Phylogeny of North American aphaenogaster species (Hymenoptera: Formicidae) reconstructed with morphological and DNA data

DeMarco, Bernice Bacon Michigan State University 2015 해외박사(DDOD)

The ant genus Aphaenogaster Mayr is an ecologically diverse group that is common throughout much of North America. Aphaenogaster has a complicated taxonomic history due to variability of taxonomic characters. Novomessor Emery was previously synonymized with Aphaenogaster, which was justified by the partial mesonotal suture observed in A. ensifera Forel. Previous studies using Bayesian phylogenies with molecular data suggest Aphaenogaster is polyphyletic. Convergent evolution and retention of ancestral similarities are two major factors contributing to non-monophyly of Aphaenogaster . Based on 42 multi-state morphological characters and five genes, we found Novomessor more closely related to Veromessor Forel and that this clade is sister to Aphaenogaster. Our results confirm the validity of Novomessor stat. r. as a separate genus and it is resurrected based on the combination of new DNA, morphological, behavioral and ecological data. Twenty-three Aphaenogaster species (Hymenoptera: Formicidae) occur in North America. While morphology and ecology define most species, the species limits of a group in the Eastern United States are unclear. In particular, the morphological and behavioral characters once thought to define A. carolinensis, A. picea and A. rudis do not associate with their hypothesized species limits. These observations suggest that these species are not monophyletic. We therefore tested the monophyly of Aphaenogaster in the context of molecular phylogenetic analyses. We used DNA data from five genes: CO1, CAD, EF1&agr;F2, Long-wavelength Rhodopsin and Wingless to reconstruct phylogenies for 44 Aphaenogaster and outgroup species. In the resulting trees, reconstructed using parsimony and Bayesian inference, species boundaries associate with well-supported monophyletic clades of individuals collected from multiple locations. For example, A. carolinensis was monophyletic and a missing CAD intron was a diagnostic trait for the clade. However, some clades were unresolved, and A. picea and A. rudis were not monophyletic. Given the short branch lengths, these results suggest that these ants have likely recently radiated, and lack of gene lineage sorting explains the non-monophyly of species. Conversely, these results may indicate that clades of multiple species represent fewer but morphologically varied species. Additional biological information concerning pre- and post-mating barriers is needed before a complete revision of species boundaries for Aphaenogaster. Aphaenogaster Mayr 1853, contains 227 species worldwide (Bolton 2006) with 23 valid North American species, several species of which are hard to separate based on morphology alone (Umphrey 1996). The difficulty in identifying some of these species is due to limited diagnostic characters and to the lack of a comprehensive illustrated key. A recent analysis returned three species from Aphaenogaster to Novomessor, thus making Aphaenogaster in North America monophyletic (DeMarco and Cognato 2015). While many species have easily identifiable morphological characters, some east coast species within the A. rudis clade in North America are difficult to differentiate. Two of these species, A. carolinensis and A. miamiana, can be diagnosed using DNA. The gene CAD was missing an intron in those taxa. Four additional taxa, all identified morphologically as A. rudis, were found to be polyphyletic (DeMarco and Cognato, in prep, or see Chapter 2).

Singular perturbation methods in power system transient stability and dynamic security analysis

DeMarco, Christopher Lawson University of California at Berkeley 1982 해외박사

Quantum behavior of an atomic Fermi gas

DeMarco, Brian Leeds University of Colorado at Boulder 2001 해외박사(DDOD)

Results from the production and study of the first degenerate Fermi gas of atoms are presented. By adapting the magnetic trapping and evaporative cooling techniques that were used to produce atomic Bose-Einstein condensation, a gas of fermionic <super>40</super>K atoms is cooled into the quantum regime. The fundamental difficulty in cooling a gas of fermionic, compared to bosonic, atoms is the lack of rethermalizing collisions in a spin polarized sample. This obstacle is explored in cold collision studies and then overcome by magnetically trapping two spinstates of <super>40</super>K and developing a technique for simultaneous evaporative cooling. The ability to cool an interacting, two-component gas to one-quarter of the Fermi temperature is demonstrated. A spin-polarized, ideal gas can be cooled to as low as ∼0.17 times the Fermi temperature. The emergence of quantum behavior at low temperature is observed both as “excess” energy in the gas and a distortion of the momentum distribution compared to the classical expectation. Furthermore, the effect of the Fermi-Dirac statistics of the gas on individual collisions via Pauli blocking is observed through measurements of the thermal relaxation time.

Molecular and Systems Analysis of Cell-Cell Communication and Social Behavior in Trypanosoma brucei

DeMarco, Stephanie Francesca ProQuest Dissertations & Theses University of Cali 2019 해외박사(DDOD)

Endemic to sub-Saharan African, African trypanosomes are devastating protozoan pathogens that present a significant medical and economic burden. Transmitted by the bite of an infected tsetse fly, Trypanosoma brucei causes Human African Trypanosomiasis (HAT) and a related diseased called Nagana in animals. In both its tsetse fly and mammalian hosts, T. brucei closely interacts with host tissue environments. Parasites must traverse a number of tissue barriers and enact specific developmental changes to complete their transmission cycle. How T. brucei senses and responds to signals from its extracellular environment, however, is not well-understood. When tsetse fly midgut stage T. brucei is cultivated on a surface in vitro, they coordinate their movements to engage in a group behavior termed social motility (SoMo), an ability that requires sensing both surfaces and other cells then engaging signal transduction cascades to respond. Thus, investigating the mechanisms that control social motility may elucidate T. brucei signaling systems that are important for their transmission through their hosts in vivo. In vitro studies have demonstrated the importance of cAMP signaling in the regulation of social motility.This dissertation describes the use of molecular and systems-level analyses to investigate the regulation of social motility and signaling systems in T. brucei. Through labeling of tsetse fly tissues in conjunction with infection of fluorescently labeled T. brucei, we show that phosphodiesterase B1 (PDEB1) knockout parasites, which are unable to engage in SoMo, are blocked in a specific step in their fly transmission cycle, demonstrating the requirement for T. brucei cAMP signaling in vivo. To identify novel regulators of social motility that may or may not act in the cAMP pathway, two different RNA sequencing experiments were performed, leading to the identification of three novel candidate genes as potential social motility regulators. Additionally, we show that when engaged in SoMo, T. brucei exhibits positive chemotaxis toward a neighboring E. coli colony. Further characterization of T. brucei signaling systems will provide greater insight into how these deadly pathogens navigate through their hosts, potentially leading to new treatments and transmission-blocking agents.

The decision-making processes of nontraditional or for sale by owner (FSBO) home sellers engaged in the listing and sale of their homes

DeMarco, Valentin, Jr State University of New York at Albany 2016 해외박사(DDOD)

In spite of promises that the Internet would allow people to buy and sell their homes without intermediaries, real-estate agents still control approximately 90% of the transactions made in the 2.5-trillion-dollar residential real-estate industry. Existing literature has yet to provide conclusive arguments as to why the expected disintermediation has not occurred. Tentative arguments include claims that policy is biased in favor of agents, or that agents have a broader social network than their customers which helps them sell faster and for a better price. Most studies make the assumption that agents matter. They analyze the real-estate market from the perspective of the intermediaries (formerly called "middlemen") or agents/brokers/realtors, as opposed to the perspective of their clients. Furthermore, academic literature relies heavily on data provided by the National Association of Realtors, which fails to provide details on transactions that do not involve agents, or that involved them in limited ways. This study suggests an alternative viewpoint on the real-estate marketplace: that of sellers who decide to work without an agent and hence implement their own unique methods to list and sell their private residences. Their perspective is enlightening in several ways. First, sellers supply the asset (the house) and typically pay for the commissions of both the seller's agent (SA) and the buyer's agent (BA). Sellers are therefore the customers of real estate services in the real-estate industry, yet their perspective is largely overlooked. Rather home buyers, who often do not pay commission, are the focus of the NAR and much research. Furthermore, by looking at how individuals attempt to sell their homes without an agent, it is possible to unbundle the services that agents typically offer as part of the full-commission model. This allows observing concretely how sellers value different services and establish their relative importance in a real-estate transaction. In turn, knowing the value that sellers attribute to the various services helps explain why they choose to pay for some of these services, or to go at it alone. Finally, focusing on "for sale by owner" (FSBO or "fizbo") sellers helps us understand how people manage to navigate in a marketplace that is heavily biased in favor of agents during a time where information is available through information and communication technologies (ICTs). Given that so little is known about FSBO sellers, this study is exploratory. It does not aim to test particular hypotheses, but on the contrary to document the diversity of practices through which individuals gather information, understand the options that are available to them, make choices, and proceed to sell their homes. In order to do this, Hawkin's and Mothersbaugh's "Consumer Decision Model" is explained and incorporated into this study for structure. The model demonstrates the five steps a consumer experiences (right side of the model) while enabling us to examine multiple internal and external influences (left side of the model) that affect this decision process. Using a series of ethnographic interviews FSBOs were invited to tell their listing and selling stories while in the midst of this process and/or after experiencing a sale retrospectively. Some FSBO individuals were interviewed a second time to reflect in more detail on the experience they had gone through. Video recordings, websites, flyers and other documents they used were also gathered. Through these cases, this research presents the FSBOs at the time when they implemented their selling strategies and explores their reasons for doing so. This study gathers findings from a range of participants who possess different backgrounds and selling experience levels. Some of the subjects were first time home sellers and others had three FSBO selling experiences. We learn from their stories how these unique backgrounds, selling experiences, and other internal and external influences affected their decision processes to list and to sell. The ethnographic design and open-ended question format exposed the critical "whys" and "hows" of their individual and unique journeys. The findings from this study reveal evidence of seller activity to include extensive social networks, comprehensive market analyses, and ICT and Internet use that combined with a high level of individual determination. Sellers demonstrated the reasons why they had chosen this method to sell. They defined the value for the services they performed themselves, and presented what they felt was an appropriate commission or fee level to pay others for these same services. Sellers revealed details about the complexity of the agency relationship as it related to privacy, information asymmetry, and in some cases agent deceit or impeccable honesty. Sellers also demonstrated how they interacted with multiple real estate agents to share ideas, address market value discrepancies and price concerns, and handle agent cold-calls while using their own prior buying agents for current selling information. This study provides a foundation for a larger quantitative or mixed method research study and will serve to extend current models of information seeking and decision making in the literature.

Routes to Improved Light Harvesting in Thin Film Photoelectrochemical Devices: Examining Nanoscale Light Absorbers at the Metal Oxide Interface

DeMarco, Erica Jane Northwestern University 2013 해외박사(DDOD)

The continuous increase in energy demand is forcing our society to search for environmentally clean and sustainable energy sources, of which solar energy is of prominent interest. Efficient conversion of sunlight to electricity and storable fuels is a compelling challenge for modern science. Dye-sensitized solar cells (DSSCs) have received considerable attention as a cost-effective technology for light-to-electrical energy conversion. Improvements in device efficiency, however, are necessary in order to realize widespread implementation. One pathway toward improved efficiency is photocurrent enhancement through increased light harvesting. The incorporation of silver nanoparticles (Ag NPs) into planar, DSSC photoelectrodes has afforded enhanced performance through amplification of light absorption of the dye sensitizer through localized surface plasmon resonance (LSPR). To explore the fundamental properties of this architecture, various metal oxide thin films, grown by atomic layer deposition (ALD), were employed to investigate the influence of dielectric environment on photocurrent enhancement in DSSCs containing Ag NPs supporting LSPR. The same planar architecture was used to evaluate plasmonic enhancement of cadmium selenide (CdSe) quantum dots (QDs), which exhibit superior light absorption relative to dye molecules. The enhancement effect was observed to sustain the exciton lifetimes in QDs and to strongly depend on the incident photon wavelength following the plasmon resonant strength of Ag NPs, confirming that the enhanced photoluminescence was mainly due to the enhancement in photon absorption (light harvesting) in CdSe QDs by the plasmon of Ag NPs. The calculated fluorescence enhancement factors suggest that a unique combination of nanostructured metal and quantum-confined semiconductors are a promising route to increasing light harvesting in photoelectrochemical (PEC) devices. The conversion of sunlight to hydrogen by means of photocatalysis is one of the most interesting ways to achieve storable, renewable energy. In order to potentially address stability issues involving hole corrosion of CdSe in PEC devices, ultrathin hole-conducting NiO films made by ALD were characterized using the oxygen evolution reaction and investigated as a prospective hole scavenger in semiconductor-semiconductor photocatalytic systems for the reduction of water. The effect of the surface linker structure on hole transfer times from the QD to NiO was examined using time-resolved fluorescence spectroscopy.

Sick Time: Medicine, Management, and Slavery in Louisiana and Cuba, 1763-1868

DeMarco, Liana ProQuest Dissertations & Theses Yale University 2022 해외박사(DDOD)

Modern, capitalist ideas of productivity became central to medicine under slavery. They shaped how physicians treated enslaved patients, crafted a scientific basis for medicine, and conceived of themselves as a profession. Between the late eighteenth century and the mid-nineteenth century, white male physicians in Louisiana and Cuba distinguished themselves from other healers: first, by aligning with Spanish colonialism, and then, by making themselves essential to a new form of plantation management that used clock-time discipline, hierarchical divisions of labor, and complex accounting systems. As these technologies became widespread in sugar and cotton production, they helped planters precisely interpret enslaved health and illness in terms of productivity. Physicians, who were seeking a rigorous foundation for medical knowledge production, latched onto planter methods of calculating and controlling enslaved health. One of those methods was what planters and physicians called “sick time,” which was an allotment of time away from work intended to manage illness enough for enslaved people to return to work.However, as physicians used plantation management to cast an air of scientific accuracy over their knowledge, enslaved people reconfigured their own medical practices to make themselves less visible and countable. Drawing on nineteen archives across the United States, Cuba, and Spain; plantation account books; agricultural trade journals; medical journals; medical dissertations; travel accounts; narratives of formerly enslaved people; and medical ethnographies, this dissertation traces the encounters between slavery management, physician medicine, and enslaved medicine. I show how enslaved people used their health and healing practices to subvert plantation time discipline, while physicians became the preferred medical consultants for managers and remained so after emancipation.

A Nurse-Driven Protocol to Increase Metabolic Screening and Interventions for Inpatients on Antipsychotic Medications

DeMarco, James T ProQuest Dissertations & Theses Yale University 2022 해외박사(DDOD)

Patients on antipsychotic medications are at higher risk of developing metabolic syndrome; nevertheless, metabolic screening for patients on antipsychotics is suboptimal. This project implemented a nurse-driven protocol on inpatient psychiatric units to increase metabolic screening compliance rates. The literature on improving metabolic screening as well as the clinical use of nurse-driven protocols were used to develop a protocol. The initial implementation of the protocol showed no change in screening rate; however, when the protocol was updated to include nursing leader involvement, metabolic screening increased. Nurses’ perception of the nurse-driven protocol was examined and found a negative perception and no change in empowerment when nurses were surveyed pre- and post-implementation. Further research is needed to better understand adoptability of nurse-driven protocols in the psychiatric inpatient setting as well as other applications, such as smoking cessation or safety sitters.

The architecture, design, and electromagnetic and thermal modeling of a retinal prosthesis to benefit the visually impaired

DeMarco, Stephen Christopher North Carolina State University 2003 해외박사(DDOD)

This dissertation describes the design and study of a retinal prosthesis for individuals who have suffered loss of vision from degeneration of the outer retina. Retinitis pigmentosa and age-related macular degeneration lead to blindness through progressive loss of retinal photoreceptors. Experiments reveal that direct electrical stimulation of remaining ganglion cells in degenerate retina elicits visual percepts in blind RP/AMD patients. This motivates research toward the development of a retinal prosthesis system involving an implantable stimulator microchip to compensate the defective photoreceptors. Many prostheses do not reside fully inside the body, but consist of an implantable stimulation unit and an external unit. This underscores a need in the retinal prosthesis to deliver power and support high-speed bi-directional communication with the implant wirelessly. The current progress in the types of non-invasive connections to bio-implants is reviewed as it relates to the power and communication needs of prostheses. The extraocular unit is a hardware-reconfigurable system based on FPGA technology which produces real-time instructions for the implantable micro-stimulator IC. The current retinal stimulator IC is designed to provide electrical stimulation to the remaining ganglion cells of post-degenerative retina. Also described is a design technique to significantly reduce the on-chip area of the stimulus circuits. This yields more output channels per chip area, thereby raising the stimulation resolution. Temperature elevation in the eye and head tissues associated with the retinal prosthesis is studied. A high resolution 2D human head and eye model is developed at 0.25mm spatial resolution with associated dielectric and thermal properties suitable for numerical simulations. The Finite Difference Time domain method (FDTD) with material independent absorbing boundary conditions is used to predict the specific absorption rate (SAR) induced from electromagnetic exposure to wireless inductive telemetry with the implant. A detailed heating pattern in the eye tissues due to the SAR and power dissipation in the implanted stimulator is computed using a time-domain numerical implementation of the bioheat equation.

Holomorphic families of rational maps: Dynamics, geometry, and potential theory

DeMarco, Laura Grace Harvard University 2002 해외박사(DDOD)

Let <italic>L</italic>(<italic>f</italic>) = ∫ log ||<italic>D</italic><italic> f</italic>|| <italic>d</italic>μ<italic>_f</italic> denote the Lyapunov exponent of a rational map, <italic>f</italic> : <bold>P</bold><super> 1</super> → <bold>P</bold><super>1</super>. For any holomorphic family of rational maps {f_λ : λ ∈ <italic>X</italic>} of degree > 1, we show that <italic>T</italic>(<italic>f</italic>) = <italic> dd<super>c</super>L</italic>(<italic>f</italic>_λ) defines a natural, positive (1,1)-current on <italic>X</italic> supported exactly on the bifurcation locus of the family. If <italic>X</italic> is a Stein manifold, then the stable regime <italic>X − B</italic>(<italic>f</italic>) is also Stein. In particular, each stable component in the space Rat<italic>_d</italic> (or Poly<italic>_d</italic>) of all rational maps (or polynomials) of degree d is a domain of holomorphy. We introduce an SL₂ <bold>C</bold>-invariant homogeneous capacity in <bold>C</bold><super>2</super>, and derive the following formula for the Lyapunov exponent of a rational map of degree <italic>d</italic>: <display-math> <fd> <fl>L<fen lp="par">f<rp post="par"></fen>=<sum align="c"></sum> G<inf>F</inf><fen lp="par">c<inf>j</inf><rp post="par"></fen> -<rf>log</rf>d+<fen lp="par">2d-2<rp post="par"></fen><rf>log</rf> <fen lp="par"><rm>cap<hsp sp="0.265"><mit>K<inf>F</inf></mit> </rm><rp post="par"></fen>.</fl> </fd> </display-math>Here <italic>F</italic> : <bold>C</bold><super>2</super> → <bold> C</bold><super>2</super> is a homogeneous polynomial lift of <italic>f</italic>; |det <italic>DF</italic>(<italic>z</italic>)| = ∏|<italic>z</italic> <math> <f> ∧</f> </math> <italic>c_j</italic>|; <italic>G_F</italic> is the escape rate function of <italic>F</italic>; and cap <italic>K_F</italic> is the homogeneous capacity of the filled Julia set of <italic>F</italic>. We show, moreover, that the capacity of <italic>K_F</italic> is given explicitly by the formula <display-math> <fd> <fl><rm>cap<hsp sp="0.265"><mit>K<inf>F</inf><hsp sp="0.212"> <rm>=<hsp sp="0.212">&vbm0;Res<fen lp="par"><mit>F</mit><rp post="par"></fen> &vbm0;^{-1/<mit>d<fen lp="par">d-<rm>1</rm><rp post="par"></fen> </mit>},</rm></mit></rm></fl> </fd> </display-math> where Res(<italic>F</italic>) is the resultant of the polynomial coordinate functions of <italic>F</italic>. For a general compact, circled and pseudoconvex set <italic>K</italic> ⊂ <bold> C</bold><super>2</super>, we show that the Levi measure (determined by the geometry of ∂<italic>K</italic>) is the unique equilibrium measure for the homogeneous capacity. Such <italic>K</italic> ⊂ <bold>C</bold><super> 2</super> correspond to metrics of non-negative curvature on <bold>P</bold><super> 1</super>, and we obtain a variational characterization of curvature.