Oak Ridge National Laboratory

About: Oak Ridge National Laboratory is a facility organization based out in Oak Ridge, Tennessee, United States. It is known for research contribution in the topics: Neutron & Ion. The organization has 31868 authors who have published 73724 publications receiving 2633689 citations. The organization is also known as: ORNL.

Fine root turnover in forest ecosystems in relation to quantity and form of nitrogen availability: a comparison of two methods.

Abstract: Two methods of estimating fine root production and turnover are compared for 13 forest ecosystems exhibiting a wide range in form (NH4+ vs. NO3-) and quantity of available nitrogen. The two methods are by comparison of seasonal maxima and minima in biomess and by nitrogen budgeting. Both methods give similar results for stands with low rates of nitrification. The budgeting method predicts higher fine root turnover and productivity than the max-min method for systems with significant rates of nitrification.

The environmental controls that govern the end product of bacterial nitrate respiration

Abstract: In the biogeochemical nitrogen cycle, microbial respiration processes compete for nitrate as an electron acceptor. Denitrification converts nitrate into nitrogenous gas and thus removes fixed nitrogen from the biosphere, whereas ammonification converts nitrate into ammonium, which is directly reusable by primary producers. We combined multiple parallel long-term incubations of marine microbial nitrate-respiring communities with isotope labeling and metagenomics to unravel how specific environmental conditions select for either process. Microbial generation time, supply of nitrite relative to nitrate, and the carbon/nitrogen ratio were identified as key environmental controls that determine whether nitrite will be reduced to nitrogenous gas or ammonium. Our results define the microbial ecophysiology of a biogeochemical feedback loop that is key to global change, eutrophication, and wastewater treatment.

Substrate and bond coat compositions: factors affecting alumina scale adhesion

Abstract: Thermally grown oxide scales that form beneath ZrO 2 top coats play an important role in determining the performance of thermal barrier coatings. Numerous factors, including the composition of both the alloy substrate and the bond coat, affect adhesion of the α -Al 2 O 3 scale. Three areas of focus in the formation of an `ideal', adherent scale encompass: (1) migration of Al and other elements in the metal substrate, (2) segregation of elements to the metal–scale interface and the scale grain boundaries, and (3) generation of stresses in the scale. Examples of the effects of reactive elements, Pt, indigenous S, and reaction temperature on scale adhesion are discussed.

Dekker encyclopedia of nanoscience and nanotechnology

Abstract: PREFACE TO SECOND EDITION The science of the ultra small nanoscience has dramatically exploded during the last few years, and the technologies operating with ultra small things the nanotechnologies acquired quickly a firm position in today s world of business, technological development, and public perception. Several factors contributed to the acceleration of scientific knowledge and technological progress in the last decades, among which the rapid development of fast computers, availability of high-resolution analytical techniques, and the progress of molecular biology and genetics are probably the most important. The result was an unprecedented expansion of the frontiers of science, which empowered the human genius with unlimited options of top-down and bottom-up methods for manipulation of materials structure and control of properties at multiple levels, from atomic to molecular, supramolecular, and biomolecular. Already a distinctive mark of 21st century, nanoscience and nanotechnology will certainly have a steadily increasing influence on the quality of life and the environment of this Planet for centuries to come. Dekker Encyclopedia of Nanoscience and Nanotechnology, Second Edition provides a comprehensive and detailed review, from multiple angles, of major developments in the human s quest for understanding and mastering of physical, chemical and biological objects and structures having at least one dimension smaller than about 100 nm. Under the expert supervision of the late Professor James A. Schwarz, Marcel Dekker, Inc. published the first edition in 2004 to great acclaim. The success of first edition, the development of the title through online updates, and the dynamics of this continuously growing field has created a high demand for a second edition only four years after the first edition. The second edition offers updated and revised entries, along with many additions that reflect the focus towards energy and environmental issues currently in the news. The new edition is expanded to six volumes. All entry titles have been revised to better reflect to the entry's content, while optimized for alphabetical listing. In addition, a comprehensive (though not exhaustive) topical table of contents has been designed, structured on 24 major topics and almost 100 subtopics. With a robust and efficient indexing system and staggered bleed tabs, this second print edition will be a useful reference tool for scientists in academia and national laboratories, engineers, students, as well as entrepreneurs, policy makers, and opinion builders. The online version of the Encyclopedia offers quick access to individual entries in HTML or PDF format, enriched graphical content, hundreds of color illustrations and photographs, and an efficient keyword search engine. Cristian I. Contescu Oak Ridge National Laboratory, Oak Ridge, Tennessee, USA Karol Putyera Shiva Technologies, Syracuse, New York, USA July 2008