In vitro phosphorylation as tool for modification of silk and keratin fibrous materials

An overview is given of the recent work on in vitro enzymatic phosphorylation of silk fibroin and human hair keratin. Opposing to many chemical "conventional" approaches, enzymatic phosphorylation is in fact a mild reaction and the treatment falls within "green chemistry" approach. Silk and keratin are not phosphorylated in vivo, but in vitro. This enzyme-driven modification is a major technological breakthrough. Harsh chemical chemicals are avoided, and mild conditions make enzymatic phosphorylation a real "green chemistry" approach. The current communication presents a novel approach stating that enzyme phosphorylation may be used as a tool to modify the surface charge of biocompatible materials such as keratin and silk.

Antibacterial properties of multifunctional coatings Ag-ZrCN for biomedical devices: a novel approach

PhD in Sciences Specialty in Physics

Optische pH-Messung unter Einsatz immobilisierter Styrylacridin-Farbstoffe

Optical pH sensor, styrylacridine dyes, fibre optics, immobilization of acidochromic dyes, porous glass

Isothermal drying of pore networks : influence of pore structure on drying kinetics

Drying of porous media, pore network, pore structure, capillary forces, viscous forces, drying kinetics

Flow and transport in electrochromatography

Analyte retention, analyte transport, axial dispersion, adsorption, charge-selectivity, concentration polarization, confocal laser scanning microscopy, donnan-exclusion, electrical double layer; electrochromatography; electrohydrodynamics, electrokinetic instability, electroosmosis; electroosmotic flow; electroosmotic mobility, electroosmotic perfusion, electrophoresis, hierarchical porous media, hydrodynamic flow, induced-charge electroosmosis, ion-permselectivity, ion-permselective transport, monolith, nonequilibrium electrical double layer, nonequilibrium electrokinetic effects, nonlinear electroosmosis, plate height, plate number, porous media, pore-scale dispersion, refractive index matching, space charge effects, sphere packing, quantitative imaging, wall effect, zeta-potential

Resum de la tasca realitzada al Center Biomedical Engineering (CBE) del Massachussets Institute of Technology (MIT). Juliol-Agost 2005

Estudi elaborat a partir d’una estada al Center Biomedical Engineering (CBE) del Massachussets Institute of Technology (MIT), durant els mesos de juliol i agost del 2005. S’investiga una metodologia amb l’objectiu d’obtenir biomaterials que puguin actuar de bastida en la interfície os/cartílag, afavorint la diferenciació i creixement cel·lular de cartílag ossificat que pugui actuar d’unió entre l’articulació i l’os. S’experimenta una metodologia per a establir quins són els péptids afavoridors de la formació de teixit ossi utilitzats en materials d’hidroxiapatita. Es conclou que la tecnologia desenvolupada permet disposar d’una plataforma per assajar l’estudi del signaling sobre cèl·lules embrionàries, que permeti desenvolupar materials amb més capacitat diferenciadora.

Transfer of ultrasmall iron oxide nanoparticles from human brain-derived endothelial cells to human glioblastoma cells.

Nanoparticles (NPs) are being used or explored for the development of biomedical applications in diagnosis and therapy, including imaging and drug delivery. Therefore, reliable tools are needed to study the behavior of NPs in biological environment, in particular the transport of NPs across biological barriers, including the blood-brain tumor barrier (BBTB), a challenging question. Previous studies have addressed the translocation of NPs of various compositions across cell layers, mostly using only one type of cells. Using a coculture model of the human BBTB, consisting in human cerebral endothelial cells preloaded with ultrasmall superparamagnetic iron oxide nanoparticles (USPIO NPs) and unloaded human glioblastoma cells grown on each side of newly developed ultrathin permeable silicon nitride supports as a model of the human BBTB, we demonstrate for the first time the transfer of USPIO NPs from human brain-derived endothelial cells to glioblastoma cells. The reduced thickness of the permeable mechanical support compares better than commercially available polymeric supports to the thickness of the basement membrane of the cerebral vascular system. These results are the first report supporting the possibility that USPIO NPs could be directly transferred from endothelial cells to glioblastoma cells across a BBTB. Thus, the use of such ultrathin porous supports provides a new in vitro approach to study the delivery of nanotherapeutics to brain cancers. Our results also suggest a novel possibility for nanoparticles to deliver therapeutics to the brain using endothelial to neural cells transfer.

Memory of Recessions

This paper reviews the evidence on the effects of recessions on potential output. In contrast to the assumption in mainstream macroeconomic models that economic fluctuations do not change potential output paths, the evidence is that they do in the case of recessions. A model is proposed to explain this phenomenon, based on an analogy with water flows in porous media. Because of the discrete adjustments made by heterogeneous economic agents in such a world, potential output displays hysteresis with regard to aggregate demand shocks, and thus retains a memory of the shocks associated with recessions.

Preparació, estudi estructural i aplicabilitat de derivats de Poli-(4R)-hidroxi-L-prolina a la separació d’enantiòmers per tècniques cromatogràfiques o relacionades

La separació d’enantiòmers (isòmers òptics) és molt important en molts diversos camps, com les síntesis quirals, biologia, i en el camp de la farmacologia especialment. És per això, que es fa necessari de disposar de tècniques i mètodes analítics ràpids, fiables i sensibles per a la separació d’enantiòmers. La present tesi s’emmarca en el camp de la separació d’enantiòmers, concretament en la preparació de fases estacionàries quirals per al seu ús en cromatografia liquida. En aquest sentit, s’ha desenvolupat la síntesi i caracterització de molècules polimèriques quirals derivades de l’aminoàcid L-prolina que incorporades en matrius de gel de sílice poden constituïr columnes quirals per a la separació d’enantiòmers per cromatografia liquida. S’han estudiat les característiques enantioselectives d’aquests nous materials en la separació de molècules quirals, trobant-se ésser satisfactòriament enantioselectius. L’interès que suscita l’obtenció d’enantiòmers a gran escala fa que la recerca s’orienti a la recerca de materials amb elevada capacitat de càrrega, és a dir, que puguin donar lloc a la separació d’elevades quantitats d’enantiòmers. Amb aquesta finalitat s’han dut a terme assaigs de capacitat de càrrega, que han posat de manifest la possible aplicació d’aquests materials a la separació preparativa d’enantiòmers. També s’ha parat especial atenció a l’estudi de les característiques de la matriu de gel de sílice, assajant-se altres materials de sílice més porosos i que permeten així treballar amb fluxos més elevats tot reduint-ne el temps d’anàlisi i els costos associats a la separació preparativa d’enantiòmers. L'estudi conformacional d'aquests nous selectors també ha estat contemplat per tal d'explicar l'enantioselectivitat específica que s'observa en certs dissolvents orgànics en els qual es duu a terme la separació dels enantiòmers.

Carbon dioxide in scree slope deposits: A pathway from atmosphere to pedogenic carbonate

A continuum of carbon, from atmospheric CO2 to secondary calcium carbonate, has been studied in a soil associ- ated with scree slope deposits in the Jura Mountains of Switzerland. This approach is based on former studies conducted in other environments. This C continuum includes atmospheric CO2, soil organic matter (SOM), soil CO2, dissolved inorganic carbon (DIC) in soil solutions, and secondary pedogenic carbonate. Soil parameters (pCO2, temperature, pH, Cmin and Corg contents), soil solution chemistry, and isotopic compositions of soil CO2, DIC, carbonate and soil organic matter (δ13CCO2, δ13CDIC, δ13Ccar and δ13CSOM values) have been monitored at different depths (from 20 to 140 cm) over one year. Results demonstrated that the carbon source in secondary carbonate (mainly needle fiber calcite) is related to the dissolved inorganic carbon, which is strongly dependent on soil respiration. The heterotrophic respiration, rather than the limestone parent material, seems to control the pedogenic carbon cycle. The correlation of δ13Corg values with Rock-Eval HI and OI indices demonstrates that, in a soil associated to scree slope deposits, the main process responsible for 13C-enrichment in SOM is related to bac- terial oxidative decarboxylation. Finally, precipitation of secondary calcium carbonate is enhanced by changes in soil pCO2 associated to the convective movement of air masses induced by temperature gradients (heat pump effect) in the highly porous scree slope deposits. The exportation of soil C-leachates from systems such as the one studied in this paper could partially explain the "gap in the European carbon budget" reported by recent studies.

A mixed finite element method for nonlinear diffusion equations

We propose a mixed finite element method for a class of nonlinear diffusion equations, which is based on their interpretation as gradient flows in optimal transportation metrics. We introduce an appropriate linearization of the optimal transport problem, which leads to a mixed symmetric formulation. This formulation preserves the maximum principle in case of the semi-discrete scheme as well as the fully discrete scheme for a certain class of problems. In addition solutions of the mixed formulation maintain exponential convergence in the relative entropy towards the steady state in case of a nonlinear Fokker-Planck equation with uniformly convex potential. We demonstrate the behavior of the proposed scheme with 2D simulations of the porous medium equations and blow-up questions in the Patlak-Keller-Segel model.

Comment on "Streaming potential dependence on water-content in Fontainebleau sand" by V. Allegre, L. Jouniaux, F. Lehmann and P. Sailhac

Allegre et al. recently presented new experimental data regarding the dependence of the streaming potential coupling coefficient with the saturation of the water phase. Such experiments are important to model the self-potential response associated with the flow of water in the vadose zone and the electroseismic/seismoelectric conversions in unsaturated porous media. However, the approach used to interpret the data is questionable and the conclusions reached by Allegre et al. likely incorrect

A study of the aging of fingerprints by GC/MS analysis.

Determining the time since deposition of fingermarks may prove necessary in order to assess their relevance to criminal investigations. The crucial factor is the initial composition of fingermarks because it represents the starting point of any ageing model. This study mainly aimed to characterize the initial composition of fingerprints, which show a high variability between donors (inter-variability), but also to investigate the variations among fingerprints from the same donor (intra-variability). Solutions to reduce this initial variability using squalene and cholesterol as target compounds are proposed and should be further investigated. The influence of substrates was also evaluated and the initial composition was observed to be larger on porous surface than non-porous surfaces. Preliminary aging of fingerprints over 30 days was finally studied on a porous and a non-porous substrate to evaluate the potential for dating of fingermarks. Squalene was observed to decrease in a faster rate on a non-porous substrate.

Obtenció de matrius poroses d'àcid polilàctic (PDLLA) mitjançant fluids comprimits per a ús en regeneració tissular

En aquest treball es pretén obtenir material porós de PDLLA, amb ús potencial com a bastida en enginyeria tissular, mitjançant l’ús de freó R-134a com a fluid escumant. Per aquest motiu, s’ha realitzat un estudi on es valoren diferents variables com la temperatura de procés, la pressió de treball i l’ús de N2 en la despressurització que poden modificar la microestructura final de la bastida.

Local-global splitting for spatiotemporal-adaptive multiscale methods

We present a novel spatiotemporal-adaptive Multiscale Finite Volume (MsFV) method, which is based on the natural idea that the global coarse-scale problem has longer characteristic time than the local fine-scale problems. As a consequence, the global problem can be solved with larger time steps than the local problems. In contrast to the pressure-transport splitting usually employed in the standard MsFV approach, we propose to start directly with a local-global splitting that allows to locally retain the original degree of coupling. This is crucial for highly non-linear systems or in the presence of physical instabilities. To obtain an accurate and efficient algorithm, we devise new adaptive criteria for global update that are based on changes of coarse-scale quantities rather than on fine-scale quantities, as it is routinely done before in the adaptive MsFV method. By means of a complexity analysis we show that the adaptive approach gives a noticeable speed-up with respect to the standard MsFV algorithm. In particular, it is efficient in case of large upscaling factors, which is important for multiphysics problems. Based on the observation that local time stepping acts as a smoother, we devise a self-correcting algorithm which incorporates the information from previous times to improve the quality of the multiscale approximation. We present results of multiphase flow simulations both for Darcy-scale and multiphysics (hybrid) problems, in which a local pore-scale description is combined with a global Darcy-like description. The novel spatiotemporal-adaptive multiscale method based on the local-global splitting is not limited to porous media flow problems, but it can be extended to any system described by a set of conservation equations.