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...
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...
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...
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...
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...
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...
A new approach towards a total synthesis of paeoniflorigenin is discussed. The approach involves the application of regio- and stereoselective [2+2] photocycloaddition for the preparation of a key intermediate, cyclobutanone 86, and model studies on diiodosamarium (Sm12) mediated pinacol coupling of a diketone. Intermolecular [2+2] photocycloaddition of a,13unsaturated lactam 33...
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...
At Site-300, Lawrence Livermore National Laboratory (LLNL), CA,
trichloroethene (TCE) is present along with tetraalkoxysilanes such as tetrabutoxysilane
(TBOS) and tetrakis(2-ethylbutoxy) silane (TKEBS), as subsurface contaminants.
Intrinsic transformation of TCE to cis-dichloroethene (c-DCE) was observed in the
groundwater at locations co-contaminated with TBOS or TKEBS. Attenuation of TBOS
and TKEBS...
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...
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 plant Senecio jacobaea (tansy ragwort) produces several macrocyclic pyrrolizidine alkaloids which cause irreversible liver cirrhosis. All of the pyrrolizidine alkaloids in Senecio jacobaea are macrocyclic diesters of the necine base retronecine, with the two most predominant being seneciphylline and jacobine. Unlike horses and cattle, sheep and goats are generally...
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 new experimental apparatus was built at Oregon State University to perform high resolution stimulated Raman spectroscopy in a pulsed molecular jet at state densities of the order of 10¹¹ cm⁻³. The technique uses a stimulated Raman step to first populate a vibrational/rotational level and then a resonantly enhanced multiphoton...
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...
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...
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...
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...
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....
An oscillating plasma glow discharge detector for gas
chromatography is used to obtain fingerprint information
about an analyte by combining both the average cell
current and oscillation frequency signals. Five homologs
each of the n-alkanes, 1-alkenes, 1-alkynes, 2-ketones and
aldehydes are studied. Although triplicate determinations
had some scatter due to...
A synthetic approach toward the two major fragments of cathedulin K-19,
euonyminol (4) and dimethyl cathate (69), was investigated. Synthesis of
dimethyl cathate was accomplished in 3 steps starting from 73. Efforts directed
towards the synthesis of euonyminol, a highly oxygenated dihydroagarofuran
sesquiterpene, was advanced to a stage in which...
The photohydrodebromination of brominated paracyclophanes was studied to
help elucidate the possible mechanistic pathways leading to product for
bromoarenes in general. Several brominated [2.2]paracyclophanes were studied to
determine the effect of substitution patterns on this reaction. [2.2]Paracyclophanes
were chosen for this study in order to investigate possible intramolecular excimer
formation...
In particle induced desorption-ionization mass spectrometry the strength of an
analyte's signal under a given set of bombardment conditions is usually considered to
be representative of the analytes relative surface activity. This rationale is generally
used to explain differences in the technique's sensitivity between and within various
classes of compound....