3,065 research outputs found

    The context of the Local Volume: structures and motions in the nearby universe

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    The 6dF Galaxy Survey (6dFGS) and the 2MASS Redshift Survey (2MRS) provide the most complete maps of the large-scale structures and motions in the nearby universe. These maps have been used to reconstruct the density field in the local volume, and to predict the corresponding velocity field and the dipole of the Local Group motion.Comment: 4 pages, to appear in "Galaxies in the Local Volume", 2008, eds B. Koribalski and H. Jerjen, Springer Astrophysics and Space Science Series (proceedings of conference held in Sydney on 8-13 July 2007

    Neutron Star Vortex Dynamics and Magnetic Field Decay: Implications for High Density Nuclear Matter

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    We investigate the effect of the density-dependent proton and neutron gaps on vortex dynamics in neutron stars. We argue that the persistence of neutron star magnetic fields on timescales of 10910^9 y suggests a superconducting gap curve with local maximum at intermediate density. We discuss the implications for exotic core phenomena such as pion/kaon condensation or a transition to quark matter.Comment: 7 pages, 2 figures, uses LaTe

    Evidence of initial-state two-center effects for (e, 2e) reactions

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    Coincidence, or (e, 2e), measurements of electron-impact ionization of atoms have established that the largest values of triply differential cross sections are obtained in collisions involving small momentum transfer to the target. Absolute measurements for these reactions are now available for hydrogen at 54.4-eV impact energy, and relative data have recently been reported at 27.2 eV. Previous theoretical works have concentrated on employing asymptotically correct two-center wave functions for the final state, leaving the initial state described by the Born approximation. Here we report results for which asymptotically correct two-center wave functions are used for both the initial and final states of the scattering system. Comparison of these results with experiment reveals that two-center effects (projectile-target correlations) are also important in the initial state

    Assessing the ecological effects of management zoning on inshore reefs of the Great Barrier Reef Marine Park: Reef 2050 Integrated Monitoring and Reporting Program milestone report 2

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    [Extract] This RIMReP project builds upon a long-term monitoring program that assesses the ecological effects of management zoning on high-use and high-value inshore coral reefs of the Great Barrier Reef Marine Park (GBRMP). The monitoring program aims to track the status and condition of benthic (coral and algae) and fish communities and quantify the ecological effects of no-take marine reserves (green zones, NTRs). It is one of the few systematic long-term monitoring projects conducted on GBRMP reefs that specifically assesses temporal dynamics in reef communities and the ecological effects of zoning managemen

    Nematode-induced syncytium - A multinucleate transfer cell

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    The formation and structure of a syncytium induced by the potato cyst-nematode (Heterodera rostochiensis Woll.) in potato roots is described. At the permanent feeding site of the nematode larva, usually in the root cortex, the larva pierces a cell with its mouth stylet and injects saliva. Cell wall dissolution occurs to incorporate neighbouring cells into a syncytium. A column of cells is incorporated towards the vascular tissue. Centripetal advance is limited by the lignifled xylem, then syncytial spread continues laterally along xylem parenchyma and pericycle cells. Wall protuberances form on syncytial walls adjacent to conducting elements. This indicates the syncytium is a multinucleate transfer cell, and by ingesting syncytial contents the larva is the nutrient sink. As syncytial expansion occurs, sieve elements are crushed and probably cease to function, hence protuberance development continues only against xylem elements. Cell alterations on incorporation into the syncytium involve expansion, loss of cell vacuole, nuclear hypertrophy and a proliferation of cytoplasmic organelles free to move through wall gaps into the communal cytoplasm. ‘Boundary formations’ and microtubules are associated with the growing ends of protuber ances, and appear to be involved in their synthesis. Fibrillar material, possibly cellulose microfibrils, occurs between the plasrnalemma and the membrane of the ‘boundary formation’, and the forming protuberance. To induce the formation of the syncytium, the larva controls the differentiation of unspecialized cells to cells with a specific physiological function. The occurrence of wall protuberances suggests that transfer cells form as a response to solute flow

    Quadratic Optimization with Bounded Linear Constraints

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    A recently developed algorithm for the solution of linear constrained differential-algebraic systems is extended to provide a systematic computational procedure for the solution of quadratic optimization problems with bounded linear constraints. The technique has rapid convergence and can be applied to minimum norm solution of algebraic equations, minimum energy control problems and linear quadratic optimal control problems with linear control and state constraints

    Iterative Solution of Constrained Differential/Algebraic Systems

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    The dynamics of a large class of engineering systems can be approximately described by coupled algebraic and differential equations of the form (e.g. see Appendix A.1

    The LD Adolescent and the Sat

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    School personnel can help LD students prepare for the SAT in a variety of ways.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/66543/2/10.1177_105345128502000402.pd

    Effect of gluon-exchange pair-currents on the ratio G(E(P))/G(M(P))

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    The effect of one-gluon-exchange (OGE) pair-currents on the ratio ÎŒpGEp/GMp\mu_p G_E^p/G_M^p for the proton is investigated within a nonrelativistic constituent quark model (CQM) starting from SU(6)×O(3)SU(6) \times O(3) nucleon wave functions, but with relativistic corrections. We found that the OGE pair-currents are important to reproduce well the ratio ÎŒpGEp/GMp\mu_p G_E^p/G_M^p. With the assumption that the OGE pair-currents are the driving mechanism for the violation of the scaling law we give a prediction for the ratio ÎŒnGEn/GMn\mu_n G_E^n/G_M^n of the neutron.Comment: 5 pages, 4 figure

    Evolution of active and polar photospheric magnetic fields during the rise of Cycle 24 compared to previous cycles

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    The evolution of the photospheric magnetic field during the declining phase and minimum of Cycle 23 and the recent rise of Cycle 24 are compared with the behavior during previous cycles. We used longitudinal full-disk magnetograms from the NSO's three magnetographs at Kitt Peak, the Synoptic Optical Long-term Investigations of the Sun (SOLIS) Vector Spectro-Magnetograph (VSM), the Spectromagnetograph and the 512-Channel Magnetograph instruments, and longitudinal full-disk magnetograms from the Mt. Wilson 150-foot tower. We analyzed 37 years of observations from these two observatories that have been observing daily, weather permitting, since 1974, offering an opportunity to study the evolving relationship between the active region and polar fields in some detail over several solar cycles. It is found that the annual averages of a proxy for the active region poloidal magnetic field strength, the magnetic field strength of the high-latitude poleward streams, and the time derivative of the polar field strength are all well correlated in each hemisphere. These results are based on statistically significant cyclical patterns in the active region fields and are consistent with the Babcock-Leighton phenomenological model for the solar activity cycle. There was more hemispheric asymmetry in the activity level, as measured by total and maximum active region flux, during late Cycle 23 (after around 2004), when the southern hemisphere was more active, and Cycle 24 up to the present, when the northern hemisphere has been more active, than at any other time since 1974. The active region net proxy poloidal fields effectively disappeared in both hemispheres around 2004, and the polar fields did not become significantly stronger after this time. We see evidence that the process of Cycle 24 field reversal has begun at both poles.Comment: Accepted for publication in Solar Physic
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