Three-dimensional contact problems with friction for a composite elastic wedge

Contact problems for a composite elastic wedge in the form of two joined wedge-shaped layers with different aperture angles joined by a sliding clamp, where the layer under the punch is incompressible, are studied in a three-dimensional formulation. Conditions for a sliding or rigid clamp or the absence of stresses are set up on one face of the composite wedge. The integral equations of the problems are derived taking account of the friction forces perpendicular to the edge of the wedge. The method of non-linear boundary integral equations of the Hammerstein type is used when the contact area is unknown. A regular asymptotic solution is constructed for an elliptic contact area. By virtue of the incompressibility of the material of the layer in contact with the punch, this solution retains the well known root singularity in the boundary of the contact area when account is taken of friction.     

Vapor–liquid equilibria of copper using hybrid Monte Carlo Wang—Landau simulations

Because of the large temperatures and pressures involved, the experimental determination of the vapor–liquid equilibria and of the critical properties of metals is fraught with difficulties. We show in this work how we determine these properties for a metal using hybrid Monte Carlo Wang–Landau simulations in the isothermal–isobaric ensemble on the example of copper. We use a many-body potential, known as the quantum corrected Sutton–Chen embedded atom model, to model the interactions between Cu atoms. We obtain the following estimates for the critical temperature _Tc=5696±50$T_c=5696\pm 50$ K, the critical density _ρc=1.80±0.03${\rho }_c=1.80\pm 0.03$ g/cm³, and the critical pressure _Pc=1141±100$P_c=1141\pm 100$ bar. Our results lie within the range of values found in experiments for the critical temperature (between 5140 K and 7696 K), for the critical pressure (between 420 bar and 5829 bar) and for the critical density (1.9 g cm⁻³).     

Relativistic density functional theory study of dioxoactinide(VI) and -(V) complexation with alaskaphyrin and related Schiff-base macrocyclic ligands

Formation of complexes of alaskaphyrin 1, bi-pyen 2 and bi-tpmd 3 ligands with actinyl ions AnO2(n+), An = U, Np, Pu and n = 1, 2, was studied using density functional theory (DFT) within the scalar relativistic four-component approximation. The alaskaphyrin complexes of the uranyl are predicted to have a bent conformation, in contrast to the experimentally available X-ray data. This deviation is likely due to crystal packing effects. Apart from these conformational differences, calculated geometry parameters and vibrational frequencies are in agreement with the available experimental data. The character of bonding in the complexes is investigated using bond order analysis and extended transition states (ETS) energy decomposition. Metal-to-ligand bonds can be described as primarily ionic although substantial charge transfer is observed as well. Based on ETS analysis, it is shown that steric and/or fit/misfit requirements of actinyl cations to the ligand cavities, among the studied complexes, are the most favorable for the bi-pyen ligand 2, because its flexibility allows for optimal metal-to-donor-atom distances. Planarity of the equatorial coordination sphere of the actinide atom is found to be less important than the ability of a ligand to provide optimal uranium-to-nitrogen bond lengths. Experimental differences in demetalation rates between similar alaskaphyrin, bi-pyen and bi-tpmd uranyl complexes are explained as a result of easier protonation of the Schiff-base nitrogen of the latter. Reduction potentials calculated for the uranium complexes show a good agreement with the experiment, both in relative and in absolute terms.     

Brønsted acidic ionic liquid–catalyzed tandem trimerization of indoles: An efficient approach towards the synthesis of indole 3,3′-trimers under solvent-free conditions

We have observed the role of 1-butane sulfonic acid-3-methylimidazolium tosylate, [BSMIM]OTs, as an organocatalyst for the tandem type trimerization of indoles to synthesize indole 3,3′-trimers under neat conditions. Using this developed protocol synthesis of indole trimers with various substituted indoles, which are biologically important, has been reported. From the control experiments and literature, a possible mechanism has been proposed via the generation of indolinium cation in the presence of the ionic liquid catalyst. The catalyst has been recycled for several times. The significant advantages of our methodology are clean reaction with very short time, no chromatography for purification, commercially available substrates, neat reaction conditions, and in the absence of metal. Using the protocol, the MDM2-p53 inhibitor has been synthesized in gram scale with high yield.     

Measurement of the nuclear magnetic moment of tritium to nine-digit accuracy

A series of ten pair spectra has been obtained by simultaneously detecting the proton and tritium NMR spectra of the gaseous TH sample, which is an analogue of molecular hydrogen. The numerical processing of the data yields the ratio F(TH)/F(HT) = 1.066 639 8933(7) of the magnetic moments of tritium and proton in the TH molecule. The relative statistical error of this result is 7 × 10⁻¹⁰. To find the nuclear magnetic moment of tritium from F(TH)/F(HT), it is sufficient to use the previously calculated correction factor δ = (1 + 20.4 × 10⁻⁹), which originates from a small asymmetry of the electron cloud of the molecule.     

Multipoint Ignition of a Gas Mixture by a Microwave Subcritical Discharge with an Extended Streamer Structure

The results of experimental studies on using an electrical discharge with an extended streamer structure in a quasioptical microwave beam in the multipoint ignition of a propane–air mixture have been reported. The pulsed microwave discharge was initiated at the interior surface of a quartz tube that was filled with the mentioned flammable mixture and introduced into a microwave beam with a subbreakdown initial field. Gas breakdown was initiated by an electromagnetic vibrator. The dependence of the type of discharge on the microwave field strength was examined, the lower concentration threshold of ignition of the propane–air mixture by the studied discharge was determined, and the dynamics of combustion of the flammable mixture with local and multipoint ignition were compared.     

Role of the phase transition at GaN QDs formation on (0001)AlN surface by ammonia molecular beam epitaxy

Journal of Thermal Analysis and Calorimetry - We report an original method of GaN/AlN quantum dots (QDs) formation with low density by ammonia MBE on the (0001)AlN...     

New design of cationic alkyl glycoglycerolipids toxic to tumor cells

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Determination of plasma characteristics in the plasma of a pulsed discharge propagating over a water surface using spectral methods

The results of spectral investigations of the electron density and excitation temperature in the plasma of a pulsed discharge propagating over a liquid surface are presented.