937 research outputs found
Galerkin least squares finite element method for the obstacle problem
We construct a consistent multiplier free method for the finite element solution of the obstacle problem. The method is based on an augmented Lagrangian formulation in which we eliminate the multiplier by use of its definition in a discrete setting. We prove existence and uniqueness of discrete solutions and optimal order a priori error estimates for smooth exact solutions. Using a saturation assumption we also prove an a posteriori error estimate. Numerical examples show the performance of the method and of an adaptive algorithm for the control of the discretization error
Solar wind interaction with comet 67P: impacts of corotating interaction regions
International audienceWe present observations from the Rosetta Plasma Consortium of the effects of stormy solar wind on comet 67P/Churyumov-Gerasimenko. Four corotating interaction regions (CIRs), where the first event has possibly merged with a coronal mass ejection, are traced from Earth via Mars (using Mars Express and Mars Atmosphere and Volatile EvolutioN mission) to comet 67P from October to December 2014. When the comet is 3.1â2.7 AU from the Sun and the neutral outgassing rate âŒ1025â1026 sâ1, the CIRs significantly influence the cometary plasma environment at altitudes down to 10â30 km. The ionospheric low-energy (âŒ5 eV) plasma density increases significantly in all events, by a factor of >2 in events 1 and 2 but less in events 3 and 4. The spacecraft potential drops below â20 V upon impact when the flux of electrons increases. The increased density is likely caused by compression of the plasma environment, increased particle impact ionization, and possibly charge exchange processes and acceleration of mass-loaded plasma back to the comet ionosphere. During all events, the fluxes of suprathermal (âŒ10â100 eV) electrons increase significantly, suggesting that the heating mechanism of these electrons is coupled to the solar wind energy input. At impact the magnetic field strength in the coma increases by a factor of 2â5 as more interplanetary magnetic field piles up around the comet. During two CIR impact events, we observe possible plasma boundaries forming, or moving past Rosetta, as the strong solar wind compresses the cometary plasma environment. We also discuss the possibility of seeing some signatures of the ionospheric response to tail disconnection events
Numerical Computations with H(div)-Finite Elements for the Brinkman Problem
The H(div)-conforming approach for the Brinkman equation is studied
numerically, verifying the theoretical a priori and a posteriori analysis in
previous work of the authors. Furthermore, the results are extended to cover a
non-constant permeability. A hybridization technique for the problem is
presented, complete with a convergence analysis and numerical verification.
Finally, the numerical convergence studies are complemented with numerical
examples of applications to domain decomposition and adaptive mesh refinement.Comment: Minor clarifications, added references. Reordering of some figures.
To appear in Computational Geosciences, final article available at
http://www.springerlink.co
âThe acceptanceâ of living with chronic pain â an ongoing process: A qualitative study of patient experiences of multimodal rehabilitation in primary care
Spatial distribution of low-energy plasma around 2 comet 67P/CG from Rosetta measurements
International audienceWe use measurements from the Rosetta plasma consortium (RPC) Langmuir probe (LAP) and mutual impedance probe (MIP) to study the spatial distribution of low-energy plasma in the near-nucleus coma of comet 67P/Churyumov-Gerasimenko. The spatial distribution is highly structured with the highest density in the summer hemisphere and above the region connecting the two main lobes of the comet, i.e. the neck region. There is a clear correlation with the neutral density and the plasma to neutral density ratio is found to be âŒ1-2·10 â6 , at a cometocentric distance of 10 km and at 3.1 AU from the sun. A clear 6.2 h modulation of the plasma is seen as the neck is exposed twice per rotation. The electron density of the collisonless plasma within 260 km from the nucleus falls of with radial distance as âŒ1/r. The spatial structure indicates that local ionization of neutral gas is the dominant source of low-energy plasma around the comet
Model for twin electromagnons and magnetically induced oscillatory polarization in multiferroic RMnO
We propose a model for the pair of electromagnon excitations observed in the
class of multiferroic materials {\it R}MnO ({\it R} is a rare-earth ion).
The model is based on a harmonic cycloid ground state interacting with a
zone-edge magnon and its twin excitation separated in momentum space by two
times the cycloid wave vector. The pair of electromagnons is activated by cross
coupling between magnetostriction and spin-orbit interactions. Remarkably, the
spectral weight of the twin electromagnon is directly related to the presence
of a magnetically induced oscillatory polarization in the ground state. This
leads to the surprising prediction that TbMnO has an oscillatory
polarization with amplitude 50 times larger than its uniform polarization.Comment: 4 pages, 3 figure
Histological response to injected gluteraldehyde cross-linked bovine collagen based implant in a rat model
BACKGROUND: The aim of present study is to investigate the short and long term histopathological alterations caused by submucosal injection of gluteraldehyde cross-linked bovine collagen based on an experimental rat model. METHODS: Sixty Sprague-Dawley rats were assigned into two groups as group I and II each containing 30 rats. 0.1 ml of saline solution and 0.1 ml of gluteraldehyde cross-linked bovine collagen were injected into the submucosa of bladder of first (control) and second groups, respectively. Both group I and II were further subdivided into 3 other groups as Group IA, IB, IC and Group IIA, IIB, IIC according to the sacrification period. Group IA and IIA, IB and IIB, IC and IIC rats (10 rats for each group) were sacrificed 3, 6, and 12 months after surgical procedure, respectively. Two slides prepared from injection site of the bladder were evaluated completely for each rat by being unaware of the groups and at random by two independent senior pathologists to determine the fibroblast invasion, collagen formation, capillary ingrowth and inflammatory reaction. Additionally, randomized brain sections from each rat were also examined to detect migration of the injection material. The measurements were made using an ocular micrometer at Ă10 magnification. The results were assessed using t-tests for paired and independent samples, with p < 0.05 considered to indicate significant differences; all values were presented as the mean (SD). RESULTS: Migration to the brain was not detected in any group. Significant histopathological changes in the gluteraldehyde cross-linked bovine collagen injected groups were fibroblast invasion in 93.3%, collagen formation in 73.3%, capillary ingrowth in 46.6%, inflamatory reaction in 20%. CONCLUSION: We emphasize that the usage of gluteraldehyde cross-linked bovine collagen in children appears to be safe for endoscopic treatment of vesicoureteral reflux
Complete Genome Sequence of Francisella endociliophora Strain FSC1006, Isolated from a Laboratory Culture of the Marine Ciliate Euplotes raikovi
A strain of Francisella endociliophora was isolated from a laboratory culture of the marine ciliate Euplotes raikovi. Here, we report the complete genome sequence of the bacterial strain FSC1006 (Francisella Strain Collection, Swedish Defence Research Agency, UmeÄ, Sweden)
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