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Articles 29581 - 29610 of 34577

Full-Text Articles in Physical Sciences and Mathematics

Mea Culpa: Formal Education And The Dis-Integrated World., Brian P. Coppola, Douglas S. Daniels Jan 1998

Mea Culpa: Formal Education And The Dis-Integrated World., Brian P. Coppola, Douglas S. Daniels

Chemistry Faculty Publications

Formal education has removed itself so far from any truly integrated view of the Natural World that fragmentation and certainty are prevailing ethics. Technological progress has resulted in increased specialization within academic disciplines and their concurrent separation from each other. Knowledge is extracted from a fully integrated world, but is examined and defined by the 'dis-integrated' objectives.

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A Kinetic Study Of The Photolysis Of Ethylferrocene In Chloroform, Son L. Phan, Patrick E. Hoggard Jan 1998

A Kinetic Study Of The Photolysis Of Ethylferrocene In Chloroform, Son L. Phan, Patrick E. Hoggard

Chemistry and Biochemistry

The photooxidation of ethylferrocene to ethylferricinium ion and tetrachloroferrate in CHCl3 under 254 nm irradiation proceeds through light absorption by both ethylferrocene and chloroform. The products remain in solution at concentrations below 10-3 M. The fraction occurring through a solvent-initiated pathway increases during the course of the reaction. A secondary thermal reaction is responsible for generating tetrachloroferrate from ethylferricinium ion. The rate of the reaction increases during the early stages, and the data throughout the course of the reaction are consistent with the rate law ( afs + bfR)/ (1 + c[R]/[P]-d[R]/[Cl ]), where [R] and [P] are the concentrations …

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Palladium-Catalyzed Carboxylation Of Allyl Stannanes And Carboxylative Coupling Of Allyl Stannanes And Allyl Halides [Abstract], Russell J. Franks Jan 1998

Palladium-Catalyzed Carboxylation Of Allyl Stannanes And Carboxylative Coupling Of Allyl Stannanes And Allyl Halides [Abstract], Russell J. Franks

Faculty Publications

The reaction of allyl stannanes with CO2 to form stannyl carboxylates (esters) is catalyzed by Pd(PR3)4 complexes. Thus, R3SnCH2CH=CH2 [R=Me and Ph]are converted to R3SnO2 CCH2CH=CH2 and R3SnO2CCH=CHCH3 under 33 atm of CO2 (70°C, THF) in moderate to excellent yield in the presence of 8 mol% Pd(PPh3)4 ; polycarboxylation of diallyldibutyltin and tetraallyltin also is effected, producing the respective di- and tetracarboxylates, Bu2Sn(O2CCH2CH=CH2)2 and Sn(O2CCH …

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Substituted Polythiophenes From Highly Reactive Zinc Reagents, Reuben D. Rieke Jan 1998

Substituted Polythiophenes From Highly Reactive Zinc Reagents, Reuben D. Rieke

Chemistry Department: Faculty Publications

A novel Zerovalent zinc species and an organozinc reagent are disclosed. The zerovalent zinc species is directly pro duced by reaction of a reducing agent on a zinc salt, preferably Zn(CN)2. The organozinc reagent results from the reaction of the zerovalent zinc species and an organic compound having one or more stable anionic leaving groups. These organozinc reagents include a wide spectrum of functional groups in the organic radical, and are useful in a variety of reactions schemes.

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Cross-Coupling Of Organic Compounds Using Cuprous Odide, Reuben D. Rieke Jan 1998

Cross-Coupling Of Organic Compounds Using Cuprous Odide, Reuben D. Rieke

Chemistry Department: Faculty Publications

Cross-coupling or addition reactions of organic compounds, including acid halides, allylic halides, and C.B-unsaturated carbonyl containing compounds, with organozinc com pounds may be readily and Safely carried out in the presence of cuprous iodide. The use of this catalyst in the coupling reaction provides for the preparation of commercially useful products in the pharmaceutical, agrochemical and other industries.

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Metathesis-Based Synthesis Of Jasmonate And Homojasmonate Lactones, Candidates For Extracellular Quorum Sensing Molecules In Candida Albicans, Su C. Cho, Patrick Dussault, Amber D. Lisec, Ellen C. Jensen, Kenneth W. Nickerson Jan 1998

Metathesis-Based Synthesis Of Jasmonate And Homojasmonate Lactones, Candidates For Extracellular Quorum Sensing Molecules In Candida Albicans, Su C. Cho, Patrick Dussault, Amber D. Lisec, Ellen C. Jensen, Kenneth W. Nickerson

Chemistry Department: Faculty Publications

Ring-closing metathesis of jasmonate esters is shown to provide a rapid entry to jasmonate lactones. The lactones were investigated as possible quorum sensing molecules for the fungi Candida albicans. Assays demonstrated no effect on fungal morphology at concentrations up to 96 mM.

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Method For The Synthesis Of Α-Oxranyl Amino Acids, David B. Berkowitz, Michelle L. Pedersen Jan 1998

Method For The Synthesis Of Α-Oxranyl Amino Acids, David B. Berkowitz, Michelle L. Pedersen

Chemistry Department: Faculty Publications

The present invention is related to a novel class of decar-boxylase enzyme inhibitors consisting of α-oxiranyl amino acids and derivatives thereof and a method of synthesizing Such compounds.

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Radicals, Metals And Magnetism, David J R Brook Jan 1998

Radicals, Metals And Magnetism, David J R Brook

David J. R. Brook

The interaction between unpaired electrons governs many physical properties of materials. Although in a fundamental sense the interaction is simple, a full understanding of the interaction in molecular systems is complicated by the presence of other bonding and non-bonding electrons. The resulting many body problem is very challenging. Nevertheless, much qualitative understanding can be obtained from applying simple molecular orbital theory and considering only the partly filled orbitals. The resulting model can be used to describe existing diradical and metal-radical systems and also has predicative value in the search for molecular magnets and design of nanoscale devices.

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Magnetic And Thermal Properties Of Pr In La₁₋ₓprxbacacu₃O₇ System With 0.0, Rajvir Singh, S. Uma, E. Gmelin, William B. Yelon, V. P. S. Awana, S. X. Dou, A. V. Narlikar, Satish K. Malik Jan 1998

Magnetic And Thermal Properties Of Pr In La₁₋ₓprxbacacu₃O₇ System With 0.0, Rajvir Singh, S. Uma, E. Gmelin, William B. Yelon, V. P. S. Awana, S. X. Dou, A. V. Narlikar, Satish K. Malik

Physics Faculty Research & Creative Works

No abstract provided.

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Pressure Induced Reversal Of The Volume Expansion Caused By Interstitial Nitrogen In Nd₂Fe₁₇N₃, R. Luo, William B. Yelon, Yusheng S.. Zhao, M. Ellouze, Ph. I'Héritier, G. K. Marasinghe, Peter C. Ezekwenna, R. B. Von Dreele, William Joseph James Jan 1998

Pressure Induced Reversal Of The Volume Expansion Caused By Interstitial Nitrogen In Nd₂Fe₁₇N₃, R. Luo, William B. Yelon, Yusheng S.. Zhao, M. Ellouze, Ph. I'Héritier, G. K. Marasinghe, Peter C. Ezekwenna, R. B. Von Dreele, William Joseph James

Physics Faculty Research & Creative Works

No abstract provided.

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Xps Investigations On Conducting Polymers, Ş. Süzer, Ö. Bi̇rer, U.A. Sevi̇l, O. Güven Jan 1998

Xps Investigations On Conducting Polymers, Ş. Süzer, Ö. Bi̇rer, U.A. Sevi̇l, O. Güven

Turkish Journal of Chemistry

X-ray photoelectron spectroscopy, XPS, was used for the characterization of electrically conducting polymeric materials. In the spectrum of polypyrrole, PPy, the Nls region exhibits two peaks, at 402.0 and 399.8 eV, corresponding to -N$^+$- and -N- moieties, respectively. The intensity of the N$^+$ peak decreases as the material loses its conductivity, hence the ratio of the experimentally derived N$^+$/C atomic ratio correlates exponentially with the measured conductivity. A similar observation also exists between the F$^-$/C atomic ratio both in polypyrrole and polythiophene. In the XPS spectrum of the composite material prepared using polyaniline, PAN and polyvinylchloride, PVC, two different kinds …

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1998 Preliminary Snowmobile Emission Survey In Yellowstone National Park, Gary A. Bishop, Donald H. Stedman Jan 1998

1998 Preliminary Snowmobile Emission Survey In Yellowstone National Park, Gary A. Bishop, Donald H. Stedman

Fuel Efficiency Automobile Test Publications

No abstract provided.

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Pressure Induced Reversal Of The Volume Expansion Caused By Interstitial Nitrogen In Nd2fe17n3, G. K. Marasinghe, William Joseph James, P. C. Ezekwenna, H. Luo, W. B. Yelon, Y. Zhao, R. B. Von Dreele, M. Ellouze, Ph L'Héritier Jan 1998

Pressure Induced Reversal Of The Volume Expansion Caused By Interstitial Nitrogen In Nd2fe17n3, G. K. Marasinghe, William Joseph James, P. C. Ezekwenna, H. Luo, W. B. Yelon, Y. Zhao, R. B. Von Dreele, M. Ellouze, Ph L'Héritier

Chemistry Faculty Research & Creative Works

Crystallographic properties of Nd2Fe17N3 have been investigated using powder neutron diffraction techniques at pressures up to 7.3 GPa. With increasing pressure, the unit cell volume of Nd 2Fe17N3 decreases almost linearly at a rate of 6.1 Å3/GPa without undergoing a phase transformation or expelling the interstitial nitrogen atoms. The observed rate of contraction corresponds to a bulk modulus of 1.4x1011 N/m2 for Nd2Fe17N3. The unit cell volume of Nd 2Fe17N3 at 7.3 GPa is approximately equal to that of Nd2Fe17 at atmospheric pressure. Even though the unit cell of Nd2Fe17 expands anisotropically due to nitrogenation, contraction of the Nd2Fe17N3 unit …

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The Evolution Of Chiral Stationary Phases For Liquid Chromatography, Daniel W. Armstrong Jan 1998

The Evolution Of Chiral Stationary Phases For Liquid Chromatography, Daniel W. Armstrong

Chemistry Faculty Research & Creative Works

The development of effective chiral stationary phases (CSPs) and separation strategies for the liquid chromatographic (LC) resolution of enantiomers has been beneficial to many scientific disciplines. Over the last decade the number and type of CSPs has expanded tremendously. Not only have new classes of chiral selectors been introduced, but also many of the first CSPs have been changed and/or improved. The second or third generation of a CSP often can be different from the original. This can be confusing and intimidating to someone just entering the area of LC enantiomeric separations. Fortunately, all CSPs can be categorized in one …

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Nano-Engineering Of Molecular Films By Self-Assembly And Langmuir-Blodgett Techniques, Erwin P. Enriquez Jan 1998

Nano-Engineering Of Molecular Films By Self-Assembly And Langmuir-Blodgett Techniques, Erwin P. Enriquez

Chemistry Faculty Publications

The availability of sophisticated and ultra-sensitive analytical tools and the maturity of organic synthesis have opened new possibilities for fabrication of molecular materials designed at the nanometer scale. Presently, the most promising and widely investigated methodologies are the self-assembly and Langmuir-Blodgett procedures. The former relies on the strong, preferential affinity of specific functional groups to solid surfaces, whereas the latter involves transfer of pre-formed mono layers at the air-water interface onto solid substrates. These techniques and their recent applications are reviewed.

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Development Of A Quantitative Competetive Polymerase Chain Reaction Assay For The Detection And Quantitation Of Perkinsus Marinus In Oyster Tissues And Environmental Water Samples, Heather A. Yarnall Jan 1998

Development Of A Quantitative Competetive Polymerase Chain Reaction Assay For The Detection And Quantitation Of Perkinsus Marinus In Oyster Tissues And Environmental Water Samples, Heather A. Yarnall

Dissertations, Theses, and Masters Projects

No abstract provided.

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A Neutron Diffraction Structural Study Of R₂Fe₁₇₋ₓalx(C) (R=Tb,Ho) Alloys, William B. Yelon, H. Luo, Mingxing Chen, W. C. Chang, S. H. Tsai Jan 1998

A Neutron Diffraction Structural Study Of R₂Fe₁₇₋ₓalx(C) (R=Tb,Ho) Alloys, William B. Yelon, H. Luo, Mingxing Chen, W. C. Chang, S. H. Tsai

Physics Faculty Research & Creative Works

No abstract provided.

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Neutron Diffraction And Frequency Dependence Of The A.C. Susceptibility Of The System Zncr₂Xal₂-₂Xs₄, M. Hamedoun, A. Hourmatallah, N. Benzakour, K. Mediouri, J. Ilali, William B. Yelon, H. Luo Jan 1998

Neutron Diffraction And Frequency Dependence Of The A.C. Susceptibility Of The System Zncr₂Xal₂-₂Xs₄, M. Hamedoun, A. Hourmatallah, N. Benzakour, K. Mediouri, J. Ilali, William B. Yelon, H. Luo

Physics Faculty Research & Creative Works

No abstract provided.

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Ab Initio And Dft Investigations Of Lithium/Hydrogen Bonded Complexes Of Trimethylamine, Dimethyl Ether And Dimethyl Sulfide, Salai Cheettu Ammal, P. Venuvanalingam Jan 1998

Ab Initio And Dft Investigations Of Lithium/Hydrogen Bonded Complexes Of Trimethylamine, Dimethyl Ether And Dimethyl Sulfide, Salai Cheettu Ammal, P. Venuvanalingam

Faculty Publications

Ab initio and DFT computations have been carried out on LiF and HF complexes of a set of n-donors viz. trimethylamine, dimethyl ether and dimethyl sulfide with a 6-31++G(d,p) basis set. The effect of correlation has been included with MP2, MP4 and DFT calculations. NBO analyses of the wavefunctions have been performed to examine the intermolecular interaction at the orbital level. Calculations reveal that these donors form strong n→σ* complexes and computed binding energies of the (CH3)2O···HF complex agree very well with the experimental binding energies from IR spectroscopy. LiF forms stronger complexes than HF, …

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Ab Initio Study Of Formazan And 3-Nitroformazan, G. Buemi, F. Zuccarello, P. Venuvanalingam, M. Ramalingam, Salai Cheettu Ammal Jan 1998

Ab Initio Study Of Formazan And 3-Nitroformazan, G. Buemi, F. Zuccarello, P. Venuvanalingam, M. Ramalingam, Salai Cheettu Ammal

Faculty Publications

Formazan and 3-nitroformazan have been investigated at abinitio level (MP2/6-31G** and B3LYP/6-31G**) in all their possible conformations, for studying the various possibilities of intramolecular hydrogen bonding formation. The trans-syn-s-cis (TSSC), known also asyellowform, has been found to be the most stable conformer (at least in the gas phase) in both compounds. This particular structure is strongly stabilized by a N–H···N hydrogen bridge, which gives rise to a hexatomic chelate ring, with the possibility of a proton transfer process.This closely resembles that of malondialdehyde, previously studied, in the evolution of the …

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Analysis Of A Mixture Of Several Dihalonicotinic Acids By Gas Chromotography And Gas Chromotography-Mass Spectrometry, Cheryl L. Fossler, Frank L. Setliff, Ali U. Shaikh Jan 1998

Analysis Of A Mixture Of Several Dihalonicotinic Acids By Gas Chromotography And Gas Chromotography-Mass Spectrometry, Cheryl L. Fossler, Frank L. Setliff, Ali U. Shaikh

Journal of the Arkansas Academy of Science

Six 2,5- and 5,6- dihalonicotinic acids in a mixture were converted to their corresponding methyl esters and then analyzed by gas chromatography and gas chromatography-mass spectrometry. Four methods of conversion were compared for their GC sensitivity, efficiency and analysis time. In Method #1, using HC1 and methanol as the reagents, the displacement of the halogens by chlorine (from HC1) at 2- and 6-positions was a common occurrence, rendering the method inefficient. In Method #2 (BF3/methanol), the displacement of halogens by methoxide was evident. Method #3 (dicyclohexylcarbodiimide/methanol) produced a mixture of derivatives with a poor yield. Method #4 (diazomethane) gave a …

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Preparation Of Methyl 5-Chloro-6-Fluoronicotinate By Fluoride-Chloride Exchange, Frank L. Setliff, Leslie B. Coop Jan 1998

Preparation Of Methyl 5-Chloro-6-Fluoronicotinate By Fluoride-Chloride Exchange, Frank L. Setliff, Leslie B. Coop

Journal of the Arkansas Academy of Science

No abstract provided.

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Chemical Interaction Of "Declorane Plus" With Antimony Trioxide In Nylon 66, Yum Min Kang Jan 1998

Chemical Interaction Of "Declorane Plus" With Antimony Trioxide In Nylon 66, Yum Min Kang

Dissertations, Theses, and Masters Projects

No abstract provided.

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Approaches And Methodologies For The Synthesis Of Aromatic Natural Products, Christina A. Goudreau Jan 1998

Approaches And Methodologies For The Synthesis Of Aromatic Natural Products, Christina A. Goudreau

Honors Theses

Chemists have been captivated by the ability of most natural products to exhibit biological activity which in effect has made them very attractive to pharmaceutical companies. Many over-the-counter drugs such as aspirin were first extracted from natural products and are now an integral part of most of our lives. More importantly, certain drugs such as taxol, which is used to treat breast cancer, initially came from the bark of a yew tree. Extracting these substances from their natural source and using them medicinally at the demand of the consumers would result in the destruction of the natural habitat. Oftentimes, the …

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Alternatives To Nitroprusside, William T. Hiscock Jan 1998

Alternatives To Nitroprusside, William T. Hiscock

Honors Theses

Any transition metal nitrosyl complex may release nitric oxide and thus has potential as a vasodilator. Nitroprusside, Na2[Fe(CN)5(NO)], is currently used, but dosages are limited because of the potential release of cyanide. Research in our group has been directed towards the synthesis of iron and ruthenium complexes containing the nitrosyl ligand and polypyridyl coligands such as 2,2-dipyridyl (bpy) and 2,2': 6',2"-terpyridine (tpy). These coligands are much less toxic than cyanide. Both [(bpy)(tpy)Fe(NO)]3+ and [(bpy)(tpy)Ru(NO)]3+ have been synthesized and characterized using infrared and ultraviolet spectroscopy, conductivity, and magnetic susceptibility. Along with the search for other possible polydentate coligands, is the search …

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The Synthesis And Characterization Of Monometallic And Bimetallic Pd-Pnp Complexes, Lorinda Asmus Jan 1998

The Synthesis And Characterization Of Monometallic And Bimetallic Pd-Pnp Complexes, Lorinda Asmus

Honors Theses, 1963-2015

The bridging ligand, 2-[bis(diphenylphosphino)methyl]pyridine (PNP), is ideal for synthesizing mono- and bi-metallic catalysts due to its potential to be bidentate (P-P or P-N) or tridentate and its ability to bind to one or more metals. Three Pd-PNP complexes, [Pd(PNP)2]+2 (1) and two complexes resulting from the removal of one or two methine pronouns (2 and 3), have been synthesized. The removal of one methine proton changes the PNP bidentate binding mode. In complex 1 and 3, the two PNP ligands are P-P bound. However, upon the removal of one methine proton, one …

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Disproportionation And Structural Changes Of Tetraarylethylene Donors Upon Successive Oxidation To Cation Radicals And To Dications, Rajendra Rathore, Sergey V. Lindeman, A. S. Kumar, Jay K. Kochi Jan 1998

Disproportionation And Structural Changes Of Tetraarylethylene Donors Upon Successive Oxidation To Cation Radicals And To Dications, Rajendra Rathore, Sergey V. Lindeman, A. S. Kumar, Jay K. Kochi

Chemistry Faculty Research and Publications

The stepwise (one-electron) chemical oxidation of the tetraphenylethylene donor and its substituted analogues (D) can be carried out by electron exchange with aromatic cations or antimony(V) oxidants to selectively afford the cation radical (D+•) initially and then the dication (D2+). The ready interchange of the latter establishes the facile disproportionation (i.e., 2D+• ⇌ D2+ + D) that was originally examined by only transient electrochemical techniques. The successful isolations of the crystalline salts of the tetraanisylethylene cation radical (1+•) as well as the …

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Overcoming The Multiplex‐Disadvantage Using Maximum‐Likelihood Inversion, Stephen E. Bialkowski Jan 1998

Overcoming The Multiplex‐Disadvantage Using Maximum‐Likelihood Inversion, Stephen E. Bialkowski

Stephen E. Bialkowski

A maximum-likelihood estimator, derived under quantum-noiselimited measurement conditions, is used to obtain wavenumber-ordered spectra produced by a model Michelson interferometer. The estimator is tested on a number of synthetic interferograms, and results are compared to similar spectra obtained by using the Fourier (cosine) transform. It is found that the maximum-likelihood inversion method does not result in white noise in the spectrum estimate when the spectrum is sparse. It thus may be used to circumvent the main disadvantage in multiplexed spectrometer measurements using quantum-noise-limited detectors for emissionbased measurements. It is also found that maximum-likelihood inversion methods can be used to obtain …

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The Alca Obsidian Source: The Origin Of Raw Material For Cuzco Type Obsidian Artifacts, Richard L. Burger, Frank Asaro, Paul B. Trawick, Fred Stross Jan 1998

The Alca Obsidian Source: The Origin Of Raw Material For Cuzco Type Obsidian Artifacts, Richard L. Burger, Frank Asaro, Paul B. Trawick, Fred Stross

Andean Past

No abstract provided.

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The Chivay Obsidian Source And The Geological Origin Of Titicaca Basin Type Obsidian Artifacts, Richard L. Burger, Frank Asaro, Guido Salas, Fred Stross Jan 1998

The Chivay Obsidian Source And The Geological Origin Of Titicaca Basin Type Obsidian Artifacts, Richard L. Burger, Frank Asaro, Guido Salas, Fred Stross

Andean Past

No abstract provided.

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