Laser-Nucleus Interactions: The Quasiadiabatic Regime

The interaction between nuclei and a strong zeptosecond laser pulse with coherent MeV photons is investigated theoretically. We provide a first semi-quantitative study of the quasiadiabatic regime where the photon absorption rate is comparable to the nuclear equilibration rate. In that regime, multiple photon absorption leads to the formation of a compound nucleus in the so-far unexplored regime of excitation energies several hundred MeV above the yrast line. The temporal dynamics of the process is investigated by means of a set of master equations that account for dipole absorption, stimulated dipole emission, neutron decay and induced fission in a chain of nuclei. That set is solved numerically by means of state-of-the-art matrix exponential methods also used in nuclear fuel burnup and radioactivity transport calculations. Our quantitative estimates predict the excitation path and range of nuclei reached by neutron decay and provide relevant information for the layout of future experiments.Comment: 14 pages, 9 figures; v2 minor modifications in text, results unchange

Improving PWR core simulations by Monte Carlo uncertainty analysis and Bayesian inference

A Monte Carlo-based Bayesian inference model is applied to the prediction of reactor operation parameters of a PWR nuclear power plant. In this non-perturbative framework, high-dimensional covariance information describing the uncertainty of microscopic nuclear data is combined with measured reactor operation data in order to provide statistically sound, well founded uncertainty estimates of integral parameters, such as the boron letdown curve and the burnup-dependent reactor power distribution. The performance of this methodology is assessed in a blind test approach, where we use measurements of a given reactor cycle to improve the prediction of the subsequent cycle. As it turns out, the resulting improvement of the prediction quality is impressive. In particular, the prediction uncertainty of the boron letdown curve, which is of utmost importance for the planning of the reactor cycle length, can be reduced by one order of magnitude by including the boron concentration measurement information of the previous cycle in the analysis. Additionally, we present first results of non-perturbative nuclear-data updating and show that predictions obtained with the updated libraries are consistent with those induced by Bayesian inference applied directly to the integral observables.Comment: 10 pages, 11 figure

Transgender identity management across social media platforms

Transgender people use social media for identity work, which takes place over time and across platforms. In this study, we interviewed 20 transgender social media users to examine transgender identity management across the social media ecosystem. We found that transgender social media users curate their social media experiences to fit their needs through creating accounts on different platforms, maintaining multiple accounts on individual platforms, and making active decisions about content they post, networks they are connected to, and content they interact with. In this way, transgender people’s social media curation is not limited to their own identity presentations, but also involves curating the content they see from others and whom they include in their networks. Together, these two types of online curation enable transgender social media users to craft social media worlds that meet their social and self-presentational needs.University of Michigan Institute for Research on Women and Gender (IRWG)University of Michigan Digital Studies Institute (DSI)University of Michigan School of InformationPeer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/168411/1/BussTransgenderIdentityManagement.pdfDescription of BussTransgenderIdentityManagement.pdf : Main articleSEL

Trans Time: Safety, Privacy, and Content Warnings on a Transgender-Specific Social Media Site

Trans people often use social media to connect with others, find and share resources, and post transition-related content. However, because most social media platforms are not built with trans people in mind and because online networks include people who may not accept one’s trans identity, sharing trans content can be difficult. We studied Trans Time, a social media site developed particularly for trans people to document transition and build community. We interviewed early Trans Time users (n = 6) and conducted focus groups with potential users (n = 21) to understand how a trans-specific site uniquely supports its users. We found that Trans Time has the potential to be a safe space, encourages privacy, and effectively enables its users to selectively view content using content warnings. Together, safety, privacy, and content warnings create an online space where trans people can simultaneously build community, find support, and express both the mundanity and excitement of trans life. Yet in each of these areas, we also learned ways that the site can improve. We provide implications for how social media sites may better support trans users, as well as insular communities of people from other marginalized groups.Institute for Research on Women and Gender (IRWG)Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/162569/1/HaimsonTransTime.pdfDescription of HaimsonTransTime.pdf : Main articleSEL

The importance of non-carbonate mineral weathering as a soil formation mechanism within a karst weathering profile in the SPECTRA Critical Zone Observatory, Guizhou Province, China

Soil degradation, including rocky desertification, of the karst regions in China is severe. Karst landscapes are especially sensitive to soil degradation as carbonate rocks are nutrient-poor and easily eroded. Understanding the balance between soil formation and soil erosion is critical for long-term soil sustainability, yet little is known about the initial soil forming processes on karst terrain. Herein we examine the initial weathering processes of several types of carbonate bedrock containing varying amounts of non-carbonate minerals in the SPECTRA Critical Zone Observatory, Guizhou Province, Southwest China. We compared the weathering mechanisms of the bedrock to the mass transfer of mineral nutrients in a soil profile developed on these rocks and found that soil formation and nutrient contents are strongly dependent upon the weathering of interbedded layers of more silicate-rich bedrock (marls). Atmospheric inputs from dust were also detected

Handling Label Uncertainty on the Example of Automatic Detection of Shepherd's Crook RCA in Coronary CT Angiography

Coronary artery disease (CAD) is often treated minimally invasively with a catheter being inserted into the diseased coronary vessel. If a patient exhibits a Shepherd's Crook (SC) Right Coronary Artery (RCA) - an anatomical norm variant of the coronary vasculature - the complexity of this procedure is increased. Automated reporting of this variant from coronary CT angiography screening would ease prior risk assessment. We propose a 1D convolutional neural network which leverages a sequence of residual dilated convolutions to automatically determine this norm variant from a prior extracted vessel centerline. As the SC RCA is not clearly defined with respect to concrete measurements, labeling also includes qualitative aspects. Therefore, 4.23% samples in our dataset of 519 RCA centerlines were labeled as unsure SC RCAs, with 5.97% being labeled as sure SC RCAs. We explore measures to handle this label uncertainty, namely global/model-wise random assignment, exclusion, and soft label assignment. Furthermore, we evaluate how this uncertainty can be leveraged for the determination of a rejection class. With our best configuration, we reach an area under the receiver operating characteristic curve (AUC) of 0.938 on confident labels. Moreover, we observe an increase of up to 0.020 AUC when rejecting 10% of the data and leveraging the labeling uncertainty information in the exclusion process.Comment: Accepted at ISBI 202