10,754 Works

Data from: Evolution and Phylogeny of the Diptera: A Molecular Phylogenetic Analysis Using 28S rDNA Sequences

Markus Friedrich & Diethard Tautz
Portions of the large ribosomal subunit RNA gene (28S rDNA) encompassing the D1 and the D7 region were obtained from 16 dipteran species and families to reconstruct early phylogenetic events in the order Diptera. For outgroup comparison, the corresponding sequences were used from representative taxa of the Siphonaptera, Mecoptera, and Lepidoptera. A subset of 488 unambiguously alignable sites was analyzed with respect to important sequence evolution parameters. We found (1) sequence variability is significantly higher...

Data from: Geometric control of ciliated band regulatory states in the sea urchin embryo

Julius C. Barsi, Enhu Li & Eric H. Davidson
The trapezoidal ciliated band (CB) of the postgastrular sea urchin embryo surrounds the oral ectoderm, separating it from adjacent embryonic territories. Once differentiated, the CB is composed of densely arranged cells bearing long cilia that endow the larva with locomotion and feeding capability. The spatial pattern from which the CB will arise is first evidenced during pregastrular stages by expression of the pioneer gene onecut. Immediately after gastrulation, the CB consists of four separate regulatory...

Data from: Octopaminergic modulation of the visual flight speed regulator of Drosophila

Floris Van Breugel, Marie P. Suver & Michael H. Dickinson
Recent evidence suggests that flies' sensitivity to large-field optic flow is increased by the release of octopamine during flight. This increase in gain presumably enhances visually mediated behaviors such as the active regulation of forward speed, a process that involves the comparison of a vision-based estimate of velocity with an internal set point. To determine where in the neural circuit this comparison is made, we selectively silenced the octopamine neurons in the fruit fly Drosophila,...

Essays in Behavioral Decision Theory

Gerelt Tserenjigmid
Many different behavioral phenomena that cannot be rationalized by standard models in economics have been well-documented both in the real world and in lab experiments. Motivated by these behavioral phenomena, the purpose of this dissertation is three-fold. First, I develop axiomatic models of individual decision-making to explain these well-documented phenomena. Second, I derive the implications and predictions of these axiomatic models for intertemporal choice, asset pricing, and other economic contexts. Third, I provide connections between...

Carbonate-Associated Microbial Ecology at Methane Seeps: Assemblage Composition, Response to Changing Environmental Conditions, and Implications for Biomarker Longevity

David Hamilton Case
Methane seeps are globally distributed geologic features in which reduced fluid from below the seafloor is advected upward and meets the oxidized bottom waters of Earth’s oceans. This redox gradient fuels chemosynthetic communities anchored by the microbially-mediated anaerobic oxidation of methane (AOM). Both today and in Earth’s past, methane seeps have supported diverse biological communities extending from microorgansisms to macrofauna and adding to the diversity of life on Earth. Simultaneously, the carbon cycling associated with...

Design, Fabrication, and Mechanical Property Analysis of 3D Nanoarchitected Materials

Lucas Rosendo Meza
Recent developments in micro- and nanoscale 3D fabrication techniques have enabled the creation of materials with a controllable nanoarchitecture that can have structural features spanning 5 orders of magnitude from tens of nanometers to millimeters. These fabrication methods in conjunction with nanomaterial processing techniques permit a nearly unbounded design space through which new combinations of nanomaterials and architecture can be realized. In the course of this work, we designed, fabricated, and mechanically analyzed a wide...

Numerical Simulations of Droplet Aerobreakup

Jomela Chen-Chen Meng
The work presented in this thesis aims to bridge an existing gap in the state of droplet aerobreakup knowledge associated with the fundamental flow physics that govern the experimentally observable droplet morphologies. Using direct numerical simulations of the aerobreakup of water cylinders and droplets in the flow behind shock waves in air, we investigate the behavior of the surrounding gas flow to gain insight into the droplet’s deformation and evolution in the stripping breakup regime....

Two Roads to Planet Detection

Michael Bottom
One of the most exciting discoveries in astrophysics of the last last decade is of the sheer diversity of planetary systems. These include "hot Jupiters", giant planets so close to their host stars that they orbit once every few days; "Super-Earths", planets with sizes intermediate to those of Earth and Neptune, of which no analogs exist in our own solar system; multi-planet systems with planets smaller than Mars to larger than Jupiter; planets orbiting binary...

Temporal Control of Ion Channel Activation

Oliver Syed Shafaat
Ion channels are a large class of integral membrane proteins that allow for the diffusion of ions across a cellular membrane and are found in all forms of life. Pentameric ligand-gated ion channels (pLGICs) comprise a large family of proteins that include the nicotinic acetylcholine receptor (nAChR) and the γ-aminobutyric acid (GABA) receptor. These ion channels are responsible for the fast synaptic transmission that occurs in humans and as a result are of fundamental biological...

Cosmic Explosions: Observations Of Infant Hydrogen-Free Supernovae Towards An Understanding Of Their Parent Systems

Yi Cao
Radiation in the first days of supernova explosions contains rich information about physical properties of the exploding stars. In the past three years, I used the intermediate Palomar Transient Factory to conduct one-day cadence surveys, in order to systematically search for infant supernovae. I show that the one-day cadences in these surveys were strictly controlled, that the realtime image subtraction pipeline managed to deliver transient candidates within ten minutes of images being taken, and that...

I. Synthetic Studies Toward the Total Synthesis of Polycyclic Natural Products – Communesin F, Perophoramidine and Ineleganolide. II. Nickel Catalyzed Intramolecular C–O Bond Formation

Seojung Han
Expedient synthetic approaches to the highly functionalized polycyclic alkaloids communesin F and perophoramidine are described using a unified approach featuring a key decarboxylative allylic alkylation to access a crucial and highly congested 3,3-disubstituted oxindole. Described are two distinct, stereoselective alkylations that produce structures in divergent diastereomeric series possessing the critical vicinal all-carbon quaternary centers needed for each synthesis. Synthetic studies toward these challenging core structures have revealed a number of unanticipated modes of reactivity inherent...

Optomechanics with Superfluid Helium-4

Laura Anne De Lorenzo
We demonstrate the utility of superfluid helium-4 as an extremely low loss optomechanical element. We form an optomechanical system with a cylindrical niobium superconducting TE011 resonator whose 40 cm3 inner cylindrical cavity is filled with 4He. [1] Coupling is realized via the variations in permittivity resulting from the density profile of the acoustic modes. Acoustic losses in helium-4 below 500 mK are governed by the intrinsic nonlinearity of sound, leading to an attenuation which drops...

Essays in Econometrics and Political Economy

Sergio Montero
This dissertation comprises three essays in Econometrics and Political Economy offering both methodological and substantive contributions to the study of electoral coalitions (Chapter 2), the effectiveness of campaign expenditures (Chapter 3), and the general practice of experimentation (Chapter 4). Chapter 2 presents an empirical investigation of coalition formation in elections. Despite its prevalence in most democracies, there is little evidence documenting the impact of electoral coalition formation on election outcomes. To address this imbalance, I...

High-Latitude Ocean Convection and Gyre Dynamics

Zhan Su
High-latitude ocean deep convection substantially contributes to vertical mixing, vertical heat transport, deep-water formation, and sea-ice budget in the World Ocean. However, the extent of this contribution remains poorly constrained. The concept of ocean convective available potential energy (OCAPE) have been developed to improve the understanding and the prediction for these deep convection events. The kinetic energy (KE) budget of deep convection is explored analytically and numerically based on the observations in the Weddell Sea....

Some Advances in Computational Geophysics: Seismic Wave and Inverse Geodynamic Modeling

Dunzhu Li
In this thesis, I develop computational methods that link theory with geophysical observations, with one part devoted to the development of forward models of seismic wave propagation through the mantle and core, and a second part devoted to the inversion of viscous flow in the mantle. First order seismic structure of the earth has been well described radially since the PREM model was introduced. With the help of seismic tomography methods, many large-scale heterogeneous structures...

Unsteady Aerodynamics and Optimal Control of an Airfoil at Low Reynolds Number

Jeesoon Choi
As opposed to conventional air vehicles that have fixed wings, small birds and insects are known to flap their wings at higher angles of attack. The vortex produced at the tip of the wing, known as the leading-edge vortex (LEV), plays an important role to enhance lift during its flight. In this thesis, we analyze the influence of these vortices on aerodynamic forces that could be beneficial to micro-air vehicle performance and efficiency. The flow...

Origin of the Earth and Moon

Miki Nakajima
According to the giant impact hypothesis, the Moon formed from a disk created by an impact between the proto-Earth and an impactor. Three major models for this hypothesis are (a) standard model: a Mars-sized impactor hit the Earth; (b) fast-spinning Earth model: a small impactor hit a rapidly spinning Earth; and (c) sub-Earths model: two half-Earth sized planets collided. These models have been supported because they can explain several observed features of the Earth-Moon system,...

Shock Wave Propagation in Composites and Electro-Thermomechanical Coupling of Ferroelectric Materials

Vinamra Agrawal
How is material behavior at the macro scale influenced by its properties and structure at the micro and meso-scales? How do heterogeneities influence the properties and the response of a material? How does nonlinear coupling of electro-thermo-mechanical properties influence the behavior of a ferroelectric material? How can design at the micro-scale be exploited to obtain selective response? These questions have been topics of significant interest in the materials and mechanics community. Recently, new materials like...

Biomimetic Accommodating Intraocular Lens

Charles Meno Theodore DeBoer
The crystalline lens allows the eye to focus on near and far objects. During the aging process, it loses its ability to focus and often becomes cloudy during cataract formation. At this point, traditional medical therapy replaces the lens with an artificial replacement lens. Although replacement lenses for the crystalline lens have been implanted since 1949 for cataract surgery, none of the FDA-approved lenses mimic the anatomy of the natural lens. Hence, they are not...

Reverse Engineering and Quantifying Context Effects in Synthetic Gene Networks

Enoch Ho-Yee Yeung
In the first part of this thesis, we undertake a quantitative investigation of how compositional context, the spatial arrangement and relative orientation of genes, affects individual gene expression in a genetic network. Taking a synthetic biology approach, we construct a series of simple two-reporter biocircuits, each expressing either an mRNA aptamer or a fluorescent protein, and show that by varying the relative orientation of the two genes we obtain a wide range of gene expression...

Modeling the Effect of Vapor Wall Deposition on the Formation of Secondary Organic Aerosol in Chamber Studies

Renee Catherine McVay
Laboratory chamber experiments are used to investigate formation of secondary organic aerosol (SOA) from biogenic and anthropogenic precursors under a variety of environmental conditions. Simulations of these experiments test our understanding of the prevailing chemistry of SOA formation as well as the dynamic processes occurring in the chamber itself. One dynamic process occurring in the chamber that was only recently recognized is the deposition of vapor species to the Teflon walls of the chamber. Low-volatility...

Investigating the Death of the Early Paleozoic Moyero River Geomagnetic Superchron: Middle Ordovician Paleomagnetism from Estonia

Joseph Michael Grappone
Flat-lying Early and Middle Ordovician limestones exposed on the North margin of Estonia provide key insights into the early Paleozoic biosphere and climatic history of the Baltic Platform, and potentially offer a site for calibrating the duration of the proposed Moyero River Reversed Superchron. Past paleomagnetic analyses on these rocks have been focused primarily on determining paleomagnetic pole positions and have been hampered by relatively weak remanent magnetizations. We therefore applied techniques of the Rock...

An Experimental and Technoeconomic Study of Silicon Microwire Arrays for Fuel Production Using Solar Energy

Matthew Reed Shaner
Direct solar energy conversion is one of few sustainable energy resources able to wholly satisfy global energy demand; however, utility scale adoption and reliance are currently limited by the lack of a cost effective energy storage technology. The production of fuel from sunlight (solar fuels) enables solar energy storage in chemical bonds, a volumetrically and gravimetrically dense form compatible with current infrastructure worldwide. Hydrogen production via water splitting is a first generation solar fuel targeted...

Plasma Loop and Strapping Field Dynamics: Reproducing Solar Eruptions in the Laboratory

Quoc Bao Nguyen Ha
Coronal mass ejections (CMEs) are dramatic eruptions of large, plasma structures from the Sun. These eruptions are important because they can harm astronauts, damage electrical infrastructure, and cause auroras. A mysterious feature of these eruptions is that plasma-filled solar flux tubes first evolve slowly, but then suddenly erupt. One model, torus instability, predicts an explosive-like transition from slow expansion to fast acceleration, if the spatial decay of the ambient magnetic field exceeds a threshold. We...

Computational Microscopy: Turning Megapixels into Gigapixels

Roarke William Horstmeyer
The layout of a typical optical microscope has remained effectively unchanged over the past century. Besides the widespread adoption of digital focal plane arrays, relatively few innovations have helped improve standard imaging with bright-field microscopes. This thesis presents a new microscope imaging method, termed Fourier ptychography, which uses an LED to provide variable sample illumination and post-processing algorithms to recover useful sample information. Examples include increasing the resolution of megapixel-scale images to one gigapixel, measuring...

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