Kinetic multi-layer model of aerosol surface and bulk chemistry (KM-SUB): the influence of interfacial transport and bulk diffusion on the oxidation of oleic acid by ozone

We present a novel kinetic multi-layer model that explicitly resolves mass transport and chemical reaction at the surface and in the bulk of aerosol particles (KM-SUB). The model is based on the PRA framework of gas–particle interactions (P¨oschl et al., 5 2007), and it includes reversible adsorption, surface reactions and surface-bulk exchange as well as bulk diffusion and reaction. Unlike earlier models, KM-SUB does not require simplifying assumptions about steady-state conditions and radial mixing. The temporal evolution and concentration profiles of volatile and non-volatile species at the gas-particle interface and in the particle bulk can be modeled along with surface 10 concentrations and gas uptake coefficients. In this study we explore and exemplify the effects of bulk diffusion on the rate of reactive gas uptake for a simple reference system, the ozonolysis of oleic acid particles, in comparison to experimental data and earlier model studies. We demonstrate how KM-SUB can be used to interpret and analyze experimental data from laboratory stud15 ies, and how the results can be extrapolated to atmospheric conditions. In particular, we show how interfacial transport and bulk transport, i.e., surface accommodation, bulk accommodation and bulk diffusion, influence the kinetics of the chemical reaction. Sensitivity studies suggest that in fine air particulate matter oleic acid and compounds with similar reactivity against ozone (C=C double bonds) can reach chemical lifetimes of 20 multiple hours only if they are embedded in a (semi-)solid matrix with very low diffusion coefficients (10−10 cm2 s−1). Depending on the complexity of the investigated system, unlimited numbers of volatile and non-volatile species and chemical reactions can be flexibly added and treated with KM-SUB. We propose and intend to pursue the application of KM-SUB 25 as a basis for the development of a detailed master mechanism of aerosol chemistry as well as for the derivation of simplified but realistic parameterizations for large-scale atmospheric and climate models.

An alternative method to study the cooling of glasses from melt to solid phase

The aim of this preliminary work was to present a novel method, suitable to investigate the glass cooling, from melt to solid state, based on a fast, non-usual and easy microwave method. The following glass system xBaO . (100-x)B(2)O(3) (x = 0% and 40%) was selected as an example for this study. The melt was poured inside a piece of waveguide and then, its cooling was monitored by the microwave signal as a function of time. The variations in the signal can provide valuable informations about some structural changes that take place during the cooling stages, such as relaxation processes. This method can be useful to investigate the cooling and heating of other materials, opening new possibilities for investigation of dielectric behavior of materials under high temperatures. (C) 2008 Elsevier Inc. All rights reserved.

Development of zirconia-magnesia/zirconia-yttria composite solid electrolytes

Composite solid electrolytes were prepared by thoroughly mixing ZrO2:8 mol% MgO (Z8Mg) and ZrO(2):3 mol% Y(2)O(3) (Z3Y) ceramic powders followed by pressing and sintering at 1500 degrees C/1 h. The properties of the sintered pellets were studied by X-ray diffraction for evaluation of the structural phases by the Rietveld method, by high-temperature dilatometry for analysis of the thermal shrinkage/expansion behavior, and by impedance spectroscopy for determination of the oxide ion conductivity. The x(Z8Mg)+(1-x)(Z3Y) specimens, x= 0.2, 0.4, 0.5, 0.6, 0.8 and 1.0, are partially stabilized (monoclinic, cubic and tetragonal phases) with density >94% of the theoretical density and show thermal shock resistance and electrical conductivity values suitable for high-temperature oxygen gas detection. One-end closed tube samples of the composite solid electrolytes were assembled in Pt/Z8Mg+Z3Y/Cr+Cr(2)O(3)/Pt electrochemical cells for exposure to different levels of oxygen in the 1-850 ppm range. The total electrical conductivity increases for increasing the relative Z3Y content. Addition of Z3Y to Z8Mg (80 wt.%-20 wt.%) suppresses the electronic contribution to the electrical conductivity at 620 degrees C. (c) 2008 Elsevier B.V. All rights reserved.

Towards coherent optical control of a single hole spin: Rabi rotation of a trion conditional on the spin state of the hole

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Synthesis, characterization and thermal studies on solid 3-methoxybenzoate of some bivalent transition metal ions

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Synthesis, characterization and thermal behaviour on solid pyruvates of light trivalent lanthanides

Foram sintetizados compostos Ln-L no estado sólido, onde Ln significa os lantanídeos leves trivalentes e L é o piruvato. Estes compostos foram caracterizados e estudados utilizando-se a Termogravimetria e Termogravimetria derivada (TG/DTG), calorimetria exploratória diferencial (DSC) difratometria de raios X pelo método do pó, espectroscopia na região do infravermelho, análise elementar e complexometria. Os resultados permitiram obter informações com respeito a composição, desidratação, sitio de coordenação, comportamento térmico e a decomposição térmica destes compotos.

Thermal studies on solid 1,4-bis(3-carboxy-3-oxo-prop-1-enyl) benzene of lighter trivalent lanthanides

Solid-state compounds of general formula Ln(2)L(3)center dot nH(2)O, where L represents 1,4-bis(3-carboxy-3-oxo-prop-1-enyl)benzene and Ln = La, Ce, Pr, Nd, Sm, were synthesized. Complexometric titrations with EDTA, thermogravimetry (TG), differential thermal analysis (DTA), differential scanning calorimetry (DSC), X-ray powder diffractometry, elemental analysis and infrared spectroscopy have been employed to characterize and to study the thermal behavior of these compounds in dynamic air atmosphere. The results led to information about the composition, dehydration, crystallinity, and thermal decomposition of the synthesized compounds.

Thermal and spectroscopic studies on solid Ketoprofen of lighter trivalent lanthanides

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Power Factor Correction Boost Converter Based on the Three-State Switching Cell

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Evaluation of solid and submerged fermentations for the production of cyclodextrin glycosyltransferase by Paenibacillus campinasensis H69-3 and characterization of crude enzyme

Cyclodextrin glycosyltransferase (CGTase) is an enzyme that produces cyclodextrins from starch by an intramolecular transglycosylation reaction. Cyclodextrins have been shown to have a number of applications in the food, cosmetic, pharmaceutical, and chemical industries. In the current study, the production of CGTase by Paenibacillus campinasensis strain H69-3 was examined in submerged and solid-state fermentations. P. campinasensis strain H69-3 was isolated from the soil, which grows at 45 C, and is a Gram-variable bacterium. Different substrate sources such as wheat bran, soybean bran, soybean extract, cassava solid residue, cassava starch, corn starch, and other combinations were used in the enzyme production. CGTase activity was highest in submerged fermentations with the greatest production observed at 48-72 h. The physical and chemical properties of CGTase were determined from the crude enzyme produced from submerged fermentations. The optimum temperature was found to be 70-75 degrees C, and the activity was stable at 55 degrees C for 1 h. The enzyme displayed two optimum pH values, 5.5 and 9.0 and was found to be stable between a pH of 4.5 and 11.0.

Synthesis, characterization and thermal behaviour on solid tartrates of some bivalent metal ions

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Synthesis, characterization and thermal behaviour on solid pyruvates of some bivalent metal ions

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Synthesis, characterization and thermal behaviour of solid 2-methoxycinnamylidenepyruvate of some bivalent metal ions in CO2 and N2 atmospheres

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Structural studies on lead-cadmium fluoride solid solutions

(1-x)PbF2-(x)CdF2 solid solutions (with 0.1 less than or equal to x less than or equal to 0.5) were obtained by hyper-quenching the melt. Structural characteristics have been studied by X-ray diffraction (XRD) and extended X-ray absorption fine structure (EXAFS). A cubic solid solution was obtained in which the lattice parameter decreases with increasing CdF2 content. High anionic disorder was evidenced from EXAFS investigations, whereas cations remain in the FCC arrangement. Pb L-3-edge EXAFS results illustrate clearly the occurrence of CdxPb1-xF2 mixed crystals by the introduction of Cd atoms in the second Pb coordination shell. (C) 2002 Elsevier B.V. B.V. All rights reserved.

THEORY OF NON-STEADY-STATE ELECTRICAL CHARACTERISTICS OF METAL-INSULATOR-METAL STRUCTURES WITH SCHOTTKY BARRIERS AND UNIFORMLY DISTRIBUTED INTERFACE IMPURITY STATES

The metal-insulator (or amorphous semiconductor) blocking contact is still not well understood. In the present paper, we discuss the non steady state characteristics of Metal-lnsulator-Metal Structure with non-intimate blocking contacts (i.e. Metal-Oxide-Insulator-Metal Structure). We consider a uniform distribution (in energy) of impurity states in addition to impurity states at a single energy level within the depletion region. We discuss thermal as well as isothermal characteristics and present expressions for the temperature of maximum current (T-m) and a method to calculate the density of uniformly distributed impurity states. The variation of mobility with electrical field has also been considered. Finally we plot the theoretical curves under different conditions. The present results are closing into available experimental results.