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451.
Christopher R. Schwalm T. Andrew Black Brian D. Amiro M. Altaf Arain Alan G. Barr Charles P.-A. Bourque Allison L. Dunn Larry B. Flanagan Marc-Andr Giasson Peter M. Lafleur Hank A. Margolis J. Harry McCaughey Alberto L. Orchansky Steve C. Wofsy 《Agricultural and Forest Meteorology》2006,140(1-4):269
Light use efficiency (LUE) is used widely in scaling and modeling contexts. However, the variation and biophysical controls on LUE remain poorly documented. Networks of eddy covariance (EC) towers offer an opportunity to quantify g, the ratio of P, gross primary productivity, to Qa, absorbed photosynthetically active radiation (PAR), across climate zones and vegetation types. Using data from the Fluxnet Canada Research Network (n = 24 sites) in 2004, we examined the relationship between daily and yearly g, driving variables, and site characteristics on a site-specific and plant functional type (PFT) basis using tree regression and linear regression. Data were available for three biomes: grassland, forest, and wetland. Yearly g values ranged from 0.1 to 3.6 g C MJ−1 Qa overall. Daily g was highest in the grassland (daily median ± interquartile range: 3.68 ± 1.98 g C MJ−1 Qa), intermediate in the forested biome (0.84 ± 0.82 g C MJ−1 Qa), and lowest for the wetlands (0.65 ± 0.54 g C MJ−1 Qa). The most important biophysical controls were light and temperature, to the exclusion of water-related variables: a homogeneity of slopes model explained c. 75% of the variation in daily g. For a subset of sites with diffuse PAR data, the ratio of diffuse to total PAR, a proxy for cloudiness, was a key predictor. On the yearly time scale, g was related to leaf area index and mean annual temperature. Aggregating to PFTs did not show functional convergence within any PFT except for the three wetland sites and the Picea mariana toposequence at the daily time step, and when using the Köppen climate classification on a yearly time step. The general lack of conservative daily g behavior within PFTs suggests that PFT-based parameterizations are inappropriate, especially when applied on shorter temporal scales. 相似文献
452.
van Koningsveld GA Walstra P Voragen AG Kuijpers IJ van Boekel MA Gruppen H 《Journal of agricultural and food chemistry》2006,54(17):6419-6427
In the present study emulsions were made with various potato protein preparations, which varied in protease inhibitor and patatin content. These emulsions were characterized with respect to average droplet size, plateau surface excess, and the occurrence of droplet aggregation. Droplet aggregation occurred only with potato protein preparations that contained a substantial amount of protease inhibitors and could be prevented only at pH 3. The average droplet size of the emulsions made with potato proteins appeared to be related to the patatin content of the preparation used. Average droplet size was found to be dominated by the patatin-catalyzed lipolytic release of surface active fatty acids and monoglycerides from the tricaprylin oil phase during the emulsification process. Addition of monoglycerides and especially fatty acids, at concentrations representative of those during emulsification, was shown to cause a stronger and much faster decrease of the interfacial tension than that with protein alone and to result in a drastic decrease in droplet size. The patatin used was shown to have a lipolytic activity of 820 units/g with emulsified tricaprylin as the substrate. Because of the droplet aggregating properties of the protease inhibitors, the patatin-rich potato preparations seem to be the most promising for food emulsion applications over a broad pH range, provided the lipolytic activity can be diminished or circumvented. 相似文献
453.
van Boxtel EL van Beers MM Koppelman SJ van den Broek LA Gruppen H 《Journal of agricultural and food chemistry》2006,54(19):7180-7186
Ara h 1, a major peanut allergen, is known as a stable trimeric protein. Nevertheless, upon purification of native Ara h 1 from peanuts using only size exclusion chromatography, the allergen appeared to exist in an oligomeric structure, rather than as a trimeric structure. The oligomeric structure was independent of the salt concentration applied. Subjecting the allergen to anion exchange chromatography induced the allergen to dissociate into trimers. Ammonium sulfate precipitation did not bring about any structural changes, whereas exposing the allergen to hydrophobic interaction chromatography caused it to partly dissociate into trimers, with increasing amounts of trimers at higher ionic strengths. The (partial) dissociation into trimers led to a change in the tertiary structure of the monomeric subunits of the allergen, with the monomers in Ara h 1 oligomers having a more compact tertiary structure compared with the monomers in Ara h 1 trimers. As structural characteristics are important for a protein's allergenicity, this finding may imply a different allergenicity for Ara h 1 than previously described. 相似文献
454.
Hamilton SR Davidson RC Sethuraman N Nett JH Jiang Y Rios S Bobrowicz P Stadheim TA Li H Choi BK Hopkins D Wischnewski H Roser J Mitchell T Strawbridge RR Hoopes J Wildt S Gerngross TU 《Science (New York, N.Y.)》2006,313(5792):1441-1443
Yeast is a widely used recombinant protein expression system. We expanded its utility by engineering the yeast Pichia pastoris to secrete human glycoproteins with fully complex terminally sialylated N-glycans. After the knockout of four genes to eliminate yeast-specific glycosylation, we introduced 14 heterologous genes, allowing us to replicate the sequential steps of human glycosylation. The reported cell lines produce complex glycoproteins with greater than 90% terminal sialylation. Finally, to demonstrate the utility of these yeast strains, functional recombinant erythropoietin was produced. 相似文献
455.
Habashi JP Judge DP Holm TM Cohn RD Loeys BL Cooper TK Myers L Klein EC Liu G Calvi C Podowski M Neptune ER Halushka MK Bedja D Gabrielson K Rifkin DB Carta L Ramirez F Huso DL Dietz HC 《Science (New York, N.Y.)》2006,312(5770):117-121
Aortic aneurysm and dissection are manifestations of Marfan syndrome (MFS), a disorder caused by mutations in the gene that encodes fibrillin-1. Selected manifestations of MFS reflect excessive signaling by the transforming growth factor-beta (TGF-beta) family of cytokines. We show that aortic aneurysm in a mouse model of MFS is associated with increased TGF-beta signaling and can be prevented by TGF-beta antagonists such as TGF-beta-neutralizing antibody or the angiotensin II type 1 receptor (AT1) blocker, losartan. AT1 antagonism also partially reversed noncardiovascular manifestations of MFS, including impaired alveolar septation. These data suggest that losartan, a drug already in clinical use for hypertension, merits investigation as a therapeutic strategy for patients with MFS and has the potential to prevent the major life-threatening manifestation of this disorder. 相似文献
456.
Jean-Marc Blazy Philippe Tixier Harry Ozier-Lafontaine Jacques Wery 《Agricultural Systems》2010,103(4):221-232
The ex ante assessment of innovative agro-ecological innovations is a key step in the development of more sustainable crop management systems. To this end, models are useful tools because they make it possible to rapidly assess numerous innovations in different contexts. Whereas many farm optimisation models focusing on the farmer’s strategic decision to adopt new crop management systems have been published, little attention has been given to the ex ante modelling of the dynamic operational impacts of innovation adoption at the farm level. BANAD, a mechanistic model for such applications, is proposed. It allows the ex ante assessment of innovative management systems including new agro-ecological techniques, while taking into account different farming contexts and policy and market conditions. It includes three components: (i) a crop management system model, (ii) a crop model (SIMBA) and (iii) a farming system model. Our results applied to the ex ante assessment of six innovative banana management systems for three contrasted farm types in Guadeloupe showed that the impacts of agro-ecological innovations, which include rotations, improved fallow, intercropping, pest-resistant cultivar, and an integrated organic system, can vary considerably according to (i) the farm type in which the innovation is integrated, (ii) the nature of the agro-ecological innovations, and (iii) the criteria considered and the temporal horizon of the assessment. Innovative intercropping systems that were effective at the field level in terms of the yield improvement and decreased pesticide use could be problematic at the farm level because they increased the workload and decreased income. The adoption of rotations or improved fallow seemed to be relevant for smallholders but could induce a critical period of 1.5-2.5 years during which income decreased drastically. Under certain conditions of markets and subsidies, very environmentally friendly innovations that are less productive can however be economically effective. 相似文献
457.
458.
Michael Grey Ian Forster Warren Dominy Harry Ako Andrew F. Giesen 《Journal of the World Aquaculture Society》2009,40(4):547-555
A protocol for testing feeding stimulants on Pacific white shrimp, Litopenaeus vannamei, is described. Thirty‐five rectangular tanks (55 L volume) served as the test system into which ten 5–6 g shrimp were stocked. Every tank contained two bowls, each of which contained either 25 feed pellets of a Reference Diet or Test Diet (consisting of the Reference Diet with one test ingredient added). After 1 h, the difference between the number of pellets consumed of the Test Diet and the Reference Diet was used as the Response. Each of the four Test Diets contained a different salmon hydrolysate made from by‐products of the Alaska fish processing industry (included at 50 g/kg). A fifth commercial shrimp diet was also tested. Each Test Diet was tested against the Reference Diet over a 4‐d period in seven replicate tanks. The data were subjected to a one‐way ANOVA and a confidence interval for each treatment response was calculated. The confidence interval was used to assess the test ingredient as a feeding stimulant. Treatment means were compared using Tukey's test (α = 5%). All the hydrolysates tested were found to act as feeding stimulants. 相似文献