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  • 1
    Electronic Resource
    Electronic Resource
    Comparison of corticosteroid derivatives by gas chromatography-mass spectrometry (1972)
    s.l. : American Chemical Society
    Analytical chemistry 44 (1972), S. 30-37 
    Details
    ISSN: 1520-6882
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/ac60309a016
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Habitat diversification tactic for improving biological control: parasitism of the western grape leafhopper (1998)
    Springer
    Entomologia experimentalis et applicata 87 (1998), S. 225-235 
    Details
    ISSN: 1570-7458
    Keywords: Anagrus epos ; Erythroneura elegantula ; habitat diversity ; grape ; Vitis vinifera ; French prune ; Prunus domestica
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract In a previous study we demonstrated greater abundance of the parasitoid Anagrus epos (Girault) in grape vineyards located downwind of prune trees that function as overwintering habitats. This study examines whether these higher A. epos numbers translated into higher egg parasitism rates of the grape leafhopper, Erythroneura elegantula (Osborn). Paired commercial wine-grape vineyard plots, one with and one without adjacent prune trees, were studied within a complete block design in northern and central California. A. epos was the key mortality factor affecting E. elegantula eggs. Point estimates of A. epos parasitism rates were significantly greater in vineyards associated with prune trees during the first E. elegantula generation in both 1991 and 1992. No consistent differences in parasitism rates were observed during the second or third generations. The results indicated that prune trees enhance early season parasitism rates. Cumulative estimates of egg parasitism across E. elegantula generations demonstrated that enhanced early-season parasitism resulted in a net season-long increase in the degree of mortality imposed by A. epos on E. elegantula eggs. Two factors were found to influence parasitism rates: the abundance of early-season A. epos adults moving into vineyards and the density of E. elegantula eggs in vineyards. Our results indicate that diversification of vineyards using prune trees supports overwintering populations of a specialist parasitoid and thereby alters host-parasitoid interactions to favor enhanced parasitism in vineyards.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1003294222162
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  • 3
    Electronic Resource
    Electronic Resource
    Schistosoma mansoni: Effect on growth, fertility, and development of distal male organs inBiomphalaria glabrata exposed to miracidia at different ages (1981)
    Springer
    Parasitology research 66 (1981), S. 121-131 
    Details
    ISSN: 1432-1955
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Description / Table of Contents: Zusammenfassung Nach Exposition gegenüber 3 Miracidien vonSchistosoma mansoni (Liberianischer Stamm) in verschiedenem Alter (1, 2, 4, 6, 8 Wochen) wurden an zu zweit gehaltenen Schnecken vonBiomphalaria glabrata (Portorico-Stamm) Wachstum, Eiablage und Mortalität bestimmt. Die Befunde an infizierten Schnecken wurden mit denen negativ gebliebener und nicht exponierter Schnecken verglichen. Jüngere Schnecken ließen sich in höherem Maße infizieren, starben aber auch signifikant mehr als negative oder unexponierte; älter infizierte unterschieden sich kaum von den Kontrollen oder negativen. Wachstumsacceleration parasitierter Tiere wurde nicht beobachtet. Lag die Präpatenz überwiegend vor Eintritt der Geschlechtsreife, so legten die infizierten Schnecken keine Eier ab. Bei späteren Infektionen sank die Zahl der abgelegten Eier schon ab der 2. Woche nach Infektion unter die der gesunden Tiere. 15 Wochen nach der Infektion wurden die Tiere seziert. Eine verzögerte Entwicklung männlicher Geschlechtsorgane (Prostata, Präputium mit Penisscheide), bezogen auf den Gehäusedurchmesser, wurde vor allem bei Tieren gefunden, die vor der Geschlechtsreife infiziert worden waren. Bei größeren Tieren erreichten die Organe annähernd die normale Endgröße. Bei einem Teil der parasitierten Tiere verformte sich das Gehäuse durch Mündungserweiterung an der rechten Seite.
    Notes: Abstract Growth, egg laying rate, and mortality ofBiomphalaria glabrata (Portorican strain), maintained in groups of two, after exposure at different ages (1, 2, 4, 6, 8 weeks) to three miracidia each ofSchistosoma mansoni (Liberian strain) were determined. The findings in infected snails were compared with those in exposed but uninfected (negative) and in unexposed snails. Younger snails were infected at higher rates, and these showed a significantly increased mortality. Young infected snails grew much slower than negative or unexposed snails; older infected snails grew at about the same rate as negative or control snails. A growth acceleration was not observed in parasitized animals. When prepatency to a high extent passed before sexual maturity, infected snails did not lay any eggs. In later infections the numbers of eggs dropped below those in healthy snails by the second week after exposure. Snails were dissected 15 weeks after exposure. Development of male reproductive organs (prostate gland, preputium plus penis sheath), in relation to shell diameter, was retarded particularly in animals infected before sexual maturity and highly retarded in growth. In larger animals the organs reached approximately their definitive size. Parasitized snails were partially deformed by an enlargement of their shell apertures on the right side.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00925719
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  • 4
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    NIHAO IX: the role of gas inflows and outflows in driving the contraction and expansion of cold dark matter haloes (2016)
    Oxford University Press
    Details
    Publication Date: 2016-07-15
    Description: We use ~100 cosmological galaxy formation ‘zoom-in’ simulations using the smoothed particle hydrodynamics code gasoline to study the effect of baryonic processes on the mass profiles of cold dark matter haloes. The haloes in our study range from dwarf ( M 200  ~ 10 10 M ) to Milky Way ( M 200  ~ 10 12 M ) masses. Our simulations exhibit a wide range of halo responses, primarily varying with mass, from expansion to contraction, with up to factor ~10 changes in the enclosed dark matter mass at 1 per cent of the virial radius. Confirming previous studies, the halo response is correlated with the integrated efficiency of star formation: SF ( M star / M 200 )/( b / m ). In addition, we report a new correlation with the compactness of the stellar system: R r 1/2 / R 200 . We provide an analytic formula depending on SF and R for the response of cold dark matter haloes to baryonic processes. An observationally testable prediction is that, at fixed mass, larger galaxies experience more halo expansion, while the smaller galaxies more halo contraction. This diversity of dark halo response is captured by a toy model consisting of cycles of adiabatic inflow (causing contraction) and impulsive gas outflow (causing expansion). For net outflow, or equal inflow and outflow fractions, f , the overall effect is expansion, with more expansion with larger f . For net inflow, contraction occurs for small f (large radii), while expansion occurs for large f (small radii), recovering the phenomenology seen in our simulations. These regularities in the galaxy formation process provide a step towards a fully predictive model for the structure of cold dark matter haloes.
    Print ISSN: 0035-8711
    Electronic ISSN: 1365-2966
    Topics: Physics
    Published by Oxford University Press
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  • 5
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    Signatures of dark matter halo expansion in galaxy populations (2015)
    Oxford University Press
    Details
    Publication Date: 2015-08-30
    Description: Dark matter cores within galaxy haloes can be formed by energy feedback from star-forming regions: an energy balance suggests that the maximum core formation efficiency arises in galaxies with M star  ~ 10 8.5 M . We show that a model population of galaxies, in which the density profile has been modified by such baryonic feedback, is able to explain the observed galaxy velocity function and Tully–Fisher relations significantly better than a model in which a universal cuspy density profile is assumed. Alternative models, namely warm or self-interacting dark matter, also provide a better match to these observed relations than a universal profile model does, but make different predictions for how halo density profiles vary with mass compared to the baryonic feedback case. We propose that different core formation mechanisms may be distinguished based on the imprint they leave on galaxy populations over a wide range of mass. Within the current observational data we find evidence of the expected signatures of the mass dependence of core formation generated by baryonic feedback.
    Print ISSN: 0035-8711
    Electronic ISSN: 1365-2966
    Topics: Physics
    Published by Oxford University Press
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  • 6
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    Expanded haloes, abundance matching and too-big-to-fail in the Local Group (2015)
    Oxford University Press
    Details
    Publication Date: 2015-05-21
    Description: Observed kinematical data of 40 Local Group (LG) members are used to derive the dark matter halo mass of such galaxies. Haloes are selected from the theoretically expected LG mass function and two different density profiles are assumed, a standard universal cuspy model and a mass-dependent profile which accounts for the effects of baryons in modifying the dark matter distribution within galaxies. The resulting relations between stellar and halo mass are compared with expectations from abundance matching. Using a universal cuspy profile, the ensemble of LG galaxies is fit in relatively low-mass haloes, leaving ‘dark’ many massive haloes of M halo   10 10  M : this reflects the ‘too-big-to-fail’ problem and results in a M star – M halo relation that differs from abundance matching predictions. Moreover, the star formation efficiency of isolated LG galaxies increases with decreasing halo mass when adopting a cuspy model. By contrast, using the mass-dependent density profile, dwarf galaxies with M star   10 6  M are assigned to more massive haloes, which have a central cored distribution of dark matter: the ‘too-big-to-fail’ problem is alleviated, the resultant M star – M halo relation follows abundance matching predictions down to the completeness limit of current surveys, and the star formation efficiency of isolated members decreases with decreasing halo mass, in agreement with theoretical expectations. Finally, the cusp/core space of LG galaxies is presented, providing a framework to understand the non-universality of their density profiles.
    Print ISSN: 0035-8711
    Electronic ISSN: 1365-2966
    Topics: Physics
    Published by Oxford University Press
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  • 7
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    The variation of rotation curve shapes as a signature of the effects of baryons on dark matter density profiles (2015)
    Oxford University Press
    Details
    Publication Date: 2015-10-09
    Description: Rotation curves of galaxies show a wide range of shapes, which can be paramaterized as scatter in V rot (1 kpc)/ V max  , i.e. the ratio of the rotation velocity measured at 1 kpc and the maximum measured rotation velocity. We examine whether the observed scatter can be accounted for by combining scatters in disc scalelengths, the concentration–halo mass relation, and the M * – M halo relation. We use these scatters to create model galaxy populations; when housed within dark matter haloes that have universal, Navarro, Frenk & White density profiles, the model does not match the lowest observed values of V rot (1 kpc)/ V max and has too little scatter in V rot (1 kpc)/ V max compared to observations. By contrast, a model using a mass-dependent dark matter profile, where the inner slope is determined by the ratio of M * / M halo , produces galaxies with low values of V rot (1 kpc)/ V max and a much larger scatter, both in agreement with observation. We conclude that the large observed scatter in V rot (1 kpc)/ V max favours density profiles that are significantly affected by baryonic processes. Alternative dark matter core formation models such as self-interacting dark matter may also account for the observed variation in rotation curve shapes, but these observations may provide important constraints in terms of core sizes, and whether they vary with halo mass and/or merger history.
    Print ISSN: 0035-8711
    Electronic ISSN: 1365-2966
    Topics: Physics
    Published by Oxford University Press
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  • 8
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    A matter of measurement: rotation velocities and the velocity function of dwarf galaxies (2015)
    Oxford University Press
    Details
    Publication Date: 2015-12-05
    Description: The velocity function derived from large-scale surveys can be compared with the predictions of cold dark matter (CDM) cosmology, by matching the measured rotation velocities V rot of galaxies to the maximum circular velocity of dark matter (DM) haloes V max . For V rot  〈 50 kms –1 , a major discrepancy arises between the observed and CDM velocity functions. However, the manner in which different observational measures of V rot are associated with V max is not straightforward in dwarf galaxies. We instead relate galaxies to DM haloes using the empirical baryon-mass to halo-mass relation, and show that different observational measures of V rot result in very different velocity functions. We show how the W50 velocity function, i.e. using the H  i profile linewidth at 50 per cent of peak H  i flux to measure V rot , can be reconciled with a CDM cosmology. Our semi-empirical methodology allows us to determine the region of rotation curves that are probed by H  i measurements ( $R_{\rm H\,\small {I}}$ ), and shows that the V rot of dwarfs are generally measured at a fraction of R max , explaining their tendency to have rising rotation curves. We provide fitting formulae for relating $R_{\rm H\,\small {I}}$ and R eff (the effective radius) to the virial radius of DM haloes. To continue to use velocity functions as a probe of CDM cosmology, it is necessary to be precise about how the different measures of rotation velocity are probing the mass of the DM haloes, dropping the assumption that any measure of rotational velocity can be equally used as a proxy for V max .
    Print ISSN: 0035-8711
    Electronic ISSN: 1365-2966
    Topics: Physics
    Published by Oxford University Press
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  • 9
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    MaGICC-WDM: the effects of warm dark matter in hydrodynamical simulations of disc galaxy formation (2013)
    Oxford University Press
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    Publication Date: 2013-12-06
    Description: We study the effect of warm dark matter (WDM) on hydrodynamic simulations of galaxy formation as part of the Making Galaxies in a Cosmological Context (MaGICC) project. We simulate three different galaxies using three WDM candidates of 1, 2 and 5 keV and compare results with pure cold dark matter simulations. WDM slightly reduces star formation and produces less centrally concentrated stellar profiles. These effects are most evident for the 1 keV candidate but almost disappear for $m_ {\rm \small {wdm}} 〉 2$  keV. All simulations form similar stellar discs independent of WDM particle mass. In particular, the disc scalelength does not change when WDM is considered. The reduced amount of star formation in the case of 1 keV particles is due to the effects of WDM on merging satellites which are on average less concentrated and less gas rich. The altered satellites cause a reduced starburst during mergers because they trigger weaker disc instabilities in the main galaxy. Nevertheless we show that disc galaxy evolution is much more sensitive to stellar feedback than it is to WDM candidate mass. Overall, we find that WDM, especially when restricted to current observational constraints ( $m_ {\rm \small {wdm}} 〉 2$  keV), has a minor impact on disc galaxy formation.
    Print ISSN: 0035-8711
    Electronic ISSN: 1365-2966
    Topics: Physics
    Published by Oxford University Press
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  • 10
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    The dependence of dark matter profiles on the stellar-to-halo mass ratio: a prediction for cusps versus cores (2013)
    Oxford University Press
    Details
    Publication Date: 2013-12-06
    Description: We use a suite of 31 simulated galaxies drawn from the MaGICC project to investigate the effects of baryonic feedback on the density profiles of dark matter haloes. The sample covers a wide mass range: 9.4 10 9  〈  M halo / M  〈 7.8 10 11 , hosting galaxies with stellar masses in the range 5.0 10 5  〈  M * / M  〈 8.3 10 10 , i.e. from dwarf to L*. The galaxies are simulated with blastwave supernova feedback and, for some of them, an additional source of energy from massive stars is included. Within this feedback scheme we vary several parameters, such as the initial mass function, the density threshold for star formation, and energy from supernovae and massive stars. The main result is a clear dependence of the inner slope of the dark matter density profile, α in    r α , on the stellar-to-halo mass ratio, M * / M halo . This relation is independent of the particular choice of parameters within our stellar feedback scheme, allowing a prediction for cusp versus core formation. When M * / M halo is low, 0.01 per cent, energy from stellar feedback is insufficient to significantly alter the inner dark matter density, and the galaxy retains a cuspy profile. At higher stellar-to-halo mass ratios, feedback drives the expansion of the dark matter and generates cored profiles. The flattest profiles form where M * / M halo  ~ 0.5 per cent. Above this ratio, stars formed in the central regions deepen the gravitational potential enough to oppose the supernova-driven expansion process, resulting in cuspier profiles. Combining the dependence of α on M * / M halo with the empirical abundance matching relation between M * and M halo provides a prediction for how α varies as a function of stellar mass. Further, using the Tully–Fisher relation allows a prediction for the dependence of the dark matter inner slope on the observed rotation velocity of galaxies. The most cored galaxies are expected to have V rot  ~ 50 km s –1 , with α decreasing for more massive disc galaxies: spirals with V rot  ~ 150 km s –1 have central slopes α ≤ –0.8, approaching again the Navarro–Frenk–White profile. This novel prediction for the dependence of α on disc galaxy mass can be tested using observational data sets and can be applied to theoretical modelling of mass profiles and populations of disc galaxies.
    Print ISSN: 0035-8711
    Electronic ISSN: 1365-2966
    Topics: Physics
    Published by Oxford University Press
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