Design and synthesis of new imidazo[1,2-b]pyrazole derivatives,in vitro α-glucosidase inhibition,kinetic and docking studies

Molecular Diversity - A new series of imidazo[1,2-b]pyrazole derivatives 4a–o was designed, synthesized, and screened for in vitro α-glucosidase inhibitory activity. All compounds showed...     

Connectivity of Pore Space as a Control on Two-Phase Flow Properties of Tight-Gas Sandstones

We predict capillary-pressure (drainage) curves in tight-gas sandstones which have little matrix or microporosity using a quantitative grain-scale model. The model accounts for the geometric results of some depositional and diagenetic processes important for porosity and permeability reduction in tight-gas sandstones, such as deformation of ductile grains during burial and quartz cementation. The model represents the original sediment as a dense, disordered packing of spheres. We simulated the evolution of this model sediment into a low-porosity sandstone by applying different amounts of ductile grains and quartz precipitation. A substantial fraction of original pore throats in the sediment is closed by the simulated diagenetic alteration. Because the percolation threshold corresponds to closure of half of the pore throats, the pore space in this type of tight-gas sandstone is poorly connected and is often close to being completely disconnected. The drainage curve for different model rocks was computed using invasion percolation in a network taken directly from the grain-scale geometry and topology of the model. Some general trends follow classical expectations and were confirmed by experimental measurements: increasing the amount of cement shifts the drainage curve to larger pressures. This is related to reduction of the connectivity of pore space resulting from closure of throats. Existence of ductile grains in the ductile grain model also reduces the connectivity of pore space but it treats the throats distribution differently causing the drainage curves to be shifted to larger irreducible water saturation when cement is added to the model. The range of porosities in which these connectivity effects are important corresponds to the range of porosities common for tight gas sandstones. Consequently these rocks can exhibit small effective permeability to gas even at large gas saturations. This problem occurs at larger porosities in rocks with significant content of ductile grains because ductile deformation blocks a significant fraction of pore throats even before cementation begins. Predicted drainage curves agree with measurements on two samples with little microporosity, one dominated by rigid grains, the other containing a significant fraction of ductile grains. We conclude that connectivity of the matrix pore space is an important factor for an understanding of flow properties of tight-gas sandstones.     

Naphthoflavone propargyl ether inhibitors of cytochrome P450

Cytochrome P450 enzymes protect the body from foreign substances through a mechanism that involves oxidation of those substances into more readily excretable polar compounds. It has been shown that some naphthoflavones function as substrates of certain P450 enzymes (CYP1A1 and CYP1B1) and with appropriate structural changes may become inhibitors. Moreover, propargyl ether derivatives of adamantane have been shown to function as selective inactivators of some P450 enzymes (CYP2B1 and CYP2B5). In an attempt to improve the potency and selectivity of inhibition, we have designed and synthesized a series of naphthoflavone propargyl ethers. We report here the synthesis, X-ray crystal structures, and inhibition data (IC₅₀ of EROD inhibition in CYP1A1 and CYP1B1 enzymes) of α-naphthoflavone 2′-propargyl ether, β-naphthoflavone 2′-propargyl ether, α-naphthoflavone 4′-propargyl ether, and β-naphthoflavone 4′-propargyl ether. Crystallographic data: α-naphthoflavone 2′-propargyl ether, , a=7.775(1) ?, b=8.062(1) ?, c=13.110(1) ?, α=84.32(1)°, β=75.42(1)°, γ=86.56(1)°, V=790.8(2) ?³; β-naphthoflavone 2′-propargyl ether, , a=7.605(2) ?, b=7.793(1) ?, c=14.167(2) ?, α=77.06(1)°, β=75.41(1)°, γ=89.54(1)°, V=790.9(2) ?³; α-naphthoflavone 4′-propargyl ether, P21/n, a=14.595(2) ?, b=4.708(1) ?, c=24.745(6) ?, β=106.31(2)°, V=1631.8(7) ?³; β-naphthoflavone 4′-propargyl ether, P1, a=4.8871(5) ?, b= 7.9597(7) ?, c=21.788(3) ?, α=81.771(9)°, β=89.918(10)°, γ=72.223(8)°, V= 797.9(2) ?³.     

A Robust Electrochemical Sensor Based on Butterfly-shaped Silver Nanostructure for Concurrent Quantification of Heavy Metals in Water Samples

Heavy metals in drinking water have become a severe threat to human health. Detection of heavy metals has been achieved by electrochemical sensors that are modified with complex nanocomposites; however, reproducibility of these sensors is still a big challenge when applied in commercial settings. Here, a simple, very robust, and sensitive electrochemical sensor based on a screen-printed carbon electrode modified with butterfly-shaped silver nanostructure (AgNS/SPCE) has been developed for the concurrent determination of cadmium (II), lead (II), copper (II), and mercury (II) in water samples. The electrochemical behavior of the modified electrodes was investigated using cyclic voltammetry and differential pulse anodic stripping voltammetry. The AgNS/SPCE showed distinct peak potentials and a significant increase in the peak currents for all heavy metals, attributed to the high electrical conductivity and electrocatalytic activity of the synthesized butterfly-shaped AgNS. Moreover, the excellent stability and sensitivity towards simultaneous quantification of heavy metals have been obtained with detection limits of 0.4 ppb, 2.5 ppb, 7.3 ppb, and 0.7 ppb for Cd (II), Pb (II), Cu (II), and Hg (II), respectively. Besides, the constructed sensor was successfully applied to simultaneously quantify target heavy metals in spiked water samples. Owing to excellent sensitivity, high robustness, affordability, and fast response, the presented electrochemical sensor could be incorporated into a portable and miniaturized potentiostat device, making it a promising method for on-site water analysis.     

Graphite oxide: a simple and efficient solid acid catalyst for the ring-opening of epoxides by alcohols

A simple, efficient, and general procedure for the ring-opening of epoxides with various alcohols to give the corresponding β-alkoxy alcohols using graphite oxide (GO) as the catalyst, under very mild reaction conditions is described. The method proceeds in good to excellent yields and in short reaction times at room temperature under metal-free conditions.     

Coherent backscattering near the two-dimensional metal-insulator transition

We have studied corrections to conductivity due to the coherent backscattering in low-disordered two-dimensional electron systems in silicon for a range of electron densities including the vicinity of the metal-insulator transition, where the dramatic increase of the spin susceptibility has been observed earlier. We show that the corrections, which exist deeper in the metallic phase, weaken upon approaching the transition and practically vanish at the critical density, thus suggesting that the localization is suppressed near and at the transition even in zero field.     

Retraction Note to: OSGA: genetic-based open-shop scheduling with consideration of machine maintenance in small and medium enterprises

Annals of Operations Research - The Editor-in-Chief has retracted this article because validity of the content of this article cannot be verified.     

The fractional q-differential transformation and its application

In this paper, the definitions and operations of the one-dimensional and two-dimensional fractional q-differential transform is proposed. A distinctive feature of the fractional q-differential transform is its ability to solve linear and nonlinear ordinary/partial fractional q-differential equations.     

A convenient route toward one‐pot multicomponent synthesis of spirochromenes and pyranopyrazoles accelerated via quinolinic acid

In the present work, the catalytic activity of quinolinic acid (QUIN) was studied for the synthesis of spirochromene and pyranopyrazole derivatives from readily available materials. The salient features of these one‐pot multicomponent protocols are the clean reaction profile, easy isolation of products, no chromatographic separation techniques, high efficiency, short reaction time, and high yield of products plus using QUIN as a new, inexpensive, commercially available, and efficient organocatalyst.