Boundary Regularity of Shear Thickening Flows

This article is concerned with the global regularity of weak solutions to systems describing the flow of shear thickening fluids under the homogeneous Dirichlet boundary condition. The extra stress tensor is given by a power law ansatz with shear exponent p≥ 2. We show that, if the data of the problem are smooth enough, the solution u of the steady generalized Stokes problem belongs to W^{1,(np+2-p)/(n-2)}(W){W^{1,(np+2-p)/(n-2)}(\Omega)} . We use the method of tangential translations and reconstruct the regularity in the normal direction from the system, together with anisotropic embedding theorem. Corresponding results for the steady and unsteady generalized Navier–Stokes problem are also formulated.     

The Nature of the Binding of Au, Ag, and Pd to Benzene, Coronene, and Graphene: From Benchmark CCSD(T) Calculations to Plane-Wave DFT Calculations

The adsorption of Ag, Au, and Pd atoms on benzene, coronene, and graphene has been studied using post Hartree-Fock wave function theory (CCSD(T), MP2) and density functional theory (M06-2X, DFT-D3, PBE, vdW-DF) methods. The CCSD(T) benchmark binding energies for benzene-M (M = Pd, Au, Ag) complexes are 19.7, 4.2, and 2.3 kcal/mol, respectively. We found that the nature of binding of the three metals is different: While silver binds predominantly through dispersion interactions, the binding of palladium has a covalent character, and the binding of gold involves a subtle combination of charge transfer and dispersion interactions as well as relativistic effects. We demonstrate that the CCSD(T) benchmark binding energies for benzene-M complexes can be reproduced in plane-wave density functional theory calculations by including a fraction of the exact exchange and a nonempirical van der Waals correction (EE+vdW). Applying the EE+vdW method, we obtained binding energies for the graphene-M (M = Pd, Au, Ag) complexes of 17.4, 5.6, and 4.3 kcal/mol, respectively. The trends in binding energies found for the benzene-M complexes correspond to those in coronene and graphene complexes. DFT methods that use empirical corrections to account for the effects of vdW interactions significantly overestimate binding energies in some of the studied systems.     

On the worst scenario method: Application to a quasilinear elliptic 2D-problem with uncertain coefficients

We apply a theoretical framework for solving a class of worst scenario problems to a problem with a nonlinear partial differential equation. In contrast to the one-dimensional problem investigated by P. Harasim in Appl. Math. 53 (2008), No. 6, 583–598, the two-dimensional problem requires stronger assumptions restricting the admissible set to ensure the monotonicity of the nonlinear operator in the examined state problem, and, as a result, to show the existence and uniqueness of the state solution. The existence of the worst scenario is proved through the convergence of a sequence of approximate worst scenarios. Furthermore, it is shown that the Galerkin approximation of the state solution can be calculated by means of the Kachanov method as the limit of a sequence of solutions to linearized problems.     

Contactless Conductivity Detection in Capillary Electrophoresis Employing Capillaries with Very Low Inner Diameters

The behaviour of a contactless conductivity detector was studied in its application to capillary electrophoresis employing quartz capillaries with inner diameters (i.d.) of 10 to 75 µm. The detector output signal was measured using KCl as the test electrolyte, within a KCl concentration range from 0 to 100 mmol/L, corresponding to specific conductivities from 0 to 1295 mS/m. When using capillaries with high inner diameters, then the signal‐to‐noise ratio is high in electrolytes of low conductivity. On the other hand, the use of capillaries with low i.d. values is useful in separations employing solutions of high conductivities. The advantages of capillaries with small i.d. values, combined with contactless conductivity detection, are demonstrated on separations of mixtures of inorganic ions and on separations of neutral mono‐ and disaccharides.     

ELISA kit for mustard protein determination: interlaboratory study

An interlaboratory study in 12 laboratories was performed to prove the validation of the ELISA method developed for the quantitative determination of mustard protein in foods. The ELISA kit used for this study is based on rabbit polyclonal antibody. This kit did not produce any false-positive results or cross-reactivity with in-house validation for a broad range of food matrixes with no detectable mustard protein. All participants obtained the Mustard ELISA kit with standard operational procedures, a list of samples, samples, and a protocol for recording test results. The study included 15 food samples and two spiked samples. Seven food matrix samples of zero mustard content and four samples with mustard declared as an ingredient showed mustard protein content lower than that of the first standard (0.42 mg/kg). Four samples with mustard declared as an ingredient revealed mustard protein content above 12.5 mg/kg (the highest standard). The statistical tests (Cochran, Dixon, and Mandel) and analysis of variance were used to evaluate the interlaboratory study results. Repeatability and reproducibility limits, as well as an LOQ (1.8 mg mustard proteins/kg) and LOD (0.5 mg mustard proteins/kg), for the kit were calculated.     

New dinuclear nickel(II) complexes: synthesis, structure, electrochemical, and magnetic properties

The reaction of [NiBr(2)(bpy)(2)] (bpy = 2,2'-bipyridine) with organic phosphinic acids ArP(O)(OH)H [Ar = Ph, 2,4,6-trimethylphenyl (Mes), 9-anthryl (Ant)] leads to the formation of binuclear nickel(II) complexes with bridging ArP(H)O(2)(-) ligands. Crystal structures of the binuclear complexes [Ni(2)(μ-O(2)P(H)Ar)(2)(bpy)(4)]Br(2) (Ar = Ph, Mes, Ant) have been determined. In each structure, the metal ions have distorted octahedral coordination and are doubly bridged by two arylphosphinato ligands. Magnetic susceptibility measurements have shown that these complexes display strong antiferromagnetic coupling between the two nickel atoms at low temperatures, apparently similar to binuclear nickel(II) complexes with bridging carboxylato ligands. Cyclic voltammetry and in situ EPR spectroelectrochemistry show that these complexes can be electrochemically reduced and oxidized with the formation of Ni(I),Ni(0)/Ni(III) derivatives.     

Comparative study of mono- and dinuclear complexes of late 3d-metal chlorides with N,N-dimethylformamide in the gas phase

Mono- and binuclear complexes of N,N-dimethylformamide (DMF) with chlorides of the divalent, late 3d metals M = Co, Ni, Cu, and Zn are investigated by means of electrospray ionization (ESI). Specifically, ESI leads to monocations of the type [(DMF)(n)MCl](+) and [(DMF)(n)M(2)Cl(3)](+), of which the species with n = 2 and 3 were selected for in-depth studies. The latter include collision-induced dissociation experiments, gas-phase infrared spectroscopy, and calculations using density functional theory. The mononuclear complexes [(DMF)(n)MCl](+) almost exclusively lose neutral DMF upon collisional activation with the notable exception of the copper complex, for which also a reduction from Cu(II) to Cu(I) concomitant with the release of atomic chlorine is observed. For the dinuclear clusters, there exists a competition between loss of a DMF ligand and cluster degradation via loss of neutral MCl(2) with decreasing cluster stability from cobalt to zinc. For the specific case of [(DMF)(n)ZnCl](+) and [(DMF)(n)Zn(2)Cl(3)](+), ion-mobility mass spectrometry indicates the existence of two isomeric cluster ions in the case of [(DMF)(2)Zn(2)Cl(3)](+) which corroborates parallel theoretical predictions.     

Layered zinc hydroxide salts: delamination, preferred orientation of hydroxide lamellae, and formation of ZnO nanodiscs

Herein, we report our analysis of the surface modification of polystyrene (PS) when treated under ambient conditions with a common biological buffer such as phosphate buffered saline (PBS) or aqueous solutions of the ionic constituents of PBS. Attenuated total reflection Fourier transform infrared spectroscopy was used for the analysis because the resultant spectra are very sensitive to minor changes in the chemical and structural properties of PS films. In addition, ultraviolet-visible spectroscopy was applied to characterize the surface modifications of PS. Treatment with PBS resulted in the most significant chemical and structural surface modifications of the PS films, as compared with each of the solutions of the constituents of PBS, which were tested separately. A multistep mechanism for the wet modification of PS is discussed. We postulate that the observed surface modifications are the result of photo-oxidation/reduction, swelling, and conformational changes and re-arrangement of the polymer chain. The resultant surface modifications could be similar to those produced by commonly used dry processes such as plasma treatments and electron, ion or ultraviolet irradiation. We found that the modifications that occurred in PBS were more stable than those initiated by dry processes. The formation of active groups on the surface of PS can be controlled by adsorption of bovine serum albumin or thermal annealing of PS before PBS treatment. This approach provides a simple and efficient method for the surface modification of PS for biomedical applications.     

Effects of the gradient profile, sample volume and solvent on the separation in very fast gradients, with special attention to the second-dimension gradient in comprehensive two-dimensional liquid chromatography

Gradient elution provides significant improvement in peak capacity with respect to isocratic conditions and therefore should be used in comprehensive two-dimensional LC×LC, both in the first and in the second dimension, where, however, gradients are limited to a short time period available for separation, usually 1 min or less. Gradient conditions spanning over a broad mobile phase composition range in each second-dimension fraction analysis are used with generic "full in fraction" (FIF) gradients. "Segment in fraction" (SIF) gradients cover a limited gradient range adjusted independently to suit changing lipophilicity range of compounds transferred to the second dimension during the first-dimension gradient run and to provide regular coverage of the two-dimensional retention space. Optimization of the gradient profiles is important tool for achieving high two-dimensional peak capacity and savings of the separation time in comprehensive LC×LC. Calculations based on the well-established gradient-elution theory can be used to predict the elution times and bandwidths in fast gradients, taking into account increased probability of pre-gradient or post-gradient elution. The fraction volumes transferred into the second dimension may significantly affect the second-dimension bandwidths, especially at high elution strength of the fraction solvent, which may cause even band distortion or splitting in combined normal-phase (HILIC)-RP systems, but also in some two-dimensional RP-RP systems. In the present work, the effects of the fast gradient profile, of the sample volume and solvent on the elution time and bandwidths were investigated on a short column packed with fused-core porous-shell particles, providing narrow bandwidths and fast separations at moderate operating pressure.     

Some new information on the formation of substituted 4‐amino‐1‐substituted phenyl‐1H‐pyrazoles from β‐enaminones and diazonium tetrafluoroborates

Upon reaction of 2‐methyl‐, 3‐ethoxycarbonyl, and 4‐ethoxycarbonylbenzenediazonium tetrafluoroborate with 1‐cyclopropyl‐3‐phenylaminohex‐2‐en‐1‐one 3‐cyclopropylcarbonyl‐1‐(substituted phenyl)‐5‐ethyl‐4‐phenylamino‐1H‐pyrazoles are formed. On the other hand, the reaction of 1‐cyclopropyl‐3‐phenylaminohex‐2‐en‐1‐one and 5‐methylaminohept‐4‐en‐3‐one with sterically more demanding 2‐ethoxycarbonylbenzenediazonium tetrafluoroborate does not give the corresponding pyrazoles but the probable intermediates on the route to the pyrazoles: 1‐cyclopropyl‐3‐phenyliminohexane‐1,2,4‐trione 2,4‐bis(2‐ethoxycarbonylphenylhydrazone) and 3‐methyliminoheptane‐2,4,5‐trione 2,4‐bis(2‐ethoxycarbonylphenylhydrazone), respectively. All the compounds were identified on the basis of ¹H‐ and ¹³C‐NMR spectra. The structure of 1‐cyclopropyl‐3‐phenyliminohexane‐1,2,4‐trione 2,4‐bis(2‐ethoxycarbonylphenylhydrazone) was confirmed by means of ¹⁵N‐NMR spectra and X‐ray. The bis(2‐ethoxycarbonylphenylhydrazones) were found to show atropoisomerism due to a hindered rotation around the bond between the carbons of imino group and the hydrazono group next to carbonyl. In the case of the crystalline cyclopropyl derivative, the unit cell was found out to contain two molecules of opposite chirality. J. Heterocyclic Chem., (2011).