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Articles 31231 - 31260 of 34554

Full-Text Articles in Physical Sciences and Mathematics

Evaluation Of A Technique To Quantify Lipids In Bivalve Larvae Crassostrea Virginica Gmelin, Using Nile Red And Epiflourescence Microscopy, Laura Liliana Castell Perez Jan 1991

Evaluation Of A Technique To Quantify Lipids In Bivalve Larvae Crassostrea Virginica Gmelin, Using Nile Red And Epiflourescence Microscopy, Laura Liliana Castell Perez

Dissertations, Theses, and Masters Projects

No abstract provided.

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Activator-Inhibitor Control Of Tissue Growth, John A. Adam Jan 1991

Activator-Inhibitor Control Of Tissue Growth, John A. Adam

Mathematics & Statistics Faculty Publications

This note develops a simple model for the competition between activator and inhibitor control mechanisms in one-dimensional tissue growth. The pedagogic usefulness of such a model is that it is easily accessible to undergraduate applied mathematicians and is suggestive of behavior known to occur in more realistic biological systems (e.g., some types of cancer). The limitations of the model are obvious and can provide a basis for discussion of the applicability of complementary levels of description in mathematical modeling.

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Dynamic And Spectroscopic Studies Of Triplet State Nitrogen, Scott M. Hurst Jan 1991

Dynamic And Spectroscopic Studies Of Triplet State Nitrogen, Scott M. Hurst

Dissertations

No abstract provided.

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Observation Of Eliminative Cationic Polymerization Within Van Der Waals Clusters, M. Samy El-Shall, K. E. Schriver Jan 1991

Observation Of Eliminative Cationic Polymerization Within Van Der Waals Clusters, M. Samy El-Shall, K. E. Schriver

Chemistry Publications

We report the first observation of eliminative cationic polymerization within van der Waals (vdW) clusters following electron impact ionization at pressures of 10−8 Torr. The elimination reactions of C2H3Cl+ within the clusters terminate after three successive steps, each involving elimination of HCl or Cl. The results provide a mechanism for the early stages of gas phase cationic polymerization of vinyl chloride and demonstrate the feasibility of using vdW clusters as a means of studying gas phase cationic polymerization.

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Spatial And Temporal Distribution Of Hydrogen Peroxide In The Equatorial Pacific Ocean, Renee Blanchard Jan 1991

Spatial And Temporal Distribution Of Hydrogen Peroxide In The Equatorial Pacific Ocean, Renee Blanchard

Honors Theses

The concentration of hydrogen peroxide in the Equatorial Pacific was determined fluorometrically using the horseradish peroxidase catalyzed dimerization of (p-hydroxyphenyl)acetic acid. Vertical profiles were obtained between 9 ON and 3 oS on a longitudinal transect along 140 oW during June and July of 1990 on the RN Wecoma. Peroxide concentrations ranged from 25-80 nmol/L at the surface and decreased to the detection limit of 1 nmol/L at a depth of about 200 meters. Diel variations of hydrogen peroxide in the surface waters were observed over the period of 8 days. The variation in surface concentration may be attributed to the …

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Deriving Clinical Prediction Rules From Stroke Outcome Research, Daniel B. Hier, Gilda Edelstein Jan 1991

Deriving Clinical Prediction Rules From Stroke Outcome Research, Daniel B. Hier, Gilda Edelstein

Chemistry Faculty Research & Creative Works

Background and Purpose. Our Purpose Was to Determine Whether Clinical Prediction Rules Could Be Derived from Current Stroke Outcome Research. Summary of Report. We Reviewed 92 Articles on Stroke Outcome Research to Determine their Suitability for Implementation as a Clinical Prediction Rule. Methodological Problems in Many of These Studies Made Implementation of their Results as a Clinical Prediction Rule Difficult. Conclusions. Implementation of Stroke Outcome Research as Clinical Prediction Rules Would Be Facilitated by Description of Patient Population Demographics; Precise Definitions of Predictor and Outcome Measures; Stratification of Patients by Stroke Mechanism; Use of Adequate Patient Sample Sizes; and Description …

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Hydrogen Sulfide And Radon In And Over The Western North Atlantic Ocean, T. W. Andreae, Gregory A. Cutter, N. Hussain, J. Radford-Knoery, M. O. Andreae Jan 1991

Hydrogen Sulfide And Radon In And Over The Western North Atlantic Ocean, T. W. Andreae, Gregory A. Cutter, N. Hussain, J. Radford-Knoery, M. O. Andreae

OES Faculty Publications

Atmospheric measurements of radon and hydrogen sulfide, and seawater measurements of total sulfide, free sulfide, and carbonyl sulfide, were made on a cruise in the western North Atlantic Ocean (October 24 to November 9, 1989). Measured values for 222Rn ranged from 3 to 70 pCi m−3, those for atmospheric hydrogen sulfide from 1 to 85 parts per trillion, and those for dissolved total and free sulfide in seawater from 33 to 930 pmol L−1 and 0 to 73 pmol L−1, respectively. A positive correlation between 222Rn and atmospheric H2S was observed. …

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Preparation Of A Series Of N-Phenylamides Of 5-Bromo-6-Chloronicontinic Acid And 5-Bromo-2-Chloronicontinic Acid, Frank L. Setliff, Jody Z. Caldwell Jan 1991

Preparation Of A Series Of N-Phenylamides Of 5-Bromo-6-Chloronicontinic Acid And 5-Bromo-2-Chloronicontinic Acid, Frank L. Setliff, Jody Z. Caldwell

Journal of the Arkansas Academy of Science

A series of N-phenylamides of 5-bromo 6-chloronicotinic acid and 5-bromo-2-chloronicotinic acid were synthesized by treatment of their freshly prepared acid chlorides with the appropriately ring substituted anilines. Thirty new compounds were prepared, and their structures were ascertained by elemental analyses and spectroscopic techniques. Spectroscopic trends in the infrared spectra of the two series were examined in an attempt to correlate structural and electronic effects to hydrogen bonding tendencies.

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Synthesis Of Aliphatic Bis(Thioureas), Donald G. Mcewen Iv '91 Jan 1991

Synthesis Of Aliphatic Bis(Thioureas), Donald G. Mcewen Iv '91

Honors Projects

The synthesis of aliphatic bifunctional thioureas have been attempted using several nucleophilic displacement reactions. The first method involved treatment of an aliphatic diamine with ammonium thiocyanate, under two different sets of reaction conditions. The first set of reaction conditions utilized water as the solvent, while second employed acetone as the solvent. Both of the reactions utilizing l,2-ethylenediamine and ammonium thiocyanate did not afford the desired bis(thioureas). In particular, the crystalline solid obtained from the reaction carried out in water was 57.8 ± 0.05 % thiocyanate by mass. The second nucleophilic addition method involved the treatment of both 1,2-ethylenediamine and 1,6-hexanediamine …

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Organic Geochemistry And Petrography Of Spanish Oil Shales, Michael A. Kruge, Isabel Suarez-Ruiz Jan 1991

Organic Geochemistry And Petrography Of Spanish Oil Shales, Michael A. Kruge, Isabel Suarez-Ruiz

Department of Earth and Environmental Studies Faculty Scholarship and Creative Works

Four of the principal oil shale units of Spain were examined by organic geochemical and petrographic methods. The samples included three lacustrine shales (Carboniferous from Puertollano, Cretaceous from Llames and Miocene from Rubielos de Mora) and one marine shale (Lower Jurassic from Punta del Cuerno ). The petrographic observations show a dominance of liptodetrinite associated with bitumen-stained mineral matter and alginite, as well as a paucity of structured terrestrial organic matter. Geochemical work shows that the soluble organic matter is a mixture of terrestrially derived and aquatic, with the lacustrine samples having the strongest land plant signatures. Low values of …

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Evaluation Of Scavenger Gases In A Helium Discharge Detector, Sandra Lynn Poteat Jan 1991

Evaluation Of Scavenger Gases In A Helium Discharge Detector, Sandra Lynn Poteat

Dissertations, Theses, and Masters Projects

No abstract provided.

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Novel Chemical Preparative Route For Semiconducting Mose2 Thin Films, K. C. Mandal, O. Savadogo Jan 1991

Novel Chemical Preparative Route For Semiconducting Mose2 Thin Films, K. C. Mandal, O. Savadogo

Faculty Publications

No abstract provided.

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Critical Phenomena From Diamagnetic Signal In High Tc Perovskites, Juana Acrivos, M. Chen Lei Jan 1991

Critical Phenomena From Diamagnetic Signal In High Tc Perovskites, Juana Acrivos, M. Chen Lei

Faculty Publications, Chemistry

Critical phenomena in nearly two-dimensional high Tc superconductors are detected by induction measurements of the shielding current produced by bulk quantization of flux vs Hz.

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Interaction Of Pyridine With Ba2casr2cu20x, Juana Acrivos, C. Lin Jan 1991

Interaction Of Pyridine With Ba2casr2cu20x, Juana Acrivos, C. Lin

Faculty Publications, Chemistry

The adsorption of of pyridine on single crystals of Bi2CaSr2Cu2Ox has been followed by optical microscopy on the crystal surface, where a blue solution is formed as a first step of reaction. The superconducting properties of the single crystal and its structure were monitored by ac susceptibility and by x-ray diffraction measurements. The results (as observed by the growth of the blue solution boundary versus time with Daa = 3.7x10-10 cm2/s.) indicate that the reaction starts at nucleation sites on the basal surface of the crystal. The edges of the crystal also show blue nucleation sites but these do not …

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Evaluation Of A Remote Sensor For Mobile Source Co Emissions, Donald H. Stedman, Gary A. Bishop, Marc Pitchford Jan 1991

Evaluation Of A Remote Sensor For Mobile Source Co Emissions, Donald H. Stedman, Gary A. Bishop, Marc Pitchford

Fuel Efficiency Automobile Test Publications

Carbon monoxide (CO) emission measurements of thousands of vehicles per day are possible with a recently evaluated remote sensor developed at the University of Denver. Funded by the Environmental Monitoring Systems Laboratory - Las Vegas (EMSL- LV) Innovative Research Program, the evaluation has demonstrated the comparability of volume concentration measurements made by this method with traditional emission monitoring instrumentation. Measurements are made unobtrusively as vehicles pass through an infrared light beam directed across one traffic lane about 25 centimeters above the pavement. A video camera records the vehicle registration number of each vehicle as its CO emissions are measured so …

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On-Road Carbon Monoxide And Hydrocarbon Remote Sensing In The Chicago Area, Donald H. Stedman, Gary A. Bishop, James E. Peterson, Paul L. Guenther, Iain F. Mcvey, Stuart P. Beaton Jan 1991

On-Road Carbon Monoxide And Hydrocarbon Remote Sensing In The Chicago Area, Donald H. Stedman, Gary A. Bishop, James E. Peterson, Paul L. Guenther, Iain F. Mcvey, Stuart P. Beaton

Fuel Efficiency Automobile Test Publications

No abstract provided.

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Ab Initio Study Of The Intermolecular Potential Of Ar–H2o, G. Chalasinski, M. M. Szczesniak, Steve Scheiner Jan 1991

Ab Initio Study Of The Intermolecular Potential Of Ar–H2o, G. Chalasinski, M. M. Szczesniak, Steve Scheiner

Chemistry and Biochemistry Faculty Publications

The combination of supermolecular Møller–Plesset treatment with the perturbation theory of intermolecular forces is applied in the analysis of the potential‐energy surface of Ar–H2O. The surface is very isotropic with the lowest barrier for rotation of ∼35 cm−1 above the absolute minimum. The lower bound for De is found to be 108 cm−1 and the complex reveals a very floppy structure, with Ar moving freely from the H‐bridged structure to the coplanar and almost perpendicular arrangement of the C2 –water axis and the Ar–O axis, ‘‘T‐shaped’’ structure. This motion is almost isoenergetic (energy change …

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Theoretical Vibrational Study Of Fx...Nh3 (X=H, D, Li) Complexes, Y. Bouteiller, Z. Latajka, H. Ratajczak, Steve Scheiner Jan 1991

Theoretical Vibrational Study Of Fx...Nh3 (X=H, D, Li) Complexes, Y. Bouteiller, Z. Latajka, H. Ratajczak, Steve Scheiner

Chemistry and Biochemistry Faculty Publications

This paper presents the first ab initio attempt to construct the stretching fundamentals νFX and νF...N (X=H, D, Li) in the FX...NH3 complexes taking into account the mechanical anharmonicity. A potential‐energy surface V(rFX,RF...N) grid was generated at the self‐consistent‐field and second‐order Møller–Plesset levels. The coefficients fitting the potential‐energy surface up to the fourth order have been used to compute the νFX and νF...N stretching modes. The vibrational problem is solved by means of a variational treatment which includes the effects of mechanical …

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Ab Initio Study Of Intermolecular Potential Of H2o Trimer, G. Chalasinski, M. M. Szczesniak, P. Cieplak, Steve Scheiner Jan 1991

Ab Initio Study Of Intermolecular Potential Of H2o Trimer, G. Chalasinski, M. M. Szczesniak, P. Cieplak, Steve Scheiner

Chemistry and Biochemistry Faculty Publications

Nonadditive contribution to the interaction energy in water trimer is analyzed in terms of Heitler–London exchange, SCF deformation, induction and dispersion nonadditivities. Nonadditivity originates mainly from the SCF deformation effect which is due to electric polarization. However, polarization does not serve as a universal mechanism for nonadditivity in water. In the double‐donor configuration, for example, the Heitler–London exchange contribution is the most important and polarization yields the wrong sign. Correlation effects do not contribute significantly to the nonadditivity. A detailed analysis of the pair potential is also provided. The present two‐body potential and its components are compared to the existing …

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Remote Sensing Enhanced Motor Vehicle Emissions Control For Pollution Reduction In The Chicago Metropolitan Area: Siting And Issue Analysis, Carol E. Lyons, Donald H. Stedman Jan 1991

Remote Sensing Enhanced Motor Vehicle Emissions Control For Pollution Reduction In The Chicago Metropolitan Area: Siting And Issue Analysis, Carol E. Lyons, Donald H. Stedman

Fuel Efficiency Automobile Test Publications

No abstract provided.

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Automobile Emissions In Mexico City, Stuart P. Beaton, Gary A. Bishop, Donald H. Stedman Jan 1991

Automobile Emissions In Mexico City, Stuart P. Beaton, Gary A. Bishop, Donald H. Stedman

Fuel Efficiency Automobile Test Publications

No abstract provided.

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Trace Elements In Estuarine And Coastal Waters: U.S. Studies From 1986-1990, Gregory A. Cutter Jan 1991

Trace Elements In Estuarine And Coastal Waters: U.S. Studies From 1986-1990, Gregory A. Cutter

OES Faculty Publications

The use of specialized analytical techniques, field studies, controlled laboratory experiments, and geochemical modeling have allowed U.S. investigators to expand our understanding of trace element cycling in coastal waters and estuaries. Considerable emphasis has been placed on quantifying the flux of trace elements within and through the coastal zone. In addition, substantial progress has been made in identifying the chemical speciation of many trace elements, providing a linkage between the geochemical and biochemical behavior of these elements. Another significant advance has been the use of trace elements as tracers of geochemical processes and water masses in the coastal environment.

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Direct Determination Of Molecular-Orbital Symmetry Of H2s Using Polarized X-Ray Emission, R. Mayer, Dennis W. Lindle, S. H. Southworth, P. L. Cowan Jan 1991

Direct Determination Of Molecular-Orbital Symmetry Of H2s Using Polarized X-Ray Emission, R. Mayer, Dennis W. Lindle, S. H. Southworth, P. L. Cowan

Chemistry and Biochemistry Faculty Research

X-ray emission from the molecule H2S is strongly polarized following excitation of a sulfur K-shell electron to an unoccupied subthreshold molecular orbital with a polarized x-ray beam. Changes in the polarization of the emission spectrum are observed as the incident beam's energy is swept across the subthreshold absorption resonance. The previously unresolved absorption resonance is shown experimentally to be primarily associated with a molecular orbital of b2 symmetry, but with a high-excitation-energy component due to an orbital with a1 symmetry. Satellite emission intensity is shown to depend on the primary photon energy and is therefore associated …

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Reactions Of Di-(1-Naphthyl) Diazomethane With Beta-Cyclodextrin, Margaret Frances Cabell Jan 1991

Reactions Of Di-(1-Naphthyl) Diazomethane With Beta-Cyclodextrin, Margaret Frances Cabell

Dissertations, Theses, and Masters Projects

No abstract provided.

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The Effects Of The Exposure Of Atomic Oxygen On Polymeric Material: I Siloxane Modified Epoxy Resins Ii Polyetherimide Films With Additives, Eugene Canlas Aquino Jan 1991

The Effects Of The Exposure Of Atomic Oxygen On Polymeric Material: I Siloxane Modified Epoxy Resins Ii Polyetherimide Films With Additives, Eugene Canlas Aquino

Dissertations, Theses, and Masters Projects

No abstract provided.

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Drop-Box Technique For Quantitative Sampling Of Macrofauna And Aquatic Plants At Restored And Natural Wetlands, J. Douglas Oliver, Andrew J. Leslie, William M. Bartodziej Jan 1991

Drop-Box Technique For Quantitative Sampling Of Macrofauna And Aquatic Plants At Restored And Natural Wetlands, J. Douglas Oliver, Andrew J. Leslie, William M. Bartodziej

Faculty Publications and Presentations

No abstract provided.

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Role Of Surface Morphology In Wafer Bonding, W.P. Maszara, B.L. Jiang, A. Yamada, G.A. Rozgonyi, H. Baumgart, A.J.R. De Kock Jan 1991

Role Of Surface Morphology In Wafer Bonding, W.P. Maszara, B.L. Jiang, A. Yamada, G.A. Rozgonyi, H. Baumgart, A.J.R. De Kock

Electrical & Computer Engineering Faculty Publications

The strain patterns detected by x-ray topography in wafers bonded for silicon-on-insulator (SOI) technology were found related to the flatness nonuniformity of the original wafers. Local stresses due to the bonding process are estimated to be about 1×108 dynes/cm2. The stress is reduced about 100 times for the thin (0.5 μm) SOI films. Most of the wafer deformation occurs during room temperature mating of the wafers. The deformation is purely elastic even at 1200 °C. The magnitude of the stress appears insignificant for complimentary metal-oxide-semiconductor devices performance.

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Second Coefficient Of Viscosity In Air, Robert L. Ash, Allan J. Zuckerwar, Zhonquan Zheng Jan 1991

Second Coefficient Of Viscosity In Air, Robert L. Ash, Allan J. Zuckerwar, Zhonquan Zheng

Mechanical & Aerospace Engineering Faculty Publications

Acoustic attenuation measurements in air were analyzed in order to estimate the second coefficient of viscosity. Data over a temperature range of 11 C to 50 C and at relative humidities between 6 percent and 91 percent were used. This analysis showed that the second coefficient of viscosity varied between 1900 and 20,000 times larger than the dynamic or first coefficient of viscosity over the temperature and humidity range of the data. In addition, the data showed that the molecular relaxation effects, which are responsible for the magnitude of the second coefficient of viscosity, place severe limits on the use …

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Development Of Ruthenium Vinylbipyridine Modified Electrode Surfaces For Use In Chemiluminescence-Based Detection Systems, Matthew F. Piescinski Jan 1991

Development Of Ruthenium Vinylbipyridine Modified Electrode Surfaces For Use In Chemiluminescence-Based Detection Systems, Matthew F. Piescinski

Masters Theses

Based upon the chemiluminescent properties of [Ru(bpy)3]2+ and the proven analytical applications of that complex in the detection of easily reduced anions in solution, a chromatographic detection system was designed utilizing an immobilized form of the Ru(ll) complex. The objective was to create, by electropolymerization, a regenerative chemiluminescent surface on a working electrode. Reductive electropolymerization was accomplished by the use of a [Ru(bpy)3]2+ analog containing the ligand vinylbipyridine. Two analogs, [Ru(vbpy)3][PF6]2 and [Ru(phen)2(vbpy)][PF6]2 were polymerized on platinum, glassy carbon and indium-doped tin oxide working …

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New Bio-Analytical Separations Utilizing Chiral Mobile Phase Additives In Thin Layer Chromatography And Chiral Stationary Phases In High Performance Liquid Chromatography, Jo Dee Duncan Jan 1991

New Bio-Analytical Separations Utilizing Chiral Mobile Phase Additives In Thin Layer Chromatography And Chiral Stationary Phases In High Performance Liquid Chromatography, Jo Dee Duncan

Doctoral Dissertations

"The problem addressed by this dissertation is the separation of optical isomers in commercial as well as biological samples. The chromatographic separation of enantiomers is an important and rapidly developing field of study. Chiral separations of pharmaceutical compounds and important organic intermediates in high performance liquid chromatography (HPLC) and thin layer chromatography (TLC) were achieved. Two methods were employed for the direct liquid chromatographic resolution of chiral analytes: chiral stationary phases (CSPs) and chiral mobile phase additives (CMAs). Native and derivatized ß-cyclodextrins (ß-CD) were used as chiral stationary phases in reverse phase and normal phase HPLC, respectively. This study marked …

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