A note on the second problem of Stokes for Newtonian fluids

New and simpler exact solutions corresponding to the second problem of Stokes for Newtonian fluids are established by the Laplace transform method. These solutions, presented as a sum of the steady-state and transient solutions are in accordance with the previous results (see Figs. 1-4). The amplitudes of the wall shear stresses corresponding to the cosine and sine oscillations are almost identical, except for a small initial time interval. The time required to attain the steady-state for the cosine oscillations of the boundary is smaller than that for the sine oscillations of the boundary. This time decreases if the frequency of the velocity of the boundary increases.     

Phosphonate mediated surface reaction and reorganization: implications for the mechanism controlling cement hydration inhibition

Vertical scanning interferometry and XPS show the reaction of CaCO3 with the hydration retarder nitrilo-tris-(methylene)phosphonic acid follows a pathway of dissolution of the calcium followed by precipitation of a calcium phosphonate; subsequent surface reorganization/restructuring of the calcium phosphonate exposes the underlying CaCO3 for further hydration.     

Blockwise approach to fragments of the O-specific polysaccharide of Shigella flexneri serotype 2a: convergent Synthesis of a decasaccharide representative of a dimer of the branched repeating unit

The D'A'B'(E')C'DAB(E)C decasaccharide representative of a dimer of a frame-shifted pentasaccharide repeating unit of the O-specific polysaccharide of Shigella flexneri 2a was synthesized as its methyl glycoside by condensing a pentasaccharide donor (D'A'B'(E')C') and a pentasaccharide acceptor (DAB(E)C-OMe). Several convergent routes to these two building blocks, involving either the AB linkage or the BC linkage as the disconnection site, were evaluated in comparison to the linear strategy. The latter was preferred. It is based on the use of the trichloroacetimidate chemistry. The target branched oligosaccharide was designed to probe the recognition at the molecular level of the natural polysaccharide by protective monoclonal antibodies.     

Exact solutions for the flow of a generalized Oldroyd-B fluid induced by a constantly accelerating plate between two side walls perpendicular to the plate

The unsteady flow of an incompressible generalized Oldroyd-B fluid induced by a constantly accelerating plate between two side walls perpendicular to the plate has been studied using Fourier sine and Laplace transforms. The obtained solutions for the velocity field and shear stresses, written in terms of the generalized G and R functions, are presented as sum of the similar Newtonian solutions and the corresponding non-Newtonian contributions. For α = β = 1 and λ_r → λ these solutions are going to the corresponding Newtonian solutions. Furthermore, the solutions for generalized Maxwell fluids as well as those for ordinary Oldroyd-B and Maxwell fluids, performing the same motion, are also obtained as limiting cases of our general solutions. In the absence of the side walls, namely when the distance between the two walls tends to infinity, the solutions corresponding to the motion over an infinite constantly accelerating plate are recovered. For λ_r → 0 and β → 1, these solutions reduce to the known solutions from the literature. Finally, the effect of the material parameters on the velocity profile is spotlighted by means of the graphical illustrations.     

Enantio- and Diastereoswitchable C−H Arylation of Methylene Groups in Cycloalkanes

A complementary set of chiral N,N-ligands enables the Pd-catalyzed β-C−H arylation of unbiased internal methylene groups in good yield and with high levels of enantio- and diastereoinduction. Both the dia- and enantioselectivity can be reversed, thus allowing the selective arylation of any of the four β-C−H bonds in cycloalkanecarboxamides of various ring sizes. The method is applicable to a broad range of aryl iodides with electron-withdrawing and -donating substituents in the o-, m-, or p-position.     

Unsteady flows of Oldroyd-B fluids in a channel of rectangular cross-section

The aim of this note is to present the exact solutions corresponding to two types of unsteady flows of an Oldroyd-B fluid in a channel of rectangular cross-section. The solutions that have been obtained satisfy both the associate partial differential equations and all imposed initial and boundary conditions. For λ_r or λ→0 they tend toward similar solutions for a Maxwell or second-grade fluid. If both λ_r and λ→0, the solutions for Navier-Stokes fluids are recovered.     

On pseudo-equality algebras

Recently, a new algebraic structure called pseudo-equality algebra has been defined by Jenei and Kóródi as a generalization of the equality algebra previously introduced by Jenei. As a main result, it was proved that the pseudo-equality algebras are term equivalent with pseudo-BCK meet-semilattices. We found a gap in the proof of this result and we present a counterexample and a correct version of the theorem. The correct version of the corresponding result for equality algebras is also given.     

Optimization of immunoaffinity enrichment and detection: toward a comprehensive characterization of the phosphotyrosine proteome of K562 cells by liquid chromatography-mass spectrometry

Phosphorylation of protein tyrosine residues regulates many cell functions and has also been proved to be involved in oncogenesis. Thus, the identification of the phosphotyrosine (pTyr) proteome of cells is a very important task. Since tyrosine phosphorylation represents only around 1% of the total human phosphoproteome, the study of pTyr proteins is rather challenging. Here we report the optimization study of the phosphotyrosine proteome using K562 cells as a model system. A substantial segment of the phosphotyrosine proteome of K562 cells was characterized by immunoaffinity enrichment with 4G10 and PYKD1 antibodies followed by LC-MS/MS analysis. 480 non-redundant pTyr peptides corresponding to 342 pTyr proteins were found. 141 pTyr peptides were not described elsewhere. The mass spectrometry approach involving high-resolving FTMS analysis of precursor ions and subsequent detection of CID fragments in a linear ion trap was considered as optimal. For detection of low abundant pTyr peptides pooling of individual immunoaffinity enrichments for one LC-MS/MS analysis was crucial. The enrichment properties of the monoclonal PYKD1 antibody were presented for the first time, also in comparison to the 4G10 antibody. PYKD1 was found to be more effective for protein enrichment (1.2 and 5% efficiency at peptide and protein level correspondingly), while 4G10 showed better results when peptide enrichment was performed (15% efficiency versus 3.6% at protein level). Substantially different subsets of the phosphoproteome were enriched by these antibodies. This finding together with previous studies demonstrates that comprehensive pTyr proteome characterization by immunoprecipitation requires multiple antibodies to be used for the affinity enrichment.