12,254 research outputs found

    Symbiotic nitrogen fixation and N-transfer in a grass-white clover mixture

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    Symbiotic N2 fixation (SNF) and transfer of fixed N from clover to grass in a grass-white clover mixture was measured during two years using 15N isotope dilution techniques. White clover derived from 87 to 99% of its N from the atmosphere. The total SNF ranged from 150 to 277 kg N ha-1 yr-1, which corresponded to 34-45 mg N fixed per gram of white clover dry weight. The transfer of fixed N from clover to grass corresponded to approximately 10 kg N ha-1 yr-1

    Cold gas in the inner regions of intermediate redshift clusters

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    Determining gas content and star formation rate has known remarkable progress in field galaxies, but has been much less investigated in galaxies inside clusters. We present the first CO observations of luminous infrared galaxies (LIRGs) inside the virial radii of two intermediate redshift clusters, CL1416+4446 (z=0.397) and CL0926+1242 (z=0.489). We detect three galaxies at high significance (5 to 10 sigma), and provide robust estimates of their CO luminosities, L'CO. In order to put our results into a general context, we revisit the relation between cold and hot gas and stellar mass in nearby field and cluster galaxies. We find evidence that at fixed LIR (or fixed stellar mass), the frequency of high L'CO galaxies is lower in clusters than in the field, suggesting environmental depletion of the reservoir of cold gas. The level of star formation activity in a galaxy is primarily linked to the amount of cold gas, rather than to the galaxy mass or the lookback time. In clusters, just as in the field, the conversion between gas and stars seems universal. The relation between LIR and L'CO for distant cluster galaxies extends the relation of nearby galaxies to higher IR luminosities. Nevertheless, the intermediate redshift galaxies fall well within the dispersion of the trend defined by local systems. Considering that L'CO is generally derived from the CO(1-0) line and sensitive to the vast majority of the molecular gas in the cold interstellar medium of galaxies, but less to the part which will actually be used to form stars, we suggest that molecular gas can be stripped before the star formation rate is affected. Combining the sample of Geach et al. (2009, 2011) and ours, we find evidence for a decrease in CO towards the cluster centers. This is the first hint of an environmental impact on cold gas at intermediate redshift.Comment: Accepted for publication in Astronomy and Astrophysic

    Brain Imaging and Privacy: How Recent Advances in Neuroimaging Implicate Privacy Concerns

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    This paper deals with recent advances in neuroimaging technologies which could begin to implicate privacy concerns in the near future

    Mathematical and computational studies of equilibrium capillary free surfaces

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    The results of several independent studies are presented. The general question is considered of whether a wetting liquid always rises higher in a small capillary tube than in a larger one, when both are dipped vertically into an infinite reservoir. An analytical investigation is initiated to determine the qualitative behavior of the family of solutions of the equilibrium capillary free-surface equation that correspond to rotationally symmetric pendent liquid drops and the relationship of these solutions to the singular solution, which corresponds to an infinite spike of liquid extending downward to infinity. The block successive overrelaxation-Newton method and the generalized conjugate gradient method are investigated for solving the capillary equation on a uniform square mesh in a square domain, including the case for which the solution is unbounded at the corners. Capillary surfaces are calculated on the ellipse, on a circle with reentrant notches, and on other irregularly shaped domains using JASON, a general purpose program for solving nonlinear elliptic equations on a nonuniform quadrilaterial mesh. Analytical estimates for the nonexistence of solutions of the equilibrium capillary free-surface equation on the ellipse in zero gravity are evaluated

    Female impersonation as an alternative reproductive strategy in giant cuttlefish

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    Out of all the animals, cephalopods possess an unrivalled ability to change their shape and body patterns. Our observations of giant cuttlefish (Sepia apama) suggest this ability has allowed them to evolve alternative mating strategies in which males can switch between the appearance of a female and that of a male in order to foil the guarding attempts of larger males. At a mass breeding aggregation in South Australia, we repeatedly observed single small males accompanying mating pairs. While doing so, the small male assumed the body shape and patterns of a female. Such males were never attacked by the larger mate-guarding male. On more than 20 occasions, when the larger male was distracted by another male intruder, these small males, previously indistinguishable from a female, were observed to change body pattern and behaviour to that of a male in mating display. These small males then attempted to mate with the female, often with success. This potential for dynamic sexual mimicry may have played a part in driving the evolution of the remarkable powers of colour and shape transformation which characterize the cephalopods

    Enclosures and Dichotomies: Coexistence vs. Distance in the Poems of John Clare

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    John Clare’s poetry emphasizes an affinity with environment by suspending the distinction between the inside (subject) and the outside (object). Clare’s identification with objects and perception rather than subjects and aesthetics renders his work as a prescient and radical example of ecological poetry in the Romantic period. Raymond Williams’ “green language” and Timothy Morton’s ambient poetics both cite Clare as an ideal figure for their above theories and evoke Clare as a writer who positions the environment as governing thought rather than thought governing the environment. This thesis especially relates Clare to Morton’s Ecology without Nature, a study of environmental aesthetics that displaces anthropocentricism and logocentrism with object-oriented ontology (OOO) and an immersion into environmental ambience. This thesis is divided into four sections, each structured by a dichotomy with a hegemonic enclosure of subjects and objects on one side and an alternative remedy that Clare gestures his readers towards. Clare’s poems frame the creation and consumption of literature as a direct connection to our immediate surroundings and by identifying with objects, detects this circumambient and sometimes mundane space as active and sublime. Finally, the arche-writing of Jacques Derrida establishes the written word as an environment not dissimilar to forests and fields and establishes Clare’s poems as a way to sense the environment as coded rather than empty. My correspondence between Derrida’s a priori arche-writing with Clare’s poetics indicates Clare’s successfully representation of uncompromised objects in space rather than objects as inextricably linked to logocentrism’s dominating signifiers and anthropocentric rationality
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