665 research outputs found
Analysis of direct segregated boundary-domain integral equations for variable-coefficient mixed bvps in exterior domains
This is the post-print version of the Article. The official published version can be accessed from the link below - Copyright @ 2013 World Scientific Publishing.Direct segregated systems of boundary-domain integral equations are formulated for the mixed (Dirichlet–Neumann) boundary value problems for a scalar second-order divergent elliptic partial differential equation with a variable coefficient in an exterior three-dimensional domain. The boundary-domain integral equation system equivalence to the original boundary value problems and the Fredholm properties and invertibility of the corresponding boundary-domain integral operators are analyzed in weighted Sobolev spaces suitable for infinite domains. This analysis is based on the corresponding properties of the BVPs in weighted Sobolev spaces that are proved as well.The work was supported by the grant EP/H020497/1 \Mathematical analysis of localised boundary-domain integral equations for BVPs with variable coefficients" of the EPSRC, UK
Biological activity of a SiO2-CaO-P2O5 sol-gel glass highlighted by PIXE-RBS methods
It is proposed in this study to observe the influence of P2O5 on the
formation of the apatite-like layer in a bioactive glass via a complete PIXE
characterization. A glass in the SiO2-CaO-P2O5 ternary system was elaborated by
sol-gel processing. Glass samples were soaked in biological fluids for periods
up to 10 days. The surface changes were characterized using Particle Induced
X-ray Emission (PIXE) associated to Rutherford Backscattering Spectroscopy
(RBS), which are efficient methods for multielemental analysis. Elemental maps
of major and trace elements were obtained at a micrometer scale and revealed
the bone bonding ability of the material. The formation of a calcium
phosphate-rich layer containing magnesium occurs after a few days of
interaction. We demonstrate that the presence of phosphorus in the material has
an impact on the development and the formation rate of the bone-like apatite
layer. Indeed, the Ca/P atomic ratio at the glass/biological fluids interface
is closer to the nominal value of pure apatite compared to P2O5 free glasses.
It would permit, in vivo, an improved chemical bond between the biomaterials
and bone.Comment: presented at CAARI 2006:19th International Conference on the
Application of Accelerators in Research and Industry, Forth Worth, Etats
Unis, 20-25 Aug 2006, 11 pp, 4 figures, submitted to NIM
Validation of Aura Microwave Limb Sounder O-3 and CO observations in the upper troposphere and lower stratosphere
International audienceGlobal satellite observations of ozone and carbon monoxide from the Microwave Limb Sounder (MLS) on the EOS Aura spacecraft are discussed with emphasis on those observations in the 215–100 hPa region (the upper troposphere and lower stratosphere). The precision, resolution and accuracy of the data produced by the MLS “version 2.2” processing algorithms are discussed and quantified. O3 accuracy is estimated at ~40 ppbv +5% (~20 ppbv +20% at 215 hPa) while the CO accuracy is estimated at ~30 ppbv +30% for pressures of 147 hPa and less. Comparisons with expectations and other observations show good agreements for the O3 product, generally consistent with the systematic errors quoted above. In the case of CO, a persistent factor of ~2 high bias is seen at 215 hPa. However, the morphology is shown to be realistic, consistent with raw MLS radiance data, and useful for scientific study. The MLS CO data at higher altitudes are shown to be consistent with other observations
Atmospheric halogen and acid rains during the main phase of Deccan eruptions: magnetic and mineral evidence
Environmental changes linked to Deccan volcanism are still poorly known. A major limitation resides in the paucity of direct Deccan volcanism markers and in the geologically short interval where both impact and volcanism occurred, making it hard to evaluate their contributions to the mass extinction. We investigated the low-magnetic-susceptibility interval just below the iridium-rich layer of the Bidart (France) section, which was recently hypothesized to be the result of paleoenvironmental perturbations linked to paroxysmal Deccan phase 2. Results show a drastic decrease of detrital magnetite and presence of scarce akaganeite, a hypothesized
reaction product formed in the aerosols derived from reaction of a volcanic plume
with water and oxygen in the high atmosphere. A weathering model of the consequences of acidic rains on a continental regolith reveals nearly complete magnetite dissolution after ~31,000 yr, which is consistent with our magnetic data and falls within the duration of the Deccan phase 2. These results highlight the nature and importance of the Deccan-related environmental changes leading up to the end-
Cretaceous mass extinction
The monoclinic phase of PZT ceramics: Raman and phenomenological theory studies
This work reports on the first Raman detection of the tetragonal to
monoclinic phase transition in PZT ceramics near morphotropic phase boundary at
low temperatures. The transition is characterized by changes in the frequency
of lattice modes with the temperature. The results presented here confirm the
previous one recently reported by Noheda et al. using high-resolution
synchrotron X-ray powder diffraction technique and dielectric measurements. The
stability of the new phase is discussed within the framework of
phenomenological Landau-Devonshire Theory.Comment: 6 pages including 4 figures, Latex, submitted to Applied Physics
Letter
BMI in childhood and adolescence is associated with impaired reproductive function-a population-based cohort study from birth to age 50 years
Peer reviewe
Modeling oscillatory Microtubule--Polymerization
Polymerization of microtubules is ubiquitous in biological cells and under
certain conditions it becomes oscillatory in time. Here simple reaction models
are analyzed that capture such oscillations as well as the length distribution
of microtubules. We assume reaction conditions that are stationary over many
oscillation periods, and it is a Hopf bifurcation that leads to a persistent
oscillatory microtubule polymerization in these models. Analytical expressions
are derived for the threshold of the bifurcation and the oscillation frequency
in terms of reaction rates as well as typical trends of their parameter
dependence are presented. Both, a catastrophe rate that depends on the density
of {\it guanosine triphosphate} (GTP) liganded tubulin dimers and a delay
reaction, such as the depolymerization of shrinking microtubules or the decay
of oligomers, support oscillations. For a tubulin dimer concentration below the
threshold oscillatory microtubule polymerization occurs transiently on the
route to a stationary state, as shown by numerical solutions of the model
equations. Close to threshold a so--called amplitude equation is derived and it
is shown that the bifurcation to microtubule oscillations is supercritical.Comment: 21 pages and 12 figure
Limiting motorboat noise on coral reefs boosts fish reproductive success
Anthropogenic noise impacts are pervasive across taxa, ecosystems and the world. Here, we experimentally test the hypothesis that protecting vulnerable habitats from noise pollution can improve animal reproductive success. Using a season-long field manipulation with an established model system on the Great Barrier Reef, we demonstrate that limiting motorboat activity on reefs leads to the survival of more fish offspring compared to reefs experiencing busy motorboat traffic. A complementary laboratory experiment isolated the importance of noise and, in combination with the field study, showed that the enhanced reproductive success on protected reefs is likely due to improvements in parental care and offspring length. Our results suggest noise mitigation could have benefits that carry through to the population-level by increasing adult reproductive output and offspring growth, thus helping to protect coral reefs from human impacts and presenting a valuable opportunity for enhancing ecosystem resilience
The University of California San Francisco, Brain Metastases Stereotactic Radiosurgery (UCSF-BMSR) MRI Dataset
The University of California San Francisco Brain Metastases Stereotactic
Radiosurgery (UCSF-BMSR) dataset is a public, clinical, multimodal brain MRI
dataset consisting of 560 brain MRIs from 412 patients with expert annotations
of 5136 brain metastases. Data consists of registered and skull stripped T1
post-contrast, T1 pre-contrast, FLAIR and subtraction (T1 pre-contrast - T1
post-contrast) images and voxelwise segmentations of enhancing brain metastases
in NifTI format. The dataset also includes patient demographics, surgical
status and primary cancer types. The UCSF-BSMR has been made publicly available
in the hopes that researchers will use these data to push the boundaries of AI
applications for brain metastases.Comment: 15 pages, 2 tables, 2 figure
Production properties of K*(892) vector mesons and their spin alignment as measured in the NOMAD experiment
First measurements of K*(892) mesons production properties and their spin
alignment in nu_mu charged current (CC) and neutral current (NC) interactions
are presented. The analysis of the full data sample of the NOMAD experiment is
performed in different kinematic regions. For K*+ and K*- mesons produced in
nu_mu CC interactions and decaying into K0 pi+/- we have found the following
yields per event: (2.6 +/- 0.2 (stat.) +/- 0.2 (syst.))% and (1.6 +/- 0.1
(stat.) +/- 0.1 (syst.))% respectively, while for the K*+ and K*- mesons
produced in nu NC interactions the corresponding yields per event are: (2.5 +/-
0.3 (stat.) +/- 0.3 (syst.))% and (1.0 +/- 0.3 (stat.) +/- 0.2 (syst.))%. The
results obtained for the rho00 parameter, 0.40 +/- 0.06 (stat) +/- 0.03 (syst)
and 0.28 +/- 0.07 (stat) +/- 0.03 (syst) for K*+ and K*- produced in nu_mu CC
interactions, are compared to theoretical predictions tuned on LEP measurements
in e+e- annihilation at the Z0 pole. For K*+ mesons produced in nu NC
interactions the measured rho00 parameter is 0.66 +/- 0.10 (stat) +/- 0.05
(syst).Comment: 20 p
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