Physical Sciences and Mathematics Commons^™

Protein S-Thiolation And Dethiolation, James Thomas, Yuh-Cherng Chai, Che-Hun Jung

Yuh-Cherng Chai

No abstract provided.

Hexagons And Squares In A Passive Nonlinear Optical System, John Geddes, R.A. Indik, J.V. Moloney, Willie Firth

John B. Geddes

Pattern formation is analyzed and simulated in a nonlinear optical system involving all three space dimensions as well as time in an essential way. This system, counterpropagation in a Kerr medium, is shown to lose stability, for sufficient pump intensity, to a nonuniform spatial pattern. We observe hexagonal patterns in a self-focusing medium, and squares in a self-defocusing one, in good agreement with analysis based on symmetry and asymptotic expansions.

Apparent And True Feature Heights In Force Microscopy, Nancy Burnham

Nancy A. Burnham

In a force microscope, the stiffness of the cantilever beam convolutes with the tip‐sample interaction stiffness to influence the data in a systematic way. The analysis presented here relates the measured feature height to the true feature height in the variable force, constant force, and constant force gradient modes of operation. In this way, one can understand previously published data: the enhanced measured atomic corrugation observed in high resolution force microscopy images, its increase with load, and the improved resolution of lateral force images. The correct interaction stiffness can be obtained for use in surface force and mechanical properties studies. …

Hexameric Lithium Phenolate: Crystal Structures And Lithium-7 Quadrupole Coupling In Solid And Solution Phases., Lloyd Jackman, Deniz Cizmeciyan, Paul Willard, Michael Nichols

Michael A Nichols

No abstract provided.

Quantitative Determination Of Surface Excess By The Semiintegral Method, Susanne Dana, Mathew Jablonski, Mark Anderson

Mark R. Anderson

In 1988 Bowling and McCreery reported that the semiintegral of voltammetric data provided an excellent method for the qualitative diagnosis of weak adsortpion of material upon an electrode. This report was important to electroanalytical chemistry because of the difficulty often encountered when trying to identify the presence of weakly adsorbed material and because of the impact that weak adsorption has upon voltammetric response. Many electrochemical analyses are dependent upon the evaluation of voltammetric wave shape, particularly kinetic analyses. Unlike strong adsorption, the presence of weakly adsorbed material does not dramatically and obviously perturb the shape of the voltammetric response; consequently, …

Solid-State Structures Of N-Butyllithium-Tmeda, -Thf, And -Dme Complexes., Michael Nichols, Paul Williard

Michael A Nichols

No abstract provided.

Burnham, Colton, And Pollock Reply, Nancy Burnham, Rj Colton, Hm Pollock

Nancy A. Burnham

It is not necessary to obtain permission to reuse this article or its components as it is available under the terms of the Creative Commons Attribution 3.0 License. This license permits unrestricted use, distribution, and reproduction in any medium, provided attribution to the author (s) and the published article's title, journal citation, and DOI are maintained. Please note that some figures may have been included with permission from other third parties. It is your responsibility to obtain the proper permission from the rights holder

Synthesis And Structure Of A Product, Formed During Dna Nicking With A Cyclometallated Nuclease, Consisting Of An Adenine Bridging Two Palladium(Ii) Complexes., J. Suggs, Michael Du\Ube, Michael Nichols

Michael A Nichols

Journal of the Chemical Society, Chemical Communications

Application Of Square Wave Voltammetry For Electrochemical Detection In Gradient Elution Hplc, John Roush, Mark Anderson

Mark R. Anderson

The utility of square-wave voltammetry with a conventionally sized indicator electrode for use in the detection of gradient elution HPLC applications is demonstrated. A redesigned electrochemical detector cell, based upon a type of wall-jet design, provides more efficient potential control and allows the voltammetric detection. The minimum detectable quantity and linear dynamic range for the new detector design were found to be 13pg and 5 orders of magnitude, respectively, comparable to other electrochemical detectors. In the separation of a test mixture containing hydroquinone. bromohydroquinone, catechol, resorcinol, and phenylhydroquinone baseline resolution of all five components is obtained in 12 minutes using …

Physics Students' Understanding Of Relative Speed: A Phenomenographic Study, Eleanor Walsh, Gloria Dall'alba, John Bowden, Elaine Martin, Ference Marton, Geoff Masters, Paul Ramsden, Andrew Stephanou

Prof Geoff Masters AO

It is important that students of physics develop both quantitative and qualitative understanding of physical concepts and principles. Although accuracy and reliability in solving quantitative problems is necessary, a qualitative understanding is required in applying concepts and principles to new problems and in real-life situations. If students are not able to understand what underlies quantitative problem-solving procedures nor interpret the solution in physical terms, it is questionable whether they have developed an adequate understanding of physics. The research reported here is part of a larger phenomenographic study that is concerned with the assessment of physics students' understanding of some basic …

Interlacement Of The Even And Odd Spectra Of Real Symmetric Toeplitz Matrices, William F. Trench

William F. Trench

No abstract provided.

Asymptotic Behavior Of Solutions Of Poincar'e Difference Equations, William F. Trench

William F. Trench

No abstract provided.

Γ-Aminobutyric Acid, Catecholamine And Indoleamine Determinations From The Same Brain Region By High-Performance Liquid Chromatography With Electrochemical Detection., T. Champney, W. Hanneman, Michael Nichols

Michael A Nichols

A new procedure for the measurement of γ-aminobutyric acid, norepinephrine, dopamine, serotonin and 5-hydroxyindoleacetic acid from the same brain region was developed. In general, two separate high-performance liquid chromatographic runs were performed, one for the γ-aminobutyric acid determination and one for the determination of the monoamines. The electrochemical detection of γ-aminobutyric acid was determined by a new procedure that utilized a small aliquot of the brain sample prepared for monoamine measurement. This assay was linear and parallel between 6 and 200 ng per 20-μl injection with 5-aminovaleric acid utilized as an internal standard. Inter-assay variability averaged 5% throughout the assay …

Work-Function Anisotropies As An Origin Of Long-Range Surface Forces, Nancy Burnham, R Colton, H Pollock

Nancy A. Burnham

Unusual effects noticed in previous force microscopy data are explained by a model based on work-function anisotropies and their associated patch charges. Measurable forces between macroscopic bodies can be due to the interaction of patch charges, with important consequences in the fields of surface forces, contact mechanics, adhesion, Schottky barriers, and the surface properties of insulators.

The Elastic Moduli Of A Sheet Containing Circular Holes, Anthony Day, K. Snyder, E. Garboczi, M. Thorpe

Anthony Roy Day

We apply computer simulation techniques to obtain the clastic moduli of a matrix containing circular holes. As the area fraction of holes increases, the Young's modulus of the composite decreases from E0 until it eventually vanishes at the percolation threshold. We study three distinct geometries: (a) periodically centered circular holes on a honeycomb lattice, (b) periodically centered circular holes on a triangular lattice, and (c) randomly centered circular holes. All three cases have the same dilute limit that can be calculated exactly. By examining the narrow necks between adjacent circles, we have calculated the critical behavior for the regular cases …

Quark-Antiquark Condensates In Strong Magnetic Fields, Alec Schramm, Berndt Muller, Stefan Schramm

Alec J Schramm

We discuss the effect of large external magnetic fields on the QCD vacuum structure. We show that the deformed vacuum leads to substantial changes in the hadronic spectrum.

W Boson Condensation In P-P Collisions?, Alec Schramm, Stefan Schramm, Berndt Muller

Alec J Schramm

We address the question of whether W+/- boson condensation can occur in high-energy collisions.

Displacement, Velocity, And Frames Of Reference: Phenomenographic Studies Of Students’ Understanding And Some Implications For Teaching And Assessment, John Bowden, Gloria Dall'alba, Elaine Martin, D Laurillard, Ference Marton, Geoff Masters, Paul Ramsden, Andrew Stephanou, E Walsh

Prof Geoff Masters AO

Student understanding of fundamental concepts in kinematics has been explored using the phenomenographic research method. University and high schoolphysics students were interviewed and their understandings of displacement, velocity, and frames of reference have been analyzed in particular problem contexts. Descriptions of the different ways students understand the concepts have been developed and relations between the different levels of understanding have been identified. The data highlight the contextual nature of learning and the need for teachers to focus on the nature of student understanding in specific contexts using questions that require qualitative explanation by students. In particular, it is demonstrated that …

A High Yield Microscale Enzymatic Synthesis And Purification Of 14c‐Labeled Nicotinamide Adenine Dinucleotide Phosphate (Nadp+), Andre Ronneberg, Gordon Metz, Richard Weld, Peter Roffey, Chris Craney

Chris L. Craney

Uniformly labeled (U) 14C nicotinamide adenine dinucleotide phosphate (NADP+) was synthesized by phosphorylating [U-14C]nicotinamide adenine dinucleotide (NAD+) in the presence of immobilized NAD+ kinase. The 15 μCi (600 μL) synthesis consistently achieved yields between 80% and radiochemical purities greater than 95%. The [U-14C]NADP+ was purified by high performance anion-exchange chromatography using a gradient elution of ammonium bicarbonate. This procedure may be applicable to the synthesis of other charged, UV-absorbing products of enzyme-catalyzed reactions.

The Logic Of Unbalanced Subobjects In A Category With Two Closed Structures, Lawrence Stout

Lawrence N. Stout

No abstract provided.

Asymptotic Behavior Of Solutions Of A Linear Second Order Difference Equation, William F. Trench

William F. Trench

No abstract provided.

Mild Integrability Conditions For Global Solutions Of An Elliptic Equation, William F. Trench

William F. Trench

No abstract provided.

Structural Characterization Of Mixed Alkali Metal Bis(Trimethylsilyl)Amide Bases., Paul Williard, Michael Nichols

Michael A Nichols

No abstract provided.

Linear Algebra By Analogy, Scott H. Hochwald

Scott H. Hochwald

No abstract provided.

The Influence Of Cation Size Upon The Infrared Spectrum Of Carbon Monoxide Adsorbed On Platinum Electrodes, Mark Anderson, Jimin Huang

Mark R. Anderson

The infrared spectrum of carbon monoxide adsorbed on polycrystalline platinum electrodes in the presence of acetonitrile solutions is examined. Acetonitrile solutions provide a wide double layer region (approximately 4 V) in which to investigate the observed potential dependence of the infrared peak position. The wider window allows for better comparisons of experimental data with theoretical predictions than those which are available from measurements conducted in aqueous solutions. It is found that (i) near-monolayer surface coverage can be obtained from solutions saturated with CO, (ii) the coverage stays constant over roughly the entire double layer region, (iii) the CO adsorbs to …

A Collaborative Summer Research Program For Community College Students, Chris Craney, Franklin Dehaan

Chris L. Craney

While the benefits of undergraduate research are well established, little attention has been paid toward involving community college students in such research. This paper describes a five-year-experience with a summer research program that includes Los Angeles area community college students working side-by-side with Occidental College students and faculty.

Chelation Of 2-Substituted 1-Lithoxides: Structural And Energetic Factors Of Relevance To Synthetic Organic Chemistry., Michael Nichols, Andrew Mcphail, Edward Arnett

Michael A Nichols

No abstract provided.

Interpretation Issues In Force Microscopy, Nancy Burnham, Richard Colton, Hubert Pollock

Nancy A. Burnham

In this paper, we will discuss force microscopy (FM) and its potential for determining mechanical properties of thin films. We will introduce the basic principles of FM, and demonstrate how FM can be used to determine materials properties as well as image surface topography, both with nanonewton or sub‐nanonewton force resolution and sub‐nanometer position resolution. As FM is still a new field, not all of the questions concerning interpretation have been fully answered. We will elucidate four current issues that must be resolved before the full potential of FM can be realized. They are: (1) the role of water vapor …

Thermochronology And Thermobarometry In Lithotectonic Zones In Eastern New England, Andrea Koziol, Robert Wintsch

Andrea M. Koziol

Sniftirs Study Of The Behavior Of The Spectrum Of Carbon Monoxide Adsorbed On A Platinum Electrode In Alcoholic Solvents, Andrea Russell, Daniel Blackwood, Mark Anderson, Stanley Pons

Mark R. Anderson

The vibrational spectrum of carbon monoxide as a function of coverage in various alcoholic solvents was investigated using the SNIFTIRS technique. At low coverage the potential dependence of the band position was found to be linearly dependent on the inverse of the bulk dielectric constant of the solvent. An electrostatic model was developed to represent the interaction between adjacent adsorbate molecules. This model provides evidence in support of an island formation mechanism.