6,844 research outputs found
Market and Welfare Effects of Livestock Feed Subsidies
Agricultural and Food Policy, Livestock Production/Industries,
Accelerated molecular dynamics simulation of low-velocity frictional sliding
Accelerated molecular dynamics (MD) simulations are implemented to model the
sliding process of AFM experiments at speeds close to those found in
experiment. In this study the hyperdynamics method, originally devised to
extend MD time scales for non-driven systems, is applied to the frictional
sliding system. This technique is combined with a parallel algorithm that
simultaneously simulates the system over a range of slider positions. The new
methodologies are tested using 2-dimensional and 3-dimensional Lennard-Jones
AFM models. Direct comparison with the results from conventional MD shows close
agreement validating the methods.Comment: 26 pages with 13 figure
Dynamic instabilities of fracture under biaxial strain using a phase field model
We present a phase field model of the propagation of fracture under plane
strain. This model, based on simple physical considerations, is able to
accurately reproduce the different behavior of cracks (the principle of local
symmetry, the Griffith and Irwin criteria, and mode-I branching). In addition,
we test our model against recent experimental findings showing the presence of
oscillating cracks under bi-axial load. Our model again reproduces well
observed supercritical Hopf bifurcation, and is therefore the first simulation
which does so
Distinct Signatures For Coulomb Blockade and Aharonov-Bohm Interference in Electronic Fabry-Perot Interferometers
Two distinct types of magnetoresistance oscillations are observed in two
electronic Fabry-Perot interferometers of different sizes in the integer
quantum Hall regime. Measuring these oscillations as a function of magnetic
field and gate voltages, we observe three signatures that distinguish the two
types. The oscillations observed in a 2.0 square micron device are understood
to arise from the Coulomb blockade mechanism, and those observed in an 18
square micron device from the Aharonov-Bohm mechanism. This work clarifies,
provides ways to distinguish, and demonstrates control over, these distinct
physical origins of resistance oscillations seen in electronic Fabry-Perot
interferometers.Comment: related papers at http://marcuslab.harvard.ed
TRUMPS SOCIAL MEDIA – THE FIRST 100 DAYS OF HIS PRESIDENCY: A CONTENT ANALYSIS
More than any time in history technology allows politicians to directly reach large audiences to increase interaction. Modern social media permits information to be more accessible, direct, and permanent. Politicians can address audiences more frequently and directly through mobile devices - a tactic which creates a perception of immediacy unseen in past political climates. Specifically, Twitter grants unfiltered communication with users, while bypassing established mainstream media. The use of Twitter politically was first revolutionized by Barak Obama. Donald Trump’s use of Twitter has elevated this social media platform to an unheard-of level. A content analysis was conducted on President Donald Trump’s Tweets from his first 100 days in office. The results indicate that the majority of these Tweets can be separated into the Burkeian categories of Identity and Division. A discussion of the substance of these Tweets, the political use of social media, and specifically President Trump’s embracing of Twitter ensues
Enhancing the Understanding of Anatomy Through the Coloration and Plastination of Anatomical Specimens
Articlehttp://deepblue.lib.umich.edu/bitstream/2027.42/96980/1/UMURF-Issue05_2008-AMarchese.pd
Elastic effects on relaxation volume tensor calculations
Relaxation volume tensors quantify the effect of stress on diffusion of
crystal defects. Continuum linear elasticity predicts that calculations of
these parameters using periodic boundary conditions do not suffer from
systematic deviations due to elastic image effects and should be independent of
supercell size or symmetry. In practice, however, calculations of formation
volume tensors of the interstitial in Stillinger-Weber silicon
demonstrate that changes in bonding at the defect affect the elastic moduli and
result in system-size dependent relaxation volumes. These vary with the inverse
of the system size. Knowing the rate of convergence permits accurate estimates
of these quantities from modestly sized calculations. Furthermore, within the
continuum linear elasticity assumptions the average stress can be used to
estimate the relaxation volume tensor from constant volume calculations.Comment: 31 pages, 6 figures, submitted to Phys. Rev.
Resistance of crucifers to root maggot complex, Delia spp. (Diptera: Anthomyiidae)
Non-Peer ReviewedIn field tests conducted at Saskatoon, Melfort, Scott, and Shellbrook, crucifer species differed in their levels of damage from crucifer-feeding root maggots of the Delia species complex. Sinapis alba was less injured than B. carinata, B. rapa, B. juncea, or B. napus. Root diameter may play a part in this difference in susceptibility. Differences in root injury levels within species occurred frequently, but were less consistent than among species. Location and year strongly influenced maggot infestation and damage levels
Threshold effects in excited charmed baryon decays
Motivated by recent results on charmed baryons from CLEO and FOCUS, we
reexamine the couplings of the orbitally excited charmed baryons. Due to its
proximity to the [Sigma_c pi] threshold, the strong decays of the
Lambda_c(2593) are sensitive to finite width effects. This distorts the shape
of the invariant mass spectrum in Lambda_{c1}-> Lambda_c pi^+pi^- from a simple
Breit-Wigner resonance, which has implications for the experimental extraction
of the Lambda_c(2593) mass and couplings. We perform a fit to unpublished CLEO
data which gives M(Lambda_c(2593)) - M(Lambda_c) = 305.6 +- 0.3 MeV and h2^2 =
0.24^{+0.23}_{-0.11}, with h2 the Lambda_{c1}-> Sigma_c pi strong coupling in
the chiral Lagrangian. We also comment on the new orbitally excited states
recently observed by CLEO.Comment: 9 pages, 3 figure
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