Syngas production from polyethylene and biogas in porous media combustion

The production of syngas from biogas (surrogate of CH₄/CO₂: 55/45 v/v) and polyethylene in a porous media combustion reactor is experimentally studied. The employed setup is novel and has not been studied before. A semi-continuous feed of solid fuel and a constant filtration velocity of the gaseous reactants of 17 cm/s were considered. Temperature, velocity of propagation, and composition of the syngas produced in the combustion waves were registered in a tubular reactor packed with a ceramic foam porous medium and two solid fuel inlets. In the first part of the study, a baseline determined by the filtration combustion of a biogas/air mixture through the ceramic foam at the equivalence ratio ($\mathrm{?}$) range $0.7\le \mathrm{?}\le 1.6$, having transient (upstream and downstream) and stationary combustion wave propagation regimes, is established. In the second part of this work, portions of the ceramic foam in two different separated zones are extracted, leaving space for the semi-continuous supply of polyethylene. In this second part the biogas-air combustion was performed only for $\mathrm{?}=0.8$ and $\mathrm{?}=1.6$. Although the combustion temperature decreased by the presence of polyethylene, it was found that the syngas (both H₂ and CO) yield was larger than for the baseline. The highest degrees of conversion to hydrogen and carbon monoxide was reached under the presence of polyethylene, having 45% and 67% for $\mathrm{?}=0.8$, and 45% and 60% for $\mathrm{?}=1.6$, respectively. These results are very promising and they demonstrate the capabilities of the presented methodology and experimental setup, which should encourage future attempts of applications of the technology.     

Polysaccharide Constituents of Coffee-Bean Mucilage

Alcohol‐insoluble residues (AIRs) were isolated from hand‐dissected and commercial mucilages of depulped coffee beans. Both AIRs had similar polysaccharide composition: pectic substances (about 30%), cellulose (about 8%), and neutral noncellulosic polysaccharides (about 18%). Crude pectins were extracted from AIRs (dry‐matter yield: about 23% to 35%) with dilute nitric acid (pH 1.5, 90 °C). Both pectins contained about 60% uronic acids with high degree of methyl esterification (about 62%) and moderate degree of acetylation (about 5%). Their molecular weights were low (about12 to 29 kDa). They did not gel in the presence of sucrose at acidic pH.     

Habitat‐mediated influence of water‐level fluctuations on waterbird occurrence in floodplain wetlands of the Parana River,Argentina

Responses of waterbirds to habitat variation could account for their responses to fluctuations in river levels because hydrological fluctuations influence habitat availability across floodplains. Relationships between water level and waterbird occurrence were examined in floodplain wetlands of the Middle Paraná River to assess (a) whether occurrences of waterbird species were associated with water‐level fluctuations of the river, (b) which habitats were associated with species that showed a relationship with water level, (c) the influence of water level on these habitats, and (d) whether influence of water level on these species was related to water‐level influence on habitats. Through the use of regressions and structural equation models, we assessed whether direct relationships between each species and water level remained important after considering the influence of habitat variation. Of 21 species analysed, occurrences of 12 species showed an association with water‐level fluctuations. Indirect effects of water level through habitats fully accounted for this association in 5 species. Variation in habitat conditions did not, however, fully account for responses of 6 species, suggesting that although habitat variation can be an important factor, other variables are necessary to explain responses of some species to water level. One species was not associated with any habitat and therefore was not included in this analysis. Our results agreed with the idea that an important fraction of waterbird responses to hydrological fluctuations is related to the effects of these fluctuations on the availability of habitats across the floodplain. Our results provide data that help delimit groups of waterbird species that respond in similar ways to hydrological fluctuations.     

Development of quantitative cell-based enzyme assays in microdroplets

We describe the development of an enzyme assay inside picoliter microdroplets. The enzyme alkaline phosphatase is expressed in Escherichia coli cells and presented in the periplasm. Droplets act as discrete reactors which retain and localize any reaction product. The catalytic turnover of the substrate is measured in individual droplets by monitoring the fluorescence at several time points within the device and exhibits kinetic behavior similar to that observed in bulk solution. Studies on wild type and a mutant enzyme successfully demonstrated the feasibility of using microfluidic droplets to provide time-resolved kinetic measurements.     

Sensible Organizations: Technology and Methodology for Automatically Measuring Organizational Behavior

We present the design, implementation, and deployment of a wearable computing platform for measuring and analyzing human behavior in organizational settings. We propose the use of wearable electronic badges capable of automatically measuring the amount of face-to-face interaction, conversational time, physical proximity to other people, and physical activity levels in order to capture individual and collective patterns of behavior. Our goal is to be able to understand how patterns of behavior shape individuals and organizations. By using on-body sensors in large groups of people for extended periods of time in naturalistic settings, we have been able to identify, measure, and quantify social interactions, group behavior, and organizational dynamics. We deployed this wearable computing platform in a group of 22 employees working in a real organization over a period of one month. Using these automatic measurements, we were able to predict employees' self-assessments of job satisfaction and their own perceptions of group interaction quality by combining data collected with our platform and e-mail communication data. In particular, the total amount of communication was predictive of both of these assessments, and betweenness in the social network exhibited a high negative correlation with group interaction satisfaction. We also found that physical proximity and e-mail exchange had a negative correlation of r = -0.55 (p 0.01), which has far-reaching implications for past and future research on social networks.     

Processes of social learning in the tool use of chimpanzees (Pan troglodytes) and human children (Homo sapiens).

Common chimpanzees (Pan troglodytes) and 2-yr-old human children (Homo sapiens) were presented with a rakelike tool and a desirable but out-of-reach object. One group of Ss observed a human demonstrator use the tool in one way, and another group observed a demonstrator use the tool in another way. Children in both cases did what the model did. Chimpanzee Ss, however, behaved identically in the 2 model conditions. Both groups performed better than Ss who saw no demonstration. This pattern of results suggests that the chimpanzees were paying attention to the general functional relations in the task and to the results obtained by the demonstrator but not to the actual methods of tool use demonstrated. Human children were focused on the demonstrator's actual methods of tool use (i.e., her behavior). The different social learning processes used by the 2 species have implications for their different forms of social organization. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Involvement of pectolytic micro-organisms in coffee fermentation

During the fermentation of Coffea arabica L., the most frequently found pectolytic bacteria were Erwinia herbicola and Klebsiella pneumoniae . These micro-organisms produce pectatelyase which is unable to depolymerize esterified pectins of mucilage without previous de-esterification. Furthermore, the optimal activities are observed at pH 8.5 whereas fermentation conditions are acidic (5.3–3.5). The major lactic acid bacteria, Leuconostoc mesenteroides , do not produce pectolytic enzymes. Only a Lactobacillus brevis strain, rarely isolated with a low frequency, shows a polygalacturonase activity compatible with fermentation conditions. Mucilage decomposition seems to be correlated to acidification and not to enzymatic pectolysis. Inoculation with pectolytic micro-organisms allows microbiological control of the fermentation but does not speed up the process. It would be preferable to use lactic acid bacteria so that the pH remained as close as possible to natural fermentation, where acidification is important. This practice would standardize the coffee fermentation microflora and therefore control the end product quality.     

Kinetics of dibenzothiophene hydrodesulfurization over MoS2 supported catalysts: modelization of the H2S partial pressure effect

The influence of H₂S partial pressure over the catalytic activity of MoS₂, supported on three different oxides: Al₂O₃, TiO₂ and ZrO₂, was studied in the hydrodesulfurization of dibenzothiophene (DBT). A complex inhibiting effect is observed and two orders of reaction relative to H₂S were determined: −1/2 and 0, as a function of H₂S partial pressure. The experimental results are in good agreement with the kinetic models whereby the DBT transformation takes place through a dihydrogenated intermediate (DH-DBT). The associated mechanism considers that the heterolytic dissociative adsorption of H₂ and H₂S occurs over an unsaturated Mo ion and over a stable sulfur ion.     

Influence of evaporation on spray flamelet structures

The structure of laminar spray flames considerably differs from their gaseous counterpart. However, most often flamelet models employed in the simulation of turbulent spray combustion are based on laminar gas flame structures neglecting the influence of spray evaporation in the laminar spray flamelets. In this work, a combined theoretical and numerical study of the impact of spray evaporation on the structure of laminar spray flames is presented. Spray flamelet equations are derived, which explicitly take into account evaporation effects – the classical gas flamelet equations are recovered for non-evaporating conditions. Two new terms accounting for evaporation and for combined mixing and evaporation, respectively, are identified, and their relative importance is evaluated by means of numerical simulations of an axisymmetric laminar mono-disperse ethanol/air counterflow spray flame. The results show that the distribution of the spray evaporation rate plays a key role in the characterization of the spray flame structure. The new source terms overweigh the dissipation term of the gas phase in most situations even for non-evaporating species. Therefore, spray evaporation should always be considered. The relevance of the present formulation for turbulent spray modeling is evaluated and discussed, and a novel spray flamelet formulation is suggested.