«Strengthening the Nation through Diversity, Innovation & Leadership in STEM San Antonio,Texas · October 3-6, 2013 Get Connected! Connect with the ...»
Heparin is an unbranched, microheterogeneous, anionic polysaccharide comprised of repeating uronic acidglucosamine disaccharides. Microheterogeneity is introduced during biosynthesis as various patterns of sulfation and uronic acid epimerization. Heparin is used pharmaceutically as an anticoagulant acting through binding of a specific pentasaccharide sequence to the protease inhibitor, antithrombin III (AT-III). An important structural component of this pentasaccharide is the 3-O-sulfated internal glucosamine residue. Deletion of this 3-O-sulfo group reduces affinity to AT-III by 1000-fold. Study of the role of heparin’s microstructure in specific protein binding requires isolation and structural characterization of well-defined oligosaccharides. Heparin is depolymerized to generate oligosaccharides of various lengths, which are then separated by size exclusion chromatography (SEC).
Typically, the size-uniform fractions obtained by SEC are pooled and separated further by strong anion exchange high performance liquid chromatography (SAX-HPLC). However, it has been demonstrated that the composition of the SEC fractions varies along the size-uniform peak. It is possible that by pooling these fractions, important and rare 3-O-sulfated oligosaccharides are diluted by more abundant oligosaccharides, obscuring their identity in the SAX-HPLC chromatogram. Recent advances in characterizing the structural properties of heparin using [1H, 15N] HSQC NMR spectra allow us to probe individual SEC fractions for the presence of 3-O-sulfated N-sulfoglucosamine residues and focus our workflow around these samples. This work will demonstrate the use of [1H, 15N]HSQC spectra to efficiently identify those SEC fractions containing the rare 3-O-sulfo group, resulting in better resolution SAX-HPLC separations and higher recovery of isolated oligosaccharides for future structural characterization and protein-binding experiments.
EARTH SCIENCES/OTHER PHYSICAL SCIENCESRoom 206B
EFFECTS OF NITROGEN FERTILIZER ON SOIL ORGANIC MATTER POOLS UNDER SWITCHGRASS
AGRICULTUREZachary Valdez1, Bill Hockaday2, Morgan Gallagher3, Carrie Masiello4.
Institute of Earth, Ecological, and Environmental Sciences, Baylor University, Waco, TX, 2Baylor University, Waco, 1 TX, 3Center on Global Change at Duke University, Durham, NC, 4Rice University, Houston, TX.
The cropping of switchgrass (Panicum virgatum) for biomass shows potential for high yields in marginal lands with low fertilizer inputs, while the extensive root system can act to improve soil quality and sequester atmospheric carbon dioxide in the soil carbon pool. We are investigating the impact of nitrogen fertilizer inputs on soil organic matter quantity and quality in a biofuels cropping trial in Michigan. Here we test the hypothesis that fertilizer application rate can affect the partitioning of organic matter into different storage pools within the soil: roots, particulate organic matter (density 1.8 g/cm3), and protected organic matter (density 1.8 g/cm3). Additionally, we use 13C nuclear magnetic resonance (NMR) spectroscopy to study the bulk chemistry (carbohydrate, lignin, lipid, and protein) of the roots and particulate soil organic matter. The NMR data also allow us to estimate the relative decomposition of the soil organic matter using a standard decomposition index (alkyl/O-alkyl peak ratio). We use these data to infer the influence of fertilizer management on the mechanisms of soil C storage and decomposition in switchgrass agriculture.
OTHER GEOLOGICAL SCIENCESRoom 206B
DARK ORGANIC MATTER IN PERMANENTLY SHADOWED CRATERS ON MERCURYEllen Harju1, David Paige1, Matt Siegler2, Mona Delitsky3.
University of California, Los Angeles, Los Angeles, CA, 2Jet Propulsion Laboratory, Pasadena, CA, 3California 1 Specialty Engineering, Flintridge, CA.
Data from the Mercury Laser Altimeter (MLA) and neutron spectrometer aboard the MESSENGER spacecraft currently orbiting Mercury have confirmed the presence of water ice in permanently shadowed craters in the north polar region of Mercury. Additional reflectivity data from the MLA shows the existence of an additional low-albedo phase associated with the ice, which is not consistent with Mercury soil or water ice. The purpose of this project was to determine if this dark layer could be an organic-rich layer similar to low albedo materials found on comets, asteroids, meteorites, and other solar system objects. Simple organic molecules (such as methane) are delivered to Mercury by cometary impacts. Although temperatures in the equatorial region of Mercury are too high to retain these organics, they can migrate to the polar region and become cold trapped in permanently shadowed craters with temperatures of approximately 100 K. Mercury has magnetic field lines which concentrate solar wind plasma in the north polar region. Laboratory experiments have shown that, when simple organic molecules are subjected to ultra violet and ion radiation, dehydrogenation can occur, resulting in the loss of molecular hydrogen. This leads to polymerization of the remaining carbon-rich species and the formation of amorphous macromolecular carbonaceous compounds. This process may continue until low-albedo elemental carbon is produced. Based on this evidence, we find that the low-albedo material found in the permanently shadowed craters on Mercury is most likely radiation processed carbon-rich material.
ANALYSIS OF TROPOSPHERIC AEROSOL PROPERTIES USING AERONET AND CALIPSO DATAAraceli Lopez-Garibay, Patrick Hamill.
San Jose State University, San Jose, CA.
During the last few years, it has become evident that aerosols play an important role in Earth’s climate. Consequently, it is important to be able to identify aerosols using instruments in satellites. We use the CALIPSO satellite aerosol data and compare those results with measurements made by AERONET. The CALIPSO instrument is a down-looking
361 ORAL ABSTRACTS
lidar which determines the backscattered laser light from aerosols near the surface. AERONET is a worldwide network of sun photometers that also measures aerosols near the surface, but from the ground. Finding coincidences in location and time between the CALIPSO data and the AERONET data allow us to compare these 2 measurements.
Since the type of aerosol observed by AERONET can be determined by methods which we will describe, we can then determine the type of aerosol measured by CALIPSO. We will present tables showing aerosol properties at coincidences as a function of date, time, and location at particular wavelengths (440 nm, 500 nm, 532 nm). We have also generated plots that present altitude vs. extinction (scattering and absorption of solar radiation) of the aerosols in the atmosphere. Moreover, we produced plots that present altitude vs. relative humidity of the marine aerosols in the atmosphere for specific locations such as Lanai. The relative humidity is necessary to determine the index of refraction of the particles. The CALIPSO and AERONET datasets of optical depths at those locations, dates, and times are compared. We will present results showing agreement or discrepancy in the measurements made by the 2 instruments.
HIGH-EFFICIENCY HYBRID SILICON NANOPILLARS-POLYMER SOLAR CELLSPushpa Raj Pudasaini, David Elam, Arturo A Ayon.
University of Texas at San Antonio, San Antonio, TX.
Recently, inorganic/organic hybrid solar cells have been studied for low-cost photovoltaic devices because the Schottky junction between inorganic and organic material can be formed by a low-temperature, solution-processable method. We present an efficient hybrid solar cell based on highly ordered silicon nanopillars (SiNPs) and poly (3,4-ethylene-dioxythiophene):polystyrenesulfonate (PEDOT:PSS). The proposed device is formed by spin coating the organic polymer PEDOT:PSS on SiNPs array fabricated by a metal-assisted electroless chemical etching process. The characteristic of the hybrid solar cells are investigated as a function of SiNP heights. A maximum power conversion efficiency (PCE) of 9.65% has been achieved for an optimized SiNPs arrays hybrid solar cell with nanopillar height 400 nm, despite a 12% shadowing loss and the absence of an antireflection coating and the back surface field enhancement. The effect of ultra-thin atomic layer deposition (ALD), grown aluminum oxide (Al2O3), as a junction passivation layer has also been studied for the enhanced electrical performance of the device.
With the inclusion of the ultra-thin ALD-deposited Al2O3 as a interfacial layer between SiNPs array textured surface and PEDOT:PSS layer, the PCE of the fabricated device is increased to 10.92%, which is ~13% greater than the corresponding device without Al2O3 layer. The proposed device is promising toward realizing low-cost and highefficiency inorganic/organic hybrid solar cells.
PSYCHOLOGY & SOCIAL SCIENCES
EXPERIMENTAL PSYCHOLOGYRoom 207B
THAT’LL TAKE THEM DOWN A PEG: PERCEIVING HYPOCRISY WHEN THREATENED BY OTHERSWillie Hale Jr., David Pillow.
University of Texas at San Antonio, San Antonio, TX.
Fiske, in 2002, proposed 5 core social motives (belongingness, understanding, control, self enhancement, and trust) that ostensibly serve to enhance people’s survival within groups. We contend that, when these needs are threatened, individuals mitigate said threat by looking for evidence of hypocrisy from the threat’s source, simultaneously denigrating or discounting the source while also bolstering and reaffirming their self-concept. Participants considered episodic memories of others’ hypocritical behavior and answered items assessing the degree to which the hypocrite’s violation of Fiske’s five core social needs influenced their perceptions of hypocrisy. A 5-factor model emerged from these items, mirroring Fiske’s model. Participants were clustered into groups based on which motive’s items exhibited the highest mean rating for that group. Within each group, the items on the highest rated motive were significantly higher than those on each other motive. Additionally, within each group, only the highest rated motive predicted subjective perceptions of hypocrisy, providing evidence that violations of each core social motive uniquely prompted individuals to see hypocrisy in others’ behavior. Defensive denigration of those who threaten one’s core social needs via identifying hypocrisy is one of many mechanisms that likely evolved to help individuals maintain their place within their social groups. Each core social motive, when violated, provides the impetus for individuals to selectively interpret the behavior of others as hypocritical. (Partially funded by NIGMS MBRS-RISE GM060655.)
AMBIGUITY RESOLUTION: TO BE OR NOT TO BE, THAT IS THE MEANINGWualú Altamira, Roberto Heredia.
Texas A&M International University, Laredo, TX.
Interlingual homographs are words across languages with competing semantic and overlapping orthographic representations (e.g., CASES = LAW in English and MARRIAGE in Spanish), while cognates are words across languages with equal or similar semantic and orthographic representations (e.g., HOSPITAL). Experiments 1 and 2 explore context effects in reading interlingual homographs and cognates embedded in English sentences. Experiment 3 investigates interlingual homographs embedded in Spanish and bilingual (Spanish/English) sentences. All three experiments address the issue of bilingual lexical access and whether homographs/cognates are activated selectively (i.e., only one meaning is activated) or non-selectively (i.e., both meanings are activated simultaneously). Using the Grammaticality Maze Task, bilinguals read contextually biased English monolingual sentences (experiment 1) as well as contextually unbiased Spanish monolingual sentences or bilingual sentences where the critical target (homograph/control) followed a conjunctional/adverbial modifier in Spanish/English joining two sentences (experiment 3). The Language Maze Task was used for experiment 2 in which bilinguals read English sentences. The preceding contextual information was either high or low towards the English meaning of the critical target (i.e., homographs, cognates, controls). Participants made lexical decisions to word-nonword pairs (e.g., butter vs. reck), and at the same time they had to integrate and understand the presented sentences. Overall, the results were suggestive of nonselectivity, in which control targets were actually faster than the critical homographs (i.e., lexical competition). The results are interpreted in terms of bilingual lexical access models.
THE RELATIONSHIP BETWEEN INTRINSIC/EXTRINSIC ACADEMIC MOTIVATION AND BURNOUT IN HISPANIC
UNDERGRADUATE COLLEGE STUDENTS: A COMPARISON ACROSS CLASSIFICATIONRebecka English, Monica Munoz.
Texas A&M International University, Laredo, TX.