Noisy Hamiltonian Monte Carlo for doubly-intractable distributions

Hamiltonian Monte Carlo (HMC) has been progressively incorporated within the statistician's toolbox as an alternative sampling method in settings when standard Metropolis-Hastings is inefficient. HMC generates a Markov chain on an augmented state space with transitions based on a deterministic differential flow derived from Hamiltonian mechanics. In practice, the evolution of Hamiltonian systems cannot be solved analytically, requiring numerical integration schemes. Under numerical integration, the resulting approximate solution no longer preserves the measure of the target distribution, therefore an accept-reject step is used to correct the bias. For doubly-intractable distributions -- such as posterior distributions based on Gibbs random fields -- HMC suffers from some computational difficulties: computation of gradients in the differential flow and computation of the accept-reject proposals poses difficulty. In this paper, we study the behaviour of HMC when these quantities are replaced by Monte Carlo estimates

Migrants becoming mathematics teachers : personal resources and professional capitals

This study traces the professional learning of student teachers who have lived and studied outside the UK, and successfully applied to follow a Post Graduate Certificate in Education (PGCE) course in London to become teachers of mathematics in English schools. It draws upon Bourdieu’s theory of habitus and field to discuss how these student teachers adapt their capitals, as described in migration studies by Erel (2010) and Nowicka (2015) and how, during initial teacher training (ITT), they develop professional capitals for the teaching of mathematics (Nolan, 2012). Recent migration flows have led to a growth of diversity, as measured by countries of origin, in London and other cities around the world, resulting in what Vertovec (2006) has called superdiversity. Through a series of semi-structured interviews with 16 PGCE student teachers hailing from 13 different countries, this study explores the implications of superdiversity for the practices of training teachers. The focus of the research is on the complications of ‘bring[ing] off’ (MacLure, 2003:55) the embodied performance of becoming a teacher, and on how student teachers develop ‘enough’ (Blommaert and Varis, 2011:5) professional capital to pass the course. This leads to a reassessment of the category ‘highly skilled migrant’, which is used to define those who have academic qualifications for teaching from outside the UK. The study uses instead the term ‘highly qualified migrant’, to argue that a mathematical degree needs to be complemented by knowledge of the national mathematics curriculum, national pedagogies and local communicative resources. It shows how London can become an ‘escalator region’ (Fielding, 1992:1), as the student teachers achieve a working life that matches their academic qualifications, and also their own aspirations and those of their families, in the UK and elsewhere. In so doing, they become part of a teaching workforce that reflects the growing superdiversity of the region’s school pupils

Population genetics and phylogeography of the pygmy nuthatch in Southern California

Uses mitochondrial DNA sequence data to examine the degree of genetic differentiation among sky island populations of two subspecies of pygmy nuthatch (Sitta pygmaea melanotis and Sitta pygmaea leuconucha) occurring in Southern California. Assesses the hypothesis that sky islands are genetically isolated and that migration (gene flow) is restricted among them. Eleven sampling locations throughout Southern California were selected based on representation of subspecies, availability of specimens, and feasibility of collection. Results indicate that pygmy nuthatch populations fragmented in the disjunct mountain ranges of Southern California exhibit low but significant levels of genetic differentiation

Migrant teachers and classroom encounters: processes of intercultural learning

Recent migration combined with strategies to diversify the teacher workforce has led to complexities in teacher diversity identified by the term 'superdiversity' (Vertovec, 2006). This article builds on recent work on the processes of convergence and superdiversity (Wessendorf, 2011) by focusing on meaningful encounters in the mathematics classroom. A sociolinguistics approach is used to discuss the performance of teacher identity, focusing on accent. An analysis of power shows tensions between Standard English and local vernaculars, involving microaggressions and opportunities for intercultural learning. The article concludes by discussing coping with microaggressions and the systemic implications for school policies and initial teacher training. It shows how microaggressions offer opportunities for intercultural learning and how classroom spaces can be developed that promote both this and the dispositions of an intercultural habitus

Differences among Watershed Sub-Populations in Willingness to Pay for Water Quality Improvements: The Impact of TMDL Development

The Opequon watershed is located in northern Virginia (VA) and the eastern panhandle of West Virginia (WV). In both states, Opequon Creek is classified as impaired based on violations of bacteria, benthic and biologic standards. Both VA and WV are using Total Maximum Daily Load (TMDL) plans to improve water quality within Opequon Creek. However, these TMDL plans are at different stages with VA being completed and WV still in progress. As part of the TMDL process in VA, this research is based on a contingent valuation survey which was developed to measure the expected monetary benefits of TMDL implementation throughout the Opequon watershed. On the basis of log-likelihood tests of grouped tobit models to explain willingness-to-pay (WTP) for watershed clean-up, VA, WV, and VA riparian landowner respondents were found to consist of different populations. Riparian landowners had the highest median annual WTP at $64, VA respondents the next highest ($49), and WV the lowest ($32). These medians were found to be statistically different from each other. When valuing out-of-state clean-up, however, VA and WV respondents were found to be similar populations with a one-time median WTP of$28. Results show that the TMDL process did impact VA respondent WTP for in-state clean-up.Resource /Energy Economics and Policy,

Essays on recruitment, training, and incentives

Thesis (Ph. D.)--Massachusetts Institute of Technology, Sloan School of Management, 2013.Cataloged from PDF version of thesis.Includes bibliographical references.This thesis is composed of three papers, each relating to labor market imperfections and their implications for firms' staffing practices. In the first paper, I examine why hospitals provide direct financial support to nursing schools and faculty. This support is striking because nursing education is clearly general, clearly paid by the firm, and information asymmetries appear minimal. Using AHA and survey data, I find hospitals employing a greater share of their MSA's registered nurses are more likely to provide such support, net of size and other institutional controls. I interpret this result as evidence that technologically-general skills training may be made defacto-specific by mobility frictions. In the second paper, I present a theory of couples' job search whereby women sort into lowerpaying geographically-dispersed occupations due to expectations of future spouses' geographically-clustered occupations and (thereby) inability to relocate for work. Results confirm men segregate into geographically-clustered occupations, and that these occupations involve more-frequent early career relocations for both sexes. I also find that the minority of the men and women who depart from this equilibrium experience delayed marriage, higher divorce, and lower earnings. Results are consistent with the theory's implication that marriage and mobility expectations foment a self-fulfilling pattern of occupational segregation, with individual departures deterred by earnings and marriage penalties. In the third paper, I examine the use and misuse of authority and incentives in organizational hierarchies. Through a principal-supervisor-agent model inspired by sales settings, I propose organizations delegate authority over salespeople to front-line sales mangers because they can decompose performance measures into ability and luck. The model yields the result that managers on the cusp of a quota have a unique personal incentive to retain and adjust quotas for poor performing subordinates, permitting me to distinguish managers' interests from those of the firm. I parametrically estimate the model using detailed person-transaction-level microdata from 244 firms that subscribe to a "cloud"-based service for automating transaction processing and compensation. I estimate 13-15% of quota adjustments and retentions among poor performers are explained by the managers' unique personal interest in meeting a quota. I use agency theory to evaluate firms' mitigation practices.by Alan Benson.Ph.D

Migrant maths teachers: deficit, translanguaging, and growing authority

This article draws from a longitudinal case study of trainee (the term used in official documentation related to Initial Teacher Training (ITT) in England and with some reservations throughout this paper) and early-career teachers (ECT) of mathematics. The sample represents migrant teachers that the Immigration Act of 2020 seeks to attract to the UK to address national shortages identified by the Migration Advisory Committee (MAC). The analysis examines how multimodal semiotic repertoires of language, bodies and pedagogical practices are entangled in classroom encounters. It shows how the ideology of Standard English can create an uncomfortable sense of different deficits amongst multilingual professionals and evidences how these can be addressed through a model of authority in which teachers get the right mix of mathematical subject knowledge (epistemic authority), the use of school practices and expectations (practical authority), and individual biography (personal authority). It uses translanguaging spaces to examine how teachers use communicative repertoires to orchestrate semiotic resources and manage their identity positions in ways that promote intercultural competencies during the daily encounters of teachers and their pupils

Mixed use industry in urban poverty areas.

Massachusetts Institute of Technology. Dept. of Architecture. Thesis. 1968. B.Arch.Text within red line border.Bibliography: leaves B-1 - B-5.B.Arch

Consequences of the Mass Spectrometric and Infrared Analysis of Oils and Asphaltenes for the Chemistry of Coal Liquefaction

Chemistr