The post-emission total kinetic energy release (TKE) in the neutron induced fission of ²³²Th was measured (using white spectrum neutrons from LANSCE) for neutron energies from En = 3 to 91 MeV. In this energy range the average post-neutron total kinetic energy release decreases from 162.3 ± 0.3 at En...
The experimental and theoretical bases of transient electric birefringence (TEB) and its application in a variety of nanomaterials, including Na-montmorillonite, cellulose nanocrystals (CNXL), and CdSe quantum dots (QDs) will be presented. TEB is a phenomenon attributed to the alignment of particles in response to an applied electric field and has...
A comparative study was made on the effect of urea denaturation
of bovine serum albumin (BSA), polyglycyl BSA and poly-L-phenylalanyl
BSA. The denaturation process was followed by ultraviolet
spectrophotometry and optical rotation.
A blue shift in the absorption maximum at 278 mμ was observed
in urea denatured proteins, In 7M...
A tracer method utilizing stable activable tracers (involving rare earth nuclides with short-lived t[subscript 1/2] < 1 day} activation products) for tracing fluid bound substances in fresh water is explored. Simulated laboratory studies showed these tracers (Dy and in) when chelated with diethylenetriamine2entaacetic acid a7i1W to be stable ( <20%)...
The Diels-Alder reaction represents a promising tool for use in
asymmetric synthesis. The reaction involves a rigid transition state
that facilitates the formation of one diastereomeric transition state
and is reversible. This satisfies two necessary criteria for
asymmetric synthesis.
The Diels-Alder reactions of 1,l-dialkylspiro[2.4]-4,6- heptadienes
with maleic anhydride and p-benzoquinone...
The effects of different nitrogen sources on the primary and secondary pathways of Azotobacter vinelandii cells were studied by means of the radiorespirometric method. C¹⁴ labeled glucose and several key amino acids related to the tricarboxylic acid cycle, such as glutamic acid, aspartic acid, alanine, serine and glycine were used...
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...
Ab initio calculations using the B3LYP and CCSD(T) methods were employed in this work to explore the most stable structure of the intriguing compound Be(BH₄)₂, for which as many as seven different structures have been proposed in the literature. Use of the B3LYP density functional method with several large basis...
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...
Pyrolysis of 4-cycloheptene-l-methyl acetate under flow conditions at 285° gives only rearranged bicyclic acetates and hydrocarbons rather than the anticipated simple elimination product methylenecyclohept- 4-ene. These rearranged acetates have the same structures and are formed in virtually the same relative percentages as those observed in the "π- route" solvolysis of...
Isomerically pure cis,cis,trans-1-pheny1-1,3,5-
heptatriene was prepared and cyclized. Ring closure
was followed by a 1,5 hydrogen shift, and the only product
observed was 1-phenyl -6-methyl -1,3-cyclohexadiene.
Rough first order rate constants for thermolysis and
the hydrogen shift were determined. Kinetic estimates
indicate that the report of disallowed product in a...
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...
Massive die-offs of Bufo bufo gargarizans were observed in May 2008 in Mangwal
Gee, Korea. To find out the causes for this disaster several different elements
were examined: pH, total nitrogen, dissolved oxygen (DO), and dissolved heavy
metal, suspension, introduced species, habitat change, disease, temperature
changes, and precipitation and humidity....
The total kinetic energy (TKE) in the fast neutron induced fission of 237Np was measured for neutron energies from En = 2.6 – 45.7 MeV at the LANSCE- WNR facility. The postTKE release decreases non-linearly with increasing incident neutron energy and can be represented as TKE(MeV) = (169.365 ± 1.551)...
The first asymmetric synthesis of (-)-7-epicylindrospermopsin via intramolecular nitrone cycloaddition is described. The synthesis utilized a convergent approach to prepare the cycloaddition precursor 176, which was assembled by condensation of hydroxylamine 175 with aldehyde 145. Hydroxylamine 175 was synthesized from ethylene glycol (166) in seven steps. Aldehyde 145 was completed...
The first part of this manuscript is about the total synthesis of the aspidosperma alkaloids leuconoxine, melodinine E and mersicarpine. Our synthetic strategy used a radical translocation-conjugate addition cascade to construct the core of the natural product. Specifically, a vinyl radical was generated from the homolysis of the C–I bond...
Dearomatization reactions exist broadly in biosynthesis and chemical synthesis. The highly functionalized atoms of arenes can be masked by it aromaticity, and upon dearomatization, those reactive atoms can be readily applied to bond formation and further manipulation. The total synthesis of (–)-cephalotaxine and (–)- homoharringtonine is described via an oxidative...
Aminal radical intermediates were generated by the method of radical translocation and reacted in C-C bond forming reactions with electronically deficient alkenes (Schiedler et al. Org. Lett. 2012, 14, 6092). Aminal radical intermediates can participate in inter- and intra-molecular reactions using both Bu3SnH and (TMS)₃SiH as hydride donors. Carbon–carbon bonds...
PART I. The preparation of (-)-ibogamine (1) in fourteen steps from benzoquinone and in 10% overall yield is a powerful illustration of the value of the asymmetric Diels-Alder reaction as a starting point in a multistep synthesis. All four cycloadducts, 70, 77, 84 and 96, obtained with the (S)-BINOL-TiCl₂ complex...
Xanthohumol [XN, (E)-6´-methoxy-3´-(3-methylbuten-2-yl)-2´,4´,4´´-trihydroxychalcone], the principal prenylated chalcone from hops, and its 2,3-dihydro- (DXN) and O6-desmethyl-2,3-dihydro- (DDXN) congeners, are of potential utility for the amelioration of metabolic syndrome; however, their complex bioactivity profiles cannot be properly studied and understood without access to appropriately produced synthetic materials.
In the first part of...
In previous work (Blakemore et al. Org. Lett. 2005, 7, 4721; Heterocycles 2006, 70, 609), successful elaborations of the lupine alkaloids (±)-α-isosparteine (dl-2) and (±)-β-isosparteine (dl-3) were realized from a common tetraoxobispidine precursor, 3,7-diallyl -2,4,6,8-tetraoxo-3,7-diazabicyclo[3.3.1]nonane (93). Herein, the tetraoxobispidine approach to lupine alkaloids was extended to a total synthesis of...
The first part of this manuscript is about the total synthesis of the Arundo donax bis(indole) natural products. The A. donax alkaloids were prepared using the first example of an ynindole Diels–Alder reaction. Each were then separated, isolated, and determined to have stable enantiomeric conformations at room temperature (Chen, J.;...
In this report, three studies are presented that aid in the development of drug discovery and their synthesis. In each, the importance of the marriage between computations and experiments is highlighted. Continued efforts in this vein are essential for future efforts towards improving human health.
The first case study investigated...
In this Dissertation, the mechanism and stereomechanics of complex organocatalysis and reaction processes are disclosed. The technologies and protocols currently being developed and utilized to efficiently investigate these systems using theory are highlighted.
A detailed computational study of peptide-catalyzed acylations is disclosed. In particular, the magnitude of all possible non-bonding...
Halogenated Polycyclic Aromatic Hydrocarbons (X-PAHs) are ubiquitous contaminants that are thought to be generated by processes such as chemical industries and incomplete combustion, including waste incineration and electronic waste (e-waste) burning. X-PAHs are a concern for environmental and human health because they are toxic, mutagenic, and are expected to be...
Femtosecond stimulated Raman spectroscopy (FSRS) is a powerful ultrafast technique which can track photoinduced excited state structural events on femtosecond (fs) to picosecond (ps) timescales. In addition to high temporal and spectral resolutions, FSRS provides a broad spectral window from ca. 100—2000 cm-1 for detection, enabling the direct mapping of...
SOCs volatility and persistence properties cause many SOCs to become ubiquitous in the environment as well as accumulate in areas with lower temperatures such as polar or orographic regions. Many anthropogenic SOCs pose a serious risk to human and ecosystem health because of their persistent, bioaccumulative, and toxic properties in...
The atmospheric transport of anthropogenic semivolatile organic compounds (SOCs) from Asian sources to the Western U.S. was investigated. In addition, the SOC extraction method was optimized. Hansen solubility parameter plots were used to aid in the pressurized liquid extraction (PLE) solvent selection of air sampling media in order to minimize...
In the 21st century, environmental deterioration is now an indisputable fact. Reliable and economically viable electricity systems based on renewable sources are urgently needed to replace the environmentally detrimental fossil fuels. The feasibility of incorporating renewable-but-intermittent solar and wind energy heavily depends on the development of cost-effective and safe technologies,...
A new approach to the discovery of high absorbing semiconductors for solar cells was taken by working under a set of design principles and taking a systemic methodology. Three transition metal chalcogenides at varying states of development were evaluated within this framework. Iron pyrite (FeS₂) is well known to demonstrate...
Inorganic structures play an important role in materials due to their versatility and diversity. A complete understanding of the structure of a material is vital to enhance the creation of new materials that fill voids in research. The rational design of these compounds is driven by the exploitation of structure-property...