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High-manganese steel (high-Mn) is valuable for its excellent mechanical properties in cryogenic environments, making it essential to understand its deformation behavior at extremely low temperatures. The deformation behavior of high-Mn steels at extremely low temperatures depends on the stacking fault energy (SFE) that can lead to the formation of deformation twins or transform to ε-martensite or α′-martensite as the temperature decreases. In this study, submerged arc welding (SAW) was applied to fabricate thick pipes for cryogenic industry applications, but it may cause problems such as an uneven distribution of manganese (Mn) and a large weldment. To address these issues, post-weld heat treatment (PWHT) is performed to achieve a homogeneous microstructure, enhance mechanical properties, and reduce residual stress. It was found that the difference in Mn content between the dendrite and interdendritic regions was reduced after PWHT, and the SFE was calculated. At cryogenic temperatures, the SFE decreased below 20 mJ/m2, indicating the martensitic transformation region. Furthermore, an examination of the deformation behavior of welded high-Mn steels was conducted. This study revealed that the tensile deformed, as-welded specimens exhibited ε and α′-martensite transformations at cryogenic temperatures. However, the heat-treated specimens did not undergo α′-martensite transformations. Moreover, regardless of whether the specimens were subjected to Charpy impact deformation before or after heat treatment, ε and α′-martensite transformations did not occur. [ABSTRACT FROM AUTHOR]

Magnetite nanoparticles (Fe3O4 NPs) have been intensively investigated because of their potential biomedical applications due to their high saturation magnetization. In this study, core–shell Fe3O4@C NPs (core = Fe3O4 NPs and shell = amorphous carbons, davg = 35.1 nm) were synthesized in an aqueous solution. Carbon coating terminated with hydrophilic –OH and –COOH groups imparted excellent biocompatibility and hydrophilicity to the NPs, making them suitable for biomedical applications. The Fe3O4@C NPs exhibited ideal relaxometric properties for T2 magnetic resonance imaging (MRI) contrast agents (i.e., high transverse and negligible longitudinal water proton spin relaxivities), making them exclusively induce only T2 relaxation. Their T2 MRI performance as contrast agents was confirmed in vivo by measuring T2 MR images in mice before and after intravenous injection. [ABSTRACT FROM AUTHOR]

Lead oxide (PbO) nanoparticles are promising candidates for X-ray contrast agents because Pb (atomic number = 82) possesses the second largest X-ray attenuation coefficient of all nonradioactive elements in the periodic table. However, few studies have been conducted on PbO nanoparticles. This study is the first to synthesize hydrophilic and biocompatible polymer-grafted ultrasmall PbO nanoparticles with a polyol method. In addition, their potential as X-ray contrast agents was investigated in vitro and in vivo. Three kinds of polymers, namely poly-(methyl vinyl ether-alt-maleic acid) (PMVEMA), poly-(acrylic acid-co-maleic acid) (PAAMA), and poly-(acrylic acid) (PAA), served as surface-grafting polymers of ultrasmall PbO nanoparticles. The synthesized polymer-grafted ultrasmall PbO nanoparticles were colloidally stable (i.e., no precipitation), nearly monodispersed in particle diameters with average particle diameters of 2.0, 1.9 and 2.0 nm for the PAA-, PAAMA-, and PMVEMA-grafted ultrasmall PbO nanoparticles, respectively, exhibiting very-low cellular cytotoxicity. Based on the identical atomic concentration and the identical number density, the X-ray attenuation efficiencies of the polymer-grafted ultrasmall PbO nanoparticles were ∼3 and ∼140 times greater, respectively, compared with those of a commercially available contrast agent Ultravist. Their potential as X-ray contrast agents was proved in vivo by observing contrast enhancements in organs after intravenous tail and intraperitoneal injections in mice. In addition, the nanoparticles demonstrated tumor-imaging ability through contrast enhancements at the tumor after intratumoral injection in tumor-model mice. [ABSTRACT FROM AUTHOR]

Hemagglutination assay has been used for blood typing and detecting viruses, thus applicable for the diagnosis of infectious diseases, including COVID-19. Therefore, the development of microfluidic devices for fast detection of hemagglutination is on-demand for point-of-care diagnosis. Here, we present a way to detect hemagglutination in 3D microfluidic devices via optical absorbance (optical density, OD) characterization. 3D printing is a powerful way to build microfluidic structures for diagnostic devices. However, mixing liquid in microfluidic chips is difficult due to laminar flow, which hampers practical applications such as antigen-antibody mixing. To overcome the issue, we fabricated 3D microfluidic chips with embedded microchannel and microwell structures to induce hemagglutination between red blood cells (RBCs) and antibodies. We named it a 3D microtrap chip. We also established an automated measurement system which is an integral part of diagnostic devices. To do this, we developed a novel way to identify RBC agglutination and non-agglutination via the OD difference. By adapting a 3D-printed aperture to the microtrap chip, we obtained a pure absorbance signal from the microchannels by eliminating the background brightness of the microtrap chip. By investigating the underlying optical physics, we provide a 3D device platform for detecting hemagglutination. [ABSTRACT FROM AUTHOR]

In recent decades, magnetic nanoparticles (MNPs) have attracted considerable research interest as versatile substances for various biomedical applications, particularly as contrast agents in magnetic resonance imaging (MRI). Depending on their composition and particle size, most MNPs are either paramagnetic or superparamagnetic. The unique, advanced magnetic properties of MNPs, such as appreciable paramagnetic or strong superparamagnetic moments at room temperature, along with their large surface area, easy surface functionalization, and the ability to offer stronger contrast enhancements in MRI, make them superior to molecular MRI contrast agents. As a result, MNPs are promising candidates for various diagnostic and therapeutic applications. They can function as either positive (T1) or negative (T2) MRI contrast agents, producing brighter or darker MR images, respectively. In addition, they can function as dual-modal T1 and T2 MRI contrast agents, producing either brighter or darker MR images, depending on the operational mode. It is essential that the MNPs are grafted with hydrophilic and biocompatible ligands to maintain their nontoxicity and colloidal stability in aqueous media. The colloidal stability of MNPs is critical in order to achieve a high-performance MRI function. Most of the MNP-based MRI contrast agents reported in the literature are still in the developmental stage. With continuous progress being made in the detailed scientific research on them, their use in clinical settings may be realized in the future. In this study, we present an overview of the recent developments in the various types of MNP-based MRI contrast agents and their in vivo applications. [ABSTRACT FROM AUTHOR]