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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 1,477 records · Page 82
All sourcesNASA NTRSDOE OSTI
DOE OSTI2018

Genome Features and Biochemical Characteristics of a Robust, Fast Growing and Naturally Transformable Cyanobacterium Synechococcus elongatus PCC 11801 Isolated from India

Cyanobacteria provide an interesting platform for biotechnological applications due to their efficient photoautotrophic growth, amenability to genetic engineering and the ability to grow on non-arable land. An ideal industrial strain of cyanobacteria would need to be fast growing and tolerant to high levels of temperature, light, carbon dioxide, salt and be naturally transformable. In this study, we report Synechococcus elongatus PCC 11801, a strain isolated from India that fulfills these requirements. The physiological and biochemical characteristics of PCC 11801 under carbon and light-limiting conditions were investigated. PCC 11801 shows a doubling time of 2.3h, that is the fastest growth for any cyanobacteria reported so far under ambient CO2 conditions. Genome sequence of PCC 11801 shows genome identity of ~83% with its closest neighbors Synechococcus elongatus PCC 7942 and Synechococcus elongatus UTEX 2973. The unique attributes of PCC 11801 genome are discussed in light of the physiological characteristics that are needed in an industrial strain. The genome of PCC 11801 shows several genes that do not have homologs in neighbor strains PCC 7942 and UTEX 2973, some of which may be responsible for adaptation to various abiotic stresses. The remarkably fast growth rate of PCC 11801 coupled with its robustness and ease of genetic transformation makes it an ideal candidate for the photosynthetic production of fuels and chemicals.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2016

Impact of post metal annealing on gate work function engineering for advanced MOS applications

Ultra thin HfO{sub 2} high-k gate dielectric has been deposited directly on strained Si{sub 0.81}Ge{sub 0.19} by Atomic Layer Deposition (ALD) technique. The influence of different types of metal gate electrodes (Al, Au, Pt) on electrical characteristics of Metal-Oxide-Semiconductor capacitors has been studied. Our results show that the electrical characteristics of MOS device are highly dependent on the gate electrodes used. The dependency of electrical characteristics on post metal annealing was studied in detail. The measured flat band (V{sub fb}) and hysteresis (ΔV{sub fb}) from high frequency C-V characteristics were used to study the pre-existing traps in the dielectric. Impact of PMA on interface state density (D{sub it}), border trap density (N{sub bt}) and oxide trap density (Q{sub f/q}) of high-k gate stack were also examined for all the devices. The N{sub bt} and frequency dispersion significantly reduces to ~2.77x1010 cm{sup −2} and ~11.34 % respectively in case of Al electrode with a Dit value of ~4x10{sup 12} eV{sup −1}cm{sup −2} after PMA (350°C) in N{sub 2}, suggesting an improvement in device performance while Pt electrode shows a much less value of ΔVfb (~0.02 V) and Dit (~3.44x10{sup 12} eV{sup −1}cm{sup −2}) after PMA.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2016

Quench degradation limit of multifilamentary AgBi 2 Sr 2 CaCu 2 O x round wires

Understanding safe operating limits of composite superconducting wires is important for the design of superconducting magnets. Here we report measurements of quench-induced critical current density Jc degradation in commercial Ag/Bi 2 Sr 2 CaCu 2 O x (Bi-2212) round wires using heater-induced quenches at 4.2 K in self magnetic field that reveal a general degradation behavior. J c degradation strongly depends on the local hot spot temperature T max , and is nearly independent of operating current, the temperature gradient along the conductor dT max /dx, and the temperature rising rate dT max /dt. Both J c and n value (where n is an index of the sharpness of the superconductor-to-normal transition) exhibit small but irreversible degradation when T max exceeds 400-450 K, and large degradation occurs when Tmax exceeds 550 K. This behavior was consistently found for a series of Bi-2212 wires with widely variable wire architectures and porosity levels in the Bi-2212 filaments, including a wire processed using a standard partial melt processing and in which Bi-2212 filaments are porous, an overpressure processed wire in which Bi-2212 filaments are nearly porosity-free and that has a J c (4.2 K, self field) exceeding 8000 A/mm 2 , and a wire that has nearly no filament to filament bridges after reaction. Microstructural observations of degraded wires reveal cracks in the Bi-2212 filaments perpendicular to the wire axis, indicating that the quench-induced I c degradation is primarily driven by strain. These results further suggest that the quench degradation temperature limit depends on the strain state of Bi-2212 filaments and this dependence shall be carefully considered when engineering a high-field Bi-2212 magnet.

43 PARTICLE ACCELERATORS↗
DOE OSTI2023

Development of genetic tools for heterologous protein expression in a pentose‐utilizing environmental isolate of Pseudomonas putida

Abstract Pseudomonas putida has emerged as a promising host for the conversion of biomass‐derived sugars and aromatic intermediates into commercially relevant biofuels and bioproducts. Most of the strain development studies previously published have focused on P. putida KT2440, which has been engineered to produce a variety of non‐native bioproducts. However, P. putida is not capable of metabolizing pentose sugars, which can constitute up to 25% of biomass hydrolysates. Related P. putida isolates that metabolize a larger fraction of biomass‐derived carbon may be attractive as complementary hosts to P. putida KT2440. Here we describe genetic tool development for P. putida M2, a soil isolate that can metabolize pentose sugars. The functionality of five inducible promoter systems and 12 ribosome binding sites was assessed to regulate gene expression. The utility of these expression systems was confirmed by the production of indigoidine from C6 and C5 sugars. Chromosomal integration and expression of non‐native genes was achieved by using chassis‐independent recombinase‐assisted genome engineering (CRAGE) for single‐step gene integration of biosynthetic pathways directly into the genome of P. putida M2. These genetic tools provide a foundation to develop hosts complementary to P. putida KT2440 and expand the ability of this versatile microbial group to convert biomass to bioproducts.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2025

Investigation of the Cyanothece nitrogenase cluster in Synechocystis : a blueprint for engineering nitrogen-fixing photoautotrophs

ABSTRACT The nitrogenase gene cluster of unicellular diazotrophic cyanobacteria, such asCyanothece, is frequently selected by nature for nitrogen-fixing partnerships with eukaryotic phototrophs. The essential cluster components that confer an advantage in such partnerships remain underexplored. To use this cluster for the development of synthetic, phototrophic nitrogen-fixing systems, a thorough and systematic analysis of its constituent genes is necessary. An initial effort to assess the possibility of engineering this cluster into non-diazotrophic phototrophs led to the generation of aSynechocystis6803 strain with significant nitrogenase activity. In the current study, a refactoring approach was taken to determine the dispensability of the non-structural genes in the cluster and define a minimal gene set for constructing a functional nitrogenase for phototrophs. Using a bottom-up strategy, thenifgenes fromCyanothece51142 were re-organized to form new operons. The genes were then seamlessly removed to determine their essentiality in the nitrogen fixation process. We demonstrate that besides the structural genesnifHDK,nifBSUENPVZTXW, as well ashesAB, are important for optimal nitrogenase function in a phototroph. We also show that optimal expression of these genes is crucial for efficient nitrogenase activity. Our findings provide a solid foundation for generating synthetic systems that will facilitate solar-powered conversion of atmospheric nitrogen into nitrogen-rich compounds, a stride toward a greener world. IMPORTANCE Integrating nitrogen fixation genes into various photosynthetic organisms is an exciting strategy for converting atmospheric nitrogen into nitrogen-rich products in a green and energy-efficient way. In order to facilitate this process, it is essential that we understand the fundamentals of the functioning of a prokaryotic nitrogen-fixing machinery in a non-diazotrophic, photoautotrophic cell. This study examines a nitrogenase gene cluster that has been naturally selected on multiple occasions for a nitrogen-fixing partnership by eukaryotic photoautotrophs and provides a basic blueprint for designing a photosynthetic organism with nitrogen-fixing ability.

Microbiology↗
NASA NTRS1972

Dimensional stability and micromechanical properties of materials for use in an Orbiting Astronomical Observatory.

This paper considers the problem of irreversible dimensional changes of the order of one thousandth of an inch per inch in several candidate materials for orbiting observatories. Although there are a number of potential sources for such dimensional changes, those given major consideration here are applied stresses and residual stresses. Results of room-temperature microyield strength (MYS) and microcreep tests to detect permanent strains associated with both short- and long-duration loading are reported for several engineering materials, including four aluminum alloys (2024, 5456, 6061, and 2014), I400 beryllium, TZM molybdenum, AZ31 magnesium, two titanium alloys (Ti-6Al-4V and Ti-5Al-2.5Sn), 321 stainless steel, a graphite/epoxy composite, and low-expansion glass ceramics. The data indicate that: metallic materials have no true elastic limit; the MYS cannot be predicted reliably from, and is appreciably less than, the conventional yield strength: significant microcreep and stress relaxation can occur at stresses somewhat below the MYS.

Marschall, C. W.↗
NASA NTRS1982

Rapid approximate determination of nonlinear solutions - Application to aerodynamic flows and design/optimization problems

Stahara et al. (1978) have considered the use of an approximation technique which employs two or more nonlinear base solutions determined by the full computational method to predict entire families of related nonlinear solutions. The present investigation provides results for several applications of that method which demonstrate both its accuracy and its utility for engineering applications. Attention is given to the perturbation concept and methods, aspects of coordinate straining, aspects of analytical formulation, and an application to surface properties. In a discussion of the results, single and multiple parameter perturbations are considered along with a combination of the approximation method with optimization procedures. The results show that it is possible to combine in certain cases large savings in computational cost with improved optimization.

Stahara, S. S.↗
NASA NTRS1982

Life prediction and constitutive behavior: Overview

The evolution of programs to investigate high temperature consititutive behavior and develop cyclic life prediction methods is reviewed. Contracts granted for developing and verifying workable engineering methods for the calculation, in advance of service, of the local stress-strain response at the critical life governing location in typical hot section components as well as the resultant cyclic crack initiation and crack growth lifetimes are listed. The Langley fatigue facility is being upgraded to include: (1) a servocontrolled testing machine for high temperature crack growth; (2) three servocontrolled tension/torsion machines for biaxial studies; (3) a HOST/satellite computer for data acquisition, processing, storage, and retrieval; and (4) HCV/LCF machines for cumulative damage studies.

Halford, G. R.↗
NASA NTRS1989

Finite element analysis of the Space Shuttle Main Engine (SSME) high pressure fuel turbopump turbine blade (HPFTP)

Cracking of the turbine blades of the SSME HPFTP is studied using two- and three-dimensional finite element analysis. The development and composition of the two- and three-dimensional models are described. Analyses are conducted under the speed, pressure, and thermal load conditions that occur during the full power level of the engine. The effects of friction on the two-dimensional model are examined. The strain and life cycle data reveal that the LCF cracking in the first stage is not probable unless the effects of fit-up tolerance between the blade and rotor are present, and for the second stage it is predicted that hydrogen assisted LCF cracking will occur under the present thermal environment. Design modifications to alleviate this cracking are discussed.

Lee, H. M.↗
NASA NTRS1995

Active Suppression Of Vibrations On Aircraft Structures

Method of active suppression of nonlinear and nonstationary vibrations developed to reduce sonic fatigue and interior noise in high-speed aircraft. Structure of aircraft exhibits periodic, chaotic, and random vibrations when forced by high-intensity sound from jet engines, shock waves, turbulence, and separated flows. Method of suppressing vibrations involves feedback control: Strain gauges or other sensors mounted in paths of propagation of vibrations on structure sense vibrations; outputs of sensors processed into control signal applied to actuator mounted on structure, inducing compensatory forces.

Maestrello, Lucio↗
NASA NTRS2004

An Assessment of Variability in the Average Tensile Properties of a Melt-Infiltrated SiC/SiC Composite

Woven SiC/SiC Ceramic Matrix Composites (CMCs), manufactured by the slurry-cast, melt-infiltration process are under consideration as combustor liner materials in aircraft gas turbine engines. Tensile properties (elastic modulus, proportional limit strength, in-plane tensile strength and strain to failure) of the CMC, manufactured during two separate time periods (9/99 and 1/01) were determined at 816 and 1024 C by conducting tensile tests on specimens machined from the CMC plates. A total of 24 tensile tests were conducted for each temperature and CMC variant combination. In this study average tensile properties of the two cMC variants were statistically compared to evaluate significant differences, if any, within the CMC's properties.

Kalluri, Sreeramesh↗
NASA NTRSDate not supplied

Use of Tardigrade Proteins for Enhancing Cellular Stress Tolerance on the Moon

With sights set on returning a human presence to the Moon and plans to explore even farther beyond, it is imperative we understand the impact of deep space radiation, partial gravity, and the lunar surface on biology. The need for countermeasures to protect future astronauts from the unique conditions of space is ever-pressing and an assessment of bioproduction capabilities in space is a crucial step for sustaining long-term missions. The Lunar Explorer Instrument for space biology Applications (LEIA) aims to investigate the cell’s response to the lunar environment and test strategies for enhancing cellular tolerance on the Moon, utilizing the budding yeast Saccharomyces cerevisiae as a biosensor. S. cerevisiae serves as an excellent model organism due to its widespread use as an analog for human cells, well-characterized set of genetic tools, and ability to survive desiccation. However, these cells must remain desiccated for up to one year prior to launch and the radiation-sensitive strains designed for LEIA will likely be more vulnerable to desiccation effects. In this work, we introduce tardigrade proteins known for their protective mechanisms into potential LEIA strains to test genetic strategies for improving desiccation and radiation tolerance. Tardigrades are extremotolerant animals well-known for their ability to survive in harsh environments. Notably, they can survive extreme desiccation and radiation due to the upregulation of intrinsically disordered proteins (IDPs). It has been shown that integration of these tardigrade IDPs, such as cytosolic abundant heat-soluble (CAHS) proteins, into yeast can confer increased desiccation tolerance in synergy with trehalose. Our ongoing testing and assessment of bioengineered radiation and desiccation tolerance will help us gain insight into optimizing strain design and selection for protecting LEIA’s biological payload as well as genetic engineering strategies for enhancing bioproduction potential for future missions beyond low Earth orbit.

Genetics↗
NASA NTRSDate not supplied

Use of Tardigrade Proteins for Enhancing Cellular Stress Tolerance on the Moon

With sights set on returning a human presence to the Moon and plans to explore even farther beyond, it is imperative we understand the impact of deep space radiation, partial gravity, and the lunar surface on biology. The need for countermeasures to protect future astronauts from the unique conditions of space is ever-pressing and an assessment of bioproduction capabilities in space is a crucial step for sustaining long-term missions. The Lunar Explorer Instrument for space biology Applications (LEIA) aims to investigate the cell’s response to the lunar environment and test strategies for enhancing cellular tolerance on the Moon, utilizing the budding yeast Saccharomyces cerevisiae as a biosensor. S. cerevisiae serves as an excellent model organism due to its widespread use as an analog for human cells, well-characterized set of genetic tools, and ability to survive desiccation. However, these cells must remain desiccated for up to one year prior to launch and the radiation-sensitive strains designed for LEIA will likely be more vulnerable to desiccation effects. In this work, we introduce tardigrade proteins known for their protective mechanisms into potential LEIA strains to test genetic strategies for improving desiccation and radiation tolerance. Tardigrades are extremotolerant animals well-known for their ability to survive in harsh environments. Notably, they can survive extreme desiccation and radiation due to the upregulation of intrinsically disordered proteins (IDPs). It has been shown that integration of these tardigrade IDPs, such as cytosolic abundant heat-soluble (CAHS) proteins, into yeast can confer increased desiccation tolerance in synergy with trehalose. Our ongoing testing and assessment of bioengineered radiation and desiccation tolerance will help us gain insight into optimizing strain design and selection for protecting LEIA’s biological payload as well as genetic engineering strategies for enhancing bioproduction potential for future missions beyond low Earth orbit.

Genetics↗
NASA NTRS2024

What is “First Ply Failure” in a Unidirectionally Loaded Quasi-Isotropic Composite (and does it exist)?

This study presents experimental results of unidirectional tension tests on quasi-isotropic laminates to observe so called “first ply failure” (FPF). The modulus of the laminates was measured throughout the test to observe any ply degradation. Quasi-isotropic (QI) laminates were tested since this is the most common layup sequence of a laminate in industry and FPF, if it exists to any practical extent, should be observed. The authors are unaware of any claim that only bi-axial loads are needed to cause FPF, thus uniaxial testing was performed since this is much simpler than bi-axial testing. Laminates can be engineered to cause anomalies (“knees” or abrupt change in modulus) in a stress-strain curve (such as sandwiching multiple 90° plies between a couple of 0° plies) but such laminates should never be used in practice. The search for FPF was examined in simple 8 ply QI laminates by stopping tension tests at various levels post predicted FPF and examining the specimen for “ply failure” and ascertaining its effect (if any) on the modulus of the laminate. The ultimate strength values were found for some specimens. Results showed that for 8 ply QI laminates, no FPF of note was found and challenges the whole notion of FPF and thus “progressive failure”.

First ply failure↗
NASA NTRS1992

Strain sensing technology for high temperature applications

This review paper discusses the status of strain sensing technology for high temperature applications. Technologies covered are those supported by NASA such as required for applications in hypersonic vehicles and engines, advanced subsonic engines, as well as material and structure development. The applications may be at temperatures of 540 C (1000 F) to temperatures in excess of 1400 C (2500 F). The most promising technologies at present are the resistance strain gage and remote sensing schemes. Resistance strain gages discussed include the BCL gage, the LaRC compensated gage, and the PdCr gage. Remote sensing schemes such as laser based speckle strain measurement, phase-shifting interferometry and X-ray extensometry will be discussed. Present status and limitations of these technologies are presented.

Williams, W. D.↗