Three dimensional thrust chamber life prediction

A study was performed to analytically determine the cyclic thermomechanical behavior and fatigue life of three configurations of a Plug Nozzle Thrust Chamber. This thrust chamber is a test model which represents the current trend in nozzle design calling for high performance coupled with weight and volume limitations as well as extended life for reusability. The study involved the use of different materials and material combinations to evaluate their application to the problem of low-cycle fatigue in the thrust chamber. The thermal and structural analyses were carried out on a three-dimensional basis. Results are presented which show plots of continuous temperature histories and temperature distributions at selected times during the operating cycle of the thrust chamber. Computed structural data show critical regions for low-cycle fatigue and the histories of strain within the regions for each operation cycle

A PLATFORM FOR THE DISCOVERY AND CHARACTERIZATION OF PROTEINS THAT ASSOCIATE WITH PSEUDOMONAS AERUGINOSA RNA POLYMERASE

Pseudomonas aeruginosa is an opportunistic bacterial pathogen notable for its ability to colonize the lungs of cystic fibrosis patients. Once the bacterium infects and colonizes humans, it is extremely difficult to eradicate. This leads to long-term infections that significantly damage the lungs and other tissues. P. aeruginosa infections are challenging to treat due to the bacterium’s natural antibiotic resistance and the rise of multidrug resistant strains. Development of novel drug treatments are a necessity. In all organisms, the regulation of gene expression is a highly controlled process. Remarkably, in P. aeruginosa bioinformatics studies showed that 20% of its genome is dedicated to regulating transcription, the first stage of gene expression. However, the vast majority of proteins that regulate transcription in P. aeruginosa are poorly understood. Understanding gene regulation is a promising strategy for discovery of novel drug targets. RNA polymerase (RNAP) is an essential enzyme controlling gene regulation, and its activity is modulated through a plethora of transcription factors or other proteins. The regulation of gene expression has been best studied in E. coli. The aim of this work was to develop a platform to study RNAP-interacting proteins in P. aeruginosa. To do this, we took advantage of an E. coli RNAP “coreome” library. The RNAP “coreome” was a term developed to describe 38 different plasmids each expressing surface exposed regions of RNAP inputted into a bacterial two-hybrid assay. In general, RNAP is a highly conserved enzyme among bacteria. Alignments of the amino acids of each piece of the E. coli RNAP coreome to specific domains of P. aeruginosa RNAP have shown a high degree of similarity (between 82-100%). The coreome was constructed based on the high-resolution structure of the bacteria Thermus aquaticus RNAP suggesting that E. coli β RNAP can be parsed into 10 sub-domains. Analysis of the E. coli β’ subunit of RNAP suggested that it could be parsed into 18 sub-domains that cover the entire gene (Nickels, 2009). A bacterial two-hybrid assay can be utilized to determine if a specific target protein interacts with domains of RNAP found within the RNAP coreome. Data from the IntAct Molecular Interaction Database identified 147 E. coli proteins that directly or indirectly interact with RNAP. We performed a bioinformatic analyses to identify P. aeruginosa homologs to these E. coli proteins. Initially, sixteen P. aeruginosa proteins were screened against the E. coli RNAP coreome in the bacterial two-hybrid assay. In this work five P. aeruginosa proteins, AlgQ, NusG, ClpA, DppF, and Tig were shown to interact with particular fragments of the E. coli RNAP coreome. Specifically, we show that AlgQ interacted with σ 528-613, NusG interacted with β’249-328 and β’264-308, ClpA interacted with β 829-930 and β 831-1059, DppF interacted with β\u27 114-190 and β 1137-1226, and Tig interacted with β\u27 735-790 and β 450-530. These results indicate the E. coli RNAP coreome can be utilized to uncover RNAP-interacting proteins in P. aeruginosa and to discover the precise domains they contact. In the future if the RNAP-binding determinants or proteins that control expression of virulence factors are identified using the RNAP coreome, it may be possible to design novel drugs that either disrupt the function of those proteins or their interaction with RNAP. Ultimately, this could lead to improved treatment options for P. aeruginosa infections

Structural/thermal considerations for design of large space platform structures

A method is described for placing a large, STS-compatible platform on orbit utilizing a construction method employing both deployable and erectable structures. A multifunctional mechanism is used for deployable structures and an on-orbit assembly is used for erectable structures. Also analyses are discussed which assess the thermal distortion of a simple open truss and a more complex truss

Bullosis diabeticorum in median nerve innervated fingers shortly after carpal tunnel release: case report.

Bullosis diabeticorum is a cutaneous manifestation of diabetes mellitus, mainly observed in the lower extremities in patients with longstanding disease. The etiology is unknown, but an association with neurologic or vascular disturbances has been suggested. We have reviewed a case of a 70-year-old man with rapid development of bullae in median nerve innervated fingertips following carpal tunnel release

Simplified thermal estimation techniques for large space structures

A tool for making rapid estimates of the response of space structures to thermal environments encountered in earth orbits is provided for the designer of these structures. Charts giving heating rates and temperatures for certain typical large spacecraft structural elements are provided. Background information for spacecraft thermal design considerations is presented. Environments, requirements, thermal control techniques, design guidelines, and approaches available for more detailed thermal response analysis are discussed

Lightweight Vacuum Jacket for Cryogenic Insulation - Appendices to Final Report

The feasibility is demonstrated of producing a lightweight vacuum jacket using state-of-the-art technology and materials. Design and analytical studies were made on an orbital maneuvering system fuel tank. Preliminary design details were completed for the tank assembly which included an optimized vacuum jacket and multilayered insulation system. A half-scale LH2 test model was designed and fabricated and a force/stiffness proof test was conducted on the vacuum jacket. A vacuum leak rate of 0.00001 was measured, approximately 1500 hours of vacuum pressure was sustained, and 29 vacuum pressure cycles were experienced prior to failure. For vol. 1, see N75-26192

Does anticoagulation prevent thrombosis for persons with fractures distal to the hip?

Low-molecular-weight heparin (LMWH) prophylaxis significantly reduces the total incidence of deep venous thrombosis (DVT) for patients with lower-limb fractures managed with surgical fixation and cast immobilization (strength of recommendation [SOR]: A, based on multiple randomized controlled studies [RCTs]). Evidence is insufficient to show whether LMWH specifically reduces the risk of clinically significant DVTs, and recommendations on its use are conflicting (SOR: C, based on expert opinion). Evidence is insufficient to recommend for or against warfarin prophylaxis for DVT in fractures distal to the hip (SOR: C, based on expert opinion)

Postural Dysfunction in Children With Cerebral Palsy: Some Implications for Therapeutic Guidance

Postural problems play a central role in the motor dysfunction of children with cerebral palsy (CP). Therefore, they spend more time in sitting than in standing to perform vital tasks of daily life. The focus of this article is to describe the pathophysiology of postural control in sitting and outline some implications for management and treatment. In general, children with CP exhibit muscular activity counteracting forces that disturb equilibrium. Only ‘non-sitting’ children with severe CP lack such ‘direction-specific’ adjustments, possibly ruling out achievement of independent sitting. Most frequently, the children display dysfunctions in the adaptation of the adjustment. Typical characteristics of this adaptation in children with CP are a top-down recruitment of pos tural muscles, an excessive degree of antagonistic coactivation, and an incomplete adaptation of the EMG-amplitude to task specific constraints. Despite our knowledge on the pathophysiology underlying the postural problems in children with CP, little ’high-level’ evidence (according to Sackett) exists on how different interventions can affect these problems. Therapeutic attention to promote motor performance in sitting focuses on adaptive seating, tilting of the support surface, and ample, variable training in motivating settings. The challenge facing us now is to provide evidence about the efficacy of specific treatment approaches facilitating that children reach an optimal level of functioning in daily life

Thermal-structural combined loads design criteria study

A study was conducted to determine methodology for combining thermal structural loads and assessing the effects of the combined loads on the design of a thermal protection system and a hot structure of a high cross range delta wing space shuttle orbiter vehicle. The study presents guidelines for establishing a basis for predicting thermal and pressure environments and for determining limit and ultimate design loads on the vehicle during reentry. Limit trajectories were determined by using dispersions on a representative nominal mission and system parameters expected during the life of the vehicle. Nine chosen locations on the vehicle surface having TPS or hot structures were examined, and weight sensitivity analyses were performed for each location

Evaluation of propellent tank insulation concepts for low-thrust chemical propulsion systems: Executive summary

Cryogenic propellant tank insulations or liquid oxygen/liquid hydrogen low-thrust 2224N (500 lbf) propulsion systems (LTPS) were assessed. The insulation studied consisted of combinations of N2-purged foam and multilayer insulation (MLI) as well as He-purged MLI-only. Heat leak and payload performance predictions were made for three shuttle-launched LTPS designed for shuttle bay packaged payload densities of 56 kg cu/m (3.5 lbm/cu ft), 40 kg/cu m (2.5 lbm/cu ft) and 24 kg/cu m (1.5 lbm/cu ft). Foam/MLI insulations were found to increase LTPS payload delivery capability when compared with He-purged MLI-only. An additional benefit of foam/MLI was reduced operational complexity because orbiter cargo bay N2 purge gas could be used for MLI purging. Maximum payload mass benefit occurred when an enhanced convection, rather than natural convection, heat transfer was specified for the insulation purge enclosure. The enhanced convection environment allowed minimum insulation thickness to be used for the foam/MLI interface temperature selected to correspond to the moisture dew point in the N2 purge gas. Experimental verification of foam/MLI benefits was recommended. A conservative program cost estimate for testing a MLI-foam insulated tank was 2.1 million dollars. This cost could be reduced significantly without increasing program risk