Chemistry Commons^™

Investigating New Guaiazulenes And Diketopyrropyrroles For Photonic Applications, Ebrahim Ghazvini Zadeh

Electronic Theses and Dissertations

?-Conjugated systems have been the focus of study in recent years in order to understand their charge transport and optical properties for use in organic electronic devices, fluorescence bioimaging, sensors, and 3D optical data storage (ODS), among others. As a result, several molecular building blocks have been designed, allowing new frontiers to be realized. While various successful building blocks have been fine-tuned at both the electronic and molecular structure level to provide advanced photophysical and optoelectronic characteristics, the azulene framework has been under-appreciated despite its unique electronic and optical properties. Among several attributes, azulenes are vibrant blue naturally occurring hydrocarbons …

Effect Of Methoxy Substituents On The Activation Barriers Of The Glutathione Peroxidase-Like Mechanism Of An Aromatic Cyclic Seleninate, Craig A. Bayse, Ashley L. Shoaf

Chemistry & Biochemistry Faculty Publications

Density functional theory (DFT) models including explicit water molecules have been used to model the redox scavenging mechanism of aromatic cyclic seleninates. Experimental studies have shown that methoxy substitutions affect the rate of scavenging of reactive oxygen species differently depending upon the position. Activities are enhanced in the para position, unaffected in the meta, and decreased in the ortho. DFT calculations show that the activation barrier for the oxidation of the selenenyl sulfide, a proposed key intermediate, is higher for the ortho methoxy derivative than for other positions, consistent with the low experimental conversion rate.

Spectroscopic Characterization Of Oceanic Dissolved Organic Matter Isolated By Reverse Osmosis Coupled With Electrodialysis, John R. Helms, Jingdong Mao, Hongmei Chen, E. Michael Perdue, Nelson W. Green, Patrick G. Hatcher, Kenneth Mopper, Aron Stubbins

Chemistry & Biochemistry Faculty Publications

Oceanic dissolved organic matter (DOM) is one of the largest pools of reduced carbon on Earth, yet DOM remains poorly chemically characterized. Studies to determine the chemical nature of oceanic DOM have been impeded by the lack of efficient and non-fractioning methods to recover oceanic DOM. Here, a DOM fraction (~40 to 86% recovery) was isolated using reverse osmosis/electrodialysis (RO/ED) and analyzed by solid-state ¹³C nuclear magnetic resonance (NMR) spectroscopy. Samples were obtained from biogeochemically distinct environments: photobleached surface gyre, productive coastal upwelling zone, oxygen minimum, North Atlantic Deep Water, and North Pacific Deep Water. A ubiquitous ‘background’ refractory …

Characterization And Photodegradation Of Dissolved Organic Matter (Dom) From A Tropical Lake And Its Dominant Primary Producer, The Cyanobacteria Microcystis Aeruginosa, Thais B. Bittar, Aron Stubbins, Armando A. H. Vieira, Kenneth Mopper

Chemistry & Biochemistry Faculty Publications

This study investigates optical and high-resolution molecular signatures and photochemical degradation of DOM from the Barra Bonita Reservoir (BB-DOM), a tropical eutrophic lake, as well as from its dominant phytoplankton species, the cyanobacteria Microcystis aeruginosa (Microcystis-DOM). Consistent with a predominantly autotrophic source, BB-DOM and Microcystis-DOM exhibited high protein-like fluorescence and contained a large number of aliphatics. Microcystis-DOM was enriched in peptide-like formulae, while BB-DOM had higher chromophoric and fluorescent DOM(CDOM and FDOM) and was enriched in moderately unsaturated formulae, indicating additions of terrigenous DOM and/or in situ processing of autochthonous material in the lake. Consistent with …

Interesting Properties Of P-, D-, And F-Block Elements When Coordinated With Dipicolinic Acid And Its Derivatives As Ligands: Their Use As Inorganic Pharmaceuticals, Michael J. Celestine, Jimmie L. Bullock, Shivani Boodram, Varma H. Rambaran, Alvin A. Holder

Chemistry & Biochemistry Faculty Publications

This is a review of the literature concerning the interesting properties of p-, d-, and f-block elements when coordinated with 2,6-pyridinedicarboxylic acid (dipicolinic acid, H₂dipic) and its derivatives as ligands, with a focus on their use as inorganic pharmaceuticals. Some of the complexes reported were used as insulin-like, bioimaging contrasting agents, antimicrobial agents, and anticancer agents.

Note: Improved Line Strengths Of Rovibrational And Rotational Transitions Within The X3Σ⁻ Ground State Of Nh, James S.A. Brooke, Peter F. Bernath, Colin M. Western

Chemistry & Biochemistry Faculty Publications

Recently, a line list including positions and transition strengths was published for the NH X³Σ⁻ rovibrational and rotational transitions. The calculation of the transition strengths requires a conversion of transition matrix elements from Hund’s case (b) to (a). The method of this conversion has recently been improved during other work on the OH X²Π rovibrational transitions, by removing an approximation that was present previously. The adjusted method has been applied to the NH line list, resulting in more accurate transition strengths. An updated line list is presented that contains all possible transitions with v′ and …

Proton-Electrostatic Localization: Explaining The Bioenergetic Conundrum In Alkalophilic Bacteria, James Weifu Lee

Chemistry & Biochemistry Faculty Publications

The decades-longstanding energetic conundrum of alkalophilic bacteria as to how they are able to synthesize ATP has now, for the first time, been clearly solved using the proton-electrostatics localization hypothesis. This is a major breakthrough advance in understanding proton-coupling bioenergetics over the Nobel-prize work of Peter Mitchell’s chemiosmotic theory. The widespread textbook Mitchellian proton motive force (pmf) equation has now been significantly revised. Use of the newly derived equation results in an overall pmf value (215~233 mV) that is more than 4 times larger than that (44.3 mV) calculated from the Mitchellian equation for the alkalophilic bacteria growing at pH …

Peptide Inhibitor Of Complement C1 (Pic1) Rapidly Inhibits Complement Activation After Intravascular Injection In Rats, Julia A. Sharp, Pamela S. Hair, Haree K. Pallera, Parvathi S. Kumar, Clifford T. Mauriello, Julius O. Nyalwidhe, Cody A. Phelps, Dalnam Park, Nicole M. Thielens, Stephen M. Pascal, Waldon Chen, Diane M. Duffy, Frank A. Lattanzio, Kenji M. Cunnion, Neel K. Krishna

Chemistry & Biochemistry Faculty Publications

The complement system has been increasingly recognized to play a pivotal role in a variety of inflammatory and autoimmune diseases. Consequently, therapeutic modulators of the classical, lectin and alternative pathways of the complement system are currently in preclinical and clinical development. Our laboratory has identified a peptide that specifically inhibits the classical and lectin pathways of complement and is referred to as Peptide Inhibitor of Complement C1 (PIC1). In this study, we determined that the lead PIC1 variant demonstrates a salt-dependent binding to C1q, the initiator molecule of the classical pathway. Additionally, this peptide bound to the lectin pathway initiator …

Experimental Demonstration Of Localized Excess Protons At A Water-Membrane Interface, Haitham A. Saeed, James W. Lee

Chemistry & Biochemistry Faculty Publications

The widespread Mitchellian proton motive force equation has recently been revised with the proton-electrostatics localization hypothesis, which, for the first time, successfully elucidates the 30-year longstanding energetic conundrum of ATP synthesis in alkalophilic bacteria. To demonstrate the fundamental behavior of localized protons in a pure water-membrane-water system in relation to the newly derived pmf equation, excess protons and excess hydroxyl anions were generated by utilizing an "open-circuit" water-electrolysis system and their distributions were tested using a proton-sensing aluminum membrane. The proton-sensing film placed at the membrane-water interface displayed dramatic localized proton activity while that placed into the bulk water phase …

Plant Species Rather Than Climate Greatly Alters The Temporal Pattern Of Litter Chemical Composition During Long-Term Decomposition, Yongfu Li, Na Chen, Mark E. Harmon, Yuan Li, Xiaoyan Cao, Mark A. Chappell, Jingdong Mao

Chemistry & Biochemistry Faculty Publications

A feedback between decomposition and litter chemical composition occurs with decomposition altering composition that in turn influences the decomposition rate. Elucidating the temporal pattern of chemical composition is vital to understand this feedback, but the effects of plant species and climate on chemical changes remain poorly understood, especially over multiple years. In a 10-year decomposition experiment with litter of four species (Acer saccharum, Drypetes glauca, Pinus resinosa, and Thuja plicata) from four sites that range from the arctic to tropics, we determined the abundance of 11 litter chemical constituents that were grouped into waxes, carbohydrates, …

Relative Drifts And Biases Between Six Ozone Limb Satellite Measurements From The Last Decade, N. Rahpoe, M. Weber, A. V. Rozanov, K. Weigel, H. Bovensmann, J. P. Burrows, A. Laeng, G. Stiller, T. Von Clarmann, E. Kyrölä, V. F. Sofieva, J. Tamminen, K. Walker, D. Degenstein, A. E. Bourassa, R. Hargreaves, P. Bernath, J. Urban, D. P. Murtagh

Chemistry & Biochemistry Faculty Publications

As part of European Space Agency's (ESA) climate change initiative, high vertical resolution ozone profiles from three instruments all aboard ESA's Envisat (GOMOS, MIPAS, SCIAMACHY) and ESA's third party missions (OSIRIS, SMR, ACE-FTS) are to be combined in order to create an essential climate variable data record for the last decade. A prerequisite before combining data is the examination of differences and drifts between the data sets. In this paper, we present a detailed analysis of ozone profile differences based on pairwise collocated measurements, including the evolution of the differences with time. Such a diagnosis is helpful to identify strengths …

Retrieval And Validation Of Carbon Dioxide, Methane, And Water Vapor For The Canary Islands Ir-Laser Occultation Experiment, V. Proschek, G. Kirchengast, S. Schweitzer, J.S. A. Brooke, P. F. Bernath, C. B. Thomas, J. G. Wang, K. A. Tereszchuk, G. González Abad, R. J. Hargreaves, C. A. Beale, J. J. Harrison, P. A. Martin, V. L. Kasyutich, C. Gerbig, O. Kolle, A. Loescher

Chemistry & Biochemistry Faculty Publications

The first ground-based experiment to prove the concept of a novel space-based observation technique for microwave and infrared-laser occultation between low-Earthorbit satellites was performed in the Canary Islands between La Palma and Tenerife. For two nights from 21 to 22 July 2011 the experiment delivered the infrared-laser differential transmission principle for the measurement of greenhouse gases (GHGs) in the free atmosphere. Such global and long-term stable measurements of GHGs, accompanied also by measurements of thermodynamic parameters and line-of-sight wind in a self-calibrating way, have become very important for climate change monitoring. The experiment delivered promising initial data for demonstrating the …

Decrease Of Carbon Tetrachloride (Ccl⁴) Over 2004-2013 As Inferred From Global Occultation Measurements With Ace-Fts, E. Mahieu, Peter F. Bernath, Christopher D. Boone, Kaley A. Walker

Chemistry & Biochemistry Faculty Publications

In this contribution, we use infrared solar occultation measurements performed by the ACE-FTS (Atmospheric Chemistry Experiment – Fourier Transform Spectrometer) instrument onboard the SCISAT-1 Canadian satellite (Bernath et al., 2005). Since its launch in August 2003, this spectrometer has been in continuous operation with no significant degradation of its performance, and global measurements are available from late February 2004 onwards, spanning now more than a decade.

Global Ozone Chemistry And Related Trace Gas Data Records For The Stratosphere (Gozcards): Methodology And Sample Results With A Focus On Hcl, H20, And 03, L. Froidevaux, J. Anderson, H. J. Wang, R. A. Fuller, M. J. Schwartz, M. L. Santee, N. J. Livesey, H. C. Pumphrey, P. F. Bernath, J. M. Russell Iii, M. P. Mccormick

Chemistry & Biochemistry Faculty Publications

We describe the publicly available data from the Global OZone Chemistry And Related trace gas Data records for the Stratosphere (GOZCARDS) project and provide some results, with a focus on hydrogen chloride (HCl), water vapor (H₂O), and ozone (O₃). This data set is a global long-term stratospheric Earth system data record, consisting of monthly zonal mean time series starting as early as 1979. The data records are based on high-quality measurements from several NASA satellite instruments and the Atmospheric Chemistry Experiment Fourier Transform Spectrometer (ACE-FTS) on SCISAT. We examine consistency aspects between the various data sets. …

Recent Increase Of Ethane Detected In The Remote Atmosphere Of The Northern Hemisphere, Bruno Franco, Whitney Bader, Benoît Bovy, Emmanuel Mahieu, Emily V. Fischer, Kimberly Strong, Stephanie Conway, James W. Hannigan, Eric Nussbaumer, Peter F. Bernath, Chris D. Boone, Kaley A. Walker

Chemistry & Biochemistry Faculty Publications

Ethane (C₂H₆) has a large impact on tropospheric composition and air quality because of its involvement in the global VOC (volatile organic compound) – HO_x – NO_x chemistry responsible for generating and destroying tropospheric ozone. By acting as a major sink for tropospheric OH radicals, the abundance of C₂H₆ influences the atmospheric content of carbon monoxide and impacts the lifetime of methane. Moreover, it is an important source of PAN, a thermally unstable reservoir for NOx radicals.

On a global scale, the main sources of C₂H₆ are leakage from the production, transport of natural gas loss, biofuel consumption …

Development Of New Linking Chemistry With The Fac-{Re(Co)3}+ Core For Eventual Applications In Radiopharmaceuticals In Imaging And Therapy, Aponsu Meregngna Pramuditha Lakmi Abhayawardhana

LSU Doctoral Dissertations

The facile labeling of biomolecules with a radionuclide is a key goal in radiopharmaceutical development. This study explores two different ligand systems for fac-[Re(CO)3L]+ complexes, that could be used in bioconjugation. The first approach uses a tridentate ligand having a sulfonamide linkage and modeled on previously evaluated fac-[Re(CO)3(N(SO2R)dpa)]PF6 complexes. The present goal was to develop new related sulfonamide complexes with more hydrophilic ligands designed to avoid the bioavailability problems that would plague the N(SO2R)dpa ligand system. A series of fac-[Re(CO)3(N(SO2R)dien)]PF6 complexes with different R groups linked to the central nitrogen of a symmetric tridentate sulfonamides were synthesized with the aim …

A Monte Carlo Approach To Studying The Hydrogen Storage Capabilities Of Potassium Magnesium Hydride (Kmgh3), Brandon L. Borill

LSU Doctoral Dissertations

Grand Canonical Monte Carlo (GCMC) simulations and the weighted histogram analysis method (WHAM) were employed at selected temperatures and pressures in the study of the hydrogen storage capabilities of KMgH3. A specially tailored addition/removal algorithm was employed to add hydrogen directly at the lattice sites. Agreement between experimental results was obtained through GCMC simulations. WHAM type studies were employed to obtain probability distributions for the purpose of learning the probability of finding hydrogen atoms at specific temperatures and hydrogen pressures. The radial distribution function was employed to study the changes in the structure of KMgH3 for the selected model as …

Synergistic Properties-Driven Synthesis Of Aluminides, Antiomonides, And Bioceramics, Pilanda Watkins-Curry

LSU Doctoral Dissertations

The synthesis, characterization, and properties of selected intermetallics and ceramic materials are presented in this dissertation. In our quest to grow single crystal intermetallics from the metal flux technique, new strategies were employed to avoid thermodynamically stable phases and to ensure sample homogeneity of the crystalline product for structure elucidation and accurate measurements of their magnetic and electrical properties. The relationship between the complex crystal structures and magnetic properties are reported for LnCo2Al8 (Ln = La-Nd, Sm, Yb), CeCo2-xMnxAl8 (0 < x < 1), and Pr2Fe4-xCoxSb5 (1 ≤ x < 3). The discovery of magnetic frustration in LnCo2Al8 (Ln = Ce, Nd) and complex magnetic ordering coupled with large positive magnetoresistance of up to 150% and 60% at 200 K with relatively low field of H = 1 T in Pr2Fe4-xCoxSb5 (x ≈ 2 and 2.5) is also reported. The demand of new inorganic solid materials as scaffolds for the engineering of bone tissue has led to the synthesis of calcium magnesium silicates such as, diopside (CaMgSi2O6), akermanite (Ca2MgSi2O7), monticellite (CaMgSiO4), and merwinite (Ca3Mg(SiO4)2)) for studying dimensionality and mechanical properties. This dissertation highlights the synergism of solid state chemistry at the interface of condensed matter physics and biological engineering. The discovery of compounds with tunable magnetic, electrical, and mechanical properties will be described herein.

I. Synthesis Of Ascarosides For Chemical Biology Studies In Caenorhabditis Elegans, Ii. A Photochemical Approach To Delavayine, And Iii. Remote Hydroxylation By Radical Translocation And Polar Crossover, Kyle Allen Hollister

LSU Doctoral Dissertations

The foci of this dissertation are the synthesis of analogs for chemical biology studies, synthetic chemistry method development (with an emphasis on photochemistry), and the application of these methods toward total synthesis. Chapter 1 outlines the synthesis of an array of pheromone analogs that are derivatives of the dideoxy sugar ascarylose. Referred to as ascarosides, such compounds have recently been shown to influence important biological processes in the model organism Caenorhabditis elegans. C. elegans secretes ascarosides into its environment, where the compounds then act as signaling molecules by providing information on factors like population density. Chapter 2 describes the biological …

Nanoscale Gumbos: Size-Control, Characterization, And Applications As Enantioselective Molecularly Imprinted Polymers And Fluorescent Materials, Suzana Hamdan

LSU Doctoral Dissertations

Nanomaterials derived from a group of uniform materials based on organic salts (GUMBOS) have been introduced into the scientific literature through many analytical, biological, and technological applications. These nanomaterials, referred to as nanoGUMBOS, have been shown to display a number of interesting properties including fluorescence, magnetism, tumor targeting, and optoelectronic properties. Herein, we present major studies on nanoGUMBOS including synthesis and size-control, chiral molecular imprinting in polymers, as well as investigation of optical properties and quantum yield of fluorescent semiconductor-based nanoGUMBOS. Various strategies were introduced for production of well-defined nanoGUMBOS. Specifically, several methods based on sonochemistry, microwave, cyclodextrin, and surfactant-assisted …

I. Synthesis Of Ascarosides For Biological Evaluation And Ii. Development Of Visible Light-Promoted Selenofunctionalization And Grafting Of Aryl Iodides, Elizabeth Susan Conner Balapitiya

LSU Doctoral Dissertations

This dissertation focuses on analog synthesis for biological evaluation and visible light promoted method development. Chapter 1 centers upon the synthesis of Caenorhabditis elegans dauer pheromone analogs. C. elegans is a nematode which, in times of environmental stress, enters a dauer stage. Two highly conserved pathways, which play important roles in some diseases in higher organisms, monitor dauer formation: TGF-β and IGF-1. Dauer formation is triggered by the nematode’s chemosensation of the dauer pheromone, consisting of a group of previously-isolated ascarosides. These compounds differ in chain length, saturation, terminal functionality of side chain, ω vs. ω-1 oxygenation and presence of …

Assessment Of Water Vapor Isotopologue Measurements By Ace-Fts And Odin-Smr, Ralf Bauer, Patrick Sheese, Kaley Walker, Joachim Urban, Donal Murtagh, Chris Boone, Peter Bernath, Gloria Manney

Chemistry & Biochemistry Faculty Publications

[Introduction] Knowing the isotopic composition of trace gases can improve our understanding of processes in the Earth's atmosphere causing isotopic fractionation. In many studies, isotopologue (molecules of identical chemical but different isotopic composition) amounts are primarily discussed as δ values, which are defined relative to a standard, e.g.:

Ace-Fts And Haloe Observations Of Hydrogen Fluoride (Hf) And Their Comparison With Slimcat Chemical Transport Model Calculations, Jeremy Harrison, Martyn Chipperfield, Chris Boone, Peter Bernath, Lucien Froidevaux, John Anderson, James Russell Iii

Chemistry & Biochemistry Faculty Publications

The majority of fluorine in the atmosphere has resulted from the anthropogenic emission of chlorofluorocarbons (CFCs), hydrochlorofluorocarbons (HCFCs), and hydrofluorocarbons (HFCs). Most tropospheric fluorine is present in its emitted 'organic' form due to the molecules having long lifetimes (up to a decade or longer). Thus they are able to reach the stratosphere where they are broken down, liberating fluorine. The principal degradation products are carbonyl fluoride (COF2), carbonyl chloride fluoride (COClF), and hydrogen fluoride (HF); of these HF is the most abundant. In fact at the top of the stratosphere most of the fluorine is present as HF, which, due …

Use Of Esi-Fticr-Ms To Characterize Dissolved Organic Matter In Headwater Streams Draining Forest-Dominated And Pasture-Dominated Watersheds, Yuehan Lu, Xiaping Li, Rajaa Mesfioui, James E. Bauer, R. M. Chambers, Elizabeth A. Canuel, Patrick G. Hatcher

Chemistry & Biochemistry Faculty Publications

Electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry (ESI-FTICR-MS) has proven to be a powerful technique revealing complexity and diversity of natural DOM molecules, but its application to DOM analysis in grazing-impacted agricultural systems remains scarce. In the present study, we presented a case study of using ESI-FTICR-MS in analyzing DOM from four headwater streams draining forest-or pasture-dominated watersheds in Virginia, USA. In all samples, most formulas were CHO compounds (71.8-87.9%), with other molecular series (CHOS, CHON, CHONS, and CHOP (N, S)) accounting for only minor fractions. All samples were dominated by molecules falling in the lignin-like region (H/C …

Wavelength Dependent Specific Plasmon Resonance Coupling Of Single Silver Nanoparticles With Egfp, Kerry J. Lee, Tao Huang, Prakash D. Nallathamby

Chemistry & Biochemistry Faculty Publications

Noble metal nanoparticles (NPs) possess unique plasmonic properties, enabling them to serve as sub-diffraction light sources and nano-antennae for a wide range of applications. Here we report the specific interaction of single Ag NPs with single EGFP molecules and a high dependence of their interaction upon localized-surface-plasmon-resonance (LSPR) spectra of single Ag NPs and EGFP. The LSPR spectra of single red Ag NPs show a stunning 60 nm blue-shift during their incubation with EGFP, whereas they remain unchanged during their incubation with bovine serum albumin (BSA). Interestingly, the peak wavelengths of the LSPR spectra of green and blue Ag NPs …

Mass Loss And Chemical Structures Of Wheat And Maize Straws In Response To Ultravoilet-B Radiation And Soil Contact, Guixiang Zhou, Jiabao Zhang, Jingdong Mao, Congzhi Zhang, Lin Chen, Xiuli Xin, Bingzi Zhao

Chemistry & Biochemistry Faculty Publications

The role of photodegradation, an abiotic process, has been largely overlooked during straw decomposition in mesic ecosystems. We investigated the mass loss and chemical structures of straw decomposition in response to elevated UV-B radiation with or without soil contact over a 12-month litterbag experiment. Wheat and maize straw samples with and without soil contact were exposed to three radiation levels: a no-sunlight control, ambient solar UV-B, and artificially elevated UV-B radiation. A block control with soil contact was not included. Compared with the no-sunlight control, UV-B radiation increased the mass loss by 14-19% and the ambient radiation by 9-16% for …

Biodegradable Poly(Ester Urea's) Scaffold Sponges Containing Platelet-Rich Plasma For Targeted Tendon-Bone Fixation, Alex B. Ellenberger Mr.

Williams Honors College, Honors Research Projects

In this report the synthesis and characterization of L-valine and L-isoleucine poly(ester ureas) (PEUs) for future use in the synthesis of biodegradable PEUs sponges will be discussed. The method of monomer and polymer synthesis will be explained along with the characterization of the monomer and polymer products. This characterization will be done by the use of Nuclear Magnetic Resonance (NMR) and Size Exclusion Chromatography (SEC). NMR is a quick and convenient method for determining structure and purity of the monomer and polymer products. SEC gives the number average molecular weight, which is the statistical average molecular weight of all the …

Determination Of The Structure Of Sphingomyelin By Tandem Mass Spectrometry And Matrix - Assisted Laser Desorption/Ionization, Antonio Ganios

Williams Honors College, Honors Research Projects

Mass spectrometry is a method that uses masses to determine the structure of a compound. This is completed by first charging the compound until it is a cation or anion, and then its molecular weight can be determined by measuring a mass to charge ratio. The focus of this study was determination of sphingomyelin’s structure. The purpose of this was that sphingomyelin has been shown to play a critical role in many biological pathways and being able to identify this lipid could prove to be beneficial for preventative medicine. Utilizing electrospray ionization (ESI) Quadruple-Time-of-flight (Q-TOF) mass spectrometry on a Waters …

Humidity And Rest Period Effects On Viscid Silk Recovery, Catherine Donley

Williams Honors College, Honors Research Projects

Spider silk applications, and applications of composite materials generally, are limited due to lack of recovery once damaged. Viscid silk, however, is known to have self-healing capabilities which restore, at least partially, its initial properties. If maximized, this ability could potentially increase viscid silk’s practicality and ultimately, provide insight into a self-healing system of use in synthetics. To that end, samples of viscid silk spun by female Larinioides cornutus spiders were tested via cyclical loading at 3 different relative humidities, with 3 different rest period lengths between complete cycles. Data from previously-performed tensile tests conducted at the same 3 humidities …

The Effects Of Substrate Roughness In Air And Water On The Gecko Adhesive System, Amanda Palecek

Williams Honors College, Honors Research Projects

In an effort to better understand the fascinating gecko adhesive system, scientists have long tested the abilities of the gecko in controlled conditions that mimic the gecko’s native environment. The effects of humidity, environmental temperature, and exposure to water have all been tested. Roughness, however has not been studied in great detail. Surfaces of varying roughnesses are all over the gecko’s natural environment. We tested geckos on hydrophilic silicon carbide sandpapers of varying roughnesses in both air and water to attempt to better study the effects of roughness on gecko adhesion. When tested on the rougher (1 µm) surface, the …