234 research outputs found
Solution of Divertor Magnetohydrodynamic Equilibria for the Study of Alpha Particle Edge Transport in Fusion Plasmas
Removal of thermalized alpha particles from deuterium- tritium (D-T) fusion plasmas can be accomplished through the use of divertor magnetic fields if the magnetohydrodynamic (MHD) equilibria is well understood [1]. Modifying a MHD variational energy principle for poloidal flux surfaces described by = (Ï, Ξ) results in an inverse Fourier representation of the three-dimensional (3-D) equilibria solution. Application of the = (Ï, Ξ) flux profile allows transformation of the magnetic field into a non-singular coordinate system along the divertor separatrix [2] and therefore, analysis of different divertor schemes. Derivation of the coupled, non-linear differential equations follows [5] except in the contravariant representation of the magnetic field. Theoretical background, formulation of the variational principle, benchmark results, and preliminary computations are presented
Subdiffusive transport in intergranular lanes on the Sun. The Leighton model revisited
In this paper we consider a random motion of magnetic bright points (MBP)
associated with magnetic fields at the solar photosphere. The MBP transport in
the short time range [0-20 minutes] has a subdiffusive character as the
magnetic flux tends to accumulate at sinks of the flow field. Such a behavior
can be rigorously described in the framework of a continuous time random walk
leading to the fractional Fokker-Planck dynamics. This formalism, applied for
the analysis of the solar subdiffusion of magnetic fields, generalizes the
Leighton's model.Comment: 7 page
Particle-in-cell Simulations of Ion Dynamics in a Pinched-beam Diode
article-in-cell simulations of a 1.6âMV, 800âkA, and 50âns pinched-beam diode have been completed with emphasis placed on the quality of the ion beams produced. Simulations show the formation of multiple regions in the electron beam flow characterized by locally high charge and current density (âhot spotsâ). As ions flow through the electron-space-charge cloud, these hot spots electrostatically attract ions to produce a non-uniform ion current distribution. The length of the cavity extending beyond the anode-to-cathode gap (i.e., behind the cathode tip) influences both the number and amplitude of hot spots. A longer cavity length increases the number of hot spots yet significantly reduces the amplitude producing a smoother, more uniform ion beam than for shorter cavities. The net current and the ion bending angles are also significantly smaller with long cavities
Combined In Silico, In Vivo, and In Vitro Studies Shed Insights into the Acute Inflammatory Response in Middle-Aged Mice
We combined in silico, in vivo, and in vitro studies to gain insights into age-dependent changes in acute inflammation in response to bacterial endotoxin (LPS). Time-course cytokine, chemokine, and NO2-/NO3- data from "middle-aged" (6-8 months old) C57BL/6 mice were used to re-parameterize a mechanistic mathematical model of acute inflammation originally calibrated for "young" (2-3 months old) mice. These studies suggested that macrophages from middle-aged mice are more susceptible to cell death, as well as producing higher levels of pro-inflammatory cytokines, vs. macrophages from young mice. In support of the in silico-derived hypotheses, resident peritoneal cells from endotoxemic middle-aged mice exhibited reduced viability and produced elevated levels of TNF-α, IL-6, IL-10, and KC/CXCL1 as compared to cells from young mice. Our studies demonstrate the utility of a combined in silico, in vivo, and in vitro approach to the study of acute inflammation in shock states, and suggest hypotheses with regard to the changes in the cytokine milieu that accompany aging. © 2013 Namas et al
Hybridization in parasites: consequences for adaptive evolution, pathogenesis and public health in a changing world
[No abstract available
275 Candidates and 149 Validated Planets Orbiting Bright Stars in K2 Campaigns 0-10
Since 2014, NASA's K2 mission has observed large portions of the ecliptic
plane in search of transiting planets and has detected hundreds of planet
candidates. With observations planned until at least early 2018, K2 will
continue to identify more planet candidates. We present here 275 planet
candidates observed during Campaigns 0-10 of the K2 mission that are orbiting
stars brighter than 13 mag (in Kepler band) and for which we have obtained
high-resolution spectra (R = 44,000). These candidates are analyzed using the
VESPA package (Morton 2012, 2015b) in order to calculate their false-positive
probabilities (FPP). We find that 149 candidates are validated with an FPP
lower than 0.1%, 39 of which were previously only candidates and 56 of which
were previously undetected. The processes of data reduction, candidate
identification, and statistical validation are described, and the demographics
of the candidates and newly validated planets are explored. We show tentative
evidence of a gap in the planet radius distribution of our candidate sample.
Comparing our sample to the Kepler candidate sample investigated by Fulton et
al. (2017), we conclude that more planets are required to quantitatively
confirm the gap with K2 candidates or validated planets. This work, in addition
to increasing the population of validated K2 planets by nearly 50% and
providing new targets for follow-up observations, will also serve as a
framework for validating candidates from upcoming K2 campaigns and the
Transiting Exoplanet Survey Satellite, expected to launch in 2018.Comment: Published in AJ, 47 pages, 18 figures, 7 tables, associated
supplementary dataset available at https://zenodo.org/record/116479
A time-fractional Borel-Pompeiu formula and a related hypercomplex operator calculus
In this paper we develop a time-fractional operator calculus in fractional Clifford analysis. Initially we study the -integrability of the fundamental solutions of the multi-dimensional time-fractional diffusion operator and the associated time-fractional parabolic Dirac operator. Then we introduce the time-fractional analogues of the Teodorescu and Cauchy-Bitsadze operators in a cylindrical domain, and we investigate their main mapping properties. As a main result, we prove a time-fractional version of the Borel-Pompeiu formula based on a time-fractional Stokes' formula. This tool in hand allows us to present a Hodge-type decomposition for the forward time-fractional parabolic Dirac operator with left Caputo fractional derivative in the time coordinate. The obtained results exhibit an interesting duality relation between forward and backward parabolic Dirac operators and Caputo and Riemann-Liouville time-fractional derivatives. We round off this paper by giving a direct application of the obtained results for solving time-fractional boundary value problems.The work of M. Ferreira, M.M. Rodrigues and N. Vieira was supported by Portuguese funds through CIDMA-Center for Research and Development in Mathematics and Applications, and FCTâFundação para a CiĂȘncia e a Tecnologia, within project UID/MAT/04106/2019. The work of the authors was supported by the project New Function Theoretical Methods in Computational Electrodynamics / Neue funktionentheoretische Methoden fĂŒr instationĂ€re PDE, funded by Programme for Cooperation in Science between Portugal and Germany (âPrograma de AçÔes Integradas Luso-AlemĂŁs 2017â - DAAD-CRUP - Acção No. A-15/17 / DAAD-PPP Deutschland-Portugal, Ref: 57340281). N. Vieira was also supported by FCT via the FCT Researcher Program 2014 (Ref: IF/00271/2014).publishe
Benthic Biofilm Controls on Fine Particle Dynamics in Streams
Este artĂculo contiene 15 pĂĄginas, 7 figuras, 3 tablas.Benthic (streambed) biofilms metabolize a substantial fraction of particulate organic matter
and nutrient inputs to streams. These microbial communities comprise a significant proportion of overall
biomass in headwater streams, and they present a primary control on the transformation and export of
labile organic carbon. Biofilm growth has been linked to enhanced fine particle deposition and retention, a
feedback that confers a distinct advantage for the acquisition and utilization of energy sources. We
quantified the influence of biofilm structure on fine particle deposition and resuspension in experimental
stream mesocosms. Biofilms were grown in identical 3 m recirculating flumes over periods of 18â47 days to
obtain a range of biofilm characteristics. Fluorescent, 8 mm particles were introduced to each flume, and
their concentrations in the water column were monitored over a 30 min period. We measured particle
concentrations using a flow cytometer and mesoscale (10 mm to 1 cm) biofilm structure using optical
coherence tomography. Particle deposition-resuspension dynamics were determined by fitting results to a
stochastic mobile-immobile model, which showed that retention timescales for particles within the
biofilm-covered streambeds followed a power-law residence time distribution. Particle retention times
increased with biofilm areal coverage, biofilm roughness, and mean biofilm height. Our findings suggest
that biofilm structural parameters are key predictors of particle retention in streams and rivers.This study was
funded by a Marie Curie Intra-
European Fellowship to WRH (FP7-
PEOPLE-2011-IEF-302297) and an
Austrian Science Fund grant to T.J.B.
(START Y420-B17). K.R.R. was
supported by a CUAHSI Pathfinder
fellowship and U.S. NSF Graduate
Research Fellowship. J.D.D. was
supported by a Fulbright-Spain
fellowship. The modeling effort was
supported by U.S. NSF grants EAR-
1215898 and EAR-1344280 to AIP.
Supporting data are provided at
doi:10.6084/m9.figshare.4252193.Peer reviewe
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