Computational Lattice-Gas Modeling of the Electrosorption of Small Molecules and Ions

We present two recent applications of lattice-gas modeling techniques to electrochemical adsorption on catalytically active metal substrates: urea on Pt(100) and (bi)sulfate on Rh(111). Both involve the specific adsorption of small molecules or ions on well-characterized single-crystal electrodes, and they provide a particularly good fit between the adsorbate geometry and the substrate structure. The close geometric fit facilitates the formation of ordered submonolayer adsorbate phases in a range of electrode potential positive of the range in which an adsorbed monolayer of hydrogen is stable. In both systems the ordered-phase region is separated from the adsorbed- hydrogen region by a phase transition, signified in cyclic voltammograms by a sharp current peak. Based on data from {\it in situ\/} radiochemical surface concentration measurements, cyclic voltammetry, and scanning tunneling micro- scopy, and {\it ex situ\/} Auger electron spectroscopy and low-energy electron diffraction, we have developed specific lattice-gas models for the two systems. These models were studied by group-theoretical ground-state calcu- lations and numerical Monte Carlo simulations, and effective lattice-gas inter- action parameters were determined so as to provide agreement with experiments.Comment: 17 pp. uuencoded postscript, FSU-SCRI-94C-9

Biomarkers of exposure to new and emerging tobacco delivery products

Accurate and reliable measurements of exposure to tobacco products are essential for identifying and confirming patterns of tobacco product use and for assessing their potential biological effects in both human populations and experimental systems. Due to the introduction of new tobaccoderived products and the development of novel ways to modify and use conventional tobacco products, precise and specific assessments of exposure to tobacco are now more important than ever. Biomarkers that were developed and validated to measure exposure to cigarettes are being evaluated to assess their use for measuring exposure to these new products. Here, we review current methods for measuring exposure to new and emerging tobacco products, such as electronic cigarettes, little cigars, water pipes, and cigarillos. Rigorously validated biomarkers specific to these new products have not yet been identified. Here, we discuss the strengths and limitations of current approaches, including whether they provide reliable exposure estimates for new and emerging products. We provide specific guidance for choosing practical and economical biomarkers for different study designs and experimental conditions. Our goal is to help both new and experienced investigators measure exposure to tobacco products accurately and avoid common experimental errors. With the identification of the capacity gaps in biomarker research on new and emerging tobacco products, we hope to provide researchers, policymakers, and funding agencies with a clear action plan for conducting and promoting research on the patterns of use and health effects of these products

THERMODYNAMICS OF CERTAIN REFRACTORY COMPOUNDS. PART II. CONTINUED THEORETICAL AND EXPERIMENTAL STUDIES ON AN EXTENDED LIST. Second Quarterly Progress Report, September 1 to November 30, 1963

The thermodynamic properties of refractory borides, carbides, nitrides, and oxides of some 31 elements are compiled. Several tables for elements and compounds not previously reported are presented, and the experimental spectroscopic studies of the vapor of boron oxide and hydroxide are discussed. (R.J.S.

Erosão hídrica em um Nitossolo Háplico submetido a diferentes sistemas de manejo sob chuva simulada. II - Perdas de nutrientes e carbono orgânico Water erosion on an Hapludox submitted to different soil managements under simulated rainfall. II - Nutrient and organic carbon losses

Com a erosão hídrica, há o transporte de nutrientes para fora das lavouras e, com isso, pode ocorrer o empobrecimento dos solos e a contaminação do ambiente fora do local da erosão. Utilizando um simulador de chuvas de braços rotativos, foram aplicadas, no campo, três chuvas simuladas no cultivo do milho e três no de feijão, com intensidade constante de 64 mm h-1 e energia cinética de 0,2083 MJ ha-1 mm-1 , no Planalto Sul Catarinense, entre março de 2001 e abril de 2003, para avaliar as perdas de nutrientes e carbono orgânico (CO) pela erosão hídrica sobre os seguintes tratamentos de manejo do solo, em duas repetições: solo sem cultivo com uma aração + duas gradagens (SSC); cultivos de milho e feijão com uma aração + duas gradagens sobre resíduos dessecados (PCO); cultivos de milho e feijão em semeadura direta sobre resíduos dessecados em solo previamente preparado (SDI); cultivos de milho e feijão em semeadura direta sobre resíduos dessecados em solo nunca preparado (SDD), cultivos de milho e feijão em semeadura direta sobre resíduos queimados em solo nunca preparado (SDQ); e solo sem cultivo com campo nativo melhorado (CNM). Utilizou-se um Nitossolo Háplico alumínico argiloso, com inclinação média do terreno de 0,165 m m-1. As concentrações dos nutrientes e do CO nos sedimentos transportados por erosão foram maiores nos preparos conservacionistas do que nos convencionais, enquanto as perdas totais comportaram-se de maneira inversa. Na água da enxurrada, as concentrações e as perdas de NH4+ e NO3- diminuíram do cultivo do milho para o do feijão, enquanto as de P aumentaram. No caso do K, ocorreu redução da concentração e aumento das perdas. As taxas de empobrecimento do solo situaram-se, em geral, próximas de um para os nutrientes e para o CO. As concentrações dos nutrientes e do CO nos sedimentos transportados correlacionaram-se, linear e positivamente, com a composição química da camada de 0-0,025 m de profundidade do solo de onde o sedimento foi removido.<br>Water erosion extracts nutrients from farming areas and causes soil impoverishment and environmental contamination outside the erosion site. A rotating-boom rainfall simulator operated at a constant rainfall intensity of 64 mm h-1 and 0.2083 MJ ha-1 mm-1 kinetic energy was used to investigate nutrient and organic carbon losses by water erosion and related parameters in six management systems in corn and bean crops. The experiments were carried out on a clayey loam structured soil (Hapludox) with 0.165 m m-1 average slope on the Southern Plateau of Santa Catarina State, Brazil, from March 2001 to April 2003. Three rainfall simulations were applied to the corn and three to the bean crop according to the following treatments: plowing + disking (bare soil) (SSC), corn and bean crop under plowing + disking on desiccated residue (PCO), corn and bean crop under no-tillage on desiccated residue on previously prepared soil (SDI), corn and bean crop under no-tillage on desiccated residue on never prepared soil (SDD), corn and bean crop under no-tillage on burned residue on never prepared soil (SDQ), and improved native pasture (CNM). Results showed that nutrients and organic carbon concentrations in runoff sediments were higher under conservation tillage than conventional tillage, while the total losses presented inverse behavior. In the water of the runoff, NH4+ and NO3- concentrations and losses were higher in the corn than in bean while P was lower. K concentrations were higher in corn and losses lower. Soil impoverishment rates were generally close to the unit for nutrients and organic carbon. Nutrients and organic carbon concentrations in erosion sediments were linearly and positively correlated with the chemical composition of the 0-0.025 m soil layer