New indications of potential rat intestinal α-glucosidase inhibition by Syzygium zeylanicum (L.) and its hypoglycemic effect in mice

Research on Chemical Intermediates - Natural α-glucosidase inhibitors (aGIs) have been considered effective agents for type 2 diabetes management. In this study, Syzygium zeylanicum (L.)...     

Synthesis and Magnetic Characteristics of Neodymium Ferrite Powders with Perovskite Structure

Russian Journal of Applied Chemistry - Nanopowders of neodymium ferrite with perovskite structure were synthesized by co-precipitation precipitation via hydrolysis of iron(III) and neodymium(III)...     

Fuzzy distribution fitting energy-based active contours for image segmentation

This paper presents an unsupervised fuzzy energy-based active contour model for image segmentation, based on techniques of curve evolution. The paper proposes a fuzzy energy functional which involves intensity distributions in regions of image to segment and value of fuzzy membership functions. The intensity distributions are derived using a Gaussian mixture model (GMM)-based intensity distribution estimator. Meanwhile, the fuzzy membership functions valued in [0,1] is used to measure the association degree of each image pixel to the region outside and inside the curve. The proposed energy functional is then incorporated into a pseudo-level set formulation. To minimize the energy functional, instead of solving Euler?CLagrange equation of underlying problem, we utilize a direct method to calculate the alterations of the fuzzy energy. In addition, since the parameters of intensity distributions are preestimated, the proposed model avoids the step of updating them at each iteration of curve evolution. The proposed model therefore overcomes the initialization problem of common gradient-descent-based active contour models and converges quickly. Besides, it can work with images with blurred object boundaries. In addition, the extension of the model for the more general case of local space-varying intensities enables dealing with images with intensity inhomogeneity. Experimental results for synthetic and real images validate the desired performances of the proposed model.     

Uniqueness of Stoneley waves in pre-stressed incompressible elastic media

The main aim of this paper is to prove, for the general case, the uniqueness of Stoneley waves propagating along the bonded interface of two pre-stressed incompressible elastic half-spaces. In order to do that the authors have used the complex function method. By this approach, it is shown that the secular equation of Stoneley waves in pre-stressed incompressible elastic half-spaces has at most one solution in the complex plane. This says that if a Stoneley wave exists, then it is unique.     

Breath Biomarkers in Diagnostic Applications

The detection of chemical compounds in exhaled human breath presents an opportunity to determine physiological state, diagnose disease or assess environmental exposure. Recent advancements in metabolomics research have led to improved capabilities to explore human metabolic profiles in breath. Despite some notable challenges in sampling and analysis, exhaled breath represents a desirable medium for metabolomics applications, foremost due to its non-invasive, convenient and practically limitless availability. Several breath-based tests that target either endogenous or exogenous gas-phase compounds are currently established and are in practical and/or clinical use. This review outlines the concept of breath analysis in the context of these unique tests and their applications. The respective breath biomarkers targeted in each test are discussed in relation to their physiological production in the human body and the development and implementation of the associated tests. The paper concludes with a brief insight into prospective tests and an outlook of the future direction of breath research.     

A chromium(III)-superoxo complex in oxygen atom transfer reactions as a chemical model of cysteine dioxygenase

Metal-superoxo species are believed to play key roles in oxygenation reactions by metalloenzymes. One example is cysteine dioxygenase (CDO) that catalyzes the oxidation of cysteine with O(2), and an iron(III)-superoxo species is proposed as an intermediate that effects the sulfoxidation reaction. We now report the first biomimetic example showing that a chromium(III)-superoxo complex bearing a macrocyclic TMC ligand, [Cr(III)(O(2))(TMC)(Cl)](+), is an active oxidant in oxygen atom transfer (OAT) reactions, such as the oxidation of phosphine and sulfides. The electrophilic character of the Cr(III)-superoxo complex is demonstrated unambiguously in the sulfoxidation of para-substituted thioanisoles. A Cr(IV)-oxo complex, [Cr(IV)(O)(TMC)(Cl)](+), formed in the OAT reactions by the chromium(III)-superoxo complex, is characterized by X-ray crystallography and various spectroscopic methods. The present results support the proposed oxidant and mechanism in CDO, such as an iron(III)-superoxo species is an active oxidant that attacks the sulfur atom of the cysteine ligand by the terminal oxygen atom of the superoxo group, followed by the formation of a sulfoxide and an iron(IV)-oxo species via an O-O bond cleavage.     

Stereochemistry-dependent, mechanoresponsive supramolecular host assemblies for fullerenes: a guest-induced enhancement of thixotropy

Self-assembly behaviors of a series of systems (G1, G2, and G3) possessing same organic building blocks based on a substituted anthracene have been investigated in decalin. G2 and G3 are dominated by head-to-tail (ht) and head-to-head (hh) type dimers of G1, respectively. G1 gives a thermoresponsive gel that behaves ideally, showing frequency-independent elastic and viscous moduli. Interestingly, G2 produces a thixotropic gel that shows the signature of structural relaxation, signifying the dynamic nature of the system. In contrast, G3 remains fluidlike. As investigated by scanning electron microscopy (SEM), in the assembly process of G2, first disklike nanoaggregates are formed, and in the second step these aggregates interact to construct the densely packed secondary assembly. A transition from secondary assembly to primary assembly under shear initiates the mechanoresponsive destruction of the gel. In the self-assembly process, G1 propagates in a one-dimensional fashion, whereas G2 and G3 can propagate in a two-dimensionional fashion. The same side orientation of the substituents in G3 facilitates the formation of a compact closed-shell-type structure, which results in the generation of isolated nanocrystals. The long-range weak interaction together with the capability of propagating in two dimensions is found to be essential for the construction of such a mechanoresponsive assembly. C(60) and C(70) could be incorporated successfully in G2 assembly to develop mechanoresponsive fullerene assemblies. The presence of fullerenes not only enhances the elastic properties of G2 but also intensifies the thixotropy. C(70) appears to be a superior guest in terms of property enhancement due to its better size fitting with the concave-shaped host.     

Dynamic models of axially moving systems: A review

Nonlinear Dynamics - In this paper, a detailed review on the dynamics of axially moving systems is presented. Over the past 60 years, vibration control of axially moving systems has attracted...     

Wave-front phase measurements of high-order harmonic beams by use of point-diffraction interferometry

We report the wave-front phase measurement of high-order harmonics employing point-diffraction interferometry. The high-order harmonics generated in a gas-filled hollow tube showed excellent spatial coherence over nearly the whole cross section of the harmonic beams. Using this coherent harmonic source in the extreme-ultraviolet-soft-x-ray region, we have demonstrated the operation of a point-diffraction interferometer and measured the wave-front phase of high-order harmonics.