Inhomogeneous superconducting state in the overdoped regime of La2−xSrxCuO4: Comparison with the superconducting state of NbSe2

We have measured the temperature dependence of the magnetic susceptibility, χ vs. T, and the magnetization curve, M vs. H, for NbSe₂ single crystals, in order to compare the superconducting (SC) state in the overdoped regime of La_2−xSr_xCuO₄ (LSCO) with the SC state of the layered conventional superconductor NbSe₂. While a plateau in χ vs. T in a moderate magnetic field and a so-called second peak in M vs. H, which is due to the marked enhancement of vortex pinning, have been observed in the overdoped regime of LSCO, these behaviors have not been observed in NbSe₂. The present results indicate that the anomalously marked enhancement of vortex pinning is a characteristic feature in the overdoped LSCO where a microscopic phase separation into SC and normal-state regions takes place.     

Damping constant of Co/Pt multilayer thin-film media

Gilbert's damping constants, α, of Co(t_Co)/Pt (1.4 nm) multilayer thin films are investigated by Q-band FMR analysis. α is calculated from the resonance width of the FMR spectrum. With decreasing t_Co, the α value decreases from 0.034 (t_Co=8.7 nm) to 0.023 (t_Co=1.8 nm), and then increases to 0.037 (t_Co=1.0 nm). The decrease of α with t_Co>1.8 nm is probably due to the eddy current loss effects. The increase of α with t_Co<1.8 nm would be caused by the increase of the distortion between the Co and the Pt layers at the interface. When the magnetic field direction was changed from θ=90° (parallel to the specimen) to θ=0° (perpendicular to the specimen), the α of all the specimens increased, and a sharp step in α was observed around θ=40°, where the α has the maximum value.     

Exponential structural relaxation of a high purity silica glass

While most other glasses exhibit non-exponential structural relaxation characteristics even when the change of fictive temperature is small, a high purity silica glass exhibited exponential structural relaxation. This was demonstrated by showing that the non-exponential exponent or β value of the KWW function of the high purity silica glass approaches unity when the change of the fictive temperature approaches zero both from higher and lower temperature sides of the heat-treatment temperature. The non-exponentiality of the structural relaxation of this glass when fictive temperature change is finite is due to the change of relaxation time during the structural relaxation.     

On the rate of convergence of solutions in free boundary problems via penalization

The rate of convergence of approximate solutions via penalization for free boundary problems are concerned. A key observation is to obtain global bounds of penalized terms which give necessary estimates on integrations by the nonlinear adjoint method by L.C. Evans.     

Cover Feature: Fluoroalkyl Sulfoximines for Versatile Photocatalytic Radical Fluoroalkylations (Chem. Rec. 9/2023)

Fluoroalkyl sulfoximines, which serve as electron-accepting fluoroalkyl radical sources, are easy-to-handle, solid, and bench-stable chemicals. Fluoroalkyl radicals can be generated from sulfoximine reagents using strong one-electron injectors, such as a highly reducing photoredox catalyst in the excited state. Our group has developed photocatalytic radical di- and mono-fluoromethylation and α-monofluoroalkylation of olefins with the corresponding fluoroalkyl sulfoximines. In this personal account, appropriate combinations of fluoroalkyl sulfoximines and photoredox catalysts, leading to successful radical fluoroalkylation, have been discussed.     

On the Singularity Structure of WKB Solution of the Boosted Whittaker Equation: its Relevance to Resurgent Functions with Essential Singularities

Inspired by the symbol calculus of linear differential operators of infinite order applied to the Borel transformed WKB solutions of simple-pole type equation [Kamimoto et al. (RIMS Kôkyûroku Bessatsu B 52:127–146, 2014)], which is summarized in Section 1, we introduce in Section 2 the space of simple resurgent functions depending on a parameter with an infra-exponential type growth order, and then we define the assigning operator \({\mathscr{A}}\) which acts on the space and produces resurgent functions with essential singularities. In Section 3, we apply the operator \({\mathscr{A}}\) to the Borel transforms of the Voros coefficient and its exponentiation for the Whittaker equation with a large parameter so that we may find the Borel transforms of the Voros coefficient and its exponentiation for the boosted Whittaker equation with a large parameter. In Section 4, we use these results to find the explicit form of the alien derivatives of the Borel transformed WKB solutions of the boosted Whittaker equation with a large parameter. The results in this paper manifest the importance of resurgent functions with essential singularities in developing the exact WKB analysis, the WKB analysis based on the resurgent function theory. It is also worth emphasizing that the concrete form of essential singularities we encounter is expressed by the linear differential operators of infinite order.     

Pancreatic lipase-inhibiting triterpenoid saponins from fruits of Acanthopanax senticosus

Sixteen triterpenoid saponins were isolated from the fruits of Acanthopanax senticosus, including a new compound, acanthopanaxoside E (1), which was established as 3-O-beta-D-glucuronopyranosyl echinocystic acid 28-O-beta-D-glucopyranoside on the basis of various spectroscopic analyses and chemical degradation. By using a pancreatic lipase-inhibiting assay system, the crude saponin fraction showed inhibitory activity on pancreatic lipase, which is a key enzyme in lipid digestion. Among the isolated compounds, silphioside F (2), copteroside B (3), hederagenin 3-O-beta-D-glucuronopyranoside 6'-O-methyl ester (4) and gypsogenin 3-O-beta-D-glucuronopyranoside (5) showed inhibitory activity toward pancreatic lipase with IC(50) values of 0.22, 0.25, 0.26 and 0.29 mM, respectively, and the free carboxylic acid groups in position 28 within their chemical structures were required for enhancement of pancreatic lipase inhibition.     

Pancreatic lipase-inhibiting triterpenoid saponins from Gypsophila oldhamiana

Three new triterpenoid saponins, gypsosaponins A-C (1-3), were isolated from the roots of Gypsophila oldhamiana (Caryophyllaceae). Their structures were established as 3-O-beta-D-galactopyranosyl-(1-->2)-[beta-D-xylopyranosyl-(1-->3)]-beta-D-glucuronopyranosyl quillaic acid 28-O-alpha-L-arabinopyranosyl-(1-->2)-alpha-L-arabinopyranosyl-(1-->3)-beta-D-xylopyranosyl-(1-->4)-alpha-L-rhamnopyranosyl-(1-->2)-beta-D-fucopyranoside (1), 3-O-beta-D-galactopyranosyl-(1-->2)-[beta-D-xylopyranosyl-(1-->3)]-methyl-beta-D-glucuronopyranosyl gypsogenin 28-O-beta-D-glucopyranosyl-(1-->3)-[beta-D-xylopyranosyl-(1-->4)]-alpha-L-rhamnopyranosyl-(1-->2)-beta-D-fucopyranoside (2), and 23-O-beta-D-glucopyranosyl gypsogenic acid 28-O-beta-D-glucopyranosyl-(1-->3)-[beta-D-glucopyranosyl-(1-->6)]-beta-D-glucopyranoside (3), on the basis of various spectroscopic analyses and chemical degradations. The biological activities of 1-3 were examined inhibitory activity against pancreatic lipase, which showed inhibition of 58.2%, 99.2% and 50.3% at concentration of 1 mg/ml, respectively.     

Simultaneous determination of amphoteric surfactants in detergents by capillary electrophoresis with indirect UV detection

A simple, rapid and simultaneous determination of four types of amphoteric surfactants, i.e., C8, C10, C12, C14, C16 and C18-homologues of alkyldimethylamine N-oxide (AO), alkylamidopropylamine N-oxide (APAO), alkylbetaine (Bt) and alkylamidopropylbetaine (APB), was performed by using capillary electrophoresis (CE) with indirect UV detection. To optimize the separation conditions, effects of pH of background solution (BGS), organic modifier and chromophore for indirect UV detection on the CE separation of the amphoteric compounds were investigated. Addition of 50% (v/v) acetonitrile to the BGS under a lower pH condition brought a good separation performance due to the suppression of micelle formation for the analytes and the adsorption onto the inner surface of the capillary. Under an optimal condition, the 24 amphoteric analytes were completely separated in a single run within 17min. The relative standard deviation of the migration time was ranging from 0.20 to 0.23% and the limit of detection values for AO, APAO, Bt and APB homologues were 10-20, 20, 20-50 and 50microg/mL, respectively. Furthermore, the developed method can provide a high resolution separation of the amphoteric surfactants in commercially available detergents and shampoo without any sample pretreatments.