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排序方式: 共有675条查询结果,搜索用时 15 毫秒
61.
Anderson WA Amasino RM Ares M Banerjee U Bartel B Corces VG Drennan CL Elgin SC Epstein IR Fanning E Guillette LJ Handelsman J Hatfull GF Hoy RR Kelley D Leinwand LA Losick R Lu Y Lynn DG Neuhauser C O'Dowd DK Olivera T Pevzner P Richards-Kortum RR Rine J Sah RL Strobel SA Walker GC Walt DR Warner IM Wessler S Willard HF Zare RN 《Science (New York, N.Y.)》2011,334(6057):760-761
62.
63.
K. Marie McIntyre Victor J. Del Rio Vilas Simon Gubbins 《Veterinary journal (London, England : 1997)》2011,187(2):207-211
Several surveillance techniques have been used to quantify the prevalence of both classical and atypical scrapie in British sheep, namely the recording of clinical suspects (RC) and the testing of animals slaughtered at abattoir (AS) or reported as fallen stock (FS). Any estimate of prevalence based on a particular source is likely to have been affected by demographic differences in the populations sampled. In this study, the demographic characteristics of scrapie-affected holdings detected by each of the surveillance streams (RC, AS, FS) in Great Britain were compared. Analyses of all three streams indicated that the probability of an affected holding being detected by a particular stream differed by geographical area, the number of animals brought onto the holding, the type of scrapie identified (classical vs. atypical) and the year. More detailed analysis of AS and FS suggested that the annual and regional differences between these surveys could be explained by differences in sampling effort. 相似文献
64.
Ruiz-de-Casta?eda R Vela AI Lobato E Briones V Moreno J 《Journal of zoo and wildlife medicine》2011,42(2):313-316
Salmonella and Yersinia are important enteropathogens in poultry and can affect birds of all ages, including embryos. These food-borne zoonotic enteropathogens are of great economic and medical concern worldwide and are intensely studied in poultry. Information regarding the prevalence of these bacteria in wild birds is scarce and biased toward avian species ecologically linked to humans, which have often been incriminated as both reservoirs and disseminators of these enteropathogens. The prevalence of Salmonella and Yersinia recovered from both the feces and eggs in a population of female pied flycatchers (Ficedula hypoleuca) breeding in nest-boxes in central Spain was evaluated. Salmonella arizonae was recovered from the feces of one female but was not recovered from eggs. Yersinia was not detected in either the feces or eggs. These results may suggest that Salmonella and Yersinia may be uncommon in this population studied and may indicate that these birds are unlikely reservoirs of Salmonella and Yersinia. 相似文献
65.
BACKGROUND: Two‐spotted spider mites (Tetranychus urticae Koch) oviposit near leaf veins or in leaf folds on the undersides of cotton (Gossypium hirsutum L.) leaves where the humid boundary layer offers protection from desiccation. The authors predicted that the boundary layer of glabrous cotton leaves should be shallower than that of hairy leaves, providing some resistance to mites. The dynamics of mite populations, leaf damage, leaf gas exchange and crop yield on two leaf hair isolines (smooth versus hairy) in two genetic backgrounds was assessed. RESULTS: Mite colonies developed faster on the hairy leaf isolines, but leaf damage per mite was higher in smooth leaf isolines, indicating more intense damage. A 50% reduction in photosynthesis on the hairy isolines required 1.8 times more mites than smooth leaves. The yield of cotton was reduced in + mite treatments, but the magnitude of reduction was similar for hairy and smooth isolines. CONCLUSION: Paradoxically, the relative inhospitality of glabrous leaves may have induced mites to concentrate in protected leaf sections, causing more localised and more severe damage, negating the yield benefits from fewer mites. These results highlight interactions between leaf microenvironment, pest behaviour and plant productivity that may have implications for other instances of plant resistance. Copyright © 2010 Society of Chemical Industry 相似文献
66.
Victor I. Okereke E. Robert Baumann T. Al Austin Donna Schulze Lutz 《Water, air, and soil pollution》1988,37(3-4):325-341
The impact of a flood control, low flow argumentation reservoir in the Midwestern part of the United States on BOD, COD, and ammonia was evaluated in this paper. Fifteen years of weekly water quality data (9 yr before impoundment and 6 yr after impoundment) from four sampling stations upstream and downstream of the reservoir were available for analysis. The annual loading rates of these parameters (kg ha?1 vr?1) were found to correlate well with annual runoff (cm yr?1). Besides, the reservoir was found to have had a significant and beneficial impact on the downstream loading rates of BOD and COD, which were reduced by 55 and 75%, respectively. As for ammonia, the results of this study indicate that its annual loadings at downstream locations were not significantly affected by the reservoir. Average non-point source contributions of BOD and ammonia loadings into the system were found to be about 80 and 55%, respectively. 相似文献
67.
68.
Intergeneric relationships in the Australian Vitaceae: new evidence from cpDNA analysis 总被引:1,自引:0,他引:1
Maurizio Rossetto Betsy R. Jackes Kirsten D. Scott Robert J. Henry 《Genetic Resources and Crop Evolution》2001,48(3):307-314
Taxa related to important agricultural species are likely to contain a considerable amount of potentially valuable genetic diversity. Nevertheless, before breeding programs or gene discovery projects can be initiated it is important to understand the phylogenetic relationships between the species involved. A component of a major gene discovery project in grapes at the Centre for Plant Conservation Genetics (Southern Cross University, Australia) is directed at the discovery of novel genes in native Vitaceae. As a result a study was conducted in order to assess the phylogenetic relationships between V. vinifera and the native members of the three major Australian genera: Cayratia, Cissus and Tetrastigma. CpDNA sequence analysis (from the trnL intron) adequately resolved intergeneric relationship between the majority of the species studied and provided some useful new information on the phylogenetic relationships within the Vitaceae. This preliminary project identified two species, C. hypoglauca and C. sterculiifolia, as being closely related to V. vinifera and worthy of further in-depth investigation. 相似文献
69.
Six novel pyranoanthocyanins were identified by HPLC-ESI-MSn in black carrot (Daucus carota L. ssp. sativus var. atrorubens Alef.) juice. The two major compounds, namely, the vinylcatechol adducts of cyanidin 3-O-(6-O-feruloyl-beta-D-glucopyranosyl)-(1-->6)-[beta-D-xylopyranosyl-(1-->2)]-beta-D-galactopyranoside and cyanidin 3-O-[beta-D-xylopyranosyl-(1-->2)]-beta-D-galactopyranoside, respectively, were isolated by a combination of high-speed countercurrent chromatography with semipreparative HPLC. Their structures were fully elucidated by means of one- and two-dimensional NMR spectroscopy and high-resolution mass spectrometry. The four remaining pigments were characterized as the vinylphenol and vinylguaiacol adducts of cyanidin 3-O-[beta-D-xylopyranosyl-(1-->2)]-beta-D-galactopyranoside, the vinylguaiacol adduct of cyanidin 3-O-(6-O-feruloyl-beta-D-glucopyranosyl)-(1-->6)-[beta-D-xylopyranosyl-(1-->2)]-beta-D-galactopyranoside, and the vinylcatechol adduct of cyanidin 3-O-(6-O-sinapoyl-beta-d-glucopyranosyl)-(1-->6)-[beta-D-xylopyranosyl-(1-->2)]-beta-D-galactopyranoside. These compounds are formed during storage of the juice through the direct reaction of either caffeic, ferulic, or coumaric acid with the respective genuine anthocyanins. 相似文献
70.
Thompson FE Midthune D Subar AF Kahle LL Schatzkin A Kipnis V 《Public health nutrition》2004,7(8):1097-1105
OBJECTIVES: We describe the methods used to develop and score a 17-item 'screener' designed to estimate intake of fruit and vegetables, percentage energy from fat and fibre. The ability of this screener and a food-frequency questionnaire (FFQ) to measure these exposures is evaluated. DESIGN: Using US national food consumption data, stepwise multiple regression was used to identify the foods to be included on the instrument; multiple regression analysis was used to develop scoring algorithms. The performance of the screener was evaluated in three different studies. Estimates of intakes measured by the screener and the FFQ were compared with true usual intake based on a measurement error model. SETTING: US adult population. SUBJECTS: For development of instrument, n=9323 adults. For testing of instrument, adult men and women in three studies completing multiple 24-hour dietary recalls, FFQ and screeners, n=484, 462 and 416, respectively. RESULTS: Median recalled intakes for examined exposures were generally estimated closely by the screener. In the various validation studies, the correlations between screener estimates and estimated true intake were 0.5-0.8. In general, the performances of the screener and the full FFQ were similar; estimates of attenuation were lower for screeners than for full FFQs. CONCLUSIONS: When coupled with appropriate reference data, the screener approach described may yield useful estimates of intake, for both surveillance and epidemiological purposes. 相似文献