A family of NADPH/NADP biosensors reveals in vivo dynamics of central redox metabolism across eukaryotes.

The NADPH/NADP redox couple is central to metabolism and redox signalling. NADP redox state is differentially regulated by distinct enzymatic machineries at the subcellular compartment level. Nonetheless, a detailed understanding of subcellular NADP redox dynamics is limited by the availability of appropriate tools.

Heterogeneously deacetylated chitosans possess an unexpected regular pattern favoring acetylation at every third position.

Chitosans are promising biopolymers for diverse applications, with material properties and bioactivities depending i.a. on their pattern of acetylation (PA).

Optically Controlled Nano-Transducers Based on Cleaved Superlattices for Monitoring Gigahertz Surface Acoustic Vibrations.

Surface acoustic waves (SAWs) convey energy at subwavelength depths along surfaces. Using interdigital transducers (IDTs) and opto-acousto-optic transducers (OAOTs), researchers have harnessed coherent SAWs with nanosecond periods and micrometer localization depth for various applications. These applications include the sensing of small amount of materials deposited on surfaces, assessing surface roughness and defects, signal processing, light manipulation, charge carrier and exciton transportation, and the study of fundamental interactions with thermal phonons, photons, magnons, and more.

Time-domain Brillouin scattering for evaluation of materials interface inclination: Application to photoacoustic imaging of crystal destruction upon non-hydrostatic compression.

Time-domain Brillouin scattering (TDBS) is a developing technique for imaging/evaluation of materials, currently used in material science and biology. Three-dimensional imaging and characterization of polycrystalline materials has been recently reported, demonstrating evaluation of inclined material boundaries. Here, the TDBS technique is applied to monitor the destruction of a lithium niobate single crystal upon non-hydrostatic compression in a diamond anvil cell.

Time-domain Brillouin scattering theory for probe light and acoustic beams propagating at an angle and acousto-optic interaction at material interfaces.

A theory has been developed to interpret time-domain Brillouin scattering (TDBS) experiments involving coherent acoustic pulse (CAP) and light pulse beams propagating at an angle to each other. It predicts the influence of the directivity pattern of their acousto-optic interaction on TDBS signals when heterodyne detection of acoustically scattered light is in backward direction to incident light. The theory reveals relationships between the carrier frequency, amplitude and duration of acoustically induced "wave packets" in light transient reflectivity signals, and factors such as CAP duration, widths of light and sound beams, and their interaction angle.

Elastic moduli and refractive index of γ-GeN.

Germanium nitride, having cubic spinel structure, γ-GeN, is a wide band-gap semiconductor with a large exciton binding energy that exhibits high hardness, elastic moduli and elevated thermal stability up to approximately 700°C. Experimental data on its bulk and shear moduli ( and , respectively) are strongly limited, inconsistent and, thus, require verification. Moreover, earlier first-principles density functional calculations provided significantly scattering values but consistently predicted much higher than the so far available experimental value.

Imaging of a Light-Induced Modification Process in Organo-Silica Films via Time-Domain Brillouin Scattering.

We applied time-domain Brillouin scattering (TDBS) for the characterization of porogen-based organosilicate glass (OGS) films deposited by spin-on-glass technology and cured under different conditions. Although the chemical composition and porosity measured by Fourier-transform infrared (FTIR) spectroscopy and ellipsometric porosimetry (EP) did not show significant differences between the films, remarkable differences between them were revealed by the temporal evolution of the Brillouin frequency (BF) shift of the probe light in the TDBS. The observed modification of the BF was a signature of the light-induced modification of the films in the process of the TDBS experiments.

Evaluation of Optical and Acoustical Properties of BaSrTiO Thin Film Material Library via Conjugation of Picosecond Laser Ultrasonics with X-ray Diffraction, Energy Dispersive Spectroscopy, Electron Probe Micro Analysis, Scanning Electron and Atomic Force Microscopies.

Wide-range continuous spatial variation of the film composition in lateral compositionally graded epitaxial films requires the development of high throughput measurement techniques for their local and non-destructive characterization with the highest possible spatial resolution. Here we report on the first application of the picosecond laser ultrasonics (PLU) technique for the evaluation of acoustical and optical parameters of lateral compositionally graded film, the BaSrTiO (0 ≤ x ≤ 1) material library. The film was not dedicatedly prepared for its opto-acousto-optic evaluation by PLU, exhibiting significant lateral variations in thickness and surface roughness.

Laser ultrasonics in a multilayer structure: Semi-analytic model and simulated examples.

Laser-generated elastic waves have been the subject of numerous experimental, theoretical, and numerical studies to describe the opto-acoustic generation process, involving electromagnetic, thermal, and elastic fields and their couplings in matter. Among the numerical methods for solving this multiphysical problem, the semi-analytic approach is one of the most relevant for obtaining fast and accurate results, when analytic solutions exist. In this paper, a multilayer model is proposed to successively solve electromagnetic, thermal, and elastodynamic problems.

Laser ultrasonics in a multilayer structure: Plane wave synthesis and inverse problem for nondestructive evaluation of adhesive bondings.

A laser ultrasonic method is proposed for the nondestructive evaluation of bonded assemblies based on the analysis of elastic plane waves reflected from the bonding interface. Plane waves are numerically synthesized from experimentally detected cylindrical waves. Several angles of incidence with respect to the bonding interface are achieved by varying the delay in the synthesis step.

Photoacoustic 3-D imaging of polycrystalline microstructure improved with transverse acoustic waves.

Non-invasive fast imaging of grain microstructure of polycrystalline ceria with sub-micrometric spatial resolution is performed via time-domain Brillouin scattering. The propagation of a nanoacoustic pulse is monitored down to 8 μm deep in a 30 × 30 μm area. Grains boundaries are reconstructed in three-dimensions via a two-step processing method, relying on the wavelet synchro-squeezed transform and the alphashape algorithm.

Imaging grain microstructure in a model ceramic energy material with optically generated coherent acoustic phonons.

Characterization of microstructure, chemistry and function of energy materials remains a challenge for instrumentation science. This active area of research is making considerable strides with methodologies that employ bright X-rays, electron microscopy, and optical spectroscopy. However, further development of instruments capable of multimodal measurements, is necessary to reveal complex microstructure evolution in realistic environments.

High-Frequency Elastic Coupling at the Interface of van der Waals Nanolayers Imaged by Picosecond Ultrasonics.

Although the topography of van de Waals (vdW) layers and heterostructures can be imaged by scanning probe microscopy, high-frequency interface elastic properties are more difficult to assess. These can influence the stability, reliability, and performance of electronic devices that require uniform layers and interfaces. Here, we use picosecond ultrasonics to image these properties in vdW layers and heterostructures based on well-known exfoliable materials, .

Picosecond laser ultrasonics for imaging of transparent polycrystalline materials compressed to megabar pressures.

Picosecond laser ultrasonics is an all-optical experimental technique based on ultrafast high repetition rate lasers applied for the generation and detection of nanometric in length coherent acoustic pulses. In optically transparent materials these pulses can be detected not only on their arrival at the sample surfaces but also all along their propagation path inside the sample providing opportunity for imaging of the sample material spatial inhomogeneities traversed by the acoustic pulse. Application of this imaging technique to polycrystalline elastically anisotropic transparent materials subject to high pressures in a diamond anvil cell reveals their significant texturing/structuring at the spatial scales exceeding dimensions of the individual crystallites.

Effect of refracted light distribution on the photoelastic generation of zero-group velocity Lamb modes in optically low-absorbing plates.

Zero-group velocity (ZGV) Lamb modes are associated with sharp local acoustic resonances and allow, among other features, local measurement of Poisson's ratio. While the thermoelastic generation of Lamb waves in metal plates has been widely studied, the case of materials of low-optical absorption remains unexplored. In materials such as glasses, the generation of bulk elastic waves has been demonstrated to be sensitive to the refracted light distribution.

Investigation of interfacial stiffnesses of a tri-layer using Zero-Group Velocity Lamb modes.

Zero-Group Velocity (ZGV) Lamb waves are studied in a structure composed of two plates bonded by an adhesive layer. The dispersion curves are calculated for a Duralumin/epoxy/Duralumin sample, where the adhesion is modeled by a normal and a tangential spring at both interfaces. Several ZGV modes are identified and their frequency dependence on interfacial stiffnesses and on the bonding layer thickness is numerically studied.

Acoustic beam steering by light refraction: illustration with directivity patterns of a tilted volume photoacoustic source.

The symmetry of a thermoelastic source resulting from laser absorption can be broken when the direction of light propagation in an elastic half-space is inclined relatively to the surface. This leads to an asymmetry of the directivity patterns of both compressional and shear acoustic waves. In contrast to classical surface acoustic sources, the tunable volume source allows one to take advantage of the mode conversion at the surface to control the directivity of specific modes.

Effect of laser beam incidence angle on the thermoelastic generation in semi-transparent materials.

When a laser beam is absorbed in a semi-transparent material, a volume acoustic source is created owing to penetration of the laser beam inside the material and to thermoelastic transduction. Many experimental and theoretical studies have been conducted to better understand this ultrasound generation process with normal laser light incidence on the material surface. The purpose of this paper is to analyze the effects of the asymmetry caused by oblique incidence of a laser line source on the generation of acoustic waves in semi-transparent isotropic materials.

Dynamic analysis of cardiac R-R intervals in normal infants and in infants who subsequently succumbed to the sudden infant death syndrome.

Infants who subsequently succumb to the sudden infant death syndrome (SIDS) have higher heart rates and reduced heart rate variation compared with other infants. We examined dynamic changes in cardiac interbeat intervals to explore these differences in cardiac control. Recordings of electrocardiographic activity and respiratory movement were acquired from 13 SIDS victims before their deaths.

Heart rate dynamics after acute cocaine administration.

We examined heart rate (HR) patterns after a bolus intravenous (i.v.) administration of a high (10 mg/kg) dose of cocaine in unrestrained cats.

Dynamic characteristics of cardiac R-R intervals during sleep and waking states.

Traditional assessment of cardiac R-R intervals during sleep-wake states uses summary statistics such as mean and interquartile range. Such summary statistics are less able to provide information about instantaneous or dynamic aspects of beat-to-beat control. We examined state-dependent beat-to-beat patterning by plotting each cardiac R-R interval against the previous interval (Poincaré plots).