3,065 research outputs found
The context of the Local Volume: structures and motions in the nearby universe
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
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 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
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
[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
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.
âBoundary formationsâ 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 âboundary formationâ, 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
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
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
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))
The effect of one-gluon-exchange (OGE) pair-currents on the ratio for the proton is investigated within a nonrelativistic
constituent quark model (CQM) starting from nucleon wave
functions, but with relativistic corrections. We found that the OGE
pair-currents are important to reproduce well the ratio .
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 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
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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