602 research outputs found
Magnetic Quay water quality and sediment baseline study 1989
A study of water quality and water column sediment loads was carried out in
the period mid-December 1988 to mid-February 1989 on the south-east facing
fringing reefs of Magnetic Island. The study aimed at providing a baseline
before construction commenced on the marina/hotel development planned for
the northern end of Nelly Bay. Although it was realized that a complete
baseline, allowing for natural seasonal and meteorological variability,
could not be produced in two months, as much data as was logistically
possible to obtain ·was collected including data from periods of contrasting
weather conditions. An associated benthic biota and sedimentation study
provided a benthos baseline and measured sediment deposition in sediment
traps in the same areas
Radiation Damage of F8 Lead Glass with 20 MeV Electrons
Using a 20 MeV linear accelerator, we investigate the effects of
electromagnetic radiation on the optical transparency of F8 lead glass.
Specifically, we measure the change in attenuation length as a function of
radiation dose. Comparing our results to similar work that utilized a proton
beam, we conclude that F8 lead glass is more susceptible to proton damage than
electron damage.Comment: 5 pages, 6 figure
Sustainable utilization of inland water resources: an integrated program for research and management
In both developed and developing countries, there is increased competition for water resources, resulting in deficiencies in supply and in various forms of pollution. In developing countries, the nutritional potential of aquatic resources is very important. To realize this potential, integrated research and management for sustainable water resource use are needed. This requires a sound understanding of the structure and function of aquatic ecosystems. A programme is presented which stresses the interrelationships of the physical, chemical and biological components of aquatic systems and their catchments. The programme consists of 16 stages in 5 phases, which are as follows: System description; System functioning and modelling; Resource assessment/dynamics; Resource potential; and, Resource utilization for sustainability. This programme enables workers within different disciplines to identify how their expertise contributes to the overall research requirements to support resource development
Quasi-infra-red fixed points and renormalisation group invariant trajectories for non-holomorphic soft supersymmetry breaking
In the MSSM the quasi-infra-red fixed point for the top-quark Yukawa coupling
gives rise to specific predictions for the soft-breaking parameters. We discuss
the extent to which these predictions are modified by the introduction of
additional ``non-holomorphic'' soft-breaking terms. We also show that in a
specific class of theories there exists an RG-invariant trajectory for the
``non-holomorphic'' terms, which can be understood using a holomorphic spurion
term.Comment: 24 pages, TeX, two figures. Uses Harvmac (big) and epsf. Minor errors
corrected, and the RG trajectory explained in terms of a holomorphic spurion
ter
Effect of root systems on preferential flow in swelling soil
Permeability problems on irrigated soils may be alleviated by root
systems that increase water flow by creating macropores. Infiltration rates have been
shown to increase where plant roots decay and serve as preferential flow paths. For
low-organic-matter swelling soil, there is a question whether macropores are able to
resist the lateral swelling forces of the soil. The objective of this study was to observe
preferential water flow paths in a swelling soil under two cropping systems. A
Holtville silty clay (clayey-over-loamy, montmorillonitic Typic Torrifluvent) was
observed in situ. Two crops, alfalfa (Medicago saliva, L.) and wheat (Triticum
turgidum, L.) provided sharply contrasting root systems, with wheat possessing fine,
fibrous roots; alfalfa on the other hand, has a taproot system. Macropores were
observed after applying soil-adsorbing methylene blue dye to irrigation water.
Shrinkage cracks failed to conduct dye after 10 minutes into a flood irrigation.
Earthworm (Lubricus terrestris) channels were also not stable. However, decaying
roots of alfalfa produced stable macropores, while wheat produced no such
macropores. The influence of alfalfa-root-induced macropores was demonstrated by
the increase in final infiltration rate during alfalfa cropping which agreed with Meek
et al.'s (1989, 1990) findings on sandy loam soils
Frame-Independence of Exclusive Amplitudes in the Light-Front Quantization
While the particle-number-conserving convolution formalism established in the
Drell-Yan-West reference frame is frequently used to compute exclusive
amplitudes in the light-front quantization, this formalism is limited to only
those frames where the light-front helicities are not changed and the good
(plus) component of the current remains unmixed. For an explicit demonstration
of such criteria, we present the relations between the current matrix elements
in the two typical reference frames used for calculations of the exclusive
amplitudes, i.e. the Drell-Yan-West and Breit frames and investigate both
pseudoscalar and vector electromagnetic currents in detail. We find that the
light-front helicities are unchanged and the good component of the current does
not mix with the other components of the current under the transformation
between these two frames. Thus, the pseudoscalar and vector form factors
obtained by the diagonal convolution formalism in both frames must indeed be
identical. However, such coincidence between the Drell-Yan-West and Breit
frames does not hold in general. We give an explicit example in which the
light-front helicities are changed and the plus component of the current is
mixed with other components under the change of reference frame. In such a
case, the relationship between the frames should be carefully analyzed before
the established convolution formalism in the Drell-Yan-West frame is used.Comment: 14 pages, 4 figure
Reducing feed costs in semi-intensive finfish culture: an update on mixed feeding schedules and an idea for enhancing endogenous food supply in ponds
Some interesting ideas on improving the cost-effectiveness of feeding in semi-intensive finfish aquaculture are presented
Reducing feed costs in semi-intensive finfish culture: an update on mixed feeding schedules and an idea for enhancing endogenous food supply in ponds
Fish culture, Feed, Cost analysis, Feeding, Pond culture
Ab initio calculations for bromine adlayers on the Ag(100) and Au(100) surfaces: the c(2x2) structure
Ab initio total-energy density-functional methods with supercell models have
been employed to calculate the c(2x2) structure of the Br-adsorbed Ag(100) and
Au(100) surfaces. The atomic geometries of the surfaces and the preferred
bonding sites of the bromine have been determined. The bonding character of
bromine with the substrates has also been studied by analyzing the electronic
density of states and the charge transfer. The calculations show that while the
four-fold hollow-site configuration is more stable than the two-fold
bridge-site topology on the Ag(100) surface, bromine prefers the bridge site on
the Au(100) surface. The one-fold on-top configuration is the least stable
configuration on both surfaces. It is also observed that the second layer of
the Ag substrate undergoes a small buckling as a consequence of the adsorption
of Br. Our results provide a theoretical explanation for the experimental
observations that the adsorption of bromine on the Ag(100) and Au(100) surfaces
results in different bonding configurations.Comment: 10 pages, 4 figure, 5 tables, Phys. Rev. B, in pres
Universal Predictions for Statistical Nuclear Correlations
We explore the behavior of collective nuclear excitations under a
multi-parameter deformation of the Hamiltonian. The Hamiltonian matrix elements
have the form , with a
parametric correlation of the type . The studies are done in both the regular and chaotic regimes of the
Hamiltonian. Model independent predictions for a wide variety of correlation
functions and distributions which depend on wavefunctions and energies are
found from parametric random matrix theory and are compared to the nuclear
excitations. We find that our universal predictions are observed in the nuclear
states. Being a multi-parameter theory, we consider general paths in parameter
space and find that universality can be effected by the topology of the
parameter space. Specifically, Berry's phase can modify short distance
correlations, breaking certain universal predictions.Comment: Latex file + 12 postscript figure
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