Thermodynamic properties of ternary alloys from Monte Carlo simulations

Methods are presented for obtaining both the integral and partial molar energies, entropies and free energies of the components in rigid ternary substitutional alloy systems from the one Monte Carlo simulation. Tests of the methods for some model systems are presented and discussed.     

A DNMR study on the ring inversion of oxazolidines

Ring inversion of eight substituted 2-phenyl-4, 4-dimethyloxazolidines in o-dichlorobenzene-d₄ was studied by ¹H DNMR. Very high inversion barriers (ΔG_o^≠ = 86.7–93.4 kJ·mol^?1) were found for these oxazolidine rings. The magnitude of the inversion barrier is dependent on the polarity of the substituent on the phenyl group. A linear correlation is present between the ΔG_o^≠ of the inversion and the substituent constant, σ+, of the substituent.     

Determination of the debris produced from poly(ethylene terephthalate) during KrF excimer laser ablation

Pulsed UV laser beams, which are widely used in the processing of polymers, have many advantages because their photon energy is higher than the binding energy of polymers. Fabricating polymers with a UV laser process is faster, cleaner, and more convenient than with other processes. Nevertheless, some problems occur in the precision microprocessing of polymers. For example, the formation and deposition of surface debris, which is produced from the breakdown of either polymer chains or radical bonds.To determine the formation and origin of surface debris, a KrF excimer laser beam (248 nm) was used in the processing of poly(ethylene terephthalate) (PET). The investigation of the debris formation was facilitated by UV-vis spectroscopy, ATR FT-IR spectroscopy, and NMR spectroscopy. The UV-vis absorption peak indicates that the primary chromophore in the PET is benzoate. Furthermore, because benzoate causes the primary absorption, the absorbed energy is transferred by heat generation to an unsaturated ester. The ATR FT-IR spectrometer measurements show that the phenyl systems in the benzoate are demolished by ablation. This phenomenon indicates that the photochemical reaction causes the benzoate bonds to break down, and this breakdown in turn causes the carbonization to leave debris on the PET.     

Instrumental neutron activation analysis of elemental compositions in particles collected during Asian Dust period

Summary Instrumental neutron activation analysis was conducted on PM 10 samples collected in Daejeon city, Korea during September 2001 to May 2002. Our measurement data were analyzed to explain the behavior of particle-bound elemental components in relationship with Asian Dust (AD) events. The results of our analysis indicated that the major crustal elements (e.g., Al, Ca, Fe, K, Mg, and Ti) showed strong enrichment (about 3 to 9 times higher concentration levels) during the AD period accompanied by the increase in the PM 10 levels (e.g., by about 3 times). However, the concentrations of anthropogenically derived elements (such as As, Br, Sb, Se and Zn) exhibited moderate change during the AD period. Hence, the computation of enrichment factor (EF) indicated that the magnitude of EF values during the AD period was even smaller in the case of toxic metals than its non-AD counterpart. The existence of relatively low EF values during the AD period can be attributed to the excessive input of crustal components. The overall results of our study suggest that both absolute and relative elemental composition of aerosol particles can be altered significantly by the AD events.     

Combination of pi and Golden Ratio in Lennard–Jones-Type and Morse-Type Potential Energy Functions

This paper tests the validity of a Lennard–Jones-type and Morse-type potential functions, consisting a combination of pi and golden ratio constants, for describing intermolecular and interatomic interaction energy. The adjustable parameter, n, can be obtained based on experimental data near the minimum well-depth or by parametric conversion from other established potential functions. The remarkably good correlation of the proposed potential functions with experimental data and other potential functions reveal an intriguing property of the relationship between pi and golden ratio within the context of chemistry.