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Rationale: Ceria‐based systems are of great interest because of their unique properties. Such systems may be used as anode materials for SOFCs or in oxygen sensors. The exploitation of these materials often requires high temperatures. In such conditions, the partial or complete evaporation of materials is possible. Therefore, knowledge of the values of partial pressures and thermodynamic properties is essential to predict and/or prevent possible consequences and accidents. Methods: Knudsen effusion mass spectrometry was used to determine partial pressures of vapor species over the SrO–CeO2 and CaO‐CeO2 systems. Measurements of partial pressures were performed with a MS‐1301 mass spectrometer. Vaporization was carried out using molybdenum or tungsten effusion cells. A theoretical study of gaseous strontium and calcium cerates was performed by several quantum chemical methods: density functional theory (DFT) M06, DFT PBE0, and MP2. Results: The minimum value of relative electron ionization cross‐section for CeO2 was estimated. In the temperature range of 2218–2249 K above the SrO‐CeO2 system and of 2128–2208 K above the CaO‐CeO2 system, gaseous M, MO, MO, CeO2, O, O2 and MCeO3 (M = Sr, Ca) were found. Energetically favorable structures of gaseous SrCeO3 and CaCeO3 were found, and vibrational frequencies were evaluated in the "rigid rotor‐harmonic oscillator" approximation. On the basis of the equilibrium constants of gaseous reaction MO + CeO2 = MCeO3, the standard formation enthalpy of gaseous SrCeO3 (−913 ± 26 kJ/mol) and of gaseous CaCeO3 (−917 ± 26 kJ/mol) at 298 K were determined. Conclusions: The estimated value of relative electron ionization cross‐section for CeO2 is in agreement with the general rule applicable for dioxides. The stability of SrCeO3 and CaCeO3 gaseous species was confirmed by KEMS. Gas‐phase reactions involving gaseous SrO (CaO) and CeO2 with gaseous SrCeO3(CaCeO3) were studied. Enthalpy of formation reaction of gaseous SrCeO3(CaCeO3) from gaseous SrO (CaO) were evaluated theoretically, and the obtained value is in agreement with the experimental one. [ABSTRACT FROM AUTHOR]

Density functional theory (DFT) and Hartree–Fock (HF) methods have been used to calculate the electronic and geometric structures of cis- and trans-[Pt(NH3)2X2] (X = Cl-, Br-, I-), [cis-Pt(NH3)2(H2O)2]2+ and its deprotonated forms. The thermodynamic parameters ΔH0298, ΔS0298, ΔG0298, and ΔCp = f(T) have been obtained from DFT force fields and normal mode frequencies. It is shown that the greater stability of the trans-isomers is due, at the molecular level, to different interligand interactions. The stability of the cis-isomers is significantly increased by intermolecular Pt…Pt and NH2-H…X nonvalence interactions between mononuclear [cis-Pt(NH3)2X2] moieties, the effect reducing in the row Cl- > Br- > I-. The thermodynamic parameters of possible phases of the hydrolysis of [cis-Pt(NH3)2(H2O)2]2+ have been also derived. Solvent effects have been investigated calculating the equilibrium constants for the proton transfer reactions both in gas phase and water solution. It is shown that in aqueous medium the hydroxobridged platinum dimer [Pt(NH3)2- (μ-OH)]2+2, characterized by a Pt…Pt distance of 3.119 Å, is the preferred hydrolysis product. It is also shown that with short metal–metal interactions, such as those found in [cis-Pt(NH3)2Cl2] and [cis-Pt(NH3)2(H2O)2]2+, the conditions for the formation of linear polynuclear complexes with Pt—Pt bonds (the so-called “platinum blues”) are created. © 2003 Wiley Periodicals, Inc. Int J Quantum Chem, 2004 [ABSTRACT FROM AUTHOR]

This paper examines the cognitive and neuropsychological functioning of children who were in utero to age 15 months at the time of the Chornobyl disaster and were evacuated to Kyiv from the 30-kilometer zone surrounding the plant. Specifically, we compared 300 evacuee children at ages 10-12 with 300 non-evacuee Kyiv classmates on objective and subjective measures of attention, memory, and school performance. The evacuee children were not significantly different from their classmates on the objective measures (grades; Symbolic Relations subtest of the Detroit Test; forms 1 and 2 of the Visual Search and Attention Test; Benton Form A; Trails A; Underline the Words Test) or on most of the subjective measures (the attention subscale of the Child Behavior Checklist completed by mothers; the attention items of the Iowa Conners Teacher's Rating Scale; mother and child perceptions of school performance). The one exception was that 31.3% of evacuee mothers compared to 7.4 %of classmate mothers indicated that their child had a memory problem. However, this subjective measure of memory problems was not significantly related to neuropsychological or school performance. No significant differences were found in comparisons of evacuees and classmates who were in utero at the time of the explosion, children from Pripyat vs. other villages in the 30-kilometer zone, and children manifesting greater generalized anxiety. For both groups, children with greater Chornobyl-focused anxiety performed significantly worse than children with less Chornobyl-focused anxiety on measures of attention. The results thus fail to confirm two previous reports that relatively more children from areas contaminated by radiation had cognitive deficits compared to controls. Possible reasons for the differences in findings among the studies are discussed. [ABSTRACT FROM AUTHOR]