Dynamics of Particle Confined Between Oscillating and Fixed Walls

In this paper, we investigate the motion of a particle confined between the oscillating and fixed walls. As the particle collides with the moving wall in the phase of oscillations, when the wall velocity grows, the wall after collision catches up with the particle. This process can be repeated many times until in finite time interval the particle is found lying on the wall and continues its motion together with the wall. When the sign of the wall acceleration changes the particle detaches from the wall with zero velocity, so that it looks as if the particle “sticks” to the wall. It has been found that if the collision is inelastic, “sticking” leads to convergence of close trajectories except for the case of weak decay. On the contrary, in the case of elastic collision “sticking” of the particle causes even a more rapid divergence of theses trajectories.     

How To Form a Phosphate Anhydride Linkage in Nucleotide Derivatives

The fundamental roles of nucleoside triphosphates and nucleotide cofactors such as NAD⁺ in biochemistry are well known. In recent decades, continuing research has revealed the key role of 5′‐capped RNA and 5′,5′‐dinucleoside polyphosphates in the regulation of vitally important physiological processes. Last but not least, the commercial potential of nucleoside triphosphate synthesis can hardly be overestimated. Nevertheless, despite decades of investigation and the obvious topicality of the research on the chemical synthesis of the nucleotide compounds containing phosphate anhydride linkages, none of the existing procedures can be considered an up‐to‐date “gold standard”. However, there are a number of fruitful synthetic approaches to forming phosphate anhydride linkages in satisfactory yield. These are summarized in this concise review, organized by the type of active phosphorous intermediate and reagents used.     

Search for New Opportunities Modification Raschig,Schiff, Andrusov,Hofmann, Colbe and Delepine Reactions

We explored new approaches to replace the nitrogen atoms of arsenic, antimony, bismuth, and discovered a new paths to modify Raschig, Schiff, Andrusov, Hofmann, Colbe, Delepine reactions with arsine, stibine and bismuthine in organometallic chemistry. We have proposed a new mechanism for possible reactions.     

Convection in a Two-Layer System with a Deformable Interface Under Low Gravity Conditions

The onset of thermal convection in a system of two horizontal layers of immiscible liquids of similar densities is studied under low gravity conditions. A constant heat flux is prescribed at both rigid boundaries. A generalized Boussinesq approach that allows correct accounting for the interface deformation is used. The long-wave perturbations emerge under low-gravity conditions; either monotonic or oscillatory modes are critical depending on the problem. Moreover, two different modes of the monotonic instability exist. For the first instability mode, the convection dominates, whereas the interface remains nearly undeformable. The second monotonic instability mode is substantially related to interface deformations. The system of non-linear amplitude equations describing the behavior of long-wave regimes at finite-amplitude interface deflection and finite supercriticalities is obtained. The analytical and numerical investigations of these equations show that the stable non-trivial stationary solutions are absent, and after a transient at least one of the layers is split into the areas not connected to each other. The nonlinear regimes of cellular convection are studied numerically by the Level Set method.     

Heat-Resistant Antifrictional Composites with a Highly Alloyed Nickel Matrix

Technology for the production of new materials based on the heat-resistant powder metallurgy nickel alloy ÉP975 was developed, and the mechanical and tribological properties of these investigated. The formation features of the metallographic structure of the materials was studied. Recommendations for the practical use of the new composites are given.     

Decomposition of toxic pollutants in landfill leachate by ozone after coagulation treatment

This study deals with evaluation of organic matter from Mexico City waste sanitary landfill leachate of Bordo Poniente (including domestic and industrial) by ozonation after a coagulation treatment with Fe2(SO4)(3) (2.5 g/L at pH 4-5). The content of humic substances after the coagulation treatment decreases up to 70%. Then leachate obtained from a solid with initial COD=1511 mg/L and the pH 8.5 was treated by ozone. The aqueous samples by a UV-vis and HPLC technique were analyzed. The partial identification of the initial composition of the organic matter as well as of intermediates and final products was carried out after the extraction of the initial and ozonated leachate with benzene, chloroform:methanol (2:1) and hexane. Then the extracts with a gas chromatograph with mass detector and FID were analyzed. In the HPLC results we identify malonic and oxalic acids. The initial concentrations of these acids were 19 mg/L and 214 mg/L, respectively. The oxalic acid is formatted and accumulated in ozonation. The obtained results show that the color disappears (visually) at 100% during 5 min of ozonation. The organic substances, extracted with chloroform-methanol, may be destructed during 15 min of ozonation; the organic matter, extracted with benzene, destructs completely by ozone during 5 min, and the organic compounds extracted with hexane have a low ozonation rate. The toxic compounds presented in leachate decompose completely during 15 min of ozonation. The ozonation rate constants for each group of organics (as observed constants) were calculated applying simplified mathematical model and the recurrent least square method using the program MATLAB 6.5.     

Oxygen-free precursor for chemical vapor deposition of gold films: thermal properties and decomposition mechanism

Thermal properties of oxygen-, phosphorus-, and halogen-free dimethylgold(III) diethyldithiocarbamate complex (CH₃)₂AuS₂CN(C₂H₅)₂ (gold, dimethyl(diethylcarbamodithioato -S,S′)-) having excellent storage stability and the mechanism of its decomposition to elemental gold were studied. Saturated vapor pressure was found to be ~10⁻³–10⁻¹ Torr at 50–90°C. Decomposition of the vapor on the surface starts at T = 210°C. The temperature dependence of gas phase composition was studied using the original mass spectrometric technique, it was established that the decomposition of the compound on the surface in vacuum follows three main pathways. Two of them result in the formation of elemental gold, saturated C2–C4 alkanes and (1) protonated ligand or (2) methylated ligand. The third one results in elemental gold and gaseous products: C2–C3 alkylmercaptanes and CH₃SCN(C₂H₅)₂. The formation of gold as a sole solid product within the temperature range 210–240°C was confirmed by X-ray photoelectron spectroscopy analysis. It was shown that the compound exhibits the best combination of volatility, thermal, and storage stability among volatile organogold complexes and thus it may be a promising precursor for obtaining gold films by chemical vapor deposition.     

Study of the compositional heterogeneity of ethylene/1–hexene copolymers produced over supported catalysts of different composition

Separation into narrow MWD fractions (liquid–liquid fractionation) and preparative TREF (temperature rising elution fractionation) with subsequent analysis of fractions by GPC, FTIR, and ¹³C NMR spectroscopy were used to study the comonomer distribution of ethylene/1–hexene copolymers produced over highly active supported titanium‐ and vanadium‐magnesium catalysts (TMC and VMC) and a supported zirconocene catalyst. These catalysts produce PE with different MWD: M_w/M_n values vary from 2.9 for zirconocene catalyst, 4.0 for TMC, and 15 for VMC. 1‐Hexene increases polydispersity to 25 for copolymer produced over VMC and hardly affects MWD of the copolymer produced over TMC and zirconocene catalysts. The most broad short chain branching distribution (SCBD) was found for ethylene/1–hexene copolymers produced over TMC. VMC and supported zirconocene catalyst produce copolymers with uniform profile of SCB content vs. molecular weight in spite of great differences in M_w/M_n values (22 and 2.5 respectively). TREF data showed that majority of copolymer produced over supported zirconocene catalyst was eluted at 70–90°C (about 85 wt %). In the case of VMC copolymer's fractions were eluted in the broad temperature interval (40–100°C). Accordingly, TREF data indicate a more homogeneous SCBD in copolymer, produced over supported zirconocene catalyst. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Magnetoresistance of Superconducting Granules and Grain Boundaries in Ceramic YBa2Cu3O7−δ High-Temperature Superconductors in Weak Magnetic Fields

The objective of the work is to establish the contribution of superconductive granules and grain boundaries (weak links) in magnetoresistance ρ value of YBa₂Cu₃O_7?δ granular high-temperature superconductor (HTS) at T<T _c. The current-voltage characteristics (CVCs) $E(j)_{H_{\mathrm{ext}} = \mathrm{const}}$ of YBa₂Cu₃O_6.95 ceramic samples were measured in H _ext (0≤H _ext≤≈500 Oe) magnetic fields. The CVCs $E(j)_{H_{\mathrm{trap}} = \mathrm{const}}$ of the samples magnetized in H _treat magnetic fields were measured at H _ext=0. Based on the CVCs, $\rho(j)_{H_{\mathrm{ext}} = \mathrm{const}}$ , ρ(H _ext) _j=const and $\rho(j)_{H_{\mathrm{treat}} = \mathrm{const}}$ dependences were reestablished. The comparative analysis of $\rho(j)_{H_{\mathrm{ext}} = \mathrm{const}}$ and ρ(H _ext) _j=const dependences indicates the magnetic field redistribution between grain boundaries and superconductive granules influence on transport and galvanomagnetic properties of granular HTS. The superconductive grain magnetoresistance ρ _g was established to be significantly lower than ρ _J value of Josephson medium.