24,995 research outputs found
Dependence of stress rupture and superplasticity on structure in Co-W alloys, part I
Dependence of stress rupture and superplasticity on structure in Co-W alloy
Observation of Single Transits in Supercooled Monatomic Liquids
A transit is the motion of a system from one many-particle potential energy
valley to another. We report the observation of transits in molecular dynamics
(MD) calculations of supercooled liquid argon and sodium. Each transit is a
correlated simultaneous shift in the equilibrium positions of a small local
group of particles, as revealed in the fluctuating graphs of the particle
coordinates versus time. This is the first reported direct observation of
transit motion in a monatomic liquid in thermal equilibrium. We found transits
involving 2 to 11 particles, having mean shift in equilibrium position on the
order of 0.4 R_1 in argon and 0.25 R_1 in sodium, where R_1 is the nearest
neighbor distance. The time it takes for a transit to occur is approximately
one mean vibrational period, confirming that transits are fast.Comment: 19 pages, 8 figure
Assessment of free-living nitrogen fixing microorganisms for commercial nitrogen fixation
Ammonia production by Klebsiella pneumoniae is not economical with present strains and improving nitrogen fixation to its theoretical limits in this organism is not sufficient to achieve economic viability. Because the value of both the hydrogen produced by this organism and the methane value of the carbon source required greatly exceed the value of the ammonia formed, ammonia (fixed nitrogen) should be considered the by-product. The production of hydrogen by KLEBSIELLA or other anaerobic nitrogen fixers should receive additional study, because the activity of nitrogenase offers a significant improvement in hydrogen production. The production of fixed nitrogen in the form of cell mass by Azotobacter is also uneconomical and the methane value of the carbon substrate exceeds the value of the nitrogen fixed. Parametric studies indicate that as efficiencies approach the theoretical limits the economics may become competitive. The use of nif-derepressed microorganisms, particularly blue-green algae, may have significant potential for in situ fertilization in the environment
Evidence Inference 2.0: More Data, Better Models
How do we most effectively treat a disease or condition? Ideally, we could
consult a database of evidence gleaned from clinical trials to answer such
questions. Unfortunately, no such database exists; clinical trial results are
instead disseminated primarily via lengthy natural language articles. Perusing
all such articles would be prohibitively time-consuming for healthcare
practitioners; they instead tend to depend on manually compiled systematic
reviews of medical literature to inform care.
NLP may speed this process up, and eventually facilitate immediate consult of
published evidence. The Evidence Inference dataset was recently released to
facilitate research toward this end. This task entails inferring the
comparative performance of two treatments, with respect to a given outcome,
from a particular article (describing a clinical trial) and identifying
supporting evidence. For instance: Does this article report that chemotherapy
performed better than surgery for five-year survival rates of operable cancers?
In this paper, we collect additional annotations to expand the Evidence
Inference dataset by 25\%, provide stronger baseline models, systematically
inspect the errors that these make, and probe dataset quality. We also release
an abstract only (as opposed to full-texts) version of the task for rapid model
prototyping. The updated corpus, documentation, and code for new baselines and
evaluations are available at http://evidence-inference.ebm-nlp.com/.Comment: Accepted as workshop paper into BioNLP Updated results from SciBERT
to Biomed RoBERT
Entanglement of internal and external angular momenta of a single atom
We consider the exchange of spin and orbital angular momenta between a
circularly polarized Laguerre-Gaussian beam of light and a single atom trapped
in a two-dimensional harmonic potential. The radiation field is treated
classically but the atomic center-of-mass motion is quantized. The spin and
orbital angular momenta of the field are individually conserved upon
absorption, and this results in the entanglement of the internal and external
degrees of freedom of the atom. We suggest applications of this entanglement in
quantum information processing.Comment: 4 pages, 2 figure
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