Sensitivity Analysis of Launch Vehicle Debris Risk Model

As part of an analysis of the loss of crew risk associated with an ascent abort system for a manned launch vehicle, a model was developed to predict the impact risk of the debris resulting from an explosion of the launch vehicle on the crew module. The model consisted of a debris catalog describing the number, size and imparted velocity of each piece of debris, a method to compute the trajectories of the debris and a method to calculate the impact risk given the abort trajectory of the crew module. The model provided a point estimate of the strike probability as a function of the debris catalog, the time of abort and the delay time between the abort and destruction of the launch vehicle. A study was conducted to determine the sensitivity of the strike probability to the various model input parameters and to develop a response surface model for use in the sensitivity analysis of the overall ascent abort risk model. The results of the sensitivity analysis and the response surface model are presented in this paper

A Failure Propagation Modeling Method for Launch Vehicle Safety Assessment

A method has been developed with the objective of making the potentially intractable problem of launch vehicle failure propagation somewhat less intractable. The approach taken is to essentially decouple the potentially multi-stepped propagation process into a series of bi-component transition probabilities. These probabilities are then used within a simple Monte Carlo simulation process through which the more complex behavior evolves. The process is described using a simple model problem and some discussion of enhancements for real-world applications is included. The role of the model within a broader analysis process for assessing abort effectiveness from launch vehicle failure modes is also described

Interior Fourier Near-Field Acoustical Holography Using Energy Density

Near-field acoustical holography (NAH) is used to reconstruct three-dimensional acoustic fields from a two-dimensional planar measurement. During previous work at BYU, a method has been developed called energy-based near-field acoustical holography (ENAH), which reduced the number of needed measurements by 75%. Other recent advances have expanded the theory to interior spaces where multiple sources and/or reflections are present. This paper presents a new method for reconstructing interior acoustic parameters using Fourier NAH and a single plane of energy density measurements. Energy density is measured using a six-microphone array. First, the probe measurements are used to create a Hermite surface pressure interpolation on two separate planes. These two planes are used to approximate the normal particle velocity as well as to separate the incoming and outgoing waves using the spatial Fourier-transform method. Once separated, traditional Fourier NAH is used to reconstruct the pressure and normal particle velocity at any point in space. Analytical and experimental results are shown and compared to exterior Fourier NAH approximations. Other drawbacks and benefits are discussed

Simulation Assisted Risk Assessment: Blast Overpressure Modeling

A probabilistic risk assessment (PRA) approach has been developed and applied to the risk analysis of capsule abort during ascent. The PRA is used to assist in the identification of modeling and simulation applications that can significantly impact the understanding of crew risk during this potentially dangerous maneuver. The PRA approach is also being used to identify the appropriate level of fidelity for the modeling of those critical failure modes. The Apollo launch escape system (LES) was chosen as a test problem for application of this approach. Failure modes that have been modeled and/or simulated to date include explosive overpressure-based failure, explosive fragment-based failure, land landing failures (range limits exceeded either near launch or Mode III trajectories ending on the African continent), capsule-booster re-contact during separation, and failure due to plume-induced instability. These failure modes have been investigated using analysis tools in a variety of technical disciplines at various levels of fidelity. The current paper focuses on the development and application of a blast overpressure model for the prediction of structural failure due to overpressure, including the application of high-fidelity analysis to predict near-field and headwinds effects

Determinants and sources of iron intakes of australian toddlers: Findings from the SMILE cohort study

© 2019 by the authors. Licensee MDPI, Basel, Switzerland. The first two years of life is a period of rapid growth and development. During this time a lack of key nutrients, including iron, can have long-lasting effects on motor and cognitive performance. The purpose of this cross-sectional study was to determine intake and sources of iron in a cohort of 828 toddlers (mean age; 13.1 mo) participating in the Adelaide-based Study of Mothers’ and Infants’ Life Events affecting oral health (SMILE), and to identify determinants of iron intake. At approximately 12 months of age, 3 non-consecutive days of dietary intake data were collected using a 24-h recall and 2-days food record. The Multiple Source Method was used to combine data from the 24-h recall and each day of the food record to estimate usual iron intake and descriptive statistics were used to report sources of iron. Linear regression was used to identify associations between iron intake and non-dietary determinants (maternal age, education, country of birth, BMI, socioeconomic position, parity, toddler sex) and primary milk feeding method at 12 months. The mean intake of iron was 7.0 (95% CI 6.7–7.2) mg/day and 18.2% of children had usual intakes below the estimated average requirement of 4 mg/day. The main sources of iron included infant and toddler cereals and formulas. Milk feeding method and parity were significantly associated with iron intake. Toddlers with siblings and those who received breast milk as their primary milk feed had significantly lower iron intakes than only children and those who received formula, respectively. The Australian Infant Feeding Guidelines promote the importance of iron-iron-rich complementary foods such as meat and meat alternatives. However, low intakes of this food group suggest that parents do not recognize the importance of these foods or understand the specific foods that toddlers should be eating

Energy-Based Tetrahedron Sensor for High-Temperature, High-Pressure Environments

An acoustic energy-based probe has been developed that incorporates multiple acoustic sensing elements in order to obtain the acoustic pressure and three-dimensional acoustic particle velocity. With these quantities, the user can obtain various energy-based quantities, including acoustic energy density, acoustic intensity, and acoustic impedance. In this specific development, the probe has been designed to operate in an environment characterized by high temperatures and high pressures as is found in the close vicinity of rocket plumes. Given these capabilities, the probe is designed to be used to investigate the acoustic conditions within the plume of a rocket engine or jet engine to facilitate greater understanding of the noise generation mechanisms in those plumes. The probe features sensors mounted inside a solid sphere. The associated electronics for the probe are contained within the sphere and the associated handle for the probe. More importantly, the design of the probe has desirable properties that reduce the bias errors associated with determining the acoustic pressure and velocity using finite sum and difference techniques. The diameter of the probe dictates the lower and upper operating frequencies for the probe, where accurate measurements can be acquired. The current probe design implements a sphere diameter of 1 in. (2.5 cm), which limits the upper operating frequency to about 4.5 kHz. The sensors are operational up to much higher frequencies, and could be used to acquire pressure data at higher frequencies, but the energy-based measurements are limited to that upper frequency. Larger or smaller spherical probes could be designed to go to lower or higher frequency rang

An Integrated Reliability and Physics-Based Risk Modeling Approach for Assessing Human Spaceflight Systems

This paper presents an integrated reliability and physics-based risk modeling approach for assessing human spaceflight systems. The approach is demonstrated using an example, end-to-end risk assessment of a generic-crewed space transportation system during a reference mission to the International Space Station. The behavior of the system is modeled using analysis techniques from multiple disciplines in order to properly capture the dynamic time- and state- dependent consequences of failures encountered in different mission phases. We discuss how to combine traditional reliability analyses with Monte Carlo simulation methods and physics-based engineering models to produce loss-of- mission and loss-of-crew risk estimates supporting risk-based decision-making and requirement verification. This approach facilitates risk-informed design by providing more realistic representation of system failures and interactions; identifying key risk-driving sensitivities, dependencies, and assumptions; and tracking multiple figures of merit within a single, responsive assessment framework that can readily incorporate evolving design information throughout system development

Binding of Pseudomonas aeruginosa Apo-Bacterioferritin Associated Ferredoxin to Bacterioferritin B Promotes Heme Mediation of Electron Delivery and Mobilization of Core Mineral Iron†

The bfrB gene from Pseudomonas aeruginosa was cloned and expressed in E. coli. The resultant protein (BfrB), which assembles into a 445.3 kDa complex0020from 24 identical subunits, binds 12 molecules of heme axially coordinated by two Met residues. BfrB, isolated with 5–10 iron atoms per protein molecule, was reconstituted with ferrous ions to prepare samples with a core mineral containing 600 ± 40 ferric ions per BfrB molecule and approximately one phosphate molecule per iron atom. In the presence of sodium dithionite or in the presence of P. aeruginosa ferredoxin NADP reductase (FPR) and NADPH the heme in BfrB remains oxidized and the core iron mineral is mobilized sluggishly. In stark contrast, addition of NADPH to a solution containing BfrB, FPR and the apo-form of P. aeruginosa bacterioferritin associated ferredoxin (apo-Bfd) results in rapid reduction of the heme in BfrB and in the efficient mobilization of the core iron mineral. Results from additional experimentation indicate that Bfd must bind to BfrB to promote heme mediation of electrons from the surface to the core to support the efficient mobilization of ferrous ions from BfrB. In this context, the thus far mysterious role of heme in bacterioferritins has been brought to the front by reconstituting BfrB with its physiological partner, apo-Bfd. These findings are discussed in the context of a model for the utilization of stored iron in which the significant upregulation of the bfd gene under low-iron conditions [Ochsner, U.A., Wilderman, P.J., Vasil, A.I., and Vasil, M.L. (2002) Mol. Microbiol. 45, 1277–1287] ensures sufficient concentrations of apo-Bfd to bind BfrB and unlock the iron stored in its core. Although these findings are in contrast to previous speculations suggesting redox mediation of electron transfer by holo-Bfd, the ability of apo-Bfd to promote iron mobilization is an economical strategy used by the cell because it obviates the need to further deplete cellular iron levels to assemble iron sulfur clusters in Bfd before the iron stored in BfrB can be mobilized and utilized

Structural Studies of Bacterioferritin B (BfrB) from Pseudomonas aeruginosa Suggest a Gating Mechanism for Iron Uptake via the Ferroxidase Center

The structure of recombinant P. aeruginosa bacterioferritin B (Pa BfrB) has been solved from crystals grown from protein devoid of core mineral iron (as-isolated) and from protein mineralized with ~ 600 iron atoms (mineralized). Structures were also obtained from crystals grown from mineralized BfrB after soaking them in FeSO4 solution (Fe soak) and in separate experiments after soaking them in FeSO4 solution followed by soaking in crystallization solution (double soak). Although the structures consist of a typical bacterioferritin fold comprised of a nearly spherical 24-mer assembly that binds 12 heme molecules, comparison of microenvironments observed in the distinct structures provided interesting insights: The ferroxidase center in the as-isolated, mineralized and double soak structures is empty. The ferroxidase ligands (except His130) are poised to bind iron with minimal conformational changes. The His130 side chain, on the other hand, must rotate toward the ferroxidase center to coordinate iron. In comparison, the structure obtained from crystals soaked in an FeSO4 solution display a fully occupied ferroxidase center and iron bound to the internal, Fe(in), and external, Fe(out), surfaces of Pa BfrB. The conformation of His130 in this structure is rotated toward the ferroxidase center and coordinates an iron ion. The structures also revealed a pore on the surface of Pa BfrB that likely serves as an entry port for Fe2+ to the ferroxidase center. On its opposite end the pore is capped by the side chain of His130 when it adopts its “gate closed” conformation that enables coordination to a ferroxidase iron. A change to its “gate-open”, non-coordinative conformation, creates a path for the translocation of iron from the ferroxidase center to the interior cavity. These structural observations, together with findings obtained from iron incorporation measurements in solution suggest that the ferroxidase pore is the dominant entry route for the uptake of iron by Pa BfrB. These findings, which are clearly distinct from those made with E. coli Bfr (Crow, A. C., Lawson, T. L., Lewin, A., Moore, G. R., and Le Brun, N. E. (2009) J. Am. Chem. Soc. 131, 6808–6813) indicate that not all bacterioferritins operate in the same manner

Identification of an unusual Brucella strain (BO2) from a lung biopsy in a 52 year-old patient with chronic destructive pneumonia

<p>Abstract</p> <p>Background</p> <p>Brucellosis is primarily a zoonotic disease caused by <it>Brucella </it>species. There are currently ten <it>Brucella </it>spp. including the recently identified novel <it>B. inopinata </it>sp. isolated from a wound associated with a breast implant infection. In this study we report on the identification of an unusual <it>Brucella</it>-like strain (BO2) isolated from a lung biopsy in a 52-year-old patient in Australia with a clinical history of chronic destructive pneumonia.</p> <p>Results</p> <p>Standard biochemical profiles confirmed that the unusual strain was a member of the <it>Brucella </it>genus and the full-length 16S rRNA gene sequence was 100% identical to the recently identified <it>B. inopinata </it>sp. nov. (type strain BO1^T). Additional sequence analysis of the <it>recA, omp2a </it>and <it>2b </it>genes; and multiple locus sequence analysis (MLSA) demonstrated that strain BO2 exhibited significant similarity to the <it>B. inopinata </it>sp. compared to any of the other <it>Brucella </it>or <it>Ochrobactrum </it>species. Genotyping based on multiple-locus variable-number tandem repeat analysis (MLVA) established that the BO2 and BO1^Tstrains form a distinct phylogenetic cluster separate from the other <it>Brucella </it>spp.</p> <p>Conclusion</p> <p>Based on these molecular and microbiological characterizations, we propose that the BO2 strain is a novel lineage of the newly described <it>B. inopinata </it>species.</p