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Frank Welle - One of the best experts on this subject based on the ideXlab platform.
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Migration measurement and modelling from poly ethylene terephthalate pet into soft drinks and fruit juices in comparison with food simulants
Food Additives and Contaminants Part A-chemistry Analysis Control Exposure & Risk Assessment, 2008Co-Authors: Roland Franz, Frank WelleAbstract:Poly(ethylene terephthalate) (PET) bottles are widely used for beverages. Knowledge about the Migration of organic compounds from the PET bottle wall into contact media is of interest especially when post-consumer recyclates are introduced into new PET bottles. Using Migration Theory, the Migration of a compound can be calculated if the concentration in the bottle wall is known. On the other hand, for any given specific Migration limit or maximum target concentration for organic chemical compounds in the bottled foodstuffs, the maximum allowable concentrations in the polymer C P,0 can be calculated. Since a food simulant cannot exactly simulate the real Migration into the foodstuff or beverages, a worse-case simulation behaviour is the intention. However, if the Migration calculation should not be too overestimative, the polymer-specific kinetic parameter for Migration modelling, the so-called A P value, should be established appropriately. One objective of the study was the kinetic determination of the s...
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Migration measurement and modelling from poly ethylene terephthalate pet into soft drinks and fruit juices in comparison with food simulants
Food Additives and Contaminants Part A-chemistry Analysis Control Exposure & Risk Assessment, 2008Co-Authors: Roland Franz, Frank WelleAbstract:Poly(ethylene terephthalate) (PET) bottles are widely used for beverages. Knowledge about the Migration of organic compounds from the PET bottle wall into contact media is of interest especially when post-consumer recyclates are introduced into new PET bottles. Using Migration Theory, the Migration of a compound can be calculated if the concentration in the bottle wall is known. On the other hand, for any given specific Migration limit or maximum target concentration for organic chemical compounds in the bottled foodstuffs, the maximum allowable concentrations in the polymer CP,0 can be calculated. Since a food simulant cannot exactly simulate the real Migration into the foodstuff or beverages, a worse-case simulation behaviour is the intention. However, if the Migration calculation should not be too overestimative, the polymer-specific kinetic parameter for Migration modelling, the so-called AP value, should be established appropriately. One objective of the study was the kinetic determination of the specific Migration behaviour of low molecular weight compounds such as solvents with relatively high diffusion rates and, therefore, with high Migration potential from the PET bottle wall into food simulants in comparison with real beverages. For this purpose, model contaminants were introduced into the bottle wall during pre-form production. The volatile compounds toluene and chlorobenzene were established at concentrations from about 20-30 mg kg(-1) to 300-350 mg kg(-1). Phenyl cyclohexane was present at concentrations of 35, 262 and 782 mg kg(-1), respectively. The low volatile compounds benzophenone and methyl stearate have bottle wall concentrations of about 100 mg kg(-1) in the low spiking level up to about 1000 mg kg(-1) in the highly spiked test bottle. From these experimental data, the polymer specific parameters (AP values) from mathematical Migration modelling were derived. The experimental determined diffusing coefficients were determined, calculated and compared with literature data and an AP' value of 1.0 was derived thereof for non-swelling food simulants like 3% acetic acid, 10% ethanol or iso-octane. For more swelling condition, e.g. 95% ethanol as food simulant, an AP' value of 3.1 seems to be suitable for Migration calculation. In relation to PET recycling safety aspects, maximum concentrations in the bottle wall were established for migrants/contaminants with different molecular weights, which correspond with a Migration limit of 10 microg kg(-1). From the experimental data obtained using food simulants and in comparison with beverages, the most appropriate food simulant for PET packed foods with a sufficient but not too overestimative worse-case character was found to be 50% ethanol. In addition, it can be shown that mass transport from PET is generally controlled by the very low diffusion in the polymer and, as a consequence, partitioning coefficients (KP/F values) of migrants between the polymer material and the foodstuff do not influence the Migration levels significantly. An important consequence is that Migration levels from PET food-contact materials are largely independent from the nature of the packed food, which on the other hand simplifies exposure estimations from PET.
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determination of the Migration of acetaldehyde from pet bottles into non carbonated and carbonated mineral water
Deutsche Lebensmittel-rundschau, 2008Co-Authors: Johann Ewender, Frank WelleAbstract:The market for PET bottles for mineral water packaging is still increasing. On packaging materials very exacting levels on neutrality of odour and taste are required. In view of PET bottles the Migration of acetaldehyde from the bottle wall into the mineral water is of special interest, due to the fact that acetaldehyde is noticeable in low concentrations in mineral water. Aim of this study was to monitor the acetaldehyde Migration at room temperature from various commercially available PET bottles into carbonated and non-carbonated mineral water. In addition the correlation between room temperature storage and a short-term test suitable for routine testing (e.g. 10 d at 40°C) should be established. Within the study the acetaldehyde concentration curves of eleven PET-bottles and mineral water combinations were determined at 23 °C. Seven bottle/mineral water combinations fit in the Migration laws similar to other organic compounds occurring in packaging materials. All these test bottles are filled with carbonated mineral water. For six bottles the diffusion coefficient of acetaldehyde in PET at 23 °C can be calculated from the experimental results to be in the range of 1.6 to 6.7 10 -12 cm 2 s -1 . One sample has a significantly lower diffusion coefficient of 3.6 10 -13 cm 2 s -1 . The other investigated samples, which are in most cases non-carbonated mineral water samples, show lower acetaldehyde concentrations in mineral water as expected by Migration Theory. In these cases most probably the acetaldehyde concentration in mineral water is influenced by additional factors. The correlation between long-term Migration (23 °C) and short-term test (10 d at 40 °C) was found to be not very good. Therefore the results of the short-term tests give only an orientation about the Migration behaviour of the investigated PET bottles in comparison to other bottle/mineral water combinations. On the other hand if the correlation is established using the same bottle/mineral water combination short-term tests are most probably appropriate for production control. In the case of refillable bottles pre-storage of empty PET bottles before filling has a positive influence on the concentration of acetaldehyde in mineral water.
Paul L Stutzman - One of the best experts on this subject based on the ideXlab platform.
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utilization of subsurface food resources for zooplankton reproduction implications for diel vertical Migration Theory
Limnology and Oceanography, 1996Co-Authors: Craig E Williamson, Robert W Sanders, Robert E Moeller, Paul L StutzmanAbstract:The water columns of lakes and oceans provide a diverse habitat gradient in which light, temperature, food, and predation risk all change with depth. Many planktonic organisms exhibit diel vertical Migrations (DVM) in response to daily oscillations in many of these variables. DVM Theory often assumes that surface waters are more food-rich than deeper, subsurface layers and proceeds to try to explain why zooplankton migrate out of these beneficial surface layers during the day. Here, we test the assumption that food is best in surface waters by feeding two common crustacean zooplankton with natural epilimnetic and metalimnetic food assemblages from a eutrophic lake and examining their egg production rates. Both Diaptomus and Daphnia showed greater reproductive rates in the metalimnetic water and significant food limitation in the epilimnetic water. Mass-specific ingestion rates were approximately three times higher in the metalimnion than in the epilimnion. In spite of the poorer food in the surface waters, these two crustaceans migrated into the epilimnion at night. These observations are contrary to the assumption that food is best in the surface water, and a review of the literature suggests that food frequently is not best in surface waters. The upward Migrations at night are best explained by the warmer temperatures and reduced predation risk in the surface waters at night.
Yuchen Chen - One of the best experts on this subject based on the ideXlab platform.
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migrating to a new virtual world exploring mmorpg switching through human Migration Theory
Computers in Human Behavior, 2011Co-Authors: Avus C Y Hou, Chingchin Chern, Houngee Chen, Yuchen ChenAbstract:Online gaming has become a popular leisure-time activity. In this study, we enlisted and adapted the Push-Pull-Mooring model, which analyzes human migratory behavior based on the Demographic Migration Theory, to study the game switching of gamers. Data was obtained via an empirical survey of 654 online gamers and then was analyzed using the Structural Equation Modeling (SEM) technique. The results indicate that the Push-Pull-Mooring model can be extended to explain the switching intentions of online gamers. The ''mooring effect'' appears to have a stronger influence on the player's switching intention than the ''pull effect'', while the ''push effect'' appears to have no influence at all. We discuss the implications of our findings and offer possible avenues of exploration for managers of online game providers in order to help them understand their customers better.
Steve Kelling - One of the best experts on this subject based on the ideXlab platform.
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Migration timing and its determinants for nocturnal migratory birds during autumn Migration
Journal of Animal Ecology, 2015Co-Authors: Frank A La Sorte, Daniel Fink, Wesley M Hochachka, Andrew Farnsworth, Daniel Sheldon, Jeffrey Geevarghese, Kevin Winner, Benjamin M Van Doren, Steve KellingAbstract:1. Migration is a common strategy used by birds that breed in seasonal environments, and multiple environmental and biological factors determine the timing of Migration. How these factors operate in combination during autumn Migration, which is considered to be under weaker time constraints relative to spring Migration, is not clear. 2. Here, we examine the patterns and determinants of Migration timing for nocturnal migrants during autumn Migration in the north-eastern USA using nocturnal reflectivity data from 12 weather surveillance radar stations and modelled diurnal probability of occurrence for 142 species of nocturnal migrants. We first model the capacity of seasonal atmospheric conditions (wind and precipitation) and ecological productivity (vegetation greenness) to predict autumn Migration intensity. We then test predictions, formulated under optimal Migration Theory, on how Migration timing should be related to assemblage-level estimates of body size and total Migration distance within the context of dietary guild (insectivore and omnivore) and level of dietary plasticity during autumn Migration. 3. Our results indicate seasonal declines in ecological productivity delineate the beginning and end of peak Migration, whose intensity is best predicted by the velocity of winds at Migration altitudes. Insectivorous migrants departed earlier in the season and, consistent with our predictions, large-bodied and long-distance insectivorous migrants departed the earliest. Contrary to our predictions, large-bodied and some long-distance omnivorous migrants departed later in the season, patterns that were replicated in part by insectivorous migrants that displayed dietary plasticity during autumn Migration. 4. Our findings indicate Migration timing in the region is dictated by optimality strategies, modified based on the breadth and flexibility of migrant's foraging diets, with declining ecological productivity defining possible resource thresholds during which Migration occurs when winds at Migration altitudes are mild. These observations provide the basis to assess how avian Migration strategies may be affected by adjustments in seasonal patterns of atmospheric circulation and ecological productivity that may occur under global climate change.
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population level scaling of avian Migration speed with body size and Migration distance for powered fliers
Ecology, 2013Co-Authors: Frank A La Sorte, Daniel Fink, Wesley M Hochachka, John P Delong, Steve KellingAbstract:Optimal Migration Theory suggests specific scaling relationships between body size and Migration speed for individual birds based on the minimization of time, energy, and risk. Here we test if the quantitative predictions originating from this Theory can be detected when Migration decisions are integrated across individuals. We estimated population-level Migration trajectories and daily Migration speeds for the combined period 2007-2011 using the eBird data set. We considered 102 North American bird species that use flapping or powered flight during Migration. Many species, especially in eastern North America, had looped Migration trajectories that traced a clockwise path with an eastward shift during autumn Migration. Population-level Migration speeds decelerated rapidly going into the breeding season, and accelerated more slowly during the transition to autumn Migration. In accordance with time minimization predictions, spring Migration speeds were faster than autumn Migration speeds. In agreement with optimality predictions, Migration speeds of powered flyers scaled negatively with body mass similarly during spring and autumn Migration. Powered fliers with longer Migration journeys also had faster Migration speeds, a relationship that was more pronounced during spring Migration. Our findings indicate that powered fliers employed a Migration strategy that, when examined at the population level, was in compliance with optimality predictions. These results suggest that the integration of Migration decisions across individuals does result in population-level patterns that agree with theoretical expectations developed at the individual level, indicating a role for optimal Migration Theory in describing the mechanisms underlying broadscale patterns of avian Migration for species that use powered flight.
Martin Wikelski - One of the best experts on this subject based on the ideXlab platform.
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towards a new understanding of Migration timing slower spring than autumn Migration in geese reflects different decision rules for stopover use and departure
Oikos, 2016Co-Authors: Andrea Kolzsch, Gerhard J D M Muskens, Helmut Kruckenberg, Peter Glazov, Rolf Weinzierl, Bart A Nolet, Martin WikelskiAbstract:According to Migration Theory and several empirical studies, long-distance migrants are more time-limited during spring Migration and should therefore migrate faster in spring than in autumn. Competition for the best breeding sites is supposed to be the main driver, but timing of Migration is often also influenced by environmental factors such as food availability and wind conditions. Using GPS tags, we tracked 65 greater white-fronted geese Anser albifrons migrating between western Europe and the Russian Arctic during spring and autumn Migration over six different years. Contrary to Theory, our birds took considerably longer for spring Migration (83 days) than autumn Migration (42 days). This difference in duration was mainly determined by time spent at stopovers. Timing and space use during Migration suggest that the birds were using different strategies in the two seasons: In spring they spread out in a wide front to acquire extra energy stores in many successive stopover sites (to fuel capital breeding), which is in accordance with previous results that white-fronted geese follow the green wave of spring growth. In autumn they filled up their stores close to the breeding grounds and waited for supportive wind conditions to quickly move to their wintering grounds. Selection for supportive winds was stronger in autumn, when general wind conditions were less favourable than in spring, leading to similar flight speeds in the two seasons. In combination with less stopover time in autumn this led to faster autumn than spring Migration. White-fronted geese thus differ from Theory that spring Migration is faster than autumn Migration. We expect our findings of different decision rules between the two migratory seasons to apply more generally, in particular in large birds in which capital breeding is common, and in birds that meet other environmental conditions along their Migration route in autumn than in spring.