1,599 research outputs found
The effects of previous-year corn hybrid and cropping system on current-year corn hybrids in second year corn
Grain yields decrease when corn (Zea mays L.) follows corn compared to corn grown in rotation with other crops. The factors that decrease grain yield of corn following corn are not well understood, and limit recommendations available to corn growers. Our objectives were to determine (i) if plant population, moisture, and yield of 2nd year corn are affected by the previous-year corn hybrid, (ii) evaluate if continued use of single hybrid over two growing seasons influences grain yield, and (iii) compare 2nd year corn yields to corn grown in rotation with soybean. The experiment was conducted at six Iowa locations in 2008 and 2009; three locations were in the Northern region of Iowa and three in the south. Three corn hybrids were planted in 18 m2 blocks as the main plots in the first year, followed by 12 hybrids planted on each of the main plots in the second year. The same 12 hybrids were planted into a nearby field on soybean residue at each location in 2008, but established as a main plot for 2009. Plant population was not influenced by the three previous-year corn hybrids. Plant populations were greater when corn followed soybean compared to 2nd year corn. Grain moisture content was not influenced by crop rotation or previous-year corn hybrid. Previous-year corn residue did not impact grain yield of the current-year hybrid, and the continued use of single hybrid over multiple growing seasons showed no influence on grain yield. Cropping system influenced grain yield in 2009, within both regions. Second-year corn yields were 11% and 14% less in the north and south regions, respectively, compared to corn rotated with soybean. Previous-year corn hybrid did not influence plant population, grain yield, or grain moisture. The influence of previous-year corn hybrid on the root and plant growth of the current-year hybrids is not well understood and may account for the decrease in grain yield. The objectives the second study were to determine (i) if current-year corn grain yields, root, and plant biomass were influenced by previous-year hybrid and/or cropping system (ii) if there are differences in plant and root biomass among modern commercial corn hybrids (iii) if root and plant biomass are correlated with grain yield. In 2008 and 2009, root and plant biomass studies were conducted at two Iowa State University research and demonstration farms. Experimental design and corn hybrids were the same as the grain yield study. At each location, root and plant biomass samplings were conducted at four different sample dates: V4, V12, VT, and R6. After sampling, roots were washed, dried, and weighed while plants were dried and weighed. Root and plant biomass were compiled and calculated for comparison. Overall, previous-year corn hybrid/cropping system did not influence root or plant biomass; however, plant biomass was greater when corn followed soybean compared to 2nd year corn at Kanawha and Ames in 2009. Current-year hybrids were variable and did not indicate strong differences in root or plant biomass. Root biomass was not correlated with grain yield within any sample date. Plant biomass was correlated with grain yield at sample date 2 and 4 in Kanawha (2009). Root to shoot correlations were strong within all sample dates indicating that root growth is correlated to shoot growth throughout the growing season. Root and plant biomass are not influenced by the previous-year hybrid and are poor indicators of final grain yield
Water conservation methods to conserve the High Plains aquifer and Arikaree River Basin: a case study on the Arikaree River
Includes bibliographical references.Throughout the United States, and especially in Colorado, farmers confront the challenges of meeting water needs for crop production, while trying to maintain natural habitats. The Arikaree River, a tributary of the Republican River in eastern Colorado, is groundwater dependent on the High Plains aquifer (HPA). The river alluvium is habitat for threatened fish species such as the Hybognathus hankinsoni (Brassy Minnow) and habitat for many terrestrial invertebrates. In addition to the demands for maintenance of habitats, the surrounding almost exclusively irrigated agricultural lands require water as well. The research presented here combined a water balance model, a water conservation model, and water conservation survey results from farmers in eastern Colorado. These models determined how water conservation alternatives identified in the water conservation survey could extend the life of the Arikaree River. The first scenario examined the impacts of no change to the current water usage throughout the High Plains aquifer and the alluvium. If no change is made in the High Plains aquifer, water levels will continue to decline at the linear rate of 0.183 m/year with the deepest pool in the upper segment drying in 8 to 12 years. In the second scenario, aerial photographs identified 18 irrigation wells, currently in operation within the alluvial aquifer that could be removed. This scenario could extend the projected pool dry up time to 30 years. The third scenario found that water conservation participation of 43%, 57%, and 62% of farmer would extend the drying time to 20, 30, and 40 years, respectively. The final analysis was to calculate the reduction in water usage in order to stop the decline of the High Plains Aquifer. The analysis found that 77% participation of farmer in all conservation alternatives or reducing pumping by 62.9% would be necessary to stabilize the High Plains Aquifer
A Bridle, a Prod and a Big Stick: An Evaluation of Class Actions, Shareholder Proposals and the Ultra Vires Doctrine as Methods for Controlling Corporate Behavior
Written for the recent conference at St. John’s University Law School on “People of Color, Women, and the Public Corporation,” this paper evaluates recently applied methods of influencing corporate behavior on employment practices and recommends that a dormant legal doctrine be revitalized and added to the “tool box” of activists and concerned shareholders. The methods of influencing corporate behavior that are evaluated include class action lawsuits and shareholder proposals to amend corporate policy. In both contexts, there are procedural hurdles to achieving success. Even when success is achieved, there are limits to the actual changes in organizational behavior that result. A third means for influencing corporate behavior would not involve the same theoretical or structural limitations. The ultra vires doctrine historically allowed a shareholder to sue to prevent a company from engaging in an activity outside of the specific parameters of its corporate charter. While the doctrine was almost done away with during the 1900s inasmuch as companies are now free to alter their field of business as they wish, a narrow slice of this doctrine remains. Namely, corporate charters typically are required to limit a corporation to “lawful activities,” and forty-nine states have statutes empowering the state to enjoin or dissolve the corporation for illegal acts. Therefore, shareholders still have the power to sue a company to prevent the violation of laws. In the context of a company such as Wal-Mart, for example, a well-documented pattern of widespread illegal gender discrimination could therefore be grounds for a shareholder bringing an ultra vires lawsuit. Unlike a shareholder proposal, the available remedies could include a court order to cease the activity and to adopt a detailed monitoring, training and compliance plan. Unlike a class action, the high hurdles of certifying the plaintiffs as class representatives would not exist. Nor would there be the same mix of practical concerns that contribute to class action attorneys emphasizing monetary rewards over long-term, disciplined equitable relief that is geared to actually altering company practices in the future. The only limitation on using the ultra vires doctrine is that there must be evidence that a company is in violation of an actual law in a jurisdiction where it operates. In those contexts, ultra vires can effectively enable a form of shareholder enforcement suit to ensure compliance with the federal laws of the United States or the statutes of foreign nations or individual states’ laws
Learning Under Pressure: Teaching Boyle’s Law through Inquiry
Boyle’s law is commonly addressed in chemistry and physical science textbooks, but rarely in a manner consistent with what we know best promotes learning (Bransford, Brown & Cocking, 2000). We present the standard syringe activity as an exploratory inquiry experience followed by a more formal development of the relationship. The activity starts and concludes by having students examine how the volume of a crushed pop bottle changes in a vacuum. Through iterative concrete experiences and guided discussions, students construct Boyle’s law to account for the class data. This article address National Science Education Standards A, B, E, G, and Iowa Teaching Standards 1, 2, 3, and 5
A Bridle, a Prod, and a Big Stick: An Evaluation of Class Actions, Shareholder Proposals, and the Ultra Vires Doctrine as Methods for Controlling Corporate Behavior
Rhyolite generation prior to a Yellowstone supereruption: insights from the Island Park-Mount Jackson rhyolite series
The Yellowstone volcanic field is one of the largest and best-studied centres of rhyolitic volcanism on Earth, yet it still contains little-studied periods of activity. Such an example is the Island Park–Mount Jackson series, which erupted between the Mesa Falls and Lava Creek caldera-forming events as a series of rhyolitic domes and lavas. Here we present the first detailed characterisation of these lavas and use our findings to provide a framework for rhyolite generation in Yellowstone between 1·3 and 0·6 Ma, as well as to assess whether magmatic evolution hints at a forthcoming super-eruption. These porphyritic (15–40% crystals) lavas contain mostly sanidine and quartz with lesser amounts of plagioclase (consistent with equilibrium magmatic modelling via rhyolite-MELTS) and a complex assemblage of mafic minerals. Mineral compositions vary significantly between crystals in each unit, with larger ranges than expected from a single homogeneous population in equilibrium with its host melt. Oxygen isotopes in quartz and sanidine indicate slight depletions (δ18Omagma of 5·0–6·1‰), suggesting some contribution by localised remelting of hydrothermally altered material in the area of the previous Mesa Falls Tuff-related caldera collapse. The preservation of variable O isotopic compositions in quartz requires crystal entrainment less than a few thousand years prior to eruption. Late entrainment of rhyolitic material is supported by the occurrence of subtly older sanidines dated by single-grain 40Ar/39Ar geochronology. The eruption ages of the lavas show discrete clusters illustrating that extended quiescence (>100 kyr) in magmatic activity may be a recurring feature in Yellowstone volcanism. Ubiquitous crystal aggregates, dominated by plagioclase, pyroxene and Fe–Ti oxides, are interpreted as cumulates co-erupted with their extracted liquid. Identical crystal aggregates are found in both normal-δ18O and low-δ18O rocks from Yellowstone, indicating that common petrogenetic processes characterise both volcanic suites, including the late-stage extraction of melt from an incrementally built upper crustal mush zone
Intelligent patient monitoring : detecting and defining significant clinical events
Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 1996.Includes bibliographical references (leaf 56).by Adam K. Hoyhtya.M.S
Did the Kentucky Education Reform Act (KERA) Reduce Residential Income Segregation Across School Districts?
In 1990, Kentucky passed the Kentucky Education Reform Act (KERA) in response to a State Supreme Court mandate regarding educational spending inequality across rich and poor school districts. A comprehensive bill, KERA completely altered the existing school funding system, and instituted a number of accountability and curricular changes. More specifically, KERA effectively equalized per pupil funding across Kentucky school districts, pulling a majority of both low-spending and poor districts up to what had been higher spending quartiles. Economic theory suggests such a dramatic transformation in school finance has the potential to increase income heterogeneity within districts, which may, in turn, improve the educational and economic outcomes of those previously segregated.
This honors thesis examines whether KERA significantly decreased residential income segregation across school districts. Differing from existing research, I focus on one of the most comprehensive reforms in history and its subsequent impact on residential sorting patterns. Using a difference-in-difference regression technique, I find that KERA had no effect on the household poverty rate across districts when compared to Tennessee. These results are robust through a number of different specifications
Public Investment in Children's Early and Elementary Years (Birth to Age 11)
Compares federal and state/local per-capita spending; funding areas such as health, education, and income support; and degree of targeting and means testing for different age groups. Discusses policy implications and the need to invest in early childhood
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