39,558 research outputs found
Rotational correlation and dynamic heterogeneity in a kinetically constrained lattice gas
We study dynamical heterogeneity and glassy dynamics in a kinetically
constrained lattice gas model which has both translational and rotational
degrees of freedom. We find that the rotational diffusion constant tracks the
structural relaxation time as density is increased whereas the translational
diffusion constant exhibits a strong decoupling. We investigate distributions
of exchange and persistence times for both the rotational and translational
degrees of freedom and compare our results on the distributions of rotational
exchange times to recent single molecule studies.Comment: 7 pages, 5 figure
The low-mass population of the Rho Ophiuchi molecular cloud
Star formation theories are currently divergent regarding the fundamental
physical processes that dominate the substellar regime. Observations of nearby
young open clusters allow the brown dwarf (BD) population to be characterised
down to the planetary mass regime, which ultimately must be accommodated by a
successful theory. We hope to uncover the low-mass population of the Rho
Ophiuchi molecular cloud and investigate the properties of the newly found
brown dwarfs. We use near-IR deep images (reaching completeness limits of
approximately 20.5 mag in J, and 18.9 mag in H and Ks) taken with the Wide
Field IR Camera (WIRCam) at the Canada France Hawaii Telescope (CFHT) to
identify candidate members of Rho Oph in the substellar regime. A spectroscopic
follow-up of a small sample of the candidates allows us to assess their
spectral type, and subsequently their temperature and membership. We select 110
candidate members of the Rho Ophiuchi molecular cloud, from which 80 have not
previously been associated with the cloud. We observed a small sample of these
and spectroscopically confirm six new brown dwarfs with spectral types ranging
from M6.5 to M8.25
POTENTIAL EFFECTS OF TECHNOLOGICAL ADVANCES IN TRANSPORTATION ON THE TRADE OF FOOD PRODUCTS BETWEEN THE U.S. AND LATIN AMERICA
International Relations/Trade, Research and Development/Tech Change/Emerging Technologies,
A PRELIMINARY ECONOMIC ASSESSMENT OF ROUNDUP READY SOYBEANS IN MISSISSIPPI
The advent of genetically altered seed has had a revolutionary effect on the cotton, soybean, and corn seed industries. The basic premise for the use of these seed are to reduce costs through lower applications of chemicals and savings on trips through the field, thus, lowering production costs. Seed companies, however, charge a premium and a fee for use of the seed. This paper compares the costs associated with conventional and roundup ready soybeans. Data were collected from the ACost of Production@ survey of Mississippi producers that is administered by Mississippi State University through the National Agricultural Statistics Service. The survey is a random sample of producers fields that allows for a derivation of the cost of production for each field. The study suggests that while costs reductions can be achieved, the cost savings are offset by the technology fees. The study is based on limited data and points to the need for continued research on the long-run profitability of genetically altered seed to the soybean producers of Mississippi.soybeans, genetically altered seed, roundup ready, costs of production, Production Economics,
Stress-stabilized sub-isostatic fiber networks in a rope-like limit
The mechanics of disordered fibrous networks such as those that make up the
extracellular matrix are strongly dependent on the local connectivity or
coordination number. For biopolymer networks this coordination number is
typically between three and four. Such networks are sub-isostatic and linearly
unstable to deformation with only central force interactions, but exhibit a
mechanical phase transition between floppy and rigid states under strain.
Introducing weak bending interactions stabilizes these networks and suppresses
the critical signatures of this transition. We show that applying external
stress can also stabilize sub-isostatic networks with only tensile central
force interactions, i.e., a rope-like potential. Moreover, we find that the
linear shear modulus shows a power law scaling with the external normal stress,
with a non-mean-field exponent. For networks with finite bending rigidity, we
find that the critical stain shifts to lower values under prestress
Results from the LSND Neutrino Oscillation Search
The Liquid Scintillator Neutrino Detector (LSND) at the Los Alamos Meson
Physics Facility sets bounds on neutrino oscillations in the appearance channel
nu_mu_bar --> nu_e_bar by searching for the signature of the reaction nu_e_bar
p --> e^+ n: an e followed by a 2.2MeV gamma ray from neutron capture. Five
e^{+/-} -- gamma coincidences are observed in time with the LAMPF beam, with an
estimated background of 6.2 events. The 90\% confidence limits obtained are:
Delta (m^2) < 0.07eV^2 for sin^2 (2theta) = 1, and sin^2(2theta) < 6 10^{-3}
for Delta (m^2) > 20 eV^2.Comment: 10 pages, uses REVTeX and epsf macro
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