844 research outputs found
Marine Monitoring Program: Annual report for inshore seagrass monitoring 2015-2016
The Marine Monitoring Program (MMP) undertaken in the Great Barrier Reef (GBR) lagoon, assesses the long-term effectiveness of the Australian and Queensland Government’s Reef Water Quality Protection Plan (Reef Plan). The MMP, established in 2005, is a critical component in the paddock to reef monitoring modelling and reporting program (P2R) that tracks changes in regional water quality and its impact on the GBR as land management practices are improved across Reef catchments.
The inshore seagrass component of the MMP assessed seagrass abundance (per cent cover), community structure, relative meadow extent, reproductive health, and nutrient status from inshore seagrass meadows at 29 locations throughout the GBR. Sites were predominately lower littoral (only exposed to air at the lowest of low tides), hereafter referred to as intertidal, although four locations also included shallow subtidal meadows. Each of the Natural Resource Management regions (Cape York, Wet Tropics, Burdekin, Mackay Whitsunday, Fitzroy and Burnett Mary) were represented, including each of the major seagrass habitat types where possible (estuarine, coastal, reef, subtidal).
Environmental pressures are also recorded including within-canopy water temperature, canopy light, sediment composition as well as macroalgae and epiphyte abundance, further data obtained from the Australian Bureau of Meteorology and from the MMP inshore water quality subprogram
Marine Monitoring Program: Inshore seagrass, annual report for the sampling period 1st June 2013 - 31st May 2014
A key component of Reef Plan is the implementation of a long-term water quality and ecosystem monitoring program in the Great Barrier Reef lagoon. James Cook University were contracted to conduct the intertidal seagrass monitoring component and produce this report, which examines the status and trend of Reef intertidal seagrass (detect long-term trends in seagrass abundance, community structure, distribution, reproductive health, and nutrient status from representative inshore seagrass meadows) and identifies response of seagrass to environmental drivers of change
Generation of Long-Lived Isomeric States via Bremsstrahlung Irradiation
A method to generate long-lived isomeric states effectively for Mossbauer
applications is reported. We demonstrate that this method is better and easier
to provide highly sensitive Mossbauer effect of long-lived isomers (>1ms) such
as 103Rh. Excitation of (gamma,gamma) process by synchrotron radiation is
painful due mainly to their limited linewidth. Instead,(gamma,gamma') process
of bremsstrahlung excitation is applied to create these long-lived isomers.
Isomers of 45Sc, 107Ag, 109Ag, and 103Rh have been generated from this method.
Among them, 103Rh is the only one that we have obtained the gravitational
effect at room temperature.Comment: ICAME 05 conference repor
Current-carrying cosmic string loops 3D simulation: towards a reduction of the vorton excess problem
The dynamical evolution of superconducting cosmic string loops with specific
equations of state describing timelike and spacelike currents is studied
numerically. This analysis extends previous work in two directions: first it
shows results coming from a fully three dimensional simulation (as opposed to
the two dimensional case already studied), and it now includes fermionic as
well as bosonic currents. We confirm that in the case of bosonic currents,
shocks are formed in the magnetic regime and kinks in the electric regime. For
a loop endowed with a fermionic current with zero-mode carriers, we show that
only kinks form along the string worldsheet, therefore making these loops
slightly more stable against charge carrier radiation, the likely outcome of
either shocks or kinks. All these combined effects tend to reduce the number
density of stable loops and contribute to ease the vorton excess problem. As a
bonus, these effects also may provide new ways of producing high energy cosmic
rays.Comment: 11 pages, RevTeX 4 format, 8 figures, submitted to PR
Spinning Q-Balls
We present numerical evidence for the existence of spinning generalizations
for non-topological Q-ball solitons in the theory of a complex scalar field
with a non-renormalizable self-interaction. To the best of our knowledge, this
provides the first explicit example of spinning solitons in 3+1 dimensional
Minkowski space. In addition, we find an infinite discrete family of radial
excitations of non-rotating Q-balls, and construct also spinning Q-balls in 2+1
dimensions.Comment: To appear in Phys.Rev.
Topological Defects and CMB anisotropies : Are the predictions reliable ?
We consider a network of topological defects which can partly decay into
neutrinos, photons, baryons, or Cold Dark Matter. We find that the degree-scale
amplitude of the cosmic microwave background (CMB) anisotropies as well as the
shape of the matter power spectrum can be considerably modified when such a
decay is taken into account. We conclude that present predictions concerning
structure formation by defects might be unreliable.Comment: 14 pages, accepted for publication in PR
New hadrons as ultra-high energy cosmic rays
Ultra-high energy cosmic ray (UHECR) protons produced by uniformly
distributed astrophysical sources contradict the energy spectrum measured by
both the AGASA and HiRes experiments, assuming the small scale clustering of
UHECR observed by AGASA is caused by point-like sources. In that case, the
small number of sources leads to a sharp exponential cutoff at the energy
E<10^{20} eV in the UHECR spectrum. New hadrons with mass 1.5-3 GeV can solve
this cutoff problem. For the first time we discuss the production of such
hadrons in proton collisions with infrared/optical photons in astrophysical
sources. This production mechanism, in contrast to proton-proton collisions,
requires the acceleration of protons only to energies E<10^{21} eV. The diffuse
gamma-ray and neutrino fluxes in this model obey all existing experimental
limits. We predict large UHE neutrino fluxes well above the sensitivity of the
next generation of high-energy neutrino experiments. As an example we study
hadrons containing a light bottom squark. These models can be tested by
accelerator experiments, UHECR observatories and neutrino telescopes.Comment: 17 pages, revtex style; v2: shortened, as to appear in PR
Statistical Theory of Spin Relaxation and Diffusion in Solids
A comprehensive theoretical description is given for the spin relaxation and
diffusion in solids. The formulation is made in a general
statistical-mechanical way. The method of the nonequilibrium statistical
operator (NSO) developed by D. N. Zubarev is employed to analyze a relaxation
dynamics of a spin subsystem. Perturbation of this subsystem in solids may
produce a nonequilibrium state which is then relaxed to an equilibrium state
due to the interaction between the particles or with a thermal bath (lattice).
The generalized kinetic equations were derived previously for a system weakly
coupled to a thermal bath to elucidate the nature of transport and relaxation
processes. In this paper, these results are used to describe the relaxation and
diffusion of nuclear spins in solids. The aim is to formulate a successive and
coherent microscopic description of the nuclear magnetic relaxation and
diffusion in solids. The nuclear spin-lattice relaxation is considered and the
Gorter relation is derived. As an example, a theory of spin diffusion of the
nuclear magnetic moment in dilute alloys (like Cu-Mn) is developed. It is shown
that due to the dipolar interaction between host nuclear spins and impurity
spins, a nonuniform distribution in the host nuclear spin system will occur and
consequently the macroscopic relaxation time will be strongly determined by the
spin diffusion. The explicit expressions for the relaxation time in certain
physically relevant cases are given.Comment: 41 pages, 119 Refs. Corrected typos, added reference
Evidence for muon neutrino oscillation in an accelerator-based experiment
We present results for muon neutrino oscillation in the KEK to Kamioka (K2K)
long-baseline neutrino oscillation experiment. K2K uses an accelerator-produced
muon neutrino beam with a mean energy of 1.3 GeV directed at the
Super-Kamiokande detector. We observed the energy dependent disappearance of
muon neutrino, which we presume have oscillated to tau neutrino. The
probability that we would observe these results if there is no neutrino
oscillation is 0.0050% (4.0 sigma).Comment: 5 pages, 4 figure
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