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RSC Advances May 2024Aliovalent doping in ceria and defect engineering are important aspects in tuning the properties of ceria for advanced technological applications, especially in the...
Aliovalent doping in ceria and defect engineering are important aspects in tuning the properties of ceria for advanced technological applications, especially in the emerging field of electrocatalytic water-splitting for harvesting renewable energy. However, the ambiguity regarding the choice of dopants/co-dopants and ways to deal with the size difference between dopants and lattice hosts remains a long-standing problem. In this study, ceria was aliovalently codoped with Sc and La while keeping the total concentration of dopants constant; the ionic radius of the former is smaller and that of the latter is larger than Ce. Variations in the relative amounts of these dopants helped to modulate the effective ionic radii and match that of the host. A systematic study on the role of these aliovalent dopants in defect evolution in ceria and in modulating the Ce fraction using powder XRD, Rietveld refinement, positron annihilation lifetime spectroscopy, X-ray photoelectron spectroscopy, Eu photoluminescence, and Raman spectroscopy is presented here. The evolved defects and their dependence on subtle factors other than charge compensation are further correlated with their electrocatalytic activity towards oxygen evolution reaction (OER) in alkaline medium. The catalyst with an optimum defect density, maximum Ce fraction at the surface and the least effective ionic radius difference between the dopants and the host demonstrated the best performance towards the OER. This study demonstrates how effective ionic radius modulation in defect-engineered ceria through a judicious choice of codopants can enhance the catalytic property of ceria and provides immensely helpful information for designing ceria-based heterogeneous catalysts with desired functionalities.
PubMed: 38832250
DOI: 10.1039/d4ra03360d -
Life (Basel, Switzerland) May 2024Fixed nitrogen species generated by the early Earth's atmosphere are thought to be critical to the emergence of life and the sustenance of early metabolisms. A previous...
Fixed nitrogen species generated by the early Earth's atmosphere are thought to be critical to the emergence of life and the sustenance of early metabolisms. A previous study estimated nitrogen fixation in the Hadean Earth's N/CO-dominated atmosphere; however, that previous study only considered a limited chemical network that produces NO species (i.e., no HCN formation) via the thermochemical dissociation of N and CO in lightning flashes, followed by photochemistry. Here, we present an updated model of nitrogen fixation on Hadean Earth. We use the Chemical Equilibrium with Applications (CEA) thermochemical model to estimate lightning-induced NO and HCN formation and an updated version of KINETICS, the 1-D Caltech/JPL photochemical model, to assess the photochemical production of fixed nitrogen species that rain out into the Earth's early ocean. Our updated photochemical model contains hydrocarbon and nitrile chemistry, and we use a Geant4 simulation platform to consider nitrogen fixation stimulated by solar energetic particle deposition throughout the atmosphere. We study the impact of a novel reaction pathway for generating HCN via HCN, inspired by the experimental results which suggest that reactions with CH radicals (from CH photolysis) may facilitate the incorporation of N into the molecular structure of aerosols. When the HCN reactions are added, we find that the HCN rainout rate rises by a factor of five in our 1-bar case and is about the same in our 2- and 12-bar cases. Finally, we estimate the equilibrium concentration of fixed nitrogen species under a kinetic steady state in the Hadean ocean, considering loss by hydrothermal vent circulation, photoreduction, and hydrolysis. These results inform our understanding of environments that may have been relevant to the formation of life on Earth, as well as processes that could lead to the emergence of life elsewhere in the universe.
PubMed: 38792622
DOI: 10.3390/life14050601 -
Molecules (Basel, Switzerland) May 2024The ability to study chemical dynamics on ultrafast timescales has greatly advanced with the introduction of X-ray free electron lasers (XFELs) providing short pulses of...
The ability to study chemical dynamics on ultrafast timescales has greatly advanced with the introduction of X-ray free electron lasers (XFELs) providing short pulses of intense X-rays tailored to probe atomic structure and electronic configuration. Fully exploiting the full potential of XFELs requires specialized experimental endstations along with the development of techniques and methods to successfully carry out experiments. The liquid jet endstation (LJE) at the Linac Coherent Light Source (LCLS) has been developed to study photochemistry and biochemistry in solution systems using a combination of X-ray solution scattering (XSS), X-ray absorption spectroscopy (XAS), and X-ray emission spectroscopy (XES). The pump-probe setup utilizes an optical laser to excite the sample, which is subsequently probed by a hard X-ray pulse to resolve structural and electronic dynamics at their intrinsic femtosecond timescales. The LJE ensures reliable sample delivery to the X-ray interaction point via various liquid jets, enabling rapid replenishment of thin samples with millimolar concentrations and low sample volumes at the 120 Hz repetition rate of the LCLS beam. This paper provides a detailed description of the LJE design and of the techniques it enables, with an emphasis on the diagnostics required for real-time monitoring of the liquid jet and on the spatiotemporal overlap methods used to optimize the signal. Additionally, various scientific examples are discussed, highlighting the versatility of the LJE.
PubMed: 38792184
DOI: 10.3390/molecules29102323 -
Nanomaterials (Basel, Switzerland) May 2024Gastric perforation refers to the complete rupture of the gastric wall, leading to the extravasation of gastric contents into the thoracic cavity or peritoneum. Without...
Gastric perforation refers to the complete rupture of the gastric wall, leading to the extravasation of gastric contents into the thoracic cavity or peritoneum. Without timely intervention, the expulsion of gastric contents may culminate in profound discomfort, exacerbating the inflammatory process and potentially triggering perilous sepsis. In clinical practice, surgical suturing or endoscopic closure procedures are commonly employed. Magnetic-driven microswarms have also been employed for sealing gastrointestinal perforation. However, surgical intervention entails significant risk of bleeding, while endoscopic closure poses risks of inadequate closure and the need for subsequent removal of closure clips. Moreover, the efficacy of microswarms is limited as they merely adhere to the perforated area, and their sealing effect diminishes upon removal of the magnetic field. Herein, we present a Fe&Mg@Lard-Paraffin micromotor (LPM) constructed from a mixture of lard and paraffin coated with magnesium (Mg) microspheres and iron (Fe) nanospheres for sutureless sealing gastric perforations. Under the control of a rotating magnetic field, this micromotor demonstrates precise control over its movement on gastric mucosal folds and accurately targets the gastric perforation area. The phase transition induced by the high-frequency magnetothermal effect causes the micromotor composed of a mixed oil phase of lard and paraffin to change from a solid to a liquid phase. The coated Mg microspheres are subsequently exposed to the acidic gastric acid environment to produce a magnesium protonation reaction, which in turn generates hydrogen (H) bubble recoil. Through a Mg-based micropower traction, part of the oil phase could be pushed into the gastric perforation, and it would then solidify to seal the gastric perforation area. Experimental results show that this can achieve long-term (>2 h) gastric perforation sealing. This innovative approach holds potential for improving outcomes in gastric perforation management.
PubMed: 38786822
DOI: 10.3390/nano14100865 -
Heliyon May 2024Natural plant-based medicines have gained in popularity, replacing artificial models and chemicals as a result of new pharmacological discoveries. The increased... (Review)
Review
Natural plant-based medicines have gained in popularity, replacing artificial models and chemicals as a result of new pharmacological discoveries. The increased popularity and acceptability of herbal medications such as arose from the assumption that all-natural products are safe, readily available, and inexpensive. The genus (Commelinaceae), which has over 200 species, has long been utilized as a treatment for a variety of ailments and conditions around the world. However, to the authors' knowledge, there are no Comprehensive scientific reports of many medicinally important species of the genus under one roof. The current narrative review aims to present an updated overview of the various species of focusing on its morphology; geographical distribution; traditional medicinal use (species type, parts of the plant used, the mode of action, ailments treated, and countries practicing); phytochemical constituents; and pharmacological properties. The data search approach was carried out utilizing English-language electronic databases such as PubMed, Web of Science, Scopus, Science Direct, Research Gates, Ethnobotany Research and Applications, and Google Scholar. Using key terms such as "medicinal plant," "genus ," "traditional medicinal usage of species," "photochemistry of species," and "pharmacological (biologic) activities of species" numerous searches and in-depth discussions are conducted. It was found that many species contain bioactive-phytochemicals (secondary metabolites) with a variety of structural kinds, including alkaloids, phenolics, flavonoids, glycosides, tannins, saponins, sterols, anthocyanins, and others which are presumed for their pharmacological activities. According to the invitro and preclinical reports, the species have shown anti-diabetic, antioxidant, anti-microbial, analgesic, anti-inflammatory, anti-cancer, hepato-protective, diuretic, fertility-inducing, anti-diarrheal, and anthelmintic activity, sedative, and anxiolytic activities. Although standardized extracts and phytochemicals derived from numerous species are presumed to provide safer alternatives for treating a variety of human ailments, the phytochemistry and pharmacology of the genus' plants have yet to be thoroughly investigated, both in preclinical studies with various animal models and in large-scale clinical trials. The authors also advocate for future collaboration among scientists, pharmaceutical firm owners, and other interested parties to develop novel drugs.
PubMed: 38784558
DOI: 10.1016/j.heliyon.2024.e30945 -
IScience Jun 2024We show that the non-canonical nucleobase 2,6-diaminopurine (D) spontaneously base pairs with uracil (U) in water and the solid state without the need to be attached...
We show that the non-canonical nucleobase 2,6-diaminopurine (D) spontaneously base pairs with uracil (U) in water and the solid state without the need to be attached to the ribose-phosphate backbone. Depending on the reaction conditions, D and U assemble in thermodynamically stable hydrated and anhydrated D-U base-paired cocrystals. Under UV irradiation, an aqueous solution of D-U base-pair undergoes photochemical degradation, while a pure aqueous solution of U does not. Our simulations suggest that D may trigger the U photodimerization and show that complementary base-pairing modifies the photochemical properties of nucleobases, which might have implications for prebiotic chemistry.
PubMed: 38783999
DOI: 10.1016/j.isci.2024.109894 -
BMC Plant Biology May 2024Drosera intermedia grows in acidic bogs in parts of valleys that are flooded in winter, and that often dry out in summer. It is also described as the sundew of the most...
Drosera intermedia grows in acidic bogs in parts of valleys that are flooded in winter, and that often dry out in summer. It is also described as the sundew of the most heavily hydrated habitats in peatlands, and it is often found in water and even underwater. This sundew is the only one that can tolerate long periods of submersion, and more importantly produces a typical submerged form that can live in such conditions for many years. Submerged habitats are occupied by D. intermedia relatively frequently. The aim of the study was to determine the environmental conditions and architecture of individuals in the submerged form of D. intermedia. The features of the morphological and anatomical structure and chlorophyll a fluorescence of this form that were measured were compared with analogous ones in individuals that occurred in emerged and peatland habitats. The submerged form occurred to a depth of 20 cm. Compared to the other forms, its habitat had the highest pH (4.71-4.92; Me = 4.71), the highest temperature and substrate hydration, and above all, the lowest photosynthetically active radiation (PAR; 20.4-59.4%). This form differed from the other forms in almost all of the features of the plant's architecture. It is particularly noteworthy that it had the largest main axis height among all of the forms, which exceeded 18 cm. The number of living leaves in a rosette was notable (18.1 ± 8.1), while the number of dead leaves was very low (6.9 ± 3.8). The most significant differences were in the shape of its submerged leaves, in which the length of the leaf blade was the lowest of all of the forms (0.493 ± 0.15 mm; p < 0.001) and usually the widest. The stem cross-sectional area was noticeably smaller in the submerged form than in the other forms, the xylem was less developed and collaterally closed vascular bundles occurred. Our analysis of the parameters of chlorophyll fluorescence in vivo revealed that the maximum quantum yield of the primary photochemistry of photosystem II is the highest for the submerged form (Me = 0.681), the same as the maximum quantum yield of the electron transport (Me φE = 0.183). The efficiency of energy use per one active reaction center of photosystem II (RC) was the lowest in the submerged form (Me = 2.978), same as the fraction of energy trapped by one active RC (Me = 1.976) and the non-photochemical energy dissipation (DI/RC; Me = 0.916). The ET/RC parameter, associated with the efficiency of the energy utilization for electron transport by one RC, in the submerged plant reached the highest value (Me = 0.489). The submerged form of D. intermedia clearly differed from the emerged and peatland forms in its plant architecture. The submerged plants had a thinner leaf blade and less developed xylem than the other forms, however, their stems were much longer. The relatively high photosynthetic efficiency of the submerged forms suggests that most of the trapped energy is utilized to drive photosynthesis with a minimum energy loss, which may be a mechanism to compensate for the relatively small size of the leaf blade.
Topics: Photosynthesis; Chlorophyll; Plant Leaves; Ecosystem; Chlorophyll A; Temperature; Hydrogen-Ion Concentration; Water
PubMed: 38783181
DOI: 10.1186/s12870-024-05155-9 -
Nature Communications May 2024Endowing the widely-used synthetic polymer nylon with high-performance organic room-temperature phosphorescence would produce advanced materials with a great potential...
Endowing the widely-used synthetic polymer nylon with high-performance organic room-temperature phosphorescence would produce advanced materials with a great potential for applications in daily life and industry. One key to achieving this goal is to find a suitable organic luminophore that can access the triplet excited state with the aid of the nylon matrix by controlling the matrix-luminophore interaction. Herein we report highly-efficient room-temperature phosphorescence nylons by doping cyano-substituted benzimidazole derivatives into the nylon 6 matrix. These homogeneously doped materials show ultralong phosphorescence lifetimes of up to 1.5 s and high phosphorescence quantum efficiency of up to 48.3% at the same time. The synergistic effect of the homogeneous dopant distribution via hydrogen bonding interaction, the rigid environment of the matrix polymer, and the potential energy transfer between doped luminophores and nylon is important for achieving the high-performance room-temperature phosphorescence, as supported by combined experimental and theoretical results with control compounds and various polymeric matrices. One-dimensional optical fibers are prepared from these doped room-temperature phosphorescence nylons that can transport both blue fluorescent and green afterglow photonic signals across the millimeter distance without significant optical attenuation. The potential applications of these phosphorescent materials in dual information encryption and rewritable recording are illustrated.
PubMed: 38782924
DOI: 10.1038/s41467-024-48836-7 -
Nature Jun 2024Observations of transiting gas giant exoplanets have revealed a pervasive depletion of methane, which has only recently been identified atmospherically. The depletion is...
Observations of transiting gas giant exoplanets have revealed a pervasive depletion of methane, which has only recently been identified atmospherically. The depletion is thought to be maintained by disequilibrium processes such as photochemistry or mixing from a hotter interior. However, the interiors are largely unconstrained along with the vertical mixing strength and only upper limits on the CH depletion have been available. The warm Neptune WASP-107b stands out among exoplanets with an unusually low density, reported low core mass, and temperatures amenable to CH, though previous observations have yet to find the molecule. Here we present a JWST-NIRSpec transmission spectrum of WASP-107b that shows features from both SO and CH along with HO, CO, and CO. We detect methane with 4.2σ significance at an abundance of 1.0 ± 0.5 ppm, which is depleted by 3 orders of magnitude relative to equilibrium expectations. Our results are highly constraining for the atmosphere and interior, which indicate the envelope has a super-solar metallicity of 43 ± 8 × solar, a hot interior with an intrinsic temperature of T = 460 ± 40 K, and vigorous vertical mixing which depletes CH with a diffusion coefficient of K = 10 cm s. Photochemistry has a negligible effect on the CH abundance but is needed to account for the SO. We infer a core mass of , which is much higher than previous upper limits, releasing a tension with core-accretion models.
PubMed: 38768633
DOI: 10.1038/s41586-024-07395-z -
Biophysical Journal Jun 2024The light-gated anion channelrhodopsin GtACR1 is an important optogenetic tool for neuronal silencing. Its photochemistry, including its photointermediates, is poorly...
The light-gated anion channelrhodopsin GtACR1 is an important optogenetic tool for neuronal silencing. Its photochemistry, including its photointermediates, is poorly understood. The current mechanistic view presumes BR-like kinetics and assigns the open channel to a blue-absorbing L intermediate. Based on time-resolved absorption and electrophysiological data, we recently proposed a red-absorbing spectral form for the open channel state. Here, we report the results of a comprehensive kinetic analysis of the spectroscopic data combined with channel current information. The time evolutions of the spectral forms derived from the spectroscopic data are inconsistent with the single chain mechanism and are analyzed within the concept of parallel photocycles. The spectral forms partitioned into conductive and nonconductive parallel cycles are assigned to intermediate states. Rejecting reversible connections between conductive and nonconductive channel states leads to kinetic schemes with two independent conductive states corresponding to the fast- and slow-decaying current components. The conductive cycle is discussed in terms of a single cycle and two parallel cycles. The reaction mechanisms and reaction rates for the wild-type protein, the A75E, and the low-conductance D234N and S97E protein variants are derived. The parallel cycles of channelrhodopsin kinetics, its relation to BR photocycle, and the role of the M intermediate in channel closure are discussed.
Topics: Kinetics; Ion Channel Gating; Rhodopsin; Animals; Anions; Light; Models, Biological; Channelrhodopsins
PubMed: 38762755
DOI: 10.1016/j.bpj.2024.05.016