Adaptive Formation Flying Maneuvers for Multiple Relative Orbits

In order to extend and preserve the mission of an earth orbiting satellite it is imperative that the on board maneuvers do not waste propulsion but maneuver the spacecraft optimally. The challenge for ground stations is to plan maneuvers for spacecraft that will achieve a desired orbit while minimizing fuel costs. Increasing this challenge is the addition of specific keep-out zones (constraints on the spacecraft). For example, a low-earth orbiter (LEO) may need to maintain a specific orbit plane for a sun-synchronous imaging mission but it now has to contend with opposing debris. Computing a maneuver to avoid the debris could have consequences to the mission constraints and cause undesired affects to the desired orbit. The purpose of this research is to develop some techniques that can aid in finding some optimal maneuvers (or maneuvers that use the least amount of energy) and will maintain mission requirements while preserving constraints. Two different models will be developed that can minimize energy used in the maneuvers. The first model is a linear set of impulsive maneuvers derived from the Clohessy-Wilshire Equations. This model can be used as a targeting equation for targeting a specific relative orbit that also minimizes the total energy among a series of maneuvers. The second method is a nonlinear model using a Lyapunov Function in a feedback control loop; where the position of a spacecraft relative to a target orbit is minimized and the reference motion can be used to create keep-out zones

Beyond the ecological fallacy: potential problems when studying healthcare organisations.

Ecological studies, which consider patient groups rather than individuals, are common in health policy research. The ‘ecological fallacy’ is a well-recognised methodological concern, but in this perspectives paper, we focus on less often appreciated but equally important limitations of such studies. In particular, we consider reliability and power as they apply to ecological studies, and make recommendations to inform the appropriate design and interpretation of these increasingly popular studies.This research received no specific grant from any funding agency in the public, commercial, or not-for-profit sectors. GL is supported by a Cancer Research UK Clinician Scientist Fellowship (A18180). The views expressed in this publication are those of the authors and not necessarily those of any funder or any other organisation or institution.This is the author accepted manuscript. The final version is available from SAGE via http://dx.doi.org/10.1177/014107681561057

Response rates to patient surveys

BACKGROUND: Patient surveys typically have variable response rates between organizations, leading to concerns that such differences may affect the validity of performance comparisons. OBJECTIVE: To explore the size and likely sources of associations between hospital-level survey response rates and patient experience. RESEARCH DESIGN, SUBJECTS, AND MEASURES: Cross-sectional mail survey including 60 patient experience items sent to 101,771 cancer survivors recently treated by 158 English NHS hospitals. Age, sex, race/ethnicity, socioeconomic status, clinical diagnosis, hospital type, and region were available for respondents and nonrespondents. RESULTS: The overall response rate was 67% (range, 39% to 77% between hospitals). Hospitals with higher response rates had higher scores for all items (Spearman correlation range, 0.03-0.44), particularly questions regarding hospital-level administrative processes, for example, procedure cancellations or medical note availability.From multivariable analysis, associations between individual patient experience and hospital-level response rates were statistically significant (P<0.05) for 53/59 analyzed questions, decreasing to 37/59 after adjusting for case-mix, and 25/59 after further adjusting for hospital-level characteristics.Predicting responses of nonrespondents, and re-estimating hypothetical hospital scores assuming a 100% response rate, we found that currently low performing hospitals would have attained even lower scores. Overall nationwide attainment would have decreased slightly to that currently observed. CONCLUSIONS: Higher response rate hospitals have more positive experience scores, and this is only partly explained by patient case-mix. High response rates may be a marker of efficient hospital administration, and higher quality that should not, therefore, be adjusted away in public reporting. Although nonresponse may result in slightly overestimating overall national levels of performance, it does not appear to meaningfully bias comparisons of case-mix-adjusted hospital results.GL is supported by a Cancer Research UK Clinician Scientist Fellowship (A18180).This is the final version of the article. It first appeared from Wolters Kluwer via http://dx.doi.org/10.1097/MLR.000000000000045

H-Diplo/ISSF Forum 25 on the Importance of White HousePresidential Tapes in Scholarship

A forum discussion on the importance of White House presidential tapes in scholarship

Rare Sarcomatoid Carcinoma of the Liver in a patient with no history of Hepatocellular Carcinoma: A Case Report

Sarcomatoid carcinoma is a rare malignant tumor of unknown pathogenesis characterized by poorly differentiated carcinoma tissue containing sarcoma-like differentiation of either spindle or giant cell and rarely occurs in the gastrointestinal tract and hepatobiliary-pancreatic system.1 Primary hepatic sarcomatoid carcinoma accounts for only 0.2 % of primary malignant liver tumors, and 1.8% of all surgically resected hepatocellular carcinomas.2 The majority of hepatic sarcomatoid carcinoma cases appear to occur simultaneously with hepatocellular or cholangiocellular carcinoma.3 The preferred treatment for hepatic sarcomatoid carcinoma is surgical resection and the overall prognosis is poor.4 This case depicts a 62-year-old female whom underwent initial resection in 2010 of a cavernous hemangioma. Seven years after her initial diagnosis she developed what was initially felt to be local recurrence of the hemangioma but additional diagnostic workup with a liver biopsy confirmed primary hepatic sarcomatoid carcinoma

The association between sociodemographic inequalities, COVID-related impacts and mental health

PURPOSE: There are concerns that the social, economic and health impacts of COVID-19 are unevenly distributed, exacerbating existing inequalities. Here we tested the hypotheses that: (H1) the magnitude of these impacts would be associated with symptoms of depression and anxiety early in the pandemic, and (H2) that these impacts would be associated with a range of sociodemographic risk factors. METHODS: Cross-sectional self-report data were collected from a UK sample (N = 632) between the 16th of May and 21st of July 2020, coinciding with the early stages of the pandemic and first UK lockdown. Data were collected on COVID-19 related impacts including financial and social stressors, symptoms of anxiety and depression, and sociodemographic/economic risk factors operationalised at multiple levels including the individual, familial, household and neighbourhood. RESULTS: Using regression analyses both financial and social impacts were independently associated with anxiety (R2 = 0.23) and depression scores (R2 = 0.24), as well as clinically significant generalised anxiety (R2 = 0.14) and depression (R2 = 0.11). In addition, many sociodemographic factors were associated with elevated levels of COVID-19 related impacts, including being younger, female, having lower educational attainment and lower income. LIMITATIONS: The main limitations of the study were its modest sample size, cross sectional design (which precluded inferences about directions of causality), and the relatively high socioeconomic status of the sample (which limited generalisability). CONCLUSIONS: These findings are consistent with a growing body of evidence that suggests that the pandemic has exacerbated existing inequalities, and further, point to particular groups that should be supported by post-COVID-19 recovery policies and initiatives