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排序方式: 共有193条查询结果,搜索用时 15 毫秒
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Frans E. Pick Pieter R. De Beer Susan M. Prinsloo Louis P. Van Dyk 《Pest management science》1987,21(1):45-49
High-pressure liquid chromatography with an ion-exchange column combined with graphite furnace atomic absorption spectrometry was used to analyse commercial formulations of sodium hydrogen methylarsonate (MSMA). No arsenite or arsenate salts or dimethylarsinic acid were detected as contaminants in the formulations, and the MSMA concentrations were found to be in accordance with the concentrations given on the containers. 相似文献
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Dana M. Calhoun Paula A. Schaffer Jacklyn R. Gregory Katherine M. Hardy Pieter T. J. Johnson 《Journal of aquatic animal health》2015,27(4):185-191
Infections by the digenetic trematode, Ribeiroia ondatrae, cause severe limb malformations in many North American amphibians. Ribeiroia ondatrae also infects fishes as second intermediate hosts, but less is known about the pathology and immune responses initiated in infected fish, even though reports of infected fish date back to early 1900s. To this end, we experimentally exposed juvenile Bluegills Lepomis macrochirus to three doses of R. ondatrae cercariae and monitored the pathology, parasite infection success, and humoral responses over 648 h. All exposed fish became infected with metacercariae, and the average infection load increased with exposure dose. Histologically, infection was associated with acute hemorrhages in the lateral line and local dermis at 36 h, followed by progressive granulomatous inflammation that led to the destruction of encysted metacercariae. Correspondingly, over the course of 648 h we observed an 85% decline in average infection load among hosts, reflecting the host's clearance of the parasite. Infection was not associated with changes in fish growth or survival, but did correlate with leukocytosis and neutrophilia in circulating host blood. Understanding the physiological responses of R. ondatrae in Bluegill will help to clarify the ecological effects of this parasite and provide a foundation for subsequent comparisons into its effects on behavior, individual health, and population dynamics of Bluegill.
Received March 4, 2015; accepted August 9, 2015 相似文献
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A selection program in three tropical maize populations aimed to improve tolerance of mid-season to late season drought environments
while maintaining grain yield (GY) potential. The selection process employed other attributes that included maintaining a
constant anthesis date (AD) and, under drought, shortening the anthesis-silking interval (ASI) and increasing ear number per
plant (EPP). Three-mode (genotypes × environments × attributes) pattern analysis, which consists of clustering and ordination,
should be able to collectively interpret these changes from ten evaluation trials. Mixture maximum likelihood clustering identified
four groups that indicated the populations' performance had changed with selection. Groups containing the advanced cycles
of selection were higher yielding in most environments and had lower ASI and higher EPP, particularly in drought environments.
Check entries with no selection for drought tolerance remained grouped with the initial cycles of selection. A 3 × 2 × 3 (genotypes
by environments by attributes) principal component model explained 70% of the variation. For the first environmental component,
ASI was shown to be highly negatively correlated with both GY and EPP while anthesis date (AD) was virtually uncorrelated
with other traits. The second environmental component (explaining 10% of the variation) contrasted droughted and well-watered
environments and showed that EPP and GY were better indicators of this contrast (in terms of changes in population performance)
than were AD or ASI. Three-mode analysis demonstrated that improvements with selection occurred in both droughted and well-watered
environments and clearly summarised the overall success of the breeding program.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
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van Koningsveld GA Walstra P Gruppen H Wijngaards G van Boekel MA Voragen AG 《Journal of agricultural and food chemistry》2002,50(26):7651-7659
In the present study, foam-forming and -stabilizing properties of potato proteins were studied using whipping and sparging tests. The soluble potato proteins are mainly composed of patatin and protease inhibitors. The whipping tests showed that less foam was formed from untreated patatin than from the protease inhibitors, but patatin foam was much more stable. The foam-forming properties of patatin could be strongly improved by partial unfolding of the protein. Whipping tests, at both low (0.5 mg/mL) and high (10 mg/mL) protein concentration, also indicated that foams made with an ethanol-precipitated protein isolate were more stable than those made with beta-casein and beta-lactoglobulin. More generally, it can be concluded that when proteins are used as a foaming agent, a high concentration is required, because the protein available is inefficiently used. Also, there are several variables that may all, in different ways, affect both foam formation (amount of foam, bubbles size distribution) and foam stability. These variables include the type and concentration of protein, solvent conditions (pH, I), and the method used to make the foam. 相似文献
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Ekstrom LB Roelfsema PR Arsenault JT Bonmassar G Vanduffel W 《Science (New York, N.Y.)》2008,321(5887):414-417
The frontal eye field (FEF) is one of several cortical regions thought to modulate sensory inputs. Moreover, several hypotheses suggest that the FEF can only modulate early visual areas in the presence of a visual stimulus. To test for bottom-up gating of frontal signals, we microstimulated subregions in the FEF of two monkeys and measured the effects throughout the brain with functional magnetic resonance imaging. The activity of higher-order visual areas was strongly modulated by FEF stimulation, independent of visual stimulation. In contrast, FEF stimulation induced a topographically specific pattern of enhancement and suppression in early visual areas, but only in the presence of a visual stimulus. Modulation strength depended on stimulus contrast and on the presence of distractors. We conclude that bottom-up activation is needed to enable top-down modulation of early visual cortex and that stimulus saliency determines the strength of this modulation. 相似文献
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Chien M Morozova I Shi S Sheng H Chen J Gomez SM Asamani G Hill K Nuara J Feder M Rineer J Greenberg JJ Steshenko V Park SH Zhao B Teplitskaya E Edwards JR Pampou S Georghiou A Chou IC Iannuccilli W Ulz ME Kim DH Geringer-Sameth A Goldsberry C Morozov P Fischer SG Segal G Qu X Rzhetsky A Zhang P Cayanis E De Jong PJ Ju J Kalachikov S Shuman HA Russo JJ 《Science (New York, N.Y.)》2004,305(5692):1966-1968
We present the genomic sequence of Legionella pneumophila, the bacterial agent of Legionnaires' disease, a potentially fatal pneumonia acquired from aerosolized contaminated fresh water. The genome includes a 45-kilobase pair element that can exist in chromosomal and episomal forms, selective expansions of important gene families, genes for unexpected metabolic pathways, and previously unknown candidate virulence determinants. We highlight the genes that may account for Legionella's ability to survive in protozoa, mammalian macrophages, and inhospitable environmental niches and that may define new therapeutic targets. 相似文献