Deformation Behavior of Nanoporous Metals (open access)

Deformation Behavior of Nanoporous Metals

Nanoporous open-cell foams are a rapidly growing class of high-porosity materials (porosity {ge} 70%). The research in this field is driven by the desire to create functional materials with unique physical, chemical and mechanical properties where the material properties emerge from both morphology and the material itself. An example is the development of nanoporous metallic materials for photonic and plasmonic applications which has recently attracted much interest. The general strategy is to take advantage of various size effects to introduce novel properties. These size effects arise from confinement of the material by pores and ligaments, and can range from electromagnetic resonances to length scale effects in plasticity. In this chapter we will focus on the mechanical properties of low density nanoporous metals and how these properties are affected by length scale effects and bonding characteristics. A thorough understanding of the mechanical behavior will open the door to further improve and fine-tune the mechanical properties of these sometimes very delicate materials, and thus will be crucial for integrating nanoporous metals into products. Cellular solids with pore sizes above 1 micron have been the subject of intense research for many years, and various scaling relations describing the mechanical properties have been developed.[4] …
Date: November 28, 2007
Creator: Biener, J.; Hodge, A. M. & Hamza, A. V.
System: The UNT Digital Library
Timescales and settings for alteration of chondritic meteorites (open access)

Timescales and settings for alteration of chondritic meteorites

Most groups of chondritic meteorites experienced diverse styles of secondary alteration to various degrees that resulted in formation of hydrous and anhydrous minerals (e.g., phyllosilicates, magnetite, carbonates, ferrous olivine, hedenbergite, wollastonite, grossular, andradite, nepheline, sodalite, Fe,Ni-carbides, pentlandite, pyrrhotite, Ni-rich metal). Mineralogical, petrographic, and isotopic observations suggest that the alteration occurred in the presence of aqueous solutions under variable conditions (temperature, water/rock ratio, redox conditions, and fluid compositions) in an asteroidal setting, and, in many cases, was multistage. Although some alteration predated agglomeration of the final chondrite asteroidal bodies (i.e. was pre-accretionary), it seems highly unlikely that the alteration occurred in the solar nebula, nor in planetesimals of earlier generations. Short-lived isotope chronologies ({sup 26}Al-{sup 26}Mg, {sup 53}Mn-{sup 53}Cr, {sup 129}I-{sup 129}Xe) of the secondary minerals indicate that the alteration started within 1-2 Ma after formation of the Ca,Al-rich inclusions and lasted up to 15 Ma. These observations suggest that chondrite parent bodies must have accreted within the first 1-2 Ma after collapse of the protosolar molecular cloud and provide strong evidence for an early onset of aqueous activity on these bodies.
Date: November 16, 2005
Creator: Krot, A. N.; Hutcheon, I. D.; Brearley, A. J.; Pravdivtseva, O. V.; Petaev, M. I. & Hohenberg, C. M.
System: The UNT Digital Library
Reconstructing Past Ocean Salinity ((delta)18Owater) (open access)

Reconstructing Past Ocean Salinity ((delta)18Owater)

Temperature and salinity are two of the key properties of ocean water masses. The distribution of these two independent but related characteristics reflects the interplay of incoming solar radiation (insolation) and the uneven distribution of heat loss and gain by the ocean, with that of precipitation, evaporation, and the freezing and melting of ice. Temperature and salinity to a large extent, determine the density of a parcel of water. Small differences in temperature and salinity can increase or decrease the density of a water parcel, which can lead to convection. Once removed from the surface of the ocean where 'local' changes in temperature and salinity can occur, the water parcel retains its distinct relationship between (potential) temperature and salinity. We can take advantage of this 'conservative' behavior where changes only occur as a result of mixing processes, to track the movement of water in the deep ocean (Figure 1). The distribution of density in the ocean is directly related to horizontal pressure gradients and thus (geostrophic) ocean currents. During the Quaternary when we have had systematic growth and decay of large land based ice sheets, salinity has had to change. A quick scaling argument following that of Broecker and Peng …
Date: November 23, 2005
Creator: Guilderson, T. P. & Pak, D. K.
System: The UNT Digital Library
Detection of Topological Patterns in Protein Networks. (open access)

Detection of Topological Patterns in Protein Networks.

Complex networks appear in biology on many different levels: (1) All biochemical reactions taking place in a single cell constitute its metabolic network, where nodes are individual metabolites, and edges are metabolic reactions converting them to each other. (2) Virtually every one of these reactions is catalyzed by an enzyme and the specificity of this catalytic function is ensured by the key and lock principle of its physical interaction with the substrate. Often the functional enzyme is formed by several mutually interacting proteins. Thus the structure of the metabolic network is shaped by the network of physical interactions of cell's proteins with their substrates and each other. (3) The abundance and the level of activity of each of the proteins in the physical interaction network in turn is controlled by the regulatory network of the cell. Such regulatory network includes all of the multiple mechanisms in which proteins in the cell control each other including transcriptional and translational regulation, regulation of mRNA editing and its transport out of the nucleus, specific targeting of individual proteins for degradation, modification of their activity e.g. by phosphorylation/dephosphorylation or allosteric regulation, etc. To get some idea about the complexity and interconnectedness of protein-protein regulations …
Date: November 17, 2003
Creator: Maslov, S. & Sneppen, K.
System: The UNT Digital Library
Improving Compressed Air System Performance: A Sourcebook for Industry (open access)

Improving Compressed Air System Performance: A Sourcebook for Industry

NREL will produce this sourcebook for DOE's Industrial Technologies Office as part of a series of documents on industrial energy equipment. The sourcebook is a reference for industrial compressed air system users, outlining opportunities to improve system efficiency.
Date: November 1, 2003
Creator: unknown
System: The UNT Digital Library
Energy Design Guidelines for High Performance Schools: Tropical Island Climates (open access)

Energy Design Guidelines for High Performance Schools: Tropical Island Climates

The Energy Design Guidelines for High Performance Schools--Tropical Island Climates provides school boards, administrators, and design staff with guidance to help them make informed decisions about energy and environmental issues important to school systems and communities. These design guidelines outline high performance principles for the new or retrofit design of your K-12 school in tropical island climates. By incorporating energy improvements into their construction or renovation plans, schools can significantly reduce energy consumption and costs.
Date: November 1, 2004
Creator: unknown
System: The UNT Digital Library
Empowering Minority Communities with Health Information - WSSU (open access)

Empowering Minority Communities with Health Information - WSSU

Environmental health focus with training conducted as part of the United Negro College Fund Special Programs Corporation/National Library of Medicine HBCU ACCESS Project at Winston-Salem State University, NC on November 10, 2010.
Date: November 10, 2010
Creator: McMurray, L. and W. Templin-Branner
System: The UNT Digital Library
Metabolic Design and Control for Production in Prokaryotes (open access)

Metabolic Design and Control for Production in Prokaryotes

Prokaryotic life on earth is manifested by its diversity and omnipresence. These microbes serve as natural sources of a large variety of compounds with the potential to serve the ever growing, medicinal, chemical and transportation needs of the human population. However, commercially viable production of these compounds can be realized only through significant improvement of the native production capacity of natural isolates. The most favorable way to achieve this goal is through the genetic manipulation of metabolic pathways that direct the production of these molecules. While random mutagenesis and screening have dominated the industrial production of such compounds in the past our increased understanding of microbial physiology over the last five decades has shifted this trend towards rational approaches for metabolic design. Major drivers of this trend include recombinant DNA technology, high throughput characterization of macromolecular cellular components, quantitative modeling for metabolic engine ring, targeted combinatorial engineering and synthetic biology. In this chapter we track the evolution of microbial engineering technologies from the black box era of random mutagenesis to the science and engineering-driven era of metabolic design.
Date: November 10, 2010
Creator: Chhabra, Swapnil R. & Keasling, J.D.
System: The UNT Digital Library
Empowering Minority Communities with Health Information - UDC (open access)

Empowering Minority Communities with Health Information - UDC

Training update with Environmental a health focus. Training conducted as part of the United Negro College Fund Special Programs Corporation/National Library of Medicine - HBCU ACCESS Project at the University of the District of Columbia, Washington, DC on November 2, 2010.
Date: November 2, 2010
Creator: McMurray, L.; Foster, R. & Womble, and R.
System: The UNT Digital Library
Empowering Minority Communities with Health Information - ASU (open access)

Empowering Minority Communities with Health Information - ASU

Training Manual updated for United Negro College Fund Special Programs Corporation/National Library of Medicine - HBCU ACCESS Project for Alcorn State University, Natchez, Mississippi, November 12, 2010
Date: November 12, 2010
Creator: McMurray, L. and W. Templin-Branner
System: The UNT Digital Library
Empowering Minority Communities with Health Information - Howard (open access)

Empowering Minority Communities with Health Information - Howard

Training conducted as a part of the United Negro College Fund Special Programs/National Library of Medicine -HBCU ACCESS Project at Howard University, Washington, DC on November 20, 2010.
Date: November 16, 2010
Creator: McMurray, L. and R. Foster
System: The UNT Digital Library
Time-resolved THz studies of carrier dynamics in semiconductors, superconductors, and strongly-correlated electron materials (open access)

Time-resolved THz studies of carrier dynamics in semiconductors, superconductors, and strongly-correlated electron materials

Perhaps the most important aspect of contemporary condensed matter physics involves understanding strong Coulomb interactions between the large number of electrons in a solid. Electronic correlations lead to the emergence of new system properties, such as metal-insulator transitions, superconductivity, magneto-resistance, Bose-Einstein condensation, the formation of excitonic gases, or the integer and fractional Quantum Hall effects. The discovery of high-Tc superconductivity in particular was a watershed event, leading to dramatic experimental and theoretical advances in the field of correlated-electron systems. Such materials often exhibit competition between the charge, lattice, spin, and orbital degrees of freedom, whose cause-effect relationships are difficult to ascertain. Experimental insight into the properties of solids is traditionally obtained by time-averaged probes, which measure e.g., linear optical spectra, electrical conduction properties, or the occupied band structure in thermal equilibrium. Many novel physical properties arise from excitations out of the ground state into energetically higher states by thermal, optical, or electrical means. This leads to fundamental interactions between the system's constituents, such as electron-phonon and electron-electron interactions, which occur on ultrafast timescales. While these interactions underlie the physical properties of solids, they are often only indirectly inferred from time-averaged measurements. Time-resolved spectroscopy, consequently, is playing an ever increasing role …
Date: November 14, 2006
Creator: Kaindl, Robert A. & Averitt, Richard D.
System: The UNT Digital Library
THE ROLE OF DIELECTRIC CONTINUUM MODELS IN ELECTRON TRANSFER: THEORETICAL AND COMPUTATIONAL ASPECTS. (open access)

THE ROLE OF DIELECTRIC CONTINUUM MODELS IN ELECTRON TRANSFER: THEORETICAL AND COMPUTATIONAL ASPECTS.

Condensed phase physical and chemical processes generally involve interactions covering a wide range of distance scales, from short-range molecular interactions requiring orbital overlap to long-range coulombic interaction between local sites of excess charge (positive or negative monopoles). Intermediate-range distances pertain to higher-order multipolar as well as inductive and dispersion interactions. Efforts to model such condensed phase phenomena typically involve a multi-tiered strategy in which quantum mechanics is employed for full electronic structural characterization of a site of primary interest (e.g., a molecular solute or cluster), while more remote sites are treated at various classical limits (e.g., a molecular force field for discrete solvent molecules or a dielectric continuum (DC) model, if the solute is charged or has permanent multipole moments). In particular, DC models have been immensely valuable in modeling chemical reactivity and spectroscopy in media of variable polarity. Simple DC models account qualitatively for many important trends in the solvent dependence of reaction free energies, activation free energies, and optical excitation energies, and many results of semiquantitative or fully quantitative significance in comparison with experiment have been obtained, especially when detailed quantum chemical treatment of the solute is combined self consistently with DC treatment of the solvent (e.g., as …
Date: November 1, 2006
Creator: NEWTON, M.D.
System: The UNT Digital Library
THE DYNAMICS OF HYDROGEN ATOM ABSTRACTION FROM POLYATOMIC MOLECULES. (open access)

THE DYNAMICS OF HYDROGEN ATOM ABSTRACTION FROM POLYATOMIC MOLECULES.

The hydrogen atom abstraction reaction is an important fundamental process that is extensively involved in atmospheric and combustion chemistry. The practical significance of this type of reaction with polyatomic hydrocarbons is manifest, which has led to many kinetics studies. The detailed understanding of these reactions requires corresponding dynamics studies. However, in comparison to the A + HX {radical} AH + X reactions, the study of the dynamics of A + HR {yields} AH + R reactions is much more difficult, both experimentally and theoretically (here and in the following, A stands for an atom, X stands for a halogen atom, and R stands for a polyatomic hydrocarbon radical). The complication stems from the structured R, in contrast to the structureless X. First of all, there are many internal degrees of freedom in R that can participate in the reaction. In addition, there are different carbon sites from which an H atom can be abstracted, and the dynamics are correspondingly different; there are also multiple identical carbon sites in HR and in the picture of a local reaction, there exist competitions between neighboring H atoms, and so on. Despite this complexity, there have been continuing efforts to obtain insight into the …
Date: November 21, 2002
Creator: Liu, X. & Suits, A. G.
System: The UNT Digital Library
Energy Design Guidelines for High Performance Schools: Arctic and Subarctic Climates (open access)

Energy Design Guidelines for High Performance Schools: Arctic and Subarctic Climates

The Energy Design Guidelines for High Performance Schools--Arctic and Subarctic Climates provides school boards, administrators, and design staff with guidance to help them make informed decisions about energy and environmental issues important to school systems and communities. These design guidelines outline high performance principles for the new or retrofit design of your K-12 school in arctic and subarctic climates. By incorporating energy improvements into their construction or renovation plans, schools can significantly reduce energy consumption and costs.
Date: November 1, 2004
Creator: unknown
System: The UNT Digital Library
Large-Scale Topological Properties of Molecular Networks. (open access)

Large-Scale Topological Properties of Molecular Networks.

Bio-molecular networks lack the top-down design. Instead, selective forces of biological evolution shape them from raw material provided by random events such as gene duplications and single gene mutations. As a result individual connections in these networks are characterized by a large degree of randomness. One may wonder which connectivity patterns are indeed random, while which arose due to the network growth, evolution, and/or its fundamental design principles and limitations? Here we introduce a general method allowing one to construct a random null-model version of a given network while preserving the desired set of its low-level topological features, such as, e.g., the number of neighbors of individual nodes, the average level of modularity, preferential connections between particular groups of nodes, etc. Such a null-model network can then be used to detect and quantify the non-random topological patterns present in large networks. In particular, we measured correlations between degrees of interacting nodes in protein interaction and regulatory networks in yeast. It was found that in both these networks, links between highly connected proteins are systematically suppressed. This effect decreases the likelihood of cross-talk between different functional modules of the cell, and increases the overall robustness of a network by localizing effects …
Date: November 17, 2003
Creator: Maslov, S. & Sneppen, K.
System: The UNT Digital Library
Annual Report Fiscal Year 2001: Office of Industrial Technologies (OIT) Chemical Industry of the Future (open access)

Annual Report Fiscal Year 2001: Office of Industrial Technologies (OIT) Chemical Industry of the Future

The Chemical Annual Report provides program highlights during the past year. Included are updates on technology R&D projects, recent success, and industry trends.
Date: November 1, 2001
Creator: unknown
System: The UNT Digital Library
Statistical Modeling of Large-Scale Scientific Simulation Data (open access)

Statistical Modeling of Large-Scale Scientific Simulation Data

With the advent of massively parallel computer systems, scientists are now able to simulate complex phenomena (e.g., explosions of a stars). Such scientific simulations typically generate large-scale data sets over the spatio-temporal space. Unfortunately, the sheer sizes of the generated data sets make efficient exploration of them impossible. Constructing queriable statistical models is an essential step in helping scientists glean new insight from their computer simulations. We define queriable statistical models to be descriptive statistics that (1) summarize and describe the data within a user-defined modeling error, and (2) are able to answer complex range-based queries over the spatiotemporal dimensions. In this chapter, we describe systems that build queriable statistical models for large-scale scientific simulation data sets. In particular, we present our Ad-hoc Queries for Simulation (AQSim) infrastructure, which reduces the data storage requirements and query access times by (1) creating and storing queriable statistical models of the data at multiple resolutions, and (2) evaluating queries on these models of the data instead of the entire data set. Within AQSim, we focus on three simple but effective statistical modeling techniques. AQSim's first modeling technique (called univariate mean modeler) computes the ''true'' (unbiased) mean of systematic partitions of the data. AQSim's …
Date: November 15, 2003
Creator: Eliassi-Rad, T.; Baldwin, C.; Abdulla, G. & Critchlow, T.
System: The UNT Digital Library
Parallel Algebraic Multigrid Methods - High Performance Preconditioners (open access)

Parallel Algebraic Multigrid Methods - High Performance Preconditioners

The development of high performance, massively parallel computers and the increasing demands of computationally challenging applications have necessitated the development of scalable solvers and preconditioners. One of the most effective ways to achieve scalability is the use of multigrid or multilevel techniques. Algebraic multigrid (AMG) is a very efficient algorithm for solving large problems on unstructured grids. While much of it can be parallelized in a straightforward way, some components of the classical algorithm, particularly the coarsening process and some of the most efficient smoothers, are highly sequential, and require new parallel approaches. This chapter presents the basic principles of AMG and gives an overview of various parallel implementations of AMG, including descriptions of parallel coarsening schemes and smoothers, some numerical results as well as references to existing software packages.
Date: November 11, 2004
Creator: Yang, U. M.
System: The UNT Digital Library
Biological Treatment of Petroleum in Radiologically Contaminated Soil (open access)

Biological Treatment of Petroleum in Radiologically Contaminated Soil

This chapter describes ex situ bioremediation of the petroleum portion of radiologically co-contaminated soils using microorganisms isolated from a waste site and innovative bioreactor technology. Microorganisms first isolated and screened in the laboratory for bioremediation of petroleum were eventually used to treat soils in a bioreactor. The bioreactor treated soils contaminated with over 20,000 mg/kg total petroleum hydrocarbon and reduced the levels to less than 100 mg/kg in 22 months. After treatment, the soils were permanently disposed as low-level radiological waste. The petroleum and radiologically contaminated soil (PRCS) bioreactor operated using bioventing to control the supply of oxygen (air) to the soil being treated. The system treated 3.67 tons of PCRS amended with weathered compost, ammonium nitrate, fertilizer, and water. In addition, a consortium of microbes (patent pending) isolated at the Savannah River National Laboratory from a petroleum-contaminated site was added to the PRCS system. During operation, degradation of petroleum waste was accounted for through monitoring of carbon dioxide levels in the system effluent. The project demonstrated that co-contaminated soils could be successfully treated through bioventing and bioaugmentation to remove petroleum contamination to levels below 100 mg/kg while protecting workers and the environment from radiological contamination.
Date: November 14, 2005
Creator: BERRY, CHRISTOPHER
System: The UNT Digital Library
PV Working with Industry Newsletter: 2000 and beyond. Our time to shine (open access)

PV Working with Industry Newsletter: 2000 and beyond. Our time to shine

NREL PV Working With Industry is a quarterly newsletter devoted to the research, development, and deployment performed by NREL staff in concert with their industry and university partners. The Third Quarter, 1999 issue focuses on planning activities of the National Center for Photovoltaics (NCPV), including the PV Industry 20-Year Roadmap and the National Photovoltaics Program Plan. The editorialist is Allen Barnett, president of AstroPower, Inc., and a member of the NCPV Advisory Board.
Date: November 30, 1999
Creator: Moon, S.; Cook, G. & Poole, L.
System: The UNT Digital Library
CHARACTERIZATION OF GEOLOGICAL MATERIALS USING ION AND PHOTON BEAMS (open access)

CHARACTERIZATION OF GEOLOGICAL MATERIALS USING ION AND PHOTON BEAMS

Geological specimens are often complex materials that require different analytical methods for their characterization. The parameters of interest may include the chemical composition of major, minor and trace elements. The chemical compounds incorporated in the minerals, the crystal structure and isotopic composition need to be considered. Specimens may be highly heterogeneous thus necessitating analytical methods capable of measurements on small sample volumes with high spatial resolution and sensitivity. Much essential information on geological materials can be obtained by using ion or photon beams. In this chapter the authors describe the principal analytical techniques based on particle accelerators, showing some applications that are hardly possible with conventional methods. In particular, the following techniques will be discussed: (1) Synchrotron radiation (SR) induced X-ray emission (SRIXE) and particle-induced X-ray emission (PEE) and other ion beam techniques for trace element analysis; and (2) Accelerator mass spectrometry (AMS) for ultra sensitive analysis of stable nuclides and long-lived radionuclides. In most of the cases also the possibilities of elemental and isotopic analysis with high resolution will be discussed.
Date: November 1998
Creator: Torok, Sz. B.; Jones, K. W. & Tuniz, C.
System: The UNT Digital Library
PROPERTIES OF SILICON ON DEFECT LAYER MATERIAL. (open access)

PROPERTIES OF SILICON ON DEFECT LAYER MATERIAL.

None
Date: November 27, 1996
Creator: Li, H.
System: The UNT Digital Library
Method of recycling hazardous waste (open access)

Method of recycling hazardous waste

The production of primary metal from ores has long been a necessary, but environmentally devastating process. Over the past 20 years, in an effort to lessen environmental impacts, the metal processing industry has developed methods for recovering metal values from certain hazardous wastes. However, these processes leave residual molten slag that requires disposal in hazardous waste landfills. A new process recovers valuable metals, metal alloys, and metal oxides from hazardous wastes, such as electric arc furnace (EAF) dust from steel mills, mill scale, spent aluminum pot liners, and wastewater treatment sludge from electroplating. At the same time, the process does not create residual waste for disposal. This new method uses all wastes from metal production processes. These hazardous materials are converted to three valuable products - mineral wool, zinc oxide, and high-grade iron.
Date: November 11, 1999
Creator: unknown
System: The UNT Digital Library