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Articles 30751 - 30780 of 34552

Full-Text Articles in Physical Sciences and Mathematics

The Effect Of Encapsulated Antibodies On Spontaneous Translocation Of A Protein Presequence Into Synthetically Produced Phospholipid Vesicles, Robert Bellin Jan 1994

The Effect Of Encapsulated Antibodies On Spontaneous Translocation Of A Protein Presequence Into Synthetically Produced Phospholipid Vesicles, Robert Bellin

Honors Theses, 1963-2015

The cytochrome oxidase subunit IV (CoxIV) protein presequence has been found by previous researchers to target proteins to the mitochondria of the cells and associate with or translocate across a membrane bilayer. In this study, the effects of encapsulating antibodies against the presequence within phospholipid vesicles on this association or translocation was studied. Kinetic and thermodynamic theories were developed which predict a higher level of association or translocation of the protein presequence into these antibody containing vesicles. Antibodies against the CoxIV presequence were produced in two rabbits and purified with a Protein A affinity column. Phospholipid vesicles were created with …


Synthesis And Characterization Of Binuclear And Unsymmetrical Phthalocyanines, Jiang Yang Jan 1994

Synthesis And Characterization Of Binuclear And Unsymmetrical Phthalocyanines, Jiang Yang

Doctoral Dissertations

"The metal free planar binuclear phthalocyanines sharing a benzene or naphthalene ring have been synthesized and characterized. The position of Q band of binuclear phthalocyanine sharing a naphthalene ring is red shifted compared to binuclear phthalocyanine sharing a benzene ring. The compounds are shown to form the liquid crystal mesophases at room temperature.

The unique unsymmetrical phthalocyanines with steric hindrance tetraphenyl or “opposite” octaphenyl substitution have been synthesized with the aid of computer modeling. The compounds are characterized by UV-visible near IR absorption and NMR spectroscopy. Mesophase is observed by optical microscopy and differential scanning calorimetry.

The aggregation behavior has …


N1-Acetyl-3'-Methylandrosta-4,16-Dieno[16,17-D]Pyrazole-3-One, Sergey V. Lindeman, Alexandr I. Yanovsky, Ezequiel Huipe Nava, Alexey V. Kamernitzky, Alina V. Skorova, Irina V. Vesela Jan 1994

N1-Acetyl-3'-Methylandrosta-4,16-Dieno[16,17-D]Pyrazole-3-One, Sergey V. Lindeman, Alexandr I. Yanovsky, Ezequiel Huipe Nava, Alexey V. Kamernitzky, Alina V. Skorova, Irina V. Vesela

Chemistry Faculty Research and Publications

In an attempt to find the structural features promoting the thermal isomerization of the N-acylated steroid [16,17-d]pyrazoles into [17,16-c]pyrazole derivatives,the X-ray structure analysis of the title compound, C23H30N2O3, (1), has been carried out. The steroid moiety of (I) has the usual conformation. The dihedral angle between the planar pyrazole ring and the N-acetyl group is very small [5.6 (2)°], but the amide C-N bond seems to be substantially elongated [1.404 (3) Å ]. The d-pyrazole ring junction via a double bond leads to deformations of …


The Synthesis Of 5-Benzoyl-1,3-Benzendediacids For The Double-Capping Of Beta-Cyclodextrin, Daniel Macdougall Williams Jan 1994

The Synthesis Of 5-Benzoyl-1,3-Benzendediacids For The Double-Capping Of Beta-Cyclodextrin, Daniel Macdougall Williams

Dissertations, Theses, and Masters Projects

No abstract provided.


Lithium Binding To Human Rbc Membranes And Substrates Of Second Messenger Systems, Qinfen Rong Jan 1994

Lithium Binding To Human Rbc Membranes And Substrates Of Second Messenger Systems, Qinfen Rong

Dissertations

No abstract provided.


Ultrasound Assisted Oxidative Cleavage Of Alpha-Keto, Alpha-Hydroxy And Alpha-Halo Ketones By Superoxide, Yi Hong Cao, A. Toland, Dominic T.C. Yang Jan 1994

Ultrasound Assisted Oxidative Cleavage Of Alpha-Keto, Alpha-Hydroxy And Alpha-Halo Ketones By Superoxide, Yi Hong Cao, A. Toland, Dominic T.C. Yang

Journal of the Arkansas Academy of Science

No abstract provided.


Thermal Decomposition Studies Of Selected Transition Metal Polysulfide Complexes. Ii. Effect Of Atmosphere On Decomposition, Benjamin Rougeau, Mark Draganjac Jan 1994

Thermal Decomposition Studies Of Selected Transition Metal Polysulfide Complexes. Ii. Effect Of Atmosphere On Decomposition, Benjamin Rougeau, Mark Draganjac

Journal of the Arkansas Academy of Science

Initial studies involved the thermal decomposition profile of five polysulfide complexes in air up to 550 °C. Since our first report to the Academy in 1990, we have obtained the capability to run samples up to 1500°C under various gases. Thermal Gravimetric Analysis (TGA) and Differential Thermal Analysis (DTA)of a series of transition metal polysulfide complexes are presented. Compounds analyzed included Cp2TiS5 ,MoS9 2",MoOS8 2", Zn(S x ) 2", Cd(S x ) 2-, Fe2S122 - and NiS82.


Investigations Of Iron Cycling In Aquatic Systems, Heather A. Lounsbury Jan 1994

Investigations Of Iron Cycling In Aquatic Systems, Heather A. Lounsbury

Honors Theses

A fully automated luminal-based chemiluminescence flow injection analysis system has been developed for rapid detection of Fe(IT) at natural levels in natural water systems. Similar detection limits are achieved for H202 by fluorometry using an enzyme mediated oxidation of the reagent p-hydroxyphenylacetic acid. Using these analytical systems, the rates of Fe(IT) oxidation by dissolved oxygen in 0.7 M NaO have been measured for nanomolar concentrations of Fe(II) over the pH range 7.0 to 8.3. When the production and decomposition of H202 in the system were considered, measured rates were in excellent agreement with a model based on previously reported rate …


Distribution Of Sedimentary Phosphorus In Gulf Of Mexico Estuaries, Weng Huanxin, Bob J. Presley, Daniel W. Armstrong Jan 1994

Distribution Of Sedimentary Phosphorus In Gulf Of Mexico Estuaries, Weng Huanxin, Bob J. Presley, Daniel W. Armstrong

Chemistry Faculty Research & Creative Works

Sediment samples were collected from all the major bays and estuaries along the US Gulf of Mexico Coastline in 1986-1988 by the NOAA NS & T Program (NOAA (1989), The National Status and Trends Program for marine environmental quality; NOAA/OMA, Rockville, MD, USA). These have been analyzed for total phosphorus as well as leachable Al-P, Ca-P and Fe-P. Total phosphorus concentration ranges from 1·8 to 45·9 μmol/g and averages 11·3 μmol/g. Higher values were found in Louisiana estuaries than in those in Texas but the highest values occur in the phosphate rock mining region of southern Florida. Ca-P is the …


Boron Phosphate And Aluminum Phosphate Aerogels, David A. Lindquist, Steven M. Poindexter, Sterling S. Rooke, D. Ritchie Stockdale, Kirk B. Babb, Alison L. Smoot, William E. Young Jan 1994

Boron Phosphate And Aluminum Phosphate Aerogels, David A. Lindquist, Steven M. Poindexter, Sterling S. Rooke, D. Ritchie Stockdale, Kirk B. Babb, Alison L. Smoot, William E. Young

Journal of the Arkansas Academy of Science

Anhydrous sol-gel condensation of triethyl phosphate [(CH3CH2O)3PO] with boron trichloride (BCL3 ) or triethyl aluminum [(CH3CH2 ) 3A1] in organic solvents, led to formation of metallophosphate gels. The pore fluid of the gels was removed under supercritical conditions in a pressurized vessel to form aerogels. The aerogels were then calcined at progressively higher temperatures to produce high surface area phosphates. Since the initial gel reagent mixtures contained several NMR active nuclei, the condensation chemistry prior to the gel point was monitored by solution nB NMR. The surface areas, distribution of pore sizes, and total pore volumes of the aerogel products …


Geochemical Characterization Of Maceral Concentrates From Herrin No. 6 Coal (Illinois Basin) And Lower Toarcian Shale Kerogen (Paris Basin), B Artur Stankiewicz, Michael A. Kruge, John C. Crelling Jan 1994

Geochemical Characterization Of Maceral Concentrates From Herrin No. 6 Coal (Illinois Basin) And Lower Toarcian Shale Kerogen (Paris Basin), B Artur Stankiewicz, Michael A. Kruge, John C. Crelling

Department of Earth and Environmental Studies Faculty Scholarship and Creative Works

Density gradient centrifugation (DGC) is a physical method for the separation of sedimentary organic matter into its constituents. Using DGC, it is possible to prepare maceral concentrates from a single sample, which are amenable to microanalysis. DGC fractions from a coal sample from the Illinois Basin (Herrin No. 6, Upper Carboniferous) and from the kerogen of a marine shale sample from the Paris Basin (Lower Toarcian) were analyzed by flash pyrolysis-gas chromatography-mass spectrometry, after extraction by CH2Cl2.

Chemical differences between the coal DGC fractions are the easiest to recognize, indicating very distinctive biological precursors. For example, …


Fossil Charcoal In Cretaceous-Tertiary Boundary Strata: Evidence For Catastrophic Firestorm And Megawave, Michael A. Kruge Jan 1994

Fossil Charcoal In Cretaceous-Tertiary Boundary Strata: Evidence For Catastrophic Firestorm And Megawave, Michael A. Kruge

Department of Earth and Environmental Studies Faculty Scholarship and Creative Works

Organic matter separated from calcareous sandstone from the upper portion of a deep-water tsunami deposit at Arroyo el Mimbral, Taumalipas (Mexico), which marks the biostratigraphically-defined Cretaceous-Tertiary boundary, consists primarily of fossil charcoal, including semifusinite and pyrofusinite. Analytical pyrolysis-gas chromatography-mass spectrometry revealed the highly aromatic and polyaromatic character of the organic matter assemblage, typical of the products of partial combustion. The organic matter probably originated as terrestrial vegetation that was caught in a firestorm and subsequently transported far offshore in the backwash of a megawave. These data are consistent with the hypothesis of combustion of large masses of vegetation triggered by …


Neutron-Scattering Study Of Librations And Intramolecular Phonons In Rb_{2.6}K_{0.4}C_{60}, D. Reznik, W. A. Kamitakahara, D. A. Neumann, J. R. D. Copley, J. E. Fischer, Robert M. Strongin, M. A. Cichy, Amos B. Smith Iii Jan 1994

Neutron-Scattering Study Of Librations And Intramolecular Phonons In Rb_{2.6}K_{0.4}C_{60}, D. Reznik, W. A. Kamitakahara, D. A. Neumann, J. R. D. Copley, J. E. Fischer, Robert M. Strongin, M. A. Cichy, Amos B. Smith Iii

Chemistry Faculty Publications and Presentations

We report the results of inelastic neutron-scattering measurements on Rb2.6K0.4C60. Librational modes were observed as broad peaks with maxima between 4.1 and 4.7 meV, as the temperature is lowered from 300 to 12 K. As in K3C60, no change in the width or position of the librational peak was observed when the sample was cooled through the superconducting transition. Thus any coupling of the librations to electronic states is small. The magnitude of the orientational potential barrier was estimated from the librational peak frequency. A flat background observed in the …


Surface Flow Structure Of The Gulf Stream From Composite Imagery And Satellite-Tracked Drifters, C. P. Mullen, A. D. Kirwan Jr. Jan 1994

Surface Flow Structure Of The Gulf Stream From Composite Imagery And Satellite-Tracked Drifters, C. P. Mullen, A. D. Kirwan Jr.

CCPO Publications

A unique set of coutemporaneous satellite-tracked drifters and five-day composite Advanced Very High Resolution Radionmeter (AVHRR) satellite imagery of the North Atlantic has been analyzed to examine the surface flow structure of the Gulf Stream. The study region was divided into two sections, greater than 37 degrees N and less than 37 degrees N, in order to answer the question of geographic variability. Fractal and spectral analyses methods were applied to the data. Fractal analysis of the Lagrangian trajectories showed a fractal dimension of 1.21 +/- 0.02 with a scaling range of 83 - 343 km. The fractal dimension of …


Initiation And Study Of Localized Corrosion By Scanning Electrochemical Microscopy, David O. Wipf Jan 1994

Initiation And Study Of Localized Corrosion By Scanning Electrochemical Microscopy, David O. Wipf

College of Arts and Sciences Publications and Scholarship

This paper describes methods to study the initiation and formation of localized corrosion pits on stainless–steel and aluminum samples. These methods are based on the use of a scanned probe microscope, the scanning electrochemical microscope (SECM). The SECM is specifically designed for operation in electrolyte solution and so is uniquely suited for examination of corrosion processes. SECM imaging of a corrosion pit on stainless steel is presented. In addition, the initiation of single pits on aluminum and stainless steel by using the SECM tip to electrogenerate a local source of Cl is described.


Oxidation Of Cyclohexene With Aqueous Potassium Peroxymonosulfate At Ph < 1.7, Wen-Qing Sun Jan 1994

Oxidation Of Cyclohexene With Aqueous Potassium Peroxymonosulfate At Ph < 1.7, Wen-Qing Sun

Theses

Glycols are often used as starting materials for pharmaceuticals. They are currently manufactured by reacting alkenes with organic peroxy acids in organic solutions that contain chlorinated solvents. The aim of this research is to find ways to avoid the use of hazardous organic solvents in the manufacture of pharmaceuticals in order to prevent pollution. Our approach is to find alternative synthetic methods using water as solvent.

Based on literature information, it was decided to determine if the aqueous potassium peroxymonosulfate oxidation of water-immiscible cyclohexene at room temperature can be scaled up to become a new method to manufacture glycols. Acidic …


Physical And Mechanical Behavior Of Amorphous Poly(Arylene Ether-Co-Imidazole)S And Poly(Arylene Ether-Co-Imidazole) Modified Epoxies, Patricia D. Roberts-Mcdaniel Jan 1994

Physical And Mechanical Behavior Of Amorphous Poly(Arylene Ether-Co-Imidazole)S And Poly(Arylene Ether-Co-Imidazole) Modified Epoxies, Patricia D. Roberts-Mcdaniel

Dissertations, Theses, and Masters Projects

Due to the high crosslink density of cured epoxy resins they generally lack damage tolerance. A significant amount of research has been expended to improve the toughness of epoxies. Research into the area of thermoplastic epoxy modifiers has begun to overcome some of the limitations of early methods of epoxy toughening (i.e. lower modulus and thermal stability).;This study examines the physical and mechanical properties of random poly(arylene ether-co-imidazole) (PAE-co-Is) and the characterization of epoxies modified with poly(arylene ether-co-imidazole)s.;Poly(arylene ether-co-imidazole)s exhibited the highest solubility in N,N,N{dollar}\rm\sp\prime,N\sp\prime,{dollar}-tetraglycidyl- 4,4{dollar}\sp\prime{dollar} diaminodiphenyl methane (TGMDA) based resins. The high molecular weight polymers caused significant decreases in …


Deuteron Nuclear Magnetic Resonance Studies Of Molecular Motion In Solids, Tak Yan Tse Jan 1994

Deuteron Nuclear Magnetic Resonance Studies Of Molecular Motion In Solids, Tak Yan Tse

Dissertations, Theses, and Masters Projects

$\sp2$H-NMR is a powerful spectroscopic technique for investigating dynamics in solids. to extend the range of motional rates that can be quantitatively investigated, a new approach for measuring the quadrupolar spin-lattice relaxation time $T\sb{1Q}$ was developed. This uses a Broadband Jeener-Broekaert (BBJB) sequence with echo-detection, which avoids the frequency-discriminated excitation profile and spectral baseline distortion intrinsic to the conventional Jeener-Broekaert (JB) experiment. By combining the BBJB experiment with an Inversion-Recovery sequence with Quadrupole-Echo detection (IRQE), two independent longitudinal relaxation times, $T\sb{1Q}$ and $T\sb{1Z}$, can be measured. Spectral densities of motion $J\sb1(\omega\sb{o}$) and $J\sb2(2\omega\sb{o}$) are extracted from these relaxation times. The …


Cyclic Voltammetry Of Polypyrroledodecylbenzenesulfonate Layers, T. Mccormac, W. Breen, A. Mcgee, John Cassidy, M. E.G. Lyons Jan 1994

Cyclic Voltammetry Of Polypyrroledodecylbenzenesulfonate Layers, T. Mccormac, W. Breen, A. Mcgee, John Cassidy, M. E.G. Lyons

Articles

Polypyrrole was deposited from solutions of NaCIO. and NaDBS, where DBS is dodecylbenzenesulfonate in aqueous solu\ion and characterizcd by voltammetry. It is found that the absence of the so-called 'double laver charging current' during cyclic voltammetry of the layers formed from solutions with surfactant is not because of' the" order in morphology of the layer, but irreversible incorporation of' the surfactant anion.


On-Road Remote Sensing Of Co And Hc Emissions In California, Donald H. Stedman, Gary A. Bishop, Stuart P. Beaton, James E. Peterson, Paul L. Guenther, Iain F. Mcvey, Yi Zhang Jan 1994

On-Road Remote Sensing Of Co And Hc Emissions In California, Donald H. Stedman, Gary A. Bishop, Stuart P. Beaton, James E. Peterson, Paul L. Guenther, Iain F. Mcvey, Yi Zhang

Fuel Efficiency Automobile Test Publications

No abstract provided.


Ab Initio Study Of He(1s)+Cl2(X 1Σg,3Πu) Potential Energy Surfaces, G. Chalasinski, M. Gutowski, M. M. Szczesniak, Steve Scheiner Jan 1994

Ab Initio Study Of He(1s)+Cl2(X 1Σg,3Πu) Potential Energy Surfaces, G. Chalasinski, M. Gutowski, M. M. Szczesniak, Steve Scheiner

Chemistry and Biochemistry Faculty Publications

The potential energy surface of the ground state He+Cl2(1Σg) is calculated by using the perturbation theory of intermolecular forces and supermolecular Møller–Plesset perturbation theory approach. The potential energy surface of the first excited triplet He+Cl2(3Πu) was evaluated using the supermolecular unrestricted Møller–Plesset perturbation theory approach. In the ground state two stable isomers are found which correspond to the linear He–Cl–Cl structure (a primary minimum, De=45.1 cm−1, Re=4.25 Å) and to the T‐shaped structure with He perpendicular to the molecular axis (a secondary …


Theoretical Study Of Hydrogen Bonding And Proton Transfer In The Ground And Lowest Excited Singlet States Of Tropolone, M. V. Vener, Steve Scheiner, N. D. Sokolov Jan 1994

Theoretical Study Of Hydrogen Bonding And Proton Transfer In The Ground And Lowest Excited Singlet States Of Tropolone, M. V. Vener, Steve Scheiner, N. D. Sokolov

Chemistry and Biochemistry Faculty Publications

Theoretical models of hydrogen bonding and proton transfer in the ground (S0) and lowest excited ππ∗ singlet (S1) states of tropolone are developed in terms of the localized OH...O fragment model and ab initio three‐dimensional potential energy surfaces (PESs). The PESs for proton transfer in the S0 and S1 states are calculated using ab initio SCF and CIS methods, respectively, with a 6–31G basis set which includes polarization functions on the atoms involved in the internal H bond. The Schrödinger equation for nuclear vibrations is solved numerically using adiabatic separation of the …


Kinetic And Chemical Modification Studies On Malate Dehydrogenase From E. Coli, Fang Jenny Zhao Jan 1994

Kinetic And Chemical Modification Studies On Malate Dehydrogenase From E. Coli, Fang Jenny Zhao

Masters Theses

Malate dehydrogenase (MDH) is the enzyme which catalyzes the conversion of malate to oxaloacetate in the TCA cycle. The object of this research was to discipher the mechanism of the reaction and the function of the enzyme. MDH from E. Coli was purified and analyzed by chemical modification studies using diethylpyrocarbonate. Results indicate the existence of a histidine residue at the active site necessary for catalysis. From kinetic studies, a group required for catalysis with a pKa of 8.5 was observed, which we believe to be a histidine residue. These studies indicate that MDH from E. Coli has a …


Determination Of Parameters Influencing The Vehicle Emissions In Greece Using A Remote Sensing System, Kostas Nikolaou, Donald H. Stedman, Stavros Papaioannou, Nikos Zoumakis, Apostolos Kelesis Jan 1994

Determination Of Parameters Influencing The Vehicle Emissions In Greece Using A Remote Sensing System, Kostas Nikolaou, Donald H. Stedman, Stavros Papaioannou, Nikos Zoumakis, Apostolos Kelesis

Fuel Efficiency Automobile Test Publications

No abstract provided.


5-Acetyl[2.2]Paracyclophane, Sergey V. Lindeman, Yuri T. Struchkov, Vyacheslav N. Guryshev Jan 1994

5-Acetyl[2.2]Paracyclophane, Sergey V. Lindeman, Yuri T. Struchkov, Vyacheslav N. Guryshev

Chemistry Faculty Research and Publications

The title compound 5-acetyltricyclo[8.2.2.24,7]hexa-deca-4,6,10,12,13,15-hexaene, C18H18O,is the first example of a mono-π-substituted [2.2]paracyclophane to be structurally characterized. The average bending angles are α = 13.2 and β = 9.9°. The distance between the 'bottoms' of the practically parallel boat-like benzene nuclei is 3.098(2) Å. The π conjugation between the acetyl group and the substituted benzene cycle is negligible (rotation angle ca 45°) because of steric hindrance.


An M-Carboranedicarboxylic Acid Dianilide, Sergey V. Lindeman, Georgii A. Kats, Lyudmila G. Komarova Jan 1994

An M-Carboranedicarboxylic Acid Dianilide, Sergey V. Lindeman, Georgii A. Kats, Lyudmila G. Komarova

Chemistry Faculty Research and Publications

The crystal structure of the 'non hydrogen-bonded' (according to IR data) polymorph of 1,7-bis(phenylcarbamoyl)-1,7-dicarba-closo-dodecaborane(12), C16-H22B10N2O2, has been determined. The two phenylamide groups have a Z configuration [the torsion angles 0-C-N-C are -2.3 (5) and -3.0 (5)°]. As a result both 'active' protons of these groups are almost completely shielded by other H atoms of the neighbouring carborane nucleus and phenyl substituents, and, therefore, no hydrogen-bonding contacts are found.


The Requirements Of Patentability As Applied To The Chemical Arts, Joy L. Bryant Jan 1994

The Requirements Of Patentability As Applied To The Chemical Arts, Joy L. Bryant

Dissertations, Theses, and Masters Projects

No abstract provided.


Direct Determination Of Trace Metals In Saline Water Samples Using Gfaas, Michael Joseph Wassell Jan 1994

Direct Determination Of Trace Metals In Saline Water Samples Using Gfaas, Michael Joseph Wassell

Dissertations, Theses, and Masters Projects

No abstract provided.


Characterization And Modeling Of Amino Epoxide Resins, Maria Anastasia Argiriadi Jan 1994

Characterization And Modeling Of Amino Epoxide Resins, Maria Anastasia Argiriadi

Dissertations, Theses, and Masters Projects

No abstract provided.


Structural Characterization Of Recombinant Polypeptides Of &-Spectrin, Yirong Xu Jan 1994

Structural Characterization Of Recombinant Polypeptides Of &-Spectrin, Yirong Xu

Dissertations

No abstract provided.