Conversion of polycarbosilane (PCS) to SiC-based ceramic Part 1. Characterisation of PCS and curing products

A commercial polycarbosilane (PCS) preceramic polymer has been characterised as-received and following curing under a variety of conditions. Elemental analysis, gel permeation chromatography (GPC), infra-red spectroscopy (FT-IR), simultaneous thermogravimetric analysis-differential thermal analysis (TG-DTA) and solid state nuclear magnetic resonance (NMR) have been employed. A number average molar mass of 1200 was found with a broad molar mass distribution ( / = 2.97). Elemental analysis gave an empirical formula of SiC_2.2H_5.3O_0.3. IR and Solid state ²⁹Si and ¹³C NMR spectra showed the presence of Si-O-Si, SiC₄, SiC₃H, Si-Si, Si-CH₃ and Si-CH₂ groups. Simultaneous TG-DTA performed under an argon flow showed that there was a weight gain which started at approximately 240 °C. DTA showed an exotherm starting at this temperature showing that there was oxidation of the polymer even in an inert atmosphere. This is perhaps due to the oxygen in the PCS and there may also be some impurities in the inert atmosphere. Evidently the PCS is very sensitive to oxygen. Above 500 °C, weight loss dominated although the exotherm continued to approximately 700 °C. The effect of heating rate and dwell time at 200 °C on the changes in the chemical composition during curing have been explored using IR and solid state NMR spectroscopies, and elemental analysis. The longer the cure time the higher was the weight gain and greater was the extent of the oxidation reactions. Elemental analysis showed that the ratio of H and C to Si decreased with holding time at the cure-temperature while the amount of oxygen increased. Use of a higher heating rate resulted in a lower weight gain when the same holding time was used. From this it is clear that curing starts below the holding temperature.     

A method for quantification from composite spectra: application to the determination of isomeric DNA photoproducts by tandem mass spectrometry

Quantification of mixture components from their composite optical or mass spectra is a common need in analytical chemistry. We encountered the need when applying a combination of enzymatic digestion with nuclease P1 and tandem mass spectrometry to a mixture of isomeric photomodified oligodeoxynucleotides. In the procedure, we collisionally activated the [M - H]- or [M + Na - 2H]- ion of trinucleotide triphosphates, which were extricated enzymatically from the larger, damaged oligodeoxynucleotides, and we measured the relative abundances of characteristic fragment ions. The results sometimes yield curved calibrations for plots of the relative fragment ion abundances in the product ion spectra of isomers versus their relative amounts. We developed a normalized linear model, which brings understanding to the nonlinear plots and allows quantification of the mixture components from their composite spectra. The outcome demonstrates a general quantification procedure and shows that different yields for generating fragment ions from different constituents of the mixture cause the curved calibration lines.     

Lysing bacterial spores by sonication through a flexible interface in a microfluidic system

Cell disruptions using ultrasonic energy transmitted through a flexible interface into a liquid region has limitations because the motion of the vibrating tip is not completely transferred into the liquid. To ensure that some degree of contact will be maintained between the ultrasonic horn tip and the flexible interface, the liquid must be pressurized. The pressure conditions that yield consistent coupling between the ultrasonic horn tip and the liquid region were explored in this study by using an analytical model of the system and test fixture experiments. The nature of the interaction between the horn tip and the flexible interface creates pulses of positive pressure rises, increase in temperature, streaming flow, and almost no cavitation in the liquid. There was sufficient energy to create a cloud of microspheres, or beads, that maintain a consistent pattern of ballistic motion in the liquid. The sonication was found to be repeatable by studying video recordings of bead motion and was shown to be statistically consistent using measurements of temperature rise. Sonication of bacterial spores to obtain measurements of released nucleic acid and SEM images of damaged spores were used to verify the effects of liquid pressure on the horn-interface-liquid coupling.     

Phosphorylcholine-based polymer coatings for stent drug delivery

Phosphorylcholine-based polymers have been used commercially to improve the biocompatibility of coronary stents. In this study, one particular polymer is assessed for its suitability as a drug delivery vehicle. Membranes of the material are characterized in terms of water content and molecular weight cut-off, and the presence of hydrophilic and hydrophobic domains investigated by use of the hydrophobic probe pyrene. The in vitro loading and elution of a variety of drugs was assessed using stents coated with the polymer. The rate of a drug's release was shown not to be simply a function of its water solubility, but rather more closely related to the drug oil/water partition coefficient. This finding was explained in terms of the more hydrophobic drugs partitioning into, and interacting with, the hydrophobic domains of the polymer coating. The suitability of the coated stent as a drug delivery vehicle was assessed in vivo using a radiolabeled analog of one of the more rapidly eluting drugs, angiopeptin. Autoradiography showed that the drug was released locally to the wall of the stented artery, and could be detected up to 28 days after implantation.     

Magnetic Targeting of Human Mesenchymal Stem Cells with Internalized Superparamagnetic Iron Oxide Nanoparticles

Cell therapies offer exciting new opportunities for effectively treating many human diseases. However, delivery of therapeutic cells by intravenous injection, while convenient, relies on the relatively inefficient process of homing of cells to sites of injury. To address this limitation, a novel strategy has been developed to load cells with superparamagnetic iron oxide nanoparticles (SPIOs), and to attract them to specific sites within the body by applying an external magnetic field. The feasibility of this approach is demonstrated using human mesenchymal stem cells (hMSCs), which may have a significant potential for regenerative cell therapies due to their ease of isolation from autologous tissues, and their ability to differentiate into various lineages and modulate their paracrine activity in response to the microenvironment. The efficient loading of hMSCs with polyethylene glycol‐coated SPIOs is achieved, and it is found that SPIOs are localized primarily in secondary lysosomes of hMSCs and are not toxic to the cells. Further, the key stem cell characteristics, including the immunophenotype of hMSCs and their ability to differentiate, are not altered by SPIO loading. Through both experimentation and mathematical modeling, it is shown that, under applied magnetic field gradients, SPIO‐containing cells can be localized both in vitro and in vivo. The results suggest that, by loading SPIOs into hMSCs and applying appropriate magnetic field gradients, it is possible to target hMSCs to particular vascular networks.     

Dynamics of Local Bond Correlations in FeSe x Te1−x by Inelastic Neutron Scattering

The dynamics of the local atomic pair correlations in the FeSe _x Te_1?x ( x = 0.1, 0.5, and 0.9) system were investigated using the dynamic pair density function analysis obtained from inelastic neutron scattering. Distinct differences are observed between the superconducting and nonsuperconducting compositions, particularly involving the local dynamics of the Fe-Fe correlations. The energy scale of the observed differences is between 25 and 30 meV. In the nonsuperconducting FeSe_0.1Te_0.9, the Fe-Fe correlations are enhanced with cooling that may signal stronger exchange interactions, while in the superconducting compositions of FeSe_0.9Te_0.1 and FeSe_0.5Te_0.5, they are suppressed.     

An Elevator Button Recognition Method Combining YOLOv5 and OCR

Fast recognition of elevator buttons is a key step for service robots to ride elevators automatically. Although there are some studies in this field, none of them can achieve real-time application due to problems such as recognition speed and algorithm complexity. Elevator button recognition is a comprehensive problem. Not only does it need to detect the position of multiple buttons at the same time, but also needs to accurately identify the characters on each button. The latest version 5 of you only look once algorithm (YOLOv5) has the fastest reasoning speed and can be used for detecting multiple objects in real-time. The advantages of YOLOv5 make it an ideal choice for detecting the position of multiple buttons in an elevator, but it’s not good at specific word recognition. Optical character recognition (OCR) is a well-known technique for character recognition. This paper innovatively improved the YOLOv5 network, integrated OCR technology, and applied them to the elevator button recognition process. First, we changed the detection scale in the YOLOv5 network and only maintained the detection scales of 40 * 40 and 80 * 80, thus improving the overall object detection speed. Then, we put a modified OCR branch after the YOLOv5 network to identify the numbers on the buttons. Finally, we verified this method on different datasets and compared it with other typical methods. The results show that the average recall and precision of this method are 81.2% and 92.4%. Compared with others, the accuracy of this method has reached a very high level, but the recognition speed has reached 0.056 s, which is far higher than other methods.     

Adipose‐Derived Biogenic Nanoparticles for Suppression of Inflammation

Extracellular vesicles secreted from adipose‐derived mesenchymal stem cells (ADSCs) have therapeutic effects in inflammatory diseases. However, production of extracellular vesicles (EVs) from ADSCs is costly, inefficient, and time consuming. The anti‐inflammatory properties of adipose tissue‐derived EVs and other biogenic nanoparticles have not been explored. In this study, biogenic nanoparticles are obtained directly from lipoaspirate, an easily accessible and abundant source of biological material. Compared to ADSC‐EVs, lipoaspirate nanoparticles (Lipo‐NPs) take less time to process (hours compared to months) and cost less to produce (clinical‐grade cell culture facilities are not required). The physicochemical characteristics and anti‐inflammatory properties of Lipo‐NPs are evaluated and compared to those of patient‐matched ADSC‐EVs. Moreover, guanabenz loading in Lipo‐NPs is evaluated for enhanced anti‐inflammatory effects. Apolipoprotein E and glycerolipids are enriched in Lipo‐NPs compared to ADSC‐EVs. Additionally, the uptake of Lipo‐NPs in hepatocytes and macrophages is higher. Lipo‐NPs and ADSC‐EVs have comparable protective and anti‐inflammatory effects. Specifically, Lipo‐NPs reduce toll‐like receptor 4‐induced secretion of inflammatory cytokines in macrophages. Guanabenz‐loaded Lipo‐NPs further suppress inflammatory pathways, suggesting that this combination therapy can have promising applications for inflammatory diseases.     

Recent Advances in Metallic Glass Nanostructures: Synthesis Strategies and Electrocatalytic Applications

Recent advances in metallic glass nanostructures (MGNs) are reported, covering a wide array of synthesis strategies, computational discovery, and design solutions that provide insight into distinct electrocatalytic applications. A brief introduction to the development and unique features of MGNs with an overview of top‐down and bottom‐up synthesis strategies is presented. Specifically, the morphology and structural analysis of several examples applying MGNs as electrodes are highlighted. Subsequently, a comprehensive discussion of commonly employed kinetic parameters and their connection with the unique material structures of MGNs on individual electrocatalytic reactions is made, including the hydrogen evolution reaction, oxygen reduction reaction, and alcohol (methanol or ethanol) oxidation reaction. Finally, a summary of the challenges and perspective on the future research and development relevant to MGNs as electrocatalysts is provided.     

Self-Assembled Microactuators Using Chiral Liquid Crystal Elastomers

Materials that undergo reversible changes in form typically require top-down processing to program the microstructure of the material. As a result, it is difficult to program microscale, 3D shape-morphing materials that undergo non-uniaxial deformations. Here, a simple bottom-up fabrication approach to prepare bending microactuators is described. Spontaneous self-assembly of liquid crystal (LC) monomers with controlled chirality within 3D micromold results in a change in molecular orientation across thickness of the microstructure. As a result, heating induces bending in these microactuators. The concentration of chiral dopant is varied to adjust the chirality of the monomer mixture. Liquid crystal elastomer (LCE) microactuators doped with 0.05 wt% of chiral dopant produce needle-shaped actuators that bend from flat to an angle of 27.2 ± 11.3° at 180 °C. Higher concentrations of chiral dopant lead to actuators with reduced bending, and lower concentrations of chiral dopant lead to actuators with poorly controlled bending. Asymmetric molecular alignment inside 3D structure is confirmed by sectioning actuators. Arrays of microactuators that all bend in the same direction can be fabricated if symmetry of geometry of the microstructure is broken. It is envisioned that the new platform to synthesize microstructures can further be applied in soft robotics and biomedical devices.