26,898 research outputs found
Reply to the comment by Jacobs and Thorpe
Reply to a comment on "Infinite-Cluster geometry in central-force networks",
PRL 78 (1997), 1480. A discussion about the order of the rigidity percolation
transition.Comment: 1 page revTe
Integrating Research Data Management into Geographical Information Systems
Ocean modelling requires the production of high-fidelity computational meshes
upon which to solve the equations of motion. The production of such meshes by
hand is often infeasible, considering the complexity of the bathymetry and
coastlines. The use of Geographical Information Systems (GIS) is therefore a
key component to discretising the region of interest and producing a mesh
appropriate to resolve the dynamics. However, all data associated with the
production of a mesh must be provided in order to contribute to the overall
recomputability of the subsequent simulation. This work presents the
integration of research data management in QMesh, a tool for generating meshes
using GIS. The tool uses the PyRDM library to provide a quick and easy way for
scientists to publish meshes, and all data required to regenerate them, to
persistent online repositories. These repositories are assigned unique
identifiers to enable proper citation of the meshes in journal articles.Comment: Accepted, camera-ready version. To appear in the Proceedings of the
5th International Workshop on Semantic Digital Archives
(http://sda2015.dke-research.de/), held in Pozna\'n, Poland on 18 September
2015 as part of the 19th International Conference on Theory and Practice of
Digital Libraries (http://tpdl2015.info/
Passive propellant system
The system utilizes a spherical tank structure A separated into two equal volume compartments by a flat bulkhead B. Each compartment has four similar gallery channel legs located in the principal vehicle axes, ensuring that bulk propellant will contact at least one gallery leg during vehicle maneuvers. The forward compartment gallery channel legs collect propellant and feed it into the aft compartment through communication screens which protrude into the aft compartment. The propellant is then collected by the screened gallery channels in the aft compartment and supplied to the propellant outlet. The invention resides in the independent gallery assembly and screen structure by means of which propellant flow from forward to aft compartments is maintained. Liquid surface tension of the liquid on the screens is used to control liquid flow. The system provides gas-free propellants in low or zero-g environments regardless of axial accelerations and propellant orientation in bulk regions of the vessel
Extended symmetrical classical electrodynamics
In the present article, we discuss a modification of classical
electrodynamics in which ``ordinary'' point charges are absent. The modified
equations contain additional terms describing the induced charges and currents.
The densities of the induced charges and currents depend on the vector k and
the vectors of the electromagnetic field E and B. It is shown that the vectors
E and B can be defined in terms of two 4-potentials and the components of k are
the components of the 4-tensor of the third rank. The Lagrangian of modified
electrodynamics is defined. The conditions are derived at which only one
4-potential determines the behavior of the electromagnetic field. It is also
shown that static modified electrodynamics can describe the electromagnetic
field in the inner region of the electric monopole. In the outer region of the
electric monopole the electric field is governed by the Maxwell equations. It
follows from boundary conditions at the interface between the inner and outer
regions of the monopole that the vector k has a discrete spectrum. The electric
and magnetic fields, energy and angular momentum of the monopole are found for
different eigenvalues of k
A Monte Carlo Method for Modeling Thermal Damping: Beyond the Brownian-Motion Master Equation
The "standard" Brownian motion master equation, used to describe thermal
damping, is not completely positive, and does not admit a Monte Carlo method,
important in numerical simulations. To eliminate both these problems one must
add a term that generates additional position diffusion. He we show that one
can obtain a completely positive simple quantum Brownian motion, efficiently
solvable, without any extra diffusion. This is achieved by using a stochastic
Schroedinger equation (SSE), closely analogous to Langevin's equation, that has
no equivalent Markovian master equation. Considering a specific example, we
show that this SSE is sensitive to nonlinearities in situations in which the
master equation is not, and may therefore be a better model of damping for
nonlinear systems.Comment: 6 pages, revtex4. v2: numerical results for a nonlinear syste
Thermal noise influences fluid flow in thin films during spinodal dewetting
Experiments on dewetting thin polymer films confirm the theoretical
prediction that thermal noise can strongly influence characteristic time-scales
of fluid flow and cause coarsening of typical length scales. Comparing the
experiments with deterministic simulations, we show that the Navier-Stokes
equation has to be extended by a conserved bulk noise term to accomplish the
observed spectrum of capillary waves. Due to thermal fluctuations the spectrum
changes from an exponential to a power law decay for large wavevectors. Also
the time evolution of the typical wavevector of unstable perturbations exhibits
noise induced coarsening that is absent in deterministic hydrodynamic flow.Comment: 4 pages, 3 figure
Dental Professionals in Non-Dental Settings
This report focuses on nine oral health innovations seeking to increase access to preventive oral health care in nondental settings. Two additional reports in this series describe the remaining programs that provide care in dental settings and care to young children. The nine innovations described here integrate service delivery and workforce models in order to reduce or eliminate socioeconomic, geographic, and cultural barriers to care. Although the programs are diverse in their approaches as well as in the specific characteristics of the communities they serve, a common factor among them is the implementation of multiple strategies to increase the number of children from low-income families who access preventive care, and also to engage families and communities in investing in and prioritizing oral health. For low-income children and their families, the barriers that must be addressed to increase access to preventive oral health care are numerous. For example, even children covered by public insurance programs face a shortage of dentists that accept Medicaid and who specialize in pediatric dentistry. The effects of poverty intersect with other barriers such as living in remote geographic areas and having a community-wide history of poor access to dental care in populations such as recent immigrants. Overcoming these barriers requires creative strategies that address transportation barriers, establish welcoming environments for oral health care, and are linguistically and culturally relevant. Each of these nine programs is based on such strategies, including:-Expanding the dental workforce through training new types of providers or adding new providers to the workforce toincrease reach and community presence;-Implementing new strategies to increase the cost-effectiveness of care so that more oral health care services are available and accessible;-Providing training and technical assistance that increase opportunities for and competence in delivering oral health education and care to children;-Offering oral health care services in existing, familiar community venues such as schools, Head Start programs and senior centers;-Developing creative service delivery models that address transportation and cultural barriers as well as the fear and stigma associated with dental care that may arise in communities with historically poor access.The findings from the EAs of these programs are synthesized to highlight diverse and innovative strategies for overcoming barriers to access. These strategies have potential for rigorous evaluation and could emerge as best practices. If proven effective, these innovative program elements could then be disseminated and replicated to increase access for populations in need of preventive oral health care
Quantum simulation of multiple-exciton generation in a nanocrystal by a single photon
We have shown theoretically that efficient multiple exciton generation (MEG)
by a single photon can be observed in small nanocrystals (NCs). Our quantum
simulations that include hundreds of thousands of exciton and multi-exciton
states demonstrate that the complex time-dependent dynamics of these states in
a closed electronic system yields a saturated MEG effect on a picosecond
timescale. Including phonon relaxation confirms that efficient MEG requires the
exciton--biexciton coupling time to be faster than exciton relaxation time
Gravitational Waves in Bianchi Type-I Universes I: The Classical Theory
The propagation of classical gravitational waves in Bianchi Type-I universes
is studied. We find that gravitational waves in Bianchi Type-I universes are
not equivalent to two minimally coupled massless scalar fields as it is for the
Robertson-Walker universe. Due to its tensorial nature, the gravitational wave
is much more sensitive to the anisotropy of the spacetime than the scalar field
is and it gains an effective mass term. Moreover, we find a coupling between
the two polarization states of the gravitational wave which is also not present
in the Robertson-Walker universe.Comment: 34 papers, written in ReVTeX, submitted to Physical Review
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