A 13-membered crown ether with an azoxy subunit in the macrocycle: Synthesis and X-ray structure

The presented azoxy compound is an example of a new crown ether analogue. It has been synthesized by the reduction of an open chain dinitro compound with stannite under strongly alkaline conditions. A method for the separation of the azo and azoxy compounds formed simultaneously has been proposed. The structures of two crystallographically independent molecules of compound2 have been determined. In spite of the small size of the macroring in compound2, the phenyl residues around the azoxy group have atrans orientation. Supplementary Data relating to this article have been deposited with the British Library as Supplementary Publication No. 82157 (11 pages).     

Limit theorems for random walks

We consider a random walk $S_{\tau }$ which is obtained from the simple random walk $S$ by a discrete time version of Bochner’s subordination. We prove that under certain conditions on the subordinator $\tau$ appropriately scaled random walk $S_{\tau }$ converges in the Skorohod space to the symmetric $\alpha$-stable process $B^{\alpha }$. We also prove asymptotic formula for the transition function of $S_{\tau }$ similar to the Pólya’s asymptotic formula for $B^{\alpha }$.     

Molecular dynamics simulation of uranyl(VI) adsorption equilibria onto an external montmorillonite surface

We used molecular dynamics simulations to study the adsorption of aqueous uranyl species (UO(2)(2+)) onto clay mineral surfaces in the presence of sodium counterions and carbonato ligands. The large system size (10,000 atoms) and long simulation times (10 ns) allowed us to investigate the thermodynamics of ion adsorption, and the atomistic detail provided clues for the observed adsorption behavior. The model system consisted of the basal surface of a low-charge Na-montmorillonite clay in contact with aqueous uranyl carbonate solutions with concentrations of 0.027 M, 0.081 M, and 0.162 M. Periodic boundary conditions were used in the simulations to better represent an aqueous solution interacting with an external clay surface. Uranyl adsorption tendency was found to decrease as the aqueous uranyl carbonate concentration was increased, while sodium adsorption remained constant. The observed behavior is explained by physical and chemical effects. As the ionic strength of the aqueous solution was increased, electrostatic factors prevented further uranyl adsorption once the surface charge had been neutralized. Additionally, the formation of aqueous uranyl carbonate complexes, including uranyl carbonato oligomers, contributed to the decreased uranyl adsorption tendency.     

The hyperfine and isotope structure of the Cd intercombination line – revisited

Careful analysis of the intercombination 5¹S₀–5³P₁ line of the ¹¹³Cd isotope with two hfs components and was carried out. The hyperfine splitting of this line was determined to uncertainty less than 10^-3 cm^-1 using neon-perturbed Doppler limited spectra.     

Cavity ring-down spectroscopy of the oxygen B-band with absolute frequency reference to the optical frequency comb

Absolute positions of several oxygen B-band lines were measured with the Pound-Drever-Hall-locked frequency-stabilized cavity ring-down spectrometer. The frequency axis of spectra was linked to the optical frequency comb. Achieved uncertainties of line positions are between 0.9 and 2.9 MHz. Self-pressure shifts coefficients are also reported.     

On massive sets for subordinated random walks

We study massive (reccurent) sets with respect to a certain random walk defined on the integer lattice , . Our random walk is obtained from the simple random walk S on by the procedure of discrete subordination. can be regarded as a discrete space and time counterpart of the symmetric α‐stable Lévy process in . In the case we show that some remarkable proper subsets of , e.g. the set of primes, are massive whereas some proper subsets of such as the Leitmann primes are massive/non‐massive depending on the function h. Our results can be regarded as an extension of the results of McKean (1961) about massiveness of the set of primes for the simple random walk in . In the case we study massiveness of thorns and their proper subsets. The case is presented in the recent paper Bendikov and Cygan 2 .     

Raman spectroscopic monitoring of droplet polymerization in a microfluidic device

Microfluidic methodologies are becoming increasingly important for rapid formulation and screening of materials, and development of analytical tools for multiple sample screening is a critical step in achieving a combinatorial 'lab on a chip' approach. This work demonstrates the application of Raman spectroscopy for analysis of monomer composition and degree of conversion of methacrylate-based droplets in a microfluidic device. Droplet formation was conducted by flow focusing on the devices, and a gradient of component composition was created by varying the flow rates of the droplet-phase fluids into the microchannels. Raman data were collected using a fiber optic probe from a stationary array of the droplets/particles on the device, followed by partial least squares (PLS) calibration of the first derivative (1600 cm(-1) to 1550 cm(-1)) allowing successful measurement of monomer composition with a standard error of calibration (SEC) of +/-1.95% by volume. Following photopolymerization, the percentage of double bond conversion of the individual particles was calculated from the depletion of the normalized intensity of the C[double bond, length as m-dash]C stretching vibration at 1605 cm(-1). Raman data allowed accurate measurement of the decrease in double bond conversion as a function of increasing crosslinker concentration. The results from the research demonstrate that Raman spectroscopy is an effective, on-chip analytical tool for screening polymeric materials on the micrometre scale.     

Zwitterionic and neutral binuclear complexes formed from copper(II) hexafluoroacetylacetonate and an amino alcohol

Reaction of anhydrous Cu(hfac)₂ (hfacH = 1,1,1,5,5,5-hexafluoro-2,4-pentanedione) with 2-(diisopropylamino)ethanol yields two different binuclear copper(II) complexes. Compound 1, [Cu(hfac)₂(-OCH₂CH₂NH(i-Pr)₂)]₂, Cu₂C₃₆H₄₂O₁₀N₂F₂₄, consists of centrosymmetric dimers containing two cis-Cu(hfac)₂ moieties that are bridged by two zwitterionic 2-(diisopropylammonio)ethoxide ions. Cell parameters are a = 11.6516(13); b = 14.0117(17); c = 15.3258(17) Å = 105.75(9)° in space group P2₁/n. The copper ions exhibit tetragonally distorted octahedral coordination, with two of the Cu—O(hfac) distances showing characteristic elongation (2.2858(16) and 2.3192(17) Å). Compound 2, [Cu(hfac)((i-Pr)₂NCH₂CH₂O)]₂, Cu₂C₂₆H₃₈O₆N₂F₁₂, also contains centrosymmetric dimers; these are formed by two square-pyramidal moieties joined at their bases. Cell parameters are a = 7.7353(5); b = 13.6166(17); c = 15.683(2) Å = 98.23(1)° in space group P2₁/n. In this structure the apical Cu—O(hfac) distance is elongated (2.254(4) Å), and the O atoms of the 2-(diisopropylamino)ethoxide ions are bridging.     

Insertion of SO2 into a sulfide-bridged M-Ge bond: synthesis, characterization, and reactivity of the O-germyl-S-sulfoxylate

Addition of SO(2) to [formula: see text](1) results in the insertion of SO(2) into the Pd-Ge bond to give the O-germyl-S-sulfoxylate insertion isomer (Et3P)2Pd(mu-S)S(O)OGe[N(SiMe3)2]2 (2). Heating solutions of 2 results in the formation of (Et3P)Pd(SGe[N(SiMe3)2]2OSOGe[N(SiMe3)2]2S) (3) and a LnPd(0) fragment. X-ray crystal structures of 2 and 3 are reported.     

A note on separation of algebraic sets and the ?ojasiewicz exponent for polynomial mappings

In the paper a global separation problem for affine algebraic sets is considered. As application an upper bound for the distance of the graph of polynomial mapping to its zero set in the form of a ?ojasiewicz inequality is given.