Nitrogen fixation is a key component of the nitrogen cycle, one of the most fundamental cycles in the biosphere. Conversion of atmospheric nitrogen into organic nitrogen compounds can be carried out only by certain bacteria and blue-green algae (cyanobacteria). Some nitrogen fixing bacteria live symbiotically with leguminous plants such as peas, beans, clover, and certain tropical trees in nodules on the plants' roots, while others live independently in the soil and aquatic habitats. By the activity of these microorganisms, the soil is enriched with the nitrogen required for plant growth and function. Thus the topic is of considerable practical as well as fundamental importance. In Biological Nitrogen Fixation, the leading researchers in nitrogen fixation from all over the world contribute up-to-the-minute general reviews on all aspects of the subject, from the molecular biology and genetics to the biochemistry, physiology, and ecology of nitrogen fixation. This compendium of current research is an indispensable reference for all involved in nitrogen fixation research, and of use to all who deal indirectly with the subject. It will also serve as a thoroughly up-to-date textbook for graduate students in microbiology, plant science, biochemistry, molecular biology, plant pathology, agronomy, and genetics.

WELDING AND METAL FABRICATION employs a unique hands-on, project-based learning strategy to teach welding skills effectively and keep you motivated. This groundbreaking new book connects each welding technique to a useful and creative take-home project, making exercises both practical and personal--and avoiding the tedium of traditional, repetitive welding practices. To further enhance the learning process, every welding project includes a set of prints with specifications, like those used in production fabrication shops. This full-featured approach to skill-building reflects the reality of professional welding, where following prints and instructions precisely and laying out, cutting out, and assembling weldment accurately are just as essential as high-quality welding. The included projects are small to conserve materials during the learning process, but detailed instructions and abundant photos and illustrations guide you through a wide range of fabrication skills. Key steps and techniques within the small projects are also linked to larger projects presented at the end of each chapter, enabling you to apply what you have learned by fabricating and welding something more substantial. This thorough, reader-friendly book also prepares you for real-world success by covering shop math and measurement, time and material tracking, and invoicing.