Intensity analysis methods for transient signals

Conventionally, the Fourier transform is applied for sound intensity analysis of stationary signals, but this method can be applied for analyzing non-stationary transient signals. Instead of the Fourier transform analysis, instantaneous spectrum analysis methods such as the Wigner-Ville distribution and the wavelet transform are proposed. By using the mathematical example as a transient signal, advantages and disadvantages of these methods including the short-time Fourier transform are compared. From calculation results, it is considered that the STFT method is the most suitable for the accurate measurement of sound intensity levels, but the WT method is also recommended from its higher resolution of transient signals.     

Total Synthesis of Zephycarinatines via Photocatalytic Reductive Radical ipso-Cyclization

We report herein a nonbiomimetic strategy for the total synthesis of the plicamine-type alkaloids zephycarinatines C and D. The key feature of the synthesis is a stereoselective reductive radical ipso-cyclization using visible-light-mediated photoredox catalysis. This cyclization enabled the construction of a 6,6-spirocyclic core structure through the addition of a carbon-centered radical onto the aromatic ring. Biological evaluation of zephycarinatines and their derivatives revealed that the synthetic derivative with a keto group displays moderate inhibitory activity against LPS-induced NO production. This approach could offer future opportunities to expand the chemical diversity of plicamine-type alkaloids as well as providing useful intermediates for their syntheses.     

A CO Adsorption Site Change Induced by Copper Substitution in a Ruthenium Catalyst for Enhanced CO Oxidation Activity

Ru is an important catalyst in many types of reactions. Specifically, Ru is well known as the best monometallic catalyst for oxidation of carbon monoxide (CO) and has been practically used in residential fuel cell systems. However, Ru is a minor metal, and the supply risk often causes violent fluctuations in the price of Ru. Performance‐improved and cost‐reduced solid‐solution alloy nanoparticles of the Cu‐Ru system for CO oxidation are now presented. Over the whole composition range, all of the Cu_xRu_1?x nanoparticles exhibit significantly enhanced CO oxidation activities, even at 70 at % of inexpensive Cu, compared to Ru nanoparticles. Only 5 at % replacement of Ru with Cu provided much better CO oxidation activity, and the maximum activity was achieved by 20 at % replacement of Ru by Cu. The origin of the high catalytic performance was found as CO site change by Cu substitution, which was investigated using in situ Fourier transform infrared spectra and theoretical calculations.     

On the electronic structure and hydrogen evolution reaction activity of platinum group metal-based high-entropy-alloy nanoparticles

We report the synthesis of high-entropy-alloy (HEA) nanoparticles (NPs) consisting of five platinum group metals (Ru, Rh, Pd, Ir and Pt) through a facile one-pot polyol process. We investigated the electronic structure of HEA NPs using hard X-ray photoelectron spectroscopy, which is the first direct observation of the electronic structure of HEA NPs. Significantly, the HEA NPs possessed a broad valence band spectrum without any obvious peaks. This implies that the HEA NPs have random atomic configurations leading to a variety of local electronic structures. We examined the hydrogen evolution reaction (HER) and observed a remarkably high HER activity on HEA NPs. At an overpotential of 25 mV, the turnover frequencies of HEA NPs were 9.5 and 7.8 times higher than those of a commercial Pt catalyst in 0.05 M H₂SO₄ and 1.0 M KOH electrolytes, respectively. Moreover, the HEA NPs showed almost no loss during a cycling test and were much more stable than the commercial Pt catalyst. Our findings on HEA NPs may provide a new paradigm for the design of catalysts.

RuRhPdIrPt high-entropy-alloy nanoparticles with a broad and featureless valence band spectrum show high hydrogen evolution reaction activity.     

Symbiodinolactone A,a new 12-membered macrolide from symbiotic marine dinoflagellate Symbiodinium sp.

A new 12-membered macrolide, symbiodinolactone A, was isolated from the culture broth of symbiotic marine dinoflagellate Symbiodinium sp. The gross structure of symbiodinolactone A was elucidated by spectroscopic analyses, and the relative configuration was elucidated by the J-based configuration analysis and density-functional theory calculations. Symbiodinolactone A is the new 12-membered macrolide possessing an E double bond between C-4 and C-5, a branched methyl group at C-7, and a 1,2,3-trihydroxybutyl group at C-11. Symbiodinolactone A is the first usual size macrolide and the first non-nitrogen-containing macrolide from dinoflagellate Symbiodinium sp. Symbiodinolactone A might be generated by the unexplained dinoflagellate polyketide biosynthetic machinery.     

Berezin transforms on the 2×2 matrix space related to theU(2)×U(2)-action

In this paper we establish the spectral decomposition of the Berezin transforms on the space Mat(2,) of complex 2×2 matrices related to the two-sided action ofU(2)×U(2). The eigenspaces are described explicitly by means of the matrix elements of a certain representation ofGL(2,) and each eigenvalue is expressed as a finite sum involving the MeijerG-functions evaluated at 1 and the Hahn polynomials.     

Clathrate-hydrate film growth along water/hydrate-former phase boundaries—numerical heat-transfer study

This paper describes two analytic models for the heat-transfer-controlled lateral growth of a clathrate-hydrate film along a planar interface between liquid water and an immiscible hydrate-forming fluid (or guest fluid), such as methane or carbon dioxide. The two models are different from each other only regarding the assumption of the film-front geometry. Either model assumes the film to be uniform and constant in thickness, ignoring possible changes in the thickness on a time scale relevant to its lateral growth. Another fundamental assumption employed in the model is that the film's hydrate-forming front is maintained at the hydrate/guest/water three-phase equilibrium temperature, thereby forming a two-dimensional temperature distribution in the surrounding three-phase space. Based on these assumptions, the transient, two-dimensional conductive heat transfer from the film front into the three phases is formulated and numerically solved to give the instantaneous rate of lateral film growth (i.e., the linear speed of the film-front) along the water/guest-fluid interface, while the film thickness is arbitrarily assumed as a fitting parameter. By comparing the predicted rates of film growth with the corresponding experimental data obtained with methane or carbon dioxide as the guest fluid, we estimated the film thickness to be about 10–20 μm for the methane hydrate at a pressure of 9.06 MPa and about 0.5 μm for the carbon-dioxide hydrate at a pressure of 5 MPa.     

Preparation and photosensitizing property of novel Cd10S16 molecular cluster dendrimer

A new Cd10S16 molecular cluster dendrimer has been prepared and characterized; photooxygenation reaction using the molecular cluster dendrimer as a photosensitizer was successful.     

Control of the optical properties of CdTe nanocrystals by selective exchange of Te with thiolate: effect of organic ligands on the formation of core-shell structures

Changes in the optical properties of CdTe nanocrystals through selective surface exchange reaction with thiolate molecules in the organic phase are studied with an aim to investigate the mechanism and the role of organic ligands. The reaction was mediated by dissociation of Te anions via oxidation in air from CdTe nanocrystals, followed by attachment of thiolate molecules in a 1:1 stoichiometric manner. This results in a gradual shell formation and a corresponding decrease in the size of the fluorescent CdTe cores, which induces a blue shift of both the absorption edge and emission wavelength in the visible region. A systematic study including the addition of ligands at different concentrations revealed that Te dissociation is the rate-determining step for the process and the degree of blue shift is significantly dependent on the amount of organic ligands present. The process could also be kinetically controlled through the addition of an excess amount of thiolate ligands, allowing systematic tuning of the emission properties of nanocrystals under ambient conditions.     

Actinoperylone, a novel perylenequinone-type shunt product, from a deletion mutant of the actVA-ORF5 and ORF6 genes for actinorhodin biosynthesis in Streptomyces coelicolor A3(2)

A novel shunt product, actinoperylone, has been isolated from a deletion mutant of the actVA-ORF5 and ORF6 genes involved in the biosynthesis of a benzoisochromanequinone (BIQ) antibiotic actinorhodin (ACT) in Streptomyces coelicolor A3(2). Spectroscopic analysis revealed its perylenequinone-type skeleton with the four chiral centers, obviously derived from the dimerization of an ACT intermediate. The structure of actinoperylone indicates the essential role of ActVA-ORF5 in the oxygen introduction at C-6, which is common to the formation of BIQ chromophore. The present results also agree with the distribution of the actVA-ORF5 homologues in all known BIQ biosynthetic clusters in streptomycetes.