16,768 research outputs found
Shelby County v. Holder - Brief Contextualized
This paper begins with three major factors that set the stage for Shelby: first, a history of the VRA; second, an overview of Northwest Austin with a focus on how it led directly to Shelby; and finally, Shelby County’s motivations for bringing the suit. An examination of racial demographics compared to statistics on voter registration and minority officeholders in Alabama and Louisiana—two states originally subject to preclearance—follows in light of the Court’s claims on the matter. A conclusion will take a brief look at laws passed since Shelby with an eye towards a future critique. [excerpt
The Shadows of Future Generations
This Note addresses the twin problems of political short-termism and intergenerational equity. Although scholars have discussed these concerns extensively, few scholars have developed proposals to modify democratic institutions-particularly legislatures-to better consider posterity\u27s interests. This Note critiques one such set of proposals by several environmental ethicists for including posterity-oriented legislators in present-generation legislatures. It then proposes a system that ties the long-term outcomes of legislators\u27 policy preferences to their pension plans by creating a new commodities market that values the decisions legislators make and their effect on posterity
Radar imagery - Salton Sea area, California
Radar imagery and geology of Salton Sea area, Californi
Companion cropping for organic field vegetables (OF0181)
Typical organic crop rotations are extensive with at least one year in four as a fertility building crop. However, the economic viability of organic systems may be compromised by having 75% or less of the farm productive at one time, limited further by the absence of the Arable Area Payments Scheme, particularly Set-aside, for vegetable crops. In addition, the system gives rise to a high fertility/low fertility sequence which is inefficient in terms of nutrient management (particularly nitrogen). To try to address this, the use of permanent beds of companion crop grown alongside the vegetable crops has been developed under various conditions around the world and is perceived as a possible alternative in organic husbandry. Companion crops also have the potential to reduce the impact of pests and weeds. A potential disadvantage of companion crops is competition with crop plants for space, light, water and nutrients. The companion crop, therefore, is likely to have to be mown or grazed to control competition and encourage nutrient transfer. On the positive side, companion crops have the potential to reduce the impact of pests, and weeds. The challenge is, therefore, to develop appropriate crop layouts and machinery to balance these interactions and result in profitable crop production.
Project OF0181 was delivered with Elm Farm Research Centre and was guided by a Steering Group. The core of the project was the further development and evaluation of a seven-crop companion crop system initially developed by Professor Martin Wolfe at Wakelyns Agroforesty, Fressingfield, Suffolk, a Soil Association registered organic farm. The system was based on 1.5 m beds, with three 20 cm vegetable rows alternating with 30 cm leguminous companion strips. Within each bed, there was a seven-course crop rotation: potatoes, alliums, Umbellifers, spring oats, legumes, brassicas and spring wheat. To establish and manage this system, Martin Wolfe and his co-workers (P. J. & M. J. Wards) had by spring 1999 developed a range of purpose-built machinery including a strip rotavator, 3 row precision seed drill, straight tine or L-blade strip cultivator with/without discs, rotary strip mower, strip irrigator and a strip compost spreader.
Two large experiments were established at Wakelyns in spring 1999; it was planned that these be continued for the full three years of the project. One experiment compared a factorial combination of a) three companion crops: white clover, vetch and nil, b) companion crop mowings left to fall, or deflected onto the vegetable rows, and c) the presence or absence of added composted manure. A second experiment compared factorial combinations of winter cover crops of rye and vetch grown in the vegetable rows with additional approved inputs of phosphorus and potassium. All seven crops were grown but assessments were made only on brassicas, alliums and carrots.
Conclusions
Companion cropping has the potential to improve economic viability, and pest, disease and annual weed control in organic cropping systems, particularly in field vegetables which are not supported by the Arable Area Payment Scheme. However, in practice, in project OF0181 these benefits were not realised:
• Grass weeds were favoured and were difficult to control once established.
• There were problems with seedbed preparation and crop establishment; these may be less on lighter soils.
• Some crop species were better suited to companion cropping. In 2000 and 2001, there was:
- a high yield in both years from beetroot, spinach, chard and kale;
- a high yield in one year from Brassicas (some cabbage, swede, turnip), endive, lettuce, parsley and parsnip;
- a low yield in both years from Allium crops (leeks, onions), Brassica (sprouts, some cabbage, calabrese), carrots, celeriac, broad and dwarf beans.
• Clover used soil available nitrogen in preference to fixed nitrogen, starving less competitive crops such as alliums of the nutrient and resulting in very low yields.
• Even with reliable yields, companion cropping in the form tested may only be suited to small-scale labour-intensive production.
A system with greater spatial separation of companion and vegetable crops, with vegetables and companion crops grown alone in separate beds or strips, may give the reported benefits of companion cropping with less competition and be practical for large scale production
The Inflation Technique for Causal Inference with Latent Variables
The problem of causal inference is to determine if a given probability
distribution on observed variables is compatible with some causal structure.
The difficult case is when the causal structure includes latent variables. We
here introduce the for tackling this problem. An
inflation of a causal structure is a new causal structure that can contain
multiple copies of each of the original variables, but where the ancestry of
each copy mirrors that of the original. To every distribution of the observed
variables that is compatible with the original causal structure, we assign a
family of marginal distributions on certain subsets of the copies that are
compatible with the inflated causal structure. It follows that compatibility
constraints for the inflation can be translated into compatibility constraints
for the original causal structure. Even if the constraints at the level of
inflation are weak, such as observable statistical independences implied by
disjoint causal ancestry, the translated constraints can be strong. We apply
this method to derive new inequalities whose violation by a distribution
witnesses that distribution's incompatibility with the causal structure (of
which Bell inequalities and Pearl's instrumental inequality are prominent
examples). We describe an algorithm for deriving all such inequalities for the
original causal structure that follow from ancestral independences in the
inflation. For three observed binary variables with pairwise common causes, it
yields inequalities that are stronger in at least some aspects than those
obtainable by existing methods. We also describe an algorithm that derives a
weaker set of inequalities but is more efficient. Finally, we discuss which
inflations are such that the inequalities one obtains from them remain valid
even for quantum (and post-quantum) generalizations of the notion of a causal
model.Comment: Minor final corrections, updated to match the published version as
closely as possibl
Network Thinking in Peace and Conflict Studies
Developments in mathematics and social theory and in techniques of communication and computation have brought network analysis to a state where it can be practically applied over a broad spectrum. Surprisingly, this mode of analysis has not been adopted by practitioners and scholars of peace and conflict studies to the extent that it ought to be. Examples of types of analysis that could have important applications are given, using network concepts such centrality, structural equivalence, and regular equivalence
A Novel Approach To Residence Time Distribution
An increased knowledge in the solids flow in multiphase flow systems can be applied in the design of industrial systems used for power generation, gasification, pneumatic transport of material, drying, and various other tasks. An instrument was constructed for the activation, injection, and measurement of phosphorescent tracer particles in a fluidized bed riser to determine the Residence Time Distribution (RTD) of solids flow within a fluidized bed riser. The instrument was implemented in a dual-stage transparent scale model fluidized bed riser. Testing of the instrument system validated the functionality of the instrument. It was proven to be capable of determining both localized and total Residence Time Distribution in a fluidized bed riser operated in the pneumatic transport flow regime with relatively short RTD. The determination of localized RTD was also achieved in the fluidized bed riser operated in the core-annular flow regime
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