Observational signatures of the macroscopic formation of strange matter during core collapse supernovae

Zach, Juergen Johann The Ohio State University 2003 해외박사(DDOD)

소속기관이 구독 중이 아닌 경우 오후 4시부터 익일 오전 9시까지 원문보기가 가능합니다.

The consequences of a first order QCD phase transition in the protoneutronstar remnant of a core collapse supernova are presented with a special focus on the effects on neutrino transport. A secondary focus is the detection of these neutrinos in terrestrial detectors. Hybrid stars are constructed such that a coexistence region of QCD-confined and deconfined phases forms in the protoneutronstar interior with possibly a pure deconfined phase in the center. The resulting Coulomb lattice (1D, 2D and 3D) in the coexistence region is shown to crystallize for temperatures relevant in supernova cores seconds after bounce. Droplet deformation modes freeze out in the same range. For the outermost ∼1 km of the coexistence region, the stability of the 3D lattice to shear stresses falls below the critical range of mechanical energy densities provided by hydrodynamical flow. This can lead to a non-spherical relief structure which, together with the enhanced neutrino opacity of the coexistence lattice; can result in anisotropic neutrino transport and therefore neutron star kicks. A computer model for neutrino diffusion coupled with quasistatic evolution of a solid lattice phase and hydrodynamical treatment of the confined matter envelope was developed to address the kick model and other problems. The state of newly formed hybrid stars is determined using a self-consistent approach of integrating the stellar structure equations with the constraint of heat flow equilibrium, resulting in relatively cool energy spheres (<italic>T</italic> ∼ 1 MeV) compared to <italic>T</italic> ∼ 10 MeV in the interior. Typical cooling timescales of hybrid stars are then τ ∼ 100 sec. This is shown to result in a statistically significant signal in a Pb-neutron spallation detector. In exploratory calculations, observed kick speeds were reproduced and the presence of a sustainable convective flow pattern to maintain a crater in the coexistence region was verified. The Pb and Fe components of a proposed neutron spallation neutrino detector concept were optimized with respect to cost-efficiency. DAMOCLES, a transport code for neutrons, capture γ rays and scintillation photons was developed for that purpose. The detection efficiency for liberated neutrons for the optimum configurations in both detectors is 38%. The available sensitivity to sparse neutrino signals is ∼1/(sec × kT) for expected radioactive background rates.

When is "enough" enough? An investigation of the information-seeking and stopping behavior of senior arts administrators

Zach, Sarah Elizabeth University of Maryland College Park 2002 해외박사(DDOD)

소속기관이 구독 중이 아닌 경우 오후 4시부터 익일 오전 9시까지 원문보기가 가능합니다.

Among managers, those who are responsible for nonprofit organizations in general and arts organizations in particular have been an understudied group. These managers have much in common with their for-profit counterparts, but their environment also differs in significant ways. The goal of this exploratory research effort was to identify how senior administrators in fine arts museums and symphony orchestras go about identifying and acquiring the information they want to complete a range of management tasks. Deciding when and where to look for information, obtaining the “right” information at the time it is needed, evaluating its credibility and utility, and determining when “enough” information has been collected are challenges facing this group of information users every day. A multiple-case studies design involving a replication strategy was selected to structure the research process. Data were collected from twelve arts administrators using a pre-tested interview protocol that included the Critical Incident Technique. Patterns in the data were identified, and the data were further reviewed for disconfirming evidence. The study resulted in a list of the types and sources of information arts administrators use as well as a list of the factors or <italic>stopping criteria</italic> that influence them to end the information-seeking process. A model describing the way in which arts administrators go about acquiring the information they want was also developed. The main findings of the study are (1) arts administrators do not consider information seeking to be a discrete management task, (2) they rely heavily on direct personal experience to fill their information-seeking needs, and (3) they are “satisficers” when it comes to seeking information. Since arts administrators have not been studied in the context of LIS research before, understanding more about where arts administrators go for information, how much effort they are willing to invest in seeking information, and how they decide when they have “enough” information provides insights into the information-seeking behavior of a new user group. Furthermore, although this research effort is focused on specific users in a specific field, the methodology and results from this study may be transferable to similar investigations in other fields.

The role of discourse context and verb class in native and nonnative Spanish postverbal subjects

Zach, Ariel A Georgetown University 2016 해외박사(DDOD)

소속기관이 구독 중이 아닌 경우 오후 4시부터 익일 오전 9시까지 원문보기가 가능합니다.

Recent research on the second language (L2) acquisition of postverbal subjects in Spanish has focused on the important role of discourse context in licensing postverbal subjects with unaccusative and unergative verbs (Hertel, 2003; Lozano, 2006; Dominguez & Arche, 2008; Dominguez, 2013). While these studies have made important advances in early L2 research within the generative framework, in which the structure was studied as a part of the pro-drop parameter (White, 1985; 1986, Liceras, 1988; 1989), they only examine intransitive verbs, do not consider the role of nuclear stress, and do not compare postverbal subject use across discourse contexts nor include contrastive focus as a discourse context. These shortcomings have led to variable performance by the native speaker controls, which make any claims of native or non-native like performance on the part of L2 learners questionable. This dissertation uses empirical data to incorporate discourse context, verb type, and nuclear stress into one experiment examining postverbal subjects in Spanish by native speakers and English-speaking L2 learners. A multi-componential experiment was conducted, consisting of two oral assessment tasks, in order to gauge native speakers' and L2 learners' ability to produce and rate sentences with postverbal subjects compared to those with preverbal subjects. It considers three discourse contexts: wide, narrow, and contrastive focus, four verb types: unaccusative, unergative, transitive, and ditransitive verbs, and transitive verbs with topicalized objects. Ninety-five L2 learners from four proficiency levels and thirty-seven native speaker controls completed the study. Results show that for the contexts in which native speakers most frequently use postverbal subjects, namely with topicalized objects and in contrastive focus, L2 learners from low through advanced proficiency can also use postverbal subjects, and knowledge of postverbal subjects increases significantly with proficiency. The optionality of pre- and postverbal subjects in narrow and contrastive focus is explained syntactically by positing a null pro[FOC] that can optionally be used in the numeration along with the lexical subject when it bears matching agreement and focus features. The Feature Reassembly Hypothesis (Lardiere, 2008; 2009) can explain L2 behavior by positing difficulty in reassembling the features from one lexical item in English, the lexical subject, to two lexical items in Spanish, the lexical subject and pro[FOC].

Controlling size dispersity, morphology and spatial orientation of nanostructures by electrodeposition and chemical vapor deposition on highly oriented pyrolytic graphite

Zach, Michael Paul University of California, Irvine 2002 해외박사(DDOD)

소속기관이 구독 중이 아닌 경우 오후 4시부터 익일 오전 9시까지 원문보기가 가능합니다.

With current manufacturing methods for electronics running into serious limitations of size, structures that self assemble from small, perfect building blocks—individual atoms, molecules, and ions—are one possibility for making smaller structures. The criticism most often expressed concerning self-assembly is lack of uniformity in fabricated structures and poor control over making patterns needed for making complex devices. The research presented here addresses some of these issues. Properties of materials are often size dependent—especially in the size range below 100 nm. Early attempts to electrochemically grow uniform particles failed due to problems that can be attributed with overlapping diffusion layers. Hydrogen Coevolution Electrodeposition Technique (HCET) is a new method for depositing materials using high overpotentials to rapidly evolve hydrogen bubbles for mixing the electrolyte solution right at the interface of developing particles thereby minimizing problems associated with the depletion layer. Wires ranging from a few nanometers to nearly a micron in diameter with lengths of up to hundreds of microns can now be made millions at a time by the simple benchtop techniques of Electrochemical Step Edge Decoration (ESED). Differences between basal plane surfaces and reactive step edges can also be exploited to grow dielectric coatings on steps by Chemical Vapor Deposition of Step Edge Decoration (CVD-SED) by highly water reactive precursors that react with water adhering to edges. In addition to parallel arrays of wires used for sensors, other potentially useful structures can be made. Wires can be structured by controlling the step edges. Methods for cleaving the graphite, thermal etching, chemical modification the step edges, and masking steps with dielectric coatings can all be used as tools to modify the final structure of metals, metal oxides, semiconductors and dielectrics which can now be deposited.

Hilbert's finitism: Historical, philosophical, and metamathematical perspectives (David Hilbert)

Zach, Richard University of California, Berkeley 2001 해외박사(DDOD)

소속기관이 구독 중이 아닌 경우 오후 4시부터 익일 오전 9시까지 원문보기가 가능합니다.

In the 1920s, David Hilbert proposed a research program with the aim of providing mathematics with a secure foundation. This was to be accomplished by first formalizing logic and mathematics in their entirety, and then showing—using only so-called finitistic principles—that these formalizations are free of contradictions. In the area of logic, the Hilbert school accomplished major advances both in introducing new systems of logic, and in developing central metalogical notions, such as completeness and decidability. The analysis of unpublished material presented in Chapter 2 shows that a completeness proof for propositional logic was found by Hilbert and his assistant Paul Bernays already in 1917–18, and that Bernays's contribution was much greater than is commonly acknowledged. Aside from logic, the main technical contribution of Hilbert's Program are the development of formal mathematical theories and proof-theoretical investigations thereof, in particular, consistency proofs. In this respect Wilhelm Ackermann's 1924 dissertation is a milestone both in the development of the Program and in proof theory in general. Ackermann gives a consistency proof for a second-order version of primitive recursive arithmetic which, surprisingly, explicitly uses a finitistic version of transfinite induction up to <math> <f> <g>w</g>^{<g>w</g>^<g>w</g>}</f> </math>. He also gave a faulty consistency proof for a system of second-order arithmetic based on Hilbert's &egr;-substitution method. Detailed analyses of both proofs in Chapter 3 shed light on the development of finitism and proof theory in the 1920s as practiced in Hilbert's school. In a series of papers, Charles Parsons has attempted to map out a notion of mathematical intuition which he also brings to bear on Hilbert's finitism. According to him, mathematical intuition fails to be able to underwrite the kind of intuitive knowledge Hilbert thought was attainable by the finitist. It is argued in Chapter 4 that the extent of finitistic knowledge which intuition can provide is broader than Parsons supposes. According to another influential analysis of finitism due to W. W. Tait, finitist reasoning coincides with primitive recursive reasoning. The acceptance of non-primitive recursive methods in Ackermann's dissertation presented in Chapter 3, together with additional textual evidence presented in Chapter 4, shows that this identification is untenable as far as Hilbert's conception of finitism is concerned. Tait's conception, however, differs from Hilbert's in important respects, yet it is also open to criticisms leading to the conclusion that finitism encompasses more than just primitive recursive reasoning.

Innovations in Randomization Inference for the Design and Analysis of Experiments and Observational Studies

Branson, Zach Harvard University ProQuest Dissertations & Theses 2019 해외박사(DDOD)

소속기관이 구독 중이 아닌 경우 오후 4시부터 익일 오전 9시까지 원문보기가 가능합니다.

Mechanisms of Scale Invariance in Embryonic Patterning Systems

Collins, Zach M Harvard University ProQuest Dissertations & Theses 2018 해외박사(DDOD)

소속기관이 구독 중이 아닌 경우 오후 4시부터 익일 오전 9시까지 원문보기가 가능합니다.

A Framework for Performance-Based Evaluation of Liquefaction Effects on Buildings

Bullock, Zach University of Colorado at Boulder ProQuest Dissert 2020 해외박사(DDOD)

소속기관이 구독 중이 아닌 경우 오후 4시부터 익일 오전 9시까지 원문보기가 가능합니다.

Liquefaction has caused significant damage to shallow-founded structures in various regions around the world. Current procedures for evaluating the risk of liquefaction-related damage to buildings are based on evaluating the liquefaction resistance of soils in free-field conditions. These procedures do not incorporate the properties of the foundation or structure, or the interaction of these properties with characteristics of the soil profile. These procedures also typically give only deterministic estimates of liquefaction consequences. As performance-based earthquake engineering methods become more commonly used, and in the face of challenges that involve high levels of uncertainty, probabilistic methods are becoming more important. This dissertation proposes probabilistic methods for estimating the settlement and tilt of shallow-founded structures on liquefiable ground.Chapter 2 identifies the ground motion intensity measures (IMs) that best serve as predictors of liquefaction consequences. A variety of IMs are considered at multiple locations in the soil-foundation-structure system, and the cumulative absolute velocity (CAV) at outcropping is found to be the optimum IM for predicting foundation settlement. A vector IM containing CAV and either the peak ground velocity (PGV) or peak incremental ground velocity (Vgi), also at outcropping rock, is found to be the optimum IM for predicting foundation tilt. The Ishihara-inspired liquefaction potential index is shown to be the best geotechnical liquefaction index for predicting foundation settlement. This index is a better predictor than outcropping rock CAV alone, but outcropping rock CAV outperforms the index if additional subsurface information is incorporated. Predictions made using ergodic ground motion prediction equations (GMPEs) are found to be better overall predictors than observed values of IMs because of their high predictability. Two sets of GMPEs for CAV are also proposed. The first predicts outcropping rock CAV, specifically. The second addresses epistemic uncertainty in the prediction of CAV by producing nine models with varying functional forms.Chapter 3 presents results from a numerical parametric study of nonlinear, 1-D site response analyses. These results are used to develop predictive models for the excess pore pressure ratio (ru) and the peak shear strain, which can be used to estimate the probability of liquefaction at a given site. These models incorporate the effects of the soil profile geometry and layer properties, including the effects of layer-to-layer interaction, as well as ground motion intensity. The model for shear strain considers the influence of ru on strains. The timing of pore pressure generation is compared to the timing of identification of liquefaction in the frequency content of the acceleration at the surface. This analysis finds that liquefaction tends to be identified at the surface after the maximum ru the topmost loose to medium-dense liquefiable layer reaches 1.0, but before the average ru in that layer reaches 0.7. Finally, this chapter proposed incremental site response analysis, a novel procedure for evaluating the probability of liquefaction in a highly site-specific context. Chapter 4 proceeds to develop probabilistic models for foundation settlement, residual tilt, and peak transient tilt. These models are based on numerical, experimental, and observational data. The numerical portion of this data consists of a large numerical parametric study performed prior to this work, which was extensively validated using centrifuge test results. The models include the influence of the soil profile, the foundation, the structure, and ground motion intensity, and characterize the uncertainty around their predictions. Finally, procedures for generating time histories of settlement and tilt are presented. These methods incorporate the model predictions of permanent settlement, residual tilt, and peak transient tilt, as well as properties of an acceleration time history, to produce time histories of foundation displacement for application in dynamic structural analysis. The methods in this chapter allow geotechnical engineers to estimate foundation damage and structural engineers to estimate structural damage in performance-based analysis of shallow-founded structures.

From Colloidal Solution to Single Particles: Investigating Energy Flow from Semiconductor Nanorcrystals to Molecules

Nilsson, Zach N Colorado State University ProQuest Dissertations & 2021 해외박사(DDOD)

소속기관이 구독 중이 아닌 경우 오후 4시부터 익일 오전 9시까지 원문보기가 가능합니다.

The Carceral Ethic and the Spirit of Ayahuasca

Levine, Zach ProQuest Dissertations & Theses Duke University 2022 해외박사(DDOD)

소속기관이 구독 중이 아닌 경우 오후 4시부터 익일 오전 9시까지 원문보기가 가능합니다.

This text is an ethnographic exploration of a carceral healing NGO inside of Porto Velho, Rondonia’s state prison system. Acuda was founded as a dream of ayahuasca’s, an indigenous plant medicine that became central to Brazil’s Catholicized ayahuasca religions in the mid-20th century, but also by way of a state-directed collaboration for filling employment quotas for the recently incarcerated. Acuda—technically an acronym, describing an association for “culturally” resocializing prisoners as workers—also draws on an antiquated language for spiritual rescue. Its work since 2002 has sought to marry the prerogatives of making people workable within a state economy with spiritually rescuing those lost inside of the state prison body. Its call to save people from that which it institutionally reproduces is the basis for a wide range of instances—those which plentifully compose this ethnography—where transformation is made to stay in place, or the “quantic healing” of prisoners augurs to fix liberation within stationary enclosures. This includes the NGO’s work to train prisoners as healers, which has the more common effect of gaining them employment, upon release, either inside the NGO itself or in political bureaus, including those that oversee the state Justice. The specific impetus for this effort in spiritual resocialization is work, which is also the term the ayahuasca religions give to the ritual where the plants are consecrated: trabalhos. For three years, and in a program with an ongoing afterlife, the NGO gained both state permission and “astral authorization” to furlough over 150 prisoners to the Barquinha ayahuasca-religious church in the south of the state. The work in your hands is an attempt to make sense of two years of ethnographic research I conducted, trailing these ongoing movements of stasis and expansion, release and incarceration, work and freedom, among the tenuous travels of political and spiritual bodies across ambivalent sovereignties where Rondonia’s state prisons enter into extraordinary entanglement with Spiritualist traditions. Throughout the text, we explore the paradoxical ways that spiritual healing, including what I call ayahuasca’s medicine of death, is used to rehabilitate prisoners within a site of social death and as a means of remaking the deepening carceral project in Brazil. It spans a wide range of concepts and cosmologies, including mediumship (mediunidade), time, labor, ritual, control, power, sexuality, gender, race, and religion. It focuses particularly on the ayahuasca religions of Santo Daime and the Barquinha, the French-descended Spiritist tradition known as Kardecism, and the Afro-Brazilian-descended religion of Umbanda, which has emerged in Rondonia in a new form involving ayahuasca in a hybrid called Umbandaime. As a whole, the text explores how spiritualized rituals of labor confine the forces they seek to control so as to “heal” a social order whose will is to expand this work eternally.