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Robust, Secure, and Efficient Key Generations Based on Physical Unclonable Functions
No full textSilicon physical unclonable functions (PUFs) are integrated circuits that produce specific measurements by exploiting the mismatch between circuits. They are widely considered in secret key generations. However, PUF outputs are biased and not precisely reproducible, which causes security and robustness issues. In addition, in most cases, one PUF cell returns only one-bit data, which is inefficient. This dissertation discusses robustness, security, and PUF-efficiency issues and presents some contributions to these aspects.Traditionally, robustness and security issues are addressed by error correction codes and debiasing schemes, respectively. In this dissertation, a key generation scheme based on wiretap polar codes is designed to address robustness and security issues together. First, the PUF-based key generation process is modeled as a wiretap channel system. Then, secure polar codings are designed for the wiretap channel system based on density evolution and Reed-Muller codes. Comparison results show that this work requires fewer PUF outputs than state-of-the-art for generating the same length key with a failure rate less than or equal to 10^(-6). To increase PUF efficiency, a non-binary response extraction scheme based on the number of `1\u27s in PUF bits is proposed. First, a one-probability distribution model is established based on the beta distribution to make analysis easy. An estimation method based on the posterior distribution of the one-probability and a maximum likelihood estimation is used to estimate the parameters of the one-probability distribution. The area under the probability density function of the one-probability is uniformly divided into several zones. The non-binary response is the zone index where the one-frequency falls in. The possibility of more entropy extraction is proved by building a new compound distribution based on the beta and binomial distributions. This design is implemented on a field-programmable gate array (FPGA). The experimental results show that this design increases the entropy of responses. In addition, the bit error rate and bias of the extracted non-binary responses are evaluated. The proposed key generation scheme based on wiretap polar codes can robustly and securely generate keys using non-binary responses
Cholinergic Modulation of the Gerbil Medial Nucleus of Trapezoid Body
No full textThe superior olivary complex (SOC) is a major computation center in the brainstem auditory system. It is well known for its function in calculating sound location based on acoustic cues. Within SOC, the medial nucleus of trapezoid body (MNTB) serves a major source of inhibition. MNTB receives contralaterally derived excitatory input and subsequently project well-timed inhibitory output to principal sound-localization nuclei in the SOC as well as other computationally important centers. Acoustic information is conveyed to MNTB neurons through a single calyx of Held excitatory synapse arising from the cochlear nucleus. The encoding efficacy of this large synapse depends on its activity rate, which is primarily determined by sound intensity and stimulus frequency. Therefore, in complex acoustic environment where sound level and composition vary, it is imperative to employ modulatory system to dynamically adjust the encoding capability of MNTB neurons to optimize the computation of MNTB and hence, the broad SOC circuitry.One potentially potent neuromodulator is the acetylcholine (ACh)-mediated cholinergic system. Happe and Morley (2004) discovered prominent expression of acetylcholine receptors (AChRs) in rat SOC, suggesting possible engagement of cholinergic modulation. Upon activation, AChRs could affect neurotransmitter release when located pre-synaptically, and could adjust neuron excitability in response to input when situated post-synaptically, rendering ACh a suitable candidate for modulatory duties in the SOC region. Despite previous reports of high expression levels of cholinergic receptors in the SOC, few studies have addressed the functional role of acetylcholine in the region, specifically in the MNTB, which serves as a pivotal relay between the entry point of acoustic information and the sound-localization circuitry. My dissertation is poised to probe the cholinergic modulation in this region. Strategically, we first anatomically identify the source of cholinergic input to the SOC by deposition of retrograde tracer in situ at SOC, in order to predict the cholinergic function and to design experiment that allow us to investigate endogenous cholinergic signaling. This study revealed not only the sound-driven nature of the cholinergic sources, but also their wide involvement in cognitive function, such as attention. Next, we use in vivo extracellular recording technique with piggyback multi-barrel electrode to pharmacologically manipulate AChRs, while monitoring the sound-evoked responses of MNTB in real time. This study demonstrated the contribution of ACh in enhancing auditory encoding and improving signal detection from noise. Lastly, we physiologically characterize the cellular mechanism underlying increased responsiveness of MNTB by using in vitro patch clamp technique. This study unmasked the mechanism that the enhancement of MNTB excitability was due to the inactivation of a voltage-dependent potassium channel by ACh
Cryptosporidium attachment to functionalized surfaces
No full textCryptosporidium is a protozoan parasite that causes severe gastrointestinal disease worldwide. Originally, Cryptosporidium was recognized as an opportunistic pathogen in immunocompromised patients but can also be found in immunocompetent hosts – typically causing asymptomatic or otherwise self-limited infections. The Cryptosporidium life cycle begins with the ingestion of food or water contaminated with oocysts, followed by an excystation process in the small intestine, infection of the intestinal epithelial cells, and lastly the production of oocysts that are then excreted and released into the environment. Despite intervention via water treatments and regulatory compliance by water suppliers, sporadic outbreaks of infections have occurred due to the oocysts\u27 small size (4-8 ?m) and chlorine resistance.Previously, the transport of C. parvum oocysts in aquatic environments was found to be influenced by interactions with naturally occurring environmental biofilms. In this body of work, polydopamine (PD) – which exhibits similar chemical moieties to that of naturally occurring environmental biofilms and serves as an excellent coating material due to its strong adhesion properties – was functionalized onto glass substrates to explore its capacity for C. parvum oocyst attachment under varying water chemistries and induced shear forces (Chapter 2). An unexpected discovery was made while observing the attachment of C. parvum oocysts to PD surfaces: the elicitation of excystation. PD surfaces decorated with glycosaminoglycans (GAGs) were shown to provide an additional stimulus for excystation – thus this study presents a potential non-cellular trigger for excystation that can easily be built into PD surfaces (Chapter 3). Our results suggest that the glycocalyx or some surface-expressed receptor plays a key role in the induction of excystation, with GAGs serving as a mediating effect.A review of the current state of knowledge on modelling Cryptosporidium oocyst – surface interactions was conducted where we examine the deviation of experimental results from theoretical predictions by the Derjaguin, Landau, Verwey, and Overbeek (DLVO) theory classical colloid filtration theory (CFT) (Chapter 4). For computational expediency, previous studies have applied DLVO modeling to C. parvum oocyst adhesion and transport using the limiting cases of constant electrostatic potential (CP) or constant charge (CC). However, these assumptions fail to accurately consider the charge regulation (CR) effect. This phenomenon occurs as an ionizable surface approaches another surface in an aqueous system there is an overlap of the surface\u27s electric double layers (EDL) resulting in the variation in the electrostatic potential, charge, and pH that occurs as a function of separation distance. Thus, the CR – zeta potential (?) approach was applied to PD aggregates and C. parvum oocysts by analyzing zeta potential data obtained at multiple pH and ionic strength values in order to obtain the equilibrium constants (K) and site densities (N) of the dominant surface functional groups that best represent the electrostatic properties of the surface (Chapter 5). These resultant values were then used to demonstrate the variations in surface charge, electrostatic potential, and pH that can occur as the charge-regulated surfaces interact.Elucidating novel factors involved in attachment and excystation of oocysts would contribute toward a myriad of potential applications, such as inactivation or disinfection strategies relevant for water treatment, the development of therapies against Cryptosporidium infection, and the design of collector surfaces for oocyst detection and removal from aquatic systems
Which causal structure do you prefer?: Domain specificity and persistency of causal structure belief
No full textWe are surrounded by incessant causal events in the world. Causal events can exist in different structures or relationships, such as where events are linked in a chain (causal chain), where one cause creates other events (common cause), or many events create one effect (common effect). While beliefs about what causal structure exists between events are crucial in our everyday causal reasoning, the nature of causal structure preferences remains a puzzle. Do people have default causal structure beliefs for how causal events are most likely interrelated? This study explored this question by examining whether people have a consensus belief of what causal structure is most plausible in five domains (natural, artifacts, social, mental health, and physical health) in Experiment 1. Results told that people have consensus causal structure beliefs in preferred structures. I examined how strongly and permanently these beliefs are held in Experiment 2. It is possible that the causal structure belief is created at the moment to answer a question and is not a strongly held belief or people internally represent a causal structure to apply to causal events in a domain and the belief is strongly held. Results showed that people maintain strong structure beliefs
Design and Implementation of a Novel Apparatus for the study of Ultracold 6Li
No full textCold atom apparatuses have proven to be an invaluable tool in quantum many-body studies as they provide a platform for quantum simulations. These systems allow us to explore thousands of avenues related to neutron stars, novel technologies, quantum many-body physics and many more. Since joining the Sommer Laboratory group, I have made significant contribution to the design and construction of an ultracold 6Li apparatus. In this work I describe the design of a \u27two-part\u27 vacuum system for the injection and manipulation of lithium atoms. Additionally, I describe the lasersystems necessary to cool and capture hot lithium atoms to temperatures on the order of several hundred micro-kelvin. Finally I discuss the design and performance of our built apparatus at the time of this dissertation\u27s submission. I will also give a brief overview of research that has led up to this point in the field of atomic physics followed by a description of our atomic apparatus and the future application of this apparatus
Making Black Power Pay: Black Banking in Philadelphia, 1900 - 1930
No full textMaking Black Power Pay: Black Banking in Philadelphia 1900 – 1930 examines Black efforts to create community and self-sufficiency through finance in early twentieth century Philadelphia. It argues that Black Philadelphians utilized Black economic nationalism, the process of retaining and circulating the Black dollar within the Black community for the benefit of Black people, to challenge the Jim Crow system of discrimination and craft safter self-sustaining communities. They did this through the development of financial institutions which drew on local resources and redistributed wealth through lending. This process required the organizing and economic work of Black men and women which is termed inter-gender mutualism. Inter-gender mutualism refers to the way Black men and women pooled their political, social, and economic resources to work toward the common goal of community building. Furthermore, it asserts that financial community building in Philadelphia required inter-gender cooperation at the organizing, operational, and investment level to be successful. This dissertation uncovered that Black Philadelphians utilized Black business and banking to offer housing and employment opportunities to Black people to create safe spaces from the growing enactment of social, political, and legal acts of discrimination collectively termed Jim Crow. As these Black institutions became successful the community funneled their newly acquired collective power to expand safe economic and social spaces and challenge political discrimination in Pennsylvania
Non-Instructional Teacher Time Use During Preparation Time
No full textTeachers are given preparation time during the school day to complete necessary tasks, however, research shows that teachers continue to work longer hours than their peers in the past. Researchers have identified non-instructional teacher time use, which are the tasks teachers need to complete that are not directly related to instruction, as a possible reason for increased workloads. The literature on non-instructional teacher time use, however, has major gaps due to a weak definition and a lack of focus in educational studies. The purpose of this study was to explore the time and composition of non-instructional teacher time use tasks during preparation time for elementary teachers. The goal of the study is add to the literature on non-instructional teacher time use as well as identify solutions that may lead to a reduction in tasks for teachers. Fifteen elementary teachers from one school district in eastern Pennsylvania agreed to participate in the study. Participants entered each non-instructional teacher time use task that occurred during their contracted preparation time during the school day. Participants also recorded the time it took to complete each task. The study ran for ten school days over a two week period during September 2022. Overall, the findings revealed that elementary teachers spent nearly half of their allotted preparation time on non-instructional teacher time use, which was far higher than reported in other literature. A list of specific tasks, the frequency of each task, the average duration of each task, and the total duration of each task were recorded. The compilation of the specific task data create a database for future researchers to compare individual tasks. The identification of trends among tasks could help administrators to better address and possibly alleviate non-instructional teacher time use tasks for teachers
Promoting the Generalization of Direct Support Professional Prompting Skills When Working with Adults with Autism
No full textThe number of direct support professionals (DSPs) needed to support the increasing numbers of adults diagnosed with autism within the United States continues to grow exponentially. DSPs receive minimal training and often fail to generalize the training they have received, which can directly lead to poor learning outcomes for the adults they serve. The purpose of this study was to develop a generalized training package designed to promote the generalization of an evidence-based practice (i.e., systematic prompting procedures) across various instructional plans, in different domain areas (e.g., personal care, vocational, daily living), environments, and adults. A concurrent multiple probe design across three staff participants working with six adult participants was used to test a two-phase staff training intervention on the generalization ofprompting. The training was delivered in two phases. The first phase consisted of the traditional behavioral skills training (BST) package with a single exemplar (plan 1). Although there were improvements from baseline in staff prompting during intervention 1 for the instructional plan taught (plan 1), the DSPs did not generalize to untrained plans 2 and 3 or the generalization plan. Therefore, all participants received the second phase of the intervention, BST incorporated into a general case training package, training plans 1-3. Staff prompting then met criteria for instructional plans 1-3 and generalized to an untrained plan. The secondary dependent variable, adult engagement during their target tasks, showed moderate effects for adult participants on at least one plan, but their improvements were inconsistent across staff and adults
Poly (lactic Acid) Modification To Impart Toughening And Enhance Biodegradation: Elucidation Of Mechanisms
No full textConventionally, two major factors navigate polymer resin and modifier selection: mechanical performance and price. Recently, material sustainability is growing in importance due to a reduction in the total amount of energy used and in the amount of plastics pollution. Industrial reduction, re-use, and recycling of energy is economically compelling, creating space in the market for innovative approaches to achieve material sustainability. At-home composting is becoming a viable option as demand for single-use plastics and consumer 3D-printing continues to bustle. Polylactic acid (PLA) is a high performing bio-based biodegradable polyester resin that has piqued the interest of materials scientists and engineers for its application in these niche markets. However, its uniquely brittle behavior limits its potential applications and requires toughness modification to slow the rate to failure when cracked. This concept is proven to work in the toughness modification of cross-linked epoxy and thermoplastic Polystyrene (PS) resins.Neat PLA resin is typically amorphous and produced through condensation polymerization. PLA resin�s mechanical behavior: stiffness, strength, and toughness, mimic that of PS and Polyamide 6 (PA6), which are two common 3D-printing resins. However, the PLA resins back-bone chemical structure has an affinity to undergo hydrolysis, reversing its polymerization reaction when exposed to heat and moisture. Melt-processing PLA resin modified with soft and biodegradable Multifunctional Particles (MP) yields a 200% higher elongation to break, 10% improvement in toughness, and rate of thermal and environmental degradation enhancement in the resin. Rigid Hemp Fibers (HF) are a secondary bio-sourced modifier added to formulate hybrid PLA resins retaining biodegradability. The use of solution, thermal, and mechanical treatments are performed on HF modifier prior to melt-processing. The treatments are investigated for their effect on the rate of degradation, stiffness, and strength enhancement imparted on PLA resin by the HF modifier. The Young�s Modulus of PLA resin is improved up to 20%. The strength reduction imparted by the MP modifier is mitigated up to 24%. The toughness of PLA resin is synergistically enhanced by hybrid modification 20%.In summary, bio-sourced modifiers improve the toughness, stiffness, strength, and degradation of PLA resin because of synergized hybridization. PLA resin�s propensity to craze and fracture strain energy release rate was accelerated by modification. Hybrid modification of PLA resin induces biodegradation mechanisms that exhibit preferential composting soil environments. Hybrid PLA resins can be applied in melt-processing applications: 3D-printing filament, extrusion, and compression molding to achieve plastics processing material sustainability and reduce plastics pollution of materials used in the plastics industry. The melt-processes employed in this study are proof of concept for further broadening of modified PLA resins melt-processing applications. The biodegradation enhancement imparted by PLA resin modification is a significant finding for solving plastics pollution
Developing Enzyme-Sensitive Peptide-Polymer Conjugates for Cell-Mediated Scaffold Degradation
No full textSynthetic, biodegradable polymer-based scaffolds have been used for tissue engineering, but the mismatch between scaffold degradation rate and new tissue formation limits complete regeneration. For example, rapid scaffold degradation fails to provide mechanical support as new tissue forms. However, scaffolds that degrade too slowly after tissue has already formed leave behind voids that compromise tissue mechanics. Designing scaffolds that degrade via cell-mediated processes allows for concurrent tissue growth to facilitate complete tissue regeneration in critical-sized tissue defects. The overall goal of this work focuses on developing biomaterials that degrade in response to cell-mediated processes that occur during tissue formation and remodeling. To achieve this, we integrated an enzyme-sensitive peptide sequence into the backbone of a biodegradable polymer polycaprolactone (PCL)-based conjugate. We identified a fast-degrading (FD) peptide sequence KRVKRRLLMET that rapidly degrades during cell culture by multiple cell types. We also generated a scrambled version of this peptide (ScFD) with the same amino acids LTRLMEKRRKV (ScFD) to demonstrate sequence specificity. We conjugated these peptides to PCL to generate PCL-peptide-PCL conjugates for scaffold fabrication. We characterized scaffold degradation in response to collagenase and cells. The FD conjugate scaffold degraded significantly more than the ScFD conjugate scaffolds over 21 days in the presence of collagenase. This proof-of-concept study showed we can fabricate solid, protease-degradable scaffolds. Notably, the peptide sequence can be modified to tailor degradation rates and target other cell and tissue types. This work lays the groundwork for cell-mediated degradation of solid polymer scaffolds