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Iowa State University

1999

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Determination Of Plate Source, Detector Separation From One Signal, Stephen D. Holland, Tadej Kosel, Richard Weaver, Wolfgang Sachse Nov 1999

Determination Of Plate Source, Detector Separation From One Signal, Stephen D. Holland, Tadej Kosel, Richard Weaver, Wolfgang Sachse

Stephen D. Holland

We address the problem of locating a transient source, such as an acoustic emission source, in a plate. We apply time-frequency analysis to the signals detected at a receiver. These highly dispersive and complex waveforms are measured for source-receiver separations ranging from 40 to 180 plate thicknesses and at frequencies such that ten to twenty Rayleigh-Lamb branches are included. Re-assigned, smoothed, pseudo-Wigner-Ville distributions are generated that exhibit the expected sharp ridges in the time-frequency plane, lying along the predicted frequency-time-of-arrival relations. The source-receiver separation can be determined from such plots.

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An Investigation Of Environmental Management Systems Motivations And Firm Performance, Robert Sroufe, Steven A. Melnyk, Frank L. Montabon, Roger Calantone Nov 1999

An Investigation Of Environmental Management Systems Motivations And Firm Performance, Robert Sroufe, Steven A. Melnyk, Frank L. Montabon, Roger Calantone

Frank L. Montabon

There are many of issues associated with Environmental Management Systems (EMS). One attempt to overcome these issues can be found in the development of IS0 14000. In this paper, a hypothesized model of the motivations influencing the decision to seek IS0 14000 certification and the relationship to firm performance is examined. The hypothesized model is tested through the use of Structural Equation Modeling (SEM). The results identify positive relationships between uncertainty and the motivations to seek EMS certification. A positive relationship is shown between the status of a firm’s EMS, the environmental options a firm will explore. Finally, a positive …

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Iso 14000: Assessing Its Perceived Impact On Corporate Performance, Frank L. Montabon, Steven A. Melnyk, Robert Sroufe, Roger J. Calantone Nov 1999

Iso 14000: Assessing Its Perceived Impact On Corporate Performance, Frank L. Montabon, Steven A. Melnyk, Robert Sroufe, Roger J. Calantone

Frank L. Montabon

The IS0 14000 environmental standard is a relatively recent development in Environmentally Responsible Manufacturing (ERM). It applies to environmental systems and processes the same approach used by its predecessor, the IS0 9000 quality standards. Being relatively new, there are numerous questions regarding the impact of this new standard both on the corporate environmental management system and corporate performance. This paper addresses some of these questions, by drawing on data generated by a large-scale survey of American managers. The results indicate that, even though IS0 14000 has achieved relatively limited acceptance, there is strong evidence to indicate that this standard can …

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Investigating The Linkage Between Total Quality Management And Environmentally Responsible Manufacturing, Sime Curkovic, Steve Melnyk, Rob Handfield, Frank L. Montabon, Robert Sroufe Nov 1999

Investigating The Linkage Between Total Quality Management And Environmentally Responsible Manufacturing, Sime Curkovic, Steve Melnyk, Rob Handfield, Frank L. Montabon, Robert Sroufe

Frank L. Montabon

This paper explicitly examines the relationship that exists between Total Quality Management (TQM) and Environmentally Responsible Manufacturing (ERM) systems. It has been presumed in numerous past studies that such a relationship does exist. It has been argued that those firms that have successfuhy implemented a TQM system are better positioned to successfully implement an ERM system. This relationship, however, has not yet been statistically and empirically evaluated. In this study, the authors evaluate this relationship using a large-scale survey of plant managers as the data source and Confirmatory Factor Analysis and Structural Equation Modeling as the statistical tools. The study …

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Measuring Partnered Project Performance, Douglas D. Gransberg, Howard L. Reynolds, Jack Boyd Oct 1999

Measuring Partnered Project Performance, Douglas D. Gransberg, Howard L. Reynolds, Jack Boyd

Douglas D. Gransberg

The results of a study of over 400 projects completed by the Texas Department of Transportation over 5 years are presented. The objective was to compare the performance of construction projects on which formal partnering agreements had been executed with projects that had been completed without partnering and measure the benefits due to partnering. The data was collected by 20 different aspects, from cost and time growth to the amount of previous experience.

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Readers' Theatre As A History Teaching Tool, Sandra D. Harmon, Pamela Riney-Kehrberg, Susan Westbury Aug 1999

Readers' Theatre As A History Teaching Tool, Sandra D. Harmon, Pamela Riney-Kehrberg, Susan Westbury

Pamela Riney-Kehrberg

LAST YEAR marked the one-hundred-and-fiftietha nniversaryo f the first women's rights convention held at Seneca Falls, New York. We wanted to celebrate the event with a dramatic presentation for our students. Lacking the skill to write a compelling play, we decided to put on a readers' theatre version of the convention. Such productions are engaging and relatively easy to stage as the actors read from scripts, usually without costumes or scenery. Readers' theatre also allows greater control over historical accuracy than a conventional play. Since history is only occasionally dramatic, the demands of theatre, whether on stage or in films …

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Solid-Liquid Phase Equilibrium For Binary Lennard-Jones Mixtures, Monica R. Hitchcock, Carol K. Hall Jun 1999

Solid-Liquid Phase Equilibrium For Binary Lennard-Jones Mixtures, Monica R. Hitchcock, Carol K. Hall

Monica H. Lamm

Solid-liquid phase diagrams are calculated for binary mixtures of Lennard-Jones spheres using Monte Carlo simulation and the Gibbs-Duhem integration technique of Kofke. We calculate solid-liquid phase diagrams for the model Lennard-Jones mixtures: argon-methane, krypton-methane, and argon-krypton, and compare our simulation results with experimental data and with Cottin and Monson's recent cell theory predictions. The Lennard-Jones model simulation results and the cell theory predictions show qualitative agreement with the experimental phase diagrams. One of the mixtures, argon-krypton, has a different phase diagram than its hard-sphere counterpart, suggesting that attractive interactions are an important consideration in determining solid-liquid phase behavior. We then …

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New Developments In A Hazard Identification Algorithm For Hormone Receptor Ligands, Steven P. Bradbury, Ovanes Mekenyan, Nina Nikolova, Stoyan Karabunarliev, Gerald T. Ankley, Bjorn Hansen Jun 1999

New Developments In A Hazard Identification Algorithm For Hormone Receptor Ligands, Steven P. Bradbury, Ovanes Mekenyan, Nina Nikolova, Stoyan Karabunarliev, Gerald T. Ankley, Bjorn Hansen

Steven P. Bradbury

Recently we described the Common REactivity PAttern (COREPA) technique to screen data sets of diverse structures for their ability to serve as ligands for steroid hormone receptors [1]. The approach identi®es and quanti®es similar global and local stereoelectronic characteristics associated with active ligands through a comparison of energeticallyreasonable conformer distributions for selected descriptors. For each stereoelectronic descriptor selected, discrete conformer distributions from a training set of ligands are evaluated and parameter ranges common for conformers from all the chemicals in the training set are identi®ed. The use of discrete partitions of parameter ranges to de®ne common reactivity patterns can, however, …

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Introduction To Engineering Problem Solving—A New Course For 1100 First Year Engineering Students, Richard L. Porter, Laura J. Bottomley, Mary Clare Robbins, Walthea V. Yarbrough, Sarah A. Rajala, Hugh Fuller Jun 1999

Introduction To Engineering Problem Solving—A New Course For 1100 First Year Engineering Students, Richard L. Porter, Laura J. Bottomley, Mary Clare Robbins, Walthea V. Yarbrough, Sarah A. Rajala, Hugh Fuller

Sarah A. Rajala

During the past several years, NC State University has offered several experimental courses designed for the first year student in engineering; IMPEC, an integrated approach to mathematics, physics, engineering, and chemistry; E123, a mechanical dissection course which is now linked with the first year writing and composition course; and ECE 292D, a hands-on team based design course offered to upper class students as well. All were offered as an alternative to the introductory course (E100) that had little academic content, no engineering problem solving, and consisted of a large lecture room format with information dissemination as the major goal. Although …

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Interpreting Shadows: Arms Control And Defense Planning In A Rapidly Changing Multi-Polar World, David R. King Jun 1999

Interpreting Shadows: Arms Control And Defense Planning In A Rapidly Changing Multi-Polar World, David R. King

David King

Cold War thinking continues to guide United States' policy in the Post-Cold War environment. Continuing to pursue policies forged during the Cold War will not be adequate to address proliferation for two reasons. First, Cold War policies do not reflect changes in the world in respect to other major or regional powers. Second, current policies overlook potential long-term counterproductive consequences. Adopting an overarching national policy on arms control will require understanding different world views of the United States, other major powers, and regional powers.

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Novel One-Phase Synthesis Of Thiol-Functionalized Gold, Palladium, And Iridium Nanoparticles Using Superhydride, Chanel K. Yee, Rainer Jordan, Abraham Ulman, Henry White, Alexander H. King, Miriam Rafailovich, Jonathan Sokolov May 1999

Novel One-Phase Synthesis Of Thiol-Functionalized Gold, Palladium, And Iridium Nanoparticles Using Superhydride, Chanel K. Yee, Rainer Jordan, Abraham Ulman, Henry White, Alexander H. King, Miriam Rafailovich, Jonathan Sokolov

Alexander H. King

A new, facile, general one-phase synthesis for thiol-functionalized gold, palladium, and iridium nanoparticles, using tetrahydrofuran (THF) as the solvent and lithium triethylborohydride (Superhydride) as the reducing agent, is presented. For octadecanethiol-functionalized gold (Au/ODT) nanoparticles, HRTEM of drop-cast particle-films revealed the formation of spherical particles of d = 4 ± 0.3 nm average size. Electron diffraction shows fcc packing arrangement, similar to that of bulk gold. The crystalline gold cores are surrounded with closely packed n-alkyl chains mainly in an all-trans conformation, adopting orthorhombic packing as confirmed by FTIR spectroscopy. Particles are arranged in a discrete solidlike assembly with a correlation …

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The Allyl Leaving Group Approach To Tricoordinate Silyl, Germyl, And Stannyl Cations, Joseph B. Lambert, Yan Zhao, Hongwei Wu, Winston C. Tse, Barbara Kuhlmann May 1999

The Allyl Leaving Group Approach To Tricoordinate Silyl, Germyl, And Stannyl Cations, Joseph B. Lambert, Yan Zhao, Hongwei Wu, Winston C. Tse, Barbara Kuhlmann

Yan Zhao

A group 14 atom bonded to three mesityl groups (2,4,6-trimethylphenyl) and to one allyl group serves as a novel precursor to tricoordinate group 14 cations, the analogues of the carbocation. The double bond of the allyl group provides an accessible reaction site that is located beyond the ortho methyl groups. Reaction of various electrophiles with the double bond releases the allyl group and leads to formation of the group 14 cations. The mesityl groups then are of sufficient steric bulk to protect the tricoordinate metal center from attack by nucleophiles. This approach is used herein with silicon, germanium, and tin …

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Incommensurate And Commensurate Antiferromagnetic Spin Fluctuations In Cr And Cr Alloys From Ab Initio Dynamical Spin Susceptibility Calculations, Duane D. Johnson, J. Pulter, B. Ginatempo, E. Bruno, J. B. Staunton Apr 1999

Incommensurate And Commensurate Antiferromagnetic Spin Fluctuations In Cr And Cr Alloys From Ab Initio Dynamical Spin Susceptibility Calculations, Duane D. Johnson, J. Pulter, B. Ginatempo, E. Bruno, J. B. Staunton

Duane D. Johnson

A scheme for making ab initio calculations of the dynamic paramagnetic spin susceptibilities of solids at finite temperatures is described. It is based on time-dependent density functional theory and employs an electronic multiple scattering formalism. Incommensurate and commensurate antiferromagnetic spin fluctuations in paramagnetic Cr and compositionally disordered Cr95V5 and Cr95Re5 alloys are studied together with the connection with the nesting of their Fermi surfaces. We find that the spin fluctuations can be described rather simply in terms of an overdamped oscillator model. Good agreement with inelastic neutron scattering data is obtained.

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Biotransformation Of 4-Methoxyphenol In Rainbow Trout (Oncorhynchus Mykiss) Hepatic Microsomes, Steven P. Bradbury, R. Kolanczyk, P. Schmieder, T. Spizzo Mar 1999

Biotransformation Of 4-Methoxyphenol In Rainbow Trout (Oncorhynchus Mykiss) Hepatic Microsomes, Steven P. Bradbury, R. Kolanczyk, P. Schmieder, T. Spizzo

Steven P. Bradbury

Rainbow trout liver microsomes were used to study the O-demethylation and ring hydroxylation of 4-methoxyphenol (4-MP) (4-hydroxyanisole) at 11 and 25°C by directly measuring the production of the primary metabolite hydroquinone (HQ), 4-methoxycatechol (4-MCAT), and additional metabolites. An HPLC method with integrated ultraviolet (UV) and electrochemical detection (ECD) was developed for metabolite identification and quantification at low concentrations. Sample handling with appropriate buffers, solvents, low temperature and light prevented loss of extremely labile metabolites. Saturation kinetics for the production of HQ via O-demethylation of 4-MP (0.66–40 mM) was never achieved, with substrate solubility being the limiting factor. The linear rate …

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Β-Silyl And Β-Germyl Carbocations Stable At Room Temperature, Joseph B. Lambert, Yan Zhao, Hongwei Wu Mar 1999

Β-Silyl And Β-Germyl Carbocations Stable At Room Temperature, Joseph B. Lambert, Yan Zhao, Hongwei Wu

Yan Zhao

Stable carbocations have been prepared at room temperature with benzene as solvent and tetrakis(pentafluorophenyl)borate (TPFPB) as anion by the addition of solvated triethylsilylium TPFPB or of tributylgermylium TPFPB to 1,1-diphenylethene. These carbocations are stabilized by σ conjugation with nonadjacent group 14 atoms and respectively constitute stable saturated β-silyl and β-germyl carbocations. NMR parameters, including the 29Si chemical shift, the 13C chemical shifts of the cationic, aryl, and methylene carbons, and the one-bond 13C−1H coupling constant of the methylene group adjacent to the group 14 element, define the distribution of positive charge between carbon and (through σ conjugation) silicon or germanium. …

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Enhanced Adhesion Of Pasteurella Multocida To Cultured Turkey Peripheral Blood Monocytes, Ingrid M. Pruimbroom, Richard B. Rimler, Mark R. Ackermann Mar 1999

Enhanced Adhesion Of Pasteurella Multocida To Cultured Turkey Peripheral Blood Monocytes, Ingrid M. Pruimbroom, Richard B. Rimler, Mark R. Ackermann

Mark R. Ackermann

Capsular hyaluronic acid (HA) mediates adhesion of serogroup A strains of Pasteurella multocida to elicited turkey air sac macrophages (TASM). In contrast, freshly isolated turkey peripheral blood monocytes (TPBM) do not bind serogroup A strains. Following culture of TPBM for 6 days in chamber slides, adhesion of the bacteria to TPBM increased gradually. Incubation in chamber slides coated with entactin-collagen IV-laminin (ECL) attachment matrix or exposure to phorbol myristate acetate (PMA) further enhanced the adhesion ofP. multocida to TPBM. Addition of HA, but not Arg-Gly-Asp peptide, to TPBM culture inhibited bacterial adherence similarly to the inhibition previously reported for TASM. …

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Facial Features Localization In Front View Head And Shoulders Images, Adnan M. Alattar, Sarah A. Rajala Mar 1999

Facial Features Localization In Front View Head And Shoulders Images, Adnan M. Alattar, Sarah A. Rajala

Sarah A. Rajala

The computerized process of locating human facial features such as the eyes, nose and mouth in a head and shoulders image is crucial to such applications as automatic face identification and model-based video coding. A new model-based algorithm for locating these major features is developed. The algorithm estimates the parameters of the ellipse which best fits the head view in the image and uses these parameters to calculate the estimated locations of the facial features. It then refines the estimated coordinates of the eyes, mouth, and nose by exploiting the vertical and horizontal projections of the pixels in windows around …

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The Challenges Of Economic Maturity: New England, 1880-1940, Joshua L. Rosenbloom Feb 1999

The Challenges Of Economic Maturity: New England, 1880-1940, Joshua L. Rosenbloom

Joshua L. Rosenbloom

This paper provides an account of the complex changes taking place within New England in the years from 1880 to 1940. After 1880, technological changes and market shifts undermined the sources of comparative advantage that had promoted the concentration of textile and footwear production within the region and propelled regional economic growth. Despite the decline of these industries after 1880, New England's history after 1880 can hardly be characterized as one of economic decline. Regional economic growth did slow in the wake of these events, but the impact of this slowdown on living standards was moderated, by market driven adjustments …

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Damper For Brake Noise Reduction, Jonathan A. Wickert, Adnan Akay Jan 1999

Damper For Brake Noise Reduction, Jonathan A. Wickert, Adnan Akay

Jonathan A. Wickert

An apparatus for reducing unwanted brake noise has a ring damper affixed around a periphery of a brake rotor in a disk brake system in a manner that permits relative motion and slippage between the ring damper and the rotor when the rotor vibrates during braking. In a preferred embodiment, the ring damper is disposed in a groove formed in the periphery of the disk and is pre-loaded against the rotor both radially and transversely. The ring damper is held in place by the groove itself and by the interference pre-load or pretension between the ring damper and the disk …

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The Effect Of Water Level Management On The Soils And Vegetation Of Two Coastal Louisiana Marshes, Brian J. Wilsey, K. M. Flynn, I. A. Mendelssohn Jan 1999

The Effect Of Water Level Management On The Soils And Vegetation Of Two Coastal Louisiana Marshes, Brian J. Wilsey, K. M. Flynn, I. A. Mendelssohn

Brian J. Wilsey

Wetland degradation and loss is the result of a combination of natural causes and anthropogenic activities and is a serious problem in coastal Louisiana, where approximately 80% of the total US coastal wetland loss since the 1930’s has occurred. One method currently used to address this wetland loss problem is structural marsh management,which is the use of levees and water control structures to control hydroperiod. The effects of structural marsh management on two managed marshes in Southern Louisiana (Unit 4 of the Rockefeller Wildlife Refuge and the Fina LaTerre Mitigation Bank) were evaluated by comparing the soils and the dominant …

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Temporal Changes In Purity And Specific Activity Of Tritium-Labeled 2,3,7,8-Tetrachlorodibenzo-Ρ-Dioxin: Radiopurity Model For Toxicology, Steven P. Bradbury, Joseph D. Fernandez, Philip M. Cook, Brian C. Butterworth Jan 1999

Temporal Changes In Purity And Specific Activity Of Tritium-Labeled 2,3,7,8-Tetrachlorodibenzo-Ρ-Dioxin: Radiopurity Model For Toxicology, Steven P. Bradbury, Joseph D. Fernandez, Philip M. Cook, Brian C. Butterworth

Steven P. Bradbury

The specific activity (S) and radiopurity (R) of tritium labeled 2,3,7,8-tetrachlorodibenzo-p-dioxin, [3H]TCDD, were measured by gas chromatography/mass spectrometry (GC/ MS) while attempting to accurately characterize TCDD doses received by invertebrates, fish, and fish embryos during several toxicology studies conducted over a 3 year period. The [3H]TCDD sample was found to consist of six TCDD analogues involving hydrogen, deuterium, and tritium substitution at the 1,6-dibenzo-p-dioxin carbon positions and a complex mixture of impurities (with and without tritium labels). Planar aromatic impurities were identified as tolyl- TCDD adducts and appeared to result from the decay of 3H radiolabels to produce TCDD carbocations …

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Derivation Of Wildlife Values For Mercury, Steven P. Bradbury, John Nichols, Jeff Swartout Jan 1999

Derivation Of Wildlife Values For Mercury, Steven P. Bradbury, John Nichols, Jeff Swartout

Steven P. Bradbury

A procedure has been developed to estimate surface water concentrations of toxicants (“wildlife values”) that will protect the viability of wildlife populations associated with aquatic resources. This procedure was designed primarily to protect piscivorous birds and mammals from compounds that bioaccumulate in fish and was used in the Great Lakes Water Quality Initiative (GLI) to calculate wildlife values (WV) for mercury, DDT/DDE, total polychlorinated biphenyls (PCBs), and 2,3,7,8-tetrachlorodibenzodioxin (TCDD). Published in 1995, and expressed as total mercury in unfiltered water, the final wildlife value (WVf) for mercury derived in the GLI was 1300 pg Hg/L. This value was selected as …

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New Testing Apparatus For Assessing Interactive Effects Of Suspended Solids And Chemical Stressors On Plankton Invertebrates, Steven P. Bradbury, Carl Herbrandson, Deborah L. Swackhamer Jan 1999

New Testing Apparatus For Assessing Interactive Effects Of Suspended Solids And Chemical Stressors On Plankton Invertebrates, Steven P. Bradbury, Carl Herbrandson, Deborah L. Swackhamer

Steven P. Bradbury

To better predict and interpret the responses of aquatic organisms to environmentally relevant chemical exposures, it is necessary to investigate the combined effects of physical (e.g., suspended solids) and chemical stressors. One of the limitations in investigating suspended solids–chemical interactions has been the lack of an appropriate testing system. The specific objective of the current study was to develop and assess a suspended solids testing apparatus (SSTA) for studies on the combined effects of suspended solids and chemicals on aquatic invertebrates. The SSTA was designed to permit the assessment of varying suspended solids concentrations on Daphnia magna at a constant …

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The Historical Development Of Agriculture In Illinois, Pamela Riney-Kehrberg Jan 1999

The Historical Development Of Agriculture In Illinois, Pamela Riney-Kehrberg

Pamela Riney-Kehrberg

Illinois' agricultural history is long and complex. Illinois' first settlers, the Native Americans, practiced hunting, gathering, and fishing and made use of the resources of the woods and prairies. By the tenth century, Native Americans combined men's hunting with women's agricultural activities to meet the needs of their communities. The earliest crop Native American women cultivated was corn, imported to Illinois from the Southwest.

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Resistivity, Thermopower And The Correlation To Infrared Active Vibrations Of Mn1.56co0.96ni0.48o4 Spinel Films Sputtered In An Oxygen Partial Pressure Series, Rand Dannenberg, S. Baliga, R. J. Gambino, Alexander H. King, A. P. Doctor Jan 1999

Resistivity, Thermopower And The Correlation To Infrared Active Vibrations Of Mn1.56co0.96ni0.48o4 Spinel Films Sputtered In An Oxygen Partial Pressure Series, Rand Dannenberg, S. Baliga, R. J. Gambino, Alexander H. King, A. P. Doctor

Alexander H. King

Mn1.56Co0.96Ni0.48O4 spinel was sputter deposited using a series of oxygen partial pressures. Electrical resistivity versus temperature and thermopower versus temperature measurements at each oxygen partial pressure were made. The variations of the thermopower and resistivity with oxygen partial pressure are consistent with a change in the ratio of Mn3+ to Mn4+ cations, which occurs due to changes of oxygen content of the material. The weak temperature dependence of the thermopower indicates small polaron hopping is the charge transport mechanism. Combining the models of Mott and Schnakenberg to analyze the transport data, we find that the Debye temperature (or frequency) is …

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The Β Effect Of Silicon And Related Manifestations Of Σ Conjugation, Joseph B. Lambert, Yan Zhao, Robert W. Emblidge, Lourdes A. Salvador, Xiaoyang Liu, Jeung-Ho So, Erik C. Chelius Jan 1999

The Β Effect Of Silicon And Related Manifestations Of Σ Conjugation, Joseph B. Lambert, Yan Zhao, Robert W. Emblidge, Lourdes A. Salvador, Xiaoyang Liu, Jeung-Ho So, Erik C. Chelius

Yan Zhao

Stabilization of carbocations through donation of ð electrons from adjacent carbon orbitals results in well-known species such as the allyl and benzyl cations. Adjacent nonbonding (n) electrons on heteroatoms also can provide considerable stabilization, as in oxonium ions such as CH2dO+CH3 and iminium ions such as CH2dN+(CH3)2. Less well known is stabilization of carbocations by ó orbitals. In its most common example this interaction provides stabilization of tertiary over secondary over primary carbocations. According to the valence bond representation of this interaction, a filled ó orbital donates electrons to an empty ð orbital, as in 1 and 2 (R ) …

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Characterization Of Oxidation Products Of Tnt Metabolism In Aquatic Phytoremediation Systems Of Myriophyllum Aquaticum, R. Bhadra, R. J. Spanggord, D. G. Wayment, J. B. Hughes, Jacqueline V. Shanks Jan 1999

Characterization Of Oxidation Products Of Tnt Metabolism In Aquatic Phytoremediation Systems Of Myriophyllum Aquaticum, R. Bhadra, R. J. Spanggord, D. G. Wayment, J. B. Hughes, Jacqueline V. Shanks

Jacqueline V. Shanks

TNT transformation processes in sediment-free, “natural”, aquatic phytoremediation systems of Myriophyllum aquaticum were investigated with specific interest in oxidation products. Extraction procedures combining liquidliquid extractions and solid-phase extractions were developed for the isolation of the mostly acidic, oxidized TNT metabolites. Six compounds unique from the reduction products of TNT were isolated and characterized by UVvis, 1H, and 13C NMR spectroscopy, by mass spectroscopy, and by chemical synthesis where feasible. These compounds include 2-amino-4,6-dinitrobenzoic acid, 2,4-dinitro-6- hydroxy-benzyl alcohol, 2-N-acetoxyamino-4,6-dinitrobenzaldehyde, 2,4-dinitro-6-hydroxytoluene, and two binuclear metabolites unique from the customary azoxytetranitrotoluenes. The monoaryl compounds show clear evidence of oxidative transformations, methyl oxidation and/or …

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Minimum Error Fickian Diffusion Coefficients For Mass Diffusion In Multicomponent Gas Mixtures, Shankar Subramaniam Jan 1999

Minimum Error Fickian Diffusion Coefficients For Mass Diffusion In Multicomponent Gas Mixtures, Shankar Subramaniam

Shankar Subramaniam

Mass diffusion in multicomponent gas mixtures is governed by a coupled system of linear equations for the diffusive mass fluxes in terms of thermodynamic driving forces, known as the generalized Stefan–Maxwell equation. In computations of mass diffusion in multicomponent gas mixtures, this coupling between the different components results in considerable computational overhead. Consequently, simplified diffusion models for the diffusive mass fluxes as explicit functions of the driving forces are an attractive alternative. These models can be interpreted as an approximate solution to the Stefan–Maxwell equation. Simplified diffusion models require the specification of “effective” diffusion coefficients which are usually expressed as …

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On Black Hole Horizon Fluctuations, Kirill Tuchin Jan 1999

On Black Hole Horizon Fluctuations, Kirill Tuchin

Kirill Tuchin

A study of the high angular momentum particles ‘atmosphere’ near the Schwarzschild black hole horizon suggested that strong gravitational interactions occur at invariant distance of the order of 3√M [2]. We present a generalization of this result to the Kerr-Newman black hole case. It is shown that the larger charge and angular momentum black hole bears, the larger invariant distance at which strong gravitational interactions occur becomes. This invariant distance is of order 3√r+2(r+ − r−). This implies that the Planckian structure of the Hawking radiation of extreme black holes is completely broken.

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Magnetic Resonance Imaging Analysis Of Molecular Mobility During Dissolution Of Poly(Vinyl Alcohol) In Water, Balaji Narasimhan, J. E.M. Snaar, R. W. Bowtell, S. Morgan, C. D. Melia, N. A. Peppas Jan 1999

Magnetic Resonance Imaging Analysis Of Molecular Mobility During Dissolution Of Poly(Vinyl Alcohol) In Water, Balaji Narasimhan, J. E.M. Snaar, R. W. Bowtell, S. Morgan, C. D. Melia, N. A. Peppas

Balaji Narasimhan

Magnetic resonance imaging is used to study changing microstructure and molecular motion during dissolution of poly(vinyl alcohol) (PVA) in water. One-dimensional water concentration profiles were measured as a function of distance from the polymer-solvent interface. Diffusion-weighted profiles were used to calculate the spatial variation of the self-diffusion coefficient of water. The results indicate that diffusion coefficient values decrease toward the glassy core of the polymer. Self-diffusion coefficient values within the dissolving polymer increase with increasing dissolution time, while those near the polymer-solvent interface remain fairly constant. The effect of PVA molecular weight on the dissolution mechanism was investigated, with MÌ„n …

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