Preparation and characterization of new hybrid organic/inorganic systems derived from calcium (aminoalkyl)-phosphonates and -phosphonocarboxylates

We have studied the phenomenon of calcium complexation by lab synthesized amphiphilic (α-aminoalkyl)-phosphonocarboxylic or -phosphonic acids. The electrical conductivity of aqueous solutions of sodium salts of all these acids was measured versus the volume of a calcium salt solution added. It appeared that calcium complexes are formed in a Ca/P atomic ratio close to 1. Calcium phosphonocarboxylates and calcium phosphonates were also precipitated by mixing aqueous solutions of disodium salts of phosphorus amphiphiles and calcium nitrate solutions. Before chemical analysis, these complexes were calcined to remove the organic part. In the mineralized products, calcium and phosphate were assayed: the Ca/P atomic ratio was equal to 1. X-ray diffraction and IR spectroscopy showed that they are made entirely of β pyrophosphate (Ca2P2O7), a result in agreement with previous chemical analysis. The chemical formula of the starting calcium complexes could be written as CaL·2H2O (L= ligand). The SEM micrographs of these complexes show plate-like structures. XRD patterns are characteristic of layered structures. These facts suggest that calcium complexes are composed of alternating bimolecular layers of calcium alkylphosphonocarboxylates or calcium alkylphosphonates, the chains being tilted and partially interdigitated

Bloch Oscillations of Einstein-Podolsky-Rosen States

Bloch Oscillations (BOs) of quantum particles manifest themselves as periodic spreading and re-localization of the associated wave functions when traversing lattice potentials subject to external gradient forces. Albeit BOs are deeply rooted into the very foundations of quantum mechanics, all experimental observations of this phenomenon so far have only contemplated dynamics of one or two particles initially prepared in separable local states, which is well described by classical wave physics. Evidently, a more general description of genuinely quantum BOs will be achieved upon excitation of a Bloch-oscillator lattice system by nonlocal states, that is, containing correlations in contradiction with local realism. Here we report the first experimental observation of BOs of two-particle Einstein-Podolsky-Rosen states (EPR), whose associated N-particle wave functions are nonlocal by nature. The time evolution of two-photon EPR states in Bloch-oscillators, whether symmetric, antisymmetric or partially symmetric, reveals unexpected transitions from particle antibunching to bunching. Consequently, the initial state can be tailored to produce spatial correlations akin to bosons, fermions or anyons. These results pave the way for a wider class of photonic quantum simulators.Comment: 21 pages, 6 figure

Colloidal and monocrystalline Ln3+ doped apatite calcium phosphate as biocompatible fluorescent probes

Ultrafine individualised mono crystalline Ca102x(PO4)62x-(HPO4)x(OH)22x deficient calcium hydroxyapatite nanocrystals displaying fluorescence under visible excitation are proposed for utilisation as biocompatible biological probes

IRANCARTO : Diffuser l'information spatiale pour analyser des questions controversées

International audienceSince 1966, the Statistical Center of Iran publishes very detailed data at detailed scales (villages neighborhoods), but these data have rarely been analyzed from a geographical point of view. The common discourse about the territory is dominated by a discourse assimilating territory with ethnicity, or social categories. These images of the 1950s are challenged by migration and socio-political changes. The public and even the analysts often hide or ignore the new shapes of territories which are a major challenge for a better understanding of the current geography of Iran and of the new conflicts or synergies. The website Irancarto open in October 2011 (CNRS Research team " Iranian and Indian Worlds " , Paris) provides the maps available (Atlas and various studies), and seeks to facilitate scientific exchange and international collaborations, especially Iranian researchers, in order to involve with more efficiency the territories in the debates. This presentation introduces the new trilingual web site Irancarto (English, French, Persian), and some examples the role of spatial analysis to understand controversial political events (electoral geography) or new social realities (demographic opposition center / periphery, the emerging suburbs).Depuis 1966 le Centre de Statistique d'Iran publie des informations très détaillées à des échelles fines (villages quartiers), mais ces données ont rarement été analysées du point de vue géographique. Le discours public sur le territoire est dominé par une doxa assimilant un territoire à une ethnie, ou à des catégories sociales. Ces images des années 1950 sont remises en cause par les migrations et changements sociaux-politiques. Le public et même les analystes ignorent ou occultent les recompositions spatiales dont la connaissance constitue pourtant un enjeu pour accéder à une connaissance rationnelle de la géographie actuelle de l'Iran et comprendre les nouveaux conflits ou synergies. Le site internet Irancarto ouvert en octobre 2011 (CNRS UMR Mondes Iranien et indien, Paris) diffuse les cartes disponibles (réédition d'Atlas et diverses études), et surtout cherche à faciliter les échanges scientifiques et collaborations internationales notamment avec les chercheurs iraniens, pour mieux intégrer l'analyse des territoires dans les débats en cours. La communication présentera notamment Irancarto et quelques exemples des apports et enjeux de l'analyse spatiale à la compréhension de faits politiques (géographie électorale) ou nouvelles réalités sociales controversées (opposition démographique centre/périphérie, émergence des banlieues…)

Dynamics of femtosecond laser absorption of fused silica in the ablation regime

International audienceWe investigate the ultrafast absorption dynamics of fused silica irradiated by a single 500 fs laser pulse in the context of micromachining applications. A 60-fs-resolution pump-probe experiment that measures the reflectivity and transmissivity of the target under excitation is developed to reveal the evolution of plasma absorption. Above the ablation threshold, an overcritical plasma with highly non-equilibrium conditions is evidenced in a thin layer at the surface. The maximum electron density is reached at a delay of 0:5 ps after the peak of the pump pulse, which is a strong indication of the occurrence of electronic avalanche. The results are further analyzed to determine the actual feedback of the evolution of the optical properties of the material on the pump pulse. We introduce an important new quantity, namely, the duration of absorption of the laser by the created plasma, corresponding to the actual timespan of laser absorption by inverse Bremsstrahlung. Our results indicate an increasing contribution of plasma absorption to the total material absorption upon raising the excitation fluence above the ablation threshold. The role of transient optical properties during the energy deposition stage is characterized and our results emphasize the necessity to take it into account for better understanding and control of femtosecond laser-dielectrics interaction

Colloidal synthesis and characterization of monocrystalline apatite nanophosphors

Here, we report the synthesis and characterization of 12 nm long, ultrafine, individualized calcium phosphate nanorods. Synthesis of these nanobuilding blocks involved the preparation of a calcium phosphate hybrid precursor containing an aminophosphate ligand. Colloidal calcium phosphate nanoparticles were achieved through the reorganization of an amorphous hybrid precursor at high temperature during a post-ageing step. These nanoparticles can be described as monocrystalline deficient calcium hydroxyapatite Ca102x(PO4)62x(HPO4)x(OH)22x, with surfaces stabilized by [PO3 22–O(CH2)2NH3 +] groups. A model is proposed in which the [ab] plane of the nanoparticles is formed by 9 unit cells surrounded by a peripheral layer composed of twelve aminoethyl phosphate (AEP)-calcium phosphate (xCa9(PO4)6 2 yCa-(AEP)2) hybrid units. Our ultrafine individualized calcium phosphate nanophosphors, synthesized in aqueous medium and displaying amino groups on their surface, are good candidates for use as fluorescent probes in biological imaging

Europium-doped calcium pyrophosphates : allotropic forms and photoluminescent properties

In a search for new luminescent biological probes, we synthesized calcium pyrophosphates doped with europium up to an atomic Eu/(Eu+Ca) ratio of 2%. They were prepared by coprecipitating a mixture of calcium and europium salts with phosphate. After heating at 900°C in air, two phases coexisted, identified as the β calcium pyrophosphate form and EuPO4. Heating near 1250°C in air, during the β→ transformation, europium ions substitute for calcium ions in the * calcium pyrophosphate structure as demonstrated by the spectroscopic study. Europium ions with both valence states (divalent and trivalent) were observed in the samples. Following the synthesis procedure, partial reduction of Eu3+ took place even in an oxidizing atmosphere. The 0.5%-doped compound could serve as a sensitive probe in biological applications. Depending on the excitation wavelength, the luminescence occurs either in the red or in the blue regions, which discriminates it from parasitic signals arising from other dyes or organelles in live cells

FLARR Pages #10: Reading and Writing

During the first four or five months, language students learn a limited number of words and structures, which allows them to write on equally limited subjects, usually personal, such as: Describe yourself, your friends and relatives, your room, your clothes, your weekly activities, etc. What do you buy when you go to the stores? Imagine a dialogue between two characters, etc. This type of composition is fine during that beginning period, but beyond, it loses its usefulness, for the learners tend to recycle the same ideas, phrases and constructions which they have been using since chapter two. Little improvement or learning takes place

FLARR Pages #35: Let Your Fingers Do the Talking

There are gestures and facial expressions that replace words and are immediately understood by natives of each country. The same signs may exist in another culture and have different meanings. Although these cultural traits are very simple, they must be performed very accurately; otherwise they are as meaningless as a mispronounced word