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Sample records for horizontal branch morphology

  1. On the red giant branch mass loss in 47 Tucanae: Constraints from the horizontal branch morphology

    NASA Astrophysics Data System (ADS)

    Salaris, Maurizio; Cassisi, Santi; Pietrinferni, Adriano

    2016-05-01

    We obtain stringent constraints on the actual efficiency of mass loss for red giant branch stars in the Galactic globular cluster 47 Tuc, by comparing synthetic modelling based on stellar evolution tracks with the observed distribution of stars along the horizontal branch in the colour-magnitude-diagram. We confirm that the observed, wedge-shaped distribution of the horizontal branch can only be reproduced by accounting for a range of initial He abundances, in agreement with inferences from the analysis of the main sequence, and a red giant branch mass loss with a small dispersion. We carefully investigated several possible sources of uncertainty that could affect the results of the horizontal branch modelling, stemming from uncertainties in both stellar model computations and cluster properties, such as heavy element abundances, reddening, and age. We determine a firm lower limit of ~0.17M⊙ for the mass lost by red giant branch stars, corresponding to horizontal branch stellar masses between ~0.65M⊙ and ~0.73M⊙ (the range driven by the range of initial helium abundances). We also derive that in this cluster the amount of mass lost along the asymptotic giant branch stars is comparable to the mass lost during the previous red giant branch phase. These results confirm, for this cluster, the disagreement between colour-magnitude-diagram analyses and inferences from recent studies of the dynamics of the cluster stars, which predict a much less efficient red giant branch mass loss. A comparison between the results from these two techniques applied to other clusters is required to gain more insights about the origin of this disagreement.

  2. Global and nonglobal parameters of horizontal-branch morphology of globular clusters

    SciTech Connect

    Milone, A. P.; Marino, A. F.; Dotter, A.; Norris, J. E.; Jerjen, H.; Asplund, M. E-mail: amarino@mso.anu.edu.au E-mail: jerjen@mso.anu.edu.au; and others

    2014-04-10

    The horizontal-branch (HB) morphology of globular clusters (GCs) is mainly determined by metallicity. However, the fact that GCs with almost the same metallicity exhibit different HB morphologies demonstrates that at least one more parameter is needed to explain the HB morphology. It has been suggested that one of these should be a global parameter that varies from GC to GC and the other a nonglobal parameter that varies within the GC. In this study we provide empirical evidence corroborating this idea. We used the photometric catalogs obtained with the Advanced Camera for Surveys of the Hubble Space Telescope and analyze the color-magnitude diagrams of 74 GCs. The HB morphology of our sample of GCs has been investigated on the basis of the two new parameters L1 and L2 that measure the distance between the red giant branch and the coolest part of the HB and the color extension of the HB, respectively. We find that L1 correlates with both metallicity and age, whereas L2 most strongly correlates with the mass of the hosting GC. The range of helium abundance among the stars in a GC, characterized by ΔY and associated with the presence of multiple stellar populations, has been estimated in a few GCs to date. In these GCs we find a close relationship among ΔY, GC mass, and L2. We conclude that age and metallicity are the main global parameters, while the range of helium abundance within a GC is the main nonglobal parameter defining the HB morphology of Galactic GCs.

  3. THE ACS SURVEY OF GALACTIC GLOBULAR CLUSTERS. IX. HORIZONTAL BRANCH MORPHOLOGY AND THE SECOND PARAMETER PHENOMENON

    SciTech Connect

    Dotter, Aaron; Sarajedini, Ata; Anderson, Jay; Bedin, Luigi R.; Paust, Nathaniel; Reid, I. Neill; Aparicio, Antonio; MarIn-Franch, A.; Rosenberg, Alfred; Majewski, Steven; Milone, Antonino; Piotto, Giampaolo; Siegel, Michael E-mail: ata@astro.ufl.ed

    2010-01-01

    The horizontal branch (HB) morphology of globular clusters (GCs) is most strongly influenced by metallicity. The second parameter phenomenon, first described in the 1960s, acknowledges that metallicity alone is not enough to describe the HB morphology of all GCs. In particular, astronomers noticed that the outer Galactic halo contains GCs with redder HBs at a given metallicity than are found inside the solar circle. Thus, at least a second parameter was required to characterize HB morphology. While the term 'second parameter' has since come to be used in a broader context, its identity with respect to the original problem has not been conclusively determined. Here we analyze the median color difference between the HB and the red giant branch, hereafter denoted as DELTA(V - I), measured from Hubble Space Telescope (HST) Advanced Camera for Surveys (ACS) photometry of 60 GCs within approx20 kpc of the Galactic center. Analysis of this homogeneous data set reveals that, after the influence of metallicity has been removed from the data, the correlation between DELTA(V - I) and age is stronger than that of any other parameter considered. Expanding the sample to include HST ACS and Wide Field Planetary Camera 2 photometry of the six most distant Galactic GCs lends additional support to the correlation between DELTA(V - I) and age. This result is robust with respect to the adopted metallicity scale and the method of age determination, but must bear the caveat that high-quality, detailed abundance information is not available for a significant fraction of the sample. Furthermore, when a subset of GCs with similar metallicities and ages is considered, a correlation between DELTA(V - I) and central luminosity density is exposed. With respect to the existence of GCs with anomalously red HBs at a given metallicity, we conclude that age is the second parameter and central density is most likely the third. Important problems related to HB morphology in GCs, notably multi

  4. HORIZONTAL BRANCH MORPHOLOGY AND MULTIPLE STELLAR POPULATIONS IN THE ANOMALOUS GLOBULAR CLUSTER M 22

    SciTech Connect

    Marino, A. F.; Milone, A. P.; Lind, K. E-mail: milone@iac.es

    2013-05-01

    M 22 is an anomalous globular cluster that hosts two groups of stars with different metallicity and s-element abundance. The star-to-star light-element variations in both groups, with the presence of individual Na-O and C-N anticorrelations, demonstrates that this Milky Way satellite has experienced a complex star formation history. We have analyzed FLAMES/UVES spectra for seven stars covering a small color interval on the reddest horizontal branch (HB) portion of this cluster and investigated possible relations between the chemical composition of a star and its location along the HB. Our chemical abundance analysis takes into account effects introduced by deviations from the local thermodynamic equilibrium (NLTE effects), which are significant for the measured spectral lines in the atmospheric parameters range spanned by our stars. We find that all the analyzed stars are barium-poor and sodium-poor, thus supporting the idea that the position of a star along the HB is strictly related to the chemical composition, and that the HB morphology is influenced by the presence of different stellar populations.

  5. Modelling realistic horizontal branch morphologies and their impact on spectroscopic ages of unresolved stellar systems

    NASA Astrophysics Data System (ADS)

    Percival, Susan M.; Salaris, Maurizio

    2011-04-01

    The presence of an extended blue horizontal branch (HB) in a stellar population is known to affect the age inferred from spectral fitting to stellar population synthesis models. This is due to the hot blue component which increases the strength of the Balmer lines and can make an old population look spuriously young. However, most population synthesis models still rely on theoretical isochrones, which do not include realistic modelling of extended HBs. In this work, we create detailed models for a range of old simple stellar populations (SSPs), with metallicities ranging from [Fe/H]=-1.3 to solar, to create a variety of realistic HB morphologies, from extended red clumps, to extreme blue HBs. We achieve this by utilizing stellar tracks from the BaSTI data base and implementing a different mass-loss prescription for each SSP created. This includes setting an average mass and a Gaussian spread in masses of individual stars coming on to the zero-age HB for each model, and hence resulting in different HB morphologies. We find that, for each metallicity, there is some HB morphology which maximizes Hβ, making an underlying 14-Gyr population look ˜5-6 Gyr old for the low- and intermediate-metallicity cases, and as young as 2 Gyr in the case of the solar metallicity SSP. We explore whether there are any spectral indices capable of breaking the degeneracy between an old SSP with extended blue HB and a truly young or intermediate-age SSP, and find that the Ca II index of Rose and the strength of the Mg II doublet at 2800 Å are promising candidates, in combination with Hβ and other metallicity indicators, such as Mgb and Fe5406. We also run Monte Carlo simulations to investigate the level of statistical fluctuations in the spectra of typical stellar clusters. We find that fluctuations in spectral indices are significant even for average to large globular clusters and that various spectral indices are affected in different ways, which has implications for full

  6. A New Spin for Understanding the Peculiar Horizontal Branch Morphology of the Galactic Globular Clusters NGC 6388 and NGC 6441

    NASA Technical Reports Server (NTRS)

    Busso, G.; Piotto, G.; Cassisi, S.; Romaniello, M.; Castelli, F.; Catelan, M.; Djorgovski, S. G.; King, I. R.; Landsman, W. B.; Blanco, A. Reico; Renzini, A.; Rich, M. R.; Sweigart, A.; Zoccali, M.

    2006-01-01

    In this paper we present multiband optical and UV Hubble Space Telescope photometry of the two Galactic globular clusters NGC 6388 and NGC 6441 Aims. We investigate the properties of their anomalous horizontal branches (HB) in different photometric planes in order to shed light on the nature of the physical mechanism(s) responsible for the existence of an extended HB blue tail, and of a slope in the HB, visible in all the color-magnitude diagrams. Methods. New photometric data have been collected and carefully reduced. Empirical data have been compared with updated stellar models of low-mass, metal-rich, He-burning structures, transformed to the observational plane with appropriate atmosphere models. Results. We have obtained the first UV color-magnitude diagrams for NGC 6388 and NGC 6441. These diagrams confirm previous results, obtained in optical bands, about the presence of a sizeable stellar population of extremely hot Horizontal Branch stars. At least in NGC 6388, we find a clear indication that at the hot end of the horizontal branch the distribution of stars forms a hook-like feature, closely resembling those observed in NGC 2808 and w Centauri. We briefly review the theoretical scenarios which have been suggested for interpreting this observational feature. We investigate also on the tilt in the horizontal branch morphology, and provide further evidence that supports early suggestions according to which this feature cannot be interpreted as an effect of differential reddening or radiative levitation, though these effects contribute to create the anomaly. We demonstrate that a possible solution of the puzzle is to assume that a small fraction (approx. 13% in NGC 6388 and approx. 8% NGC 6441) of the stellar population in the two clusters is strongly helium enriched (Y approx. 0.40 in NGC6388 and Y approx. 0.35 in NGC 6441). This solution necessarily implies the presence of a double generation of stars in the two clusters.

  7. A New Spin for Understanding the Peculiar Horizontal Branch Morphology of the Galactic Globular Clusters NGC 6388 and NGC 6441

    NASA Technical Reports Server (NTRS)

    Busso, G.; Piotto, G.; Cassisi, S.; Romaniello, M.; Castelli, F.; Catelan, M.; Djorgovski, S. G.; King, I. R.; Landsman, W. B.; Blanco, A. Reico; hide

    2006-01-01

    In this paper we present multiband optical and UV Hubble Space Telescope photometry of the two Galactic globular clusters NGC 6388 and NGC 6441 Aims. We investigate the properties of their anomalous horizontal branches (HB) in different photometric planes in order to shed light on the nature of the physical mechanism(s) responsible for the existence of an extended HB blue tail, and of a slope in the HB, visible in all the color-magnitude diagrams. Methods. New photometric data have been collected and carefully reduced. Empirical data have been compared with updated stellar models of low-mass, metal-rich, He-burning structures, transformed to the observational plane with appropriate atmosphere models. Results. We have obtained the first UV color-magnitude diagrams for NGC 6388 and NGC 6441. These diagrams confirm previous results, obtained in optical bands, about the presence of a sizeable stellar population of extremely hot Horizontal Branch stars. At least in NGC 6388, we find a clear indication that at the hot end of the horizontal branch the distribution of stars forms a hook-like feature, closely resembling those observed in NGC 2808 and w Centauri. We briefly review the theoretical scenarios which have been suggested for interpreting this observational feature. We investigate also on the tilt in the horizontal branch morphology, and provide further evidence that supports early suggestions according to which this feature cannot be interpreted as an effect of differential reddening or radiative levitation, though these effects contribute to create the anomaly. We demonstrate that a possible solution of the puzzle is to assume that a small fraction (approx. 13% in NGC 6388 and approx. 8% NGC 6441) of the stellar population in the two clusters is strongly helium enriched (Y approx. 0.40 in NGC6388 and Y approx. 0.35 in NGC 6441). This solution necessarily implies the presence of a double generation of stars in the two clusters.

  8. The period-shift effect in Oosterhoff type II globular clusters with blue horizontal-branch morphologies

    NASA Astrophysics Data System (ADS)

    Catelan, Marcio

    1994-06-01

    It is shown, on the basis of data available in the literature, that the mean periods of RR Lyrae variables in Oosterhoff type II (OoII) galactic globular clusters are not significantly correlated with the HB morphology, as represented by the parameter (B - R)/(B + V + R), for objects with blue horizontal-branch (HB) morphology types (B - R)/(B + V + R) greater than 0.65. This result is compared with detailed synthetic HB model predictions based upon the evolutionary tracks of Lee & Demarque (1990). The predicted period shifts are found to be strongly correlated with (B - R)/(B + V + R), as a consequence of the effect of evolution away from the zero-age HB becoming progressively more important as the latter quantity approaches +1.0. The slopes of the predicted and observed (log P) - (B - R)/(B + V + R) relations are found to differ at confidence levels greater than or approximately equal to 88%. We argue that these results are likely not a spurious consequence of statistical fluctuations affecting the clusters with the bluest HB types, nor of our choices of metallicities Z, HB morphology parameters (B - R)/(B + V + R), and mass dispersions on the HB sigmaM, for the adopted sample of 8 OoII clusters with statistically significant numbers of RR Lyrae variables (NRR greater than or equal to 11 and/or Nab greater than or equal to 7). We show that reconciliation between the models and the observations cannot be achieved without dramatic changes in the instability strip topology and/or period-mean density relation, and thus suggest that either the adopted evolutionary tracks are inadequate -- we find evidence that the Castellani et al. (1991) tracks already lead to a significantly better, though not fully satisfactory, agreement between the models and the observations -- or other parameters vary among our sample of clusters besides age and/or mass loss on the red-giant branch, in which case a strong impact would be expected upon the interpretation of the second

  9. The horizontal branch morphology of M 31 globular clusters. Extreme second parameter effect in outer halo clusters

    NASA Astrophysics Data System (ADS)

    Perina, S.; Bellazzini, M.; Buzzoni, A.; Cacciari, C.; Federici, L.; Fusi Pecci, F.; Galleti, S.

    2012-10-01

    We use deep, high quality color magnitude diagrams obtained with the Hubble Space Telescope to compute a simplified version of the Mironov index (SMI; B/(B+R)) to parametrize the horizontal branch (HB) morphology for 23 globular clusters in the M 31 galaxy (Sample A), all located in the outer halo at projected distances between 10 kpc and 100 kpc. This allows us to compare them with their Galactic counterparts, for which we estimated the SMI exactly in the same way, in the SMI vs. [Fe/H] plane. We find that the majority of the considered M 31 clusters lie in a significantly different locus, in this plane, with respect to Galactic clusters lying at any distance from the center of the Milky Way. In particular they have redder HB morphologies at a given metallicity, or, in other words, clusters with the same SMI value are ≈ 0.4 dex more metal rich in the Milky Way than in M 31. We discuss the possible origin of this difference and we conclude that the most likely explanation is that many globular clusters in the outer halo of M 31 formed ≈1-2 Gyr later than their counterparts in the outer halo of the Milky Way, while differences in the cluster-to-cluster distribution of He abundance of individual stars may also play a role. The analysis of another sample of 25 bright M 31 clusters (eighteen of them with MV ≤ -9.0, Sample B), whose SMI estimates are much more uncertain as they are computed on shallow color magnitude diagrams, suggests that extended blue HB tails can be relatively frequent among the most massive M 31 globular clusters, possibly hinting at the presence of multiple populations. Based on observations made with the NASA/ESA Hubble Space Telescope, obtained from the Hubble Legacy Archive, which is a collaboration between the Space Telescope Science Institute (STScI/NASA), the Space Telescope European Coordinating Facility (ST-ECF/ESA) and the Canadian Astronomy Data Centre (CADC/NRC/CSA). STScI is operated by the Association of Universities for

  10. Horizontal-branch stellar evolution

    NASA Technical Reports Server (NTRS)

    Sweigart, Allen V.

    1990-01-01

    The results of canonical theory for the evolution of horizontal-branch (HB) stars are examined. Particular attention is given to how an HB star maintains the appropriate composition distribution within the semiconvective zone and how this composition is affected by the finite time-dependence with which convective boundaries actually move. Newly developed models based on time-dependent overshooting are presented for both the core-helium-exhaustion and main HB phases.

  11. Rotational Velocities of Field Blue Horizontal Branch Stars

    NASA Astrophysics Data System (ADS)

    Weafer, V. K.; Fulbright, J. P.

    2001-12-01

    This study is motivated by interest in the much-debated ``second-parameter" problem. Deep mixing, driven by angular momentum, has been proposed as a second parameter controlling horizontal-branch colour morphology (Sweigart & Mengel 1979). Observations of low-metallicity field giant stars show little evidence of deep mixing (Kraft 1994, Wallerstein et al. 1997, Gratton et al. 2000). We therefore expect that field horizontal branch stars may show little evidence of rotation. We have used high-resolution spectra from Keck and Lick observatories to find the projected rotational velocity (v sin i) of 44 blue (-0.04 <= B-V <= 0.20) horizontal branch stars in the halo field. Selected Fe and Ti absorption lines were co-added in velocity space to create an average line profile for each star. To find v sin i, the average profile was compared to similarly-averaged synthesised lines. We have compared the v sin i values of the sample to those of the blue horizontal branch stars in the second-parameter globular-cluster pair, M3 and M13 (Peterson et al. 1995). Although further work is needed to completely establish the velocity distribution of the sample, we have found that the sample has rotational velocities more similar to M13 than to M3, with at least 5 stars showing v sin i > = 25 km/s.

  12. Photometric identification of blue horizontal branch stars

    NASA Astrophysics Data System (ADS)

    Smith, K. W.; Bailer-Jones, C. A. L.; Klement, R. J.; Xue, X. X.

    2010-11-01

    We investigate the performance of some common machine learning techniques in identifying blue horizontal branch (BHB) stars from photometric data. To train the machine learning algorithms, we use previously published spectroscopic identifications of BHB stars from Sloan digital sky survey (SDSS) data. We investigate the performance of three different techniques, namely k nearest neighbour classification, kernel density estimation for discriminant analysis and a support vector machine (SVM). We discuss the performance of the methods in terms of both completeness (what fraction of input BHB stars are successfully returned as BHB stars) and contamination (what fraction of contaminating sources end up in the output BHB sample). We discuss the prospect of trading off these values, achieving lower contamination at the expense of lower completeness, by adjusting probability thresholds for the classification. We also discuss the role of prior probabilities in the classification performance, and we assess via simulations the reliability of the dataset used for training. Overall it seems that no-prior gives the best completeness, but adopting a prior lowers the contamination. We find that the support vector machine generally delivers the lowest contamination for a given level of completeness, and so is our method of choice. Finally, we classify a large sample of SDSS Data Release 7 (DR7) photometry using the SVM trained on the spectroscopic sample. We identify 27 074 probable BHB stars out of a sample of 294 652 stars. We derive photometric parallaxes and demonstrate that our results are reasonable by comparing to known distances for a selection of globular clusters. We attach our classifications, including probabilities, as an electronic table, so that they can be used either directly as a BHB star catalogue, or as priors to a spectroscopic or other classification method. We also provide our final models so that they can be directly applied to new data. Full Tables 7, A.3

  13. The structure of horizontal-branch models. I - The zero-age horizontal branch

    NASA Technical Reports Server (NTRS)

    Dorman, Ben

    1992-01-01

    A detailed study of the structure of zero-age horizontal-branch (ZAHB) models is studied in order to show how the hydrostatic structure of these models changes with the input parameters and determines the H-R diagram location of a given model. The properties of composite polytropes on the homology-invariant (U,V)-plane are demonstrated. A variety of test models and sequences were constructed to elucidate the underlying factors that give rise to the wide variation in HB model properties with composition. The roles of the CNO elements as nuclear catalysts and of the envelope sources, as well as the envelope helium abundance are reexamined. It is found that, for stars of a fixed range of mass arriving on the HB, the stellar distribution is determined mainly by CNO for low metallicities (Fe/H of less than about -1), but mainly by opacity sources for high metallicities. The value of Fe/H where CNO ceases to dominate depends significantly on the adopted opacity and will decrease if and when opacity estimates are revised upward.

  14. The structure of horizontal-branch models. I - The zero-age horizontal branch

    NASA Technical Reports Server (NTRS)

    Dorman, Ben

    1992-01-01

    A detailed study of the structure of zero-age horizontal-branch (ZAHB) models is studied in order to show how the hydrostatic structure of these models changes with the input parameters and determines the H-R diagram location of a given model. The properties of composite polytropes on the homology-invariant (U,V)-plane are demonstrated. A variety of test models and sequences were constructed to elucidate the underlying factors that give rise to the wide variation in HB model properties with composition. The roles of the CNO elements as nuclear catalysts and of the envelope sources, as well as the envelope helium abundance are reexamined. It is found that, for stars of a fixed range of mass arriving on the HB, the stellar distribution is determined mainly by CNO for low metallicities (Fe/H of less than about -1), but mainly by opacity sources for high metallicities. The value of Fe/H where CNO ceases to dominate depends significantly on the adopted opacity and will decrease if and when opacity estimates are revised upward.

  15. The horizontal branch of the Sculptor dwarf galaxy

    NASA Astrophysics Data System (ADS)

    Salaris, Maurizio; de Boer, Thomas; Tolstoy, Eline; Fiorentino, Giuliana; Cassisi, Santi

    2013-11-01

    We have performed the first detailed simulation of the horizontal branch (HB) of the Sculptor dwarf spheroidal galaxy by means of synthetic modelling techniques, taking consistently into account the star formation history and metallicity evolution as determined from the main sequence and red giant branch spectroscopic observations. The only free parameter in the whole analysis is the integrated mass loss of red giant branch stars. This is the first time that synthetic HB models, consistent with the complex star formation history of a galaxy, are calculated and matched to the observed HB. We find that the metallicity range covered by the star formation history, as constrained by the red giant branch spectroscopy, plus a simple mass loss law, enable us to cover both the full magnitude and colour range of HB stars. In addition, the number count distribution along the observed HB can be also reproduced provided that the red giant branch mass loss is mildly metallicity dependent, with a very small dispersion at fixed metallicity. The magnitude, metallicity and period distribution of the RR Lyrae stars are also well reproduced. There is no excess of bright objects that require enhanced-He models. The lack of signatures of enhanced-He stars along the HB is consistent with the lack of the O-Na anticorrelation observed in Sculptor and other dwarf galaxies, and confirms the intrinsic difference between Local Group dwarf galaxies and globular cluster populations. We also compare the brightness of the observed red giant branch bump with the synthetic counterpart, and find a discrepancy. The theoretical bump is brighter than the observed one, which is similar to what is observed in Galactic globular clusters.

  16. Abundances in A-type Horizontal Branch Stars

    NASA Astrophysics Data System (ADS)

    Wilhelm, R.; Smith, V. V.

    1998-12-01

    As part of a program to explore correlations between abundance anomilies and physical parameters (e.g. Teff, vsini) in horizontal branch stars, we present preliminary results from high-resolution (R ~ 18,000) spectral observations of a small sample of A-type, horizontal branch stars. The sample was obtained using the 2.1m telescope and Sandiford Echelle at McDonald Observatory. A total of six standard FHB stars were observed including two, HD 130095 and HD 167105, which have been previously shown by Adleman and Philip to posses anomalously low [Ca/Fe] values. We have also obtained observations of eight of the brighter (B = 11.5-12.5) FHB stars from the HK objective-prism survey and two BHB stars from the globular cluster, M4. We will present abundance results that include [Ca/Fe], [Mg/Fe], and vsini values for the sample along with O and Na results for the two M4 stars. Our findings will be compared to previously published results for cluster BHB and field HB stars.

  17. Oxygen-enhanced models for globular cluster stars. III - Horizontal-branch sequences

    NASA Technical Reports Server (NTRS)

    Dorman, Ben

    1992-01-01

    A large grid of horizontal-branch (HB) evolutionary sequences which have been calculated with core expansion and semiconvection and with enhanced oxygen composition are presented and described. Tracks for 10 different metallicities are computed; they range from (Fe/H) = -0.47 to -2.26 and comprise a total of 115 sequences. The evolution is traced from the zero-age horizontal-branch (ZAHB) to the lower AGB at a point where log L/solar luminosity = 2.25. All of the sequences are illustrated on both the theoretical H-R diagram and on the B, V color-magnitude diagram. A complete set of tables for the ZAHB models and a representative sample of tabulations of the track parameters are provided. The phenomena which control HB evolution morphology, and existing certainties in theoretical HB models are discussed.

  18. The horizontal-branch stars in globular clusters. 2: The second parameter phenomenon

    NASA Technical Reports Server (NTRS)

    Lee, Young-Wook; Demarque, Pierre; Zinn, Robert

    1994-01-01

    Using synthetic horizontal-branch models, we have investigated the origin of the systematic variation in horizontal-branch (HB) morphology with galactocentric distance (R(sub G)) among globular clusters. The variations in He abundance, CNO abundance, and core mass required separately to explain this effect are inconsistent with either the observed properties of the RR Lyrae variables or the observed main-sequence turnoffs in the clusters. There is also no clear evidence that the trend with R(sub G) is related to the central concentrations, central densities, or absolute magnitudes of the clusters. The variations in cluster age required to explain this effect are not in conflict with any observations. A detailed comparison of our synthetic HB calculations with pairs of clusters of very different HB morphology but similar (Fe/H) reveals reasonably good agreement between the age differences inferred from HB morphology and the main-sequence turnoff. The major source of uncertainty is the need for ad hoc hypotheses in the modeling of the HB morphologies of a few peculiar clusters (e.g., NGC 6752). Nonetheless, there is firm evidence for age variations of several gigayears (as much as approximately 5 Gyr) among the halo globular clusters. Our results support the hypothesis of Searle & Zinn that the inner halo is more uniform in age and is older in the mean than the outer halo, and we estimate this difference to be approximately 2 Gyr.

  19. IDENTIFYING BLUE HORIZONTAL BRANCH STARS USING THE z FILTER

    SciTech Connect

    Vickers, John J.; Grebel, Eva K.; Huxor, Avon P.

    2012-04-15

    In this paper we present a new method for selecting blue horizontal branch (BHB) candidates based on color-color photometry. We make use of the Sloan Digital Sky Survey z band as a surface gravity indicator and show its value for selecting BHB stars from quasars, white dwarfs, and main-sequence A-type stars. Using the g, r, i, and z bands, we demonstrate that extraction accuracies on a par with more traditional u, g, and r photometric selection methods may be achieved. We also show that the completeness necessary to probe major Galactic structure may be maintained. Our new method allows us to efficiently select BHB stars from photometric sky surveys that do not include a u-band filter such as the Panoramic Survey Telescope and Rapid Response System.

  20. Dark matter and thermal pulses in horizontal-branch stars

    NASA Astrophysics Data System (ADS)

    Dearborn, David; Raffelt, Georg; Salati, Pierre; Silk, Joseph; Bouquet, Alain

    1990-05-01

    The evolution of horizontal-branch (HB) stars, including the effect of energy transfer by dark matter particles ('WIMPs' or 'cosmions') is investigated numerically. If HB stars contain enough cosmions to break core convection, thermal pulses ensue on the core Kelvin-Helmholtz time scale until the central helium abundance is exhausted. These pulses involve brief phases of violent helium burning which establish short episodes of convection where the convective core extends further than it would in the absence of cosmions. The overall duration of the HB phase slightly decreases, and the luminosity dispersion of the HB increases, but neither effect is pronounced enough to conflict with observations. The magnitude difference between the HB and the main-sequence turnoff increases and leads to an overestimate of globular cluster ages. The observed period changes of RR Lyrae stars are consistent with, and even implied by, this scenario.

  1. Morphology of branching trees related to entropy.

    PubMed

    Horsfield, K

    1977-04-01

    Analyses of river systems by geomorphologists have suggested that for minimal entropy production in the movement of water down the river the fall in altitude should be equal in each order of branching of the tributaries. In this paper the same concepts have been applied to the bronchial tree and pulmonary arterial tree, assuming that the energy associated with pressure difference is analogous to that associated with altitude difference in rivers. The morphology of the bronchial tree is such that, given laminar flow or air, the calculated pressure difference across each order is equal. This may indicate that the bronchial tree is designed for minimal entropy production. In the arterial tree, however, this result is not obtained, probably because we do not know how to calculate the pressure drop in blood flowing through a branching system. It is therefore not currently possible, on the basis of this approach, to say whether the pulmonary arterial tree is designed for minimal entropy production or not.

  2. Red horizontal-branch stars in the galactic disk

    NASA Astrophysics Data System (ADS)

    Rose, J. A.

    1985-05-01

    A class of red horizontal-branch (RHB) stars, similar to those in the "metal-rich" globular cluster M71, has been identified in the Galactic disk, using a quantitative three-dimensional spectral classification system developed earlier (Rose 1984) that uses 2.5-Å resolution spectra in the blue. A prototype for this class is the G5 III star HD 79452, which has been found by Helfer and Wallerstein (1968) to have [Fe/H] = -0.85 and MV = +1. The RHB stars are shown to be evolved stars on the basis of the strength of their Sr II λ4077 line, and are distinguished from post-main-sequence stars evolving through the same region of the HR diagram because of the unique appearance of their CN λ3883 and λ4216 bands. A preliminary estimate has been made of their space density, scale height perpendicular to the Galactic plane, and kinematics by surveying G5 - G7 stars in the Upgren (1962) North Galactic Pole survey.

  3. Pulsational instabilities in hot pre-horizontal branch stars

    NASA Astrophysics Data System (ADS)

    Battich, Tiara; Miller Bertolami, Marcelo M.; Córsico, Alejandro H.; Althaus, Leandro G.

    2017-09-01

    The ɛ mechanism is a self-excitation mechanism of pulsations which acts on the regions where nuclear burning takes place. It has been shown that the ɛ mechanism can excite pulsations in models of hot helium-core flash, and that the pulsations of LS IV-14· 116, a He-enriched hot subdwarf star, could be explained that way. We aim to study the ɛmechanism effects on models of hot pre-horizontal branch stars and determine, if possible, a domain of instability in the log g — log Teff plane. We compute non-adiabatic non-radial pulsations on such stellar models, adopting different values of initial chemical abundances and mass of the hydrogen envelope at the time of the main helium flash. We find an instability domain of long-period (400 s ≲ P ≲ 2500 s) g-modes for models with 22000K ≲ Teff ≲ 50000K and 4.67 ≲ log g ≲ 6.15.

  4. Mapping Milky Way Halo Structure with Blue Horizontal Branch Stars

    NASA Astrophysics Data System (ADS)

    Martin, Charles; Newberg, Heidi Jo; Carlin, Jeffrey L.

    2017-01-01

    The use of blue horizontal brach (BHB) and red giant branch stars as tracers of stellar debris streams is a common practice and has been useful in the confirmation of kinematic properties of previously identified streams. This work explores less common ways of untangling the velocity signatures of streams traveling radially to our line of sight, and to peer toward the higher density region of the Galactic Center using data from the Sloan Digital Sky Survey (SDSS). Using spectra of BHB stars, we are able to kinematically distinguish moving groups in the Milky Way halo. The results of this thesis advance our knowledge of the following stellar halo substructures: the Pisces Stellar Stream, the Hercules-Aquila Cloud, the Hercules Halo Stream, and the Hermus Stream. A study of red giant stars led to the kinematic discovery of the Pisces Stellar Stream. Red giant stars were also examined to determine that the previously identified velocity signature that was suggested for the Hercules-Aquila Cloud was due to disk star contamination and errors in preliminary SDSS velocities. The Hercules Halo Stream is a previously unidentified structure that could be related to the Hercules-Aquila Cloud, and was discovered as a velocity excess of SDSS BHB stars. We identify a group of 10 stars with similar velocities that are spatially coincident with the Hermus Stream. An orbit is fit to the Hermus Stream that rules out a connection with the Phoenix Stream.This work was supported by NSF grants AST 09-37523, 14-09421, 16-15688, the NASA/NY Space Grant fellowship, and contributions made by The Marvin Clan, Babette Josephs, Manit Limlamai, and the 2015 Crowd Funding Campaign to Support Milky Way Research.

  5. Mapping the Extreme Horizontal Branch instability strip in omega Centauri

    NASA Astrophysics Data System (ADS)

    Randall, Suzanna

    2014-10-01

    We request far-UV spectroscopy for the hottest and the coolest members of the recently discovered class of rapid subdwarf O pulsators on the Extreme Horizontal Branch (EHB) in omega Centauri. Our main aim is to derive reliable temperature estimates and thus map the location of the omega Cen EHB instability strip in the Teff-log g plane. Current estimates based on optical spectroscopy suggest the pulsators to be clustered around 50,000 K, which is distinctly cooler than the red edge of the predicted instability strip. We suspect that this discrepancy is due, at least in part, to the known problem of the temperatures being significantly underestimated from optical spectroscopy (compared to the more realistic values from FUV spectroscopy) for very hot stars. Given the successful pulsational modeling of the cooler (~31,000 K) rapid subdwarf B pulsators found among the Galactic field population, the inability to reproduce the omega Cen pulsators would point towards fundamental differences between the two EHB populations. On the other hand, if we are able to reconcile the predicted and observed instability regions for the omega Cen pulsators, this will open them up to exploitation via asteroseismology. Asteroseismology has proven to be a very powerful tool for determining the internal stellar structure in the subdwarf B pulsators, providing valuable constraints on competing evolutionary scenarios. In light of the currently raging debate as to the origin of EHB stars particularly in Globular Clusters, the prospect of applying asteroseismology to EHB stars in a Globular Cluster for the first time is highly enticing.

  6. The Hot Horizontal-Branch Stars in omega Centauri

    NASA Technical Reports Server (NTRS)

    Moehler, S.; Dreizler, S.; Lanz, T.; Bono, G.; Sweigart, A. V.; Calamida, A.; Nonino, M.

    2010-01-01

    Context. UV observations of some massive globular clusters have revealed a significant population of stars hotter and fainter than the hot end of the horizontal branch (HB), the so-called blue hook stars. This feature might be explained either by the late hot flasher scenario where stars experience the helium flash while on the white dwarf cooling curve or by the progeny of the helium-enriched sub-population recently postulated to exist in some clusters. Previous spectroscopic analyses of blue hook stars in co Cen and NGC 2808 support the late hot flasher scenario, but the stars contain much less helium than expected and the predicted C, N enrichment could not be verified. Aims. We compare observed effective temperatures, surface gravities, helium abundances, and carbon line strengths (where detectable) of our targets stars to the predictions of the two scenarios. Methods. Moderately high resolution spectra of hot HB stars in the globular cluster omega-Cen were analysed for radial velocity variations, atmospheric parameters and abundances using LTE and non-LTE model atmospheres. Results. We find no evidence for close binaries among our target stars. All stars below 30 000 K are helium-poor and very similar to HB stars observed in that temperature range in other globular clusters. In the temperature range 30000 K to 50000 K we find that 28% of our stars are helium-poor (log ((sup n)He/(sup n )H)< - 1.6), while 72% have roughly solar or super-solar helium abundance (log ((sup n)He/(sup n )H) >/= -1.5). We also find carbon enrichment strongly correlated with helium enrichment, with a maximum carbon enrichment of 3% by mass. Conclusions. The strong carbon enrichment in tandem with helium enrichment is predicted by the late hot flasher scenario, but not by the helium-enrichment scenario. We conclude that the helium-rich HB stars in omega-Cen cannot be explained solely by the helium-enrichment scenario invoked to explain the blue main sequence.

  7. The Hot Horizontal-Branch Stars in omega Centauri

    NASA Technical Reports Server (NTRS)

    Moehler, S.; Dreizler, S.; Lanz, T.; Bono, G.; Sweigart, A. V.; Calamida, A.; Nonino, M.

    2010-01-01

    Context. UV observations of some massive globular clusters have revealed a significant population of stars hotter and fainter than the hot end of the horizontal branch (HB), the so-called blue hook stars. This feature might be explained either by the late hot flasher scenario where stars experience the helium flash while on the white dwarf cooling curve or by the progeny of the helium-enriched sub-population recently postulated to exist in some clusters. Previous spectroscopic analyses of blue hook stars in co Cen and NGC 2808 support the late hot flasher scenario, but the stars contain much less helium than expected and the predicted C, N enrichment could not be verified. Aims. We compare observed effective temperatures, surface gravities, helium abundances, and carbon line strengths (where detectable) of our targets stars to the predictions of the two scenarios. Methods. Moderately high resolution spectra of hot HB stars in the globular cluster omega-Cen were analysed for radial velocity variations, atmospheric parameters and abundances using LTE and non-LTE model atmospheres. Results. We find no evidence for close binaries among our target stars. All stars below 30 000 K are helium-poor and very similar to HB stars observed in that temperature range in other globular clusters. In the temperature range 30000 K to 50000 K we find that 28% of our stars are helium-poor (log ((sup n)He/(sup n )H)< - 1.6), while 72% have roughly solar or super-solar helium abundance (log ((sup n)He/(sup n )H) >/= -1.5). We also find carbon enrichment strongly correlated with helium enrichment, with a maximum carbon enrichment of 3% by mass. Conclusions. The strong carbon enrichment in tandem with helium enrichment is predicted by the late hot flasher scenario, but not by the helium-enrichment scenario. We conclude that the helium-rich HB stars in omega-Cen cannot be explained solely by the helium-enrichment scenario invoked to explain the blue main sequence.

  8. Spectroscopy of horizontal branch stars in ω Centauri⋆

    NASA Astrophysics Data System (ADS)

    Moni Bidin, C.; Villanova, S.; Piotto, G.; Moehler, S.; Cassisi, S.; Momany, Y.

    2012-11-01

    Aims: We analyze the reddening, surface helium abundance and spectroscopic mass of 115 blue horizontal branch (HB) and blue hook (BH) stars in ω Centauri, spanning the cluster HB from the blue edge of the instability strip (Teff = 8000 K) to BH objects with Teff ≈ 50 000 K. Methods: The temperatures, gravities, and surface helium abundances were measured on low-resolution spectra fitting the Balmer and helium lines with a grid of synthetic spectra. From these parameters, the mass and reddening were estimated. Results: The mean cluster reddening is E(B - V) = 0.115 ± 0.004, in good agreement with previous estimates, but we evidence a pattern of differential reddening in the cluster area. The stars in the western half are more reddened than in the southwest quadrant by 0.03-0.04 mag. We find that the helium abundances measured on low-resolution spectra are systematically higher by 0.20-0.25 dex than the measurements based on higher resolution. No difference in surface helium abundance is detected between HB stars in ω Centauri and in three comparison clusters, and the stars in the range 11 500-20 000 K follow a trend with temperature, which probably reflects a variable efficiency of the diffusion processes. There is mild evidence that two families of extreme HB (EHB) cluster stars (Teff ≥ 20 000 K) could exist, as observed in the field, with ~15% of the objects being helium depleted by a factor of ten with respect to the main population. The distribution of helium abundance above 30 000 K is bimodal, but we detect a fraction of He-poor objects lower than previous investigations. The observations are consistent with these being stars evolving off the HB. Their spatial distribution is not uniform across the cluster, but this asymmetric distribution is only marginally significative. We also find that EHB stars with anomalously high spectroscopic mass could be present in ω Centauri, as previously found in other clusters. The derived temperature-color relation

  9. Inclusion of horizontal branch stars in the derivation of star formation histories of dwarf galaxies: The Carina dSph

    NASA Astrophysics Data System (ADS)

    Savino, Alessandro; Salaris, Maurizio; Tolstoy, Eline

    2015-11-01

    We present a detailed analysis of the horizontal branch of the Carina dwarf spheroidal galaxy by means of synthetic modelling techniques, taking consistently into account the star formation history and metallicity evolution as determined from main sequence and red giant branch spectroscopic observations. We found that a range of integrated red giant branch mass loss values of 0.1-0.14 M⊙ increasing with metallicity is able to reproduce the colour extension of the old horizontal branch. Nonetheless, leaving the mass loss as the only free parameter is not enough to match the detailed morphology of Carina horizontal branch. We then investigated the role played by the star formation history on the discrepancies between synthetic and observed horizontal branches. We derived a "toy" bursty star formation history that reproduces well the observed horizontal branch star counts, and also matches qualitatively the red giant and the turn-off regions. This bursty star formation history is made of a subset of age and [M/H] components of the star formation history based on turn off and red giants only, and entails four separate bursts of star formation of different strengths, centred at 2, 5, 8.6, and 11.5 Gyr, respectively, with mean [M/H] decreasing from ~-1.7 to ~-2.2 when the age of the burst increases, and with a Gaussian spread of σ 0.1 dex around these mean values. The comparison between the metallicity distribution function of our bursty star formation history and the one measured from the infrared CaT feature using a CaT-[Fe/H] calibration shows a qualitative agreement, once the range of [Ca/Fe] abundances measured in a sample of Carina stars have been taken into account, that causes a bias of the derived [Fe/H] distribution toward values that are too low. In conclusion, we show how the information contained within the horizontal branch of Carina (and dwarf galaxies in general) can be extracted and interpreted to refine the star formation history derived exclusively

  10. CN and CH inhomogeneities among red horizontal branch stars in M71

    SciTech Connect

    Smith, G.H.; Penny, A.J.

    1989-05-01

    Spectra have been obtained of a sample of horizontal branch stars in the globular cluster M71. These display clear variations in the strengths of the 3883-A and 4215-A CN bands, with the former of these features showing a bimodal distribution. A clear anticorrelation exists between the strength of the 3883-A CN band and the CH absorption in the region of the 4300-A G band, indicating that part of the surface material of the CN-strong stars has been processed through the CN cycle of hydrogen burning. The percentage of CN-strong stars found on the horizontal branch is consistent with that observed by Smith and Norris (1982) on the giant branch of M71. Hence, there is no evidence from the available data that the percentage of these stars increases during the transition between the red giant and horizontal branch stages of evolution. 39 refs.

  11. A Catalog of Candidate Field Horizontal-Branch and A-Type Stars. II.

    NASA Astrophysics Data System (ADS)

    Beers, Timothy C.; Wilhelm, Ronald; Doinidis, Stephen P.; Mattson, Caroline J.

    1996-04-01

    We present coordinates and brightness estimates for 4175 candidate field horizontal-branch and A-type stars, in the magnitude range 10 ≤ B ≤ 15.5, selected using an objective-prism/interference-filter survey technique. The candidates lie primarily in the northern Galactic hemisphere and complement a previously published sample of southern Galactic hemisphere candidates. Available spectroscopy and photometry indicates that the great majority of the candidates are likely to be bona fide members of either the field blue horizontal-branch population or the blue, metal-deficient, high surface gravity stars referred to by Preston, Beers, & Shectman as BMP stars. The remaining stars in the catalog are likely to be a mix of metal-deficient turnoff stars, metallic-line (Am) stars, field red horizontal-branch stars, optical doubles with overlapping objective-prism spectra, and (particularly among the fainter candidates) inadvertently included late-type stars.

  12. The Origin of Hot Subluminous Horizontal-Branch Stars in (omega) Centauri and NGC 2808

    NASA Technical Reports Server (NTRS)

    Sweigart, Allen V.; Brown, Thomas M.; Lanz, Thierry; Landsman, Wayne B.; Hubeny, Ivan

    2001-01-01

    Hot subluminous stars lying up to 0.7 mag below the extreme horizontal branch (EHB) are found in the ultraviolet (UV) color magnitude diagrams of both (omega) Cen and NGC 2808. In order to explore the evolutionary status of these subluminous stars, we have evolved a set of low-mass stars continuously from the main sequence through the helium-core flash to the HB (horizontal branch) for a wide range in the mass loss along the red-giant branch (RGB). Stars with the largest mass loss evolve off the RGB to high effective temperatures before igniting helium in their cores. Our results indicate that the subluminous EHB stars, as well as the gap within the EHB of NGC 2808, can be explained if these stars undergo a late helium-core flash while descending the white-dwarf cooling curve. Under these conditions the convection zone produced by the helium flash will penetrate into the stellar envelope, thereby mixing most, if not all, of the envelope hydrogen into the hot helium-burning interior, where it is rapidly consumed. This phenomenon is analogous to the 'born-again' scenario for producing hydrogen-deficient stars following a very late helium-shell flash. This 'flash mixing' of the stellar envelope greatly enhances the envelope helium and carbon abundances and, as a result, leads to a discontinuous jump in the HB effective temperature. We argue that the EHB gap in NGC 2808 is associated with this theoretically predicted dichotomy in the HB morphology. Using new helium- and carbon-rich stellar atmospheres, we show that these changes in the envelope abundances of the flash-mixed stars will suppress the UV flux by the amount needed to explain the hot subluminous EHB stars in (omega) Cen and NGC 2808. Moreover, we demonstrate that models without flash mixing lie, at most, only approximately 0.1 mag below the EHB, and hence fail to explain the observations. Flash mixing may also provide a new evolutionary channel for producing the high gravity, helium-rich sdO and sdB stars.

  13. SODIUM-OXYGEN ANTICORRELATION AMONG HORIZONTAL BRANCH STARS IN THE GLOBULAR CLUSTER M4

    SciTech Connect

    Marino, A. F.; Lind, K.; Villanova, S.; Geisler, D.; Milone, A. P.; Piotto, G.; Stetson, P. B.

    2011-04-01

    The horizontal branch (HB) morphology of globular clusters (GCs) is mainly governed by metallicity. The second parameter problem, well known since the 1960s, states that metallicity alone is not enough to describe the observed HB morphology of many GCs. Despite many efforts to resolve this issue, the second parameter phenomenon still remains without a satisfactory explanation. We have analyzed blue-HB, red-HB, and RR-Lyrae stars in the GC M4 and studied their Fe, Na, and O abundances. Our goal is to investigate possible connections between the bimodal HB of M4 and the chemical signatures of the two stellar populations recently discovered among red giants of this cluster. We obtained FLAMES-UVES/GIRAFFE spectra of a sample of 22 stars covering the HB from the red to the blue region. While iron has the same abundance in both the red-HB and blue-HB segments, the red-HB is composed of stars with scaled-solar sodium abundances, while the blue-HB stars are all sodium enhanced and oxygen depleted. The RR-Lyrae are Na-poor, as the red-HB stars, and O-rich. This is what we expect if the blue-HB consists of a second generation of stars formed from the ejecta produced by an earlier stellar population through high-temperature hydrogen-burning processes that include the CNO, NeNa, and MgAl cycles and are therefore expected to be He-rich. According to this scenario, the sodium and oxygen pattern detected in the blue-HB and red-HB segments suggests helium as the second parameter that rules the HB morphology in M4.

  14. Double Horizontal Branches in NGC 6440 and NGC 6569 Unveiled by the VVV Survey

    NASA Astrophysics Data System (ADS)

    Mauro, Francesco; Moni Bidin, Christian; Cohen, Roger; Geisler, Doug; Minniti, Dante; Catelan, Marcio; Chené, André-Nicolas; Villanova, Sandro

    2012-12-01

    We report the discovery of a peculiar horizontal branch (HB) in NGC 6440 and NGC 6569, two massive and metal-rich Galactic globular clusters (GGCs) located in the Galactic bulge, within 4 kpc from the Galactic center. In both clusters, two distinct clumps are detected at the level of the cluster HB, separated by only ~0.1 mag in the K s band. They were detected with IR photometric data collected with the "VISTA Variables in the Vía Láctea" Survey, and confirmed in independent IR catalogs available in the literature and Hubble Space Telescope optical photometry. Our analysis demonstrates that these clumps are real cluster features, not a product of field contamination or interstellar reddening. The observed split HBs could be a signature of two stellar sub-populations with different chemical composition and/or age, as recently found in Terzan 5, but it cannot be excluded that they are caused by evolutionary effects, in particular for NGC 6440. This interpretation, however, requires an anomalously high helium content (Y > 0.30). Our discovery suggests that such a peculiar HB morphology could be a common feature of massive, metal-rich bulge GGCs. Based on observations gathered with ESO-VISTA telescope (proposal ID 172.B-2002).

  15. Helium enhanced stars and multiple populations along the horizontal branch of NGC 2808: direct spectroscopic measurements

    NASA Astrophysics Data System (ADS)

    Marino, A. F.; Milone, A. P.; Przybilla, N.; Bergemann, M.; Lind, K.; Asplund, M.; Cassisi, S.; Catelan, M.; Casagrande, L.; Valcarce, A. A. R.; Bedin, L. R.; Cortés, C.; D'Antona, F.; Jerjen, H.; Piotto, G.; Schlesinger, K.; Zoccali, M.; Angeloni, R.

    2014-01-01

    We present an abundance analysis of 96 horizontal branch (HB) stars in NGC 2808, a globular cluster exhibiting a complex multiple stellar population pattern. These stars are distributed in different portions of the HB and cover a wide range of temperature. By studying the chemical abundances of this sample, we explore the connection between HB morphology and the chemical enrichment history of multiple stellar populations. For stars lying on the red HB, we use GIRAFFE and UVES spectra to determine Na, Mg, Si, Ca, Sc, Ti, Cr, Mn, Fe, Ni, Zn, Y, Ba and Nd abundances. For colder, blue HB stars, we derive abundances for Na, primarily from GIRAFFE spectra. We were also able to measure direct non-local thermodynamic equilibrium He abundances for a subset of these blue HB stars with temperature higher than ˜9000 K. Our results show that: (i) HB stars in NGC 2808 show different content in Na depending on their position in the colour-magnitude diagram, with blue HB stars having higher Na than red HB stars; (ii) the red HB is not consistent with a uniform chemical abundance, with slightly warmer stars exhibiting a statistically significant higher Na content; and (iii) our subsample of blue HB stars with He abundances shows evidence of enhancement with respect to the predicted primordial He content by ΔY = +0.09 ± 0.01 ± 0.05 (internal plus systematic uncertainty). Our results strongly support theoretical models that predict He enhancement among second-generation(s) stars in globular clusters and provide observational constraints on the second-parameter governing HB morphology.

  16. Developmental morphology of branching flowers in Nymphaea prolifera.

    PubMed

    Grob, Valentin; Moline, Philip; Pfeifer, Evelin; Novelo, Alejandro R; Rutishauser, Rolf

    2006-11-01

    Nymphaea and Nuphar (Nymphaeaceae) share an extra-axillary mode of floral inception in the shoot apical meristem (SAM). Some leaf sites along the ontogenetic spiral are occupied by floral primordia lacking a subtending bract. This pattern of flower initiation in leaf sites is repeated inside branching flowers of Nymphaea prolifera (Central and South America). Instead of fertile flowers this species usually produces sterile tuberiferous flowers that act as vegetative propagules. N. prolifera changes the meristem identity from reproductive to vegetative or vice versa repeatedly. Each branching flower first produces some perianth-like leaves, then it switches back to the vegetative meristem identity of the SAM with the formation of foliage leaves and another set of branching flowers. This process is repeated up to three times giving rise to more than 100 vegetative propagules. The developmental morphology of the branching flowers of N. prolifera is described using both microtome sections and scanning electron microscopy.

  17. Physical Parameters of Hot Horizontal-Branch Stars in NGC 6752: Deep Mixing and Radiative Levitation

    NASA Technical Reports Server (NTRS)

    Moehler, S.; Sweigart, A. V.; Landsman, W. B.; Heber, U.; Catelan, M.

    1999-01-01

    Atmospheric parameters (T(sub eff), log g and log n(sub He)/n(sub H-dot)) are derived for 42 hot horizontal branch (HB) stars in the globular cluster NGC 6752. For 19 stars Mg II and Fe II lines are detected indicating an iron enrichment by a factor 50 on average with respect to the cluster abundance whereas the magnesium abundances are consistent with the cluster metallicity. This finding adds to the growing evidence that radiative levitation plays a significant role in determining the physical parameters of blue HB stars. Indeed, we find that iron enrichment can explain part, but not all, of the problem of anomalously low gravities along the blue HB. Thus the physical parameters of horizontal branch stars hotter than about 11,500 K in NGC 6752, as derived in this paper, are best explained by a combination of helium mixing and radiative levitation effects.

  18. Abundance anomalies in hot horizontal-branch stars of the globular cluster NGC 6752

    SciTech Connect

    Glaspey, J.W.; Michaud, G.; Moffat, A.F.J.; Demers, S.

    1989-04-01

    High-resolution spectra of two blue stars on the horizontal branch of the metal-poor globular cluster NGC 6752 have been obtained with an echelle spectrograph and a CCD detector on the CTIO 4 m telescope. A helium underabundance is confirmed in the blue star CL 1083 (Teff = 16,000 K). An overabundance of iron by a factor of 50 compared to the cluster metallicity is also obtained. No abundance anomaly is measured in the cooler star CL 1007 (Teff = 10,000 K). Presumably all stars of this cluster had the same original abundances; hence, the anomalies must be explained by the different properties of individual stars. These results are discussed in the context of the diffusion model originally developed to explain the He underabundance in horizontal-branch stars. 47 refs.

  19. Spectroscopy of Blue Horizontal Branch Stars in the Globular Cluster NGC 6752

    NASA Astrophysics Data System (ADS)

    Cote, P.; Bolte, M.; Wilson, C. D.; Patel, K.

    1993-12-01

    Optical spectra (at 0.9 Angstroms /pixel dispersion) for 24 candidate blue horizontal branch stars in the globular cluster NGC 6752 have been obtained with ARGUS, the multi-object spectrograph on the CTIO 4.0m telescope. In addition to strong hydrogen lines, ten of the stars exhibit the 4471 Angstroms line of neutral helium. The equivalent widths of this line, the full widths of H_γ and H_δ at the 20% absorption level and BV CCD photometry have been used to derive effective temperatures, surface gravities and surface helium abundances for our program objects. With the exception of one star which has an exceptionally strong 4471 Angstroms line, all of the objects with detected helium are consistent with the rather low value of N(He)/N(H) =~ 0.008, suggesting that neither enhanced atmospheric helium nor increased stellar rotation is responsible for the extremely blue horizontal branch observed in this intermediate metallicity cluster.

  20. Extreme horizontal branch stars - Puzzling objects dominating the UV-light in early-type galaxies

    NASA Astrophysics Data System (ADS)

    Geier, Stephan

    2015-08-01

    Extreme horizontal branch stars (also known as hot subdwarf stars, sdO/Bs) are located at the bluest extension of the horizontal branch in the HR-diagram. They burn helium in their cores and are the sources of the UV-excess in elliptical galaxies and other old stellar populations. However, the formation of those stars is still unclear. SdO/B stars in the field show a high binary fraction and are likely formed via binary interactions with low-mass stars, substellar objects or compact stellar remnants. Similar objects in globular clusters on the other hand have a significantly lower binary fraction and might therefore be formed in a different way. I will review the state-of-the-art and confront theories of sdO/B formation with most recent observational evidence.

  1. Semi-Empirical Determination of the Mass Distribution of Horizontal Branch Stars in M3

    NASA Astrophysics Data System (ADS)

    Valcarce, A.; Catelan, M.

    2006-06-01

    We determine, by means of a semi-empirical study, the masses of horizontal branch stars in the glo-bular cluster M3 (NGC 5272). We used the most recent and reliable observational datasets (broadband BVI photometry) available for the cluster, both for variable and nonvariable stars, to infer the most likely masses of individual horizontal branch stars by comparison against theoretical evolutionary tracks, suitably transformed to the observational planes. We found a mass distribution that is adequately described by a Gaussian, with = 0.64M_⊙ and σ = 0.020M⊙, thus su-pporting the Gaussian shape previously obtained by Rood & Crocker (1989, in The Use of Pulsating Stars in Fundamental Problems of Astronomy, 218) without taking evolutionary effects into account. A recent suggestion of strong mass bimodality in M3 (Castellani et al. 2005, A&A, 437, 1017) is not supported by our analysis.

  2. THE TEMPERATURE DISTRIBUTION OF HORIZONTAL BRANCH STARS: METHODS AND FIRST RESULTS

    SciTech Connect

    Lagioia, E. P.; Dalessandro, E.; Ferraro, F. R.; Lanzoni, B.; Salaris, M.; Pietrinferni, A.; Cassisi, S.

    2015-02-10

    As part of a large project aimed at characterizing the ultraviolet (UV) properties of globular clusters, we present here a theoretical and observational analysis aimed at setting the framework for the determination of horizontal branch (HB) temperature distributions. Indeed this is crucial information needed to understand the physical parameters shaping the HB morphology in globular clusters and to interpret the UV emission from unresolved stellar systems. We found that the use of zero age HB color-T {sub eff} relations is a robust way to derive effective temperatures of individual HB stars. We investigated the most suitable colors for temperature estimates and the effect on the color-T {sub eff} relations of variations of the initial chemical composition and the evolution off the zero age HB. As a test case, we applied our color-T {sub eff} calibrations to the Galactic globular cluster M15. The photometry of M15 has been obtained with the Wide Field and Planetary Camera 2 on board the Hubble Space Telescope. The HB of M15 turned out to have a multimodal distribution, with a main component peaking at T{sub eff} ∼ 8000 K and confined below T{sub eff} ∼ 10,000 K. The second component peaks at T{sub eff} ∼ 14,000 K and extends up to T{sub eff} ∼ 20,000 K. The vast majority ( ∼ 95%) of the HB stars in M15 is below 20,000 K, in agreement with the lack of a well populated extreme HB observed in other metal-poor globular clusters. We also verified that the temperatures derived with our analysis are consistent with spectroscopic estimates available in the literature.

  3. THE CURIOUS RADIAL DISTRIBUTIONS OF HORIZONTAL BRANCH STARS IN NGC 6441

    SciTech Connect

    Krogsrud, David A.; Sandquist, Eric L.; Kato, Tadafumi E-mail: erics@sciences.sdsu.edu

    2013-04-20

    NGC 6441 is one of the most massive and most metal-rich globular clusters in the galaxy, and is noted for an unusual extended horizontal branch that reaches past the instability strip. We find evidence that there are two different populations of stars within the heavily populated red clump. Once a differential reddening correction is applied, a large but compact group of stars is found at the faint red end of the clump in the color-magnitude diagram. Brighter, bluer stars in the clump are found to be more centrally concentrated within the cluster at a very high level of significance. Curiously, the blue horizontal branch stars show a more complex distribution and are not more centrally concentrated than the brighter red clump stars. The spatial distributions of clump stars are in agreement with the idea that the brighter bluer part of the clump is a helium-enriched second generation. The blue horizontal branch stars may be showing evidence that they are being dynamically evaporated.

  4. The time-delay spectrum of GX 5-1 in its horizontal branch

    NASA Technical Reports Server (NTRS)

    Vaughan, B.; Van Der Klis, M.; Lewin, W. H. G.; Wijers, R. A. M. J.; Van Paradijs, J.; Dotani, T.; Mitsuda, K.

    1994-01-01

    Using a cross-spectral technique we investigate time delays between intensity variations of GX 5-1 in 10 X-ray spectral channels. The data were taken during a 1989 Ginga observation during which the source was in its horizontal-branch spectral state. We develope a new method to measure 'time-delay spectra' in fixed Fourier frequency ranges and use it to determine the energy and intensity dependence of time delays in the low-frequency noise (nu less than 2 Hz), the horizontal branch quasi-periodic oscillations (QPO), and the QPO second harmonic. These are the first time-delay spectra of a Z-source in its horizontal branch, and the first detection of time delays in the second harmonic. We consider two mechanisms for the production of the time lags: Comptonization and evolving shots. We perform Monte Carlo simulations of Compton scattering in a homogeneous, isotropic, central corona and show that it qualitatively explain the observed energy and time-delay spectra, but that it cannot explain the differences in the QPO first and second harmomnic time-delay spectra, nor the observed dependence of the QPO fractional rms variability upon energy. We consider implications of our results for millisecond pulsar searches in low-mass X-ray binaries.

  5. The morphology of blends of linear and branched polyethylenes

    SciTech Connect

    Wignall, G.D.; Londono, J.D.; Alamo, R.G.; Mandelkern, L.

    1995-12-31

    The state of mixing in blends of high density (HD), low density (LD) and linear low density (LLD) polyethylenes (PE) in the melt and solid states has been examined by small-angle x-ray and neutron scattering (SAXS and SANS). In the melt, SANS results indicate that HDPE/LDPE mixtures (with 1-2 branches/100 C) form a single phase. HDPE/LLDPE blends are also homogeneous when the branch content is low, but phase separate as the branching increases. In the solid state, after slow-cooling from the melt, the HDPE/LDPE system segregates into domains {approximately}10{sup 2} in size. For high concentrations of linear polymer ({phi} {ge} 0.5), there are separate stacks of HDPE and LDPE lamellae, and the measured SANS cross section agrees closely with the theoretical calculation based on the assumption of complete phase separation of the components. For predominantly branched blends ({phi} < 0.5), the phase segregation is less complete, and the components are separated within the same lamellar stack. Moreover, the phases no longer consist of the pure components, and the HDPE lamellae contain up to 15% LDPE. The segregation of components in the solid state is a consequence of crystallization mechanisms and the blend morphology is a strong function of the cooling rate. Rapid quenching to -78{degrees}C produces only one lamellar stack and these blends show extensive cocrystallization. Samples quenched less rapidly (e.g., into water at 23{degrees}C) show a similar structure to slowly cooled samples. The solid state morphology also depends on the type of branching and differences between HDPE/LDPE and HDPE/LLDPE blends will be reviewed.

  6. Horizontal-branch models and the second-parameter phenomeon: The caseof NGC 288 and NGC 362

    NASA Astrophysics Data System (ADS)

    Catelan, M.; de Freitas Pacheco, J. A.

    1994-09-01

    It has been argued in the recent literature that the horizontal-branch (HB) evolutionary tracks of Castellani, Chieffi, & Pulone (1991) are superior to those of Lee & Demarque (1990) in accounting for the properties of RR Lyrae variables in Galactic globular clusters (GGCs). In the present study, we show that the conclusions reached by Catelan & de Freitas Pacheco (1993) on the role played by age as a second parameter affecting the HB morphologies of the GGCs NGC 288 and NGC 362, originally based upon the analysis of the latter tracks, are confirmed when the Castellani et al. set is employed instead. More specifically, we confirm that an age difference between these clusters as small as approximately 2-3 Gyr can only be consistent with HB models if additional parameters are varying between them, and/or both clusters are younger than approximately 10 Gry, and/or stellar evolution at the core He-burning phase is not properly understood.

  7. The Na-O anticorrelation in horizontal branch stars. V. NGC 6723

    NASA Astrophysics Data System (ADS)

    Gratton, R. G.; Lucatello, S.; Sollima, A.; Carretta, E.; Bragaglia, A.; Momany, Y.; D'Orazi, V.; Salaris, M.; Cassisi, S.; Stetson, P. B.

    2015-01-01

    We used FLAMES+GIRAFFE (Medusa mode) at the VLT to obtain moderately high resolution spectra for 30 red horizontal branch (RHB) stars, 4 RR Lyrae variables, and 17 blue horizontal branch (BHB) stars in the low-concentration, moderately metal-rich globular cluster NGC 6723 ([Fe/H] = -1.22 ± 0.08 from our present sample). The spectra were optimized to derive O and Na abundances. In addition, we obtained abundances for other elements, including N, Fe, Mg, Ca, Ni, and Ba. We used these data to discuss the evidence of a connection between the distribution of stars along the horizontal branch (HB) and the multiple populations that are typically present in globular clusters. We found that all RHB and most (13 out of 17) BHB stars are O-rich, Na-poor, and N-poor; these stars probably belong to the first stellar generation in this cluster. Only the four warmest observed stars are (moderately) O-poor, Na-rich, and N-rich, and they probably belong to the second generation. While our sample is not fully representative of the whole HB population in NGC 6723, our data suggest that in this cluster only HB stars warmer than ~9000 K, that is one fourth of the total, belong to the second generation, if at all. Since in many other clusters this fraction is about two thirds, we conclude that the fraction of first/second generation in globular clusters may be strongly variable. In addition, the wide range in colour of chemically homogeneous first-generation HB stars requires a considerable spread in mass loss (>0.10 M⊙). The reason for this spread is yet to be understood. Finally, we found a high Ba abundance, with a statistically significant radial abundance gradient. Based on observations collected at ESO telescopes under programme 087.D-0230.Tables 2, 3, 5, 7, and 8 are available in electronic form at http://www.aanda.org

  8. A Hot, Extended Horizontal Branch in the Massive M31 Globular Cluster G1

    NASA Astrophysics Data System (ADS)

    Rich, Robert M.; Piotto, G.; Reitzel, D.; Origlia, L.; Bedin, L.

    2013-01-01

    The globular cluster G1 in M31 is among the most massive in the Local Group and may host a supermassive central black hole of ~20,000 Msun. We have used WFC3 on HST to image G1 in the F275, B, and V bands. G1 has also been proposed as likely to host a complex stellar population like that of ω Cen, which has been proposed as a possible nucleus of a dwarf galaxy. We find an extended blue horizontal branch in G1, although it appears the blue HB is <20% of the red clump population. Although we detect a wide red giant branch, neither the RGB nor HB have the complexity of those observed in Omega Cen. We have a solid detection of an extended HB in G1, but we do not strong evidence for the extreme complexity exhibited by ω Cen.

  9. The blue horizontal branch of the globular cluster M15 Photographic photometry with the GALAXY machine

    NASA Astrophysics Data System (ADS)

    Battistini, P.; Bregoli, G.; Fusi Pecci, F.; Lolli, M.; Epps Bingham, E. A.

    1985-09-01

    Photographic observations of 295 stars in the globular cluster M15 are reported. The photographic plates were analyzed using the GALAXY machine attached to the 152-cm Ritchey-Chretien F/8 telescope of the University of Bologna at Loiano, Italy. B and V plates for a region having a distance from the center greater than 5.0 arcmin and less than 12.0 arcmin. On the basis of an analysis of the entire sample, the presence of a gap in the horizontal branch was confirmed. The ratio of the populations of stars in the three main branches (RGB, AGB, and HB) was constant within an acceptable range of error over the entire cluster. The ratios of populations among the bluer stars suggested a possible radial trend. The magnitudes, positions, and colors of the stars are given in a table.

  10. Helium-burning evolutionary phases in population II stars. I Breathing pulses in horizontal branch stars

    NASA Astrophysics Data System (ADS)

    Castellani, V.; Chieffi, A.; Tornambe, A.; Pulone, L.

    1985-09-01

    The result of an investigation into the evolutionary characteristics of a typical horizontal-branch (HB) model are presented. A new treatment of semiconvection has been used which overlaps Robertson and Faulkner's prescription in the major phase of central He burning and which allows a meaningful treatment of the last phases of He exhaustion at the center. The occurrence of convective instabilities near the He exhaustion in the central core is confirmed, finding that three major convection pulses occur before the exhaustion of He. Consequences regarding HB lifetimes and post-HB evolution are briefly discussed.

  11. The Origin of Hot Subluminous Horizontal-Branch Stars in Omega Cen and NGC 2808

    NASA Technical Reports Server (NTRS)

    Sweigart, A. V.; Brown, T. M.; Moehler, S.; Lanz, T.; Landsman, W. B.; Hubeny, I.; Napiwotzki, R.; Driezler, S.; Fisher, Richard R. (Technical Monitor)

    2001-01-01

    Ultraviolet observations of the globular clusters omega Cen and NGC 2808 have revealed an unexpected population of hot subluminous stars lying up to 0.7 mag below the extreme horizontal branch (EHB), which axe not explained by canonical stellar models. In order to explore the evolutionary status of these stars, we have evolved a set of low-mass stars from the main sequence through the helium flash to the horizontal branch (HB) for a wide range in the mass loss along the red-giant branch (RGB). Stars with the largest mass loss evolve off the RGB to high effective temperatures before igniting helium in their cores. Our results indicate that the subluminous stars can be explained if these stars undergo a late helium flash while descending the white dwarf cooling curve. Under these conditions the convection zone produced by the helium flash will penetrate into the stellar envelope, thereby mixing the envelope hydrogen into the hot helium-burning interior, where it is rapidly consumed. Such "flashmixed" stars will have helium- and carbon-rich envelopes and will lie at higher effective temperatures than the hottest canonical (i.e., unmixed) EHB stars. Using new stellar atmospheres, we show that these changes in the envelope abundances will suppress the ultraviolet flux in the spectra of the flash-mixed stars by the amount needed to explain the hot subluminous stars in w Cen and NGC 2808. To test this evolutionary scenario, we have obtained medium resolution spectra of a sample of the hottest HB stars in omega Cen. We find that these stars axe indeed helium-rich compared to classical EHB stars and also considerably hotter than the hottest EHB models without flash mixing.

  12. HST Observations of New Horizontal Branch Structures in the Globular Cluster w Centauri

    NASA Technical Reports Server (NTRS)

    Stecher, Theodore

    1999-01-01

    The globular cluster omega Centauri contains the largest known population of very hot horizontal branch (HB) stars. We have used the Hubble Space Telescope to obtain a far-UV/optical color-magnitude diagram of three fields in omega Cen. We find that over 30% of the HB objects are "extreme" HB or hot post-HB stars. A wide gap in the color distribution of the hot HB stars may correspond to gaps found earlier in several other clusters, which argues for a common mass loss mechanism. The diagram contains a significant population of hot sub-HB stars, which we interpret as the "blue-hook" objects predicted by D'Cruz (1996a). These are produced by late He-flashes in stars which have undergone unusually large giant branch mass loss. Omega Cen has a well-known spread of metal abundance, and the diagram is consistent with a giant branch mass loss efficiency which increases with metallicity. There is no evidence for a dynamical origin of the hot HB stars.

  13. The Hottest Horizontal-Branch Stars in Omega Centauri: Late Hot Flasher vs. Helium Enrichment

    NASA Technical Reports Server (NTRS)

    Moehler, S.; Dreizler, S.; Lanz, T.; Bono, G.; Sweigart, A V.; Calamida, A.; Monelli, M.; Nonino, M.

    2007-01-01

    UV observations of some massive globular clusters uncovered a significant population of very hot stars below the hot end of the horizontal branch (HB), the so-called blue hook stars. This feature might be explained either by the late hot flasher scenario here stars experience the helium flash while on the white dwarf cooling curve or by the helium-rich sub-population recently postulated to exist in some clusters. Spectroscopic analyses of blue hook stars in omega Cen and NGC 2808 support the late hot flasher scenario, but the stars contain much less helium than expected and the predicted C, N enrichment could not be verified from existing data. We want to determine effective temperatures, surface gravities and abundances of He, C, N in blue hook and canonical extreme horizontal branch (EHB) star candidates. Moderately high resolution spectra of stars at the hot end of the blue horizontal branch in the globular cluster omega Cen were analysed for atmospheric parameters (T(sub eff), log g) and abundances using LTE and Non-LTE model atmospheres. In the temperature range 30,000 K to 50,000 K we find that 37% of our stars are helium-poor (log nHe/nH less than -2), 49% have solar helium abundance within a factor of 3 (-1.5 less than or equal to log nHe/nH less than or equal to -0.5) and 14% are helium rich (log nHe/nH greater than -0.4). We also find carbon enrichment in step with helium enrichment, with a maximum carbon enrichment of 3% by mass. At least 30% of the hottest HB stars in omega Centauri show helium abundances well above the predictions from the helium enrichment scenario (Y = 0.42 corresponding to log nHe/nH approximately equal to -0.74). In addition the most helium-rich stars show strong carbon enrichment as predicted by the late hot flasher scenario. We conclude that the helium-rich HB stars in omega Cen cannot be explained solely by the helium-enrichment scenario invoked to explain the blue main sequence.

  14. A study of two high-velocity red horizontal branch stars

    NASA Astrophysics Data System (ADS)

    Pereira, C. B.; Jilinski, E. G.; Drake, N. A.; Ortega, V. G.; Roig, F.

    2013-11-01

    Context. High-velocity halo stars provide important information about the properties of the extreme Galactic halo. The study of Population II unbound and bound stars enables us better estimate the mass of the halo. Aims: We carried out a detailed spectroscopic and kinematic study of two red horizontal branch stars, CD-41°15048 and HD 214362. Methods: The atmospheric parameters, chemical abundances, and kinematical properties were determined using high-resolution optical spectroscopy and employing the local thermodynamic equilibrium model atmospheres of Kurucz and the spectral analysis code moog. Results: We found that CD-41°15048 and HD 214362 are metal-poor red horizontal branch stars. Their abundance patterns are similar to other metal-poor halo stars already investigated. Our kinematic analysis of the 3D space motions shows that HD 214362 has a highly eccentric (e = 0.95) orbit and passes at 2 kpc from the Galactic center. CD-41°15048, for an adopted distance of 1.3 kpc, has an extreme retrograde motion and travels with very high velocity relative to the Galactocentric reference frame (VGRF = 583 km s-1). Conclusions: CD-41°15048 is a bound or an unbound star, depending on the adopted Galactic potential. We also show that the red horizontal branch star BD+09°3223 is another example of a hypervelocity star. Whether it is bound or unbound to the Galaxy depends on the assumed mass and adopted Galactic potential. Possible origins of these two high-velocity stars are briefly discussed. CD-41°15048 and BD+09°3223 are further examples of evolved stars to join the restricted group of hypervelocity stars. Finally, our results seem to contradict the idea that a passage of a star very close to the Galactic center is the only possible origin of hypervelocity stars. Based on observations made with the 2.2 m telescope at the European Southern Observatory (La Silla, Chile) under the agreement between ESO and Observatório Nacional (2007-2010).Figures 3-5, 8, 10

  15. Identification and Analysis of Horizontal-Branch and Other A-Type Stars in the Galaxy

    NASA Astrophysics Data System (ADS)

    Rossi, Silvia C. F.; Beers, Timothy C.; Wilhelm, Ronald J.

    New techniques are being developed for the identification of Field Horizontal-Branch (FHB) and other A-type stars based on moderate-resolution spectroscopic observations and broadband UBV photometry. Physical parameters (T_eff, log g, and feh\\ ) for these stars can be estimated with accuracy on the order of sigma (T_eff) = 250 K, sigma (log g) = 0.35 dex, and sigma (feh ) = 0.30 dex, respectively. Detailed analysis such as this is required in order to form a ``clean'' sample of FHB stars, as such samples are easily confounded by the presence of halo blue stragglers (or BMP stars) and other high-gravity A-type stars. We summarize these analysis techniques, and discuss their application to a new large sample of FHB/A stars identified as part of the ongoing HK interference-filter/objective-prism survey of Beers and collaborators.

  16. Constraints on Helium Enhancement in the Globular Cluster M3 (NGC 5272): The Horizontal Branch Test

    NASA Technical Reports Server (NTRS)

    Catelan, M.; Grundahl, F.; Sweigart, A. V.; Valcarce, A. A. R.; Cortes, C.

    2007-01-01

    It has recently been suggested that the presence of multiple populations showing various amounts of helium enhancement is a common feature among globular star clusters. In this scenario, such a helium enhancement would be particularly apparent in the enhanced luminosity of thc blue horizontal branch (HB) stars compared to the red HB stars. In this Letter, wc test this scenario in the case of the Galactic globular cluster M3 (NGC 5272), using high-precision Stromgren photometry and spectroscopic gravities for blue HB stars. We find that any helium enhancement among the cluster's blue HB stars must be significantly less than I%, thus ruling out the much higher helium enhancements that have been proposed in the literature.

  17. Blue horizontal branch field stars in the galactic halo - Observations versus kinematic models

    NASA Astrophysics Data System (ADS)

    Sommer-Larsen, Jesper; Christensen, Per Rex

    1989-07-01

    A sample of 185 blue horizontal branch field (BHBF) stars situated in four fields in the galactic halo at galactocentric distances r of less than 40 kpc has been analyzed. The BHBF stars are found to constitute a well mixed system. The Sommer-Larsen (1986, 1987) model is shown to provide a better fit to the kinematical data in all four fields than either the White (1985, 1988) or Ratnatunga and Freeman (1985, 1989) models. A formation scenario for the galactic halo which includes the effects of gas dynamical processes is proposed to account for the feature of the Sommer-Larsen model that the velocity distribution of halo stars is radially anisotropic in the inner halo, but tangentially anisotropic in the outer parts of the halo.

  18. VizieR Online Data Catalog: NGC 288 hot horizontal branch stars abundances (Moehler+, 2014)

    NASA Astrophysics Data System (ADS)

    Moehler, S.; Dreizler, S.; Leblanc, F.; Khalack, V.; Michaud, G.; Richer, J.; Sweigart, A. V.; Grundahl, F.

    2014-03-01

    Temperatures, surface gravities, and abundances for hot (Teff>9000K) horizontal branch stars in NGC 288 as derived from medium-resolution FLAMES-GIRAFFE spectra (resolution about 0.7Å). Effective temperatures and surface gravities are derived from line profile fits. The abundances were derived via spectrum synthesis, using the presviously defined effective temperature and surface gravity. Errors are about ±5% in Teff, ±0.1 in logg, ±0.2 (He), ±0.28 (Mg), ±0.34 (Si, P, Fe), ±0.58 (Ti, Mn, Ni). 0.00 means that no abundance could be determined. (2 data files).

  19. 1969 - 2010: Multicolor Photometric Observations of Population II Field Horizontal-Branch Stars

    NASA Astrophysics Data System (ADS)

    Philip, A. G. Davis

    2010-05-01

    From 1969 to 2010 I have been involved in a photometric study of Population II Field Horizontal-Branch stars. I started by making Stromgren four-color observations at Kitt Peak National Observatory and then Cerro Tololo Inter-American Observatory. I had taken spectral plates of all my selected areas on which I marked all the A-type stars. These stars were then observed photometrically. New FHB stars could be identified by their large c1 indices, caused by their greater (u-b) colors. Later four new filters were added ( U V B S ). With Richard Boyle of the Vatican Observatory we observed on Mt. Graham (Arizona) on the Vatican Advanced Technology Telescope.We plan follow-up observations of the new FHB stars found.

  20. 1969 to 2010: Multicolor Photometric Observations of Population II Field Horizontal-Branch Stars

    NASA Astrophysics Data System (ADS)

    Philip, A. G. D.

    2011-04-01

    From 1969 to 2010 I have been involved in a photometric study of Population II Field Horizontal-Branch Stars and published several papers on this topic in BOTT from 1967 thru 1972. I started by making Strömgren four-color observations at Kitt Peak National Observatory and then at Cerro Tololo Inter-American Observatory. I had taken spectral plates of all my selected areas on which I marked all the A-type stars. These stars were then observed photometrically. New FHB stars could be identified by their large c indices, caused by their greater (u-b) colors. Later four new filters were added (U, V, B, S). With Richard Boyle of the Vatican Observatory we observed on Mt. Graham (Arizona) on the Vatican Advanced Technology Telescope. We are making follow-up observations of the new FHB stars found.

  1. The ultraviolet IUE spectrum of the population II horizontal-branch A star HD 109995

    NASA Technical Reports Server (NTRS)

    Adelman, S. J.; Leckrone, D. S.

    1986-01-01

    Eight SWP and six LWP high dispersion IUE images of the field horizontal-branch A star HD 109995 have been averaged to increase the signal-to-noise ratio. The line density in the UV is greater than that of the optical region, but less than that of comparable population I A stars. Many of the identified lines are those of Fe II. Lines of C I, C II, N I, O I, Mg I, Mg II, Al II, Al III, Si I, Si II, P II, S I, Cl I, Ti II, V II, Cr II, Mn II, Fe I, Co II, Ni II, Zn II, and Ge II are also present. Definite interstellar lines of C II, Mg I, Mg II, Al II, Si II, and Fe II were found.

  2. Deep HST Photometry of NGC 6388: Age and Horizontal Branch Luminosity

    NASA Technical Reports Server (NTRS)

    Stetson, Peter B.; Catelan, M.; Pritzl, Barton J.; Smith, Horace A.; Kinemuchi, Karen; Layden, Andrew C.; Sweigart, Allen V.; Rich, R. M.

    2006-01-01

    We present the first deep color-magnitude diagram (CMD) of the Galactic globular cluster NGC 6388, obtained with the Hubble Space Telescope, that is able to reach the main-sequence turnoff point of the cluster. From a detailed comparison between the cluster CMD and that of 47 Tucanae (NGC 104), we find that the bulk of the stars in these two clusters have nearly the same age and chemical composition. On the other hand, our results indicate that the blue horizontal branch and RR Lyrae components in NGC 6388 are intrinsically over-luminous, which must be due to one or more, still undetermined, non-canonical second parameter(s) affecting a relatively minor fraction of the stars in NGC 6388.

  3. VizieR Online Data Catalog: Horizontal-branch and A-type star catalog. II (Beers+ 1996)

    NASA Astrophysics Data System (ADS)

    Beers, T. C.; Wilhelm, R.; Doinidis, S. P.; Mattson, C. J.

    1996-09-01

    We present coordinates and brightness estimates for 4175 candidate field horizontal-branch and A-type stars, in the magnitude range 10<=B<=15.5, selected using an objective-prism/interference-filter survey technique. The candidates lie primarily in the northern Galactic hemisphere and complement a previously published sample of southern Galactic hemisphere candidates. Available spectroscopy and photometry indicates that the great majority of the candidates are likely to be bona fide members of either the field blue horizontal- branch population or the blue, metal-deficient, high surface gravity stars referred to by Preston, Beers, & Schectman (1994AJ....108..538P) as BMP stars. The remaining stars in the catalog are likely to be a mix of metal-deficient turnoff stars, metallic-line (Am) stars, field red horizontal-branch stars, optical doubles with overlapping objective-prism spectra, and (particularly among the fainter candidates) inadvertently included late-type stars. (1 data file).

  4. CHEMICAL AND KINEMATICAL PROPERTIES OF BLUE STRAGGLER STARS AND HORIZONTAL BRANCH STARS IN NGC 6397

    SciTech Connect

    Lovisi, L.; Mucciarelli, A.; Lanzoni, B.; Ferraro, F. R.; Dalessandro, E.; Contreras Ramos, R.; Gratton, R.

    2012-08-01

    We used three sets of high-resolution spectra acquired with the multifiber facility FLAMES at the Very Large Telescope of the European Southern Observatory to investigate the chemical and kinematical properties of a sample of 42 horizontal branch (HB) stars, 18 blue straggler stars (BSSs), and 86 main-sequence (MS) turnoff (TO) and sub-giant branch stars in the nearby globular cluster NGC 6397. We measured rotational velocities and Fe, O, and Mg abundances. All of the unevolved stars in our sample have low rotational velocites (vsin i < 10 km s{sup -1}), while the HB stars and BSSs show a broad distribution, with values ranging from 0 to {approx}70 km s{sup -1}. For HB stars with T < 10,500 K there is a clear temperature-oxygen anticorrelation that can be understood if the star position along the HB is mainly determined by the He content. The hottest BSSs and HB stars (with temperatures T > 8200 K and T > 10,500 K, respectively) also show significant deviations in their iron abundance with respect to the cluster metallicity (as traced by the unevolved stars, [Fe/H] = -2.12). While similar chemical patterns have already been observed in other hot HB stars, this is the first evidence ever collected for BSSs. We interpret these abundance anomalies as due to the metal radiative levitation, occurring in stars with shallow or no convective envelopes.

  5. POSSIBLE IMPLICATIONS OF THE PLANET ORBITING THE RED HORIZONTAL BRANCH STAR HIP 13044

    SciTech Connect

    Bear, Ealeal; Soker, Noam; Harpaz, Amos E-mail: soker@physics.technion.ac.il

    2011-06-01

    We propose a scenario to account for the surprising orbital properties of the planet orbiting the metal-poor red horizontal branch star HIP 13044. The orbital period of 16.2 days implies that the planet went through a common envelope phase inside the red giant branch (RGB) stellar progenitor of HIP 13044. The present properties of the star imply that it maintained a substantial envelope mass of 0.3 M{sub sun}, raising the question of how the planet survived the common envelope before the envelope itself was lost? If such a planet enters the envelope of an RGB star, it is expected to spiral-in to the very inner region within {approx}< 100 yr, and be evaporated or destroyed by the core. We speculate that the planet was engulfed by the star as a result of the core helium flash that caused this metal-poor star to swell by a factor of {approx}3-4. The evolution following the core helium flash is very rapid, and some of the envelope is lost due to the interaction with the planet, and the rest of the envelope shrinks within about a hundred years. This is about equal to the spiraling-in time, and the planet survived.

  6. The mosaic multiple stellar populations in ω Centauri: the horizontal branch and the main sequence

    NASA Astrophysics Data System (ADS)

    Tailo, M.; Di Criscienzo, M.; D'Antona, F.; Caloi, V.; Ventura, P.

    2016-04-01

    We interpret the stellar population of ω Centauri by means of a population synthesis analysis, following the most recent observational guidelines for input metallicities, helium and [(C+N+O)/Fe] contents. We deal at the same time with the main sequences, sub-giant and horizontal branch (HB) data. The reproduction of the observed colour-magnitude features is very satisfying and bears interesting hints concerning the evolutionary history of this peculiar stellar ensemble. Our main results are: (1) no significant spread in age is required to fit the colour-magnitude diagram. Indeed, we can use coeval isochrones for the synthetic populations, and we estimate that the ages fall within a ˜0.5 Gyr time interval; in particular the most metal-rich population can be coeval (in the above meaning) with the others, if its stars are very helium-rich (Y ˜ 0.37) and with the observed CNO enhancement ([(C+N+O)/Fe] = +0.7); (2) a satisfactory fit of the whole HB is obtained, consistent with the choice of the populations providing a good reproduction of the main sequence and sub-giant data; (3) the split in magnitude observed in the red HB is well reproduced assuming the presence of two stellar populations in the two different sequences observed: a metal-poor population made of stars evolving from the blue side (luminous branch) and a metal richer one whose stars are in a stage closer to the zero age HB (dimmer branch). This modelization also fits satisfactorily the period and the [Fe/H] distribution of the RR Lyrae stars.

  7. Branch morphology in young poplar clones on floodplain sites in Missouri

    Treesearch

    Stephen G. Pallardy; Daniel E. Gibbins

    2003-01-01

    Four Populus clones were grown in central Missouri for 2 years at 1 x 1 m spacing to study total biomass production on floodplain sites previously in forage grasses. Branch morphology (living, first-order proleptic, and sylleptic shoots) was assessed for 2-year-old plants. All 2-year-old plants had lateral branches, and clones varied significantly in certain branch...

  8. KIC 1718290: A HELIUM-RICH V1093-Her-LIKE PULSATOR ON THE BLUE HORIZONTAL BRANCH

    SciTech Connect

    Ostensen, R. H.; Degroote, P.; Vos, J.; Aerts, C.; Telting, J. H.; Jeffery, C. S.; Green, E. M.; Reed, M. D.; Heber, U.

    2012-07-01

    We introduce the first g-mode pulsator found to reside on the classical blue horizontal branch. One year of Kepler observations of KIC 1718290 reveals a rich spectrum of low-amplitude modes with periods between 1 and 12 hr, most of which follow a regular spacing of 276.3 s. This mode structure strongly resembles that of the V1093 Her pulsators, with only a slight shift toward longer periods. Our spectroscopy, however, reveals KIC 1718290 to be quite distinct from the sdB stars that show V1093 Her pulsations, which all have surface gravities higher than log g = 5.1 and helium abundances depleted by at least an order of magnitude relative to the solar composition. We find that KIC 1718290 has T{sub eff} = 22,100 K, log g = 4.72, and a super-solar helium abundance (log N{sub He}/N{sub H} = -0.45). This places it well above the extreme horizontal branch, rather on the very blue end of the classical horizontal branch, where shell hydrogen burning is present. We conclude that KIC 1718290 must have suffered extreme mass loss during its first giant stage, but not sufficient to reach the extreme horizontal branch.

  9. Chemical and Kinematical Properties of Blue Straggler Stars and Horizontal Branch Stars in NGC 6397

    NASA Astrophysics Data System (ADS)

    Lovisi, L.; Mucciarelli, A.; Lanzoni, B.; Ferraro, F. R.; Gratton, R.; Dalessandro, E.; Contreras Ramos, R.

    2012-08-01

    We used three sets of high-resolution spectra acquired with the multifiber facility FLAMES at the Very Large Telescope of the European Southern Observatory to investigate the chemical and kinematical properties of a sample of 42 horizontal branch (HB) stars, 18 blue straggler stars (BSSs), and 86 main-sequence (MS) turnoff (TO) and sub-giant branch stars in the nearby globular cluster NGC 6397. We measured rotational velocities and Fe, O, and Mg abundances. All of the unevolved stars in our sample have low rotational velocites (vsin i < 10 km s-1), while the HB stars and BSSs show a broad distribution, with values ranging from 0 to ~70 km s-1. For HB stars with T < 10,500 K there is a clear temperature-oxygen anticorrelation that can be understood if the star position along the HB is mainly determined by the He content. The hottest BSSs and HB stars (with temperatures T > 8200 K and T > 10,500 K, respectively) also show significant deviations in their iron abundance with respect to the cluster metallicity (as traced by the unevolved stars, [Fe/H] = -2.12). While similar chemical patterns have already been observed in other hot HB stars, this is the first evidence ever collected for BSSs. We interpret these abundance anomalies as due to the metal radiative levitation, occurring in stars with shallow or no convective envelopes. Based on FLAMES observations collected at the European Southern Observatory, proposal numbers 073.D-0058, 075.D-0125, and 081.D-0356.

  10. Constraints on helium enhancement in the globular cluster M4 (NGC 6121): The horizontal branch test

    SciTech Connect

    Valcarce, A. A. R.; De Medeiros, J. R.; Catelan, M.; Alonso-García, J.; Cortés, C.

    2014-02-20

    Recent pieces of evidence have revealed that most, and possibly all, globular star clusters are composed of groups of stars that formed in multiple episodes with different chemical compositions. In this sense, it has also been argued that variations in the initial helium abundance (Y) from one population to the next are also the rule, rather than the exception. In the case of the metal-intermediate globular cluster M4 (NGC 6121), recent high-resolution spectroscopic observations of blue horizontal branch (HB) stars (i.e., HB stars hotter than the RR Lyrae instability strip) suggest that a large fraction of blue HB stars are second-generation stars formed with high helium abundances. In this paper, we test this scenario by using recent photometric and spectroscopic data together with theoretical evolutionary computations for different Y values. Comparing the photometric data with the theoretically derived color-magnitude diagrams, we find that the bulk of the blue HB stars in M4 have ΔY ≲ 0.01 with respect to the cluster's red HB stars (i.e., HB stars cooler than the RR Lyrae strip)—a result which is corroborated by comparison with spectroscopically derived gravities and temperatures, which also favor little He enhancement. However, the possible existence of a minority population on the blue HB of the cluster with a significant He enhancement level is also discussed.

  11. A helium-carbon correlation on the extreme horizontal branch in ω Centauri

    SciTech Connect

    Latour, M.; Fontaine, G.; Brassard, P.; Randall, S. K.; Bono, G.; Calamida, A.

    2014-11-10

    Taking advantage of a recent FORS2/VLT spectroscopic sample of extreme horizontal branch (EHB) stars in ω Cen, we isolate 38 spectra well suited for detailed atmospheric studies and determine their fundamental parameters (T {sub eff}, log g, and log N(He)/N(H)) using NLTE, metal line-blanketed models. We find that our targets can be divided into three groups: 6 stars are hot (T {sub eff} ≳ 45,000 K) H-rich subdwarf O stars, 7 stars are typical H-rich sdB stars (T {sub eff} ≲ 35,000 K), and the remaining 25 targets at intermediate effective temperatures are He-rich (log N(He)/N(H) ≳ –1.0) subdwarfs. Surprisingly, and quite interestingly, these He-rich hot subdwarfs in ω Cen cluster in a narrow temperature range (∼35,000 K to ∼40,000 K). We additionally measure the atmospheric carbon abundance and find a most interesting positive correlation between the carbon and helium atmospheric abundances. This correlation certainly bears the signature of diffusion processes—most likely gravitational settling impeded by stellar winds or internal turbulence—but also constrains possible formation scenarios proposed for EHB stars in ω Cen. For the He-rich objects in particular, the clear link between helium and carbon enhancement points toward a late hot flasher evolutionary history.

  12. Optical Spectroscopy of the Red Horizontal Branch Stars of NGC 6791

    NASA Astrophysics Data System (ADS)

    Hufnagel, Beth; Smith, Graeme H.; Janes, Kenneth A.

    1995-08-01

    We have obtained 3600-4600 Å spectra at ˜5 Å resolution for 31 stars in the field of NGC 6791, one of the oldest and most "globular-cluster-like" of the Galactic open clusters. Based on spectroscopic analysis of 19 of these stars considered to be red horizontal branch (RHB) members of NGC 6791, we conclude that there is no evidence for significant variations in the CR band or the Ca and Fe line strengths among these stars, although there are strong indications of intrinsic differences among the CN band strengths. There is also no evidence for correlations between the CN band, CR band, or Fe line strengths of these stars, although there may be a weak correlation between CN band and Ca line strengths. The nature of the CN-band inhomogeneity is in marked contrast to the bimodal CN distributions discovered among the RHB stars of the two globular clusters 47 Tuc and M71 by Norris & Freeman [ApJ, 254, 143 (1982)] and Smith & Penny [M, 97, 1397 (1989)]. These results imply that either the environment within which globular clusters formed resulted in initial C and N abundance inhomogeneities that were lacking in NGC 6791, or that the evolutional processes which alter stellar surface abundances prior to or during the core helium-burning phase of evolution, differ in some respect between the disk globular clusters and NGC 6791.

  13. The RR Lyrae Instability Strip in the Split Horizontal Branch Globular Cluster NGC 6569

    NASA Astrophysics Data System (ADS)

    Kunder, A.; Stetson, P. B.; Catelan, M.; Walker, A.; Cassisi, S.; Johnson, C.; Soto, M.

    2015-05-01

    The first calibrated broadband BVI time-series photometry is obtained for the RR Lyrae variable stars in the split horizontal branch (HB) cluster NGC 6569. As a result, a sizeable population of 27 RR Lyrae variables has been identified. An eclipsing binary in the RR Lyrae instability strip was also found, which is most likely a field star. The 12 fundamental-mode RR Lyrae variables (RR0) have an average period of [P]RR0= 0.57±0.02 d and the 15 first-overtone variables (RR1) have an average period of [P]RR1=0.30±0.01 d. The mean periods of the RR Lyrae stars are consistent with an Oosterhoff I designation, and the number ratio of RR1- to RR0-type variables, N1/NRR=0.56, is more consistent with an Oosterhoff II designation. Compared to the M3 variables, the NGC 6569 RR Lyrae variables are not shifted to a longer periods at a given amplitude, making it unlikely that these stars are He-enhanced. The similarity in the periods and amplitudes between the RR Lyrae stars in NGC 6569 and the bulge field RR Lyrae population may indicate similar formation conditions.

  14. A Helium-Carbon Correlation on the Extreme Horizontal Branch in ω Centauri

    NASA Astrophysics Data System (ADS)

    Latour, M.; Randall, S. K.; Fontaine, G.; Bono, G.; Calamida, A.; Brassard, P.

    2014-11-01

    Taking advantage of a recent FORS2/VLT spectroscopic sample of extreme horizontal branch (EHB) stars in ω Cen, we isolate 38 spectra well suited for detailed atmospheric studies and determine their fundamental parameters (T eff, log g, and log N(He)/N(H)) using NLTE, metal line-blanketed models. We find that our targets can be divided into three groups: 6 stars are hot (T eff >~ 45,000 K) H-rich subdwarf O stars, 7 stars are typical H-rich sdB stars (T eff <~ 35,000 K), and the remaining 25 targets at intermediate effective temperatures are He-rich (log N(He)/N(H) >~ -1.0) subdwarfs. Surprisingly, and quite interestingly, these He-rich hot subdwarfs in ω Cen cluster in a narrow temperature range (~35,000 K to ~40,000 K). We additionally measure the atmospheric carbon abundance and find a most interesting positive correlation between the carbon and helium atmospheric abundances. This correlation certainly bears the signature of diffusion processes—most likely gravitational settling impeded by stellar winds or internal turbulence—but also constrains possible formation scenarios proposed for EHB stars in ω Cen. For the He-rich objects in particular, the clear link between helium and carbon enhancement points toward a late hot flasher evolutionary history. Based on observations collected at the European Organisation for Astronomical Research in the Southern Hemisphere, Chile (proposal IDs 386.D-0669 and 091.D-0791).

  15. THE ABSOLUTE MAGNITUDES OF RED HORIZONTAL BRANCH STARS IN THE ugriz SYSTEM

    SciTech Connect

    Chen, Y. Q.; Zhao, G.; Zhao, J. K.

    2009-09-10

    Based on photometric data of the central parts of eight globular clusters and one open cluster presented by An and his collaborators, we select red horizontal branch (RHB) stars in the (g - r){sub 0}-g {sub 0} diagram and make a statistical study of the distributions of their colors and absolute magnitudes in the SDSS ugriz system. Meanwhile, absolute magnitudes in the Johnson VRI system are calculated through the translation formulae between gri and VRI in the literature. The calibrations of absolute magnitude as functions of metallicity and age are established by linear regressions of the data. It is found that metallicity coefficients in these calibrations decrease, while age coefficients increase, from the blue u filter to the red z filter. The calibration of M{sub i} = 0.06[Fe/H] + 0.040t + 0.03 has the smallest scatter of 0.04 mag, and thus i is the best filter in the ugriz system when RHB stars are used for distance indicators. The comparison of the M{sub I} calibration from our data with that from red clump stars indicates that the previous suggestion that the I filter is better than the V filter in distance determination may not be true because of its significant dependence on age.

  16. A giant planet orbiting the 'extreme horizontal branch' star V 391 Pegasi.

    PubMed

    Silvotti, R; Schuh, S; Janulis, R; Solheim, J-E; Bernabei, S; Østensen, R; Oswalt, T D; Bruni, I; Gualandi, R; Bonanno, A; Vauclair, G; Reed, M; Chen, C-W; Leibowitz, E; Paparo, M; Baran, A; Charpinet, S; Dolez, N; Kawaler, S; Kurtz, D; Moskalik, P; Riddle, R; Zola, S

    2007-09-13

    After the initial discoveries fifteen years ago, over 200 extrasolar planets have now been detected. Most of them orbit main-sequence stars similar to our Sun, although a few planets orbiting red giant stars have been recently found. When the hydrogen in their cores runs out, main-sequence stars undergo an expansion into red-giant stars. This expansion can modify the orbits of planets and can easily reach and engulf the inner planets. The same will happen to the planets of our Solar System in about five billion years and the fate of the Earth is matter of debate. Here we report the discovery of a planetary-mass body (Msini = 3.2M(Jupiter)) orbiting the star V 391 Pegasi at a distance of about 1.7 astronomical units (au), with a period of 3.2 years. This star is on the extreme horizontal branch of the Hertzsprung-Russell diagram, burning helium in its core and pulsating. The maximum radius of the red-giant precursor of V 391 Pegasi may have reached 0.7 au, while the orbital distance of the planet during the stellar main-sequence phase is estimated to be about 1 au. This detection of a planet orbiting a post-red-giant star demonstrates that planets with orbital distances of less than 2 au can survive the red-giant expansion of their parent stars.

  17. Metallicity and Kinematic Distributions of Red Horizontal-branch Stars from the SDSS Survey

    NASA Astrophysics Data System (ADS)

    Chen, Y. Q.; Zhao, G.; Zhao, J. K.; Xue, X. X.; Schuster, W. J.

    2010-08-01

    On the basis of a recently derived color-metallicity relation and stellar parameters from the Sloan Digital Sky Survey Data Release 7 spectroscopic survey, a large sample of red horizontal-branch (RHB) candidates have been selected to serve as standard candles. The metallicity and kinematic distributions of these stars indicate that they mainly originate from the thick-disk and the halo populations. The typical thick disk is characterized by the first group peaking at [Fe/H] ~ -0.6, V rot ~ 170 km s-1 with a vertical scale height around |Z| ~ 1.2 kpc, while stars with [Fe/H] < -0.9 are dominated by the halo population. Two sub-populations of the halo are suggested by the RHB stars peaking at [Fe/H] ~ -1.3: one component with V rot > 0 km s-1 (Halo I) shows a sign of metallicity gradient in the [Fe/H] versus |Z| diagram, while the other with V rot < 0 km s-1 (Halo II) does not. The Halo I mainly clumps at the inner halo with R < 10 kpc and the Halo II comes both from the inner halo with R < 10 kpc and the outer halo with R > 10 kpc based on the star distribution in the R versus |Z| diagram.

  18. METALLICITY AND KINEMATIC DISTRIBUTIONS OF RED HORIZONTAL-BRANCH STARS FROM THE SDSS SURVEY

    SciTech Connect

    Chen, Y. Q.; Zhao, G.; Zhao, J. K.; Xue, X. X.; Schuster, W. J. E-mail: schuster@astrosen.unam.m

    2010-08-15

    On the basis of a recently derived color-metallicity relation and stellar parameters from the Sloan Digital Sky Survey Data Release 7 spectroscopic survey, a large sample of red horizontal-branch (RHB) candidates have been selected to serve as standard candles. The metallicity and kinematic distributions of these stars indicate that they mainly originate from the thick-disk and the halo populations. The typical thick disk is characterized by the first group peaking at [Fe/H] {approx} -0.6, V{sub rot} {approx} 170 km s{sup -1} with a vertical scale height around |Z| {approx} 1.2 kpc, while stars with [Fe/H] < -0.9 are dominated by the halo population. Two sub-populations of the halo are suggested by the RHB stars peaking at [Fe/H] {approx} -1.3: one component with V{sub rot} > 0 km s{sup -1} (Halo I) shows a sign of metallicity gradient in the [Fe/H] versus |Z| diagram, while the other with V{sub rot} < 0 km s{sup -1} (Halo II) does not. The Halo I mainly clumps at the inner halo with R < 10 kpc and the Halo II comes both from the inner halo with R < 10 kpc and the outer halo with R > 10 kpc based on the star distribution in the R versus |Z| diagram.

  19. A New Formation Mechanism for the Hottest Horizontal-Branch Stars

    NASA Technical Reports Server (NTRS)

    Sweigart, Allen V.; Oegerle, William R. (Technical Monitor)

    2002-01-01

    Hot subluminous stars lying up to 0.7 mag below the extreme horizontal branch (EHB) are found in the ultraviolet color-magnitude diagrams (CMDs) of both omega Cen and NGC 2808. In order to investigate the origin of these subluminous stars, we have constructed a detailed set of evolutionary sequences that follow the evolution of low-mass stars continuously from the zero-age main sequence through the helium-core flash to the HB for a wide range in the mass loss along the red-giant branch (RGB). Stars with the largest mass loss evolve off the RGB to high effective temperatures before igniting helium in their cores. Our results indicate that the subluminous EHB stars, as well as the high temperature gap along the EHB of NGC 2808, can be explained if these stars undergo a late helium-core flash while descending the white-dwarf cooling curve. Under these conditions the convection zone produced by the main helium flash will penetrate into the stellar envelope, thereby mixing most, if not all, of the envelope hydrogen into the hot helium-burning interior, where it is rapidly consumed. This phenomenon is analogous to the 'born-again' scenario for producing hydrogen-deficient stars following a very late helium-shell flash. This 'flash mixing' of the envelope during a late helium-core flash greatly enhances the envelope helium and carbon abundances and, as a result, leads to a discontinuous increase in the HB effective temperature. We argue that the hot HB gap observed in NGC 2808 is associated with this theoretically predicted dichotomy in the RB properties. Using new helium- and carbon-rich stellar atmospheres, we show that the changes in the envelope abundances due to flash mixing will suppress the ultraviolet flux in the spectra of hot EHB stars. We suggest that such changes in the emergent spectral energy distribution are primarily responsible for explaining the hot subluminous EHB stars in omega Cen and NGC 2808. Moreover, we demonstrate that models without flash mixing

  20. A New Formation Mechanism for the Hottest Horizontal-Branch Stars

    NASA Technical Reports Server (NTRS)

    Sweigart, Allen V.; Oegerle, William R. (Technical Monitor)

    2002-01-01

    Hot subluminous stars lying up to 0.7 mag below the extreme horizontal branch (EHB) are found in the ultraviolet color-magnitude diagrams (CMDs) of both omega Cen and NGC 2808. In order to investigate the origin of these subluminous stars, we have constructed a detailed set of evolutionary sequences that follow the evolution of low-mass stars continuously from the zero-age main sequence through the helium-core flash to the HB for a wide range in the mass loss along the red-giant branch (RGB). Stars with the largest mass loss evolve off the RGB to high effective temperatures before igniting helium in their cores. Our results indicate that the subluminous EHB stars, as well as the high temperature gap along the EHB of NGC 2808, can be explained if these stars undergo a late helium-core flash while descending the white-dwarf cooling curve. Under these conditions the convection zone produced by the main helium flash will penetrate into the stellar envelope, thereby mixing most, if not all, of the envelope hydrogen into the hot helium-burning interior, where it is rapidly consumed. This phenomenon is analogous to the 'born-again' scenario for producing hydrogen-deficient stars following a very late helium-shell flash. This 'flash mixing' of the envelope during a late helium-core flash greatly enhances the envelope helium and carbon abundances and, as a result, leads to a discontinuous increase in the HB effective temperature. We argue that the hot HB gap observed in NGC 2808 is associated with this theoretically predicted dichotomy in the RB properties. Using new helium- and carbon-rich stellar atmospheres, we show that the changes in the envelope abundances due to flash mixing will suppress the ultraviolet flux in the spectra of hot EHB stars. We suggest that such changes in the emergent spectral energy distribution are primarily responsible for explaining the hot subluminous EHB stars in omega Cen and NGC 2808. Moreover, we demonstrate that models without flash mixing

  1. The Origin of Hot Subluminous Horizontal-Branch Stars in Omega Centauri and NGC 2808

    NASA Technical Reports Server (NTRS)

    Sweigart, Allen V.; Brown, T. M.; Lanz, T.; Landsman, W. B.; Hubeny, I.; Fisher, Richard R. (Technical Monitor)

    2001-01-01

    Hot subluminous stars lying up to 0.7 mag below the extreme horizontal branch (EHB) are found in the ultraviolet color-magnitude diagrams of both omega Cen (DCruz et.al. 2000) and NGC 2808 (Brown et al. 2001). In order to investigate the origin of these subluminous stars, we have constructed a detailed set of evolutionary sequences that follow the evolution of low-mass stars continuously from the zero-age main sequence through the helium-core flash to the HB for a wide range in the mass loss along the red-giant branch (RGB). Stars with the largest mass loss evolve off the RGB to high effective temperatures before igniting helium in their cores (Castellani & Castellani 1993). Our results indicate that the location of the subluminous EHB stars, as well as the high temperature gap along the EHB of NGC 2808, can be explained if these stars undergo a late helium-core flash while descending the white-dwarf cooling curve. Under these conditions the convection zone produced by the main helium flash will penetrate into the stellar envelope, thereby mixing most, if not all, of the envelope hydrogen into the hot helium-burning interior, where it is rapidly consumed (Sweigart 1997). This phenomenon is analogous to the "born-again" scenario for producing hydrogen-deficient stars following a very late helium-shell flash. This "flash mixing" of the envelope during a late helium-core flash greatly enhances the envelope helium and carbon abundances and, as a result, leads to a discontinuous increase in the HB effective temperature. We argue that the hot HB gap observed in NGC 2808 is associated with this theoretically predicted dichotomy in the HB properties. Using new helium- and carbon-rich stellar atmospheres, we show that the changes in the envelope abundances due to flash mixing will suppress the ultraviolet flux in the spectra of hot EHB stars. We suggest that such changes in the emergent spectral energy distribution are primarily responsible for explaining the hot

  2. The Origin of Hot Subluminous Horizontal-Branch Stars in Omega Centauri and NGC 2808

    NASA Technical Reports Server (NTRS)

    Sweigart, Allen V.; Brown, T. M.; Lanz, T.; Landsman, W. B.; Hubeny, I.; Fisher, Richard R. (Technical Monitor)

    2001-01-01

    Hot subluminous stars lying up to 0.7 mag below the extreme horizontal branch (EHB) are found in the ultraviolet color-magnitude diagrams of both omega Cen (DCruz et.al. 2000) and NGC 2808 (Brown et al. 2001). In order to investigate the origin of these subluminous stars, we have constructed a detailed set of evolutionary sequences that follow the evolution of low-mass stars continuously from the zero-age main sequence through the helium-core flash to the HB for a wide range in the mass loss along the red-giant branch (RGB). Stars with the largest mass loss evolve off the RGB to high effective temperatures before igniting helium in their cores (Castellani & Castellani 1993). Our results indicate that the location of the subluminous EHB stars, as well as the high temperature gap along the EHB of NGC 2808, can be explained if these stars undergo a late helium-core flash while descending the white-dwarf cooling curve. Under these conditions the convection zone produced by the main helium flash will penetrate into the stellar envelope, thereby mixing most, if not all, of the envelope hydrogen into the hot helium-burning interior, where it is rapidly consumed (Sweigart 1997). This phenomenon is analogous to the "born-again" scenario for producing hydrogen-deficient stars following a very late helium-shell flash. This "flash mixing" of the envelope during a late helium-core flash greatly enhances the envelope helium and carbon abundances and, as a result, leads to a discontinuous increase in the HB effective temperature. We argue that the hot HB gap observed in NGC 2808 is associated with this theoretically predicted dichotomy in the HB properties. Using new helium- and carbon-rich stellar atmospheres, we show that the changes in the envelope abundances due to flash mixing will suppress the ultraviolet flux in the spectra of hot EHB stars. We suggest that such changes in the emergent spectral energy distribution are primarily responsible for explaining the hot

  3. Field Red Horizontal Branch Star Chemical Compositions from High Resolution Infrared Spectra

    NASA Astrophysics Data System (ADS)

    Sneden, Chris; Afsar, Melike; Bozkurt, Zeynep; Bocek-Topcu, Gamze; Mace, Gregory N.; Kim, Hwihyun; Kaplan, Kyle; Kidder, Benjamin; McLane, Jacob

    2017-06-01

    We have observed three field red horizontal branch stars with the Immersion Grating Infrared Spectrograph (IGRINS). The high resolution (R~45000) high signal-to-noise (S/N > 200) spectra obtained with IGRINS cover the complete H-band (1.50-1.80 micron) and K-band (1.90-2.45 micron). We analyzed hundreds of lines of the ubiquitous OH, CN, and CO molecular bands, and found more than 80 lines of atomic species that were useful for abundance work. A combination of good laboratory transition probabilities (when available) and ones derived from reverse solar analyses were employed. Our transition data were checked through studies of the Arcturus Atlas spectrum. We derived abundances from synthetic spectra instead of from equivalent widths. With IGRINS data we were able to extract metallicities and abundance ratios for more than 20 elements, including several not detectable or poorly represented in optical wavelength regions. Our abundances from IGRINS spectra are in excellent accord with those derived from optical spectrum studies. These results are directly applicable to calibrations of results from lower-resolution and/or S/N infrared spectral surveys. IGRINS observations will give high reolution spectroscopic access to heavily obscured normal red giants and other cool stars with unusual element mixes.This work used the Immersion Grating Infrared Spectrograph (IGRINS) that was developed under a collaboration between the University of Texas at Austin and the Korea Astronomy and Space Science Institute (KASI) with the financial support of the US National Science Foundation (NSF; grant AST-1229522), of the University of Texas at Austin, and of the Korean GMT Project of KASI. Our project also has been supported by NSF grants AST~1211585 and AST~1616040, by the University of Texas Rex G. Baker, Jr. Centennial Research Endowment, and by The Scientific and Technological Research Council of Turkey (TUBITAK, project No. 112T929).

  4. Characterizing stellar halo populations II: the age gradient in blue horizontal-branch stars

    NASA Astrophysics Data System (ADS)

    Das, Payel; Williams, Angus; Binney, James

    2016-12-01

    The distribution of Milky Way halo blue horizontal-branch (BHB) stars is examined using action-based extended distribution functions (EDFs) that describe the locations of stars in phase space, metallicity, and age. The parameters of the EDFs are fitted using stars observed in the Sloan Extension for Galactic Understanding and Exploration-II (SEGUE-II) survey that traces the phase-space kinematics and chemistry out to ˜70 kpc. A maximum a posteriori probability (MAP) estimate method and a Markov Chain Monte Carlo method are applied, taking into account the selection function in positions, distance, and metallicity for the survey. The best-fitting EDF declines with actions less steeply at actions characteristic of the inner halo than at the larger actions characteristic of the outer halo, and older ages are found at smaller actions than at larger actions. In real space, the radial density profile steepens smoothly from -2 at ˜2 kpc to -4 in the outer halo, with an axis ratio ˜0.7 throughout. There is no indication for rotation in the BHBs, although this is highly uncertain. A moderate level of radial anisotropy is detected, with βs varying from isotropic to between ˜0.1 and ˜0.3 in the outer halo depending on latitude. The BHB data are consistent with an age gradient of -0.03 Gyr kpc-1, with some uncertainty in the distribution of the larger ages. These results are consistent with a scenario in which older, larger systems contribute to the inner halo, whilst the outer halo primarily comprises younger, smaller systems.

  5. Chronography of the Milky Way's Halo System with Field Blue Horizontal-branch Stars

    NASA Astrophysics Data System (ADS)

    Santucci, Rafael M.; Beers, Timothy C.; Placco, Vinicius M.; Carollo, Daniela; Rossi, Silvia; Lee, Young Sun; Denissenkov, Pavel; Tumlinson, Jason; Tissera, Patricia B.

    2015-11-01

    In a pioneering effort, Preston et al. reported that the colors of blue horizontal-branch (BHB) stars in the halo of the Galaxy shift with distance, from regions near the Galactic center to about 12 kpc away, and interpreted this as a correlated variation in the ages of halo stars, from older to younger, spanning a range of a few Gyrs. We have applied this approach to a sample of some 4700 spectroscopically confirmed BHB stars selected from the Sloan Digital Sky Survey to produce the first “chronographic map” of the halo of the Galaxy. We demonstrate that the mean de-reddened g - r color, < {(g-r)}0> , increases outward in the Galaxy from -0.22 to -0.08 (over a color window spanning [-0.3: 0.0]) from regions close to the Galactic center to ˜40 kpc, independent of the metallicity of the stars. Models of the expected shift in the color of the field BHB stars based on modern stellar evolutionary codes confirm that this color gradient can be associated with an age difference of roughly 2-2.5 Gyr, with the oldest stars concentrated in the central ˜15 kpc of the Galaxy. Within this central region, the age difference spans a mean color range of about 0.05 mag (˜0.8 Gyr). Furthermore, we show that chronographic maps can be used to identify individual substructures, such as the Sagittarius Stream, and overdensities in the direction of Virgo and Monoceros, based on the observed contrast in their mean BHB colors with respect to the foreground/background field population.

  6. Just how hot are the ω Centauri extreme horizontal branch pulsators?

    NASA Astrophysics Data System (ADS)

    Latour, M.; Randall, S. K.; Chayer, P.; Fontaine, G.; Calamida, A.; Ely, J.; Brown, T. M.; Landsman, W.

    2017-04-01

    Context. Past studies based on optical spectroscopy suggest that the five ω Cen pulsators form a rather homogeneous group of hydrogen-rich subdwarf O stars with effective temperatures of around 50 000 K. This places the stars below the red edge of the theoretical instability strip in the log g-Teff diagram, where no pulsation modes are predicted to be excited. Aims: Our goal is to determine whether this temperature discrepancy is real, or whether the stars' effective temperatures were simply underestimated. Methods: We present a spectral analysis of two rapidly pulsating extreme horizontal branch (EHB) stars found in ω Cen. We obtained Hubble Space Telescope/COS UV spectra of two ω Cen pulsators, V1 and V5, and used the ionisation equilibrium of UV metallic lines to better constrain their effective temperatures. As a by-product we also obtained FUV lightcurves of the two pulsators. Results: Using the relative strength of the N iv and N v lines as a temperature indicator yields Teff values close to 60 000 K, significantly hotter than the temperatures previously derived. From the FUV light curves we were able to confirm the main pulsation periods known from optical data. Conclusions: With the UV spectra indicating higher effective temperatures than previously assumed, the sdO stars would now be found within the predicted instability strip. Such higher temperatures also provide consistent spectroscopic masses for both the cool and hot EHB stars of our previously studied sample. Based on observations (proposal GO-13707) with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS5-26666.

  7. Detailed abundance analysis of five field blue horizontal-branch stars

    NASA Astrophysics Data System (ADS)

    Kafando, I.; LeBlanc, F.; Robert, C.

    2016-06-01

    Previous studies have shown that hot blue horizontal-branch (BHB) stars in globular clusters present abundance anomalies of certain chemical elements in their atmosphere; some metals are overabundant while helium is underabundant. Vertical stratification of chemical species, including iron, is also found in the atmosphere of a number of these objects. The aim of our work is to do a detailed abundance analysis of BHB stars found in the field. We studied the stars HD 128801, HD 143459, HD 213781, and HZ 27, using our high-resolution spectra in the visible region obtained with ESPaDOnS at the Canada-France-Hawaii Telescope, and also Feige 86, using existing Ultraviolet and Visual Echelle Spectrograph visible spectra from the ESO archives. We searched for vertical stratification of the elements identified in our five stars, with the ZEEMAN2 code and stellar model atmospheres of PHOENIX. We confirm here the star rotational and radial velocities previously found, along with their average abundances. For the three cooler stars in our sample (HD 128801, HD 143459, and HZ 27), most elements detected are underabundant. For the two hotter stars (Feige 86 and HD 213781), the abundances of most elements are near or above their solar value. Of all the elements studied, only phosphorus is clearly found to be vertically stratified in the atmosphere of HD 213781. Marginal indications of vertical stratification of iron is observed for Feige 86. The chemical properties of the five field BHB stars are consistent with those of their globular-cluster counterparts.

  8. Rapidly Pulsating Hot Subdwarfs in ω Centauri: A New Instability Strip on the Extreme Horizontal Branch?

    NASA Astrophysics Data System (ADS)

    Randall, S. K.; Calamida, A.; Fontaine, G.; Bono, G.; Brassard, P.

    2011-08-01

    Pulsating extreme horizontal branch (EHB) stars offer the unique opportunity to use asteroseismology to probe their fundamental parameters and thus constrain one of the more poorly understood phases of stellar evolution. However, they have been observed only among the field population, which necessarily prevents asteroseismological tools from being applied to globular cluster EHB stars. We launched a search for rapid EHB pulsators in ω Cen on the basis of fast time-series photometry obtained with EFOSC2 at the New Technology Telescope. Fourier analysis uncovered four multi-mode oscillators with rather similar periods between 84 and 124 s and amplitudes up to 2.7% of the mean stellar brightness. Initially, it was assumed that these stars constitute the globular cluster counterparts to the EC 14026 stars, rapid subdwarf B pulsators with T eff ~ 31,000 K that have been extensively studied among the field population, yet a subsequent atmospheric analysis of FORS MXU spectra reveals effective temperatures closely clustered around 50,000 K, implying that the four ω Cen variables are in fact helium-poor subdwarf O (sdO) stars rather than EC 14026 pulsators. It remains to be seen whether they are related to the one significantly hotter sdO oscillator known among the field star population, or belong to a hitherto unknown class of stellar pulsator that can now be subjected to asteroseismological scrutiny. Based on observations collected at the European Organisation for Astronomical Research in the Southern Hemisphere, Chile (proposal ID 083.D-0833 and 386.D-0669).

  9. Vertical abundance stratification in the blue horizontal branch star HD 135485

    NASA Astrophysics Data System (ADS)

    Khalack, V. R.; Leblanc, F.; Bohlender, D.; Wade, G. A.; Behr, B. B.

    2007-05-01

    Context: It is commonly believed that the observed overabundances of many chemical species relative to the expected cluster metallicity in blue horizontal branch (BHB) stars appear as a result of atomic diffusion in the photosphere. The slow rotation of BHB stars (with T_eff > 11 500 K), typically v sin{i} < 10 km s-1, is consistent with this idea. Aims: In this work we search for observational evidence of vertical chemical stratification in the atmosphere of HD 135485. If this evidence exists, it will demonstrate the importance of atomic diffusion processes in the atmospheres of BHB stars. Methods: We undertake an extensive abundance stratification analysis of the atmosphere of HD 135485, based on recently acquired high resolution and S/N CFHT ESPaDOnS spectra and a McDonald-CE spectrum. Results: Our numerical simulations show that nitrogen and sulfur reveal signatures of vertical abundance stratification in the stellar atmosphere. It appears that the abundances of these elements increase toward the upper atmosphere. This fact cannot be explained by the influence of microturbulent velocity, because oxygen, carbon, neon, argon, titanium and chromium do not show similar behavior and their abundances remain constant throughout the atmosphere. It seems that the iron abundance may increase marginally toward the lower atmosphere. This is the first demonstration of vertical abundance stratification of metals in a BHB star. Based on observations made with ESPaDOnS at the Canada-France-Hawaii Telescope (CFHT) operated by the National Research Council (NRC) of Canada, the Institut des Sciences de l'Univers of the Centre National de la Recherche Scientifique (CNRS) and the University of Hawaii and on observations made with Echelle Spectrograph on the McDonald Observatory 2.1-m Otto Struve Telescope. Full Table 2 is only available in electronic form at http://www.aanda.org

  10. THE KINEMATICS AND CHEMISTRY OF RED HORIZONTAL BRANCH STARS IN THE SAGITTARIUS STREAMS

    SciTech Connect

    Shi, W. B.; Chen, Y. Q.; Carrell, K.; Zhao, G. E-mail: cyq@bao.ac.cn E-mail: gzhao@nao.cas.cn

    2012-06-01

    We have selected 556 red horizontal branch stars along the streams of the Sagittarius (Sgr) dwarf galaxy from Sloan Digital Sky Survey DR7 spectroscopic data using a theoretical model. The metallicity and {alpha}-element distributions are investigated for stars in the Sgr streams and for Galactic stars at the same locations. We find that the Sgr stars have two peaks in the metallicity distribution while the Galactic stars have a more prominent metal-poor peak. Meanwhile, [{alpha}/Fe] ratios of the Sgr stars are lower than those of the Galactic stars. Among the Sgr stars, we find a difference in the metallicity distribution between the leading and trailing arms of the Sgr tidal tails. The metallicity and [{alpha}/Fe] distribution of the leading arm is similar to that of the Galaxy. The trailing arm is composed mainly of a metal-rich component and [{alpha}/Fe] is obviously lower than that of the Galactic stars. The metallicity gradient is -(1.8 {+-} 0.3) Multiplication-Sign 10{sup -3} dex deg{sup -1} in the first wrap of the trailing arm and -(1.5 {+-} 0.4) Multiplication-Sign 10{sup -3} dex deg{sup -1} in the first wrap of the leading arm. No significant gradient exists along the second wraps of the leading or trailing arms. It seems that the Sgr dwarf galaxy initially lost the metal-poor component in the second wrap (older) arms due to the tidal force of our Galaxy and then the metal-rich component is disrupted in the first wrap (younger) arms. Finally, we found that the velocity dispersion of the trailing arm from 88 Degree-Sign < {Lambda}{sub Sun} < 112 Degree-Sign is {sigma} = 9.808 {+-} 1.0 km s{sup -1}, which is consistent with previous work in the literature.

  11. ANCIENT STARS BEYOND THE LOCAL GROUP: RR LYRAE VARIABLES AND BLUE HORIZONTAL BRANCH STARS IN SCULPTOR GROUP DWARF GALAXIES

    SciTech Connect

    Da Costa, G. S.; Jerjen, H.; Rejkuba, M.; Grebel, E. K.

    2010-01-10

    We have used Hubble Space Telescope Advanced Camera for Surveys images to generate color-magnitude diagrams that reach below the magnitude of the horizontal branch in the Sculptor Group dwarf galaxies ESO294-010 and ESO410-005. In both diagrams, blue horizontal branch stars are unambiguously present, a signature of the existence of an ancient stellar population whose age is comparable to that of the Galactic halo globular clusters. The result is reinforced by the discovery of numerous RR Lyrae variables in both galaxies. The occurrence of these stars is the first direct confirmation of the existence of ancient stellar populations beyond the Local Group and indicates that star formation can occur at the earliest epochs even in low-density environments.

  12. Controlling the morphology of multi-branched gold nanoparticles

    NASA Astrophysics Data System (ADS)

    Ahmed, Waqqar; Kooij, E. Stefan; van Silfhout, Arend; Poelsema, Bene

    2010-03-01

    We demonstrate a simple and versatile way to achieve high yield synthesis of shape- and size-controlled multi-branched gold nanoparticles (MBNPs). Control over the shape of the MBNPs was achieved by varying the ratio of gold to the mild reducing agent ascorbic acid, using a seed-mediated growth approach. Higher ascorbate concentrations resulted in the smoothing of branches, leading to the yield of relatively more isotropic particles. Furthermore, we found that using much higher silver concentrations in the growth solution resulted in the formation of rod-shaped micro-features together with MBNPs; we postulate them to be cetyltrimethyl ammonium silver bromide crystals. The as-prepared MBNPs show interesting tunable optical properties that are strongly influenced by the particle shape. The results are discussed in terms of plasmon coupling between the core and branches of the MBNPs.

  13. CLASP1 regulates endothelial cell branching morphology and directed migration.

    PubMed

    Myer, Nicole M; Myers, Kenneth A

    2017-08-31

    Endothelial cell (EC) branching is critically dependent upon the dynamic nature of the microtubule (MT) cytoskeleton. Extracellular matrix (ECM) mechanosensing is a prominent mechanism by which cytoskeletal reorganization is achieved; yet how ECM-induced signaling is able to target cytoskeletal reorganization intracellularly to facilitate productive EC branching morphogenesis is not known. Here, we set out to test the hypothesis that the composition and density of the ECM drive the regulation of MT growth dynamics in ECs by targeting the MT stabilizing protein, CLASP1. High-resolution fluorescent microscopy coupled with computational image analysis reveal that CLASP1 promotes slow MT growth on glass ECMs and promotes short-lived MT growth on high-density collagen-I and fibronectin ECMs. Within EC branches, engagement of either high-density collagen or high-density fibronectin ECMs results in reduced MT growth speeds, while CLASP1-dependent effects on MT dynamics promotes elevated numbers of short, branched protrusions that guide persistent and directional EC migration. © 2017. Published by The Company of Biologists Ltd.

  14. Spectral Calibration and Kinematic Properties of the Field Horizontal Branch Stars

    NASA Astrophysics Data System (ADS)

    Wilhelm, Ronald Joseph

    1995-01-01

    An understanding of the kinematic properties of the Galactic halo is an essential component to the ultimate understanding of the Galactic formation history. The blue field horizontal branch stars (FHB) are excellent stellar probes with which to explore these properties. The FHB stars are both intrinsically luminous, which allows kinematic exploration beyond the confines of the local solar neighborhood, and numerous, which is important for good statistical results. In the past, however, isolating a pure sample of FHB stars from their main sequence, A-star, counterparts has proven to be a difficult and highly uncertain task leaving the FHB kinematic results open to skepticism. This dissertation explores the kinematic properties of an FHB sample identified through the use of a new spectral calibration technique. Medium resolution (1-2 A) spectroscopic and UBV photometric observations have been completed for 1213 FHB and main sequence A-type stars (FHB/A) drawn from the candidates in the HK objective prism surveys of Beers et al. A new spectral calibration was developed using synthetic spectra and colors to calculate the physical parameters for the program stars. The corresponding parameter uncertainties of sigma Teff= +/-250 K, sigma log g=+/-0.25, and sigma[ Fe/H]= +/-0.30, are sufficient to push the stellar class misidentifications below 10%. A statistical kinematic analysis of the FHB stars indicates the halo is composed of at least two components. The dominant component is flattened with a vertical velocity dispersion of ~70 km/s and has a mild pro-grade systemic rotation of ~ 20 km/s. The second appears to have a more isotropic velocity ellipsoid and a systemic counter-rotation of {~-90} km/s. The kinematics of the metal-poor main sequence A-stars (BMP) indicate an isotropic velocity ellipsoid of ~90 km/s and a systemic rotation of ~90 km/s. These values are different from either the halo or thick-disk populations. The kinematic evidence from the FHB stars

  15. Chronography of the Milky Way's Halo System with Field Blue Horizontal-Branch Stars

    NASA Astrophysics Data System (ADS)

    Beers, Timothy C.; Placco, Vinicius M.; Carollo, Daniela; Santucci, Rafael; Rossi, Siliva; Lee, Young Sun; Denissenkov, Pavel; Tumlinson, Jason; Tissera, Patricia; Lentner, Geoffrey

    2016-01-01

    In a pioneering effort, Preston et al. (1991, AJ 375, 121) reported that the colors of blue horizontal-branch (BHB) stars in the halo of the Galaxy shift with distance, from regions near the Galactic center to about 12 kpc away, and interpreted this as a correlated variation in the ages of halo stars, from older to younger, spanning a range of a few Gyrs. We have applied this approach to a sample of some 4700 spectroscopically confirmed BHB stars selected from the Sloan Digital Sky Survey to produce the first "chronographic map" of the halo of the Galaxy.We demonstrate that the mean de-reddened g-r color increases outward in the Galaxy from -0.22 to -0.08 (over a color window spanning [-0.3:0.0]) from regions close to the Galactic center to ~40 kpc, independent of the metallicity of the stars. Models of the expected shift in the color of the field BHB stars based on modern stellar evolutionary codes confirm that this color gradient can be associated with an age difference of roughly 2-2.5 Gyrs, with the oldest stars concentrated in the central ~15 kpc of the Galaxy. Within this centralregion, which we refer to as the Ancient Chronographic Sphere (ACS), the age difference spans a mean color range of about 0.05 mag (~0.8 Gyrs). Interestingly, the ACS extends far enough to include the Solar Neighborhood, suggesting that ancient metal-poor stars should be readily detectable in the vicinity of the Sun. Furthermore, we show that chronographic maps can be used to identify individual substructures, such as the Sagittarius Stream, and overdensities in the direction of Virgo and Monoceros, based on the observed contrast in their mean BHB colors with respect to the foreground/background field population.We acknowledge partial support from the grant PHY 14-30152; Physics Frontier Center/JINA Center for the Evolution of the Elements (JINA-CEE), awarded by the US National Science Foundation.

  16. Hot horizontal branch stars in NGC 288 - effects of diffusion and stratification on their atmospheric parameters

    NASA Astrophysics Data System (ADS)

    Moehler, S.; Dreizler, S.; LeBlanc, F.; Khalack, V.; Michaud, G.; Richer, J.; Sweigart, A. V.; Grundahl, F.

    2014-05-01

    Context. NGC 288 is a globular cluster with a well-developed blue horizontal branch (HB) covering the u-jump that indicates the onset of diffusion. It is therefore well suited to study the effects of diffusion in blue HB stars. Aims: We compare observed abundances with predictions from stellar evolution models calculated with diffusion and from stratified atmospheric models. We verify the effect of using stratified model spectra to derive atmospheric parameters. In addition, we investigate the nature of the overluminous blue HB stars around the u-jump. Methods: We defined a new photometric index sz from uvby measurements that is gravity-sensitive between 8000 K and 12 000 K. Using medium-resolution spectra and Strömgren photometry, we determined atmospheric parameters (Teff, log g) and abundances for the blue HB stars. We used both homogeneous and stratified model spectra for our spectroscopic analyses. Results: The atmospheric parameters and masses of the hot HB stars in NGC 288 show a behaviour seen also in other clusters for temperatures between 9000 K and 14 000 K. Outside this temperature range, however, they instead follow the results found for such stars in ω Cen. The abundances derived from our observations are for most elements (except He and P) within the abundance range expected from evolutionary models that include the effects of atomic diffusion and assume a surface mixed mass of 10-7 M⊙. The abundances predicted by stratified model atmospheres are generally significantly more extreme than observed, except for Mg. When effective temperatures, surface gravities, and masses are determined with stratified model spectra, the hotter stars agree better with canonical evolutionary predictions. Conclusions: Our results show definite promise towards solving the long-standing problem of surface gravity and mass discrepancies for hot HB stars, but much work is still needed to arrive at a self-consistent solution. Based on observations with the ESO Very Large

  17. The horizontal branch luminosity vs. metallicity in M 31 globular clusters

    NASA Astrophysics Data System (ADS)

    Federici, L.; Cacciari, C.; Bellazzini, M.; Fusi Pecci, F.; Galleti, S.; Perina, S.

    2012-08-01

    Context. Thanks to the outstanding capabilites of the HST, our current knowledge about the M 31 globular clusters (GCs) is similar to our knowledge of the Milky Way GCs in the 1960s - 1970s, which set the basis for studying the halo and galaxy formation using these objects as tracers, and established their importance in defining the cosmic distance scale. Aims: We intend to derive a new calibration of the MV(HB)-[Fe/H] relation by exploiting the large photometric database of old GCs in M 31 in the HST archive. Methods: We collected the BVI data for 48 old GCs in M 31 and analysed them by applying the same methods and procedures to all objects. We obtained a set of homogeneous colour-magnitude diagrams (CMDs) that were best-fitted with the fiducial CMD ridge lines of selected Milky Way template GCs. Reddening, metallicity, horizontal branch (HB) luminosity and distance were determined self-consistently for each cluster. Results: There are three main results of this study: i) the relation MV(HB) = 0.25( ± 0.02)[Fe/H] + 0.89( ± 0.03), which is obtained from the above parameters and is calibrated on the distances of the template Galactic GCs; ii) the distance modulus to M 31 of (m - M)0 = 24.42 ± 0.06 mag, obtained by normalising this relation at the reference value of [Fe/H] = -1.5 to a similar relation using V0(HB). This is the first determination of the distance to M 31 based on the characteristics of its GC system, which is calibrated on Galactic GCs, iii) the distance to the Large Magellanic Cloud (LMC), which is estimated to be 18.54 ± 0.07 mag as a consequence of the previous results. These values agree excellently with the most recent estimate based on HST parallaxes of Galactic Cepheid and RR Lyrae stars, as well as with recent methods. Based on observations made with the NASA/ESA Hubble Space Telescope, obtained from the Hubble Legacy Archive, which is a collaboration between the Space Telescope Science Institute (STScI/NASA), the Space Telescope European

  18. Level of helium enhancement among M3's horizontal branch stars

    NASA Astrophysics Data System (ADS)

    Valcarce, A. A. R.; Catelan, M.; Alonso-García, J.; Contreras Ramos, R.; Alves, S.

    2016-05-01

    Context. The color and luminosity distribution of horizontal branch (HB) stars in globular clusters (GCs) are sensitive probes of the original helium abundances of those clusters. In this sense, recently the distributions of HB stars in GC color-magnitude diagrams (CMDs) have been extensively used as indicators of possible variations in the helium content Y among the different generations of stars within individual GCs. However, recent analyses based on visual and near-ultraviolet (UV) CMDs have provided conflicting results. Aims: To clarify the situation, we address the optimum ranges of applicability (in terms of the Teff range covered by the HB stars) for visual and near-UV CMDs, as far as application of this "HB Y test" goes. Methods: We considered both Strömgren and Hubble Space Telescope (HST) bandpasses. In particular, we focus on the F336W filter of the HST, but also discuss several bluer UV bandpasses, such as F160BW, F255W, and F300W. Using the Princeton-Goddard-PUC (PGPUC) code, we computed a large set of zero-age HB (ZAHB) loci and HB evolutionary models for masses ranging from MHB = 0.582 to 0.800 M⊙, assuming an initial helium abundance Y = 0.246, 0.256, and 0.266, with a global metallicity Z = 0.001. The results of these calculations were compared against the observations of M3 (NGC 5272), with special attention on the y vs. (b - y) and F336W vs. (F336W-F555W) CMDs. Results: Our results indicate that, from an evolutionary perspective, the distributions of HB stars in the y vs. (b - y) plane can be a reliable indicator of the He content in cool blue HB (BHB) stars, particularly when a differential comparison between blue and red HB stars is carried out in the range Teff ≲ 8300 K. Conversely, we demonstrate that CMDs using the F336W filter have a much less straightforward interpretation at the cool end of the BHB because the distributions of HB stars in the F336W vs. (F336W-F555W) plane, for instance, are affected by a triple degeneracy effect. In

  19. HST/ACS color-magnitude diagrams of candidate intermediate-age M 31 globular clusters. The role of blue horizontal branches

    NASA Astrophysics Data System (ADS)

    Perina, S.; Galleti, S.; Fusi Pecci, F.; Bellazzini, M.; Federici, L.; Buzzoni, A.

    2011-07-01

    We present deep (V ≃ 28.0) BV photometry obtained with the wide field channel of the Advanced Camera for Surveys on board HST for four M 31 globular clusters that were identified as candidate intermediate-age (age ~ 1-9 Gyr) by various authors, based on their integrated spectra and/or broad/intermediate-band colors. Two of them (B292 and B350) display an obvious blue horizontal branch, indicating that they are as old as the oldest Galactic globulars. On the other hand, for the other two (B058 and B337), which display red horizontal branches, it was not possible either to confirm or disconfirm the age estimate from integrated spectra. The analysis of the distribution in the spectral indices Mg2 and Hβ of the M 31 and Milky Way clusters whose horizontal branch can be classified as red or blue based on existing CMDs, strongly suggests that classical age diagnostics from integrated spectra may be significantly influenced by the HB morphology of the clusters and can lead to erroneous age-classifications. We also provide the CMD for another two clusters that fall into the field of the main targets, B336, an old and metal-poor globular with a significant population of RR Lyrae variables, and the newly discovered B531, a cluster with a very red red giant branch. Based on observations made with the NASA/ESA Hubble Space Telescope, obtained from the data archive at the Space Telescope Science Institute. STScI is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555. These observations are associated with program GO-10631 [P.I.: T. Puzia].Photometric catalogs are 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/531/A155 and at http://www.bo.astro.it/M31/hstcatalog/

  20. Spectral Calibration and Kinematic Properties of the Field Horizontal Branch Stars

    NASA Astrophysics Data System (ADS)

    Wilhelm, Ronald

    1996-08-01

    An understanding of the kinematic properties of the Galactic halo is an essential component to the ultimate understanding of the Galactic formation history. The blue field horizontal branch stars (FHB) are excellent stellar probes with which to explore these properties. The FHB stars are both intrinsically luminous, which allows kinematic exploration beyond the confines of the local solar neighborhood, and numerous, which is important for good statistical results. In the past, however, isolating a pure sample of FHB stars from their main sequence, A-star, counter-parts has proven to be a difficult and highly uncertain task leaving the FHB kinematic results open to skepticism. This dissertation explores the kinematic properties of an FHB sample identified through the use of a new spectral calibration technique. Follow up medium resolution (1-2 A), low S/N (10 < S/N < 20) spectroscopy and UBV photometry have been obtained for 1213 FHB and main sequence A-type stars (FHB/A) drawn from the candidates in the HK objective prism surveys of Beers et al. (1988, ApJS, 67, 461). This data was used to determine stellar radial velocities, metal abundance, and to separate the FHB/A candidates, by exploiting the inherent differences in surface gravity between the two classes. To determine the stellar physical parameters, an 833 point calibration grid was constructed spanning the range of T_eff, log g and [Fe/H] for the program objects. The grid includes the widths of H-delta, H-gamma and the CaII K line, determined from synthetic spectra, and the Kurucz Atlas9 color relations. A calibration technique was then developed which gives varying weights to the observables in accord with their dependency on the physical parameters. Comparison to standard stars, noise-injected synthetic spectra, and globular cluster HB stars indicate an uncertainty in the derived physical parameters of sigma T_eff = +/- 250 K, sigma log g = +/- 0.25, and sigma [Fe/H] = +/- 0.30. Results from the noisy

  1. HUBBLE SPACE TELESCOPE Observations of Galactic Globular Cluster Cores. II. NGC 6273 and the Problem of Horizontal-Branch Gaps

    NASA Astrophysics Data System (ADS)

    Piotto, G.; Zoccali, M.; King, I. R.; Djorgovski, S. G.; Sosin, C.; Rich, R. M.; Meylan, G.

    1999-10-01

    We present observations of the center of the Galactic globular cluster NGC 6273, obtained with the Hubble Space Telescope Wide Field Planetary Camera 2 as part of the snapshot program GO-7470. A BV color-magnitude diagram (CMD) for ~28,000 stars is presented and discussed. The most prominent feature of the CMD, identified for the first time in this paper, is the extended horizontal-branch blue tail (EBT) with a clear double-peaked distribution and a significant gap. The EBT of NGC 6273 is compared with the EBTs of seven other globular clusters for which we have a CMD in the same photometric system. From this comparison, we conclude that all the globular clusters in our sample with an EBT show at least one gap along the horizontal branch, which could have similar origins. A comparison with theoretical models suggests that at least some of these gaps may be occurring at a particular value of the stellar mass, common to a number of different clusters. From the CMD of NGC 6273 we obtain a distance modulus (m-M)_V=16.27+/-0.20. We also estimate an average reddening E(B-V)=0.47+/-0.03, though the CMD is strongly affected by differential reddening, with the relative reddening spanning a ΔE(B-V)~0.2 mag in the WFPC2 field. A luminosity function for the evolved stars in NGC 6273 is also presented and compared with the most recent evolutionary models.

  2. Multiple populations on the horizontal branch. I - Observations in the (log g, log T/eff/)-diagram

    NASA Technical Reports Server (NTRS)

    Crocker, Deborah A.; Rood, Robert T.; O'Connell, Robert W.

    1988-01-01

    Log T(eff) and log g have been determined for blue horizontal branch (HB) stars in the globular clusters M15, M3, M5, M92, and NGC 288 as a first step in determining the physical origin of gaps or bimodal distributions in the blue horizontal branches of a number of globular clusters. The (log g, log T/eff/) diagram for the 'normal' HB cluster M5 matches the standard theory quite well. The stars blueward of the gap in NGC 288 and the blue extension of the M3 HB have significantly lower gravity than predicted by the standard theory. The cooler stars in M3 agree well with the standard theory while those of NGC 2988 lie at slightly lower gravity. In M92, the sequence of stars is broadened toward the low gravity side more than expected either from standard evolution or from observational error. The data for M15 are too scattered to support firm conclusions but seem consistent with NGC 288.

  3. Kinematic structure in the Galactic halo at the North Galactic Pole: RR Lyrae and blue horizontal branch stars show different kinematics

    NASA Astrophysics Data System (ADS)

    Kinman, T. D.; Cacciari, C.; Bragaglia, A.; Buzzoni, A.; Spagna, A.

    2007-03-01

    Radial velocities and proper motions (derived from the GSC-II data base) are given for 38 RR Lyrae (RRL) stars and 79 blue horizontal branch (BHB) stars in a ~200 deg2 area around the North Galactic Pole (NGP). Both heliocentric (UVW) and galactocentric (VR, Vφ, Vz) space motions are derived for these stars using a homogeneous distance scale consistent with (m - M)0 = 18.52 for the Large Magellanic Cloud (LMC). An analysis of the 26 RRL and 52 BHB stars whose height (Z) above the plane is less than 8 kpc shows that this halo sample is not homogeneous. Our BHB sample (like that of Sirko et al.) has a zero galactic rotation (Vφ) and roughly isotropic velocity dispersions. The RRL sample shows a definite retrograde rotation (Vφ = -95 +/- 29 kms-1) and non-isotropic velocity dispersions. The combined BHB and RRL sample has a retrograde galactic rotation (V) that is similar to that found by Majewski for his sample of subdwarfs in Selected Area (SA) 57. The velocity dispersion of the RRL stars that have a positive W motion is significantly smaller than the dispersion of those `streaming down' with a negative W. Also, the ratio of RRL to BHB stars is smaller for the sample that has positive W. Our halo sample occupies 10.4 kpc3 at a mean height of 5 kpc above the Galactic plane. In this volume, one component (rich in RRL stars) shows retrograde rotation and the streaming motion that we associate with the accretion process. The other component (traced by the BHB stars) shows essentially no rotation and less evidence of streaming. These two components have horizontal branch (HB) morphologies that suggest that they may be the field star equivalents of the young and old halo globular clusters, respectively. Clearly, it is quite desirable to use more than one tracer in any kinematic analysis of the halo.

  4. Patterns of morphological integration in marine modular organisms: supra-module organization in branching octocoral colonies.

    PubMed Central

    Sánchez, Juan Armando; Lasker, Howard R

    2003-01-01

    Despite the relative simplicity of their modular growth, marine invertebrates such as arborescent gorgonian octocorals (Octocorallia: Cnidaria) generate complex colonial forms. Colony form in these taxa is a consequence of modular (polyp) replication, and if there is a tight integration among modular and supramodular traits (e.g. polyp aperture, inter-polyp spacing, branch thickness, internode and branch length), then changes at the module level may lead to changes in colony architecture. Alternatively, different groups of traits may evolve semi-independently (or conditionally independent). To examine the patterns of integration among morphological traits in Caribbean octocorals, we compared five morphological traits across 21 species, correcting for the effects of phylogenetic relationships among the taxa. Graphical modelling and phylogenetic independence contrasts among the five morphological characters indicate two groups of integrated traits based on whether they were polyp- or colony-level traits. Although all characters exhibited bivariate associations, multivariate analyses (partial correlation coefficients) showed the strongest integration among the colony-level characters (internode distance and branch length). It is a quantitative demonstration that branching characters within the octocorals studied are independent of characters of the polyps. Despite the universally recognized modularity of octocorals at the level of polyps, branching during colony development may represent an emergent level of integration and modularity. PMID:14561292

  5. The field horizontal-branch star HD 109995: New results with coadded ultraviolet and optical region spectra

    NASA Technical Reports Server (NTRS)

    Adelman, S. J.; Leckrone, D. S.

    1985-01-01

    A comprehensive ultraviolet and optical region abundance analysis of the field horizontal branch Population 2 A-type star HD 109995 is described. Coaddition of IUE high dispersion images and DAO 6.5 A/mm IIaO spectrograms improved the signal-to-noise ratio of the data. We have identified ultraviolet lines whose analysis will provide more complete and accurate elemental abundances than those obtained from optical region spectra alone. A preliminary elemental abundance analysis of the optical region shows that log Z/Z (solar) approx. = -2. A first attempt to synthesize two Fe 2 ultraviolet resonance lines yields an iron abundance a few tenths of a deg higher than the average obtained from optical region Fe 2 lines.

  6. CCD time-series photometry of variable stars in globular clusters and the metallicity dependence of the horizontal branch luminosity

    NASA Astrophysics Data System (ADS)

    Arellano Ferro, A.; Bramich, D. M.; Giridhar, S.

    2017-04-01

    We describe and summarize the findings from our CCD time-series photometry of globular clusters (GCs) program and the use of difference image analysis (DIA) in the extraction of precise light curves down to V≍19 mag in crowded regions. We have discovered approximately 250 variable stars in a sample of 23 selected GCs. The absolute magnitude and [Fe/H] for each individual RR Lyrae is obtained via the Fourier decomposition of the light curve. An average of these parameters leads to the distance and metallicity of the host GCs. We present the mean [Fe/H], MV and distance for 26 GCs based exclusively on the RR Lyrae light curve Fourier decomposition technique on an unprecedented homogeneous scale. We also discuss the luminosity dependence of the horizontal branch (HB) via the MV-[Fe/H] relation. We find that this relation should be considered separately for the RRab and RRc stars.

  7. The far-ultraviolet energy distribution of two globular cluster blue horizontal-branch stars in M13

    NASA Technical Reports Server (NTRS)

    De Boer, K. S.; Code, A. D.

    1981-01-01

    The far-UV energy distribution of two blue horizontal-branch (BHB) stars detected in the nucleus of M13 is presented. Their continua can be characterized by a model atmosphere of an effective temperature of 15,000 to 20,000 K and log g = 4.5, and it follows that V is in the range 15.9-16.7 for these stars. Comparison with integrated photometry by OAO 2 and by ANS indicates that, at wavelengths smaller than 1800 A, the integrated light is from BHB stars only, of which M13 contains about 200. For these far-UV wavelengths, the color of the BHB stars is also very similar to the integrated color of the elliptical galaxy M87.

  8. The evolution of high-metallicity horizontal-branch stars and the origin of the ultraviolet light in elliptical galaxies

    NASA Technical Reports Server (NTRS)

    Horch, E.; Demarque, P.; Pinsonneault, M.

    1992-01-01

    Evolutionary calculations of high-metallicity horizontal-branch stars show that for the relevant masses and helium abundances, post-HB evolution in the HR diagram does not proceed toward and along the AGB, but rather toward a 'slow blue phase' in the vicinity of the helium-burning main sequence, following the extinction of the hydrogen shell energy source. For solar and twice solar metallicity, the blue phase begins during the helium shell-burning phase (in agreement with the work of Brocato and Castellani and Tornambe); for 3 times solar metallicity, it begins earlier, during the helium core-burning phase. This behavior differs from what takes place at lower metallicities. The implications for high-metallicity old stellar populations in the Galactic bulge and for the integrated colors of elliptical galaxies are discussed.

  9. The evolution of high-metallicity horizontal-branch stars and the origin of the ultraviolet light in elliptical galaxies

    NASA Astrophysics Data System (ADS)

    Horch, E.; Demarque, P.; Pinsonneault, M.

    1992-04-01

    Evolutionary calculations of high-metallicity horizontal-branch stars show that for the relevant masses and helium abundances, post-HB evolution in the HR diagram does not proceed toward and along the AGB, but rather toward a 'slow blue phase' in the vicinity of the helium-burning main sequence, following the extinction of the hydrogen shell energy source. For solar and twice solar metallicity, the blue phase begins during the helium shell-burning phase (in agreement with the work of Brocato and Castellani and Tornambe); for 3 times solar metallicity, it begins earlier, during the helium core-burning phase. This behavior differs from what takes place at lower metallicities. The implications for high-metallicity old stellar populations in the Galactic bulge and for the integrated colors of elliptical galaxies are discussed.

  10. The far-ultraviolet energy distribution of two globular cluster blue horizontal-branch stars in M13

    NASA Technical Reports Server (NTRS)

    De Boer, K. S.; Code, A. D.

    1981-01-01

    The far-UV energy distribution of two blue horizontal-branch (BHB) stars detected in the nucleus of M13 is presented. Their continua can be characterized by a model atmosphere of an effective temperature of 15,000 to 20,000 K and log g = 4.5, and it follows that V is in the range 15.9-16.7 for these stars. Comparison with integrated photometry by OAO 2 and by ANS indicates that, at wavelengths smaller than 1800 A, the integrated light is from BHB stars only, of which M13 contains about 200. For these far-UV wavelengths, the color of the BHB stars is also very similar to the integrated color of the elliptical galaxy M87.

  11. MAPPING THE GALACTIC HALO WITH BLUE HORIZONTAL BRANCH STARS FROM THE TWO-DEGREE FIELD QUASAR REDSHIFT SURVEY

    SciTech Connect

    De Propris, Roberto; Harrison, Craig D.; Mares, Peter J.

    2010-08-20

    We use 666 blue horizontal branch stars from the 2Qz Redshift Survey to map the Galactic halo in four dimensions (position, distance, and velocity). We find that the halo extends to at least 100 kpc in Galactocentric distance, and obeys a single power-law density profile of index {approx}-2.5 in two different directions separated by about 150{sup 0} on the sky. This suggests that the halo is spherical. Our map shows no large kinematically coherent structures (streams, clouds, or plumes) and appears homogeneous. However, we find that at least 20% of the stars in the halo reside in substructures and that these substructures are dynamically young. The velocity dispersion profile of the halo appears to increase toward large radii while the stellar velocity distribution is non-Gaussian beyond 60 kpc. We argue that the outer halo consists of a multitude of low luminosity overlapping tidal streams from recently accreted objects.

  12. The Hot Horizontal-Branch Stars in NGC288 - Effects of Diffusion and Stratification on Their Atmospheric Parameters*

    NASA Technical Reports Server (NTRS)

    Moehler, S.; Dreizler, S.; LeBlanc, F.; Khalack, V.; Michaud, G.; Richer, J.; Sweigart, Allen V.; Grundahl, F.

    2014-01-01

    Context. NGC288 is a globular cluster with a well developed blue horizontal branch covering the so-called u-jump which indicates the onset of diffusion. It is therefore well suited to study the effects of diffusion in blue horizontal branch (HB) stars. Aims. We compare observed abundances to predictions from stellar evolution models calculated with diffusion and from stratified atmospheric models. We verify the effect of using stratified model spectra to derive atmospheric parameters. In addition we investigate the nature of the overluminous blue HB stars around the u-jump. Methods. We define a new photometric index sz from uvby measurements that is gravity sensitive between 8 000K and 12 000 K. Using medium-resolution spectra and Stroemgren photometry we determine atmospheric parameters (Teff, logg) and abundances for the blue HB stars. We use both homogeneous and stratified model spectra for our spectroscopic analyses. Results. The atmospheric parameters and masses of the hot HB stars in NGC288 show a behaviour seen also in other clusters for temperatures between 9 000K and 14 000 K. Outside this temperature range, however, they follow rather the results found for such stars in (omega)Cen. The abundances derived from our observations are for most elements (except He and P) within the abundance range expected from evolutionary models that include the effects of atomic diffusion and assume a surface mixed mass of 10(exp -7) M. The abundances predicted by stratified model atmospheres are generally significantly more extreme than observed, except for Mg. The use of stratified model spectra to determine effective temperatures, surface gravities and masses moves the hotter stars to a closer agreement with canonical evolutionary predictions. Conclusions. Our results show definite promise towards solving the long-standing issue of surface gravity and mass discrepancies for hot HB stars, but there is still much work needed to arrive at a self-consistent solution.

  13. A Detailed Study of Giants and Horizontal Branch Stars in M68: Atmospheric Parameters and Chemical Abundances

    NASA Astrophysics Data System (ADS)

    Schaeuble, M.; Preston, G.; Sneden, C.; Thompson, I. B.; Shectman, S. A.; Burley, G. S.

    2015-06-01

    In this paper, we present a detailed high-resolution spectroscopic study of post main sequence stars in the globular cluster (GC) M68. Our sample, which covers a range of 4000 K in {{T}eff}, and 3.5 dex in log(g), is comprised of members from the red giant, red horizontal, and blue horizontal branch, making this the first high-resolution GC study covering such a large evolutionary and parameter space. Initially, atmospheric parameters were determined using photometric as well as spectroscopic methods, both of which resulted in unphysical and unexpected {{T}eff}, log(g), {{ξ }t}, and [Fe/H] combinations. We therefore developed a hybrid approach that addresses most of these problems, and yields atmospheric parameters that agree well with other measurements in the literature. Furthermore, our derived stellar metallicities are consistent across all evolutionary stages, with < [Fe/H]> = -2.42 (σ = 0.14) from 25 stars. Chemical abundances obtained using our methodology also agree with previous studies and bear all the hallmarks of GCs, such as a Na-O anti-correlation, constant Ca abundances, and mild r-process enrichment.

  14. Melatonin Inhibits Embryonic Salivary Gland Branching Morphogenesis by Regulating Both Epithelial Cell Adhesion and Morphology

    PubMed Central

    Miura, Jiro; Sakai, Manabu; Uchida, Hitoshi; Nakamura, Wataru; Nohara, Kanji; Maruyama, Yusuke; Hattori, Atsuhiko; Sakai, Takayoshi

    2015-01-01

    Many organs, including salivary glands, lung, and kidney, are formed by epithelial branching during embryonic development. Branching morphogenesis occurs via either local outgrowths or the formation of clefts that subdivide epithelia into buds. This process is promoted by various factors, but the mechanism of branching morphogenesis is not fully understood. Here we have defined melatonin as a potential negative regulator or “brake” of branching morphogenesis, shown that the levels of it and its receptors decline when branching morphogenesis begins, and identified the process that it regulates. Melatonin has various physiological functions, including circadian rhythm regulation, free-radical scavenging, and gonadal development. Furthermore, melatonin is present in saliva and may have an important physiological role in the oral cavity. In this study, we found that the melatonin receptor is highly expressed on the acinar epithelium of the embryonic submandibular gland. We also found that exogenous melatonin reduces salivary gland size and inhibits branching morphogenesis. We suggest that this inhibition does not depend on changes in either proliferation or apoptosis, but rather relates to changes in epithelial cell adhesion and morphology. In summary, we have demonstrated a novel function of melatonin in organ formation during embryonic development. PMID:25876057

  15. Liquid entrainment at an upward oriented vertical branch line from a horizontal pipe

    NASA Astrophysics Data System (ADS)

    Welter, Kent Byron

    Under simulated accident conditions, tees in the primary coolant loop of a Pressurized Water Reactor (PWR) can deviate from their original design purpose and become separators that effectively remove core heat sink capacity. This method of primary coolant removal is a phenomenological subset of phase separation known as liquid entrainment, whereby liquid is forced from its original path by the inertia of the gas. A comprehensive literature review revealed common deficiencies in previous studies. The Westinghouse AP600 advanced reactor design was chosen to assess the validity of entrainment models. Following a systematic scaling analysis of the prototypic design a model separate effects test was proposed and constructed at Oregon State University. Just under 100 tests were run to fill the deficiencies found in the literature review. New data from the Air-water Test Loop for Advanced Thermal-hydraulic Studies (ATLATS) could not be predicted by published correlations. A new theoretical model for predicting liquid entrainment onset and steady state entrainment was developed. Comparison with all available data shows a marked improvement for predicting the mass flow rate out the vertical branch.

  16. Shear-induced enhancements of crystallization kinetics and morphological transformation for long chain branched polylactides with different branching degrees

    PubMed Central

    Wang, Junyang; Bai, Jing; Zhang, Yaqiong; Fang, Huagao; Wang, Zhigang

    2016-01-01

    The effects of long chain branching (LCB) degree on the shear-induced isothermal crystallization kinetics of a series of LCB polylactides (LCB PLAs) have been investigated by using rotational rheometer, polarized optical microscopy (POM) and scanning electron microscopy (SEM). Dynamic viscoelastic properties obtained by small-amplitude oscillatory shear (SAOS) tests indicate that LCB PLAs show more broadened relaxation time spectra with increasing LCB degree. Upon a pre-shear at the shear rate of 1 s−1 LCB PLAs show much faster crystallization kinetics than linear PLA and the crystallization kinetics is enhanced with increasing LCB degree. By modeling the system as a suspension the quantitative evaluation of nucleation density can be derived from rheological experiments. The nucleation density is greatly enhanced with increasing LCB degree and a saturation in shear time is observed. Crystalline morphologies for LCB PLAs observed by POM and SEM demonstrate the enhancement of nucleation density with increasing LCB degree and a transformation from spherulitic to orientated crystalline morphologies. The observation can be ascribed to longer relaxation time of the longest macromolecular chains and broadened, complex relaxation behaviors due to the introduction of LCB into PLA, which is essential in stabilizing the orientated crystal nuclei after pre-shear. PMID:27246803

  17. Shear-induced enhancements of crystallization kinetics and morphological transformation for long chain branched polylactides with different branching degrees.

    PubMed

    Wang, Junyang; Bai, Jing; Zhang, Yaqiong; Fang, Huagao; Wang, Zhigang

    2016-06-01

    The effects of long chain branching (LCB) degree on the shear-induced isothermal crystallization kinetics of a series of LCB polylactides (LCB PLAs) have been investigated by using rotational rheometer, polarized optical microscopy (POM) and scanning electron microscopy (SEM). Dynamic viscoelastic properties obtained by small-amplitude oscillatory shear (SAOS) tests indicate that LCB PLAs show more broadened relaxation time spectra with increasing LCB degree. Upon a pre-shear at the shear rate of 1 s(-1) LCB PLAs show much faster crystallization kinetics than linear PLA and the crystallization kinetics is enhanced with increasing LCB degree. By modeling the system as a suspension the quantitative evaluation of nucleation density can be derived from rheological experiments. The nucleation density is greatly enhanced with increasing LCB degree and a saturation in shear time is observed. Crystalline morphologies for LCB PLAs observed by POM and SEM demonstrate the enhancement of nucleation density with increasing LCB degree and a transformation from spherulitic to orientated crystalline morphologies. The observation can be ascribed to longer relaxation time of the longest macromolecular chains and broadened, complex relaxation behaviors due to the introduction of LCB into PLA, which is essential in stabilizing the orientated crystal nuclei after pre-shear.

  18. Shear-induced enhancements of crystallization kinetics and morphological transformation for long chain branched polylactides with different branching degrees

    NASA Astrophysics Data System (ADS)

    Wang, Junyang; Bai, Jing; Zhang, Yaqiong; Fang, Huagao; Wang, Zhigang

    2016-06-01

    The effects of long chain branching (LCB) degree on the shear-induced isothermal crystallization kinetics of a series of LCB polylactides (LCB PLAs) have been investigated by using rotational rheometer, polarized optical microscopy (POM) and scanning electron microscopy (SEM). Dynamic viscoelastic properties obtained by small-amplitude oscillatory shear (SAOS) tests indicate that LCB PLAs show more broadened relaxation time spectra with increasing LCB degree. Upon a pre-shear at the shear rate of 1 s-1 LCB PLAs show much faster crystallization kinetics than linear PLA and the crystallization kinetics is enhanced with increasing LCB degree. By modeling the system as a suspension the quantitative evaluation of nucleation density can be derived from rheological experiments. The nucleation density is greatly enhanced with increasing LCB degree and a saturation in shear time is observed. Crystalline morphologies for LCB PLAs observed by POM and SEM demonstrate the enhancement of nucleation density with increasing LCB degree and a transformation from spherulitic to orientated crystalline morphologies. The observation can be ascribed to longer relaxation time of the longest macromolecular chains and broadened, complex relaxation behaviors due to the introduction of LCB into PLA, which is essential in stabilizing the orientated crystal nuclei after pre-shear.

  19. Functional morphology and biomechanics of branch-stem junctions in columnar cacti.

    PubMed

    Schwager, Hannes; Masselter, Tom; Speck, Thomas; Neinhuis, Christoph

    2013-12-07

    Branching in columnar cacti features morphological and anatomical characteristics specific to the subfamily Cactoideae. The most conspicuous features are the pronounced constrictions at the branch-stem junctions, which are also present in the lignified vascular structures within the succulent cortex. Based on finite-element analyses of ramification models, we demonstrate that these indentations in the region of high flexural and torsional stresses are not regions of structural weakness (e.g. allowing vegetative propagation). On the contrary, they can be regarded as anatomical adaptations to increase the stability by fine-tuning the stress state and stress directions in the junction along prevalent fibre directions. Biomimetic adaptations improving the functionality of ramifications in technical components, inspired, in particular, by the fine-tuned geometrical shape and arrangement of lignified strengthening tissues of biological role models, might contribute to the development of alternative concepts for branched fibre-reinforced composite structures within a limited design space.

  20. Streamer knotwilg branching: sudden transition in morphology of positive streamers in high-purity nitrogen

    NASA Astrophysics Data System (ADS)

    Heijmans, L. C. J.; Clevis, T. T. J.; Nijdam, S.; van Veldhuizen, E. M.; Ebert, U.

    2015-09-01

    We describe a peculiar branching phenomenon in positive repetitive streamer discharges in high purity nitrogen. We name it knotwilg branching after the Dutch word for a pollard willow tree. In a knotwilg branching a thick streamer suddenly splits into many thin streamers. Under some conditions this happens for all streamers in a discharge at about the same distance from the high-voltage electrode tip. At this distance, the thick streamers suddenly bend sharply and appear to propagate over a virtual surface surrounding the high-voltage electrode, rather than following the background electric field lines. From these bent thick streamers many, much thinner, streamers emerge that roughly follow the background electric field lines, creating the characteristic knotwilg branching. We have only found this particular morphology in high purity nitrogen at pressures in the range 50 to 200 mbar and for pulse repetition rates above 1 Hz; the experiments were performed for an electrode distance of 16 cm and for fast voltage pulses of 20 or 30 kV. These observations clearly disagree with common knowledge on streamer propagation. We have analyzed the data of several tens of thousands of discharges to clarify the phenomena. We also present some thoughts on how the ionization of the previous discharges could concentrate into some pre-ionization region near the needle electrode and create the knotwilg morphology, but we present no final explanation.

  1. THE RR LYRAE VARIABLES AND HORIZONTAL BRANCH OF NGC 6656 (M22) {sup ,}

    SciTech Connect

    Kunder, Andrea; Walker, Alistair R.; Paredes Alvarez, Leonardo; Stetson, Peter B.; Cassisi, Santi; Layden, Andrew; Bono, Giuseppe; Catelan, Márcio; Clem, James L.; Matsunaga, Noriyuki; Salaris, Maurizio; Lee, Jae-Woo; Chaboyer, Brian E-mail: mcatelan@astro.puc.cl

    2013-11-01

    The first calibrated broadband UBVI time-series photometry is presented for the RR Lyrae variable stars in NGC 6656 (M22), with observations spanning a range of 22 years. We have also redetermined the variability types and periods for the RR Lyrae stars identified previously by photographic observations, revising the number of fundamental-mode RR Lyrae variables (RR0) to 10 and the number of first-overtone variables (RR1) to 16. The mean periods of the RR0 and RR1 variables are (P) {sub RR0} = 0.66 ± 0.02 days and (P) {sub RR1} = 0.33 ± 0.01 days, respectively, supporting an Oosterhoff II classification for the cluster. The number ratio of RR1-type to all RR-type variables is N {sub 1}/N{sub RR} = 0.61, also consistent with an Oosterhoff II designation. Both the RR Lyrae stars' minimum light colors and the blue edge of the RR Lyrae instability strip suggest E( B – – V) = 0.36 ± 0.02 mag toward M22. Regarding the HB morphology of M22, we find (B-R)/(B+V+R) = +0.97 ± 0.1 and at least one ''gap'' located in an unusual part of the blue HB, in the middle of the so-called hot HB stars.

  2. The RR Lyrae Variables and Horizontal Branch of NGC 6656 (M22)

    NASA Astrophysics Data System (ADS)

    Kunder, Andrea; Stetson, Peter B.; Cassisi, Santi; Layden, Andrew; Bono, Giuseppe; Catelan, Márcio; Walker, Alistair R.; Paredes Alvarez, Leonardo; Clem, James L.; Matsunaga, Noriyuki; Salaris, Maurizio; Lee, Jae-Woo; Chaboyer, Brian

    2013-11-01

    The first calibrated broadband UBVI time-series photometry is presented for the RR Lyrae variable stars in NGC 6656 (M22), with observations spanning a range of 22 years. We have also redetermined the variability types and periods for the RR Lyrae stars identified previously by photographic observations, revising the number of fundamental-mode RR Lyrae variables (RR0) to 10 and the number of first-overtone variables (RR1) to 16. The mean periods of the RR0 and RR1 variables are langPrang RR0 = 0.66 ± 0.02 days and langPrang RR1 = 0.33 ± 0.01 days, respectively, supporting an Oosterhoff II classification for the cluster. The number ratio of RR1-type to all RR-type variables is N 1/NRR = 0.61, also consistent with an Oosterhoff II designation. Both the RR Lyrae stars' minimum light colors and the blue edge of the RR Lyrae instability strip suggest E( B - - V) = 0.36 ± 0.02 mag toward M22. Regarding the HB morphology of M22, we find (B-R)/(B+V+R) = +0.97 ± 0.1 and at least one "gap" located in an unusual part of the blue HB, in the middle of the so-called hot HB stars.

  3. Observations of the Hot Horizontal Branch Stars in the Metal-Rich Bulge Globular Cluster NGC 6388

    NASA Technical Reports Server (NTRS)

    Moehler, S.; Sweigart, A. V.

    2006-01-01

    The metal-rich bulge globular cluster NGC 6388 shows a distinct blue horizontal-branch tail in its colour-magnitude diagram (Rich et al. 1997) and is thus a strong case of the well-known 2nd Parameter Problem. In addition, its horizontal branch (HB) shows an upward tilt toward bluer colours, which cannot be explained by canonical evolutionary models. Several non-canonical scenarios have been proposed to explain these puzzling observations. In order to test the predictions of these scenarios, we have obtained medium resolution spectra to determine the atmospheric parameters of a sample of the blue HB stars in NGC 6388.Using the medium resolution spectra, we determine effective temperatures, surface gravities and helium abundances by fitting the observed Balmer and helium lines with appropriate theoretical stellar spectra. As we know the distance to the cluster, we can verify our results by determining masses for the stars. During the data reduction we took special care to correctly subtract the background, which is dominated by the overlapping spectra of cool stars. The cool blue tail stars in our sample with T(sub eff) approximately 10000 K have lower than canonical surface gravities, suggesting that these stars are, on average, approximately equal to 0.4 mag brighter than canonical HB stars in agreement with the observed upward slope of the HB in NGC 6388. Moreover, the mean mass of these stars agrees well with theoretical predictions. In contrast, the hot blue tail stars in our sample with T(sub eff) greater than or equal to 12000 K show significantly lower surface gravities than predicted by any scenario, which can reproduce the photometric observations. Their masses are also too low by about a factor of 2 compared to theoretical predictions. The physical parameters of the blue HB stars at about 10,000 K support the helium pollution scenario. The low gravities and masses of the hot blue tail stars, however, are probably caused by problems with the data reduction

  4. Observations of the Hot Horizontal Branch Stars in the Metal-Rich Bulge Globular Cluster NGC 6388

    NASA Technical Reports Server (NTRS)

    Moehler, S.; Sweigart, A. V.

    2006-01-01

    The metal-rich bulge globular cluster NGC 6388 shows a distinct blue horizontal-branch tail in its colour-magnitude diagram (Rich et al. 1997) and is thus a strong case of the well-known 2nd Parameter Problem. In addition, its horizontal branch (HB) shows an upward tilt toward bluer colours, which cannot be explained by canonical evolutionary models. Several non-canonical scenarios have been proposed to explain these puzzling observations. In order to test the predictions of these scenarios, we have obtained medium resolution spectra to determine the atmospheric parameters of a sample of the blue HB stars in NGC 6388.Using the medium resolution spectra, we determine effective temperatures, surface gravities and helium abundances by fitting the observed Balmer and helium lines with appropriate theoretical stellar spectra. As we know the distance to the cluster, we can verify our results by determining masses for the stars. During the data reduction we took special care to correctly subtract the background, which is dominated by the overlapping spectra of cool stars. The cool blue tail stars in our sample with T(sub eff) approximately 10000 K have lower than canonical surface gravities, suggesting that these stars are, on average, approximately equal to 0.4 mag brighter than canonical HB stars in agreement with the observed upward slope of the HB in NGC 6388. Moreover, the mean mass of these stars agrees well with theoretical predictions. In contrast, the hot blue tail stars in our sample with T(sub eff) greater than or equal to 12000 K show significantly lower surface gravities than predicted by any scenario, which can reproduce the photometric observations. Their masses are also too low by about a factor of 2 compared to theoretical predictions. The physical parameters of the blue HB stars at about 10,000 K support the helium pollution scenario. The low gravities and masses of the hot blue tail stars, however, are probably caused by problems with the data reduction

  5. Effect of thermal transport on spatiotemporal emergence of lamellar branching morphology during polymer spherulitic growth.

    PubMed

    Xu, Haijun; Keawwattana, Wirunya; Kyu, Thein

    2005-09-22

    Spatiotemporal emergence of lamellar branching morphology of polymer spherulite has been investigated theoretically in the framework of a phase field model by coupling a crystal solidification potential pertaining to a nonconserved crystal order parameter with a temperature field generated by latent heat of crystallization. A local free-energy density having an asymmetric double well has been utilized to account for a first-order phase transition such as crystallization. To account for the polymorphous nature of polymer crystallization, the phase field order parameter of crystal at the solidification potential of the double-well local free-energy density is modified to be supercooling dependent. The heat conduction equation, incorporating liberation of latent heat along the nonuniform solid-liquid interface, has led to directional growth of various hierarchical structures including lamella, sheaflike structure, and spherulite. Two-dimensional calculations have been carried out based on experimentally accessible material parameters and experimental conditions for the growth of syndiotactic polypropylene spherulite. The simulations illustrate that, under self-generated thermal field, the initial nucleus is anisotropic having lamellar stacks that transforms to a sheaflike structure and eventually to a lamellar branching morphology with a dual-eye-pocket texture at the core. It appears that the released latent heat is responsible for the lamellar side branching and splaying from the main lamellae. On the same token, the heat build-up seemingly prevents the interface boundaries of neighboring spherulites from over running on each other during impingement, thereby forming the grain boundary.

  6. Shape-controlled synthesis of NIR absorbing branched gold nanoparticles and morphology stabilization with alkanethiols.

    PubMed

    Van de Broek, B; Frederix, F; Bonroy, K; Jans, H; Jans, K; Borghs, G; Maes, G

    2011-01-07

    Gold nanoparticles are ideal candidates for clinical applications if their plasmon absorption band is situated in the near infrared region (NIR) of the electromagnetic spectrum. Various parameters, including the nanoparticle shape, strongly influence the position of this absorption band. The aim of this study is to produce stabilized NIR absorbing branched gold nanoparticles with potential for biomedical applications. Hereto, the synthesis procedure for branched gold nanoparticles is optimized varying the different synthesis parameters. By subsequent electroless gold plating the plasmon absorption band is shifted to 747.2 nm. The intrinsic unstable nature of the nanoparticles' morphology can be clearly observed by a spectral shift and limits their use in real applications. However, in this article we show how the stabilization of the branched structure can be successfully achieved by exchanging the initial capping agent for different alkanethiols and disulfides. Furthermore, when using alkanethiols/disulfides with poly(ethylene oxide) units incorporated, an increased stability of the gold nanoparticles is achieved in high salt concentrations up to 1 M and in a cell culture medium. These achievements open a plethora of opportunities for these stabilized branched gold nanoparticles in nanomedicine.

  7. Separated components of root exudate and cytosol stimulate different morphologically identifiable types of branching responses by arbuscular mycorrhizal fungi.

    PubMed

    Nagahashi, Gerald; Douds, David

    2007-04-01

    Two morphologically distinct hyphal branching responses by the AM fungus, Glomus intraradices, were stimulated by separated components of carrot root exudate. Complex branching up to the sixth order was induced by compounds most soluble in 35% methanol, whereas the formation of more lateral branches (second order) was stimulated by compounds most soluble in 70% methanol. This same 70% alcohol soluble fraction also stimulated a completely different type of branching pattern in another fungus, Gigaspora gigantea. This pattern consisted of a very periodic distribution of dense clusters of hyphal branches that had a very high degree of complexity. In contrast to exudate components, separated cytosolic components of carrot roots did not stimulate any of the observed hyphal branching patterns. Alcohol-soluble fractions actually inhibited hyphal tip growth of G. gigantea and induced the formation of "recovery" branches that were identical to those induced by an inhibitor found in the exudate of Chard (Beta vulgaris ssp. cicla), a non-host plant.

  8. Functional differentiation of trailing and leading forelimbs during locomotion on the ground and on a horizontal branch in the European red squirrel (Sciurus vulgaris, Rodentia).

    PubMed

    Schmidt, André

    2011-06-01

    Mammalian locomotion is characterized by the frequent use of in-phase gaits in which the footfalls of the left and right fore- or hindlimbs are unevenly spaced in time. Although previous studies have identified a functional differentiation between the first limb (trailing limb) and the second limb (leading limb) to touch the ground during terrestrial locomotion, the influence of a horizontal branch on limb function has never been explored. To determine the functional differences between trailing and leading forelimbs during locomotion on the ground and on a horizontal branch, X-ray motion analysis and force measurements were carried out in two European red squirrels (Sciurus vulgaris, Rodentia). The differences observed between trailing and leading forelimbs were minimal during terrestrial locomotion, where both limbs fulfill two functions and go through a shock-absorbing phase followed by a generating phase. During locomotion on a horizontal branch, European red squirrels reduce speed and all substrate reaction forces transmitted may be due to the reduction of vertical oscillation of the center of mass. Further adjustments during locomotion on a horizontal branch differ significantly between trailing and leading forelimbs and include limb flexion, lead intervals, limb protraction and vertical displacement of the scapular pivot. Consequently, trailing and leading forelimbs perform different functions. Trailing forelimbs function primarily as shock-absorbing elements, whereas leading forelimbs are characterized by a high level of stiffness. This functional differentiation indicates that European red squirrels 'test' the substrate for stability with the trailing forelimb, while the leading forelimb responds to or counteracts swinging or snapping branches. Copyright © 2011 Elsevier GmbH. All rights reserved.

  9. Duration of the Early Galactic Formation Epoch: HST Photometry for Red-Horizontal Branch Clusters in the Outer Halo

    NASA Astrophysics Data System (ADS)

    Hesser, J. E.; Stetson, P. B.; McClure, R. D.; van den Bergh, S.; Bolte, M.; Harris, W. E.; van den Berg, D. A.; Bell, R. A.; Fahlman, G. G.; Richer, H. B.; Bond, H. E.

    1997-12-01

    Last year we presented evidence from HST photometry of the low-metallicity cluster NGC 2419 (M_V = -9.5, R_⊙ ~ 90 kpc, [Fe/H] = -2.2) that globular cluster formation began at essentially the same time throughout a region of the Galactic halo now almost 200 kpc in diameter (Harris et al. 1997 AJ 114, 1030). We now turn to the time spread of halo formation, with the ultimate aim of addressing the relative roles of mergers over the first 4 or more Gyrs (Searle & Zinn 1978, ApJ, 225, 357; Lee, Demarque & Zinn 1994 ApJ, 423, 248) versus models favoring a rapid collapse (Eggen, Lynden-Bell & Sandage 1962, ApJ, 236, 748; Stetson, VandenBerg & Bolte 1996, PASP, 108, 560), or some combination of those and other processes. We provide the first reliable measurements from the giant branch through the main-sequence turnoffs of red-horizontal-branch clusters in the outer halo, which are frequently postulated to be younger than most other globular clusters. From WFPC2 F555W (`V') and F814W (`I') photometry for Pal 3 (M_V = -5.2, R_⊙ ~ 87 kpc), Pal 4 (M_V = -5.8, R_⊙ ~ 98 kpc), and Eridanus (M_V = -4.8, R_⊙ ~ 78 kpc), all with [Fe/H] ~ -1.5, we estimate their relative ages by making differential comparisons among them and with respect to inner-halo objects of, presumably, comparable chemical compositions. It seems likely at this stage of our analysis that (a) the three clusters are the same age to our measurement precision of ~ 1 Gyr, and, (b) the CMDs of all three outer halo clusters differ from those of M 3 and M 5 (our template clusters of similar metallicity), in the sense that the outer halo clusters are younger by ~ 3 Gyr, or they are ~ 0.5 dex more metal-rich than currently thought. Large uncertainties in chemical compositions (He, [alpha /Fe], [CNO/Fe]) for outer halo and template clusters alike mask the true interpretation.

  10. Kinematics of the Stellar Halo and the Mass Distribution of the Milky Way Using Blue Horizontal Branch Stars

    NASA Astrophysics Data System (ADS)

    Kafle, Prajwal R.; Sharma, Sanjib; Lewis, Geraint F.; Bland-Hawthorn, Joss

    2012-12-01

    Here, we present a kinematic study of the Galactic halo out to a radius of ~60 kpc, using 4664 blue horizontal branch stars selected from the SDSS/SEGUE survey to determine key dynamical properties. Using a maximum likelihood analysis, we determine the velocity dispersion profiles in spherical coordinates (σ r , σθ, σphi) and the anisotropy profile (β). The radial velocity dispersion profile (σ r ) is measured out to a galactocentric radius of r ~ 60 kpc, but due to the lack of proper-motion information, σθ, σphi, and β could only be derived directly out to r ~ 25 kpc. From a starting value of β ≈ 0.5 in the inner parts (9 < r/kpc < 12), the profile falls sharply in the range r ≈ 13-18 kpc, with a minimum value of β = -1.2 at r = 17 kpc, rising sharply at larger radius. In the outer parts, in the range 25 < r/kpc < 56, we predict the profile to be roughly constant with a value of β ≈ 0.5. The newly discovered kinematic anomalies are shown not to arise from halo substructures. We also studied the anisotropy profile of simulated stellar halos formed purely by accretion and found that they cannot reproduce the sharp dip seen in the data. From the Jeans equation, we compute the stellar rotation curve (v circ) of the Galaxy out to r ~ 25 kpc. The mass of the Galaxy within r <~ 25 kpc is determined to be 2.1 × 1011 M ⊙, and with a three-component fit to v circ(r), we determine the virial mass of the Milky Way dark matter halo to be M vir = 0.9+0.4 -0.3 × 1012 M ⊙ (R vir = 249+34 -31 kpc).

  11. Flash Mixing on the White-Dwarf Cooling Curve: Understanding Hot Horizontal Branch Anomalies in NGC 2808

    NASA Technical Reports Server (NTRS)

    Brown, Thomas M.; Sweigart, Allen V.; Lanz, Thierry; Landsman, Wayne B.; Hubeny, Ivan; Fisher, Richard R. (Technical Monitor)

    2001-01-01

    We present an ultraviolet color-magnitude diagram (CMD) spanning the hot horizontal branch (HB), blue straggler, and white dwarf populations of the globular cluster NGC 2808. These data, obtained with the Space Telescope Imaging Spectrograph (STIS), demonstrate that NGC 2808 harbors a significant population of hot subluminous HB stars, an anomaly only previously reported for the globular cluster omega Cen. Our theoretical modeling indicates that the location of these subluminous stars in the CMD, as well as the high temperature gap along the HB of NGC 2808, can be explained if these stars underwent a late helium-core flash while descending the white dwarf cooling curve. We show that the convective zone produced by such a late helium flash will penetrate into the hydrogen envelope, thereby mixing hydrogen into the hot helium-burning interior, where it is rapidly consumed. This phenomenon is analogous to the "born again" scenario for producing hydrogen-deficient stars following a late helium-shell flash. The flash mixing of the envelope greatly enhances the envelope helium and carbon abundances that, in turn, leads to a discontinuous increase in the HB effective temperatures. We argue that the hot HB gap is associated with this theoretically predicted dichotomy in the HB properties. Moreover, the changes in the emergent spectral energy distribution caused by these abundance changes are primarily responsible for explaining the hot subluminous HB stars. Although further evidence is needed to confirm that a late helium-core flash can account for the subluminous HB stars and the hot HB gap, we demonstrate that an understanding of these stars requires the use of appropriate theoretical models for their evolution, atmospheres, and spectra.

  12. Flash Mixing on the White-Dwarf Cooling Curve: Understanding Hot Horizontal Branch Anomalies in NGC 2808

    NASA Technical Reports Server (NTRS)

    Brown, Thomas M.; Sweigart, Allen V.; Lanz, Thierry; Landsman, Wayne B.; Hubeny, Ivan; Fisher, Richard R. (Technical Monitor)

    2001-01-01

    We present an ultraviolet color-magnitude diagram (CMD) spanning the hot horizontal branch (HB), blue straggler, and white dwarf populations of the globular cluster NGC 2808. These data, obtained with the Space Telescope Imaging Spectrograph (STIS), demonstrate that NGC 2808 harbors a significant population of hot subluminous HB stars, an anomaly only previously reported for the globular cluster omega Cen. Our theoretical modeling indicates that the location of these subluminous stars in the CMD, as well as the high temperature gap along the HB of NGC 2808, can be explained if these stars underwent a late helium-core flash while descending the white dwarf cooling curve. We show that the convective zone produced by such a late helium flash will penetrate into the hydrogen envelope, thereby mixing hydrogen into the hot helium-burning interior, where it is rapidly consumed. This phenomenon is analogous to the "born again" scenario for producing hydrogen-deficient stars following a late helium-shell flash. The flash mixing of the envelope greatly enhances the envelope helium and carbon abundances that, in turn, leads to a discontinuous increase in the HB effective temperatures. We argue that the hot HB gap is associated with this theoretically predicted dichotomy in the HB properties. Moreover, the changes in the emergent spectral energy distribution caused by these abundance changes are primarily responsible for explaining the hot subluminous HB stars. Although further evidence is needed to confirm that a late helium-core flash can account for the subluminous HB stars and the hot HB gap, we demonstrate that an understanding of these stars requires the use of appropriate theoretical models for their evolution, atmospheres, and spectra.

  13. Structures in the Milky Way’s Halo System using the Age Distribution of Field Horizontal-Branch Stars

    NASA Astrophysics Data System (ADS)

    Lentner, Geoffrey; Beers, Timothy C.; Placco, Vinicius M.; Carollo, Daniela; Whitten, Deven; Denissenkov, Pavel; Santucci, Rafael; Rossi, Silvia

    2017-01-01

    Twenty five years ago it was demonstrated that the colors of blue horizontal-branch (BHB) stars in the halo of the Milky Way correlate with age (Preston et al., 1991). More recently, this property of BHB stars has been used to construct chronographic (age) maps of the Galaxy (Santucci et al., 2015; Carollo et al., 2016), which revealed the presence of substructures on the basis of the age contrast between younger accreted satellites with respect to the diffuse halo field stars, and, for the first time, obtained an empirical estimate of the age gradient for the halo of the Galaxy based on field BHB stars. These maps also indicated the presence of an ancient chronographic sphere, including the oldest BHB stars, extending from close to the Galactic center out to some 10-15 kpc.We extend these studies making use of deeper u-band photometry from the recent public data release of the SCUSS survey (Zou et al., 2016). We also describe application of a new grid of ages that takes into account both metallicity and colors for BHB stars.By building deeper chronographic maps we can better explore the age structures that are revealed. Up- coming large surveys, including the public release of Pan-STARRS, as well as photometry from the Dark Energy Survey, will further add to these efforts.This work received partial support from PHY 14-30152; Physics Frontier Center/JINA Center for the Evolution of the Elements (JINA-CEE), awarded by the US National Science Foundation.

  14. Size effect on morphology and optical properties of branched ZnO/Si nanowire arrays

    NASA Astrophysics Data System (ADS)

    Yang, Qianqian; Li, Dingguo; Yu, Binbin; Huang, Shengli; Wang, Jiayuan; Li, Shuping; Kang, Junyong

    2016-03-01

    Branched ZnO/Si nanowire arrays have been synthesized by integration of metal-assisted chemical etching and hydrothermal growth. Experiments for different etching duration and hydrothermal growth time were carried out to investigate their effect on the final morphology of the heterogeneous material as well as its photoluminescence and antireflectance. The results demonstrated that the Si nanowires got longer with extending etching period, on which the branched ZnO nanowires were shorter in length and smaller in diameter in the set time period. The branched ZnO nanowires became longer and gradually filled up the interval among Si nanowires with prolonging hydrothermal growth. The emission spectra indicated that the nanostructure became better with less defects and impurities for the long Si nanowires. The diffuse reflectance spectra of the ZnO/Si nanowires showed an optimal growth period for the reflectivity lower than 4% in the visible region. In this article, possible mechanisms for the nanowire arrays growth and optical properties and their evolution were also discussed, which might provide guidance for the architecture and application of the heterogeneous tree-like nanowire arrays.

  15. Interactions of neurons with topographic nano cues affect branching morphology mimicking neuron-neuron interactions.

    PubMed

    Baranes, Koby; Kollmar, Davida; Chejanovsky, Nathan; Sharoni, Amos; Shefi, Orit

    2012-08-01

    We study the effect of topographic nano-cues on neuronal growth-morphology using invertebrate neurons in culture. We use photolithography to fabricate substrates with repeatable line-pattern ridges of nano-scale heights of 10-150 nm. We plate leech neurons atop the patterned-substrates and compare their growth pattern to neurons plated atop non-patterned substrates. The model system allows us the analysis of single neurite-single ridge interactions. The use of high resolution electron microscopy reveals small filopodia processes that attach to the line-pattern ridges. These fine processes, that cannot be detected in light microscopy, add anchoring sites onto the side of the ridges, thus additional physical support. These interactions of the neuronal process dominantly affect the neuronal growth direction. We analyze the response of the entire neuronal branching tree to the patterned substrates and find significant effect on the growth patterns compared to non-patterned substrates. Moreover, interactions with the nano-cues trigger a growth strategy similarly to interactions with other neuronal cells, as reflected in their morphometric parameters. The number of branches and the number of neurites originating from the soma decrease following the interaction demonstrating a tendency to a more simplified neuronal branching tree. The effect of the nano-cues on the neuronal function deserves further investigation and will strengthen our understanding of the interplay between function and form.

  16. Functional morphology, biomechanics and biomimetic potential of stem-branch connections in Dracaena reflexa and Freycinetia insignis.

    PubMed

    Masselter, Tom; Eckert, Sandra; Speck, Thomas

    2011-01-01

    Branching in plants is one of the most important assets for developing large arborescent growth forms with complex crowns. While the form and development of branching in gymnosperms and dicotyledonous trees is widely understood, very little is known about branching patterns and the structure of branch-stem-junctions in arborescent monocotyledons. For a better and quantitative understanding of the functional morphology of branch-stem-junctions in arborescent monocotyledons, we investigated the two species Dracaena reflexa and Freycinetia insignis. While D. reflexa is able to develop large arborescent forms with conspicuous crowns by anomalous secondary growth, F. insignis remains relatively small and is only capable of primary growth. Biomechanical investigations were performed by applying vertical loads up to rupture to lateral branches of both species. This allows the analysis of the fracture mechanics and the determination of the maximal force, stress and strain at rupture as well as the fracture toughness. Functional morphology was correlated with the mechanical behaviour of these plants and compared to data of other dicotyledonous trees. The high energy absorption found in the rupture process of lateral branches of D. reflexa and F. insignis makes them promising biological concept generators with a high potential for biomimetic implementation, i.e., for the development of branched fibre-reinforced technical composites. A wide range of constructional elements with branched (sub-)structures can be optimised by using solutions inspired by plant ramifications, e.g., in automotive and aerospace engineering, architecture, sports equipment and prosthetic manufacturing.

  17. The Hubble Space Telescope UV Legacy Survey of Galactic Globular Clusters. VII. Implications from the Nearly Universal Nature of Horizontal Branch Discontinuities

    NASA Astrophysics Data System (ADS)

    Brown, T. M.; Cassisi, S.; D'Antona, F.; Salaris, M.; Milone, A. P.; Dalessandro, E.; Piotto, G.; Renzini, A.; Sweigart, A. V.; Bellini, A.; Ortolani, S.; Sarajedini, A.; Aparicio, A.; Bedin, L. R.; Anderson, J.; Pietrinferni, A.; Nardiello, D.

    2016-05-01

    The UV-initiative Hubble Space Telescope Treasury survey of Galactic globular clusters provides a new window into the phenomena that shape the morphological features of the horizontal branch (HB). Using this large and homogeneous catalog of UV and blue photometry, we demonstrate that the HB exhibits discontinuities that are remarkably consistent in color (effective temperature). This consistency is apparent even among some of the most massive clusters hosting multiple distinct sub-populations (such as NGC 2808, ω Cen, and NGC 6715), demonstrating that these phenomena are primarily driven by atmospheric physics that is independent of the underlying population properties. However, inconsistencies arise in the metal-rich clusters NGC 6388 and NGC 6441, where the discontinuity within the blue HB (BHB) distribution shifts ˜1000-2000 K hotter. We demonstrate that this shift is likely due to a large helium enhancement in the BHB stars of these clusters, which in turn affects the surface convection and evolution of such stars. Our survey also increases the number of Galactic globular clusters known to host blue-hook stars (also known as late hot flashers) from 6 to 23 clusters. These clusters are biased toward the bright end of the globular cluster luminosity function, confirming that blue-hook stars tend to form in the most massive clusters with significant self-enrichment. Based on observations made with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555. These observations are associated with program GO-13297.

  18. Cervical vertebral column morphology related to craniofacial morphology and head posture in preorthodontic children with Class II malocclusion and horizontal maxillary overjet.

    PubMed

    Arntsen, Torill; Sonnesen, Liselotte

    2011-07-01

    In preorthodontic children with Class II malocclusion and horizontal maxillary overjet, cervical column morphology was examined and related to craniofacial morphology and head posture for the first time. Two hundred thirteen children (aged 7-15 years) with a horizontal maxillary overjet of more than 6 mm were divided into 2 groups of skeletal and dentoalveolar overjets. The skeletal overjet group comprised 99 patients (43 girls, 56 boys). The dentoalveolar overjet group comprised 114 subjects (58 girls, 56 boys). Visual assessments of the cervical column and measurements of craniofacial morphology and head posture were made on profile radiographs. Deviations in the cervical vertebral column morphology occurred significantly more often in the skeletal overjet group (28%) compared with the dentoalveolar overjet group (17%) (P <0.05). Fusion anomalies were associated with a large sagittal jaw relationship, retrognathia of the jaws, large inclination of the jaws, and extended head posture (P <0.05 and 0.01, respectively). Furthermore, a partial cleft was significantly associated with a large cranial base angle (P <0.01). New associations were found between cervical column morphology, craniofacial morphology, and head posture in preorthodontic children with horizontal maxillary overjet. These findings are considered important for diagnostics and thus for a more accurate treatment plan of these patients. Copyright © 2011 American Association of Orthodontists. Published by Mosby, Inc. All rights reserved.

  19. Pulsating hot O subdwarfs in ω Centauri: mapping a unique instability strip on the extreme horizontal branch

    NASA Astrophysics Data System (ADS)

    Randall, S. K.; Calamida, A.; Fontaine, G.; Monelli, M.; Bono, G.; Alonso, M. L.; Van Grootel, V.; Brassard, P.; Chayer, P.; Catelan, M.; Littlefair, S.; Dhillon, V. S.; Marsh, T. R.

    2016-05-01

    We present the results of an extensive survey for rapid pulsators among Extreme Horizontal Branch (EHB) stars in ω Cen. The observations performed consist of nearly 100 h of time-series photometry for several off-centre fields of the cluster, as well as low-resolution spectroscopy for a partially overlapping sample. We obtained photometry for some 300 EHB stars, for around half of which we are able to recover light curves of sufficient quality to either detect or place meaningful non-detection limits for rapid pulsations. Based on the spectroscopy, we derive reliable values of log g, Teff and log N(He) /N(H) for 38 targets, as well as good estimates of the effective temperature for another nine targets, whose spectra are slightly polluted by a close neighbour in the image. The survey uncovered a total of five rapid variables with multi-periodic oscillations between 85 and 125 s. Spectroscopically, they form a homogeneous group of hydrogen-rich subdwarf O stars clustered between 48 000 and 54 000 K. For each of the variables we are able to measure between two and three significant pulsations believed to constitute independent harmonic oscillations. However, the interpretation of the Fourier spectra is not straightforward due to significant fine structure attributed to strong amplitude variations. In addition to the rapid variables, we found an EHB star with an apparently periodic luminosity variation of ~2700 s, which we tentatively suggest may be caused by ellipsoidal variations in a close binary. Using the overlapping photometry and spectroscopy sample we are able to map an empirical ω Cen instability strip in log g - Teff space. This can be directly compared to the pulsation driving predicted from the Montréal "second-generation" models regularly used to interpret the pulsations in hot B subdwarfs. Extending the parameter range of these models to higher temperatures, we find that the region where p-mode excitation occurs is in fact bifurcated, and the well

  20. Pd@Pt Core–Shell Nanoparticles with Branched Dandelion-like Morphology as Highly Efficient Catalysts for Olefin Reduction

    EPA Science Inventory

    A facile synthesis based on the addition of ascorbic acid to a mixture of Na2PdCl4, K2PtCl6, and Pluronic P123 results in highly branched core–shell nanoparticles (NPs) with a micro–mesoporous dandelion-like morphology comprising Pd core and Pt shell. The slow reduction kinetics ...

  1. Pd@Pt Core–Shell Nanoparticles with Branched Dandelion-like Morphology as Highly Efficient Catalysts for Olefin Reduction

    EPA Science Inventory

    A facile synthesis based on the addition of ascorbic acid to a mixture of Na2PdCl4, K2PtCl6, and Pluronic P123 results in highly branched core–shell nanoparticles (NPs) with a micro–mesoporous dandelion-like morphology comprising Pd core and Pt shell. The slow reduction kinetics ...

  2. Morphological, anatomical, and chemical characteristics of needle and branch samples of Siberian fir (Abies Siberica)

    NASA Technical Reports Server (NTRS)

    Rock, B. N.; Williams, D. L.; Kharuk, V. I.; Wessman, C. A.; Moss, D. M.

    1992-01-01

    In August, 1991, needle and branch samples of Siberian fir were collected from undisturbed forest stands along an elevation gradient ranging from 2300 ft to 4450 ft. Four study sites were selected on west-facing slopes, and a standard set of measurements and collections was made. First-, second-, and third-year needles were collected for anatomical assessment. A visual assessment of the forest stand conditions at each site included an evaluation of canopy morphology needle, coloration, increment growth, and the state of health of a specific type of lichen. The heaviest damage to forest stands (extensive foliar loss, needle discoloration, dieback of terminal growth) occurs at an intermediate elevation site (3400 ft/1037 m). The least amount of damage was recorded at the lowest elevation site (2300 ft/701 m). Only slight damage occurs at the highest elevation site (4450 ft/1357 m). Some degree of flagging occurs at all sites. Several lines of evidence suggest that the damage occurring in this area is recent in origin (incipient).

  3. Morphological, anatomical, and chemical characteristics of needle and branch samples of Siberian fir (Abies Siberica)

    NASA Technical Reports Server (NTRS)

    Rock, B. N.; Williams, D. L.; Kharuk, V. I.; Wessman, C. A.; Moss, D. M.

    1992-01-01

    In August, 1991, needle and branch samples of Siberian fir were collected from undisturbed forest stands along an elevation gradient ranging from 2300 ft to 4450 ft. Four study sites were selected on west-facing slopes, and a standard set of measurements and collections was made. First-, second-, and third-year needles were collected for anatomical assessment. A visual assessment of the forest stand conditions at each site included an evaluation of canopy morphology needle, coloration, increment growth, and the state of health of a specific type of lichen. The heaviest damage to forest stands (extensive foliar loss, needle discoloration, dieback of terminal growth) occurs at an intermediate elevation site (3400 ft/1037 m). The least amount of damage was recorded at the lowest elevation site (2300 ft/701 m). Only slight damage occurs at the highest elevation site (4450 ft/1357 m). Some degree of flagging occurs at all sites. Several lines of evidence suggest that the damage occurring in this area is recent in origin (incipient).

  4. Statistical Properties of Blue Horizontal Branch Stars in the Spheroid: Detection of a Moving Group approximately 50 kpc from the Sun

    SciTech Connect

    Harrigan, Matthew J.; Newberg, Heidi Jo; Newberg, Lee A.; Yanny, Brian; Beers, Timothy C.; Lee, Young Sun; Fiorentin, Paola Re; /Ljubljana U. /Heidelberg, Max Planck Inst. Astron.

    2010-02-01

    A new moving group comprising at least four Blue Horizontal Branch (BHB) stars is identified at (l; b) = (65{sup o}; 48{sup o}). The horizontal branch at g{sub 0} = 18.9 magnitude implies a distance of 50 kpc from the Sun. The heliocentric radial velocity is = -157 {+-} 4 km s{sup -1}, corresponding to V{sub gsr} = -10 km s{sup -1}; the dispersion in line-of-sight velocity is consistent with the instrumental errors for these stars. The mean metallicity of the moving group is [Fe/H] {approx} -2.4, which is significantly more metal poor than the stellar spheroid. We estimate that the BHB stars in the outer halo have a mean metallicity of [Fe/H]=-2.0, with a wide scatter and a distribution that does not change much as a function of distance from the Sun. We explore the systematics of SDSS DR7 surface gravity metallicity determinations for faint BHB stars, and present a technique for estimating the significance of clumps discovered in multidimensional data. This moving group cannot be distinguished in density, and highlights the need to collect many more spectra of Galactic stars to unravel the merger history of the Galaxy.

  5. War of the Iguanas: conflicting molecular and morphological phylogenies and long-branch attraction in iguanid lizards.

    PubMed

    Wiens, J J; Hollingsworth, B D

    2000-03-01

    Recent studies based on different types of data (i.e., morphology, molecules) have found strongly conflicting phylogenies for the genera of iguanid lizards but have been unable to explain the basis for this incongruence. We reanalyze published data from morphology and from the mitochondrial ND4, cytochrome b, 12S, and 16S genes to explore the sources of incongruence and resolve these conflicts. Much of the incongruence centers on the genus Cyclura, which is the sister taxon of Iguana, according to parsimony analyses of the morphology and the ribosomal genes, but is the sister taxon of all other Iguanini, according to the protein-coding genes. Maximum likelihood analyses show that there has been an increase in the rate of nucleotide substitution in Cyclura in the two protein-coding genes (ND4 and cytochrome b), although this increase is not as clear when parsimony is used to estimate branch lengths. Parametric simulations suggest that Cyclura may be misplaced by the protein-coding genes as a result of long-branch attraction; even when Cyclura and Iguana are sister taxa in a simulated phylogeny, Cyclura is still placed as the basal member of the Iguanini by parsimony analysis in 55% of the replicates. A similar long-branch attraction problem may also exist in the morphological data with regard to the placement of Sauromalus with the Galápagos iguanas (Amblyrhynchus and Conolophus). The results have many implications for the analysis of diverse data sets, the impact of long branches on parsimony and likelihood methods, and the use of certain protein-coding genes in phylogeny reconstruction.

  6. Dartmouth Stellar Evolution Database and the ACS Survey of Galactic Globular Clusters II. Stellar Evolution Tracks, Isochrones, Luminosity Functions, and Synthetic Horizontal-Branch Models

    DOE Data Explorer

    Dotter, A; Chaboyer, B; Jevremovic, D; Kostov, V; Baron, E; Ferguson, J; Sarajedini, A; Anderson, J

    The Dartmouth Stellar Evolution Database is a collection of stellar evolution tracks and isochrones that spans a range of [Fe/H] from -2.5 to +0.5, [a/Fe] from -0.2 to +0.8 (for [Fe/H]<=0) or +0.2 (for [Fe/H]>0), and initial He mass fractions from Y=0.245 to 0.40. Stellar evolution tracks were computed for masses between 0.1 and 4 Msolar, allowing isochrones to be generated for ages as young as 250 Myr. For the range in masses where the core He flash occurs, separate He-burning tracks were computed starting from the zero age horizontal branch. The tracks and isochrones have been transformed to the observational plane in a variety of photometric systems including standard UBV(RI)C, Stromgren uvby, SDSS ugriz, 2MASS JHKs, and HST ACS/WFC and WFPC2. The Dartmouth Stellar Evolution Database is accessible through a Web site at http://stellar.dartmouth.edu/~models/ where all tracks, isochrones, and additional files can be downloaded. [Copied from online abstract of paper titled "Darmouth Stellar Evolution Database" authored by Dotter, Chaboyer, Jevremovic, Kostov, Baron, Ferguson, and Jason. Abstract is located at http://adsabs.harvard.edu/abs/2008ApJS..178...89D] Web tools are also available at the home page (http://stellar.dartmouth.edu/~models/index.html). These tools allow users to create isochrones and convert them to luminosity functions or create synthetic horizontal branch models.

  7. Elemental abundance analyses with coadded DAO spectrograms. I - The field horizontal-branch stars HD-64488, 109995 and 161817

    NASA Technical Reports Server (NTRS)

    Adelman, Saul J.; Hill, Graham

    1987-01-01

    It is possible to improve the quality of elemental-abundance analyses by using higher-S/N data than has been the practice at high resolution. The procedures developed at the Dominion Astrophysical Observatory to coadd high-dispersion coude spectrograms are used with a minimum of 10 6.5-A/mm IIa-O spectrograms of each of three field hoorizontal-branch (FHB) A stars to increase the S/N of the photographic data over a considerable wavelength region. Fine analyses of the sharp-lined prototype FHB stars HD 109995 and 161817 show an internal consistency which justifies this effort. Their photospheric elemental abundances are similar to those of Population II globular cluster giants. As their photometric and spectrophotometric properties are similar to blue HB stars in such clusters, they are confirmed to be the brighter analogs of such stars. HD 64488, which is photometrically and spectrophotometrically similar to the FHB stars, is found to be metal-poor (Fe/H = -1) with much broader lines (v sin i = 147 km/s). The implications of the abundance anomalies of all three stars are discussed.

  8. Cux1 and Cux2 regulate dendritic branching, spine morphology and synapses of the upper layer neurons of the cortex

    PubMed Central

    Cubelos, Beatriz; Sebastián-Serrano, Alvaro; Beccari, Leonardo; Calcagnotto, Maria Elisa; Cisneros, Elsa; Kim, Seonhee; Dopazo, Ana; Alvarez-Dolado, Manuel; Redondo, Juan Miguel; Bovolenta, Paola; Walsh, Christopher A.; Nieto, Marta

    2010-01-01

    Summary Dendrite branching and spine formation determines the function of morphologically distinct and specialized neuronal subclasses. However, little is known about the programs instructing specific branching patterns in vertebrate neurons and whether such programs influence dendritic spines and synapses. Using knockout and knockdown studies combined with morphological, molecular and electrophysiological analysis we show that the homeobox Cux1 and Cux2 are intrinsic and complementary regulators of dendrite branching, spine development and synapse formation in layer II–III neurons of the cerebral cortex. Cux genes control the number and maturation of dendritic spines partly through direct regulation of the expression of Xlr3b and Xlr4b, chromatin remodeling genes previously implicated in cognitive defects. Accordingly, abnormal dendrites and synapses in Cux2−/− mice correlate with reduced synaptic function and defects in working memory. These demonstrate critical roles of Cux in dendritogenesis and highlight novel subclass-specific mechanisms of synapse regulation that contribute to the establishment of cognitive circuits. PMID:20510857

  9. Spectroscopy of Hot Stars in the Galactic Halo. III. Analysis of a Large Sample of Field Horizontal-Branch and Other A-Type Stars

    NASA Astrophysics Data System (ADS)

    Wilhelm, Ronald; Beers, Timothy C.; Sommer-Larsen, Jesper; Pier, Jeffrey R.; Layden, Andrew C.; Flynn, Chris; Rossi, Silvia; Christensen, Per Rex

    1999-05-01

    We present results from an analysis of medium-resolution spectroscopy and UBV photometry for a sample of 1121 A-type stars in the halo (and disk) of the Galaxy. A previously developed calibration technique is used to assign estimates of effective temperature, surface gravity, and stellar metal abundance, as parameterized by [Fe/H]. Radial velocities are reported with an accuracy of ~10 km s^-1. Distance estimates are obtained for the stars with well-determined luminosity classes. Note that although we refer to ``A-type'' stars, which dominate the present sample, the present data set includes roughly 100 stars of later spectral types, as a result of the temperature range we have chosen to explore in this paper (6000 K<=T_eff<=10,000 K). Included in the hot star sample are 444 stars we classify as field horizontal-branch stars, 416 we classify as main-sequence-gravity A-type (or slightly later) stars (including stars that are likely members of the blue metal-poor population, the so-called BMPs), 140 stars we classify as likely metallic-line (Am) or peculiar (Ap) stars, and 121 stars that cannot be unambiguously classified based on the present data. Examination of the distributions in metallicity and velocity indicates that the field horizontal-branch and main-sequence A-type samples are quite distinct; hence we expect only a modest amount of cross-contamination between the subsamples. We identify 58 RR Lyrae candidates among the hot star sample, based on incompatibilities in their photometric and spectroscopic data. There are 19 stars in the sample that have been previously classified as RR Lyrae variables, and one additional star that had been previously suggested as a variable, though not necessarily of the RR Lyrae class. There are 115 stars in the sample that were previously classified as BMPs by Preston, Beers, & Shectman, most of which fall into the main-sequence A-type category, but 10 of which are found among the Am/Ap classifications. Furthermore, 53 of

  10. Supravital morphology of small branches of lateral striate arteries as observed with Nomarski optics.

    PubMed

    Gouveia, C J

    1996-01-01

    Lateral striate arteries were dissected from the fixed brains of 6 patients of increasing age. Small branches of arteries were observed--unprocessed and unstained--by Nomarski optics. Among the findings there was fibrous intimal proliferation, replacement of medial muscle by collagen, tortuosity, twisting or coiling. The severity of changes seemed to progress with aging. The advantages of the used methodology that aims at avoiding artifacts of processing are discussed briefly.

  11. CAPILLARY NONPERFUSION AND PHOTORECEPTOR LOSS IN BRANCH RETINAL VEIN OCCLUSION: Spatial Correlation and Morphologic Characteristics.

    PubMed

    Kanakis, Menelaos G; Giannouli, Konstantina; Andreanos, Konstantinos; Papaconstantinou, Dimitrios; Koutsandrea, Chrysanthi; Ladas, Ioannis; Georgalas, Ilias; Petrou, Petros; Kotsolis, Athanasios I

    2017-09-01

    To evaluate the photoreceptor layer in eyes with branch retinal vein occlusion associated with macular ischemia, using a method of en face optical coherence tomography (OCT) representation of the ellipsoid zone. Customized macular OCT scans of 9 patients (10 eyes) with branch retinal vein occlusion and macular ischemia were exported and subsequently postprocessed (removal of vascular and cystic spaces' shadows, segmentation, and alignment to the retinal pigment epithelium). The ellipsoid band was then isolated, aligned, and used to produce an en face OCT image. Areas with photoreceptor loss (hyporeflective ellipsoid) were compared with ischemic areas as identified in an early-phase fluorescein angiography. The areas of capillary nonperfusion (as detected in fluorescein angiography) were closely associated with disruption of the ellipsoid zone (depicted as areas of low reflectance in the en face reconstruction of the OCT images). The ellipsoid zone disruption had a patchy appearance and either sharp or fuzzy borders, depending on the grade of the loss of reflectance. En face OCT reconstruction and subsequent representation of ellipsoid zone revealed a close association between capillary nonperfusion and photoreceptor disruption in eyes with branch retinal vein occlusion. It seems that the deep capillary plexus plays an important role on the metabolic demands of outer retina and, consequently, an ischemia at the level of deep capillary plexus has significant impact on the integrity of the photoreceptors.

  12. The Hubble Space Telescope UV Legacy Survey of Galactic globular clusters - XI. The horizontal branch in NGC 6388 and NGC 6441

    NASA Astrophysics Data System (ADS)

    Tailo, M.; D'Antona, F.; Milone, A. P.; Bellini, A.; Ventura, P.; Di Criscienzo, M.; Cassisi, S.; Piotto, G.; Salaris, M.; Brown, T. M.; Vesperini, E.; Bedin, L. R.; Marino, A. F.; Nardiello, D.; Anderson, J.

    2017-02-01

    The Hubble Space Telescope UV Legacy survey of Galactic globular clusters (GC) is characterizing many different aspects of their multiple stellar populations. The `Grundahl-jump' (G-jump) is a discontinuity in ultraviolet brightness of blue horizontal branch (HB) stars, signalling the onset of radiative metal levitation. The HB Legacy data confirmed that the G-jump is located at the same Teff (≃11 500 K) in nearly all clusters. The only exceptions are the metal-rich clusters NGC 6388 and NGC 6441, where the G-jump occurs at Teff ≃ 13-14 000 K. We compute synthetic HB models based on new evolutionary tracks including the effect of helium diffusion, and approximately accounting for the effect of metal levitation in a stable atmosphere. Our models show that the G-jump location depends on the interplay between the time-scale of diffusion and the time-scale of the evolution in the Teff range 11 500 K≲Teff≲14 000 K. The G-jump becomes hotter than 11 500 K only for stars that have, in this Teff range, a helium mass fraction Y ≳ 0.35. Similarly high Y values are also consistent with the modelling of the HB in NGC 6388 and NGC 6441. In these clusters, we predict that a significant fraction of HB stars show helium in their spectra above 11 500 K, and full helium settling should only be found beyond the hotter G-jump.

  13. Quantifying morphological parameters of the terminal branching units in a mouse lung by phase contrast synchrotron radiation computed tomography.

    PubMed

    Hwang, Jeongeun; Kim, Miju; Kim, Seunghwan; Lee, Jinwon

    2013-01-01

    An effective technique of phase contrast synchrotron radiation computed tomography was established for the quantitative analysis of the microstructures in the respiratory zone of a mouse lung. Heitzman's method was adopted for the whole-lung sample preparation, and Canny's edge detector was used for locating the air-tissue boundaries. This technique revealed detailed morphology of the respiratory zone components, including terminal bronchioles and alveolar sacs, with sufficiently high resolution of 1.74 µm isotropic voxel size. The technique enabled visual inspection of the respiratory zone components and comprehension of their relative positions in three dimensions. To check the method's feasibility for quantitative imaging, morphological parameters such as diameter, surface area and volume were measured and analyzed for sixteen randomly selected terminal branching units, each consisting of a terminal bronchiole and a pair of succeeding alveolar sacs. The four types of asymmetry ratios concerning alveolar sac mouth diameter, alveolar sac surface area, and alveolar sac volume are measured. This is the first ever finding of the asymmetry ratio for the terminal bronchioles and alveolar sacs, and it is noteworthy that an appreciable degree of branching asymmetry was observed among the alveolar sacs at the terminal end of the airway tree, despite the number of samples was small yet. The series of efficient techniques developed and confirmed in this study, from sample preparation to quantification, is expected to contribute to a wider and exacter application of phase contrast synchrotron radiation computed tomography to a variety of studies.

  14. The red giant branches of Galactic globular clusters in the [(V-I)0,MV] plane: metallicity indices and morphology

    NASA Astrophysics Data System (ADS)

    Saviane, I.; Rosenberg, A.; Piotto, G.; Aparicio, A.

    2000-03-01

    The purpose of this study is to carry out a thorough investigation of the changes in morphology of the red giant branch (RGB) of Galactic globular clusters (GGC) as a function of metallicity, in the V,I bands. To this aim, two key points are developed in the course of the analysis. (a) Using our photometric V,I database for Galactic globular clusters (the largest homogeneous data sample to date; Rosenberg et al. \\cite{rsp99}) we measure a complete set of metallicity indices, based on the morphology and position of the red-giant branch. In particular, we provide here the first calibration of the S, Delta V1.1 and Delta V1.4 indices in the (V-I,V) plane. We show that our indices are internally consistent, and we calibrate each index in terms of metallicity, both on the Zinn & West (1984) and the Carretta & Gratton (1997) scales. Our new calibrations of the (V-I)_{0,g}, Delta V1.2, (V-I)-3.0 and (V-I)-3.5 indices are consistent with existing relations. (b) Using a grid of selected RGB fiducial points, we define a function in the (V-I)0,MI,[Fe/H] space which is able to reproduce the whole set of GGC giant branches in terms of a single parameter (the metallicity). As a first test, we show that the function is able to predict the correct trend of our observed indices with metallicity. The usage of this function will improve the current determinations of metallicity and distances within the Local Group, since it allows to easily map (V-I)0,MI coordinates into [Fe/H],MI ones. To this aim the ``synthetic'' RGB distribution is generated both for the currently used Lee et al. (1990) distance scale, and for the most recent results on the RR Lyr distance scale.

  15. The morphology of blends of linear and branched polyethylenes in solid state by small-angle scattering

    SciTech Connect

    Wignall, G.D.; Londono, J.D.; Alamo, R.G.

    1995-12-01

    We have used small-angle neutron and x-ray scattering (SANS And SAXS) to investigate the solid state morphology of blends of high-density and low-density polyethylenes (HDPE and LDPE). The blends are homogenous in the melt as demonstrated by SANS using the contrast obtained by deuterating the linear polymer, though they phase segregate on slow cooling (0.75{degree}C/min). For high concentrations ({theta} {ge} 0.5) of linear polymer, there are separate stacks of HDPE and LDPE lamellae, as indicated by 2-peak SAXS curves. For predominantly branched blends, the phase separation is less complete, and the components are separated within the same lamellar stack, with alternating HDPE and LDPE lamellae. Moreover, the phases no longer consist of the pure components and the HDPE lamellae contain up to 15% LDPE. Rapid quenching into dry-ice/acetone (-78{degree}C) produces only one lamellar stack over the whole concentration range. The blends show extensive cocrystallization with a tendency for the branched material to be preferentially located in the amorphous regions. For high concentrations ({theta} {ge} 0.5) of HDPE-D the overall scattering length density is high and the excess concentration of LDPE between the lamellae enhances the contrast between the crystalline and amorphous phases. Thus, the interlamellar spacing (long period) is clearly visible in the SANS pattern. The blend morphology is a strong function of the quench rate and samples quenched less rapidly (e.g., into water at 23{degree}C) show a similar morphology to slowly cooled samples.

  16. Multi-color photometry of the Galactic globular cluster M 75 = NGC 6864. A new sensitive metallicity indicator and the position of the horizontal branch in UV

    NASA Astrophysics Data System (ADS)

    Kravtsov, V.; Alcaíno, G.; Marconi, G.; Alvarado, F.

    2007-07-01

    Aims:We carry out and analyze new multi-color photometry of the Galactic globular cluster (GC) M 75 in UBVI and focus on the brighter sequences of the color-magnitude diagram (CMD), with particular emphasis on their location in U-based CMD. Specifically, we study the level both of the horizontal (HB) and red giant branches (RGB) relative to the main-sequence turnoff (TO) in the U magnitude. Methods: Along with the presented photometry of M 75, we use our collection of photometric data on GCs belonging to the metal-poor range, [Fe/H]{ZW}<-1.1 dex, obtained from observations with different equipment, but calibrated by standard stars situated in the observed cluster fields. Results: We confirm our earlier finding, and extend it to a larger magnitude range. We demonstrate that Δ U_TO^BHB expressing the difference in U magnitude between the TO point and the level of the blue HB, near its red boundary, of the metal-poor GCs observed with the EMMI camera of the NTT/ESO telescope is about 0.4-0.5 mag smaller as compared to GCs observed with the 100 arcsec telescope and 1.3 m Warsaw telescope of the Las Campanas Observatory. At the same time, Δ U_TO^RGB, the difference in U magnitude between the TO and RGB inflection (brightest) points, does not show such an apparent dependence on the characteristics of U filters used, but it depends on cluster metallicity. We have shown, for the first time, the dependence of the parameter Δ U_TO^RGB on [Fe/H] and have estimated its analytical expression, by assuming a linear relation between the parameter and metallicity. Its slope, Δ U_TO^RGB/Δ[Fe/H] 1.2 mag/dex, is approximately a factor of two steeper than that of the dependence of the RGB bump position in the V magnitude on metallicity. The asymptotic giant branch (AGB) clump and features of the RGB luminosity function (LF) of M 75 are also discussed. Based on observations with the 1.3 m Warsaw telescope at Las Campanas Observatory. Individual photometry measurements are only

  17. The brachial plexus branches to the pectoral muscles in adult rats: morphological aspects and morphometric normative data.

    PubMed

    Riva, Nilo; Domi, Teuta; Lopez, Ignazio Diego; Triolo, Daniela; Fossaghi, Andrea; Dina, Giorgia; Podini, Paola; Comi, Giancarlo; Quattrini, Angelo

    2012-01-01

    Animal models provide an important tool to investigate the pathogenesis of neuromuscular disorders. In the present study, we analyze fiber composition of the brachial plexus branches to the pectoral muscles: the medial anterior thoracic nerve (MATN) and the lateral anterior thoracic nerve (LATN). The morphological and morphometric characteristics and the percentage of motor fibers within each nerve are here reported, adding information to microscopic anatomy knowledge of the rat brachial plexus. As control, we employed the quadriceps nerve, commonly used for the evaluation of motor fibers at hindlimbs. We demonstrated that the MATN and the LATN are predominantly composed of large motor fibers and therefore could be employed to evaluate the peripheral nervous system (PNS) involvement at forelimbs in neurological diseases models, predominantly affecting the motor fiber compartment.

  18. The brachial plexus branches to the pectoral muscles in adult rats: morphological aspects and morphometric normative data

    PubMed Central

    Riva, Nilo; Domi, Teuta; Lopez, Ignazio Diego; Triolo, Daniela; Fossaghi, Andrea; Dina, Giorgia; Podini, Paola; Comi, Giancarlo; Quattrini, Angelo

    2012-01-01

    Animal models provide an important tool to investigate the pathogenesis of neuromuscular disorders. In the present study, we analyze fiber composition of the brachial plexus branches to the pectoral muscles: the medial anterior thoracic nerve (MATN) and the lateral anterior thoracic nerve (LATN). The morphological and morphometric characteristics and the percentage of motor fibers within each nerve are here reported, adding information to microscopic anatomy knowledge of the rat brachial plexus. As control, we employed the quadriceps nerve, commonly used for the evaluation of motor fibers at hindlimbs. We demonstrated that the MATN and the LATN are predominantly composed of large motor fibers and therefore could be employed to evaluate the peripheral nervous system (PNS) involvement at forelimbs in neurological diseases models, predominantly affecting the motor fiber compartment. PMID:23087618

  19. Pd@Pt Core-Shell Nanoparticles with Branched Dandelion-like Morphology as Highly Efficient Catalysts for Olefin Reduction.

    PubMed

    Datta, Kasibhatta Josena; Datta, Kasibhatta Kumara Ramanatha; Gawande, Manoj B; Ranc, Vaclav; Čépe, Klára; Malgras, Victor; Yamauchi, Yusuke; Varma, Rajender S; Zboril, Radek

    2016-01-26

    A facile synthesis based on the addition of ascorbic acid to a mixture of Na2 PdCl4, K2 PtCl6, and Pluronic P123 results in highly branched core-shell nanoparticles (NPs) with a micro-mesoporous dandelion-like morphology comprising Pd core and Pt shell. The slow reduction kinetics associated with the use of ascorbic acid as a weak reductant and suitable Pd/Pt atomic ratio (1:1) play a principal role in the formation mechanism of such branched Pd@Pt core-shell NPs, which differs from the traditional seed-mediated growth. The catalyst efficiently achieves the reduction of a variety of olefins in good to excellent yields. Importantly, higher catalytic efficiency of dandelion-like Pd@Pt core-shell NPs was observed for the olefin reduction than commercially available Pt black, Pd NPs, and physically admixed Pt black and Pd NPs. This superior catalytic behavior is not only due to larger surface area and synergistic effects but also to the unique micro-mesoporous structure with significant contribution of mesopores with sizes of several tens of nanometers. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  20. Evaluation of T-Wave Morphology in Patients With Left Bundle Branch Block and Suspected Acute Coronary Syndrome.

    PubMed

    Meyers, H Pendell; Jaffa, Elias; Smith, Stephen W; Drake, Weiying; Limkakeng, Alexander T

    2016-09-01

    T-wave morphology in the setting of left bundle branch block (LBBB) has been proposed as an indicator of myocardial ischemia. We sought to identify T-wave morphology findings in patients with LBBB that predict non-ST-segment elevation myocardial infarction (NSTEMI). We hypothesized that two or more contiguous leads with concordant T waves would be predictive of NSTEMI. This was a retrospective cohort study performed by chart review in a tertiary care center emergency department. We identified a consecutive cohort who presented with LBBB and symptoms consistent with acute coronary syndrome. Exclusion criteria were diastolic blood pressure > 120 mm Hg, heart rate > 130 beats/min, positive pressure ventilation, potassium > 5.5 mEq/L, and cardiac arrest without prearrest electrocardiogram (ECG) available. We collected ECGs and classified T waves into five categories based on morphology, blinded to clinical outcome. Clinical outcome data were collected blinded to ECG findings. Those with ECG diagnostic of STEMI by modified Sgarbossa criteria were excluded from the primary analysis, which was sensitivity and specificity of two or more contiguous leads with concordant T waves for NSTEMI. There were 246 patients included. Mean age was 73 years; 160 (65%) were female, and 32 had myocardial infarction. Thirty percent had two or more contiguous precordial leads with partially or completely concordant T waves. For NSTEMI, the sensitivity and specificity of this finding were 19% (95% confidence interval [CI] 8-37) and 68% (95% CI 61-74). We found no clinically useful relationship between T-wave concordance and myocardial infarction in our patient population. Future investigation of LBBB T-wave morphology should focus on alternative populations and findings. Copyright © 2016 Elsevier Inc. All rights reserved.

  1. The morphology of blends of linear and branched polyethylenes in solid state by SANS

    SciTech Connect

    Wignall, G.D.; Londono, J.D.; Alamo, R.G.; Mandelkern, L.

    1995-03-01

    In a previous paper, the authors have shown how small-angle neutron and X-ray scattering (SANS, SAXS) can be used to determine the melt compatibility of different polyolefins, including high-density (HD), low-density (LD), and linear low density (LLD) polyethylene. Such blends have attained widespread commercial applications, though the understanding of the mechanical and melt-flow properties of such blends has hitherto been handicapped by the absence of a consensus concerning the degree of mixing of the components, both in the melt and solid states. Recent SANS data indicate that for HDPE/LDPE blends, the melt is homogeneous for all compositions after proper accounting for H/D isotope effects. In this publication the authors use complementary SANS, DSC, and SAXS to examine the types of morphologies and the different degrees of phase separation which may arise via crystallization effects on cooling from a homogeneous melt.

  2. Allometry of root branching and its relationship to root morphological and functional traits in three range grasses.

    PubMed

    Arredondo, J Tulio; Johnson, Douglas A

    2011-11-01

    The study of proportional relationships between size, shape, and function of part of or the whole organism is traditionally known as allometry. Examination of correlative changes in the size of interbranch distances (IBDs) at different root orders may help to identify root branching rules. Root morphological and functional characteristics in three range grasses {bluebunch wheatgrass [Pseudoroegneria spicata (Pursh) Löve], crested wheatgrass [Agropyron desertorum (Fisch. ex Link) Schult.×A. cristatum (L.) Gaert.], and cheatgrass (Bromus tectorum L.)} were examined in response to a soil nutrient gradient. Interbranch distances along the main root axis and the first-order laterals as well as other morphological and allocation root traits were determined. A model of nutrient diffusivity parameterized with root length and root diameter for the three grasses was used to estimate root functional properties (exploitation efficiency and exploitation potential). The results showed a significant negative allometric relationship between the main root axis and first-order lateral IBD (P ≤ 0.05), but only for bluebunch wheatgrass. The main root axis IBD was positively related to the number and length of roots, estimated exploitation efficiency of second-order roots, and specific root length, and was negatively related to estimated exploitation potential of first-order roots. Conversely, crested wheatgrass and cheatgrass, which rely mainly on root proliferation responses, exhibited fewer allometric relationships. Thus, the results suggested that species such as bluebunch wheatgrass, which display slow root growth and architectural root plasticity rather than opportunistic root proliferation and rapid growth, exhibit correlative allometry between the main axis IBD and morphological, allocation, and functional traits of roots.

  3. Anatomy of the lamprey ear: morphological evidence for occurrence of horizontal semicircular ducts in the labyrinth of Petromyzon marinus

    PubMed Central

    Maklad, Adel; Reed, Caitlyn; Johnson, Nicolas S; Fritzsch, Bernd

    2014-01-01

    In jawed (gnathostome) vertebrates, the inner ears have three semicircular canals arranged orthogonally in the three Cartesian planes: one horizontal (lateral) and two vertical canals. They function as detectors for angular acceleration in their respective planes. Living jawless craniates, cyclostomes (hagfish and lamprey) and their fossil records seemingly lack a lateral horizontal canal. The jawless vertebrate hagfish inner ear is described as a torus or doughnut, having one vertical canal, and the jawless vertebrate lamprey having two. These observations on the anatomy of the cyclostome (jawless vertebrate) inner ear have been unchallenged for over a century, and the question of how these jawless vertebrates perceive angular acceleration in the yaw (horizontal) planes has remained open. To provide an answer to this open question we reevaluated the anatomy of the inner ear in the lamprey, using stereoscopic dissection and scanning electron microscopy. The present study reveals a novel observation: the lamprey has two horizontal semicircular ducts in each labyrinth. Furthermore, the horizontal ducts in the lamprey, in contrast to those of jawed vertebrates, are located on the medial surface in the labyrinth rather than on the lateral surface. Our data on the lamprey horizontal duct suggest that the appearance of the horizontal canal characteristic of gnathostomes (lateral) and lampreys (medial) are mutually exclusive and indicate a parallel evolution of both systems, one in cyclostomes and one in gnathostome ancestors. PMID:24438368

  4. Anatomy of the lamprey ear: morphological evidence for occurrence of horizontal semicircular ducts in the labyrinth of Petromyzon marinus.

    PubMed

    Maklad, Adel; Reed, Caitlyn; Johnson, Nicolas S; Fritzsch, Bernd

    2014-04-01

    In jawed (gnathostome) vertebrates, the inner ears have three semicircular canals arranged orthogonally in the three Cartesian planes: one horizontal (lateral) and two vertical canals. They function as detectors for angular acceleration in their respective planes. Living jawless craniates, cyclostomes (hagfish and lamprey) and their fossil records seemingly lack a lateral horizontal canal. The jawless vertebrate hagfish inner ear is described as a torus or doughnut, having one vertical canal, and the jawless vertebrate lamprey having two. These observations on the anatomy of the cyclostome (jawless vertebrate) inner ear have been unchallenged for over a century, and the question of how these jawless vertebrates perceive angular acceleration in the yaw (horizontal) planes has remained open. To provide an answer to this open question we reevaluated the anatomy of the inner ear in the lamprey, using stereoscopic dissection and scanning electron microscopy. The present study reveals a novel observation: the lamprey has two horizontal semicircular ducts in each labyrinth. Furthermore, the horizontal ducts in the lamprey, in contrast to those of jawed vertebrates, are located on the medial surface in the labyrinth rather than on the lateral surface. Our data on the lamprey horizontal duct suggest that the appearance of the horizontal canal characteristic of gnathostomes (lateral) and lampreys (medial) are mutually exclusive and indicate a parallel evolution of both systems, one in cyclostomes and one in gnathostome ancestors.

  5. Anatomy of the lamprey ear: morphological evidence for occurrence of horizontal semicircular ducts in the labyrinth of Petromyzon marinus

    USGS Publications Warehouse

    Maklad, Adel; Reed, Caitlyn; Johnson, Nicholas S.; Fritzsch, Bernd

    2014-01-01

    In jawed (gnathostome) vertebrates, the inner ears have three semicircular canals arranged orthogonally in the three Cartesian planes: one horizontal (lateral) and two vertical canals. They function as detectors for angular acceleration in their respective planes. Living jawless craniates, cyclostomes (hagfish and lamprey) and their fossil records seemingly lack a lateral horizontal canal. The jawless vertebrate hagfish inner ear is described as a torus or doughnut, having one vertical canal, and the jawless vertebrate lamprey having two. These observations on the anatomy of the cyclostome (jawless vertebrate) inner ear have been unchallenged for over a century, and the question of how these jawless vertebrates perceive angular acceleration in the yaw (horizontal) planes has remained open. To provide an answer to this open question we reevaluated the anatomy of the inner ear in the lamprey, using stereoscopic dissection and scanning electron microscopy. The present study reveals a novel observation: the lamprey has two horizontal semicircular ducts in each labyrinth. Furthermore, the horizontal ducts in the lamprey, in contrast to those of jawed vertebrates, are located on the medial surface in the labyrinth rather than on the lateral surface. Our data on the lamprey horizontal duct suggest that the appearance of the horizontal canal characteristic of gnathostomes (lateral) and lampreys (medial) are mutually exclusive and indicate a parallel evolution of both systems, one in cyclostomes and one in gnathostome ancestors.

  6. Anatomy and morphology in developing vegetative buds on detached Norway spruce branches in controlled conditions before bud burst.

    PubMed

    Sutinen, Sirkka; Partanen, Jouni; Viherä-Aarnio, Anneli; Häkkinen, Risto

    2009-11-01

    We studied the light and stereomicroscopic structure of developing vegetative buds from a 16-year-old Norway spruce [Picea abies (L.) Karst.] of southern Finnish origin in relation to temperature sum and to externally visible changes in the buds before and during bud burst in forcing conditions. Branches were collected on 17 January and transferred to the greenhouse where they were first subjected to preforcing conditions (darkness, +4 degrees C) for 7 days and then to the forcing conditions (day length 12 h, +20 degrees C). Buds were sampled 20 times between 17 January and 13 February. Air temperature was recorded hourly throughout the study period. The first microscopic change was a temporary increase in the size and number of lipid droplets before the onset of temperature sum (T > or = +5 degrees C) accumulation. From the 4th to the 9th day under the forcing conditions, tracheids started to develop from the base up to the top of the bud. This was closely synchronized with an observed morphological change in the shape of needle tip from rounded to pointed ones. Development from the first visible change in the bud scales on the 12th forcing day to bud burst took 9 days when the temperature sum was 313 d.d. The temperature sums in our experiment overestimated the requirements of temperature sum for bud development phases measured in the field. Bud development could be divided into four structural phases. The first two phases, i.e., morphological changes in the primary needles, occurred without any externally visible changes in the buds. Thus, these phases have a potential for testing and improving the phenological models, which, up to now, have mainly been based on the bud burst observation by the naked eye.

  7. Functional-morphological parameters, aqueous flare and cytokines in macular oedema with branch retinal vein occlusion after ranibizumab.

    PubMed

    Noma, Hidetaka; Mimura, Tatsuya; Yasuda, Kanako; Shimura, Masahiko

    2017-02-01

    Correlations among functional-morphological parameters, the aqueous flare value (an indicator of inflammation) and aqueous humour levels of cytokines/inflammatory factors were investigated in patients with branch retinal vein occlusion (BRVO) and macular oedema who received intravitreal ranibizumab injection (IRI) and were followed for 6 months. Aqueous humour levels of 11 cytokines or growth inflammatory/factors were measured in 45 patients with BRVO and macular oedema who received IRI. Patients with recurrent macular oedema were given further IRI as needed. Aqueous humour levels of vascular endothelial growth factor (VEGF), soluble VEGF receptor (sVEGFR) and other cytokines/inflammatory factors were measured by the suspension array method. Aqueous flare values were measured with a laser flare metre and macular oedema was examined by optical coherence tomography. There were significant correlations between the aqueous flare and the aqueous levels of sVEGFR-1, placental growth factor, monocyte chemoattractant protein 1, soluble intercellular adhesion molecule-1, interleukin (IL)-6 and IL-8. There were also significant correlations between the change of the aqueous flare and improvement of central macular thickness after 1 month, after 6 months and at the 1st recurrence. Furthermore, a significant correlation was noted between the change of the aqueous flare and improvement of best-corrected visual acuity at 6 months after IRI, but not at 1 month or at the 1st recurrence. These findings suggest that the aqueous flare is associated with inflammatory factors/cytokines, and that the change of the aqueous flare value may influence the long-term prognosis in patients with BRVO receiving IRI therapy for macular oedema. Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://www.bmj.com/company/products-services/rights-and-licensing/.

  8. Morphology-controlled cactus-like branched anatase TiO2 arrays with high light-harvesting efficiency for dye-sensitized solar cells

    NASA Astrophysics Data System (ADS)

    Wu, Wu-Qiang; Rao, Hua-Shang; Feng, Hao-Lin; Guo, Xin-Dong; Su, Cheng-Yong; Kuang, Dai-Bin

    2014-08-01

    The present work establishes a facile process for one-step hydrothermal growth of vertically aligned anatase cactus-like branched TiO2 (CBT) arrays on a transparent conducting oxide (TCO) substrate. Various CBT morphologies are obtained by adjusting the potassium titanium oxide oxalate (PTO) reactant concentration (from 0.05 M to 0.15 M) and this yields a morphologically-controllable branched TiO2 arrays geometry. The CBT arrays consist of a vertically oriented nanowire (NW) or nanosheet (NS) stem and a host of short nanorod (NR) branches. The hierarchical CBT arrays demonstrate their excellent candidatures as photoanodes, which are capable of exhibiting high light-harvesting efficiency in dye-sensitized solar cells (DSSCs). Consequently, DSSCs based on 7 μm long optimized CBT arrays (0.05 M PTO), which are assembled with high density and high aspect-ratio NR branches, exhibit an impressive power conversion efficiency of 6.43% under AM 1.5G one sun illumination. The high performance can be attributed to the prominent light-harvesting efficiency, resulting from larger surface area and superior light-scattering capability.

  9. Tomographic reconstruction reveals the morphology of a unique cellular organelle, the aggregated macrotubules (Macrotubuli aggregati) of human retinal horizontal cells.

    PubMed

    Jastrow, Holger; Yarwood, Andrew; Majorovits, Endre; Harris, J Robin

    2015-04-01

    Horizontal cells of the human retina contain unique tubular organelles that have a diameter which is about 10 times larger than that of microtubules (~230 nm). These macrotubuli in most cases form regular aggregates. Therefore we propose to introduce them as Macrotubuli aggregati in the Terminologia histologica. Tomographic investigation of the structures revealed that the walls of the tubules most probably consist of intermediate filaments running nearly parallel to each other and show somewhat regularly attached ribosomes on their inner and also outer surface. About 2% of the organelles exhibit double- to multiple layered walls and less than 1% resemble large scrolls. The tubules may extend 10 to over 20 μm in the cytoplasm and are also encountered in soma-near processes extending into the outer plexiform layer. It remains unclear why these structures are only present in humans and few other species and why almost only in horizontal cells. Speculations on possible functions are discussed. Copyright © 2015 Elsevier Ltd. All rights reserved.

  10. Branching Morphogenesis

    PubMed Central

    Horowitz, Arie; Simons, Michael

    2009-01-01

    Tubular structures are a fundamental anatomical theme recurring in a wide range of animal species. In mammals, tubulogenesis underscores the development of several systems and organs, including the vascular system, the lungs, and the kidneys. All tubular systems are hierarchical, branching into segments of gradually diminishing diameter. There are only two cell types that form the lumen of tubular systems – either endothelial cells in the vascular system, or epithelial cells in all other organs. The most important feature in determining the morphology of the tubular systems is the frequency and geometry of branching. Hence, deciphering the molecular mechanisms underlying the sprouting of new branches from pre-existing ones is the key to understanding the formation of tubular systems. The morphological similarity between the various tubular systems is underscored by similarities between the signaling pathways which control their branching. A prominent feature common to these pathways is their duality – an agonist counterbalanced by an inhibitor. The formation of the tracheal system in Drosophila melanogaster is driven by fibroblast growth factor (FGF) and inhibited by Sprouty/Notch. In vertebrates, the analogous pathways are FGF and transforming growth factor β in epithelial tubular systems, or vascular endothelial growth factor and Notch in the vascular system. PMID:19179661

  11. Responses of foliar delta13C, gas exchange and leaf morphology to reduced hydraulic conductivity in Pinus monticola branches.

    PubMed

    Cernusak, L A; Marshall, J D

    2001-10-01

    We tested the hypothesis that branch hydraulic conductivity partly controls foliar stable carbon isotope ratio (delta13C) by its influence on stomatal conductance in Pinus monticola Dougl. Notching and phloem-girdling treatments were applied to reduce branch conductivity over the course of a growing season. Notching and phloem girdling reduced leaf-specific conductivity (LSC) by about 30 and 90%, respectively. The 90% reduction in LSC increased foliar delta13C by about 1 per thousand (P < 0.0001, n = 65), whereas the 30% reduction in LSC had no effect on foliar delta13C (P = 0.90, n = 65). Variation in the delta13C of dark respiration was similar to that of whole-tissues when compared among treatments. These isotopic measurements, in addition to instantaneous gas exchange measurements, suggested only minor adjustments in the ratio of intercellular to atmospheric CO2 partial pressures (ci/ca) in response to experimentally reduced hydraulic conductivity. A strong correlation was observed between stomatal conductance (gs) and photosynthetic demand over a tenfold range in gs. Although ci/ca and delta13C appeared to be relatively homeostatic, current-year leaf area varied linearly as a function of branch hydraulic conductivity (r2 = 0.69, P < 0.0001, n = 18). These results suggest that, for Pinus monticola, adjustment of leaf area is a more important response to reduced branch conductivity than adjustment of ci/ca.

  12. Na-O anticorrelation and horizontal branches. IV. Detection of He-rich and He-poor stellar populations in the globular cluster NGC 6218

    NASA Astrophysics Data System (ADS)

    Carretta, E.; Bragaglia, A.; Gratton, R. G.; Catanzaro, G.; Leone, F.; Sabbi, E.; Cassisi, S.; Claudi, R.; D'Antona, F.; François, P.; James, G.; Piotto, G.

    2007-03-01

    We used the multifiber spectrograph FLAMES on the ESO Very Large Telescope UT2 to derive atmospheric parameters, metallicities and abundances of O and Na for 79 red giant stars in the Galactic globular cluster NGC 6218 (M 12). We analyzed stars in the magnitude range from about 1 mag below the bump to the tip of the Red Giant Branch. The average metallicity we derive is [Fe/H]=-1.31± 0.004± 0.028 dex (random and systematic errors, respectively), with a very small star-to-star scatter (rms=0.033 dex), from moderately high-resolution Giraffe spectra. This is the first extensive spectroscopic abundance analysis in this cluster. Our results indicate that NGC 6218 is very homogeneous as far as heavy elements are concerned. On the other hand, light elements involved in the well known proton-capture reactions of H-burning at high temperature, such as O and Na, show large variations, anticorrelated with each other, at all luminosities along the red giant branch. The conclusion is that the Na-O anticorrelation must be established in early times at the cluster formation. We interpret the variation of Na found near the RGB-bump as the effect of two distinct populations having different bump luminosities, as predicted for different He content. To our knowledge, NGC 6218 is the first GC where such a signature has been spectroscopically detected, when combined with consistent and homogeneous data obtained for NGC 6752 to gain in statistical significance. Based on observations collected at ESO telescopes under programme 073.D-0211. Full Tables 2, 3, and 5 are only available in electronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/464/939

  13. Constraints on the Distance Moduli, Helium and Metal Abundances, and Ages of Globular Clusters from their RR Lyrae and Non-variable Horizontal-branch Stars. I. M3, M15, and M92

    NASA Astrophysics Data System (ADS)

    VandenBerg, Don A.; Denissenkov, P. A.; Catelan, Márcio

    2016-08-01

    Up-to-date isochrones, zero-age horizontal-branch (ZAHB) loci, and evolutionary tracks for core He-burning stars are applied to the color-magnitude diagrams of M3, M15, and M92, focusing in particular on their RR Lyrae populations. Periods for the ab- and c-type variables are calculated using the latest theoretical calibrations of {log} {P}{ab} and {log} {P}c as a function of luminosity, mass, effective temperature ({T}{{eff}}), and metallicity. Our models are generally able to reproduce the measured periods to well within the uncertainties implied by the stellar properties on which pulsation periods depend, as well as the mean periods and cluster-to-cluster differences in < {P}{ab}> and < {P}c> , on the assumption of well-supported values of E(B-V), {(m-M)}V, and [Fe/H]. While many of RR Lyrae in M3 lie close to the same ZAHB that fits the faintest horizontal-branch (HB) stars at bluer or redder colors, the M92 variables are all significantly evolved stars from ZAHB locations on the blue side of the instability strip. M15 appears to contain a similar population of HB stars as M92, along with additional helium-enhanced populations not present in the latter which comprise most of its RR Lyrae stars. The large number of variables in M15 and the similarity of the observed values of < {P}{ab}> and < {P}c> in M15 and M92 can be explained by HB models that allow for variations in Y. Similar ages (˜12.5 Gyr) are found for all three clusters, making them significantly younger than the field halo subgiant HD 140283. Our analysis suggests a preference for stellar models that take diffusive processes into account.

  14. Age-related hearing loss and ear morphology affect vertical but not horizontal sound-localization performance.

    PubMed

    Otte, Rik J; Agterberg, Martijn J H; Van Wanrooij, Marc M; Snik, Ad F M; Van Opstal, A John

    2013-04-01

    Several studies have attributed deterioration of sound localization in the horizontal (azimuth) and vertical (elevation) planes to an age-related decline in binaural processing and high-frequency hearing loss (HFHL). The latter might underlie decreased elevation performance of older adults. However, as the pinnae keep growing throughout life, we hypothesized that larger ears might enable older adults to localize sounds in elevation on the basis of lower frequencies, thus (partially) compensating their HFHL. In addition, it is not clear whether sound localization has already matured at a very young age, when the body is still growing, and the binaural and monaural sound-localization cues change accordingly. The present study investigated sound-localization performance of children (7-11 years), young adults (20-34 years), and older adults (63-80 years) under open-loop conditions in the two-dimensional frontal hemifield. We studied the effect of age-related hearing loss and ear size on localization responses to brief broadband sound bursts with different bandwidths. We found similar localization abilities in azimuth for all listeners, including the older adults with HFHL. Sound localization in elevation for the children and young adult listeners with smaller ears improved when stimuli contained frequencies above 7 kHz. Subjects with larger ears could also judge the elevation of sound sources restricted to lower frequency content. Despite increasing ear size, sound localization in elevation deteriorated in older adults with HFHL. We conclude that the binaural localization cues are successfully used well into later stages of life, but that pinna growth cannot compensate the more profound HFHL with age.

  15. Expression of an engineered granule-bound Escherichia coli glycogen branching enzyme in potato results in severe morphological changes in starch granules.

    PubMed

    Huang, Xing-Feng; Nazarian-Firouzabadi, Farhad; Vincken, Jean-Paul; Ji, Qin; Suurs, Luc C J M; Visser, Richard G F; Trindade, Luisa M

    2013-05-01

    The Escherichia coli glycogen branching enzyme (GLGB) was fused to either the C- or N-terminus of a starch-binding domain (SBD) and expressed in two potato genetic backgrounds: the amylose-free mutant (amf) and an amylose-containing line (Kardal). Regardless of background or construct used, a large amount of GLGB/SBD fusion protein was accumulated inside the starch granules, however, without an increase in branching. The presence of GLGB/SBD fusion proteins resulted in altered morphology of the starch granules in both genetic backgrounds. In the amf genetic background, the starch granules showed both amalgamated granules and porous starch granules, whereas in Kardal background, the starch granules showed an irregular rough surface. The altered starch granules in both amf and Kardal backgrounds were visible from the initial stage of potato tuber development. High-throughput transcriptomic analysis showed that expression of GLGB/SBD fusion protein in potato tubers did not affect the expression level of most genes directly involved in the starch biosynthesis except for the up-regulation of a beta-amylase gene in Kardal background. The beta-amylase protein could be responsible for the degradation of the extra branches potentially introduced by GLGB.

  16. Morphology of blends of linear and long-chain-branched polyethylenes in the solid state: A study by SANS, SAXS, and DSC

    SciTech Connect

    Wignall, G.D.; Londono, J.D.; Lin, J.S.; Alamo, R.G.; Galante, M.J.; Mandelkern, L.

    1995-04-24

    Differential scanning calorimetry (DSC), small-angle neutron scattering (SANS), and X-ray scattering (SAXS) have been used to investigate the solid-state morphology of blends of linear (high density) and long-chain-branched (low-density) polyethylenes (HDPE/LDPE). The blends are homogeneous in the melt, as previously demonstrated by SANS using the contrast obtained by deuterating the linear polymer. However, due to the structural and melting point differences ({approximately} 20 C) between HDPE and LDPE, the components may phase segregate on slow cooling (0.75 C/min). For high concentrations ({phi} {ge} 0.5) of HDPE, relatively high rates of crystallization of the linear component lead to the formation of separate stacks of HDPE and LDPE lamellae, as indicated by two-peak SAXS curves. For predominantly branched blends, the difference in crystallization rate of the components becomes smaller and only one SAXS peak is observed, indicating that the two species are in the same lamellar stack. Moreover, the phases no longer consist of the pure component and the HDPE lamellae contain up to 15--20% LDPE (and vice versa). Rapid quenching into dry ice/2-propanol ({minus}78 C) produces only one SAXS peak (and hence one lamellar stack) over the whole concentration range. The blends show extensive cocrystallization, along with a tendency for the branched material to be preferentially located in the amorphous interlamellar regions. For high concentrations ({phi} > 0.5) of HDPE-D, the overall scattering length density (SLD) is high and the excess concentration of LDPE between the lamellae enhances the SLD contrast between the crystalline and amorphous phases. Thus, the interlamellar spacing (long period) is clearly visible in the SANS pattern. The blend morphology is a strong function of the quenching rate, and samples quenched less rapidly (e.g., into water at 23 C) are similar to slowly cooled blends.

  17. Fault Branching

    NASA Astrophysics Data System (ADS)

    Dmowska, R.; Rice, J. R.; Poliakov, A. N.

    2001-12-01

    Theoretical stress analysis for a propagating shear rupture suggests that the propensity of the rupture path to branch is determined by rupture speed and by the preexisting stress state. See Poliakov, Dmowska and Rice (JGR, submitted April 2001, URL below). Deviatoric stresses near a mode II rupture tip are found to be much higher to both sides of the fault plane than directly ahead, when rupture speed becomes close to the Rayleigh speed. However, the actual pattern of predicted Coulomb failure on secondary faults is strongly dependent on the angle between the fault and the direction of maximum compression Smax in the pre-stress field. Steep Smax angles lead to more extensive failure on the extensional side, whereas shallow angles give comparable failure regions on both. Here we test such concepts against natural examples. For crustal thrust faults we may assume that Smax is horizontal. Thus nucleation on a steeply dipping plane, like the 53 ° dip for the 1971 San Fernando earthquake, is consistent with rupture path kinking to the extensional side, as inferred. Nucleation on a shallow dip, like for the 12 ° -18 ° of the 1985 Kettleman Hills event, should activate both sides, as seems consistent with aftershock patterns. Similarly, in a strike slip example, Smax is inferred to be at approximately 60 ° with the Johnson Valley fault where it branched to the extensional side onto the Landers-Kickapoo fault in the 1992 event, and this too is consistent. Further, geological examination of the activation of secondary fault features along the Johnson Valley fault and the Homestead Valley fault consistently shows that most activity occurs on the extensional side. Another strike-slip example is the Imperial Valley 1979 earthquake. The approximate Smax direction is north-south, at around 35 ° with the main fault, where it branched, on the extensional side, onto Brawley fault, again interpretable with the concepts developed.

  18. AMPLITUDE FINE STRUCTURE IN THE CEPHEID P-L RELATION. I. AMPLITUDE DISTRIBUTION ACROSS THE RR LYRAE INSTABILITY STRIP MAPPED USING THE ACCESSIBILITY RESTRICTION IMPOSED BY THE HORIZONTAL BRANCH

    SciTech Connect

    Sandage, Allan

    2010-10-10

    The largest amplitude light curves for both RR Lyrae (RRL) variables and classical Cepheids with periods less than 10 days and greater than 20 days occur at the blue edge of the respective instability strips. It is shown that the equation for the decrease in amplitude with penetration into the strip from the blue edge, and hence the amplitude fine structure within the strip, is the same for RRL and the Cepheids despite their metallicity differences. However, the manifestation of this identity is different between the two classes of variables because the sampling of the RRL strip is restricted by the discrete strip positions of the horizontal branch, a restriction that is absent for the Cepheids in stellar aggregates with a variety of ages. To show the similarity of the strip amplitude fine structure for RRL and Cepheids, we make a grid of lines of constant amplitude in the H-R diagram of the strip using amplitude data for classical Cepheids in the Galaxy, LMC, and SMC. The model implicit in the grid, that also contains lines of constant period, is used to predict the correlations between period, amplitude, and color for the two Oosterhoff RRL groups in globular clusters. The good agreement of the predictions with the observations using the classical Cepheid amplitude fine structure also for the RRL shows one aspect of the unity of the pulsation processes between the two classes of variables.

  19. [Effects of thinning on fine-root morphology, biomass and N concentration of different branch orders of Chinese fir].

    PubMed

    Wang, Zu-Hua; Li, Rui-Xia; Guan, Qing-Wei

    2013-06-01

    Taking a 25-year old Chinese fir (Cunninghamia lanceolata) plantation as the object, this paper studied the effects of thinning on the biomass, morphological traits, and nitrogen concentration of the first five orders roots. With the increase of root order (from the first to the fifth order), there was a significant increase in the fine-root biomass, diameter, and tissue density, and a significantly decrease in the specific root length (SRL), root length density (RLD), and root number (RN). Thinning increased the biomass, RLD, and RN of the first and second orders roots as well as the tissue density of the first, third, fourth, and fifth orders roots significantly, but had no effects on the SRL and nitrogen concentration of each order root. In contrast, thinning decreased the diameter of the first, third, and fourth orders roots significantly. The diameter of the second order roots was obviously smaller in surface (0-10 cm) soil than in subsurface (10-20 cm) soil, while the RLD of the first three orders roots and the RN and nitrogen concentration of the first two orders roots were larger in surface soil than in subsurface soil. The interaction of thinning and soil layer only decreased the diameter of the first two orders roots. It was suggested that the fine-root biomass and morphological traits of Chinese fir were closely related to the vegetation growth and regeneration after thinning.

  20. Ca. Similichlamydia in Epitheliocystis Co-infection of Gilthead Seabream Gills: Unique Morphological Features of a Deep Branching Chlamydial Family

    PubMed Central

    Seth-Smith, Helena M. B.; Katharios, Pantelis; Dourala, Nancy; Mateos, José M.; Fehr, Alexander G. J.; Nufer, Lisbeth; Ruetten, Maja; Guevara Soto, Maricruz; Vaughan, Lloyd

    2017-01-01

    The Planctomycetes-Verrucomicrobia-Chlamydiae (PVC) bacterial superphylum constitutes a broad range of organisms with an intriguing array of ultrastructural morphologies, including intracellular membranes and compartments and their corresponding complex genomes encoding these forms. The phylum Chlamydiae are all obligate intracellular bacteria and, although much is already known of their genomes from various families and how these regulate the various morphological forms, we know remarkably little about what is likely the deepest rooting clade of this phylum, which has only been found to contain pathogens of marine and fresh water vertebrates. The disease they are associated with is called epitheliocystis; however, analyses of the causative agents is hindered by an inability to cultivate them for refined in vitro experimentation. For this reason, we have developed tools to analyse both the genomes and the ultrastructures of bacteria causing this disease, directly from infected tissues. Here we present structural data for a member of the family Ca. Similichlamydiaceae from this deep-rooted clade, which we have identified using molecular tools, in epitheliocystis lesions of gilthead seabream (Sparus aurata) in Greece. We present evidence that the chlamydial inclusions appear to develop in a perinuclear location, similar to other members of the phylum and that a chlamydial developmental cycle is present, with chlamydial forms similar to reticular bodies (RBs) and elementary bodies (EBs) detected. Division of the RBs appeared to follow a budding process, and larger RBs with multiple condensed nucleoids were detected using both transmission electron microscopy (TEM) and by focused-ion beam, scanning electron microscopy (FIB-SEM). As model hosts, fish offer many advantages for investigation, and we hope by these efforts to encourage others to explore the biology of fish pathogens from the PVC. PMID:28424665

  1. Three-dimensional reconstruction of Haversian systems in human cortical bone using synchrotron radiation-based micro-CT: morphology and quantification of branching and transverse connections across age.

    PubMed

    Maggiano, Isabel S; Maggiano, Corey M; Clement, John G; Thomas, C David L; Carter, Yasmin; Cooper, David M L

    2016-05-01

    This study uses synchrotron radiation-based micro-computed tomography (CT) scans to reconstruct three-dimensional networks of Haversian systems in human cortical bone in order to observe and analyse interconnectivity of Haversian systems and the development of total Haversian networks across different ages. A better knowledge of how Haversian systems interact with each other is essential to improve understanding of remodeling mechanisms and bone maintenance; however, previous methodological approaches (e.g. serial sections) did not reveal enough detail to follow the specific morphology of Haversian branching, for example. Accordingly, the aim of the present study was to identify the morphological diversity of branching patterns and transverse connections, and to understand how they change with age. Two types of branching morphologies were identified: lateral branching, resulting in small osteon branches bifurcating off of larger Haversian canals; and dichotomous branching, the formation of two new osteonal branches from one. The reconstructions in this study also suggest that Haversian systems frequently target previously existing systems as a path for their course, resulting in a cross-sectional morphology frequently referred to as 'type II osteons'. Transverse connections were diverse in their course from linear to oblique to curvy. Quantitative assessment of age-related trends indicates that while in younger human individuals transverse connections were most common, in older individuals more evidence of connections resulting from Haversian systems growing inside previously existing systems was found. Despite these changes in morphological characteristics, a relatively constant degree of overall interconnectivity is maintained throughout life. Altogether, the present study reveals important details about Haversian systems and their relation to each other that can be used towards a better understanding of cortical bone remodeling as well as a more accurate

  2. Phylogenetics of Anthyllis (Leguminosae: Papilionoideae: Loteae): Partial incongruence between nuclear and plastid markers, a long branch problem and implications for morphological evolution.

    PubMed

    Degtjareva, Galina V; Valiejo-Roman, Carmen M; Samigullin, Tahir H; Guara-Requena, Miguel; Sokoloff, Dmitry D

    2012-02-01

    Phylogenetic relationships in the genus Anthyllis (Leguminosae: Papilionoideae: Loteae) were investigated using data from the nuclear ribosomal internal transcribed spacer regions (ITS) and three plastid regions (psbA-trnH intergenic spacer, petB-petD region and rps16 intron). Bayesian and maximum parsimony (MP) analysis of a concatenated plastid dataset recovered well-resolved trees that are topologically similar, with many clades supported by unique indels. MP and Bayesian analyses of the ITS sequence data recovered trees that have several well-supported topological differences, both among analyses, and to trees inferred from the plastid data. The most substantial of these concerns A. vulneraria and A. lemanniana, whose placement in the parsimony analysis of the ITS data appears to be due to a strong long-branch effect. Analysis of the secondary structure of the ITS1 spacer showed a strong bias towards transitions in A. vulneraria and A. lemanniana, many of which were also characteristic of certain outgroup taxa. This may contribute to the conflicting placement of this clade in the MP tree for the ITS data. Additional conflicts between the plastid and ITS trees were more taxonomically focused. These differences may reflect the occurrence of reticulate evolution between closely related species, including a possible hybrid origin for A. hystrix. The patterns of incongruence between the plastid and the ITS data seem to correlate with taxon ranks. All of our phylogenetic analyses supported the monophyly of Anthyllis (incl. Hymenocarpos). Although they are often taxonomically associated with Anthyllis, the genera Dorycnopsis and Tripodion are shown here to be more closely related to other genera of Loteae. We infer up to six major clades in Anthyllis that are morphologically well-characterized, and which could be recognized as sections. Four of these agree with various morphology-based classifications, while the other two are novel. We reconstruct the evolution of

  3. Multiaxonal horizontal cells in the retina of the tree shrew, Tupaia glis.

    PubMed

    Mariani, A P

    1985-03-22

    The retinas of most vertebrates contain two or more morphologically distinct types of horizontal cell, and usually one of these types lacks an axon. Among mammals, in which two types are observed, primates are exceptional in that both types of horizontal cell have axons. It then seemed of interest to study the horizontal cells of tree shrews (Tupaia glis), insectivores thought to be closely related to primates. Golgi impregnations of whole, flat-preparations revealed two types of horizontal cell. Uniaxonal cells have a compact dendritic organization with clusters of terminals, and a single thin axon with short collaterals and a few terminals, located along its length. Multiaxonal cells have a relatively large dendritic tree, and arising from the tips of about four to eight dendrites of an individual cell are thin axonlike processes which terminate as profusely branched telodendritic arborizations. This identification of the multiaxonal horizontal cells in Tupaia retina is the first time any vertebrate horizontal cell has been found to possess more than a single axon. A comparison of horizontal cells in tree shrew, monkey, cat, and squirrel retinas shows a remarkable morphological diversity within this class of mammalian retinal neuron.

  4. Investigation of retinal morphology alterations using spectral domain optical coherence tomography in a mouse model of retinal branch and central retinal vein occlusion.

    PubMed

    Ebneter, Andreas; Agca, Cavit; Dysli, Chantal; Zinkernagel, Martin S

    2015-01-01

    Retinal vein occlusion is a leading cause of visual impairment. Experimental models of this condition based on laser photocoagulation of retinal veins have been described and extensively exploited in mammals and larger rodents such as the rat. However, few reports exist on the use of this paradigm in the mouse. The objective of this study was to investigate a model of branch and central retinal vein occlusion in the mouse and characterize in vivo longitudinal retinal morphology alterations using spectral domain optical coherence tomography. Retinal veins were experimentally occluded using laser photocoagulation after intravenous application of Rose Bengal, a photo-activator dye enhancing thrombus formation. Depending on the number of veins occluded, variable amounts of capillary dropout were seen on fluorescein angiography. Vascular endothelial growth factor levels were markedly elevated early and peaked at day one. Retinal thickness measurements with spectral domain optical coherence tomography showed significant swelling (p<0.001) compared to baseline, followed by gradual thinning plateauing two weeks after the experimental intervention (p<0.001). Histological findings at day seven correlated with spectral domain optical coherence tomography imaging. The inner layers were predominantly affected by degeneration with the outer nuclear layer and the photoreceptor outer segments largely preserved. The application of this retinal vein occlusion model in the mouse carries several advantages over its use in other larger species, such as access to a vast range of genetically modified animals. Retinal changes after experimental retinal vein occlusion in this mouse model can be non-invasively quantified by spectral domain optical coherence tomography, and may be used to monitor effects of potential therapeutic interventions.

  5. Investigation of Retinal Morphology Alterations Using Spectral Domain Optical Coherence Tomography in a Mouse Model of Retinal Branch and Central Retinal Vein Occlusion

    PubMed Central

    Ebneter, Andreas; Agca, Cavit; Dysli, Chantal; Zinkernagel, Martin S.

    2015-01-01

    Retinal vein occlusion is a leading cause of visual impairment. Experimental models of this condition based on laser photocoagulation of retinal veins have been described and extensively exploited in mammals and larger rodents such as the rat. However, few reports exist on the use of this paradigm in the mouse. The objective of this study was to investigate a model of branch and central retinal vein occlusion in the mouse and characterize in vivo longitudinal retinal morphology alterations using spectral domain optical coherence tomography. Retinal veins were experimentally occluded using laser photocoagulation after intravenous application of Rose Bengal, a photo-activator dye enhancing thrombus formation. Depending on the number of veins occluded, variable amounts of capillary dropout were seen on fluorescein angiography. Vascular endothelial growth factor levels were markedly elevated early and peaked at day one. Retinal thickness measurements with spectral domain optical coherence tomography showed significant swelling (p<0.001) compared to baseline, followed by gradual thinning plateauing two weeks after the experimental intervention (p<0.001). Histological findings at day seven correlated with spectral domain optical coherence tomography imaging. The inner layers were predominantly affected by degeneration with the outer nuclear layer and the photoreceptor outer segments largely preserved. The application of this retinal vein occlusion model in the mouse carries several advantages over its use in other larger species, such as access to a vast range of genetically modified animals. Retinal changes after experimental retinal vein occlusion in this mouse model can be non-invasively quantified by spectral domain optical coherence tomography, and may be used to monitor effects of potential therapeutic interventions. PMID:25775456

  6. Multiple populations along the asymptotic giant branch of the globular cluster M4

    NASA Astrophysics Data System (ADS)

    Lardo, C.; Salaris, M.; Savino, A.; Donati, P.; Stetson, P. B.; Cassisi, S.

    2017-04-01

    Nearly all Galactic globular clusters host stars that display characteristic abundance anticorrelations, like the O-rich/Na-poor pattern typical of field halo stars, together with O-poor/Na-rich additional components. A recent spectroscopic investigation questioned the presence of O-poor/Na-rich stars amongst a sample of asymptotic giant branch (AGB) stars in the cluster M4, at variance with the spectroscopic detection of a O-poor/Na-rich component along both the cluster red giant branch (RGB) and horizontal branch. This is contrary to what is expected from the cluster horizontal branch morphology and horizontal branch stellar evolution models. Here, we have investigated this issue by employing the CUBI = (U - B) - (B - I) index, that previous studies have demonstrated to be very effective in separating multiple populations along both the RGB and AGB sequences. We confirm previous results that the RGB is intrinsically broad in the V-CUBI diagram, with the presence of two components that nicely correspond to the two populations identified by high-resolution spectroscopy. We find that AGB stars are distributed over a wide range of CUBI values, in close analogy with what is observed for the RGB, demonstrating that the AGB of M4 also hosts multiple stellar populations.

  7. Effect of the precise branching of polyethylene at each 21st CH2 group on its phase transitions, crystal structure, and morphology

    SciTech Connect

    Qui, Wulin; Sworen, John; Pyda, Marek {nmn}; Nowak-Pyda, Elisabieta; Habenschuss, Anton {Tony}; Wagener, Kenneth; Wunderlich, Bernhard {nmn}

    2006-01-01

    Three linear polyethylenes with branches at every 21st backbone atom have been analyzed by differential scanning calorimetry (DSC) and quasi-isothermal, temperature-modulated DSC. The branches were methyl (PE1M), dimethyl (PE2M), and ethyl groups (PE1E). Linear polyethylene (HDPE) and atactic poly(octadecyl acrylate) (PODA) were also analyzed. All were compared to a random poly(ethylene-co-octene-1) of similar branch concentration (LLDPE) and poly(4,4'-phthaloimidobenzoyldoeicosyleneoxycarbonyl) (PEIM-22). The HDPE has the highest melting temperature and crystallinity with relatively large contributions of reversing melting when grown as folded-chain crystals. The precisely branched polyethylenes and copolymers have lower melting temperatures and heats of fusion. Of the branched samples, PE1M crystallizes more readily, followed by PE1E and PE2M, with PE2M showing cold crystallization. In contrast to paraffins of equal length which melt fully reversibly, the precisely designed, branched polymers melt largely irreversibly with small amounts of reversing melting, which is least for the best-grown crystals. The PE1M forms monoclinic, PE1E, pseudohexagonal, or triclinic crystals, and PE2M has a multitude of crystal structures.

  8. A roundabout approach to control morphological orientation and solar-cell performance by modulating side-chain branching position in benzodithiophene-based polymers.

    PubMed

    Lee, Kyu Cheol; Song, Seyeong; Lee, Junghoon; Kim, Dong Suk; Kim, Jin Young; Yang, Changduk

    2015-04-27

    To be meaningful to guide the rational design of novel high-performance conjugated semiconductors, we prepared three benzo[1,2-b:4,5-b']dithiophene (BDT)-based polymers by systematically moving the branching point of the alkyl chain. The effect of side-chain engineering was thoroughly investigated by a range of techniques. We demonstrate that a subtle change in the branching position in the BDT core can have a critical impact on polymer packing and preferential backbone orientation in thin films; copolymers made from BDT and thieno[3,4-c]pyrrole-4,6-dione units (TPD) adopt more of a face-on orientation as the branching point is shifted closer to the backbone, which can be correlated with a dramatic difference in solar-cells performance. The high short-circuit current density (11.6 mA cm(-2) ) for the copolymer with one carbon atom between the alkoxylated oxygen atom and the branching point results from its predominantly face-on orientation and smoother surface in thin films, which results in power conversion efficiencies as high as 4.56 %.

  9. One-step growth of Si{sub 3}N{sub 4} stem-branch featured nanostructures: Morphology control by VS and VLS mode

    SciTech Connect

    Wang Qiushi; Gao Wei; Shan Lianchen; Zhang Jian; Jin Yunxia; Cong Ridong; Cui Qiliang

    2011-09-15

    We report here one-step synthesis of Si{sub 3}N{sub 4} nanodendrites by selectively applying a vapor-solid (VS) and vapor-liquid-solid (VLS) strategy via direct current arc discharge method. The resultant nanodendrites were characterized by scanning electron microscopy, energy-dispersive X-ray spectroscopy, transmission electron microscopy and X-ray powder diffraction. The spine-shaped nanodendrites were generated by a noncatalytic growth following a VS mode. The uniform secondary nanowire branches were epitaxial grown from two side surfaces of the nanowire stems. The pine-shaped nanodendrites were obtained through a catalytic growth in a VLS process. These branch nanowires were unsystematically grown from the nanocone-like stems. The photoluminescence spectra of the nanodendrites show a strong white light emission around 400-750 nm, suggesting their potential applications in light and electron emission devices. - Graphical abstract: Spine-shaped and pine-shaped Si{sub 3}N{sub 4} hierarchical nanostructures were synthesized by VS and VLS mode with plasma-assisted dc arc discharge method. Highlights: > Si{sub 3}N{sub 4} stem-branch featured nanostructures have been prepared. > Spine-shaped nanodendrites were generated by a noncatalytic growth following a VS mode. > Pine-shaped nanodendrites were obtained through a catalytic growth in a VLS process.

  10. Detection of second-generation asymptotic giant branch stars in metal-poor globular clusters

    NASA Astrophysics Data System (ADS)

    García-Hernández, D. A.

    2017-03-01

    Multiple stellar populations are actually known to be present in Galactic globular clusters (GCs). The first generation (FG) displays a halo-like chemical pattern, while the second generation (SG) one is enriched in Al and Na (depleted in Mg and O).Both generations of stars are found at different evolutionary stages like the main-sequence turnoff, the subgiant branch, and the red giant branch (RGB), but the SG seems to be absent - especially in metal-poor ([Fe/H] < -1) GCs - in more evolved evolutionary stages such as the asymptotic giant branch (AGB) phase. This suggests that not all SG stars experience the AGB phase and that AGB-manqué stars may be quite common in metal-poor GCs, which represents a fundamental problem for the theories of GC formation and evolution and stellar evolution. Very recently, we have combined the H-band Al abundances obtained by the APOGEE survey with ground-based optical photometry, reporting the first detection of SG Al-rich AGB stars in several metal-poor GCs with different observational properties such as horizontal branch (HB) morphology, metallicity, and age. The APOGEE observations thus resolve the apparent problem for stellar evolution, supporting the existing horizontal branch star canonical models, and may help to discern the nature of the GC polluters.

  11. Metamorphopsia Associated with Branch Retinal Vein Occlusion

    PubMed Central

    Manabe, Koichiro; Tsujikawa, Akitaka; Osaka, Rie; Nakano, Yuki; Fujita, Tomoyoshi; Shiragami, Chieko; Hirooka, Kazuyuki; Uji, Akihito; Muraoka, Yuki

    2016-01-01

    Purpose To apply M-CHARTS for quantitative measurements of metamorphopsia in eyes with acute branch retinal vein occlusion (BRVO) and to elucidate the pathomorphology that causes metamorphopsia. Methods This prospective study consisted of 42 consecutive patients (42 eyes) with acute BRVO. Both at baseline and one month after treatment with ranibizumab, metamorphopsia was measured with M-CHARTS, and the retinal morphological changes were examined with optical coherence tomography. Results At baseline, metamorphopsia was detected in the vertical and/or horizontal directions in 29 (69.0%) eyes; the mean vertical and horizontal scores were 0.59 ± 0.57 and 0.52 ± 0.67, respectively. The maximum inner retinal thickness showed no association with the M-CHARTS score, but the M-CHARTS score was correlated with the total foveal thickness (r = 0.43, p = 0.004), the height of serous retinal detachment (r = 0.31, p = 0.047), and the maximum outer retinal thickness (r = 0.36, p = 0.020). One month after treatment, both the inner and outer retinal thickness substantially decreased. However, metamorphopsia persisted in 26 (89.7%) of 29 eyes. The posttreatment M-CHARTS score was not correlated with any posttreatment morphological parameters. However, the posttreatment M-CHARTS score was weakly correlated with the baseline total foveal thickness (r = 0.35. p = 0.024) and closely correlated with the baseline M-CHARTS score (r = 0.78, p < 0.001). Conclusions Metamorphopsia associated with acute BRVO was quantified using M-CHARTS. Initial microstructural changes in the outer retina from acute BRVO may primarily account for the metamorphopsia. PMID:27123642

  12. Spatial Arrangement of Branches in Relation to Slope and Neighbourhood Competition

    PubMed Central

    SUMIDA, AKIHIRO; TERAZAWA, IKUE; TOGASHI, ASAKO; KOMIYAMA, AKIRA

    2002-01-01

    To gain a better understanding of the effects of spatial structure on patterns of neighbourhood competition among hardwood trees, the three‐dimensional extension of primary branches was surveyed for ten community‐grown Castanea crenata (Fagaceae) trees with respect to the positioning of neighbouring branches and the slope of the forest floor. There were significantly more branches extending towards the lower side of the slope than towards the upper side, but structural properties such as branch length and vertical angle were not affected by slope. When horizontal extension of a branch towards its neighbour was compared for a C. crenata branch and a neighbouring heterospecific, the former was significantly narrower than the latter when the inter‐branch distance (horizontal distance between the base positions of two neighbouring branches) was short (< approx. 5 m). Castanea crenata branches tended to extend in a direction avoiding neighbouring branches of heterospecifics when the inter‐branch distance was short. Furthermore, for an inter‐branch distance <3 m, the horizontal extension of a C. crenata branch was less when it was neighbouring a heterospecific branch than when neighbouring a conspecific branch. These results suggest that horizontal extension of C. crenata branches is more prone to spatial invasion by nearby neighbouring branches of heterospecifics, and that the invasion can be lessened when C. crenata trees are spatially aggregated. The reason why such an arrangement occurs is discussed in relation to the later leaf‐flush of C. crenata compared with that of other species in the forest. PMID:12096742

  13. Horizontal drilling developments

    SciTech Connect

    Gust, D.

    1997-05-01

    The advantages of horizontal drilling are discussed. Use of horizontal drilling has climbed in the past half decade as technology and familiarity offset higher costs with higher production rates and greater recoveries from new and existing wells. In essence, all types of horizontal wells expose a larger section of the reservoir to the wellbore with a resulting increase in flow rates. (A horizontal well may also be drilled to provide coning control or to intersect vertical fractures.) Thus, drilling horizontally, both onshore and offshore, reduces the number of wells necessary to develop a field.

  14. Tree branching: Leonardo da Vinci's rule versus biomechanical models.

    PubMed

    Minamino, Ryoko; Tateno, Masaki

    2014-01-01

    This study examined Leonardo da Vinci's rule (i.e., the sum of the cross-sectional area of all tree branches above a branching point at any height is equal to the cross-sectional area of the trunk or the branch immediately below the branching point) using simulations based on two biomechanical models: the uniform stress and elastic similarity models. Model calculations of the daughter/mother ratio (i.e., the ratio of the total cross-sectional area of the daughter branches to the cross-sectional area of the mother branch at the branching point) showed that both biomechanical models agreed with da Vinci's rule when the branching angles of daughter branches and the weights of lateral daughter branches were small; however, the models deviated from da Vinci's rule as the weights and/or the branching angles of lateral daughter branches increased. The calculated values of the two models were largely similar but differed in some ways. Field measurements of Fagus crenata and Abies homolepis also fit this trend, wherein models deviated from da Vinci's rule with increasing relative weights of lateral daughter branches. However, this deviation was small for a branching pattern in nature, where empirical measurements were taken under realistic measurement conditions; thus, da Vinci's rule did not critically contradict the biomechanical models in the case of real branching patterns, though the model calculations described the contradiction between da Vinci's rule and the biomechanical models. The field data for Fagus crenata fit the uniform stress model best, indicating that stress uniformity is the key constraint of branch morphology in Fagus crenata rather than elastic similarity or da Vinci's rule. On the other hand, mechanical constraints are not necessarily significant in the morphology of Abies homolepis branches, depending on the number of daughter branches. Rather, these branches were often in agreement with da Vinci's rule.

  15. Horizontal Cross Bracing Detail, Vertical Cross Bracing Detail, Horizontal Cross ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    Horizontal Cross Bracing Detail, Vertical Cross Bracing Detail, Horizontal Cross Bracing Detail, Vertical Cross Bracing-End Detail - Cumberland Covered Bridge, Spanning Mississinewa River, Matthews, Grant County, IN

  16. Epithelial dynamics of pancreatic branching morphogenesis

    PubMed Central

    Villasenor, Alethia; Chong, Diana C.; Henkemeyer, Mark; Cleaver, Ondine

    2010-01-01

    The mammalian pancreas is a highly branched gland, essential for both digestion and glucose homeostasis. Pancreatic branching, however, is poorly understood, both at the ultrastructural and cellular levels. In this article, we characterize the morphogenesis of pancreatic branches, from gross anatomy to the dynamics of their epithelial organization. We identify trends in pancreatic branch morphology and introduce a novel mechanism for branch formation, which involves transient epithelial stratification and partial loss of cell polarity, changes in cell shape and cell rearrangements, de novo tubulogenesis and epithelial tubule remodeling. In contrast to the classical epithelial budding and tube extension observed in other organs, a pancreatic branch takes shape as a multi-lumen tubular plexus coordinately extends and remodels into a ramifying, single-lumen ductal system. Moreover, our studies identify a role for EphB signaling in epithelial remodeling during pancreatic branching. Overall, these results illustrate distinct, step-wise cellular mechanisms by which pancreatic epithelium shapes itself to create a functional branching organ. PMID:21098570

  17. Polyphyly of true branching cyanobacteria (Stigonematales).

    PubMed

    Gugger, Muriel F; Hoffmann, Lucien

    2004-03-01

    Cyanobacteria with true branching are classified in Subsection V (formerly order Stigonematales) in the phylum CYANOBACTERIA: They exhibit a high degree of morphological complexity and are known from particular biotopes. Only a few stigonematalean morphotypes have been cultured, and therefore the high variability of morphotypes found in nature is under-represented in culture. Axenic cultures of Chlorogloeopsis and Fischerella sensu Rippka et al. were, to date, the only representatives of this Subsection in phylogenetic studies. The 16S rDNA sequence analysis data in this report confirm that heterocyst-forming cyanobacteria are a monophyletic group. However, unlike previous studies have suggested, these 16S rDNA data on new Stigonematales strains show that the true branching cyanobacteria are polyphyletic and can be separated into at least two major groups defined by their branching type, the first group being characterized by T-branching and the second group by Y-branching. Cyanobacteria with intercalary heterocysts and either no branching or false-branching also formed separate clusters. In consequence, our phylogenetic data do not correlate with the bacteriological and traditional classifications, which distinguish filamentous heterocystous cyanobacteria with or without true branching (Nostocales/Stigonematales).

  18. Bundle Branch Reentrant Ventricular Tachycardia

    PubMed Central

    Mazur, Alexander; Kusniec, Jairo; Strasberg, Boris

    2005-01-01

    Bundle branch reentrant (BBR) tachycardia is an uncommon form of ventricular tachycardia (VT) incorporating both bundle branches into the reentry circuit. The arrhythmia is usually seen in patients with an acquired heart disease and significant conduction system impairment, although patients with structurally normal heart have been described. Surface ECG in sinus rhythm (SR) characteristically shows intraventricular conduction defects. Patients typically present with presyncope, syncope or sudden death because of VT with fast rates frequently above 200 beats per minute. The QRS morphology during VT is a typical bundle branch block pattern, usually left bundle branch block, and may be identical to that in SR. Prolonged His-ventricular (H-V) interval in SR is found in the majority of patients with BBR VT, although some patients may have the H-V interval within normal limits. The diagnosis of BBR VT is based on electrophysiological findings and pacing maneuvers that prove participation of the His- Purkinje system in the tachycardia mechanism. Radiofrequency catheter ablation of a bundle branch can cure BBR VT and is currently regarded as the first line therapy. The technique of choice is ablation of the right bundle. The reported incidence of clinically significant conduction system impairment requiring implantation of a permanent pacemaker varies from 0% to 30%. Long-term outcome depends on the underlying cardiac disease. Patients with poor systolic left ventricular function are at risk of sudden death or death from progressive heart failure despite successful BBR VT ablation and should be considered for an implantable cardiovertor-defibrillator. PMID:16943949

  19. 10. VIEW EAST, RECESS AREA WITH BOTTOM HORIZONTAL BEAM FOR ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    10. VIEW EAST, RECESS AREA WITH BOTTOM HORIZONTAL BEAM FOR EAST GATE - Bald Eagle Cross-Cut Canal Lock, North of Water Street along West Branch of Susquehanna River South bank, 500 feet East of Jay Street Bridge, Lock Haven, Clinton County, PA

  20. Horizontal Advanced Tensiometer

    SciTech Connect

    Hubbell, Joel M.; Sisson, James B.

    2004-06-22

    An horizontal advanced tensiometer is described that allows the monitoring of the water pressure of soil positions, particularly beneath objects or materials that inhibit the use of previous monitoring wells. The tensiometer includes a porous cup, a pressure transducer (with an attached gasket device), an adaptive chamber, at least one outer guide tube which allows access to the desired horizontal position, a transducer wire, a data logger and preferably an inner guide tube and a specialized joint which provides pressure on the inner guide tube to maintain the seal between the gasket of the transducer and the adaptive chamber.

  1. Horizontal Advanced Tensiometer

    DOEpatents

    Hubbell, Joel M.; Sisson, James B.

    2004-06-22

    An horizontal advanced tensiometer is described that allows the monitoring of the water pressure of soil positions, particularly beneath objects or materials that inhibit the use of previous monitoring wells. The tensiometer includes a porous cup, a pressure transducer (with an attached gasket device), an adaptive chamber, at least one outer guide tube which allows access to the desired horizontal position, a transducer wire, a data logger and preferably an inner guide tube and a specialized joint which provides pressure on the inner guide tube to maintain the seal between the gasket of the transducer and the adaptive chamber.

  2. Bundle Branch Block

    MedlinePlus

    ... your heart to pump blood efficiently through your circulatory system. There's no specific treatment for bundle branch block itself. However, any underlying health condition that caused bundle branch block, such as heart disease, will need to be treated. In most people, ...

  3. Melons are Branched Polymers

    NASA Astrophysics Data System (ADS)

    Gurau, Razvan; Ryan, James P.

    2014-11-01

    Melonic graphs constitute the family of graphs arising at leading order in the 1/N expansion of tensor models. They were shown to lead to a continuum phase, reminiscent of branched polymers. We show here that they are in fact precisely branched polymers, that is, they possess Hausdorff dimension 2 and spectral dimension 4/3.

  4. Randomized branch sampling

    Treesearch

    Harry T. Valentine

    2002-01-01

    Randomized branch sampling (RBS) is a special application of multistage probability sampling (see Sampling, environmental), which was developed originally by Jessen [3] to estimate fruit counts on individual orchard trees. In general, the method can be used to obtain estimates of many different attributes of trees or other branched plants. The usual objective of RBS is...

  5. Horizontal Cross Bracing Detail, Vertical Cross Bracing Detail, Horizontal Cross ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    Horizontal Cross Bracing Detail, Vertical Cross Bracing Detail, Horizontal Cross Bracing Joint, Vertical Cross Bracing End Detail - Ceylon Covered Bridge, Limberlost Park, spanning Wabash River at County Road 900 South, Geneva, Adams County, IN

  6. Fine-Branched Ridges

    NASA Image and Video Library

    2015-10-14

    This image from NASA Mars Reconnaissance Orbiter spacecraft shows numerous branching ridges with various degrees of sinuosity. These branching forms resemble tributaries funneling and draining into larger channel trunks towards the upper portion of the scene. The raised relief of these branching ridges suggests that these are ancient channels are inverted due to lithification and cementation of the riverbed sediment, which made it more resistant to erosion than the surrounding material. Wind-blown bedforms are abundant and resemble small ridges that are aligned in an approximately north-south direction. http://photojournal.jpl.nasa.gov/catalog/PIA20006

  7. Materials Test Branch

    NASA Technical Reports Server (NTRS)

    Gordon, Gail

    2012-01-01

    The Materials Test Branch resides at Marshall Space Flight Center's Materials and Processing laboratory and has a long history of supporting NASA programs from Mercury to the recently retired Space Shuttle. The Materials Test Branch supports its customers by supplying materials testing expertise in a wide range of applications. The Materials Test Branch is divided into three Teams, The Chemistry Team, The Tribology Team and the Mechanical Test Team. Our mission and goal is to provide world-class engineering excellence in materials testing with a special emphasis on customer service.

  8. Dicyclic horizontal symmetries

    NASA Astrophysics Data System (ADS)

    Kong, Otto Cho Wing

    In the very successful standard theory of particle physics, the occurrence of repeated quark and lepton flavors, and especially their peculiar mass spectrum, can be accommodated parametrically but is largely unexplained. The present dissertation is an investigation into dicyclic horizontal symmetries as a theory addressing this elusive problem of flavor, as well as some other related issues in particle physics. A horizontal symmetry is a supplement to the perspective based on the experimentally well-established standard model, and its (supersymmetric) unification theories. Dicyclic groups are a special class of discrete non- abelian groups. The most pressing part of the flavor problem in the standard model is the existence of three families of (fermionic) matter and the unnaturally large hierarchy among the parameters describing their masses and mixing. In particular, the top quark is singled out as the only fermion having a natural mass at electroweak breaking scale. While bottom and tau masses may be suppressed by the Higgs vacuum expectation value, the small masses of the other two families beg an explanation. The supersymmetric counterpart of the problem is the need for a high degree of degeneracy especially among the squarks of the lighter two families. We first analyze the phenomenologically-viable quark and squark mass matrix textures using a simple algebraic method, paying particular attention to a 2 + 1 family structure. These serve as inputs for our model building exercises. We next illustrate how the various theoretical and phenomenological constraints single out a gauged dicyclic group as the most appealing candidate for a horizontal symmetry and discuss systematically our major model building strategies. A few models obtained along this line are then presented. These include a supersymmetric SU(5) /otimes Q12 /otimes U(1) model that successfully produces a phenomenologically-viable mass matrix texture pattern for the quarks and squarks.

  9. Restoration technology branch

    USGS Publications Warehouse

    ,

    2007-01-01

    The mission of Leetown Science Center (LSC), Restoration Technology Branch (RTB) is to conduct research needed to restore or protect the chemical, physical and biological integrity of desirable aquatic systems.

  10. The Olive Branch Awards.

    ERIC Educational Resources Information Center

    Harnack, William

    1984-01-01

    The first annual Olive Branch Awards, sponsored by the Writers' and Publishers Alliance and the Editors' Organizing Committee, were given to ten magazines, out of 60 that submitted entries. Winning entries are described briefly. (IM)

  11. The Olive Branch Awards.

    ERIC Educational Resources Information Center

    Harnack, William

    1984-01-01

    The first annual Olive Branch Awards, sponsored by the Writers' and Publishers Alliance and the Editors' Organizing Committee, were given to ten magazines, out of 60 that submitted entries. Winning entries are described briefly. (IM)

  12. Horizontal baffle for nuclear reactors

    DOEpatents

    Rylatt, John A.

    1978-01-01

    A horizontal baffle disposed in the annulus defined between the core barrel and the thermal liner of a nuclear reactor thereby physically separating the outlet region of the core from the annular area below the horizontal baffle. The horizontal baffle prevents hot coolant that has passed through the reactor core from thermally damaging apparatus located in the annulus below the horizontal baffle by utilizing the thermally induced bowing of the horizontal baffle to enhance sealing while accommodating lateral motion of the baffle base plate.

  13. Developmental Programming of Branching Morphogenesis in the Kidney.

    PubMed

    Sampogna, Rosemary V; Schneider, Laura; Al-Awqati, Qais

    2015-10-01

    The kidney developmental program encodes the intricate branching and organization of approximately 1 million functional units (nephrons). Branching regulation is poorly understood, as is the source of a 10-fold variation in nephron number. Notably, low nephron count increases the risk for developing hypertension and renal failure. To better understand the source of this variation, we analyzed the complete gestational trajectory of mouse kidney development. We constructed a computerized architectural map of the branching process throughout fetal life and found that organogenesis is composed of two distinct developmental phases, each with stage-specific rate and morphologic parameters. The early phase is characterized by a rapid acceleration in branching rate and by branching divisions that repeat with relatively reproducible morphology. The latter phase, however, is notable for a significantly decreased yet constant branching rate and the presence of nonstereotyped branching events that generate progressive variability in tree morphology until birth. Our map identifies and quantitates the contribution of four developmental mechanisms that guide organogenesis: growth, patterning, branching rate, and nephron induction. When applied to organs that developed under conditions of malnutrition or in the setting of growth factor mutation, our normative map provided an essential link between kidney architecture and the fundamental morphogenetic mechanisms that guide development. This morphogenetic map is expected to find widespread applications and help identify modifiable targets to prevent developmental programming of common diseases. Copyright © 2015 by the American Society of Nephrology.

  14. Branching habit and the allocation of reproductive resources in conifers

    PubMed Central

    Leslie, Andrew B.

    2012-01-01

    Background and Aims Correlated relationships between branch thickness, branch density, and twig and leaf size have been used extensively to study the evolution of plant canopy architecture, but fewer studies have explored the impact of these relationships on the allocation of reproductive resources. This study quantifies pollen cone production in conifers, which have similar basic reproductive biology but vary dramatically in branching habit, in order to test how differences in branch diameter influence pollen cone size and the density with which they are deployed in the canopy. Methods Measurements of canopy branch density, the number of cones per branch and cone size were used to estimate the amount of pollen cone tissues produced by 16 species in three major conifer clades. The number of pollen grains produced was also estimated using direct counts from individual pollen cones. Key Results The total amount of pollen cone tissues in the conifer canopy varied little among species and clades, although vegetative traits such as branch thickness, branch density and pollen cone size varied over several orders of magnitude. However, branching habit controls the way these tissues are deployed: taxa with small branches produce small pollen cones at a high density, while taxa with large branches produce large cones relatively sparsely. Conclusions Conifers appear to invest similar amounts of energy in pollen production independent of branching habit. However, similar associations between branch thickness, branch density and pollen cone size are seen across conifers, including members of living and extinct groups not directly studied here. This suggests that reproductive features relating to pollen cone size are in large part a function of the evolution of vegetative morphology and branching habit. PMID:22782240

  15. HORIZONTAL BOILING REACTOR SYSTEM

    DOEpatents

    Treshow, M.

    1958-11-18

    Reactors of the boiling water type are described wherein water serves both as the moderator and coolant. The reactor system consists essentially of a horizontal pressure vessel divided into two compartments by a weir, a thermal neutronic reactor core having vertical coolant passages and designed to use water as a moderator-coolant posltioned in one compartment, means for removing live steam from the other compartment and means for conveying feed-water and water from the steam compartment to the reactor compartment. The system further includes auxiliary apparatus to utilize the steam for driving a turbine and returning the condensate to the feed-water inlet of the reactor. The entire system is designed so that the reactor is self-regulating and has self-limiting power and self-limiting pressure features.

  16. Coupling between horizontal cells in the carp retina revealed by diffusion of Lucifer yellow.

    PubMed

    Kaneko, A; Stuart, A E

    1984-06-01

    Electrical coupling among 4 different types of horizontal cells in Cyprinus carpio was examined from the diffusion of the intracellularly injected Lucifer yellow. The type of horizontal cells was identified by a spectral response and by a distinct morphology when the retina was viewed in flat mounts under a fluorescence microscope. Lucifer yellow diffused from the injected cell into surrounding cells, and in all of these preparations, diffusion was limited to horizontal cells of the same morphological type. Axons of horizontal cells were found to be coupled, and also at axons the coupling is likely to be limited to the same cell type.

  17. Damage Tolerance Assessment Branch

    NASA Technical Reports Server (NTRS)

    Walker, James L.

    2013-01-01

    The Damage Tolerance Assessment Branch evaluates the ability of a structure to perform reliably throughout its service life in the presence of a defect, crack, or other form of damage. Such assessment is fundamental to the use of structural materials and requires an integral blend of materials engineering, fracture testing and analysis, and nondestructive evaluation. The vision of the Branch is to increase the safety of manned space flight by improving the fracture control and the associated nondestructive evaluation processes through development and application of standards, guidelines, advanced test and analytical methods. The Branch also strives to assist and solve non-aerospace related NDE and damage tolerance problems, providing consultation, prototyping and inspection services.

  18. Pen Branch delta expansion

    SciTech Connect

    Nelson, E.A.; Christensen, E.J.; Mackey, H.E.; Sharitz, R.R.; Jensen, J.R.; Hodgson, M.E.

    1984-02-01

    Since 1954, cooling water discharges from K Reactor ({anti X} = 370 cfs {at} 59 C) to Pen Branch have altered vegetation and deposited sediment in the Savannah River Swamp forming the Pen Branch delta. Currently, the delta covers over 300 acres and continues to expand at a rate of about 16 acres/yr. Examination of delta expansion can provide important information on environmental impacts to wetlands exposed to elevated temperature and flow conditions. To assess the current status and predict future expansion of the Pen Branch delta, historic aerial photographs were analyzed using both basic photo interpretation and computer techniques to provide the following information: (1) past and current expansion rates; (2) location and changes of impacted areas; (3) total acreage presently affected. Delta acreage changes were then compared to historic reactor discharge temperature and flow data to see if expansion rate variations could be related to reactor operations.

  19. Horizontal microscopy in square capillaries

    NASA Astrophysics Data System (ADS)

    Moroz, Pavel E.

    1992-07-01

    Intracellular protoplasmic movements may, due to gravity, have a vertical component greater or different from the horizontal one. This makes horizontal microscopy indispensable in the search for the cellular sensor of gravity. The possibility of the latter being a cell organelle assigns special significance to high-resolution microscopy. A horizontal suction device for picking up a cell and its high-resolution horizontal microscopy in a rectangular capillary may be helpful for detection of gravity-related shifts of cellular organelles in vivo.

  20. Branched Hamiltonians and supersymmetry

    DOE PAGES

    Curtright, Thomas L.; Zachos, Cosmas K.

    2014-03-21

    Some examples of branched Hamiltonians are explored both classically and in the context of quantum mechanics, as recently advocated by Shapere and Wilczek. These are in fact cases of switchback potentials, albeit in momentum space, as previously analyzed for quasi-Hamiltonian chaotic dynamical systems in a classical setting, and as encountered in analogous renormalization group flows for quantum theories which exhibit RG cycles. In conclusion, a basic two-worlds model, with a pair of Hamiltonian branches related by supersymmetry, is considered in detail.

  1. Morphology of spiny neurons in the human entorhinal cortex: intracellular filling with lucifer yellow.

    PubMed

    Mikkonen, M; Pitkänen, A; Soininen, H; Alafuzoff, I; Miettinen, R

    2000-01-01

    The present study was designed to investigate the morphology of spiny neurons in the human entorhinal cortex. Coronal entorhinal slices (n = 67; 200 microm thick) were obtained from autopsies of three subjects. Spiny neurons (n = 132) filled with Lucifer Yellow were analysed in different subfields and layers of the entorhinal cortex. Based on the shape of the somata and primary dendritic trees, spiny neurons were divided into four morphological categories; (i) classical pyramidal, (ii) stellate, (iii) modified stellate, and (iv) horizontal tripolar cells. The morphology of filled neurons varied more in different layers than in the different subfields of the entorhinal cortex. In layer II, the majority (81%) of spiny neurons had stellate or modified stellate morphology, but in the rostromedial subfields (olfactory subfield and rostral subfield) there were also horizontal tripolar neurons. Dendritic branches of layer II neurons extended to layer I (94%) and to layer III (83%). Unlike in layer II, most (74%) of the filled neurons in layers III, V and VI were classical pyramidal cells. The majority of pyramidal cells in the superficial portion of layer III had dendrites that extended up to layer II, occupying the space between the neuronal clusters. Some dendrites reached down to the deep portion of layer III. Apical dendrites of layer V and VI pyramidal cells traveled up to the deep portion of layer III.Our data indicate that the morphology of spiny neurons in different layers of the human entorhinal cortex is variable. Vertical extension of dendritic branches to adjacent layers supports the idea that inputs terminating in a specific lamina influence target cells located in various entorhinal layers. There appears to be more overlap in the dendritic fields between superficial layers II and III than between the superficial (II/III) and deep (V/VI) layers, thus supporting the idea of segregation of information flow targeted to the superficial or deep layers in the human

  2. Study on the Optimization of Staged Fracturing for Horizontal Wells

    NASA Astrophysics Data System (ADS)

    Qin, J.; Wang, S.; Hu, J. H.

    In order to connect natural fracture with hydraulic fracture formed in staged fracturing for horizontal wells, forming a complex fracture network to improve the production of single well. Geometric model of hydraulic fracture induced stress field has been established, we studied the induced stress distribution of staged fracturing for horizontal well, compared the different effect of induced stress under the condition of different fracturing technology showed that: Induced stress along the minimum horizontal principal stress direction is the largest, with the increase of crack distance, induced stress decreased. Different fracturing technology can lead to different induced stress, the third crack fractured between two former cracks; induced stress of the third crack is obviously bigger than induced stress of crack by sequential fracturing. By comparing induced stress in the condition of fracturing three cracks, five cracks, seven cracks, found that induced stress increased with the increase of quantity of cracks. The larger induced stress made the branch crack shifted, enhancing connectivity among branch crack, main crack and natural fracture to improve channel structure for oil and gas flowing to the main crack, and finally achieve the purpose of improving productivity for oil and gas well. The study results had important guiding significance for efficient development of reservoir and optimization of parameters for horizontal wells.

  3. Almost horizontal turbulence

    NASA Astrophysics Data System (ADS)

    Kolmogorov, A. N.

    2004-04-01

    The paper is published without modifications. Kolmogorov's manuscript was apparently prepared during his participation in one of expeditions of the ship "D. Mendeleev" to the Atlantic Ocean (1969) or in a circumnavigation of the world (1971) organized by the Institute for Oceanology led at the time by A.S. Monin. As Kolmogorov himself wrote, the choice of the topic was stimulated by observations concerning "...meanders with horizontal sizes of hundreds of kilometers on a flow involving a layer of hundreds of meters, with subsequent disintegration of these meanders into vortices gradually decreasing in size to several kilometers." In modern terminology, the paper is devoted to the problem of intensive mixing in pycnoclines, that is, thin layers of stratified fluid, caused by internal waves whose frequencies are less than the Brent-Väisälä frequency. Here I would like to note two circumstances. The first is the scientific insight characteristic for Kolmogorov; this very approach was later reflected in numerous publications (see, for instance, the monograph by V.S. Modevich, V.I. Nikulin, and A.G. Stetsenko "Dynamics of internal mixing in a stratified medium," Institute for Hydromechanics, Academy of Sciences of Ukraine, Naukova Dumka, Kiev 1988). The second, the more significant in my opinion, is the genuine intellectual curiosity and breadth of thought of this great thinker, who studied not only the most abstract mathematical constructions but also got his head out of the clouds with great interest to solve concrete applied problems.

  4. Inferring Horizontal Gene Transfer

    PubMed Central

    Lassalle, Florent; Dessimoz, Christophe

    2015-01-01

    Horizontal or Lateral Gene Transfer (HGT or LGT) is the transmission of portions of genomic DNA between organisms through a process decoupled from vertical inheritance. In the presence of HGT events, different fragments of the genome are the result of different evolutionary histories. This can therefore complicate the investigations of evolutionary relatedness of lineages and species. Also, as HGT can bring into genomes radically different genotypes from distant lineages, or even new genes bearing new functions, it is a major source of phenotypic innovation and a mechanism of niche adaptation. For example, of particular relevance to human health is the lateral transfer of antibiotic resistance and pathogenicity determinants, leading to the emergence of pathogenic lineages [1]. Computational identification of HGT events relies upon the investigation of sequence composition or evolutionary history of genes. Sequence composition-based ("parametric") methods search for deviations from the genomic average, whereas evolutionary history-based ("phylogenetic") approaches identify genes whose evolutionary history significantly differs from that of the host species. The evaluation and benchmarking of HGT inference methods typically rely upon simulated genomes, for which the true history is known. On real data, different methods tend to infer different HGT events, and as a result it can be difficult to ascertain all but simple and clear-cut HGT events. PMID:26020646

  5. Branching in rice.

    PubMed

    Wang, Yonghong; Li, Jiayang

    2011-02-01

    Rice branching, including the formation of tillers and panicle branches, has been well investigated over the past several years because of its agronomic importance. A major breakthrough in elucidating rice tillering in the recent years was the discovery of strigolactones, a specific group of terpenoid lactones that can inhibit axillary bud outgrowth. Since that discovery, new tillering mutants, that is, dwarf 27 (d27) or dwarf14 (d14, also reported as d88 or htd2), have been identified with reduced strigolactone levels or strigolactone response. DWARF27 (D27) and DWARF14 (D14) probably act on strigolactone biosynthesis and signal transduction, respectively. Additionally, several genes controlling panicle branches have been identified recently. DEP1 and IPA1/WFP are essential dominant/semidominant regulators that determine rice panicle branches and thus affect the grain yields. More importantly, dep1 and ipa1 alleles have been shown to be applicable for the improvement of rice grain yields in molecular breeding. Copyright © 2010 Elsevier Ltd. All rights reserved.

  6. New branched DNA constructs.

    PubMed

    Chandra, Madhavaiah; Keller, Sascha; Gloeckner, Christian; Bornemann, Benjamin; Marx, Andreas

    2007-01-01

    The Watson-Crick base pairing of DNA is an advantageous phenomenon that can be exploited when using DNA as a scaffold for directed self-organization of nanometer-sized objects. Several reports have appeared in the literature that describe the generation of branched DNA (bDNA) with variable numbers of arms that self-assembles into predesigned architectures. These bDNA units are generated by using cleverly designed rigid crossover DNA molecules. Alternatively, bDNA can be generated by using synthetic branch points derived from either nucleoside or non-nucleoside building blocks. Branched DNA has scarcely been explored for use in nanotechnology or from self-assembling perspectives. Herein, we wish to report our results for the synthesis, characterization, and assembling properties of asymmetrical bDNA molecules that are able to generate linear and circular bDNA constructs. Our strategy for the generation of bDNA is based on a branching point that makes use of a novel protecting-group strategy. The bDNA units were generated by means of automated DNA synthesis methods and were used to generate novel objects by employing chemical and biological techniques. The entities generated might be useful building blocks for DNA-based nanobiotechnology.

  7. Front Range Branch Officers

    NASA Astrophysics Data System (ADS)

    The Front Range Branch of AGU has installed officers for 1990: Ray Noble, National Center for Atmospheric Research, chair; Sherry Oaks, U.S. Geological Survey, chair-elect; Howard Garcia, NOAA, treasurer; Catharine Skokan, Colorado School of Mines, secretary. JoAnn Joselyn of NOAA is past chair. Members at large are Wallace Campbell, NOAA; William Neff, USGS; and Stephen Schneider, NCAR.

  8. Radioiodinated branched carbohydrates

    DOEpatents

    Goodman, Mark M.; Knapp, Jr., Furn F.

    1989-01-01

    A radioiodinated branched carbohydrate for tissue imaging. Iodine-123 is stabilized in the compound by attaching it to a vinyl functional group that is on the carbohydrate. The compound exhibits good uptake and retention and is promising in the development of radiopharmaceuticals for brain, heart and tumor imaging.

  9. Understanding Horizontal Governance. Research Brief

    ERIC Educational Resources Information Center

    Ferguson, Daniel

    2009-01-01

    Horizontal governance is an umbrella term that covers a range of approaches to policy development, service delivery issues, and management practices. A horizontal initiative may take place across levels of government, across boundaries between units of a single department or agency or among multiple departments or agencies, or across public,…

  10. Branching structure and strain hardening of branched metallocene polyethylenes

    SciTech Connect

    Torres, Enrique; Li, Si-Wan; Costeux, Stéphane; Dealy, John M.

    2015-09-15

    There have been a number of studies of a series of branched metallocene polyethylenes (BMPs) made in a solution, continuous stirred tank reactor (CSTR) polymerization. The materials studied vary in branching level in a systematic way, and the most highly branched members of the series exhibit mild strain hardening. An outstanding question is which types of branched molecules are responsible for strain hardening in extension. This question is explored here by use of polymerization and rheological models along with new data on the extensional flow behavior of the most highly branched members of the set. After reviewing all that is known about the effects of various branching structures in homogeneous polymers and comparing this with the structures predicted to be present in BMPs, it is concluded that in spite of their very low concentration, treelike molecules with branch-on-branch structure provide a large number of deeply buried inner segments that are essential for strain hardening in these polymers.

  11. Dissecting Genetic Network of Fruit Branch Traits in Upland Cotton by Association Mapping Using SSR Markers

    PubMed Central

    Fan, Shuli; Song, Meizhen; Pang, Chaoyou; Pei, Wenfeng; Yu, Shuxun

    2017-01-01

    Genetic architecture of branch traits has large influences on the morphological structure, photosynthetic capacity, planting density, and yield of Upland cotton (Gossypium hirsutum L.). This research aims to reveal the genetic effects of six branch traits, including bottom fruit branch node number (BFBNN), bottom fruit branch length (BFBL), middle fruit branch node number (MFBNN), middle fruit branch length (MFBL), upper fruit branch node number (UFBNN), and upper fruit branch length (UFBL). Association mapping was conducted for these traits of 39 lines and their 178 F1 hybrids in three environments. There were 20 highly significant Quantitative Trait SSRs (QTSs) detected by mixed linear model approach analyzing a full genetic model with genetic effects of additive, dominance, epistasis and their environment interaction. The phenotypic variation explained by genetic effects ranged from 32.64 ~ 91.61%, suggesting these branch traits largely influenced by genetic factors. PMID:28121983

  12. Curved branching crystals and differentiation in comb-layered rocks

    NASA Technical Reports Server (NTRS)

    Lofgren, G. E.; Donaldson, C. H.

    1975-01-01

    An investigation is conducted concerning two common features of comb layered rocks. Attention is given to the curvature of oriented, elongate, branching crystals and the tendency to form highly differentiated layers. Crystallization studies of plagioclase show that some degree of supercooling is necessary to produce the skeletal, curved, and branching plagioclase crystal morphologies found in comb-layered rocks and that curved crystals can be grown without the presence of a directed stress.

  13. Postotic laterosensory canal and pterotic branch homology in catfishes.

    PubMed

    Schaefer, S A; Aquino, A E

    2000-12-01

    Morphology of the postotic laterosensory canal was surveyed across loricarioid and outgroup catfishes in order to resolve conflicting statements regarding homology and phylogenetic significance of intrinsic character variation. A pterotic branch is widespread among catfishes and has been identified as a synapomorphy for siluriforms, but its presence in loricarioid catfishes has been disputed. In contrast to previous statements that absence of a pterotic branch is synapomorphic for loricarioids, we confirm the presence of a pterotic branch in Nematogenys inermis and other trichomycterids, callichthyids, and loricariids. The pterotic branch is secondarily absent in scoloplacids and astroblepids. We present criteria for establishing homology of the pterotic branch and review character state optimization schemes on the currently accepted phylogeny. The postotic region of loricariids is further specialized in having an expanded swimbladder capsule that incorporates the trunk lateral line canal and has a lateral opening covered by a greatly expanded pterotic complex. The trunk lateral line enters the swimbladder capsule mesial to the pterotic lateral wall and passes anteromedially as a fleshy tube before forming the postotic canal in the pterotic, a morphology reported previously for a single loricariid representative. Variation in the relative extent and topographic position of postotic canal branches and other morphologies is diagnostic of certain loricariid taxa, suggesting a rich character complex of potential utility in phylogeny reconstruction.

  14. Branching instability in expanding bacterial colonies

    PubMed Central

    Giverso, Chiara; Verani, Marco; Ciarletta, Pasquale

    2015-01-01

    Self-organization in developing living organisms relies on the capability of cells to duplicate and perform a collective motion inside the surrounding environment. Chemical and mechanical interactions coordinate such a cooperative behaviour, driving the dynamical evolution of the macroscopic system. In this work, we perform an analytical and computational analysis to study pattern formation during the spreading of an initially circular bacterial colony on a Petri dish. The continuous mathematical model addresses the growth and the chemotactic migration of the living monolayer, together with the diffusion and consumption of nutrients in the agar. The governing equations contain four dimensionless parameters, accounting for the interplay among the chemotactic response, the bacteria–substrate interaction and the experimental geometry. The spreading colony is found to be always linearly unstable to perturbations of the interface, whereas branching instability arises in finite-element numerical simulations. The typical length scales of such fingers, which align in the radial direction and later undergo further branching, are controlled by the size parameters of the problem, whereas the emergence of branching is favoured if the diffusion is dominant on the chemotaxis. The model is able to predict the experimental morphologies, confirming that compact (resp. branched) patterns arise for fast (resp. slow) expanding colonies. Such results, while providing new insights into pattern selection in bacterial colonies, may finally have important applications for designing controlled patterns. PMID:25652464

  15. Horizontal violence among nursing students.

    PubMed

    Longo, Joy

    2007-06-01

    In a research study student nurses in the clinical setting reported experiencing horizontal violence or "nurses eating their young." The types of behaviors most frequently encountered were emotional and verbal attacks. Some students did not report incidences of horizontal violence to their instructors, so it is important that the faculty be cognizant that such behaviors can occur and establish open communication to assist students in dealing with such behaviors.

  16. Thermal Energy Conversion Branch

    NASA Technical Reports Server (NTRS)

    Bielozer, Matthew C.; Schreiber, Jeffrey, G.; Wilson, Scott D.

    2004-01-01

    The Thermal Energy Conversion Branch (5490) leads the way in designing, conducting, and implementing research for the newest thermal systems used in space applications at the NASA Glenn Research Center. Specifically some of the most advanced technologies developed in this branch can be broken down into four main areas: Dynamic Power Systems, Primary Solar Concentrators, Secondary Solar Concentrators, and Thermal Management. Work was performed in the Dynamic Power Systems area, specifically the Stirling Engine subdivision. Today, the main focus of the 5490 branch is free-piston Stirling cycle converters, Brayton cycle nuclear reactors, and heat rejection systems for long duration mission spacecraft. All space exploring devices need electricity to operate. In most space applications, heat energy from radioisotopes is converted to electrical power. The Radioisotope Thermoelectric Generator (RTG) already supplies electricity for missions such as the Cassini Spacecraft. The focus of today's Stirling research at GRC is aimed at creating an engine that can replace the RTG. The primary appeal of the Stirling engine is its high system efficiency. Because it is so efficient, the Stirling engine will significantly reduce the plutonium fuel mission requirements compared to the RTG. Stirling is also being considered for missions such as the lunar/Mars bases and rovers. This project has focused largely on Stirling Engines of all types, particularly the fluidyne liquid piston engine. The fluidyne was developed by Colin D. West. This engine uses the same concepts found in any type of Stirling engine, with the exception of missing mechanical components. All the working components are fluid. One goal was to develop and demonstrate a working Stirling Fluidyne Engine at the 2nd Annual International Energy Conversion Engineering Conference in Providence, Rhode Island.

  17. Combustion Branch Website Development

    NASA Technical Reports Server (NTRS)

    Bishop, Eric

    2004-01-01

    The NASA combustion branch is a leader in developing and applying combustion science to focused aerospace propulsion systems concepts. It is widely recognized for unique facilities, analytical tools, and personnel. In order to better communicate the outstanding research being done in this Branch to the public and other research organization, a more substantial website was desired. The objective of this project was to build an up-to-date site that reflects current research in a usable and attractive manner. In order to accomplish this, information was requested from all researchers in the Combustion branch, on their professional skills and on the current projects. This information was used to fill in the Personnel and Research sections of the website. A digital camera was used to photograph all personnel and these photographs were included in the personnel section as well. The design of the site was implemented using the latest web standards: xhtml and external css stylesheets. This implementation conforms to the guidelines recommended by the w3c. It also helps to ensure that the web site is accessible by disabled users, and complies with Section 508 Federal legislation (which mandates that all Federal websites be accessible). Graphics for the new site were generated using the gimp (www.gimp.org) an open-source graphics program similar to Adobe Photoshop. Also, all graphics on the site were of a reasonable size (less than 20k, most less than 2k) so that the page would load quickly. Technologies such as Macromedia Flash and Javascript were avoided, as these only function on some clients which have the proper software installed or enabled. The website was tested on different platforms with many different browsers to ensure there were no compatibility issues. The website was tested on windows with MS IE 6, MSIE 5 , Netscape 7, Mozilla and Opera. On a Mac, the site was tested with MS IE 5 , Netscape 7 and Safari.

  18. Combustion Branch Website Development

    NASA Technical Reports Server (NTRS)

    Bishop, Eric

    2004-01-01

    The NASA combustion branch is a leader in developing and applying combustion science to focused aerospace propulsion systems concepts. It is widely recognized for unique facilities, analytical tools, and personnel. In order to better communicate the outstanding research being done in this Branch to the public and other research organization, a more substantial website was desired. The objective of this project was to build an up-to-date site that reflects current research in a usable and attractive manner. In order to accomplish this, information was requested from all researchers in the Combustion branch, on their professional skills and on the current projects. This information was used to fill in the Personnel and Research sections of the website. A digital camera was used to photograph all personnel and these photographs were included in the personnel section as well. The design of the site was implemented using the latest web standards: xhtml and external css stylesheets. This implementation conforms to the guidelines recommended by the w3c. It also helps to ensure that the web site is accessible by disabled users, and complies with Section 508 Federal legislation (which mandates that all Federal websites be accessible). Graphics for the new site were generated using the gimp (www.gimp.org) an open-source graphics program similar to Adobe Photoshop. Also, all graphics on the site were of a reasonable size (less than 20k, most less than 2k) so that the page would load quickly. Technologies such as Macromedia Flash and Javascript were avoided, as these only function on some clients which have the proper software installed or enabled. The website was tested on different platforms with many different browsers to ensure there were no compatibility issues. The website was tested on windows with MS IE 6, MSIE 5 , Netscape 7, Mozilla and Opera. On a Mac, the site was tested with MS IE 5 , Netscape 7 and Safari.

  19. Flight Dynamics Analysis Branch

    NASA Technical Reports Server (NTRS)

    Stengle, Tom; Flores-Amaya, Felipe

    2000-01-01

    This report summarizes the major activities and accomplishments carried out by the Flight Dynamics Analysis Branch (FDAB), Code 572, in support of flight projects and technology development initiatives in fiscal year 2000. The report is intended to serve as a summary of the type of support carried out by the FDAB, as well as a concise reference of key accomplishments and mission experience derived from the various mission support roles. The primary focus of the FDAB is to provide expertise in the disciplines of flight dynamics, spacecraft trajectory, attitude analysis, and attitude determination and control. The FDAB currently provides support for missions and technology development projects involving NASA, government, university, and private industry.

  20. Mass-loss on the red giant branch: the value and metallicity dependence of Reimers' η in globular clusters

    NASA Astrophysics Data System (ADS)

    McDonald, I.; Zijlstra, A. A.

    2015-03-01

    The impact of metallicity on the mass-loss rate from red giant branch (RGB) stars is studied through its effect on the parameters of horizontal branch (HB) stars. The scaling factors from Reimers and Schröder and Cuntz are used to measure the efficiency of RGB mass-loss for typical stars in 56 well-studied Galactic globular clusters (GCs). The median values among clusters are, respectively, η _R = 0.477 ± 0.070 ^{+0.050}_{-0.062} and η _SC = 0.172 ± 0.024 ^{+0.018}_{-0.023} (standard deviation and systematic uncertainties, respectively). Over a factor of 200 in iron abundance, η varies by ≲30 per cent, thus mass-loss mechanisms on the RGB have very little metallicity dependence. Any remaining dependence is within the current systematic uncertainties on cluster ages and evolution models. The low standard deviation of η among clusters (≈14 per cent) contrasts with the variety of HB morphologies. Since η incorporates cluster age, this suggests that age accounts for the majority of the `second parameter problem', and that a Reimers-like law provides a good mass-loss model. The remaining spread in η correlates with cluster mass and density, suggesting helium enrichment provides the third parameter explaining HB morphology of GCs. We close by discussing asymptotic giant branch (AGB) mass-loss, finding that the AGB tip luminosity is better reproduced and η has less metallicity dependence if GCs are more co-eval than generally thought.

  1. Strigolactone inhibition of shoot branching.

    PubMed

    Gomez-Roldan, Victoria; Fermas, Soraya; Brewer, Philip B; Puech-Pagès, Virginie; Dun, Elizabeth A; Pillot, Jean-Paul; Letisse, Fabien; Matusova, Radoslava; Danoun, Saida; Portais, Jean-Charles; Bouwmeester, Harro; Bécard, Guillaume; Beveridge, Christine A; Rameau, Catherine; Rochange, Soizic F

    2008-09-11

    A carotenoid-derived hormonal signal that inhibits shoot branching in plants has long escaped identification. Strigolactones are compounds thought to be derived from carotenoids and are known to trigger the germination of parasitic plant seeds and stimulate symbiotic fungi. Here we present evidence that carotenoid cleavage dioxygenase 8 shoot branching mutants of pea are strigolactone deficient and that strigolactone application restores the wild-type branching phenotype to ccd8 mutants. Moreover, we show that other branching mutants previously characterized as lacking a response to the branching inhibition signal also lack strigolactone response, and are not deficient in strigolactones. These responses are conserved in Arabidopsis. In agreement with the expected properties of the hormonal signal, exogenous strigolactone can be transported in shoots and act at low concentrations. We suggest that endogenous strigolactones or related compounds inhibit shoot branching in plants. Furthermore, ccd8 mutants demonstrate the diverse effects of strigolactones in shoot branching, mycorrhizal symbiosis and parasitic weed interaction.

  2. A tree canopy height delineation method based on Morphological Reconstruction—Open Crown Decomposition

    NASA Astrophysics Data System (ADS)

    Liu, Q.; Jing, L.; Li, Y.; Tang, Y.; Li, H.; Lin, Q.

    2016-04-01

    For the purpose of forest management, high resolution LIDAR and optical remote sensing imageries are used for treetop detection, tree crown delineation, and classification. The purpose of this study is to develop a self-adjusted dominant scales calculation method and a new crown horizontal cutting method of tree canopy height model (CHM) to detect and delineate tree crowns from LIDAR, under the hypothesis that a treetop is radiometric or altitudinal maximum and tree crowns consist of multi-scale branches. The major concept of the method is to develop an automatic selecting strategy of feature scale on CHM, and a multi-scale morphological reconstruction-open crown decomposition (MRCD) to get morphological multi-scale features of CHM by: cutting CHM from treetop to the ground; analysing and refining the dominant multiple scales with differential horizontal profiles to get treetops; segmenting LiDAR CHM using watershed a segmentation approach marked with MRCD treetops. This method has solved the problems of false detection of CHM side-surface extracted by the traditional morphological opening canopy segment (MOCS) method. The novel MRCD delineates more accurate and quantitative multi-scale features of CHM, and enables more accurate detection and segmentation of treetops and crown. Besides, the MRCD method can also be extended to high optical remote sensing tree crown extraction. In an experiment on aerial LiDAR CHM of a forest of multi-scale tree crowns, the proposed method yielded high-quality tree crown maps.

  3. Clear Evidence for the Presence of Second-generation Asymptotic Giant Branch Stars in Metal-poor Galactic Globular Clusters

    NASA Astrophysics Data System (ADS)

    García-Hernández, D. A.; Mészáros, Sz.; Monelli, M.; Cassisi, S.; Stetson, P. B.; Zamora, O.; Shetrone, M.; Lucatello, S.

    2015-12-01

    Galactic globular clusters (GCs) are known to host multiple stellar populations: a first generation (FG) with a chemical pattern typical of halo field stars and a second generation (SG) enriched in Na and Al and depleted in O and Mg. Both stellar generations are found at different evolutionary stages (e.g., the main-sequence turnoff, the subgiant branch, and the red giant branch (RGB)). The non detection of SG asymptotic giant branch (AGB) stars in several metal-poor ([Fe/H] < -1) GCs suggests that not all SG stars ascend the AGB phase, and that failed AGB stars may be very common in metal-poor GCs. This observation represents a serious problem for stellar evolution and GC formation/evolution theories. We report fourteen SG-AGB stars in four metal-poor GCs (M13, M5, M3, and M2) with different observational properties: horizontal branch (HB) morphology, metallicity, and age. By combining the H-band Al abundances obtained by the Apache Point Observatory Galactic Evolution Experiment survey with ground-based optical photometry, we identify SG Al-rich AGB stars in these four GCs and show that Al-rich RGB/AGB GC stars should be Na-rich. Our observations provide strong support for present, standard stellar models, i.e., without including a strong mass-loss efficiency, for low-mass HB stars. In fact, current empirical evidence is in agreement with the predicted distribution of FG and SG stars during the He-burning stages based on these standard stellar models.

  4. Branching toughens fibrous networks.

    PubMed

    Koh, C T; Oyen, M L

    2012-08-01

    Fibrous collagenous networks are not only stiff but also tough, due to their complex microstructures. This stiff yet tough behavior is desirable for both medical and military applications but it is difficult to reproduce in engineering materials. While the nonlinear hyperelastic behavior of fibrous networks has been extensively studied, the understanding of toughness is still incomplete. Here, we identify a microstructure mimicking the branched bundles of a natural type I collagen network, in which partially cross-linked long fibers give rise to novel combinations of stiffness and toughness. Finite element analysis shows that the stiffness of fully cross-linked fibrous networks is amplified by increasing the fibril length and cross-link density. However, a trade-off of such stiff networks is reduced toughness. By having partially cross-linked networks with long fibrils, the networks have comparable stiffness and improved toughness as compared to the fully cross-linked networks. Further, the partially cross-linked networks avoid the formation of kinks, which cause fibril rupture during deformation. As a result, the branching allows the networks to have stiff yet tough behavior.

  5. Pen Branch Fault Program

    SciTech Connect

    Price, V.; Stieve, A.L.; Aadland, R.

    1990-09-28

    Evidence from subsurface mapping and seismic reflection surveys at Savannah River Site (SRS) suggests the presence of a fault which displaces Cretaceous through Tertiary (90--35 million years ago) sediments. This feature has been described and named the Pen Branch fault (PBF) in a recent Savannah River Laboratory (SRL) paper (DP-MS-88-219). Because the fault is located near operating nuclear facilities, public perception and federal regulations require a thorough investigation of the fault to determine whether any seismic hazard exists. A phased program with various elements has been established to investigate the PBF to address the Nuclear Regulatory Commission regulatory guidelines represented in 10 CFR 100 Appendix A. The objective of the PBF program is to fully characterize the nature of the PBF (ESS-SRL-89-395). This report briefly presents current understanding of the Pen Branch fault based on shallow drilling activities completed the fall of 1989 (PBF well series) and subsequent core analyses (SRL-ESS-90-145). The results are preliminary and ongoing: however, investigations indicate that the fault is not capable. In conjunction with the shallow drilling, other activities are planned or in progress. 7 refs., 8 figs., 1 tab.

  6. Horizontal Cells, the Odd Ones Out in the Retina, Give Insights into Development and Disease

    PubMed Central

    Boije, Henrik; Shirazi Fard, Shahrzad; Edqvist, Per-Henrik; Hallböök, Finn

    2016-01-01

    Thorough investigation of a neuronal population can help reveal key aspects regarding the nervous system and its development. The retinal horizontal cells have several extraordinary features making them particularly interesting for addressing questions regarding fate assignment and subtype specification. In this review we discuss and summarize data concerning the formation and diversity of horizontal cells, how morphology is correlated to molecular markers, and how fate assignment separates the horizontal lineage from the lineages of other retinal cell types. We discuss the novel and unique features of the final cell cycle of horizontal cell progenitors and how they may relate to retinoblastoma carcinogenesis. PMID:27486389

  7. Synthesis of branched polysaccharides with tunable degree of branching.

    PubMed

    Ciric, Jelena; Loos, Katja

    2013-03-01

    An in vitro enzyme-catalyzed tandem reaction using the enzymes phosphorylase b from rabbit muscle and Deinococcus geothermalis glycogen branching enzyme (Dg GBE) to obtain branched polyglucans with tunable degree of branching (2% ÷ 13%) is presented. The tunable degree of branching is obtained by varying the reaction conditions such as pH value, the choice of reducing agent and its concentration and reaction time. Linear amylose is formed by the phosphorylase-catalyzed propagation of glucose-1-phosphate while Dg GBE introduces branching points on the α-(1→6) position by relocating short oligosaccharide chains. Our results show that the best way to obtain different degrees of branching with this set of enzymes is by regulation of the reaction time.

  8. Cone size is related to branching architecture in conifers.

    PubMed

    Leslie, Andrew B; Beaulieu, Jeremy M; Crane, Peter R; Donoghue, Michael J

    2014-09-01

    The relationship between branch diameter and leaf size has been widely used to understand how vegetative resources are allocated in plants. Branching architecture influences reproductive allocation as well, but fewer studies have explored this relationship at broad phylogenetic or ecological scales. In this study, we tested whether pollen-producing and seed-producing cone size scales with branch diameter in conifers, a diverse and globally distributed lineage of nonflowering seed plants. Branch diameter and cone size were analyzed using multiple regression models and evolutionary models of trait evolution for a data set of 293 extant conifer species within an explicit phylogenetic framework. Branch diameter is a strong predictor of cone size across conifer species, particularly for pollen cones and dry seed cones. However, these relationships are complex in detail because leaf morphology and seed dispersal biology influence the specific ways in which they are expressed. The ubiquity and strength of these scaling relationships across conifers suggest that reproductive and vegetative morphologies are coupled in the group, and it is therefore difficult to disentangle the evolution of cone size from the evolution of branching architecture.

  9. Nurses’ Perceptions of Horizontal Violence

    PubMed Central

    Taylor, Rosemary

    2016-01-01

    In this article, I describe a study exploring horizontal violence and nurses’ perceptions of the phenomenon within the context of two 28-bed inpatient hospital units. The purpose of the study was to develop a clearer understanding of horizontal violence, incorporating observation and inquiry to identify the language nurses use to describe their experiences and factors in the nursing work environment that may perpetuate the phenomenon. Observation, review and analysis of policies, and interviews with staff were completed between June and November 2012. Thematic analysis resulted in five themes: (a) behaviors are minimized and not recognized, (b) fear inhibits all reporting, (c) avoidance and isolation are coping strategies, (d) lack of respect and support, and (e) organizational chaos. The findings suggest future interventions must address a range of factors that perpetuate horizontal violence within the nursing work environment with consideration for the embeddedness and complexity of the phenomenon. PMID:28462334

  10. Nuclear component horizontal seismic restraint

    DOEpatents

    Snyder, Glenn J.

    1988-01-01

    A nuclear component horizontal seismic restraint. Small gaps limit horizontal displacement of components during a seismic occurrence and therefore reduce dynamic loadings on the free lower end. The reactor vessel and reactor guard vessel use thicker section roll-forged rings welded between the vessel straight shell sections and the bottom hemispherical head sections. The inside of the reactor guard vessel ring forging contains local vertical dovetail slots and upper ledge pockets to mount and retain field fitted and installed blocks. As an option, the horizontal displacement of the reactor vessel core support cone can be limited by including shop fitted/installed local blocks in opposing alignment with the reactor vessel forged ring. Beams embedded in the wall of the reactor building protrude into apertures in the thermal insulation shell adjacent the reactor guard vessel ring and have motion limit blocks attached thereto to provide to a predetermined clearance between the blocks and reactor guard vessel ring.

  11. URBAN MORPHOLOGY FOR HOUSTON TO DRIVE MODELS-3/CMAQ AT NEIGHBORHOOD SCALES

    EPA Science Inventory

    Air quality simulation models applied at various horizontal scales require different degrees of treatment in the specifications of the underlying surfaces. As we model neighborhood scales ( 1 km horizontal grid spacing), the representation of urban morphological structures (e....

  12. URBAN MORPHOLOGY FOR HOUSTON TO DRIVE MODELS-3/CMAQ AT NEIGHBORHOOD SCALES

    EPA Science Inventory

    Air quality simulation models applied at various horizontal scales require different degrees of treatment in the specifications of the underlying surfaces. As we model neighborhood scales ( 1 km horizontal grid spacing), the representation of urban morphological structures (e....

  13. Success in horizontal barrier developments

    SciTech Connect

    Pettit, P.J.; Ridenour, D.E.; Jalovec, J.

    1996-06-01

    A successful proof of concept demonstration has been conducted of operational methods and tooling for the in situ construction of underground horizontal barriers for the control and containment of groundwater and contamination. The method involves jet grouting with specially adapted tools guided between twin, parallel wells for the placement of a grout beneath a waste site. The objective of the work is to develop reliable methods of constructing extensive, competent horizontal barriers underneath waste sites without excavating or penetrating the waste during the process.

  14. Speckle Imaging Over Horizontal Paths

    SciTech Connect

    Carrano, C J

    2002-05-21

    Atmospheric aberrations reduce the resolution and contrast in surveillance images recorded over horizontal or slant paths. This paper describes our recent horizontal and slant path imaging experiments of extended scenes as well as the results obtained using speckle imaging. The experiments were performed with an 8-inch diameter telescope placed on either a rooftop or hillside and cover ranges of interest from 0.5 km up to 10 km. The scenery includes resolution targets, people, vehicles, and other structures. The improvement in image quality using speckle imaging is dramatic in many cases, and depends significantly upon the atmospheric conditions. We quantify resolution improvement through modulation transfer function measurement comparisons.

  15. Functional morphology of the hallucal metatarsal with implications for inferring grasping ability in extinct primates.

    PubMed

    Goodenberger, Katherine E; Boyer, Doug M; Orr, Caley M; Jacobs, Rachel L; Femiani, John C; Patel, Biren A

    2015-03-01

    Primate evolutionary morphologists have argued that selection for life in a fine branch niche resulted in grasping specializations that are reflected in the hallucal metatarsal (Mt1) morphology of extant "prosimians", while a transition to use of relatively larger, horizontal substrates explains the apparent loss of such characters in anthropoids. Accordingly, these morphological characters-Mt1 torsion, peroneal process length and thickness, and physiological abduction angle-have been used to reconstruct grasping ability and locomotor mode in the earliest fossil primates. Although these characters are prominently featured in debates on the origin and subsequent radiation of Primates, questions remain about their functional significance. This study examines the relationship between these morphological characters of the Mt1 and a novel metric of pedal grasping ability for a large number of extant taxa in a phylogenetic framework. Results indicate greater Mt1 torsion in taxa that engage in hallucal grasping and in those that utilize relatively small substrates more frequently. This study provides evidence that Carpolestes simpsoni has a torsion value more similar to grasping primates than to any scandentian. The results also show that taxa that habitually grasp vertical substrates are distinguished from other taxa in having relatively longer peroneal processes. Furthermore, a longer peroneal process is also correlated with calcaneal elongation, a metric previously found to reflect leaping proclivity. A more refined understanding of the functional associations between Mt1 morphology and behavior in extant primates enhances the potential for using these morphological characters to comprehend primate (locomotor) evolution.

  16. Methods and Technologies Branch (MTB)

    Cancer.gov

    The Methods and Technologies Branch focuses on methods to address epidemiologic data collection, study design and analysis, and to modify technological approaches to better understand cancer susceptibility.

  17. Branches in the Everett interpretation

    NASA Astrophysics Data System (ADS)

    Cunningham, Arthur J.

    2014-05-01

    Hugh Everett III describes a quantum measurement as resulting in the "branching" of the quantum state of observer and measured system, with all possible measurement outcomes represented by the ensuing branches of the total quantum state. But Everett does not specify a general rule for decomposing a quantum state into branches, and commentators have long puzzled over how, and even whether, to regard Everett's notion of branching states as physically meaningful. It is common today to appeal to decoherence considerations as a way of giving physical content to the Everettian notion of branches, but these appeals to decoherence are often regarded as considerations foreign to Everett's own approach. This paper contends that this assessment is only half right: though he does not invoke environmental decoherence, Everett does appeal to decoherence considerations, broadly understood, in his treatment of measurement. Careful consideration of his idealized models of measurement, and of the significance he ascribes to the branching of states corresponding to definite measurement outcomes, reveals that his notion of branching refers to a special physical characteristic of elements of a particular decomposition, namely the absence of interference between these component states as a result of the particular dynamics governing the evolution of the system. Characterizations of branching that appeal to the results of modern decoherence theory should therefore be regarded as a natural development of Everett's own physically meaningful conception of branching.

  18. The control of branching morphogenesis

    PubMed Central

    Iber, Dagmar; Menshykau, Denis

    2013-01-01

    Many organs of higher organisms are heavily branched structures and arise by an apparently similar process of branching morphogenesis. Yet the regulatory components and local interactions that have been identified differ greatly in these organs. It is an open question whether the regulatory processes work according to a common principle and how far physical and geometrical constraints determine the branching process. Here, we review the known regulatory factors and physical constraints in lung, kidney, pancreas, prostate, mammary gland and salivary gland branching morphogenesis, and describe the models that have been formulated to analyse their impacts. PMID:24004663

  19. Analysis of long branch extraction and long branch shortening

    PubMed Central

    2010-01-01

    Background Long branch attraction (LBA) is a problem that afflicts both the parsimony and maximum likelihood phylogenetic analysis techniques. Research has shown that parsimony is particularly vulnerable to inferring the wrong tree in Felsenstein topologies. The long branch extraction method is a procedure to detect a data set suffering from this problem so that Maximum Likelihood could be used instead of Maximum Parsimony. Results The long branch extraction method has been well cited and used by many authors in their analysis but no strong validation has been performed as to its accuracy. We performed such an analysis by an extensive search of the branch length search space under two topologies of six taxa, a Felsenstein-like topology and Farris-like topology. We also examine a long branch shortening method. Conclusions The long branch extraction method seems to mask the majority of the search space rendering it ineffective as a detection method of LBA. A proposed alternative, the long branch shortening method, is also ineffective in predicting long branch attraction for all tree topologies. PMID:21047381

  20. Horizontal electric fields from lightning return strokes

    NASA Technical Reports Server (NTRS)

    Thomson, E. M.; Medelius, P. J.; Rubinstein, M.; Uman, M. A.; Johnson, J.

    1988-01-01

    An experiment to measure simultaneously the wideband horizontal and vertical electric fields from lightning return strokes is described. Typical wave shapes of the measured horizontal and vertical fields are presented, and the horizontal fields are characterized. The measured horizontal fields are compared with calculated horizontal fields obtained by applying the wavetilt formula to the vertical fields. The limitations and sources of error in the measurement technique are discussed.

  1. Horizontal drilling installs dutch waterline

    SciTech Connect

    Not Available

    1986-08-01

    A 32-in. potable water line system, installed by Van Eijk Leidingen B.V. in Holland, was laid through an intensively cultivated vegetable gardening area, and designed to furnish additional irrigation water. Using a horizontally drilled 42-in. hole under the Maasdijk, though a difficult job, reduced the length by more than 3 miles.

  2. Modeling branching in cereals.

    PubMed

    Evers, Jochem B; Vos, Jan

    2013-10-10

    Cereals and grasses adapt their structural development to environmental conditions and the resources available. The primary adaptive response is a variable degree of branching, called tillering in cereals. Especially for heterogeneous plant configurations the degree of tillering varies per plant. Functional-structural plant modeling (FSPM) is a modeling approach allowing simulation of the architectural development of individual plants, culminating in the emergent behavior at the canopy level. This paper introduces the principles of modeling tillering in FSPM, using (I) a probability approach, forcing the dynamics of tillering to correspond to measured probabilities. Such models are particularly suitable to evaluate the effect structural variables on system performance. (II) Dose-response curves, representing a measured or assumed response of tillering to an environmental cue. (III) Mechanistic approaches to tillering including control by carbohydrates, hormones, and nutrients. Tiller senescence is equally important for the structural development of cereals as tiller appearance. Little study has been made of tiller senescence, though similar concepts seem to apply as for tiller appearance.

  3. A Branch Meeting in Avon

    ERIC Educational Resources Information Center

    Vaughan, Kathryn; Coles, Alf

    2011-01-01

    The Association of Teachers of Mathematics (ATM) exists for, and is run by, its members. Branch meetings are so much more than the "grass roots" of the association--it can be a powerhouse of inspiration and creativity. In this article, the authors provide commentaries on a recent branch meeting.

  4. A Branch Meeting in Avon

    ERIC Educational Resources Information Center

    Vaughan, Kathryn; Coles, Alf

    2011-01-01

    The Association of Teachers of Mathematics (ATM) exists for, and is run by, its members. Branch meetings are so much more than the "grass roots" of the association--it can be a powerhouse of inspiration and creativity. In this article, the authors provide commentaries on a recent branch meeting.

  5. A positive approach to branching.

    PubMed

    Janssen, Bart J; Drummond, Revel S M; Ledger, Susan E; Snowden, Kimberley C

    2010-04-01

    Plants regulate the development of branches in response to environmental and developmental signals in order to maximize reproductive success. A number of hormone signals are involved in the regulation of branching and both their production and transmission affect axillary meristem outgrowth. With the identification of strigolactones as root-derived branch inhibitors it seems likely that a biochemical pathway starting from a carotenoid and resulting in production of a strigolactone hormone is present in most plants. Our observation that loss of CCD7 or CCD8 also results in production of a promoter of branching from roots shows the branching pathway has multiple levels of control which allows a high degree of sensitivity to subtle differences in environmental and developmental signals.

  6. Airplanes in Horizontal Curvilinear Flight

    NASA Technical Reports Server (NTRS)

    Kann, Heinrich

    1924-01-01

    War airplanes require not only high speed and the ability to climb rapidly, but also the ability to transverse sharp curves quickly. Here, an attempt is made to give a simple method of calculating horizontal curvilinear flight. A method for determining the area of the aileron and rubber surfaces are also indicated. The discussion given here applies primarily to single and two-seater airplanes, although it can be extended to larger airplanes.

  7. Genetic species delineation among branching Caribbean Porites corals

    NASA Astrophysics Data System (ADS)

    Prada, C.; DeBiasse, M. B.; Neigel, J. E.; Yednock, B.; Stake, J. L.; Forsman, Z. H.; Baums, I. B.; Hellberg, M. E.

    2014-12-01

    Coral species are difficult to discern because of their morphological plasticity, long generation times, and slow rates of mitochondrial DNA evolution. Among Caribbean representatives of the genus Porites are three named species ( P. divaricata, P. furcata, and P. porites) with branching colony morphologies whose validity as genetically isolated species has been debated. We present sequence data from the mitochondrial control region, nuclear ITS, and nine single-copy nuclear loci for the Caribbean Porites and a related eastern Pacific species. mtDNA sequences were nearly invariant among the three branching species and their crustose sister P. branneri, and ITS sequences from these four were intermingled. An information theoretic analysis provided no support for upholding the three named Caribbean branching species. Both a clustering analysis and an analysis of molecular variance showed that sequence variation from the three branching forms is partitioned more by geography than by taxonomy. Multi-locus coalescent phylogenetic analysis provided a calibrated estimate for the nuclear DNA substitution rate (0.14 % Ma-1) close to that for other corals. Because no generalities have emerged from genetic investigations of the validity of morphologically defined coral species, the use of single-copy nuclear data is likely to be important in testing problematic species designations.

  8. Universal features of dendrites through centripetal branch ordering

    PubMed Central

    Effenberger, Felix; Muellerleile, Julia

    2017-01-01

    Dendrites form predominantly binary trees that are exquisitely embedded in the networks of the brain. While neuronal computation is known to depend on the morphology of dendrites, their underlying topological blueprint remains unknown. Here, we used a centripetal branch ordering scheme originally developed to describe river networks—the Horton-Strahler order (SO)–to examine hierarchical relationships of branching statistics in reconstructed and model dendritic trees. We report on a number of universal topological relationships with SO that are true for all binary trees and distinguish those from SO-sorted metric measures that appear to be cell type-specific. The latter are therefore potential new candidates for categorising dendritic tree structures. Interestingly, we find a faithful correlation of branch diameters with centripetal branch orders, indicating a possible functional importance of SO for dendritic morphology and growth. Also, simulated local voltage responses to synaptic inputs are strongly correlated with SO. In summary, our study identifies important SO-dependent measures in dendritic morphology that are relevant for neural function while at the same time it describes other relationships that are universal for all dendrites. PMID:28671947

  9. Branch strategies - Modeling and optimization

    NASA Technical Reports Server (NTRS)

    Dubey, Pradeep K.; Flynn, Michael J.

    1991-01-01

    The authors provide a common platform for modeling different schemes for reducing the branch-delay penalty in pipelined processors as well as evaluating the associated increased instruction bandwidth. Their objective is twofold: to develop a model for different approaches to the branch problem and to help select an optimal strategy after taking into account additional i-traffic generated by branch strategies. The model presented provides a flexible tool for comparing different branch strategies in terms of the reduction it offers in average branch delay and also in terms of the associated cost of wasted instruction fetches. This additional criterion turns out to be a valuable consideration in choosing between two strategies that perform almost equally. More importantly, it provides a better insight into the expected overall system performance. Simple compiler-support-based low-implementation-cost strategies can be very effective under certain conditions. An active branch prediction scheme based on loop buffers can be as competitive as a branch-target-buffer based strategy.

  10. Branching geometry induced by lung self-regulated growth

    NASA Astrophysics Data System (ADS)

    Clément, Raphaël; Douady, Stéphane; Mauroy, Benjamin

    2012-12-01

    Branching morphogenesis is a widely spread phenomenon in nature. In organogenesis, it results from the inhomogeneous growth of the epithelial sheet, leading to its repeated branching into surrounding mesoderm. Lung morphogenesis is an emblematic example of tree-like organogenesis common to most mammals. The core signalling network is well identified, notably the Fgf10/Shh couple, required to initiate and maintain branching. In a previous study, we showed that the restriction by SHH of Fgf10 expression domain to distal mesenchyme spontaneously induces differential epithelial proliferation leading to branching. A simple Laplacian model qualitatively reproduced FGF10 dynamics in the mesenchyme and the spontaneous self-avoiding branching morphogenesis. However, early lung geometry has several striking features that remain to be addressed. In this paper, we investigate, through simulations and data analysis, if the FGF10-diffusion scenario accounts for the following aspects of lung morphology: size dispersion, asymmetry of branching events, and distal epithelium-mesothelium equilibrium. We report that they emerge spontaneously in the model, and that most of the underlying mechanisms can be understood as dynamical interactions between gradients and shape. This suggests that specific regulation may not be required for the emergence of these striking geometrical features.

  11. Industry survey for horizontal wells. Final report

    SciTech Connect

    Wilson, D.D.; Kaback, D.S.; Denhan, M.E.; Watkins, D.

    1993-07-01

    An international survey of horizontal environmental wells was performed during May and June of 1993. The purpose of the survey was to provide the environmental industry with an inventory of horizontal environmental wells and information pertaining to the extent of the use of horizontal environmental wells, the variety of horizontal environmental well applications, the types of geologic and hydrogeologic conditions within which horizontal environmental wells have been installed, and the companies that perform horizontal environmental well installations. Other information, such as the cost of horizontal environmental well installations and the results of tests performed on the wells, is not complete but is provided as general information with the caveat that the information should not be used to compare drilling companies. The result of the survey is a catalogue of horizontal environmental wells that are categorized by the objective or use of the wells, the vertical depth of the wells, and the drilling company contracted to install the wells.

  12. Lateral contacts and interactions of horizontal cell dendrites in the retina of the larval tiger salamander.

    PubMed

    Lasansky, A

    1980-04-01

    1. The contacts of horizontal cell dendrites with processes of other second order neurones were studied at the level of the electron microscope in serial sections of the salamander retina. Intracellular recordings of the responses to light of horizontal and bipolar cells were used to investigate the possible significance of some of the morphological findings.2. Horizontal cell dendrites make close membrane appositions (gap junctions) with one another and are post-synaptic to bipolar cell dendrites at presumed chemical synapses. On the other hand, there is no clear evidence that horizontal cell dendrites are presynaptic to any other neuronal processes at the outer plexiform layer, so that the output connexions of horizontal cell bodies remain a matter of speculation.3. It is suggested that the bipolar cell input and the gap junctions between dendrites contribute, respectively, depolarizing and hyperpolarizing components to the responses of horizontal cell bodies to surround illumination. In addition, the facilitatory effect of central illumination on the surround response of horizontal cell bodies may result, although perhaps only partly, from observed properties of the surround response of bipolar cells.4. In the course of these observations, bipolar cells were found to be presynaptic at the outer plexiform layer not only to horizontal cell dendrites, but also to other bipolar cells, horizontal cell axon terminals and certain processes belonging to an as yet unidentified neurone.

  13. Asymmetric Branching in Biological Resource Distribution Networks

    NASA Astrophysics Data System (ADS)

    Brummer, Alexander Byers

    There is a remarkable relationship between an organism's metabolic rate (resting power consumption) and the organism's mass. It may be a universal law of nature that an organism's resting metabolic rate is proportional to its mass to the power of 3/4. This relationship, known as Kleiber's Law, appears to be valid for both plants and animals. This law is important because it implies that larger organisms are more efficient than smaller organisms, and knowledge regarding metabolic rates are essential to a multitude of other fields in ecology and biology. This includes modeling the interactions of many species across multiple trophic levels, distributions of species abundances across large spatial landscapes, and even medical diagnostics for respiratory and cardiovascular pathologies. Previous models of vascular networks that seek to identify the origin of metabolic scaling have all been based on the unrealistic assumption of perfectly symmetric branching. In this dissertation I will present a theory of asymmetric branching in self-similar vascular networks (published by Brummer et al. in [9]). The theory shows that there can exist a suite of vascular forms that result in the often observed 3/4 metabolic scaling exponent of Kleiber's Law. Furthermore, the theory makes predictions regarding major morphological features related to vascular branching patterns and their relationships to metabolic scaling. These predictions are suggestive of evolutionary convergence in vascular branching. To test these predictions, I will present an analysis of real mammalian and plant vascular data that shows: (i) broad patterns in vascular networks across entire animal kingdoms and (ii) within these patterns, plant and mammalian vascular networks can be uniquely distinguished from one another (publication in preparation by Brummer et al.). I will also present results from a computational study in support of point (i). Namely, that asymmetric branching may be the optimal strategy to

  14. Portable Horizontal-Drilling And Positioning Device

    NASA Technical Reports Server (NTRS)

    Smigocki, Edmund; Johnson, Clarence

    1988-01-01

    Portable horizontal-drilling and positioning device, constructed mainly of off-the-shelf components, accurately drills horizontal small holes in irregularly shaped objects. Holes precisely placed and drilled in objects that cannot be moved to shop area. New device provides three axes of movement while maintaining horizontal drilling.

  15. Fault branching and rupture directivity

    NASA Astrophysics Data System (ADS)

    Fliss, Sonia; Bhat, Harsha S.; Dmowska, Renata; Rice, James R.

    2005-06-01

    Could the directivity of a complex earthquake be inferred from the ruptured fault branches it created? Typically, branches develop in forward orientation, making acute angles relative to the propagation direction. Direct backward branching of the same style as the main rupture (e.g., both right lateral) is disallowed by the stress field at the rupture front. Here we propose another mechanism of backward branching. In that mechanism, rupture stops along one fault strand, radiates stress to a neighboring strand, nucleates there, and develops bilaterally, generating a backward branch. Such makes diagnosing directivity of a past earthquake difficult without detailed knowledge of the branching process. As a field example, in the Landers 1992 earthquake, rupture stopped at the northern end of the Kickapoo fault, jumped onto the Homestead Valley fault, and developed bilaterally there, NNW to continue the main rupture but also SSE for 4 km forming a backward branch. We develop theoretical principles underlying such rupture transitions, partly from elastostatic stress analysis, and then simulate the Landers example numerically using a two-dimensional elastodynamic boundary integral equation formulation incorporating slip-weakening rupture. This reproduces the proposed backward branching mechanism based on realistic if simplified fault geometries, prestress orientation corresponding to the region, standard lab friction values for peak strength, and fracture energies characteristic of the Landers event. We also show that the seismic S ratio controls the jumpable distance and that curving of a fault toward its compressional side, like locally along the southeastern Homestead Valley fault, induces near-tip increase of compressive normal stress that slows rupture propagation.

  16. Novel side branch ostial stent.

    PubMed

    Chen, Shao-Liang; Lv, Shu-Zheng; Kwan, Tak W

    2009-04-01

    Bifurcation lesions are technically challenging and plagued by a high incidence of restenosis, especially at the side branch orifice, which results in a more frequent need for revascularization during the follow-up period. This report discusses two clinical experiences with a novel side branch ostial stent, the BIGUARD stent, designed for the treatment of bifurcation lesions; procedural success with no in-hospital complications was observed in types IVb and Ia lesions.

  17. Soils of Walker Branch Watershed

    SciTech Connect

    Lietzke, D.A.

    1994-01-01

    The soil survey of Walker Branch Watershed (WBW) utilized the most up-to-date knowledge of soils, geology, and geohydrology in building the soils data base needed to reinterpret past research and to begin new research in the watershed. The soils of WBW were also compared with soils mapped elsewhere along Chestnut Ridge on the Oak Ridge Reservation to (1) establish whether knowledge obtained elsewhere could be used within the watershed, (2) determine whether there were any soils restricted to the watershed, and (3) evaluate geologic formation lateral variability. Soils, surficial geology, and geomorphology were mapped at a scale of 1:1200 using a paper base map having 2-ft contour intervals. Most of the contours seemed to reasonably represent actual landform configurations, except for dense wooded areas. For example, the very large dolines or sinkholes were shown on the contour base map, but numerous smaller ones were not. In addition, small drainageways and gullies were often not shown. These often small but important features were located approximately as soil mapping progressed. WBW is underlain by dolostones of the Knox Group, but only a very small part of the surface area contains outcroppings of rock and most outcrops were located in the lower part. Soil mapping revealed the presence of both ancient alluvium and ancient colluvium deposits, not recognized in previous soil surveys, that have been preserved in high-elevation stable portions of present-day landforms. An erosional geomorphic process of topographic inversion requiring several millions of years within the Pleistocene is necessary to bring about the degree of inversion that is expressed in the watershed. Indeed, some of these ancient alluvial and colluvial remnants may date back into the Tertiary. Also evident in the watershed, and preserved in the broad, nearly level bottoms of dolines, are multiple deposits of silty material either devoid or nearly devoid of coarse fragments. Recent research

  18. Single-crystalline self-branched anatase titania nanowires for dye-sensitized solar cells

    NASA Astrophysics Data System (ADS)

    Li, Zhenquan; Yang, Huang; Wu, Fei; Fu, Jianxun; Wang, Linjun; Yang, Weiguang

    2017-03-01

    The morphology of the anatase titania plays an important role in improving the photovoltaic performance in dye-sensitized solar cells. In this work, single-crystalline self-branched anatase TiO2 nanowires have been synthesized by hydrothermal method using TBAH and CTAB as morphology controlling agents. The obtained self-branched TiO2 nanowires dominated by a large percentage of (010) facets. The photovoltaic conversion efficiency (6.37%) of dye-sensitized solar cell (DSSC) based on the self-branched TiO2 nanowires shows a significant improvement (26.6%) compared to that of P25 TiO2 (5.03%). The enhanced performance of the self-branched TiO2 nanowires-based DSSC is due to heir large percent of exposed (010) facets which have strong dye adsorption capacity and effective charge transport of the self-branched 1D nanostructures.

  19. Single-crystalline self-branched anatase titania nanowires for dye-sensitized solar cells

    NASA Astrophysics Data System (ADS)

    Li, Zhenquan; Yang, Huang; Wu, Fei; Fu, Jianxun; Wang, Linjun; Yang, Weiguang

    2016-12-01

    The morphology of the anatase titania plays an important role in improving the photovoltaic performance in dye-sensitized solar cells. In this work, single-crystalline self-branched anatase TiO2 nanowires have been synthesized by hydrothermal method using TBAH and CTAB as morphology controlling agents. The obtained self-branched TiO2 nanowires dominated by a large percentage of (010) facets. The photovoltaic conversion efficiency (6.37%) of dye-sensitized solar cell (DSSC) based on the self-branched TiO2 nanowires shows a significant improvement (26.6%) compared to that of P25 TiO2 (5.03%). The enhanced performance of the self-branched TiO2 nanowires-based DSSC is due to heir large percent of exposed (010) facets which have strong dye adsorption capacity and effective charge transport of the self-branched 1D nanostructures.

  20. Structural Mechanics and Dynamics Branch

    NASA Technical Reports Server (NTRS)

    Stefko, George

    2003-01-01

    The 2002 annual report of the Structural Mechanics and Dynamics Branch reflects the majority of the work performed by the branch staff during the 2002 calendar year. Its purpose is to give a brief review of the branch s technical accomplishments. The Structural Mechanics and Dynamics Branch develops innovative computational tools, benchmark experimental data, and solutions to long-term barrier problems in the areas of propulsion aeroelasticity, active and passive damping, engine vibration control, rotor dynamics, magnetic suspension, structural mechanics, probabilistics, smart structures, engine system dynamics, and engine containment. Furthermore, the branch is developing a compact, nonpolluting, bearingless electric machine with electric power supplied by fuel cells for future "more electric" aircraft. An ultra-high-power-density machine that can generate projected power densities of 50 hp/lb or more, in comparison to conventional electric machines, which generate usually 0.2 hp/lb, is under development for application to electric drives for propulsive fans or propellers. In the future, propulsion and power systems will need to be lighter, to operate at higher temperatures, and to be more reliable in order to achieve higher performance and economic viability. The Structural Mechanics and Dynamics Branch is working to achieve these complex, challenging goals.

  1. Long chain branching of PLA

    NASA Astrophysics Data System (ADS)

    Gu, Liangliang; Xu, Yuewen; Fahnhorst, Grant; Macosko, Christopher W.

    2017-05-01

    A trifunctional aziridine linker, trimethylolpropane tris(2-methyl-1-aziridinepropionate) (TTMAP), was melt blended with linear polylactic acid (PLA) to make star branched PLA. Adding pyromellitic dianhydride (PMDA) led to long chain branched (LCB) PLA. Mixing torque evolution during melt processing revealed high reactivity of aziridine with the carboxyl end group on PLA and an incomplete reaction of PMDA with the hydroxyl end group. Star-shaped PLA exhibited higher viscosity but no strain hardening in extensional flow while LCB PLA showed significant extensional hardening. Excess TTMAP in the branching reaction resulted in gel formation, which led to failure at low strain in extension. PMDA conversion was estimated based on gelation theory. The strain rate dependence of extensional hardening indicated that the LCB PLA had a low concentration of long chain branched molecules with an H-shaped topology. Unlike current methods used to branch PLA, free radical chemistry or use of an epoxy functional oligomers, our branching strategy produced strain hardening with less increase in shear viscosity. This study provides guidelines for design of polymers with low shear viscosity, which reduces pressure drop in extrusion, combined with strong extensional hardening, which enhances performance in processes that involve melt stretching.

  2. Panspermia and horizontal gene transfer

    NASA Astrophysics Data System (ADS)

    Klyce, Brig

    2009-08-01

    Evidence that extremophiles are hardy and ubiquitous is helping to make panspermia a respectable theory. But even if life on Earth originally came from space, biologists assume that the subsequent evolution of life is still governed by the darwinian paradigm. In this review we show how panspermia could amend darwinism and point to a cosmic source for, not only extremophiles but, all of life. This version of panspermia can be called "strong panspermia." To support this theory we will discuss recent evidence pertaining to horizontal gene transfer, viruses, genes apparently older than the Earthly evolution of the features they encode, and primate-specific genes without identifiable precursors.

  3. Multigraft Copolymer Superelastomers: Synthesis Morphology, and Properties

    SciTech Connect

    Uhrig, David; Schlegel, Ralf; Weidisch, Roland; Mays, Jimmy

    2011-01-01

    The synthesis of well-defined multigraft copolymers having a polydiene backbone with polystyrene side chains is briefly reviewed, with particular focus on controlling branch point spacing and branch point functionality. Use of living anionic polymerization and chlorosilane linking chemistry has led to the synthesis of series of materials having regularly spaced trifunctional (comb), tetrafunctional (centipede), and hexafunctional (barbwire) branch points. The morphologies of these materials were characterized by transmission electron microscopy and small-angle X-ray scattering, and it was found that the morphologies were controlled by the local architectural asymmetry associated with each branch point. Mechanical properties studies revealed that such multigraft copolymers represent a new class of thermoplastic elastomers (TPEs) with superior elongation at break and low residual strains as compared to conventional TPEs.

  4. Principles of branch formation and branch patterning in Hydrozoa.

    PubMed

    Berking, Stefan

    2006-01-01

    The freshwater polyp Hydra produces buds which separate from the parent. Other Hydrozoa produce branches which remain connected to the parent, thus forming a colony. Some Hydrozoa grow by means of an organ that is like a shoot apical meristem. Others display a sympodial type of growth. In this article, I propose that these different types of branches are organized by a common pattern-forming system. This system has self-organizing properties. It causes branch tip formation and is kept active in the tip when the tip finally differentiates into a hypostome of a polyp. The system does not cause structure formation directly but rather, determines a tissue property called positional value, in such a way that a gradient of values forms in the tissue of the bud or branch. The local value determines the local morphodynamic processes, including differentiation of the hypostome (highest positional value), tentacles and basal disc and of the exoskeleton pattern along the shoot. A high positional value favors the onset of a new self-organizing process and by lateral inhibition, such a process prevents the initiation of a further process in its surroundings. Small quantitative differences in the range of the signals involved determine whether a bud or a branch forms and whether monopodial and sympodial growth follows.

  5. Quantitative macroinvertebrate survey of Pen Branch and Indian Grave Branch

    SciTech Connect

    Not Available

    1989-02-01

    A total of 80 species were collected at all sites on Pen Branch and Indian Grave Branch during the 28 day period for colonization of the multiplate artificial substrate samplers. The two upstream sites demonstrated the highest species richness. During the sampling interval a release of significant proportion entered Indian Grave Branch, affecting all downstream sites. This effect was most severe at sites 3, 4, and 7, apparently resulting in heavy scouring of the multiplate samplers. Nevertheless, much colonization did occur at sites 3 and 4, with hydropsychid caddisflies, blackflies and midges predominant. At sites 5 and 6 a greater degree of recovery was noted, due to the lessened scouring in the broad floodplain. These downstream sites had significant numbers of mayflies along with the numerous midges. Considered overall, colonization during the period since the K Reactor has ceased releasing thermal effluent into Pen Branch and Indian Grave Branch has been substantial, introducing a substantial proportion of the species known from other nearby streams. 29 tabs.

  6. Application of morphologic burrow architects: lungfish or crayfish?

    USGS Publications Warehouse

    Hasiotis, Stephen T.; Mitchell, Charles E.; Dubiel, Russell R.

    1993-01-01

    A methodology for trace fossil identification using burrowing signatures is tested by evaluating ancient and modern lungfish and crayfish burrows and comparing them to previously undescribed burrows in a stratigraphic interval thought to contain both lungfish and crayfish burrows. Permian burrows that bear skeletal remains of the lungfish Gnathorhiza, from museum collections, were evaluated to identify unique burrow morphologies that could be used to distinguish lungfish from crayfish burrows when fossil remains are absent. The lungfish burrows were evaluated for details of the burrowing mechanism preserved in the burrow morphologies together forming burrowing signatures and were compared to new burrows in the Chinle Formation of western Colorado to test the methodology of using burrow signatures to identify unknown burrows. Permian lungfish aestivation burrows show simple, nearly vertical, unbranched architectures and relatively smooth surficial morphologies with characteristic quasi‐horizontal striae on the burrow walls and vertical striae on the bulbous terminus. Burrow lengths do not exceed 0.5 m. In contrast, modern and ancient crayfish burrows exhibit simple to highly complex architectures with highly textured surficial morphologies. Burrow lengths may reach 4 to 5 m. Burrow morphologies unlike those identified in Gnathorhiza aestivation burrows were found in four burrow groups from museum collections. Two of these groups exhibit simple architectures and horizontal striae that were greater in sinuosity and magnitude, respectively. One of these burrows contains the remains of Lysorophus, but the burrow surface reveals no reliable surficial characteristics. It is not clear whether Lysorophus truly burrowed or merely occupied a pre‐existing structure. The other two groups exhibit surficial morphologies similar to those found on modern and ancient crayfish burrows and may provide evidence of freshwater crayfish in the Permian. Burrows from the Upper Triassic

  7. VizieR Online Data Catalog: Horizontal branch stars in NGC 6723 (Gratton+, 2015)

    NASA Astrophysics Data System (ADS)

    Gratton, R. G.; Lucatello, S.; Sollima, A.; Carretta, E.; Bragaglia, A.; Momany, Y.; D'Orazi, V.; Salaris, M.; Cassisi, S.; Stetson, P. B.

    2015-02-01

    We observed a total of 58 candidate HB stars of NGC 6723 with FLAMES + GIRAFFE at the VLT. The instrument was used in MEDUSA mode, with fibres pointing to each star and several (~20) fibres used for determining the local sky background. Observations were made between 2011-07-11 and 2011-08-27. (5 data files).

  8. VizieR Online Data Catalog: Horizontal branch stars in NGC 1851 (Gratton+, 2012)

    NASA Astrophysics Data System (ADS)

    Gratton, R. G.; Lucatello, S.; Carretta, E.; Bragaglia, A.; D'Orazi, V.; Al Momany, Y.; Sollima, A.; Salaris, M.; Cassisi, S.

    2012-10-01

    We acquired spectra for 35 stars on the BHB, 1 RR Lyrae variable, 57 stars on the RHB, and 13 on the lower RGB (luminosity below the bump) of NGC 1851 using the GIRAFFE fibre-fed spectrograph at VLT . (3 data files).

  9. [Morphogenesis of proximal branch leaves in mosses].

    PubMed

    Ignatov, M S; Spirina, U N

    2012-01-01

    The formation of deeply dissected and compound leaves at the bases of branches, their homology between different groups of mosses, and probable factors responsible for their development are considered. Previous authors differ in the interpretation of such leaves and in most cases describe them as special morphological structures named pseudoparaphyllia. It is shown, however, that this term has been applied both to whole leaves and to separate leaf parts. Among the patterns of leaf formation deviating from the basic type, a special place belongs to the Hampeella variant, where deeply dissected and compound leaves are formed due to the delayed development of branch primordia. The families representing this variant occupy a basal position in the phylogenetic tree of pleurocarpous mosses. The Leucodon variant, where splitting of leaves into lobes is apparently explained by strong stem extension, is not specific for any definite phylogenetic group and manifests itself in different families. The Hypnum variant is also not associated with certain phylogenetic lineages, but it provides an example of more profound specialization.

  10. Body size and the small branch niche: using marsupial ontogeny to model primate locomotor evolution.

    PubMed

    Shapiro, Liza J; Young, Jesse W; VandeBerg, John L

    2014-03-01

    Recently proposed ancestral locomotor and morphological 'stages' leading to the evolution of primates have emphasized small body size, and a transition from a clawed non-grasping stage, to a clawed, grasping stage with clawless opposable hallux, to a fully-nailed primate with grasping extremities. This evolutionary transition was presumably associated with frequent use of the small branch niche. To model elements of these evolutionary transitions, we investigate how body size, substrate size, substrate orientation and grasping morphology interact to influence quadrupedal kinematics within and between ontogenetic samples of two small-bodied marsupials, one arboreal (Petaurus breviceps) and the other mainly terrestrial (Monodelphis domestica). Longitudinal morphometric and kinematic data were collected from four juvenile P. breviceps (33-75 g) and two juvenile M. domestica (18-95 g) walking across poles of three diameters (2.5, 1.0, and 0.5 cm) and three orientations (horizontal, 30° incline, 30° decline). The two species responded similarly to some substrate conditions, but diverged in response to others. Kinematic divergence between the two species reflects Monodelphis' relatively shorter digits, reduced grasping ability and greater need for stabilizing mechanisms on narrow substrates. At a given relative body size or pole orientation, Monodelphis used higher limb duty factors, more limbs in support per stride, lower limb phases, and in some conditions, faster speeds compared with Petaurus. Interspecific differences were the least distinct on declined poles, highlighting the particular challenge of this substrate condition, even for arboreally adapted species. Small-bodied, arboreal primate ancestors would likely have employed the kinematic mechanisms common to our model taxa, but those with enhanced grasping adaptations would most likely not have required the increased level of stabilizing mechanisms exhibited by Monodelphis. Thus, using these two species

  11. Horizontal gene transfer in chromalveolates

    PubMed Central

    Nosenko, Tetyana; Bhattacharya, Debashish

    2007-01-01

    Background Horizontal gene transfer (HGT), the non-genealogical transfer of genetic material between different organisms, is considered a potentially important mechanism of genome evolution in eukaryotes. Using phylogenomic analyses of expressed sequence tag (EST) data generated from a clonal cell line of a free living dinoflagellate alga Karenia brevis, we investigated the impact of HGT on genome evolution in unicellular chromalveolate protists. Results We identified 16 proteins that have originated in chromalveolates through ancient HGTs before the divergence of the genera Karenia and Karlodinium and one protein that was derived through a more recent HGT. Detailed analysis of the phylogeny and distribution of identified proteins demonstrates that eight have resulted from independent HGTs in several eukaryotic lineages. Conclusion Recurring intra- and interdomain gene exchange provides an important source of genetic novelty not only in parasitic taxa as previously demonstrated but as we show here, also in free-living protists. Investigating the tempo and mode of evolution of horizontally transferred genes in protists will therefore advance our understanding of mechanisms of adaptation in eukaryotes. PMID:17894863

  12. Branched tellurium hollow nanofibers by galvanic displacement reaction and their sensing performance toward nitrogen dioxide.

    PubMed

    Park, Hosik; Jung, Hyunsung; Zhang, Miluo; Chang, Chong Hyun; Ndifor-Angwafor, N George; Choa, Yongho; Myung, Nosang V

    2013-04-07

    Electrospinning and galvanic displacement reaction were combined to synthesize ultra-long hollow tellurium (Te) nanofibers with controlled dimensions, morphology and crystallinity by simply tailoring the electrolyte concentration applied. Within different morphologies of nanofibers, the branched Te nanostructure shows the greatest sensing performance towards NO2 at room temperature.

  13. Photovoltaic measurements and performance branch

    NASA Astrophysics Data System (ADS)

    Asher, S. E.; Dippo, P.

    1990-05-01

    The Photovoltaic (PV) Measurements and Performance Branch of the Solar Energy Research Institute (SERI) provides comprehensive PV materials, device and component characterization, measurement, fabrication, and modeling research and support for the international PV research community in the context of the U.S. Department of Energy's PV m goals. The progress of the Branch is summarized. The seven technical sections present a succinct overview of the capabilities and accomplishments of each group in the Branch. The Branch is comprised of the following groups; Surface and Interface Analysis, Materials Characterization, Device Development, Electro-Optical Characterization, Cell Performance, Advanced Module Testing and Performance, and Surface and Interface Modification and Stability. The main research projects completed in FY 1989 are highlighted including measurements and tests of PV materials, cells, submodules and modules. The report contains a comprehensive bibliography of the more than 80 branch-originated journal and conference publications which were authored in collaboration with, or in support of, approximately 130 university, industrial, government, and in-house research groups.

  14. Afferent input regulates the formation of distal dendritic branches.

    PubMed

    Mizrahi, Adi; Libersat, Frederic

    2002-10-07

    During postembryonic development, the dendritic arbors of neurons grow to accommodate new incoming synaptic inputs. Our goal was to examine which features of dendritic architecture of postsynaptic interneurons are regulated by these synaptic inputs. To address this question, we took advantage of the cockroach cercal system where the morphology of the sensory giant interneurons (GIs) is uniquely identified and, therefore, amenable to quantitative analysis. We analyzed the three-dimensional architecture of chronically deafferented vs. normally developed dendritic trees of a specific identified GI, namely GI2. GI2 shows five prominent dendrites, four of which were significantly altered after deafferentation. De-afferentation induced an average of 55% decrease in metric measures (number of branch points, total length, and total surface area) on the entire dendritic tree. Sholl and branch order analysis showed a decrease in the most distal and higher order branches. We suggest that afferent input plays a specific role in shaping the morphology of dendritic trees by regulating the formation or maintenance of high-order distal branches.

  15. Stress Induced Branching of Growing Crystals on Curved Surfaces.

    PubMed

    Köhler, Christian; Backofen, Rainer; Voigt, Axel

    2016-04-01

    If two-dimensional crystals grow on a curved surface, the Gaussian curvature of the surface induces elastic stress and affects the growth pathway. The elastic stress can be alleviated by incorporating defects or, if this is energetically unfavorable, via an elastic instability which leads to anisotropic growth with branched ribbonlike structures. This instability provides a generic route to grow defect-free crystals on curved surfaces. Depending on the elastic properties of the crystal and the geometric properties of the surface, different growth morphologies with two-, four-, and sixfold symmetry develop. Using a phase field crystal type modeling approach, we provide a microscopic understanding of the morphology selection.

  16. Alternating morphology transitions in crystallization of NH4Cl on agar plates

    NASA Astrophysics Data System (ADS)

    Tu, Ya-Fang; Wei, Rong-Bin; Sang, Jian-Ping; Huang, Sheng-You; Zou, Xian-Wu

    2008-04-01

    Two types of alternating morphology transitions have been observed in crystallization of NH4Cl on agar plates. One is the alternating morphology transitions between dense branching morphology and sparse branching morphology, and the other is the alternating morphology transitions between dense branching morphology and zigzag branching morphology. The appearance of them is found to depend on the mass proportion of agar to NH4Cl in the initial solution and the relative humidity. It is suggested that both the two alternating morphology transitions result from the oscillation of solute concentration in front of the growing interface caused by the competition of crystal growth and solute transfer at a moderate mass proportion. Which one of them occurs depends on the relative humidity, which controls the supersaturation.

  17. Alternating morphology transitions in crystallization of NH4Cl on agar plates.

    PubMed

    Tu, Ya-Fang; Wei, Rong-Bin; Sang, Jian-Ping; Huang, Sheng-You; Zou, Xian-Wu

    2008-04-01

    Two types of alternating morphology transitions have been observed in crystallization of NH4Cl on agar plates. One is the alternating morphology transitions between dense branching morphology and sparse branching morphology, and the other is the alternating morphology transitions between dense branching morphology and zigzag branching morphology. The appearance of them is found to depend on the mass proportion of agar to NH4Cl in the initial solution and the relative humidity. It is suggested that both the two alternating morphology transitions result from the oscillation of solute concentration in front of the growing interface caused by the competition of crystal growth and solute transfer at a moderate mass proportion. Which one of them occurs depends on the relative humidity, which controls the supersaturation.

  18. Horizon-T experiment status

    NASA Astrophysics Data System (ADS)

    Beznosko, Dmitriy; Beisembaev, Rashid; Baigarin, Kanat; Beisembaeva, Elena; Dalkarov, Oleg; Ryabov, Vladimi; Sadykov, Turlan; Shaulov, Sergei; Stepanov, Alekse; Vildanova, Marina; Vildanov, Nikolay; Zhukov, Valeriy

    2017-06-01

    Horizon-T is an innovative detector system constructed to study Extensive Air Showers (EAS) in the energy range above 1016 eV coming from a wide range of zenith angles (0°-85°). The system is located at the Tien Shan High-altitude Science Station of the Lebedev Physical Institute of the Russian Academy of Sciences at ˜ 3340 meters above sea level. It consists of eight charged particle detection points separated by distances up to one kilometer as well as an optical detector subsystem to measure the Vavilov-Cherenkov light from the EAS. The time resolution of charged particles and Vavilov-Cherenkov light photons passage of the detector system is a few ns. This level of resolution allows conducting a research of the atmospheric development of individual EAS. This report focuses on a general description of the detector system and the individual sub-systems providing an overview of the operations and latest results.

  19. Starting earthquakes under horizontal action

    NASA Astrophysics Data System (ADS)

    Babeshko, V. A.; Evdokimova, O. V.; Babeshko, O. M.

    2017-06-01

    The vector case of the static problem for semi-infinite lithospheric plates with rectilinear boundaries parallel to each other in two states is considered. In the first case, the distance between the plate ends is different from zero; in the second case, it is zero although the plates do not interact with each other. It is assumed that the horizontal actions on the plates (which, as is well known, move very slowly) are so strong that the vertical components of contact stresses can be neglected. In this work, it is shown that, even in this case, contact stresses at the edges of approaching plates acquire singular concentrations capable of leading to starting earthquakes. It has been shown that the theoretical calculation of the consequences of such earthquakes on the Earth's surface yields a coincidence with their real consequences.

  20. Explorando nuevos horizontes en NASA

    NASA Astrophysics Data System (ADS)

    Villanueva, G. L.

    A pesar de la incesante expansión del Universo iniciada con el Big Bang 14 mil millones de años atrás, nuestro Universo se siente cada día más cercano. La inquebrantable vocación de la humanidad por descubrir nuevos horizontes ha permitido el acercamiento de civilizaciones en nuestro planeta y nos ha permitido conocer nuestro lugar en el Universo como nunca antes. En este artículo presento una breve sinopsis de nuestro trabajo que se relaciona con diversas investigaciones con implicaciones astrobiológicas, desde el origen de los ingredientes de la "sopa de la vida", hasta la evolución y composición de la atmósfera de Marte.

  1. Fault Branching and Rupture Directivity

    NASA Astrophysics Data System (ADS)

    Dmowska, R.; Rice, J. R.; Kame, N.

    2002-12-01

    Can the rupture directivity of past earthquakes be inferred from fault geometry? Nakata et al. [J. Geogr., 1998] propose to relate the observed surface branching of fault systems with directivity. Their work assumes that all branches are through acute angles in the direction of rupture propagation. However, in some observed cases rupture paths seem to branch through highly obtuse angles, as if to propagate ``backwards". Field examples of that are as follows: (1) Landers 1992. When crossing from the Johnson Valley to the Homestead Valley (HV) fault via the Kickapoo (Kp) fault, the rupture from Kp progressed not just forward onto the northern stretch of the HV fault, but also backwards, i.e., SSE along the HV [Sowers et al., 1994, Spotila and Sieh, 1995, Zachariasen and Sieh, 1995, Rockwell et al., 2000]. Measurements of surface slip along that backward branch, a prominent feature of 4 km length, show right-lateral slip, decreasing towards the SSE. (2) At a similar crossing from the HV to the Emerson (Em) fault, the rupture progressed backwards along different SSE splays of the Em fault [Zachariasen and Sieh, 1995]. (3). In crossing from the Em to Camp Rock (CR) fault, again, rupture went SSE on the CR fault. (4). Hector Mine 1999. The rupture originated on a buried fault without surface trace [Li et al., 2002; Hauksson et al., 2002] and progressed bilaterally south and north. In the south it met the Lavic Lake (LL) fault and progressed south on it, but also progressed backward, i.e. NNW, along the northern stretch of the LL fault. The angle between the buried fault and the northern LL fault is around -160o, and that NNW stretch extends around 15 km. The field examples with highly obtuse branch angles suggest that there may be no simple correlation between fault geometry and rupture directivity. We propose that an important distinction is whether those obtuse branches actually involved a rupture path which directly turned through the obtuse angle (while continuing

  2. Immunocytochemical evidence for SNARE protein-dependent transmitter release from guinea pig horizontal cells

    PubMed Central

    Lee, Helen; Brecha, Nicholas C.

    2013-01-01

    Horizontal cells are lateral interneurons that participate in visual processing in the outer retina but the cellular mechanisms underlying transmitter release from these cells are not fully understood. In non-mammalian horizontal cells, GABA release has been shown to occur by a non-vesicular mechanism. However, recent evidence in mammalian horizontal cells favors a vesicular mechanism as they lack plasmalemmal GABA transporters and some soluble NSF attachment protein receptor (SNARE) core proteins have been identified in rodent horizontal cells. Moreover, immunoreactivity for GABA and the molecular machinery to synthesize GABA have been found in guinea pig horizontal cells, suggesting that if components of the SNARE complex are expressed they could contribute to the vesicular release of GABA. In this study we investigated whether these vesicular and synaptic proteins are expressed by guinea pig horizontal cells using immunohistochemistry with well-characterized antibodies to evaluate their cellular distribution. Components of synaptic vesicles including vesicular GABA transporter, synapsin I and synaptic vesicle protein 2A were localized to horizontal cell processes and endings, along with the SNARE core complex proteins, syntaxin-1a, syntaxin-4 and synaptosomal-associated protein 25 (SNAP-25). Complexin I/II, a cytosolic protein that stabilizes the activated SNARE fusion core, strongly immunostained horizontal cell soma and processes. In addition, the vesicular Ca2+-sensor, synaptotagmin-2, which is essential for Ca2+-mediated vesicular release, was also localized to horizontal cell processes and somata. These morphological findings from guinea pig horizontal cells suggest that mammalian horizontal cells have the capacity to utilize a regulated Ca2+-dependent vesicular pathway to release neurotransmitter, and that this mechanism may be shared among many mammalian species. PMID:20384779

  3. 30 CFR 56.6403 - Branch circuits.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 30 Mineral Resources 1 2010-07-01 2010-07-01 false Branch circuits. 56.6403 Section 56.6403... Blasting § 56.6403 Branch circuits. (a) If electric blasting includes the use of branch circuits, each branch shall be equipped with a safety switch or equivalent method to isolate the circuits to be used. (b...

  4. 30 CFR 57.6403 - Branch circuits.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 30 Mineral Resources 1 2010-07-01 2010-07-01 false Branch circuits. 57.6403 Section 57.6403... Blasting-Surface and Underground § 57.6403 Branch circuits. (a) If electric blasting includes the use of branch circuits, each branch shall be equipped with a safety switch or equivalent method to isolate the...

  5. 30 CFR 56.6403 - Branch circuits.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 30 Mineral Resources 1 2013-07-01 2013-07-01 false Branch circuits. 56.6403 Section 56.6403... Blasting § 56.6403 Branch circuits. (a) If electric blasting includes the use of branch circuits, each branch shall be equipped with a safety switch or equivalent method to isolate the circuits to be used. (b...

  6. 30 CFR 56.6403 - Branch circuits.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 30 Mineral Resources 1 2011-07-01 2011-07-01 false Branch circuits. 56.6403 Section 56.6403... Blasting § 56.6403 Branch circuits. (a) If electric blasting includes the use of branch circuits, each branch shall be equipped with a safety switch or equivalent method to isolate the circuits to be used. (b...

  7. 30 CFR 57.6403 - Branch circuits.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 30 Mineral Resources 1 2011-07-01 2011-07-01 false Branch circuits. 57.6403 Section 57.6403... Blasting-Surface and Underground § 57.6403 Branch circuits. (a) If electric blasting includes the use of branch circuits, each branch shall be equipped with a safety switch or equivalent method to isolate the...

  8. 30 CFR 57.6403 - Branch circuits.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 30 Mineral Resources 1 2014-07-01 2014-07-01 false Branch circuits. 57.6403 Section 57.6403... Blasting-Surface and Underground § 57.6403 Branch circuits. (a) If electric blasting includes the use of branch circuits, each branch shall be equipped with a safety switch or equivalent method to isolate the...

  9. 30 CFR 57.6403 - Branch circuits.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 30 Mineral Resources 1 2013-07-01 2013-07-01 false Branch circuits. 57.6403 Section 57.6403... Blasting-Surface and Underground § 57.6403 Branch circuits. (a) If electric blasting includes the use of branch circuits, each branch shall be equipped with a safety switch or equivalent method to isolate the...

  10. 30 CFR 56.6403 - Branch circuits.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 30 Mineral Resources 1 2012-07-01 2012-07-01 false Branch circuits. 56.6403 Section 56.6403... Blasting § 56.6403 Branch circuits. (a) If electric blasting includes the use of branch circuits, each branch shall be equipped with a safety switch or equivalent method to isolate the circuits to be used. (b...

  11. 30 CFR 56.6403 - Branch circuits.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 30 Mineral Resources 1 2014-07-01 2014-07-01 false Branch circuits. 56.6403 Section 56.6403... Blasting § 56.6403 Branch circuits. (a) If electric blasting includes the use of branch circuits, each branch shall be equipped with a safety switch or equivalent method to isolate the circuits to be used. (b...

  12. 30 CFR 57.6403 - Branch circuits.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 30 Mineral Resources 1 2012-07-01 2012-07-01 false Branch circuits. 57.6403 Section 57.6403... Blasting-Surface and Underground § 57.6403 Branch circuits. (a) If electric blasting includes the use of branch circuits, each branch shall be equipped with a safety switch or equivalent method to isolate the...

  13. 17 CFR 166.4 - Branch offices.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 17 Commodity and Securities Exchanges 1 2010-04-01 2010-04-01 false Branch offices. 166.4 Section... RULES § 166.4 Branch offices. Each branch office of each Commission registrant must use the name of the.... The act, omission or failure of any person acting for the branch office, within the scope of...

  14. REVEALING PROBABLE UNIVERSAL FEATURES IN THE LOWER RED GIANT BRANCH LUMINOSITY FUNCTIONS OF GALACTIC GLOBULAR CLUSTERS

    SciTech Connect

    Kravtsov, V. V.

    2009-06-15

    This paper aims at demonstrating, for the first time, very probable universal peculiarities of the evolution of stars in the lower red giant branch (RGB) of Galactic globular clusters (GCs), reflected in two corresponding dips in the luminosity functions (LFs). By relying on the database of Hubble Space Telescope photometry of GCs, we analyze the lower RGB LFs of a sample of 18 GCs in a wide metallicity range, {delta}[Fe/H] {approx} 1.9 dex. We first show that in the F555W-(F439W-F555W) color-magnitude diagrams (CMDs), the lower RGB of GCs, except for the most metal-poor of them, frequently shows an apparent 'knee'. It reveals itself as a fairly abrupt change of the RGB slope. At the same luminosity level, the RGB LFs show a feature in the form of a more or less pronounced dip. We find that the magnitude difference between the RGB base and the given feature is, on average, around {delta} F555W{sup dip} {sub base}{approx} 1.4 mag. It shows a marginal variation with metallicity, if any, comparable to the error. At the same time, the magnitude difference between the dip and the RGB bump, {delta} F555W{sup bump} {sub dip}, decreases with increasing metallicity and falls within the range 0.8 {approx}< {delta} F555W{sup bump} {sub dip} {approx}< 1.7 mag. Generalized LFs (GLFs) have been obtained for three subsamples of GCs within limited metallicity ranges and with different horizontal branch (HB) morphology. They reproduce the 'knee-related' dip that is statistically significant in two of the GLFs. This feature turns out to be more pronounced in the GLFs of GCs with either the blue or red HB morphology than with the intermediate one. The same GLFs also reveal an additional probable universal dip. It shows up below the RGB bump at {delta} F555W slightly increasing from {approx}0.3 to {approx}0.5 mag with increasing metallicity. Also, the statistical significance of this 'prebump' dip increases, on average, toward higher metallicity. Except for the well known RGB bump, no

  15. Two intensified fluorescence colors' switching achieved by branched dye nanoaggregates.

    PubMed

    Ding, Ge; Lu, Yao; Su, Jihong; Qin, Xiaozhuan; Luo, Ziping; Gao, Fang; Chen, Lingyun; Li, Hongru

    2017-08-10

    In this study, a variety of branched target dyes containing double internal proton transfer segments were synthesized. For comparison, some linear analogs including a single internal proton transfer part were synthesized. The corresponding reference molecules lacking proton transfer segments were also prepared. The properties and aggregation modes of these dye aggregates were investigated on the basis of scanning electron microscopy images, transmission electron microscopy images, dynamic light scattering, X-ray diffraction, UV/visible absorption spectra and fluorescence emission spectra. The results showed that molecular aggregates with the morphologies of nano-scaled rounded or cubic particles of the target branched dyes could be yielded in mixed organic solvent/H2O solution. A remarkable emission enhancement and fluorescence switching process (from bright yellow to luminous pure blue) under 365 nm lamp irradiation was observed for these target branched dye nanoaggregates. However, no aggregates of the reference branched dyes free of hydroxyl groups were formed and no obvious spectral variations were found. In contrast, all the studied linear dyes yielded molecular nanoaggregates in mixed organic solvent/H2O solution, and only intensified single normal blue fluorescence emission was presented. This study provided real examples of some branched organic dye aggregates which were capable of displaying naked-eye enhanced fluorescence color switching under an UV lamp.

  16. Double-branched vortex generator

    NASA Technical Reports Server (NTRS)

    Cantwell, E. R.; Westphal, R. V.; Mehta, R. D.

    1985-01-01

    In order to assess the suitability of using a double branched vortex generator in parametric studies involving vortex interactions, an experimental study of the main vortex and secondary flows produced by a double branched vortex generator was conducted in a 20-by-40 cm indraft wind tunnel. Measurements of the cross flow velocities were made with a five hole pressure probe from which vorticity contours and vortex parameters were derived. The results showed that the optimum configuration consisted of chord extensions with the absence of a centerbody.

  17. Pattern formation in the flow between two horizontal coaxial cylinders with a partially filled gap

    NASA Astrophysics Data System (ADS)

    Mutabazi, Innocent; Hegseth, John J.; Andereck, C. David; Wesfreid, Jose E.

    1988-11-01

    Flow between two horizontal coaxial cylinders with a partially filled gap is subject to several types of centrifugal instabilities which lead to the formation of a variety of spatial patterns. An experimental investigation has shown that there are five distinct branches of primary instabilities occurring in the system and that four codimension-2 points are easily reached. Theoretical predictions are in qualitative agreement with the observations.

  18. The role of branched fibres in the pathogenesis of Duchenne muscular dystrophy.

    PubMed

    Chan, S; Head, S I

    2011-06-01

    Branched fibres are a well-documented phenomenon of regenerating skeletal muscle. They are found in the muscles of boys with Duchenne muscular dystrophy (DMD), a severe condition of progressive muscle wasting caused by an absence of the sarcolemmal protein dystrophin, and in the muscles of the mdx mouse, an animal model of DMD. However, only a handful of studies have investigated how the physiological properties of these morphologically deformed fibres differ from those of normal fibres. These studies have found an association between the extent of fibre branching in mdx muscles and the susceptibility of these muscles to damage from eccentric contractions. They have also found that branched mdx muscle fibres cannot sustain maximal contractions in buffered Ca(2+) solutions, that branch points are sites of increased mechanical stress and that myofibrillar structure is greatly disturbed at branch points. These findings have important implications for understanding the function of dystrophin. It is commonly thought that the role of dystrophin is mechanical stabilization of the sarcolemma, as numerous studies have shown that eccentric contractions damage mdx muscle more than normal muscle. However, the finding that branched mdx fibres are mechanically weakened raises the question, is it the lack of dystrophin or is it the fibre branching that leads to the vulnerability of mdx muscle to contractile damage? The importance of this question to our understanding of the function of dystrophin warrants further research into the physiological properties of branched fibres and how they differ from morphologically normal fibres.

  19. Horizontal gene transfer and the evolution of methanogenic pathways.

    PubMed

    Fournier, Greg

    2009-01-01

    Horizontal gene transfer (HGT) is a driving force in the evolution of metabolic pathways, allowing novel enzymatic functions that provide a selective advantage to be rapidly incorporated into an organism's physiology. Here, the role of two HGT events in the evolution of methanogenesis is described. First, the acetoclastic sub-pathway of methanogenesis is shown to have evolved via a transfer of the ackA and pta genes from a cellulolytic clostridia to a family of methanogenic archaea. Second, the system for encoding the amino acid pyrrolysine, used for the synthesis of enzymes for methanogenesis from methylamines, is shown to likely have evolved via transfer from an ancient, unknown, deeply branching organismal lineage.

  20. System for Estimating Horizontal Velocity During Descent

    NASA Technical Reports Server (NTRS)

    Johnson, Andrew; Cheng, Yang; Wilson, Reg; Goguen, Jay; Martin, Alejandro San; Leger, Chris; Matthies, Larry

    2007-01-01

    The descent image motion estimation system (DIMES) is a system of hardware and software, designed for original use in estimating the horizontal velocity of a spacecraft descending toward a landing on Mars. The estimated horizontal velocity is used in generating rocket-firing commands to reduce the horizontal velocity as part of an overall control scheme to minimize the landing impact. DIMES can also be used for estimating the horizontal velocity of a remotely controlled or autonomous aircraft for purposes of navigation and control.

  1. Developmental asymmetries between horizontal and vertical tracking.

    PubMed

    Grönqvist, Helena; Gredebäck, Gustaf; Hofsten, Claes von

    2006-05-01

    The development of the asymmetry between horizontal and vertical eye tracking was investigated longitudinally at 5, 7, and 9 months of age. The target moved either on a 2D circular trajectory or on a vertical or horizontal 1D sinusoidal trajectory. Saccades, smooth pursuit, and head movements were measured. Vertical tracking was found to be inferior to horizontal tracking at all age levels. The results also show that the mechanisms responsible for horizontal and vertical tracking mutually influence one another in the production of 2D visual pursuit. Learning effects were observed within-trials but no transfer between trials was found.

  2. Risk Factor Assessment Branch (RFAB)

    Cancer.gov

    The Risk Factor Assessment Branch (RFAB) focuses on the development, evaluation, and dissemination of high-quality risk factor metrics, methods, tools, technologies, and resources for use across the cancer research continuum, and the assessment of cancer-related risk factors in the population.

  3. NCI: DCTD: Biometric Research Branch

    Cancer.gov

    The Biometric Research Branch (BRB) is the statistical and biomathematical component of the Division of Cancer Treatment, Diagnosis and Centers (DCTDC). Its members provide statistical leadership for the national and international research programs of the division in developmental therapeutics, developmental diagnostics, diagnostic imaging and clinical trials.

  4. NCI: DCTD: Biometric Research Branch

    Cancer.gov

    The Biometric Research Branch (BRP) is the statistical and biomathematical component of the Division of Cancer Treatment, Diagnosis and Centers (DCTDC). Its members provide statistical leadership for the national and international research programs of the division in developmental therapeutics, developmental diagnostics, diagnostic imaging and clinical trials.

  5. Cash efficiency for bank branches.

    PubMed

    Cabello, Julia García

    2013-01-01

    Bank liquidity management has become a major issue during the financial crisis as liquidity shortages have intensified and have put pressure on banks to diversity and improve their liquidity sources. While a significant strand of the literature concentrates on wholesale liquidity generation and on the alternative to deposit funding, the management of an inventory of cash holdings within the banks' branches is also a relevant issue as any significant improvement in cash management at the bank distribution channels may have a positive effect in reducing liquidity tensions. In this paper, we propose a simple programme of cash efficiency for the banks' branches, very easy to implement, which conform to a set of instructions to be imposed from the bank to their branches. This model proves to significantly reduce cash holdings at branches thereby providing efficiency improvements in liquidity management. The methodology we propose is based on the definition of some stochastic processes combined with renewal processes, which capture the random elements of the cash flow, before applying suitable optimization programmes to all the costs involved in cash movements. The classical issue of the Transaction Demand for the Cash and some aspects of Inventory Theory are also present. Mathematics Subject Classification (2000) C02, C60, E50.

  6. 76 FR 13272 - Branch Offices

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-03-10

    ... From the Federal Register Online via the Government Publishing Office DEPARTMENT OF THE TREASURY Office of Thrift Supervision Branch Offices AGENCY: Office of Thrift Supervision (OTS), Treasury. ACTION... 1995, 44 U.S.C. 3507. The Office of Thrift Supervision within the Department of the Treasury...

  7. Multiple pathways regulate shoot branching

    PubMed Central

    Rameau, Catherine; Bertheloot, Jessica; Leduc, Nathalie; Andrieu, Bruno; Foucher, Fabrice; Sakr, Soulaiman

    2015-01-01

    Shoot branching patterns result from the spatio-temporal regulation of axillary bud outgrowth. Numerous endogenous, developmental and environmental factors are integrated at the bud and plant levels to determine numbers of growing shoots. Multiple pathways that converge to common integrators are most probably involved. We propose several pathways involving not only the classical hormones auxin, cytokinins and strigolactones, but also other signals with a strong influence on shoot branching such as gibberellins, sugars or molecular actors of plant phase transition. We also deal with recent findings about the molecular mechanisms and the pathway involved in the response to shade as an example of an environmental signal controlling branching. We propose the TEOSINTE BRANCHED1, CYCLOIDEA, PCF transcription factor TB1/BRC1 and the polar auxin transport stream in the stem as possible integrators of these pathways. We finally discuss how modeling can help to represent this highly dynamic system by articulating knowledges and hypothesis and calculating the phenotype properties they imply. PMID:25628627

  8. Legislative Branch Appropriations Act, 2010

    THOMAS, 111th Congress

    Rep. Wasserman Schultz, Debbie [D-FL-20

    2009-06-17

    10/01/2009 Became Public Law No: 111-68. (TXT | PDF) (All Actions) Notes: Division A is the Legislative Branch Appropriations Act, 2010. Division B is the Continuing Appropriations Resolution, 2010. Tracker: This bill has the status Became LawHere are the steps for Status of Legislation:

  9. NCI: DCTD: Biometric Research Branch

    Cancer.gov

    The Biometric Research Branch (BRB) is the statistical and biomathematical component of the Division of Cancer Treatment, Diagnosis and Centers (DCTDC). Its members provide statistical leadership for the national and international research programs of the division in developmental therapeutics, developmental diagnostics, diagnostic imaging and clinical trials.

  10. Branching of keratin intermediate filaments.

    PubMed

    Nafeey, Soufi; Martin, Ines; Felder, Tatiana; Walther, Paul; Felder, Edward

    2016-06-01

    Keratin intermediate filaments (IFs) are crucial to maintain mechanical stability in epithelial cells. Since little is known about the network architecture that provides this stiffness and especially about branching properties of filaments, we addressed this question with different electron microscopic (EM) methods. Using EM tomography of high pressure frozen keratinocytes, we investigated the course of several filaments in a branching of a filament bundle. Moreover we found several putative bifurcations in individual filaments. To verify our observation we also visualized the keratin network in detergent extracted keratinocytes with scanning EM. Here bifurcations of individual filaments could unambiguously be identified additionally to bundle branchings. Interestingly, identical filament bifurcations were also found in purified keratin 8/18 filaments expressed in Escherichia coli which were reassembled in vitro. This excludes that an accessory protein contributes to the branch formation. Measurements of the filament cross sectional areas showed various ratios between the three bifurcation arms. This demonstrates that intermediate filament furcation is very different from actin furcation where an entire new filament is attached to an existing filament. Instead, the architecture of intermediate filament bifurcations is less predetermined and hence consistent with the general concept of IF formation. Copyright © 2016 Elsevier Inc. All rights reserved.

  11. Legislative Branch Appropriations Act, 2010

    THOMAS, 111th Congress

    Rep. Wasserman Schultz, Debbie [D-FL-20

    2009-06-17

    10/01/2009 Became Public Law No: 111-68. (TXT | PDF) (All Actions) Notes: Division A is the Legislative Branch Appropriations Act, 2010. Division B is the Continuing Appropriations Resolution, 2010. Tracker: This bill has the status Became LawHere are the steps for Status of Legislation:

  12. National Zoological Park Branch Library.

    ERIC Educational Resources Information Center

    Kenyon, Kay A.

    1988-01-01

    Describes the functions of the National Zoological Park Branch of the Smithsonian Institution Libraries, which is dedicated to supporting the special information needs of the zoo. Topics covered include the library's history, collection, programs, services, future plans, and relations with other zoo libraries. (two references) (Author/CLB)

  13. Legislative Branch Appropriations Act, 2010

    THOMAS, 111th Congress

    Rep. Wasserman Schultz, Debbie [D-FL-20

    2009-06-17

    10/01/2009 Became Public Law No: 111-68. (PDF) (All Actions) Notes: Division A is the Legislative Branch Appropriations Act, 2010. Division B is the Continuing Appropriations Resolution, 2010. Tracker: This bill has the status Became LawHere are the steps for Status of Legislation:

  14. The history of horizontal glottectomy.

    PubMed

    Folz, Benedikt J; Rinaldo, Alessandra; Silver, Carl E; Ferlito, Alfio

    2010-02-01

    The history of horizontal glottectomy (HG) for the treatment of bilateral vocal cord lesions is not entirely clear. The present investigation analyzes the history of HG on the basis of cross-referenced database searches in general and professional medical literature databases. Books, original historical articles and medical history reviews were evaluated. The initial work was done by Moser in years from 1959 to 1965, and in 1961 he published the first paper on HG. Follow-up publications were reported in 1977 by Gramowski and in 1984 by Wilke. In 1970, Romanian laryngologists headed by Calaraşu described a HG via excision of a rhomboid-shaped portion of the thyroid cartilage, but the authors had neither sufficient numbers of patients nor a sufficiently long follow-up for the procedure to gain widespread acceptance. In 1978, Calearo and Teatini described HG similar to Calaraşu's method, but slightly more extended by the eventual inclusion of an arytenoid cartilage in the operative specimen. Theses authors have often been credited as the originators of the procedure, but actually were the first to publish in an English language journal. The procedure, while quite effective for treatment of bilateral and anterior commissure lesions, has never gained general acceptance in the United States, and in current practice, has been supplanted by endoscopic and non-surgical treatments.

  15. Widespread horizontal transfer of retrotransposons

    PubMed Central

    Walsh, Ali Morton; Kortschak, R. Daniel; Gardner, Michael G.; Bertozzi, Terry; Adelson, David L.

    2013-01-01

    In higher organisms such as vertebrates, it is generally believed that lateral transfer of genetic information does not readily occur, with the exception of retroviral infection. However, horizontal transfer (HT) of protein coding repetitive elements is the simplest way to explain the patchy distribution of BovB, a long interspersed element (LINE) about 3.2 kb long, that has been found in ruminants, marsupials, squamates, monotremes, and African mammals. BovB sequences are a major component of some of these genomes. Here we show that HT of BovB is significantly more widespread than believed, and we demonstrate the existence of two plausible arthropod vectors, specifically reptile ticks. A phylogenetic tree built from BovB sequences from species in all of these groups does not conform to expected evolutionary relationships of the species, and our analysis indicates that at least nine HT events are required to explain the observed topology. Our results provide compelling evidence for HT of genetic material that has transformed vertebrate genomes. PMID:23277587

  16. On the Hydraulics of Flowing Horizontal Wells

    NASA Astrophysics Data System (ADS)

    Bian, A.; Zhan, H.

    2003-12-01

    A flowing horizontal well is a special type of horizontal well that does not have pumping/injecting facility. The discharge rate of a flowing horizontal well is controlled by the hydraulic gradient between the aquifer and the well and it generally varies with time if the hydraulic head of the aquifer is transient. This type of well has been used in landslide control, mining dewatering, water table control, underground water transportation through a horizontal tunnel, agricultural water drainage, and other applications. Flowing horizontal wells have quite different hydrodynamic characteristics from horizontal wells with fixed pumping or injecting rates because their discharge rates are functions of the aquifer hydraulic heads (Zhan et al, 2001; Zhan and Zlotnik, 2002). Hydraulics of flowing horizontal wells have rarely been studied although the hydraulics of flowing vertical wells have been extensively investigated before. The purpose of this paper is to obtain analytical solutions of groundwater flow to a flowing horizontal-well in a confined aquifer, in a water table aquifer without precipitation, and in a water table aquifer with precipitation. The functions of the flowing horizontal well discharge rates versus time will be obtained under above mentioned different aquifer conditions. The relationships of the aquifer hydraulic heads versus the discharge rates of the well will be investigated. The rate of water table decline due to the dewatering of the well will also be computed, and this solution is particularly useful for landslide control and mining dewatering. The theoretical solutions will be compared with results of experiments that will be conducted in the hydrological laboratory at Texas A&M University. Reference: Zhan, H., Wang, L.V., and Park, E, On the horizontal well pumping tests in the anisotropic confined aquifers, J. hydrol., 252, 37-50, 2001. Zhan, H., and Zlotnik, V. A., Groundwater flow to a horizontal or slanted well in an unconfined aquifer

  17. To branch or not to branch: Numerical modeling of dynamically branching faults

    NASA Astrophysics Data System (ADS)

    Dedontney, N. L.; Templeton Barrett, E. L.; Rice, J. R.; Dmowska, R.

    2009-12-01

    Branched fault geometries, and branched rupture paths, occur in strike-slip as well as dip-slip settings [e.g., Poliakov et al., JGR, 2002; Kame et al., JGR, 2003]. The Wenchuan earthquake illustrates such a branched geometry [Hubbard and Shaw, 2009] in a fold and thrust belt, and surface ruptures provide constraints on which faults were activated co-seismically. Additionally, a branched structure, the Central Basin Decollement [Shaw & Suppe, 1996], underlies the Los Angeles Basin. By simulating the dynamic rupture path selection, using explicit finite element methods here, we are able to estimate which faults should be activated under given conditions. Factors that influence coseismic branch activation have been extensively studied [Poliakov et al.; Kame et al.; Oglesby et al., 2003, 2004; Bhat et al., 2004, 2007]. The results show that the rupture velocity, pre-stress orientation and fault geometry influence rupture path selection. We show further that the ratio of σ1/σ3 (equivalently, the seismic S ratio) and the relative frictional fault strength also play a significant role in determining which faults are activated. Our methodology has recently included the use of a regularized friction routine [Ranjith & Rice, 2001; Cochard & Rice, 2000] which reduces the growth of numerical noise throughout the simulations. A difficulty arises in the treatment of surface interactions at the branch junction. When local opening does not occur there, slip on the branch fault must vanish at the junction, a constraint that we impose on the FE model. However, the FE contact routine used demands that slip always be constrained to zero on one or the other fault at such a junction, which is problematic when opening occurs. There is then no fundamental basis for constraining slip at the junction to zero on either fault, and the choice made affects the slip distributions and rupture path selection. Many analyses that we perform are elastic and the same material is used on both sides

  18. Branching processes in disease epidemics

    NASA Astrophysics Data System (ADS)

    Singh, Sarabjeet

    Branching processes have served as a model for chemical reactions, biological growth processes and contagion (of disease, information or fads). Through this connection, these seemingly different physical processes share some common universalities that can be elucidated by analyzing the underlying branching process. In this thesis, we focus on branching processes as a model for infectious diseases spreading between individuals belonging to different populations. The distinction between populations can arise from species separation (as in the case of diseases which jump across species) or spatial separation (as in the case of disease spreading between farms, cities, urban centers, etc). A prominent example of the former is zoonoses -- infectious diseases that spill from animals to humans -- whose specific examples include Nipah virus, monkeypox, HIV and avian influenza. A prominent example of the latter is infectious diseases of animals such as foot and mouth disease and bovine tuberculosis that spread between farms or cattle herds. Another example of the latter is infectious diseases of humans such as H1N1 that spread from one city to another through migration of infectious hosts. This thesis consists of three main chapters, an introduction and an appendix. The introduction gives a brief history of mathematics in modeling the spread of infectious diseases along with a detailed description of the most commonly used disease model -- the Susceptible-Infectious-Recovered (SIR) model. The introduction also describes how the stochastic formulation of the model reduces to a branching process in the limit of large population which is analyzed in detail. The second chapter describes a two species model of zoonoses with coupled SIR processes and proceeds into the calculation of statistics pertinent to cross species infection using multitype branching processes. The third chapter describes an SIR process driven by a Poisson process of infection spillovers. This is posed as a

  19. Standard Giant Branches in the Washington Photometric System

    NASA Astrophysics Data System (ADS)

    Geisler, Doug; Sarajedini, Ata

    1999-01-01

    We have obtained CCD photometry in the Washington system C, T_1 filters for some 850,000 objects associated with 10 Galactic globular clusters and two old open clusters. These clusters have well-known metal abundances, spanning a metallicity range of 2.5 dex from [Fe/H]~-2.25 to +0.25 at a spacing of ~0.2 dex. Two independent observations were obtained for each cluster, and internal checks, as well as external comparisons with existing photoelectric photometry, indicate that the final colors and magnitudes have overall uncertainties of <~0.03 mag. Analogous to the method employed by Da Costa & Armandroff for V, I photometry, we then proceed to construct standard [M_T_1, (C-T_1)_0] giant branches for these clusters adopting the Lee et al. distance scale, using some 350 stars per globular cluster to define the giant branch. We then determine the metallicity sensitivity of the (C-T_1)_0 color at a given M_T_1 value. The Washington system technique is found to have 3 times the metallicity sensitivity of the V, I technique. At M_T_1=-2 (about a magnitude below the tip of the giant branch, roughly equivalent to M_I=-3), the giant branches of 47 Tuc and M15 are separated by 1.16 mag in (C-T_1)_0 and only 0.38 mag in (V-I)_0. Thus, for a given photometric accuracy, metallicities can be determined 3 times more precisely with the Washington technique. We find a linear relationship between (C-T_1)_0 (at M_T_1=-2) and metallicity (on the Zinn scale) exists over the full metallicity range, with an rms of only 0.04 dex. We also derive metallicity calibrations for M_T_1=-2.5 and -1.5, as well as for two other metallicity scales. The Washington technique retains almost the same metallicity sensitivity at faint magnitudes, and indeed the standard giant branches are still well separated even below the horizontal branch. The photometry is used to set upper limits in the range 0.03-0.09 dex for any intrinsic metallicity dispersion in the calibrating clusters. The calibrations are

  20. Wnt/PCP proteins regulate stereotyped axon branch extension in Drosophila

    PubMed Central

    Ng, Julian

    2012-01-01

    Branching morphology is a hallmark feature of axons and dendrites and is essential for neuronal connectivity. To understand how this develops, I analyzed the stereotyped pattern of Drosophila mushroom body (MB) neurons, which have single axons branches that extend dorsally and medially. I found that components of the Wnt/Planar Cell Polarity (PCP) pathway control MB axon branching. frizzled mutant animals showed a predominant loss of dorsal branch extension, whereas strabismus (also known as Van Gogh) mutants preferentially lost medial branches. Further results suggest that Frizzled and Strabismus act independently. Nonetheless, branching fates are determined by complex Wnt/PCP interactions, including interactions with Dishevelled and Prickle that function in a context-dependent manner. Branching decisions are MB-autonomous but non-cell-autonomous as mutant and non-mutant neurons regulate these decisions collectively. I found that Wnt/PCP components do not need to be asymmetrically localized to distinct branches to execute branching functions. However, Prickle axonal localization depends on Frizzled and Strabismus. PMID:22147954

  1. Electrodeposition of InSb branched nanowires: Controlled growth with structurally tailored properties

    SciTech Connect

    Das, Suprem R.; Mohammad, Asaduzzaman; Janes, David B.; Akatay, Cem; Khan, Mohammad Ryyan; Alam, Muhammad A.; Maeda, Kosuke; Deacon, Russell S.; Ishibashi, Koji; Chen, Yong P.; Sands, Timothy D.

    2014-08-28

    In this article, electrodeposition method is used to demonstrate growth of InSb nanowire (NW) arrays with hierarchical branched structures and complex morphology at room temperature using an all-solution, catalyst-free technique. A gold coated, porous anodic alumina membrane provided the template for the branched NWs. The NWs have a hierarchical branched structure, with three nominal regions: a “trunk” (average diameter of 150 nm), large branches (average diameter of 100 nm), and small branches (average diameter of sub-10 nm to sub-20 nm). The structural properties of the branched NWs were studied using scanning transmission electron microscopy, transmission electron microscopy, scanning electron microscopy, x-ray diffraction, energy dispersive x-ray spectroscopy, and Raman spectroscopy. In the as-grown state, the small branches of InSb NWs were crystalline, but the trunk regions were mostly nanocrystalline with an amorphous boundary. Post-annealing of NWs at 420 °C in argon produced single crystalline structures along 〈311〉 directions for the branches and along 〈111〉 for the trunks. Based on the high crystallinity and tailored structure in this branched NW array, the effective refractive index allows us to achieve excellent antireflection properties signifying its technological usefulness for photon management and energy harvesting.

  2. Fractal branching organizations of Ediacaran rangeomorph fronds reveal a lost Proterozoic body plan

    PubMed Central

    Hoyal Cuthill, Jennifer F.; Conway Morris, Simon

    2014-01-01

    The branching morphology of Ediacaran rangeomorph fronds has no exact counterpart in other complex macroorganisms. As such, these fossils pose major questions as to growth patterns, functional morphology, modes of feeding, and adaptive optimality. Here, using parametric Lindenmayer systems, a formal model of rangeomorph morphologies reveals a fractal body plan characterized by self-similar, axial, apical, alternate branching. Consequent morphological reconstruction for 11 taxa demonstrates an adaptive radiation based on 3D space-filling strategies. The fractal body plan of rangeomorphs is shown to maximize surface area, consistent with diffusive nutrient uptake from the water column (osmotrophy). The enigmas of rangeomorph morphology, evolution, and extinction are resolved by the realization that they were adaptively optimized for unique ecological and geochemical conditions in the late Proterozoic. Changes in ocean conditions associated with the Cambrian explosion sealed their fate. PMID:25114255

  3. Branching Patterns of Medial and Inferior Calcaneal Nerves Around the Tarsal Tunnel

    PubMed Central

    Kim, Beom Suk; Choung, Phil Woo; Kwon, Soon Wook; Rhyu, Im Joo

    2015-01-01

    Objective To demonstrate the bifurcation pattern of the tibial nerve and its branches. Methods Eleven legs of seven fresh cadavers were dissected. The reference line for the bifurcation point of tibial nerve branches was an imaginary horizontal line passing the tip of the medial malleolus. The distances between the reference line and the bifurcation points were measured. The bifurcation branching patterns were categorized as type I, the pattern in which the medial calcaneal nerve (MCN) branched most proximally; type II, the pattern in which the three branches occurred at the same point; and type III, in which MCN branched most distally. Results There were seven cases (64%) of type I, three cases (27%) of type III, and one case (9%) of type II. The median MCN branching point was 0.2 cm (range, -1 to 3 cm). The median bifurcation points of the lateral plantar nerves and inferior calcaneal nerves was -0.6 cm (range, -1.5 to 1 cm) and -2.5 cm (range, -3.5 to -1 cm), respectively. Conclusion MCN originated from the tibial nerve in most cases, and plantar nerves were bifurcated below the medial malleolus. In all cases, inferior calcaneal nerves originated from the lateral plantar nerve. These anatomical findings could be useful for performing procedures, such as nerve block or electrophysiologic studies. PMID:25750872

  4. Neuropilin-2 promotes branching morphogenesis in the mouse mammary gland.

    PubMed

    Goel, Hira Lal; Bae, Donggoo; Pursell, Bryan; Gouvin, Lindsey M; Lu, Shaolei; Mercurio, Arthur M

    2011-07-01

    Although the neuropilins were characterized as semaphorin receptors that regulate axon guidance, they also function as vascular endothelial growth factor (VEGF) receptors and contribute to the development of other tissues. Here, we assessed the role of NRP2 in mouse mammary gland development based on our observation that NRP2 is expressed preferentially in the terminal end buds of developing glands. A floxed NRP2 mouse was bred with an MMTV-Cre strain to generate a mammary gland-specific knockout of NRP2. MMTV-Cre;NRP2(loxP/loxP) mice exhibited significant defects in branching morphogenesis and ductal outgrowth compared with either littermate MMTV-Cre;NRP2(+/loxP) or MMTV-Cre mice. Mechanistic insight into this morphological defect was obtained from a mouse mammary cell line in which we observed that VEGF(165), an NRP2 ligand, induces branching morphogenesis in 3D cultures and that branching is dependent upon NRP2 as shown using shRNAs and a function-blocking antibody. Epithelial cells in the mouse mammary gland express VEGF, supporting the hypothesis that this NRP2 ligand contributes to mammary gland morphogenesis. Importantly, we demonstrate that VEGF and NRP2 activate focal adhesion kinase (FAK) and promote FAK-dependent branching morphogenesis in vitro. The significance of this mechanism is substantiated by our finding that FAK activation is diminished significantly in developing MMTV-Cre;NRP2(loxP/loxP) mammary glands compared with control glands. Together, our data reveal a VEGF/NRP2/FAK signaling axis that is important for branching morphogenesis and mammary gland development. In a broader context, our data support an emerging hypothesis that directional outgrowth and branching morphogenesis in a variety of tissues are influenced by signals that were identified initially for their role in axon guidance.

  5. Growth of modern branched columnar stromatolites in Lake Joyce, Antarctica.

    PubMed

    Mackey, T J; Sumner, D Y; Hawes, I; Jungblut, A D; Andersen, D T

    2015-07-01

    Modern decimeter-scale columnar stromatolites from Lake Joyce, Antarctica, show a change in branching pattern during a period of lake level rise. Branching patterns correspond to a change in cyanobacterial community composition as preserved in authigenic calcite crystals. The transition in stromatolite morphology is preserved by mineralized layers that contain microfossils and cylindrical molds of cyanobacterial filaments. The molds are composed of two populations with different diameters. Large diameter molds (>2.8 μm) are abundant in calcite forming the oldest stromatolite layers, but are absent from younger layers. In contrast, <2.3 μm diameter molds are common in all stromatolites layers. Loss of large diameter molds corresponds to the transition from smooth-sided stromatolitic columns to branched and irregular columns. Mold diameters are similar to trichome diameters of the four most abundant living cyanobacteria morphotypes in Lake Joyce: Phormidium autumnale morphotypes have trichome diameters >3.5 μm, whereas Leptolyngbya antarctica, L. fragilis, and Pseudanabaena frigida morphotypes have diameters <2.3 μm. P. autumnale morphotypes were only common in mats at <12 m depth. Mats containing abundant P. autumnale morphotypes were smooth, whereas mats with few P. autumnale morphotypes contained small peaks and protruding bundles of filaments, suggesting that the absence of P. autumnale morphotypes allowed small-scale topography to develop on mats. Comparisons of living filaments and mold diameters suggest that P. autumnale morphotypes were present early in stromatolite growth, but disappeared from the community through time. We hypothesize that the mat-smoothing behavior of P. autumnale morphotypes inhibited nucleation of stromatolite branches. When P. autumnale morphotypes were excluded from the community, potentially reflecting a rise in lake level, short-wavelength roughness provided nuclei for stromatolite branches. This growth history provides a

  6. Global horizontal shear velocity structure

    NASA Astrophysics Data System (ADS)

    Ho, T. M.; Priestley, K. F.; Debayle, E.; Chapman, C. H.

    2013-12-01

    Rayleigh wave data have been used extensively to produce various SV-wave tomographic models of the upper mantle. Love wave data are more difficult to deal with resulting in fewer SH-wave tomographic models. The models also do not incorporate higher mode information which can place better constraints on the model. We have assembled a large, horizontal component data set and have inverted these seismogram in the 4-13 mHz band including higher mode information. We use a version of the automated waveform inversion technique modified for Love waves. We have explored the effects of various crustal models and because of the greater sensitivity of Love waves to the crustal structure, at present, we limit our inversion to this lower frequency band. Due to the higher mode Love waves having similar group velocities between the periods of 50-100 s for oceanic paths, interference occurs which partition techniques have difficulties dealing with. The modified technique used here does not require partitioning the data and can help extract the data more easily at these period bands. We present a new VSH and Xi model for the upper mantle. High VSH extending to about 250 km depth occurs beneath the cratons and Tibet; Low VSH occurs beneath the mid-ocean ridges, the back arc basins and beneath the Afar hotspot. The Xi model shows that VSH is greater by approximately 3% at 100km and rapidly drops to zero at around 300 km depth where the mantle becomes isotropic. At 250 km depth, there are regions where SV is greater than SH, suggesting more vertical flow beneath mid-ocean ridges at these depths.

  7. New branches of massive gravity

    NASA Astrophysics Data System (ADS)

    Comelli, D.; Crisostomi, M.; Koyama, K.; Pilo, L.; Tasinato, G.

    2015-06-01

    The basic building block for Lorentz-invariant and ghost-free massive gravity is the square root of the combination g-1η , where g-1 is the inverse of the physical metric and η is a reference metric. Since the square root of a matrix is not uniquely defined, it is possible to have physically inequivalent potentials corresponding to different branches. We show that around the Minkowski background, the only perturbatively well-defined branch is the potential proposed by de Rham, Gabadadze and Tolley. On the other hand, if Lorentz symmetry is broken spontaneously, other potentials exist with a standard perturbative expansion. We show this explicitly building new Lorentz-invariant, ghost-free massive gravity potentials for theories that in the background preserve rotational invariance but break Lorentz boosts.

  8. Morphology and Functional Anatomy of the Recurrent Laryngeal Nerve with Extralaryngeal Terminal Bifurcation

    PubMed Central

    Dogan, Sami

    2016-01-01

    Anatomical variations of the recurrent laryngeal nerve (RLN), such as an extralaryngeal terminal bifurcation (ETB), threaten the safety of thyroid surgery. Besides the morphology of the nerve branches, intraoperative evaluation of their functional anatomy may be useful to preserve motor activity. We exposed 67 RLNs in 36 patients. The main trunk, bifurcation point, and terminal branches of bifid nerves were macroscopically determined and exposed during thyroid surgery. The functional anatomy of the nerve branches was evaluated by intraoperative nerve monitoring (IONM). Forty-six RLNs with an ETB were intraoperatively exposed. The bifurcation point was located along the prearterial, arterial, and postarterial segments in 11%, 39%, and 50% of bifid RLNs, respectively. Motor activity was determined in all anterior branches. The functional anatomy of terminal branches detected motor activity in 4 (8.7%) posterior branches of 46 bifid RLNs. The motor activity in posterior branches created a wave amplitude at 25–69% of that in the corresponding anterior branches. The functional anatomy of bifid RLNs demonstrated that anterior branches always contained motor fibres while posterior branches seldom contained motor fibres. The motor activity of the posterior branch was weaker than that of the anterior branch. IONM may help to differentiate between motor and sensory functions of nerve branches. The morphology and functional anatomy of all nerve branches must be preserved to ensure a safer surgery. PMID:27493803

  9. Flood-plain delineation for Horsepen Run, Sugarland Run, Nichols Run, Pond Branch, Clarks Branch, and Mine Run Branch basins, Fairfax County, Virginia

    USGS Publications Warehouse

    Soule, Pat LeRoy

    1978-01-01

    Water-surface profiles of the 25-, 50-, and 100-year recurrence interval discharges have been computed for all streams and reaches of channels in Fairfax County, Virginia, having a drainage area greater than 1 square mile except for Dogue Creek, Little Hunting Creek, and that portion of Cameron Run above Lake Barcroft. Maps have a 2-foot contour interval and a horizontal scale of 1 inch equals 100 feet were used for base on which flood boundaries were delineated for 25-, 50-, and 100-year floods to be expected in each basin under ultimate development conditions. This report is one of a series and presents a discussion of techniques employed in computing discharges and profiles as well as the flood profiles and maps on which flood boundaries have been delineated for the Horsepen Run, Sugarland Run, Nichols Run, and Pond Branch basins in Fairfax County. (Woodard-USGS)

  10. Solid State Photovoltaic Research Branch

    SciTech Connect

    Not Available

    1990-09-01

    This report summarizes the progress of the Solid State Photovoltaic Research Branch of the Solar Energy Research Institute (SERI) from October 1, 1988, through September 30,l 1989. Six technical sections of the report cover these main areas of SERIs in-house research: Semiconductor Crystal Growth, Amorphous Silicon Research, Polycrystalline Thin Films, III-V High-Efficiency Photovoltaic Cells, Solid-State Theory, and Laser Raman and Luminescence Spectroscopy. Sections have been indexed separately for inclusion on the data base.

  11. Geodynamics Branch research report, 1982

    NASA Technical Reports Server (NTRS)

    Kahn, W. D. (Editor); Cohen, S. C. (Editor)

    1983-01-01

    The research program of the Geodynamics Branch is summarized. The research activities cover a broad spectrum of geoscience disciplines including space geodesy, geopotential field modeling, tectonophysics, and dynamic oceanography. The NASA programs which are supported by the work described include the Geodynamics and Ocean Programs, the Crustal Dynamics Project, the proposed Ocean Topography Experiment (TOPEX) and Geopotential Research Mission. The individual papers are grouped into chapters on Crustal Movements, Global Earth Dynamics, Gravity Field Model Development, Sea Surface Topography, and Advanced Studies.

  12. DIVERGENT HORIZONTAL SUB-SURFACE FLOWS WITHIN ACTIVE REGION 11158

    SciTech Connect

    Jain, Kiran; Tripathy, S. C.; Hill, F. E-mail: stripathy@nso.edu

    2015-07-20

    We measure the horizontal subsurface flow in a fast emerging active region (AR; NOAA 11158) using the ring-diagram technique and the Helioseismic and Magnetic Imager high spatial resolution Dopplergrams. This AR had a complex magnetic structure and displayed significant changes in morphology during its disk passage. Over a period of six days from 2011 February 11 to 16, the temporal variation in the magnitude of the total velocity is found to follow the trend of magnetic field strength. We further analyze regions of individual magnetic polarity within AR 11158 and find that the horizontal velocity components in these sub-regions have significant variation with time and depth. The leading and trailing polarity regions move faster than the mixed-polarity region. Furthermore, both zonal and meridional components have opposite signs for trailing and leading polarity regions at all depths showing divergent flows within the AR. We also find a sharp decrease in the magnitude of total horizontal velocity in deeper layers around major flares. It is suggested that the re-organization of magnetic fields during flares, combined with the sunspot rotation, decreases the magnitude of horizontal flows or that the flow kinetic energy has been converted into the energy released by flares. After the decline in flare activity and sunspot rotation, the flows tend to follow the pattern of magnetic activity. We also observe less variation in the velocity components near the surface but these tend to increase with depth, further demonstrating that the deeper layers are more affected by the topology of ARs.

  13. Synthesis of hierarchical TiO2 nanowires with densely-packed and omnidirectional branches.

    PubMed

    Lee, Daeho; Rho, Yoonsoo; Allen, Frances I; Minor, Andrew M; Ko, Seung Hwan; Grigoropoulos, Costas P

    2013-11-21

    In this study, a hierarchical TiO2 nanostructure with densely-packed and omnidirectional branches grown by a hydrothermal method is introduced. This morphology is achieved via high-concentration TiCl4 treatment of upright backbone nanowires (NWs) followed by hydrothermal growth. Secondary nanobranches grow in all directions from densely distributed, needle-like seeds on the jagged round surface of the backbone NWs. In addition, hierarchical, flower-like branches grow on the top surface of each NW, greatly increasing the surface area. For dye-sensitized solar cell (DSSC) applications, the TiO2 nanostructure demonstrated a photoconversion efficiency of up to 6.2%. A parametric study of the DSSC efficiency showed that branched TiO2 DSSCs can achieve nearly four times the efficiency of non-branched TiO2 nanowire DSSCs, and up to 170% the efficiency of previously-reported sparsely-branched TiO2 NW DSSCs.

  14. Synthesis of hierarchical TiO2 nanowires with densely-packed and omnidirectional branches

    NASA Astrophysics Data System (ADS)

    Lee, Daeho; Rho, Yoonsoo; Allen, Frances I.; Minor, Andrew M.; Ko, Seung Hwan; Grigoropoulos, Costas P.

    2013-10-01

    In this study, a hierarchical TiO2 nanostructure with densely-packed and omnidirectional branches grown by a hydrothermal method is introduced. This morphology is achieved via high-concentration TiCl4 treatment of upright backbone nanowires (NWs) followed by hydrothermal growth. Secondary nanobranches grow in all directions from densely distributed, needle-like seeds on the jagged round surface of the backbone NWs. In addition, hierarchical, flower-like branches grow on the top surface of each NW, greatly increasing the surface area. For dye-sensitized solar cell (DSSC) applications, the TiO2 nanostructure demonstrated a photoconversion efficiency of up to 6.2%. A parametric study of the DSSC efficiency showed that branched TiO2 DSSCs can achieve nearly four times the efficiency of non-branched TiO2 nanowire DSSCs, and up to 170% the efficiency of previously-reported sparsely-branched TiO2 NW DSSCs.

  15. [The synthesis of mathematical models of the branched axons and dendrites].

    PubMed

    Korogod, S M

    1988-01-01

    A mathematical apparatus of computer modelling was elaborated reflecting more completely the real morphological and electrophysiological features of axons and dendrites without restrictions and simplifications which were typical of the existing models of these structures. Equivalent electrical circuits of branching axons and dendrites were constructed with in-series and node connections of standard four-terminal networks corresponding to elementary segments with active or passive membrane. Basing on these circuits the equations were obtained describing electrical phenomena in branching neuronal processes. They were generalized for the case of multiple binary branching with arbitrary symmetry and geometry of the branches. A difference scheme common for the whole class of models under consideration was also constructed and an algorithm was elaborated for numerical solution of the obtained system of difference equations. The suggested model allows synthetizing a variety of models of branching axons and dendrites, that promotes the possibilities of model investigation of electrotonus, propagated excitation and their interactions.

  16. Walker Branch Watershed Ecosystems Data

    DOE Data Explorer

    Walker Branch Watershed is located on the U. S. Department of Energy's Oak Ridge Reservation near Oak Ridge, in Anderson County, Tennessee. The Walker Branch Watershed Project began in 1967 under sponsorship of the U. S. Atomic Energy Commission (now the U. S. Department of Energy). Initially, the project centered primarily on the geologic and hydrologic processes that control the amounts and chemistry of water moving through the watershed. Past projects have included: • U. S. Department of Energy funded studies of watershed hydrology and forest nutrient dynamics • National Oceanic and Atmospheric Administration funded studies of forest micrometeorology • Studies of atmospheric deposition under the National Atmospheric Deposition Program • The International Biological Program Eastern Deciduous Forest Biome Project • National Science Foundation sponsored studies of trace element cycling and stream nutrient spiraling • Electric Power Research Institute funded studies of the effects of acidic deposition on canopy processes and soil chemistry. These projects have all contributed to a more complete understanding of how forest watersheds function and have provided insights into the solution of energy-related problems associated with air pollution, contaminant transport, and forest nutrient dynamics. This is one of a few sites in the world characterized by long-term, intensive environmental studies. The Walker Branch Watershed website at http://walkerbranch.ornl.gov/ provides maps, photographs, and data on climate, precipitation, atmospheric deposition, stream discharge and runoff, stream chemistry, and vegetation. [Taken from http://walkerbranch.ornl.gov/ABOUTAAA.HTM

  17. Neocortical neuronal morphology in the Siberian Tiger (Panthera tigris altaica) and the clouded leopard (Neofelis nebulosa).

    PubMed

    Johnson, Cameron B; Schall, Matthew; Tennison, Mackenzie E; Garcia, Madeleine E; Shea-Shumsky, Noah B; Raghanti, Mary Ann; Lewandowski, Albert H; Bertelsen, Mads F; Waller, Leona C; Walsh, Timothy; Roberts, John F; Hof, Patrick R; Sherwood, Chet C; Manger, Paul R; Jacobs, Bob

    2016-12-01

    Despite extensive investigations of the neocortex in the domestic cat, little is known about neuronal morphology in larger felids. To this end, the present study characterized and quantified the somatodendritic morphology of neocortical neurons in prefrontal, motor, and visual cortices of the Siberian tiger (Panthera tigris altaica) and clouded leopard (Neofelis nebulosa). After neurons were stained with a modified Golgi technique (N = 194), dendritic branching and spine distributions were analyzed using computer-assisted morphometry. Qualitatively, aspiny and spiny neurons in both species appeared morphologically similar to those observed in the domestic cat. Although the morphology of spiny neurons was diverse, with the presence of extraverted, inverted, horizontal, and multiapical pyramidal neurons, the most common variant was the typical pyramidal neuron. Gigantopyramidal neurons in the motor cortex were extremely large, confirming the observation of Brodmann ([1909] Vergleichende Lokalisationlehre der Grosshirnrinde in ihren Prinzipien dargestellt auf Grund des Zellenbaues. Leipzig, Germany: J.A. Barth), who found large somata for these neurons in carnivores in general, and felids in particular. Quantitatively, a MARSplines analysis of dendritic measures differentiated typical pyramidal neurons between the Siberian tiger and the clouded leopard with 93% accuracy. In general, the dendrites of typical pyramidal neurons were more complex in the tiger than in the leopards. Moreover, dendritic measures in tiger pyramidal neurons were disproportionally large relative to body/brain size insofar as they were nearly as extensive as those observed in much larger mammals (e.g., African elephant). Comparison of neuronal morphology in a more diverse collection of larger felids may elucidate the comparative context for the relatively large size of the pyramidal neurons observed in the present study. J. Comp. Neurol. 524:3641-3665, 2016. © 2016 Wiley Periodicals, Inc.

  18. Bird exclosures for branches and whole trees.

    Treesearch

    Robert W. Campbell; Torolf R. Torgersen; Steven C. Forrest; Lorna C. Youngs

    1981-01-01

    Two types of lightweight, portable bird exclosures are described. One is for individual branches or branch tips; the other is for whole trees up to 9 m tall. Several alternative configurations and uses of these exclosures are discussed.

  19. Managing occurrence branching in qualitative simulation

    SciTech Connect

    Tokuda, L.

    1996-12-31

    Qualitative simulators can produce common sense abstractions of complex behaviors given only partial knowledge about a system. One of the problems which limits the applicability of qualitative simulators is the intractable branching of successor states encountered with model of even modest size. Some branches may be unavoidable due to the complex nature of a system. Other branches may be accidental results of the model chosen. A common source of intractability is occurrence branching. Occurrence branching occurs when the state transitions of two variables are unordered with respect to each other. This paper extends the QSIM model to distinguish between interesting occurrence branching and uninteresting occurrence branching. A representation, algorithm, and simulator for efficiently handling uninteresting branching is presented.

  20. Incidence and angiographic predictors of side branch occlusion following high-pressure intracoronary stenting.

    PubMed

    Aliabadi, D; Tilli, F V; Bowers, T R; Benzuly, K H; Safian, R D; Goldstein, J A; Grines, C L; O'Neill, W W

    1997-10-15

    We evaluated the incidence, angiographic predictors, and clinical outcome of side branch occlusion (SBO) following high-pressure intracoronary stenting in 175 patients. All stent implants during a 7-month period were reviewed for the incidence of major (>1 mm) SBO. Side branches were further characterized based on side branch and index lesion morphology. Clinical events (death, myocardial infarction, and target vessel revascularization rates) were determined at 9 months. A total of 175 patients (182 lesions) had 224 major side branches covered by intracoronary stents. Of these, 43 (19%) occluded. Most SBOs (29 of 43 [67%]) occurred after poststent dilation using high-pressure inflations (15.3 +/- 3.3 atmospheres). No clinical characteristics correlated with SBO. By multivariate analysis, those side branches with >50% ostial narrowing that arose from within or just beyond the diseased portion of the parent vessel (threatened side branch morphologies) were a powerful angiographic predictor of SBO (odds ratio 40, 95% confidence interval, 14 to 130, p <0.0001). At 9-month follow-up there was no difference in combined clinical events between those patients with and without SBO. These data demonstrate that side branches with ostial stenoses in continuity with diseased parent lesions were at risk of occlusion following stenting. SBO, however, was not associated with adverse clinical outcome. These findings lend support to plaque shift ("snow plow effect") as the mechanism behind SBO following stent placement.

  1. QUANTITATIVE MORPHOLOGY

    EPA Science Inventory

    Abstract: In toxicology, the role of quantitative assessment of brain morphology can be understood in the context of two types of treatment-related alterations. One type of alteration is specifically associated with treatment and is not observed in control animals. Measurement ...

  2. QUANTITATIVE MORPHOLOGY

    EPA Science Inventory

    Abstract: In toxicology, the role of quantitative assessment of brain morphology can be understood in the context of two types of treatment-related alterations. One type of alteration is specifically associated with treatment and is not observed in control animals. Measurement ...

  3. The Effects of a Branch Campus

    ERIC Educational Resources Information Center

    Lien, Donald; Wang, Yaqin

    2012-01-01

    We examine the effects of a branch campus on the social welfare of the host country and the foreign university. Overall, we find that a branch campus increases both the domestic social welfare (measured by the aggregate student utility) and the tuition revenue of the foreign university. The effect of a branch campus on the brain drain is…

  4. Structural dynamics branch research and accomplishments

    NASA Technical Reports Server (NTRS)

    1990-01-01

    Summaries are presented of fiscal year 1989 research highlights from the Structural Dynamics Branch at NASA Lewis Research Center. Highlights from the branch's major work areas include aeroelasticity, vibration control, dynamic systems, and computation structural methods. A listing of the fiscal year 1989 branch publications is given.

  5. Introduction of Branching Degrees of Octane Isomers.

    PubMed

    Perdih, Anton

    2016-01-01

    The concept of branching degrees is introduced. In the case of octane isomers it is derived from the values of a set of their physicochemical properties, calculating for each isomer the average of the normalized values and these averages are defined as branching degrees of octane isomers. The sequence of these branching degrees of octane isomers does not differ much from the »regular« one defined earlier. 2,2-Dimethylhexane appears to be less branched than 3,4-dimethylhexane and 3-ethyl, 2-methylpentane, whereas 2,3,4-trimethylpentane appears to be less branched than 3-ethyl, 3-methylpentane. While the increasing number of branches gives rise to increasing branching degrees, the peripheral position of branches and the separation between branches decreases the value of the branching degree. The central position of branches increases it. A bigger branch increases it more than a smaller one. The quantification of these structural features and their correlations with few indices is given as well.

  6. Guide to the Seattle Archives Branch.

    ERIC Educational Resources Information Center

    Hobbs, Richard, Comp.

    The guide presents an overview of the textual and microfilmed records located at the Seattle Branch of the National Archives of the United States. Established in 1969, the Seattle Archives Branch is one of 11 branches which preserve and make available for research those U.S. Government records of permanent value created and maintained by Federal…

  7. Tubing and casing buckling in horizontal wells

    SciTech Connect

    Chen, Y.C.; Lin, Y.H.; Cheatham, J.B. )

    1990-02-01

    This paper describes new theoretical results for predicting the buckling behavior of pipe in horizontal holes. Pipe buckling in horizontal holes occurs initially in a sinusoidal mode along the low side of the hole; at higher axial compression a helix is formed. Equations are given for computing the forces required to initiate these different buckling modes. Simple experimental laboratory results confirm the theory. Results presented in this paper apply to friction modeling of buckled tubulars to help predict when pipe can be forced to move along a long section of a horizontal well.

  8. Horizontal atmospheric turbulence, beam propagation, and modeling

    NASA Astrophysics Data System (ADS)

    Wilcox, Christopher C.; Santiago, Freddie; Martinez, Ty; Judd, K. Peter; Restaino, Sergio R.

    2017-05-01

    The turbulent effect from the Earth's atmosphere degrades the performance of an optical imaging system. Many studies have been conducted in the study of beam propagation in a turbulent medium. Horizontal beam propagation and correction presents many challenges when compared to vertical due to the far harsher turbulent conditions and increased complexity it induces. We investigate the collection of beam propagation data, analysis, and use for building a mathematical model of the horizontal turbulent path and the plans for an adaptive optical system to use this information to correct for horizontal path atmospheric turbulence.

  9. Horizontal fields generated by return strokes

    NASA Technical Reports Server (NTRS)

    Cooray, Vernon

    1991-01-01

    Horizontal fields generated by return strokes play an important role in the interaction of lightning generated electric fields with power lines. In many of the recent investigations on the interaction of lightning electromagnetic fields with power lines, the horizontal field was calculated by employing the expression for the tilt of the electric field of a plane wave propagating over finitely conducting earth. The method is suitable for calculating horizontal fields generated by return strokes at distances as close as 200m. At these close ranges, the use of the wavetilt expression can cause large errors.

  10. S-branch CARS applicability to thermometry

    SciTech Connect

    Akihama, K.; Asai, T. )

    1990-07-20

    The pressure and temperature dependence of background-free {ital S}-branch CARS spectra of N{sub 2} are investigated in the temperature range of 300--700 K for pressures of 1--20 atm. Collisional narrowing for {ital S}-branch CARS spectra is proved to be negligible. Individual {ital S}-branch lines are clearly resolved in the entire range, enabling unequivocal determination of temperatures by their peak ratios. Advantages and disadvantages of {ital S}-branch CARS thermometry are discussed on the basis of experimental results. The dual narrowband Stokes CARS technique is also discussed as a practical method of {ital S}-branch CARS thermometry.

  11. S-branch CARS applicability to thermometry.

    PubMed

    Akihama, K; Asai, T

    1990-07-20

    The pressure and temperature dependence of background-free S-branch CARS spectra of N(2) are investigated in the temperature range of 300-700 K for pressures of 1-20 atm. Collisional narrowing for S-branch CARS spectra is proved to be negligible. Individual S-branch lines are clearly resolved in the entire range, enabling unequivocal determination of temperatures by their peak ratios. Advantages and disadvantages of S-branch CARS thermometry are discussed on the basis of experimental results. The dual narrowband Stokes CARS technique is also discussed as a practical method of S-branch CARS thermometry.

  12. Horizontal steam generator thermal-hydraulics

    SciTech Connect

    Ubra, O.; Doubek, M.

    1995-09-01

    Horizontal steam generators are typical components of nuclear power plants with pressure water reactor type VVER. Thermal-hydraulic behavior of horizontal steam generators is very different from the vertical U-tube steam generator, which has been extensively studied for several years. To contribute to the understanding of the horizontal steam generator thermal-hydraulics a computer program for 3-D steady state analysis of the PGV-1000 steam generator has been developed. By means of this computer program, a detailed thermal-hydraulic and thermodynamic study of the horizontal steam generator PGV-1000 has been carried out and a set of important steam generator characteristics has been obtained. The 3-D distribution of the void fraction and 3-D level profile as functions of load and secondary side pressure have been investigated and secondary side volumes and masses as functions of load and pressure have been evaluated. Some of the interesting results of calculations are presented in the paper.

  13. Melt Stirring by Horizontal Crucible Vibration

    NASA Technical Reports Server (NTRS)

    Wolf, M. F.; Elwell, D.; Feigelson, R. S.

    1985-01-01

    Horizontal vibration suggested as technique for more effective stirring of melts in crystal-growth apparatus. Vibrational technique may replace accelerated crucible rotation. Potential superiority of vibrational technique shown by preliminary experiments in which ink stirred into water.

  14. Productivity and injectivity of horizontal wells

    SciTech Connect

    Aziz, Khalid

    2000-03-06

    One of the key issues addressed was pressure drop in long horizontal wells and its influence on well performance. Very little information is available in the literature on flow in pipes with influx through pipe walls. Virtually all of this work has been in small diameter pipes and with single-phase flow. In order to address this problem new experimental data on flow in horizontal and near horizontal wells have been obtained. Experiments were conducted at an industrial facility on typical 6 1/8 ID, 100 feet long horizontal well model. The new data along with available information in the literature have been used to develop new correlations and mechanistic models. Thus it is now possible to predict, within reasonable accuracy, the effect of influx through the well on pressure drop in the well.

  15. Granular slumping on a horizontal surface

    NASA Astrophysics Data System (ADS)

    Lajeunesse, E.; Monnier, J. B.; Homsy, G. M.

    2005-10-01

    We report the results of an experimental investigation of the flow induced by the collapse of a column of granular material (glass beads of diameter d) over a horizontal surface. Two different setups are used, namely, a rectangular channel and a semicircular tube, allowing us to compare two-dimensional and axisymmetric flows, with particular focus on the internal flow structure. In both geometries the flow dynamics and the deposit morphologies are observed to depend primarily on the initial aspect ratio of the granular column a =Hi/Li, where Hi is the height of the initial granular column and Li its length along the flow direction. Two distinct regimes are observed depending on a: an avalanche of the column flanks producing truncated deposits for small a and a column free fall leading to conical deposits for large a. In both geometries the characteristic time scale is the free fall of the granular column τc=√Hi/g . The flow initiated by Coulomb-like failure never involves the whole granular heap but remains localized in a surface layer whose size and shape depend on a and vary in both space and time. Except in the vicinity of the pile foot where the flow is pluglike, velocity profiles measured at the side wall are identical to those commonly observed in steady granular surface flows: the velocity varies linearly with depth in the flowing layer and decreases exponentially with depth in the static layer. Moreover, the shear rate is constant, γ˙=0.3√g /d , independent of the initial aspect ratio, the flow geometry, position along the heap, or time. Despite the rather complex flow dynamics, the scaled deposit height Hf/Li and runout distance ΔL /Li both exhibit simple power laws whose exponents depend on a and on the flow geometry. We show that the physical origin of these power laws can be understood on the basis of a dynamic balance between acceleration, pressure gradient, and friction forces at the foot of the granular pile. Two asymptotic behaviors can be

  16. The anatomy of the fundic branches of the stomach: preliminary results.

    PubMed

    Gregorczyk, M; Dabkowska, A; Tarka, S; Ciszek, B

    2008-05-01

    The fundic branches of the stomach can be defined as a group of vessels that can arise either directly or indirectly from the following source arteries: the left inferior phrenic artery, the accessory left hepatic artery, the left gastric artery, the left middle suprarenal artery, the main trunk of the splenic artery, the posterior gastric artery, the superior polar artery, the gastrosplenic artery, the left gastroepiploic artery and the splenic artery with its inferior and superior terminal branches. It is worth mentioning that the fundic branches of the left gastroepiploic artery and the superior and inferior terminal branches of the splenic artery, like other vessels arising from these three source arteries and supplying the stomach, are defined as short gastric arteries. The anatomy of these fundic branches, particularly relevant to some surgical procedures, is not sufficiently described, and the current literature suffers from lack of publications on this particular topic. We therefore decided to explore in detail the arterial vascularisation of the gastric fundus. The research was carried out on material consisting of 15 human stomach specimens. The anatomical analysis comprised the following: the number of occurrences of fundic branches in each of the source arteries defined above, the distance between the origins of the source artery and its arising fundic branch, the way in which the fundic branches arose, the length, diameter at point of origin and morphology of the fundic branches, as well as the exact point of perforation of each fundic branch on the fundus. The highest incidence of the direct-branching pattern of fundic branches was in the left middle suprarenal artery, the gastrosplenic artery and the left gastrosplenic artery. The accessory left hepatic artery, the left gastric artery and the main trunk of the splenic artery were the most frequent site of the indirectly arising pattern of fundic branch. The highest median value of fundic branch

  17. Evolutionary branching under slow directional evolution.

    PubMed

    Ito, Hiroshi C; Dieckmann, Ulf

    2014-11-07

    Evolutionary branching is the process by which ecological interactions induce evolutionary diversification. In asexual populations with sufficiently rare mutations, evolutionary branching occurs through trait-substitution sequences caused by the sequential invasion of successful mutants. A necessary and sufficient condition for evolutionary branching of univariate traits is the existence of a convergence stable trait value at which selection is locally disruptive. Real populations, however, undergo simultaneous evolution in multiple traits. Here we extend conditions for evolutionary branching to bivariate trait spaces in which the response to disruptive selection on one trait can be suppressed by directional selection on another trait. To obtain analytical results, we study trait-substitution sequences formed by invasions that possess maximum likelihood. By deriving a sufficient condition for evolutionary branching of bivariate traits along such maximum-likelihood-invasion paths (MLIPs), we demonstrate the existence of a threshold ratio specifying how much disruptive selection in one trait direction is needed to overcome the obstruction of evolutionary branching caused by directional selection in the other trait direction. Generalizing this finding, we show that evolutionary branching of bivariate traits can occur along evolutionary-branching lines on which residual directional selection is sufficiently weak. We then present numerical analyses showing that our generalized condition for evolutionary branching is a good indicator of branching likelihood even when trait-substitution sequences do not follow MLIPs and when mutations are not rare. Finally, we extend the derived conditions for evolutionary branching to multivariate trait spaces.

  18. Growth of branched actin networks against obstacles.

    PubMed Central

    Carlsson, A E

    2001-01-01

    A method for simulating the growth of branched actin networks against obstacles has been developed. The method is based on simple stochastic events, including addition or removal of monomers at filament ends, capping of filament ends, nucleation of branches from existing filaments, and detachment of branches; the network structure for several different models of the branching process has also been studied. The models differ with regard to their inclusion of effects such as preferred branch orientations, filament uncapping at the obstacle, and preferential branching at filament ends. The actin ultrastructure near the membrane in lamellipodia is reasonably well produced if preferential branching in the direction of the obstacle or barbed-end uncapping effects are included. Uncapping effects cause the structures to have a few very long filaments that are similar to those seen in pathogen-induced "actin tails." The dependence of the growth velocity, branch spacing, and network density on the rate parameters for the various processes is quite different among the branching models. An analytic theory of the growth velocity and branch spacing of the network is described. Experiments are suggested that could distinguish among some of the branching models. PMID:11566765

  19. Horizontal sidetrack taps reservoir sweet spots''

    SciTech Connect

    Wible, J.R. )

    1994-02-21

    Cutting a window at 85[degree] deviation allowed a sidetrack to pass through the high-resistivity sections in a Gulf of Mexico reservoir. Results from logging-while-drilling (LWD) tools indicated the original horizontal bore dropped too low in the reservoir, possibly leading to a low productivity well. The subsequent sidetrack successfully delivered the desired well bore, and the increased productivity justified the efforts in cutting a window in the horizontal section.

  20. Report of the Horizontal Launch Study

    NASA Technical Reports Server (NTRS)

    Wilhite, Alan W.; Bartolotta, Paul A.

    2011-01-01

    A study of horizontal launch concepts has been conducted. This study, jointly sponsored by the Defense Advanced Research Projects Agency (DARPA) and the National Aeronautics and Space Administration (NASA) was tasked to estimate the economic and technical viability of horizontal launch approaches. The study team identified the key parameters and critical technologies which determine mission viability and reported on the state of the art of critical technologies, along with objectives for technology development.

  1. Emotion recognition (sometimes) depends on horizontal orientations

    PubMed Central

    Huynh, Carol M; Balas, Benjamin

    2014-01-01

    Face recognition depends critically on horizontal orientations (Goffaux & Dakin, 2010). Face images that lack horizontal features are harder to recognize than those that have that information preserved. Presently, we asked if facial emotional recognition also exhibits this dependency by asking observers to categorize orientation-filtered happy and sad expressions. Furthermore, we aimed to dissociate image-based orientation energy from object-based orientation by rotating images 90-degrees in the picture-plane. In our first experiment, we showed that the perception of emotional expression does depend on horizontal orientations and that object-based orientation constrained performance more than image-based orientation. In Experiment 2 we showed that mouth openness (i.e. open versus closed-mouths) also influenced the emotion-dependent reliance on horizontal information. Lastly, we describe a simple computational analysis that demonstrates that the impact of mouth openness was not predicted by variation in the distribution of orientation energy across horizontal and vertical orientation bands. Overall, our results suggest that emotion recognition does largely depend on horizontal information defined relative to the face, but that this bias is modulated by multiple factors that introduce variation in appearance across and within distinct emotions. PMID:24664854

  2. Gait kinetics of above- and below-branch quadrupedal locomotion in lemurid primates.

    PubMed

    Granatosky, Michael C; Tripp, Cameron H; Schmitt, Daniel

    2016-01-01

    For primates and other mammals moving on relatively thin branches, the ability to effectively adopt both above- and below-branch locomotion is seen as critical for successful arboreal locomotion, and has been considered an important step prior to the evolution of specialized suspensory locomotion within our Order. Yet, little information exists on the ways in which limb mechanics change when animals shift from above- to below-branch quadrupedal locomotion. This study tested the hypothesis that vertical force magnitude and distribution do not vary between locomotor modes, but that the propulsive and braking roles of the forelimb change when animals shift from above- to below-branch quadrupedal locomotion. We collected kinetic data on two lemur species (Varecia variegata and Lemur catta) walking above and below an instrumented arboreal runway. Values for peak vertical, braking and propulsive forces as well as horizontal impulses were collected for each limb. When walking below branch, both species demonstrated a significant shift in limb kinetics compared with above-branch movement. The forelimb became both the primary weight-bearing limb and propulsive organ, while the hindlimb reduced its weight-bearing role and became the primary braking limb. This shift in force distribution represents a shift toward mechanics associated with bimanual suspensory locomotion, a locomotor mode unusual to primates and central to human evolution. The ability to make this change is not accompanied by significant anatomical changes, and thus likely represents an underlying mechanical flexibility present in most primates. © 2016. Published by The Company of Biologists Ltd.

  3. Branched-Chain Amino Acids.

    PubMed

    Yamamoto, Keisuke; Tsuchisaka, Atsunari; Yukawa, Hideaki

    Branched-chain amino acids (BCAAs), viz., L-isoleucine, L-leucine, and L-valine, are essential amino acids that cannot be synthesized in higher organisms and are important nutrition for humans as well as livestock. They are also valued as synthetic intermediates for pharmaceuticals. Therefore, the demand for BCAAs in the feed and pharmaceutical industries is increasing continuously. Traditional industrial fermentative production of BCAAs was performed using microorganisms isolated by random mutagenesis. A collection of these classical strains was also scientifically useful to clarify the details of the BCAA biosynthetic pathways, which are tightly regulated by feedback inhibition and transcriptional attenuation. Based on this understanding of the metabolism of BCAAs, it is now possible for us to pursue strains with higher BCAA productivity using rational design and advanced molecular biology techniques. Additionally, systems biology approaches using augmented omics information help us to optimize carbon flux toward BCAA production. Here, we describe the biosynthetic pathways of BCAAs and their regulation and then overview the microorganisms developed for BCAA production. Other chemicals, including isobutanol, i.e., a second-generation biofuel, can be synthesized by branching the BCAA biosynthetic pathways, which are also outlined.

  4. Chiral methyl-branched pheromones.

    PubMed

    Ando, Tetsu; Yamakawa, Rei

    2015-07-01

    Insect pheromones are some of the most interesting natural products because they are utilized for interspecific communication between various insects, such as beetles, moths, ants, and cockroaches. A large number of compounds of many kinds have been identified as pheromone components, reflecting the diversity of insect species. While this review deals only with chiral methyl-branched pheromones, the chemical structures of more than one hundred non-terpene compounds have been determined by applying excellent analytical techniques. Furthermore, their stereoselective syntheses have been achieved by employing trustworthy chiral sources and ingenious enantioselective reactions. The information has been reviewed here not only to make them available for new research but also to understand the characteristic chemical structures of the chiral pheromones. Since biosynthetic studies are still limited, it might be meaningful to examine whether the structures, particularly the positions and configurations of the branched methyl groups, are correlated with the taxonomy of the pheromone producers and also with the function of the pheromones in communication systems.

  5. Retinal horizontal cells: challenging paradigms of neural development and cancer biology.

    PubMed

    Poché, Ross A; Reese, Benjamin E

    2009-07-01

    A group of retinal interneurons known as horizontal cells has recently been shown to exhibit a variety of unique biological properties, as compared with other nerve cells, that challenge many long-standing assumptions in the fields of neural development and cancer biology. These features include their unusual migratory behavior, their unique morphological plasticity, and their propensity to divide at a relatively late stage during development. Here, we review these novel features, discuss their relevance for other cell types, outline open questions in our understanding of horizontal cell development and consider their implications.

  6. Horizontal oil shale and tar sands retort

    SciTech Connect

    Thomas, D.D.

    1982-08-31

    A horizontal retorting apparatus and method are disclosed designed to pyrolyze tar sands and oil shale, which are often found together in naturally occurring deposits. The retort is based on a horizontal retorting tube defining a horizontal retort zone having an upstream and a downstream end. Inlet means are provided for introducing the combined tar sands and oil shale into the upstream end of the retort. A screw conveyor horizontally conveys tar sands and oil shale from the upstream end of the retort zone to the downstream end of the retort zone while simultaneously mixing the tar sands and oil shale to insure full release of product gases. A firebox defining a heating zone surrounds the horizontal retort is provided for heating the tar sands and oil shale to pyrolysis temperatures. Spent shale and tar sands residue are passed horizontally beneath the retort tube with any carbonaceous residue thereon being combusted to provide a portion of the heat necessary for pyrolysis. Hot waste solids resulting from combustion of spent shale and tar sands residue are also passed horizontally beneath the retort tube whereby residual heat is radiated upward to provide a portion of the pyrolysis heat. Hot gas inlet holes are provided in the retort tube so that a portion of the hot gases produced in the heating zone are passed into the retort zone for contacting and directly heating the tar sands and oil shale. Auxiliary heating means are provided to supplement the heat generated from spent shale and tar sands residue combustion in order to insure adequate pyrolysis of the raw materials with varying residual carbonaceous material.

  7. Kinetics and Morphology of Living Polymer Systems

    NASA Astrophysics Data System (ADS)

    Gopinathan, Ajay; Schwarz, J. M.; Lee, Kun-Chun; Liu, Andrea J.

    2004-03-01

    The biopolymer F-actin is a key component of the cellular cytoskeleton and is important for cell motility.The actin cytoskeleton is not static but evolves via kinetic processes such as actin polymerization, depolymerization and branching. Various proteins are used to regulate these processses in order for the cell to crawl. Here we model the kinetics using a rate equation approach and focus on the resulting steady-state morphology. We determine such characteristics as the length distribution of filaments, density of branches and crawling rate as functions of the concentration of actin and associated proteins.

  8. Investigating the antifungal activity of TiO2 nanoparticles deposited on branched carbon nanotube arrays

    NASA Astrophysics Data System (ADS)

    Darbari, S.; Abdi, Y.; Haghighi, F.; Mohajerzadeh, S.; Haghighi, N.

    2011-06-01

    Branched carbon nanotube (CNT) arrays were synthesized by plasma-enhanced chemical vapour deposition on a silicon substrate. Ni was used as the catalyst and played an important role in the realization of branches in vertically aligned nanotubes. TiO2 nanoparticles on the branched CNTs were produced by atmospheric pressure chemical vapour deposition followed by a 500 °C annealing step. Transmission and scanning electron microscopic techniques were used to study the morphology of the TiO2/branched CNT structures while x-ray diffraction and Raman spectroscopy were used to verify the characteristics of the prepared nanostructures. Their antifungal effect on Candida albicans biofilms under visible light was investigated and compared with the activity of TiO2/CNT arrays and thin films of TiO2. The TiO2/branched CNTs showed a highly improved photocatalytic antifungal activity in comparison with the TiO2/CNTs and TiO2 film. The excellent visible light-induced photocatalytic antifungal activity of the TiO2/branched CNTs was attributed to the generation of electron-hole pairs by visible light excitation with a low recombination rate, in addition to the high surface area provided for the interaction between the cells and the nanostructures. Scanning electron microscopy was used to observe the resulting morphological changes in the cell body of the biofilms existing on the antifungal samples.

  9. Recursive Branching Simulated Annealing Algorithm

    NASA Technical Reports Server (NTRS)

    Bolcar, Matthew; Smith, J. Scott; Aronstein, David

    2012-01-01

    This innovation is a variation of a simulated-annealing optimization algorithm that uses a recursive-branching structure to parallelize the search of a parameter space for the globally optimal solution to an objective. The algorithm has been demonstrated to be more effective at searching a parameter space than traditional simulated-annealing methods for a particular problem of interest, and it can readily be applied to a wide variety of optimization problems, including those with a parameter space having both discrete-value parameters (combinatorial) and continuous-variable parameters. It can take the place of a conventional simulated- annealing, Monte-Carlo, or random- walk algorithm. In a conventional simulated-annealing (SA) algorithm, a starting configuration is randomly selected within the parameter space. The algorithm randomly selects another configuration from the parameter space and evaluates the objective function for that configuration. If the objective function value is better than the previous value, the new configuration is adopted as the new point of interest in the parameter space. If the objective function value is worse than the previous value, the new configuration may be adopted, with a probability determined by a temperature parameter, used in analogy to annealing in metals. As the optimization continues, the region of the parameter space from which new configurations can be selected shrinks, and in conjunction with lowering the annealing temperature (and thus lowering the probability for adopting configurations in parameter space with worse objective functions), the algorithm can converge on the globally optimal configuration. The Recursive Branching Simulated Annealing (RBSA) algorithm shares some features with the SA algorithm, notably including the basic principles that a starting configuration is randomly selected from within the parameter space, the algorithm tests other configurations with the goal of finding the globally optimal

  10. Multiparameter Parallel Search Branch Switching

    NASA Astrophysics Data System (ADS)

    Henderson, Michael E.

    A continuation method (sometimes called path following) is a way to compute solution curves of a nonlinear system of equations with a parameter. We derive a simple algorithm for branch switching at bifurcation points for multiple parameter continuation, where surfaces bifurcate along singular curves on a surface. It is a generalization of the parallel search technique used in the continuation code AUTO, and avoids the need for second derivatives and a full analysis of the bifurcation point. The one parameter case is special. While the generalization is not difficult, it is nontrivial, and the geometric interpretation may be of some interest. An additional tangent calculation at a point near the singular point is used to estimate the tangent to the singular set.

  11. The power of phylogenetic approaches to detect horizontally transferred genes

    PubMed Central

    Poptsova, Maria S; Gogarten, J Peter

    2007-01-01

    Background Horizontal gene transfer plays an important role in evolution because it sometimes allows recipient lineages to adapt to new ecological niches. High genes transfer frequencies were inferred for prokaryotic and early eukaryotic evolution. Does horizontal gene transfer also impact phylogenetic reconstruction of the evolutionary history of genomes and organisms? The answer to this question depends at least in part on the actual gene transfer frequencies and on the ability to weed out transferred genes from further analyses. Are the detected transfers mainly false positives, or are they the tip of an iceberg of many transfer events most of which go undetected by current methods? Results Phylogenetic detection methods appear to be the method of choice to infer gene transfers, especially for ancient transfers and those followed by orthologous replacement. Here we explore how well some of these methods perform using in silico transfers between the terminal branches of a gamma proteobacterial, genome based phylogeny. For the experiments performed here on average the AU test at a 5% significance level detects 90.3% of the transfers and 91% of the exchanges as significant. Using the Robinson-Foulds distance only 57.7% of the exchanges and 60% of the donations were identified as significant. Analyses using bipartition spectra appeared most successful in our test case. The power of detection was on average 97% using a 70% cut-off and 94.2% with 90% cut-off for identifying conflicting bipartitions, while the rate of false positives was below 4.2% and 2.1% for the two cut-offs, respectively. For all methods the detection rates improved when more intervening branches separated donor and recipient. Conclusion Rates of detected transfers should not be mistaken for the actual transfer rates; most analyses of gene transfers remain anecdotal. The method and significance level to identify potential gene transfer events represent a trade-off between the frequency of erroneous

  12. Morphological instabilities of polymer crystals.

    PubMed

    Grozev, N; Botiz, I; Reiter, G

    2008-09-01

    We present experimental observations at comparatively low supercooling of morphology transitions from dendritic to faceted structures in polymer crystals growing in thin films of a poly-2-vinylpyridine-block-polyethyleneoxid copolymer. Our results are compared with theoretical concepts describing morphological instabilities of single crystals. Although these concepts originally were not developed for polymers, they allow to describe and interpret our experimental results quite well. In particular, the measured temperature dependence of the width W and frequency of dendritic side branches and the radius of curvature p of the growth tips of the crystals follow these concepts. We present preliminary evidence for the influence of polymer attachment kinetics and reorganisation processes behind the growth front. Polymer thin films provide valuable model systems for studying general concepts of crystallisation and allow to distinguish at which point the connectivity of the crystallising units within chain-like molecules starts to play a measurable role.

  13. How to drill horizontal sections faster

    SciTech Connect

    Chaffin, M. )

    1991-12-01

    This paper reports that fewer trips, reduced slide time and lower drag during sliding have resulted from the application of downhole-adjustable stabilizers to horizontal drilling. Faster drilling times mean lower measurement while drilling (MWD) cost, and less wear on downhole equipment, motors and bits. These advantages combined with reduced drilling shocks have increased drilling rates and efficiency. Applying existing technology in new situations is an important way of reducing the cost of finding, exploring for and developing reserves. Engineers are responsible for using current technology to its fullest and developing new technology to reduce drilling expenses. Horizontal drilling was used in its early stages to develop the Austin chalk formation in Pearsall oil field more effectively. As procedures were generated to drill horizontal wells, Oryx drilling engineers began to develop new technology and investigate ways for existing technology to be used or altered to fit horizontal drilling programs. The new technology of downhole-adjustable stabilizers has been used successfully to further improve horizontal drilling efficiency.

  14. Unusual and Unique Variant Branches of Lateral Cord of Brachial Plexus and its Clinical Implications- A Cadaveric Study

    PubMed Central

    Padur, Ashwini Aithal; Shanthakumar, Swamy Ravindra; Shetty, Surekha Devadas; Prabhu, Gayathri Sharath; Patil, Jyothsna

    2016-01-01

    Introduction Adequate knowledge on variant morphology of brachial plexus and its branches are important in clinical applications pertaining to trauma and surgical procedures of the upper extremity. Aim Current study was aimed to report variations of the branches of the lateral cord of brachial plexus in the axilla and their possible clinical complications. Materials and Methods Total number of 82 upper limbs from 41 formalin embalmed cadavers was dissected. Careful observation was made to note the formation and branching pattern of lateral cord. Meticulous inspection for absence of branches, presence of additional or variant branches and presence of abnormal communications between its branches or with branches of other cords was carried out. Results In the present study, we noted varied branching pattern of lateral cord in 6 out of 82 limbs (7%). In one of the limb, the median nerve was formed by three roots; two from lateral cord and one from medial cord. Two limbs had absence of lateral pectoral nerve supplemented by medial pectoral nerves. One of which had an atypical ansa pectoralis. In 2 upper limbs, musculocutaneous nerve was absent and in both cases it was supplemented by median nerve. In one of the limb, coracobrachialis had dual nerve supply by musculocutaneous nerve and by an additional branch from the lateral cord. Conclusion Variations of brachial plexus and its branches could pose both intraoperative and postoperative complications which eventually affect the normal sensory and motor functions of the upper limb. PMID:27190783

  15. Vegetation survey of PEN Branch wetlands

    SciTech Connect

    Not Available

    1991-01-01

    A survey was conducted of vegetation along Pen Branch Creek at Savannah River Site (SRS) in support of K-Reactor restart. Plants were identified to species by overstory, understory, shrub, and groundcover strata. Abundance was also characterized and richness and diversity calculated. Based on woody species basal area, the Pen Branch delta was the most impacted, followed by the sections between the reactor and the delta. Species richness for shrub and groundcover strata were also lowest in the delta. No endangered plant species were found. Three upland pine areas were also sampled. In support of K Reactor restart, this report summarizes a study of the wetland vegetation along Pen Branch. Reactor effluent enters Indian Grove Branch and then flows into Pen Branch and the Pen Branch Delta.

  16. Vegetation survey of PEN Branch wetlands

    SciTech Connect

    Not Available

    1991-01-01

    A survey was conducted of vegetation along Pen Branch Creek at Savannah River Site (SRS) in support of K-Reactor restart. Plants were identified to species by overstory, understory, shrub, and groundcover strata. Abundance was also characterized and richness and diversity calculated. Based on woody species basal area, the Pen Branch delta was the most impacted, followed by the sections between the reactor and the delta. Species richness for shrub and groundcover strata were also lowest in the delta. No endangered plant species were found. Three upland pine areas were also sampled. In support of K Reactor restart, this report summarizes a study of the wetland vegetation along Pen Branch. Reactor effluent enters Indian Grove Branch and then flows into Pen Branch and the Pen Branch Delta.

  17. Research program of the Geodynamics Branch

    NASA Technical Reports Server (NTRS)

    Kahn, W. D. (Editor); Cohen, S. C. (Editor); Boccucci, B. S. (Editor)

    1986-01-01

    This report is the Fourth Annual Summary of the Research Program of the Geodynamics Branch. The branch is located within the Laboratory for Terrestrial Physics of the Space and Earth Sciences Directorate of the Goddard Space Flight Center. The research activities of the branch staff cover a broad spectrum of geoscience disciplines including: tectonophysics, space geodesy, geopotential field modeling, and dynamic oceanography. The NASA programs which are supported by the work described in this document include the Geodynamics and Ocean Programs, the Crustal Dynamics Project and the proposed Ocean Topography Experiment (TOPEX). The reports highlight the investigations conducted by the Geodynamics Branch staff during calendar year 1985. The individual papers are grouped into chapters on Crustal Movements and Solid Earth Dynamics, Gravity Field Modeling and Sensing Techniques, and Sea Surface Topography. Further information on the activities of the branch or the particular research efforts described herein can be obtained through the branch office or from individual staff members.

  18. Combining living anionic polymerization with branching reactions in an iterative fashion to design branched polymers.

    PubMed

    Higashihara, Tomoya; Sugiyama, Kenji; Yoo, Hee-Soo; Hayashi, Mayumi; Hirao, Akira

    2010-06-16

    This paper reviews the precise synthesis of many-armed and multi-compositional star-branched polymers, exact graft (co)polymers, and structurally well-defined dendrimer-like star-branched polymers, which are synthetically difficult, by a commonly-featured iterative methodology combining living anionic polymerization with branched reactions to design branched polymers. The methodology basically involves only two synthetic steps; (a) preparation of a polymeric building block corresponding to each branched polymer and (b) connection of the resulting building unit to another unit. The synthetic steps were repeated in a stepwise fashion several times to successively synthesize a series of well-defined target branched polymers.

  19. Mechanical Components Branch Test Facilities and Capabilities

    NASA Technical Reports Server (NTRS)

    Oswald, Fred B.

    2004-01-01

    The Mechanical Components Branch at NASA Glenn Research Center formulates, conducts, and manages research focused on propulsion systems for both present and advanced aeronautical and space vehicles. The branch is comprised of research teams that perform basic research in three areas: mechanical drives, aerospace seals, and space mechanisms. Each team has unique facilities for testing aerospace hardware and concepts. This report presents an overview of the Mechanical Components Branch test facilities.

  20. Naturally occurring branched-chain polyamines induce a crosslinked meshwork structure in a giant DNA

    NASA Astrophysics Data System (ADS)

    Muramatsu, Akira; Shimizu, Yuta; Yoshikawa, Yuko; Fukuda, Wakao; Umezawa, Naoki; Horai, Yuhei; Higuchi, Tsunehiko; Fujiwara, Shinsuke; Imanaka, Tadayuki; Yoshikawa, Kenichi

    2016-12-01

    We studied the effect of branched-chain polyamines on the folding transition of genome-sized DNA molecules in aqueous solution by the use of single-molecule observation with fluorescence microcopy. Detailed morphological features of polyamine/DNA complexes were characterized by atomic force microscopy (AFM). The AFM observations indicated that branched-chain polyamines tend to induce a characteristic change in the higher-order structure of DNA by forming bridges or crosslinks between the segments of a DNA molecule. In contrast, natural linear-chain polyamines cause a parallel alignment between DNA segments. Circular dichroism measurements revealed that branched-chain polyamines induce the A-form in the secondary structure of DNA, while linear-chain polyamines have only a minimum effect. This large difference in the effects of branched- and linear-chain polyamines is discussed in relation to the difference in the manner of binding of these polyamines to negatively charged double-stranded DNA.

  1. Toward improved branch prediction through data mining.

    SciTech Connect

    Hemmert, K. Scott; Johnson, D. Eric

    2009-09-01

    Data mining and machine learning techniques can be applied to computer system design to aid in optimizing design decisions, improving system runtime performance. Data mining techniques have been investigated in the context of branch prediction. Specifically, a comparison of traditional branch predictor performance has been made to data mining algorithms. Additionally, the possiblity of whether additional features available within the architectural state might serve to further improve branch prediction has been evaluated. Results show that data mining techniques indicate potential for improved branch prediction, especially when register file contents are included as a feature set.

  2. Stochastic model for supersymmetric particle branching process

    NASA Astrophysics Data System (ADS)

    Zhang, Yuanyuan; Chan, Aik Hui; Oh, Choo Hiap

    2017-01-01

    We develop a stochastic branching model to describe the jet evolution of supersymmetric (SUSY) particles. This model is a modified two-phase branching process, or more precisely, a two-phase simple birth process plus Poisson process. Both pure SUSY partons initiated jets and SUSY plus ordinary partons initiated jets scenarios are considered. The stochastic branching equations are established and the Multiplicity Distributions (MDs) are derived for these two scenarios. We also fit the distribution of the general case (SUSY plus ordinary partons initiated jets) with experimental data. The fitting shows the SUSY particles have not participated in branching at current collision energy yet.

  3. Branched silver nanowires as controllable plasmon routers.

    PubMed

    Fang, Yurui; Li, Zhipeng; Huang, Yingzhou; Zhang, Shunping; Nordlander, Peter; Halas, Naomi J; Xu, Hongxing

    2010-05-12

    Using polarization dependent scattering spectroscopy, we investigate plasmon propagation on branched silver nanowires. By controlling the polarization of the incident laser light, the wire plasmons can be routed into different wire branches and result in light emission from the corresponding wire ends. This routing behavior is found to be strongly dependent on the wavelength of light. Thus for certain incident polarizations, light of different wavelength will be routed into different branches. The branched nanowire can thus serve as a controllable router and multiplexer in integrated plasmonic circuits.

  4. Clinical and Translational Epidemiology Branch (CTEB)

    Cancer.gov

    The Clinical and Translational Epidemiology Branch focuses on factors that influence cancer progression, recurrence, survival, and other treatment outcomes, and factors associated with cancer development.

  5. The horizontal computerized rotational impulse test.

    PubMed

    Furman, Joseph M; Shirey, Ian; Roxberg, Jillyn; Kiderman, Alexander

    2016-01-01

    Whole-body impulsive rotations were used to overcome several limitations associated with manual head impulse testing. A computer-controlled rotational chair delivered brief, whole-body, earth-vertical axis yaw impulsive rotations while eye movements were measured using video-oculography. Results from an unselected group of 20 patients with dizziness and a group of 22 control subjects indicated that the horizontal computerized rotational head impulse test (crHIT) is well-tolerated and provides an estimate of unidirectional vestibulo-ocular reflex gain comparable to results from caloric testing. This study demonstrates that the horizontal crHIT is a new assessment tool that overcomes many of the limitations of manual head impulse testing and provides a reliable laboratory-based measure of unilateral horizontal semicircular canal function.

  6. ESP's placed in horizontal lateral increase production

    SciTech Connect

    Gallup, A.; Wilson, B.L. ); Marshall, R. )

    1990-06-18

    By design, the electric submersible pump (ESP) is an effective method of lifting fluids from horizontal wells. But this ESP application does have unique installation and operating parameters that need to be considered. ESP's have been used for many years in directional wells. This application provides an experience base for understanding deflection limits on the unit. To avoid damaging the ESP, special equipment may be required in some horizontal installations. This paper discusses how several ESP's have been designed specifically for medium-radius wells. In these applications, the deeper pump setting provides for a significant increase in production rate. In general, to realize the full benefit of a horizontal installation, the ESP should be considered when planning, drilling, and completing the well.

  7. Molecular thermodynamics for micellar branching in solutions of ionic surfactants.

    PubMed

    Andreev, Vasily A; Victorov, Alexey I

    2006-09-26

    We develop an analytical molecular-thermodynamic model for the aggregation free energy of branching portions of wormlike ionic micelles in 1:1 salt solution. The junction of three cylindrical aggregates is represented by a combination of pieces of the torus and bilayer. A geometry-dependent analytical solution is obtained for the linearized Poisson-Boltzmann equation. This analytical solution is applicable to saddle-like structures and reduces to the solutions known previously for planar, cylindrical, and spherical aggregates. For micellar junctions, our new analytical solution is in excellent agreement with numerical results over the range of parameters typical of ionic surfactant systems with branching micelles. Our model correctly predicts the sequence of stable aggregate morphologies, including a narrow bicontinuous zone, in dependence of hydrocarbon tail length, head size, and solution salinity. For predicting properties of a spatial network of wormlike micelles, our aggregation free energy is used in the Zilman-Safran theory. Our predictions are compared with experimental data for branching micelles of ionic surfactants.

  8. Hydroquinone-assisted synthesis of branched au-ag nanoparticles with polydopamine coating as highly efficient photothermal agents.

    PubMed

    Li, Jing; Wang, Wenjing; Zhao, Liang; Rong, Li; Lan, Shijie; Sun, Hongchen; Zhang, Hao; Yang, Bai

    2015-06-03

    Despite the success of galvanic replacement in preparing hollow nanostructures with diversified morphologies via the replacement reaction between sacrificial metal nanoparticles (NPs) seeds and less active metal ions, limited advances are made for producing branched alloy nanostructures. In this paper, we report an extended galvanic replacement for preparing branched Au-Ag NPs with Au-rich core and Ag branches using hydroquinone (HQ) as the reductant. In the presence of HQ, the preformed Ag seeds are replaceable by Au and, in turn, supply the growth of Ag branches. By altering the feed ratio of Ag seeds, HAuCl4, and HQ, the size and morphology of the NPs are tunable. Accordingly, the surface plasmon resonance absorption is tuned to near-infrared (NIR) region, making the branched NPs as potential materials in photothermal therapy. The branched NPs are further coated with polydopamine (PDA) shell via dopamine polymerization at room temperature. In comparison with bare NPs, PDA-coated branched Au-Ag (Au-Ag@PDA) NPs exhibit improved stability, biocompatibility, and photothermal performance. In vitro experiments indicate that the branched Au-Ag@PDA NPs are competitive agents for photothermal ablation of cancer cells.

  9. Horizontal drilling in shallow, geologically complex reservoirs

    SciTech Connect

    Venable, S.D.

    1992-05-01

    Hillin-Simon Oil Company, in connection with the U.S. Department of Energy proposes to drill a horizontal well in the Niobrara formation, Yuma County, Colorado. The objective of this project is to test the concept that multiple hydraulic fracturing from a directionally-drilled horizontal well, using the medium radius build rate method, can increase gas production sufficiently to justify economic viability over conventional stimulated vertical wells. The test well is located in a favorable area of established production to avoid exploration risks.

  10. Space shuttle horizontal flight test plan

    NASA Technical Reports Server (NTRS)

    Mosley, R. L.

    1972-01-01

    A horizontal takeoff flight test concept for testing space shuttle vehicles is presented. The guidelines used in planning and support requirements for the flight tests are developed. Details of the test program are provided. The instrumentation requirements are defined. The limitations imposed by the short flight endurance and restricted maneuvering capability of the shuttle booster/orbiter in the horizontal mode are described. The test program covers the following investigations. (1) stall and lift boundary tests, (2)takeoff and landing tests, (3) level flight speed power tests, (4) longitudinal and laterial directional dynamic stability, and (5) static directional stability.

  11. Horizontal Roll Vortices and Crown Fires.

    NASA Astrophysics Data System (ADS)

    Haines, Donald A.

    1982-06-01

    Observational evidence from nine crown fires suggests that horizontal roll vortices are a major mechanism in crown-fire spread. Post-burn aerial photography indicates that unburned tree-crown streets are common with crown fire. Investigation of the understory of these crown streets after two fires showed uncharred tree trunks along a center line. This evidence supports a hypothesis of vortex action causing strong downward motion of air along the streets. Additionally, photographs of two ongoing crown fires show apparent horizontal roll vortices. Discussion also includes laboratory and numerical studies in fluid dynamics that may apply to crown fires.

  12. N-cadherin regulates primary motor axons growth and branching during zebrafish embryonic development

    PubMed Central

    Brusés, Juan L

    2013-01-01

    N-cadherin is a classical type I cadherin that contributes to the formation of neural circuits by regulating growth cone migration and the formation of synaptic contacts. This study analyzed the role of N-cadherin in primary motor axons growth during development of the zebrafish (Danio rerio) embryo. After exiting the spinal cord, primary motor axons migrate ventrally through a common pathway and form the first neuromuscular junction with the muscle pioneer cells located at the horizontal myoseptum, which serves as a choice point for cell-type specific pathway selection. Analysis of N-cadherin mutants (cdh2hi3644Tg) and embryos injected with N-cadherin antisense morpholinos showed primary motor axons extending aberrant axonal branches at the choice point in ~40% of the somitic hemisegments, and an ~150% increase in the number of branches per axon length within the ventral myotome. Analysis of individual axons trajectories showed that the caudal (CaP) and rostral (RoP) motor neurons axons formed aberrant branches at the choice point which abnormally extended in the rostrocaudal axis and ventrally to the horizontal myoseptum. Expression of a dominant-interfering N-cadherin cytoplasmic domain in primary motor neurons caused some axons to abnormally stall at the horizontal myoseptum and to impair their migration into the ventral myotome. However, in N-cadherin depleted embryos the majority of primary motor axons innervated their appropriate myotomal territories indicating that N-cadherin regulates motor axon growth and branching without severely affecting the mechanisms that control axonal target selection. PMID:21452216

  13. Oscillatory modes in the flow between two horizontal corotating cylinders with a partially filled gap

    NASA Astrophysics Data System (ADS)

    Mutabazi, I.; Normand, C.; Peerhossaini, H.; Wesfreid, J. E.

    1989-01-01

    The linear stability of viscous flow between two rotating coaxial horizontal cylinders with a partially filled gap is investigated. It is shown that, for a range of values of the rotation ratio μ, the stability diagram for stationary modes consists of two separate curves connected by an oscillatory branch. For 0.26<μ<0.61 the critical point is on the oscillatory branch. Therefore it can be expected that, at onset, the instability will set in as an oscillatory mode. We have established the existence of codimension-2 points for two particular values of the rotation ratio μ=0.26 and 0.61, where the onset of instability for stationary as well as oscillatory modes occurs for the same value of the Taylor number.

  14. An extracellular adhesion molecule complex patterns dendritic branching and morphogenesis

    PubMed Central

    Dong, Xintong; Liu, Oliver W.; Howell, Audrey S.; Shen, Kang

    2014-01-01

    Summary Robust dendrite morphogenesis is a critical step in the development of reproducible neural circuits. However, little is known about the extracellular cues that pattern complex dendrite morphologies. In the model nematode C. elegans, the sensory neuron PVD establishes stereotypical, highly-branched dendrite morphology. Here, we report the identification of a tripartite ligand-receptor complex of membrane adhesion molecules that is both necessary and sufficient to instruct spatially restricted growth and branching of PVD dendrites. The ligand complex SAX-7/L1CAM and MNR-1 function at defined locations in the surrounding hypodermal tissue, while DMA-1 acts as the cognate receptor on PVD. Mutations in this complex lead to dramatic defects in the formation, stabilization, and organization of the dendritic arbor. Ectopic expression of SAX-7 and MNR-1 generates a predictable, unnaturally patterned dendritic tree in a DMA-1 dependent manner. Both in vivo and in vitro experiments indicate that all three molecules are needed for interaction. PMID:24120131

  15. Dynamics of a Bose-Einstein condensate in a horizontally vibrating shallow optical lattice

    SciTech Connect

    Valizadeh, A.; Jahanbani, Kh.; Kolahchi, M. R.

    2010-02-15

    We consider a solitonic solution of the self-attractive Bose-Einstein condensate in a one-dimensional external potential of a shallow optical lattice with large periodicity when the lattice is horizontally shaken. We investigate the dynamics of the bright soliton through the properties of the fixed points. The special type of bifurcation results in a simple criterion for the stability of the fixed points depending only on the amplitude of the shaking lattice. Because of the similarity of the equations with those of an ac-driven Josephson junction, some results may find applications in other branches of physics.

  16. Dynamics of a Bose-Einstein condensate in a horizontally vibrating shallow optical lattice

    NASA Astrophysics Data System (ADS)

    Valizadeh, A.; Jahanbani, Kh.; Kolahchi, M. R.

    2010-02-01

    We consider a solitonic solution of the self-attractive Bose-Einstein condensate in a one-dimensional external potential of a shallow optical lattice with large periodicity when the lattice is horizontally shaken. We investigate the dynamics of the bright soliton through the properties of the fixed points. The special type of bifurcation results in a simple criterion for the stability of the fixed points depending only on the amplitude of the shaking lattice. Because of the similarity of the equations with those of an ac-driven Josephson junction, some results may find applications in other branches of physics.

  17. Asymptotics of Simple Branching Populations

    NASA Astrophysics Data System (ADS)

    Huillet, Thierry; Kłopotowski, Andrzej; Porzio, Anna

    1995-09-01

    In this paper we study a simple deterministic tree structure: an initial individual generates a finite number of offspring, each of which has given integer valued lifetime, iterating the same procedure when dying. Three asymptotic distributions of this asynchronous deterministic branching procedure are considered: the generation distribution, the ability of individuals to generate offspring and the age distribution. Thermodynamic formalism is then developped to reveal the multifractal nature of the mass splitting associated to our process. On considère l'itération d'une structure déterministe arborescente selon laquelle un ancêtre engendre un nombre fini de descendants dont la durée de vie (à valeurs entières) est donnée. Dans un premier temps on s'intéresse aux trois distributions asymptotiques suivantes : répartition des générations, aptitude à engendrer des descendants et répartition selon l'âge. Ensuite nous développons le formalisme thermodynamique pour mettre en évidence le caractère multifractal de la scission d'une masse unitaire associée à cette arborescence.

  18. On an Integral with Two Branch Points

    ERIC Educational Resources Information Center

    de Oliveira, E. Capelas; Chiacchio, Ary O.

    2006-01-01

    The paper considers a class of real integrals performed by using a convenient integral in the complex plane. A complex integral containing a multi-valued function with two branch points is transformed into another integral containing a pole and a unique branch point. As a by-product we obtain a new class of integrals which can be calculated in a…

  19. An archetypal mechanism for branching organogenesis.

    PubMed

    Clément, Raphaël; Mauroy, Benjamin

    2014-02-01

    Branched structures are ubiquitous in nature, both in living and non-living systems. While the functional benefits of branching organogenesis are straightforward, the developmental mechanisms leading to the repeated branching of epithelia in surrounding mesoderm remain unclear. Both molecular and physical aspects of growth control seem to play a critical role in shape emergence and maintenance. On the molecular side, the existence of a gradient of growth-promoting ligand between epithelial tips and distal mesenchyme seems to be common to branched organs. On the physical side, the branching process seems to require a mechanism of real-time adaptation to local geometry, as suggested by the self-avoiding nature of branching events. In this paper, we investigate the outcomes of a general three-dimensional growth model, in which epithelial growth is implemented as a function of ligand income, while the mesenchyme is considered as a proliferating viscous medium. Our results suggest that the existence of a gradient of growth-promoting ligand between distal and proximal mesenchyme implies a growth instability of the epithelial sheet, resulting in spontaneous self-avoiding branching morphogenesis. While the general nature of the model prevents one from fitting the development of specific organs, it suggests that few ingredients are actually required to achieve branching organogenesis.

  20. Anaphora and Branching Direction in Japanese.

    ERIC Educational Resources Information Center

    O'Grady, William; And Others

    1994-01-01

    This paper constitutes a response to Lust and Mazuka's (1989) defense of the Principal Branching parameter and their critique of O'Grady, Suzuki-Wei, and Cho's (1986) experiment, which purported to show that even children learning left-branching languages exhibit a preference for forward patterns of anaphora. (Contains 16 references.) (JL)

  1. On an Integral with Two Branch Points

    ERIC Educational Resources Information Center

    de Oliveira, E. Capelas; Chiacchio, Ary O.

    2006-01-01

    The paper considers a class of real integrals performed by using a convenient integral in the complex plane. A complex integral containing a multi-valued function with two branch points is transformed into another integral containing a pole and a unique branch point. As a by-product we obtain a new class of integrals which can be calculated in a…

  2. Pacific Coastal Ecology Branch: Research Overview

    EPA Science Inventory

    The Pacific Coastal Ecology Branch, Newport, Oregon is part of the Western Ecology Division of the National Health and Environmental Effects Research Laboratory of the U.S. EPA. The Branch conducts research and provides scientific technical support to Headquarters and Regional O...

  3. Branching out Has So Much to Offer

    ERIC Educational Resources Information Center

    Murray, Joe

    2012-01-01

    In 1989 there were thirty ATM branches nationally. In January 2012 there were just twelve ATM branches with another three "proposed". How can that happen? How did it happen? Maybe the most pertinent question is: Why did it happen? There is no single answer to the last question, but perhaps it was something to do with the changes that…

  4. Phytochrome regulation of branching in Arabidopsis.

    PubMed

    Finlayson, Scott A; Krishnareddy, Srirama R; Kebrom, Tesfamichael H; Casal, Jorge J

    2010-04-01

    The red light:far-red light ratio perceived by phytochromes controls plastic traits of plant architecture, including branching. Despite the significance of branching for plant fitness and productivity, there is little quantitative and mechanistic information concerning phytochrome control of branching responses in Arabidopsis (Arabidopsis thaliana). Here, we show that in Arabidopsis, the negative effects of the phytochrome B mutation and of low red light:far-red light ratio on branching were largely due to reduced bud outgrowth capacity and an increased degree of correlative inhibition acting on the buds rather than due to a reduced number of leaves and buds available for branching. Phytochrome effects on the degree of correlative inhibition required functional BRANCHED1 (BRC1), BRC2, AXR1, MORE AXILLARY GROWTH2 (MAX2), and MAX4. The analysis of gene expression in selected buds indicated that BRC1 and BRC2 are part of different gene networks. The BRC1 network is linked to the growth capacity of specific buds, while the BRC2 network is associated with coordination of growth among branches. We conclude that the branching integrators BRC1 and BRC2 are necessary for responses to phytochrome, but they contribute differentially to these responses, likely acting through divergent pathways.

  5. Lung epithelial branching program antagonizes alveolar differentiation.

    PubMed

    Chang, Daniel R; Martinez Alanis, Denise; Miller, Rachel K; Ji, Hong; Akiyama, Haruhiko; McCrea, Pierre D; Chen, Jichao

    2013-11-05

    Mammalian organs, including the lung and kidney, often adopt a branched structure to achieve high efficiency and capacity of their physiological functions. Formation of a functional lung requires two developmental processes: branching morphogenesis, which builds a tree-like tubular network, and alveolar differentiation, which generates specialized epithelial cells for gas exchange. Much progress has been made to understand each of the two processes individually; however, it is not clear whether the two processes are coordinated and how they are deployed at the correct time and location. Here we show that an epithelial branching morphogenesis program antagonizes alveolar differentiation in the mouse lung. We find a negative correlation between branching morphogenesis and alveolar differentiation temporally, spatially, and evolutionarily. Gain-of-function experiments show that hyperactive small GTPase Kras expands the branching program and also suppresses molecular and cellular differentiation of alveolar cells. Loss-of-function experiments show that SRY-box containing gene 9 (Sox9) functions downstream of Fibroblast growth factor (Fgf)/Kras to promote branching and also suppresses premature initiation of alveolar differentiation. We thus propose that lung epithelial progenitors continuously balance between branching morphogenesis and alveolar differentiation, and such a balance is mediated by dual-function regulators, including Kras and Sox9. The resulting temporal delay of differentiation by the branching program may provide new insights to lung immaturity in preterm neonates and the increase in organ complexity during evolution.

  6. Suppression of branches in Eucalyptus trees.

    PubMed

    Senthalir, P; Sharanya, S; Paramathma, M

    2004-06-01

    The effect of neem oil, which acts as a suckericide in tobacco, on branch suppression in Eucalyptus tereticornis was assessed to help maximize stem biomass. Lateral branches of selected trees were pruned, and neem oil solutions at concentrations of either 80%, 40%, 20%, 10%, or 0% (untreated control) were applied to leaf axils of the pruned branches. Regeneration of branches was suppressed, and the magnitude of suppression was proportional to the concentration of neem oil. Compared to the control, the percentage reduction in branching at 80% neem oil was 41.6%. When regenerated branches were repruned and neem oil applied at either 100%, 80%, or 0% (control), the regenerating ability of these branches was severely repressed by 78% at 100% neem oil relative to the control. Apical shoots were also topped and treated at either 100% or 0% (control) neem oil to identify the principal suppressive component in neem oil. The principal component azadirachtin was tested at 375, 750, 1500, 3125, 6250, 12 500, 25 000, 50 000, and 100 000 ppm and 0 ppm as the control. Reduction in the coppicing shoot was as high as 85%. Azadirachtin was responsible for the suppression. By pruning the lateral branches with neem oil, wasteful consumption of photosynthates can be precluded and the stem biomass maximized.

  7. Existing branches correlatively inhibit further branching in Trifolium repens: possible mechanisms

    PubMed Central

    Thomas, R. G.; Hay, M. J. M.

    2011-01-01

    In Trifolium repens removal of any number of existing branches distal to a nodal root stimulates development of axillary buds further along the stem such that the complement of branches distal to a nodal root remains constant. This study aimed to assess possible mechanisms by which existing branches correlatively inhibit the outgrowth of axillary buds distal to them. Treatments were applied to basal branches to evaluate the roles of three postulated inhibitory mechanisms: (I) the transport of a phloem-mobile inhibitory feedback signal from branches into the main stem; (II) the polar flow of auxin from branches into the main stem acting to limit further branch development; or (III) the basal branches functioning as sinks for a net root-derived stimulatory signal (NRS). Results showed that transport of auxin, or of a non-auxin phloem-mobile signal, from basal branches did not influence regulation of correlative inhibition and were consistent with the possibility that the intra-plant distribution of NRS could be involved in the correlative inhibition of distal buds by basal branches. This study supports existing evidence that regulation of branching in T. repens is dominated by a root-derived stimulatory signal, initially distributed via the xylem, the characterization of which will progress the generic understanding of branching regulation. PMID:21071681

  8. Electroluminescence from completely horizontally oriented dye molecules

    NASA Astrophysics Data System (ADS)

    Komino, Takeshi; Sagara, Yuta; Tanaka, Hiroyuki; Oki, Yuji; Nakamura, Nozomi; Fujimoto, Hiroshi; Adachi, Chihaya

    2016-06-01

    A complete horizontal molecular orientation of a linear-shaped thermally activated delayed fluorescent guest emitter 2,6-bis(4-(10Hphenoxazin-10-yl)phenyl)benzo[1,2-d:5,4-d'] bis(oxazole) (cis-BOX2) was obtained in a glassy host matrix by vapor deposition. The orientational order of cis-BOX2 depended on the combination of deposition temperature and the type of host matrix. Complete horizontal orientation was obtained when a thin film with cis-BOX2 doped in a 4,4'-bis(N-carbazolyl)-1,1'-biphenyl (CBP) host matrix was fabricated at 200 K. The ultimate orientation of guest molecules originates from not only the kinetic relaxation but also the kinetic stability of the deposited guest molecules on the film surface during film growth. Utilizing the ultimate orientation, a highly efficient organic light-emitting diode with the external quantum efficiency of 33.4 ± 2.0% was realized. The thermal stability of the horizontal orientation of cis-BOX2 was governed by the glass transition temperature (Tg) of the CBP host matrix; the horizontal orientation was stable unless the film was annealed above Tg.

  9. A Case Study of Horizontal Teacher Evaluation.

    ERIC Educational Resources Information Center

    Johnson, Trav D.

    Horizontal teacher evaluation increases understanding of teaching through the critical examination of educational goals and classroom practices. This examination includes teachers' classroom observations of one another coupled with in-depth teacher conversations or dialogue about teaching aims and practices. A qualitative case study of a…

  10. Horizontal Axis Levitron--A Physics Demonstration

    ERIC Educational Resources Information Center

    Michaelis, Max M.

    2014-01-01

    After a brief history of the Levitron, the first horizontal axis Levitron is reported. Because it is easy to operate, it lends itself to educational physics experiments and analogies. Precession and nutation are visualized by reflecting the beam from a laser pointer off the "spignet". Precession is fundamental to nuclear magnetic…

  11. Detecting Highways of Horizontal Gene Transfer

    NASA Astrophysics Data System (ADS)

    Bansal, Mukul S.; Gogarten, J. Peter; Shamir, Ron

    In a horizontal gene transfer (HGT) event a gene is transferred between two species that do not share an ancestor-descendant relationship. Typically, no more than a few genes are horizontally transferred between any two species. However, several studies identified pairs of species between which many different genes were horizontally transferred. Such a pair is said to be linked by a highway of gene sharing. We present a method for inferring such highways. Our method is based on the fact that the evolutionary histories of horizontally transferred genes disagree with the corresponding species phylogeny. Specifically, given a set of gene trees and a trusted rooted species tree, each gene tree is first decomposed into its constituent quartet trees and the quartets that are inconsistent with the species tree are identified. Our method finds a pair of species such that a highway between them explains the largest (normalized) fraction of inconsistent quartets. For a problem on n species, our method requires O(n 4) time, which is optimal with respect to the quartets input size. An application of our method to a dataset of 1128 genes from 11 cyanobacterial species, as well as to simulated datasets, illustrates the efficacy of our method.

  12. Detecting highways of horizontal gene transfer.

    PubMed

    Bansal, Mukul S; Banay, Guy; Gogarten, J Peter; Shamir, Ron

    2011-09-01

    In a horizontal gene transfer (HGT) event, a gene is transferred between two species that do not have an ancestor-descendant relationship. Typically, no more than a few genes are horizontally transferred between any two species. However, several studies identified pairs of species between which many different genes were horizontally transferred. Such a pair is said to be linked by a highway of gene sharing. We present a method for inferring such highways. Our method is based on the fact that the evolutionary histories of horizontally transferred genes disagree with the corresponding species phylogeny. Specifically, given a set of gene trees and a trusted rooted species tree, each gene tree is first decomposed into its constituent quartet trees and the quartets that are inconsistent with the species tree are identified. Our method finds a pair of species such that a highway between them explains the largest (normalized) fraction of inconsistent quartets. For a problem on n species and m input quartet trees, we give an efficient O(m + n(2))-time algorithm for detecting highways, which is optimal with respect to the quartets input size. An application of our method to a dataset of 1128 genes from 11 cyanobacterial species, as well as to simulated datasets, illustrates the efficacy of our method.

  13. Cutting Down the Tall Poppies: Horizontal Violence.

    ERIC Educational Resources Information Center

    Funk, Carole

    Many women in educational leadership positions experience negative treatment from female teachers and female superintendents. This phenomenon is known as horizontal violence, "the curious behavior of members of oppressed groups who often lash out at their peers in response to oppression instead of attacking their oppressors." This paper explores…

  14. Horizontal Transfer of a Plant Transposon

    PubMed Central

    Diao, Xianmin; Freeling, Michael

    2006-01-01

    The majority of well-documented cases of horizontal transfer between higher eukaryotes involve the movement of transposable elements between animals. Surprisingly, although plant genomes often contain vast numbers of these mobile genetic elements, no evidence of horizontal transfer of a nuclear-encoded transposon between plant species has been detected to date. The most mutagenic known plant transposable element system is the Mutator system in maize. Mu-like elements (MULEs) are widespread among plants, and previous analysis has suggested that the distribution of various subgroups of MULEs is patchy, consistent with horizontal transfer. We have sequenced portions of MULE transposons from a number of species of the genus Setaria and compared them to each other and to publicly available databases. A subset of these elements is remarkably similar to a small family of MULEs in rice. A comparison of noncoding and synonymous sequences revealed that the observed similarity is not due to selection at the amino acid level. Given the amount of time separating Setaria and rice, the degree of similarity between these elements excludes the possibility of simple vertical transmission of this class of MULEs. This is the first well-documented example of horizontal transfer of any nuclear-encoded genes between higher plants. PMID:16336045

  15. Teaching Activities on Horizontal Nuclear Proliferation.

    ERIC Educational Resources Information Center

    Zola, John

    1990-01-01

    Provides learning activities concerning the horizontal proliferation of nuclear weapons. Includes step-by-step directions for four activities: (1) the life cycle of nuclear weapons; (2) nuclear nonproliferation: pros and cons; (3) the nuclear power/nuclear weapons connection; and (4) managing nuclear proliferation. (NL)

  16. Comparing cost and performance of horizontal wells

    SciTech Connect

    Pocovi, A.S.; Gustavino, L.L. ); Pozzo, A.; Musmarra, J.A. )

    1991-02-01

    Argentina's state oil company, YPF, was forced through technical and economic constraints to undertake a four-well pilot horizontal drilling program in its Neuquen fields. This article discusses techniques used, the results and costs, and compares them to costs incurred by the area's original vertical wells.

  17. Uniform head in horizontal and vertical wells

    USDA-ARS?s Scientific Manuscript database

    The steady-state head within a fully penetrating well may be estimated by evaluating the Thiem equation at the radius of the well. A method is presented here to extend results from the Thiem equation to horizontal wells and to partially penetrating wells. The particular model used in this investigat...

  18. Horizontal Axis Levitron--A Physics Demonstration

    ERIC Educational Resources Information Center

    Michaelis, Max M.

    2014-01-01

    After a brief history of the Levitron, the first horizontal axis Levitron is reported. Because it is easy to operate, it lends itself to educational physics experiments and analogies. Precession and nutation are visualized by reflecting the beam from a laser pointer off the "spignet". Precession is fundamental to nuclear magnetic…

  19. Wayne field: A horizontal drilling case study

    SciTech Connect

    Jennings, J.B.; Johnson, R.P.

    1996-06-01

    Beginning in the spring of 1994, studies of Wayne field located on the northeastern flank of the Williston Basin were initiated to determine the feasibility of using horizontal drilling to increase recoverable reserves in the field. The Wayne subinterval is one of several shoaling-upwards cycles within the Mission Canyon Formation of the Mississippian Madison Group. The reservoir pay averages 24% porosity, 100 millidarcys permeability, and 50% water saturation. Vertical wells, since field discovery in 1957, typically IP for 70 bopd and 20% water with a rapid decline within a few months to 10 bopd and 90% water. This type of well performance is characteristic of severe water coning for which horizontal development can help to minimize. In late 1994 and early 1995 the Ballantyne Hedges No.7H and GeoResources O. Fossum No.H1 were drilled. The wells recorded IP`s of 280 bopd/5 bwpd and 390 bopd/80 bwpd respectively. After six months of production both wells stabilized at approximately 110 bopd with a 35% water cut. Projections indicate that each horizontal well will recover 250,000 bbls of oil as compared to 115,000 bbls for an average vertical well and will do so in half the time. These early results provide a significant improvement over the vertical production and would seem to be reducing water coning. Three more horizontal wells are planned for the fourth quarter of 1995.

  20. Electroluminescence from completely horizontally oriented dye molecules

    SciTech Connect

    Komino, Takeshi; Sagara, Yuta; Tanaka, Hiroyuki; Oki, Yuji; Nakamura, Nozomi; Fujimoto, Hiroshi; and others

    2016-06-13

    A complete horizontal molecular orientation of a linear-shaped thermally activated delayed fluorescent guest emitter 2,6-bis(4-(10Hphenoxazin-10-yl)phenyl)benzo[1,2-d:5,4-d′] bis(oxazole) (cis-BOX2) was obtained in a glassy host matrix by vapor deposition. The orientational order of cis-BOX2 depended on the combination of deposition temperature and the type of host matrix. Complete horizontal orientation was obtained when a thin film with cis-BOX2 doped in a 4,4′-bis(N-carbazolyl)-1,1′-biphenyl (CBP) host matrix was fabricated at 200 K. The ultimate orientation of guest molecules originates from not only the kinetic relaxation but also the kinetic stability of the deposited guest molecules on the film surface during film growth. Utilizing the ultimate orientation, a highly efficient organic light-emitting diode with the external quantum efficiency of 33.4 ± 2.0% was realized. The thermal stability of the horizontal orientation of cis-BOX2 was governed by the glass transition temperature (T{sub g}) of the CBP host matrix; the horizontal orientation was stable unless the film was annealed above T{sub g}.

  1. Teaching Activities on Horizontal Nuclear Proliferation.

    ERIC Educational Resources Information Center

    Zola, John

    1990-01-01

    Provides learning activities concerning the horizontal proliferation of nuclear weapons. Includes step-by-step directions for four activities: (1) the life cycle of nuclear weapons; (2) nuclear nonproliferation: pros and cons; (3) the nuclear power/nuclear weapons connection; and (4) managing nuclear proliferation. (NL)

  2. Orthodontic extrusion of horizontally impacted mandibular molars

    PubMed Central

    Ma, Zhigui; Yang, Chi; Zhang, Shanyong; Xie, Qianyang; Shen, Yuqing; Shen, Pei

    2014-01-01

    Objective: To introduce and evaluate a novel approach in treating horizontally impacted mandibular second and third molars. Materials and methods: An orthodontic technique was applied for treatment of horizontally impacted mandibular second and third molars, which included a push-type spring for rotation first, and then a cantilever for extrusion. There were 8 mandibular third molars (M3s) and 2 second molars (M2s) in this study. Tooth mobility, extraction time, the inclination and parallelism of the impacted tooth, alveolar bone height of the adjacent tooth, and the relationship of impacted M3 and the inferior alveolar nerve (IAN) were evaluated. Results: Two horizontally impacted M2s could be upright in the arch and good occlusal relationships were obtained after treatment. All impacted M3s were successfully separated from the IAN, without any neurologic consequences. The average extraction time was 5 minutes. There was a significant change in the inclination and parallelism of the impacted tooth after treatment. A new bone apposition with the average height of 3.2 mm was noted distal to the adjacent tooth. Conclusions: This two-step orthodontic technique as presented here may be a safe and feasible alternative in management of severely horizontally impacted mandibular molars, which achieves a successful separation of M3s from the IAN and an excellent position for M2s. PMID:25419364

  3. Horizontal Gene Transfer and Ecosystem Function Dynamics.

    PubMed

    van de Guchte, Maarten

    2017-09-01

    Horizontal gene transfer can provide bacteria with new functions that confer an important competitive advantage, and is therefore likely to affect the dynamics of bacterial ecosystems. Two studies by Wolfe et al. and Bonham et al. prepare the way to study this hypothesis in a model ecosystem with reproducible properties. Copyright © 2017 Elsevier Ltd. All rights reserved.

  4. Stereoscopic watermarking by horizontal noise mean shifting

    NASA Astrophysics Data System (ADS)

    Lee, Ji-Won; Kim, Hee-Dong; Choi, Hak-Yeol; Choi, Sung-Hee; Lee, Heung-Kyu

    2012-03-01

    Depth-image-based rendering (DIBR) is a method to represent a stereoscopic content. The DIBR consists of a monoscopic center view and an associated per-pixel depth map. Using these two components and given depth condition from a user, the DIBR renders left and right views. The advantages of DIBR are numerous. The user can choose not only the monoscopic or stereoscopic view selectively, but also the depth condition what he prefers when he watches a stereoscopic content. However, in the view of copyright protection, since not only the center view but also each left or right view can be used as a monoscopic content when they are illegally distributed, the watermark signal which is embedded in the center view must have an ability to protect the respective three views. In this study, we solve this problem by exploiting the horizontal noise mean shifting (HNMS) technique. We exploit the fact that the objects in the view are shifted only to horizontal way when the center view renders to the left and right views. Using this fact, the proposed stereoscopic watermarking scheme moves the mean of horizontal noise histogram which is invariant to horizontal shifting, and we achieve good performance as shown in the experimental results.

  5. Horizontally separated 1-in-1 crossing insertions

    SciTech Connect

    Syphers, M.J.

    1985-10-01

    Previous to this workshop, realistic lattices have been developed for vertically separated l-in-l (e.g., D.E. Johnson, A.A. Garren) and 2-in-1 (e.g., S. Heifets) magnets as well as for horizontally separated 2-in-l magnets (e.g., SSC RDS). Bringing together the widely separated ({approximately}60-70 cm) beams in a reasonable length of tunnel and keeping the dispersion zero at the interaction point has been difficult in the vertical l-in-l case. Most designs have required spacial 2-in-1 quadrupoles near the interaction point where the beams are separated by 15 cm or less. It is not clear that such magnets, as dictated by some of these lattice designs, can easily be built. The purpose of this exercise is to provide a crossing insertion for a realistic lattice which involves horizontally separated l-in-l magnets. The following horizontal crossing insertions, which incorporate the dispersion suppressors and phase trombones into the major arcs, need no special 2-in-1 magnets near the interaction point. The dispersion at the IP created by the horizontal crossing can be cancelled by the dispersion suppressor and one set of triplets.

  6. Using branching simulations in treatment fidelity plans.

    PubMed

    Kovach, Christine R; Rababa, Mohammad

    2014-01-01

    The purpose of this article is to present a new approach to treatment fidelity using branching simulations. Branching simulations are case scenarios that require the user to generate a series of step-by-step decisions and actions. The user is given immediate feedback on the consequences of his or her decisions and actions. Branching simulations may be a particularly useful fidelity strategy for interventions that require clinical decision making represented in terms of a flow of critical thinking and action steps. Results of fidelity testing in the current study using branching simulations revealed that 15 (22%) of 67 interventionists scored below the study's a priori 80% criterion for full retraining and retesting. Thirty (45%) interventionists needed partial retraining in using specific components of the intervention. Potential threats to internal validity posed by inadequate or erroneous adherence to multicomponent intervention protocols can be decreased through treatment fidelity using branching simulations.

  7. Toward an understanding of fibrin branching structure

    NASA Astrophysics Data System (ADS)

    Fogelson, Aaron L.; Keener, James P.

    2010-05-01

    The blood clotting enzyme thrombin converts fibrinogen molecules into fibrin monomers which polymerize to form a fibrous three-dimensional gel. The concentration of thrombin affects the architecture of the resulting gel, in particular, a higher concentration of thrombin produces a gel with more branch points per unit volume and with shorter fiber segments between branch points. We propose a mechanism by which fibrin branching can occur and show that this mechanism can lead to dependence of the gel’s structure (at the time of gelation) on the rate at which monomer is supplied. A higher rate of monomer supply leads to a gel with a higher branch concentration and with shorter fiber segments between branch points. The origin of this dependence is explained.

  8. [Croatian Medical Association--Branch Istria].

    PubMed

    Labinac-Peteh, Loredana

    2014-01-01

    Istrian branch of Croatian Medical Association was established at the Assembly in 1948. at the General Hospital Pula. From the beginning, the seat of the branch is located in Pula. During the last time the work of branch went through different periods, but has never stopped its activity, leading to the basic postulates of professionality in addition with promotion of collegiality. Istrian branch od Croatian Medical Association now has 630 members, most of members are doctors of medicine, slightly less doctors of dental medicine. At the local level Istrian branch today is recognized as expert entity for the helth and as adviser is involved in work of Department of Health in the Istrian County.

  9. Root branching: mechanisms, robustness, and plasticity.

    PubMed

    Dastidar, Mouli Ghosh; Jouannet, Virginie; Maizel, Alexis

    2012-01-01

    Plants are sessile organisms that must efficiently exploit their habitat for water and nutrients. The degree of root branching impacts the efficiency of water uptake, acquisition of nutrients, and anchorage. The root system of plants is a dynamic structure whose architecture is determined by modulation of primary root growth and root branching. This plasticity relies on the continuous integration of environmental inputs and endogenous developmental programs controlling root branching. This review focuses on the cellular and molecular mechanisms involved in the regulation of lateral root distribution, initiation, and organogenesis with the main focus on the root system of Arabidopsis thaliana. We also examine the mechanisms linking environmental changes to the developmental pathways controlling root branching. Recent progress that emphasizes the parallels to the formation of root branches in other species is discussed.

  10. Toward an understanding of fibrin branching structure.

    PubMed

    Fogelson, Aaron L; Keener, James P

    2010-05-01

    The blood clotting enzyme thrombin converts fibrinogen molecules into fibrin monomers which polymerize to form a fibrous three-dimensional gel. The concentration of thrombin affects the architecture of the resulting gel, in particular, a higher concentration of thrombin produces a gel with more branch points per unit volume and with shorter fiber segments between branch points. We propose a mechanism by which fibrin branching can occur and show that this mechanism can lead to dependence of the gel's structure (at the time of gelation) on the rate at which monomer is supplied. A higher rate of monomer supply leads to a gel with a higher branch concentration and with shorter fiber segments between branch points. The origin of this dependence is explained.

  11. The devil in the details: interactions between the branch-length prior and likelihood model affect node support and branch lengths in the phylogeny of the Psoraceae.

    PubMed

    Ekman, Stefan; Blaalid, Rakel

    2011-07-01

    In popular use of Bayesian phylogenetics, a default branch-length prior is almost universally applied without knowing how a different prior would have affected the outcome. We performed Bayesian and maximum likelihood (ML) inference of phylogeny based on empirical nucleotide sequence data from a family of lichenized ascomycetes, the Psoraceae, the morphological delimitation of which has been controversial. We specifically assessed the influence of the combination of Bayesian branch-length prior and likelihood model on the properties of the Markov chain Monte Carlo tree sample, including node support, branch lengths, and taxon stability. Data included two regions of the mitochondrial ribosomal RNA gene, the internal transcribed spacer region of the nuclear ribosomal RNA gene, and the protein-coding largest subunit of RNA polymerase II. Data partitioning was performed using Bayes' factors, whereas the best-fitting model of each partition was selected using the Bayesian information criterion (BIC). Given the data and model, short Bayesian branch-length priors generate higher numbers of strongly supported nodes as well as short and topologically similar trees sampled from parts of tree space that are largely unexplored by the ML bootstrap. Long branch-length priors generate fewer strongly supported nodes and longer and more dissimilar trees that are sampled mostly from inside the range of tree space sampled by the ML bootstrap. Priors near the ML distribution of branch lengths generate the best marginal likelihood and the highest frequency of "rogue" (unstable) taxa. The branch-length prior was shown to interact with the likelihood model. Trees inferred under complex partitioned models are more affected by the stretching effect of the branch-length prior. Fewer nodes are strongly supported under a complex model given the same branch-length prior. Irrespective of model, internal branches make up a larger proportion of total tree length under the shortest branch

  12. Short branches lead to systematic artifacts when BLAST searches are used as surrogate for phylogenetic reconstruction.

    PubMed

    Dick, Amanda A; Harlow, Timothy J; Gogarten, J Peter

    2017-02-01

    Long Branch Attraction (LBA) is a well-known artifact in phylogenetic reconstruction when dealing with branch length heterogeneity. Here we show another phenomenon, Short Branch Attraction (SBA), which occurs when BLAST searches, a phenetic analysis, are used as a surrogate method for phylogenetic analysis. This error also results from branch length heterogeneity, but this time it is the short branches that are attracting. The SBA artifact is reciprocal and can be returned 100% of the time when multiple branches differ in length by a factor of more than two. SBA is an intended feature of BLAST searches, but becomes an issue, when top scoring BLAST hit analyses are used to infer Horizontal Gene Transfers (HGTs), assign taxonomic category with environmental sequence data in phylotyping, or gather homologous sequences for building gene families. SBA can lead researchers to believe that there has been a HGT event when only vertical descent has occurred, cause slowly evolving taxa to be over-represented and quickly evolving taxa to be under-represented in phylotyping, or systematically exclude quickly evolving taxa from analyses. SBA also contributes to the changing results of top scoring BLAST hit analyses as the database grows, because more slowly evolving taxa, or short branches, are added over time, introducing more potential for SBA. SBA can be detected by examining reciprocal best BLAST hits among a larger group of taxa, including the known closest phylogenetic neighbors. Therefore, one should look for this phenomenon when conducting best BLAST hit analyses as a surrogate method to identify HGTs, in phylotyping, or when using BLAST to gather homologous sequences.

  13. Node-specific branching and heterochronic changes underlie population-level differences in Mimulus guttatus (Phrymaceae) shoot architecture.

    PubMed

    Baker, Robert L; Diggle, Pamela K

    2011-12-01

    Shoot architecture is a fundamentally developmental aspect of plant biology with implications for plant form, function, reproduction, and life history evolution. Mimulus guttatus is morphologically diverse and becoming a model for evolutionary biology. Shoot architecture, however, has never been studied from a developmental perspective in M. guttatus. We examined the development of branches and flowers in plants from two locally adapted populations of M. guttatus with contrasting flowering times, life histories, and branch numbers. We planted second-generation seed in growth chambers to control for maternal and environmental effects. Most branches occurred at nodes one and two of the main axis. Onset of branching occurred earlier and at a greater frequency in perennials than in annuals. In perennials, almost all flowers occurred at the fifth or more distal nodes. In annuals, most flowers occurred at the third and more distal nodes. Accessory axillary meristems and higher-order branching did not influence shoot architecture. We found no evidence for trade-offs between flowers and branches because axillary meristem number was not limiting: a large number of meristems remained quiescent. If, however, quiescence is a component of meristem allocation strategy, then meristems may be limited despite presence of quiescent meristems. At the two basalmost nodes, branch number was determined by mechanisms governing either meristem initiation or outgrowth, rather than flowering vs. branching. At the third and more distal nodes, heterochronic processes contributed to flowering time and branch number differences between populations.

  14. Silver nanocombs and branched nanowires formation in aqueous binary surfactants solution

    NASA Astrophysics Data System (ADS)

    Umar, Akrajas Ali; Oyama, Munetaka; Salleh, Muhamad Mat; Majlis, Burhanuddin Yeop

    2012-07-01

    Branched nanocrystals, particularly nanocombs, are a unique 1D-morphology that is normally formed in polytypic materials, such as ZnO, and rarely occurs in the highly symmetric fcc metallic system. Here, we report the chemical synthesis of nanocombs of a highly symmetrical fcc silver system that is realized by reducing the silver ions in the presence of a mixture of silver nanoseeds and binary surfactants, namely cetyltrimethylammonium bromide (CTAB) and hexamethylenetetramine (hexamine or HMT), under an alkaline condition. The silver nanocombs feature a high-degree branching orientation toward a single direction with good branch-to-branch spacing. The nanocombs formation was very sensitive to the concentrations of CTAB, HMT and NaOH in the reaction in which, in a typical case, nanocombs or curly nanowires were produced by controlling the concentration of these chemicals in the reaction. We hypothesized that the branching could be due to: (i) a kind of polytypism in such highly symmetrical fcc nanocrystals that was enabled by a selective surfactant adhesion process on the growing crystalline plane and (ii) lattice defects or twinning induced growth redirection in the nanocrystals. The silver nanocombs might generate a peculiar characteristic that is probably superior to those produced by other morphologies, such as nanorods, nanowires, and so on. Thus, it should find extensive use in the currently existing applications.

  15. Self-generated morphology in lagoon reefs.

    PubMed

    Blakeway, David; Hamblin, Michael G

    2015-01-01

    The three-dimensional form of a coral reef develops through interactions and feedbacks between its constituent organisms and their environment. Reef morphology therefore contains a potential wealth of ecological information, accessible if the relationships between morphology and ecology can be decoded. Traditionally, reef morphology has been attributed to external controls such as substrate topography or hydrodynamic influences. Little is known about inherent reef morphology in the absence of external control. Here we use reef growth simulations, based on observations in the cellular reefs of Western Australia's Houtman Abrolhos Islands, to show that reef morphology is fundamentally determined by the mechanical behaviour of the reef-building organisms themselves-specifically their tendency to either remain in place or to collapse. Reef-building organisms that tend to remain in place, such as massive and encrusting corals or coralline algae, produce nodular reefs, whereas those that tend to collapse, such as branching Acropora, produce cellular reefs. The purest reef growth forms arise in sheltered lagoons dominated by a single type of reef builder, as in the branching Acropora-dominated lagoons of the Abrolhos. In these situations reef morphology can be considered a phenotype of the predominant reef building organism. The capacity to infer coral type from reef morphology can potentially be used to identify and map specific coral habitat in remotely sensed images. More generally, identifying ecological mechanisms underlying other examples of self-generated reef morphology can potentially improve our understanding of present-day reef ecology, because any ecological process capable of shaping a reef will almost invariably be an important process in real time on the living reef.

  16. Self-generated morphology in lagoon reefs

    PubMed Central

    Hamblin, Michael G.

    2015-01-01

    The three-dimensional form of a coral reef develops through interactions and feedbacks between its constituent organisms and their environment. Reef morphology therefore contains a potential wealth of ecological information, accessible if the relationships between morphology and ecology can be decoded. Traditionally, reef morphology has been attributed to external controls such as substrate topography or hydrodynamic influences. Little is known about inherent reef morphology in the absence of external control. Here we use reef growth simulations, based on observations in the cellular reefs of Western Australia’s Houtman Abrolhos Islands, to show that reef morphology is fundamentally determined by the mechanical behaviour of the reef-building organisms themselves—specifically their tendency to either remain in place or to collapse. Reef-building organisms that tend to remain in place, such as massive and encrusting corals or coralline algae, produce nodular reefs, whereas those that tend to collapse, such as branching Acropora, produce cellular reefs. The purest reef growth forms arise in sheltered lagoons dominated by a single type of reef builder, as in the branching Acropora-dominated lagoons of the Abrolhos. In these situations reef morphology can be considered a phenotype of the predominant reef building organism. The capacity to infer coral type from reef morphology can potentially be used to identify and map specific coral habitat in remotely sensed images. More generally, identifying ecological mechanisms underlying other examples of self-generated reef morphology can potentially improve our understanding of present-day reef ecology, because any ecological process capable of shaping a reef will almost invariably be an important process in real time on the living reef. PMID:26175962

  17. Disruptive selection as a driver of evolutionary branching and caste evolution in social insects.

    PubMed

    Planqué, R; Powell, S; Franks, N R; van den Berg, J B

    2016-11-01

    Theory suggests that evolutionary branching via disruptive selection may be a relatively common and powerful force driving phenotypic divergence. Here, we extend this theory to social insects, which have novel social axes of phenotypic diversification. Our model, built around turtle ant (Cephalotes) biology, is used to explore whether disruptive selection can drive the evolutionary branching of divergent colony phenotypes that include a novel soldier caste. Soldier evolution is a recurrent theme in social insect diversification that is exemplified in the turtle ants. We show that phenotypic mutants can gain competitive advantages that induce disruptive selection and subsequent branching. A soldier caste does not generally appear before branching, but can evolve from subsequent competition. The soldier caste then evolves in association with specialized resource preferences that maximize defensive performance. Overall, our model indicates that resource specialization may occur in the absence of morphological specialization, but that when morphological specialization evolves, it is always in association with resource specialization. This evolutionary coupling of ecological and morphological specialization is consistent with recent empirical evidence, but contrary to predictions of classical caste theory. Our model provides a new theoretical understanding of the ecology of caste evolution that explicitly considers the process of adaptive phenotypic divergence and diversification.

  18. Articulating Support for Horizontal Resistive Exercise

    NASA Technical Reports Server (NTRS)

    Gundo, Daniel; Schaffner, Grant; Bentley, Jason; Loehr, James A.

    2005-01-01

    A versatile mechanical device provides support for a user engaged in any of a variety of resistive exercises in a substantially horizontal orientation. The unique features and versatility of the device promise to be useful in bedrest studies, rehabilitation, and specialized strength training. The device affords a capability for selectively loading and unloading of portions of the user s body through its support mechanisms, so that specific parts of the body can be trained with little or no effect on other parts that may be disabled or in the process of recovery from injury. Thus, the device is ideal for rehabilitation exercise programs prescribed by physicians and physical therapists. The capability for selective loading and support also offers potential benefits to strength and conditioning trainers and athletes who wish to selectively strengthen selected parts. The principal innovative aspect of the device is that it supports the subject s weight while enabling the subject, lying substantially horizontally, to perform an exercise that closely approximates a full standing squat. The device includes mechanisms that support the subject in such a way that the hips are free to translate both horizontally and vertically and are free to rotate about the line connecting the hips. At the same time, the shoulders are free to translate horizontally while the upper back is free to rotate about the line connecting the shoulders. Among the mechanisms for hip motion and support is a counterbalance that offsets the weight of the subject as the subject s pelvis translates horizontally and vertically and rotates the pelvis about the line connecting the hips. The counterbalance is connected to a pelvic support system that allows these pelvic movements. The subject is also supported at the shoulder by a mechanism that can tilt to provide continuous support of the upper back while allowing the rotation required for arching the back as the pelvis is displaced. The shoulder support

  19. Mechanisms of Side Branching and Tip Splitting in a Model of Branching Morphogenesis

    PubMed Central

    Guo, Yina; Sun, Mingzhu; Garfinkel, Alan; Zhao, Xin

    2014-01-01

    Recent experimental work in lung morphogenesis has described an elegant pattern of branching phenomena. Two primary forms of branching have been identified: side branching and tip splitting. In our previous study of lung branching morphogenesis, we used a 4 variable partial differential equation (PDE), due to Meinhardt, as our mathematical model to describe the reaction and diffusion of morphogens creating those branched patterns. By altering key parameters in the model, we were able to reproduce all the branching styles and the switch between branching modes. Here, we attempt to explain the branching phenomena described above, as growing out of two fundamental instabilities, one in the longitudinal (growth) direction and the other in the transverse direction. We begin by decoupling the original branching process into two semi-independent sub-processes, 1) a classic activator/inhibitor system along the growing stalk, and 2) the spatial growth of the stalk. We then reduced the full branching model into an activator/inhibitor model that embeds growth of the stalk as a controllable parameter, to explore the mechanisms that determine different branching patterns. We found that, in this model, 1) side branching results from a pattern-formation instability of the activator/inhibitor subsystem in the longitudinal direction. This instability is far from equilibrium, requiring a large inhomogeneity in the initial conditions. It successively creates periodic activator peaks along the growing stalk, each of which later on migrates out and forms a side branch; 2) tip splitting is due to a Turing-style instability along the transversal direction, that creates the spatial splitting of the activator peak into 2 simultaneously-formed peaks at the growing tip, the occurrence of which requires the widening of the growing stalk. Tip splitting is abolished when transversal stalk widening is prevented; 3) when both instabilities are satisfied, tip bifurcation occurs together with side

  20. Branch architecture, light interception and crown development in saplings of a plagiotropically branching tropical tree, Polyalthia jenkinsii (Annonaceae).

    PubMed

    Osada, Noriyuki; Takeda, Hiroshi

    2003-01-01

    To investigate crown development patterns, branch architecture, branch-level light interception, and leaf and branch dynamics were studied in saplings of a plagiotropically branching tree species, Polyalthia jenkinsii Hk. f. & Thoms. (Annonaceae) in a Malaysian rain forest. Lengths of branches and parts of the branches lacking leaves ('bare' branches) were smaller in upper branches than in lower branches within crowns, whereas lengths of 'leafy' parts and the number of leaves per branch were larger in intermediate than in upper and lower branches. Maximum diffuse light absorption (DLA) of individual leaves was not related to sapling height or branch position within crowns, whereas minimum DLA was lower in tall saplings. Accordingly, branch-level light interception was higher in intermediate than in upper and lower branches. The leaf production rate was higher and leaf loss rate was smaller in upper than in intermediate and lower branches. Moreover, the branch production rate of new first-order branches was larger in the upper crowns. Thus, leaf and branch dynamics do not correspond to branch-level light interception in the different canopy zones. As a result of architectural constraints, branches at different vertical positions experience predictable light microenvironments in plagiotropic species. Accordingly, this pattern of carbon allocation among branches might be particularly important for growth and crown development in plagiotropic species.

  1. Disassortativity of random critical branching trees.

    PubMed

    Kim, J S; Kahng, B; Kim, D

    2009-06-01

    Random critical branching trees (CBTs) are generated by the multiplicative branching process, where the branching number is determined stochastically, independent of the degree of their ancestor. Here we show analytically that despite this stochastic independence, there exists the degree-degree correlation (DDC) in the CBT and it is disassortative. Moreover, the skeletons of fractal networks, the maximum spanning trees formed by the edge betweenness centrality, behave similarly to the CBT in the DDC. This analytic solution and observation support the argument that the fractal scaling in complex networks originates from the disassortativity in the DDC.

  2. Elf cites 5 advantages of horizontal drilling

    SciTech Connect

    Not Available

    1984-06-01

    ELF Aquitaine used horizontal drilling during a pilot test program to bring commercial production from its Rospo Mare oil discovery in the Adriatic, which would have been a costly disappointment if drilled by a conventional vertical well bore. Rospo Mare is a large reservoir containing a top column of highly viscous crude underlain by a water column. The company felt that a well bore that penetrated the reservoir vertically would bring early flooding of the oil column and yield only water. By penetrating the reservoir with a horizontal well drilled high in the oil column, the well successfully produced on numerous tests from Oct. 1982 until the end of the test program in 1983. Production was termed excellent, with productivity during tests reportedly reaching ca 15 times the rate produced from nearby vertical wells. However, ELF said the results usually average ca 5 times the usual rate of vertical wells.

  3. Stability of vertical and horizontal axis Levitrons

    NASA Astrophysics Data System (ADS)

    Michaelis, M. M.; Taylor, D. B.

    2015-11-01

    The stability of the new horizontal axis Levitron3 is compared with that of the vertical axis device. The rotation frequency ranges are similar because they are determined by the same precessional micro-trap, for which some theory is given. But the macro-trap of the horizontal axis system gives it far greater mechanical stability. Field-line studies allow this to be more easily visualized. The greater stability allows for educational experiments which could only be contemplated with the old Levitron: driven precession and nutation and motion along the field lines. These experiments illustrate some very fundamental space dynamics and several other topics. The enhanced stability may also lead to electro-mechanical applications.

  4. Kinematics of horizontal and vertical caterpillar crawling.

    PubMed

    van Griethuijsen, Linnea I; Trimmer, Barry A

    2009-05-01

    Unlike horizontal crawling, vertical crawling involves two counteracting forces: torque rotating the body around its center of mass and gravity resisting forward movement. The influence of these forces on kinematics has been examined in the soft-bodied larval stage of Manduca sexta. We found that crawling and climbing are accomplished using the same movements, with both segment timing and proleg lift indistinguishable in horizontal and vertical locomotion. Minor differences were detected in stride length and in the delay between crawls, which led to a lower crawling speed in the vertical orientation. Although these differences were statistically significant, they were much smaller than the variation in kinematic parameters between animals. The ability of Manduca to crawl and climb using the same movements is best explained by Manduca's relatively small size, slow speed and strong, controlled, passive grip made possible by its proleg/crochets.

  5. Active vibration suppression of helicopter horizontal stabilizers

    NASA Astrophysics Data System (ADS)

    Cinquemani, Simone; Cazzulani, Gabriele; Resta, Ferruccio

    2017-04-01

    Helicopters are among the most complex machines ever made. While ensuring high performance from the aeronautical point of view, they are not very comfortable due to vibration mainly created by the main rotor and by the interaction with the surrounding air. One of the most solicited structural elements of the vehicle are the horizontal stabilizers. These elements are particularly stressed because of their composite structure which, while guaranteeing lightness and strength, is characterized by a low damping. This work makes a preliminary analysis on the dynamics of the structure and proposes different solutions to actively suppress vibrations. Among them, the best in terms of the relationship between performance and weight / complexity of the system is that based on inertial actuators mounted on the inside of the horizontal stabilizers. The work addresses the issue of the design of the device and its use in the stabilizer from both the numerical and the experimental points of view.

  6. Sand removal from heavy oil horizontal wells

    SciTech Connect

    Dedora, G.

    1995-12-31

    Oil production from heavy oil horizontal wells continues to be hindered by sand production and bridging resulting in total or partial shut-off of the wellbore. These bridges cannot be removed using circulation due to the low pressure of most heavy oil reservoirs. Removing these bridges using vertical or slanted well cleanout technology has proven to be difficult and costly, particularly if the production lateral is greater than 300-400 metres. With most laterals stretching beyond 1000 metres, producers and service companies have been in search of more effective alternatives. This challenge brought forth several new concepts in horizontal well cleanout technology involving artificial lift systems capable of continuous advancement into the lateral while producing high concentrations of sand. During the cleanout procedures, wellbore pressure is controlled thus avoiding high volumes of lost workover fluids. This presentation discusses these cleanout techniques as well as the positive and negative features of each.

  7. Horizontal Bilayer for Electrical and Optical Recordings

    PubMed Central

    Bartsch, Philipp; Walter, Claudius; Selenschik, Philipp; Honigmann, Alf; Wagner, Richard

    2012-01-01

    Artificial bilayer containing reconstituted ion channels, transporters and pumps serve as a well-defined model system for electrophysiological investigations of membrane protein structure–function relationship. Appropriately constructed microchips containing horizontally oriented bilayers with easy solution access to both sides provide, in addition, the possibility to investigate these model bilayer membranes and the membrane proteins therein with high resolution fluorescence techniques up to the single-molecule level. Here, we describe a bilayer microchip system in which long-term stable horizontal free-standing and hydrogel-supported bilayers can be formed and demonstrate its prospects particularly for single-molecule fluorescence spectroscopy and high resolution fluorescence microscopy in probing the physicochemical properties like phase behavior of the bilayer-forming lipids, as well as in functional studies of membrane proteins.

  8. Horizontal modular dry irradiated fuel storage system

    DOEpatents

    Fischer, Larry E.; McInnes, Ian D.; Massey, John V.

    1988-01-01

    A horizontal, modular, dry, irradiated fuel storage system (10) includes a thin-walled canister (12) for containing irradiated fuel assemblies (20), which canister (12) can be positioned in a transfer cask (14) and transported in a horizontal manner from a fuel storage pool (18), to an intermediate-term storage facility. The storage system (10) includes a plurality of dry storage modules (26) which accept the canister (12) from the transfer cask (14) and provide for appropriate shielding about the canister (12). Each module (26) also provides for air cooling of the canister (12) to remove the decay heat of the irradiated fuel assemblies (20). The modules (26) can be interlocked so that each module (26) gains additional shielding from the next adjacent module (26). Hydraulic rams (30) are provided for inserting and removing the canisters (12) from the modules (26).

  9. Film condensation in a horizontal rectangular duct

    NASA Technical Reports Server (NTRS)

    Lu, Qing; Suryanarayana, N. V.

    1993-01-01

    Condensation heat transfer in a horizontal rectangular duct was experimentally and analytically investigated. To prevent the dripping of condensate on the film, the experiment was conducted inside a horizontal rectangular duct with vapor condensing only on the bottom cooled plate of the duct. R-113 and FC-72 (Fluorinert Electronic Fluid developed by the 3M Company) were used as the condensing fluids. The experimental program included measurements of film thickness, local and average heat transfer coefficients, wave length, wave speed, and a study of wave initiation. The measured film thickness was used to obtain the local heat transfer coefficient. The wave initiation was studied both with condensation and with an adiabatic air-liquid flow. The test sections used in both experiments were identical.

  10. Rational growth of branched nanowire heterostructures with synthetically encoded properties and function

    PubMed Central

    Jiang, Xiaocheng; Tian, Bozhi; Xiang, Jie; Qian, Fang; Zheng, Gengfeng; Wang, Hongtao; Mai, Liqiang; Lieber, Charles M.

    2011-01-01

    Branched nanostructures represent unique, 3D building blocks for the “bottom-up” paradigm of nanoscale science and technology. Here, we report a rational, multistep approach toward the general synthesis of 3D branched nanowire (NW) heterostructures. Single-crystalline semiconductor, including groups IV, III–V, and II–VI, and metal branches have been selectively grown on core or core/shell NW backbones, with the composition, morphology, and doping of core (core/shell) NWs and branch NWs well controlled during synthesis. Measurements made on the different composition branched NW structures demonstrate encoding of functional p-type/n-type diodes and light-emitting diodes (LEDs) as well as field effect transistors with device function localized at the branch/backbone NW junctions. In addition, multibranch/backbone NW structures were synthesized and used to demonstrate capability to create addressable nanoscale LED arrays, logic circuits, and biological sensors. Our work demonstrates a previously undescribed level of structural and functional complexity in NW materials, and more generally, highlights the potential of bottom-up synthesis to yield increasingly complex functional systems in the future. PMID:21730174

  11. GLABROUS INFLORESCENCE STEMS (GIS) is required for trichome branching through gibberellic acid signaling in Arabidopsis.

    PubMed

    An, Lijun; Zhou, Zhongjing; Su, Sha; Yan, An; Gan, Yinbo

    2012-02-01

    Cell differentiation generally corresponds to the cell cycle, typically forming a non-dividing cell with a unique differentiated morphology, and Arabidopsis trichome is an excellent model system to study all aspects of cell differentiation. Although gibberellic acid is reported to be involved in trichome branching in Arabidopsis, the mechanism for such signaling is unclear. Here, we demonstrated that GLABROUS INFLORESCENCE STEMS (GIS) is required for the control of trichome branching through gibberellic acid signaling. The phenotypes of a loss-of-function gis mutant and an overexpressor showed that GIS acted as a repressor to control trichome branching. Our results also show that GIS is not required for cell endoreduplication, and our molecular and genetic study results have shown that GIS functions downstream of the key regulator of trichome branching, STICHEL (STI), to control trichome branching through the endoreduplication-independent pathway. Furthermore, our results also suggest that GIS controls trichome branching in Arabidopsis through two different pathways and acts either upstream or downstream of the negative regulator of gibbellic acid signaling SPINDLY (SPY).

  12. Controlled synthesis of hyper-branched inorganic nanocrystals withrich three-dimensional structures

    SciTech Connect

    Kanaras, Antonios G.; Sonnichsen, Carsten; Liu, Haitao; Alivisatos, A. Paul

    2005-07-27

    Studies of crystal growth kinetics are tightly integrated with advances in the creation of new nanoscale inorganic building blocks and their functional assemblies 1-11. Recent examples include the development of semiconductor nanorods which have potential uses in solar cells 12-17, and the discovery of a light driven process to create noble metal particles with sharp corners that can be used in plasmonics 18,19. In the course of studying basic crystal growth kinetics we developed a process for preparing branched semiconductor nanocrystals such as tetrapods and inorganic dendrimers of precisely controlled generation 20,21. Here we report the discovery of a crystal growth kinetics regime in which a new class of hyper-branched nanocrystals are formed. The shapes range from 'thorny balls', to tree-like ramified structures, to delicate 'spider net'-like particles. These intricate shapes depend crucially on a delicate balance of branching and extension. The multitudes of resulting shapes recall the diverse shapes of snowflakes 22.The three dimensional nature of the branch points here, however, lead to even more complex arrangements than the two dimensionally branched structures observed in ice. These hyper-branched particles not only extend the available three-dimensional shapes in nanoparticle synthesis ,but also provide a tool to study growth kinetics by carefully observing and modeling particle morphology.

  13. Spin stabilized magnetic levitation of horizontal rotors.

    SciTech Connect

    Romero, Louis Anthony

    2004-10-01

    In this paper we present an analysis of a new configuration for achieving spin stabilized magnetic levitation. In the classical configuration, the rotor spins about a vertical axis; and the spin stabilizes the lateral instability of the top in the magnetic field. In this new configuration the rotor spins about a horizontal axis; and the spin stabilizes the axial instability of the top in the magnetic field.

  14. Horizontal-parallax-only electronic holography

    NASA Astrophysics Data System (ADS)

    Poon, T.-C.; Akin, T.; Indebetouw, G.; Kim, T.

    2005-04-01

    The principle of optical scanning holography (OSH) is proposed to acquire horizontal-parallax-only (HPO) holographic information electronically. We first briefly summarize the results of OSH and then discuss how HPO-electronic holographic information can be acquired using OSH. Finally we provide simulations to illustrate and clarify the proposed idea. Although many ideas of HPO-holography have been proposed and studied, to the best of our knowledge, this is the first proposed electronic technique to acquire HPO-holographic information.

  15. Horizontal drilling in shallow, geologically complex reservoirs

    SciTech Connect

    Venable, S.D.

    1992-01-01

    The objective of this project is to test the concept that multiple hydraulic fracturing from a directionally-drilled horizontal well, using the medium radius build rate method, can increase gas production sufficiently to justify economic viability over conventional stimulated vertical wells. The test well is located in Yuma County, Colorado, in a favorable area of established production to avoid exploration risks. This report presents: background information; project description which covers location selection/geologic considerations; and preliminary work plan. (AT)

  16. Horizontal drilling in shallow, geologically complex reservoirs

    SciTech Connect

    Venable, S.D.

    1992-10-01

    The objective of this project is to test the concept that multiple hydraulic fracturing from a directionally-drilled horizontal well, using the medium radius build rate method, can increase gas production sufficiently to justify economic viability over conventional stimulated vertical wells. The test well is located in Yuma County, Colorado, in a favorable area of established production to avoid exploration risks. This report presents: background information; project description which covers location selection/geologic considerations; and preliminary work plan. (AT)

  17. A study of horizontal-wellbore failure

    SciTech Connect

    Hsiao, C. )

    1988-11-01

    A theoretical model of horizontal-wellbore failure has been developed based on maximum-normal-stress theory (for tensile fracturing) and Drucker-Prager failure theory (for compressive failure) under openhole conditions. This model may be used to help determine the permissible borehole operating-pressure range, providing a convenient scheme for selecting borehole pressure to minimize the risk of borehole failure during drilling and production.

  18. Natural Convection Above A Horizontal Heat Source

    DTIC Science & Technology

    1993-03-01

    surface was a thermochromic liquid crystal (TLC) sheet. Used to ensure a smooth flat surface, the sheet also provided a visualization of the temperature...a flat horizontal heated surface surrounded by an unheated area. This can contribute significantly to studies in liquid immersion cooling...Gebhart, B., "The Transition of Plane Plumes," Int. J. Heat Mass Transfer, v.18., pp. 513-526, 1975. 13. Gaiser, A.O., "Natural Convection Liquid

  19. Management of horizontally impacted dilacerated lateral incisor

    PubMed Central

    Katta, Anil Kumar; Peddu, Revathi; Vannala, Venkataramana; Dasari, Vaishnavi

    2015-01-01

    Impaction of maxillary lateral incisor with odontome and retained deciduous tooth is not often seen in regular dental practice. Impaction of anterior teeth cause generalized spacing which affects the esthetics of the face. Here we report a case of an 18-year-old patient with horizontally impacted dilacerated lateral incisor, which was bought into occlusion with the help of orthodontic tooth movement within a span of 18 months. PMID:26538954

  20. Search for horizontal bosons at the SSC

    SciTech Connect

    Albright, C.H.; Deshpande, N.G.; Gunion, J.F.; Haber, H.E.

    1984-01-01

    The production process anti p p ..-->.. l/sup -/l'/sup +/ + X, where the leptons belong to two different generations and X refers to spectator jets, provides a clear signature for horizontal (generation-changing) bosons when the leptons are emitted nearly back-to-back and p/sub T//sup miss/ = 0. Cross sections and p/sub T/ distributions for each lepton are presented, and discovery limits on M/sub H/ are extracted for several different channels.

  1. Productivity and Injectivity of Horizontal Wells

    SciTech Connect

    Arbabi, Sepehr; Aziz, Khalid; Hewett, Thomas A.; Smith, Marilyn

    1999-11-08

    The work on modeling hydraulically fractured horizontal wells has moved forward. A literature review on the subject was done and some of the existing models have been coded and applied to example problems for evaluation purposes. Previous work on the elects of heterogeneities on the performance of horizontal wells was continued by conducting a sensitivity study on various parameters that were kept constant in the earlier study. For example, we have studied the elect of gas cap and aquifer size, well location, fluid viscosity, etc. The experimental work on using horizontal wells as injectors and producers in a gas injection gravity drainage process continued. New and repeat experiments were conducted. Work on streamline grids was advanced by considering example problems with highly distorted grids which cannot be directly used for flow simulation. Grid smoothing and domain mapping techniques were investigated to handle such situations. A technique was developed for the computation o f well index with consideration to wellbore pressure drop. A recently developed reservoir/wellbore coupling model was used for this purpose.

  2. New "horizontal" curriculum in family medicine residency.

    PubMed Central

    Tannenbaum, D. W.

    1998-01-01

    PROBLEM ADDRESSED: Opportunities for residents in a family medicine program to experience continuity of care with a group of patients and to be immersed in the role of a family physician were thought by faculty to be insufficient. OBJECTIVES OF THE PROGRAM: To enhance residents' experience of continuity of care with a group of patients; to create a model for training that better simulates clinical practice; and to position core family medicine experiences as the central and continuing focus of the residency program. MAIN COMPONENTS OF THE PROGRAM: The new curriculum replaces block rotations in family medicine with "horizontal" experiences comprising 3 half-days of patient care and 1 half-day seminar each week for all residents through both years of the program. The remaining time in first year is spent on the major disciplines--medicine, pediatrics, emergency, and obstetrics--for which a horizontal family medicine-centred experience has also been introduced. The second-year curriculum is flexible and largely self-directed. Initial evaluations indicate improved continuity of care of family practice patients and broadened clinical exposure for residents. The program has been fully accredited by the College. CONCLUSIONS: A horizontal curriculum in family medicine, designed to address perceived deficiencies in the traditional block rotational model of training, can be developed and implemented in an urban teaching hospital. PMID:9721423

  3. Vertical and horizontal seismometric observations of tides

    NASA Astrophysics Data System (ADS)

    Lambotte, S.; Rivera, L.; Hinderer, J.

    2006-01-01

    Tidal signals have been largely studied with gravimeters, strainmeters and tiltmeters, but can also be retrieved from digital records of the output of long-period seismometers, such as STS-1, particularly if they are properly isolated. Horizontal components are often noisier than the vertical ones, due to sensitivity to tilt at long periods. Hence, horizontal components are often disturbed by local effects such as topography, geology and cavity effects, which imply a strain-tilt coupling. We use series of data (duration larger than 1 month) from several permanent broadband seismological stations to examine these disturbances. We search a minimal set of observable signals (tilts, horizontal and vertical displacements, strains, gravity) necessary to reconstruct the seismological record. Such analysis gives a set of coefficients (per component for each studied station), which are stable over years and then can be used systematically to correct data from these disturbances without needing heavy numerical computation. A special attention is devoted to ocean loading for stations close to oceans (e.g. Matsushiro station in Japon (MAJO)), and to pressure correction when barometric data are available. Interesting observations are made for vertical seismometric components; in particular, we found a pressure admittance between pressure and data 10 times larger than for gravimeters for periods larger than 1 day, while this admittance reaches the usual value of -3.5 nm/s 2/mbar for periods below 3 h. This observation may be due to instrumental noise, but the exact mechanism is not yet understood.

  4. Horizontal transmission of streptococcus mutans in schoolchildren

    PubMed Central

    Castillo, Ana M.; Liébana, Maria J.; Castillo, Francisca; Martín-Platero, Antonio; Liébana, José

    2012-01-01

    Objetive: The aim of this study was to analyze possible horizontal transmission patterns of S. mutans among 6-7-yr-old schoolchildren from the same class, identifying genotypes and their diversity and relationship with caries disease status. Study Design: Caries indexes and saliva mutans streptococci and lactobacilli counts were recorded in 42 schoolchildren. Mutans streptococci colonies were identified by means of biochemical tests and all S. mutans strains were genotyped by arbitrarily primed polymerase chain reaction. A child was considered free of S. mutans when it could not be isolated in 3 samples at 1-week intervals. Results: S. mutans was isolated in 30 schoolchildren: 20 having one genotype and 10 two genotypes. Higher mutans streptococci and caries index values were found in those with two genotypes. Five genotypes were isolated in more than 1 schoolchild and one of these was isolated in 3 schoolchildren. Our results suggest that horizontal transmission may take place. Conclusion: Schoolchildren aged 6-7 yrs may be the source of mutual transmission of S. mutans. Key words:Streptococcus mutans, Horizontal transmission, AP-PCR, genotyping PMID:22143733

  5. Adaptive Horizontal Gene Transfers between Multiple Cheese-Associated Fungi

    PubMed Central

    Ropars, Jeanne; Rodríguez de la Vega, Ricardo C.; López-Villavicencio, Manuela; Gouzy, Jérôme; Sallet, Erika; Dumas, Émilie; Lacoste, Sandrine; Debuchy, Robert; Dupont, Joëlle; Branca, Antoine; Giraud, Tatiana

    2015-01-01

    Summary Domestication is an excellent model for studies of adaptation because it involves recent and strong selection on a few, identified traits [1–5]. Few studies have focused on the domestication of fungi, with notable exceptions [6–11], despite their importance to bioindustry [12] and to a general understanding of adaptation in eukaryotes [5]. Penicillium fungi are ubiquitous molds among which two distantly related species have been independently selected for cheese making—P. roqueforti for blue cheeses like Roquefort and P. camemberti for soft cheeses like Camembert. The selected traits include morphology, aromatic profile, lipolytic and proteolytic activities, and ability to grow at low temperatures, in a matrix containing bacterial and fungal competitors [13–15]. By comparing the genomes of ten Penicillium species, we show that adaptation to cheese was associated with multiple recent horizontal transfers of large genomic regions carrying crucial metabolic genes. We identified seven horizontally transferred regions (HTRs) spanning more than 10 kb each, flanked by specific transposable elements, and displaying nearly 100% identity between distant Penicillium species. Two HTRs carried genes with functions involved in the utilization of cheese nutrients or competition and were found nearly identical in multiple strains and species of cheese-associated Penicillium fungi, indicating recent selective sweeps; they were experimentally associated with faster growth and greater competitiveness on cheese and contained genes highly expressed in the early stage of cheese maturation. These findings have industrial and food safety implications and improve our understanding of the processes of adaptation to rapid environmental changes. PMID:26412136

  6. Adaptive Horizontal Gene Transfers between Multiple Cheese-Associated Fungi.

    PubMed

    Ropars, Jeanne; Rodríguez de la Vega, Ricardo C; López-Villavicencio, Manuela; Gouzy, Jérôme; Sallet, Erika; Dumas, Émilie; Lacoste, Sandrine; Debuchy, Robert; Dupont, Joëlle; Branca, Antoine; Giraud, Tatiana

    2015-10-05

    Domestication is an excellent model for studies of adaptation because it involves recent and strong selection on a few, identified traits [1-5]. Few studies have focused on the domestication of fungi, with notable exceptions [6-11], despite their importance to bioindustry [12] and to a general understanding of adaptation in eukaryotes [5]. Penicillium fungi are ubiquitous molds among which two distantly related species have been independently selected for cheese making-P. roqueforti for blue cheeses like Roquefort and P. camemberti for soft cheeses like Camembert. The selected traits include morphology, aromatic profile, lipolytic and proteolytic activities, and ability to grow at low temperatures, in a matrix containing bacterial and fungal competitors [13-15]. By comparing the genomes of ten Penicillium species, we show that adaptation to cheese was associated with multiple recent horizontal transfers of large genomic regions carrying crucial metabolic genes. We identified seven horizontally transferred regions (HTRs) spanning more than 10 kb each, flanked by specific transposable elements, and displaying nearly 100% identity between distant Penicillium species. Two HTRs carried genes with functions involved in the utilization of cheese nutrients or competition and were found nearly identical in multiple strains and species of cheese-associated Penicillium fungi, indicating recent selective sweeps; they were experimentally associated with faster growth and greater competitiveness on cheese and contained genes highly expressed in the early stage of cheese maturation. These findings have industrial and food safety implications and improve our understanding of the processes of adaptation to rapid environmental changes. Copyright © 2015 The Authors. Published by Elsevier Ltd.. All rights reserved.

  7. Biomimetic optimisation of branched fibre-reinforced composites in engineering by detailed analyses of biological concept generators.

    PubMed

    Masselter, T; Hesse, L; Böhm, H; Gruhl, A; Schwager, H; Leupold, J; Gude, M; Milwich, M; Neinhuis, C; Speck, T

    2016-09-07

    The aim of this study is the biomimetic optimisation of branched fibre-reinforced composites based on the detailed analysis of biological concept generators. The methods include analyses of the functional morphology and biomechanics of arborescent monocotyledons and columnar cacti as well as measurements and modelling of mechanical properties of biomimetic fibre-reinforced composites. The key results show evidence of notch stress reduction by optimised stem-branch-attachment morphology in monocotyledons and columnar cacti. It could be shown that some of these highly interesting properties can be transferred into biomimetic fibre-reinforced composites.

  8. Standard Giant Branches in the Washington Photometric System

    NASA Technical Reports Server (NTRS)

    Geisler, Doug; Sarajedini, Ata

    1998-01-01

    We have obtained CCD photometry in the Washington system C, T(sub 1) filters for some 850,000 objects associated with 10 Galactic globular clusters and 2 old open clusters. These clusters have well-known metal abundances, spanning a metallicity range of 2.5 dex from [Fe/H] approx -2.25 to +0.25 at a spacing of approx. 0.2 dex. Two independent observations were obtained for each cluster and internal checks, as well as external comparisons with existing photoelectric photometry, indicate that the final colors and magnitudes have overall uncertainties of 0.03 mag. Analogous to the method employed by Da Costa and Armandroff for V, I photometry , we then proceed to construct standard ((M(sub T),(C - T(sub 1))(sub 0)) giant branches for these clusters adopting the Lee et distance scale, using some 350 stars per globular cluster to define the giant branch. We then determine the metallicity sensitivity of the ((C - T(sub 1))(sub 0) color at a given M((sub T)(sub 1)) value. The Washington system technique is found to have three times the metallicity sensitivity of the V, I technique. At M((sub T)(sub 1)) = -2 (about a magnitude below the tip of the giant branch, roughly equivalent to M(sub I) = -3), the giant branches of 47 Tuc and M15 are separated by 1.16 magnitudes in (V - l)(sub 0) and only 0.38 magnitudes in (V - I)(sub 0). Thus, for a given photometric accuracy, metallicities can be determined three times more precisely with the Washington technique. We find a linear relationship between (C - T(sub l)(sub 0) (at M(sub T)(sub 1) = -2) and metallicity exists over the full metallicity range, with an rms of only 0.04 dex. We also derive metallicity calibrations for M(sub T)(sub 1) = -2.5 and -1.5, as well as for two other metallicity scales. The Washington technique retains almost the same metallicity sensitivity at faint magnitudes , and indeed the standard giant branches are still well separated even below the horizontal branch. The photometry is used to set upper

  9. Code 672 observational science branch computer networks

    NASA Technical Reports Server (NTRS)

    Hancock, D. W.; Shirk, H. G.

    1988-01-01

    In general, networking increases productivity due to the speed of transmission, easy access to remote computers, ability to share files, and increased availability of peripherals. Two different networks within the Observational Science Branch are described in detail.

  10. Overview of the Advanced High Frequency Branch

    NASA Technical Reports Server (NTRS)

    Miranda, Felix A.

    2015-01-01

    This presentation provides an overview of the competencies, selected areas of research and technology development activities, and current external collaborative efforts of the NASA Glenn Research Center's Advanced High Frequency Branch.

  11. FY 1990 Applied Sciences Branch annual report

    SciTech Connect

    Keyes, B.M.; Dippo, P.C.

    1991-11-01

    The Applied Sciences Branch actively supports the advancement of DOE/SERI goals for the development and implementation of the solar photovoltaic technology. The primary focus of the laboratories is to provide state-of-the-art analytical capabilities for materials and device characterization and fabrication. The branch houses a comprehensive facility which is capable of providing information on the full range of photovoltaic components. A major objective of the branch is to aggressively pursue collaborative research with other government laboratories, universities, and industrial firms for the advancement of photovoltaic technologies. Members of the branch disseminate research findings to the technical community in publications and presentations. This report contains information on surface and interface analysis, materials characterization, development, electro-optical characterization module testing and performance, surface interactions and FTIR spectroscopy.

  12. Applied Aeroscience and CFD Branch Overview

    NASA Technical Reports Server (NTRS)

    LeBeau, Gerald J.; Kirk, Benjamin S.

    2014-01-01

    The principal mission of NASA Johnson Space Center is Human Spaceflight. In support of the mission the Applied Aeroscience and CFD Branch has several technical competencies that include aerodynamic characterization, aerothermodynamic heating, rarefied gas dynamics, and decelerator (parachute) systems.

  13. Sharing Fiscal Information: A Legislative Branch View.

    ERIC Educational Resources Information Center

    Rivlin, Alice M.

    1978-01-01

    Decisions regarding budget matters are complex; therefore, information sharing between the executive and legislative branches is helpful and necessary. Budget reforms have been initiated, but future trends indicate the need for flexibility and revision of information pathways. (MBR)

  14. Residence times of branching diffusion processes

    NASA Astrophysics Data System (ADS)

    Dumonteil, E.; Mazzolo, A.

    2016-07-01

    The residence time of a branching Brownian process is the amount of time that the mother particle and all its descendants spend inside a domain. Using the Feynman-Kac formalism, we derive the residence-time equation as well as the equations for its moments for a branching diffusion process with an arbitrary number of descendants. This general approach is illustrated with simple examples in free space and in confined geometries where explicit formulas for the moments are obtained within the long time limit. In particular, we study in detail the influence of the branching mechanism on those moments. The present approach can also be applied to investigate other additive functionals of branching Brownian process.

  15. Enzyme-instructed self-assembly of taxol promotes axonal branching

    NASA Astrophysics Data System (ADS)

    Mei, Bin; Miao, Qingqing; Tang, Anming; Liang, Gaolin

    2015-09-01

    Axonal branching is important for vertebrate neuron signaling. Taxol has a biphasic effect on axonal branching (i.e., high concentration inhibits axonal growth but low concentration restores it). To the best of our knowledge, low concentration of taxol to promote axonal branching has not been reported yet. Herein, we rationally designed a taxol derivative Fmoc-Phe-Phe-Lys(taxol)-Tyr(H2PO4)-OH (1) which could be subjected to alkaline phosphatase (ALP)-catalyzed self-assembly to form taxol nanofibers. We found that, at 10 μM, 1 has a microtubule (MT) condensation effect similar to that of taxol on mammalian cells but with more chronic toxicity than taxol on the cells. At a low concentration of 10 nM, 1 not only promoted neurite elongation as taxol did but also promoted axonal branching which was not achieved by using taxol. We propose that self-assembly of 1 along the MTs prohibited their lateral contacts and thus promoted axonal branching. Our strategy of enzyme-instructed self-assembly (EISA) of a taxol derivative provides a new tool for scientists to study the morphology of neurons, as well as their behaviours.Axonal branching is important for vertebrate neuron signaling. Taxol has a biphasic effect on axonal branching (i.e., high concentration inhibits axonal growth but low concentration restores it). To the best of our knowledge, low concentration of taxol to promote axonal branching has not been reported yet. Herein, we rationally designed a taxol derivative Fmoc-Phe-Phe-Lys(taxol)-Tyr(H2PO4)-OH (1) which could be subjected to alkaline phosphatase (ALP)-catalyzed self-assembly to form taxol nanofibers. We found that, at 10 μM, 1 has a microtubule (MT) condensation effect similar to that of taxol on mammalian cells but with more chronic toxicity than taxol on the cells. At a low concentration of 10 nM, 1 not only promoted neurite elongation as taxol did but also promoted axonal branching which was not achieved by using taxol. We propose that self-assembly of 1

  16. 12 CFR 5.70 - Federal branches and agencies.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... acquisition; (iv) Convert a state branch or state agency operated by a foreign bank, or a commercial lending company controlled by a foreign bank, into a Federal branch or agency; (v) Relocate a Federal branch or...

  17. Perivascular exudates in frosted branch angiitis.

    PubMed

    He, Lingmin; Moshfeghi, Darius M; Wong, Ira G

    2014-01-01

    Three cases of young, minimally symptomatic patients found to have vitritis and extensive perivenous vitreous exudates resembling frosted branch angiitis are presented. Optical coherence tomography showed that these exudates appear to be extravascated from the vasculature. The material persisted over 1 year on immunosuppressive therapy, suggesting that its resolution should not be a treatment end point. These cases add to our understanding of the spectrum of clinical findings in frosted branch angiitis.

  18. Ancient horizontal gene transfer and the last common ancestors.

    PubMed

    Fournier, Gregory P; Andam, Cheryl P; Gogarten, Johann Peter

    2015-04-22

    The genomic history of prokaryotic organismal lineages is marked by extensive horizontal gene transfer (HGT) between groups of organisms at all taxonomic levels. These HGT events have played an essential role in the origin and distribution of biological innovations. Analyses of ancient gene families show that HGT existed in the distant past, even at the time of the organismal last universal common ancestor (LUCA). Most gene transfers originated in lineages that have since gone extinct. Therefore, one cannot assume that the last common ancestors of each gene were all present in the same cell representing the cellular ancestor of all extant life. Organisms existing as part of a diverse ecosystem at the time of LUCA likely shared genetic material between lineages. If these other lineages persisted for some time, HGT with the descendants of LUCA could have continued into the bacterial and archaeal lineages. Phylogenetic analyses of aminoacyl-tRNA synthetase protein families support the hypothesis that the molecular common ancestors of the most ancient gene families did not all coincide in space and time. This is most apparent in the evolutionary histories of seryl-tRNA synthetase and threonyl-tRNA synthetase protein families, each containing highly divergent "rare" forms, as well as the sparse phylogenetic distributions of pyrrolysyl-tRNA synthetase, and the bacterial heterodimeric form of glycyl-tRNA synthetase. These topologies and phyletic distributions are consistent with horizontal transfers from ancient, likely extinct branches of the tree of life. Of all the organisms that may have existed at the time of LUCA, by definition only one lineage is survived by known progeny; however, this lineage retains a genomic record of heterogeneous genetic origins. The evolutionary histories of aminoacyl-tRNA synthetases (aaRS) are especially informative in detecting this signal, as they perform primordial biological functions, have undergone several ancient HGT events, and

  19. Morphological study of penumbral formation

    NASA Astrophysics Data System (ADS)

    Kitai, Reizaburo; Watanabe, Hiroko; Otsuji, Ken'ichi

    2014-12-01

    Penumbrae are known to be areas of mainly horizontal magnetic field surrounding umbrae of relatively large and mature sunspots. In this paper, we observationally studied the formation of penumbrae in NOAA 10978, where several penumbral formations were observed in G-band images of the Solar Optical Telescope on board Hinode. Thanks to the continuous observation by Hinode, we could morphologically follow the evolution of sunspots and found that there are several paths to the penumbral formation: (1) active accumulation of magnetic flux, (2) rapid emergence of magnetic field, and (3) appearance of twisted or rotating magnetic tubes. In all of these cases, magnetic fields are expected to sustain high inclination at the edges of flux tube concentration longer than the characteristic growth time of downward magnetic pumping.

  20. NRAGE: a potential rheostat during branching morphogenesis.

    PubMed

    Nikopoulos, George N; Martins, Joao Ferreira; Adams, Tamara L; Karaczyn, Aldona; Adams, Derek; Vary, Calvin; Oxburgh, Leif; Verdi, Joseph M

    2009-01-01

    Branching morphogenesis is a developmental process characteristic of many organ systems. Specifically, during renal branching morphogenesis, its been postulated that the final number of nephrons formed is one key clinical factor in the development of hypertension in adulthood. As it has been established that BMPs regulate, in part, renal activity of p38 MAP kinase (p38(MAPK)) and it has demonstrated that the cytoplasmic protein Neurotrophin Receptor MAGE homologue (NRAGE) augments p38(MAPK) activation, it was hypothesized that a decrease in the expression of NRAGE during renal branching would result in decreased branching of the UB that correlated with changes in p38(MAPK) activation. To verify this, the expression of NRAGE was reduced in ex vivo kidney explants cultures using antisense morpholino. Morpholino treated ex vivo kidney explants expression were severely stunted in branching, a trait that was rescued with the addition of exogenous GDNF. Renal explants also demonstrated a precipitous drop in p38(MAPK) activation that too was reversed in the presence of recombinant GDNF. RNA profiling of NRAGE diminished ex vivo kidney explants resulted in altered expression of GDNF, Ret, BMP7 and BMPRIb mRNAs. Our results suggested that in early kidney development NRAGE might have multiple roles during renal branching morphogenesis through association with both the BMP and GDNF signaling pathways.