Nonlinear multiscale wavelet diffusion for speckle suppression and edge enhancement in ultrasound images

This paper introduces a novel nonlinear multiscale wavelet diffusion method for ultrasound speckle suppression and edge enhancement. This method is designed to utilize the favorable denoising properties of two frequently used techniques: the sparsity and multiresolution properties of the wavelet, and the iterative edge enhancement feature of nonlinear diffusion. With fully exploited knowledge of speckle image models, the edges of images are detected using normalized wavelet modulus. Relying on this feature, both the envelope-detected speckle image and the log-compressed ultrasonic image can be directly processed by the algorithm without need for additional preprocessing. Speckle is suppressed by employing the iterative multiscale diffusion on the wavelet coefficients. With a tuning diffusion threshold strategy, the proposed method can improve the image quality for both visualization and auto-segmentation applications. We validate our method using synthetic speckle images and real ultrasonic images. Performance improvement over other despeckling filters is quantified in terms of noise suppression and edge preservation indices.     

Mitigating Jahn–Teller Effect in Layered Cathode Material Via Interstitial Doping for High-Performance Sodium-Ion Batteries

Layered transition metal oxides are promising cathode materials for sodium-ion batteries due to their high energy density and appropriate operating potential. However, the poor structural stability is a major drawback to their widespread application. To address this issue, B³⁺ is successfully introduced into the tetrahedral site of Na_0.67Fe_0.5Mn_0.5O₂, demonstrating the effectiveness of small-radius ion doping in improving electrochemical performance. The obtained Na_0.67Fe_0.5Mn_0.5B_0.04O₂ exhibits excellent cycling performance with 88.8% capacity retention after 100 cycles at 1 C and prominent rate performance. The structure-property relationship is constructed subsequently by neutron powder diffraction, in situ X-ray diffraction and X-ray absorption spectroscopy, which reveal that the Jahn–Teller distortion and the consequent P2-P2' phase transformation are effectively mitigated because of the occupancy of B³⁺ at the interstitial site. Furthermore, it is found that the transition metal layers are stabilized and the transition metal dissolution are suppressed, resulting in excellent cycling performance. Besides, the prominent rate performance is attributed to the enhanced diffusion kinetics associated with the rearrangement of Na⁺. This work provides novel insight into the action mechanism of interstitial site doping and demonstrates a universal approach to improve the electrochemical properties of P2-type manganese-based sodium cathode materials.     

Skin-Mountable Vibrotactile Stimulator Based on Laterally Multilayered Dielectric Elastomer Actuators

Skin-stimulation technology has attracted intense attention for virtual/augmented reality applications and tactile-feedback systems. However, bulky, heavy, and stiff characteristics of existing skin-stimulating devices limit their wearability and comfort, thus disturbing the immersive experience of users. This study presents a new type of thin and lightweight dielectric elastomer actuator for developing a skin-mountable vibrotactile stimulator. A new methodology is suggested to enhance the operating efficiency of dielectric elastomer actuators based on a laterally aligned dielectric multilayer structure (≈900 layer) with short dielectric distance (≈10 µm) and a soft elastomer/ionic liquid composite with low modulus and high dielectric constant. With the improved structural/material properties, the flexible actuator exhibits high displacements at low operating voltage (<200 V) over a wide frequency range (≈800 Hz). Therefore, the finger-band type vibrotactile stimulator based on the laterally multilayered dielectric elastomer actuators can exert indentations that have the ability of stimulating all mechanoreceptors in human skin over the full perception frequency/amplitude range. In addition, the actuator shows a high electromechanical stability for long-term operation due to time-efficient and precise fabrication process using sophisticated photolithography and secondary sputtering. Therefore, this vibrotactile stimulator shows high promise for use in tactile-assistive devices, tactile communications, haptic feedback, and beyond.     

The effects of organic additives on induction time and characteristics of precipitated calcium carbonate

The effects of an organic additive, polyoxyethylene sorbitan trioleate (Tween 85), on the induction time for the precipitation of calcium carbonate are experimentally and theoretically investigated. Calcium carbonate was precipitated from aqueous solutions of K₂CO₃ and Ca(NO)₃ at moderate supersaturations ranging between 5 and 16 with and without the organic additive. Experimentally it has been noticed that the induction period for CaCO₃ precipitation increases at low supersaturation and is also influenced by temperature. An increase of the induction time was noticed when Tween 85 was added in the system. The “cluster coagulation model” proposed by Qian and Botsaris (1997), which combines nucleation models and coagulation theory, was used to explain the effects of operating parameters on the induction time in terms of interfacial energy and cluster sizes.     

Hybrid magnetite nanoparticles/Rosmarinus officinalis essential oil nanobiosystem with antibiofilm activity

Biofilms formed by fungal organisms are associated with drastically enhanced resistance against most antimicrobial agents, contributing to the persistence of the fungi despite antifungal therapy. The purpose of this study is to combine the unique properties of nanoparticles with the antimicrobial activity of the Rosmarinus officinalis essential oil in order to obtain a nanobiosystem that could be pelliculised on the surface of catheter pieces, in order to obtain an improved resistance to microbial colonization and biofilm development by Candida albicans and C. tropicalis clinical strains. The R. officinalis essential oils were extracted in a Neo-Clevenger type apparatus, and its chemical composition was settled by GC-MS analysis. Functionalized magnetite nanoparticles of up to 20 nm size had been synthesized by precipitation method adapted for microwave conditions, with oleic acid as surfactant. The catheter pieces were coated with suspended core/shell nanoparticles (Fe₃O₄/oleic acid:CHCl₃), by applying a magnetic field on nanofluid, while the CHCl₃ diluted essential oil was applied by adsorption in a secondary covering treatment. The fungal adherence ability was investigated in six multiwell plates, in which there have been placed catheters pieces with and without hybrid nanoparticles/essential oil nanobiosystem pellicle, by using culture-based methods and confocal laser scanning microscopy (CLSM). The R. officinalis essential oil coated nanoparticles strongly inhibited the adherence ability and biofilm development of the C. albicans and C. tropicalis tested strains to the catheter surface, as shown by viable cell counts and CLSM examination. Due to the important implications of Candida spp. in human pathogenesis, especially in prosthetic devices related infections and the emergence of antifungal tolerance/resistance, using the new core/shell/coated shell based on essential oil of R. officinalis to inhibit the fungal adherence could be of a great interest for the biomedical field, opening new directions for the design of film-coated surfaces with antibiofilm properties.     

Investigation of electrochemical oxidation of methanol in a cyclone flow cell

Electrochemical oxidation of methanol on carbon supported Pt/Ru gas diffusion electrodes was investigated in a cyclone flow cell at room temperature using chronoamperometry, cyclic voltammetry and electrochemical impedance spectroscopy. The influence of the flow rate was checked. It was proved that the cyclone cell is suitable for the investigation of methanol electrooxidation and provides additional information on the mass transfer limitations in the electrode assembly. Chronoamperometric measurements showed slow, but constant current decay at all investigated potentials. Impedance measurements in water and methanol containing solutions were performed and the experimental data were fitted to an appropriate equivalent circuit.     

Synthesis of polysulfone block copolymers containing polydimethylsiloxane

The synthesis of polysulfone-polydimethylsiloxane (PSU-PDMS)linear block copolymers has been carried out in solution by condensation of chloro-terminated bisphenol A, diphenylsulfone and , -di (hydrogensilyl)-polydimethylsiloxane with Si–C bond. ¹H-NMR spectra of the block copolymers allow the estimation of siloxane and polysulfone ratio. The molecular weight of the polysulfone and polysiloxane oligomers and the block copolymers was determined by GPC. Thermogravimetric analysis indicates a thermal stability of block copolymers up to 400°C and allows estimation of the process activation energy. Microphase separation of the block copolymers was observed by differential scanning calorimetry (DSC).