Microwave‐Assisted Rapid Modification of Zein by Octenyl Succinic Anhydride     

Atanu Biswas  David J. Sessa  John W. Lawton  Sherald H. Gordon  J. L. Willett 《Cereal Chemistry》2005,82(1):1-3

Corn is one of the most important food and industrial crops in the United States. Zein constitutes about half of the endosperm proteins in corn. Potential applications of zein include use in fibers, adhesives, inks, cosmetics, textiles, and chewing gum. Recently, attempts have been made to utilize zein for food coatings and biodegradable materials. The new applications of zein require it to be resistant to water. Thus, we are interested in new routes for chemical modification of zein (Biswas et al, unpublished). 2‐Octenyl succinic anhydride (OSA) is extensively used in modifying food starches. Our objective was to take advantage of OSA hydophobicity, flexibility, and compatibility with nonpolar groups and incorporate OSA onto zein. This OSA‐modified zein would possess the best of both OSA and zein. A zein solution in dimethyl formamide (DMF) was reacted with various levels of OSA to give modified zein. In a microwave reactor, the reactions proceeded tremendously fast and they were over in 5 min. The anhydride group of OSA reacted with the hydroxyl/amine group of zein to form ester/amide of zein. The reaction of OSA‐modified zein was confirmed by proton nuclear magnetic resonance (NMR) and IR spectroscopy. The preliminary evaluation showed that zein and OSA‐modified zein had comparable mechanical properties.  相似文献   

The impact of a hydroelectric dam on Neotropical fish communities: A spatio-temporal analysis of the Trophic Upsurge Hypothesis     

Kieran A. Monaghan  Carlos S. Agostinho  Fernando M. Pelicice  Amadeu M. V. M. Soares 《Ecology of Freshwater Fish》2020,29(2):384-397

We employed the trophic upsurge hypothesis as an analytical framework to describe the response of Neotropical fish communities to terrestrial inundation associated with river damming. Data were collected for the impact assessment of the Peixe Angical Dam, Tocantins River, Brazil. Monthly surveys were conducted at nine sites (seven upstream, two downstream) from 15 months before to 20 months after dam closure and a follow-up survey 60–83 months after closure. Fish responses differed in timing and magnitude across sites. In the new reservoir, populations peaked 8–13 months after flooding, demonstrating increases in richness (84 ± 52%), biomass (329 ± 266%) and abundance (681 ± 348%) with the maxima for richness and abundance tending to precede biomass maxima. Populations of all families increased but were greatest for Engraulidae, Hemiodontidae, Serrasalmidae and Characidae, and lower for the benthic catfish: Sciaenidae, Dorididae, Pimelodidae. Downstream populations peaked 5–12 months after closure or showed consistent decline. Five years after dam-closure richness and abundance were lower compared to predam levels, with populations at all sites demonstrating an ongoing decline. Reservoir creation triggers reproductive recruitment and otherwise pools spatially disparate populations from across the flooded valley. If the rise in richness is largely explained by the increased catchability of species otherwise present prior to flooding, it may be more appropriate to estimate species loss with reference to upsurge data. As peak biomass coincides with declining richness, modelling fisheries production from annually aggregated data may risk overestimating the potential for sustainable harvests. Upsurge–response curves can help identify the timing of critical ecological thresholds for flood-managed fisheries.  相似文献   

Modelling daily catches of silver-phase European eel (Anguilla anguilla) in two hydropower-regulated rivers     

Eamonn S. Lenihan  T. Kieran McCarthy  Colin Lawton 《Fisheries Management and Ecology》2021,28(1):53-64

Estimation of silver eel production, Anguilla anguilla L., is fundamental for the management of eel stocks. In the hydropower-regulated rivers Shannon and Erne, Ireland, production is calculated using catch data from a conservation trap and transport programme. However, in both rivers gaps in silver eel catch datasets tend to occur, which can lead to biases in production estimates. Generalised additive models (GAMs) were used to model daily catch in these rivers based on a variety of environmental variables. Final models for the Shannon and Erne explained 83.7% and 78.8% of deviance in daily catch, respectively. A second model on the Erne included catch from a nearby fishing site in an attempt to increase explanatory power and explained 91.7% of deviance. Although model accuracy was increased, reliance on catch from another site may limit the applicability of the model. Model predictions were combined with estimates of fishing efficiency to predict production for the Shannon (36,210 kg; 0.85 kg/ha) and Erne (66,899–67,047 kg; 2.55–2.56 kg/ha). These values represented a 9.3% and 2.8%–3.0% increase on production estimated from incomplete catch records alone for the Shannon and Erne, respectively.  相似文献   

Optimality in evolution     

Lawton JH 《Science (New York, N.Y.)》1979,204(4389):165-166

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Re: Porcine dermatitis and nephropathy syndrome in New Zealand     

Johnstone AC  Lawton DE 《New Zealand veterinary journal》2008,56(3):150

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OBSERVATIONS ON THE WHEAT STEM FLY WITH SPECIAL REFERENCE TO OVIPOSITION     

R. Lawton 《Plant pathology》1956,5(4):123-127

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Earth system science     

Lawton J 《Science (New York, N.Y.)》2001,292(5524):1965

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Metapopulation dynamics, abundance, and distribution in a microecosystem     

A Gonzalez  JH Lawton  FS Gilbert  TM Blackburn  I Evans-Freke 《Science (New York, N.Y.)》1998,281(5385):2045-2047

The experimental fragmentation of landscapes of a natural ecosystem resulted in declines in the abundance and distribution of most species in the multispecies animal community inhabiting the landscapes and the extinction of many species. These declines caused the deterioration of the positive interspecific relation between local population abundance and distributional extent in this community. However, when patches were connected by habitat corridors, an immigration "rescue effect" arrested declines in both abundance and distribution and maintained the observed positive relation between them. These results demonstrate the importance of metapopulation dynamics and landscape connectivity for the persistence of populations in fragmented landscapes.  相似文献   

Accidental Poisoning by Death Cap Mushrooms: Be Careful What You Eat     

Luke D. Lawton  Sinead Ni Bhraonain 《The Forestry Chronicle》2013,24(2):168-170

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Corn Gluten Meal as a Thermoplastic Resin: Effect of Plasticizers and Water Content     

J. W. Lawton  G. W. Selling  J. L. Willett 《Cereal Chemistry》2008,85(2):102-108

Corn gluten meal (CGM) was studied to investigate the effect plasticizers and water have on its melt processing, and how this melting affects its mechanical properties. GCM containing varying amounts of water were mixed with 23% (w/w) plasticizers; (glycerol, triethylene glycol (TEG), dibutyl tartrate, and octanoic acid in a Haake bowl mixer at 80°C. The amount of water in the CGM affected the amount of torque produced in the Haake mixer. This increase in torque was correlated with how well the CGM melted in the mixer. SEM images of CGM melted in the mixer showed a more uniform homogenous structure when processed at its optimum moisture content. Glycerol, TEG, and dibutyl tartrate produced the greatest torque when the CGM contained <1% water. Octanoic acid produced the greatest torque when the CGM was processed at 8% moisture. CGM plasticized with TEG and octanoic acid were mixed at either their optimum moisture or at 9.6% moisture and then compression molded into tensile bars. The tensile strengths of the bars that were mixed at their optimum moisture content were significantly greater than the bars mixed at 9.6% moisture. The tensile properties of the CGM samples were affected by relative humidity (rh). The tensile strength decreased and elongation increased as relative humidity increased. CGM plasticized with TEG saw a greater changes in its tensile properties due to relative humidity than did octanoic acid plasticized CGM.  相似文献