Geometrical Dissipation for Dynamical Systems

On a Riemannian manifold (M, g) we consider the k?+?1 functions F ₁, . . . , F _k , G and construct the vector fields that conserve F ₁, . . . , F _k and dissipate G with a prescribed rate. We study the geometry of these vector fields and prove that they are of gradient type on regular leaves corresponding to F ₁, . . . , F _k . By using these constructions we show that the cubic Morrison dissipation and the Landau-Lifschitz equation can be formulated in a unitary form.     

1,3-bis(2,4,6-trinitrophenylaminooxy)propane and its 4-cyano-2,6-dinitrophenyl congener: Synthesis and properties

Starting from N-hydroxyphthalimide (5) and 1,3-dibromopropane (6) we obtained 1,3-bis(phthalimidooxy)propane (7) which led to 1,3-bis(aminooxy)propane dihydrochloride (8). From its reaction with picryl chloride or 4-cyano-2,6-dinitrochlorobenzene, the two title compounds (4b, 4a) were obtained. ¹H-NMR and ¹³C-NMR spectra are presented. For comparison with the analogous N-methoxy-2,6-dinitro-4-R-anilines 1a, 1b (R=CN or R=NO₂), wer report the hydrophobic characteristics (by RPTLC), electronic spectra for the neutral compounds and their anions, pK _a values, and the behavior towards oxidizers (DPPH, PbO₂, Pb(CH₃COO)₄, KMnO₄ and Ag₂O); DPPH converts compounds 1a, 1b and 4a, 4b into betainic structures 2a, 2b respectively.     

Dipole-dipole interactions in spin-labeled au nanoparticles as a measure of interspin distances

A series of Au nanoparticles modified with a nitroxide-functionalized ligand was prepared with a range of spin-label coverage. The X-band EPR spectra of frozen solutions of these nanoparticles showed coverage-dependent line-broadening due to dipole-dipole interactions between spin labels. We developed a methodology to analyze such spectra in terms of geometrical features of the nanoparticles (e.g., Au core size and the length of the spin-labeled ligand). Our method is based on the assumption that the spectral line shape is determined by the average distance between nearest-neighboring spin labels adsorbed on the Au particle. Geometrical and statistical analysis then relates this distance to the line shape parameter d1/d, which was calibrated using a model system. Application of this methodology to the experimental spectra provided information about the conformation of ligands on the Au surface. We found that, if the spin-labeled ligand is substantially longer than the surrounding protecting layer, it does not adopt a fully stretched conformation but wraps around the particle immediately above the layer of surrounding ligand. Our results also show that the ligands do not adsorb cooperatively on the Au surface.     

The effect of hydration/dehydration on the AC electrical conductivity of H4PVMo11O40 and some of its cesium salts used as catalysts

Changes in AC electrical conductance G of vanadium substituted 12-molybdophosphoric acid and of its (mono)-acid and neutral cesium salts were studied. Depending on the environment, the electrical conductivity is a combination of protonic and electronic conduction, the protonic one dominating at low temperature.     

Structure investigation of conductive breakdown filaments in electrophotography

The breakdown of a selenium electrophotographic layer (EPL) often occurs during its charging process. The amount of surface charge flowing down a conductive filament may be determined from the current kinetics of layer charging. The active area of the conductive breakdown filament has been determined from the potential distribution and the spots of the developed image. Using an electron microscopy method the investigations of thin selenium sections have shown that under the influence of local Joule's heating selenium in the conductive filament melts; and immediately after the charging it cools off transforming into the vitreous phase. Numerous breakdown at the same place lead to the formation of a crystalline filament. It has been established that under influence of the tangential component of electric field, surface conductive filaments are formed around the conductive bulk filament: this is the main difference between breakdown in a system of free surfaces and breakdown or switching in a system with electrodes.     

Host–Guest Complexes of some Stable Free Radicals

Hydrophobic host–guest complexes of some water soluble stable free radicals – potassium nitrosodisulfonate (Fremy's salt), 2-$p$-phenylsulphonic acid-2-phenyl-1-picrylhydrazyl (KSO₃-DPPH^.) and 2,2-p-phenylsulphonic acid-1-picrylhydrazyl ((KSO₃)₂DPPH^.), both of them as potassium salts, with 18-C-6, B18-C-6 and DB18-C-6 crown ethers, were obtained and characterised by elemental analysis, IR, ESR and UV-Vis.     

Three-dimensional space charge cartographies by FLIMM in electron irradiated polymers

High resolution three-dimensional space charge cartographies obtained on 50 μm PTFE samples by using FLIMM technique are presented in this article. Samples were irradiated by a 30 keV electron beam. Charges were injected according to the grid pattern put on the sample during irradiation. A new measurement strategy associated with a new set-up leads to an improvement in measurements accuracy and precision. With this new strategy, measurements were performed rapidly, at a chosen depth and with a low lateral resolution in order to map the space charge profile in the whole sample and to choose a study area. After selecting an interesting area, space charge cartographies were carried out with a very high lateral resolution of about 1 μm. The irradiated zones according to the grid pattern were well reconstructed and the injection depth did not exceed 4 μm.     

Mass spectrometric characterization of the zein protein composition in maize flour extracts upon protein separation by SDS‐PAGE and 2D gel electrophoresis

Highly homogenous α zein protein was isolated from maize kernels in an environment‐friendly process using 95% ethanol as solvent. Due to the polyploidy and genetic polymorphism of the plant source, the application of high resolution separation methods in conjunction with precise analytical methods, such as MALDI‐TOF‐MS, is required to accurately estimate homogeneity of products that contain natural zein protein. The α zein protein product revealed two main bands in SDS‐PAGE analysis, one at 25 kDa and other at 20 kDa apparent molecular mass. Yet, high resolution 2DE revealed approximately five protein spot groups in each row, the first at ca. 25 kDa and the second at ca. 20 kDa. Peptide mass fingerprinting data of the proteins in the two dominant SDS‐PAGE bands matched to 30 amino acid sequence entries out of 102 non‐redundant data base entries. MALDI‐TOF‐MS peptide mapping of the proteins from all spots indicated the presence of only α zein proteins. The most prominent ion signals in the MALDI mass spectra of the protein mixture of the 25 kDa SDS gel band after in‐gel digestion were found at m/z 1272.6 and m/z 2009.1, and the most prominent ion signals of the protein mixture of the 20 kDa band after in‐gel digestion were recorded at m/z 1083.5 and m/z 1691.8. These ion signals have been found typical for α zein proteins and may serve as marker ion signals which upon chymotryptic digestion reliably indicate the presence of α zein protein in two hybrid corn products.     

Olefin-alkyl group exchange of B-alkyl-9-borabicyclo-[3.3.1]nonanes. Evidence for a dehydroboration-hydroboration process

B-Alkyl-9-borabicyclo[3.3.1]nonanes (9-BBN) undergo a rather facile olefin-alkyl group exchange process when refluxed with an olefin in tetrahydrofuran. Kinetic and competition studies support a dehydroboration-hydroboration process.