The General Mission Analysis Tool (GMAT) System Test Plan

This document serves as the System Test Approach for the GMAT Project. Preparation for system testing consists of three major stages: 1) The Test Approach sets the scope of system testing, the overall strategy to be adopted, the activities to be completed, the general resources required and the methods and processes to be used to test the release. It also details the activities, dependencies and effort required to conduct the System Test. 2) Test Planning details the activities, dependencies and effort required to conduct the System Test. 3) Test Cases documents the tests to be applied, the data to be processed, the automated testing coverage and the expected results. This document covers the first two of these items, and established the framework used for the GMAT test case development. The test cases themselves exist as separate components, and are managed outside of and concurrently with this System Test Plan

The General Mission Analysis Tool (GMAT): Current Features And Adding Custom Functionality

The General Mission Analysis Tool (GMAT) is a software system for trajectory optimization, mission analysis, trajectory estimation, and prediction developed by NASA, the Air Force Research Lab, and private industry. GMAT's design and implementation are based on four basic principles: open source visibility for both the source code and design documentation; platform independence; modular design; and user extensibility. The system, released under the NASA Open Source Agreement, runs on Windows, Mac and Linux. User extensions, loaded at run time, have been built for optimization, trajectory visualization, force model extension, and estimation, by parties outside of GMAT's development group. The system has been used to optimize maneuvers for the Lunar Crater Observation and Sensing Satellite (LCROSS) and ARTEMIS missions and is being used for formation design and analysis for the Magnetospheric Multiscale Mission (MMS)

Longitudinal and cross-sectional modelling of health related quality of life in people with cystic fibrosis

People with cystic fibrosis (CF) must endure up to four hours treatment per day to maintain health and are vulnerable to complications. The Cystic Fibrosis Quality of Life Questionnaire was developed to measure health related quality of life (HRQoL) in the UK. Most studies on HRQoL are cross-sectional in design with HRQoL measured once per patient. However, the Cystic Fibrosis Quality of Life Questionnaire has been used to monitor HRQoL longitudinally with measures taken over a 12 year period at one clinic in the UK. These data were modelled with a binomial distribution for a domain score and with fixed and random coefficients for the patient-level clinical and demographic variables. The longitudinal study included 182 patients whose HRQoL was first measured within a single calendar year and were then followed-up. These data provided an opportunity to compare, directly and by simulation, the modelling of a cross-sectional with the modelling of a longitudinal study and so provided insights into the statistical merits of longitudinal studies compared to cross-sectional studies in HRQoL

Is reduction in the risk of vision loss the only benefit of photodynamic therapy in predominantly classic subfoveal choroidal neovascularization?

Nicola G Ghazi, rian P Conway, James S Tiedeman, Steven J YoonUniversity of Virginia Health System, Department of Ophthalmology, Charlottesville, VA, USAPurpose: To emphasize the effect of photodynamic therapy (PDT) on the size and progression of the neovascular lesion (NL) and evolution of the disciform scar (DS) in predominantly classic subfoveal choroidal neovascularization (SFCNV).Methods: A retrospective study of 62 eyes treated with PDT for SFCNV was performed. The greatest linear dimension (GLD) before and at last follow-up after treatment and the size of the DS post-PDT were analyzed. A subgroup of patients with DS in their fellow eye at presentation without prior PDT was also studied. The size of the scar in these eyes was compared to that following PDT.Results: After an average follow-up at 9 months, the size of the NL was stabilized or reduced in 64% of the study eyes with absence of fluorescein leakage in 45%. Only 3 eyes (5%) developed DS. At presentation, 14 patients already had DS in their fellow eye, the size of which was significantly larger than that post-PDT (p = 0.044). It was also significantly larger than that of the potential scar in the study eyes of the same subgroup of patients (p = 0.002) and of the rest of the patients (p = 0.0001).Conclusion: This study demonstrates a beneficial effect for PDT on the size of the NL and DS in SFCNV, which might be of great significance, particularly when PDT fails to prevent severe vision loss.Keywords: age-related macular degeneration, choroidal neovascularization, classic choroidal neovascularization, disciform scarring, fluorescein angiography, photodynamic therap

General Mission Analysis Tool (GMAT) Architectural Specification. Draft

Early in 2002, Goddard Space Flight Center (GSFC) began to identify requirements for the flight dynamics software needed to fly upcoming missions that use formations of spacecraft to collect data. These requirements ranged from low level modeling features to large scale interoperability requirements. In 2003 we began work on a system designed to meet these requirement; this system is GMAT. The General Mission Analysis Tool (GMAT) is a general purpose flight dynamics modeling tool built on open source principles. The GMAT code is written in C++, and uses modern C++ constructs extensively. GMAT can be run through either a fully functional Graphical User Interface (GUI) or as a command line program with minimal user feedback. The system is built and runs on Microsoft Windows, Linux, and Macintosh OS X platforms. The GMAT GUI is written using wxWidgets, a cross platform library of components that streamlines the development and extension of the user interface Flight dynamics modeling is performed in GMAT by building components that represent the players in the analysis problem that is being modeled. These components interact through the sequential execution of instructions, embodied in the GMAT Mission Sequence. A typical Mission Sequence will model the trajectories of a set of spacecraft evolving over time, calculating relevant parameters during this propagation, and maneuvering individual spacecraft to maintain a set of mission constraints as established by the mission analyst. All of the elements used in GMAT for mission analysis can be viewed in the GMAT GUI or through a custom scripting language. Analysis problems modeled in GMAT are saved as script files, and these files can be read into GMAT. When a script is read into the GMAT GUI, the corresponding user interface elements are constructed in the GMAT GUI. The GMAT system was developed from the ground up to run in a platform agnostic environment. The source code compiles on numerous different platforms, and is regularly exercised running on Windows, Linux and Macintosh computers by the development and analysis teams working on the project. The system can be run using either a graphical user interface, written using the open source wxWidgets framework, or from a text console. The GMAT source code was written using open source tools. GSFC has released the code using the NASA open source license

Precolonized Human Commensal \u3cem\u3eEscherichia coli\u3c/em\u3e Strains Serve as a Barrier to \u3cem\u3eE. coli\u3c/em\u3e O157:H7 Growth in the Streptomycin-Treated Mouse Intestine

Different Escherichia coli strains generally have the same metabolic capacity for growth on sugars in vitro, but they appear to use different sugars in the streptomycin-treated mouse intestine (Fabich et al., Infect. Immun. 76:1143-1152, 2008). Here, mice were precolonized with any of three human commensal strains (E. coli MG1655, E. coli HS, or E. coli Nissle 1917) and 10 days later were fed 105 CFU of the same strains. While each precolonized strain nearly eliminated its isogenic strain, confirming that colonization resistance can be modeled in mice, each allowed growth of the other commensal strains to higher numbers, consistent with different commensal E. coli strains using different nutrients in the intestine. Mice were also precolonized with any of five commensal E. coli strains for 10 days and then were fed 105 CFU of E. coli EDL933, an O157:H7 pathogen. E. coli Nissle 1917 and E. coli EFC1 limited growth of E. coli EDL933 in the intestine (103 to 104 CFU/gram of feces), whereas E. coli MG1655, E. coli HS, and E. coli EFC2 allowed growth to higher numbers (106 to 107 CFU/gram of feces). Importantly, when E. coli EDL933 was fed to mice previously co-colonized with three E. coli strains (MG1655, HS, and Nissle 1917), it was eliminated from the intestine (/gram of feces). These results confirm that commensal E. coli strains can provide a barrier to infection and suggest that it may be possible to construct E. coli probiotic strains that prevent growth of pathogenic E. coli strains in the intestine

l-Fucose Stimulates Utilization of d-Ribose by \u3cem\u3eEscherichia coli\u3c/em\u3e MG1655 ΔfucAO and \u3cem\u3eE. coli\u3c/em\u3e Nissle 1917 ΔfucAO Mutants in the Mouse Intestine and in M9 Minimal Medium

Escherichia coli MG1655 uses several sugars for growth in the mouse intestine. To determine the roles of l-fucose and d-ribose, an E. coli MG1655 ΔfucAO mutant and an E. coli MG1655 ΔrbsK mutant were fed separately to mice along with wild-type E. coli MG1655. The E. coli MG1655 ΔfucAO mutant colonized the intestine at a level 2 orders of magnitude lower than that of the wild type, but the E. coli MG1655 ΔrbsK mutant and the wild type colonized at nearly identical levels. Surprisingly, an E. coli MG1655 ΔfucAO ΔrbsK mutant was eliminated from the intestine by either wild-type E. coli MG1655 or E. coli MG1655 ΔfucAO, suggesting that the ΔfucAO mutant switches to ribose in vivo. Indeed, in vitro growth experiments showed that l-fucose stimulated utilization of d-ribose by the E. coli MG1655 ΔfucAO mutant but not by an E. coli MG1655 ΔfucK mutant. Since the ΔfucK mutant cannot convert l-fuculose to l-fuculose-1-phosphate, whereas the ΔfucAO mutant accumulates l-fuculose-1-phosphate, the data suggest that l-fuculose-1-phosphate stimulates growth on ribose both in the intestine and in vitro. An E. coli Nissle 1917 ΔfucAO mutant, derived from a human probiotic commensal strain, acted in a manner identical to that of E. coli MG1655 ΔfucAO in vivo and in vitro. Furthermore, l-fucose at a concentration too low to support growth stimulated the utilization of ribose by the wild-type E. coli strains in vitro. Collectively, the data suggest that l-fuculose-1-phosphate plays a role in the regulation of ribose usage as a carbon source by E. coli MG1655 and E. coli Nissle 1917 in the mouse intestine

Mouse Intestine Selects Nonmotile \u3cem\u3eflhDC\u3c/em\u3e Mutants of \u3cem\u3eEscherichia coli\u3c/em\u3e MG1655 with Increased Colonizing Ability and Better Utilization of Carbon Sources

d-Gluconate which is primarily catabolized via the Entner-Doudoroff (ED) pathway, has been implicated as being important for colonization of the streptomycin-treated mouse large intestine by Escherichia coli MG1655, a human commensal strain. In the present study, we report that an MG1655 Δedd mutant defective in the ED pathway grows poorly not only on gluconate as a sole carbon source but on a number of other sugars previously implicated as being important for colonization, including l-fucose, d-gluconate, d-glucuronate, N-acetyl-d-glucosamine, d-mannose, and d-ribose. Furthermore, we show that the mouse intestine selects mutants of MG1655 Δedd and wild-type MG1655 that have improved mouse intestine-colonizing ability and grow 15 to 30% faster on the aforementioned sugars. The mutants of MG1655 Δedd and wild-type MG1655 selected by the intestine are shown to be nonmotile and to have deletions in the flhDC operon, which encodes the master regulator of flagellar biosynthesis. Finally, we show that ΔflhDC mutants of wild-type MG1655 and MG1655 Δedd constructed in the laboratory act identically to those selected by the intestine; i.e., they grow better than their respective parents on sugars as sole carbon sources and are better colonizers of the mouse intestine

Respiration of \u3cem\u3eEscherichia coli\u3c/em\u3e in the Mouse Intestine

Mammals are aerobes that harbor an intestinal ecosystem dominated by large numbers of anaerobic microorganisms. However, the role of oxygen in the intestinal ecosystem is largely unexplored. We used systematic mutational analysis to determine the role of respiratory metabolism in the streptomycin-treated mouse model of intestinal colonization. Here we provide evidence that aerobic respiration is required for commensal and pathogenic Escherichia coli to colonize mice. Our results showed that mutants lacking ATP synthase, which is required for all respiratory energy-conserving metabolism, were eliminated by competition with respiratory-competent wild-type strains. Mutants lacking the high-affinity cytochrome bd oxidase, which is used when oxygen tensions are low, also failed to colonize. However, the low-affinity cytochrome bo3 oxidase, which is used when oxygen tension is high, was found not to be necessary for colonization. Mutants lacking either nitrate reductase or fumarate reductase also had major colonization defects. The results showed that the entire E. coli population was dependent on both microaerobic and anaerobic respiration, consistent with the hypothesis that the E. coli niche is alternately microaerobic and anaerobic, rather than static. The results indicate that success of the facultative anaerobes in the intestine depends on their respiratory flexibility. Despite competition for relatively scarce carbon sources, the energy efficiency provided by respiration may contribute to the widespread distribution (i.e., success) of E. coli strains as commensal inhabitants of the mammalian intestine