Chemistry Commons^™

Sans From Tetradecylpyridinium Bromide Based Microemulsions, Paul M. Lindemuth, Boualem Hammouda, Raymond L. Venable

Chemistry Faculty Research & Creative Works

Small-angle neutron scattering is used to investigate tetradecyl pyridinium bromide/pentanol/heptane/heavy water microemulsions in the water-in-oil (W/O) microemulsion phase diagram region. The heavy water content is increased while the other components (surfactant, cosurfactant, hydrocarbon) are kept constant. With use of a simple model assuming spherical micelles interacting with a hard-sphere potential (Percus-Yevick model), aggregate sizes and packing fractions have been extracted and found to agree with values determined from the mixing conditions. These experiments clearly show the transition from the single-particle (heavy water + Stern layer droplet) scattering regime at low water concentration to the mixed single/interdroplet scattering regime when the …

Coatings And Surface Modification By Methane Plasma Polymerization, Chung‐Peng ‐P Ho, H. Yasuda

Chemistry Faculty Research & Creative Works

Polymers formed from plasma‐polymerized methane were employed to modify the surface properties of silicone rubber membrane. Polymers were evaluated based on the energy input parameter W/FM, where W is the discharge power, F is the monomer flow rate, and M is the molecular weight of the monomer. Dealing with the characteristics of plasma polymerization and the deposited polymer film, the effect of pumping rate on deposition rate and the coating thickness, surface energy, and gas permeabilities of methane‐plasma‐polymer‐coated silicone rubber membrane were investigated in three plasma regions. Because more reactive species are expelled at high pumping rates, the monomer‐deficient region …

Plasma Surface Treatment On Nylon Fabrics By Fluorocarbon Compounds, Yu Iriyama, Takeshi Yasuda, D. L. Cho, H. Yasuda

Chemistry Faculty Research & Creative Works

Nylon fabrics were treated by low temperature fluorocarbon plasmas. All of the fluorocarbon plasmas applied altered the surface of nylon fabrics to be hydrophobic and water‐repellent. The durability of hydrophobicity and water repellency was examined by measurements of the water contact angle, the water droplet rolling‐off angle, and the breakthrough water pressure after plasma‐treated fabrics were washed. It was found that the structure of starting fluorocarbon and the plasma energy input were important factors in the durability. After washing, surface dynamics were investigated on different drying conditions. It was found that chemical composition and water repellency were dependent on drying …

Derivatized Cyclodextrins For Normal-Phase Liquid Chromatographic Separation Of Enantiorners, Daniel W. Armstrong, San Chun Chang, Apryll M. Stalcup, Martha L. Hilton, Jo Dee Duncan, James R. Faulkner

Chemistry Faculty Research & Creative Works

Several different derivatized β-cyclodextrins were synthesized and used as chiral stationary phases in normal-phase liquid chromatography. The multiply substituted derivatives were made with acetic anhydride, (R)-and (S)-1-(1-naphthyl) ethyl isocyanate, 2, 6-dimethylphenyl isocyanate, and p-toluoyl chloride. The first successful cyclodextrln-based, normal-phase separation of enantiomers was accomplished on these derivative phases. In contrast to chiral separations on the native β-cyclodextrin stationary phase, the enantiomeric separation mechanism on these new phases is not thought to be dependent on inclusion complexation. The similarities and differences between the derivatized cyclodextrin stationary phases and the cellulosic stationary phases are discussed. © 1990, American Chemical Society. All …

Dementia In Stroke Survivors In The Stroke Data Bank Cohort: Prevalence, Incidence, Risk Factors, And Computed Tomographic Findings, Thomas K. Tatemichi, Mary A. Foulkes, J. P. Mohr, Jeffrey R. Hewitt, Daniel B. Hier, Thomas R. Price, Philip A. Wolf

Chemistry Faculty Research & Creative Works

We Determined the Prevalence of Dementia in 927 Patients with Acute Ischemic Stroke Aged ≥60 Years in the Stroke Data Bank Cohort based on the Examining Neurologist's Best Judgment Diagnostic Agreement among Examiners Was 68% (K=0.34). of 726 Testable Patients, 116 (16%) Were Demented. Prevalence of Dementia Was Related to Age But Not to Sex, Race, Handedness, Educational Level, or Employment Status Before the Stroke. Previous Stroke and Previous Myocardial Infarction Were Related to Prevalence of Dementia Although Hypertension, Diabetes Mellitus, Atrial Fibrillation, and Previous Use of Antithrombotic Drugs Were Not Prevalence of Dementia Was Most Frequent in Patients with …

On The Kelvin Electrostatic Generator, S. Desmet, F. Orban, Fernande Grandjean

Chemistry Faculty Research & Creative Works

The Kelvin generator is an amazing electrostatic device which poses many questions. The authors report the results of their investigations of this device under various controlled conditions with both nonpolar and polar liquids and a sodium chloride aqueous solution. They have found that the generator works well even if the two liquid streams originate from different electrically insulated reservoirs. In addition they propose a model in which the electric charge results from the separation of the hydrogen and hydroxyl ions as the water droplets form.

Condensation Coefficient Measurement For Water In The Umr Cloud Simulation Chamber, Donald E. Hagen, John L. Schmitt, Max B. Trueblood, John C. Carstens, Daniel R. White, Darryl J. Alofs

Physics Faculty Research & Creative Works

A systematic series of condensation coefficient measurements of water have been made using the University of Missouri-Rolla cooled-wall expansion chamber which simulates the thermodynamics of cloud. This coefficient is seen to decrease from a value near unity, at the outset of simulation, to a value in the neighborhood of 0.01 toward the end of a simulation. Final values of this coefficient are sufficiently low as to contribute significantly to the broadening of the drop-size distribution in cloud.

Measured Spectra Of The Hygroscopic Fraction Of Atmospheric Aerosol Particles, Darryl J. Alofs, Donald E. Hagen, Max B. Trueblood

Mechanical and Aerospace Engineering Faculty Research & Creative Works

The relation between dry diameter (X₀) and critical supersaturation (S_c) for atmospheric submicron aerosol particles is investigated using a long term air sampling program at Rolla, Missouri. The particles are passed through an electrostatic aerosol size classifier, and then through an isothermal haze chamber. Results are reported in terms of an apparent volume fraction of soluble material, ε_v defined such that for particles composed only of ammonium sulfate and water insoluble compounds, ε_v is the actual volume fraction of soluble material. The probability distribution of ε_v is found to be approximately Gaussian in …

Mössbauer Effect Studies Of Nd₂Fe₁₄₋ₓsiₓb And Y₃Fe₁₄₋ₓsiₓb, Oran Allan Pringle, Gary J. Long, G. K. Marasinghe, William Joseph James, Antoni T. Pedziwiatr, W. E. Wallace, Fernande Grandjean

Physics Faculty Research & Creative Works

No abstract provided.

Polymerization Of Methane, Ashok K. Sharma, H. Yasuda

Chemistry Faculty Research & Creative Works

Plasma polymerization of methane in a magnetically enhanced capacitively coupled bell jar reactor operating at a frequency of 10 kHz is reported. Dependence of polymer deposition rate on monomer feed rate (F), composite power parameter (W/FM), electrode temperature, and electrode cleanliness have been examined. Such functional properties as wettability, adhesion, and thermal stability of the polymer are found to depend on the composite power parameter (W/FM) of the plasma. The permeability studies indicate highly crosslinked nature of the polymer. ESCA studies reveal code position of electrode material with the polymer under high W/FM conditions, potential applications of plasma polymer of …

Reversibility Of Ct And Mr Findings In Neuro-Behçet Disease, Dushyant V. Patel, Michael J. Neuman, Daniel B. Hier

Chemistry Faculty Research & Creative Works

A Woman with Neuro-Behçet Disease Characterized by Recurrent Attacks of Meningoencephalitis is Reported. during an Attack of Brain Stem Dysfunction Characterized by Dysarthria, Diplopia, and Ataxia, the Postcontrast CT Showed an Enhancing Lesion of the Upper Brain Stem. during a Subsequent Attack Characterized by Subcortical Dementia and Amnesia, Magnetic Resonance (MR) Showed Abnormal Signal Intensity in the Hypothalamus and Upper Brain Stem. Upon Remission of Her Symptoms, Follow-Up Contrast Enhanced CT and MR Were Entirely Normal. Magnetic Resonance is Especially Useful in Localizing Acute Inflammatory Lesions in Behçet Disease. This Case Suggests that Abnormal MR and CT Findings in Neuro-Behçet …

Plasma Polymerization By Magnetron Glow Discharge. I. Effect Of Magnetic Field On Breakdown Of Monomers In Low Pressure, K. Sato, Y. Iriyama, D. L. Cho, H. Yasuda

Chemistry Faculty Research & Creative Works

The breakdown voltage Vb of glow discharge of an organic monomer generally decreases as the system pressure decreases; however, below a certain threshold pressure, the breakdown voltage increases with decreasing system pressure. In the pressure range below 100 mTorr, the breakdown voltage generally increases as a linear function of 1 /p, where p is the system pressure of the reactor. In this region, glow discharge without magnetic enhancement often yields unstable discharge, which is associated with a very steep slope of a line in the Vh vs /p plot. The similar plots for glow discharges of non-polymer-forming gases, such as …

Morning Increase In Onset Of Ischemic Stroke, John R. Marler, Thomas R. Price, Gregory L. Clark, James E. Muller, Thomas Robertson, Jay P. Mohr, Daniel B. Hìer, Philip A. Wolf, Louis R. Caplan, Mary A. Foulkes

Chemistry Faculty Research & Creative Works

The Time of Onset of Ischemic Stroke Was Determined for 1,167 of 1,273 Patients during the Collection of Data by Four Academic Hospital Centers between June 30, 1983, and June 30, 1986. More Strokes Occurred in Awake Patients from 10:00 Am to Noon Than during Any Other 2-Hour Interval. the Incidence of Stroke Onset Declined Steadily during the Remainder of the Day and Early Evening. the Onset of Stroke is Least Likely to Occur in the Late Evening, Before Midnight. © 1989 American Heart Association, Inc.

Determinants Of Early Recurrence Of Cerebral Infarction: The Stroke Data Bank, R. L. Sacco, M. A. Foulkes, J. P. Mohr, P. A. Wolf, D. (Daniel) B. Hier, T. R. Price

Chemistry Faculty Research & Creative Works

We Studied 1,273 Patients with Ischemic Cerebral Infarction Who Were Entered into the Stroke Data Bank, a Prospective, Observational Study Involving Four University Hospitals and the Biometry and Field Studies Branch of the National Institute of Neurological Disorders and Stroke. Forty Patients Had Non-Iatrogenic Recurrent Stroke within 30 Days after the Index Cerebral Infarction. using Life Tables, the 30-Day Cumulative± SE Risk of Early Recurrence for All Infarctions Was 3.3±0.4%. the Risk of Early Recurrence Was Greatest for Atherothrombotic Infarction (7.9±2.2%, Eight of 113 Patients) and Least for Lacunar Infarction (2.2±1.2%, Eight of 337 Patients). Both Cardioembolic Infarction (4.3±0.9%, 10 …

Predictors Of Survival In Clinically Diagnosed Alzheimer's Disease And Multi-Infarct Dementia, Daniel B. Hier, Joshua D. Warach, Philip B. Gorelick, Joseph Thomas

Chemistry Faculty Research & Creative Works

No abstract provided.

Measured Spectra Of The Hygroscopic Fraction Of Atmospheric Aerosol Particles, Darryl J. Alofs, Donald E. Hagen, Max B. Trueblood

Mechanical and Aerospace Engineering Faculty Research & Creative Works

The Relation between Dry Diameter (Xo) and Critical Supersaturation (Sc) for Atmospheric Submicron Aerosol Particles is Investigated. the Particles Are Passed through an Electrostatic Aerosol Size Classifier, and Then through an Isothermal Haze Chamber. Results Are Reported in Terms of an Apparent Volume Fraction of Soluble Material, Εv, Defined Such that for Particles Composed Only of Ammonium Sulfate and Water Insoluble Compounds, Εv is the Actual Volume Fraction of Soluble Material. the Probability Distribution of Εv is Found to Be Approximately Gaussian in the Εv Range 0.2 to 1.3. the Mean Εv is 0.5, for Electrostatic Aerosol Classifier Settings of …

A Neutron Diffraction And Mössbauer Spectral Study Of The Structure And Magnetic Properties Of The Y₂Fe₁₄₋ₓsiₓb Solid Solutions, Gaya Kanishka Marasinghe, Oran Allan Pringle, Gary J. Long, William B. Yelon, Fernande Grandjean

Physics Faculty Research & Creative Works

A neutron diffraction and Mössbauer spectral study of Y₂Fe_14-xSi_xB shows that silicon preferentially occupies the 4c, and to a lesser extent, the 8j₁ sites in Y₂Fe_14-xSi_xB. The trend in the site occupancy is the same as in Nd₂Fe_14-xSi_xB. The Curie temperature of Y₂Fe_14-xSi_xB increases with increasing silicon content. Neutron diffraction data show that the increase in Curie temperature is accompanied by a contraction of the unit cell. Wigner-Seitz cell calculations, using the Y₂Fe …

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(Fe_1-xAl_x) 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

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 (pK_a = 7.60-11.1), the data fit the rate expression k_obsd - K_OH-⨯ [OH-] = k₁[amine]_free. This rate equation is in contrast to the two-term rate equation (k_obsd = 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

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

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.

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

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

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

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

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 …

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 …

Thermal, Mechanical And Interfacial Characterization Of A Fiberglass Reinforced Plastic Composite, Theodore J. Williams

Masters Theses

The effects of a glass fiber reinforcer on the properties of poly(methyl methacrylate) were evaluated. A silane coupling agent (M8550 Petrarch Systems, Inc.) was employed to promote adhesion between the materials. FTIR analysis, ESCA/Auger and SEM techniques were used to characterize the silane coating.

The mechanical properties, such as bending strength, improved with an increase in the volume percent of fiber. The addition of the M8550 silane directly into the monomer solution showed the most improvement, 23 percent increase, when compared to the uncoated glass fiber. The glass transition temperature as measured by DSC and the heat distortion temperature (HDT) …

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. 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 …