SOLVENT AND STRUCTURAL EFFECTS ON ELECTRON TRANSFER IN INTERMOLECULAR CHARGE-TRANSFER COMPLEXES AND PHOTOEXCITED ORGANOSILANES

Understanding how molecular structure and local chemical environment impact photoinduced charge transfer and the stability of donor-acceptor charge-transfer complexes is critical for controlling the formation and separation of charge pairs for applications relevant in the field of optoelectronics. The first part of this thesis discusses solvent effects on the formation of charge transfer complexes (CTC) between a fluorinated quinone acceptor and a phenylenediamine donor that results from integer charge transfer (ICT). Utilizing temperature dependent steady-state UV-Vis, we demonstrate charge separation is favorable and strongly supported in moderately polar solvent environments where ion-pair interactions aid in stabilizing complexes. Spontaneous charge separation is still observed (but is less favorable) for lower polarity solvents where charge separation is still entropically favored. These results provide insight for forming and supporting integer charge separation in environments characterized by low dielectric constants, which needs to be considered for applications involving polymer films or devices. The photoresponses of these complexes were characterized via ultrafast transient absorption spectroscopy to compare CTC photo-physics and photo-dynamics in solution phase and doped polymer films. These experiments reveal that the radical anion of the acceptor dominates the transient dynamics, with anion excited-state relaxation in solution involving rapid internal conversion to a vibrationally hot ground state. Doped polymer films are shown to support both ICT and partial charge transfer states (PCT) upon film drying. Transient responses follow the same relaxation mechanism but on faster timescales where it is concluded these complexes introduce photon losses in working materials due to rapid relaxation. The second part of this thesis presents studies of intramolecular charge separation in hybrid σ-π organosilane molecules and how this process depends on solvent environment and chemical structure. We have previously characterized the photophysics of a series of ester, cyanovinyl capped organosilanes which have an optical σ-π* intramolecular charge transfer transition. Charge recombination was shown to occur in the Marcus inverted region where recombination rates follow a gap-law behavior. Using transient absorption spectroscopy, charge-transfer dynamics were characterized for organosilanes consisting of di-ester and di-cyano vinyl acceptor units with weak vs. strong electron accepting ability, respectively. We find the strength of the electron acceptor governs whether electronic coupling (rather than thermodynamic driving force) will dictate the rate of charge recombination. Weak acceptors result in fast recombination in moderately polar solvents, whereas strong acceptors better stabilize photoinduced charge separation and prolonged lifetimes are observed. The charge separation lifetime in the strongest donor-acceptor pairing can be further extended in low polarity solvents with low reorganization energy, as this places back-electron transfer deeper into the Marcus inverted region. However, for weak to moderate donor-acceptor structures, this results in larger electronic couplings where very rapid recombination approaches the adiabatic limit. Collectively these findings aid in the understanding of the structure-function relationships and the role chemical environment plays for controlling charge separation in organosilanes

Molecular and rheological characterization of hyaluronic acid : determination of its role in thrombin-catalyzed fibrin clotting and viscosupplementation of joints

Three samples of the biopolymer hyaluronic acid (HA) were characterized in the following manner: the molecular weights were obtained via multi-angle laser light scattering; the intrinsic viscosities were calculated through dilute solution viscometry, and the rheology of HA solutions was determined with constant rate rotational viscometry and dynamical mechanical testing. In addition, the highly debated role of hyaluronic acid in wound healing was examined by studying the effect that HA has upon thrombin-catalyzed fibrin clotting. Fibrin, in phosphate-buffered saline, was clotted both alone and after being incubated with HA. It was determined that the presence of hyaluronic acid resulted in a slower clotting process; in effect, HA acts as an anti-coagulant. Based upon the experimental evidence, it is proposed that this anti-coagulant phenomenon arises through a combination of two mechanisms: 1) specific binding between HA and fibrin, which acts to retard fibrin clotting through steric hindrance, and 2) the formation of an HA network which slows fibrin clotting by hindering free diffusion of fibrin and thrombin. Finally, creation of a synthetic replacement for synovial fluid was attempted using xanthan gum and locust bean gum in phosphate-buffered saline. The phenomenon of gum synergism was utilized in an effort to exert some degree of fine-tuning over the final rheological properties of the solution. This also would provide the side benefit of reducing the weight of gum required per unit volume. By mixing the solutions at different temperatures, it was possible to exploit the tendency of xanthan gum to uncoil at higher temperatures and therefore bind more strongly to locust bean gum. However, it was determined that no combination of gum concentrations and processing conditions resulted in a gum solution that adequately mimicked the rheology of a hyaluronan solution

A Principal Components Analysis Approach to Quantifying Foot Clearance and Foot Clearance Variability

Low foot clearance and high variability may be related to falls risk. Foot clearance is often defined as the local minimum in toe height during swing; however, not all strides have this local minimum. The primary purpose of this study was to identify a nondiscrete measure of foot clearance during all strides, and compare discrete and nondiscrete measures in ability to rank individuals on foot clearance and variability. Thirty-five participants (young adults [n = 10], older fallers [n = 10], older nonfallers [n = 10], and stroke survivors [n = 5]) walked overground while lower extremity 3D kinematics were recorded. Principal components analysis (PCA) of the toe height waveform yielded representation of toe height when it was closest to the ground. Spearman\u27s rank order correlation assessed the association of foot clearance and variability between PCA and discrete variables, including the local minimum. PCA had significant (P \u3c.05) moderate or strong associations with discrete measures of foot clearance and variability. An approximation of the discrete local minimum had a weak association with PCA and other discrete measures of foot clearance. A PCA approach to quantifying foot clearance can be used to identify the behavioral components of toe height when it is closest to the ground, even for strides without a local minimum

Ancient Polyploidy and Genome Evolution in Palms

Mechanisms of genome evolution are fundamental to our understanding of adaptation and the generation and maintenance of biodiversity, yet genome dynamics are still poorly characterized in many clades. Strong correlations between variation in genomic attributes and species diversity across the plant tree of life suggest that polyploidy or other mechanisms of genome size change confer selective advantages due to the introduction of genomic novelty. Palms (order Arecales, family Arecaceae) are diverse, widespread, and dominant in tropical ecosystems, yet little is known about genome evolution in this ecologically and economically important clade. Here, we take a phylogenetic comparative approach to investigate palm genome dynamics using genomic and transcriptomic data in combination with a recent, densely sampled, phylogenetic tree. We find conclusive evidence of a paleopolyploid event shared by the ancestor of palms but not with the sister clade, Dasypogonales. We find evidence of incremental chromosome number change in the palms as opposed to one of recurrent polyploidy. We find strong phylogenetic signal in chromosome number, but no signal in genome size, and further no correlation between the two when correcting for phylogenetic relationships. Palms thus add to a growing number of diverse, ecologically successful clades with evidence of whole-genome duplication, sister to a species-poor clade with no evidence of such an event. Disentangling the causes of genome size variation in palms moves us closer to understanding the genomic conditions facilitating adaptive radiation and ecological dominance in an evolutionarily successful, emblematic tropical clade

Integrated Systems Design of a Cargo Aircraft with Environmentally Responsible Goals

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/97068/1/AIAA2012-1759.pd

The Grizzly, April 20, 1999

Seventeenth Annual Airband Draws Crowd • Turnout Low for Ritter Rave • Medieval Sports Fest Continues Caring Tradition • National Poetry Month Celebrated at Ursinus • Ursinus Baseball Pitches in for Cancer • Myrin Library Holds Technology Day • Regal Marketplace 24 in Oaks: Off to a Disappointing Start • Softball Slips into Second • Baseball Bats Awake As UC Tops Centennial Conference • Lacrosse Downs Dickinson for 400th Winhttps://digitalcommons.ursinus.edu/grizzlynews/1441/thumbnail.jp

GA Pilot Perceptions of Speech Systems to Transcribe and Submit PIREPs

Flying into hazardous weather can be a cause of aviation incidents and accidents. Accidents involving general aviation (GA) pilots who are not instrument rated who fly into instrument meteorological conditions (IMC) are often fatal. Pilot weather reports (PIREPs) can increase the accuracy and timeliness of current and forecasted weather conditions. They are an essential tool used by pilots to avoid flying into hazardous weather as well as meteorologists to develop and update aviation forecasts. Thus, a large number of accurate PIREPs with the best source of current weather coming from pilots and air traffic controllers are needed. Pilots are often unable to make PIREPs because of workload in the cockpit or because it is cumbersome to leave the air traffic control (ATC) frequency to contact flight the flight service station (FSS). Currently, air traffic controllers must solicit and disseminate PIREPs. However, air traffic controllers’ primary obligation is to provide traffic separation and traffic alerts. During poor weather, when PIREPs are needed the most, controllers are often too busy to solicit and disseminate PIREPs (NTSB, 2017a). This study administered a descriptive survey to inquire about how likely pilots would be to use a speech recognition system (SRS) to transcribe and submit PIREPs automatically while flying in three distinct flight regimes: instrument flight rules (IFR), visual flight rules (VFR) with flight following, and VFR without flight following. The survey employed cross-section design and included Likert scale questions. For each flight regime, additional information was obtained through an open-ended follow-up question. The Likert scale responses indicated that pilots were neutral about using a SRS to transcribe and submit PIREPs in each flight regime.Spradley’s (1979) domain analysis was used to identify common themes and patterns from the open-ended responses. Major findings from flying IFR were that pilots found it easier to speak directly to air traffic control, or pilots were too busy to submit PIREPs while flying IFR. Major findings from flying VFR with flight following were that pilots thought it was easier to report PIREPs directly to air traffic control or to a flight service station, and it was more accurate to report PIREPs directly to an aviation professional. However, they were willing to try a SRS. Major findings from flying VFR without flight following were that pilots wanted the opportunity to review a PIREP submission for accuracy and were willing to try the system. Significant differences were determined by making a comparison between the three groups

Coastal Texas Oceans II: Enhancing Remote Sensing Capabilities of the Sargassum Early Advisory System (SEAS) Through the Use of NASA EOS and Open Source GIS

No abstract availabl

Radiographic Union Scoring Scale for Determining Consolidation Rates in the Calcaneus.

The reliable evaluation of osseous consolidation after hindfoot osteotomy can be difficult. Concomitant hindfoot osteotomies often dictate the advancement of weightbearing, and radiographs are the mainstay imaging tool owing to cost, efficiency, and radiation exposure. Understanding the radiographic parameters that can be used to reliably determine osseous healing is paramount. However, currently, no reliable or validated method is available to determine osseous healing of hindfoot osteotomies in irregular bones of the foot. The purpose of the present study was to develop a radiographic healing scoring system that would enhance the diagnostic healing assessment after elective calcaneal osteotomy. We adapted existing orthopedic scales validated for healing in the leg for application in the irregular bones of the foot. A total of 168 cases were evaluated by 6 blinded assessors to test the interrater reliability of subjective healing assessment compared with the proposed scoring system. The radiographs were classified by postoperative period: ≤4 weeks, 5 to 12 weeks, and \u3e12 weeks. The proposed scale had high interrater reliability but was burdensome. Using a priori item reduction protocols, a limited 6-item scale further improved internal consistency and reduced the burden. The result was excellent interrater reliability (α = 0.98, standard deviation 0.02, 95% confidence interval 0.91 to 0.96) among all assessors when using the scoring scale compared with unacceptable reliability (α = 0.438) for subjective osteotomy healing. The reliability of our system appeared superior to that of subjective assessment of osseous healing alone, even in the absence of clinical correlates after osteotomy of the calcaneus