Chemistry Commons^™

Growth And Fabrication With Single-Walled Carbon Nanotube Probe Microscopy Tips, Chin Li Cheung, Jason H. Hafner, Teri W. Odom, Kyoungha Kim, Charles M. Lieber

Barry Chin Li Cheung Publications

Single-walled carbon nanotube (SWNT) probe microscopy tips were grown by a surface growth chemical vapor deposition method. Tips consisting of individual SWNTs (1.5–4 nm in diameter) and SWNT bundles (4–12 nm in diameter) have been prepared by design through variations in the catalyst and growth conditions. In addition to high-resolution imaging, these tips have been used to fabricate SWNT nanostructures by spatially controlled deposition of specific length segments of the nanotube tips.

Determination Of The Wavelength Dependence On The Metal Catalyzed Degradation Of The Herbicide Atrazine, Timothy Bertram

Honors Theses

Since the advent of modern herbicide use in the early twentieth century, researchers have been plagued with the obvious problem of herbicide disposal. Most herbicides are specifically designed to resist natural degradation processes so that they can remain effective in the field for a substantial amount of time. In addition, they are also made water soluble so that they can be easily applied to crops. Finally, they are specifically produced to kill undesirable plant species in the quickest and often crudest fashions. Due to these specific properties herbicides pose a general threat to other organisms living in the same geographic …

Femtosecond Luminescence Dynamics In A Nonlinear Optical Organic Dendrimer, O. Varnavski, A. Leanov, L. Liu, James M. Takacs, T. Goodson Iii

James M. Takacs Publications

The ultrafast intrinsic dynamics of an organic dendrimer in solution and in a thin film is reported using fluorescence upconversion spectroscopy. Femtosecond decay is detected at higher emission energies, while at lower energies a fluorescence rise time (∼3 ps) was observed that is dependent on the solvent’s polarity. A strong excitation energy dependence of the decay pattern was also observed. Different synthetic functional groups that comprise the macromolecular dendrimer structure were investigated. The mechanism, which describes the complex dynamics in the dendrimer system, was found to be associated with the excitation of the attached chromophore nitroaminostilbene. These results indicate the …

The Melting Temperature Of Proton-Disordered Hexagonal Ice: A Computer Simulation Of 4-Site Transferable Intermolecular Potential Model Of Water, G.T. Gao, Xiao Cheng Zeng, Hideki Tanaka

Xiao Cheng Zeng Publications

We report computer simulation results of free energies of proton-disordered hexagonal ice and liquid water at atmospheric pressure with the 4-site transferable intermolecular potential model of water. A new reference system is used to calculate the free energy of the ice phase. The melting point of proton-disordered hexagonal ice at atmospheric pressure is found to be T_m=238 (±7) K. This result is consistent with a previous estimation, 230K< T_mK, from molecular dynamic simulation of the surface melting of the proton-disordered hexagonal ice [G.-J. Kroes, Surf. Sci. 275, 365 (1992)].

An Addictive Cycle Of Chemical Dependence: Pesticides And The Link To Breast Cancer, Misty Sanford

Whittier Scholars Program

This year, an estimated 40,800 women in the United states will die of breast cancer and another 182,800 will be diagnosed with the disease. Breast cancer is the second leading cause of death among women, exceeded only by lung cancer. As the result of earlier detection and improved treatment, death rates among young women have declined since 1992. Yet, at the same time, the incidence of breast cancer in American women has increased by a startling forty-four percent. The most pressing question is: what is causing this increase? Established risk factors include a family history of breast cancer , early …

Phage Therapy : An Alternative To Antibiotics, Maria A. Appeaning

Electronic Dissertations and Theses

Bacteria resistant to most or all available antibiotics are causing increasingly serious problems and raising widespread fears of returning to a pre-antibiotic era of untreatable infections and epidemics. Despite intensive work by drug companies, no new classes of antibiotics have been found in the last 30 years . There are hopes that the newfound ability to sequence entire microbial genomes and to determine the molecular bases of pathogenicity will open new avenues for treating infectious disease, but other approaches are also being sought with increasing fervor. One result is a renewed interest in the possibilities of bacteriophage (phage) therapy - …

Quantitative Measurement Of Guest–Host Interactions In Supramolecular Systems: A Comparative Brillouin Scattering Study Of The Dianin’S Compound Clathrand And Two Of Its Isostructural Clathrates, C.A. Sandstedt, D. Michalski, Craig J. Eckhardt

Craig J. Eckhardt Publications

Single, isomorphous crystals of the guest-free clathrand of Dianin’s compound and two of its clathrates containing two ethanols and a heptanol, respectively, have been studied by Brillouin scattering to obtain their complete elastic constant tensors. The values found for individual elastic constants are related to microscopic interactions of the guests and host cage using the clathrand as the reference. Direct correlation of the interference of the guest heptanol molecule with the hexamer hydrogen-bonded network of the host cage to reduced stiffness of this clathrate is demonstrated. In contrast, the ethanol-containing clathrate is demonstrated to have negligible interaction of the guests …

Rotational Structure Of Extremely Floppy Van Der Waals Complexes: Adiabatic Separation Of Angular And Radial Motion, P. Daniel Ward

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

The adiabatic or Born-Oppenheimer approximation is often used in molecular calculations to simplify the solution to the Schrödinger equation. The basis of the approximation is the large difference in the relative motions of the nuclei and electrons in the molecule—the electrons are able to respond almost instantly to the movements of the nuclei. Thus, the nuclei may be regarded as being fixed in a certain position and the Schrödinger equation can then be solved using the potential obtained by solving the electronic problem at fixed nuclear configuration.

A similar argument can be used to decouple the angular and radial motions …

Studies On The Roles Of Atp In Nitrogenase Catalysis, Wei Wu

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

Nitrogenase is the enzyme that catalyzes the reduction of nitrogen to ammonia in a reaction requiring MgATP hydrolysis. Two component proteins of nitrogenase are the iron protein (Fe protein) and the molybdenum-iron protein (MoFe protein).

Nitrogenase contains two nucleotide binding sites. During catalysis, the Fe protein binds two MgATP first. The conformational changes induced upon MgATP binding allow the Fe protein to associate with the MoFe protein. After the formation of the Fe protein-MoFe protein complex, a single electron is transferred from the Fe protein to the MoFe protein, an event that is coupled to MgATP hydrolysis in the Fe …

Ac Susceptibility Of Sr3CuptXIr1-XO6: A Magnetic System With Competing Interactions And Dimensionality, S H. Irons, T D. Sangrey, K M. Beauchamp, M D. Smith, Hans Conrad Zur Loye

Faculty Publications

Sr₃CuPt_xIr_1-xO₆ has been cited as an example of a one-dimensional quantum spin chain with competing ferromagnetic and antiferromagnetic interactions. We have measured the ac susceptibility of Sr₃CuPt_xIr_1-xO₆ with x=0, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, and 0.7, in magnetic fields of 0–60 kOe, and at temperatures down to 0.275 K. Our data show that the x=endpoint Sr₃CuIrO₆, exhibits long-range ferromagnetic order at T=20.1 K, contrary to results from dc susceptibility studies which indicated that it remained a one-dimensional ferromagnet to below 4 …

Atmospheric Organochlorine Pesticides In The Western Canadian Arctic: Evidence Of Transpacific Transport, R. Bailey, L. A. Barrie, C. J. Halsall, P. Fellin, D. C. G. Muir

Department of Chemistry and Biochemistry Faculty Scholarship and Creative Works

Concentrations of hexachlorocyclohexanes (HCHs), chlordane, and dichlorodiphenyltrichloroethane (DDT) were measured in ambient air samples on a weekly basis between December 1992 and January 1995 at Tagish Yukon, Canada. In winter, unusually high air concentrations of HCHs, DDT, and chlordanes at Tagish were predominantly influenced by transpacific long-range atmospheric transport from eastern Asia that generally occurred within 5 days. HCH and heptachlor epoxide concentrations were correlated with the time that air spent over eastern Asia prior to arrival at Tagish. Chlordane and DDT, which also increase with transpacific transport, do not show a correlation with the time the upwind airshed included …

A Magnetic And Crystallographic Study Of (Sm/Gd)₂(Fe/Si)₁₇CZ Solid Solutions, Peter C. Ezekwenna, G. K. Marasinghe, J. H. Nam, William Joseph James, William B. Yelon, M. Ellouze, Ph. I'Héritier

Chemistry Faculty Research & Creative Works

The crystallographic and magnetic properties of Sm_yGd_2-yFe_17-xSi_x (0 ≤ x ≤ 3 and y = 1 and 1.5) solid solutions and their interstitial carbides have been investigated using x-ray diffraction and magnetic measurements. The Sm_yGd_2-yFe_17-xSi_x samples crystallized in the rhombohedral Th₂Zn₁₇ structure with less than 5 mol % of impurities. The unit cells of the mixed rare-earth (R) samples are smaller than those of Sm₂Fe₁₇ and Gd₂Fe₁₇. The carbided samples contain up to a total of …

The Atomic And Magnetic Structure Of Ndmn(₆₋ₓ)Feₓge₆ Solid Solutions, J. Han, G. K. Marasinghe, William Joseph James, Muguo Chen, William B. Yelon, I. Dubenko, Naushad Ali

Chemistry Faculty Research & Creative Works

The magnetic and crystallographic properties of induction-melted NdMn_(6-x)Fe_xGe₆ intermetallics (x = 0, 1.0, and 1.5) in the temperature range of 30-475 K have been studied by x-ray and neutron diffraction techniques and SQUID measurements. All of the samples crystallized in the YCo₆Ge₆-type structure (P6/mmm). A small amount ( < 5 mol%) of Nd(MnFe)₂Ge₂ is present as an impurity. As expected, iron replaces manganese at the 3g site. The unit cell volume decreases slightly with increasing iron content at an average rate of 1.3% per substituted atom. Lattice parameters a and c contract at …

Fundamental Capillary Electrophoresis: An Evaluation Of Electrokinetic Sampling, Cindy Ann Mleziva Blake

Seton Hall University Dissertations and Theses (ETDs)

Capillary electrophoresis has become a powerful separation technique in fields of biochemical separations, inorganic ions, and chiral separations. The technique has experienced exponential growth since the historic publication of Zone Electrophoresis in Open-Tubular Glass Capillaries by Lukacs and Jorgenson in 1981. However, the use of capillary electrophoresis as a primary research analysis tool still remains to be seen in many pharmaceutical laboratories. One of the main reasons for this is that it remains difficult to validate CE methods using the criteria of quantitation and accuracy posed by the current government regulating agencies, as developed for high performance liquid chromatography and …

Visual Test Using Color Frequency Doubling, Scott Whittenburg

Chemistry Faculty Publications

A novel psychophysical visual test is proposed for testing a person for glaucoma, and based on the discovery that a frequency doubling phenomenon is produced by isoluminent color visual stimuli. More specifically, it is proposed to construct a visual stimulus for which alternating colors in a grating pattern is the only basis for producing the frequency doubling phenomenon. That is, the colors are of the same luminance or intensity level, i.e., isoluminent, but each grating or pattern alternates from one color to another. Preferably, the colors are complementary color pairs, such as blue and yellow.

Synthesis Of Fluroxypyr For The Use On Broad Leaf Plants, Shena Ruane

Masters

Fluroxypyr, 1-methylheptyl (4-amino-3,5-dichloro-6-fluoro-2-pyridinyloxy) acetate is used for the control of annual broad leaf weeds in cereals and perennial rye grass. The objective of this work was to develop an economically viable process for the bench synthesis of an organic herbicide fluroxypyr and to scale up the reaction to two litres. This was carried out according to a technical bulletin received from Agriguard Ltd. In addition an investigation into the synthesis and characterisation of impurities formed and reported to be formed, in the reaction process was carried out. The process developed began with pentachloropyridine which on reaction with potassium fluoride in …

Retention Of Ionizable Compounds In Hplc, Rosario Lobrutto

Seton Hall University Dissertations and Theses (ETDs)

No abstract provided.

Phorboxazole Synthetic Studies: The C3–C15 Bis-Oxane Segment, Patrick Bernard Greer, William A. Donaldson

Chemistry Faculty Research and Publications

The enantioselective synthesis of the C3–C15 bis-oxane segment of the phorboxazoles has been accomplished from 3-t-butyldiphenylsilyloxypropanal in 9 steps (>90% ee).

Charge-Transfer Bonding In Metal–Arene Coordination, S. M. Hubig, Sergey V. Lindeman, Jay K. Kochi

Chemistry Faculty Research and Publications

X-ray crystallographic structures of donor–acceptor complexes of aromatic hydrocarbons with transition metals are re-examined with the focus on the arene ligands. Thus, significant structural and electronic changes are revealed in the arene moiety due to coordination to the metal center including: (i) expansion of the aromatic six-carbon ring; (ii) endocyclic π-bond localization; (iii) distortion of the planarity (folding) of the arene ring; and (iv) shortening of the metal-arene bond distances. All structural features are characteristic of metal–arene (π- or σ-) complexes that exhibit various degrees of (metal-to-ligand) charge transfer. The concept of charge-transfer bonding not only explains the structural details …

A Study Of The Solvolysis Reactions Of Tetrahydrofurfuryl Tosylate, Rebecca Centko '00

Honors Projects

The solvolysis of epoxycarbinyl substrates 1 has been the subject of several mechanistic studies. In spite of these investigations, it has not been established whether these solvolysis reactions proceed with anchimeric assistance from the epoxide oxygen and involve an oxabicyclobutonium ion intermediate or whether unassisted solvolysis occurs. Conflicting data in the literature suggest that the ability of the epoxide oxygen to provide anchimeric assistance is dependant upon structural and electronic features of the epoxycarbinyl substrate in question. The aim of this project was to study the nucleophilic substitution reactions of tetrahydrofurfuryl and tetrahydropyranyl sulfonates 2a and 2b as well as …

Role Of The Carbohydrate Moieties In Chiral Recognition On Teicoplanin- Based Lc Stationary Phases, Alain Berthod, Xianghong Chen, John P. Kullman, Daniel W. Armstrong, Francesco Gasparrini, Ilaria D'Acquarica, Claudio Villani, Angelo Carotti

Chemistry Faculty Research & Creative Works

For this study, we used the macrocyclic antibiotic teicoplanin, a molecule consisting of an aglycone peptide 'basket' with three attached carbohydrate (sugar) moieties. The sugar units were removed and the aglycone was purified. Two chiral stationary phases (CSPs) were prepared in a similar way, one with the native teicoplanin molecule and the other with the aglycone. Twenty-six compounds were evaluated on the two CSPs with seven RPLC mobile phases and two polar organic mobile phases. The compounds were 13 amino acids or structurally related compounds (including DOPA, folinic acid, etc.) and 13 other compounds (such as carnitine, bromacil, etc.). The …

Carbon Nanotube Atomic Force Microscopy Tips: Direct Growth By Chemical Vapor Deposition And Application To High-Resolution Imaging, Chin Li Cheung, Jason H. Hafner, Charles M. Lieber

Barry Chin Li Cheung Publications

Carbon nanotubes are potentially ideal atomic force microscopy probes because they can have diameters as small as one nanometer, have robust mechanical properties, and can be specifically functionalized with chemical and biological probes at the tip ends. This communication describes methods for the direct growth of carbon nanotube tips by chemical vapor deposition (CVD) using ethylene and iron catalysts deposited on commercial silicon-cantilever-tip assemblies. Scanning electron microscopy and transmission electron microscopy measurements demonstrate that multiwalled nanotube and single-walled nanotube tips can be grown by predictable variations in the CVD growth conditions. Force-displacement measurements made on the tips show that they …

Binding Of Pb And Zn To Aluminium Oxide And Proton Stoichiometry, Wing H. Leung, A. Kimaro

Virginia Journal of Science

The interaction of Pb and Zn with Al₂O₃ in aqueous solution was studied as a function of pH and metal ion concentration. Results indicated the complexation of metal ions by oxide surfaces is strongly pH dependent; the extent of adsorption is a function of pH with an abrupt change within approximately 2 pH units. The adsorption of Pb and Zn on aluminium oxide can be interpreted in terms of a surface complexation formed by association with one surface AlOH group, thus releasing one bound hydrogen ion. -AlOH + M²⁺ = -AlOM⁺ + H⁺ . …

Fertilisers For Wine Grapes : An Information Package To Promote Efficient Fertiliser Practices, B. H. Goldspink, Neil Lantzke, Bob Paulin, Diana Louise Fisher, Colin Gordon, N. Cross, J M. Campbell-Clause

Bulletins 4000 -

No abstract provided.

Jeffress Research Grant Awards

Virginia Journal of Science

Announcements of the Jeffress Research Grants that have been awarded in 1999.

Thermolysis Of Semicarbazones To The Corresponding Azines Through Reactive N-Substituted Isocyanate Intermediates, Shailesh N. Shah, N.K. Chudgar

Faculty Publications

Thermolysis of semicarbazones (I) to azines (II) occurs through reactive N-substituted isocyanate intermediates (Ia) which can be converted in situ to carbamates and N-substituted ureas.

Photodegradation Of Pcbs In Natural Waters, Adriana R. Nicolaescu

Masters Theses

PCBs are widely distributed in the environment and they are biologically refractory and toxic compounds. There is great interest in understanding their fate in the environment, and also for finding safe and effective degradation methods.

This study is concerned with the photodegradation of four PCB congeners: PCB 5, PCB 18, PCB 77, PCB 128 in natural waters. Natural waters contain humic substances which can greatly influence the environmental fate of the PCBs. The different degradation of the four congeners was studied in standardized systems and in humic acid or nitrate solutions, under environmental conditions. DMDE and Methoxyclor (whose environmental half-lifetimes …

A Systematic Study Of The Correlations Between Meteorite Impacts And Soot Formation, Susanna L. Widicus '00

Honors Projects

A massive extinction of more than 50 percent of existing life forms on Earth occurred 65 million years (Ma) ago. This event is marked in the geological record by the Cretaceous-Tertiary (KT) boundary and corresponds to the Chicxulub meteorite impact in the Yucatan Peninsula. Since 1985, large quantities ofreduced elemental carbon in the form of characteristic spheroidal clusters of soot have been found in twelve KT boundary sites from across the globe. Because ofthe wide geographic distribution ofthese sites, the data was interpreted to indicate that deposition ofsoot was a global phenomenon. The source of this global soot layer is …

Solid-State Deuterium Nuclear Magnetic Resonance Of The Methyl Dynamics Of Poly(Alpha-Methylstyrene) And Polymethylphenylsilane, Robert D. O'Connor, Eric J. Ginsburg, Frank D. Blum

Chemistry Faculty Research & Creative Works

The methyl-d3 dynamics of two relatively similar polymers, poly(alpha-methylstyrene) (PAMS-d3) and polymethylphenylsilane (PMPS-d3), are investigated via deuterium NMR relaxation experiments. Our analysis of the relaxation data uses the entire solid-echo spectra to maximize the precision of the experiments with regard to the information available on the methyl dynamics. The analysis is novel in that it does not use M[infinity] or M0 to fit the relaxation data. Additionally, the three-site symmetric jump model is shown to not have an observable azimuthal angular dependence for T1 relaxation. The methyl dynamics are quantified with taum, sigma, and f which are the log-average correlation …

The Noesy Jigsaw: Automated Protein Secondary Structure And Main-Chain Assignment From Sparse, Unassigned Nmr Data, Chris Bailey-Kellogg, Alik Widge, John J. Kelley Iii, Marcelo J. Berardi, John H. Bushweller, Bruce Randall Donald

Dartmouth Scholarship

High-throughput, data-directed computational protocols for Structural Genomics (or Proteomics) are required in order to evaluate the protein products of genes for structure and function at rates comparable to current gene-sequencing technology. This paper presents the Jigsaw algorithm, a novel high-throughput, automated approach to protein structure characterization with nuclear magnetic resonance (NMR). Jigsaw consists of two main components: (1) graph-based secondary structure pattern identification in unassigned heteronuclear NMR data, and (2) assignment of spectral peaks by probabilistic alignment of identified secondary structure elements against the primary sequence. Jigsaw's deferment of assignment until after secondary structure identification differs greatly from traditional approaches, …