More that just magnificent views of atoms and
molecules, Scanning Tunneling Microscopy, STM, images have
the potential to answer some fundamental questions relating
to surface molecular dynamics and bonding characteristics of
localized species versus more common analytical tools that
provide average of bulk sample information. A special
feature of the...
The photoelectron spectra of a series of ketone
compounds have been investigated in the gas phase. Core
ionization energies were measured to probe the effects of
molecular size and connectivity number on core ionization
energies.
It was found that core ionization energies roughly
decrease with increasing connectivity number as expected....
The change in the oscillation frequency in the current of
an atmospheric helium glow discharge is a sensitive detector
for gas chromatography. The response of the detector is in
the femtomole and picomole range for nonane and decane. The
effluent of a capillary column is directed into a glow
discharge...
Two related techniques, based upon ion-exchange solid phase extraction, have been
developed for the determination of arsenic speciation. The inorganic arsenic species
arsenite (As(III)) and arsenate (As(V)) are separated by anion-exchange and detected with
graphite furnace atomic absorption spectrophotometry (GFAAS) with a nickel matrix
modifier. The first separation technique, which...
Three aspects of glow discharges have been studied: glow discharge oscillations,
sputtering, and coupling between cathode and anode regions the two most important
regions in a glow discharge. Cathode and anode processes are tightly coupled by electron
and ion coupling effects. Both electron and ion coupling effects were observed by...
A procedure for evaluating the precision of atomic absorption
measurements is presented and applied to 21 elements under varying
instrumental conditions. The experimental relative standard deviations
(RSD's) in absorbance obtained from repetitive measurements made
with a high resolution voltmeter and on-line computer, are compared
to those predicted by a recently...
An atmospheric pressure argon glow discharge is shown
to detect trace levels of carbohydrates in aqueous flowing
systems, using either of two glow discharge solution
interface configurations. The first configuration consists
of an oscillating glow discharge sustained between a flowing
aqueous cathode and platinum anode. Picomole and micromolar
mass and...
The interactions of a model synthetic liquid fuel reactant (furan) with a model
hydrodeoxygenation catalyst (clean and sulfided single crystal molybdenum)
were investigated using the following UHV tools: Auger electron spectroscopy
(AES), low energy electron diffraction (LEED), and temperature programed
reaction spectroscopy (TPRS). In addition to furan, the reactions of...
Linear alkylbenzenesulfonate (LAS) is the most widely used anionic surfactant in
commercial detergent formulations. The environmental fate of LAS is of interest because
of its disposal to wastewater treatment facilities and subsequent occurrence as a
micropollutant in surface waters and groundwater. While LAS fate in wastewater
treatment systems and surface...
2,5-dihydroxyacetanilide epoxidase from Streptomyces LL-C10037 (DHAE I)
catalyzes the epoxidation of hydroquinone 4, to form epoxyquinone 7. DHAE I has been
purified to homogeneity, with an overall purification factor greater than 23,000. N-terminal
and internal amino acid sequences have been obtained from the purified enzyme so
that the epoxidase gene...
A three part study involving aspects of radical properties of various
aromatic species was accomplished.
Experiments to ascertain the importance of geometric and electronic
effects on the intramolecular transfer of a pi-complexed radical to a terminal double bond
was performed. Several 4-aryl-1-butenes were reacted in competition with 1-undecene
with a...
Rapamycin (5) was isolated in 1975 from the soil bacteria Streptomyces hygroscopicus and its structure was determined from spectroscopic techniques and an x-ray crystallographic analysis. Although it was initially found to exhibit antibiotic activity, it was subsequently shown to possess potent immunosuppressive activity as well.
Three approaches to the synthesis...
The migration of chloride ions in concrete with steel reinforcement under cathodic protection was investigated. Mortar blocks (15 cm x 15 cm x 17 cm) of various composition (water to cement ratio, chloride ion content) were cast with an iron mesh cathode embedded along one face and a thermally sprayed...
The electronegativities of -SF₅, -CF₃SO₂, and -SO₂F have been measured with gas phase X-ray photoelectron spectroscopy. Of these three groups previously measured values were found only for -SF₅. The electronegativities of -Cl, -Br, -CF₃, and -CF₃, were concurrently measured to determine how the findings of this research compare with other...
Regiochemistry of intramolecular [2+2] photocycloadditions of oxygenated
6-alkenyl-3-alkoxy-2-cyclohexenones is studied. Application of this methodology
to construct a key intermediate [3.3.2] bicyclic skeleton of ryanodol is described
as well. Irradiation of (3-butenyl)compounds 3, 11, 14 and of (4-pentenyl)compound 6 afforded exclusively the linear photoadducts 4, 12, 15 and
7 respectively. Irradiation...
The carbon is photoelectron spectrum of CO₂ has been measured with very high photon energy resolution. The natural lifetime of the carbon is hole state has been determined from a series of spectra taken at photon energies of 308, 320, and 330 eV. The measured values of the lifetimes show...
High-precision instrumental neutron activation analysis has
been used to determine Al, Na, Mn, Sc, Cr, Fe, Co, and Ni in a
suite of more than 500 chondrules from 26 distinct meteorites. These
meteorite specimens represent the H, L, LL and C chemical classes
and most of the petrologic types. In...
An asymmetric approach to the synthesis of byssochlamic acid (1) is
described. Regioisomeric enzymatic differentiation is described in the selective
hydrolysis of dimethyl ester 30 by porcine liver esterase. Chiral dimethyl ester 42
was prepared by desymmetrization of cyclopentene 34 using porcine liver
esterase. A key intramolecular [2+2]cycloaddition-cycloreversion
photometathesis of...
Polyhalogenated benzenes have been analyzed by standard electron capture
chemical ionization mass spectrometry (ECCI/MS), and electron monochromator mass
spectrometer (EM/MS) systems. The EM/MS experiments distinguished electronegative
compounds (especially isomers) by transient negative ions (TNIs) of the same mass but
differing energies and/or the formation of distinct TNIs of different masses...
Fusion reactions with radioactive neutron-rich projectiles have been the subject of much recent theoretical and experimental interest. Predictions of enhancement of the cross section due to the use of a neutron-rich projectile may have implications for synthesis of heavy nuclei. In this work, the fusion-fission excitation functions were measured for...
In spite of their importance in many systems, liquid surfaces have been
explored at the microscopic level to a much lesser extent than solids. Most surface
analysis must take place in vacuum, a major drawback for liquids. The technique of
time-of-flight scattering and recoil spectrometry (TOF-SARS) has been applied to...
The challenges prompted by miniaturization of chromatographic systems have led scientists to explore new avenues in the synthesis of stationary phases. Packed capillary columns have found limited application in routine analysis due to a number of technical difficulties, most of which are attributable to the frits. New column designs insure...
Contaminant transport in ground water is an important environmental process that
affects a host of natural systems. Transport of contaminants is affected by many
processes, including aqueous complexation, adsorption, and redox reactions. One of the
most important components of an aquifer that controls transport is iron-oxide. In this
study, the...
The melt intercalation of poly(ethylene oxide) (PEO) between layers of MoO₃ and MPS3 (M=Mn,Cd) is obtained by heating the ground mixture and LiₓMoO₃, KₓMn₁-ₓ/₂PS₃, or KCd₁-ₓ/₂PS₃. The products are characterized by powder X-ray diffraction (XRD). Below the melting temperature of PEO (66 °C), intercalation rates and yields are low. By...
PART I. Asymmetric syntheses of both natural (+)- and nonnatural (-)-byssochlamic acid via a [2+2] photoaddition-cycloreversion strategy are described. X-ray crystallographic analysis of the cyclohexylamine salt 99 showed that the structure of the monomethyl ester 100 from esterase hydrolysis of 44 was originally misassigned as 56. The enantiomeric relationship of...
For a number of reasons, miniaturization of chromatographic columns has been a general trend over the past three decades. Methods designed to enhance selectivity and efficiency can offer improved separation power and speed, expanding on the advantages of miniaturized columns. This dissertation describes novel approaches in this direction, focusing on...
The emphasis of this work has been in two areas of optical materials - the
crystal-chemical development of new optical frequency converters and the synthesis
and study of new hosts for Cr³⁺ luminescence and lasing.
A simple method has been developed to identify promising frequency-doubling
materials containing triangular oxoanions by...
In situ, reduction of Cp*ReO₃ by PPh₃ to form (Cp*ReO)₂(μ-O)₂ allows catalytic deoxygenation of epoxides, however, conproportionation between Reⱽ and Reⱽᴵᴵ species to form clusters of ((Cp*Re)₃(μ-O)₆}²⁺(ReO₄⁻)2 and new compound {(Cp*Re)₃(μ²-O)₃(μ³-O⁾³ReO₃}⁺(ReO₄⁻) leads to removal of rhenium from the catalytic cycle and loss of activity, The epoxide deoxygenation mediated by (Cp*ReO)₂(μ-O)₂...
In situ reduction of hydrido-tris-(3,5-dimethylpyrazolyl)borato(trioxo) rhenium(V) with triphenylphosphine or triethylphosphite leads to a reactive rhenium(V) species that catalytically deoxygenates epoxides at 75-105°C. The reaction is stereospecific, except for trans- and cis-butene oxide which formed minor amounts of the opposite isomer. A variety of different functional groups were tolerated and even...
The rhenium dithiodiolate, Hydrido-tris-(3 ,5-dimethyl- 1 -pyrazol yl) borato(ethane- 1 ,2-dithiodiolato)(oxo)rheni um(V), and Hydrido-tris-(3 ,5-dimethyl- 1 -pyrazolyl)borato(phenylethanedithiodiolato)(oxo)rhenium(V), were synthesized by reductive cyclocondensation of alkane-1,2-dithiols with Tp'Re0₃ in a one pot fashion. The rhemium monothiodiolate, Hydrido-tris-(3 ,5-dimethyl- 1 -pyrazolyl) borato(ethane- 1 ,2-monothiodiolato)(oxo)rhenium(V), and Hydrido-tris-(3 ,5- dimethyl- 1 -pyrazolyl)borato(propanemonothiodiolato)(oxo)rhenium(V), were also synthesized...
Two framework oxide materials of the MO₃ network type have been synthesized and structurally characterized by synchrotron and X-ray powder diffraction and the Rietveld method in the temperature range 25~500 K. The results show one of them to be a low thermal expansion material. Theoretical studies of negative thermal expansion...
A novel, portable, filter fluorometer was developed for the determination of chloroform and TCE at environmentally-relevant levels when coupled with improved sampling techniques and reagents. Reagents selective for the TCE or chloroform convert these toxic species into fluorescent species that can be monitored. The fluorometer is based on LED excitation...
A series of compounds, 7-8 and 20-25, were tested as competitive inhibitors of 2,5-dihydroxyacetanilide epoxidase I (DHAE I) and DHAE II. A Hammett plot was constructed for each enzyme to determine the effect of electron density on inhibition. DHAE I gave a linear, highly correlated plot (r²=0.91) that signifies the...
A spectrometer, here denoted a Simple, Low-power, Inexpensive. Microcontroller-based or SLIM spectrometer. was developed that exploits the small size and low cost of solid-state electronic devices. This approach results in customizable spectrometers that are considerably less expensive and smaller than traditional instrumentation. The performance of the SLIM spectrometer was evaluated...
In this dissertation, I present electronic spectroscopy of a few biologically relevant species and their complexes with solvent molecules in the gas phase using a variety of techniques, including resonantly enhanced multiphoton ionization (REMPI), laser induced fluorescence (LIF), and zero kinetic energy (ZEKE) photoelectron spectroscopy. My work on several methylated...
Enzymes play an important role in the environment, they breakdown natural-occurring and anthropogenic molecules so that they can be transported into cells and utilized. Enzyme assays are routinely used in soil science and oceanography to measure the activities of specific processes and to serve as general indicators of microbial activity....
Neurofilament proteins are intermediate filaments found in the neuronal cytoskeleton. Phosphorylation of these proteins is considered important for the assembly and stability of the filaments. Accurate molecular weights have been difficult to measure, largely because the high degree of phosphorylation results in M[subscript r]'S that are significantly greater than dictated...
Benzylsuccinate (BSA), methylbenzylsuccinate (methylBSA), and ethylbenzylsuccinate (ethylBSA) are unambiguous anaerobic biotransformation products from toluene, xylenes, and ethylbenzene decay, respectively, and may be used to indicate intrinsic bioremediation is occurring at hydrocarbon-contaminated sites. In order to improve upon current methods that detect and quantify anaerobic hydrocarbon metabolites in field samples, solid-phase-extraction...