Magnetic Field Mapping of a 2.5 T Fixed-Field HTS Gantry Magnet for Proton Therapy

We present results from testing a high-temperature superconducting (HTS) magnet prototype for proton therapy. This magnet is specifically designed for a novel rotating gantry capable of delivering the entire proton beam energy range (70–225 MeV) while maintaining a fixed magnetic field in the superconducting magnets. The gantry layout simplifies the magnet design, enabling the use of straight, flat racetrack Bi-2223 (DI-BSCCO) coil technology and operation at higher temperatures (10–15 K). The magnet has a non-linear field distribution for bending and focusing the proton beams. To validate this feature, we developed a system for measuring the magnetic field distribution in the magnet aperture. We present the design of this hall probe array and experimental results from two different magnet tests at 4.2 K in a liquid helium bath. These results are compared with the simulated field distribution and discussed in the context of the required field quality for the application

Safely Debriefing Unexpected Simulation Death: How We Did It

PURPOSE: Medical students feel inadequately prepared to cope with patient death. Simulation training may provide learners with the opportunity to experience death in a safe environment with a structured debriefing. METHODS: Nineteen fourth-year medical students who matched into surgical specialties participated in a 2-week surgical intern preparatory course. During an individual surgical decision-making simulation, 6 learners experienced unexpected patient death at the hands of a facilitator who deviated from the simulation script. Subjectively, these learners displayed high anxiety before the debriefing. Objectively, their self-reported anxiety after the structured debriefing was similar to the self-reported anxiety of learners who did not experience simulation death. RESULTS: We formalized a bi-directional debriefing instrument using the Gather Analyze Summarize (GAS) model as a framework. We recognized that learners who experienced simulation death need to debrief on 2 aspects of the simulation: 1) Simulation death and 2) Scientific content. CONCLUSION: Our unexpected experience with simulation death led to the development of a debriefing tool that can be used by other surgical educators. Learning how to process the ensuing emotional response to patient death in simulation may benefit trainees provided they undergo a structured debriefing

Essays in Personnel and Development Economics

The state plays an important role in economic development, and there is growing interest in understanding how government employees, their characteristics, and the institutional context they operate in, affect public goods provision and public service delivery. Governments are also among the largest employers, and their personnel decisions are complex, as they are not directly guided by market forces. Additionally, the diversity of the government workforce itself may influence policy outcomes. U.S. history offers an ideal setting to explore these topics, given its rich historical panel data on government personnel and significant policy variation.In Chapter 1, Socorro Martinez and I study the impact of pay standardization in the US Civil Service on gender equity. Pay standardization schemes are commonly implemented in organizations to address pay gaps based on gender, race, or ethnicity. These schemes limit managerial discretion to determine wages, thereby limiting gender inequality within job titles. However, this may shift inequality to other margins, such as position quality or promotions. This study examines the effects of the Classification Act of 1923, which standardized pay grades and position categories and required "equal pay for equal work" in the US Civil Service, on women's earnings relative to men's. Using a triple difference approach, we exploit the fact that the policy applied to civil servants working in Washington, D.C., but not to those working in federal field offices, and allow for differential effects of the policy by gender. We find that the law did not improve women's relative pay within job titles. Further, the law lowered women's relative compensation without controlling for job titles, suggesting changes in women's positions. We indeed find large negative effects on the position margin. In response to the law, departments downgraded women to lower-quality positions. These negative consequences predominantly affected newly hired women. Our findings underscore the importance of unintended margins of adjustment for policies related to gender equity.Data collection in development economics research is rapidly evolving, driven by new technologies that enable researchers to survey households in different ways and by the increasing availability of administrative data from sources such as satellites and smartphones. Researchers face numerous design decisions when planning data collection for impact evaluations, including sampling strategies, sample size, and questionnaire design. Importantly, the choice of data collection mode may meaningfully influence findings in impact evaluations.In Chapter 2, co-authored with Travis Lybbert, Ashish Shenoy, Rupika Singh, and Daniel Stein and published in the Journal of Development Economics, we measure differences in responses between phone and in-person household agricultural surveys and test for differences in randomized control trial treatment effects by mode of data collection. Ubiquitous mobile phone ownership makes phone surveying an attractive method of low-cost data collection. We explore differences between in-person and phone survey measures of agricultural production collected for an impact evaluation in India. Phone responses have greater mean and variance, a difference that persists even within a subset of respondents that answered the same question over both modes. Treatment effect estimation remains stable across survey mode, but estimates are less precise when using phone data. These patterns are informative for cost and sample size considerations in study design and for aggregating evidence across study sites or time periods.Multi-intervention agricultural development programs are often expensive to implement at scale and sustain over the long term. Therefore, identifying the most cost-effective combination of interventions to achieve program goals is particularly important. This task becomes especially relevant given that policymakers must frequently make decisions under resource constraints, prioritizing interventions that deliver the greatest impact at the lowest cost. In Chapter 3, co-authored with Rupika Singh, Daniel Stein, and Kate Sturla, we measure the cost-effectiveness of different packages of input subsidies and extension interventions, designed to encourage the adoption of modern pulse cultivation. India is the largest producer and consumer of pulses, but in recent years has needed to import pulses to meet domestic demand. In order to keep prices stable and control the balance of trade, increasing domestic pulse production has become a national policy priority. However, farmers face multiple constraints to pulse cultivation.We design an experiment to measure the relative importance of these constraints to design an optimal short-term policy for pulse promotion. We conduct an RCT testing three different implementation models designed to ease different constraints: the "high intensity" provides seed distribution, extension services, and demonstration plots, the "medium intensity" provides seed distribution and extension services, and the "low intensity" only provides seed distribution via a voucher system. Overall, we find that all three models are effective in promoting pulse cultivation, with no statistically significant differences between the models. Treatment increased farmers’ propensity to grow pulses over two seasons by 12 and 15 percentage points, respectively. These results suggest that, at least for the initial phase of pulse adoption, access to quality seeds is the key constraint, as opposed to information. Therefore, seed distribution is likely a cost effective way to quickly increase the adoption and production of pulse crops

Latent Diffeomorphic Dynamic Mode Decomposition

We present Latent Diffeomorphic Dynamic Mode Decomposition (LDDMD), a new data reduction approach for the analysis of non-linear systems that combines the interpretability of Dynamic Mode Decomposition (DMD) with the predictive power of Recurrent Neural Networks (RNNs). Notably, LDDMD maintains simplicity, which enhances interpretability, while effectively modeling and learning complex non-linear systems with memory, enabling accurate predictions. This is exemplified by its successful application in streamflow prediction

The upgraded summing NaI(Tl) (SuN++) absorption spectrometer

Simulations of astrophysical processes require a plethora of nuclear physics input. In particular, models of neutron-capture nucleosynthesis like the s, i, and r processes require β-decay information and experimentally constrained neutron-capture reaction rates. Past experiments with the 4π Summing NaI(Tl) (SuN) total absorption spectrometer have provided these physics quantities. Here, we outline an upgrade of SuN to SuN++, where 20 new segments (12 NaI(Tl) and 8 CeBr3) have been integrated into the pre-existing SuN total absorption spectrometer to provide increased energy and time resolution in β-decay experiments. The details of the newly upgraded SuN++ total absorption spectrometer are discussed with results from the commissioning experiment at the Facility for Rare Isotope Beams (FRIB) utilizing a 70Cu beam

Continuum framework for multiscale contact mechanics of elastic-plastic fractal interfaces with intervening boundary film

A comprehensive mechanics theory was developed to analyze multiscale contact and friction behavior of elastic-plastic fractal surfaces coated with a boundary film. This approach accounts for the size-dependent behavior of asperity microcontacts that arise from the inherent roughness of fractal topographies. To capture the fundamental mechanisms governing interfacial friction, representative single-asperity models were formulated to describe both elastic and plastic deformation modes at the microscale. These models were then systematically extended across the entire asperity population, enabling an accurate representation of contact interactions over a broad range of length scales. In the elastic regime, frictional resistance is primarily attributed to shearing of the boundary film between opposing asperities. Conversely, in the plastic regime, asperities indent and plow through the softer counterface material, while the boundary film remains attached to the deformed surface contributing additional resistance through interfacial shear. The total frictional force is obtained by integrating the contributions from both elastic and plastic microcontacts, which are weighted according to the asperity-size distribution that characterizes the fractal contact interface. The developed theoretical framework provides a rigorous and scalable model for predicting the frictional behavior of rough contact interfaces covered by a strongly adhered boundary film and yields fundamental insight into the interplay between surface topography, prevalent deformation mode at the asperity scale, and boundary film shear resistance, which is especially relevant for the design and analysis of engineered surfaces in contact-mode mechanical systems

A cost–benefit framework to evaluate capacity upgrade options in overhead line transmission planning

This paper presents the methodology behind the new Reconductoring Economic and Financial Analysis (REFA) tool, an open-access software, used by transmission utilities to evaluate transmission capacity enhancement options. The proposed methodology is intended to be used in a new planning stage, after the capacity expansion and prior to the individual transmission project engineering, allowing capacity upgrade options (reconductoring, rebuild or voltage upgrade), and respective conductor selection, to be compared under the same economic basis. The REFA tool implements a methodology to rank project options and conductor types based on economic criteria, considering an approximation of the ampacity and sag constraints. Results, using 5 real transmission lines in the US, show that least-cost combinations of project and conductor types can be very diverse, which emphasizes the need for the proposed methodology and tool