Molecular size evolution of oligomers in organic aerosols collected in urban atmospheres and generated in a smog chamber

Only a minor fraction of the total organic aerosol mass can be resolved on a molecular level. High molecular weight compounds in organic aerosols have recently gained much attention because this class of compound potentially explains a major fraction of the unexplained organic aerosol mass. These compounds have been identified with different mass spectrometric methods, and compounds with molecular masses up to 1000 Da are found in secondary organic aerosols (SOA) generated from aromatic and terpene precursors in smog chamber experiments. Here, we apply matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) to SOA particles from two biogenic precursors, alpha-pinene and isoprene. Similar oligomer patterns are found in these two SOA systems, but also in SOA from trimethylbenzene, an anthropogenic SOA precursor. However, different maxima molecular sizes were measured for these three SOA systems. While oligomers in alpha-pinene and isoprene have sizes mostly below 600-700 Da, they grow up to about 1000 Da in trimethylbenzene-SOA. The final molecular size of the oligomers is reached early during the particle aging process, whereas other particle properties related to aging, such as the overall acid concentration or the oligomer concentration, increase continuously over a much longer time scale. This kinetic behavior of the oligomer molecular size growth can be explained by a chain growth kinetic regime. Similar oligomer mass patterns were measured in aqueous extracts of ambient aerosol samples (measured with the same technique). Distinct differences between summer and winter were observed. In summer a few single mass peaks were measured with much higher intensity than in winter, pointing to a possible difference in the formation processes of these compounds in winter and summer.     

Hydrogen by glycerol steam reforming on a nickel–alumina catalyst: Deactivation processes and regeneration

Hydrogen energy has attracted considerable attention because of its efficiency and environmental benefits, and the increasing demand requires finding renewable sources of raw materials to produce it. Glycerol, by-product of biodiesel production and coming from renewable raw materials, could be a bio-renewable substrate to produce hydrogen. The glycerol steam reforming to obtain hydrogen was evaluated using a 5.1 wt% Ni impregnated on Al₂O₃ catalyst, characterized by nitrogen adsorption, XRD, and FTIR. Deactivation processes were analyzed in successive cycles of reaction at 700 °C, atmospheric pressure, 5 h⁻¹ WHSV, and 3:1 water:glycerol molar ratio, during 12 h. Between reaction cycles, regenerating took place using a He/Air stream. Hydrogen was the main product on the fresh catalyst, following by CO and CH₄; during reaction, carbonaceous deposits deactivated catalyst, decreasing H₂ and increasing both CO and CH₄. Carbonaceous deposits were characterized by TPO, showing a main peak centered at 690 °C; the carbon content reached 11.9%.     

Selective charge transfer in donor/acceptor systems bridged by Tröger base derivatives

Recently, unusual charge transfer properties of two triarylamines bridged through an aliphatic bridge (Tröger base) have been reported. The donor/acceptor couple was shown to have an important electronic coupling between its centers for the hole transfer, although in the absence of a π linker. In contrast, we here show, by combining first principles calculations with experimental studies, that the bridge has a practically null role in coupling the electron transfer. This sharp contrast might present an interesting potential in the design of molecular devices.     

Colloidal silver complex as an alternative to sulphur dioxide in winemaking

The use of sulphur dioxide in the food industry has come increasingly into question because it can lead to pseudo-allergies. The aim of this work was to study the effectiveness of a colloidal silver complex (CSC) as an antiseptic instead of SO₂ in both white and red winemaking. We show that the CSC at doses of 1 g/kg of grape is an effective antiseptic, able to control acetic acid and lactic acid bacteria development, allowing the growth of Saccharomyces cerevisiae at rates similar to those observed with SO₂, up to sugars were exhausted. Silver concentration in finished white and red wines, 18.4 μg/L and 6.5 μg/L, respectively, was well below the legal limits. Wine composition was slightly affected, but CSC wines had a lower alcoholic degree and acetaldehyde content than SO₂ wines. CSC is a promising antiseptic for wine industry, although a major drawback, its lack of antioxidant activity, should be considered.     

Microsatellite Loci in the Gypsophyte Lepidium subulatum (Brassicaceae), and Transferability to Other Lepidieae

Polymorphic microsatellite markers were developed for the Ibero-North African, strict gypsophyte Lepidium subulatum to unravel the effects of habitat fragmentation in levels of genetic diversity, genetic structure and gene flow among its populations. Using 454 pyrosequencing 12 microsatellite loci including di- and tri-nucleotide repeats were characterized in L. subulatum. They amplified a total of 80 alleles (2–12 alleles per locus) in a sample of 35 individuals of L. subulatum, showing relatively high levels of genetic diversity, H_O = 0.645, H_E = 0.627. Cross-species transferability of all 12 loci was successful for the Iberian endemics Lepidium cardamines, Lepidium stylatum, and the widespread, Lepidium graminifolium and one species each of two related genera, Cardaria draba and Coronopus didymus. These microsatellite primers will be useful to investigate genetic diversity, population structure and to address conservation genetics in species of Lepidium.     

Physicochemical and functional properties of whole and defatted meals from Mexican (Cucurbita pepo) pumpkin seeds

Chemical composition and some functional and thermal properties in whole pumpkin seed meal (WPSM) and defatted pumpkin seed meal (DPSM) were determined. The DPSM exhibited higher water absorption capacity (3 g H₂O per g sample), water solubility capacity (8.75%), oil absorption capacity (2.73 g oil per g sample), emulsifying capacity (61.71%), foaming capacity (51.92%) and gelling capacity (12% w/v) than the WPSM. The DPSM also had better swelling power (3.33% at 60 °C, rising to 4.31% at 90 °C), higher phase transition temperatures (T₀ = 80.04 °C, T_p = 86.50 °C and T_f = 93.20 °C) and a higher phase transition energy (0.93 J g^?1). However, the WPSM had higher bulk density (0.57 g cm^?3) and better foam stability (from 30 to 120 min). Micrographs showed defatting to cause microstructural changes in meal starch granules and proteins. Its high protein content makes the DPSM a potential alternative input in the food industry.     

WebSpec: a visual language for specifying interaction and navigation requirements in web applications

Web application development is a complex and time-consuming process that involves different stakeholders (ranging from customers to developers); these applications have some unique characteristics like navigational access to information, sophisticated interaction features, etc. However, there have been few proposals to represent those requirements that are specific to Web applications. Consequently, validation of requirements (e.g., in acceptance tests) is usually informal and as a result troublesome. To overcome these problems, we present WebSpec, a domain-specific language for specifying the most relevant and characteristic requirements of Web applications: those involving interaction and navigation. We describe WebSpec diagrams, discussing their abstraction and expressive power. With a simple though realistic example, we show how we have used WebSpec in the context of an agile Web development approach discussing several issues such as automatic test generation, management of changes in requirements, and improving the understanding of the diagrams through application simulation.     

Kinetic study of the partial hydrogenation of 1‐heptyne on tungsten oxide supported on alumina

BACKGROUND: Partial hydrogenation of alkynes have industrial and academic relevance on a large scale; industries such as petrochemical, pharmacology and agrochemical use these compounds as raw material. Typical commercial catalysts contains palladium. Finding an economic, active and selective catalyst for the production of alkenes via partial hydrogenation of alkynes is thus an important challenge. On the other hand, the literature on kinetic studies of partial hydrogenation of heavy alkynes is scarce. So the main objectives of this work were to prepare a cheaper catalyst based on low W loading, and study the kinetic of the partial hydrogenation of 1‐heptyne. A pseudo‐homogeneous and six heterogeneous kinetic models were analyzed. The catalyst was characterized by ICP, XPS, DRX, TPR and hydrogen chemisorption techniques. RESULTS: The characterization results indicate that only WO_x species are present on the alumina surface. The WO_x/Al₂O₃ catalyst was active and selective for producing 1‐heptene even at low reaction temperatures, the partial hydrogenation of 1‐heptyne proceeds via two irreversible reactions in parallel. CONCLUSION: The best fit of the experimental data was achieved with a heterogeneous Langmuir‐Hinshelwood‐Hougen‐Watson model in which the rate controlling step is the dissociative adsorption of hydrogen. The activation energy was estimated as E_H2 = 34.8 kJ mol^?1. Copyright © 2012 Society of Chemical Industry     

Effects of split attention revisited: A new display technology for troubleshooting tasks

Knowledge acquisition processes benefit from presentations that depict related information – like diagrams and formulas – in an integrated way. In contrast, disconnecting interrelated information impairs learning. However, not every task is suitable for an integrated presentation. In the current study, 80 naïve college students were presented with a troubleshooting task preventing an integrated presentation format. We compared performance in a split screen setup depicting two images side-by side with performance in a vexing-image setup. The latter enables the presentation of two images such that participants are able to switch between them without moving the visual focus. Compared to the split screen condition in which participants have to shift their visual focus frequently, troubleshooting performance of correctly identified malfunctioning mechanical devices was higher in the vexing image mode. Thus, not the separation of external representations but re-orientation processes after switching the visual focus seems to be responsible for split attention effects.