Physical Sciences and Mathematics Commons^™

Principal Resonance Contributors To High-Valent, Transition-Metal Alkylidene Complexes, Thomas R. Cundiari, Mark S. Gordon

Mark S. Gordon

The results of ab initio calculations are reported for prototypical high-valent, alkylidene complexes. Stationary points on each potential energy surface are characterized and compared to experimental information where available; as long as a suitably flexible valence basis set is used, good agreement between theoretically calculated and experimentally determined geometries is obtained. The complexes of interest include group IVB (Ti, Zr and Hf) and group VB (Nb and Ta) alkylidenes with hydride ligands as well as models for the four-coordinate, olefin metathesis catalysts (Mo-, W-, and Re-alkylidenes) which have been recently synthesized and characterized. In light of the fact that much …

Interpretation Issues In Force Microscopy, Nancy Burnham, Richard Colton, Hubert Pollock

Nancy A. Burnham

In this paper, we will discuss force microscopy (FM) and its potential for determining mechanical properties of thin films. We will introduce the basic principles of FM, and demonstrate how FM can be used to determine materials properties as well as image surface topography, both with nanonewton or sub‐nanonewton force resolution and sub‐nanometer position resolution. As FM is still a new field, not all of the questions concerning interpretation have been fully answered. We will elucidate four current issues that must be resolved before the full potential of FM can be realized. They are: (1) the role of water vapor …

Setting Time Effects On Bentonite Water-Well Annulus Seals, Fred L. Ogden

Fred L. Ogden

Shear strength tests are conducted in a model of a water well on four, commercially available, granular bentonite well sealing products. The time dependency of annulus seal shear strength and resistance to piping is examined. Dry bentonite samples are placed through water in the annular space between the casing and borehole and allowed to set for a specified time. Pressure is applied at a constant rate to one end of the clay seal until shear or piping failure occurs. Pressure and seal displacement data are recorded on a digital data acquisition system. Annulus seal strength and resistance to piping increase …

The Influence Of Cation Size Upon The Infrared Spectrum Of Carbon Monoxide Adsorbed On Platinum Electrodes, Mark Anderson, Jimin Huang

Mark R. Anderson

No abstract is currently available.

Finger Formation In A Driven Diffusive System, D. H. Boal, Beate Schmittmann, R. K. P. Zia

Beate Schmittmann

A driven diffusive lattice gas is studied in a rectangular geometry: particles are fed in at one side and extracted at the other, after being swept through the system by a uniform driving field. Being periodic in the transverse direction, the lattice lies on the surface of a cylinder. The resulting nonequilibrium steady state depends strongly on this choice of boundary conditions. Both Monte Carlo and analytic techniques are employed to investigate the structure of typical configurations, the density profile, the steady-state current, and the nearest-neighbor correlations. As the temperature is lowered in a finite system, the simulations indicate a …

The Influence Of Cation Size Upon The Infrared Spectrum Of Carbon Monoxide Adsorbed On Platinum Electrodes, Mark Anderson, Jimin Huang

Mark R. Anderson

No abstract is currently available.

A New Twist On Pseudorotation, Theresa L. Windus, Mark S. Gordon, Larry W. Burggraf, Larry P. Davis

Mark S. Gordon

For pentacoordinated structures in a trigonal bipyramidal ar· rangement, Berry1 proposed a "pseudorotation" mechanism whereby two such isomers can interconvert through a tetragonal transition state (TS). This Berry pseudorotation mechanism was demonstrated explicitly for SiH5- by following the MP22/6· 31G(d)3 minimum energy path4 (MEP).

Observability Of The Anapole Moment And Neutrino Charge Radius, Mj Musolf, Br Holstein

Barry R Holstein

The properties of the neutrino charge radius (NCR) and anapole moments (AM's) of elementary fermions, nucleons, and nuclei are discussed. The dependence of these off-shell electromagnetic couplings on the weak gauge parameter is explicitly demonstrated by a calculation performed in the Rξ gauge. The gauge dependence of the AM's and NCR implies that they cannot be observed in isolation from other second-order, electroweak effects. It is shown, however, that the AM's of various hadronic systems having an SU(2)L quantum number TL3=0 can be considered ``observables'' in certain formal, though unphysical, limits. It is argued that, apart from these special limits, …

Thermochronology And Thermobarometry In Lithotectonic Zones In Eastern New England, Andrea Koziol, Robert Wintsch

Andrea M. Koziol

Sniftirs Study Of The Behavior Of The Spectrum Of Carbon Monoxide Adsorbed On A Platinum Electrode In Alcoholic Solvents, Andrea Russell, Daniel Blackwood, Mark Anderson, Stanley Pons

Mark R. Anderson

The vibrational spectrum of carbon monoxide as a function of coverage in various alcoholic solvents was investigated using the SNIFTIRS technique. At low coverage the potential dependence of the band position was found to be linearly dependent on the inverse of the bulk dielectric constant of the solvent. An electrostatic model was developed to represent the interaction between adjacent adsorbate molecules. This model provides evidence in support of an island formation mechanism.

Transport Processes And Traveling Waves In Systems With Local Nonequilibrium, Sergey Sobolev

Sergey Sobolev

No abstract provided.

Gas-Phase Chemistry Of The Dimethylaluminum Oxide Ion And Related Aluminum Oxide Ions: Comparison Of Reactivity With Siloxide Ions, Robert Damrauer, Michèle Krempp, Michael W. Schmidt, Mark S. Gordon

Mark S. Gordon

The anion [(CH3hAIOt (1) has been prepared in a flowing afterglow selected ion flow tube (FA-SIFT) by ion selection from the reaction mixture of trimethylaluminum dimer and hydroxide. This unusual ion is quite reactive and has been extensively studied. It reacts with halogen-containing compounds of several types, including fluorobenzene, chlorobenzene, bromofluorobenzene, acetyl chloride, and HF, to give [(CH3hAI(OH)Xt, where X = F, Cl, and Br. Its chemistry with hexafluorobenzene and silicon tetrafluoride has also been detailed as have a number of reactions with carboxylic acids, esters, anhydrides, sulfur-containing neutrals, alcohols, water, and ammonia. The dominant reaction pattern of 1 involves …

Origins Of Compositional Order In Nipt Alloys, F. J. Pinski, B. Ginatempo, Duane D. Johnson, J. B. Staunton, G. M. Stocks, B. L. Gyorffy

Duane D. Johnson

We investigate the cause of compositional ordering in fcc Ni0.50Pt0.50 on the basis of a first-principles theory of electronic structure and finite-temperature concentration fluctuations. We treat the size effect, electronegativity, and band filling on an equal footing and find that the first of these dominates, leading to L10 ordering in agreement with experiment. An electronic origin is given for the metallurgical ‘‘rule of thumb’’ that alloys comprised of big atoms and little atoms tend to order into simple stuctures.

The Interaction Between Dislocations And Intergranular Cracks, H. Zhang, Alexander H. King, R. Thomson

Alexander H. King

The elastic interactions of dislocations and intergranular cracks in isotropic materials have been studied. In the first part of the paper, a model based on the Rice–Thomson theory is established under which the conditions for dislocation emission and crack propagation can be described in terms of an emission surface, cleavage surface, and loading line in the local k-space associated with a mixed mode intergranular crack. For a given crack, the local k-field changes with the emission of dislocations from the crack tip, which alters the balance of cleavage and emission. In the second part, we present experimental results of in …

Effect Of Hydration And Dimerization Of The Formamidine Rearrangement, Kiet A. Nguyen, Mark S. Gordon, Donald G. Truhlar

Mark S. Gordon

Ab initio molecular orbital theory is used to predict the geometry of the transition state and the energy barrier for the double-proton transfer in formamidine dimer, using SCF /6-31 G(d,p) and MP2/6-31 G(d,p) wave functions, respectively. Intramolecular hydrogen transfer in the uncomplexed monomer (I) and double-proton transfer in the mixed dimer of formamidine and water (2) are also investigated at several levels of theory. All computational levels predict the barrier for the uncomplexed reaction (I) to be approximately twicdhat for the hydrated reaction (2). Isomerization by double-proton transfer in the dimer (3) is predicted to be the most favorable process. …

Experimental Studies Of Fe-Mg Carbonates As Indicators Of Martian Near-Surface Conditions, Andrea Koziol

Andrea M. Koziol

Critical Properties Of A Randomly Driven Diffusive System, Beate Schmittmann, R. K. P. Zia

Beate Schmittmann

We consider a system of interacting particles, diffusing under the influence of both thermal noise and a random, external electric field which acts in a subspace of m dimensions. In the nonequilibrium steady state, the net current is zero. When the interparticle interaction is short ranged and attractive, a second-order phase transition is expected. Analyzing this system in field-theoretic terms, we find the upper critical dimension to be 4-m and its behavior to fall outside the universality classes of the equilibrium Ising model and the usual driven diffusive system. A new fixed point and critical exponents are computed.

Cluster As Solitons On The Nuclear Surface, Andrei Ludu

Andrei Ludu

No abstract provided.

The T-Designs On 13 Points With A Primitive Group Of Order 78 As A Group Of Automorphism, M. R. Darafsheh, M. Rajabi Tarkhorani, Saeid Abbasbandy

Saeid Abbasbandy

No abstract provided.

A Software World, David Morgan Lochhead

Dr. David Morgan Lochhead

What are the consequences when software defines reality? This essay was prepared for presentation at a church related computer event in 1991, but was never presented after the event was cancelled

Estimating County Percentages Of People Without Health Insurance, Paula Diehr

Paula Diehr

County data on the percentage of people without health insurance are seldom available, although state program planning requires such information. As part of an evaluation of Washington's Basic Health Plan (BHP), we conducted a telephone survey in nine Washington counties to estimate the percentage of people under the age of 65 who were uninsured. We used regression analysis to estimate the percentage uninsured in a county as a function of the percentage unemployed. Two validation approaches yielded very good results, suggesting that the equation could be used to estimate the percentage uninsured in unsurveyed counties. The variation ranged from 15% …

Characterization Of Sh Groups In Porin Of Bovine Heart Mitochondria. Porin Cysteines Are Localized In The Channel Walls., Philadelphia University

Philadelphia University, Jordan

No abstract provided.

Inhibition Of Alcohol Dehydrogenase Activity By Acetylenic And Allylic Alcohols: Concordance With In Vivo Electrophile Reactivity In Fish, Steven P. Bradbury, Glenn M. Christensen

Steven P. Bradbury

Acetylenic and al!ylic alcohols have been reported to be 20 to 5,000 times more acutely toxic to fathead minnows (Pimephales promelas) than would be expected from a narcosis-based mechanism of action. The greater-than-expected toxicity of these alcohols has been proposed to be a result of metabolic activation to the corresponding reactive a ,)3-unsaturated aldehydes or allene derivatives. Using purified horse liver and rainbow trout (Oncorhynchus mykiss) hepatic cytosol alcohol dehydrogenase (ADH) preparations, the propensity of a series of acetylenic and allylic alcohols to inhibit enzyme activity, in both the presence and the absence of reduced glutathione, was ascertained. Those alcohols …

Use Of Respiratory-Cardiovascular Responses Of Rainbow Trout (Oncorhynchus Mykiss) In Identifying Acute Toxicity Syndromes In Fish: Part 4. Central Nervous System Seizure Agents, Steven P. Bradbury, Richard W. Carlson, Gerald J. Niemi, Tala R. Henry

Steven P. Bradbury

The respiratory-cardiovascular responses of spinally transected rainbow trout to acutely lethal concentrations of chlorpyrifos, cypermethrin, fenvalerate, endosulfan, endrin, and strychnine were examined. Common to all six toxicants, the most striking change in respiratory-cardiovascular parameters was an increased cough frequency. Ventilation frequency and volume dropped in strychnine-exposed trout, but both remained near predose levels (frequency) or elevated (volume) in the pyrethroid- and cyclodiene-exposed trout. In chlorpyrifos-intoxicated trout, ventilation frequency decreased while volume increased. Oxygen consumption remained near predose levels in the chlorpyrifos-, pyrethroid-, and strychnine-exposed trout, but increased dramatically in the cyclodiene-exposed trout. Arterial oxygen, carbon dioxide, and pH declined in …

Lignin Distribution In Thermomechanically Pulped Wood Fibers Via X-Ray Microanalysis, Douglas Stokke, Xuerong Wang

Douglas D. Stokke

The three major framework organic constituents of the secondary xylem (wood) of trees are cellulose, hemicelluloses, and lignin. Lignin imparts a number of important physical properties to the woody cell wall. In addition, lignin serves as the "cement" which binds cells together, and is the material which must be softened, altered, or removed during pulping processes. The distribution of lignin within pulp cell walls is of importance with respect to use of the pulp fibers. In this study, x-ray analysis was used to investigate lignin distribution in thermomechanically pulped (i.e., pulped with heat and pressure, with no chemical treatment) aspen …

Optimering Van Koagulasie En Flokkulasie In Die Herwinning Van Koelwater Uit Oliesintese-Afvalwater, Johannes Van Leeuwen, P. Wille

Johannes van Leeuwen

The activated sludge process, which is used in the purification of an oil synthesis effiuent, produces an effiuent which is high in turbidity. The water also contains a lot of dispersed bacterial growth which is not removed during sedimentation. Flocculation is essential to remove these materials. The average diameter of the colloids was found to be 0,92/'m. The zeta potential of the colloids was determined in an attempt to correlate it to the amount of flocculant required. The value was relatively constant at -13,88 mV, which indicates that a cationic·coagulant was required. The required dosage to achieve clarification by means …

The Slater–Pauling Curve: First Principles Calculations Of The Moments Of Fe1 − C Ni C And V1 − C Fe C, Duane Johnson, F. Pinski, J. Staunton

Duane D. Johnson

We have performed calculations of the electronic structure of the random substitutional alloys Fe1−c Ni c and V1−c Fe c using the spin‐polarized, self‐consistent Korringa–Kohn–Rostoker coherent‐potential approximation (KKR‐CPA) method. This is a first principles method based on spin density functionaltheory and a local spin density approximation for the exchange and correlation functional. For fcc Fe1−c Ni c , a range of volumes were considered for 0.25

Novel Ce Magnetism In Cedipnictide And Di‐Ce Pnictide Structures, Paul C. Canfield, J. D. Thompson, Z. Fisk

Paul C. Canfield

Results of electrical resistance and magnetic susceptibility measurements on Ce2Bi, Ce2Sb, CeScGe, CeScSi and CeSb2 are presented. Ce2Bi and Ce2Sb have antiferromagnetictransitions at low temperatures, while CeSb2, CeScGe and CeScSi have ferromagnetictransitions, CeScGe having a T c = 46 K. The data are analyzed with respect to the similarities of the two crystal structure groups that these materials fall into: CeSb2 having the LaSb2structure and the other materials all having the La2Sb structure.

Magnetism And Heavy Fermion‐Like Behavior In The Rbipt Series, Paul C. Canfield, J. D. Thompson, W. P. Beyermann, A. Lacerda, M. F. Hundley, E. Peterson, Z. Fisk, H. R. Ott

Paul C. Canfield

Members of the RBiPt (R=Ce–Lu with the exceptions of Pm and Eu) series have been grown as single crystals.Magnetic susceptibility and electrical resistance have been measured on all members of the series, and specific heatmeasurements have been performed on representatives. The high temperature resistance uniformly changes from that of a small‐gap semiconductor or semimetal seen in NdBiPt to that of a heavy‐fermion metal seen in YbBiPt, which shows a linear coefficient of specific heat at low temperatures of 8 J/K2 mole. Further, the lighter rare earth members show an unusually sharp increase in their resistance associated with antiferromagnetic ordering at …

Ion Irradiation Effects On Graphite With Scanning Tunneling Microscope, T. -C. Shen, R. T. Brockenbrough, J. R. Tucker, J. W. Lyding

T. -C. Shen

Scanning tunneling microscope is used to create local surface modifications by means of ion impact damage. Graphite has been used as a test case to demonstrate this local surface sputtering. Using 0.1-µs voltage pulse of - 30 to - 140 V applied to the sample in a rough vacuum of 10-2 Torr, a confined area of damage (typically about 100 Å in diameter) is usually obtained. The damaged area consists of several layers of terraces. Defects of the size of a few atoms can also be found. Electronic perturbations caused by defects can form superlattices with a spacing three times …