1,244 research outputs found
Numerical Evidence for Divergent Burnett Coefficients
In previous papers [Phys. Rev. A {\bf 41}, 4501 (1990), Phys. Rev. E {\bf
18}, 3178 (1993)], simple equilibrium expressions were obtained for nonlinear
Burnett coefficients. A preliminary calculation of a 32 particle Lennard-Jones
fluid was presented in the previous paper. Now, sufficient resources have
become available to address the question of whether nonlinear Burnett
coefficients are finite for soft spheres. The hard sphere case is known to have
infinite nonlinear Burnett coefficients (ie a nonanalytic constitutive
relation) from mode coupling theory. This paper reports a molecular dynamics
caclulation of the third order nonlinear Burnett coefficient of a Lennard-Jones
fluid undergoing colour flow, which indicates that this term is diverges in the
thermodynamic limit.Comment: 12 pages, 9 figure
The influence of ridge geometry at the ultraslow-spreading Southwest Indian Ridge (9º-25ºE) : basalt composition sensitivity to variations in source and process
Submitted in partial fulfillment of the requirements for the degree of
Doctor of Philosophy at the Massachusetts Institute of Technology
and the Woods Hole Oceanographic Institution February 2006Between 9º-25º E on the ultraslow-spreading Southwest Indian Ridge lie two sharply
contrasting supersegments. One 630 km long supersegment erupts N-MORB that is
progressively enriched in incompatible element concentrations from east to west. The
second 400 km long supersegment contains three separate volcanic centers erupting EMORB
and connected by long amagmatic accretionary segments, where mantle is
emplaced directly to the seafloor with only scattered N-MORB and E-MORB erupted.
Rather than a major break in mantle composition at the discontinuity between the
supersegments, this sharp contrast in geometry, physiography, and chemistry reflects
“source” versus “process” dominated generation of basalt.
Robust along-axis correlation of ridge characteristics (i.e. morphology, upwelling rate,
lithospheric thickness), basalt chemistry, and crustal thickness (estimated from gravity)
provides a unique opportunity to compare the influence of spreading geometry and rate
on MORB generation. What had not been well established until now is the importance of
melting processes rather than source at spreading rates < 20 mm/yr. Along the
orthogonally spreading supersegment (14 mm/yr) moderate degrees of partial melting
effectively sample the bulk mantle source, while on the obliquely spreading
supersegment (7-14 mm/yr) suppression of mantle melting to low degrees means that the
bulk source is not uniformly sampled, and thus “process” rather than “source” dominates
melt chemistry.The main
body of work consisting of major element, trace element, and isotopic data acquisition
and interpretation (Chapter 2 & 3) was funded by H. Dick’s grant from the National
Science Foundation-OCE 9907630. National Science Foundation-OCE 0137325
supported the U-series work described in Chapter 4. The published work of Chapter 5
was funded by National Science Foundation-EAR 9804891, NSF-OCE 9416620, and
NSF-OCE 0096634
Statistics of Certain Models of Evolution
In a recent paper, Newman surveys the literature on power law spectra in
evolution, self-organised criticality and presents a model of his own to arrive
at a conclusion that self-organised criticality is not necessary for evolution.
Not only did he miss a key model (Ecolab) that has a clear self-organised
critical mechanism, but also Newman's model exhibits the same mechanism that
gives rise to power law behaviour as does Ecolab. Newman's model is, in fact, a
``mean field'' approximation of a self-organised critical system. In this
paper, I have also implemented Newman's model using the Ecolab software,
removing the restriction that the number of species remains constant. It turns
out that the requirement of constant species number is non-trivial, leading to
a global coupling between species that is similar in effect to the species
interactions seen in Ecolab. In fact, the model must self-organise to a state
where the long time average of speciations balances that of the extinctions,
otherwise the system either collapses or explodes. In view of this, Newman's
model does not provide the hoped-for counter example to the presence of
self-organised criticality in evolution, but does provide a simple, almost
analytic model that can used to understand more intricate models such as
Ecolab.Comment: accepted in Phys Rev E.; RevTeX; See
http://parallel.hpc.unsw.edu.au/rks/ecolab.html for more informatio
Bound on the Dark Matter Density in the Solar System from Planetary Motions
High precision planet orbital data extracted from direct observation,
spacecraft explorations and laser ranging techniques enable to put a strong
constraint on the maximal dark matter density of a spherical halo centered
around the Sun. The maximal density at Earth's location is of the order
and shows only a mild dependence on the slope of the halo
profile, taken between 0 and -2. This bound is somewhat better than that
obtained from the perihelion precession limits.Comment: 7 pages, 1 figur
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The septum and behavior : an experimental analysis of functional anatomy.
PsychologyDoctor of Philosophy (PhD
The motion of a satellite of the moon
Analytical solution for motion of lunar orbital satellit
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Septal lesion-induced hyper-reactivity anatomical and neurochemical aspects.
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Applied phosphorus has long-term impacts on vegetation responses in restored jarrah forest
Nutrient enrichment can result in long-term negative impacts on a range of native and semi-native plant communities worldwide. Despite this knowledge, fertiliser application is generally viewed as a necessary step in re-establishing native plant communities in post-mining restoration. However, long-term effects of nutrient addition to restored plant communities, particularly in native ecosystems that are adapted to inherently low-nutrient soils, have received little attention. Here we report results of two experiments run for 15 and 20 years, respectively, to investigate the effect of applied P fertiliser on responses of Eucalyptus marginata (jarrah) forest re-sprouter understorey species in sites restored after bauxite mining in Western Australia. Re-sprouter species are abundant in unmined forest but are under-represented in restored sites. At the end of the two experiments (i.e. after 15 and 20 years), the abundance of three groups of re-sprouter understorey species was reduced, compared with the zero-fertiliser treatment, when P fertiliser was applied at rates from 20 to 120 kg P ha-1. In both experiments, the cover associated with P responsive legumes increased with increasing P application rates. This result suggests that when fertiliser is applied, slow-growing re-sprouter species are susceptible to being outcompeted by more vigorous understorey species. Consequently, if the goal of restoration is to re-establish a diverse plant community, then minimising fertiliser application rates may be appropriate
Genome-wide analysis of acute low salinity tolerance in the eastern oyster Crassostrea virginica and potential of genomic selection for trait improvement
As the global demand for seafood increases, research into the genetic basis of traits that can increase aquaculture production is critical. The eastern oyster (Crassostrea virginica) is an important aquaculture species along the Atlantic and Gulf Coasts of the United States, but increases in heavy rainfall events expose oysters to acute low salinity conditions, which negatively impact production. Low salinity survival is known to be a moderately heritable trait, but the genetic architecture underlying this trait is still poorly understood. In this study, we used ddRAD sequencing to generate genome-wide single-nucleotide polymorphism (SNP) data for four F2 families to investigate the genomic regions associated with survival in extreme low salinity (\u3c3). SNP data were also used to assess the feasibility of genomic selection (GS) for improving this trait. Quantitative trait locus (QTL) mapping and combined linkage disequilibrium analysis revealed significant QTL on eastern oyster chromosomes 1 and 7 underlying both survival and day to death in a 36-day experimental challenge. Significant QTL were located in genes related to DNA/RNA function and repair, ion binding and membrane transport, and general response to stress. GS was investigated using Bayesian linear regression models and prediction accuracies ranged from 0.48 to 0.57. Genomic prediction accuracies were largest using the BayesB prior and prediction accuracies did not substantially decrease when SNPs located within the QTL region on Chr1 were removed, suggesting that this trait is controlled by many genes of small effect. Our results suggest that GS will likely be a viable option for improvement of survival in extreme low salinity
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