The molecular approach to heterogeneous nucleation

A molecular approach to heterogeneous nucleation has been developed. The expressions for the equilibrium cluster distribution, the reversible work of the cluster formation, and the nucleation rate have been derived. Two separate statements for the work of formation were formulated. If the equilibrium cluster distribution is normalized on the monomer concentration near the substrate surface, the reversible work of formation is expressed by DeltaG(het) (I) = (F(n) (het)-F(n) (hom))-(F(1) (het)-F(1) (hom)) + DeltaG(hom) where F(n) (het) and F(n) (hom) are the Helmholtz free energies of a cluster interacting with a substrate and a cluster not interacting with the substrate, respectively. If the equilibrium cluster distribution is normalized on the monomer concentration far from the substrate surface, the work of cluster formation is given by DeltaG(het) (II) = (F(n) (het)-F(n) (hom)) + DeltaG(hom). The former expression corresponds to the approach of the classical heterogeneous nucleation theory. The cluster partition function appears to be dependent on the location of a virtual plane, which separates the volume, where the interaction of the clusters with the substrate is effective from the one where interaction is negligible. Our Monte Carlo simulations have shown that the dependence is rather weak and thus the location of the plane is not very important. According to the simulations the variation of the plane position in the range from 20 to 50 Angstroms does not lead to a considerable change of the heterogeneous nucleation rate.     

Analysis of ALD-processed thin films by ion-beam techniques

This review introduces the possibilities of ion-beam techniques for the analysis of thin films and thin-film structures processed by atomic layer deposition (ALD). The characteristic features of ALD are also presented. The analytical techniques discussed include RBS, NRA and ERDA with its variants, viz. the TOF-ERDA and HI-ERDA. The thin film examples are taken from flat-panel display technology (TFEL structures) and the semiconductor industry (high-k insulators).Dedicated to the memory of Wilhelm Fresenius     

Reactivity of α-acylated β-enamino ketones and esters: Synthesis of pyrazoles

The reactivity of the enamino compounds 4-amino-3-phenylamino(thio)carbonyl-3-penten-2-one 1 and 2 and ethyl 3-amino-2-phenylamino(thio)carbonyl-2-butyrate 7 and 8 was studied using the reaction with hydrazine hydrate and hydrazine hydrochloride to evaluate the 1,3 electrophilic center of the compounds by the formation of the pyrazole rings. The pyrazoles 3, 4, 5, 9, 11 and 13 were obtained depending on the reaction conditions employed.     

Simple polytopes without small separators,II: Thurston’s bound

We construct a diffeomorphism of T³ admitting any finite or countable number of physical measures with intermingled basins. The examples are partially hyperbolic with splitting TT³ = E ^cs ⊕ E ^u and can be made volume hyperbolic and topologically mixing.     

Determination of Organic Chlorine by Aluminium Monochloride Molecular Absorption Spectrometry Using Lead Atomic Line

The present study was conducted to investigate the molecular absorption by AlCl in a carbon rod furnace for determination of chlorine in organic compounds, by using the lead atomic line at 261.418 nm emitted from a Pb-hollow cathode lamp. A deuterium lamp was used for the simultaneous background correction. The method enables rapid and accurate determination of trace chlorine in varying organic samples with good precision. The method was tested on different organic chloro-coumpounds and α-pinene products.     

Mineral matter effect on the decomposition of Ca-rich oil shale

Four oil shale samples with different amounts of organic and mineral matter were analysed through non-isothermal thermogravimetric analysis using a heating rate of 50 °C min^?1 in nitrogen. The goal of the paper is to study the supposed catalytic effect of the indigenous and removed minerals. The samples contained 30, 49, 70 and 90% of organic matter, respectively. X-ray diffraction analysis was used to identify the minerals in the samples. Thermal analysis experiments were carried out up to temperatures of 850 °C in pyrolysis conditions. The mass loss data were used to study the variations in the conversion profiles of the organic matter depending on the content of the mineral matter. The obtained data and the comparison of the sample composition show that the effect of the mineral matter amount on the course of the pyrolysis processes is insignificant.     

Pentakis(trifluoromethyl)phenyl, a sterically crowded and electron-withdrawing group: synthesis and acidity of pentakis(trifluoromethyl)benzene, -toluene, -phenol, and -aniline

A general route to functionalized pentakis(trifluoromethyl)phenyl (C6(CF3)5) derivatives, promising building blocks for designing novel stable carbenes, radical species, superacids, weakly coordinating anions and other practically and theoretically useful species, is presented. This pertrifluoromethylation route proceeds via conveniently pregenerated (trifluoromethyl)copper (CF3Cu) species in DMF, stabilized by addition of 1,3-dimethyl-2-imidazolidinone (DMI). These species react with hexaiodobenzene at ambient temperature to give the potassium pentakis(trifluoromethyl)phenoxide along with hexakis(trifluoromethyl)benzene and pentakis(trifluoromethyl)benzene in a combined yield of 80%. A possible reaction pathway explaining the formation of pentakis(trifluoromethyl)phenoxide is proposed. Pentakis(trifluoromethyl)phenol gives rise to easily functionalized pentakis(trifluoromethyl)chlorobenzene and pentakis(trifluoromethyl)aniline. Pertrifluoromethylation of pentaiodochlorobenzene and pentaiodotoluene allows straightforward access to pentakis(trifluoromethyl)chlorobenzene and pentakis(trifluoromethyl)toluene, respectively. XRD structures of several C6(CF3)5 derivatives were determined and compared with the calculated structures. Due to the steric crowding the aromatic rings in all C6(CF3)5 derivatives are significantly distorted. The gas-phase acidities (Delta Gacid) and pKa values in different solvents (acetonitrile (AN), DMSO, water) for the title compounds and a number of related compounds have been measured. The origin of the acidifying effect of the C6(CF3)5 group has been explored using the isodesmic reactions approach.     

Surface Characterization and the Gas Response of a Mixed,Fe2O3?Fe2(MoO4)3, Oxide to Low Concentrations of H2S in Air

The preparation and H₂S sensing potential of thick‐films of a mixed oxide, Fe₂O₃? Fe₂(MoO₄)₃, were investigated. A Fourier‐transform infrared (FTIR) study confirmed the existence of sulfur species at the surface after the interaction of H₂S gas with the mixed oxide. The starting material, β‐FeMoO₄, was synthesized by a solvothermal method, followed by supercritical drying. Heat treatment of this material (oxidation) above 500 °C resulted in the formation of Fe₂O₃? Fe₂(MoO₄)₃ mixed oxide, where Fe₂O₃ was a by‐product. An increase in the conductivity of the films in the presence of H₂S gas (concentration range 1–20 ppm in air) was observed with the simultaneous formation of water and sulfide ions at 225 °C. An improvement of the H₂S sensing potential is obtained, using an intermediate short heat treatment at higher temperature (500 °C) in the beginning of recovery (desorption) phase. This intermediate high temperature, used before every expected exposure to H₂S gas, may contribute the formation of an initial surface coverage of O^2?.     

Uniqueness for a seismic inverse source problem modeling a subsonic rupture

We consider an inverse source problem for an inhomogeneous wave equation with discrete-in-time sources, modeling a seismic rupture. The inverse source problem, with an arbitrary source term on the right-hand side of the wave equation, is not uniquely solvable. Here we formulate conditions on the source term that allow us to show uniqueness and that provide a reasonable model for the application of interest. We assume that the source term is supported on a finite set of times and that the support in space moves with subsonic velocity. Moreover, we assume that the spatial part of the source is singular on a hypersurface, an application being a seismic rupture along a fault plane. Given data collected over time on a detection surface that encloses the spatial projection of the support of the source, we show how to recover the times and locations of sources microlocally and then reconstruct the smooth part of the source assuming that it is the same at each source location.