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Examining the Effect of Microbial Community on CRISPR-Cas Activity in Enterococcus Faecalis
No full textEnterococcus faecalis is an opportunistic pathogen involved in causing various hospital-acquired
infections. Their propensity to develop antibiotic resistance by horizontal gene transfer via
conjugative mobile genetic elements makes the treatment of E. faecalis infection increasingly
difficult. Pheromone-responsive plasmids are involved in the transfer of mobile genetic elements
in E. faecalis. CRISPR-Cas acts as a barrier against foreign genome transfer in bacteria. E.
faecalis CRISPR-Cas activity varies in vivo (murine intestinal model) and in vitro. The
functional differences may be due to various biotic and abiotic factors such as nutrient
availability, community diversity, donor-to-recipient ratios, and cas9 regulatory differences. A
previous study has shown that the efficacy of CRISPR-Cas varies in the presence of a microbial
community. Here we study the effect of Escherichia coli, also a resident of the mammalian gut,
on CRISPR-Cas defense in vitro using E. faecalis containing pAM714 plasmid. Through our
work, we are able to demonstrate that CRISPR-Cas efficacy is not altered by the presence of E.
coli during conjugation between donor OG1SSp (pAM714) and recipients T11RF and
T11RFΔcas9. Our goal is to provide insights into CRISPR-Cas function of Gram-positive
bacteria in the microbial community
Hannah Höch: Unmasking Gender Myths of the Weimar Republic
No full textThe work of artist Hannah Höch questions social constructions of gender in early twentieth century Germany. In her series From an Ethnographical Museum (1924-1930), Höch’s use of
photomontage functions as a mode of shock to destabilize what were then normative values
within art and gender. Through this series, she potentially comments on women's status as a
lesser gender in Weimar German society, satirizing gender ideals of beauty. However, she does
so by the figure of the African other, thus appropriating one culture for the uplift of another. The
series is an ironic commentary on women's treatment in Weimar Germany — a culture that
equated women to what society considered primitive people, such as those of the tribes in Africa
and Oceania — prompting Höch to include tribal and ethnographic references in this series
Speech Perception of Hearing-impaired Listeners in Challenging Listening Environments and Personalization of Hearing Assistive Devices via Inverse Reinforcement Learning
No full textListening to a speech in presence of a noise has always been a challenge specially for individuals
with hearing impairment. There are many aspects that needs to be considered in designing and
fitting of hearing assistive devices to provide users with a more preferred hearing experience or
increase the perceived quality of speech and decrease the listening effort. This dissertation focuses
on this topic in two major research thrust. In the first research thrust, the speech perception of
hearing impaired listeners has been studied in challenging hearing environments. Behavioral and
electrophysiological experiments have been designed to evaluate the effect of speech and noise
levels on the perceived quality of speech and selective auditory attention in normal hearing and
hearing impaired listeners. The perception of degraded speeches in normal hearing and hearing
impaired listeners have been measured and the differences between the hearing patterns in these
groups have been described. It has been shown that to achieve an optimal hearing experience, the
listener’s hearing situation should be taken into account. In the second research thrust, the
maximum likelihood inverse reinforcement learning approach has been followed to develop an
algorithm to personalize the hearing aids fitting in an online manner. The results of the experiments
conducted on subjects with hearing loss demonstrates the outperformance of the developed
personalized setting over the standard prescriptive setting
The Algebraic Geometry of Character Varieties of Double Twist Links
No full textThe thesis focuses on the study of SL2(C) character varieties for hyperbolic 3-manifolds,
which encode topological information about the manifold such as the number of cusps and
the genus. Specifically, the thesis explores the canonical component of the character variety of
the double twist link J(2m+1, 2m+1), which contains a character corresponding to a discrete
faithful representation. Even though character varieties have been used to study the topology
of hyperbolic 3-manifolds, there is still a lot we don’t know about their properties. The
thesis investigates the canonical component of character variety of two-component double
twist links, which form an infinite family of two-bridge links, and fills a gap in previous
research (Petersen and Tran, 2016) by proving that the singularities obtained in that paper
are of order one. The main result of the thesis is Theorem 1.0.1, which states that the
desingularization of the projective model for the canonical component of SL2(C) character
variety of the double twist link J(2m + 1, 2m + 1) is a rational surface isomorphic to P1 × P1
blown up at 6m + 1, for m ≥ 1 and (−6m − 3) times if m ≤ −2
Optimal Control of Human Balance Models With Reflex Delay
No full textFalls are the leading cause of injury-related deaths among the elderly, and scientists are
increasingly interested in understanding the mechanism of human balance control. A
single inverted pendulum is used to model the musculoskeletal dynamics of the human
body with an ankle torque. There is a brief period of time between detecting a problem in
proper positioning and applying torque to correct it. We present a mathematical optimal
control model with delay for identifying human balance postural dynamics considering
humans as a single inverted pendulum with an ankle torque. The equation of motion is a
second-order delay differential equation, and it is solved numerically. Optimal feedback
gains obtained from the optimal control problem with linear quadratic regulator function
vary in time for a short period of time before becoming constant. These optimal feed-
back gains are time and delay-dependent to compensate for the effect of the delay. We
provide numerical simulations for different parameter values and scenarios to investigate
human postural dynamics’ stability and demonstrate the model’s capabilities. Finally, we
extend our study by investigating the dynamics of ankle and hip movement in response
to perturbations using a double-inverted pendulum
Theoretical Study of Electronic Transport in Two-dimensional Materials
No full textTheoretical methods are critical for evaluating two-dimensional materials as possible channel
materials in future field-effect transistors (FETs). The majority of modeling attempts concentrate on electronic transport in ideal free-standing layers, ignoring the dielectric environment’s effect on transport characteristics. We study the carrier transport in two-dimensional
(2D) transition metal dichalcogenides (TMDs) by extending our Monte-Carlo model for a
free-standing monolayer to include the effect of dielectric environment on the 2D layer. The
major effects of the dielectric environment are the dielectric screening and the scattering of
electrons with the coupled (hybrid) optical-phonon/plasmon excitations that are present at
the interfaces in a field-effect transistors with a channel consisting of a monolayer of a polar
semiconductor (TMDs) with top and bottom gates in a double-gate geometry.
We perform an extensive study of the electron mobility in supported and/or gated monolayer
TMDs in the presence of dielectric environment, to study of the carrier mobility of six TMDs
(MoS2, MoSe2, MoTe2, WS2, WSe2, and WTe2) with all TMDs assumed to be supported by
SiO2 and with SiO2, HfO2, Al2O3, AlN, and hBN as gate insulators.
The carrier mobility improves significantly when considering only the effect of dielectric
screening by the free carriers and the surrounding dielectrics. However, these positive effects
are countered by the detrimental effects due to the interface plasmon/phonon (IPP) scattering. The carrier mobility decreases significantly below its value in free-standing monolayers
with increasing dielectric constant of the insulator(s). The carrier mobility decreases almost
monotonically with increasing dielectric constant of the gate insulator, with two exceptions:
1. The beneficial effects of dielectric screening of the ‘out-of-plane’ field lines are seen for
hBN, thanks to its relatively low ionic polarization and the high phonon frequencies
resulting from the light weight of the B and N ions.
2. On the contrary, resonance effects among the optical phonons of the substrate, of the
TMD layer, and of the top oxide result in a low carrier mobility when AlN and/or
Al2O3 are taken as gate insulators.
We also evaluate the temperature dependence, carrier density dependence and the dependence of the dielectric constant of the 2D layer on the carrier mobility in the presence of the
dielectric environment. We then extend our model to evaluate the high-field characteristics
and simulate a 2D material based field effect transistor (FET), considering the TMD as the
channel. Despite the TMDs having a low electron mobility, in most cases, under the effect
of dielectric environment. Though we see a comparable carrier mobility with hBN as gate-
insulator, the comparatively low dielectric constant of hBN negates the scaling benefits of
high-κ insulators. Unfortunately, the transport properties of the ideal stack of gate-insulator
of HfO2 with SiO2 as substrate and the 2D TMD between them, remain disappointing
Molokhya: First-person Filmmaking and Trauma Articulation
No full textThis practice-based research and creative dissertation experiment with and document how first-
person documentary filmmaking aids the process of articulating trauma. In a conventional realist
documentary style, I directed a first-person documentary titled Molokhya featuring my
experience with sexual assault. In this dissertation, I claim that the process of first-person
filmmaking is ideal for articulating trauma and for creating a fantasy of healing. In Chapter 2, I
argue that first-person documentary filmmaking has the potential to create what Elaine Scarry
calls a language of agency and what Alisa Lebow calls a first-person plural. However, as a
Muslim and Arab woman, my agency is often represented in Western media (including some
feminist films) as something I lack. Therefore, in Chapter 3, I examine representations of sexual
violence against Muslim and Arab women in several documentaries within the archive of the
feminist organization Women Make Movies (WMM). I argue that the films included in WMM
about the rape of Arab and Muslim women perpetuate what I call a double alienation: Muslim
women survivors of sexual assault face the emotional trauma of assault, and they also have to
endure the damaging effect of questioning their own religion as the source of their oppression.
But where do we go from here? Is a transnational feminist collaboration between the Global
North and the Global South even possible within the contemporary neoliberal discourses? These
questions guide the work of Chapter 4, in which I introduce Between Women Filmmakers
Caravan as an example of transnational feminist solidarity in praxis through filmmaking and
exhibition
Magnetic Properties and Coordination Polymerization of Lanthanide Phosphate Complexes
No full textThe intrinsic properties of lanthanides give steric and electronic advantages in rare earth
organometallics. Lanthanides have the potential to accomplish unique applications which cannot
be done using transition metals. The first chapter describes the structure of the lanthanide
complexes and the potential applications of the f block chemistry because of their magnetic and
catalytic properties. The second chapter highlights a discrete neodymium complex for the
polymerization of dienes and polar vinyl monomers. The study of the kinetics of polymerization
shows a quasi-living polymerization which is beneficial to control the molecular weight and
synthesize new materials using block copolymers.
The third chapter focuses on the application of polynuclear lanthanide organophosphate complexes
as molecular magnets. Lanthanide organophosphate complexes based on a triethyl phosphate
ligand have been prepared using azeotropic distillation to explore their structure and properties.
Single crystal X-ray diffraction studies show isomorphic complexes having a unique one-dimensional polymer with the bridging ligand connecting the LnIII ions. A series of the three
lanthanide coordination polymers display the phosphate groups as an irregular distorted
tetrahedron. These complexes were synthesized in search of new single-molecule magnets. SQUID
magnetometry studies show high magnetic susceptibility
Aerodynamic Design and Control of Vertical Axis Wind Turbines
No full textThe need to combat climate change and find alternate solutions to fossil fuel is at an all time
high. Researchers continue to drive the advancement of wind turbine technology since it is a
viable alternate solution towards a sustainable future. With the advancement of wind turbine
technology over the last 20 years, horizontal axis wind turbines (HAWTs) particularly have
received more attention. But there is an alternate turbine configuration called vertical axis
wind turbine (VAWTs). Some of the advantages of VAWTs over HAWTs are namely, it’s
independent of wind direction, low sound emissions, easy access to turbine components like
generator and gearbox (due to placement at tower base) and lower topside center of gravity
compared to HAWTs. This thesis focuses on the aerodynamic design study and development
of control strategy of conventional troposkein shaped Darrieus vertical axis wind turbines
(VAWTs) using CACTUS (Code for Axial and Crossflow TUrbine Simulation), which is
a 3D numerical vortex based lifting line aerodynamic model. The first half of the thesis
focuses on the detailed aerodynamic design study of VAWTs and how the selection of various
design variables affect this design process. This study systematically analyzes the effect of
different design variables including the number of blades (N), aspect ratio (AR) and blade
tapering in a comprehensive loads analysis of both the parked and operating aerodynamic
loads including turbine power performance analysis. The second half of the thesis focuses on the development of a novel method to control rotor dynamics named intracycle RPM
control strategy, for VAWTs. VAWTs perform sub-optimally in regions 2 and 3 due to the
absence of a pitch mechanism and low starting torque, which significantly affects their annual
energy production. But introducing a pitching mechanism in VAWTs also takes away one
of its biggest advantages over its competitors, which is mechanical simplicity. An alternate
control strategy named intracycle RPM control or intracycle angular velocity control is
presented, where the rotational speed of the turbine is allowed to vary with the azimuthal
location of blades, which is able to alter the rotor inflow conditions to maximize power
output while having constraining the loads. With the help of an optimizer named GPOPSII, which optimizes the rotational speed over a single revolution at a particular wind speed,
coupled with CACTUS, which measures the performance of the rotor, it is shown that the
aerodynamic AEP can be increased while restraining loads at prescribed limits
Grid Forming Energy Router: A utility interface for Renewable Energy Sources and Energy Storage Grid Integration Applications
No full textLarge scale integration of Renewable Energy Sources (RES) (Solar/Photovoltaic (PV), Fuel
Cells (FC), wind) with smart devices into the grid is becoming an attractive concept to
meet increasing energy demand and to reduce stress on the conventional grid. Smart grid
which is an advanced automated power grid is a fascinating idea of bringing RES closer
to centralized generation with smart sensing devices, advanced control and integrated communications. This convergence provides more reliable and efficient renewable power while
reducing the carbon footprint, with reduction in power transmission distance, cost and associated transmission losses. However, intermittent nature of RES impacts power quality, grid
stability and reliability, which makes it imperative to integrate RES with Energy Storage
(ES) for their widespread adoption. Also, real-time control of data, information exchange,
and energy management in smart grid are crucial for a fast, reliable, and secure system.
Thus, the design of a utility interface known as Energy router (ER) for RES, ES, and grid
integration application, which is smart, intelligent, portable, resilient and easy to operate
was the primary source of motivation for this research.
This dissertation discusses the design and development of ER architecture and control for
RES, ES, and grid integration application. To ensure seamless interaction and power transfer
(bidirectional, if required) among the RES, ES, grid, and load, in ER a compact and efficient
Multi-Port Converter (MPC) is required. Apart from selection of suitable MPC and hence,
the structure for ER, the ER control also needs attention. Due to the presence of inverterbased RES with zero/low inertia, the ER does not respond dynamically to frequency changes
and leads to frequency swings during load disturbances which can cause load tripping issues.
This dissertation discusses the development of control for ER, which enables ER to synchronize autonomously with the grid and emulate the behavior of Synchronous Machine (SM) to
stabilize and regulate the voltage and frequency of the system during disturbances. This is
done by adding virtual inertia and damping into the system and the control is known as Grid
Forming (GFM) droop control. To harvest maximum performance efficiency, real-time and
dynamic control with energy management from ER in the smart-grid network this dissertation also explores the development of a dedicated communication module to be integrated
with the ER.
First, the proposed ER architecture and it’s control were simulated in MATLAB/Plecs and
various operating scenarios were evaluated. Simulation results prove the viability of the ER,
and its control algorithm for various operating scenarios involving RES and ES systems.
Subsequently, the ER blocks were implemented using GaN devices and experimentally verified. Measurements indicate that this small-scale laboratory prototype is able to transfer
around 1.2kW of power in both directions between battery and dc bus