Investigation of polynuclear Zr(IV) hydroxide complexes by nanoelectrospray mass-spectrometry combined with XAFS

Polynuclear species of zirconium in acidic aqueous solution are investigated by combining X-ray absorption spectroscopy (XAFS) and nanoelectrospray mass spectrometry (ESI-MS). Species distributions are measured between pH_C 0 and pH_C 3 for [Zr] = 1.5–10 mM. While the monomer remains a minor species, with increasing pH the degree of polymerization increases and the formation of tetramers, pentamers, octamers, and larger polymers is observed. The high resolution of the mass spectrometer permits the unambiguous determination of polynuclear zirconium hydroxide complexes by means of their isotopic patterns. The relative abundances of mononuclear and polynuclear species present simultaneously in solution are measured, even if one of the species contributes only 0.1% of the Zr concentration. For the first time it has been directly observed that the hydrolysis of polynuclear Zr species is a continuous process which leads to charge compensation through the sequential substitution of water molecules by hydroxide ligands until doubly charged polymers dominate at conditions (H⁺ and Zr concentrations) close to the solubility of Zr(OH)₄(am). The invasiveness of the electrospray process was minimized by using very mild declustering conditions, leaving the polynuclear species within a solvent shell of approximately 20 water molecules. Figure Schematic Diagram of Multiplexed Measurement of 9 Anti-Nuclear Antibodies Using the AtheNa Multilyte Assay     

Catalytic Activity of Amines Hydrochlorides,Intramolecular Catalysis and Stereoselectivity of Phosphorylation of Hydroxylcontaining Nucleophiles with P(III)-N-Ethylanilines

Abstract

The effect of acid-base properties of amines hydrochlorides (AH) on their catalytic activity in methanolysis of P(III)-N-ethylaniline has been studied. The analysis of Bronsted correlation equation was indicative of general acid catalysis and it was thus confirmed, that general regularities had place during alcoholysis of P(III)-amines under catalysis with AH. In addition, the increasing of alcohol polarity leads to the increasing of proton transfer degree (α) from acid catalysts to phospho(III)amine substrate and to the increasing of the positive charge at the phosphorus in the transition state. Besides, the comparison of α values indicates that in more polar methanol (in comparison with tbutanol) the catalysis is more sensitive to the acidity change of used catalysts.     

Dynamics of charge transfer at Au/Si metal-semiconductor nano-interface

An ab initio analysis of the periodic array of Au/Si nanostructure composed of gold clusters linked to silicon quantum dot (QD) co-doped by aluminium and phosphorus along [111] direction is presented in this paper. The density functional theory (DFT) is used to compute the electronic structure of the simulated system. Non-adiabatic coupling implemented in the form of dissipative equation of motion for reduced density matrix is used to study the phonon-induced relaxation in the simulated system. The density of states clearly shows that the formation of Au–Si bonds contributes states to the band gap of the model. Dynamics of selected photo-excitations shows that hole relaxation in energy and in space is much faster than electron relaxation, which is due to the higher density of states of the valence band.     

Remarks on the Balance Relations for the Two-Dimensional Navier–Stokes Equation with Random Forcing

We use the balance relations for the stationary in time solutions of the randomly forced 2D Navier-Stokes equations, found in [10], to study these solutions further. We show that the vorticity ξ(t,x) of a stationary solution has a finite exponential moment, and that for any the expectation of the integral of over the level-set , up to a constant factor equals the expectation of the integral of over the same set.     

Area Spaces: First Steps

We show that a Riemannian manifold of dimension at least 3 can be recovered from the space of boundaries of rectifiable integral 2-currents (the “lcycles”) equipped with the filling area distance, and discuss possible approaches to “spaces with area structures”.     

Influence of Co amount on the efficiency of energy absorption of Fe-Co ferrite nanoparticles

We present the chemical synthesis, structural characterization and efficiency of AC field energy absorption of Fe-Co ferrite particles sized between 35 and 100 nm and containing different cobalt amounts up to 3 wt%. Dynamic magnetic measurements in an AC field with frequency of 430 Hz and amplitude of up to 1200 Oe were performed for both solid and liquid dispersions of obtained particles. The energy absorption per one field cycle in function of the field amplitude and Co content was always bigger in liquid systems, under the same conditions, than in solid systems. The obtained results are of significance for the technology of low-frequency ferromagnetic hyperthermia of tumors.     

Simulation of Counter-Current Spontaneous Imbibition Based on Momentum Equations with Viscous Coupling,Brinkman Terms and Compressible Fluids

Transport in Porous Media - A numerical model is investigated representing counter-current spontaneous imbibition of water to displace oil or gas from a core plug. The model is based on mass and...     

Entropy Bounds in R×S Geometries

Exact calculations are given for the Casimir energy for various fields in R×S³ geometry. The Green's function method naturally gives a result in a form convenient in the high-temperature limit, while the statistical-mechanical approach gives a form convenient for low temperatures. The equivalence of these two representations is demonstrated. Some discrepancies with previous work are noted. In no case, even for N=4 SUSY, is the ratio of entropy to energy found to be bounded. This deviation, however, occurs for low temperature, where the equilibrium approach may not be relevant. The same methods are used to calculate the energy and free energy for the transverse electric modes in a half-Einstein universe bounded by a perfectly conducting 2-sphere.     

Completely spirocyclopropanated macrocyclic oligodiacetylenes and their permethylated analogues: preparation and properties

The acyclic dehydrotrimer (12) and -hexamer (28) of 1,1-diethynyl-2,2,3,3-tetramethylcyclopropane were prepared from 1-chloro-1-(trimethylsilylethynyl)-2,2,3,3-tetramethylcyclopropane (4) in six and nine steps, respectively, in 36 and 8 % overall yield, respectively, using Cadiot-Chodkiewicz or Hay coupling procedures as key steps. Mono-tert-butyldimethylsilyl (TBDMS) protection of the acyclic dehydrotrimer (20) and -hexamer (23) of 1,1-diethynylcyclopropane followed by Hay coupling and protiodesilylation furnished the acyclic dehydrohexamer (23) and -dodecamer (29) in 35 and 56 % overall yield, respectively. Subsequent cyclizing oxidative dimerization of 12 or cyclization of 28 using a modified Glaser protocol produced the first completely permethylspirocyclopropanated macrocyclic oligodiacetylene, compound 30 in 49 and 21 % yield, respectively. The cyclic dehydrohexa- (31) and dehydrododecamer (32) have been prepared from 23 and 29 in 49 and 7 % yield by applying the same protocol. The macrocycle 32 is particularly interesting in that it contains 60 carbon atoms in the inner ring, and indeed a decomposition mode consecutively cleaving off ethylene units from it as well as from 31 and tetramethylethylene from the permethylated exp-[6]rotane 30 has been proved by differential scanning calorimetry with evolved gas analysis. The thermal decomposition of these "exploding" [6]rotanes 31 and 30 set on at 100 and 135 degrees C, respectively, and release energies of 478 and 285 kcal. mol(-1), respectively, significantly more than the energy release of the explosive hexogen with 143 kcal mol(-1).