Study of an approximate relation between the energy of an atom and the electronic potential at the nucleus

This paper provides an analysis of the reasons for the approximate validity of the relation \documentclass{article}\pagestyle{empty}\begin{document}$ E = \frac{3}{7}NV(0) $\end{document}, between the total energy E of a neutral atom, the number N of electrons, and the electronic potential at the nucleus V(0). Using the density functional formalism we find that the right-hand side of the above equation also appears (and is the leading term) in density functional approximations more sophisticated than the Thomas–Fermi (TF ) approximation (the above equation is exact in the TF approximation). Systematic improvements to the equation appear to be difficult because the main corrections come from those terms which are more difficult to handle in the density functional formalism. After this analysis we propose a kinetic energy functional for neutral atoms in the Hartree–Fock approximation. The first term of this new functional is a rescaled Thomas–Fermi term , where γ = ?0.0063 for light atoms and γ = 0.0085 for the others. The second term is the first gradient correction due to Kirzhnits . For lithium to krypton atoms, this new functional gives an average error of 0.22%.     

Thermogravimetry of the products in an imbalance condensation of an aromatic diamine and dichloride

Imbalance condensation of diaminophenylbenzimidazole, DAPBI, with terephthaloyl chloride, TPC was conducted for the purpose of synthesis of macromonomers, expected to be used in syntheses of aromatic polyamides with structural regularities. The products are soluble in dimethylsulfoxide—d6, and their 1H NMR spectra indicate that all the products are carboxyl-terminated. The signal of carboxyphenyl linked to chain ends is different from that of terephthaloyl in the 1H NMR spectra. By use of the ratio of the signal intensity of the former to that of the latter, the number-average degree of polymerization, DP _NMR is determined. With the mole ratio in feed, DP _NMR of the product increases. The TG thermograms of the products are a multistage one. Each stage is classified by temperature and mass loss at an inflection point. Mass loss of each stage classified by temperature at an inflection point corresponds to mass fraction of an aromatic amide with a characteristic degree of polymerization, DP, and that is, the DP distribution of the products is roughly estimated from the TG thermograms. The DP distribution of macromonomers influences performance of aromatic polyamides with structural regularities, derived from the macromonomers. The convenient estimation method of DP distribution by TG is useful in industries of high-performance polymers. To the knowledge, such convenient technique has never reported.     

The silver salt of 12-tungstophosphoric acid: an efficient catalyst for the three-component coupling of an aldehyde, an amine and an alkyne

A three-component coupling of an aldehyde, an alkyne and an amine to prepare propargylamines was performed using the silver salt of 12-tungstophosphoric acid (Ag₃PW₁₂O₄₀) as a heterogeneous catalyst under mild reaction conditions in the absence of any co-catalyst. A variety of aldehydes and amines were converted to the corresponding propargylamines demonstrating the versatility of the reaction. The Ag₃PW₁₂O₄₀ (AgTPA) catalyst was recovered quantitatively by a simple filtration and reused several times.     

Combination of an e-nose, an e-tongue and an e-eye for the characterisation of olive oils with different degree of bitterness

An electronic panel has been used to characterise the organoleptic characteristics of twenty-five extra virgin olive oils from varieties Hojiblanca, Picual and Arbequina, with different degree of bitterness. The method consists in the combination of three systems: electronic nose, electronic tongue and electronic eye. The Principal Component Analysis (PCA), where PC1, PC2 and PC3 explained 59% of the total variance between the samples, has demonstrated that the capability of discrimination of the combined system is superior to that obtained with the three instruments separately. This improvement is due to the increased information extracted from each sample. Partial Least Squares-Discriminant Analysis (PLS-DA) has allowed separation of the groups in function of olive variety with a root mean square error of prediction (RMSEP) lower than 0.099.Using PLS1 and PLS2 regression models, good correlations have been found between the signals obtained from the electronic tongue and the polyphenolic content (measured by chromatographic methods) or the bitterness index (scored by a panel of experts) with correlation coefficients higher than 0.9 in calibration and validation.These preliminary results indicate that the combination of an e-nose, an e-tongue and an e-eye can be a useful tool for the analysis of olive oil bitterness.     

Synthesis and characterization of an isocyanate functionalized polyhedral oligosilsesquioxane and the subsequent formation of an organic-inorganic hybrid polyurethane

Organic-inorganic hybrids are an important class of new materials that offer improved thermal and mechanical properties over normal polymers. They may be produced by either the sol-gel route or through the use of inorganic compounds possessing reactive functional groups. Polyhedral oligosilsesquioxanes (POSS) are completely defined molecules of nanoscale dimensions that may be functionalized with reactive groups suitable for the synthesis of new organic-inorganic hybrids. Here we report the synthesis and characterization of a novel POSS possessing eight isocyanate groups via the hydrosilylation of octakis(hydridodimethylsiloxy)octasilsesquioxane (Q8M8H) and m-isopropenyl-alpha,alpha'-dimethylbenzyl isocyanate (m-TMI). The suitability of this new macromer to the synthesis of a organic-hybrids has been explored by forming a new type of highly cross-linked polyurethane elastomer via reaction of the macromer with poly(ethylene glycol) using dibutyltin dilaurate catalyst.     

Behavior of an Emulsion in a Centrifugal Field: Kinetics of an Increase in the Excess Pressure and Destruction of an Emulsion

The effect of centrifugal forces on a decrease in the content of the dispersion medium in an emulsion (increase in its expansion), decrease in the pressure in this medium, and increase in the capillary pressure was conductometrically studied, as well as the effect of these forces on the destruction of the emulsion as a whole. At low rotational speed of the centrifuge (< 500 rpm), the hydrostatically equilibrium capillary pressure and expansion are established in the emulsion. At higher angular velocities, the emulsion column is rapidly destroyed, as a certain critical pressure is reached in Plateau borders of the emulsion; this pressure is smaller than the pressure balancing the forces of the centrifugal field.     

Ostwald ripening and the stability of emulsion systems: an explanation for the effect of an added third component

The destabilizing effect of Ostwald ripening has been considered in relation to O/W hexane emulsions stabilized by sodium dodecyl sulfate. The addition of a third component to the oil phase gives rise to stability provided it has a lower vapor pressure than the oil itself. The stabilizing effects of small quantities of hexadecane and perfluorochemical oils are discussed with reference to the Kelvin effect and Raoult's law.     

The ring opening and oligomerisation reactions of an epoxide and an episulfide on aluminosilicates in the liquid phase

The ring opening reactions of propylene oxide (methyloxirane) or ethylene sulfide )thiirane) were studied in the liquid phase over HZSM-5, HY-FAU or AlMCM-41 at 363 K or 423 K and under 1 or 20 bar pressure in a batch reactor. The proportion of these routes were identified: (i) single C−O scission providing non-cyclic products, (ii) double C−O cleavage leading to the loss of the heteroatom, (iii) oligomerisation resulting in cyclic dimers and the trimer of thiirane and a non-cyclic dimer of methyloxirane. The reaction pathway depended on the conditions and the solid acids used. Findings are compared to those in the gas phase over the same solid acids. Transformation mechanisms are also suggested.     

Electrochemistry as an Attractive and Effective Tool for the Synthesis and Immobilization of Porphyrins on an Electrode Surface

Magnesium(II) 10‐phenyl‐5,15‐p‐ditolylporphyrin is easily and cleanly transformed by electrolysis. A nitro group is first introduced at the free meso position by anodic substitution. Hydrogenation into the amine is then carried out electrocatalytically under ambient conditions with water as a hydrogen supplier. The synthesized porphyrin under the nickel(II) form can be covalently grafted onto a platinum electrode by electrochemical reduction of the diazonium cation, generated in situ by a reaction of the nickel(II) aminoporphyrin with sodium nitrite and trifluoroacetic acid. The electrosynthesized thin film gives an electrochemical response typical of a porphyrin material. Films grown under our conditions have a maximum surface coverage of approximately 5×10^?10 mol cm^?2. The modified electrode exhibits a reproducible electrochemical behavior and a good level of stability over potential cycling and exposition to air.     

Isolation, characterization of an intermediate in an oxygen atom-transfer reaction, and the determination of the bond dissociation energy

The synthesis and structure of a phosphine oxide-bound intermediate molecule originating from a dioxo-molybdenum(VI) complex is described. The loss of phosphine oxide has been followed by surface-induced dissociation mass spectrometry that gave the bond dissociation energy of 29.5 (+/- 3.5) kcal/mol. Considering the bond dissociation energy for a Mo=O bond to be 100 kcal/mol, this value suggests that the primary driving force for the reaction is the formation of the intermediate complex.     

Universality of an estimate of the minimum size of an equilibrium phase

The universality of an estimate of the minimum size of small particles with equilibrium phase properties is discussed. Liquid drops in the vapor phase and liquid in porous solids are considered. It is found that the sizes of thermodynamically-stable liquid drops and pore sizes are similar when there is stratifying of a fluid on two phases. It is suggested that the minimum sizes of particles with equilibrium phase properties are the same for magnetic materials as well. Examples of experimental data favoring this suggestion are shown.     

Generalized theoretical and practical treatment of the kinetics of an enzyme-catalyzed reaction in the presence of an enzyme equimolar irreversible inhibitor

We revisit a previous analysis of the classical Michaelis-Menten enzyme reaction for the case in which the free enzyme incurs the loss of its activity by an irreversible inhibitor concentration dependent but time unaltered rate constant (see Golicnik, M. J. Chem. Inf. Comput. Sci. 2002, 42, 157-161). We study the kinetic model of an enzyme-catalyzed reaction in the presence of an equimolar irreversible inhibitor showing a time dependent inactivation rate constant because of considerable inhibitor amount depletion during the course of the reaction. We show that an analytical solution containing the nonelementary Gauss hypergeometric function can be found for the reactants in equation Phi of an implicit type that precludes direct calculation of the extent of reaction at any time. The transformation theory of the hypergeometric function is used to obtain rapidly convergent power series, and for the root calculation of equation Phi the divergence-proof root bracketing algorithm according to Van Wijngaarden-Dekker-Brent is performed. Numerically generated data are analyzed according to this mathematical procedures, and the results are compared with ones obtained by the numerical integration treatment.     

Photochemical charge transfer and trapping at the interface between an organic adlayer and an oxide semiconductor

Identification of charge transfer and trapping sites on semiconducting oxide surfaces is of fundamental importance in furthering the field of heterogeneous photocatalysts. Using scanning tunneling microscopy, electron energy loss spectroscopy, and photodesorption, we observed both electron trapping and hole transfer events on the (110) surface of TiO2 rutile. UV irradiation of a saturated monolayer of trimethyl acetate (TMA) on TiO2(110) at room temperature resulted in hole transfer to the carboxylate group, followed by (CH3)3C-COO bond cleavage and desorption of CO2 and isobutene/isobutane. Hole transfer to TMA proceeded in the absence of a gas-phase electron scavenger (which is typically O2) because the accompanying photogenerated electrons could be trapped at the surface as Ti3+ cations bound to bridging OH groups. The extent of electron trapping, gauged by electron spectroscopy, correlated directly with the yields of photodesorption fragments resulting from the hole transfer channel. Charge at the Ti3+ sites was titrated in the dark via a reaction between O2 and the Ti3+-OH groups.     

Dynamics of the Spatial Distribution of Atomic and Molecular Absorbing Layers in the Electrothermal Vaporization and Electrostatic Precipitation of an Analyte in an Atomizer

An experimental device was described for atomic absorption analysis with the electrothermal vaporization of the initial sample followed by the condensation of vaporization products and the electrostatic precipitation of the resulting aerosol in the secondary atomizer. Working conditions ensuring the maximum transfer of the sample to the atomizer were determined. The dynamics of the spatial distribution of the absorbing atomic and molecular layers was studied for atomization in a graphite furnace after the direct sample injection and electrostatic precipitation. The contribution of some physicochemical processes to the formation of the structure of cadmium atomic layers was assessed for different methods of sample injection into the atomizer. It was shown that an additional vaporization–condensation step significantly decreases the level of nonselective absorption and smoothes its gradients.