Exploring the Role of Coinage Metalates in Trifluoromethylation: A Combined Experimental and Theoretical Study

Despite the known nucleophilic nature of [M(CF₃)₂]⁻ (M=Cu, Ag, Au) complexes, their participation in trifluoromethylation reactions of aryl halides remains unexplored. Here, for the first time, selective access to a [Cu(CF₃)₂]⁻ species is reported, which is ubiquitous in Cu-mediated trifluoromethylations, and we rationalize its complex mechanistic scenario as well as its behavior compared to its silver and gold congeners through a combination of experimental and computational approaches.     

Micro‐structured integrated electro‐optic LiNbO3 modulators

In this paper, we will review the state‐of‐the‐art of LiNbO₃ based integrated electro‐optic modulators and will show how micro‐structuring techniques such as etching, domain inversion and thin film processing can be used to realize new configurations which can take the performance to unprecedented levels. In particular, we will review recent results on the use of domain inversion on a micron scale and we report on the fabrication of a chirp‐free modulator having ∼ 2 V switching voltage and bandwidth of 15 GHz designed by placing the waveguide arms of the Mach‐Zehnder interferometer in opposite domain oriented regions. We also review some of the new modulation formats (e.g. DQPSK) that can represent an application development of the presented micro‐structured devices. Finally, we address the issue of the integration of the modulator chip in a transmitter board comprising tunable laser, bias‐control electronics and RF driver. The requirements of integration can even push further the reduction in size of modulator chips, thus making more crucial the use of micro‐ and nano‐structuring techniques.     

Cation Redistribution along the Spiral of Ni-Doped Phyllosilicate Nanoscrolls: Energy Modelling and STEM/EDS Study

Here, we study the stress-induced self-organization of Mg²⁺ and Ni²⁺ cations in the crystal structure of multiwalled (Mg_1–x,Ni_x)₃Si₂O₅(OH)₄ phyllosilicate nanoscrolls. The phyllosilicate layer strives to compensate size and surface energy difference between the metal oxide and silica sheets by curling. But as soon as the layer grows, the scrolling mechanism becomes a spent force. An energy model proposes secondary compensation of strain: two cations distribute along the nanoscroll spiral in accordance with preferable radii of curvature. To reveal this, we study synthetic (Mg_1–x,Ni_x)₃Si₂O₅(OH)₄ nanoscrolls by the scanning transmission electron microscopy/energy-dispersive X-ray spectroscopy (STEM/EDS) technique. For a number of scrolls, we have found indeed a change of Ni concentration with increase in distance from the nanoscroll central axis. The concentration gradient, according to our estimates, can reach 50 at.% over 25 nm of the wall thickness.     

Self-propelled particle model for cell-sorting phenomena

A self-propelled particle model is introduced to study cell sorting occurring in some living organisms. This allows us to evaluate the influence of intrinsic cell motility separately from differential adhesion with fluctuations, a mechanism previously shown to be sufficient to explain a variety of cell rearrangement processes. We find that the tendency of cells to actively follow their neighbors greatly reduces segregation time scales. A finite-size analysis of the sorting process reveals clear algebraic growth laws as in physical phase-ordering processes, albeit with unusual scaling exponents.     

Dynamic patterns and self-knotting of a driven hanging chain

When shaken vertically, a hanging chain displays a startling variety of distinct behaviors. We find experimentally that instabilities occur in tonguelike bands of parameter space, to swinging or rotating pendular motion, or to chaotic states. Mathematically, the dynamics are described by a nonlinear wave equation. A linear stability analysis predicts instabilities within the well-known resonance tongues; their boundaries agree very well with experiment. Full simulations of the 3D dynamics reproduce and elucidate many aspects of the experiment. The chain is also observed to tie knots in itself, some quite complex. This is beyond the reach of the current analysis and simulations.     

Synthesis of Carbon–Metal Multi-Strand Nanocomposites by Discharges in Heptane Between Two Metallic Electrodes

We studied composite wires assembled from electric field-driven nanoparticles in a dielectric liquid (heptane) to elucidate the exact processes and controlling factors involved in the synthesis of the multi-phase nanocomposites. Filamentary wires are synthesized by a two-step process: (1) abundant nanoparticle production, mostly of carbonaceous types, from heptane decomposition by spark discharge and of metal nanoparticles by electrode erosion and (2) assembly of hydrogenated amorphous carbonaceous nano-clusters with incorporated metal nanoparticles forming wires by dielectrophoretic transport while maintaining a high electric field between electrodes kept sufficiently separated to avoid breakdown. Four types of nanocomposites products are identified to form at different steps in distinctive zones of the setup. The black carbonaceous agglomerates with metal spherules made by electrode erosion represent the pyrolytic residues of heptane decomposition by spark discharge during step 1. The filamentary wires grown in the interelectrode gap during step 2 get assembled by dielectrophoretic transport and chaining forces. Their great stability is shown to express the concurrent effect of polymerization favoured by the abundance of metal catalysts. The nature, abundance, and transformation of solid particles from the source materials versus discharge conditions control the morphological and compositional diversity of the wires. The production of mineral and metal nano-particles traces the efficiency of dielectrophoresis to separate compound particle mixtures by size and to co-synthesize nanostructured microcrystals and nanocomposites. The link between impurities and the variability from nano- to micro-scales of the synthesized products provides an innovative contribution to the knowledge of nanocomposite synthesis triggered by electric field.     

Study by Optical Spectroscopy of Bismuth Emission in a Nanosecond-Pulsed Discharge Created in Liquid Nitrogen

Time-resolved optical emission spectroscopy of nanosecond-pulsed discharges ignited in liquid nitrogen between two bismuth electrodes is used to determine the main discharge parameters (electron temperature, electron density and optical thickness). Nineteen lines belonging to the Bi I system and seven to the Bi II system could be recorded by directly plunging the optical fibre into the liquid in close vicinity to the discharge. The lack of data for the Stark parameters to evaluate the broadening of the Bi I lines was solved by taking advantage of the time-resolved information supported by each line to determine them. The electron density was found to decrease exponentially from 6.5 ± 1.5 × 10¹⁶ cm⁻³ 200 ns after ignition to 1.0 ± 0.5 × 10¹⁶ cm⁻³ after 1050 ns. The electron temperature was found to be 0.35 eV, close to the value given by Saha’s equation.     

Sensitivity of the resonant ultrasound spectroscopy to weak gradients of elastic properties

The applicability of resonant ultrasound spectroscopy on materials with weak spatial gradients in elastic coefficients and density is analyzed. It is shown that such gradients do not affect measurably the resonant spectrum but have a significant impact on the modal shapes. A numerical inverse procedure is proposed to explore the possibility of reconstructing the gradients from experimentally obtained modal shapes. This procedure is tested on synthetic data and applied to determine the gradient of the shear modulus in a continuously graded silicon nitride ceramic material. The results are in a good agreement with the gradient calculated for the examined material theoretically as well as with the results of other experimental methods.     

Self-homodyne detection of the light orbital angular momentum

A simple optical system for the self-homodyne detection of the orbital angular momentum (OAM) carried by optical beams is introduced. We propose two different schemes based on the use of optical hybrids, which could detect the OAM mode number, even when the input beam might be slightly distorted. A balanced receiver is used to perform a self-homodyne measure of the optical signal from two different locations at the beam wavefront.