Identification and characterisation of coumarins from the roots of Angelica dahurica and their inhibitory effects against cholinesterase

The current research was the first to investigate coumarins and their cholinesterase inhibitory activities from Angelica dahurica roots. The ethanol extract of this species (100 μg/ml) possessed inhibitory effects against human acetylcholinesterase (hAChE) and butylcholinesterase (BChE) with IC₅₀ values of 26.40 and 14.71 μg/ml, respectively. To evaluate the compounds responsible for these activities, the ethanol extract was chromatographed, which yielded ten coumarins, including isoimperatorin (1), imperatorin (2), senbyakangelicol (3), oxypeucedanin (4), byakangelicol (5), t-OMe-oxypeucedanin hydrate (6), t-OMe-byakangelicin (7), angelol H (8), byakangelicin (9), and oxypeucedanin hydrate (10). Among them, coumarin 5, 7, and 9 showed potent inhibition with IC₅₀s of 46.3, 39.0, and 55.4 μM (hAChE) as well as 45.2, 25.6, and 42.4 μM (BChE), respectively. Moreover, their inhibition modes against two cholinesterases exhibited noncompetitive. The individual coumarin contents were remarkable differences, especially, oxypeucedanin (4) was the most predominant compound (8710.9 μg/g), representing approximately 55.0% of the total content.     

Combined Intercritical Annealing and Q&P Processing of Medium Mn Steel

The microstructure and mechanical properties of intercritically annealed medium Mn steel are dependent on the selection of the intercritical annealing (IA) temperature. While the yield strength (YS) decreases with increasing IA temperature, the ultimate tensile strength increases with increasing IA temperature. Strain aging phenomena, both static and dynamic, are also often observed. The present contribution shows that, by combining IA with the quench and partitioning processing of the intercritical austenite, it is possible to obtain non-aging mechanical properties which combine a high YS with an ultra-high tensile strength. These properties are particularly suitable for automotive parts related to passenger safety.     

Energy Dissipation and Tool-Workpiece Contact in Ultra-Precision Machining

An experimental investigation was conducted to examine the dissipation of mechanical energy when machining at depths of cut less than several micrometers. Cutting and thrust forces which resulted in the orthogonal ultra-precision flycutting of Al 6061-T6 were measured over a range of depth of cut of 20 μ-m down to 0.01 μm at a cutting speed of 0.8 m-sec^?1. Measurement of the tool-workpiece contact length indicated that it may become the characteristic length scale when machining al submicrometer depths of cut. Evidence suggests that the process may be viewed as transitioning from a cutting-dominant to plowing/sliding indentation-dominant process. Tool edge condition was seen to have a significant effect on the resulting forces when the depth of cut was below the tool edge radius.     

Reduced-order dynamic observer error linearisation: a natural extension of observer error linearisation

This paper introduces the concept of reduced-order dynamic observer error linearisation (RDOEL) for multi-output systems, which is the problem of transforming a nonlinear system into a nonlinear observer canonical form with the aid of auxiliary dynamics. The proposed RDOEL framework is not only a modified version of dynamic observer error linearisation (DOEL) but also a natural extension of observer error linearisation (OEL). We provide three necessary conditions for the RDOEL problem, and then derive a necessary and sufficient condition described in terms of Lie algebras of vector fields. Furthermore, from the result, we also give a geometric necessary and sufficient condition for the OEL problem, which has not yet been completely established in the case where a diffeomorphism on the output of general form is considered.     

Acoustic emission activities and damage evaluation of reinforced concrete beams strengthened with CFRP sheets

In this study, the applicability of acoustic emission (AE) techniques to monitor damage evolution in reinforced concrete (RC) beams strengthened in flexure with carbon fiber reinforced polymer (CFRP) sheets is investigated. The objective is to initiate the creation of a user-friendly health monitoring system for RC structures strengthened with CFRP sheets using AE techniques. Five beams, 200 mm×300 mm in cross-section, were tested under three-point bending over a span of 1700 mm. One of the beams was tested in its virgin condition to serve as reference; the remaining four beams were tested after being strengthened with CFRP sheets bonded on the tension face. The parameters investigated in this study include both the amount of CFRP sheets and construction imperfections (the CFRP sheets were intentionally bonded without adhesive in the centermost 10% and 20% bonding area). The AE signals were collected and analyzed for all specimens. The AE parameters were analyzed for four levels of damage based on initial crack, propagation, yielding of main bars, and fracture or rip-off of the CFRP sheets. The frequency-peak magnitude distribution of the AE parameters was used to determine the b-value, defined by the Gutenberg–Richter relationship, for evaluating the damage evolution and fracture process of RC beams strengthened in flexure with CFRP sheets. From the results of this study, the signal characteristics – event, amplitude versus frequency, and amplitude versus duration – show clear differences in the different loading stages, depending upon the active damage mechanism. The b-value is correlated to the fracture process of the RC beams bonded with CFRP sheets and the degree of localization of damage. The AE technique is a useful nondestructive technique for monitoring the behavior of RC beams that are externally reinforced in flexure with CFRP sheets.     

Structural Basis for Design of New Purine-Based Inhibitors Targeting the Hydrophobic Binding Pocket of Hsp90

Inhibition of the molecular chaperone heat shock protein 90 (Hsp90) represents a promising approach for cancer treatment. BIIB021 is a highly potent Hsp90 inhibitor with remarkable anticancer activity; however, its clinical application is limited by lack of potency and response. In this study, we aimed to investigate the impact of replacing the hydrophobic moiety of BIIB021, 4-methoxy-3,5-dimethylpyridine, with various five-membered ring structures on the binding to Hsp90. A focused array of N⁷/N⁹-substituted purines, featuring aromatic and non-aromatic rings, was designed, considering the size of hydrophobic pocket B in Hsp90 to obtain insights into their binding modes within the ATP binding site of Hsp90 in terms of π–π stacking interactions in pocket B as well as outer α-helix 4 configurations. The target molecules were synthesized and evaluated for their Hsp90α inhibitory activity in cell-free assays. Among the tested compounds, the isoxazole derivatives 6b and 6c, and the sole six-membered derivative 14 showed favorable Hsp90α inhibitory activity, with IC₅₀ values of 1.76 µM, 0.203 µM, and 1.00 µM, respectively. Furthermore, compound 14 elicited promising anticancer activity against MCF-7, SK-BR-3, and HCT116 cell lines. The X-ray structures of compounds 4b, 6b, 6c, 8, and 14 bound to the N-terminal domain of Hsp90 were determined in order to understand the obtained results and to acquire additional structural insights, which might enable further optimization of BIIB021.     

Prediction of Behavior of Alumina Inclusion in Front of Solid–Liquid Interface in SPFH590 Steel

Metallurgical and Materials Transactions B - To predict the behavior of an alumina inclusion in front of the solid–liquid interface during solidification, the interfacial tension between...     

Color tunable and thermally stable luminescence of Tb3+ doped Li4SrCa(SiO4)2 phosphors

Tb³⁺ ions activated Li₄SrCa(SiO₄)₂ phosphors were synthesized using a solid state reaction method. The phase impurity was checked by XRD. The photoluminescence (PL) excitation spectrum, emission spectra at room and high temperature, decay curves of samples with different Tb³⁺ ions concentration were studied in detail. Cross-relaxation and the Inokuti–Hirayama model were used to analyze the experimental results. Li₄SrCa(SiO₄)₂:xTb³⁺ are thermally stable and color tunable phosphors.