We couple a laser-based, space-resolved dynamic light scattering apparatus to a universal testing machine for mechanical extensional tests. We perform simultaneous optical and mechanical measurements on polyether ether ketone, a semi-crystalline polymer widely used in the industry. Due to the high turbidity of the sample, light is multiply scattered by the sample and the diffusing wave spectroscopy (DWS) formalism is used to interpret the data. Space-resolved DWS yields spatial maps of the sample strain and of the microscopic dynamics. An excellent agreement is found between the strain maps thus obtained and those measured by a conventional stereo-correlation bench. The microscopic dynamics reveals both affine motion and plastic rearrangements. Thanks to the extreme sensitivity of DWS to displacements as small as 1 nm, plastic activity and its spatial localization can be detected at an early stage of the sample deformation, making the technique presented here a valuable complement to existing material characterization methods.

Cavity optomechanical systems with an enhanced coupling between mechanical motion and electromagnetic radiation have permitted the investigation of many novel physical effects. The optomechanical coupling in the majority of these systems is of dispersive nature: the cavity resonance frequency is modulated by the vibrations of the mechanical oscillator. Dissipative optomechanical interaction, where the photon lifetime in the cavity is modulated by the mechanical motion, has recently attracted considerable interest and opens new avenues in optomechanical control and sensing. In this work we demonstrate an external optical control over the dissipative optomechanical coupling strength mediated by the modulation of the absorption of a quantum dot layer in a hybrid optomechanical system. Such control enhances the capability of tailoring the optomechanical coupling of our platform, which can be used in complement to the previously demonstrated control of the relative (dispersive to dissipative) coupling strength via the geometry of the integrated access waveguide.

The Wheat Grain as a cemented granular material: Nanoscale investigation of its mechanical properties. 3. International Conference on Structural Nano Composites (NANOSTRUC 2016)

Demand for efficient terahertz (THz) radiation detectors resulted in intensive study of the asymmetric carbon nanostructures as a possible solution for that problem. In this work, we systematically investigate the response of asymmetric carbon nanodevices to sub-terahertz radiation using different sensing elements: from dense carbon nanotube (CNT) network to individual CNT. We conclude that the detectors based on individual CNTs both semiconducting and quasi-metallic demonstrate much stronger response in sub-THz region than detectors based on disordered CNT networks at room temperature. We also demonstrate the possibility of using asymmetric detectors based on CNT for imaging in the THz range at room temperature. Further optimization of the device configuration may result in appearance of novel terahertz radiation detectors.

We demonstrate the instability of the free surface of a soft elastic layer facing downwards. Experiments are carried out using a system consisting in a gel of constant density and shear modulus , put in a rigid cylindrical dish of depth h. When turned upside down, the free surface of the gel undergoes a normal outgoing acceleration g., whereas a steady pattern spontaneously appears in the opposite case. This phenomenon results from the interplay between the gravitational energy and the elastic energy of deformation of the system

Proper treatment of dental caries demands detection of carious lesions at an early stage and a minimal invasive cavity preparation to preserve the maximum tooth structure. Various devices use fluorescence for caries detection via recording the red fluorescence generated by dentin caries under illumination.The aim of this study was to evaluate the porphyrin and pentosidine involvement in the red fluorescence observed in enamel and dentin caries when illuminated with the Soprolife® camera (Sopro, Acteon Group, La Ciotat, France) and Vistacam® camera (Dürr Dental AG, Bietigheim-Bissingen, Germany). Three techniques were used: single photon fluorescence spectroscopy, micro-Raman spectroscopy, and color analysis with ImajeJ software. Cross-sections of human teeth, scored from 0-6 with the International Caries Detection and Assessment System (ICDAS), were examined by fluorescence microscopy. Teeth spectra of each ICDAS score were compared with those of protoporphyrin IX (PpIX), porphyrin I, and pentosidine solutions. A specific confocal Raman microscopy analysis was realized and a Red-Green-Blue model analysis of Soprolife® images was performed using ImageJ software to compare the color variations on ICDAS score 1 and 2. Fluorescence spectroscopy and micro- Raman spectroscopy revealed the presence of PpIX in carious enamel and dentin. The clinical relevance of this experimentation was that the increased knowledge of the fluorescence aids for caries detection could improve the preventive approach, thus reducing the operative one.