Generalized Descent Methods for Asymmetric Systems of Equations and Variational Inequalities

We consider generalizations of the steepest descent algorithm for solving asymmetric systems of equations. We first show that if the system is linear and is defined by a matrix M, then the method converges if M2 is positive definite. We also establish easy to verify conditions on the matrix M that ensure that M is positive definite, and develop a scaling procedure that extends the class of matrices that satisfy the convergence conditions. In addition, we establish a local convergence result for nonlinear systems defined by uniformly monotone maps, and discuss a class of general descent methods. Finally, we show that a variant of the Frank-Wolfe method will solve a certain class of variational inequality problems. All of the methods that we consider reduce to standard nonlinear programming algorithms for equivalent optimization problems when the Jacobian of the underlying problem map is symmetric. We interpret the convergence conditions for the generalized steepest descent algorithms as restricting the degree of asymmetry of the problem map

Hypercalcemia Caused by Metastatic Adamantinoma: Response to Radiotherapy

Purpose. To describe successful palliation of a patient with metastatic adamantinoma presenting with lung metastases and hypercalcemia resulting from a parathormone-like substance released from the tumor

A power comparison of generalized additive models and the spatial scan statistic in a case-control setting

<p>Abstract</p> <p>Background</p> <p>A common, important problem in spatial epidemiology is measuring and identifying variation in disease risk across a study region. In application of statistical methods, the problem has two parts. First, spatial variation in risk must be detected across the study region and, second, areas of increased or decreased risk must be correctly identified. The location of such areas may give clues to environmental sources of exposure and disease etiology. One statistical method applicable in spatial epidemiologic settings is a generalized additive model (GAM) which can be applied with a bivariate LOESS smoother to account for geographic location as a possible predictor of disease status. A natural hypothesis when applying this method is whether residential location of subjects is associated with the outcome, i.e. is the smoothing term necessary? Permutation tests are a reasonable hypothesis testing method and provide adequate power under a simple alternative hypothesis. These tests have yet to be compared to other spatial statistics.</p> <p>Results</p> <p>This research uses simulated point data generated under three alternative hypotheses to evaluate the properties of the permutation methods and compare them to the popular spatial scan statistic in a case-control setting. Case 1 was a single circular cluster centered in a circular study region. The spatial scan statistic had the highest power though the GAM method estimates did not fall far behind. Case 2 was a single point source located at the center of a circular cluster and Case 3 was a line source at the center of the horizontal axis of a square study region. Each had linearly decreasing logodds with distance from the point. The GAM methods outperformed the scan statistic in Cases 2 and 3. Comparing sensitivity, measured as the proportion of the exposure source correctly identified as high or low risk, the GAM methods outperformed the scan statistic in all three Cases.</p> <p>Conclusions</p> <p>The GAM permutation testing methods provide a regression-based alternative to the spatial scan statistic. Across all hypotheses examined in this research, the GAM methods had competing or greater power estimates and sensitivities exceeding that of the spatial scan statistic.</p

Initial Estimates of Optical Constants of Mars Candidate Materials

Data obtained at visible and near-infrared wavelengths by OMEGA on Mars Express and CRISM on MRO provide definitive evidence for the presence of phyllosilicates and other hydrated phases on Mars. A diverse range of both Fe/Mg-OH and Al- OH-bearing phyllosilicates were identified including the smectites, nontronite, saponite, and montmorillonite. To constrain the abundances of these phyllosilicates, spectral analyses of mixtures are needed. We report on our effort to enable the quantitative evaluation of the abundance of hydrated-hydroxylated silicates when they are contained in mixtures. We include two component mixtures of hydrated/ hydroxylated silicates with each other and with two analogs for other Martian materials; pyroxene (enstatite) and palagonitic soil (an alteration product of basaltic glass, hereafter referred to as palagonite). For the hydrated-hydroxylated silicates we include saponite and montmorillonite (Mg- and Al-rich smectites). We prepared three size separates of each end-member for study: 20-45, 63-90, and 125-150 micron

A multilevel non-hierarchical study of birth weight and socioeconomic status

<p>Abstract</p> <p>Background</p> <p>It is unclear whether the socioeconomic status (SES) of the community of residence has a substantial association with infant birth weight. We used multilevel models to examine associations of birth weight with family- and community-level SES in the Cape Cod Family Health Study. Data were collected retrospectively on births to women between 1969 and 1983 living on Cape Cod, Massachusetts. The sample included siblings born in different residences with differing community-level SES.</p> <p>Methods</p> <p>We used cross-classified models to account for multiple levels of correlation in a non-hierarchical data structure. We accounted for clustering at family- and community-levels. Models included extensive individual- and family-level covariates. SES variables of interest were maternal education; paternal occupation; percent adults living in poverty; percent adults with a four year college degree; community mean family income; and percent adult unemployment.</p> <p>Results</p> <p>Residual correlation was detected at the family- but not the community-level. Substantial effects sizes were observed for family-level SES while smaller magnitudes were observed for community-level SES. Overall, higher SES corresponded to increased birth weight though neither family- nor community-level variables had significant associations with the outcome. In a model applied to a reduced sample that included a single child per family, enforcing a hierarchical data structure, paternal occupation was found to have a significant association with birth weight (p = 0.033). Larger effect sizes for community SES appeared in models applied to the full sample that contained limited covariates, such as those typically found on birth certificates.</p> <p>Conclusions</p> <p>Cross-classified models allowed us to include more than one child per family even when families moved between births. There was evidence of mild associations between family SES and birth weight. Stronger associations between paternal occupation and birth weight were observed in models applied to reduced samples with hierarchical data structures, illustrating consequences of excluding observations from the cross-classified analysis. Models with limited covariates showed associations of birth weight with community SES. In models adjusting for a complete set of individual- and family-level covariates, community SES was not as important.</p

Expression of TCR-Vβ peptides by murine bone marrow cells does not identify T-cell progenitors

Germline transcription has been described for both immunoglobulin and T-cell receptor (TCR) genes, raising questions of their functional significance during haematopoiesis. Previously, an immature murine T-cell line was shown to bind antibody to TCR-Vβ8.2 in absence of anti-Cβ antibody binding, and an equivalent cell subset was also identified in the mesenteric lymph node. Here, we investigate whether germline transcription and cell surface Vβ8.2 expression could therefore represent a potential marker of T-cell progenitors. Cells with the TCR phenotype of Vβ8.2(+) Cβ(-) are found in several lymphoid sites, and among the lineage-negative (Lin(-) ) fraction of hematopoietic progenitors in bone marrow (BM). Cell surface marker analysis of these cells identified subsets reflecting common lymphoid progenitors, common myeloid progenitors and multipotential progenitors. To assess whether the Lin(-) Vβ8.2(+) Cβ(-) BM subset contains hematopoietic progenitors, cells were sorted and adoptively transferred into sub-lethally irradiated recipients. No T-cell or myeloid progeny were detected following introduction of cells via the intrathymic or intravenous routes. However, B-cell development was detected in spleen. This pattern of restricted in vivo reconstitution disputes Lin(-) Vβ8.2(+) Cβ(-) BM cells as committed T-cell progenitors, but raises the possibility of progenitors with potential for B-cell development.This study was supported by grants to H.C.O. from the National Health and Medical Research Council of Australia. J.A. was supported by a fellowship from the Australian Academy of Science

On-Going Laboratory Efforts to Quantitatively Address Clay Abundance on Mars

Data obtained at visible and near-infrared wavelengths by OMEGA on MarsExpress and CRISM on MRO provide definitive evidence for the presence of phyllosilicates and other hydrated phases on Mars. A diverse range of both Fe/Mg-OH and Al-OH-bearing phyllosilicates were identified including the smectites, nontronite, saponite, and montmorillonite. In order to constrain the abundances of these phyllosilicates spectral analyses of mixtures are needed. We report on our on-going effort to enable the quantitative evaluation of the abundance of hydrated-hydroxylated silicates when they are contained in mixtures. We include two component mixtures of hydrated/hydroxylated silicates with each other and with two analogs for other martian materials; pyroxene (enstatite) and palagonitic soil (an alteration product of basaltic glass). For the hydrated-hydroxylated silicates we include saponite and montmorillonite (Mg- and Al- rich smectites). We prepared three size separates of each end-member for study: 20-45, 63-90, and 125-150 m. As the second phase of our effort we used scanning electron microscopy imaging and x-ray diffraction to characterize the grain size distribution, and structural nature, respectively, of the mixtures. Visible and near-infrared reflectance spectra of the 63-90 micrometers grain size of the mixture samples are shown in Figure 1. We discuss the results of our measurements of these mixtures

Intersectionality at work: The case of Ruth Bates Harris and NASA

One challenge we face as diversity and gender scholars is how to apply intersectionality in organizational studies. We present one possible application of intersectionality to demonstrate that it can be put to work beyond the bounds of theorization alone. To achieve this goal, we focused on the organizational experiences of Ruth Bates Harris, the first woman and the first African American hired to a senior management position at the United States National Aeronautics and Space Administration (U.S. NASA). We recreated Bates Harris retrospectively, via a plausible story, by applying the critical sensemaking (CSM) framework. We then analyzed this story by applying once again the CSM framework with a focus on: (1) intersecting identity (micro) (re)constructions; (2) the rules surrounding NASA occupational roles, vague professional practices, and financial resources, and the influence of these rules on identity reconstructions; and, (3) two dominant social values in the Cold War-Civil Rights era, and their relationship to the marginalization of an individual. The analysis of the plausible story, resulting in the recreation of a complex individual via her range of anchor points and the influence of NASA’s rules, meta-rules and social values on her identities, contributes to our understanding of how to put intersectionality to work

Shared decision-making during virtual care regarding rheumatologic and chronic conditions: Qualitative study of benefits, pitfalls, and optimization

OBJECTIVE: Virtual care (VC) is an accepted modality of care delivery, and shared decision-making (SDM) benefits patients with rheumatologic and chronic conditions (RCCs). Unfortunately, research suggests reduced quality of SDM during VC. This study explores the benefits and shortcomings of SDM regarding RCCs during VC with suggestions for optimally using VC during SDM. METHODS: Following Stiggelbout\u27s framework for SDM, we conducted focus groups of patients with RCCs and providers to understand their experiences with SDM during VC, probing for facilitating and challenging factors. We conducted content analysis of the transcripts, defining themes, and inductively reasoned to identify relationships among themes. We summarized the facilitators, barriers, and opportunities for improving SDM during VC that participants proposed. RESULTS: Virtual SDM shares several similarities with in-person practice, as both draw upon trusting patient-provider relationships, following the same general steps, and relying on effective communication. VC presents solutions for known barriers to in-person SDM, expanding time for making decisions and access to care. Technology and virtual health systems introduce new barriers to SDM, and participants list opportunities for overcoming these concerns. CONCLUSION: VC is a tool that can enhance and even support superior SDM compared with in-person visits when implemented successfully, a condition requiring the development of nuanced skills to correctly identify when and how to best use VC for SDM as well as technology and health care structures that integrate SDM into VC. Therefore, patients, providers, insurance carriers, and policy makers all contribute to the success of SDM among RCCs during VC