Voltage-controlled narrowband and wide, variable-range four-segment quartz crystal oscillator

In this work, our goal is to develop a voltage-controlled variable-frequency quartz crystal oscillator with narrowband response, wide, variable frequency range and the capacity to oscillate across the series resonance frequency using a four-segment configuration of a quartz crystal oscillator. In conventional quartz oscillators, the quartz resonator is inserted in the feedback loop between the input and the output of the active circuit, providing sufficient gain and the phase relation. In the oscillator developed here, the quartz crystal resonator is inserted between the loop circuit and the ground potential. The performance of the voltage-controlled variable-frequency oscillator is demonstrated across the series resonance frequency.     

Kinetics study of hydrogen adsorption over Pt/MoO3

The rate controlling step and the energy barrier involved in the hydrogen adsorption over Pt/MoO₃ were studied. Rates of hydrogen adsorption on Pt/MoO₃ were measured at the adsorption temperature range of 323–573 K and at the initial hydrogen pressure of 6.7 kPa. The rate of hydrogen uptake was very high for the initial few minutes for adsorption at and above 473 K, and reached equilibrium within 2 h. At and below 423 K, the hydrogen uptake still continued and did not reach equilibrium after 10 h. The hydrogen uptake exceeded the H/Pt ratio of unity for adsorption at and above 423 K, indicating that hydrogen adsorption involves hydrogen atom spillover and surface diffusion of the spiltover hydrogen atom over the bulk surface of MoO₃ followed by formation of H_xMoO₃. The hydrogen uptake was scarcely appreciable for Pt-free MoO₃. The rate controlling step of the hydrogen adsorption on Pt/MoO₃ was the surface diffusion of the spiltover hydrogen with the activation energy of 83.1 kJ/mol. The isosteric heats of hydrogen adsorption on Pt/MoO₃ were 18.1–16.9 kJ/mol for the hydrogen uptake range 2.4–2.8 × 10¹⁹ H-atom/g-cat. Similarities and differences in hydrogen adsorption on Pt/SO₄^2?–ZrO₂, Pt/WO₃–ZrO₂ and Pt/MoO₃ catalysts are discussed.     

Synthesis,structure and photocatalytic properties of nanoparticles from a carbon-containing composite based on silicon oxide modified with titanium dioxide

A pulsed plasmochemical method was used to obtain carbon-containing nanocomposites based on silicon oxide modified with titanium dioxide. The material contained a Si_xC_yO_z carrier with an average size of 50–150?nm and a shell of fine particles with an average size of 5–10?nm. The phase composition and morphology of the synthesized composites was studied by X-ray diffraction and transmission electron microscopy. The optical and photocatalytic properties of the nanoparticles from the carbon-based composite based on silicon oxide encapsulated in titanium dioxide were studied. The synthesized composite showed a high photocatalytic activity due to the decomposition of methylene blue under the influence of visible light in the wavelength range of 460–630?nm.     

Optimization of Strength‐Electrical Conductivity Properties in Al–2Fe Alloy by Severe Plastic Deformation and Heat Treatment

High‐pressure torsion at room temperature followed by two processing routes, either 1) annealing at 200 °C for 8 h or 2) elevated temperature (200 °C) high‐pressure torsion, are employed to obtain simultaneous increase in mechanical strength and electrical conductivity of Al–2 wt%Fe. The comparative study of microstructure, particle distribution, mechanical properties, and electrical conductivity for both processing routes gives the optimal combination of high mechanical strength and high electrical conductivity in Al–2Fe alloy. It is shown that while the mechanical strength is approximately the same for both processing routes (>320 MPa), high‐pressure torsion at elevated temperature results in higher conductivity (≥52% IACS) due to reduction of Fe solute atom concentration in Al matrix compared to annealing treatment. High‐pressure torsion at 200 °C has been demonstrated as a new and effective way for obtaining combination of high mechanical strength and electrical conductivity in Al–Fe alloys.

     

Plasma‐beam alignment of passive liquid crystals (Invited Paper)

Abstract— A plasma‐beam process, developed for the alignment of liquid crystals (LC) in electro‐optic applications, has been successfully applied to align “non‐standard” LC, such as crystalline materials with LC phases at elevated temperatures and reactive mesogenes. In addition to the high alignment quality of the materials, there is no need for an intermediate layer between the substrate and the LC layer. Furthermore, the construction of our source simplifies the alignment procedure of large‐area rigid substrates and the roll‐to‐roll processing of flexible films. This method opens new horizons for optical retarders and polarizers, as well as anisotropic semiconducting films for organic electronics.     

液晶共面取向的等离子处理方法

在受等离子辐照过的一些有机和无机的基板上，获得了高质量的液晶共面取向。与已知的用来改善顶部锚定及预倾角各向同性的等离子处理方法不同，新方法是将等离子束调整到倾斜射向待取向的基板。在所用的辐射参数范围内，所有基板上的LC取向的易取向轴(easy axis)都平行于等离子体传播方向。研究了LC的预倾角和锚定能与等离子束的入射角、辐照时间、能量以及辐照电流密度等的依赖关系。经等离子处理过的基板上，方位角、锚定能与用光取向方法得到的相近，而预倾角与摩擦产生的类似。透过率-电压曲线与等离子处理的和摩擦工艺处理的非常接近。与摩擦取向相同，等离子诱导的取向具有很高的温度和光照的稳定性。也考虑了采用等离子／偏振紫外光和等离子／摩擦处理等组合方法来制作LC图形。     

Nanostructuring of metals by severe plastic deformation for advanced properties

Despite rosy prospects, the use of nanostructured metals and alloys as advanced structural and functional materials has remained controversial until recently. Only in recent years has a breakthrough been outlined in this area, associated both with development of new routes for the fabrication of bulk nanostructured materials and with investigation of the fundamental mechanisms that lead to the new properties of these materials. Although a deep understanding of these mechanisms is still a topic of basic research, pilot commercial products for medicine and microdevices are coming within reach of the market. This progress article discusses new concepts and principles of using severe plastic deformation (SPD) to fabricate bulk nanostructured metals with advanced properties. Special emphasis is laid on the relationship between microstructural features and properties, as well as the first applications of SPD-produced nanomaterials.     

Cytoskeleton Rearrangements Modulate TRPC6 Channel Activity in Podocytes

The actin cytoskeleton of podocytes plays a central role in the functioning of the filtration barrier in the kidney. Calcium entry into podocytes via TRPC6 (Transient Receptor Potential Canonical 6) channels leads to actin cytoskeleton rearrangement, thereby affecting the filtration barrier. We hypothesized that there is feedback from the cytoskeleton that modulates the activity of TRPC6 channels. Experiments using scanning ion-conductance microscopy demonstrated a change in migration properties in podocyte cell cultures treated with cytochalasin D, a pharmacological agent that disrupts the actin cytoskeleton. Cell-attached patch-clamp experiments revealed that cytochalasin D increases the activity of TRPC6 channels in CHO (Chinese Hamster Ovary) cells overexpressing the channel and in podocytes from freshly isolated glomeruli. Furthermore, it was previously reported that mutation in ACTN4, which encodes α-actinin-4, causes focal segmental glomerulosclerosis and solidifies the actin network in podocytes. Therefore, we tested whether α-actinin-4 regulates the activity of TRPC6 channels. We found that co-expression of mutant α-actinin-4 K255E with TRPC6 in CHO cells decreases TRPC6 channel activity. Therefore, our data demonstrate a direct interaction between the structure of the actin cytoskeleton and TRPC6 activity.     

On the influence of methanol addition on the performances of PEM fuel cells operated at subzero temperatures

The storage and the operation of proton exchange membrane fuel cells (PEM FCs) at subzero temperatures result in the ageing and degradation of membrane-electrode assemblies (MEAs). In this study, we investigated the effect of a freeze-thaw temperature cycles (from ambient down to ?80 °C) on various properties of PFSA membranes and on the performance level of MEAs. The beneficial effects resulting from the addition of methanol vapor to the hydrogen have been put into evidence. Small angle x-ray scattering (SAXS) data have been measured on membranes swollen with water and water-methanol mixtures, to identify possible microstructure differences. It was found that the addition of methanol tends to increase the ionic resistivity of the membranes but has a protective effect on the catalytic layers during the freeze-thaw cycles. The degradation rate of the catalytic layer was reduced by almost a factor of two as a result of optimal methanol addition.