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131.
dos Santos Dayana M. Williams Mike Kookana Rai de Marchi Mary Rosa R. 《Journal of Soils and Sediments》2018,18(4):1720-1728
Journal of Soils and Sediments - A comparison was made between three chemical methods to predict bioaccessibility of triclosan (TCS), bisphenol A (BPA), and 17α-ethynylestradiol (EE2) in... 相似文献
132.
Riccardo Izzo Flavia Navari‐Izzo Mike F. Quartacci 《Journal of plant nutrition》2013,36(10):1175-1193
Abstract The effects of polyethylene glycol (PEG) solutions of increasing osmotic potentials (ψπ=?0.44 and ‐0.88 MPa) on the growth of the seedlings and on the concentrations of Mn, Cu, Pb, Zn, Ni, Co, Mo, Cr, Cl, Fe, Ca, Mg, K, Na, P, and N were determined in the shoots and roots of maize (Zea mays L. cv. Summer II) grown in Hoagland's solution in a growth chamber. Water stress was imposed for three days with PEG 4000 on six‐day‐old seedlings. Despite a reduction in the leaf water potential (ψw), which decreased with increasing PEG concentrations, and despite an increase in the water saturation deficit (W.S.D.), the pressure potentials (ψp) were maintained in both treatments at levels quite similar to that in the control seedlings. At ψπ=?0.44 MPa of the growth medium, both the length and dry weight of the shoots and roots significantly decreased, whereas at ψπ=?0.88 MPa only the root length continued to decrease with the consequence of an increase in the total mass production of the seedlings. At ψπ=?0.88 MPa, PEG was absorbed by the seedlings in significant amounts, although the roots were undamaged. The effects of the imposed water stress on nutrient absorption and accumulation differed in the two treatments, depending on the plant tissue and nutrient; nevertheless, the element contents generally showed their lowest values at ψπ=?0.44 MPa, as consequence of the reduction in dry matter. The water stress experienced by the maize seedlings grown at ψπ=?0.88 MPa did not induce further decreases in either the macro‐ or micronutrients. 相似文献
133.
134.
Roberta Gentile Mike Dodd Mark Lieffering Shona C. Brock Phil W. Theobald Paul C. D. Newton 《Biology and Fertility of Soils》2012,48(3):357-362
Altered soil nutrient cycling under future climate scenarios may affect pasture production and fertilizer management. We conducted
a controlled-environment study to test the hypothesis that long-term exposure of pasture to enriched carbon dioxide (CO2) would lower soil nutrient availability. Perennial ryegrass was grown for 9 weeks under ambient and enriched (ambient + 120 ppm)
CO2 concentrations in soil collected from an 11.5-year free air CO2 enrichment experiment in a grazed pasture in New Zealand. Nitrogen (N) and phosphorus (P) fertilizers were applied in a full
factorial design at rates of 0, 12.5, 25 or 50 kg N ha−1 and 0, 17.5 or 35 kg P ha−1. Compared to ambient CO2, under enriched CO2 without P fertilizer, total plant biomass did not respond to N fertilizer, and tissue N/P ratio was increased indicating
that P was co-limiting. This limitation was alleviated with the lowest rate of P fertilizer (17.5 kg P ha−1). Plant biomass in both CO2 treatments increased with increasing N fertilizer when sufficient P was available. Greater inputs of P fertilizer may be
required to prevent yield suppression under enriched CO2 and to stimulate any response to N. 相似文献
135.
Blackspot bruise is a major problem in the fresh market and frozen french fry industry. The blackspot bruise potential of Russet Burbank and Ranger Russet in Idaho potato fields was determined by surveying commercial fields during 1993 and 1994. Management factors were monitored to determine what practices were contributing to blackspot susceptibility in addition to mechanical damage. The survey included 17 Russet Burbank and 3 Ranger Russet fields in 1993, and 28 Russet Burbank and 8 Ranger Russet fields in 1994. The 1993 season was unusually cool and wet whereas 1994 was warmer than normal, resulting in a wide range of environmental conditions for the 2 year study. Blackspot bruise potential was determined at different stages of tuber physiological maturity by collecting samples several weeks prior to normal harvest, immediately before harvest, and after storing sub-samples for several months. The blackspot bruise potential was measured by both impact and abrasive peel tests. Field maturity was the factor most consistently related to blackspot potential both years. In 1994 a multiple regression of 3 independent variables — field maturity index, specific gravity, and percent available soil water at tuber sampling, compared with the blackspot potential as the dependent variable gave a correlation coefficient of r = 0.73 (p = 0.001). Due to the cool, wet growing season in 1993, there was not enough variability in specific gravity and available soil water among the fields sampled for these factors to correlate with the blackspot potential. The available fertility data, although not complete for all fields, indicated no direct relationship between N, P, or K fertilization and blackspot potential. Preharvest samples in late August had lower blackspot potential than harvest samples in mid September, and storage samples in February had the highest susceptibility. There was a consistent increase in blackspot severity when tubers were equilibrated at 4 C compared with 10 C prior to bruising. 相似文献
136.
Lowry SC Fitzsimmons A Pravec P Vokrouhlicky D Boehnhardt H Taylor PA Margot JL Galád A Irwin M Irwin J Kusnirák P 《Science (New York, N.Y.)》2007,316(5822):272-274
The Yarkovsky-O'Keefe-Radzievskii-Paddack (YORP) effect is believed to alter the spin states of small bodies in the solar system. However, evidence for the effect has so far been indirect. We report precise optical photometric observations of a small near-Earth asteroid, (54509) 2000 PH5, acquired over 4 years. We found that the asteroid has been continuously increasing its rotation rate omega over this period by domega/dt = 2.0 (+/-0.2) x 10(-4) degrees per day squared. We simulated the asteroid's close Earth approaches from 2001 to 2005, showing that gravitational torques cannot explain the observed spin rate increase. Dynamical simulations suggest that 2000 PH5 may reach a rotation period of approximately 20 seconds toward the end of its expected lifetime. 相似文献
137.
Kreysing M Pusch R Haverkate D Landsberger M Engelmann J Ruiter J Mora-Ferrer C Ulbricht E Grosche J Franze K Streif S Schumacher S Makarov F Kacza J Guck J Wolburg H Bowmaker JK von der Emde G Schuster S Wagner HJ Reichenbach A Francke M 《Science (New York, N.Y.)》2012,336(6089):1700-1703
Despite their diversity, vertebrate retinae are specialized to maximize either photon catch or visual acuity. Here, we describe a functional type that is optimized for neither purpose. In the retina of the elephantnose fish (Gnathonemus petersii), cone photoreceptors are grouped together within reflecting, photonic crystal-lined cups acting as macroreceptors, but rod photoreceptors are positioned behind these reflectors. This unusual arrangement matches rod and cone sensitivity for detecting color-mixed stimuli, whereas the photoreceptor grouping renders the fish insensitive to spatial noise; together, this enables more reliable flight reactions in the fish's dim and turbid habitat as compared with fish lacking this retinal specialization. 相似文献
138.
Woodward G Gessner MO Giller PS Gulis V Hladyz S Lecerf A Malmqvist B McKie BG Tiegs SD Cariss H Dobson M Elosegi A Ferreira V Graça MA Fleituch T Lacoursière JO Nistorescu M Pozo J Risnoveanu G Schindler M Vadineanu A Vought LB Chauvet E 《Science (New York, N.Y.)》2012,336(6087):1438-1440
Excessive nutrient loading is a major threat to aquatic ecosystems worldwide that leads to profound changes in aquatic biodiversity and biogeochemical processes. Systematic quantitative assessment of functional ecosystem measures for river networks is, however, lacking, especially at continental scales. Here, we narrow this gap by means of a pan-European field experiment on a fundamental ecosystem process--leaf-litter breakdown--in 100 streams across a greater than 1000-fold nutrient gradient. Dramatically slowed breakdown at both extremes of the gradient indicated strong nutrient limitation in unaffected systems, potential for strong stimulation in moderately altered systems, and inhibition in highly polluted streams. This large-scale response pattern emphasizes the need to complement established structural approaches (such as water chemistry, hydrogeomorphology, and biological diversity metrics) with functional measures (such as litter-breakdown rate, whole-system metabolism, and nutrient spiraling) for assessing ecosystem health. 相似文献
139.
Niall Bromage Mike Bruce Ngappa Basavaraja Krishen Rana Robin Shields Carl Young John Dye Peter Smith Malcolm Gillespie John Gamble 《Journal of the World Aquaculture Society》1994,25(1):13-21
Egg quality, those characteristics of the egg that determine its capacity to survive, is a significant problem for many species of fish currently being farmed. Little is known about the determinants of egg quality and there is little agreement regarding reliable methods for its assessment. To be of practical benefit, assessments should be simple to perform and should be carried out as early in development as is possible. Fertilization rates are often used as measures of quality. For the Atlantic halibut Hippoglossus hippoglossus, fertilization rate and assessments of cell symmetry at early cleavage stages provide reasonable indicators of quality. Regardless of assessment method, it is strongly recommended that performance data from all batches of each broodfish be examined when surveying the overall quality of a stock. The misleading effects of pooling such information are demonstrated for a rainbow trout Oncorhynchus mykiss broodstock. Although a large number of factors have been implicated as possible determinants of egg quality, only 1) bacterial colonization of the eggs, 2) nutritional status of the broodfish and, 3) overripening, the process of aging that occurs when eggs are retained within the broodfish after ovulation, have been clearly shown to affect egg quality. The effect of overripening on fish egg quality is discussed in detail. Species-specific differences in the time scale of overripening are pointed out and related to spawning strategy and water temperature. Rainbow trout eggs and those of other salmonids should be fertilized within approximately one week of ovulation. Overripening proceeds much more rapidly in warm water species, e.g., tilapia eggs must be fertilized within an hour or so of ovulation. Egg viability also decreases rapidly for batch spawning species. Fertilization data are presented for Atlantic halibut demonstrating that egg quality decreases 4–6 h after ovulation. The rate of overripening was comparable for eggs held in vitro in ovarian fluid to those retained within the ovarian lumen. These halibut data, combined with information from other marine and freshwater fish, indicate that overripening is a significant determinant of egg quality for many if not all fish. 相似文献
140.
Curtis W. Stofferahn Cordell A. Fontaine Douglas J. McDonald Mike Spletto Holly Jeanotte 《Agriculture and Human Values》1991,8(3):25-34
In our paper we will try to connect the dynamics of community decline to individual responses. We will operate on two levels of reality. At the first level we will discuss the circumstances surrounding the recent decline of small communities in North Dakota. At the second level we will discuss how this decline affects small town residents' attitudes toward economic development. In the first level analysis we examine the thesis that the natural environment of community growth is economic exploitation; therefore, the decline of resource-based communities is natural and inevitable. We discuss the circumstances surrounding the recent decline of small communities in North Dakota. At the second level analysis, we operate at the level at which life circumstances and environments are shaped by political-economic institutions that in turn shape the behavior and mentality of communities, families, and individuals. We hypothesize that residents of declining small towns deny their powerlessness and adapt to their situation through intense dedication to economic growth. We develop a series of hypotheses to test this thesis using data from the North Dakota Rural Life Poll. In our conclusion, we discuss implications for rural development practitioners working in declining small towns where this intense dedication to economic development in prevalent.Dr. Stofferahn is an assistant professor in the Department of Sociology and director of the Social Science Research Institute at the University of North Dakota. He received his Ph.D. and M.S. in rural sociology from Iowa State University. Prior to coming to the University of North Dakota, Dr. Stofferahn was employed by the North Dakota Economic Development Commission. Mr. Fontaine received his M.S. in sociology from the University of North Dakota and is presently employed as the assistant director of the Social Science Research Institute. Douglas McDonald, Mike Spletto and Holly Jeanotte are graduate students in the Department of Sociology at the University of North Dakota. This paper originally was written as a class project in a graduate seminar in rural development. 相似文献