Modifying of etching anisotropy of silicon substrates by surface active agents

The influence of alcohol additives on etch rate anisotropy of Si(hkl) planes has been studied. The etching processes were carried out in 3 and 5 M KOH aqueous solutions saturated and non-saturated with alcohols. Isopropanol, 1-propanol and tert-butanol were examined. It has been showed that the etching process cannot be controlled only by the surface tension of the solution. Saturation of the etching solution with alcohols modifies etch rate anisotropy, lowering the ratio of the etch rate of (110) and vicinal planes to the etch rate of (100) plane. The morphology of Si(hkl) planes etched in 3 M KOH solution saturated with tert-butyl alcohol has been studied in detail. Smooth (331) and (221) planes have been achieved in this solution. The (100) plane turned out to be densely covered by hillocks, opposite to the (100) plane etched in weak-alkaline solution saturated with isopropanol. To explain this phenomenon, the mechanism of hillocks formation on Si(100) surface has been proposed.     

Effect of partial fluorination on the Lewis sites of microcrystalline γ-alumina studied by adsorption of pyridine as a probe molecule: A quantum chemical cluster model study

The influence of fluorination of microcrystalline γ-alumina on the acidity of Lewis sites was studied by quantum chemical cluster model approach. B3LYP and HF/6-31++G(d,p) levels of theory were employed, considering the standard and counterpoise-corrected potential energy surfaces (PESs). Explicit inclusion of dynamical electron correlation effects along with the elimination of the basis set superposition effects in geometry optimization and harmonic vibrational analysis were found to be crucial to reproduce the experimental trends in the shifts of the pyridine ν_19b and ν_8a modes upon fluorination. The acidity of surface-exposed Al-sites was found to increase upon fluorination, which is manifested as a ~ 10% increase of the interaction energies, and also in the characteristics of the electronic density and density Laplacian at the intermolecular bond critical point. Bader analysis of the electronic density has shown that pyridine adsorption on pure and fluorinated γ-alumina can be classified as non-covalent interaction.     

Applications of mapping cones over Clements–Lindström rings

We prove that Gotzmann's Persistence Theorem holds over every Clements–Lindström ring. We also construct the infinite minimal free resolution of a square-free Borel ideal over such a ring.     

Correction to: Aziridine-2-Carboxylic Acid Derivatives and Its Open-Ring Isomers as a Novel PDIA1 Inhibitors

Chemistry of Heterocyclic Compounds -     

Evaluation of Bookkeeper mass deacidification based on historical book papers

Cellulose - Bookkeeper, the most widely used deacidification process based on MgO particles, was systematically evaluated on two sets of nonvaluable historical paper samples. Established analytical...     

Changes of organic acids and phenolic compounds contents in grapevine berries during their ripening

Changes of total content of phenolic substances, alteration in total titratable acidity and differences in tartaric acid content in grapes of four white (Müller-Thurgau — MT, Pinot Blanc — Rulandské bílé in Czech, RB, Sauvignon (Sg), and Muscat Ottonel — Mu?kát Ottonel in Czech, MO) and two blue (Dornfelder — Df and Blue Frankish — Frankovka in Czech, Fr) grapevine varieties throughout their growth, ripening and maturing (July–November). Potentiometric titration was applied for the determination of total titratable acids in grapes (expressed as tartaric acid equivalents in g L^?1). A spectrophotometric method according Rebelein based on the formation of a colored complex of ammonium metavanadate and tartaric acid was used for determination of tartaric acid in green juice made by pressing unripe grapes. A spectrophotometric method based on reduction of phosphomolybdato-tungsten complex in alkaline solution using Folin-Ciocalteau reagent was applied for determination of total content of phenolic substances (TCP).

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Nonionic diethanolamide amphiphiles with unsaturated C18 hydrocarbon chains: thermotropic and lyotropic liquid crystalline phase behavior

The neat and lyotropic liquid crystalline phase behavior of three nonionic diethanolamide amphiphiles with C18 hydrocarbon chains containing one, two or three unsaturated bonds has been examined. This has allowed the effect of degree of unsaturation on the phase behavior of diethanolamide amphiphiles to be investigated. Neat linoleoyl and linolenoyl diethanolamide undergo a transition from a glassy liquid crystal to a liquid crystal at ～-85 °C, while neat oleoyl diethanolamide undergoes a transition at ～-60 °C to a liquid crystalline material before re-crystallizing at -34 °C. Oleoyl diethanolamide then undergoes a third transition from a crystalline phase to a smectic liquid crystalline phase at ～5 °C. In the absence of water, the transition temperature from a smectic liquid crystal to an isotropic liquid decreases with increasing unsaturation. The addition of water results in the formation of a lamellar phase (L(α)) for all three amphiphiles. The lamellar phase is stable under excess water conditions up to temperatures of at least 70 °C. Approximate partial binary amphiphile-water phase diagrams generated for the three unsaturated C18 amphiphiles indicate that the excess water point for each amphiphile occurs at ～60% (w/w) amphiphile.     

Attractors for Second-Order Evolution Equations with a Nonlinear Damping

We study long-time dynamics of abstract nonlinear second-order evolution equations with a nonlinear damping. Under suitable hypotheses we prove existence of a compact global attractor and finiteness of its fractal dimension. We also show that any solution is stabilized to an equilibrium and estimate the rate of the convergence which, in turn, depends on the behaviour at the origin of the function describing the dissipation. If the damping is bounded below by a linear function, this rate is exponential. Our approach is based on far reaching generalizations of the Ceron–Lopes theorem on asymptotic compactness and Ladyzhenskayas theorem on the dimension of invariant sets. An application of our results to nonlinear damped wave and plate equations allow us to obtain new results pertaining to structure and properties of global attractors for nonlinear waves and plates.