Physical Sciences and Mathematics Commons^™

The Roles Of Introduced Eucalyptus In The Conservation And Expansion Of Ethiopian Orthodox Church Forests In The Northern Ethiopian Highlands, Janice Liang

Honors Theses

Species of the genus Eucalyptus (common name eucalyptus) are widely planted all across Ethiopia – including on large areas of land previously allocated to food production. In recent decades eucalyptus has also increasingly been planted on lands around and within “church forests,” sacred groves of old-aged Afromontane trees surrounding Ethiopian Orthodox Tewahido churches. These revered holy sites have long been recognized for their cultural values and also for their ecosystem services – including their potential to support species conservation and restoration, as church forests are some of the only remaining sanctuaries for many of Ethiopia’s indigenous and endemic plant and …

Resonant Collisions Of Potassium Atoms, Philip Michael Adamson

Honors Theses

This thesis discusses an approach to excite potassium atoms to very highly excited states (Rydberg states), and then tune their energy levels to induce resonant collisions between atoms. Potassium gas is super-cooled to 1 mK and confined to a small volume in a magneto-optical trap. A 405 nm laser diode, electronically locked to a potassium vapor cell via Doppler free spectroscopy, excites these atoms from the 4s_1/2 state (ground state) to the 5p_3/2 state. A 978 nm laser then excites the 5p_3/2 to nd_3/2 or nd_5/2 transition, creating Rydberg atoms. Since there is no ground …

The Impact Of Endocrine-Disrupting Chemicals On Wildlife Conservation, Eda Reed

Honors Theses

Endocrine-disrupting chemicals (EDCs), such as those from plastics and pesticides, have been hypothesized to affect wildlife populations. According to the U.S. National Institute of Environmental Health Sciences, EDCs ‘are chemicals that may interfere with the body’s endocrine system and produce adverse developmental, reproductive, neurological, and immune effects in both humans and wildlife.’ A growing number of studies suggest wildlife are being exposed to EDCs, but how EDCs affect wildlife health and wildlife conservation is less well-understood. Through scientific literature analysis and a survey of wildlife conservationists and practitioners, this study aims to determine the current state of knowledge and data …

Petrography, Mineralogy, And Geochemistry Of Greenish- And Reddish-Gray Siltstones Straddling The Vertebrate-Defined Permian–Triassic Boundary In South Africa, Jiawen Li

Honors Theses

The Permian–Triassic Mass Extinction (PTME) is considered the largest in Earth’s history, yet the terrestrial response is not well understood. The Karoo Basin, South Africa, hosts abundant exposures of terrestrial deposits that span the Permian– Triassic Boundary (PTB). The terrestrial PTB is defined by a turnover in vertebrate assemblage zones and has been associated with a transition from greenish-gray to reddish-gray siltstone. The current PTME model states that the siltstone color change is a reflection of aridification and eolian deposition, which is believed to represent rapid climate change directly linked with the event. Greenish- and reddish-gray siltstones were collected from …

Part I: Photochemical Generation Of Cyclohexyne From A Hydrocarbon Precursor Part Ii: A Triptycenyl Flower, Daniel Maurer

Honors Theses

Part I

Photolysis of phenanthrene-based methylenecyclopropane derivatives have previously been shown to generate alkylidenecarbenes, which readily rearrange to form alkynes. In this work, we show that photolysis of an analogous cyclic alkylidenecarbene precursor at ambi- ent temperature forms cyclohexyne via the putative cyclopentylidenecarbene, and can be trapped by dienes via a Diels-Alder reaction. Cyclohexyne and other strained cycloalkynes are of much interest to theoreticians and experimentalists alike. Results of coupled-cluster and DFT calculations on the potential energy surface of cyclopentylidenecarbene and the corresponding strained cyclohexyne are also presented. The photochemical generation of cy- clopentylidenecarbene, and thus cyclohexyne, from a hydrocarbon …

Phenanthrene...With A Twist!, Nicholas S. Kim

Honors Theses

The twisted and sterically hindered 4,5-dibromophenanthrene, was synthesized from 2,6-dibromoiodobenzene in a four-step pathway, or from 1,3-dibromobenzene in a three-step pathway. Then, 4,5-dibromophenanthrene was subjected to a Kumada coupling, leading to the synthesis of an even more twisted 4-bromo-5-tert-butylphenanthrene. Computational studies using density functional theory were performed to compare experimental and theoretical characteristics of these compounds, such as dihedral angles, optimized structures, and transition state energy barriers.

The purpose of these experiments is to fill gaps in chemical databases, synthesize more pronounced twists in normally planar phenanthrene molecules, and to ultimately synthesize 4,5-bis-tert-butylphenanthrene, which may have …

Pharmaceutical And Personal Care Products Concentrations In The Belgrade Lakes: A Possible Threat To Aquatic Ecosystems And Human Health, Serena Haver

Honors Theses

Pharmaceuticals and active ingredients from personal care products (PPCPs) include prescription and over-the-counter drugs, sunscreen, fragrances, and soaps. Recently researchers have detected PPCPs in surface waters, posing a threat to aquatic biota and human health. These compounds can enter the environment through dumping, direct excretion, or sewage effluent streams. We tested 14 water samples from East Pond, Great Pond, and Long Pond in Maine for the presence of 23 different PPCPs. Of those, we only detected significant levels of caffeine, 1,7-dimethylxanthine, and amphetamine all below 1µg/L. There were no significant differences between any of the three lakes for any of …

Experimental And Computational Study Of Methylphenylvinylidene And Its Rearrangements, Xi Yang

Honors Theses

In this study, the synthesis and properties were explored of the compound methylphenylvinylidene (MPV), a vinylidene carbene with methyl and phenyl groups as substituents. A phenanthrene-based precursor, 1-(1-phenylethylidene)-1a,9b-dihydro-1H-cyclopropa[l]phenanthrene, was synthesized in three steps and was subjected to photolysis in C₆D₆ at ambient temperature. During photolysis, the MPV carbene rearranged into 1-phenylpropyne via a 1,2-phenyl shift, instead of 1,2-methyl shift, confirmed by photolysis of ¹³C-labeled precursor. This experimental result is consistent with computational results using the CCSD(T)/cc-pVTZ//B3LYP/6-31+G* method. The calculations suggest that the 1,2-phenyl shift in singlet carbene requires 3.8 kcal/mol to overcome …

Using Genetic Algorithms To Evolve Artificial Neural Networks, William T. Kearney

Honors Theses

This paper demonstrates that neuroevolution is an effective method to determine an optimal neural network topology. I provide an overview of the NeuroEvolution of Augmenting Topologies (NEAT) algorithm, and describe how unique characteristics of this algorithm solve various problem inherent to neuroevolution (namely the competing conventions problem and the challenges associated with protecting topological innovation). Parallelization is shown to greatly speed up efficiency, further reinforcing neuroevolution as a potential alternative to traditional backpropagation. I also demonstrate that appropriate parameter selection is critical in order to efficiently converge to an optimal topology. Lastly, I produce an example solution to a medical …

Missing The Trees For The Forest: The Socioecological Significance Of Dispersed Farmland Trees In Northern Ethiopia, Jacob A. Wall

Honors Theses

Scattered trees are prominent features in the agricultural landscape of the Ethiopian highlands. The dry Afromontane forests of the Amhara Region in northern Ethiopia have faced centuries of deforestation - the FAO estimates only 3% of the region is forested today. The remaining landscape has been largely converted into agricultural and grazing lands, with the exception of some limited government-protected lands, as well as thousands of small forest fragments left around Orthodox Churches (“church forests”). But while a growing body of scholarship has highlighted the ecological and cultural importance of church forests and other natural forest fragments, the roles of …