Hydride generation interface for speciation analysis coupling capillary electrophoresis to inductively coupled plasma mass spectrometry

A novel hydride generation (HG) interface for coupling capillary electrophoresis (CE) with inductively coupled plasma mass spectrometry (ICPMS) is presented in this work. The CE-HG-ICPMS interface was applied to the separation and quantitation of common arsenic species. Lack of a commercially available HG interface for CE-ICPMS led to a three concentric tube design allowing alleviation of back pressure commonly observed in CE-HG-ICPMS. Due to the high sensitivity and element-specific detection of ICPMS, quantitative analysis of As(III), As(V), monomethylarsonic acid, and dimethylarsinic acid was achieved. Optimization of CE separation conditions resulted in the use of 20 mmol L(-1) sodium borate with 2% osmotic flow modifier (pH 9.0) and -20 kV applied potential for baseline resolution of each arsenic species in the shortest time. Hydride generation conditions were optimized through multiple electrophoretic separation analyses with 5% HCl and 3% NaBH(4) (in 0.2% NaOH) determined to be the optimum conditions. After completion of system optimization, detection limits obtained for the arsenic species were less than 40 ng L(-1) with electromigration time precision less than 1% within a total analysis time of 9.0 min. Finally, the interface was used for speciation analysis of arsenic in river and tap water samples.     

Fatty acid metabolism in the calanoid copepodParacalanus parvus: 1. Polyunsaturated fatty acids

The metabolic fate of radioactive linoleate and α-linolenate administered to the South Atlantic copepodParacalanus parvus was studied. The wild copepod was able to incorporate the labeled acids dissolved in seawater. The radioactive linoleate was elongated to 20∶2ω6 and 22∶2ω6 and desaturated by a Δ6 desaturase to 18∶3ω6. α-Linolenate was also desaturated by a Δ6 desaturase to 18∶4ω3 and elongated to 20∶3ω3. The copepod was able to convert α-18∶3 to 20∶5ω3 and 22∶6ω3. Member of the Carrera del Investigador Científico of the Comisión de Investigaciones Científicas de la Provincia de Buenos Aires. Member of the Carrera del Investigador Científico of the Consejo Nacional de Investigaciones Cientificas y Tècnicas.     

Model-checking timed automata with deadlines with Uppaal

Timed automata with deadlines (TAD) are a form of timed automata that admit a more natural representation of urgent actions, with the additional advantage of avoiding the most common form of timelocks. We offer a compositional translation of a practically useful subset of TAD to timed safety automata (the well-known variant of timed automata where time progress conditions are expressed by invariants). More precisely, we translate networks of TAD to the modeling language of Uppaal, a state-of-the-art verification tool for timed automata. We also describe an implementation of this translation, which allows Uppaal to aid the design and analysis of TAD models.     

Photofermentation of tequila vinasses by Rhodopseudomonas pseudopalustris to produce hydrogen

Hydrogen production by photofermentation of tequila vinasses (VT) was studied using Rhodopseudomonas pseudopalustris DSM 123. To the best of our knowledge this is the first report on hydrogen production by photofermentation on VT. Hydrogen production was doubled on VT (260 m$props_value{literPattern}/L) as compared to a synthetic medium. Storing VT changed its chemical composition; however, in photofermentations of a sixty-day old stock, growth and hydrogen production were similar to fresh VT. The periodic displacement of hydrogen with nitrogen resulted in a three-fold increase in both hydrogen and growth of R. pseudopalustris (860 mL H₂/L and 4.5 g/L respectively) as compared to non-displaced headspace. Hydrogen almost doubled at a light intensity of 270 W/m² (2249 mL H₂) as compared to 68 W/m². In dark-light cycles, biomass and hydrogen production were highest with continuous illumination. The potential of VT to produce hydrogen in high amounts using R. pseudopalustris has been demonstrated.     

From wave to jet and from jet to hydrogen: A promising hybrid system

One of the main challenges that our society must overcome in this century is that of finding alternative energy sources to fossil fuels. These, ideally, must be inexpensive, less polluting than current fuels and available for a substantial time. One promising alternative is hydrogen, which has the great advantage that it can be produced by coupling renewable energy devices with water electrolysis. Several projects devoted to connecting photovoltaic and wind systems with electrolysis devices have been successful; however, little research has been done into the coupling of ocean wave energy converters with water electrolysis. The work here proposes a basic system that stores the energy from waves in the form of hydrogen. The WEC considered is a novel design known as a Blow-Jet, which captures waves and converts them into a water jet. The performance of the Blow-Jet is found to depend more on wavelength than on wave height. The electrolyser results show, at 0.200 A and 1.88 V, that the electrolysis of water produces 0.082 Nl h⁻¹ of hydrogen and a current efficiency (η_I) of 90.58%.     

Effect of organic poultry purchase frequency on consumer attitudes toward organic poultry meat

Because of the growing consumers' interest in organic meat, consumers' (N = 976) attitude toward organic meat was evaluated. Most respondents (59%) occasionally purchased organic chicken. To determine the organic chicken consumer profile, the organic chicken consumption frequencies of different demographic groups were compared. The results show dependence on age (P= 0.039) and ethnicity (P = 0.015). Older respondents as well as respondents who identified themselves as Caucasians tended to buy organic chicken more frequently. However, many other socio-demographic factors were not correlated with organic chicken consumption: gender (P = 0.185), education (P = 0.235), household income (0.867), living with partner or not (P = 0.235), and number of children (P = 0.883). Taste was identified as the most important meat quality attribute (perceived as [very] important by 94% of the respondents). Other important meat quality criteria were: general appearance, overall health, price, nutritional value, and containing no medical residues. "Organically produced" appeared to not be that important compared with other criteria. When respondents bought organic chicken more often, the importance of most of the meat quality attributes shifted to higher levels of importance, except for the price where an adverse effect was shown. The main motivation factors to buy organic chicken were the perception that organic chicken has fewer residues (pesticides, hormones, antibiotics), is safer, and healthier. The high price for organic meats was the strongest limiting factor for organic meat purchases followed by poor availability. Approximately 41% of the non-buyers and 30% of the occasional buyers perceived organic meat as not or hardly likely to be available in their supermarket. PRACTICAL APPLICATION: This study obtained a better knowledge of consumers' attitudes and perception of organic chicken as well as the effect of various demographics on the likelihood of buying organic chicken. For marketing purposes of organic meats, it helps to know which attributes consumers perceive as important, where the consumer purchases organic chicken, and what the perceived availability of organic chicken is. Additionally, the motivation and deterrent factors are described indicating why the consumer does or does not purchase organic chicken. This information can be valuable to help promoting organic meats to the consumers.     

Mass transfer kinetics and regressional‐desirability optimisation during osmotic dehydration of pumpkin,kiwi and pear

Mass transfer kinetics and optimisation of osmotic dehydration (OD) of fruits and vegetables with diverse structures were studied. Different concentrations of sucrose (20–60 °Brix) and process times (0–24 h) were used. Magee’s model was appropriate for predicting water loss (WL), while Azuara’s model fitted well solids gain (SG) data and represented more accurately the evolution of the complete process close to equilibrium. Polynomial equations for each kinetic variable [WL, SG and weight reduction (WR) – for pumpkin, kiwi and pear] using multiple linear regression were fitted for a selected range of experimental data (30–240 min, 20–60 °Brix). A complete solution algorithm for desirability function was coded in Matlab^® 7.2 (Mathworks, Natick, MA, USA) with the aim to optimise osmotic dehydration process in terms of WL, SG and WR; optimal conditions were found for each fruit. Besides, an optimal common zone was identified for OD corresponding to process time from 114 to 240 min and sucrose concentration from 54 to 60 °Brix.     

Short communication: Characterization of Salmonella phages from dairy calves on farms with history of diarrhea

Salmonella enterica can cause disease and mortality in calves. This pathogen is also a zoonosis that can be transmitted by animal contact or by food. The prevalence of Salmonella in dairy farms has been reported to range from 0 to 64%, and, due to the diversity of Salmonella serovars that can be circulating, Salmonella is an important concern for dairy production. Bacteriophages that infect Salmonella have been documented to be abundant and widely distributed in the dairy environment. The current study investigated the diversity of Salmonella serovars and Salmonella phages in 8 dairy farms with a history of diarrhea in southern Chile. A total of 160 samples from sick calves, healthy calves, and the environment were analyzed for Salmonella and phage. Isolated phages were characterized and classified by their host range using a panel of 26 Salmonella isolates representing 23 serovars. Host ranges were classified according to lysis profiles (LP) and their spatial distribution was mapped. Salmonella-infecting phages were identified, but none of the 160 samples were positive for Salmonella. A total of 45 phage isolates were obtained from sick calves (11), healthy calves (16), or the environment (18). According to their host range, 19 LP were identified, with LP1 being the most common on all 8 farms; LP1 represents phages that only lyse serogroup D Salmonella. The identification of Salmonella phages but not Salmonella in the same samples could suggest that these phages are controlling Salmonella in these farms.     

Wind generator potentiality in Somalia

The wind data of several measurement sites in Somalia have been analysed in order to characterize the wind potentiality in relation to the type of wind generators; these have been defined by a simple model of the system output. The relation between machine and local frequency distribution as to energy extraction can be defined by a parameter (“site effectiveness”), which is maximized by a suitable combination of the rated and cut-in wind speed. On this basis it is shown that Somalia is characterized by wind frequency distributions that can be exploited in the best way by relatively slow rather than fast wind machines.     

Global stabilization of nonlinear cascade systems

We present sufficient conditions for the global stabilizability of two cascade connected nonlinear systems. These are based on general results concerning global asymptotic stability of triangular systems which are proved in the last section. For polynomial systems, in particular, the stabilizing feedback is given explicitly.