3,705 research outputs found
Velocity fluctuations and hydrodynamic diffusion in sedimentation
We study non-equilibrium velocity fluctuations in a model for the
sedimentation of non-Brownian particles experiencing long-range hydrodynamic
interactions. The complex behavior of these fluctuations, the outcome of the
collective dynamics of the particles, exhibits many of the features observed in
sedimentation experiments. In addition, our model predicts a final relaxation
to an anisotropic (hydrodynamic) diffusive state that could be observed in
experiments performed over longer time ranges.Comment: 7 pages, 5 EPS figures, EPL styl
The Politics of Municipal Incorporation in South Florida
In the past few years, more affluent unincorporated communities have chosen incorporation, particularly in South Florida. This Article addresses the recent incorporation phenomenon in Florida, examining the causes and effects of the movement. The first part of the Article provides background on the structure of Florida\u27s local government system. Additionally, the Article discusses the advantages of incorporation to Florida\u27s communities, explaining the impetus for this new trend. Next, the Article explores the revenue tax base erosion resulting from these recent incorporations and discusses other problems caused by the incorporation wave. Lastly, the Article presents potential options to assuage the incorporation crisis, examining the advantages and disadvantages of each of these proposals
Remote sensing applications in forestry. The development of an earth resources information system using aerial photographs and digital computers photographs and digital computers
Remote aerial sensing and automatic mapping for forest resources information syste
Self-assembly of the simple cubic lattice with an isotropic potential
Conventional wisdom presumes that low-coordinated crystal ground states
require directional interactions. Using our recently introduced optimization
procedure to achieve self-assembly of targeted structures (Phys. Rev. Lett. 95,
228301 (2005), Phys. Rev. E 73, 011406 (2006)), we present an isotropic pair
potential for a three-dimensional many-particle system whose classical
ground state is the low-coordinated simple cubic (SC) lattice. This result is
part of an ongoing pursuit by the authors to develop analytical and
computational tools to solve statistical-mechanical inverse problems for the
purpose of achieving targeted self-assembly. The purpose of these methods is to
design interparticle interactions that cause self-assembly of technologically
important target structures for applications in photonics, catalysis,
separation, sensors and electronics. We also show that standard approximate
integral-equation theories of the liquid state that utilize pair correlation
function information cannot be used in the reverse mode to predict the correct
simple cubic potential. We report in passing optimized isotropic potentials
that yield the body-centered cubic and simple hexagonal lattices, which provide
other examples of non-close-packed structures that can be assembled using
isotropic pair interactions.Comment: 16 pages, 12 figures. Accepted for publication in Physical Review
Contrasting abundance and residency patterns of two sympatric populations of transient killer whales (Orcinus orca) in the northern Gulf of Alaska
Two sympatric populations of “transient” (mammal-eating)
killer whales were photo-identified over 27 years (1984–2010) in Prince William Sound and Kenai Fjords, coastal waters of the northern Gulf of Alaska (GOA). A total of 88 individuals were identified during 203 encounters with “AT1” transients (22 individuals) and 91 encounters with “GOA” transients (66 individuals). The median number of individuals identified annually was similar for both populations (AT1=7; GOA=8), but mark-recapture estimates showed the AT1 whales to have much higher fidelity to the study area, whereas the GOA whales had a higher exchange of
individuals. Apparent survival estimates were generally high for both populations, but there was a significant
reduction in the survival of AT1 transients after the Exxon Valdez oil spill in 1989, with an abrupt decline in estimated abundance from a high of 22 in 1989 to a low of seven whales at the end of 2010. There was no detectable decline in GOA population abundance or survival over the same period, but abundance ranged from just 6 to 18 whales annually. Resighting data from adjacent coastal waters
and movement tracks from satellite tags further indicated that the GOA whales are part of a larger population with a more extensive range, whereas AT1 whales are resident to
the study area
An order parameter equation for the dynamic yield stress in dense colloidal suspensions
We study the dynamic yield stress in dense colloidal suspensions by analyzing
the time evolution of the pair distribution function for colloidal particles
interacting through a Lennard-Jones potential. We find that the equilibrium
pair distribution function is unstable with respect to a certain anisotropic
perturbation in the regime of low temperature and high density. By applying a
bifurcation analysis to a system near the critical state at which the stability
changes, we derive an amplitude equation for the critical mode. This equation
is analogous to order parameter equations used to describe phase transitions.
It is found that this amplitude equation describes the appearance of the
dynamic yield stress, and it gives a value of 2/3 for the shear thinning
exponent. This value is related to the mean field value of the critical
exponent in the Ising model.Comment: 8 pages, 2 figure
LONTalk as a Standard Protocol For Underwater Sensor Platforms
Proceedings IEEE, Oceans 97, Halifax, Oct. 1997 IEEE CD-ROM 0-7803-4111-
Recommended from our members
Dynamics of Post-Injection Fuel Flow in Mini-Sac Diesel Injectors Part 1: Admission of 1 External Gases and Implications for Deposit Formation
Samples of unadditized, middle distillate diesel fuel were injected through real-size optically accessible mini-sac diesel injectors into ambient air at common rail pressures of 250 bar and 350 bar respectively. High-resolution images of white light scattered from the internal mini-sac and nozzle flow were captured on a high-speed monochrome video camera. Following the end of each injection, the momentum-driven evacuation of fuel liquid from the mini-sac and nozzle holes resulted in the formation of a vapour cloud and bubbles in the mini-sac, and vapour capsules in the nozzle holes. This permitted external gas to gain entrance to the nozzle holes.
The diesel fuel in the mini-sac was observed to rotate with large initial vorticity, which decayed until the fuel became stationary. The diesel fuel remaining in the nozzle holes was observed to move inwards towards the mini-sac or outwards towards the nozzle exit in concert with the rotational flow in the mini-sac. The mini-sac bubbles’ internal pressure differences revealed that the bubbles must have contained previously dissolved oxygen and nitrogen. Under diesel engine operating conditions, this multi-phase mixture would be highly reactive and could initiate local pyrolysis and/or oxidation reactions. Finally, the dynamical behaviour of the diesel fuel in the nozzle holes would support the admission of external hot combustion gases into the nozzle holes, establishing the conditions for oxidation/pyrolysis reactions with surrounding liquid fuel films
Production of a Higgs pseudoscalar plus two jets in hadronic collisions
We consider the production of a Higgs pseudoscalar accompanied by two jets in
hadronic collisions. We work in the limit that the top quark is much heavier
than the Higgs pseudoscalar and use an effective Lagrangian for the
interactions of gluons with the pseudoscalar. We compute the amplitudes
involving: 1) four gluons and the pseudoscalar, 2) two quarks, two gluons and
the pseudoscalar and 3) four quarks and the pseudoscalar. We find that the
pseudoscalar amplitudes are nearly identical to those for the scalar case, the
only differences being the overall size and the relative signs between terms.
We present numerical cross sections for proton-proton collisions with
center-of-mass energy 14 TeV.Comment: 12 pages, LaTeX, 4 Postscript figures, submitted to Phys. Rev.
Quantifying the Reversible Association of Thermosensitive Nanoparticles
Under many conditions, biomolecules and nanoparticles associate by means of
attractive bonds, due to hydrophobic attraction. Extracting the microscopic
association or dissociation rates from experimental data is complicated by the
dissociation events and by the sensitivity of the binding force to temperature
(T). Here we introduce a theoretical model that combined with light-scattering
experiments allows us to quantify these rates and the reversible binding energy
as a function of T. We apply this method to the reversible aggregation of
thermoresponsive polystyrene/poly(N-isopropylacrylamide) core-shell
nanoparticles, as a model system for biomolecules. We find that the binding
energy changes sharply with T, and relate this remarkable switchable behavior
to the hydrophobic-hydrophilic transition of the thermosensitive nanoparticles
- …