Science.gov

Sample records for low-valence metal center

  1. Method of reforming gasoline to raise the octane thereof utilizing low valence chromium composited with non-oxidizing high surface area support

    SciTech Connect

    Gleim, W.K.T.

    1984-05-15

    This invention relates to a method of reforming gasoline to raise the octane number thereof utilizing a novel catalyst comprising a low valence chromium metallic component composited with a non-oxidizing high surface area support. The low valence metallic component is present in divalent form or as a combination of the metallic state and the divalent form-preferably as a chloride and/or bromide. The preferred support is a high surface area coke.

  2. Clustering of low-valence particles: structure and kinetics.

    PubMed

    Markova, Olga; Alberts, Jonathan; Munro, Edwin; Lenne, Pierre-François

    2014-08-01

    We compute the structure and kinetics of two systems of low-valence particles with three or six freely oriented bonds in two dimensions. The structure of clusters formed by trivalent particles is complex with loops and holes, while hexavalent particles self-organize into regular and compact structures. We identify the elementary structures which compose the clusters of trivalent particles. At initial stages of clustering, the clusters of trivalent particles grow with a power-law time dependence. Yet at longer times fusion and fission of clusters equilibrates and clusters form a heterogeneous phase with polydispersed sizes. These results emphasize the role of valence in the kinetics and stability of finite-size clusters.

  3. Effects of phase fraction on superconductivity of low-valence eutectic titanate films

    NASA Astrophysics Data System (ADS)

    Kurokawa, Hikaru; Yoshimatsu, Kohei; Sakata, Osami; Ohtomo, Akira

    2017-08-01

    Creation and characterization of mixed valence states in transition-metal oxides are a fundamental approach to search for the unprecedented electronic and magnetic properties. In contrast to complex oxides, mixed-valence simple oxides tend to form binary or ternary phases, and turning a valence from one to next must be accompanied by structural transformations owing to a lower tolerance for oxygen non-stoichiometry. In this paper, epitaxial growth and transport properties of low-valence titanate thin films are reported to shed light on recently discovered superconducting γ-phase Ti3O5 (γ-Ti3O5). Single-phase TiO and Ti2O3 films and eutectic films including TiO, Ti2O3, and γ-Ti3O5 phases were independently grown on α-Al2O3 (0001) substrates by using pulsed-laser deposition. The X-ray diffraction measurements revealed clear epitaxial relationships with substrates and among three eutectic phases. Temperature dependence of the resistivity revealed that the γ-Ti3O5-rich films exhibited superconductivity with a maximum of transition temperature (TC) of 6.3 K. Distinct effects of the phase fraction on TC are found between TiO- and Ti2O3-enriched samples, suggesting the complex mechanisms of the superconducting proximity effect.

  4. Metals Processing Laboratory User Center (MPLUS)

    SciTech Connect

    Mackiewicz-Ludtka, G.; Hayden, H.W.

    1997-04-01

    The Metals Processing Laboratory User (MPLUS) Center was officially designated as a DOE User Facility in February, 1996. It`s primary purpose is to assist researchers in key U.S. industries, universities, and federal laboratories in improving energy efficiency and enhancing U.S. competitiveness in the world market. The MPLUS Center provides users the unique opportunity to address technology-related issues to solve metals-processing problems from a fully integrated approach. DOE facilitates the process and catalyzes industrial interactions that enables technical synergy and financial leveraging to take place between the industrial sector identifying and prioritizing their technological needs, and MPLUS, which provides access to the technical expertise and specialized facilities to address these needs. MPLUS is designed to provide U.S. industries with access to the specialized technical expertise and equipment needed to solve metals-processing issues that limit the development and implementation of emerging metals-processing technologies. As originated, MPLUS includes the following four primary user centers: Metals Processing, Metals Joining, Metals Characterization, and Metals Process Modeling. These centers are devoted to assisting U.S. industries in adjusting to rapid changes in the marketplace and in improving products and processes. This approach optimizes the complementary strengths of industry and government. Tremendous industrial response, has resulted in MPLUS expanding to meet the ever-growing technical needs and requests initiated by U.S. industry.

  5. Metals and Ceramics Information Center.

    DTIC Science & Technology

    1982-07-01

    Information Center Box 8618 "Cameron Station (2) Ann Arbor, MI 48107 Alexandria, VA 22314 Mr. Ronald D. Brown DCASNA Chemical Propulsion Information Agency...MMh Tmnooq Pv.3wls addw S aidnm ENEfftbY AND CHEMICAL PROCESSES 10*1- R&D t-d P h nmmago * So-s Cnms. a"d W.ft l... *solid MW HmmI..s401 *we *Chmeal P o...staff have attended both the Regional and Annual DROLS Users meetings to be available to assist users of the MM4C and other IAC databses . ’I 40 Z ad C4

  6. Atomization of metal (Materials Preparation Center)

    SciTech Connect

    2010-01-01

    Atomization of metal requires high pressure gas and specialized chambers for cooling and collecting the powders without contamination. The critical step for morphological control is the impingement of the gas on the melt stream. The video is a color video of a liquid metal stream being atomized by high pressure gas. This material was cast at the Ames Laboratorys Materials Preparation Center http://www.mpc.ameslab.gov WARNING - AUDIO IS LOUD.

  7. The construction of metal centers in proteins by rational design.

    PubMed

    Hellinga, H W

    1998-01-01

    Metalloprotein properties result from the interplay between coordination requirements of the metal center, protein stability, and modulation of the metal center by the surrounding protein matrix. Simple metal centers, which exercise control over the protein by affecting stability or enzyme activity, have been created by rational design. Complex centers, which require control by the protein matrix, have also been constructed.

  8. PASSIVE VENTILATION DETAIL (CORRESPONDS WITH METAL GRATE IN CENTER OF ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    PASSIVE VENTILATION DETAIL (CORRESPONDS WITH METAL GRATE IN CENTER OF BATTERY STREET). LOOKING SOUTH AT GRATE IN SOUTHBOUND TUNNEL BORE. - Alaskan Way Viaduct and Battery Street Tunnel, Seattle, King County, WA

  9. Effective interatomic potential for body-centered-cubic metals

    SciTech Connect

    Wang, Y.R.; Boercker, D.B.

    1995-07-01

    An effective interatomic potential suitable for all body-centered-cubic (bcc) metals is developed based on the embedded atom method. The potential predicts all major anomalies displayed in the phonon spectra of the bcc transition metals, as well as the large relaxation of the (100) surface of V, Nb, and Ta. {copyright} {ital 1995} {ital American} {ital Institute} {ital of} {ital Physics}.

  10. 75 FR 76037 - General Motors Corporation Grand Rapids Metal Center Metal Fabricating Division Including On-Site...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-12-07

    ... Employment and Training Administration General Motors Corporation Grand Rapids Metal Center Metal Fabricating..., applicable to workers of General Motors Corporation, Grand Rapids Metal Center, Metal Fabricating Division... related to the production of metal stampings and sub- assembled metal sheet components. The...

  11. Metallicity of the Stars at the Galactic Center

    NASA Astrophysics Data System (ADS)

    Kohler, Susanna

    2015-08-01

    A recent study suggests that the stars in the central parsec of our galaxy are not a single, roughly solar-metallicity population, as previously thought. Instead, these stars have a large variation in metallicities which has interesting implications for the formation history of the Milky Ways nuclear star cluster.Clues from AbundancesWhy do we care about the metallicity of stars and stellar populations? Metallicity measurements can help us to separate multiple populations of stars and figure out when and where they were formed.Measurements of the chemical abundances of stars in the Milky Way have demonstrated that theres a metallicity gradient in the galaxy: on average, its below solar metallicity at the outer edges of the disk and increases to above solar metallicity within the central 5 kpc of the galaxy.So far, measurements of stars in the very center of the galaxy are consistent with this galactic trend: theyre all slightly above solar metallicity, with little variation between them. But these measurements exist for only about a dozen stars within the central 10 pc of the galaxy! Due to the high stellar density in this region, a larger sample is needed to get a complete picture of the abundances and thats what this study set out to find.Different PopulationsLed by Tuan Do (Dunlap Fellow at the University of Toronto and member of the Galactic Center Group at UCLA), the authors of this study determined the metallicities of 83 late-type giant stars within the central parsec of the galaxy. The metallicities were found by fitting the stars K-band spectra from observations by the NIFS instrument on the Gemini North telescope.In contrast to the previous studies, the authors found that the 83 stars exhibited a wide range of metallicities, from a tenth of solar metallicity all the way to super-solar metallicities.The abundances of the low-metallicity stars they found are consistent with globular cluster metallicities, suggesting that these stars (about 6% of the sample

  12. MCPB.py: A Python Based Metal Center Parameter Builder.

    PubMed

    Li, Pengfei; Merz, Kenneth M

    2016-04-25

    MCPB.py, a python based metal center parameter builder, has been developed to build force fields for the simulation of metal complexes employing the bonded model approach. It has an optimized code structure, with far fewer required steps than the previous developed MCPB program. It supports various AMBER force fields and more than 80 metal ions. A series of parametrization schemes to derive force constants and charge parameters are available within the program. We give two examples (one metalloprotein example and one organometallic compound example), indicating the program's ability to build reliable force fields for different metal ion containing complexes. The original version was released with AmberTools15. It is provided via the GNU General Public License v3.0 (GNU_GPL_v3) agreement and is free to download and distribute. MCPB.py provides a bridge between quantum mechanical calculations and molecular dynamics simulation software packages thereby enabling the modeling of metal ion centers. It offers an entry into simulating metal ions in a number of situations by providing an efficient way for researchers to handle the vagaries and difficulties associated with metal ion modeling.

  13. Ultrahigh hardness on a face-centered cubic metal

    NASA Astrophysics Data System (ADS)

    Zhang, Zhenyu; Huang, Siling; Chen, Leilei; Wang, Bo; Wen, Bin; Zhang, Bi; Guo, Dongming

    2017-09-01

    Nanotwinned (NT) surfaces are developed on a face-centered cubic (fcc) metal with ultrahigh hardness under cyclic loading using plastic deformation at room temperature. The hardness on NT surfaces remains constant at 7.9 and 8.5 GPa indented at 1 and 7 N under 0-100 cycles respectively, which are about three times that of their pristine surfaces. This is different from the NT metals and nonmetallic materials, on which the hardness is about two times that of their pristine counterparts. Moreover, NT metals usually consist of randomly oriented twin and grain boundaries, making it difficult to control the uniform mechanical property. Here, novel nt structure is proposed on an fcc metal, in which all the twin boundaries are along (-1-11) orientation, forming bundles of nanotwins to several micrometers in length.

  14. Emission properties of body-centered cubic elemental metal photocathodes

    SciTech Connect

    Li, Tuo; Rickman, Benjamin L. Schroeder, W. Andreas

    2015-04-07

    A first principles analysis of photoemission is developed to explain the lower than expected rms transverse electron momentum measured using the solenoid scan technique for the body-centered cubic Group Vb (V, Nb, and Ta) and Group VIb (Cr, Mo, and W) metallic photocathodes. The density functional theory based analysis elucidates the fundamental role that the electronic band structure (and its dispersion) plays in determining the emission properties of solid-state photocathodes and includes evaluation of work function anisotropy using a thin-slab method.

  15. Metallicity in the Galactic Center: The Arches Cluster

    NASA Astrophysics Data System (ADS)

    Najarro, Francisco; Figer, Donald F.; Hillier, D. John; Kudritzki, Rolf P.

    2004-04-01

    We present a quantitative spectral analysis of five very massive stars in the Arches cluster, located near the Galactic center, to determine stellar parameters, stellar wind properties, and, most importantly, metallicity content. The analysis uses a new technique, presented here for the first time, and uses line-blanketed non-LTE wind/atmosphere models fitted to high-resolution near-infrared spectra of late-type nitrogen-rich Wolf-Rayet stars and OfI+ stars in the cluster. It relies on the fact that massive stars reach a maximum nitrogen abundance that is related to initial metallicity when they are in the WNL phase. We determine the present-day nitrogen abundance of the WNL stars in the Arches cluster to be 1.6% (mass fraction) and constrain the stellar metallicity in the cluster to be solar. This result is invariant to assumptions about the mass-luminosity relationship, the mass-loss rates, and rotation speeds. In addition, from this analysis, we find the age of the Arches cluster to be 2-2.5 Myr, assuming coeval formation.

  16. Theory for plasticity of face-centered cubic metals.

    PubMed

    Jo, Minho; Koo, Yang Mo; Lee, Byeong-Joo; Johansson, Börje; Vitos, Levente; Kwon, Se Kyun

    2014-05-06

    The activation of plastic deformation mechanisms determines the mechanical behavior of crystalline materials. However, the complexity of plastic deformation and the lack of a unified theory of plasticity have seriously limited the exploration of the full capacity of metals. Current efforts to design high-strength structural materials in terms of stacking fault energy have not significantly reduced the laborious trial and error works on basic deformation properties. To remedy this situation, here we put forward a comprehensive and transparent theory for plastic deformation of face-centered cubic metals. This is based on a microscopic analysis that, without ambiguity, reveals the various deformation phenomena and elucidates the physical fundaments of the currently used phenomenological correlations. We identify an easily accessible single parameter derived from the intrinsic energy barriers, which fully specifies the potential diversity of metals. Based entirely on this parameter, a simple deformation mode diagram is shown to delineate a series of convenient design criteria, which clarifies a wide area of material functionality by texture control.

  17. Immobilization of photosynthetic reaction centers on metal surfaces

    SciTech Connect

    Cotton, T.M.; Chumanov, G.; Gual, D.

    1993-12-31

    Membrane-bound proteins are ideal candidates for immobilization on surfaces because of their distinct hydrophobic and hydrophilic regions. Their interaction with a particular surface should depend upon its hydrophilicity. Variation of the surface properties is expected to result in changes in the orientation of an absorbed protein. In this study, two methods for immobilization of reaction centers from Rhodobacter sphaeroids on metal surfaces have been compared, including self-assembly or spontaneous adsorption and Langmuir-Blodgett transfer of monolayers from an air/water interface. The effect of the immobilization procedure on the structure of the protein complex has been determined from photochemical activity and optical measurements. The experimental variables which are critical for maintaining the structure and function of the protein in the adsorbed state will be discussed.

  18. Final report for the DOE Metal Hydride Center of Excellence.

    SciTech Connect

    Keller, Jay O.; Klebanoff, Leonard E.

    2012-01-01

    This report summarizes the R&D activities within the U.S. Department of Energy Metal Hydride Center of Excellence (MHCoE) from March 2005 to June 2010. The purpose of the MHCoE has been to conduct highly collaborative and multi-disciplinary applied R&D to develop new reversible hydrogen storage materials that meet or exceed DOE 2010 and 2015 system goals for hydrogen storage materials. The MHCoE combines three broad areas: mechanisms and modeling (which provide a theoretically driven basis for pursuing new materials), materials development (in which new materials are synthesized and characterized) and system design and engineering (which allow these new materials to be realized as practical automotive hydrogen storage systems). This Final Report summarizes the organization and execution of the 5-year research program to develop practical hydrogen storage materials for light duty vehicles. Major results from the MHCoE are summarized, along with suggestions for future research areas.

  19. Quantum dot photosensitizers. Interactions with transition metal centers.

    PubMed

    Burks, Peter T; Ford, Peter C

    2012-11-14

    Semiconductor quantum dots (QDs) are attractive for potential use as photosensitizers for a variety of applications. These nanomaterials have very high absorption cross-sections and often display strong photoluminescence (PL). Furthermore, QD absorption and emission spectra can be tuned simply by varying their size, and QD surfaces can be modified to access multiple sites for attaching potential acceptors as well as other functionalities. Here we provide an overview of recent studies concerned with the photosensitization of transition metal centers and other acceptors. Particular focus is directed towards potential therapeutic applications and to our own interest in the delivery of small molecule bioregulators to physiological targets. Studies that have addressed factors that control likely energy and charge transfer processes between QD donors and acceptor molecules are also discussed. Understanding the mechanisms of these photosensitization processes can provide design guidelines for successful applications.

  20. 5-year review of Metal Hydride Center of Excellence.

    SciTech Connect

    Keller, Jay O.; Klebanoff, Leonard E.

    2010-05-01

    The purpose of the DOE Metal Hydride Center of Excellence (MHCoE) is to develop hydrogen storage materials with engineering properties that allow the use of these materials in a way that satisfies the DOE/FreedomCAR Program system requirements for automotive hydrogen storage. The Center is a multidisciplinary and collaborative effort with technical interactions divided into two broad areas: (1) mechanisms and modeling (which provide a theoretically driven basis for pursuing new materials) and (2) materials development (in which new materials are synthesized and characterized). Driving all of this work are the hydrogen storage system specifications outlined by the FreedomCAR Program for 2010 and 2015. The organization of the MHCoE during the past year is show in Figure 1. During the past year, the technical work was divided into four project areas. The purpose of the project areas is to organize the MHCoE technical work along appropriate and flexible technical lines. The four areas summarized are: (1) Project A - Destabilized Hydrides, The objective of this project is to controllably modify the thermodynamics of hydrogen sorption reactions in light metal hydrides using hydride destabilization strategies; (2) Project B - Complex Anionic Materials, The objective is to predict and synthesize highly promising new anionic hydride materials; (3) Project C - Amides/Imides Storage Materials, The objective of Project C is to assess the viability of amides and imides (inorganic materials containing NH{sub 2} and NH moieties, respectively) for onboard hydrogen storage; and (4) Project D - Alane, AlH{sub 3}, The objective of Project D is to understand the sorption and regeneration properties of AlH{sub 3} for hydrogen storage.

  1. Hydrogen Storage Engineering Center of Excellence Metal Hydride Final Report

    SciTech Connect

    Motyka, T.

    2014-05-31

    The Hydrogen Storage Engineering Center of Excellence (HSECoE) was established in 2009 by the U.S. Department of Energy (DOE) to advance the development of materials-based hydrogen storage systems for hydrogen-fueled light-duty vehicles. The overall objective of the HSECoE is to develop complete, integrated system concepts that utilize reversible metal hydrides, adsorbents, and chemical hydrogen storage materials through the use of advanced engineering concepts and designs that can simultaneously meet or exceed all the DOE targets. This report describes the activities and accomplishments during Phase 1 of the reversible metal hydride portion of the HSECoE, which lasted 30 months from February 2009 to August 2011. A complete list of all the HSECoE partners can be found later in this report but for the reversible metal hydride portion of the HSECoE work the major contributing organizations to this effort were the United Technology Research Center (UTRC), General Motors (GM), Pacific Northwest National Laboratory (PNNL), the National Renewable Energy Laboratory (NREL) and the Savannah River National Laboratory (SRNL). Specific individuals from these and other institutions that supported this effort and the writing of this report are included in the list of contributors and in the acknowledgement sections of this report. The efforts of the HSECoE are organized into three phases each approximately 2 years in duration. In Phase I, comprehensive system engineering analyses and assessments were made of the three classes of storage media that included development of system level transport and thermal models of alternative conceptual storage configurations to permit detailed comparisons against the DOE performance targets for light-duty vehicles. Phase 1 tasks also included identification and technical justifications for candidate storage media and configurations that should be capable of reaching or exceeding the DOE targets. Phase 2 involved bench-level testing and

  2. Molecular hydrogen "pairing" interaction in a metal organic framework system with unsaturated metal centers (MOF-74).

    PubMed

    Nijem, Nour; Veyan, Jean-François; Kong, Lingzhu; Wu, Haohan; Zhao, Yonggang; Li, Jing; Langreth, David C; Chabal, Yves J

    2010-10-27

    Infrared (IR) absorption spectroscopy measurements of molecular hydrogen in MOF-74-M (M = metal center) are performed as a function of temperature and pressure [to 45 kTorr (60 bar) at 300 K, and at lower pressures in the 20-200 K range] to investigate the nature of H(2) interactions with the unsaturated metal centers. A small shift (∼ -30 cm(-1) with respect to the unperturbed H(2) molecule) is observed for the internal stretch frequency of H(2) molecules adsorbed on the metal site at low loading. This finding is in contrast to much larger shifts (∼ -70 cm(-1)) observed in previous studies of MOFs with unsaturated metal centers (including MOF-74) and the general assumption that H(2) stretch shifts depend on adsorption energies (FitzGerald et al., Phys. Rev. B 2010, 81, 104305). We show that larger shifts (∼ -70 cm(-1)) do occur, but only when the next available site ("oxygen" site) is occupied. This larger shift originates from H(2)-H(2) interactions on neighboring sites of the same pore, consistent with the short distance between H(2) in these two sites ∼2.6 Å derived from an analysis of neutron diffraction experiments of D(2)-D(2) at 4 K (Liu et al., Langmuir 2008, 24, 4772-4777). Our results at 77 K and low loading can be explained by a diffusion barrier against pair disruption, which should be enhanced by this interaction. Calculations indicate that the vibrational shifts do not correlate with binding energies and are instead very sensitive to the environment (interaction potential and H(2)-H(2) interactions), which complicates the use of variable temperature IR methods to calculate adsorption energies of specific adsorption sites.

  3. Orbital-like motion of hydride ligands around low-coordinate metal centers.

    PubMed

    Ortuño, Manuel A; Vidossich, Pietro; Conejero, Salvador; Lledós, Agustí

    2014-12-15

    Hydrogen atoms in the coordination sphere of a transition metal are highly mobile ligands. Here, a new type of dynamic process involving hydrides has been characterized by computational means. This dynamic event consists of an orbital-like motion of hydride ligands around low-coordinate metal centers containing N-heterocyclic carbenes. The hydride movement around the carbene-metal-carbene axis is the lowest energy mode connecting energy equivalent isomers. This understanding provides crucial information for the interpretation of NMR spectra.

  4. Increasing the density of adsorbed hydrogen with coordinatively unsaturated metal centers in metal-organic frameworks.

    PubMed

    Liu, Yun; Kabbour, Houria; Brown, Craig M; Neumann, Dan A; Ahn, Channing C

    2008-05-06

    Storing molecular hydrogen in porous media is one of the promising avenues for mobile hydrogen storage. In order to achieve technologically relevant levels of gravimetric density, the density of adsorbed H2 must be increased beyond levels attained for typical high surface area carbons. Here, we demonstrate a strong correlation between exposed and coordinatively unsaturated metal centers and enhanced hydrogen surface density in many framework structures. We show that the MOF-74 framework structure with open Zn(2+) sites displays the highest surface density for physisorbed hydrogen in framework structures. Isotherm and neutron scattering methods are used to elucidate the strength of the guest-host interactions and atomic-scale bonding of hydrogen in this material. As a metric with which to compare adsorption density with other materials, we define a surface packing density and model the strength of the H(2-)surface interaction required to decrease the H(2)-H(2) distance and to estimate the largest possible surface packing density based on surface physisorption methods.

  5. Dual-Metal Centered Zirconium-Organic Framework: A Metal-Affinity Probe for Highly Specific Interaction with Phosphopeptides.

    PubMed

    Peng, Jiaxi; Zhang, Hongyan; Li, Xin; Liu, Shengju; Zhao, Xingyun; Wu, Jing; Kang, Xiaohui; Qin, Hongqiang; Pan, Zaifa; Wu, Ren'an

    2016-12-28

    The highly specific affinity between probes and phosphopeptides is the fundamental interaction for selective identification of phosphoproteomes that uncover the mechanisms of signal transduction, cell cycle, enzymatic regulation, and gene expression in biological systems. In this study, a metal-affinity probe possessing both interactions of metal oxide affinity chromatography (MOAC) and immobilized metal ion affinity chromatography (IMAC) was facilely prepared by immobilizing zirconium(IV) on a zirconium-organic framework of UiO-66-NH2, which holds dual-metal centers of not only the inherent Zr-O cluster but also the immobilized Zr(IV) center. This dual-metal centered zirconium-organic framework (DZMOF) demonstrates as a highly specific metal-affinity probe toward the extraction of phosphopeptides due to the metal-affinity interactions of MOAC and IMAC toward either mono-phosphorylated or multi-phosphorylated peptides. The binding energies of zirconium 3d5/2 and 3d3/2 in this DZMOF are 183.07 and 185.47 eV, respectively, which are higher than those of the intact UiO-66-NH2 (182.84 and 185.17 eV, respectively), confirming the higher metal-affinity interaction between the DZMOF and phosphopeptides. This high metal-affinity probe presents an unprecedented strong performance in anti-nonspecific interference during the capturing of phosphopeptides of β-casein with the molar ratio of β-casein vs bovine serum albumin up to ca. 1:5000. The enrichment of phosphopeptides from a human saliva sample by DZMOF further confirms the great potential of DZMOF in the extraction of low-abundance phosphopeptides for real complex biological samples.

  6. Economizer Based Data Center Liquid Cooling with Advanced Metal Interfaces

    SciTech Connect

    Timothy Chainer

    2012-11-30

    A new chiller-less data center liquid cooling system utilizing the outside air environment has been shown to achieve up to 90% reduction in cooling energy compared to traditional chiller based data center cooling systems. The system removes heat from Volume servers inside a Sealed Rack and transports the heat using a liquid loop to an Outdoor Heat Exchanger which rejects the heat to the outdoor ambient environment. The servers in the rack are cooled using a hybrid cooling system by removing the majority of the heat generated by the processors and memory by direct thermal conduction using coldplates and the heat generated by the remaining components using forced air convection to an air- to- liquid heat exchanger inside the Sealed Rack. The anticipated benefits of such energy-centric configurations are significant energy savings at the data center level. When compared to a traditional 10 MW data center, which typically uses 25% of its total data center energy consumption for cooling this technology could potentially enable a cost savings of up to $800,000-$2,200,000/year (assuming electricity costs of 4 to 11 cents per kilowatt-hour) through the reduction in electrical energy usage.

  7. ETV METAL FINISHING TECHNOLOGIES CENTER AND POLLUTION PREVENTION, RECYCLING AND WASTE TREATMENT SYSTEMS CENTER BRIEFING

    EPA Science Inventory

    USEPA's ETV program has completed it's 5-year pilot-phase activities and is now in the implementation phase. The 12 environmental media-focused pilots have evolved into 6 center one of which is the new Pollution prevention, Recycling, and Waste Treatment Systems Center. The P2/R/...

  8. U.S. Department of Energy National Center of Excellence for Metals Recycle

    SciTech Connect

    Adams, V.; Bennett, M.; Bishop, L.

    1998-05-01

    The US Department of Energy (DOE) National Center of Excellence for Metals Recycle has recently been established. The vision of this new program is to develop a DOE culture that promotes pollution prevention by considering the recycle and reuse of metal as the first and primary disposition option and burial as a last option. The Center of Excellence takes the approach that unrestricted release of metal is the first priority because it is the most cost-effective disposition pathway. Where this is not appropriate, restricted release, beneficial reuse, and stockpile of ingots are considered. Current recycling activities include the sale of 40,000 tons of scrap metal from the East Tennessee Technology Park (formerly K-25 Plant) K-770 scrap yard, K-1064 surplus equipment and machinery, 7,000 PCB-contaminated drums, 12,000 tons of metal from the Y-l2 scrap yard, and 1,000 metal pallets. In addition, the Center of Excellence is developing a toolbox for project teams that will contain a number of specific tools to facilitate metals recycle. This Internet-based toolbox will include primers, computer programs, and case studies designed to help sites to perform life cycle analysis, perform ALARA (As Low As is Reasonably Achievable) analysis for radiation exposures, provide pollution prevention information and documentation, and produce independent government estimates. The use of these tools is described for two current activities: disposition of scrap metal in the Y-12 scrapyard, and disposition of PCB-contaminated drums.

  9. U.S. Department of Energy National Center of Excellence for Metals Recycle

    SciTech Connect

    Adams, V.; Bennett, M.; Bishop, L.

    1998-06-01

    The US Department of Energy (DOE) National Center of Excellence for Metals Recycle has recently been established. The vision of this new program is to develop a DOE culture that promotes pollution prevention by considering the recycle and reuse of metal as the first and primary disposition option and burial as a last option. The Center of Excellence takes the approach that unrestricted release of metal is the first priority because it is the most cost-effective disposition pathway. Where this is not appropriate, restricted release, beneficial reuse, and stockpile of ingots are considered. The Center has gotten off to a fast start. Current recycling activities include the sale of 40,000 tons of scrap metal from the East Tennessee Technology Park (formerly K-25 Plant) K-770 scrap yard, K-1064 surplus equipment and machinery, 7,000 PCB-contaminated drums, 12,000 tons of metal from the Y-12 scrap yard, and 1,000 metal pallets. In addition, the Center of Excellence is developing a toolbox for project teams that will contain a number of specific tools to facilitate metals recycle. This Internet-based toolbox will include primers, computer software, and case studies designed to help sites to perform life cycle analysis, perform ALARA (As Low As is Reasonably Achievable) analysis for radiation exposures, produce pollution prevention information and documentation, manage their materials inventory, produce independent government estimates, and implement sale/service contracts. The use of these tools is described for two current activities: disposition of scrap metal in the Y-12 scrap yard, and disposition of PCB-contaminated drums. Members of the Center look forward to working with all DOE sites, regulatory authorities, the private sector, and other stakeholders to achieve the metals recycle goals.

  10. The mononuclear metal center of type-I dihydroorotase from aquifex aeolicus

    PubMed Central

    2013-01-01

    Background Dihydroorotase (DHO) is a zinc metalloenzyme, although the number of active site zinc ions has been controversial. E. coli DHO was initially thought to have a mononuclear metal center, but the subsequent X-ray structure clearly showed two zinc ions, α and β, at the catalytic site. Aquifex aeolicus DHO, is a dodecamer comprised of six DHO and six aspartate transcarbamoylase (ATC) subunits. The isolated DHO monomer, which lacks catalytic activity, has an intact α-site and conserved β-site ligands, but the geometry of the second metal binding site is completely disrupted. However, the putative β-site is restored when the complex with ATC is formed and DHO activity is regained. Nevertheless, the X-ray structure of the complex revealed a single zinc ion at the active site. The structure of DHO from the pathogenic organism, S. aureus showed that it also has a single active site metal ion. Results Zinc analysis showed that the enzyme has one zinc/DHO subunit and the addition of excess metal ion did not stimulate catalytic activity, nor alter the kinetic parameters. The metal free apoenzyme was inactive, but the full activity was restored upon the addition of one equivalent of Zn2+ or Co2+. Moreover, deletion of the β-site by replacing the His180 and His232 with alanine had no effect on catalysis in the presence or absence of excess zinc. The 2.2 Å structure of the double mutant confirmed that the β-site was eliminated but that the active site remained otherwise intact. Conclusions Thus, kinetically competent A. aeolicus DHO has a mononuclear metal center. In contrast, elimination of the putative second metal binding site in amidohydrolyases with a binuclear metal center, resulted in the abolition of catalytic activity. The number of active site metal ions may be a consideration in the design of inhibitors that selectively target either the mononuclear or binuclear enzymes. PMID:24314009

  11. Interaction of molecular hydrogen with open transition metal centers for enhanced binding in metal-organic frameworks: a computational study.

    PubMed

    Lochan, Rohini C; Khaliullin, Rustam Z; Head-Gordon, Martin

    2008-05-19

    Molecular hydrogen is known to form stable, "nonclassical" sigma complexes with transition metal centers that are stabilized by donor-acceptor interactions and electrostatics. In this computational study, we establish that strong H2 sorption sites can be obtained in metal-organic frameworks by incorporating open transition metal sites on the organic linkers. Using density functional theory and energy decomposition analysis, we investigate the nature and characteristics of the H2 interaction with models of exposed open metal binding sites {half-sandwich piano-stool shaped complexes of the form (Arene)ML(3- n)(H2)n [M=Cr, Mo, V(-), Mn(+); Arene = C6H5X (X=H, F, Cl, OCH3, NH2, CH3, CF3) or C6H3Y2X (Y=COOH, X=CF3, Cl; L=CO; n=1-3]}. The metal-H2 bond dissociation energy of the studied complexes is calculated to be between 48 and 84 kJ/mol, based on the introduction of arene substituents, changes to the metal core, and of charge-balancing ligands. Thus, design of the binding site controls the H2 binding affinity and could be potentially used to control the magnitude of the H2 interaction energy to achieve reversible sorption characteristics at ambient conditions. Energy decomposition analysis illuminates both the possibilities and present challenges associated with rational materials design.

  12. Synthesis and microstructure of electrodeposited and sputtered nanotwinned face-centered-cubic metals

    SciTech Connect

    Bufford, Daniel C.; Wang, Morris; Liu, Yue; Lu, Lei

    2016-04-01

    The remarkable properties of nanotwinned (NT) face-centered-cubic (fcc) metals arise directly from twin boundaries, the structures of which can be initially determined by growth twinning during the deposition process. When we understand the synthesis process and its relation to the resulting microstructure, and ultimately to material properties, we realize how key it is to understanding and utilizing these materials. Furthermore, our article presents recent studies on electrodeposition and sputtering methods that produce a high density of nanoscale growth twins in fcc metals. Nanoscale growth twins tend to form spontaneously in monolithic and alloyed fcc metals with lower stacking-fault energies, while engineered approaches are necessary for fcc metals with higher stacking-fault energies. Finally, growth defects and other microstructural features that influence nanotwin behavior and stability are introduced here, and future challenges in fabricating NT materials are highlighted.

  13. Synthesis and microstructure of electrodeposited and sputtered nanotwinned face-centered-cubic metals

    DOE PAGES

    Bufford, Daniel C.; Wang, Morris; Liu, Yue; ...

    2016-04-01

    The remarkable properties of nanotwinned (NT) face-centered-cubic (fcc) metals arise directly from twin boundaries, the structures of which can be initially determined by growth twinning during the deposition process. When we understand the synthesis process and its relation to the resulting microstructure, and ultimately to material properties, we realize how key it is to understanding and utilizing these materials. Furthermore, our article presents recent studies on electrodeposition and sputtering methods that produce a high density of nanoscale growth twins in fcc metals. Nanoscale growth twins tend to form spontaneously in monolithic and alloyed fcc metals with lower stacking-fault energies, whilemore » engineered approaches are necessary for fcc metals with higher stacking-fault energies. Finally, growth defects and other microstructural features that influence nanotwin behavior and stability are introduced here, and future challenges in fabricating NT materials are highlighted.« less

  14. Detailed Abundance Analysis of a Metal-poor Giant in the Galactic Center

    NASA Astrophysics Data System (ADS)

    Ryde, N.; Fritz, T. K.; Rich, R. M.; Thorsbro, B.; Schultheis, M.; Origlia, L.; Chatzopoulos, S.

    2016-11-01

    We report the first results from our program to examine the metallicity distribution of the Milky Way nuclear star cluster connected to Sgr A*, with the goal of inferring the star formation and enrichment history of this system, as well as its connection and relationship with the central 100 pc of the bulge/bar system. We present the first high-resolution (R ˜ 24,000), detailed abundance analysis of a K = 10.2 metal-poor, alpha-enhanced red giant projected at 1.5 pc from the Galactic center, using NIRSPEC on Keck II. A careful analysis of the dynamics and color of the star locates it at about {26}-16+54 pc line-of-sight distance in front of the nuclear cluster. It probably belongs to one of the nuclear components (cluster or disk), not to the bar/bulge or classical disk. A detailed spectroscopic synthesis, using a new line list in the K band, finds [Fe/H] ˜ -1.0 and [α/Fe] ˜ +0.4, consistent with stars of similar metallicity in the bulge. As known giants with comparable [Fe/H] and alpha enhancement are old, we conclude that this star is most likely to be a representative of the ˜10 Gyr old population. This is also the most metal-poor-confirmed red giant yet discovered in the vicinity of the nuclear cluster of the Galactic center. We consider recent reports in the literature of a surprisingly large number of metal-poor giants in the Galactic center, but the reported gravity of {log}g˜ 4 for these stars calls into question their reported metallicities.

  15. Photochemical reactions of metal nitrosyl complexes. Mechanisms of NO reactions with biologically relevant metal centers

    DOE PAGES

    Ford, Peter C.

    2001-01-01

    Tmore » he discoveries that nitric oxide (a.k.a. nitrogen monoxide) serves important roles in mammalian bioregulation and immunology have stimulated intense interest in the chemistry and biochemistry of NO and derivatives such as metal nitrosyl complexes. Also of interest are strategies to deliver NO to biological targets on demand. One such strategy would be to employ a precursor which displays relatively low thermal reactivity but is photochemically active to release NO.his proposition led us to investigate laser flash and continuous photolysis kinetics of nitrosyl complexes such as the Roussin's iron-sulfur-nitrosyl cluster anions Fe 2 S 2 ( NO ) 4 2 − and Fe 4 S 3 ( NO ) 7 − and several ruthenium salen and porphyrin nitrosyls.hese include studies using metal-nitrosyl photochemistry as a vehicle for delivering NO to hypoxic cell cultures in order to sensitize γ -radiation damage. Also studied were the rates and mechanisms of NO “on” reactions with model water soluble heme compounds, the ferriheme protein met-myoglobin and various ruthenium complexes using ns laser flash photolysis techniques. An overview of these studies is presented.« less

  16. Understanding H2- H2 interactions in Metal Organic Frameworks (MOFs) with unsaturated metal centers

    NASA Astrophysics Data System (ADS)

    Nijem, Nour; Veyan, Jean F.; Kong, Lingzhu; Zhao, Yonggang; Li, Jing; Langreth, David; Chabal, Yves J.

    2011-03-01

    Unsaturated Metal Organic Frameworks (MOFs) are particularly interesting due to their high H2 uptakes with relatively large isosteric heats of adsorption (Qst > 8 kJ / mol) . ThisworkexploresH 2 - H 2 interactionsbetweenadsorbedH 2 atthedifferentsitesinMOF - 74 (M 2 (dhtp) , dhtp = 2 , 5 - dihydroxyterephthalate) andcombinesIRspectroscopywithvdW - DFTcalculations . TheadsorptionsitesinMOF - 74 arefromhighesttolowestbindingenergiesthemetal , oxygen , benzeneandpore - centersites . ThefrequencyofadsorbedH 2 atthemetalsitesuffersanadditional ~ - 30 cm -1 redshift (forMgandZn) and ~ - 84 cm -1 (forCo) whentheneighboringoxygensiteisoccupied . ThedipolemomentofadsorbedH 2 isalsoaffected . TheseinteractionsextendtothebenzenesitesforMOF - 74 - Co . AdecreaseindipolemomentofH 2 adsorbedatthemetalsiteisobservedwiththepartialoccupationofthebenzenesites . However , thecompleteoccupationofthebenzenesitesinducesanadditional ~ - 10 cm -1 red shift. DOE Grant No. DE-FG02-08ER46491.

  17. Low-valence triruthenium compounds via substitution of a bridging acetate in the parent Ru(3)O(OAc)(6) cluster core by 2,2'-azobispyridine (abpy) or 2,2'-azobis(5-chloropyrimidine) (abcp).

    PubMed

    Ye, Heng-Yun; Dai, Feng-Rong; Zhang, Li-Yi; Chen, Zhong-Ning

    2007-07-23

    Reaction of oxo-centered Ru(3)(III,III,III) precursor [Ru(3)O(OAc)(6)(py)(2)(CH(3)OH)](PF(6)) (1) with 1 equiv of 2,2'-azobispyridine (abpy) or 2,2'-azobis(5-chloropyrimidine) (abcp) induced the formation of stable Ru(3)(III,III,II) derivatives [Ru(3)O(OAc)(5){mu-eta(1)(N),eta(2)(N,N)-L}(py)(2)](PF(6)) (L = abpy (2), abcp (3)). As established in the structure of 3 by X-ray crystallography, 2 or 3 is derived from 1 by substitution of the axial methanol and one of the bridging acetates in the parent Ru(3)O(OAc)(6) cluster core with abpy or abcp in an mu-eta(1)(N),eta(2)(N,N) bonding mode. Reduction of 3 by hydrazine induces isolation of one-electron reduced neutral Ru(3)(III,II,II) product Ru(3)O(OAc)(5){mu-eta(1)(N),eta(2)(N,N)-abcp}(py)(2) (3a). As revealed by electrochemical and spectroscopic studies, substituting one of the bridging acetates in the parent Ru(3)O(OAc)(6) cluster core by abcp or abpy modifies dramatically the electronic and redox characteristics in the triruthenium derivatives. Relative to that for the parent compound [Ru(3)O(OAc)(6)(py)(3)](PF(6)) (E(1/2) = -0.46 V), triruthenium-based redox potential in the redox process Ru(3)O(III,III,III)/Ru(3)O(III,III,II) is significantly anodic-shifted to E(1/2) = +0.36 V for 2 and E(1/2) = +0.53 V for 3. Furthermore, the anodic shifts of redox potentials are progressively enhanced with a decrease of the formal oxidation states in the triruthenium cluster cores. As a consequence of remarkable positive shifts for redox potentials, the low-valence Ru(3)(III,III,II) and Ru(3)(III,II,II) species are stabilized and accessible.

  18. Femtosecond Time-Resolved Infrared Spectra of Organometallic Complexes Bound to a Dinuclear Metal Center

    NASA Astrophysics Data System (ADS)

    Brown-Xu, Samantha E.; Durr, Christopher B.

    2012-06-01

    Compounds of the form M2L2L'2, where M2 is a quadruply bonded metal center (M = Mo or W) and L and L' are conjugated organic ligands, are known to show interesting photophysical properties and exhibit intense metal-to-ligand charge transfer (MLCT) transitions throughout the visible spectrum. Recently, we have modified one of the ligands to incorporate a transition metal carbonyl complex bound to an organic moiety. Following excitation into the MLCT band, the vibrational modes of the organometallic ligand can be observed by fs time-resolved infrared (TRIR) spectroscopy. This allows for a visualization of where the electron density resides in the excited states, which provides useful information for designing new materials that could later be incorporated into solar devices.

  19. Development of Li-Metal Battery Cell Chemistries at NASA Glenn Research Center

    NASA Technical Reports Server (NTRS)

    Lvovich, Vadim F.

    2015-01-01

    State-of-the-Art lithium-ion battery technology is limited by specific energy and thus not sufficiently advanced to support the energy storage necessary for aerospace needs, such as all-electric aircraft and many deep space NASA exploration missions. In response to this technological gap, our research team at NASA Glenn Research Center has been active in formulating concepts and developing testing hardware and components for Li-metal battery cell chemistries. Lithium metal anodes combined with advanced cathode materials could provide up to five times the specific energy versus state-of-the-art lithium-ion cells (1000 Whkg versus 200 Whkg). Although Lithium metal anodes offer very high theoretical capacity, they have not been shown to successfully operate reversibly.

  20. Beyond Metal-Hydrides: Non-Transition-Metal and Metal-Free Ligand-Centered Electrocatalytic Hydrogen Evolution and Hydrogen Oxidation.

    PubMed

    Haddad, Andrew Z; Garabato, Brady D; Kozlowski, Pawel M; Buchanan, Robert M; Grapperhaus, Craig A

    2016-06-29

    A new pathway for homogeneous electrocatalytic H2 evolution and H2 oxidation has been developed using a redox active thiosemicarbazone and its zinc complex as seminal metal-free and transition-metal-free examples. Diacetyl-bis(N-4-methyl-3-thiosemicarbazone) and zinc diacetyl-bis(N-4-methyl-3-thiosemicarbazide) display the highest reported TOFs of any homogeneous ligand-centered H2 evolution catalyst, 1320 and 1170 s(-1), respectively, while the zinc complex also displays one of the highest reported TOF values for H2 oxidation, 72 s(-1), of any homogeneous catalyst. Catalysis proceeds via ligand-centered proton-transfer and electron-transfer events while avoiding traditional metal-hydride intermediates. The unique mechanism is consistent with electrochemical results and is further supported by density functional theory. The results identify a new direction for the design of electrocatalysts for H2 evolution and H2 oxidation that are not reliant on metal-hydride intermediates.

  1. Dioxygen activation by non-adiabatic oxidative addition to a single metal center [O2 activation by non-adiabatic oxidative addition to a single metal center

    DOE PAGES

    Akturk, Eser S.; Yap, Glenn P. A.; Theopold, Klaus H.

    2015-10-16

    A chromium(I) dinitrogen complex reacts rapidly with O2 to form the mononuclear dioxo complex [TptBu,MeCrV(O)2] (TptBu,Me=hydrotris(3-tert-butyl-5-methylpyrazolyl)borate), whereas the analogous reaction with sulfur stops at the persulfido complex [TptBu,MeCrIII(S2)]. The transformation of the putative peroxo intermediate [TptBu,MeCrIII(O2)] (S=3/2) into [TptBu,MeCrV(O)2] (S=1/2) is spin-forbidden. The minimum-energy crossing point for the two potential energy surfaces has been identified. Finally, although the dinuclear complex [(TptBu,MeCr)2(μ-O)2] exists, mechanistic experiments suggest that O2 activation occurs on a single metal center, by an oxidative addition on the quartet surface followed by crossover to the doublet surface.

  2. Two-Center/Three-Electron Sigma Half-Bonds in Main Group and Transition Metal Chemistry.

    PubMed

    Berry, John F

    2016-01-19

    First proposed in a classic Linus Pauling paper, the two-center/three-electron (2c/3e) σ half-bond challenges the extremes of what may or may not be considered a chemical bond. Two electrons occupying a σ bonding orbital and one electron occupying the antibonding σ* orbital results in bond orders of ∼0.5 that are characteristic of metastable and exotic species, epitomized in the fleetingly stable He2(+) ion. In this Account, I describe the use of coordination chemistry to stabilize such fugacious three-electron bonded species at disparate ends of the periodic table. A recent emphasis in the chemistry of metal-metal bonds has been to prepare compounds with extremely short metal-metal distances and high metal-metal bond orders. But similar chemistry can be used to explore metal-metal bond orders less than one, including 2c/3e half-bonds. Bimetallic compounds in the Ni2(II,III) and Pd2(II,III) oxidation states were originally examined in the 1980s, but the evidence collected at that time suggested that they did not contain 2c/3e σ bonds. Both classes of compounds have been re-examined using EPR spectroscopy and modern computational methods that show the unpaired electron of each compound to occupy a M-M σ* orbital, consistent with 2c/3e Ni-Ni and Pd-Pd σ half-bonds. Elsewhere on the periodic table, a seemingly unrelated compound containing a trigonal bipyramidal Cu3S2 core caused a stir, leaving prominent theorists at odds with one another as to whether the compound contains a S-S bond. Due to my previous experience with 2c/3e metal-metal bonds, I suggested that the Cu3S2 compound could contain a 2c/3e S-S σ half-bond in the previously unknown oxidation state of S2(3-). By use of the Cambridge Database, a number of other known compounds were identified as potentially containing S2(3-) ligands, including a noteworthy set of cyclopentadienyl-supported compounds possessing diamond-shaped Ni2E2 units with E = S, Se, and Te. These compounds were subjected to

  3. High dose effects in neutron irradiated face-centered cubic metals

    SciTech Connect

    Garner, F.A.; Toloczko, M.B.

    1993-06-01

    During neutron irradiation, most face-centered cubic metals and alloys develop saturation or quasi-steady state microstructures. This, in turn, leads to saturation levels in mechanical properties and quasi-steady state rates of swelling and creep deformation. Swelling initially plays only a small role in determining these saturation states, but as swelling rises to higher levels, it exerts strong feedback on the microstructure and its response to environmental variables. The influence of swelling, either directly or indirectly via second order mechanisms, such as elemental segregation to void surfaces, eventually causes major changes, not only in irradiation creep and mechanical properties, but also on swelling itself. The feedback effects of swelling on irradiation creep are particularly complex and lead to problems in applying creep data derived from highly pressurized creep tubes to low stress situations, such as fuel pins in liquid metal reactors.

  4. Void nucleation in biaxially strained ultrathin films of face-centered cubic metals

    NASA Astrophysics Data System (ADS)

    Kolluri, Kedarnath; Gungor, M. Rauf; Maroudas, Dimitrios

    2007-05-01

    We report an analysis of void nucleation as a relaxation mechanism in freestanding biaxially strained ultrathin films of face-centered cubic metals based on large-scale molecular-dynamics simulations. Above a critical strain level, multiple threading dislocations are emitted from the film surface. The surface step traces formed by gliding dislocations on intersecting and on adjacent parallel glide planes lead to formation and growth of surface pits and grooves, while vacancies form due to gliding of jogged dislocations and dislocation intersections. Coalescence of the surface pits with vacancy clusters is the precursor to the formation of a larger void extending across the film.

  5. Transition Metal Impurities on the Bond-Centered Site in Germanium

    SciTech Connect

    Decoster, S.; Vries, B. de; Vantomme, A.; Cottenier, S.; Emmerich, H.; Wahl, U.; Correia, J. G.

    2009-02-13

    We report on the lattice location of ion implanted Fe, Cu, and Ag impurities in germanium from a combined approach of emission channeling experiments and ab initio total energy calculations. Following common expectation, a fraction of these transition metals (TMs) was found on the substitutional Ge position. Less expected is the observation of a second fraction on the sixfold coordinated bond-centered site. Ab initio calculated heats of formation suggest this is the result of the trapping of a vacancy by a substitutional TM impurity, spontaneously forming an impurity-vacancy complex in the split-vacancy configuration. We also present an approach to displace the TM impurities from the electrically active substitutional site to the bond-centered site.

  6. Metal-centered polymers: Using controlled polymerization methodologies for the generation of responsive materials

    NASA Astrophysics Data System (ADS)

    Johnson, Robert Matthew

    Controlled polymerization methods were used to prepare highly modular polymeric metal complexes via convergent and divergent strategies. In these materials, the metal center provides a versatile hub for preparing diverse architectures through coordinative bonds. Moreover, the metal complex introduces various properties to the polymer such as luminescence, magnetism, or electroactivity. Suitably functionalized metal complexes have been used for the atom transfer radical polymerization of acrylate and methacrylate monomers by metalloinitiation to generate luminescent biocompatible materials through a divergent synthesis. By cleaving the tert-butyl groups from poly(tert -butyl acrylate), water soluble [Ru(bpyPAA2)3] 2+ has been prepared as well as the amphiphilic star block copolymer [Ru{bpy(PLA-PAA)2}3]2+ (PLA = poly(lactic acid), PAA = poly(acrylic acid) Bipyridine-centered polymeric macroligands may be chelated to a variety of metal salts. The polymer size greatly influences the formation of [Fe(bpy) 3]2+ centered polymers. As the molecular weight increases (> ˜25 kDa) tris complex formation decreases. Tris(bpy) synthesis is also impacted by chemical composition. BpyPtBA2 (PtBA = poly(tert-butyl acrylate) generates an iron mono(bpy) complex before giving rise to the bis(bpy) iron complex; no tris complex is observed. In contrast, the combination of bpyPEG2 (3 equiv) (PEG = (poly(ethylene glycol)) results in the formation of some iron tris(bpy) compound; however, complete tris(bpy) product formation is suppressed, presumably because of the chelating ability of the PEG chains. These examples contrast with other polymeric macroligands such as bpyPS2, bpyPMMA2, bpyPCL2 and bpyPLA 2 (PS = polystyrene; PMMA = poly(methyl methacrylate); PCL = poly(epsilon-caprolactone); PLA = poly(DL-lactic acid)) for which chelation reactions are facile for low molecular weight macroligands (<15 kDa), with chelation efficiencies (defined as (epsilonPMC/epsilonbpy) x 100%) only declining

  7. Alkyl Chain Growth on a Transition Metal Center: How Does Iron Compare to Ruthenium and Osmium?

    PubMed

    Sainna, Mala A; de Visser, Sam P

    2015-09-28

    Industrial Fischer-Tropsch processes involve the synthesis of hydrocarbons usually on metal surface catalysts. On the other hand, very few homogeneous catalysts are known to perform a Fischer-Tropsch style of reaction. In recent work, we established the catalytic properties of a diruthenium-platinum carbene complex, [(CpRu)₂(μ²-H) (μ²-NHCH₃)(μ³-C)PtCH₃(P(CH₃)₃)₂](CO)n⁺ with n=0, 2 and Cp=η⁵-C₅(CH₃)₅, and showed it to react efficiently by initial hydrogen atom transfer followed by methyl transfer to form an alkyl chain on the Ru-center. In particular, the catalytic efficiency was shown to increase after the addition of two CO molecules. As such, this system could be viewed as a potential homogeneous Fischer-Tropsch catalyst. Herein, we have engineered the catalytic center of the catalyst and investigated the reactivity of trimetal carbene complexes of the same type using iron, ruthenium and osmium at the central metal scaffold. The work shows that the reactivity should increase from diosmium to diruthenium to diiron; however, a non-linear trend is observed due to multiple factors contributing to the individual barrier heights. We identified all individual components of these reaction steps in detail and established the difference in reactivity of the various complexes.

  8. The Systematic Study of the Organotransition Metal Compounds.

    ERIC Educational Resources Information Center

    Carriedo, Gabino A.

    1990-01-01

    Discussed is an extension of the conventional method for studying the organometallic chemistry of transition metals that may be useful to show how the various existing types of low-valence complexes can be constructed. This method allows students to design new types of complexes that may still be nonexistent. (CW)

  9. The Systematic Study of the Organotransition Metal Compounds.

    ERIC Educational Resources Information Center

    Carriedo, Gabino A.

    1990-01-01

    Discussed is an extension of the conventional method for studying the organometallic chemistry of transition metals that may be useful to show how the various existing types of low-valence complexes can be constructed. This method allows students to design new types of complexes that may still be nonexistent. (CW)

  10. Ab Initio Study of the Adsorption of Small Molecules on Metal-Organic Frameworks with Oxo-centered Trimetallic Building Units: The Role of the Undercoordinated Metal Ion.

    PubMed

    Mavrandonakis, Andreas; Vogiatzis, Konstantinos D; Boese, A Daniel; Fink, Karin; Heine, Thomas; Klopper, Wim

    2015-09-08

    The interactions of H2, CO, CO2, and H2O with the undercoordinated metal centers of the trimetallic oxo-centered M3(III)(μ3-O)(X) (COO)6 moiety are studied by means of wave function and density functional theory. This trimetallic oxo-centered cluster is a common building unit in several metal-organic frameworks (MOFs) such as MIL-100, MIL-101, and MIL-127 (also referred to as soc-MOF). A combinatorial computational screening is performed for a large variety of trimetallic oxo-centered units M3(III)O (M = Al(3+), Sc(3+), V(3+), Cr(3+), Fe(3+), Ga(3+), Rh(3+), In(3+), Ir(3+)) interacting with H2O, H2, CO, and CO2. The screening addresses interaction energies, adsorption enthalpies, and vibrational properties. The results show that the Rh and Ir analogues are very promising materials for gas storage and separations.

  11. Steering Asymmetric Lewis Acid Catalysis Exclusively with Octahedral Metal-Centered Chirality.

    PubMed

    Zhang, Lilu; Meggers, Eric

    2017-02-21

    Catalysts for asymmetric synthesis must be chiral. Metal-based asymmetric catalysts are typically constructed by assembling chiral ligands around a central metal. In this Account, a new class of effective chiral Lewis acid catalysts is introduced in which the octahedral metal center constitutes the exclusive source of chirality. Specifically, the here discussed class of catalysts are composed of configurationally stable, chiral-at-metal Λ-configured (left-handed propeller) or Δ-configured (right-handed propeller) iridium(III) or rhodium(III) complexes containing two bidentate cyclometalating 5-tert-butyl-2-phenylbenzoxazole (dubbed IrO and RhO) or 5-tert-butyl-2-phenylbenzothiazole (dubbed IrS and RhS) ligands in addition to two exchange-labile acetonitriles. They are synthetically accessible in an enantiomerically pure fashion through a convenient auxiliary-mediated synthesis. Such catalysts are of interest due to their intrinsic structural simplicity (only achiral ligands) and the prospect of an especially effective asymmetric induction due to the intimate contact between the chiral metal center and the metal-coordinated substrates or reagents. With respect to chiral Lewis acid catalysis, the bis-cyclometalated iridium and rhodium complexes provide excellent catalytic activities and asymmetric inductions for a variety of reactions including Michael additions, Friedel-Crafts reactions, cycloadditions, α-aminations, α-fluorinations, Mannich reactions, and a cross-dehydrogenative coupling. Mechanistically, substrates such as 2-acyl imidazoles are usually activated by two-point binding. Exceptions exist as for example for an efficient iridium-catalyzed enantioselective transfer hydrogenation of arylketones with ammonium formate, which putatively proceeds through an iridium-hydride intermediate. The bis-cyclometalated iridium complexes catalyze visible-light-induced asymmetric reactions by intertwining asymmetric catalysis and photoredox catalysis in a unique

  12. Spectroscopic evidence for the influence of the benzene sites on tightly bound H2 in metal-organic frameworks with unsaturated metal centers: MOF-74-cobalt.

    PubMed

    Nijem, Nour; Kong, Lingzhu; Zhao, Yonggang; Wu, Haohan; Li, Jing; Langreth, David C; Chabal, Yves J

    2011-04-06

    The role of low binding energy sites on the adsorption of H(2) in metal-organic frameworks (MOFs) with unsaturated metal centers has not been identified. For instance, the importance of the benzene sites on H(2) adsorption at the metal site in MOF-74 has not been established. We report here experimental evidence that unambiguously shows that the internal mode of H(2) adsorbed at the metal site undergoes both a frequency shift and a marked change in its dynamic dipole moment when H(2) is adsorbed at the next nearest neighbor "benzene" site in MOF-74-Co. The effect of loading (i.e., occupation of all benzene sites) also induces spectroscopic shifts in H(2) at the metal site. These interactions highlight the role of lower binding energy sites in H(2) adsorption. © 2011 American Chemical Society

  13. Experimental study of grain interactions on rolling texture development in face-centered cubic metals

    NASA Astrophysics Data System (ADS)

    Kumar Ray, Atish

    There exists considerable debate in the texture community about whether grain interactions are a necessary factor to explain the development of deformation textures in polycrystalline metals. Computer simulations indicate that grain interactions play a significant role, while experimental evidence shows that the material type and starting orientation are more important in the development of texture and microstructure. A balanced review of the literature on face-centered cubic metals shows that the opposing viewpoints have developed due to the lack of any complete experimental study which considers both the intrinsic (material type and starting orientation) and extrinsic (grain interaction) factors. In this study, a novel method was developed to assemble ideally orientated crystalline aggregates in 99.99% aluminum (Al) or copper (Cu) to experimentally evaluate the effect of grain interactions on room temperature deformation texture. Ideal orientations relevant to face-centered cubic rolling textures, Cube {100} <001>, Goss {110} <001>, Brass {110} <11¯2> and Copper {112} <111¯> were paired in different combinations and deformed by plane strain compression to moderate strain levels of 1.0 to 1.5. Orientation dependent mechanical behavior was distinguishable from that of the neighbor-influenced behavior. In interacting crystals the constraint on the rolling direction shear strains (gammaXY , gammaXZ) was found to be most critical to show the effect of interactions via the evolution of local microstructure and microtexture. Interacting crystals with increasing deformations were observed to gradually rotate towards the S-component, {123} <634>. Apart from the average lattice reorientations, the interacting crystals also developed strong long-range orientation gradients inside the bulk of the crystal, which were identified as accumulating misorientations across the deformation boundaries. Based on a statistical procedure using quaternions, the orientation and

  14. Face-centered-cubic B80 metal: Density functional theory calculations

    NASA Astrophysics Data System (ADS)

    Yan, Qing-Bo; Zheng, Qing-Rong; Su, Gang

    2008-06-01

    By means of ab initio calculations within the density functional theory, we have found that B80 fullerenes can condense to form stable face-centered-cubic (fcc) solids. It is shown that when forming a crystal, B80 cages are geometrically distorted, the Ih symmetry is lowered to Th , and four boron-boron chemical bonds are formed between every two nearest neighbor B80 cages. The cohesive energy of B80 fcc solid is 0.23 eV/atom with respect to the isolated B80 fullerene. The calculated electronic structure reveals that the fcc B80 solid is a metal. The predicted solid phase would constitute a form of pure boron and might have diverse implications. In addition, a simple electron counting rule is proposed, which could explain the stability of B80 fullerene and the recently predicted stable boron sheet.

  15. Metal centers in the anaerobic microbial metabolism of CO and CO2

    PubMed Central

    Bender, Güneş; Pierce, Elizabeth; Hill, Jeffrey A.; Darty, Joseph E.

    2014-01-01

    Carbon dioxide and carbon monoxide are important components of the carbon cycle. Major research efforts are underway to develop better technologies to utilize the abundant greenhouse gas, CO2, for harnessing ‘green’ energy and producing biofuels. One strategy is to convert CO2 into CO, which has been valued for many years as a synthetic feedstock for major industrial processes. Living organisms are masters of CO2 and CO chemistry and, here, we review the elegant ways that metalloenzymes catalyze reactions involving these simple compounds. After describing the chemical and physical properties of CO and CO2, we shift focus to the enzymes and the metal clusters in their active sites that catalyze transformations of these two molecules. We cover how the metal centers on CO dehydrogenase catalyze the interconversion of CO and CO2 and how pyruvate oxidoreductase, which contains thiamin pyrophosphate and multiple Fe4S4 clusters, catalyzes the addition and elimination of CO2 during intermediary metabolism. We also describe how the nickel center at the active site of acetyl-CoA synthase utilizes CO to generate the central metabolite, acetyl-CoA, as part of the Wood-Ljungdahl pathway, and how CO is channelled from the CO dehydrogenase to the acetyl-CoA synthase active site. We cover how the corrinoid iron–sulfur protein interacts with acetyl-CoA synthase. This protein uses vitamin B12 and a Fe4S4 cluster to catalyze a key methyltransferase reaction involving an organometallic methyl-Co3+ intermediate. Studies of CO and CO2 enzymology are of practical significance, and offer fundamental insights into important biochemical reactions involving metallocenters that act as nucleophiles to form organometallic intermediates and catalyze C–C and C–S bond formations. PMID:21647480

  16. Stacking fault energy of face-centered cubic metals: thermodynamic and ab initio approaches

    NASA Astrophysics Data System (ADS)

    Li, Ruihuan; Lu, Song; Kim, Dongyoo; Schönecker, Stephan; Zhao, Jijun; Kwon, Se Kyun; Vitos, Levente

    2016-10-01

    The formation energy of the interface between face-centered cubic (fcc) and hexagonal close packed (hcp) structures is a key parameter in determining the stacking fault energy (SFE) of fcc metals and alloys using thermodynamic calculations. It is often assumed that the contribution of the planar fault energy to the SFE has the same order of magnitude as the bulk part, and thus the lack of precise information about it can become the limiting factor in thermodynamic predictions. Here, we differentiate between the interfacial energy for the coherent fcc(1 1 1)/hcp(0 0 0 1) interface and the ‘pseudo-interfacial energy’ that enters the thermodynamic expression for the SFE. Using first-principles calculations, we determine the coherent and pseudo-interfacial energies for six elemental metals (Al, Ni, Cu, Ag, Pt, and Au) and three paramagnetic Fe-Cr-Ni alloys. Our results show that the two interfacial energies significantly differ from each other. We observe a strong chemistry dependence for both interfacial energies. The calculated pseudo-interfacial energies for the Fe-Cr-Ni steels agree well with the available literature data. We discuss the effects of strain on the description of planar faults via thermodynamic and ab initio approaches.

  17. Multiscale modeling of crowdion and vacancy defects in body-centered-cubic transition metals

    SciTech Connect

    Derlet, P. M.; Nguyen-Manh, D.

    2007-08-01

    We investigate the structure and mobility of single self-interstitial atom and vacancy defects in body-centered-cubic transition metals forming groups 5B (vanadium, niobium, and tantalum) and 6B (chromium, molybdenum, and tungsten) of the Periodic Table. Density-functional calculations show that in all these metals the axially symmetric <111> self-interstitial atom configuration has the lowest formation energy. In chromium, the difference between the energies of the <111> and the <110> self-interstitial configurations is very small, making the two structures almost degenerate. Local densities of states for the atoms forming the core of crowdion configurations exhibit systematic widening of the ''local'' d band and an upward shift of the antibonding peak. Using the information provided by electronic structure calculations, we derive a family of Finnis-Sinclair-type interatomic potentials for vanadium, niobium, tantalum, molybdenum, and tungsten. Using these potentials, we investigate the thermally activated migration of self-interstitial atom defects in tungsten. We rationalize the results of simulations using analytical solutions of the multistring Frenkel-Kontorova model describing nonlinear elastic interactions between a defect and phonon excitations. We find that the discreteness of the crystal lattice plays a dominant part in the picture of mobility of defects. We are also able to explain the origin of the non-Arrhenius diffusion of crowdions and to show that at elevated temperatures the diffusion coefficient varies linearly as a function of absolute temperature.

  18. Beavers indicate metal pollution away from industrial centers in northeastern Poland.

    PubMed

    Giżejewska, Aleksandra; Spodniewska, Anna; Barski, Dariusz; Fattebert, Julien

    2015-03-01

    Heavy metals are persistent environmental contaminants, and wild animals are increasingly exposed to the harmful effects of compounds of anthropogenic origin, even in areas distant from industrial centers. We used atomic absorption spectrometry to determine levels of cadmium (Cd), lead (Pb), copper (Cu), and zinc (Zn) in liver and kidney of wild Eurasian beavers (Castor fiber) in Poland. Cd concentrations in liver (0.21 ± 0.44 μg/g) and in kidney (2.81 ± 4.52 μg/g) were lower in juvenile than in adult beavers. Pb concentrations in liver (0.08 ± 0.03 μg/g) and kidney (0.08 ± 0.03 μg/g) were similar among all individuals, while both Cu and Zn levels were higher in liver (Cu 9.2 ± 4.5 μg/g; Zn 35.7 ± 3.5 μg/g) than in kidney (Cu 3.7 ± 1.1 μg/g; Zn 21.5 ± 2.7 μg/g). Cu levels also differed between juveniles and adults. We reviewed the literature reporting metal concentrations in beavers. Our results indicate metal contamination in beavers away from important industrial emission sources and suggest the natural environment should be regularly monitored to ensure their levels are below recommended, legal values.

  19. Substrate activation for O2 reactions by oxidized metal centers in biology.

    PubMed

    Pau, Monita Y M; Lipscomb, John D; Solomon, Edward I

    2007-11-20

    The uncatalyzed reactions of O(2) (S = 1) with organic substrates (S = 0) are thermodynamically favorable but kinetically slow because they are spin-forbidden and the one-electron reduction potential of O(2) is unfavorable. In nature, many of these important O(2) reactions are catalyzed by metalloenzymes. In the case of mononuclear non-heme iron enzymes, either Fe(II) or Fe(III) can play the catalytic role in these spin-forbidden reactions. Whereas the ferrous enzymes activate O(2) directly for reaction, the ferric enzymes activate the substrate for O(2) attack. The enzyme-substrate complex of the ferric intradiol dioxygenases exhibits a low-energy catecholate to Fe(III) charge transfer transition that provides a mechanism by which both the Fe center and the catecholic substrate are activated for the reaction with O(2). In this Perspective, we evaluate how the coupling between this experimentally observed charge transfer and the change in geometry and ligand field of the oxidized metal center along the reaction coordinate can overcome the spin-forbidden nature of the O(2) reaction.

  20. KENNEDY SPACE CENTER, FLA. - Launch Pad 39A undergoes sandblasting of its metal structures and surfaces. Routine maintenance includes sandblasting and repainting as preventive means to minimize corrosion.

    NASA Image and Video Library

    2003-09-12

    KENNEDY SPACE CENTER, FLA. - Launch Pad 39A undergoes sandblasting of its metal structures and surfaces. Routine maintenance includes sandblasting and repainting as preventive means to minimize corrosion.

  1. Driving forces of heavy metal changes in agricultural soils in a typical manufacturing center.

    PubMed

    Qiu, Menglong; Li, Fangbai; Wang, Qi; Chen, Junjian; Yang, Guoyi; Liu, Liming

    2015-05-01

    Heavy metal concentrations in 2002 and 2012 in agricultural soils in Dongguan, a manufacturing center in southern China, were analyzed to determine the impact of rapid economic development on soil pollution. The level of pollution was assessed using the Nemerow synthetic pollution index (NPI), and its changing characteristics and driving forces were analyzed using multivariate statistical and geostatistical methods. The results indicate that the mean NPI was 0.79 in 2002 and 0.84 in 2012, which indicates aggravated heavy metal contamination in the agricultural soils. The concentrations of Cd and Zn increased 54.7 and 20.8 %, respectively, whereas Hg and Pb decreased 35.3 and 24.5 %, respectively. Cr, As, Cu, and Ni remained relatively stable. The Hg and Cd concentrations were highly correlated with soil types (P < 0.01), the secondary industrial output per unit of land (P < 0.01), proportion of cereal fields (P < 0.01), proportion of vegetable fields (P < 0.01), population density (P < 0.05), and road density (P < 0.05). The Pb and As concentrations were greatly influenced by soil types (P < 0.01), river density (P < 0.01), fertilizer rate (P < 0.01), and road density (P < 0.05). Cr, Zn, Cu, and Ni concentrations were primarily driven by soil types (P < 0.01), river density (P < 0.01), and fertilizer rate (P < 0.05).

  2. Recombinant purple acid phosphatase isoform 3 from sweet potato is an enzyme with a diiron metal center.

    PubMed

    Waratrujiwong, Teerawit; Krebs, Bernt; Spener, Friedrich; Visoottiviseth, Pornsawan

    2006-04-01

    Purple acid phosphatases (PAPs) from sweet potato (sp) have been classified on the basis of their primary structure and the dinuclear metal center into isoforms spPAP1 [Fe(III)-Zn(II)] and spPAP2 [Fe(III)-Mn(II)]; for spPAP3 only the cDNA is known. With the aim of unraveling the character of the dinuclear metal center we report here the characterization of this isoform at the protein level. We cloned spPAP3 cDNA in a baculovirus and overexpressed this enzyme in Sf9 insect cells. Preparation of recombinant spPAP3 in two steps afforded pure enzyme with yields of 4.5 mg.L(-1) culture medium. This enzyme is a dimeric, disulfide-linked PAP of 110 kDa, similar to known PAP isoforms from higher plants. Enzymatic studies and spectroscopic properties (max. absorption at 550-565 nm) indicated a diiron enzyme; quantitative and semiquantitative metal analysis using ICP-OES and TOF-SIMS, respectively, revealed the presence of only iron in purified spPAP3. Metal replacement in the second metal-binding site upon preparation of the semiapo-enzyme with Fe(II), Zn(II), or Mn(II) showed highest activities with Fe(II). The data show that recombinant spPAP3 has a diiron metal center. Site-directed mutagenesis was conducted to check catalytic efficiency at the atomic level. Tyr291 at the substrate-binding site in spPAP3 was mutated to His and Ala, the respective residues found in spPAP1 and spPAP2. Kinetic analysis showed that conversion of Tyr291 to His further optimized the performance of this protein as a diiron enzyme, whereas the Ala mutation weakened the catalytic efficiency regardless of the metal present in the second binding site.

  3. Numerical Modeling of the Stability of Face-Centered Cubic Metals with High Vacancy Concentration

    SciTech Connect

    Brian P. Somerday; M. I. Baskes

    1998-12-01

    The objective of this research is to assess the possibility of forming an atomically porous structure in a low-density metal, e.g., Al with vacancies up to 0.20/lattice site; and to examine the effects of hydrogen and vacancy concentration on the stability of an atomically porous structure that has been experimentally produced in nickel. The approach involves numerical modeling using the Embedded-Atom Method (EAM). High vacancy concentrations cause the Al lattice to disorder at 300K. In contrast, Ni retains the face-centered-cubic structure at 300K for vacancy concentrations up to 0.15 Vac/lattice site. Unexpectedly, the lattice with 0.15 Vac/lattice site is more stable than the lattice with 0.10 or 0.20 Vac/lattice site. The Ni systems with 0.10 and 0.15 Vac/lattice site exhibit domains consisting of uniform lattice rotations. The Ni lattice with 0.15 Vac/lattice site is more stable with an initial distribution of random vacancies compared to ordered vacancies. The equilibrium lattice structures of Ni a d Al containing vacancies and H are less ordered to structures with vacancies only at 300K.

  4. Size-Dependent Surface Energy Density of Spherical Face-Centered-Cubic Metallic Nanoparticles.

    PubMed

    Wei, Yaochi; Chen, Shaohua

    2015-12-01

    The surface energy density of nano-sized elements exhibits a significantly size-dependent behavior. Spherical nanoparticle, as an important element in nano-devices and nano-composites, has attracted many interesting studies on size effect, most of which are molecular dynamics (MD) simulations. However, the existing MD calculations yield two opposite size-dependent trends of surface energy density of nanoparticles. In order to clarify such a real underlying problem, atomistic calculations are carried out in the present paper for various spherical face-centered-cubic (fcc) metallic nanoparticles. Both the embedded atom method (EAM) potential and the modified embedded atom method (MEAM) one are adopted. It is found that the size-dependent trend of surface energy density of nanoparticles is not governed by the chosen potential function or variation trend of surface energy, but by the defined radius of spherical nanoparticles in MD models. The finding in the present paper should be helpful for further theoretical studies on surface/interface effect of nanoparticles and nanoparticle-reinforced composites.

  5. Spirocyclic sulfur and selenium ligands as molecular rigid rods in coordination of transition metal centers.

    PubMed

    Petrukhina, Marina A; Henck, Colin; Li, Bo; Block, Eric; Jin, Jin; Zhang, Shao-Zhong; Clerac, Rodolphe

    2005-01-10

    polymer structures having alternating metal units cis-M(hfac)(2) and ligands 2 with intermolecuar M...Se separations of 2.6046(8) and 2.5523(16) A, respectively. In all products 7-10 the initial cis or trans geometry of M(hfac)(2) complexes is preserved and the spiro[3.3]heptane ligands act as bidentate linkers bridging transition metal centers via both donor ends. The magnetic properties of this series of new Cu(II), Co(II), and Ni(II) complexes have been tested by variable-temperature magnetic susceptibility measurements.

  6. Using NV centers to probe magnetization dynamics in normal metal/magnetic insulator hybrid system at the nanoscale

    NASA Astrophysics Data System (ADS)

    Zhang, Huiliang; Ku, Mark J. H.; Han, Minyong; Casola, Francesco; van der Sar, Toeno; Yacoby, Amir; Walsworth, Ronald L.

    2016-05-01

    Understanding magnetization dynamics induced by electric current is of great interest for both fundamental and practical reasons. Great endeavor has been dedicated to spin-orbit torques (SOT) in metallic structures, while quantitative study of analogous phenomena in magnetic insulators remains challenging where transport measurements are not feasible. Recently we have developed techniques using nitrogen vacancy (NV) centers in diamond to probe few-nanometre-scale correlated-electron magnetic excitations (i.e., spin waves). Here we demonstrate how this powerful tool can be implemented to study magnetization dynamics inside ferromagnetic insulator, Yttrium iron garnet (YIG) with spin injection from electrical current through normal metal (Platinum in our case). Particularly our work will focus on NV magnetic detection, imaging, and spectroscopy of coherent auto-oscillations in Pt/YIG microdisc. Magnetic fluctuations and local temperature measurements, both with nearby NV centers, will also be interesting topics relevant to SOT physics in Pt/YIG hybrid system.

  7. Some surprising features of the plastic deformation of body-centered cubic metals and alloys

    SciTech Connect

    Christian, J.W.

    1983-07-01

    The metals which have the bcc structure at and below room temperature include iron, refractory metals of Groups VA and VIA, and alkali metals. Experimental and theoretical investigations of deformation behavior carried out in the last twenty years are reviewed. Attention is concentrated mainly on low temperature properties where many anomalous features have been discovered. The phenomena discussed include slip asymmetry, failure of the Schmid law of critical resolved shear stress, the observation of anomalous slip in very pure metals and alloys, solution softening, and the ductile-brittle transition.

  8. Insights into intramolecular Trp and His side-chain orientation and stereospecific π interactions surrounding metal centers: an investigation using protein metal-site mimicry in solution.

    PubMed

    Yang, Chi Ming; Zhang, Jie

    2010-09-17

    Metal-binding scaffolds incorporating a Trp/His-paired epitope are instrumental in giving novel insights into the physicochemical basis of functional and mechanistic versatility conferred by the Trp-His interplay at a metal site. Herein, by coupling biometal site mimicry and (1)H and (13)C NMR spectroscopy experiments, modular constructs EDTA-(L-Trp, L-His) (EWH; EDTA=ethylenediamino tetraacetic acid) and DTPA-(L-Trp, L-His) (DWH; DTPA=diethylenetriamino pentaacetic acid) were employed to dissect the static and transient physicochemical properties of hydrophobic/hydrophilic aromatic interactive modes surrounding biometal centers. The binding feature and identities of the stoichiometric metal-bound complexes in solution were investigated by using (1)H and (13)C NMR spectroscopy, which facilitated a cross-validation of the carboxylate, amide oxygen, and tertiary amino groups as the primary ligands and indole as the secondary ligand, with the imidazole (Im) N3 nitrogen being weakly bound to metals such as Ca(2+) owing to a multivalency effect. Surrounding the metal centers, the stereospecific orientation of aromatic rings in the diastereoisomerism is interpreted with the Ca(2+)-EWH complex. With respect to perturbed Trp side-chain rotamer heterogeneity, drastically restricted Trp side-chain flexibility and thus a dynamically constrained rotamer interconversion due to π interactions is evident from the site-selective (13)C NMR spectroscopic signal broadening of the Trp indolyl C3 atom. Furthermore, effects of Trp side-chain fluctuation on indole/Im orientation were the subject of a 2D NMR spectroscopy study by using the Ca(2+)-bound state; a C-H2(indolyl)/C-H5(Im(+)) connectivity observed in the NOESY spectra captured direct evidence that the N-H1 of the Ca(2+)-Im(+) unit interacted with the pyrrole ring of the indole unit in Ca(2+)-bound EWH but not in DWH, which is assignable to a moderately static, anomalous, T-shaped, interplanar π(+)-π stacking alignment

  9. Incoherent Bi off-centering in Bi₂Ti₂O₆O' and Bi₂Ru₂O₆O': Insulator versus metal

    DOE PAGES

    Shoemaker, Daniel P.; Seshadri, Ram; Tachibana, Makoto; ...

    2011-08-24

    In the cubic, stoichiometric oxide compounds Bi₂Ti₂O₆O' (also written as Bi₂Ti₂O₇) and Bi₂Ru₂O₆O' (also written as Bi₂Ru₂O₇) Bi³⁺ ions on the pyrochlore A site display a propensity to off-center. Unlike Bi₂Ti₂O₆O', Bi₂Ru₂O₆O' is a metal, so it is of interest to ask whether conduction electrons and/or involvement of Bi 6s states at the Fermi energy influence Bi³⁺ displacements. The Bi³⁺ off-centering in Bi₂Ti₂O₆O' has previously been revealed to be incoherent from detailed reverse Monte Carlo analysis of total neutron scattering. Similar analysis of Bi₂Ru₂O₆O' reveals incoherent off-centering as well, but of smaller magnitude and with distinctly different orientational preference. Analysismore » of the distributions of metal to oxygen distances presented suggests that Bi in both compounds is entirely Bi³⁺. Disorder in Bi₂Ti₂O₆O' has the effect of stabilizing valence while simultaneously satisfying the steric constraint imposed by the presence of the lone pair of electrons. In Bi₂Ru₂O₆O', off-centering is not required to satisfy valence and seems to be driven by the lone pair. Decreased volume of the lone pair may be a result of partial screening by conduction electrons.« less

  10. Incoherent Bi off-centering in Bi₂Ti₂O₆O' and Bi₂Ru₂O₆O': Insulator versus metal

    SciTech Connect

    Shoemaker, Daniel P.; Seshadri, Ram; Tachibana, Makoto; Hector, Andrew L.

    2011-08-24

    In the cubic, stoichiometric oxide compounds Bi₂Ti₂O₆O' (also written as Bi₂Ti₂O₇) and Bi₂Ru₂O₆O' (also written as Bi₂Ru₂O₇) Bi³⁺ ions on the pyrochlore A site display a propensity to off-center. Unlike Bi₂Ti₂O₆O', Bi₂Ru₂O₆O' is a metal, so it is of interest to ask whether conduction electrons and/or involvement of Bi 6s states at the Fermi energy influence Bi³⁺ displacements. The Bi³⁺ off-centering in Bi₂Ti₂O₆O' has previously been revealed to be incoherent from detailed reverse Monte Carlo analysis of total neutron scattering. Similar analysis of Bi₂Ru₂O₆O' reveals incoherent off-centering as well, but of smaller magnitude and with distinctly different orientational preference. Analysis of the distributions of metal to oxygen distances presented suggests that Bi in both compounds is entirely Bi³⁺. Disorder in Bi₂Ti₂O₆O' has the effect of stabilizing valence while simultaneously satisfying the steric constraint imposed by the presence of the lone pair of electrons. In Bi₂Ru₂O₆O', off-centering is not required to satisfy valence and seems to be driven by the lone pair. Decreased volume of the lone pair may be a result of partial screening by conduction electrons.

  11. Rapid, sensitive, and selective fluorescent DNA detection using iron-based metal-organic framework nanorods: Synergies of the metal center and organic linker.

    PubMed

    Tian, Jingqi; Liu, Qian; Shi, Jinle; Hu, Jianming; Asiri, Abdullah M; Sun, Xuping; He, Yuquan

    2015-09-15

    Considerable recent attention has been paid to homogeneous fluorescent DNA detection with the use of nanostructures as a universal "quencher", but it still remains a great challenge to develop such nanosensor with the benefits of low cost, high speed, sensitivity, and selectivity. In this work, we report the use of iron-based metal-organic framework nanorods as a high-efficient sensing platform for fluorescent DNA detection. It only takes about 4 min to complete the whole "mix-and-detect" process with a low detection limit of 10 pM and a strong discrimination of single point mutation. Control experiments reveal the remarkable sensing behavior is a consequence of the synergies of the metal center and organic linker. This work elucidates how composition control of nanostructures can significantly impact their sensing properties, enabling new opportunities for the rational design of functional materials for analytical applications.

  12. New mechanistic insight into stepwise metal-center exchange in a metal-organic framework based on asymmetric Zn(4) clusters.

    PubMed

    Meng, Wei; Li, Huijun; Xu, Zhouqing; Du, Shanshan; Li, Yunxia; Zhu, Yanyan; Han, Yi; Hou, Hongwei; Fan, Yaoting; Tang, Mingsheng

    2014-03-03

    Herein, a mechanism of stepwise metal-center exchange for a specific metal-organic framework, namely, [Zn4 (dcpp)2 (DMF)3 (H2 O)2 ]n (H4 dcpp=4,5-bis(4'-carboxylphenyl)phthalic acid), is disclosed for the first time. The coordination stabilities between the central metal atoms and the ligands as well as the coordination geometry are considered to be dominant factors in this stepwise exchange mechanism. A new magnetic analytical method and a theoretical model confirmed that the exchange mechanism is reasonable. When the metathesis reaction occurs between Cu(II) ions and framework Zn(II) ions, the magnetic exchange interaction of each pair of Cu(II) centers gradually strengthens with increasing amount of framework Cu(II) ions. By analyzing the changes of coupling constants in the Cu-exchanged products, it was deduced that Zn4 and Zn3 are initially replaced, and then Zn1 and Zn2 are replaced later. The theoretical calculation further verified that Zn4 is replaced first, Zn3 next, then Zn1 and Zn2 last, and the coordination stability dominates the Cu/Zn exchange process. For the Ni/Zn and Co/Zn exchange processes, besides the coordination stability, the preferred coordination geometry was also considered in the stepwise-exchange behavior. As Ni(II) and Co(II) ions especially favor octahedral coordination geometry in oxygen-ligand fields, Ni(II) ions and Co(II) ions could only selectively exchange with the octahedral Zn(II) ions, as was also confirmed by the experimental results. The stepwise metal-exchange process occurs in a single crystal-to-single crystal fashion.

  13. Binding and Activation of N2O at Transition Metal Centers: Recent Mechanistic Insights

    PubMed Central

    Tolman, William B.

    2010-01-01

    No laughing matter, nitrous oxide’s role in stratospheric ozone depletion and as a greenhouse gas has stimulated great interest in developing and understanding its decomposition, particularly through the use of transition metal promoters. Recent advances in our understanding of the reaction pathways for N2O reduction by metal ions in the gas phase and in heterogeneous, homogeneous, and biological catalytic systems have provided provocative ideas about the structure and properties of metal-N2O adducts and derived intermediates. These ideas are likely to inform efforts to design more effective catalysts for N2O remediation. PMID:20058284

  14. Electronic structure analysis of the dinuclear metal center in the bioremediator glycerophosphodiesterase (GpdQ) from Enterobacter aerogenes.

    PubMed

    Hadler, Kieran S; Mitić, Natasa; Yip, Sylvia Hsu-Chen; Gahan, Lawrence R; Ollis, David L; Schenk, Gerhard; Larrabee, James A

    2010-03-15

    The glycerophosphodiesterase (GpdQ) from Enterobacter aerogenes is a promiscuous, dinuclear metallohydrolase that has potential application in the remediation of organophosphate nerve agents and pesticides. GpdQ employs an unusual reaction mechanism in which the enzyme is predominantly mononuclear in the resting state, and substrate binding induces the formation of the catalytically competent dinuclear center (Hadler et al. J. Am. Chem. Soc. 2008, 130, 14129). Reactivity is further modulated by the coordination flexibility of Asn80, a ligand that binds to the second, loosely bound metal ion (Hadler et al. J. Am. Chem. Soc. 2009, 131, 11900). It is proposed that hydrolysis is initiated by a terminal, metal-bound hydroxide molecule which is activated at unusually low pH by electrostatic/hydrogen bonding interactions with a bridging hydroxide species. In this study, electronic structure analysis of the dinuclear center is employed to study the coordination environment of the dinuclear center at the resting and product-bound stage of catalysis. This is achieved through the use of variable temperature, variable field magnetic circular dichroism experiments involving the Co(II)-substituted wild type enzyme and its Asn80Asp variant. The data support the above model for the catalytic mechanism whereby the metal ion-bridging hydroxide molecule activates a terminally bound hydroxide nucleophile. Replacement of Asn80 by an aspartate residue does prevent coordination flexibility but also leads to cleavage of the mu-hydroxide bridge and reduced reactivity. This is the first study to investigate the electronic structure of an enzyme with a mu-1,1-carboxylate bridged dicobalt(II) center.

  15. Mechanism of peptide hydrolysis by co-catalytic metal centers containing leucine aminopeptidase enzyme: a DFT approach.

    PubMed

    Zhu, Xiaoxia; Barman, Arghya; Ozbil, Mehmet; Zhang, Tingting; Li, Shanghao; Prabhakar, Rajeev

    2012-02-01

    In this density functional theory study, reaction mechanisms of a co-catalytic binuclear metal center (Zn1-Zn2) containing enzyme leucine aminopeptidase for two different metal bridging nucleophiles (H(2)O and -OH) have been investigated. In addition, the effects of the substrate (L-leucine-p-nitroanilide → L-leucyl-p-anisidine) and metal (Zn1 → Mg and Zn2 → Co, i.e., Mg1-Zn2 and Mg1-Co2 variants) substitutions on the energetics of the mechanism have been investigated. The general acid/base mechanism utilizing a bicarbonate ion followed by this enzyme is divided into two steps: (1) the formation of the gem-diolate intermediate, and (2) the cleavage of the peptide bond. With the computed barrier of 17.8 kcal/mol, the mechanism utilizing a hydroxyl nucleophile was found to be in excellent agreement with the experimentally measured barrier of 18.7 kcal/mol. The rate-limiting step for reaction with L-leucine-p-nitroanilide is the cleavage of the peptide bond with a barrier of 17.8 kcal/mol. However, for L-leucyl-p-anisidine all steps of the mechanism were found to occur with similar barriers (18.0-19.0 kcal/mol). For the metallovariants, cleavage of the peptide bond occurs in the rate-limiting step with barriers of 17.8, 18.0, and 24.2 kcal/mol for the Zn1-Zn2, Mg1-Zn2, and Mg1-Co2 enzymes, respectively. The nature of the metal ion was found to affect only the creation of the gem-diolate intermediate, and after that all three enzymes follow essentially the same energetics. The results reported in this study have elucidated specific roles of both metal centers, the nucleophile, indirect ligands, and substrates in the catalytic functioning of this important class of binuclear metallopeptidases.

  16. A novel structure type for isolated rare-earth-metal clusters centered by transition metals: Cs{sub 4}R{sub 6}I{sub 13}Z (R = Ce, Pr; Z = Co, Os)

    SciTech Connect

    Lulei, M.; Corbett, J.D.

    1996-06-19

    The research reported here has been focused on the introduction of alkali-metal atoms into rare-earth-metal cluster structures in order to expand the variety of quaternary compounds with discrete rare-earth-metal clusters centered by transition metals. This direction was encouraged by other recent results with isolated clusters centered only by small main-group elements, such as Cs{sub 4}Pr{sub 6}I{sub 13}C{sub 2} and Cs{sub 4}Sc{sub 6}I{sub 13}C,{sup 11} and by any examples in the chemistry of reduced zirconium halides.

  17. Simple metal binary phases based on the body centered cubic structure: Electronic origin of distortions and superlattices

    NASA Astrophysics Data System (ADS)

    Degtyareva, Valentina F.; Afonikova, Nataliya S.

    2013-01-01

    Binary alloy phases of the noble metals with the main group elements are analyzed in relation to the body centered cubic structure with distortions, vacancies and superlattices. The stability of these distorted phases is studied in terms of the Fermi sphere-Brillouin-Jones zone interaction within the nearly free-electron model in order to understand the importance of the band structure energy contribution to the overall crystal energy. Examination of Brillouin-Jones zone configurations with respect to the Fermi sphere for several representative phases has shown how significant the electron energy contribution is in forming the distorted structures with superlattices and ordered vacancies. This approach may be useful for understanding the complex structures recently found in compressed simple alkali metals.

  18. A new family of Ln₇ clusters with an ideal D(3h) metal-centered trigonal prismatic geometry, and SMM and photoluminescence behaviors.

    PubMed

    Mazarakioti, Eleni C; Poole, Katye M; Cunha-Silva, Luis; Christou, George; Stamatatos, Theocharis C

    2014-08-14

    The first use of the flexible Schiff base ligand N-salicylidene-2-aminocyclohexanol in metal cluster chemistry has afforded a new family of Ln7 clusters with ideal D(3h) point group symmetry and metal-centered trigonal prismatic topology; solid-state and solution studies revealed SMM and photoluminescence behaviors.

  19. Metal-ion-center assembly of ferredoxin and plastocyanin in isolated chloroplasts

    SciTech Connect

    Li, Hsoumin; Theg, S.M.; Bauerle, C.M.; Keegstra, K. )

    1990-09-01

    Most chloroplastic proteins are cytosolically synthesized andposttranslationally transported to their proper locations. Two examples of this group of proteins are ferredoxin and plastocyanin, both of which are metal-containing components of the photosynthetic electron-transport chain. The import process for these two proteins includes the insertion of the metal ions to produce the holo forms of the proteins. The authors show here that in vitro translated precursor proteins of ferredoxin and plastocyanin are synthesized as apo forms and are assembled into their respective holo forms after being imported into isolated chloroplasts. They also provide evidence that only mature-sized proteins are competent to be assembled into holo forms.

  20. Homogeneous catalytic transfer dehydrogenation of alkanes with a group 10 metal center.

    PubMed

    Khaskin, Eugene; Lew, Daniel L; Pal, Shrinwantu; Vedernikov, Andrei N

    2009-11-07

    Unambiguous catalytic homogeneous alkane transfer dehydrogenation was observed with a group 10 metal complex catalyst, LPt(II)(cyclo-C6H10)H, supported by a lipophilic dimethyl-di(4-tert-butyl-2-pyridyl)borate anionic ligand and tert-butylethene as the sacrificial hydrogen acceptor.

  1. Retention behavior of amino acids and peptides on protoporphyrin-silica stationary phases with varying metal ion centers.

    PubMed

    Xiao, J; Meyerhoff, M E

    1996-09-01

    Various metalloprotoporphyrins (MProP) covalently linked to silica supports are examined as novel immobilized metal ion affinity chromatography (IMAC) stationary phases for separations of amino acids/peptides. Under reversed-phase HPLC conditions, the MProP-silicas exhibit high affinity toward L-histidine via metal-nitrogen axial ligation interactions, with an increasing degree of histidine retention highly dependent on the specific metal ion (M) in the center of the protoporphyrin (ProP) structure: Fe(III) > Ni(II) > Cu(II) > Zn (II) approximately Cd(II). Aromatic amino acids (i.e., L-trytophan and L-phenylalanine) are also retained on MProP columns through pi-pi interactions with the immobilized porphyrins, with the greatest affinity for L-trytophan observed on CuProP-silica columns. Peptides rich in L-histidine and L-tryptophan residues are selectively retained on most of the MProP-silica phases examined; however, the addition of an organic modifier and/or lowering the pH of the mobile phase can be used independently to attenuate the pi-pi and metal ion-nitrogen ligation interactions, respectively. Reproducible separations of His-Phe and trytophan releasing hormone are achieved on a FeProP-silica column even after extensive washing with 50 mM EDTA, demonstrating a fundamental advantage of the new MProP-silica over existing IMAC stationary phases, in which the metal ion is anchored weakly to the support via immobilized iminodiacetate and related ligands.

  2. Emission and fs/ns-TRANSIENT Absorption of Organometallic Complexes Bound to a Dinuclear Metal Center

    NASA Astrophysics Data System (ADS)

    Durr, Christopher B.; Brown-Xu, Samantha E.; Chisholm, Malcolm H.

    2012-06-01

    Compounds containing a MM quadruple bond (M = Mo or W) of the form M2L2L'2, where L and L' are conjugated organic ligands, show interesting photophysical properties along with a metal-to-ligand charge transfer (MLCT) band that is tunable throughout the UV-Vis-NIR spectra. Recently, our attention has shifted towards ligands that incorporate a secondary transition metal complex bound to an organic moiety. Along with allowing for a second tunable MLCT band for better coverage of the solar spectrum, these hybrid molecules show unique spectroscopic properties that were explored using fs/ns-transient absorption and UV-Vis/NIR emission. These techniques allow for the elucidation of the electronic character of the excited states as well as their lifetimes. This knowledge will be put to use in the design of new materials that could later be incorporated into next generation photovoltaic devices.

  3. In situ observation of deformation processes in nanocrystalline face-centered cubic metals.

    PubMed

    Kobler, Aaron; Brandl, Christian; Hahn, Horst; Kübel, Christian

    2016-01-01

    The atomistic mechanisms active during plastic deformation of nanocrystalline metals are still a subject of controversy. The recently developed approach of combining automated crystal orientation mapping (ACOM) and in situ straining inside a transmission electron microscope was applied to study the deformation of nanocrystalline Pd x Au1- x thin films. This combination enables direct imaging of simultaneously occurring plastic deformation processes in one experiment, such as grain boundary motion, twin activity and grain rotation. Large-angle grain rotations with ≈39° and ≈60° occur and can be related to twin formation, twin migration and twin-twin interaction as a result of partial dislocation activity. Furthermore, plastic deformation in nanocrystalline thin films was found to be partially reversible upon rupture of the film. In conclusion, conventional deformation mechanisms are still active in nanocrystalline metals but with different weighting as compared with conventional materials with coarser grains.

  4. In situ observation of deformation processes in nanocrystalline face-centered cubic metals

    PubMed Central

    Kobler, Aaron; Brandl, Christian; Hahn, Horst

    2016-01-01

    Summary The atomistic mechanisms active during plastic deformation of nanocrystalline metals are still a subject of controversy. The recently developed approach of combining automated crystal orientation mapping (ACOM) and in situ straining inside a transmission electron microscope was applied to study the deformation of nanocrystalline PdxAu1− x thin films. This combination enables direct imaging of simultaneously occurring plastic deformation processes in one experiment, such as grain boundary motion, twin activity and grain rotation. Large-angle grain rotations with ≈39° and ≈60° occur and can be related to twin formation, twin migration and twin–twin interaction as a result of partial dislocation activity. Furthermore, plastic deformation in nanocrystalline thin films was found to be partially reversible upon rupture of the film. In conclusion, conventional deformation mechanisms are still active in nanocrystalline metals but with different weighting as compared with conventional materials with coarser grains. PMID:27335747

  5. Computer-simulation analysis of the ESR spectra of V-type centers in irradiated heavy-metal fluoride glasses

    NASA Astrophysics Data System (ADS)

    Griscom, D. L.; Friebele, E. J.

    1991-04-01

    Computer line-shape simulations were carried out on the electron-spin-resonance spectra of several heavy-metal fluoride glasses following exposure to ioniziong radiation at cryogenic temperatures. The primary objects of this study were certain spectra circumstantially attributable to holes trapped on a cluster of two or more inequivalent fluoride or foreign halide ions. The earlier attribution of certain spectral features to FCl- and FBr- species was confirmed in Cl- and Br-doped glasses, respectively, although the simulations show that FCl- in the glasses has a structure quite different from the same species in mixed alkali halide crystals. Two other spectra-universally observed in irradiated glasses composed of ZrF4 (or HfF4), BaF2, and virtually any number of other fluoride constituents-were also examined in detail. The previous assignment of one of these spectral components to F-2 molecular ions is sustained, although the specific nature of these defects is now argued to be interstitial fluorine atoms in configurations analogous to VKA and VH centers (rather than VK centers) in the alkaline-earth fluorides. The second ubiquitous component, which was previously ascribed to ``interstitial F0,'' is demonstrated to arise from an F2-3 species similar to the Vt center in LiF. The F-2 and F2-3 can be thought of as ``on-center'' and ``off-center'' configurations of the interstitial fluorine atom, and it appears that the former may undergo a thermal transmutation into the latter.

  6. Inorganic–organic hybrids presenting high basic center content: SBA-15 incorporation, toxic metals sorption and energetic behavior

    SciTech Connect

    Oliveira, Fernando J.V.E.; Melo, Maurício A.; Airoldi, Claudio

    2013-03-15

    Highlights: ► Mesoporous SBA-15 silicas were organofunctionalized with new silylant agents. ► Thiocarbamate was used to enhance the silylating agent chains and basic centers. ► The synthesized pendant chains contain nitrogen and sulfur basic centers. ► The new hybrids sorb toxic cations from aqueous solutions with high efficiency. ► The thermodynamic data demonstrated favorable cation/basic center interactions. - Abstract: Mesoporous SBA-15 samples were organofunctionalized with mono, di- and tri-aminosilanes that previously reacted with thiocarbamide to enhance the organic chains and attach nitrogen and sulfur basic centers to the surface of the solids. These new organosilanes were synthesized through a non-solvent approach to reduce both cost and hazardous wastes. The high affinities for both hard and soft Lewis acids due to the combination of nitrogen and sulfur atoms attached to the same pendant chain enabled favorable sorption capacities for Cu{sup 2+}, Cd{sup 2+} and Pb{sup 2+} cations, with maximum capacities of 1.90, 3.48 and 5.30 mmol g{sup −1}, respectively, for the most efficient mesoporous silica. Microcalorimetric investigations allowed the calculation of the thermodynamic data at the solid/liquid interface. All Gibbs energy are negative as expected for spontaneous cation/basic center interactions and the positive entropic values from 49 ± 3 to 108 ± 5 J K{sup −1} mol{sup −1}, also reinforced this favorable interactive process in heterogeneous system. The designed organosilanes covalently bonded to the inorganic siliceous skeleton can be suggested as new materials for toxic metal removal from a wastewater with high efficiency.

  7. Electronic structure and properties of rare earth and 3d transition metal compounds

    SciTech Connect

    Dagys, R.; Babonas, G.J. )

    1994-03-01

    Excitation energies of various electronic configurations in rare earth and 3d transition metal compounds are considered and related to the peculiarities of the observed electrical and optical properties. Intraionic excitations of 4f, 3d electrons to less localized nl states are shown to be equally important as interionic d-d or charge transfer transitions usually considered, and to be even more significant in compounds containing low valence metals.

  8. Synthesis and characterization of metal-centered, six-membered, mixed-valent, heterometallic wheels of iron, manganese, and indium.

    PubMed

    Saalfrank, Rolf W; Prakash, Raju; Maid, Harald; Hampel, Frank; Heinemann, Frank W; Trautwein, Alfred X; Böttger, Lars H

    2006-03-08

    Heptanuclear metal-centered, six-membered, mixed-valent, heterometallic wheels 1-3 of iron, manganese, and indium were prepared in a one-pot reaction from N-benzyldiethanolamine (H2L(1)), cesium carbonate, [PPh4]2[MnCl4], and FeCl3 or InCl3. All three complexes were characterized by the combination of elemental analysis, FAB mass spectroscopy, X-ray diffraction and cyclic voltammetry and in the case of 1 additionally by Mössbauer spectroscopy. In 1, four Mn(II) ions in the periphery are arranged in pairs alternating with one Fe(III) ion each, with an Fe(III) ion located in the center. In 2, three Mn(II) ions alternate with three In(III) ions, whereas in 3, four In(III) ions are arranged in pairs and alternate with one Mn(II) ion each. In 2 and 3 an Mn(II) ion is encapsulated in the center.

  9. Effects of stacking fault energy on defect formation process in face-centered cubic metals

    NASA Astrophysics Data System (ADS)

    Okita, Taira; Yang, Yingjuan; Hirabayashi, Junichi; Itakura, Mitsuhiro; Suzuki, Katsuyuki

    2016-05-01

    To elucidate the effect of stacking fault energies (SFEs) on defect formation by the collision cascade process for face-centred cubic metals, we used six sets of interatomic potentials with different SFEs while keeping the other properties almost identical. Molecular dynamic simulations of the collision cascade were carried out using these potentials with primary knock-on atom energies (EPKA) of 10 and 20 keV at 100 K. Neither the number of residual defects nor the size distributions for both self-interstitial atom (SIA) type and vacancy type clusters were affected by the difference in the SFE. In the case of EPKA = 20 keV, the ratio of glissile SIA clusters increased as the SFE decreased, which was not expected by a prediction based on the classical dislocation theory. The trend did not change after annealing at 1100 K for 100 ps. For vacancy clusters, few stacking fault tetrahedrons (SFTs) formed before the annealing. However, lower SFEs tended to increase the SFT fraction after the annealing, where large vacancy clusters formed at considerable densities. The findings of this study can be used to characterise the defect formation process in low SFE metals such as austenitic stainless steels.

  10. Insights on activation enthalpy for non-Schmid slip in body-centered cubic metals

    DOE PAGES

    Hale, Lucas M.; Lim, Hojun; Zimmerman, Jonathan A.; ...

    2014-12-18

    We use insights gained from atomistic simulation to develop an activation enthalpy model for dislocation slip in body-centered cubic iron. Furthermore, using a classical potential that predicts dislocation core stabilities consistent with ab initio predictions, we quantify the non-Schmid stress-dependent effects of slip. The kink-pair activation enthalpy is evaluated and a model is identified as a function of the general stress state. Thus, our model enlarges the applicability of the classic Kocks activation enthalpy model to materials with non-Schmid behavior.

  11. Low-temperature thermostatics of face-centered-cubic metallic hydrogen

    NASA Technical Reports Server (NTRS)

    Caron, L. G.

    1974-01-01

    The thermostatic properties of a high-symmetry phase of metallic hydrogen with atomic sphere radius between 0.1 and 1.5 bohr are studied, with special emphasis accorded to electronic screening and quantum proton motion. The electron-proton and proton-proton interactions receive a perturbation treatment based on the Singwi dielectric function, while the proton motion is handled by self-consistent harmonic approximation. Quantum behavior is found to be less pronounced than expected, and nuclear magnetism is absent. The phonon spectrum is, however, affected by screening and large proton motion. The zero-point vibrational energy and the superconducting critical temperature are below previous estimates. The crystalline-defect formation energies are a few times the Debye energy, which implies that defects contribute significantly to melting at the lower particle densities.

  12. Oxidative addition of C--H bonds in organic molecules to transition metal centers

    SciTech Connect

    Bergman, R.G.

    1989-04-01

    Alkanes are among the most chemically inert organic molecules. They are reactive toward a limited range of reagents, such as highly energetic free radicals and strongly electrophilic and oxidizing species. This low reactivity is a consequence of the C--H bond energies in most saturated hydrocarbons. These values range from 90 to 98 kcal/mole for primary and secondary C--H bonds; in methane, the main constituent of natural gas, the C--H bond energy is 104 kcal/mole. This makes methane one of the most common but least reactive organic molecules in nature. This report briefly discusses the search for metal complexes capable of undergoing the C--H oxidative addition process allowing alkane chemistry to be more selective than that available using free radical reagents. 14 refs.

  13. High-Frequency (13)C and (29)Si NMR Chemical Shifts in Diamagnetic Low-Valence Compounds of Tl(I) and Pb(II): Decisive Role of Relativistic Effects.

    PubMed

    Vícha, Jan; Marek, Radek; Straka, Michal

    2016-02-15

    The (13)C and (29)Si NMR signals of ligand atoms directly bonded to Tl(I) or Pb(II) heavy-element centers are predicted to resonate at very high frequencies, up to 400 ppm for (13)C and over 1000 ppm for (29)Si, outside the typical experimental NMR chemical-shift ranges for a given type of nuclei. The large (13)C and (29)Si NMR chemical shifts are ascribed to sizable relativistic spin-orbit effects, which can amount to more than 200 ppm for (13)C and more than 1000 ppm for (29)Si, values unexpected for diamagnetic compounds of the main group elements. The origin of the vast spin-orbit contributions to the (13)C and (29)Si NMR shifts is traced to the highly efficient 6p → 6p* metal-based orbital magnetic couplings and related to the 6p orbital-based bonding together with the low-energy gaps between the occupied and virtual orbital subspaces in the subvalent Tl(I) and Pb(II) compounds. New NMR spectral regions for these compounds are suggested based on the fully relativistic density functional theory calculations in the Dirac-Coulomb framework carefully calibrated on the experimentally known NMR data for Tl(I) and Pb(II) complexes.

  14. Formation of recrystallization cube texture in high purity face-centered cubic metal sheets

    NASA Astrophysics Data System (ADS)

    Mao, W.

    1999-10-01

    An investigation on recrystallization textures in high purity face-centered cubic (fcc) aluminum, copper, and nickel indicated that the cube texture is a unique dominant final texture. In a macroview of rolling deformation, a balanced activation of four slip systems can result in certain stability of some substructure with cube orientation in the deformed matrix. In the stable substructure the dislocation density is very low, and the dislocation configuration is rather simple in comparison to other orientations so that the cube substructure can easily be transformed into cube recrystallization nuclei by a recovery process. A high orientation gradient and correspondingly high angle boundaries to the deformed matrix are usually expected around the cube nuclei, which, therefore, grow rapidly. After the primary recrystallization, the size of cube grains is much larger than the grains with other orientations, which will be expensed as the cube grains grow further, so that the cube texture can finally become a dominant texture component.

  15. Fatigue damage in cross-ply titanium metal matrix composites containing center holes

    NASA Technical Reports Server (NTRS)

    Bakuckas, J. G., Jr.; Johnson, W. S.; Bigelow, C. A.

    1992-01-01

    The development of fatigue damage in (0/90) sub SCS-6/TI-15-3 laminates containing center holes was studied. Stress levels required for crack initiation in the matrix were predicted using an effective strain parameter and compared to experimental results. Damage progression was monitored at various stages of fatigue loading. In general, a saturated state of damage consisting of matrix cracks and fiber matrix debonding was obtained which reduced the composite modulus. Matrix cracks were bridged by the 0 deg fibers. The fatigue limit (stress causing catastrophic fracture of the laminates) was also determined. The static and post fatigue residual strengths were accurately predicted using a three dimensional elastic-plastic finite element analysis. The matrix damage that occurred during fatigue loading significantly reduced the notched strength.

  16. Liquid Metal Processing and Casting Experiences at the U.S. Department of Energy's Albany Research Center

    SciTech Connect

    Jablonski, Paul D.; Turner, Paul C.

    2005-09-01

    In this paper we will discuss some of the early pioneering work as well as some of our more recent research. The Albany Research Center (ARC) has been involved with the melting and processing of metals since it was established in 1942. In the early days, hardly anything was known about melting refractory or reactive metals and as such, virtually everything had to be developed in-house. Besides the more common induction heated air-melt furnaces, ARC has built and/or utilized a wide variety of furnaces including vacuum arc remelt ingot and casting furnaces, cold wall induction furnaces, electric arc furnaces, cupola furnaces and reverberatory furnaces. The melt size of these furnaces range from several grams to a ton or more. We have used these furnaces to formulate custom alloys for wrought applications as well as for such casting techniques as spin casting, investment casting and lost foam casting among many. Two early spin-off industrializations were Wah Chang (wrought zirconium alloys for military and commercial nuclear applications) and Oremet (both wrought and cast Ti). Both of these companies are now part of the ATI Allegheny Ludlum Corporation.

  17. Elastic-plastic deformation of a metal-matrix composite coupon with a center slot

    NASA Technical Reports Server (NTRS)

    Post, D.; Czarnek, R.; Joh, D.; Jo, J.; Guo, Y.

    1985-01-01

    A comprehensive experimental analysis of deformations of the surface of a metal-matrix specimen is reported. The specimen is a 6-ply 0 + or - 45 sub s boron-aluminum tensile coupon with a central slot. Moire interferometry is used for high-sensitivity whole-field measurements of in-plane displacements. Normal and shear strains are calculated from displacement gradients. Displacement fields are analyzed at various load levels from 15% to 95% of the failure load. Deformations of the boron fibers could be distinguished from those of the matrix. Highly localized plastic slip zones occur tangent to the ends of the slot. Shear strains and concurrent transverse compressive strains in the slip zones reach approximately 10% and 1%, respectively. Upon unloading, elastic recovery in surrounding regions causes a reverse plastic shear strain in the slip zone of about 4%. Longitudinal normal strains on the unslotted ligament peak at the slot boundary at about 1% strain. The strain concentration factor at the end of the slot decreases with load level and the advance of plasticity.

  18. Analysis of endoscopic management of occluded metal biliary stents at a single tertiary care center.

    PubMed

    Rogart, Jason N; Boghos, Ara; Rossi, Federico; Al-Hashem, Hashem; Siddiqui, Uzma D; Jamidar, Priya; Aslanian, Harry

    2008-10-01

    A significant number of self-expandable metal stents (SEMSs) placed to palliate malignant biliary obstruction will occlude. Few data exist as to what constitutes optimal management. Our purpose was to review the management and outcomes of patients with biliary SEMS occlusion. Retrospective chart review at a single tertiary care hospital. From January 1999 to October 2005, a total of 90 patients had SEMSs placed for malignant biliary obstruction, and 27 of these occluded. Technical success of treating SEMS occlusion, stent patency and need for reintervention, and incremental cost analysis. A total of 60 ERCPs were performed to treat SEMS occlusions in 27 patients. The success rate was 95%; however, 52% of patients eventually required more than 1 intervention. Placing a second SEMS through the existing SEMS (n = 14) provided the lowest reocclusion rate (43% vs 55% and 100%), the longest time to reintervention (172 days vs 66 and 43 days, P = .03), and a trend toward longer survival (285 days vs 188 and 194 days) compared with plastic stent and mechanical balloon cleaning, respectively. Incremental cost analysis showed both uncovered SEMSs and plastic stents to be cost effective strategies. Small number of patients, retrospective study. Treatment of biliary SEMS occlusion with SEMS insertion provides for longer patency and survival, decreases the number of subsequent ERCPs by 50% compared with plastic stents, and is cost-effective.

  19. Multifunctional, defect-engineered metal-organic frameworks with ruthenium centers: sorption and catalytic properties.

    PubMed

    Kozachuk, Olesia; Luz, Ignacio; Llabrés i Xamena, Francesc X; Noei, Heshmat; Kauer, Max; Albada, H Bauke; Bloch, Eric D; Marler, Bernd; Wang, Yuemin; Muhler, Martin; Fischer, Roland A

    2014-07-01

    A mixed-linker solid-solution approach was employed to modify the metal sites and introduce structural defects into the mixed-valence Ru(II/III) structural analogue of the well-known MOF family [M3(II,II)(btc)2] (M=Cu, Mo, Cr, Ni, Zn; btc=benzene-1,3,5-tricarboxylate), with partly missing carboxylate ligators at the Ru2 paddle-wheels. Incorporation of pyridine-3,5-dicarboxylate (pydc), which is the same size as btc but carries lower charge, as a second, defective linker has led to the mixed-linker isoreticular derivatives of Ru-MOF, which display characteristics unlike those of the defect-free framework. Along with the creation of additional coordinatively unsaturated sites, the incorporation of pydc induces the partial reduction of ruthenium. Accordingly, the modified Ru sites are responsible for the activity of the "defective" variants in the dissociative chemisorption of CO2, the enhanced performance in CO sorption, the formation of hydride species, and the catalytic hydrogenation of olefins.

  20. Structural Models for the Metal Centers in the Nitrogenase Molybdenum-Iron Protein

    NASA Astrophysics Data System (ADS)

    Kim, Jongsun; Rees, D. C.

    1992-09-01

    Structural models for the nitrogenase FeMo-cofactor and P-clusters are proposed based on crystallographic analysis of the nitrogenase molybdenum-iron (MoFe)-protein from Azotobacter vinelandii at 2.7 angstrom resolution. Each center consists of two bridged clusters; the FeMo-cofactor has 4Fe:3S and 1Mo:3Fe:3S clusters bridged by three non-protein ligands, and the P-clusters contain two 4Fe:4S clusters bridged by two cysteine thiol ligands. Six of the seven Fe sites in the FeMo-cofactor appear to have trigonal coordination geometry, including one ligand provided by a bridging group. The remaining Fe site has tetrahedral geometry and is liganded to the side chain of Cys^α275. The Mo site exhibits approximate octahedral coordination geometry and is liganded by three sulfurs in the cofactor, two oxygens from homocitrate, and the imidazole side chain of His^α442. The P-clusters are liganded by six cysteine thiol groups, two which bridge the two clusters, α88 and β95, and four which singly coordinate the remaining Fe sites, α62, α154, β70, and β153. The side chain of Ser^β188 may also coordinate one iron. The polypeptide folds of the homologous α and β subunits surrounding the P-clusters are approximately related by a twofold rotation that may be utilized in the binding interactions between the MoFe-protein and the nitrogenase Fe-protein. Neither the FeMo-cofactor nor the P-clusters are exposed to the surface, suggesting that substrate entry, electron transfer, and product release must involve a carefully regulated sequence of interactions between the MoFe-protein and Fe-protein of nitrogenase.

  1. Examination of metals from aerospace-related activity in surface water samples from sites surrounding the Kennedy Space Center (KSC), Florida.

    PubMed

    Bowden, John A; Cantu, Theresa M; Scheidt, Douglas M; Lowers, Russell H; Nocito, Brian A; Young, Vaneica Y; Guillette, Louis J

    2014-05-06

    Metal contamination from Space Shuttle launch activity was examined using inductively coupled plasma-atomic emission spectroscopy in a two-tier study sampling surface water collected from several sites at the Kennedy Space Center (KSC) and associated Merritt Island National Wildlife Refuge in east central Florida. The primary study examined both temporal changes in baseline metal concentrations (19 metals) in surface water (1996 to 2009, 11 sites) samples collected at specific long-term monitoring sites and metal deposition directly associated with Space Shuttle launch activity at two Launch Complexes (LC39A and LC39B). A secondary study examined metal concentrations at additional sites and increased the amount of elements measured to 48 elements. Our examination places a heavy focus on those metals commonly associated with launch operations (e.g., Al, Fe, Mn, and Zn), but a brief discussion of other metals (As, Cu, Mo, Ni, and Pb) is also included. While no observable accumulation of metals occurred during the time period of the study, the data obtained postlaunch demonstrated a dramatic increase for Al, Fe, Mn, and Zn. Comparing overall trends between the primary and secondary baseline surface water concentrations, elevated concentrations were generally observed at sampling stations located near the launch complexes and from sites isolated from major water systems. While there could be several natural and anthropogenic sources for metal deposition at KSC, the data in this report indicate that shuttle launch events are a significant source.

  2. Dioxygen activation by non-adiabatic oxidative addition to a single metal center [O2 activation by non-adiabatic oxidative addition to a single metal center

    SciTech Connect

    Akturk, Eser S.; Yap, Glenn P. A.; Theopold, Klaus H.

    2015-10-16

    A chromium(I) dinitrogen complex reacts rapidly with O2 to form the mononuclear dioxo complex [TptBu,MeCrV(O)2] (TptBu,Me=hydrotris(3-tert-butyl-5-methylpyrazolyl)borate), whereas the analogous reaction with sulfur stops at the persulfido complex [TptBu,MeCrIII(S2)]. The transformation of the putative peroxo intermediate [TptBu,MeCrIII(O2)] (S=3/2) into [TptBu,MeCrV(O)2] (S=1/2) is spin-forbidden. The minimum-energy crossing point for the two potential energy surfaces has been identified. Finally, although the dinuclear complex [(TptBu,MeCr)2(μ-O)2] exists, mechanistic experiments suggest that O2 activation occurs on a single metal center, by an oxidative addition on the quartet surface followed by crossover to the doublet surface.

  3. Are dangling bond centers important interface traps in 4H-SiC metal oxide semiconductor field effect transistors?

    NASA Astrophysics Data System (ADS)

    Anders, M. A.; Lenahan, P. M.; Lelis, A. J.

    2016-10-01

    Silicon carbide (SiC) based metal-oxide-semiconductor field-effect transistors (MOSFETs) have great promise in high power and high temperature applications. Unfortunately, effective channel mobilities remain disappointingly low, typically about 30 cm2/Vs. A major contributor to the disappointing effective channel mobilities is the presence of substantial densities of interface traps at the SiC/SiO2 interface. Many investigators have invoked silicon or carbon dangling bonds to be the dominating source of these interface defects, but very little, if any, direct experimental evidence exists to support this assumption in the SiC/SiO2 system. Cantin et al. [Phys. Rev. Lett. 92, 1 (2004)] have used conventional electron paramagnetic resonance measurements on porous oxidized SiC structures to measure the g tensor for the SiC/SiO2 interface carbon dangling bond. These results provide a particularly straightforward means to search for the presence of carbon dangling bonds in fully processed SiC MOSFETs using electrically detected magnetic resonance. Additionally, simple theory provides guidance to search for silicon dangling bond defects. In this study, we utilize K band electrically detected magnetic resonance via spin dependent charge pumping measurements in which almost all of the SiC band gap at the SiC/SiO2 interface is accessed. Although quite high signal to noise measurements are achieved, we are unable to detect any trace of the carbon dangling bond spectra. However, in very poor quality p-channel devices, we observe a spectrum which could be consistent with silicon dangling bonds. Other defect centers are clearly present and we conclude that these other centers dominate the interface trap density of states.

  4. Kinetic and Mechanistic Studies of Carbon-to-Metal Hydrogen Atom Transfer Involving Os-Centered Radicals: Evidence for Tunneling

    SciTech Connect

    Lewandowska-Androlojc, Anna; Grills, David C.; Zhang, Jie; Bullock, R. Morris; Miyazawa, Akira; Kawanishi, Yuji; Fujita, Etsuko

    2014-03-05

    We have investigated the kinetics of novel carbon-to-metal hydrogen atom transfer reactions, in which homolytic cleavage of a C-H bond is accomplished by a single metal-centered radical. Studies by means of time-resolved IR spectroscopic measurements revealed efficient hydrogen atom transfer from xanthene, 9,10-dihydroanthracene and 1,4-cyclohexadiene to Cp(CO)2Os• and (n5-iPr4C5H)(CO)2Os• radicals, formed by photoinduced homolysis of the corresponding osmium dimers. The rate constants for hydrogen abstraction from these hydrocarbons were found to be in the range 1.54 × 105 M 1 s 1 -1.73 × 107 M 1 s-1 at 25 °C. For the first time, kinetic isotope effects for carbon-to-metal hydrogen atom transfer were determined. Large primary kinetic isotope effects of 13.4 ± 1.0 and 16.6 ± 1.4 were observed for the hydrogen abstraction from xanthene to form Cp(CO)2OsH and (n5-iPr4C5H)(CO)2OsH, respectively, at 25 °C. Temperature-dependent measurements of the kinetic isotope effects over a 60 -C temperature range were carried out to obtain the difference in activation energies and the pre-exponential factor ratio. For hydrogen atom transfer from xanthene to (n5-iPr4C5H)(CO)2Os•, the (ED - EH) = 3.25 ± 0.20 kcal/mol and AH/AD = 0.056 ± 0.018 values are greater than the semi-classical limits and thus suggest a quantum mechanical tunneling mechanism. The work at BNL was carried out under contract DE-AC02-98CH10886 with the U.S. Department of Energy and supported by its Division of Chemical Sciences, Geosciences & Biosciences, Office of Basic Energy Sciences. RMB also thanks the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, Division of Chemical Sciences, Geosciences & Biosciences for support. Pacific Northwest National Laboratory is operated by Battelle for the U.S. Department of Energy.

  5. Large amplitude oscillatory shear of block copolymer spheres on a body-centered cubic lattice: are micelles like metals?

    PubMed

    Torija, Maria A; Choi, Soo-Hyung; Lodge, Timothy P; Bates, Frank S

    2011-05-19

    Small-angle X-ray diffraction experiments have uncovered a remarkable mechanism of grain alignment during plastic deformation of ordered sphere-forming diblock copolymer micelles when subjected to large amplitude dynamic shearing. A nearly monodisperse poly(styrene-b-ethylene-alt-propylene) (SEP) diblock copolymer with block molecular weights of 42,000 and 60,000 was mixed with squalane (C(30)H(62)), an EP selective solvent, at a concentration of 10 wt%. After high temperature annealing, the sample formed an ordered polydomain morphology containing glassy S cores at room temperature. SAXS powder patterns confirm body-centered cubic (BCC) symmetry and reveal the development of a complex array of two-dimensionally resolved Bragg reflections following the application, and cessation, of oscillatory shearing. These diffraction results are interpreted on the basis of the classic mechanism of crystalline slip, which accounts for plastic deformation of ductile materials such as metals. Four distinct slip systems are shown to be active in this work, suggesting a robust basis for deforming and mixing of soft ordered solids.

  6. Face-centered-cubic K3B80 and Mg3B80 metals: Covalent and ionic bondings

    NASA Astrophysics Data System (ADS)

    Yan, Qing-Bo; Zheng, Qing-Rong; Su, Gang

    2009-09-01

    By means of first-principles calculations within the density-functional theory, we find that stable face-centered-cubic (fcc) K3B80 and Mg3B80 solids can be formed. For both solids, two possibly stable geometrical phases (identified as phase A and phase B ) with different lattice parameters can exist, where phase A has a lattice parameter smaller than phase B . In phase A , B80 clusters are significantly distorted and two or four intercluster covalent bonds are formed for K3B80 or Mg3B80 , respectively. In phase B , B80 units are slightly distorted and no intercluster covalent bonds exist. The phase A of Mg3B80 bears the largest cohesive energy among them and is more stable than the fcc B80 solid. The charge population analysis shows that K and Mg are ionized and donate electrons to the other boron atoms of K3B80 and Mg3B80 solids. The different ionic radii of K and Mg lead to major geometrical differences between K3B80 and Mg3B80 solids and the competition of the covalent and ionic bondings could explain the emergence of two different geometrical phases for both. The electronic structural calculations reveal that both fcc K3B80 and Mg3B80 solids are metals.

  7. First-principles path-integral molecular dynamics study of diffusion process of hydrogen in face-centered cubic metals

    NASA Astrophysics Data System (ADS)

    Kimizuka, Hajime; Ogata, Shigenobu

    We investigated the H diffusivity in face-centered cubic Pd and Al by performing path-integral molecular dynamics (PIMD) modeling in the framework of density functional theory (DFT); in our calculations, we took nuclear quantum effects into consideration. The DFT results showed that the H-migration barriers (Em) in Pd and Al exhibited similar values (approximately 0.16 eV), while the H atoms were stable at octahedral (O) sites for Pd and at tetrahedral (T) sites for Al. The PIMD-based free-energy profiles for H migration between the O-site and T-site were evaluated using the thermodynamic integration of the centroid forces at 150-600 K. We confirmed that the quantum effects significantly affected the Em and the difference between the energies of the H atom at the O-site and the T-site (EO - T); The Em and EO - T values in Pd at 300 K increased by 32% and 98%, respectively, relative to the classical limit. On the other hand, the Em and ET - O (i.e., -EO - T) values in Al at 300 K decreased by 3% and 41%, respectively. This suggested that the quantum nature of H nuclei was essential for understanding the H-diffusion kinetics in these metals even above ambient temperature.

  8. Multifrequency EPR Spectroscopy: A Toolkit for the Characterization of Mono- and Di-nuclear Metal Ion Centers in Complex Biological Systems

    NASA Astrophysics Data System (ADS)

    Hanson, Graeme R.

    Metalloenzymes are ubiquitous in nature containing complex metal ion cofactors intimately involved in the enzymes' biological function. The application of multifrequency continuous wave and orientation selective pulsed EPR in conjunction with computer simulation and density functional theory calculations has proven to be a powerful toolkit for the geometric and electronic structural characterization of these metal ion cofactors in the resting enzyme, enzyme-substrate and -product complexes, which in turn provides a detailed understanding of the enzymes' catalytic mechanism. In this chapter, a brief description of the multifrequency EPR toolkit used to structurally (geometric and electronic) characterize metal ion binding sites in complex biological systems and its application in the structural characterization of (i) molybdenum containing enzymes and model complexes, (ii) mono- and di-nuclear copper(II) cyclic peptide complexes (marine and synthetic analogues) and (iii) dinuclear metal ion centers in purple acid phosphatases will be presented.

  9. Final Technical Report on DE-SC00002460 [Bimetallic or trimetallic materials with structural metal centers based on Mn, Fe or V

    SciTech Connect

    Takeuchi, Esther Sans; Takeuchi, Kenneth James; Marschilok, Amy Catherine

    2013-07-26

    Bimetallic or trimetallic materials with structural metal centers based on Mn, Fe or V were investigated under this project. These metal centers are the focus of this research as they have high earth abundance and have each shown success as cathode materials in lithium batteries. Silver ion, Ag{sup +}, was initially selected as the displacement material as reduction of this center should result in increased conductivity as Ag{sup 0} metal particles are formed in-situ upon electrochemical reduction. The in-situ formation of metal nanoparticles upon electrochemical reduction has been previously noted, and more recently, we have investigated the resulting increase in conductivity. Layered materials as well as materials with tunnel or channel type structures were selected. Layered materials are of interest as they can provide 2-dimensional ion mobility. Tunnel or channel structures are also of interest as they provide a rigid framework that should remain stable over many discharge/charge cycles. We describe some examples of materials we have synthesized that demonstrate promising electrochemistry.

  10. Electron work function and surface energy of body-centered and face-centered cubic modifications of 4 d- and 5 d-metals

    NASA Astrophysics Data System (ADS)

    Aref'eva, L. P.; Shebzukhova, I. G.

    2016-07-01

    A technique for the evaluation of the electron work function of metallic single crystals and the electron work function anisotropy has been developed in the framework of the electron-statistical method. The surface energy and the electron work function have been calculated for crystal faces of allotropic modifications of 4 d- and 5 d-metals. A change in the electron work function due to the allotropic transformations has been estimated, and the periodic dependence of the electron work function has been determined. It has been shown that the results obtained using the proposed technique correlate with the available experimental data for polycrystals.

  11. Palliation of Obstructing Malignant Colonic Lesions Using Self-Expanding Metal Stents: A Single-Center Experience

    SciTech Connect

    Shrivastava, Vivek; Tariq, Omar; Tiam, ReeNee; Nyhsen, Christiane; Marsh, Ralph

    2008-09-15

    To evaluate the efficacy, risks, and survival after palliative colorectal stenting at a single center, we conducted a retrospective review of consecutive patients who had colorectal self-expanding metal stents (SEMSs) inserted over an 8-year period (September 1998 to September 2006) to relieve an obstructing colorectal tumor. All patients either had proven distant metastases or were unfit for surgical decompression. A single interventional radiologist (R.M.) inserted the stents, which were either Memotherm or WallFlex. Ninety-one patients with a median age of 73 years had a colorectal stent inserted for palliation of an obstructing colorectal malignancy. Technical success was achieved in 81 of 91 (89%) patients, and clinical success in 80 of 81 (99%). At the time of analysis (December 2006), 13 of 91 (14.2%) patients were alive. The patients who died had a median survival of 59 days, IQR 17-181 days. Seven (7/81) patients suffered stent migration, which occurred 10.3 days (IQR, 5-14 days) after the procedure. Three patients (3/81) re-presented with intestinal obstruction secondary to tumor ingrowth and 10 (10.9%) patients suffered bowel perforation. Ten patients (10.9%) had two stents inserted coaxially and overlapping in one procedure. This was performed in cases where the stricture was too long to be easily crossed by a single stent. We conclude that colorectal SEMS is a safe and effective mode of treatment for the palliation of obstructing colorectal cancers, which avoids high-risk surgery.

  12. A semi-empirical analysis of ZFS parameters for transition metal (TM) ions (Cr3+ and Mn2+) centers in K2MgF4

    NASA Astrophysics Data System (ADS)

    Açıkgöz, Muhammed

    2016-11-01

    The local structure around the transition metal (TM) ions (Cr3+ and Mn2+) centers in K2MgF4, namely tetragonal (TE) center I, monoclinic (MO) center II and orthorhombic (OR) centers III, have been explored by semi-empirical calculations in the frame of superposition model (SPM). We proposed the most appropriate structural model for each center by matching the theoretically predicted zero-field splitting parameters (ZFSPs) with the experimental ones obtained by EPR spectroscopy. It is shown that the tetragonality of MgF6 octahedra increases with the substitution of both Cr3+ and Mn2+ for Mg2+ sites as well as with a rather higher value for the latter one. A tilt angle of 12.51° is found for MO Cr3+ center, which is comparatively small, as compared to the other A2BF4 crystals such as K2ZnF4 and Tl2ZnF4. Almost three times larger relaxation of intervening F-ligand than that of other equatorial F-ligands is also indicated for OR Cr3+ center.

  13. Mechanismic investigation on the cleavage of phosphate monoester catalyzed by unsymmetrical macrocyclic dinuclear complexes: the selection of metal centers and the intrinsic flexibility of the ligand.

    PubMed

    Zhang, Xuepeng; Zhu, Yajie; Zheng, Xiaowei; Phillips, David Lee; Zhao, Cunyuan

    2014-04-07

    The hydrolysis mechanisms of phosphor-monoester monoanions NPP(-) (p-nitrophenyl phosphate) catalyzed by unsymmetrical bivalent dinuclear complexes are explored using DFT calculations in this report. Four basic catalyst-substrate binding modes are proposed, and two optional compartments for the location of the nucleophile-coordinated metal center are also considered. Five plausible mechanisms are examined in this computational study. Mechanisms 1, 2, and 3 employ an unsymmetrical dizinc complex. All three mechanisms are based on concerted SN2 addition-substitution pathways. Mechanism 1, which involves more electronegative oxygen atoms attached to the imine nitrogen atoms in the nucleophile-coordinated compartment, was found to be more competitive compared to the other two mechanisms. Mechanisms 4 and 5 are based on consideration of the substitution of the bivalent metal centers and the intrinsic flexibility of the ligand. Both mechanisms 4 and 5 are based on stepwise SN2-type reactions. Magnesium ions with hard base properties and more available coordination sites were found to be good candidates as a substitute in the M(II) dinuclear phosphatases. The reaction energy barriers for the more distorted complexes are lower than those of the less distorted complexes. The proper intermediate distance and a functional second coordination sphere lead to significant catalytic power in the reactions studied. More importantly, the mechanistic differences between the concerted and the stepwise pathways suggest that a better nucleophile with more available coordination sites (from either the metal centers or a functional second coordination sphere) favors concerted mechanisms for the reactions of interest. The results reported in the paper are consistent with and provide a reasonable interpretation for experimental observations in the literature. More importantly, our present results provide some practical suggestions for the selection of the metal centers and how to approach

  14. Transition-Metal-Free Cyclopropanation of 2-Aminoacrylates with N-Tosylhydrazones: A General Route to Cyclopropane α-Amino Acid with Contiguous Quaternary Carbon Centers.

    PubMed

    Zhu, Chuanle; Li, Jiawei; Chen, Pengquan; Wu, Wanqing; Ren, Yanwei; Jiang, Huanfeng

    2016-03-18

    Cyclopropanation of 2-aminoacrylates with N-tosylhydrazones could proceed smoothly under transition-metal-free conditions via a [3 + 2] cycloaddition process. This robust protocol exhibits excellent generality, delivering a wide spectrum of cyclopropane α-amino acid esters bearing contiguous quaternary carbon centers in high yields and diastereoselectivities. With these readily available products, the steric convergence of cyclopropane α-amino acids could be readily obtained.

  15. Binding of Copper and Silver to Single-Site Variants of Peptidylglycine Monooxygenase Reveals the Structure and Chemistry of the Individual Metal Centers

    PubMed Central

    2015-01-01

    Peptidylglycine monooxygenase (PHM) catalyzes the final step in the biosynthesis of amidated peptides that serve as important signaling molecules in numerous endocrine pathways. The catalytic mechanism has attracted much attention because of a number of unique attributes, including the presence of a pair of uncoupled copper centers separated by 11 Å (termed CuH and CuM), an unusual Cu(I)SMet interaction at the oxygen binding M-site, and the postulated Cu(II)–superoxo intermediate. Understanding the mechanism requires determining the catalytic roles of the individual copper centers and how they change during catalysis, a task made more difficult by the overlapping spectral signals from each copper center in the wild-type (WT) protein. To aid in this effort, we constructed and characterized two PHM variants that bound metal at only one site. The H242A variant bound copper at the H-center, while the H107AH108A double mutant bound copper at the M-center; both mutants were devoid of catalytic activity. Oxidized Cu(II) forms showed electron paramagnetic resonance and extended X-ray absorption fine structure (EXAFS) spectra consistent with their previously determined Cu(II)His3O and Cu(II)His2O2 ligand sets for the H- and M-centers, respectively. Cu(I) forms, on the other hand, showed unique chemistry. The M-center bound two histidines and a methionine at all pHs, while the H-center was two-coordinate at neutral pH but coordinated a new methionine S ligand at low pH. Fourier transform infrared studies confirmed and extended previous assignments of CO binding and showed unambiguously that the 2092 cm–1 absorbing species observed in the WT and many variant forms is an M-site Cu(I)–CO adduct. Silver binding was also investigated. When H107AH108A and M109I (a WT analogue with both sites intact) were incubated with excess AgNO3, each variant bound a single Ag(I) ion, from which it was inferred that Ag(I) binds selectively at the M-center with little or no affinity for

  16. Binding of copper and silver to single-site variants of peptidylglycine monooxygenase reveals the structure and chemistry of the individual metal centers.

    PubMed

    Chauhan, Shefali; Kline, Chelsey D; Mayfield, Mary; Blackburn, Ninian J

    2014-02-18

    Peptidylglycine monooxygenase (PHM) catalyzes the final step in the biosynthesis of amidated peptides that serve as important signaling molecules in numerous endocrine pathways. The catalytic mechanism has attracted much attention because of a number of unique attributes, including the presence of a pair of uncoupled copper centers separated by 11 Å (termed CuH and CuM), an unusual Cu(I)SMet interaction at the oxygen binding M-site, and the postulated Cu(II)-superoxo intermediate. Understanding the mechanism requires determining the catalytic roles of the individual copper centers and how they change during catalysis, a task made more difficult by the overlapping spectral signals from each copper center in the wild-type (WT) protein. To aid in this effort, we constructed and characterized two PHM variants that bound metal at only one site. The H242A variant bound copper at the H-center, while the H107AH108A double mutant bound copper at the M-center; both mutants were devoid of catalytic activity. Oxidized Cu(II) forms showed electron paramagnetic resonance and extended X-ray absorption fine structure (EXAFS) spectra consistent with their previously determined Cu(II)His3O and Cu(II)His2O2 ligand sets for the H- and M-centers, respectively. Cu(I) forms, on the other hand, showed unique chemistry. The M-center bound two histidines and a methionine at all pHs, while the H-center was two-coordinate at neutral pH but coordinated a new methionine S ligand at low pH. Fourier transform infrared studies confirmed and extended previous assignments of CO binding and showed unambiguously that the 2092 cm(-1) absorbing species observed in the WT and many variant forms is an M-site Cu(I)-CO adduct. Silver binding was also investigated. When H107AH108A and M109I (a WT analogue with both sites intact) were incubated with excess AgNO3, each variant bound a single Ag(I) ion, from which it was inferred that Ag(I) binds selectively at the M-center with little or no affinity for the H-center

  17. Revision of metal-on-metal hip arthroplasty in a tertiary center: a prospective study of 39 hips with between 1 and 4 years of follow-up.

    PubMed

    Liddle, Alexander D; Satchithananda, Keshtra; Henckel, Johann; Sabah, Shiraz A; Vipulendran, Karuniyan V; Lewis, Angus; Skinner, John A; Mitchell, Adam W M; Hart, Alister J

    2013-06-01

    Operative findings during revision of metal-on-metal hip arthroplasty (MOMHA) vary widely and can involve massive soft tissue and bone disruption. As a result, planning of theater time and resources is difficult, surgery is challenging, and outcomes are often poor. We describe our experience with revision of MOMHA and provide recommendations for management. We present the findings and outcomes of 39 consecutive MOMHAs (in 35 patients) revised in a tertiary unit (median follow-up time 30 (12-54) months). The patients underwent a preoperative work-up including CT, metal artifact reduction sequence (MARS) MRI, and blood metal ion levels. We determined 5 categories of failure. 8 of 39 hips had conventional failure mechanisms including infection and impingement. Of the other 31 hips, 14 showed synovitis without significant disruption of soft tissue; 6 had a cystic pseudotumor with significant soft tissue disruption; 7 had significant osteolysis; and 4 had a solid pseudotumor. Each category of failure had specific surgical hazards that could be addressed preoperatively. There were 2 reoperations and 1 patient (2 hips) died of an unrelated cause. Median Oxford hip score (OHS) was 37 (9-48); median change (ΔOHS) was 17 (-10 to 41) points. ΔOHS was similar in all groups-except those patients with solid pseudotumors and those revised to metal-on-metal bearings, who fared worse. Planning in revision MOMHA is aided by knowledge of the different categories of failure to enable choice of appropriate personnel, theater time, and equipment. With this knowledge, satisfactory outcomes can be achieved in revision of metal-on-metal hip arthroplasty.

  18. Incoherent Bi off-centering in Bi2Ti2O6O' and Bi2Ru2O6O': Insulator versus metal

    NASA Astrophysics Data System (ADS)

    Shoemaker, Daniel P.; Seshadri, Ram; Tachibana, Makoto; Hector, Andrew L.

    2011-08-01

    In the cubic, stoichiometric oxide compounds Bi2Ti2O6O' (also written as Bi2Ti2O7) and Bi2Ru2O6O' (also written as Bi2Ru2O7) Bi3+ ions on the pyrochlore A site display a propensity to off-center. Unlike Bi2Ti2O6O', Bi2Ru2O6O' is a metal, so it is of interest to ask whether conduction electrons and/or involvement of Bi 6s states at the Fermi energy influence Bi3+ displacements. The Bi3+ off-centering in Bi2Ti2O6O' has previously been revealed to be incoherent from detailed reverse Monte Carlo analysis of total neutron scattering. Similar analysis of Bi2Ru2O6O' reveals incoherent off-centering as well, but of smaller magnitude and with distinctly different orientational preference. Analysis of the distributions of metal to oxygen distances presented suggests that Bi in both compounds is entirely Bi3+. Disorder in Bi2Ti2O6O' has the effect of stabilizing valence while simultaneously satisfying the steric constraint imposed by the presence of the lone pair of electrons. In Bi2Ru2O6O', off-centering is not required to satisfy valence and seems to be driven by the lone pair. Decreased volume of the lone pair may be a result of partial screening by conduction electrons.

  19. Squeezing and Heating Rock to Scope Out How Metallic Iron Dribbled to the Center of the Earth

    NASA Astrophysics Data System (ADS)

    Taylor, G. J.

    2005-07-01

    Formation of Earth's metallic core was one of the most important events in the history of the planet. Metallic iron is much denser than rock, so it sank to the middle, taking other elements that concentrate in metal rather than silicate (rock) with it. However, we do not understand everything about core formation. One particularly niggling puzzle is why cobalt (Co) and nickel (Ni) have the same concentration (relative to primitive carbonaceous chondrites) as one another in Earth's mantle. At low pressure these elements concentrate in metallic iron to different extents. Calculations show that if metal segregated from silicate at low pressure, nickel ought to be 100 times less abundant (normalized to chondrites) than cobalt, not equal. Cosmochemists have tackled this problem by doing experiments at high pressure and temperature to map out how cobalt and nickel partitioning between metal and silicate differs compared to low pressure. However, the studies differ in their predictions of the behavior because of differences in the assumed pressure, temperature, and oxidation state during core formation. Nancy Chabot (Case Western Reserve University, now at the Johns Hopkins Applied Physics Laboratory), and David Draper and Carl Agee from the University of New Mexico addressed the discrepancies by designing a series of experiments over a wide range in temperature. Their results plot out the conditions under which metal can sink to the core while leading to the observed cobalt and nickel concentrations in the mantle. While the results do not lead to a unique solution, they point the way for further studies of other elements that tend to concentrate in metallic iron, and they show clearly that the equal nickel and cobalt concentrations in the mantle can be the product of core formation in the early Earth.

  20. Double aromaticity in transition metal centered double-ring boron clusters M@B2n (M = Ti, Cr, Fe, Ni, Zn; n = 6, 7, 8)

    NASA Astrophysics Data System (ADS)

    Xu, Chang; Cheng, Longjiu; Yang, Jinlong

    2014-09-01

    It is well known that double-ring boron clusters have got the special double aromaticity with delocalized π orbitals in two directions (tangential and radial), which are potential ligands centered by a transition metal. In this article, the transition metal centered double-ring boron clusters M@B2n (M = Ti, Cr, Fe, Ni, Zn; n = 6, 7, 8) are theoretically investigated by density functional theory calculations. These endohedral compounds have also got double aromaticity in both tangential and radial directions. Interestingly, the tangential delocalized π orbitals of boron ligands following the Huckle's (4n + 2) rule do not interact with the central metal, while the radial π orbitals of boron ligands are bonded with the central mental to form spd-π endohedral bonding. The spd-π endohedral bonding follows the 18e-principle in Ni@B14 and Fe@B16. However, due to the flat shape of the compounds, 14e (Cr@B14) and 16e (Ni@B12) can also be electronically very stable where the energy levels of the spd-π orbitals delocalized in z-direction rise up. This intriguing bonding model makes sense in further study of the boron chemistry.

  1. Metal-ion effects on the polarization of metal-bound water and infrared vibrational modes of the coordinated metal center of Mycobacterium tuberculosis pyrazinamidase via quantum mechanical calculations.

    PubMed

    Salazar-Salinas, Karim; Baldera-Aguayo, Pedro A; Encomendero-Risco, Jimy J; Orihuela, Melvin; Sheen, Patricia; Seminario, Jorge M; Zimic, Mirko

    2014-08-28

    Mycobacterium tuberculosis pyrazinamidase (PZAse) is a key enzyme to activate the pro-drug pyrazinamide (PZA). PZAse is a metalloenzyme that coordinates in vitro different divalent metal cofactors in the metal coordination site (MCS). Several metals including Co(2+), Mn(2+), and Zn(2+) are able to reactivate the metal-depleted PZAse in vitro. We use quantum mechanical calculations to investigate the Zn(2+), Fe(2+), and Mn(2+) metal cofactor effects on the local MCS structure, metal-ligand or metal-residue binding energy, and charge distribution. Results suggest that the major metal-dependent changes occur in the metal-ligand binding energy and charge distribution. Zn(2+) shows the highest binding energy to the ligands (residues). In addition, Zn(2+) and Mn(2+) within the PZAse MCS highly polarize the O-H bond of coordinated water molecules in comparison with Fe(2+). This suggests that the coordination of Zn(2+) or Mn(2+) to the PZAse protein facilitates the deprotonation of coordinated water to generate a nucleophile for catalysis as in carboxypeptidase A. Because metal ion binding is relevant to enzymatic reaction, identification of the metal binding event is important. The infrared vibrational mode shift of the C═Nε (His) bond from the M. tuberculosis MCS is the best IR probe to metal complexation.

  2. Determination of the nitrogen vacancy as a shallow compensating center in GaN doped with divalent metals.

    PubMed

    Buckeridge, J; Catlow, C R A; Scanlon, D O; Keal, T W; Sherwood, P; Miskufova, M; Walsh, A; Woodley, S M; Sokol, A A

    2015-01-09

    We report accurate energetics of defects introduced in GaN on doping with divalent metals, focusing on the technologically important case of Mg doping, using a model that takes into consideration both the effect of hole localization and dipolar polarization of the host material, and includes a well-defined reference level. Defect formation and ionization energies show that divalent dopants are counterbalanced in GaN by nitrogen vacancies and not by holes, which explains both the difficulty in achieving p-type conductivity in GaN and the associated major spectroscopic features, including the ubiquitous 3.46 eV photoluminescence line, a characteristic of all lightly divalent-metal-doped GaN materials that has also been shown to occur in pure GaN samples. Our results give a comprehensive explanation for the observed behavior of GaN doped with low concentrations of divalent metals in good agreement with relevant experiment.

  3. [CrF(O2CtBu)2]9: Synthesis and Characterization of a Regular Homometallic Ring with an Odd Number of Metal Centers and Electrons

    PubMed Central

    Woolfson, Robert J.; Timco, Grigore A.; Chiesa, Alessandro; Vitorica‐Yrezabal, Inigo J.; Tuna, Floriana; Guidi, Tatiana; Pavarini, Eva; Santini, Paolo; Carretta, Stefano

    2016-01-01

    Abstract The first regular homometallic ring containing an odd number of metal centers is reported. The ring was synthesized by means of amine‐templated self‐assembly. Extensive physical characterization studies, including magnetic measurements, powder inelastic neutron scattering (INS), and DFT calculations, show that the molecule has a near perfect match to the expected behavior for a frustrated system with the lowest energy pair of S=1/2 spin states separated by only 0.1 meV (0.8 cm−1). PMID:27294807

  4. High-temperature fatigue in metals - A brief review of life prediction methods developed at the Lewis Research Center of NASA

    NASA Technical Reports Server (NTRS)

    Halford, G. R.

    1983-01-01

    The presentation focuses primarily on the progress we at NASA Lewis Research Center have made. The understanding of the phenomenological processes of high temperature fatigue of metals for the purpose of calculating lives of turbine engine hot section components is discussed. Improved understanding resulted in the development of accurate and physically correct life prediction methods such as Strain-Range partitioning for calculating creep fatigue interactions and the Double Linear Damage Rule for predicting potentially severe interactions between high and low cycle fatigue. Examples of other life prediction methods are also discussed. Previously announced in STAR as A83-12159

  5. High-temperature fatigue in metals - A brief review of life prediction methods developed at the Lewis Research Center of NASA

    NASA Technical Reports Server (NTRS)

    Halford, G. R.

    1983-01-01

    The presentation focuses primarily on the progress we at NASA Lewis Research Center have made. The understanding of the phenomenological processes of high temperature fatigue of metals for the purpose of calculating lives of turbine engine hot section components is discussed. Improved understanding resulted in the development of accurate and physically correct life prediction methods such as Strain-Range partitioning for calculating creep fatigue interactions and the Double Linear Damage Rule for predicting potentially severe interactions between high and low cycle fatigue. Examples of other life prediction methods are also discussed. Previously announced in STAR as A83-12159

  6. Analysis of the twin spacing and grain size effects on mechanical properties in hierarchically nanotwinned face-centered cubic metals based on a mechanism-based plasticity model

    NASA Astrophysics Data System (ADS)

    Zhu, Linli; Qu, Shaoxing; Guo, Xiang; Lu, Jian

    2015-03-01

    Hierarchical twin lamellae in polycrystalline face-centered cubic (fcc) metals possess a possibility to achieve higher strength with keeping an acceptable elongation. The present work is concerned with the analysis of twin spacing and grain size-dependent plastic performance in hierarchically nanotwinned fcc metals using a generalized strain-gradient plasticity model. The dislocation density-based physical model for constitutive description of nanotwinned fcc metals is expanded for the hierarchical structures of nanotwins. The strengthening mechanism and the failure behavior in these hierarchical nanostructures are studied to evaluate the strength and ductility. Moreover, the transition twin spacing between the strengthening and softening is obtained in different order of twin lamellae. A dislocation-based model on nucleating deformation twins is presented to predict the critical twin spacing in the lowest twin lamellae for generating the subordinate twin lamellae. Our simulation results demonstrate that the existence of the hierarchical nanotwins gives rise to a significant enhancement in the strength, and the resulting global flow stresses are sensitive to the twin spacings of the hierarchical twin lamellae and the grain size. Two softening stages are observed with variation of twin spacing, and the relevant transition twin spacing depends on the microstructural size in hierarchically nanotwinned metals. We further find that the predicted failure strain decreases with decreasing the twin spacing, which is quite different from the case of the individually nanotwinned fcc metals. The critical twin spacing for generating subordinate twins also depends on the twin spacing of superordinate twin lamellae and the grain size. These findings suggest that the high yield strength and good ductility can be achieved by optimizing the grain size and the twin spacings in the hierarchical twins.

  7. Metal-Ion Effects on the Polarization of Metal-Bound Water and Infrared Vibrational Modes of the Coordinated Metal Center of Mycobacterium tuberculosis Pyrazinamidase via Quantum Mechanical Calculations

    PubMed Central

    2014-01-01

    Mycobacterium tuberculosis pyrazinamidase (PZAse) is a key enzyme to activate the pro-drug pyrazinamide (PZA). PZAse is a metalloenzyme that coordinates in vitro different divalent metal cofactors in the metal coordination site (MCS). Several metals including Co2+, Mn2+, and Zn2+ are able to reactivate the metal-depleted PZAse in vitro. We use quantum mechanical calculations to investigate the Zn2+, Fe2+, and Mn2+ metal cofactor effects on the local MCS structure, metal–ligand or metal–residue binding energy, and charge distribution. Results suggest that the major metal-dependent changes occur in the metal–ligand binding energy and charge distribution. Zn2+ shows the highest binding energy to the ligands (residues). In addition, Zn2+ and Mn2+ within the PZAse MCS highly polarize the O–H bond of coordinated water molecules in comparison with Fe2+. This suggests that the coordination of Zn2+ or Mn2+ to the PZAse protein facilitates the deprotonation of coordinated water to generate a nucleophile for catalysis as in carboxypeptidase A. Because metal ion binding is relevant to enzymatic reaction, identification of the metal binding event is important. The infrared vibrational mode shift of the C=Nε (His) bond from the M. tuberculosis MCS is the best IR probe to metal complexation. PMID:25055049

  8. Probing the location and distribution of paramagnetic centers in alkali metal-loaded zeolites through (7)Li MAS NMR.

    PubMed

    Terskikh, Victor V; Ratcliffe, Christopher I; Ripmeester, John A; Reinhold, Catherine J; Anderson, Paul A; Edwards, Peter P

    2004-09-15

    The nature and surroundings of lithium cations in lithium-exchanged X and A zeolites following loading with the alkali metals Na, K, Rb, and Cs have been studied through (7)Li solid-state NMR spectroscopy. It is demonstrated that the lithium in these zeolites is stable with respect to reduction by the other alkali metals. Even though the lithium cations are not directly involved in chemical interactions with the excess electrons introduced in the doping process, the corresponding (7)Li NMR spectra are extremely sensitive to paramagnetic species that are located inside the zeolite cavities. This sensitivity makes (7)Li NMR a useful probe to study the formation, distribution, and transformation of such species.

  9. Design of a non-precious metal electrocatalyst for alkaline electrolyte oxygen reduction by using soybean biomass as the nitrogen source of electrocatalytically active center structures

    NASA Astrophysics Data System (ADS)

    Guo, Chao-Zhong; Liao, Wen-Li; Chen, Chang-Guo

    2014-12-01

    The development of less expensive, more active, and more stable catalyst substitute for Pt/C catalysts for oxygen reduction has recently become a hot topic. In this paper, we report a new strategy to design nitrogen-doped non-precious metal catalysts via the copyrolysis of metallic iron, soybean biomass, and carbon support at high temperatures. The results show that the nitrogen in electrocatalysts is mainly in the form of pyridinic and pyrrolic N species. The metallic Fe in the precursor can facilitate the transformation of quaternary N with a three-dimensional structure to planar pyridinic and pyrrolic N inside carbon matrix during pyrolysis, thereby improving the electrocatalytic activity of the prepared catalysts. We suggest that the planar N species may be the catalytically active center structures and may contribute to the enhancement of oxygen reduction reaction performance in an alkaline electrolyte. The prepared catalyst has superior tolerance against methanol crossover effect and outstanding stability compared with commercial Pt/C catalysts.

  10. Assembly of a homochiral, body-centered cubic network composed of vertex-shared Mg12 cages: use of electrospray ionization mass spectrometry to monitor metal carboxylate nucleation.

    PubMed

    Rood, Jeffrey A; Boggess, William C; Noll, Bruce C; Henderson, Kenneth W

    2007-11-07

    Reaction of Mg(NO3)2.6H2O with (+)-camphoric acid (H2cam) in acetonitrile results in the immediate formation of soluble, dimetallic [Mg2(Hcam)3]+ cations. The formation of these stable cations in solution was determined by electrospray ionization mass spectrometry (ESI-MS). These dimers are 3-fold paddle-wheels, which associate together through the neutral acid units to build the metal-organic framework [Mg2(Hcam)3.3H2O].NO3.MeCN, 1. The network consists of a series of fused Mg12 cages that have 12 water molecules at their centers, creating isolated 0D cavities within the structure. Overall, the extended structure of 1 is a body-centered cubic (bcu) lattice, with the Mg12 cages being utilized as eight-connected nodes. The framework of 1 is chiral and adopts the very unusual space group I23. Use of 1,3-propanediol as an additive results in the formation of the simple 1D polymer [Mg(cam){HO(CH2)3OH}2], 2. In 2, each carboxylate-bridged metal center is chelated by two diols. ESI-MS studies confirm the formation of new ions in these solutions. The identities of 1 and 2 were confirmed by a combination of single-crystal X-ray diffraction, elemental analyses, IR, NMR, themogravimetric analyses, and ESI-MS data. ESI-MS has proven to be a valuable technique in the identification of stable SBUs in solution prior to network formation.

  11. Simulation of changes in heavy metal contamination in farmland soils of a typical manufacturing center through logistic-based cellular automata modeling.

    PubMed

    Qiu, Menglong; Wang, Qi; Li, Fangbai; Chen, Junjian; Yang, Guoyi; Liu, Liming

    2016-01-01

    A customized logistic-based cellular automata (CA) model was developed to simulate changes in heavy metal contamination (HMC) in farmland soils of Dongguan, a manufacturing center in Southern China, and to discover the relationship between HMC and related explanatory variables (continuous and categorical). The model was calibrated through the simulation and validation of HMC in 2012. Thereafter, the model was implemented for the scenario simulation of development alternatives for HMC in 2022. The HMC in 2002 and 2012 was determined through soil tests and cokriging. Continuous variables were divided into two groups by odds ratios. Positive variables (odds ratios >1) included the Nemerow synthetic pollution index in 2002, linear drainage density, distance from the city center, distance from the railway, slope, and secondary industrial output per unit of land. Negative variables (odds ratios <1) included elevation, distance from the road, distance from the key polluting enterprises, distance from the town center, soil pH, and distance from bodies of water. Categorical variables, including soil type, parent material type, organic content grade, and land use type, also significantly influenced HMC according to Wald statistics. The relative operating characteristic and kappa coefficients were 0.91 and 0.64, respectively, which proved the validity and accuracy of the model. The scenario simulation shows that the government should not only implement stricter environmental regulation but also strengthen the remediation of the current polluted area to effectively mitigate HMC.

  12. Influence of the solvent and metal center on supramolecular chirality induction with bisporphyrin tweezer receptors. Strong metal modulation of effective molarity values.

    PubMed

    Pintre, Inmaculada C; Pierrefixe, Simon; Hamilton, Alex; Valderrey, Virginia; Bo, Carles; Ballester, Pablo

    2012-04-16

    We describe the synthesis of a bisporphyrin tweezer receptor 1·H(4) and its metalation with Zn(II) and Rh(III) cations. We report the thermodynamic characterization of the supramolecular chirality induction process that takes place when the metalated bisporphyrin receptors coordinate to enantiopure 1,2-diaminocyclohexane in two different solvents, toluene and dichloromethane. We also performed a thorough study of several simpler systems that were used as models for the thermodynamic characterization of the more complex bisporphyrin systems. The initial complexation of the chiral diamine with the bisporphyrins produces a 1:1 sandwich complex that opens up to yield a simple 1:2 complex in the presence of excess diamine. The CD spectra associated with the 1:1 and 1:2 complexes of both metalloporphyrins, 1·Zn(2) and 1·Rh(2), display bisignate Cotton effects when the chirogenesis process is studied in toluene solutions. On the contrary, in dichloromethane solutions, only 1·Zn(2) yields CD-active 1:1 and 1:2 complexes, while the 1:2 complex of 1·Rh(2) is CD-silent. In both solvents, porphyrin 1·Zn(2) features a stoichiometrically controlled chirality inversion process, which is the sign of the Cotton effect of the 1:1 complex is opposite to that of the 1:2 complex. In contrast, porphyrin 1·Rh(2) affords 1:1 and 1:2 complexes in toluene solutions with the same sign for their CD couplets. Interestingly, in both solvents, the signs of the CD couplets associated with the 1:1 sandwich complexes of 1·Zn(2) and 1·Rh(2) are opposite. The amplitudes of the CD couplets are higher for 1·Zn(2) than for 1·Rh(2). This observation is in agreement with 1·Rh(2) having a smaller extinction coefficient than 1·Zn(2). We performed DFT-based calculations and assigned molecular structures to the 1:1 and 1:2 complexes that explain the observed signs for their CD couplets. Unexpectedly, the quantification of the thermodynamic stability of the two metallobisporphyrin/diamine 1

  13. UTSA-74: A MOF-74 Isomer with Two Accessible Binding Sites per Metal Center for Highly Selective Gas Separation.

    PubMed

    Luo, Feng; Yan, Changsheng; Dang, Lilong; Krishna, Rajamani; Zhou, Wei; Wu, Hui; Dong, Xinglong; Han, Yu; Hu, Tong-Liang; O'Keeffe, Michael; Wang, Lingling; Luo, Mingbiao; Lin, Rui-Biao; Chen, Banglin

    2016-05-04

    A new metal-organic framework Zn2(H2O)(dobdc)·0.5(H2O) (UTSA-74, H4dobdc = 2,5-dioxido-1,4-benzenedicarboxylic acid), Zn-MOF-74/CPO-27-Zn isomer, has been synthesized and structurally characterized. It has a novel four coordinated fgl topology with one-dimensional channels of about 8.0 Å. Unlike metal sites in the well-established MOF-74 with a rod-packing structure in which each of them is in a five coordinate square pyramidal coordination geometry, there are two different Zn(2+) sites within the binuclear secondary building units in UTSA-74 in which one of them (Zn1) is in a tetrahedral while another (Zn2) in an octahedral coordination geometry. After activation, the two axial water molecules on Zn2 sites can be removed, generating UTSA-74a with two accessible gas binding sites per Zn2 ion. Accordingly, UTSA-74a takes up a moderately high and comparable amount of acetylene (145 cm(3)/cm(3)) to Zn-MOF-74. Interestingly, the accessible Zn(2+) sites in UTSA-74a are bridged by carbon dioxide molecules instead of being terminally bound in Zn-MOF-74, so UTSA-74a adsorbs a much smaller amount of carbon dioxide (90 cm(3)/cm(3)) than Zn-MOF-74 (146 cm(3)/cm(3)) at room temperature and 1 bar, leading to a superior MOF material for highly selective C2H2/CO2 separation. X-ray crystal structures, gas sorption isotherms, molecular modeling, and simulated and experimental breakthroughs comprehensively support this result.

  14. Prospective, multi-center evaluation of a silicon carbide coated cobalt chromium bare metal stent for percutaneous coronary interventions: two-year results of the ENERGY Registry.

    PubMed

    Erbel, Raimund; Eggebrecht, Holger; Roguin, Ariel; Schroeder, Erwin; Philipp, Sebastian; Heitzer, Thomas; Schwacke, Harald; Ayzenberg, Oded; Serra, Antonio; Delarche, Nicolas; Luchner, Andreas; Slagboom, Ton

    2014-01-01

    Novel bare metal stents with improved stent design may become a viable alternative to drug-eluting stents in certain patient groups, particularly, when long-term dual antiplatelet therapy should be avoided. The ENERGY registry aimed to assess the safety and benefits of a cobalt-chromium thin strut bare metal stent with a passive coating in a large series of patients under real-world conditions. This prospective registry recruited 1016 patients with 1074 lesions in 48 centers from April to November 2010. The primary endpoint was the rate of major adverse cardiac events (MACEs), a composite of cardiac death, myocardial infarction and clinically driven target lesion revascularization. More than half of the lesions (61.0%) were type A/B1 lesions, mean lesion length was 14.5±6.5mm and mean reference vessel diameter 3.2±0.5mm. MACE rates at 6, 12 and 24months were 4.9%, 8.1% and 9.4%, target lesion revascularization rates 2.8%, 4.9% and 5.4% and definite stent thrombosis rates 0.5%, 0.6% and 0.6%. Subgroups showed significant differences in baseline and procedural characteristics which did not translate into significantly different clinical outcomes. Specifically, MACE rates at 24months were 13.5% in diabetics, 8.6% in small stents and 9.6% in acute coronary syndrome patients. The population of ENERGY reflects real-world conditions with bare metal stents being mainly used in simple lesions. In this setting, percutaneous coronary intervention using a cobalt-chromium thin strut bare metal stent with a passive coating showed very good results up to 24months. (ClinicalTrials.gov:NCT01056120) SUMMARY FOR ANNOTATED TABLE OF CONTENTS: The ENERGY international registry evaluated the safety and benefits of a cobalt-chromium thin strut bare metal stent with passive coating in 1016 patients under real-world conditions until 2years. Results were encouraging with a low composite rate of cardiac death, myocardial infarction and clinically driven target lesion revascularization, even

  15. 3d-4f Metal-Organic Framework with Dual Luminescent Centers That Efficiently Discriminates the Isomer and Homologues of Small Organic Molecules.

    PubMed

    Zeng, Guang; Xing, Shanghua; Wang, Xiuru; Yang, Yulin; Ma, Dingxuan; Liang, Hongwei; Gao, Lu; Hua, Jia; Li, Guanghua; Shi, Zhan; Feng, Shouhua

    2016-02-01

    A 3d-4f luminescent metal-organic framework (MOF), [Tb2(Cu8I8)(C12H8NO2)6(H2O)4]·5C4H8O2 (4), and three analogues {[La2(Cu8I8)(C12H8NO2)6(C4H8O2)2(H2O)2]·3C4H8O2·2H2O (1), [Ce2(Cu8I8)(C12H8NO2)6(H2O)4]·5C4H8O2 (2), and [Eu2(Cu8I8)(C12H8NO2)6(H2O)4]·5C4H8O2 (3)}, were self-assembled from copper(I) halide clusters and lanthanide metal ions with an organic linker [3-(pyridin-4-yl)benzoic acid] under solvothermal conditions. Compound 4 with high quantum yield (Φ = 68%) exhibits reversible luminescence behavior, accompanying the removal and recovery of guest molecules (1,4-dioxane). Because of the unique porous structure and dual luminescent centers of compound 4, it can efficiently differentiate benzene series with different sizes and provide readouts in corresponding optical signals. Furthermore, it also can unambiguously discriminate the isomers, homologues, and other small molecules with similar structural motifs from one another. The luminescent color of the MOF sensor in different guest solvents has obvious changes that can be clearly distinguished by the naked eye. This multicolor luminescence originates from emissions of the dual luminescent centers, and the emissions have shifted, enhanced, weakened, or quenched to different degrees.

  16. Self-assembly of cobalt-centered metal organic framework and multiwalled carbon nanotubes hybrids as a highly active and corrosion-resistant bifunctional oxygen catalyst

    NASA Astrophysics Data System (ADS)

    Fang, Yiyun; Li, Xinzhe; Li, Feng; Lin, Xiaoqing; Tian, Min; Long, Xuefeng; An, Xingcai; Fu, Yan; Jin, Jun; Ma, Jiantai

    2016-09-01

    Metal organic frameworks (MOF) derived carbonaceous materials have emerged as promising bifunctional oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) catalysts for electrochemical energy conversion and storage. But previous attempts to overcome the poor electrical conductivity of MOFs hybrids involve a harsh high-template pyrolytic process to in situ form carbon, which suffer from extremely complex operation and inevitable carbon corrosion at high positive potentials when OER is operated. Herein, a self-assembly approach is presented to synthesize a non-precious metal-based, high active and strong durable Co-MOF@CNTs bifunctional catalyst for OER and ORR. CNTs not only improve the transportation of the electrons but also can sustain the harsh oxidative environment of OER without carbon corrosion. Meanwhile, the unique 3D hierarchical structure offers a large surface area and stable anchoring sites for active centers and CNTs, which enables the superior durability of hybrid. Moreover, a synergistic catalysis of Co(II), organic ligands and CNTs will enhance the bifunctional electrocatalytic performance. Impressively, the hybrid exhibits comparable OER and ORR catalytic activity to RuO2 and 20 wt% Pt/C catalysts and superior stability. This facile and versatile strategy to fabricating MOF-based hybrids may be extended to other electrode materials for fuel cell and water splitting applications.

  17. Ames Research Center cryogenic mirror testing program - A comparison of the cryogenic performance of metal and glass mirrors with different types of mounts

    NASA Technical Reports Server (NTRS)

    Miller, Jacob H.; Melugin, Ramsey K.; Augason, Gordon C.; Howard, Steven D.; Pryor, G. Mark

    1989-01-01

    A summary of the cryogenic testing of glass and metal mirrors performed at NASA Ames Research Center (ARC) and two other places is presented. Recent improvements to the ARC Cryogenic Optics Test Facility are described. The purposes of the tests were to determine: (1) how glass mirrors would perform at cryogenic temperatures compared with metal mirrors and (2) how various mirror mounts would affect the cryogenic performance of mirrors. Details of a cryogenic test of a 50 cm 'double arch', fused-silica mirror with a three-point mount and with a radially-compliant, flexured mount are given. Within the accuracy of the measurements, it was determined that the flexured mount did not induce appreciable distortion in the double arch mirror. Results of the cryogenic tests of a number of glass mirrors and two beryllium mirrors are included. The cryogenic distortion of the glass mirrors was found to be less than that for the beryllium mirrors. Within the accuracy of the measurements, no hysteresis was found in the glass mirrors. It was possible to measure hysteresis in one of the beryllium mirrors.

  18. Unusual non-bifunctional mechanism for Co-PNP complex catalyzed transfer hydrogenation governed by the electronic configuration of metal center.

    PubMed

    Hou, Cheng; Jiang, Jingxing; Li, Yinwu; Zhang, Zhihan; Zhao, Cunyuan; Ke, Zhuofeng

    2015-10-07

    The mimic of hydrogenases has unleashed a myriad of bifunctional catalysts, which are widely used in the catalytic hydrogenation of polar multiple bonds. With respect to ancillary ligands, the bifunctional mechanism is generally considered to proceed via the metal-ligand cooperation transition state. Inspired by the interesting study conducted by Hanson et al. (Chem Commun., 2013, 49, 10151), we present a computational study of a distinctive example, where a Co(II)-PNP catalyst with an ancillary ligand exhibits efficient transfer hydrogenation through a non-bifunctional mechanism. Both the bifunctional and non-bifunctional mechanisms are discussed. The calculated results, which are based on a full model of the catalyst, suggest that the inner-sphere non-bifunctional mechanism is more favorable (by ∼11 kcal mol(-1)) than the outer-sphere bifunctional mechanism, which is in agreement with the experimental observations. The origin of this mechanistic preference of the Co(II)-PNP catalyst can be attributed to its preference for the square planar geometry. A traditional bifunctional mechanism is less plausible for Co(II)-PNP due to the high distortion energy caused by the change in electronic configuration with the varied ligand field. Considering previous studies that focus on the development of ligands more often, this computational study indicates that the catalytic hydrogenation mechanism is controlled not only by the structure of the ligand but also by the electronic configuration of the metal center.

  19. Mechanistic Insight into the Intramolecular Benzylic C-H Nitrene Insertion Catalyzed by Bimetallic Paddlewheel Complexes: Influence of the Metal Centers.

    PubMed

    Zhang, Xuepeng; Xu, Huiying; Liu, Xueping; Phillips, David Lee; Zhao, Cunyuan

    2016-05-17

    The intramolecular benzylic C-H amination catalyzed by bimetallic paddlewheel complexes was investigated by using density functional theory calculations. The metal-metal bonding characters were investigated and the structures featuring either a small HOMO-LUMO gap or a compact SOMO energy scope were estimated to facilitate an easier one-electron oxidation of the bimetallic center. The hydrogen-abstraction step was found to occur through three manners, that is, hydride transfer, hydrogen migration, and proton transfer. The imido N species are more preferred in the Ru-Ru and Pd-Mn cases whereas coexisting N species, namely, singlet/triplet nitrene and imido, were observed in the Rh-Rh and Pd-Co cases. On the other hand, the triplet nitrene N species were found to be predominant in the Pd-Ni and Pd-Zn systems. A concerted asynchronous mechanism was found to be modestly favorable in the Rh-Rh-catalyzed reactions whereas the Pd-Co-catalyzed reactions demonstrated a slight preference for a stepwise pathway. Favored stepwise pathways were seen in each Ru-Ru- and Pd-Mn-catalyzed reactions and in the triplet nitrene involved Pd-Ni and Pd-Zn reactions. The calculations suggest the feasibility of the Pd-Mn, Pd-Co, and Pd-Ni paddlewheel complexes as being economical alternatives for the expensive dirhodium/diruthenium complexes in C-H amination catalysis. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  20. ATR-FTIR detection of metal-sensitive structural changes in the light-harvesting 1 reaction center complex from the thermophilic purple sulfur bacterium Thermochromatium tepidum.

    PubMed

    Li, Yong; Kimura, Yukihiro; Arikawa, Teruhisa; Wang-Otomo, Zheng-Yu; Ohno, Takashi

    2013-12-17

    Thermochromatium tepidum grows at the highest temperature among purple bacteria, and the light-harvesting 1 reaction center (LH1-RC) complex enhances the thermal stability by utilizing Ca(2+), although the molecular mechanism has yet to be resolved. Here, we applied perfusion-induced attenuated total reflection (ATR) Fourier transform infrared (FTIR) spectroscopy to highly purified LH1-RC complexes from Tch. tepidum and detected for the first time metal-sensitive fine structural changes involved in the enhanced thermal stability of this complex. The Tch. tepidum LH1-RC complex exhibited Sr(2+)/Ca(2+) ATR-FTIR difference bands that reflect changes in the polypeptide backbones and amino acid residues upon the replacement of native Ca(2+) with Sr(2+). The difference bands also appeared in the following Ca(2+)/Sr(2+) difference spectra with almost identical intensities but inverse signs, demonstrating that the structural changes induced by the metal exchange are fully reversible. In contrast, these ATR-FTIR signals were faintly detected in the mesophilic counterpart Allochromatium vinosum . A comparative analysis using LH1 complexes lacking the RCs strongly indicated that the metal-sensitive bands originate from polypeptide backbones and amino acid residues near the putative Ca(2+)-binding site at the C-terminal region of the Tch. tepidum LH1 complexes. Structural changes induced by Sr(2+) and Ba(2+) substitutions were essentially identical. However, Cd(2+) substitution exhibited unique structural modifications, which may be responsible for the severely deteriorated thermal stability of Cd(2+)-substituted complexes. Possible assignments for the present ATR-FTIR signals and their relation with the molecular mechanism of enhancing the thermal stability of Tch. tepidum LH1-RC proteins are discussed on the basis of the recent structural information on the Ca(2+)-binding site.

  1. Friction Stir Welding for Aluminum Metal Matrix Composites (MMC's) (Center Director's Discretionary Fund, Project No. 98-09)

    NASA Technical Reports Server (NTRS)

    Lee, J. A.; Carter, R. W.; Ding, J.

    1999-01-01

    This technical memorandum describes an investigation of using friction stir welding (FSW) process for joining a variety of aluminum metal matrix composites (MMC's) reinforced with discontinuous silicon-carbide (SiC) particulate and functional gradient materials. Preliminary results show that FSW is feasible to weld aluminum MMC to MMC or to aluminum-lithium 2195 if the SiC reinforcement is <25 percent by volume fraction. However, a softening in the heat-affected zone was observed and is known to be one of the major limiting factors for joint strength. The pin tool's material is made from a low-cost steel tool H-13 material, and the pin tool's wear was excessive such that the pin tool length has to be manually adjusted for every 5 ft of weldment. Initially, boron-carbide coating was developed for pin tools, but it did not show a significant improvement in wear resistance. Basically, FSW is applicable mainly for butt joining of flat plates. Therefore, FSW of cylindrical articles such as a flange to a duct with practical diameters ranging from 2-5 in. must be fully demonstrated and compared with other proven MMC joining techniques for cylindrical articles.

  2. Long-Range Orientational Self-Assembly, Spatially Controlled Deprotonation, and Off-Centered Metalation of an Expanded Porphyrin.

    PubMed

    Cirera, Borja; Trukhina, Olga; Björk, Jonas; Bottari, Giovanni; Rodríguez-Fernández, Jonathan; Martin-Jimenez, Alberto; Islyaikin, Mikhail K; Otero, Roberto; Gallego, José M; Miranda, Rodolfo; Torres, Tomás; Ecija, David

    2017-09-27

    Expanded porphyrins are large-cavity macrocycles with enormous potential in coordination chemistry, anion sensing, photodynamic therapy, and optoelectronics. In the last two decades, the surface science community has assessed the physicochemical properties of tetrapyrrolic-like macrocycles. However, to date, the sublimation, self-assembly and atomistic insights of expanded porphyrins on surfaces have remained elusive. Here, we show the self-assembly on Au(111) of an expanded aza-porphyrin, namely, an "expanded hemiporphyrazine", through a unique growth mechanism based on long-range orientational self-assembly. Furthermore, a spatially controlled "writing" protocol on such self-assembled architecture is presented based on the STM tip-induced deprotonation of the inner protons of individual macrocycles. Finally, the capability of these surface-confined macrocycles to host lanthanide elements is assessed, introducing a novel off-centered coordination motif. The presented findings represent a milestone in the fields of porphyrinoid chemistry and surface science, revealing a great potential for novel surface patterning, opening new avenues for molecular level information storage, and boosting the emerging field of surface-confined coordination chemistry involving f-block elements.

  3. Arsenicum-centered Molybdenum Vanadium polyoxometalates bearing transition metal complexes: Hydrothermal syntheses, crystal structures and magnetic properties

    NASA Astrophysics Data System (ADS)

    Li, Fengyan; Xu, Lin; Wei, Yongge; Wang, Xinlong; Wang, Wenju; Wang, Enbo

    2005-10-01

    The tetra-capped Keggin anion-supported Cobalt-Phenanthroline complex [Co 2(phen) 2(OH) 2(H 2O) 4] 0.5[{Co(phen) 2(H 2O)} 2AsMo 6VIMo 2VV 8IVO 44]·2H 2O ( 1) and the bicapped Keggin anion-based Nickel-phenanthroline compound [Ni(phen) 2H 2O] 2[AsMo 11VIMo VO 40(V IVO 2) 0.5].2H 2O( 2), have been hydrothermally synthesized and structurally characterized by elemental analyses, single crystal X-ray diffraction, IR and X-ray photoelectron spectrum. The interesting structural feature of 1 is that there are two types of free complex cation [Co 2(phen) 2(OH) 2(H 2O) 4] 2+ in different orientations in the crystal structure of 1, and these free complex cations coexist in the space between polyoxometalate clusters. The structure of compound 2 is very like compound 1 except that the Keggin unit is bi-capped instead of tetra-capped. Compounds 1 and 2 are examples that Arsenicum-centered vanadomolybdate anion acts as an active building block in the fabrication of polyoxometalates-supported hybrid solids. Then, the magnetic characteristic of 1 is typical of a dominant ferromagnetic interactions in the 6-300 K temperature range and a succedent antiferromagnetic interactions in the very low temperature range (2-6 K), while the magnetic behavior for 2 is characteristic of a dominant ferromagnetic interactions in the 6-300 K temperature range and succedent antiferromagnetic interactions in the very low temperature range (2-6 K).

  4. Structures, Interconversions, and Spectroscopy of Iron Carbonyl Clusters with an Interstitial Carbide: Localized Metal Center Reduction by Overall Cluster Oxidation.

    PubMed

    Kuppuswamy, Subramaniam; Wofford, Joshua D; Joseph, Chris; Xie, Zhu-Lin; Ali, Azim K; Lynch, Vincent M; Lindahl, Paul A; Rose, Michael J

    2017-05-15

    The syntheses, interconversions, and spectroscopic properties of a set of iron carbonyl clusters containing an interstitial carbide are reported. This includes the low temperature X-ray structures of the six-iron clusters (Y)2[Fe6(μ6-C)(μ2-CO)4(CO)12] (1a-c; where Y = NMe4, NEt4, PPh4); the five-iron cluster [Fe5(μ5-C)(CO)15] (3); and the novel formulation of the five-iron cluster (NMe4)2[Fe5(μ5-C)(μ2-CO)(CO)13] (4). Also included in this set is the novel charge-neutral cluster, [Fe6(μ6-C)(CO)18] (2), for which we were unable to obtain a crystallographic structure. As synthetic proof for the identity of 2, we performed a closed loop of interconversions within a family of crystallographically defined species (1, 3, and 4): [Fe6](2-) → [Fe6](0) → [Fe5](0) → [Fe5](2-) → [Fe6](2-). The structural, spectroscopic, and electronic properties of this "missing link" cluster 2 were investigated by IR, Raman, XPS, and Mössbauer spectroscopies-as well as by DFT calculations. A single νCO feature (1965 cm(-1)) in the IR spectrum of 2, as well as a prominent Raman feature (νsymm = 1550 cm(-1)), are consistent with the presence of terminal carbonyls and a {(μ6-C)Fe6} arrangement of iron centers around the central carbide. The XPS of 2 exhibits a higher energy Fe 2p3/2 feature (707.4 eV) as compared to that of 1 (705.5 eV), consistent with the two-electron oxidation induced by treatment of 1 with two equivalents of [Fc](PF6) under CO atmosphere (for the two added CO ligands). DFT calculations indicate two axial and four equatorial Fe sites in 1, all of which have the same or similar oxidation states, for example, two Fe(0) and four Fe(+0.5). These assignments are supported by Mössbauer spectra for 1, which exhibit two closely spaced quadrupole doublets with δ = 0.076 and 0.064 mm s(-1). The high-field Mössbauer spectrum of 2 (4.2 K) exhibits three prominent quadrupole doublets with δ = -0.18, -0.11, and +0.41 mm s(-1). This indicates three pairs of chemically

  5. Alkali metal ion catalysis and inhibition in nucleophilic displacement reactions at phosphorus centers: ethyl and methyl paraoxon and ethyl and methyl parathion.

    PubMed

    Um, Ik-Hwan; Shin, Young-Hee; Lee, Seung-Eun; Yang, Kiyull; Buncel, Erwin

    2008-02-01

    We report on the ethanolysis of the P=O and P=S compounds ethyl and methyl paraoxon (1a and 1b) and ethyl and methyl parathion (2a and 2b). Plots of spectrophotometrically measured rate constants, kobsd versus [MOEt], the alkali ethoxide concentration, show distinct upward and downward curvatures, pointing to the importance of ion-pairing phenomena and a differential reactivity of free ions and ion pairs. Three types of reactivity and selectivity patterns have been discerned: (1) For the P=O compounds 1a and 1b, LiOEt > NaOEt > KOEt > EtO-; (2) for the P=S compound 2a, KOEt > EtO- > NaOEt > LiOEt; (3) for P=S, 2b, 18C6-crown-complexed KOEt > KOEt = EtO(-) > NaOEt > LiOEt. These selectivity patterns are characteristic of both catalysis and inhibition by alkali-metal cations depending on the nature of the electrophilic center, P=O vs P=S, and the metal cation. Ground-state (GS) vs transition-state (TS) stabilization energies shed light on the catalytic and inhibitory tendencies. The unprecedented catalytic behavior of crowned-K(+) for the reaction of 2b is noteworthy. Modeling reveals an extreme steric interaction for the reaction of 2a with crowned-K(+), which is responsible for the absence of catalysis in this system. Overall, P=O exhibits greater reactivity than P=S, increasing from 50- to 60-fold with free EtO(-) and up to 2000-fold with LiOEt, reflecting an intrinsic P=O vs P=S reactivity difference (thio effect). The origin of reactivity and selectivity differences in these systems is discussed on the basis of competing electrostatic effects and solvational requirements as function of anionic electric field strength and cation size (Eisenman's theory).

  6. Metal- and ligand-directed one-pot syntheses, crystal structures, and properties of novel oxo-centered tetra- and hexametallic clusters.

    PubMed

    Saalfrank, Rolf W; Reimann, Uwe; Göritz, Mareike; Hampel, Frank; Scheurer, Andreas; Heinemann, Frank W; Büschel, Michael; Daub, Jörg; Schünemann, Volker; Trautwein, Alfred X

    2002-08-16

    Starting from closely related metal-ligand combinations, completely different oligomeric metal clusters are synthesized. Whereas, picoline-tetrazolylamide HL(1) (1) and zinc or nickel acetate afforded [2x2] grids [M(4)(L(1))(8)] (2), slightly different N-(2-methylthiazole-5-yl)-thiazole-2-carboxamide HL(2) (5 a) and nickel acetate yielded the monometallic complex [Ni(L(2))(2)(OH(2))(2)] (6). In contrast, reaction of 5 a with zinc acetate produced the tetrametallic zinc cluster [Zn(4)O(L(2))(4)(OAc)(2)] (7). Even more surprising, when 3-methyl-substituted HL(3) (5 b) instead of 2-methyl-substituted HL(2) (5 a) was allowed to react under identical conditions with zinc acetate, the cluster [Zn(4)O(L(3))(4)Cl(2)] (8) crystallized from dichloromethane. Clusters 7 and 8 are isostructural. As for 7, in 8 two of the edges of the tetrahedron of zinc ions are doubly bridged, two are singly bridged, and the other two are nonbridged. On the other hand, when iron(II) acetate under aerobic conditions was allowed to react with 5 a, the unprecedented complex [[Fe(3)O(L(2))(2)(OAc)(4)](2)O] (9) was isolated. Cluster 9 is composed of two trimetallic, triangular mu(3)-O(2-)-centered [Fe(3)O(L(2))(2)(OAc)(4)](+) modules, linked by an almost linear mu(2)-O(2-) bridge. The Mössbauer spectrum together with cyclic voltammetric and square-wave voltammetric measurements of 9 are reported, and 6-9 were characterized unequivocally by single-crystal X-ray structure analyses.

  7. EPR investigation of Cu{sup 2+}-substituted photosynthetic bacterial reaction centers : evidence for histidine ligation at the surface metal site.

    SciTech Connect

    Utschig, L. M.; Poluektov, O.; Tiede, D. M.; Thurnauer, M. C.; Chemistry

    2000-01-01

    The coordination environments of two distinct metal sites on the bacterial photosynthetic reaction center (RC) protein were probed with pulsed electron paramagnetic resonance (EPR) spectroscopy. For these studies, Cu{sup 2+} was bound specifically to a surface site on native Fe{sup 2+}-containing RCs from Rhodobacter sphaeroides R-26 and to the native non-heme Fe site in biochemically Fe-removed RCs. The cw and pulsed EPR results clearly indicate two spectroscopically different Cu{sup 2+} environments. In the dark, the RCs with Cu{sup 2+} bound to the surface site exhibit an axially symmetric EPR spectrum with g{sub {parallel}} = 2.24, A{sub {parallel}} = 160 G, g{sub {perpendicular}} = 2.06, whereas the values g{sub {parallel}} = 2.31, A{sub {parallel}} = 143 G, and g{sub {perpendicular}} = 2.07 were observed when Cu{sup 2+} was substituted in the Fe site. Examination of the light-induced spectral changes indicate that the surface Cu{sup 2+} is at least 23 {angstrom} removed from the primary donor (P{sup +}) and reduced quinone acceptor (Q{sub A}{sup -}). Electron spin-echo envelope modulation (ESEEM) spectra of these Cu-RC proteins have been obtained and provide the first direct solution structural information about the ligands in the surface metal site. From these pulsed EPR experiments, modulations were observed that are consistent with multiple weakly hyperfine coupled {sup 14}N nuclei in close proximity to Cu{sup 2+}, indicating that two or more histidines ligate the Cu{sup 2+} at the surface site. Thus, metal and EPR analyses confirm that we have developed reliable methods for stoichiometrically and specifically binding Cu{sup 2+} to a surface site that is distinct from the well characterized Fe site and support the view that Cu{sup 2+} is bound at or near the Zn site that modulates electron transfer between the quinones Q{sub A} and Q{sub B} (Q{sub A}{sup -}Q{sub B} {yields} Q{sub A}Q{sub B}{sup -}) (Utschig, L. M., Ohigashi, Y., Thurnauer, M. C., and Tiede

  8. Rare-earth-metal iodide clusters centered by transition metals: Synthesis, structure, and bonding of R sub 7 I sub 12 M compounds (R = Sc, Y, Pr, Gd; M = Mn, Fe, Co, Ni)

    SciTech Connect

    Hughbanks, T.; Corbett, J.D. )

    1988-06-15

    The compounds R{sub 7}I{sub 12}M (M = Co, Ni for R = Sc; M = Fe, Co for R = Y; M = Mn, Fe, Co for R = Gd; M = Mn, Fe, Co, Ni for R = Pr) have been synthesized by reactions of RI{sub 3}, MI{sub 2}, and R metals at 750-950{degree}C in sealed Nb or Ta containers. These compounds all adopt the Sc(Sc{sub 6}Cl{sub 12}B) structure (space group R{bar 3}, Z = 3) with a transition metal at the cluster center (in place of boron). The seventh isolated R{sup 3+} ion can be substituted by Ca{sup 2+} in several of the Pr and Gd cases. The structural details of Sc{sub 7}I{sub 12}Co, Y{sub 7}I{sub 12}Fe, and (Ca{sub 0.65}Pr{sub 0.35})(Pr{sub 6}I{sub 12}Co) were determined by single-crystal x-ray diffraction methods (a = 14.800, 15.351, 15.777 {angstrom}; c = 10.202, 10.661, 10.925 {angstrom}; R = 3.3, 3.8, 3.4%; R{sub w} = 6.7, 3.3, 3.5%, respectively). The last of these presented twinning difficulties endemic to this structure type, but these were overcome satisfactorily by an approximate separation procedure. R-M distances in the clusters are short; Pr-Co = 2.770, Y-Fe = 2.621, and Sc-Co = 2.431 {angstrom}. While MO theory provides some useful guides to these compounds stability, the true breadth of the chemistry possible remains to be explored. 28 refs., 2 figs., 4 tabs.

  9. Evaluation of the role of the metal-support interfacial centers in the dry reforming of methane on alumina-supported rhodium catalysts

    SciTech Connect

    Ferreira-Aparicio, P.; Fernandez-Garcia, M.; Guerrero-Ruiz, A.; Rodriguez-Ramos, I.

    2000-03-10

    The reforming of CH{sub 4} with CO{sub 2} (dry reforming) has been studied on a series of Al{sub 2}O{sub 3}-supported Rh-Cu catalysts. The reaction has been found to proceed on these systems through a bifunctional mechanism, in which the activation on methane takes place on the rhodium phase while carbon dioxide is activated on the support surface via formate intermediates. The addition of a metal, such as copper, inactive for methane activation, has allowed the authors to evaluate the role of the interfacial Rh-Al{sub 2}O{sub 3} sites in the reaction. The presence of copper reduces the stability of the catalysts, though it does not have any effect on the initial activity per surface exposed site. It indicates that the dry reforming of methane is not a structure-sensitive reaction and that catalytic activity, largely affected by the alumina support, is dependent on the number of surface exposed rhodium centers.

  10. Hydrolysis mechanisms of BNPP mediated by facial copper(II) complexes bearing single alkyl guanidine pendants: cooperation between the metal centers and the guanidine pendants.

    PubMed

    Zhang, Xuepeng; Liu, Xueping; Phillips, David Lee; Zhao, Cunyuan

    2016-01-28

    The hydrolysis mechanisms of DNA dinucleotide analogue BNPP(-) (bis(p-nitrophenyl) phosphate) catalyzed by mononuclear/dinuclear facial copper(ii) complexes bearing single alkyl guanidine pendants were investigated using density functional theory (DFT) calculations. Active catalyst forms have been investigated and four different reaction modes are proposed accordingly. The [Cu2(L(1))2(μ-OH)](3+) (L(1) is 1-(2-guanidinoethyl)-1,4,7-triazacyclononane) complex features a strong μ-hydroxo mediated antiferromagnetic coupling between the bimetallic centers and the corresponding more stable open-shell singlet state. Three different reaction modes involving two catalysts and a substrate were proposed for L(1) entries and the mode 1 in which an inter-complex nucleophilic attack by a metal bound hydroxide was found to be more favorable. In the L(3)-involved reactions (L(3) is 1-(4-guanidinobutyl)-1,4,7-triazacyclononane), the reaction mode in which an in-plane intracomplex scissoring-like nucleophilic attack by a Cu(ii)-bound hydroxide was found to be more competitive. The protonated guanidine pendants in each proposed mechanism were found to play crucial roles in stabilizing the reaction structures via hydrogen bonds and in facilitating the departure of the leaving group via electrostatic attraction. The calculated results are consistent with the experimental observations that the Cu(ii)-L(3) complexes are hydrolytically more favorable than their L(1)-involved counterparts.

  11. Determination of magnetic and structural properties in solids containing antiferromagnetically coupled metal centers using NMR methods. Magneto-structural correlations in anhydrous copper(II) n-butyrate

    SciTech Connect

    Campbell, G.C.; Haw, J.F.

    1988-10-19

    A new approach to the investigation of magneto-structural correlations in solids containing antiferromagnetically coupled transition-metal centers is described that illustrates the potential of NMR spectroscopy in such work. The results of a variable-temperature (VT) /sup 13/C cross-polarization magic-angle-spinning (CP/MAS) NMR investigation of anhydrous copper(II) n-butyrate, (Cu(C/sub 3/H/sub 7/COO)/sub 2/)/sub 2/ are reported. Isotropic shifts are found to be primarily contact in origin, and a statistical analysis of their temperature dependence allows the calculation of singlet-triplet energy level separations (-2J), diamagnetic shifts (delta/sub dia/), and electron-nucleus hyperfine coupling constants (A), which are shown to give insight into the mechanisms of electron delocalization along the superexchange pathway. Signal multiplicity can be related to compound structure, which was determined by using x-ray crystallography. The title compound is triclinic and has a space group of P/anti 1/ with a = 9.035 (2) /angstrom/, b = 5.192 (2) /angstrom/, c = 11.695 (3) /angstrom/, ..cap alpha.. = 85.88 (2)/degrees/, ..gamma.. = 109.32 (2)/degrees/, Z = 1, and V = 515.2 (3) /angstrom//sup 3/; the final weighted R value for 2169 reflections was 0.048. 21 references, 4 figures, 4 tables.

  12. Center on Centers.

    ERIC Educational Resources Information Center

    Utah System Approach to Individualized Learning Project.

    Classroom areas organized into centers for specific study purposes are discussed. These centers are used for individual or small group work. The physical arrangement of the area used for a study center is described, including the organization of furniture, materials, and preferred locations. Suggestions are made for the management and stocking of…

  13. Metals and Ceramics Information Center.

    DTIC Science & Technology

    1981-07-01

    received was $22,315 which included $19,975 from MCIC products and services, plus $2,340 from ManTech Journal subscriptions.] (e) Of these, 13 were on a...Fee X Lear Fan Reno, NV 2019 Mr. F. Schneider X Lewis Eisner & Co. New York, NY 2021 Mr. D. Goslee X Cordis Corp. Miami, FL 2022 Mr. A. Federico X

  14. Can Electron-rich Oxygen (O2-) Withdraw Electrons from Metal Centers? -A DFT Study on Oxoanion-caged Polyoxometalates.

    PubMed

    Takazaki, Aki; Eda, Kazuo; Osakai, Toshiyuki; Nakajima, Takahito

    2017-09-19

    The answer to the question "Can electron-rich oxygen (O2-) withdraw electrons from metal centers?" is seemingly simple, but "how the electron population on the M atom behaves when the O-M distance changes" is a matter of controversy. A case study has been conducted for Keggin-type polyoxometalate (POM) complexes, and the first-principles electronic structure calculations were carried out not only for real POM species but also for "hypothetical" ones whose hetero atom was replaced with a point charge. From the results of natural population analysis, it was proved that even an electron-rich O2-, owing to its larger electronegativity as a neutral atom, withdraws electrons when electron redistribution occurs by the change of the bond length. In the case where O2- coexists with a cation having a large positive charge (e.g., 5+(O2-)4 = [PO4]3-), the gross electron population (GEP) on the M atom seemingly increases as the O atom comes closer, but this increment in GEP is not due to the role of the O atom but due to a coulombic effect of the positive charge located on the cation. Furthermore, it was suggested that not GEP but net electron population (NEP) should be responsible for the redox properties.

  15. Synthesis of, characterization of, and photoinduced processes in polymetallic triad complexes containing Fe(II), Ru(II), and Rh(III) metal centers

    SciTech Connect

    Ronco, S.E. |; Thompson, D.W.; Gahan, S.L.; Petersen, J.D. |

    1998-04-20

    A series of new trimetallic mixed complexes containing Fe(II), Ru(II), and Rh(III) metal centers have been prepared and characterized, and their excited-state properties in a nanosecond time domain have been investigated. These new compounds were synthesized by following a building block strategy from monomeric Rh(III) and Ru(II) polyazines and tetracyanoferrate(II) ions. The products generated in each synthetic step were fully characterized and their excited-state properties investigated. These new trimetallic complexes, [(CN){sub 4}Fe{sup II}(BL(1))Ru{sup II}(bpy)-(BL(2))Rh{sup III}(tpy)(MQ{sup +})](PF{sub 6}){sub 4} (tpy = 2,2{prime}:6{prime}:2{double_prime}-terpyridine; BL(1) = 2,3-bis(2-pyridyl)pyrazine (dpp) or 2,2{prime}-bipyrimidine (bpm); BL(2) = dpp or bpm; MQ{sup +} = N-methyl-4,4{prime}-bipyridinium (monoquat)), consist of three fundamental parts linked by bridging ligands (1) an electron donor group, the tetracyanoferrate(II) unit; (2) an antenna fragment, the Ru(II) polypyridyl moiety; and (3) an electron acceptor group. The electron acceptor group is a Rh(III) polypyridyl that contains the ligands tpy and MQ{sup +}. No emission was observed in any of the reported complexes either in fluid solutions at room temperature or in glassy solutions at 77 K. Time-resolved experiments conducted on these triads showed formation of a transient intermediate within the laser pulse. Redox properties and transient absorption observations helped the authors to identify the nature of this intermediate as an Fe(III)/Ru(II) mixed-valence species that decays exponentially by following a first-order law with a lifetime of {tau} {le} 70 ns in fluid solution at room temperature.

  16. Metal-mediated controllable creation of secondary, tertiary, and quaternary carbon centers: a powerful strategy for the synthesis of iron, cobalt, and copper complexes with in situ generated substituted 1-pyridineimidazo[1,5-a]pyridine ligands.

    PubMed

    Chen, Yanmei; Li, Lei; Chen, Zhou; Liu, Yonglu; Hu, Hailiang; Chen, Wenqian; Liu, Wei; Li, Yahong; Lei, Tao; Cao, Yanyuan; Kang, Zhenghui; Lin, Miaoshui; Li, Wu

    2012-09-17

    An efficient strategy for the synthesis of a wide variety of coordination complexes has been developed. The synthetic protocol involves a solvothermal in situ metal-ligand reaction of picolinaldehyde, ammonium acetate, and transition-metal ions, leading to the generation of 12 coordination complexes supported by a novel class of substituted 1-pyridineimidazo[1,5-a]pyridine ligands (L1-L5). The ligands L1-L5 were afforded by metal-mediated controllable conversion of the aldehyde group of picolialdehyde into a ketone and secondary, tertiary, and quaternary carbon centers, respectively. Complexes of various nuclearities were obtained: from mono-, di-, and tetranuclear to 1D chain polymers. The structures of the in situ formed complexes could be controlled rationally via the choice of appropriate starting materials and tuning of the ratio of the starting materials. The plausible mechanisms for the formation of the ligands L1-L5 were proposed.

  17. Site Preference in Multimetallic Nanoclusters: Incorporation of Alkali Metal Ions or Copper Atoms into the Alkynyl-Protected Body-Centered Cubic Cluster [Au7 Ag8 (C≡C(t) Bu)12 ]().

    PubMed

    Wang, Yu; Su, Haifeng; Ren, Liting; Malola, Sami; Lin, Shuichao; Teo, Boon K; Häkkinen, Hannu; Zheng, Nanfeng

    2016-11-21

    The synthesis, structure, substitution chemistry, and optical properties of the gold-centered cubic monocationic cluster [Au@Ag8 @Au6 (C≡C(t) Bu)12 ](+) are reported. The metal framework of this cluster can be described as a fragment of a body-centered cubic (bcc) lattice with the silver and gold atoms occupying the vertices and the body center of the cube, respectively. The incorporation of alkali metal atoms gave rise to [Mn Ag8-n Au7 (C≡C(t) Bu)12 ](+) clusters (n=1 for M=Na, K, Rb, Cs and n=2 for M=K, Rb), with the alkali metal ion(s) presumably occupying the vertex site(s), whereas the incorporation of copper atoms produced [Cun Ag8 Au7-n (C≡C(t) Bu)12 ](+) clusters (n=1-6), with the Cu atom(s) presumably occupying the capping site(s). The parent cluster exhibited strong emission in the near-IR region (λmax =818 nm) with a quantum yield of 2 % upon excitation at λ=482 nm. Its photoluminescence was quenched upon substitution with a Na(+) ion. DFT calculations confirmed the superatom characteristics of the title compound and the sodium-substituted derivatives.

  18. VVV SURVEY NEAR-INFRARED PHOTOMETRY OF KNOWN BULGE RR LYRAE STARS: THE DISTANCE TO THE GALACTIC CENTER AND ABSENCE OF A BARRED DISTRIBUTION OF THE METAL-POOR POPULATION

    SciTech Connect

    Dékány, I.; Minniti, D.; Catelan, M.; Zoccali, M.; Hempel, M.; Saito, R. K.

    2013-10-20

    We have combined optical and near-infrared data of known RR Lyrae (RRL) stars in the bulge in order to study the spatial distribution of its metal-poor component by measuring precise reddening values and distances of 7663 fundamental-mode RRL stars with high-quality photometry. We obtain a distance to the Galactic center of R {sub 0} = 8.33 ± 0.05 ± 0.14 kpc. We find that the spatial distribution of the RRL stars differs from the structures traced by the predominantly metal-rich red clump (RC) stars. Unlike the RC stars, the RRL stars do not trace a strong bar, but have a more spheroidal, centrally concentrated distribution, showing only a slight elongation in its very center. We find a hint of bimodality in the density distribution at high southern latitudes (b < –5°), which needs to be confirmed by extending the areal coverage of the current census. The different spatial distributions of the metal-rich and metal-poor stellar populations suggest that the Milky Way has a composite bulge.

  19. Conducting polymers containing in-chain metal centers: electropolymerization of oligothienyl-substituted {M(tpy)2} complexes and in situ conductivity studies, M = Os(II), Ru(II).

    PubMed

    Hjelm, Johan; Handel, Robyn W; Hagfeldt, Anders; Constable, Edwin C; Housecroft, Catherine E; Forster, Robert J

    2005-02-21

    The electropolymerization of a series of Ru and Os bis-terpyridine complexes that form rodlike polymers with bithienyl, quaterthienyl, or hexathienyl bridges has been studied. Absorption spectroscopy, scanning electron microscopy, and cyclic voltammetry have been used to characterize the monomers and resulting polymer films. The absolute dc conductivity of the quaterthienyl-bridged {Ru(tpy)2} and {Os(tpy)2} polymers is unusually large and independent of the identity of the metal center at 1.6 x 10(-3) S cm(-1). The maximum conductivity occurs at the formal potential of each redox process, which typically is observed for systems where redox conduction is the dominant charge transport mechanism. Significantly, the dc conductivity of the metal-based redox couple observed in these polymers is 2 orders of magnitude higher thanthat of a comparable nonconjugated system.

  20. Measurement of Heavy Ion Irradiation Induced In-Plane Strain in Patterned Face-Centered-Cubic Metal Films: An in Situ Study

    DOE PAGES

    Yu, K. Y.; Chen, Y.; Li, J.; ...

    2016-11-28

    Nanocrystalline Ag, Cu, and Ni thin films and their coarse grained counterparts are patterned in this paper using focused ion beam and then irradiated by Kr ions within an electron microscope at room temperature. Irradiation induced in-plane strain of the films is measured by tracking the location of nanosized holes. The magnitude of the strain in all specimens is linearly dose-dependent and the strain rates of nanocrystalline metals are significantly greater as compared to that of the coarse grained metals. Finally, real-time microscopic observation suggests that substantial grain boundary migration and grain rotation are responsible for the significant in-plane strain.

  1. Measurement of Heavy Ion Irradiation Induced In-Plane Strain in Patterned Face-Centered-Cubic Metal Films: An in Situ Study

    SciTech Connect

    Yu, K. Y.; Chen, Y.; Li, J.; Liu, Y.; Wang, H.; Kirk, M. A.; Li, M.; Zhang, X.

    2016-11-28

    Nanocrystalline Ag, Cu, and Ni thin films and their coarse grained counterparts are patterned in this paper using focused ion beam and then irradiated by Kr ions within an electron microscope at room temperature. Irradiation induced in-plane strain of the films is measured by tracking the location of nanosized holes. The magnitude of the strain in all specimens is linearly dose-dependent and the strain rates of nanocrystalline metals are significantly greater as compared to that of the coarse grained metals. Finally, real-time microscopic observation suggests that substantial grain boundary migration and grain rotation are responsible for the significant in-plane strain.

  2. Electron Irradiation Induced Phase Transition of an Amorphous Phase and Face-Centered Cubic Solid Solutions in Zr66.7Pd33.3 Metallic Glass

    NASA Astrophysics Data System (ADS)

    Nagase, Takeshi; Hosokawa, Takashi; Umakoshi, Yukichi

    2007-02-01

    Both amorphization and crystallization were observed in Zr66.7Pd33.3 metallic glass under electron irradiation. The melt-spun amorphous phase was not stable under 2.0 MV electron irradiation and two kinds of fcc-solid solution were precipitated through electron irradiation induced crystallization at 103 and 298 K. The fcc-solid solution obtained by electron irradiation induced crystallization at 298 K transformed to an amorphous phase during irradiation at 103 K. Electron irradiation induced phase transformation behavior in Zr66.7Pd33.3 metallic glass can be explained by phase stability of an amorphous phase and crystalline phases against electron irradiation.

  3. Metal-organic framework based upon the synergy of a Brønsted acid framework and Lewis acid centers as a highly efficient heterogeneous catalyst for fixed-bed reactions.

    PubMed

    Li, Baiyan; Leng, Kunyue; Zhang, Yiming; Dynes, James J; Wang, Jian; Hu, Yongfeng; Ma, Dingxuan; Shi, Zhan; Zhu, Liangkui; Zhang, Daliang; Sun, Yinyong; Chrzanowski, Matthew; Ma, Shengqian

    2015-04-01

    We report a strategy of combining a Brønsted acid metal-organic framework (MOF) with Lewis acid centers to afford a Lewis acid@Brønsted acid MOF with high catalytic activity, as exemplified in the context of MIL-101-Cr-SO3H·Al(III). Because of the synergy between the Brønsted acid framework and the Al(III) Lewis acid centers, MIL-101-Cr-SO3H·Al(III) demonstrates excellent catalytic performance in a series of fixed-bed reactions, outperforming two benchmark zeolite catalysts (H-Beta and HMOR). Our work therefore not only provides a new approach to achieve high catalytic activity in MOFs but also paves a way to develop MOFs as a new type of highly efficient heterogeneous catalysts for fixed-bed reactions.

  4. Metal Preferences and Metallation*

    PubMed Central

    Foster, Andrew W.; Osman, Deenah; Robinson, Nigel J.

    2014-01-01

    The metal binding preferences of most metalloproteins do not match their metal requirements. Thus, metallation of an estimated 30% of metalloenzymes is aided by metal delivery systems, with ∼25% acquiring preassembled metal cofactors. The remaining ∼70% are presumed to compete for metals from buffered metal pools. Metallation is further aided by maintaining the relative concentrations of these pools as an inverse function of the stabilities of the respective metal complexes. For example, magnesium enzymes always prefer to bind zinc, and these metals dominate the metalloenzymes without metal delivery systems. Therefore, the buffered concentration of zinc is held at least a million-fold below magnesium inside most cells. PMID:25160626

  5. Incoherent Bi off-centering in Bi{sub 2}Ti{sub 2}O{sub 6}O' and Bi{sub 2}Ru{sub 2}O{sub 6}O' : insulator versus metal.

    SciTech Connect

    Shoemaker, D. P.; Seshadri, R.; Tachibana, M.; Hector, A. L.

    2011-01-01

    In the cubic, stoichiometric oxide compounds Bi{sub 2}Ti{sub 2}O{sub 6}O' (also written as Bi{sub 2}Ti{sub 2}O7) and Bi{sub 2}Ru{sub 2}O{sub 6}O' (also written as Bi{sub 2}Ru{sub 2}O7) Bi{sup 3+} ions on the pyrochlore A site display a propensity to off-center. Unlike Bi{sub 2}Ti{sub 2}O{sub 6}O', Bi{sub 2}Ru{sub 2}O{sub 6}O' is a metal, so it is of interest to ask whether conduction electrons and/or involvement of Bi 6s states at the Fermi energy influence Bi{sup 3+} displacements. The Bi{sup 3+} off-centering in Bi{sub 2}Ti{sub 2}O{sub 6}O' has previously been revealed to be incoherent from detailed reverse Monte Carlo analysis of total neutron scattering. Similar analysis of Bi{sub 2}Ru{sub 2}O{sub 6}O' reveals incoherent off-centering as well, but of smaller magnitude and with distinctly different orientational preference. Analysis of the distributions of metal to oxygen distances presented suggests that Bi in both compounds is entirely Bi{sup 3+}. Disorder in Bi{sub 2}Ti{sub 2}O{sub 6}O' has the effect of stabilizing valence while simultaneously satisfying the steric constraint imposed by the presence of the lone pair of electrons. In Bi{sub 2}Ru{sub 2}O{sub 6}O', off-centering is not required to satisfy valence and seems to be driven by the lone pair. Decreased volume of the lone pair may be a result of partial screening by conduction electrons.

  6. Contamination and risk assessment (based on bioaccessibility via ingestion and inhalation) of metal(loid)s in outdoor and indoor particles from urban centers of Guangzhou, China.

    PubMed

    Huang, Minjuan; Wang, Wei; Chan, Chuen Yu; Cheung, Kwai Chung; Man, Yu Bong; Wang, Xuemei; Wong, Ming Hung

    2014-05-01

    Road dust, household air-conditioning (AC) filter dust and PM2.5 were collected to investigate the contamination of metal(loid)s (Cr, Mn, Ni, Cu, Zn, As, Cd, Sn, Sb, Hg and Pb) in outdoor and indoor urban environments of Guangzhou. Zinc was found to be the most abundant element in road dust and household PM2.5, while the concentration of Pb was the highest in AC filter dust. Enrichment factor (EF) was used to assess the influence of human activity on the contamination of these metal(loid)s. Ingestion and inhalation were the two exposure pathways applied for risk assessment. Physiologically based extraction test (PBET) was used to estimate the oral bioaccessibilities of metal(loid)s in road dust and AC filter dust. Respiratory bioaccessible fraction of metal(loid)s via household PM2.5 was extracted with lung simulating solution. Household AC filter dust was more hazardous to human health than road dust, especially to children. Arsenic was found to be the most risky element based on the risk assessment.

  7. Schottky barrier height reduction for holes by Fermi level depinning using metal/nickel oxide/silicon contacts

    SciTech Connect

    Islam, Raisul Shine, Gautam; Saraswat, Krishna C.

    2014-11-03

    We report the experimental demonstration of Fermi level depinning using nickel oxide (NiO) as the insulator material in metal-insulator-semiconductor (M-I-S) contacts. Using this contact, we show less than 0.1 eV barrier height for holes in platinum/NiO/silicon (Pt/NiO/p-Si) contact. Overall, the pinning factor was improved from 0.08 (metal/Si) to 0.26 (metal/NiO/Si). The experimental results show good agreement with that obtained from theoretical calculation. NiO offers high conduction band offset and low valence band offset with Si. By reducing Schottky barrier height, this contact can be used as a carrier selective contact allowing hole transport but blocking electron transport, which is important for high efficiency in photonic applications such as photovoltaics and optical detectors.

  8. Center Size and Center Performance.

    ERIC Educational Resources Information Center

    Helburn, Suzanne; Morris, John

    1996-01-01

    Examined the impact of child care center size on cost, quality, and profits per child. Examined centers ranging from 40 to 80 children and found total cost and revenue per child were similar for small, medium, and large centers. Found profits per child were highest in large centers and that there was no relationship between center quality and…

  9. Assemblies of a new flexible multicarboxylate ligand and d10 metal centers toward the construction of homochiral helical coordination polymers: structures, luminescence, and NLO-active properties.

    PubMed

    Zang, Shuangquan; Su, Yang; Li, Yizhi; Ni, Zhaoping; Meng, Qingjin

    2006-01-09

    Hydro(solvo)thermal reactions between a new flexible multicarboxylate ligand of 2,2',3,3'-oxydiphthalic acid (2,2',3,3'-H(4)ODPA) and M(NO(3))(2).xH(2)O (M = Zn, x = 6; M = Cd, x = 4) in the presence of 4,4'-bipyridine (bpy) afford two novel homochiral helical coordination polymers [[Zn(2)(2,2',3,3'-ODPA)(bpy)(H(2)O)(3)].(H(2)O)(2) for 1 and [Cd(2)(2,2',3,3'-ODPA)(bpy)(H(2)O)(3)].(H(2)O)(2) for 2]. Though having almost the same chemical formula, they have different space groups (P2(1)2(1)2(1) for 1 and P2(1) for 2) and different bridging modes of the 2,2',3,3'-ODPA ligand. Two kinds of homochiral helices (right-handed) are found in both 1 and 2, each of which discriminates only one kind of crystallographical nonequivalent metal atom. 1 has a 2D metal-organic framework and can be seen as the unity of two parallel homochiral Zn1 and Zn2 helices, in which the nodes are etheric oxygen atoms. In contrast, 2 has a 3D metal-organic framework and consists of two partially overlapped homochiral Cd1 and Cd2 helices in the two dimensions. Moreover, metal-ODPA helices give a 2D chiral herringbone structural motif in both 1 and 2 in the two dimensions, which are further strengthened by the second ligand of bpy. Bulk materials for 1 and 2 all have good second-harmonic generation activity, approximately 1 and 0.8 times that of urea.

  10. Characterization, heavy metal content and health risk assessment of urban road dusts from the historic center of the city of Thessaloniki, Greece.

    PubMed

    Bourliva, Anna; Christophoridis, Christophoros; Papadopoulou, Lambrini; Giouri, Katerina; Papadopoulos, Argyrios; Mitsika, Elena; Fytianos, Konstantinos

    2016-05-30

    In the present study, an investigation of the mineralogy and morphology, the heavy metal content and the health risk of urban road dusts from the second largest city of Greece was conducted. For this reason road dust samples from selected sites within the city core area were collected. No differences were observed in the mineralogy of road dusts coming from different sampling sites, and they were mainly consisted of quartz and calcite, while an elevated amorphous content was detected. Morphologically road dusts presented Ca-rich, Fe-rich and silicates particles with various shapes and sizes. The mean concentrations of Cd, Cr, Cu, Mn, Ni, Pb and Zn in road dust were 1.76, 104.9, 662.3, 336.4, 89.43, 209 and 452.8 μg g(-1), respectively. A series of spatial distribution patterns revealed that the hotspot areas were tended to associate with major road junctions and regions with high traffic. Combination of pollution indexes and statistical analyses (correlation analysis, cluster analysis and principal component analysis) revealed that road dusts have a severe influence by anthropogenic activities. In attempt to identify the source of metals through geostatistical and multivariate statistical analyses, it was concluded as follows: Cr, Cu, Fe and Zn mainly originated from tire/break wear and vehicle abrasions, while Cd, Mn and Pb were mainly related to fuel/oil leakage from automobiles along with oil lubricants and vehicle abrasion. Hazard quotient values for children based on total metal concentrations for the road dust ingestion route were lower than safe level (=1). However, the fact that the Hazard Index value for Pb (0.459) which is a particularly toxic metal, was close to safe level, renders essential further investigation in order to provide more reliable characterizations of potential health risks.

  11. METALS (Minority Education Through Traveling and Learning in the Sciences) and the Value of Collaborative Field-centered Experiences in the Geosciences (Invited)

    NASA Astrophysics Data System (ADS)

    White, L. D.

    2013-12-01

    METALS (Minority Education Through Traveling and Learning in the Sciences) is a field-based, geoscience diversity program developed by a collaborative venture among San Francisco State University, the University of Texas at El Paso, the University of New Orleans, and Purdue University. Since 2010, this program has created meaningful geoscience experiences for underrepresented minorities by engaging 30 high school students in experiential learning opportunities each year. During METALS field trips, the primarily urban students observe natural landforms, measure water quality, conduct beach profiles, and interpret stratigraphic and structural features in locations that have included southern Utah, southern Louisiana, central Wyoming, and northern California. In these geological settings participants are also able to focus on societally relevant, community-related issues. Results from program evaluation suggest that student participants view METALS as: (1) opening up new opportunities for field-based science not normally available to them, (2) engaging in a valuable science-based field experience, (3) an inspirational, but often physically challenging, undertaking that combines high-interest geology content with an exciting outdoor adventure, and (4) a unique social experience that brings together people from various parts of the United States. Further evaluation findings from the four summer trips completed thus far demonstrate that active learning opportunities through direct interaction with the environment is an effective way to engage students in geoscience-related learning. Students also seem to benefit from teaching strategies that include thoughtful reflection, journaling, and teamwork, and mentors are positive about engaging with these approaches. Participants appear motivated to explore geoscience topics further and often discuss having new insights and new perspectives leading to career choices in geosciences. Additionally, students who had a prior and

  12. Asymmetric Desymmetrization via Metal-Free C-F Bond Activation: Synthesis of 3,5-Diaryl-5-fluoromethyloxazolidin-2-ones with Quaternary Carbon Centers.

    PubMed

    Tanaka, Junki; Suzuki, Satoru; Tokunaga, Etsuko; Haufe, Günter; Shibata, Norio

    2016-08-01

    We disclose the first asymmetric activation of a non-activated aliphatic C-F bond in which a conceptually new desymmetrization of 1,3-difluorides by silicon-induced selective C-F bond scission is a key step. The combination of a cinchona alkaloid based chiral ammonium bifluoride catalyst and N,O-bis(trimethylsilyl)acetoamide (BSA) as the silicon reagent enabled the efficient catalytic cycle of asymmetric Csp3 -F bond cleavage under mild conditions with high enantioselectivities. The ortho effect of the aryl group at the prostereogenic center is remarkable. This concept was applied for the asymmetric synthesis of promising agrochemical compounds, 3,5-diaryl-5-fluoromethyloxazolidin-2-ones bearing a quaternary carbon center.

  13. X-ray absorption spectroscopy to analyze nuclear geometry and electronic structure of biological metal centers--potential and questions examined with special focus on the tetra-nuclear manganese complex of oxygenic photosynthesis.

    PubMed

    Dau, Holger; Liebisch, Peter; Haumann, Michael

    2003-07-01

    X-ray absorption spectroscopy (XAS) has become a prominent tool for the element-specific analysis of transition metals at the catalytic center of metalloenzymes. In the present study the information content of X-ray spectra with respect to the nuclear geometry and, in particular, to the electronic structure of the protein-bound metal ions is explored using the manganese complex of photosystem II (PSIII) as a model system. The EXAFS range carries direct information on the number and distances of ligands as well as on the chemical type of the ligand donor function. For first-sphere ligands and second-sphere metals (in multinuclear complexes), the determination of precise distances is mostly straightforward, whereas the determination of coordination numbers clearly requires more effort. The EXAFS section starts with an exemplifying discussion of a PSII spectrum data set with focus on the coordination number problem. Subsequently, the method of linear dichroism EXAFS spectroscopy is introduced and it is shown how the EXAFS data leads to an atomic resolution model for the tetra-manganese complex of PSII. In the XANES section the following aspects are considered: (1) Alternative approaches are evaluated for determination of the metal-oxidation state by comparison with a series of model compounds. (2) The interpretation of XANES spectra in terms of molecular orbitals (MOs) is approached by comparative multiple-scattering calculations and MO calculations. (3) The underlying reasons for the oxidation-state dependence of the XANES spectra are explored. Furthermore, the potential of modern XANES theory is demonstrated by presenting first simulations of the dichroism in the XANES spectra of the PSII manganese complex.

  14. Mimicking the protein access channel to a metal center: effect of a funnel complex on dissociative versus associative copper redox chemistry.

    PubMed

    Le Poul, Nicolas; Douziech, Bénédicte; Zeitouny, Joceline; Thiabaud, Grégory; Colas, Hélène; Conan, Françoise; Cosquer, Nathalie; Jabin, Ivan; Lagrost, Corinne; Hapiot, Philippe; Reinaud, Olivia; Le Mest, Yves

    2009-12-16

    The control of metal-ligand exchange in a confined environment is of primary importance for understanding thermodynamics and kinetics of the electron transfer process governing the reactivity of enzymes. This study reveals an unprecedented change of the Cu(II)/Cu(I) binding and redox properties through a subtle control of the access to the labile site by a protein channel mimic. The cavity effect was estimated from cyclic voltammetry investigations by comparison of two complexes displaying the same coordination sphere (tmpa) and differing by the presence or absence of a calix[6]arene cone surrounding the metal labile site L. Effects on thermodynamics are illustrated by important shifts of E(1/2) toward higher values for the calix complexes. This is ascribable to the protection of the labile site of the open-shell system from the polar medium. Such a cavity control also generates specific stabilizations. This is exemplified by an impressively exalted affinity of the calixarene system for MeCN, and by the detection of a kinetic intermediate, a noncoordinated DMF guest molecule floating inside the cone. Kinetically, a unique dissymmetry between the Cu(I) and Cu(II) ligand exchange capacity is highlighted. At the CV time scale, the guest interconversion is only feasible after reduction of Cu(II) to Cu(I). Such a redox-switch mechanism results from the blocking of the associative process at the Cu(II) state, imposed by the calixarene funnel. All of this suggests that the embedment of a reactive redox metal ion in a funnel-like cavity can play a crucial role in catalysis, particularly for metallo-enzymes associating electron transfer and ligand exchange.

  15. Stent Grafts Provided Superior Primary Patency for Central Venous Stenosis Treatment in Comparison with Angioplasty and Bare Metal Stent: A Retrospective Single Center Study on 70 Hemodialysis Patients.

    PubMed

    Quaretti, Pietro; Galli, Franco; Moramarco, Lorenzo Paolo; Corti, Riccardo; Leati, Giovanni; Fiorina, Ilaria; Tinelli, Carmine; Montagna, Giovanni; Maestri, Marcello

    2016-05-01

    To compare patency in dialysis patients following different endovascular treatment of symptomatic central venous stenosis. A 10-year retrospective evaluation in 70 patients (32 men) dialyzing through vascular access (33, 47%) and tunneled catheters (37, 53%) was made. Three cohorts were compared: angioplasty alone (22), bare metal stent (28), and stent graft (20). Patencies were described with Kaplan-Meier method, and Cox uni- and multivariate models were analyzed to find factors associated. All patients had a favorable anatomical and clinical outcome. Restenosis occurred in 22 (31%) of 70 patients requiring 41 additional interventions; 34 of 70 patients died (median follow-up 19.4 months). Primary patency at 3, 6, 12, and 24 months was 100%, 100%, 100%, and 84% for stent graft versus 90%, 79%, 58%, and 43% for angioplasty (P = .014) versus 84%, 80%, 75%, and 46% for bare-metal stent (P = .062). The overall comparison was more favorable for stent graft (P = .020) when the sites of lesions were matched. Patencies for angioplasty and bare-metal stents were equivalent (P = .141). A lower risk of restenosis (hazard rate [HR] 0.20, confidence interval [CI] 0.06-0.7) and fewer reinterventions (P < .01) were associated with stent graft, whereas age (HR 1.04, CI 1.001-1.08) and cardiovascular disease (HR 2.26, CI 1.06-4.84) influenced the overall survival. No difference in assisted primary patency was found. Stent graft seems to improve primary patency for central venous stenosis and requires fewer reinterventions in a dialysis population with a high prevalence of long-term catheters. © The Author(s) 2016.

  16. Y-Shaped Bilateral Self-Expandable Metallic Stent Placement for Malignant Hilar Biliary Obstruction: Data from a Referral Center for Palliative Care

    PubMed Central

    Di Mitri, R.; Mocciaro, F.

    2014-01-01

    Background and Aim. Malignant hilar strictures are a clinical challenge because of the current therapeutic approach and the poor prognosis. In recent years, self-expandable metallic stents have proven more effective than plastic stents for palliation of malignant hilar strictures, with the bilateral stent-in-stent technique registering a high success rate. We report our experience with Y-shaped endoscopic self-expandable metallic stents placement for treatment of advanced malignant hilar strictures. Methods. From April 2009 to August 2012, we prospectively collected data on patients treated with Y-shaped SEMS placement for advanced malignant hilar carcinoma. Data on technical success, clinical success, and complications were collected. Results. Twenty patients (9 males) were treated (mean age 64.2 ± 15.3 years). The grade of malignant hilar strictures according to the Bismuth classification was II in 5 patients (25%), IIIa in 1 (5%), and IV in 14 (70%). The mean bilirubin level was 14.7 ± 4.9 mg/dL. Technical success was achieved in all patients, with a significant reduction in bilirubin levels (2.9 ± 1.7 mg/dL). One patient experienced cholangitis as early complication, while in 2 patients stent ingrowth was observed. No stents migration was recorded. There was no procedure-related mortality. At the end of the follow-up (7.1 ± 3.1 months), 13 of the 20 patients (65%) had died. Conclusions. Our experience confirms endoscopic bilateral self-expandable metallic stents placement with stent-in-stent technique (Y-shaped configuration) as a feasible, effective, and safe procedure for palliation of unresectable malignant hilar strictures. PMID:24790548

  17. First-principles calculations of the twin boundary energies and adhesion energies of interfaces for cubic face-centered transition-metal nitrides and carbides

    NASA Astrophysics Data System (ADS)

    Li, Tengfei; Liu, Tianmo; Wei, Hongmei; Hussain, Shahid; Wang, Jinxing; Zeng, Wen; Peng, Xianghe; Wang, Zhongchang

    2015-11-01

    The twin boundary energies of TiN, ZrN, HfN, TiC, ZrC, HfC, VC, NbC and TaC and the adhesion energies of twin interfaces and interfaces of TiN/ZrN, VC/TiC and TiN/TiC were calculated using first-principles methods. A new route in the preparation of mechanically superhard films has been proposed by introducing twin into the multilayer of transition-metal nitrides and carbides.

  18. [The application of Y-shaped self-expandable covered metal stents in the thoracostomach-airway fistula: a single center, 11 years experience].

    PubMed

    Fang, Yi; Li, Tengfei; Han, Xinwei; Wu, Gang; Ren, Jianzhuang; Ren, Kewei; Lu, Huibin; Zhang, Quanhui; Li, Zongming

    2015-08-01

    To investigate the clinical feasibility and efficacy of Y-shaped self-expandable covered metal stents (Y-stents) in the management of thoracostomach-airway fistula. Retrospective analysis was performed for 108 patients treated for thoracostomach-airway fistula with Y-shaped self-expandable coated metal stents between April 2003 and October 2014. Y-stents were designed based on the dimensions of trachea and bronchus and sites of the fistula and then were inserted under DSA monitoring. There were 65 cases with single big Y-stent placement, 26 cases with single small Y-stent placement, 23 cases with double Y-stents placement, and 1 case with 3 Y-stents placement. Stent implantation was successfully accomplished with single manipulation in all patients. Complete occlusion of the fistula was obtained in 104 patients after the primary manipulation, and 4 patients required a secondary manipulation where a double Y-stents was inserted because of failure of primary manipulate. Ninety-two patients completed the follow-up , while 16 were lost. Fifty-nine patients died while 33 were alive with marked improvement in their quality of life. The placement of Y-stents can effectively occlude the thoracostomach-airway fistula in patients who had had the esophageal tumors resected. The technique is not only feasible but reliable to improve the quality of life of the patients.

  19. Orange Zinc Germanate with Metallic Ge-Ge Bonds as a Chromophore-Like Center for Visible-Light-Driven Water Splitting.

    PubMed

    Qian, Ling; Chen, Jian Fu; Li, Yu Hang; Wu, Long; Wang, Hai Feng; Chen, Ai Ping; Hu, P; Zheng, Li Rong; Yang, Hua Gui

    2015-09-21

    The efficiency of solar-energy-conversion devices depends on the absorption region and intensity of the photon collectors. Organic chromophores, which have been widely stabilized on inorganic semiconductors for light trapping, are limited by the interface between the chromophore and semiconductor. Herein we report a novel orange zinc germanate (Zn-Ge-O) with a chromophore-like structure, by which the absorption region can be dramatically expanded. Structural characterizations and theoretical calculations together reveal that the origin of visible-light response can be attributed to the unusual metallic Ge-Ge bonds which act in a similar way to organic chromophores. Benefiting from the enhanced light harvest, the orange Zn-Ge-O demonstrates superior capacity for solar-driven hydrogen production.

  20. Introduction of Artificial Pinning Center into PLD-YBCO Coated Conductor on IBAD and Self-Epitaxial CeO2 Buffered Metal Substrate

    SciTech Connect

    Kobayashi, H.; Yamada, Y.; Ishida, S.; Takahashi, K.; Konishi, M.; Ibi, A.; Miyata, S.; Kato, T.; Hirayama, T.; Shiohara, Y.

    2006-03-31

    In order to fabricate YBa2Cu3O7-x (YBCO) coated conductors with high critical current density Jc in magnetic fields, we fabricated YBCO coated conductors with artificial pinning centers by the pulsed laser deposition (PLD) method on a self epitaxial PLD-CeO2 layer and ion-beam assisted deposition (IBAD)-Gd2Zr2O7 (GZO) buffered Hastelloy tape. Artificial pinning centers were introduced by the PLD deposition using the yttria-stabilized zirconia (YSZ) oxide target (nano-dot method) and YBCO target including YSZ particles (mixed target method). In the experiments using YSZ oxide target, YSZ nano-dots were observed. They were approximately 15 nm in height and 10 nm to 70 nm in diameter. We found that the density of nano-dots was controlled by the number of laser pulses. These samples exhibited higher Jc than YBCO films in magnetic fields. Furthermore, a similar improvement of Jc was observed in the experiments using YBCO target including YSZ particles. TEM observation revealed that columnar nano-structure made of BaZrO3 was formed during YBCO deposition and it was effective for pinning. We call this new epitaxial nano-structure 'bamboo structure' from its anisotropic growth and morphology.

  1. Development of new transition metal oxide catalysts for the destruction of PCDD/Fs.

    PubMed

    Yu, Ming-Feng; Li, Wen-Wei; Li, Xiao-Dong; Lin, Xiao-Qing; Chen, Tong; Yan, Jian-Hua

    2016-08-01

    Various transition metal oxide and vanadium-containing multi-metallic oxide catalysts were developed for the destruction of PCDD/Fs (polychlorinated dibenzo-p-dioxins and furans). A stable PCDD/Fs generating system was installed to support the catalytic destruction tests in this study. Nano-titania supported vanadium catalyst (VOx/TiO2) showed the highest activity, followed by CeOx, MnOx, WOx and finally MoOx. Multi-metallic oxide catalysts, prepared by doping WOx, MoOx, MnOx and CeOx into VOx/TiO2 catalysts, showed different activities on the decomposition of PCDD/Fs. The highest destruction efficiency of 92.5% was observed from the destruction test over VOxCeOx/TiO2 catalyst. However, the addition of WOx and MoOx even played a negative role in multi-metallic VOx/TiO2 catalysts. Characterizations of transition metal oxides and multi-metallic VOx/TiO2 catalysts were also investigated with XRD and TPR. After the catalysts were used, the conversion from high valent metals to low valence states was observed by XPS. Copyright © 2016 Elsevier Ltd. All rights reserved.

  2. Macroscopic and bulk-controlled elastic modes in an interaction of interstitial alcali metal cations within a face-centered cubic crystalline fullerine

    SciTech Connect

    Tatarenko, V.A.; Tsysman, C.L.; Oltarzhevskaya, Y.T.

    1994-12-31

    The calculations in a majority of previous works for the fulleride (AqC{sub 60}) crystals were performed within the framework of the rigid-lattice model, neglecting the distoration relaxation of the host fullerene (C{sub 60}) crystal caused by the interstitial alkali-metal (A) cations. However, an each cation is a source of a static distoration field, and the resulting field is a superposition of such fields generated by all cations. This is a reason why the host-crystal distortions depend on the A-cations configurations, i.e. on a type of a spatial bulk distribution of interstitial cations. This paper seeks to find a functional relation between the amplitudes of the doping-induced structure-distortion waves and of statistic concentration ones. A semiphenomenological model is constructed here within the scope of statistical-thermodynamic treatment and using the lattice-statistics simulation method. In this model the effects due to the presence of q solute A cations over available interstices (per unit cell) on the statistic inherent reorientation and/or displacements of the solvent molecules from the average-lattice sites as well as on the lattice parameter a of the elastically-anysotropic cubic C{sub 60} crystal are taken into account.

  3. Macroscopic and bulk-controlled elastic modes in an interaction of interstitial alcali metal cations within a face-centered cubic crystalline fullerine

    NASA Technical Reports Server (NTRS)

    Tatarenko, Valentine A.; Tsysman, Constantin L.; Oltarzhevskaya, Yelena T.

    1995-01-01

    The calculations in a majority of previous works for the fulleride (AqC-60) crystals were performed within the framework of the rigid-lattice model, neglecting the distortion relaxation of the host fullerene (C-60) crystal caused by the interstitial alkali-metal (A) cations. However, an each cation is a source of a static distortion field, and the resulting field is a superposition of such fields generated by all cations. This is a reason why the host-crystal distortions depend on the A-cations configurations, i.e. on a type of a spatial bulk distribution of interstitial cations. The given paper seeks to find a functional relation between the amplitudes of the doping-induced structure-distortion waves and of static concentration ones. A semiphenomenological model is constructed here within the scope of statistical-thermodynamic treatment and using the lattice-statistics simulation method(*). In this model the effects due to the presence of q solute A cations over available interstices (per unit cell) on the static inherent reorientation and/or displacements of the solvent molecules from the 'average-lattice' sites' as well as on the lattice parameter a of a elastically-anysotropic 'cubic' C-60 crystal are taken into account.

  4. Theoretical study of structural and optical properties of noble metal cluster-dipeptide hybrids at defect centers of MgO.

    PubMed

    Kulesza, Alexander; Mitrić, Roland; Bonačić-Koutecký, Vlasta

    2012-07-14

    We present the theoretical investigation of structural and optical properties of silver and gold cluster-dipeptide hybrids bound to the F(S) defect of the MgO (100) surface. We use DFT and its TDDFT variant combined with the polarizable embedded cluster model for the description of the extended MgO environment. As model peptide we have chosen CysTrp since the cysteine residue interacts strongly with metal particles through the sulfur atom and tryptophan is the most important chromophoric amino acid. Our results show that in the case of CysTrp bound to the supported Ag(4) cluster an intense optical signal arises at 400 nm. In contrast, in the case of gold no strongly localized absorption is present since the optical response of supported gold-peptide hybrids is dominated by a large number of low intensity d-electron excitations spread over a broad energy range. Such a localized optical signal which is present in supported silver hybrids can be exploited for the optical detection of peptides and thus can serve as basis for the development of biosensing materials.

  5. Materials Characterization Center state-of-the-art report on corrosion data pertaining to metallic barriers for nuclear-waste repositories

    SciTech Connect

    Merz, M.D.

    1982-10-01

    A compilation of published corrosion data on metals that have been suggested as canisters and overpack materials is presented. The data were categorized according to the solutions used in testing and divided into two parts: high-ionic strength solutions (such as seawater and brine) and low-ionic-strength waters (such as basalt and tuff waters). This distinction was made primarily because of the general difference in aggressiveness of these solutions with respect to general corrosion. A considerable amount of data indicated that titanium alloys have acceptably low uniform corrosion rates in anticipated repository sites; the other possible corrosion failure modes for titanium alloys, such as stress corrosion cracking and delayed failure due to hydrogen, have not been sufficiently studied to make any similar conclusions about lifetime with respect to these particular degradation processes. Other data suggested that iron-base alloys are sufficiently resistant to corrosion in basalt and tuff waters, although the effects of radiation and radiation combined with elevated temperature have not been reported in enough detail to conclusively qualify iron-base alloys for any particular barrier thickness in regard to uniform corrosion rate. The effect of overpack size on corrosion rate has been given little attention. A review of long-term underground data indicated that temperature and accessibility to oxygen were too different for deep geologic repositories to make the underground corrosion data directly applicable. However, the characteristics of corrosion attack, statistical treatment of data, and kinetics of corrosion showed that corrosion proceeds in a systematic and predictable way.

  6. Final Scientific Report: Bacterial Nanowires and Extracellular Electron Transfer to Heavy Metals and Radionuclides by Bacterial Isolates from DOE Field Research Centers

    SciTech Connect

    Nealson, Kenneth

    2016-12-20

    This proposal involved the study of bacteria capable of transferring electrons from the bacterial cells to electron acceptors located outside the cell. These could be either insoluble minerals that were transformed into soluble products upon the addition of electrons, or they could be soluble salts like uranium or chromium, that become insoluble upon the addition of electrons. This process is called extracellular electron transport or EET, and can be done directly by cellular contact, or via conductive appendages called bacterial nanowires. In this work we examined a number of different bacteria for their ability to perform EET, and also looked at their ability to produce conductive nanowires that can be used for EET at a distance away from the EET-capable cells. In the work, new bacteria were isolated, new abilities of EET were examined, and many new methods were developed, and carefully described in the literature. These studies set the stage for future work dealing with the bioremediation of toxic metals like uranium and chromium. They also point out that EET (and conductive nanowires) are far more common that had been appreciated, and may be involved with energy transfer not only in sediments, but in symbioses between different bacteria, and in symbiosis/pathogenesis between bacteria and higher organisms.

  7. Outcomes of Self-Expanding Metal Stents in Malignant Colonic Obstruction are Independent of Location or Length of the Stenosis: Results of a Retrospective, Single-Center Series.

    PubMed

    Schoonbeek, Paul K; Genzel, Pim; van den Berg, Eline H; van Dobbenburgh, O Aart; Ter Borg, Frank

    2017-08-16

    To evaluate the length and location of stenosis in the colon as predictors of technical and clinical outcomes of stent placement in patients presenting with obstructive colorectal cancer. A prospective single-center cohort study of patients treated with a colonic stent for malignant obstruction, regardless of stenosis length or location. Stenosis length was assessed globally on the appropriate CT slice as well as by 3D CT reconstruction. We analyzed whether outcomes were different in patients with a right sided-tumor and/or a stenosis >4 cm long. One hundred forty-one patients were evaluated, 63 with a stenosis >4 cm, 48 with a stenosis proximal to the splenic flexure. Technical failure (n = 9) was mainly caused because of looping or due to the difficulty in engaging the stenosis precluding analysis of the relation between the stenosis length and technical success. Both measurement methods showed good agreement. Clinical outcomes were not associated with stenosis length or location. Clinical outcomes of stenting did not differ between groups regardless of stenosis length or location. Measuring stenosis length more precisely using 3D CT reconstructions is not of help. © 2017 S. Karger AG, Basel.

  8. Endoscopic treatment of large pancreatic fluid collections (PFC) using self-expanding metallic stents (SEMS) – a two-center experience

    PubMed Central

    Chaves, Dalton Marques; Mönkemüller, Klaus; Carneiro, Fred; Medrado, Bruno; dos Santos, Marcos; Wodak, Stephanie; Reimão, Sílvia; Sakai, Paulo; de Moura, Eduardo

    2014-01-01

    Background/study aim: During the last several years, endoscopic ultrasound (EUS)-guided pancreatic fluid collections’ (PFC) drainage has evolved into the preferred drainage technique. Recently, self-expanding metallic stents (SEMS) have been used as an alternative to double pigtail stents, with the advantage of providing a larger diameter fistula, thereby decreasing the risk of early obstruction and also allowing for direct endoscopic exploration of the cavity. The aim of this study was to evaluate the technical and clinical success, safety, and outcome of patients undergoing EUS-guided drainage of complex PFC using SEMS. Patients/materials and methods: The study was conducted at two tertiary hospitals from January 2010 to January 2013. All patients with PFC referred for endoscopic drainage were enrolled in a prospective database. The inclusion criteria were: (1) patients with pseudocysts or walled-off necrosis based on the revised Atlanta classification; (2) symptomatic patients with thick PFC; (3) PFC that persisted more than 6 weeks; and (4) large PFC diameter (≥ 9 cm). The exclusion criteria consisted of coagulation disorders, PFC bleeding or infection, and failure-to-inform written consent. Results: A total of 16 patients (9 females, 7 males; mean age 52.6, range 20 – 82) underwent EUS drainage with SEMS. There were 14 cases of pseudocysts and 2 cases of walled-off necrosis. The etiologies of the PFC were mainly gallstones (8 of 16 patients, 50 %) and alcohol (5 of 16 patients, 31 %). Technical success was achieved in 100 % of the cases. All patients had a complete resolution of the PFC. Conclusion: Transmural EUS-guided drainage of complex PFC using SEMS is feasible, appears safe, and is efficacious. However, the exchange of the UC (uncovered)-SEMS for plastic stents is mandatory within 1 week. Future prospective studies, preferably multicenter studies, comparing SEMS versus traditional plastic stents for the drainage of PFC are

  9. Comparison of patency and cost-effectiveness of self-expandable metal and plastic stents used for malignant biliary strictures: a Polish single-center study.

    PubMed

    Budzyńska, Agnieszka; Nowakowska-Duława, Ewa; Marek, Tomasz; Hartleb, Marek

    2016-10-01

    Most patients with malignant biliary obstruction are suited only for palliation by endoscopic drainage with plastic stents (PS) or self-expandable metal stents (SEMS). To compare the clinical outcome and costs of biliary stenting with SEMS and PS in patients with malignant biliary strictures. A total of 114 patients with malignant jaundice who underwent 376 endoscopic retrograde biliary drainage (ERBD) were studied. ERBD with the placement of PS was performed in 80 patients, with one-step SEMS in 20 patients and two-step SEMS in 14 patients. Significantly fewer ERBD interventions were performed in patients with one-step SEMS than PS or the two-step SEMS technique (2.0±1.12 vs. 3.1±1.7 or 5.7±2.1, respectively, P<0.0001). The median hospitalization duration per procedure was similar for the three groups of patients. The patients' survival time was the longest in the two-step SEMS group in comparison with the one-step SEMS and PS groups (596±270 vs. 276±141 or 208±219 days, P<0.001). Overall median time to recurrent biliary obstruction was 89.3±159 days for PS and 120.6±101 days for SEMS (P=0.01). The total cost of hospitalization with ERBD was higher for two-step SEMS than for one-step SEMS or PS (1448±312, 1152±135 and 977±156&OV0556;, P<0.0001). However, the estimated annual cost of medical care for one-step SEMS was higher than that for the two-step SEMS or PS groups (4618, 4079, and 3995&OV0556;, respectively). Biliary decompression by SEMS is associated with longer patency and reduced number of auxiliary procedures; however, repeated PS insertions still remain the most cost-effective strategy.

  10. Site-isolated luminescent europium complexes with polyester macroligands: metal-centered heteroarm stars and nanoscale assemblies with labile block junctions.

    PubMed

    Bender, Jessica L; Corbin, Perry S; Fraser, Cassandra L; Metcalf, David H; Richardson, Frederick S; Thomas, Edwin L; Urbas, Augustine M

    2002-07-24

    The synthesis of a series of polymeric Eu(III) complexes with polyester ligands, along with supporting emission spectra, luminescence lifetimes, and, for a Eu block copolymer film, atomic force microscopy (AFM) data, is presented. Dibenzoylmethane was derivatized with a hydroxyl initiator site (dbmOH, 1) for tin octoate catalyzed ring opening polymerization of dl-lactide. The resulting poly(lactic acid) macroligand, dbmPLA (2), was combined with EuCl3 to generate Eu(dbmPLA)3 (3). Chelation of both dbmPLA and a polycaprolactone-functionalized bipyridine ligand (bpyPCL2) led to the Eu(III)-centered heteroarm star Eu(dbmPLA)3(bpyPCL2) (4). Unpolarized emission spectra and luminescence lifetimes were recorded for the Eu polymers in CH2Cl2 and for Eu(dbmPLA)3, as a film. Solution data for Eu(dbm)3 and Eu(dbm)3(bpy) were collected for comparison. For Eu tris(dbm) complexes, data were fit to a double exponential decay, indicating the presence of multiple species. Relative amounts of the longer lifetime component increase in the series Eu(dbm)3 solutions to Eu(dbmPLA)3 solutions to Eu(dbmPLA)3 films, perhaps suggesting benefits of the "polymer shell effect" and the diminishment of aquo adducts known to shorten lifetimes. As with the nonpolymeric analogue, data for Eu(dbmPLA)3(bpyPCL2) fit to a single-exponential decay. The sharpness of the feature at 579.7 nm, attributable to the 5D0 --> 7F0 transition in the emission spectrum of 4, lends further support for a homogeneous sample. AFM studies of "as cast" thin films of 4 reveal a lamellar structure with a 17.5 nm repeat. These microstructures, inferred to contain Eu luminophores at the glassy PLA-crystalline PCL domain interfaces, are modified by thermal treatment.

  11. Electron transfer. 93. Further reactions of transition-metal-center oxidants with vitamin B/sub 12s/ (Cob(I)alamin)

    SciTech Connect

    Pillai, G.C.; Ghosh, S.K.; Gould, E.S.

    1988-06-01

    Vitamin B/sub 12s/ (cob(I)alamin) reduces europium(III), titanium(IV) (TiO(C/sub 2/O/sub 4/)/sub 2//sup 2/minus//), and uranium(VI) in aqueous solution. These oxidants undergo one-electron changes, leading in each case to the cobalt product cob(II)alamin (B/sub 12r/). The reduction of Eu/sup 3+/, which is inhibited by TES buffer, but not by glycine, is outer sphere. Its limiting specific rate (1 /times/ 10/sup 2/ M/sup /minus/1/ s/sup /minus/1/), incorporated in the Marcus treatment, yields a B/sub 12s/,B/sub 12r/ self-exchange rate of 10/sup 4.8/plus minus/0.5/ M/sup /minus/1/ s/sup /minus/1/. Reductions of TiO(C/sub 2/O/sub 4/)/sub 2//sup 2/minus// are accelerated by H/sub +/ and by acetic acid. Kinetic patterns suggest three competing reaction paths involving varying degrees of protonation of the Ti(IV) center or its association with acetic acid. The very rapid reduction of U(VI) (k = 4 /times/ 10/sup 6/ M/sup /minus/1/ s/sup /minus/1/) yields U(V) in several buffering media, even when B/sub 12s/ is taken in excess. The much slower conversion of U(V) to U(IV), although thermodynamically favored, appears to be retarded by the extensive reorganization of the coordination sphere of oxo-bound U(V) that must accompany its acceptance of an additional electron. The observed specific rate for the B/sub 12s/-U(VI) reaction is in reasonable agreement, in the framework of the Marcus formalism, with reported values of the formal potential and the self-exchange rate for U(V,VI). 37 references, 4 tables.

  12. Structure of a conserved hypothetical protein SA1388 from S. aureus reveals a capped hexameric toroid with two PII domain lids and a dinuclear metal center

    SciTech Connect

    Saikatendu, Kumar Singh; Zhang, Xuejun; Kinch, Lisa; Leybourne, Matthew; Grishin, Nick V.; Zhang, Hong

    2009-01-26

    The protein encoded by the SA1388 gene from Staphylococcus aureus was chosen for structure determination to elucidate its domain organization and confirm our earlier remote homology based prediction that it housed a nitrogen regulatory PII protein-like domain. SA1388 was predicted to contain a central PII-like domain and two flanking regions, which together belong to the NIF3-like protein family. Proteins like SA1388 remain a poorly studied group and their structural characterization could guide future investigations aimed at understanding their function. The structure of SA1388 has been solved to 2.0{angstrom} resolution by single wavelength anomalous dispersion phasing method using selenium anomalous signals. It reveals a canonical NIF3-like fold containing two domains with a PII-like domain inserted in the middle of the polypeptide. The N and C terminal halves of the NIF3-like domains are involved in dimerization, while the PII domain forms trimeric contacts with symmetry related monomers. Overall, the NIF3-like domains of SA1388 are organized as a hexameric toroid similar to its homologs, E. coli ybgI and the hypothetical protein SP1609 from Streptococcus pneumoniae. The openings on either side of the toroid are partially covered by trimeric 'lids' formed by the PII domains. The junction of the two NIF3 domains has two zinc ions bound at what appears to be a histidine rich active site. A well-defined electron density corresponding to an endogenously bound ligand of unknown identity is observed in close proximity to the metal site. SA1388 is the third member of the NIF3-like family of proteins to be structurally characterized, the other two also being hypothetical proteins of unknown function. The structure of SA1388 confirms our earlier prediction that the inserted domain that separates the two NIF3 domains adopts a PII-like fold and reveals an overall capped toroidal arrangement for the protein hexamer. The six PII-like domains form two trimeric 'lids' that

  13. Skills Center.

    ERIC Educational Resources Information Center

    Canter, Patricia; And Others

    The services of the Living Skills Center for the Visually Handicapped, a habilitative service for blind young adults, are described. It is explained that the Center houses its participants in their own apartments in a large complex and has served over 70 young people in 4 years. The evaluation section describes such assessment instruments as an…

  14. KENNEDY SPACE CENTER, FLA. - Japanese astronaut Koichi Wakata looks at the spars installed on the wing of the orbiter Atlantis. Reinforced Carbon Carbon (RCC) panels are mechanically attached to the wing via the spars - a series of floating joints - to reduce loading on the panels caused by wing deflections. The aluminum and the metallic attachments are protected from exceeding temperature limits by internal insulation.

    NASA Image and Video Library

    2003-09-05

    KENNEDY SPACE CENTER, FLA. - Japanese astronaut Koichi Wakata looks at the spars installed on the wing of the orbiter Atlantis. Reinforced Carbon Carbon (RCC) panels are mechanically attached to the wing via the spars - a series of floating joints - to reduce loading on the panels caused by wing deflections. The aluminum and the metallic attachments are protected from exceeding temperature limits by internal insulation.

  15. Coastal Center

    NASA Astrophysics Data System (ADS)

    The U.S. Geological Survey dedicated its new Center for Coastal Geology June 12 at the University of South Florida in St. Petersburg. Robert Halley leads the staff of nine USGS scientists studying coastal erosion and pollution and underwater mineral resources in cooperation with the university's Marine Science Department. Current research is on erosion along Lake Michigan and the Gulf Coast of Louisiana. The number of USGS scientists at the center should increase to 30 over five years.

  16. Caltech Center for Structural and Amorphous Metals

    DTIC Science & Technology

    2005-05-10

    fracture resistance and subcritical-crack growth behavior in BMG’s and their composites. We have shown that hydrogen significantly increases the glass...Science des Materiaux , 2713], 2002 L. Shadowspeaker, M. B. Shah and R. Busch, "On the crystalline equilibrium phases of the Zr5 7 Nb 5 Cu 15 .4Ni12.6 A lI0...Lowhaphandu, L.A. Ludrosky, and J.J. Lewandowski "Fracture Resistance of Zr-Ti-Ni-Cu-Be Bulk Amorphous Alloy",, TMS-AIME Fall Meeting, Cincinnati, OH

  17. DEFENSE METALS INFORMATION CENTER SELECTED ACCESSIONS

    DTIC Science & Technology

    Surgical trauma, *Kidneys, Pathology, Traumatic shock. H art arr st, *Plasma volume, Respiration.) (*Wounds, Bacteria, Clostridium ... histolyticum .) (*Orthopedics, Stainless steel, Surgery, Arthroplasty.) Contents: The effect of operative trauma upo r l function Factor leading to

  18. Two closely related structure types with unprecedented bioctahedral rare-earth-metal clusters centered by transition metals: A{sub 2}R{sub 10}I{sub 17}Z{sub 2} (A = Rb, Cs; R = La, Ce, Pr; Z = Co, Ni, Ru, Os) and La{sub 10}I{sub 15}Os{sub 2}

    SciTech Connect

    Lulei, M.; Martin, J.D.; Hoistad, L.M.; Corbett, J.D.

    1997-01-22

    A family of compounds has been discovered in which pairs of octahedral rare-earth-metal clusters, each centered by a late transition metal Z, share a common edge. This R{sub 10}Z{sub 2} units, sheathed and interbridged by iodine atoms, occur in the quaternary phases Rb{sub 2}La{sub 10}I{sub 17}Co{sub 2}, Cs{sub 2}La{sub 10}I{sub 17}Z{sub 2} (Z = Co, Ni, Ru, Os), Cs{sub 2}Ce{sub 10}I{sub 17}Os{sub 2}, and Cs{sub 2}Pr{sub 10}I{sub 17}Z{sub 2}(Z = Co, Ru, Os) and in the ternary La{sub 10} I{sub 15}Os{sub 2}. All are obtained as black, air-sensitive crystals from reactions of RI{sub 3}, R, Z, and RbI or CsI as appropriate in welded Nb containers at 800-850{degree}C. The structure of Cs{sub 2} Ce{sub 10}I{sub 17}Os{sub 2} has been refined by single-crystal X-ray diffraction methods for comparison with the isotypic Cs{sub 2}La{sub 10}I{sub 17}Co{sub 2}, and the structure of a unique ternary La{sub 10}I{sub 15}Os{sub 2} has been defined. These new bioctahedral clusters may be regarded as the missing links between discrete clusters and infinite chains of condensed octahedral clusters among rare-earth-metal cluster halides that are stabilized by interstitial transition metals. The biclusters in both structures are extensively interconnected into three-dimensional arrays through bridging iodine atoms. The structural interconversion between Cs{sub 2}La{sub 10}I{sub 17}Os{sub 2} and La{sub 10}I{sub 15}Os{sub 2} + 2CsI may be easily visualized in terms of changes in iodide bridging modes and accommodation of cesium cations. 29 refs., 7 figs., 7 tabs.

  19. Metallated metal-organic frameworks

    DOEpatents

    Bury, Wojciech; Farha, Omar K.; Hupp, Joseph T.; Mondloch, Joseph E.

    2017-08-22

    Porous metal-organic frameworks (MOFs) and metallated porous MOFs are provided. Also provided are methods of metallating porous MOFs using atomic layer deposition and methods of using the metallated MOFs as catalysts and in remediation applications.

  20. Metallated metal-organic frameworks

    DOEpatents

    Bury, Wojciech; Farha, Omar K.; Hupp, Joseph T.; Mondloch, Joseph E.

    2017-02-07

    Porous metal-organic frameworks (MOFs) and metallated porous MOFs are provided. Also provided are methods of metallating porous MOFs using atomic layer deposition and methods of using the metallated MOFs as catalysts and in remediation applications.

  1. Comparative Evaluation of Friction Resistance of Titanium, Stainless Steel, Ceramic and Ceramic with Metal Insert Brackets with Varying Dimensions of Stainless Steel Wire: An In vitro Multi-center Study

    PubMed Central

    Kumar, B Sunil; Miryala, Suresh; Kumar, K Kiran; Shameem, K; Regalla, Ravindra Reddy

    2014-01-01

    Background: The orthodontist seeks an archwire–bracket combination that has both good biocompatibility and low friction. Hence, the aim of this multicenter in vitro study was to evaluate and compare the frictional resistance generated between titanium (Ti), stainless steel (SS), ceramic and ceramic with metal insert (CMI) brackets with SS wires of varying dimensions in a specially designed apparatus. Materials and Methods: The material used in this study were Ti, SS, Ceramic and CMI with 0.018″ slot manufactured with zero degree tip and −7° torque premolar brackets (3M, Unitek) and SS wires of varying dimensions (0.016″ round, 0.016 × 0.016″ square, 0.016 × 0.022″ rectangular and 0.017 × 0.025″ rectangular) used. The frictional resistance was measured using Instron Universal testing machine (Model no. 4301). The specimen population in each center composed each of 160 brackets and wires. Differences among the all bracket/wire combinations were tested using (one-way) ANOVA, followed by the student Newman Keuls multiple comparisons of means ranking (at P < 0.05) for the determination of differences among the groups. Results: Ti bracket in combination with 0.017 × 0.025″ SS rectangular wire produced significant force levels for an optimum orthodontic movement with least frictional resistance. Conclusion: Ti brackets have least resistance and rectangular wires produced significant force. These can be used to avoid hazards of Nickel. SS brackets revealed higher static frictional force values as the wire dimension increased and showed lower static friction than Ti brackets for all wires except the thicker wire. Our study recommends the preclusion of brackets with rough surface texture (Ti brackets) with SS ligature wire for ligating bracket and archwire are better to reduce friction. PMID:25395796

  2. Comparative Evaluation of Friction Resistance of Titanium, Stainless Steel, Ceramic and Ceramic with Metal Insert Brackets with Varying Dimensions of Stainless Steel Wire: An In vitro Multi-center Study.

    PubMed

    Kumar, B Sunil; Miryala, Suresh; Kumar, K Kiran; Shameem, K; Regalla, Ravindra Reddy

    2014-09-01

    The orthodontist seeks an archwire-bracket combination that has both good biocompatibility and low friction. Hence, the aim of this multicenter in vitro study was to evaluate and compare the frictional resistance generated between titanium (Ti), stainless steel (SS), ceramic and ceramic with metal insert (CMI) brackets with SS wires of varying dimensions in a specially designed apparatus. The material used in this study were Ti, SS, Ceramic and CMI with 0.018″ slot manufactured with zero degree tip and -7° torque premolar brackets (3M, Unitek) and SS wires of varying dimensions (0.016″ round, 0.016 × 0.016″ square, 0.016 × 0.022″ rectangular and 0.017 × 0.025″ rectangular) used. The frictional resistance was measured using Instron Universal testing machine (Model no. 4301). The specimen population in each center composed each of 160 brackets and wires. Differences among the all bracket/wire combinations were tested using (one-way) ANOVA, followed by the student Newman Keuls multiple comparisons of means ranking (at P < 0.05) for the determination of differences among the groups. Ti bracket in combination with 0.017 × 0.025″ SS rectangular wire produced significant force levels for an optimum orthodontic movement with least frictional resistance. Ti brackets have least resistance and rectangular wires produced significant force. These can be used to avoid hazards of Nickel. SS brackets revealed higher static frictional force values as the wire dimension increased and showed lower static friction than Ti brackets for all wires except the thicker wire. Our study recommends the preclusion of brackets with rough surface texture (Ti brackets) with SS ligature wire for ligating bracket and archwire are better to reduce friction.

  3. 2.10 Titanium-centered radicals

    NASA Astrophysics Data System (ADS)

    Howard, J. A.

    This document is part of Subvolume A1 `Inorganic Radicals, Metal Complexes and Nonconjugated Carbon Centered Radicals' of Volume 26 `Magnetic Properties of Free Radicals' of Landolt-Börnstein Group II `Molecules and Radicals'.

  4. 1.35 Ruthenium-centered radicals

    NASA Astrophysics Data System (ADS)

    Claridge, R. F. C.

    This document is part of Subvolume A1 `Inorganic Radicals, Metal Complexes and Nonconjugated Carbon Centered Radicals' of Volume 26 `Magnetic Properties of Free Radicals' of Landolt-Börnstein Group II `Molecules and Radicals'.

  5. 2.33 Mercury-centered radicals

    NASA Astrophysics Data System (ADS)

    Howard, J. A.

    This document is part of Subvolume A1 `Inorganic Radicals, Metal Complexes and Nonconjugated Carbon Centered Radicals' of Volume 26 `Magnetic Properties of Free Radicals' of Landolt-Börnstein Group II `Molecules and Radicals'.

  6. 2.32 Gold-centered radicals

    NASA Astrophysics Data System (ADS)

    Howard, J. A.

    This document is part of Subvolume A1 `Inorganic Radicals, Metal Complexes and Nonconjugated Carbon Centered Radicals' of Volume 26 `Magnetic Properties of Free Radicals' of Landolt-Börnstein Group II `Molecules and Radicals'.

  7. 2.8 Potassium-centered radicals

    NASA Astrophysics Data System (ADS)

    Howard, J. A.

    This document is part of Subvolume A1 `Inorganic Radicals, Metal Complexes and Nonconjugated Carbon Centered Radicals' of Volume 26 `Magnetic Properties of Free Radicals' of Landolt-Börnstein Group II `Molecules and Radicals'.

  8. 2.28 Tantalum-centered radicals

    NASA Astrophysics Data System (ADS)

    Howard, J. A.

    This document is part of Subvolume A1 `Inorganic Radicals, Metal Complexes and Nonconjugated Carbon Centered Radicals' of Volume 26 `Magnetic Properties of Free Radicals' of Landolt-Börnstein Group II `Molecules and Radicals'.

  9. 1.42 Iodine-centered radicals

    NASA Astrophysics Data System (ADS)

    Claridge, R. F. C.

    This document is part of Subvolume A1 `Inorganic Radicals, Metal Complexes and Nonconjugated Carbon Centered Radicals' of Volume 26 `Magnetic Properties of Free Radicals' of Landolt-Börnstein Group II `Molecules and Radicals'.

  10. 1.48 Gold-centered radicals

    NASA Astrophysics Data System (ADS)

    Claridge, R. F. C.

    This document is part of Subvolume A1 `Inorganic Radicals, Metal Complexes and Nonconjugated Carbon Centered Radicals' of Volume 26 `Magnetic Properties of Free Radicals' of Landolt-Börnstein Group II `Molecules and Radicals'.

  11. 2.7 Phosphorus-centered radicals

    NASA Astrophysics Data System (ADS)

    Howard, J. A.

    This document is part of Subvolume A1 `Inorganic Radicals, Metal Complexes and Nonconjugated Carbon Centered Radicals' of Volume 26 `Magnetic Properties of Free Radicals' of Landolt-Börnstein Group II `Molecules and Radicals'.

  12. 1.46 Iridium-centered radicals

    NASA Astrophysics Data System (ADS)

    Claridge, R. F. C.

    This document is part of Subvolume A1 `Inorganic Radicals, Metal Complexes and Nonconjugated Carbon Centered Radicals' of Volume 26 `Magnetic Properties of Free Radicals' of Landolt-Börnstein Group II `Molecules and Radicals'.

  13. 2.16 Zinc-centered radicals

    NASA Astrophysics Data System (ADS)

    Howard, J. A.

    This document is part of Subvolume A1 `Inorganic Radicals, Metal Complexes and Nonconjugated Carbon Centered Radicals' of Volume 26 `Magnetic Properties of Free Radicals' of Landolt-Börnstein Group II `Molecules and Radicals'.

  14. 1.38 Cadmium-centered radicals

    NASA Astrophysics Data System (ADS)

    Claridge, R. F. C.

    This document is part of Subvolume A1 `Inorganic Radicals, Metal Complexes and Nonconjugated Carbon Centered Radicals' of Volume 26 `Magnetic Properties of Free Radicals' of Landolt-Börnstein Group II `Molecules and Radicals'.

  15. 2.15 Copper-centered radicals

    NASA Astrophysics Data System (ADS)

    Howard, J. A.

    This document is part of Subvolume A1 `Inorganic Radicals, Metal Complexes and Nonconjugated Carbon Centered Radicals' of Volume 26 `Magnetic Properties of Free Radicals' of Landolt-Börnstein Group II `Molecules and Radicals'.

  16. 2.4 Sodium-centered radicals

    NASA Astrophysics Data System (ADS)

    Howard, J. A.

    This document is part of Subvolume A1 `Inorganic Radicals, Metal Complexes and Nonconjugated Carbon Centered Radicals' of Volume 26 `Magnetic Properties of Free Radicals' of Landolt-Börnstein Group II `Molecules and Radicals'.

  17. 2.17 Gallium-centered radicals

    NASA Astrophysics Data System (ADS)

    Howard, J. A.

    This document is part of Subvolume A1 `Inorganic Radicals, Metal Complexes and Nonconjugated Carbon Centered Radicals' of Volume 26 `Magnetic Properties of Free Radicals' of Landolt-Börnstein Group II `Molecules and Radicals'.

  18. 2.31 Iridium-centered radicals

    NASA Astrophysics Data System (ADS)

    Howard, J. A.

    This document is part of Subvolume A1 `Inorganic Radicals, Metal Complexes and Nonconjugated Carbon Centered Radicals' of Volume 26 `Magnetic Properties of Free Radicals' of Landolt-Börnstein Group II `Molecules and Radicals'.

  19. 2.21 Niobium-centered radicals

    NASA Astrophysics Data System (ADS)

    Howard, J. A.

    This document is part of Subvolume A1 `Inorganic Radicals, Metal Complexes and Nonconjugated Carbon Centered Radicals' of Volume 26 `Magnetic Properties of Free Radicals' of Landolt-Börnstein Group II `Molecules and Radicals'.

  20. 1.36 Palladium-centered radicals

    NASA Astrophysics Data System (ADS)

    Claridge, R. F. C.

    This document is part of Subvolume A1 `Inorganic Radicals, Metal Complexes and Nonconjugated Carbon Centered Radicals' of Volume 26 `Magnetic Properties of Free Radicals' of Landolt-Börnstein Group II `Molecules and Radicals'.

  1. 2.3 Boron-centered radicals

    NASA Astrophysics Data System (ADS)

    Howard, J. A.

    This document is part of Subvolume A1 `Inorganic Radicals, Metal Complexes and Nonconjugated Carbon Centered Radicals' of Volume 26 `Magnetic Properties of Free Radicals' of Landolt-Börnstein Group II `Molecules and Radicals'.

  2. 1.37 Silver-centered radicals

    NASA Astrophysics Data System (ADS)

    Claridge, R. F. C.

    This document is part of Subvolume A1 `Inorganic Radicals, Metal Complexes and Nonconjugated Carbon Centered Radicals' of Volume 26 `Magnetic Properties of Free Radicals' of Landolt-Börnstein Group II `Molecules and Radicals'.

  3. 2.24 Silver-centered radicals

    NASA Astrophysics Data System (ADS)

    Howard, J. A.

    This document is part of Subvolume A1 `Inorganic Radicals, Metal Complexes and Nonconjugated Carbon Centered Radicals' of Volume 26 `Magnetic Properties of Free Radicals' of Landolt-Börnstein Group II `Molecules and Radicals'.

  4. 2.18 Rubidium-centered radicals

    NASA Astrophysics Data System (ADS)

    Howard, J. A.

    This document is part of Subvolume A1 `Inorganic Radicals, Metal Complexes and Nonconjugated Carbon Centered Radicals' of Volume 26 `Magnetic Properties of Free Radicals' of Landolt-Börnstein Group II `Molecules and Radicals'.

  5. 2.20 Zirconium-centered radicals

    NASA Astrophysics Data System (ADS)

    Howard, J. A.

    This document is part of Subvolume A1 `Inorganic Radicals, Metal Complexes and Nonconjugated Carbon Centered Radicals' of Volume 26 `Magnetic Properties of Free Radicals' of Landolt-Börnstein Group II `Molecules and Radicals'.

  6. 1.40 Tin-centered radicals

    NASA Astrophysics Data System (ADS)

    Claridge, R. F. C.

    This document is part of Subvolume A1 `Inorganic Radicals, Metal Complexes and Nonconjugated Carbon Centered Radicals' of Volume 26 `Magnetic Properties of Free Radicals' of Landolt-Börnstein Group II `Molecules and Radicals'.

  7. 1.41 Tellurium-centered radicals

    NASA Astrophysics Data System (ADS)

    Claridge, R. F. C.

    This document is part of Subvolume A1 `Inorganic Radicals, Metal Complexes and Nonconjugated Carbon Centered Radicals' of Volume 26 `Magnetic Properties of Free Radicals' of Landolt-Börnstein Group II `Molecules and Radicals'.

  8. 2.2 Lithium-centered radicals

    NASA Astrophysics Data System (ADS)

    Howard, J. A.

    This document is part of Subvolume A1 `Inorganic Radicals, Metal Complexes and Nonconjugated Carbon Centered Radicals' of Volume 26 `Magnetic Properties of Free Radicals' of Landolt-Börnstein Group II `Molecules and Radicals'.

  9. 2.5 Aluminum-centered radicals

    NASA Astrophysics Data System (ADS)

    Howard, J. A.

    This document is part of Subvolume A1 `Inorganic Radicals, Metal Complexes and Nonconjugated Carbon Centered Radicals' of Volume 26 `Magnetic Properties of Free Radicals' of Landolt-Börnstein Group II `Molecules and Radicals'.

  10. 2.22 Molybdenum-centered radicals

    NASA Astrophysics Data System (ADS)

    Howard, J. A.

    This document is part of Subvolume A1 `Inorganic Radicals, Metal Complexes and Nonconjugated Carbon Centered Radicals' of Volume 26 `Magnetic Properties of Free Radicals' of Landolt-Börnstein Group II `Molecules and Radicals'.

  11. 2.12 Chromium-centered radicals

    NASA Astrophysics Data System (ADS)

    Howard, J. A.

    This document is part of Subvolume A1 `Inorganic Radicals, Metal Complexes and Nonconjugated Carbon Centered Radicals' of Volume 26 `Magnetic Properties of Free Radicals' of Landolt-Börnstein Group II `Molecules and Radicals'.

  12. 2.14 Cobalt-centered radicals

    NASA Astrophysics Data System (ADS)

    Howard, J. A.

    This document is part of Subvolume A1 `Inorganic Radicals, Metal Complexes and Nonconjugated Carbon Centered Radicals' of Volume 26 `Magnetic Properties of Free Radicals' of Landolt-Börnstein Group II `Molecules and Radicals'.

  13. 2.9 Scandium-centered radicals

    NASA Astrophysics Data System (ADS)

    Howard, J. A.

    This document is part of Subvolume A1 `Inorganic Radicals, Metal Complexes and Nonconjugated Carbon Centered Radicals' of Volume 26 `Magnetic Properties of Free Radicals' of Landolt-Börnstein Group II `Molecules and Radicals'.

  14. 2.6 Silicon-centered radicals

    NASA Astrophysics Data System (ADS)

    Howard, J. A.

    This document is part of Subvolume A1 `Inorganic Radicals, Metal Complexes and Nonconjugated Carbon Centered Radicals' of Volume 26 `Magnetic Properties of Free Radicals' of Landolt-Börnstein Group II `Molecules and Radicals'.

  15. 2.19 Yttrium-centered radicals

    NASA Astrophysics Data System (ADS)

    Howard, J. A.

    This document is part of Subvolume A1 `Inorganic Radicals, Metal Complexes and Nonconjugated Carbon Centered Radicals' of Volume 26 `Magnetic Properties of Free Radicals' of Landolt-Börnstein Group II `Molecules and Radicals'.

  16. 2.27 Lanthanum-centered radicals

    NASA Astrophysics Data System (ADS)

    Howard, J. A.

    This document is part of Subvolume A1 `Inorganic Radicals, Metal Complexes and Nonconjugated Carbon Centered Radicals' of Volume 26 `Magnetic Properties of Free Radicals' of Landolt-Börnstein Group II `Molecules and Radicals'.

  17. 2.23 Rhodium-centered radicals

    NASA Astrophysics Data System (ADS)

    Howard, J. A.

    This document is part of Subvolume A1 `Inorganic Radicals, Metal Complexes and Nonconjugated Carbon Centered Radicals' of Volume 26 `Magnetic Properties of Free Radicals' of Landolt-Börnstein Group II `Molecules and Radicals'.

  18. 2.13 Manganese-centered radicals

    NASA Astrophysics Data System (ADS)

    Howard, J. A.

    This document is part of Subvolume A1 `Inorganic Radicals, Metal Complexes and Nonconjugated Carbon Centered Radicals' of Volume 26 `Magnetic Properties of Free Radicals' of Landolt-Börnstein Group II `Molecules and Radicals'.

  19. 1.34 Molybdenum-centered radicals

    NASA Astrophysics Data System (ADS)

    Claridge, R. F. C.

    This document is part of Subvolume A1 `Inorganic Radicals, Metal Complexes and Nonconjugated Carbon Centered Radicals' of Volume 26 `Magnetic Properties of Free Radicals' of Landolt-Börnstein Group II `Molecules and Radicals'.

  20. 1.43 Lanthanum-centered radicals

    NASA Astrophysics Data System (ADS)

    Claridge, R. F. C.

    This document is part of Subvolume A1 `Inorganic Radicals, Metal Complexes and Nonconjugated Carbon Centered Radicals' of Volume 26 `Magnetic Properties of Free Radicals' of Landolt-Börnstein Group II `Molecules and Radicals'.

  1. 2.30 Osmium-centered radicals

    NASA Astrophysics Data System (ADS)

    Howard, J. A.

    This document is part of Subvolume A1 `Inorganic Radicals, Metal Complexes and Nonconjugated Carbon Centered Radicals' of Volume 26 `Magnetic Properties of Free Radicals' of Landolt-Börnstein Group II `Molecules and Radicals'.

  2. 2.29 Tungsten-centered radicals

    NASA Astrophysics Data System (ADS)

    Howard, J. A.

    This document is part of Subvolume A1 `Inorganic Radicals, Metal Complexes and Nonconjugated Carbon Centered Radicals' of Volume 26 `Magnetic Properties of Free Radicals' of Landolt-Börnstein Group II `Molecules and Radicals'.

  3. 1.47 Platinum-centered radicals

    NASA Astrophysics Data System (ADS)

    Claridge, R. F. C.

    This document is part of Subvolume A1 `Inorganic Radicals, Metal Complexes and Nonconjugated Carbon Centered Radicals' of Volume 26 `Magnetic Properties of Free Radicals' of Landolt-Börnstein Group II `Molecules and Radicals'.

  4. 2.26 Cesium-centered radicals

    NASA Astrophysics Data System (ADS)

    Howard, J. A.

    This document is part of Subvolume A1 `Inorganic Radicals, Metal Complexes and Nonconjugated Carbon Centered Radicals' of Volume 26 `Magnetic Properties of Free Radicals' of Landolt-Börnstein Group II `Molecules and Radicals'.

  5. 1.45 Osmium-centered radicals

    NASA Astrophysics Data System (ADS)

    Claridge, R. F. C.

    This document is part of Subvolume A1 `Inorganic Radicals, Metal Complexes and Nonconjugated Carbon Centered Radicals' of Volume 26 `Magnetic Properties of Free Radicals' of Landolt-Börnstein Group II `Molecules and Radicals'.

  6. 1.44 Tantalum-centered radicals

    NASA Astrophysics Data System (ADS)

    Claridge, R. F. C.

    This document is part of Subvolume A1 `Inorganic Radicals, Metal Complexes and Nonconjugated Carbon Centered Radicals' of Volume 26 `Magnetic Properties of Free Radicals' of Landolt-Börnstein Group II `Molecules and Radicals'.

  7. 2.11 Vanadium-centered radicals

    NASA Astrophysics Data System (ADS)

    Howard, J. A.

    This document is part of Subvolume A1 `Inorganic Radicals, Metal Complexes and Nonconjugated Carbon Centered Radicals' of Volume 26 `Magnetic Properties of Free Radicals' of Landolt-Börnstein Group II `Molecules and Radicals'.

  8. 2.25 Cadmium-centered radicals

    NASA Astrophysics Data System (ADS)

    Howard, J. A.

    This document is part of Subvolume A1 `Inorganic Radicals, Metal Complexes and Nonconjugated Carbon Centered Radicals' of Volume 26 `Magnetic Properties of Free Radicals' of Landolt-Börnstein Group II `Molecules and Radicals'.

  9. 1.49 Mercury-centered radicals

    NASA Astrophysics Data System (ADS)

    Claridge, R. F. C.

    This document is part of Subvolume A1 `Inorganic Radicals, Metal Complexes and Nonconjugated Carbon Centered Radicals' of Volume 26 `Magnetic Properties of Free Radicals' of Landolt-Börnstein Group II `Molecules and Radicals'.

  10. 1.39 Indium-centered radicals

    NASA Astrophysics Data System (ADS)

    Claridge, R. F. C.

    This document is part of Subvolume A1 `Inorganic Radicals, Metal Complexes and Nonconjugated Carbon Centered Radicals' of Volume 26 `Magnetic Properties of Free Radicals' of Landolt-Börnstein Group II `Molecules and Radicals'.

  11. The materials processing research base of the Materials Processing Center

    NASA Technical Reports Server (NTRS)

    Flemings, M. C.; Bowen, H. K.; Kenney, G. B.

    1980-01-01

    The goals and activities of the center are discussed. The center activities encompass all engineering materials including metals, ceramics, polymers, electronic materials, composites, superconductors, and thin films. Processes include crystallization, solidification, nucleation, and polymer synthesis.

  12. Physics in a Many-Centered Environment

    NASA Astrophysics Data System (ADS)

    Chubb, Talbot A.

    2007-03-01

    Physics in a many-center environment was born as the electron physics of metals. Electrons moving from the electrolyte of a battery to anode metal become quasi-particles with a many-centers geometry. The Ion Band State Theory of cold fusion assumes that a fraction of the deuterons in PdDx reconfigure to a many-centers geometry. Many-center geometry seems to apply to deuteron populations in nano-metal crystals as studied by Arata and Zhang, to Bloch-sensitive nuclei created in Iwamura's permeation studies, to the metastable nuclei forming alpha shower flakes as discovered by Oriani and Fisher and reproducibly produced by P. Mosier-Boss. T.A. Chubb, Infinite Energy, Issue 70, in press (2006) T.A. Chubb, ``Many-Centers Nuclei,'' submitted to Infinite Energy T.A. Chubb and S.R. Chubb, Fusion Technol.,20, 93 (1991).

  13. Low valency in lanthanides: A theoretical study of NdF and LuF

    SciTech Connect

    Schoendorff, George; Wilson, Angela K.

    2014-06-14

    The ground and low-lying excited state potential energy curves of neodymium monofluoride were calculated using multireference (CASSCF) and single reference (EOM-CR-CCSD(T)) methods. Optimized bond lengths were obtained and accurate bond dissociation energies were computed. The EOM-CR-CCSD(T) method was used to determine the bond dissociation energy of lutetium monofluoride, and it is shown that core correlation is required to produce bond dissociation energies in agreement with experiment.

  14. Glycosylated asterisks are among the most potent low valency inducers of Concanavalin A aggregation.

    PubMed

    Sleiman, Mazen; Varrot, Annabelle; Raimundo, Jean-Manuel; Gingras, Marc; Goekjian, Peter G

    2008-12-28

    A new class of sulfurated, semi-rigid, radial and low-valent glycosylated asterisk ligands with potential dual function as ligand and probe has some of the highest inhibition potencies of Con A-induced hemagglutination, by using a cross-linking mechanism of Con A which amplifies the enhancement to near nanomolar concentrations with the alpha-d-mannose asterisk.

  15. Metals Sector

    EPA Pesticide Factsheets

    Find environmental regulatory information about the metals sector (NAICS 331 & 332), including NESHAPs for metal coatings, effluent guidelines for metal products, combustion compliance assistance, and information about foundry sand recycling.

  16. Stereodivergent-at-Metal Synthesis of [60]Fullerene Hybrids.

    PubMed

    Marco-Martínez, Juan; Vidal, Sara; Fernández, Israel; Filippone, Salvatore; Martín, Nazario

    2017-02-13

    Chiral fullerene-metal hybrids with complete control over the four stereogenic centers, including the absolute configuration of the metal atom, have been synthesized for the first time. The stereochemistry of the four chiral centers formed during [60]fullerene functionalization is the result of both the chiral catalysts employed and the diastereoselective addition of the metal complexes used (iridium, rhodium, or ruthenium). DFT calculations underpin the observed configurational stability at the metal center, which does not undergo an epimerization process.

  17. Metal aminoboranes

    DOEpatents

    Burrell, Anthony K.; Davis, Benjamin J.; Thorn, David L.; Gordon, John C.; Baker, R. Thomas; Semelsberger, Troy Allen; Tumas, William; Diyabalanage, Himashinie Vichalya Kaviraj; Shrestha, Roshan P.

    2010-05-11

    Metal aminoboranes of the formula M(NH.sub.2BH.sub.3).sub.n have been synthesized. Metal aminoboranes are hydrogen storage materials. Metal aminoboranes are also precursors for synthesizing other metal aminoboranes. Metal aminoboranes can be dehydrogenated to form hydrogen and a reaction product. The reaction product can react with hydrogen to form a hydrogen storage material. Metal aminoboranes can be included in a kit.

  18. The Metal-Rich Universe

    NASA Astrophysics Data System (ADS)

    Israelian, Garik; Meynet, Georges

    2012-10-01

    Preface; Part I. Abundances in the Galaxy: Field Stars: 1. Metal-rich stars and stellar populations: A brief history and new results; 2. The metal-rich nature of stars with planets; 3. Solar chemical peculiarities; 4. Kinematics of metal-rich stars with and without planets; 5. Elemental abundance trends in the metal-rich thin and thick disks; 6. Metal-rich massive stars - how metal-rich are they?; 7. Hercules stream stars and the metal-rich thick disk; 8. Abundance survey of the galactic thick disk; Part II. Abundances in the Galaxy: Galactic Stars in Clusters, Bulges and Centre: 9. Galactic open clusters with super solar metallicities; 10. Old and very metal-rich open clusters in the BOCCE project; 11. Massive stars vs. nebular abundances in the Orion nebula; 12. Abundance surveys of metal-rich bulge stars; 13. Metal abundances in the galactic center; 14. Light elements in the galactic bulge; 15. Metallicity and ages of selected G-K giants; Part III. Observations - Abundances in Extragalactic Contexts: 16. Stellar abundances of early-type galaxies and galactic spheroids: Evidence for metal-rich stars; 17. Measuring chemical abundances in extragalactic metal-rich HII regions; 18. On the maximum oxygen abundance in metal-rich spiral galaxies; 19. Starbursts and their contribution to metal enrichment; 20. High metallicities at high redshifts; 21. Evolution of dust and elemental abundances in quasar DLAs and GRB afterglows as a function of cosmic time; 22. Dust, metals and diffuse interstellar bands in damped Lyman Alpha systems; 23. Tracing metallicities in the Universe with the James Webb Space Telescope; Part IV. Stellar Populations and Mass Functions: 24. The stellar initial mass function of metal-rich populations; 25. IMF effects on the metallicity and colour evolution of disk galaxies; 26. The metallicity of circumnuclear star forming regions; 27. The stellar population of bulges; 28. The metallicity distribution of the stars in elliptical galaxies; 29. Wolf

  19. Concurrent engineering research center

    NASA Technical Reports Server (NTRS)

    Callahan, John R.

    1995-01-01

    The projects undertaken by The Concurrent Engineering Research Center (CERC) at West Virginia University are reported and summarized. CERC's participation in the Department of Defense's Defense Advanced Research Project relating to technology needed to improve the product development process is described, particularly in the area of advanced weapon systems. The efforts committed to improving collaboration among the diverse and distributed health care providers are reported, along with the research activities for NASA in Independent Software Verification and Validation. CERC also takes part in the electronic respirator certification initiated by The National Institute for Occupational Safety and Health, as well as in the efforts to find a solution to the problem of producing environment-friendly end-products for product developers worldwide. The 3M Fiber Metal Matrix Composite Model Factory Program is discussed. CERC technologies, facilities,and personnel-related issues are described, along with its library and technical services and recent publications.

  20. Remote Operations Control Center (ROCC)

    NASA Technical Reports Server (NTRS)

    1997-01-01

    Students at Rensselaer Polytechnic Institute (RPI) in Troy, NY, monitor the progress of the Isothermal Dendritic Growth Experiment (IDGE) during the U.S. Microgravity Payload-4 (USMP-4) mission (STS-87, Nov. 19 - Dec. 5, 1997). Remote Operation Control Center (ROCC) like this one will become more common during operations with International Space Station. IDGE, flown on three Space Shuttle missions, is yielding new insights into virtually all industrially relevant metal and alloy forming operations. Photo credit: Renssenlaer Polythnic Institute (RPI)

  1. Bond-Energy and Surface-Energy Calculations in Metals

    ERIC Educational Resources Information Center

    Eberhart, James G.; Horner, Steve

    2010-01-01

    A simple technique appropriate for introductory materials science courses is outlined for the calculation of bond energies in metals from lattice energies. The approach is applied to body-centered cubic (bcc), face-centered cubic (fcc), and hexagonal-closest-packed (hcp) metals. The strength of these bonds is tabulated for a variety metals and is…

  2. Bond-Energy and Surface-Energy Calculations in Metals

    ERIC Educational Resources Information Center

    Eberhart, James G.; Horner, Steve

    2010-01-01

    A simple technique appropriate for introductory materials science courses is outlined for the calculation of bond energies in metals from lattice energies. The approach is applied to body-centered cubic (bcc), face-centered cubic (fcc), and hexagonal-closest-packed (hcp) metals. The strength of these bonds is tabulated for a variety metals and is…

  3. Polyamorphism in metalic glass.

    SciTech Connect

    Sheng, H. W.; Liu, H. Z.; Cheng, Y. Q.; Wen, J.; Lee, P.L.; Luo, W.K.; Shastri, S.D.; Ma, E.; X-Ray Science Division; Johns Hopkins Univ.; Chinese Academy of Sciences

    2007-03-01

    A metal, or an alloy, can often exist in more than one crystal structure. The face-centered-cubic and body-centered-cubic forms of iron (or steel) are a familiar example of such polymorphism. When metallic materials are made in the amorphous form, is a parallel 'polyamorphism' possible? So far, polyamorphic phase transitions in the glassy state have been observed only in glasses involving directional and open (such as tetrahedral) coordination environments. Here, we report an in situ X-ray diffraction observation of a pressure-induced transition between two distinct amorphous polymorphs in a Ce{sub 55}Al{sub 45} metallic glass. The large density difference observed between the two polyamorphs is attributed to their different electronic and atomic structures, in particular the bond shortening revealed by ab initio modeling of the effects of f-electron delocalization. This discovery offers a new perspective of the amorphous state of metals, and has implications for understanding the structure, evolution and properties of metallic glasses and related liquids. Our work also opens a new avenue towards technologically useful amorphous alloys that are compositionally identical but with different thermodynamic, functional and rheological properties due to different bonding and structural characteristics.

  4. Metal inks

    DOEpatents

    Ginley, David S; Curtis, Calvin J; Miedaner, Alex; van Hest, Marinus Franciscus Antonius Maria; Kaydanova, Tatiana

    2014-02-04

    Self-reducing metal inks and systems and methods for producing and using the same are disclosed. In an exemplary embodiment, a method may comprise selecting metal-organic (MO) precursor, selecting a reducing agent, and dissolving the MO precursor and the reducing agent in an organic solvent to produce a metal ink that remains in a liquid phase at room temperature. Metal inks, including self-reducing and fire-through metal inks, are also disclosed, as are various applications of the metal inks.

  5. Casimir Repulsion between Metallic Objects in Vacuum

    SciTech Connect

    Levin, Michael; McCauley, Alexander P.; Rodriguez, Alejandro W.; Reid, M. T. Homer; Johnson, Steven G.

    2010-08-27

    We give an example of a geometry in which two metallic objects in vacuum experience a repulsive Casimir force. The geometry consists of an elongated metal particle centered above a metal plate with a hole. We prove that this geometry has a repulsive regime using a symmetry argument and confirm it with numerical calculations for both perfect and realistic metals. The system does not support stable levitation, as the particle is unstable to displacements away from the symmetry axis.

  6. Mississippi Technology Transfer Center

    NASA Technical Reports Server (NTRS)

    1987-01-01

    The Mississippi Technology Transfer Center at the John C. Stennis Space Center in Hancock County, Miss., was officially dedicated in 1987. The center is home to several state agencies as well as the Center For Higher Learning.

  7. Center Director's Update

    NASA Image and Video Library

    2016-03-01

    In the Space Shuttle Atlantis exhibit facility at the Kennedy Space Center's Visitor Complex, center director Bob Cabana, in the center background, speaks to guests as he updates community leaders on current and future activities at the space center.

  8. Complex [Cd(dafo) 2(tphpo)(CH 3COO)]ClO 4 (dafo=4,5-diazafluoren-9-one, tphpo=triphenylphosphine oxide) with chiral metal centers. Helical packing induced by π-π stacking interactions of dafo rings

    NASA Astrophysics Data System (ADS)

    Wu, B.-L.; Zhang, H.-Y.; Wu, Q.-A.; Hou, H.-W.; Zh, Y.

    2003-08-01

    The first complex of 4,5-diazafluoren-9-one (dafo) and cadmium: [Cd(dafo) 2(tphpo)(CH 3COO)]ClO 4 (triphenylphosphine oxide=tphpo) is a quaternary complex with chiral metal centers and crystallizes in a monoclinic cell with space group P2(1)/ n. Cadmium centers with 7-fold coordination adopt a distorted monocapped trigonal prismatic geometry. Two oxygen atoms of acetate and one oxygen atom of triphenylphosphine oxide form the top triangle of the trigonal prism, while three nitrogen atoms from two dafo groups construct the bigger bottom triangle. The last nitrogen atom of dafo groups occupies the monocapped position. Here, dafo molecules display two different coordination patterns, namely unsymmetric and symmetric chelation. Moreover, the interesting linking of screw related cations is fabricated by inter-molecular π-π stacking interactions in the complex.

  9. Metallization failures

    NASA Technical Reports Server (NTRS)

    Beatty, R.

    1971-01-01

    Metallization-related failure mechanisms were shown to be a major cause of integrated circuit failures under accelerated stress conditions, as well as in actual use under field operation. The integrated circuit industry is aware of the problem and is attempting to solve it in one of two ways: (1) better understanding of the aluminum system, which is the most widely used metallization material for silicon integrated circuits both as a single level and multilevel metallization, or (2) evaluating alternative metal systems. Aluminum metallization offers many advantages, but also has limitations particularly at elevated temperatures and high current densities. As an alternative, multilayer systems of the general form, silicon device-metal-inorganic insulator-metal, are being considered to produce large scale integrated arrays. The merits and restrictions of metallization systems in current usage and systems under development are defined.

  10. METAL PHTHALOCYANINES

    DOEpatents

    Frigerio, N.A.

    1962-03-27

    A process is given for preparing heavy metal phthalocyanines, sulfonated or not. The process comprises mixing an inorganic metal salt with dimethyl formamide or methyl sulfoxide; separating the metal complex formed from the solution; mixing the complex with an equimolar amount of sodium, potassium, lithium, magnesium, or beryllium sulfonated or unsulfonated phthalocyanine whereby heavy-metal phthalocyanine crystals are formed; and separating the crystals from the solution. Uranyl, thorium, lead, hafnium, and lanthanide rare earth phthalocyanines can be produced by the process. (AEC)

  11. Silicone metalization

    SciTech Connect

    Maghribi, Mariam N.; Krulevitch, Peter; Hamilton, Julie

    2008-12-09

    A system for providing metal features on silicone comprising providing a silicone layer on a matrix and providing a metal layer on the silicone layer. An electronic apparatus can be produced by the system. The electronic apparatus comprises a silicone body and metal features on the silicone body that provide an electronic device.

  12. Silicone metalization

    SciTech Connect

    Maghribi, Mariam N.; Krulevitch, Peter; Hamilton, Julie

    2006-12-05

    A system for providing metal features on silicone comprising providing a silicone layer on a matrix and providing a metal layer on the silicone layer. An electronic apparatus can be produced by the system. The electronic apparatus comprises a silicone body and metal features on the silicone body that provide an electronic device.

  13. Silicone metalization

    DOEpatents

    Maghribi, Mariam N.; Krulevitch, Peter; Hamilton, Julie

    2008-12-09

    A system for providing metal features on silicone comprising providing a silicone layer on a matrix and providing a metal layer on the silicone layer. An electronic apparatus can be produced by the system. The electronic apparatus comprises a silicone body and metal features on the silicone body that provide an electronic device.

  14. AFRD WAREHOUSE, SOUTH SIDE. FACING NORTH. METAL AWNING ALONG LENGTH ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    AFRD WAREHOUSE, SOUTH SIDE. FACING NORTH. METAL AWNING ALONG LENGTH OF BUILDING AND VERTICAL METAL SIDING ARE ALTERATIONS MAD BY THE AFRD. - Minidoka Relocation Center Warehouse, 111 South Fir Street, Shoshone, Lincoln County, ID

  15. Metal Halide Optical Glasses.

    DTIC Science & Technology

    1988-01-01

    HEAVY METAL FLUORIDE GLASSES C. T. Moynihan, R. Mossadegh and S. N. Crichton Materials Engineering Department, Rensselaer Polytechnic Institute Troy...and Tesar, A. A., J. Am. Ceram. Soc., 67, p. C-164 (1984). 11. Crichton , S. N., Mossadegh, R., Schroeder, J., and Moynihan, C. T., unpublished data. 12...FLUORIDE GLASSES C. T. Moynihan, S. M. Opalka, R. Mossadegh, S. N. Crichton and A. J. Bruce Center for Glass Science and Technology Materials Engineering

  16. Photoelectron and extended-Hueckel study of the double-metal-layered zirconium monochloride, the related zirconium and scandium chloride carbides M/sub 2/Cl/sub 2/C, and their relationship to carbon-centered clusters

    SciTech Connect

    Ziebarth, R.P.; Hwu, S.J.; Corbett, J.D.

    1986-05-14

    The bonding in the double-metal-layered ZrCl(AbcA), the hypothetical reordered ZrCl(AbaB), and the product of insertion of carbon into the latter to give M/sub 2/Cl/sub 2/C (Ab(c)aB), M = Zr, Sc, have been examined by photoelectron spectroscopy (UPS, XPS) and by extended-Hueckel band calculations. The compounds characteristically exhibit well-resolved chlorine 3p and carbon 2p (when present) valence bands and a zirconium conduction band, with the substantial metal-nonmetal covalency in the first two bands. A significant amount of M-M bonding is contained within the carbon-binding states. The calculated density-of-states curves are in good agreement with UPS data for all three compounds in both energy and band shape, with the zirconium phases being metallic by both criteria. Bonding correlations between the known Zr/sub 6/Cl/sub 12/C-type clusters and Zr/sub 2/Cl/sub 2/C condensation product of these are examined. The energies of the chlorine, carbon, and metal MO's (bands) in the two limits show a close correspondence in both experiment and theory. The orbital description of the relatively localized bonding of carbon within the Zr/sub 6/C cluster unit is also preserved on condensation. On the other hand, substantial delocalization leads to marked dispersion of the Zr-Zr bonding HOMO and LUMO cluster orbitals within the conduction band. Theoretical predictions of unknown derivatives of the title phases are also considered.

  17. Binding to Redox-Inactive Alkali and Alkaline Earth Metal Ions Strongly Deactivates the C-H Bonds of Tertiary Amides toward Hydrogen Atom Transfer to Reactive Oxygen Centered Radicals.

    PubMed

    Salamone, Michela; Carboni, Giulia; Mangiacapra, Livia; Bietti, Massimo

    2015-09-18

    The effect of alkali and alkaline earth metal ions on the reactions of the cumyloxyl radical (CumO(•)) with N,N-dimethylformamide (DMF) and N,N-dimethylacetamide (DMA) was studied by laser flash photolysis. In acetonitrile, a >2 order of magnitude decrease in the rate constant for hydrogen atom transfer (HAT) from the C-H bonds of these substrates (kH) was measured after addition of Li(+). This behavior was explained in terms of a strong interaction between Li(+) and the oxygen atom of both DMF and DMA that increases the extent of positive charge on the amide, leading to C-H bond deactivation toward HAT to the electrophilic radical CumO(•). Similar effects were observed after addition of Ca(2+), which was shown to strongly bind up to four equivalents of the amide substrates. With Mg(2+), weak C-H deactivation was observed for the first two substrate equivalents followed by stronger deactivation for two additional equivalents. No C-H deactivation was observed in DMSO after addition of Li(+) and Mg(2+). These results point toward the important role played by metal ion Lewis acidity and solvent Lewis basicity, indicating that C-H deactivation can be modulated by varying the nature of the metal cation and solvent and allowing for careful control over the HAT reactivity of amide substrates.

  18. Webinar Presentation: The MATCH Study (Metals Assessment Targeting Community Health)

    EPA Pesticide Factsheets

    This presentation, The MATCH Study (Metals Assessment Targeting Community Health), was given at the NIEHS/EPA Children's Centers 2015 Webinar Series: Historical Perspectives and Research Updates from Previously Funded Children's Centers held on 11/18/15.

  19. Design of dinuclear manganese cofactors for bacterial reaction centers.

    PubMed

    Olson, Tien L; Espiritu, Eduardo; Edwardraja, Selvakumar; Simmons, Chad R; Williams, JoAnn C; Ghirlanda, Giovanna; Allen, James P

    2016-05-01

    A compelling target for the design of electron transfer proteins with novel cofactors is to create a model for the oxygen-evolving complex, a Mn4Ca cluster, of photosystem II. A mononuclear Mn cofactor can be added to the bacterial reaction center, but the addition of multiple metal centers is constrained by the native protein architecture. Alternatively, metal centers can be incorporated into artificial proteins. Designs for the addition of dinuclear metal centers to four-helix bundles resulted in three artificial proteins with ligands for one, two, or three dinuclear metal centers able to bind Mn. The three-dimensional structure determined by X-ray crystallography of one of the Mn-proteins confirmed the design features and revealed details concerning coordination of the Mn center. Electron transfer between these artificial Mn-proteins and bacterial reaction centers was investigated using optical spectroscopy. After formation of a light-induced, charge-separated state, the experiments showed that the Mn-proteins can donate an electron to the oxidized bacteriochlorophyll dimer of modified reaction centers, with the Mn-proteins having additional metal centers being more effective at this electron transfer reaction. Modeling of the structure of the Mn-protein docked to the reaction center showed that the artificial protein likely binds on the periplasmic surface similarly to cytochrome c2, the natural secondary donor. Combining reaction centers with exogenous artificial proteins provides the opportunity to create ligands and investigate the influence of inhomogeneous protein environments on multinuclear redox-active metal centers. This article is part of a Special Issue entitled Biodesign for Bioenergetics--the design and engineering of electronic transfer cofactors, proteins and protein networks, edited by Ronald L. Koder and J.L. Ross Anderson.

  20. The Watergate Learning Center

    ERIC Educational Resources Information Center

    Training in Business and Industry, 1971

    1971-01-01

    The Watergate Learning Center, recently opened by Sterling Learning Center in Washington, D. C., blueprints the plan established by Sterling and Marriott Hotels for a national chain of learning centers with much the same facilities. (EB)

  1. The Watergate Learning Center

    ERIC Educational Resources Information Center

    Training in Business and Industry, 1971

    1971-01-01

    The Watergate Learning Center, recently opened by Sterling Learning Center in Washington, D. C., blueprints the plan established by Sterling and Marriott Hotels for a national chain of learning centers with much the same facilities. (EB)

  2. Children's cancer centers

    MedlinePlus

    Pediatric cancer center; Pediatric oncology center; Comprehensive cancer center ... Treating childhood cancer is not the same as treating adult cancer. The cancers are different. So are the treatments and the ...

  3. Alkali Metal Handling Practices at NASA MSFC

    NASA Technical Reports Server (NTRS)

    Salvail, Patrick G.; Carter, Robert R.

    2002-01-01

    NASA Marshall Space Flight Center (MSFC) is NASA s principle propulsion development center. Research and development is coordinated and carried out on not only the existing transportation systems, but also those that may be flown in the near future. Heat pipe cooled fast fission cores are among several concepts being considered for the Nuclear Systems Initiative. Marshall Space Flight Center has developed a capability to handle high-purity alkali metals for use in heat pipes or liquid metal heat transfer loops. This capability is a low budget prototype of an alkali metal handling system that would allow the production of flight qualified heat pipe modules or alkali metal loops. The processing approach used to introduce pure alkali metal into heat pipe modules and other test articles are described in this paper.

  4. Alkali Metal Handling Practices at NASA MSFC

    NASA Astrophysics Data System (ADS)

    Salvail, Patrick G.; Carter, Robert R.

    2003-01-01

    NASA Marshall Space Flight Center (MSFC) is NASA's principle propulsion development center. Research and development is coordinated and carried out on not only the existing transportation systems, but also those that may be flown in the near future. Heat pipe cooled fast fission cores are among several concepts being considered for the Nuclear Systems Initiative. Marshall Space Flight Center has developed a capability to handle high-purity alkali metals for use in heat pipes or liquid metal heat transfer loops. This capability is a low budget prototype of an alkali metal handling system that would allow the production of flight qualified heat pipe modules or alkali metal loops. The processing approach used to introduce pure alkali metal into heat pipe modules and other test articles are described in this paper.

  5. Remote Operations Control Center (ROCC)

    NASA Technical Reports Server (NTRS)

    1997-01-01

    Undergraduate students Kristina Wines and Dena Renzo at Rensselaer Poloytech Institute (RPI) in Troy, NY, monitor the progress of the Isothermal Dendritic Growth Experiment (IDGE) during the U.S. Microgravity Payload-4 (USMP-4) mission (STS-87), Nov. 19 - Dec.5, 1997). Remote Operations Control Center (ROCC) like this one will become more common during operations with the International Space Station. The Isothermal Dendritic Growth Experiment (IDGE), flown on three Space Shuttle missions, is yielding new insights into virtually all industrially relevant metal and alloy forming operations. Photo credit: Rensselaer Polytechnic Institute (RPI)

  6. Remote Operations Control Center (ROCC)

    NASA Technical Reports Server (NTRS)

    1997-01-01

    Matthew Koss (forground) and Martin Glicksman (rear), principal investigator and lead scientist (respectively), review plans for the next step in the Isothermal Dendritic Growth Experiment (IDGE) during the U.S. Microgravity Payload-4 (USMP-4) mission (STS-87, Nov. 19 - Dec. 5, 1997). Remote Operations Control Center (ROCC) like this one, at Rensselaer Polytechnic Institute (RPI) in Troy, NY, will become more common during operations with the International Space Station. IDGE, flown on three Space Shuttle missions, is yielding new insights into virtually all industrially relavent metal and alloy forming operations. Photo credit: Rensselaer Polytechnic Institute (RPI)

  7. 18. View west from the center of the structure noting ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    18. View west from the center of the structure noting Sections 1 and 2 of the Metal Bent portions of the structure. - Augustine Bridge, Brandywine River,Augustine Cutoff, Wilmington, New Castle County, DE

  8. 17. View west from the center of the structure noting ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    17. View west from the center of the structure noting detail of structural work in Section 1 of the Metal Bent portions of the structure. - Augustine Bridge, Brandywine River,Augustine Cutoff, Wilmington, New Castle County, DE

  9. KENNEDY SPACE CENTER, FLA. - Japanese astronaut Koichi Wakata gestures as he examines the spar installation (behind him) on the wing of the orbiter Atlantis. Reinforced Carbon Carbon (RCC) panels are mechanically attached to the wing via the spars - a series of floating joints - to reduce loading on the panels caused by wing deflections. The aluminum and the metallic attachments are protected from exceeding temperature limits by internal insulation.

    NASA Image and Video Library

    2003-09-05

    KENNEDY SPACE CENTER, FLA. - Japanese astronaut Koichi Wakata gestures as he examines the spar installation (behind him) on the wing of the orbiter Atlantis. Reinforced Carbon Carbon (RCC) panels are mechanically attached to the wing via the spars - a series of floating joints - to reduce loading on the panels caused by wing deflections. The aluminum and the metallic attachments are protected from exceeding temperature limits by internal insulation.

  10. KENNEDY SPACE CENTER, FLA. - Japanese astronaut Koichi Wakata (front) listens to William Gaetjens, with the Vehicle Integration Test Team (VITT), who is providing details about the spar installation (left) on the wing of the orbiter Atlantis. Reinforced Carbon Carbon (RCC) panels are mechanically attached to the wing via the spars - a series of floating joints - to reduce loading on the panels caused by wing deflections. The aluminum and the metallic attachments are protected from exceeding temperature limits by internal insulation.

    NASA Image and Video Library

    2003-09-05

    KENNEDY SPACE CENTER, FLA. - Japanese astronaut Koichi Wakata (front) listens to William Gaetjens, with the Vehicle Integration Test Team (VITT), who is providing details about the spar installation (left) on the wing of the orbiter Atlantis. Reinforced Carbon Carbon (RCC) panels are mechanically attached to the wing via the spars - a series of floating joints - to reduce loading on the panels caused by wing deflections. The aluminum and the metallic attachments are protected from exceeding temperature limits by internal insulation.

  11. KENNEDY SPACE CENTER, FLA. - In the Orbiter Processing Facility, Mike Hyatt, with United Space Alliance, installs a spar on the wing of the orbiter Atlantis. Reinforced Carbon Carbon (RCC) panels are mechanically attached to the wing with a series of floating joints - spars - to reduce loading on the panels caused by wing deflections. The aluminum and the metallic attachments are protected from exceeding temperature limits by internal insulation.

    NASA Image and Video Library

    2003-09-04

    KENNEDY SPACE CENTER, FLA. - In the Orbiter Processing Facility, Mike Hyatt, with United Space Alliance, installs a spar on the wing of the orbiter Atlantis. Reinforced Carbon Carbon (RCC) panels are mechanically attached to the wing with a series of floating joints - spars - to reduce loading on the panels caused by wing deflections. The aluminum and the metallic attachments are protected from exceeding temperature limits by internal insulation.

  12. KENNEDY SPACE CENTER, FLA. - In the Orbiter Processing Facility, John Newport, with United Space Alliance, inspects the wing of the orbiter Atlantis before installing a spar. Reinforced Carbon Carbon (RCC) panels are mechanically attached to the wing with a series of floating joints - spars - to reduce loading on the panels caused by wing deflections. The aluminum and the metallic attachments are protected from exceeding temperature limits by internal insulation.

    NASA Image and Video Library

    2003-09-04

    KENNEDY SPACE CENTER, FLA. - In the Orbiter Processing Facility, John Newport, with United Space Alliance, inspects the wing of the orbiter Atlantis before installing a spar. Reinforced Carbon Carbon (RCC) panels are mechanically attached to the wing with a series of floating joints - spars - to reduce loading on the panels caused by wing deflections. The aluminum and the metallic attachments are protected from exceeding temperature limits by internal insulation.

  13. KENNEDY SPACE CENTER, FLA. - In the Orbiter Processing Facility, John Newport, with United Space Alliance, inspects spar installation on the wing of the orbiter Atlantis. Reinforced Carbon Carbon (RCC) panels are mechanically attached to the wing with a series of floating joints - spars - to reduce loading on the panels caused by wing deflections. The aluminum and the metallic attachments are protected from exceeding temperature limits by internal insulation.

    NASA Image and Video Library

    2003-09-04

    KENNEDY SPACE CENTER, FLA. - In the Orbiter Processing Facility, John Newport, with United Space Alliance, inspects spar installation on the wing of the orbiter Atlantis. Reinforced Carbon Carbon (RCC) panels are mechanically attached to the wing with a series of floating joints - spars - to reduce loading on the panels caused by wing deflections. The aluminum and the metallic attachments are protected from exceeding temperature limits by internal insulation.

  14. KENNEDY SPACE CENTER, FLA. - In the Orbiter Processing Facility, Mike Hyatt (above) and Saul Ngy (below), with United Space Alliance, install a spar on the wing of the orbiter Atlantis. Reinforced Carbon Carbon (RCC) panels are mechanically attached to the wing with a series of floating joints - spars - to reduce loading on the panels caused by wing deflections. The aluminum and the metallic attachments are protected from exceeding temperature limits by internal insulation.

    NASA Image and Video Library

    2003-09-04

    KENNEDY SPACE CENTER, FLA. - In the Orbiter Processing Facility, Mike Hyatt (above) and Saul Ngy (below), with United Space Alliance, install a spar on the wing of the orbiter Atlantis. Reinforced Carbon Carbon (RCC) panels are mechanically attached to the wing with a series of floating joints - spars - to reduce loading on the panels caused by wing deflections. The aluminum and the metallic attachments are protected from exceeding temperature limits by internal insulation.

  15. KENNEDY SPACE CENTER, FLA. - In the Orbiter Processing Facility, John Newport, with United Space Alliance, inspects a piece of equipment for spar installation on the wing of the orbiter Atlantis. Reinforced Carbon Carbon (RCC) panels are mechanically attached to the wing with a series of floating joints - spars - to reduce loading on the panels caused by wing deflections. The aluminum and the metallic attachments are protected from exceeding temperature limits by internal insulation.

    NASA Image and Video Library

    2003-09-04

    KENNEDY SPACE CENTER, FLA. - In the Orbiter Processing Facility, John Newport, with United Space Alliance, inspects a piece of equipment for spar installation on the wing of the orbiter Atlantis. Reinforced Carbon Carbon (RCC) panels are mechanically attached to the wing with a series of floating joints - spars - to reduce loading on the panels caused by wing deflections. The aluminum and the metallic attachments are protected from exceeding temperature limits by internal insulation.

  16. KENNEDY SPACE CENTER, FLA. - Japanese astronaut Koichi Wakata (right) listens to William Gaetjens, with the Vehicle Integration Test Team (VITT), who is providing details about the spar installation (left) on the wing of the orbiter Atlantis. Reinforced Carbon Carbon (RCC) panels are mechanically attached to the wing via the spars - a series of floating joints - to reduce loading on the panels caused by wing deflections. The aluminum and the metallic attachments are protected from exceeding temperature limits by internal insulation.

    NASA Image and Video Library

    2003-09-05

    KENNEDY SPACE CENTER, FLA. - Japanese astronaut Koichi Wakata (right) listens to William Gaetjens, with the Vehicle Integration Test Team (VITT), who is providing details about the spar installation (left) on the wing of the orbiter Atlantis. Reinforced Carbon Carbon (RCC) panels are mechanically attached to the wing via the spars - a series of floating joints - to reduce loading on the panels caused by wing deflections. The aluminum and the metallic attachments are protected from exceeding temperature limits by internal insulation.

  17. KENNEDY SPACE CENTER, FLA. - Mike Hyatt (left) and Saul Ngy, technicians with United Space Alliance, prepare to install a spar on the wing of the orbiter Atlantis. The Reinforced Carbon Carbon (RCC) panels are mechanically attached to the wing with a series of floating joints - spars - to reduce loading on the panels caused by wing deflections. The aluminum and the metallic attachments are protected from exceeding temperature limits by internal insulation.

    NASA Image and Video Library

    2003-08-22

    KENNEDY SPACE CENTER, FLA. - Mike Hyatt (left) and Saul Ngy, technicians with United Space Alliance, prepare to install a spar on the wing of the orbiter Atlantis. The Reinforced Carbon Carbon (RCC) panels are mechanically attached to the wing with a series of floating joints - spars - to reduce loading on the panels caused by wing deflections. The aluminum and the metallic attachments are protected from exceeding temperature limits by internal insulation.

  18. KENNEDY SPACE CENTER, FLA. - In the Orbiter Processing Facility, John Newport, with United Space Alliance, inspects a spar to be installed on the wing of the orbiter Atlantis. Reinforced Carbon Carbon (RCC) panels are mechanically attached to the wing with a series of floating joints - spars - to reduce loading on the panels caused by wing deflections. The aluminum and the metallic attachments are protected from exceeding temperature limits by internal insulation.

    NASA Image and Video Library

    2003-09-04

    KENNEDY SPACE CENTER, FLA. - In the Orbiter Processing Facility, John Newport, with United Space Alliance, inspects a spar to be installed on the wing of the orbiter Atlantis. Reinforced Carbon Carbon (RCC) panels are mechanically attached to the wing with a series of floating joints - spars - to reduce loading on the panels caused by wing deflections. The aluminum and the metallic attachments are protected from exceeding temperature limits by internal insulation.

  19. KENNEDY SPACE CENTER, FLA. - William Gaetjens (background), with the Vehicle Integration Test Team (VITT) directs Japanese astronaut Koichi Wakata’s attention to the spars installed on the wing of the orbiter Atlantis. Reinforced Carbon Carbon (RCC) panels are mechanically attached to the wing via the spars - a series of floating joints - to reduce loading on the panels caused by wing deflections. The aluminum and the metallic attachments are protected from exceeding temperature limits by internal insulation.

    NASA Image and Video Library

    2003-09-05

    KENNEDY SPACE CENTER, FLA. - William Gaetjens (background), with the Vehicle Integration Test Team (VITT) directs Japanese astronaut Koichi Wakata’s attention to the spars installed on the wing of the orbiter Atlantis. Reinforced Carbon Carbon (RCC) panels are mechanically attached to the wing via the spars - a series of floating joints - to reduce loading on the panels caused by wing deflections. The aluminum and the metallic attachments are protected from exceeding temperature limits by internal insulation.

  20. KENNEDY SPACE CENTER, FLA. - In the Orbiter Processing Facility, Mike Hyatt (left) and Saul Ngy (right), with United Space Alliance, finish installing a spar on the wing of the orbiter Atlantis. Reinforced Carbon Carbon (RCC) panels are mechanically attached to the wing with a series of floating joints - spars - to reduce loading on the panels caused by wing deflections. The aluminum and the metallic attachments are protected from exceeding temperature limits by internal insulation.

    NASA Image and Video Library

    2003-09-04

    KENNEDY SPACE CENTER, FLA. - In the Orbiter Processing Facility, Mike Hyatt (left) and Saul Ngy (right), with United Space Alliance, finish installing a spar on the wing of the orbiter Atlantis. Reinforced Carbon Carbon (RCC) panels are mechanically attached to the wing with a series of floating joints - spars - to reduce loading on the panels caused by wing deflections. The aluminum and the metallic attachments are protected from exceeding temperature limits by internal insulation.

  1. KENNEDY SPACE CENTER, FLA. - Technician Saul Ngy, with United Space Alliance, prepares to install a spar on the wing of the orbiter Atlantis. The Reinforced Carbon Carbon (RCC) panels are mechanically attached to the wing with a series of floating joints - spars - to reduce loading on the panels caused by wing deflections. The aluminum and the metallic attachments are protected from exceeding temperature limits by internal insulation.

    NASA Image and Video Library

    2003-08-22

    KENNEDY SPACE CENTER, FLA. - Technician Saul Ngy, with United Space Alliance, prepares to install a spar on the wing of the orbiter Atlantis. The Reinforced Carbon Carbon (RCC) panels are mechanically attached to the wing with a series of floating joints - spars - to reduce loading on the panels caused by wing deflections. The aluminum and the metallic attachments are protected from exceeding temperature limits by internal insulation.

  2. KENNEDY SPACE CENTER, FLA. - Mike Hyatt (left) and Saul Ngy, technicians with United Space Alliance, install a spar on the wing of the orbiter Atlantis. The Reinforced Carbon Carbon (RCC) panels are mechanically attached to the wing with a series of floating joints - spars - to reduce loading on the panels caused by wing deflections. The aluminum and the metallic attachments are protected from exceeding temperature limits by internal insulation.

    NASA Image and Video Library

    2003-08-22

    KENNEDY SPACE CENTER, FLA. - Mike Hyatt (left) and Saul Ngy, technicians with United Space Alliance, install a spar on the wing of the orbiter Atlantis. The Reinforced Carbon Carbon (RCC) panels are mechanically attached to the wing with a series of floating joints - spars - to reduce loading on the panels caused by wing deflections. The aluminum and the metallic attachments are protected from exceeding temperature limits by internal insulation.

  3. Metal Detectors.

    ERIC Educational Resources Information Center

    Harrington-Lueker, Donna

    1992-01-01

    Schools that count on metal detectors to stem the flow of weapons into the schools create a false sense of security. Recommendations include investing in personnel rather than hardware, cultivating the confidence of law-abiding students, and enforcing discipline. Metal detectors can be quite effective at afterschool events. (MLF)

  4. Dryden Flight Research Center: Center Overview

    NASA Technical Reports Server (NTRS)

    Ratnayake, Nalin

    2009-01-01

    This viewgraph presentation describes a general overview of Dryden Flight Research Center. Strategic partnerships, Dryden's mission activity, exploration systems and aeronautics research programs are also described.

  5. Student Success Center Toolkit

    ERIC Educational Resources Information Center

    Jobs For the Future, 2014

    2014-01-01

    "Student Success Center Toolkit" is a compilation of materials organized to assist Student Success Center directors as they staff, launch, operate, and sustain Centers. The toolkit features materials created and used by existing Centers, such as staffing and budgeting templates, launch materials, sample meeting agendas, and fundraising…

  6. Conceptualizing the Learning Center.

    ERIC Educational Resources Information Center

    Peterson, Gary T.

    The learning center is an integrated, fully-coordinated facility, combining a number of traditional library, media development, and personalized learning functions. Conceptualizing the learning center is facilitated through a description of the premises for such a center, the components, and guidelines for developing a learning center. De Anza…

  7. Metal oxide films on metal

    DOEpatents

    Wu, Xin D.; Tiwari, Prabhat

    1995-01-01

    A structure including a thin film of a conductive alkaline earth metal oxide selected from the group consisting of strontium ruthenium trioxide, calcium ruthenium trioxide, barium ruthenium trioxide, lanthanum-strontium cobalt oxide or mixed alkaline earth ruthenium trioxides thereof upon a thin film of a noble metal such as platinum is provided.

  8. Teacher Education Centers: The CMTEC Centers.

    ERIC Educational Resources Information Center

    Sentz, Erma I.; Perry, Floyd

    Central Minnesota Teacher Education Council (CMTEC) Centers are public school districts under contract with CMTEC who designate "cluster buildings" that serve a minimum of 10 student teachers per quarter each. In all CMTEC Centers, emphasis is placed on providing opportunities for student teachers to teach under guidance in both major and minor…

  9. From Teacher Centered to Student Centered Learning.

    ERIC Educational Resources Information Center

    Lockemy, M. J.; Summers, Sylvia

    In 1991, staff at the Business Resource Center (BRC) at Tacoma Community College, in Washington, began to reevaluate their approach to serving students. Up to that point, the BRC had been teacher centered, with staff operating under the assumptions that only the students who succeeded were actually "college material," that students would cheat if…

  10. Ytterbium: Transition at High Pressure from Face-Centered Cubic to Body-Centered Cubic Structure.

    PubMed

    Hall, H T; Barnett, J D; Merrill, L

    1963-01-11

    Pressure of 40,000 atmospheres at 25 degrees C induces a phase transformation in ytterbium metal; the face-centered cubic structure changes to body-centered cubic. The radius of the atom changes from 1.82 to 1.75 A. At the same time the atom's volume decreases by 11 percent and the volume, observed macroscopically, decreases 3.2 percent.

  11. Metal Coatings

    NASA Technical Reports Server (NTRS)

    1994-01-01

    During the Apollo Program, General Magnaplate Corporation developed process techniques for bonding dry lubricant coatings to space metals. The coatings were not susceptible to outgassing and offered enhanced surface hardness and superior resistance to corrosion and wear. This development was necessary because conventional lubrication processes were inadequate for lightweight materials used in Apollo components. General Magnaplate built on the original technology and became a leader in development of high performance metallurgical surface enhancement coatings - "synergistic" coatings, - which are used in applications from pizza making to laser manufacture. Each of the coatings is designed to protect a specific metal or group of metals to solve problems encountered under operating conditions.

  12. Noble metals in oncology

    PubMed Central

    Markowska, Anna; Jaszczyńska-Nowinka, Karolina; Lubin, Jolanta; Markowska, Janina

    2015-01-01

    Worldwide research groups are searching for anticancer compounds, many of them are organometalic complexes having platinum group metals as their active centers. Most commonly used cytostatics from this group are cisplatin, carboplatin and oxaliplatin. Cisplatin was used fot the first time in 1978, from this time many platinum derivatives were created. In this review we present biological properties and probable future clinical use of platinum, gold, silver, iridium and ruthenium derivatives. Gold derivative Auranofin has been studied extensively. Action of silver nanoparticles on different cell lines was analysed. Iridium isotopes are commonly used in brachyterapy. Ruthenium compound new anti-tumour metastasis inhibitor (NAMI-A) is used in managing lung cancer metastases. Electroporation of another ruthenium based compound KP1339 was also studied. Most of described complexes have antiproliferative and proapoptotic properties. Further studies need to be made. Nevertheless noble metal based chemotherapheutics and compounds seem to be an interesting direction of research. PMID:26557773

  13. Metals 2000

    SciTech Connect

    Allison, S.W.; Rogers, L.C.; Slaughter, G.; Boensch, F.D.; Claus, R.O.; de Vries, M.

    1993-05-01

    This strategic planning exercise identified and characterized new and emerging advanced metallic technologies in the context of the drastic changes in global politics and decreasing fiscal resources. In consideration of a hierarchy of technology thrusts stated by various Department of Defense (DOD) spokesmen, and the need to find new and creative ways to acquire and organize programs within an evolving Wright Laboratory, five major candidate programs identified are: C-17 Flap, Transport Fuselage, Mach 5 Aircraft, 4.Fighter Structures, and 5. Missile Structures. These results were formed by extensive discussion with selected major contractors and other experts, and a survey of advanced metallic structure materials. Candidate structural applications with detailed metal structure descriptions bracket a wide variety of uses which warrant consideration for the suggested programs. An analysis on implementing smart skins and structures concepts is given from a metal structures perspective.

  14. Metal oxide chemistry in solution: the early transition metal polyoxoanions.

    PubMed

    Day, V W; Klemperer, W G

    1985-05-03

    Many of the early transition elements form large polynuclear metal-oxygen anions containing up to 200 atoms or more. Although these polyoxoanions have been investigated for more than a century, detailed studies of structure and reactivity were not possible until the development of modern x-ray crystallographic and nuclear magnetic resonance spectroscopic techniques. Systematic studies of small polyoxoanions in inert, aprotic solvents have clarified many of the principles governing their structure and reactivity, and also have made possible the preparation of entirely new types of covalent derivatives such as CH(2)Mo(4)O(15)H(3-), C(5)H(5)TiMo(5)O(18)(3-), and (OC)(3)Mn(Nb(2)W(4)O(19))(3-). Since most early transition metal polyoxoanions have structures based on close-packed oxygen arrays containing interstitial metal centers, their chemistry offers a rare opportunity to study chemical transformations in detail on well-defined metal oxide surfaces.

  15. Metals--Endangered Resources.

    ERIC Educational Resources Information Center

    Crowder, William W.

    1979-01-01

    Suggests activities for elementary teachers to use in teaching about metals and their use. Specific areas addressed include: history of metals, metal use, consumption statistics, beauty of metals, sources of metals, conservation, and other projects. (JMB)

  16. CNC electrical discharge machining centers

    SciTech Connect

    Jaggars, S.R.

    1991-10-01

    Computer numerical control (CNC) electrical discharge machining (EDM) centers were investigated to evaluate the application and cost effectiveness of establishing this capability at Allied-Signal Inc., Kansas City Division (KCD). In line with this investigation, metal samples were designed, prepared, and machined on an existing 15-year-old EDM machine and on two current technology CNC EDM machining centers at outside vendors. The results were recorded and evaluated. The study revealed that CNC EDM centers are a capability that should be established at KCD. From the information gained, a machine specification was written and a shop was purchased and installed in the Engineering Shop. The older machine was exchanged for a new model. Additional machines were installed in the Tool Design and Fabrication and Precision Microfinishing departments. The Engineering Shop machine will be principally used for the following purposes: producing deep cavities in small corner radii, machining simulated casting models, machining difficult-to-machine materials, and polishing difficult-to-hand polish mold cavities. 2 refs., 18 figs., 3 tabs.

  17. NIST Diffusion Data Center

    National Institute of Standards and Technology Data Gateway

    NIST Diffusion Data Center (Web, free access)   The NIST Diffusion Data Center is a collection of over 14,100 international papers, theses, and government reports on diffusion published before 1980.

  18. Regional Instrumentation Centers.

    ERIC Educational Resources Information Center

    Cromie, William J.

    1980-01-01

    Focuses on the activities of regional instrumentation centers that utilize the state-of-the-art instruments and methodology in basic scientific research. The emphasis is on the centers involved in mass spectroscopy, magnetic resonance spectroscopy, lasers, and accelerators. (SA)

  19. Evaluating Teacher Centers

    ERIC Educational Resources Information Center

    Feiman, Sharon

    1977-01-01

    Considers what teacher centers actually are, what they do, what they are supposed to do, and how they are formed. Discusses three types of centers, their organizational structure and function, and the theory underlying them. (Editor/RK)

  20. ACTS data center

    NASA Technical Reports Server (NTRS)

    Syed, Ali; Vogel, Wolfhard J.

    1993-01-01

    Viewgraphs on ACTS Data Center status report are included. Topics covered include: ACTS Data Center Functions; data flow overview; PPD flow; RAW data flow; data compression; PPD distribution; RAW Data Archival; PPD Audit; and data analysis.

  1. Nonschool Learning Center

    ERIC Educational Resources Information Center

    Brown, Doris B.

    1972-01-01

    Describes a privately financed science center, museum and planetarium - observatory in Twin Falls, Idaho. Centers three hour program includes a lecture on archaeology, time to look at displays, a lunch break, and a planetarium lecture. (RB)

  2. Automating the Media Center.

    ERIC Educational Resources Information Center

    Holloway, Mary A.

    1988-01-01

    Discusses the need to develop more efficient information retrieval skills by the use of new technology. Lists four stages used in automating the media center. Describes North Carolina's pilot programs. Proposes benefits and looks at the media center's future. (MVL)

  3. Nonschool Learning Center

    ERIC Educational Resources Information Center

    Brown, Doris B.

    1972-01-01

    Describes a privately financed science center, museum and planetarium - observatory in Twin Falls, Idaho. Centers three hour program includes a lecture on archaeology, time to look at displays, a lunch break, and a planetarium lecture. (RB)

  4. BKG Data Center

    NASA Technical Reports Server (NTRS)

    Thorandt, Volkmar; Wojdziak, Reiner

    2013-01-01

    This report summarizes the activities and background information of the IVS Data Center for the year 2012. Included is information about functions, structure, technical equipment, and staff members of the BKG Data Center.

  5. Regional Instrumentation Centers.

    ERIC Educational Resources Information Center

    Cromie, William J.

    1980-01-01

    Focuses on the activities of regional instrumentation centers that utilize the state-of-the-art instruments and methodology in basic scientific research. The emphasis is on the centers involved in mass spectroscopy, magnetic resonance spectroscopy, lasers, and accelerators. (SA)

  6. Tornadoes: A Center Approach.

    ERIC Educational Resources Information Center

    Christman-Rothlein, Liz; Meinbach, Anita M.

    1981-01-01

    Information is given on how to put together a learning center. Discusses information and activity packets for a complete learning center on tornadoes including objectives, directions, materials, photographs of physical arrangements, and posttest. (DC)

  7. The Comprehensive Learning Center

    ERIC Educational Resources Information Center

    Peterson, Gary T.

    1975-01-01

    This paper describes the results of a study of community college learning resource centers as they exist today and examines some emerging functions which point toward the role of the center in the future. (DC)

  8. Human Motion Tracking at Marshall Space Flight Center's Collaborative Engineering Center ANVIL

    NASA Technical Reports Server (NTRS)

    Henderson, Steven J.; Hamilton, George S.

    2004-01-01

    The installation and use of electromagnetic human motion trackers requires a specially designed and metal-free environment for optimal performance. Such an area is not readily available at the Marshall Space Flight Center Collaborative Engineering Center ANVIL. Our paper details a systems engineering approach to installing and operating Ascension Technologies Ethernet MotionStar tracking system in a sub-optimal environment, used with the JACK human computer model's motion capture capabilities. We also discuss how this system is integrated into the Marshall Space Flight Center's Human Engineering process.

  9. Metallic Hydrogen

    NASA Astrophysics Data System (ADS)

    Silvera, Isaac; Zaghoo, Mohamed; Salamat, Ashkan

    2015-03-01

    Hydrogen is the simplest and most abundant element in the Universe. At high pressure it is predicted to transform to a metal with remarkable properties: room temperature superconductivity, a metastable metal at ambient conditions, and a revolutionary rocket propellant. Both theory and experiment have been challenged for almost 80 years to determine its condensed matter phase diagram, in particular the insulator-metal transition. Hydrogen is predicted to dissociate to a liquid atomic metal at multi-megabar pressures and T =0 K, or at megabar pressures and very high temperatures. Thus, its predicted phase diagram has a broad field of liquid metallic hydrogen at high pressure, with temperatures ranging from thousands of degrees to zero Kelvin. In a bench top experiment using static compression in a diamond anvil cell and pulsed laser heating, we have conducted measurements on dense hydrogen in the region of 1.1-1.7 Mbar and up to 2200 K. We observe a first-order phase transition in the liquid phase, as well as sharp changes in optical transmission and reflectivity when this phase is entered. The optical signature is that of a metal. The mapping of the phase line of this transition is in excellent agreement with recent theoretical predictions for the long-sought plasma phase transition to metallic hydrogen. Research supported by the NSF, Grant DMR-1308641, the DOE Stockpile Stewardship Academic Alliance Program, Grant DE-FG52-10NA29656, and NASA Earth and Space Science Fellowship Program, Award NNX14AP17H.

  10. Language Resource Centers Program

    ERIC Educational Resources Information Center

    Office of Postsecondary Education, US Department of Education, 2012

    2012-01-01

    The Language Resource Centers (LRC) program provides grants to institutions of higher education to establish, strengthen, and operate resource centers that serve to improve the nation's capacity to teach and learn foreign languages. Eligible applicants are institutions of higher education. Duration of the grant is four years. Center activities…

  11. Equality of Fitness Centers

    ERIC Educational Resources Information Center

    Swoyer, Jesse O.

    2008-01-01

    The author, who has been a personal trainer for the past ten years, recently realized that all fitness centers are not equal. In February, he was able to participate in the grand opening of the Center for Independent Living of Central PA (CILCP), a fitness center that is designed to accommodate persons with disabilities living in the Central…

  12. Data center cooling method

    DOEpatents

    Chainer, Timothy J.; Dang, Hien P.; Parida, Pritish R.; Schultz, Mark D.; Sharma, Arun

    2015-08-11

    A method aspect for removing heat from a data center may use liquid coolant cooled without vapor compression refrigeration on a liquid cooled information technology equipment rack. The method may also include regulating liquid coolant flow to the data center through a range of liquid coolant flow values with a controller-apparatus based upon information technology equipment temperature threshold of the data center.

  13. Center Director's Update

    NASA Image and Video Library

    2016-03-01

    In the Space Shuttle Atlantis exhibit facility at the Kennedy Space Center's Visitor Complex, guests get a close-up look at a plant growth experiment similar to one aboard the International Space Station. This followed a presentation by center director Bob Cabana who updated community leaders on current and future activities at the space center.

  14. A call center primer.

    PubMed

    Durr, W

    1998-01-01

    Call centers are strategically and tactically important to many industries, including the healthcare industry. Call centers play a key role in acquiring and retaining customers. The ability to deliver high-quality and timely customer service without much expense is the basis for the proliferation and expansion of call centers. Call centers are unique blends of people and technology, where performance indicates combining appropriate technology tools with sound management practices built on key operational data. While the technology is fascinating, the people working in call centers and the skill of the management team ultimately make a difference to their companies.

  15. The MSFC complementary metal oxide semiconductor (including multilevel interconnect metallization) process handbook

    NASA Technical Reports Server (NTRS)

    Bouldin, D. L.; Eastes, R. W.; Feltner, W. R.; Hollis, B. R.; Routh, D. E.

    1979-01-01

    The fabrication techniques for creation of complementary metal oxide semiconductor integrated circuits at George C. Marshall Space Flight Center are described. Examples of C-MOS integrated circuits manufactured at MSFC are presented with functional descriptions of each. Typical electrical characteristics of both p-channel metal oxide semiconductor and n-channel metal oxide semiconductor discrete devices under given conditions are provided. Procedures design, mask making, packaging, and testing are included.

  16. Metallized Products

    NASA Technical Reports Server (NTRS)

    1980-01-01

    Since the early 1960's, virtually all NASA spacecraft have used metallized films for a variety of purposes, principally thermal radiation insulation. King Seeley manufactures a broad line of industrial and consumer oriented metallized film, fabric, paper and foam in single layer sheets and multi-layer laminates. A few examples, commercialized by MPI Outdoor Safety Products, are the three ounce Thermos Emergency Blanket which reflects and retains up to 80 percent of the user's body heat helping prevent post accident shock or keeping a person warm for hours under emergency cold weather conditions.

  17. Photobiomolecular metallic particles and films

    DOEpatents

    Hu, Zhong-Cheng

    2003-05-06

    The method of the invention is based on the unique electron-carrying function of a photocatalytic unit such as the photosynthesis system I (PSI) reaction center of the protein-chlorophyll complex isolated from chloroplasts. The method employs a photo-biomolecular metal deposition technique for precisely controlled nucleation and growth of metallic clusters/particles, e.g., platinum, palladium, and their alloys, etc., as well as for thin-film formation above the surface of a solid substrate. The photochemically mediated technique offers numerous advantages over traditional deposition methods including quantitative atom deposition control, high energy efficiency, and mild operating condition requirements.

  18. Emergency Operations Center at Johnson Space Center

    NASA Technical Reports Server (NTRS)

    Caylor, Gary C.

    1997-01-01

    In June 1966, at the start of the Gulf Coast hurricane season, the Johnson Space Center (JSC) celebrated the opening of its new 4,000-square foot, state-of-the-art Emergency Operations Center (EOC). The new EOC has been upgraded and enhanced to support a wide spectrum of emergencies affecting JSC and neighboring communities. One of the main features of the EOC is its premier computerized dispatch center. The new system unites many of JSC's critical emergency functions into one integrated network. It automatically monitors fire alarms, security entrances, and external cameras. It contains the JSC inventory of hazardous materials, by building and room, and can call up Material Safety Data Sheets for most of the generic hazardous materials used on-site. The EOC is available for community use during area emergencies such as hurricanes and is a welcome addition to the Clear Lake/Galveston Bay Area communities' emergency response resources.

  19. Emergency Operations Center at Johnson Space Center

    NASA Technical Reports Server (NTRS)

    Caylor, Gary C.

    1997-01-01

    In June 1966, at the start of the Gulf Coast hurricane season, the Johnson Space Center (JSC) celebrated the opening of its new 4,000-square foot, state-of-the-art Emergency Operations Center (EOC). The new EOC has been upgraded and enhanced to support a wide spectrum of emergencies affecting JSC and neighboring communities. One of the main features of the EOC is its premier computerized dispatch center. The new system unites many of JSC's critical emergency functions into one integrated network. It automatically monitors fire alarms, security entrances, and external cameras. It contains the JSC inventory of hazardous materials, by building and room, and can call up Material Safety Data Sheets for most of the generic hazardous materials used on-site. The EOC is available for community use during area emergencies such as hurricanes and is a welcome addition to the Clear Lake/Galveston Bay Area communities' emergency response resources.

  20. Isolation and Structural Characterization of a Mackay 55-Metal-Atom Two-Shell Icosahedron of Pseudo-Ih Symmetry, Pd55L12(μ3-CO)20 (L = PR3, R = Isopropyl): Comparative Analysis with Interior Two-Shell Icosahedral Geometries in Capped Three-Shell Pd145, Pt-Centered Four-Shell Pd-Pt M165, and Four-Shell Au133 Nanoclusters.

    PubMed

    Erickson, Jeremiah D; Mednikov, Evgueni G; Ivanov, Sergei A; Dahl, Lawrence F

    2016-02-10

    We present the first successful isolation and crystallographic characterization of a Mackay 55-metal-atom two-shell icosahedron, Pd55L12(μ3-CO)20 (L = PPr(i)3) (1). Its two-shell icosahedron of pseudo-Ih symmetry (without isopropyl substituents) enables a structural/bonding comparison with interior 55-metal-atom two-shell icosahedral geometries observed within the multi-shell capped 145-metal-atom three-shell Pd145(CO)72(PEt3)30 and 165-metal-atom four-shell Pt-centered (μ12-Pt)Pd164-xPtx(CO)72(PPh3)20 (x ≈ 7) nanoclusters, and within the recently reported four-shell Au133(SC6H4-p-Bu(t))52 nanocluster. DFT calculations carried out on a Pd55(CO)20(PH3)12 model analogue, with triisopropyl phosphine substituents replaced by H atoms, revealed a positive +0.84 e charge for the entire Pd55 core, with a highly positive second-shell Pd42 surface of +1.93 e.

  1. Metallic Hydrogen

    NASA Astrophysics Data System (ADS)

    Silvera, Isaac F.; Dias, Ranga; Noked, Ori; Salamat, Ashkan; Zaghoo, Mohamed

    2017-04-01

    One of the great challenges in condensed matter physics has been to produce metallic hydrogen (MH) in the laboratory. There are two approaches: solid molecular hydrogen can be compressed to high density at extreme pressures of order 5-6 megabars. The transition to MH should take place at low temperatures and is expected to occur as a structural first-order phase transition with dissociation of molecules into atoms, rather than the closing of a gap. A second approach is to produce dense molecular hydrogen at pressures of order 1-2 megabars and heat the sample. With increasing temperature, it was predicted that molecular hydrogen first melts and then dissociates to atomic metallic liquid hydrogen as a first-order phase transition. We have observed this liquid-liquid phase transition to metallic hydrogen, also called the plasma phase transition. In low-temperature studies, we have pressurized HD to over 3 megabars and observed two new phases. Molecular hydrogen has been pressurized to 4.2 megabars. A new phase transition has been observed at 3.55 megabars, but it is not yet metallic.

  2. Heavy Metal.

    ERIC Educational Resources Information Center

    Shoemaker, W. Lee

    1998-01-01

    Discusses the advantages, both functional and economic, of using a standing-seam metal roof in both new roof installations and reroofing projects of educational facilities. Structural versus non-structural standing-seam roofs are described as are the types of insulation that can be added and roof finishes used. (GR)

  3. METAL COMPOSITIONS

    DOEpatents

    Seybolt, A.U.

    1959-02-01

    Alloys of uranium which are strong, hard, and machinable are presented, These alloys of uranium contain bctween 0.1 to 5.0% by weight of at least one noble metal such as rhodium, palladium, and gold. The alloys may be heat treated to obtain a product with iniproved tensile and compression strengths,

  4. Heavy Metal.

    ERIC Educational Resources Information Center

    Shoemaker, W. Lee

    1998-01-01

    Discusses the advantages, both functional and economic, of using a standing-seam metal roof in both new roof installations and reroofing projects of educational facilities. Structural versus non-structural standing-seam roofs are described as are the types of insulation that can be added and roof finishes used. (GR)

  5. Induction brazing at the Kennedy Space Center

    NASA Technical Reports Server (NTRS)

    Clautice, W. E.

    1974-01-01

    A description of the joint design, materials, equipment, qualification testing, inspection methods, and applications involved in performing induction brazing on hyperbolic propellants tubing at Kennedy Space Center. Induction brazing is a form of brazing in which the energy is transmitted to the workpiece by electrical induction; the eddy currents generated in the metal produce heat by resistance losses. Since induction heating is fast and highly localized, undesirable heat effects are minimized and the resulting braze is of high quality.

  6. Induction brazing at the Kennedy Space Center

    NASA Technical Reports Server (NTRS)

    Clautice, W. E.

    1974-01-01

    A description of the joint design, materials, equipment, qualification testing, inspection methods, and applications involved in performing induction brazing on hyperbolic propellants tubing at Kennedy Space Center. Induction brazing is a form of brazing in which the energy is transmitted to the workpiece by electrical induction; the eddy currents generated in the metal produce heat by resistance losses. Since induction heating is fast and highly localized, undesirable heat effects are minimized and the resulting braze is of high quality.

  7. Composite metal membrane

    DOEpatents

    Peachey, N.M.; Dye, R.C.; Snow, R.C.; Birdsell, S.A.

    1998-04-14

    A composite metal membrane including a first metal layer of Group IVB met or Group VB metals, the first metal layer sandwiched between two layers of an oriented metal of palladium, platinum or alloys thereof is provided together with a process for the recovery of hydrogen from a gaseous mixture including contacting a hydrogen-containing gaseous mixture with a first side of a nonporous composite metal membrane including a first metal of Group IVB metals or Group VB metals, the first metal layer sandwiched between two layers of an oriented metal of palladium, platinum or alloys thereof, and, separating hydrogen from a second side of the nonporous composite metal membrane.

  8. Composite metal membrane

    DOEpatents

    Peachey, Nathaniel M.; Dye, Robert C.; Snow, Ronny C.; Birdsell, Stephan A.

    1998-01-01

    A composite metal membrane including a first metal layer of Group IVB met or Group VB metals, the first metal layer sandwiched between two layers of an oriented metal of palladium, platinum or alloys thereof is provided together with a process for the recovery of hydrogen from a gaseous mixture including contacting a hydrogen-containing gaseous mixture with a first side of a nonporous composite metal membrane including a first metal of Group IVB metals or Group VB metals, the first metal layer sandwiched between two layers of an oriented metal of palladium, platinum or alloys thereof, and, separating hydrogen from a second side of the nonporous composite metal membrane.

  9. Metalization of lipid vesicles via electroless plating

    SciTech Connect

    Ferrar, W.T.; O'Brien, D.F.; Warshawsky, A.; Voycheck, C.L.

    1988-01-06

    The encapsulation of metallic particles and metallic oxides within lipid vesicles has recently been of interest for applications such as catalysis, water splitting, and magnetic control of spin coupling. In this communication the authors introduce the concept and practice of the deposition of metal on vesicles by using electroless plating techniques. Coordination of low valent transition metals to organic functional groups on the surface of the bilayer membrane provides a means of binding metal atoms to vesicles. Chemical reduction produced zero valent atoms which serve as sites for further metal deposition by the chemical reduction techniques of electroless plating. Specifically, this procedure involved the binding of a small amount of tetrachloropalladate to the vesicle bilayer, reduction of the palladium(II) to palladium(0), followed by the deposition of much larger amounts of metal from an electroless plating solution. Electroless plating solutions were used for the deposition of palladium, nickel, cobalt, or copper metal onto the catalytic palladium centers. Since the metallic particles were associated with the vesicles, colloids were formed that were stable in water for much longer periods than the control metal particles formed in water alone. If the vesicles were composed in part of unsaturated lipids, with the olefinic groups on the hydrocarbon chains, the initial evidence suggests the transition metal was directed into the bilayer, rather than staying on the surface.

  10. Metal-silica sol-gel materials

    NASA Technical Reports Server (NTRS)

    Stiegman, Albert E. (Inventor)

    2002-01-01

    The present invention relates to a single phase metal-silica sol-gel glass formed by the co-condensation of a transition metal with silicon atoms where the metal atoms are uniformly distributed within the sol-gel glass as individual metal centers. Any transition metal may be used in the sol-gel glasses. The present invention also relates to sensor materials where the sensor material is formed using the single phase metal-silica sol-gel glasses. The sensor materials may be in the form of a thin film or may be attached to an optical fiber. The present invention also relates to a method of sensing chemicals using the chemical sensors by monitoring the chromatic change of the metal-silica sol-gel glass when the chemical binds to the sensor. The present invention also relates to oxidation catalysts where a metal-silica sol-gel glass catalyzes the reaction. The present invention also relates to a method of performing oxidation reactions using the metal-silica sol-gel glasses. The present invention also relates to organopolymer metal-silica sol-gel composites where the pores of the metal-silica sol-gel glasses are filled with an organic polymer polymerized by the sol-gel glass.

  11. Heavy Metal - Exploring a magnetised metallic asteroid

    NASA Astrophysics Data System (ADS)

    Wahlund, Jan-Erik; Andrews, David; Futaana, Yoshifumi; Masters, Adam; Thomas, Nicolas; De Sanctis, Maria Cristina; Herique, Alain; Retherford, Kurt; Tortora, Paolo; Trigo-Rodriguez, Joseph; Ivchenko, Nickolay; Simon, Sven

    2017-04-01

    We propose a spacecraft mission (Heavy Metal) to orbit and explore (16) Psyche - the largest M-class metallic asteroid in the main belt. Recent estimates of the shape, 279×232×189 km and mass, 2.7×10(19) kg make it one of the largest and densest of asteroids, and together with the high surface radar reflectivity and the spectral data measured from Earth it is consistent with a bulk composition rich in iron-nickel. The M5 mission Heavy Metal will investigate if (16) Psyche is the exposed metallic core of a planetesimal, formed early enough to melt and differentiate. High-resolution mapping of the surface in optical, IR, UV and radar wavebands, along with the determination of the shape and gravity field will be used to address the formation and subsequent evolution of (16) Psyche, determining the origin of metallic asteroids. It is conceivable that a cataclysmic collision with a second body led to the ejection of all or part of the differentiated core of the parent body. Measurements at (16) Psyche therefore provide a possibility to directly examine an iron-rich planetary core, similar to that expected at the center of all the major planets including Earth. A short-lived dynamo producing a magnetic field early in the life of (16) Psyche could have led to a remnant field (of tens of micro Tesla) being preserved in the body today. (16) Psyche is embedded in the variable flow of the solar wind. Whereas planetary magnetospheres and induced magnetospheres are the result of intense dynamo fields and dense conductive ionospheres presenting obstacles to the solar wind, (16) Psyche may show an entirely new 'class' of interaction as a consequence of its lack of a significant atmosphere, the extremely high bulk electrical conductivity of the asteroid, and the possible presence of intense magnetic fields retained in iron-rich material. The small characteristic scale of (16) Psyche ( 200 km) firmly places any solar wind interaction in the "sub-MHD" scale, in which kinetic

  12. Dimensionality-induced insulator-metal crossover in layered nickelates La{sub n+1}Ni{sub n}O{sub 2n+2} (n = 2, 3, and ∞)

    SciTech Connect

    Liu, Ting; Jia, Ting; Zhang, Xiaoli; Wu, Hua; Zeng, Zhi; Lin, H. Q.; Li, X. G.

    2014-04-15

    Low-valence layered nickelates are a structural analog to the superconducting cuprates and possess interesting properties. In this work, we have systematically studied the electronic structure of La{sub n+1}Ni{sub n}O{sub 2n+2} using first-principles calculations. Our results reveal that the Ni-3d 3z{sup 2} − r{sup 2} orbital state is active and evolves from discrete molecular levels to a continuous solid band and its filling varies as the dimensionality (or n) increases. The two-dimensional (2D) La{sub 3}Ni{sub 2}O{sub 6} and La{sub 4}Ni{sub 3}O{sub 8} are thus found to have a molecular insulating state. In contrast, the 3D LaNiO{sub 2} is metallic and its 3z{sup 2} − r{sup 2} band surprisingly becomes 3D due to the Ni-La hybridization, and the La-5d xy orbital also forms a 2D metallic band. Therefore, La{sub n+1}Ni{sub n}O{sub 2n+2} is a dimensionality-controlled insulator-metal crossover system.

  13. EROS Data Center

    USGS Publications Warehouse

    ,

    1980-01-01

    The Earth Resources Observation Systems (EROS) Data Center, located in Sioux Falls, SD, is a data management, systems development, and research field center of the U.S. Geological Survey's National Mapping Division. The Center was established in the early 1970's to receive, process, and distribute data from National Aeronautics and Space Administration (NASA) Landsat satellites. The Center holds the world's largest collection of space and aircraft acquired imagery of the Earth. These holdings include over 2 million images acquired from satellites and over 8 million aerial photographs. The Center is also a major focal point for information concerning the holdings of foreign Landsat ground reception stations and data acquired by other countries' Earth observing satellites. The central U.S. location provides the Center with a unique capability to receive real-time electronic signals from Earth orbiting satellites, used for developing data sets of most of the North American continent.

  14. Relativistic Guiding Center Equations

    SciTech Connect

    White, R. B.; Gobbin, M.

    2014-10-01

    In toroidal fusion devices it is relatively easy that electrons achieve relativistic velocities, so to simulate runaway electrons and other high energy phenomena a nonrelativistic guiding center formalism is not sufficient. Relativistic guiding center equations including flute mode time dependent field perturbations are derived. The same variables as used in a previous nonrelativistic guiding center code are adopted, so that a straightforward modifications of those equations can produce a relativistic version.

  15. Test Control Center exhibit

    NASA Technical Reports Server (NTRS)

    2000-01-01

    Have you ever wondered how the engineers at John C. Stennis Space Center in Hancock County, Miss., test fire a Space Shuttle Main Engine? The Test Control Center exhibit at StenniSphere can answer your questions by simulating the test firing of a Space Shuttle Main Engine. A recreation of one of NASA's test control centers, the exhibit explains and portrays the 'shake, rattle and roar' that happens during a real test firing.

  16. Protection of open-metal V(III) sites and their associated CO₂/CH₄/N₂/O₂/H₂O adsorption properties in mesoporous V-MOFs.

    PubMed

    Yang, Jiangfeng; Wang, Yong; Li, Libo; Zhang, Zhuoming; Li, Jinping

    2015-10-15

    Metal-organic frameworks with open metal site are potential sorbents for the separation of gas mixtures; however, low valence metal will bind to oxygen in the open air causing a decrease in adsorption ability. We now report open-metal sites V(III) on both MIL-100V(III/IV) and MIL-101V(III/IV) that can be protected with water molecules, and which associated CO2/CH4/N2/O2 adsorption properties on these two mesoporous V-MOFs were investigated. The protective properties of water were investigated and evaluated using density functional theory simulations. The binding energy of single O2 on open-metal V(III) site was 93.278 kJ/mol, which decreased to 26.5 kJ/mol when H2O occupies the site. When the water coating is removed, the X-ray photoelectron spectroscopy pattern of V2p showed that the V-MOF changes to MIL-100V(IV) and MIL-101V(IV) at 298 K because of the action of O2. Under these conditions, O2 binds strongly on the open V site significantly reducing the BET (Brunauer-Emmett-Teller) surface and CH4 adsorption volume of the V-MOFs. From the ideal adsorbed solution theory calculated, the adsorption selectivity of CH4/N2 is higher before than after binding of O2 (with V(III) site). In contrast, the adsorption selectivity of CO2/CH4 is higher after than before O2 binding (with no more V(III) sites). Copyright © 2015 Elsevier Inc. All rights reserved.

  17. Forensic Science Center

    SciTech Connect

    Andresen, B.; Grant, P.M.

    1994-03-01

    Since 1991, the Laboratory's Forensic Science Center has focused a comprehensive range of analytical expertise on issues related to non proliferation, counterterrorism, and domestic law enforcement. During this short period, LLNL's singular combination of human and technological resources has made the Center among the best of its kind in the world. The Forensic Science Center houses a variety of state-of-the-art analytical tools ranging from gas chromatograph/mass spectrometers to ultratrace DNA detection techniques. The Center's multidisciplinary staff provides expertise in organic and inorganic analytical chemistry, nuclear science, biochemistry, and genetics useful for supporting law enforcement and for verifying compliance with international treaties and agreements.

  18. Data Center at NICT

    NASA Technical Reports Server (NTRS)

    Ichikawa, Ryuichi; Sekido, Mamoru

    2013-01-01

    The Data Center at the National Institute of Information and Communications Technology (NICT) archives and releases the databases and analysis results processed at the Correlator and the Analysis Center at NICT. Regular VLBI sessions of the Key Stone Project VLBI Network were the primary objective of the Data Center. These regular sessions continued until the end of November 2001. In addition to the Key Stone Project VLBI sessions, NICT has been conducting geodetic VLBI sessions for various purposes, and these data are also archived and released by the Data Center.

  19. 13. SAC command center, weather center, underground structure, building 501, ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    13. SAC command center, weather center, underground structure, building 501, undated - Offutt Air Force Base, Strategic Air Command Headquarters & Command Center, Command Center, 901 SAC Boulevard, Bellevue, Sarpy County, NE

  20. Magnetic endohedral transition-metal-doped semiconducting-nanoclusters.

    PubMed

    Matxain, Jon M; Formoso, Elena; Mercero, Jose M; Piris, Mario; Lopez, Xabier; Ugalde, Jesus M

    2008-01-01

    Endohedral first-row transition-metal-doped TM@Zn(i)S(i) nanoclusters, in which TM stands for the first-row transition-metals from Sc to Zn, and i=12, 16, have been characterized. In these structures the dopant metals are trapped inside spheroidal hollow semiconducting nanoclusters. It is observed that some of the transition metals are trapped in the center of mass of the cluster, whereas others are found to be displaced from that center, leading to structures in which the transition metals display a complex dynamical behavior upon encapsulation. This fact was confirmed by quantum molecular dynamics calculations, which further confirmed the thermal stability of endohedral compounds. In the endohedrally-doped nanoclusters in which the transition-metal atom sits on the center of mass, the host hollow cluster structure remains undistorted after dopant encapsulation. Conversely, if the encapsulated transition-metal atom is displaced from the center of mass, the host hollow cluster structure suffers a very tiny distortion. Additionally, it is found that there is negligible charge transfer between the dopant transition-metal atom and its hollow cluster host and, after encapsulation, the spin densities remain localized on the transition-metal atom. This allows for the atomic-like behavior of the trapped transition-metal atom, which gives rise to their atomic-like magnetic properties. The encapsulation free energies are negative, suggesting that these compounds are thermodynamically stable.

  1. Nanoparticles of Low-Valence Vanadium Oxyhydroxides: Reaction Mechanisms and Polymorphism Control by Low-Temperature Aqueous Chemistry.

    PubMed

    Besnardiere, Julie; Petrissans, Xavier; Ribot, François; Briois, Valérie; Surcin, Christine; Morcrette, Mathieu; Buissette, Valérie; Le Mercier, Thierry; Cassaignon, Sophie; Portehault, David

    2016-11-07

    An aqueous synthetic route at 95 °C is developed to reach selectively three scarcely reported vanadium oxyhydroxides. Häggite V2O3(OH)2, Duttonite VO(OH)2, and Gain's hydrate V2O4(H2O)2 are obtained as nanowires, nanorods, and nanoribbons, with sizes 1 order of magnitude smaller than previously reported. X-ray absorption spectroscopy provides evidence that vanadium in these phases is V(+IV). Combined with FTIR, XRD, and electron microscopy, it yields the first insights into formation mechanisms, especially for Häggite and Gain's hydrate. This study opens the way for further investigations of the properties of novel V(+IV) (oxyhydr)oxides nanostructures.

  2. Extended metal-atom chains with an inert second row transition metal: [Ru5(mu5-tpda)4X2] (tpda2- = tripyridyldiamido dianion, X = Cl and NCS).

    PubMed

    Yin, Caixia; Huang, Gin-Chen; Kuo, Ching-Kuo; Fu, Ming-Dung; Lu, Hao-Cheng; Ke, Jhih-Hong; Shih, Kai-Neng; Huang, Yi-Lin; Lee, Gene-Hsiang; Yeh, Chen-Yu; Chen, Chun-hsien; Peng, Shie-Ming

    2008-08-06

    EMACs (extended metal-atom chains) offer a unique platform for the exploration of metal-metal interactions. There has been significant advances on the synthesis of EMACs, such as lengthening the chains up to 11 metal atoms thus far, integrating naphthyridine moieties for tuning the charge carried at metal centers, and manipulation of metal-metal interactions. However, the metal centers in EMACs hitherto are limited to first row transition metals which are more labile than those relatively inert ones with electrons filled in the 4d and 5d shells. In this Communication, the synthesis, crystallographic, magnetic, and electrical conducting studies of [Ru5(mu5-tpda)4Cl2] and [Ru5(mu5-tpda)4(NCS)2], the first pentanuclear EMACs of second-row transition metal, are reported.

  3. Two Approaches to Rehabilitation of Metal Roofing at Wheeler Army Airfield Hawaii

    DTIC Science & Technology

    2009-02-01

    Center Approach/Technologies • Polyurea coating over existing metal roof • New metal roofing system over existing metal roof US Army Corps of Engineers...Engineer Research & Development Center Wheeler Army Airfield US Army Corps of Engineers Engineer Research & Development Center Polyurea Coating... Polyurea Coating Restoration Existing Conditions • Overlay with coating • Some rusting • Persistent leaking US Army Corps of Engineers Engineer

  4. Heavy Metal.

    ERIC Educational Resources Information Center

    Black, Susan

    2001-01-01

    The Centers for Disease Control and Prevention (CDC) estimate that more than 1 million children ages 5 and under are afflicted with unsafe amounts of lead. Schools can be a source of lead poisoning. Other sources include playgrounds near freeways, playground equipment, contaminated soil, and technology rooms with lead-bearing supplies. Sidebars…

  5. Heavy Metal.

    ERIC Educational Resources Information Center

    Black, Susan

    2001-01-01

    The Centers for Disease Control and Prevention (CDC) estimate that more than 1 million children ages 5 and under are afflicted with unsafe amounts of lead. Schools can be a source of lead poisoning. Other sources include playgrounds near freeways, playground equipment, contaminated soil, and technology rooms with lead-bearing supplies. Sidebars…

  6. Handbook for Learning Centers.

    ERIC Educational Resources Information Center

    Norwalk Board of Education, CT.

    The handbook for learning centers contains guidelines, forms, and supplementary information to be used with all children identified as having a learning disability, mild retardation, or sensory deprivation in the Norwalk, Connecticut public schools. It is stressed that the learning center should provide supportive services for at least 35 minutes…

  7. Outfitting Campus Fitness Centers.

    ERIC Educational Resources Information Center

    Fickes, Michael

    1999-01-01

    Explains how universities and colleges, both private and public, are including fitness centers as ways of increasing their student enrollment levels. Comments are provided on school experiences in fitness-center design, equipment purchasing, and maintenance and operating-costs issues. (GR)

  8. Simple Machine Science Centers

    ERIC Educational Resources Information Center

    Chessin, Debby

    2007-01-01

    Science centers can engage students; accommodate different learning styles and individual interests; help students become independent and confident learners; and encourage social skills among students. In this article, the author worked with third-grade students as they completed activities at learning centers during a week-long unit on simple…

  9. Science Center and Attitude

    ERIC Educational Resources Information Center

    Daneshamooz, Saeed; Alamolhodaei, Hassan; Darvishian, Saeed; Daneshamooz, Soniya

    2013-01-01

    The project team gathered data with the assistance of Recreational and Cultural Organization of Mashhad Municipality, Organization of Mashhad Municipality and Science and Astronomy Science Center of Mashhad Municipality, Khorasan Razavi, Islamic Republic of Iran. This paper discusses the effect of science center on attitude of students who visit…

  10. Accredited Birth Centers

    MedlinePlus

    ... Bellingham, WA 98225 360-752-2229 Accredited since July 2015 Best Start Birth Center Accredited 3343 4th Avenue San Diego, CA 92103 619-299-0840 ... Corvallis, OR 97330 541-286-4030 Accredited since July 2017 Dar a Luz Birth and Health Center Accredited 7708 4th Street NW Los Ranchos, NM 87107 505-924- ...

  11. Assessing the Assessment Center.

    ERIC Educational Resources Information Center

    LaRue, James

    1989-01-01

    Describes the historical use of assessment centers as staff development and promotional tools and their current use in personnel selection. The elements that constitute a true assessment center are outlined, and a discussion of the advantages and disadvantages for employers and applicants focuses on positions in library administration. (10…

  12. NASA News Center

    NASA Image and Video Library

    2003-10-31

    The NASA News Center, seen here, is the hub of news operations for the media, providing information and contacts about Space Shuttle processing and other activities around KSC. News Center staff also conduct media tours, escorting journalists and photo/videographers to key sites such as the launch pads and Vehicle Assembly Building as needed.

  13. Developing a Teacher Center.

    ERIC Educational Resources Information Center

    Parsons, Theodore W.

    This paper begins by outlining six functions of a teacher center that are seen as generally accepted and by remarking on certain realities, like the overworked teacher and dearth of funds, that are pertinent to establishing a teacher center. The majority of the text is devoted to an explanation of a large number of specific principles that should…

  14. The Alexandria Research Center

    Treesearch

    John T. Cassady; William F. Mann

    1954-01-01

    This booklet describes the work of the Alexandria Research Center. The Center is a field unit of the Southern Forest Experiment Station, Forest Service, U. S. Department of Agriculture. Its special mission is to find practical solutions to the most urgent land-management problems of the cutover longleaf pine lands west of the Mississippi River. The...

  15. Student Media Center Manual.

    ERIC Educational Resources Information Center

    Ellis, Dorothy Ann

    A simple guide to using the schools media center is provided. Students are told how to find and use the print and nonprint resources in the media center, including the card catalog, microfilm, video and audio equipment, and films and filmstrips. (SK)

  16. Simple Machine Science Centers

    ERIC Educational Resources Information Center

    Chessin, Debby

    2007-01-01

    Science centers can engage students; accommodate different learning styles and individual interests; help students become independent and confident learners; and encourage social skills among students. In this article, the author worked with third-grade students as they completed activities at learning centers during a week-long unit on simple…

  17. GSFC VLBI Analysis Center

    NASA Technical Reports Server (NTRS)

    Gordon, David; Ma, Chopo; MacMillan, Dan; Gipson, John; Bolotin, Sergei; Le Bail, Karine; Baver, Karen

    2013-01-01

    This report presents the activities of the GSFC VLBI Analysis Center during 2012. The GSFC VLBI Analysis Center analyzes all IVS sessions, makes regular IVS submissions of data and analysis products, and performs research and software development aimed at improving the VLBI technique.

  18. World Saver Center.

    ERIC Educational Resources Information Center

    Kennedy, Theresa; And Others

    Conservation is a concern for all cultures, and children are familiar with this concept because of recycling in their homes and home towns. The World Saver Center, an example of the thematic approach to learning, is designed to allow children to experiment with concepts of conservation in a familiar setting. The center, designed to resemble an…

  19. One Stop Career Center.

    ERIC Educational Resources Information Center

    Wilson, Patricia

    With the aid of a U.S. Department of Labor grant, a number of one-stop career centers are being developed or have been implemented in California. A one-stop career center is a physical and electronic site where comprehensive services to job seekers and employers are available. These services include the following: assessment and eligibility…

  20. Early Childhood Centers

    ERIC Educational Resources Information Center

    Butin, Dan; Woolums, Jennifer

    2009-01-01

    Early childhood centers have become a common and necessary part of millions of Americans' lives. More women in the workforce, longer workweeks, and educational research supporting the importance of early education have all contributed to the rise of early childhood centers throughout the United States. Today, more than 30 percent of children under…

  1. GSFC VLBI Analysis center

    NASA Technical Reports Server (NTRS)

    Gordon, David; Ma, Chopo; MacMillan, Dan; Petrov, Leonid; Baver, Karen

    2005-01-01

    This report presents the activities of the GSFC VLBI Analysis Center during 2004. The GSFC Analysis Center analyzes all IVS sessions, makes regular IVS submissions of data and analysis products, and performs research and software development activities aimed at improving the VLBI technique.

  2. The Revitalized Tutoring Center

    ERIC Educational Resources Information Center

    Koselak, Jeremy

    2017-01-01

    One high-leverage strategy rooted in a strong research base--the revitalized tutoring center--provides a wealth of opportunity to students who may be otherwise underserved. This embedded, open-all-day tutoring center supports collaborative teacher teams by using peer tutors and community volunteers. By centralizing resources and providing supports…

  3. Science Center and Attitude

    ERIC Educational Resources Information Center

    Daneshamooz, Saeed; Alamolhodaei, Hassan; Darvishian, Saeed; Daneshamooz, Soniya

    2013-01-01

    The project team gathered data with the assistance of Recreational and Cultural Organization of Mashhad Municipality, Organization of Mashhad Municipality and Science and Astronomy Science Center of Mashhad Municipality, Khorasan Razavi, Islamic Republic of Iran. This paper discusses the effect of science center on attitude of students who visit…

  4. The Revitalized Tutoring Center

    ERIC Educational Resources Information Center

    Koselak, Jeremy

    2017-01-01

    One high-leverage strategy rooted in a strong research base--the revitalized tutoring center--provides a wealth of opportunity to students who may be otherwise underserved. This embedded, open-all-day tutoring center supports collaborative teacher teams by using peer tutors and community volunteers. By centralizing resources and providing supports…

  5. Assessing the Assessment Center.

    ERIC Educational Resources Information Center

    LaRue, James

    1989-01-01

    Describes the historical use of assessment centers as staff development and promotional tools and their current use in personnel selection. The elements that constitute a true assessment center are outlined, and a discussion of the advantages and disadvantages for employers and applicants focuses on positions in library administration. (10…

  6. National Technology Transfer Center

    NASA Technical Reports Server (NTRS)

    Rivers, Lee W.

    1992-01-01

    Viewgraphs on the National Technology Transfer Center (NTTC) are provided. The NTTC mission is to serve as a hub for the nationwide technology-transfer network to expedite the movement of federally developed technology into the stream of commerce. A description of the Center is provided.

  7. NASA Propagation Information Center

    NASA Technical Reports Server (NTRS)

    Smith, Ernest K.; Flock, Warren L.

    1989-01-01

    The NASA Propagation Information Center became formally operational in July 1988. It is located in the Department of Electrical and Computer Engineering of the University of Colorado at Boulder. The Center is several things: a communications medium for the propagation with the outside world, a mechanism for internal communication within the program, and an aid to management.

  8. Tribal Business Assistance Center.

    ERIC Educational Resources Information Center

    Lansdowne, Michele

    The Salish Kootenai College Tribal Business Assistance Center was established in 1994 to provide technical assistance to individuals who are pursuing a small business. The center assists the entrepreneur by way of individual consultation with business advisors, small business workshops, and business administration courses that have been created…

  9. Funding Opportunity: Genomic Data Centers

    Cancer.gov

    Funding Opportunity CCG, Funding Opportunity Center for Cancer Genomics, CCG, Center for Cancer Genomics, CCG RFA, Center for cancer genomics rfa, genomic data analysis network, genomic data analysis network centers,

  10. ARO Geoscience Center fellowships

    NASA Astrophysics Data System (ADS)

    Vonderhaar, Thomas H.; Behunek, Jan L.; Bringi, Viswanathan N.; Brubaker, Thomas H.; Julien, Pierre Y.

    1992-01-01

    The fellowship grant was supported by the ARO Center for Geosciences located at the Foothills Campus at Colorado State University under the auspices of the Cooperative Institute for Research in the Atmosphere (CIRA). The center for Geosciences at Colorado State University was established in collaboration with the Army Research Office on October 1, 1986. The center brought together a wide range of expertise into one focused multidisciplinary research framework. Under the administrative structure of CIRA, the center involved investigators from the University's Departments of Atmospheric Science, Civil Engineering, Electrical Engineering, Earth Resources, Forest and Wood Science, Physics, and Psychology. The technical components of the center are in atmospheric and surface remote and in-situ sensing; atmospheric modeling; hydrologic modeling; and geoscience information extraction.

  11. Clad metal joint closure

    SciTech Connect

    Siebert, O.W.

    1985-04-09

    A plasma arc spray overlay of cladding metals is used over joints between clad metal pieces to provide a continuous cladding metal surface. The technique permits applying an overlay of a high melting point cladding metal to a cladding metal surface without excessive heating of the backing metal.

  12. Twinning in nanocrystalline fcc and bcc metals

    NASA Astrophysics Data System (ADS)

    Boyko, Vladimir S.; Kezerashvili, Roman Ya.

    2013-03-01

    The deformation twinning in nanocrystalline (nc) face-centered cubic (fcc) metals, body-centered cubic (bcc) metals, and in nc Si is analyzed. The phenomenological approach is used to make a bridge between microscopical mechanisms of twin nucleation and macroscopical characteristics of twinning with different crystal structures and to calculate the grain size range of the twinning propensity, the requisite external stress for twinning propagation in nc polycrystals, and the grain size at which the slip begins to prevail over the twinning. The developed approach allows to derive analytical expressions and estimate lower and and upper limits of grain sizes at which a twinning propensity is occurred. Results of calculations for the nc fcc metals Al, Cu, Ni, Pd, Au, nc bcc metals Ta, Fe, Mo, W, Nb, and nc diamond-cubic Si are compared with the experimental data, otherwise predictions are made.

  13. Broadband monolithic extractor for metal-metal waveguide based terahertz quantum cascade laser frequency combs

    NASA Astrophysics Data System (ADS)

    Rösch, Markus; Benea-Chelmus, Ileana-Cristina; Bonzon, Christopher; Süess, Martin J.; Beck, Mattias; Faist, Jérôme; Scalari, Giacomo

    2017-07-01

    We present a monolithic solution to extract efficiently light from terahertz quantum cascade lasers with metal-metal waveguides suitable for broadband frequency comb applications. The design is optimized for a bandwidth of 400 GHz around a center frequency of 2.5 THz. A five-fold increase in total output power is observed compared to standard metal-metal waveguides. The extractor features a single-lobed far-field pattern and increases the frequency comb dynamical range to cover more than 50% of the laser dynamic range. Frequency comb operation up to a spectral bandwidth of 670 GHz is achieved.

  14. Transition metal oxide nanowires synthesized by heating metal substrates

    SciTech Connect

    Yan, Hui; Sun, Yi; He, Lin; Nie, Jia-Cai

    2011-11-15

    Highlights: {center_dot} This paper describes a simple and general method to synthesize 3d metal oxide nanowires. {center_dot} Self-catalysis growth mechanism was proposed to explain the growth of the nanowires. {center_dot} The temperature range for the growth of nanowires was estimated by taking into account the Gibbs free energy of reaction. {center_dot} This synthesis approach could be applied to synthesize other one-dimensional structures, such as FeSe and Bi{sub 2}Te{sub 3} nanowires. -- Abstract: Here we reported a simple method to synthesize transition metal oxide nanowires. Copper oxide (CuO), zinc oxide (ZnO), and cobalt oxide (Co{sub 3}O{sub 4}) nanowires were synthesized by heating the copper, zinc, and cobalt substrates under atmosphere condition. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were used to analyze the morphology and microstructure of the nanowires. According to our experimental results, self-catalysis growth mechanism was proposed to explain the growth of the nanowires. The temperature window for the growth of nanowires was estimated by taking into account the Gibbs free energy of reaction. The synthesis approach observed in our experiment could be applied to synthesize other one-dimensional structures, such as FeSe and Bi{sub 2}Te{sub 3} nanowires.

  15. Energy efficient data centers

    SciTech Connect

    Tschudi, William; Xu, Tengfang; Sartor, Dale; Koomey, Jon; Nordman, Bruce; Sezgen, Osman

    2004-03-30

    Data Center facilities, prevalent in many industries and institutions are essential to California's economy. Energy intensive data centers are crucial to California's industries, and many other institutions (such as universities) in the state, and they play an important role in the constantly evolving communications industry. To better understand the impact of the energy requirements and energy efficiency improvement potential in these facilities, the California Energy Commission's PIER Industrial Program initiated this project with two primary focus areas: First, to characterize current data center electricity use; and secondly, to develop a research ''roadmap'' defining and prioritizing possible future public interest research and deployment efforts that would improve energy efficiency. Although there are many opinions concerning the energy intensity of data centers and the aggregate effect on California's electrical power systems, there is very little publicly available information. Through this project, actual energy consumption at its end use was measured in a number of data centers. This benchmark data was documented in case study reports, along with site-specific energy efficiency recommendations. Additionally, other data center energy benchmarks were obtained through synergistic projects, prior PG&E studies, and industry contacts. In total, energy benchmarks for sixteen data centers were obtained. For this project, a broad definition of ''data center'' was adopted which included internet hosting, corporate, institutional, governmental, educational and other miscellaneous data centers. Typically these facilities require specialized infrastructure to provide high quality power and cooling for IT equipment. All of these data center types were considered in the development of an estimate of the total power consumption in California. Finally, a research ''roadmap'' was developed through extensive participation with data center professionals, examination of case

  16. Characterization of new color center and transition metal ion lasers

    SciTech Connect

    Carrig, T.J.

    1992-01-01

    This thesis describes efforts to develop and characterize promising new solid-state laser materials. The author has been interested in lasers in the 1 to 2 [mu]m spectral region, with emphasis on developing a tunable laser at 1.3 [mu]m. The aim is for broadly tunable systems that deliver high continuous-wave (cw) output powers ([approximately]1 W), are efficient, can be diode pumped, can be operated as single longitudinal mode devices (narrow linewidth), and can be used to generate ultrashort (subpicosecond) pulses. This thesis involves the NaCl F[sub 2][sup +]:O[sup 2[minus

  17. Visualization Center Dedicated

    NASA Image and Video Library

    2003-10-17

    The dedication ceremony of the University of Southern Mississippi Center of Higher Learning (CHL) High-Performance Visualization Center at SSC was held Oct. 17. The center's RAVE II 3-D visualization system, available to both on- and off-site scientists, turns data into a fully immersive environment for the user. Cutting the ribbon are, from left, Rear Adm. Thomas Donaldson, commander of the Naval Meteorology and Oceanography Command; Jim Meredith, former director of the CHL; USM President Dr. Shelby Thames; Lt. Gov. Amy Tuck; Dr. Peter Ranelli, director of the CHL; Dewey Herring, chairman of the policy board for the CHL; and former Sen. Cecil Burge.

  18. Visualization Center Dedicated

    NASA Technical Reports Server (NTRS)

    2003-01-01

    The dedication ceremony of the University of Southern Mississippi Center of Higher Learning (CHL) High-Performance Visualization Center at SSC was held Oct. 17. The center's RAVE II 3-D visualization system, available to both on- and off-site scientists, turns data into a fully immersive environment for the user. Cutting the ribbon are, from left, Rear Adm. Thomas Donaldson, commander of the Naval Meteorology and Oceanography Command; Jim Meredith, former director of the CHL; USM President Dr. Shelby Thames; Lt. Gov. Amy Tuck; Dr. Peter Ranelli, director of the CHL; Dewey Herring, chairman of the policy board for the CHL; and former Sen. Cecil Burge.

  19. Visitors Center activities

    NASA Technical Reports Server (NTRS)

    1997-01-01

    Astronaut Katherine Hire and LEGO-Master Model Builders assisted children from Mississippi, Louisiana and Mississippi in the building of a 12-foot tall Space Shuttle made entirely from tiny LEGO bricks at the John C. Stennis Space Center Visitors Center in South Mississippi. The shuttle was part of an exhibit titled ' Travel in Space' World Show which depicts the history of flight and space travel from the Wright brothers to future generations of space vehicles. For more information concerning hours of operation or Visitors Center educational programs, call 1-800-237-1821 in Mississippi and Louisiana or (601) 688-2370.

  20. Visitors Center activities

    NASA Technical Reports Server (NTRS)

    1997-01-01

    More than 2,000 children and adults from Mississippi, Louisiana and Alabama recently build a 12-foot tall Space Shuttle made entirely from tiny LEGO bricks at the John C. Stennis Space Center Visitors Center in South Mississippi. The shuttle was part of an exhibit titled 'Travel in Space' World Show which depicts the history of flight and space travel from the Wright brothers to future generations of space vehicles. For more information concerning hours of operation or Visitors Center educational programs, call 1-800-237-1821 in Mississippi and Louisiana or (601) 688-2370.

  1. Mechanochemical processing for metals and metal alloys

    DOEpatents

    Froes, Francis H.; Eranezhuth, Baburaj G.; Prisbrey, Keith

    2001-01-01

    A set of processes for preparing metal powders, including metal alloy powders, by ambient temperature reduction of a reducible metal compound by a reactive metal or metal hydride through mechanochemical processing. The reduction process includes milling reactants to induce and complete the reduction reaction. The preferred reducing agents include magnesium and calcium hydride powders. A process of pre-milling magnesium as a reducing agent to increase the activity of the magnesium has been established as one part of the invention.

  2. Facility Focus: Athletic Centers.

    ERIC Educational Resources Information Center

    College Planning & Management, 2002

    2002-01-01

    Describes the designs of the Jesse Owens Memorial Stadium at Ohio State University and the fitness center of Scottsdale Community College in Arizona. Discusses design goals and unique features and includes photographs. (EV)

  3. NMA Analysis Center

    NASA Technical Reports Server (NTRS)

    Kierulf, Halfdan Pascal; Andersen, Per Helge

    2013-01-01

    The Norwegian Mapping Authority (NMA) has during the last few years had a close cooperation with Norwegian Defence Research Establishment (FFI) in the analysis of space geodetic data using the GEOSAT software. In 2012 NMA has taken over the full responsibility for the GEOSAT software. This implies that FFI stopped being an IVS Associate Analysis Center in 2012. NMA has been an IVS Associate Analysis Center since 28 October 2010. NMA's contributions to the IVS as an Analysis Centers focus primarily on routine production of session-by-session unconstrained and consistent normal equations by GEOSAT as input to the IVS combined solution. After the recent improvements, we expect that VLBI results produced with GEOSAT will be consistent with results from the other VLBI Analysis Centers to a satisfactory level.

  4. Precision Joining Center

    NASA Technical Reports Server (NTRS)

    Powell, John W.

    1991-01-01

    The establishment of a Precision Joining Center (PJC) is proposed. The PJC will be a cooperatively operated center with participation from U.S. private industry, the Colorado School of Mines, and various government agencies, including the Department of Energy's Nuclear Weapons Complex (NWC). The PJC's primary mission will be as a training center for advanced joining technologies. This will accomplish the following objectives: (1) it will provide an effective mechanism to transfer joining technology from the NWC to private industry; (2) it will provide a center for testing new joining processes for the NWC and private industry; and (3) it will provide highly trained personnel to support advance joining processes for the NWC and private industry.

  5. Principal Center Updates

    NASA Technical Reports Server (NTRS)

    Barry, William

    2001-01-01

    NASA's Occupational Health Program Manager briefed attendees on current Agency initiatives and projects affecting Center Occupational Health personnel. Plans, insight, and expectations for the coming year will be discussed.

  6. Tsukuba VLBI Analysis Center

    NASA Technical Reports Server (NTRS)

    Kurihara, Shinobu; Nozawa, Kentaro

    2013-01-01

    The Tsukuba Analysis Center is funded by the Geospatial Information Authority of Japan (GSI). The c5++ analysis software is regularly used for the IVS-INT2 analysis and the ultra-rapid EOP experiments.

  7. America's Blood Centers

    MedlinePlus

    ... Spokesperson Biographies Statements Logo & Style Guidelines Every two seconds someone needs blood. It's About Life. Please Donate ... from the Foundation for America’s Blood Centers. 2 SECONDS Every 2 seconds, someone in the United States ...

  8. Advanced Cancer Detection Center

    DTIC Science & Technology

    2009-01-01

    Vasculitis Clinical Research Network - Dr. Peter A. Merkel -- Children’s Hospital Medical Center, Cincinnati, OH - Rare Lung Diseases Clinical...cytopenias, including granular lymphocyte leukemia, pure red cell aplasia, and myelodysplastic syndromes; vasculitis disorders; inborn defects in steroid

  9. Proteome Characterization Centers - TCGA

    Cancer.gov

    The centers, a component of NCI’s Clinical Proteomic Tumor Analysis Consortium, will analyze a subset of TCGA samples to define proteins translated from cancer genomes and their related biological processes.

  10. Mental Health Screening Center

    MedlinePlus

    ... to help us make DBSAlliance.org better! Go! Mental Health Screening Center These online screening tools are not ... you have any concerns, see your doctor or mental health professional. Depression This screening form was developed from ...

  11. The EROS Data Center

    USGS Publications Warehouse

    ,

    1975-01-01

    The EROS Data Center, 16 miles (25 km) northeast of Sioux Falls, South Dakota, is operated by the EROS Program to provide access to NASA's LANDSAT [formerly Earth Resources Technology Satellite (ERTS)] imagery, aerial photography acquired by the U.S. Department of the Interior, and photography and imagery acquired by the National Aeronautics and Space Administration (NASA) from research aircraft and from Skylab, Apollo, and Gemini spacecraft. The primary functions of the Center are data storage and reproduction, and user assistance and training. This publication describes the Data Center operations, data products, services, and procedures for ordering remotely sensed data. The EROS Data Center and its principal facility, the 120,000-square-foot (11,200 m2) Karl E. Mundt Federal Building, were dedicated August 7, 1973.

  12. Soviet Mission Control Center

    NASA Technical Reports Server (NTRS)

    2003-01-01

    This photo is an overall view of the Mission Control Center in Korolev, Russia during the Expedition Seven mission. The Expedition Seven crew launched aboard a Soyez spacecraft on April 26, 2003. Photo credit: NASA/Bill Ingalls

  13. Chapels/Worship Centers.

    ERIC Educational Resources Information Center

    American School & University, 2002

    2002-01-01

    Describes the design of notable school chapels and worship centers, including the educational context and design goals. Includes information on architects, suppliers, and cost, as well as photographs. (EV)

  14. Fermi Galactic Center Zoom

    NASA Image and Video Library

    This animation zooms into an image of the Milky Way, shown in visible light, and superimposes a gamma-ray map of the galactic center from NASA's Fermi. Raw data transitions to a view with all known...

  15. Test Control Center

    NASA Technical Reports Server (NTRS)

    2000-01-01

    At the test observation periscope in the Test Control Center exhibit in StenniSphere at the John C. Stennis Space Center in Hancock County, Miss., visitors can observe a test of a Space Shuttle Main Engine exactly as test engineers might see it during a real engine test. The Test Control Center exhibit exactly simulates not only the test control environment, but also the procedure of testing a rocket engine. Designed to entertain while educating, StenniSphere includes informative dispays and exhibits from NASA's lead center for rocket propulsion and remote sensing applications. StenniSphere is open free of charge from 9 a.m. to 5 p.m. daily.

  16. Science Center Goes Underground

    ERIC Educational Resources Information Center

    Modern Schools, 1977

    1977-01-01

    A unique underground science center at Bluffton College, designed to save energy and preserve trees, rolling landscape, and other environmental features of the campus, is under construction in Bluffton, Ohio. (Author)

  17. Facility Focus: Athletic Centers.

    ERIC Educational Resources Information Center

    College Planning & Management, 2002

    2002-01-01

    Describes the designs of the Jesse Owens Memorial Stadium at Ohio State University and the fitness center of Scottsdale Community College in Arizona. Discusses design goals and unique features and includes photographs. (EV)

  18. Test Control Center

    NASA Technical Reports Server (NTRS)

    2000-01-01

    At the test observation periscope in the Test Control Center exhibit in StenniSphere at the John C. Stennis Space Center in Hancock County, Miss., visitors can observe a test of a Space Shuttle Main Engine exactly as test engineers might see it during a real engine test. The Test Control Center exhibit exactly simulates not only the test control environment, but also the procedure of testing a rocket engine. Designed to entertain while educating, StenniSphere includes informative dispays and exhibits from NASA's lead center for rocket propulsion and remote sensing applications. StenniSphere is open free of charge from 9 a.m. to 5 p.m. daily.

  19. A Center for All.

    ERIC Educational Resources Information Center

    Leisner, Hava

    2002-01-01

    Describes the building of Princeton University's $42 million Frist Student Center, which incorporates the original physics building, Palmer Hall, and a new addition. Provides information on the architect, construction manager, and product suppliers. Includes photographs. (EV)

  20. Test Control Center

    NASA Image and Video Library

    2000-10-25

    At the test observation periscope in the Test Control Center exhibit in StenniSphere at the John C. Stennis Space Center in Hancock County, Miss., visitors can observe a test of a Space Shuttle Main Engine exactly as test engineers might see it during a real engine test. The Test Control Center exhibit exactly simulates not only the test control environment, but also the procedure of testing a rocket engine. Designed to entertain while educating, StenniSphere includes informative dispays and exhibits from NASA's lead center for rocket propulsion and remote sensing applications. StenniSphere is open free of charge from 9 a.m. to 5 p.m. daily.

  1. Reliability Centered Maintenance - Methodologies

    NASA Technical Reports Server (NTRS)

    Kammerer, Catherine C.

    2009-01-01

    Journal article about Reliability Centered Maintenance (RCM) methodologies used by United Space Alliance, LLC (USA) in support of the Space Shuttle Program at Kennedy Space Center. The USA Reliability Centered Maintenance program differs from traditional RCM programs because various methodologies are utilized to take advantage of their respective strengths for each application. Based on operational experience, USA has customized the traditional RCM methodology into a streamlined lean logic path and has implemented the use of statistical tools to drive the process. USA RCM has integrated many of the L6S tools into both RCM methodologies. The tools utilized in the Measure, Analyze, and Improve phases of a Lean Six Sigma project lend themselves to application in the RCM process. All USA RCM methodologies meet the requirements defined in SAE JA 1011, Evaluation Criteria for Reliability-Centered Maintenance (RCM) Processes. The proposed article explores these methodologies.

  2. Kennedy Space Center

    NASA Technical Reports Server (NTRS)

    Simpkins, Patrick A.

    2010-01-01

    This slide presentation reviews the importance of the Kennedy Space Center both in terms to the economy of Florida and to spaceflight. It reviews the general NASA direction,the challenges of the coming year and the accomplishments.

  3. Soviet Mission Control Center

    NASA Technical Reports Server (NTRS)

    2003-01-01

    This photo is an overall view of the Mission Control Center in Korolev, Russia during the Expedition Seven mission. The Expedition Seven crew launched aboard a Soyez spacecraft on April 26, 2003. Photo credit: NASA/Bill Ingalls

  4. Metal filled porous carbon

    DOEpatents

    Gross, Adam F.; Vajo, John J.; Cumberland, Robert W.; Liu, Ping; Salguero, Tina T.

    2011-03-22

    A porous carbon scaffold with a surface and pores, the porous carbon scaffold containing a primary metal and a secondary metal, where the primary metal is a metal that does not wet the surface of the pores of the carbon scaffold but wets the surface of the secondary metal, and the secondary metal is interspersed between the surface of the pores of the carbon scaffold and the primary metal.

  5. Combination of metal-metal bonding and antiferromagnetic exchange interaction in the d{sup 2}-d{sup 2} complex [V{sub 2}O(SPh){sub 4}(Me{sub 2}-bpy){sub 2}]{center_dot}THF (Me{sub 2}-bpy = 4,4{prime}-dimethylbipyridine)

    SciTech Connect

    Dean, N.S.; Bartley, S.L.; Streib, W.E.

    1995-03-15

    Synthetic procedures leading to the preparation of V{sup III} and V{sup IV} complexes of PhS{sup {minus}} are described, including the mononuclear complex (NEt{sub 4})[V(SPh){sub 4}(bpy)] (1). Controlled aerial oxidation of its 4,4{prime}-Me{sub 2}-bpy (Me{sub 2}-bpy) analogue generated in situ with 0.5 equiv of O{sub 2} leads to generation of [VO(SPh){sub 3}(Me{sub 2}-bpy)]{sup {minus}} that can be isolated as the NR{sub 4}{sup +} salts; (NMe{sub 4})[VO(SPh){sub 3}(Me{sub 2}-bpy)] (2) has been structurally characterized and contains a distorted-octahedral anion with three equatorial PhS{sup {minus}} groups and one Me{sub 2}-bpy N atom of the chelate trans to the multiply-bonded O atom. The same oxidation reaction with the related ion [V(SPh){sub 2}(bpy){sub 2}]{sup +} leads to [VO(SPh)(bpy){sub 2}](PF{sub 6}) (3). Controlled hydrolysis of [V(SPh){sub 4}(Me{sub 2}-bpy)]{sup {minus}}, generated in situ, leads to isolation of V{sub 2}O(SPh){sub 4}(Me{sub 2}-bpy){sub 2} (4) which has a [V{sub 2}({mu}-O)({mu}-SPh){sub 2}]{sup 2+} core with a terminal PhS{sup {minus}} and chelating Me{sub 2}-bpy on each metal; the V-V separation of 2.579(3) {angstrom} is suggestive of a V{sup III}-V{sup III} single bond. EHT calculations on the model complex V{sub 2}O(SH){sub 4}(NH{sub 3}){sub 4} indicate a V-V {sigma} bond arising from V d{sub z}{sup 2} overlap, with the HOMO and LUMO comprising {delta} and {delta}{sup *} orbitals, respectively, formed by V d{sub xy} orbitals. A small HOMO-LUMO gap ({approx}0.02 eV) suggests the weak room-temperature paramagnetism is due to thermal population of the LUMO. Variable-temperature solid-state studies on 4 indicate an effective magnetic moment per dimer ({mu}{sub eff}/V{sub 2}) of 1.35 {mu}{sub B} at 330 K decreasing to 0.095 {mu}{sub B} at 5.0 K.

  6. Metallic substrates for high temperature superconductors

    DOEpatents

    Truchan, Thomas G.; Miller, Dean J.; Goretta, Kenneth C.; Balachandran, Uthamalingam; Foley, Robert

    2002-01-01

    A biaxially textured face-centered cubic metal article having grain boundaries with misorientation angles greater than about 8.degree. limited to less than about 1%. A laminate article is also disclosed having a metal substrate first rolled to at least about 95% thickness reduction followed by a first annealing at a temperature less than about 375.degree. C. Then a second rolling operation of not greater than about 6% thickness reduction is provided, followed by a second annealing at a temperature greater than about 400.degree. C. A method of forming the metal and laminate articles is also disclosed.

  7. Advanced Cancer Detection Center

    DTIC Science & Technology

    2000-10-01

    flSttfiferrces ReferentHistory Alternative Medicine Alternative and Complementary/Integrative Nutritional Therapies in Cancer Prevention and Treatment ...to meet a clear and compelling need to respond to Florida’s "cancer epidemic." Building a major cancer research and treatment center at the... Medicine . This Department includes all the basic science faculty recruited by the Cancer Center and will be the academic home for a new interdisciplinary

  8. Transportation Systems Center

    SciTech Connect

    Greer, G.S.

    1992-07-01

    The Transportation Systems Center at Sandia Laboratory performs research, development, and implementation of technologies that enhance the safe movement of people, goods, and information. Our focus is on systems engineering. However, we realize that to understand the puzzle, you must also understand the pieces. This brochure describes some of the activities currently underway at the Center and presents the breadth and depth of our capabilities. Please contact the noted, individuals for more, information.

  9. Data center cooling system

    DOEpatents

    Chainer, Timothy J; Dang, Hien P; Parida, Pritish R; Schultz, Mark D; Sharma, Arun

    2015-03-17

    A data center cooling system may include heat transfer equipment to cool a liquid coolant without vapor compression refrigeration, and the liquid coolant is used on a liquid cooled information technology equipment rack housed in the data center. The system may also include a controller-apparatus to regulate the liquid coolant flow to the liquid cooled information technology equipment rack through a range of liquid coolant flow values based upon information technology equipment temperature thresholds.

  10. Patient-centered Communication

    PubMed Central

    Swenson, Sara L; Buell, Stephanie; Zettler, Patti; White, Martha; Ruston, Delaney C; Lo, Bernard

    2004-01-01

    OBJECTIVE To investigate patient preferences for a patient-centered or a biomedical communication style. DESIGN Randomized study. SETTING Urgent care and ambulatory medicine clinics in an academic medical center. PARTICIPANTS We recruited 250 English-speaking adult patients, excluding patients whose medical illnesses prevented evaluation of the study intervention. INTERVENTION Participants watched one of three videotaped scenarios of simulated patient-physician discussions of complementary and alternative medicine (CAM). Each participant watched two versions of the scenario (biomedical vs. patient-centered communication style) and completed written and oral questionnaires to assess outcome measurements. MEASUREMENTS AND MAIN RESULTS Main outcome measures were 1) preferences for a patient-centered versus a biomedical communication style; and 2) predictors of communication style preference. Participants who preferred the patient-centered style (69%; 95% confidence interval [CI], 63 to 75) tended to be younger (82%[51/62] for age < 30; 68%[100/148] for ages 30–59; 55%[21/38] for age > 59; P < .03), more educated (76%[54/71] for postcollege education; 73%[94/128] for some college; 49%[23/47] for high school only; P = .003), use CAM (75%[140/188] vs. 55%[33/60] for nonusers; P = .006), and have a patient-centered physician (88%[74/84] vs. 30%[16/54] for those with a biomedical physician; P < .0001). On multivariate analysis, factors independently associated with preferring the patient-centered style included younger age, use of herbal CAM, having a patient-centered physician, and rating a “doctor's interest in you as a person” as “very important.” CONCLUSIONS Given that a significant proportion of patients prefer a biomedical communication style, practicing physicians and medical educators should strive for flexible approaches to physician-patient communication. PMID:15566435

  11. Patient Safety Center Organization

    DTIC Science & Technology

    2006-06-01

    Enterectomy Bariatric 7/20/05 4 hours/course (28 hours/year) Surgery R 7 Dr. Karen Horvath R5 Lap Enterectomy & Colectomy 11/30/05 4...areas in the UW Schools of Nursing and Dentistry, at the Harborview Research Center Microvascular Surgery lab, with the Seattle Children’s Hospital and...1 laboratory complex (2500 sq ft) has been designed within the University of Washington Medical Center, in the Surgery Pavilion complex

  12. Center for Space Construction

    NASA Technical Reports Server (NTRS)

    Su, Renjeng

    1998-01-01

    The Center for Space Construction (CSC) at University of Colorado at Boulder is one of eight University Space Engineering Research Centers established by NASA in 1988. The mission of the Center is to conduct research into space technology and to directly contribute to space engineering education. The Center reports to the Department of Aerospace Engineering Sciences and resides in the College of Engineering and Applied Sciences. The College has a long and successful track record of cultivating multi-disciplinary research and education programs. The Center for Space Construction represents prominent evidence of this record. The basic concept on which the Center was founded is the in-space construction of large space systems, such as space stations, interplanetary space vehicles, and extraterrestrial space structures. Since 1993, the scope of CSC research has evolved to include the design and construction of all spacecraft, large and small. With the broadened scope our research projects seek to impact the technological basis for spacecraft such as remote sensing satellites, communication satellites and other special-purpose spacecraft, as well as large space platforms. A summary of accomplishments, including student participation and degrees awarded, during the contract period is presented.

  13. Metal Building Insulation System Provides Energy Savings and Noise Control.

    ERIC Educational Resources Information Center

    School Business Affairs, 1979

    1979-01-01

    Thermal efficiency increased substantially when an underdeck metal building insulation system was used at the North Valley Occupational Center, an aircraft mechanic's school located at the edge of the Van Nuys, California, airport. (Author)

  14. Metal Building Insulation System Provides Energy Savings and Noise Control.

    ERIC Educational Resources Information Center

    School Business Affairs, 1979

    1979-01-01

    Thermal efficiency increased substantially when an underdeck metal building insulation system was used at the North Valley Occupational Center, an aircraft mechanic's school located at the edge of the Van Nuys, California, airport. (Author)

  15. 4. Panama Mount. Note concrete ring and metal rail. Note ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    4. Panama Mount. Note concrete ring and metal rail. Note cliff erosion under foundation at left center. Looking 297° W. - Fort Funston, Panama Mounts for 155mm Guns, Skyline Boulevard & Great Highway, San Francisco, San Francisco County, CA

  16. Metallic ions in the equatorial ionosphere

    NASA Technical Reports Server (NTRS)

    Aikin, A. C.; Goldberg, R. A.

    1972-01-01

    Four positive ion composition measurements of the equatorial E region made at Thumba, India, are presented. During the day, the major ions between 90 and 125 km are NO(+) and O2(+). A metallic ion layer centered at 92 km is observed, and found to contain Mg(+), Fe(+), Ca(+), K(+), Al(+), and Na(+) ions. The layer is explained in terms of a similarly shaped latitude distribution of neutral atoms which are photoionized and charge-exchanged with NO(+) and O2(+). Three body reactions form molecular metallic ions which are rapidly lost by dissociative ion-electron recombination. Nighttime observations show downward drifting of the metallic ion layer caused by equatorial dynamo effects. These ions react and form neutral metals which exchange charges with NO(+) and O2(+) to produce an observed depletion of those ions within the metallic ion region.

  17. Reusable Metallic Thermal Protection Systems Development

    NASA Technical Reports Server (NTRS)

    Blosser, Max L.; Martin, Carl J.; Daryabeigi, Kamran; Poteet, Carl C.

    1998-01-01

    Metallic thermal protection systems (TPS) are being developed to help meet the ambitious goals of future reusable launch vehicles. Recent metallic TPS development efforts at NASA Langley Research Center are described. Foil-gage metallic honeycomb coupons, representative of the outer surface of metallic TPS were subjected to low speed impact, hypervelocity impact, rain erosion, and subsequent arcjet exposure. TPS panels were subjected to thermal vacuum, acoustic, and hot gas flow testing. Results of the coupon and panel tests are presented. Experimental and analytical tools are being developed to characterize and improve internal insulations. Masses of metallic TPS and advanced ceramic tile and blanket TPS concepts are compared for a wide range of parameters.

  18. Investigation of Selectively-Reinforced Metallic Lugs

    NASA Technical Reports Server (NTRS)

    Farley, Gary L.; Abada, Christopher H.

    2007-01-01

    An investigation of the effects of material and geometric variables on the response of U-shaped band-reinforced metallic lugs was performed. Variables studied were reinforcement, adhesive and metallic lug mechanical properties, hole diameter, reinforcement and adhesive thickness, and the distance from the hole s center to the end of the lug. Generally, U-shaped band reinforced lugs exhibited superior performance than non-reinforced lugs, that is higher load at the conventional lug design criteria of four percent hole elongation. Depending upon the reinforcement configuration the increase in load may be negligible to 15 or 20 percent. U-shaped band reinforcement increases lug load carrying capability primarily through two mechanisms; increasing the slope of the response curve after the initial knee and restraining overall deformation of the metallic portion of the lug facilitating increased yielding of metallic material between the hole and the edge of the metallic portion of the lug.

  19. Half-metallicity in 2D organometallic honeycomb frameworks

    NASA Astrophysics Data System (ADS)

    Sun, Hao; Li, Bin; Zhao, Jin

    2016-10-01

    Half-metallic materials with a high Curie temperature (T C) have many potential applications in spintronics. Magnetic metal free two-dimensional (2D) half-metallic materials with a honeycomb structure contain graphene-like Dirac bands with π orbitals and show excellent aspects in transport properties. In this article, by investigating a series of 2D organometallic frameworks with a honeycomb structure using first principles calculations, we study the origin of forming half-metallicity in this kind of 2D organometallic framework. Our analysis shows that charge transfer and covalent bonding are two crucial factors in the formation of half-metallicity in organometallic frameworks. (i) Sufficient charge transfer from metal atoms to the molecules is essential to form the magnetic centers. (ii) These magnetic centers need to be connected through covalent bonding, which guarantee the strong ferromagnetic (FM) coupling. As examples, the organometallic frameworks composed by (1,3,5)-benzenetricarbonitrile (TCB) molecules with noble metals (Au, Ag, Cu) show half-metallic properties with T C as high as 325 K. In these organometallic frameworks, the strong electronegative cyano-groups (CN groups) drive the charge transfer from metal atoms to the TCB molecules, forming the local magnetic centers. These magnetic centers experience strong FM coupling through the d-p covalent bonding. We propose that most of the 2D organometallic frameworks composed by molecule—CN—noble metal honeycomb structures contain similar half metallicity. This is verified by replacing TCB molecules with other organic molecules. Although the TCB-noble metal organometallic framework has not yet been synthesized, we believe the development of synthesizing techniques and facility will enable the realization of them. Our study provides new insight into the 2D half-metallic material design for the potential applications in nanotechnology.

  20. Half-metallicity in 2D organometallic honeycomb frameworks.

    PubMed

    Sun, Hao; Li, Bin; Zhao, Jin

    2016-10-26

    Half-metallic materials with a high Curie temperature (T C) have many potential applications in spintronics. Magnetic metal free two-dimensional (2D) half-metallic materials with a honeycomb structure contain graphene-like Dirac bands with π orbitals and show excellent aspects in transport properties. In this article, by investigating a series of 2D organometallic frameworks with a honeycomb structure using first principles calculations, we study the origin of forming half-metallicity in this kind of 2D organometallic framework. Our analysis shows that charge transfer and covalent bonding are two crucial factors in the formation of half-metallicity in organometallic frameworks. (i) Sufficient charge transfer from metal atoms to the molecules is essential to form the magnetic centers. (ii) These magnetic centers need to be connected through covalent bonding, which guarantee the strong ferromagnetic (FM) coupling. As examples, the organometallic frameworks composed by (1,3,5)-benzenetricarbonitrile (TCB) molecules with noble metals (Au, Ag, Cu) show half-metallic properties with T C as high as 325 K. In these organometallic frameworks, the strong electronegative cyano-groups (CN groups) drive the charge transfer from metal atoms to the TCB molecules, forming the local magnetic centers. These magnetic centers experience strong FM coupling through the d-p covalent bonding. We propose that most of the 2D organometallic frameworks composed by molecule-CN-noble metal honeycomb structures contain similar half metallicity. This is verified by replacing TCB molecules with other organic molecules. Although the TCB-noble metal organometallic framework has not yet been synthesized, we believe the development of synthesizing techniques and facility will enable the realization of them. Our study provides new insight into the 2D half-metallic material design for the potential applications in nanotechnology.

  1. An environment-dependent semi-empirical tight binding model suitable for electron transport in bulk metals, metal alloys, metallic interfaces, and metallic nanostructures. I. Model and validation

    SciTech Connect

    Hegde, Ganesh Povolotskyi, Michael; Kubis, Tillmann; Klimeck, Gerhard; Boykin, Timothy

    2014-03-28

    Semi-empirical Tight Binding (TB) is known to be a scalable and accurate atomistic representation for electron transport for realistically extended nano-scaled semiconductor devices that might contain millions of atoms. In this paper, an environment-aware and transferable TB model suitable for electronic structure and transport simulations in technologically relevant metals, metallic alloys, metal nanostructures, and metallic interface systems are described. Part I of this paper describes the development and validation of the new TB model. The new model incorporates intra-atomic diagonal and off-diagonal elements for implicit self-consistency and greater transferability across bonding environments. The dependence of the on-site energies on strain has been obtained by appealing to the Moments Theorem that links closed electron paths in the system to energy moments of angular momentum resolved local density of states obtained ab initio. The model matches self-consistent density functional theory electronic structure results for bulk face centered cubic metals with and without strain, metallic alloys, metallic interfaces, and metallic nanostructures with high accuracy and can be used in predictive electronic structure and transport problems in metallic systems at realistically extended length scales.

  2. Regulating cellular trace metal economy in algae

    DOE PAGES

    Blaby-Haas, Crysten E.; Merchant, Sabeeha S.

    2017-06-30

    As indispensable protein cofactors, Fe, Mn, Cu and Zn are at the center of multifaceted acclimation mechanisms that have evolved to ensure extracellular supply meets intracellular demand. In starting with selective transport at the plasma membrane and ending in protein metalation, metal homeostasis in algae involves regulated trafficking of metal ions across membranes, intracellular compartmentalization by proteins and organelles, and metal-sparing/recycling mechanisms to optimize metal-use efficiency. Overlaid on these processes are additional circuits that respond to the metabolic state as well as to the prior metal status of the cell. Here, we focus on recent progress made toward understanding themore » pathways by which the single-celled, green alga Chlamydomonas reinhardtii controls its cellular trace metal economy. We also compare these mechanisms to characterized and putative processes in other algal lineages. Photosynthetic microbes continue to provide insight into cellular regulation and handling of Cu, Fe, Zn and Mn as a function of the nutritional supply and cellular demand for metal cofactors. We found that new experimental tools such as RNA-Seq and subcellular metal imaging are bringing us closer to a molecular understanding of acclimation to supply dynamics in algae and beyond.« less

  3. Regulating cellular trace metal economy in algae.

    PubMed

    Blaby-Haas, Crysten E; Merchant, Sabeeha S

    2017-10-01

    As indispensable protein cofactors, Fe, Mn, Cu and Zn are at the center of multifaceted acclimation mechanisms that have evolved to ensure extracellular supply meets intracellular demand. Starting with selective transport at the plasma membrane and ending in protein metalation, metal homeostasis in algae involves regulated trafficking of metal ions across membranes, intracellular compartmentalization by proteins and organelles, and metal-sparing/recycling mechanisms to optimize metal-use efficiency. Overlaid on these processes are additional circuits that respond to the metabolic state as well as to the prior metal status of the cell. In this review, we focus on recent progress made toward understanding the pathways by which the single-celled, green alga Chlamydomonas reinhardtii controls its cellular trace metal economy. We also compare these mechanisms to characterized and putative processes in other algal lineages. Photosynthetic microbes continue to provide insight into cellular regulation and handling of Cu, Fe, Zn and Mn as a function of the nutritional supply and cellular demand for metal cofactors. New experimental tools such as RNA-Seq and subcellular metal imaging are bringing us closer to a molecular understanding of acclimation to supply dynamics in algae and beyond. Copyright © 2017 Elsevier Ltd. All rights reserved.

  4. An environment-dependent semi-empirical tight binding model suitable for electron transport in bulk metals, metal alloys, metallic interfaces, and metallic nanostructures. I. Model and validation

    NASA Astrophysics Data System (ADS)

    Hegde, Ganesh; Povolotskyi, Michael; Kubis, Tillmann; Boykin, Timothy; Klimeck, Gerhard

    2014-03-01

    Semi-empirical Tight Binding (TB) is known to be a scalable and accurate atomistic representation for electron transport for realistically extended nano-scaled semiconductor devices that might contain millions of atoms. In this paper, an environment-aware and transferable TB model suitable for electronic structure and transport simulations in technologically relevant metals, metallic alloys, metal nanostructures, and metallic interface systems are described. Part I of this paper describes the development and validation of the new TB model. The new model incorporates intra-atomic diagonal and off-diagonal elements for implicit self-consistency and greater transferability across bonding environments. The dependence of the on-site energies on strain has been obtained by appealing to the Moments Theorem that links closed electron paths in the system to energy moments of angular momentum resolved local density of states obtained ab initio. The model matches self-consistent density functional theory electronic structure results for bulk face centered cubic metals with and without strain, metallic alloys, metallic interfaces, and metallic nanostructures with high accuracy and can be used in predictive electronic structure and transport problems in metallic systems at realistically extended length scales.

  5. Extracting metals directly from metal oxides

    DOEpatents

    Wai, Chien M.; Smart, Neil G.; Phelps, Cindy

    1997-01-01

    A method of extracting metals directly from metal oxides by exposing the oxide to a supercritical fluid solvent containing a chelating agent is described. Preferably, the metal is an actinide or a lanthanide. More preferably, the metal is uranium, thorium or plutonium. The chelating agent forms chelates that are soluble in the supercritical fluid, thereby allowing direct removal of the metal from the metal oxide. In preferred embodiments, the extraction solvent is supercritical carbon dioxide and the chelating agent is selected from the group consisting of .beta.-diketones, halogenated .beta.-diketones, phosphinic acids, halogenated phosphinic acids, carboxylic acids, halogenated carboxylic acids, and mixtures thereof. In especially preferred embodiments, at least one of the chelating agents is fluorinated. The method provides an environmentally benign process for removing metals from metal oxides without using acids or biologically harmful solvents. The chelate and supercritical fluid can be regenerated, and the metal recovered, to provide an economic, efficient process.

  6. Extracting metals directly from metal oxides

    DOEpatents

    Wai, C.M.; Smart, N.G.; Phelps, C.

    1997-02-25

    A method of extracting metals directly from metal oxides by exposing the oxide to a supercritical fluid solvent containing a chelating agent is described. Preferably, the metal is an actinide or a lanthanide. More preferably, the metal is uranium, thorium or plutonium. The chelating agent forms chelates that are soluble in the supercritical fluid, thereby allowing direct removal of the metal from the metal oxide. In preferred embodiments, the extraction solvent is supercritical carbon dioxide and the chelating agent is selected from the group consisting of {beta}-diketones, halogenated {beta}-diketones, phosphinic acids, halogenated phosphinic acids, carboxylic acids, halogenated carboxylic acids, and mixtures thereof. In especially preferred embodiments, at least one of the chelating agents is fluorinated. The method provides an environmentally benign process for removing metals from metal oxides without using acids or biologically harmful solvents. The chelate and supercritical fluid can be regenerated, and the metal recovered, to provide an economic, efficient process. 4 figs.

  7. Characterization of photosynthetic reaction centers by surface-enhanced resonance Raman scattering

    NASA Astrophysics Data System (ADS)

    Chumanov, George D.; Cotton, Therese M.; Zhou, Chengli; Gaul, Dale; Picorel, Rafael; Seibert, Michael

    1993-06-01

    Surface-enhanced Resonance Raman scattering (SERRS) spectra were obtained for the reaction center complexes of the photosynthetic bacterium Rhodobacter sphaeroides (RC) and from photosystem II (PSII) of spinach, adsorbed on Ag and Au surfaces. These preliminary results demonstrate the considerable potential of this technique for selectively exciting resonance Raman scattering from reaction center components within their distinct absorption bands. Because of the high sensitivity afforded by SERRS, spectra could be measured from a single monolayer of reaction centers adsorbed on a metal surface. The surface-sensitivity provides new information indicating the topology of the PSII reaction center 47 kD light-harvesting protein complex. The activity of the PSII reaction center complex adsorbed on metal surfaces was monitored by photochemical reduction of cyt b-559. Measurement of fluorescence emission was shown to be a new and sensitive method for monitoring the structural and functional integrity of the PSII reaction center complex on the metal surface.

  8. Neurotoxicity of metals.

    PubMed

    Caito, Samuel; Aschner, Michael

    2015-01-01

    Metals are frequently used in industry and represent a major source of toxin exposure for workers. For this reason governmental agencies regulate the amount of metal exposure permissible for worker safety. While essential metals serve physiologic roles, metals pose significant health risks upon acute and chronic exposure to high levels. The central nervous system is particularly vulnerable to metals. The brain readily accumulates metals, which under physiologic conditions are incorporated into essential metalloproteins required for neuronal health and energy homeostasis. Severe consequences can arise from circumstances of excess essential metals or exposure to toxic nonessential metal. Herein, we discuss sources of occupational metal exposure, metal homeostasis in the human body, susceptibility of the nervous system to metals, detoxification, detection of metals in biologic samples, and chelation therapeutic strategies. The neurologic pathology and physiology following aluminum, arsenic, lead, manganese, mercury, and trimethyltin exposures are highlighted as classic examples of metal-induced neurotoxicity.

  9. Laser generating metallic components

    NASA Astrophysics Data System (ADS)

    McLean, Marc A.; Shannon, G. J.; Steen, William M.

    1997-04-01

    Recent developments in rapid prototyping have led to the concept of laser generating, the first additive manufacturing technology. This paper presents an innovative process of depositing multi-layer tracks, by fusing successive powder tracks, to generate three dimensional components, thereby offering an alternative to casting for small metal component manufacture. A coaxial nozzle assembly has been designed and manufactured enabling consistent omni-directional multi-layer deposition. In conjunction with this the software route from a CAD drawing to machine code generation has been established. The part is manufactured on a six axes machining center incorporating a 1.8 kW carbon-dioxide laser, providing an integrated opto-mechanical workstation. The part build-up program is controlled by a P150 host computer, linked directly to the DNC machining center. The direct manufacturing route is shown, including initial examples of simple objects (primitives -- cube, cylinder, cone) leading to more complex turbine blade generation, incorporating build-up techniques and the associated mechanical properties.

  10. Building reactive copper center(s) in human carbonic anhydrase II

    PubMed Central

    Song, He; Weitz, Andrew C.; Hendrich, Michael P.; Lewis, Edwin A.; Emerson, Joseph P.

    2014-01-01

    Re-engineering metalloproteins to generate new biologically relevant metal centers is an effective a way to test our understanding of the structural and mechanistic features that steer chemical transformations in biological systems. Here we report thermodynamic data characterizing the formation of two type-2 (T2) copper sites in carbonic anhydrase and experimental evidence showing one of these new copper centers has characteristics similar to a variety of well-characterized copper centers in synthetic models and in enzymatic systems. Human CA II is known to bind two Cu2+ ions; herein, these binding events are explored using modern isothermal titration calorimetry (ITC) techniques that have become a proven method to accurately measure metal-binding thermodynamic parameters. The two Cu2+-binding events have different affinities (Ka ∼ 5 × 1012 and 1 × 1010) and both are enthalpically driven processes. Reconstituting these Cu2+ sites under a range of conditions has allowed us to assign the Cu2+-binding event to the three-histidine, native, metal binding site. Our initial efforts to characterize these Cu2+ sites have yielded data that show distinctive (and noncoupled) EPR signals associated with each copper-binding site, and that this reconstituted enzyme can activate hydrogen peroxide to catalyze the oxidation of 2-aminophenol. PMID:23744511

  11. Lens auto-centering

    NASA Astrophysics Data System (ADS)

    Lamontagne, Frédéric; Desnoyers, Nichola; Doucet, Michel; Côté, Patrice; Gauvin, Jonny; Anctil, Geneviève; Tremblay, Mathieu

    2015-09-01

    In a typical optical system, optical elements usually need to be precisely positioned and aligned to perform the correct optical function. This positioning and alignment involves securing the optical element in a holder or mount. Proper centering of an optical element with respect to the holder is a delicate operation that generally requires tight manufacturing tolerances or active alignment, resulting in costly optical assemblies. To optimize optical performance and minimize manufacturing cost, there is a need for a lens mounting method that could relax manufacturing tolerance, reduce assembly time and provide high centering accuracy. This paper presents a patent pending lens mounting method developed at INO that can be compared to the drop-in technique for its simplicity while providing the level of accuracy close to that achievable with techniques using a centering machine (usually < 5 μm). This innovative auto-centering method is based on the use of geometrical relationship between the lens diameter, the lens radius of curvature and the thread angle of the retaining ring. The autocentering principle and centering test results performed on real optical assemblies are presented. In addition to the low assembly time, high centering accuracy, and environmental robustness, the INO auto-centering method has the advantage of relaxing lens and barrel bore diameter tolerances as well as lens wedge tolerances. The use of this novel lens mounting method significantly reduces manufacturing and assembly costs for high performance optical systems. Large volume productions would especially benefit from this advancement in precision lens mounting, potentially providing a drastic cost reduction.

  12. Metals production

    NASA Technical Reports Server (NTRS)

    Beck, Theodore S.

    1992-01-01

    Existing procedures for design of electrochemical plants can be used for design of lunar processes taking into consideration the differences in environmental conditions. These differences include: 1/6 Earth gravity, high vacuum, solar electrical and heat source, space radiation heat sink, long days and nights, and different availability and economics of materials, energy, and labor. Techniques have already been developed for operation of relatively small scale hydrogen-oxygen fuel cell systems used in the U.S. lunar landing program. Design and operation of lunar aqueous electrolytic process plants appears to be within the state-of-the-art. Finding or developing compatible materials for construction and designing of fused-magma metal winning cells will present a real engineering challenge.

  13. Metals production

    NASA Astrophysics Data System (ADS)

    Beck, Theodore S.

    1992-02-01

    Existing procedures for design of electrochemical plants can be used for design of lunar processes taking into consideration the differences in environmental conditions. These differences include: 1/6 Earth gravity, high vacuum, solar electrical and heat source, space radiation heat sink, long days and nights, and different availability and economics of materials, energy, and labor. Techniques have already been developed for operation of relatively small scale hydrogen-oxygen fuel cell systems used in the U.S. lunar landing program. Design and operation of lunar aqueous electrolytic process plants appears to be within the state-of-the-art. Finding or developing compatible materials for construction and designing of fused-magma metal winning cells will present a real engineering challenge.

  14. Sorption of H2 to open metal sites in a metal-organic framework: a symmetry-adapted perturbation theory analysis.

    PubMed

    Goings, Joshua J; Ohlsen, Suzanna M; Blaisdell, Kara M; Schofield, Daniel P

    2014-09-04

    Metal-organic frameworks (MOFs) show considerable promise as materials for gas storage and separation. Many MOF structures have open metal sites, which allow for coordination of gas molecules to the metal centers. In this work, we use coupled-cluster and symmetry-adapted perturbation theory to probe the interaction between hydrogen gas and unsaturated metal sites in mimic structures based on the MOF HKUST-1. The interactions are of a mixed electrostatic/dispersive nature, with the relative magnitudes of these components dependent on the metal center. The strongest binding was found for magnesium- and zinc-containing MOFs, with an overall interaction energy of -4.5 kcal mol(-1).

  15. "Infotonics Technology Center"

    SciTech Connect

    Fritzemeier, L.; Boysel, M. B.; Smith, D. R.

    2004-09-30

    During this grant period July 15, 2002 thru September 30, 2004, the Infotonics Technology Center developed the critical infrastructure and technical expertise necessary to accelerate the development of sensors, alternative lighting and power sources, and other specific subtopics of interest to Department of Energy. Infotonics fosters collaboration among industry, universities and government and operates as a national center of excellence to drive photonics and microsystems development and commercialization. A main goal of the Center is to establish a unique, world-class research and development facility. A state-of-the-art microsystems prototype and pilot fabrication facility was established to enable rapid commercialization of new products of particular interest to DOE. The Center has three primary areas of photonics and microsystems competency: device research and engineering, packaging and assembly, and prototype and pilot-scale fabrication. Center activities focused on next generation optical communication networks, advanced imaging and information sensors and systems, micro-fluidic systems, assembly and packaging technologies, and biochemical sensors. With targeted research programs guided by the wealth of expertise of Infotonics business and scientific staff, the fabrication and packaging facility supports and accelerates innovative technology development of special interest to DOE in support of its mission and strategic defense, energy, and science goals.

  16. Core Operations of the Metals and Ceramics Information Center (A DoD information Analysis Center)

    DTIC Science & Technology

    1990-08-30

    Stainless Steel 12 Dec 4305 Stellite 31 37 1986 Mar 1306 Type 314 Stainless Steel 8 Mar 4302 L-605 37 Jun 1209 E9310 Steel 12 Jun 4103 Inconel 718 58 Sep...Code Chapter Title Pages 1988 Mar 1301 Types 301 & 302 Stainless Steel 68 Mar 1401 Types 403, 410 & 416 Stainless Steel 34 Jun 1307 Types 316 & 317...440 ok 04 lx N4£ If, 0 4 - , - 1 cc - CO R " - - -40% In i Is I it = : " ,,em u 14II 11 II I II If I II4 II + U I M 0o fm £0 £o -o 410 o es o 1

  17. NATIONAL METAL FINISHING ENVIRONMENTAL R&D PLAN - AN UPDATE

    EPA Science Inventory

    This document is an update to the National Metal Finishing Environmental R&D Plan (EPA/600/R-97/095), dated September 1997. The 1997 Plan and Update are available on the National Metal Finishing Resource Center's web site, www.nmfrc.org. The primary purpose in preparing an up...

  18. A Simple Method for Drawing Chiral Mononuclear Octahedral Metal Complexes

    ERIC Educational Resources Information Center

    Mohamadou, Aminou; Haudrechy, Arnaud

    2008-01-01

    Octahedral transition-metal complexes are involved in a number of reactions and octahedral coordination geometry, frequently observed for metallic centers, includes important topographical stereochemistry. Depending on the number and nature of different ligands, octahedral coordination units with at least two different monodentate ligands give…

  19. A Simple Method for Drawing Chiral Mononuclear Octahedral Metal Complexes

    ERIC Educational Resources Information Center

    Mohamadou, Aminou; Haudrechy, Arnaud

    2008-01-01

    Octahedral transition-metal complexes are involved in a number of reactions and octahedral coordination geometry, frequently observed for metallic centers, includes important topographical stereochemistry. Depending on the number and nature of different ligands, octahedral coordination units with at least two different monodentate ligands give…

  20. Overview of Boiler House and Sheet Metal and Electrical Shops ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    Overview of Boiler House and Sheet Metal and Electrical Shops Building (center - with single large chimney), note the monitor on the original section of the Boiler House Building, view facing north - Kahului Cannery, Plant No. 28, Boiler House, Sheet Metal and Electrical Shops, 120 Kane Street, Kahului, Maui County, HI

  1. Survey: National Meteorological Center

    NASA Technical Reports Server (NTRS)

    1977-01-01

    The National Meteorological Center (NMC) is comprised of three operational divisions (Development, Automation, and Forecast) and an Administrative Division. The Development Division develops and implements mathematical models for forecasting the weather. The Automation Division provides the software and processing services to accommodate the models used in daily forecasts. The Forecasting Division applies a combination of numerical and manual techniques to produce analyses and prognoses up to 120 hr into the future. This guidance material is combined with severe storm information from the National Hurricane Center and the National Severe Storms Forecasting Center to develop locally tailored forecasts by the Weather Service Forecast Offices and, in turn, by the local Weather Service Offices. A very general flow of this information is shown. A more detailed illustration of data flow into, within, and from the NMC is given. The interrelations are depicted between the various meteorological organizations and activities.

  2. International Water Center

    NASA Astrophysics Data System (ADS)

    The urban district of Nancy and the Town of Nancy, France, have taken the initiative of creating an International Center of Water (Centre International de l'Eau à Nancy—NAN.C.I.E.) in association with two universities, six engineering colleges, the Research Centers of Nancy, the Rhine-Meuse Basin Agency, and the Chamber of Commerce and Industry. The aim of this center is to promote research and technology transfer in the areas of water and sanitation. In 1985 it will initiate a research program drawing on the experience of 350 researchers and engineers of various disciplines who have already been assigned to research in these fields. The research themes, the majority of which will be multidisciplinary, concern aspects of hygiene and health, the engineering of industrial processes, water resources, and the environment and agriculture. A specialist training program offering five types of training aimed at university graduates, graduates of engineering colleges, or experts, will start in October 1984.

  3. Earth Science Information Center

    USGS Publications Warehouse

    ,

    1991-01-01

    An ESIC? An Earth Science Information Center. Don't spell it. Say it. ESIC. It rhymes with seasick. You can find information in an information center, of course, and you'll find earth science information in an ESIC. That means information about the land that is the Earth, the land that is below the Earth, and in some instances, the space surrounding the Earth. The U.S. Geological Survey (USGS) operates a network of Earth Science Information Centers that sell earth science products and data. There are more than 75 ESIC's. Some are operated by the USGS, but most are in other State or Federal agencies. Each ESIC responds to requests for information received by telephone, letter, or personal visit. Your personal visit.

  4. MARS Mission research center

    NASA Technical Reports Server (NTRS)

    1991-01-01

    The Mars Mission Research Center (M2RC) is one of nine University Space Engineering Research Centers established by NASA in June 1988. It is a cooperative effort between NCSU and A&T in Greensboro. The goal of the Center is to focus on research and educational technologies for planetary exploration with particular emphasis on Mars. The research combines Mission Analysis and Design, Hypersonic Aerodynamics and Propulsion, Structures and Controls, Composite Materials, and Fabrication Methods in a cross-disciplined program directed towards the development of space transportation systems for lunar and planetary travel. The activities of the students and faculty in the M2RC for the period 1 Jul. 1990 to 30 Jun. 1991 are described.

  5. Virtual center arraying

    NASA Technical Reports Server (NTRS)

    Deutsch, L. J.; Lipes, R. G.; Miller, R. L.

    1981-01-01

    Methods to increase the amount of data that can be received from outer planet missions are described with emphasis on antenna arraying systems designed to increase the total effective aperture of the receiving system. One such method is virtual center arraying (VCA). In VCA, a combined carrier reference is derived at a point that is, conceptually, the geometric center of the array. This point need not coincide with any of the actual antennas of the array. A noise analysis of the VCA system is given along with formulas for the phase jitter as a function of loop bandwidths and the amount of loop damping. If the ratio of the loop bandwidths of the center loop to the vertex loops is greater than 100, then the jitter is very nearly equal to that expected for ideal combined carrier referencing.

  6. Metallic Winds in Dwarf Galaxies

    NASA Astrophysics Data System (ADS)

    Robles-Valdez, F.; Rodríguez-González, A.; Hernández-Martínez, L.; Esquivel, A.

    2017-02-01

    We present results from models of galactic winds driven by energy injected from nuclear (at the galactic center) and non-nuclear starbursts. The total energy of the starburst is provided by very massive young stellar clusters, which can push the galactic interstellar medium and produce an important outflow. Such outflow can be a well or partially mixed wind, or a highly metallic wind. We have performed adiabatic 3D N-Body/Smooth Particle Hydrodynamics simulations of galactic winds using the gadget-2 code. The numerical models cover a wide range of parameters, varying the galaxy concentration index, gas fraction of the galactic disk, and radial distance of the starburst. We show that an off-center starburst in dwarf galaxies is the most effective mechanism to produce a significant loss of metals (material from the starburst itself). At the same time, a non-nuclear starburst produces a high efficiency of metal loss, in spite of having a moderate to low mass loss rate.

  7. Metal halide perovskite light emitters

    PubMed Central

    Kim, Young-Hoon; Cho, Himchan; Lee, Tae-Woo

    2016-01-01

    Twenty years after layer-type metal halide perovskites were successfully developed, 3D metal halide perovskites (shortly, perovskites) were recently rediscovered and are attracting multidisciplinary interest from physicists, chemists, and material engineers. Perovskites have a crystal structure composed of five atoms per unit cell (ABX3) with cation A positioned at a corner, metal cation B at the center, and halide anion X at the center of six planes and unique optoelectronic properties determined by the crystal structure. Because of very narrow spectra (full width at half-maximum ≤20 nm), which are insensitive to the crystallite/grain/particle dimension and wide wavelength range (400 nm ≤ λ ≤ 780 nm), perovskites are expected to be promising high-color purity light emitters that overcome inherent problems of conventional organic and inorganic quantum dot emitters. Within the last 2 y, perovskites have already demonstrated their great potential in light-emitting diodes by showing high electroluminescence efficiency comparable to those of organic and quantum dot light-emitting diodes. This article reviews the progress of perovskite emitters in two directions of bulk perovskite polycrystalline films and perovskite nanoparticles, describes current challenges, and suggests future research directions for researchers to encourage them to collaborate and to make a synergetic effect in this rapidly emerging multidisciplinary field. PMID:27679844

  8. Hospitals report on cancer centers.

    PubMed

    Rees, T

    2001-01-01

    Woman's Hospital, Baton Rouge, La., is first-place winner among cancer centers. Holy Cross Hospital's Michael and Dianne Bienes Comprehensive Cancer Center, Ft. Lauderdale, Fla., is named second; and, Cardinal Health System's Ball Cancer Center, Muncie, Ind., third.

  9. Metal-phosphate binders

    DOEpatents

    Howe, Beth Ann [Lewistown, IL; Chaps-Cabrera, Jesus Guadalupe [Coahuila, MX

    2009-05-12

    A metal-phosphate binder is provided. The binder may include an aqueous phosphoric acid solution, a metal-cation donor including a metal other than aluminum, an aluminum-cation donor, and a non-carbohydrate electron donor.

  10. Patient-centered Care.

    PubMed

    Reynolds, April

    2009-01-01

    Patient-centered care focuses on the patient and the individual's particular health care needs. The goal of patient-centered health care is to empower patients to become active participants in their care. This requires that physicians, radiologic technologists and other health care providers develop good communication skills and address patient needs effectively. Patient-centered care also requires that the health care provider become a patient advocate and strive to provide care that not only is effective but also safe. For radiologic technologists, patient-centered care encompasses principles such as the as low as reasonably achievable (ALARA) concept and contrast media safety. Patient-centered care is associated with a higher rate of patient satisfaction, adherence to suggested lifestyle changes and prescribed treatment, better outcomes and more cost-effective care. This article is a Directed Reading. Your access to Directed Reading quizzes for continuing education credit is determined by your area of interest. For access to other quizzes, go to www.asrt.org/store. According to one theory, most patients judge the quality of their healthcare much like they rate an airplane flight. They assume that the airplane is technically viable and is being piloted by competent people. Criteria for judging a particular airline are personal and include aspects like comfort, friendly service and on-time schedules. Similarly, patients judge the standard of their healthcare on nontechnical aspects, such as a healthcare practitioner's communication and "soft skills." Most are unable to evaluate a practitioner's level of technical skill or training, so the qualities they can assess become of the utmost importance in satisfying patients and providing patient-centered care.(1).

  11. Metal-Coated Optical Fibers for High Temperature Applications

    NASA Technical Reports Server (NTRS)

    Zeakes, Jason; Murphy, Kent; Claus, Richard; Greene, Jonathan; Tran, Tuan

    1996-01-01

    This poster will highlight on-going research at the Virginia Tech Fiber & Electro-Optics Research Center (FEORC) in the area of thin films on optical fibers. Topics will include the sputter deposition of metals and metal; alloys onto optical fiber and fiber optic sensors for innovative applications. Specific information will be available on thin film fiber optic hydrogen sensors, corrosion sensors, and metal-coated optical fiber for high temperature aerospace applications.

  12. Mars mission research center

    NASA Technical Reports Server (NTRS)

    1988-01-01

    The Mars Mission Research Center is one of nine University Space Engineering Research Centers established by NASA to broaden the nation's engineering capability to meet the critical needs of the civilian space program. It has the goal of focusing on research and training technologies for planetary exploration with particular emphasis on Mars. The research combines: (1) composite materials and fabrication, (2) light weight structures and controls, and (3) hypersonic aerodynamics and propulsion in a cross disciplined program directed towards the development of the space transportation system for planetary travel.

  13. Vet Centers. Final rule.

    PubMed

    2016-03-02

    The Department of Veterans Affairs (VA) adopts as final an interim final rule that amends its medical regulation that governs Vet Center services. The National Defense Authorization Act for Fiscal Year 2013 (the 2013 Act) requires Vet Centers to provide readjustment counseling services to broader groups of veterans, members of the Armed Forces, including a member of a reserve component of the Armed Forces, and family members of such veterans and members. This final rule adopts as final the regulatory criteria to conform to the 2013 Act, to include new and revised definitions.

  14. Ocean Pollution Research Center

    SciTech Connect

    Not Available

    1994-10-01

    The Ocean Pollution Research Center (OPRC) is a University of Miami center based at the Rosenstiel School of Marine and Atmospheric Science (RSMAS) and with significant involvement by the College of Engineering. It was formed in 1992 out of concerns for potential oil spills placing at risk the fragile ecosystems of the Florida Keys. OPRC's scope also includes the Caribbean Sea, Gulf of Mexico, and the South Atlantic Bight. Focus is on the physical transport of oil spills and information management for response operations. Studies of the fates and effects of oil spills are also undertaken.

  15. Minor Planet Center

    NASA Technical Reports Server (NTRS)

    Marsden, Brian G.

    1999-01-01

    This paper reports on the activities of the Minor Planet Center for the year of 1998. The main product of this center is the Minor Planet Circulars, augmented by the Minor Planet Circulars Supplement which is a new series introduced in 1997 to include the actual observations, which are now only summarized MPC. The introduction of the Daily Orbit Update (DOU) lists all the orbits computed and identification found since the previous issue. There has been a fivefold increase in the reported Near Earth Objects, which includes the addition of 55 potentially hazardous asteroids.

  16. Emergency Operation Center

    NASA Technical Reports Server (NTRS)

    Chinea, Anoushka Z.

    1995-01-01

    The Emergency Operation Center (EOC) is a site from which NASA LaRC Emergency Preparedness Officials exercise control and direction in an emergency. Research was conducted in order to determine what makes an effective EOC. Specifically information concerning the various types of equipment and communication capability that an efficient EOC should contain (i.e., computers, software, telephone systems, radio systems, etc.) was documented. With this information a requirements document was written stating a brief description of the equipment and required quantity to be used in an EOC and then compared to current capabilities at the NASA Langley Research Center.

  17. Towards cheaper control centers

    NASA Technical Reports Server (NTRS)

    Baize, Lionel

    1994-01-01

    Today, any approach to the design of new space systems must take into consideration an important constraint, namely costs. This approach is our guideline for new missions and also applies to the ground segment, and particularly to the control center. CNES has carried out a study on a recent control center for application satellites in order to take advantage of the experience gained. This analysis, the purpose of which is to determine, a posteriori, the costs of architecture needs and choices, takes hardware and software costs into account and makes a number of recommendations.

  18. Lied Transplant Center

    SciTech Connect

    1996-02-01

    The Department of Energy has prepared an Environmental Assessment (DOE/EA-1143) evaluating the construction, equipping and operation of the proposed Lied Transplant Center at the University of Nebraska Medical Center in Omaha, Nebraska. Based on the analysis in the EA, the DOE has determined that the proposed action does not constitute a major federal action significantly affecting the quality of the human environment within the meaning of the National Environmental Policy Act of 1969 (NEPA). Therefore, the preparation of an Environmental Statement in not required.

  19. Zero Robotics at Kennedy Space Center Visitor Complex

    NASA Image and Video Library

    2017-08-11

    NASA Kennedy Space Center's Trent Smith conducts a quantum levitation demonstration, using liquid nitrogen, metal and a magnetic track, for students and their sponsors in the Center for Space Education at NASA’s Kennedy Space Center in Florida. Teams from across the state of Florida were gathered at Kennedy for the finals of the Zero Robotics Middle School Summer Program national championship. The five-week program allows rising sixth- through ninth-graders to write programs for small satellites called SPHERES (Synchronized, Position, Hold, Engage, Reorient, Experimental Satellites). Finalists saw their code tested aboard the International Space Station.

  20. Present state of metal-on-metal hybrid hip resurfacing.

    PubMed

    Amstutz, Harlan C

    2008-01-01

    Bone conservation and preservation, joint stability, and low wear of the large metal-on-metal resurfacing bearings have been convincingly demonstrated in the current literature. The clinical results of 600 MM Hybrid Conserve Plus Resurfacing in 519 patients with an average follow-up of 6.9 years (range, 4.0-10.4 years) have been excellent. The average age was 48.9 years, 74% of the patients were male, and the study included all etiologies of the young with arthritis. The complication rates other than dislocation and fracture of the femoral neck are comparable between resurfacing and conventional total hip replacement. The incidence of femoral neck fracture is low (1.2% worldwide) with less than 0.6% in this series and none occurring in the last 5 years due to proper patient selection and improved surgical technique. Component loosening after metal-on-metal resurfacing has been significantly reduced and acetabular component loosening is uncommon and has not happened in this series. Femoral bone preparation and optimal cementing techniques are paramount to prevention of femoral loosening. Clearance between the cylindrically reamed part of the head and the component varies in different designs, and the surgeon must note the need for different cementing strategies for different recommended clearances. The learning curve of a surgeon undertaking resurfacing can be greatly reduced by observation and hands-on training in specialized centers with surgeons experienced in resurfacing.

  1. Ceramic/metal seals. [refractory materials for hermetic seals for lighium-metal sulfide batteries

    NASA Technical Reports Server (NTRS)

    Bredbenner, A. M.

    1977-01-01

    Design criteria are discussed for a hermetic seal capable of withstanding the 450 C operating temperature of a lithium-metal sulfide battery system. A mechanical seal consisting of two high strength alloy metal sleeves welded or brazed to a conductor assembly and pressed onto a ceramic is described. The conductor center passes through the ceramic but is not sealed to it. The seal is effected on the outside of the taper where the tubular part is pressed down over and makes contact.

  2. The Hydrogen Technology Center at Wyle Laboratories

    NASA Astrophysics Data System (ADS)

    Wheelock, H.; Smith, D.; Frazier, J.

    1990-10-01

    A deactivated storable propellant test area with numerous test cells, large open concrete pads of up to 65-ft length, and two enclosed metal storage buildings, has been converted into a Hydrogen Technology Center. The conversion strategy involved extensive use of modified surplus equipment, well established testing technologies, and innovative engineering to obviate long-delivery time items. Simple, high heat flux water-to-cryogen heat exchangers are used to generate ambient temperature H2 and N gas. Hydrogen-fueled combustors were designed and fabricated to power the specialized heat exchangers required to support high-temperature hydrogen experiments. The facility has operated productively and safely since October, 1988.

  3. Control Center Technology Conference Proceedings

    NASA Technical Reports Server (NTRS)

    1991-01-01

    Conference papers and presentations are compiled and cover evolving architectures and technologies applicable to flight control centers. Advances by NASA Centers and the aerospace industry are presented.

  4. Failure Analysis at the Kennedy Space Center

    NASA Technical Reports Server (NTRS)

    Salazar, Victoria L.; Wright, M. Clara

    2010-01-01

    History has shown that failures occur in every engineering endeavor, and what we learn from those failures contributes to the knowledge base to safely complete future missions. The necessity of failure analysis is at its apex at the end of one aged program and at the beginning of a new and untested program. The information that we gain through failure analysis corrects the deficiencies in the current vehicle to make the next generation of vehicles more efficient and safe. The Failure Analysis and Materials Evaluation Branch in the Materials Science Division at the Kennedy Space Center performs metallurgical, mechanical, electrical, and non-metallic materials failure analyses and accident investigations on both flight hardware and ground support equipment for the Space Shuttle, International Space Station, Constellation, and Launch Services Programs. This paper will explore a variety of failure case studies at the Kennedy Space Center and the lessons learned that can be applied in future programs.

  5. Abundant Metals Give Precious Hydrogenation Performance

    SciTech Connect

    Bullock, R. Morris

    2013-11-29

    Homogeneous catalysts based on precious (noble) metals have had a profound influence on modern synthetic methods, enabling highly selective synthesis of organic compounds but typically require precious metal catalysts (Ru, Rh, Ir, Pt, and Pd). Increasing efforts have been devoted to the design and discovery of homogeneous catalysts using base metals (e.g., Mn, Fe, Co, Ni, Cu, Mo). Morris et al. report Fe catalysts for asymmetric hydrogenation of C=O bonds. Cobalt catalysts for asymmetric hydrogenation of C=C bonds are described by Chirik et al., and Beller et al. report new nanoscale iron catalysts for synthesis of functionalized anilines through hydrogenation of nitroarenes. The author’s work in this area is supported as part of the Center for Molecular Electrocatalysis, an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science, Basic Energy Sciences. Pacific Northwest National Laboratory is operated by Battelle for the U.S. Department of Energy.

  6. Memory Metals

    NASA Technical Reports Server (NTRS)

    1995-01-01

    Under contract to NASA during preparations for the space station, Memry Technologies Inc. investigated shape memory effect (SME). SME is a characteristic of certain metal alloys that can change shape in response to temperature variations. In the late 1980s and early 1990s, Memry used its NASA-acquired expertise to produce a line of home and industrial safety products, and refined the technology in the mid-1990s. Among the new products they developed are three MemrySafe units which prevent scalding from faucets. Each system contains a small valve that reacts to temperature, not pressure. When the water reaches dangerous temperatures, the unit reduces the flow to a trickle; when the scalding temperature subsides, the unit restores normal flow. Other products are the FIRECHEK 2 and 4, heat-activated shutoff valves for industrial process lines, which sense excessive heat and cut off pneumatic pressure. The newest of these products is Memry's Demand Management Water Heater which shifts the electricity requirement from peak to off-peak demands, conserving energy and money.

  7. Employability Skills Center.

    ERIC Educational Resources Information Center

    Sweetwater Union High School District, Chula Vista, CA.

    The Employability Skills Center (ESC) of the Division of Adult and Continuing Education (DACE) of the Sweetwater Union High School District (California) was created out of a need to help adult students develop the basic skills that are required for success in their chosen vocational programs but not taught in regular adult basic education classes.…

  8. Starting a sleep center.

    PubMed

    Epstein, Lawrence J; Valentine, Paul S

    2010-05-01

    The demand for sleep medicine services has grown tremendously during the last decade and will likely continue. To date, growth in demand has been met by growth in the number of new sleep centers. The need for more new centers will be dependent on market drivers that include increasing regulatory requirements, personnel shortages, integration of home sleep testing, changes in reimbursement, a shift in emphasis from diagnostics to treatment, and an increased consumer focus on sleep. The decision to open a new center should be based on understanding the market dynamics, completing a market analysis, and developing a business plan. The business plan should include an overview of the facility, a personnel and organizational structure, an evaluation of the business environment, a financial plan, a description of services provided, and a strategy for obtaining, managing, and extending a referral base. Implementation of the business plan and successful operation require ongoing planning and monitoring of operational parameters. The need for new sleep centers will likely continue, but the shifting market dynamics indicate a greater need for understanding the marketplace and careful planning.

  9. Queering the Writing Center

    ERIC Educational Resources Information Center

    Denny, Harry

    2010-01-01

    Composition classrooms and writing centers are spaces where negotiation of academic, social, cultural, and political identities are ubiquitous, yet research has not produced adequate theory and practice to help tutors and writers navigate identity production and its politics. This article seeks to begin conversations that might lead to better…

  10. Alternative Fuels Data Center

    SciTech Connect

    2013-06-01

    Fact sheet describes the Alternative Fuels Data Center, which provides information, data, and tools to help fleets and other transportation decision makers find ways to reduce petroleum consumption through the use of alternative and renewable fuels, advanced vehicles, and other fuel-saving measures.

  11. Johnson Space Center Overview

    NASA Technical Reports Server (NTRS)

    Gafka, Tammy; Terrier, Doug; Smith, James

    2011-01-01

    This slide presentation is a review of the work of Johnson Space Center. It includes a section on technology development areas, (i.e., composite structures, non-destructive evaluation, applied nanotechnology, additive manufacturing, and fracture and fatigue analytical methods), a section on structural analysis capabilities within NASA/JSC and a section on Friction stir welding and laser peening.

  12. Community Learning Centers

    ERIC Educational Resources Information Center

    Jennings, Wayne

    2005-01-01

    The Community Learning Centers plan provides a systemically changed model for the 21st century. This top-to-bottom transformation of current education addresses all aspects of schools with a detailed framework to guide serious educational reformers. This fresh approach to principles of learning, curriculum, staffing, facilities, student as…

  13. National Response Center

    EPA Pesticide Factsheets

    The NRC is the federal government's national communications center, which is staffed 24 hours a day by U.S. Coast Guard officers and marine science technicians. Sole federal point of contact for reporting all hazardous substance releases and oil spills

  14. Nicolaus Copernicus Astronomical Center

    NASA Astrophysics Data System (ADS)

    Murdin, P.

    2000-11-01

    Nicolaus Copernicus Astronomical Center is the largest astronomical institution in Poland, located in Warsaw and founded in 1956. At present it is a government-funded research institute supervised by the Polish Academy of Sciences and licensed by the government of Poland to award PhD and doctor habilitatus degrees in astronomy and astrophysics. In September 1999 staff included 21 senior scientist...

  15. Carolinas Energy Career Center

    SciTech Connect

    Classens, Anver; Hooper, Dick; Johnson, Bruce

    2013-03-31

    Central Piedmont Community College (CPCC), located in Charlotte, North Carolina, established the Carolinas Energy Career Center (Center) - a comprehensive training entity to meet the dynamic needs of the Charlotte region's energy workforce. The Center provides training for high-demand careers in both conventional energy (fossil) and renewable energy (nuclear and solar technologies/energy efficiency). CPCC completed four tasks that will position the Center as a leading resource for energy career training in the Southeast: • Development and Pilot of a New Advanced Welding Curriculum, • Program Enhancement of Non-Destructive Examination (NDE) Technology, • Student Support through implementation of a model targeted toward Energy and STEM Careers to support student learning, • Project Management and Reporting. As a result of DOE funding support, CPCC achieved the following outcomes: • Increased capacity to serve and train students in emerging energy industry careers; • Developed new courses and curricula to support emerging energy industry careers; • Established new training/laboratory resources; • Generated a pool of highly qualified, technically skilled workers to support the growing energy industry sector.

  16. A Learner Centered Education.

    ERIC Educational Resources Information Center

    Ballard, Florence N.

    This paper proposes a learner-centered educational system, focusing on aspects that are intrinsically associated with the modern educational system, such as the curriculum, school community, parents, learners, and educational support personnel. It examines: primary level preparation (literacy, numeracy, and basic knowledge; examination and…

  17. Mobile PET Center Project

    NASA Astrophysics Data System (ADS)

    Ryzhikova, O.; Naumov, N.; Sergienko, V.; Kostylev, V.

    2017-01-01

    Positron emission tomography is the most promising technology to monitor cancer and heart disease treatment. Stationary PET center requires substantial financial resources and time for construction and equipping. The developed mobile solution will allow introducing PET technology quickly without major investments.

  18. Dayton's neighborhood school centers.

    PubMed

    Ferguson, Dick

    2009-01-01

    When Dayton Public Schools committed to return to neighborhood K-8 schools, the community organized to refocus many youth programs in schools and neighborhoods. This article describes the planning and implementation of Dayton's Neighborhood School Centers. Special emphasis is placed on the role of the University of Dayton, especially the Fitz Center for Leadership in Community. The Fitz Center plays a pivotal role in implementing this highly collaborative effort, including project leadership; community organizing; coaching of five site coordinators at neighborhood school sites; and faculty-mentored student interns to assist with programming for student success, family support, health and team sports, and extensive service-learning coordination. The Dayton Foundation, Dayton Public Schools, City of Dayton, Montgomery County, and sixteen foundation and corporate supporters are partners with the Fitz Center in a bold initiative to reconnect five Dayton public elementary schools to their neighborhoods, after more than thirty years of court-ordered busing, and create full-service, year-round opportunities for neighborhood families and youth at these new schools. More than forty programs have been started at each site, all emphasizing youth and community assets.

  19. Libraries/Media Centers.

    ERIC Educational Resources Information Center

    American School & University, 2003

    2003-01-01

    Presents K-12 and college libraries/media centers considered outstanding in a competition, which judged the most outstanding learning environments at educational institutions nationwide. Jurors spent two days reviewing projects, highlighting concepts and ideas that made them exceptional. For each citation, the article offers information on the…

  20. The Pupil Appraisal Center.

    ERIC Educational Resources Information Center

    Wilborn, Bobbie; Gentile, Lance M.

    The primary purpose of the Pupil Appraisal Center (PAC) is to promote teacher education by providing teachers and students direct experience in resolving behavioral disorders and learning problems. PAC provides specialized teacher training in counseling, reading, hearing, speech, and language development and provides service to area schools for…