Clearing algorithms and network centrality

I show that the solution of a standard clearing model commonly used in contagion analyses for financial systems can be expressed as a specific form of a generalized Katz centrality measure under conditions that correspond to a system-wide shock. This result provides a formal explanation for earlier empirical results which showed that Katz-type centrality measures are closely related to contagiousness. It also allows assessing the assumptions that one is making when using such centrality measures as systemic risk indicators. I conclude that these assumptions should be considered too strong and that, from a theoretical perspective, clearing models should be given preference over centrality measures in systemic risk analyses

Computational Aeroheating Predictions for X-34

Radiative equilibrium surface temperatures, heating rates, streamlines, surface pressures, and flow-field features as predicted by the Langley Aerothermodynamic Upwind Relaxation Algorithm (Laura) are presented for the X-34 Technology Demonstrator. Results for two trajectory points corresponding to entry peak heating and two control surface deflections are discussed. This data is also discussed in context of Thermal Protection System (TPS) design issues. The work presented in this report is part of a larger effort to define the X-34 aerothermal environment, including the application of engineering codes and wind-tunnel studies

Macrostate Data Clustering

We develop an effective nonhierarchical data clustering method using an analogy to the dynamic coarse graining of a stochastic system. Analyzing the eigensystem of an interitem transition matrix identifies fuzzy clusters corresponding to the metastable macroscopic states (macrostates) of a diffusive system. A "minimum uncertainty criterion" determines the linear transformation from eigenvectors to cluster-defining window functions. Eigenspectrum gap and cluster certainty conditions identify the proper number of clusters. The physically motivated fuzzy representation and associated uncertainty analysis distinguishes macrostate clustering from spectral partitioning methods. Macrostate data clustering solves a variety of test cases that challenge other methods.Comment: keywords: cluster analysis, clustering, pattern recognition, spectral graph theory, dynamic eigenvectors, machine learning, macrostates, classificatio

Pressure Gradient Effects on Hypersonic Cavity Flow Heating

The effect of a pressure gradient on the local heating disturbance of rectangular cavities tested at hypersonic freestream conditions has been globally assessed using the two-color phosphor thermography method. These experiments were conducted in the Langley 31-Inch Mach 10 Tunnel and were initiated in support of the Space Shuttle Return-To-Flight Program. Two blunted-nose test surface geometries were developed, including an expansion plate test surface with nearly constant negative pressure gradient and a flat plate surface with nearly zero pressure gradient. The test surface designs and flow characterizations were performed using two-dimensional laminar computational methods, while the experimental boundary layer state conditions were inferred using the measured heating distributions. Three-dimensional computational predictions of the entire model geometry were used as a check on the design process. Both open-flow and closed-flow cavities were tested on each test surface. The cavity design parameters and the test condition matrix were established using the computational predictions. Preliminary conclusions based on an analysis of only the cavity centerline data indicate that the presence of the pressure gradient did not alter the open cavity heating for laminar-entry/laminar-exit flows, but did raise the average floor heating for closed cavities. The results of these risk-reduction studies will be used to formulate a heating assessment of potential damage scenarios occurring during future Space Shuttle flights

Prevalence of Campy/obacter spp. and Yersinia enterocolitica in Fattening Pig Herds in Lower Saxony, Germany

The results of a study on the occurrence of two bacteria that cause zoonoses, Campylobacter spp. and Yersmia enterocolilica were presented and the results of bacteriological and serological methods of detection were compared. The study was carried out on 30 fattening herds in Lower Saxony, Germany Bacteriological findings of Campylobacter spp. in the faeces indicated that 69.7% of the fattening pigs were positive, but 81 .2% tested positive serologically. All herds tested here were both bacteriologically and serologically positive for Campylobacter spp. Furthermore, only 8.4 % tested pos1t1ve for Yersinia enterocolitica in the faecal samples, but 66.8 % of the animals were serologically positive for that bacterium. At herd level 43.3 % of the herds tested bactenologically positive for Yersinia enterocolitica, whereas serological testing showed that 83.3 % of the units had one or more reacting animal

Risk factors for acquisition of hepatitis C virus infection: a case series and potential implications for disease surveillance

BACKGROUND: Transmission of hepatitis C vims (HCV) is strongly associated with use of contaminated blood products and injection drugs. Other "non-parental" modes of transmission including sexual activity have been increasingly recognized. We examined risk factors for acquiring HCV in patients who were referred to two tertiary care centers and enrolled in an antiviral therapy protocol. METHODS: Interviews of 148 patients were conducted apart from their physician evaluation using a structured questionnaire covering demographics and risk factors for HCV acquisition. RESULTS: Risk factors (blood products, injection/intranasal drugs, razor blades/ toothbrushes, body/ear piercing, occupational exposure, sexual activity) were identified in 141 (95.3%) of participants; 23 (15.5%) had one (most frequently blood or drug exposure), 41 (27.7%) had two, and 84 (53.4%) had more than two risk factors. No patient reported sexual activity as a sole risk factor. Body piercing accounted for a high number of exposures in women. Men were more likely to have exposure to street drugs but less exposure to blood products than women. Blood product exposure was less common in younger than older HCV patients. CONCLUSION: One and often multiple risk factors could be identified in nearly all HCV-infected patients seen in a referral practice. None named sexual transmission as the sole risk factor. The development of a more complete profile of factors contributing to transmission of HCV infection may assist in clinical and preventive efforts. The recognition of the potential presence of multiple risk factors may have important implications in the approach to HCV surveillance, and particularly the use of hierarchical algorithms in the study of risk factors

Self-Control in Cyberspace: Applying Dual Systems Theory to a Review of Digital Self-Control Tools

Many people struggle to control their use of digital devices. However, our understanding of the design mechanisms that support user self-control remains limited. In this paper, we make two contributions to HCI research in this space: first, we analyse 367 apps and browser extensions from the Google Play, Chrome Web, and Apple App stores to identify common core design features and intervention strategies afforded by current tools for digital self-control. Second, we adapt and apply an integrative dual systems model of self-regulation as a framework for organising and evaluating the design features found. Our analysis aims to help the design of better tools in two ways: (i) by identifying how, through a well-established model of self-regulation, current tools overlap and differ in how they support self-control; and (ii) by using the model to reveal underexplored cognitive mechanisms that could aid the design of new tools.Comment: 11.5 pages (excl. references), 6 figures, 1 tabl

Demographic and psychological predictors of community pharmacists’ cancer-related conversations with patients: a cross-sectional analysis and survey study

BACKGROUND: There is increasing interest in the role of community pharmacy in the early diagnosis and prevention of cancer. This study set out to examine how often community pharmacists (CPs) encourage patients to spot or respond to potential signs and symptoms of cancer, and how often they help people to make an informed decision about taking part in bowel cancer screening. METHODS: Data from 400 UK CPs, who completed the 2018 Cancer Research UK Healthcare Professional Tracker survey, were analysed. The primary outcomes were: ‘how often CPs encourage patients to spot or respond to potential signs and symptoms of cancer’ and ‘how often CPs encourage eligible people to make an informed decision to participate in bowel cancer screening’. Associations between behaviours and demographic and psychological variables (Capability, Opportunity and Motivation) were assessed using multivariate logistic regression. RESULTS: Most (n = 331, 82.8%) CPs reported occasionally, frequently or always encouraging patients to spot or respond to potential signs and symptoms of cancer, while only half (n = 203, 50.8%) reported occasionally, frequently or always helping people make an informed decision to participate in bowel cancer screening. Female sex (aOR: 3.20, 95%CI: 1.51, 6.81; p < 0.01) and increased Opportunity (aOR: 1.72, 95%CIs: 1.12, 2.64; p < 0.05) and Motivation (aOR: 1.76, 95%CIs: 1.37, 2.27; p < 0.001) were associated with encouraging patients to spot or respond to potential signs and symptoms of cancer; all three psychological variables were associated with helping people to make an informed decision to participate in bowel cancer screening (Capability: aOR: 1.39, 95%CIs: 1.26, 1.52, p < 0.001; Opportunity: aOR: 1.44, 95%CIs: 1.11, 1.87; p < 0.01; Motivation: aOR: 1.45, 95%CIs: 1.05, 2.00; p < 0.05). CONCLUSIONS: Most CPs encourage patients to spot or respond to potential cancer symptoms, while only half help them make an informed decision to participate in bowel cancer screening. A multifaceted approach, targeting multiple COM-B components, is required to change these behaviours

Implementation of an Optimal First-Order Method for Strongly Convex Total Variation Regularization

We present a practical implementation of an optimal first-order method, due to Nesterov, for large-scale total variation regularization in tomographic reconstruction, image deblurring, etc. The algorithm applies to $\mu$-strongly convex objective functions with $L$-Lipschitz continuous gradient. In the framework of Nesterov both $\mu$ and $L$ are assumed known -- an assumption that is seldom satisfied in practice. We propose to incorporate mechanisms to estimate locally sufficient $\mu$ and $L$ during the iterations. The mechanisms also allow for the application to non-strongly convex functions. We discuss the iteration complexity of several first-order methods, including the proposed algorithm, and we use a 3D tomography problem to compare the performance of these methods. The results show that for ill-conditioned problems solved to high accuracy, the proposed method significantly outperforms state-of-the-art first-order methods, as also suggested by theoretical results.Comment: 23 pages, 4 figure

Functional Equivalence Acceptance Testing of FUN3D for Entry Descent and Landing Applications

The functional equivalence of the unstructured grid code FUN3D to the the structured grid code LAURA (Langley Aerothermodynamic Upwind Relaxation Algorithm) is documented for applications of interest to the Entry, Descent, and Landing (EDL) community. Examples from an existing suite of regression tests are used to demonstrate the functional equivalence, encompassing various thermochemical models and vehicle configurations. Algorithm modifications required for the node-based unstructured grid code (FUN3D) to reproduce functionality of the cell-centered structured code (LAURA) are also documented. Challenges associated with computation on tetrahedral grids versus computation on structured-grid derived hexahedral systems are discussed