448 research outputs found
The (p,d) Reaction at E_p=121 MeV
This work was supported by National Science Foundation Grant PHY 75-00289 and Indiana Universit
The (p,t) Reaction at Higher Energy
This work was supported by National Science Foundation Grant PHY 76-84033 and Indiana Universit
Spectroscopy of A=12 at High Excitation
Supported by the National Science Foundation and Indiana Universit
Angle-dependent normalization of neutron-proton differential cross sections
Systematic errors in the database of differential cross sections below
350 MeV are studied. By applying angle-dependent normalizations with the help
of the energy-dependent Nijmegen partial-wave analysis PWA93 the
-values of some seriously flawed data sets can be reduced significantly
at the expense of a few degrees of freedom. It turns out that in these special
cases the renormalized data sets can be made statistically acceptable such that
they do not have to be discarded any longer in partial-wave analyses of the
two-nucleon scattering data.Comment: 11 pages, 1 figure; expanded versio
Self-consistent description of nuclear compressional modes
Isoscalar monopole and dipole compressional modes are computed for a variety
of closed-shell nuclei in a relativistic random-phase approximation to three
different parametrizations of the Walecka model with scalar self-interactions.
Particular emphasis is placed on the role of self-consistency which by itself,
and with little else, guarantees the decoupling of the spurious
isoscalar-dipole strength from the physical response and the conservation of
the vector current. A powerful new relation is introduced to quantify the
violation of the vector current in terms of various ground-state form-factors.
For the isoscalar-dipole mode two distinct regions are clearly identified: (i)
a high-energy component that is sensitive to the size of the nucleus and scales
with the compressibility of the model and (ii) a low-energy component that is
insensitivity to the nuclear compressibility. A fairly good description of both
compressional modes is obtained by using a ``soft'' parametrization having a
compression modulus of K=224 MeV.Comment: 28 pages and 10 figures; submitted to PR
The ^4He trimer as an Efimov system
We review the results obtained in the last four decades which demonstrate the
Efimov nature of the He three-atomic system.Comment: Review article for a special issue of the Few-Body Systems journal
devoted to Efimov physic
A dynamic neural field approach to natural and efficient human-robot collaboration
A major challenge in modern robotics is the design of autonomous robots
that are able to cooperate with people in their daily tasks in a human-like way. We
address the challenge of natural human-robot interactions by using the theoretical
framework of dynamic neural fields (DNFs) to develop processing architectures that
are based on neuro-cognitive mechanisms supporting human joint action. By explaining
the emergence of self-stabilized activity in neuronal populations, dynamic
field theory provides a systematic way to endow a robot with crucial cognitive functions
such as working memory, prediction and decision making . The DNF architecture
for joint action is organized as a large scale network of reciprocally connected
neuronal populations that encode in their firing patterns specific motor behaviors,
action goals, contextual cues and shared task knowledge. Ultimately, it implements
a context-dependent mapping from observed actions of the human onto adequate
complementary behaviors that takes into account the inferred goal of the co-actor.
We present results of flexible and fluent human-robot cooperation in a task in which
the team has to assemble a toy object from its components.The present research was conducted in the context of the fp6-IST2 EU-IP
Project JAST (proj. nr. 003747) and partly financed by the FCT grants POCI/V.5/A0119/2005 and
CONC-REEQ/17/2001. We would like to thank Luis Louro, Emanuel Sousa, Flora Ferreira, Eliana
Costa e Silva, Rui Silva and Toni Machado for their assistance during the robotic experiment
Shrinking a large dataset to identify variables associated with increased risk of Plasmodium falciparum infection in Western Kenya
Large datasets are often not amenable to analysis using traditional single-step approaches. Here, our general objective was to apply imputation techniques, principal component analysis (PCA), elastic net and generalized linear models to a large dataset in a systematic approach to extract the most meaningful predictors for a health outcome. We extracted predictors for Plasmodium falciparum infection, from a large covariate dataset while facing limited numbers of observations, using data from the People, Animals, and their Zoonoses (PAZ) project to demonstrate these techniques: data collected from 415 homesteads in western Kenya, contained over 1500 variables that describe the health, environment, and social factors of the humans, livestock, and the homesteads in which they reside. The wide, sparse dataset was simplified to 42 predictors of P. falciparum malaria infection and wealth rankings were produced for all homesteads. The 42 predictors make biological sense and are supported by previous studies. This systematic data-mining approach we used would make many large datasets more manageable and informative for decision-making processes and health policy prioritization
Global Search for New Physics with 2.0/fb at CDF
Data collected in Run II of the Fermilab Tevatron are searched for
indications of new electroweak-scale physics. Rather than focusing on
particular new physics scenarios, CDF data are analyzed for discrepancies with
the standard model prediction. A model-independent approach (Vista) considers
gross features of the data, and is sensitive to new large cross-section
physics. Further sensitivity to new physics is provided by two additional
algorithms: a Bump Hunter searches invariant mass distributions for "bumps"
that could indicate resonant production of new particles; and the Sleuth
procedure scans for data excesses at large summed transverse momentum. This
combined global search for new physics in 2.0/fb of ppbar collisions at
sqrt(s)=1.96 TeV reveals no indication of physics beyond the standard model.Comment: 8 pages, 7 figures. Final version which appeared in Physical Review D
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