Three dimensional tracking of gold nanoparticles using digital holographic microscopy

In this paper we present a digital holographic microscope to track gold colloids in three dimensions. We report observations of 100nm gold particles in motion in water. The expected signal and the chosen method of reconstruction are described. We also discuss about how to implement the numerical calculation to reach real-time 3D tracking

Holographic microscopy for the three-dimensional exploration of light scattering from gold nanomarkers in biological media

The 3D structure of light scattering from dark-field illuminated live 3T3 cells marked with 40 nm gold nanomarkers is explored. For this purpose, we use a high resolution holographic microscope combining the off-axis heterodyne geometry and the phase-shifting acquisition of the digital holograms. Images are obtained using a novel 3D reconstruction method providing longitudinally undistorted 3D images. A comparative study of the 3D reconstructions of the scattered fields allows us to locate the gold markers which yield, contrarily to the cellular structures, well defined bright scattering patterns that are not angularly titled and clearly located along the optical axis. This characterization is an unambiguous signature of the presence of the gold biological nanomarkers, and validates the capability of digital holographic microscopy to discriminate them from background signals in live cells

Chemical synthesis, DNA incorporation and biological study of a new photocleavable 2′-deoxyadenosine mimic

The phototriggered cleavage of chemical bonds has found numerous applications in biology, particularly in the field of gene sequencing through photoinduced DNA strand scission. However, only a small number of modified nucleosides that are able to cleave DNA at selected positions have been reported in the literature. Herein, we show that a new photoactivable deoxyadenosine analogue, 3-nitro-3-deaza-2′-deoxyadenosine (d(3-NiA)), was able to induce DNA backbone breakage upon irradiation (λ > 320 nm). The d(3-NiA) nucleoside was chemically incorporated at desired positions into 40-mer oligonucleotides as a phosphoramidite monomer and subsequent hybridization studies confirmed that the resulting modified duplexes display a behaviour that is close to that of the related natural sequence. Enzymatic action of the Klenow fragment exonuclease free revealed the preferential incorporation of dAMP opposite the 3-NiA base. On the other hand, incorporation of the analogous 3-NiA triphosphate to a primer revealed high enzyme efficiency and selectivity for insertion opposite thymine. Furthermore, only the enzymatically synthesized base pair 3-NiA:T was a substrate for further extension by the enzyme. All the hybridization and enzymatic data indicate that this new photoactivable 3-NiA triphosphate can be considered as a photochemically cleavable dATP analogue

Artothèque comme média (L\u27)

Cette étude se propose, selon les termes de la lettre de mission de la directrice générale de la création artistique, Régine Hatchondo, de "définir les spécificités des artothèques ainsi que leurs évolutions possibles dans un environnement national, territorial, artistique, culturel et technologique en mutation" de manière à formuler "des propositions permettant de mieux prendre en compte et développer l’activité spécifique des artothèques en matière de démocratisation culturelle".Après un exposé des problématiques posées dans un chapitre inaugural, une analyse des mutations du « multiple de création » dans un second chapitre introduisant quelques propositions, suit une chronologie commentée intitulée "Histoire commentée des artothèques (1906-2017)" où sont également exposées des initiatives remarquables des artothèques. En conclusion sont formulées "douze propositions pour une meilleure connaissance, reconnaissance et valorisation des artothèques, outil de démocratisation artistique et culturelle". Ces propositions – dont deux ont été élaborées avec des spécialistes du domaine dont l\u27expertise a été sollicitée – constituent les bases de la proposition d\u27un programme d\u27actions qui clôt cette étude

The diffusion constant of a labeled protein sliding along DNA

International audienc

Heterodyne holographic microscopy of gold particles

We report experimental results on heterodyne holographic microscopy of subwavelength-sized gold particles. The apparatus uses continuous green laser illumination of the metal beads in a total internal reflection configuration for dark-field operation. Detection of the scattered light at the illumination wavelength on a charge-coupled device array detector enables 3D localization of brownian particles in wate

Three-body decay of a rubidium Bose-Einstein condensate

We have measured the three-body decay of a Bose-Einstein condensate of rubidium ($^{87}$Rb) atoms prepared in the doubly polarized ground state $F=m_F=2$. Our data are taken for a peak atomic density in the condensate varying between $2\times 10^{14}$ cm$^{-3}$ at initial time and $7\times 10^{13}$ cm$^{-3}$, 16 seconds later. Taking into account the influence of the uncondensed atoms onto the decay of the condensate, we deduce a rate constant for condensed atoms $L=1.8 (\pm 0.5) \times 10^{-29}$ cm$^{6}$s$^{-1}$. For these densities we did not find a significant contribution of two-body processes such as spin dipole relaxation.Comment: 14 pages, 4 figure

Parallel heterodyne detection of dynamic light scattering spectra from gold nanoparticles diffusing in viscous fluids.

International audienceWe developed a microscope intended to probe, using a parallel heterodyne receiver, the fluctuation spectrum of light quasi-elastically scattered by gold nanoparticles diffusing in viscous fluids. The cutoff frequencies of the recorded spectra scale up linearly with those expected from single scattering formalism in a wide range of dynamic viscosities (1 to 15 times water viscosity at room temperature). Our scheme enables ensemble-averaged optical fluctuations measurements over multispeckle recordings in low light, at temporal frequencies up to 10 kHz, with a 12 Hz framerate array detector

Supporting a values-filled approach in Aotearoa through Indigenous Tourism

This conceptual paper offers an exploratory insight into the example of Māori tourism in New Zealand which illustrates how Indigenous tourism can demonstrate a values-filled approach to tourism. Māori engagement with tourism is based on Māori culture and values and this shapes tourism in distinct ways. These values include: whanaungatanga emphasizing attaining and maintaining relationships; kaitiakitanga referring to guardianship, care and protection;and . manaakitanga defined as hospitality and is manifested as caring and/or sharing with others. Māori have engaged with tourism since the colonization of New Zealand and there is extensive research detailing these Māori values in action through tourism. Our analysis builds on this to suggest that this models a “values-filled” approach to tourism of important significance. Māori culture and values shape an engagement with tourism that is unique and supports Māori thriving, tourists’ satisfaction and enhancement of New Zealand tourism. This analysis is supported with illustrative cases