Comparison of Model Chemistry and Density Functional Theory Thermochemical Predictions with Experiment for Formation of Ionic Clusters of the Ammonium Cation Complexed with Water and Ammonia; Atmospheric Implications

The G2, G3, CBS-QB3, and CBS-APNO model chemistry methods and the B3LYP, B3P86, mPW1PW, and PBE1PBE density functional theory (DFT) methods have been used to calculate ΔH° and ΔG° values for ionic clusters of the ammonium ion complexed with water and ammonia. Results for the clusters NH4+(NH3)n and NH4+(H2O)n, where n = 1−4, are reported in this paper and compared against experimental values. Agreement with the experimental values for ΔH° and ΔG° for formation of NH4+(NH3)n clusters is excellent. Comparison between experiment and theory for formation of the NH4+(H2O)n clusters is quite good considering the uncertainty in the experimental values. The four DFT methods yield excellent agreement with experiment and the model chemistry methods when the aug-cc-pVTZ basis set is used for energetic calculations and the 6-31G* basis set is used for geometries and frequencies. On the basis of these results, we predict that all ions in the lower troposphere will be saturated with at least one complete first hydration shell of water molecules.

Comparison of CBS-QB3, CBS-APNO, G2, and G3 thermochemical predictions with experiment for formation of ionic clusters of hydronium and hydroxide ions complexed with water

The GAUSSIAN 2, GAUSSIAN 3, complete basis set-QB3, and complete basis set-APNO methods have been used to calculate ΔH∘ and ΔG∘ values for ionic clusters of hydronium and hydroxide ions complexed with water. Results for the clusters H3O+(H2O)n andOH−(H2O)n, where n=1–4 are reported in this paper, and compared against experimental values contained in the National Institutes of Standards and Technology (NIST) database. Agreement with experiment is excellent for the three ab initio methods for formation of these clusters. The high accuracy of these methods makes them reliable for calculating energetics for the formation of ionic clusters containing water. In addition this allows them to serve as a valuable check on the accuracy of experimental data reported in the NIST database, and makes them useful tools for addressing unresolved issues in atmospheric chemistry.

Atmospheric Implications for Formation of Clusters of Ammonium and 1−10 Water Molecules

A mixed molecular dynamics/quantum mechanics model has been applied to the ammonium/water clustering system. The use of the high level MP2 calculation method and correlated basis sets, such as aug-cc-pVDZ and aug-cc-pVTZ, lends confidence in the accuracy of the extrapolated energies. These calculations provide electronic and free energies for the formation of clusters of ammonium and 1−10 water molecules at two different temperatures. Structures and thermodynamic values are in good agreement with previous experimental and theoretical results. The estimated concentration of these clusters in the troposphere was calculated using atmospheric amounts of ammonium and water. Results show the favorability of forming these clusters and implications for ion-induced nucleation in the atmosphere.

Impact of random and systematic recall errors and selection bias in case--control studies on mobile phone use and brain tumors in adolescents (CEFALO study)

Whether the use of mobile phones is a risk factor for brain tumors in adolescents is currently being studied. Case--control studies investigating this possible relationship are prone to recall error and selection bias. We assessed the potential impact of random and systematic recall error and selection bias on odds ratios (ORs) by performing simulations based on real data from an ongoing case--control study of mobile phones and brain tumor risk in children and adolescents (CEFALO study). Simulations were conducted for two mobile phone exposure categories: regular and heavy use. Our choice of levels of recall error was guided by a validation study that compared objective network operator data with the self-reported amount of mobile phone use in CEFALO. In our validation study, cases overestimated their number of calls by 9% on average and controls by 34%. Cases also overestimated their duration of calls by 52% on average and controls by 163%. The participation rates in CEFALO were 83% for cases and 71% for controls. In a variety of scenarios, the combined impact of recall error and selection bias on the estimated ORs was complex. These simulations are useful for the interpretation of previous case-control studies on brain tumor and mobile phone use in adults as well as for the interpretation of future studies on adolescents.

Where Is "Home"? Value Conflicts, Identity Crises and the Formation of Cosmopolitan Identity in Myanmar Students Studying in the United States

Fully engaging in a new culture means translating oneself into a different set of cultural values, and many of the values can be foreign to the individual. The individual may face conflicting tensions between the psychological need to be a part of the new society and feelings of guilt or betrayal towards the former society, culture or self. Many international students from Myanmar, most of whom have little international experience, undergo this value and cultural translation during their time in American colleges. It is commonly assumed that something will be lost in the process of translation and that the students become more Westernized or never fit into both Myanmar and US cultures. However, the study of the narratives of the Myanmar students studying in the US reveals a more complex reality. Because individuals have multifaceted identities and many cultures and subcultures are fluctuating and intertwined with one another, the students¿ cross-cultural interactions can also help them acquire new ways of seeing things. Through their struggle to engage in the US college culture, many students display the theory of ¿cosmopolitanism¿ in their transformative identity formation process and thus, define and identify themselves beyond one set of cultural norms.

Effect of Methodological and Ecological Approaches on Heterogeneity of Nest-Site Selection of a Long-Lived Vulture

The application of scientific-based conservation measures requires that sampling methodologies in studies modelling similar ecological aspects produce comparable results making easier their interpretation. We aimed to show how the choice of different methodological and ecological approaches can affect conclusions in nest-site selection studies along different Palearctic meta-populations of an indicator species. First, a multivariate analysis of the variables affecting nest-site selection in a breeding colony of cinereous vulture (Aegypius monachus) in central Spain was performed. Then, a meta-analysis was applied to establish how methodological and habitat-type factors determine differences and similarities in the results obtained by previous studies that have modelled the forest breeding habitat of the species. Our results revealed patterns in nesting-habitat modelling by the cinereous vulture throughout its whole range: steep and south-facing slopes, great cover of large trees and distance to human activities were generally selected. The ratio and situation of the studied plots (nests/random), the use of plots vs. polygons as sampling units and the number of years of data set determined the variability explained by the model. Moreover, a greater size of the breeding colony implied that ecological and geomorphological variables at landscape level were more influential. Additionally, human activities affected in greater proportion to colonies situated in Mediterranean forests. For the first time, a meta-analysis regarding the factors determining nest-site selection heterogeneity for a single species at broad scale was achieved. It is essential to homogenize and coordinate experimental design in modelling the selection of species' ecological requirements in order to avoid that differences in results among studies would be due to methodological heterogeneity. This would optimize best conservation and management practices for habitats and species in a global context.

Formation of Exchange Rates on the Russian Market: Dynamics and Modelling

Galina Kovaleva. The Formation of the Exchange Rate on the Russian Market: Dynamics and Modelling. The Russian financial market is fast becoming one of the major sectors of the Russian economy. Assets have been increasing steadily, while new market segments and new financial market instruments have emerged. Kovaleva attempted to isolate the factors influencing exchange rates, determine patterns in the dynamic changes to the rouble/dollar exchange rate, construct models of the processes, and on the basis of these activities make forecasts. She studied the significance of economic indicators influencing the rouble/dollar exchange rate at different times, and developed multi-factor econometric models. In order to reveal the inner structure of the financial indicators and to work out ex-post forecasts for different time intervals, she carried out a series of calculations with the aim of constructing trend-cyclical (TC) and harmonic models, and Box and Jenkins models. She found that: 1. The Russian financial market is dependant on the rouble/dollar exchange rate. Its dynamics are formed under the influence of the short-term state treasury notes and government bonds markets, interbank loans, the rouble/DM exchange rate, the inflation rate, and the DM/dollar exchange rate. The exchange rate is influenced by sales on the Moscow Interbank Currency Exchange and the mechanism of those sales. 2. The TC model makes it possible to conduct an in-depth study of the structure of the processes and to make forecasts of the dynamic changes to currency indicators. 3. The Russian market is increasingly influenced by the world currency market and its prospects are of crucial interest for the world financial community.