The particle size effect of Pd nanoparticles supported on alumina with various crystalline phases on methane combustion was investigated. Pd/θ, α‐Al2O3 with weak metal‐support interaction showed a ...volcano‐shaped dependence of the catalytic activity on the size of Pd particles, and the catalytic activity of the strongly interacted Pd/γ‐Al2O3 increased with the particle size. Based on a structural analysis of Pd nanoparticles using CO adsorption IR spectroscopy and spherical aberration‐corrected scanning/transmission electron microscopy, the dependence of catalytic activity on Pd particle size and the alumina crystalline phase was due to the fraction of step sites on Pd particle surface. The difference in fraction of the step site is derived from the particle shape, which varies not only with Pd particle size but also with the strength of metal–support interaction. Therefore, this interaction perturbs the particle size effect of Pd/Al2O3 for methane combustion.
Size and phase matters: Pd/θ‐Al2O3 and Pd/α‐Al2O3 exhibit a different size effect from Pd/γ‐Al2O3. Based on a structural analysis using spectroscopy and microscopy, the dependence of catalytic activity on size and the alumina crystalline phase was due to the fraction of step sites on the Pd particle. This difference in fraction is derived from the particle shape, which varies with Pd particle size and strength of metal–support interaction.
The redox properties of supported Pd catalysts can directly affect their methane combustion activity. Here, the effect of the support on methane combustion was elucidated using Pd nanoparticles ...supported on various metal oxides (θ-Al2O3, γ-Al2O3, ZrO2, CeO2, MgO, La2O3, TiO2, SnO2, and Nb2O5). To eliminate the effect of Pd particle size and morphology, uniform Pd particles were synthesized in the liquid phase. Interestingly, the methane combustion activity formed a volcano plot when plotted against the oxide formation enthalpy (Δf H M‑O°) of the support. Combining X-ray photoelectron spectroscopy and scanning transmission electron microscopy–electron energy loss spectroscopy, the structure of the Pd nanoparticles on the support in an oxidizing atmosphere was identified. Pd particles on θ-Al2O3, γ-Al2O3, ZrO2, and CeO2 with moderate Δf H M‑O° adopted a metal-core–oxide-shell structure and showed the highest activities for methane combustion. In contrast, completely oxidized Pd particles were present on MgO and La2O3, which have lower Δf H M‑O° and were not very active. Pd metal particles on TiO2, SnO2, and Nb2O5 with higher Δf H M‑O° were not effective catalysts for methane combustion.
The hydrogen oxidation reaction (HOR) in alkaline electrolyte was conducted on carbon-supported Ru nanoparticles (Ru/C) of which size was controlled in the range from approximately 2 to 7 nm. The HOR ...activity of Ru/C normalized by the metal surface area showed volcano shaped dependence on the particle size with a maximum activity at approximately 3 nm. The HOR activity of approximately 3 nm Ru/C was higher than commercially available Pt nanoparticles (ca. 2 nm) supported on carbon. The structural analysis of Ru/C using Cs-corrected scanning transmission electron microscopy with atomic resolution revealed the unique structural change of Ru/C different from Pt/C: Ru nanoparticle structure changed from amorphous-like structure below 3 nm to metal nanocrystallite with roughened surface at approximately 3 nm and then to that with well-defined facets above 3 nm, although Pt/C kept well-defined facets even at approximately 2 nm. It is proposed that the generation of unique structure observed on approximately 3 nm Ru nanoparticles, that is, long bridged coordinatively unsaturated Ru metal surface atoms on its nanocrystallite, is a key to achieve high HOR activity.
Distinct from inert bulk gold, nanoparticulate gold has been found to possess remarkable catalytic activity towards oxidation reactions. The catalytic performance of nanoparticulate gold strongly ...depends on size and support, and catalytic activity usually cannot be observed at characteristic sizes larger than 5 nm. Interestingly, significant catalytic activity can be retained in dealloyed nanoporous gold (NPG) even when its feature lengths are larger than 30 nm. Here we report atomic insights of the NPG catalysis, characterized by spherical-aberration-corrected transmission electron microscopy (TEM) and environmental TEM. A high density of atomic steps and kinks is observed on the curved surfaces of NPG, comparable to 3-5 nm nanoparticles, which are stabilized by hyperboloid-like gold ligaments. In situ TEM observations provide compelling evidence that the surface defects are active sites for the catalytic oxidation of CO and residual Ag stabilizes the atomic steps by suppressing {111} faceting kinetics.
Vibration energy harvesters are expected to become a new source of electrical power. Piezoelectric vibration energy harvesters that employ a piezoelectric transducer, a rectifier, and a storage ...capacitor are being used widely as electro-mechanical harvesters. Synchronized switch harvesting on inductor enhances harvesting performance due to employing a simple additional circuit and incorporating suitable switch control functionality. Switching is usually based on the displacement of a vibrating structure; hence, sensing the vibrational states is of critical importance. Conventionally, the structural displacement is measured by displacement sensors or accelerometers attached to the target vibrating structure. Although enhancement of performance through synchronized switch harvesting on inductor equipped with sensors is important, the arrangement requirements of sensors have adverse effects on the compactness and usability of the harvesters. This study aimed to eliminate the use of sensors from switch-controlled harvesters. We developed a new state estimation method that uses the piezoelectric transducer’s voltage as an observation value. Using the proposed state estimation method, the modal state values of the vibrating structure can be determined by simply measuring the voltage of the transducer. With the switch device being controlled by the estimated modal state values, no sensors are required for ensuring effective harvesting. A comparison of the harvesting performances by the proposed self-sensing state estimation method and the conventional sensor-equipped state estimation method showed that there is little difference in harvested power between the two methods over a wide range of load resistances. The proposed method is superior to the sensor-equipped method in terms of compactness and usability as it does not require any external sensors.
Carbon nitride nanosheets (NS‐C3N4) were found to undergo robust binding with a binuclear ruthenium(II) complex (RuRu′) even in basic aqueous solution. A hybrid material consisting of NS‐C3N4 ...(further modified with nanoparticulate Ag) and RuRu′ promoted the photocatalytic reduction of CO2 to formate in aqueous media, in conjunction with high selectivity (approximately 98 %) and a good turnover number (>2000 with respect to the loaded Ru complex). These represent the highest values yet reported for a powder‐based photocatalytic system during CO2 reduction under visible light in an aqueous environment. We also assessed the desorption of RuRu′ from the Ag/C3N4 surface, a factor that can contribute to a loss of activity. It was determined that desorption is not induced by salt additives, pH changes, or photoirradiation, which partly explains the high photocatalytic performance of this material.
Fixed to fix: Carbon nitride nanosheets bind strongly with a binuclear ruthenium(II) complex even in basic aqueous solution, enabling durable, selective CO2 reduction into formate under visible light.
Advances in scanning transmission electron microscopy (STEM) techniques have enabled us to automatically obtain electron energy-loss (EELS)/energy-dispersive X-ray (EDX) spectral datasets from a ...specified region of interest (ROI) at an arbitrary step width, called spectral imaging (SI). Instead of manually identifying the potential constituent chemical components from the ROI and determining the chemical state of each spectral component from the SI data stored in a huge three-dimensional matrix, it is more effective and efficient to use a statistical approach for the automatic resolution and extraction of the underlying chemical components. Among many different statistical approaches, we adopt a non-negative matrix factorization (NMF) technique, mainly because of the natural assumption of non-negative values in the spectra and cardinalities of chemical components, which are always positive in actual data. This paper proposes a new NMF model with two penalty terms: (i) an automatic relevance determination (ARD) prior, which optimizes the number of components, and (ii) a soft orthogonal constraint, which clearly resolves each spectrum component. For the factorization, we further propose a fast optimization algorithm based on hierarchical alternating least-squares. Numerical experiments using both phantom and real STEM-EDX/EELS SI datasets demonstrate that the ARD prior successfully identifies the correct number of physically meaningful components. The soft orthogonal constraint is also shown to be effective, particularly for STEM-EELS SI data, where neither the spatial nor spectral entries in the matrices are sparse.
•Automatic resolution of chemical components from spectral imaging is considered.•We propose a new non-negative matrix factorization with two new penalties.•The first penalty is sparseness to choose the number of components from data.•Experimental results with real data demonstrate effectiveness of our method.
Lansoprazole, a proton pump inhibitor, can exert antioxidant effects through the induction of the nuclear factor erythroid 2-related factor 2 (Nrf2) pathway, independently of the inhibition of acid ...secretion in the gastrointestinal tract. Lansoprazole has been reported to provide hepatoprotection in a drug-induced hepatitis animal model through the Nrf2/heme oxygenase-1 (HO1) pathway. We sought to investigate the molecular mechanism of cytoprotection by lansoprazole. An in vitro experimental model was conducted using cultured rat hepatic cells treated with lansoprazole to analyze the expression levels of Nrf2 and its downstream genes, the activity of Nrf2 using luciferase reporter assays, cisplatin-induced cytotoxicity, and signaling pathways involved in Nrf2 activation. Lansoprazole treatment of rat liver epithelial RL34 cells induced transactivation of Nrf2 and the expression of the Nrf2-dependent antioxidant genes encoding HO1, NAD(P)H quinone oxidoreductase-1, and glutathione S-transferase A2. Furthermore, cycloheximide chase experiments revealed that lansoprazole prolongs the half-life of the Nrf2 protein. Notably, cell viability was significantly increased by lansoprazole treatment in a cisplatin-induced cytotoxicity model. Moreover, the siRNA knockdown of Nrf2 fully abolished the cytoprotective effect of lansoprazole, whereas the inhibition of HO1 by tin-mesoporphyrin only partially abolished this. Finally, lansoprazole promoted the phosphorylation of p38 mitogen-activated protein kinase (MAPK) but not that of the extracellular signal-regulated kinase or the c-Jun N-terminal kinase. Using SB203580, a specific inhibitor for p38 MAPK, the lansoprazole-induced Nrf2/antioxidant response elements pathway activation and cytoprotective effects were shown to be exclusively p38 MAPK dependent. Lansoprazole was shown by these results to exert a cytoprotective effect on liver epithelial cells against the cisplatin-induced cytotoxicity through the p38 MAPK signaling pathway. This could have potential applications for the prevention and treatment of oxidative injury in the liver.
We prepared a polyclonal antibody against a teicoplanin (TEIC)-bovine serum albumin conjugate that was specific to both conjugated and free forms of TEIC. We demonstrated that this antibody could be ...used to detect the time-dependent localization of TEIC in rat kidneys. Immunohistochemistry revealed immunoreactivity specifically in the microvilli and apical cytoplasm of epithelial cells in proximal tubule segments S1 and S2, 1 h after intravenous TEIC injection, with higher staining intensity in the S2 segments. The epithelial cells of S3 segments showed moderate immunostaining with a few cells exhibiting nuclear staining. Furthermore, we found that the distal tubules and collecting ducts contained both TEIC-positive and -negative cells. TEIC immunoreactivity decreased rapidly over time; only weak staining remained in the S3 segments, distal tubules, and collecting ducts 24 h after administration. No staining was detected 7 days after injection. These results were significantly different from those of our previous study obtained using vancomycin, which showed moderate staining in the proximal tubule segments S1 and S2, distal tubules, and the collecting ducts 8 days after administration. The lower TEIC accumulation in tissues may account for a lower risk of adverse events compared to that using vancomycin.
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