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Articles 1081 - 1110 of 1553
Full-Text Articles in Chemistry
Neutron Diffraction And Magnetic Studies Of Nd₂Fe₁₇₋ₓtₓ (T=Si, Mn) Alloys, William B. Yelon, Z. Hu, Mingxing Chen, H. Luo, F. Pourarian, Peter C. Ezekwenna, G. K. Marasinghe, K. H. J. Buschow, D. P. Middleton, William Joseph James
Neutron Diffraction And Magnetic Studies Of Nd₂Fe₁₇₋ₓtₓ (T=Si, Mn) Alloys, William B. Yelon, Z. Hu, Mingxing Chen, H. Luo, F. Pourarian, Peter C. Ezekwenna, G. K. Marasinghe, K. H. J. Buschow, D. P. Middleton, William Joseph James
Physics Faculty Research & Creative Works
We have carried out neutron and magnetic studies on Nd2Fe17-xTx (T=Si, Mn) alloys. the unit cell of the compounds contracts with both Si and Mn substitution. Si atoms avoid the 6c site, prefer the 18h site strongly, fill the 9d site steadily and fill the 18f site only at relatively high Si concentration. Mn atoms avoid the 9d sites but prefer the 6c site strongly, while the 18f site and 18h site fill slowly. the Si site occupancies appear to be dominated by the crystal environment while the Mn site occupancies are dominated by steric …
1,1′-Diacetyl-2,2′-Biimidazole, Paula M. Secondo, Colin A. Hester, Harvest L. Collier, Russell G. Baughman, A. W. Cordes
1,1′-Diacetyl-2,2′-Biimidazole, Paula M. Secondo, Colin A. Hester, Harvest L. Collier, Russell G. Baughman, A. W. Cordes
Chemistry Faculty Research & Creative Works
A crystallographic twofold rotation axis passes through the C-C bond joining the imidazole rings of the title compound, C10H10N4O2. the molecule crystallizes in a cis disposition. the planar acetyl group is twisted by 5.0 (3)° with respect to the imidazole ring and the two imidazole rings are tilted by 60.53 (5)° in relation to one another.
1,1′-Diketone And 1,1′-Dinitrile Derivatives Of 2,2′-Biimidazole, Paula M. Secondo, William M. Barnett, Harvest L. Collier, Russell G. Baughman
1,1′-Diketone And 1,1′-Dinitrile Derivatives Of 2,2′-Biimidazole, Paula M. Secondo, William M. Barnett, Harvest L. Collier, Russell G. Baughman
Chemistry Faculty Research & Creative Works
The crystal structures of 2,2′-biimidazole-1,1′-diacetone, C12H14N4O2, and 2,2′-biimidazole-1,1′-diacetonitrile, C10H8N6, have been determined. Both molecules crystallize with coplanar rings having substituents in a trans disposition with a center of inversion located midway between the bridging C atoms.
Biodegradation Of Nonionic Surfactants And Effects Of Oxidative Pretreatment, Craig D. Adams, S. Spitzer, R. M. Cowan
Biodegradation Of Nonionic Surfactants And Effects Of Oxidative Pretreatment, Craig D. Adams, S. Spitzer, R. M. Cowan
Civil, Architectural and Environmental Engineering Faculty Research & Creative Works
The aerobic biodegradability of nonionic, ethoxylated surfactants and model compounds, and the effect of advanced oxidation pretreatment on the biodegradability of the biorefractory surfactants were examined. Bioassays conducted using a mixed microbial seed showed that the linear primary alcohol ethoxylates, the fatty acid ethoxylates, and also polyethylene glycol were all degradable. The biomineralization of the linear secondary alcohol ethoxylate, ethylene oxide/propylene oxide block copolymer, and alkylphenol ethoxylate was observed to be inhibited to varying degrees. Additional bioassays were conducted on model compounds to examine the effect of specific structural components on biodegradability. Advanced oxidation pretreatment using hydrogen peroxide in combination …
Sixth International Symposium On Chiral Discrimination, Daniel W. Armstrong
Sixth International Symposium On Chiral Discrimination, Daniel W. Armstrong
Chemistry Faculty Research & Creative Works
No abstract provided.
Treatability Of S-Triazine Herbicide Metabolites Using Powdered Activated Carbon, Craig D. Adams, Tammy L. Watson
Treatability Of S-Triazine Herbicide Metabolites Using Powdered Activated Carbon, Craig D. Adams, Tammy L. Watson
Civil, Architectural and Environmental Engineering Faculty Research & Creative Works
Widespread use of s-triazine herbicides such as atrazine, simazine, and cyanazine has led to the contamination of many ground-water and surface-water supplies with the parent compounds as well as by primary metabolites (e.g., deethylatrazine, deisopropylatrazine, and deethylcyanazine). Ozonation has been shown to produce many of the same byproducts. Activated carbon adsorption has been designated by the U.S. Environmental Protection Agency as the best available technology (BAT) for the treatment of herbicides in drinking water. Little data is available, however, on the applicability of activated carbon treatment for the control of the primary degradation products of herbicides. In this study, the …
Capillary Electrophoretic Enantiomeric Separations Using The Glycopeptide Antibiotic, Teicoplanin, Kimber L. Rundlett, Mary P. Gasper, Eve Y. Zhou, Daniel W. Armstrong
Capillary Electrophoretic Enantiomeric Separations Using The Glycopeptide Antibiotic, Teicoplanin, Kimber L. Rundlett, Mary P. Gasper, Eve Y. Zhou, Daniel W. Armstrong
Chemistry Faculty Research & Creative Works
Teicoplanin is the third in a series of macrocyclic glycopeptide antibiotics that has been evaluated as a chiral selector in capillary electrophoresis (CE). It was used to resolve over 100 anionic racemates at low selector concentrations. Like the other related glycopeptide antibiotics, its enantioselectivity tends to be opposite to that of the ansa-type antibiotics which prefers cationic compounds-particularly amines. Factors that affect teicoplanin-based enantioseparations include the selector concentration, pH, and the concentration of the organic modifier. The temperature and the nature and strength of the buffer are also known to affect the stability of the chiral selector as well as …
Dynamics Of Poly(Vinyl Acetate) In Bulk And On Silica, Frank D. Blum, Gu Xu, Minghua Liang, Charles G. Wade
Dynamics Of Poly(Vinyl Acetate) In Bulk And On Silica, Frank D. Blum, Gu Xu, Minghua Liang, Charles G. Wade
Chemistry Faculty Research & Creative Works
Quadrupole echo deuterium NMR has been used to probe the dynamics of poly(vinyl acetate-d3) in bulk and at saturation coverage (from toluene) on silica at the solid-air interface. In bulk and at lower temperatures, the deuterium powder pattern of the labeled methyl group was found to be consistent with fast threefold jumps with a small asymmetry due to the interaction of the methyl deuteron with the carbonyl oxygen. This apparent asymmetry was a result either of a distortion in the C-C-D bond angle or a reduction of the axial symmetry of the electric field gradient along the C-D bond vector. …
Structures, Thermochemistry, And Electron Affinities Of The Pfn And Pfn- Series, N=1-6, Gregory S. Tschumper, Justin T. Fermann, Henry F. Schaefer
Structures, Thermochemistry, And Electron Affinities Of The Pfn And Pfn- Series, N=1-6, Gregory S. Tschumper, Justin T. Fermann, Henry F. Schaefer
Chemistry Faculty Research & Creative Works
A quantum mechanical study of the phosphorus fluorides and their singly charged anions was carried out. A range of density functional methods was used. Optimized geometries, adiabatic electron affinities, vertical electron affinities, vertical detachment energies, and stabilities toward the loss of a single fluorine atom or fluorine ion are reported. These properties were evaluated exhaustively using four exchange-correlation functionals: Becke's 1988 exchange functional with the correlation functional of Lee, Yang, and Parr, Becke's 1988 exchange functional with the 1986 correlation functional of Perdew, Becke's three parameter Hartree-Fock/density functional hybrid exchange functional with the correlation functional of Lee, Yang, and Parr …
Segmental Motion Of Surface-Bound Swollen Poly(Methyl Acrylate)-D, Minghua Liang
Segmental Motion Of Surface-Bound Swollen Poly(Methyl Acrylate)-D, Minghua Liang
Masters Theses
"Poly (methyl acrylate)-da (PMA-da) was prepared and adsorbed on silica then swollen with toluene and carbon tetrachloride. Comparisons of deuterium NMR spin-lattice relaxation time, T1, and spin-spin relaxation time, T2, for the adsorbed polymer at different temperatures were made to obtain information about the backbone motion of the surface-bound polymer. The results suggest that the local fast motions may be similar to those in the corresponding solution, but the longer-range molecular motions were more restricted than those in solution. The log-normal distribution yielded mean correlation times which were 4-10 times slower for the …
Enantiomeric Composition And Prevalence Of Some Bicyclic Monoterpenoids In Amber, Daniel W. Armstrong, Eve Y. Zhou, Janusz Zukowski, Barbara Kosmowska-Ceranowicz
Enantiomeric Composition And Prevalence Of Some Bicyclic Monoterpenoids In Amber, Daniel W. Armstrong, Eve Y. Zhou, Janusz Zukowski, Barbara Kosmowska-Ceranowicz
Chemistry Faculty Research & Creative Works
Among the more prevalent chiral monoterpenoid compounds in conifers are α-pinene, β-pinene, and smaller amounts of camphene and limonene. The most prevalent chiral monoterpenoid compounds in fossilized resin (referred to as amber in this paper) appear to be borneol, isoborneol, and camphene. Most of these compounds have easily measured enantiomeric excesses. The borneol and isoborneol in some amber samples have pronounced enantiomeric excesses despite the fact that they are tens of millions of years old. The enantiomeric ratios of the monoterpenoids in different ambers vary tremendously and often are distinct. However, in any single amber sample, the stereochemistry (absolute configuration) …
Upper-Tropospheric Aerosol Sampled During Project Fire Ifo Ii, Donald E. Hagen, Josef Podzimek, Max B. Trueblood
Upper-Tropospheric Aerosol Sampled During Project Fire Ifo Ii, Donald E. Hagen, Josef Podzimek, Max B. Trueblood
Physics Faculty Research & Creative Works
Aerosols can play a role in the cloud formation process through the heterogeneous nucleation mechanism, and in turn, once formed, cirrus clouds can impact the ambient aerosol through scavenging and other collection mechanisms. University of Missouri aerosol sampling facilities were employed on aircraft for in situ collection and characterization of the particulates near cirrus cloud level. Tandem differential mobility analyzer and impactor techniques were used to measure aerosol size distribution, hydration capability, and particle composition information. Evidence of aerosol layering was observed near the tropospause, and there was a tendency toward depletion of the ambient aerosol at both ends of …
A Magnetic, Neutron-Diffraction, And Mössbauer Spectral Study Of The Ce₂Fe₁₇₋ₓsiₓ Solid Solutions, D. P. Middleton, Sanjay R. Mishra, Gary J. Long, Oran Allan Pringle, Zhongbo Hu, William B. Yelon, Fernande Grandjean, K. H. J. Buschow
A Magnetic, Neutron-Diffraction, And Mössbauer Spectral Study Of The Ce₂Fe₁₇₋ₓsiₓ Solid Solutions, D. P. Middleton, Sanjay R. Mishra, Gary J. Long, Oran Allan Pringle, Zhongbo Hu, William B. Yelon, Fernande Grandjean, K. H. J. Buschow
Chemistry Faculty Research & Creative Works
The magnetic properties of a series of Ce2Fe17-xSix solid solutions with x equal to 0.0, 0.23, 0.4, 0.6, 0.8, 1.02, 1.98, and 3.20 have been studied by magnetic measurements, neutron diffraction, and Mössbauer spectroscopy. An x-ray-diffraction study indicates that the compounds adopt the rhombohedral Th2Zn 17-type structure. The substitution of silicon for iron in Ce 2Fe17 leads to a contraction of the a axis by 0.2%, an expansion of the c axis by 0.2%, and a consequent reduction of the unit-cell volume by about 0.2% per substituted silicon. Magnetization studies …
Effect Of Micelles And Mixed Micelles On Efficiency And Selectivity Of Antibiotic-Based Capillary Electrophoretic Enantioseparations, Kimber L. Rundlett, Daniel W. Armstrong
Effect Of Micelles And Mixed Micelles On Efficiency And Selectivity Of Antibiotic-Based Capillary Electrophoretic Enantioseparations, Kimber L. Rundlett, Daniel W. Armstrong
Chemistry Faculty Research & Creative Works
Vancomycin (an oligophenolic, glycopeptide, macrocyclic antibiotic) has been shown to be a superb chiral selector for anionic and neutral compounds. It was found that adding sodium dodecyl sulfate to the run buffer increased efficiency by over 1 order of magnitude, decreased analysis times, and reversed the elution order of the enantiomers. This allows for control of the retention order as well as the resolution of enantiomers in complex mixtures in a single run. A mechanism is proposed which explains all of the observed effects and is verified experimentally. Since vancomycin is present in both the micelle and in free solution, …
Composition Profiles In Electrodeposited Ceramic Superlattices, Jay A. Switzer, Richard J. Phillips, Teresa D. Golden
Composition Profiles In Electrodeposited Ceramic Superlattices, Jay A. Switzer, Richard J. Phillips, Teresa D. Golden
Chemistry Faculty Research & Creative Works
Superlattices in the Pb-Tl-O system with layer thicknesses in the 4-6 nm range were electrodeposited from a single aqueous solution by pulsing the applied potential during deposition. The current-time transients that resulted from the potential steps were monitored to both calculate and tailor the composition profiles of the superlattices during growth. The Cottrell method was used to determine that Tl(l) oxidation was diffusion limited at high potentials. The diffusion limitation resulted in a composition profile that was graded throughout the layer with a t-1/2 dependence. Superlattices grown at lower potentials in which both reactants were under kinetic control had …
Highly Enantioselective Capillary Electrophoretic Separations With Dilute Solutions Of The Macrocyclic Antibiotic Ristocetin A, Daniel W. Armstrong, Mary P. Gasper, Kimber L. Rundlett
Highly Enantioselective Capillary Electrophoretic Separations With Dilute Solutions Of The Macrocyclic Antibiotic Ristocetin A, Daniel W. Armstrong, Mary P. Gasper, Kimber L. Rundlett
Chemistry Faculty Research & Creative Works
Ristocetin A is one of a series of structurally related amphoteric, glycopeptide, macrocyclic antibiotics. These compounds have several features that make them attractive as chiral selectors. These include spatially oriented functional groups that are known to provide the types of interactions that are conducive to enantio-recognition, a somewhat rigid "pocket" that can provide a site for hydrophobic interactions and polar, flexible arms (i.e., pendent sugar moieties) that can rotate to hydrogen bond and otherwise interact with a variety of chiral analytes. In addition, these compounds are sufficiently soluble in water, aqueous buffers and aqueous-organic solvents that are commonly used in …
Neutron Diffraction Studies Of Erni₅₋ₓcoₓ (X=0.68, 1.68, 2.26) Alloys, Z. Zu, William B. Yelon, G. K. Marasinghe, William Joseph James
Neutron Diffraction Studies Of Erni₅₋ₓcoₓ (X=0.68, 1.68, 2.26) Alloys, Z. Zu, William B. Yelon, G. K. Marasinghe, William Joseph James
Physics Faculty Research & Creative Works
ErNi5-xCox alloys were prepared by RF induction melting and analyzed using neutron powder diffraction. Rietveld analysis neutron diffraction data indicates the unit cell volume increases with Co content while the a and c lattice parameters show different dependencies on the composition. the Co atoms show higher affinity for the 3g sites than for the 2c sites. the Co sublattice tends to couple antiferromagnetically to the Er sublattice. the easy magnetization direction is along the c axis.
Neutron Investigations Of Novel Magnetic Phases, William B. Yelon
Neutron Investigations Of Novel Magnetic Phases, William B. Yelon
Physics Faculty Research & Creative Works
Recent years have seen a renewed search for Fe based permanent magnets, spurred by the discovery of Nd2Fe14B and interstitially modified rare-earth iron binaries. The insights derived from those compounds have suggested a number of routes to the development of such systems, including selective site substitution and combinations of site substitution and interstitial modification. Neutron diffraction is an essential component of this work, since it provides systematic information about the location of substitutional and interstitial atoms, and about the effects these changes have on the magnetic interactions in the systems of interest
Determination And Use Of Rohrschneider-Mcreynolds Constants For Chiral Stationary Phases Used In Capillary Gas Chromatography, Alain Berthod, Eve Yiwen Zhou, Kang Le, Daniel W. Armstrong
Determination And Use Of Rohrschneider-Mcreynolds Constants For Chiral Stationary Phases Used In Capillary Gas Chromatography, Alain Berthod, Eve Yiwen Zhou, Kang Le, Daniel W. Armstrong
Chemistry Faculty Research & Creative Works
The overall polarity of 22 chiral stationary phases (CSPs) used in capillary open tubular gas chromatography columns was estimated using the first five Rohrschneider-McReynolds constants. Most of the columns (i.e., 18) were wall-coated, and four were of the wall-immobilized or of the so-called "bonded" type. A wall-coated capillary squalane column was specially prepared as a polarity reference column. All but two of the CSPs were based on derivatized cyclodextrins (CDs) of different sizes. The overall properties of the CSPs are discussed in terms of the five Rohrschneider-McReynolds constants and their average values. It was found that the derivatized cyclodextrin CSP …
Foam Flotation Enrichment Of Enantiomers, Daniel W. Armstrong, Eve Y. Zhou, Shushi Chen, Kang Le, Yubing Tang
Foam Flotation Enrichment Of Enantiomers, Daniel W. Armstrong, Eve Y. Zhou, Shushi Chen, Kang Le, Yubing Tang
Chemistry Faculty Research & Creative Works
Adsorptive bubble separation methods are known to be useful for processing large amounts of material at a relatively low cost These techniques have been used to enrich components from both heterogeneous and homogeneous solutions. There is a need for economical process-scale enantiomeric separations. Thus far there has been little evidence to support the feasibility of using an adsorptive bubble process to enrich enantiomers. We demonstrate that foam-forming chiral collectors can be used in conjunction with an inexpensive glass device to enantiomerically enrich some pharmaceutically important compounds as well as derivatized and underivatized amino acids. Factors that appeared to affect this …
A Magnetic, Neutron Diffraction, And Mössbauer Spectral Study Of The Nd₂Fe₁₇₋ₓalₓ Solid Solutions, Gary J. Long, Gaya Kanishka Marasinghe, Sanjay R. Mishra, Oran Allan Pringle, Zhongbo Hu, William B. Yelon, D. P. Middleton, K. H. J. Buschow, Fernande Grandjean
A Magnetic, Neutron Diffraction, And Mössbauer Spectral Study Of The Nd₂Fe₁₇₋ₓalₓ Solid Solutions, Gary J. Long, Gaya Kanishka Marasinghe, Sanjay R. Mishra, Oran Allan Pringle, Zhongbo Hu, William B. Yelon, D. P. Middleton, K. H. J. Buschow, Fernande Grandjean
Chemistry Faculty Research & Creative Works
The magnetic properties of a series of Nd2Fe17-xAlx solid solutions, with x equal to 2.04, 4.01, 5.97, 7.94, and 9.06, have been studied by magnetic measurements, neutron diffraction, and Mössbauer spectroscopy. Magnetization studies indicate that the Curie temperature increases from 330 K in Nd2Fe17 to a maximum of ~470 K at an x of 3.5. The compounds crystallize in the Th2Zn17 structure with lattice parameters and unit cell volumes which increase linearly with increasing aluminum content. The neutron diffraction results indicate that aluminum atoms are excluded from the 9d …
Neutron Diffraction And Mössbauer Effect Study Of Several Nd₂Fe₁₇₋ₓalₓ Solid Solutions, William B. Yelon, H. Xie, Gary J. Long, Oran Allan Pringle, Fernande Grandjean, K. H. J. Buschow
Neutron Diffraction And Mössbauer Effect Study Of Several Nd₂Fe₁₇₋ₓalₓ Solid Solutions, William B. Yelon, H. Xie, Gary J. Long, Oran Allan Pringle, Fernande Grandjean, K. H. J. Buschow
Physics Faculty Research & Creative Works
Aluminum-substituted Nd2Fe17-xAlx solid solutions with x=2.30, 4.44, 6.13, 8.00, and 9.40 have been studied by neutron diffraction and Mössbauer spectroscopy. A Rietveld analysis of the neutron scattering indicates that the aluminum atoms have a high initial affinity for the 18h site, show a high affinity for the 6c site at high aluminum concentrations, and are absent from the 9d site at all aluminum concentrations. The Mössbauer spectra show a maximum in both the maximum and weighted average hyperfine field for x≅2. This indicates that the lattice expansion which occurs with aluminum substitution is sufficient, at …
Neutron-Diffraction And Mössbauer Effect Study Of The Tb₂Fe₁₇₋ₓalₓ Solid Solutions, Gaya Kanishka Marasinghe, Sanjay R. Mishra, Oran Allan Pringle, Gary J. Long, Zhong Bo Hu, William B. Yelon, Fernande Grandjean, D. P. Middleton, K. H. J. Buschow
Neutron-Diffraction And Mössbauer Effect Study Of The Tb₂Fe₁₇₋ₓalₓ Solid Solutions, Gaya Kanishka Marasinghe, Sanjay R. Mishra, Oran Allan Pringle, Gary J. Long, Zhong Bo Hu, William B. Yelon, Fernande Grandjean, D. P. Middleton, K. H. J. Buschow
Physics Faculty Research & Creative Works
The magnetic properties of a series of Tb2Fe17-xAlx solid solutions, with nominal x compositions of 0, 2, 3, 4, 5, 6, 7, and 8, have been studied by neutron diffraction and Mössbauer spectroscopy. Neutron-diffraction data indicate that the compounds all crystallize with the Th2Zn17 structure and that the aluminum atoms are excluded from the 9d site and show a distinct preference for the 6c site only for an aluminum content greater than 6. The unit-cell volume increases by approximately 1% per aluminum atom substituted in the formula unit. The magnetic moment per …
A Magnetic, Neutron Diffraction, And Mössbauer Spectral Study Of Nd₂Fe₁₅Ga₂ And The Tb₂Fe₁₇₋ₓgaₓ Solid Solutions, Zhong Bo Hu, William B. Yelon, Sanjay R. Mishra, Gary J. Long, Oran Allan Pringle, D. P. Middleton, K. H. J. Buschow, Fernande Grandjean
A Magnetic, Neutron Diffraction, And Mössbauer Spectral Study Of Nd₂Fe₁₅Ga₂ And The Tb₂Fe₁₇₋ₓgaₓ Solid Solutions, Zhong Bo Hu, William B. Yelon, Sanjay R. Mishra, Gary J. Long, Oran Allan Pringle, D. P. Middleton, K. H. J. Buschow, Fernande Grandjean
Physics Faculty Research & Creative Works
An x-ray diffraction study of the substitution of gallium in Tb 2Fe17 to form the Tb2Fe17-xGax solid solutions indicates that the compounds adopt the rhombohedral Th2Zn17 structure. The unit cell volume and the a-axis lattice parameter increase linearly with increasing gallium content. The c-axis lattice parameter increases linearly from x=0 to 6 and then decreases between x=7 and 8. Magnetic studies show the Curie temperature increases by ~150° above that of Tb2Fe17 to reach a maximum between x=3 and 4, and then decreases with further increases in …
Comparative Mössbauer Effect Study Of Several R₂Fe₁₇ And R₂Fe₁₇Nₓ Compounds, Gary J. Long, Sanjay R. Mishra, Oran Allan Pringle, Fernande Grandjean, K. H. Buschow
Comparative Mössbauer Effect Study Of Several R₂Fe₁₇ And R₂Fe₁₇Nₓ Compounds, Gary J. Long, Sanjay R. Mishra, Oran Allan Pringle, Fernande Grandjean, K. H. Buschow
Chemistry Faculty Research & Creative Works
The Mössbauer spectra of Sm2Fe17 and Ho 2Fe17 and their nitrides have been measured between 295 and 85 K and analyzed with a model which is consistent with our earlier work on R2Fe17 and R2Fe17Nx compounds, where R is Pr, Nd, and Th. This model is completely consistent throughout these rare-earth compounds and is in agreement with the crystallographic changes occurring upon nitrogenation and with the prediction of band structure calculations. The dramatic increase in Curie temperature in the nitrides results from the expansion of the crystallographic …
Use Of A Macrocyclic Antibiotic, Rifamycin B, And Indirect Detection For The Resolution Of Racemic Amino Alcohols By Ce, Daniel W. Armstrong, Kumber Rundlett, George L. Reid
Use Of A Macrocyclic Antibiotic, Rifamycin B, And Indirect Detection For The Resolution Of Racemic Amino Alcohols By Ce, Daniel W. Armstrong, Kumber Rundlett, George L. Reid
Chemistry Faculty Research & Creative Works
Ansamycins are a very specific class of macrocyclic antibiotics of which the rifamycins are among the better-known members. Rifamycins bind to and inhibit DNA polymerase. Rifamycin B (the most easily obtained ansamycin) is negatively charged and is shown to associate with and enantioselectively resolve several chiral amino alcohols including terbutaline, isoproterenol, bamethan, metaproterenoi, synephrine, metanephrine, salbutamol, epinephrine, norphenylephrine, ephedrine, ψ-ephedrine, octopamine, norepinephrine, normetanephrine, metoprolol, alprenolol, atenolol, and oxprenolol. A description of the structure and properties of rifamycins, in general, and rifamycin B, in particular, is given. The complexation and chiral recognition of the aforementioned racemic compounds by rifamycin B is …
Macrocyclic Antibiotics As A New Class Of Chiral Selectors For Liquid Chromatography, Daniel W. Armstrong, Yublng Tang, Shushi Chen, Yiwen Zhou, Christina Bagwlll, Jing Ran Chen
Macrocyclic Antibiotics As A New Class Of Chiral Selectors For Liquid Chromatography, Daniel W. Armstrong, Yublng Tang, Shushi Chen, Yiwen Zhou, Christina Bagwlll, Jing Ran Chen
Chemistry Faculty Research & Creative Works
There are a large number of antibiotic macrocycles which include several different structural types. Three representative macrocyclic compounds were covalently linked to silica gel and evaluated by HPLC for their ability to resolve racemic mixtures as well as for their stability and loadability. Over 70 compounds were resolved. In some cases separations were achieved that have not been reported on any other chiral stationary phase (CSP). These stationary phases appear to be multimodal in that they can be used in both the normal-phase and reversed-phase modes. Different compounds are resolved in each mode. There does not appear to be any …
Modified Recycled Glass As An Additive In Coatings Applications, Garth D. Brown
Modified Recycled Glass As An Additive In Coatings Applications, Garth D. Brown
Opportunities for Undergraduate Research Experience Program (OURE)
The feasibility of using chemically modified, finely pulverized recycled glass as an additive in coatings was investigated. The ground glass was added as partial replacement for the conventional pigment titanium dioxide (TiO2). The loss of TiO2 pigment was compensated with an optical brightening agent (OB agents). OB agents can help contribute to a coating’s hiding capacity by absorbing light in the UV range, releasing light of a lower energy in the visible spectrum. Glass supplemented coatings were formulated and common paint tests were performed. The glass changed the optical and physical properties of the coating formulations. The …
Macrocyclic Antibiotics As A New Class Of Chiral Selectors For Liquid Chromatography, Christine Bagwill
Macrocyclic Antibiotics As A New Class Of Chiral Selectors For Liquid Chromatography, Christine Bagwill
Opportunities for Undergraduate Research Experience Program (OURE)
In the field of chromatographic separations, the need for new chiral stationary phases is always in demand. Many stationary phases already exist, some of the more popular being cyclodextrin or protein based phases. During this research, a new class of chiral selectors were discovered and evaluated for chiral recognition. Vancomycin, thiostrepton, and rifamycin B all belong to the macrocyclic antibiotic family. Not only can this new class of chiral selectors be used to resolve compounds that cannot be separated on any other column, but it is also more stable and has much greater capacity than protein based columns.
Synthesis Evaluation Of New High Performance Polymer Systems Involving Tetrachlorohydroquinone, Jason A. Giles
Synthesis Evaluation Of New High Performance Polymer Systems Involving Tetrachlorohydroquinone, Jason A. Giles
Opportunities for Undergraduate Research Experience Program (OURE)
New high performance transparent polymers are in demand in the aerospace and automotive industries to replace current glass and composite systems. Tetrachlorohydroquinone (TCHQ) was used as the base monomer for various copolymer formulations. Different acid chloride monomers lead to polyester formation with TCHQ. Polycarbonates were formed with triphosgene and diethyl carbonate. This base monomer added rigidity, transparency, and high temperature resistance, however, resulting polymers were brittle and difficult to process. Polymers were characterized by IR and DSC.