Physical Sciences and Mathematics Commons^™

Dibenzimidazolium Salts And Their Interactions With 1,5-Dinaphtho-38-Crown-10, David B. Bernthal

Masters Theses

The use of imidazolium salts in mechanically interlocked molecules, like pseudorotaxanes, is of interest because they can be functionalized with side arms that allow for coordination chemistry. It has been previously shown that tetraakylbenzobisimidazolium salts successfully thread through crown ethers, such as 15DN38C10 or BPP34C10, to form pseudorotaxanes. As an extension of the results that were gathered about this novel template, it was our goal to explore the degree to which larger imidazolium salts interact with such crown ethers. This research focused on the interactions between 15DN38C10 and dibenzimidazolium cations that were tetra-substituted with methyl groups, butyl groups, and benzyl …

Internal Motion In Weakly Bound Halomethane Complexes, Amelia J. Thomas

Masters Theses

No abstract provided.

Utilization Of Phosphorus Ylides Towards The Synthesis Of Extended Cinnamaldehydes And Stellettins, John M. Saathoff

Masters Theses

No abstract provided.

Ruthenium Polypyridyl Complexes That Utilize Azo-Dyes To Enhance Absorption Of Visible Photons, Akram Hazeen

Masters Theses

No abstract provided.

Sensitivity Of Noncovalent Bonds To Intermolecular Separation: Hydrogen, Halogen, Chalcogen, And Pnicogen Bonds, Steve Scheiner

Chemistry and Biochemistry Faculty Publications

It is well known that noncovalent bonds are weakened when stretched from their equilibrium intermolecular separation. Quantum chemical calculations are used to examine and compare the sensitivity to stretches of hydrogen, halogen, chalcogen, and pnicogen bonds. NH3 was taken as the universal electron donor, paired with HOH and FH in H-bonds, as well as with FPH2, FSH, and FCl. Even though the binding energies span a wide range, stretching the intermolecular separation by 1 Å cuts this quantity by the same proportion, roughly in half, for each system. Taking the sum of van der Waals radii as an arbitrary cutoff, …

Contributions Of Various Noncovalent Bonds To The Interaction Between An Amide And S-Containing Molecules, U. Adhikari, Steve Scheiner

Chemistry and Biochemistry Faculty Publications

N-Methylacetamide, a model of the peptide unit in proteins, is allowed to interact with CH3SH, CH3SCH3, and CH3SSCH3 as models of S-containing amino acid residues. All of the minima are located on the ab initio potential energy surface of each heterodimer. Analysis of the forces holding each complex together identifies a variety of different attractive forces, including SH⋅⋅⋅O, NH⋅⋅⋅S, CH⋅⋅⋅O, CH⋅⋅⋅S, SH⋅⋅⋅π, and CH⋅⋅⋅π H-bonds. Other contributing noncovalent bonds involve charge transfer into σ* and π* antibonds. Whereas some of the H-bonds are strong enough that they represent the sole attractive force in several dimers, albeit not usually in the …

Detailed Comparison Of The Pnicogen Bond With Chalcogen, Halogen And Hydrogen Bonds, Steve Scheiner

Chemistry and Biochemistry Faculty Publications

The characteristics of the pnicogen bond are explored using a variety of quantum chemical techniques. In particular, this interaction is compared with its halogen and chalcogen bond cousins, as well as with the more common H-bond. In general, these bonds are all of comparable strength. More specifically, they are strengthened by the presence of an electronegative substituent on the electron-acceptor atom, and each gains strength as one moves down the appropriate column of the periodic table, for example, from N to P to As. These noncovalent bonds owe their stability to a mixture in nearly equal parts of electrostatic attraction …

Effects Of Carbon Chain Substituent On The P∙∙∙N Noncovalent Bond, U. Adhikari, Steve Scheiner

Chemistry and Biochemistry Faculty Publications

The effects of carbon chains placed on the electron-accepting P atom of a P⋯N bond are examined via ab initio calculations. Saturated alkyl groups have a mild weakening effect, regardless of chain length. In contrast, incorporation of double bonds into the chain strengthens the interaction, Ctriple bond; length of mdashC triple bonds even more so. These effects are only slightly enhanced by additional conjugated double bonds or an aromatic ring. Placing F atoms onto the carbon chains strengthens the P⋯N bond, but only by a small amount, which wanes as the F atom is displaced further from the P along …

First Steps In Growth Of A Polypeptide Toward Β-Sheet Structure, U. Adhikari, Steve Scheiner

Chemistry and Biochemistry Faculty Publications

The full conformational energy surface is examined for a molecule in which a dipeptide is attached to the same spacer group as another peptide chain, so as to model the seminal steps of β-sheet formation. This surface is compared with the geometrical preferences of the isolated dipeptide to extract the perturbations induced by interactions with the second peptide strand. These interpeptide interactions remove any tendency of the dipeptide to form a C5 ring structure, one of its two normally stable geometries. A C7 structure, the preferred conformation of the isolated dipeptide, remains as the global minimum in the full molecule. …

Extrapolation To The Complete Basis Set Limit For Binding Energies Of Noncovalent Interactions, Steve Scheiner

Chemistry and Biochemistry Faculty Publications

A means of extrapolating from double and triple-valence basis sets to a complete basis set is examined in the context of the pnicogen bonds in the BH2P⋯NH3 complexes, with B = CH3, H, NH2, CF3, OH, Cl, F, and NO2. Binding energies converge smoothly, and the trends for the various substituents B are unaffected by the basis set size, extrapolation, or level of inclusion of electron correlation, including MP2 and CCSD(T). The approach appears to be successful also for H-bonded systems, in particular the water dimer. In the event that full extrapolation within the context of CCSD(T) is not feasible, …

Evaluation Of Dft Methods To Study Reactions Of Benzene With Oh Radical, Steve Scheiner

Chemistry and Biochemistry Faculty Publications

Several density functional theory” (DFT) methods are applied to two different reaction channels involving OH• + C6H6, and the results compared with high-level ab initio calculations. The OH• adds directly to one C atom in the first channel, first forming an encounter complex with the OH• poised above the aromatic plane. B3LYP, BH&HLYP, and MPW1K compute an accurate estimate of the overall exothermicity, whereas M05-2X, PBE0, and PBEPBE overestimate this quantity to some degree. With the exceptions of PBEPBE and PBE0, the other methods produce an acceptable barrier to addition. All approaches except BH&HLYP correctly predict an exothermic H• abstraction, …

Metal Catalyzed Activation Of E-H Bonds, E = Si, Ge, Sn, Renzo Nelson Arias Ugarte

Open Access Theses & Dissertations

The present project covers the use of complexes of the type: (C5H5)M(CO)nLMe, (M = Fe, n = 1; L = CO, Ph3P; M = Mo, n = 2; L = CO, Ph3P); M(CO)6, (M = Cr, Mo, W) and M(CO)5NMe3 as catalysts for the activation of E-H bonds (E = Si, Ge and Sn). The work is divided in three sections; the first two involves dehydrogenation and the last one amide reduction.

An Investigation Of Guiding Of Positrons Through Insulating Capillaries, Robert D. Dubois, K. Tökési

Physics Faculty Research & Creative Works

Guiding of diffuse low-intensity positron and electron beams through macroscopic tapered insulating capillaries was investigated. Transmitted positrons and electrons were observed. However, further investigations are necessary to clarify whether the transmitted particles are a true indication of guiding or simply due to a range of diffuse angles of the incoming beams.

Triply Differential Measurements For Single Ionization Of Molecular Nitrogen By 250 Ev Positron Impact, Robert D. Dubois, O. G. De Lucio

Physics Faculty Research & Creative Works

Triply differential cross sections are presented for 250 eV positron impact single ionization of molecular nitrogen. Data are presented for binary and recoil interactions resulting from projectiles being scattered between 0 and 5 degrees and energy losses up to approximately 50 eV.

X-Ray Emission Cross Sections Following Charge Exchange Collisions On Neutral Targets: The Role Of Multiple Electron Capture, Sebastian Otranto, Ronald E. Olson

Physics Faculty Research & Creative Works

Line emission and charge exchange cross sections obtained from a three-active electrons CTMC code allow us to determine the role of multiple electron capture for charge exchange collisions on neutral argon and neon. the present results can be compared to recent experimental data from EBIT groups operating at Liver-more, NIST and Berlin.

Reaction Dynamics In Double Ionization Of Helium By Electron Impact, Michael Schulz, M. F. Ciappina, T. Kirchner

Physics Faculty Research & Creative Works

Multiple differential cross sections for double ionization of helium by electron impact were calculated within various models. using a Monte Carlo Event Generator technique, additional physics, not included in the primary calculations, are modeled and cross sections are convoluted with the experimental resolution.

Electron Loss By Fast Heavy Ions: Target Scaling Dependence, Robert D. Dubois, A. C.F. Santos, G. M. Sigaud, E. C. Montenegro

Physics Faculty Research & Creative Works

Using data taken from the literature, the scaling of electron loss cross sections as a function of target Z was investigated. It was found that for energies /u, a wide range of systems demonstrated very similar target Z dependences where, for heavier targets, the slope increased very slowly with impact energy. at higher energies, this increase was much faster. a "universal" formula capable of fitting these dependences is being developed.

Scattering Angle Dependence Of Double Differential Cross Sections For Dissociative Ionization Of H2 By Proton Impact, Michael Schulz, K. Egodapitiya, S. Sharma, A. C. Laforge

Physics Faculty Research & Creative Works

We have measured double differential cross sections for dissociative ionization of H₂ by 75 keV proton impact for fixed energy losses as a function scattering angle. the data exhibit an oscillating pattern with a frequency about twice as large as found earlier for non-dissociative ionization. © Published under licence by IOP Publishing Ltd.

Electron Transfer And Ionization In Collisions Of He-Like Ions With Na(3s) And Na(3p), I. Blank, S. Otrantcr, C. Meinema, Ronald E. Olson, R. Hoekstra

Physics Faculty Research & Creative Works

Single electron transfer and ionization in collisions of He-like ions (N⁵⁺, O⁶⁺, Ne⁸⁺) and Na has been investigated both experimentally and theoretically at energies around the matching velocity of the valence electron (2 to 10 keV/amu). State selective cross sections and scattering angle distributions were obtained using recoil-ion momentum spectroscopy in combination with a magneto-optically cooled Na atom target. a strong dependence of the relative cross sections on the collision energy is observed. the results are compared with Classical-Trajectory Monte Carlo (CTMC) calculations and show an overall very good agreement.

Systematic Analysis Of Four-Particle Dalitz Plots For Double Ionization, Michael Schulz, D. Fischer, K. Schneider, R. Moshammer, J. Ullrich, M. F. Ciappina, T. Kirchner

Physics Faculty Research & Creative Works

Four particle Dalitz plots for double ionization of helium by ion impact were analyzed.

Review: The Dirichlet Space: A Survey, Stephan Ramon Garcia

Pomona Faculty Publications and Research

No abstract provided.

In Defense Of Frivolous Questions, Gizem Karaali

Pomona Faculty Publications and Research

Is there any reason for today's academic institutions to encourage the pursuit of answers to seemingly frivolous questions? The opinionated business leader who does not give a darn about your typical liberal arts classes "because they do not prepare today’s students for tomorrow's work force" might snicker knowingly here: Have you seen some of the ridiculous titles of the courses offered by the English / literature / history / (fill in the blank) studies department in the University of So-And-So? Why should any student take "Basketweaving in the Andes during the Peloponnesian Wars"? Just what would anyone gain from …

Humanistic Mathematics: An Oxymoron?, Gizem Karaali

Pomona Faculty Publications and Research

Mathematics faculty are trained as mathematicians, first and foremost. If we did not experience the soul-expanding possibilities of liberal education during our own undergraduate years, we may hesitate to bridge disciplinary divides when pursuing our core human need to inquire and understand. Although most mathematicians I know are amazing teachers, communicators, and mentors, many still teach the same material that their professors and their professors’ professors taught. This time-tested approach can be powerful, fascinating, and even quite entertaining. But it can also seem far removed from the world we inhabit. Yes, we teach “real world applications” of mathematical concepts. Yet …

Two Remarks About Nilpotent Operators Of Order Two, Stephan Ramon Garcia, Bob Lutz '13, D. Timotin

Pomona Faculty Publications and Research

We present two novel results about Hilbert space operators which are nilpotent of order two. First, we prove that such operators are indestructible complex symmetric operators, in the sense that tensoring them with any operator yields a complex symmetric operator. In fact, we prove that this property characterizes nilpotents of order two among all nonzero bounded operators. Second, we establish that every nilpotent of order two is unitarily equivalent to a truncated Toeplitz operator.

U.S. Oil Reserves And Peak Oil, Trang Luong

Undergraduate Journal of Mathematical Modeling: One + Two

We use calculus methods to estimate the quantity of U.S. oil reserves. We consider a model that consists of an exponential function with four unknown constants. We fit real oil production data to determine the unknown constants. With the constants determined we use the function to find the year in which the U.S. oil production reached its peak. We also estimate the amount of petroleum produced until the end of 2006, and the undiscovered oil reserves to be produced in the future.

The Elevation To Area Relationship Of Lake Behnke, Kaitlin Deutsch

Undergraduate Journal of Mathematical Modeling: One + Two

The objective of this project was to determine the area-to-depth relationship in Lake Behnke, which acts as the principal stormwater drainage basin for the University of South Florida campus in Tampa, Florida. Data previously collected in a stormwater management study by Jeffery Earhart illustrated a linear correlation between the lake's area and depth; however, that study was conducted in 1998, and this present work serves to double check that correlation. We analyzed a bathymetric map of Lake Behnke that displayed several contour lines indicating depth and approximated the area inside each closed curve with a contour integral. The resulting relationship …

Speleothem Laminae Counting And Growth Rate, Corey Wilson

Undergraduate Journal of Mathematical Modeling: One + Two

The goal of this project is to determine if there is a correlation between annual laminae in speleothems and Uranium dating. To do this, we counted laminae using high-resolution images and calculated a line of the best fit for the resulting data. We found that our data could supplement Uranium dating, but unless more data is obtained, laminae counting gives relatively imprecise age and growth rate estimates.

Simultaneous Electrochemical Determination Of Tryptamine And Barbituric Acid, Luxshani Thangarajah

Masters Theses

No abstract provided.

Electrochemical Characterization Of Thin-Film Perovskite-Type La1-Xsrxmno3 Electrodes Obtained By Pulsed Laser Deposition (Pld), Keerthi Chandra

Masters Theses

The implementation of fuel cells into commercial usage is prenominally dependent on the activity of cathode at which oxygen reduction reaction (ORR) takes place. Fuel cells currently use noble metals like platinum, palladium etc as cathode for the reduction reaction. These metals showed poor performance during changes in red ox environment. Perovskite oxides which were proven to be efficient as cathodes in solid oxide fuel cells operating at high temperature was studied to understand its ability to carry out ORR in alkaline fuel cells operating at room temperature.

La_1-XSr_xMnO₃ (LSMO), thin film perovskite oxide, a …

Exploring Phenyl Embrace Interactions In Trityloxy And Tritylamino Aromatic Compounds, Premnath Basa

Masters Theses

The area of supramolecular chemistry seeks to understand the organization of molecular structures and the interactions that hold such assemblies together by non-covalent interactions such as electrostatic, hydrogen bonding, π-π stacking interactions, and hydrophobic or solvatophobic effects. One such example that comes under supramolecular chemistry is the phenyl embrace interaction. These interactions occur due to the cooperative participation of at least three or more neighboring phenyl groups arranged as an interlocking propeller configuration to give complementary edge-to-face or offset face-to-face interactions. In order to understand the effect of functional groups on the tendencies of organic compounds to form phenyl embrace …