Investigations into the photoinduced reactions of deoxyribonucleic acid (DNA) bases are important for human health. Herein, we have synthesized colloidal CdS nanoparticles by a method reported in the literature. The mean particle diameter of the semiconductor was about 55 nm. The colloidal CdS particles were used as a photocatalyst to investigate the organic transformation of guanine (2-amino-6-oxopurine). The products of the semiconductor-induced reaction were analyzed by liquid chromatography-mass chromatography (LC-MS) measurements. The solitary product of the photocatalytic reaction of guanine was revealed as 2,5-diamino-4H-imidazol-4-one. The likely reaction pathway for the formation of the product has been presented. To our understanding, the present work is the first account on the mechanistic aspects of the semiconductor-induced photocatalytic reaction of guanine.
A2B2O7 complex oxides have a great potential to be used in high-temperature catalytic processes. Herein, a series of A2B2O7 (A = La, Nd, Sm, Gd, Er, Yb; B = Ti, Sn, Zr, Ce) compounds with all four kinds of typical sub-crystalline phases were synthesized to study their bulk and surface properties. FTIR spectroscopy was adopted as a novel method in this study to identify distinctively these phases. Whereas, it cannot be used to distinguish the subtle structure difference between disordered and ordered pyrochlores, nor that between the disordered defect fluorite and the rare earth. To discriminate these exquisite phase differences, XPS spectra must be supplementarily used. Specifically, it was discovered that the coordination numbers of the A- and B-site cations are the key factor affecting their binding energies. Furthermore, the electronegativity of the A- and B-site elements significantly influences the binding energy of surface lattice oxygen, reflecting their electrophilic and nucleophilic properties, which can thus be used to effectively identify the sub-crystalline phase. The oxygen vacancy concentration of different sub-crystalline phases is the primary factor controlling the amount of surface chemisorbed oxygen species on A2B2O7 compounds, with superoxide anions (O2−) identified as the major species.
Refractory high-entropy alloys (RHEAs) show promising properties for applications as structural materials in high-temperature applications, such as high solidus temperature and high strength. Improving their density, oxidation resistance, and room temperature ductility are still the aims of research in alloy development. In this study, Al-rich diffusion coatings by pack cementation are developed for three different alloys in the system Al-Cr-Mo-Ta-Ti in order to improve their high-temperature oxidation resistance. Equimolar AlCrMoTaTi, Al-rich Al3CrMoTaTi, and Ti-rich AlCrMoTaTi3 are synthesized by vacuum arc melting with subsequent milling to powder, consolidation to bulk material by field-assisted sintering technology/spark plasma sintering (FAST/SPS), and homogenization heat treatment. The applied aluminizing coatings are investigated by gravimetry, scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), and X-ray diffraction (XRD). Experimental analyses are supplemented by CALPHAD simulations. Compact, uniform, and adhesive Al-rich diffusion coatings are produced on all three substrate RHEAs and exhibit single-layered D022 Al3(Cr,Mo,Ta,Ti) intermetallic compound analogous to Al3Ti in the binary Al-Ti system. Isothermal oxidation at 1000 °C for 48 h in ambient air results in the formation of 1–2 µm thin protective single-layered alumina scale—in contrast to multi-layered oxide scales in uncoated condition—and mass gains as low as binary Al3Ti and Ni-based superalloys.
Several studies have attempted to clarify the role of exosomes and/or microvesicles derived from mesenchymal stromal cells (MSCs) (collectively indicated as extracellular vesicles: MSCs-EVs) in pulmonary fibrosis. Depending on their origin and on the micro-environmental context, MSCs-EVs may support or attenuate the fibrotic invasion of the lung, a hallmark of all Interstitial Lung Diseases (ILDs). Indeed, EVs have emerged as pivotal intercellular mediators and their potential diagnostic and therapeutic applications have been suggested. We aim here to elucidate the dual role of MSCs-derived exosomes and microvesicles: the contribution to pulmonary fibrosis progression, exerted by the MSCs-EVs originated from resident MSCs, or the potential therapeutic activity of those generated from healthy MSCs. Actually, MCSs-EVs appear as the frontiers of cell-free therapy and nano-medicine research in a great number of pre-clinical studies, but developments are needed to optimize and standardize their isolation, production and delivery. Interestingly, since the respiratory system directly communicates with the external environment, lung treatment could be approached by MSCs-EVs nebulization as a preferential administration route, integrating targeted pulmonary delivery with an enhanced patient’s compliance. Hence MSCs-EVs may contribute to ILD pathogenesis, display a potential as biomarkers, and still hold promise as therapeutic agents to reduce lung fibrosis. However further researches are needed to validate their clinical application.
The grass ring phenomenon remains an interesting and enduring puzzle. Previous research has proposed various mechanisms, including Environmental stress and physical disturbance, Nutrient and water depletion, and the Self-Organization hypothesis, to explain ring formation. However, this process is highly complex and dynamic, hindering the development of a unified theory. This is primarily because grass rings of different origins, and even those at different developmental stages, are influenced by diverse factors. Furthermore, existing studies have often been limited to isolated cases, which highlights the need for more comprehensive, global-scale studies. Through a systematic analysis of publications, this review proposes three claims. First, they are classified based on genetic origin into single and multiple individual origins, which align with formation driven primarily by death-based and growth-based formation modes, respectively. Second, the grass ring is essentially a superorganism. Third, although grass rings are globally widespread, their formation mechanisms in regions above 4000 m remain elusive. Future research should prioritize key directions, including quantifying complete life cycles and elucidating mechanisms of high-altitude formation. This requires establishing international monitoring networks that integrate multi-omics with hyperspectral remote sensing to predict how grass rings develop under global climate change.
