Touching the upper limit for ferromagnetic interactions in hetero-bridged dinuclear [Cu2(II)] complexes using a novel N5-dinucleating ligand bearing an endogenous monoatomic amido(R-NH(-))-bridging group

A novel N(5)-dinucleating ligand 4-amino-3,5-bis(bipyridine-2-yl)-1,2,4-triazole allows the preparation for the first time, and under mild conditions, of single and mixed amido(R-NH(-))-bridged copper(II) complexes, the latter exhibiting very strong ferromagnetic coupling.     

Saddle-point solutions and grazing bifurcations in an impacting system

This paper focuses on the intricate relationship between smooth and nonsmooth phenomena in an impacting system. In particular a boundary saddle-point solution, that is born in a nonsmooth fold, is analysed. Accessible boundary saddle-point solutions play a key role in determining the global dynamics of a system and here we will show how grazing bifurcations can affect their existence.     

Elements on the Concept and Design of a Tracked Mini Robot – “ROBO GENIU” – Destined for Special Applications

The authors of this paper aim to highlight issues related to the organology and the integration of the hardware component in the mechanical structure of a tracked mini robot, called Robo Geniu, part of the unmanned ground vehicles category having the ability to act autonomously and enabling its endowment with means of observation, listening, tapping, relaying and jamming. This paper reveals, in detail, the composing parts of the hardware component, as well as the way they are assembled in the mechanical structure of the mini robot under study. (© 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Adsorption behavior and activity of hexokinase

The study on the adsorption of hexokinase (HK) onto silicon wafers was carried out by means of in situ ellipsometry and atomic force microscopy in the liquid. The thickness values of the adsorbed HK layer determined by both techniques were in excellent agreement and evidenced HK monolayer formation. The adsorption of HK onto Si wafers was favored at low ionic strength, indicating that the adsorption is mainly driven by electrostatic forces, since salt screens not only the segment-segment repulsion but also the segment-surface attraction when the salt concentration increases. The enzymatic activity of free HK and of adsorbed HK was measured as a function of time. Free HK in solution lost activity upon storage. Contrarily, adsorbed HK kept its activity level even after 48 h storage at room temperature. This outstanding behavior was attributed to specific orientation of the HK active site to the solution.     

Mild organocatalytic alpha-methylenation of aldehydes

A rapid and extremely convenient method for alpha-methylenation of aldehydes with aqueous formaldehyde is described. Two optimal catalytic systems are presented that allow short reaction times and afford the functionalized products in good to excellent yields (up to 99%) and chemoselectivity.     

19F single-quantum and 19F-33S heteronuclear multiple-quantum coherence NMR of SF6 in thermotropic nematogens and in the gas phase

(19)F single-quantum (SQC) and (19)F-(33)S heteronuclear multiple-quantum coherence (HMQC) NMR spectroscopy of sulfur hexafluoride (SF(6)) dissolved in thermotropic liquid crystals (TLCs) were used to investigate the properties of TLCs. On one hand, environmental effects on the NMR parameters of SF(6), (19)F nuclear shielding, (19)F-(33)S spin-spin coupling, secondary isotope effects of sulfur on (19)F shielding, and the self-diffusion coefficient in the direction of the external magnetic field were studied as well. The temperature dependence of the (19)F shielding of SF(6) in TLCs was modeled with a function that takes into account the properties of both TLC and SF(6). It appears that the TLC environment deforms the electronic system of SF(6) so that the (19)F shielding tensor becomes slightly anisotropic, with the anisotropy being from -0.5 to -1.4 ppm, depending upon the TLC solvent. On the contrary, no sign of residual dipolar coupling between (19)F and (33)S was found, meaning that the so-called deformational effects, which arise from the interaction between vibrational and reorientational motions of the molecule, on the geometry of the molecule are insignificant. Diffusion activation energies, E(a), were determined from the temperature dependence of the self-diffusion coefficients. In each TLC, E(a) increases when moving from an isotropic phase to a nematic phase. The spin-spin coupling constant, J((19)F,(33)S), increases by ca. 10 Hz when moving from the gas phase to TLC solutions. The secondary isotope shifts of (19)F shielding are practically independent of TLC solvent and temperature. For the first time, (19)F-(33)S heteronuclear multiple-quantum NMR spectra were recorded for SF(6) in the gas phase and in a liquid-crystalline solution.     

On the evolution governed by the infinity Laplacian

We investigate the basic properties of the degenerate and singular evolution equation which is a parabolic version of the increasingly popular infinity Laplace equation. We prove existence and uniqueness results for both Dirichlet and Cauchy problems, establish interior and boundary Lipschitz estimates and a Harnack inequality, and also provide numerous explicit solutions. The first author is partially supported by the ESF program ``Global and Geometric Aspects of Nonlinear Partial Differential Equations'     

Effect of pH on the adsorption and activity of creatine phosphokinase

The combination of in situ ellipsometry with atomic force microscopy in the liquid for the study of adsorption of creatine phosphokinase (CPK) onto silicon wafers was shown for the first time. The thickness, adsorbed amount, and topographic information of the adsorbed CPK layers were obtained under different pH conditions. The thickness values of adsorbed CPK layer determined by both techniques were in excellent agreement. At pH 4, CPK monomers present in solution adsorb, forming a very thin (approximately 0.8 nm) layer, indicating CPK unfolding. Upon increasing the pH to 6.8, the adsorbed layer is composed of a mixture of CPK dimers (native structure) and intermediates, increasing the film thickness (approximately 2.4 nm). At pH 9, CPK dimers form monolayers with the highest thickness (approximately 4.0 nm). The nature of interactions between CPK and Si wafers associated with the hydration force seems to control the degree of CPK unfolding upon adsorbing. The enzymatic activity of free CPK and of adsorbed CPK at pH 4, pH 6.8, and pH 9 was measured as a function of pH. In comparison to free CPK in solution, adsorbed CPK presented a shift of the optimal pH from 6.8 toward alkaline pH.