Determination of 4‐Nitrobenzaldehyde in Water Samples by Combination of Switchable Solvent Based Microextraction and Electrochemical Detection on MWCNTs Modified Electrode

A novel approach is presented to determine 4‐nitrobenzaldehyde in water samples. The procedure is based on switchable solvent based liquid‐liquid microextraction (SS‐LLME) and then determination by differential pulse voltammetry at multi‐walled carbon nanotubes modified glassy carbon electrode. Dipropylamine, a solvent with switchable polarity, was used as an extraction solvent that can be miscible/immiscible upon the changes of pH of sample solution. Effects of experimental conditions on SS‐LLME were investigated using a one‐factor‐at‐a‐time methodology. Under optimized conditions, a calibration curve was linear in the concentration range of 1.0 and 350 μg L^?1. Limits of quantification and detection were empirically 1.0 μg L^?1 and 0.3 μg L^?1, respectively. Intraday and Interday RSDs%, calculated in three concentration levels, were in the range of 6.2–7.8 % confirm the proper precision of the method. Finally, the performance of the method was evaluated successfully in real samples including drinking water, tap water and river water.     

Third-Order Optical Nonlinearity in Two-Dimensional Transition Metal Dichalcogenides

We present a detailed calculation of the linear and nonlinear optical response of four types of monolayer twodimensional (2D) transition-metal dichalcogenides (TMDCs), having the formula MX2 with M=Mo, W and X=S, Se.The calculations are based on 6-band tight-binding model of TMDCs, and then performing a semi-classical perturbation analysis of response functions. We numerically calculate the linearχ(1)μν(-ω;ω) and nonlinear surface susceptibility tensorsχ(3)μνζη(-ωΣ;ωr,ωs,ωt) withωΣ=ωr+ωs+ωt. Both non-degenerate and degenerate cases are studied for thirdharmonic generation and nonlinear refractive index, respectively. Computational results obtained with no external fitting parameters are discussed regarding two recent reported experiments on Mo S2, and thus we can confirm the extraordinarily strong optical nonlinearity of TMDCs. As a possible application, we demonstrate generation of aπ/4-rotated squeezed state by means of nonlinear response of TMDCs, in a silica micro-disk resonator covered with the 2D material. Our proposed method will enable accurate calculations of nonlinear optical response, such as four-wave mixing and highharmonic generation in 2D materials and their heterostructures, thus enabling study of novel functionalities of 2D photonic integrated circuits.     

Mechanical recoverability and damage process of ionic‐covalent PAAm‐alginate hybrid hydrogels

Hydrogels consisting of interpenetrating networks of ionically and covalently crosslinked polymers showed high toughness and mechanical recoverability as a result of the dissociation and re‐formation of ionic crosslinks. The present investigation aimed to provide a quantitative study on the mechanical recoverability and damage process of an example hybrid gel of calcium crosslinked alginate and covalently crosslinked polyacrylamide. Three series of load/unload tests were performed sequentially with the mechanical properties of the gel fully retrieved between the 2nd and 3rd load/unload series while only the partial recovery of mechanical properties was evident from the 1st to 2nd series. The load/unload curves in the three series were modeled by existing mechanical models, and the fitted model parameters clearly demonstrate a damage process for the hybrid gel. When a hybrid gel was deformed above its historic maximum strain, the shortest alginate chains were fully‐stretched, pulling apart the weak ionic crosslinks and dissipating fracture energy. Consequently, the strand density of the intact gel network was reduced and the contour length of the remaining next‐shortest load‐bearing alginate chains became longer. A log‐normal distribution was used to describe the probability distribution for the strand fracture and also to describe the strand length distribution of the ionic network. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2016 , 54, 53–63     

D-glycopyranosyl phenylsulfones: Their use in a stereocontrolledsynthesis of cis-2,6-disubstituted tetrahydropyrans (β-d-c-clycosides)

The lithiated anion derived from 3,4,6-tri-O-t-butyldimethylsilyl-2-deoxy-α, β-D-gluco-pyranosyl phenylsulfones 1 reacts with various electrophiles leading to alkylated products, precursors of β-D-C-glycosides 5–g after stereocontrolled desulfonylation and hydrolysis.     

Structural increment system for 11-vertex nido-boranes and carboranes

An increment system forming a set of quantitative rules that govern the relative stabilities of 11-vertex nido-boranes and carboranes is presented. Density functional theory computations at the B3LYP/6-311+G//B3LYP/6-31G level with ZPE corrections were carried out for 61 different boron hydride and carborane structures from [B(11)H(14)](-) to C(4)B(7)H(11) to determine their relative stabilities. Disfavored structural features that destabilize a cluster structure relative to a hypothetical ideal situation were identified and weighted by so-called energy penalties. The latter show additive behavior and allow us to reproduce (within 5 kcal mol(-)(1)) the DFT computed relative energies. Energy penalties for four structural features, i.e., adjacent carbon atoms, CC, a hydrogen atom bridging between a carbon and a boron atom, CH-B, an endo-terminal hydrogen atom at an open face carbon atom, CH(2) and an endo-H between two carbon atoms, C(BH(2))C for the 11-vertex nido-cluster are quite similar to those reported for the 6-vertex nido-cluster, thus showing a behavior independent of the cluster size. Hydrogen structural features, however, vary strongly with the cluster size. Two unknown 11-vertex nido-carboranes were identified which are thermodynamically more stable than known positional isomers.     

Stability of a family of multi-time-level difference schemes for the advection equation

Summary For the linear advection equation we consider explicit multi-time-level schemes of highest order which are one step in space direction only. If a stencil involvesk time steps we show that it is stable in theL ₂-sense for Courant numbers in the interval (0, 1/k). Since the order is 2k–1 one can use these schemes for high order discretization of the boundary conditions in hyperbolic initial value problems.Part of this work has been performed in the project Mehrschritt-Differenzenschemata of the Schwerpunktprogramm Finite Approximationen in der Strömungsmechanik which has been supported by the DFG     

Alum (KAl(SO4)2 · 12H2O) Catalyzed One-Pot Synthesis of Coumarins under Solvent-Free Conditions

Alum (KAl(SO₄)₂ · 12H₂O) is used as an efficient catalyst in the Pechmann condensation of phenol derivatives with β-keto esters leading to the formation of coumarins in excellent yields under solvent-free conditions. This methodology offers significant improvements for the synthesis of coumarins with regard to the yield of products, simplicity in operation, and green aspects by avoiding toxic catalysts and solvents.     

Optimal economic load dispatch based on wind energy and risk constrains through an intelligent algorithm

This article focus on optimal economic load dispatch based on an intelligent method of shark smell optimization (SSO). In this problem, the risk constrains has been considered which has root in uncertainity and unpredictable behavior of wind power. Regarding to increasing of this clean energy in power systems and un‐dispatchable behavior of wind power, its conditional value at risk index considered in this article which consists of loss from load and "spilling" wind energy connected with unpredictable imbalances among generation and load. This problem has been considered as an optimization problem based on SSO that evaluate the balance between cost and risk. This algorithm is based on distinct shark smell abilities for localizing the prey. In sharks' movement, the concentration of the odor is an important factor to guide the shark to the prey. In other words, the shark moves in the way with higher odor concentration. This characteristic is used in the proposed SSO algorithm to find the solution of an optimization problem. Effectiveness of the proposed method has been applied over 30‐bus power system in comparison with other techniques. © 2016 Wiley Periodicals, Inc. Complexity 21: 494–506, 2016     

Towards a Precise NMR Quantification of Acute Phase Inflammation Proteins from Human Serum

Nuclear Magnetic Resonance (NMR) spectra of human serum and plasma show, besides metabolites and lipoproteins, two characteristic signals termed GlycA and B arising from the acetyl groups of glycoprotein glycans from acute phase proteins, which constitute good markers for inflammatory processes. Here, we report a comprehensive assignment of glycoprotein glycan NMR signals observed in human serum, showing that GlycA and GlycB signals originate from Neu5Ac and GlcNAc moieties from N-glycans, respectively. Diffusion-edited NMR experiments demonstrate that signal components can be associated with specific acute phase proteins. Conventionally determined concentrations of acute phase glycoproteins correlate well with distinct features in NMR spectra (R² up to 0.9422, p-value <0.001), allowing the simultaneous quantification of several acute phase inflammation proteins. Overall, a proteo-metabolomics NMR signature of significant diagnostic potential is obtained within 10–20 min acquisition time. This is exemplified in serum samples from COVID-19 and cardiogenic shock patients showing significant changes in several acute phase proteins compared to healthy controls.