Generating the Pfaffian closure with total Pfaffian functions

Given an ominimal expansion R of the real field, we show that the structure obtained from R by iterating the operation of adding all total Pfaffian functions over R defines the same sets as the Pfaffian closure of

Supply of pigeonpea genetic resources in local markets of Eastern Kenya:

"Smallholder producers in marginal and semiarid areas of eastern Kenya have not benefited greatly from research investments made in improvement of crops grown in such environments (sorghum, millet, and legumes, including pigeonpea) either by the international community or the national agricultural research system because of poorly developed seed systems. However, informal and local market purchases are the major sources of seed for non-maize cereals and legumes. In the absence of any formalized seed system for dryland crops, more and more farmers rely on local markets to supply seed during normal and disaster periods. We determined the factors affecting the quantities of pigeonpea traded by vendors during the 2006 short-rains season using simple OLS estimation. We found that the participation of traders and farmers was higher and traded larger quantities of pigeonpea in weekly markets located in areas where seed-based intervention programs in place than in non-intervention areas. Also agro-ecologically, markets located in slightly wetter regions offered more varieties and handled higher sales compared with marketsheds in dry regions. Among the traders, the grain traders dominated through their sheer volume of sales, higher investment, and storage capacity in these markets though the distinction between seeds and grains was poor. Of the vendor characteristics, young, educated vendors traded higher quantities of pigeonpea during the planting season. The amount of time spent selling by different vendors in the village fairs also had a significant influence on the pigeonpea quantity traded. Certain market infrastructure variables such as distance to the local markets and the access to information sources (mobile phones) also significantly influenced the amount of pigeonpea sold among vendors in these markets. The existing pigeonpea value chain in local markets could be improved further, provided proper synergies exist between different actors in the system. This would enhance local crop diversity levels as well as improve access to quality plant materials for farming communities in the marginal environments of eastern Kenya." from authors' abstractLocal markets, village markets, Seed systems, Drylands, legumes,

Bunch-Kaufman factorization for real symmetric indefinite banded matrices

The Bunch-Kaufman algorithm for factoring symmetric indefinite matrices was rejected for banded matrices because it destroys the banded structure of the matrix. Herein, it is shown that for a subclass of real symmetric matrices which arise in solving the generalized eigenvalue problem using Lanczos's method, the Bunch-Kaufman algorithm does not result in major destruction of the bandwidth. Space time complexities of the algorithm are given and used to show that the Bunch-Kaufman algorithm is a significant improvement over LU factorization

The use of Lanczos's method to solve the large generalized symmetric definite eigenvalue problem

The generalized eigenvalue problem, Kx = Lambda Mx, is of significant practical importance, especially in structural enginering where it arises as the vibration and buckling problem. A new algorithm, LANZ, based on Lanczos's method is developed. LANZ uses a technique called dynamic shifting to improve the efficiency and reliability of the Lanczos algorithm. A new algorithm for solving the tridiagonal matrices that arise when using Lanczos's method is described. A modification of Parlett and Scott's selective orthogonalization algorithm is proposed. Results from an implementation of LANZ on a Convex C-220 show it to be superior to a subspace iteration code

Informal learning evidence in online communities of mobile device enthusiasts

This chapter describes a study that investigated the informal learning practices of enthusiastic mobile device owners. Informal learning is far more widespread than is often realized. Livingston (2000) pointed out that Canadian adults spend an average of fifteen hours per week on informal learning activities, more than they spend on formal learning activities. The motivation for these learning efforts generally comes from the individual, not from some outside force such as a school, university, or workplace. Therefore, in the absence of an externally imposed learning framework, informal learners will use whatever techniques,resources, and tools best suit their learning needs and personal preferences. As ownership of mobile technologies becomes increasingly widespread in the western world, it is likely that learners who have access to this technology will use it to support their informal learning efforts. This chapter presents the findings of a study into the various and innovative ways in which PDA and Smartphone users exploit mobile device functionality in their informal learning activities. The findings suggested that mobile device users deploy the mobile, connective, and collaborative capabilities of their devices in a variety of informal learning contexts, and in quite innovative ways. Trends emerged, such as the increasing importance of podcasting and audio and the use of built-in GPS, which may have implications for future studies. Informal learners identified learning activities that could be enhanced by the involvement of mobile technology, and developed methods and techniques that helped them achieve their learning goals

An Analysis of the EQIP program for Lesser Prairie Chickens in the Northern Texas Panhandle

The Environmental Quality Incentives Program (EQIP) for the Lesser Prairie Chicken provides monetary compensation to agricultural producers for species habitat development. The advantages and disadvantages of program enrollment, as well as the overall economic impact are evaluated for a typical ranch operation in the Northern Texas Panhandle from 2009-2013.Prairie Chicken, FARM Assistance, EQIP, Environmental Economics and Policy,

Economic Considerations for Playa Management Alternatives

Playa lakes are very important to the Texas High Plains. They provide habitat for a wide variety of wildlife, and are the Ogallala Aquifer’s primary recharge source. Plowing and sedimentation have caused substantial damage to the overall health of many playas. A need exists to protect this resource for future generations. Several government programs are available to assist landowners with playa preservation including CP23A, the Wetlands Reserve Program, and the Wildlife Habitat Incentive Program. This study evaluates each conservation program and weighs the economic benefits and costs of program implementation.Southern Great Plains, Playa Lakes, CP23A, Conservation Reserve Program, Wetlands Reserve Program, Wildlife Habitat Incentive Program, Environmental Economics and Policy,

Seed provision and dryland crops in the semiarid regions of Eastern Kenya:

"Over the last two decades, several seed-related programs have been initiated in eastern Kenya to improve farmers' access to quality seeds of dryland cereals and legumes. They are provided during two occasions, regular and emergency times. But very often, the formal supply mechanisms limit their role in provision of seeds other than maize. In the absence of any formalized systems of seed provision for other dryland crops, such as sorghum and pigeon pea, farmers have preferred local markets for their seed needs, especially during distress periods. Here we have examined the role of various seed-intervention programs in eastern Kenya, along with the strengths and weaknesses of each program. We have also underscored the importance of local markets and their actors in meeting the needs for non-maize and bean seeds in these marginal environments. For this purpose, detailed, informal interviews were conducted during October–December 2005 with all the stakeholders, namely public and private institutions and vendors in eight major local markets in eastern Kenya. The results of the study call for synergies between existing formal (private, public, and other development initiative) systems and informal (local market) seed systems to enhance crop yields and the diversity of dryland cereals and legumes through effective seed-supply interventions." from Author's AbstractSeed interventions, Local markets, Seed systems, Dry lands, Seed access, Eastern Kenya,

A language comparison for scientific computing on MIMD architectures

Choleski's method for solving banded symmetric, positive definite systems is implemented on a multiprocessor computer using three FORTRAN based parallel programming languages, the Force, PISCES and Concurrent FORTRAN. The capabilities of the language for expressing parallelism and their user friendliness are discussed, including readability of the code, debugging assistance offered, and expressiveness of the languages. The performance of the different implementations is compared. It is argued that PISCES, using the Force for medium-grained parallelism, is the appropriate choice for programming Choleski's method on the multiprocessor computer, Flex/32