Sol-Gel Processing of Nanostructured Inorganic Scintillating

The development of scintillating materials is believed to reach a new step by controlling their preparation on a nanometric level. Sol-Gel chemistry offers very unique tools for nanoscale mastering of the materials preparation. In particular, shaping of the materials as thin films or nanoparticles offers new application in medical imaging. The control of doping ions dispersion thanks to soft chemistry is also a great advantage of such synthetic routes. In this paper, we will review recent work devoted to the sol-gel preparation of inorganic scintillating materials. We will focus on the new possibilities and advantages offered by sol-gel chemistry for the preparation of new scintillators and improvement of existing ones

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

Analysis of segregated boundary-domain integral equations for mixed variable-coefficient 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 @ 2011 Birkhäuser Boston.Some direct segregated systems of boundary–domain integral equations (LBDIEs) associated with the mixed boundary value problems for scalar PDEs with variable coefficients in exterior domains are formulated and analyzed in the paper. The LBDIE equivalence to the original boundary value problems and the invertibility of the corresponding boundary–domain integral operators are proved in weighted Sobolev spaces suitable for exterior domains. This extends the results obtained by the authors for interior domains in non-weighted Sobolev spaces.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

Correction: Preferential site substitution of Eu3+ ions in Ca10(PO4)6Cl2 nanoparticles obtained usinga microwave stimulated wet chemistry technique

International audience“In accordance with the rule of 2J + 1 at Cs symmetry a maximum of five sublevels should be present for the 5D0 → 7F1 andeight in the case of the 5D0 → 7F2 transitions whereas at C3 symmetry the 5D0 → 7F1 splits into two and the 5D0 → 7F2 into threeStark components.”Should have read:In accordance with the rule of 2J + 1 at Cs symmetry a maximum of three sublevels should be present for the 5D0 → 7F1 andfive in the case of the 5D0 → 7F2 transitions whereas at C3 symmetry the 5D0 → 7F1 splits into two and the 5D0 → 7F2 into threeStark components.The Royal Society of Chemistry apologises for these errors and any consequent inconvenience to authors and readers.2780

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

Proposing a Pedigree Risk Measurement Strategy: Capturing the Intergenerational Transmission of Antisocial Behavior in a Nationally Representative Sample of Adults

An impressive literature has revealed that variation in virtually every measurable phenotype is the result of a combination of genetic and environmental influences. Based on these findings, studies that fail to use genetically informed modeling strategies risk model misspecification and biased parameter estimates. Twin- and adoption-based research designs have frequently been used to overcome this limitation. Despite the many advantages of such approaches, many available datasets do not contain samples of twins, siblings or adoptees, making it impossible to utilize these modeling strategies. The current study proposes a measurement strategy for estimating the intergenerational transmission of antisocial behavior (ASB) within a nationally representative sample of singletons using an extended pedigree risk approach that relies on information from first- and second-degree relatives. An evaluation of this approach revealed a pattern of findings that directly aligned with studies examining ASB using more traditional twin- and adoption-based research designs. While the proposed pedigree risk approach is not capable of effectively isolating genetic and environmental influences, this overall alignment in results provides tentative evidence suggesting that the proposed pedigree risk measure effectively captures genetic influences. Future replication studies are necessary as this observation remains preliminary. Whenever possible, more traditional quantitative genetic methodologies should be favored, but the presented strategy remains a viable alternative for more limited samples

Dynamic concentration of motors in microtubule arrays

We present experimental and theoretical studies of the dynamics of molecular motors in microtubule arrays and asters. By solving a convection-diffusion equation we find that the density profile of motors in a two-dimensional aster is characterized by continuously varying exponents. Simulations are used to verify the assumptions of the continuum model. We observe the concentration profiles of kinesin moving in quasi two-dimensional artificial asters by fluorescent microscopy and compare with our theoretical results.Comment: 4pages, 4 figures revte

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

Enhanced reaction kinetics in biological cells

The cell cytoskeleton is a striking example of "active" medium driven out-of-equilibrium by ATP hydrolysis. Such activity has been shown recently to have a spectacular impact on the mechanical and rheological properties of the cellular medium, as well as on its transport properties : a generic tracer particle freely diffuses as in a standard equilibrium medium, but also intermittently binds with random interaction times to motor proteins, which perform active ballistic excursions along cytoskeletal filaments. Here, we propose for the first time an analytical model of transport limited reactions in active media, and show quantitatively how active transport can enhance reactivity for large enough tracers like vesicles. We derive analytically the average interaction time with motor proteins which optimizes the reaction rate, and reveal remarkable universal features of the optimal configuration. We discuss why active transport may be beneficial in various biological examples: cell cytoskeleton, membranes and lamellipodia, and tubular structures like axons.Comment: 10 pages, 2 figure

Anomalous fluctuations of active polar filaments

Using a simple model, we study the fluctuating dynamics of inextensible, semiflexible polar filaments interacting with active and directed force generating centres such as molecular motors. Taking into account the fact that the activity occurs on time-scales comparable to the filament relaxation time, we obtain some unexpected differences between both the steady-state and dynamical behaviour of active as compared to passive filaments. For the statics, the filaments have a {novel} length-scale dependent rigidity. Dynamically, we find strongly enhanced anomalous diffusion.Comment: 5 pages, 3 figure