Autoregressive modeling of lung sounds: characterization of sourceand transmission

In this communication, we discuss the application of autoregressive modeling to lung sounds analysis. The lung sounds source in the airway is modeled as a white noise source, consisting of one or a combination of the following sources: random white noise sequence, periodic train of impulses, and impulsive bursts of energy. The acoustic transmission through the lung parenchyma and chest wall is modeled as an all-pole filter. Using this method, the source and transmission characteristics of lung sounds are estimated separately, based on the lung sounds at the chest wall. To illustrate the potential validity of the model, lung sound segments in known disease conditions were selected from teaching tapes and the source and transmission characteristics were estimated by applying the model. The estimated characteristics were found to be consistent with current knowledge of the generation and transmission of lung sounds in the known conditions.     

Thermoelectric power of single-phase samples of Tl2CaBa2Cu2O y and Ba2CaSr2Cu2O y

Single-phase 2122 samples of thallium and bismuth superconductors were made by the precursor matrix method. The thermopower of these samples was measured in the temperature range 250 K-T _c . The thermopower was positive and decreased linearly with increasing temperature aboveT _c (onset). The exponential enhancement of thermopower seen in the undoped and doped YBCO was not observed in these samples. The linear variation of thermopower can be explained on the basis of either a two-band model or a narrow band model.     

Micropatterning of Electrospun Polyurethane Fibers Through Control of Surface Topography

A novel technique was developed to control the deposition of electrospun polyurethane fibers using a silicone collector substrate patterned with soft lithography. This method can be used to control selective fiber deposition with broad pattern dimensions (50–500 µm) over a large area. The combination of ease of use, low cost, tunability, and generation of relatively large fiber mats available with this technique is expected to advance our ability to mimic the orientation and anisotropic properties of native tissues to generate improved tissue engineering scaffolds.

     

Cover Feature: Molecular Highway Patrol for Ribosome Collisions (ChemBioChem 20/2023)

During translation, messenger RNAs (mRNAs) are decoded by ribosomes which can stall for various reasons. These include chemical damage, codon composition, starvation, or translation inhibition. Trailing ribosomes can collide with stalled ribosomes, potentially leading to dysfunctional or toxic proteins. Such aberrant proteins can form aggregates and favor diseases, especially neurodegeneration. To prevent this, both eukaryotes and bacteria have evolved different pathways to remove faulty nascent peptides, mRNAs and defective ribosomes from the collided complex. In eukaryotes, ubiquitin ligases play central roles in triggering downstream responses and several complexes have been characterized that split affected ribosomes and facilitate degradation of the various components. As collided ribosomes signal translation stress to affected cells, in eukaryotes additional stress response pathways are triggered when collisions are sensed. These pathways inhibit translation and modulate cell survival and immune responses. Here, we summarize the current state of knowledge about rescue and stress response pathways triggered by ribosome collisions.     

Overview and perspectives of solid electrolytes for sodium batteries

Quoting the abundance and cost of sodium reserve and robustly safe and high-energy solid electrolytes, sodium solid-state batteries (SSBs) exhibit huge promise for future energy storage applications compared to battery systems using organic liquid electrolytes and Li counterparts. However, the progress and application are still in infancy, experiencing numerous challenges for sodium SSBs due to inherent properties, interface complications, and fabrication. These are recently receiving unprecedented research attention by understanding and steadily resolving the issues associated with sodium SSBs. In this review, the governing bulk and interfacial issues and dynamics, background research correlations from Li counterparts, and strategies to address them are investigated for various ceramic-, polymer-, and ceramic–polymer composite based solid electrolytes. Particular attention is devoted to issues with ceramic electrolytes (such as interfacial stability, brittleness, porosity, and grain–grain boundary resistance) and polymer electrolytes (like dendrite formation, passivation layer, electrochemical instability, and ionic conductivity), and finally, robustness in overall performance and a few drawbacks (such as filler agglomeration, interface dynamics, and crack propagation) on the composited state-of-the-art ceramic–polymer electrolytes are highlighted. To end with, crucial inferences and future research perspectives are condensed on the development of enhanced solid electrolytes for sodium SSBs overcoming the shortcomings illustrated for different electrolytes.     

Low temperature crystallographic data on Kevlar 49 fibres

Using X-ray diffraction data, the behaviour of Kevlar 49 fibres at low temperatures, up to –100°C, has been analysed. During cooling, the basal plane of the monoclinic unit cell shrinks whereas the c- (unique, chain axis) length is not significantly affected. In contrast, in the return heating cycle to ambient temperature, the basal plane expands and contraction occurs along the chain direction. The unit cell registers a reduction in volume in both the cooling and heating cycles. Conspicuously, after a cycle of cooling and heating, the unit cell does not return to its initial volume.     

Environmental effects on low cycle fatigue of 2024-T351 and 7075-T651 aluminum alloys

The environmental effects on the low cycle fatigue (LCF) behavior of 2024-T351 and 7075-T651 aluminum alloys were studied at room temperature. The specimens were subjected to identical LCF tests at strain ratio R of −1 and frequency of 5 Hz in three environments: vacuum, air and 1% NaCl solution of pH 2. A separate group of specimens was pre-corroded in 1% NaCl solution and then LCF-tested in air. Their strain–life relations and cyclic stress–strain responses were investigated and compared. Furthermore, the fracture surface morphology was evaluated to find the association of LCF behavior and fractographic features under different environmental conditions.     

Plasma immersion ion implantation for SOI synthesis: SIMOX and ion-cut

We have demonstrated feasibility to form silicon-on-insulator (SOI) substrates using plasma immersion ion implantation (PIII) for both separation by implantation of oxygen and ion-cut. This high throughput technique can substantially lower the high cost of SOI substrates due to the simpler implanter design as well as ease of maintenance. For separation by plasma implantation of oxygen wafers, secondary ion mass spectrometry analysis and cross-sectional transmission electron micrographs show continuous buried oxide formation under a single-crystal silicon overlayer with sharp Si/SiO₂ interfaces after oxygen plasma implantation and high-temperature (1300°C) annealing. Ion-cut SOI wafer fabrication technique is implemented for the first time using PIII. The hydrogen plasma can be optimized so that only one ion species is dominant in concentration and there are minimal effects by other residual ions on the ion-cut process. The physical mechanism of hydrogen induced silicon surface layer cleavage has been investigated. An ideal gas law model of the microcavity internal pressure combined with a two-dimensional finite element fracture mechanics model is used to approximate the fracture driving force which is sufficient to overcome the silicon fracture resistance.