Bis(ethyl-3-Oxo-Butanolato-O1,O3) -bis(2-propanolato)titanium (tyzor) DCR) as a reactant and catalyst in the polymerization of 2-isocyanatoethyl methacrylate (IEM)

The reaction of bis(ethyl-3-oxo-butanolato-O¹,O³)-bis(2-propanolato)titanium(Tyzor DC^R and 2-isocyanatoethyl methacrylate (IEM) in refluxing hexane produced a mixture of trimer and polymers of 2-isocyanatoethyl methacrylate which varied considerably from 23 to 92% polymer as the molar ratio of bis(ethyl-3-oxo-butanolato-O¹,O³)-bis(2-propanolato)titanium(Tyzor DC^R) to 2-isocyanatoethyl methacrylate (IEM) varied from 1:4 to 1:32. The IEM 1-nylon polymer which was soluble in cresol and phenol was characterized by FTIR, ¹H-NMR, and ¹³C-NMR. This analysis also showed that the methacrylate carbon–carbon double bond survived our reaction conditions intact. Based on atomic absorption determination of titanium, the molecular weight of the polymer ranged between 3000 and 4000 g/mol. Thermal gravimetric analysis (TGA) showed the polymer to be stable in air to approximately 250°C.     

Asymmetric oxidation of some 1,3-dithianes in presence of chiral titanium complexes

Various 2-substituted 1,3-dithianes have been oxidized to the corresponding 1-oxides by cumene hydroperoxide in presence of a titanium complex (Ti(O-i-Pr)₄/(+)-DET/H₂O = 1/2/1) used in stoichiometric or lesser amounts. Enantioselectivity of up to 80% and excellent diastereoselectivity were achieved by a careful control of experimental conditions. The reaction temperature was found to be an important parameter. The relative stereochemistries of the new substituted monosulfoxides were determined by NMR spectroscopy.     

An algorithm for self-consistent field MO LCAO computations on conjugated systems with allowance for configuration interaction

The Pariser-Parr-Pople method is described briefly. An algorithm is presented for quantum-mechanical computation of molecular structures. A program for the BESM-2M computer is presented.     

Anomalous resistivity of lithium at high dynamic pressure

The experimental investigation of lithium compressed by multiple shock waves to a pressure of 210 GPa demonstrates the abnormal dependence of electrical resistivity. Contrary to normal metal behavior, the resistivity monotonically increases in the pressure range 30–150 GPa by more than 15 times from a typical metallic value at ambient conditions and reverts to a metallic value at a pressure higher than 160–210 GPa. The obtained results demonstrate the anomalous resistivity of lithium both in solid and in liquid states.     

Isobaric vapor–liquid equilibria for binary and ternary mixtures with cyclohexane,cyclohexene, and morpholine at 100 kPa

Vapor–liquid equilibria (VLE) data at 100 kPa have been determinated for the ternary system cyclohexane + cyclohexene + morpholine and two constituent binary systems cyclohexane + morpholine and cyclohexene + morpholine. The thermodynamic consistency of experimental data has been verified. Both binary systems deviate moderately from ideality without the presence of an azeotrope. The VLE data have been well correlated using local composition models (Wilson, NRTL and UNIQUAC) and have been also predicted with the original UNIFAC.     

As(III) Determination in the Presence of Pb(II) by Differential Alternative Pulses Voltammetry

Differential Alternative Pulses Voltammetry (DAPV), introduced by the authors earlier, was applied with HMDE for direct As(III) determination in the presence of Pb(II) in natural water without sample pretreatment. Distinguishable peaks of As(III) and Pb(II) were registered in 1 M HCl supporting electrolyte at a concentration ratio as high as 1 : 6, while complete peak overlapping occurs applying DPP at any concentration ratio at the same experimental conditions. In‐situ As(III) determinations in the presence of Pb(II) in contaminated ground waters in Mexico were performed, using especially designed disposable safe mercury drop electrodes.     

Erratum to: Solution behavior of aqueous mixtures of low and high molecular weight hydrophobic amphiphiles

Mixtures of a hydrophobic triblock copolymer (L121, PEO₅PPO₆₈PEO₅) and a hydrophobic anionic surfactant (AOT, Sodium bis(2-ethylhexyl)sulfosuccinate), each alone forming turbid vesicular solutions in water, aggregate to produce a thermodynamically stable, transparent and isotropic solution. Mixed AOT/L121 aggregates could be confirmed by fluorescence, surface tension, differential scanning calorimetry (DSC) and isothermal titration calorimetry (ITC). In an isotropic region, where mixed aggregates are formed, there is a synergistic interaction between monomers of AOT and L121 in the mixture. In addition, Small Angle Neutron Scattering (SANS) experiments provided evidence that mixed aggregates have the shape of either spheres (with a certain polydispersity) or very short ellipsoids (axial ratio below 2), confirming a transition from giant multilamellar vesicles to small aggregates upon mixing the two hydrophobic amphiphiles. Upon dilution, the morphology changes to disk-like. From an examination of the results of all the methods the peculiar behavior of the mixed AOT/L121 system is explained.     

Fresnel entropic characterization of optical Laguerre-Gaussian beams

A novel approach, based on Fresnel tomography, to determine the entropy of two-dimensional optical Laguerre-Gaussian beams is presented and discussed. Numerical evaluations of the entropy distribution in the phase space associated with Laguerre-Gauss modes are presented. It is shown that the concept of Fresnel entropy provides a general criterion for studying and characterizing the vorticity of Laguerre-Gauss modes.     

Investigation of Multi Wall Carbon Nanotubes and Nanotube assemblies by a molecular mechanics approach

The present work describes the modeling techniques applied for the investigation of assemblies of Carbon Nanotubes (CNTs) and Multi Wall Carbon Nanotubes (MWNTs). Motivated from possible future applications, for instance in new composite materials, the investigations of the interaction behavior of individual Carbon Nanotubes within an assembly of Carbon Nanotubes is mandatory in order to understand the behavior of larger scale structures made from CNTs, e.g. Carbon Nanotube fibers. The present research applies the Lennard-Jones potential for modeling the van-der-Waals interaction occurring between the nanotubes realizing the interaction behavior. The individual Carbon Nanotubes within the assembly are assumed to be rigid. All van-der-Waals bonds are taken into account in order to calculate an overall potential surface describing the behavior of the investigated structure. An example consisting of a Multi Wall Carbon Nanotube made of three armchair Single Wall Carbon Nanotubes (SWNTs) is investigated (with and without additional outer force) with respect to equilibrium positions of the structure. (© 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Expanded Conformations of Monomeric Tau Initiate Its Amyloidogenesis**

Understanding early amyloidogenesis is key to rationally develop therapeutic strategies. Tau protein forms well-characterized pathological deposits but its aggregation mechanism is still poorly understood. Using single-molecule force spectroscopy based on a mechanical protection strategy, we studied the conformational landscape of the monomeric tau repeat domain (tau-RD_244-368). We found two sets of conformational states, whose frequency is influenced by mutations and the chemical context. While pathological mutations Δ280K and P301L and a pro-amyloidogenic milieu favored expanded conformations and destabilized local structures, an anti-amyloidogenic environment promoted a compact ensemble, including a conformer whose topology might mask two amyloidogenic segments. Our results reveal that to initiate aggregation, monomeric tau-RD_244-368 decreases its polymorphism adopting expanded conformations. This could account for the distinct structures found in vitro and across tauopathies.