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Chemistry

Stephen F. Austin State University

2013

Articles 1 - 13 of 13

Full-Text Articles in Physical Sciences and Mathematics

Electron Transfer By Excited Benzoquinone Anions: Slow Rates For Two-Electron Transitions, Matibur Zamadar, Andrew R. Cook, Anna Lewandowska-Andralojc, Richard Holroyd, Yan Jiang, Jin Bikalis, John R. Miller Jul 2013

Electron Transfer By Excited Benzoquinone Anions: Slow Rates For Two-Electron Transitions, Matibur Zamadar, Andrew R. Cook, Anna Lewandowska-Andralojc, Richard Holroyd, Yan Jiang, Jin Bikalis, John R. Miller

Faculty Publications

Electron transfer (ET) rate constants from the lowest excited state of the radical anion of benzoquinone, BQ−•*, were measured in THF solution. Rate constants for bimolecular electron transfer reactions typically reach the diffusion-controlled limit when the free-energy change, ΔG°, reaches −0.3 eV. The rate constants for ET from BQ−•* are one-to-two decades smaller at this energy and do not reach the diffusion-controlled limit until −ΔG° is 1.5−2.0 eV. The rates are so slow probably because a second electron must also undergo a transition to make use of the energy of the excited state. Similarly, ET, from solvated electrons to neutral …

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A Computational Study Of The Vibrational Spectra Of Mono-Nitrated Fluoranthenes, Jorge Ojeda Apr 2013

A Computational Study Of The Vibrational Spectra Of Mono-Nitrated Fluoranthenes, Jorge Ojeda

Undergraduate Research Conference

No abstract provided.

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A Determination Of The Aspartame Content In Select Diet Beverages, Jorge Ojeda Apr 2013

A Determination Of The Aspartame Content In Select Diet Beverages, Jorge Ojeda

Undergraduate Research Conference

Millions of dollars are spent every year on diet beverages and there has been much controversy on the contents in these beverages, mainly the artificial sweetener aspartame. It is known that aspartame is included in many diet beverages, but the actual amount of aspartame used is not listed in the nutritional facts or provided by the beverage manufacturers. For this reason, the aspartame content of various soft drinks, Coke Zero, Pepsi Max, Diet Pepsi, and Pepsi Next, was analyzed and compared to a calibration plot utilizing Diet Coke as a standard. Diet Coke was used due to the unavailablity of …

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Toward Designed Singlet Fission: Solution Photophysics Of Two Indirectly Coupled Covalent Dimers Of 1,3-Diphenylisobenzofuran, Justin C. Johnson, Akin Akdag, Matibur Zamadar, Xudong Chen, Andrew F. Schwerin, Irina Paci, Millicent B. Smith, Zdenek Havlas, John R. Miller, Mark A. Ratner, Arthur J. Nozik, Josef Michl Feb 2013

Toward Designed Singlet Fission: Solution Photophysics Of Two Indirectly Coupled Covalent Dimers Of 1,3-Diphenylisobenzofuran, Justin C. Johnson, Akin Akdag, Matibur Zamadar, Xudong Chen, Andrew F. Schwerin, Irina Paci, Millicent B. Smith, Zdenek Havlas, John R. Miller, Mark A. Ratner, Arthur J. Nozik, Josef Michl

Faculty Publications

In order to identify optimal conditions for singlet fission, we are examining the photophysics of 1,3- diphenylisobenzofuran (1) dimers covalently coupled in various ways. In the two dimers studied presently, the coupling is weak. The subunits are linked via the para position of one of the phenyl substituents, in one case (2) through a CH2 linker and in the other (3) directly, but with methyl substituents in ortho positions forcing a nearly perpendicular twist between the two joint phenyl rings. The measurements are accompanied with density functional theory (DFT) and timedependent DFT (TD-DFT) calculations. Although in neat solid state, 1 …

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Ammonium Sulfate Precipitation Combined With Liquid Chromatography Is Sufficient For Purification Of Bovine Serum Albumin That Is Suitable For Most Routine Laboratory Applications, Odutayo O. Odunuge, Alina Shazhko Jan 2013

Ammonium Sulfate Precipitation Combined With Liquid Chromatography Is Sufficient For Purification Of Bovine Serum Albumin That Is Suitable For Most Routine Laboratory Applications, Odutayo O. Odunuge, Alina Shazhko

Faculty Publications

The use of bovine serum albumin (BSA) in routine biochemical assays such as restriction enzyme digestion and immunodetection is plagued largely by two common contaminants, DNase and immunoglobulins G (IgGs). Acetylation of BSA to inactivate DNase limits its use as a protein standard due to interference with color development in assays such as Lowry’s. In spite of the availability of inexpensive BSA, its purification involves several cumbersome and time-consuming steps. In this work, we employed a modified strategy of ammonium sulfate precipitation coupled with liquid chromatography to purify BSA that is free of DNase and IgGs. Purified BSA tested negative …

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A Dft Study Of Vibrational Spectra And Mutagenicity Predictions Of Mononitrated Fluoranthenes [Abstract], Kefa Karimu Onchoke, Jorge Ojeda Jan 2013

A Dft Study Of Vibrational Spectra And Mutagenicity Predictions Of Mononitrated Fluoranthenes [Abstract], Kefa Karimu Onchoke, Jorge Ojeda

Faculty Publications

No abstract provided.

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Synthesis: What We Have Learned From The East Texas Radiocarbon Database, Robert Z. Selden Jr., Timothy K. Perttula Jan 2013

Synthesis: What We Have Learned From The East Texas Radiocarbon Database, Robert Z. Selden Jr., Timothy K. Perttula

CRHR: Archaeology

This poster provides a short overview of what we have learned from the East Texas Radiocarbon Database since it became available on the Council of Texas Archeologists’ website in 2011. These successes are numerous and include the advancement of novel methodological approaches; an improvement in our comprehension of the temporal nuances within the East Texas Archaic; the division of the East Texas Woodland period into Early, Middle and Late; the refinement of Caddo temporal chronology – particularly from a geographic perspective -- and it has provided one line of evidence to use to argue for the fluorescence of corn-based agriculture …

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Radiocarbon Trends And The East Texas Caddo Tradition (Ca. A.D. 800-1680), Robert Z. Selden Jr., Timothy K. Perttula Jan 2013

Radiocarbon Trends And The East Texas Caddo Tradition (Ca. A.D. 800-1680), Robert Z. Selden Jr., Timothy K. Perttula

CRHR: Archaeology

Through the employment of radiocarbon (14C) dates as data, we use the date combination process to refine site-specific summed probability distributions for 555 dates from Caddo sites (n = 19) in East Texas with 10 or more 14C dates. Summed probability distributions are then contrasted across river basins and natural regions with the remainder of the East Texas Caddo Radiocarbon Database (n = 338 dates from 132 other Caddo sites), highlighting the temporal and spatial character of Caddo archaeological sites throughout East Texas.

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A Preliminary Temporal Analysis Of The East Texas Archaic, Robert Z. Selden Jr. Jan 2013

A Preliminary Temporal Analysis Of The East Texas Archaic, Robert Z. Selden Jr.

CRHR: Archaeology

This article presents preliminary findings of a temporal analysis of the East Texas Archaic based upon the examination of radiocarbon dates that have deposits that date to the period. All assays employed in this effort were collected from research and cultural resource management reports and publications, synthesized, then recalibrated in version 4.1.7 of OxCal.

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Additional New Radiocarbon Dates From East Texas Caddo Sites, Timothy K. Perttula, Robert Z. Selden Jr. Jan 2013

Additional New Radiocarbon Dates From East Texas Caddo Sites, Timothy K. Perttula, Robert Z. Selden Jr.

CRHR: Archaeology

As a follow-up to the radiocarbon analyses reported by Perttula and Selden (2013), in this article, we report on five new radiocarbon dates obtained from Caddo sites in East Texas. The radiocarbon samples are charred organic remains scraped off of one surface of whole vessels or sherds. These samples are from the Ware Acres site (41GG31), the H. C. Slider site in Cherokee County, an unknown site in the upper Neches River basin in Smith County (9-SC), and an unknown Titus phase site (11-BCJ) in the Big Cypress Creek basin. All of the dates are calibrated using OxCal v4.1.7.

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Temporal Dynamics Of East Texas Caddo Sites With 10 Or More Radiocarbon Dates, Robert Z. Selden Jr., Timothy K. Perttula Jan 2013

Temporal Dynamics Of East Texas Caddo Sites With 10 Or More Radiocarbon Dates, Robert Z. Selden Jr., Timothy K. Perttula

CRHR: Archaeology

This article represents supplementary data (see Selden and Perttula 2013) highlighting the specifics of date combination and the subsequent production of summed probability distribution samples for Caddo sites in East Texas. All radiocarbon (14C ) dates employed in this effort were collected from research and cultural resource management (CRM) reports and publications, synthesized, then recalibrated in version 4.1.7 of OxCal (Bronk Ramsey 2012) using IntCal09 (Reimer et al. 2009) (Perttula and Selden 2011).

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New Radiocarbon Dates From East Texas Caddo Sites, Timothy K. Perttula, Robert Z. Selden Jr. Jan 2013

New Radiocarbon Dates From East Texas Caddo Sites, Timothy K. Perttula, Robert Z. Selden Jr.

CRHR: Archaeology

In this article, we report on new radiocarbon dates obtained from five Caddo sites in East Texas. The radiocarbon samples are charred organic remains scraped off of one surface of whole vessels or sherds. These samples are from the Johns (41CP12), Shelby Mound (41CP71), Gilbert (41RA13), Henry Spencer (41UR315), and Henry Williams (41UR318) sites. All of the dates are calibrated using OxCal v4.1.7 (Bronk Ramsey 2012), with atmospheric data from Reimer et al. (2009).

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Oxidation Of Gold Clusters By Thiols, Brian M. Barngrover, Christine M. Aikens Jan 2013

Oxidation Of Gold Clusters By Thiols, Brian M. Barngrover, Christine M. Aikens

Faculty Publications

The formation of gold–thiolate nanoparticles via oxidation of gold clusters by thiols is examined in this work. Using the BP86 density functional with a triple ζ basis set, the adsorption of methylthiol onto various gold clusters AunZ (n = 1–8, 12, 13, 20; Z = 0, −1, +1) and Au384+ is investigated. The rate-limiting step for the reaction of one thiol with the gold cluster is the dissociation of the thiol proton; the resulting hydrogen atom can move around the gold cluster relatively freely. The addition of a second thiol can lead to H2 …

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