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Full-waveform Inversion of Seismic Input Motions in a Near-surface Domain
No full textThis research aims to develop a new inverse modeling approach to allow engineers to identify the spatial and temporal distribution of unknown seismic input motion (i.e., incoming seismic wavefield) in a near-surface domain by using sparsely-available measurement data of vibrational motions in the domain.Because existing methods are limited due to complexity, inaccuracies, and uncertainties, this research explores a new computational method for identifying seismic input motion. The main body of this dissertation is composed of three main Chapters. First, Chapter 2 considers out-of-plane (henceforth, SH) wave motions in a two-dimensional (2D) bounded domain. The partial-differential-equation (PDE)-constrained optimization framework is employed to search a set of control parameters, by which a misfit between measured responses at sensors on the top surface induced by targeted traction and their computed counterparts induced by estimated traction is minimized. To mitigate the solution multiplicity of the presented inverse problem, we employ the Tikhonov (TN) regularization on the estimated traction function and test its performance. We present the mathematical modeling and numerical implementation of both optimize-then-discretize (OTD) and discretize-then-optimize (DTO) approaches. We also compare their performances with each other. The finite element method (FEM) is employed to obtain the numerical solutions of state and adjoint problems. Newton's method is utilized for estimating an optimal step length in combination with the conjugate-gradient scheme, calculating the desired search direction, throughout a minimization process. The numerical results in Chapter 2 present that, first, the complexity of a material profile in a domain increases the error between reconstructed traction and its target. Second, the OTD and DTO approaches lead to the same inversion result. Third, when the sampling rate of the measurement is equal to the timestep for discretizing estimated traction, the ratio of the size of measurement data to the number of the control parameters can be as small as 1:12 in the presented work. Fourth, it is acceptable to tackle the presented inverse modeling of dynamic traction without the TN regularization. Fifth, the inversion performance is more compromised when the noise of a more significant level is added to the measurement data, and using the TN regularization does not improve the inversion performance when noise is added to the measurement. Sixth, our minimizer suffers from solution multiplicity less when it identifies dynamic traction of lower frequency content than that of higher frequency content.Second, Chapter 3 presents a new inversion modeling method for reconstructing complex, incoherent seismic input motions in a domain that is truncated by a wave-absorbing boundary condition (WABC). In a set of numerical examples, targeted dynamic traction at the WABC mimics seismic incident wavefield, and FEM is used to solve state and adjoint problem. In Chapter 3, we use only the DTO approach without any regularization because the numerical examples in Chapter 2 show that the DTO approach performs as successfully as the OTD counterpart, and the TN regularization is not necessary.The numerical results in Chapter 3 show that the incident, inclined plane waves, cannot be fully reconstructed by using the sensors only on the top surface. It is necessary to include a vertical array of sensors on the side boundary of a domain. Second, the minimizer suffers more from solution multiplicity when it identifies traction of a higher dominant frequency. Third, the inversion solver can reconstruct traction of a complex, realistic seismic signal. Lastly, the error between the reconstructed traction and its counterpart is slightly higher in a two-layered background domain with inclusions than in a single-layered counterpart with inclusions.In Chapters 2 and 3 of the presented work, the material proprieties of the domain are assumed to be known in advance. This assumption does not always hold in realistic settings. Chapter 4 is focused on investigating the feasibility of resolving this challenge, in structural health monitoring problem settings where the proprieties are not known, by using a new joint inversion perspective. Accordingly, Chapter 4 presents a computational study to investigate the feasibility of simultaneous identification of a material property of a Timoshenko continuous beam and a moving vibration source on the beam by using the data of measured vibrations. The finite element method is employed to solve the wave equations of a Timoshenko beam subject to a moving vibrational source. It uses the Genetic Algorithm (GA) as an inversion solver to identify the values of targeted control parameters that characterize the material property of the beam and a moving vibration source. The numerical results in Chapter 4 show that the presented inversion method can detect the characteristics of a moving wave source as well as the spatial variation of the elastic modulus of a Timoshenko-beam continuous bridge model, which is set to be piece wisely homogeneous in this computational study.The contributions of the presented dissertation are as follows. Our newly-developed adjoint equation-based inverse-source procedure can fully reconstruct seismic traction inputs propagating into a multi-dimensional, bounded heterogeneous soil domain and in a domain truncated by using WABC. We also found that it is feasible to identify the characteristics of a moving wave source as well as the spatial variation of the elastic modulus of a Timoshenko-beam continuous bridge model by using measured vibration data induced by a random moving wave source (e.g., a vehicle).Civil engineeringComputer engineeringGeophysical engineeringFull-waveform Inversion, Incoherent dynamic traction inversion, Inverse problem, limited seismic measurement data, PDE-constrained optimization, Seismic Input Motions in a Near-surface DomainCivil EngineeringDegree Awarded: D.Engr. Civil Engineering. The Catholic University of Americ
Protective immunity against Plasmodium berghei infection: characterization of liver tissue resident memory CD8 T cells according to fine specificities and functional attributes
No full textApproximately one-third of the world’s population is at risk for malaria infection. According to the WHO 2018 report, there were 219 million cases of malaria and 435,000 deaths, mostly in Sub-Saharan Africa and Southeast Asia. Plasmodium parasites are the causative agents of malaria and Plasmodium falciparum is considered the most deadly. In the mammalian host, malaria infection begins when a Plasmodium-infected female Anopheles mosquito deposits sporozoites (spz) into the skin during its blood meal. From the skin, spz travel to the liver and invade hepatocytes where they undergo development into liver stage (LS) parasites, before being released as merozoites that infect red blood cells; this last stage marks the start of clinical malaria. Exposure to infectious Plasmodium spz induces anti-disease immunity, but does not lead to protective immunity against repeated spz infections. In contrast, immunization with radiation-attenuated spz (RAS) induces lasting protective immunity. Like infectious spz, RAS infect hepatocytes but undergo developmental arrest in the liver, and thus are unable to infect red blood cells and cause clinical malaria. The liver-arrested parasites express liver stage antigens (LS Ags) such as the middle domain of initiation factor 4G-, (MIF-4G protein); serine hydroxymethyltransferase (SHMT); and sporozoite and liver-stage asparagine-rich protein (SLARP). These LS Ags activate adaptive immune cellular responses, which are required for protection against infectious spz challenge. The immunization of mice with Plasmodium berghei (Pb) RAS induces lasting protection, and liver CD8 T cells are considered the key effectors. Two distinct populations of liver CD8 T cells are involved in protection: central memory (TCM) and effector memory (TEM). Recently, a third population of memory CD8 T cells, termed tissue resident memory (TRM) cells, has been shown to target Plasmodium LS Ag following infection with spz. In malaria, liver CD8 TRM cells appear to induce lasting protective immunity by participating in the surveillance of liver sinusoids and eliminating LS parasites. Despite these numerous findings, our understanding of the interactions of these different liver CD8 T cell subsets in protective immunity induced by LS Ags remains incomplete. Therefore, in this project we focused on the characterization of CD8 T cells in an attempt to facilitate a better understanding of the cellular requirements necessary for the induction of lasting and sterile immune protection by malaria vaccines. Specifically, we sought to identify protective immunity, functional attributes, and fine peptide specificities of LS Ags -induced liver CD8 T cells in the Pb animal model of protective immunity. Using C57Bl/6 (B6) mice, we demonstrated that immunization with Pb RAS by the intravenous (IV) but not by intradermal (ID) route leads to development of protection against infectious spz challenge. There are several reasons for the superior protection induced by IV; among them is the ability of IV immunization to induce different liver CD8 T cell subsets especially CD8 TRM cells. Protection, as determined by liver parasite burden (LPB), was induced by 3 Pb LS Ags: MIF-4G, SHMT, and SLARP. Like Pb RAS-induced protection, protective immunity induced by the 3 LS Ags was CD8 T cell dependent. CD8 T cells arising from immunization with the Pb LS Ags exhibited discrete peptide recognition patterns. Kb17 peptide, derived from MIF-4G Ag, induced CD8 TRM cells by Prime-Trap immunization. Importantly, immune responses against the Kb17 peptide were MHC class I restricted and were partially mediated by the in vivo secretion of IFN. In summary, the results from this study provide new critical information regarding correlates of protection induced by Pb LS Ag-specific cellular immune responses against Pb spz challenge.Immunologyliver stage, malaria, resident memory, tetramerBiologyDegree Awarded: Ph.D. Biology. The Catholic University of Americ
(In)citing action to realize an equitable future
No full textNeuron, Volume 106, Issue 6, 17 June 2020, Pages 890-894.Reference lists of neuroscience articles show marked gender imbalances. To mitigate this disparity, we discuss relevant ethical considerations and offer practical recommendations to scientists of all ages. We envision an equitable future by all scientists for all scientists. Reference lists of neuroscience articles show marked gender imbalances. To mitigate this disparity and realize an equitable future, Dworkin et al. discuss relevant ethical considerations and offer practical recommendations to trainees, senior scientists, laboratory heads, editors, reviewers, mentors, and instructors
Exterior view of Lincoln Park United Methodist Church
No full textExterior view of Lincoln Park United Methodist Church on North Carolina Avenue NE. Signs are visible in the doorway
Robert Lowry: Last stand: Letters to my psychiatrist
No full textUnpublished letters from writer Robert Lowry to his psychiatrist Dr. Maxwell - edited and with an introduction and commentary by James Reidel
Sign on the door of Copycat Co. on H Street NE
No full textSign on the door of Copycat Co. announcing delivery and takeout only services, contact information, hours of operation, and where to follow the bar on social media. The sign features and illustration of dinosaurs
Corporate governance in entrepreneurial firms: a systematic review and research agenda
No full textSmall Business Economics, Volume 54, Issue 1, 1 January 2020, Pages 43-74.This systematic review covers the extant literature on corporate governance in entrepreneurial firms. Using a sample of 137 research papers published from pre-1990 through June 2018 in 60 journals, we categorize outlets, research methods (quantitative, qualitative, review, and non-empirical), theoretical perspectives, and research questions, highlighting key patterns. We then summarize the concepts under study in the sample literature, and the geographical sources and model specification of quantitative empirical studies. The conclusion highlights the quite fragmented nature of the field and the substantial knowledge gaps, and then proposes an actionable agenda for future research in terms of theories, research questions, research settings, and research designs. In particular, we describe the need to explore how corporate governance mechanisms interact with one another and affect firm outcomes, by applying novel theoretical perspectives and methods that could provide a better understanding of entrepreneurial firms’ functioning
Self-compassion, body dissatisfaction, and disordered eating
No full textThe current study assesses a self-compassion writing task as an intervention for body dissatisfaction in women with varying levels of disordered eating while considering the effects of both positive and negative affect as well as shame. Seventy-one women between the ages of 18 and 30 completed several questionnaires along with a 15-minute self-compassionate letter writing task. Intervention interacted with disordered eating to predict changes in body dissatisfaction, such that those with less disordered eating were less dissatisfied with their bodies following the self-compassion writing task, B = -0.015, se(B) = 0.006, t(64) = -2.694, p = 0.009. There was an indirect effect of intervention on changes in body dissatisfaction through changes in shame, B = -0.142, se(B) = .063, 95% CI = -0.278, -0.032. There was a significant reduction in negative affect, F(1, 68) = 7.829, p = .007, partial η2 = .103, and shame, F(1, 68) = 8.106, p = .006, partial η2 = .107, in the self-compassion group. This study provides support for the use of self-compassionate letter writing as an intervention for body dissatisfaction in women with low levels of disordered eating and demonstrates that such interventions can be useful in reducing shame and negative affect more generally.Psychologyaffect, body dissatisfaction, disordered eating, self-compassion, shamePsychologyDegree Awarded: M.A. Psychology. American Universit
