ANOTHER CORN SEED PARASITE     

Norton JB  Chen CC 《Science (New York, N.Y.)》1920,52(1341):250-251

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A NEW METHOD OF DRIVING AN INDUCTION COIL     

Norton CL  Lawrence RR 《Science (New York, N.Y.)》1897,5(113):335-336

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THE X-RAYS IN MEDICINE AND SURGERY     

Norton CL 《Science (New York, N.Y.)》1896,3(72):730-731

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High-speed centrifugation of extender of freeze-thaw boar semen     

Camila R. C. de Brito  Antonio Sergio Varela Junior  Stela Mari M. Gheller  Izani B. Acosta  Andreia N. Anciuti  Norton Luiz S. Gatti  Edenara A. Silva  Nathalia W. Knabah  Carine D. Corcini 《Reproduction in domestic animals》2021,56(5):821-825

In semen cryopreservation, egg yolk is still widely used as a non-penetrating cryoprotectant. Much has been developed in the search for alternatives for this biological product. This work aimed to evaluate the processed egg yolk through ultracentrifugation and/or sonication in the cryopreservation of swine semen. Twenty-seven semen doses were purchased from a commercial boar stud and processed for cryopreservation using egg yolk lactose 11% (control) extender, processed using two different methods: high-speed centrifugation and sonication. Then, they were submitted to freeze-thawing protocol and were assessed for kinematic and cell structural parameters. Samples in which extenders underwent centrifugation had better results in velocity parameters, meanwhile those that only sonication was performed had poorest results in this parameter. The preservation of the membrane and mitochondria structure had better results when the diluent was only centrifuged in comparison with the other treatments. Therefore, centrifugation of extender containing egg yolk is important for better cryopreservation of swine semen.  相似文献   

Changes in the concentrations and speciation of aluminum in response to an experimental addition of ammonium sulfate to the bear Brook Watershed,Maine, USA     

K. M. Postek  C. T. Driscoll  J. S. Kahl  S. A. Norton 《Water, air, and soil pollution》1995,85(3):1733-1738

An understanding of the biogeochemistry of aluminum (Al) in acid-sensitive terrestrial and aquatic ecosystems is critical to assessments of the effects of acidic deposition. Bear Brook Watershed, Maine, USA includes paired watersheds, East Bear and West Bear. Starting in November 1989, experimental additions of ammonium sulfate ((NH₄)₂SO₄; 900 mol/ha-yr) have been made to West Bear Brook Watershed. Chemical analysis of soil and stream waters were conducted to evaluate the speciation of Al prior to (1987–89) and following (1989–92) the experimental treatments. Before the treatments, soilwater Al occurred largely as inorganic monomeric Al (Ali). Concentrations of organic monomeric Al (Alo), Ali and dissolved organic C (DOC) were high in soil solutions draining the E horizon, and decreased in the lower mineral soilwater (Bs horizon) and streamwater. Streamwater concentrations of monomeric Al (Alm) were largely in the form of Alo. After the (NH₄)₂SO₄ treatments were initiated in the West Bear Brook Watershed, concentrations of Alm increased in soilwater and streamwater, largely as Ali. These increases in Al accompanied decreases in pH and increases in concentrations of SO₄ ^2? and NO₃ ^? in drainage waters. Increases in stream concentrations of Al were particularly evident during high flow events. This pattern, coupled with the increases in concentrations of Ali in upper soilwaters in response to the (NH₄)₂SO₄ addition, suggests that episodic increases in Ali were due to inputs of water entering the stream from shallow hydrologic flowpaths.  相似文献   

Modern and paleolimnological evidence for accelerated leaching and metal accumulation in soils in New England,caused by atmospheric deposition     

Denis W. Hanson  Stephen A. Norton  John S. Williams 《Water, air, and soil pollution》1982,18(1-3):227-239

Empirical field evidence for changing chemical processes in soils caused by atmospheric deposition of pollutants consists of: (1) Long-term water quality data including total dissolved solids, concentrations of specific metals (e.g. Ca), and conductivity; (2) Cation exchange capacity and base saturation values for soils located on precipitation pH gradients; (3) Lysimeter studies; and (4) Chemical analysis of organic soils on precipitation pH and metal gradients. For well-drained organic soils, as precipitation pH decreases, metals are differentially leached at an accelerated rate (Mn>Ca>Mg≥Zn>Cd and Na>Al). Experimental field and laboratory lysimeter studies on soil columns yield similar results, with increases in leaching rates for soil solutions with pH=3 up to 100 × values for soil solutions with pH=5. Nearly 100% of the Pb from precipitation is accumulating in the organic soil layer or sediments. Zn is accumulating in soils and sediments where the pH's of precipitation, soil solutions, and surface waters are generally above 5 to 5.5. At lower pH values Zn and other chemically similar elements are desorbed/leached (net) at an accelerated rate. Chemical analyses of dated sediment cores from high and low altitude lakes, with drainage basins relatively undisturbed for the last 200+ yr, reveal that increased deposition of metals on a regional scale started in the northeastern United States as early as 1880, consistent with increased fossil fuel consumption. This suggests acidified precipitation as early as 1880. Cores from historically acidified lakes (pH<≈5.3 to 5.5) indicate that, as acidification of surface waters occurs (caused by acidic deposition), concentrations of Zn, Mn, and Ca decrease in the sediment. Apparently the metals are leached from the detritus prior to sedimentation. This conclusion results from data from experimental acidification of sediment cores and the general observation that precipitation pH is generally ≥0.5 pH units lower than lake water pH. Accelerated leaching of soil in New England dates to earlier than 1900.  相似文献   

Reply to comment by Mattson and likens: April 5, 1994     

J. S. Kahl  T. A. Haines  S. A. Norton  R. B. Davis 《Water, air, and soil pollution》1995,83(1-2):101-104

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Developing a magnetic tracer to study soil erosion   总被引：6，自引：0，他引：6  

Eusebio VenturaJr.  Mark A. Nearing  L. Darrell Norton 《CATENA》2001,43(4)

Soil erosion is commonly measured as the quantity of sediment leaving a plot or watershed. The techniques for measuring soil erosion patterns and sediment redistribution within plots or watersheds by direct monitoring are very limited. The objective of this study was to develop a direct and non-intrusive tracer method to study the sources, patterns and rates of erosion and deposition of sediments in erosion plots. The magnetic tracer developed in this study consisted of polystyrene plastic beads embedded with a magnetic powder (magnetite). The “magnetized” beads, with a mean weight diameter of 3.2 mm and particle density of about 1.2 g cm⁻³, were uniformly mixed with soil and tested in the laboratory using simulated rainfall and inflow studies to simulate the interrill and rill components of soil erosion, respectively. In the interrill and rill experiments, the tracer was transported in the same proportion it was initially mixed with the soil. Given this fact, a magnetometer, which measures the soil's magnetic susceptibility, could be used to identify areas of deposition or detachment. The magnetic susceptibility would be increased or reduced depending on whether deposition or detachment occurs. To simulate detachment and deposition, a magnetometer was tested for different tracer concentrations and different thickness of soil containing the tracer. The magnetometer promises to be a sensitive, accurate, and useful tool to study the spatial variation of soil erosion when magnetic tracers are used.  相似文献   

The potential of Acacia albida for desertification control and increased productivity in Chad     

Robert D. Kirmse  Brien E. Norton 《Biological conservation》1984,29(2):121-141

Reforestation using Acacia albida has been preposed as a mechanismsfor combating desertification trends in the Sahel. This tree is characterised by a deciduous habit in the wet season; it is valuable for fodder, as a hardwood in woodwork industries, and for enhancing soil fertility of cropland. In a three-year project described in this paper, the establishment of Acacia albida platations in cultivated field in central Chad is conceived as a focal point to coordinate resource conservation and land development programmes. Several hundred thousand young trees were established and about 2500 farmers and their families participated in the revegetation programme. The success of the project must be evaluated, however, in terms of the prospects for long-term benefit and recognising the sociological problems of assistance programmes.  相似文献   

Predicting Recovery from Acidic Deposition: Applying a Modified TAF (Tracking and Analysis Framework) Model to Maine (USA) High Elevation Lakes     

Joshua J. Lawler  Jonathan Rubin  Bernard J. Cosby  Ivan J. Fernandez  Jeffrey S. Kahl  Stephen A. Norton 《Water, air, and soil pollution》2005,164(1-4):383-399

We adapted a reduced-form model, built to predict the aquatic effects of alternative nitrogen and sulfur emissions scenarios on Adirondack lakes, New York, for use on high elevation lakes of Maine (HELM), USA. The Tracking and Analysis Framework (TAF) model was originally designed to evaluate the biotic, economic, and health effects of acid deposition. The TAF model developed in our study was used to assess the biotic effects of different levels of sulfate deposition resulting from alternative emissions scenarios. The aquatic portion of the model is based on a lumped-parameter watershed chemistry model, MAGIC (Model of Acidification of Groundwater in Catchments). The original TAF model was built by calibrating MAGIC to 33 lakes in the Adirondack Mountains. We calibrated MAGIC to 78 HELM lakes, and built reduced-form models from these MAGIC predictions. We evaluated TAF predictions of acid neutralizing capacity (ANC), a fish acid stress index (ASI), and the probability of fish presence in 2030 for four different SO₂ emissions-reduction scenarios. The most dramatic emissions reduction scenario produced only modest increases in mean ANC (16.8 μeq/L ± 7.9 μeq/L) and slight increases in mean predicted probability of presence of acid-sensitive fish (0.07± 0.09) across all lakes. However, a small number of lakes were predicted to have more substantial increases in ANC and improvements in other conditions for acid-sensitive fish. Our results reflect the reality that many of the high elevation lakes of Maine historically had low ANC and that some were even acidic in pre-industrial times. Thus, ’recovery’ for most of the high elevation lakes of Maine will be modest under any scenario of reduced acidic deposition.  相似文献