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A Mössbauer Effect Study Of Y₂Fe₁₄B And Its Aluminum Solid Solutions, Dwayne E. Tharp, Gary J. Long, Oran Allan Pringle, Gaya Kanishka Marasinghe, William Joseph James, Fernande Grandjean
A Mössbauer Effect Study Of Y₂Fe₁₄B And Its Aluminum Solid Solutions, Dwayne E. Tharp, Gary J. Long, Oran Allan Pringle, Gaya Kanishka Marasinghe, William Joseph James, Fernande Grandjean
Chemistry Faculty Research & Creative Works
The Mössbauer spectra of Y2Fe14B have been measured from 85 to 296 K. Analysis of the spectra indicates that the near-neighbor rare-earth atoms directly influence the orientation of the principal axis of the electric field gradient. The hyperfine parameters are very similar to those of Nd2Fe14B, but the internal fields are somewhat smaller at room temperature in the yttrium compound. The Mösssbauer spectra of Y2(Fe1-xAlx) 14B, where x equals 0.00, 0.02, 0.04, 0.06, and 0.08, have been measured at 85 K. The average internal hyperfine …
Kinetics And Mechanisms Of The Aminolysis Of N-Hydroxysuccinimide Esters In Aqueous Buffers, Gary W. Cline, Samir B. Hanna
Kinetics And Mechanisms Of The Aminolysis Of N-Hydroxysuccinimide Esters In Aqueous Buffers, Gary W. Cline, Samir B. Hanna
Chemistry Faculty Research & Creative Works
Rate constants for the aminolysis of the N-hydroxysuccinimide (NHS) ester of ρ-methoxybenzoic acid, in aqueous buffer systems (20% dioxane), have been determined under pseudo-first-order conditions. For the amines studied (pKa = 7.60-11.1), the data fit the rate expression kobsd - KOH-⨯ [OH-] = k1[amine]free. This rate equation is in contrast to the two-term rate equation (kobsd = k1[amine] + k2[amine]2) obtained for this reaction in anhydrous dioxane (Cline, G. W.; Hanna, S. B. J. Am. Chem. Soc. 1987,109, 3087) and is suggestive of a disproportionate …
Enantiomeric Resolution And Chiral Recognition Of Racemic Nicotine And Nicotine Analogues By Β-Cyclodextrin Complexation: Structure-Enantiomeric Resolution Relationships In Host-Guest Interactions, Jeffrey I. Seeman, Henry V. Secor, Daniel W. Armstrong, Karen D. Timmons, Timothy J. Ward
Enantiomeric Resolution And Chiral Recognition Of Racemic Nicotine And Nicotine Analogues By Β-Cyclodextrin Complexation: Structure-Enantiomeric Resolution Relationships In Host-Guest Interactions, Jeffrey I. Seeman, Henry V. Secor, Daniel W. Armstrong, Karen D. Timmons, Timothy J. Ward
Chemistry Faculty Research & Creative Works
High-performance liquid chromatography using β-cyclodextrin bonded phases was examined for the enantiomeric separation of racemic nicotine and 19 racemic nicotine analogues. Ten pairs of enantiomers were separated by this technique. This represents the first reported facile and direct separation of these racemates. Effects of pH, mobile phase composition, and structural features of the substrates (i.e., position and size of substituents, presence of pyrrolidine ring or hydrogen bonding functionalities, basicity) on the enantioselectivity are examined. Various structural aspects of the compounds were related to retention to the cyclodextrln-modlfied support and to the enantiomeric separations observed. Implications of this work to host-guest …
Use Of Secondary Equilibria For The Separation Of Small Solutes By Field-Flow Fractionation, Alain Berthod, Daniel W. Armstrong, J. Calvin Giddings, Marcus N. Myers
Use Of Secondary Equilibria For The Separation Of Small Solutes By Field-Flow Fractionation, Alain Berthod, Daniel W. Armstrong, J. Calvin Giddings, Marcus N. Myers
Chemistry Faculty Research & Creative Works
The dynamic range and selectivity of field-flow fractionation (FFF) can be Increased by using secondary chemical equilibria (SCE). SCE are established by adding a macromolecular additive or aggregate, which strongly Interacts with the field, to the carrier solution. In this study an oil-ln-water (O/W) microemulsion was used as the carrier solution in a sedimentation FFF apparatus. The microemulsion droplets (referred to as the "support") interact with the field and are retained relative to the bulk water. Small solutes that partition or bind to the microemulsion droplets are also retained relative to solutes that do not Interact with the support. In …
Transport Properties Of Ground State Oxygen Atoms, Paul M. Holland, Louis Biolsi Jr.
Transport Properties Of Ground State Oxygen Atoms, Paul M. Holland, Louis Biolsi Jr.
Chemistry Faculty Research & Creative Works
The transport properties of dilute monatomic gases depend on the two body interactions between like atoms. When two ground state oxygen atoms interact, they can follow any of 18 potential energy curves corresponding to O2, all of which contribute to the transport properties of the ground state atoms. Transport collision integrals have been calculated for those interactions with an attractive minimum in the potential by accurately representingab initio quantum mechanical potential energy curves with the Hulburt-Hirschfelder potential. Repulsive ab initio potential energy curves have been accurately represented either with the exponential repulsive potential or with an exponential …
Theoretical Study Of Structure And Reactions Of Metalated Oximes And Oxime Ethers, Rainer Glaser, Andrew J. Streitwieser
Theoretical Study Of Structure And Reactions Of Metalated Oximes And Oxime Ethers, Rainer Glaser, Andrew J. Streitwieser
Chemistry Faculty Research & Creative Works
The potential energy surfaces of acetaldoxime carbanion and its ion pairs formed with lithium and sodium cations ions have been explored with ab initio methods to model and study the regiochemistry of metalated oxime ethers. Planar structures of the carbanions produced by deprotonating acetaldoxime are minima on the potential energy surface. The syn-isomer is 2.6 Kcal/mole more stable than the anti. This difference is not a manifestation of cyclic conjugation but more likely is a result of electrostatic effects. Two chiral and almost isoenergetic minima have been located for the ion pairs formed by either of the isomeric carbanions with …
Gelled Emulsions With A High Water Content, C. Solans, J. G. Dominguez, J. L. Parra, J. Heuser, Stig Friberg
Gelled Emulsions With A High Water Content, C. Solans, J. G. Dominguez, J. L. Parra, J. Heuser, Stig Friberg
Chemistry Faculty Research & Creative Works
The structure of a gel containing 99% water, 0.5% of a nonionic surfactant and 0.5% of a hydrocarbon was investigated by analysis of its equilibrium phases and their state of dispersion by liquid helium freeze fracture electron microscopy. The gel consisted of aqueous droplets of micron size separated by a thin membrane of a lamellar liquid crystal and a W/O microemulsion with droplets varying between 200 and 1000 Å in diameter. © 1988 Steinkopff.
Theoretical Considerations Concerning The Separation Of Enantiomeric Solutes By Liquid Chromatography, Richard E. Boehm, Daniel E. Martire, Daniel W. Armstrong
Theoretical Considerations Concerning The Separation Of Enantiomeric Solutes By Liquid Chromatography, Richard E. Boehm, Daniel E. Martire, Daniel W. Armstrong
Chemistry Faculty Research & Creative Works
A statistical thermodynamic theory of chiral solute retention and separation using chiral stationary phase high-performance liquid chromatography (CSP-HPLC) is formulated and applied in the limit of infinite dilution of solute to models of chemically bonded CSPs consisting of either chiral tetrahedral moieties or chiral molecular cavities intended to simulate a cyclodextrin CSP. Explicit expressions are derived for the corresponding separation factors and the likelihood of enantiomeric separation is investigated as a function of the multitude of possible interactions and retention modes for the enantiomers and CSPs considered. The separation factor reduces to a simple Boltzmann factor whenever a dominant retention …
Chalcogen Elements In Snow: Relation To Emission Source, Kuen Y. Chlou, Oliver Manuel
Chalcogen Elements In Snow: Relation To Emission Source, Kuen Y. Chlou, Oliver Manuel
Chemistry Faculty Research & Creative Works
We have measured the concentrations of S, Se, and Te in samples of 1986 snow and compared our results with those of earlier measurements. We were unable to find any earlier reports on Te in snow, but values of the Se/S concentration ratio in 1986 are about a factor of 6 lower than that in snow and glacial ice of 800 B.C. Measurements on intermediate samples demonstrate that most of the decline in the Se/S ratio occurred during the past 200 years, i.e., since the start of the Industrial Revolution. This temporal change in values of the Se/S ratio probably …
Evaluation Of Dye-Micelle Binding Constants Using Diffusion Sensitive Band Broadening Effects, Daniel W. Armstrong, R. A. Menges, S. M. Han
Evaluation Of Dye-Micelle Binding Constants Using Diffusion Sensitive Band Broadening Effects, Daniel W. Armstrong, R. A. Menges, S. M. Han
Chemistry Faculty Research & Creative Works
The diffusion coefficients of small solutes can be significantly altered by the presence of association colloids such as micelles. A relationship is utilized that relates the diffusion coefficient of a solute to its partitioning or binding behavior to a micellar pseudo phase. The Taylor-Aris dispersion method was used to evaluate the diffusion coefficient of several dyes in the presence and absence of sodium dodecyl sulfate micelles. With this approach, all binding constants can be determined easily and reproducibly. The theory, experimental approach, and advantages of this technique are discussed. © 1988.
A Study Of Surface Dynamics Of Polymers. Ii. Investigation By Plasma Surface Implantation Of Fluorine–Containing Moieties, T. Yasuda, T. Okuno, K. Yoshida, H. Yasuda
A Study Of Surface Dynamics Of Polymers. Ii. Investigation By Plasma Surface Implantation Of Fluorine–Containing Moieties, T. Yasuda, T. Okuno, K. Yoshida, H. Yasuda
Chemistry Faculty Research & Creative Works
Macromolecules at the surface of a polymeric solid have considerable mobility, and the specific arrangement of functional groups of macromolecules at the surface is dictated by the environmental conditions in which the surface is placed. Consequently, the change of environmental conditions, such as immersion in water or placement in a biological surrounding, could cause a considerable degree of change in the surface characteristics of a polymer from those evaluated in the laboratory against ambient air. The mobile nature of a polymer surface can be investigated by surface‐implanting fluorine‐containing moieties, mainly—CF3, by the plasma implantation technique and following the disappearance and …
A Study Of Surface Dynamics Of Polymers. Iii. Surface Dynamic Stabilization By Plasma Polymerization, T. Yasuda, K. Yoshida, T. Okuno, H. Yasuda
A Study Of Surface Dynamics Of Polymers. Iii. Surface Dynamic Stabilization By Plasma Polymerization, T. Yasuda, K. Yoshida, T. Okuno, H. Yasuda
Chemistry Faculty Research & Creative Works
As demonstrated in Part II of this series of studies, the hydrophobic character of CF4 plasma‐treated Nylon 6 and poly (ethylene terephthalate) (PET) decay with time of water immersion, and the rate of decay can be used as a measure for the surface mobility of (substrate) polymers. The same method of using fluorine‐containing moieties introduced by CF4 plasma treatment as surface labeling is applied to investigate the influence of a thin layer of plasma polymer of methane applied onto the surface of those polymers. An ultrathin layer of plasma polymer provides a barrier to the rotational and diffusional migration of …
The Stroke Data Bank: Design, Methods, And Baseline Characteristics, Mary A. Foulkes, Philip A. Wolf, Thomas R. Price, J. P. Mohr, Daniel B. Hier
The Stroke Data Bank: Design, Methods, And Baseline Characteristics, Mary A. Foulkes, Philip A. Wolf, Thomas R. Price, J. P. Mohr, Daniel B. Hier
Chemistry Faculty Research & Creative Works
The National Institute of Neurological and Communicative Disorders and Stroke Initiated the Stroke Data Bank, which is a Multicenter Project to Prospectively Collect Data on the Clinical Course and Sequelae of Stroke. Additional Objectives Were to Provide Information that Would Enable a Standard Diagnostic Clinical Evaluation, to Identify Prognostic Factors, and to Provide Planning Data for Future Studies. a Brief Description of the Structure and Methods Precede the Baseline Characterization of 1,805 Patients Enrolled in the Stroke Data Bank between July 1983 and June 1986. Two Thirds of These Patients Were Admitted within 24 Hours after Stroke Onset. Medical History, …
Highly Selective Protein Separations With Reversed Micellar Liquid Membranes, Daniel W. Armstrong, Weiyong Li
Highly Selective Protein Separations With Reversed Micellar Liquid Membranes, Daniel W. Armstrong, Weiyong Li
Chemistry Faculty Research & Creative Works
No abstract provided.