Physical Sciences and Mathematics Commons^™

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Substituent Effects On The Gas-Phase Acidity Of Silane, Mark S. Gordon, David E. Volk, David R. Gano

Mark S. Gordon

In a previous paper, the gas-phase acidities of XHn compounds (X= C, N, 0, F, Si, P, S, Cl) were predicted with ab initio wave functions. At the MP4 level of theory with extended basis sets (6-311++G(3df,2pd)3 for second-period atoms and 6-3l++G- (3df,2pd) for third-period atoms], the calculated gas-phase acidities for these species were determined to be within 2 kcaljmol of experimental values. Similar results for the second period were obtained by DeFrees and McLean.

Iupac 32nd International Congress On Macromolecules "Macro 88", Otto Vogl, Naohuki Koide, Tatsuki Kitayama, Koichi Hatada

Otto Vogl

No abstract provided.

Kaon Transitions And Predictions Of Chiral Symmetry, Jf Donoghue, Br Holstein

Barry R Holstein

We describe a set of kaonic electromagnetic and semileptonic weak decay processes which are completely predicted within the framework of chiral symmetry (and, therefore, of low-energy QCD), emphasizing where present problems exist and suggesting future experiments.

Stepwise Synthesis And Structural Characterization Of The Molybdenum-Iron-Sulfur {[Mofe3s4cl2(Cl4cat)]2(.Mu.2-S)2}6- And {[Mofe3s4cl2(Cl4cat)]2(.Mu.2-S)(.Mu.2-Oh}5- Doubly Bridged Double Cubanes Obtained By The Coupling Of [Mofe3s4] Clusters, Dimitri Coucouvanis, Paul Challen, Sang Koo, W. Davis, W. Butler, W. Dunham

Paul R. Challen

No abstract provided.

Treatment Modality And Quality Differences For Black And White Breast Cancer Patients Treated In Community Hospitals, Paula Diehr

Paula Diehr

This study assessed the relationship of race and patterns of care, defined by an expert NCI-appointed committee, for 7,781 patients with breast cancer treated in 107 hospitals in 45 communities between 1982 and 1985. After control for age and stage of disease, black patients had significantly different care from white patients for four of the ten patterns examined. They were less likely to have a progesterone receptor assay or to be referred for postmastectomy rehabilitation, two patterns deemed desirable for all patients. Black patients were also more likely to receive liver scans and radiation therapy in situations in which these …

The Search For Medicinal Plants Among Madagascar’S Tsimihety Ethnic Group, Nat Quansah

Nat Quansah

No abstract provided.

Student Perceptions Of The Relative Importance Of Selected Attributes Of An Institution Of Higher Education: A Conjoint Approach, John Fraas, Ronald Paugh

John W. Fraas

A study investigated the relative importance of certain college attributes to the freshmen of Ashland University, a small, private university in Ohio. Five institutional characteristics were examined: availability and variety of financial aid, dorm life (living conditions and food quality), quality of education (quality of teaching, career relevance of the curriculum, and overall institutional reputation), student-faculty relationships and interaction (availability of faculty to students, faculty promotion of student development, and degree of faculty advice given to students on personal as well as academic matters), and campus social life.

Equatorial F-Regionvertical Plasma Drifts During Solar Maxima, Bela G. Fejer, E. R. De Paula, I. S. Batista, E. Bonelli, R. F. Woodman

Bela G. Fejer

Incoherent scatter radar measurements at Jicamarca are used to study the effects of large solar fluxes and magnetic activity on the F region vertical plasma drifts. The average drifts from the two last solar maxima are almost identical except in the late afternoon-early evening sector where their variations with solar flux and magnetic activity are strongly season dependent. The average evening winter (May-August) drifts appear to remain almost constant after a certain solar flux level is reached but increase with magnetic activity. The equinoctial evening drifts increase systematically with solar-flux but decrease with magnetic activity. Very large prereversal enhancement velocities, …

Toxicology Of Synthetic Pyrethroids In Aquatic Organisms: An Overview, Steven P. Bradbury, Joel R. Coats, D. M. Symonik, S. D. Dyer, L. K. Timson, G. J. Atchison

Steven P. Bradbury

The aquatic toxicology of the photostable synthetic pyrethroid insecticides as it affects two important groups of susceptible organisms — fish and aquatic insects — is discussed. The sensitivity of these aquatic species to the pyrethroids is dependent on several factors, including toxicokinetics, target site (nervous system), sensitivity and possible secondary mechanisms of action, as well as chemical and physical properties of the aquatic medium that influence toxicity and bioavailability. Uptake rates and routes of fenvalerate greatly affected the toxicity of fenvalerate to mosquito larvae. LD50 values were determined for cuticular and dietary exposure routes by utilizing radiolabeled fenvalerate at the …

Predicted Heats Of Formation For Methylsilylene And Dimethylsilylene, Mark S. Gordon, Jarry A. Boatz

Mark S. Gordon

Ab initio calculations at the MP216-31G(d,p) level of computation, combined with a sequence of isodesmic reactions, have been used to predict the heats of formation of methylsilylene and dimethylsilylene to be 49.2 and 32-33 kcallmol, respectively. These results are discussed in the light of recent experimental determinations in the accompanying experimental papers.

The Recent Climate Record: What It Can And Cannot Tell Us, Thomas R. Karl, J. Dan Tarpley, Robert G. Quayle, Henry F. Diaz, David A. Robinson, Raymond S. Bradley

Raymond S Bradley

While a great deal of climate data have been gathered over the past hundred years, there remains a number of problems limiting our ability to fully utilize these data in reconstructing the climate of the past century. This is particularly true for research demanding high precision and/or detailed local or regional-scale climate analyses. In this review we consider our ability to quantify climate change with respect to near-surface air temperature (measured 1.25-2 m above ground), sea surface temperature, .precipitation, snow cover, sea ice, and vegetation measured from space and the Earth's surface. Among the data issues we discuss are calibration, …

Conformal Transformations In Quantum Mechanics, Alec Schramm, Alfons Stahlhofen

Alec J Schramm

We discuss the occurrence of orientation- or area-preserving diffeomorphism groups in quantum mechanics. We show that the generators of these groups are contained in the generators of the symmetry group of a central potential, as is demonstrated by the example of the Coulomb problem. Our approach is based on the recently introduced concept of a factor space of scattering states.

Structures Of Two Organosilyl Azides, Steven S. Zigler, Kenneth J. Haller, Robert West, Mark S. Gordon

Mark S. Gordon

X-ray crystal structures were determined for trimesitylazidosilane (3) and 1,1-dimesityl-2,2-diphenyl- 2-tert-butylazidodisilane (4). The NcN2 and N2-N3 bond lengths (pm) in both compounds are nearly equal, being 115.8 and 117.0 for 3 and 117.0 and 114.7 for 4, respectively. These silyl azides thus differ markedly from organic azides, in which N2-N3 is much shorter than NcN2• Molecular orbital calculations predict N2-N3 to be 6 pm shorter than NcN2 in H3SiN3 (5). The N-N-N angle is 173.7° for 3 and 174.9° for 4, in good agreement with the calculated value for 5.

Intrinsic Frequency Analysis Of The Generalized Normal-Mode Vibrations For The Reaction H 2 + Ch3 - H + Ch4, Jerry A. Boatz, Mark S. Gordon

Mark S. Gordon

Vibrational energy distributions and intrinsic frequencies are computed at selected points along the H 2 + CH 3 - H + CH4 intrinsic reaction coordinate, calculated at the UHF /ST0-3G level. The energy distributions and intrinsic frequencies are shown to provide a clear and intuitively pleasing picture of the evolution of generalized normal coordinates along the reaction path. Furthermore, these quantities aid in the identification of avoided crossings between distinct generalized normal modes and between generalized normal modes and the reaction coordinate.

Infrared Spectroelectrochemical Measurements Of The Electrochemical Double Layer: Using Carbon Monoxide As A Double Layer Probe Molecule, Mark Anderson, Andrea Russell, Stanley Pons

Mark R. Anderson

No abstract is currently available.

On The Dimension Of Bivariate Superspline Spaces, Tian-Xiao He

Tian-Xiao He

A bivariate piecewise polynomial function of total degree d on some grid partition △ that has rth order continuous partial derivatives everywhere may have higher-order partial derivatives at the vertices of the grid partition. In finite element considerations and in the construction of vertex splines, it happens that only those functions with continuous partial derivatives of order higher than r at the vertices are needed to give the same full approximation order as the entire space of piecewise polynomials. This is certainly the case for d > 4r + 1. Such piecewise polynomial functions are called supersplines. This …

Ab Initio Reaction Paths And Direct Dynamics Calculations, Kim K. Baldridge, Mark S. Gordon, Rozeanne Steckler, Donald G. Truhlar

Mark S. Gordon

A detailed study of methods for generating the minimum energy path of a chemical reaction using ab initio electronic structure calculations is presented; the convergence with respect to step size of the geometry and energy along this path is studied with several algorithms. The investigations are extended to the calculation of chemical reaction rate coefficients by interfacing the POLYRATE code for variational transition-state theory and semiclassical tunneling calculations with a locally modified GAUSSIAN82 electronic structure package that now contains reaction path following capabilities at both the Hartree-Fock and perturbation theory levels. This combined package is used to study the kinetics …

Nife Invar Alloys: Theoretical Insights Into The Underlying Mechanisms Responsible For Their Physical Properties, Duane D. Johnson, F. J. Pinski, J. B. Staunton, B. L. Gyorffy, G. M. Stocks

Duane D. Johnson

What are the "driving forces" responsible for various physical properties of alloys? What causes alloy systems to order chemically and/or magnetically? To answer these questions, we have been using a quantum mechanical (QM) method to calculate cohesive energies, magnetic properties, and thermodynamic phase instability of alloys. This scheme directly incorporates the inherent disorder of the high-temperature solid solution and in this sense goes beyond traditional "band theory." Although approximations have been made at various steps in the thermodynamical averaging, and in the QM treatment of the electrons, adjustable parameters have not been used. Recently, for FCC NiFe (INVAR) alloys, we …

Toxicokinetics And Toxicodynamics Of Pyrethroid Insecticides In Fish, Steven P. Bradbury, Joel R. Coats

Steven P. Bradbury

The pyrethroid insecticides are extremely toxic to fish, with 96—h LC50 values generally below 10 μg/L and i.p. and i.v. LD50 values below 20 mg/kg. Corresponding LD50 values in mammals and birds are in the range of several hundred to several thousand milligrams per kilogram. This review examines pyrethroid toxicokinetics and toxicodynamics in fish as critical factors associated with species selectivity. Studies with permethrin, cypermethrin and fenvalerate have established that rates of metabolism and elimination in rainbow trout are significantly lower than those reported for birds and mammals. Comparatively low lethal brain pyrethroid concentrations and nonneural aspects of pyrethroid intoxication …

Molecular And Electronic Structure Of Siladiimide And Other Allenic X=Y=X Compounds, Mark S. Gordon, Michael W. Schmidt, S. Koseki

Mark S. Gordon

The preferred geometric structures of the allene analogues CH2=Si=CH2 (1), NH=Si=NH (2), PH=Si=PH (3), NH= C=NH (4), and NH=Si=CH2 (5) are examined at the RHF /6-31 G(d) level of theory, and that of 2 is further examined at the MP2/6-31G(d) computational level. The prediction that at the SCF level compounds 1, 3, 4, and 5 prefer orthogonal geometries like allene, while 2 prefers a planar structure, is examined with the aid of localized molecular orbitals, correlated energies, and, in the case of 2, a detailed analysis of the potential energy surface. The latter is very flat, and at the highest …

The Electrochemical And Sniftirs Behavior Of Copper(I)Tetrakisbenzonitrile, Mark Anderson, Daniel Blackwood, Thomas Richmond, Stanley Pons

Mark R. Anderson

No abstract is currently available.

Progress In The Development Of Hemp Protection Standards For C3i Facilities, George H. Baker, Clinton R. Gordon

George H Baker

DoD is involved in EMP standards development efforts which culminate 25 years of research. This paper previews an EMP protection standard for fixed, ground-based communication facilities. The standard uses a low-risk hardening approach which depends on an electromagnetic barrier comprised of a conducting shield to prevent harmful transients from reaching communication electronics. The standard is the first of its kind and is being instituted as MIL-STD-188-125.

Us Patent: Probe Sampler For Atomic Spectroscopy, John Marshall, D Littlejohn

Professor John Marshall

UK Patent Application No. 8305745, filed 2nd March 1983 and United States Patent 4824241 granted 25th April 1989

Phase Transitions In A Driven Lattice Gas With Repulsive Interactions, K.-T. Leung, Beate Schmittmann, R. K. P. Zia

Beate Schmittmann

We study a lattice gas with repulsive nearest-neighbor interactions driven to steady state by an external electric field E. Using Monte Carlo techniques on a two-dimensional system, we find, in the E-T plane, a line of second-order transitions joining a line of first-order ones, at a point which is probably tricritical. From a field theoretical model, we show that the operator associated with E is naively irrelevant for critical behavior. This expectation is borne out by the Monte Carlo result β=(1/8.

Ozonation For Non-Filamentous Bulking Control In An Activated Sludge Plant Fuel Synthesis Waste Transfer, Johannes Van Leeuwen

Johannes van Leeuwen

A zero discharge mode of operation at the South African fuel synthesis plants necessitates the infinite recycle of treated industrial waste water. The treatment process incorporates activated sludge units in which non-filamentous bulking and carry-over of solids often occurs. The use of ozone for the control of this non-filamentous binding was investigated on a 33 l/d small pilot-scale plant. An ozone dosage of 1 g per kg mixed liquor suspended solids per day could reduce the diluted sludge volume index from an average of 125 to about 70 ml/g mainly by preventing zoogleal growths, the main contributor to the non-filamentous …

Theoretical Studies Of Three-Membered Ring Compounds Y2h4x (Y = C, Si; X = Ch2, Nh, O, Sih2, Ph, S), Jerry A. Boatz, Mark S. Gordon

Mark S. Gordon

The heats of formation of the three-membered ring compounds Y 2H4X (Y = C, Si; X = CH2, NH, 0, SiH2, PH, S) and the thermodynamics of the insertion reactions X+ YH2=YH2 -- c-Y2H4X are predicted by using MP2/6-31G(d) energies at the 6-31G(d) geometries. Bent bond lengths are calculated by tracing the path of maximum electron density connecting two nuclei, with the 6-31G(2d) basis set at the 6-31G(d) structures. The short Si-Si internuclear distances in Si2H4X (X = CH2, NH, 0, PH, S) apparently are the result of severe bond bending rather than significant 1r character in the Si-Si bonds.

Theoretical Studies Of Bond Stretch Isomerism In Silabicyclobutanes, Jerry A. Boatz, Mark S. Gordon

Mark S. Gordon

The structures and relative energies of the bond stretch isomers of tetrasilabicyclo[l.l.O]butane (1), 1,2,3-trisilabicyclo[ l:l.O]butane (2), and 1,3-disilabicyclo[l.l.O]butane (3) are predicted at the GVB/3-21G* level, with the u and u* bridge bond molecular orbitals correlated in the GVB wave function. The transition-state structure and intrinsic reaction coordinate connecting each pair of bond stretch isomers are calculated. Two transition states joining the bond stretch isomers of 3 are located. The more stable isomer in all three molecules is the one with the longer bridge bond.

Use Of Respiratory-Cardiovascular Responses Of Rainbow Trout (Salmo Gairdneri) In Identifying Acute Toxicity Syndromes In Fish: Part 3. Polar Narcotics, Steven P. Bradbury, Tala R. Henry, Gerald J. Niemi, Richard W. Carlson, Virginia M. Snarski

Steven P. Bradbury

The physiological responses of rainbow trout to acutely lethal aqueous concentrations of the suspected polar narcotics phenol, 2,4-dimethylphenol, aniline, 2-chloroaniline and 4-chloroaniline were examined. Visible signs of intoxication included tremors that progressed to whole-organism clonic seizures, followed by general depression and respiratory-cardiovascular collapse. Tremors and seizures were usually initiated with coughs. The most striking changes in the respiratory-cardiovascular parameters for all five toxicants included elevated cough frequency (coincident with seizures), ventilation frequency and hematocrit, and depressed gill oxygen uptake efficiency, arterial pH, total arterial oxygen and total arterial carbon dioxide. The physiological responses noted were attributed to the initial muscular …

Decomposition Of Normal-Coordinate Vibrational Frequencies, Jerry A. Boatz, Mark S. Gordon

Mark S. Gordon

A decomposition scheme for the partitioning of normal-coordinate vibrational frequencies into individual internal-coordinate "intrinsic~ frequencies is presented. This scheme assigns to each internal coordinate a frequency that is representative of a vibration described solely by motion of that particular coordinate. This facilitates the interpretation of harmonic vibrational frequencies and their associated normal-coordinate displacements, especially in those cases where the normal coordinates are best described by the coupling of several internal coordinates. The utility of the method is demonstrated via application to several simple hydrides and cycloalkanes, using ab initio SCF molecular structures and Cartesian force constant matrices.