Investigation of Thermoplasticity of Zein and Kafirin Proteins: Mixing Process and Mechanical Properties

Conventional direct melt mixing technology was investigated on zein and kafirin, two vegetable proteins extracted, respectively, from maize and sorghum. A lab scale internal mixer has been used to thoroughly study the thermo-plasticization process of the proteins with several plasticizers. Different compositions were investigated under different processing conditions. In particular, the lengthy procedures of forming the protein/solvent/plasticizer solution followed by drying or the protein/plasticizer emulsion followed by the precipitation of the extrudable resin, reported in the literature for these systems, were avoided and the protein and plasticizer were directly fed into the mixer to obtain a plastic-like material. The effect of plasticizer type and content and mixing process variables on the mechanical properties was analyzed. Compression molded slabs were transparent, strong and flexible, with properties similar to the cast films reported in the literature, prepared with the same type of plasticizers. However, lower plasticizer content was sufficient to produce equally flexible films, proving an enhanced plasticization efficiency of the mixing process, as compared to casting.     

Carbon Monoxide Trend,Meteorology, and Three-Way Catalysts in Mexico City

ABSTRACT

From the analysis of data of the Inspection/Maintenance (I/M) program, and of the long-term trend of ambient CO concentrations in Mexico City, it is inferred that three-way catalysts (TWCs) have a 45% efficiency, well below the expected 90% value. The most probable causes are sulfur poisoning, lead contamination, and ceramic breakage due to bumps and potholes on the streets. Also, we have found a ratio between the average daily peak value of atmospheric CO and gasoline consumption: (11 ± 1) ppbCO/MLm (million liters of gasoline per month) in 1988 decaying to (10 ±1) in 1991 for Mexico City before the introduction of TWCs. In addition, we found a correlation between the monthly averages of CO daily peak and meteorological variables, explaining most of the seasonal changes using only the intensity of the inversion layer and surface wind speed.     

Experimental analysis of gas explosions at non-atmospheric initial conditions in cylindrical vessel

Accidental gas explosions in industrial equipment are seldom initiated at atmospheric conditions. Furthermore, fuel–air mixtures are generally turbulent due to rotating parts or flows. Despite these considerations, few studies have been devoted to the analysis of explosion properties at conditions of temperature and pressure different from ambient and in the presence of turbulence; therefore, experiments are still needed, even at lab-scale, e.g. for the design of mitigation system as venting devices.In this work, experimental explosion tests have been performed in 5 l, cylindrical tank reactor with stoichiometric methane–air mixtures at initial pressure and temperature up to 600 kPa and 400 K, centrally ignited or top ignited, and with the effect of initial turbulence level by varying the velocity of the mechanical stirrer.     

Physiological correlates of genetic variation for rate of behavioral development in the honeybee, Apis mellifera

Two factors that influence age at onset of foraging in honeybees are juvenile hormone (JH) and colony age demography (older bees inhibit behavioral development of younger bees). We tested the hypothesis that genetic variation among bees for these factors influences genetic variation in behavioral development. Pairs of colonies showing genetic differences in rates of behavioral development were identified in a screening experiment and bees from these colonies were used for physiological and behavioral assays. Six pairs were assayed, three with European bees only and three with both European and Africanized bees. There was genetic variation for the following four components: (1) production of JH in four pairs (experiment 1); (2) sensitivity to JH in three pairs (experiment 2); (3) sensitivity to social inhibition in three pairs (experiment 3), and (4) potency of social inhibition in four pairs (experiment 4). Cross-fostering assays (experiment 5), which allowed all four components to be evaluated simultaneously, revealed genetic variation for production of JH, sensitivity to JH, or sensitivity to social inhibition in five of six pairs, and potency of social inhibition in five of six pairs. There was often evidence for genotypic differences in more than one component, and no consistent pattern of association among any of the components. Africanized bees had faster rates of behavioral development than European bees, but there were no racial differences in patterns of variation among the four components. These results indicate that there are at least several, apparently distinct, physiological processes associated with JH and colony age demography upon which natural selection can act to alter the rate of behavioral development in honeybees. Received: 8 December 1998 / Received in revised form: 29 July 1999 / Accepted: 8 August 1999     

Manganese toxicity in Drosophila melanogaster: extension of the life span by resveratrol

The effect of resveratrol was studied on the life span and motor activity of Drosophila melanogaster treated with manganese (Mn). Two days after emerging from the pupa, male wild type D. melanogaster were fed for 13 days with corn media containing 15?mM Mn. Thereafter, Drosophila were divided into six groups of 300 flies each: (1) the flies remained treated with Mn; (2) began treatment with 0.43?mM resveratrol (Mn-resveratrol group); (3) received no additional treatment (Mn-no treatment group); (4) simultaneously fed with Mn and resveratrol (Mn?+?resveratrol group). In addition, a control (5) with no treatment and another group (6) fed only with resveratrol after emerging from the pupa were included. All Mn-treated flies (group 1) were dead on the 25th day. The life span in the resveratrol group was 91?±?0.33 days (mean?±?S.E.M.) and in Mn-resveratrol flies was 83?±?2 days. These two values were significantly higher than those detected in the control (5) and Mn-no treatment (group 3) flies whose life span were 68?±?0.33 and 67?±?2.31 days, respectively. The Mn?+?resveratrol-fed flies had a markedly higher life span (31?±?1.53 days) than Mn-fed flies (23?±?0.88 days). In the flies that received Mn (Mn and Mn?+?resveratrol groups), the motor activity decreased significantly with respect to control (groups 5) and the Mn–resveratrol and resveratrol groups. In conclusion, resveratrol increased significantly the life span of Mn-treated D. melanogaster.     

Tracking the evolution of waste recycling research using overlay maps of science

Tracking the evolution of research in waste recycling science (WRS) can be valuable for environmental agencies, as well as for recycling businesses. Maps of science are visual, easily readable representations of the cognitive structure of a branch of science, a particular area of research or the global spectrum of scientific production. They are generally built upon evidence collected from reliable sources of information, such as patent and scientific publication databases. This study uses the methodology developed by Rafols et al. (2010) to make a "double overlay map" of WRS upon a basemap reflecting the cognitive structure of all journal-published science, for the years 2005 and 2010. The analysis has taken into account the cognitive areas where WRS articles are published and the areas from where it takes its intellectual nourishing, paying special attention to the growing trends of the key areas. Interpretation of results lead to the conclusion that extraction of energy from waste will probably be an important research topic in the future, along with developments in general chemistry and chemical engineering oriented to the recovery of valuable materials from waste. Agricultural and material sciences, together with the combined economics, politics and geography field, are areas with which WRS shows a relevant and ever increasing cognitive relationship.     

A qualitative analysis of the stability of the root-microorganism soil system II. Combined effect of several factors

This is the second part of a study aimed at achieving some qualitative understanding of the stability properties of the root-microorganism soil system. The first part concentrated on the effect on this stability of different patterns of either nitrogen- or energy-limiting conditions. To this end, a mathematical model has been developed. The model, the theory and some results of the first part are extended here to more complex situations.A factor is first defined to measure the likelihood of the danger of extinction of the roots. It is found that this danger is increased with increasing specific mortality rates, decreasing nitrogen input and/or increasing periods of time during which decomposers are nitrogen-limited. It is also found that the danger of extinction is not directly proportional to absolute nitrogen losses from the system. Some possible explanations in terms of compensatory mechanisms of the roots are discussed.     

Vent Sizing Criteria for Partial Volume Deflagration

The accidental spill of volatile solvents or the release of flammable gases within equipment and buildings is likely to form fuel concentration gradients unless efficient mixing is provided. As a consequence, even small amounts of fuel can form flammable clouds, and partial volume deflagrations may occur. Nevertheless, few indications are given in international guidelines for vent sizing and only over-conservative well-mixed stoichiometric assumptions are used. In this paper, we propose a predictive methodology for the evaluation of the dynamics of partial volume deflagration, aiming at defining useful correlations for the design of vent devices, starting from the fundamental equation for the rate of pressure rise and flame propagation in closed vessel. We define a ‘stratified gas deflagration index’ K_G(m), where m is the filling ratio, and use it with the most common design equations for vent sizing. The approach has been validated by means of a CFD code for the simulation of stratified laminar methane–air explosion by varying both filling ratio and volume.     

Pollinator diversity increases fruit production in Mexican coffee plantations: The importance of rustic management systems

Pollination is an ecological process that provides important services to humans. Pollination service in agroecosystems depends on several factors, including the land management systems used by farmers. Here we focused on the effects of insect pollinator diversity on coffee fruit production along a gradient of management systems in central Veracruz, Mexico. The gradient ranged from low environmental impact management systems (the native forest is not completely removed) to high environmental impact management systems (the native forest is completely removed). We hypothesized that pollinator diversity should be higher in low-impact systems. Then, if fruit production is positively related to pollinator diversity, plantations with low-impact management systems should display higher fruit production than plantations with high-impact management systems. We used observational and experimental data to test this hypothesis. Our results indicated that low-impact management systems have higher species richness and relative diversity (measured with the Shannon-Wiener diversity index) of pollinators than high-impact management systems. In all cases, fruit production was positively related with species richness and diversity of pollinators. Moreover, fruit production was higher in low-impact than in high-impact management systems. These results suggest that the diversity of insect pollinators can be influenced by the management system applied by farmers, and that such effects may have strong consequences on coffee fruit production.