Janus acoustic metascreen with nonreciprocal and reconfigurable phase modulations.

Integrating different reliable functionalities in metastructures and metasurfaces has become of remarkable importance to create innovative multifunctional compact acoustic, optic or mechanical metadevices. In particular, implementing different wave manipulations in one unique material platform opens an appealing route for developing integrated metamaterials. Here, the concept of Janus acoustic metascreen is proposed and demonstrated, producing two-faced and independent wavefront manipulations for two opposite incidences. The feature of two-faced sound modulations requires nonreciprocal phase modulating elements. An acoustic resonant unit cell with rotating inner core, which produces a bias by a circulating fluid, is designed to achieve high nonreciprocity, leading to decoupled phase modulations for both forward and backward directions. In addition, the designed unit cell consisting of tunable phase modulators is reconfigurable. A series of Janus acoustic metascreens including optional combinations of extraordinary refraction, acoustic focusing, sound absorption, acoustic diffusion, and beam splitting are demonstrated through numerical simulations and experiments, showing their great potential for acoustic wavefront manipulation.

In silico and in vitro screening of licensed antimalarial drugs for repurposing as inhibitors of hepatitis E virus.

ABSTRACT: Hepatitis E virus (HEV) infection is emerging in Cameroon and represents one of the most common causes of acute hepatitis and jaundice. Moreover, earlier reports showed evidence of falciparum malaria/HEVcoexistence. Although the Sofosbuvir/Ribavirin combination was recently proposed in the treatment of HEV-infected patients, no specific antiviral drug has been approved so far, thereby urging the search for new therapies. Fortunately, drug repurposing offers a good alternative to this end. In this study, we report the in silico and in vitro activities of 8 licensed antimalarial drugs and two anti-hepatitis C virus agents used as references (Sofosbuvir, and Ribavirin), for repurposing as antiviral inhibitors against HEV. Compounds were docked against five HEV-specific targets including the Zinc-binding non-structural protein (6NU9), RNA-dependent RNA polymerase (RdRp), cryoEM structure of HEV VLP, genotype 1 (6LAT), capsid protein ORF-2, genotype 3 (2ZTN), and the E2s domain of genotype 1 (3GGQ) using the iGEMDOCK software and their pharmacokinetic profiles and toxicities were predicted using ADMETlab2.0. Their in vitro effects were also assessed on a gt 3 p6Gluc replicon system using the luciferase reporter assay. The docking results showed that Sofosbuvir had the best binding affinities with 6NU9 (- 98.22 kcal/mol), RdRp (- 113.86 kcal/mol), 2ZTN (- 106.96 kcal/mol), while Ribavirin better collided with 6LAT (- 99.33 kcal/mol). Interestingly, Lumefantrine showed the best affinity with 3GGQ (-106.05 kcal/mol). N-desethylamodiaquine and Amodiaquine presented higher binding scores with 6NU9 (- 93.5 and - 89.9 kcal/mol respectively vs - 80.83 kcal/mol), while Lumefantrine had the greatest energies with RdRp (- 102 vs - 84.58), and Pyrimethamine and N-desethylamodiaquine had stronger affinities with 2ZTN compared to Ribavirin (- 105.17 and - 102.65 kcal/mol vs - 96.04 kcal/mol). The biological screening demonstrated a significant (P < 0.001) antiviral effect on replication with 1 µM N-desethylamodiaquine, the major metabolite of Amodiaquine. However, Lumefantrine showed no effect at the tested concentrations (1, 5, and 10 µM). The biocomputational analysis of the pharmacokinetic profile of both drugs revealed a low permeability of Lumefantrine and a specific inactivation by CYP3A2 which might partly contribute to the short half-time of this drug. In conclusion, Amodiaquine and Lumefantrine may be good antimalarial drug candidates for repurposing against HEV. Further in vitro and in vivo experiments are necessary to validate these predictions. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1007/s40203-021-00093-y.

Natural limonoids protect mice from alcohol-induced liver injury.

Background Alcoholic liver disease (ALD) is regarded as a global health problem with limited therapeutic options. Previous studies highlighted some anticancer, antiviral, and hepatoprotective activities of limonoids, but the effects of these compounds on ALD remain unknown. The present study aimed to evaluate the effect of some natural limonoids on ethanol-induced liver injury. Methods Thirty-five albino mice (Mus musculus) were administered with 40% ethanol in the presence or absence of the different limonoids [including three havanensin-type limonoids, TS1, TS3, Rubescin D isolated from an African medicinal plant, Trichilia rubescens Oliv. (Meliaceae), and one limonin], or silymarin at 50 mg/kg for 3 days. Thereafter, the effect of the most active compound was evaluated in a chronic model of ALD. For this purpose, 24 mice with each group consisting of six mice were administered orally with 40% ethanol and limonoid at different doses (50, 75, and 100 mg/kg) for 28 days. Finally, biochemical parameters such as alanine aminotransferase (ALT), superoxide dismutase (SOD), catalase (CAT), malondialdehyde (MDA), triglyceride (TG), and tumor necrosis factor α (TNF-α) levels were quantified in liver homogenates. Results All tested limonoids significantly (p < 0.01) reduced ALT levels relative to the negative control in the acute model. However, in comparison to other limonoids, limonin at 50 and 75 mg/kg significantly reduced TG, MDA, and TNF-α levels (1.8-fold); alleviated leukocyte infiltration in liver tissue; significantly increased the activity of SOD; and decreased those of CAT better than silymarin used as a positive control at 50 mg/kg. Conclusions These data suggest that limonin possesses protective effects on long-term alcohol poisoning partially due to antioxidant and anti-inflammatory mechanisms.

A new device for real-time peroperative monitoring of ossicular chain reconstruction during middle ear surgery.

To limit functional surgical failure and reduce the rate of revision surgery in case of surgical ossicular chain reconstruction, a piezoelectric device was developed for assessment of ossicular chain vibrations during the middle ear surgery. The device resembled a pen and consisted of a reusable main body and a disposable sensitive head including piezoelectric polymer sensor. Almost all of components of the device were made of polymer for light weight and for acoustic impedance matching to the middle ear system. Several frequencies can be analyzed simultaneously and several measures can be taken by time. The results showed that the device can record normal and reconstructed ossicular chain vibration in response to an acoustic stimulation, with similar results to those achieved by laser Doppler vibrometer. This light, handheld and low-cost device allows fast, easy and safe assessments of normal ossicular chain mobility and ossicular chain reconstruction efficiency. Primary pre-clinical trial showed very promising performance of the device that could be used to qualitatively control ossiculoplasty during real-time surgical procedure. Clinical assessments will be done to further evaluate the real-life performance of the device.

Low-Temperature Variation of Acoustic Velocity in PDMS for High-Frequency Applications.

Polydimethylsiloxane (PDMS) and other related silicon-based polymers are among the most widely employed elastomeric materials in microsystems, owing to their physical and chemical properties. Meanwhile, surface acoustic wave (SAW) and bulk acoustic wave (BAW) sensors and filters have been vastly explored for sensing and wireless applications. Many fields could benefit from the combined use of acoustic wave devices, and polydimethylsiloxane-based soft-substrates, microsystems, or packaging elements. The mechanical constants of PDMS strongly depend on frequency, similar to rubber materials. This brings to the exploration of the specific mechanical properties of PDMS encountered at high frequency, required for its exploitation in SAW or BAW devices. First, low-frequency mechanical behavior is confirmed from stress strain measurements, remaining useful for the exploitation of PDMS as a soft substrate or packaging material. The study, then, proposes a temperature-dependent, high-frequency mechanical study of PDMS based on Brillouin spectroscopy to determine the evolution of the longitudinal acoustic velocity in this material, which constitutes the main mechanical parameter for the design of acoustic wave devices. The PDMS glass transition is then retrieved by differential scanning calorimetry in order to confirm the observations made by Brillouin spectroscopy. This paper validates Brillouin spectroscopy as a very suitable characterization technique for the retrieval of longitudinal mechanical properties at low temperature, as a preliminary investigation for the design of acoustic wave devices coupled with soft materials.

Dispersion of nanoparticles: from organic solvents to polymer solutions.

This work is devoted to a systematic study of nanoparticle dispersion by ultrasonication in different solutions: from organic solvents to polymer solutions. The cluster size of nanoparticles at different concentrations in both organic solvents and polymer solutions were directly characterized by Dynamic Light Scattering to study the effect of solid concentration, surfactant and polymer on the dispersion. It reveals that in stabilized suspensions, the smallest attainable size or aggregate size of nanoparticles is independent of solvent type and solid content over the tested range. Furthermore, nanoparticles in simple solvent and in polymer solutions had the similar evolution of cluster size and almost the same final size, which could be very helpful to optimize the dispersion of nanofillers in polymer solutions and nanocomposites. It is also shown that, with appropriate sonication amplitudes, the dispersion procedure developed for very dilute suspensions could be transferred to higher concentration suspensions or even to polymer suspensions.

Flexible over-moded resonators based on P(VDF-TrFE) thin films with very high temperature coefficient.

This work presents for the first time a flexible over-moded resonator (OMR) based on P(VDF-TrFE) thin films. The devices were manufactured on commercially available elastic substrate with inkjet-printed electrodes. The sensing copolymer films used in the devices were polarized by the corona method after electrode deposition. The main performance parameters of the component were then determined. The manufactured OMRs on P(VDF-TrFE) exhibited a linear variation of frequency versus temperature and a very large value of temperature coefficient of frequency (TCF ≫ 1600 ppm/°C). These properties suggest a great potential for using such components as low-cost and high-precision temperature sensors. The electromechanical coupling coefficient and the quality factor of the resonator were also characterized versus temperature.

Preparation and characterization of P(VDF-TrFE)/Al2O3 nanocomposite.

Hybrid nanocomposites based on crystalline nanoparticles dispersed in polymer matrix have been widely studied in the past few years because of the ability of these materials to combine the properties of organic polymer and inorganic nanoparticles. The aim of this work is to tune the mechanical properties of a piezoelectric polymer by adding nanoparticles to the matrix. In this paper, alumina nanoparticles were dispersed in the copolymer P(VDF-TrFE), which exhibits high piezoelectric coefficient after polarization under high electric field without needing stretching during the polarization process. Transmission electron microscopy and scanning electron microscopy demonstrate the high rate of welldispersed nanoparticles with 10% of alumina nanoparticles added to the matrix. Piezoelectric measurements indicate that P(VDF-TrFE) may be filled by up to 10 wt% of alumina while retaining its high piezoelectric properties and increasing its elastic constant by more than 20%, measured by Brillouin spectroscopy. This work opens a wide range of applications using nanoparticles with nonlinear optical, pyroelectric, magnetic, or ferroelectric properties.

Effect of ultrasonication and dispersion stability on the cluster size of alumina nanoscale particles in aqueous solutions.

This study deals with the deagglomeration of nanoparticles in low concentration suspensions in water, protic polar solvent for polymers such as poly(vinyl alcohol) (PVA). The influence of the main parameters of ultrasonication such as time, power and irradiation modes (continuous, pulsed) on the cluster size of aluminium oxide nanoparticles 1 mg/ml in aqueous solutions was investigated. Power-law dependence of size reduction on ultrasonic time was observed. The study indicated an optimum power input, i.e. at higher vibration amplitude the break up of nanoparticle clusters was no better and there was a risk of reagglomeration occurring during a long ultrasonication. Under optimal conditions, continuous and pulsed irradiations showed almost the same efficiency of deagglomeration over a given time. This result provides alternative operating conditions for attaining the smallest size of the alumina aggregates in suspension. The influence of stabilization on the cluster size was also studied. Alumina nanoparticles were stabilized by electrostatic forces against reagglomeration without the need for dispersants, and the enhancement of dispersion stability using electrostatic, steric effects had no significant effect on the aggregate size. On the contrary, the adsorption of high molecular weight polyelectrolytes onto the particle surface could lead to reagglomeration due to material bridges between particle surfaces and even flocculation.

New synthesis of nanosized niobium oxides and lithium niobate particles and their characterization by XPS analysis.

This work presents a new synthesis of nano-sized lithium niobate particles by a low temperature three steps procedure. The complete protocol implies a LiH induced reduction of NbCl5 followed by in situ spontaneous oxidation into low valence niobium nano-oxides. These niobium oxides are exposed to air atmosphere leading to pure Nb2O5 formation. Finally, the stable Nb2O5 is converted into lithium niobate LiNbO3 nanoparticles during the controlled hydrolysis of the LiH excess. The nano-sized lithium niobate particles as well as their formation processes were characterized using X-ray photoelectron spectroscopy.

Temperature study of potassium niobate (KNbO(3)) elastic constants by Brillouin spectroscopy.

This study deals with using Brillouin spectroscopy to determine the temperature variation of potassium niobate elastic constants. Two different samples have been used (Y- and Z-cut), and all the measurements were done in the temperature range between 300 K and 420 K. The calculations concern only the first-order coefficients. The acoustic velocity is then determined for each sample in 3 directions of propagation. Results are given for C( 22), C( 55), and C( 66) elastic constants and accuracy problems are discussed.

Phononic crystals based on LiNbO3 realized using domain inversion by electron-beam irradiation.

We report in this paper about the realization of domain inversion in z-cut lithium niobate by electron beam irradiation in order to perform phononic crystals. The fabrication of these phononic crystals on z-cut LiNbO3, which is, in our case, a periodic repetition of voids and LiNbO3, was achieved by domain inversion followed by wet etching, taking advantage of the large difference in etching rate between z+ and z- faces. A pertinent choice of irradiation conditions such as accelerating voltage, beam current, and charge density was determined and optimized. Two-dimensional structures at the micrometer scale were then realized on z-cut LiNbO3. We demonstrate the achievement of hexagons with diameters between 2 microm and 18 microm, with a very important depth close to 30 microm, which depends on the etching time and the hole size. The obtained structures, which exhibit a filling fraction varying from 1% to 64%, were characterized before etching by polarizing microscope to visualize the inverted domains. After HF etching, scanning electron microscopy was used to observe the obtained phononic structures. Taking into account the obtained filling fraction values and the size of created hexagons, the frequency band gap of these structures is expected at a range of 200 to 350 MHz. As expected in this frequency range, we have proven experimentally the existence of the phononic band gap on z-cut LiNbO3 by combination of a realized phononic crystal with a surface acoustic wave (SAW) device.

Optical planar and channel waveguides in the new nonlinear crystal Ca4YO(BO3)3 (YCOB) fabricated by He+ implantation.

We report the first study of optical planar and channel waveguides fabricated in the new nonlinear crystal Ca4YO(BO3) by use of MeV He+-implantations. The nx, ny, and nz refractive index modifications are studied. Losses in nonannealed YCOB waveguides measured with a CCD camera are found to be less than 2 dB cm(-1). This work is the first step toward the investigation of frequency conversion within the obtained guiding structures.

Channel waveguides in Ca4GdO(BO3)3 fabricated by He+ implantation for blue-light generation.

Blue light at 405 nm is generated by frequency doubling of a Ti:sapphire tunable laser in He(+)-implanted channel waveguides in gadolinium calcium oxoborate crystal. A conversion efficiency of approximately 2% W(-1) cm(-2) is achieved between TM00 fundamental and TE01 harmonic modes.