS light curve database, we achieve a retrieval rate of 98% and a false-positive rate of 2% for eclipsing binaries. We achieve similarly high retrieval rates for most other periodic variable-star classes, including RR Lyrae, Mira, and delta Scuti. However, the classifier currently has difficulty discriminating between different sub-classes of eclipsing binaries, and suffers a relatively low (∼60%) retrieval rate for multi-mode delta Cepheid stars. We find that it is imperative to train the classifier's neural network with exemplars that include the full range of light curve quality to which the classifier will be expected to perform; the classifier performs well on noisy light curves only when trained with noisy exemplars. The classifier source code, ancillary programs, a trained neural net, and a guide for use, are provided.

  3. Polarization variablity among Wolf-Rayet stars. IV. A complete lack of circular polarization in the optical continuum

    International Nuclear Information System (INIS)

    Robert, C.; Moffat, A.F.J.

    1989-01-01

    Quasi-simultaneous blue and red, broadband optical monitoring in linear and circular polarization and in intensity has been carried out over an interval of three weeks for several Wolf-Rayet stars that show relatively large Delta P variations in linear polarization. No significant varying Delta V component of circular polarization is detected in any of these stars. The lower upper limit Delta V/Delta P implies that the intrinsic linearly polarized light which does vary cannot be produced by electrons gyrating in a magnetic field, unless they are ultrarelativistic - a rather unlikely situation. The low mean circular polarization typically observed is probably interstellar in origin. Lack of periodicity in the observed variations of linear polarization implies that even weak magnetic field loops are unlikely to be involved in confining pockets of wind plasma. The observed linear polarization variations are related mainly to electron scattering. 25 refs

  4. The incidence of chemically peculiar stars in open clusters

    Energy Technology Data Exchange (ETDEWEB)

    Netopil, M.

    2013-07-01

    The formation and evolution of chemically peculiar (CP) stars is still a matter of debate, although the first representatives were detected already more than 110 years ago. From the astrophysical point of view, these objects are of particular interest, since they combine a wide variety of specific properties. This work deals with a subgroup of CP stars, showing beside overabundances of some iron-peak (e.g. Chromium) and rare earth elements like Europium, also strong ordered magnetic fields as well as a slow rotation. Based on a selection of well investigated close field stars, the possible connections of these properties were examined. However, the main research focus was the analysis of a relationship between the number of CP stars and their age. For this purpose, the results of the extensive Delta-a survey in open clusters were used. This photometric filter system allows an efficient and economic detection of magnetic CP stars due to a characteristic flux depression at 520 nm. Compared to field stars, open clusters offer the big advantage that for example the age and the distance can be determined more accurately on a statistical basis, since all member stars of an open cluster originate more or less at the same time from a single molecular cloud. After the membership analysis of all in Delta a investigated objects and the determination of the cluster parameters, it was shown that the occurrence of CP stars depend on age, but can be explained by the general evolution of stars. This entails amongst others that CP stars show their typical characteristics already as soon as they have arrived the main-sequence, or even before. Furthermore, we were able to detect at least one representative, probably still in its pre-main-sequence phase. (author) [German] Die Entstehung und Entwicklung von chemisch pekuliaren (CP) Sternen ist nach wie vor nicht restlos geklärt, und das obwohl die ersten Vertreter dieser Sterngruppe bereits vor mehr als 110 Jahren entdeckt wurden. Aus

  5. Corrections to the Hipparcos Proper Motions in Declination for 807 Stars

    Directory of Open Access Journals (Sweden)

    Damljanović, G.

    2008-12-01

    Full Text Available We used the data on latitude variations obtained from observations with 10 classical photographic zenith tubes (PZT in order to improve the Hipparcos proper motions in declinations $mu_{delta} $ for 807 stars. Part of observing programmes, carried out during the last century for the purpose of studying the Earth's rotation, were realized by using PZT instruments. These observations were performed within in the intervals (tens of years much longer than that of the Hipparcos mission (less than 4 years. In addition, the annual number of observations for every PZT-programme star is several hundreds on the average. Though the accuracy of the star coordinates in the Hipparcos Catalogue is by two orders of magnitude better than that of the star coordinates from the PZT observations, the large number of observations performed a much longer time interval makes it possible to correct the Hipparcos proper motions and to improve their accuracy with respect to the accuracy given in the Hipparcos Catalogue. Long term examinations of latitude and time variations were used to form the Earth Orientation Catalogue (EOC-2, aimed at a more accurate determination of positions and proper motions for the stars included. Our method of calculating the corrections of the proper motions in declination from the latitude variations is different from the method used in obtaining the EOC-2 Catalogue. Comparing the results we have established a good agreement between our $mu_ {delta} $ and the EOC-2 ones for the star sample used in the present paper.

  6. Performance Comparison of Conventional Synchronous Reluctance Machines and PM-Assisted Types with Combined Star–Delta Winding

    Directory of Open Access Journals (Sweden)

    Mohamed Nabil Fathy Ibrahim

    2017-09-01

    Full Text Available This paper compares four prototype Synchronous Reluctance Motors (SynRMs having an identical geometry of iron lamination stacks in the stator and rotor. Two different stator winding layouts are employed: a conventional three-phase star connection and a combined star–delta winding. In addition, two rotors are considered: a conventional rotor without magnets and a rotor with ferrite magnets. The performance of the four SynRMs is evaluated using a two-dimensional (2D Finite Element Model (FEM. For the same copper volume and current, the combined star–delta-connected stator with Permanent Magnets (PMs in the rotor corresponds to an approximately 22% increase in the output torque at rated current and speed compared to the conventional machine. This improvement is mainly thanks to adding ferrite PMs in the rotor as well as to the improved winding factor of the combined star–delta winding. The torque gain increases up to 150% for low current. Moreover, the rated efficiency is 93.60% compared to 92.10% for the conventional machine. On the other hand, the impact on the power factor and losses of SynRM when using the star–delta windings instead of the star windings is merely negligible. The theoretical results are experimentally validated using four identical prototype machines with identical lamination stacks but different rotors and winding layouts.

  7. DELTAS: A new Global Delta Sustainability Initiative (Invited)

    Science.gov (United States)

    Foufoula-Georgiou, E.

    2013-12-01

    Deltas are economic and environmental hotspots, food baskets for many nations, home to a large part of the world population, and hosts of exceptional biodiversity and rich ecosystems. Deltas, being at the land-water interface, are international, regional, and local transport hubs, thus providing the basis for intense economic activities. Yet, deltas are deteriorating at an alarming rate as 'victims' of human actions (e.g. water and sediment reduction due to upstream basin development), climatic impacts (e.g. sea level rise and flooding from rivers and intense tropical storms), and local exploration (e.g. sand or aggregates, groundwater and hydrocarbon extraction). Although many efforts exist on individual deltas around the world, a comprehensive global delta sustainability initiative that promotes awareness, science integration, data and knowledge sharing, and development of decision support tools for an effective dialogue between scientists, managers and policy makers is lacking. Recently, the international scientific community proposed to establish the International Year of Deltas (IYD) to serve as the beginning of such a Global Delta Sustainability Initiative. The IYD was proposed as a year to: (1) increase awareness and attention to the value and vulnerability of deltas worldwide; (2) promote and enhance international and regional cooperation at the scientific, policy, and stakeholder level; and (3) serve as a launching pad for a 10-year committed effort to understand deltas as complex socio-ecological systems and ensure preparedness in protecting and restoring them in a rapidly changing environment. In this talk, the vision for such an international coordinated effort on delta sustainability will be presented as developed by a large number of international experts and recently funded through the Belmont Forum International Opportunities Fund. Participating countries include: U.S., France, Germany, U.K., India, Japan, Netherlands, Norway, Brazil, Bangladesh

  8. New variable stars discovered in the fields of three Galactic open clusters using the VVV survey

    Science.gov (United States)

    Palma, T.; Minniti, D.; Dékány, I.; Clariá, J. J.; Alonso-García, J.; Gramajo, L. V.; Ramírez Alegría, S.; Bonatto, C.

    2016-11-01

    This project is a massive near-infrared (NIR) search for variable stars in highly reddened and obscured open cluster (OC) fields projected on regions of the Galactic bulge and disk. The search is performed using photometric NIR data in the J-, H- and Ks- bands obtained from the Vista Variables in the Vía Láctea (VVV) Survey. We performed in each cluster field a variability search using Stetson's variability statistics to select the variable candidates. Later, those candidates were subjected to a frequency analysis using the Generalized Lomb-Scargle and the Phase Dispersion Minimization algorithms. The number of independent observations range between 63 and 73. The newly discovered variables in this study, 157 in total in three different known OCs, are classified based on their light curve shapes, periods, amplitudes and their location in the corresponding color-magnitude (J -Ks ,Ks) and color-color (H -Ks , J - H) diagrams. We found 5 possible Cepheid stars which, based on the period-luminosity relation, are very likely type II Cepheids located behind the bulge. Among the newly discovered variables, there are eclipsing binaries, δ Scuti, as well as background RR Lyrae stars. Using the new version of the Wilson & Devinney code as well as the "Physics Of Eclipsing Binaries" (PHOEBE) code, we analyzed some of the best eclipsing binaries we discovered. Our results show that these studied systems turn out to be ranging from detached to double-contact binaries, with low eccentricities and high inclinations of approximately 80°. Their surface temperatures range between 3500 K and 8000 K.

  9. Journal of Astrophysics and Astronomy | Indian Academy of Sciences

    Indian Academy of Sciences (India)

    2016-01-27

    Jan 27, 2016 ... We give an overview of past and present efforts to make seismology of Scuti and Doradus stars possible. Previous work has not led to the observational detection and identification of a sufficient number of pulsation modes for these pulsators for the construction of unique seismic models. However ...

  10. HDE 229189 - A variable Ae star in the field of NGC 6910

    International Nuclear Information System (INIS)

    Halbedel, E.M.

    1991-01-01

    The star HDE 229189 (BD + 40 4145; in the field, though probably not a member, of the open cluster NGC 6910) has been found to exhibit large photometric changes in V magnitude over relatively short time scales. The total observed range was 0.416 V magnitude. An outburst in 1982 showed an even greater V range (Delta V = 1.66) and concomitant color changes. A coude spectrum of the star taken a week before a minor outburst showed emission at H-alpha but no other unusual lines. The star is likely an A3 (V)e star, an unusual object in itself (since stars as late as A3 seldom show emission at H-α), or else possibly a member of a binary system undergoing mass transfer between the members. 19 refs

  11. Variability of X-ray emission from OB stars

    International Nuclear Information System (INIS)

    Collura, A.; Sciortino, S.; Serio, S.; Vaiana, G. S.; Harnden, F.R. JR.; Osservatorio Astronomico, Palermo, Italy; Harvard-Smithsonian Center for Astrophysics, Cambridge, MA)

    1989-01-01

    The variability in soft X-ray emission of 12 OB stars is studied. Two different methods of analysis, one more suitable for detecting short-term variations, the other aimed at detecting long time-scale variations, are applied to all stars in the sample. The long-term variability analysis shows that Cyg-OB2 8A Zeta Pup and Delta Ori exhibit significant count rate variations between different data sections. Similar variations are marginally detected in 15 Mon; the count rate variations for the other eight stars are consistent with statistical fluctuations. The light curve of Cyg-OB2 8A suggests the existence of two different emission levels. The short-term variability analysis detects marginal variability in Tau Sco with an effective amplitude of about 30 percent and a time scale of about 50 s. The upper limits to the effective short-term variability amplitude for all other sample stars are in the 10-30 percent range. 30 refs

  12. New bound on neutrino dipole moments from globular-cluster stars

    Science.gov (United States)

    Raffelt, Georg G.

    1990-01-01

    Neutrino dipole moments mu(nu) would increase the core mass of red giants at the helium flash by delta(Mc) = 0.015 solar mass x mu(nu)/10 to the -12th muB (where muB is the Bohr magneton) because of enhanced neutrino losses. Existing measurements of the bolometric magnitudes of the brightest red giants in 26 globular clusters, number counts of horizontal-branch stars and red giants in 15 globular clusters, and statistical parallax determinations of field RR Lyr luminosities yield delta(Mc) = 0.009 + or - 0.012 solar mass, so that conservatively mu(nu) is less than 3 x 10 to the -12th muB.

  13. Influence of different organic fertilizers on quality parameters and the delta(15)N, delta(13)C, delta(2)H, delta(34)S, and delta(18)O values of orange fruit (Citrus sinensis L. Osbeck).

    Science.gov (United States)

    Rapisarda, Paolo; Camin, Federica; Fabroni, Simona; Perini, Matteo; Torrisi, Biagio; Intrigliolo, Francesco

    2010-03-24

    To investigate the influence of different types of fertilizers on quality parameters, N-containing compounds, and the delta(15)N, delta(13)C, delta(2)H, delta (34)S, and delta(18)O values of citrus fruit, a study was performed on the orange fruit cv. 'Valencia late' (Citrus sinensis L. Osbeck), which was harvested in four plots (three organic and one conventional) located on the same farm. The results demonstrated that different types of organic fertilizers containing the same amount of nitrogen did not effect important changes in orange fruit quality parameters. The levels of total N and N-containing compounds such as synephrine in fruit juice were not statistically different among the different treatments. The delta(15)N values of orange fruit grown under fertilizer derived from animal origin as well as from vegetable compost were statistically higher than those grown with mineral fertilizer. Therefore, delta(15)N values can be used as an indicator of citrus fertilization management (organic or conventional), because even when applied organic fertilizers are of different origins, the natural abundance of (15)N in organic citrus fruit remains higher than in conventional ones. These treatments also did not effect differences in the delta(13)C, delta(2)H, delta(34)S, and delta(18)O values of fruit.

  14. Challenges, Approaches and Experiences from Asian Deltas and the Rhine-Meuse Delta : Regional Training Workshop on Delta Planning and Management

    NARCIS (Netherlands)

    Wosten, J.H.M.; Douven, W.; Long Phi, H.; Fida Abdullah Khan, M.

    2013-01-01

    River delta's, like the Mekong Delta (Vietnam), Ganges-Brahmaputra Delta (Bangladesh), Ayeyarwady Delta (Myanmar), Nile (Egypt) and Ciliwung Delta (Indonesia) are developing rapidly and are characterised by large-scale urbanisation and industrialization processes. They are facing serious planning

  15. Delta Plaza kohvik = Delta Plaza cafe

    Index Scriptorium Estoniae

    2010-01-01

    Tallinnas Pärnu mnt 141 asuva kohviku Delta Plaza sisekujundusest. Sisearhitektid Tiiu Truus ja Marja Viltrop (Stuudio Truus OÜ). Tiiu Truusi tähtsamate tööde loetelu. Büroohoone Delta Plaza arhitektid Marika Lõoke ja Jüri Okas (AB J. Okas & M. Lõoke)

  16. Growth laws for sub-delta crevasses in the Mississippi River Delta

    Science.gov (United States)

    Yocum, T. A.; Georgiou, I. Y.; Straub, K. M.

    2017-12-01

    River deltas are threatened by environmental change, including subsidence, global sea level rise, reduced sediment inputs and other local factors. In the Mississippi River Delta (MRD) these impacts are exemplified, and have led to proposed solutions to build land that include sediment diversions to reinitiate the delta cycle. Deltas were studied extensively using numerical models, theoretical and conceptual frameworks, empirical scaling relationships, laboratory models and field observations. But predicting the future of deltas relies on field observations where for most deltas data are still lacking. Moreover, empirical and theoretical scaling laws may be influenced by the data used to develop them, while laboratory deltas may be influenced by scaling issues. Anthropogenic crevasses in the MRD are large enough to overcome limitations of laboratory deltas, and small enough to allow for rapid channel and wetland development, providing an ideal setting to investigate delta development mechanics. Here we assessed growth laws of sub-delta crevasses (SDC) in the MRD, in two experimental laboratory deltas (LD - weakly and strongly cohesive) and compared them to river dominated deltas worldwide. Channel and delta geometry metrics for each system were obtained using geospatial tools, bathymetric datasets, sediment size, and hydrodynamic observations. Results show that SDC follow growth laws similar to large river dominated deltas, with the exception of some that exhibit anomalous behavior with respect to the frequency and distance to a bifurcation and the fraction of wetted delta shoreline (allometry metrics). Most SDC exhibit a systematic decrease of non-dimensional channel geometries with increased bifurcation order, indicating that channels are adjusting to decreased flow after bifurcations occur, and exhibit linear trends for land allometry and width-depth ratio, although geometries decrease more rapidly per bifurcation order. Measured distance to bifurcations in SDC

  17. The Open Cluster NGC 6811: An Eclipsing Binary, the Turnoff, and Age

    DEFF Research Database (Denmark)

    Sandquist, Eric L.; Jessen-Hansen, Jens; Shetrone, Matthew D.

    . The cluster's turnoff also falls completely within the instability strip, and the majority of the brightest main sequence stars have now been identified as δ Scuti pulsators. The eclipsing binary KIC 9777062/Sanders 195 is a cluster member slightly fainter than the turnoff, containing one star that falls...... stars to produce an improved age determination.We gratefully acknowledge support from the NSF to E.L.S. under grant AST-0908536 and for M.L. as part of the REU program at San Diego State University under grant AST-0850564, and from NASA under grants NNX12AC88G and NNX13AC19G....

  18. Deformation characteristics of {delta} phase in the delta-processed Inconel 718 alloy

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, H.Y., E-mail: haiyanzhang@imr.ac.cn [Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110016 (China); Zhang, S.H., E-mail: shzhang@imr.ac.cn [Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110016 (China); Cheng, M. [Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110016 (China); Li, Z.X. [Beijing Institute of Aeronautica1 Materials, Beijing 100095 (China)

    2010-01-15

    The hot working characteristics of {delta} phase in the delta-processed Inconel 718 alloy during isothermal compression deformation at temperature of 950 deg. C and strain rate of 0.005 s{sup -1}, were studied by using optical microscope, scanning electron microscope and quantitative X-ray diffraction technique. The results showed that the dissolution of plate-like {delta} phase and the precipitation of spherical {delta} phase particles coexisted during the deformation, and the content of {delta} phase decreased from 7.05 wt.% to 5.14 wt.%. As a result of deformation breakage and dissolution breakage, the plate-like {delta} phase was spheroidized and transferred to spherical {delta} phase particles. In the center with largest strain, the plate-like {delta} phase disappeared and spherical {delta} phase appeared in the interior of grains and grain boundaries.

  19. Delta antibody radioimmunoassay

    Energy Technology Data Exchange (ETDEWEB)

    Kselikova, M; Urbankova, J

    1985-11-15

    The principle and procedure are described of the radioimmunoassay of delta antibody (delta-Ab) using the ABBOTT ANTI-DELTA kit by Abbott Co. A description is given of the kit, the working procedure and the method of evaluation. The results are reported of the incidence of delta-Ab in sera of patients with viral hepatitis B, in haemophiliacs, carriers of the hepatitis B virus surface antigen (HBsAg) and blood donors. The presence was detected of delta-Ab in one HBsAg carrier. The necessity is emphasized of delta-Ab determinations in the blood of donors in view of the antibody transfer with blood and blood preparations.

  20. A novel mouse PKC{delta} splice variant, PKC{delta}IX, inhibits etoposide-induced apoptosis

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Jung D. [School of Biological Sciences, University of Ulsan, Ulsan (Korea, Republic of); Seo, Kwang W. [Department of Internal Medicines, Ulsan University Hospital and School of Medicine, University of Ulsan, Ulsan (Korea, Republic of); Lee, Eun A.; Quang, Nguyen N. [School of Biological Sciences, University of Ulsan, Ulsan (Korea, Republic of); Cho, Hong R. [Department of Surgery, Ulsan University Hospital and School of Medicine, University of Ulsan, Ulsan (Korea, Republic of); Biomedical Research Center, Ulsan University Hospital and School of Medicine, University of Ulsan, Ulsan (Korea, Republic of); Kwon, Byungsuk, E-mail: bskwon@mail.ulsan.as.kr [School of Biological Sciences, University of Ulsan, Ulsan (Korea, Republic of); Biomedical Research Center, Ulsan University Hospital and School of Medicine, University of Ulsan, Ulsan (Korea, Republic of)

    2011-07-01

    Highlights: {yields} A novel PKC{delta} isoform, named PKC{delta}IX, that lacks the C1 domain and the ATP-binding site is ubiquitously expressed. {yields} PKC{delta}IX inhibits etoposide-induced apoptosis. {yields} PKC{delta}IX may function as an endogenous dominant negative isoform for PKC{delta}. -- Abstract: Protein kinase C (PKC) {delta} plays an important role in cellular proliferation and apoptosis. The catalytic fragment of PKC{delta} generated by caspase-dependent cleavage is essential for the initiation of etoposide-induced apoptosis. In this study, we identified a novel mouse PKC{delta} isoform named PKC{delta}IX (Genebank Accession No. (HQ840432)). PKC{delta}IX is generated by alternative splicing and is ubiquitously expressed, as seen in its full-length PKC{delta}. PKC{delta}IX lacks the C1 domain, the caspase 3 cleavage site, and the ATP binding site but preserves an almost intact c-terminal catalytic domain and a nuclear localization signal (NLS). The structural characteristics of PKC{delta}IX provided a possibility that this PKC{delta} isozyme functions as a novel dominant-negative form for PKC{delta} due to its lack of the ATP-binding domain that is required for the kinase activity of PKC{delta}. Indeed, overexpression of PKC{delta}IX significantly inhibited etoposide-induced apoptosis in NIH3T3 cells. In addition, an in vitro kinase assay showed that recombinant PKC{delta}IX protein could competitively inhibit the kinase activity of PKC{delta}. We conclude that PKC{delta}IX can function as a natural dominant-negative inhibitor of PKC{delta}in vivo.

  1. A Physical Model of Pulsars as Gravitational Shielding and Oscillating Neutron Stars

    Directory of Open Access Journals (Sweden)

    Zhang T. X.

    2015-04-01

    Full Text Available Pulsars are thought to be fast rotating neutron stars, synchronously emitting periodic Dirac-delta-shape radio-frequency pulses and Lorentzian-shape oscillating X-rays. The acceleration of charged particles along the magnetic field lines of neutron stars above the magnetic poles that deviate from the rotating axis initiates coherent beams of ra- dio emissions, which are viewed as pulses of radiation whenever the magnetic poles sweep the viewers. However, the conventional lighthouse model of pulsars is only con- ceptual. The mechanism through which particles are accelerated to produce coherent beams is still not fully understood. The process for periodically oscillating X-rays to emit from hot spots at the inner edge of accretion disks remains a mystery. In addition, a lack of reflecting X-rays of the pulsar by the Crab Nebula in the OFF phase does not support the lighthouse model as expected. In this study, we develop a physical model of pulsars to quantitatively interpret the emission characteristics of pulsars, in accor- dance with the author’s well-developed five-dimensional fully covariant Kaluza-Klein gravitational shielding theory and the physics of thermal and accelerating charged par- ticle radiation. The results obtained from this study indicate that, with the significant gravitational shielding by scalar field, a neutron star nonlinearly oscillates and produces synchronous periodically Dirac-delta-shape radio-frequency pulses (emitted by the os- cillating or accelerating charged particles as well as periodically Lorentzian-shape os- cillating X-rays (as the thermal radiation of neutron stars whose temperature varies due to the oscillation. This physical model of pulsars broadens our understanding of neu- tron stars and develops an innovative mechanism to model the emissions of pulsars.

  2. Stellar Variability at the Main-sequence Turnoff of the Intermediate-age LMC Cluster NGC 1846

    Science.gov (United States)

    Salinas, R.; Pajkos, M. A.; Vivas, A. K.; Strader, J.; Contreras Ramos, R.

    2018-04-01

    Intermediate-age (IA) star clusters in the Large Magellanic Cloud (LMC) present extended main-sequence turn-offs (MSTO) that have been attributed to either multiple stellar populations or an effect of stellar rotation. Recently it has been proposed that these extended main sequences can also be produced by ill-characterized stellar variability. Here we present Gemini-S/Gemini Multi-Object Spectrometer (GMOS) time series observations of the IA cluster NGC 1846. Using differential image analysis, we identified 73 new variable stars, with 55 of those being of the Delta Scuti type, that is, pulsating variables close the MSTO for the cluster age. Considering completeness and background contamination effects, we estimate the number of δ Sct belonging to the cluster between 40 and 60 members, although this number is based on the detection of a single δ Sct within the cluster half-light radius. This amount of variable stars at the MSTO level will not produce significant broadening of the MSTO, albeit higher-resolution imaging will be needed to rule out variable stars as a major contributor to the extended MSTO phenomenon. Though modest, this amount of δ Sct makes NGC 1846 the star cluster with the highest number of these variables ever discovered. Lastly, our results present a cautionary tale about the adequacy of shallow variability surveys in the LMC (like OGLE) to derive properties of its δ Sct population. Based on observations obtained at the Gemini Observatory, which is operated by the Association of Universities for Research in Astronomy, Inc., under a cooperative agreement with the NSF on behalf of the Gemini partnership: the National Science Foundation (United States), the National Research Council (Canada), CONICYT (Chile), Ministerio de Ciencia, Tecnología e Innovación Productiva (Argentina), and Ministério da Ciência, Tecnologia e Inovação (Brazil).

  3. INFRARED ECLIPSES OF THE STRONGLY IRRADIATED PLANET WASP-33b, AND OSCILLATIONS OF ITS HOST STAR

    Energy Technology Data Exchange (ETDEWEB)

    Deming, Drake; Fraine, Jonathan D. [Department of Astronomy, University of Maryland, College Park, MD 20742 (United States); Sada, Pedro V. [Department of Mathematics and Physics, Universidad de Monterrey, Monterrey (Mexico); Madhusudhan, Nikku [Department of Astrophysical Sciences, Princeton University, Princeton, NJ 08544-1001 (United States); Knutson, Heather A. [Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, CA 91125 (United States); Harrington, Joseph; Blecic, Jasmina; Nymeyer, Sarah [Planetary Sciences Group, Department of Physics, University of Central Florida, Orlando, FL 32816-2385 (United States); Smith, Alexis M. S. [Astrophysics Group, Keele University, Staffordshire ST5 5BG (United Kingdom); Jackson, Brian, E-mail: ddeming@astro.umd.edu [Department of Terrestrial Magnetism, Carnegie Institution of Washington, Washington, DC 20015 (United States)

    2012-08-01

    We observe two secondary eclipses of the strongly irradiated transiting planet WASP-33b, in the K{sub s} band at 2.15 {mu}m, and one secondary eclipse each at 3.6 {mu}m and 4.5 {mu}m using Warm Spitzer. This planet orbits an A5V {delta}-Scuti star that is known to exhibit low-amplitude non-radial p-mode oscillations at about 0.1% semi-amplitude. We detect stellar oscillations in all of our infrared eclipse data, and also in one night of observations at J band (1.25 {mu}m) out of eclipse. The oscillation amplitude, in all infrared bands except K{sub s} , is about the same as in the optical. However, the stellar oscillations in K{sub s} band (2.15 {mu}m) have about twice the amplitude (0.2%) as seen in the optical, possibly because the Brackett-{gamma} line falls in this bandpass. As regards the exoplanetary eclipse, we use our best-fit values for the eclipse depth, as well as the 0.9 {mu}m eclipse observed by Smith et al., to explore possible states of the exoplanetary atmosphere, based on the method of Madhusudhan and Seager. On this basis we find two possible states for the atmospheric structure of WASP-33b. One possibility is a non-inverted temperature structure in spite of the strong irradiance, but this model requires an enhanced carbon abundance (C/O > 1). The alternative model has solar composition, but an inverted temperature structure. Spectroscopy of the planet at secondary eclipse, using a spectral resolution that can resolve the water vapor band structure, should be able to break the degeneracy between these very different possible states of the exoplanetary atmosphere. However, both of those model atmospheres absorb nearly all of the stellar irradiance with minimal longitudinal re-distribution of energy, strengthening the hypothesis of Cowan and Agol that the most strongly irradiated planets circulate energy poorly. Our measurement of the central phase of the eclipse yields ecos {omega} = 0.0003 {+-} 0.00013, which we regard as being consistent with a

  4. Delta Dynamics

    DEFF Research Database (Denmark)

    Bendixen, Mette

    . The warming air temperature affects the soil temperature and permafrost thaws and destabilizes the material in the coastal zone. In Greenland, the warming temperature lowers the surface mass balance of the Greenland Ice Sheet and more material is transported to the coastal zone. The sea ice extent is thinning...... of a fjord and the second type is a wider fan-shaped open delta. Most deltas are directly coupled to the Greenland Ice Sheet or local icecaps and are highly influenced by the dynamics in the catchments. It is demonstrated how a modern changing climate directly affects delta dynamics, and that Greenlandic...... deltas are prograding, contrary to the global trend showing eroding Arctic coasts. Moreover, it is revealed that the increasing proglacial freshwater runoff, caused by a lowering of the surface mass balance of the Greenland Ice Sheet is the main determining agent in delta progradation. The final part...

  5. Holocene evolution of a wave-dominated fan-delta: Godavari delta, India

    Science.gov (United States)

    Saito, Y.; Nageswara Rao, K.; Nagakumar, K.; Demudu, G.; Rajawat, A.; Kubo, S.; Li, Z.

    2013-12-01

    The Godavari delta is one of the world's largest wave-dominated deltas. The Godavari River arises in the Western Ghats near the west coast of India and drains an area of about 3.1x10^5 km^2, flowing about 1465 km southeast across the Indian peninsula to the Bay of Bengal. The Godavari delta consists of a gentle seaward slope from its apex (12 m elevation) at Rajahmundry and a coastal beach-ridge plain over a distance of about 75 km and covers ~5200 km^2 as a delta plain. The river splits into two major distributary channels, the Gautami and the Vasishta, at a barrage constructed in the mid-1800s. The coastal environment of the deltaic coast is microtidal (~1 m mean tidal range) and wave-dominated (~1.5 m mean wave height in the June-September SW monsoon season, ~0.8 m in the NE monsoon season). Models of the Holocene evolution of the Godavari delta have changed from a zonal progradation model (e.g. Nageswara Rao & Sadakata, 1993) to a truncated cuspate delta model (Nageswara Rao et al., 2005, 2012). Twelve borehole cores (340 m total length), taken in the coastal delta plain during 2010-2013, yielded more than 100 C-14 dates. Sediment facies and C-14 dates from these and previous cores and remote-sensing data support a new delta evolution model. The Holocene coastal delta plain is divided into two parts by a set of linear beach ridges 12-14 km landward from the present shoreline in the central part of the delta. The location of the main depocenter (lobe) has shifted during the Holocene from 1) the center to 2) the west, 3) east, 4) center, 5) west, and 6) east. The linear beach ridges separate the first three from the last three stages. These lobe shifts are controlled by river channel shifts near the apex. Just as the current linear shoreline of the central part of the delta and the concave-up nearshore topography are the result of coastal erosion of a cuspate delta, the linear beach ridges indicate a former eroded shoreline. An unconformity within the deltaic

  6. Instabilities in Interacting Binary Stars

    Science.gov (United States)

    Andronov, I. L.; Andrych, K. D.; Antoniuk, K. A.; Baklanov, A. V.; Beringer, P.; Breus, V. V.; Burwitz, V.; Chinarova, L. L.; Chochol, D.; Cook, L. M.; Cook, M.; Dubovský, P.; Godlowski, W.; Hegedüs, T.; Hoňková, K.; Hric, L.; Jeon, Y.-B.; Juryšek, J.; Kim, C.-H.; Kim, Y.; Kim, Y.-H.; Kolesnikov, S. V.; Kudashkina, L. S.; Kusakin, A. V.; Marsakova, V. I.; Mason, P. A.; Mašek, M.; Mishevskiy, N.; Nelson, R. H.; Oksanen, A.; Parimucha, S.; Park, J.-W.; Petrík, K.; Quiñones, C.; Reinsch, K.; Robertson, J. W.; Sergey, I. M.; Szpanko, M.; Tkachenko, M. G.; Tkachuk, L. G.; Traulsen, I.; Tremko, J.; Tsehmeystrenko, V. S.; Yoon, J.-N.; Zola, S.; Shakhovskoy, N. M.

    2017-07-01

    parts of the ILA project are “Stellar Bell” (interesting pulsating variables of different types and periods - M, SR, RV Tau, RR Lyr, Delta Sct with changes of characteristics) and “Novice”(=“New Variable”) discoveries and classification based on special own observations and data mining with a subsequent monitoring for searching and studying possible multiple components of variability. Special mathematical methods have been developed to create a set of complementary software for statistically optimal modeling of variable stars of different types.

  7. Anaerobic Transformation of Furfural by Methanococcus deltae (Delta)LH

    Science.gov (United States)

    Belay, N.; Boopathy, R.; Voskuilen, G.

    1997-01-01

    Methanococcus deltae (Delta)LH was grown on H(inf2)-CO(inf2) in the presence of various concentrations of furfural. Furfural at higher concentrations, namely, 20 and 25 mM, inhibited growth of this organism. At concentration of 5 and 10 mM, no inhibition of growth was observed. The other methanogens in this study were not inhibited by 10 mM furfural. Among the methanogens tested, M. deltae was capable of transforming furfural, whereas Methanobacterium thermoautotrophicum Marburg, Methanosarcina barkeri 227, Methanococcus thermolithotrophicus, and Methanobrevibacter ruminantium lacked this capability. One hundred percent removal of furfural was observed within 48 h of incubation in M. deltae cultures. The end product observed during furfural metabolism was furfuryl alcohol. An almost stoichiometric amount of furfuryl alcohol was produced by M. deltae. This transformation is likely to be of value in the detoxification of furfural and in its ultimate conversion to methane and CO(inf2) by anaerobic digestion. PMID:16535618

  8. delta-vision

    Data.gov (United States)

    California Natural Resource Agency — Delta Vision is intended to identify a strategy for managing the Sacramento-San Joaquin Delta as a sustainable ecosystem that would continue to support environmental...

  9. First Student Project at the University of Tennessee at Martin Observatory

    Science.gov (United States)

    Crews, Lionel J.; Turner, K.; Wesner, P.

    2011-05-01

    The University of Tennessee at Martin has recently completed the construction and setup of an observatory. The dome houses a 16" Meade telescope with SBIG STL-11000M CCD. For its first project, observations of the Delta Scuti type variable SZ Lynx were taken in March and analyzed using MiraPRO. A simple ephemeris calculation was done, and compared to previous results. This project was done under the University Scholars program, a four year scholarship program which includes a faculty-mentored research project.

  10. Growth laws for delta crevasses in the Mississippi River Delta: observations and modeling

    Science.gov (United States)

    Yocum, T. A.; Georgiou, I. Y.

    2016-02-01

    River deltas are accumulations of sedimentary deposits delivered by rivers via a network of distributary channels. Worldwide they are threatened by environmental changes, including subsidence, global sea level rise and a suite of other local factors. In the Mississippi River Delta (MRD) these impacts are exemplified, and have led to proposed solutions to build land that include sediment diversions, thereby reinitiating the delta cycle. While economically efficient, there are too few analogs of small deltas aside from laboratory studies, numerical modeling studies, theoretical approaches, and limited field driven observations. Anthropogenic crevasses in the modern delta are large enough to overcome limitations of laboratory deltas, and small enough to allow for "rapid" channel and wetland development, providing an ideal setting to investigate delta development mechanics. Crevasse metrics were obtained using a combination of geospatial tools, extracting key parameters (bifurcation length and width, channel order and depth) that were non-dimensionalized and compared to river-dominated delta networks previously studied. Analysis showed that most crevasses in the MRD appear to obey delta growth laws and delta allometry relationships, suggesting that crevasses do exhibit similar planform metrics to larger Deltas; the distance to mouth bar versus bifurcation order demonstrated to be a very reasonable first order estimate of delta-top footprint. However, some crevasses exhibited different growth metrics. To better understand the hydrodynamic and geomorphic controls governing crevasse evolution in the MRD, we assess delta dynamics via a suite of field observations and numerical modeling in both well-established and newly constructed crevasses. Our analysis suggests that delta development is affected by the relative influence of external (upstream and downstream) and internal controls on the hydrodynamic and sediment transport patterns in these systems.

  11. On p-mode oscillations in stars from 1 solar mass to 2 solar masses

    Science.gov (United States)

    Audard, N.; Provost, J.

    1994-06-01

    The structure of stars more massive than about 1.2 solar masses is characterized by a convective core. We have studied the evolution with age and mass of acoustic frequencies of high radical order n and low degree l for models of stars of 1, 1.5 and 2 solar masses. Using a polynomial approximation for the frequency, the p-mode spectrum can be characterized by derived global asteroseismic coefficients, i.e. the mean separation nu0 is approximately equal to nun, l - nun - 1, l and the small frequency separation Delta nu0, 2 is approximately equal to nun, l = 0 - nun - 1, l = 2. The diagram (nu0, delta nu0, 2/nu0) plotted along the evolutionary tracks would help to separate the effects of age and mass. We study the sensitivity of these coefficients and other observable quantities, like the radius and luminosity, to stellar parameters in the vicinity of 1 solar mass and 2 solar masses; this sensitivity substantially depends on the stellar mass and must be taken into account for asteroseismic calibration of stellar clusters. Considering finally some rapid variations of the internal structure, we show that the second frequency difference delta2 nu = nu(subn, l) - 2 nun - 1, l + nun - 2, l exponent gamma in the He II ionization zone.

  12. RED GIANTS IN ECLIPSING BINARY AND MULTIPLE-STAR SYSTEMS: MODELING AND ASTEROSEISMIC ANALYSIS OF 70 CANDIDATES FROM KEPLER DATA

    International Nuclear Information System (INIS)

    Gaulme, P.; McKeever, J.; Rawls, M. L.; Jackiewicz, J.; Mosser, B.; Guzik, J. A.

    2013-01-01

    Red giant stars are proving to be an incredible source of information for testing models of stellar evolution, as asteroseismology has opened up a window into their interiors. Such insights are a direct result of the unprecedented data from space missions CoRoT and Kepler as well as recent theoretical advances. Eclipsing binaries are also fundamental astrophysical objects, and when coupled with asteroseismology, binaries provide two independent methods to obtain masses and radii and exciting opportunities to develop highly constrained stellar models. The possibility of discovering pulsating red giants in eclipsing binary systems is therefore an important goal that could potentially offer very robust characterization of these systems. Until recently, only one case has been discovered with Kepler. We cross-correlate the detected red giant and eclipsing-binary catalogs from Kepler data to find possible candidate systems. Light-curve modeling and mean properties measured from asteroseismology are combined to yield specific measurements of periods, masses, radii, temperatures, eclipse timing variations, core rotation rates, and red giant evolutionary state. After using three different techniques to eliminate false positives, out of the 70 systems common to the red giant and eclipsing-binary catalogs we find 13 strong candidates (12 previously unknown) to be eclipsing binaries, one to be a non-eclipsing binary with tidally induced oscillations, and 10 more to be hierarchical triple systems, all of which include a pulsating red giant. The systems span a range of orbital eccentricities, periods, and spectral types F, G, K, and M for the companion of the red giant. One case even suggests an eclipsing binary composed of two red giant stars and another of a red giant with a δ-Scuti star. The discovery of multiple pulsating red giants in eclipsing binaries provides an exciting test bed for precise astrophysical modeling, and follow-up spectroscopic observations of many of the

  13. COMMD1 regulates the delta epithelial sodium channel ({delta}ENaC) through trafficking and ubiquitination

    Energy Technology Data Exchange (ETDEWEB)

    Chang, Tina; Ke, Ying; Ly, Kevin [Department of Physiology, University of Otago, P.O. Box 913, Dunedin 9054 (New Zealand); McDonald, Fiona J., E-mail: fiona.mcdonald@otago.ac.nz [Department of Physiology, University of Otago, P.O. Box 913, Dunedin 9054 (New Zealand)

    2011-08-05

    Highlights: {yields} The COMM domain of COMMD1 mediates binding to {delta}ENaC. {yields} COMMD1 reduces the cell surface population of {delta}ENaC. {yields} COMMD1 increases the population of {delta}ENaC-ubiquitin. {yields} Both endogenous and transfected {delta}ENaC localize with COMMD1 and transferrin suggesting they are located in early/recycling endosomes. -- Abstract: The delta subunit of the epithelial sodium channel ({delta}ENaC) is a member of the ENaC/degenerin family of ion channels. {delta}ENaC is distinct from the related {alpha}-, {beta}- and {gamma}ENaC subunits, known for their role in sodium homeostasis and blood pressure control, as {delta}ENaC is expressed in brain neurons and activated by external protons. COMMD1 (copper metabolism Murr1 domain 1) was previously found to associate with and downregulate {delta}ENaC activity. Here, we show that COMMD1 interacts with {delta}ENaC through its COMM domain. Co-expression of {delta}ENaC with COMMD1 significantly reduced {delta}ENaC surface expression, and led to an increase in {delta}ENaC ubiquitination. Immunocytochemical and confocal microscopy studies show that COMMD1 promoted localization of {delta}ENaC to the early/recycling endosomal pool where the two proteins were localized together. These results suggest that COMMD1 downregulates {delta}ENaC activity by reducing {delta}ENaC surface expression through promoting internalization of surface {delta}ENaC to an intracellular recycling pool, possibly via enhanced ubiquitination.

  14. Future Deltas Utrecht University research focus area: towards sustainable management of sinking deltas

    Science.gov (United States)

    Stouthamer, E.; van Asselen, S.

    2015-11-01

    Deltas are increasingly under pressure from human impact and climate change. To deal with these pressures that threat future delta functioning, we need to understand interactions between physical, biological, chemical and social processes in deltas. This requires an integrated approach, in which knowledge on natural system functioning is combined with knowledge on spatial planning, land and water governance and legislative frameworks. In the research focus area Future Deltas of Utrecht University an interdisciplinary team from different research groups therefore works together. This allows developing integrated sustainable and resilient delta management strategies, which is urgently needed to prevent loss of vital delta services.

  15. Constraints on stellar evolution from pulsations

    International Nuclear Information System (INIS)

    Cox, A.N.

    1983-01-01

    Consideration of the many types of intrinsic variable stars, that is, those that pulsate, reveals that perhaps a dozen classes can indicate some constraints that affect the results of stellar evolution calculations, or some interpretations of observations. Many of these constraints are not very strong or may not even be well defined yet. In this review we discuss only the case for six classes: classical Cepheids with their measured Wesselink radii, the observed surface effective temperatures of the known eleven double-mode Cepheids, the pulsation periods and measured surface effective temperatures of three R CrB variables, the delta Scuti variable VZ Cnc with a very large ratio of its two observed periods, the nonradial oscillations of our sun, and the period ratios of the newly discovered double-mode RR Lyrae variables. Unfortunately, the present state of knowledge about the exact compositions; mass loss and its dependence on the mass, radius, luminosity, and composition; ;and internal mixing processes, as well as sometimes the more basic parameters such as luminosities and surface effective temperatures prevent us from applying strong constraints for every case where currently the possibility exists

  16. Linear radial pulsation theory. Lecture 5

    International Nuclear Information System (INIS)

    Cox, A.N.

    1983-01-01

    We describe a method for getting an equilibrium stellar envelope model using as input the total mass, the envelope mass, the surface effective temperature, the total surface luminosity, and the composition of the envelope. Then wih the structure of the envelope model known, we present a method for obtaining the raidal pulsation periods and growth rates for low order modes. The large amplitude pulsations observed for the yellow and red giants and supergiants are always these radial models, but for the stars nearer the main sequence, as for all of our stars and for the white dwarfs, there frequently are nonradial modes occuring also. Application of linear theory radial pulsation theory is made to the giant star sigma Scuti variables, while the linear nonradial theory will be used for the B stars in later lectures

  17. Tidal Love numbers and moment-Love relations of polytropic stars

    Science.gov (United States)

    Yip, Kenny L. S.; Leung, P. T.

    2017-12-01

    The physical significance of tidal deformation in astronomical systems has long been known. The recently discovered universal I-Love-Q relations, which connect moment of inertia, quadrupole tidal Love number and spin-induced quadrupole moment of compact stars, also underscore the special role of tidal deformation in gravitational wave astronomy. Motivated by the observation that such relations also prevail in Newtonian stars and crucially depend on the stiffness of a star, we consider the tidal Love numbers of Newtonian polytropic stars whose stiffness is characterized by a polytropic index n. We first perturbatively solve the Lane-Emden equation governing the profile of polytropic stars through the application of the scaled delta expansion method and then formulate perturbation series for the multipolar tidal Love number about the two exactly solvable cases with n = 0 and n = 1, respectively. Making use of these two series to form a two-point Padé approximant, we find an approximate expression of the quadrupole tidal Love number, whose error is less than 2.5 × 10-5 per cent (0.39 per cent) for n ∈ [0, 1] (n ∈ [0, 3]). Similarly, we also determine the mass moments for polytropic stars accurately. Based on these findings, we are able to show that the I-Love-Q relations are in general stationary about the incompressible limit irrespective of the equation of state of a star. Moreover, for the I-Love-Q relations, there is a secondary stationary point near n ≈ 0.4444, thus showing the insensitivity to n for n ∈ [0, 1]. Our investigation clearly tracks the universality of the I-Love-Q relations from their validity for stiff stars such as neutron stars to their breakdown for soft stars.

  18. Connectivity in river deltas

    Science.gov (United States)

    Passalacqua, P.; Hiatt, M. R.; Sendrowski, A.

    2016-12-01

    Deltas host approximately half a billion people and are rich in ecosystem diversity and economic resources. However, human-induced activities and climatic shifts are significantly impacting deltas around the world; anthropogenic disturbance, natural subsidence, and eustatic sea-level rise are major causes of threat to deltas and in many cases have compromised their safety and sustainability, putting at risk the people that live on them. In this presentation, I will introduce a framework called Delta Connectome for studying connectivity in river deltas based on different representations of a delta as a network. Here connectivity indicates both physical connectivity (how different portions of the system interact with each other) as well as conceptual (pathways of process coupling). I will explore several network representations and show how quantifying connectivity can advance our understanding of system functioning and can be used to inform coastal management and restoration. From connectivity considerations, the delta emerges as a leaky network that evolves over time and is characterized by continuous exchanges of fluxes of matter, energy, and information. I will discuss the implications of connectivity on delta functioning, land growth, and potential for nutrient removal.

  19. Delta 2.0

    DEFF Research Database (Denmark)

    Skott, Jeppe; Skott, Charlotte Krog; Jess, Kristine

    DELTA 2.0 er en ny og helt opdateret udgave af Delta, der i ti år været brugt i matematiklærernes grund-, efter- og videreuddannelse. DELTA 2.0 er seriens almene fagdidaktik. Der er også fagdidaktiske overvejelser i de øvrige bøger i serien, men de er knyttet til specifikt matematisk indhold. DELTA...... 2.0 behandler mere generelle matematikdidaktiske problemstillinger såsom læringsteoretiske overvejelser i forbindelse med matematik, centrale aspekter af det at undervise i matematik og digitale teknologier som værktøj til at støtte elevers faglige læring af matematik....

  20. Peat compaction in deltas : implications for Holocene delta evolution

    NARCIS (Netherlands)

    van Asselen, S.

    2010-01-01

    Many deltas contain substantial amounts of peat, which is the most compressible soil type. Therefore, peat compaction potentially leads to high amounts of subsidence in deltas. The main objective of this research was to quantify subsidence due to peat compaction in Holocene fluvial-deltaic settings

  1. Formation of conjugated delta8,delta10-double bonds by delta12-oleic-acid desaturase-related enzymes: biosynthetic origin of calendic acid.

    Science.gov (United States)

    Cahoon, E B; Ripp, K G; Hall, S E; Kinney, A J

    2001-01-26

    Divergent forms of the plant Delta(12)-oleic-acid desaturase (FAD2) have previously been shown to catalyze the formation of acetylenic bonds, epoxy groups, and conjugated Delta(11),Delta(13)-double bonds by modification of an existing Delta(12)-double bond in C(18) fatty acids. Here, we report a class of FAD2-related enzymes that modifies a Delta(9)-double bond to produce the conjugated trans-Delta(8),trans-Delta(10)-double bonds found in calendic acid (18:3Delta(8trans,10trans,12cis)), the major component of the seed oil of Calendula officinalis. Using an expressed sequence tag approach, cDNAs for two closely related FAD2-like enzymes, designated CoFADX-1 and CoFADX-2, were identified from a C. officinalis developing seed cDNA library. The deduced amino acid sequences of these polypeptides share 40-50% identity with those of other FAD2 and FAD2-related enzymes. Expression of either CoFADX-1 or CoFADX-2 in somatic soybean embryos resulted in the production of calendic acid. In embryos expressing CoFADX-2, calendic acid accumulated to as high as 22% (w/w) of the total fatty acids. In addition, expression of CoFADX-1 and CoFADX-2 in Saccharomyces cerevisiae was accompanied by calendic acid accumulation when induced cells were supplied exogenous linoleic acid (18:2Delta(9cis,12cis)). These results are thus consistent with a route of calendic acid synthesis involving modification of the Delta(9)-double bond of linoleic acid. Regiospecificity for Delta(9)-double bonds is unprecedented among FAD2-related enzymes and further expands the functional diversity found in this family of enzymes.

  2. Main sequence mass loss

    International Nuclear Information System (INIS)

    Brunish, W.M.; Guzik, J.A.; Willson, L.A.; Bowen, G.

    1987-01-01

    It has been hypothesized that variable stars may experience mass loss, driven, at least in part, by oscillations. The class of stars we are discussing here are the δ Scuti variables. These are variable stars with masses between about 1.2 and 2.25 M/sub θ/, lying on or very near the main sequence. According to this theory, high rotation rates enhance the rate of mass loss, so main sequence stars born in this mass range would have a range of mass loss rates, depending on their initial rotation velocity and the amplitude of the oscillations. The stars would evolve rapidly down the main sequence until (at about 1.25 M/sub θ/) a surface convection zone began to form. The presence of this convective region would slow the rotation, perhaps allowing magnetic braking to occur, and thus sharply reduce the mass loss rate. 7 refs

  3. $\\delta$-Expansion at Finite Temperature

    OpenAIRE

    Ramos, Rudnei O.

    1996-01-01

    We apply the $\\delta$-expansion perturbation scheme to the $\\lambda \\phi^{4}$ self-interacting scalar field theory in 3+1 D at finite temperature. In the $\\delta$-expansion the interaction term is written as $\\lambda (\\phi^{2})^{ 1 + \\delta}$ and $\\delta$ is considered as the perturbation parameter. We compute within this perturbative approach the renormalized mass at finite temperature at a finite order in $\\delta$. The results are compared with the usual loop-expansion at finite temperature.

  4. Variation in leaf water delta D and delta 18O values during the evapotranspiration process

    International Nuclear Information System (INIS)

    Leopoldo, P.R.; Foloni, L.L.

    1984-01-01

    A theoretical model was developed to evaluate leaf water delta D and delta 18 O variation in relation to: leaf temperature, relative humidity converted to leaf temperature and delta D and delta 18 O values of atmospheric water vapour and soil water. (M.A.C.) [pt

  5. Rise and Fall of one of World's largest deltas; the Mekong delta in Vietnam

    Science.gov (United States)

    Minderhoud, P. S. J.; Eslami Arab, S.; Pham, H. V.; Erkens, G.; van der Vegt, M.; Oude Essink, G.; Stouthamer, E.; Hoekstra, P.

    2017-12-01

    The Mekong delta is the third's largest delta in the world. It is home to almost 20 million people and an important region for the food security in South East Asia. As most deltas, the Mekong delta is the dynamic result of a balance of sediment supply, sea level rise and subsidence, hosting a system of fresh and salt water dynamics. Ongoing urbanization, industrialization and intensification of agricultural practices in the delta, during the past decades, resulted in growing domestic, agricultural and industrial demands, and have led to a dramatic increase of fresh water use. Since the year 2000, the amount of fresh groundwater extracted from the subsurface increased by 500%. This accelerated delta subsidence as the groundwater system compacts, with current sinking rates exceeding global sea level rise up to an order of magnitude. These high sinking rates have greatly altered the sediment budget of the delta and, with over 50% of the Mekong delta surface elevated less than 1 meter above sea level, greatly increase vulnerability to flooding and storm surges and ultimately, permanent inundation. Furthermore, as the increasingly larger extractions rapidly reduce the fresh groundwater reserves, groundwater salinization subsequently increases. On top of that, dry season low-flows by the Mekong river cause record salt water intrusion in the delta's estuarine system, creating major problems for rice irrigation. We present the work of three years research by the Dutch-Vietnamese `Rise and Fall' project on land subsidence and salinization in both groundwater and surface water in the Vietnamese Mekong delta.

  6. Losing ground in mega-deltas: basin-scale response to existential threats to the Mekong Delta

    Science.gov (United States)

    Arias, M. E.; Kondolf, G. M.; Schmitt, R. J. P.; Carling, P. A.; Darby, S. E.; Bizzi, S.; Castelletti, A.; Cochrane, T. A.; Gibson, S.; Kummu, M.; Oeurng, C.; Rubin, Z.; Wild, T. B.

    2017-12-01

    The Mekong Delta is, in terms of the number of livelihoods it supports, its economic importance, and in its vulnerability to climate change and sinking lands, one of the world's critically threatened mega-deltas. Livelihoods depend on the mere existence of the delta, but also on ecosystem services provided by the delta's drainage basin spanning 795,000 km2 in six abutting countries. These ecosystem services include delivery of sand required to build delta land in the face of rising sea-levels and sediment bound nutrients, provision of spawning habitat for fish that are ultimately harvested in the delta, and hydrologic regulation driving the delta's unique flood-pulse regime. However, while the delta is mainly located in Vietnam, the basin of the Mekong River is shared among China, Myanmar, Laos, Thailand, Cambodia, and Vietnam. In the context of the region's dynamic growth, individual countries are pushing their own development agendas, which include extensive dam building, in-channel sand mining, construction of dykes and canals, and groundwater pumping, all of which contribute to subsidence and erosion of the Delta. Our synthesis of recent research indicates that most of the Mekong's delta land will likely fall below sea-level by 2100 as result of these drivers, exacerbating the impacts of global climatic changes. In this context, local infrastructural projects and changes in land- and water-management may temporarily mitigate some negative effects, but do not address the existential threat to the delta as a whole. To prevent, or at least substantially postpone, the drowning of the Mekong Delta requires identification of the key drivers and immediate concerted management actions on the basin-scale to change the trajectory of subsidence and sediment deficit. A specific challenge is to find the institutional arrangements in this transnational context that could support the needed management changes and equitably distribute costs and impacts. The Mekong Delta is

  7. Hepatitis delta genotypes in chronic delta infection in the northeast of Spain (Catalonia).

    Science.gov (United States)

    Cotrina, M; Buti, M; Jardi, R; Quer, J; Rodriguez, F; Pascual, C; Esteban, R; Guardia, J

    1998-06-01

    Based on genetic analysis of variants obtained around the world, three genotypes of the hepatitis delta virus have been defined. Hepatitis delta virus variants have been associated with different disease patterns and geographic distributions. To determine the prevalence of hepatitis delta virus genotypes in the northeast of Spain (Catalonia) and the correlation with transmission routes and clinical disease, we studied the nucleotide divergence of the consensus sequence of HDV RNA obtained from 33 patients with chronic delta hepatitis (24 were intravenous drug users and nine had no risk factors), and four patients with acute self-limited delta infection. Serum HDV RNA was amplified by the polymerase chain reaction technique and a fragment of 350 nucleotides (nt 910 to 1259) was directly sequenced. Genetic analysis of the nucleotide consensus sequence obtained showed a high degree of conservation among sequences (93% of mean). Comparison of these sequences with those derived from different geographic areas and pertaining to genotypes I, II and III, showed a mean sequence identity of 92% with genotype I, 73% with genotype II and 61% with genotype III. At the amino acid level (aa 115 to 214), the mean identity was 87% with genotype I, 63% with genotype II and 56% with genotype III. Conserved regions included the RNA editing domain, the carboxyl terminal 19 amino acids of the hepatitis delta antigen and the polyadenylation signal of the viral mRNA. Hepatitis delta virus isolates in the northeast of Spain are exclusively genotype I, independently of the transmission route and the type of infection. No hepatitis delta virus subgenotypes were found, suggesting that the origin of hepatitis delta virus infection in our geographical area is homogeneous.

  8. Deltas on the move. Making deltas cope with the effects of climate change

    International Nuclear Information System (INIS)

    Reker, J.; Van Winden, A.; Braakhekke, W.; Vermaat, J.; Eleveld, M.; Janssen, R.; De Reus, N.; Omzigt, N.

    2006-01-01

    This scoping study is the first phase of a study aimed at: (a) providing knowledge on the potential of a system-based approach to deal with the effects of climate change as an alternative for the more traditional technical measures such as dams, dikes and surge barriers. This should be shown for both rich and poor countries and should address hydrological, ecological as well as socio-economic aspects; and (b) identifying the potential to market these results worldwide. To reach these objectives four research steps are defined: (1) to make an inventory of deltas: their vulnerability to the effects of climate change; (2) development of indicators for successful use of a system-based approach; (3) to provide an overview of the potential of soft measures for these deltas; (4) to select a number of deltas with potential for marketing system-based measures and the development of strategies to link economic and ecological objectives. This scoping study addresses step 1 only. The results from step 1 will be used as a starting point for steps 2 and 3. The outputs of this scoping study are threefold: a background report (this report); a flyer with a brief description of the findings; a website with information on delta's and how these may be affected by climate change. The scoping study will roughly outline which deltas are still functioning in a more or less natural manner - or could be (re)developed in that direction - and thus would be good candidates for a system-based approach. Chapter 2 gives a description of the geomorphological and ecological processes in a delta. In addition, those aspects of climate change that can have an effect on deltas are described. The third chapter deals with human interventions in deltas and whether or not they fit within a system-based approach. In a system-based approach, as presented in Chapter 4, natural processes are given free reign where possible. Chapter 5 shows how available data on deltas could be used in such a system

  9. Tides Stabilize Deltas until Humans Interfere

    Science.gov (United States)

    Hoitink, T.; Zheng Bing, W.; Vermeulen, B.; Huismans, Y.; Kastner, K.

    2017-12-01

    Despite global concerns about river delta degradation caused by extraction of natural resources, sediment retention by reservoirs and sea-level rise, human activity in the world's largest deltas intensifies. In this review, we argue that tides tend to stabilize deltas until humans interfere. Under natural circumstances, delta channels subject to tides are more stable than their fluvial-dominated counterparts. The oscillatory tidal flow counteracts the processes responsible for bank erosion, which explains why unprotected tidal channels migrate only slowly. Peak river discharges attenuate the tides, which creates storage space to accommodate the extra river discharge during extreme events and as a consequence, reduce flood risk. With stronger tides, the river discharge is being distributed more evenly over the various branches in a delta, preventing silting up of smaller channels. Human interference in deltas is massive. Storm surge barriers are constructed, new land is being reclaimed and large-scale sand excavation takes place, to collect building material. Evidence from deltas around the globe shows that in human-controlled deltas the tidal motion often plays a destabilizing role. In channels of the Rhine-Meuse Delta, some 100 scour holes are identified, which relates to the altered tidal motion after completion of a storm surge barrier. Sand mining has led to widespread river bank failures in the tidally-influenced Mekong Delta. The catastrophic flood event in the Gauges-Brahmaputra Delta by Cyclone Aila, which caused the inundation of an embanked polder area for over two years, was preceded by river bank erosion at the mouths of formal tidal channels that were blocked by the embankment. Efforts to predict the developments of degrading deltas are few. Existing delta models are capable of reproducing expanding deltas, which is essentially a matter of simulating the transport of sediment from source in a catchment to the sink in a delta. Processes of soil

  10. Effects of Δ baryon in hyperon stars in a modified quark meson coupling model

    International Nuclear Information System (INIS)

    Sahoo, H.S.; Mishra, R.N.; Panda, P.K.; Barik, N.

    2016-01-01

    Recent studies on the appearance of the Δ (1232) isobars in neutron stars has ignited much debate on the possibility of its existence in neutron stars satisfying the observational limit of 2 M_⊙. Given the fact that the presence of the Δ tends to soften the equation of state (EoS) and reduce the maximum mass, theoretical and observational contradictions have given rise to the so called Δ puzzle, similar to the hyperon puzzle. In the present work we develop the EoS for dense matter with the inclusion of the nucleons, hyperons and the Delta isobars and study the effects of such inclusion on stellar properties using a Modified Quark-Meson coupling model (MQMC)

  11. In vivo metabolism of the methyl homologues of delta-8-tetrahydrocannabinol, delta-9-tetrahydrocannabinol and abn-delta-8-tetrahydrocannabinol in the mouse.

    Science.gov (United States)

    Brown, N K; Harvey, D J

    1988-04-01

    Methyl-delta-8-tetrahydrocannabinol (methyl-delta-8-THC), methyl-delta-9-THC and abn-methyl-delta-8-THC were synthesized by condensation of orcinol and (1S)-cis-verbenol and were administered to male Charles River CD-1 mice. Extracted hepatic metabolites were isolated by chromatography on Sephadex LH-20 and examined by gas chromatography/mass spectrometry as trimethylsilyl (TMS), (2H9)TMS and methyl ester/TMS derivatives. In addition, metabolic fractions were reduced with lithium aluminium deuteride to convert carboxylic acids to alcohols for structural correlation. Metabolites from methyl-delta-8-THC were similar with respect to the positions substituted to those produced by higher homologues; the major metabolite was methyl-delta-8-THC-11-oic acid. abn-Methyl-delta-8-THC was metabolized in a different manner. The location of the aromatic methyl group at the position adjacent to ring fusion appeared to inhibit metabolism at C(11) to a considerable extent and also to reduce the amount of the resulting alcohol from being oxidized to a carboxylic acid. This caused other metabolic pathways to become dominant, with the result that a compound containing a hydroxy group at the gem-methyl position was the major metabolite. Hydroxylation at this position has not been confirmed with any other cannabinoid, although it is thought to result in trace concentrations of hydroxy metabolites from some compounds. Metabolism of methyl-delta-9-THC was also similar to that of the higher homologues, with the exception that less metabolism occurred at C(8) and a higher percentage of the total metabolic fraction was accounted for by the 11-oic acid metabolite. Minor metabolites were mainly dihydroxy compounds and hydroxylated derivatives of delta-9-THC-11-oic acid.

  12. Phenotypic expressions of CCR5-Delta 32/Delta 32 homozygosity

    NARCIS (Netherlands)

    Nguyen, GT; Carrington, M; Beeler, JA; Dean, M; Aledort, LM; Blatt, PM; Cohen, AR; DiMichele, D; Eyster, ME; Kessler, CM; Konkle, B; Leissinger, C; Luban, N; O'Brien, SJ; Goedert, JJ; O'Brien, TR

    1999-01-01

    Objective: As blockade of CC-chemokine receptor 5 (CCR5) has been proposed as therapy for HIV-1, we examined whether the CCR5-Delta 32/Delta 32 homozygous genotype has phenotypic expressions other than those related to HIV-1. Design: Study subjects were white homosexual men or men with hemophilia

  13. Migration in Deltas: An Integrated Analysis

    Science.gov (United States)

    Nicholls, Robert J.; Hutton, Craig W.; Lazar, Attila; Adger, W. Neil; Allan, Andrew; Arto, Inaki; Vincent, Katharine; Rahman, Munsur; Salehin, Mashfiqus; Sugata, Hazra; Ghosh, Tuhin; Codjoe, Sam; Appeaning-Addo, Kwasi

    2017-04-01

    Deltas and low-lying coastal regions have long been perceived as vulnerable to global sea-level rise, with the potential for mass displacement of exposed populations. The assumption of mass displacement of populations in deltas requires a comprehensive reassessment in the light of present and future migration in deltas, including the potential role of adaptation to influence these decisions. At present, deltas are subject to multiple drivers of environmental change and often have high population densities as they are accessible and productive ecosystems. Climate change, catchment management, subsidence and land cover change drive environmental change across all deltas. Populations in deltas are also highly mobile, with significant urbanization trends and the growth of large cities and mega-cities within or adjacent to deltas across Asia and Africa. Such migration is driven primarily by economic opportunity, yet environmental change in general, and climate change in particular, are likely to play an increasing direct and indirect role in future migration trends. The policy challenges centre on the role of migration within regional adaptation strategies to climate change; the protection of vulnerable populations; and the future of urban settlements within deltas. This paper reviews current knowledge on migration and adaptation to environmental change to discern specific issues pertinent to delta regions. It develops a new integrated methodology to assess present and future migration in deltas using the Volta delta in Ghana, Mahanadi delta in India and Ganges-Brahmaputra-Meghna delta across India and Bangladesh. The integrated method focuses on: biophysical changes and spatial distribution of vulnerability; demographic changes and migration decision-making using multiple methods and data; macro-economic trends and scenarios in the deltas; and the policies and governance structures that constrain and enable adaptation. The analysis is facilitated by a range of

  14. Mystery of the delta(980)

    International Nuclear Information System (INIS)

    Cahn, R.N.; Landshoff, P.V.

    1986-01-01

    The apparent conflict between the dominance of the decay delta->etaπ in D->deltaπ and its absence in iota->deltaπ is analyzed. Explicit models are presented in which the nearby Kanti K threshold plays an important role in resolving the conflict. (orig.)

  15. Niger Delta Development Commission and Sustainable ...

    African Journals Online (AJOL)

    Niger Delta Development Commission and Sustainable Development of Niger Delta Region of Nigeria: The Case of Rivers State. Goddey Wilson. Abstract. The study is on Niger Delta Development Commission and sustainable development of Niger Delta region of Nigeria, the case of Rivers State. The main objective of the ...

  16. MULTI-WAVELENGTH CHARACTERIZATION OF STELLAR FLARES ON LOW-MASS STARS USING SDSS AND 2MASS TIME-DOMAIN SURVEYS

    Energy Technology Data Exchange (ETDEWEB)

    Davenport, James R. A.; Becker, Andrew C.; Kowalski, Adam F.; Hawley, Suzanne L.; Schmidt, Sarah J.; Hilton, Eric J. [Department of Astronomy, University of Washington, Box 351580, Seattle, WA 98195 (United States); Sesar, Branimir [Division of Physics, Mathematics and Astronomy, Caltech, Pasadena, CA 91125 (United States); Cutri, Roc, E-mail: jrad@astro.washington.edu [Infrared Processing and Analysis Center, California Institute of Technology, Pasadena, CA 91125 (United States)

    2012-03-20

    We present the first rates of flares from M dwarf stars in both red optical and near-infrared (NIR) filters. We have studied {approx}50,000 M dwarfs from the Sloan Digital Sky Survey (SDSS) Stripe 82 area and 1321 M dwarfs from the Two Micron All Sky Survey (2MASS) Calibration Scan Point Source Working Database that overlap SDSS imaging fields. We assign photometric spectral types from M0 to M6 using (r - i) and (i - z) colors for every star in our sample. Stripe 82 stars each have 50-100 epochs of data, while 2MASS Calibration stars have {approx}1900 epochs. From these data we estimate the observed rates and theoretical detection thresholds for flares in eight photometric bands as a function of spectral type. Optical flare rates are found to be in agreement with previous studies, while the frequency per hour of NIR flare detections is found to be more than two orders of magnitude lower. An excess of small-amplitude flux increases in all bands exhibits a power-law distribution, which we interpret as the result of flares below our detection thresholds. In order to investigate the recovery efficiency for flares in each filter, we extend a two-component flare model into the NIR. Quiescent M0-M6 spectral templates were used with the model to predict the photometric response of flares from u to K{sub s} . We determine that red optical filters are sensitive to flares with u-band amplitudes {approx}>2 mag, and NIR filters to flares with {Delta}u {approx}> 4.5 mag. Our model predicts that M0 stars have the best color contrast for J-band detections, but M4-M6 stars should yield the highest rate of NIR flares with amplitudes of {Delta}J {>=} 0.01 mag. Characterizing flare rates and photometric variations at longer wavelengths is important for predicting the signatures of M dwarf variability in next-generation surveys, and we discuss their impact on surveys such as the Large Synoptic Survey Telescope.

  17. Large old trees influence patterns of delta13C and delta15N in forests.

    Science.gov (United States)

    Weber, Pascale; Bol, Roland; Dixon, Liz; Bardgett, Richard D

    2008-06-01

    Large old trees are the dominant primary producers of native pine forest, but their influence on spatial patterns of soil properties and potential feedback to tree regeneration in their neighbourhood is poorly understood. We measured stable isotopes of carbon (delta(13)C) and nitrogen (delta(15)N) in soil and litter taken from three zones of influence (inner, middle and outer zone) around the trunk of freestanding old Scots pine (Pinus sylvestris L.) trees, to determine the trees' influence on below-ground properties. We also measured delta(15)N and delta(13)C in wood cores extracted from the old trees and from regenerating trees growing within their three zones of influence. We found a significant and positive gradient in soil delta(15)N from the inner zone, nearest to the tree centre, to the outer zone beyond the tree crown. This was probably caused by the higher input of (15)N-depleted litter below the tree crown. In contrast, the soil delta(13)C did not change along the gradient of tree influence. Distance-related trends, although weak, were visible in the wood delta(15)N and delta(13)C of regenerating trees. Moreover, the wood delta(15)N of small trees showed a weak negative relationship with soil N content in the relevant zone of influence. Our results indicate that large old trees control below-ground conditions in their immediate surroundings, and that stable isotopes might act as markers for the spatial and temporal extent of these below-ground effects. John Wiley & Sons, Ltd

  18. An analytical framework for strategic delta planning : negotiating consent for long-term sustainable delta development

    NARCIS (Netherlands)

    Seijger, C.; Douven, W; Hermans, L.M.; Evers, J.; Phi, H. L.; Brunner, J.; Pols, L.; Ligtvoet, W.; Koole, S.; Slager, K.; Vermoolen, M.S.; Hasan, S.; Hoang, V. T M; van Halsema, G

    2016-01-01

    Sectoral planning on water, agriculture and urban development has not been able to prevent increased flood risks and environmental degradation in many deltas. Governments conceive strategic delta planning as a promising planning approach and develop strategic delta plans. Such plans are linked to

  19. Catalyzing action towards the sustainability of deltas: deltas as integrated socio-ecological systems and sentinels of regional and global change

    Science.gov (United States)

    Foufoula-Georgiou, E.; Tessler, Z. D.; Brondizio, E.; Overeem, I.; Renaud, F.; Sebesvari, Z.; Nicholls, R. J.; Anthony, E.

    2016-12-01

    Deltas are highly dynamic and productive environments: they are food baskets of the world, home to biodiverse and rich ecosystems, and they play a central role in food and water security. However, they are becoming increasingly vulnerable to risks arising from human activities, land subsidence, regional water management, global sea-level rise, and climate extremes. Our Belmont Forum DELTAS project (BF-DELTAS: Catalyzing actions towards delta sustainability) encompasses an international network of interdisciplinary research collaborators with focal areas in the Mekong, Ganges Brahmaputra, and the Amazon deltas. The project is organized around five main modules: (1) developing an analytical framework for assessing delta vulnerability and scenarios of change (Delta-SRES), (2) developing an open-acess, science-based integrative modeling framework for risk assessment and decision support (Delta-RADS), (3) developing tools to support quantitative mapping of the bio-physical and socio-economic environments of deltas and consolidate bio-physical and social data within shared data repositories (Delta-DAT), (4) developing Global Delta Vulnerability Indices (Delta-GDVI) that capture current and projected scenarios for major deltas around the world , and (5) collaborating with regional stakeholders to put the science, modeling, and data into action (Delta-ACT). In this talk, a research summary will be presented on three research domains around which significant collaborative work was developed: advancing biophysical classification of deltas, understanding deltas as coupled socio-ecological systems, and analyzing and informing social and environmental vulnerabilities in delta regions.

  20. Delta Morphodynamics Matters! Ecosystem Services, Poverty and Morphodynamic Change in the Ganges-Brahmaputra Mega-Delta

    Science.gov (United States)

    Nicholls, R. J.; Adger, N.; Allan, A.; Darby, S. E.; Hutton, C.; Matthews, Z.; Rahman, M.; Whitehead, P. G.; Wolf, J.

    2013-12-01

    The world's deltas are probably the most vulnerable type of coastal environment, and they face multiple stresses in the coming decades. These stresses include, amongst others, local drivers due to land subsidence, population growth and urbanisation within the deltas, regional drivers due to changes in catchment management (e.g. upstream land use and dam construction), as well as global climate change impacts such as sea-level rise. At the same time, the ecosystem services of river deltas support high population densities, with around 14% of the global population inhabiting deltas. A large proportion of these people experience extremes of poverty and they are therefore severely exposed to vulnerability from environmental and ecological stress and degradation. In areas close to or below the poverty boundary, both subsistence and cash elements of the economy tend to rely disproportionately heavily on ecosystem services which underpin livelihoods. Therefore, to sustainably manage delta environments they must be viewed as complex social-environmental systems where change is only partially driven by physical drivers such as sea level rise and climate change, and human-induced development activities are also critical. Here we outline a new conceptual framework for the development of methods to understand and characterise the key drivers of change in ecosystem services that affect the environment and economic status of populous deltas, focusing specifically on the Ganges-Brahmaputra-Meghna (GBM) mega-delta. The GBM delta is characterised by densely populated coastal lowlands with significant poverty, with livelihoods supported to a large extent by natural ecosystems such as the Sunderbahns (the largest mangrove forest in the world). However, the GBM delta is under severe development pressure due to many growing cities. At present the importance of ecosystems services to poverty and livelihoods is poorly understood. This is due to due to the complexity of interactions

  1. Asteroseismology of δ Scuti and γ Doradus Stars Gerald Handler

    Indian Academy of Sciences (India)

    led to the observational detection and identification of a sufficient number ... satellite missions, theoretical advances on mode identification methods, ... The observational borders of the two pulsational instability strips (Rodriguez & Breger 2001; Handler & Shobbrook. 2002), with the thicker lines corresponding to the γ ...

  2. Infrared variability and nature of symbiotic stars

    Energy Technology Data Exchange (ETDEWEB)

    Feast, M W; Robertson, B S.C.; Catchpole, R M [Royal Observatory, Cape Town (South Africa)

    1977-05-01

    Most symbiotic stars may be placed in one of two classes according to their infrared colours. In one group the systems contain an M type giant. In the other there is evidence for a star plus infrared emission from dust. JHKL photometry is given for three members of each class. Photometry of the VV Cephei system FR Sct is also given. No evidence for variability was found for systems without dust. The three systems with dust (RX Pup, RR Tel and PK 280-2/sup 0/.1) each show large variations of the stellar component (..delta..J, 1sup(m).6 to 2sup(m).7). It is concluded that these dusty systems contain Mira variables. For the systems without dust the mass transfer in the system is presumably through the inner Lagrangian point. For systems containing Miras it is possible that the companion accretes matter from a general stellar wind. Symbiotic systems containing Mira variables have more dust than average Mira variables. Either an unusually dense stellar wind is needed to produce a symbiotic system or such a system produces dust, perhaps in a high-density region resulting from the interaction of the stellar wind with the companion.

  3. Future Change to Tide-Influenced Deltas

    Science.gov (United States)

    Nienhuis, Jaap H.; Hoitink, A. J. F. (Ton); Törnqvist, Torbjörn E.

    2018-04-01

    Tides tend to widen deltaic channels and shape delta morphology. Here we present a predictive approach to assess a priori the effect of fluvial discharge and tides on deltaic channels. We show that downstream channel widening can be quantified by the ratio of the tide-driven discharge and the fluvial discharge, along with a second metric representing flow velocities. A test of our new theory on a selection of 72 deltas globally shows good correspondence to a wide range of environments, including wave-dominated deltas, river-dominated deltas, and alluvial estuaries. By quantitatively relating tides and fluvial discharge to delta morphology, we offer a first-order prediction of deltaic change that may be expected from altered delta hydrology. For example, we expect that reduced fluvial discharge in response to dam construction will lead to increased tidal intrusion followed by enhanced tide-driven sediment import into deltas, with implications for navigation and other human needs.

  4. From Natural to Design River Deltas

    Science.gov (United States)

    Giosan, Liviu

    2016-04-01

    Productive and biologically diverse, deltaic lowlands attracted humans since prehistory and may have spurred the emergence of the first urban civilizations. Deltas continued to be an important nexus for economic development across the world and are currently home for over half a billion people. But recently, under the double whammy of sea level rise and inland sediment capture behind dams, they have become the most threatened coastal landscape. Here I will address several deceptively simple questions to sketch some unexpected answers using example deltas from across the world from the Arctic to the Tropics, from the Danube to the Indus, Mississippi to Godavari and Krishna, Mackenzie to Yukon. What is a river delta? What is natural and what is not in a river delta? Are the geological and human histories of a delta important for its current management? Is maintaining a delta the same to building a new one? Can we design better deltas than Nature? These answers help us see clearly that survival of deltas in the next century depends on human intervention and is neither assured nor simple to address or universally applicable. Empirical observations on the hydrology, geology, biology and biochemistry of deltas are significantly lagging behind modeling capabilities endangering the applicability of numerical-based reconstruction solutions and need to be ramped up significantly and rapidly across the world.

  5. Neutron Stars and NuSTAR

    Science.gov (United States)

    Bhalerao, Varun

    2012-05-01

    My thesis centers around the study of neutron stars, especially those in massive binary systems. To this end, it has two distinct components: the observational study of neutron stars in massive binaries with a goal of measuring neutron star masses and participation in NuSTAR, the first imaging hard X-ray mission, one that is extremely well suited to the study of massive binaries and compact objects in our Galaxy. The Nuclear Spectroscopic Telescope Array (NuSTAR) is a NASA Small Explorer mission that will carry the first focusing high energy X-ray telescope to orbit. NuSTAR has an order-of-magnitude better angular resolution and has two orders of magnitude higher sensitivity than any currently orbiting hard X-ray telescope. I worked to develop, calibrate, and test CdZnTe detectors for NuSTAR. I describe the CdZnTe detectors in comprehensive detail here - from readout procedures to data analysis. Detailed calibration of detectors is necessary for analyzing astrophysical source data obtained by the NuSTAR. I discuss the design and implementation of an automated setup for calibrating flight detectors, followed by calibration procedures and results. Neutron stars are an excellent probe of fundamental physics. The maximum mass of a neutron star can put stringent constraints on the equation of state of matter at extreme pressures and densities. From an astrophysical perspective, there are several open questions in our understanding of neutron stars. What are the birth masses of neutron stars? How do they change in binary evolution? Are there multiple mechanisms for the formation of neutron stars? Measuring masses of neutron stars helps answer these questions. Neutron stars in high-mass X-ray binaries have masses close to their birth mass, providing an opportunity to disentangle the role of "nature" and "nurture" in the observed mass distributions. In 2006, masses had been measured for only six such objects, but this small sample showed the greatest diversity in masses

  6. Improved γ-linolenic acid production in Mucor circinelloides by homologous overexpressing of delta-12 and delta-6 desaturases.

    Science.gov (United States)

    Zhang, Yao; Luan, Xiao; Zhang, Huaiyuan; Garre, Victoriano; Song, Yuanda; Ratledge, Colin

    2017-06-21

    γ-Linolenic acid (GLA) is important because of its nutritional value and medicinal applications. Although the biosynthetic pathways of some plant and microbial GLA have been deciphered, current understanding of the correlation between desaturases and GLA synthesis in oleaginous fungi is incomplete. In previous work, we found that a large amount of oleic acid (OA) had not been converted to linoleic acid (LA) or GLA in Mucor circinelloides CBS 277.49, which may be due to inadequate activities of the delta-12 or delta-6 desaturases, and thus leading to the accumulation of OA and LA. Thus, it is necessary to explore the main contributing factor during the process of GLA biosynthesis in M. circinelloides. To enhance GLA production in M. circinelloides, homologous overexpression of delta-12 and two delta-6 desaturases (named delta-6-1 and delta-6-2, respectively) were analyzed. When delta-6 desaturase were overexpressed in M. circinelloides, up to 43% GLA was produced in the total fatty acids, and the yield of GLA reached 180 mg/l, which were, respectively, 38 and 33% higher than the control strain. These findings revealed that delta-6 desaturase (especially for delta-6-1 desaturase) plays an important role in GLA synthesis by M. circinelloides. The strain overexpressing delta-6-1 desaturase may have potential application in microbial GLA production.

  7. Entropy and optimality in river deltas

    Science.gov (United States)

    Tejedor, Alejandro; Longjas, Anthony; Edmonds, Douglas A.; Zaliapin, Ilya; Georgiou, Tryphon T.; Rinaldo, Andrea; Foufoula-Georgiou, Efi

    2017-10-01

    The form and function of river deltas is intricately linked to the evolving structure of their channel networks, which controls how effectively deltas are nourished with sediments and nutrients. Understanding the coevolution of deltaic channels and their flux organization is crucial for guiding maintenance strategies of these highly stressed systems from a range of anthropogenic activities. To date, however, a unified theory explaining how deltas self-organize to distribute water and sediment up to the shoreline remains elusive. Here, we provide evidence for an optimality principle underlying the self-organized partition of fluxes in delta channel networks. By introducing a suitable nonlocal entropy rate (nER) and by analyzing field and simulated deltas, we suggest that delta networks achieve configurations that maximize the diversity of water and sediment flux delivery to the shoreline. We thus suggest that prograding deltas attain dynamically accessible optima of flux distributions on their channel network topologies, thus effectively decoupling evolutionary time scales of geomorphology and hydrology. When interpreted in terms of delta resilience, high nER configurations reflect an increased ability to withstand perturbations. However, the distributive mechanism responsible for both diversifying flux delivery to the shoreline and dampening possible perturbations might lead to catastrophic events when those perturbations exceed certain intensity thresholds.

  8. The evolution of a subaqueous delta in the Anthropocene: A stratigraphic investigation of the Brazos River delta, TX USA

    Science.gov (United States)

    Carlin, Joseph A.; Dellapenna, Timothy M.

    2015-12-01

    Globally, deltas are increasingly threatened by anthropogenic activities. As a result, deltas now evolve through the combined effects of natural and human-induced processes occurring throughout the fluvial-deltaic system. The Brazos River delta, located along the Texas coast in the northwestern Gulf of Mexico, and its watershed have been impacted by direct and indirect human activities since the late 19th century. This provides an opportunity to investigate how such alterations have shaped the evolution of a delta in the Anthropocene, a time when humans are drivers of geological change. Historic alteration to the delta and watershed include extensive agricultural activity, jetty construction at the mouth in the late 1890s, mouth diversion ~10 km to the southwest in 1929, and reservoir construction throughout the early and mid 20th Century. Three subaerial deltaic geometries provided the framework to connect subaerial deltaic responses, to the anthropogenic alterations, to the resulting stratigraphic characteristics observed in the subaqueous delta. This study utilized high-resolution geophysical data (swath bathymetry, side scan sonar, CHIRP subbottom profiling) on the subaqueous delta to investigate the subaqueous delta stratigraphy and infer the processes that shaped the deltaic record over time. The results showed distinct areas across the subaqueous delta that were dominated by erosion and deposition. Erosional areas corresponded to earlier growth phase depocenters being exposed at the surface, while the depositional areas corresponded to areas with the most recent growth phase depocenter overlying the earlier depocenters. These results highlight that the subaqueous depocenter has migrated westward over time, consistent with the observed changes to the subaerial delta. Additionally, the data showed that evidence for these past growth phases and depocenters may be preserved within the subaqueous delta, even after subaerial portions of the delta returned to pre

  9. deltaPlotR: An R Package for Di?erential Item Functioning Analysis with Ango? s Delta Plot

    OpenAIRE

    David Magis; Bruno Facon

    2014-01-01

    Angoff's delta plot is a straightforward and not computationally intensive method to identify differential item functioning (DIF) among dichotomously scored items. This approach was recently improved by proposing an optimal threshold selection and by considering several item purification processes. Moreover, to support practical DIF analyses with the delta plot and these improvements, the R package deltaPlotR was also developed. The purpose of this paper is twofold: to outline the delta plot ...

  10. Monte Carlo simulation of star/linear and star/star blends with chemically identical monomers

    Energy Technology Data Exchange (ETDEWEB)

    Theodorakis, P E [Department of Materials Science and Engineering, University of Ioannina, 45110 Ioannina (Greece); Avgeropoulos, A [Department of Materials Science and Engineering, University of Ioannina, 45110 Ioannina (Greece); Freire, J J [Departamento de Ciencias y Tecnicas FisicoquImicas, Universidad Nacional de Educacion a Distancia, Facultad de Ciencias, Senda del Rey 9, 28040 Madrid (Spain); Kosmas, M [Department of Chemistry, University of Ioannina, 45110 Ioannina (Greece); Vlahos, C [Department of Chemistry, University of Ioannina, 45110 Ioannina (Greece)

    2007-11-21

    The effects of chain size and architectural asymmetry on the miscibility of blends with chemically identical monomers, differing only in their molecular weight and architecture, are studied via Monte Carlo simulation by using the bond fluctuation model. Namely, we consider blends composed of linear/linear, star/linear and star/star chains. We found that linear/linear blends are more miscible than the corresponding star/star mixtures. In star/linear blends, the increase in the volume fraction of the star chains increases the miscibility. For both star/linear and star/star blends, the miscibility decreases with the increase in star functionality. When we increase the molecular weight of linear chains of star/linear mixtures the miscibility decreases. Our findings are compared with recent analytical and experimental results.

  11. Monte Carlo simulation of star/linear and star/star blends with chemically identical monomers

    Science.gov (United States)

    Theodorakis, P. E.; Avgeropoulos, A.; Freire, J. J.; Kosmas, M.; Vlahos, C.

    2007-11-01

    The effects of chain size and architectural asymmetry on the miscibility of blends with chemically identical monomers, differing only in their molecular weight and architecture, are studied via Monte Carlo simulation by using the bond fluctuation model. Namely, we consider blends composed of linear/linear, star/linear and star/star chains. We found that linear/linear blends are more miscible than the corresponding star/star mixtures. In star/linear blends, the increase in the volume fraction of the star chains increases the miscibility. For both star/linear and star/star blends, the miscibility decreases with the increase in star functionality. When we increase the molecular weight of linear chains of star/linear mixtures the miscibility decreases. Our findings are compared with recent analytical and experimental results.

  12. Monte Carlo simulation of star/linear and star/star blends with chemically identical monomers

    International Nuclear Information System (INIS)

    Theodorakis, P E; Avgeropoulos, A; Freire, J J; Kosmas, M; Vlahos, C

    2007-01-01

    The effects of chain size and architectural asymmetry on the miscibility of blends with chemically identical monomers, differing only in their molecular weight and architecture, are studied via Monte Carlo simulation by using the bond fluctuation model. Namely, we consider blends composed of linear/linear, star/linear and star/star chains. We found that linear/linear blends are more miscible than the corresponding star/star mixtures. In star/linear blends, the increase in the volume fraction of the star chains increases the miscibility. For both star/linear and star/star blends, the miscibility decreases with the increase in star functionality. When we increase the molecular weight of linear chains of star/linear mixtures the miscibility decreases. Our findings are compared with recent analytical and experimental results

  13. Delta hedging strategies comparison

    DEFF Research Database (Denmark)

    De Giovanni, Domenico; Ortobelli, S.; Rachev, S.T.

    2008-01-01

    In this paper we implement dynamic delta hedging strategies based on several option pricing models. We analyze different subordinated option pricing models and we examine delta hedging costs using ex-post daily prices of S&P 500. Furthermore, we compare the performance of each subordinated model...

  14. The Enabling Delta Life Initiative - Global Programme of Action on Deltas - Programme description

    NARCIS (Netherlands)

    Driel, van W.F.; Skyllerstedt, S.; Wosten, J.H.M.

    2014-01-01

    Being ‘hotspots’ of human activity with generally high population densities, deltas are vulnerable to changes induced by a range of driving forces, both natural and anthropogenic. In addition to already existing challenges, uncertainty of the possible impacts of climate change, low lying deltas

  15. Cloud Screening and Quality Control Algorithm for Star Photometer Data: Assessment with Lidar Measurements and with All-sky Images

    Science.gov (United States)

    Ramirez, Daniel Perez; Lyamani, H.; Olmo, F. J.; Whiteman, D. N.; Navas-Guzman, F.; Alados-Arboledas, L.

    2012-01-01

    This paper presents the development and set up of a cloud screening and data quality control algorithm for a star photometer based on CCD camera as detector. These algorithms are necessary for passive remote sensing techniques to retrieve the columnar aerosol optical depth, delta Ae(lambda), and precipitable water vapor content, W, at nighttime. This cloud screening procedure consists of calculating moving averages of delta Ae() and W under different time-windows combined with a procedure for detecting outliers. Additionally, to avoid undesirable Ae(lambda) and W fluctuations caused by the atmospheric turbulence, the data are averaged on 30 min. The algorithm is applied to the star photometer deployed in the city of Granada (37.16 N, 3.60 W, 680 ma.s.l.; South-East of Spain) for the measurements acquired between March 2007 and September 2009. The algorithm is evaluated with correlative measurements registered by a lidar system and also with all-sky images obtained at the sunset and sunrise of the previous and following days. Promising results are obtained detecting cloud-affected data. Additionally, the cloud screening algorithm has been evaluated under different aerosol conditions including Saharan dust intrusion, biomass burning and pollution events.

  16. Components in the interstellar medium toward epsilon persei and delta persei

    International Nuclear Information System (INIS)

    Martin, E.R.; York, D.G.

    1982-01-01

    We analyze the lines of sight toward epsilon Persei and delta Persei with a procedure that gives velocity components for various interstellar ions. The column densities found for ions expected to be relatively undepleted are used to estimate the column density of neutral hydrogen in each component. The velocities found correspond well with those determined from previous optical studies when the optical components can be resolved. Whenever possible we calculate electron density, calcium and titanium depletion, molecular hydrogen excitation temperature, and hydrogen volume density for each component. Toward each star there is one dominent component with high column density, low LSR velocity, a large depletion in Ca and Ti, and low H 2 excitation temperature. The H 2 results also indicate that the dominant component has a high hydrogen volume density. The components at higher velocities are characterized by lower column densities and less Ca and Ti depletion, relative to the dominant component. There is also evidence that there is one component toward each star which contains mostly ionized gas. While the electron densities found seem consistent with previous results, questions are raised concerning the formation rate of H 2 and the abundance variations of certain species from cloud to cloud

  17. Neutron stars

    International Nuclear Information System (INIS)

    Irvine, J.M.

    1978-01-01

    The subject is covered in chapters entitled: introduction (resume of stellar evolution, gross characteristics of neutron stars); pulsars (pulsar characteristics, pulsars as neutron stars); neutron star temperatures (neutron star cooling, superfluidity and superconductivity in neutron stars); the exterior of neutron stars (the magnetosphere, the neutron star 'atmosphere', pulses); neutron star structure; neutron star equations of state. (U.K.)

  18. QCD in the {delta}-regime

    Energy Technology Data Exchange (ETDEWEB)

    Bietenholz, W. [Universidad Nacional Autonoma de Mexico, Mexico City (Mexico). Inst. de Ciencias Nucleares; Cundy, N. [Seoul National Univ. (Korea, Republic of). Lattice Gauge Theory Research Center; Goeckeler, M. [Regensburg Univ. (Germany). Inst. fuer Theoretische Physik; Horsley, R.; Zanotti, J.M. [Edinburgh Univ. (United Kingdom). School of Physics; Nakamura, Y. [Tsukuba Univ., Ibaraki (Japan). Center for Computational Sciences; Pleiter, D. [Deutsches Elektronen-Synchrotron (DESY), Zeuthen (Germany); Rakow, P.E.L. [Liverpool Univ. (United Kingdom). Theoretical Physics Div.; Schierholz, G. [Regensburg Univ. (Germany). Inst. fuer Theoretische Physik; Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany)

    2011-03-15

    The {delta}-regime of QCD is characterised by light quarks in a small spatial box, but a large extent in (Euclidean) time. In this setting a specific variant of chiral perturbation theory - the {delta}-expansion - applies, based on a quantum mechanical treatment of the quasi onedimensional system. In particular, for vanishing quark masses one obtains a residual pion mass M{sup R}{sub {pi}}, which has been computed to the third order in the {delta}-expansion. A comparison with numerical measurements of this residual mass allows for a new determination of some Low Energy Constants, which appear in the chiral Lagrangian. We first review the attempts to simulate 2-flavour QCD directly in the {delta}-regime. This is very tedious, but results compatible with the predictions for M{sup R}{sub {pi}} have been obtained. Then we show that an extrapolation of pion masses measured in a larger volume towards the {delta}-regime leads to good agreement with the theoretical predictions. From those results, we also extract a value for the (controversial) sub-leading Low Energy Constant anti l{sub 3}. (orig.)

  19. Tidal controls on river delta morphology

    Science.gov (United States)

    Hoitink, A. J. F.; Wang, Z. B.; Vermeulen, B.; Huismans, Y.; Kästner, K.

    2017-09-01

    River delta degradation has been caused by extraction of natural resources, sediment retention by reservoirs, and sea-level rise. Despite global concerns about these issues, human activity in the world’s largest deltas intensifies. Harbour development, construction of flood defences, sand mining and land reclamation emerge as key contemporary factors that exert an impact on delta morphology. Tides interacting with river discharge can play a crucial role in the morphodynamic development of deltas under pressure. Emerging insights into tidal controls on river delta morphology suggest that--despite the active morphodynamics in tidal channels and mouth bar regions--tidal motion acts to stabilize delta morphology at the landscape scale under the condition that sediment import during low flows largely balances sediment export during high flows. Distributary channels subject to tides show lower migration rates and are less easily flooded by the river because of opposing non-linear interactions between river discharge and the tide. These interactions lead to flow changes within channels, and a more uniform distribution of discharge across channels. Sediment depletion and rigorous human interventions in deltas, including storm surge defence works, disrupt the dynamic morphological equilibrium and can lead to erosion and severe scour at the channel bed, even decades after an intervention.

  20. Delta Semantics Defined By Petri Nets

    DEFF Research Database (Denmark)

    Jensen, Kurt; Kyng, Morten; Madsen, Ole Lehrmann

    and the possibility of using predicates to specify state changes. In this paper a formal semantics for Delta is defined and analysed using Petri nets. Petri nets was chosen because the ideas behind Petri nets and Delta concide on several points. A number of proposals for changes in Delta, which resulted from...

  1. Pulsation of IU Per from the Ground-based and ‘Integral’ Photometry

    Directory of Open Access Journals (Sweden)

    Kundra E.

    2013-06-01

    Full Text Available IU Per is an eclipsing semi-detached binary with a pulsating component. Using our own ground-based, as well as INTEGRAL satellite photometric observations in the B and V passbands, we derived geometrical and physical parameters of this system. We detected the short-term variations of IU Per in the residuals of brightness after the subtraction of synthetic light curves. Analysis of these residuals enabled us to characterize and localize the source of short-term variations as the pulsations of the primary component typical to δ Scuti-type stars.

  2. Optimality and self-organization in river deltas

    Science.gov (United States)

    Tejedor, A.; Longjas, A.; Edmonds, D. A.; Zaliapin, I. V.; Georgiou, T. T.; Rinaldo, A.; Foufoula-Georgiou, E.

    2017-12-01

    Deltas are nourished by channel networks, whose connectivity constrains, if not drives, the evolution, functionality and resilience of these systems. Understanding the coevolution of deltaic channels and their flux organization is crucial for guiding maintenance strategies of these highly stressed systems from a range of anthropogenic activities. However, in contrast to tributary channel networks, to date, no theory has been proposed to explain how deltas self-organize to distribute water and sediment to the delta top and the shoreline. Here, we hypothesize the existence of an optimality principle underlying the self-organized partition of fluxes in delta channel networks. Specifically, we hypothesize that deltas distribute water and sediment fluxes on a given delta topology such as to maximize the diversity of flux delivery to the shoreline. By introducing the concept of nonlocal Entropy Rate (nER) and analyzing ten field deltas in diverse environments, we present evidence that supports our hypothesis, suggesting that delta networks achieve dynamically accessible maxima of their nER. Furthermore, by analyzing six simulated deltas using the Delf3D model and following their topologic and flux re-organization before and after major avulsions, we further study the evolution of nER and confirm our hypothesis. We discuss how optimal flux distributions in terms of nER, when interpreted in terms of resilience, are configurations that reflect an increased ability to withstand perturbations.

  3. Houtman Abrolhos Isotope (delta 18O, delta 13C) Data for 1795 to 1994

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — DESCRIPTION: VARIABLES AND UNITS: Column #1: core depth in mm Column #2: delta C-13 vs V-PDB Column #3: delta O-18 vs V-PDB Column #4: assigned date in years A.D....

  4. Delta infection evidenced by radioimmunoanalysis in selected collectives

    Energy Technology Data Exchange (ETDEWEB)

    Kselikova, M; Horejsi, J; Urbankova, J

    1987-01-01

    The presence of the Delta agent within the population was tested by means of the Delta-antibody radioimmunoassay using competitive kits of the firms ABBOTT (ABBOTT-ANTI-DELTA) and SORIN (AB-DELTAK). The Delta-antibody was found in 3.2% HBV patients, 5% HBsAg carriers, and in 20.8% of specific anti-Hbs-immunoglobulin. In hemophiliacs and blood donors no Delta-antibody was seen.

  5. Delta infection evidenced by radioimmunoanalysis in selected collectives

    International Nuclear Information System (INIS)

    Kselikova, M.; Horejsi, J.; Urbankova, J.

    1987-01-01

    The presence of the Delta agent within the population was tested by means of the Delta-antibody radioimmunoassay using competitive kits of the firms ABBOTT (ABBOTT-ANTI-DELTA) and SORIN (AB-DELTAK). The Delta-antibody was found in 3.2% HBV patients, 5% HBsAg carriers, and in 20.8% of specific anti-Hbs-immunoglobulin. In hemophiliacs and blood donors no Delta-antibody was seen. (author)

  6. Dermal absorption of the insecticide lindane (1 delta, 2 delta, 3 beta, 4 delta, 5 delta, 6 beta-hexachlorocyclohexane) in rats and rhesus monkeys: Effect of anatomical site

    International Nuclear Information System (INIS)

    Moody, R.P.; Ritter, L.

    1989-01-01

    Dermal absorption of the insecticide lindane (1 delta, 2 delta, 3 beta, 4 delta, 5 delta, 6 beta-hexachlorocyclohexane) was determined in rats and rhesus monkeys. Lindane is in widespread use as a 1% cream or lotion scabicide formulation and as a 1% miticide shampoo for body lice control in humans. Results obtained following our in vivo dermal absorption procedure demonstrated that 18 +/- 4.1%, 34 +/- 5.2%, and 54 +/- 26.3% of the applied dose was absorbed following topical applications at a rate of 1.5 micrograms/cm2 (6.2 micrograms/100 microliters of acetone) of the 14C-labeled pesticide to 4.2-cm2 regions of the forearm (n = 8), forehead (n = 7), and palm (n = 4) of rhesus monkeys, respectively. Dose sites were washed with soapy water 24 h posttreatment. Comparative studies in rats (n = 5) dosed middorsally demonstrated 31 +/- 9.5% absorption. Statistical analysis of the 14C excretion kinetics demonstrated slower clearance of lindane from rats than monkey forearm, forehead, or palm. Intramuscular (im) injections of 14C-lindane gave 52 +/- 7.1% recovery in monkey (n = 8) and 64 +/- 5.9% in rats (n = 5), suggesting body storage of this lipophilic chemical

  7. Determination of the positions and residues of the. delta. /sup + +/ and. delta. /sup 0/ poles. [Phase shifts,coulomb corrections

    Energy Technology Data Exchange (ETDEWEB)

    Vasan, S S [Carnegie-Mellon Univ., Pittsburgh, Pa. (USA). Dept. of Physics

    1976-04-19

    The poles and the associated residues in the ..pi..N P/sub 33/ amplitude corresponding to the resonances ..delta../sup + +/ and ..delta../sup 0/ are determined by fitting the ..pi../sup +/p and ..pi../sup -/p hadronic phase shifts from the Carter 73 analysis. The ..delta../sup + +/ and ..delta../sup 0/ pole positions are determined also from the nuclear phase shifts, these being the phase shifts made up of the hadronic phase shifts plus the Coulomb corrections. The pole positions obtained from the two sets of phase shifts are different, the differences being larger in the case of the ..delta../sup + +/.

  8. Neutron Star Science with the NuSTAR

    Energy Technology Data Exchange (ETDEWEB)

    Vogel, J. K. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)

    2015-10-16

    The Nuclear Spectroscopic Telescope Array (NuSTAR), launched in June 2012, helped scientists obtain for the first time a sensitive high-­energy X-­ray map of the sky with extraordinary resolution. This pioneering telescope has aided in the understanding of how stars explode and neutron stars are born. LLNL is a founding member of the NuSTAR project, with key personnel on its optics and science team. We used NuSTAR to observe and analyze the observations of different neutron star classes identified in the last decade that are still poorly understood. These studies not only help to comprehend newly discovered astrophysical phenomena and emission processes for members of the neutron star family, but also expand the utility of such observations for addressing broader questions in astrophysics and other physics disciplines. For example, neutron stars provide an excellent laboratory to study exotic and extreme phenomena, such as the equation of state of the densest matter known, the behavior of matter in extreme magnetic fields, and the effects of general relativity. At the same time, knowing their accurate populations has profound implications for understanding the life cycle of massive stars, star collapse, and overall galactic evolution.

  9. The Concentration Dependence of the (Delta)s Term in the Gibbs Free Energy Function: Application to Reversible Reactions in Biochemistry

    Science.gov (United States)

    Gary, Ronald K.

    2004-01-01

    The concentration dependence of (delta)S term in the Gibbs free energy function is described in relation to its application to reversible reactions in biochemistry. An intuitive and non-mathematical argument for the concentration dependence of the (delta)S term in the Gibbs free energy equation is derived and the applicability of the equation to…

  10. 78 FR 21491 - DeltaPoint Capital IV, L.P., DeltaPoint Capital IV (New York), L.P.; Notice Seeking Exemption...

    Science.gov (United States)

    2013-04-10

    ... SMALL BUSINESS ADMINISTRATION [License No. 02/02-0662, 02/02-0661] DeltaPoint Capital IV, L.P., DeltaPoint Capital IV (New York), L.P.; Notice Seeking Exemption Under Section 312 of the Small Business Investment Act, Conflicts of Interest Notice is hereby given that DeltaPoint Capital IV, L.P. and DeltaPoint...

  11. Mida pakub Delta? / Teele Kurm

    Index Scriptorium Estoniae

    Kurm, Teele

    2011-01-01

    Politsei- ja Piirivalveamet võtab kasutusele ühise Siseministeeriumi infotehnoloogia- ja arenduskeskuse ning Webmedia AS koostööna loodud dokumendihaldussüsteemi Delta. Kust sai Delta oma nime? Projekti "Dokumendihaldussüsteemi juurutamine Siseministeeriumi haldusalas" eesmärgid

  12. O stars and Wolf-Rayet stars

    International Nuclear Information System (INIS)

    Conti, P.S.; Underhill, A.B.; Jordan, S.; Thomas, R.

    1988-01-01

    Basic information is given about O and Wolf-Rayet stars indicating how these stars are defined and what their chief observable properties are. Part 2 of the volume discussed four related themes pertaining to the hottest and most luminous stars. Presented are: an observational overview of the spectroscopic classification and extrinsic properties of O and Wolf-Rayet stars; the intrinsic parameters of luminosity, effective temperature, mass, and composition of the stars, and a discussion of their viability; stellar wind properties; and the related issues concerning the efforts of stellar radiation and wind on the immediate interstellar environment are presented

  13. O stars and Wolf-Rayet stars

    Science.gov (United States)

    Conti, Peter S.; Underhill, Anne B.; Jordan, Stuart (Editor); Thomas, Richard (Editor)

    1988-01-01

    Basic information is given about O and Wolf-Rayet stars indicating how these stars are defined and what their chief observable properties are. Part 2 of the volume discussed four related themes pertaining to the hottest and most luminous stars. Presented are: an observational overview of the spectroscopic classification and extrinsic properties of O and Wolf-Rayet stars; the intrinsic parameters of luminosity, effective temperature, mass, and composition of the stars, and a discussion of their viability; stellar wind properties; and the related issues concerning the efforts of stellar radiation and wind on the immediate interstellar environment are presented.

  14. Changes in the areal extents of the Athabasca River, Birch River, and Cree Creek Deltas, 1950-2014, Peace-Athabasca Delta, Canada

    Science.gov (United States)

    Timoney, Kevin; Lee, Peter

    2016-04-01

    Deltas form where riverborne sediment accumulates at the interface of river mouths and their receiving water bodies. Their areal extent is determined by the net effect of processes that increase their extent, such as sediment accumulation, and processes that decrease their extent, such as erosion and subsidence. Through sequential mapping and construction of river discharge and sediment histories, this study examined changes in the subaerial extents of the Cree Creek and Athabasca River Deltas (both on the Athabasca River system) and the Birch River Delta in northern Canada over the period 1950-2014. The purpose of the study was to determine how, when, and why the deltas changed in areal extent. Temporal growth patterns were similar across the Athabasca and Birch River systems indicative of a climatic signal. Little or no areal growth occurred from 1950 to 1968; moderate growth occurred between 1968 and the early to mid-1980s; and rapid growth occurred between 1992 and 2012. Factors that affected delta progradation included dredging, sediment supply, isostatic drowning, delta front bathymetry, sediment capture efficiency, and storms. In relation to sediment delivered, areal growth rates were lowest in the Athabasca Delta, intermediate in the Birch Delta, and highest in the Cree Creek Delta. Annual sediment delivery is increasing in the Cree Creek Delta; there were no significant trends in annual sediment delivery in the Birch and Athabasca Deltas. There was a lag of up to several years between sediment delivery events and progradation. Periods of delta progradation were associated with low water levels of the receiving basins. Predicted climate-change driven declines in river discharge and lake levels may accelerate delta progradation in the region. In the changing ecosystems of northeastern Alberta, inadequate monitoring of vegetation, landforms, and sediment regimes hampers the elucidation of the nature, rate, and causality of ecosystem changes.

  15. An analytical framework for strategic delta planning

    NARCIS (Netherlands)

    Seijger, C.; Douven, W.; Halsema, van G.; Hermans, L.; Evers, J.; Phi, H.L.; Khan, M.F.; Brunner, J.; Pols, L.; Ligtvoet, W.; Koole, S.; Slager, K.; Vermoolen, M.S.; Hasan, S.; Thi Minh Hoang, Vo

    2017-01-01

    Sectoral planning on water, agriculture and urban development has not been able to prevent increased flood risks and environmental degradation in many deltas. Governments conceive strategic delta planning as a promising planning approach and develop strategic delta plans. Such plans are linked to

  16. A robust star identification algorithm with star shortlisting

    Science.gov (United States)

    Mehta, Deval Samirbhai; Chen, Shoushun; Low, Kay Soon

    2018-05-01

    A star tracker provides the most accurate attitude solution in terms of arc seconds compared to the other existing attitude sensors. When no prior attitude information is available, it operates in "Lost-In-Space (LIS)" mode. Star pattern recognition, also known as star identification algorithm, forms the most crucial part of a star tracker in the LIS mode. Recognition reliability and speed are the two most important parameters of a star pattern recognition technique. In this paper, a novel star identification algorithm with star ID shortlisting is proposed. Firstly, the star IDs are shortlisted based on worst-case patch mismatch, and later stars are identified in the image by an initial match confirmed with a running sequential angular match technique. The proposed idea is tested on 16,200 simulated star images having magnitude uncertainty, noise stars, positional deviation, and varying size of the field of view. The proposed idea is also benchmarked with the state-of-the-art star pattern recognition techniques. Finally, the real-time performance of the proposed technique is tested on the 3104 real star images captured by a star tracker SST-20S currently mounted on a satellite. The proposed technique can achieve an identification accuracy of 98% and takes only 8.2 ms for identification on real images. Simulation and real-time results depict that the proposed technique is highly robust and achieves a high speed of identification suitable for actual space applications.

  17. Star-Branched Polymers (Star Polymers)

    KAUST Repository

    Hirao, Akira

    2015-09-01

    The synthesis of well-defined regular and asymmetric mixed arm (hereinafter miktoarm) star-branched polymers by the living anionic polymerization is reviewed in this chapter. In particular, much attention is being devoted to the synthetic development of miktoarm star polymers since 2000. At the present time, the almost all types of multiarmed and multicomponent miktoarm star polymers have become feasible by using recently developed iterative strategy. For example, the following well-defined stars have been successfully synthesized: 3-arm ABC, 4-arm ABCD, 5-arm ABCDE, 6-arm ABCDEF, 7-arm ABCDEFG, 6-arm ABC, 9-arm ABC, 12-arm ABC, 13-arm ABCD, 9-arm AB, 17-arm AB, 33-arm AB, 7-arm ABC, 15-arm ABCD, and 31-arm ABCDE miktoarm star polymers, most of which are quite new and difficult to synthesize by the end of the 1990s. Several new specialty functional star polymers composed of vinyl polymer segments and rigid rodlike poly(acetylene) arms, helical polypeptide, or helical poly(hexyl isocyanate) arms are introduced.

  18. Spatio-temporal distributions of delta18O, delta D and salinity in the Arabian Sea: Identifying processes and controls

    Digital Repository Service at National Institute of Oceanography (India)

    Deshpande, R.D; Muraleedharan, P.M.; Singh, R.L.; Kumar, B.; Rao, M.S.; Dave, M.; Sivakumar, K.U.; Gupta, S.K.

    the geographic distributions of the delta18O and S; (2) in spite of a large scatter, a statistically significant delta18O–S relationship can be identified in much of the investigated part of the AS; (3) the delta18Odelta...

  19. Statistical investigation of flare stars. III. Flare stars in the general galactic star field

    International Nuclear Information System (INIS)

    Mirzoyan, L.V.; Ambaryan, V.V.; Garibdzhanyan, A.T.; Mirzoyan, A.L.

    1989-01-01

    Some questions relating to the existence of a large number of flare stars in the general star field of the Galaxy are discussed. It is shown that only a small proportion of them can be found by photographic observations, and the fraction of field flare stars among such stars found in the regions of star clusters and associations does not exceed 10%. The ratio of the numbers of flare stars of the foreground and the background for a particular system depends on its distance, reaching zero at a distance of about 500 pc. The spatial density of flare stars in the Pleiades is at least two orders of magnitude greater than in the general galactic field. A lower limit for the number of flare stars in the Galaxy is estimated at 4.2 ·10 9 , and the number of nonflare red dwarfs at 2.1·10 10 . There are grounds for believing that they were all formed in star clusters and associations

  20. Neutron star/red giant encounters in globular clusters

    International Nuclear Information System (INIS)

    Bailyn, C.D.

    1988-01-01

    The author presents a simple expression for the amount by which xsub(crit) is diminished as a star evolves xsub(crit) Rsub(crit)/R*, where Rsub(crit) is the maximum distance of closest approach between two stars for which the tidal energy is sufficient to bind the system, and R* is the radius of the star on which tides are being raised. Also it is concluded that tidal capture of giants by neutron stars resulting in binary systems is unlikely in globular clusters. However, collisions between neutron stars and red giants, or an alternative process involving tidal capture of a main-sequence star into an initially detached binary system, may result either in rapidly rotating neutron stars or in white dwarf/neutron star binaries. (author)

  1. Symbiotic stars

    International Nuclear Information System (INIS)

    Boyarchuk, A.A.

    1975-01-01

    There are some arguments that the symbiotic stars are binary, where one component is a red giant and the other component is a small hot star which is exciting a nebula. The symbiotic stars belong to the old disc population. Probably, symbiotic stars are just such an evolutionary stage for double stars as planetary nebulae for single stars. (Auth.)

  2. Adaptive Delta Management: cultural aspects of dealing with uncertainty

    Science.gov (United States)

    Timmermans, Jos; Haasnoot, Marjolijn; Hermans, Leon; Kwakkel, Jan

    2016-04-01

    Deltas are generally recognized as vulnerable to climate change and therefore a salient topic in adaptation science. Deltas are also highly dynamic systems viewed from physical (erosion, sedimentation, subsidence), social (demographic), economic (trade), infrastructures (transport, energy, metropolization) and cultural (multi-ethnic) perspectives. This multi-faceted dynamic character of delta areas warrants the emergence of a branch of applied adaptation science, Adaptive Delta Management, which explicitly focuses on climate adaptation of such highly dynamic and deeply uncertain systems. The application of Adaptive Delta Management in the Dutch Delta Program and its active international dissemination by Dutch professionals results in the rapid dissemination of Adaptive Delta Management to deltas worldwide. This global dissemination raises concerns among professionals in delta management on its applicability in deltas with cultural conditions and historical developments quite different from those found in the Netherlands and the United Kingdom where the practices now labelled as Adaptive Delta Management first emerged. This research develops an approach and gives a first analysis of the interaction between the characteristics of different approaches in Adaptive Delta Management and their alignment with the cultural conditions encountered in various delta's globally. In this analysis, first different management theories underlying approaches to Adaptive Delta Management as encountered in both scientific and professional publications are identified and characterized on three dimensions: The characteristics dimensions used are: orientation on today, orientation on the future, and decision making (Timmermans, 2015). The different underlying management theories encountered are policy analysis, strategic management, transition management, and adaptive management. These four management theories underlying different approaches in Adaptive Delta Management are connected to

  3. Complex rearrangements within the human J delta-C delta/J alpha-C alpha locus and aberrant recombination between J alpha segments

    NARCIS (Netherlands)

    Baer, R.; Boehm, T.; Yssel, H.; Spits, H.; Rabbitts, T. H.

    1988-01-01

    We have examined DNA rearrangements within a 120 kb cloned region of the human T cell receptor J delta-C delta/J alpha-C alpha locus. Three types of pattern emerge from an analysis of T cell lines and clones. Firstly, cells with two rearrangements within J delta-C delta; secondly, cells with one

  4. Quark core stars, quark stars and strange stars

    International Nuclear Information System (INIS)

    Grassi, F.

    1988-01-01

    A recent one flavor quark matter equation of state is generalized to several flavors. It is shown that quarks undergo a first order phase transition. In addition, this equation of state depends on just one parameter in the two flavor case, two parameters in the three flavor case, and these parameters are constrained by phenomenology. This equation of state is then applied to the hadron-quark transition in neutron stars and the determination of quark star stability, the investigation of strange matter stability and possible strange star existence. 43 refs., 6 figs

  5. Sediment and Vegetation Controls on Delta Channel Networks

    Science.gov (United States)

    Lauzon, R.; Murray, A. B.; Piliouras, A.; Kim, W.

    2016-12-01

    Numerous factors control the patterns of distributary channels formed on a delta, including water and sediment discharge, grain size, sea level rise rates, and vegetation type. In turn, these channel networks influence the shape and evolution of a delta, including what types of plant and animal life - such as humans - it can support. Previous fluvial modeling and flume experiments, outside of the delta context, have addressed how interactions between sediment and vegetation, through their influence on lateral transport of sediment, determine what type of channel networks develops. Similar interactions likely also shape delta flow patterns. Vegetation introduces cohesion, tending to reduce channel migration rates and strengthen existing channel banks, reinforcing existing channels and resulting in localized, relatively stable flow patterns. On the other hand, sediment transport processes can result in lateral migration and frequent switching of active channels, resulting in flow resembling that of a braided stream. While previous studies of deltas have indirectly explored the effects of vegetation through the introduction of cohesive sediment, we directly incorporate key effects of vegetation on flow and sediment transport into the delta-building model DeltaRCM to explore how these effects influence delta channel network formation. Model development is informed by laboratory flume experiments at UT Austin. Here we present initial results of experiments exploring the effects of sea level rise rate, sediment grain size, vegetation type, and vegetation growth rate on delta channel network morphology. These results support the hypothesis that the ability for lateral transport of sediment to occur plays a key role in determining the evolution of delta channel networks and delta morphology.

  6. Kinematic and spatial distributions of barium stars - are the barium stars and Am stars related?

    International Nuclear Information System (INIS)

    Hakkila, J.

    1989-01-01

    The possibility of an evolutionary link between Am stars and barium stars is considered, and an examination of previous data suggests that barium star precursors are main-sequence stars of intermediate mass, are most likely A and/or F dwarfs, and are intermediate-mass binaries with close to intermediate orbital separations. The possible role of mass transfer in the later development of Am systems is explored. Mass transfer and loss from systems with a range of masses and orbital separations may explain such statistical peculiarities of barium stars as the large dispersion in absolute magnitude, the large range of elemental abundances from star to star, and the small number of stars with large peculiar velocities. 93 refs

  7. The effect of tides on self-driven stellar pulsations

    Science.gov (United States)

    Balona, L. A.

    2018-06-01

    In addition to rotation, a tidal force in a binary introduces another axis of symmetry joining the two centres of mass. If the stars are in circular orbit and synchronous rotation, a pulsation with spherical harmonic degree l is split into l + 1 frequencies. In the observer's frame of reference, these in turn are further split into equidistant frequencies spaced by multiples of the orbital frequency. In the periodogram of a pulsating star, tidal action can be seen as low-amplitude equidistant splitting of each oscillation mode which are not harmonics of the orbital frequency. This effect is illustrated using Kepler observations of the heartbeat variable, KIC 4142768, which is also a δ Scuti star. Even though the theory is only applicable to circular orbits, the expected equidistant splitting is clearly seen in all four of the highest amplitude modes. This results in amplitude variability of each pulsation mode with a period equal to the orbital period.

  8. Perspectives on bay-delta science and policy

    Science.gov (United States)

    Healey, Michael; Dettinger, Michael; Norgaard, Richard

    2016-01-01

    The State of Bay–Delta Science 2008 highlighted seven emerging perspectives on science and management of the Delta. These perspectives had important effects on policy and legislation concerning management of the Delta ecosystem and water exports. From the collection of papers that make up the State of Bay–Delta Science 2016, we derive another seven perspectives that augment those published in 2008. The new perspectives address nutrient and contaminant concentrations in Delta waters, the failure of the Delta food web to support native species, the role of multiple stressors in driving species toward extinction, and the emerging importance of extreme events in driving change in the ecosystem and the water supply. The scientific advances that underpin these new perspectives were made possible by new measurement and analytic tools. We briefly discuss some of these, including miniaturized acoustic fish tags, sensors for monitoring of water quality, analytic techniques for disaggregating complex contaminant mixtures, remote sensing to assess levee vulnerability, and multidimensional hydrodynamic modeling. Despite these new tools and scientific insights, species conservation objectives for the Delta are not being met. We believe that this lack of progress stems in part from the fact that science and policy do not incorporate sufficiently long-term perspectives. Looking forward half a century was central to the Delta Visioning process, but science and policy have not embraced this conceptual breadth. We are also concerned that protection and enhancement of the unique cultural, recreational, natural resource, and agricultural values of the Delta as an evolving place, as required by the Delta Reform Act, has received no critical study and analysis. Adopting wider and longer science and policy perspectives immediately encourages recognition of the need for evaluation, analysis, and public discourse on novel conservation approaches. These longer and wider perspectives

  9. Perspectives on Bay–Delta Science and Policy

    Directory of Open Access Journals (Sweden)

    Michael Healey

    2016-12-01

    Full Text Available doi: https://doi.org/10.15447/sfews.2016v14iss4art6The State of Bay–Delta Science 2008 highlighted seven emerging perspectives on science and management of the Delta. These perspectives had important effects on policy and legislation concerning management of the Delta ecosystem and water exports. From the collection of papers that make up the State of Bay–Delta Science 2016, we derive another seven perspectives that augment those published in 2008. The new perspectives address nutrient and contaminant concentrations in Delta waters, the failure of the Delta food web to support native species, the role of multiple stressors in driving species toward extinction, and the emerging importance of extreme events in driving change in the ecosystem and the water supply. The scientific advances that underpin these new perspectives were made possible by new measurement and analytic tools. We briefly discuss some of these, including miniaturized acoustic fish tags, sensors for monitoring of water quality, analytic techniques for disaggregating complex contaminant mixtures, remote sensing to assess levee vulnerability, and multidimensional hydrodynamic modeling. Despite these new tools and scientific insights, species conservation objectives for the Delta are not being met. We believe that this lack of progress stems in part from the fact that science and policy do not incorporate sufficiently long-term perspectives. Looking forward half a century was central to the Delta Visioning process, but science and policy have not embraced this conceptual breadth. We are also concerned that protection and enhancement of the unique cultural, recreational, natural resource, and agricultural values of the Delta as an evolving place, as required by the Delta Reform Act, has received no critical study and analysis. Adopting wider and longer science and policy perspectives immediately encourages recognition of the need for evaluation, analysis, and public discourse on

  10. Expansion in higher harmonics of boson stars using a generalized Ruffini-Bonazzola approach. Part 1. Bound states

    Energy Technology Data Exchange (ETDEWEB)

    Eby, Joshua; Suranyi, Peter; Wijewardhana, L. C. R.

    2018-04-01

    The method pioneered by Ruffini and Bonazzola (RB) to describe boson stars involves an expansion of the boson field which is linear in creation and annihilation operators. This expansion constitutes an exact solution to a non-interacting field theory, and has been used as a reasonable ansatz for an interacting one. In this work, we show how one can go beyond the RB ansatz towards an exact solution of the interacting operator Klein-Gordon equation, which can be solved iteratively to ever higher precision. Our Generalized Ruffini-Bonazzola approach takes into account contributions from nontrivial harmonic dependence of the wavefunction, using a sum of terms with energy $k\\,E_0$, where $k\\geq1$ and $E_0$ is the chemical potential of a single bound axion. The method critically depends on an expansion in a parameter $\\Delta \\equiv \\sqrt{1-E_0{}^2/m^2}<1$, where $m$ is the mass of the boson. In the case of the axion potential, we calculate corrections which are relevant for axion stars in the transition or dense branches. We find with high precision the local minimum of the mass, $M_{min}\\approx 463\\,f^2/m$, at $\\Delta\\approx0.27$, where $f$ is the axion decay constant. This point marks the crossover from transition to dense branches of solutions, and a corresponding crossover from structural instability to stability.

  11. Late quaternary evolution of the Orinoco Delta, Venezuela

    Science.gov (United States)

    Warne, A.G.; Guevara, E.H.; Aslan, A.

    2002-01-01

    The modern Orinoco Delta is the latest of a series of stacked deltas that have infilled the Eastern Venezuelan Basin (EVB) since the Oligocene. During the late Pleistocene sea-level lowstand (20,000 to 16,000 yrs BP), bedrock control points at the position of the present delta apex prevented the river channel from incising as deeply as many other major river systems. Shallow seismic data indicate that the late Pleistocene Orinoco incised into the present continental shelf, where it formed a braided-river complex that transported sediment to a series of shelf-edge deltas. As sea level rose from 16,000 to 9,500 yrs BP, the Orinoco shoreline shifted rapidly landward, causing shallow-marine waves and currents to form a widespread transgressive sand unit. Decelerating sea-level rise and a warmer, wetter climate during the early Holocene (9,500 to 6,000 yrs BP) induced delta development within the relatively quiet-water environment of the EVB embayment. Sea level approached its present stand in the middle Holocene (6,000 to 3,000 yrs BP), and the Orinoco coast prograded, broadening the delta plain and infilling the EVB embayment. Significant quantities of Amazon sediment began to be transported to the Orinoco coast by littoral currents. Continued progradation in the late Holocene caused the constriction at Boca de Serpientes to alter nearshore and shelf hydrodynamics and subdivide the submarine delta into two distinct areas: the Atlantic shelf and the Gulf of Paria. The increased influence of littoral currents along the coast promoted mudcape development. Because most of the water and sediment were transported across the delta plain through the Rio Grande distributary in the southern delta, much of the central and northwestern delta plain became sediment starved, promoting widespread accumulation of peat deposits. Human impacts on the delta are mostly associated with the Volca??n Dam on Can??o Manamo. However, human activities have had relatively little effect on the

  12. Water and nitrogen conditions affect the relationships of Delta13C and Delta18O to gas exchange and growth in durum wheat.

    Science.gov (United States)

    Cabrera-Bosquet, Llorenç; Molero, Gemma; Nogués, Salvador; Araus, José Luis

    2009-01-01

    Whereas the effects of water and nitrogen (N) on plant Delta(13)C have been reported previously, these factors have scarcely been studied for Delta(18)O. Here the combined effect of different water and N regimes on Delta(13)C, Delta(18)O, gas exchange, water-use efficiency (WUE), and growth of four genotypes of durum wheat [Triticum turgidum L. ssp. durum (Desf.) Husn.] cultured in pots was studied. Water and N supply significantly increased plant growth. However, a reduction in water supply did not lead to a significant decrease in gas exchange parameters, and consequently Delta(13)C was only slightly modified by water input. Conversely, N fertilizer significantly decreased Delta(13)C. On the other hand, water supply decreased Delta(18)O values, whereas N did not affect this parameter. Delta(18)O variation was mainly determined by the amount of transpired water throughout plant growth (T(cum)), whereas Delta(13)C variation was explained in part by a combination of leaf N and stomatal conductance (g(s)). Even though the four genotypes showed significant differences in cumulative transpiration rates and biomass, this was not translated into significant differences in Delta(18)O(s). However, genotypic differences in Delta(13)C were observed. Moreover, approximately 80% of the variation in biomass across growing conditions and genotypes was explained by a combination of both isotopes, with Delta(18)O alone accounting for approximately 50%. This illustrates the usefulness of combining Delta(18)O and Delta(13)C in order to assess differences in plant growth and total transpiration, and also to provide a time-integrated record of the photosynthetic and evaporative performance of the plant during the course of crop growth.

  13. Initial isotopic geochemistry ({delta} 18 O, {delta} D) of fluids from wells of the Los Humeros, Pue., geothermal field; Geoquimica isotopica ({delta} 18 O, {delta} D) inicial de fluidos de pozos del campo geotermico de Los Humeros, Pue.

    Energy Technology Data Exchange (ETDEWEB)

    Barragan Reyes, Rosa Maria; Arellano Gomez, Victor Manuel [Instituto de Investigaciones Electricas, Gerencia de Geotermia, Cuernavaca, Morelos (Mexico)]. E-mail: rmb@iie.org.mx; Ramirez Montes, Miguel; Tovar Aguado, Rigoberto [Comision Federal de Electricidad, Gerencia de Proyectos Geotermoelectricos, Morelia, Michoacan (Mexico)

    2010-01-15

    Isotopic data ({delta} 18 O, {delta} D) from fluids from production wells at the Los Humeros, Pue., geothermal field were analyzed to investigate the possible origin of these fluids and the dominant processes of the reservoir at its initial state. According to pre-exploitation data, it is suggested the Los Humeros reservoir fluids are made of a mixture of meteoric water of very light isotopic composition (paleo-fluids) and andesitic water. The relationship {delta} D vs {delta} 18 O from pre-exploitation data indicates the produced fluids are composed of a mixture of (at least) two fluids with distinct isotopic compositions. At the more enriched end of the mixing relationship are the isotopic compositions of the wells H-23 and H-18 (located in the southern area of the field), while the lighter fluids were found in well H-16 (originally) and then in well H-16 (repaired). It was found that the liquid phases of deep wells are more enriched in {delta} 18 O while the shallow wells present lower values, suggesting a convection process at the initial state. Based on this isotopic profile, it is considered that even the production depths of the wells H-1, H-12 and H-16 (repaired) are just about the same, but their respective isotopic compositions are quite different. The {delta} 18 O value for well H-16 (repaired) seems to be that of condensate steam, while the corresponding values for wells H-1 and H-12 fall within the value interval of the deep wells (H-23). This suggests wells H-1 and H-12 are collecting very deep fluids enriched in {delta} 18 O. These results could be useful in creating a conceptual model of the reservoir. [Spanish] Se analizaron datos isotopicos ({delta}18 O, {delta}D) de los fluidos de pozos productores del campo geotermico de Los Humeros, Pue., para investigar el posible origen de los fluidos asi como los procesos dominantes del yacimiento en su estado inicial. De acuerdo con datos previos a la explotacion, se plantea que los fluidos del yacimiento

  14. Conceptualizing delta forms and processes in Arctic coastal environments

    DEFF Research Database (Denmark)

    Bendixen, Mette; Kroon, Aart

    2017-01-01

    Climate warming in the Arctic directly causes two opposite changes in Arctic coastal systems: increased melt-water discharge through rivers induces extra influx of sediments and extended open water season increases wave impact which reworks and erodes the shores. A shoreline change analysis along...... and popped up as hotspots. The Tuapaat delta and Skansen delta showed large progradation rates (1.5 and 7m/yr) and migration of the adjacent barriers and spits. The dynamic behavior at the delta mouths was mainly caused by classic delta channel lobe switching at one delta (Tuapaat), and by a breach...... of the fringing spit at the other delta (Skansen). The longshore and cross-shore transports are responsible for reworking the sediment with a result of migrating delta mouths and adjacent subaqueous mouth bars. Seaward progradation of the deltas is limited due to the steep nature of the bathymetry in Disko Bay...

  15. Delta-ray spectroscopy of quasi-atoms

    International Nuclear Information System (INIS)

    Kozhuharov, C.

    1983-01-01

    The spectroscopy of high energy delta-rays, emitted in collisions of very heavy ions, is studied. The ''orange''-type beta-spectrometer and the achromatic electron channel are the experimental setups. Delta ray production probabilities are studied as a function of the distance of closest approach R /SUB min/ or the impact parameter b. Coulomb ionization, ion trajectory, scaling laws, double differential cross sections, and K-X-rays information is extracted from the experiment. The dependence of delta-ray emission on the united charge number Z /SUB u/ is discussed. Asymmetric collision systems with Z x alpha approx. = 1 (delta ray spectrum from Pb→Sn collisions) are studied. Finally, very heavy collisions, such as 208 Pb + 208 Pb collisions at bombarding energy fas below the Coulomb barrier are touched upon

  16. Multimode delta-E effect magnetic field sensors with adapted electrodes

    Energy Technology Data Exchange (ETDEWEB)

    Zabel, Sebastian; Fichtner, Simon; Kirchhof, Christine; Quandt, Eckhard; Faupel, Franz, E-mail: ff@tf.uni-kiel.de [Faculty of Engineering, Institute for Materials Science, Kiel University, Kaiserstraße 2, 24143 Kiel (Germany); Reermann, Jens; Schmidt, Gerhard [Faculty of Engineering, Institute for Electrical Engineering, Kiel University, Kaiserstraße 2, 24143 Kiel (Germany); Wagner, Bernhard [Fraunhofer Institute for Silicon Technology ISIT, Fraunhoferstraße 1, 25524 Itzehoe (Germany)

    2016-05-30

    We present an analytical and experimental study on low-noise piezoelectric thin film resonators that utilize the delta-E effect of a magnetostrictive layer to measure magnetic fields at low frequencies. Calculations from a physical model of the electromechanical resonator enable electrode designs to efficiently operate in the first and second transversal bending modes. As predicted by our calculations, the adapted electrode design improves the sensitivity by a factor of 6 and reduces the dynamic range of the sensor output by 16 dB, which significantly eases the requirements on readout electronics. Magnetic measurements show a bandwidth of 100 Hz at a noise level of about 100 pTHz{sup −0.5}.

  17. Adaptive delta management : Roots and branches

    NARCIS (Netherlands)

    Timmermans, J.S.; Haasnoot, M.; Hermans, L.M.; Kwakkel, J.H.; Rutten, M.M.; Thissen, W.A.H.

    2015-01-01

    Deltas are generally recognized as vulnerable to climate change and therefore a salient topic in adaptation science. Deltas are also highly dynamic systems viewed from physical (erosion, sedimentation, subsidence), social (demographic), economic (trade), infrastructures (transport, energy,

  18. Adaptive Delta Management : Roots and Branches

    NARCIS (Netherlands)

    Timmermans, Jos; Haasnoot, Marjolijn; Hermans, Leon; Kwakkel, Jan H.; Rutten, Maarten; Thissen, Wil A.H.; Mynett, Arthur

    2015-01-01

    Deltas are generally recognized as vulnerable to climate change and therefore a salient topic in adaptation science. Deltas are also highly dynamic systems viewed from physical (erosion, sedimentation, subsidence), social (demographic), economic (trade), infrastructures (transport, energy,

  19. The dynamics of central Main Ethiopian Rift waters: Evidence from {delta}D, {delta}{sup 18}O and {sup 87}Sr/{sup 86}Sr ratios

    Energy Technology Data Exchange (ETDEWEB)

    Rango, Tewodros, E-mail: tewodros.godebo@duke.edu [Division of Earth and Ocean Sciences, Nicholas School of the Environment, Duke University, Durham, NC 27708 (United States)] [Addis Ababa University, Department of Earth Sciences, P.O. Box 1176, Addis Ababa (Ethiopia); Petrini, Riccardo; Stenni, Barbara [University of Trieste, Department of Geosciences, Via Weiss 1, I-34100 Trieste (Italy); Bianchini, Gianluca [Istituto di Geoscienze e Georisorse-CNR, Pisa (Italy)] [Department of Earth Sciences, University of Ferrara, Via Saragat 1, 44100 Ferrara (Italy); Slejko, Francesca [University of Trieste, Department of Geosciences, Via Weiss 1, I-34100 Trieste (Italy); Beccaluva, Luigi [Department of Earth Sciences, University of Ferrara, Via Saragat 1, 44100 Ferrara (Italy); Ayenew, Tenalem [Addis Ababa University, Department of Earth Sciences, P.O. Box 1176, Addis Ababa (Ethiopia)

    2010-12-15

    Research highlights: {yields} Chemical and isotope ({delta}D, {delta}{sup 18}O and {sup 87}Sr/{sup 86}Sr) techniques are applied to understand various hydrological processes in the Main Ethiopian Rift. {yields} Some of the studied groundwaters display a depleted {delta}D-{delta}{sup 18}O composition when compared to the present-day average precipitation, thus suggesting that the rift floor aquifers also contains paleo-meteoric waters recharge associated with deep flow system. {yields} The pristine waters coming from the highlands display isotopic compositions characterized by less radiogenic {sup 87}Sr/{sup 86}Sr (and more depleted {delta}D, {delta}{sup 18}O). This isotopic signature subsequently evolves towards higher {sup 87}Sr/{sup 86}Sr by an interaction with the more radiogenic rhyolites of the rift and their weathered and redeposited products. - Abstract: Water samples from cold and geothermal boreholes, hot springs, lakes and rivers were analyzed for {delta}D, {delta}{sup 18}O and {sup 87}Sr/{sup 86}Sr compositions in order to investigate lake water-groundwater mixing processes, water-rock interactions, and to evaluate groundwater flow paths in the central Main Ethiopian Rift (MER) of the Ziway-Shala basin. Different ranges of isotopic values were recorded for different water types: hot springs show {delta}{sup 18}O -3.36 to +3.69 and {delta}D -15.85 to +24.23, deep Aluto-Langano geothermal wells show {delta}{sup 18}O -4.65 to -1.24 and {delta}D -12.39 to -9.31, groundwater wells show {delta}{sup 18}O -3.99 to +5.14 and {delta}D -19.69 to +32.27, whereas the lakes show {delta}{sup 18}O and {delta}D in the range +3.98 to +7.92 and +26.19 to +45.71, respectively. The intersection of the Local Meteoric Water Line (LMWL: {delta}D = 7 {delta}{sup 18}O + 11.2, R{sup 2} = 0.94, n = 42) and the Local Evaporation Line (LEL: {delta}D = 5.63{delta}{sup 18}O + 8, n = 14, R{sup 2} = 0.82) was used to estimate the average isotopic composition of recharge water into the

  20. delta 6 Hexadecenoic acid is synthesized by the activity of a soluble delta 6 palmitoyl-acyl carrier protein desaturase in Thunbergia alata endosperm.

    Science.gov (United States)

    Cahoon, E B; Cranmer, A M; Shanklin, J; Ohlrogge, J B

    1994-11-04

    delta 6 Hexadecenoic acid (16:1 delta 6) composes more than 80% of the seed oil of Thunbergia alata. Studies were conducted to determine the biosynthetic origin of the double bond of this unusual fatty acid. Assays of fractions of developing T. alata seed endosperm with [1-14C]palmitoyl (16:0)-acyl carrier protein (ACP) revealed the presence of a soluble delta 6 desaturase activity. This activity was greatest when 16:0-ACP was provided as a substrate, whereas no desaturation of the coenzyme A ester of this fatty acid was detected. In addition, delta 6 16:0-ACP desaturase activity in T. alata endosperm extracts was dependent on the presence of ferredoxin and molecular oxygen and was stimulated by catalase. To further characterize this enzyme, a cDNA encoding a diverged acyl-ACP desaturase was isolated from a T. alata endosperm cDNA library using polymerase chain reaction with degenerate oligonucleotides corresponding to conserved amino acid sequences in delta 9 stearoyl (18:0)- and delta 4 16:0-ACP desaturases. The primary structure of the mature peptide encoded by this cDNA shares 66% identity with the mature castor delta 9 18:0-ACP desaturase and 57% identity with the mature coriander delta 4 16:0-ACP desaturase. Extracts of Escherichia coli that express the T. alata cDNA catalyzed the delta 6 desaturation of 16:0-ACP. These results demonstrate that 16:1 delta 6 in T. alata endosperm is formed by the activity of a soluble delta 6 16:0-ACP desaturase that is structurally related to the delta 9 18:0- and delta 4 16:0-ACP desaturases. Implications of this work to an understanding of active site structures of acyl-ACP desaturases are discussed.

  1. THE APACHE POINT OBSERVATORY GALACTIC EVOLUTION EXPERIMENT: FIRST DETECTION OF HIGH-VELOCITY MILKY WAY BAR STARS

    Energy Technology Data Exchange (ETDEWEB)

    Nidever, David L.; Zasowski, Gail; Majewski, Steven R.; Beaton, Rachael L.; Wilson, John C.; Skrutskie, Michael F.; O' Connell, Robert W. [Department of Astronomy, University of Virginia, Charlottesville, VA 22904-4325 (United States); Bird, Jonathan; Schoenrich, Ralph; Johnson, Jennifer A.; Sellgren, Kris [Department of Astronomy and the Center for Cosmology and Astro-Particle Physics, The Ohio State University, Columbus, OH 43210 (United States); Robin, Annie C.; Schultheis, Mathias [Institut Utinam, CNRS UMR 6213, OSU THETA, Universite de Franche-Comte, 41bis avenue de l' Observatoire, F-25000 Besancon (France); Martinez-Valpuesta, Inma; Gerhard, Ortwin [Max-Planck-Institut fuer Extraterrestrische Physik, Giessenbachstrasse, D-85748 Garching (Germany); Shetrone, Matthew [McDonald Observatory, University of Texas at Austin, Fort Davis, TX 79734 (United States); Schiavon, Ricardo P. [Gemini Observatory, 670 North A' Ohoku Place, Hilo, HI 96720 (United States); Weiner, Benjamin [Steward Observatory, 933 North Cherry Street, University of Arizona, Tucson, AZ 85721 (United States); Schneider, Donald P. [Department of Astronomy and Astrophysics, The Pennsylvania State University, University Park, PA 16802 (United States); Allende Prieto, Carlos, E-mail: dln5q@virginia.edu [Instituto de Astrofisica de Canarias, E-38205 La Laguna, Tenerife (Spain); and others

    2012-08-20

    Commissioning observations with the Apache Point Observatory Galactic Evolution Experiment (APOGEE), part of the Sloan Digital Sky Survey III, have produced radial velocities (RVs) for {approx}4700 K/M-giant stars in the Milky Way (MW) bulge. These high-resolution (R {approx} 22, 500), high-S/N (>100 per resolution element), near-infrared (NIR; 1.51-1.70 {mu}m) spectra provide accurate RVs ({epsilon}{sub V} {approx} 0.2 km s{sup -1}) for the sample of stars in 18 Galactic bulge fields spanning -1 Degree-Sign delta} > -32 Degree-Sign . This represents the largest NIR high-resolution spectroscopic sample of giant stars ever assembled in this region of the Galaxy. A cold ({sigma}{sub V} {approx} 30 km s{sup -1}), high-velocity peak (V{sub GSR} Almost-Equal-To +200 km s{sup -1}) is found to comprise a significant fraction ({approx}10%) of stars in many of these fields. These high RVs have not been detected in previous MW surveys and are not expected for a simple, circularly rotating disk. Preliminary distance estimates rule out an origin from the background Sagittarius tidal stream or a new stream in the MW disk. Comparison to various Galactic models suggests that these high RVs are best explained by stars in orbits of the Galactic bar potential, although some observational features remain unexplained.

  2. Multiple stellar generations in the Large Magellanic Cloud Star Cluster NGC 1846

    Science.gov (United States)

    Milone, Antonino

    2010-09-01

    The recent discovery of multiple stellar populations in massive Galactic globular clusters poses a serious challenge for models of star cluster formation and evolution. The finding of multiple main sequences in the massive clusters NGC 2808 and omega Centauri, and multiple sub-giant-branch in NGC 1851 and many other globulars have demonstrated that star clusters are not as simple as we have imagined for decades. Surprisingly the only way to explain the main sequence splitting appears to be Helium enrichment, up to an astonishingly high Y 0.40.An unique angle on this problem can be provided by intermediate-age clusters in the Magellanic Clouds with peculiar main-sequence turn-off morphologies. Recent discoveries, based on ACS data of unparalleled photometric accuracy, have demonstrated that the CMDs of a large fraction of these clusters { 70 %} are not consistent with the simple, single stellar population hypothesis. Explanations for what conditions could give rise to multiple populations in Galactic Globular Clusters remain controversial; this is even more the case for LMC clustersTo properly constraint the multipopulation phenomenon in Magellanic Cloud star clusters, we propose deep UV/IR imaging of NGC 1846, a star cluster where multiple populations have already been identified. The proposed observation will allow us to accurately measure the age difference between the stellar populations providing fundamental clues on the formation mechanism. Our simulations of WFC3 performance suggest that we will be able to detect even the main sequence splitting caused by small He differences {Delta Y 0.02}.

  3. Migration in Vulnerable Deltas: A Research Strategy

    Science.gov (United States)

    Hutton, C.; Nicholls, R. J.; Allan, A.

    2015-12-01

    C. Hutton1, & R. J. Nicholls1, , 1 University of Southampton, University Road, Southampton, Hampshire, United Kingdom, SO17 1BJ. cwh@geodata. soton.ac.ukAbstractGlobally, deltas contain 500 million people and with rising sea levels often linked to large number of forced migrants are expected in the coming century. However, migration is already a major process in deltas, such as the growth of major cities such as Dhaka and Kolkata. Climate and environmental change interacts with a range of catchment and delta level drivers, which encompass a nexus of sea-level rise, storms, freshwater and sediment supply from the catchment, land degradation, subsidence, agricultural loss and socio-economic stresses. DECCMA (Deltas, Vulnerability and Climate Change: Migration and Adaptation/CARRIA) is investigating migration in the Ganges-Brahmaputra-Meghna (GBM), Mahanadi and Volta Deltas, including the influence of climate change. The research will explore migration from a range of perspectives including governance and stakeholder analysis, demographic analysis, household surveys of sending and receiving areas, macro-economic analysis, and hazards and hotspot analysis both historically and into the future. Migration under climate change will depend on other adaptation in the deltas and this will be examined. Collectively, integrated analysis will be developed to examine migration, other adaptation and development pathways with a particular focus on the implications for the poorest. This will require the development of input scenarios, including expert-derived exogenous scenarios (e.g., climate change) and endogenous scenarios of the delta developed in a participatory manner. This applied research will facilitate decision support methods for the development of deltas under climate change, with a focus on migration and other adaptation strategies.

  4. Upper-division student difficulties with the Dirac delta function

    Directory of Open Access Journals (Sweden)

    Bethany R. Wilcox

    2015-03-01

    Full Text Available The Dirac delta function is a standard mathematical tool that appears repeatedly in the undergraduate physics curriculum in multiple topical areas including electrostatics, and quantum mechanics. While Dirac delta functions are often introduced in order to simplify a problem mathematically, students still struggle to manipulate and interpret them. To characterize student difficulties with the delta function at the upper-division level, we examined students’ responses to traditional exam questions and a standardized conceptual assessment, and conducted think-aloud interviews. Our analysis was guided by an analytical framework that focuses on how students activate, construct, execute, and reflect on the Dirac delta function in the context of problem solving in physics. Here, we focus on student difficulties using the delta function to express charge distributions in the context of junior-level electrostatics. Common challenges included invoking the delta function spontaneously, translating a description of a charge distribution into a mathematical expression using delta functions, integrating 3D or non-Cartesian delta function expressions, and recognizing that the delta function can have units. We also briefly discuss implications of these difficulties for instruction.

  5. A Brightness-Referenced Star Identification Algorithm for APS Star Trackers

    Science.gov (United States)

    Zhang, Peng; Zhao, Qile; Liu, Jingnan; Liu, Ning

    2014-01-01

    Star trackers are currently the most accurate spacecraft attitude sensors. As a result, they are widely used in remote sensing satellites. Since traditional charge-coupled device (CCD)-based star trackers have a limited sensitivity range and dynamic range, the matching process for a star tracker is typically not very sensitive to star brightness. For active pixel sensor (APS) star trackers, the intensity of an imaged star is valuable information that can be used in star identification process. In this paper an improved brightness referenced star identification algorithm is presented. This algorithm utilizes the k-vector search theory and adds imaged stars' intensities to narrow the search scope and therefore increase the efficiency of the matching process. Based on different imaging conditions (slew, bright bodies, etc.) the developed matching algorithm operates in one of two identification modes: a three-star mode, and a four-star mode. If the reference bright stars (the stars brighter than three magnitude) show up, the algorithm runs the three-star mode and efficiency is further improved. The proposed method was compared with other two distinctive methods the pyramid and geometric voting methods. All three methods were tested with simulation data and actual in orbit data from the APS star tracker of ZY-3. Using a catalog composed of 1500 stars, the results show that without false stars the efficiency of this new method is 4∼5 times that of the pyramid method and 35∼37 times that of the geometric method. PMID:25299950

  6. Delta-nucleus dynamics: proceedings of symposium

    Energy Technology Data Exchange (ETDEWEB)

    Lee, T.S.H.; Geesaman, D.F.; Schiffer, J.P. (eds.)

    1983-10-01

    The appreciation of the role in nuclear physics of the first excited state of the nucleon, the delta ..delta..(1232), has grown rapidly in the past decade. The delta resonance dominates nuclear reactions induced by intermediate energy pions, nucleons, and electromagnetic probes. It is also the most important non-nucleonic degree of freedom needed to resolve many fundamental problems encountered in the study of low-energy nuclear phenomena. Clearly, a new phase of nuclear physics has emerged and conventional thinking must be extended to account for this new dimension of nuclear dynamics. The most challenging problem we are facing is how a unified theory can be developed to describe ..delta..-nucleus dynamics at all energies. In exploring this new direction, it is important to have direct discussions among researchers with different viewpoints. Separate entries were prepared for the 49 papers presented. (WHK)

  7. On the origin of delta spots

    International Nuclear Information System (INIS)

    Tang, F.

    1983-01-01

    Mount Wilson sunspot drawings from 1966 through 1980 were used in conjunction with Hα filtergrams from Big Bear Solar Observatory to examine the origin of delta spots, spots with bipolar umbrae within one penumbra. Of the six cases we studied, five were formed by the union of non-paired spots. They are either shoved into one another by two neighboring growing bipoles or by a new spot born piggy-back style on an existing spot of opposite polarity. Proper motions of the growing spots take on curvilinear paths around one another to avoid a collision. This is the shear motion observed in delta spots (Tanaka, 1979). In the remaining case, the delta spot was formed by spots that emerged as a pair. Our findings indicate no intrinsic differences in the formation or the behavior between delta spots of normal magnetic configuration. (orig.)

  8. Holocene evolution of the western Orinoco Delta, Venezuela

    Science.gov (United States)

    Aslan, A.; White, W.A.; Warne, A.G.; Guevara, E.H.

    2003-01-01

    The pristine nature of the Orinoco Delta of eastern Venezuela provides unique opportunities to study the geologic processes and environments of a major tropical delta. Remote-sensing images, shallow cores, and radiocarbon-dating of organic remains form the basis for describing deltaic environments and interpreting the Holocene history of the delta. The Orinoco Delta can be subdivided into two major sectors. The southeast sector is dominated by the Rio Grande-the principal distributary-and complex networks of anastomosing fluvial and tidal channels. The abundance of siliciclastic deposits suggests that fluvial processes such as over-bank flooding strongly influence this part of the delta. In contrast, the northwest sector is represented by few major distributaries, and overbank sedimentation is less widespread relative to the southeast sector. Peat is abundant and occurs in herbaceous and forested swamps that are individually up to 200 km2 in area. Northwest-directed littoral currents transport large volumes of suspended sediment and produce prominent mudcapes along the northwest coast. Mapping of surface sediments, vegetation, and major landforms identified four principal geomorphic systems within the western delta plain: (1) distributary channels, (2) interdistributary flood basins, (3) fluvial-marine transitional environments, and (4) marine-influenced coastal environments. Coring and radiocarbon dating of deltaic deposits show that the northern delta shoreline has prograded 20-30 km during the late Holocene sea-level highstand. Progradation has been accomplished by a combination of distributary avulsion and mudcape progradation. This style of deltaic progradation differs markedly from other deltas such as the Mississippi where distributary avulsion leads to coastal land loss, rather than shoreline progradation. The key difference is that the Orinoco Delta coastal zone receives prodigious amounts of sediment from northwest-moving littoral currents that transport

  9. Hot deformation behavior of delta-processed superalloy 718

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Y., E-mail: wangyanhit@yahoo.cn [State Key Laboratory of Powder Metallurgy, Central South University, Changsha 410083 (China); School of Aeronautics and Astronautics, Central South University, Changsha 410083 (China); Shao, W.Z.; Zhen, L.; Zhang, B.Y. [School of Materials Science and Engineering, Harbin Institute of Technology, Harbin 150001 (China)

    2011-03-25

    Research highlights: {yields} The peak stress for hot deformation can be described by the Z parameter. {yields} The grain size of DRX was inversely proportional to the Z parameter. {yields} The dissolution of {delta} phases was greatly accelerated under hot deformation. {yields}The {delta} phase stimulated nucleation can serve as the main DRX mechanism. - Abstract: Flow stress behavior and microstructures during hot compression of delta-processed superalloy 718 at temperatures from 950 to 1100 deg. C with strain rates of 10{sup -3} to 1 s{sup -1} were investigated by optical microscopy (OM), electron backscatter diffraction (EBSD) technique and transmission electron microscopy (TEM). The relationship between the peak stress and the deformation conditions can be expressed by a hyperbolic-sine type equation. The activation energy for the delta-processed superalloy 718 is determined to be 467 kJ/mol. The change of the dominant deformation mechanisms leads to the decrease of stress exponent and the increase of activation energy with increasing temperature. The dynamically recrystallized grain size is inversely proportional to the Zener-Hollomon (Z) parameter. It is found that the dissolution rate of {delta} phases under hot deformation conditions is much faster than that under static conditions. Dislocation, vacancy and curvature play important roles in the dissolution of {delta} phases. The main nucleation mechanisms of dynamic recrystallization (DRX) for the delta-processed superalloy 718 include the bulging of original grain boundaries and the {delta} phase stimulated DRX nucleation, which is closely related to the dissolution behavior of {delta} phases under certain deformation conditions.

  10. Primary production in the Delta: Then and now

    Science.gov (United States)

    Cloern, James E.; Robinson, April; Richey, Amy; Grenier, Letitia; Grossinger, Robin; Boyer, Katharyn E.; Burau, Jon; Canuel, Elizabeth A.; DeGeorge, John F.; Drexler, Judith Z.; Enright, Chris; Howe, Emily R.; Kneib, Ronald; Mueller-Solger, Anke; Naiman, Robert J.; Pinckney, James L.; Safran, Samuel M.; Schoellhamer, David H.; Simenstad, Charles A.

    2016-01-01

    To evaluate the role of restoration in the recovery of the Delta ecosystem, we need to have clear targets and performance measures that directly assess ecosystem function. Primary production is a crucial ecosystem process, which directly limits the quality and quantity of food available for secondary consumers such as invertebrates and fish. The Delta has a low rate of primary production, but it is unclear whether this was always the case. Recent analyses from the Historical Ecology Team and Delta Landscapes Project provide quantitative comparisons of the areal extent of 14 habitat types in the modern Delta versus the historical Delta (pre-1850). Here we describe an approach for using these metrics of land use change to: (1) produce the first quantitative estimates of how Delta primary production and the relative contributions from five different producer groups have been altered by large-scale drainage and conversion to agriculture; (2) convert these production estimates into a common currency so the contributions of each producer group reflect their food quality and efficiency of transfer to consumers; and (3) use simple models to discover how tidal exchange between marshes and open water influences primary production and its consumption. Application of this approach could inform Delta management in two ways. First, it would provide a quantitative estimate of how large-scale conversion to agriculture has altered the Delta's capacity to produce food for native biota. Second, it would provide restoration practitioners with a new approach—based on ecosystem function—to evaluate the success of restoration projects and gauge the trajectory of ecological recovery in the Delta region.

  11. Casscf/ci Calculations for First Row Transition Metal Hydrides - the TIH(4-PHI), VH(5-DELTA), CRH(6-SIGMA-PLUS), MNH(7-SIGMA-PLUS), FEH(4,6-DELTA) and NIH(2-DELTA) States

    Science.gov (United States)

    Walch, S. P.; Bauschlicher, C. W., Jr.

    1983-04-01

    Calculations are performed for the predicted ground states of TiH(4-phi), VH(5-delta), CrH(6-sigma-plus), MnH(7-sigma-plus), Fett(4,6-delta) and NiH(2-delta). For FeH both the 6-delta and 4-delta states are studied, since both are likely candidates for the ground state. The ground state symmetries are predicted based on a combination of atomic coupling arguments and coupling of 4s(2)3d(n) and 4s(1)3d(n+1) terms in the molecular system. Electron correlation is included by a CASSCF/CI (SD) treatment. The CASSCF includes near-degeneracy effects, while correlation of the 3d electrons in included at the CI level.

  12. Design and application of star map simulation system for star sensors

    Science.gov (United States)

    Wu, Feng; Shen, Weimin; Zhu, Xifang; Chen, Yuheng; Xu, Qinquan

    2013-12-01

    Modern star sensors are powerful to measure attitude automatically which assure a perfect performance of spacecrafts. They achieve very accurate attitudes by applying algorithms to process star maps obtained by the star camera mounted on them. Therefore, star maps play an important role in designing star cameras and developing procession algorithms. Furthermore, star maps supply significant supports to exam the performance of star sensors completely before their launch. However, it is not always convenient to supply abundant star maps by taking pictures of the sky. Thus, star map simulation with the aid of computer attracts a lot of interests by virtue of its low price and good convenience. A method to simulate star maps by programming and extending the function of the optical design program ZEMAX is proposed. The star map simulation system is established. Firstly, based on analyzing the working procedures of star sensors to measure attitudes and the basic method to design optical system by ZEMAX, the principle of simulating star sensor imaging is given out in detail. The theory about adding false stars and noises, and outputting maps is discussed and the corresponding approaches are proposed. Then, by external programming, the star map simulation program is designed and produced. Its user interference and operation are introduced. Applications of star map simulation method in evaluating optical system, star image extraction algorithm and star identification algorithm, and calibrating system errors are presented completely. It was proved that the proposed simulation method provides magnificent supports to the study on star sensors, and improves the performance of star sensors efficiently.

  13. Tidal controls on river delta morphology

    NARCIS (Netherlands)

    Hoitink, A.J.F.; Wang, Z.B.; Vermeulen, B.; Huismans, Y.; Kästner, K.

    2017-01-01

    River delta degradation has been caused by extraction of natural resources, sediment retention by reservoirs, and sea-level rise. Despite global concerns about these issues, human activity in the world's largest deltas intensifies. Harbour development, construction of flood defences, sand mining and

  14. Tidal controls on river delta morphology

    NARCIS (Netherlands)

    Hoitink, A.J.F.; Wang, Zhengbing; Vermeulen, B.; Huismans, Y; Kästner, K

    River delta degradation has been caused by extraction of natural resources, sediment retention by reservoirs, and sea-level rise. Despite global concerns about these issues, human activity in the world’s largest deltas intensifies. Harbour development, construction of flood defences, sand mining and

  15. Non-invasive perfusion imaging by modified STAR using asymmetric inversion slabs (ASTAR)

    International Nuclear Information System (INIS)

    Kimura, Tokunori

    2000-01-01

    Arterial spin labeling (ASL) such as STAR, EPISTAR, and FAIR have been used as imaging techniques of tissue perfusion and blood vessels (in MRA). We have developed 'ASTAR', a modified version of STAR by using asymmetric inversion slabs. ASTAR solves the problems of suppression of venous inflow and subtraction error of stationary tissue signal caused by the imbalance of signal variations. The signal variations are dependent on MT effects. In order to avoid overlapping the control slab to the tissue (including large veins), the control and tag slabs are arranged asymmetrically to preserve the same offset of modulation frequency. We evaluated both the subtraction error caused by the MT effects, and the imperfection of an IR slab using a stationary phantom. We then measured the vessel signal on the brain of a volunteer, using the above methods. Two indexes were used for the evaluation: ASL signal to control signal ratio (ASLR [%]=100*deltaS/S cont ) and ASL signal to noise ratio (ASLNR=delatS/Noise) where deltaS=|S cont -S tag |. Phantom study: each ASLR and ASLNR between ASTAR and EPISTAR was comparable and showed a decrease in noise signal level. This means that the ASL signal from the stationary tissue with an imbalance in MT effects and the imperfection in inversion slab profiles were cancelled out almost perfectly. When calculating CBF, ASLR for zero perfusion stationary tissue should be below 0.1%. We were able to satisfy this requirement in our ASTAR experiment. ASLR and ASLNR in FAIR were 40% larger than in EPISTAR and ASTAR. Volunteer brain study: compared with each ASL image, the MT effects were cancelled out in EPISTAR and ASTAR. Veins (sagittal sinus etc) disappeared in STAR and ASTAR, but were visible in EPISTAR and FAIR. Perfusion signals were similar in ASTAR and EPISTAR, indicating that both cancellation of MT effects and venous inflow from the opposite side of the tag were suppressed in ASTAR. In conclusion, ASTAR is a practical method to image blood

  16. Environmental challenges in Nigeria's Delta Region and Agriculture ...

    African Journals Online (AJOL)

    The paper discussed the environmental challenges in the Niger-Delta region of Nigeria with emphasis on the impacts on agricultural production. It thus discussed the concepts of Niger-Delta, Environmental pollution, Niger-Delta crises and Agriculture. The paper posits that there are positive relationships between these ...

  17. Regular Generalized Star Star closed sets in Bitopological Spaces

    OpenAIRE

    K. Kannan; D. Narasimhan; K. Chandrasekhara Rao; R. Ravikumar

    2011-01-01

    The aim of this paper is to introduce the concepts of τ1τ2-regular generalized star star closed sets , τ1τ2-regular generalized star star open sets and study their basic properties in bitopological spaces.

  18. Losses of Sacramento River Chinook Salmon and Delta Smelt to Entrainment in Water Diversions in the Sacramento–San Joaquin Delta

    Directory of Open Access Journals (Sweden)

    Wim J. Kimmerer

    2008-06-01

    Full Text Available Pumping at the water export facilities in the southern Sacramento-San Joaquin Delta kills fish at and near the associated fish-salvage facilities. Correlative analyses of salvage counts with population indices have failed to provide quantitative estimates of the magnitude of this mortality. I estimated the proportional losses of Sacramento River Chinook salmon (Oncorhynchus tshawytscha and delta smelt (Hypomesus transpacificus to place these losses in a population context. The estimate for salmon was based on recoveries of tagged smolts released in the upper Sacramento River basin, and recovered at the fish-salvage facilities in the south Delta and in a trawling program in the western Delta. The proportion of fish salvaged increased with export flow, with a mean value around 10% at the highest export flows recorded. Mortality was around 10% if pre-salvage losses were about 80%, but this value is nearly unconstrained. Losses of adult delta smelt in winter and young delta smelt in spring were estimated from salvage data (adults corrected for estimated pre-salvage survival, or from trawl data in the southern Delta (young. These losses were divided by population size and accumulated over the respective seasons. Losses of adult delta smelt were 1–50% (median 15% although the highest value may have been biased upward. Daily losses of larvae and juveniles were 0–8%, and seasonal losses accumulated were 0–25% (median 13%. The effect of these losses on population abundance was obscured by subsequent 50-fold variability in survival from summer to fall.

  19. Displacement waves in La2CuO(4-delta) and La(1.85)Sr(0.15)CuO(4-delta)

    Science.gov (United States)

    Kajitani, Tsuyoshi; Onozuka, Takashi; Yamaguchi, Yasuo; Hirabayashi, Makoto; Syono, Yasuhiko

    1987-11-01

    Structural investigation of orthorhombic La2CuO(4-delta) and La(1.85)Sr(0.15)CuO(4-delta) was carried out by means of X-ray and neutron diffraction on the basis of the space group Cmmm. The periodic expansion/contraction type distortion of CuO6 octahedra was found in both orthorhombic compounds. The distortion is nearly one-dimensional in La2CuO(4-delta) but is two-dimensional in La(1.85)Sr(0.15)CuO(4-delta). The existence of a charge-density wave is highly possible in the structures.

  20. First-principles elastic constants and phonons of delta-Pu

    DEFF Research Database (Denmark)

    Söderlind, P.; Landa, A.; Sadigh, B.

    2004-01-01

    Elastic constants and zone-boundary phonons of delta-plutonium have been calculated within the density-functional theory. The paramagnetic state of delta-Pu is modeled by disordered magnetism utilizing either the disordered local moment or the special quasirandom structure techniques. The anomalo......Elastic constants and zone-boundary phonons of delta-plutonium have been calculated within the density-functional theory. The paramagnetic state of delta-Pu is modeled by disordered magnetism utilizing either the disordered local moment or the special quasirandom structure techniques....... The anomalously soft C-' as well as a large anisotropy ratio (C-44/C-') of delta-Pu is reproduced by this theoretical model. Also the recently measured phonons for delta-Pu compare relatively well with their theoretical counterpart at the zone boundaries....

  1. I-Love relations for incompressible stars and realistic stars

    Science.gov (United States)

    Chan, T. K.; Chan, AtMa P. O.; Leung, P. T.

    2015-02-01

    In spite of the diversity in the equations of state of nuclear matter, the recently discovered I-Love-Q relations [Yagi and Yunes, Science 341, 365 (2013), 10.1126/science.1236462], which relate the moment of inertia, tidal Love number (deformability), and the spin-induced quadrupole moment of compact stars, hold for various kinds of realistic neutron stars and quark stars. While the physical origin of such universality is still a current issue, the observation that the I-Love-Q relations of incompressible stars can well approximate those of realistic compact stars hints at a new direction to approach the problem. In this paper, by establishing recursive post-Minkowskian expansion for the moment of inertia and the tidal deformability of incompressible stars, we analytically derive the I-Love relation for incompressible stars and show that the so-obtained formula can be used to accurately predict the behavior of realistic compact stars from the Newtonian limit to the maximum mass limit.

  2. Stimulation of accumbal GABAA receptors inhibits delta2-, but not delta1-, opioid receptor-mediated dopamine efflux in the nucleus accumbens of freely moving rats.

    Science.gov (United States)

    Aono, Yuri; Kiguchi, Yuri; Watanabe, Yuriko; Waddington, John L; Saigusa, Tadashi

    2017-11-15

    The nucleus accumbens contains delta-opioid receptors that may reduce inhibitory neurotransmission. Reduction in GABA A receptor-mediated inhibition of accumbal dopamine release due to delta-opioid receptor activation should be suppressed by stimulating accumbal GABA A receptors. As delta-opioid receptors are divided into delta2- and delta1-opioid receptors, we analysed the effects of the GABA A receptor agonist muscimol on delta2- and delta1-opioid receptor-mediated accumbal dopamine efflux in freely moving rats using in vivo microdialysis. Drugs were administered intracerebrally through the dialysis probe. Doses of compounds indicate total amount administered (mol) during 25-50min infusions. The delta2-opioid receptor agonist deltorphin II (25.0nmol)- and delta1-opioid receptor agonist DPDPE (5.0nmol)-induced increases in dopamine efflux were inhibited by the delta2-opioid receptor antagonist naltriben (1.5nmol) and the delta1-opioid receptor antagonist BNTX (150.0pmol), respectively. Muscimol (250.0pmol) inhibited deltorphin II (25.0nmol)-induced dopamine efflux. The GABA A receptor antagonist bicuculline (50.0pmol), which failed to affect deltorphin II (25.0nmol)-induced dopamine efflux, counteracted the inhibitory effect of muscimol on deltorphin II-induced dopamine efflux. Neither muscimol (250.0pmol) nor bicuculline (50.0 and 500.0pmol) altered DPDPE (5.0nmol)-induced dopamine efflux. The present results show that reduction in accumbal GABA A receptor-mediated inhibition of dopaminergic activity is necessary to produce delta2-opioid receptor-induced increase in accumbal dopamine efflux. This study indicates that activation of delta2- but not delta1-opioid receptors on the cell bodies and/or terminals of accumbal GABAergic interneurons inhibits GABA release and, accordingly, decreases GABA A receptor-mediated inhibition of dopaminergic terminals, resulting in enhanced accumbal dopamine efflux. Copyright © 2017 Elsevier B.V. All rights reserved.

  3. Tidal modulated flow and sediment flux through Wax Lake Delta distributary channels: Implications for delta development

    Directory of Open Access Journals (Sweden)

    K. Hanegan

    2015-03-01

    Full Text Available In this study, a Delft3D model of the Wax Lake Delta was developed to simulate flow and sediment flux through delta distributary channels. The model was calibrated for tidal constituents as well as velocity and sediment concentration across channel transects. The calibrated model was then used to simulate full spring–neap tidal cycles under constant low flow upstream boundary conditions, with grain size variation in suspended load represented using two sediment fractions. Flow and sediment flux results through distributary channel cross-sections were examined for spatial and temporal variability with the goal of characterizing the role of tides in sediment reworking and delta development. The Wax Lake Delta has prograded through channel extension, river mouth bar deposition, and channel bifurcation. Here we show that tidal modulation of currents influences suspended sand transport, and spatial acceleration through distributary channels at low tides is sufficient to suspend sand in distal reaches during lower flows. The basinward-increasing transport capacity in distributary channels indicates that erosive channel extension could be an important process, even during non-flood events.

  4. Delta Vegetation and Land Use [ds292

    Data.gov (United States)

    California Natural Resource Agency — Vegetation and land use are mapped for the approximately 725,000 acres constituting the Legal Delta portion of the Sacramento and San Joaquin River Delta area....

  5. Primary Production in the Delta: Then and Now

    Directory of Open Access Journals (Sweden)

    James E. Cloern

    2016-10-01

    Full Text Available doi: http://dx.doi.org/10.15447/sfews.2016v14iss3art1To evaluate the role of restoration in the recovery of the Delta ecosystem, we need to have clear targets and performance measures that directly assess ecosystem function. Primary production is a crucial ecosystem process, which directly limits the quality and quantity of food available for secondary consumers such as invertebrates and fish. The Delta has a low rate of primary production, but it is unclear whether this was always the case. Recent analyses from the Historical Ecology Team and Delta Landscapes Project provide quantitative comparisons of the areal extent of 14 habitat types in the modern Delta versus the historical Delta (pre-1850. Here we describe an approach for using these metrics of land use change to: (1 produce the first quantitative estimates of how Delta primary production and the relative contributions from five different producer groups have been altered by large-scale drainage and conversion to agriculture; (2 convert these production estimates into a common currency so the contributions of each producer group reflect their food quality and efficiency of transfer to consumers; and (3 use simple models to discover how tidal exchange between marshes and open water influences primary production and its consumption. Application of this approach could inform Delta management in two ways. First, it would provide a quantitative estimate of how large-scale conversion to agriculture has altered the Delta's capacity to produce food for native biota. Second, it would provide restoration practitioners with a new approach—based on ecosystem function—to evaluate the success of restoration projects and gauge the trajectory of ecological recovery in the Delta region.

  6. Search for OB stars running away from young star clusters. II. The NGC 6357 star-forming region

    Science.gov (United States)

    Gvaramadze, V. V.; Kniazev, A. Y.; Kroupa, P.; Oh, S.

    2011-11-01

    Dynamical few-body encounters in the dense cores of young massive star clusters are responsible for the loss of a significant fraction of their massive stellar content. Some of the escaping (runaway) stars move through the ambient medium supersonically and can be revealed via detection of their bow shocks (visible in the infrared, optical or radio). In this paper, which is the second of a series of papers devoted to the search for OB stars running away from young ( ≲ several Myr) Galactic clusters and OB associations, we present the results of the search for bow shocks around the star-forming region NGC 6357. Using the archival data of the Midcourse Space Experiment (MSX) satellite and the Spitzer Space Telescope, and the preliminary data release of the Wide-Field Infrared Survey Explorer (WISE), we discovered seven bow shocks, whose geometry is consistent with the possibility that they are generated by stars expelled from the young (~1-2 Myr) star clusters, Pismis 24 and AH03 J1725-34.4, associated with NGC 6357. Two of the seven bow shocks are driven by the already known OB stars, HD 319881 and [N78] 34. Follow-up spectroscopy of three other bow-shock-producing stars showed that they are massive (O-type) stars as well, while the 2MASS photometry of the remaining two stars suggests that they could be B0 V stars, provided that both are located at the same distance as NGC 6357. Detection of numerous massive stars ejected from the very young clusters is consistent with the theoretical expectation that star clusters can effectively lose massive stars at the very beginning of their dynamical evolution (long before the second mechanism for production of runaway stars, based on a supernova explosion in a massive tight binary system, begins to operate) and lends strong support to the idea that probably all field OB stars have been dynamically ejected from their birth clusters. A by-product of our search for bow shocks around NGC 6357 is the detection of three circular

  7. Do All O Stars Form in Star Clusters?

    Science.gov (United States)

    Weidner, C.; Gvaramadze, V. V.; Kroupa, P.; Pflamm-Altenburg, J.

    The question whether or not massive stars can form in isolation or only in star clusters is of great importance for the theory of (massive) star formation as well as for the stellar initial mass function of whole galaxies (IGIMF-theory). While a seemingly easy question it is rather difficult to answer. Several physical processes (e.g. star-loss due to stellar dynamics or gas expulsion) and observational limitations (e.g. dust obscuration of young clusters, resolution) pose severe challenges to answer this question. In this contribution we will present the current arguments in favour and against the idea that all O stars form in clusters.

  8. Giant CP stars

    International Nuclear Information System (INIS)

    Loden, L.O.; Sundman, A.

    1989-01-01

    This study is part of an investigation of the possibility of using chemically peculiar (CP) stars to map local galactic structure. Correct luminosities of these stars are therefore crucial. CP stars are generally regarded as main-sequence or near-main-sequence objects. However, some CP stars have been classified as giants. A selection of stars, classified in literature as CP giants, are compared to normal stars in the same effective temperature interval and to ordinary 'non giant' CP stars. There is no clear confirmation of a higher luminosity for 'CP giants', than for CP stars in general. In addition, CP characteristics seem to be individual properties not repeated in a component star or other cluster members. (author). 50 refs., 5 tabs., 3 figs

  9. Bursting star formation and the overabundance of Wolf-Rayet stars

    International Nuclear Information System (INIS)

    Bodigfee, G.; Deloore, C.

    1985-01-01

    The ratio of the number of WR-stars to their OB progenitors appears to be significantly higher in some extragalactic systems than in our Galaxy. This overabundance of Wolf-Rayet-stars can be explained as a consequence of a recent burst of star formation. It is suggested that this burst is the manifestation of a long period nonlinear oscillation in the star formation process, produced by positive feedback effects between young stars and the interstellar medium. Star burst galaxies with large numbers of WR-stars must generate gamma fluxes but due to the distance, all of them are beyond the reach of present-day detectors, except probably 30 Dor

  10. TRIGGERED STAR FORMATION SURROUNDING WOLF-RAYET STAR HD 211853

    Energy Technology Data Exchange (ETDEWEB)

    Liu Tie; Wu Yuefang; Zhang Huawei [Department of Astronomy, Peking University, 100871 Beijing (China); Qin Shengli, E-mail: liutiepku@gmail.com [I. Physikalisches Institut, Universitaet zu Koeln, Zuelpicher Str. 77, 50937 Koeln (Germany)

    2012-05-20

    The environment surrounding Wolf-Rayet (W-R) star HD 211853 is studied in molecular, infrared, as well as radio, and H I emission. The molecular ring consists of well-separated cores, which have a volume density of 10{sup 3} cm{sup -3} and kinematic temperature {approx}20 K. Most of the cores are under gravitational collapse due to external pressure from the surrounding ionized gas. From the spectral energy distribution modeling toward the young stellar objects, the sequential star formation is revealed on a large scale in space spreading from the W-R star to the molecular ring. A small-scale sequential star formation is revealed toward core 'A', which harbors a very young star cluster. Triggered star formations are thus suggested. The presence of the photodissociation region, the fragmentation of the molecular ring, the collapse of the cores, and the large-scale sequential star formation indicate that the 'collect and collapse' process functions in this region. The star-forming activities in core 'A' seem to be affected by the 'radiation-driven implosion' process.

  11. TRIGGERED STAR FORMATION SURROUNDING WOLF-RAYET STAR HD 211853

    International Nuclear Information System (INIS)

    Liu Tie; Wu Yuefang; Zhang Huawei; Qin Shengli

    2012-01-01

    The environment surrounding Wolf-Rayet (W-R) star HD 211853 is studied in molecular, infrared, as well as radio, and H I emission. The molecular ring consists of well-separated cores, which have a volume density of 10 3 cm –3 and kinematic temperature ∼20 K. Most of the cores are under gravitational collapse due to external pressure from the surrounding ionized gas. From the spectral energy distribution modeling toward the young stellar objects, the sequential star formation is revealed on a large scale in space spreading from the W-R star to the molecular ring. A small-scale sequential star formation is revealed toward core 'A', which harbors a very young star cluster. Triggered star formations are thus suggested. The presence of the photodissociation region, the fragmentation of the molecular ring, the collapse of the cores, and the large-scale sequential star formation indicate that the 'collect and collapse' process functions in this region. The star-forming activities in core 'A' seem to be affected by the 'radiation-driven implosion' process.

  12. The influence of delta formation mechanism on geotechnical property sequence of the late Pleistocene–Holocene sediments in the Mekong River Delta

    Directory of Open Access Journals (Sweden)

    Truong Minh Hoang

    2016-11-01

    Full Text Available The aim of the study was to characterize a variety of microstructure development-levels and geotechnical property sequences of the late Pleistocene–Holocene deposits in the Mekong River delta (MRD, and the paper furthermore discusses the influences of delta formation mechanisms on them. The survey associated the geotechnical engineering and the sedimentary geology of the late Pleistocene–Holocene deposits at five sites and also undifferentiated Pleistocene sediments. A cross-section which was rebuilt in the delta progradation-direction and between the Mekong and Bassac rivers represents the stratigraphy. Each sedimentary unit was formed under a different delta formation mechanism and revealed a typical geotechnical property sequence. The mechanical behaviors of the sediment succession in the tide-dominated delta with significant fluvial-activity and material source tend to be more cohesionless soils and strengths than those in the tide- and wave-dominated delta and even the coast. The particular tendency of the mechanical behavior of the deposit succession can be reasonably estimated from the delta formation mechanism. The characteristics of the clay minerals from the Mekong River produced the argillaceous soil which does not have extremely high plasticity. The microstructure development-levels are low to very high indicating how to choose hydraulic conductivity value, k, for estimating overconsolidation ratio, OCR, by the piezocone penetration tests (CPTU. The OCR of sediments in the delta types strangely change with depth but none less than 1. The post-depositional processes significantly influenced the microstructure development, particularly the dehydrating and oxidizing processes.

  13. Star Polymers.

    Science.gov (United States)

    Ren, Jing M; McKenzie, Thomas G; Fu, Qiang; Wong, Edgar H H; Xu, Jiangtao; An, Zesheng; Shanmugam, Sivaprakash; Davis, Thomas P; Boyer, Cyrille; Qiao, Greg G

    2016-06-22

    Recent advances in controlled/living polymerization techniques and highly efficient coupling chemistries have enabled the facile synthesis of complex polymer architectures with controlled dimensions and functionality. As an example, star polymers consist of many linear polymers fused at a central point with a large number of chain end functionalities. Owing to this exclusive structure, star polymers exhibit some remarkable characteristics and properties unattainable by simple linear polymers. Hence, they constitute a unique class of technologically important nanomaterials that have been utilized or are currently under audition for many applications in life sciences and nanotechnologies. This article first provides a comprehensive summary of synthetic strategies towards star polymers, then reviews the latest developments in the synthesis and characterization methods of star macromolecules, and lastly outlines emerging applications and current commercial use of star-shaped polymers. The aim of this work is to promote star polymer research, generate new avenues of scientific investigation, and provide contemporary perspectives on chemical innovation that may expedite the commercialization of new star nanomaterials. We envision in the not-too-distant future star polymers will play an increasingly important role in materials science and nanotechnology in both academic and industrial settings.

  14. Displacement waves in La/sub 2/CuO(4-delta) and La(1. 85)Sr(0. 15)CuO(4-delta)

    Energy Technology Data Exchange (ETDEWEB)

    Kajitani, T.; Onozuka, T.; Yamaguchi, Y.; Hirabayashi, M.; Syono, Y.

    1987-11-01

    Structural investigation of orthorhombic La/sub 2/CuO(4-delta) and La(1.85)Sr(0.15)CuO(4-delta) was carried out by means of X-ray and neutron diffraction on the basis of the space group Cmmm. The periodic expansion/contraction type distortion of CuO6 octahedra was found in both orthorhombic compounds. The distortion is nearly one-dimensional in La/sub 2/CuO(4-delta) but is two-dimensional in La(1.85)Sr(0.15)CuO(4-delta). The existence of a charge-density wave is highly possible in the structures. 20 references.

  15. How yield relates to ash content, Delta 13C and Delta 18O in maize grown under different water regimes.

    Science.gov (United States)

    Cabrera-Bosquet, Llorenç; Sánchez, Ciro; Araus, José Luis

    2009-11-01

    Stable isotopes have proved a valuable phenotyping tool when breeding for yield potential and drought adaptation; however, the cost and technical skills involved in isotope analysis limit its large-scale application in breeding programmes. This is particularly so for Delta(18)O despite the potential relevance of this trait in C(4) crops. The accumulation of minerals (measured as ash content) has been proposed as an inexpensive way to evaluate drought adaptation and yield in C(3) cereals, but little is known of the usefulness of this measure in C(4) cereals such as maize (Zea mays). The present study investigates how yield relates to ash content, Delta(13)C and Delta(18)O, and evaluates the use of ash content as an alternative or complementary criterion to stable isotopes in assessing yield potential and drought resistance in maize. A set of tropical maize hybrids developed by CIMMYT were subjected to different water availabilities, in order to induce water stress during the reproductive stages under field conditions. Ash content and Delta(13)C were determined in leaves and kernels. In addition, Delta(18)O was measured in kernels. Water regime significantly affected yield, ash content and stable isotopes. The results revealed a close relationship between ash content in leaves and the traits informing about plant water status. Ash content in kernels appeared to reflect differences in sink-source balance. Genotypic variation in grain yield was mainly explained by the combination of ash content and Delta(18)O, whilst Delta(13)C did not explain a significant percentage of such variation. Ash content in leaves and kernels proved a useful alternative or complementary criterion to Delta(18)O in kernels for assessing yield performance in maize grown under drought conditions.

  16. FUNDAMENTAL PROPERTIES OF STARS USING ASTEROSEISMOLOGY FROM KEPLER AND CoRoT AND INTERFEROMETRY FROM THE CHARA ARRAY

    Energy Technology Data Exchange (ETDEWEB)

    Huber, D.; Ireland, M. J.; Bedding, T. R.; Maestro, V.; White, T. R. [Sydney Institute for Astronomy (SIfA), School of Physics, University of Sydney, NSW 2006 (Australia); Brandao, I. M.; Sousa, S. G.; Cunha, M. S. [Centro de Astrofo Latin-Small-Letter-Dotless-I sica and Faculdade de Ciencias, Universidade do Porto, Rua das Estrelas, P-4150-762 Porto (Portugal); Piau, L. [Department of Physics and Astronomy, Michigan State University, East Lansing, MI 48823-2320 (United States); Bruntt, H.; Aguirre, V. Silva; Christensen-Dalsgaard, J. [Stellar Astrophysics Centre, Department of Physics and Astronomy, Aarhus University, Ny Munkegade 120, DK-8000 Aarhus C (Denmark); Casagrande, L. [Research School of Astronomy and Astrophysics, Mount Stromlo Observatory, The Australian National University, ACT 2611 (Australia); Molenda-Zakowicz, J. [Astronomical Institute of the University of Wroclaw, ul. Kopernika 11, 51-622 Wroclaw (Poland); Barclay, T. [Bay Area Environmental Research Institute/NASA Ames Research Center, Moffett Field, CA 94035 (United States); Burke, C. J. [SETI Institute/NASA Ames Research Center, Moffett Field, CA 94035 (United States); Chaplin, W. J. [School of Physics and Astronomy, University of Birmingham, Birmingham B15 2TT (United Kingdom); De Ridder, J. [Instituut voor Sterrenkunde, K. U. Leuven, B-3001 Leuven (Belgium); Farrington, C. D. [Center for High Angular Resolution Astronomy, Georgia State University, P.O. Box 3969, Atlanta, GA 30302 (United States); Frasca, A., E-mail: daniel.huber@nasa.gov [INAF Osservatorio Astrofisico di Catania, I-95123 Catania (Italy); and others

    2012-11-20

    We present results of a long-baseline interferometry campaign using the PAVO beam combiner at the CHARA Array to measure the angular sizes of five main-sequence stars, one subgiant and four red giant stars for which solar-like oscillations have been detected by either Kepler or CoRoT. By combining interferometric angular diameters, Hipparcos parallaxes, asteroseismic densities, bolometric fluxes, and high-resolution spectroscopy, we derive a full set of near-model-independent fundamental properties for the sample. We first use these properties to test asteroseismic scaling relations for the frequency of maximum power ({nu}{sub max}) and the large frequency separation ({Delta}{nu}). We find excellent agreement within the observational uncertainties, and empirically show that simple estimates of asteroseismic radii for main-sequence stars are accurate to {approx}< 4%. We furthermore find good agreement of our measured effective temperatures with spectroscopic and photometric estimates with mean deviations for stars between T {sub eff} = 4600-6200 K of -22 {+-} 32 K (with a scatter of 97 K) and -58 {+-} 31 K (with a scatter of 93 K), respectively. Finally, we present a first comparison with evolutionary models, and find differences between observed and theoretical properties for the metal-rich main-sequence star HD 173701. We conclude that the constraints presented in this study will have strong potential for testing stellar model physics, in particular when combined with detailed modeling of individual oscillation frequencies.

  17. Wolf-Rayet stars

    Energy Technology Data Exchange (ETDEWEB)

    Sahade, J

    1981-12-01

    Aspects of the problems of the Wolf-Rayet stars related to their chemical composition, their evolutionary status, and their apparent dichotomy in two spectral sequences are discussed. Dogmas concerning WR stars are critically discussed, including the belief that WR stars lack hydrogen, that they are helium stars evolved from massive close binaries, and the existence of a second WR stage in which the star is a short-period single-lined binary. The relationship of WR stars with planetary nebulae is addressed, as is the membership of these stars in clusters and associations. The division of WR stars into WN and WC sequences is considered, questioning the reasonability of accounting for WR line formation in terms of abundance differences.

  18. StarDOM: From STAR format to XML

    International Nuclear Information System (INIS)

    Linge, Jens P.; Nilges, Michael; Ehrlich, Lutz

    1999-01-01

    StarDOM is a software package for the representation of STAR files as document object models and the conversion of STAR files into XML. This allows interactive navigation by using the Document Object Model representation of the data as well as easy access by XML query languages. As an example application, the entire BioMagResBank has been transformed into XML format. Using an XML query language, statistical queries on the collected NMR data sets can be constructed with very little effort. The BioMagResBank/XML data and the software can be obtained at http://www.nmr.embl-heidelberg.de/nmr/StarDOM/

  19. STARS no star on Kauai

    International Nuclear Information System (INIS)

    Jones, M.

    1993-01-01

    The island of Kuai, home to the Pacific Missile Range Facility, is preparing for the first of a series of Star Wars rocket launches expected to begin early this year. The Strategic Defense Initiative plans 40 launches of the Stategic Target System (STARS) over a 10-year period. The focus of the tests appears to be weapons and sensors designed to combat multiple-warhead ICBMs, which will be banned under the START II Treaty that was signed in January. The focus of this article is to express the dubious value of testing the STARS at a time when their application will not be an anticipated problem

  20. Hydrological and Climatic Significance of Martian Deltas

    Science.gov (United States)

    Di Achille, G.; Vaz, D. A.

    2017-10-01

    We a) review the geomorphology, sedimentology, and mineralogy of the martian deltas record and b) present the results of a quantitative study of the hydrology and sedimentology of martian deltas using modified version of terrestrial model Sedflux.

  1. Abraham Reef Stable Isotope Data (delta 13C, delta 18O, delta 14C) for 1635-1957

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Site: Abraham Reef, 22ó 06'S, 153ó 00'E, Porites australiensus, Radiocarbon (delta 14C) and Stable Isotope (del 18O and del 13C) results from bi-annual samples from...

  2. Delta Plaza kohvik = The Delta Plaza Café / Margit Mutso

    Index Scriptorium Estoniae

    Mutso, Margit, 1966-

    2010-01-01

    Tallinnas Pärnu mnt. 141 asuva kohviku Delta Plaza sisekujundusest. Sisearhitektid Tiiu Truus ja Marja Viltrop (Stuudio Truus OÜ). Hoone arhitektid Jüri Okas ja Marika Lõoke (AB J. Okas & M. Lõoke). Žürii liikme Mait Summataveti arvamus kohvikust

  3. Studying medium effects with the optimized {delta} expansion

    Energy Technology Data Exchange (ETDEWEB)

    Krein, G [Instituto de Fisica Teorica (IFT), Sao Paulo, SP (Brazil); Menezes, D P [Santa Catarina Univ., Florianopolis, SC (Brazil). Dept. de Fisica; Nielsen, M [Sao Paulo Univ., SP (Brazil). Inst. de Fisica; Pinto, M B [Montpellier-2 Univ., 34 (France). Lab. de Physique Mathematique

    1995-04-01

    The possibility of using the optimized {delta} expansion for studying medium effects on hadronic properties in quark or nuclear matter is investigated. The {delta} expansion is employed to study density effects with two commonly used models in hadron and nuclear physics, the Nambu-Jona-Lasinio model for the dynamical chiral symmetry breaking and the Walecka model for the equation of state of nuclear matter. The results obtained with the {delta} expansion are compared to those obtained with the traditional Hartree-Fock approximation. Perspectives for using the {delta} expansion in other field theoretic models in hadron and nuclear physics are discussed. (author). 17 refs, 9 figs.

  4. Antinociceptive activity of Delta9-tetrahydrocannabinol non-ionic microemulsions.

    Science.gov (United States)

    Lazzari, P; Fadda, P; Marchese, G; Casu, G L; Pani, L

    2010-06-30

    Delta(9)-Tetrahydrocannabinol (Delta(9)-THC), the major psychoactive constituent of Cannabis sativa L., has been widely studied for its potential pharmaceutical application in the treatment of various diseases and disturbs. This sparingly soluble terpeno-phenolic compound is not easy to handle and to be formulated in pharmaceutical preparations. The aim of this work was to develop a stable aqueous Delta(9)-THC formulation acceptable for different ways of administration, and to evaluate the therapeutic properties of the new Delta(9)-THC based preparation for pain treatment. Due to the thermodynamic stability and advantages of microemulsion based systems, the study was focused on the identification of aqueous microemulsion based systems containing Delta(9)-THC. Oil in water Delta(9)-THC microemulsions were individuated through phase diagrams construction, using the non-ionic surfactant Solutol HS15, being this surfactant acceptable for parenteral administration in human. A selected microemulsion samples containing 0.2 wt% of Delta(9)-THC, stable up to 52 degrees C, was successfully assayed on animal models of pain. Significant antinociceptive activity has been detected by both intraperitoneal and intragastric administration of the new Delta(9)-THC pharmaceutical preparation. The effect has been highlighted in shorter time if compared to a preparation of the same active principle based on previously reported conventional preparation. 2010 Elsevier B.V. All rights reserved.

  5. LIVER TRANSPLANTATION IN HEPATITIS DELTA: SOUTH AMERICA EXPERIENCE

    Directory of Open Access Journals (Sweden)

    Daniel Souza LIMA

    Full Text Available ABSTRACT BACKGROUND: The Amazon region is one of the main endemic areas of hepatitis delta in the world and the only one related to the presence of genotype 3 of the delta virus. OBJECTIVE: To analyze the profile, mortality and survival of cirrhotic patients submitted to liver transplantation for chronic hepatitis delta virus and compare with those transplanted by hepatitis B virus monoinfection. METHODS: Retrospective, observational and descriptive study. From May 2002 to December 2011, 629 liver transplants were performed at the Walter Cantídio University Hospital, of which 29 patients were transplanted due to cirrhosis caused by chronic delta virus infection and 40 by hepatitis B chronic monoinfection. The variables analyzed were: age, sex, MELD score, Child-Pugh score, upper gastrointestinal bleeding and hepatocellular carcinoma occurrence before the transplantation, perioperative platelet count, mortality and survival. RESULTS: The Delta Group was younger and all came from the Brazilian Amazon Region. Group B presented a higher proportion of male patients (92.5% compared to Group D (58.6%. The occurrence of upper gastrointestinal bleeding before transplantation, MELD score, and Child-Pugh score did not show statistical differences between groups. The occurrence of hepatocellular carcinoma and mortality were higher in the hepatitis B Group. The survival in 4 years was 95% in the Delta Group and 75% in the B Group, with a statistically significant difference (P=0.034. Patients with hepatitis delta presented more evident thrombocytopenia in the pre-transplantation and in the immediate postoperative period. CONCLUSION: The hepatitis by delta virus patients who underwent liver transplantation were predominantly male, coming from the Brazilian Amazon region and with similar liver function to the hepatitis B virus patients. They had a lower incidence of hepatocellular carcinoma, more marked perioperative thrombocytopenia levels and frequent

  6. Transcriptomic profiling of pancreatic alpha, beta and delta cell populations identifies delta cells as a principal target for ghrelin in mouse islets

    DEFF Research Database (Denmark)

    Adriaenssens, Alice E; Svendsen, Berit; Lam, Brian Y H

    2016-01-01

    cytometry and analysed by RNA sequencing. The role of the ghrelin receptor was validated by imaging delta cell calcium concentrations using islets with delta cell restricted expression of the calcium reporter GCaMP3, and in perfused mouse pancreases. RESULTS: A database was constructed of all genes...... expressed in alpha, beta and delta cells. The gene encoding the ghrelin receptor, Ghsr, was highlighted as being highly expressed and enriched in delta cells. Activation of the ghrelin receptor raised cytosolic calcium levels in primary pancreatic delta cells and enhanced somatostatin secretion in perfused...... pancreases, correlating with a decrease in insulin and glucagon release. The inhibition of insulin secretion by ghrelin was prevented by somatostatin receptor antagonism. CONCLUSIONS/INTERPRETATION: Our transcriptomic database of genes expressed in the principal islet cell populations will facilitate...

  7. Geochronology of priority pollutants in sedimentation zones of the Volga and Danube delta in comparison with the Rhine delta

    International Nuclear Information System (INIS)

    Winkels, H.J.; Kroonenberg, S.B.; Lychagin, M.Y.; Marin, G.; Rusakov, G.V.; Kasimov, N.S.

    1998-01-01

    Six sediment cores were taken in sedimentation zones of the Volga river (located in the southern part of the Russian Federation) and, additionally, 6 sediment cores were taken in several lakes (sedimentation zones) in the central and western part of the Danube delta in Romania. Priority pollutants (8 metals, 7 polychlorinated biphenyls and 10 polycyclic aromatic hydrocarbons) were determined in all samples of all cores. Present-day and historical levels of pollutants since the late 1930s were established through the use of radionuclide time tracers ( 137 Cs, 134 Cs). For the persistent metals and polycyclic aromatic hydrocarbons, trends in the concentration profiles during the last 5 decades are described. Low and hardly changing concentrations of As, Cu, Zn and all studied PAHs were observed during the last five decades in the sediments of the Volga river. Recently deposited sediments show slightly increasing levels for the heavy metals Zn and Cr and As in the Volga delta. For the studied metals and PAHs, maximum concentrations were found around 1987 in the sediments of the Danube delta. Sediments deposited around 1940 and recently deposited sediments in the Danube delta showed lower pollutant levels. If the contents of heavy metals, PAHs and PCBs in the aquatic sediments in the deltas of the rivers Rhine, Danube and Volga are compared, it is clear that the Volga delta is and was the cleanest delta during the last 5 decades. Nowadays the contents of heavy metals (except Cu and Ni), PAHs and PCBs in the aquatic sediments of the river Rhine are still highest compared to the other two rivers. The recent load of heavy metals (except Cd and Zn) in the sediments of the river Danube is the highest compared to the other two rivers. (Copyright (c) 1998 Elsevier Science B.V., Amsterdam. All rights reserved.)

  8. Doubly truncated FosB isoform (Delta2DeltaFosB) induces osteosclerosis in transgenic mice and modulates expression and phosphorylation of Smads in osteoblasts independent of intrinsic AP-1 activity

    DEFF Research Database (Denmark)

    Sabatakos, George; Rowe, Glenn C; Kveiborg, Marie

    2008-01-01

    DeltaFosB and a further truncated isoform (Delta2DeltaFosB) that lacks known transactivation domains but, like DeltaFosB, induces increased expression of osteoblast marker genes. MATERIALS AND METHODS: To test Delta2DeltaFosB's ability to induce bone formation in vivo, we generated transgenic mice......6 expression. CONCLUSIONS: DeltaFosB's AP-1 transactivating function is not needed to induce increased bone formation, and Delta2DeltaFosB may act, at least in part, by increasing Smad1 expression, phosphorylation, and translocation to the nucleus....

  9. Unexpected {delta}{sup 18}O and {delta}{sup 2}H Variability of Groundwater in the Eastern Paris Basin

    Energy Technology Data Exchange (ETDEWEB)

    Gourcy, L.; Petelet-Giraud, E. [BRGM Service EAU, Orleans (France)

    2013-07-15

    The Paris Basin covers about one-third of the total surface area of France. In 2009, two campaigns sampling 25 boreholes tapping Tertiary aquifers were carried out in the Basin. These aquifers are recharged at a similar altitude and the groundwater age is too young to have registered climate change. In the past, regional studies included the use of isotopes to understand groundwater origin and dynamics. Both {delta}{sup 18}O and {delta}{sup 2}H as well as ages (CFC/SF{sub 6)} and chemical components were determined in all collected samples. A noticeable stable isotope 'anomaly' appears in the south-western part of the Basin, where the average {delta}{sup 18}O and {delta}{sup 2}H values are more depleted and do not fit the pattern given by the continental effect in this area. A regional particularity of the spatial distribution of such isotopes in precipitation may be possible, but should be confirmed by additional work. (author)

  10. Delta Cafés (Portugal: Sustainable Business Development

    Directory of Open Access Journals (Sweden)

    Olgierd Swiatkiewicz

    2017-12-01

    Full Text Available In the case study of Delta Cafés we discuss the sustainable development of the Portuguese company and brand over the 55 years of their existence. Delta Cafés has already been analyzed in terms of marketing activity, social responsibility, management control systems, etc. In this paper, we refer to these studies, and we reach the sources, i.e. the information provided by the Delta Cafés itself. Due to the nature of the coffee market and the use of case study methodology, we start the presentation of this case from a broader context, describing the coffee market in the world and characterizing the coffee market in Portugal as well. Then we present the history of the development of the company and the brand Delta Cafés. The paper ends with concluding remarks in which we discuss the issues of social and environmental responsibility in the light of the development of Delta Cafés business and brand strategies. 

  11. Measurement of delta-rays in ATLAS silicon sensors

    CERN Document Server

    The ATLAS collaboration

    2013-01-01

    In the inner detector of the ATLAS experiment at the LHC, $\\delta$-rays originating from particle interactions in the silicon sensors may cause additional hit channels. A method for identifying silicon hit clusters that are enlarged due to the emission of a $\\delta$-ray is presented. Using pp collision data the expectation is confirmed that the $\\delta$-ray production rate depends linearly on the path length of the particle in silicon, independently of layer radius and detector technology. The range of the $\\delta$-rays, which is a property of the material and should not depend on anything else, is indeed found to be constant as a function of detector layer, path length in silicon and momentum of the particle traversing the silicon. As a by-product of this analysis a method is proposed that could correct for the effect of these $\\delta$-rays, and this could be used to improve track reconstruction.

  12. Studies of Louisiana's Deltas and Wetlands using SAR

    Science.gov (United States)

    Jones, C. E.

    2017-12-01

    Sustainable coastal environments exist in delicate balance between subsidence, erosion, and sea level rise on one hand and accretion of sediment and retention of decomposing organic matter on the other. In this talk we present results from a series of studies using an airborne L-band SAR (UAVSAR) to measure changing conditions in the Mississippi River Delta and coastal wetlands of Louisiana. Change within the Mississippi River delta (MRD), which is a highly engineered environment, is contrasted to those in the Wax Lake Delta, a small, naturally evolving delta located to the west of the current-day lobe of the MRD. The UAVSAR studies provide evidence that in the MRD subsidence and erosion related to human activities are increasing risk of flooding, submergence, and land loss. These are not seen in the Wax Lake Delta, where new land is forming. We evaluate geomorphic and hydrologic changes In the Wax Lake Delta and wetlands hydrologically connected to the Wax Lake Outlet canal that are apparent on the timescales of the UAVSAR data set, which consists of both near-yearly acquisitions (2009-2016) and several series of repeat acquisitions in 2015 and 2016 capturing conditions across a tidal cycle. Using the yearly data, we observe the evolution of subaqueous channels and crevasses in the delta and changes in distributary channels within the wetlands. We use water level change derived from InSAR applied to the rapid repeat data acquired during different stages of a tidal cycle to study the natural pattern of water flux within the delta and the coastal wetlands. The studies, results, and plans for future work will be presented. This work was carried out in part at the Jet Propulsion Laboratory, California Institute of Technology, under contracts with the California Dept. of Water Resources and with the National Aeronautics and Space Administration.

  13. Floating City IJmeer : Accelerator for Delta Technology

    NARCIS (Netherlands)

    De Graaf, R.; Fremouw, M.; Van Bueren, B.; Czapiewska, K.; Kuijper, M.

    2006-01-01

    Climate change, sea level rise, population growth and ongoing urbanization result in higher vulnerability of the Rhine delta because it will result in increased flooding frequency, increasing investments and increased use of water, energy and other resources. The Rhine Delta also faces strong

  14. Star-forming galaxy models: Blending star formation into TREESPH

    Science.gov (United States)

    Mihos, J. Christopher; Hernquist, Lars

    1994-01-01

    We have incorporated star-formation algorithms into a hybrid N-body/smoothed particle hydrodynamics code (TREESPH) in order to describe the star forming properties of disk galaxies over timescales of a few billion years. The models employ a Schmidt law of index n approximately 1.5 to calculate star-formation rates, and explicitly include the energy and metallicity feedback into the Interstellar Medium (ISM). Modeling the newly formed stellar population is achieved through the use of hybrid SPH/young star particles which gradually convert from gaseous to collisionless particles, avoiding the computational difficulties involved in creating new particles. The models are shown to reproduce well the star-forming properties of disk galaxies, such as the morphology, rate of star formation, and evolution of the global star-formation rate and disk gas content. As an example of the technique, we model an encounter between a disk galaxy and a small companion which gives rise to a ring galaxy reminiscent of the Cartwheel (AM 0035-35). The primary galaxy in this encounter experiences two phases of star forming activity: an initial period during the expansion of the ring, and a delayed phase as shocked material in the ring falls back into the central regions.

  15. EMACSS: Evolve Me A Cluster of StarS

    Science.gov (United States)

    Alexander, Poul E. R.; Gieles, Mark

    2012-03-01

    The star cluster evolution code Evolve Me A Cluster of StarS (EMACSS) is a simple yet physically motivated computational model that describes the evolution of some fundamental properties of star clusters in static tidal fields. The prescription is based upon the flow of energy within the cluster, which is a constant fraction of the total energy per half-mass relaxation time. According to Henon's predictions, this flow is independent of the precise mechanisms for energy production within the core, and therefore does not require a complete description of the many-body interactions therein. Dynamical theory and analytic descriptions of escape mechanisms is used to construct a series of coupled differential equations expressing the time evolution of cluster mass and radius for a cluster of equal-mass stars. These equations are numerically solved using a fourth-order Runge-Kutta integration kernel; the results were benchmarked against a data base of direct N-body simulations. EMACSS is publicly available and reproduces the N-body results to within 10 per cent accuracy for the entire post-collapse evolution of star clusters.

  16. Is there a self-organization principle of river deltas?

    Science.gov (United States)

    Tejedor, Alejandro; Longjas, Anthony; Foufoula-Georgiou, Efi

    2017-04-01

    River deltas are known to possess a complex topological and flux-partitioning structure which has recently been quantified using spectral graph theory [Tejedor et al., 2015a,b]. By analysis of real and simulated deltas it has also been shown that there is promise in formalizing relationships between this topo-dynamic delta structure and the underlying delta forming processes [e.g., Tejedor et al., 2016]. The question we pose here is whether there exists a first order organizational principle behind the self-organization of river deltas and whether this principle can be unraveled from the co-evolving topo-dynamic structure encoded in the delta planform. To answer this question, we introduce a new metric, the nonlocal Entropy Rate (nER) that captures the information content of a delta network in terms of the degree of uncertainty in delivering fluxes from any point of the network to the shoreline. We hypothesize that if the "guiding principle" of undisturbed deltas is to efficiently and robustly build land by increasing the diversity of their flux pathways over the delta plane, then they would exhibit maximum nonlocal Entropy Rate at states at which geometry and flux dynamics are at equilibrium. At the same time, their nER would be non-optimal at transient states, such as before and after major avulsions during which topology and dynamics adjust to each other to reach a new equilibrium state. We will present our results for field and simulated deltas, which confirm this hypothesis and open up new ways of thinking about self-organization, complexity and robustness in river deltas. One particular connection of interest might have important implications since entropy rate and resilience are related by the fluctuation theorem [Demetrius and Manke, 2005], and therefore our results suggest that deltas might in fact self-organize to maximize their resilience to structural and dynamic perturbations. References: Tejedor, A., A. Longjas, I. Zaliapin, and E. Foufoula

  17. Understanding delta-sigma data converters

    CERN Document Server

    Pavan, Shanti; Temes, Gabor C

    2017-01-01

    This new edition introduces novel analysis and design techniques for delta-sigma (ΔΣ) converters in physical and conceptual terms, and includes new chapters that explore developments in the field over the last decade. This book explains the principles and operation of delta-sigma analog-to-digital converters (ADCs) in physical and conceptual terms in accordance with the most recent developments in the field. The interest of ΔΣ converter designers has shifted significantly over the past decade, due to many new applications for data converters at the far ends of the frequency spectrum. Continuous-time delta-sigma A/D converters with GHz clocks, of both lowpass and bandpass types, are required for wireless applications. At the other extreme, multiplexed ADCs with very narrow (sometimes 10 Hz wide) signal bandwidths, but very high accuracy are needed in the interfaces of biomedical and environmental sensors. To reflect the changing eeds of designers, the second edition includes significant new material on bo...

  18. Barium and Tc-poor S stars: Binary masqueraders among carbon stars

    OpenAIRE

    Jorissen, A.; Van Eck, S.

    1997-01-01

    The current understanding of the origin of barium and S stars is reviewed, based on new orbital elements and binary frequencies. The following questions are addressed: (i) Is binarity a necessary condition to produce a barium star? (ii) What is the mass transfer mode (wind accretion or RLOF?) responsible for their formation? (iii) Do barium stars form as dwarfs or as giants? (iv) Do barium stars evolve into Tc-poor S stars? (v) What is the relative frequency of Tc-rich and Tc-poor S stars?

  19. Open source integrated modeling environment Delta Shell

    Science.gov (United States)

    Donchyts, G.; Baart, F.; Jagers, B.; van Putten, H.

    2012-04-01

    In the last decade, integrated modelling has become a very popular topic in environmental modelling since it helps solving problems, which is difficult to model using a single model. However, managing complexity of integrated models and minimizing time required for their setup remains a challenging task. The integrated modelling environment Delta Shell simplifies this task. The software components of Delta Shell are easy to reuse separately from each other as well as a part of integrated environment that can run in a command-line or a graphical user interface mode. The most components of the Delta Shell are developed using C# programming language and include libraries used to define, save and visualize various scientific data structures as well as coupled model configurations. Here we present two examples showing how Delta Shell simplifies process of setting up integrated models from the end user and developer perspectives. The first example shows coupling of a rainfall-runoff, a river flow and a run-time control models. The second example shows how coastal morphological database integrates with the coastal morphological model (XBeach) and a custom nourishment designer. Delta Shell is also available as open-source software released under LGPL license and accessible via http://oss.deltares.nl.

  20. Technical Communications in Urban Operations (Les communications techniques en operations urbaines)

    Science.gov (United States)

    2010-09-01

    SCUTI – Scuola Trasmissioni ed Informatica dell’Esercito Italiano Via dei Genieri, 287, 00143-Roma Cecchignola Email: Mario.DiStefano@selex...comms.com Lt. Fabrizio LAMBIASE SCUTI – Scuola Trasmissioni ed Informatica dell’Esercito Italiano Via dei Genieri, 287, 00143 Roma Cecchignola

  1. Radio stars

    International Nuclear Information System (INIS)

    Hjellming, R.M.

    1976-01-01

    Any discussion of the radio emission from stars should begin by emphasizing certain unique problems. First of all, one must clarify a semantic confusion introduced into radio astronomy in the late 1950's when most new radio sources were described as radio stars. All of these early 'radio stars' were eventually identified with other galactic and extra-galactic objects. The study of true radio stars, where the radio emission is produced in the atmosphere of a star, began only in the 1960's. Most of the work on the subject has, in fact, been carried out in only the last few years. Because the real information about radio stars is quite new, it is not surprising that major aspects of the subject are not at all understood. For this reason this paper is organized mainly around three questions: what is the available observational information; what physical processes seem to be involved; and what working hypotheses look potentially fruitful. (Auth.)

  2. TURBOVELOCITY STARS: KICKS RESULTING FROM THE TIDAL DISRUPTION OF SOLITARY STARS

    International Nuclear Information System (INIS)

    Manukian, Haik; Guillochon, James; Ramirez-Ruiz, Enrico; O'Leary, Ryan M.

    2013-01-01

    The centers of most known galaxies host supermassive black holes (SMBHs). In orbit around these black holes are a centrally concentrated distribution of stars, both in single and in binary systems. Occasionally, these stars are perturbed onto orbits that bring them close to the SMBH. If the star is in a binary system, the three-body interaction with the SMBH can lead to large changes in orbital energy, depositing one of the two stars on a tightly-bound orbit, and its companion into a hyperbolic orbit that may escape the galaxy. In this Letter, we show that the disruption of solitary stars can also lead to large positive increases in orbital energy. The kick velocity depends on the amount of mass the star loses at pericenter, but not on the ratio of black hole to stellar mass, and are at most the star's own escape velocity. We find that these kicks are usually too small to result in the ejection of stars from the Milky Way, but can eject the stars from the black hole's sphere of influence, reducing their probability of being disrupted again. We estimate that ∼ 10 5 stars, ∼ 1% of all stars within 10 pc of the galactic center, are likely to have had mass removed by the central black hole through tidal interaction, and speculate that these 'turbovelocity' stars will at first be redder, but eventually bluer, and always brighter than their unharassed peers.

  3. The Keenan and Wing bands in S stars

    International Nuclear Information System (INIS)

    Lambert, D.L.; Clegg, R.E.S.

    1980-01-01

    New observations of the near infrared spectra of S stars are presented as part of a survey of the unidentified Keenan and Wing bands. Bandhead wavelengths accurate to 0.5 A are presented. A new band is found at 9014 A. The bands are not present in normal M giants and dwarfs. Laboratory spectroscopy of heavy element oxides is reported. Several new identifications are proposed. The 10 300 A Wing band is identified with the Δv = - 1 sequence of the ZrO 9300 A Δv = 0 bands. The ZrO B 1 PI-A 1 Δ (Δv = 0) system may be responsible for either the 9736 A or the 10 515 A Wing bands. Two new bands in the near infrared at 8219 and 8235 A are provided by CeO. A new band with heads at 7503 and 7509 A in a spectrum of R And is tentatively attributed to YS. A band at 8268 A in M stars is the TiO delta(2-1) head. The 8610 A Keenan band is not due to CrH. Potential carriers of the Keenan and Wing bands are reviewed. It is suggested that the heavy element sulphides and, perhaps, chlorides are leading candidates. Identification of YS in R And may provide the first evidence for these sulphides. ZrS is a leading candidate for which laboratory spectroscopy is needed. (author)

  4. RELATIONSHIP BETWEEN LOW AND HIGH FREQUENCIES IN δ SCUTI STARS: PHOTOMETRIC KEPLER AND SPECTROSCOPIC ANALYSES OF THE RAPID ROTATOR KIC 8054146

    International Nuclear Information System (INIS)

    Breger, M.; Robertson, P.; Fossati, L.; Balona, L.; Kurtz, D. W.; Bohlender, D.; Lenz, P.; Müller, I.; Lüftinger, Th.; Clarke, Bruce D.; Hall, Jennifer R.; Ibrahim, Khadeejah A.

    2012-01-01

    Two years of Kepler data of KIC 8054146 (δ Sct/γ Dor hybrid) revealed 349 statistically significant frequencies between 0.54 and 191.36 cycles day –1 (6.3 μHz to 2.21 mHz). The 117 low frequencies cluster in specific frequency bands, but do not show the equidistant period spacings predicted for gravity modes of successive radial order, n, and reported for at least one other hybrid pulsator. The four dominant low frequencies in the 2.8-3.0 cycles day –1 (32-35 μHz) range show strong amplitude variability with timescales of months and years. These four low frequencies also determine the spacing of the higher frequencies in and beyond the δ Sct pressure-mode frequency domain. In fact, most of the higher frequencies belong to one of three families with spacings linked to a specific dominant low frequency. In the Fourier spectrum, these family regularities show up as triplets, high-frequency sequences with absolutely equidistant frequency spacings, side lobes (amplitude modulations), and other regularities in frequency spacings. Furthermore, within two families the amplitude variations between the low and high frequencies are related. We conclude that the low frequencies (gravity modes, rotation) and observed high frequencies (mostly pressure modes) are physically connected. This unusual behavior may be related to the very rapid rotation of the star: from a combination of high- and low-resolution spectroscopy we determined that KIC 8054146 is a very fast rotator (υ sin i = 300 ± 20 km s –1 ) with an effective temperature of 7600 ± 200 K and a surface gravity log g of 3.9 ± 0.3. Several astrophysical ideas explaining the origin of the relationship between the low and high frequencies are explored.

  5. Multicolour photometry and spectroscopy of the slow nova V475 Sct (Nova Scuti 2003)

    Czech Academy of Sciences Publication Activity Database

    Chochol, D.; Katysheva, N.A.; Pribulla, T.; Schmidtobreick, L.; Shugarov, S.Yu.; Škoda, Petr; Šlechta, Miroslav; Vittone, A.A.; Volkov, I. M.

    2006-01-01

    Roč. 6, č. 1 (2006), s. 137-142 ISSN 1009-9271 Institutional research plan: CEZ:AV0Z10030501 Keywords : cataclysmic variables * circumstellar matter * stars: novae Subject RIV: BN - Astronomy, Celestial Mechanics, Astrophysics Impact factor: 0.746, year: 2006

  6. How Rapid Change Affects Deltas in the Arctic Region

    Science.gov (United States)

    Overeem, I.; Bendixen, M.

    2017-12-01

    Deltas form where the river drains into the ocean. Consequently, delta depositional processes are impacted by either changes in the respective river drainage basin or by changes in the regional marine environment. In a warming Arctic region rapid change has occurred over the last few decades in both the terrestrial domain as well as in the marine domain. Important terrestrial controls include 1) change in permafrost possibly destabilizing river banks, 2) strong seasonality of river discharge due to a short melting season, 3) high sediment supply if basins are extensively glaciated, 4) lake outbursts and ice jams favoring river flooding. Whereas in the Arctic marine domain sea ice loss promotes wave and storm surge impact, and increased longshore transport. We here ask which of these factors dominate any morphological change in Arctic deltas. First, we analyze hydrological data to assess change in Arctic-wide river discharge characteristics and timing, and sea ice concentration data to map changes in sea ice regime. Based on this observational analysis we set up a number of scenarios of change. We then model hypothetical small-scale delta formation considering change in these primary controls by setting up a numerical delta model, and combining it dynamically with a permafrost model. We find that for typical Greenlandic deltas changes in river forcing due to ice sheet melt dominate the morphological change, which is corroborated by mapping of delta progradation from aerial photos and satellite imagery. Whereas in other areas, along the North Slope and the Canadian Arctic small deltas are more stable or experienced retreat. Our preliminary coupled model allows us to further disentangle the impact of major forcing factors on delta evolution in high-latitude systems.

  7. The State of Bay–Delta Science 2016: An Introduction

    Directory of Open Access Journals (Sweden)

    Michael Healey

    2016-07-01

    Full Text Available doi: http://dx.doi.org/10.15447/sfews.2016v14iss2art5The State of Bay–Delta Science 2016 (SBDS is a collection of papers that summarizes the scientific understanding of the Sacramento–San Joaquin Delta, emphasizing progress made during the past decade.It builds on the first SBDS edition (Healey et al. 2008. Paper topics for this edition address the most relevant scientific issues in the Delta identified by senior scientists and managers. The topical papers cover issues ranging from contaminants in the Delta to levee stability, and from Delta food webs to recent discoveries about salmon migration. These papers are written for a scientific audience. Two additional papers, one describing the challenges of managing water and ecosystems in the Delta and another that discusses policy implications of the recent scientific findings, are written for a general audience. The papers will be published in at least two issues of San Francisco Estuary and Watershed Science and will be available as a set electronically.

  8. Nuclear matter in relativistic mean field theory with isovector scalar meson.

    Energy Technology Data Exchange (ETDEWEB)

    Kubis, S.; Kutschera, M. [Institute of Nuclear Physics, Cracow (Poland)

    1996-12-01

    Relativistic mean field (RMF) theory of nuclear matter with the isovector scalar mean field corresponding to the {delta}-meson [a{sub 0}(980)] is studied. While the {delta}-meson field vanishes in symmetric nuclear matter, it can influence properties of asymmetric nuclear matter in neutron stars. The RMF contribution due to {delta}-field to the nuclear symmetry energy is negative. To fit the empirical value, E{sub s}{approx}30 MeV, a stronger {rho}-meson coupling is required than in absence of the {delta}-field. The energy per particle of neutron star matter is than larger at high densities than the one with no {delta}-field included. Also, the proton fraction of {beta}-stable matter increases. Splitting of proton and neutron effective masses due to the {delta}-field can affect transport properties of neutron star matter. (author). 4 refs, 6 figs.

  9. Radio stars

    International Nuclear Information System (INIS)

    Hjellming, R.M.; Gibson, D.M.

    1985-01-01

    Studies of stellar radio emission became an important field of research in the 1970's and have now expanded to become a major area of radio astronomy with the advent of new instruments such as the Very Large Array in New Mexico and transcontinental telescope arrays. This volume contains papers from the workshop on stellar continuum radio astronomy held in Boulder, Colorado, and is the first book on the rapidly expanding field of radio emission from stars and stellar systems. Subjects covered include the observational and theoretical aspects of stellar winds from both hot and cool stars, radio flares from active double star systems and red dwarf stars, bipolar flows from star-forming regions, and the radio emission from X-ray binaries. (orig.)

  10. Capabilities of a Laser Guide Star for a Large Segmented Space Telescope

    Science.gov (United States)

    Clark, James R.; Carlton, Ashley; Douglas, Ewan S.; Males, Jared R.; Lumbres, Jennifer; Feinberg, Lee; Guyon, Olivier; Marlow, Weston; Cahoy, Kerri L.

    2018-01-01

    Large segmented mirror telescopes are planned for future space telescope missions such as LUVOIR (Large UV Optical Infrared Surveyor) to enable the improvement in resolution and contrast necessary to directly image Earth-like exoplanets, in addition to making contributions to general astrophysics. The precision surface control of these complex, large optical systems, which may have over a hundred meter-sized segments, is a challenge. Our initial simulations show that imaging a star of 2nd magnitude or brighter with a Zernike wavefront sensor should relax the segment stability requirements by factors between 10 and 50 depending on the wavefront control strategy. Fewer than fifty stars brighter than magnitude 2 can be found in the sky. A laser guide star (LGS) on a companion spacecraft will allow the telescope to target a dimmer science star and achieve wavefront control to the required stability without requiring slew or repointing maneuvers.We present initial results for one possible mission architecture, with a LGS flying at 100,000 km range from the large telescope in an L2 halo orbit, using a laser transmit power of 8 days) for an expenditure of system, it can be accommodated in a 6U CubeSat bus, but may require an extended period of time to transition between targets and match velocities with the telescope (e.g. 6 days to transit 10 degrees). If the LGS uses monopropellant propulsion, it must use at least a 27U bus to achieve the the same delta-V capability, but can transition between targets much more rapidly (flight are being refined. A low-cost prototype mission (e.g. between a small satellite in LEO and an LGS in GEO) to validate the feasibility is in development.

  11. An automated technique for measuring deltaD and delta18O values of porewater by direct CO2 and H2 equilibration.

    Science.gov (United States)

    Koehler, G; Wassenaar, L I; Hendry, M J

    2000-11-15

    The stable-oxygen and -hydrogen isotopic values (deltaD, delta18O) of porewater in geologic media are commonly determined on water obtained by extraction techniques such as centrifugation, mechanical squeezing, vacuum heating and cryogenic microdistillation, and azeotropic distillation. Each of these techniques may cause isotopic fractionation as part the extraction process and each is laborious. Here we demonstrate a new approach to obtain automated, high-precision deltaD and delta18O measurements of porewater in geologic sediments by direct H2- and CO2-porewater equilibration using a modified commercial CO2-water equilibrator. This technique provides an important and cost-effective improvement over current extraction methods, because many samples can be rapidly analyzed with minimal handling, thereby reducing errors and potential for isotopic fractionation. The precision and accuracy of direct H2- and CO2-porewater equilibration is comparable to or better than current porewater extraction methods. Finally, the direct equilibration technique allows investigators to obtain high-resolution (cm scale) porewater deltaD and delta18O profiles using cores from individual boreholes, eliminating the need for costly piezometers or conventional porewater extractions.

  12. The low-temperature structures of Hgsub(3-delta)SbF6 and Hgsub(3-delta)TaF6

    International Nuclear Information System (INIS)

    Tun, Z.; Brown, I.D.

    1986-01-01

    The Hg chains in both Hgsub(3-delta)SbF 6 and Hgsub(3-delta)TaF 6 order below room temperature. Down to about 190 K the ordering results from the interaction between parallel chains. It is short range and is different for the two compounds. Below 190 K both compounds transform to an isostructural long-range-ordered phase which is driven by the interaction between perpendicular chains. The structure of this phase in both compounds has been determined. Hgsub(3-delta)SbF 6 at 173 K, delta=0.134(1), Msub(r)=810.6(2). It is monoclinic but pseudotetragonal with I4 1 /amd, a=7.655(1), c=12.558(1) A, V=735.9(2) A 3 , Z=4, Dsub(x)=7.314(3) Mg m -3 , graphite-monochromated Mo Kα radiation, lambda=0.71069 A, μ=64.8 mm -1 , F(000)=1337.1(3). Hgsub(3-delta)TaF 6 at 150 K is isostructural but has delta=0.142(1), Msub(r)=868.2(2), a=7.634(1), c=12.610(2) A, V=734.9(2) A, Dsub(x)=7.844(3) Mg m -3 , μ=76.4 mm -1 , F(000)=1422.6(3). Comparison of the low-temperature structures with those at room temperature shows that the thermal contraction results from the shortening of interatomic distances associated with the weak bonds, with the result that the MF 6 (M=Sb, Ta) host lattice shrinks more than the Hg chains. Variation of the atomic displacement parameters with temperature indicates that the large librational displacements of the MF 6 ion result from thermal motion rather than static disorder. (orig.)

  13. A hybrid method for accurate star tracking using star sensor and gyros.

    Science.gov (United States)

    Lu, Jiazhen; Yang, Lie; Zhang, Hao

    2017-10-01

    Star tracking is the primary operating mode of star sensors. To improve tracking accuracy and efficiency, a hybrid method using a star sensor and gyroscopes is proposed in this study. In this method, the dynamic conditions of an aircraft are determined first by the estimated angular acceleration. Under low dynamic conditions, the star sensor is used to measure the star vector and the vector difference method is adopted to estimate the current angular velocity. Under high dynamic conditions, the angular velocity is obtained by the calibrated gyros. The star position is predicted based on the estimated angular velocity and calibrated gyros using the star vector measurements. The results of the semi-physical experiment show that this hybrid method is accurate and feasible. In contrast with the star vector difference and gyro-assisted methods, the star position prediction result of the hybrid method is verified to be more accurate in two different cases under the given random noise of the star centroid.

  14. Star Products and Applications

    OpenAIRE

    Iida, Mari; Yoshioka, Akira

    2010-01-01

    Star products parametrized by complex matrices are defined. Especially commutative associative star products are treated, and star exponentials with respect to these star products are considered. Jacobi's theta functions are given as infinite sums of star exponentials. As application, several concrete identities are obtained by properties of the star exponentials.

  15. Effective star tracking method based on optical flow analysis for star trackers.

    Science.gov (United States)

    Sun, Ting; Xing, Fei; Wang, Xiaochu; Li, Jin; Wei, Minsong; You, Zheng

    2016-12-20

    Benefiting from rapid development of imaging sensor technology, modern optical technology, and a high-speed computing chip, the star tracker's accuracy, dynamic performance, and update rate have been greatly improved with low power consumption and miniature size. The star tracker is currently one of the most competitive attitude measurement sensors. However, due to restrictions of the optical imaging system, difficulties still exist in moving star spot detection and star tracking when in special motion conditions. An effective star tracking method based on optical flow analysis for star trackers is proposed in this paper. Spot-based optical flow, based on a gray gradient between two adjacent star images, is analyzed to distinguish the star spot region and obtain an accurate star spot position so that the star tracking can keep continuous under high dynamic conditions. The obtained star vectors and extended Kalman filter (EKF) are then combined to conduct an angular velocity estimation to ensure region prediction of the star spot; this can be combined with the optical flow analysis result. Experiment results show that the method proposed in this paper has advantages in conditions of large angular velocity and large angular acceleration, despite the presence of noise. Higher functional density and better performance can be achieved; thus, the star tracker can be more widely applied in small satellites, remote sensing, and other complex space missions.

  16. Experimental river delta size set by multiple floods and backwater hydrodynamics.

    Science.gov (United States)

    Ganti, Vamsi; Chadwick, Austin J; Hassenruck-Gudipati, Hima J; Fuller, Brian M; Lamb, Michael P

    2016-05-01

    River deltas worldwide are currently under threat of drowning and destruction by sea-level rise, subsidence, and oceanic storms, highlighting the need to quantify their growth processes. Deltas are built through construction of sediment lobes, and emerging theories suggest that the size of delta lobes scales with backwater hydrodynamics, but these ideas are difficult to test on natural deltas that evolve slowly. We show results of the first laboratory delta built through successive deposition of lobes that maintain a constant size. We show that the characteristic size of delta lobes emerges because of a preferential avulsion node-the location where the river course periodically and abruptly shifts-that remains fixed spatially relative to the prograding shoreline. The preferential avulsion node in our experiments is a consequence of multiple river floods and Froude-subcritical flows that produce persistent nonuniform flows and a peak in net channel deposition within the backwater zone of the coastal river. In contrast, experimental deltas without multiple floods produce flows with uniform velocities and delta lobes that lack a characteristic size. Results have broad applications to sustainable management of deltas and for decoding their stratigraphic record on Earth and Mars.

  17. A Modal Logic for Abstract Delta Modeling

    NARCIS (Netherlands)

    F.S. de Boer (Frank); M. Helvensteijn (Michiel); J. Winter (Joost)

    2012-01-01

    htmlabstractAbstract Delta Modeling is a technique for implementing (software) product lines. Deltas are put in a partial order which restricts their application and are then sequentially applied to a core product in order to form specific products in the product line. In this paper we explore the

  18. Delta Evolution at Røde Elv, Disko Island, Greenland

    Science.gov (United States)

    Kroon, A.; Arngrimson, J.; Bendixen, M.; Sigsgaard, C.

    2017-12-01

    Ice, snow and freezing temperatures have a large impact on coastal morphodynamics in Arctic polar environments. A recent warming of the Arctic climate induces many changes along the arctic shorelines. Sea-levels are rising due to thermal expansion and due to an increased fresh water flux from the glaciers and land ice masses. At the same time, the ice coverage of the coastal waters reduces and the open water periods in summer extend. There is a strong seasonal variation with open waters and active rivers in summer and ice-covered coastal waters and inactive rivers in winter. Coastal processes by waves and tides are thus limited to the summer and early fall. Besides, there is also a strong daily variation in fluvial discharges due to the daily variations in glacier melt with maximum melt in the afternoon and minimum values at night. At the same time, the actual flux of the river to the coastal bay is influenced by the tidal phase. Low tides will enhance the transport to the delta front, while high tides will create stagnant waters over the delta plain. The delta of the Røde Elv is located in southwestern Disko Island in west Greenland. It has a relatively small (ca. 101 km2) and partly glaciated drainage basin (ca. 20%) and its sediments consist of a mixture of basaltic sands and gravels. The Røde Elv delta is located at the end of a pro-glacial and fluvial valley at about 20 km from the glacier. The shores of the delta are reworked by waves, predominantly from southwestern, southern (largest fetch, over 50 km), and southeastern directions. The environment has a micro- to meso- tidal range with a spring tidal range of 2.7 m. The morphologic changes on the delta over the last decades clearly showed a seaward extension of the delta and a periodic shift in the location of the main delta channel. In this presentation, we focus on quantification of water discharges and suspended sediment fluxes to the Røde Elv delta in western Greenland, and on the morphological

  19. Implications for future survival of delta smelt from four climate change scenarios for the Sacramento–San Joaquin Delta, California

    Science.gov (United States)

    Brown, Larry R.; Bennett, William A.; Wagner, R. Wayne; Morgan-King, Tara; Knowles, Noah; Feyrer, Frederick; Schoellhamer, David H.; Stacey, Mark T.; Dettinger, Mike

    2013-01-01

    Changes in the position of the low salinity zone, a habitat suitability index, turbidity, and water temperature modeled from four 100-year scenarios of climate change were evaluated for possible effects on delta smelt Hypomesus transpacificus, which is endemic to the Sacramento–San Joaquin Delta. The persistence of delta smelt in much of its current habitat into the next century appears uncertain. By mid-century, the position of the low salinity zone in the fall and the habitat suitability index converged on values only observed during the worst droughts of the baseline period (1969–2000). Projected higher water temperatures would render waters historically inhabited by delta smelt near the confluence of the Sacramento and San Joaquin rivers largely uninhabitable. However, the scenarios of climate change are based on assumptions that require caution in the interpretation of the results. Projections like these provide managers with a useful tool for anticipating long-term challenges to managing fish populations and possibly adapting water management to ameliorate those challenges.

  20. Morphodynamics of a cyclic prograding delta: the Red River, Vietnam

    NARCIS (Netherlands)

    Maren, D.S. van

    2004-01-01

    River deltas are inhabited by over 60% of the world population, and are, consequently, of paramount agricultural and economical importance. They constitute unique wetland envi ronments which gives river deltas ecological importance as well. Additionally, many deltas contain large accumulations of

  1. Changes to subaqueous delta bathymetry following a high river flow event, Wax Lake Delta, LA, USA

    Science.gov (United States)

    Whaling, A. R.; Shaw, J.

    2017-12-01

    Sediment transport capacity is increased during high river flow (flood) events which are characterized by discharges that exceed the 15 year median daily statistic. The Wax Lake Delta (WLD) in coastal Louisiana has experienced 19 of these high flow events in the past 20 years, yet the depositional patterns of single floods are rarely measured in a field-scale deltaic setting. We characterize flood deposition and erosion patterns on the subaqueous portion of the WLD by differencing two Digital Elevation Models (DEMs) constructed from bathymetric surveys before and after the third largest flood in the WLD's recorded history. The total suspended sediment discharge for the 496 day inter-survey period was 2.14x107 cubic meters measured 21 km upstream of the delta apex. The difference map showed 1.06x107 cubic meters of sediment was deposited and 8.2x106 cubic meters was eroded, yielding 2.40x106 cubic meters of net deposition in the survey area ( 79.7 km2 ). Therefore the average deposition rate was 0.061 mm/day. Channel planform remained relatively unchanged for five out of six distributary passes however Gadwall Pass experienced a maximum channel displacement of 166 m ( 1 channel width) measured from the thalweg centerline. Channel tip extension was negligible. In addition, channel displacement was not concentrated at any portion along the channel centerline. Maximum erosion occurred within channel margins and increased upstream whereas maximum deposition occurred immediately outside the channel margins. Sediment eroded from the survey area was either subsequently re-deposited or transported out of the system. Our results show that up to 77.4% of deposition in the survey area originated from sediment eroded during the flood. Surprisingly, only 11.2% of the total suspended sediment discharge was retained in the subaqueous portion of the delta after the flood. We conclude that a high flow event does not produce channel progradation. Rather, high flow causes delta

  2. Formation of stars and star clusters in colliding galaxies

    International Nuclear Information System (INIS)

    Belles, Pierre-Emmanuel

    2012-01-01

    Mergers are known to be essential in the formation of large-scale structures and to have a significant role in the history of galaxy formation and evolution. Besides a morphological transformation, mergers induce important bursts of star formation. These starburst are characterised by high Star Formation Efficiencies (SFEs) and Specific Star Formation Rates, i.e., high Star Formation Rates (SFR) per unit of gas mass and high SFR per unit of stellar mass, respectively, compared to spiral galaxies. At all redshifts, starburst galaxies are outliers of the sequence of star-forming galaxies defined by spiral galaxies. We have investigated the origin of the starburst-mode of star formation, in three local interacting systems: Arp 245, Arp 105 and NGC 7252. We combined high-resolution JVLA observations of the 21-cm line, tracing the HI diffuse gas, with UV GALEX observations, tracing the young star-forming regions. We probe the local physical conditions of the Inter-Stellar Medium (ISM) for independent star-forming regions and explore the atomic-to-dense gas transformation in different environments. The SFR/HI ratio is found to be much higher in central regions, compared to outer regions, showing a higher dense gas fraction (or lower HI gas fraction) in these regions. In the outer regions of the systems, i.e., the tidal tails, where the gas phase is mostly atomic, we find SFR/HI ratios higher than in standard HI-dominated environments, i.e., outer discs of spiral galaxies and dwarf galaxies. Thus, our analysis reveals that the outer regions of mergers are characterised by high SFEs, compared to the standard mode of star formation. The observation of high dense gas fractions in interacting systems is consistent with the predictions of numerical simulations; it results from the increase of the gas turbulence during a merger. The merger is likely to affect the star-forming properties of the system at all spatial scales, from large scales, with a globally enhanced turbulence

  3. Stars Just Got Bigger - A 300 Solar Mass Star Uncovered

    Science.gov (United States)

    2010-07-01

    Using a combination of instruments on ESO's Very Large Telescope, astronomers have discovered the most massive stars to date, one weighing at birth more than 300 times the mass of the Sun, or twice as much as the currently accepted limit of 150 solar masses. The existence of these monsters - millions of times more luminous than the Sun, losing weight through very powerful winds - may provide an answer to the question "how massive can stars be?" A team of astronomers led by Paul Crowther, Professor of Astrophysics at the University of Sheffield, has used ESO's Very Large Telescope (VLT), as well as archival data from the NASA/ESA Hubble Space Telescope, to study two young clusters of stars, NGC 3603 and RMC 136a in detail. NGC 3603 is a cosmic factory where stars form frantically from the nebula's extended clouds of gas and dust, located 22 000 light-years away from the Sun (eso1005). RMC 136a (more often known as R136) is another cluster of young, massive and hot stars, which is located inside the Tarantula Nebula, in one of our neighbouring galaxies, the Large Magellanic Cloud, 165 000 light-years away (eso0613). The team found several stars with surface temperatures over 40 000 degrees, more than seven times hotter than our Sun, and a few tens of times larger and several million times brighter. Comparisons with models imply that several of these stars were born with masses in excess of 150 solar masses. The star R136a1, found in the R136 cluster, is the most massive star ever found, with a current mass of about 265 solar masses and with a birthweight of as much as 320 times that of the Sun. In NGC 3603, the astronomers could also directly measure the masses of two stars that belong to a double star system [1], as a validation of the models used. The stars A1, B and C in this cluster have estimated masses at birth above or close to 150 solar masses. Very massive stars produce very powerful outflows. "Unlike humans, these stars are born heavy and lose weight as

  4. The Destructive Birth of Massive Stars and Massive Star Clusters

    Science.gov (United States)

    Rosen, Anna; Krumholz, Mark; McKee, Christopher F.; Klein, Richard I.; Ramirez-Ruiz, Enrico

    2017-01-01

    Massive stars play an essential role in the Universe. They are rare, yet the energy and momentum they inject into the interstellar medium with their intense radiation fields dwarfs the contribution by their vastly more numerous low-mass cousins. Previous theoretical and observational studies have concluded that the feedback associated with massive stars' radiation fields is the dominant mechanism regulating massive star and massive star cluster (MSC) formation. Therefore detailed simulation of the formation of massive stars and MSCs, which host hundreds to thousands of massive stars, requires an accurate treatment of radiation. For this purpose, we have developed a new, highly accurate hybrid radiation algorithm that properly treats the absorption of the direct radiation field from stars and the re-emission and processing by interstellar dust. We use our new tool to perform a suite of three-dimensional radiation-hydrodynamic simulations of the formation of massive stars and MSCs. For individual massive stellar systems, we simulate the collapse of massive pre-stellar cores with laminar and turbulent initial conditions and properly resolve regions where we expect instabilities to grow. We find that mass is channeled to the massive stellar system via gravitational and Rayleigh-Taylor (RT) instabilities. For laminar initial conditions, proper treatment of the direct radiation field produces later onset of RT instability, but does not suppress it entirely provided the edges of the radiation-dominated bubbles are adequately resolved. RT instabilities arise immediately for turbulent pre-stellar cores because the initial turbulence seeds the instabilities. To model MSC formation, we simulate the collapse of a dense, turbulent, magnetized Mcl = 106 M⊙ molecular cloud. We find that the influence of the magnetic pressure and radiative feedback slows down star formation. Furthermore, we find that star formation is suppressed along dense filaments where the magnetic field is

  5. First stars X. The nature of three unevolved carbon-enhanced metal-poor stars

    DEFF Research Database (Denmark)

    Sivarani, T.; Beers, T.C.; Bonifacio, P.

    2006-01-01

    Stars: abundances, stars: population II, Galaxy: abundances, stars: AGB and post-AGB Udgivelsesdato: Nov.......Stars: abundances, stars: population II, Galaxy: abundances, stars: AGB and post-AGB Udgivelsesdato: Nov....

  6. Multi-technique investigation of the binary fraction of A-F type candidate hybrid variable stars discovered by Kepler

    Science.gov (United States)

    Lampens, P.; Frémat, Y.; Vermeylen, L.; Sódor, Á.; Skarka, M.; De Cat, P.; Bognár, Zs.; De Nutte, R.; Dumortier, L.; Escorza, A.; Oomen, G. M.; Van de Steene, G.; Kamath, D.; Laverick, M.; Samadi, A.; Triana, S.; Lehmann, H.

    2018-02-01

    Context. Hundreds of candidate hybrid pulsators of intermediate type A-F were revealed by recent space missions. Hybrid pulsators allow us to study the full stellar interiors, where both low-order p- and high-order g-modes are simultaneously excited. The true hybrid stars must be identified since other processes, related to stellar multiplicity or rotation, might explain the presence of (some) low frequencies observed in their periodograms. Aims: We measured the radial velocities of 50 candidate δ Scuti -γ Doradus hybrid stars from the Kepler mission with the Hermes and ACE spectrographs over a time span of months to years. We aim to derive the fraction of binary and multiple systems and to provide an independent and homogeneous determination of the atmospheric properties and v sin i for all targets. The long(er)-term objective is to identify the (probable) physical cause of the low frequencies. Methods: We computed one-dimensional cross-correlation functions (CCFs) in order to find the best set of parameters in terms of the number of components, spectral type(s), and v sin i for each target. Radial velocities were measured using spectrum synthesis and a two-dimensional cross-correlation technique in the case of double- and triple-lined systems. Fundamental parameters were determined by fitting (composite) synthetic spectra to the normalised median spectra corrected for the appropriate Doppler shifts. Results: We report on the analysis of 478 high-resolution Hermes and 41 ACE spectra of A/F-type candidate hybrid pulsators from the Kepler field. We determined their radial velocities, projected rotational velocities, and atmospheric properties and classified our targets based on the shape of the CCFs and the temporal behaviour of the radial velocities. We derived orbital solutions for seven new systems. Three preliminary long-period orbital solutions are confirmed by a photometric time-delay analysis. Finally, we determined a global multiplicity fraction of 27% in

  7. Haematological and genetic features of delta beta-thalassaemia in Pakistan

    International Nuclear Information System (INIS)

    Ahmad, S.; Anwar, M.

    2006-01-01

    Objective: To describe the hematological and genetic features of delta beta-thalassaemia in Pakistani patients. Design: Descriptive case series. Place and Duration of Study: Department of Pathology, PNS Shifa, Karachi and Department of Hematology, Armed Forces Institute of Pathology, Rawalpindi, from January 1994 to April 2004. Patients and Methods: Thirteen individuals from six unrelated Pakistani families with a hematological diagnosis of delta beta-thalassaemia were studied. A brief clinical history, and the results of blood counts, absolute values, Hb-F, Hb-A/sub 2/, and hemoglobin electrophoresis were recorded. The DNA from each subject was first screened for the delta beta-thalassaemia mutations found in the Pakistani population. The samples were then screened for the Invl Del sup G/gamma(sup A/gamma delta beta). Results: The subjects included six heterozygote, six homozygotes and one compound heterozygote of delta beta and delta beta-thalassaemia. All heterozygote and 4/6 homozygotes were asymptomatic. One homo zygote had thalassaemia intermedia while another had transfusion dependent anemia. The mean Hb, TRBC, MCV, MCH, Hb-F and Hb-A/sub 2/ in delta beta-thalassaemia heterozygote were 11.6 g/dl, 5.37 x 1012/L, 70.9 fl, and 21.7 pg, 14% and 2.6% respectively. The same values in the four un transfused homo zygote were 10.6 g/dl, 5.34x1012/L, 69.211, and 20.8pg, 100% and 0% respectively. The mutation analysis revealed that all 13 individuals had the same Invl Del sup G/gamma(sup A/gamma delta beta). Conclusion: delta beta-thalassaemia is a rare disorder in Pakistan. Although the clinical picture is very mild its combination with delta beta-thalassaemia trait can produce a sever transfusion dependent thalassaemia. The DNA based diagnosis is possible in the prenatal as well as the postnatal period. (author)

  8. False star detection and isolation during star tracking based on improved chi-square tests.

    Science.gov (United States)

    Zhang, Hao; Niu, Yanxiong; Lu, Jiazhen; Yang, Yanqiang; Su, Guohua

    2017-08-01

    The star sensor is a precise attitude measurement device for a spacecraft. Star tracking is the main and key working mode for a star sensor. However, during star tracking, false stars become an inevitable interference for star sensor applications, which may result in declined measurement accuracy. A false star detection and isolation algorithm in star tracking based on improved chi-square tests is proposed in this paper. Two estimations are established based on a Kalman filter and a priori information, respectively. The false star detection is operated through adopting the global state chi-square test in a Kalman filter. The false star isolation is achieved using a local state chi-square test. Semi-physical experiments under different trajectories with various false stars are designed for verification. Experiment results show that various false stars can be detected and isolated from navigation stars during star tracking, and the attitude measurement accuracy is hardly influenced by false stars. The proposed algorithm is proved to have an excellent performance in terms of speed, stability, and robustness.

  9. Modern sedimentation and morphology of the subaqueous Mekong Delta, Southern Vietnam

    Science.gov (United States)

    Unverricht, Daniel; Szczuciński, Witold; Stattegger, Karl; Jagodziński, Robert; Le, Xuan Thuyen; Kwong, Laval Liong Wee

    2013-11-01

    The Mekong River Delta is among the Asian mega-deltas and is influenced by various factors including tides (meso-tidal system), waves, coastal currents, monsoon-driven river discharge and human impact (agriculture, fishing, sand dredging, tourism). The present study aims to document the seafloor relief, sediment distribution and sediment accumulation rates to interpret modern sediment transport directions and main sedimentation processes in the subaqueous Mekong Delta. The major results of this investigation include the detection of two delta fronts 200 km apart, one at the mouth of the Bassac River (the biggest branch of the Mekong Delta) and the other around Cape Ca Mau (most south-western end of the Mekong Delta). Additionally, a large channel system runs in the subaqueous delta platform parallel to the shore and between the two fronts. The sediment accumulation rates vary greatly according to the location in the subaqueous delta and have reached up to 10 cm/yr for the last century. A cluster analysis of surface sediment samples revealed two different sediment types within the delta including a well-sorted sandy sediment and a poorly sorted, silty sediment. In addition, a third end member with medium to coarse sand characterised the distant parts of the delta at the transition to the open shelf. The increase of organic matter and carbonate content to the bottom set area and other sedimentary features such as shell fragments, foraminiferas and concretions of palaeo-soils that do not occur in delta sediments, supported grain size-based classification. Beginning in front of the Bassac River mouth, sedimentary pattern indicates clockwise sediment transport alongshore in the western direction to a broad topset area and the delta front around Cape Ca Mau. Our results clearly show the large lateral variability of the subaqueous Mekong Delta that is further complicated by strong monsoon-driven seasonality. River, tidal and wave forcing vary at local and seasonal scales

  10. River Delta Subsidence Measured with Interferometric Synthetic Aperture Radar (InSAR)

    Science.gov (United States)

    Higgins, Stephanie

    This thesis addresses the need for high-resolution subsidence maps of major world river deltas. Driven by a combination of rising water, sediment compaction, and reduced sediment supply due to damming and flood control, many deltas are sinking relative to sea level. A lack of data constraining rates and patterns of subsidence has made it difficult to determine the relative contributions of each factor in any given delta, however, or to assess whether the primary drivers of land subsidence are natural or anthropogenic. In recent years, Interferometric Synthetic Aperture Radar (InSAR) has emerged as a satellite-based technique that can map ground deformation with mm-scale accuracy over thousands of square kilometers. These maps could provide critical insight into the drivers of subsidence in deltas, but InSAR is not typically applied to non-urban delta areas due to the difficulties of performing the technique in wet, vegetated settings. This thesis addresses those difficulties and achieves high-resolution measurements of ground deformation in rural deltaic areas. Chapter 1 introduces the processes that drive relative sea level rise in river deltas and investigates open questions in delta subsidence research. Chapter 2 assesses the performance of InSAR in delta settings and reviews interferogram generation in the context of delta analysis, presenting delta-specific processing details and guiding interpretation in these challenging areas. Chapter 3 applies Differential (D-) InSAR to the coast of the Yellow River Delta in China. Results show that subsidence rates are as high as 250 mm/y due to groundwater extraction at aquaculture facilities, a rate that exceeds local and global average sea level rise by nearly two orders of magnitude and suggests a significant hazard for Asian megadeltas. Chapter 4 applies interferometric stacking and Small Baseline Subset (SBAS)-InSAR to the Ganges-Brahmaputra Delta, Bangladesh. Results show that stratigraphy controls subsidence in

  11. The Great Diversion: Danube Delta under Human Control (Invited)

    Science.gov (United States)

    Giosan, L.

    2009-12-01

    Many deltas around the world are suffering from sediment deficits that render them unstable to current and predicted rates of sea level rise. One solution proposed to alleviate the complete or partial drowning of such deltas is the use of river diversions to increase the quantity of sediment supplied to the delta plain to support marsh accretion. We examine the results of a half century old program of diversion in the Danube delta that led to the creation of an extensive diversion channel network akin in scope and size to a natural deltaic network. Danube’s importance as a shipping route increased after the Crimean War in the 1850s; the European Danube Commission was charged with maintaining the Sulina distributary as a shipping channel until 1940s. In the same period, several canals were dug to aid fishing in lakes and bring freshwater to brackish lagoons. After World War II, Communist authorities dramatically increased the number of canals for fishing, fish-farming and reed harvesting. New data on sedimentation rates and estimates of sediment fluxes suggest that the intensive canalization in the second half of the 20th Century led to increased sediment deposition that compensated the decreasing sediment discharge linked to damming within the internal fluvial part of the delta; however, the external marine delta has become increasingly sediment starved during the same interval. We emphasize the similarities and contrasts between the “human-controlled” and natural deltaic channel networks of the Danube delta and discuss the sustainability of the delta as a sediment budget problem within a sea level rise context.

  12. Population dynamics, delta vulnerability and environmental change: comparison of the Mekong, Ganges–Brahmaputra and Amazon delta regions

    OpenAIRE

    Szabo, S.; Brondizio, E.; Renaud, F.G.; Hetrick, S.; Nicholls, R.; Matthews, Z.; Tessler, Z; Tejedor, A; Sebesvari, Z; Foufoula-Georgiou, E; da Costa, S; Dearing, J.A.

    2016-01-01

    Tropical delta regions are at risk of multiple threats including relative sea level rise and human alterations, making them more and more vulnerable to extreme floods, storms, surges, salinity intrusion, and other hazards which could also increase in magnitude and frequency with a changing climate. Given the environmental vulnerability of tropical deltas, understanding the interlinkages between population dynamics and environmental change in these regions is crucial for ensuring efficient pol...

  13. White Dwarf Stars

    OpenAIRE

    Kepler, S. O.; Romero, Alejandra Daniela; Pelisoli, Ingrid; Ourique, Gustavo

    2017-01-01

    White dwarf stars are the final stage of most stars, born single or in multiple systems. We discuss the identification, magnetic fields, and mass distribution for white dwarfs detected from spectra obtained by the Sloan Digital Sky Survey up to Data Release 13 in 2016, which lead to the increase in the number of spectroscopically identified white dwarf stars from 5000 to 39000. This number includes only white dwarf stars with log g >= 6.5 stars, i.e., excluding the Extremely Low Mass white dw...

  14. THE PREVALENCE AND IMPACT OF WOLF–RAYET STARS IN EMERGING MASSIVE STAR CLUSTERS

    Energy Technology Data Exchange (ETDEWEB)

    Sokal, Kimberly R.; Johnson, Kelsey E.; Indebetouw, Rémy [Department of Astronomy, University of Virginia, P.O. Box 3818, Charlottesville, VA 22903 (United States); Massey, Philip, E-mail: krs9tb@virginia.edu [Lowell Observatory, 1400 W Mars Hill Road, Flagstaff, AZ 86001 (United States)

    2016-08-01

    We investigate Wolf–Rayet (WR) stars as a source of feedback contributing to the removal of natal material in the early evolution of massive star clusters. Despite previous work suggesting that massive star clusters clear out their natal material before the massive stars evolve into the WR phase, WR stars have been detected in several emerging massive star clusters. These detections suggest that the timescale for clusters to emerge can be at least as long as the time required to produce WR stars (a few million years), and could also indicate that WR stars may be providing the tipping point in the combined feedback processes that drive a massive star cluster to emerge. We explore the potential overlap between the emerging phase and the WR phase with an observational survey to search for WR stars in emerging massive star clusters hosting WR stars. We select candidate emerging massive star clusters from known radio continuum sources with thermal emission and obtain optical spectra with the 4 m Mayall Telescope at Kitt Peak National Observatory and the 6.5 m MMT.{sup 4} We identify 21 sources with significantly detected WR signatures, which we term “emerging WR clusters.” WR features are detected in ∼50% of the radio-selected sample, and thus we find that WR stars are commonly present in currently emerging massive star clusters. The observed extinctions and ages suggest that clusters without WR detections remain embedded for longer periods of time, and may indicate that WR stars can aid, and therefore accelerate, the emergence process.

  15. Egyptian "Star Clocks"

    Science.gov (United States)

    Symons, Sarah

    Diagonal, transit, and Ramesside star clocks are tables of astronomical information occasionally found in ancient Egyptian temples, tombs, and papyri. The tables represent the motions of selected stars (decans and hour stars) throughout the Egyptian civil year. Analysis of star clocks leads to greater understanding of ancient Egyptian constellations, ritual astronomical activities, observational practices, and pharaonic chronology.

  16. Stable Isotope (delta OXYGEN-18, Delta Deuterium, Delta CARBON-13) Dendroclimatological Studies in the Waterloo Region of Southern Ontario, Canada, Between AD 1610 and 1990.

    Science.gov (United States)

    Buhay, William Mark

    Oxygen (delta^{18} O), hydrogen (delta^2H) and carbon (delta^{13}C) isotopes were measured in wood cellulose from elm, white pine and maple trees that grew in southwestern Ontario, Canada. The measured oxygen and hydrogen isotopic data were used for model-based reconstructions of delta^{18}{O}_{meteoric water}, mean annual temperature (MAT) and relative humidity for a period, AD 1610 to 1880, that precedes instrumental records of climate. The carbon isotope measurements were compared with the Cellulose Model inferred climate data to reveal additional environmental information. Modifications made to the Cellulose Model focused on the dynamics of oxygen and hydrogen isotopic fractionation in plants during evapotranspiration and photosynthetic assimilation. For instance, kinetic fractionation of ^{18}O was found to be predictable from theoretical considerations of leaf energy balance and boundary layer dynamics. Kinetic fractionation during evapotranspiration is sensitive to the nature of the boundary layer, which is controlled by leaf size and morphology. Generally, plants with small segmented leaves have a lower component of turbidity in the leaf boundary layer, which results in higher kinetic fractionation values, than do plants having large simple leaves and more turbulent boundary layers. Kinetic ^2H enrichment in plant leaf water can also be rationalized in terms of leaf size and morphology when an apparent temperature-dependent isotope effect, acting in opposition to evaporative enrichment, is taken into account. Accounting for this temperature -dependent isotope effect helps to: (1) reconcile hydrogen kinetic fractionation inconsistencies for different leaves; (2) explain a temperature effect previously attributed to variable biochemical fractionation during cellulose synthesis, and; (3) verify hydrogen biochemical effects in plants. This improved characterization of the oxygen and hydrogen isotopic effects in plants, using the modified Cellulose Model, helped

  17. Symbiotic stars

    International Nuclear Information System (INIS)

    Kafatos, M.; Michalitsianos, A.G.

    1984-01-01

    Among the several hundred million binary systems estimated to lie within 3000 light years of the solar system, a tiny fraction, no more than a few hundred, belong to a curious subclass whose radiation has a wavelength distribution so peculiar that it long defied explanation. Such systems radiate strongly in the visible region of the spectrum, but some of them do so even more strongly at both shorter and longer wavelengths: in the ultraviolet region and in the infrared and radio regions. This odd distribution of radiation is best explained by the pairing of a cool red giant star and an intensely hot small star that is virtually in contact with its larger companion. Such objects have become known as symbiotic stars. On photographic plate only the giant star can be discerned, but evidence for the existence of the hot companion has been supplied by satellite-born instruments capable of detecting ultraviolet radiation. The spectra of symbiotic stars indicate that the cool red giant is surrounded by a very hot ionized gas. Symbiotic stars also flared up in outbursts indicating the ejection of material in the form of a shell or a ring. Symbiotic stars may therefore represent a transitory phase in the evolution of certain types of binary systems in which there is substantial transfer of matter from the larger partner to the smaller

  18. Star tracking method based on multiexposure imaging for intensified star trackers.

    Science.gov (United States)

    Yu, Wenbo; Jiang, Jie; Zhang, Guangjun

    2017-07-20

    The requirements for the dynamic performance of star trackers are rapidly increasing with the development of space exploration technologies. However, insufficient knowledge of the angular acceleration has largely decreased the performance of the existing star tracking methods, and star trackers may even fail to track under highly dynamic conditions. This study proposes a star tracking method based on multiexposure imaging for intensified star trackers. The accurate estimation model of the complete motion parameters, including the angular velocity and angular acceleration, is established according to the working characteristic of multiexposure imaging. The estimation of the complete motion parameters is utilized to generate the predictive star image accurately. Therefore, the correct matching and tracking between stars in the real and predictive star images can be reliably accomplished under highly dynamic conditions. Simulations with specific dynamic conditions are conducted to verify the feasibility and effectiveness of the proposed method. Experiments with real starry night sky observation are also conducted for further verification. Simulations and experiments demonstrate that the proposed method is effective and shows excellent performance under highly dynamic conditions.

  19. B- AND A-TYPE STARS IN THE TAURUS-AURIGA STAR-FORMING REGION

    International Nuclear Information System (INIS)

    Mooley, Kunal; Hillenbrand, Lynne; Rebull, Luisa; Padgett, Deborah; Knapp, Gillian

    2013-01-01

    We describe the results of a search for early-type stars associated with the Taurus-Auriga molecular cloud complex, a diffuse nearby star-forming region noted as lacking young stars of intermediate and high mass. We investigate several sets of possible O, B, and early A spectral class members. The first is a group of stars for which mid-infrared images show bright nebulae, all of which can be associated with stars of spectral-type B. The second group consists of early-type stars compiled from (1) literature listings in SIMBAD, (2) B stars with infrared excesses selected from the Spitzer Space Telescope survey of the Taurus cloud, (3) magnitude- and color-selected point sources from the Two Micron All Sky Survey, and (4) spectroscopically identified early-type stars from the Sloan Digital Sky Survey coverage of the Taurus region. We evaluated stars for membership in the Taurus-Auriga star formation region based on criteria involving: spectroscopic and parallactic distances, proper motions and radial velocities, and infrared excesses or line emission indicative of stellar youth. For selected objects, we also model the scattered and emitted radiation from reflection nebulosity and compare the results with the observed spectral energy distributions to further test the plausibility of physical association of the B stars with the Taurus cloud. This investigation newly identifies as probable Taurus members three B-type stars: HR 1445 (HD 28929), τ Tau (HD 29763), 72 Tau (HD 28149), and two A-type stars: HD 31305 and HD 26212, thus doubling the number of stars A5 or earlier associated with the Taurus clouds. Several additional early-type sources including HD 29659 and HD 283815 meet some, but not all, of the membership criteria and therefore are plausible, though not secure, members.

  20. Life of a star

    International Nuclear Information System (INIS)

    Henbest, Nigel.

    1988-01-01

    The paper concerns the theory of stellar evolution. A description is given of:- how a star is born, main sequence stars, red giants, white dwarfs, supernovae, neutron stars and black holes. A brief explanation is given of how the death of a star as a supernova can trigger off the birth of a new generation of stars. Classification of stars and the fate of our sun, are also described. (U.K.)

  1. Understand B-type stars

    Science.gov (United States)

    1982-01-01

    When observations of B stars made from space are added to observations made from the ground and the total body of observational information is confronted with theoretical expectations about B stars, it is clear that nonthermal phenomena occur in the atmospheres of B stars. The nature of these phenomena and what they imply about the physical state of a B star and how a B star evolves are examined using knowledge of the spectrum of a B star as a key to obtaining an understanding of what a B star is like. Three approaches to modeling stellar structure (atmospheres) are considered, the characteristic properties of a mantle, and B stars and evolution are discussed.

  2. Groundwater Flow Model of Göksu Delta Coastal Aquifer System

    Science.gov (United States)

    Erdem Dokuz, Uǧur; Çelik, Mehmet; Arslan, Şebnem; Engin, Hilal

    2016-04-01

    Like many other coastal areas, Göksu Delta (Mersin-Silifke, Southern Turkey) is a preferred place for human settlement especially due to its productive farmlands and water resources. The water dependent ecosystem in Göksu delta hosts about 332 different plant species and 328 different bird species besides serving for human use. Göksu Delta has been declared as Special Environmental Protection Zone, Wildlife Protection Area, and RAMSAR Convention for Wetlands of International Importance area. Unfortunately, rising population, agricultural and industrial activities cause degradation of water resources both by means of quality and quantity. This problem also exists for other wetlands around the world. It is necessary to prepare water management plans by taking global warming issues into account to protect water resources for next generations. To achieve this, the most efficient tool is to come up with groundwater management strategies by constructing groundwater flow models. By this aim, groundwater modeling studies were carried out for Göksu Delta coastal aquifer system. As a first and most important step in all groundwater modeling studies, geological and hydrogeological settings of the study area have been investigated. Göksu Delta, like many other deltaic environments, has a complex structure because it was formed with the sediments transported by Göksu River throughout the Quaternary period and shaped throughout the transgression-regression periods. Both due to this complex structure and the lack of observation wells penetrating deep enough to give an idea of the total thickness of the delta, it was impossible to reveal out the hydrogeological setting in a correct manner. Therefore, six wells were drilled to construct the conceptual hydrogeological model of Göksu Delta coastal aquifer system. On the basis of drilling studies and slug tests that were conducted along Göksu Delta, hydrostratigraphic units of the delta system have been obtained. According to

  3. Isotopic variations ({delta}{sup 13} C and {delta}{sup 18} O) in Siderastrea stellata (Cnidaria-Anthozoa), Itamaraca island, State of Pernambuco, Northeastern Brazil

    Energy Technology Data Exchange (ETDEWEB)

    Ferreira, Valderez P.; Sial, Alcides N. [Pernambuco Univ., Recife, PE (Brazil). Dept. de Geologia. Lab. de Isotopos Estaveis; Mayeal, Elga M.; Exner, Marco Antonio [Pernambuco Univ., Recife, PE (Brazil). Dept. de Zoologia. Lab. de Macro e Megabentos

    1998-12-01

    Isotopic determinations for O and C were performed in coral skeletons collected in beach rocks from two localities (Orange and Catuama), Itamaraca Island, north littoral of the State of pernambuco, northeastern Brazil. Large variations of {delta}{sup 18} O and {delta}{sup 13} C in corals from both localities are found, the largest ones being observed at the Orange locality {delta}{sup 13} C in this locality varies from -0.8 to +1.8% PDB and {delta}{sup 1.8} O from -5.3 to -1.8% PDB, while at the Catuama locality, they vary from -1.8 to 0.1% PDB and -3.8 to -2.7% PDB, respectively. Large variations in {delta}{sup 18} O (up to 2.5%) coupled with weakly defined positive correlation between {delta}{sup 18} O and {delta}{sup 13} C, can be attributed to temperature variations as consequence of climatic perturbations. Temperature estimates, calculated from {delta}{sup 18} O values, assuming isotopic equilibrium with seawater, yield values between 24.9 deg C and 43.1 deg C at Orange, and from 28.4 deg C to 35 deg C at Catuama, all of them (expect one growth band from one sample) are high enough for the full development of the coral colony. Temperature average is 31.4 deg C at Orange, which is a little bit higher than that at Catuama, but both of them indicate thermal stress conditions. In all analyzed specimens, expect for one, at Orange, T increases was accompanied by decreasing in the organic activity, as suggested by corresponding negative {delta}{sup 13} C anomaly. Therefore, the observed bleaching is possibly related to thermal stress and the high T may be related to the El Nino-Southern Oscillation (ENSO) warning event. On the other hand, anthropogenic action at Orange, local of intense tourism throughout the year, coupled with high rate of sedimentation in the region, may contribute to the observed coral bleaching. (author)

  4. Mesquite Risk Mapping and Assessment in Tokar Delta-Eastern Sudan

    OpenAIRE

    Suliman, Mahgoub; NAWATA, Hiroshi; Hoshino, Buho; Karamalla, Abdelaziz

    2015-01-01

    Tokar Delta is a name given to a small delta of approximately 161,000 hectares situated in the southern area of the Red Sea in Eastern Sudan. Beginning of 1980, mesquite species (Prosopis chilensis & Prosopis juliflora) were introduced to Tokar area to be planted as a shelterbelt for the city Tokar, but after while; it spread out to the delta area and became an invasive plant to the agricultural lands and along Khor Barak banks. Nowadays mesquite covers more than half of the delta area, decre...

  5. (p,. pi. /sup -/) reaction and. delta. /sup + +/ components of nuclei

    Energy Technology Data Exchange (ETDEWEB)

    Kisslinger, L S; Miller, G A [Carnegie-Mellon Univ., Pittsburgh, Pa. (USA). Dept. of Physics

    1975-12-08

    The use of the (p,..pi../sup -/) reaction as a probe to determine ..delta../sup + +/(1232) components of nuclear wave functions is examined within the framework of a model which treats baryon resonances on the same footing as nucleons. Nuclear structure properties which affect the ..delta..-probability are discussed. Estimates of cross sections, at several energies, are made for the ..delta../sup + +/ transfer contribution as well as for the competing processes: proton charge exchange (p,n) followed by an (n,..gamma../sup -/) reaction; emission of a ..pi../sup 0/ followed by pion charge exchange (..pi../sup -/,..pi../sup 0/). Even with ..delta..-probabilities as small as 0.0001 the ..delta..-transfer process can compete with ordinary background charge-exchange reactions.

  6. Flare stars

    International Nuclear Information System (INIS)

    Nicastro, A.J.

    1981-01-01

    The least massive, but possibly most numerous, stars in a galaxy are the dwarf M stars. It has been observed that some of these dwarfs are characterized by a short increase in brightness. These stars are called flare stars. These flare stars release a lot of energy in a short amount of time. The process producing the eruption must be energetic. The increase in light intensity can be explained by a small area rising to a much higher temperature. Solar flares are looked at to help understand the phenomenon of stellar flares. Dwarfs that flare are observed to have strong magnetic fields. Those dwarf without the strong magnetic field do not seem to flare. It is believed that these regions of strong magnetic fields are associated with star spots. Theories on the energy that power the flares are given. Astrophysicists theorize that the driving force of a stellar flare is the detachment and collapse of a loop of magnetic flux. The mass loss due to stellar flares is discussed. It is believed that stellar flares are a significant contributor to the mass of interstellar medium in the Milky Way

  7. By Draconis Stars

    Science.gov (United States)

    Bopp, Bernard W.

    An optical spectroscopic survey of dK-M stars has resulted in the discovery of several new H-alpha emission objects. Available optical data suggest these stars have a level of chromospheric activity midway between active BY Dra stars and quiet dM's. These "marginal" BY Dra stars are single objects that have rotation velocities slightly higher than that of quiet field stars but below that of active flare/BY Dra objects. The marginal BY Dra stars provide us with a class of objects rotating very near a "trigger velocity" (believed to be 5 km/s) which appears to divide active flare/BY Dra stars from quiet dM's. UV data on Mg II emission fluxes and strength of transition region features such as C IV will serve to fix activity levels in the marginal objects and determine chromosphere and transition-region heating rates. Simultaneous optical magnetic field measures will be used to explore the connection between fieldstrength/filling-factor and atmospheric heating. Comparison of these data with published information on active and quiet dM stars will yield information on the character of the stellar dynamo as it makes a transition from "low" to "high" activity.

  8. Shooting stars

    International Nuclear Information System (INIS)

    Maurette, M.; Hammer, C.

    1985-01-01

    A shooting star passage -even a star shower- can be sometimes easily seen during moonless black night. They represent the partial volatilization in earth atmosphere of meteorites or micrometeorites reduced in cosmic dusts. Everywhere on earth, these star dusts are searched to be gathered. This research made one year ago on the Greenland ice-cap is this article object; orbit gathering projects are also presented [fr

  9. The Vixen Star Book user guide how to use the star book ten and the original star book

    CERN Document Server

    Chen, James

    2016-01-01

    This book is for anyone who owns, or is thinking of owning, a Vixen Star Book Ten telescope mount or its predecessor. A revolution in amateur astronomy has occurred in the past decade with the wide availability of high tech, computer-driven, Go-To telescopes. Vixen Optics is leading the way by offering the Star Book Ten system, with its unique star map graphics software. The Star Book Ten is the latest version of computer telescope control using star map graphics as a user interface, first introduced in the original Star Book first offered in 2003. The increasingly complicated nature of this software means that learning to optimize this program is not straightforward, and yet the resulting views when all features are correctly deployed can be phenomenal. After a short history of computerized Go-To telescopes for the consumer amateur astronomer market, Chen offers a treasury of technical information. His advice, tips, and solutions aid the user in getting the most out of the Star Book Ten system in observing s...

  10. Polarized antiquark flavor asymmetry DELTA anti u(x)-DELTA anti d(x) and the pion cloud

    CERN Document Server

    Fries, R J; Weiss, C

    2003-01-01

    The flavor asymmetry of the unpolarized antiquark distributions in the proton, anti u(x)- anti d(x)0. Using a simple chiral linear sigma model as an example, we demonstrate that in the meson cloud picture a large positive DELTA anti u(x)-DELTA anti d(x) can be obtained from pi-sigma interference contributions. This calls into question previous estimates based on rho-meson contributions alone, and indicates how the results of the meson cloud picture may be reconciled with those of quark-based models. (orig.)

  11. STAR-TO-STAR IRON ABUNDANCE VARIATIONS IN RED GIANT BRANCH STARS IN THE GALACTIC GLOBULAR CLUSTER NGC 3201

    International Nuclear Information System (INIS)

    Simmerer, Jennifer; Ivans, Inese I.; Filler, Dan; Francois, Patrick; Charbonnel, Corinne; Monier, Richard; James, Gaël

    2013-01-01

    We present the metallicity as traced by the abundance of iron in the retrograde globular cluster NGC 3201, measured from high-resolution, high signal-to-noise spectra of 24 red giant branch stars. A spectroscopic analysis reveals a spread in [Fe/H] in the cluster stars at least as large as 0.4 dex. Star-to-star metallicity variations are supported both through photometry and through a detailed examination of spectra. We find no correlation between iron abundance and distance from the cluster core, as might be inferred from recent photometric studies. NGC 3201 is the lowest mass halo cluster to date to contain stars with significantly different [Fe/H] values.

  12. Star-to-star Iron Abundance Variations in Red Giant Branch Stars in the Galactic Globular Cluster NGC 3201

    Science.gov (United States)

    Simmerer, Jennifer; Ivans, Inese I.; Filler, Dan; Francois, Patrick; Charbonnel, Corinne; Monier, Richard; James, Gaël

    2013-02-01

    We present the metallicity as traced by the abundance of iron in the retrograde globular cluster NGC 3201, measured from high-resolution, high signal-to-noise spectra of 24 red giant branch stars. A spectroscopic analysis reveals a spread in [Fe/H] in the cluster stars at least as large as 0.4 dex. Star-to-star metallicity variations are supported both through photometry and through a detailed examination of spectra. We find no correlation between iron abundance and distance from the cluster core, as might be inferred from recent photometric studies. NGC 3201 is the lowest mass halo cluster to date to contain stars with significantly different [Fe/H] values.

  13. Delta agent (Hepatitis D)

    Science.gov (United States)

    ... this page: //medlineplus.gov/ency/article/000216.htm Hepatitis D (Delta agent) To use the sharing features on this page, please enable JavaScript. Hepatitis D is a viral infection caused by the ...

  14. The first stars: CEMP-no stars and signatures of spinstars

    Science.gov (United States)

    Maeder, André; Meynet, Georges; Chiappini, Cristina

    2015-04-01

    Aims: The CEMP-no stars are "carbon-enhanced-metal-poor" stars that in principle show no evidence of s- and r-elements from neutron captures. We try to understand the origin and nucleosynthetic site of their peculiar CNO, Ne-Na, and Mg-Al abundances. Methods: We compare the observed abundances to the nucleosynthetic predictions of AGB models and of models of rotating massive stars with internal mixing and mass loss. We also analyze the different behaviors of α- and CNO-elements, as well the abundances of elements involved in the Ne-Na and Mg-Al cycles. Results: We show that CEMP-no stars exhibit products of He-burning that have gone through partial mixing and processing by the CNO cycle, producing low 12C/13C and a broad variety of [C/N] and [O/N] ratios. From a 12C/13C vs. [C/N] diagram, we conclude that neither the yields of AGB stars (in binaries or not) nor the yields of classic supernovae can fully account for the observed CNO abundances in CEMP-no stars. Better agreement is obtained once the chemical contribution by stellar winds of fast-rotating massive stars is taken into account, where partial mixing takes place, leading to various amounts of CNO being ejected. The [(C+N+O)/H] ratios of CEMP-no stars vary linearly with [Fe/H] above [Fe/H] = -4.0 indicating primary behavior by (C+N+O). Below [Fe/H] = -4.0, [(C+N+O)/H] is almost constant as a function of [Fe/H], implying very high [(C+N+O)/Fe] ratios up to 4 dex. In view of the timescales, such abundance ratios reflect more individual nucleosynthetic properties, rather than an average chemical evolution. The high [(C+N+O)/Fe] ratios (as well as the high [(C+N+O)/α-elements]) imply that stellar winds from partially mixed stars were the main source of these excesses of heavy elements now observed in CEMP-no stars. The ranges covered by the variations of [Na/Fe], [Mg/Fe], and [Al/Fe] are much broader than for the α-elements (with an atomic mass number above 24) and are comparable to the wide ranges covered

  15. Contaminant Effects on California Bay–Delta Species and Human Health

    Directory of Open Access Journals (Sweden)

    Stephanie Fong

    2016-12-01

    Full Text Available doi: https://doi.org/10.15447/sfews.2016v14iss4art5Many contaminants in the California Bay–Delta (Bay–Delta exceed regulatory standards, affect aquatic species, and potentially affect human health. Recent studies provide multiple lines of evidence that contaminants affect species of concern in the Bay–Delta (e.g., the decline of several important fish species referred to as the “Pelagic Organism Decline” or POD. Contaminants occur as dynamic complex mixtures and exert effects at multiple levels of biological organization. Multiple chemicals impair processes at cellular and physiological levels (measured as growth, development, and behavior abnormalities, and when viability and reproductive output are affected, populations are affected. As an important example, the population decline of the endangered Delta Smelt (Hypomesus transpacificus is significantly associated with multiple stressors, including insecticide use. New analyses presented in this paper show significant correlations between pyrethroid use and declining abundance of POD fish species. Water sampled from the Bay–Delta causes multiple deleterious effects in fish, and Delta Smelt collected from the Bay–Delta exhibit contaminant effects. Fish prey items are also affected by contaminants; this may have an indirect effect on their populations. Co-occurrence with thermal changes or disease can exacerbate contaminant effects. Contaminants also pose threats to human health via consumption of fish and shellfish, drinking water, and contact recreation, in particular, mercury, cyanobacteria toxins, disinfection byproducts, pathogens, pesticides, and pharmaceuticals and personal care products. The role of contaminants in the decline of Bay–Delta species is difficult to accurately assess in a complex, dynamic system. However, tools and approaches are available to evaluate contaminant effects on Bay–Delta species, and separate the effects of multiple stressors. Integrated

  16. Hepatitis delta in HIV-infected individuals in Europe

    DEFF Research Database (Denmark)

    Soriano, Vincent; Grint, Daniel; Monforte, Antonellad'arminio

    2011-01-01

    BACKGROUND:: Hepatitis delta virus (HDV) infection results in the most aggressive form of chronic viral hepatitis. There is scarce information about the prevalence, epidemiology, virological profile and natural historyof hepatitis delta in HIV patients. METHODS:: From 16,597 HIV patients enrolled......-RNA was quantified using a real-time PCR method. RESULTS:: A total of 61/422 HBsAg+ carriers were anti-HDV+ (prevalence: 14.5%). Hepatitis delta predominated in intravenous drug users and for this reason in South and/or East Europe. Serum HDV-RNA was detectable in 87% of tested anti-HDV+ patients, with a median...... titer of 1.76x10¿copies/ml. Overall, delta hepatitis patients showed lower serum HBV-DNA than the rest of HBsAg+ carriers, although the inhibitory effect of HDV on HBV replication was not recognized in HBV genotype D patients.Whereas HDV was not associated with progression to AIDS, it significantly...

  17. Star Cluster Structure from Hierarchical Star Formation

    Science.gov (United States)

    Grudic, Michael; Hopkins, Philip; Murray, Norman; Lamberts, Astrid; Guszejnov, David; Schmitz, Denise; Boylan-Kolchin, Michael

    2018-01-01

    Young massive star clusters (YMCs) spanning 104-108 M⊙ in mass generally have similar radial surface density profiles, with an outer power-law index typically between -2 and -3. This similarity suggests that they are shaped by scale-free physics at formation. Recent multi-physics MHD simulations of YMC formation have also produced populations of YMCs with this type of surface density profile, allowing us to narrow down the physics necessary to form a YMC with properties as observed. We show that the shallow density profiles of YMCs are a natural result of phase-space mixing that occurs as they assemble from the clumpy, hierarchically-clustered configuration imprinted by the star formation process. We develop physical intuition for this process via analytic arguments and collisionless N-body experiments, elucidating the connection between star formation physics and star cluster structure. This has implications for the early-time structure and evolution of proto-globular clusters, and prospects for simulating their formation in the FIRE cosmological zoom-in simulations.

  18. Within-canopy and ozone fumigation effects on delta13C and Delta18O in adult beech (Fagus sylvatica) trees: relation to meteorological and gas exchange parameters.

    Science.gov (United States)

    Gessler, Arthur; Löw, Markus; Heerdt, Christian; de Beeck, Maarten Op; Schumacher, Johannes; Grams, Thorsten E E; Bahnweg, Günther; Ceulemans, Reinhart; Werner, Herbert; Matyssek, Rainer; Rennenberg, Heinz; Haberer, Kristine

    2009-11-01

    In this study, the effects of different light intensities either in direct sunlight or in the shade crown of adult beech (Fagus sylvatica L.) trees on delta13C and Delta18O were determined under ambient (1 x O3) and twice-ambient (2 x O3) atmospheric ozone concentrations during two consecutive years (2003 and 2004). We analysed the isotopic composition in leaf bulk, leaf cellulose, phloem and xylem material and related the results to (a) meteorological data (air temperature, T and relative humidity, RH), (b) leaf gas exchange measurements (stomatal conductance, g(s); transpiration rate, E; and maximum photosynthetic activity, A(max)) and (c) the outcome of a steady-state evaporative enrichment model. Delta13C was significantly lower in the shade than in the sun crown in all plant materials, whilst Delta18O was increased significantly in the shade than in the sun crown in bulk material and cellulose. Elevated ozone had no effect on delta13C, although Delta18O was influenced by ozone to varied degrees during single months. We observed significant seasonal changes for both parameters, especially in 2004, and also significant differences between the study years. Relating the findings to meteorological data and gas exchange parameters, we conclude that the differences in Delta18O between the sun and the shade crown were predominantly caused by the Péclet effect. This assumption was supported by the modelled Delta18O values for leaf cellulose. It was demonstrated that independent of RH, light-dependent reduction of stomatal conductance (and thus transpiration) and of A(max) can drive the pattern of Delta18O increase with the concomitant decrease of delta13C in the shade crown. The effect of doubling ozone levels on time-integrated stomatal conductance and transpiration as indicated by the combined analysis of Delta18O and delta13C was much lower than the influence caused by the light exposure.

  19. The Niger Delta Crisis

    African Journals Online (AJOL)

    chifaou.amzat

    2013-09-28

    Sep 28, 2013 ... Department of History & International Studies, Delta State University, Abraka,. Nigeria. .... democracy implies popular power. That is ... Okonta (2006:5) draws attention to Anna Zalik's treatise called 'Petro-Vio- lence' and ...

  20. Motion-blurred star acquisition method of the star tracker under high dynamic conditions.

    Science.gov (United States)

    Sun, Ting; Xing, Fei; You, Zheng; Wei, Minsong

    2013-08-26

    The star tracker is one of the most promising attitude measurement devices used in spacecraft due to its extremely high accuracy. However, high dynamic performance is still one of its constraints. Smearing appears, making it more difficult to distinguish the energy dispersive star point from the noise. An effective star acquisition approach for motion-blurred star image is proposed in this work. The correlation filter and mathematical morphology algorithm is combined to enhance the signal energy and evaluate slowly varying background noise. The star point can be separated from most types of noise in this manner, making extraction and recognition easier. Partial image differentiation is then utilized to obtain the motion parameters from only one image of the star tracker based on the above process. Considering the motion model, the reference window is adopted to perform centroid determination. Star acquisition results of real on-orbit star images and laboratory validation experiments demonstrate that the method described in this work is effective and the dynamic performance of the star tracker could be improved along with more identified stars and guaranteed position accuracy of the star point.

  1. T gamma/delta lymphocytes in renal transplant recipients

    NARCIS (Netherlands)

    Raasveld, M. H.; Bloemena, E.; Surachno, S.; ten Berge, R. J.

    1992-01-01

    T gamma/delta lymphocytes are able to perform allospecific cytotoxicity and natural killer cytotoxicity in vitro. However, very little is known about their function in vivo. To investigate the possible involvement of T gamma/delta lymphocytes in the immune response to renal allografts, fine-needle

  2. An integrated assessment framework for land subsidence in delta cities

    Directory of Open Access Journals (Sweden)

    T. H. M. Bucx

    2015-11-01

    Full Text Available In many delta cities land subsidence exceeds absolute sea level rise up to a factor of ten by excessive groundwater extraction related to rapid urbanization and population growth. Without change, parts of Jakarta, Ho Chi Minh City, Bangkok and numerous other delta (and coastal cities will sink below sea level. Increased flooding and also other widespread impacts of land subsidence result already in damage of billions of dollars per year. In order to gain insight in the complex, multi-sectoral aspects of subsidence, to raise awareness and to support decision making on appropriate adaptation strategies and measures, an Integrated Assessment Framework (IAF for subsidence is introduced, illustrated by several (delta case studies. Based on that a list of 10 generic key issues and possible solutions is presented in order to further develop and support a (generic approach how to deal with subsidence in current and future subsidence-prone areas. For exchange of experiences and knowledge development.on subsidence in deltas the Delta Alliance, a knowledge network of deltas worldwide, can be supportive.

  3. Delta ferrite in the weld metal of reduced activation ferritic martensitic steel

    Energy Technology Data Exchange (ETDEWEB)

    Sam, Shiju, E-mail: shiju@ipr.res.in [Institute for Plasma Research, Gandhinagar, Gujarat 382 428 (India); Das, C.R.; Ramasubbu, V.; Albert, S.K.; Bhaduri, A.K.; Jayakumar, T. [Indira Gandhi Centre for Atomic Research, Kalpakkam 603 102 (India); Rajendra Kumar, E. [Institute for Plasma Research, Gandhinagar, Gujarat 382 428 (India)

    2014-12-15

    Formation of delta(δ)-ferrite in the weld metal, during autogenous bead-on-plate welding of Reduced Activation Ferritic Martensitic (RAFM) steel using Gas Tungsten Arc Welding (GTAW) process, has been studied. Composition of the alloy is such that delta-ferrite is not expected in the alloy; but examination of the weld metal revealed presence of delta-ferrite in the weld metal. Volume fraction of delta-ferrite is found to be higher in the weld interface than in the rest of the fusion zone. Decrease in the volume fraction of delta-ferrite, with an increase in preheat temperature or with an increase in heat input, is observed. Results indicate that the cooling rate experienced during welding affects the volume fraction of delta-ferrite retained in the weld metal and variation in the delta-ferrite content with cooling rate is explained with variation in the time that the weld metal spends in various temperature regimes in which delta-ferrite is stable for the alloy during its cooling from the liquid metal to the ambient temperature. This manuscript will discuss the effect of welding parameters on formation of delta-ferrite and its retention in the weld metal of RAFM steel.

  4. Average of delta: a new quality control tool for clinical laboratories.

    Science.gov (United States)

    Jones, Graham R D

    2016-01-01

    Average of normals is a tool used to control assay performance using the average of a series of results from patients' samples. Delta checking is a process of identifying errors in individual patient results by reviewing the difference from previous results of the same patient. This paper introduces a novel alternate approach, average of delta, which combines these concepts to use the average of a number of sequential delta values to identify changes in assay performance. Models for average of delta and average of normals were developed in a spreadsheet application. The model assessed the expected scatter of average of delta and average of normals functions and the effect of assay bias for different values of analytical imprecision and within- and between-subject biological variation and the number of samples included in the calculations. The final assessment was the number of patients' samples required to identify an added bias with 90% certainty. The model demonstrated that with larger numbers of delta values, the average of delta function was tighter (lower coefficient of variation). The optimal number of samples for bias detection with average of delta was likely to be between 5 and 20 for most settings and that average of delta outperformed average of normals when the within-subject biological variation was small relative to the between-subject variation. Average of delta provides a possible additional assay quality control tool which theoretical modelling predicts may be more valuable than average of normals for analytes where the group biological variation is wide compared with within-subject variation and where there is a high rate of repeat testing in the laboratory patient population. © The Author(s) 2015.

  5. Delta count-rate monitoring system

    International Nuclear Information System (INIS)

    Van Etten, D.; Olsen, W.A.

    1985-01-01

    A need for a more effective way to rapidly search for gamma-ray contamination over large areas led to the design and construction of a very sensitive gamma detection system. The delta count-rate monitoring system was installed in a four-wheel-drive van instrumented for environmental surveillance and accident response. The system consists of four main sections: (1) two scintillation detectors, (2) high-voltage power supply amplifier and single-channel analyzer, (3) delta count-rate monitor, and (4) count-rate meter and recorder. The van's 6.5-kW generator powers the standard nuclear instrument modular design system. The two detectors are mounted in the rear corners of the van and can be run singly or jointly. A solid-state bar-graph count-rate meter mounted on the dashboard can be read easily by both the driver and passenger. A solid-state strip chart recorder shows trends and provides a permanent record of the data. An audible alarm is sounded at the delta monitor and at the dashboard count-rate meter if a detected radiation level exceeds the set background level by a predetermined amount

  6. Carbon storage in the Mississippi River delta enhanced by environmental engineering

    Science.gov (United States)

    Shields, Michael R.; Bianchi, Thomas S.; Mohrig, David; Hutchings, Jack A.; Kenney, William F.; Kolker, Alexander S.; Curtis, Jason H.

    2017-11-01

    River deltas have contributed to atmospheric carbon regulation throughout Earth history, but functioning in the modern era has been impaired by reduced sediment loads, altered hydrologic regimes, increased global sea-level rise and accelerated subsidence. Delta restoration involves environmental engineering via river diversions, which utilize self-organizing processes to create prograding deltas. Here we analyse sediment cores from Wax Lake delta, a product of environmental engineering, to quantify the burial of organic carbon. We find that, despite relatively low concentrations of organic carbon measured in the cores (about 0.4%), the accumulation of about 3 T m-2 of sediment over the approximate 60 years of delta building resulted in the burial of a significant amount of organic carbon (16 kg m-2). This equates to an apparent organic carbon accumulation rate of 250 +/- 23 g m-2 yr-1, which implicitly includes losses by carbon emissions and erosion. Our estimated accumulation rate for Wax Lake delta is substantially greater than previous estimates based on the top metre of delta sediments and comparable to those of coastal mangrove and marsh habitats. The sedimentation of carbon at the Wax Lake delta demonstrates the capacity of engineered river diversions to enhance both coastal accretion and carbon burial.

  7. The impact of human activities in the Wulan Delta Estuary, Indonesia

    Science.gov (United States)

    Fadlillah, L. N.; Sunarto; Widyastuti, M.; Marfai, M. A.

    2018-04-01

    The increasing of human population in the watershed and the coastal area and the need of life exert pressure in the delta that provides various resources. Wulan Delta is one of active Delta in Central Java, Indonesia. It has been experienced multiple pressures because of natural factors and human factors. In order to provide the scientific solution and to analyze the impact of human intervention in delta, we collected several pieces of evidence based on secondary data and primary data. The secondary data is water quality data on sites 6 and 7, meanwhile the secondary data is the water quality data in site 1 to 5. This paper present a review and problems identification in Wulan Delta, based on hydrological condition, land use, and human activities in the delta. Meanwhile, the human intervention in the land which is land use exchange leads to several problems such as the land use changes, high sediment load, and water degradation. Almost 80% of Delta has been transformed into the fish pond by local communities.

  8. Challenges and Approaches in River Delta Planning - report on training workshop

    NARCIS (Netherlands)

    Wosten, J.H.M.; Douven, W.; Long Phi, H.; Fida Abdullah Khan, M.

    2012-01-01

    River delta’s, like the Mekong Delta (Vietnam), Ganges-Brahmaputra Delta (Bangladesh), Irrawady (Myanmar) and Ciliwung Delta (Indonesia) are developing rapidly and characterized by large-scale urbanization and industrialization processes. They are facing serious planning challenges related to issues

  9. Diet-tissue stable isotope (delta¹³C and delta¹⁵N) discrimination factors for multiple tissues from terrestrial reptiles (rock iguanas, Cyclura species)

    OpenAIRE

    Steinitz, Ronnie

    2015-01-01

    Trophic interactions can drive community structure; therefore, studying food webs is key in understanding ecological communities. Stable isotope analysis is a powerful tool for reconstructing foraging patterns. However, stable isotope discrimination factors (delta¹³C and delta¹⁵N) are needed to best use this tool. We determined the first delta¹³C and delta¹⁵N values for Rock Iguanas (Cyclura spp.) to better understand isotope fractionation patterns in reptiles and estimate wild reptile diets....

  10. Energy production in stars

    International Nuclear Information System (INIS)

    Bethe, Hans.

    1977-01-01

    Energy in stars is released partly by gravitation, partly by nuclear reactions. For ordinary stars like our sun, nuclear reactions predominate. However, at the end of the life of a star very large amounts of energy are released by gravitational collapse; this can amount to as much as 10 times the total energy released nuclear reactions. The rotational energy of pulsars is a small remnant of the energy of gravitation. The end stage of small stars is generally a white dwarf, of heavy stars a neutron star of possibly a black hole

  11. Conflict resolution among Niger delta communities: A historical ...

    African Journals Online (AJOL)

    Conflict related issues have assumed endemic proportion in the Niger Delta. A proper assessment of the critical factors in motion must take cognizance of their historical underpinnings. Peaceful co-existence, the hallmark of conflict resolution, can be feasible in the Niger Delta, through sustainable dialogue. These, among

  12. Environmental Risk Profiling of the Volta Delta, Ghana

    Science.gov (United States)

    Nyarko, B. K.; Appeaning-Addo, K.; Amisigo, B.

    2017-12-01

    Volta Delta communities find it difficult to absorb or bear risk at different levels, because of the physical and economic impacts of environmental hazards. In this regards various agencies and organizations have in recent years launched initiatives to measure and identify risk areas with a set of indicators and indices. The theory underpinning this study is concepts of Modern Portfolio Theory (MPT). The Cox proportional hazards regression model will be used as the model for the risk profile. Finding the optimal level of environmental risk for activities in the Volta Delta considering the risk required, risk capacity and risk tolerance. Using data from different sources, an environmental risk profile was developed for the Volta Delta. The result indicates that risks are distributed across the Delta. However, areas that have government interventions, such as sea defense system and irrigation facilities have less threat. In addition wealthy areas do effectively reduce the threat of any form of disaster.

  13. Stars and Flowers, Flowers and Stars

    Science.gov (United States)

    Minti, Hari

    2012-12-01

    The author, a graduated from the Bucharest University (1964), actually living and working in Israel, concerns his book to variable stars and flowers, two domains of his interest. The analogies includes double stars, eclipsing double stars, eclipses, Big Bang. The book contains 34 chapters, each of which concerns various relations between astronomy and other sciences and pseudosciences such as Psychology, Religion, Geology, Computers and Astrology (to which the author is not an adherent). A special part of the book is dedicated to archeoastronomy and ethnoastronomy, as well as to history of astronomy. Between the main points of interest of these parts: ancient sanctuaries in Sarmizegetusa (Dacia), Stone Henge(UK) and other. The last chapter of the book is dedicated to flowers. The book is richly illustrated. It is designed for a wide circle of readers.

  14. Biomass co-firing for Delta Electricity

    International Nuclear Information System (INIS)

    Anon

    2014-01-01

    Electricity generator Delta Electricity has implemented a biomass co-firing program at its Vales Point power station on the Central Coast to reduce its reliance on coal and emissions of CO 2 . The program comprises two parts: direct co-firing with coal of up to 5% biomass; and development of Continuous Biomass Converter (CBC) technology with the Crucible Group to remove technology constraints and enable much higher rates of biomass co-firing. It is talking industrial scale tests. Delta increased biomass co-firing in 2013/14 to 32,000 tonnes, up from just 3,000 tonnes the previous year, and conducted biochar co-firing trials at a rate equivalent to 400,000 tonnes per annum to demonstrate the potential of CBC technology. It reduced CO 2 emissions in 2013/14 by more than 32,000 tonnes. 'Legislation and regulations define biomass as renewable,' said Delta Electricity sustainability manager Justin Flood. 'By preferring biomass over coal, the carbon in the coal is not burnt and remains locked up.' One biomass source is wood waste that would normally go to landfill, but the primary driver of Delta's recent increase in co-firing is sawmill residues. 'Previously there was a higher value market for the residues for paper pulp. However, when that market evaporated the timber industry was left with a sizable problem in terms of what to do with its residues and the loss of revenue,' said Flood. The way greenhouse gas accounting is conducted in Australia, with carbon emissions based on site activities, makes it difficult to undertake a life cycle assessment of the program. 'However, some of the international studies looking at this issue have concluded that the net carbon emissions of the biomass system are significantly lower than the coal system because of the uptake of carbon during biomass growth,' said Flood. Delta identified two challenges, sourcing the feedstock and that biomass conversion to electricity is slightly less

  15. How bright planets became dim stars: planetary speculations in John Herschel's double star astronomy.

    Science.gov (United States)

    Case, Stephen

    2014-03-01

    Previous research on the origins of double star astronomy in the early nineteenth century emphasized the role mathematical methods and instrumentation played in motivating early observations of these objects. The work of the British astronomer John Herschel, however, shows that questions regarding the physical nature of double stars were also important. In particular, an analysis of John Herschel's early work on double stars illustrates the way in which speculations regarding these objects were shaped by assumptions of the properties of stars themselves. For Herschel, a major consideration in double star astronomy was distinguishing between types of double stars. Optical doubles were useful in determining parallax while binary doubles were not. In practice, classification of a specific double star pair into one of these categories was based on the assumption that stars were of approximately the same luminosity and thus differences in relative brightness between stars were caused by difference in distances. Such assumptions, though ultimately abandoned, would lead Herschel in the 1830s to advance the possibility that the dim companion stars in certain double star pairs were not stars at all but in fact planets. Copyright © 2014 Elsevier Ltd. All rights reserved.

  16. Spectrophotometry of peculiar B and A stars. II. Eleven mercury-manganese stars

    International Nuclear Information System (INIS)

    Adelman, S.J.; Pyper, D.M.

    1979-01-01

    Spectrophotometry of eleven HgMn stars is presented for the optical region. As found in Paper I, the HgMn stars have systematically larger Δiota* and Δa values than the normal main sequence stars due to differences with respect to the mean continuum particularly of the lambda4464 values and the lambda5200 region, respectively. The HgMn stars exhibit a continuous range in the behavior of both the lambda4200 and lambda5200 regions between those stars that have index values larger than the appropriate criterion of presence and present definite evidence for the features to those stars with only a slight possibility of such features. The strengths of the lambda4200 and lambda5200 features appear not to be correlated. In the HgMn stars, both features may be due to differential line blocking. In the energy distribution of all eleven stars, the Balmer jump regions best fit the predictions of slightly hotter solar composition, log g=4.0, fully line blanketed model atmospheres than do the corresponding Paschen continua

  17. VTVH-MCD study of the Delta nifB Delta nifZ MoFe protein from Azotobacter vinelandii.

    Science.gov (United States)

    Cotton, Marcia S; Rupnik, Kresimir; Broach, Robyn B; Hu, Yilin; Fay, Aaron W; Ribbe, Markus W; Hales, Brian J

    2009-04-08

    NifZ is a member of a series of proteins associated with the maturation of the nitrogenase MoFe protein. An MCD spectroscopic study was undertaken on the Delta nifB Delta nifZ MoFe protein generated in the absence of both NifZ and NifB (deletion of NifB generates an apo-MoFe protein lacking the FeMo cofactor). Results presented here show that, in the absence of NifZ, only one of the two P-clusters of the MoFe protein is matured to the ultimate [8Fe-7S] structure. The other P-cluster site in the protein contains a [4Fe-4S] cluster pair, representing a P-cluster precursor that is electronically identical to the analogous clusters observed in the Delta nifH MoFe protein. These results suggest that the MoFe protein is synthesized in a stepwise fashion where NifZ is specifically required for the formation of the second P-cluster.

  18. Discriminating strange star mergers from neutron star mergers by gravitational-wave measurements

    International Nuclear Information System (INIS)

    Bauswein, A.; Oechslin, R.; Janka, H.-T.

    2010-01-01

    We perform three-dimensional relativistic hydrodynamical simulations of the coalescence of strange stars and explore the possibility to decide on the strange matter hypothesis by means of gravitational-wave measurements. Self-binding of strange quark matter and the generally more compact stars yield features that clearly distinguish strange star from neutron star mergers, e.g. hampering tidal disruption during the plunge of quark stars. Furthermore, instead of forming dilute halo structures around the remnant as in the case of neutron star mergers, the coalescence of strange stars results in a differentially rotating hypermassive object with a sharp surface layer surrounded by a geometrically thin, clumpy high-density strange quark matter disk. We also investigate the importance of including nonzero temperature equations of state in neutron star and strange star merger simulations. In both cases we find a crucial sensitivity of the dynamics and outcome of the coalescence to thermal effects, e.g. the outer remnant structure and the delay time of the dense remnant core to black hole collapse depend on the inclusion of nonzero temperature effects. For comparing and classifying the gravitational-wave signals, we use a number of characteristic quantities like the maximum frequency during inspiral or the dominant frequency of oscillations of the postmerger remnant. In general, these frequencies are higher for strange star mergers. Only for particular choices of the equation of state the frequencies of neutron star and strange star mergers are similar. In such cases additional features of the gravitational-wave luminosity spectrum like the ratio of energy emitted during the inspiral phase to the energy radiated away in the postmerger stage may help to discriminate coalescence events of the different types. If such characteristic quantities could be extracted from gravitational-wave signals, for instance with the upcoming gravitational-wave detectors, a decision on the

  19. 78 FR 45592 - DeltaPoint Capital IV, LP;

    Science.gov (United States)

    2013-07-29

    ..., Suite 160, Pittsford, NY 14534. The financing was contemplated for working capital. The financing is... SMALL BUSINESS ADMINISTRATION [License No. 02/02-0662] DeltaPoint Capital IV, LP; Notice Seeking... given that DeltaPoint Capital IV, L.P., 45 East Avenue, 6th Floor, Rochester, NY 14604, Federal...

  20. Towards a Comprehensive Framework for Adaptive Delta Management

    NARCIS (Netherlands)

    Marchand, M.; Ludwig, F.

    2014-01-01

    Deltas are dynamic landforms at the boundary of land and sea, involving intricate mazes of rivers and small waterways, wetlands, estuaries and coastal barrier islands. They are home to over half a billion people. Deltas are also home to rich ecosystems, such as mangroves and marshes. They are

  1. ASTEROSEISMIC DIAGRAMS FROM A SURVEY OF SOLAR-LIKE OSCILLATIONS WITH KEPLER

    Energy Technology Data Exchange (ETDEWEB)

    White, Timothy R.; Bedding, Timothy R.; Stello, Dennis; Benomar, Othman; Huber, Daniel [Sydney Institute for Astronomy (SIfA), School of Physics, University of Sydney, NSW 2006 (Australia); Appourchaux, Thierry; Gaulme, Patrick [Institut d' Astrophysique Spatiale, UMR8617, Universite Paris XI, Batiment 121, 91405 Orsay Cedex (France); Ballot, Jerome [Institut de Recherche en Astrophysique et Planetologie, CNRS, 14 avenue E. Belin, 31400 Toulouse (France); Bonanno, Alfio; Corsaro, Enrico [INAF Observatorio Astrofisico di Catania, Via S. Sofia 78, 95123 Catania (Italy); Broomhall, Anne-Marie; Chaplin, William J.; Elsworth, Yvonne P.; Hekker, Saskia [School of Physics and Astronomy, University of Birmingham, Birmingham B15 2TT (United Kingdom); Campante, Tiago L. [Centro de Astrofisica and Faculdade de Ciencias, Universidade do Porto, Rua das Estrelas, 4150-762 Porto (Portugal); Christensen-Dalsgaard, Jorgen; Dogan, Guelnur; Handberg, Rasmus [Danish AsteroSeismology Centre (DASC), Department of Physics and Astronomy, Aarhus University, DK-8000 Aarhus C (Denmark); Fletcher, Stephen T. [Materials Engineering Research Institute, Faculty of Arts, Computing, Engineering and Sciences, Sheffield Hallam University, Sheffield, S1 1WB (United Kingdom); Garcia, Rafael A., E-mail: t.white@physics.usyd.edu.au [Laboratoire AIM, CEA/DSM-CNRS, Universite Paris 7 Diderot, IRFU/SAp, Centre de Saclay, 91191 Gif-sur-Yvette (France); and others

    2011-11-20

    Photometric observations made by the NASA Kepler Mission have led to a dramatic increase in the number of main-sequence and subgiant stars with detected solar-like oscillations. We present an ensemble asteroseismic analysis of 76 solar-type stars. Using frequencies determined from the Kepler time-series photometry, we have measured three asteroseismic parameters that characterize the oscillations: the large frequency separation ({Delta}{nu}), the small frequency separation between modes of l = 0 and l = 2 ({delta}{nu}{sub 02}), and the dimensionless offset ({epsilon}). These measurements allow us to construct asteroseismic diagrams, namely the so-called Christensen-Dalsgaard diagram of {delta}{nu}{sub 02} versus {Delta}{nu}, and the recently re-introduced {epsilon} diagram. We compare the Kepler results with previously observed solar-type stars and with theoretical models. The positions of stars in these diagrams places constraints on their masses and ages. Additionally, we confirm the observational relationship between {epsilon} and T{sub eff} that allows for the unambiguous determination of radial order and should help resolve the problem of mode identification in F stars.

  2. Assessing Niger-Delta Wetland Resources: A Case-Study of Mangrove Ecosystem

    Science.gov (United States)

    Anwan, R. H.; Ndimele, P. E.; Whenu, O. O.; Anetekhai, M. A.; Essien-Ibok, M. A.; Erondu, E. S.

    2016-02-01

    The Niger Delta is located in the Atlantic coast of Southern Nigeria and is the world's second largest delta with a coastline of about 450km. The Niger Delta region occupies a surface area of about 112,110km2, representing about 12% of Nigeria's total surface area. The Delta's environment can be broken down into four ecological zones: coastal barrier islands, mangrove swamp forests, freshwater swamps, and lowland rainforests. The mangrove swamps of Niger Delta, which is the largest delta in Africa constitute the dominant wetland ecosystem in the Niger Delta region and covers an area of about 1,900km2. Mangroves constitute important nurseries for fishes, crustaceans, sponges, algae and other invertebrates, and also acts as a sink, retaining pollutants from contaminated tidal water. The Niger Delta mangrove together with the creeks and rivers are a major source of food and livelihood for about 30 million people, which represents more than 17% of Nigeria's population. Other ecosystem services provided by this unique environment are flood control, ground water re-fill, reservoir of biodiversity, fuel wood, cultural values etc. This ecosystem also plays important role in climate change mitigation because of its high blue carbon sequestration potential. This is particularly important because of continuous gas flaring in Niger Delta from petroleum operations, which releases carbon dioxide among other gases into the atmosphere. This wetland is potentially a good site for ecotourism and also qualifies to be a world heritage site and Ramsar site if proper steps are taken. The benefits derivable from this fragile ecosystem are under severe threat by anthropogenic stressors. These include the installation of pipelines and seismic exploration by oil companies, crude oil pollution, deforestation, urbanization etc. This paper discusses the extent of depletion and loss of mangrove ecosystem in the Niger Delta region and the value of its goods and services.

  3. Conservative Delta Hedging

    Science.gov (United States)

    1997-09-01

    an exact method for converting such intervals into arbitrage based prices of financial derivatives or industrial or contractual options. We call this...procedure conservative delta hedging . As existing procedures are of an ad hoc nature, the proposed approach will permit an institution’s man agement a greater oversight of its exposure to risk.

  4. Sedimentation patterns in floodplains of the Mekong Delta - Vietnam

    Science.gov (United States)

    Van Manh, Nguyen; Merz, Bruno; Viet Dung, Nguyen; Apel, Heiko

    2013-04-01

    Quantification of floodplain sedimentation during the flood season in the Mekong Delta (MD) plays a very important role in the assessment of flood deposits for a sustainable agro-economic development. Recent studies on floodplain sedimentation in the region are restricted to small pilot sites because of the large extend of the Delta, and the complex channel. This research aims at a quantification of the sediment deposition in floodplains of the whole Mekong Delta, and to access the impacts of the upstream basin development on the sedimentation in the Delta quantitatively. To achieve this, a suspended sediment transport model is developed based on the quasi-2D hydrodynamic model of the whole Mekong Delta developed by Dung et al. (2011). The model is calibrated and validated using observed data derived from several sediment measurement campaigns in channel networks and floodplains. Measured sediment data and hydrodynamic model quantify the spatio-temporal variability of sediment depositions in different spatial units: individual dyke compartments, and the sub-regions Plain of Reeds, Long Xuyen Quadrangle and the area between Tien River and Hau River. It is shown that the distribution of sediment deposition over the delta is highly depended on the flood magnitude, that in turn drives the operation policy of flood control systems in floodplains of the Mekong Delta. Thus, the sedimentation distribution is influenced by the protection level of the dyke systems in place and the distance to the Tien River and Hau River, the main branches of the Mekong in the Delta. This corroborates the main findings derived from data analysis obtained from a small scale test site by Hung et al, (2011, 2012a). Moreover, the results obtained here underlines the importance of the main channels for the sediment transport into the floodplains, and the deposition rate in floodplains is strongly driven by the intake locations and the distance from these to the main channels as well.

  5. Flipped SU(5) predicts {delta}T/T

    Energy Technology Data Exchange (ETDEWEB)

    Kyae, Bumseok [School of Physics, Korea Institute for Advanced Study, 207-43, Cheongnyangni-Dong, Dongdaemun-Gu, Seoul 130-722 (Korea, Republic of)]. E-mail: bkyae@kias.re.kr; Shafi, Qaisar [Bartol Research Institute, Department of Physics and Astronomy, University of Delaware, Newark, DE 19716 (United States)]. E-mail: shafi@bartol.udel.edu

    2006-04-20

    We discuss hybrid inflation in supersymmetric flipped SU(5) model such that the cosmic microwave anisotropy {delta}T/T is essentially proportional to (M/M{sub P}){sup 2}, where M denotes the symmetry breaking scale and M{sub P} (=2.4x10{sup 18} GeV) is the reduced Planck mass. The magnitude of M determined from {delta}T/T measurements can be consistent with the value inferred from the evolution of SU(3) and SU(2) gauge couplings. In other words, one could state that flipped SU(5) predicts (more precisely 'postdicts') {delta}T/T. The scalar spectral index n{sub s}=0.993+/-0.007, the scalar to tensor ratio satisfies r-bar 10{sup -6}, while dn{sub s}/dlnk-bar 4x10{sup -4}.

  6. X-ray sources in regions of star formation. I. The naked T Tauri stars

    International Nuclear Information System (INIS)

    Walter, F.M.

    1986-01-01

    Einstein X-ray observations of regions of active star formation in Taurus, Ophiuchus, and Corona Australis show a greatly enhanced surface density of stellar X-ray sources over that seen in other parts of the sky. Many of the X-ray sources are identified with low-mass, pre-main-sequence stars which are not classical T Tauri stars. The X-ray, photometric, and spectroscopic data for these stars are discussed. Seven early K stars in Oph and CrA are likely to be 1-solar-mass post-T Tauri stars with ages of 10-million yr. The late K stars in Taurus are not post-T Tauri, but naked T Tauri stars, which are coeval with the T Tauri stars, differing mainly in the lack of a circumstellar envelope. 72 references

  7. Thermostatted delta f

    International Nuclear Information System (INIS)

    Krommes, J.A.

    2000-01-01

    The delta f simulation method is revisited. Statistical coarse-graining is used to rigorously derive the equation for the fluctuation delta f in the particle distribution. It is argued that completely collisionless simulation is incompatible with the achievement of true statistically steady states with nonzero turbulent fluxes because the variance of the particle weights w grows with time. To ensure such steady states, it is shown that for dynamically collisionless situations a generalized thermostat or W-stat may be used in lieu of a full collision operator to absorb the flow of entropy to unresolved fine scales in velocity space. The simplest W-stat can be implemented as a self-consistently determined, time-dependent damping applied to w. A precise kinematic analogy to thermostatted nonequilibrium molecular dynamics (NEMD) is pointed out, and the justification of W-stats for simulations of turbulence is discussed. An extrapolation procedure is proposed such that the long-time, steady-state, collisionless flux can be deduced from several short W-statted runs with large effective collisionality, and a numerical demonstration is given

  8. Wave Star

    DEFF Research Database (Denmark)

    Kramer, Morten; Brorsen, Michael; Frigaard, Peter

    Denne rapport beskriver numeriske beregninger af forskellige flydergeometrier for bølgeenergianlæget Wave Star.......Denne rapport beskriver numeriske beregninger af forskellige flydergeometrier for bølgeenergianlæget Wave Star....

  9. Lava delta deformation as a proxy for submarine slope instability

    Science.gov (United States)

    Di Traglia, Federico; Nolesini, Teresa; Solari, Lorenzo; Ciampalini, Andrea; Frodella, William; Steri, Damiano; Allotta, Benedetto; Rindi, Andrea; Marini, Lorenzo; Monni, Niccolò; Galardi, Emanuele; Casagli, Nicola

    2018-04-01

    The instability of lava deltas is a recurrent phenomenon affecting volcanic islands, which can potentially cause secondary events such as littoral explosions (due to interactions between hot lava and seawater) and tsunamis. It has been shown that Interferometric Synthetic Aperture Radar (InSAR) is a powerful technique to forecast the collapse of newly emplaced lava deltas. This work goes further, demonstrating that the monitoring of lava deltas is a successful strategy by which to observe the long-term deformation of subaerial-submarine landslide systems on unstable volcanic flanks. In this paper, displacement measurements derived from Synthetic Aperture Radar (SAR) imagery were used to detect lava delta instability at Stromboli volcano (Italy). Recent flank eruptions (2002-2003, 2007 and 2014) affected the Sciara del Fuoco (SdF) depression, created a "stacked" lava delta, which overlies a pre-existing scar produced by a submarine-subaerial tsunamigenic landslide that occurred on 30 December 2002. Space-borne X-band COSMO-SkyMED (CSK) and C-band SENTINEL-1A (SNT) SAR data collected between February 2010 and October 2016 were processed using the SqueeSAR algorithm. The obtained ground displacement maps revealed the differential ground motion of the lava delta in both CSK and SNT datasets, identifying a stable area (characterized by less than 2 mm/y in both datasets) within the northern sector of the SdF and an unstable area (characterized by velocity fields on the order of 30 mm/y and 160 mm/y in the CSK and SNT datasets, respectively) in the central sector of the SdF. The slope stability of the offshore part of the SdF, as reconstructed based on a recently performed multibeam bathymetric survey, was evaluated using a 3D Limit Equilibrium Method (LEM). In all the simulations, Factor of Safety (F) values between 0.9 and 1.1 always characterized the submarine slope between the coastline and -250 m a.s.l. The critical surfaces for all the search volumes corresponded to

  10. Descendants of the first stars: the distinct chemical signature of second generation stars

    Science.gov (United States)

    Hartwig, Tilman; Yoshida, Naoki; Magg, Mattis; Frebel, Anna; Glover, Simon C. O.; Gómez, Facundo A.; Griffen, Brendan; Ishigaki, Miho N.; Ji, Alexander P.; Klessen, Ralf S.; O'Shea, Brian W.; Tominaga, Nozomu

    2018-05-01

    Extremely metal-poor (EMP) stars in the Milky Way (MW) allow us to infer the properties of their progenitors by comparing their chemical composition to the metal yields of the first supernovae. This method is most powerful when applied to mono-enriched stars, i.e. stars that formed from gas that was enriched by only one previous supernova. We present a novel diagnostic to identify this subclass of EMP stars. We model the first generations of star formation semi-analytically, based on dark matter halo merger trees that yield MW-like halos at the present day. Radiative and chemical feedback are included self-consistently and we trace all elements up to zinc. Mono-enriched stars account for only ˜1% of second generation stars in our fiducial model and we provide an analytical formula for this probability. We also present a novel analytical diagnostic to identify mono-enriched stars, based on the metal yields of the first supernovae. This new diagnostic allows us to derive our main results independently from the specific assumptions made regarding Pop III star formation, and we apply it to a set of observed EMP stars to demonstrate its strengths and limitations. Our results may provide selection criteria for current and future surveys and therefore contribute to a deeper understanding of EMP stars and their progenitors.

  11. Parametrization of the. delta. residue function. [Complex functions

    Energy Technology Data Exchange (ETDEWEB)

    Vasan, S S [Carnegie-Mellon Univ., Pittsburgh, Pa. (USA). Dept. of Physics

    1976-04-19

    The complex residues at the ..delta..(1236) and ..delta..(1950) poles in the relevant partial-wave amplitudes provide information on the behaviour of the ..delta.. Regge residue function in the resonance region u>0. Attempts to incorporate this information in parametrizations of the residue by functions that are real on the real u-axis result in residues which have unsatisfactory behaviour in the region u<1GeV/sup 2/. The choice of complex functions for the trajectory and residue removes this undesirable feature and provides a better representation of the residue in the resonance region, suggesting that complex parametrizations would be better suited to Regge analyses of near-backward scattering.

  12. Neutron star formation in theoretical supernovae. Low mass stars and white dwarfs

    International Nuclear Information System (INIS)

    Nomoto, K.

    1986-01-01

    The presupernova evolution of stars that form semi-degenerate or strongly degenerate O + Ne + Mg cores is discussed. For the 10 to 13 Msub solar stars, behavior of off-center neon flashes is crucial. The 8 to 10 m/sub solar stars do not ignite neon and eventually collapse due to electron captures. Properties of supernova explosions and neutron stars expected from these low mass progenitors are compared with the Crab nebula. The conditions for which neutron stars form from accretion-induced collapse of white dwarfs in clsoe binary systems is also examined

  13. Central Delta languages: An overview | Kari | Stellenbosch Papers ...

    African Journals Online (AJOL)

    This paper presents an overview of the phonology, morphology and syntax of Central Delta languages. It also provides information on the geo-linguistic, demographic and sociolinguistic situation of these languages. It notes that Central Delta languages have a 20-vowel system, which divides into two sets of 10 vowels ...

  14. Topological Mappings via B&delta;g-Closed Sets

    OpenAIRE

    Maruthamuthu, Raja; Narayanasamy, Seenivasagan; Otchanathevar, Ravi

    2018-01-01

    In this paper we introduce a new class of functions called  B&delta;g-continuous functions. We obtain several characterizations and some their properties. Also we investigate its relationship with other types of functions. Further we introduce and study a new class of functions namely B&delta;g-irresolute.

  15. Sand transport, shear stress, and the building of a delta

    Science.gov (United States)

    Wagner, W.; Miller, K. L.; Hiatt, M. R.; Mohrig, D. C.

    2017-12-01

    River deltas distribute sediment to the coastal sea through a complex branching network of channels; however, the routing and storage of this sediment in and through the delta is poorly understood. We present results from field studies of the sediment and water transport through the branching Wax Lake Delta on the coast of Louisiana. Two channels studied, Main Pass and East Pass, maintain a near-equal total partitioning of flow and sediment. However, East Pass is narrower and has higher river velocities, lower tidal velocity fluctuations, less alluvial bed cover, and more sediment flux per unit width than Main Pass. We connect these differences to small differences in the geometry of the two channels and feedbacks between these differences. We link trends in measured sediment deposits to both measured and modeled shear velocities in Wax Lake Delta's channels and open water `islands' to understand how hydrologic processes shaped the sedimentary architecture of the delta. These connections define the sediment transport and deposition regimes in the WLD. We extend the results herein to suggest that the relationships between the available sediment and shear stress determines the basic planform of the Wax Lake Delta and cross-sectional geometries of its channels.

  16. General Relativity and Compact Stars

    International Nuclear Information System (INIS)

    Glendenning, Norman K.

    2005-01-01

    Compact stars--broadly grouped as neutron stars and white dwarfs--are the ashes of luminous stars. One or the other is the fate that awaits the cores of most stars after a lifetime of tens to thousands of millions of years. Whichever of these objects is formed at the end of the life of a particular luminous star, the compact object will live in many respects unchanged from the state in which it was formed. Neutron stars themselves can take several forms--hyperon, hybrid, or strange quark star. Likewise white dwarfs take different forms though only in the dominant nuclear species. A black hole is probably the fate of the most massive stars, an inaccessible region of spacetime into which the entire star, ashes and all, falls at the end of the luminous phase. Neutron stars are the smallest, densest stars known. Like all stars, neutron stars rotate--some as many as a few hundred times a second. A star rotating at such a rate will experience an enormous centrifugal force that must be balanced by gravity or else it will be ripped apart. The balance of the two forces informs us of the lower limit on the stellar density. Neutron stars are 10 14 times denser than Earth. Some neutron stars are in binary orbit with a companion. Application of orbital mechanics allows an assessment of masses in some cases. The mass of a neutron star is typically 1.5 solar masses. They can therefore infer their radii: about ten kilometers. Into such a small object, the entire mass of our sun and more, is compressed

  17. A Novel Sigma-Delta Modulator with Fractional-Order Digital Loop Integrator

    Directory of Open Access Journals (Sweden)

    Chi Xu

    2017-01-01

    Full Text Available This paper proposes using a fractional-order digital loop integrator to improve the robust stability of Sigma-Delta modulator, thus extending the integer-order Sigma-Delta modulator to a non-integer-order (fractional-order one in the Sigma-Delta ADC design field. The proposed fractional-order Sigma-Delta modulator has reasonable noise characteristics, dynamic range, and bandwidth; moreover the signal-to-noise ratio (SNR is improved remarkably. In particular, a 2nd-order digital loop integrator and a digital PIλDμ controller are combined to work as the fractional-order digital loop integrator, which is realized using FPGA; this will reduce the ASIC analog circuit layout design and chip testing difficulties. The parameters of the proposed fractional-order Sigma-Delta modulator are tuned by using swarm intelligent algorithm, which offers opportunity to simplify the process of tuning parameters and further improve the noise performance. Simulation results are given and they demonstrate the efficiency of the proposed fractional-order Sigma-Delta modulator.

  18. Star formation

    International Nuclear Information System (INIS)

    Woodward, P.R.

    1978-01-01

    Theoretical models of star formation are discussed beginning with the earliest stages and ending in the formation of rotating, self-gravitating disks or rings. First a model of the implosion of very diffuse gas clouds is presented which relies upon a shock at the edge of a galactic spiral arm to drive the implosion. Second, models are presented for the formation of a second generation of massive stars in such a cloud once a first generation has formed. These models rely on the ionizing radiation from massive stars or on the supernova shocks produced when these stars explode. Finally, calculations of the gravitational collapse of rotating clouds are discussed with special focus on the question of whether rotating disks or rings are the result of such a collapse. 65 references

  19. Dark stars: a new study of the first stars in the Universe

    International Nuclear Information System (INIS)

    Freese, Katherine; Bodenheimer, Peter; Gondolo, Paolo; Spolyar, Douglas

    2009-01-01

    We have proposed that the first phase of stellar evolution in the history of the Universe may be dark stars (DSs), powered by dark matter (DM) heating rather than by nuclear fusion. Weakly interacting massive particles, which may be their own antipartners, collect inside the first stars and annihilate to produce a heat source that can power the stars. A new stellar phase results, a DS, powered by DM annihilation as long as there is DM fuel, with lifetimes from millions to billions of years. We find that the first stars are very bright (∼10 6 L o-dot ) and cool (T surf surf > 50 000 K); hence DS should be observationally distinct from standard Pop III stars. Once the DM fuel is exhausted, the DS becomes a heavy main sequence star; these stars eventually collapse to form massive black holes that may provide seeds for supermassive black holes observed at early times as well as explanations for recent ARCADE data and for intermediate black holes.

  20. Challenges and Approaches in River Delta Planning - Annexes to report on training workshop

    NARCIS (Netherlands)

    Wosten, J.H.M.; Douven, W.; Long Phi, H.; Fida Abdullah Khan, M.

    2012-01-01

    Programme, participants and all powerpoint presentations of the Delta Alliance Training Workshop: Challenges and approaches in river delta planning, sharing experiences from SE Asian Deltas and the Rhine-Meuse Delta. 22-26 October 2012, WACC, Vietnam National University, Ho Chi Minh City, Vietnam

  1. Introduction to neutron stars

    Energy Technology Data Exchange (ETDEWEB)

    Lattimer, James M. [Dept. of Physics and Astronomy, Stony Brook University, Stony Brook, NY 11794-3800 (United States)

    2015-02-24

    Neutron stars contain the densest form of matter in the present universe. General relativity and causality set important constraints to their compactness. In addition, analytic GR solutions are useful in understanding the relationships that exist among the maximum mass, radii, moments of inertia, and tidal Love numbers of neutron stars, all of which are accessible to observation. Some of these relations are independent of the underlying dense matter equation of state, while others are very sensitive to the equation of state. Recent observations of neutron stars from pulsar timing, quiescent X-ray emission from binaries, and Type I X-ray bursts can set important constraints on the structure of neutron stars and the underlying equation of state. In addition, measurements of thermal radiation from neutron stars has uncovered the possible existence of neutron and proton superfluidity/superconductivity in the core of a neutron star, as well as offering powerful evidence that typical neutron stars have significant crusts. These observations impose constraints on the existence of strange quark matter stars, and limit the possibility that abundant deconfined quark matter or hyperons exist in the cores of neutron stars.

  2. Polarization of Be stars

    International Nuclear Information System (INIS)

    Johns, M.W.

    1975-01-01

    Linear polarization of starlight may be produced by electron scattering in the extended atmospheres of early type stars. Techniques are investigated for the measurement and interpretation of this polarization. Polarimetric observations were made of twelve visual double star systems in which at least one member was a B type star as a means of separating the intrinsic stellar polarization from the polarization produced in the interstellar medium. Four of the double stars contained a Be star. Evidence for intrinsic polarization was found in five systems including two of the Be systems, one double star with a short period eclipsing binary, and two systems containing only normal early type stars for which emission lines have not been previously reported. The interpretation of these observations in terms of individual stellar polarizations and their wavelength dependence is discussed. The theoretical basis for the intrinsic polarization of early type stars is explored with a model for the disk-like extended atmospheres of Be stars. Details of a polarimeter for the measurement of the linear polarization of astronomical point sources are also presented with narrow band (Δ lambda = 100A) measurements of the polarization of γ Cas from lambda 4000 to lambda 5800

  3. Cerebral correlates of delta waves during non-REM sleep revisited.

    Science.gov (United States)

    Dang-Vu, Thien Thanh; Desseilles, Martin; Laureys, Steven; Degueldre, Christian; Perrin, Fabien; Phillips, Christophe; Maquet, Pierre; Peigneux, Philippe

    2005-10-15

    We aimed at characterizing the neural correlates of delta activity during Non Rapid Eye Movement (NREM) sleep in non-sleep-deprived normal young adults, based on the statistical analysis of a positron emission tomography (PET) sleep data set. One hundred fifteen PET scans were obtained using H(2)(15)O under continuous polygraphic monitoring during stages 2-4 of NREM sleep. Correlations between regional cerebral blood flow (rCBF) and delta power (1.5-4 Hz) spectral density were analyzed using statistical parametric mapping (SPM2). Delta power values obtained at central scalp locations negatively correlated during NREM sleep with rCBF in the ventromedial prefrontal cortex, the basal forebrain, the striatum, the anterior insula, and the precuneus. These regions embrace the set of brain areas in which rCBF decreases during slow wave sleep (SWS) as compared to Rapid Eye Movement (REM) sleep and wakefulness (Maquet, P., Degueldre, C., Delfiore, G., Aerts, J., Peters, J.M., Luxen, A., Franck, G., 1997. Functional neuroanatomy of human slow wave sleep. J. Neurosci. 17, 2807-S2812), supporting the notion that delta activity is a valuable prominent feature of NREM sleep. A strong association was observed between rCBF in the ventromedial prefrontal regions and delta power, in agreement with electrophysiological studies. In contrast to the results of a previous PET study investigating the brain correlates of delta activity (Hofle, N., Paus, T., Reutens, D., Fiset, P., Gotman, J., Evans, A.C., Jones, B.E., 1997. Regional cerebral blood flow changes as a function of delta and spindle activity during slow wave sleep in humans. J. Neurosci. 17, 4800-4808), in which waking scans were mixed with NREM sleep scans, no correlation was found with thalamus activity. This latter result stresses the importance of an extra-thalamic delta rhythm among the synchronous NREM sleep oscillations. Consequently, this rCBF distribution might preferentially reflect a particular modulation of the

  4. Rates of star formation

    International Nuclear Information System (INIS)

    Larson, R.B.

    1977-01-01

    It is illustrated that a theoretical understanding of the formation and evolution of galaxies depends on an understanding of star formation, and especially of the factors influencing the rate of star formation. Some of the theoretical problems of star formation in galaxies, some approaches that have been considered in models of galaxy evolution, and some possible observational tests that may help to clarify which processes or models are most relevant are reviewed. The material is presented under the following headings: power-law models for star formation, star formation processes (conditions required, ways of achieving these conditions), observational indications and tests, and measures of star formation rates in galaxies. 49 references

  5. Adaptive delta management: a comparison between the Netherlands and Bangladesh Delta Program

    NARCIS (Netherlands)

    Zevenbergen, Chris; Khan, Shah Alam; Alphen, van Jos; Terwisscha van Scheltinga, Catharien; Veerbeek, William

    2018-01-01

    In the Netherlands, the central government, water authorities, provinces and municipalities are working together on a new Delta Program on Flood Risk Management and Fresh Water Supply (DP). Its primary goal is to protect the Netherlands against floods and ensure the availability of fresh water, now

  6. Cohesive Sedimentary Processes on River-Dominated Deltas: New Perspectives from the Mississippi River Delta Front, Gulf of Mexico

    Science.gov (United States)

    Bentley, S. J.; Keller, G. P.; Obelcz, J.; Maloney, J. M.; Xu, K.; Georgiou, I. Y.; Miner, M. D.

    2016-12-01

    On river deltas dominated by proximal sediment accumulation (Mississippi, Huang He, others), the delta front region is commonly dominated by rapid accumulation of cohesive fluvial sediments, and mass-wasting processes that remobilize recently deposited sediments. Mass transport is preconditioned in sediments by high water content, biogenic gas production, over steepening, and is commonly triggered by strong wave loading and other processes. This understanding is based on extensive field studies in the 1970's and 80's. Recent studies of the Mississippi River Delta Front are yielding new perspectives on these processes, in a time of anthropogenically reduced sediment loads, rising sea level, and catastrophic deltaic land loss. We have synthesized many industry data sets collected since ca. 1980, and conducted new pilot field and modeling studies of sedimentary and morphodynamic processes. These efforts have yielded several key findings that diverge from historical understanding of this dynamic setting. First, delta distributary mouths have ceased seaward progradation, ending patterns that have been documented since the 18th century. Second, despite reduced sediment supply, offshore mass transport continues, yielding vertical displacements at rates of 1 m/y. This displacement is apparently forced by wave loading from storm events of near-annual return period, rather than major hurricanes that have been the focus of most previous studies. Third, core analysis indicates that this vertical displacement is occurring along failure planes >3 m in the seabed, rather than in more recently deposited sediments closer to the sediment-water interface. These seabed morphodynamics have the potential to destabilize both nearshore navigation infrastructure, and seabed hydrocarbon infrastructure offshore. As well, these findings raise more questions regarding the future seabed evolution offshore of major river deltas, in response to anthropogenic and climatic forcing.

  7. Grain-size sorting in grainflows at the lee side of deltas

    NARCIS (Netherlands)

    Kleinhans, M.G.

    2005-01-01

    The sorting of sediment mixtures at the lee slope of deltas (at the angle of repose) is studied with experiments in a narrow, deep flume with subaqueous Gilbert-type deltas using varied flow conditions and different sediment mixtures. Sediment deposition and sorting on the lee slope of the delta

  8. The Drifting Star

    Science.gov (United States)

    2008-04-01

    By studying in great detail the 'ringing' of a planet-harbouring star, a team of astronomers using ESO's 3.6-m telescope have shown that it must have drifted away from the metal-rich Hyades cluster. This discovery has implications for theories of star and planet formation, and for the dynamics of our Milky Way. ESO PR Photo 09a/08 ESO PR Photo 09a/08 Iota Horologii The yellow-orange star Iota Horologii, located 56 light-years away towards the southern Horologium ("The Clock") constellation, belongs to the so-called "Hyades stream", a large number of stars that move in the same direction. Previously, astronomers using an ESO telescope had shown that the star harbours a planet, more than 2 times as large as Jupiter and orbiting in 320 days (ESO 12/99). But until now, all studies were unable to pinpoint the exact characteristics of the star, and hence to understand its origin. A team of astronomers, led by Sylvie Vauclair from the University of Toulouse, France, therefore decided to use the technique of 'asteroseismology' to unlock the star's secrets. "In the same way as geologists monitor how seismic waves generated by earthquakes propagate through the Earth and learn about the inner structure of our planet, it is possible to study sound waves running through a star, which forms a sort of large, spherical bell," says Vauclair. The 'ringing' from this giant musical instrument provides astronomers with plenty of information about the physical conditions in the star's interior. And to 'listen to the music', the astronomers used one of the best instruments available. The observations were conducted in November 2006 during 8 consecutive nights with the state-of-the-art HARPS spectrograph mounted on the ESO 3.6-m telescope at La Silla. Up to 25 'notes' could be identified in the unique dataset, most of them corresponding to waves having a period of about 6.5 minutes. These observations allowed the astronomers to obtain a very precise portrait of Iota Horologii: its

  9. INFRARED TWO-COLOR DIAGRAMS FOR AGB STARS, POST-AGB STARS, AND PLANETARY NEBULAE

    Energy Technology Data Exchange (ETDEWEB)

    Suh, Kyung-Won, E-mail: kwsuh@chungbuk.ac.kr [Department of Astronomy and Space Science, Chungbuk National University, Cheongju-City, 362-763 (Korea, Republic of)

    2015-08-01

    We present various infrared two-color diagrams (2CDs) for asymptotic giant branch (AGB) stars, post-AGB stars, and Planetary Nebulae (PNe) and investigate possible evolutionary tracks. We use catalogs from the available literature for the sample of 4903 AGB stars (3373 O-rich; 1168 C-rich; 362 S-type), 660 post-AGB stars (326 post-AGB; 334 pre-PN), and 1510 PNe in our Galaxy. For each object in the catalog, we cross-identify the IRAS, AKARI, Midcourse Space Experiment, and 2MASS counterparts. The IR 2CDs can provide useful information about the structure and evolution of the dust envelopes as well as the central stars. To find possible evolutionary tracks from AGB stars to PNe on the 2CDs, we investigate spectral evolution of post-AGB stars by making simple but reasonable assumptions on the evolution of the central star and dust shell. We perform radiative transfer model calculations for the detached dust shells around evolving central stars in the post-AGB phase. We find that the theoretical dust shell model tracks using dust opacity functions of amorphous silicate and amorphous carbon roughly coincide with the densely populated observed points of AGB stars, post-AGB stars, and PNe on various IR 2CDs. Even though some discrepancies are inevitable, the end points of the theoretical post-AGB model tracks generally converge in the region of the observed points of PNe on most 2CDs.

  10. Governance of ‘long term delta planning’ in Bangladesh, Vietnam and the Netherlands

    NARCIS (Netherlands)

    Staveren, van M.F.

    2014-01-01

    The Deltas in Times of Climate Change Conference II, taking place in September 2014, Rotterdam, presented a suitable occasion to discuss both delta challenges and interesting approaches to how ‘delta dynamics’ are being dealt with worldwide.1 Delta dynamics include here both environmental (including

  11. Interacting binary stars

    CERN Document Server

    Sahade, Jorge; Ter Haar, D

    1978-01-01

    Interacting Binary Stars deals with the development, ideas, and problems in the study of interacting binary stars. The book consolidates the information that is scattered over many publications and papers and gives an account of important discoveries with relevant historical background. Chapters are devoted to the presentation and discussion of the different facets of the field, such as historical account of the development in the field of study of binary stars; the Roche equipotential surfaces; methods and techniques in space astronomy; and enumeration of binary star systems that are studied

  12. Structure of the [delta]-opioid receptor bound to naltrindole

    Energy Technology Data Exchange (ETDEWEB)

    Granier, Sébastien; Manglik, Aashish; Kruse, Andrew C.; Kobilka, Tong Sun; Thian, Foon Sun; Weis, William I.; Kobilka, Brian K. (Stanford-MED)

    2012-07-11

    The opioid receptor family comprises three members, the {mu}-, {delta}- and {kappa}-opioid receptors, which respond to classical opioid alkaloids such as morphine and heroin as well as to endogenous peptide ligands like endorphins. They belong to the G-protein-coupled receptor (GPCR) superfamily, and are excellent therapeutic targets for pain control. The {delta}-opioid receptor ({delta}-OR) has a role in analgesia, as well as in other neurological functions that remain poorly understood. The structures of the {mu}-OR and {kappa}-OR have recently been solved. Here we report the crystal structure of the mouse {delta}-OR, bound to the subtype-selective antagonist naltrindole. Together with the structures of the {mu}-OR and {kappa}-OR, the {delta}-OR structure provides insights into conserved elements of opioid ligand recognition while also revealing structural features associated with ligand-subtype selectivity. The binding pocket of opioid receptors can be divided into two distinct regions. Whereas the lower part of this pocket is highly conserved among opioid receptors, the upper part contains divergent residues that confer subtype selectivity. This provides a structural explanation and validation for the 'message-address' model of opioid receptor pharmacology, in which distinct 'message' (efficacy) and 'address' (selectivity) determinants are contained within a single ligand. Comparison of the address region of the {delta}-OR with other GPCRs reveals that this structural organization may be a more general phenomenon, extending to other GPCR families as well.

  13. Wolf-Rayet stars and O-star runaways with HIPPARCOS - I. Kinematics

    NARCIS (Netherlands)

    Moffat, AFJ; Marchenko, SV; Seggewiss, W; van der Hucht, KA; Schrijver, H; Stenholm, B; Lundstrom, [No Value; Gunawan, DYAS; Sutantyo, W; van den Heuvel, EPJ; De Cuyper, JP; Gomez, AE

    Reliable systemic radial velocities are almost impossible to secure for Wolf-Rayet stars, difficult for O stars. Therefore, to study the motions - both systematic in the Galaxy and peculiar - of these two related types of hot, luminous star, we have examined the Hipparcos proper motions of some 70

  14. Evolution of variable stars

    International Nuclear Information System (INIS)

    Becker, S.A.

    1986-08-01

    Throughout the domain of the H R diagram lie groupings of stars whose luminosity varies with time. These variable stars can be classified based on their observed properties into distinct types such as β Cephei stars, δ Cephei stars, and Miras, as well as many other categories. The underlying mechanism for the variability is generally felt to be due to four different causes: geometric effects, rotation, eruptive processes, and pulsation. In this review the focus will be on pulsation variables and how the theory of stellar evolution can be used to explain how the various regions of variability on the H R diagram are populated. To this end a generalized discussion of the evolutionary behavior of a massive star, an intermediate mass star, and a low mass star will be presented. 19 refs., 1 fig., 1 tab

  15. A new method for determining which stars are near a star sensor field-of-view

    Science.gov (United States)

    Yates, Russell E., Jr.; Vedder, John D.

    1991-01-01

    A new method is described for determining which stars in a navigation star catalog are near a star sensor field of view (FOV). This method assumes that an estimate of spacecraft inertial attitude is known. Vector component ranges for the star sensor FOV are computed, so that stars whose vector components lie within these ranges are near the star sensor FOV. This method requires no presorting of the navigation star catalog, and is more efficient than tradition methods.

  16. Monitoring the High-Energy Radiation Environment of Exoplanets Around Low-mass Stars with SPARCS (Star-Planet Activity Research CubeSat)

    Science.gov (United States)

    Shkolnik, Evgenya L.; Ardila, David; Barman, Travis; Beasley, Matthew; Bowman, Judd D.; Gorjian, Varoujan; Jacobs, Daniel; Jewell, April; Llama, Joe; Meadows, Victoria; Nikzad, Shouleh; Scowen, Paul; Swain, Mark; Zellem, Robert

    2018-01-01

    Roughly seventy-five billion M dwarfs in our galaxy host at least one small planet in the habitable zone (HZ). The stellar ultraviolet (UV) radiation from M dwarfs is strong and highly variable, and impacts planetary atmospheric loss, composition and habitability. These effects are amplified by the extreme proximity of their HZs (0.1–0.4 AU). Knowing the UV environments of M dwarf planets will be crucial to understanding their atmospheric composition and a key parameter in discriminating between biological and abiotic sources for observed biosignatures. The Star-Planet Activity Research CubeSat (SPARCS) will be a 6U CubeSat devoted to photometric monitoring of M stars in the far-UV and near-UV, measuring the time-dependent spectral slope, intensity and evolution of M dwarf stellar UV radiation. For each target, SPARCS will observe continuously over at least one complete stellar rotation (5 - 45 days). SPARCS will also advance UV detector technology by flying high quantum efficiency, UV-optimized detectors developed at JPL. These Delta-doped detectors have a long history of deployment demonstrating greater than five times the quantum efficiency of the detectors used by GALEX. SPARCS will pave the way for their application in missions like LUVOIR or HabEx, including interim UV-capable missions. SPARCS will also be capable of ‘target-of-opportunity’ UV observations for the rocky planets in M dwarf HZs soon to be discovered by NASA’s TESS mission, providing the needed UV context for the first habitable planets that JWST will characterize.Acknowledgements: Funding for SPARCS is provided by NASA’s Astrophysics Research and Analysis program, NNH16ZDA001N.

  17. THE AGE-METALLICITY RELATIONSHIP OF THE LARGE MAGELLANIC CLOUD FIELD STAR POPULATION FROM WIDE-FIELD WASHINGTON PHOTOMETRY

    Energy Technology Data Exchange (ETDEWEB)

    Piatti, Andres E. [Instituto de Astronomia y Fisica del Espacio, CC 67, Suc. 28, 1428 Ciudad de Buenos Aires (Argentina); Geisler, Doug, E-mail: andres@iafe.uba.ar [Departamento de Astronomia, Universidad de Concepcion, Casilla 160-C, Concepcion (Chile)

    2013-01-01

    We analyze age and metallicity estimates for an unprecedented database of some 5.5 million stars distributed throughout the Large Magellanic Cloud (LMC) main body, obtained from CCD Washington CT{sub 1} photometry, reported on in Piatti et al. We produce a comprehensive field star age-metallicity relationship (AMR) from the earliest epoch until {approx}1 Gyr ago. This AMR reveals that the LMC has not evolved chemically as either a closed-box or bursting system, exclusively, but as a combination of both scenarios that have varied in relative strength over the lifetime of the galaxy, although the bursting model falls closer to the data in general. Furthermore, while old and metal-poor field stars have been preferentially formed in the outer disk, younger and more metal-rich stars have mostly been formed in the inner disk, confirming an outside-in formation. We provide evidence for the formation of stars between 5 and 12 Gyr, during the cluster age gap, although chemical enrichment during this period was minimal. We find no significant metallicity gradient in the LMC. We also find that the range in the metallicity of an LMC field has varied during the lifetime of the LMC. In particular, we find only a small range of the metal abundance in the outer disk fields, whereas an average range of {Delta}[Fe/H] = +0.3 {+-} 0.1 dex appears in the inner disk fields. Finally, the cluster and field AMRs show a satisfactory match only for the last 3 Gyr, while for the oldest ages (>11 Gyr), the cluster AMR is a remarkable lower envelope to the field AMR. Such a difference may be due to the very rapid early chemical evolution and lack of observed field stars in this regime, whereas the globular clusters are easily studied. This large difference is not easy to explain as coming from stripped ancient Small Magellanic Cloud (SMC) clusters, although the field SMC AMR is on average {approx}0.4 dex more metal-poor at all ages than that of the LMC but otherwise very similar.

  18. T-cell receptor gamma delta bearing cells in normal human skin

    NARCIS (Netherlands)

    Bos, J. D.; Teunissen, M. B.; Cairo, I.; Krieg, S. R.; Kapsenberg, M. L.; Das, P. K.; Borst, J.

    1990-01-01

    T-cell antigen receptors (TCR) are divided into common alpha beta and less common gamma delta types. In the murine skin, TCR gamma delta+ cells have been reported to form the great majority of epidermal T lymphocytes. We have examined the relative contribution of TCR alpha beta+ and TCR gamma delta+

  19. Star identification methods, techniques and algorithms

    CERN Document Server

    Zhang, Guangjun

    2017-01-01

    This book summarizes the research advances in star identification that the author’s team has made over the past 10 years, systematically introducing the principles of star identification, general methods, key techniques and practicable algorithms. It also offers examples of hardware implementation and performance evaluation for the star identification algorithms. Star identification is the key step for celestial navigation and greatly improves the performance of star sensors, and as such the book include the fundamentals of star sensors and celestial navigation, the processing of the star catalog and star images, star identification using modified triangle algorithms, star identification using star patterns and using neural networks, rapid star tracking using star matching between adjacent frames, as well as implementation hardware and using performance tests for star identification. It is not only valuable as a reference book for star sensor designers and researchers working in pattern recognition and othe...

  20. On the evolution of stars

    International Nuclear Information System (INIS)

    Kippenhahn, R.

    1989-01-01

    A popular survey is given of the present knowledge on evolution and ageing of stars. Main sequence stars, white dwarf stars, and red giant stars are classified in the Hertzsprung-Russell (HR)-diagram by measurable quantities: surface temperature and luminosity. From the HR-diagram it can be concluded to star mass and age. Star-forming processes in interstellar clouds as well as stellar burning processes are illustrated. The changes occurring in a star due to the depletion of the nuclear energy reserve are described. In this frame the phenomena of planetary nebulae, supernovae, pulsars, neutron stars as well as of black holes are explained

  1. MAGNETIC FIELDS OF STARS

    OpenAIRE

    Bychkov, V. D.; Bychkova, L. V.; Madej, J.

    2008-01-01

    Now it is known about 1212 stars of the main sequence and giants (from them 610 stars - it is chemically peculiarity (CP) stars) for which direct measurements of magnetic fields were spent (Bychkov et al.,2008). Let's consider, what representations were generated about magnetic fields (MT) of stars on the basis of available observations data.

  2. Which of Kepler's Stars Flare?

    Science.gov (United States)

    Kohler, Susanna

    2017-12-01

    The habitability of distant exoplanets is dependent upon many factors one of which is the activity of their host stars. To learn about which stars are most likely to flare, a recent study examines tens of thousands of stellar flares observed by Kepler.Need for a Broader SampleArtists rendering of a flaring dwarf star. [NASAs Goddard Space Flight Center/S. Wiessinger]Most of our understanding of what causes a star to flare is based on observations of the only star near enough to examine in detail the Sun. But in learning from a sample size of one, a challenge arises: we must determine which conclusions are unique to the Sun (or Sun-like stars), and which apply to other stellar types as well.Based on observations and modeling, astronomers think that stellar flares result from the reconnection of magnetic field lines in a stars outer atmosphere, the corona. The magnetic activity is thought to be driven by a dynamo caused by motions in the stars convective zone.HR diagram of the Kepler stars, with flaring main-sequence (yellow), giant (red) and A-star (green) stars in the authors sample indicated. [Van Doorsselaere et al. 2017]To test whether these ideas are true generally, we need to understand what types of stars exhibit flares, and what stellar properties correlate with flaring activity. A team of scientists led by Tom Van Doorsselaere (KU Leuven, Belgium) has now used an enormous sample of flares observed by Kepler to explore these statistics.Intriguing TrendsVan Doorsselaere and collaborators used a new automated flare detection and characterization algorithm to search through the raw light curves from Quarter 15 of the Kepler mission, building a sample of 16,850 flares on 6,662 stars. They then used these to study the dependence of the flare occurrence rate, duration, energy, and amplitude on the stellar spectral type and rotation period.This large statistical study led the authors to several interesting conclusions, including:Flare star incidence rate as a a

  3. Symbiotic stars

    Science.gov (United States)

    Kafatos, M.; Michalitsianos, A. G.

    1984-01-01

    The physical characteristics of symbiotic star systems are discussed, based on a review of recent observational data. A model of a symbiotic star system is presented which illustrates how a cool red-giant star is embedded in a nebula whose atoms are ionized by the energetic radiation from its hot compact companion. UV outbursts from symbiotic systems are explained by two principal models: an accretion-disk-outburst model which describes how material expelled from the tenuous envelope of the red giant forms an inwardly-spiralling disk around the hot companion, and a thermonuclear-outburst model in which the companion is specifically a white dwarf which superheats the material expelled from the red giant to the point where thermonuclear reactions occur and radiation is emitted. It is suspected that the evolutionary course of binary systems is predetermined by the initial mass and angular momentum of the gas cloud within which binary stars are born. Since red giants and Mira variables are thought to be stars with a mass of one or two solar mass, it is believed that the original cloud from which a symbiotic system is formed can consist of no more than a few solar masses of gas.

  4. Massive stars in galaxies

    International Nuclear Information System (INIS)

    Humphreys, R.M.

    1987-01-01

    The relationship between the morphologic type of a galaxy and the evolution of its massive stars is explored, reviewing observational results for nearby galaxies. The data are presented in diagrams, and it is found that the massive-star populations of most Sc spiral galaxies and irregular galaxies are similar, while those of Sb spirals such as M 31 and M 81 may be affected by morphology (via differences in the initial mass function or star-formation rate). Consideration is also given to the stability-related upper luminosity limit in the H-R diagram of hypergiant stars (attributed to radiation pressure in hot stars and turbulence in cool stars) and the goals of future observation campaigns. 88 references

  5. Hole states in diamond p-delta-doped field effect transistors

    International Nuclear Information System (INIS)

    Martinez-Orozco, J C; Rodriguez-Vargas, I; Mora-Ramos, M E

    2009-01-01

    The p-delta-doping in diamond allows to create high density two-dimensional hole gases. This technique has already been applied in the design and fabrication of diamond-based field effect transistors. Consequently, the knowledge of the electronic structure is of significant importance to understand the transport properties of diamond p-delta-doped systems. In this work the hole subbands of diamond p-type delta-doped quantum wells are studied within the framework of a local-density Thomas-Fermi-based approach for the band bending profile. The calculation incorporates an independent three-hole-band scheme and considers the effects of the contact potential, the delta-channel to contact distance, and the ionized impurity density.

  6. Hole states in diamond p-delta-doped field effect transistors

    Energy Technology Data Exchange (ETDEWEB)

    Martinez-Orozco, J C; Rodriguez-Vargas, I [Unidad Academica de Fisica, Universidad Autonoma de Zacatecas, Calzada Solidaridad Esquina con Paseo la Bufa S/N, CP 98060 Zacatecas, ZAC. (Mexico); Mora-Ramos, M E, E-mail: jcmover@correo.unam.m [Facultad de Ciencias, Universidad Autonoma del Estado de Morelos, Av. Universidad 1001, Col. Chamilpa, CP 62209 Cuernavaca, MOR. (Mexico)

    2009-05-01

    The p-delta-doping in diamond allows to create high density two-dimensional hole gases. This technique has already been applied in the design and fabrication of diamond-based field effect transistors. Consequently, the knowledge of the electronic structure is of significant importance to understand the transport properties of diamond p-delta-doped systems. In this work the hole subbands of diamond p-type delta-doped quantum wells are studied within the framework of a local-density Thomas-Fermi-based approach for the band bending profile. The calculation incorporates an independent three-hole-band scheme and considers the effects of the contact potential, the delta-channel to contact distance, and the ionized impurity density.

  7. GMC Collisions as Triggers of Star Formation. III. Density and Magnetically Regulated Star Formation

    Energy Technology Data Exchange (ETDEWEB)

    Wu, Benjamin [National Astronomical Observatory of Japan, Mitaka, Tokyo 181-8588 (Japan); Tan, Jonathan C. [Department of Physics, University of Florida, Gainesville, FL 32611 (United States); Christie, Duncan [Department of Astronomy, University of Florida, Gainesville, FL 32611 (United States); Nakamura, Fumitaka [National Astronomical Observatory, Mitaka, Tokyo 181-8588 (Japan); Van Loo, Sven [School of Physics and Astronomy, University of Leeds, Leeds LS2 9JT (United Kingdom); Collins, David, E-mail: ben.wu@nao.ac.jp [Department of Physics, Florida State University, Tallahassee, FL 32306-4350 (United States)

    2017-06-01

    We study giant molecular cloud (GMC) collisions and their ability to trigger star cluster formation. We further develop our three-dimensional magnetized, turbulent, colliding GMC simulations by implementing star formation subgrid models. Two such models are explored: (1) “Density-Regulated,” i.e., fixed efficiency per free-fall time above a set density threshold and (2) “Magnetically Regulated,” i.e., fixed efficiency per free-fall time in regions that are magnetically supercritical. Variations of parameters associated with these models are also explored. In the non-colliding simulations, the overall level of star formation is sensitive to model parameter choices that relate to effective density thresholds. In the GMC collision simulations, the final star formation rates and efficiencies are relatively independent of these parameters. Between the non-colliding and colliding cases, we compare the morphologies of the resulting star clusters, properties of star-forming gas, time evolution of the star formation rate (SFR), spatial clustering of the stars, and resulting kinematics of the stars in comparison to the natal gas. We find that typical collisions, by creating larger amounts of dense gas, trigger earlier and enhanced star formation, resulting in 10 times higher SFRs and efficiencies. The star clusters formed from GMC collisions show greater spatial substructure and more disturbed kinematics.

  8. An Autonomous Star Identification Algorithm Based on One-Dimensional Vector Pattern for Star Sensors.

    Science.gov (United States)

    Luo, Liyan; Xu, Luping; Zhang, Hua

    2015-07-07

    In order to enhance the robustness and accelerate the recognition speed of star identification, an autonomous star identification algorithm for star sensors is proposed based on the one-dimensional vector pattern (one_DVP). In the proposed algorithm, the space geometry information of the observed stars is used to form the one-dimensional vector pattern of the observed star. The one-dimensional vector pattern of the same observed star remains unchanged when the stellar image rotates, so the problem of star identification is simplified as the comparison of the two feature vectors. The one-dimensional vector pattern is adopted to build the feature vector of the star pattern, which makes it possible to identify the observed stars robustly. The characteristics of the feature vector and the proposed search strategy for the matching pattern make it possible to achieve the recognition result as quickly as possible. The simulation results demonstrate that the proposed algorithm can effectively accelerate the star identification. Moreover, the recognition accuracy and robustness by the proposed algorithm are better than those by the pyramid algorithm, the modified grid algorithm, and the LPT algorithm. The theoretical analysis and experimental results show that the proposed algorithm outperforms the other three star identification algorithms.

  9. Subluminous Wolf-Rayet stars: Observations

    International Nuclear Information System (INIS)

    Heap, S.R.

    1982-01-01

    The author has used the fact that some central stars are WR stars and others are say, O stars, as a focal point for his presentation. In attempting to answer this question he has considered how the properties of WR-type central stars differ from those of O-type stars. The study begins with the classification and calibration of WR spectra, then goes on to the physical properties of WR-type central stars, and at the end returns to the question of what distinguishes a Wolf-Rayet star. The observational data for central stars are neither complete nor precise. Nevertheless, they suggest that what distinguishes a WR central star is not so much its present physical properties (e.g. temperature, gravity), but rather, its fundamental properties (initial and evolutionary history). (Auth.)

  10. Linking rapid erosion of the Mekong River delta to human activities.

    Science.gov (United States)

    Anthony, Edward J; Brunier, Guillaume; Besset, Manon; Goichot, Marc; Dussouillez, Philippe; Nguyen, Van Lap

    2015-10-08

    As international concern for the survival of deltas grows, the Mekong River delta, the world's third largest delta, densely populated, considered as Southeast Asia's most important food basket, and rich in biodiversity at the world scale, is also increasingly affected by human activities and exposed to subsidence and coastal erosion. Several dams have been constructed upstream of the delta and many more are now planned. We quantify from high-resolution SPOT 5 satellite images large-scale shoreline erosion and land loss between 2003 and 2012 that now affect over 50% of the once strongly advancing >600 km-long delta shoreline. Erosion, with no identified change in the river's discharge and in wave and wind conditions over this recent period, is consistent with: (1) a reported significant decrease in coastal surface suspended sediment from the Mekong that may be linked to dam retention of its sediment, (2) large-scale commercial sand mining in the river and delta channels, and (3) subsidence due to groundwater extraction. Shoreline erosion is already responsible for displacement of coastal populations. It is an additional hazard to the integrity of this Asian mega delta now considered particularly vulnerable to accelerated subsidence and sea-level rise, and will be exacerbated by future hydropower dams.

  11. America's Star Libraries

    Science.gov (United States)

    Lyons, Ray; Lance, Keith Curry

    2009-01-01

    "Library Journal"'s new national rating of public libraries, the "LJ" Index of Public Library Service, identifies 256 "star" libraries. It rates 7,115 public libraries. The top libraries in each group get five, four, or three Michelin guide-like stars. All included libraries, stars or not, can use their scores to learn from their peers and improve…

  12. Observing Double Stars

    Science.gov (United States)

    Genet, Russell M.; Fulton, B. J.; Bianco, Federica B.; Martinez, John; Baxter, John; Brewer, Mark; Carro, Joseph; Collins, Sarah; Estrada, Chris; Johnson, Jolyon; Salam, Akash; Wallen, Vera; Warren, Naomi; Smith, Thomas C.; Armstrong, James D.; McGaughey, Steve; Pye, John; Mohanan, Kakkala; Church, Rebecca

    2012-05-01

    Double stars have been systematically observed since William Herschel initiated his program in 1779. In 1803 he reported that, to his surprise, many of the systems he had been observing for a quarter century were gravitationally bound binary stars. In 1830 the first binary orbital solution was obtained, leading eventually to the determination of stellar masses. Double star observations have been a prolific field, with observations and discoveries - often made by students and amateurs - routinely published in a number of specialized journals such as the Journal of Double Star Observations. All published double star observations from Herschel's to the present have been incorporated in the Washington Double Star Catalog. In addition to reviewing the history of visual double stars, we discuss four observational technologies and illustrate these with our own observational results from both California and Hawaii on telescopes ranging from small SCTs to the 2-meter Faulkes Telescope North on Haleakala. Two of these technologies are visual observations aimed primarily at published "hands-on" student science education, and CCD observations of both bright and very faint doubles. The other two are recent technologies that have launched a double star renaissance. These are lucky imaging and speckle interferometry, both of which can use electron-multiplying CCD cameras to allow short (30 ms or less) exposures that are read out at high speed with very low noise. Analysis of thousands of high speed exposures allows normal seeing limitations to be overcome so very close doubles can be accurately measured.

  13. Neutron star natal kicks and the long-term survival of star clusters

    Science.gov (United States)

    Contenta, Filippo; Varri, Anna Lisa; Heggie, Douglas C.

    2015-04-01

    We investigate the dynamical evolution of a star cluster in an external tidal field by using N-body simulations, with focus on the effects of the presence or absence of neutron star natal velocity kicks. We show that, even if neutron stars typically represent less than 2 per cent of the total bound mass of a star cluster, their primordial kinematic properties may affect the lifetime of the system by up to almost a factor of 4. We interpret this result in the light of two known modes of star cluster dissolution, dominated by either early stellar evolution mass-loss or two-body relaxation. The competition between these effects shapes the mass-loss profile of star clusters, which may either dissolve abruptly (`jumping'), in the pre-core-collapse phase, or gradually (`skiing'), after having reached core collapse.

  14. Plant delta 15N correlates with the transpiration efficiency of nitrogen acquisition in tropical trees.

    Science.gov (United States)

    Cernusak, Lucas A; Winter, Klaus; Turner, Benjamin L

    2009-11-01

    Based upon considerations of a theoretical model of (15)N/(14)N fractionation during steady-state nitrate uptake from soil, we hypothesized that, for plants grown in a common soil environment, whole-plant delta(15)N (deltaP) should vary as a function of the transpiration efficiency of nitrogen acquisition (F(N)/v) and the difference between deltaP and root delta(15)N (deltaP - deltaR). We tested these hypotheses with measurements of several tropical tree and liana species. Consistent with theoretical expectations, both F(N)/v and deltaP - deltaR were significant sources of variation in deltaP, and the relationship between deltaP and F(N)/v differed between non-N(2)-fixing and N(2)-fixing species. We interpret the correlation between deltaP and F(N)/v as resulting from variation in mineral nitrogen efflux-to-influx ratios across plasma membranes of root cells. These results provide a simple explanation of variation in delta(15)N of terrestrial plants and have implications for understanding nitrogen cycling in ecosystems.

  15. Hyperfast pulsars as the remnants of massive stars ejected from young star clusters

    Science.gov (United States)

    Gvaramadze, Vasilii V.; Gualandris, Alessia; Portegies Zwart, Simon

    2008-04-01

    Recent proper motion and parallax measurements for the pulsar PSR B1508+55 indicate a transverse velocity of ~1100kms-1, which exceeds earlier measurements for any neutron star. The spin-down characteristics of PSR B1508+55 are typical for a non-recycled pulsar, which implies that the velocity of the pulsar cannot have originated from the second supernova disruption of a massive binary system. The high velocity of PSR B1508+55 can be accounted for by assuming that it received a kick at birth or that the neutron star was accelerated after its formation in the supernova explosion. We propose an explanation for the origin of hyperfast neutron stars based on the hypothesis that they could be the remnants of a symmetric supernova explosion of a high-velocity massive star which attained its peculiar velocity (similar to that of the pulsar) in the course of a strong dynamical three- or four-body encounter in the core of dense young star cluster. To check this hypothesis, we investigated three dynamical processes involving close encounters between: (i) two hard massive binaries, (ii) a hard binary and an intermediate-mass black hole (IMBH) and (iii) a single stars and a hard binary IMBH. We find that main-sequence O-type stars cannot be ejected from young massive star clusters with peculiar velocities high enough to explain the origin of hyperfast neutron stars, but lower mass main-sequence stars or the stripped helium cores of massive stars could be accelerated to hypervelocities. Our explanation for the origin of hyperfast pulsars requires a very dense stellar environment of the order of 106- 107starspc-3. Although such high densities may exist during the core collapse of young massive star clusters, we caution that they have never been observed.

  16. Heavy Metal Stars

    Science.gov (United States)

    2001-08-01

    La Silla Telescope Detects Lots of Lead in Three Distant Binaries Summary Very high abundances of the heavy element Lead have been discovered in three distant stars in the Milky Way Galaxy . This finding strongly supports the long-held view that roughly half of the stable elements heavier than Iron are produced in common stars during a phase towards the end of their life when they burn their Helium - the other half results from supernova explosions. All the Lead contained in each of the three stars weighs about as much as our Moon. The observations show that these "Lead stars" - all members of binary stellar systems - have been more enriched with Lead than with any other chemical element heavier than Iron. This new result is in excellent agreement with predictions by current stellar models about the build-up of heavy elements in stellar interiors. The new observations are reported by a team of Belgian and French astronomers [1] who used the Coude Echelle Spectrometer on the ESO 3.6-m telescope at the La Silla Observatory (Chile). PR Photo 26a/01 : A photo of HD 196944 , one of the "Lead stars". PR Photo 26b/01 : A CES spectrum of HD 196944 . The build-up of heavy elements Astronomers and physicists denote the build-up of heavier elements from lighter ones as " nucleosynthesis ". Only the very lightest elements (Hydrogen, Helium and Lithium [2]) were created at the time of the Big Bang and therefore present in the early universe. All the other heavier elements we now see around us were produced at a later time by nucleosynthesis inside stars. In those "element factories", nuclei of the lighter elements are smashed together whereby they become the nuclei of heavier ones - this process is known as nuclear fusion . In our Sun and similar stars, Hydrogen is being fused into Helium. At some stage, Helium is fused into Carbon, then Oxygen, etc. The fusion process requires positively charged nuclei to move very close to each other before they can unite. But with increasing

  17. Laboratory investigation on effects of flood intermittency on river delta dynamics

    Science.gov (United States)

    Miller, K. L.; Kim, W.

    2015-12-01

    In order to simplify the complex hydrological variability of flow conditions, experiments modeling delta evolution are often conducted using a representative "channel-forming" flood flow and then relate results to field settings using an intermittency factor, defined as the fraction of total time at flood conditions. Although this intermittency factor makes it easier to investigate how variables, such as relative base level and/or sediment supply, affect delta dynamics, little is known about how this generalization to a single flow condition affects delta processes. We conducted a set of laboratory experiments with periodic flow conditions to determine the effects of intermittent discharges on delta evolution. During the experiment, flood with a set water discharge and sediment supply, cycles between periods of normal flow where the water flux is halved and the sediment discharge is turned off. For each run, the magnitude of the flood is held constant, but the duration is assigned differently, thus varying the intermittency between 1 and 0.2. We find that as the intermittency factor decreases (duration of each flood period decreases), the delta topset has a larger, more elongated area with a shallower slope as a result of reworking on the delta topset during normal flow conditions. During periods of normal flow, the system adjusts towards a new equilibrium state that then in turn acts as the initial condition for the subsequent flood period. Furthermore, the natural delta avulsion cycle becomes obscured by the flood cycles as the flood duration becomes shorter than the autogenic behavior. These results suggest that the adjustment timescale for differing flow conditions is a factor in determining the overall shape of the delta and behavior of the fluviodeltaic channels. We conclude, periods of normal flow when topset sediment is reworked, may be just as important to delta dynamics as periods of flood when sediment is supplied to the system.

  18. Plasticity of gamma delta T cells: impact on the anti-tumor response

    Directory of Open Access Journals (Sweden)

    Virginie eLafont

    2014-12-01

    Full Text Available The tumor immune microenvironment contributes to tumor initiation, progression and response to therapy. Among the immune cell subsets that play a role in the tumor microenvironment, innate-like T cells that express T cell receptors composed of gamma and delta chains (gamma delta T cells are of particular interest. gamma delta T cells can contribute to the immune response against many tumor types (lymphoma, myeloma, melanoma, breast, colon, lung, ovary and prostate cancer directly through their cytotoxic activity and indirectly by stimulating or regulating the biological functions of other cell types required for the initiation and establishment of the anti-tumor immune response, such as dendritic cells and cytotoxic CD8+ T cells. However, the notion that tumor-infiltrating gamma delta T cells are a good prognostic marker in cancer was recently challenged by studies showing that the presence of these cells in the tumor microenvironment was associated with poor prognosis in both breast and colon cancer. These findings suggest that gamma delta T cells may also display pro-tumor activities. Indeed, breast tumor-infiltrating gamma deltaT cells could exert an immunosuppressive activity by negatively regulating DC maturation. Furthermore, recent studies demonstrated that signals from the microenvironment, particularly cytokines, can confer some plasticity to gamma delta T cells and promote their differentiation into gamma delta T cells with regulatory functions. This review focuses on the current knowledge on the functional plasticity of gamma delta T cells and its effect on their anti-tumor activities. It also discusses the putative mechanisms underlying gamma delta T cell expansion, differentiation and recruitment in the tumor microenvironment.

  19. Oil and Security in Nigeria: The Niger Delta Crisis | Owolabi | Africa ...

    African Journals Online (AJOL)

    This paper examines oil and security in Nigeria, with special reference to the crisis-ravaged Niger Delta. Its focus on the Niger Delta and its festering crisis stems from that region's critical importance to Nigeria. As the nation's treasure base, the Niger Delta provides over 80 percent of government revenues, 95 percent of ...

  20. Effects of recharge and discharge on delta2H and delta18O composition and chloride concentration of high arsenic/fluoride groundwater from the Datong Basin, northern China.

    Science.gov (United States)

    Xie, Xianjun; Wang, Yanxin; Su, Chunli; Duan, Mengyu

    2013-02-01

    To better understand the effects of recharge and discharge on the hydrogeochemistry of high levels of arsenic (As) and fluoride (F) in groundwater, environmental isotopic composition (delta2H and delta18O) and chloride (Cl) concentrations were analyzed in 29 groundwater samples collected from the Datong Basin. High arsenic groundwater samples (As > 50 micog/L) were found to be enriched in lighter isotopic composition that ranged from -92 to -78 per thousand for deuterium (delta2H) and from -12.5 to -9.9 per thousand for oxygen-18 (delta18O). High F-containing groundwater (F > 1 mg/L) was relatively enriched in heavier isotopic composition and varied from -90 to -57 per thousand and from -12.2 to -6.7 per thousand for delta2H and delta18O, respectively. High chloride concentrations and delta18O values were primarily measured in groundwater samples from the northern and southwestern portions of the study area, indicating the effect of evaporation on groundwater. The observation of relatively homogenized and low delta18O values and chloride concentrations in groundwater samples from central part of the Datong Basin might be a result of fast recharge by irrigation returns, which suggests that irrigation using arsenic-contaminated groundwater affected the occurrence of high arsenic-containing groundwater in the basin.

  1. Ultracompact X-ray binary stars

    NARCIS (Netherlands)

    Haaften, L.M. van

    2013-01-01

    Ultracompact X-ray binary stars usually consist of a neutron star and a white dwarf, two stars bound together by their strong gravity and orbiting each other very rapidly, completing one orbit in less than one hour. Neutron stars are extremely compact remnants of the collapsed cores of massive stars

  2. Star Masses and Star-Planet Distances for Earth-like Habitability.

    Science.gov (United States)

    Waltham, David

    2017-01-01

    This paper presents statistical estimates for the location and duration of habitable zones (HZs) around stars of different mass. The approach is based upon the assumption that Earth's location, and the Sun's mass, should not be highly atypical of inhabited planets. The results support climate-model-based estimates for the location of the Sun's HZ except models giving a present-day outer-edge beyond 1.64 AU. The statistical approach also demonstrates that there is a habitability issue for stars smaller than 0.65 solar masses since, otherwise, Earth would be an extremely atypical inhabited world. It is difficult to remove this anomaly using the assumption that poor habitability of planets orbiting low-mass stars results from unfavorable radiation regimes either before, or after, their stars enter the main sequence. However, the anomaly is well explained if poor habitability results from tidal locking of planets in the HZs of small stars. The expected host-star mass for planets with intelligent life then has a 95% confidence range of 0.78 M ⊙ planets with at least simple life is 0.57 M ⊙  < M < 1.64 M ⊙ . Key Words: Habitability-Habitable zone-Anthropic-Red dwarfs-Initial mass function. Astrobiology 17, 61-77.

  3. Peroxisome proliferator-activated receptor delta activation leads to increased transintestinal cholesterol efflux

    NARCIS (Netherlands)

    Vrins, Carlos L. J.; van der Velde, Astrid E.; van den Oever, Karin; Levels, Johannes H. M.; Huet, Stephane; Elferink, Ronald P. J. Oude; Kuipers, Folkert; Groen, Albert K.

    2009-01-01

    Peroxisome proliferator-activated receptor delta (PPAR delta) is involved in regulation of energy homeostasis. Activation of PPAR delta markedly increases fecal neutral sterol secretion, the last step in reverse cholesterol transport. This phenomenon can neither be explained by increased

  4. X-ray sources in stars formation areas: T Tauri stars and proto-stars in the rho Ophiuchi dark cloud

    International Nuclear Information System (INIS)

    Grosso, Nicolas

    1999-01-01

    This thesis studies from large to small scales, X-ray sources in the rho Ophiuchi dark cloud. After some background on the formation of the low-mass young stars (Chapter 1), Chapter 2 takes an interest in the T Tauri star population. Chapter 3 tackles the search of the magnetic activity at the younger stage of protostar, presenting a powerful X-ray emission from an IR protostar, called YLW15, during a flare, and a quasi-periodic flare of the same source; as well as a new detection of another IR protostar in the ROSAT archives. It ends with a review of protostar detections. Some IR protostar flares show a very long increasing phase. Chapter 4 links this behaviour with a modulation by the central star rotation. The standard model of jet emission assumes that the central star rotates at the same speed that the inner edge of its accretion disk. This chapter shows that the observation of the YLW15 quasi-periodic flare suggests rather that the forming star rotates faster than its accretion disk, at the break up limit. The synchronism with the accretion disk, observed on T Tauri stars, must be reach progressively by magnetic breaking during the IR protostar stage, and more or less rapidly depending on the forming star mass. Recent studies have shown that T Tauri star X-ray emission could ionize the circumstellar disk, and play a role in the instability development, as well as stimulate the accretion. The protostar X-ray emission might be higher than the T Tauri star one, Chapter 5 presents a millimetric interferometric observation dedicated to measure this effect on YLW15. Finally, Chapter 6 reassembles conclusions and perspectives of this work. (author) [fr

  5. Implementation of an ESA delta-DOR capability

    Science.gov (United States)

    James, Nick; Abello, Ricard; Lanucara, Marco; Mercolino, Mattia; Maddè, Roberto

    2009-06-01

    This paper describes the implementation of delta-DOR (delta-differential one-way ranging) receivers within the ESA Deep Space ground station network. Delta-DOR provides very accurate plane-of-sky measurements of spacecraft position which complement existing line-of-sight ranging and Doppler measurements. We discuss how this technique has been adapted and implemented at the two ESA deep-space ground stations using existing equipment and infrastructure. These new capabilities were added by writing new software modules for the standard ESA digital receiver (the intermediate frequency modem system—IFMS). With these upgrades the receiver has the ability to record accurately timetagged signals from up to eight IF sub-channels. These sub-channels can have bandwidths of 50 kHz-2 MHz with a sample quantization of 1-16 bits per component. The IF samples are stored locally for subsequent retrieval over a WAN by the correlator facility at ESOC.

  6. Dynamic controls on shallow clinoform geometry: Mekong Delta, Vietnam

    Science.gov (United States)

    Eidam, E. F.; Nittrouer, C. A.; Ogston, A. S.; DeMaster, D. J.; Liu, J. P.; Nguyen, T. T.; Nguyen, T. N.

    2017-09-01

    Compound deltas, composed of a subaerial delta plain and subaqueous clinoform, are common termini of large rivers. The transition between clinoform topset and foreset, or subaqueous rollover point, is located at 25-40-m water depth for many large tide-dominated deltas; this depth is controlled by removal of sediment from the topset by waves, currents, and gravity flows. However, the Mekong Delta, which has been classified as a mixed-energy system, has a relatively shallow subaqueous rollover at 4-6-m depth. This study evaluates dynamical measurements and seabed cores collected in Sep 2014 and Mar 2015 to understand processes of sediment transfer across the subaqueous delta, and evaluate possible linkages to geometry. During the southwest rainy monsoon (Sep 2014), high river discharge, landward return flow under the river plume, and regional circulation patterns facilitated limited sediment flux to the topset and foreset, and promoted alongshore flux to the northeast. Net observed sediment fluxes in Sep 2014 were landward, however, consistent with hypotheses about seasonal storage on the topset. During the northeast rainy monsoon, low river discharge and wind-driven currents facilitated intense landward and southwestward fluxes of sediment. In both seasons, bed shear velocities frequently exceeded the 0.01-0.02 m/s threshold of motion for sand, even in the absence of strong wave energy. Most sediment transport occurred at water depths 4 cm/yr at energy-limited, and thus rollover depths cannot be predicted solely by bed-stress distributions. In systems like the subaqueous Mekong Delta, direction of transport may have a key impact on morphology.

  7. A new identification method for energetic ion {delta}E-E telescopes

    Energy Technology Data Exchange (ETDEWEB)

    Martin, Cesar [Departamento de Fisica, Universidad de Alcala, 28871 Alcala de Henares, Madrid (Spain); Institut fuer Experimentelle und Angewandte Physik, Christian-Albrechts, Universitaet zu Kiel, 24118 Kiel (Germany); Bronchalo, Enrique [Departamento de Fisica, Universidad de Alcala, 28871 Alcala de Henares, Madrid (Spain); Departamento de Fisica y Arquitectura de Computadores, Universidad Miguel Hernandez, Avda. Universidad s/n, 03202 Elche, Alicante (Spain)], E-mail: ebronchalo@umh.es; Medina, Jose [Departamento de Fisica, Universidad de Alcala, 28871 Alcala de Henares, Madrid (Spain)

    2007-11-21

    A new ion identification method for {delta}E-E telescopes is presented. The method works by counting data points under {delta}E(E) curves on {delta}E-E diagrams. These curves are obtained by simulating the telescope response to a flux of energetic ions. The method is checked against three published methods applied to several experimental data sets.

  8. Inclusive production of. delta. /sup + +/(1232) in pn interactions at 19 GeV/c

    Energy Technology Data Exchange (ETDEWEB)

    Bakken, V.; Breivik, F.O.; Jacobsen, T.; Rudjord, A.L. (Oslo Univ. (Norway) Fysisk Inst.)

    1982-12-21

    We present a study of ..delta../sup + +/ production in pn interactions at 19 GeV/c, where the ..delta../sup + +/ is emitted in the protonlike (..delta..sub(F)/sup + +/) and neutron-like (..delta..sub(B)/sup + +/) c.m. hemispheres. The cross-section sigma(pn->..delta..sub(F)/sup + +/+X)=(3.09+-0.43) mb is about three times larger than sigma(pn->..delta..sub(B)/sup + +/+X)=(0.94+-0.34) mb. About 2/3 of ..delta..sub(F)/sup + +/ is peripherally produced with vertical stroketsub(p,..delta..)vertical stroke<1 (GeV/c)/sup 2/, while the cross-section for ..delta..sub(B)/sup + +/ production is nearly zero for vertical stroketsub(n,..delta..)vertical stroke<1 (GeV/c)/sup 2/. We have made a detailed study of the energy dependence of the reaction ap->..delta../sup + +/+X (a=p, anti p, n, ..pi..sup(+-), Ksup(+-)) for vertical stroketsub(p,..delta..)vertical stroke<1 (GeV/c)/sup 2/, by applying the same fitting procedure to extract the ..delta../sup + +/ cross-section to all available mass spectra. All the normalized cross-sections R=sigma(..delta../sup + +/)/sigmasub(inel) can be well described by R=R/sub 0/+R/sub 1/sup(a)psup(-..cap alpha..)sub(lab), where R/sub 0/ and ..cap alpha.. are the same for all reactions, while R/sub 1/sup(a) varies with the beam type a. The value of ..cap alpha.. is slightly below unity. The differential cross section of pn->..delta..sub(F)/sup + +/+X has been determined as a function of the variables t, t', x, y, psub(T)/sup 2/ and Msub(X)/sup 2/ both in the whole kinematical region and for vertical stroketsub(p,..delta..)vertical stroke<1 (GeV/c)/sup 2/. We show that the peripherally produced ..delta..sub(F)/sup + +/ is consistent with the dominance of the one-pion exchange mechanism. This follows from a study of the density matrix elements, the comparison of some properties of the system X with real ..pi../sup +/p data and from the results of a triple-Regge analysis.

  9. Quaternary lacustrine braid deltas on Lake General Carrera in southern Chile Deltas entrelazados lacustres del Cuaternario en el lago General Carrera, sur de Chile

    Directory of Open Access Journals (Sweden)

    C. Mike Bell

    2009-01-01

    Full Text Available A series of Quaternary lacustrine braid deltas on the shores of Lake General Carrera in southern Chile formed as a result of falls in lake level. Each delta comprises two components, the delta fan and the beach embayment, each in turn comprising an onshore subaerial and an offshore subaqueous element. The delta fans have a classic Gilbert form with a braided delta top and a steeply inclined delta front. Adjacent to the fans are concave beach embayments that formed parallel with the deltas as they prograded into the lake. The delta sediments consist predominantly of matrix- and clast-supported gravéis to a total composite thickness exceeding 400 m. The depositional environments are dominated by ephemeral river flooding and by storm-driven waves. Beach sediment is sorted, rounded, winnowed and transported alongshore by waves to fill the beach embayment with ridges of very well sorted and well-rounded gravel. A gently-dipping shoreface platform occurs up to 100 m offshore between the beach and the brink point. From the brink point, in water depth of about 8 m, sediment cascades down the steep delta front slope to form long foresets extending to the lake floor. The sedimentary successions therefore wedge in the opposite direction from those of tectonically controlled basin margins where fan growth keeps pace with basin subsidence.Una serie de deltas entrelazados lacustres, pertenecientes al Cuaternario, ubicados en las costas del lago General Carrera, en el sur de Chile, se formaron como resultado de caídas en el nivel del lago. Cada delta consta de dos componentes: el abanico deltaico y la zona de embahiamiento. Cada uno de ellos tiene, a su vez, un elemento subaéreo costero y un elemento subacuático. Los abanicos deltaicos tienen una forma Gilbert clásica con una parte superior de ríos entrelazados y un frente deltaico empinado. Adyacente a los abanicos aluviales existen bahías cóncavas de playa que se formaron de manera paralela a los

  10. THE GALACTIC O-STAR SPECTROSCOPIC SURVEY (GOSSS). II. BRIGHT SOUTHERN STARS

    International Nuclear Information System (INIS)

    Sota, A.; Apellániz, J. Maíz; Alfaro, E. J.; Morrell, N. I.; Barbá, R. H.; Arias, J. I.; Walborn, N. R.; Gamen, R. C.

    2014-01-01

    We present the second installment of GOSSS, a massive spectroscopic survey of Galactic O stars, based on new homogeneous, high signal-to-noise ratio, R ∼ 2500 digital observations from both hemispheres selected from the Galactic O-Star Catalog (GOSC). In this paper we include bright stars and other objects drawn mostly from the first version of GOSC, all of them south of δ = –20°, for a total number of 258 O stars. We also revise the northern sample of Paper I to provide the full list of spectroscopically classified Galactic O stars complete to B = 8, bringing the total number of published GOSSS stars to 448. Extensive sequences of exceptional objects are given, including the early Of/WN, O Iafpe, Ofc, ON/OC, Onfp, Of?p, and Oe types, as well as double/triple-lined spectroscopic binaries. The new spectral subtype O9.2 is also discussed. The magnitude and spatial distributions of the observed sample are analyzed. We also present new results from OWN, a multi-epoch high-resolution spectroscopic survey coordinated with GOSSS that is assembling the largest sample of Galactic spectroscopic massive binaries ever attained. The OWN data combined with additional information on spectroscopic and visual binaries from the literature indicate that only a very small fraction (if any) of the stars with masses above 15-20 M ☉ are born as single systems. In the future we will publish the rest of the GOSSS survey, which is expected to include over 1000 Galactic O stars

  11. Lithium in the barium stars

    International Nuclear Information System (INIS)

    Pinsonneault, M.H.; Sneden, C.

    1984-01-01

    New high-resolution spectra of the lithium resonance doublet have provided lithium abundances or upper limits for 26 classical and mild barium stars. The lithium lines always are present in the classical barium stars. Lithium abundances in these stars obey a trend with stellar masses consistent with that previously derived for ordinary K giants. This supports the notion that classical barium stars are post-core-He-flash or core-He-burning stars. Lithium contents in the mild barium stars, however, often are much smaller than those of the classical barium stars sometimes only upper limits may be determined. The cause for this difference is not easily understood, but may be related to more extensive mass loss by the mild barium stars. 45 references

  12. How to deal with subsidence in the Dutch delta?

    NARCIS (Netherlands)

    Stouthamer, E.; Erkens, G.

    2017-01-01

    In many deltas worldwide subsidence still is an underestimated problem, while the threat posed by land subsidence low-lying urbanizing and urbanized deltas exceeds the threat of sea-level rise induced by climate change. Human-induced subsidence is driven by the extraction of hydrocarbons and

  13. Evaluation of DELTA(1232) components in sup 1 sup 2 C

    CERN Document Server

    Bystritsky, V M; Krechetov, Yu F; Saigushkin, O K; Tabachenko, A N; Schuvalov, E N; Grabmayr, R; Fiks, A I

    2001-01-01

    One measured cross section of sup 1 sup 2 C(gamma, pi sup + p) reaction within DELTA(1232)-isobar range. Data analysis was carried out using model taking account of both nucleon and isobar degrees of freedom of sup 1 sup 2 C nucleus. One makes a conclusion that within high transmitted pulses pi sup + p-pairs are formed during DELTA sup + sup + -isobar direct knocking-out of a nucleus. One estimated the probability to determine DELTA-isobar in sup 1 sup 2 C nucleus ground state equal to 0.018 +- 0.005 DELTA-isobar per nucleon

  14. Improved autonomous star identification algorithm

    International Nuclear Information System (INIS)

    Luo Li-Yan; Xu Lu-Ping; Zhang Hua; Sun Jing-Rong

    2015-01-01

    The log–polar transform (LPT) is introduced into the star identification because of its rotation invariance. An improved autonomous star identification algorithm is proposed in this paper to avoid the circular shift of the feature vector and to reduce the time consumed in the star identification algorithm using LPT. In the proposed algorithm, the star pattern of the same navigation star remains unchanged when the stellar image is rotated, which makes it able to reduce the star identification time. The logarithmic values of the plane distances between the navigation and its neighbor stars are adopted to structure the feature vector of the navigation star, which enhances the robustness of star identification. In addition, some efforts are made to make it able to find the identification result with fewer comparisons, instead of searching the whole feature database. The simulation results demonstrate that the proposed algorithm can effectively accelerate the star identification. Moreover, the recognition rate and robustness by the proposed algorithm are better than those by the LPT algorithm and the modified grid algorithm. (paper)

  15. Autonomous Star Tracker Algorithms

    DEFF Research Database (Denmark)

    Betto, Maurizio; Jørgensen, John Leif; Kilsgaard, Søren

    1998-01-01

    Proposal, in response to an ESA R.f.P., to design algorithms for autonomous star tracker operations.The proposal also included the development of a star tracker breadboard to test the algorithms performances.......Proposal, in response to an ESA R.f.P., to design algorithms for autonomous star tracker operations.The proposal also included the development of a star tracker breadboard to test the algorithms performances....

  16. Design Principles of A Sigma-delta Flux-gate Magnetometer

    Science.gov (United States)

    Magnes, W.; Valavanoglou, A.; Pierce, D.; Frank, A.; Schwingenschuh, K.

    A state-of-the-art flux-gate magnetometer is characterised by magnetic field resolution of several pT in a wide frequency range, low power consumption, low weight and high robustness. Therefore, flux-gate magnetometers are frequently used for ground-based Earth's field observation as well as for measurements aboard scientific space missions. But both traditional analogue and recently developed digital flux-gate magnetometers need low power and high-resolution analogue-to-digital converters for signal quan- tization. The disadvantage of such converters is the low radiation hardness. This fact has led to the idea of combining a traditional analogue flux-gate regulation circuit with that of a discretely realized sigma-delta converter in order to get a radiation hard and further miniaturized magnetometer. The name sigma-delta converter is derived from putting an integrator in front of a 1-bit delta modulator which forms the sigma-delta loop. It is followed by a digital decimation filter realized in a field-programmable gate array (FPGA). The flux-gate regulation and the sigma-delta loop are quite similar in the way of realizing the integrator and feedback circuit, which makes it easy to com- bine these two systems. The presented talk deals with the design principles and the results of a first bread board model.

  17. Stratigraphy and Evolution of Delta Channel Deposits, Jezero Crater, Mars

    Science.gov (United States)

    Goudge, T. A.; Mohrig, D.; Cardenas, B. T.; Hughes, C. M.; Fassett, C. I.

    2017-01-01

    The Jezero impact crater hosted an open-basin lake that was active during the valley network forming era on early Mars. This basin contains a well exposed delta deposit at the mouth of the western inlet valley. The fluvial stratigraphy of this deposit provides a record of the channels that built the delta over time. Here we describe observations of the stratigraphy of the channel deposits of the Jezero western delta to help reconstruct its evolution.

  18. Nuclear physics of stars

    CERN Document Server

    Iliadis, Christian

    2015-01-01

    Most elements are synthesized, or ""cooked"", by thermonuclear reactions in stars. The newly formed elements are released into the interstellar medium during a star's lifetime, and are subsequently incorporated into a new generation of stars, into the planets that form around the stars, and into the life forms that originate on the planets. Moreover, the energy we depend on for life originates from nuclear reactions that occur at the center of the Sun. Synthesis of the elements and nuclear energy production in stars are the topics of nuclear astrophysics, which is the subject of this book

  19. Alpha-, gamma- and delta-tocopherols reduce inflammatory angiogenesis in human microvascular endothelial cells.

    Science.gov (United States)

    Wells, Shannon R; Jennings, Merilyn H; Rome, Courtney; Hadjivassiliou, Vicky; Papas, Konstantinos A; Alexander, Jonathon S

    2010-07-01

    Vitamin E, a micronutrient (comprising alpha-, beta-, gamma- and delta-tocopherols, alpha-, beta-, gamma- and delta-tocotrienols), has documented antioxidant and non-antioxidant effects, some of which inhibit inflammation and angiogenesis. We compared the abilities of alpha-, gamma- and delta-tocopherols to regulate human blood cytotoxicity (BEC) and lymphatic endothelial cytotoxicity (LEC), proliferation, invasiveness, permeability, capillary formation and suppression of TNF-alpha-induced VCAM-1 as in vitro models of inflammatory angiogenesis. alpha-, gamma- and delta-tocopherols were not toxic to either cell type up to 40 microM. In BEC, confluent cell density was decreased by all concentrations of delta- and gamma-tocopherol (10-40 microM) but not by alpha-tocopherol. LEC showed no change in cell density in response to tocopherols. delta-Tocopherol (40 microM), but not other isomers, decreased BEC invasiveness. In LEC, all doses of gamma-tocopherol, as well as the highest dose of alpha-tocopherol (40 microM), decreased cell invasiveness. delta-Tocopherol had no effect on LEC invasiveness at any molarity. delta-Tocopherol dose dependently increased cell permeability at 48 h in BEC and LEC; alpha- and gamma-tocopherols showed slight effects. Capillary tube formation was decreased by high dose (40 microM) concentrations of alpha-, gamma- and delta-tocopherol, but showed no effects with smaller doses (10-20 microM) in BEC. gamma-Tocopherol (10-20 microM) and alpha-tocopherol (10 microM), but not delta-tocopherol, increased LEC capillary tube formation. Lastly, in BEC, alpha-, gamma- and delta-tocopherol each dose-dependently reduced TNF-alpha-induced expression of VCAM-1. In LEC, there was no significant change to TNF-alpha-induced VCAM-1 expression with any concentration of alpha-, gamma- or delta-tocopherol. These data demonstrate that physiological levels (0-40 microM) of alpha-, gamma- and delta-tocopherols are nontoxic and dietary tocopherols, especially delta

  20. Subsidence, Sea Level Rise, and Seismicity in the Sacramento–San Joaquin Delta

    Directory of Open Access Journals (Sweden)

    Jeffrey Mount

    2005-03-01

    Full Text Available Anthropogenic accommodation space, or that space in the Delta that lies below sea level and is filled neither with sediment nor water, serves as a useful measure of the regional consequences of Delta subsidence and sea level rise. Microbial oxidation and compaction of organic-rich soils due to farming activity is the primary cause of Delta subsidence. During the period 1900-2000, subsidence created approximately 2.5 billion cubic meters of anthropogenic accommodation space in the Delta. From 2000-2050, subsidence rates will slow due to depletion of organic material and better land use practices. However, by 2050 the Delta will contain more than 3 billion cubic meters of anthropogenic accommodation space due to continued subsidence and sea level rise. An Accommodation Space Index, which relates subaqueous accommodation space to anthropogenic accommodation space, provides an indicator of past and projected Delta conditions. While subsidence and sea level rise create increasing anthropogenic accommodation space in the Delta, they also lead to a regional increase in the forces that can cause levee failure. Although these forces take many forms, a Levee Force Index can be calculated that is a proxy for the cumulative forces acting on levees. The Levee Force Index increases significantly over the next 50 years demonstrating regional increases in the potential for island flooding. Based on continuing increases in the Levee Force Index and the Accommodation Space Index, and limited support for Delta levee upgrades, there will be a tendency for increases in and impacts of island flooding, with escalating costs for repairs. Additionally, there is a two-in-three chance that 100-year recurrence interval floods or earthquakes will cause catastrophic flooding and significant change in the Delta by 2050. Currently, the California Bay-Delta Authority has no overarching policy that addresses the consequences of, and potential responses to, gradual or abrupt

  1. Dependence of {delta}E effect on internal stresses in nickel: Experimental results by laser interferometry

    Energy Technology Data Exchange (ETDEWEB)

    Chicharro, J.M. [Dept. de Mecanica Aplicada e Ingenieria de Proyectos, E.T.S.I. Industriales, Universidad de Castilla-La Mancha, Avd. Camilo Jose Cela s/n, 13071 Ciudad Real (Spain)]. E-mail: josemanuel.chicharro@uclm.es; Bayon, A. [Dept. de Fisica Aplicada a los Recursos Naturales, E.T.S.I. Minas, Universidad Politecnica de Madrid, c/Rios Rosas, 21, 28003 Madrid (Spain); Salazar, F. [Dept. de Fisica Aplicada a los Recursos Naturales, E.T.S.I. Minas, Universidad Politecnica de Madrid, c/Rios Rosas, 21, 28003 Madrid (Spain)

    2006-02-15

    The speckle heterodyne interferometry is applied to the study of the dependence of Young's modulus on both the magnetic field and the internal stresses in a soft ferromagnetic material. Young's modulus is determined from the first natural longitudinal frequency of a slender magnetic rod positioned within a solenoid. Vibration of the sample is detected by an optical heterodyne system with a wide bandwidth. The samples are heated to above the Curie point and then cooled at several rates in order to induce different internal stresses. The study refers to nickel rods 10mm in diameter and 110mm in length. The grain sizes of the samples are also determined and related to changes in {delta}E.

  2. The delta-Sobolev approach for modeling solar spectral irradiance and radiance

    International Nuclear Information System (INIS)

    Xiang, Xuwu.

    1990-01-01

    The development and evaluation of a solar radiation model is reported, which gives irradiance and radiance results at the bottom and top of an atmosphere of specified optical depth for each of 145 spectral intervals from 0.29 to 4.05 microns. Absorption by water vapor, aerosols, ozone, and uniformly mixed gases; scattering by molecules and aerosols; and non-Lambertian surface reflectance are included in the model. For solving the radiative transfer equation, an innovative delta-Sobolev method is developed. It applies a delta-function modification to the conventional Sobolev solutions in a way analogous to the delta-Eddington method. The irradiance solution by the delta-Sobolev method turns out to be mathematically identical to the delta-Eddington approximation. The radiance solution by the delta-Sobolov method provides a convenient way to obtain the directional distribution pattern of the radiation transfer field, a feature unable to be obtained by most commonly used approximation methods. Such radiance solutions are also especially useful in models for satellite remote sensing. The model is tested against the rigorous Dave model, which solves the radiation transfer problem by the spherical harmonic method, an accurate but very time consuming process. Good agreement between the current model results and those of Dave's model are observed. The advantages of the delta-Sobolev model are simplicity, reasonable accuracy and capability for implementation on a minicomputer or microcomputer

  3. The geographic spread of the CCR5 Delta32 HIV-resistance allele.

    Directory of Open Access Journals (Sweden)

    John Novembre

    2005-11-01

    Full Text Available The Delta32 mutation at the CCR5 locus is a well-studied example of natural selection acting in humans. The mutation is found principally in Europe and western Asia, with higher frequencies generally in the north. Homozygous carriers of the Delta32 mutation are resistant to HIV-1 infection because the mutation prevents functional expression of the CCR5 chemokine receptor normally used by HIV-1 to enter CD4+ T cells. HIV has emerged only recently, but population genetic data strongly suggest Delta32 has been under intense selection for much of its evolutionary history. To understand how selection and dispersal have interacted during the history of the Delta32 allele, we implemented a spatially explicit model of the spread of Delta32. The model includes the effects of sampling, which we show can give rise to local peaks in observed allele frequencies. In addition, we show that with modest gradients in selection intensity, the origin of the Delta32 allele may be relatively far from the current areas of highest allele frequency. The geographic distribution of the Delta32 allele is consistent with previous reports of a strong selective advantage (>10% for Delta32 carriers and of dispersal over relatively long distances (>100 km/generation. When selection is assumed to be uniform across Europe and western Asia, we find support for a northern European origin and long-range dispersal consistent with the Viking-mediated dispersal of Delta32 proposed by G. Lucotte and G. Mercier. However, when we allow for gradients in selection intensity, we estimate the origin to be outside of northern Europe and selection intensities to be strongest in the northwest. Our results describe the evolutionary history of the Delta32 allele and establish a general methodology for studying the geographic distribution of selected alleles.

  4. How the First Stars Regulated Star Formation. II. Enrichment by Nearby Supernovae

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Ke-Jung [Division of Theoretical Astronomy, National Astronomical Observatory of Japan, Tokyo 181-8588 (Japan); Whalen, Daniel J. [Institute of Cosmology and Gravitation, Portsmouth University, Portsmouth (United Kingdom); Wollenberg, Katharina M. J.; Glover, Simon C. O.; Klessen, Ralf S., E-mail: ken.chen@nao.ac.jp [Zentrum für Astronomie, Institut für Theoretische Astrophysik, Universität Heidelberg (Germany)

    2017-08-01

    Metals from Population III (Pop III) supernovae led to the formation of less massive Pop II stars in the early universe, altering the course of evolution of primeval galaxies and cosmological reionization. There are a variety of scenarios in which heavy elements from the first supernovae were taken up into second-generation stars, but cosmological simulations only model them on the largest scales. We present small-scale, high-resolution simulations of the chemical enrichment of a primordial halo by a nearby supernova after partial evaporation by the progenitor star. We find that ejecta from the explosion crash into and mix violently with ablative flows driven off the halo by the star, creating dense, enriched clumps capable of collapsing into Pop II stars. Metals may mix less efficiently with the partially exposed core of the halo, so it might form either Pop III or Pop II stars. Both Pop II and III stars may thus form after the collision if the ejecta do not strip all the gas from the halo. The partial evaporation of the halo prior to the explosion is crucial to its later enrichment by the supernova.

  5. Morphodynamic evolution of two deltas in arctic environments, east coast of Greenland

    DEFF Research Database (Denmark)

    Kroon, Aart; Pedersen, Jørn Bjarke Torp; Sigsgaard, Charlotte

    2011-01-01

    Changes in fluvial channel patterns on deltas have a significant impact on the coastal morphology along its fringes. Lateral channel migration can locally cause cliff erosion and introduce an extra sediment source in the local budget of an active delta plain. Stabilization of channels or even...... channel lobe switching reduce the fluvial impact on the delta and introduce the formation of beach ridges and spits along the (former) delta edge. These accumulative features are formed in the ice-free summer periods and fed by alongshore sediment input from adjacent shores due to wave-driven alongshore...... currents, and by the reworking of the sediments on the delta plain by wave-driven cross-shore processes....

  6. Novel urinary metabolite of d-delta-tocopherol in rats

    International Nuclear Information System (INIS)

    Chiku, S.; Hamamura, K.; Nakamura, T.

    1984-01-01

    A novel metabolite of d-delta-tocopherol was isolated from the urine of rats given d-3,4-[ 3 H 2 ]-delta-tocopherol intravenously. The metabolite was collected from the urine of rats given d-delta-tocopherol in the same manner as that of the labeled compound. It was found that the metabolites consisted of sulfate conjugates. The portion of the major metabolite released with sulfatase was determined to be 2,8-dimethyl-2-(2'-carboxyethyl)-6-chromanol by infrared spectra, nuclear magnetic resonance spectra, and mass spectra. The proposed structure was confirmed by comparing the analytical results with those of a synthetically derived compound. As a result of the structural elucidation of this novel metabolite, a pathway for the biological transformation of delta-tocopherol is proposed which is different from that of alpha-tocopherol. A characteristic feature of the pathway is the absence of any opening of the chroman ring throughout the sequence

  7. CMOS sigma-delta converters practical design guide

    CERN Document Server

    De la Rosa, Jose M

    2013-01-01

    A comprehensive overview of Sigma-Delta Analog-to-Digital Converters (ADCs) and a practical guide to their design in nano-scale CMOS for optimal performance. This book presents a systematic and comprehensive compilation of sigma-delta converter operating principles, the new advances in architectures and circuits, design methodologies and practical considerations - going from system-level specifications to silicon integration, packaging and measurements, with emphasis on nanometer CMOS implementation. The book emphasizes practical design issues - from high-level behavioural modelling i

  8. Stratigraphy and paleohydrology of delta channel deposits, Jezero crater, Mars

    Science.gov (United States)

    Goudge, Timothy A.; Mohrig, David; Cardenas, Benjamin T.; Hughes, Cory M.; Fassett, Caleb I.

    2018-02-01

    The Jezero crater open-basin lake contains two well-exposed fluvial sedimentary deposits formed early in martian history. Here, we examine the geometry and architecture of the Jezero western delta fluvial stratigraphy using high-resolution orbital images and digital elevation models (DEMs). The goal of this analysis is to reconstruct the evolution of the delta and associated shoreline position. The delta outcrop contains three distinct classes of fluvial stratigraphy that we interpret, from oldest to youngest, as: (1) point bar strata deposited by repeated flood events in meandering channels; (2) inverted channel-filling deposits formed by avulsive distributary channels; and (3) a valley that incises the deposit. We use DEMs to quantify the geometry of the channel deposits and estimate flow depths of ∼7 m for the meandering channels and ∼2 m for the avulsive distributary channels. Using these estimates, we employ a novel approach for assessing paleohydrology of the formative channels in relative terms. This analysis indicates that the shift from meandering to avulsive distributary channels was associated with an approximately four-fold decrease in the water to sediment discharge ratio. We use observations of the fluvial stratigraphy and channel paleohydrology to propose a model for the evolution of the Jezero western delta. The delta stratigraphy records lake level rise and shoreline transgression associated with approximately continuous filling of the basin, followed by outlet breaching, and eventual erosion of the delta. Our results imply a martian surface environment during the period of delta formation that supplied sufficient surface runoff to fill the Jezero basin without major drops in lake level, but also with discrete flooding events at non-orbital (e.g., annual to decadal) timescales.

  9. Mechanism of mRNA-STAR domain interaction: Molecular dynamics simulations of Mammalian Quaking STAR protein.

    Science.gov (United States)

    Sharma, Monika; Anirudh, C R

    2017-10-03

    STAR proteins are evolutionary conserved mRNA-binding proteins that post-transcriptionally regulate gene expression at all stages of RNA metabolism. These proteins possess conserved STAR domain that recognizes identical RNA regulatory elements as YUAAY. Recently reported crystal structures show that STAR domain is composed of N-terminal QUA1, K-homology domain (KH) and C-terminal QUA2, and mRNA binding is mediated by KH-QUA2 domain. Here, we present simulation studies done to investigate binding of mRNA to STAR protein, mammalian Quaking protein (QKI). We carried out conventional MD simulations of STAR domain in presence and absence of mRNA, and studied the impact of mRNA on the stability, dynamics and underlying allosteric mechanism of STAR domain. Our unbiased simulations results show that presence of mRNA stabilizes the overall STAR domain by reducing the structural deviations, correlating the 'within-domain' motions, and maintaining the native contacts information. Absence of mRNA not only influenced the essential modes of motion of STAR domain, but also affected the connectivity of networks within STAR domain. We further explored the dissociation of mRNA from STAR domain using umbrella sampling simulations, and the results suggest that mRNA binding to STAR domain occurs in multi-step: first conformational selection of mRNA backbone conformations, followed by induced fit mechanism as nucleobases interact with STAR domain.

  10. Making star teams out of star players.

    Science.gov (United States)

    Mankins, Michael; Bird, Alan; Root, James

    2013-01-01

    Top talent is an invaluable asset: In highly specialized or creative work, for instance, "A" players are likely to be six times as productive as "B" players. So when your company has a crucial strategic project, why not multiply all that firepower and have a team of your best performers tackle it? Yet many companies hesitate to do this, believing that all-star teams don't work: Big egos will get in the way. The stars won't be able to work with one another. They'll drive the team Leader crazy. Mankins, Bird, and Root of Bain & Company believe it's time to set aside that thinking. They have seen all-star teams do extraordinary work. But there is a right way and a wrong way to organize them. Before you can even begin to assemble such a team, you need to have the right talent management practices, so you hire and develop the best people and know what they're capable of. You have to give the team appropriate incentives and leaders and support staffers who are stars in their own right. And projects that are ill-defined or small scale are not for all-star teams. Use them only for critical missions, and make sure their objectives are clear. Even with the right setup, things can still go wrong. The wise executive will take steps to manage egos, prune non-team-players, and prevent average coworkers from feeling completely undervalued. She will also invest a lot of time in choosing the right team Leader and will ask members for lots of feedback to monitor how that leader is doing.

  11. Construction and maintenance of the Ganges-Brahmaputra-Meghna delta: linking process, morphology, and stratigraphy.

    Science.gov (United States)

    Wilson, Carol A; Goodbred, Steven L

    2015-01-01

    We present a review of the processes, morphology, and stratigraphy of the Ganges-Brahmaputra-Meghna delta (GBMD), including insights gained from detailed elevation data. The review shows that the GBMD is best characterized as a composite system, with different regions having morphologic and stratigraphic attributes of an upland fluvial fan delta; a lowland, backwater-reach delta; a downdrift tidal delta plain; and an offshore subaqueous-delta clinoform. These distinct areas of upland and lowland fluvial reaches and tidal dominance vary in time and space, and we distinguish late-Holocene phases of delta construction, maintenance, and decline similar to delta-lobe cycling in other systems. The overall stability of the GBMD landform, relative to many deltas, reflects the efficient, widespread dispersal of sediment by the large monsoon discharge and high-energy tides that affect this region. However, we do identify portions of the delta that are in decline and losing elevation relative to sea level owing to insufficient sediment delivery. These areas, some of which are well inland of the coast, represent those most at risk to the continued effect of sea-level rise.

  12. Climate change and the Delta

    Science.gov (United States)

    Dettinger, Michael; Anderson, Jamie; Anderson, Michael L.; Brown, Larry R.; Cayan, Daniel; Maurer, Edwin P.

    2016-01-01

    Anthropogenic climate change amounts to a rapidly approaching, “new” stressor in the Sacramento–San Joaquin Delta system. In response to California’s extreme natural hydroclimatic variability, complex water-management systems have been developed, even as the Delta’s natural ecosystems have been largely devastated. Climate change is projected to challenge these management and ecological systems in different ways that are characterized by different levels of uncertainty. For example, there is high certainty that climate will warm by about 2°C more (than late-20th-century averages) by mid-century and about 4°C by end of century, if greenhouse-gas emissions continue their current rates of acceleration. Future precipitation changes are much less certain, with as many climate models projecting wetter conditions as drier. However, the same projections agree that precipitation will be more intense when storms do arrive, even as more dry days will separate storms. Warmer temperatures will likely enhance evaporative demands and raise water temperatures. Consequently, climate change is projected to yield both more extreme flood risks and greater drought risks. Sea level rise (SLR) during the 20th century was about 22cm, and is projected to increase by at least 3-fold this century. SLR together with land subsidence threatens the Delta with greater vulnerabilities to inundation and salinity intrusion. Effects on the Delta ecosystem that are traceable to warming include SLR, reduced snowpack, earlier snowmelt and larger storm-driven streamflows, warmer and longer summers, warmer summer water temperatures, and water-quality changes. These changes and their uncertainties will challenge the operations of water projects and uses throughout the Delta’s watershed and delivery areas. Although the effects of climate change on Delta ecosystems may be profound, the end results are difficult to predict, except that native species will fare worse than invaders. Successful

  13. Holocene Flexural Deformation over the Nile Delta: Evidence from Radar Interferometry

    Science.gov (United States)

    Gebremichael, E.; Sultan, M.; Becker, R.

    2017-12-01

    Isostatic adjustment and subsequent subsidence and uplift due to sediment and water loading and unloading mechanisms is one of the major factors that produce regional deformational patterns across river deltas. Using 84 Envisat ASAR scenes that were acquired (2004 - 2010) along three tracks and applying Persistent scatterer (PS) radar interferometric techniques, we documented flexural deformational patterns over the entire Nile Delta (length: 186 km; width: 240 km) of Egypt. The passive continental margin of Africa subsided from Jurassic time onwards due to isostatic loading creating an accommodation space and consequently, the deposition of relatively younger sediments on the oceanic crust. In river deltas, the flexural isostasy model dictates that a subsidence in the oceanic crust side should be balanced by a bulge (uplift) in the flanking regions. Using radar interferometry, we were able to identify the flexural deformation pattern and map its spatial extent over the northern and central Nile Delta region. Findings include: (1) the northern Nile Delta region (block) is separated from the southern delta region by an east-west trending, extensively faulted, hinge line that signifies the boundary between two deformational patterns (subsidence and uplift). It separates the highly subsiding (up to 9.8 mm/yr) northern delta block (up to 85 km long) from the nearly stable (0.4 mm/yr; averaged) southern delta block (up to 91 km long). The hinge line marks the end of the passive continental margin of Africa and the beginning of the oceanic crust of the Mediterranean. (2) We mapped the extent of a 20-40 km wide flexural uplift zone to the south of the hinge line. Within the flexural uplift zone (2.5 mm/yr; averaged), there is a gradual increase in uplift rate reaching peak value (up to 7 mm/yr) near the midpoint of the zone. (3) The uplift rate gradually decreases south of the flexure boundary reaching 0.3 mm/yr at the southern periphery of the delta. (4) The flexural

  14. Strangeon and Strangeon Star

    Science.gov (United States)

    Xiaoyu, Lai; Renxin, Xu

    2017-06-01

    The nature of pulsar-like compact stars is essentially a central question of the fundamental strong interaction (explained in quantum chromo-dynamics) at low energy scale, the solution of which still remains a challenge though tremendous efforts have been tried. This kind of compact objects could actually be strange quark stars if strange quark matter in bulk may constitute the true ground state of the strong-interaction matter rather than 56Fe (the so-called Witten’s conjecture). From astrophysical points of view, however, it is proposed that strange cluster matter could be absolutely stable and thus those compact stars could be strange cluster stars in fact. This proposal could be regarded as a general Witten’s conjecture: strange matter in bulk could be absolutely stable, in which quarks are either free (for strange quark matter) or localized (for strange cluster matter). Strange cluster with three-light-flavor symmetry is renamed strangeon, being coined by combining “strange nucleon” for the sake of simplicity. A strangeon star can then be thought as a 3-flavored gigantic nucleus, and strangeons are its constituent as an analogy of nucleons which are the constituent of a normal (micro) nucleus. The observational consequences of strangeon stars show that different manifestations of pulsarlike compact stars could be understood in the regime of strangeon stars, and we are expecting more evidence for strangeon star by advanced facilities (e.g., FAST, SKA, and eXTP).

  15. Upper-Division Student Difficulties with the Dirac Delta Function

    Science.gov (United States)

    Wilcox, Bethany R.; Pollock, Steven J.

    2015-01-01

    The Dirac delta function is a standard mathematical tool that appears repeatedly in the undergraduate physics curriculum in multiple topical areas including electrostatics, and quantum mechanics. While Dirac delta functions are often introduced in order to simplify a problem mathematically, students still struggle to manipulate and interpret them.…

  16. Downstream hydraulic geometry of a tidally influenced river delta

    NARCIS (Netherlands)

    Sassi, M.G.; Hoitink, A.J.F.; Brye, de B.; Deleersnijder, E.

    2012-01-01

    Channel geometry in tidally influenced river deltas can show a mixed scaling behavior between that of river and tidal channel networks, as the channel forming discharge is both of river and tidal origin. We present a method of analysis to quantify the tidal signature on delta morphology, by

  17. Homosexuality amongst migrant oil workers in the Niger Delta ...

    African Journals Online (AJOL)

    Aims: To determine the prevalence of homosexuality among migrant oil workers in Niger Delta. Methods: A prospective questionnaire – based study was conducted among migrant oil workers in the Niger Delta region of Nigeria. The design was to determine the prevalence of homosexuality in the workers in oil workers.

  18. Continuous time sigma delta ADC design and non-idealities analysis

    International Nuclear Information System (INIS)

    Yuan Jun; Chen Zhenhai; Yang Yintang; Zhang Zhaofeng; Wu Jun; Wang Chao; Qian Wenrong

    2011-01-01

    A wide bandwidth continuous time sigma delta ADC is implemented in 130 nm CMOS. A detailed non-idealities analysis (excess loop delay, clock jitter, finite gain and GBW, comparator offset and DAC mismatch) is performed developed in Matlab/Simulink. This design is targeted for wide bandwidth applications such as video or wireless base-stations. Athird-order continuous time sigma delta modulator comprises a third-order RC operational-amplifier-based loop filter and 3-bit internal quantizer operated at 512 MHz clock frequency. The sigma delta ADC achieves 60 dB SNR and 59.3 dB SNDR over a 16-MHz signal band at an OSR of 16. The power consumption of the CT sigma delta modulator is 22 mW from the 1.2-V supply. (semiconductor integrated circuits)

  19. Rotating Stars in Relativity

    Directory of Open Access Journals (Sweden)

    Stergioulas Nikolaos

    2003-01-01

    Full Text Available Rotating relativistic stars have been studied extensively in recent years, both theoretically and observationally, because of the information they might yield about the equation of state of matter at extremely high densities and because they are considered to be promising sources of gravitational waves. The latest theoretical understanding of rotating stars in relativity is reviewed in this updated article. The sections on the equilibrium properties and on the nonaxisymmetric instabilities in f-modes and r-modes have been updated and several new sections have been added on analytic solutions for the exterior spacetime, rotating stars in LMXBs, rotating strange stars, and on rotating stars in numerical relativity.

  20. Wave Star

    DEFF Research Database (Denmark)

    Kramer, Morten; Brorsen, Michael; Frigaard, Peter

    Nærværende rapport beskriver numeriske beregninger af den hydrodynamiske interaktion mellem 5 flydere i bølgeenergianlægget Wave Star.......Nærværende rapport beskriver numeriske beregninger af den hydrodynamiske interaktion mellem 5 flydere i bølgeenergianlægget Wave Star....

  1. Design and DSP implementation of star image acquisition and star point fast acquiring and tracking

    Science.gov (United States)

    Zhou, Guohui; Wang, Xiaodong; Hao, Zhihang

    2006-02-01

    Star sensor is a special high accuracy photoelectric sensor. Attitude acquisition time is an important function index of star sensor. In this paper, the design target is to acquire 10 samples per second dynamic performance. On the basis of analyzing CCD signals timing and star image processing, a new design and a special parallel architecture for improving star image processing are presented in this paper. In the design, the operation moving the data in expanded windows including the star to the on-chip memory of DSP is arranged in the invalid period of CCD frame signal. During the CCD saving the star image to memory, DSP processes the data in the on-chip memory. This parallelism greatly improves the efficiency of processing. The scheme proposed here results in enormous savings of memory normally required. In the scheme, DSP HOLD mode and CPLD technology are used to make a shared memory between CCD and DSP. The efficiency of processing is discussed in numerical tests. Only in 3.5ms is acquired the five lightest stars in the star acquisition stage. In 43us, the data in five expanded windows including stars are moved into the internal memory of DSP, and in 1.6ms, five star coordinates are achieved in the star tracking stage.

  2. [Application of small remote sensing satellite constellations for environmental hazards in wetland landscape mapping: taking Liaohe Delta, Liaoning Province of Northeast China as a case].

    Science.gov (United States)

    Yang, Yuan-Zheng; Chang, Yu; Hu, Yuan-Man; Liu, Miao; Li, Yue-Hui

    2011-06-01

    To timely and accurately acquire the spatial distribution pattern of wetlands is of significance for the dynamic monitoring, conservation, and sustainable utilization of wetlands. The small remote sensing satellite constellations A/B stars (HJ-1A/1B stars) for environmental hazards were launched by China for monitoring terrestrial resources, which could provide a new data source of remote sensing image acquisition for retrieving wetland types. Taking Liaohe Delta as a case, this paper compared the accuracy of wetland classification map and the area of each wetland type retrieved from CCD data (HJ CCD data) and TM5 data, and validated and explored the applicability and the applied potential of HJ CCD data in wetland resources dynamic monitoring. The results showed that HJ CCD data could completely replace Landsat TM5 data in feature extraction and remote sensing classification. In real-time monitoring, due to its 2 days of data acquisition cycle, HJ CCD data had the priority to Landsat TM5 data (16 days of data acquisition cycle).

  3. A VOLUME-LIMITED PHOTOMETRIC SURVEY OF 114 γ DORADUS CANDIDATES

    International Nuclear Information System (INIS)

    Henry, Gregory W.; Fekel, Francis C.; Henry, Stephen M.

    2011-01-01

    We have carried out a photometric survey of a complete, volume-limited sample of γ Doradus candidates. The sample was extracted from the Hipparcos catalog and consists of 114 stars with colors and absolute magnitudes within the range of known γ Doradus stars and that also lie within a specified volume of 266,600 pc 3 . We devoted one year of observing time with our T12 0.8 m automatic photometric telescope to acquire nightly observations of the complete sample of stars. From these survey observations, we identify 37 stars with intrinsic variability of 0.002 mag or more. Of these 37 variables, 8 have already been confirmed as γ Doradus stars in our earlier papers; we scheduled the remaining 29 variables on our T3 0.4 m automatic telescope to acquire more intensive observations over the next two years. As promising new γ Doradus candidates were identified from the photometry, we obtained complementary spectroscopic observations of each candidate with the Kitt Peak coude feed telescope. Analysis of our new photometric and spectroscopic data reveals 15 new γ Doradus variables (and confirms two others), 8 new δ Scuti variables (and confirms one other), and 3 new variables with unresolved periodicity. Therefore, of the 114 γ Doradus candidates in our volume-limited sample, we find 25 stars that are new or previously known γ Doradus variables. This results in an incidence of 22% for γ Doradus variability among candidate field stars for this volume of the solar neighborhood. The corresponding space density of γ Doradus stars in this volume of space is 0.094 stars per 10 3 pc 3 or 94 stars per 10 6 pc 3 . We provide an updated list of 86 bright, confirmed, γ Doradus field stars.

  4. Orbiting radiation stars

    International Nuclear Information System (INIS)

    Foster, Dean P; Langford, John; Perez-Giz, Gabe

    2016-01-01

    We study a spherically symmetric solution to the Einstein equations in which the source, which we call an orbiting radiation star (OR-star), is a compact object consisting of freely falling null particles. The solution avoids quantum scale regimes and hence neither relies upon nor ignores the interaction of quantum mechanics and gravitation. The OR-star spacetime exhibits a deep gravitational well yet remains singularity free. In fact, it is geometrically flat in the vicinity of the origin, with the flat region being of any desirable scale. The solution is observationally distinct from a black hole because a photon from infinity aimed at an OR-star escapes to infinity with a time delay. (paper)

  5. New decision criteria for selecting delta check methods based on the ratio of the delta difference to the width of the reference range can be generally applicable for each clinical chemistry test item.

    Science.gov (United States)

    Park, Sang Hyuk; Kim, So-Young; Lee, Woochang; Chun, Sail; Min, Won-Ki

    2012-09-01

    Many laboratories use 4 delta check methods: delta difference, delta percent change, rate difference, and rate percent change. However, guidelines regarding decision criteria for selecting delta check methods have not yet been provided. We present new decision criteria for selecting delta check methods for each clinical chemistry test item. We collected 811,920 and 669,750 paired (present and previous) test results for 27 clinical chemistry test items from inpatients and outpatients, respectively. We devised new decision criteria for the selection of delta check methods based on the ratio of the delta difference to the width of the reference range (DD/RR). Delta check methods based on these criteria were compared with those based on the CV% of the absolute delta difference (ADD) as well as those reported in 2 previous studies. The delta check methods suggested by new decision criteria based on the DD/RR ratio corresponded well with those based on the CV% of the ADD except for only 2 items each in inpatients and outpatients. Delta check methods based on the DD/RR ratio also corresponded with those suggested in the 2 previous studies, except for 1 and 7 items in inpatients and outpatients, respectively. The DD/RR method appears to yield more feasible and intuitive selection criteria and can easily explain changes in the results by reflecting both the biological variation of the test item and the clinical characteristics of patients in each laboratory. We suggest this as a measure to determine delta check methods.

  6. Investigation of the biodistribution, breakdown and excretion of delta inulin adjuvant.

    Science.gov (United States)

    Wang, Lixin; Barclay, Thomas; Song, Yunmei; Joyce, Paul; Sakala, Isaac G; Petrovsky, Nikolai; Garg, Sanjay

    2017-08-03

    Insoluble, nanostructured delta inulin particles enhance the immunogenicity of co-administered protein antigens and consequently are used as a vaccine adjuvant (Advax™). To better understand their immunomodulatory properties, the in vitro hydrolysis and in vivo distribution of delta inulin particles were investigated. Delta inulin particle hydrolysis under bio-relevant acidic conditions resulted in no observable change to the bulk morphology using SEM, and HPLC results showed that only 6.1% of the inulin was hydrolysed over 21days. However, 65% of the terminal glucose groups were released, showing that acid hydrolysis relatively rapidly releases surface bound chemistries. This was used to explain in vivo biodistribution results in which delta inulin particles surface-labelled with fluorescein-5-thiosemicabizide were administered to mice using intramuscular (I.M.) or subcutaneous (S.C.) routes. Comparison analysis of the fluorescence of soluble inulin in the supernatants of homogenised tissues maintained at room temperature or heated to 100°C to solubilise particulate inulin was used to distinguish between fluorescent probe on soluble inulin and probe bound to inulin within particles. Following both I.M. and S.C. injection delta inulin exhibited a depot behaviour with local injection site residence for several weeks. Over this time, as injection site inulin reduced, there was measurable transport of intact delta inulin particles by macrophages to secondary lymphoid organs and the liver. Ultimately, the injected delta inulin became solubilised resulting in its detection in the plasma and in the urine. Thus injected delta inulin particles are initially taken up by macrophages at the site of injection, trafficked to secondary lymphoid tissue and the liver, and hydrolysed resulting in their becoming soluble and diffusing into the blood stream, from whence they are glomerularly filtered and excreted into the urine. These results provide important insights into the

  7. Inhabiting the Delta: A Landscape Approach to Transformative Socio-Ecological Restoration

    Directory of Open Access Journals (Sweden)

    Brett Milligan

    2017-09-01

    Full Text Available doi: https://doi.org/10.15447/sfews.2017v15iss3art3Current legislation and plans for the Sacramento–San Joaquin Delta (Delta call for large-scale restoration of aquatic and terrestrial habitats, which will require significant changes in waterways, land uses, and cultural patterns. These re-made landscapes will be subject to a variety of new human uses, which Delta planning and adaptive management literature has yet to adequately consider. Failing to account for human uses and evolving place values can lead to diminished performance and public support for Delta restoration efforts. Our empirical study examined restored and naturalized Delta landscapes using an integrative landscape approach that seeks to reconcile multiple goals and land-use agendas that span ecological, social, economic, and political domains. The research design consisted of six overlapping methods that included a planning, policy, and law review specific to the Delta; surveys and interviews with approximately 100 land managers, scientists, land-owners, law-enforcement personnel, agency representatives, and Delta residents; nine case studies of restored and naturalized delta landscapes; GIS mapping; and extensive field work. Findings derived from the synthesis of these methods show that human uses of the Delta’s re-wilded landscapes are diverse and pervasive. Given the infrastructural and urbanized context of the region, these environments are subject to multiple and sometimes conflicting uses, perceptions, and place values. Though these myriad uses cannot be fully predicted or controlled (nor should they be, findings showed that more proactive and inclusive planning for human uses can encourage or discourage particular uses while also building constituency, support, and active engagement in ecological restoration efforts. We conclude that reconciling human uses with ecological recovery in the Delta will require a more localized, multi-functional, and creative approach to

  8. Identification of anthropogenic and natural inputs of sulfate and chloride into the karstic ground water of Guiyang, SW China: combined delta37Cl and delta34S approach.

    Science.gov (United States)

    Liu, Cong-Qiang; Lang, Yun-Chao; Satake, Hiroshi; Wu, Jiahong; Li, Si-Liang

    2008-08-01

    Because of active exchange between surface and groundwater of a karstic hydrological system, the groundwater of Guiyang, the capital city of Guizhou Province, southwest China, has been seriously polluted by anthropogenic inputs of NO3-, SO4(2-), Cl-, and Na+. In this work, delta37Cl of chloride and delta34S variations of sulfate in the karstic surface/groundwater system were studied, with a main focus to identify contaminant sources, including their origins. The surface, ground, rain, and sewage water studied showed variable delta37Cl and delta34S values, in the range of -4.1 to +2.0 per thousand, and -20.4 to +20.9 per thousand for delta37Cl and delta34S (SO4(2-)), respectively. The rainwater samples yielded the lowest delta37Cl values among those observed to date for aerosols and rainwater. Chloride in the Guiyang area rain waters emanated from anthropogenic sources rather than being of marine origin, probably derived from HCl (g) emitted by coal combustion. By plotting 1/SO4(2-) vs delta34S and 1/Cl- vs delta37Cl, respectively, we were able to identify some clusters of data, which were assigned as atmospheric deposition (acid rain component), discharge from municipal sewage, paleo-brine components in clastic sedimentary rocks, dissolution of gypsum mainly in dolomite, oxidation of sulfide minerals in coal-containing clastic rocks, and possibly degradation of chlorine-containing organic matter. We conclude that human activities give a significant input of sulfate and chloride ions, as well as other contaminants, into the studied groundwater system through enhanced atmospheric deposition and municipal sewage, and that multiple isotopic tracers constitute a powerful tool to ascertain geochemical characteristics and origin of complex contaminants in groundwater.

  9. Accreting neutron stars, black holes, and degenerate dwarf stars.

    Science.gov (United States)

    Pines, D

    1980-02-08

    During the past 8 years, extended temporal and broadband spectroscopic studies carried out by x-ray astronomical satellites have led to the identification of specific compact x-ray sources as accreting neutron stars, black holes, and degenerate dwarf stars in close binary systems. Such sources provide a unique opportunity to study matter under extreme conditions not accessible in the terrestrial laboratory. Quantitative theoretical models have been developed which demonstrate that detailed studies of these sources will lead to a greatly increased understanding of dense and superdense hadron matter, hadron superfluidity, high-temperature plasma in superstrong magnetic fields, and physical processes in strong gravitational fields. Through a combination of theory and observation such studies will make possible the determination of the mass, radius, magnetic field, and structure of neutron stars and degenerate dwarf stars and the identification of further candidate black holes, and will contribute appreciably to our understanding of the physics of accretion by compact astronomical objects.

  10. Experimental transonic flutter characteristics of two 72 deg-sweep delta-wing models

    Science.gov (United States)

    Doggett, Robert V., Jr.; Soistmann, David L.; Spain, Charles V.; Parker, Ellen C.; Silva, Walter A.

    1989-01-01

    Transonic flutter boundaries are presented for two simple, 72 deg. sweep, low-aspect-ratio wing models. One model was an aspect-ratio 0.65 delta wing; the other model was an aspect-ratio 0.54 clipped-delta wing. Flutter boundaries for the delta wing are presented for the Mach number range of 0.56 to 1.22. Flutter boundaries for the clipped-delta wing are presented for the Mach number range of 0.72 to 0.95. Selected vibration characteristics of the models are also presented.

  11. Search for OB stars running away from young star clusters. I. NGC 6611

    Science.gov (United States)

    Gvaramadze, V. V.; Bomans, D. J.

    2008-11-01

    N-body simulations have shown that the dynamical decay of the young (~1 Myr) Orion Nebula cluster could be responsible for the loss of at least half of its initial content of OB stars. This result suggests that other young stellar systems could also lose a significant fraction of their massive stars at the very beginning of their evolution. To confirm this expectation, we used the Mid-Infrared Galactic Plane Survey (completed by the Midcourse Space Experiment satellite) to search for bow shocks around a number of young (⪉several Myr) clusters and OB associations. We discovered dozens of bow shocks generated by OB stars running away from these stellar systems, supporting the idea of significant dynamical loss of OB stars. In this paper, we report the discovery of three bow shocks produced by O-type stars ejected from the open cluster NGC 6611 (M16). One of the bow shocks is associated with the O9.5Iab star HD165319, which was suggested to be one of “the best examples for isolated Galactic high-mass star formation” (de Wit et al. 2005, A&A, 437, 247). Possible implications of our results for the origin of field OB stars are discussed.

  12. Sediment budgets, transport, and depositional trends in a large tidal delta

    Science.gov (United States)

    Morgan, Tara; Wright, Scott A.

    2016-01-01

    The Sacramento-San Joaquin Delta is the largest delta on the west coast of the United States. It is formed where the confluence of California’s two largest rivers (the Sacramento and San Joaquin) meet the ocean tides and has a significant physical gradient from fluvial to tidal. It is a semidiurnal system (two high and two low tides per day). Today, the Delta is one of the most manipulated in the United States. Once composed of many shallow, meandering and braided dendritic channels and dead-end sloughs and wetlands, it is now a network of leveed canals moving clear water around subsided islands. It historically has supported a biologically diverse tidal wetland complex, of which only 3% remains today (Whipple et al., 2012). It has also witnessed a collapse in the native fish populations. The Delta provides critical habitat for native species, however the hydrology and water quality are complicated by manipulations and diversions to satisfy multiple statewide objectives. Today water managers face co-equal goals of water supply to Californians and maintenance of ecosystem health and function. The Delta is a hub for both a multi-hundred-million dollar agricultural industry and a massive north-to-south water delivery system, supplying the primary source of freshwater to Central Valley farmers and drinking water for two-thirds of California’s population. Large pump facilities support the water demand and draw water from the Delta, further altering circulation patterns and redirecting the net flow toward the export facilities (Monsen et al., 2007). Fluvial sedimentation, along with organic accumulation, creates and sustains the Delta landscape. Hydraulic mining for gold in the watershed during the late 1800s delivered an especially large sediment pulse to the Delta. More recently, from 1955 to the present, a significant sediment decline has been observed that is thought to have been caused mostly by the construction of water storage reservoirs that trap the upstream

  13. Relationship between characteristics of fan-delta sandstone bodies and in-situ leachable sandstone-type uranium mineralization

    International Nuclear Information System (INIS)

    Nie Fengjun; Zhou Weixun; Guan Taiyang; Li Sitian

    2000-01-01

    Like normal deltas, fan-deltas are composed of three parts, i.e., fan-delta plain, fan-delta front and pre-fin-delta, In-situ leachable uranium deposits are commonly distributed along the margins of in-land basins. The author analyzes the possible relationship between the basic characteristics of fan-delta sandstone bodies and uranium mineralization. Two examples, e.g., the fan delta depositional systems in the eastern part of Jungger basin and the southern part of Yili basin, are given to illustrate the fan-delta vertical sequence and planar distribution of sedimentary facies. It has been pointed out that the braided channel sandstone bodies on delta plain, sub-aqueous distributional channel sandstone bodies and delta front sandstone bodies may be the favourable host rocks for in-situ leachable sandstone uranium deposits

  14. Spectrophotometry of Symbiotic Stars (Abstract)

    Science.gov (United States)

    Boyd, D.

    2017-12-01

    (Abstract only) Symbiotic stars are fascinating objects - complex binary systems comprising a cool red giant star and a small hot object, often a white dwarf, both embedded in a nebula formed by a wind from the giant star. UV radiation from the hot star ionizes the nebula, producing a range of emission lines. These objects have composite spectra with contributions from both stars plus the nebula and these spectra can change on many timescales. Being moderately bright, they lend themselves well to amateur spectroscopy. This paper describes the symbiotic star phenomenon, shows how spectrophotometry can be used to extract astrophysically useful information about the nature of these systems, and gives results for three symbiotic stars based on the author's observations.

  15. BINARY DISRUPTION BY MASSIVE BLACK HOLES: HYPERVELOCITY STARS, S STARS, AND TIDAL DISRUPTION EVENTS

    Energy Technology Data Exchange (ETDEWEB)

    Bromley, Benjamin C. [Department of Physics and Astronomy, University of Utah, 115 S 1400 E, Rm 201, Salt Lake City, UT 84112 (United States); Kenyon, Scott J.; Geller, Margaret J.; Brown, Warren R., E-mail: bromley@physics.utah.edu, E-mail: skenyon@cfa.harvard.edu, E-mail: mgeller@cfa.harvard.edu, E-mail: wbrown@cfa.harvard.edu [Smithsonian Astrophysical Observatory, 60 Garden Street, Cambridge, MA 02138 (United States)

    2012-04-20

    We examine whether disrupted binary stars can fuel black hole growth. In this mechanism, tidal disruption produces a single hypervelocity star (HVS) ejected at high velocity and a former companion star bound to the black hole. After a cluster of bound stars forms, orbital diffusion allows the black hole to accrete stars by tidal disruption at a rate comparable to the capture rate. In the Milky Way, HVSs and the S star cluster imply similar rates of 10{sup -5} to 10{sup -3} yr{sup -1} for binary disruption. These rates are consistent with estimates for the tidal disruption rate in nearby galaxies and imply significant black hole growth from disrupted binaries on 10 Gyr timescales.

  16. N-Type delta Doping of High-Purity Silicon Imaging Arrays

    Science.gov (United States)

    Blacksberg, Jordana; Hoenk, Michael; Nikzad, Shouleh

    2005-01-01

    A process for n-type (electron-donor) delta doping has shown promise as a means of modifying back-illuminated image detectors made from n-doped high-purity silicon to enable them to detect high-energy photons (ultraviolet and x-rays) and low-energy charged particles (electrons and ions). This process is applicable to imaging detectors of several types, including charge-coupled devices, hybrid devices, and complementary metal oxide/semiconductor detector arrays. Delta doping is so named because its density-vs.-depth characteristic is reminiscent of the Dirac delta function (impulse function): the dopant is highly concentrated in a very thin layer. Preferably, the dopant is concentrated in one or at most two atomic layers in a crystal plane and, therefore, delta doping is also known as atomic-plane doping. The use of doping to enable detection of high-energy photons and low-energy particles was reported in several prior NASA Tech Briefs articles. As described in more detail in those articles, the main benefit afforded by delta doping of a back-illuminated silicon detector is to eliminate a "dead" layer at the back surface of the silicon wherein high-energy photons and low-energy particles are absorbed without detection. An additional benefit is that the delta-doped layer can serve as a back-side electrical contact. Delta doping of p-type silicon detectors is well established. The development of the present process addresses concerns specific to the delta doping of high-purity silicon detectors, which are typically n-type. The present process involves relatively low temperatures, is fully compatible with other processes used to fabricate the detectors, and does not entail interruption of those processes. Indeed, this process can be the last stage in the fabrication of an imaging detector that has, in all other respects, already been fully processed, including metallized. This process includes molecular-beam epitaxy (MBE) for deposition of three layers, including

  17. Fast pulsars, strange stars

    International Nuclear Information System (INIS)

    Glendenning, N.K.

    1990-02-01

    The initial motivation for this work was the reported discovery in January 1989 of a 1/2 millisecond pulsar in the remnant of the spectacular supernova, 1987A. The status of this discovery has come into grave doubt as of data taken by the same group in February, 1990. At this time we must consider that the millisecond signal does not belong to the pulsar. The existence of a neutron star in remnant of the supernova is suspected because of recent observations on the light curve of the remnant, and of course by the neutrino burst that announced the supernova. However its frequency is unknown. I can make a strong case that a pulsar rotation period of about 1 ms divides those that can be understood quite comfortably as neutron stars, and those that cannot. What we will soon learn is whether there is an invisible boundary below which pulsar periods do not fall, in which case, all are presumable neutron stars, or whether there exist sub- millisecond pulsars, which almost certainly cannot be neutron stars. Their most plausible structure is that of a self-bound star, a strange-quark-matter star. The existence of such stars would imply that the ground state of the strong interaction is not, as we usually assume, hadronic matter, but rather strange quark matter. Let us look respectively at stars that are bound only by gravity, and hypothetical stars that are self-bound, for which gravity is so to speak, icing on the cake

  18. Wolf-Rayet Stars

    Science.gov (United States)

    Hamann, Wolf-Rainer; Sander, Andreas; Todt, Helge

    Nearly 150 years ago, the French astronomers Charles Wolf and Georges Rayet described stars with very conspicuous spectra that are dominated by bright and broad emission lines. Meanwhile termed Wolf-Rayet Stars after their discoverers, those objects turned out to represent important stages in the life of massive stars. As the first conference in a long time that was specifically dedicated to Wolf-Rayet stars, an international workshop was held in Potsdam, Germany, from 1.-5. June 2015. About 100 participants, comprising most of the leading experts in the field as well as as many young scientists, gathered for one week of extensive scientific exchange and discussions. Considerable progress has been reported throughout, e.g. on finding such stars, modeling and analyzing their spectra, understanding their evolutionary context, and studying their circumstellar nebulae. While some major questions regarding Wolf-Rayet stars still remain open 150 years after their discovery, it is clear today that these objects are not just interesting stars as such, but also keystones in the evolution of galaxies. These proceedings summarize the talks and posters presented at the Potsdam Wolf-Rayet workshop. Moreover, they also include the questions, comments, and discussions emerging after each talk, thereby giving a rare overview not only about the research, but also about the current debates and unknowns in the field. The Scientific Organizing Committee (SOC) included Alceste Bonanos (Athens), Paul Crowther (Sheffield), John Eldridge (Auckland), Wolf-Rainer Hamann (Potsdam, Chair), John Hillier (Pittsburgh), Claus Leitherer (Baltimore), Philip Massey (Flagstaff), George Meynet (Geneva), Tony Moffat (Montreal), Nicole St-Louis (Montreal), and Dany Vanbeveren (Brussels).

  19. Anadromous salmonids in the Delta: New science 2006–2016

    Science.gov (United States)

    Perry, Russell W.; Buchanan, Rebecca A.; Brandes, Patricia L.; Burau, Jon R.; Israel, Joshua A

    2016-01-01

    As juvenile salmon enter the Sacramento–SanJoaquin River Delta (“the Delta”) they disperse among its complex channel network where they are subject to channel-specific processes that affect their rate of migration, vulnerability to predation, feeding success, growth rates, and ultimately, survival. In the decades before 2006, tools available to quantify growth, dispersal, and survival of juvenile salmon in this complex channel network were limited.Fortunately, thanks to technological advances such as acoustic telemetry and chemical and structural otolith analysis, much has been learned over the past decade about the role of the Delta in the life cycle of juvenile salmon. Here, we review new science between 2006and 2016 that sheds light on how different life stages and runs of juvenile salmon grow, move, and survive in the complex channel network of the Delta. One of the most important advances during the past decade has been the widespread adoption of acoustic telemetry techniques. Use of telemetry has shed light on how survival varies among alternative migration routes and the proportion of fish that use each migration route. Chemical and structural analysis of otoliths has provided insights about when juveniles left their natal river and provided evidence of extended rearing in the brackish or saltwater regions of the Delta. New advancements in genetics now allow individuals captured by trawls to be assigned to specific runs. Detailed information about movement and survival in the Delta has spurred development of agent-based models of juvenile salmon that are coupled to hydrodynamic models. Although much has been learned, knowledge gaps remain about how very small juvenile salmon (fry and parr) use the Delta. Understanding how all life stages of juvenile salmon grow, rear, and survive in the Delta is critical for devising management strategies that support a diversity of life history strategies.

  20. Conceptual model of sedimentation in the Sacramento-San Joaquin River Delta

    Science.gov (United States)

    Schoellhamer, David H.; Wright, Scott A.; Drexler, Judith Z.

    2012-01-01

    Sedimentation in the Sacramento–San Joaquin River Delta builds the Delta landscape, creates benthic and pelagic habitat, and transports sediment-associated contaminants. Here we present a conceptual model of sedimentation that includes submodels for river supply from the watershed to the Delta, regional transport within the Delta and seaward exchange, and local sedimentation in open water and marsh habitats. The model demonstrates feedback loops that affect the Delta ecosystem. Submerged and emergent marsh vegetation act as ecosystem engineers that can create a positive feedback loop by decreasing suspended sediment, increasing water column light, which in turn enables more vegetation. Sea-level rise in open water is partially countered by a negative feedback loop that increases deposition if there is a net decrease in hydrodynamic energy. Manipulation of regional sediment transport is probably the most feasible method to control suspended sediment and thus turbidity. The conceptual model is used to identify information gaps that need to be filled to develop an accurate sediment transport model.

  1. Challenges Facing the Sacramento–San Joaquin Delta: Complex, Chaotic, or Simply Cantankerous?

    Directory of Open Access Journals (Sweden)

    Samuel N. Luoma

    2015-09-01

    Full Text Available doi: http://dx.doi.org/10.15447/sfews.2015v13iss3art7Freshwater is a scarce and precious resource in California; its overall value is being made clear by the current severe drought. The Sacramento–San Joaquin Delta is a critical node in a complex water supply system that extends throughout much of the western U.S. wherein demand is exceeding supply. The Delta also underpins a major component of the U.S. economy, helps feed a substantial part of the country, is a unique and valuable ecological resource, and is a place with a rich cultural heritage. Sustaining the Delta is a problem that manifests itself in many dimensions including the physical structure of the Delta, the conflicting demands for water, changing water quality, rapidly evolving ecological character, and high institutional complexity. The problems of the California Delta are increasingly complex, sometimes chaotic, and always contentious. There is general agreement that current management will sustain neither the Delta ecosystem nor high-quality water exports, as required under the Delta Reform Act, so there is a renewed urgency to address all dimensions of the problem aggressively. Sustainable management of the Delta ecosystem and California’s highly variable water supply, in the face of global climate change, will require bold political decisions that include adjustments to the infrastructure but give equal emphasis to chronic overuse and misuse of water, promote enhanced efficiency of water use, and facilitate new initiatives for ecosystem recovery. This new approach will need to be underpinned by collaborative science that supports ongoing evaluation and re-adjustment of actions. Problems like the Delta are formally “wicked" problems that cannot be “solved” in the traditional sense, but they can be managed with appropriate knowledge and flexible institutions. Where possible, it is advisable to approach major actions incrementally, with an eye toward avoiding

  2. An annotated list of Fishes from the Niger Delta

    NARCIS (Netherlands)

    Boeseman, M.

    1963-01-01

    At the end of November 1960, the Leiden Museum received an interesting collection of animals, mostly fishes, from the Niger delta. All specimens were collected by Mr. H. J. G. Beets, at the time employed by Shell B.P. — Delta Investigations, during the period May to August 1960, and in the region

  3. Quark sea and the. delta. I=1/2 rule

    Energy Technology Data Exchange (ETDEWEB)

    Donoghue, J F [Carnegie-Mellon Univ., Pittsburgh, Pa. (USA). Dept. of Physics; Golowich, E [Massachusetts Univ., Amherst (USA)

    1977-08-29

    The effect on nonleptonic processes of quark-antiquark pairs due to quantum chromodynamics is studied. Their presence improves agreement between theory and experiment for hyperon decays. In kaon decays a new ..delta..I=1/2 contribution is found, but ..delta..I=3/2 effects are still too large to be in agreement.

  4. Low-mass stars with mass loss and low-luminosity carbon star formation

    International Nuclear Information System (INIS)

    Boothroyd, A.I.

    1987-01-01

    The effects of large carbon enrichments in static stellar envelopes were investigated, using new Los Alamos opacities (including low-temperature carbon and molecular opacities) and including carbon ionizations. To search for the production of low-mass,low-luminosity carbon stars, detailed stellar evolutionary computations were carried out for a grid of low-mass stars of two different metallicities. The stars were evolved from the main sequence through all intermediate stages and through helium-shell flashes on the asymptotic giant branch. The effects of the latest nuclear reaction rates, the new Los Alamos opacities, Reimers-type wind mass loss, and detailed treatment of convection and semi-convection were investigated. Two low-luminosity carbon stars were achieved, in excellent agreement with observations. Conditions favoring dredge-up (and thus carbon-star production) include a reasonably large convective mixing length, low metallicity, relatively large envelope mass, and high flash strength. Mass loss was of major importance, tending to oppose dredge-up; the total mass-loss amounts inferred from observations suffice to prevent formation of high-mass, high-luminosity carbon stars

  5. A Delta-V map of the known Main Belt Asteroids

    Science.gov (United States)

    Taylor, Anthony; McDowell, Jonathan C.; Elvis, Martin

    2018-05-01

    With the lowered costs of rocket technology and the commercialization of the space industry, asteroid mining is becoming both feasible and potentially profitable. Although the first targets for mining will be the most accessible near Earth objects (NEOs), the Main Belt contains 106 times more material by mass. The large scale expansion of this new asteroid mining industry is contingent on being able to rendezvous with Main Belt asteroids (MBAs), and so on the velocity change required of mining spacecraft (delta-v). This paper develops two different flight burn schemes, both starting from Low Earth Orbit (LEO) and ending with a successful MBA rendezvous. These methods are then applied to the ∼700,000 asteroids in the Minor Planet Center (MPC) database with well-determined orbits to find low delta-v mining targets among the MBAs. There are 3986 potential MBA targets with a delta-v < 8 km s-1 , but the distribution is steep and reduces to just 4 with delta-v < 7 km s-1. The two burn methods are compared and the orbital parameters of low delta-v MBAs are explored.

  6. Heavy baryon chiral perturbation theory and the spin 3/2 delta resonances

    Energy Technology Data Exchange (ETDEWEB)

    Kambor, J.

    1996-12-31

    Heavy baryon chiral perturbation theory is briefly reviewed, paying particular attention to the role of the spin 3/2 delta resonances. The concept of resonance saturation for the baryonic sector is critically discussed. Starting from a relativistic formulation of the pion-nucleon-delta system, the heavy baryon chiral Lagrangian including spin 3/2 resonances is constructed by means of a 1/m-expansion. The effective theory obtained admits a systematic expansion in terms of soft momenta, the pion mass M{sub {pi}} and the delta-nucleon mass difference {Delta}. (author). 22 refs.

  7. Spectroscopic survey of Kepler stars - II. FIES/NOT observations of A- and F-type stars

    Science.gov (United States)

    Niemczura, E.; Polińska, M.; Murphy, S. J.; Smalley, B.; Kołaczkowski, Z.; Jessen-Hansen, J.; Uytterhoeven, K.; Lykke, J. M.; Triviño Hage, A.; Michalska, G.

    2017-09-01

    We have analysed high-resolution spectra of 28 A and 22 F stars in the Kepler field, observed using the Fibre-Fed Échelle Spectrograph at the Nordic Optical Telescope. We provide spectral types, atmospheric parameters and chemical abundances for 50 stars. Balmer, Fe I and Fe II lines were used to derive effective temperatures, surface gravities and microturbulent velocities. We determined chemical abundances and projected rotational velocities using a spectrum synthesis technique. Effective temperatures calculated by spectral energy distribution fitting are in good agreement with those determined from the spectral line analysis. The stars analysed include chemically peculiar stars of the Am and λ Boo types, as well as stars with approximately solar chemical abundances. The wide distribution of projected rotational velocity, vsin I, is typical for A and F stars. The microturbulence velocities obtained are typical for stars in the observed temperature and surface gravity ranges. Moreover, we affirm the results of Niemczura et al. that Am stars do not have systematically higher microturbulent velocities than normal stars of the same temperature.

  8. Another Possibility for Boyajian's Star

    Science.gov (United States)

    Kohler, Susanna

    2017-07-01

    The unusual light curve of the star KIC 8462852, also known as Tabbys star or Boyajians star, has puzzled us since its discovery last year. A new study now explores whether the stars missing flux is due to internal blockage rather than something outside of the star.Mysterious DipsMost explanations for the flux dips of Boyajians star rely on external factors, like this illustrated swarm of comets. [NASA/JPL-Caltech]Boyajians star shows unusual episodes of dimming in its light curve by as much as 20%, each lasting a few to tens of days and separated by periods of typically hundreds of days. In addition, archival observations show that it has gradually faded by roughly 15% over the span of the last hundred years. What could be causing both the sporadic flux dips and the long-term fading of this odd star?Explanations thus far have varied from mundane to extreme. Alien megastructures, pieces of smashed planets or comets orbiting the star, and intervening interstellar medium have all been proposed as possible explanations but these require some object external to the star. A new study by researcher Peter Foukal proposes an alternative: what if the source of the flux obstruction is the star itself?Analogy to the SunDecades ago, researchers discovered that our own stars total flux isnt as constant as we thought. When magnetic dark spots on the Suns surface block the heat transport, the Suns luminosity dips slightly. The diverted heat is redistributed in the Suns interior, becoming stored as a very small global heating and expansion of the convective envelope. When the blocking starspot is removed, the Sun appears slightly brighter than it did originally. Its luminosity then gradually relaxes, decaying back to its original value.Model of a stars flux after a 1,000-km starspot is inserted at time t = 0 and removed at time t = ts at a depth of 10,000 km in the convective zone. The stars luminosity dips, then becomes brighter than originally, and then gradually decays. [Foukal

  9. Stability of boson stars

    International Nuclear Information System (INIS)

    Gleiser, M.

    1988-01-01

    Boson stars are gravitationally bound, spherically symmetric equilibrium configurations of cold, free, or interacting complex scalar fields phi. As these equilibrium configurations naturally present local anisotropy, it is sensible to expect departures from the well-known stability criteria for fluid stars. With this in mind, I investigate the dynamical instability of boson stars against charge-conserving, small radial perturbations. Following the method developed by Chandrasekhar, a variational base for determining the eigenfrequencies of the perturbations is found. This approach allows one to find numerically an upper bound for the central density where dynamical instability occurs. As applications of the formalism, I study the stability of equilibrium configurations obtained both for the free and for the self-interacting [with V(phi) = (λ/4)chemical bondphichemical bond 4 ] massive scalar field phi. Instabilities are found to occur not for the critical central density as in fluid stars but for central densities considerably higher. The departure from the results for fluid stars is sensitive to the coupling λ; the higher the value of λ, the more the stability properties of boson stars approach those of a fluid star. These results are linked to the fractional anisotropy at the radius of the configuration

  10. Strange-quark-matter stars

    International Nuclear Information System (INIS)

    Glendenning, N.K.

    1989-11-01

    We investigate the implications of rapid rotation corresponding to the frequency of the new pulsar reported in the supernovae remnant SN1987A. It places very stringent conditions on the equation of state if the star is assumed to be bound by gravity alone. We find that the central energy density of the star must be greater than 13 times that of nuclear density to be stable against the most optimistic estimate of general relativistic instabilities. This is too high for the matter to consist of individual hadrons. We conclude that it is implausible that the newly discovered pulsar, if its half-millisecond signals are attributable to rotation, is a neutron star. We show that it can be a strange quark star, and that the entire family of strange stars can sustain high rotation if strange matter is stable at an energy density exceeding about 5.4 times that of nuclear matter. We discuss the conversion of a neutron star to strange star, the possible existence of a crust of heavy ions held in suspension by centrifugal and electric forces, the cooling and other features. 34 refs., 10 figs., 1 tab

  11. Effect of environmental change on the morphology of tidally influenced deltas over multi-decadal timescale

    Science.gov (United States)

    Angamuthu, Balaji; Darby, Stephen; Nicholls, Robert

    2017-04-01

    An understanding of the geomorphological processes affecting deltas is essential to improve our understanding of the risks that deltas face, especially as human impacts are likely to intensify in the future. Unfortunately, there is limited reliable data on river deltas, meaning that the task of demonstrating the links between morphodynamic and environmental change is challenging. This presentation aims to answer the questions of how delta morphology evolves over multi-decadal timescales under multiple drivers, focussing on tidally-influenced deltas, as some of these, such as the Ganges-Brahmaputra-Meghna (GBM) delta are heavily populated. A series of idealised model simulations over 102 years were used to explore the influence of three key drivers on delta morphodynamics, both individually and together: (i) varying combinations of water and sediment discharges from the upstream catchment, (ii) varying rates of relative sea-level rise (RSLR), and (iii) selected human interventions within the delta, such as polders, cross-dams and changing land cover. Model simulations revealed that delta progradation rates are more sensitive to variations in water discharge than variations in fluvial sediment supply. Unlike mere aggradation during RSLR, the delta front experienced aggradational progradation due to tides. As expected, the area of the simulated sub-aerial delta increases with increasing sediment discharge, but decreases with increasing water discharge. But, human modifications are important. For example, the sub-aerial delta shrinks with increasing RSLR, but it does not when the sub-aerial delta is polderised, provided the polders are restricted from erosion. However, the polders are vulnerable to flooding as they lose relative elevation and can make the delta building process unsustainable. Cross-dams built to steer zones of land accretion within the delta accomplish their local goal, but may not result in net land gain at the scale of the delta. Applying these

  12. VLA observations of dwarf M flare stars and magnetic stars

    Science.gov (United States)

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

    1988-01-01

    The VLA has been used to search for 6 cm emission from 16 nearby dwarf M stars, leading to the detection of only one of them - Gliese 735. The dwarf M flare stars AD Leonis and YZ Canis Minoris were also monitored at 6 cm and 20 cm wavelength in order to study variability. Successive oppositely circularly polarized bursts were detected from AD Leo at 6 cm, suggesting the presence of magnetic fields of both magnetic polarities. An impulsive 20-cm burst from YZ CMi preceded slowly varying 6-cm emission. The VLA was also used, unsuccessfully, to search for 6-cm emission from 13 magnetic Ap stars, all of which exhibit kG magnetic fields. Although the Ap magnetic stars have strong dipolar magnetic fields, the failure to detect gyroresonant radiation suggests that these stars do not have hot, dense coronae. The quiescent microwave emission from GL 735 is probably due to nonthermal radiation, since unusually high (H = 50 kG or greater) surface magnetic fields are inferred under the assumption that the 6-cm radiation is the gyroresonant radiation of thermal electrons.

  13. The Economic Dimensions of the Niger Delta Ethnic Conflicts (Pp ...

    African Journals Online (AJOL)

    User

    1970, the price of international oil stepped upwards following the Middle. Eastern Yom Kippur .... Over the years, the pleas of the Niger Delta people for accommodation are ignored or .... In a labour surplus region like the Niger Delta, budget.

  14. Soft controller switching technique to minimize the torque and current pulsations of a SCIM during its reswitching

    International Nuclear Information System (INIS)

    Larik, A.S.

    2010-01-01

    The direct-on-line starting of induction motor draws heavy current and to limit this Inrush current to a safe level normally a star-delta switch is used. However, the switching over from star to delta causes over current transients and this leads to torque pulsations. Therefore, in this paper the current and torque pulsations developed during the switching process are focused and a soft-switched controller is devised to minimize the re-closure transient currents and torque pulsations during star-delta switching of induction motor. The designed system can readily handles the sensing of favorable conditions of re closure of a switched-off running induction motor and it minimizes the inrush current and hence the pulsations of torque of all types of induction motors, whether, single-phase or three phase. An investigation is made into the transient currents and pulsation torques generated due to opening the circuit of a running induction motor and the switching pattern of star-delta switching. The re-switching control scheme for the induction motor is practically tested in the laboratory with and without soft controller. (author)

  15. Little Bear’s pulsating stars: Variable star census of UMi dSph Galaxy

    Directory of Open Access Journals (Sweden)

    Kinemuchi K.

    2017-01-01

    Full Text Available Recent observations and a photometric search for variable stars in the Ursa Minor dwarf spheroidal galaxy (UMi dSph are presented. Our observations were taken at Apache Point Observatory in 2014 and 2016 using the 0.5m ARCSAT telescope and the West Mountain Observatory (WMO 0.9m telescope of Brigham Young University in 2016. Previously known RR Lyrae stars in our field of view of the UMi dSph are identified, and we also catalog new variable star candidates. Tentative classifications are given for some of the new variable stars. We have conducted period searches with the data collected with the WMO telescope. Our ultimate goal is to create an updated catalog of variable stars in the UMi dSph and to compare the RR Lyrae stellar characteristics to other RR Lyrae stars found in the Local Group dSph galaxies.

  16. Star Imager

    DEFF Research Database (Denmark)

    Madsen, Peter Buch; Jørgensen, John Leif; Thuesen, Gøsta

    1997-01-01

    The version of the star imager developed for Astrid II is described. All functions and features are described as well as the operations and the software protocol.......The version of the star imager developed for Astrid II is described. All functions and features are described as well as the operations and the software protocol....

  17. Wolf-Rayet stars associated to giant regions of star formation

    International Nuclear Information System (INIS)

    D'Odorico, S.; Rosa, M.

    1982-01-01

    Data on Wolf-Rayet (WR) stars in extragalactic H II regions and emission line galaxies are presented and discussed. The sample is still limited and inhomogeneous but two important points appear to be already established: a) The WR stars are more numerous than the blue supergiants at least in same phase of the evolution of the stellar clusters which ionize the giant H II regions, b) When the WR stars are detected, two cases are apparently observed, one in which only WN, the other in which both WN and WC, are present. (Auth.)

  18. Salinity Impacts on Agriculture and Groundwater in Delta Regions

    Science.gov (United States)

    Clarke, D.; Salehin, M.; Jairuddin, M.; Saleh, A. F. M.; Rahman, M. M.; Parks, K. E.; Haque, M. A.; Lázár, A. N.; Payo, A.

    2015-12-01

    Delta regions are attractive for high intensity agriculture due to the availability of rich sedimentary soils and of fresh water. Many of the world's tropical deltas support high population densities which are reliant on irrigated agriculture. However environmental changes such as sea level rise, tidal inundation and reduced river flows have reduced the quantity and quality of water available for successful agriculture. Additionally, anthropogenic influences such as the over abstraction of ground water and the increased use of low quality water from river inlets has resulted in the accumulation of salts in the soils which diminishes crop productivity. Communities based in these regions are usually reliant on the same water for drinking and cooking because surface water is frequently contaminated by commercial and urban pollution. The expansion of shallow tube well systems for drinking water and agricultural use over the last few decades has resulted in mobilisation of salinity in the coastal and estuarine fringes. Sustainable development in delta regions is becoming constrained by water salinity. However salinity is often studied as an independent issue by specialists working in the fields of agriculture, community water supply and groundwater. The lack of interaction between these disciplines often results in corrective actions being applied to one sector without fully assessing the effects of these actions on other sectors. This paper describes a framework for indentifying the causes and impacts of salinity in delta regions based on the source-pathway-receptor framework. It uses examples and scenarios from the Ganges-Brahmaputra-Meghna delta in Bangladesh together with field measurements and observations made in vulnerable coastal communities. The paper demonstrates the importance of creating an holistic understanding of the development and management of water resources to reduce the impact of salinity in fresh water in delta regions.

  19. Asteroseismology of white dwarf stars

    OpenAIRE

    Córsico, A. H.

    2014-01-01

    Most of low- and intermediate-mass stars that populate the Universe will end their lives as white dwarf stars. These ancient stellar remnants have encrypted inside a precious record of the evolutionary history of the progenitor stars, providing a wealth of information about the evolution of stars, star formation, and the age of a variety of stellar populations, such as our Galaxy and open and globular clusters. While some information like surface chemical composition, temperature and gravity ...

  20. Delta-gamma-theta Hedging of Crude Oil Asian Options

    Directory of Open Access Journals (Sweden)

    Juraj Hruška

    2015-01-01

    Full Text Available Since Black-Scholes formula was derived, many methods have been suggested for vanilla as well as exotic options pricing. More of investing and hedging strategies have been developed based on these pricing models. Goal of this paper is to derive delta-gamma-theta hedging strategy for Asian options and compere its efficiency with gamma-delta-theta hedging combined with predictive model. Fixed strike Asian options are type of exotic options, whose special feature is that payoff is calculated from the difference of average market price and strike price for call options and vice versa for the put options. Methods of stochastic analysis are used to determine deltas, gammas and thetas of Asian options. Asian options are cheaper than vanilla options and therefore they are more suitable for precise portfolio creation. On the other hand their deltas are also smaller as well as profits. That means that they are also less risky and more suitable for hedging. Results, conducted on chosen commodity, confirm better feasibility of Asian options compering with vanilla options in sense of gamma hedging.