Fluorinated NH-iminophosphonates and iminocarboxylates: novel synthons for the preparation of biorelevant α-aminophosphonates and carboxylates

A convenient synthetic approach to previously unknown N–H α-iminophosphonates and iminotrifluoropropionates was developed. The synthetic potential of N–H iminophosphonates and iminotrifluoropropionates, existing as an equilibrium mixture of E/Z-isomers, was demonstrated by their easy functionalization to afford biorelevant fluorinated α-aminophosphonic and α-aminocarboxylic acid derivatives.     

Zeno phenomenon in hybrid dynamical systems

A way to prolong Zeno solutions to hybrid dynamical system beyond Zeno time is proposed. Additionally, we provide a new definition of asymptotic stability that is equipped with sufficient conditions for its verification. It allows to investigate long-term behavior of the prolonged solutions to hybrid dynamical systems. (© 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)     

An exploratory study of the reactive Ni-GaAs (1 1 0) interface

Soft X-ray photoemission spectroscopy measurements have been carried out on cleaved n-type GaAs (1 1 0) surfaces covered with Ni overlayers ranging in thickness from 0.05 to 53 Å. The results of these room temperature measurements show that we have band bending effects occurring in conjunction with strong interfacial chemical reactions. Deconvolution of the Ga 3d core line into substrate and metallic components shows dissolution of the substrate at the interface with Ga diffusing into the surface of the metal overlayer for the intermediate coverages (1–15 Å). Observation of the As 3d core level shows out-diffusion of As to the surface over the entire Ni coverage range. Using this deconvolution scheme we are able to follow the band bending of the Schottky barrier formed here up to the 8 Å coverage. The Schottky barrier height is 1.0 ± 0.1 eV for this overlayer thickness.     

Possibility of deriving kinetic parameters from integrated DTA peaks

Three DTA peaks (two endo and one exothermic) were replotted in the form of peak area.a, or peak magnitude,T, as a function of temperature. The integral sigmoid curves were plotted in the form of logg() vs. 1/T or log logg()/T ² vs. 1/T. Both of the proposed summation methods gave satisfactory straight lines (F ₁ function), characterized by the same activation energies, correlation coefficients and standard deviations. Integration of the peak areas by Simpson's rule resulted in the same values as obtained by the summation procedure. Analysis by the suggested integral method resulted in activation energies that show a logarithmic divergence relative to the magnitude ofE _a estimated directly from the DTA peaks.     

Desorption kinetic detection of different adsorption sites on opened carbon single walled nanotubes: The adsorption of n-nonane and CCl4

We show that thermal desorption kinetics clearly resolve adsorbates bound in different sites on single walled carbon nanotube bundles. The molecules n-C₉H₂₀ and CCl₄ were compared and it was found that the nanotube internal sites exhibited the highest desorption temperature, whereas external groove sites exhibited the next highest desorption temperature for both molecules. When n-C₉H₂₀ and CCl₄ coadsorb, the more strongly bound n-C₉H₂₀ quantitatively displaces CCl₄ from internal sites to groove sites. Molecular shape governs the capacity of the different sites for the two molecules.     

Complex kinetics of the electron transfer between the photoactive redox label TUPS and the heme of cytochrome c

The photoinduced covalent redox label 8-thiouredopyrene-1,3,6-trisulfonate (TUPS) has been attached to two lysine residues (K8 and K39) at opposite sides of horse heart cytochrome c, as well as to cysteines, at the same positions, introduced by site-directed mutagenesis. Electron transfer between TUPS and the heme of cytochrome c deviates from the expected monoexponential kinetic behavior. Neither the overall rate nor the individual exponential components of electron transfer, as followed by kinetic absorption spectroscopy, correlate with the length of the covalent link connecting the dye with the protein. Molecular dynamics calculations show that TUPS can approach the protein surface and occupy several such positions. This heterogeneity may explain the multiexponential electron-transfer kinetics. The calculated optimal electron-transfer pathways do not follow the covalent link but involve through space jumps from the dye to the protein moiety, effectively decoupling the length of the covalent link and the electron-transfer rates.     

Fluorous 2-chloropyridinium salt (Mukaiyama condensation reagent) for amide formation reactions

A new fluorous 2-chloropyridinium hexafluorophosphate was prepared as a modified Mukaiyama condensation reagent, and it was applied in amide formation reactions. Good to excellent purities of amides were obtained after fluorous solid-phase extraction of reaction mixtures without additional chromatography.     

Development of a relatively cheap and simple automated separation system for a routine separation procedure based on extraction chromatography

A robust analytical method has been developed in our laboratory for the separation of radionuclides by means of extraction chromatography using an automated separation system. The proposed method is both cheap and simple and provides the advantageous, rapid and accurate separation of the element of interest. The automated separation system enables a shorter separation time by maintaining a constant flow rate of solution and by avoiding clogging or bubbling in the chromatographic column. The present separation method was tested with two types of samples (water and urine) using UTEVA-, TRU- and Sr-specific resins for the separation of U, Th, Am, Pu and Sr. The total separation time for one radionuclide ranged from 60 to 100 min with the separation yield ranging from 68 to 98% depending on the elements separated. We used ICP-QMS, multi-low-level counter and alpha spectroscopy to measure the corresponding elements.     

Boundary-value problem for density-velocity model of collective motion of organisms

The collective motion of organisms is observed at almost all levels of biological systems. In this paper the density-velocity model of the collective motion of organisms is analyzed. This model consists of a system of nonlinear parabolic equations, a forced Burgers equation for velocity and a mass conservation equation for density. These equations are supplemented with the Neumann boundary conditions for the density and the Dirichlet boundary conditions for the velocity. The existence, uniqueness and regularity of solution for the density-velocity problem is proved in a bounded 1D domain. Moreover, a priori estimates for the solutions are established, and existence of an attractor is proved. Finally, some numerical approximations for asymptotical behavior of the density-velocity model are presented.     

Enantiomeric N-(tert-Butylsulfinyl) Polyfluoroalkyl Aldimines in aza-Henry Reaction: Effective Route to Chiral Polyfluoroalkyl Nitroamines and Diamines

A highly diastereoselective addition of nitromethane to the C=N bond of enantiomeric fluorine containing Ellman's aldimines, R_FCH=NS(O)tert-Bu (R_F=CF₃, CF₂Br, C₂F₅, HC₂F₄), has been successfully developed. The synthetic potential of the resulting β-nitrosulfinylamides was demonstrated through their conversion into optically active α-fluoroalkylated 1,3-nitroamines, 1,3-diamines, and 4-fluoroalkylated imidazolidin-2-ones.